A density functional theory study of CO methanation mechanism on Ni4/SiC catalyst

Abstract The reaction mechanism of CO methanation on the Ni 4 /3C-SiC(1 1 1) catalyst surface was explored by the density functional theory in this paper. The configuration of Ni 4 /3C-SiC(1 1 1) is built and the binding energy of Ni 4 cluster on Ni 4 /3C-SiC(1 1 1) is higher than that on Ni 4 / t -ZrO 2 and Ni 4 /Al 2 O 3 surface, which may be contributed to improve the dispersion and stability of Ni-based catalyst. And the main pathway of CH 4 formation on Ni 4 /3C-SiC(1 1 1) surface is CO + H → CHO + H → CH 2 O + H → CH 3 O → CH 3  + H → CH 4 . The results show that the rate-determining step for CO methanation on Ni 4 /3C-SiC(1 1 1) is the formation of CH 3 from CH 3 O dissociation with an energy barrier of 241.3 kJ/mol, which is lower than that on Ni 4 / t -ZrO 2 . In addition, the activation energy of CH 3 OH formation is higher than that of CH 4 synthesis on Ni 4 /3C-SiC(1 1 1) surface (254.5 vs. 241.3 kJ/mol). Different from Ni(1 1 1), Ni 4 / γ -Al 2 O 3 , and Ni 4 / t -ZrO 2 catalysts, the Ni 4 /3C-SiC(1 1 1) catalyst has a much higher selectivity for CH 4 in the reaction of CO methanation, which may be attributed to the lower activation energy of CH 3 O dissociation to CH 3 than that hydrogenation to CH 3 OH. Therefore, Ni 4 /3C-SiC(1 1 1) can be recommended preferentially for CH 4 synthesis via CO hydrogenation, rather than CH 3 OH formation.