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CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
1
CHAPTER-I
Sr
No
Title Page
no
11 General 2
111 Need of Supercapacitor 2
112 Nanomaterials for Supercapacitors 7
12 Literature Survey on Tin Oxide (SnO2) and Ruthenium
Oxide (RuO2) Thin Films
8
121 Literature Survey on SnO2 Thin Films 8
122 Literature Survey on RuO2 Thin Films 10
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
12
131 Literature Survey on SnO2 based
Supercapacitor Electrodes
12
132 Literature Survey on RuO2 based
Supercapacitor Electrodes
13
133 Literature Survey on SnO2-RuO2 based
Supercapacitor Electrodes
17
14 Orientation and Purpose of Dissertation 19
References 22
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
2
11 General
111 Need of Supercapacitor
The growing demand of energy sources in recent few years has
become the concern topic for researchers due to the lack of renewable
energy sources The use of fossil fuels for energy production is also a
burning issue regarding the worldrsquos ecology and economical concern
Global warming fuel dependency and pollution are few examples to divert
from fuel-based economy to electricity-based civilization Some
conventional sources of energy are solar energy wind energy etc but this
energy production is highly depending on natural phenomena and we do
not have control over these phenomenarsquos Therefore there is immense
need to develop energy storage devices to store the generated energy for
future use In this aspect the electrochemical power sources are emerged
as the new sources for store and production of electrical energy The
electrochemical power sources are more efficient than the fuel-based
system because they provide clean energy which is necessary demand
according to environmental issues
Electrical energy storage is required in many applications such as
telecommunication devices cell phones standby power systems and
electric hybrid vehicles [1] Many applications are demanding local storage
or local generation of electrical energy Therefore there is a strong need of
development of improved methods for storing energy when it is available
and retrieving when it is needed The electrochemical power sources
include batteries fuel cells and supercapacitors The electrical energy
storage in these sources is according to fundamentally in two different
ways [2]
a) Indirectly in batteries as potentially available chemical energy
required Faradic oxidation and reduction of the electroactive
reagents to release charges that can perform electrical work
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
3
when they flow between two electrodes having different
electrode potential and
b) Directly in an electrostatic way as a negative and positive
electric charges on plates of capacitor
The most common electrical energy storage device is battery
Batteries are closed systems with anode and cathode are charge transfer
mediums that take part in redox reactions This means the energy storage
and conversion occurs in same compartment in batteries Whereas in case
of fuel cells the anode and cathode are only the charge transfer media and
active masses undergoing redox reaction are supplied from outside the
system means they are open systems [3] Batteries can store large amount
of energy in relatively small volume and weight The power performance
of battery is limited by its electrochemical reaction kinetics active
materials their conductivity and mass transport Most Batteries exhibit
relatively constant operating voltage because of the thermodynamics of
the battery reactants as a result it is difficult to measure their state-of-
charge (SOC) correctly [4] The irreversible chemical reactions in batteries
leads to the transformations of the active mass which limits the cycle life of
the batteries up to only several hundred cycles In recent years the power
requirement for various applications increased markedly and this leads to
design special high power pulse batteries often with sacrifice of energy
density and cycle life
Capacitors are fundamental electrical circuit elements that store
electrical energy in the order of microfarads and assist in filtering
Capacitors store electrical charge Because the charge is stored physically
with no chemical or phase changes taking place the process is highly
reversible Conventional capacitors consist of two conducting electrodes
separated by an insulating dielectric material When a voltage is applied to
a capacitor opposite charges accumulate on the surfaces of each electrode
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
4
The charges are kept separate by the dielectric thus producing an electric
field that allows the capacitor to store energy
The capacitance C of a capacitor is given by the ratio of stored
charge (Q) to the applied voltage (V) as
V
QC = (11)
For a dielectric capacitor the capacitance is dependent on the
dielectric constant (K) thickness of the dielectric material (d) and
geometric area (A) [1]
d
KAC = (12)
The two important parameters for electrical energy storage devices
are energy density and power density The energy (E) stored in capacitor
is directly proportional to its capacitance
2
CV2
1E =
(13)
The power density (P) of capacitor is energy expended per unit time and is
given by [5]
ESR4
VP
2
times
= (14)
Where ESR is the equivalent series resistance which is the net
resistance offered by the internal components of capacitor ESR plays an
important role in lowering the capacitance of a capacitor
Conventional capacitors have high power density but they have low
energy density they are able to deliver the stored energy at very high
discharge rates but the stored energy is less compared with batteries and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
5
fuel cells On the other hand batteries can store very large amount of
energy but deliver that energy at very slow rates Therefore the new
energy storage device named electrochemical capacitor or supercapacitor
is invented to minimize the disadvantages offered by both conventional
capacitors and batteries and coupled the advantages of both [6 7] The
reason why supercapacitors are able to raise considerable attention is
visualized in Fig 11 where typical energy storage and conversion devices
are presented in the so-called lsquoRagone plotrsquo in terms of their specific
energy (horizontal axis) and specific power (vertical axis)
Fig 11 Ragone chart showing logarithmic plot of specific power vs
specific energy for various energy-storage devices [8]
A simplified Ragone plot explains that the fuel cells can be
considered as high-energy systems whereas supercapacitors are
considered as high-power systems Supercapacitors fill in the gap between
batteries and conventional capacitors in terms of specific energy as well
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
6
as in terms of specific power this gap covers several orders of magnitude
Thus supercapacitors may improve battery performance in terms of
specific power or may improve capacitor performance in terms of specific
energy when combined with the respective device
The various advantages of supercapacitors are [9] a) High specific
capacitance value in Farads and several hundred Farads (greater than
ordinary capacitor) b) Virtually unlimited cycle life in thousands or
millions c) Rapid charging and discharging the energy stored d) High
power density and e) Do not contain hazardous or toxic materials so easy
to dispose
Supercapacitors can stand alone as energy storage device for high
power applications or for hybrid supercapacitor-battery system that can
address simultaneously power and energy requirements Supercapacitors
coupled with batteries fuel cells are considered promising mid and long-
term solutions for low and zero emission transport vehicles by providing
the power peaks for startndashstop acceleration and recovering the breaking
energy Supercapacitors will supply power to the system when there are
surges or energy bursts since supercapacitors can be charged and
discharged quickly Supercapacitors are making a difference or better
performance in many areas like automotive industrial traction and
consumer electronic
The capacitance of a supercapacitor can arise from the charging or
discharging of the electrical double layers (electrical double layer
capacitance) or from Faradaic redox reactions (pseudocapacitance) In
former case storage of energy is achieved in a way as a traditional
capacitor The high capacitance value than ordinary capacitor is due to the
charge separation takes place at the very small distance in the electrical
double layer that constitutes the interphase between an electrode and the
adjacent electrolyte [6] Increased amount of charge is stored on the highly
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
7
extended electrode surface-area created by a large number of pores In
later case of pseudocapacitance most of the charge is transferred at the
surface or in the bulk near the surface of the solid electrode material
Hence in this case the interaction between the solid material and the
electrolyte involves Faradaic reactions which in most instances can be
described as charge transfer reactions The charge transferred in these
reactions is voltage-dependent resulting in the pseudocapacitance [1]
112 Nanomaterials for Supercapacitors
Nowadays many researches on the supercapacitors aim to increase
both power and energy density as well as lower the fabrication costs using
environment friendly materials This can be achieved by making high
surface area electrodes having high reversible redox reactions In this
aspect nanostructured materials have attracted considerable interest due
to their unique properties arising from quantum size effect It is realized
that the properties of materials at nanoscale can be significantly different
from the bulk properties and have profound influence on the physico-
chemical characteristics of a material such as electrical optical magnetic
catalytic etc [10-17] that have vast technological applications The
electrode materials used for supercapacitors are carbon conducting
polymers and metal oxides Among them oxide nanomaterials exhibit
unique physical and chemical properties due to the high density of surface
defect sites that are observed for structures with nanoscale dimensions
However to afford the production needs of cheap clean reliable and
durable materials with controlled properties for realistic and practical
applications of nanotechnology the request of mass production of thin film
will probably represent one of the most important issues of producing
nanomaterials Chemical methods for design of nanomaterials [18] would
probably contribute to a great extent
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
8
12 Literature Survey on Tin Oxide (SnO2) and Ruthenium Oxide
(RuO2) Thin Films
121 Literature Survey on SnO2 Thin Films
SnO2 is n type wide band gap semiconductor material that
crystallizes in rutile structure The basic building blocks of the rutile
structure (Fig 12) are a tin (Sn) atom surrounded by six oxygen (O) atoms
placed approximately the corners of a regular octahedron The lattice
parameters are a=b=4737 Aring and c=3186 Aring [19 20]
Fig 12 Crystal structure of rutile SnO2 [21]
There are two main oxides of tin stannic oxide (SnO2) and stannous
oxide (SnO) The existence of these two oxides reflects the dual valency of
tin with oxidation states of +2 and +4 SnO2 possesses the rutile structure
and SnO has the less common litharge structure [22] The optical bandgap
of SnO is not exactly known but it lies somewhere in the range of 25ndash3 eV
which is less than the optical bandgap of SnO2 which is commonly quoted
to be 36 eV [23] Thus SnO exhibits a smaller band gap than SnO2 In its
stoichiometric form SnO2 acts as an insulator but in its oxygen-deficient
form SnO2 behaves as an n-type semiconductor
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
9
Due to wide bandgap SnO2 has been used extensively as a
transparent antireflection coating in optoelectronic devices such as flat
panel displays and thin film solar energy cells [24] More interestingly the
conductivity of the SnO2 semiconductor is modulated by the chemisorbed
species on its surface For example the absorbed oxygen receiving
electrons from the conduction band produces an electron depletion layer
under the absorbing surface and a potential barrier between particles and
thus decreases the conductivity of the SnO2 [25 27] This makes SnO2 a
good candidate for gas sensors whose conductivity will increase sharply
when exposed to a reducing gas SnO2 has been actively explored as the
functional component in detecting combustible gases such as CO H2 and
CH4 [28] Korotcenkov et al studied the gas response of nanosize SnO2
thin films deposited by SILD (successive ionic layer deposition) method
and observed good gas response for ozone and H2 [29] Due to the high
gravimetric lithium storage capacity of SnO2 and its low potential for
lithium ion intercalation it is regarded as one of the most promising
candidate for anode materials in Li-ion batteries [30] In addition SnO2 is
chemically inert very hard and can resist high temperatures during
heating
To continue to exploit the possible applications of SnO2 it is
essential to control its size and morphology to achieve tailored properties
Recently these useful properties have stimulated the search for new
synthetic methodologies for well-controlled SnO2 nanostructures Several
reports on high-temperature physical SnO2 synthesis have been published
[31 32] Chemical methods for the preparation of thin films studied
extensively because such processes facilitate the designing of materials on
molecular level Murakami et al used spray pyrolysis method for
deposition of SnO2 thin films using organotin compounds which led the (1
1 0) and (2 0 0) orientated films on glass substrate [33] Deshpande et al
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
10
used M-SILAR (modified successive ionic layer adsorption and reaction)
method for deposition of nanocrystalline SnO2 thin films at room
temperature the films have agglomerated structure [34] Her et al used a
hydrothermal process for large-scale production of SnO2 nanoblades on
glass substrate in a controlled aqueous solution at temperatures below
373 K [35]
Compared with high-temperature physical synthetic methods the
chemical methods appear to be of particular interest for deposition of SnO2
thin films because they offer the potential of facile scale-up and can occur
at moderate temperatures
122 Literature Survey on RuO2 Thin Films
Ruthenium (Ru) is a polyvalent hard white metal is a member of the
platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are
known though oxidation states of +2 +3 and +4 are more common Fig
13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom
is coordinated with six oxygen (O) atoms
Fig 13 Crystal structure of rutile RuO2 [36]
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
References
[1] A Burke J Power Sources 91 (2000) 37
[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656
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[14] Y Q Zhu W K Hsu H W Kroto D R M Walton Chem Commun 21 (2001)
2184
[15] J Hu M Ouyang P Yang C M Lieber Nature 399 (1999) 48
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23
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[18] C N R Rao Pure Appl Chem 69 (1997) 199
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199C
[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551
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[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
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[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
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[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
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24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
2
11 General
111 Need of Supercapacitor
The growing demand of energy sources in recent few years has
