Carbon nanofibers prepared via electrospinning

Modifying porous carbon nanofibers with MnOx–CeO2–Al2O3 mixed oxides for NO catalytic oxidation at room temperature

MnO_x–CeO₂–Al₂O₃ mixed oxides dispersed in CNFs to form a composite which displays remarkable activity for NO oxidation at room temperature.

Free standing hollow carbon nanofiber mats for supercapacitor electrodes

Free standing hollow carbon nanofiber (CNF) mats with high graphitic content have been fabricated through co-axial electrospinning followed by high temperature pyrolysis.

A highly flexible and conductive graphene-wrapped carbon nanofiber membrane for high-performance electrocatalytic applications

Graphene-wrapped electrospun carbon nanofiber membranes with greatly improved electrical conductivity have been synthesized through an effective surface-induced assembly strategy.

Graphitized porous carbon nanofibers prepared by electrospinning as anode materials for lithium ion batteries

Graphitized porous carbon nanofibers were prepared by electrospinning and subsequent calcining, exhibiting high capacity and good cycling stability.

Multi-dimensional construction of a novel active yolk@conductive shell nanofiber web as a self-standing anode for high-performance lithium-ion batteries

A novel active yolk@conductive shell nanofiber web with a unique synergistic advantage of various hierarchical nanodimensional objects including the 0D monodisperse SiO2 yolks, the 1D continuous carbon shell and the 3D interconnected non-woven fabric web has been developed by an innovative multi-dimensional construction method, and thus demonstrates excellent electrochemical properties as a self-standing LIB anode.

Lignin-Derived Advanced Carbon Materials

Lignin is a highly abundant source of renewable carbon that can be considered as a valuable sustainable source of biobased materials. By applying specific pretreatments and manufacturing methods, lignin can be converted into a variety of value-added carbon materials. However, the physical and chemical heterogeneities of lignin complicate its use as a feedstock. Herein lignin manufacturing process, the effects of pretreatments and manufacturing methods on the properties of product lignin, and structure-property relationships in various applications of lignin-derived carbon materials, such as carbon fibers, carbon mats, activated carbons, carbon films, and templated carbon, are discussed.

Membranes of MnO Beading in Carbon Nanofibers as Flexible Anodes for High-Performance Lithium-Ion Batteries

Freestanding yet flexible membranes of MnO/carbon nanofibers are successfully fabricated through incorporating MnO₂ nanowires into polymer solution by a facile electrospinning technique. During the stabilization and carbonization processes of the as-spun membranes, MnO₂ nanowires are transformed to MnO nanoparticles coincided with a conversion of the polymer from an amorphous state to a graphitic structure of carbon nanofibers. The hybrids consist of isolated MnO nanoparticles beading in the porous carbon and demonstrate superior performance when being used as a binder-free anode for lithium-ion batteries. With an optimized amount of MnO (34.6 wt%), the anode exhibits a reversible capacity of as high as 987.3 mAh g⁻¹ after 150 discharge/charge cycles at 0.1 A g⁻¹, a good rate capability (406.1 mAh g⁻¹ at 3  A g⁻¹) and an excellent cycling performance (655 mAh g⁻¹ over 280 cycles at 0.5 A g⁻¹). Furthermore, the hybrid anode maintains a good electrochemical performance at bending state as a flexible electrode.

Carbon-Based Materials for Lithium-Ion Batteries, Electrochemical Capacitors, and Their Hybrid Devices

A rapidly developing market for portable electronic devices and hybrid electrical vehicles requires an urgent supply of mature energy-storage systems. As a result, lithium-ion batteries and electrochemical capacitors have lately attracted broad attention. Nevertheless, it is well known that both devices have their own drawbacks. With the fast development of nanoscience and nanotechnology, various structures and materials have been proposed to overcome the deficiencies of both devices to improve their electrochemical performance further. In this Review, electrochemical storage mechanisms based on carbon materials for both lithium-ion batteries and electrochemical capacitors are introduced. Non-faradic processes (electric double-layer capacitance) and faradic reactions (pseudocapacitance and intercalation) are generally explained. Electrochemical performance based on different types of electrolytes is briefly reviewed. Furthermore, impedance behavior based on Nyquist plots is discussed. We demonstrate the influence of cell conductivity, electrode/electrolyte interface, and ion diffusion on impedance performance. We illustrate that relaxation time, which is closely related to ion diffusion, can be extracted from Nyquist plots and compared between lithium-ion batteries and electrochemical capacitors. Finally, recent progress in the design of anodes for lithium-ion batteries, electrochemical capacitors, and their hybrid devices based on carbonaceous materials are reviewed. Challenges and future perspectives are further discussed.

