Micro-nanoporous MoO2@CoMo heterostructure catalyst for hydrogen evolution reaction

The synergetic effect at the interfaces between metal oxide and metal in heterostructures plays an essential role in electrocatalytic hydrogen production via water electrolysis. Here, a micro-nanoporous MoO2@CoMo heterostructure with high catalytic performance was simply fabricated electrochemically at room temperature and under ambient pressure. Controllable microporous CoMo networks were formed on the gas diffusion layer using hydrogen bubble-assisted electrodeposition. The following electrochemical etching at an appropriate potential produced a nanoporous surface via selective Co dissolution, accompanied by the formation of Mo oxide. Due to the significantly roughened morphology and the interfacial effect, the optimized MoO2@CoMo heterostructure catalyst exhibited a low overpotential of 76 mV for hydrogen evolution at −50 mA/cm2. Further analysis verified the crucial role of the Mo4+ ratio in the intrinsic activity. The insoluble Mo species passivated the MoO2 surface layer and sustained the Mo4+ ratio, leading to excellent stability of the MoO2@CoMo heterostructure catalyst in long-term operation.