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Chinese Materials Research Society
Progress in Natural Science: Materials International
Progress in Natural Science: Materials International 2012;22(6):616–623
1002-0071 & 2012 Ch
http://dx.doi.org/10.1
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fax: þ91 44 2257 420
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www.elsevier.com/locate/pnsmiwww.sciencedirect.com
ORIGINAL RESEARCH
Platinum-supported mesoporous carbon (Pt/CMK-3) as
anodic catalyst for direct methanol fuel cell applications:
The effect of preparation and deposition methods
Balaiah Kuppan, Parasuraman Selvamn
National Centre for Catalysis Research and Department of Chemistry, Indian Institute of Technology-Madras, Chennai 600 036, India
Received 31 August 2012; accepted 7 October 2012
Dedicated to Professor M.M. Sharma, FRS on the occasion of his 75th birthday.
Available online 9 January 2013
KEYWORDS
Mesoporous carbon;
CMK-3;
Nano-platinum;
Electrocatalyst;
Methanol oxidation;
Fuel cell
inese Materials R
016/j.pnsc.2012.11
thor. Tel.: þ91 44
2.
r responsibility of
Abstract Platinum-supported ordered mesoporous carbon catalysts were prepared employing
colloidal platinum reduced by four different reducing agents, viz., paraformaldehyde, sodium
borohydride, ethylene glycol and hydrogen, and deposited over ordered mesoporous carbon
(CMK-3) synthesized by silica hard template (SBA-15). The resulting platinum nanoparticles
supported mesoporous carbon, designated as Pt/CMK-3, catalysts were tested for the electocata-
lytic oxidation of methanol. The effect of the various reduction methods on the influence of particle
size vis-�a-vis on the electrocatalytic effect is investigated. All the catalysts were systematically
characterized by XRD, BET and TEM. The results of the synthetic methods, characterization
techniques and the electrocatalytic performance indicate that the Pt/CMK-3 catalysts are superior
to that prepared with activated carbon (Pt/AC) as well as with that of the commercial platinum-
supported carbon catalyst (Pt/E-TEK). In particular, the catalyst, Pt/CMK-3, prepared using
paraformaldehyde reduced platinum showed much higher activity and long-term stability as
compared to the other reducing methods.
& 2012 Chinese Materials Research Society. Production and hosting by Elsevier Ltd. All rights reserved.
esearch Society. Production and ho
.005
2257 4235;
(P. Selvam).
Chinese Materials Research
1. Introduction
Generally, for fuel cell electrode applications, platinum sup-
ported on high surface area carbon is employed [1–3]. The
choice of supports is based on the possibility of high disper-
sion stable metal crystallites with favorable electronic and
geometric properties as well as the interaction of the active
metal and the supports [4,5]. Designing porous carbon
materials as support for electrode application is important
sting by Elsevier Ltd. All rights reserved.
Platinum-supported mesoporous carbon (Pt/CMK-3) as anodic catalyst for direct methanol fuel cell applications 617
for high performance of fuel cell and/or battery technology.
Therefore, careful choice of porous carbon supported catalysts
for facile transport of reactants and products, good electronic
conductivity, high surface reactivity, and ionic conductivity,
would enhance the molecular conversion [6–10]. In this regard,
ordered (meso) porous carbon architecture with high surface
area with tailor-made surface properties, large pore volume
with tunable pore size, and narrow pore size distribution with
interconnected pore network is highly desirable in many
electrochemical applications including fuel cells, lithium ion
batteries, etc. On the other hand, mesostructured carbon
materials synthesized by nanocasting method, viz., manipula-
tion of ordered mesoporous silica templates, are of great
technological interest in many applications encompassing
catalysis and materials science [11–13].
One of the most successful examples of such exploitation is
the synthesis of ordered mesoporous (or nanoporous) carbons
using ordered silica frameworks such as MCM-41, MCM-48,
SBA-51, KIT-6, IITM-56, etc. as templates [14–17]. This
approach is based on a multi-step process via polymerization/
carbonization of carbon precursors diffused within inorganic
matrix followed by removal of the inorganic framework by
leaching so as to replicate the mesoporous structure of the
inorganic templates, viz., silica [2–4]. In this way, several
mesoporous carbons with a variety of porous structures have
been prepared employing sucrose, furfuryl alcohol, etc. as
carbon precursors over ordered silica templates [18–21].
