Structure Of Carbon Nanofibers Research Articles

Carbon-encapsulated CoS2 nanoparticles anchored on N-doped carbon nanofibers derived from ZIF-8/ZIF-67 as anode for sodium-ion batteries

Utilized Zn/Co-based metal-organic framework, we successfully fabricate 1D N-doped porous carbon nanofibers anchoring amorphous and graphite carbon-encapsulated CoS2 nanoparticles, using a facile electrospinning strategy combined with annealing treatment. Remarkably, the composite as superior anode for sodium ion battery is rationally designed, and also exhibit enhanced Na-storage performance. The composite shows a large specific capacity of 876 mAh g−1 at 100 mA g−1 in the initial cycles and an outstanding long-term performance (148 mAh g−1 at a current density of 3.2 A g−1 over 1000 cycles). The improved electrochemical performance is ascribed to the 1D porous carbon nanofibers structure and the amorphous and graphite carbon coating, which can relatively inhibit agglomeration of CoS2 nanoparticles, mitigate the volume of the material changes in the process of circulation and provide stabilized electrical conductivity. This research paves the way for extending the 1D metal sulfides and metal-organic framework composites toward potential applications.

Derivation of both EDLC and pseudocapacitance characteristics based on synergistic mixture of NiCo2O4 and hollow carbon nanofiber: An efficient electrode towards high energy density supercapacitor

In this study we fabricated a hollow carbon nanofiber (CNF) via a facile dual nozzle electrospinning process and directly used as low-cost and environmental friendly carbon source material, which were incorporated to NiCo2O4 (NCO). We designed a hybrid nanocomposite based on synergistic mixture of hollow structure CNF and spinel NCO, with 3D dandelion like morphology, hierarchical mesoporous surface, high specific surface area, and directly grown onto the surface of nickel foam substrate. We modified the structural properties of hybrid NCO–CNF nanocomposite in aim to improve its overall electrochemical performance towards supercapacitor application. In here, we fabricated our hollow CNF using dual concentric nozzle electrospinning method, comprising of poly (vinyl pyrrolidone) (PVP) as soluble core and polyacrylonitrile (PAN) as shell. It was essential in our study to fully leach out the PVP to obtain a hollow structure: this hollow structure of CNF provided a conductive network that guaranteed the high speed movement of electron/electrolyte. Furthermore, the overall specific capacitance and energy density of the hybrid NCO–CNF electrode were remarkably boost up due to the derivation of both electric double layer capacitance and pseudocapacitance characteristics based on the synergistic mixture of graphitic carbon and transition metal oxides. The fabricated binder-free hybrid NCO–CNF electrode displayed efficient charge transfer and achieved outstanding specific capacitance and energy density as high as 1188.19 F g−1 and 37.23 W h kg−1, respectively, even at high current density of 50 A g−1.

Structure and Biological Properties of Surface-Engineered Carbon Nanofibers

The aim of this work was to manufacture, using the electrospinning technique, polyacrylonitrile- (PAN-) based carbon nanofibers in the form of mats for biomedical applications. Carbon nanofibers obtained by carbonization of the PAN nanofibers to 1000°C (electrospun carbon nanofibers (ECNF)) were additionally oxidized in air at 800°C under reduced pressure (electrospun carbon nanofibers oxidized under reduced pressure (ECNFV)). The oxidative treatment led to partial removal of a structurally less-ordered carbon phase from the near-surface region of the carbon nanofibers. Both types of carbon fibrous mats were studied using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TEM), XRD, and Raman spectroscopy. The morphology, microstructure, and surface properties of both materials were analyzed. The oxidative treatment of carbon nanofibers significantly changed their surface morphology and physical properties (wettability, surface electrical resistance). Biological tests (genotoxicity, fibroblast, and human osteoblast-like MG63 cultures) were carried out in contact with both materials. Genotoxicity study conducted by means of comet assays revealed significant differences between both carbon nanofibers. Fibroblasts contacted with the as-received carbon nanofibers (ECNF) showed a significantly higher level of DNA damage compared to control and oxidized carbon nanofibers (ECNFV). The ECNFV nanofibers were not cytotoxic, whereas ECNF nanofibers contacted with both types of cells indicated a cytotoxic effect. The ECNFV introduced into cell culture did not affect the repair processes in the cells contacting them.

Encapsulation of SeS2 into Nitrogen-Doped Free-Standing Carbon Nanofiber Film Enabling Long Cycle Life and High Energy Density K-SeS2 Battery.

