Ru/CeO2 catalysts with enriched oxygen vacancies by plasma treatment for efficient CO2 methanation

•The Ru/CeO2 catalyst treated by dielectric barrier discharge plasma (Ru/CeO2-P) exhibits more abundant oxygen vacancies.•An excellent CO2 conversion (83%) and CH4 selectivity (100%) were achieved in Ru/CeO2-P.•The formate and CO pathways coexist on Ru/CeO2-P and the CO pathway is significantly enhanced. Plasma treatment has become a promising approach to enhance oxygen vacancies and hence promote the catalytic performance of CO2 methanation. However, distinct challenges remain on characterizing the enhancement of oxygen vacancies, limiting the understanding of plasma treatment mechanisms. Here, we successfully fabricated Ru/CeO2 catalysts via the wet impregnation method, treated them to thermal calcination and dielectric barrier discharge plasma respectively, and investigated the mechanism for different performances of CO2 methanation. It is found that the Ru/CeO2 catalyst treated by plasma (Ru/CeO2-P) exhibits more abundant oxygen vacancies than the untreated counterpart (Ru/CeO2-C), which contribute to a much higher CO2 conversion (83 %) and CH4 selectivity (100 %) at 350 °C. The in-situ DRIFTS and DFT calculations reveal the coexistence of the formate and CO pathways on the Ru/CeO2 catalysts, where the CO pathway is significantly enhanced after plasma treatment. The comprehensive study demonstrates the significance of effectively and precisely regulating the concentration of oxygen vacancies by plasma treatment, thereby enhancing the performance of CO2 hydrogenation.