S-scheme heterojunction and heterovalent ion doping synergistically promote the visible light photocatalytic performance of hierarchical nanoflowers

This study proposes a combined strategy of defect engineering and construction of S-scheme heterojunction that produces synergistic photovoltaic effects and significantly enhances photocatalysis degradation of organic pollutants under visible-light. A three-dimensional hierarchical flower-like photocatalyst CdS@Gd-ZnO featuring S-scheme heterojunction was rationally constructed. CdS@Gd-ZnO was able to degrade 99 % of rhodamine B (RhB) (10 mg/L, 75 min) and 95 % of methylene blue (MB) (10 mg/L, 60 min) under visible-light. Also, it has an excellent ability to degrade antibiotics, with 93 % of tetracycline hydrochloride (TCH) (20 mg/L, 60 min) and 90 % of oxytetracycline (OTC) (20 mg/L, 60 min), respectively. It was found that a small amount of Gd3+ doping was not only conducive to introducing more oxygen defects, which provides a powerful tool for trapping electrons for charge transfer, but also caused the change of energy band structure, and ultimately enhanced the degradation of cationic pollutants. Accordingly, this strategy enhances the photocatalytic performance of CdS@Gd-ZnO, and the combined effect is significantly stronger than either alone. This work provides a new idea for the design of efficient heterojunction photocatalysts for energy and environmental applications.