Nanocrystalline cobalt–nickel–boron (metal boride) catalysts for efficient hydrogen production from the hydrolysis of sodium borohydride

Innovative metal boride nanocatalysts containing crystalline Co–Ni based binary/ternary boride phases were synthesized and used in the hydrolysis of NaBH₄. All the as-prepared catalysts were in high-purity with average particle sizes ranging between ~51 and 94 nm and consisting of different crystalline phases (e.g. CoB, Co₂B, Co₅B₁₆, NiB, Ni₄B₃, Ni₂Co_0·67B_0.33). The synergetic effect of the different binary/ternary boride phases in the composite catalysts had a positive role on the catalytic performances thus, while the binary boride containing phases of unstable cobalt borides or single Ni₄B₃ were not showing any catalytic activity. The Co–Ni–B based catalyst containing crystalline phases of CoB–Ni₄B₃ exhibited the highest H₂ production rate (500.0 mL H₂ min^?1 g_cat^?1), with an apparent activation energy of 32.7 kJ/mol. The recyclability evaluations showed that the catalyst provides stability even after the 5th cycle. The results suggested that the composite structures demonstrate favorable catalytic properties compared to those of their single components and they can be used as alternative and stable catalysts for efficient hydrogen production from sodium borohydride.