Synergistic effects of N/S co-doped carbon and oxygen vacancies on peony-like BiOBr toward enhanced photocatalytic degradation of pollutants.

Photocatalytic membrane technology presents a promising strategy to remove emerging contaminants from aquatic environments, effectively resolving the issues of powder photocatalyst recovery and secondary pollution. Herein, an N/S co-doped carbon-coated BiOBr (NSCB) heterojunction with oxygen vacancies (OVs) was successfully prepared using a hydrothermal method and subsequently immobilized into a porous polyvinylidene fluoride (PVDF) membrane via the phase inversion. The synergistic effects of N/S co-doped biomass-derived carbon and OVs on peony-like BiOBr effectively facilitate the separation of photogenerated electron-hole (e--h+) pairs, thereby boosting the photocatalytic degradation performance. The N/S co-doped carbon coating promotes the visible light absorption of the composites, while the peony-like structure of BiOBr-OV provides a larger specific surface area, offering more active sites for photocatalytic reactions. After 60 min visible light irradiation, the optimized 30-NSCB-OV photocatalyst and its composite membrane exhibit significantly higher efficiency (92.7% and 91.0%) for ciprofloxacin (CIP) degradation compared to pristine BiOBr and BiOBr-OV. Based on experimental and theoretical calculations, superoxide radicals (•O2-) and h+ were identified as the main active species for degrading CIP, and a S-scheme heterojunction photocatalytic mechanism and interfacial charge transfer direction were proposed. This study provides a new insight for constructing non-metallic organic carbon and inorganic oxides heterojunctions, further promoting the development of photocatalytic membranes for dynamic aquatic environmental remediation.