One-pot synthesis of S-scheme WO3/BiOBr heterojunction nanoflowers enriched with oxygen vacancies for enhanced tetracycline photodegradation

Construction of S-scheme heterojunctions that efficiently separate photogenerated electrons and holes is an emerging strategy for the development of high-efficiency performance photocatalysts for the photodegradation of organic pollutants. In this study, S-scheme WO3/BiOBr heterojunction nanoflowers enriched with oxygen vacancies (Vo) were synthesized for the first time via a one-pot hydrothermal method without the addition of surfactants. The XPS characterization of the WO3/BiOBr-Vo indicated the formation of internal electric field at the WO3/BiOBr interface, which facilitated charge separation and charge transfer. The superior ability of WO3/BiOBr-Vo to separate photoinduced electron–hole pairs was confirmed by photoluminescence and photocurrent responses. As a result, the optimal 25WO3/BiOBr-Vo photocatalyst decomposed 100% tetracycline after 50 min of visible light irradiation while pure BiOBr-Vo and WO3 decomposed less than 90% and 40% of tetracycline, respectively. The EPR analysis and free radicals trapping experiments found that the O2− was the main active species in the photocatalytic mechanism. The oxygen vacancies provided readily accessible reaction sites for the conversion of O2 to O2−. Toxicity assessment revealed that the aquatic toxicity of tetracycline was efficiently reduced after photodegradation. This study demonstrated a promising method for the development of high-performance photocatalysts based on band structure optimization and crystal defect engineering.