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 H₂ 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-vacancy-containing 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 H₂ of 2CN/Vs-ZIS under visible light (λ > 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 μM, ∼4.72 and ∼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.