In situ FTIR spectroscopic studies of ethylene glycol electrooxidation on Pd electrode in alkaline solution: The effects of concentration

We investigated the electrooxidation of ethylene glycol (EG) on polycrystalline Pd electrode in alkaline by in situ FTIR reflection spectroscopy, and focused on the effects of EG concentration (2 mM–1 M) on the reaction pathways. Voltammetric result shows the reaction order of EG is near 0.5. In situ FTIR results demonstrated that the reaction pathways and the product contribution strongly depend on the EG concentration. The oxidation degree of EG decreases with increasing EG concentration, and the main products gradually varies from CO 3 2 - , C 2 O 4 2 - , glyoxylate, to glycolate. Bridge-bonded CO (COB), generated from dissociative adsorption of EG, can be easily oxidized at low EG concentration. These facts were attributed to the competitive adsorption of EG itself and reaction intermediates with water, which inhibits the formation of oxygen species from water dissociation, a key oxygen donor for deep oxidation of EG. Even though, EG is still much better than ethanol as candidate fuel for alkaline direct alcohol fuel cells. The present study is of importance for understanding reaction mechanism of EG electrooxidation.