In recent years, mesoporous carbon materials such as
CMK-3 is attracted much attention, which is obtained by
replicating well ordered mesoporous silica, SBA-15. The
obtained mesoporous carbons possess highly ordered 2D
hexagonal structure with excellent textural characteristics
[22–24]. Owing to such exceptional surface properties of these
structured porous carbons, they are used to deposit several
noble metals, in particular platinum and its alloys, and testes
as electrode materials for direct methanol fuel cell (DMFC)
applications [25–27]. However, for an effective and efficient
DMFC usage, a few technological barriers remain to be
overcome before successful commercial applications can be
achieved. One such difficulty is the poisoning of the active
platinum by carbon monoxide, which prevents fuel (methanol)
oxidation [28–30]. One of the possible strategies to overcome
such difficulty is alloying of platinum with oxophilic elements
such as ruthenium, palladium, gold or nickel. In this direction,
considerable effects have been focused, and there appears
to be two possible pathways to explain the improved tolerance
carbon monoxide poisoning [31–34]. Among the various
alloying components, the element ruthenium shows promise
as the platinum–ruthenium alloy follows a bifunctional
mechanistic mode where the adsorbed �OH species, gene-
rated by water dissociation, at the platinum/ruthenium edge
promote the oxidation of carbon monoxide and that ruthe-
nium modifies the electronic structure of neighboring platinum
atoms, thus reducing the affinity for carbon monoxide
species. It is remarkable that the additional element reduces
catalyst poisoning to a significant extent but its incorporation
makes the DMFC is expensive [31–34]. On the other hand,
large discrepancies in the methanol oxidation activities
between well-defined crystal surfaces and electrodes formed
by nanoparticles are not fully understood. It is possible that
non-uniform distributions of platinum atoms in nanoparticles
contribute to the differences. However, the various methods
adopted for the preparation of platinum nanoparticles fol-
lowed by reduction and deposition do not allow good control
over the size and shape, or particle distribution of individual
nanoparticles.
A major component that contributes to the high electro-
catalytic activity is the nature of the carbon material support,
which can help in dispersing the metal catalyst and in
facilitating electron transport, as well as in promoting mass
transfer kinetics at the electrode surface. The oxidation of the
carbon supports, prior to the catalyst deposition, was found to
increase the electrode activity for room temperature methanol
oxidation [35,36]. The presence of small amount surface
functional groups modifies the chemical and physical proper-
ties of the carbon, improving wettability and accessibility of
methanol to the electroactive surface. In addition, the oxygen
functional groups act as nucleation centers or anchoring sites,
limiting the particle growth, improving the dispersion of
metallic crystallites, and enhancing the stability of the sup-
ported catalysts. At present, there is a lack of understanding
on the role of oxygen groups on the CO tolerance, and this
issue has rarely been investigated. Moreover, heavily oxidized
supports have been avoided because of their low electrical
conductivity [37,38]. The present work is focused on the
reduction of platinum nanoparticles followed by deposition
on mesoporous CMK-3 carbon. The physicochemical and
electrochemical characteristics of the mesoporous carbon
supports and the corresponding platinum supported catalyst,
Pt/CMK-3 were investigated. The influence of the platinum
nanoparticles deposition method and the mesoporous carbon
material properties on the dispersion and size distribution of
platinum nanoparticles on CMK-3 mesoporous carbon has
been discussed. The Pt/CMK-3 electrode catalysts with a
uniform dispersion is comparable to platinum nanoparticles
supported on activated carbon (AC) were achieved. Further-
more, the influence of the electrode fabrication method on the
performance of the Pt/CMK-3 electrode catalyst based fuel
cell was revealed.
2. Experimental section
2.1. Starting materials
All the chemicals used were of analytical grade. Pluronic P123
triblock co-polymer, tetraethoxysilane (99.0%) (TEOS) and
hexachloro platonic acid (99.9%) (H2PtCl6) from sigma Aldrich.
Paraformaldehyde (95.0%), sodium carbonate (99.0%), sodium
borohydride (NaBH4), ethylene glycol, methanol (99.9%),
hydrofluoric acid (48.0%), hydrochloric acid (32.0%) and
sulfuric acid (98.0%) were obtained from Merck.
2.2. Synthesis of SBA-15
Mesoporous silica SBA-15 was prepared by adding tetra-
ethoxysilane (TEOS) into the hydrochloric acid solution of
triblock co-polymer P123. The molar composition was 1: 5.9:
193: 0.017 TEOS/HCl/H2O/P123. The mixture was stirred at
40 1C for 20 h, followed by aging at 100 1C for 48 h. The solid
was filtered and dried at 80 1C overnight. SBA-15 was
obtained by calcinations at 550 1C for 6 h in presence of air
atmosphere [39].
