Upcycling Polyethylene Terephthalate Plastic to C2 Chemicals in Parallel With Nitrate Reduction to Ammonia or Electric Energy Generation

Abstract

The resource utilization of waste plastics and nitrogen-containing wastewater has an important environmental impact. Herein, we present self-supporting CuPd alloy nanosheets as bifunctional catalysts for selective electrooxidation of ethylene glycol (EG) from polyethylene terephthalate (PET) hydrolysate to glycolic acid (GA, a C–C bond preserved product with more than 20-time added value) and for efficient electroreduction of nitrate in wastewater to ammonium. Remarkable Faraday efficiencies of ∼93% for GA production and ∼92% for nitrate reduction were achieved. In situ Fourier transform infrared spectroscopy identified crucial intermediates in GA production, elucidating the C–C bond preserved C2 pathway for EG-to-GA conversion. Meanwhile, density functional theory calculations revealed a deeper d-band center arising from the synergistic interaction between Pd and Cu atoms, which facilitates GA desorption, thereby avoiding overoxidation for high selectivity. For nitrate reduction, differential electrochemical mass spectrometry and theoretical calculations were applied, identifying NO₂* hydrogenation as the rate-determining step. Furthermore, we propose an innovative electroforming architecture integrating EG oxidation with a nitrate reduction or oxygen reduction reaction. This architecture, activated by CuPd/NF electrodes, can operate in switching mode throughout the day. It allows the production of high-value GA from PET hydrolysate while simultaneously producing NH₄⁺ in the daytime by coupling with nitrate reduction, or generating electricity during the night by coupling with ORR, offering a competitive solution for resource utilization of wastes.