Hydrogen generation from a sodium borohydride-nickel core@shell structure under hydrolytic conditions.

Sodium borohydride (NaBH 4 ) is an attractive hydrogen carrier owing to its reactivity with water: it can generate 4 equivalents of H 2 by hydrolysis (NaBH 4 + 4H 2 O → NaB(OH) 4 + 4H 2 ). Since using NaBH 4 in the solid state is the most favorable way to achieve a high gravimetric hydrogen storage capacity (theoretical maximum of 7.3 wt%), we have investigated the possibility of developing a core@shell nanocomposite (NaBH 4 @Ni) where a metallic nickel catalyst facilitating the hydrolysis is directly supported onto NaBH 4 nanoparticles. Following our initial work on core-shell hydrides, the successful preparation of NaBH 4 @Ni has been confirmed by TEM, EDS, IR, XRD and XPS. During hydrolysis, the intimately combined Ni 0 and NaBH 4 allow the production of H 2 at high rates ( e.g. 6.1 L min -1 g -1 at 39 °C) when water is used in excess. After H 2 generation, the spent fuel is composed of an aqueous solution of NaB(OH) 4 and a nickel-based agglomerated material in the form of Ni(OH) 2 as evidenced by TEM, XPS and XRD. The effective gravimetric hydrogen storage capacity of nanosized NaBH 4 @Ni has been optimized by adjusting the required amount of water for hydrolysis and an effective hydrogen capacity of 4.4 wt% has been achieved. This is among the best reported values.