B. Kuppan, P. Selvam618
2.3. Synthesis of CMK-3
Ordered mesoporous carbon CMK-3 was synthesized by
adopting the following procedure [15], before impregnating
sucrose solution the silica template was dried in vacuum at
100 1C for 30 min. the carbon replica were prepared similar to
the procedure reported previously. Typically 1.0 g of SBA-15
mesoporous silica was impregnated with acidic sucrose solu-
tion; the mixture was dried at 100 1C for 6 h and subsequently
at 160 1C for 6 h. the impregnation step was repeated once
again. The obtained dark brown/black sample was carbonized
at 900 1C under nitrogen or argon flow for 6 h with heating
rate of 5 1C min�1. The carbon-silica composite obtained after
pyrolysis was washed with hydrofluoric (HF) acid at room
temperature, to remove the silica template. The template-free
carbon product thus obtained was filtered, washed with
ethanol, and dried at 120 1C. The obtained carbon materials
were designated as CMK-3.
2.4. Preparation of Pt/CMK-3
2.4.1. Paraformaldehyde reduction method
Platinum nanoparticles with 20 wt% loading was supported
on CMK-3 by a Paraformaldehyde reduction method [40]
typically 40 mg carbon and 0.0488 M H2PtCl6.xH2O aqueous
solution were homogenously dispersed in 30 ml water and
ultrasonicated for 30 min. The mixture was heated to 70 1C
while simultaneously string with simultaneous purging N2 to
remove soluble O2. Then 10 ml solution containing Parafor-
maldehyde and sodium carbonate was slowly added dropwise,
and the mixture was stirred for 2.5 h. finally, the sample was
filtered, washed with deionized water, and dried.
2.4.2. Sodium borohydride reduction method
Platinum nanoparticles with 20 wt% loading was supported
on CMK-3 by a wet chemical reduction method [41,42]
typically 40 mg carbon and 0.0488 M H2PtCl6.xH2O aqueous
solution were homogenously dispersed in 30 ml water and
ultrasonicated for 30 min, then this solution was stirred for
1 h. 20 ml of NaBH4 solution was added drop wise to the
carbon suspension with stirring at room temperature. Stirring
was continued for 6 h before the suspension was filtered to
recover the solid product and was washed with large amount
of water. The recovered catalyst was dried at 80 1C for
overnight.
2.4.3. Ethylene glycol reduction method
20 wt% of Pt was loaded on CMK-3 mesoporous carbon
using ethylene glycol reduction method [43,44]. 40 mg of
CMK-3 carbon was dispersed in water and required amount
of hexachloroplatinic acid was added to the above solution.
30 ml of ethylene glycol (EG) were added under vigorous
stirring. The solution was refluxed at 140 1C for 4 h. After
reaction, the obtained products were filtered, washed with
water and ethanol, and then dried.
2.4.4. Hydrogen reduction method
The dispersion of platinum electrocatalyst was carried out by
adopting a required amount of hexachloroplatinic acid to the
mesoporous carbon synthesized followed by evaporation to
dryness at 80 1C and reduction in H2 at 350 1C for 3 h [45].
2.5. Characterization
Powder X-ray diffraction (XRD) measurements were carried
out on a Rigaku Miniflex II desktop model advanced powder
X-ray diffractometer with a Cu Ka (l¼1.5405 A) radiation
source, operating at 30 kV and 15 mA. Wide and small angles
were obtained at scanning rate of 31 min�1 and 0.51 min�1,
respectively. Transition electron microscope (TEM) images
were obtained with JEOL 3010 UHR TEM equipped with a
Gatan Imaging Filter. Prior to observation, carbon sample
was sonicated in absolute ethanol for 10 min and then
dropped on to a carbon film supported on a copper grid.
Nitrogen adsorption-desorption isotherms were obtained at
77 K on a Micrometrics ASAP 2020 apparatus. The specific
surface area of the samples were calculated according to the
Brunaur–Emmet–Teller (BET) method, and pore size distribu-
tion curves were obtained from the analysis of nitrogen
adsorption isotherms using Barrett–Joyner–Halenda (BJH)
method. Hydrogen chemisorption measurements for the sup-
ported catalysts were performed on a Micrometrics ASAP
2020 system.
