Recent Advances Inog. Nonostruct.

7/31/2019 Recent Advances Inog. Nonostruct.

1/13

Recent Advances in Hydrogen Storage inMetal-Containing Inorganic Nanostructures

and Related MaterialsBy Abdul M. Seayad and David M. Antonelli*

1. Introduction

The demand for an efficient and clean fuel alternative has

increased in recent years[1] and is expected to become more

pronounced in the future,[2,3] since many automotive compa-

nies have announced the potential appearance of commer-

cially available fuel cell vehicles as soon as 2010. Hydrogen is

considered one of the best alternative fuels[46] due its abun-

dance, easy synthesis, and non-polluting nature when used in

fuel cells.[7,8] However, the main concern is the efficient

storage and transport of this highly flammable gas.[9] The ex-

pected hazards involved in storing and using gaseous hydro-

gen in high-pressure vessels has triggered research worldwide

on more safe and efficient ways for hydrogen storage for sta-

tionary or mobile applications.[10] While stationary hydrogen

fuel cells are less exacting in terms of component sizes andstorage capacities, extremely efficient hydrogen storage meth-

ods, from both the gravimetric and volumetric standpoints,

are essential for vehicular applications.[11] A reversible hydro-

gen sorption capacity of 56 wt.-% at 100 C and 0.1 MPa are

targeted for automotive applications.

The main challenges in the field of hydrogen storage are to

devise new materials or combinations of materials to exhibit1) high volumetric/gravimetric[12] capacity, 2) fast sorption ki-

netics at near-ambient temperatures, and 3) high tolerance to

recycling. One of the most promising classes of materials for

hydrogen storage are nanostructured composites, because

they have dramatically different chemical, physical, thermo-

dynamic, and transport properties as compared to their bulk

counterparts. Due to the wide range of compositions, the abil-

ity to tailor pore and grain sizes, and the capacity to intimately

weave two or more phases together at the nanometer level,

nanophase composite materials may open the window to

greater hydrogen-storage capacities and lower kinetic adsorp-

tion barriers as compared to coarse-grained materials.

[13]

Car-bon nanotubes (CNTs)[14] continue to be an important cate-

gory of nanomaterials for possible applications in hydrogen

storage,[1517] displaying an acceptable capacity range of

24 wt.-% under suitable conditions;[18] however, recent inter-

est has shifted away from this area because performance un-

der operating conditions is not as efficient as originally antici-

pated. For example, single-walled carbon nanotubes after

ultra-sonication show hydrogen uptake at room temperature,

although this storage may be due to metal particles incorpo-

rated during the sonication treatment. Reactive high-energy

ball-milling of graphite leads to a material with a high hydro-

gen-loading capacity, but the temperatures required for hy-

Adv. Mater. 2004, 16, No. 910, May 17 DOI: 10.1002/adma.200306557 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 76

An overview of recent advances in the application of non-carbonaceous

nanostructured and composite materials in hydrogen storage is

presented in this review. The main focus is on complex hydrides, non-

graphitic nanotubes, and other porous composite and framework

materials, since carbon nanotubes have been the subject of numerous

other reviews. Recent advances in the area of alanates show a promising reversible absorption

capability of up to 5 %, closing in on the projected Department of Energy (DOE) target of 6 %.

Non-carbon nanotubes mainly showed a sorption capacity of 13 wt.-%, although a promising

level of 4.2 wt.-% is shown by boron nitride nanotubes after collapse of their walls. Other

interesting materials included here are lithium nitride and porous metallo-organic frameworks.

[*] Prof. D. M. Antonelli, Dr. A. M. Seayad[+]

Department of Chemistry and BiochemistryUniversity of WindsorWindsor, Ontario, N9B 3P4 (Canada)E-mail: [email protected]

[+] Present address: Max-Planck Institut fr Kohlenforschung,Kaiser-Wilhelm-Platz 1, D-45470 Mlheim an der Ruhr, Germany.


2/13

drogen release are far too high for applications.[19] In view of

today's knowledge, the amount of hydrogen required for

automotive applications greatly exceeds that offered by car-

bon nanotubes.[20] Other carbon structures[21,22] and doped

CNTs have improved hydrogen sorption capacities, so appli-

cations may yet be on the horizon.[23] Several reviews have

recently appeared on this subject and interested readers may

refer to them.[2427]

In this review we present recent developments in hydrogen

storage using nanostructured and composite materials other

than carbon nanotubes, as these materials show great promise

in this exciting and rapidly expanding area of research. The

main focus is on nanocrystalline complex hydrides, inorganic

nanotubes such as boron nitride (BN), titanium sulfide (TiS2)

and molybdenum sulfide (MoS2), as well as lithium nitride,

metalorganic frameworks, and low-valency mesoporous tita-

nium.

2. Metal Hydrides

Metal hydrides are a promising means of effectively storing

hydrogen due to their high storage capacities at low pressures,

whilst they also maintaining volumetric densities comparable

to that of liquid hydrogen.[28] The highest volumetric densities

of hydrogen in any material are found in metal hydrides

(Fig. 1), which are defined as a concentrated single-phase

compounds involving the host metal and hydrogen.[29]

Hydrides can be broadly classified as 1) ionic hydrides in

which hydrogen exists as H (e.g., MH, M is mainly alkali or

alkaline earth metals), 2) covalent hydrides in which hydro-

gen shares the electron pair with non-metals or atoms with

similar electronegativities (e.g., H2O, H2S, SiH4, hydrocar-

bons, etc.) and metal hydrides in which hydrogen acts as a

metal and are formed mainly with transition metals including

the rare earth and actinide series. Metallic hydrides form a

wide range of stoichiometric and non-stoichiometric com-

pounds by direct interaction of hydrogen with metals.[30] The

hydrogen atom enters the metal lattice to form a solid solu-

tion and the metal hydride begins to crystallize when the local

hydrogen concentration exceeds a certain limit. The rate of

entry and reaction[31] depends in part on the metal particle

size, and for this reason more efficient hydrogen sorption ca-

pacity can be achieved with nanosized metals as compared to

their bulk counterparts. Metal hydrides containing only one

metal have limited practical applications in hydrogen storage

because of the high thermodynamic stability of these com-pounds. For this reason, a wide range of alloys with two or

more metals have been investigated over the past several

decades in order to find a material that meets the practical

requirements. These alloys show more complex thermody-

namics and phase diagrams than the pure metal hydrides, and

may therefore lead to a material with commercial hydrogen

storage applications.[32]

A wide range of nanocrystalline metal hydrides can be pre-

pared by mechanochemical process such as high-energy ball-

A. M. Seayad, D. M. Antonelli/Hydrogen Storage in Inorganic Nanostructures

66 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim http://www.advmat.de Adv. Mater. 2004, 16, No. 910, May 17

David Antonelli was born in Chicago in 1963 and raised in the United States, Great Britain, and

Canada. He completedhis BSCat theUniversityof Albertain 1987 andhis Ph.D. in organometallic

chemistry with Martin Cowie at the University of Alberta in 1990. He was an NSERC postdoctoral

fellow in organometallic chemistry at Oxford University with Malcolm Green in 1991, and at

Caltech in 199293 with John E. Bercaw. He later studied nanoporous materials as a postdoctoral

associate with Prof. Jackie Ying at the Massachusetts Institute of Technology Department of

Chemical Engineering from 19941996. He is currently an Associate Professor in Chemistry at the

University of Windsor and directs a research group focused on the electronic and catalytic

properties of nanoporous materials with variable oxidation states and conducting molecular wires

in the pores. Prof. Antonelli is the author of over 50 publications and was the winner of several

awards, including the Ontario Premier's Research Excellence Award, a Royal Society of Britain

Research Award, and a prestigious NSERC AGENO award.

