Kinetics of monomer-monomer surface catalytic reactions

Abstract

We study the kinetics of an irreversible monomer-monomer model of heterogeneous catalysis. In this model, two reactive species, A and B, adsorb and stick to single sites of a catalytic substrate. Surface reactions are assumed to occur only between dissimilar species that are nearest neighbors on the substrate. The kinetics of the process are studied in the reaction-controlled limit. We map the monomer-monomer model of heterogeneous catalysis onto a kinetic Ising model and find that the dynamics of the process is a superposition of zero-temperature spin-flip dynamics and infinite-temperature spin-exchange dynamics. We solve the kinetics analytically and determine the rate at which the catalyst becomes ‘‘saturated,’’ i.e., completely covered by only one species. We show that the saturation time is proportional to N ln(N), where N is the number of catalyst sites. We also discuss the monomer-monomer process with desorption.