become the concern topic for researchers due to the lack of renewable
energy sources The use of fossil fuels for energy production is also a
burning issue regarding the worldrsquos ecology and economical concern
Global warming fuel dependency and pollution are few examples to divert
from fuel-based economy to electricity-based civilization Some
conventional sources of energy are solar energy wind energy etc but this
energy production is highly depending on natural phenomena and we do
not have control over these phenomenarsquos Therefore there is immense
need to develop energy storage devices to store the generated energy for
future use In this aspect the electrochemical power sources are emerged
as the new sources for store and production of electrical energy The
electrochemical power sources are more efficient than the fuel-based
system because they provide clean energy which is necessary demand
according to environmental issues
Electrical energy storage is required in many applications such as
telecommunication devices cell phones standby power systems and
electric hybrid vehicles [1] Many applications are demanding local storage
or local generation of electrical energy Therefore there is a strong need of
development of improved methods for storing energy when it is available
and retrieving when it is needed The electrochemical power sources
include batteries fuel cells and supercapacitors The electrical energy
storage in these sources is according to fundamentally in two different
ways [2]
a) Indirectly in batteries as potentially available chemical energy
required Faradic oxidation and reduction of the electroactive
reagents to release charges that can perform electrical work
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
3
when they flow between two electrodes having different
electrode potential and
b) Directly in an electrostatic way as a negative and positive
electric charges on plates of capacitor
The most common electrical energy storage device is battery
Batteries are closed systems with anode and cathode are charge transfer
mediums that take part in redox reactions This means the energy storage
and conversion occurs in same compartment in batteries Whereas in case
of fuel cells the anode and cathode are only the charge transfer media and
active masses undergoing redox reaction are supplied from outside the
system means they are open systems [3] Batteries can store large amount
of energy in relatively small volume and weight The power performance
of battery is limited by its electrochemical reaction kinetics active
materials their conductivity and mass transport Most Batteries exhibit
relatively constant operating voltage because of the thermodynamics of
the battery reactants as a result it is difficult to measure their state-of-
charge (SOC) correctly [4] The irreversible chemical reactions in batteries
leads to the transformations of the active mass which limits the cycle life of
the batteries up to only several hundred cycles In recent years the power
requirement for various applications increased markedly and this leads to
design special high power pulse batteries often with sacrifice of energy
density and cycle life
Capacitors are fundamental electrical circuit elements that store
electrical energy in the order of microfarads and assist in filtering
Capacitors store electrical charge Because the charge is stored physically
with no chemical or phase changes taking place the process is highly
reversible Conventional capacitors consist of two conducting electrodes
separated by an insulating dielectric material When a voltage is applied to
a capacitor opposite charges accumulate on the surfaces of each electrode
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
4
The charges are kept separate by the dielectric thus producing an electric
field that allows the capacitor to store energy
The capacitance C of a capacitor is given by the ratio of stored
charge (Q) to the applied voltage (V) as
V
QC = (11)
For a dielectric capacitor the capacitance is dependent on the
dielectric constant (K) thickness of the dielectric material (d) and
geometric area (A) [1]
d
KAC = (12)
The two important parameters for electrical energy storage devices
are energy density and power density The energy (E) stored in capacitor
is directly proportional to its capacitance
2
CV2
1E =
(13)
The power density (P) of capacitor is energy expended per unit time and is
given by [5]
ESR4
VP
2
times
= (14)
Where ESR is the equivalent series resistance which is the net
resistance offered by the internal components of capacitor ESR plays an
important role in lowering the capacitance of a capacitor
Conventional capacitors have high power density but they have low
energy density they are able to deliver the stored energy at very high
discharge rates but the stored energy is less compared with batteries and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
5
fuel cells On the other hand batteries can store very large amount of
energy but deliver that energy at very slow rates Therefore the new
energy storage device named electrochemical capacitor or supercapacitor
is invented to minimize the disadvantages offered by both conventional
capacitors and batteries and coupled the advantages of both [6 7] The
reason why supercapacitors are able to raise considerable attention is
visualized in Fig 11 where typical energy storage and conversion devices
are presented in the so-called lsquoRagone plotrsquo in terms of their specific
energy (horizontal axis) and specific power (vertical axis)
Fig 11 Ragone chart showing logarithmic plot of specific power vs
specific energy for various energy-storage devices [8]
A simplified Ragone plot explains that the fuel cells can be
considered as high-energy systems whereas supercapacitors are
considered as high-power systems Supercapacitors fill in the gap between
batteries and conventional capacitors in terms of specific energy as well
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
6
as in terms of specific power this gap covers several orders of magnitude
Thus supercapacitors may improve battery performance in terms of
specific power or may improve capacitor performance in terms of specific
energy when combined with the respective device
The various advantages of supercapacitors are [9] a) High specific
capacitance value in Farads and several hundred Farads (greater than
ordinary capacitor) b) Virtually unlimited cycle life in thousands or
millions c) Rapid charging and discharging the energy stored d) High
power density and e) Do not contain hazardous or toxic materials so easy
to dispose
Supercapacitors can stand alone as energy storage device for high
power applications or for hybrid supercapacitor-battery system that can
address simultaneously power and energy requirements Supercapacitors
coupled with batteries fuel cells are considered promising mid and long-
term solutions for low and zero emission transport vehicles by providing
the power peaks for startndashstop acceleration and recovering the breaking
energy Supercapacitors will supply power to the system when there are
surges or energy bursts since supercapacitors can be charged and
discharged quickly Supercapacitors are making a difference or better
performance in many areas like automotive industrial traction and
consumer electronic
The capacitance of a supercapacitor can arise from the charging or
discharging of the electrical double layers (electrical double layer
capacitance) or from Faradaic redox reactions (pseudocapacitance) In
former case storage of energy is achieved in a way as a traditional
capacitor The high capacitance value than ordinary capacitor is due to the
charge separation takes place at the very small distance in the electrical
double layer that constitutes the interphase between an electrode and the
adjacent electrolyte [6] Increased amount of charge is stored on the highly
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
7
extended electrode surface-area created by a large number of pores In
later case of pseudocapacitance most of the charge is transferred at the
surface or in the bulk near the surface of the solid electrode material
Hence in this case the interaction between the solid material and the
electrolyte involves Faradaic reactions which in most instances can be
described as charge transfer reactions The charge transferred in these
reactions is voltage-dependent resulting in the pseudocapacitance [1]
112 Nanomaterials for Supercapacitors
Nowadays many researches on the supercapacitors aim to increase
both power and energy density as well as lower the fabrication costs using
environment friendly materials This can be achieved by making high
surface area electrodes having high reversible redox reactions In this
aspect nanostructured materials have attracted considerable interest due
to their unique properties arising from quantum size effect It is realized
that the properties of materials at nanoscale can be significantly different
from the bulk properties and have profound influence on the physico-
chemical characteristics of a material such as electrical optical magnetic
catalytic etc [10-17] that have vast technological applications The
electrode materials used for supercapacitors are carbon conducting
polymers and metal oxides Among them oxide nanomaterials exhibit
unique physical and chemical properties due to the high density of surface
defect sites that are observed for structures with nanoscale dimensions
However to afford the production needs of cheap clean reliable and
durable materials with controlled properties for realistic and practical
applications of nanotechnology the request of mass production of thin film
will probably represent one of the most important issues of producing
nanomaterials Chemical methods for design of nanomaterials [18] would
probably contribute to a great extent
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
8
12 Literature Survey on Tin Oxide (SnO2) and Ruthenium Oxide
(RuO2) Thin Films
121 Literature Survey on SnO2 Thin Films
SnO2 is n type wide band gap semiconductor material that
crystallizes in rutile structure The basic building blocks of the rutile
structure (Fig 12) are a tin (Sn) atom surrounded by six oxygen (O) atoms
placed approximately the corners of a regular octahedron The lattice
parameters are a=b=4737 Aring and c=3186 Aring [19 20]
Fig 12 Crystal structure of rutile SnO2 [21]
There are two main oxides of tin stannic oxide (SnO2) and stannous
oxide (SnO) The existence of these two oxides reflects the dual valency of
tin with oxidation states of +2 and +4 SnO2 possesses the rutile structure
and SnO has the less common litharge structure [22] The optical bandgap
of SnO is not exactly known but it lies somewhere in the range of 25ndash3 eV
which is less than the optical bandgap of SnO2 which is commonly quoted
to be 36 eV [23] Thus SnO exhibits a smaller band gap than SnO2 In its
stoichiometric form SnO2 acts as an insulator but in its oxygen-deficient
form SnO2 behaves as an n-type semiconductor
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
9
Due to wide bandgap SnO2 has been used extensively as a
transparent antireflection coating in optoelectronic devices such as flat
panel displays and thin film solar energy cells [24] More interestingly the
conductivity of the SnO2 semiconductor is modulated by the chemisorbed
species on its surface For example the absorbed oxygen receiving
electrons from the conduction band produces an electron depletion layer
under the absorbing surface and a potential barrier between particles and
thus decreases the conductivity of the SnO2 [25 27] This makes SnO2 a
good candidate for gas sensors whose conductivity will increase sharply
when exposed to a reducing gas SnO2 has been actively explored as the
functional component in detecting combustible gases such as CO H2 and
CH4 [28] Korotcenkov et al studied the gas response of nanosize SnO2
thin films deposited by SILD (successive ionic layer deposition) method
and observed good gas response for ozone and H2 [29] Due to the high
gravimetric lithium storage capacity of SnO2 and its low potential for
lithium ion intercalation it is regarded as one of the most promising
candidate for anode materials in Li-ion batteries [30] In addition SnO2 is
chemically inert very hard and can resist high temperatures during
heating
To continue to exploit the possible applications of SnO2 it is
essential to control its size and morphology to achieve tailored properties
Recently these useful properties have stimulated the search for new
synthetic methodologies for well-controlled SnO2 nanostructures Several
reports on high-temperature physical SnO2 synthesis have been published
[31 32] Chemical methods for the preparation of thin films studied
extensively because such processes facilitate the designing of materials on
molecular level Murakami et al used spray pyrolysis method for
deposition of SnO2 thin films using organotin compounds which led the (1
1 0) and (2 0 0) orientated films on glass substrate [33] Deshpande et al
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
10
used M-SILAR (modified successive ionic layer adsorption and reaction)
method for deposition of nanocrystalline SnO2 thin films at room
temperature the films have agglomerated structure [34] Her et al used a
hydrothermal process for large-scale production of SnO2 nanoblades on
glass substrate in a controlled aqueous solution at temperatures below
373 K [35]
Compared with high-temperature physical synthetic methods the
chemical methods appear to be of particular interest for deposition of SnO2
thin films because they offer the potential of facile scale-up and can occur
at moderate temperatures
122 Literature Survey on RuO2 Thin Films
Ruthenium (Ru) is a polyvalent hard white metal is a member of the
platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are
known though oxidation states of +2 +3 and +4 are more common Fig
13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom
is coordinated with six oxygen (O) atoms
Fig 13 Crystal structure of rutile RuO2 [36]
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
3
when they flow between two electrodes having different
electrode potential and
b) Directly in an electrostatic way as a negative and positive
electric charges on plates of capacitor
The most common electrical energy storage device is battery
Batteries are closed systems with anode and cathode are charge transfer
mediums that take part in redox reactions This means the energy storage
and conversion occurs in same compartment in batteries Whereas in case
of fuel cells the anode and cathode are only the charge transfer media and
active masses undergoing redox reaction are supplied from outside the
system means they are open systems [3] Batteries can store large amount
of energy in relatively small volume and weight The power performance
of battery is limited by its electrochemical reaction kinetics active
materials their conductivity and mass transport Most Batteries exhibit
relatively constant operating voltage because of the thermodynamics of
the battery reactants as a result it is difficult to measure their state-of-
charge (SOC) correctly [4] The irreversible chemical reactions in batteries
leads to the transformations of the active mass which limits the cycle life of
the batteries up to only several hundred cycles In recent years the power
requirement for various applications increased markedly and this leads to
design special high power pulse batteries often with sacrifice of energy
density and cycle life
Capacitors are fundamental electrical circuit elements that store
electrical energy in the order of microfarads and assist in filtering
Capacitors store electrical charge Because the charge is stored physically
with no chemical or phase changes taking place the process is highly
reversible Conventional capacitors consist of two conducting electrodes
separated by an insulating dielectric material When a voltage is applied to
a capacitor opposite charges accumulate on the surfaces of each electrode
