Ethylene Glycol Electrooxidation on Smooth and Nanostructured Pd Electrodes in Alkaline Media

The electrooxidation of ethylene glycol (EG) has been studied either in situ on a smooth Pd electrode by FTIR spectroscopy or on nanostructured Pd-based catalysts by cyclic voltammetry. The electrooxidation on the Pd electrode is dramatically influenced by the pH. Below pH 12, CO2 is formed and detected in the thin layer by FTIR, while at higher pH values glycolate, carbonate and oxalate are formed almost simultaneously at a potential of ca. 0.4 V versus RHE. Above 0.9 V glycolate is oxidised to oxalate and carbonate. The nanostructured electrocatalysts Pd–(Ni–Zn)/C, Pd–(Ni–Zn–P)/C and Pd/C are much more active than the smooth Pd electrode (up to 3,300 A g(Pd)–1) and give different distributions of the oxidation products. Pd/C is the most selective catalyst yielding glycolate, while mixtures of glycolate (major>60%), oxalate and carbonate are obtained with Pd–(Ni–Zn)/C or Pd–(Ni–Zn–P)/C. Carbonate is produced by oxidation of both glycolate (major contribution) and oxalate, while the major part of oxalate seems to be produced by the direct oxidation of EG.