Hydrogen Generation by Electrocatalyic Reforming of Biomass-Related Compounds: Ethylene Glycol

Abstract

Electrocatalytic reforming (ECR) of ethylene glycol (EG) was studied in an effort to determine the feasibility of ECR for hydrogen production from biomass. Measurements were made in a proton exchange membrane (PEM) reactor with Pt/C anode and cathode and Nafion electrolyte. Electrooxidation of EG in aqueous phase was studied over the temperature range of 40--137 °C. Reaction progress was followed by cyclic voltammetry, potential-step chronoamperometry, and chromatographic analysis of reaction products. Sustained reaction occurred at an overpotential as low as 0.49 V at 137 °C. A variety of partial oxidation products were observed; glycolaldehyde, glycolic acid, and traces of oxalic acid; mostly at low temperatures. The results were interpreted according to the dual pathways mechanism, in which path A involves a series reaction through a CO ads intermediate, and path B is parallel route to CO2 that bypasses CO ads . Activation energies of 18 and 43 kJ/mol were measured for EG conversion and CO2 production. The lower value is attributed to formation of partial oxidation products, and the higher value to CO ads electrooxidation in path A. The sustained reaction at low overpotential along with near complete oxidation, both of which occur at high temperature, show that ECR can be a viable process in biomass reforming, and that further studies must be conducted at higher temperatures for a more complete understanding of this process.