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
4
The charges are kept separate by the dielectric thus producing an electric
field that allows the capacitor to store energy
The capacitance C of a capacitor is given by the ratio of stored
charge (Q) to the applied voltage (V) as
V
QC = (11)
For a dielectric capacitor the capacitance is dependent on the
dielectric constant (K) thickness of the dielectric material (d) and
geometric area (A) [1]
d
KAC = (12)
The two important parameters for electrical energy storage devices
are energy density and power density The energy (E) stored in capacitor
is directly proportional to its capacitance
2
CV2
1E =
(13)
The power density (P) of capacitor is energy expended per unit time and is
given by [5]
ESR4
VP
2
times
= (14)
Where ESR is the equivalent series resistance which is the net
resistance offered by the internal components of capacitor ESR plays an
important role in lowering the capacitance of a capacitor
Conventional capacitors have high power density but they have low
energy density they are able to deliver the stored energy at very high
discharge rates but the stored energy is less compared with batteries and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
5
fuel cells On the other hand batteries can store very large amount of
energy but deliver that energy at very slow rates Therefore the new
energy storage device named electrochemical capacitor or supercapacitor
is invented to minimize the disadvantages offered by both conventional
capacitors and batteries and coupled the advantages of both [6 7] The
reason why supercapacitors are able to raise considerable attention is
visualized in Fig 11 where typical energy storage and conversion devices
are presented in the so-called lsquoRagone plotrsquo in terms of their specific
energy (horizontal axis) and specific power (vertical axis)
Fig 11 Ragone chart showing logarithmic plot of specific power vs
specific energy for various energy-storage devices [8]
A simplified Ragone plot explains that the fuel cells can be
considered as high-energy systems whereas supercapacitors are
considered as high-power systems Supercapacitors fill in the gap between
batteries and conventional capacitors in terms of specific energy as well
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
6
as in terms of specific power this gap covers several orders of magnitude
Thus supercapacitors may improve battery performance in terms of
specific power or may improve capacitor performance in terms of specific
energy when combined with the respective device
The various advantages of supercapacitors are [9] a) High specific
capacitance value in Farads and several hundred Farads (greater than
ordinary capacitor) b) Virtually unlimited cycle life in thousands or
millions c) Rapid charging and discharging the energy stored d) High
power density and e) Do not contain hazardous or toxic materials so easy
to dispose
Supercapacitors can stand alone as energy storage device for high
power applications or for hybrid supercapacitor-battery system that can
address simultaneously power and energy requirements Supercapacitors
coupled with batteries fuel cells are considered promising mid and long-
term solutions for low and zero emission transport vehicles by providing
the power peaks for startndashstop acceleration and recovering the breaking
energy Supercapacitors will supply power to the system when there are
surges or energy bursts since supercapacitors can be charged and
discharged quickly Supercapacitors are making a difference or better
performance in many areas like automotive industrial traction and
consumer electronic
The capacitance of a supercapacitor can arise from the charging or
discharging of the electrical double layers (electrical double layer
capacitance) or from Faradaic redox reactions (pseudocapacitance) In
former case storage of energy is achieved in a way as a traditional
capacitor The high capacitance value than ordinary capacitor is due to the
charge separation takes place at the very small distance in the electrical
double layer that constitutes the interphase between an electrode and the
adjacent electrolyte [6] Increased amount of charge is stored on the highly
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
7
extended electrode surface-area created by a large number of pores In
later case of pseudocapacitance most of the charge is transferred at the
surface or in the bulk near the surface of the solid electrode material
Hence in this case the interaction between the solid material and the
electrolyte involves Faradaic reactions which in most instances can be
described as charge transfer reactions The charge transferred in these
reactions is voltage-dependent resulting in the pseudocapacitance [1]
112 Nanomaterials for Supercapacitors
Nowadays many researches on the supercapacitors aim to increase
both power and energy density as well as lower the fabrication costs using
environment friendly materials This can be achieved by making high
surface area electrodes having high reversible redox reactions In this
aspect nanostructured materials have attracted considerable interest due
to their unique properties arising from quantum size effect It is realized
that the properties of materials at nanoscale can be significantly different
from the bulk properties and have profound influence on the physico-
chemical characteristics of a material such as electrical optical magnetic
catalytic etc [10-17] that have vast technological applications The
electrode materials used for supercapacitors are carbon conducting
polymers and metal oxides Among them oxide nanomaterials exhibit
unique physical and chemical properties due to the high density of surface
defect sites that are observed for structures with nanoscale dimensions
However to afford the production needs of cheap clean reliable and
durable materials with controlled properties for realistic and practical
applications of nanotechnology the request of mass production of thin film
will probably represent one of the most important issues of producing
nanomaterials Chemical methods for design of nanomaterials [18] would
probably contribute to a great extent
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
8
12 Literature Survey on Tin Oxide (SnO2) and Ruthenium Oxide
(RuO2) Thin Films
121 Literature Survey on SnO2 Thin Films
SnO2 is n type wide band gap semiconductor material that
crystallizes in rutile structure The basic building blocks of the rutile
structure (Fig 12) are a tin (Sn) atom surrounded by six oxygen (O) atoms
placed approximately the corners of a regular octahedron The lattice
parameters are a=b=4737 Aring and c=3186 Aring [19 20]
Fig 12 Crystal structure of rutile SnO2 [21]
There are two main oxides of tin stannic oxide (SnO2) and stannous
oxide (SnO) The existence of these two oxides reflects the dual valency of
tin with oxidation states of +2 and +4 SnO2 possesses the rutile structure
and SnO has the less common litharge structure [22] The optical bandgap
of SnO is not exactly known but it lies somewhere in the range of 25ndash3 eV
which is less than the optical bandgap of SnO2 which is commonly quoted
to be 36 eV [23] Thus SnO exhibits a smaller band gap than SnO2 In its
stoichiometric form SnO2 acts as an insulator but in its oxygen-deficient
form SnO2 behaves as an n-type semiconductor
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
9
Due to wide bandgap SnO2 has been used extensively as a
transparent antireflection coating in optoelectronic devices such as flat
panel displays and thin film solar energy cells [24] More interestingly the
conductivity of the SnO2 semiconductor is modulated by the chemisorbed
species on its surface For example the absorbed oxygen receiving
electrons from the conduction band produces an electron depletion layer
under the absorbing surface and a potential barrier between particles and
thus decreases the conductivity of the SnO2 [25 27] This makes SnO2 a
good candidate for gas sensors whose conductivity will increase sharply
when exposed to a reducing gas SnO2 has been actively explored as the
functional component in detecting combustible gases such as CO H2 and
CH4 [28] Korotcenkov et al studied the gas response of nanosize SnO2
thin films deposited by SILD (successive ionic layer deposition) method
and observed good gas response for ozone and H2 [29] Due to the high
gravimetric lithium storage capacity of SnO2 and its low potential for
lithium ion intercalation it is regarded as one of the most promising
candidate for anode materials in Li-ion batteries [30] In addition SnO2 is
chemically inert very hard and can resist high temperatures during
heating
To continue to exploit the possible applications of SnO2 it is
essential to control its size and morphology to achieve tailored properties
Recently these useful properties have stimulated the search for new
synthetic methodologies for well-controlled SnO2 nanostructures Several
reports on high-temperature physical SnO2 synthesis have been published
[31 32] Chemical methods for the preparation of thin films studied
extensively because such processes facilitate the designing of materials on
molecular level Murakami et al used spray pyrolysis method for
deposition of SnO2 thin films using organotin compounds which led the (1
1 0) and (2 0 0) orientated films on glass substrate [33] Deshpande et al
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
10
used M-SILAR (modified successive ionic layer adsorption and reaction)
method for deposition of nanocrystalline SnO2 thin films at room
temperature the films have agglomerated structure [34] Her et al used a
hydrothermal process for large-scale production of SnO2 nanoblades on
glass substrate in a controlled aqueous solution at temperatures below
373 K [35]
Compared with high-temperature physical synthetic methods the
chemical methods appear to be of particular interest for deposition of SnO2
thin films because they offer the potential of facile scale-up and can occur
at moderate temperatures
122 Literature Survey on RuO2 Thin Films
Ruthenium (Ru) is a polyvalent hard white metal is a member of the
platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are
known though oxidation states of +2 +3 and +4 are more common Fig
13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom
is coordinated with six oxygen (O) atoms
Fig 13 Crystal structure of rutile RuO2 [36]
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
References
[1] A Burke J Power Sources 91 (2000) 37
[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656
[3] M Winter and R J Brodd Chem Rev 104 (2004) 4245
[4] J R Miller and P Simon The Electrochem Soc Interface Spring 2008
[5] A Chu and P Braatz J Power Sources 112 (2002) 236
[6] B E Conway Electrochemical Supercapacitors Scientific Fundamentals
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[7] R Kotz and M Carlen Electrochim Acta 45 (2002) 2483
[8] httpdeptswashingtonedu
[9] M Anderman J Power Sources 127 (2004) 2
[10] Z Y Pan X J Liu S Y Zhang G J Shen L G Zhang Z H Lu J Z Liu J Phys
Chem B 101 (1997) 9703
[11] Y Wu H Yan P Yang Chem Eur J 8 (2002) 1260
[12] J Hu T W Odom C M Lieber Acc Chem Res 32 (1999) 435
[13] P C Ohara J R Heath W M Gelbart Angew Chem Int Ed Engl 36 (1997)
1078
[14] Y Q Zhu W K Hsu H W Kroto D R M Walton Chem Commun 21 (2001)
2184
[15] J Hu M Ouyang P Yang C M Lieber Nature 399 (1999) 48
[16] X Duan Y Huang Y Cui J Wang C M Lieber Nature 409 (2001) 66
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
23
[17] J F Colomer G Bister I Willems Z Konya A Fonseca G Van Tendeloo J B
Nagy Chem Commun 14 (1999) 1343
[18] C N R Rao Pure Appl Chem 69 (1997) 199
[19] Z Jarzebski and J Marton J Electrochem Soc Rev and News 123 (1976)
199C
[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551
[21] httpWikipediacomtin(IV) oxide
[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
(2001) 195
[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
Sci 25 (2002) 231
[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
4
The charges are kept separate by the dielectric thus producing an electric
field that allows the capacitor to store energy
The capacitance C of a capacitor is given by the ratio of stored
charge (Q) to the applied voltage (V) as
V
QC = (11)
For a dielectric capacitor the capacitance is dependent on the
dielectric constant (K) thickness of the dielectric material (d) and
geometric area (A) [1]
d
KAC = (12)
The two important parameters for electrical energy storage devices
are energy density and power density The energy (E) stored in capacitor
is directly proportional to its capacitance
2
CV2
1E =
(13)
The power density (P) of capacitor is energy expended per unit time and is
given by [5]
ESR4
VP
2
times
= (14)
Where ESR is the equivalent series resistance which is the net
resistance offered by the internal components of capacitor ESR plays an
important role in lowering the capacitance of a capacitor
Conventional capacitors have high power density but they have low
energy density they are able to deliver the stored energy at very high
discharge rates but the stored energy is less compared with batteries and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
5
fuel cells On the other hand batteries can store very large amount of
energy but deliver that energy at very slow rates Therefore the new
energy storage device named electrochemical capacitor or supercapacitor
is invented to minimize the disadvantages offered by both conventional
capacitors and batteries and coupled the advantages of both [6 7] The
reason why supercapacitors are able to raise considerable attention is
visualized in Fig 11 where typical energy storage and conversion devices
are presented in the so-called lsquoRagone plotrsquo in terms of their specific
energy (horizontal axis) and specific power (vertical axis)
Fig 11 Ragone chart showing logarithmic plot of specific power vs
specific energy for various energy-storage devices [8]
A simplified Ragone plot explains that the fuel cells can be
considered as high-energy systems whereas supercapacitors are
considered as high-power systems Supercapacitors fill in the gap between
batteries and conventional capacitors in terms of specific energy as well
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
6
as in terms of specific power this gap covers several orders of magnitude
Thus supercapacitors may improve battery performance in terms of
specific power or may improve capacitor performance in terms of specific
energy when combined with the respective device
The various advantages of supercapacitors are [9] a) High specific
capacitance value in Farads and several hundred Farads (greater than
ordinary capacitor) b) Virtually unlimited cycle life in thousands or
millions c) Rapid charging and discharging the energy stored d) High
power density and e) Do not contain hazardous or toxic materials so easy
to dispose
Supercapacitors can stand alone as energy storage device for high
power applications or for hybrid supercapacitor-battery system that can
address simultaneously power and energy requirements Supercapacitors
coupled with batteries fuel cells are considered promising mid and long-
term solutions for low and zero emission transport vehicles by providing
the power peaks for startndashstop acceleration and recovering the breaking
energy Supercapacitors will supply power to the system when there are
surges or energy bursts since supercapacitors can be charged and
discharged quickly Supercapacitors are making a difference or better
performance in many areas like automotive industrial traction and
consumer electronic
The capacitance of a supercapacitor can arise from the charging or
discharging of the electrical double layers (electrical double layer
capacitance) or from Faradaic redox reactions (pseudocapacitance) In
former case storage of energy is achieved in a way as a traditional
capacitor The high capacitance value than ordinary capacitor is due to the
charge separation takes place at the very small distance in the electrical
double layer that constitutes the interphase between an electrode and the
