Accelerate charge separation in Cu₂O/MoO₂ photocathode for photoelectrocatalytic hydrogen evolution

Photoelectrocatalyzing water reduction is a potential approach to building a green and sustainable society. As a benchmark photocathode, Cu₂O receives much attention but faces serious charge recombination and photocorrosion. This work prepared an excellent Cu₂O/MoO₂ photocathode via in situ electrodeposition. A systematical study of theory and experiment demonstrates that MoO₂ not only effectively passivates the surface state of Cu₂O 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, MoO₂ can inhibit the reduction of Cu⁺ in Cu₂O 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.