Electroreductive 5‐Hydroxymethylfurfural Dimerization on Carbon Electrodes

Green fuel: The electrohydrodimerization of biomass-based 5-hydroxymethlfurfural to the fuel precursor 5,5’-bis(hydroxymethyl)hydrofuroin on carbon electrodes is a promising pathway towards renewable fuels. The effect of the hybridization of the carbon electrode on the HMF electroreduction activity and selectivity is studied, as well as the influence of applied potential and initial HMF concentration. The electrochemical conversion of biomass-based compounds to fuels and fuel precursors can aid the defossilization of the transportation sector. Herein, the electrohydrodimerization of 5-hydroxymethylfurfural (HMF) to the fuel precursor 5,5’-bis(hydroxymethyl)hydrofuroin (BHH) was investigated on different carbon electrodes. Compared to boron-doped diamond (BDD) electrodes, on glassy carbon (GC) electrodes a less negative HMF reduction onset potential and a switch in product selectivity from BHH to the electrocatalytic hydrogenation product 2,5-di(hydroxymethyl)furan (DHMF) with increasing overpotential was found. On BDD, the electrohydrodimerization was the dominant process independent of the applied potential. An increase in the initial HMF concentration led to suppression of the competing hydrogen evolution reaction and DHMF formation, resulting in higher BHH faradaic efficiencies. In contrast, BHH selectivity decreased with higher initial HMF concentration, which was attributed to increased electrochemically induced HMF degradation. Finally, it was demonstrated that even a simple graphite foil can function as an active HMF electroreduction catalyst