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 is inhibited by high interfacial resistance and severe charge carrier recombination. In this study, a CuO interlayer was introduced between fluorine-doped tin oxide (FTO) and CuBi2O4 to construct CuO/CuBi2O4 photocathodes, aiming to improve interfacial charge transfer. The results showed that CuO/CuBi2O4-200 exhibited a photocurrent density of −1.71 mA/cm2 at 0 V vs. RHE, which was more than 3.5 times higher than that of bare CuBi2O4. The incident photon-to-current efficiency (IPCE) at 365 nm was enhanced to ~13% and the maximum applied bias photon-to-current efficiency (ABPE) reached 0.17%. Water splitting experiments revealed a hydrogen yield of 2.05 μmol/cm2, significantly surpassing that of the unmodified photoelectrode. The enhanced PEC performance indicated that the CuO layer established a favorable band alignment, promoted hole transport toward the FTO substrate and effectively suppressed interfacial carrier recombination. This work demonstrated a simple and efficient interfacial engineering strategy, offering new insights and guidance for the design and development of high-performance semiconductor-based PEC photoelectrodes.