Enhanced Photocatalytic Activity of Lead-Free Cs₂TeBr₆/g-C₃N₄ Heterojunction Photocatalyst and Its Mechanism

In this study, a new type of lead-free double perovskite Cs2TeBr6 combined with metal-free semiconductor g-C3N4 heterojunction is constructed and used for photocatalytic CO2 reduction for the first time. The S-scheme charge transfer mechanism between Cs2TeBr6 and g-C3N4 is systematically verified by X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) and in situ Fourier infrared spectroscopy(FT-IR). The formation of S-type heterojunction makes the photocatalyst have higher charge separation ability and highest redox ability. The results show that 5%-CTB/CN heterojunction material has the best photocatalytic reduction effect on CO2 under visible light irradiation. After 3 h of illumination, the yield of CO and CH4 are 468.9 mu mol g(-1) and 61.31 mu mol g(-1), respectively. The yield of CO is 1.5 times and 32 times that of pure Cs2TeBr6 and g-C3N4, and the yield of CH4 is doubled compared with pure Cs2TeBr6. However, g-C3N4 almost does not produce CH4, which indicates that the construction of heterojunction helps to further improve the photocatalytic performance of the material. This study provides a new idea for the preparation of Cs2TeBr6/g-C3N4 heterojunction and its effective interfacial charge separation.