2.6. Electrochemical studies
The performance of Pt supported on CMK-3 mesoporous
carbons, activated carbon and E-TEK commercial catalyst for
room temperature electro oxidation reaction was evaluated by
cyclic voltammetry (CV) using a BAS 100 electrochemical
analyzer. A conventional three-electrode cell consisting of the
glassy carbon (GC, 0.07 cm2) working electrode, Pt wire as
counter electrode and SCE reference electrode were used for
the cyclic voltammetry studies. The catalyst ink was prepared
by ultrasonically dispersing 5.0 mg catalyst in 0.50 ml water
and the working electrode was prepared by casting 10 ml into a
GC disk electrode with 3.0 mm diameter. The CV experiments
were performed using 1 M H2SO4 solution in the absence and
presence of 1 M CH3OH at a scan rate of 25 mV s�1. All the
solutions were prepared by using double distilled pure water.
3. Results and discussion
Fig. 1 depicts the low-angle XRD patterns of ordered
mesoporous silica (SBA-15), carbon (CMK-3) and platinum
supported carbon (Pt/CMK-3). It can be seen from this figure
that all the materials show well resolved reflections character-
istic of 2D- hexagonal lattice having MCM-41-type structure.
In particular, the diffraction pattern of CMK-3 indicates that
the mesoporous carbon is replicated the parent structure of
SBA-15 with a reduce unit cell constant (Table 1). Fig. 2
shows the wide-angle XRD patterns of platinum nanoparticles
supported mesoporous carbon by different deposition meth-
ods. The diffraction patterns represent all the reflections
corresponding to face centered cubic lattice of platinum
supported on mesoporous carbon. The computed values the
crystallite size of the platinum nanoparticles are listed in
Table 2. It is clear from Fig. 1 and Table 2 that the
paraformaldehyde reduction method gives raise to relatively
smaller particle size while the hydrogen reduction method
yield much larger particle platinum particles which is in good
agreement with the literature [46,47]. Figs. 3 and 4 illustrate
the nitrogen-sorption isotherms of SBA-15 and CMK-3,
Platinum-supported mesoporous carbon (Pt/CMK-3) as anodic catalyst for direct methanol fuel cell applications 619
respectively. These isotherms conform the uniform mesopores
typical of type-IV isotherms which exhibit H1 hysteresis loop
with a capillary condensation at relative pressure (P/P0)
0.45–0.9, however, with a difference in micropores which
could be accounted for the broadness of hysteresis loops
[15,48].
Figs. 5 and 6 present the TEM images of SBA-15 and
CMK-3. The figures indicate well ordered hexagonal symme-
try and that the mesoporous carbon represents exactly an
inverse replica of parent mesoporous silica with a calculated
pore diameter of �4.0 and 6.5 nm, respectively. This observa-
tion in good agreement with the values obtained from nitrogen
sorption data (see also Table 1). Shown in Figs. 7–10 are the
TEM images, SEAD, and particle size distribution of platinum
nanoparticles supported mesoporous carbon prepared by
various methods. It is clear from these images that the
paraformaldehyde reduced platinum depicts fine dispersion
on CMK-3 with a narrow size distribution in the range,
4–5 nm (Fig. 7). Whereas the sodium borohydride (Fig. 8)
and ethylene glycol (Fig. 9) reduction methods give �6–7 nm
particle sizes with a similar size distribution. On the other
hand, as expected, hydrogen reduction method gives much
large particle size (�18–20 nm; Fig. 10). Further, TEM
(Fig. 11) of a representative sample, i.e., 10 wt% Pt/CMK-3
preparted by paraformaldehyde reduction method clearly
depicts that the platinum nanoparticles (�4 nm) are well
1 2 3 4 5 6 7
200100
100
Inte
nsi
ty (
a.u.)
2θ (deg.)
Fig. 1 Low-angle XRD patterns of: (a) SBA-15, (b) CMK-3 and
(c) 20 wt% Pt/CMK-3.
Table 1 Structural and textural properties of mesoporous silica
Material Lattice constant, a0 (nm) Surface area, SBET (m
SBA-15 10.4 720
CMK-3 9.6 997
distributed within the mesopores of the framework structure
CMK-3. The calculated platinum nanoparticles sizes from
TEM images are in excellent with the computed values from
XRD (see also Table 2). Thus, it is evident that a narrow
particle size distribution of �4–5 nm is achieved in the
paraformaldehyde reduction method, and therefore if forms
one the most preferable method over other reduction methods
for the preparation of uniform and smaller platinum clusters.
