Recent progress, trends, and new challenges in the electrochemical production of green hydrogen coupled to selective electrooxidation of 5-hydroxymethylfurfural (HMF)

Abstract

The production of clean electrical energy and the correct use of waste materials are two topics that currently concern humanity. In order to face both problems, extensive work has been done on the electrolytic production of green H₂ coupled with the electrooxidative upgrading of biomass platform molecules. 5-Hydroxymethylfurfural (HMF) is obtained from forest waste biomass and can be selectively oxidized to 2,5-furandicarboxylic acid (FDCA) by electrochemical pathways. FDCA is an attractive precursor to polyethylene furanoate (PEF), with the potential to replace petroleum-based polyethylene terephthalate (PET). An integrated electrochemical system can simultaneously produce H₂ and FDCA at a lower energy cost than that required for electrolytic water splitting. Here, the benefits of the electrochemical production of H₂ and FDCA over other production methods are presented, as well as the innovative applications of each reaction product and the advantages of carrying out both reactions in a coupled system. The recently reported progress is disclosed, through an exploration of electrocatalyst materials used in simultaneous production, including the use of nickel foams (NF) as modification substrates, noble and non-noble metals, metal non-oxides, metal oxides, spinel oxides and the introduction of oxygen vacancies. Based on the latest trends, the next challenges associated with its large-scale production are proposed for its implementation in the industrial world. This work can offer a guideline for the detailed understanding of the electrooxidation of HMF towards FDCA with the production of H₂, as well as the design of advanced electrocatalysts for the sustainable use of renewable resources.

Fig. 1. Operation of a PEM fuel cell.

Fig. 2. (a) Traditional water electrolysis with simultaneous O₂ and H₂ production, (b) simultaneous production of H₂ and value-added products.

Fig. 3. Steps involved in obtaining food and beverage packaging. (a) dehydration of C6 carbohydrates obtained from biomass, (b) oxidation of HMF to FDCA and (c) polymerization treatments.

Fig. 4. Oxidation scheme of HMF to FDCA (2,5 furan dicarboxylic acid) in 3 steps, with an exchange of 6 total electrons, through two possible routes: via DFF (diformyl furan) and via HMFCA (5-hydroxymethyl-2 furan carboxylic acid), where FFCA (5-formyl-furoic acid) is intermediary.

Fig. 5. Simultaneous production of H₂ and 2,5-furandicarboxylic acid (FDCA).

Fig. 6. Representation of an H-type electrolysis cell suitable for the simultaneous electrochemical production of liquid FDCA and gaseous H₂. Both products can be followed by HPLC and GC respectively.