Ti-doped alkali metal aluminium hydrides as potential novel reversible hydrogen storage materials

Bogdanović, Borislav; Schwickardi, Manfred

doi:10.1016/s0925-8388(96)03049-6

Cited by 1,745 publications

(1,720 citation statements)

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“…In the case of the hydrides doped with Ti halides, it is believed and also experimentally shown that the high-valance Ti n+ is rapidly reduced to Ti 0 via the highly exothermic reaction between the host hydrides and dopant precursors. 2,5,17 Thus formed, Ti 0 has achieved an atomic-level dispersion in the hydride matrix that is much more favorable than that obtained by mechanically milling the hydrides with metallic Ti powder. As a result, the thermodynamically favorable formation of Ti hydride(s) during the doping and/or subsequent hydriding processes should be further kinetically facilitated.…”

Section: Discussionmentioning

confidence: 99%

“…One is that the surface-localized species consisting of titanium metal or Al-Ti alloy acts as an active catalyst and is present in the hydride matrix in an X-ray amorphous form. 2,5,[16][17][18][19][20][21][22][23] This hypothesis was partially supported by the observed H 2 evolution during the doping process, X-ray absorption and electron microscopy studies of the doped hydride at various states, 2,5,[16][17][18][19][20][21][22] and also by theoretical calculation. 23 Alternatively, on the basis of the observation that lattice parameters of NaAlH 4 changed upon Ti doping, Sun et al proposed that Ti cations with variable valence were incorporated into the host lattice and substituted for Na + .…”

Section: Introductionmentioning

confidence: 91%

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Exploration of the Nature of Active Ti Species in Metallic Ti-Doped NaAlH₄

2005

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Clarification of the nature of active Ti species has been a key challenge in developing Ti-doped NaAlH 4 as a potential hydrogen storage medium. Previously, it has been greatly hindered by the invisibility of Ticontaining species in conventional analysis techniques. In the present study, for the first time, the catalytically active Ti-containing species have been definitely identified by X-ray diffraction in the hydrides doped with metallic Ti. It was found that mechanical milling of a NaH/Al mixture or NaAlH 4 with metallic Ti powder resulted in the formation of nanocrystalline Ti hydrides. The variation of the preparation conditions during the doping process leads to a slight composition variation of the Ti hydrides. The catalytic enhancement arising upon doping the hydride with commercial TiH 2 was quite similar to that achieved in the hydrides doped with metallic Ti. Moreover, the cycling stability that was previously established in metallic Ti-doped hydrides was also observed in the hydrides doped with TiH 2 . These results clearly demonstrate that the in situ formed Ti hydrides act as active species to catalyze the reversible dehydrogenation of NaAlH 4 . The mechanism by which Ti hydrides catalyze the reversible de-/hydrogenation reactions of NaAlH 4 was discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 91%

Exploration of the Nature of Active Ti Species in Metallic Ti-Doped NaAlH₄

2005

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“…These perceived limitations were challenged in 1996 with the demonstration of reversible hydrogen storage in NaAlH 4 at moderate conditions upon the addition of a titanium-based catalyst. 32 This result re-ignited interest in complex hydrides. Over the last decade several novel approaches for improving the thermodynamic and/or kinetic properties of various complex hydrides have been explored.…”

Section: Complex Hydridesmentioning

confidence: 97%

“…often lightweight alkali or alkaline earth Li, Na, Mg, or Ca cations) and hydrogen-containing ''complex'' anions such as borohydrides (BH 4 À ), [29][30][31] alanates (AlH 4 À ), 32 and amides (NH 2 À ). 33 In this anionic complex, hydrogen atoms are covalently bonded to central atoms, for example boron, aluminium or nitrogen (see Fig.…”

