Resolution of the mechanism of CO electrooxidation on steady state and evaluation of the kinetic parameters for Pt and Ru electrodes

M.S. RAU; M.R. GENNERO DE CHIALVO; A.C. CHIALVO

JOURNAL OF SOLID STATE ELECTROCHEMISTRY (PRINT)

SPRINGER

Año: 2012 vol. 16 p. 1893 - 1900

1432-8488

The carbon monoxide oxidation reaction (COOR) was studied on steady state conditions by chronoamperometry on polycrystalline smooth platinum and ruthenium rotating disc electrodes in CO saturated acid solution. The chronoamperometric response did not show current oscillations and therefore the current density (j) vs. overpotential (eta) curves on steady state could be obtained. In order to interpret these results, kinetic expressions were derived starting from the mechanism proposed by S. Gilman, which considers two adsorbed reaction intermediates, carbon monoxide (COad) and hydroxyl (OHad). Analytical expressions as a function of overpotential for the current density, the surface coverage of the adsorbed species (CO and OH) and the CO and CO2 pressures at the electrode surface on steady state were obtained. This set of equations was used for the correlation of the experimental polarization curves and the evaluation of the corresponding kinetic parameters. The results obtained allowed to establish the behaviour of the adsorbed intermediates and demonstrated that the Gilman´s mechanism accurately describes the experimental results on steady state of the COOR on these metals. It was also shown that potentiodynamic methods are not appropriate for the kinetic analysis of the reaction.