Electrooxidation of adsorbed CO on polycrystalline platinum in alkaline solutions

Abstract

The electrooxidation of adsorbed CO on polycristalline platinum in 1 M KOH was investigated under potentiodynamic conditions. A micro flux cell was used to avoid CO readsorption during the oxidation process. Three oxidation current peaks are observed at low sweep rates for the electrooxidation of (CO) ad obtained from CO-saturated electrolyte. The corresponding peak potentials shift towards more positive values, but the three peaks gradually overlap to give a single broad asymmetric current peak as v is increased. The multiplicity in the oxidation current peaks for (CO) ad under adsorption saturation is interpreted in terms of reactions involving different OH—substrate and CO—substrate interactions, instead of the existence of the “linear” or “bridge” adsorbed structures for (CO) ad. For (CO) ad below saturation values, a complex model involving different (CO) ad structures interacting with energetically different (OH) ad should be considered. From the dependence of peak potential on log v, a chemical reaction between adsorbed CO and platinum oxides can in principle be postulated as the rds. The splitting of the initial stages of oxide electroformation in the presence of adsorbed CO is evident from the triangular modulated linear potential sweep (TMLPS).