Porous Nitrogen-Doped Carbon Nanotubes Derived from Tubular Polypyrrole for Energy-Storage Applications

Preparation of an N-doped mesoporous carbon sphere and sheet composite as a high-performance supercapacitor

Carbon-based materials with multidimensional structures generally exhibit improved properties compared with single-morphology carbon materials for various applications including catalysis, adsorption, and energy storage. Here, an N-doped mesoporous carbon sphere and sheet composite is prepared by a co-assembly strategy using an ionic liquid ([C18Mim]Br) as the structure-directing agent, ethylenediamine as the catalyst, tetraethyl orthosilicate as the pore-forming agent, and resorcinol formaldehyde resin as the carbon precursor. [C18Mim]Br and ethylenediamine not only induce formation of the unique structure but also lead to in situ nitrogen doping on the N-doped mesoporous carbon skeleton. The obtained N-doped mesoporous carbon shows a unique composite structure of thin sheets embedded with carbon spheres, having high a specific surface area and uniform mesopore distribution. When used as an electrode material, the N-doped mesoporous carbon shows a good specific capacity of 273 F g−1 at a current density of 0.5 A g−1 and a good rate capability (82.1% of the capacitance is retained at a high current density of 10 A g−1). Moreover, the N-doped mesoporous carbon exhibited ideal stability behavior (91.6% capacitive retention after 10,000 cycles), indicating a promising role as an electrode material for excellent performance supercapacitors.

Polyaniline-derived carbons: Remarkable adsorbents to remove atrazine and diuron herbicides from water

The contamination of water resources by hazardous organic compounds is becoming severe worldwide. In this study, the adsorptive removal of atrazine (ATZ) and diuron (DUR), two widely used herbicides, from water by polyaniline-derived carbons (PDCs) was investigated for the first time, under various conditions. A selected PDC, fabricated at optimum conditions, i.e., by pyrolysis at 800 °C (and labeled PDC(800)), showed remarkable adsorptivity for both herbicides, that is, 7.7 and 11.3 times the maximum adsorption capacity (Q₀) for ATZ and DUR, respectively, compared to activated carbon (AC). Or, the Q₀ values of PDC(800) for ATZ and DUR were 943 and 884 mg/g, respectively; however, the Q₀ values of AC were only 123 and 78.0 mg/g, respectively. Moreover, the optimum adsorbent PDC(800) had 4.5 and 3.1 times Q₀ that of the best adsorbent, that showed the highest performances, so far, for ATZ and DUR, respectively. Plausible adsorption mechanisms were suggested based on the porosity and the adsorption in a wide pH range. The new adsorbent was reusable via simple solvent washing. Based on its remarkable adsorption performance and facile reusability, PDC(800) can be considered a promising adsorbent to remove herbicides such as ATZ and DUR from contaminated water.

Adsorptive removal of bulky dye molecules from water with mesoporous polyaniline-derived carbon

Polyaniline-derived carbon (PDC) was obtained via pyrolysis of polyaniline under different temperatures and applied for the purification of water contaminated with dye molecules of different sizes and charge by adsorption. With increasing pyrolysis temperature, it was found that the hydrophobicity, pore size and mesopore volume increased. A mesoporous PDC sample obtained via pyrolysis at 900 °C showed remarkable performance in the adsorption of dye molecules, irrespective of dye charge, especially in the removal of bulky dye molecules, such as acid red 1 (AR1) and Janus green B (JGB). For example, the most competitive PDC material showed a Q ₀ value (maximum adsorption capacity) 8.1 times that of commercial, activated carbon for AR1. The remarkable adsorption of AR1 and JGB over KOH-900 could be explained by the combined mechanisms of hydrophobic, π-π, electrostatic and van der Waals interactions.

Synthesis of mesoporous carbon with tunable pore size for supercapacitors

Mesoporous carbon (MC) has wide applications, including in drug delivery, catalysis, absorption, energy storage/conversion, etc.

