Tapping high photocatalytic activity in an S-scheme CuBi2O4-TiO2 heterojunction via robust interfacial electronic interactions for enhanced solar‑hydrogen production

Solar water splitting represents a sustainable strategy for the production of clean hydrogen fuel. Nevertheless, the photocatalytic efficiency of water splitting remains limited by rapid electron-hole recombination and insufficient redox capability in conventional photocatalysts. Constructing S-scheme heterojunction photocatalysts offers an effective strategy to promote charge-carrier separation while retaining strong redox capabilities for solar-to‑hydrogen conversion. Herein, we report a rationally designed S-scheme p-n heterojunction comprising p -type CuBi 2 O 4 and n -type TiO 2 for photocatalytic hydrogen evolution without a noble-metal cocatalyst. Under the employed reaction conditions, pristine CuBi 2 O 4 exhibits no detectable H 2 evolution, whereas the optimized 1 wt% CuBi 2 O 4 -TiO 2 heterostructure achieves a hydrogen evolution rate of 639.8 μmol.g −1 .h −1 , representing an approximately 5.0-fold enhancement compared with pristine TiO 2 . The enhanced photocatalytic performance is associated with favorable interfacial charge transfer and separation arising from the CuBi 2 O 4 -TiO 2 interface. Experimental results, supported by density functional theory (DFT) calculations, provide evidence for the proposed S-scheme charge-transfer mechanism, which promotes efficient utilization of photogenerated charge carriers. This work demonstrates the potential of low-loading CuBi 2 O 4 -TiO 2 heterostructures for noble-metal-free photocatalytic hydrogen production and highlights the importance of interfacial electronic interactions in designing efficient heterojunction photocatalysts.