New results for the electrosorption of methanol on polycrystalline platinum in acid medium obtained by programmed potential voltammetry

Abstract

The adsorption of methanol at a fixed potential on a polycrystalline Pt electrode is investigated using programmed potential voltammetry. The degree of coverage of the methanolic adsorption residues, θ org, and the number of electrons per site, N eps, necessary to its complete oxidation, are determined by integration of the voltammograms after some corrections are made to take into account the modification of the double layer by the adsorbed species, and a small methanol bulk oxidation. θ org, which is relatively constant between 0.2 and 0.55 V/RHE, is always smaller than 1, even for concentrated solutions (5 M CH 3OH) at long adsorption times (1000 s). N eps is also practically constant, having a value close to 2, except in the potential range outside which θ org varies, or at very small adsorption times ( t ads < 1 s), for which it is smaller than 2. Such results, which suggest that linearly bonded CO is the main adsorbed species, are in agreement with the data obtained by Infrared Reflectance Spectroscopy.