Electrocatalytic Refinery of Biomass-Based 5-Hydroxymethylfurfural to Fine Chemicals

Because of depleting fossil-fuel reserves, together with the impacts of climate change, alternative eco-friendly production of high-value chemicals and renewables is needed. Biomass feedstock is of particular research interest. 5-Hydroxymethylfural (HMF) is a versatile precursor that can be converted to high-value chemicals via electrolysis. Reduction generates precursors for ethers, ketones, polyurethanes, polyesters, and polyethers, e.g., 2,5-dihydroxymethylfuran (DHMF) and 2,5-dimethyletrahydrofuran (DHMTHF), together with high-energy-density premium biofuels, e.g., 2,5-dimethylfuran (DMF), 2,5-hexanedione (HD) and 5,5′-bis(hydroxymethyl) hydrofuroin (BHH). Oxidation HMF yields valuable chemical products, including 2,5-diformyl furan (DFF), 5-hydroxymethyl-2-furan carboxylic acid (HMFCA), 2,5-furan dicarboxylic acid (FDCA), and maleic acid (MA) that are precursors/intermediates for the polymer industry and chemical/pharmaceutical production(s). In this review, we 1) report a comparative summary of the electrocatalytic refinery of HMF, both electro-oxidation and electroreduction pathways, 2) appraise advances in HMF electroreduction reaction (HRR) and HMF electro-oxidation reaction (HOR), 3) assess reaction pathways and mechanisms, 4) establish a design for electrocatalysts including selection of metal materials, design of the geometric structure, and electronic structural modifications to boost HRR and HOR activity and selectivity, 5) evaluate the impact of reaction parameters including pH, electrolyte composition, applied potential, and initial substrate concentration on HRR and HOR, and 6) provide a prospect on future electrochemical refinement of HMF. We conclude that an improved understanding of reaction conditions is needed to practically boost selectivity and activity for the electrochemical refinement of HMF. Findings will benefit in design for electrochemistry and eco-friendly chemistry in generating fine chemicals and, therefore, are of interest to researchers and manufacturers.