Oxygen Vacancy Drives CoO Atomic Layers Directional Photoreduction of CO2 to CH4

Plagued by the dual challenges of energy scarcity and environmental pollution, photocatalytic CO2 reduction has emerged as a vital engineering for collecting solar energy to convert CO2 into renewable fuels. Herein, the ultrathin CoO atomic layers with varying concentrations of oxygen vacancies are designed to photoreduce CO2 and explore the mechanism of oxygen vacancy for CO2 photoreduction. Density functional theory calculations illustrate that the oxygen vacancy not only enhances the available photoelectrons efficiency of CoO structures by improving the absorption of solar light and promoting the surface separation of electron–hole pairs, but decreases the highest occupied molecular orbital of CO2 and the potential barrier of *CO conversion to *CHO, driving the CO2 directed photoreduction toward CH4. Finally, the rich‐oxygen vacancies CoO atomic layers significantly enhance the effective photoelectrons efficiency with 136.3 μmol g−1 h−1 compared to 44.6 μmol g−1 h−1 for 2D‐CoO atomic layers. Moreover, the CH4 selectivity also rises from 39.4% to 72.4% through the regulation of oxygen vacancies. This work promotes the development of Co‐based semiconductors for CO2 photocatalytic reduction, and elucidates the mechanism of oxygen vacancy for CO2 photoreduction, which provides valuable insights for the design and optimization of similar photocatalysts in both experimental and theoretical domains.