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

Sodium borohydride (NaBH) is an attractive hydrogen carrier owing to its reactivity with water: it can generate 4 equivalents of H by hydrolysis (NaBH + 4HO → NaB(OH) + 4H). Since using NaBH 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@Ni) where a metallic nickel catalyst facilitating the hydrolysis is directly supported onto NaBH nanoparticles. Following our initial work on core-shell hydrides, the successful preparation of NaBH@Ni has been confirmed by TEM, EDS, IR, XRD and XPS. During hydrolysis, the intimately combined Ni and NaBH allow the production of H at high rates ( 6.1 L min g at 39 °C) when water is used in excess. After H generation, the spent fuel is composed of an aqueous solution of NaB(OH) and a nickel-based agglomerated material in the form of Ni(OH) as evidenced by TEM, XPS and XRD. The effective gravimetric hydrogen storage capacity of nanosized NaBH@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.