Section: Complex Hydridesmentioning

confidence: 99%

High capacity hydrogenstorage materials: attributes for automotive applications and techniques for materials discovery

et al. 2010

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Widespread adoption of hydrogen as a vehicular fuel depends critically upon the ability to store hydrogen on-board at high volumetric and gravimetric densities, as well as on the ability to extract/insert it at sufficiently rapid rates. As current storage methods based on physical means-high-pressure gas or (cryogenic) liquefaction-are unlikely to satisfy targets for performance and cost, a global research effort focusing on the development of chemical means for storing hydrogen in condensed phases has recently emerged. At present, no known material exhibits a combination of properties that would enable high-volume automotive applications. Thus new materials with improved performance, or new approaches to the synthesis and/or processing of existing materials, are highly desirable. In this critical review we provide a practical introduction to the field of hydrogen storage materials research, with an emphasis on (i) the properties necessary for a viable storage material, (ii) the computational and experimental techniques commonly employed in determining these attributes, and (iii) the classes of materials being pursued as candidate storage compounds. Starting from the general requirements of a fuel cell vehicle, we summarize how these requirements translate into desired characteristics for the hydrogen storage material. Key amongst these are: (a) high gravimetric and volumetric hydrogen density, (b) thermodynamics that allow for reversible hydrogen uptake/release under near-ambient conditions, and (c) fast reaction kinetics. To further illustrate these attributes, the four major classes of candidate storage materials-conventional metal hydrides, chemical hydrides, complex hydrides, and sorbent systems-are introduced and their respective performance and prospects for improvement in each of these areas is discussed. Finally, we review the most valuable experimental and computational techniques for determining these attributes, highlighting how an approach that couples computational modeling with experiments can significantly accelerate the discovery of novel storage materials (155 references).

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“…[3][4][5][6][7][8][9][10][11][12][13] Thus, the particle size reduction of the NaAlH 4 , induced by the presence of Ti, in NaAlH 4 -Ti/CNF explained, at least partially, the lowest T max in the TPD profile of Fig. 1.…”

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confidence: 88%

Towards a structure-performance relationship for hydrogen storage in Ti-doped NaAlH₄nanoparticles

et al. 2011

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Hydrogen storage properties of Ti-doped nanosized (B20 nm) NaAlH 4 supported on carbon nanofibers were affected by the stage at which Ti was introduced. When Ti was deposited first followed by NaAlH 4, sorption properties were superior to the case where NaAlH 4 was deposited first followed by NaAlH 4 . This was the result of both a smaller NaAlH 4 particle size and the more extensive catalytic action of Ti in the former material.Sodium alanate has become a show-case for research on lightweight complex metal hydrides for hydrogen storage. 1 Nevertheless, hydrogen release rates and absorption rates are often impeded in metal hydrides and need to be improved. 2 Most effective in improving the performance of metal hydrides are reducing the particle size to the nm range (typically below 30 nm) 3-13 or adding one or more promoters/catalysts to bulk materials. [14][15][16][17][18][19][20][21][22][23][24][25]

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Ti-doped alkali metal aluminium hydrides as potential novel reversible hydrogen storage materials

Cited by 1,745 publications

References 11 publications

Exploration of the Nature of Active Ti Species in Metallic Ti-Doped NaAlH₄

Exploration of the Nature of Active Ti Species in Metallic Ti-Doped NaAlH₄

High capacity hydrogenstorage materials: attributes for automotive applications and techniques for materials discovery

Towards a structure-performance relationship for hydrogen storage in Ti-doped NaAlH₄nanoparticles

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Ti-doped alkali metal aluminium hydrides as potential novel reversible hydrogen storage materials

Cited by 1,745 publications

References 11 publications

Exploration of the Nature of Active Ti Species in Metallic Ti-Doped NaAlH4

Exploration of the Nature of Active Ti Species in Metallic Ti-Doped NaAlH4

High capacity hydrogenstorage materials: attributes for automotive applications and techniques for materials discovery

Towards a structure-performance relationship for hydrogen storage in Ti-doped NaAlH4nanoparticles

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Product

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Exploration of the Nature of Active Ti Species in Metallic Ti-Doped NaAlH₄

Exploration of the Nature of Active Ti Species in Metallic Ti-Doped NaAlH₄

Towards a structure-performance relationship for hydrogen storage in Ti-doped NaAlH₄nanoparticles