Significantly Enhanced Photocatalytic Performance of the g-C₃N₄/ Sulfur-Vacancy-Containing Zn₃In₂S₆ Heterostructure for Photocatalytic H₂ and H₂O₂ Generation by Coupling Defects with Heterojunction Engineering

Light-driven splitting of water to produce H-2 and reduction of molecular oxygen to synthesize H2O2 from water are the emerging environmentally friendly methods for converting solar energy into green energy and chemicals. In this paper, vacancy defect and heterojunction engineering effectively adjusted the conduction band position of Zn3In2S6, enriched the electron density, broadened the optical absorption range, increased the specific surface area, and accelerated the charge carrier transfer and separation of g-C3N4/sulfur-vacancycontaining Zn3In2S6 (CN/Vs-ZIS) heterostructures. As a result, all of the CN/Vs-ZIS heterostructures possessed greatly enhanced photocatalytic activities and the optimized sample 2CN/Vs-ZIS exhibited the highest visible-light photocatalytic performance. The rate of generation of H-2 of 2CN/Vs-ZIS under visible light (lambda > 420 nm) was 6.55 mmol g(-1) h(-1), which was 1.76 and 6.06 times higher than those of Vs-Zn3In2S6 and g-C3N4, respectively, and the apparent quantum yield (AQY) was 18.6% at 420 nm. Meanwhile, the 2 h yield of H2O2 of 2CN/Vs-ZIS was 792.02 mu M, similar to 4.72 and similar to 6.04 times higher than those of pure Vs-Zn3In2S6 and g-C3N4, respectively. The enhanced reaction mechanisms for the production of photocatalytic H2 and H2O2 were also investigated. This work undoubtedly demonstrates that the synergistic effects of defect and heterojunction engineering will be the great promise for improving the photocatalytic efficiency of Zn3In2S6-based materials.