K-SeS2 batteries could provide a low-cost and high energy density energy storage system, because the earth-abundant element potassium (K) shows a low reduction potential and a high gravimetric capacity. But the K-SeS2 battery has never been reported because of the lack of high-performance electrode materials. Herein, we design an advanced K-SeS2 battery by encapsulation of SeS2 in the nitrogen-doped free-standing porous carbon matrix (SeS2@NCNFs). The self-supported SeS2@NCNFs electrode achieves a high reversible capacity of 417 mAh g-1 after 1000 cycles with 85% capacity retention at 0.5 Ag1- with nearly 100% Coulombic efficiency. The nanosized SeS2 nanoparticles are encapsulated in the carbon matrix, which minimizes the volume expansion during cycling and shortens the ion transport pathways, thus enhancing the rate capability. The interconnected porous carbon nanofiber structure could improve the flexibility and offer a continuous pathway for rapid ionic/electronic transport. The DFT calculations confirm that high content N-doping (11.2 at. %) can enhance the chemical affinity between the discharge product and the N-doped carbon. The pyrrolic and pyridinic N-doping lead to stronger adsorption than that of the graphitic N-doping. This proposed design holds great promise for practical application of high energy density K-SeS2 batteries.

Low-temperature fabrication of carbon nanofibers with improved graphitization via incorporating carbonaceous inclusions

Owning to one-dimensional nanostructure, excellent electrical and thermal conductivities, carbon nanofibers should be suitable applied in composite, gas storages and electronic devices. Generally, carbon nanofibers have been fabricated by electrospinning and following high-temperature thermal treatment. Here, we report fabrication of graphitized carbon nanofibers via nozzle-less electrospinning and subsequent low-temperature thermal treatment. The graphitization of carbon nanofibers have been improved through incorporating graphite, graphene and carbon nanotubes in precursor solution. Morphology, structure and electrochemical performance of carbon nanofibers with different inclusions have been characterized, and results indicate carbon nanofibers with graphite show the highest graphitization degree and excellent electrochemical performance.

Long-cycle stability for Li-S batteries by carbon nanofibers/reduced graphene oxide as host cathode material

3D network structure of carbon nanofibers (CNF) chemically cross-linked with reduced graphene oxide (RGO) sheet was successfully prepared by electrospinning a dispersion of polyacrylonitrile (PAN) and graphene oxide (GO) sheets in dimethylformamide followed by heat treatment. Cathodes made with such composites after infused with sulfur (CNF-RGO/S) were able to deliver an initial reversible capacity of 730 mAh/g and 378 mAh/g after 500 cycles at 0.1 C. Even at a high rate of 5 C, the CNF-RGO/S experienced the capacity of 227 mAh/g and no capacity fade after 400 cycles. In contrast, the capacity of an electrode without adding RGO decayed dramatically. The CNF matrix provides stable mechanical stability and shortens diffusion paths. The addition of RGO sheets increase the contact area with the electrolyte and speed up the reaction rate. These results demonstrate that the 3D network structure is of great potential as the cathode for long-cycle and high-rate rechargeable Li-S batteries.

Improving Supercapacitance of Electrospun Carbon Nanofibers through Increasing Micropores and Microporous Surface Area

AbstractPrevious papers about electrospun carbon nanofibers do not provide systemic understandings about how in situ activation agents affect the porous structure of carbon nanofibers. In this study, poly(vinylpyrrolidone), poly(methyl methacrylate), and high‐amylose starch (HAS) are used as activation agent to separately prepare porous carbon nanofibers from electrospun polyacrylonitrile nanofibers, and the effects of the polymer activation agents on the porous structure and supercapacitive properties of the resulting carbon nanofibers are examined. The studies indicate that melting point and decomposition temperature are two important parameters deciding the pore size profile. The one with high melting point and low decomposition temperature, such as HAS, allows to form micropore‐dominant porous structure with large specific surface area. The HAS‐activated carbon nanofibers have a micropore specific surface area as high as ≈809 m2 g−1, total pore volume of ≈0.42 cm3 g−1, and micropore content as high as ≈59%. The corresponding electrodes have a capacitance of 282 F g−1 at the current density of 1.0 A g−1 with excellent cycling durability. These novel understandings may be useful for the development of effective carbon nanofibers for high‐performance supercapacitor and other applications.

