Theoretical study on the synthesis of methane by CO2 hydrogenation on Ni3Fe(111) surface

Density functional theory methods are used to explore the possible mechanism of CO2 methanation on Ni3Fe (111) surface. The optimal adsorption site and adsorption energy of all species are determined. Meanwhile, for the adsorption of CO2, the obvious orbital hybridization between CO2 and Ni3Fe(111) surface indicates that CO2 is commendably activated, which is conducive to further hydrogenation reaction. Subsequently, the optimal pathway for CO2 methanation is determined through a detailed study of the activation barrier. The lower activation barrier (1.60 eV) of rate-determining step on Ni3Fe(111) surface than that on Ni(111) and Pt-doped Ni (111) surfaces suggests excellent catalytic activity of Ni3Fe(111) surface towards CO2 methanation. Moreover, the formation of CH4 is more favorable in kinetics compared with that of HCOOH and CH3OH, indicating the high selectivity of CO2 methanation on Ni3Fe(111). In addition, the calculated results also reveal that the Ni3Fe (111) surface can effectively suppress the carbon deposition compared with Ni(111) surface, which can be attributed to the obvious enhancement of the activation barrier for the reactions of surface C* formation (3.27 eV for CO* -> C*, 2.23 eV for COH* -> C*, and 1.70 eV for CH* -> C*).