The electrocatalytic properties of the various Pt/CMK-3
catalysts towards the methanol oxidation reactions were
tested. To investigate the electrocatalytic activity of the
prepared Pt/CMK-3 electrocatalysts, room temperature CV
measurements of the methanol oxidation reaction were carried
out in 1 M H2SO4 and 1 M CH3OH aqueous solution at
potential scan rate of 25 mVs�1 (Fig. 12). The forward anodic
peak, If around 0.7-0.8 V versus SCE, is due to the oxidation
methanol. In the backward scan, Ib the oxidation peak around
0.5–0.6 V versus SCE is attributed to the oxidation of COads
like species, generated via incomplete oxidation of methanol
during the forward scan. The If value relates directly to the
methanol oxidation activity of the electrocatalysts. Among the
prepared electrocatalysts, the paraformaldehyde reduction
method gives better activity over the other methods. The ratio
of the anodic peak current densities in the forward and reverse
scans could give another measure of its catalytic perfor-
mances. That is, a higher If/Ib ratio indicate superior oxidation
activity of methanol during the anodic scan and less accumu-
lation of carbonaceous species on the nanocatalyst surface,
and thus shows better CO tolerance [49,50]. On the other
hand, the entire Pt/CMK-3 catalysts show higher If/Ib ratio
than commercial platinum supported carbon catalysts, for
example, the commercial Pt/E-TEK catalyst shows a much
lower ratio (0.72). The higher electrocatalytic activity of the
and carbon.
2g�1) Pore volume, Vp (cm3g�1) Pore size, D (nm)
1.1 6.5
1.3 4.0
20 30 40 50 60 70 80 90
22231
1
22020
0111
Inte
nsity
(a.
u.)
2 (deg.)
Fig. 2 Wide-angle XRD patterns of 20 wt% Pt/CMK-3 prepared
with different reduction methods loadings.
Table 2 Microtructural and electrochemical data of various Pt/CMK-3 electrocatalysts.
Catalysta Reduction method Crystallite size, Pt EAS (m2g�1) Onset
potential (V)
Current, I at 0.7 V
(mA (mg.Pt) �1)
Activity
loss (%)
If/Ib
XRD (nm) TEM (nm)
Pt/CMK-3 Paraformaldehyde 4.3 4.5 84 0.14 185 65 1.33
Pt/CMK-3 Sodium Borohydride 6.0 6.0 78 0.14 157 58 1.57
Pt/CMK-3 Ethylene Glycol 5.5 6.0 72 0.16 165 95 0.76
Pt/CMK-3 Hydrogen 18.0 20.0 70 0.11 105 92 1.55
a20 wt% Platinum supported mesoporous carbon.
0.0 0.2 0.4 0.6 0.8 1.00
200
400
600
P/P0
Qua
ntity
Ads
orbe
d (c
m³/
gST
P)
SBA-15
5 10 15 200
5
10
15
20
Pore
Vol
ume
(cm
³/g)
D (nm)
Fig. 3 N2 sorption isotherms of SBA-15. The inset shows pore
size distribution of SBA-15.
0.0 0.2 0.4 0.6 0.8 1.00
250
500
750
1000
P/P0
Qua
ntity
Ads
orbe
d (c
m³/
gST
P)
CMK-3
Fig. 4 N2 sorption isotherms of CMK-3. The inset shows pore
size distribution of CMK-3.
Fig. 5 TEM image of SBA15. The inset shows SAED pattern of
SBA-15.
Fig. 6 TEM image of CMK-3. The inset shows SAED pattern of
CMK-3.
B. Kuppan, P. Selvam620
former is due high dispersion of uniform sized platinum
nanoparticles on the mesoporous carbon support [29,49,51].
In practical cases, highly dispersed Pt catalysts with large
surface areas are extremely important to increase the electro-
catalytic activity. The large EAS is due to the fact that Pt
nanoparticles are smaller and more uniformly dispersed on the
surfaces of CMK-3 prepared by paraformaldehyde reduction
method. Moreover, it is also well known that smaller catalyst
particles show higher electrochemical active surface area
(EAS), see also Table 2. Furthermore, Pt nanoparticles
dispersed on CMK-3 allows uniform dispersion of the Pt
nanoparticles, thereby producing much more accessible Pt
sites for efficient catalytic activity.
