Co-Ni-B nanocatalyst for efficient hydrogen evolution reaction in wide pH range

Amorphous Co-Ni-B nanocatalyst with high electrocatalytic activity toward hydrogen evolution reaction (HER) in wide pH range was successfully synthesized. The content of Ni was varied by adjusting the molar ratio Ni/(Ni + Co) in Co-Ni-B from 10% to 50% to identify the most suitable composition for HER. Co-30Ni-B (with 30% Ni/(Ni + Co)) showed the highest catalytic activity and could reach a current density of 10 mA/cm(2) at just 170 mV in pH 7 and 133 mV in pH 14. It also exhibited a Tafel slope value of 51 mV/dec in pH 7 suggesting Volmer-Heyrovsky reaction mechanism for HER. The role of each element in improving the activity was justified with results from XPS, XAS and DFT calculations. It was observed that the presence of Ni promotes higher electron density at Co active sites of Co-Ni-B which in turn facilitates efficient reduction reaction to enhance HER rate. Co-30Ni-B could sustain 1000 cycles and prolonged hours of operation for about 40 h without losing activity making it an excellent low-cost electrocatalyst material.