Selective CO2 Photoreduction into CH4 Triggered by the Synergy between Oxygen Vacancy and Ru Substitution under Near-Infrared Light Irradiation.

Near-infrared (NIR) light powdered CO₂ photoreduction reaction is generally restricted to the separation efficiency of photogenerated carriers and the supply of active hydrogen (*H). Herein, the study reports a retrofitting hydrogenated MoO_3-x (H-MoO_3-x) nanosheet photocatalysts with Ru single atom substitution (Ru@H-MoO_3-x) fabricated by one-step solvothermal method. Experiments together with theoretical calculations demonstrate that the synergistic effect of Ru substitution and oxygen vacancy can not only inhibit the recombination of photogenerated carriers, but also facilitate the CO₂ adsorption/activation as well as the supply of *H. Compared with H-MoO_3-x, the Ru@H-MoO_3-x exhibit more favorable formation of *CHO in the process of *CO conversion due to the fast *H generation on electron-rich Ru sites and transfer to *CO intermediates, leading to the preferential photoreduction of CO₂ to CH₄ with high selectivity. The optimized Ru@H-MoO_3-x exhibits a superior CO₂ photoreduction activity with CH₄ evolution rate of 111.6 and 39.0 µmol g_catalyst ^-1 under full spectrum and NIR light irradiation, respectively, which is 8.8 and 15.0 times much higher than that of H-MoO_3-x. This work provides an in-depth understanding at the atomic level on the design of NIR responsive photocatalyst for achieving the goal of carbon neutrality.