Favorable surface reconstruction with strong reducibility on the high-entropy sulfide for efficient electrochemical oxidation of 5-hydroxymethylfurfural at high concentrations

Electrochemical oxidation of 5-hydroxymethylfurfural (HMFOR), featuring favorable thermodynamics, presents a promising alternative to the conventional oxygen evolution reaction for energy-saving hydrogen (H₂) production coupled with biomass upgrading. However, the multiple proton-coupled electron transfer steps in HMFOR result in sluggish kinetics, highlighting the development of highly efficient electrocatalysts. Herein, a high-entropy amorphous MoCrCoNiZn-S grown on nickel foam (HEAS@NF) is constructed via a metal organic framework-derived strategy to efficiently convert HMF to 2,5-furandicarboxylic acid (FDCA). The abundant active sites on the HEAS@NF facilitate the structural evolution to oxyhydroxides that possess strong reducibility for HMF dehydrogenation, leading to superior HMFOR performance compared to sulfides with fewer metal elements. In situ electrochemical impedance spectroscopy results confirm significantly favored kinetics to HMFOR over OER on the HEAS@NF, resulting in a remarkable 98% HMF conversion, with FDCA yield and Faradaic efficiency of 98% and 94% even at a concentrated 100 mM HMF. A two-electrode flow electrolyzer equipped with the bifunctional HEAS@NF enables simultaneous cathodic H₂ and anodic FDCA production with an electricity saving of 10.8%. This study presents an effective strategy to inspire the exploration of high-entropy catalysts for biomass-assisted H₂ production.

Graphical abstract