Modulating <i>e</i>_g Occupancy by A‐Site Vacancy to Boost Photocatalytic CO₂ Reduction on Perovskite Oxides

Abstract For photocatalytic CO 2 reduction, traditional ABO 3 perovskite oxides have suffered from the natural surface covered by the passivated AO layer, resulting in low photocatalytic activity. Herein, the double perovskite Sr 2 TiFeO 6 is used as a precursor and citric acid is employed to selectively dissolve the A‐site cation, obtaining Sr v ‐Sr 2 TiFeO 6 with abundant A‐site vacancies. Without using any co‐catalysts or sacrificial agents, the Sr v ‐Sr 2 TiFeO 6 achieves efficient photoreduction of CO 2 to CH 4 with 91% selectivity and 43.17 µmol g −1 h −1 yield, which is almost five times that of the original Sr 2 TiFeO 6 . The results indicate that selectively removing A‐site can increase the concentration of oxygen vacancies and significantly reduce the exciton binding energy from 0.61 to 0.32 eV, thereby enhancing the charge transfer efficiency. Furthermore, the A‐site vacancies can adjust the surface electronic structure, leading to a decrease of e g electrons occupancy on the active B‐site. This results in a shift of the reaction intermediates from strong adsorption to moderate adsorption. Specifically, the energy barrier of the water oxidation reaction, the rate‐determining step for the overall CO 2 reduction, is greatly reduced. This work provides a vivid case for modulating the electronic structure of perovskite oxide through introducing A‐site defects for efficient photoreduction of CO 2 .