Abdul Majeed Seayad was born and brought up in Kerala, India. After completing an M.Sc. in

Chemistry at the University of Kerala (1995), he joined the homogeneous catalysis division of the

National Chemical Laboratory, Pune, India as a CSIR (India) research fellow (19952000) for his

doctoral thesis under the guidance of Dr. R. V. Chaudhari, and received his Ph.D. degree in

Chemistry in 2000 from the University of Pune. Between2001and 2003 he worked as an Alexander

vonHumboldt research fellow in the research group of Professor Mathias Beller at Leibniz-Institut

fr Organische Katalyse (IfOK), Universitt Rostock e.V., Rostock, Germany. He then worked with

Professor David M. Antonelli, University of Windsor, Canada as a postdoctoral research fellow

working with hydrogen-storage materials. Presently he is working as a postdoctoral researchfellow

at the Max-Planck Institut fr Kohlenforschung, Mlheim, Germany in the research group of

Professor Benjamin List. His research interests include C1 chemistry, catalytic organic synthesis

and hydrogen-storage materials.


3/13

milling.[3336] This technique provides easy preparation of sam-

ples,[37] flexible grain-size control, as well as easy scale-up,[38]

and the nanosized metal hydrides[39] thus-formed show higher

hydrogen sorption capacities compared to the bulk hydride

materials. Once ball-milled, these metal hydrides and inter-

metallic compounds[40] generally need to be activated, and the

first cycles of hydrogenation and dehydrogenation should be

performed under relatively high temperatures and pressures.

The hydrogen-sorption kinetics were found to be increased by

ball-milling in the presence of certain organic additives.[4144]

For example, when magnesium and graphite are milled in the

presence of benzene,[45] cyclohexane,[46] or tetrahydrofur-

an,[47,48] the hydriding characteristics were increased as com-

pared to that of magnesium alone, or magnesium and graphite

milled together. During this milling process, the graphite

layered structure breaks apart to form graphite lamellae of

approximately 20 nm dispersed on magnesium particles.

When the pure metals (Ti, V, or Mg) or intermetallics such as

FeTi, Mg2Ni, etc., or the nanocomposites such as MgV[4951]

are milled for about 30 min in the presence of 10 wt.-%

graphite, the initial hydrogenation kinetics were found to in-

crease considerably.[52] A recent review on this subject (nano-

crystalline materials for hydrogen storage) is presented by

Huot[53] and interested readers may refer to this for further

reading on the preparation, properties, and hydrogen-storage

capabilities of various nanostructured metal hydrides and

related intermetallic compounds. From recent research it is

apparent that the main disadvantages of metal hydrides, even

in their nanocrystalline form, are their low gravimetric hydro-

gen content, the higher temperature needed for desorption of

hydrogen, and problems associated with their regeneration.

Other problems associated with their use include the cost, low

specific uptake by weight in many cases, unfavorable kinetics

requiring heating cycles, and susceptibility to contamination

by impurities.

2.1. Complex Hydrides

Complex hydrides are inorganic salt-like compounds of an-

ions such as [BH4], [AlH4]

, stabilized mainly with light metal

cations. The hydrogen in the complex hydrides is located at


Adv. Mater. 2004, 16, No. 910, May 17 http://www.advmat.de 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 76

Figure 1. Gravimetric and volumetric densities, and corresponding specific energies and energy densities, of a variety of different hydrogen-storagemedia, including two common fossil fuels: gasoline and propane. The FreedomCar targets for 2005, 2010, and 2015 are indicated within the shadedregions. The gravimetric hydrogen densities for pressurized hydrogen gas and cryogenic liquid hydrogen (diamond symbols) include the mass of the

storage container, whereas the values reported for the metal hydrides, complex hydrides, and other hydrogen-storage materials are based on the abso-lute (theoretical) amount of hydrogen. (Reproduced with permission from [2b]. Copyright Elsevier 2003.)


4/13

the corners of a tetrahedron with the metal in the center, and

the negative charge of the anion, [BH4] and [AlH4]

, is com-

pensated by a cation such as Li or Na. The hydride complexes

of boron, the tetrahydroborates M(BH4), and of aluminum,

the tetrahydroaluminate M(AlH4), are perhaps the most

promising hydrogen-storage materials discovered to date, as

they have shown promising levels of reversible adsorption ac-

cording to the DOE targets of 56 wt.-%. In their pure bulk

form they are thermodynamically quite stable and decompose

only at elevated temperatures, often above the melting point.

However, the decomposition temperature can be reduced and

the hydrogen adsorption efficiency improved by using various

dopants or reducing the grain size. Some of the recent devel-

opments in complex alanates and borates are reviewed below.

2.1.1. Aluminum Hydrides

Aluminum hydrides of light alkali metals are all very prom-

ising hydrogen-storage materials. This is because they all con-tain a high weight percentage of hydrogen, much of which can

be removed and replaced continuously. One drawback of al-

kali aluminum hydrides, however, is that they are not always

easy to prepare. Na3AlH6 can be synthesized by reaction of

NaH and NaAlH4 in heptane at 165 K and 140 bar of hydro-

gen[54] or by direct reaction of sodium and aluminum in tolu-

ene (438 K and 350 bar hydrogen).[55] Similarly, Na2LiAlH6can be prepared from LiAlH4 and NaH in toluene under

300 bar of hydrogen at 160C.[56] It can also be formed by the

reaction of NaAlH4, LiH, and NaH in heptane under hydro-

gen pressure.[57] NaAlH4 prepared and purified in different

ways leads to materials of different morphologies and grain

sizes. For example, Bogdanovic et al.[58]

have shown that dif-ferent methods of isolation of NaAlH4 from a tetrahydrofuran

(THF) solution of commercial Na alanate leads to crystalliza-

tion of NaAlH4 of different particle sizes and shapes, all of

which were characterized by scanning electron microscopy

(SEM) investigations (Fig. 2).

