A DFT Study of Hydrogen Dissociation on CO- and C-Precovered Fe(100) Surfaces

A DFT model of the Fe(100) surface was used to study the dissociation process of H 2 . The dissociation of H 2 was considered on a clean surface as well as CO- and C-precovered surfaces. The presence of CO and C is shown to block several sites for hydrogen adsorption, as well as increasing various hydrogen dissociation barriers. At CO and C coverages up to 0.25 ML the main contributor to the barrier increase is the CO−H and C−H repulsion. In these cases, off-symmetry sites will play an important role in the dissociation of the approaching hydrogen molecules. At coverages of 0.5 ML of CO and C, adsorption site blocking occurred, and the dissociation barriers increased to more than 3 times larger values than that of the clean surface. This increase in the barriers will result in a significant decrease in the rate constant of the dissociative H 2 adsorption process.