adjacent electrolyte [6] Increased amount of charge is stored on the highly
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
7
extended electrode surface-area created by a large number of pores In
later case of pseudocapacitance most of the charge is transferred at the
surface or in the bulk near the surface of the solid electrode material
Hence in this case the interaction between the solid material and the
electrolyte involves Faradaic reactions which in most instances can be
described as charge transfer reactions The charge transferred in these
reactions is voltage-dependent resulting in the pseudocapacitance [1]
112 Nanomaterials for Supercapacitors
Nowadays many researches on the supercapacitors aim to increase
both power and energy density as well as lower the fabrication costs using
environment friendly materials This can be achieved by making high
surface area electrodes having high reversible redox reactions In this
aspect nanostructured materials have attracted considerable interest due
to their unique properties arising from quantum size effect It is realized
that the properties of materials at nanoscale can be significantly different
from the bulk properties and have profound influence on the physico-
chemical characteristics of a material such as electrical optical magnetic
catalytic etc [10-17] that have vast technological applications The
electrode materials used for supercapacitors are carbon conducting
polymers and metal oxides Among them oxide nanomaterials exhibit
unique physical and chemical properties due to the high density of surface
defect sites that are observed for structures with nanoscale dimensions
However to afford the production needs of cheap clean reliable and
durable materials with controlled properties for realistic and practical
applications of nanotechnology the request of mass production of thin film
will probably represent one of the most important issues of producing
nanomaterials Chemical methods for design of nanomaterials [18] would
probably contribute to a great extent
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
8
12 Literature Survey on Tin Oxide (SnO2) and Ruthenium Oxide
(RuO2) Thin Films
121 Literature Survey on SnO2 Thin Films
SnO2 is n type wide band gap semiconductor material that
crystallizes in rutile structure The basic building blocks of the rutile
structure (Fig 12) are a tin (Sn) atom surrounded by six oxygen (O) atoms
placed approximately the corners of a regular octahedron The lattice
parameters are a=b=4737 Aring and c=3186 Aring [19 20]
Fig 12 Crystal structure of rutile SnO2 [21]
There are two main oxides of tin stannic oxide (SnO2) and stannous
oxide (SnO) The existence of these two oxides reflects the dual valency of
tin with oxidation states of +2 and +4 SnO2 possesses the rutile structure
and SnO has the less common litharge structure [22] The optical bandgap
of SnO is not exactly known but it lies somewhere in the range of 25ndash3 eV
which is less than the optical bandgap of SnO2 which is commonly quoted
to be 36 eV [23] Thus SnO exhibits a smaller band gap than SnO2 In its
stoichiometric form SnO2 acts as an insulator but in its oxygen-deficient
form SnO2 behaves as an n-type semiconductor
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
9
Due to wide bandgap SnO2 has been used extensively as a
transparent antireflection coating in optoelectronic devices such as flat
panel displays and thin film solar energy cells [24] More interestingly the
conductivity of the SnO2 semiconductor is modulated by the chemisorbed
species on its surface For example the absorbed oxygen receiving
electrons from the conduction band produces an electron depletion layer
under the absorbing surface and a potential barrier between particles and
thus decreases the conductivity of the SnO2 [25 27] This makes SnO2 a
good candidate for gas sensors whose conductivity will increase sharply
when exposed to a reducing gas SnO2 has been actively explored as the
functional component in detecting combustible gases such as CO H2 and
CH4 [28] Korotcenkov et al studied the gas response of nanosize SnO2
thin films deposited by SILD (successive ionic layer deposition) method
and observed good gas response for ozone and H2 [29] Due to the high
gravimetric lithium storage capacity of SnO2 and its low potential for
lithium ion intercalation it is regarded as one of the most promising
candidate for anode materials in Li-ion batteries [30] In addition SnO2 is
chemically inert very hard and can resist high temperatures during
heating
To continue to exploit the possible applications of SnO2 it is
essential to control its size and morphology to achieve tailored properties
Recently these useful properties have stimulated the search for new
synthetic methodologies for well-controlled SnO2 nanostructures Several
reports on high-temperature physical SnO2 synthesis have been published
[31 32] Chemical methods for the preparation of thin films studied
extensively because such processes facilitate the designing of materials on
molecular level Murakami et al used spray pyrolysis method for
deposition of SnO2 thin films using organotin compounds which led the (1
1 0) and (2 0 0) orientated films on glass substrate [33] Deshpande et al
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
10
used M-SILAR (modified successive ionic layer adsorption and reaction)
method for deposition of nanocrystalline SnO2 thin films at room
temperature the films have agglomerated structure [34] Her et al used a
hydrothermal process for large-scale production of SnO2 nanoblades on
glass substrate in a controlled aqueous solution at temperatures below
373 K [35]
Compared with high-temperature physical synthetic methods the
chemical methods appear to be of particular interest for deposition of SnO2
thin films because they offer the potential of facile scale-up and can occur
at moderate temperatures
122 Literature Survey on RuO2 Thin Films
Ruthenium (Ru) is a polyvalent hard white metal is a member of the
platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are
known though oxidation states of +2 +3 and +4 are more common Fig
13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom
is coordinated with six oxygen (O) atoms
Fig 13 Crystal structure of rutile RuO2 [36]
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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23
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[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
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24
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[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
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104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
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[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
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25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
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[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
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26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
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27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
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28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
5
fuel cells On the other hand batteries can store very large amount of
energy but deliver that energy at very slow rates Therefore the new
energy storage device named electrochemical capacitor or supercapacitor
is invented to minimize the disadvantages offered by both conventional
capacitors and batteries and coupled the advantages of both [6 7] The
reason why supercapacitors are able to raise considerable attention is
visualized in Fig 11 where typical energy storage and conversion devices
are presented in the so-called lsquoRagone plotrsquo in terms of their specific
energy (horizontal axis) and specific power (vertical axis)
Fig 11 Ragone chart showing logarithmic plot of specific power vs
specific energy for various energy-storage devices [8]
A simplified Ragone plot explains that the fuel cells can be
considered as high-energy systems whereas supercapacitors are
considered as high-power systems Supercapacitors fill in the gap between
batteries and conventional capacitors in terms of specific energy as well
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
6
as in terms of specific power this gap covers several orders of magnitude
Thus supercapacitors may improve battery performance in terms of
specific power or may improve capacitor performance in terms of specific
energy when combined with the respective device
The various advantages of supercapacitors are [9] a) High specific
capacitance value in Farads and several hundred Farads (greater than
ordinary capacitor) b) Virtually unlimited cycle life in thousands or
millions c) Rapid charging and discharging the energy stored d) High
power density and e) Do not contain hazardous or toxic materials so easy
to dispose
Supercapacitors can stand alone as energy storage device for high
power applications or for hybrid supercapacitor-battery system that can
address simultaneously power and energy requirements Supercapacitors
coupled with batteries fuel cells are considered promising mid and long-
term solutions for low and zero emission transport vehicles by providing
the power peaks for startndashstop acceleration and recovering the breaking
energy Supercapacitors will supply power to the system when there are
surges or energy bursts since supercapacitors can be charged and
discharged quickly Supercapacitors are making a difference or better
performance in many areas like automotive industrial traction and
consumer electronic
The capacitance of a supercapacitor can arise from the charging or
discharging of the electrical double layers (electrical double layer
capacitance) or from Faradaic redox reactions (pseudocapacitance) In
former case storage of energy is achieved in a way as a traditional
capacitor The high capacitance value than ordinary capacitor is due to the
charge separation takes place at the very small distance in the electrical
double layer that constitutes the interphase between an electrode and the
adjacent electrolyte [6] Increased amount of charge is stored on the highly
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
7
extended electrode surface-area created by a large number of pores In
later case of pseudocapacitance most of the charge is transferred at the
surface or in the bulk near the surface of the solid electrode material
Hence in this case the interaction between the solid material and the
electrolyte involves Faradaic reactions which in most instances can be
described as charge transfer reactions The charge transferred in these
reactions is voltage-dependent resulting in the pseudocapacitance [1]
112 Nanomaterials for Supercapacitors
Nowadays many researches on the supercapacitors aim to increase
both power and energy density as well as lower the fabrication costs using
environment friendly materials This can be achieved by making high
surface area electrodes having high reversible redox reactions In this
aspect nanostructured materials have attracted considerable interest due
to their unique properties arising from quantum size effect It is realized
that the properties of materials at nanoscale can be significantly different
from the bulk properties and have profound influence on the physico-
chemical characteristics of a material such as electrical optical magnetic
catalytic etc [10-17] that have vast technological applications The
electrode materials used for supercapacitors are carbon conducting
polymers and metal oxides Among them oxide nanomaterials exhibit
unique physical and chemical properties due to the high density of surface
defect sites that are observed for structures with nanoscale dimensions
However to afford the production needs of cheap clean reliable and
durable materials with controlled properties for realistic and practical
applications of nanotechnology the request of mass production of thin film
will probably represent one of the most important issues of producing
nanomaterials Chemical methods for design of nanomaterials [18] would
probably contribute to a great extent
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
8
12 Literature Survey on Tin Oxide (SnO2) and Ruthenium Oxide
(RuO2) Thin Films
121 Literature Survey on SnO2 Thin Films
SnO2 is n type wide band gap semiconductor material that
crystallizes in rutile structure The basic building blocks of the rutile
structure (Fig 12) are a tin (Sn) atom surrounded by six oxygen (O) atoms
placed approximately the corners of a regular octahedron The lattice
parameters are a=b=4737 Aring and c=3186 Aring [19 20]
Fig 12 Crystal structure of rutile SnO2 [21]
There are two main oxides of tin stannic oxide (SnO2) and stannous
oxide (SnO) The existence of these two oxides reflects the dual valency of
tin with oxidation states of +2 and +4 SnO2 possesses the rutile structure
and SnO has the less common litharge structure [22] The optical bandgap
of SnO is not exactly known but it lies somewhere in the range of 25ndash3 eV
which is less than the optical bandgap of SnO2 which is commonly quoted
to be 36 eV [23] Thus SnO exhibits a smaller band gap than SnO2 In its
stoichiometric form SnO2 acts as an insulator but in its oxygen-deficient
form SnO2 behaves as an n-type semiconductor
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
9
Due to wide bandgap SnO2 has been used extensively as a
transparent antireflection coating in optoelectronic devices such as flat
panel displays and thin film solar energy cells [24] More interestingly the
conductivity of the SnO2 semiconductor is modulated by the chemisorbed
species on its surface For example the absorbed oxygen receiving
electrons from the conduction band produces an electron depletion layer
under the absorbing surface and a potential barrier between particles and
thus decreases the conductivity of the SnO2 [25 27] This makes SnO2 a
good candidate for gas sensors whose conductivity will increase sharply
when exposed to a reducing gas SnO2 has been actively explored as the
functional component in detecting combustible gases such as CO H2 and
CH4 [28] Korotcenkov et al studied the gas response of nanosize SnO2
thin films deposited by SILD (successive ionic layer deposition) method
and observed good gas response for ozone and H2 [29] Due to the high
gravimetric lithium storage capacity of SnO2 and its low potential for
lithium ion intercalation it is regarded as one of the most promising
candidate for anode materials in Li-ion batteries [30] In addition SnO2 is
chemically inert very hard and can resist high temperatures during
heating
To continue to exploit the possible applications of SnO2 it is
essential to control its size and morphology to achieve tailored properties
Recently these useful properties have stimulated the search for new
synthetic methodologies for well-controlled SnO2 nanostructures Several
reports on high-temperature physical SnO2 synthesis have been published
[31 32] Chemical methods for the preparation of thin films studied
extensively because such processes facilitate the designing of materials on
molecular level Murakami et al used spray pyrolysis method for
deposition of SnO2 thin films using organotin compounds which led the (1
1 0) and (2 0 0) orientated films on glass substrate [33] Deshpande et al
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
10
used M-SILAR (modified successive ionic layer adsorption and reaction)
method for deposition of nanocrystalline SnO2 thin films at room
temperature the films have agglomerated structure [34] Her et al used a
hydrothermal process for large-scale production of SnO2 nanoblades on
glass substrate in a controlled aqueous solution at temperatures below
373 K [35]
Compared with high-temperature physical synthetic methods the
