Low-temperature CO2 methanation over Ru/CeO2: Investigation into Ru loadings

•The catalytic performance of Ru/CeO2 showed a volcanic trend as loading increased.•An excellent CO2 conversion (86%) and CH4 selectivity were achieved in 1 %Ru/CeO2.•The synergistic of oxygen vacancies and metal-support interactions was studied.•CO* is a key intermediate on 0.5 %Ru/CeO2 in CO2 methanation at low temperature. The in-depth study of reaction intermediates, especially metal-support interactions, has brought great promise and challenges to the application of Ru-based catalysts in CO2 methanation. In this study, catalysts with different Ru loadings were prepared by wet impregnation method using CeO2 as the support. It is found that 1%Ru/CeO2 had excellent low-temperature methanation activity compared with other catalysts. As the metal loading increases, the oxygen vacancy concentration of the catalyst shows a volcano-type trend and the metal-support interaction increases. In addition, in situ DRIFTS showed that the low-temperature conditions are conducive to the formation of CO intermediates, making the CO2 methanation pathway more inclined to proceed along the CO pathway; while high temperature conditions are conducive to the formation of HCOO* intermediates, making the CO2 methanation pathway more inclined to proceed along the HCOO* pathway. This study demonstrates the importance of precisely determining the influence of metal active sites on the interaction between metal supports and oxygen vacancies for identifying critical reaction pathway intermediates and predicting CO2 methanation performance.