Electrochemical oxidation of glucose in alkaline environment—A comparative study of Ni and Au electrodes

Abstract

The glucose oxidation reaction (GOR) was studied on Au and Ni electrodes by cyclic voltammetry (CV), rotating disk electrode (RDE) measurements coupled with Koutecky–Levich analysis, Differential Electrochemical Mass Spectrometry (DEMS), in situ Fourier Transform Infrared spectroscopy (FTIRS) and High Performance Liquid Chromatography (HPLC) analysis of the reaction products after electrolysis in potentiostatic mode under continuous flow conditions. This study allowed to identify the reaction products and propose tentative reaction mechanisms. On gold, glucose is adsorbed on metallic sites through its anomeric function (C1) resulting in the formation of gluconate as the main GOR product at potentials close to 0.6 V vs. RHE, with a selectivity towards gluconate close to 100% and a projected faradaic efficiency of ca. 70%. The conversion rate is rather low, close to 20%, due to poisoning of the surface, leading to a strong deactivation. At potentials above 0.7 V vs. RHE, the selectivity towards gluconate decreases and non-selective GOR oxidation proceeds through CC bond cleavage. On nickel, the GOR occurs at high potentials (close to 1.2 V vs. RHE) on Ni(OH)2 and NiOOH sites, and proceeds through C1C2 bond breaking, resulting in arabinose and formate. At higher potentials, the selectivity towards arabinose decreases, formate being the main reaction product.