S-Scheme WO3/SnIn4S8 Heterojunction for Water Purification: Enhanced Photocatalytic Performance and Mechanism

Photocatalysis is a promising technology for removing micropollutants in water. However, developing efficient and stable catalysts remains a challenge. In this work, a novel step-scheme (S-scheme) heterojunction of WO3/SnIn4S8 (WSI) was constructed through the combined process of in situ precipitation with hydrothermal synthesis to simultaneously realize photocatalytic degradation of bisphenol A(BPA) and reduction of Cr(VI) in contaminated water. Results showed that the WSI S-scheme heterojuction has a synergistic effect for the removal of BPA and Cr(VI). An optimum case of the WSI-12% heterojunction exhibited the highest photocatalytic efficiency in the degradation of BPA under visible light, which is ca. 2.5 and 3.8 times more than the pure WO(3 )and SIS, respectively. The enhanced photocatalytic activity is attributed to the formation of the WSI S-scheme heterojunctions which facilitate the spatial separation of charge carriers and preserve strong photoredox ability. Further, the S-scheme mechanism of enhanced photocatalysis was examined by the radical-trapping experiment and ESR, and superoxide and hydroxyl radicals were determined to be the major reactive oxygen species responsible for BPA degradation and Cr(VI) reduction by WSI. This work provides a novel strategy for tailoring high-performance S-scheme heterojunctions and shows the promising application in purifying wastewater with complex pollutants.