Iron oxide and phosphide encapsulated within N,P-doped microporous carbon nanofibers as advanced tri-functional electrocatalyst toward oxygen reduction/evolution and hydrogen evolution reactions and zinc-air batteries

Developing cheap, efficient and stable tri-functional catalysts can reduce the producing process of catalysts for different electrochemical energy conversion devices, therefore being important to their commercialization. In light of this, we firstly report an advanced catalyst with both FeP and Fe3O4 nanoparticles embedded in N,P-doped microporous carbon nanofibers obtained by electrospinning. The resultant catalyst exhibits robust catalytic activities towards oxygen reduction reaction, hydrogen evolution reaction and oxygen evolution reaction, all of which surpass or are comparable to previously reported tri-functional catalysts. The Fe3O4 nanoparticles and N-doped carbon are the main active species toward oxygen reduction reaction and oxygen evolution reaction, while FeP nanoparticles remarkably promote the hydrogen evolution reaction. The catalyst also shows excellent oxygen reduction stability due to the unique nanoparticle-embedded microporous carbon nanofibers structure. Furthermore, the obtained tri-functional catalyst is also applied in a disposable zinc-air battery, showing good performance. This work offers an effective method to construct a tri-functional catalyst in electrochemical energy devices.

Electrospun nitrogen-doped carbon nanofiber as negative electrode for vanadium redox flow battery

Carbon nanofiber (CNF) was developed via electrospinning technique with polyacrylonitrile as precursor. Nitrogen-doped carbon nanofiber (NCNF), synthesized by liquid phase dispersion and carbonization processes with urea at 800–1000 °C, were investigated as negative electrode for vanadium redox flow battery (VRFB). Morphology and structure of CNF and NCNF were systematically investigated by SEM, Raman, XPS, etc. The morphology of CNF is not changed by nitrogen doping. However, nitrogen doping can lead to marked enhancement of surface defect and hydrophilicity. Electrochemical test results show that NCNF treated at 900 °C (CNF-N9) exhibits the best electrochemical performance. The excellent energy storage performance of the cell is obtained by using CNF-N9. Discharge capacity of cell for CNF-N9 arrives at 98.0 mA h, 30.0 mA h higher than that of the pristine cell at 90 mA cm−2. And energy efficiency of the cell using CNF-N9 increases by 6.3% compared with pristine cell. Outstanding performances of CNF-N9 come from the increase of surface defect and the improvement of hydrophilicity and conductivity resulting from nitrogen doping, further promoting the electron and mass transfer between vanadium ion and electrode.

Enhanced Ammonia Adsorption on Directly Deposited Nanofibrous Carbon Films

The ammonia adsorption on the nanostructured carbon thin film was significantly influenced by the choice of deposition temperature and deposition time of thin film synthesis. The thin films were prepared on Si/SiO2 substrates by chemical vapour deposition in Ar/C2H2 gas mixture using iron catalytic nanoparticles. The analysis of the grown layer by the scanning and transmission electron microscopy showed the transition from long multiwalled nanotubes (MWCNTs) to bamboo-like hollow carbon nanofiber structure with the decrease of the deposition temperature from 700 to 600°C. Further, the material was analyzed by energy-dispersive X-ray spectroscopy and Raman spectroscopy confirmed the transition from graphitic sp2 structure to highly defective structure at lower deposition temperature. The resistance of the prepared layer strongly depends on deposition temperature (Td) and deposition time (td). High resistance layer, 38.6 kΩ, was formed at Td 600°C and td 10 min, while at Td 700°C and td 60 min, the resistance decreased to 860 ohms. Such behaviour is consistent with MWCNTs being responsible for the formation of the conductive network. Such system was studied using chemiresistor ammonia gas sensor configuration. The sensor resistance increased when exposed to ammonia in all the cases, but their response varied considerably. A decrease in deposition time, from 60 to 10 min, and the deposition temperature, from 700 to 600°C, led to the 10-fold increase in the sensor response. The measurements carried out at room temperature showed the higher sensor response than the measurements carried out at 200°C. This behaviour can be explained by the change in adsorption-desorption equilibrium at different temperatures. Analysis of dependence of the sensor response on the ammonia concentration proved that the underlying resistance change mechanism is chemisorption of ammonia molecules on the carbon network corresponding to the Langmuir isotherm.

Sulfur-Deficient Bismuth Sulfide/Nitrogen-Doped Carbon Nanofibers as Advanced Free-Standing Electrode for Asymmetric Supercapacitors.