Recent advances in cathode materials for rechargeable lithium-sulfur batteries

Lithium-sulfur batteries (Li-S) are regarded as a promising candidate for next-generation energy storage systems due to their high specific capacity (1675 mA h g^-1) and energy density (2600 W h kg^-1) as well as the abundance, safety and low cost of sulfur materials. However, many disadvantages hinder the further development of Li-S batteries, such as the insulating nature of the active materials, the dissolution of intermediate products, large volume expansion and safety concerns related to metal lithium anodes. During the past decade, tremendous efforts have been made in the design and synthesis of electrode materials. In this review, we briefly discuss the electrochemical mechanism of Li-S batteries and their practical problems. Then, we systematically summarize the current strategies for designing cathode materials with stable and long cycling performance, including sulfur cathodes and Li₂S cathodes; subsequently, the current development of solid-state electrolytes and protective strategies for lithium metal anodes are briefly discussed. Finally, the current challenges and future perspectives of Li-S batteries are presented.

Heteroatom-doped hollow carbon spheres made from polyaniline as an electrode material for supercapacitors

In this work, novel heteroatom-doped hollow carbon spheres (HHCSs) were prepared via the carbonization of polyaniline hollow spheres (PHSs), which were synthesized by one-pot polymerization. It was found that the carbonized PHSs at 700 °C exhibit high specific capacitance of 241 F g-1 at a current density of 0.5 A g-1 and excellent rate capability. The excellent electrochemical performance can be attributed to the heteroatom-doping and hollow carbon nanostructure of the HHCSs electrodes. Heteroatom groups in the HHCSs not only improve the wettability of the carbon surface, but also enhance the capacitance by addition of a pseudocapacitive redox process. Their unique structure provides a large specific surface area along with reduced diffusion lengths for both mass and charge transport.

Mass production of hierarchically porous carbon nanosheets by carbonizing "real-world" mixed waste plastics toward excellent-performance 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.

Strategies for Building Robust Traffic Networks in Advanced Energy Storage Devices: A Focus on Composite Electrodes

The charge transport system in an energy storage device (ESD) fundamentally controls the electrochemical performance and device safety. As the skeleton of the charge transport system, the "traffic" networks connecting the active materials are primary structural factors controlling the transport of ions/electrons. However, with the development of ESDs, it becomes very critical but challenging to build traffic networks with rational structures and mechanical robustness, which can support high energy density, fast charging and discharging capability, cycle stability, safety, and even device flexibility. This is especially true for ESDs with high-capacity active materials (e.g., sulfur and silicon), which show notable volume change during cycling. Therefore, there is an urgent need for cost-effective strategies to realize robust transport networks, and an in-depth understanding of the roles of their structures and properties in device performance. To address this urgent need, the primary strategies reported recently are summarized here into three categories according to their controllability over ion-transport networks, electron-transport networks, or both of them. More specifically, the significant studies on active materials, binders, electrode designs based on various templates, pore additives, etc., are introduced accordingly. Finally, significant challenges and opportunities for building robust charge transport system in next-generation energy storage devices are discussed.

Carbon and Nitrogen Based Nanosheets as Fluorescent Probes with Tunable Emission

2D carbon and nitrogen based semiconductors (CN) have attracted widespread attention for their possible use as low-cost and environmentally friendly materials for various applications. However, their limited solution-dispersibility and the difficulty in preparing exfoliated sheets with tunable photophysical properties restrain their exploitation in imaging-related applications. Here, the synthesis of carbon and nitrogen organic scaffolds with highly tunable optical properties, excellent dispersion in water and DMSO, and good bioimaging properties is reported. Tailored photophysical and chemical properties are acquired by the synthesis of new starting monomers containing different substituent chemical groups with varying electronic properties. Upon monomer condensation at moderate temperature, 350 °C, the starting chemical groups are fully preserved in the final CN. The low condensation temperature and the effective molecular-level modification of the CN scaffold lead to well-dispersed photoluminescent CN thin sheets with a wide range of emission wavelengths. The good bioimaging properties and the tunable fluorescence properties are exemplified by in situ visualization of giant unilamellar vesicles in a buffered aqueous solution as a model system. This approach opens the possibility for the design of tailor-made CN materials with tunable photophysical and chemical properties toward their exploitation in various fields, such as photocatalysis, bioimaging, and sensing.

