Bifunctional MoNi4/Nickel Foam Electro‐Catalyst for Ultra‐Efficient Oxidation of High‐Concentration 5‐Hydroxymethylfurfural and HER

The electro-catalytic oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) provides an attractive route to produce 2, 5-furandicarboxylic acid (FDCA) as a substitute for terephthalic acid used in the plastics industry. Herein, we prepared MoNi₄ alloy on nickel foam (NF) using a simple hydrothermal method followed by hydrogen reduction. Applied MoNi₄/NF as the bifunctional electrodes for the electro-catalytic HMF oxidation reaction (HMFOR) and HER, 98.7 % FDCA yield and 97.3 % Faraday efficiency (FE) can be achieved even with HMF concentration as high as 200 mM. Notably, no obvious deactivation was observed after ten consecutive cycles. In-situ Raman, XANES and EXAFS results show that the nickel species of MoNi₄/NF is first oxidized to Ni³⁺ species under the applied voltage, and after undergoing the electro-catalytic HMFOR, then reduced to Ni^2-δ state (with a valence between 0 and +2) due to the electron-donating effect from Mo. MoNi₄/NF with more than one electron transfer between Ni³⁺ and Ni^2-δ during the HMFOR enables it to have excellent electro-catalytic oxidation ability toward HMFOR.