Mechanistic analysis of 5-hydroxymethyl furfural electro-oxidation via in situ quantification of intermediates using rotating ring-disk electrodes

Abstract

Understanding the reaction pathway of 5-hydroxymethylfurfural (HMF) oxidation is important for designing electrocatalysts that can selectively convert biomass into valuable chemicals. By leveraging the advantages of rotating ring-disk electrode (RRDE) voltammetry as an in situ electrochemical method, we directly probed the formation of key intermediates during HMF oxidation. By systematically varying the electrolyte pH and applying selective ring electrode potentials, transient intermediates such as 2,5-diformylfuran and 5-formyl-2-furancarboxylic acid were quantitatively detected at the ring electrode. The electrooxidation of HMF on nickel- and cobalt-based electrocatalysts was analysed by monitoring the intermediates at the ring electrode. The potential-dependent percentage of electroactive intermediates and the apparent electron transfer number are used to assess Co- and Ni-based electrocatalysts. This approach avoids the time-consuming chromatographic product analysis commonly used to study this reaction and provides a general strategy for quantitatively resolving complex multi-electron electrochemical pathways.