MECHANISTIC STUDY OF THE ELECTROOXIDATION OF ETHYLENE-GLYCOL ON GOLD AND ADATOM-MODIFIED GOLD ELECTRODES IN ALKALINE-MEDIUM

A mechanistic investigation of the electrochemical oxidation of ethylene glycol (EG), on gold and adatom-modified gold electrodes, was carried out in alkaline medium. Besides the purely kinetic electrochemical study, and for a complete survey of the electrochemical mechanism, analyses of the reaction products in solution were performed by liquid chromatography (HPLC) and infrared spectroscopy (FTIRS). Additional information on the nature of the adsorbates was also provided by means of in situ infrared reflectance spectroscopy (EMIRS). The kinetic parameters, estimated from the electrochemical data, suggest a one-electron step to be rate determining. In contrast to the case in acid medium, the spectroscopic results show clearly that almost no C-C bond scission occurs during adsorption in alkaline medium. Depending on the potential of electrolysis, the major products of the reaction are found to be glycolate alone, or a mixture of glycolate, oxalate, carbonate and formate. The shift of the polarization curves towards more negative potentials, observed when the oxidation of EG is carried out on some of the adatom-modified electrodes (Pb+Au and Bi+Au), may be explained through modification of the coverage of the electrode surface by organic adsorption residues. © 1990.