MOF-derived interface-rich silver/silver oxide nano-structures as an effective electrocatalyst for oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid (FDCA) with spontaneous FDCA separation in acid media

Abstract

The electrochemical oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) has attracted considerable attention as it could replace terephthalic acid to synthesize green polymers such as polyethylene 2,5-furandicarboxylate (PEF). In this report, MOF-derived silver/silver oxide (Ag/AgO_x–CN_x) is prepared for synthesis and simultaneous separation of 2,5-furandicarboxylic acid from the 5-hydroxymethylfurfural oxidation reaction in acid media. Typically, basic conditions are used to oxidize HMF to FDCA. To filter out FDCA, the pH must be lowered until it is insoluble. Therefore, scaling up the process would result in high operating costs due to the purchase of acids and bases and the disposal of salt waste. Ag/AgO_x–CN_x takes only 1.453 and 1.668 V (vs. RHE) potential to reach 10 mA cm⁻² current density for HMF and water oxidation with good stability, respectively. In addition, Ag/AgO_x–CN_x also possesses ∼75.61% faradaic efficiency for FDCA production under ambient conditions at 10 mA cm⁻² current density. HMF oxidation is an alternative anodic reaction for the evolution of H₂ in water-splitting cells, which has a higher oxidation rate than water at a particular potential. Ag/AgO_x–CN_x (anode) shows remarkable overall HMF oxidation reaction with 10 mA cm⁻² current density at 1.544 V cell potential while coupling with commercial Pt/C (cathode). The high electrocatalytic activity is due to the presence of interfaces, synergistic interaction between the components, and high electrochemical surface area. This work demonstrates that Ag/AgO_x–CN_x is an effective electrocatalyst for the simultaneous production of value-added chemicals from biomass-derived compounds and clean hydrogen fuels under ambient conditions using electrochemical devices.