Abstract

Despite growing interest in the electrocatalytic upcycling of polyethylene terephthalate (PET) plastic waste, the correlation between ethylene glycol (EG) oxidation reaction (EGOR) selectivity, where EG is the primary PET-derived monomer, and the key surface intermediate adsorption behavior remains poorly understood. Moreover, sluggish EGOR kinetics and competing C–C bond activation pathways severely limit catalyst design. Herein, we present a rapid CO₂ laser irradiation approach to stabilize Ru single-atoms (Ru-SAs) on two-dimensional NiO nanosheets (Ru-SA/NiO). Laser treatment (λ ≈ 10.6 μm, power ≈ 7 W) induces oxygen vacancies in NiO and promotes interfacial electron transfer from NiO to Ru-SAs and optimizing EGOR critical intermediate adsorption. This study establishes hybrid secondary ion mass spectrometry (hybrid-SIMS, integrating time-of-flight SIMS and Orbitrap-SIMS) as a powerful platform for mechanistic elucidation of EGOR, enabling identification of bias-conditioned surface-bound EGOR intermediates. Combined in situ spectroelectrochemical analyses and density functional theory calculations reveal a stepwise oxidative dehydrogenation mechanism involving sequential O–H and C–H activation that promotes controlled C–C bond cleavage during PET upcycling. The synergistic Ru-SA–NiO interface preferentially stabilizes C₁ intermediates, delivering highly selective formate generation with a Faradaic efficiency of 86.37% and yield rate of 0.18 mmol h⁻¹ cm⁻² at 1.6 V vs. RHE, with excellent stability over 300 h. Technoeconomic analysis further confirms the feasibility of PET upcycling, achieving 96.7% potassium diformate and 96.1% terephthalic acid yields, with a projected net profit of ~USD 380.7 per ton of processed PET. This study delivers new insights into the role of surface-adsorbed intermediates and new perspectives for catalyst design for plastic upcycling toward a circular economy.