High-Performance Supercapacitor Electrode Materials from Cellulose-Derived Carbon Nanofibers

Nitrogen-functionalized carbon nanofibers (N-CNFs) were prepared by carbonizing polypyrrole (PPy)-coated cellulose NFs, which were obtained by electrospinning, deacetylation of electrospun cellulose acetate NFs, and PPy polymerization. Supercapacitor electrodes prepared from N-CNFs and a mixture of N-CNFs and Ni(OH)2 showed specific capacitances of ∼236 and ∼1045 F g(-1), respectively. An asymmetric supercapacitor was further fabricated using N-CNFs/Ni(OH)2 and N-CNFs as positive and negative electrodes. The supercapacitor device had a working voltage of 1.6 V in aqueous KOH solution (6.0 M) with an energy density as high as ∼51 (W h) kg(-1) and a maximum power density of ∼117 kW kg(-1). The device had excellent cycle lifetime, which retained ∼84% specific capacitance after 5000 cycles of cyclic voltammetry scans. N-CNFs derived from electrospun cellulose may be useful as an electrode material for development of high-performance supercapacitors and other energy storage devices.

Porous Carbon Nanofibers from Electrospun Biomass Tar/Polyacrylonitrile/Silver Hybrids as Antimicrobial Materials

A novel route to fabricate low-cost porous carbon nanofibers (CNFs) using biomass tar, polyacrylonitrile (PAN), and silver nanoparticles has been demonstrated through electrospinning and subsequent stabilization and carbonization processes. The continuous electrospun nanofibers had average diameters ranging from 392 to 903 nm. The addition of biomass tar resulted in increased fiber diameters, reduced thermal stabilities, and slowed cyclization reactions of PAN in the as-spun nanofibers. After stabilization and carbonization, the resultant CNFs showed more uniformly sized and reduced average diameters (226-507 nm) compared to as-spun nanofibers. The CNFs exhibited high specific surface area (>400 m(2)/g) and microporosity, attributed to the combined effects of phase separations of the tar and PAN and thermal decompositions of tar components. These pore characteristics increased the exposures and contacts of silver nanoparticles to the bacteria including Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, leading to excellent antimicrobial performances of as-spun nanofibers and CNFs. A new strategy is thus provided for utilizing biomass tar as a low-cost precursor to prepare functional CNFs and reduce environmental pollutions associated with direct disposal of tar as an industrial waste.

Carbon-Coated Germanium Nanowires on Carbon Nanofibers as Self-Supported Electrodes for Flexible Lithium-Ion Batteries

A hybrid structure with carbon-coated germanium nanowires grown on the surface of carbon nanofibers is fabricated using an in situ vapor-liquid-solid process. It is used as a self-supported and flexible anode for Li-ion batteries.

Si nanoparticles encapsulated in elastic hollow carbon fibres for Li-ion battery anodes with high structural stability

Silicon has a large specific capacity which is an order of magnitude beyond that of conventional graphite, making it a promising anode material for lithium ion batteries. However, the large volume changes (∼ 300%) during cycling caused material pulverization and instability of the solid-electrolyte interphase resulting in poor cyclability which prevented its commercial application. Here, we have prepared a novel one-dimensional core-shell nanostructure in which the Si nanoparticles have been confined within hollow carbon nanofibres. Such a unique nanostructure exhibits high conductivity and facile ion transport, and the uniform pores within the particles which are generated during magnesiothermic reduction can serve as a buffer zone to accommodate the large volume changes of Si during electrochemical lithiation. Owing to these advantages, the composite shows high rate performance and good cycling stability. The optimum design of the core-shell nanostructure shows promise for the synthesis of a variety of high-performance electrode materials.

