NiOxHy/nickel foam with highly accessible Ni(III) for efficient electrooxidation of 5-hydroxymethylfurfural

The electrocatalytic production of 2,5-furandicarboxylic acid (FDCA) via the 5-hydroxymethylfurfural oxidation reaction (HMFOR) is an effective and more suitable alternative to the oxygen evolution reaction (OER) in electrocatalytic water splitting. High-valence Ni(III) is critical for the HMFOR, but the formation is greatly limited by the difficult in situ self-oxidation. In this study, the pre-oxidization-derived amorphous NiO x H y nanosheet presents more accessible Ni(III) for efficient HMFOR. In addition, NiO x H y /NF exhibits a low onset potential of 1.35 V, a high FDCA yield of 98.5 %, and a high Faradaic efficiency of 98.3 % for the HMFOR in 0.1 M KOH with 10 mM HMF. In situ Raman spectroscopy results indicate that Ni(III)OOH is an active intermediate in the electrochemical HMFOR. This work provides a strategy for promoting the formation of high-valence Ni(III) and boosting biomass oxidation.