Modulation of d-Orbital Electronic State for Boosting Electrocatalytic Upcycling of Plastic Waste

Abstract Coupling the electrocatalytic oxidation of ethylene glycol (EG) to value-added chemicals with the hydrogen evolution reaction provides a sustainable approach for the upcycling of polyethylene terephthalate (PET) waste and energy-efficient hydrogen generation. Precisely regulating the electronic structure, specifically the orbital state of the active site near the Fermi level, plays a key role in optimizing the electrocatalytic performance. Herein, iron (Fe) is introduced to modulate the d-orbital electronic states of Ni active sites for governing their intrinsic activities during ethylene glycol oxidation reaction (EGOR). The electronic modulation brings the dx2-y2 orbital of the Ni2+ state closer to the Fermi level to promote the deprotonation step. Meanwhile, the broadening of the dx2-y2 orbital in the Ni3+ state enhances the spontaneous chemical reactivity and intermediate adsorption. Consequently, the Fe@Ni3N-Co3N delivers excellent EGOR activity, featuring a low onset potential of 1.225 V vs RHE and a high Faradaic efficiency of 93.6% toward formate production. When employed in an alkaline seawater flow cell for coupled PET upcycling and hydrogen production, the system enables steady co-production of formate and H2 at 100 mA cm−2 over 120 h. The present insights into modulating the electronic states of active sites via introducing heteroatoms offer an efficient strategy for developing high-performance electrocatalysts.