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Due to the ever-increasing plastic waste causing serious environmental problems, it is highly desirable to recycle it into high-value-added products, such as carbon nanomaterials. However, the traditional catalytic carbonization of hydrocarbon polymers is severely prohibited by the complexity of real-world plastic waste due to the existence of halogen-containing polymers. In this study, through a universal combined template based on magnesium oxide and iron(III) acetylacetonate (Fe(acac)3), a three-dimensional hollow carbon sphere/porous carbon flake hybrid nanostructure is prepared from carbonization of plastic waste with high yields (>70 wt%). This approach is not only suitable for hydrocarbon polymers, but also for halogen-containing polymers. Interestingly, the obtained advanced carbon framework exhibits excellent performance in lithium-ion batteries (802 mA h g−1 after 500 cycles at 0.5 A g−1). The present research paves a new avenue to upcycle plastic waste into a high value-added product. [ABSTRACT FROM AUTHOR]

ABSTRACT Three kinds of metal oxide nanoparticles (Fe3O4, Co3O4, and Ni2O3) are produced on carbon nanotubes (CNTs). The synergistic effects rendered by the CNTs and metal oxide nanoparticles on carbonization of polyethylene (PE) are studied and applications to flame retardancy of PE are investigated systematically. The CNT-Ni2O3 delivers the best performance and the mechanism pertaining to the enhanced flame retardancy is proposed and discussed. It is found that under the same conditions, the carbonization rate can be a factor to influence the flame retardancy performance. Among Fe, Co, and Ni, Ni has the fastest carbonation rate, which leads to the best flame retardancy performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45233. [ABSTRACT FROM AUTHOR]

Catalytic conversion of waste plastics into high value-added carbon nanomaterials (CNMs) has attracted increasing attention; however, the role of lattice oxygen in the carbonization of plastics still remains ambiguous. In this work, firstly, a nickel catalyst with different content of lattice oxygen was prepared by the sol–gel combustion synthesis method. Subsequently, the effect of lattice oxygen in the nickel catalyst on the catalytic carbonization of polypropylene (PP, an example of plastics) into CNMs was investigated. It was found that the yield of CNMs increased dramatically with the increasing content of lattice oxygen. Large and short platelet-like carbon fibers were obtained when the content of lattice oxygen was low. With the increasing content of lattice oxygen, small, winding and short carbon nanofibers were produced. When the content of lattice oxygen further increased, long, small and straight cup-stacked carbon nanotubes were formed. Besides, it was demonstrated that lattice oxygen not only prevented the coalescence of nickel catalyst nanoparticles into large particles and promoted their reconstruction into rhombic shape, but also facilitated the catalytic carbonization of PP degradation products. This work provides new insights into the carbonization mechanism of plastics and puts forward a novel chemical method to prepare CNMs with diverse morphologies by controlling the content of lattice oxygen in the catalyst. [ABSTRACT FROM AUTHOR]

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]

Converting waste plastics into valuable carbon materials has obtained increasing attention. In addition, carbon materials have shown to be the ideal electrode materials for double‐layer supercapacitors owing to their large specific surface area, high electrical conductivity, and stable physicochemical properties. Herein, an easily operated approach is established to efficiently convert waste poly(ethylene terephthalate) beverage bottles into porous carbon nanosheet (PCNS) through the combined processes of catalytic carbonization and KOH activation. PCNS features an ultrahigh specific surface area (2236 m2 g−1), hierarchically porous architecture, and a large pore volume (3.0 cm3 g−1). Such excellent physicochemical properties conjointly contribute to the outstanding supercapacitive performance: 169 F g−1 (6 M KOH) and 135 F g−1 (1 M Na2SO4). Furthermore, PCNS shows a high capacitance of 121 F g−1 and a corresponding energy density of 30.6 Wh kg−1 at 0.2 A g−1 in the electrolyte of 1 M TEATFB/PC. When the current density increases to 10 A g−1, the capacitance remains at 95 F g−1, indicating the extraordinary rate capability. This work not only proposes a facile approach to synthesize PCNS for supercapacitors, but also puts forward a potential sustainable way to recycle waste plastics and further hopefully mitigates the waste plastics‐related environmental issues. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48338. [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]

