Sulfide-based S-scheme heterojunction photocatalysts

Photocatalytic solar-to-chemical energy conversion offers a promising route to address energy and environmental challenges. S-scheme heterojunctions are particularly attractive because they promote charge separation while retaining strong redox capability. Sulfide semiconductors, featuring visible-light absorption, tunable electronic structures, and suitable reduction potentials, are important components of S-scheme photocatalysts. This review summarizes the fundamentals, charge-transfer mechanisms, and characterization methods of S-scheme heterojunctions, followed by recent advances in inorganic–inorganic and inorganic–organic sulfide-based systems for H 2 evolution, CO 2 reduction, H 2 O 2 production, and environmental purification. Representative CdS, ZnIn 2 S 4 , and In 2 S 3 systems are discussed. Emerging enhancement strategies, including internal electric field modulation, defect engineering, localized surface plasmon resonance, and multiple S-scheme interfaces, are highlighted. Finally, key challenges involving charge separation, photocorrosion, interfacial characterization, and practical applications are discussed, together with future directions toward efficient and scalable sulfide-based S-scheme photocatalysts.