Large NaAlH4 crystals of about 50 25 lm size and

0.8 m2 g1 specific surface area are obtained through ether

precipitation (Fig. 2a), due to low rate of nucleation and uni-

form crystal growth. Precipitation by pentane (Fig. 2b) pro-

duced NaAlH4 as an agglomerate of particles of average 10

20 lm size and specific surface of approx. 2.5 m2 g1 with a

small amount in the range of 50 lm. Still finer NaAlH4 parti-

cles of approx. 510 lm size (Fig. 2c) were obtained by pour-

ing solutions of NaAlH4 in THF into pentane. These two fine

Na alanate samples (obtained through pentane precipitation)

showed a higher hydrogen-sorption capacity compared to that

of the large-grained samples when doped with Ti particles.

Further reduction of the size of Na alanates to the nanoscale

is expected to be advantageous. Most of these preparations

require filtration, washing, and drying to obtain a purified

product. Hence a low temperature and pressure preparation

method that gives high yield without purification steps may be

more suitable for commercial applications. Huot et al.[59] have

shown that nanocrystalline Na3AlH6 and Na2LiAlH6 can easi-

ly be produced by energetic ball-milling of NaH, LiH, and

NaAlH4 in stoichiometric composition. Thus, high-energy

ball-milling can produce nanoscale hydrides quickly and easi-

ly with potentially improved performances as compared to

the bulk materials.

The mechanism and dynamics of hydrogen desorption have

been extensively studied. Thermal decomposition of NaAlH4at higher temperatures takes place in two steps to give NaH,



Figure 2. Scanning electron microscopy (SEM) images of NaAlH crystalsobtained by precipitation of NaAlH from THF solutions by addition ofether (a) or pentane (b), or by pouring THF solutions of NaAlH into pen-tane (c). (Reproducedwith permission from [58]. Copyright Elsevier 2000.)

0 4 8 12 16 20 24

Cycle-No.

Capacity[wt%]

5,5

5

4,5

43,5

3

2,5

2

1,5

1

0,5

0

Figure 3. Hydrogen-storage capacity level in a 25 cycle test of NaAlH4doped with 2 mol-% TiN nanoparticles. Dehydrogenation at 120/180Cand normal pressure; hydrogenation at 100 C and 10085 bar pressure.


5/13

Al, and H2. In principle the first step can give 3.7 wt.-% H2,

and up to 5.5 wt.-% in the second step:

NaAlH4 1/3 Na3AlH6 + 2/3Al + H2 (3.7 wt.-% H2) (1)

1/3Na3AlH6 NaH + Al + 3/2 H2 (1.8 wt.-% H2) (2)

Decomposition of NaH to Na and hydrogen requires a still

higher temperature. The first two steps of decomposition can

be accelerated and the decomposition temperature can be

substantially reduced by doping with other metal cations such

as Ti3+, Ti4+, Zr4+, Fe3+, etc., as demonstrated by Bogdanovic

et al.[57,58,63,64] and others.[6062] X-ray diffraction (XRD) analy-

sis and solid-state NMR spectroscopy shows that the majority

of phases involved are NaAlH4, Na3AlH6, Al, and NaH.[63]

Other traces of unidentified phases are also observed, one of

which has been tentatively assigned to an AlTi alloy. By vari-

ation of NaAlH4 particle sizes, dopants (catalysts), and doping

procedures, kinetics and the de- and rehydrogenation stabili-ties within different cycles can be substantially improved,[58]

underscoring the importance of nanocrystalline processing in

this field. Recently Bogdanovic et al.[64] reported that doping

Na alanate with TiN nanoparticles could substantially reduce

the temperature required for decomposition as well as the

hydrogenation time required for practical purposes, and the

desorbed hydrogen could reach close to the theoretical limit.

However, the hydrogenation capacity for these materials is

found to slightly decrease over the course of several cycles be-

fore stabilizing (Fig. 3).

Anton[65] has recently studied the effect of a wide range of

different dopants on the hydrogen-sorption capacity and ki-

netics of Na alanate. In general, it was found that the amountand type of dopant had a substantial effect on these parame-

ters, with Ti providing the best results. In other work, it was

shown that hydrogenation kinetics can be improved by the ad-

dition of 10 wt.-% carbon to sodium alanates.[66] XRD[67] and

microstructural[68] characterization were performed on a se-

ries of doped alanates to understand the mechanism of action

of these catalysts; the results of this study, however, were am-

biguous.[69] Recently Vajeeston et al.[70] attempted to elucidate

the pressure-induced structural changes occurring during hy-

drogen adsorption, but the detailed mechanism of this process

was not completely resolved.

In contrast to NaAlH4, KAlH4 smoothly decomposes with-

out a transition metal catalyst (Eqs. 35) to give ~ 3.5 wt.-%

(about 80 % of the theoretical) at a temperature range of

250350 C and is reversible.[71]

3KAlH4 K3AlH6 + 2Al + 3H2 (H = 2.9 wt.-%) (3)

K3AlH6 3 KH + Al + 3/2 H2 (H = 1.4 wt.-%) (4)

3 KH 3 K + 3/2 H2 (H = 1.4 wt.-%) (5)

Magnesium alanate is another interesting complex hy-

dride, which has a theoretical hydrogen-storage capacity of

9.3 wt.-%. Studies have shown that it decomposes in two

major steps (Eqs. 6,7). The first decomposition temperature

is 163 C and the resulting residue at 200 C consists of MgH

and Al, which continues to release hydrogen in the tempera-

ture range of 240380 C and transforms into a mixture of Al

and the intermetallic compound Al3Mg2 (Eq. 8) at still high-

er temperatures (400 C).[72]

Mg(AlH4)2 MgH2 + 2Al + 3 H2 (6)

MgH2Mg + H2 (7)

2 Al + Mg 1/2Al2Mg3 + 1/2 Al (8)

In the first decomposition step, 6.6 wt.-% of hydrogen is re-

leased. Synthesis of Mg(AlH4)2 is generally achieved via a

metathesis reaction between sodium alanate and magnesium

chloride.[73,74] Peak-shape analysis of the XRD pattern indi-

cates that the magnesium alanate produced is a nanocrystal-line material with a mean grain size of 30 nm. The main differ-

ence in the decomposition of Mg(AlH4)2 as compared to

other Li and Na alanates is that it transforms into a non-ala-

nate metal hydride during the first decomposition step. Dop-

ing with TiCl3 and reducing the grain size by ball-milling was

not found to be beneficial to the dehydrogenation tempera-

ture or the kinetics in this case. The formation of stable MgH

as an intermediate, or Al2Mg3 as an end product, negatively

influences the re-adsorption of hydrogen and is the main

drawback of this system. The effects of grain size and doping

need to be further investigated before promising reversible

hydrogen-storage behavior is achieved.

