Potential oscillations during electro-oxidation of ethanol on platinum in alkaline media: The role of surface sites

Abstract

The electro-oxidation of small organic molecules is one of the major areas of interest in electrocatalysis due to its potential use in energy conversion. Instabilities in alkaline solution, particularly in comparison with kinetic properties in a conventional regime, are rarely reported in the literature, despite the fact that the catalytic activity is higher in this medium and the onset potential is shifted to lower values compared to acidic media. Ethanol oxidation on polycrystalline platinum exhibits oscillations under galvanostatic control. As the reaction is structure-sensitive, it is possible to study the contribution of the three platinum basal planes to the complex kinetics. We found that Pt(100) has the major influence in the overall non-linear kinetics of ethanol electro-oxidation on Pt(poly), possibly because it has the highest formation and accumulation rate of COads. Based on the differences observed in the galvanostatic transients on Pt(poly), Pt(110) and\\ Pt(100), and the absence of this behavior on Pt(111), it is possible to infer that surface sites strongly influence the kinetic scenario during the ethanol oxidation reaction.