Vacancy-Mediated Nanostructured ZnIn ₂ S ₄ /CdS S-Scheme Heterojunctions for Enhanced Photocatalytic Hydrogen Production

The S-scheme heterojunction has been recognized as an effective strategy to boost photocatalytic hydrogen evolution performance. However, the insufficient separation and transfer of photogenerated carriers still is a critical bottleneck that limits further activity improvement. Here, we rationally constructed defect-rich nanostructured Sv-ZnIn 2 S 4 /CdS (Sv-ZIS/CdS) S-scheme heterojunctions by introducing sulfur vacancies (Sv) into ZnIn 2 S 4 and systematically explored the role of S vacancy defects in the regulation of interfacial charge dynamics. Experimental results demonstrate that the synergistic combination of S-scheme heterojunction and Sv effectively extends visible-light absorption and accelerates charge separation. Specifically, sulfur vacancies enhance the built-in internal electric field (IEF) within the heterostructures, thereby driving the spatial separation and directional migration of photogenerated carriers. Density functional theory (DFT) calculation further reveals that Sv-induced charge redistribution reduces the surface kinetic barrier, facilitating the adsorption and activation of H 2 O and H* intermediates and thus boosting the hydrogen evolution reaction. Benefiting from these synergistic effects, the optimized Sv-ZIS/CdS photocatalyst exhibits a remarkable hydrogen evolution rate (3.852 mmol g –1 h –1 ). This work provides profound insights into the manipulation of heterojunction interfacial charge behavior via defect engineering, offering a feasible paradigm for designing high-performance nanostructured photocatalysts for solar-to-hydrogen conversion.