Bismuth-rich strategy intensifies the molecular oxygen activation and internal electrical field for the photocatalytic degradation of tetracycline hydrochloride

Bismuth-rich photocatalyst (Bi3O4Br) and BiOBr were prepared by a simple hydrothermal method with different pH values. The increase in the atomic ratio of Bi/Br led to an upshift in the conduction band minimum and enhancement of hybridization. Therefore, molecular oxygen activation and the internal electrical field were strengthened by the rich bismuth strategy, and it resulted in better photocatalytic degradation and mineralization of tetracycline hydrochloride (TC). Trapping agent experiments and ESR results indicated that the degradation process was dominated by ·O2- while 1O2 was also a key factor. The upshift of CBM from −0.34 eV (BiOBr) to −0.43 eV (Bi3O4Br) accelerated the production of ·O2-. At the same time, the highly efficient separation of photogenerated electron-hole pairs could be attributed to the transformation of O2/·O2- and enhancement of hybridization, which were proven by photoelectrochemical measurement, PL and time-resolved PL spectra. The degradation pathway of TC dominated by ·O2- and 1O2 was also discussed.