chemical methods appear to be of particular interest for deposition of SnO2
thin films because they offer the potential of facile scale-up and can occur
at moderate temperatures
122 Literature Survey on RuO2 Thin Films
Ruthenium (Ru) is a polyvalent hard white metal is a member of the
platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are
known though oxidation states of +2 +3 and +4 are more common Fig
13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom
is coordinated with six oxygen (O) atoms
Fig 13 Crystal structure of rutile RuO2 [36]
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
6
as in terms of specific power this gap covers several orders of magnitude
Thus supercapacitors may improve battery performance in terms of
specific power or may improve capacitor performance in terms of specific
energy when combined with the respective device
The various advantages of supercapacitors are [9] a) High specific
capacitance value in Farads and several hundred Farads (greater than
ordinary capacitor) b) Virtually unlimited cycle life in thousands or
millions c) Rapid charging and discharging the energy stored d) High
power density and e) Do not contain hazardous or toxic materials so easy
to dispose
Supercapacitors can stand alone as energy storage device for high
power applications or for hybrid supercapacitor-battery system that can
address simultaneously power and energy requirements Supercapacitors
coupled with batteries fuel cells are considered promising mid and long-
term solutions for low and zero emission transport vehicles by providing
the power peaks for startndashstop acceleration and recovering the breaking
energy Supercapacitors will supply power to the system when there are
surges or energy bursts since supercapacitors can be charged and
discharged quickly Supercapacitors are making a difference or better
performance in many areas like automotive industrial traction and
consumer electronic
The capacitance of a supercapacitor can arise from the charging or
discharging of the electrical double layers (electrical double layer
capacitance) or from Faradaic redox reactions (pseudocapacitance) In
former case storage of energy is achieved in a way as a traditional
capacitor The high capacitance value than ordinary capacitor is due to the
charge separation takes place at the very small distance in the electrical
double layer that constitutes the interphase between an electrode and the
adjacent electrolyte [6] Increased amount of charge is stored on the highly
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
7
extended electrode surface-area created by a large number of pores In
later case of pseudocapacitance most of the charge is transferred at the
surface or in the bulk near the surface of the solid electrode material
Hence in this case the interaction between the solid material and the
electrolyte involves Faradaic reactions which in most instances can be
described as charge transfer reactions The charge transferred in these
reactions is voltage-dependent resulting in the pseudocapacitance [1]
112 Nanomaterials for Supercapacitors
Nowadays many researches on the supercapacitors aim to increase
both power and energy density as well as lower the fabrication costs using
environment friendly materials This can be achieved by making high
surface area electrodes having high reversible redox reactions In this
aspect nanostructured materials have attracted considerable interest due
to their unique properties arising from quantum size effect It is realized
that the properties of materials at nanoscale can be significantly different
from the bulk properties and have profound influence on the physico-
chemical characteristics of a material such as electrical optical magnetic
catalytic etc [10-17] that have vast technological applications The
electrode materials used for supercapacitors are carbon conducting
polymers and metal oxides Among them oxide nanomaterials exhibit
unique physical and chemical properties due to the high density of surface
defect sites that are observed for structures with nanoscale dimensions
However to afford the production needs of cheap clean reliable and
durable materials with controlled properties for realistic and practical
applications of nanotechnology the request of mass production of thin film
will probably represent one of the most important issues of producing
nanomaterials Chemical methods for design of nanomaterials [18] would
probably contribute to a great extent
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
8
12 Literature Survey on Tin Oxide (SnO2) and Ruthenium Oxide
(RuO2) Thin Films
121 Literature Survey on SnO2 Thin Films
SnO2 is n type wide band gap semiconductor material that
crystallizes in rutile structure The basic building blocks of the rutile
structure (Fig 12) are a tin (Sn) atom surrounded by six oxygen (O) atoms
placed approximately the corners of a regular octahedron The lattice
parameters are a=b=4737 Aring and c=3186 Aring [19 20]
Fig 12 Crystal structure of rutile SnO2 [21]
There are two main oxides of tin stannic oxide (SnO2) and stannous
oxide (SnO) The existence of these two oxides reflects the dual valency of
tin with oxidation states of +2 and +4 SnO2 possesses the rutile structure
and SnO has the less common litharge structure [22] The optical bandgap
of SnO is not exactly known but it lies somewhere in the range of 25ndash3 eV
which is less than the optical bandgap of SnO2 which is commonly quoted
to be 36 eV [23] Thus SnO exhibits a smaller band gap than SnO2 In its
stoichiometric form SnO2 acts as an insulator but in its oxygen-deficient
form SnO2 behaves as an n-type semiconductor
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
9
Due to wide bandgap SnO2 has been used extensively as a
transparent antireflection coating in optoelectronic devices such as flat
panel displays and thin film solar energy cells [24] More interestingly the
conductivity of the SnO2 semiconductor is modulated by the chemisorbed
species on its surface For example the absorbed oxygen receiving
electrons from the conduction band produces an electron depletion layer
under the absorbing surface and a potential barrier between particles and
thus decreases the conductivity of the SnO2 [25 27] This makes SnO2 a
good candidate for gas sensors whose conductivity will increase sharply
when exposed to a reducing gas SnO2 has been actively explored as the
functional component in detecting combustible gases such as CO H2 and
CH4 [28] Korotcenkov et al studied the gas response of nanosize SnO2
thin films deposited by SILD (successive ionic layer deposition) method
and observed good gas response for ozone and H2 [29] Due to the high
gravimetric lithium storage capacity of SnO2 and its low potential for
lithium ion intercalation it is regarded as one of the most promising
candidate for anode materials in Li-ion batteries [30] In addition SnO2 is
chemically inert very hard and can resist high temperatures during
heating
To continue to exploit the possible applications of SnO2 it is
essential to control its size and morphology to achieve tailored properties
Recently these useful properties have stimulated the search for new
synthetic methodologies for well-controlled SnO2 nanostructures Several
reports on high-temperature physical SnO2 synthesis have been published
[31 32] Chemical methods for the preparation of thin films studied
extensively because such processes facilitate the designing of materials on
molecular level Murakami et al used spray pyrolysis method for
deposition of SnO2 thin films using organotin compounds which led the (1
1 0) and (2 0 0) orientated films on glass substrate [33] Deshpande et al
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
10
used M-SILAR (modified successive ionic layer adsorption and reaction)
method for deposition of nanocrystalline SnO2 thin films at room
temperature the films have agglomerated structure [34] Her et al used a
hydrothermal process for large-scale production of SnO2 nanoblades on
glass substrate in a controlled aqueous solution at temperatures below
373 K [35]
Compared with high-temperature physical synthetic methods the
chemical methods appear to be of particular interest for deposition of SnO2
thin films because they offer the potential of facile scale-up and can occur
at moderate temperatures
122 Literature Survey on RuO2 Thin Films
Ruthenium (Ru) is a polyvalent hard white metal is a member of the
platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are
known though oxidation states of +2 +3 and +4 are more common Fig
13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom
is coordinated with six oxygen (O) atoms
Fig 13 Crystal structure of rutile RuO2 [36]
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
References
[1] A Burke J Power Sources 91 (2000) 37
[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656
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[7] R Kotz and M Carlen Electrochim Acta 45 (2002) 2483
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[9] M Anderman J Power Sources 127 (2004) 2
[10] Z Y Pan X J Liu S Y Zhang G J Shen L G Zhang Z H Lu J Z Liu J Phys
Chem B 101 (1997) 9703
[11] Y Wu H Yan P Yang Chem Eur J 8 (2002) 1260
[12] J Hu T W Odom C M Lieber Acc Chem Res 32 (1999) 435
[13] P C Ohara J R Heath W M Gelbart Angew Chem Int Ed Engl 36 (1997)
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[14] Y Q Zhu W K Hsu H W Kroto D R M Walton Chem Commun 21 (2001)
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[16] X Duan Y Huang Y Cui J Wang C M Lieber Nature 409 (2001) 66
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[17] J F Colomer G Bister I Willems Z Konya A Fonseca G Van Tendeloo J B
Nagy Chem Commun 14 (1999) 1343
[18] C N R Rao Pure Appl Chem 69 (1997) 199
[19] Z Jarzebski and J Marton J Electrochem Soc Rev and News 123 (1976)
199C
[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551
[21] httpWikipediacomtin(IV) oxide
[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
(2001) 195
[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
Sci 25 (2002) 231
[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
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24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
7
extended electrode surface-area created by a large number of pores In
later case of pseudocapacitance most of the charge is transferred at the
surface or in the bulk near the surface of the solid electrode material
Hence in this case the interaction between the solid material and the
electrolyte involves Faradaic reactions which in most instances can be
described as charge transfer reactions The charge transferred in these
reactions is voltage-dependent resulting in the pseudocapacitance [1]
112 Nanomaterials for Supercapacitors
Nowadays many researches on the supercapacitors aim to increase
both power and energy density as well as lower the fabrication costs using
environment friendly materials This can be achieved by making high
surface area electrodes having high reversible redox reactions In this
aspect nanostructured materials have attracted considerable interest due
to their unique properties arising from quantum size effect It is realized
that the properties of materials at nanoscale can be significantly different
from the bulk properties and have profound influence on the physico-
chemical characteristics of a material such as electrical optical magnetic
catalytic etc [10-17] that have vast technological applications The
electrode materials used for supercapacitors are carbon conducting
polymers and metal oxides Among them oxide nanomaterials exhibit
unique physical and chemical properties due to the high density of surface
defect sites that are observed for structures with nanoscale dimensions
However to afford the production needs of cheap clean reliable and
durable materials with controlled properties for realistic and practical
applications of nanotechnology the request of mass production of thin film
will probably represent one of the most important issues of producing
nanomaterials Chemical methods for design of nanomaterials [18] would
probably contribute to a great extent
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
8
12 Literature Survey on Tin Oxide (SnO2) and Ruthenium Oxide
(RuO2) Thin Films
121 Literature Survey on SnO2 Thin Films
SnO2 is n type wide band gap semiconductor material that
crystallizes in rutile structure The basic building blocks of the rutile
structure (Fig 12) are a tin (Sn) atom surrounded by six oxygen (O) atoms
placed approximately the corners of a regular octahedron The lattice
parameters are a=b=4737 Aring and c=3186 Aring [19 20]
Fig 12 Crystal structure of rutile SnO2 [21]
There are two main oxides of tin stannic oxide (SnO2) and stannous
oxide (SnO) The existence of these two oxides reflects the dual valency of
tin with oxidation states of +2 and +4 SnO2 possesses the rutile structure
and SnO has the less common litharge structure [22] The optical bandgap
of SnO is not exactly known but it lies somewhere in the range of 25ndash3 eV
which is less than the optical bandgap of SnO2 which is commonly quoted
to be 36 eV [23] Thus SnO exhibits a smaller band gap than SnO2 In its
stoichiometric form SnO2 acts as an insulator but in its oxygen-deficient
form SnO2 behaves as an n-type semiconductor
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
9
Due to wide bandgap SnO2 has been used extensively as a
transparent antireflection coating in optoelectronic devices such as flat
panel displays and thin film solar energy cells [24] More interestingly the
conductivity of the SnO2 semiconductor is modulated by the chemisorbed
species on its surface For example the absorbed oxygen receiving
electrons from the conduction band produces an electron depletion layer
under the absorbing surface and a potential barrier between particles and
thus decreases the conductivity of the SnO2 [25 27] This makes SnO2 a
good candidate for gas sensors whose conductivity will increase sharply
when exposed to a reducing gas SnO2 has been actively explored as the
functional component in detecting combustible gases such as CO H2 and
CH4 [28] Korotcenkov et al studied the gas response of nanosize SnO2
thin films deposited by SILD (successive ionic layer deposition) method
and observed good gas response for ozone and H2 [29] Due to the high
gravimetric lithium storage capacity of SnO2 and its low potential for
lithium ion intercalation it is regarded as one of the most promising
candidate for anode materials in Li-ion batteries [30] In addition SnO2 is
chemically inert very hard and can resist high temperatures during
heating
To continue to exploit the possible applications of SnO2 it is
essential to control its size and morphology to achieve tailored properties
Recently these useful properties have stimulated the search for new
synthetic methodologies for well-controlled SnO2 nanostructures Several
reports on high-temperature physical SnO2 synthesis have been published
[31 32] Chemical methods for the preparation of thin films studied
extensively because such processes facilitate the designing of materials on
molecular level Murakami et al used spray pyrolysis method for
deposition of SnO2 thin films using organotin compounds which led the (1
1 0) and (2 0 0) orientated films on glass substrate [33] Deshpande et al
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
10
used M-SILAR (modified successive ionic layer adsorption and reaction)
method for deposition of nanocrystalline SnO2 thin films at room
temperature the films have agglomerated structure [34] Her et al used a
hydrothermal process for large-scale production of SnO2 nanoblades on
glass substrate in a controlled aqueous solution at temperatures below
373 K [35]
Compared with high-temperature physical synthetic methods the
chemical methods appear to be of particular interest for deposition of SnO2
thin films because they offer the potential of facile scale-up and can occur
at moderate temperatures
122 Literature Survey on RuO2 Thin Films
Ruthenium (Ru) is a polyvalent hard white metal is a member of the
platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are
known though oxidation states of +2 +3 and +4 are more common Fig
13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom
is coordinated with six oxygen (O) atoms
Fig 13 Crystal structure of rutile RuO2 [36]
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
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24
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[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
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[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
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[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
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104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
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[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
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[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
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26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
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27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
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28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
8
12 Literature Survey on Tin Oxide (SnO2) and Ruthenium Oxide
(RuO2) Thin Films
121 Literature Survey on SnO2 Thin Films
SnO2 is n type wide band gap semiconductor material that
crystallizes in rutile structure The basic building blocks of the rutile
structure (Fig 12) are a tin (Sn) atom surrounded by six oxygen (O) atoms
placed approximately the corners of a regular octahedron The lattice
parameters are a=b=4737 Aring and c=3186 Aring [19 20]
Fig 12 Crystal structure of rutile SnO2 [21]
There are two main oxides of tin stannic oxide (SnO2) and stannous
oxide (SnO) The existence of these two oxides reflects the dual valency of
tin with oxidation states of +2 and +4 SnO2 possesses the rutile structure
and SnO has the less common litharge structure [22] The optical bandgap
of SnO is not exactly known but it lies somewhere in the range of 25ndash3 eV
which is less than the optical bandgap of SnO2 which is commonly quoted
to be 36 eV [23] Thus SnO exhibits a smaller band gap than SnO2 In its
stoichiometric form SnO2 acts as an insulator but in its oxygen-deficient
form SnO2 behaves as an n-type semiconductor
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
9
Due to wide bandgap SnO2 has been used extensively as a
transparent antireflection coating in optoelectronic devices such as flat
panel displays and thin film solar energy cells [24] More interestingly the
conductivity of the SnO2 semiconductor is modulated by the chemisorbed
species on its surface For example the absorbed oxygen receiving
electrons from the conduction band produces an electron depletion layer
under the absorbing surface and a potential barrier between particles and
thus decreases the conductivity of the SnO2 [25 27] This makes SnO2 a
good candidate for gas sensors whose conductivity will increase sharply
when exposed to a reducing gas SnO2 has been actively explored as the
functional component in detecting combustible gases such as CO H2 and
CH4 [28] Korotcenkov et al studied the gas response of nanosize SnO2
thin films deposited by SILD (successive ionic layer deposition) method
and observed good gas response for ozone and H2 [29] Due to the high
gravimetric lithium storage capacity of SnO2 and its low potential for
lithium ion intercalation it is regarded as one of the most promising
candidate for anode materials in Li-ion batteries [30] In addition SnO2 is
chemically inert very hard and can resist high temperatures during
heating
To continue to exploit the possible applications of SnO2 it is
essential to control its size and morphology to achieve tailored properties
Recently these useful properties have stimulated the search for new
synthetic methodologies for well-controlled SnO2 nanostructures Several
reports on high-temperature physical SnO2 synthesis have been published
[31 32] Chemical methods for the preparation of thin films studied
extensively because such processes facilitate the designing of materials on
molecular level Murakami et al used spray pyrolysis method for
deposition of SnO2 thin films using organotin compounds which led the (1
1 0) and (2 0 0) orientated films on glass substrate [33] Deshpande et al
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
10
used M-SILAR (modified successive ionic layer adsorption and reaction)
method for deposition of nanocrystalline SnO2 thin films at room
temperature the films have agglomerated structure [34] Her et al used a
hydrothermal process for large-scale production of SnO2 nanoblades on
glass substrate in a controlled aqueous solution at temperatures below
373 K [35]
Compared with high-temperature physical synthetic methods the
chemical methods appear to be of particular interest for deposition of SnO2
thin films because they offer the potential of facile scale-up and can occur
at moderate temperatures
122 Literature Survey on RuO2 Thin Films
Ruthenium (Ru) is a polyvalent hard white metal is a member of the
platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are
known though oxidation states of +2 +3 and +4 are more common Fig
13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom
is coordinated with six oxygen (O) atoms
Fig 13 Crystal structure of rutile RuO2 [36]
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
9
Due to wide bandgap SnO2 has been used extensively as a
transparent antireflection coating in optoelectronic devices such as flat
panel displays and thin film solar energy cells [24] More interestingly the
conductivity of the SnO2 semiconductor is modulated by the chemisorbed
species on its surface For example the absorbed oxygen receiving
electrons from the conduction band produces an electron depletion layer
under the absorbing surface and a potential barrier between particles and
thus decreases the conductivity of the SnO2 [25 27] This makes SnO2 a
good candidate for gas sensors whose conductivity will increase sharply
when exposed to a reducing gas SnO2 has been actively explored as the
functional component in detecting combustible gases such as CO H2 and
CH4 [28] Korotcenkov et al studied the gas response of nanosize SnO2
thin films deposited by SILD (successive ionic layer deposition) method
and observed good gas response for ozone and H2 [29] Due to the high
gravimetric lithium storage capacity of SnO2 and its low potential for
lithium ion intercalation it is regarded as one of the most promising
candidate for anode materials in Li-ion batteries [30] In addition SnO2 is
chemically inert very hard and can resist high temperatures during
heating
To continue to exploit the possible applications of SnO2 it is
essential to control its size and morphology to achieve tailored properties
Recently these useful properties have stimulated the search for new
synthetic methodologies for well-controlled SnO2 nanostructures Several
reports on high-temperature physical SnO2 synthesis have been published
[31 32] Chemical methods for the preparation of thin films studied
extensively because such processes facilitate the designing of materials on
molecular level Murakami et al used spray pyrolysis method for
deposition of SnO2 thin films using organotin compounds which led the (1
1 0) and (2 0 0) orientated films on glass substrate [33] Deshpande et al
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
10
used M-SILAR (modified successive ionic layer adsorption and reaction)
method for deposition of nanocrystalline SnO2 thin films at room
temperature the films have agglomerated structure [34] Her et al used a
hydrothermal process for large-scale production of SnO2 nanoblades on
glass substrate in a controlled aqueous solution at temperatures below
373 K [35]
Compared with high-temperature physical synthetic methods the
chemical methods appear to be of particular interest for deposition of SnO2
thin films because they offer the potential of facile scale-up and can occur
at moderate temperatures
122 Literature Survey on RuO2 Thin Films
Ruthenium (Ru) is a polyvalent hard white metal is a member of the
platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are
known though oxidation states of +2 +3 and +4 are more common Fig
13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom
is coordinated with six oxygen (O) atoms
Fig 13 Crystal structure of rutile RuO2 [36]
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
10
used M-SILAR (modified successive ionic layer adsorption and reaction)
method for deposition of nanocrystalline SnO2 thin films at room
temperature the films have agglomerated structure [34] Her et al used a
hydrothermal process for large-scale production of SnO2 nanoblades on
glass substrate in a controlled aqueous solution at temperatures below
373 K [35]
Compared with high-temperature physical synthetic methods the
chemical methods appear to be of particular interest for deposition of SnO2
thin films because they offer the potential of facile scale-up and can occur
at moderate temperatures
122 Literature Survey on RuO2 Thin Films
Ruthenium (Ru) is a polyvalent hard white metal is a member of the
platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are
known though oxidation states of +2 +3 and +4 are more common Fig
13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom
is coordinated with six oxygen (O) atoms
Fig 13 Crystal structure of rutile RuO2 [36]
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
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[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
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27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
11
The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the
stable oxide of Ru at room temperature and in a wide temperature range
RuO3 is unstable at room temperature and readily decomposes to give
RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal
stability up 1073 K it is finding numerous applications as a buffer layer or
contact electrode material for ferroelectric memory devices and high k or
ferroelectric thin film capacitors [37] In electronics this metallic oxide
plays a significant role for example as field emission (FE) cathodes for
vacuum microelectronic devices and as promising candidates for
integrated circuit development [38] RuO2 have been reported as an
effective low temperature oxidative dehydrogenation (ODH) catalyst [39]
It is used as an electrode for chlorine evaluation for dimensionally stable
anodes [40] In energy storageconversion devices ruthenium hydroxide
is an essential element for removing the CO-like poisoning in the Pt Ru
anodes of the direct methanol fuel cells [41]
There are various ways including physical as well as chemical
methods used to prepare RuO2 RuO2 films can be prepared by using
physical methods like pulsed laser deposition (PLD) and sputtering The
chemical methods like dip coating sol-gel SILAR spray pyrolysis were
reported for the preparation of RuO2 thin film The RuO2 films are also
synthesized using electrochemical methods The commonly used
precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the
present work is based on chemical methods the literature survey for
deposition of RuO2 is concentrated on chemical methods only Patake and
Lokhande used single step chemical method for deposition amorphous and
porous RuO2 thin films with optical band gap of 22 eV [42] A spray
pyrolysis method used by Gujar et al [43] for deposition of amorphous
RuO2 thin films with network like morphology at 573 K substrate
temperature the films showed an optical band gap of 24 eV RuO2 thin
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
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26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
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[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
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[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
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[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
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27
Electrochem Sol State Lett 3 (2000) 113
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Electrochim Acta 48 (2003) 3805
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7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
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Phys Chem C 112 (2008) 14843
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[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
12
films was prepared by pyrolysis process in a nitrate melt at 573 K and
used as anode catalyst for water electrolysis the impedance results in
oxygen evolution region showed the electrocatalytic activity of RuO2 [44]
RuO2 nanocrystalline films were obtained by dip coating from alcoholic
solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al
electrosynthesized RuO2 films on different substrates via hydrolysis by an
electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al
used the anodic deposition method for deposition of hydrous RuO2 from
RuCl3xH2O in aqueous media withwithout adding acetate ions as the
complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)
deposition of RuO2 from aqueous RuCl3 solutions was investigated using
stationary and rotating disk electrodes (RDE) by Jow et al [49]
13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based
Supercapacitor Electrodes
131 Literature Survey on SnO2 based Supercapacitor Electrodes
In recent years SnO2 is considered as promising electrode material
for supercapacitors due its low cost high chemical stability and
environmental friendly nature Sb doped SnO2 powder was prepared by
Wu using sol gel process showed a maximum specific capacitance of 105
Fg-1 for electrode annealed above 900 K [50] Prasad and Miura
potendynamically deposited SnO2 thin films which showed a specific
capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and
hydrophilic SnO2 thin films at room temperature using an electrochemical
method a mixed phase of SnO2 was observed with maximum specific
capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous
tin oxide (SnOx) on graphite substrate a maximum specific capacitance of
298 Fg-1 was observed [53]
SnO2 is also used as second component material in composite
electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
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[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
13
composite electrodes by sol-gel method which showed a specific
capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed
oxide by using single step hydrothermal process with specific capacitance
of 119 Fg-1 [55] Hu studied the supercapacitive performance of
nanostructured SnO2Polyaniline composite which showed a specific
capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by
hydrothermal method showed a specific capacitance of 121 Fg-1 [57]
132 Literature Survey on RuO2 based Supercapacitor Electrodes
Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a
good electrode material for supercapacitors In 1971 Trasatti et al studied
the electrochemical behavior of RuO2-based dimensionally stable anodes
(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2
crystals show capacitive-like i-E responses [58] Furthermore Conway et
al investigated extremely high redox reversibility of RuO2 from the studies
of hydrous hyper-extended RuO2 thin film on Ru metal [59]
A sol-gel method was used by Zheng et al to prepare RuO2
electrode a specific capacitance of 720 Fg-1 was observed for electrode
heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath
deposition route at room temperature to synthesize amorphous RuO2 thin
films of spherical nanoregime grains which showed a specific capacitance
of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition
