Construction of Type-II Zn–SnO2/BiOBr heterojunctions with Dual-oxygen vacancies for enhanced photocatalytic degradation

Zn–SnO₂/BiOBr, a novel heterojunction material for photocatalytic dye degradation, was synthesized successfully using the one-step hydrothermal method. The formation of the heterojunction enhanced the vacancy coupling effect. The photocatalytic experiment results showed that the degradation rate of Rhodamine B (RhB) due to 0.3Zn–SnO₂/BiOBr (the heterojunction formed when the molar ratio of Zn–SnO₂ to BiOBr was 0.3) within 15 min was 9.27 and 476.9 times that of BiOBr and Zn–SnO₂, respectively. Additionally, the degradation rate of basic fuchsin (BF) due to 0.3Zn–SnO₂/BiOBr was 4.2 and 21.9 times that of BiOBr and Zn–SnO₂, respectively. The significantly improved photocatalytic performance was because many oxygen vacancies in Zn–SnO₂/BiOBr collaborated with the type-II heterojunction to promote a narrow bandgap value efficiently, increasing the photogenerated electrons (e^–) and hole (h⁺), an increased charge separation efficiency under visible light, and favored the photocatalytic degradation of dyes.