Accelerate charge separation in CuO/MoO photocathode for photoelectrocatalytic hydrogen evolution.

Photoelectrocatalyzing water reduction is a potential approach to building a green and sustainable society. As a benchmark photocathode, CuO receives much attention but faces serious charge recombination and photocorrosion. This work prepared an excellent CuO/MoO photocathode via in situ electrodeposition. A systematical study of theory and experiment demonstrates that MoO not only effectively passivates the surface state of CuO as well as accelerates reaction kinetics as a cocatalyst, but also promotes the directional migration and separation of photogenerated charge. As expected, the constructed photocathode exhibits a highly enhanced photocurrent density and an appealing energy transformation efficacy. Importantly, MoO can inhibit the reduction of Cu in CuO via a formed internal electric field and shows excellent photoelectrochemical stability. These findings pave the way to designing a high-activity photocathode with high stability.