Hydrogen release from Li alanates originates in molecular lattice instability emerging at <b>∼</b>100 K

Tomiyasu, Keisuke; Sato, Toyoto; Horigane, Kazumasa; Orimo, Shin Ichi; Yamada, K.

doi:10.1063/1.4712053

Cited by 9 publications

(7 citation statements)

References 23 publications

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“…4). Although a prominent softening is confirmed in [AlH 4 ] À librational modes as observed in LiAlH 4 , 6 a shift in the translational modes to lower frequencies are also observed (see Fig. 4) in this study because of the high resolution of INS spectroscopy.…”

supporting

confidence: 50%

“…5a,b,d-f Recently, we observed intrinsic anharmonicity of librational modes of the complex anion [AlH 4 ] À on LiAlH 4 before hydrogen release. 6 Such a phenomenon was also observed in a complex hydride, LiBH 4 , with Li + ionic conduction. 7 Although the vibrational dynamics (librational modes of a complex anion) could be one key issue to understand the functionality of complex hydrides, the relationship has not been elucidated properly yet.…”

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confidence: 75%

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Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations

et al. 2016

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confidence: 50%

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confidence: 75%

Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations

et al. 2016

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“…Tomiyasu et al recently showed that in the case of LiAlH 4 , the decomposition stems from a lattice instability attributed to the weak of binding of the complex anions in the lattice [81].…”

Section: Thermodynamics and Decomposition Pathwaysmentioning

confidence: 99%

“…• C [37,38,81,83]: [33], and (c) LiAlH 4 [27] showing exothermic (positive peaks) and endothermic (negative peaks) transitions.…”

Section: ∼100mentioning

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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“…The hydrogen states in LaMg 2 NiH 7 and LaMg 2 NiH 4.6 were investigated by inelastic neutron scattering (INS), which provides access to all hydrogen-vibrational modes in materials. In particular, the hydrogen contributions to hydrogen vibrations, which are related to the hydrogen-state environments in compounds, can be clearly observed by INS − because hydrogen is approximately 10 times larger than other elements in a coherent neutron-scattering cross section (80.26 barns, 1 barn = 1 × 10 –24 cm 2 ). Furthermore, INS can assess hydrogen-vibrational dynamics in metallic hydrides, such as LaMg 2 NiH 4.6 , whereas it is difficult to observe vibrations in metallic compounds by the conventional Raman and infrared spectroscopies, so that vibrational dynamics in these metallic systems cannot be properly studied by methods other than INS.…”

Section: Introductionmentioning

confidence: 99%

Evidence of Intermediate Hydrogen States in the Formation of a Complex Hydride

et al. 2017

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A complex hydride (LaMgNiH) composed of La, two Mg, [NiH] with a covalently bonded hydrogen, and three H was formed from an intermetallic LaMgNi via an intermediate phase (LaMgNiH) composed of La, Mg, NiH, NiH units, and H atoms at tetrahedral sites. The NiH and NiH units in LaMgNiH were reported as precursors for [NiH] in LaMgNiH [ Miwa et al. J. Phys. Chem. C 2016 , 120 , 5926 - 5931 ]. To further understand the hydrogen states in the precursors (the NiH and NiH units) and H atoms at the tetrahedral sites in the intermediate phase, LaMgNiH, we observed the hydrogen vibrations in LaMgNiH and LaMgNiH by using inelastic neutron scattering. A comparison of the hydrogen vibrations of the NiH and NiH units with that of [NiH] shows that the librational modes of the NiH and NiH units were nonexistent; librational modes are characteristic modes for complex anions, such as [NiH]. Furthermore, the hydrogen vibrations for the H atoms in the tetrahedral sites showed a narrower wavenumber range than that for H and a wider range than that for typical interstitial hydrogen. The results indicated the presence of intermediate hydrogen states before the formation of [NiH] and H.

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Hydrogen release from Li alanates originates in molecular lattice instability emerging at ∼100 K

Cited by 9 publications

References 23 publications

Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations

Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations

Metastable Metal Hydrides for Hydrogen Storage

Evidence of Intermediate Hydrogen States in the Formation of a Complex Hydride

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