Boosting C‐C Coupling for Efficient Ethylene Production via Interfacial Charge Engineering in In 2 S 3 /Co 3 S 4 S‑Scheme Photocatalyst

ABSTRACT The photocatalytic conversion of CO 2 to high‐value multicarbon products is a promising sustainable energy route, however, efficient and selective C 2 H 4 production is hindered by sluggish C‐C dimerization and rapid charge recombination. In this work, a tightly coupled S‐scheme In 2 S 3 /Co 3 S 4 heterojunction photocatalyst was constructed via a facile solvothermal method for visible‐light‐driven CO 2 reduction without a sacrificial agent. The optimal catalyst (2IS2CS) exhibits a remarkable C 2 H 4 production rate of 17.58 µmol g −1 h −1 , which is 5.38 times higher than that of pure Co 3 S 4 with an ethylene selectivity of 83.9%. The heterojunction boosts spontaneous hot electron transfer from Co 3 S 4 to In 2 S 3 , establishing a built‐in electric field (BEF) that enhances the separation efficiency of photogenerated carriers. Moreover, the interfacial charge redistribution enriches photogenerated electron density at Co 2+ sites, strengthening CO 2 adsorption and activation. Crucially, this redistribution also modulates the electronic structure of the Co sites, leading to an upward shift of the spin‐down d z2 orbital. The optimized electronic configuration enhances the bonding interaction with key C‐C coupling intermediates, effectively lowering the energy barrier for ethylene formation. This work provides atomic‐level insights into interface engineering for steering photocatalytic CO 2 reduction toward multicarbon products and offers a strategic guideline for designing high‐performance heterojunction photocatalysts.