Structures and thermodynamics of the mixed alkali alanates

Graetz, Jason; Lee, Yong Jae; Reilly, J.J.; Park, S.; Vogt, Thomas

doi:10.1103/physrevb.71.184115

Cited by 85 publications

(107 citation statements)

References 32 publications

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“…Catalyzed sodium aluminum hydride is capable of cycling approximately twice the hydrogen (on a weight basis) of any of the conventional metal hydrides (e.g., FeTiHx). Since this discovery, hydrogen reversibility has been demonstrated in other complex hydrides including Na 2 LiAlH 6 , KAlH 4 , K 3 AlH 6 , K 2 LiAlH 6 , and K 2 NaAlH 6 [9][10][11].…”

Section: Metal Hydrides and Complex Hydridesmentioning

confidence: 99%

Metastable Metal Hydrides for Hydrogen Storage

Graetz

2012

ISRN Materials Science

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The possibility of using hydrogen as a reliable energy carrier for both stationary and mobile applications has gained renewed interest in recent years due to improvements in high temperature fuel cells and a reduction in hydrogen production costs. However, a number of challenges remain and new media are needed that are capable of safely storing hydrogen with high gravimetric and volumetric densities. Metal hydrides and complex metal hydrides offer some hope of overcoming these challenges; however, many of the high capacity "reversible" hydrides exhibit a large endothermic decomposition enthalpy making it difficult to release the hydrogen at low temperatures. On the other hand, the metastable hydrides are characterized by a low reaction enthalpy and a decomposition reaction that is thermodynamically favorable under ambient conditions. The rapid, low temperature hydrogen evolution rates that can be achieved with these materials offer much promise for mobile PEM fuel cell applications. However, a critical challenge exists to develop new methods to regenerate these hydrides directly from the reactants and hydrogen gas. This spotlight paper presents an overview of some of the metastable metal hydrides for hydrogen storage and a few new approaches being investigated to address the key challenges associated with these materials.

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Section: Metal Hydrides and Complex Hydridesmentioning

confidence: 99%

Metastable Metal Hydrides for Hydrogen Storage

Graetz

2012

ISRN Materials Science

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“…Several mixed M 3 AlH 6 compounds have also been observed experimentally or shown theoretically to be stable under ambient conditions. The compounds Na 2 LiAlH 6 , K 2 NaAlH 6 , and K 2 LiAlH 6 all crystallize in the face centered cubic m Fm3 structure at atmospheric pressure [36], but nothing is yet known about possible high-pressure phases of these materials.…”

mentioning

confidence: 99%

“…KAlH 4 is predicted to be stable under pressure and to keep its orthorhombic Pnma structure at least up to 100 GPa [15,35], while the closely related K 3 AlH 6 is predicted to have two structural transformations under pressure [36]. The monoclinic P2 1 /n α phase should first transform near 53 GPa into a tetragonal I4/mmm structure, then near 60 GPa into a high pressure Pnnm orthorhombic structure.…”

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confidence: 99%

Pressure-Temperature Phase Relations in Complex Hydrides

Sundqvist

2009

SSP

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Abstract. Interest in hydrogen as a future energy carrier in mobile applications has led to a strong increase in research on the structural properties of complex alkali metal and alkaline earth hydrides, with the aim to find structural phases with higher hydrogen densities. This contribution reviews recent work on the structural properties and phase diagrams of these complex hydrides under elevated pressures, an area where rapid progress has been made over the last few years. The materials discussed in greatest detail are LiAlH 4 , NaAlH 4 , Li 3 AlH 6 , Na 3 AlH 6 , LiBH 4 , NaBH 4 , and KBH 4 . All of these have been studied under high pressure by various methods such as X-ray or neutron scattering, Raman spectroscopy, differential thermal analysis or thermal conductivity measurements in order to find information on their structural phase diagrams. Based mainly on experimental studies, preliminary or partial phase diagrams are also given for six of these materials. In addition to this information, data are provided also on experimental results for a number of other complex hydrides, and theoretical predictions of new phases and structures under high pressures are reviewed for several materials not yet studied experimentally under high pressure.

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“…NaK 2 AlH 6 can be readily formed by ball milling alone [32] as well as by the molten state process as is shown in Figure 3. Sorby et al [33] found that NaK 2 AlH 6 is more thermodynamically stable than both Na 3 AlH 6 and K 3 AlH 6 .…”

Section: Resultsmentioning

confidence: 99%

Investigation of the thermodynamics governing metal hydride synthesis in the molten state process

Stowe

Berseth

Farrell

et al. 2008

Journal of Alloys and Compounds

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Complex metal hydrides have been synthesized for hydrogen storage through a new synthetic technique utilizing high hydrogen overpressure at elevated temperatures (molten state processing). This synthesis technique holds the potential of fusing different complex hydrides at elevated temperatures and pressures to form new species with enhanced hydrogen storage properties. Formation of these compounds is driven by thermodynamic and kinetic considerations. We report on investigations of the thermodynamics. Novel synthetic complexes were formed, structurally characterized, and their hydrogen desorption properties investigated. The effectiveness of the molten state process is compared with mechanicosynthetic ball milling.

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Structures and thermodynamics of the mixed alkali alanates

Cited by 85 publications

References 32 publications

Metastable Metal Hydrides for Hydrogen Storage

Metastable Metal Hydrides for Hydrogen Storage

Pressure-Temperature Phase Relations in Complex Hydrides

Investigation of the thermodynamics governing metal hydride synthesis in the molten state process

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