2.1.2. Borohydrides

Borohydride complexes with suitable alkali or alkaline

earth metals are a promising class of compounds for hydrogen

storage. The hydrogen content can reach values of up to

18 wt.-% for LiBH4. Thermal analysis shows mainly three de-

composition peaks for LiBH4 (Eqs. 911).[75] The first peak

occurs at around 100C and corresponds to a structural transi-

tion from orthorhombic to polycrystalline with a small libera-

tion (0.3 wt.-%) of hydrogen. A fusion is then observed

around 270 C without liberation of hydrogen. At 320 C the

first significant hydrogen desorption peak occurs as the mate-

rial liberates an additional 1 wt.-% of hydrogen. The second

desorption peak begins at 400 C and reaches its maximum

around 500 C. The total amount of hydrogen desorbed up to

the temperature of 600C is 9 wt.-%,[76] which corresponds

exactly to half of the hydrogen in the starting compound. The

end product has the nominal composition LiBH2''.[77]

LiBH4 LiBH4e + 1/2 (e)H2(structural transition at T= 108 C) (9)

LiBH4e LiBH2 + 1/2(1e)H2(first hydrogen peak starting at T= 200 C) (10)




6/13


7/13

polymerized nanobells (Fig. 6b), usually exhibit a more defec-

tive structure and have many open-edge layers on the exterior

surface that may contribute to a higher hydrogen-absorption

capacity.

The mechanism of absorption is believed to be chemical,

and about 70 % of the absorbed hydrogen is retained after

depressurizing. The slow equilibration time (approx. 4 h) also

suggests that the adsorption is mainly due to a chemical inter-

action. Highly ball-milled nanocrystalline BN powders can

also absorb up to 2.6 wt.-% of hydrogen.[89] A higher hydro-

gen-absorption capacity of up to 4.2 wt.-% at 10 MPa was

observed for BN nanotubes with collapsed walls.[90] The struc-

tural collapse, as shown in the transmission electron microsco-

py (TEM) and high-resolution TEM (HRTEM) images

(Fig. 7), significantly increases the surface area from 254.2 to

789.1 m2 g1. This indicates that surface area is more impor-

tant in hydrogen uptake than mesoporosity. These materials

are prepared by heating BN nanotubes (prepared by the

CVD method using a mixture of B2O2 and Mg) to 1500 C on

the surface of platinum plates. In contrast, BN nanomaterials

prepared in the presence of LaB6 and Pd/boron powder show

a hydrogen storage capacity of 3 wt.-%. [91]

3.2. Titanium Sulfide Nanotubes (TiS2)

Titanium sulfide is an interesting material for hydrogen

storage, since foreign atoms can be easily intercalated in

between the STiS layers that are held by van der Waals' in-

teractions. This gives facile compositional flexibility. Chen et

al.[92] have synthesized multiwalled TiS2 nanotubes with uni-

form open-ended tubular structures (Fig. 8) with an outer

diameter of ~ 30 nm, an inner diameter of ~ 10 nm, and an

interlayer spacing of~ 0.57 nm.

These nanostructures are composed of nanocrystalline TiS2with a hexagonal structure. These materials reversibly absorb

2.5 wt.-% hydrogen at 25 C and about 4 MPa. The absorp-

tion capacity was found to decrease with rising temperature,

as shown in Figure 9. TiS2 nanotubes absorb hydrogen both

chemically (40 %) and physically (60 %).

3.3. Molybdenum Sulfide Nanotubes (MoS2)

Nanotubes of the type MS2 (M=Mo, W)[9395] are analo-

gous to pure carbon nanotubes. MoS2 nanotubes were synthe-

sized by direct reaction of (NH4)2MoS4[96] and hydrogen.[97]

Polycrystalline (NH4)2MoS4 is first ball-milled in an atmo-

sphere of hydrogen. The fine powder is then transferred onto



Figure 5. Hydrogen adsorption as a function of pressure in multiwalledBN nanotubes and bamboo nanotubes as compared to bulk BN powderat 10 MPa. (Reproduced with permission from [86]. Copyright AmericanChemical Society 2002.)

a

b

Figure 6. The morphologies of BN nanotubes: a) multiwall nanotubesand b) bamboo-like nanotubes. Scale bar: 100 nm. (Reproduced withpermission from [86]. Copyright American Chemical Society 2002.)

Figure 7. a) TEM image of BN nanotubes after heating at 1500 C for 6 hin the presence of platinum; the arrow points to a platinum nanoparticle.b) High-resolution TEM image of the collapsed BN nanotubes. (Repro-duced with permission from [90]. Copyright American Chemical Society2002.)


8/13

an alumina substrate and sintered in floating hydrogen/thio-

phene at the relatively low temperature of 400 C for 1 h to

form the wire-like nanotubes in 90 % purity with lengths of

several hundred nanometers. These are shown along with

polycrystalline MoS2 in Figure 10. When treated with KOH,

the surface area of the nanotubes increased, mainly because

of defects induced in the nanotube multiwalls as evidenced

form SEM and HRTEM analysis.

The HRTEM images demonstrate that the nanotube tip is

completely open, as shown in Figure 11. The outer diameter

of a typical hollow tube is ~ 25 nm, while the inner diameter is

~ 10 nm. The average distance between each two neighboring

fringes (c/2) is 0.63 nm, which corresponds to the interlayer

(002) d-spacing of the 2H-MoS lattice. It is also shown that

after KOH treatment, more defects are introduced around

the nanotube. The KOH-treated MoS2 nanotubes showed

higher hydrogen-sorption capacity as compared to the un-

treated and the polycrystalline MoS2. This is shown in Fig-ure 12.[98] The adsorption and desorption is claimed to be

highly reversible at 25 C and the specific surface area of the

KOH treated material is approx. 28 m2 g1 as compared to 22

and 3.6 m2 g1 in the untreated and polycrystalline MoS2, re-

spectively.

4. Miscellaneous Materials

In this section we review a small number of materials that

cannot be included in the above sections. In general, metal



Figure 8. TEM (a,b) and HRTEM (c) images of the as-synthesized TiS2 nanotubes. (Reproduced with permission from [92]. Copyright American Chemi-cal Society 2003.)

Figure 9. PCT curves for hydrogen absorption and desorption of TiS2nanotubes at 25, 75, and 125 C. (Reproduced with permission from [92].Copyright American Chemical Society 2003.)


9/13

nitrides, organic framework materials, and porous oxides ab-

sorb only small amounts of hydrogen, however the examples

from each of these three classes below are all potential com-

petitors to metal hydride and nanotube technology. This

makes them particularly intriguing, as they awaken new inter-

est in classes of materials that were thought to be uninterest-

ing from the standpoint of hydrogen-storage performance.

4.1. Lithium Nitride

Lithium nitride (Li3N) has a maximum theoretical hydro-

gen-sorption capacity of 11.5 wt.-%. It was reported as early

as 1910 by Dafert and Miklauz[99] that the reaction between

Li3N and H2 generates Li3NH4, which is a mixture of 2 LiH

and LiNH2,[100] as per the equation below

Li3N + 2 H2 Li3NH4 (2 LiH + LiNH2) (12)

Hu and Ruckenstein[101,102] later showed that the complete

recovery of Li3N from the hydrogenated compounds is a diffi-

cult process that requires high temperatures (above 430 C)and long times during which sintering occurs and leads to inef-

ficient recovery of Li3N. For this reason, the reversible storage

capacity of Li3N was thought to be limited to about 5 wt.-%.

