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

摘要

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 ℃ and pressure of up to 7 atm. 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 ℃. 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 CO_2 that bypasses CO_(ads). Activation energies of 18 and 43 kJ/mol were measured for EG conversion and CO_2 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.