In addition, it is also important to address the long time
stability of the electrocatalysts for application view point.
In this regard, the stability of all the Pt/CMK-3 catalysts
were tested by chronoamperometric measurement studies at
the corresponding forward peak potential (0.7 V) for 3 h in
Fig. 7 TEM image of 20 wt% Pt/CMK-3, Inset: SAED pattern
of mesoporous carbon 20 wt% Pt/CMK-3 and particle size
distribution of 20Pt/CMK-3 by paraformaldehyde reduction
method.
Fig. 8 TEM image of 20 wt% Pt/CMK-3, Inset: SAED pattern
of mesoporous carbon 20 wt% Pt/CMK-3 and particle size
distribution of 20 wt% Pt/CMK-3 by sodium borohydride reduc-
tion method.
Fig. 9 TEM image of 20 wt% Pt/CMK-3, Inset: SAED pattern
of mesoporous carbon 20 wt% Pt/CMK-3 and particle size
distribution of 20 wt% Pt/CMK-3 by ethylene glycol reduction
method.
Fig. 10 TEM image of 20 wt% Pt/CMK-3, Inset: SAED pattern
of mesoporous carbon 20 wt% Pt/CMK-3 and particle size
distribution of 20 wt% Pt/CMK-3 by hydrogen reduction
method.
Platinum-supported mesoporous carbon (Pt/CMK-3) as anodic catalyst for direct methanol fuel cell applications 621
1 M H2SO4 and 1 M CH3OH. The results are presented as
inset in Fig. 11. It can be seen from this figure that all the
electrodes display an initial fast current decay followed by
slower attenuation upon long time operation, reaching a
quasi-equilibrium steady state. This initial fast decay is
attributed to the formation of intermediate species such as
COads, CH3OHads, and CHOads during electrochemical
methanol oxidation reaction. The slow attenuation at longer
times may be due to the adsorption of sulfate anions on the
electrocatalyst surface. The lower stability of some of the
catalyst can be attributed partly due to larger and/or
agglomerated platinum nanoparticles. However, the long
term stability of the Pt/CMK-3, in general, is consistent
with the view that the high dispersion of platinum nano-
particles on the high surface area mesoporous carbons
provides much better dispersion of metal nanoparticles
and better utilization and therefore accelerates the rate of
COads oxidation.
4. Conclusion
In a summary, platinum nanoparticles deposited over meso-
porous CMK-3 carbon by paraformaldehyde reduction
method is superior than the other reduction methods
employed in this study, viz., sodium borohydride, ethylene
glycol and hydrogen reduction methods. Furthermore, the
paraformaldyde method is more suitable for the preparation
of the high dispersed uniform seized platinum nanoparticles
on the mesorporous support with an average particle size of
�4 nm. Thus, the dispersion and particle size distribution of
plkatinum nanoparticles on CMK-3 is strongly dependent on
both the deposition method and the carbon support properties.
Fig. 11 TEM image of 10%Pt/CMK-3 by paraformaldehyde
reduction method.
-0.2 0.0 0.2 0.4 0.6 0.8 1.0
0
100
200
300
E(V) vs SCE, sat.KCl
Cur
rent
den
sity
(m
A/m
g Pt
)
Paraformaldehyde
Ethylene Glycol
Sodium borohydride
Hydrogen
Fig. 12 CVs of 20 wt% Pt/CMK-3 recorded in mixture of 1 M
H2SO4 and 1 M CH3OH with a scan rate of 25 mV at 25 1C. Inset:
Corresponding chronoamperometric curves.
B. Kuppan, P. Selvam622
On the other hand, the performance of the Pt/CMK-3 catalysts
exhibit higher activity and better stability than commercial
platinum supported carbon catalysts. The enhanced activity is
of the platinum supported mesoporous carbon is attributed to
better dispersion and utilization of the platinum, which essen-
tially originate from a higher surface area, large pore volume and
narrow pore size distribution of thee mesoporous carbon
materials. Thus the present study demonstrates that optimized
reduction methods and appropriate choice of carbon supports
can offer significant cost savings by lowering the catalyst loading.
Acknowledgment
Thank are due to the Department of Science and Technology,
New Delhi for funding NCCR, IIT-Madras. This work is
partially supported by a grant-in-aid for the Scientific
Research by the Ministry of New and Renewable Energy
under Grant no. 103/140/2008-NT. The authors thank Pro-
fessor B. Viswanathan for fruitful discussion.
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