In a recent reinvestigation of this system, Chen et al. [103] re-

ported that lithium nitride (Li3N) is a promising candidate for

reversible hydrogen storage. Figure 13 shows the absorption



Figure 10. SEM images of MoS2: a) polycrystalline, b) nanotubes without KOH treatment, and c) nanotubes after KOH treatment. (Reproduced withpermission from [98]. Copyright American Chemical Society 2003.)

Figure 11. a) TEM and b) HRTEM images of MoS2 nanotubes withoutKOH treatment, and c) HRTEM image of KOH-treated MoS nanotubes.(Reproduced with permission from [98]. Copyright American ChemicalSociety 2003.)

Figure 12. The hydrogen adsorption amount versus pressure of polycrys-talline MoS2, and nanotubes without and after KOH treatment at 25 C.(Reproduced with permission from [98]. Copyright American ChemicalSociety 2003.)

Figure 13. Weight variations during hydrogen absorption and desorptionprocesses over Li3N samples; Abs: absorption; Des: desorption. (Repro-duced with permission from [103]. Copyright Nature Publishing Group2002.)


10/13

desorption characteristics of a fresh Li3N sample. The absorp-

tion starts at a temperature of around 100C and a rapid

weight gain is observed in the temperature range of 170

210 C. Total hydrogen absorption of about 9.3 wt.-% was re-

ported after maintaining the sample at 255 C for half an hour.

Substantial absorption can also be obtained below 200 C if

sufficient time is provided. About 6.3 wt.-% of hydrogen was

desorbed below 200 C under vacuum (105 mbar), and the re-

maining hydrogen could only be desorbed at elevated temper-

atures (above 320C). No ammonia formation[102] was de-

tected under these conditions. Unlike most of the metal

hydrides, which exhibit one plateau in the pressurecomposi-

tion (PC) isotherm, Li3N has two. The first one has a rather

low equilibrium pressure (below 0.07 bar) and the second pla-

teau is sloped (Fig. 13); the overall equilibrium pressure is be-

low 0.2 bar at 195 C, 0.5 bar at 230 C, and 1.5 bar at 255 C.

The hydrogen absorbed during the first plateau might not be

easily desorbed, and should correspond to the high tempera-

ture desorbed portion. XRD measurements of samples withdifferent degrees of hydrogenation showed clear phase and

composition changes during the hydrogen absorption and de-

sorption. Pristine hexagonal Li3N phase shifted to face-cen-

tered cubic (fcc) lithium imide and hydride phases after being

half-hydrogenated. The fully hydrogenated Li3N sample is

composed of body-centered tetragonal (bct) lithium amide

(LiNH2) and an enhanced lithium hydride phase.[104] Phase

changes in desorption follow a path that is almost the reverse

of that observed during adsorption. Hence it can be deduced

that the hydrogen sorption in Li3N may occur as per the

following equation (Eq. 13) and the molar ratio of absorbed

hydrogen to Li3N is four, about 11.5 wt.-%

Li3N + 2 H2 Li2NH + LiH + H2 LiNH2 + 2 LiH (13)

A similar hydrogen-storage phenomenon was observed in a

related CaNH system. A reversibly hydrogen-storage ca-

pacity of 1.9 wt.-% (theoretical maximum is 2.1 wt.-%) is

achieved for Ca2NH over a temperature range of 350600 C.

The hydrogenated Ca2NH sample is composed of CaNH and

CaH2, indicating that hydrogen is stored according to the

following the reaction:

Ca2NH + H2 CaNH + CaH2 (14)

All of these nitrides showed relatively fast kinetics in hydro-

gen storage. For a 500 mg sample, almost all hydrogen (for

Li2NH and Ca2NH) or a substantial amount of hydrogen (for

Li3N) can be absorbed within 10 min under 30 bar of hydro-

gen and at temperatures differing for each compound. The de-

sorption rate strongly depends on temperature and hydrogen

pressure. Though the nitride systems offer excellent potential,

in order to meet practical applications at moderate tempera-

tures with improved chemical stability, further improvements

are required. It is conceivable that nanocrystalline grains and

doped composite lithium and calcium nitride materials may

offer substantially improved performance over the pure bulk

phases, with much lower adsorption temperatures, much clos-er to the practical goal.

4.2. Microporous MetalOrganic Frameworks

Rosi et al.[105] recently reported an interesting metalloor-

ganic framework (MOF)[107] material with hydrogen-sorption

capacities at 78 K or ambient temperature under safe pres-

sures (up to 20 bar). These materials are crystalline metalor-

ganic frameworks with cubic cavities of uniform size and

internal structure. This work is of special interest because the

majority of microporous framework materials composed of

metal oxides (zeolites, etc.) have only moderate to poorhydrogen-storage capacities. The material MOF-5[107,108]

(Fig. 14a), in which inorganic [OZn4]6+ groups are joined to

an octahedral array of [O2CC6H4CO2]2 (1,4-benzenedicar-

boxylate, BDC) groups to form porous cubic framework,

showed 4.5 wt.-% hydrogen absorption at 78 K and moderate

pressures. However, only 1 wt.-% absorption was achieved at



Figure 14. Single-crystal X-ray structures of MOF-5 (a), IRMOF-6 (b), and IRMOF-8 (c) illustrated for a single cube fragment of their respective cubicthree-dimensional extended structure. On each of the corners is a cluster [OZn4(CO2)6] of an oxygen-centered Zn4 tetrahedron that is bridged by sixcarboxylates of an organic linker (Zn: blue polyhedron; O: red spheres; C: black spheres). The large yellow spheres represent the largest sphere thatwould fit in the cavities without touching the van der Waals' atoms of the frameworks. Hydrogen atoms have been omitted. (Reproduced with permis-sion from [105]. Copyright American Association for the Advancement of Science 2003.)


11/13

room temperature and 20 bar pressure, and the absorption

capacity was found to increase with pressure as shown in

Figure 15.

The MOF-5 structure motif and related compounds are

ideal for gas absorption, because the linkers are isolated from

each other and accessible from all sides to sorbate gas mole-

cules. The scaffolding-like nature of MOF-5 and its deriva-

tives leads to extraordinarily high apparent surface areas

(25003000 m2 g1) for these structures.

In other similar structures, such as IRMOF-6 (Fig. 14b, with

cyclobutylbenzene linker) and IRMOF-8 (Fig. 14c, with

naphthalene linker), the specific H2 uptake is approximatelydoubled and quadrupled, respectively, compared to MOF-5 at

room temperature and 20 bar pressure. The hydrogen-absorp-

tion capacity of these structures at room temperature is com-

parable to that of carbon nanotubes at cryogenic tempera-

tures and can be fine tuned by modifying the structure with

suitable linkers.

