Oxidation of the Partly Oxidized Ethylene Glycol Oxidation Products Glycolaldehyde, Glyoxal, Glycolic Acid, Glyoxylic Acid, and Oxalic Acid on Pt Electrodes: A Combined ATR-FTIRS and DEMS Spectroelectrochemical Study

Abstract

Adsorption and oxidation of the partly oxidized C2 products of ethylene glycol oxidation glycolaldehyde, glyoxal, glycolic acid, glyoxylic acid, and oxalic acid on a Pt thin film electrode were investigated using a combined spectroelectrochemical approach under continuous flow conditions. Potentiostatic as well as potentiodynamic experiments were preformed. The potential-dependent development of the adlayer resulting from the interaction of the organic molecules with the Pt film electrode was followed by highly surface sensitive, in situ ATR-FTIR spectroscopy, while the volatile products were simultaneously monitored by online differential electrochemical mass spectrometry (DEMS). The ATR-FTIR spectra recorded in the initial phase of the adsorption of the small organic molecules show characteristic bands in the range 1630–1705 cm–1 when glyoxal (1645 cm–1), glyoxylic acid (1705 cm–1), glycolaldehyde, or ethylene glycol is admitted, which are assigned to adsorbed 2-oxoacetyl and 2-carboxyacteyl, or 2-hydroxyacetyl, respectively. The potential-dependent initial COad formation rates are determined showing high rates for the aldehydes at low potentials with glyoxal having the highest rates. With increasing potential, the hydroxyl group becomes more active, while the COad formation rate from the carbonyl group decreases.