Electrooxidation of oxalic acid on platinum in acidic solutions: A combined mechanism

It is shown that, when considering the electrochemical behavior of oxalic a cid (OA) on platinum, it is necessary to account for the presence of three types of adsorbates of OA. It is established that kinetic parameters of the OA electrooxidation are sensitive to the electrolyte's temperature and com position, which explains contradictions in the literature data. The electro oxidation reaction order by OA is 0.2-0.6 at pH 0.3-2.8 and depends on both the potential and the OA concentration. Such order points to the participa tion of the OA adsorption products in the rate-determining stage of the pro cess. The OA electrooxidation reaction order by hydroxyl ions is 0.8 at ele vated temperatures, pH 0.3-2.8, and a constant potential; at room temperatu re, it diminishes to -0.4 in the oxygen range of potentials. The experiment al data suggest that two OA oxidation processes occur in parallel (with and without participation of adsorbed oxygen-containing species). The balance between the rates of these processes is potential-dependent.