A high-performance asymmetric supercapacitor based on vanadyl phosphate/carbon nanocomposites and polypyrrole-derived carbon nanowires

A novel asymmetric supercapacitor device in an aqueous electrolyte is fabricated using a vanadyl phosphate/carbon nanocomposite as the positive electrode and a polypyrrole-derived carbon nanowire as the negative electrode. The vanadyl phosphate/carbon nanocomposites are synthesized by a simple two-step approach in which layered VOPO₄·2H₂O is first intercalated by dodecylamine and then annealed at high temperature, leading to the in situ carbonization of the intercalated dodecylamine. It is found that the sample in which the incorporated carbon with a high degree of graphitization exhibits a high specific capacitance of 469 F g^-1 at a current density of 1 A g^-1 and excellent rate performance (retained 77% capacitance at 10 A g^-1). A polypyrrole-derived carbon nanowire is synthesized by the direct carbonization of nanowire-shaped polypyrrole, revealing a rough surface of nanowire-like frameworks and good electrochemical behavior. Taking advantage of both positive and negative materials, the assembled asymmetric supercapacitor device exhibits a high energy density of 30.6 W h kg^-1 at a high power density of 813 W kg^-1 in a wide voltage region of 0-1.6 V, as well as a good electrochemical stability (84.3% capacitance retention after 5000 cycles). The present work can shed light on the fabrication of novel asymmetric supercapacitors with high-performance.

Pyridinic-nitrogen highly doped nanotubular carbon arrays grown on a carbon cloth for high-performance and flexible supercapacitors

Pyridinic-nitrogen highly doped nanotubular carbon (NTC) arrays with multimodal pores in the wall were synthesized via a one-step template strategy using 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) as both carbon and nitrogen precursors and ZnO nanowire (ZnO NW) arrays grown on carbon clothes as templates for high-performance supercapacitors (SCs). A strikingly high N-doping level of 14.3% and pyridine N (N-6) dominance as high as 69.1% of the total N content were achieved. Both the N content and N configuration can be well tailored by adjusting the carbonization temperatures of TATB. When directly applied as flexible SCs, the N-doped NTC yields a high specific capacitance of 310.7 F g^-1 (0.8 A g^-1), a cycling retention ratio of 105.1% after 20 000 charge-discharge cycles, and excellent capacitance retention rates of 93.6%, 74.2%, and 53.6% at 8 A g^-1, 40 A g^-1, and 80 A g^-1, respectively, as compared to the value at 0.8 g^-1. TATB, as the only precursor of C and N, is expected to be of great significance for the further design and synthesis of N-doped sp² carbon nanostructures with selective N configurations and controlled N content.

Enhancement in electrochemical performances of Li–S batteries by electrodeposition of sulfur on polyaniline–dodecyl benzene sulfonic acid–sulfuric acid (PANI–DBSA–H2SO4) honeycomb structure film

A sulfur cathode for advanced lithium–sulfur batteries was prepared by electrodeposition of elemental sulfur on honeycomb polyaniline–dodecyl benzene sulphonic acid (hPANI–DBSA–H₂SO₄/S) prepared through the breath figure (BF) method and its electrochemical performances were reported.

Nitrogen-doped carbon nanotube supported double-shelled hollow composites for asymmetric supercapacitors

A double-shelled hollow structure N–C@NiMoO₄ composite was prepared taking N-doped carbon nanotubes as a skeleton, and exhibited high electrochemical performance for supercapacitors.

Thin sandwich graphene oxide@N-doped carbon composites for high-performance supercapacitors

An ultrathin layer of ca. ∼1.9 nm N-doped carbon was deposited on GO via dehalogenation of PVDC.

Polypyrrole Nanotubes and Their Carbonized Analogs: Synthesis, Characterization, Gas Sensing Properties

Polypyrrole (PPy) in globular form and as nanotubes were prepared by the oxidation of pyrrole with iron(III) chloride in the absence and presence of methyl orange, respectively. They were subsequently converted to nitrogen-containing carbons at 650 °C in an inert atmosphere. The course of carbonization was followed by thermogravimetric analysis and the accompanying changes in molecular structure by Fourier Transform Infrared and Raman spectroscopies. Both the original and carbonized materials have been tested in sensing of polar and non-polar organic vapors. The resistivity of sensing element using globular PPy was too high and only nanotubular PPy could be used. The sensitivity of the PPy nanotubes to ethanol vapors was nearly on the same level as that of their carbonized analogs (i.e., ~18% and 24%, respectively). Surprisingly, there was a high sensitivity of PPy nanotubes to the n-heptane vapors (~110%), while that of their carbonized analog remained at ~20%. The recovery process was significantly faster for carbonized PPy nanotubes (in order of seconds) compared with 10 s of seconds for original nanotubes, respectively, due to higher specific surface area after carbonization.

