Synergistic High‐Valent NiCo Sites for Electrified Refinery of Concentrated 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid Under Ultra‐Low Alkalinity

ABSTRACT Electro‐oxidation of 5‐hydroxymethylfurfural (HMF) is a sustainable route to convert biomass into valuable 2,5‐furandicarboxylic acid (FDCA). The typical HMF oxidation reaction (HMFOR) process often faces a severe carbon loss due to the degradation tendency of substrates and intermediates in highly alkaline environments, while low‐alkaline HMFOR is restricted by slow reaction kinetics and moderate Faradaic efficiency (FE) due to the insufficient supply of OH − . Herein, an in‐situ MOF‐assisted synthetic strategy was proposed to fabricate a Ni‐doped CoOOH x catalyst on nickel foam (MASS‐Ni‐CoOOH x /NF). The optimized MASS‐Ni‐CoOOH x /NF feathered 95.8% FDCA yield and 99.4% FE with 300 m m HMF under ultra‐low alkaline conditions (pH 11). Gram‐scale synthesis of FDCA was achieved in a flow electrolyzer, which delivered long‐term durability for 100 h. White crystalline FDCA (2.08 g) was obtained from the flow electrolyzer with 96.7% yield, 97.2% FE, and 99.6% purity. Mechanistic investigations confirmed that the Ni‐O‐Co structure featured low dehydrogenation free energy, readily forming high‐valent MOOH species to expedite substrate oxidation, whereas the introduction of Ni enhanced HMF adsorption capacity, thus accelerating its adsorptive activation. This work highlights the importance of developing advanced catalysts for HMF electro‐oxidation under low‐alkaline conditions and sheds light on the scalable biomass upgrading via electrochemical technologies.