Unlocking the role of oxygen vacancies in FeO / NiO /Ni for boosting 5‐hydroxymethylfurfural electrooxidation

Abstract Electrocatalytic oxidation of 5‐hydroxymethylfurfural (HMFOR) offers an energy‐efficient route to high value‐added chemicals. There is an urgent demand for high‐performance non‐precious metal catalysts. Herein, the oxygen‐deficient FeO/NiO/Ni was synthesized, which has high performance for HMFOR with a conversion rate of 100%, a selectivity of 98.6% for 2,5‐furandicarboxylic acid (FDCA), and a Faradaic efficiency of 94.1% at 1.5 V (vs. RHE), superior to most reported non‐precious metal catalysts. The efficient catalytic activity of FeO/NiO/Ni is attributed to the high specific surface area and enhanced adsorption and activation of HMF by oxygen vacancies, thereby reducing the rate‐limiting step energy barrier of 5‐hydroxymethyl‐2‐furancarboxylic acid to 5‐formyl‐furancarboxylic acid (*HMFCA→*FFCA). Ni 3+ acts as the active site for direct HMF oxidation catalysis, while Fe doping induces oxygen vacancies that facilitate the formation and stabilization of Ni 3+ species, enhancing their formation and catalytic functionality.