S Species-Evoked High-valence Ni 2+δ of the Evolved β-Ni(OH) 2 Electrode for Selective Oxidation of 5-hydroxymethylfurfural.

This work reports an efficient NiS x -modified β-Ni(OH) 2 electrode for the selective oxidation of 5-hydroxymethylfurfural (HMFOR) with excellent electrocatalytic HMF selectivity (99.4%), conversion (97.7%) and Faraday efficiency (98.3%). The decoration of NiS x would evoke high-valent Ni 2+δ species in the reconstructed β-Ni(OH) 2 electrode, which are the real active species for HMFOR. The generated NiS x /Ni(OH)O modulated 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 OER competes with the HMFOR when NiS x /Ni(OH)O continues to accumulate to generate the NiS x /NiO x (OH) y intermediate. Density functional theory (DFT) calculations and experimental results verify that the adsorption energy of HMF can be optimized through the increased NiS x composition for more efficient capture of protons and electrons in the HMFOR. This article is protected by copyright. All rights reserved.