Selective electrooxidation of 5-hydroxymethylfurfural to value-added 2,5-furanodiformic acid: mechanism, electrolyzer system, and electrocatalyst regulation.

Value-added chemical products derived from biomass have attracted wide attention in addressing global warming and fossil fuel pollution. Among them, 2,5-furanodiformic acid (FDCA), the oxidized product of 5-hydroxymethylfurfural (HMF), is an effective substitute for terylene acid extracted from petroleum to synthesize biodegradable plastics. Electrochemical oxidation is an environmentally friendly, mild reaction condition, high-efficiency process for converting HMF to FDCA. However, the electrooxidation of HMF involves six-electron transfer, normally leading to the formation of many by-products. Thus, there is still a need to construct highly selective catalysts for HMF electrooxidation to FDCA. In this review, first we have investigated the mechanism of HMF electrooxidation and summarized the electrolytic cells and product analysis methods for electrooxidation of HMF to FDCA. The factors influencing HMF electrooxidation to FDCA are also discussed. Then, the electronic structure regulation methods of various electrocatalysts including heteroatom doping, heterostructure construction, interfacial engineering, and defect engineering are systematically summarized for the highly selective electrooxidation of HMF to FDCA. Finally, future challenges and prospects are proposed for further deep understanding. It is expected that this review could provide new guidance for large-scale electrooxidation of HMF to FDCA in industry.