Rational Design of Hierarchical CoFe@NiFe LDH for Electrocatalytic Furfural Valorization: Interfacial Charge Modulation and Continuous-Flow Performance

Abstract

Electrocatalytic oxidation of furfural to furoic acid offers a sustainable route for biomass valorization, yet remains challenged by sluggish kinetics and limited stability. Herein, a hierarchical core–shell CoFe@NiFe-LDH/NF heterostructure was fabricated on nickel foam via a hydrothermal-electrodeposition method. Vertically aligned CoFe-LDH nanosheets induce directional growth of NiFe-LDH, and XPS confirms strong electronic interactions and interfacial charge rearrangement. In an H-type cell, the catalyst achieves an overpotential of 540 mV at 100 mA cm–2 with furfural conversion of 84.7%, selectivity of 98.3%, and Faradaic efficiency of 95.1%. In a continuous-flow electrolyzer, it delivers a current of 1.5 A (310 mA cm–2) at 1.45 V with 82.9% conversion and 70.4% selectivity. In situ electrochemical infrared spectroscopy confirms the stepwise oxidation of the furfural C═O bond to carboxyl group (−COOH) and reveals a hydrogen-bond-mediated stabilization mechanism. DFT calculations show that the heterostructure exhibits spin-polarized, narrow-bandgap semimetallic characteristics, with a low furfural adsorption energy (0.617 eV) at the Ni site and interfacial charge transfer (ΔQ = 0.0048 e) upon adsorption. Furthermore, comparison of nucleophilic attack mechanisms reveals that the OH– pathway, despite a higher-energy initial adduct (0.67 eV), is kinetically more favorable than the H2O pathway (which forms a stable diol intermediate at −1.29 eV) because it requires only two strongly exothermic dehydrogenation steps instead of three.