Co(OH)2 promoting the catalytic activity of CoP/Ni2P heterojunction for hydrogen evolution in both alkaline and acid media

Developing non-precious metal catalysts to replace commercial Pt for hydrogen evolution reaction (HER) is extremely significant for practical application of water splitting. Here, we synthesized a composite CoP/Ni2P@Co(OH)2 catalyst via the sequential phase growth strategy. Owing to the cooperative effect between CoP/Ni2P and Co(OH)2, the CoP/Ni2P@Co(OH)2 catalyst presents excellent HER catalytic performance with 39 mV overpotential in 1 M KOH and 68 mV overpotential in 0.5 M H2SO4 to deliver the current density of 10 mA cm−2. By designing a control experiment, we found that the Co(OH)2 may promote water dissociation effectively in alkaline media and accelerate the generation of M-H∗ in acidic media, while CoP/Ni2P can serve as the active sites for the adsorption and desorption of hydrogen. The synergistic effects of CoP/Ni2P and Co(OH)2 greatly boost its HER catalytic performance in both alkaline and acid media. In short, the new finding of introducing Co(OH)2 into the CoP/Ni2P can accelerate the development of high-performance HER catalysts.