Electrocatalytic Effect of NiOOH/Ni⁴⁺ Formed by Crystal Reconstruction for 5-Hydroxymethylfurfural in Alkaline Media

Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) to high value-added 2,5-furandicarboxylic acid (FDCA) is significant for sustainable development of biomass resources. However, it is still a challenge to construct efficient active species and explore their effects on key reaction intermediates in alkaline media. In this work, a crystal reconstruction strategy was proposed to form the active species NiOOH/Ni4+ and its regulatory effects on HMFCA and FFCA in different concentrations of KOH were investigated. The concentrations of HMFCA and FFCA were successfully regulated and reached relative equilibrium in 0.5 M KOH. Notably, the active species NiOOH/Ni4+ exhibited remarkable catalytic performance with a 99.2% FDCA yield and 99.4% Faraday efficiency. After 16 consecutive cycles, the retention rate of the FDCA yield still reached 99.3%. Therefore, this work provides a new perspective for gaining in-depth insight into the mechanism of electrolyte effects on HMF oxidation.