Stabilization of alkaline 5-HMF electrolytes via Cannizzaro reaction for the electrochemical oxidation to FDCA

Abstract

The electrochemical oxidation of 5-(hydroxymethyl)furfural (HMF) to 2,5-furandicarboxylic acid (FDCA), a monomer for biopolymer production, caught attention as a route to renewable materials. However, this process is mostly performed in alkaline media, which causes HMF to degrade into humins. In this study, we demonstrate that alkaline degradation of HMF yielded 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) and dihydroxymethylfuran (DHMF), which are both stable in alkaline media, and both of which can be electrooxidized to FDCA. Furthermore, the stability of the Cannizzaro products allowed the “indirect” electrooxidation of HMF to FDCA at unprecedentedly high concentrations of substrate and base, leading to current densities on the order of technical processes (∼1 A cm⁻²) and increased space–time-yields.