Theoretical study of methylidyne chemisorption on Ni(111) and Co(0001) surfaces

Methylidyne is a key intermediate in hydrocarbon growth reactions over transition metal surfaces. However, experimental data characterizing its interaction with various surfaces are scarce. Therefore, to deepen our understanding of the chemisorption of methylidyne and to quantify its role in the catalytic formation of hydrocarbons, we have calculated the binding energy of methylidyne on Ni(111) and Co(0001) surfaces using density-functional theory within the generalized gradient approximation and the full-potential linearized augmented planewave (FP-LAPW) method. The dependence of the binding energy on both the adsorption site and the surface coverage was significant on both surfaces. The binding energy of CH adsorbed in the fcc threefold hollow site of Ni(111) decreased by 1.1 eV as the surface coverage increased from 0.25 to 1.0 ML, whereas the increase of 0.74 eV observed over Co(0001) for the hcp threefold hollow site was slightly less pronounced. The density-of-state plots revealed that rehybridization of the carbon atom interacting with the surface occurred, and the electronic changes induced upon chemisorption were similar for both surfaces.