A model for the catalytic oxidation of CO that includes CO desorption and diffusion, O repulsion, and impurities in the gas phase

Abstract

We present kinetic Monte Carlo simulations exploring the nonequilibrium phase diagram of a modified Ziff–Gulari–Barshad (ZGB) dynamic lattice-gas model for the catalytic oxidation of carbon monoxide (CO) on a surface. The modified model includes the simultaneous presence of contaminants in the gas phase, CO desorption, CO diffusion, and strong repulsion between adsorbed oxygen (O) atoms; all of which have been observed in experimental systems. We find that the strong O–O repulsion produces higher reaction rates, albeit in a reduced reactive pressure window. In systems with impurities, the CO2 production rate is greatly reduced, but this effect is mitigated by CO desorption and diffusion. CO desorption has the effect of widening the reactive pressure window, while CO diffusion has the effect of increasing the reaction rate. In some parameter regimes the presence of impurities destroys the discontinuous transition between the reactive and high CO coverage phases.