Hydrogen storage in complex metal hydrides

Abstract

Complex metal hydrides such as sodium aluminohydride (NaAlH 4 ) and sodium borohydride (NaBH 4 ) are solid-state hydrogen-storage materials with high hydrogen capacities. They can be used in combination with fuel cells as a hydrogen source thus enabling longer operation times compared with classical metal hydrides. The most important point for a wide application of these materials is the reversibility under moderate technical conditions. At present, only NaAlH 4 has favourable thermodynamic properties and can be employed as a thermally reversible means of hydrogen storage. By contrast, NaBH 4 is a typical non--reversible complex metal hydride; it reacts with water to produce hydrogen.

Combined x-ray photoelectron spectroscopy and scanning electron microscopy studies of the LiBH4–MgH2 reactive hydride composite with and without a Ti-based additive

“…The texture of the LiBH 4 matrix shows a strong rugosity most probably due to the characteristic decomposition of borohydrides under electron beam irradiation. 22,34,35 Oxygen appears in most regions although some MgH 2 particles are poorer in oxygen ͑as the one showed in Fig. 12͒.…”

“…28 The Auger parameter corresponding to MgB 2 is evaluated to be 1234.9 eV in our measurements in agreement with the 1234. 35 28,30 The B 1s peak in LiBH 4 shows two different chemical states: the hydride phase and the associated oxide. The hydride phase LiBH 4 appears at 187.8 eV whereas the oxide phase at 192.0 eV corresponds to B 2 O 3 which are both in agreement with the literature values.…”

Sodium-based hydrides for thermal energy applications

“…[12][13][14] although the overall process was not reversible under more moderate conditions until 1997 [92]. This was achieved by the addition of a suitable titanium-based catalyst and since then multiple investigations have been undertaken into this process [34,[93][94][95][96][97][98][99][100][101][102]. Binary alkali aluminium hexahydrides (SBHs Category I) decompose via a very similar pathway (Eq.…”

Lightweight sodium alanate thin films grown by reactive sputtering

“…Among them, sodium alanate ͑NaAlH 4 ͒ is regarded as the most promising candidate, due to its high hydrogen capacity ͑5.6 wt %͒ and suitable thermodynamic stability for reversible hydrogen storage in conjunction with proton exchange membrane fuel cells. [1][2][3] The thermodynamic and kinetic conditions for hydrogen absorption and desorption can be improved by adding a Ticontaining dopant ͓metallic Ti or TiCl 3 ͑Refs. 4 and 5͔͒.…”

“…This result opens the route to the analysis of the storage properties of the sodium alanate and other lightweight complex metal hydrides, such as LiAlH 4 , with combinatorial techniques. 3 A schematic view of the setup used for the deposition and optical characterization is shown in Fig. 1.…”