Synergistic effect of cobalt-induced phase transition and S-scheme heterojunction engineering for photothermal-enhanced photocatalytic hydrogen production over ZnIn2S4/Co0.15Fe0.85S2

While semiconductor photocatalysis holds great promise for solar-to‑hydrogen conversion, the intrinsic limitations of rapid charge recombination and narrow spectral response continue to impede practical implementation. Herein, this study successfully constructed a ZnIn 2 S 4 /Co 0.15 Fe 0.85 S 2 (ZIS/Co-FS) S-scheme heterojunction with photothermal enhancement effects. Cobalt (Co) doping not only induced a phase transition of FS from the marcasite phase to the pyrite phase, transforming its morphology from interlaced flakes into nanoparticles, but also adjusted the conduction band position to a more negative potential, effectively optimizing the energy band structure. Performance tests revealed that the optimal sample, ZIS/Co-FS-2%, achieved a photocatalytic hydrogen production rate of 2.2 mmol·g −1 ·h −1 , which was 7.3 times and 2.2 times higher than those of pure ZIS and undoped ZIS/FS, respectively. By combining various characterization results along with density functional theory calculations, the charge transfer pathway following the S-scheme heterojunction was further validated, suppressing the recombination of photoinduced charges. The photothermal effect raised the surface temperature of photocatalyst particles and thus significantly accelerated the reaction kinetics. This study offers a novel strategy for designing efficient metal sulfide photocatalysts through the synergistic integration of transition metal doping, heterojunction engineering, and photothermal.