Oxygen defects and S-scheme heterojunctions synergistically promote the photocatalytic hydrogen evolution activity and stability of WO2.72/Zn0.5Cd0.5S-DETA nanocomposites

Abstract

The study analyzed the impact of oxygen defects and S-scheme heterojunction on the performance and stability of WO2.72/Zn0.5Cd0.5S-DETA (WO/ZCS) nanocomposites photocatalysts for hydrogen evolution. Results showed that ZCS alone under visible light had good photocatalytic hydrogen evolution activity (1.762 mmol g−1h−1) and stability (79.5 % activity retention rate after seven cycles, 21 h). The WO3/ZCS nanocomposites with S-scheme heterojunction had better hydrogen evolution activity (2.287 mmol g−1h−1), but poor stability (41.6 % activity retention rate). The WO/ZCS nanocomposites with S-scheme heterojunction and oxygen defects showed excellent photocatalytic hydrogen evolution activity (3.94 mmol g−1h−1) and stability (89.7 % activity retention rate). The specific surface area measurement and ultraviolet–visible spectroscopy diffuse reflectance spectroscopy indicate that oxygen defects lead to larger specific surface area and improved light absorption, respectively. The charge density difference confirms the existence of the S-scheme heterojunction and the amount of charge transfer, which accelerates the separation of photogenerated electron-hole pairs and enhances the utilization efficiency of light and charge. This study offers a new approach using the synergistic impact of oxygen defects and S-scheme heterojunction to enhance the photocatalytic hydrogen evolution activity and stability.