Precursor mechanism for a dimer–dimer catalytic reaction on the surface of square lattice: a Monte-Carlo simulation study

We have studied a model for a dimer–dimer surface catalytic reaction on the surface of square lattice through Monte-Carlo simulations. This reaction corresponds to catalytic oxidation of hydrogen and assumes that the reaction can proceed via a “precursor mechanism”. According to this mechanism, a molecule incident at a metal site breaks apart into two single atoms. Due to the exothermicity of the chemisorption reaction, these atoms gain excess energy. Therefore, they are mobile on the surface and can hop between neighbouring sites. Since these atoms are not in thermal equilibrium with the surface, they are referred as “precursors”. During this motion a precursor can either react with chemisorbed species or lose sufficient energy to become immobily attached to a particular site. The model predicts a steady reactive window, which is limited by continuous and discontinuous irreversible transitions, respectively. The width of this reactive window depends upon the mobility of the precursors.