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 Ni2‐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 Ni2‐δ during the HMFOR enables it to have excellent electro‐catalytic oxidation ability toward HMFOR.