A RING-DISK STUDY OF THE COMPETITION BETWEEN ANODIC OXYGEN-TRANSFER AND DIOXYGEN EVOLUTION REACTIONS

Voltammetric data obtained at a rotated ring-disk electrode for oxidat ion of dimethyl sulfoxide (DMSO) to dimethyl sulfone support the concl usion that anodic O-transfer and O-2(aq)-evolution reactions are in co mpetition for a common reaction precursor, That species is concluded t o be the adsorbed OH radical generated by anodic discharge of H2O, Bec ause of this competition, an increase in the nux of the reactant in th e O-transfer reaction causes a decrease in the rate of O-2(aq) evoluti on, Therefore, difference voltammetry and hydrodynamically modulated v oltammetry cannot be considered reliable for accurate deconvolution of the total electrode current resulting from these concomitant processe s. A simple mathematical model is developed to describe the total curr ent resulting from these simultaneous processes, and results of prelim inary tests of this model are in good agreement with experimental data for DMSO oxidation.