NiFeCo wrinkled nanosheet electrode for selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

Abstract

Quantitative and selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) via electrocatalysis is a crucial milestone for biomass conversion. In this study, FeCo-modified β-Ni(OH)₂ wrinkled nanosheet electrode were prepared by a hydrothermal method and used for the electrocatalytic oxidation of HMF to afford 100% conversion, 98.7% FDCA yield and a Faraday efficiency (FE) of 98%. The wrinkled nanosheet structure design increased the surface area (26.3 m² g⁻¹) and introduced oxygen-rich active sites (35.26%), enabling a current density of 10 mA cm⁻² for HMF oxidation at 1.26 V vs. RHE. In situ electrochemical characterization established that β-NiOOH was the actual oxidation active site. The decoration of FeCo promoted the formation of β-NiOOH species, in which Ni³⁺ was converted into Ni²⁺ via the hydroxy and aldehyde groups in HMF, while HMF was dehydrogenated to the oxidative derivative (FDCA) at the anode. Electrochemical cyclic voltammetry confirmed that the substrate and product species followed a Langmuir–Hinshelwood (L–H) adsorption mechanism. Density functional theory (DFT) calculations verified that the Gibbs free energy and adsorption energy of HMF can be adjusted through the co-doping of the FeCo composition, which was more effective in capturing protons and electrons and activating HMF. This work lays the foundation for a deeper understanding of polymetallic site synergies and provides a practical technique for the upgrading of electrochemical substance derivatives into structural unit chemicals.