Displacement of inactive phases by the reactive regime in a lattice gas model for a dimer-monomer irreversible surface reaction

A lattice gas model for the catalytic reaction A + 1/2B(2) --> AB is used for the study of the adsorbate displacement on fully covered surfaces with B and A species (i.e., poisoned phases) by the reactive state. The geometry used mimics narrow channels of width L whose ends are in contact with B-2 and A sources. Also, the channels are in contact with a reservoir of A and B-2 species in the gas phase, P-A and 1-P-A being the adsorption probabilities or such species, respectively. The displacement of the B-poisoned phase is slower than the A-poisoned one; however, both displacements stop at certain critical probabilities, P-A(c1)(L) and P-A(c2)(L), respectively, which depend on the channel width. Extrapolation to the asymptotic regime L --> oo leads us to conclude that such critical probabilities can be correlated with the critical points P-1A and P-2A at which the model exhibits irreversible phase transitions between a stationary reactive regime and B- and A-poisoned states. During the displacement of A-poisoned phases, it is found that the interface width w(2)(t) of the reactive regime diverges for P-A less than or equal to P-A(c2) but remains bounded for higher P-A values. Just at the critical point one has w(2)(t) x t(B), with beta-->1 for L --> oo. Above the critical threshold, the time and adsorption probability dependence of w(2) is well described using general dynamic scaling arguments.