• Carbon nanosheets (CNSs) was prepared from "real-world" mixed waste plastics. • Organically-modified montmorillonite was selected as the catalytic template. • Porous carbon nanosheets (PCNSs) was fabricated by KOH activation of CNSs. • PCNSs were featured on hierarchically micro-/mesoporous structures. • PCNSs showed high capacitance and excellent rate capability for supercapacitors. Recently, sustainable development and serious energy crisis called for appropriate managements for the large number of municipal and industrial waste plastics as well as the development of low-cost, advanced materials for energy storage. However, the complexity of waste plastics significantly hampers the application of ever used methods, and little attention is paid to the utilization of waste plastics-derived carbon in energy storage. Herein, porous carbon nanosheets (PCNSs) was produced by catalytic carbonization of "real-world" mixed waste plastics on organically-modified montmorillonite (OMMT) and the subsequent KOH activation. PCNSs was featured on hierarchically micro-/mesoporous structures with the pore size distribution centered on 0.57, 1.42 and 3.63 nm and partially exfoliated graphitic layers, and showed a high specific surface area of 2198 m2 g−1 and a large pore volume of 3.026 cm3 g−1. Benefiting from these extraordinary properties, PCNSs displayed a superior performance for supercapacitors with high specific capacitances approaching 207 and 120 F g−1 at a current density of 0.2 A g−1 in aqueous and organic electrolytes, respectively. Importantly, when the current density increased to 10 A g−1, the specific capacitances remained at 150 F g−1 (72.5%) and 95 F g−1 (79.2%) in aqueous and organic electrolytes, respectively. The outstanding rate capability of PCNSs was in sharp contrast to the performance of traditional activated carbons. This work not only provides a potential way to recycle mixed waste plastics, but also puts forward a facile sustainable approach for the large-scale production of PCNSs as a promising candidate for supercapacitors. [ABSTRACT FROM AUTHOR]

Undoped, N-doped, and S-doped porous carbons were prepared via the hard-template method by direct carbonization of aromatic precursors on MgO at 500 °C and autogenic pressure. The influence of aromatic precursors on the yield, morphology, structure, surface composition, and textural properties of the carbons was investigated. The side-chain and number of the benzene ring promoted the yield of carbon. Acenes produced more carbon among the polycyclic aromatic hydrocarbons. The highest yield of carbon was 52.9 wt% using pyrrole as precursor on a commercial sheet MgO. The size of micropores and macropores as well as nitrogen content was also dependent on the aromatics. Three types of MgO were compared using pyrrole as precursor. Morphology of MgO played a key role on the yield of porous carbon. The yield of carbon reached 50.5 wt% and the surface area of carbon was 671 m 2  g −1 on a home-made MgO. After KOH activation, the surface area of the porous carbon increased dramatically to 2788 m 2  g −1 and exhibited a high adsorption capacity up to 980.4 mg g −1 for methylene blue. [ABSTRACT FROM AUTHOR]

Catalyzing carbonization of polymer itself to form a protective carbonaceous layer has been proven to be an effective way to improve polymer's flame retardancy, but there is still a great challenge to achieve synchronous enhancement in traditional test standards (such as LOI and UL-94 testing). In this study, a stiffener skeleton strategy combined with catalyzing carbonization was proposed to improve the flame retardancy of polycarbonate (PC). The synergistic effect of nanosized carbon black (CB)/Ni 2 O 3 on carbon yield and combustion properties of PC were investigated. An improvement with 31.4% in LOI, V0 in UL-94, and 50% reduction for PHRR in cone calorimeter test was achieved. According to char morphology and structure analysis, the flame retardancy mechanism was attributed to the enhanced barrier effect of carbon layer with interconnected structure and self-supporting capacity, which was promoted by the formation of carbon skeleton framework from PC and the catalytic carbonization from combined catalysts. [ABSTRACT FROM AUTHOR]

Highlights: [•] Catalytic carbonization of PP into cup-stacked carbon nanotubes (CS-CNTs). [•] Yield and morphology of CS-CNTs were modulated by halogenated compound content. [•] Halogenated compound significantly influenced the degradation products of PP. [•] Coalescence and reconstruction of NiO were affected by PP degradation products. [•] Acid-treated CS-CNT showed high performances in adsorption of metallic ions and dyes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A green and high-yield route to recycle waste masks into CNTs/Ni hybrids. • The yield of carbon as high as 64.4 g/100 g waste masks. • The Ni(OH) 2 /NiCl 2 as universal catalysts to catalytic carbonization waste masks form different environments. • Superior microwave absorption performances with reflection loss of -56.3 dB and absorption bandwidth of 4.3 GHz. With the worldwide pandemic of COVID-19, a tremendous amount of face masks have been consumed and discarded, resulting in serious environment pollution and infectious hazards. Herein a green and high-yield route has been developed to recycle waste masks (WMs) into CNTs/Ni hybrids via catalytic carbonization. Our results exhibited that the yield of carbon was as high as 64.4 g/100 g WMs. Furthermore, the as-fabricated CNTs/Ni hybrids were applied for microwave absorption, which displayed superior performances, including a strong reflection loss of -56.3 dB and an absorption bandwidth of 4.3 GHz with absorber thickness of only 2.0 mm. The mechanism was mainly ascribed to the favorable synergistic effects of CNTs and Ni on conduction and magnetic losses, dipolar polarization, interfacial polarization and impedance matching. Thus, this work provides an environmentally friendly, scalable and cost-effective strategy for recycling waste masks into high-valuable carbon nanomaterials, and exploits their potential application for microwave absorption. [ABSTRACT FROM AUTHOR]