The use of free-standing carbon-based hybrids plays a crucial role to help fulfil ever-increasing energy storage demands, but is greatly hindered by the limited number of active sites for fast charge adsorption/desorption processes. Herein, an efficient strategy is demonstrated for making defect-rich bismuth sulfides in combination with surface nitrogen-doped carbon nanofibers (dr-Bi2 S3 /S-NCNF) as flexible free-standing electrodes for asymmetric supercapacitors. The dr-Bi2 S3 /S-NCNF composite exhibits superior electrochemical performances with an enhanced specific capacitance of 466 F g-1 at a discharge current density of 1 A g-1 . The high performance of dr-Bi2 S3 /S-NCNF electrodes originates from its hierarchical structure of nitrogen-doped carbon nanofibers with well-anchored defect-rich bismuth sulfides nanostructures. As modeled by density functional theory calculation, the dr-Bi2 S3 /S-NCNF electrodes exhibit a reduced OH- adsorption energy of -3.15 eV, compared with that (-3.06 eV) of defect-free bismuth sulfides/surface nitrogen-doped carbon nanofiber (df-Bi2 S3 /S-NCNF). An asymmetric supercapacitor is further fabricated by utilizing dr-Bi2 S3 /S-NCNF hybrid as the negative electrode and S-NCNF as the positive electrode. This composite exhibits a high energy density of 22.2 Wh kg-1 at a power density of 677.3 W kg-1 . This work demonstrates a feasible strategy to construct advanced metal sulfide-based free-standing electrodes by incorporating defect-rich structures using surface engineering principles.

Carbon black enhanced conductivity, carbon yield and dye adsorption of sustainable cellulose derived carbon nanofibers

A new carbon nanofibrous mat with necklace-like structures have been prepared by carbonization of cellulose/carbon black (CB) nanofibers through electrospinning of cellulose acetate/CB blend solution followed by deacetylation. The effect of carbon black on the thermal stability of the precursor and morphology of the CNFs were investigated using thermogravimetric analysis, field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy. The FE-SEM images showed that cellulose derived CNFs form matrix for accomplishing necklace-like fibers containing spherical CB nanoparticles with diameter between 30 and 60 nm after heating of cellulose/CB nanofibers. It is demonstrated that the incorporation of CB particles increases the electrical conductivity from 1.4 to 16 mS and carbon yield from 12 to 30%. Carbon nanofibers based on cellulose/CB was evaluated as a suitable adsorbent for removal of methylene blue (MB) from water. The final dye removal was found to be 97% at the initial MB concentration of 20 mg L−1. This study suggests a new carbon nanofiber structure that will be potentially useful for energy applications and water treatment.

Core-shell structured carbon nanofibers yarn@polypyrrole@graphene for high performance all-solid-state fiber supercapacitors

Carbon nanofibers yarns (CNY) have been prepared by carbonizing twisted electrospun PAN nanofibers, which can be used as the electrode of fiber-shaped all-solid-state supercapacitor after depositing conductive polymer of polypyrrole (PPy) and reduced graphene oxide (rGO) on their surface to form a core-shell structure (CNY@PPy@rGO). The flexible and binder-free fiber supercapacitors with PVA/H3PO4 gel electrolyte have a high specific capacitance (92.57 F/g, 80.46 F/cm3, 836.87 mF/cm2, and 111.46 mF/cm of CM, CV, CA, and CL, respectively, at the scan rate of 2 mV/s) thanks to the core-shell structure and synergistic effects of three conponents. It also shows high cycling performance with 86% capacitance retention after 10000 cycles with excellent flexibility and stability at different bending angles.

Preparation of Polymer-Derived Nitrogen-Doped Hollow Carbon Nanofiber As a Free Standing Oxygen Electrode for Li-O2 Battery

