Ru-O_V Site-Mediated Product Selectivity Switch for Overall Photocatalytic CO₂ Reduction

The photocatalytic reduction of carbon dioxide (CO₂) to methane (CH₄) 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 TiO₂ 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 CO₂ 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 CH₄ instead of CO. Consequently, the Ru-O_V/TiO₂ exhibits a 195.4-fold improvement in the CH₄ yield compared to TiO₂, accompanied by an increase in selectivity to 81%.