2D defect-engineered Ag-doped γ-FeO/BiVO: The effect of noble metal doping and oxygen vacancies on exciton-triggering photocatalysis production of singlet oxygen.

The selectivity of singlet oxygen (O) holds promising applications in complex environmental systems due to its ability to preferentially oxidize target pollutants. Usually, O in photocatalytic systems is generated via the electron transfer pathway and •O plays an important role as an intermediate, while the exciton-based energy transfer pathway for O generation has been less studied. Here, a 2D Ag-γ-FeO/BiVO with oxygen vacancies was designed which was capable of generating O by an exciton-based energy transfer-dominated approach, as strongly demonstrated by the results of steady-state fluorescence spectroscopy and phosphorescence spectroscopy. In the Z-type heterojunction photocatalyst system, Ag acted as an electron mediator to promote not only the generation of free carriers but also the generation of singlet excitons, while the appropriate concentration of oxygen vacancies further promotes the exciton-triggering photocatalysis production of O. The Ag-γ-FeO/BiVO could degrade 99.4% of sulfadiazine within 90 min, and O played an important role in the degradation of sulfadiazine, as shown by EPR and active species capture experiments. Ecotoxicity predictions indicated that the main byproducts of sulfadiazine degradation by Ag-γ-FeO/BiVO were low in toxicity. The prepared photocatalysts provide a new idea for obtaining O and designing photocatalysts with selectivity.