Electronic Engineering of Ni3S2 via Mo/Cl Co-doping for Upcycling Polyethylene Terephthalate into Formate with Concurrent Hydrogen Evolution

Abstract

Electrocatalytic conversion of polyethylene terephthalate (PET) plastic waste into formate coupled with hydrogen generation represents a sustainable pathway for plastic upcycling. Herein, a nickel sulfide catalyst (Mo,Cl-Ni3S2) is developed for efficient and stable ethylene glycol (PET monomer) oxidation reaction (EGOR) through a Mo and Cl co-doping strategy. The optimized catalyst Mo,Cl-Ni3S2 possesses a high formate Faradaic efficiency of 94.0% at 1.55 V vs. RHE. Moreover, it maintains 83.3% of its initial activity after 95 hours continuous operation at an industrial current density of 300 mA/cm2. Experiment and theoretical simulations demonstrate Mo and Cl co-doping optimizes the electronic structure of Ni3S2 by upshifting the Ni d-band center and facilitates the in situ structure reconstruction during EGOR. Finally, an integrated acidification-precipitation-recrystallization strategy is proposed to separate and recover terephthalic acid (TPA) and potassium formate. This method offers a holistic approach for upcycling PET waste into value-added chemicals and hydrogen.