Numerical simulation of the voltammetric electrooxidation of CO adsorbed on Pt(111)

Numerical simulations of the voltammetric electrooxidation of CO adsorbed o n Pt(111) surfaces are presented. For CO dosage, the numerical results conf irm previous proposals, based upon current experimental information, concer ning the CO distribution on the Pt surface. Specifically, whereas at low co verages (below 1/3) CO forms easily oxidizable open structures, at high cov erages compact domains hinder the oxidation process. The two peaks observed in the voltammetric profiles are thus a consequence of topological differe nces between the CO distributions at low and high coverages. We also presen t new experiments on the electrooxidation of CO adlayers on Pt(111) formed upon the dissociative adsorption of formic acid. In this case our results i ndicate that a single oxidation peak remains up to coverages near 2/3. This striking new result is also reproduced in our simulations by taking the sa me kinetic parameters as in the previous case, and assuming that the CO are distributed on a honeycomb lattice, an assumption consistent with the char acteristics of the dissociative adsorption of formic acid. (C) 1998 Elsevie r Science Ltd. All rights reserved.