Optimized electrospinning synthesis of iron-nitrogen-carbon nanofibers for high electrocatalysis of oxygen reduction in alkaline medium

To achieve iron-nitrogen-carbon (Fe-N-C) nanofibers with excellent electrocatalysis for replacing high-cost Pt-based catalysts in the cathodes of fuel cells and metal-air batteries, we have investigated and evaluated the effects of polyacrylonitrile (PAN) concentration and the proportion of iron to PAN, along with voltage and flow rate during the electrospinning process, and thus proposed three criteria to optimize these parameters for ideal nanofiber catalysts. The best half-wave potential of an optimized catalysts is 0.82 V versus reversible hydrogen electrode in an alkaline medium, which reaches the best range of the non-precious-metal catalysts reported and is very close to that of commercial Pt/C catalysts. Furthermore, the electron-transfer number of our catalysts is superior to that of the Pt/C, indicating the catalysts undergo a four-electron process. The durability of the optimized Fe-N-C nanofibers is also better than that of the Pt/C, which is attributed to the homogeneous distribution of the active sites in our catalysts.

Organized chromophoric assemblies for nonlinear optical materials: towards (sub)wavelength scale architectures

Photonic circuits are expected to greatly contribute to the next generation of integrated chips, as electronic integrated circuits become confronted with bottlenecks such as heat generation and bandwidth limitations. One of the main challenges for the state-of-the-art photonic circuits lies in the development of optical materials with high nonlinear optical (NLO) susceptibilities, in particular in the wavelength and subwavelength dimensions which are compatible with on-chip technologies. In this review, the varied approaches to micro-/nanosized NLO materials based on building blocks of bio- and biomimetic molecules, as well as synthetic D-π-A chromophores, have been categorized as supramolecular self-assemblies, molecular scaffolds, and external force directed assemblies. Such molecular and supramolecular NLO materials have intrinsic advantages, such as structural diversities, high NLO susceptibilities, and clear structure-property relationships. These "bottom-up" fabrication approaches are proposed to be combined with the "top-down" techniques such as lithography, etc., to generate multifunctionality by coupling light and matter on the (sub)wavelength scale.

Oxygen-rich hierarchical porous carbon derived from artemia cyst shells with superior electrochemical performance

In this study, three-dimensional (3D) hierarchical porous carbon with abundant functional groups is produced through a very simple low-cost carbonization of Artemia cyst shells. The unique hierarchical porous structure of this material, combining large numbers of micropores and macropores, as well as reasonable amount of mesopores, is proven favorable to capacitive behavior. The abundant oxygen functional groups from the natural carbon precursor contribute stable pseudocapacitance. As-prepared sample exhibits high specific capacitance (369 F g(-1) in 1 M H2SO4 and 349 F g(-1) in 6 M KOH), excellent cycling stability with capacitance retention of 100% over 10 000 cycles, and promising rate performance. This work not only describes a simple way to produce high-performance carbon electrode materials for practical application, but also inspires an idea for future structure design of porous carbon.

Influence of earth-abundant bimetallic (Fe–Ni) nanoparticle-embedded CNFs as a low-cost counter electrode material for dye-sensitized solar cells

Earth-abundant bimetallic (Fe–Ni) nanoparticle-embedded carbon nanofibers (CNFs) have been prepared by electrospinning technique and used as counter electrode (CE) material for dye-sensitized solar cells (DSSCs).

Rational design of polyaniline/MnO2/carbon cloth ternary hybrids as electrodes for supercapacitors

A ternary hybrid was fabricated by sequentially depositing polyaniline and MnO₂ on carbon cloth. It displayed a unique porous structure and possessed a good electrochemical performance with a high areal capacitance of 421.6 mF cm⁻² (0.2 mA cm⁻²).

High-performance flexible supercapacitors based on mesoporous carbon nanofibers/Co3O4/MnO2 hybrid electrodes

Ultrathin MnO₂ nanosheets on flexible electrospun Co₃O₄ doped carbon nanofiber membranes were synthesized via electrospinning combined with in situ redox reaction and used as high-performance supercapacitor electrodes.

Graphene/polypyrrole-coated carbon nanofiber core–shell architecture electrode for electrochemical capacitors

In this study, a two-step electrospinning and potentiostatic electrodeposition method was used to fabricate the graphene/polypyrrole-coated carbon nanofiber core–shell architecture electrode for supercapacitor applications.