Heteroatom-Doped Carbon Nanostructures Derived from Conjugated Polymers for Energy Applications

Heteroatom-doped carbon materials have been one of the most remarkable families of materials with promising applications in fuel cells, supercapacitors, and batteries. Among them, conjugated polymer (CP)-derived heteroatom-doped carbon materials exhibit remarkable electrochemical performances because the heteroatoms can be preserved at a relatively high content and keep stable under harsh working conditions. In this review, we summarized recent advances in the rational design and various applications of CP-derived heteroatom-doped carbon materials, including polyaniline (PANI), polypyrrole (PPy), and their ramification-derived carbons, as well as transition metal-carbon nanocomposites. The key point of considering CP-derived heteroatom-doped carbon materials as important candidates of electrode materials is that CPs contain only nonmetallic elements and some key heteroatoms in their backbones which provide great chances for the synthesis of metal-free heteroatom-doped carbon nanostructures. The presented examples in this review will provide new insights in designing and optimizing heteroatom-doped carbon materials for the development of anode and cathode materials for electrochemical device applications.

Fabrication of Nitrogen-Doped Hollow Mesoporous Spherical Carbon Capsules for Supercapacitors

A novel "dissolution-capture" method for the fabrication of nitrogen-doped hollow mesoporous spherical carbon capsules (N-HMSCCs) with high capability for supercapacitor is developed. The fabrication process is performed by depositing mesoporous silica on the surface of the polyacrylonitrile nanospheres, followed by a dissolution-capture process occurring in the polyacrylonitrile core and silica shell. The polyacrylonitrile core is dissolved by dimethylformamide treatment to form a hollow cavity. Then, the polyacrylonitrile is captured into the mesochannel of silica. After carbonization and etching of silica, N-HMSCCs with uniform mesopore size are produced. The N-HMSCCs show a high specific capacitance of 206.0 F g(-1) at a current density of 1 A g(-1) in 6.0 M KOH due to its unique hollow nanostructure, high surface area, and nitrogen content. In addition, 92.3% of the capacitance of N-HMSCCs still remains after 3000 cycles at 5 A g(-1). The "dissolution-capture" method should give a useful enlightenment for the design of electrode materials for supercapacitor.

Good Low-Temperature Properties of Nitrogen-Enriched Porous Carbon as Sulfur Hosts for High-Performance Li-S Batteries

Despite the increased attention devoted to exploring cathode construction based on various nitrogen-enriched carbon scaffolds at room temperature, the low-temperature behaviors of Li-S cathodes have yet to be studied. Herein, we demonstrate the good low-temperature electrochemical performances of nitrogen-enriched carbon/sulfur composite cathodes. Electrochemical evaluation indicates that a reversible capacity of 368 mAh g(-1) (0.5 C) over 100 cycles is achieved at -20 °C. After returning to 25 °C, a capacity of 620 mAh g(-1) (0.5 C) is achieved over 350 cycles with a low-capacity attenuation rate (0.071% per cycle) and an initial capacity of 1151 mAh g(-1) (0.1C). This positive electrochemical property was speculated to result from the good surface chemistry of the various amine groups in the nitrogen-enriched carbon materials with enhanced polysulfide immobilization.

Hierarchical sulfur-impregnated hydrogenated TiO2 mesoporous spheres comprising anatase nanosheets with highly exposed (001) facets for advanced Li-S batteries

In this contribution, we purposefully designed hierarchical hydrogenated TiO2 spheres (HTSs) constructed from ultrathin anatase nanosheets with highly exposed (001) facets, and further utilized them as an efficient encapsulated host of sulfur species for advanced Li-S batteries (LSBs). Strikingly, the as-fabricated hybrid S/HTSs cathode exhibited high Coulombic efficiency (>94%), exceptional long cycling performance (capacity decay of ∼0.399% per cycle at 0.5 C), and large reversible discharge capacity (∼579 mAh g(-1) at 2.0 C) at high C rates, benefiting from better electronic conductivity, smaller charge transfer resistance and strong chemical bonding between [Formula: see text] and the reduced (001) facets of HTSs, according to experimental measurements and systematical theoretical calculations. More significantly, our in-depth insights into the mechanism involved in the hybrid S/HTSs could efficiently guide future design, optimization and synthesis of other metal oxide-based matrixes with specific exposed crystal facets for next-generation advanced LSBs.

