Ni-based catalysts, which are widely used, have produced promising results for methane formation from syngas. The key to rational design of catalysts and corresponding technological parameters is an understanding of the underlying mechanism of CO methanation at the molecular level. In the present study, the mechanism of CO methanation on Ni(111) and carbon-doped Ni(111) (C-Ni(111)) surfaces was investigated by means of temperature-programmed surface reaction and density functional theory method. Our conclusion is that the energy barrier of CO dissociation decreases significantly on the C-Ni(111) surface. The rate-limiting steps of CO methanation on the Ni(111) and C-Ni(111) surfaces are CO dissociation. and CH3 species hydrogenation, respectively. Results from comparison of the activation barriers and rate-limiting steps indicate that CH4 production may be improved by slight deposition of carbon. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.