S‐Species‐Evoked High‐Valence Ni2+δ of the Evolved β‐Ni(OH)2 Electrode for Selective Oxidation of 5‐Hydroxymethylfurfural

An efficient NiSx -modified β-Ni(OH)2 electrode is reported for the selective oxidation reaction of 5-hydroxymethylfurfural (HMFOR) with excellent electrocatalytic 5-hydroxymethylfurfural (HMF) selectivity (99.4%), conversion (97.7%), and Faradaic efficiency (98.3%). The decoration of NiSx will evoke high-valence Ni2+δ species in the reconstructed β-Ni(OH)2 electrode, which are the real active species for HMFOR. The generated NiSx /Ni(OH)O modulates the proton-coupled electron-transfer (PCET) process of HMFOR, where the electrocatalytically generated Ni(OH)O can effectively trap the protons from the CHO end in HMF to realize electron transfer. The oxygen evolution reaction (OER) competes with the HMFOR when NiSx /Ni(OH)O continues to accumulate, to generate the NiSx /NiOx (OH)y intermediate. Density functional theory (DFT) calculations and experimental results verify that the adsorption energy of HMF can be optimized through the increased NiSx composition for more efficient capture of protons and electrons in the HMFOR.