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 CO2 reduction to C2+ products, increasing the number of CO2 adsorption sites and lowering the energy barriers for key intermediates are critical. A ZnIn2S4 (ZIS)/MoO3‐x (Z‐M) photocatalyst is presented, in which plasmonic MoO3‐x generates hot electrons, creating a multielectron environment in ZIS that facilitates efficient C─C coupling reactions. Density functional theory (DFT) calculations reveal that MoO3‐x reduces the formation energy of sulfur vacancies (SV) in ZIS, thereby enhancing CO2 adsorption and activation. The SV‐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 *CH2, which converts to *CH3 with an energy barrier of −0.63 eV. The energy barrier for *CH3‐CH3 coupling is 0.54 eV, which is lower than the 0.73 eV for *CH2‐CH2 coupling to form *C2H4. Thus, Z‐M preferentially produces C2H6 over C2H4. Under visible light, Z‐M achieves a CO2‐to‐C2H6 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 CO2 adsorption and improving C2+ production in CO2 reduction.