Nitrogen-doped electrospun reduced graphene oxide–carbon nanofiber composite for capacitive deionization

A nitrogen-doped electrospun reduced graphene oxide–carbon nanofiber composite was synthesized though electrospinning and ammonia treatment for an electrode for capacitive deionization.

Controllable synthesis of porous iron–nitrogen–carbon nanofibers with enhanced oxygen reduction electrocatalysis in acidic medium

Porous Fe–N–C nanofibers were synthesized as non-precious metal electrocatalysts with a 20 times enhancement in oxygen reduction performance.

Hierarchical porous carbon nanofibrous membranes with an enhanced shape memory property for effective adsorption of proteins

A hierarchical porous CNF membrane with robust mechanical properties, exhibiting intriguing shape memory properties and efficient protein adsorption performance.

Nanofibrous microspheres via emulsion gelation and carbonization

Nanofibrous hydrogel microspheres are formed by pH gelation in emulsion droplets, which can then be freeze-dried and carbonized to produce nanofibrous carbon microspheres, showing high performance as electrode materials for supercapacitors.

Graphene/carbon composite nanofibers for NO oxidation at room temperature

The novel structure of composite CNFs was preparedviaembedding reduced graphene oxide sheets for oxidation of NO at room temperature.

Preparation of Rh–SiO2 fiber catalyst with superior activity and reusability by electrospinning

Rh–SiO₂ fiber catalyst prepared by electrospinning for room temperature hydrogenation of alkenes with superior catalytic activity and reusability.

Controllable synthesis and enhanced electrocatalysis of iron-based catalysts derived from electrospun nanofibers

Electrospun carbon nanofibers containing iron and nitrogen are designed to catalyze the oxygen reduction reaction instead of Pt-based catalysts. Their surface morphology is modified finely by using ultralow oxygen flow, and their onset and half-wave potentials are improved to 0.88 V and 0.76 V versus the reversible hydrogen electrode, respectively, approaching those of Pt-based catalysts.

Influence of KMnO4 concentration and treatment time on PAN precursor and the resulting carbon nanofibers’ properties

Electrospun polyacrylonitrile (PAN) nanofibers were impregnated with KMnO4 under varying conditions of concentration and time. The morphological structures, chemical and thermal properties were studied by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The original and preoxidized samples were stabilized and carbonized for characterization with SEM and FTIR. The coloration, weight gain and solubility in N,N-dimethylformamide were also evaluated. A clear peak at 2340 cm-1 corresponding to MnO4–C=N conjugation, together with a wide peak at 1650 cm-1, was revealed in the FTIR spectrum of the preoxidized samples. Based on the DSC results, the cyclization reactions in the preoxidized samples were accelerated by initiating the exothermic reaction at lower temperatures. The modified samples had higher reaction times and ΔH values, broad exotherms, lower initial induction time and lower Ti values than the untreated ones.

Free-standing porous carbon nanofibers-sulfur composite for flexible Li-S battery cathode

Flexible and free-standing sulphur/(PCNFs-CNT) composite (S@PCNFs-CNT) electrode was successfully prepared by infiltrating sulfur into microporous carbon nanofibers-carbon nanotube (PCNFs-CNT) composite. When used as a cathode material for Li-S batteries, the S@PCNFs-CNT exhibits much better cycle performance and rate performance compared to CNT-free S@PCNFs. It delivers a reversible capacity of 637 mA h g(-1) after 100 cycles at 50 mA g(-1) and a rate capability of 437 mA h g(-1) at 1 A g(-1). The improved electrochemical performance is attributed to synergistic effect of the 3D interconnected structure, the additive of CNT, and the uniform distribution of micropores (<2 nm) in the PCNFs-CNT matrix. Our results indicate the potential suitability of PCNFs-CNT for efficient, free-standing, and high-performance batteries.

