Unravelling the CO2 methanation mechanisms on a Ni-BaTiO3 catalyst: A theoretical investigation

Abstract

Solar-induced photothermal catalysis of CO2 reduction is an effective method for chemical CO2 conversion with great potential. Understanding its reaction mechanism is crucial for the development of new catalysts. In this work, the mechanism of CO2 reduction on a BaTiO3 supported Ni catalyst was studied using density functional theory (DFT). The presence of the BaTiO3 base was found to have great significance in the adsorption and activation of CO2. The dominant reaction pathway of CO2 reduction on the BaTiO3 supported Ni catalyst is calculated as CO2(g)→CO2→CO→COH→HCOH→CH→CH2→CH3→CH4→CH4(g) and is rate-limited by the reduction of CO, with a corresponding energy barrier of 0.94 eV, which is nearly 1.00 eV lower than that on the pure Ni surface. The BaTiO3 base not only induces wrinkling distortion of the Ni surface, which facilitates the step of CO hydrogenation, but also results in an upshift of the d-band centre and Fermi level of the catalyst, which enhances the binding strength of the catalyst with the reaction intermediates. Based on the projected density of states (PDOS) analysis, the BaTiO3 base strongly promotes the σ-bonding interaction between the Ni surface and CO. The stronger adsorption of CO on the surface of the BaTiO3 supported Ni catalyst results in the reduction reaction selectively generating CH4 but not CO.