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

New reversible hydrogen storage systems are proposed, based on catalyzed reactions (Eqs. 4-6). The catalytic acceleration of the reactions in both directions is achieved by doping alkali metal aluminium hydrides with a few mol% of selected Ti compounds. The PCI diagrams of the Ti catalyzed systems show an absence of hysteresis and nearly horizontal pressure plateaus. The PCI of the NaAlH4 system reveals two temperature-dependent pressure plateaus, corresponding to the two-step reversible dissociation of NaAlH4. The PCI of the Na3AlH6 system shows only one pressure plateau; the latter can be lowered by partial substitution of Na by Li. Ln cyclic tests, reversible H-2 capacities of 4.2-3.1 and 2.7-2.1 wt% H have been achieved.