Monte Carlo simulation of CO adlayers electrooxidation on Pt(111)

Numerical simulations of the electrooxidation of CO adsorbed on Pt(111) surfaces are presented. For adlayers prepared by CO dosage, the numerical results confirm previous proposals, based upon current experimental information, concerning the CO distribution on the Pt surface. Specifically, whereas at low coverages (below 1/3) CO forms open and easily oxidizable structures, at high coverages compact domains hinder the oxidation process. The two peaks observed in the voltametric profiles are thus a consequence of topological differences between the CO distributions at low and high coverages. We also present new experiments on the electrooxidation of CO adsorbed on Pt(111) upon the dissociative adsorption of formic acid. In this case our results indicate that a single oxidation peak remains up to coverages below 2/3. This striking new result is also reproduced in our simulations by laking the same kinetic parameters as in the previous case, and assuming that the CO are distributed on a honeycomb lattice, an assumption consistent with the characteristics of the dissociative adsorption of formic acid. (C) 1998 Elsevier Science B.V. All rights reserved.