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Polyethylene terephthalate (PET) plastic has been extensively used in our social life, but its poor biodegradability has led to serious environmental pollution and aroused worldwide concern. Up to now, various strategies have been proposed to address the issue, yet such strategies remain seriously impeded by many obstacles. Herein, waste PET plastic was selectively carbonized into three-dimensional (3D) porous carbon nanosheets (PCS) with high yield of 36.4 wt%, to be further hybridized with MnO2 nanoflakes to form PCS-MnO2 composites. Due to the introduction of an appropriate amount of MnO2 nanoflakes, the resulting PCS-MnO2 composite exhibited a specific capacitance of 210.5 F g−1 as well as a high areal capacitance of 0.33 F m−2. Furthermore, the PCS-MnO2 composite also showed excellent cycle stability (90.1% capacitance retention over 5000 cycles under a current density of 10 A g−1). The present study paved an avenue for the highly efficient recycling of PET waste into high value-added products (PCSs) for electrochemical energy storage. [ABSTRACT FROM AUTHOR]

The controlled carbonization of polymers is one of the most important polymer reactions. It represents the conversion process of polymeric precursors into carbonaceous materials in a "controlled" manner. In this review, we summarize the research progress on the controlled carbonization of (waste) polymers in preparing functional carbon materials with well-defined microstructures, fabricating advanced polymer composites with enhanced flame retardancy, and converting waste polymers into high value-added nanocarbon materials. The carbonization mechanisms of polymers with different compositions and chain structures are highlighted. How to match the degradation reaction of polymers with the carbonization reaction of the degradation products is addressed to improve the carbonization efficiency and optimize the growth of carbon materials. The applications of (waste) polymer-derived carbon materials in electrochemical energy storage and environmental remediation are reviewed. Current existing limitations and future perspectives are also given. [ABSTRACT FROM AUTHOR]

The wide application of carbon nanosheets (CNS) is still restricted by low production. Meanwhile, the accumulation of waste plastic generates serious environmental pollution. Nowadays, the conversion of waste plastic into two-dimensional CNS is regarded as a promising way to address these issues due to the high carbon content of waste plastic. However, this conversion process is still impeded by low-efficient catalysts so far. Herein, the highly efficient carbonization of waste polypropylene (PP) into CNS is achieved using a combined catalyst of ferrocene and sulfur. The carbonization process in sealed space ensures an ultrahigh carbon yield (62.8%) and a thin thickness (4–4.5 nm) of as-prepared CNS, even though little catalyst is used. After activation, the activated carbon nanosheets (ACNS) show a well-defined hierarchical porous structure with a large specific surface area (3200 m2 g−1) and a big pore volume (3.71 cm3 g−1). The ACNS based electrode delivers a high specific capacitance of 349 F g−1 at 0.5 A g−1. The fabricated symmetric supercapacitor manifests a high energy density of 23 Wh kg−1 at 225 W kg−1. These findings provide a reference for the efficient conversion of waste plastic into energy storage materials. Image 1 • Waste PP is converted into thin carbon nanosheets (4–4.5 nm) using combined catalyst. • Vapor-phase reaction endows the prepared CNS with a high carbon yield (62.8%). • Activated carbon nanosheets show a large specific surface area and a big pore volume. • A high specific capacitance with superior cycling stability is proved. • This work reports an efficient conversion of waste plastic into electrode material. [ABSTRACT FROM AUTHOR]