On the self-poisoning of small particles upon island formation of the reactants in a model for a heterogeneously catalyzed reaction

Assuming the Langmuir–Hinshelwood mechanism, the reaction A+(1/2) B2■AB is studied on both small homogeneous and disordered surfaces by means of computer simulations. The occurrence of a new self-poisoning regime, where for a determined initial condition the substrata could be completely covered for each of the reactants with a certain probability, is observed and discussed. Large fluctuations in the size of adsorbed islands formed by A and B particles would cause the observed behavior. A crossover from the new self-poisoning regime to a steady state with AB production occurs at L≂30±5 and pA≂0.36±0.02 for incipient percolation clusters and at L≂12±2 and pA≂0.51±0.02 on the square lattice, where L and pA are the lattice size and the mole fraction of the specie A in the gas phase, respectively. It is shown that surface diffusion of A particle does not influence the location of the self-poisoning regime.