Electrospun carbon nanofibers decorated with Ag-Pt bimetallic nanoparticles for selective detection of dopamine

Electrospun nanoporous carbon nanofibers (pCNFs) decorated with Ag-Pt bimetallic nanoparticles have been successfully synthesized by combining template carbonization and seed-growth reduction approach. Porous-structured polyacrylonitrile (PAN) nanofibers (pPAN) were first prepared by electrospinning PAN/polyvinylpyrrolidone (PVP) blend solution, followed by subsequent water extraction and heat treatment to obtain pCNFs. Ag-Pt/pCNFs were then obtained by using pCNFs as support for bimetallic nanoparticle loading. Thus, the obtained Ag-Pt/pCNFs were used to modify glassy carbon electrode (GCE) for selective detection of dopamine (DA) in the presence of uric acid (UA) and ascorbic acid (AA). This novel sensor exhibits fast amperometric response and high sensitivity toward DA with a wide linear concentration range of 10-500 μM and a low detection limit of 0.11 μM (S/N = 3), wherein the interference of UA and AA can be eliminated effectively.

Interfacial engineering of carbon nanofiber-graphene-carbon nanofiber heterojunctions in flexible lightweight electromagnetic shielding networks

Lightweight carbon materials of effective electromagnetic interference (EMI) shielding have attracted increasing interest because of rapid development of smart communication devices. To meet the requirement in portable electronic devices, flexible shielding materials with ultrathin characteristic have been pursued for this purpose. In this work, we demonstrated a facile strategy for scalable fabrication of flexible all-carbon networks, where the insulting polymeric frames and interfaces have been well eliminated. Microscopically, a novel carbon nanofiber-graphene nanosheet-carbon nanofiber (CNF-GN-CNF) heterojunction, which plays the dominant role as the interfacial modifier, has been observed in the as-fabricated networks. With the presence of CNF-GN-CNF heterojunctions, the all-carbon networks exhibit much increased electrical properties, resulting in the great enhancement of EMI shielding performance. The related mechanism for engineering the CNF interfaces based on the CNF-GN-CNF heterojunctions has been discussed. Implication of the results suggests that the lightweight all-carbon networks, whose thickness and density are much smaller than other graphene/polymer composites, present more promising potential as thin shielding materials in flexible portable electronics.

Carbon Nanofibers and Their Composites: A Review of Synthesizing, Properties and Applications

Carbon nanofiber (CNF), as one of the most important members of carbon fibers, has been investigated in both fundamental scientific research and practical applications. CNF composites are able to be applied as promising materials in many fields, such as electrical devices, electrode materials for batteries and supercapacitors and as sensors. In these applications, the electrical conductivity is always the first priority need to be considered. In fact, the electrical property of CNF composites largely counts on the dispersion and percolation status of CNFs in matrix materials. In this review, the electrical transport phenomenon of CNF composites is systematically summarized based on percolation theory. The effects of the aspect ratio, percolation backbone structure and fractal characteristics of CNFs and the non-universality of the percolation critical exponents on the electrical properties are systematically reviewed. Apart from the electrical property, the thermal conductivity and mechanical properties of CNF composites are briefly reviewed, as well. In addition, the preparation methods of CNFs, including catalytic chemical vapor deposition growth and electrospinning, and the preparation methods of CNF composites, including the melt mixing and solution process, are briefly introduced. Finally, their applications as sensors and electrode materials are described in this review article.

Germanium nanoparticles encapsulated in flexible carbon nanofibers as self-supported electrodes for high performance lithium-ion batteries

Germanium is a promising high-capacity anode material for lithium ion batteries, but still suffers from poor cyclability due to its huge volume variation during the Li-Ge alloy/dealloy process. Here we rationally designed a flexible and self-supported electrode consisting of Ge nanoparticles encapsulated in carbon nanofibers (Ge-CNFs) by using a facile electrospinning technique as potential anodes for Li-ion batteries. The Ge-CNFs exhibit excellent electrochemical performance with a reversible specific capacity of ∼1420 mA h g(-1) after 100 cycles at 0.15 C with only 0.1% decay per cycle (the theoretical specific capacity of Ge is 1624 mA h g(-1)). When cycled at a high current of 1 C, they still deliver a reversible specific capacity of 829 mA h g(-1) after 250 cycles. The strategy and design are simple, effective, and versatile. This type of flexible electrodes is a promising solution for the development of flexible lithium-ion batteries with high power and energy densities.