method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin
film an average specific capacitance of 650 Fg-1 with good high rate
capability was observed [62] RuO2xH2O was prepared by electrophoretic
deposition and heat-treated at 523 K a network of nanoparticles (10 nm)
was developed with porous structure showed a specific capacitance of
734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated
by cathodic electrodeposition on titanium substrates showed a specific
capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
14
done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake
and Lokhande used M-CBD method for deposition amorphous and porous
RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]
obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by
spray pyrolysis method Park et al studied the effect of film thickness on
supercapacitive performance of RuO2 thin films deposited by cathodic
electrodeposition a maximum specific capacitance of 788 Fg-1 was
observed [65] RuO2 films were grown on metal substrates at
temperatures from 373 to 573 K using ruthenium ethoxide solution as the
precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of
RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and
Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted
a two-phase thermal route for synthesis of RuO2 nanoparticles which
showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of
anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared
via chemical vapor deposition (CVD) followed by electrochemical
deposition the electrodes were thermally reduced which showed a
specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was
synthesized by a simple non-ionic surfactant templating method using
Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]
Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the
effect of annealing temperature on the specific capacitance was studied
which showed the specific capacitance increased from 738 to 982 Fg-1
with increase in annealing temperature upto 423 K above which decrease
in specific capacitance was observed which is attributed to the
improvement in electronic pathways in high temperature treated samples
[71] Liang et al used a solid-state route for preparation of nanoscale
hydrous RuO2 that showed amorphous nature at lower temperature with
maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
15
electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)
material which showed the specific capacitance of 391 Fg-1 with an energy
density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al
[74] studied the charge storage mechanism of nanostructured anhydrous
and hydrous RuO2 based oxides evaluated by various electrochemical
techniques (cyclic voltammetry hydrodynamic voltammetry
chronoamperometry and electrochemical impedance spectroscopy) The
effects of various factors such as particle size hydrous state and
structure on the pseudocapacitive property were characterized Hu et al
studied the effect of sodium acetate (NaCH3COO) concentration plating
temperature and oxide loading on the pseudocapacitive characteristics of
RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a
maximum specific capacitance of 760 Fg-1 was observed [75] RuO2
nanoparticles were synthesized by instant method using Li2CO3 as
stabilizing agent under microwave irradiation at 333 K which showed a
specific capacitance of 737 Fg-1 [76]
RuO2 based materials have the advantage of offering higher energy
density but the cost and relative scarcity of Ru precursors are major
disadvantage Considerable efforts have been devoted to the development
and characterization of new electrode materials with lower cost and
improved performance The research is going on combining RuO2 with
second electrode material in order to increase the dispersion of the oxide
RuO2 was electrochemically prepared onto a carbon nanotube
(CNT) film substrate with a three-dimensional nanoporous structure
showed both a very high specific capacitance of 1170 Fg-1 and a high rate
capability [77] RuO2 was loaded into various types of activated carbon by
suspending the activated carbon in an aqueous RuCl3 solution followed by
neutralization a maximum specific capacitance of 308 Fg-1 for activated
carbon loaded with 71 wt Ru was observed [78] A hydrous
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
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[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
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[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
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1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
16
RuO2carbon black nanocomposite was prepared by the incipient wetness
method using a fumed silica nanoparticles the electrode exhibited a
specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic
et al prepared RuOxHycarbon black nanocomposite material by the
impregnation method starting from RuOxHy sol as a precursor The
highest specific capacitance of about 700 Fg-1 of composite was registered
[79] Liu et al has been reported a new method for preparation of
RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and
Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes
(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]
RuO2carbon composites with microporous or mesoporous carbon as
support were and prepared by two procedures which consists i) repetitive
impregnations of the carbons with RuCl3middot05H2O solutions and ii)
impregnation of the carbons with Ru vapor It was observed that
mesoporous carbon is better support than microporous carbon prepared
using method (i) with maximum specific capacitance of 650 Fg-1 [81]
Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading
various amounts of RuO2 on TiO2 nanotubes The symmetric
supercapacitors based on these nanocomposites were fabricated by using
gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance
of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline
binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by
Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs
at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu
et al used a co-precipitation method for the synthesis of mesoporous
Co3O4RuO2middotxH2O composite with various Ru content by using
Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for
the composite (Co Ru = 11) annealed at 423 K which is greater than for
the composite prepared without template [84] Pico et al prepared
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
References
[1] A Burke J Power Sources 91 (2000) 37
[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656
[3] M Winter and R J Brodd Chem Rev 104 (2004) 4245
[4] J R Miller and P Simon The Electrochem Soc Interface Spring 2008
[5] A Chu and P Braatz J Power Sources 112 (2002) 236
[6] B E Conway Electrochemical Supercapacitors Scientific Fundamentals
and Technological Applications Kluwer-Plenum New York 1999
[7] R Kotz and M Carlen Electrochim Acta 45 (2002) 2483
[8] httpdeptswashingtonedu
[9] M Anderman J Power Sources 127 (2004) 2
[10] Z Y Pan X J Liu S Y Zhang G J Shen L G Zhang Z H Lu J Z Liu J Phys
Chem B 101 (1997) 9703
[11] Y Wu H Yan P Yang Chem Eur J 8 (2002) 1260
[12] J Hu T W Odom C M Lieber Acc Chem Res 32 (1999) 435
[13] P C Ohara J R Heath W M Gelbart Angew Chem Int Ed Engl 36 (1997)
1078
[14] Y Q Zhu W K Hsu H W Kroto D R M Walton Chem Commun 21 (2001)
2184
[15] J Hu M Ouyang P Yang C M Lieber Nature 399 (1999) 48
[16] X Duan Y Huang Y Cui J Wang C M Lieber Nature 409 (2001) 66
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
23
[17] J F Colomer G Bister I Willems Z Konya A Fonseca G Van Tendeloo J B
Nagy Chem Commun 14 (1999) 1343
[18] C N R Rao Pure Appl Chem 69 (1997) 199
[19] Z Jarzebski and J Marton J Electrochem Soc Rev and News 123 (1976)
199C
[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551
[21] httpWikipediacomtin(IV) oxide
[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
(2001) 195
[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
Sci 25 (2002) 231
[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
17
RuO2middotxH2ONiO composites by a coprecipitation method it was observed
that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2
content increased from 0 to 100 wt [85] An ultra thin layer of RuO2
produced by magnetron sputtering deposition method was grown on the
well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The
modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)
which is higher than that of WACNP by three times [86] Hydrous RuO2
particles were electrochemically loaded into poly (3 4-
ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS
matrix by employing various potential cycles in cyclic voltammetry and to
fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in
specific capacitance with loaded amount of hydrous RuO2 particles in
PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was
achieved [87]
133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes
As RuO2 is the most promising electrode material for
supercapacitors more research is now focused on the developing methods
in order to achieve highest utilization of RuO2 It was observed that the
high specific capacitance of hydrous RuO2 could not be maintained under
the ultrahigh-power operation which is an unavoidable issue in
developing an electrode material for supercapacitors Due to the high cost
of Ru precursors and the possible synergistic effects occurring among
RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and
ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed
and studied
Among the various oxides studied as co material for RuO2 SnO2
with proper doping has advantage of high conductivity [92 93] SnO2 and
RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice
parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
References
[1] A Burke J Power Sources 91 (2000) 37
[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656
[3] M Winter and R J Brodd Chem Rev 104 (2004) 4245
[4] J R Miller and P Simon The Electrochem Soc Interface Spring 2008
[5] A Chu and P Braatz J Power Sources 112 (2002) 236
[6] B E Conway Electrochemical Supercapacitors Scientific Fundamentals
and Technological Applications Kluwer-Plenum New York 1999
[7] R Kotz and M Carlen Electrochim Acta 45 (2002) 2483
[8] httpdeptswashingtonedu
[9] M Anderman J Power Sources 127 (2004) 2
[10] Z Y Pan X J Liu S Y Zhang G J Shen L G Zhang Z H Lu J Z Liu J Phys
Chem B 101 (1997) 9703
[11] Y Wu H Yan P Yang Chem Eur J 8 (2002) 1260
[12] J Hu T W Odom C M Lieber Acc Chem Res 32 (1999) 435
[13] P C Ohara J R Heath W M Gelbart Angew Chem Int Ed Engl 36 (1997)
1078
[14] Y Q Zhu W K Hsu H W Kroto D R M Walton Chem Commun 21 (2001)
2184
[15] J Hu M Ouyang P Yang C M Lieber Nature 399 (1999) 48
[16] X Duan Y Huang Y Cui J Wang C M Lieber Nature 409 (2001) 66
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
23
[17] J F Colomer G Bister I Willems Z Konya A Fonseca G Van Tendeloo J B
Nagy Chem Commun 14 (1999) 1343
[18] C N R Rao Pure Appl Chem 69 (1997) 199
[19] Z Jarzebski and J Marton J Electrochem Soc Rev and News 123 (1976)
199C
[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551
[21] httpWikipediacomtin(IV) oxide
[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
(2001) 195
[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
Sci 25 (2002) 231
[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
18
47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]
RuO2-SnO2 binary oxide coated titanium electrodes are one of the most
important anodes in the chlor-alkali industry because they can be easily
formed a rutile-phase that is regarded as a favorite structure The SnO2
additive stabilizes RuO2 based electrodes and enhances their catalytic
activity for oxygen evolution [95-97] and chlorine evolution [98 99]
Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-
gel method using citric acid as complexing agent Pure fine and
amorphous powders were obtained at 433 K the crystalline and single-
phase powders of (Sn Ru)O2 were produced at 673 K the material
obtained has good thermal resistant properties It benefits for the
preparation for the active oxide coatings [100]
In the application as supercapacitor electrode Hu et al [101] used
modified sol-gel process for deposition of rutheniumndashtin oxide composites
It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h
showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn
content of 02 Kim et al used a DC reactive sputtering method for
preparation of composite RuO2-SnO2 electrode a maximum specific
capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild
hydrothermal process to synthesize hydrous ruthenium oxide tin oxide
composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1
was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient
wetness method was used for preparation of Sb doped SnO2 xerogel
impregnated with RuO2 nanocrystallites by Wu et al [104] a specific
capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild
hydrothermal process is applied by Yuan et al to synthesize hydrous
rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric
supercapacitor can operate with a high upper cell voltage limit of 145 V in
1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
References
[1] A Burke J Power Sources 91 (2000) 37
[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656
[3] M Winter and R J Brodd Chem Rev 104 (2004) 4245
[4] J R Miller and P Simon The Electrochem Soc Interface Spring 2008
[5] A Chu and P Braatz J Power Sources 112 (2002) 236
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[9] M Anderman J Power Sources 127 (2004) 2
[10] Z Y Pan X J Liu S Y Zhang G J Shen L G Zhang Z H Lu J Z Liu J Phys
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2184
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[16] X Duan Y Huang Y Cui J Wang C M Lieber Nature 409 (2001) 66
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Nagy Chem Commun 14 (1999) 1343
[18] C N R Rao Pure Appl Chem 69 (1997) 199
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[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
(2001) 195
[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
Sci 25 (2002) 231
[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
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[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
19
stability with 852 of the initial capacitance over consecutive 1000 cycle
numbers [105] A composite SnO2-RuO2 supercapacitor electrode was
synthesized by cyclic voltammetric plating of RuO2 onto a porous and
highly conductive Sb (6 mol) doped SnO2 particulate substrate that
possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1
for the RuO2 component was observed [106]
31 Orientation and Purpose of Dissertation
Supercapacitors have the potential to emerge as promising energy
storage technology with an acceptable capacity and long cycle life The
performance of the supercapacitor is highly dependent on the active
electrode material involved in its fabrication that must have
characteristics such as high surface area as well as highly reversible redox
reaction The main electrode materials for supercapacitors are porous
activated carbon (AC) transition metal oxides conducting polymers
mixed metal oxides or their composites Moreover a relatively high-
frequency response is an essential requirement for supercapacitor
delivering pulse power which should be achieved by reducing the
equivalent series resistance (ESR) Accordingly developing and designing
active materials as well as electrodes meeting the above requirements
becomes an interesting subject for many electrochemists In addition it is
possible to obtain high working voltage and high energy density of
supercapacitors by choosing a proper electrode material Both increase of
the working voltage and high energy density of the metal oxide electrode
result in a significant increase of the overall energy density of the
supercapacitors
