Zn3In2S6/Bi3O4Br nanoflowers with oxygen vacancies and heterojunctions: A strategy for enhanced nitrofurazone photodegradation

The degradation of antibiotics in wastewater poses a critical environmental challenge, necessitating the development of advanced photocatalysts capable of efficiently generating active species. Hence, a novel Zn 3 In 2 S 6 /Bi 3 O 4 Br (ZB) heterojunction enriched with oxygen vacancies (OVs) was designed. The optimized ZB-1 (mass percentage of Bi 3 O 4 Br to Zn 3 In 2 S 6  = 1 %) exhibited the highest nitrofurazone (NFZ) degradation rate constant ( k ) of 0.24 min −1 after 20 min illumination, which was 6.6 and 26.3 folds of the original Zn 3 In 2 S 6 and Bi 3 O 4 Br, respectively. ZB-1 also demonstrated excellent cycling durability and resistance to pH fluctuation. The OVs potentiated O 2 adsorption and drew the photogenerated electrons for oxygen (O 2 ) activation, thereby enhancing carrier mobility. Furthermore, the constructed heterojunction facilitated light absorption and carrier migration for O 2 activation. The OVs and heterojunctions collaboratively meliorated carrier utilization and active species generation. As a result, abundant superoxide radicals ( O 2 − ) were generated and significantly contributed to eliminating NFZ. Meanwhile, the photocatalytic mechanism was clarified by theoretical calculation. The degradation pathway of NFZ and the biotoxicity of its intermediates were systematically conjectured. This research provides a new perspective for designing efficient, durable, and reproducible photocatalysts, which can help address environmental issues related to antibiotic contamination.