Vacancy engineering of the nickel-based catalysts for enhanced CO2 methanation

It is challenging to elucidate the mechanism of CO2 methanation reaction over nickel-based catalysts and precisely tune the kinetics of rate-determining-step. In this work, we propose a strategy to engineer the oxygen vacancies of nickel-based catalysts for enhanced CO2 methanation. A Y2O3-promoted NiO-CeO2 catalyst is prepared and found to exhibit an outstanding methanation activity that is up to three folds higher than NiO-CeO2 and six folds higher than NiO-Y2O3 at mild reaction temperatures (<300 °C). We demonstrate both theoretically and experimentally that the introduction of Y2O3 to CeO2 greatly facilitates the generation of surface oxygen vacancies during the reaction. Using spectrokinetics analysis, we further revealed that these sites promote the direct dissociation of CO2, which is kinetically more favorable than the associative route. Thus, it dramatically improved the CO2 methanation activity. The vacancy engineering strategy will potentially guide the rational design of a broad range of heterogeneous catalysts for CO2 hydrogenation.