4.3. Mesoporous Transition Metal Oxides

Recently, we became interested in mesoporous transition

metal oxides[109,110] as a possible material for hydrogen-stor-

age applications. These materials possess the high surface

area and porosity of nanotubes and framework structures,

with accessible variable oxidation states that may be impor-

tant in adsorption of hydrogen by chemical pathways. High

surface area mesoporous titanium oxide[111] showed only

below 1 wt.-% absorption at 200 C and 20 bar pressure.

However these materials showed a promising reversible

absorption level of 35 wt.-% when suitably reduced by

bis(toluene)titanium, bis(toluene)vanadium, or a variety of

lithium fullerides.[112] The mechanism of this adsorption is

currently under investigation and further optimization of

adsorption levels and temperatures is ongoing. During hy-

drogen cycling the porosity is lost, which may suggest that

the role of the porosity is to allow uniform surface reduc-

tion and initial access of hydrogen to all of these sites. The

poor performance of the unreduced materials underscores

the importance of surface reduction in this system. Further

work is in progress to optimize the conditions for maximum

reversible absorption capacity. Suitably modified titaniumoxide nanotubes[113115] may also be promising as an alterna-

tive for efficient hydrogen storage and need to be explored

along with other non-carbon nanotubes[116119] and nanoma-

terials.[120122]

5. Summary

Suitable nanocrystalline materials such as metal hydrides

or complex hydrides are attracting increased interest and

showing promise for onboard hydrogen-storage applica-

tions. Control of composition and grain size and/or porosity

as well as the synergistic effect of metals such as Ti and Feor Ti and Zr, have been shown to play key roles in enhanc-

ing reversible hydrogen storage in a wide variety of metal

alanate and porous inorganic systems. However, issues such

as their hydrogenation kinetics, grain growth, and phase

separation that serve to reduce the storage capacity need to

be considered further. Various non-carbon nanotube materi-

als are also worth analyzing for further improvements with

respect to preparation, mechanism of hydrogen sorption,

sorption kinetics, storage capacity, etc. Further, possibilities

of easily prepared mesoporous and organic framework

materials should be explored as alternative materials for

hydrogen-storage applications. A summary of all the materi-

als discussed here and their theoretical and observed hydro-

gen-sorption capacities is presented in Table 1.

The main concerns and barriers for mobile applications of

most of these materials are the cost, weight and volume, effi-

ciency, durability, refueling time, codes and standards, and

life-cycle and efficiency analyses. In considering the overall

hydrogen economy, its impact on atmosphere[123] and climate

change[124] due to the hydrogen leakage are also needs to be

considered. The efficient collection/recycle of water exhaust

from automotives should also be taken into account.

Received: December 1, 2003Final version: March 18, 2004



Figure 15. Hydrogen gas-sorption isotherm for MOF-5 at a) 78 K andb) 298 K. (Reproduced with permission from [105]. Copyright AmericanAssociation for the Advancement of Science 2003.)


12/13

[1] D. Sperling, M. A. DeLuchi, Annu. Rev. Energy 1989, 14, 375.

[2] a) C. C. Elam, C. E. G. Padr, G. Sandrock, A. Luzzi, P. Lindblad,

E. F. Hagen, Int. J. Hydrogen Energy 2003, 28, 601. b) J. A. Ritter,

A. D. Ebner, J. Wang, R Zidan, Mater. Today 2003, September, 18.

[3] M. Conte, A. Iacobazzi, M. Ronchetti, R. Vellone, J. Power Sources

2001, 100, 171.

[4] M. A. Paevey, Fuel from Water, Merit, Louisville, KY 1998.

[5] P. Hoffmann, The Forever Fuel, Westview Press, Boulder, CO 1981.

[6] R. M. Dell, D. A. J. Rand, J. Power Sources 2001, 100, 2.

[7] B. D. McNicol, D. A. J. Rand, K. R. Williams, J. Power Sources

2001, 100, 47.

[8] A. B. Stambouli, E. Traversa, Renewable Sustainable Energy Rev.

2002, 6, 297.

[9] J. M. Ogden, Annu. Rev. Energy Environ. 1999, 24, 227.

[10] L. Schlapbach, A. Zttel, Nature 2001, 414, 353.

[11] G. D. Berry, S. M. Aceves, Energy Fuels 1998, 12, 49.

[12] S. Louis, Hydrogen in Intermetallic Compounds I, in: Topics in

Applied Physics, Vol.63, Springer, Berlin 1988, p.350.

[13] A. Zaluska, L. Zaluski, J. O. Strom-Olsen, J. Alloys Compd. 2000,

298, 125.

[14] C. N. R. Rao, A. Govindaraj, Acc. Chem. Res. 2002, 35, 998.

[15] C. Dillon, K. M. Jenes, T. A. Bekkedehi, C. H. Kiang, D. S. Bethune,

M. J. Heben, Nature 1997, 386, 377.

[16] P. Chen, X. Wu, J. Lin, K. L. Tan Science 1999, 285, 91.

[17] F. E. Pinkerton, B. G. Wicke, C. H. Olk, G. G. Tibbetts, G. P. Meis-

ner, M. S. Meyer, J. F. Herbst, J. Phys. Chem. B 2000, 104, 9460.

[18] B. Liu, Y. Y. Fan, M. Liu, H. T. Cong, H. M. Cheng, M. S. Dressel-

haus, Science 1999, 286, 1127.

[19] R. Strobel, L. Jorissen, T. Schliermann, V. Trapp, W. Schutz,

K. Bohmhammel, G. Wolf, J. Garche, J. Power Sources 1999, 84, 221.

[20] M. Hirscher, M. Becher, M. Haluska, F. v. Zeppelin, X. Chen,

U. Dettlaff-Weglikowska,S.Roth,J.Alloys Compd.2003,356357,433.

[21] A. Chambers, C. Park, R. T. Baker, N. M. Rodriguez, J. Phys.

Chem. B 1998, 102, 4253.

[22] V. V. Simonyan, J. K. Johnson, J. Alloys Compd. 2002, 330332, 659.

[23] F. L. Darkrim, P. Malbrunot, G. P. Tartaglia, Int. J. Hydrogen Energy

2002, 27, 193.

[24] R. G. Ding, G. Q. Lu, Z. F. Yan, M. A. Wilson, J. Nanosci. Nano-

technol. 2001, 1, 7.

[25] J. E. Fischer, Chem. Innovation 2000, 30, 21.

[26] M. Hirscher, M. Becher, J. Nanosci. Nanotechnol. 2003, 3, 3.

[27] H.-M. Cheng, Q.-H. Yang, C. Liu, Carbon 2001, 39, 1447.

[28] J. J. Reilly, Z. Phys. Chem. Neue Fol. 1979, 117, 155.

