Hot-Electron-assisted *CO-*CHOH coupling enables selective CO₂-to-C₂H₆ Photoreduction on Plasmonic ZnIn₂S₄/W₁₈O₄₉ S-scheme heterojunction interfaces

Precise construction of electron-rich interfacial environments is crucial for directing photocatalytic CO₂ reduction toward C₂₊ products. Herein, a sulfur-vacancy (S_V)-rich ZnIn₂S₄/W₁₈O₄₉ S-scheme heterojunction is constructed for selective CO₂-to-C₂H₆ conversion. Oxygen-deficient W₁₈O₄₉ serves as a plasmonic interfacial modulator that promotes S_V formation in ZnIn₂S₄, regulates S-scheme charge redistribution, and extends visible-to-near-infrared light harvesting. The S-scheme-retained photogenerated electrons on ZnIn₂S₄, together with plasmon-derived hot-electron contribution from W₁₈O₄₉, establish an electron-rich reduction environment around ZnIn₂S₄-side S_V sites, thereby favoring CO₂ adsorption, activation, and CO-derived intermediate retention. In situ FTIR spectroscopy and DFT calculations reveal that this defect-interface environment promotes the protonation of CO-derived intermediates and favors the key *CO-*CHOH coupling step with a low energy barrier of 0.63 eV. After CC coupling, the C₂ intermediate preferentially undergoes hydrogenation rather than desorption as C₂H₄, directing the reaction pathway toward C₂H₆. As a result, the optimized Z-W_0.12 photocatalyst delivers a C₂H₆ production rate of 54.2 ± 1.5 μmol g^-1 h^-1 with a product selectivity of 82.7 ± 1.9% under visible-light irradiation. This work demonstrates a defect-plasmonic S-scheme interface strategy for coupling S_V regulation, directional electron accumulation, and plasmon-assisted hot-electron contribution to promote selective CO-derived CC coupling in photocatalytic CO₂ reduction.