Electronic Modulation of NiO by Cu Doping Toward Enhanced Electrocatalytic Ethylene Glycol Oxidation to Formate

Electrocatalytic upgrading of waste polyethylene terephthalate (PET) into value-added chemicals not only alleviates environmental pressure but also offers significant economic benefits. In this work, Cu was successfully incorporated into NiO structure with varying contents and applied to the ethylene glycol oxidation reaction (EGOR). Among all the synthesized samples, the electrode based on the optimized 4Cu-NiO sample exhibited significantly enhanced electrochemical performance, delivering a high current density of 113.4 mA cm^-2 at 1.6 V versus RHE in 1 M KOH with 1 M EG, along with faster reaction kinetics compared to the conventional oxygen evolution reaction (OER). Moreover, even after a 35 h long-term stability test, this optimal electrode retained 74.3 mA cm^-2, while delivering formate as the dominant product with a Faradaic efficiency of 91.6% and a selectivity of 89.1%, underscoring its high efficiency for the conversion of ethylene glycol into value-added chemicals. Furthermore, density functional theory calculations reveal that Cu incorporation shifts the d-band center closer to the Fermi level, which strengthens the interaction with ethylene glycol molecules and reduces the energy barrier for the rate-determining step, thereby improving the overall catalytic performance.