Dual-path glucose electrooxidation reaction on Ni(OH)2/NiOOH catalysts in alkaline media

Abstract

Glucose electrooxidation has been widely studied for its application in biosensors, fuel cells and electrosynthesis of value-added products. Nickel is known to catalyze the glucose oxidation reaction (GOR) in alkaline media, but the mechanism, the nature of the active sites, and reaction products are still being debated. This study focuses on elucidating the reaction pathways of the GOR on a Ni(OH)2/NiOOH electrode through electrochemical measurements, in-situ Fourier transform infrared spectroscopy (FTIRS) and microkinetic modeling. The electrode was prepared by Ni electrodeposition on glassy carbon (NiED/GC) followed by electrochemical oxidation into Ni(OH)2/NiOOH. The shape of the cyclic voltammograms obtained during the GOR was found to be significantly influenced by the presence of Fe impurities in the NaOH electrolyte. With the help of microkinetic modeling, a dual-path mechanism was proposed for the glucose electrooxidation on the Ni(OH)2/NiOOH surface, comprised of Eley–Rideal and Langmuir-Hinshelwood pathways, with NiOOH reacting either with glucose from solution or adsorbed on Ni(OH)2 sites. In-situ FTIR measurements reveal the formation of formate at potentials as low as 1.17 V vs. RHE.