Electrocatalytic oxidation of biomass-derived furans to 2,5-furandicarboxylic acid – a review

Abstract

Electrocatalytic conversion of biomass will become necessary for achieving the sustainable production of many kinds of chemicals. In this review, an analysis of catalysts, cell design, coupling reactions, separation and production methods is given for the conversion of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) via electrochemical oxidation. Transition metal-based catalysts (e.g. Ni) can achieve a balance between activity and selectivity. However, issues such as low stability and insufficient active sites hinder the electrocatalytic efficiency of the conversion of HMF into FDCA with transition metal-based catalysts. Enhancements can be achieved through controlling the catalyst morphology and particle size, doping with heteroatoms (N, S, P), crystal structure regulation, and defect/vacancy creation. The design of the electrolytic cell is critical to the stability of the electrocatalytic oxidation of HMF, and the membrane electrolytic cell (MEA) combined with feed separation can reduce side-product formation (e.g. <10% humins) at high HMF concentrations (100 mM) in alkaline electrolytes (1 M KOH). Coupling the electrocatalytic oxidation of HMF with reduction reactions (e.g. hydrogen evolution reaction, nitrogen reduction reaction) can achieve up to twice the energy efficiency, while bifunctional electrocatalysts can balance the potentials and electrocatalytic rates of the cathode and anode. Using organic solvents (e.g. methanol or isobutanol) and controlled temperatures (393 K to 413 K), FDCA (>90%) can be effectively separated and purified at production rates of up to an estimated 33 000 tonnes of FDCA per year (95% HMF conversion) from a feed stream in which KOH can be separated from HMF with current technology. The stability of electrolytic systems under high current densities (>500 mA cm⁻²) is an important factor in industrial applications. Increasing the electrode area or modifying the coordination bonds of the sites can help to remove bottleneck issues associated with long operating hours at high current densities.