Glucose electrooxidation reaction on Ni-based nanocatalysts for replacing OER in alkaline electrolyser

With a backdrop of energy transition and geopolitical tensions, efficient biomass-assisted hydrogen production with non-platinum group metals is sought. Understanding of the related reaction mechanisms is crucial for the rational development of effective electrocatalytic materials but said mechanisms can sometimes be uncritically trusted and cited extensively in contexts deviating from the original working hypotheses. This is the case for Fleischmann's mechanism for the glucose oxidation reaction (GOR) on nickel, where the initial information was progressively modified and extrapolated carelessly. In line with recent research, this work attempts to tackle some preconceptions about the glucose oxidation reaction on nickel and nickel-based electrodes. The electrooxidation of xylose, another major product of lignocellulosic biomass, but very scarcely discussed in the literature, is also studied, alone and in a biomass-like mixture with glucose. Based on electrochemical (cyclic voltammetry, chronoamperometry and impedance spectroscopy) and analytical (product distribution obtained during 5 hours aldose electrolysis experiments) results on different anode materials (Ni foam, Ni@Ni(O_xH_y)/C and Ni₅Mn₅O_x/C), the aldose electrooxidation mechanisms are revisited. Additionally, this study addresses some previously unexplored questions concerning this system such as material poisoning, the viability of using a membrane in GOR electrolysis cells, or the impact of aldose chemical degradation by the alkaline electrolyte on selectivity interpretation.