[29] L. Schlapbach, I. Anderson, J. P. Burger, in Electronic and Magnetic

Properties of Metals and Ceramics Part III, Vol. 3B. (Ed: K. H. J.

Buschow), VCH, Weinheim, Germany 1994, pp.271331.

[30] T. P. Perng, J. K. Wu, Mater. Lett. 2003, 57, 3437.

[31] W. B. Jung, K. S. Nahm, W. Y. Lee, Int. J. Hydrogen Energy 1990, 15,

641.

[32] M. Yamaguchi, E. Akiba, in Electronic and Magnetic Properties ofMetals and Ceramics Part II, Vol. 3B (Ed: K. H. J. Buschow), VCH,

Weinheim, Germany 1994, pp.333398.

[33] J. S. Benjamin, Sci. Am. 1976, 235, 40.

[34] D. R. Maurice, T. H. Courtney, Metall. Trans. A 1990, 21, 289.

[35] L. Lue, M. O. Lai, Mechanical Alloying, Kluwer Academic, Boston

1997.

[36] P. R. Sony, Mechanical Alloying Fundamentals and Applications,

Cambridge International Science Publishing, Cambridge, UK 2000.

[37] R. A. Varin, T. Czujko, Mater. Manuf. Process 2002, 17, 129.

[38] C. C. Koch, Nanostruct. Mater. 1997, 9, 3.

[39] J. Huot, G. Liang, R. Schulz, Appl. Phys. A: Mater. Sci. Process. 2001,

72, 187.

[40] P. Dantzer, Mater. Sci. Eng. 2002, A329331, 313.

[41] H. Imamura, T. Takahashi, R. Galleguillos, S. Tsuchiya, J. Less-Com-

mon Met. 1983, 89, 251.

[42] H. Imamura, J. Less-Common Met. 1989, 153, 16.

[43] H. Imamura, Y. Takesue, S. Tabata, N. Shigetomi, Y. Sakata, S. Tsu-

chiya, Chem. Commun. 1999, 2277.

[44] H. Imamura, S. Tabata, Y. Takesue, N. Sakata, S. Kamazaki, Int. J.

Hydrogen Energy 2000, 25, 837.

[45] H. Imamura, Y. Takesue, T. Akimoto, Tabata, J. Alloys Compd.

1999, 293295, 564.

[46] H. Imamura, N. Sakasai, T. Fujinaga, J. Alloys Compd. 1997,

253254, 34.

[47] H. Imamura, N. Sakasai, Y. Kajii, J. Alloys Compd. 1996, 232, 218.

[48] H. Imamura, N. Sakasai, J. Alloys Compd. 1995, 231, 810.

[49] G. Liang, J. Huot, S. Boily, A. V. Neste, R. Schutz, J. Alloys Compd.

1999, 292, 247.


1999, 291, 295.


2000, 305, 239.

[52] S. Bouaricha, J.-P. Dodelet, D. Guay, J. Hout, R. Schutz, J. Alloys

Compd. 2001, 325, 245.

[53] J. Huot, Nanocrystalline Materials for Hydrogen Storage, in

Nanoclusters and Nanocrystals (Ed: H. S. Nalwa), American Scien-

tific Publishers, Stevenson Ranch, CA 2003, Ch.2.

[54] L. I. Zakharkin, V. V. Gavrilenko, Dokl. Akad. Nauk. SSSR 1962,

145, 793.

[55] E. C. Ashby, P. Kobetz, Inorg. Chem. 1966, 5, 1615.

[56] P. Claudy, B. Bonnetot, J.-P. Bastide, J.-M. Letoffe, Mater. Res. Bull.

1982, 17, 1499.

[57] B. Bogdanovic, M. Schwickardi, J. Alloys Compd. 1997, 253254, 1.

[58] B. Bogdanovic, R. A. Brand, A. Marjanovic, M. Schwickardi, J. Tolle,

J. Alloys Compd. 2000, 302, 36.

[59] J. Huot, S. Boily, V. Guther, R. Schulz,J. Alloys Compd. 1999,304, 383.

[60] R. A. Zedan, S. Takara, A. G. Hee, C. M. Jensen, J. Alloys Compd.

1999, 285, 119.

[61] C. M. Jensen, R. A. Zedan, N. Mariels, A. G. Hee, C. Hagen, Int. J.

Hydrogen Energy 1999, 24, 461.

[62] G. Sandrock, K. Gross, G. Thomas, C. Jensen, D. Meeker, S. Takara,

J. Alloys Compd. 2002, 330332, 696.

[63] B. Bogdanovic, M. Felderhoff, M. Germann, M. Hartel, A. Pommer-

in, F. Schuth, C. Weidenthaler, B. Zibrowius, J. Alloys Compd. 2003,

350, 246.

[64] B. Bogdanovic, M. Felderhoff, S. Kaskel, A. Pommerin, K. Schlichte,

F. Schth, Adv. Mater. 2003, 15, 1012.

[65] D. L. Anton, J. Alloys Compd. 2003, 356357, 400.



Table 1. Summary of reversible hydrogen-storage capacity of variousnanostructured materials.

MaterialH2 sorption capacity

[wt.-%]

Theoretica l Max imum Achieved

Complex hydridesNaAlH4 7.5 5.3 [64]

KAlH4 5.7 3.5 [71]

Mg(AlH4)2 9.3 6.6 [72]

LiBH4 18 13.3 [78]

Nanotubes

BN 4.2 [90]

TiS2 2.5 [92]

MoS2 1.2 [98]

Nitrides

Li3N 11.3 9.3 [103]

Ca2NH 2.1 1.9 [103]

Microporous MOF 4.5 [105]


13/13

[66] A. Zaluska, L. Zaluski, J. O. Strom-Olsen, J. Alloys Compd. 2000,

298, 125.

[67] K. J. Gross, G. Sandrock, G. J. Thomas, J. Alloys Compd. 2002,

330332, 691.

[68] G. J. Thomas, K. J. Gross, N. Y. C. Yang, C. Jensen, J. Alloys Compd.

2002, 330332, 702.

[69] K. J. Gross, G. J. Thomas, C. M. Jensen, J. Alloys Compd. 2002,

330332, 683.[70] P. Vajeeston, P. Ravindran, R. Vidya, H. Fjellvag, A. Kjekshus, Appl.

Phys. Lett. 2003, 80, 2257.

[71] H. Morioka, K. Kakizaki, S.-C. Chung, A. Yamada, J. Alloys Compd.

2003, 353, 310.

[72] M. Fichtner, O. Fuhr, O. Kircher, J. Alloys Compd. 2003, 356357,

418.

[73] E. Wiberg, R. Bauer, Z. Naturforsch. 1950, 5b, 397.

[74] M. Fichtner, O. Fuhr, J. Alloys Compd. 2002, 345, 286.

[75] E. M. Fedneva, V. L. Alpatova, V. I. Mikheeva, Russ. J. Inorg.

