Synergistic Effects of Oxygen Vacancies, Bismuth-Rich Modification and Interface Electric Field: Boosting Visible-Light Photocatalytic Degradation of Tetracycline over Bi2WO6

Pure bismuth tungsten oxide (BWO) photocatalysts suffer from inherent limitations, including low charge carrier separation efficiency, a narrow visible light response range, and insufficient active surface sites, which restrict their practical applications in the treatment of organic pollutants in water. In this study, we successfully prepared bismuth-rich pentabismuth heptaoxide iodide (Bi 5 O 7 I)/oxygen vacancy bismuth tungsten oxide (Ov-Bi 2 WO 6 , OvBWO) composite photocatalysts with Bi 5 O 7 I mass fractions of 5%, 7%, 9%, 11%, and 13% through a simple ultrasonic-assisted self-assembly method. Photocatalytic performance tests revealed that the Bi 5 O 7 I/OvBWO composite with an 11% Bi 5 O 7 I mass fraction exhibited the optimal degradation rate, achieving a tetracycline (TC) removal rate of 89.3% within 60 min of visible light irradiation, representing improvements of 33.0% and 27.9% compared to BWO and BiOI, respectively. Experimental characterizations and density functional theory (DFT) calculations demonstrate that oxygen vacancies introduce defect levels into the bandgap of BWO, not only extending the visible light response range but also significantly increasing the specific surface area. The integration of bismuth-rich Bi 5 O 7 I with OvBWO forms a type II heterojunction, effectively enhancing the separation and migration efficiency of charge carriers. The synergistic effects of oxygen vacancies, bismuth-rich modification, and interfacial electric fields enhance both the mass transfer performance and photocatalytic activity of BWO, while markedly boosting the capacity for TC degradation. This research provides novel insights for the structural design and performance optimization of BWO-based photocatalysts and offers important technical references for the efficient remediation of organic pollutants in water.