Electronic state reconfiguration of NiMoCo_x boosts electrocatalytic upcycling of polyethylene terephthalate plastic wastes for simultaneous production of formate and green hydrogen

The electrocatalytic upcycling of polyethylene terephthalate (PET) plastic wastes into formate represents a sustainable approach to address the growing PET waste volume, while simultaneously generating valuable hydrogen. The key challenge is to develop highly active electrocatalysts for accelerating the sluggish conversion kinetics of the PET hydrolysate (i.e., ethylene glycol, EG). Herein, the bifunctional and noble-metal-free NiMoCo_x alloys are synthesized to catalyze both the EG-to-formate oxidation at anode and hydrogen evolution reaction (HER) at cathode, achieving a one-stone-two-birds process for PET upcycling paired with hydrogen production. The NiMoCo_0.3 catalyst exhibits a remarkable Faradaic efficiency of 93.5 % for EG-to-formate at an electrode potential as low as 1.4 V vs. reversible hydrogen electrode (RHE). In situ spectral measurements and theoretical simulations demonstrate that Ni acts as the active site for EG oxidation, whereas Co induces electron redistribution around Ni sites, thereby optimizing the adsorptions of intermediates. Furthermore, an anion exchange membrane (AEM) electrolyzer, when processing real PET waste with NiMoCo catalysts, produces high-purity terephthalic acid (TPA) and potassium diformate (KDF) alongside H₂ gas. This work provides novel insights into upcycling PET waste for the production of value-added chemicals and green hydrogen.