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.

光电化学（Photoelectrochemical，PEC）分解水是一种将太阳能直接转化为清洁氢能的有效途径。作为可见光响应型p型半导体，二铋酸铜（CuBi₂O₄）具有适宜的带隙与良好的化学稳定性，但其性能仍受限于较高的界面电阻与严重的载流子复合问题。本研究在氟掺杂氧化锡（Fluorine-doped Tin Oxide，FTO）与CuBi₂O₄之间引入CuO中间层，构建CuO/CuBi₂O₄光阴极，以优化界面电荷传输过程。研究结果表明，CuO/CuBi₂O₄-200在相对于可逆氢电极（Reversible Hydrogen Electrode，RHE）0 V电位下的光电流密度可达-1.71 mA/cm²，为纯相CuBi₂O₄的3.5倍以上；其365 nm处的入射光子-电流转换效率（Incident Photon-to-Current Efficiency，IPCE）提升至约13%，最大应用偏置光子-电能转换效率（Applied Bias Photon-to-Electrical Efficiency，ABPE）可达0.17%。析气实验结果显示，其氢气产率可达2.05 μmol/cm²，显著优于未修饰的光电阴极。机理研究表明，CuO中间层可实现匹配度优异的能带排布，促进空穴向FTO基底传输，并有效抑制界面载流子复合，从而显著提升电荷分离与传输效率。本工作提出了一种简便高效的界面调控策略，为基于半导体的高性能PEC光电阴极的设计与应用提供了新的思路与指导。