Monte Carlo study of surface reactions: Bidirectional monomer-dimer reaction on modified surfaces

The Monte Carlo simulation method is used to study monomer-dimer bidirectio nal reactions on modified surfaces. The assumed model predicts that reactio n leads to different products depending on the state of reacting molecules, which depends on the state of adjacent adsorbing sites. The model assumes that the catalyst surface is precovered by. a certain amount of modifier, w hich partially deactivates the surface and changes the state of the adsorbe d reactant species. It is demonstrated that the surface concentration of th e modifier atoms and the topography of their distribution over the surface are both important factors which influence the behavior of systems consider ed in this paper. In particular, it has been found that the reaction direct ion, the reaction window location and its width depend strongly on the surf ace morphology. The results are in a good qualitative agreement with the ex perimentally observed changes in the direction of the methanol oxidation on the sulfur-modified Fe(100) catalyst.