Hierarchical CoFe-LDH with nanoneedle-assembled architecture for selective and efficient electrocatalytic oxidation of ethylene glycol to formate

The electrocatalytic conversion of polyethylene terephthalate (PET)-derived ethylene glycol (EG) into value-added chemicals such as formate and glycolate has significant economic and environmental benefits. However, the development of low-cost electrocatalysts for highly selective formate production remains challenging. This study employed an electrodeposition method to fabricate a non-noble CoFe-Layered Double Hydroxide (CoFe-LDH) catalyst for the ethylene glycol oxidation reaction (EGOR). By regulating the substrate and electrodeposition time, the CoFe-LDH/NF-10 min (NF-10) catalyst exhibited a double-layer capacitance (C_dl) of 0.92 mF cm⁻². During EGOR, this catalyst required only 1.44 V vs. RHE to achieve a current density of 10 mA cm⁻², which is significantly reduced by 240 mV compared with 1.68 V vs. RHE of oxygen evolution reaction (OER). The NF-10 demonstrated a low Tafel slope of 36.41 mV dec⁻¹ and low charge transfer resistance. At a current density of 10 mA cm⁻², the NF-10 catalyst enabled continuous electrooxidation of EG to formate, achieving a formate selectivity of 86.01 %, and a formate Faradaic efficiency (FE) of 49.67 %. This enhanced performance is attributed to the synergistic effect between Co and Fe in the bimetallic catalyst: High-valent CoOOH sites catalyze the formation of the CH₂OH-CO* intermediate, while Fe sites effectively promote the formation of CoOOH, suppress side reactions associated with glycolate formation, and facilitate the cleavage of CC bonds. Consequently, the selectivity toward formate is significantly improved. This study provides novel insights for designing catalysts to enhance the electrocatalytic activity of polyols and regulate product selectivity.