Bifunctional PtAg-enabled oscillation electrorefining of PET waste-derived ethylene glycol and water for rapid glycolic acid and H2 coproduction

Abstract

Selectively partial electrooxidation of polyethylene terephthalate (PET) waste-derived ethylene glycol (EG) in water is promising to replace the sluggish oxygen evolution reaction for energy-saving cogeneration of value-added glycolic acid (GA) and H₂. However, the involved electrocatalysts often suffer from poor selectivity due to multiple reaction pathways (e.g., overoxidation) and rapid deactivation poisoned by oxidative intermediates (e.g., CO), leading to low productivity of GA. Herein, we report bifunctional PtAg on Ni foam-driven oscillation electrolysis for selective, rapid and long-term GA/H₂ cogeneration at a high current density of over 250 mA cm⁻² and a low cell voltage of 0.8 V for 100 h, with respective faradaic efficiencies of 95.2% and 99.5%. Specifically, the productivities of both GA and H₂ in the oscillation mode are 6.1 times higher than those in traditional constant electrolysis, along with almost 40% energy saving. Combined physicochemical characterization studies including operando infrared spectroscopy and quasi-in situ electron paramagnetic resonance, with theoretical calculations reveal that introducing Ag into Pt downshifts the d-band center for promoted rate-limiting *OH generation and *GA desorption, and the alternating oxidation/reduction enabled by the bifunctionality of PtAg alleviates the accumulation of oxidative intermediates for inhibited poisoning, jointly beneficial for selective and rapid GA/H₂ coproduction.