Effect of K on carbon adsorption and deposition on the Co(111) surface

Theoretical calculations were performed to investigate the effect of potassium on carbon adsorption and deposition on the Co(111) surface. Cn species are expected, and the C2 dimer may be a critical elementary unit. Increasing the carbon coverage, some carbon atoms may diffuse into the subsurface. However, kinetically, the formation of Cn species is more favorable, and there is no driving force for carbon migrating into the subsurface. With increasing of the carbon concentration, the adsorbed carbons form carbon chains and then graphene sheets parallel to the surface. The potassium promoter has little effect on the most stable configurations but increases the adsorption energy, which can be explained by the decrease in the work function resulting from the electronic effects of the potassium promoter. Potassium promotes carbon deposition and carbonization of the cobalt surface to a certain extent. These results could provide useful information for carbon deposition and cobalt carbide formation. The theoretical calculation results show that carbon atoms tend to form Cn species on the Co(111) surface. As the carbon concentration increases, the adsorbed carbon atoms form carbon chains and then graphene sheets parallel to the surface. The potassium promoter has little effect on the most stable configurations but increases the adsorption energy of carbon species due to the electronic effects.