Li-O2 battery has got much attention as a beyond Li-ion battery (LIB), due to its higher energy density and exceeding specific capacity than those of commercial LIB. Though it has a promising potential for large-scale energy storage device, Li-O2 battery still has several problems to be overcome in aspects of poor rate capability and limited stability. Especially, the oxygen electrode is one of the most closely related component to the performance of Li-O2 battery since it is the actual site for formation and decomposition of discharge products. Thus, in order to achieve the Li-O2 battery with improved performance, the oxygen electrode should provide favorable structure for not only discharge product storage, but also facile transfer of reactants such as Li ion and O2. Moreover, bicatalytic activity for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is also significant on oxygen electrode by determining the morphology of discharge product. Furthermore, the oxygen electrode has to be chemically and electrochemically stable as well for extended durability of Li-O2 battery. In this regards, we develop a binder free oxygen electrode composed of nitrogen-doped hollow carbon nanofiber, which is derived from nitrogen-containing polymer. Each carbon nanofiber has an empty space inside the fiber even after the heat treatment at high temperature of 900 °C, and it can facilitate the mass transfer of reactants. Due to this unique structure and high nitrogen content of 4.5 at. %, nitrogen-doped hollow carbon nanofiber indicates the lower ORR overpotential and larger discharge capacity than commercial carbon material, Super P, as shown in Fig. 1. Interestingly, it shows the reduced ORR/OER overpotential which is lower than 1 V with the curtaining capacity of 500 mAh g-1 carbon. The notably reduced overpotential might be attributable to the synergetic effect of nitrogen doping, unique structure of hollow carbon nanofiber and absence of binder by promoting the catalytic activity, facilitating the mass transfer and suppressing the side reactions, respectively. The effects of heat treatment temperature and metal incorporation are also investigated and optimized. As for the result, it can be demonstrated that the binder-free nitrogen-doped hollow carbon nanofiber is an enhanced oxygen electrode of Li-O2 battery. Figure 1

Modeling to study the role of catalyst in the formation of graphitic shells during carbon nanofiber growth subjected to reactive plasma

An analytical model to study the role of a metal catalyst nanofilm in the nucleation, growth, and resulting structure of carbon nanofibers (CNFs) in low-temperature hydrogen diluted acetylene plasma has been developed. The model incorporates the nanostructuring of thin catalyst films, growth of CNF, restructuring of catalyst nanoparticles during growth, and its repercussion on the resulting structure (alignment of rolled graphene sheets around catalyst nanoparticles) by taking into account the plasma sheath formalization, kinetics of neutrals and positively charged species in the reactive plasma, flux of plasma species onto the catalyst front surface, and numerous surface reactions for carbon generation. In order to examine the influence of the catalyst film on the growth of CNFs, the numerical solutions of the model equations have been obtained for experimentally determined initial conditions and glow discharge plasma parameters. From the solutions obtained, we found that nanostructuring of thin films leads to the formation of small nanoparticles with high surface number density. The CNF nucleates over these small-sized nanoparticles grow faster and attain early saturation because of the quick poisoning of small-sized catalyst particles, and contain only a few graphitic shells. However, thick nanofilms result in shorter CNFs with large diameters composed of many graphitic shells. Moreover, we found that the inclination of graphitic shells also depends on the extent up to which the catalyst can reconstruct itself during the growth. The small nanoparticles show much greater elongation along the growth axis and also show a very small difference between their tip and base diameter during the growth due to which graphitic shells align at very small angles as compared to the larger nanoparticles. The present study is useful to synthesize the thin and more extended CNFs/CNTs having a smaller opening angle (inclination angle of graphene layers) as the opening angle has a significant influence on their field emission properties. The comparisons of these theoretical findings to the experimental observations confirm the adequacy of the proposed model.

Carbon nanofibers obtained from electrospinning process

In recent years, reinforcements consisting of carbon nanostructures, such as carbon nanotubes, fullerenes, graphenes, and carbon nanofibers have received significant attention due mainly to their chemical inertness and good mechanical, electrical and thermal properties. Since carbon nanofibers comprise a continuous reinforcing with high specific surface area, associated with the fact that they can be obtained at a low cost and in a large amount, they have shown to be advantageous compared to traditional carbon nanotubes. The main objective of this work is the processing of carbon nanofibers, using polyacrylonitrile (PAN) as a precursor, obtained by the electrospinning process via polymer solution, with subsequent use for airspace applications as reinforcement in polymer composites. In this work, firstly PAN nanofibers were produced by electrospinning with diameters in the range of (375 ± 85) nm, using a dimethylformamide solution. Using a furnace, the PAN nanofiber was converted into carbon nanofiber. Morphologies and structures of PAN and carbon nanofibers were investigated by scanning electron microscopy, Raman Spectroscopy, thermogravimetric analyses and differential scanning calorimeter. The resulting residual weight after carbonization was approximately 38% in weight, with a diameters reduction of 50%, and the same showed a carbon yield of 25%. From the analysis of the crystalline structure of the carbonized material, it was found that the material presented a disordered structure.

Confined metal Ge quantum dots in carbon nanofibers for stable rechargeable batteries.

