Electrochemical valorization of HMF using Ni/Graphite electrodes

The electrooxidation of 5-hydroxymethylfurfural (HMF) into 2,5- furandicarboxilic acid (FDCA) has been successfully accomplished using cost-effective NiO-OH electrodes, prepared through Ni electrodeposition on pencil graphite rods (Ni/PGR). Through meticulous optimization of the reaction conditions to prevent HMF degradation, we achieved almost complete conversion of HMF into FDC, in less than 2 h, with a remarkable 88 % Faraday efficiency. Electrochemical analyses have confirmed that our Ni(OH)2/NiOOH center dot catalyst requires a 0.16 V lower overpotential for HMF oxidation compared to water oxidation. Fitting the Impedance Spectroscopy (IS) spectra of the system have allowed us to elucidate, the details of the electrical response associated to HMF oxidation. These studies have revealed that following HMF activation, the surface of the Ni/PGR electrode remains coated with the reaction intermediates, thus triggering the complete oxidation to FDCA.