Constructing an Active Sulfur‐Vacancy‐Rich Surface for Selective *CH3‐CH3 Coupling in CO2‐to‐C2H6 Conversion With 92% Selectivity

Abstract To achieve high selectivity in photocatalytic CO 2 reduction to C 2+ products, increasing the number of CO 2 adsorption sites and lowering the energy barriers for key intermediates are critical. A ZnIn 2 S 4 (ZIS)/MoO 3‐x (Z‐M) photocatalyst is presented, in which plasmonic MoO 3‐x generates hot electrons, creating a multielectron environment in ZIS that facilitates efficient C─C coupling reactions. Density functional theory (DFT) calculations reveal that MoO 3‐x reduces the formation energy of sulfur vacancies (S V ) in ZIS, thereby enhancing CO 2 adsorption and activation. The S V ‐rich surface lowers the energy barrier for forming HCOO * to −0.33 eV whereas the energy barrier for forming * COOH is 0.77 eV. Successive hydrogenation of HCOO * leads to * CH 2 , which converts to * CH 3 with an energy barrier of −0.63 eV. The energy barrier for * CH 3 ‐CH 3 coupling is 0.54 eV, which is lower than the 0.73 eV for * CH 2 ‐CH 2 coupling to form * C 2 H 4 . Thus, Z‐M preferentially produces C 2 H 6 over C 2 H 4 . Under visible light, Z‐M achieves a CO 2 ‐to‐C 2 H 6 conversion rate of 467.3 µmol g −1 h −1 with 92.0% selectivity. This work highlights the dual role of plasmonic photocatalysts in enhancing CO 2 adsorption and improving C 2+ production in CO 2 reduction.