Sulfur Vacancy-Engineered 2D/2D ZnIn₂S₄/Zn-TCPP S-Scheme Heterojunction for Efficient Photocatalytic H₂O₂ Production

The sustainable and efficient synthesis of hydrogen peroxide (H₂O₂) through photocatalysis remains highly desirable but challenging due to sluggish reaction kinetics and charge recombination. Herein, we report a sulfur vacancy-engineered 2D/2D S-scheme heterojunction constructed via the in situ growth of sulfur-vacancy-rich ZnIn₂S₄ (Vs-ZIS) nanosheets on Zn-TCPP (ZT) nanosheets for efficient H₂O₂ production. The intimate heterojunction interface facilitates rapid and directional separation of photogenerated electron-hole pairs while simultaneously retaining strong redox capability. Moreover, experimental results and density functional theory (DFT) calculations reveal that the introduced sulfur vacancies act as critical active sites, which significantly enhance the adsorption and activation of both O₂ and H₂O molecules. As a result, the optimized Vs-ZIS/ZT-20 heterojunction photocatalyst achieves a superior photocatalytic H₂O₂ production rate of 658.0 µmol·g^-1·h^-1 under visible-light irradiation (300 W) in pure water without sacrificial electron donors, which is 4.3 and 5.1 times higher than that of pristine Vs-ZIS and ZT nanosheets, respectively. Crucially, the as-prepared catalyst exhibits robust photocatalytic activity across diverse water sources, confirming its practical applicability. This work provides new insights into designing defect-rich S-scheme photocatalysts for green energy applications.