CO Adsorption on Fe4C (100), (110), and (111) Surfaces in Fischer-Tropsch Synthesis

The adsorption of CO at various coverage on the termination surfaces of the low-indexed (100), (110), and (111) surfaces of Fe4C has been performed at the level of density functional theory. It is found that CO prefers to adsorb around Fe atoms. It is also found that there is no significant lateral interaction between the adsorbed CO at 1/4 monolayer (ML) coverage, whereas there is stronger repulsive interaction at I ML for (100) and (110) surfaces, and 1/2 ML for (111) surface. It is also interesting to note that the surface ketenylidene (C=C=O) species on (100) T-Fe/C, (110) (Fe/C), and (111) T-C may be the precursor for CO dissociation. On all surfaces, the adsorbed CO is partially negatively charged, indicating the enhanced electron transfer from the Fe4C Surface to CO, and the more the electron transfer, the stronger the CO activation.