Stripping and bulk CO electro-oxidation at the Pt-electrode interface: Dynamic Monte Carlo simulations

We perform dynamic Monte Carlo simulations to understand the kinetics of CO oxidation on Pt surface. Our simulations are performed on a model for CO electro-oxidation, where oxygen-containing species (adsorbed OH) formed on the Pt surface reacts with adsorbed CO by a Langmuir-Hinshelwood mechanism to form CO2. A systematic study of the model parameters shows that we obtain better electrocatalytic activity by increasing the surface diffusion coefficient of CO (k(D)) or the rate of reaction between adsorbed CO and adsorbed OH. We also show that if the initial state of adsorbed CO is a closely packed structure, increasing the surface coverage can result in negative voltammetry peak shifts because of the formation of weakly adsorbed states of CO. We have also modeled bulk CO voltammetry by introducing a CO adsorption rate, k(4). We show that near-zero currents are obtained for the potentials (E) where the rate of OH adsorption, k(1)(E), is much smaller than k(4). We also note that k(D) plays no significant role in CO oxidation when k(D)<>k(4), whereas they vary significantly when k(4)congruent tok(1)(E). (C) 2001 American Institute of Physics.