Amorphous Co₂B Grown on CoSe₂ Nanosheets as a Hybrid Catalyst for Efficient Overall Water Splitting in Alkaline Medium

In this work, we synthesized a novel hybrid catalyst (Co 2 B/CoSe 2 ) by growing amorphous Co 2 B on the surface of CoSe 2 nanosheets. Benefiting from the prominent coupled effects between Co 2 B and CoSe 2 nanosheets, an efficient oxygen evolution reaction catalyst Co 2 B/CoSe 2 exhibits a very low overpotential of 320 mV @ 10 mA cm –2 with a Tafel slope of 56.0 mV dec –1 in alkaline medium. An overpotential of 300 mV can also be achieved by Co 2 B/CoSe 2 at the same condition for hydrogen evolution reaction. Notably, at the applied potential of 1.73 V, the electrocatalyst Co 2 B/CoSe 2 demonstrates a current density of 10 mA cm –2 for overall water splitting and displays an outstanding long-term stability. The faradaic efficiencies of Co 2 B/CoSe 2 for both hydrogen and oxygen evolution are close to 100%.