Interface Regulation for Enhanced Photoelectrochemical Performance of CuBi2O4 Photocathodes

• • The optimized CuO/CuBi2O4-200 photocathode achieved a photocurrent density of −1.71 mA/cm² at 0 V vs. RHE, a 3.5-fold improvement over bare CuBi2O4, directly addressing the bottleneck of low charge separation efficiency in PEC water splitting. • • IPCE at 365 nm was enhanced to ~13%, and the maximum ABPE reached 0.17%, indicating significant improvement in photon-to-current conversion efficiency, which is critical for practical solar-to-hydrogen conversion. • • Hydrogen yield reached 2.05 μmol/cm², surpassing the unmodified photoelectrode, demonstrating the CuO interlayer's effectiveness in promoting interfacial charge transfer and suppressing recombination, essential for scalable hydrogen production. • • The CuO interlayer functions as a hole-transport layer, reducing interfacial resistance and improving charge separation and injection efficiencies, as confirmed by mechanistic investigations, providing a robust strategy for enhancing PEC performance and operational stability.