S-scheme POM/MIL-101(Fe) heterojunction for photocatalytic decontamination of Cr(VI)

Heterojunction construction effectively enhances carrier separation efficiency and photocatalytic performance in semiconductors. In this study, a series of FePMo/MIL-101(Fe) heterojunctions with varying FePMo content were synthesized for the photocatalytic removal of Cr(VI) from wastewater. The photoinduced carriers were effectively separated via the S-scheme mechanism resulting from the spontaneously formed interfacial electric field. Tafel curves confirmed that the photoelectrochemical stability of the 2% FePMo/MIL-101(Fe) heterojunction was significantly improved, with a corrosion current density 100 times greater than that of MIL-101(Fe) under light, indicating superior photogenerated carrier separation and photocatalytic activity. Furthermore, the 2% FePMo/ MIL-101(Fe) heterojunction exhibited strong resistance to both anionic and cationic interference, demonstrating good adaptability in real water applications. After 10 consecutive cycles, the Cr(VI) removal efficiency remained high at 89%, substantially outperforming FePMo and MIL-101(Fe), which achieved removal efficiencies of 48% and 45%, respectively. Scavenger experiments demonstrated that photogenerated electrons played a dominant role in the photocatalytic reduction of Cr(VI), while superoxide radicals had a secondary contribution. This study highlights the potential of the FePMo/MIL-101(Fe) heterojunction in photocatalysis and offers insights for designing novel S-scheme heterojunction photocatalysts, enhancing the practical application of photocatalytic technology.