Unlocking the Potential of Oxide‐Based Catalysts for CO2 Photo‐Hydrogenation: Oxygen Vacancies Promoted C─O Bond Cleavage in Key Intermediates

Abstract Oxygen vacancies are generally recognized to play significant roles in CO 2 adsorption and activation during CO 2 hydrogenation. However, by revisiting its structural/electronic affinity for a range of oxygen‐containing intermediates in CO 2 hydrogenation processes, the additional roles of oxygen vacancies can be long overlooked and underestimated. Herein, using CO 2 (photo‐)methanation as a model reaction, Co 3 O 4 with abundant oxygen vacancies is employed to investigate the relationship between oxygen vacancies and the formation/conversion of oxygen‐containing intermediates. Combined analyses of in situ diffuse reflectance infrared Fourier transform spectroscopy and theoretical calculations reveal that the key intermediate is formate, whose C─O bond cleavage is inferred to be the rate‐limiting step during CO 2 methanation on Co 3 O 4 . Remarkably, leveraging the oxygen vacancy‐mediated C─O bond scission to accelerate the conversion of formate, the CH 4 production activity (1108.1 mmol g −1 h −1 ) and selectivity (93%) are improved significantly. This comprehensive study provides valuable insights into the multifaceted roles of oxygen vacancies in CO 2 hydrogenation reactions, establishing a solid foundation toward the design and development of high‐performance oxide‐containing/‐based catalysts for the conversion of CO 2 into various valuable chemicals.