Ru‐O _V Site‐Mediated Product Selectivity Switch for Overall Photocatalytic CO ₂ Reduction

Abstract The photocatalytic reduction of carbon dioxide (CO ₂ ) to methane (CH ₄ ) represents a sustainable route for directly converting greenhouse gases into chemicals but poses a significant challenge in achieving high selectivity due to thermodynamic and kinetic limitations during the reaction process. This work establishes Ru‐O _V active sites on the surface of TiO ₂ by anchoring coordination unsaturated Ru single‐atoms, which stabilize crucial reaction intermediates and facilitate local mass transfer to achieve dual optimization of the thermodynamics and kinetics of the overall photocatalytic CO ₂ reduction. Combining operando spectroscopy with density functional theory (DFT) calculations indicates that oxygen vacancies (O _V ) inhibits the desorption of *CO, whereas Ru facilitates proton extraction. This configuration not only lowers the overall activation energy barrier but has also been engineered to serve as a selectivity switch, changing the reaction route to produce CH ₄ instead of CO. Consequently, the Ru‐O _V /TiO ₂ exhibits a 195.4‐fold improvement in the CH ₄ yield compared to TiO ₂ , accompanied by an increase in selectivity to 81%.