CuCrO₂ layer protected Cu₂O/CuO thin film as an efficient and stable photocathode for hydrogen evolution reaction

The practical application of Cu₂O/CuO photoelectrodes for solar-to-chemical conversion is severely limited by their rapid photocorrosion and insufficient operational stability. To address this challenge, we develop a triple-layered Cu₂O/CuO/CuCrO₂ heterostructure, in which a solution-processed CuCrO₂ layer serves as a stable and optically transparent protection barrier for the narrow-bandgap Cu₂O/CuO light absorber. The photocurrent density of Cu₂O/CuO/CuCrO₂ retained 71% of its initial value after extended stability tests, demonstrating over threefold enhancement versus unprotected Cu₂O/CuO electrode. Further surface modification with a NiO_x hydrogen evolution reaction catalyst yields a Cu₂O/CuO/CuCrO₂/NiO_x composite, which retains 76% of initial photocurrent after 120 min of continuous operation. The CuCrO₂ layer mitigates photocorrosion by preventing direct contact between Cu₂O/CuO and electrolyte, while NiO_x facilitates electrode-electrolyte interfacial charge transfer. This contribution demonstrates a cost-efficient method with great potential for constructing durable photocathodes, and provides a versatile material design principle for promoting the practical deployment of PEC energy conversion systems.