Although amorphous hydrous RuO2 is the most promising electrode
material for supercapacitors high cost and scarcity of Ru precursors made
researchers to find possible alternatives for RuO2 electrodes for
commercial applications Another approach developed is to combine RuO2
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
References
[1] A Burke J Power Sources 91 (2000) 37
[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656
[3] M Winter and R J Brodd Chem Rev 104 (2004) 4245
[4] J R Miller and P Simon The Electrochem Soc Interface Spring 2008
[5] A Chu and P Braatz J Power Sources 112 (2002) 236
[6] B E Conway Electrochemical Supercapacitors Scientific Fundamentals
and Technological Applications Kluwer-Plenum New York 1999
[7] R Kotz and M Carlen Electrochim Acta 45 (2002) 2483
[8] httpdeptswashingtonedu
[9] M Anderman J Power Sources 127 (2004) 2
[10] Z Y Pan X J Liu S Y Zhang G J Shen L G Zhang Z H Lu J Z Liu J Phys
Chem B 101 (1997) 9703
[11] Y Wu H Yan P Yang Chem Eur J 8 (2002) 1260
[12] J Hu T W Odom C M Lieber Acc Chem Res 32 (1999) 435
[13] P C Ohara J R Heath W M Gelbart Angew Chem Int Ed Engl 36 (1997)
1078
[14] Y Q Zhu W K Hsu H W Kroto D R M Walton Chem Commun 21 (2001)
2184
[15] J Hu M Ouyang P Yang C M Lieber Nature 399 (1999) 48
[16] X Duan Y Huang Y Cui J Wang C M Lieber Nature 409 (2001) 66
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
23
[17] J F Colomer G Bister I Willems Z Konya A Fonseca G Van Tendeloo J B
Nagy Chem Commun 14 (1999) 1343
[18] C N R Rao Pure Appl Chem 69 (1997) 199
[19] Z Jarzebski and J Marton J Electrochem Soc Rev and News 123 (1976)
199C
[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551
[21] httpWikipediacomtin(IV) oxide
[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
(2001) 195
[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
Sci 25 (2002) 231
[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
20
with second electrode material to form composite electrode and thus to
minimize the uses of Ru precursors The SnO2 is selected as second
electrode material in order to form the tin oxide-ruthenium oxide (SnO2-
RuO2) composite This is because SnO2 has the same rutile structure as
RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases
the effective surface area and electrochemical stability of net composite
electrode The addition of SnO2 into RuO2 increases the utilization
efficiency of RuO2 All these properties of SnO2 are favorable for formation
of composite electrode with good supercapacitive properties by using
fewer amounts of Ru precursors This will also reduce the cost so it is
useful for the commercial application Recently there has been an increase
interest in nanocrystalline materials where the physical properties are
different from the bulk materials There are two approaches for making
nanocrystalline materials physical methods and chemical methods As
considering the drawbacks of physical methods like expensive need of
sophisticated instrumentation etc chemical methods are more useful as
they are simple and inexpensive
This work is concerned with the development of supercapacitor
electrodes of SnO2-RuO2 composite thin films by simple chemical methods
Among various other deposition methods CBD and SILAR methods have
many advantages over physical method These deposition methods result
in pinhole free uniform films Since the basic building blocks are ions
instead of atoms also the preparative parameters are easily controllable
These methods can be used for the large area deposition
It is possible to deposit SnO2-RuO2 composite thin films by varying
different preparative parameters such as suitable metal ion sources pH
deposition time temperature etc The X-ray diffraction (XRD) technique
will be used for the phase identification and crystallite size determination
The chemical bonding in the present material will be studied by fourier
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
References
[1] A Burke J Power Sources 91 (2000) 37
[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656
[3] M Winter and R J Brodd Chem Rev 104 (2004) 4245
[4] J R Miller and P Simon The Electrochem Soc Interface Spring 2008
[5] A Chu and P Braatz J Power Sources 112 (2002) 236
[6] B E Conway Electrochemical Supercapacitors Scientific Fundamentals
and Technological Applications Kluwer-Plenum New York 1999
[7] R Kotz and M Carlen Electrochim Acta 45 (2002) 2483
[8] httpdeptswashingtonedu
[9] M Anderman J Power Sources 127 (2004) 2
[10] Z Y Pan X J Liu S Y Zhang G J Shen L G Zhang Z H Lu J Z Liu J Phys
Chem B 101 (1997) 9703
[11] Y Wu H Yan P Yang Chem Eur J 8 (2002) 1260
[12] J Hu T W Odom C M Lieber Acc Chem Res 32 (1999) 435
[13] P C Ohara J R Heath W M Gelbart Angew Chem Int Ed Engl 36 (1997)
1078
[14] Y Q Zhu W K Hsu H W Kroto D R M Walton Chem Commun 21 (2001)
2184
[15] J Hu M Ouyang P Yang C M Lieber Nature 399 (1999) 48
[16] X Duan Y Huang Y Cui J Wang C M Lieber Nature 409 (2001) 66
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
23
[17] J F Colomer G Bister I Willems Z Konya A Fonseca G Van Tendeloo J B
Nagy Chem Commun 14 (1999) 1343
[18] C N R Rao Pure Appl Chem 69 (1997) 199
[19] Z Jarzebski and J Marton J Electrochem Soc Rev and News 123 (1976)
199C
[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551
[21] httpWikipediacomtin(IV) oxide
[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
(2001) 195
[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
Sci 25 (2002) 231
[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
21
transform infrared spectroscopy (FT-IR) and fourier transform Raman
spectroscopy (FT-Raman) Surface morphology of the films will be studied
using scanning electron microscopy (SEM) The compositional study will
be carried out by energy-dispersive X-ray analysis (EDAX) technique
Surface wettability of the film will be studied by measuring the water
contact angle
The supercapacitive properties of the SnO2-RuO2 composite films
will be studied by cyclic voltammetry (CV) using Potentiostat forming a
electrochemical cell comprising platinum as a counter electrode saturated
calomel electrode (SCE) as a reference electrode in a suitable electrolyte
The effect of electrolyte concentration thickness of electrode scan rate
and number of cycles on the performance of supercapacitor electrode will
be studied The charge-discharge mechanism will be studied using
chronopotentiometry and the parameters such as specific energy and
specific power will be calculated The electrochemical impedance
spectroscopic (EIS) study will be carried out to measure ESR of the formed
material Further the effect of surface treatments such as air annealing
ultrasonic weltering and anodization on the supercapacitive properties of
SnO2-RuO2 composite films will be studied
The present study will be performed to prepare SnO2-RuO2
composite films by minimal uses of Ru precursors The simple and
inexpensive SILAR and CBD methods will be used for fabrication SnO2-
RuO2 composite film The supercapacitive behavior of composite films will
be studied for supercapacitor application
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
References
[1] A Burke J Power Sources 91 (2000) 37
[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656
[3] M Winter and R J Brodd Chem Rev 104 (2004) 4245
[4] J R Miller and P Simon The Electrochem Soc Interface Spring 2008
[5] A Chu and P Braatz J Power Sources 112 (2002) 236
[6] B E Conway Electrochemical Supercapacitors Scientific Fundamentals
and Technological Applications Kluwer-Plenum New York 1999
[7] R Kotz and M Carlen Electrochim Acta 45 (2002) 2483
[8] httpdeptswashingtonedu
[9] M Anderman J Power Sources 127 (2004) 2
[10] Z Y Pan X J Liu S Y Zhang G J Shen L G Zhang Z H Lu J Z Liu J Phys
Chem B 101 (1997) 9703
[11] Y Wu H Yan P Yang Chem Eur J 8 (2002) 1260
[12] J Hu T W Odom C M Lieber Acc Chem Res 32 (1999) 435
[13] P C Ohara J R Heath W M Gelbart Angew Chem Int Ed Engl 36 (1997)
1078
[14] Y Q Zhu W K Hsu H W Kroto D R M Walton Chem Commun 21 (2001)
2184
[15] J Hu M Ouyang P Yang C M Lieber Nature 399 (1999) 48
[16] X Duan Y Huang Y Cui J Wang C M Lieber Nature 409 (2001) 66
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
23
[17] J F Colomer G Bister I Willems Z Konya A Fonseca G Van Tendeloo J B
Nagy Chem Commun 14 (1999) 1343
[18] C N R Rao Pure Appl Chem 69 (1997) 199
[19] Z Jarzebski and J Marton J Electrochem Soc Rev and News 123 (1976)
199C
[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551
[21] httpWikipediacomtin(IV) oxide
[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
(2001) 195
[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
Sci 25 (2002) 231
[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
22
References
[1] A Burke J Power Sources 91 (2000) 37
[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656
[3] M Winter and R J Brodd Chem Rev 104 (2004) 4245
[4] J R Miller and P Simon The Electrochem Soc Interface Spring 2008
[5] A Chu and P Braatz J Power Sources 112 (2002) 236
[6] B E Conway Electrochemical Supercapacitors Scientific Fundamentals
and Technological Applications Kluwer-Plenum New York 1999
[7] R Kotz and M Carlen Electrochim Acta 45 (2002) 2483
[8] httpdeptswashingtonedu
[9] M Anderman J Power Sources 127 (2004) 2
[10] Z Y Pan X J Liu S Y Zhang G J Shen L G Zhang Z H Lu J Z Liu J Phys
Chem B 101 (1997) 9703
[11] Y Wu H Yan P Yang Chem Eur J 8 (2002) 1260
[12] J Hu T W Odom C M Lieber Acc Chem Res 32 (1999) 435
[13] P C Ohara J R Heath W M Gelbart Angew Chem Int Ed Engl 36 (1997)
1078
[14] Y Q Zhu W K Hsu H W Kroto D R M Walton Chem Commun 21 (2001)
2184
[15] J Hu M Ouyang P Yang C M Lieber Nature 399 (1999) 48
[16] X Duan Y Huang Y Cui J Wang C M Lieber Nature 409 (2001) 66
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
23
[17] J F Colomer G Bister I Willems Z Konya A Fonseca G Van Tendeloo J B
Nagy Chem Commun 14 (1999) 1343
[18] C N R Rao Pure Appl Chem 69 (1997) 199
[19] Z Jarzebski and J Marton J Electrochem Soc Rev and News 123 (1976)
199C
[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551
[21] httpWikipediacomtin(IV) oxide
[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
(2001) 195
[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
Sci 25 (2002) 231
[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
23
[17] J F Colomer G Bister I Willems Z Konya A Fonseca G Van Tendeloo J B
Nagy Chem Commun 14 (1999) 1343
[18] C N R Rao Pure Appl Chem 69 (1997) 199
[19] Z Jarzebski and J Marton J Electrochem Soc Rev and News 123 (1976)
199C
[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551
[21] httpWikipediacomtin(IV) oxide
[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47
[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465
[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67
(2001) 195
[25] S Seal and S Shukla J Met 54 (2002) 35
[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater
Sci 25 (2002) 231
[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789
[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)
186
[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia
Sens Actuators B 96 (2003) 602
[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645
[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
24
[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493
[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557
[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587
[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115
[36] httpWikipediacomruthenium (IV) oxide
[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)
2987
[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)
3860
[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155
[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B
104 (2000) 9772
[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774
[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820
[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo
Electrochem Commun 9 (2007) 504
[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7
[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364
[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155
[47] I Zhitomirsky Mat Lett 33 (1998) 305
[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
25
[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52
(2007) 2625
[50] N L Wu Mater Chem Phys 75 (2002) 6
[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849
[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han
Curr Appl Phys 9 (2009) 87
[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)
669
[54] S Hwang and S Hyun J Power Sources 172 (2007) 451
[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources
158 (2006) 1538
[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114
(2009) 990
[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166
(2007) 578
[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1
[59] B E Conway J Electrochem Soc 125 (1978) 1471
[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699
[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han
Electrochem Sol State Lett 10 (2007) A225
[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62
[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
26
[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381
[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources
134 (2004) 148
[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148
(2001) A833
[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958
[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219
[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C
111 (2007) 9530
[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175
(2004) 511
[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)
A2049
[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599
[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335
[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52
(2006) 1742
[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679
[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted
Manuscript doi101016jjpowsour201011149
[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369
[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
27
Electrochem Sol State Lett 3 (2000) 113
[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic
Electrochim Acta 48 (2003) 3805
[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)
7141
[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M
Amarilla J M Rojo Electrochim Acta 54 (2009) 2239
[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957
[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749
[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296
[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J
M Rojo Electrochim Acta 51 (2006) 4693
[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J
Phys Chem C 112 (2008) 14843
[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)
1058
[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB
Elsevier Amsterdam 1980 eg
[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265
[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158
[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858
[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136
[93] T Minami Mater Res Soc Bull 25 (2000) 38
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85
CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY
28
[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95
[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J
Electerochem Soc 143 (1996) 32
[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570
[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987
[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239
[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386
[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626
[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691
[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid
Films 475 (2005) 54
[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573
[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62
[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)
1645
[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85