APPLICATIONS OF REAL-TIME FTIR SPECTROSCOPY TO THE ELUCIDATION OF COMPLEX ELECTROORGANIC PATHWAYS - ELECTROOXIDATION OF ETHYLENE-GLYCOL ON GOLD, PLATINUM, AND NICKEL IN ALKALINE-SOLUTION

The electrooxidation pathways of ethylene glycol in alkaline aqueous solution on gold, platinum, and nickel electrodes are explored by means of real-time FTIR spectroscopy in conjunction with cyclic voltammetry. The former enables a quantitative assay of specific intermediates and products formed during the reaction evolution. The electrooxidation on gold features the successive formation of partially oxidized C2 Solution species en route to oxalate and carbonate production. The latter species is produced predominantly via the formation of the dialdehyde, glyoxal, based on comparisons with electrooxidative spectral sequences for candidate intermediate species. In contrast, ethylene glycol electrooxidation on platinum exhibits markedly different kinetics and product distributions to those for the partially oxidized C2 species, inferring that at least carbonate production from ethylene glycol occurs largely through sequences of chemisorbed, rather than solution-phase, intermediates. Electrooxidation of ethylene glycol and higher polyols on nickel display a remarkably selective production of formate. This efficient oxidative C-C bond cleavage on nickel is displayed in somewhat different fashion for partially oxidized C2 reactants in that carbonate is predominantly formed. Some possible surface chemical factors responsible for these striking mechanistic differences are discussed.