Synergistic Enhancement of Visible-Light-Driven Photocatalytic H2O2 Production over g-C3N4/ZnCdS by Zn Vacancies and Heterointerface Engineering

Hydrogen peroxide (H2O2) is an important green oxidant, and developing efficient visible-light-driven routes for its synthesis is highly desirable. Herein, a CN/ZnV-ZCS composite photocatalyst was constructed by coupling g-C3N4 (CN) with Zn-vacancy-containing ZnCdS (ZnV-ZCS) for photocatalytic H2O2 production. The optimized CN/ZnV-10 delivered 44.58 mmol g−1 H2O2 within 60 min under 425 nm LED irradiation, outperforming pristine CN, ZCS, ZnV-ZCS, and vacancy-free CN/ZCS, with good cycling stability. Trapping and EPR results identify O2 as the key electron acceptor and ·O2− as an important intermediate. Structural characterization and XPS results indicate successful Zn-vacancy introduction, intimate heterointerface formation, and interfacial electron redistribution. Combined VB-XPS, photoelectrochemical, and reactive-species analyses suggest that Zn vacancies are favorable for O2 adsorption/activation, whereas the CN/ZnV-ZCS heterointerface promotes charge separation and migration. Based on the available evidence, a Z-scheme interfacial charge-transfer pathway is established in the CN/ZnV-ZCS system.