Chem. 1964, 9, 826.

[76] A. Zttel, S. Rentsch, P. Fischer, P. Wenger, P. Sudan, P. Mauron,

C. Emmenegger, J. Alloys Compd. 2003, 356357, 515.

[77] D. S. Stasinevich, G. A. Egorenko, Russ. J. Inorg. Chem. 1968, 13,

341.

[78] A. Zttel, P. Wenger, S. Rentsch, P. Sudan, P. Mauron, C. Emmeneg-

ger, J. Power Sources 2003, 118, 1.

[79] H. J. Schlesinger, H. C. Brown, J. Am. Chem. Soc. 1940, 62, 3429.

[80] H. J. Schlesinger, H. C. Brown, H. R. Hoekstra, L. R. Rapp, J. Am.

Chem. Soc. 1953, 75, 199.

[81] Y. Wu, R. M. Mohring, Prepr. Symp. - Am. Chem. Soc., Div. Fuel

Chem. 2003, 48, 940.

[82] C. Weixiang, T. Zhiyan, G. Hetong, Dianchi 1998, 28, 157.

[83] R. Aliello, M. A. Matthews, D. L. Reger, J. E. Collins, Int. J. Hydro-

gen Energy 1998, 23, 1103.

[84] a) S. C. Amendola, S. L. Sharp-Goldman, M. S. Janjua, M. T. Kelly,

P. J. Petillo, M. A. Binder, J. Power Sources 2000, 85, 186. b) S. C.

Amendola, S. L. Sharp-Goldman, M. S. Janjua, M. T. Kelly,

P. J. Petillo, M. A. Binder, Int. J. Hydrogen Energy 2000, 25, 969.

[85] D. Hua, Y. Hanxi, A. Xinping, C. Chuansin, Int. J. Hydrogen Energy

2003, 28, 1095.

[86] R. Ma, Y. Bando, H. Zhu, T. Sato, C. Xu, D. Wu, J. Am. Chem. Soc.

2002, 124, 7672.

[87] T. Ishii, T. Sato, Y. Sekikawa, M. Iwata, J. Cryst. Growth 1981, 52,

285.

[88] R. Ma, Y. Bando, T. Sato, Adv. Mater. 2002, 14, 366.

[89] P. Wang, S. Orimo, T. Matsushima, H. Fujii, G. Majer, Appl. Phys.

Lett. 2002, 80, 318.

[90] C. Tang, Y. Bando, X. Ding, S. Qi, D. Golberg, J. Am. Chem. Soc.

2002, 124, 14 550.

[91] T. Oku, M. Kuno, Diamond Relat. Mater. 2003, 12, 840.

[92] J. Chen, S.-L. Li, Z.-L. Tao, Y.-T. Shen, C.-X. Cui, J. Am. Chem. Soc.

2003, 125, 5284.

[93] R. Tenne, L. Margulis, M. Genut, G. Hodes, Nature 1992, 360, 444.

[94] M. Hershfinkel, L. A. Gheber, V. Volterra, J. L. Hutchison,

R. Tenne, J. Am. Chem. Soc. 1994, 116, 1914.

[95] Y. Feldman, E. Wasserman, D. J. Srolovitz, R. Tenne, Science 1995,

267, 222.

[96] W. H. Pan, M. E. Leonowicz, E. I. Stiefel, Inorg. Chem. 1983, 22,

672.

[97] J. Chen, N. Kuriyama, H. Yuan, H. T. Takeshita, T. Sakai, J. Am.Chem. Soc. 2001, 123, 11813.

[98] J. Chen, S. L. Li, Z. L. Tao, J. Alloys Compd. 2003, 356357, 413.

[99] F. W. Dafert, R. Miklauz, Monatsh. Chem. 1910, 31, 981.

[100] O. Ruff, H. Goeres, Chem. Ber. 1910, 44, 502.

[101] Y. H. Hu, E. Ruckenstein, Ind. Eng. Chem. Res. 2003, 42, 5135.

[102] Y. H. Hu, E. Ruckenstein, J. Phys. Chem. A 2003, 107, 9737.

[103] P. Chen, Z. Xiong, J. Luo, J. Lin, K. L. Tan, Nature 2002, 420, 302.

[104] Power Diffraction File TM Data Sets: 149, International Center for

Diffraction Data (ICDD), Pennsylvania, PA 1999.

[105] N. L. Rosi, J. Eckert, M. Eddaoudi, D. T. Vodak, J. Kim,

M. O'Keeffe, O. M. Yaghi, Science 2003, 300, 1127.

[106] M. Eddaoudi, D. B. Moler, H. Li, B. Chen, T. M. Reineke,

M. O'Keeffe, O. M. Yaghi, Acc. Chem. Res. 2001, 34, 319.

[107] H. Li, M. Eddaoudi, M. O'Keeffe, O. M. Yaghi, Nature 1999, 402,

276.

[108] M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J. Wachter, M. O'Keeffe,

O. M. Yaghi, Science 2002, 295, 469.

[109] X. He and D. M. Antonelli, Angew. Chem. Int. Ed. 2002, 41, 214.

[110] J. Y. Ying, C. P. Mehnert, M. S. Wong, Angew. Chem. Int. Ed. 1999,

38, 56.

[111] Y. Wang, X. Tang, L. Yin, W. Huang, Y. R. Hacohen, A. Gedanken,

Adv. Mater. 2000, 12, 1183.

[112] a) M. Vettraino, M. Trudeau, A. Y. H. Lo, R. W. Schurko, D. M. An-

tonelli J. Am. Chem. Soc. 2002, 124, 9567. b) U. S. Patent Pending.

[113] T. Kasuga, M. Hiramatsu, A. Hoson, T. Sekino, K. Niihara, Adv. Ma-

ter. 1999, 11, 1307.

[114] P. Hoyer, Langmuir 1996, 12, 1411.

[115] Y. Zhu, H. Li, Y. Koltypin, Y. R. Hacohen, A. Gedanken, Chem.

Commun. 2001, 2616.

[116] V. V. Pokropivnyi, Powder Metall. Met. Ceram. 2001, 40, 485.



[119] A. L. Ivanovskii, Russ. Chem. Rev. 2002, 71, 175.

[120] D. Li, Y. Xia, Nano Lett. 2003, 3, 555.

[121] K. Tanaka, Thin Solid Films 1999, 341, 120.

[122] S. Kaskel, K. Schlichte, G. Chaplais, M. Khanna, J. Mater. Chem.

2003, 13, 1496.

[123] T. K. Tromp, R.-L. Shia, M. Allen, J. M. Eiler, Y. L. Yung, Science

2003, 300, 1740.

[124] M. G. Schultz, T. Diehl, G. P. Brasseur, W. Zittel, Science 2003, 302,

624.

______________________



Recent Advances Inog. Nonostruct.

Documents

Transcript of Recent Advances Inog. Nonostruct.