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%.