As a promising alloy-type anode material for rechargeable batteries, the metal germanium (Ge) shows high capacity, but it suffers from a fast capacity fading problem caused by a large volume expansion during lithiation/delithiation cycles. In this study, via a facile electrospinning method, we optimized the combination structure of Ge quantum dots (QDs) and carbon nanofibers (CNFs). Specifically, Ge QDs with a diameter of 4-7 nm were highly dispersed in porous (pore size 10-150 nm) CNFs. The hybridized Ge/CNF nanocomposite exhibited remarkable Li storage performances such as high reversible capacity (1204 mA h g-1 at a current density of 200 mA g-1), high capacity retention (87.1% after 100 cycles) and excellent rate property (760 mA h g-1 at 3000 mA g-1). The improved electrochemical performance was due to the synergistic effects of Ge QDs and carbon nanofibers; this effectively alleviated the volume expansion problem, prevented the agglomeration of Ge, maintained the structural stability of the nanocomposite, and improved the electrode kinetics of diffusion of Li ions.

Variations in performance-degradation behavior of Pt/CNF and Pt/C MEAs for the same degree of carbon corrosion

Carbon corrosion due to high voltages encountered during the operation of fuel cells and the accompanying deterioration of cell performance are among the main issues affecting the durability of fuel cells. In this study, the carbon-corrosion durability of membrane electrode assemblies (MEAs) fabricated with Pt/CNF and Pt/C catalysts is studied using an accelerated stress test (AST) while applying high potentials. We compare the cell performance for the same degree of carbon corrosion, and the two MEAs show almost the same degradation behavior at the early stage of carbon corrosion. However, as the degree of carbon corrosion is increased, the performance-decay behavior of the two MEAs differs significantly, with there being a more serious performance decay in Pt/C than Pt/CNF, even at the same degree of carbon corrosion. The different behavior of the performance degradation between the two MEAs is due to the different catalyst layer structure, which results from the different catalyst-support morphologies between the three-dimensional (3D) high-structure Vulcan carbon (VC) and the one-dimensional (1D) structure of platelet carbon nanofibers (PCNFs). The support structure-dependent performance-degradation characteristic is analyzed in a single cell by performing an electrochemical analysis of the kinetic resistance, ohmic resistance, and diffusion resistance. In addition, the characterization of the catalyst layer structure before and after the deterioration is performed to understand the deactivation mechanism. This study is expected to provide a design strategy from a structural perspective of carbon support for the development of highly durable MEAs.

Free-standing N-doped carbon nanofibers/carbon nanotubes hybrid film for flexible, robust half and full lithium-ion batteries

The development of flexible electronics requires the power sources with matchable flexibility, robust mechanic property, as well as high power and energy density that would maintain the durability of flexible electronics during use. Herein, newly designed free-standing N-doped carbon films with hierarchical structure of carbon nanofibers and carbon nanotubes (CNFs/CNTs hybrids) are prepared via a simple electrospinning process. This interconnected hybrid film displays high conductivity and excellent flexibility. As a free-standing and binder-free anode material, the CNFs/CNTs hybrid electrode can achieve a reversible capacity of 1099.5 mAh g−1 at a current density of 0.05 A g−1 with superior rate capabilities and excellent cyclic stability. What's more, utilizing the CNFs/CNTs hybrid film as the electrode, this assembled highly flexible half and full batteries also show attractive performances and can easily light up a group of 12 light emission diodes at flat and various bending positions, making it possible to be applied in the flexible electronic devices.

Facile synthesis of NiS anchored carbon nanofibers for high-performance supercapacitors

Transition metal sulfide compounds with carbon materials are promising for high-performance supercapacitors. Carbon nanofibers (CNFs) wrapped with NiS nanoparticles were herein obtained through electrospinning and calcination. NiS nanoparticles in composite nanofibers are covered by a layer of graphitic carbon, which not only increase the conductivity but also provide active regions for nanoparticle growth to prevent aggregation. The CNFs-NiS electrode has high specific capacity of 177.1mAhg−1 at 1Ag−1 (0.41mAhcm−2 at a current density of 2.3mAcm−2) and long-term cycling stability, with 88.7% capacitance retention after 5000 cycles. The excellent electrochemical activity may be attributed to the accessible specific surface, unique porous structure of CNFs and high specific capacitance of NiS. In addition, the asymmetric supercapacitor has an enhanced volumetric energy density of 13.32 mWh cm−3 at a volumetric power density of 180mWcm−3 and high cycling stability, with 89.5% capacitance retention after 5000 cycles. It also successfully lights up a light-emitting diode. The CNFs-NiS composite has significant potential applications in supercapacitor.