A magnetically recyclable core-shell heterojunction photocatalyst with oxygen vacancies for efficient upcycling of plastic waste.

Abstract

Photocatalytic depolymerization of plastic waste into high-value-added chemicals is a sustainable and promising strategy driven by solar energy under ambient conditions. Herein, we report a magnetically separable Fe₃O₄@CeO₂, heterojunction photocatalyst, in which the interfacial heterojunction between the Fe₃O₄ core and CeO₂ shell enhances charge separation, while surface oxygen vacancies further promote electron migration. This synergistic design enables complete depolymerization of real-world polyethylene terephthalate (PET) (100 % conversion), achieving >85 % terephthalic acid (TPA) yield, with plastic bottles reaching exceptional yields up to 95 %. The system maintains excellent recyclability, retaining >90 % of its initial activity after four consecutive cycles. Molecular simulations indicate that the photogenerated chlorine radical first mediates CH abstraction from the PET backbone to produce an alkyl radical. This radical then reacts with oxygen to generate a peroxy radical, which finally cleaves the low-energy ester CO bond, leading to depolymerization and the formation of terephthalic acid. The Ce⁴⁺/Ce³⁺ redox cycle further enhances radical generation, facilitating the catalytic process. The photocatalyst demonstrates remarkable versatility, exhibiting efficient depolymerization activity toward polypropylene, polystyrene, and polyethylene. Life cycle assessment confirms its environmental and economic advantages. This work provides fundamental insights into interfacial engineering of heterojunction photocatalysts for efficient plastic upcycling.