Engineering Oxygen Intermediates Adsorption on Amorphous NiFe Alloys for Highly Active and Selective Electrochemical Biomass Conversion

Electrochemical 5-hydroxymethylfurfural (HMF) oxidation reaction (HMFOR) offers a promising route to transform biomass into value-added chemicals. However, the competing oxygen evolution reaction (OER) greatly limits the HMFOR selectivity. Herein, we report a facile doping strategy to engineer oxygen intermediates adsorption on amorphous NiFe alloys to boost highly selective electrochemical HMF oxidation to produce 2,5-furandicarboxylic acid (FDCA), among which, amorphous Mn-doped NiFeB alloy displays a low HMFOR onset potential of 1.35 V vs. RHE, achieving 100 % HMF conversion with 88 % FDCA selectivity at an applied potential of 1.4 V vs. RHE, outperforming amorphous NiFeB (73 % FDCA selectivity) and Mo-doped NiFeB (65 % FDCA selectivity) alloys. Experimental characterizations suggest that the introduction of Mn/Mo into amorphous NiFeB alloy can increase/decrease its electronic density and thus strengthen/weaken oxygen intermediates adsorption. Operando experiments indicate that the amorphous Mn-doped NiFeB alloy can significantly reduce the onset potential to form active Ni³⁺ species, which spontaneously react with HMF via nucleophile dehydrogenation to form FDCA. Furthermore, in situ infrared spectroscopy measurements verify that the HMF oxidation pathway follows the 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) route rather than the 2,5-diformyfuran (DFF) route.