Work

What Drives the Selectivity of 5-(Hydroxymethyl)furfural Electroreduction over Copper in Mildly Basic Medium?

Year: 2026

Type: article

Abstract: 2,5-bishydroxymethylfuran (BHMF) is a key bio-monomer that can be obtained by the electrochemical reduction of 5-(hydroxymethyl)furfural (HMF), bypassing the need for molecular hydrogen. Mildly alkaline conditions favor BHMF over hydrogenolysis products; however, on the cheapest Cu electrodes, they also promote side reactions such as hydrodimerization into 5,5'-bis(hydroxymethyl)hydrofuroin (BHH) and oligomerization at HMF concentrations above 20mM, thus hindering process scalability. The mechanistic understanding of HMF electroreduction under mildly basic conditions remains limited compared to acidic environments, preventing rational improvements in selectivity at industrially relevant concentrations. In this work, using a combination of experimental and computational studies, we investigated the competition between BHMF formation and unwanted hydrodimerization into BHH at pH 9.2 on Cu foam electrocatalysts with different electroactive surface area. Our findings reveal that BHH formation and carbon loss (C-loss) by oligomerization originate from two distinct pathways. The dimerization results from the surface-catalyzed C-C coupling of two HMF adsorbates, whereas oligomerization is related to the desorption of the ketyl intermediate into the double layer, a process increasingly favored at more cathodic potentials. In contrast, BHMF formation proceeds preferably via hydrogenation of an alkoxyl intermediate. The contribution of each pathway is modified with the electroactive Cu surface area. A larger surface area of the Cu foam, obtained by Cu nanoparticles electrodeposition, results in an increase in BHMF selectivity from 40% to 58% at 50mM HMF and a remarkable decrease of the oligomerization when performing the reaction at -0.51V vs RHE. Our findings provide mechanistic insight into how catalyst morphology and electrochemical conditions control selectivity in HMF electroreduction for Cu electrocatalysts, offering design principles to optimize BHMF production while minimizing hydrodimerization and carbon loss by oligomerization.

Source: ACS Catalysis

DOI: 10.1021/acscatal.6c05142