S-scheme ZnIn2S4/α-Fe2O3 heterojunction with interfacial SO bonds accelerating the Fe3+/Fe2+ cycle for Photoelectro self-Fenton degradation of tetracycline hydrochloride

The visible-light-driven photoelectro-Fenton technology integrates the synergistic advantages of photoelectrocatalysis and the Fenton reaction. However, the design of current photoanode materials still suffers from issues such as low interfacial charge transfer efficiency and insufficient exposure of active sites. In this study, a novel S-scheme ZnIn 2 S 4 /α-Fe 2 O 3 heterojunction photoanode was successfully constructed. The built-in electric field established at the S-scheme heterointerface effectively facilitates the spatial separation of photogenerated charge carriers. The S O bonds formed at the two-phase interface serve as atomic-level electron transport channels, enabling rapid and directional transfer of photogenerated electrons enriched in the conduction band of ZnIn 2 S 4 to the Fe 3+ sites on the α-Fe 2 O 3 surface, where Fe 3+ is reduced to Fe 2+ . The generated Fe 2+ promotes the conversion of H 2 O 2 to produce hydroxyl radicals (·OH), while the regenerated Fe 3+ from the reaction is again reduced to Fe 2+ by photogenerated electrons, establishing a self-sustaining cycle that endows the system with highly efficient oxidative degradation capability. The results demonstrate that the synergistic mechanism leads to a 5.55-fold increase in the degradation rate. Benefiting from the efficient directional charge transfer and separation, the total organic carbon (TOC) removal efficiency reaches 80.09% within 60 min.