Interface Regulation for Enhanced Photoelectrochemical Performance of CuBi2O4 Photocathodes

Photoelectrochemical (PEC) water splitting is an effective approach to directly convert solar energy into clean hydrogen fuel. As a visible-light-responsive p-type semiconductor, CuBi2O4 possesses a suitable bandgap and good stability; however, its performance remains limited by high interfacial resistance and severe charge carrier recombination. In this study, a CuO interlayer was introduced between FTO and CuBi2O4 to construct CuO/CuBi2O4 photocathodes, aiming to improve interfacial charge transfer. The results showed that CuO/CuBi2O4-200 exhibits a photocurrent density of -1.71mA/cm2 at 0 V vs. RHE, which was more than 3.5 times higher than that of bare CuBi2O4. The IPCE at 365 nm was enhanced to ~13%, and the maximum ABPE reached 0.17%. Gas evolution experiments revealed a hydrogen yield of 2.05 μmol/cm2, significantly surpassing the unmodified photoelectrode. Mechanistic studies indicated that the CuO layer realizes favorable band alignment, enhances hole transport toward the FTO substrate, and effectively suppresses interfacial carrier recombination, thereby markedly improving charge separation and transfer. This work demonstrates a simple and efficient interfacial modulation strategy, providing new insights and guidance for the design and application of high-performance PEC photoelectrodes based on semiconductors.