Product Oriented Upcycling of Waste Polyethylene Terephthalate Plastic and Carbon Dioxide via Decoupled Electrolysis

Abstract

End-of-life plastics and carbon dioxide (CO2) are anthropogenic waste carbon resources; it is imperative to develop efficient technologies to convert them to value-added products. Here we report the upcycling of polyethylene terephthalate (PET) plastic and CO2 toward valuable potassium diformate, terephthalic acid, and H2 fuel via decoupled electrolysis. This product-oriented process is realized by two electrolyzers: (1) a solid-state-electrolyte based CO2 electrolyzer and (2) a solid-polymer-electrolyte-based PET electrolyzer. Using a bismuth-based catalyst, the CO2 electrolyzer showed more than 140 h continuous operation at current of 250 mA, resulting in 850 mL pure HCOOH solution with a concentration of 683 mM. Furthermore, we constructed a solid-polymer-electrolyte electrolyzer with an electrode area of 50 cm2 for the electrooxidation of ethylene glycol to formate, achieving 30 A of current at ~1.9 V cell voltage and 80 % formate Faradaic efficiency. With this electrolyzer, we demonstrated the efficient transformation of PET hydrolysate to a mixture of terephthalate and formate. Additionally, combining CO2 derived HCOOH and PET electrolyte, we obtained recycled terephthalic acid and potassium diformate. This work provides an integrated strategy for the valorization of waste carbon resources with less using external resources.