Structural Engineering Modulation of Metal Sulfide Photocatalysts from Charge Regulation Mechanisms to Practical Applications

Metal sulfide semiconductors have attracted considerable attention in solar-driven energy conversion and environmental remediation because of their strong visible-light response, tunable electronic structures, and abundant surface-active sites. Nevertheless, further improvements in their photocatalytic performance remain constrained by rapid charge-carrier recombination, photocorrosion, insufficient reaction selectivity, and limited operational stability under practical conditions. Existing reviews have largely focused on specific sulfide materials, individual photocatalytic reactions, or a single structural-regulation strategy, whereas the intrinsic relationships among material composition, structural engineering, charge-carrier dynamics, and application requirements have not been systematically examined. Following the conceptual framework of "material composition-structural regulation-charge-carrier dynamics-reaction pathways-engineering applications," this review provides a systematic overview of the design principles and application advances of metal sulfide photocatalysts. First, the crystal structures, band characteristics, surface-active sites, and photocorrosion behavior of different classes of metal sulfides are analyzed to clarify how their intrinsic properties govern catalytic processes. The effects of morphology engineering, defect regulation, compositional optimization, interface construction, and cocatalyst modification on light absorption, charge transport, and surface reaction kinetics are then discussed, with particular attention to how these strategies balance activity enhancement and stability retention. The distinctive features of metal sulfides in photocatalytic hydrogen evolution, biomass photoreforming, CO₂ reduction, H₂O₂ synthesis, pollutant degradation, and photoelectrochemical sensing are further summarized, revealing the distinct requirements of different reaction systems for electronic structures and active sites. Finally, current challenges and future research directions are discussed in terms of mechanistic reliability, material stability, adaptability to realistic systems, and sustainable development. This review aims to establish an application-oriented framework for the rational design of metal sulfide photocatalysts and to provide a theoretical basis for developing efficient, stable, and sustainable photocatalytic systems.