PAA/PEDOT:PSS as a multifunctional, water-soluble binder to improve the capacity and stability of lithium–sulfur batteries

An improved cycling performance of sulfur cathodes is attributed to the synergistic effect of PAA and PEDOT:PSS.

Highly flexible all-solid-state supercapacitors based on carbon nanotube/polypyrrole composite films and fibers

A film-shaped supercapacitor (2.5 cm²) showed good flexibility and high stability when undergoing bending and twisting.

Enhanced electrochemical performance by a three-dimensional interconnected porous nitrogen-doped graphene/carbonized polypyrrole composite for lithium–sulfur batteries

3D interconnected porous nitrogen-doped graphene/carbonized polypyrrole nanotubes are employed as sulfur hosts, they exhibit excellent electrochemical performance for lithium–sulfur batteries.

Nitrogen-doped carbon microspheres counter electrodes for dye-sensitized solar cells by microwave assisted method

Nitrogen-doped carbon microspheres were synthesized for counter electrodes of dye-sensitized solar cells with a high efficiency of 6.28%.

3D coral-like nitrogen-sulfur co-doped carbon-sulfur composite for high performance lithium-sulfur batteries

3D coral-like, nitrogen and sulfur co-doped mesoporous carbon has been synthesized by a facile hydrothermal-nanocasting method to house sulfur for Li-S batteries. The primary doped species (pyridinic-N, pyrrolic-N, thiophenic-S and sulfonic-S) enable this carbon matrix to suppress the diffusion of polysulfides, while the interconnected mesoporous carbon network is favourable for rapid transport of both electrons and lithium ions. Based on the synergistic effect of N, S co-doping and the mesoporous conductive pathway, the as-fabricated C/S cathodes yield excellent cycling stability at a current rate of 4 C (1 C = 1675 mA g(-1)) with only 0.085% capacity decay per cycle for over 250 cycles and ultra-high rate capability (693 mAh g(-1) at 10 C rate). These capabilities have rarely been reported before for Li-S batteries.

Nano-to-Microdesign of Marimo-Like Carbon Nanotubes Supported Frameworks via In-spaced Polymerization for High Performance Silicon Lithium Ion Battery Anodes

Silicon (Si) has been perceived as a promising anode material for lithium-ion batteries for decades due to its superior theoretical capacity, environmental benignity, and earth abundance. To accommodate the drastic volume expansion during lithiation, which is the primary drawback leading to poor cycling life, a novel structural design via fabricating the Marimo-like carbon nanotubes frameworks with silicon nanoparticle (SiNP) filling in internal space has been developed. This facile fabrication procedure involves an in-spaced polymerization process through ex situ polymerization, using pyrrole monomers with a soft organic template in which well-dispersed SiNPs are present. Carbonization post-treatment is then performed to construct rigid conductive networks. The thus-fabricated 3D Marimo-like hybrid structure exhibits a remarkably improved electrochemical performance compared with that of the simple ball-milling method, which mainly originates from their structural advantages, including the built-in buffer spaces and the robust line-to-line contact mode between the components. The state-of-the-art structure exhibits an optimal high-rate capability (422 mAh g(-1) at a current rate of 2 A g(-1)) and long cycling stability (916 mAh g(-1) for 200th cycles at a current rate of 0.2 A g(-1)) and achieves the requirements for industrial production with the facile and cost-effective synthetic approach.

Holey tungsten oxynitride nanowires: novel anodes efficiently integrate microbial chemical energy conversion and electrochemical energy storage

Holey tungsten oxynitride nanowires with superior conductivity, good biocompatibility, and good stability achieve excellent performance as anodes for both asymmetric supercapacitors and microbial fuel cells. Moreover, an innovative system is devised based on these as-prepared tungsten oxynitride anodes, which can simultaneously realize both energy conversion from chemical to electric energy and its storage.