Porous Pd@m-C/SiO2 nanopeapods are prepared by a nanoconfinement method. The Pd nanoparticles show high efficiency and stability in chemical reactions such as reduction of nitrobenzene by H2 and reduction of NO by NH3. The high catalytic activity is attributed to the unique peapod structure, mesoporous wall, and large specific surface area on Pd@m-C/SiO2 rendering the Pd nanoparticles highly active in chemical reactions.

Novel porous cup-stacked carbon nanotube (P-CSCNT) with special stacked morphology consisting of many truncated conical graphene layers was synthesized by KOH activating CSCNT from polypropylene. The morphology, microstructure, textural property, phase structure, surface element composition and thermal stability of P-CSCNT were investigated by field-emission scanning electron microscope, transmission electron microscope (TEM), high-resolution TEM, N2 sorption, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and thermal gravimetric analysis. A part of oblique graphitic layers were etched by KOH, and many holes with a diameter of several to a doze of nanometers connecting inner tube with outside were formed, which endowed P-CSCNT with high specific surface area (558.7 m2/g), large pore volume (1.993 cm3/g) and abundant surface functional groups. Subsequently, P-CSCNT was used for adsorption of methylene blue (MB) from wastewater. Langmuir model closely fitted the adsorption results, and the maximum adsorption capacity of P-CSCNT was as high as 319.1 mg/g. This was ascribed to multiple adsorption mechanisms including pore filling, hydrogen bonding, π–π and electrostatic interactions. Pseudo second-order kinetic model was more valid to describe the adsorption behavior. Besides, P-CSCNT showed good recyclablity and reusability. These results demonstrated that P-CSCNT had potential application in wastewater treatment.

The present paper reports a facile method to synthesize CNT-Fe2O3 and CNTs-Fe3O4@C beaded structures by deposition of Fe2O3 and carbon layers on CNTs, which integrate both electronic conductivity and buffering matrix design strategies. The CNT-Fe2O3 and CNTs-Fe3O4@C were tested as anode materials for lithium-ion batteries, CNT-Fe2O3 showed excellent cycling performance, the reversible capacity retention after 80 cycles is stable at 410 mA h g−1. However, CNTs-Fe3O4@C exhibited improved reversible capacity and better cycling performance when compared to CNT and CNTs-Fe2O3. The highly improved reversible capacities are attributed to the combination of (a) the network structured CNTs, which improve the matrix electrical conductivity, (b) the mesopores created by the carbon coating on Fe3O4 nanoparticles and CNTs, which increases lithium-ion mobility and storage, and (c) the Fe3O4 nanoparticles attached to the CNTs facilitate the transport of electrons and shorten the distance for Li+ diffusion. This study provides a cost-effective, highly efficient method to fabricate nanomaterials which combines carbon nanotubes with iron oxide nanoparticles for the development of lithium ion batteries with high-performance.

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.

A facile, efficient and environment friendly method is established to prepare poly(vinyl alcohol) (PVA) based graphene oxide-montmorillonite (GO-MMT) nanocomposites in aqueous media. GO-MMT nanohybrid is obtained by the combination of GO and MMT in water without any reducing or stabilizing agents. The formation of GO-MMT nanohybrid is due to the hydrogen bonding and crosslinking effects. The sodium ions within MMT sheets act as crosslinkers between GO sheets and MMT platelets. The resultant nanocomposites are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and mechanical testing. Compared to that of pure PVA, PVA nanocomposites show enhanced thermal stabilities and mechanical properties, which results from strong interfacial adhesion of the nanoadditives in PVA matrix. The further increase in the tensile strength and modulus results from strong interaction between PVA chains and layered GO-MMT as well as good mechanical properties of GO-MMT hybrid, compared to PVA/GO and PVA/MMT nanocompsoites.

