Tunable oxygen vacancies in BiOBr nanosheets: Enhanced photocatalytic degradation of tetracycline hydrochloride and perfluorooctanoic acid with distinct mechanisms

Perfluorooctanoic acid (PFOA) and tetracycline hydrochloride (TTCH) are typical emerging pollutants with distinct molecular structures. TTCH contains C–H bonds in its molecule, but PFOA does not contain C-H bonds. The absence of C–H bonds makes PFOA insensitive to free radicals such as •OH. This structural difference poses a significant challenge for the efficient degradation of both pollutants. In this study, BiOBr nanosheets with adjustable concentrations of oxygen vacancies (OVs) were synthesized through a facile hydrothermal process.The photocatalytic efficiencies of MP2-BiOBr for PFOA and TTCH degradation were 3.93 and 3.89 times those of BiOBr. Electrochemical results indicated that the improvement in charge separation efficiency was the primary factor enhancing the photocatalytic performance of catalysts after the introduction of OVs. Additionally, the photocatalytic degradation of TTCH mainly involved active species •O 2 − , while PFOA was degraded through a direct oxidation process by photogenerated h + . Two possible decomposition pathways of PFOA over MP2-BiOBr are illustrated. Furthermore, The structure-performance relationship between OV-modified BiOBr and improved photocatalytic performance was established. This study presents a facile method for introducing OVs into BiOBr and provides some new insights into the mechanisms of pollutant degradation. It offers a promising strategy for the efficient treatment of complex wastewater containing diverse contaminants.