Stabilizing Unsaturated S at Interface for the Enhanced Photothermal Evolution of CH₄ From CO₂

Abstract Highly selective photocatalytic CO 2 reduction (PCR) to methane is restricted severely due to the multiple consecutive proton‐coupled electron transfer steps and the stabilization of crucial intermediates. Herein, an In 2 O 3 /CuInS 2 composite with multifunction is meticulously fabricated via heterojunction engineering and achieves a remarkable selectivity of CH 4 (95.73%) and a yield of 54.9 umol·g −1 ·h −1 . The electrons are enriched around S atoms to form unsaturated S sites, thereby improving the efficiency of photocatalytic reduction reactions involving multiple electrons. The interfacial effect induces electron/photogenerated electron transfer from In 2 O 3 to the unsaturated S sites, suppressing excessive oxidation states and reducing local positive charge accumulation, thereby stabilizing the unsaturated S sites. Unsaturated S sites acts as electron‐rich centers for CO 2 adsorption and activation function, enhancing the coverage of * CO species on the surface of photocatalyst and lowering the energy barrier of * CHO intermediate, thereby inducing the generation of CH 4 . The photothermal effect improves the sluggish kinetics of the PCR efficiency, which is ascribed to the transferred electrons that are excited into hot electrons on CuInS 2 via the LSPR effect, accelerating the activation of adsorbed CO 2 molecules.