Abstract
ZnIn2S4 is a visible-light-responsive ternary sulfide used in photocatalytic hydrogen evolution, CO2 conversion, pollutant treatment, selective organic reactions and photoelectric sensing. Its layered structure and adaptable surface chemistry make it convenient for preparing nanosheets, porous assemblies, defect-containing surfaces and semiconductor junctions. These structural changes, however, influence different steps of a reaction, and the measured performance depends strongly on the donor, reactor, illumination and product analysis. This review examines ZnIn2S4 from the working structure to the measured reaction or sensing signal. The structural basis is followed by discussion of morphology, vacancies, composition, cocatalysts and heterojunctions. Representative applications are then considered with attention to product selectivity, carbon or oxygen balance, sulfide stability and analytical validation. Particular care is taken to distinguish sacrificial hydrogen evolution from overall water splitting, pollutant disappearance from mineralization, and a large photocurrent from a reliable sensor response. The aim is to summarize the available evidence while indicating which controls are still needed for meaningful comparison.