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.