Zn Vacancy-Regulated Zn0.4Cd0.6S for Enhanced Charge Separation and Boosted Photocatalytic H₂O₂ Generation

Photocatalytic H2O2 synthesis from O2 is a green and environmentally friendly route. However, due to the limitations of quick recombination of photogenerated electrons and limited O2 activation ability, photocatalytic reactions often exhibit low efficiency. In this study, Zn vacancy-engineered Zn0.4Cd0.6S (ZnV-ZCS) photocatalysts were successfully constructed via a hydrothermal strategy using L-cysteine as a coordination agent. The optimized ZnV-ZCS-10 catalyst achieves an impressive H2O2 production rate of 44.39 mmol/g within 1 h under 425 nm irradiation, approximately 2.3 times higher than that of pristine Zn0.4Cd0.6S (ZCS). Structural characterization and cycling performance tests confirm that the introduction of Zn vacancies does not alter the pristine hexagonal crystal phase of the material, demonstrating good stability. Photoelectrochemical and spectroscopic analyses reveal that Zn vacancies effectively enhance charge carrier separation and reduce charge transfer resistance. Meanwhile, the presence of cation vacancies reconstructs the local electronic environment, promoting the activity of the Zn0.4Cd0.6S catalyst for H2O2 production via the superoxide radical (·O2−)-mediated pathway. This work highlights the crucial role of cation vacancies in modulating carrier dynamics in sulfide semiconductors for efficient photocatalytic H2O2 production.