EFFECT OF INERT SITES ON THE KINETIC OSCILLATIONS IN THE CATALYTIC COOXIDATION ON PT(100)

The effect of inert sites in the global oscillations in the oxidation of CO on Pt(100) for both random and clustered inert sites is simulate d by use of the cellular automaton technique. The cellular automaton r ules account for the structural phase transformations of the Pt substr ate, the reaction kinetics of the adsorbed phase and diffusion of adso rbed species. The introduction of a fraction ed of inert sites reduces the extent of the oscillatory region on the bifurcation diagram. The effect of added impurities on the transition from oscillatory to CO po isoned state is found to be quite different depending on the initial p osition on the bifurcation diagram. Points located near the rightmost branch on the bifurcation diagram will reach inert state through a ver y abrupt transition, whereas points located far from it undergo a much softer transition. Clustered impurities tend to soften the transition , and higher values of theta(d) are needed to trigger the transition t o the poisoned state. The study of a mean-field model without the osci llatory kinetics explains some of the basic features of the effect of increasing densities of impurities on the catalytic surface, for insta nce the dependence of the location of the transition point theta(d) on the adsorption rate of CO. (C) 1998 American Institute of Physics. [S 0021-9606(98)70143-6].