Insights into nitrogen-doped BiOBr with oxygen vacancy and carbon quantum dots photocatalysts for the degradation of sulfonamide antibiotics: Actions to promote exciton dissociation and carrier migration

[Display omitted] •Significantly enhances exciton dissociation and facilitates carrier transfer.•Featuring abundant oxygen vacancies and achieving notable O2 activation efficiency.•Demonstrates outstanding photocatalytic activity under low-power blue LED.•Detailed photocatalytic mechanisms and degradation pathways were proposed. The strong excitonic effect significantly influences the efficiency of electron-hole pair generation. Therefore, promoting the dissociation of excitons into free charge carriers has drawn much attention. In this study, nitrogen (N)-doped BiOBr photocatalyst (BOBNC) modified with carbon quantum dots (CQDs) was synthesized via a solvothermal method. We demonstrated through photoluminescence and photoelectrochemical techniques the synergistic effect of oxygen vacancies and CQDs, facilitating exciton dissociation and charge carrier migration, consequently significantly enhancing the electron density in the material. Compared to pure BiOBr, degradation experiments revealed that the optimized doping ratio of 0.5BOBNC with CQDs increased the rate constant for sulfamethoxazole (SIZ) by 19.89 times. Furthermore, based on quenching experiments, electron spin resonance (ESR) tests, and DFT calculations, h+, O2•− and 1O2 were identified as the primary reactive species for SIZ degradation, and a photocatalytic mechanism was proposed. Additionally, the influence of various environmental factors on the photocatalytic system was investigated. In conclusion, this work not only contributes to a profound understanding of BiOBr exciton dissociation but also presents a promising photocatalytic technique for the remediation of diverse water environments.