Elegant design and construction of S-scheme ZnWO₄/Zn₃In₂S₆ heterojunction photocatalysts for efficient hydrogen evolution

Novel S-scheme ZnWO₄/Zn₃In₂S₆ heterojunction photocatalysts were designed and constructed herein by a facile two-step hydrothermal method to enhance photocatalytic performance for hydrogen evolution. The experimental results and analysis demonstrated that the heterojunction structure effectively promotes separation of photogenerated electron-hole pairs, suppresses charge carrier recombination and retains charge carriers with high redox capacity participating in the catalytic reaction, thereby significantly improving the photocatalytic activity. For instance, 0.2ZnWO₄/Zn₃In₂S₆ (0.2ZW/ZIS) heterojunction photocatalyst achieved the highest hydrogen evolution rate of 42.66 mmol g−1 h−1 under visible-light irradiation, which is approximately 7.28 times that of pure Zn₃In₂S₆. Both X-ray photoelectron spectroscopy and photoluminescence spectroscopy analysis confirmed that strong interfacial interactions exist between ZnWO₄ and Zn₃In₂S₆, following an S-scheme charge transfer mechanism rather than the conventional Type-II heterojunction pathway. It is believed that this study provides new insights for developing efficient, stable, and noble-metal-free S-scheme heterojunction photocatalysts towards hydrogen evolution.