Ru-based catalysts for efficient CO₂ methanation: Synergistic catalysis between oxygen vacancies and basic sites

The fundamental insights of the reaction mechanism, especially the synergistic effect between oxygen vacancies and basic sites, are highly promising yet challenging for Ru-based catalysts during carbon dioxide (CO₂) methanation. Herein, a series of Ru-based catalysts were employed to study the mechanism of CO₂ methanation. It is found that Ru/CeO₂ catalyst exhibits a much higher CO₂ conversion (86%) and CH₄ selectivity (100%), as well as excellent stability of 30 h due to the existence of abundant oxygen vacancies and weak basic sites. Additionally, the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations reveal that the formate formation step dominated the hydrogenation route on Ru/CeO₂ catalyst, and the b-HCOO* could be the key intermediate due to b-HCOO* is more easily hydrogenated to methane than m-HCOO*. The systematic study marks the significance of precise tailoring of the synergistic relationship between oxygen vacancies and basic sites for achieving the desired performance in CO₂ methanation.