Bio-inspired proton relay for promoting continuous 5-hydroxymethylfurfural electrooxidation in a flowing system

Abstract

Electrooxidation of 5-hydroxymethylfurfural (HMF) to produce the platform molecule 2,5-furandicarboxylic acid (FDCA) provides a promising approach for biomass upgrading and green hydrogen production. However, the slow reaction kinetics and poor stability of the anode catalyst hinder continuous FDCA production in flowing systems at industrial current densities (>200 mA cm⁻²). Herein, a ligand-modified catalyst, Ni(OH)₂–TPA (TPA: terephthalic acid), is synthesized for efficient HMF oxidation, wherein the uncoordinated carboxylate functions as the proton relay center, significantly enhancing oxidation performances. The current density is increased 16-fold compared to that of pure Ni(OH)₂, and the faradaic efficiency of FDCA reaches 96.9 ± 0.2% at even 1000 mA cm⁻². Consequently, an anion exchange membrane electrolyzer (25 cm²) is constructed that shows a current of 10.3 A at 1.80 V. The system operates stably for over 240 hours at 7500 mA, producing hectogram-level FDCA continuously with an overall productivity of 2.85 kg m⁻² h⁻¹. These results offer insightful strategies for designing catalysts and fabricating electrolyzers for industrial applications.