S‐Species‐Evoked High‐Valence Ni<sup>2+</sup><sup>δ</sup> of the Evolved β‐Ni(OH)<sub>2</sub> Electrode for Selective Oxidation of 5‐Hydroxymethylfurfural
Chaofan Liu, Xue‐Rong Shi, Kaihang Yue, Peijie Wang, Ke Zhan, Ding Wang, Bao Yu Xia, Ya Yan
Abstract
Abstract An efficient NiS x ‐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 NiS x will evoke high‐valence 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 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 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.