Monomer-dimer reaction model with asymmetric adsorption of monomer and dimer on the catalyst surface - art. no. 056102

The irreversible kinetics of the Ziff-Gulari-Barshad model in the presence of inhomogeneity on a catalyst surface is investigated by means of Monte Ca rlo simulation. We assume that only part of catalyst surface sites are acti ve for surface catalytic reaction and randomly distributed on the catalyst surface. The adsorption of a O-2 molecule is permitted if one site of a nea rest-neighbor vacant pair is active. CO can adsorb on all vacant sites, but the adsorption probability is p (p<1) if the site is not active. In our mo dified model, the O-passivated phase disappears and the continuous phase tr ansition between the O passivated and the reactive state is eliminated. We also find that the transition between the CO passivated and the reactive st ate is continuous if the concentration of the active sites is small, and it becomes discontinuous with increasing concentrations of active sites. Furt hermore, it is shown that a hysteresis loop exists whether the CO-passivate d transition is continuous or discontinuous. Our simulation results are in good agreement with many relevant experimental results and may provide an a lternative explanation for the experimental observations.