Strengthened Built-In Electric Field in Sulfur-Doped BiOBr Facilitates Exciton Dissociation and Boosts Photocatalytic Activity

The effective promotion of exciton dissociation to increase the electron density in BiOBr has garnered significant attention. Here, we effectively promote exciton dissociation and enhance photocatalytic activity through a simple sulfur-doped strategy. We demonstrated that sulfur doping markedly increased the built-in electric field (BIEF) strength of BiOBr, which in turn provided the driving force for exciton dissociation and promoted the rapid separation and transport of charge carriers. Additionally, the introduction of abundant oxygen vacancies on BiOBr enhanced its ability to activate oxygen. Consequently, in degradation experiments, S-doped BiOBr exhibited an 8.07-fold increase in the degradation rate of sulfisoxazole (SIZ) compared to that of pure BiOBr. Following this, quenching experiments and electron spin resonance identified holes, superoxide, and singlet oxygen as the primary reactive species involved in photocatalysis, leading to the proposal of a photocatalytic mechanism. Furthermore, liquid chromatography-mass spectrometry identified 8 intermediate products and elucidated three degradation pathways. Finally, the impact of different influencing conditions on the degradation of the SIZ was thoroughly examined. To summarize, this study proposes a strategy to enhance photocatalytic activity by adjusting the BIEF and manipulating exciton effects, providing a new perspective on charge transfer mechanisms in photocatalytic systems.