Conversion of waste plastics into high value-added carbon nanomaterials has gained wide research interest due to the requirement of sustainable development and the ever-increasing generation of waste plastics. However, most of studies are limited to single component plastic; besides, little attention has been paid to carbon nanosheets (CNS). Herein, CNS were prepared by catalytic carbonization of mixed plastics consisting of polypropylene, polyethylene, polystyrene, poly(ethylene terephthalate), and polyvinyl chloride on organically modified montmorillonite. After KOH activation, porous CNS (PCNS) were produced. The morphology, microstructure, phase structure, textural property, surface element composition, and thermal stability of PCNS were investigated. PCNS contained randomly oriented lattice fringes and showed a layered morphology consisting of thin, leaf-like, agglomerated nanosheets ranging from hundreds of nanometers to several micrometers in length. Besides, PCNS exhibited high specific surface area (1734 m2/g) and large pore volume (2.441 cm3/g). More importantly, PCNS displayed high performances in the uptake of carbon dioxide and storage of hydrogen. It is believed that this work not only paves the way for utilization of mixed waste plastics but also provides a facile sustainable approach for the large-scale production of valuable PCNS for energy storage and environmental remediation.Keywords: Carbon dioxide; Hydrogen; Mixed plastics; Porous carbon nanosheet; Sustainable approach

The porous carbon nanotubes were selectively prepared from the pristine carbon nanotubes. The surface of carbon nanotubes was firstly functionalized with Fe2O3 nanoparticles and subsequent heat treatment induced CNT etching. After removal of Fe2O3 nanoparticles, mesopores were formed in carbon nanotubes and thus porous structure was obtained. The obtained material of porous carbon nanotubes with higher specific surface area and larger pore sizes was tested as anode material of lithium ion batteries and showed improved performance with respect to the pristine carbon nanotubes.

Here, we report an efficient method for the transformation of waste car bumpers into mesoporous magnetic carbon material. Nearly 25 wt% of polypropylene was transformed into carbon material when an optimized amount of catalysts was introduced into the bumper composite. In addition, due to the presence of Fe and Co nanoparticles, the carbon nanomaterial exhibits magnetic properties. The obtained product was used as an effective adsorbent for the removal of dye pollutants from water – nearly 100% of rhodamine B (RhB) and methylene blue (MB) can be efficiently removed from an aqueous solution in a short duration. Furthermore, benefiting from their strong saturation magnetization, the obtained carbon materials can be easily separated from the solution by a magnet and reused multiple times. Based on the experimental results, the proposed route can pave a way to recycle waste plastics to provide large amounts of highly valuable carbon products in the future.

A one-pot approach was established to effectively convert polypropylene (PP) and linear low density polyethylene (LLDPE) into carbon nanomaterials (CNMs) including cup-stacked carbon nanotubes and carbon nanofibers under the combined catalysis of HZSM-5/NiO or HZSM-5/Ni2O3 at 700 °C. The effects of HZSM-5 content, a nickel catalyst, and the carbon precursor on the morphology, microstructure, phase structure, and thermal stability of CNMs were investigated with scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray diffraction, Raman spectroscopy, and thermal gravimetric analysis. The effect of HZSM-5 content on the degradation products of PP and LLDPE was analyzed by gas chromatography and gas chromatography–mass spectrometry. With increasing HZSM-5 content, the yields of light hydrocarbons and aromatics increased due to proton acid sites on the surface of HZSM-5 catalyzing cracking of PP or LLDPE degradation products. This one-pot approach provides a novel potential way to largely transform mixed waste polyolefin into high value-added CNMs.

The porous carbon nanotubes were selectively prepared from the pristine carbon nanotubes. The surface of carbon nanotubes was firstly functionalized with Fe2O3 nanoparticles and subsequent heat treatment induced CNT etching. After removal of Fe2O3 nanoparticles, mesopores were formed in carbon nanotubes and thus porous structure was obtained. The obtained material of porous carbon nanotubes with higher specific surface area and larger pore sizes was tested as anode material of lithium ion batteries and showed improved performance with respect to the pristine carbon nanotubes.

Porous Pd@m-C/SiO2 nanopeapods are prepared by a nanoconfinement method. The Pd nanoparticles show high efficiency and stability in chemical reactions such as reduction of nitrobenzene by H2 and reduction of NO by NH3. The high catalytic activity is attributed to the unique peapod structure, mesoporous wall, and large specific surface area on Pd@m-C/SiO2 rendering the Pd nanoparticles highly active in chemical reactions.