3D Zn3In2S6/TiO2 S-scheme heterojunctions with strong 2D/2D hetero-interface interaction enable highly efficient photocatalytic H2 production simultaneous with TC degradation

Abstract

Heterojunction-based photocatalysts have garnered significant attention for their potential in addressing energy shortages and environmental pollution through efficient H₂ production and antibiotic degradation. However, the development of bifunctional photocatalysts with high efficiency, stability, and broad-spectrum light absorption remains a challenge. In this study, we designed and synthesized 3D Zn₃In₂S₆/TiO₂ S-scheme heterojunctions with strong 2D/2D hetero-interface interactions via a two-step hydrothermal method. The primary objective was to enhance solar-driven photocatalytic performance for simultaneous H₂ production and tetracycline (TC) degradation. The key innovation lied in the optimized 2D/2D interfacial coupling and S-scheme charge transfer mechanism, which significantly improved charge separation efficiency and light utilization. When the molar ratio of Zn₃In₂S₆ to TiO₂ was 0.5:1, the Zn₃In₂S₆/TiO₂-II composite exhibited exceptional photocatalytic activity and stability, obtaining H₂ evolution rate of 6.74 mmol g⁻¹ h⁻¹ within 6 h and a TC degradation efficiency of 98 % within 60 min, both of which were substantially higher than those of pristine Zn₃In₂S₆ and TiO₂. The enhanced photocatalytic activities had been confirmed to be attributed to the increased specific surface area, accelerated charge separation, and the broadened light absorption range, as confirmed by various characterizations and density functional theory (DFT) calculations. Our findings pave the way for the development of advanced photocatalytic systems to simultaneously tackle environmental pollution and energy crises.