Self-accelerating kinetics of CO2 formation on Ir(110)

We report measurements of CO oxidation by CO molecular beam titration measurements on an Ir(110) surface precovered with atomically bonded oxygen. During the course of the titration, both the reaction product CO2 and the backscattered CO intensity were detected. The oxygen precoverage, the kinetic energy of the molecular CO and the surface temperature were varied. The CO2 formation rate increases with increasing CO exposure time and depends strongly on surface temperature. The self-accelerating CO2 formation kinetics are semi-quantitatively discussed using computer simulations with rate equations of the Langmuir-Hinshelwood type with coverage-dependent reaction rate coefficients and adsorption probabilities. (C) 1998 Elsevier Science B.V.