Synergetic effect and oscillatory behavior of CO oxidation over a bimetallic composite catalyst

This article describes the results of simulations of CO oxidation under low pressure conditions over a bimetallic Pt/Rh composite catalyst. The model is represented by a system of four differential algebraic equations (DAEs) for the coverages of COads and C-ads, on the two parts of the composite surface. Surface diffusion of both adsorbates is assumed to be fast. The experimentally observed synergetic effect concerning CO oxidation on a Rh surface partly covered by Pt monolayer islands is reproduced in the simulations. It is shown that this synergetic effect is due to the difference in the CO sticking coefficients on Pt and Rh surfaces. In addition, a new type of kinetic oscillations, namely synergetic kinetic oscillations are predicted by the simulations. These oscillations exist under conditions at which no oscillations can exist over Pt and Rh monometallic catalysts. The driving force of this new type of oscillations is connected to the large difference in binding energy of adsorbed oxygen atoms on Rh and Pt. (C) 2015 Elsevier B.V. All rights reserved.