Ultrasmall CeO2 Nanoparticles with Rich Oxygen Defects as Novel Catalysts for Efficient Glycolysis of Polyethylene Terephthalate

Chemical recycling of polyethylene terephthalate (PET) attracts increasing attention worldwide since it is a sustainable way to tackle the escalating plastic waste problem and create a circular plastic economy. Herein, defect-rich CeO2 nanoparticles (NPs) with tunable sizes and shapes were conveniently synthesized by one-step precipitation with KH550 modification and first used as novel catalysts for the glycolysis of PET. Among the obtained CeO2 catalysts, CeO2–2.7 nm NPs possessed the best performance for depolymerization at 196 °C, completing the reaction in 15 min with a PET conversion of 98.6% and a monomer yield of 90.3%. The glycolysis mechanism study reveals the relationship between defect engineering and catalytic activity. An ultrasmall size of 2.7 nm minimizes oxygen defect formation energy of CeO2 NPs and increases the dispersity in ethylene glycol (EG). Rich oxygen defects on CeO2 nanoparticles accelerate the glycolysis reaction evidently via inducing the generation of Ce3+ and providing sites for the adsorption and activation. This work provides the application prospect of defective heterogeneous catalysts in the depolymerization reaction under low energy consumption.