Enhanced carrier separation and photocatalytic degradation of oxytetracycline via S-scheme MIL-53(Fe)/FeOCl heterojunction composites with peroxydisulfate activation

Visible light-driven photocatalysis often struggles with fast recombination of photogenerated electron-hole pair and unsatisfactory degradation efficiency of hazardous micropollutants, such as antibiotics. Constructing an effective heterojunction can address these challenges. In this study, a novel S-scheme MIL-53(Fe)/FeOCl heterojunction composite was synthesized using a hydrothermal method. Factors influencing oxytetracycline (OTC) removal and the underlying reaction mechanism were investigated. The MF-10 composite demonstrated a remarkable removal efficiency of 90 %, significantly higher than that of MIL-53(Fe), which was 54 %. Even after six cycles, the degradation efficiency only decreased by 8 %, and the composition of MF-10 remained unchanged, indicating excellent durability. The photocatalytic process involves crucial reactive species such as · OH, SO 4 • – , O 2 • – , and h + . The heterojunction construction extends the absorption range of visible light, and the internal electric field enhances the separation of photogenerated electron-hole pairs while maintaining robust electron and hole activity. Additionally, photogenerated electrons facilitate the Fe(II)/Fe(III) cycling, resulting in the production of more reactive species for OTC degradation. This work introduces a novel approach to enhance the activity of photocatalysts and provides valuable insights into the design of peroxydisulfate activators.