Three-dimensional Carbon Nanofiber Research Articles

Multi-dimensional assembly of ZnO nanodots in the reticular carbon nanofibers for high-performance lithium-ion batteries

Due to the high theoretical specific capacity, abundant resources, easy availability, and environmental amicability, zinc oxide (ZnO) has been regarded as a promising alternative for lithium-ion battery anode. However, the further application of ZnO anode is still faced with great challenges such as huge volume transformation and intrinsic low conductivity. Herein, we propose a simple strategy for the preparation of ZnO/carbon clusters (∼50 nm) which are assembled with uniformly distributed ZnO nanodots (∼5 nm) in the three-dimensional carbon nanofibers (ZnO/CNFs) through an electrospinning and subsequent carbonization process using gallic acid-zinc coordination polymer (GAZ) as precursor. The multi-dimensional assembly of ZnO nanodots and reticular formation of conductive carbon network can effectively alleviate the volume change of ZnO anode during long-term cycling process and promote the fast transfer of electrolyte ions/electrons, greatly improving the rate and cycle performance. As a result, the ZnO/CNFs electrode exhibits excellent rate performance of 375.3 mAh g−1 at 2 A g−1 and long cycling stability with capacity retention of 92% over 600 cycles at 1 A g−1. These features indicate that the systematic combination of electrospinning and metal-organic coordination polymers have significant promise for the construction of high-performance metal derivative anodes.

Multistage pore structure legume-like UiO-66-NH2@carbon nanofiber aerogel modified electrode as an electrochemical sensor for high sensitivity detection of HMIs

Electrode material is the core component of electrochemical sensor, which has a decisive influence on the detection performance of heavy metal ions. A novel electrochemical sensor based on amino modified metal-organic frameworks loaded three-dimensional carbon nanofiber aerogel composite material was proposed. The UiO-66-NH2 was embedded into nanofibers through one-step electrospinning technology to forming a legume-like structure, ensuring the number of active sites N coordination with HMIs, which improved enrichment capacity of the sensor. 3D carbon nanofiber aerogel with multistage pore structure was developed by one-dimensional nanofibers as unit modules, which increases conductive path and HMIs transport channel. Accordingly, the UiO-66-NH2 @carbon nanofiber aerogel modified electrode (N-U@CFA/GCE) as an electrochemical sensor exhibited an ultra-high sensitivity and the low limit of detection for the simultaneous detection of Cd2+ (0.52 nM) and Pb2+ (0.46 nM) using the differential pulse anode stripping voltammetry and was feasible and accurate for the detection of actual environmental water. The novel sensor platform has high sensitivity, stability and anti-interference, which showing great potential on HMIs monitoring.

Graphene sheets assembled into three-dimensional networks of carbon nanofibers: A nano-engineering approach for binder-free supercapacitor electrodes

The design and synthesis of flexible and free-standing carbon nanofibers membrane with good electrochemical properties have recently attracted much attention in energy storage applications. Herein, we fabricated graphene sheets-incorporated three-dimensional carbon nanofibers membrane (3D-GCNFs) as effective electrode materials for supercapacitors. The electrospun two-dimensional (2D) graphene oxide sheets-incorporated polyacrylonitrile nanofibers (GO/PAN NFs) were transformed into 3D membrane by a gas-forming technique using sodium borohydride. Subsequent thermal treatment converted the 2D-assembled GO/PAN NFs membrane into the low-density 3D-GCNFs membrane. The morphology and electrochemical performances of the as-prepared 3D membrane were systematically investigated using state-of-the-art techniques. It was found that the electrochemical performance of the as-obtained 3D-GCNFs membrane was greatly improved compared to the 2D counterparts. As a binder-free electrode, the materials exhibited a high areal capacitance of 318 mF/cm2 at a current density of 1 mA/cm2 and good cyclic stability of up to 98.5% after 5000 cycles. In addition, a symmetrical supercapacitor was constructed using the 3D-GCNFs membrane as both negative and positive electrodes. The device exhibited areal capacitance of 240 mF/cm2 at a current density of 1 mA/cm2, an energy density of 33.33 mWh/cm2, a power density of 1000 mW/cm2, and capacitance retention of 103% after 5000 cycles. The improved performance of the 3D-GCNFs membrane was attributed to its high electrical conductivity due to the absence of binders, high porosity, and conductive networks that form efficient channels for electrolyte penetration and effectively shorten the transmission distance. We believe that this study not only provides a reference for the introduction of 3D CNFs-based composite membranes, but also demonstrates their great potential for energy storage applications.

Nanoarchitectonics of Three-Dimensional Carbon Nanofiber-Supported Hollow Copper Sulfide Spheres for Asymmetric Supercapacitor Applications.

Three-dimensional carbon nanofiber (3D-CNF)-supported hollow copper sulfide (HCuS) spheres were synthesized by the facile hydrothermal method. The morphology of the as-synthesized HCuS@3D-CNF composite clearly revealed that the 3D-CNFs act as a basement for HCuS spheres. The electrochemical performance of as-synthesized HCuS@3D-CNFs was evaluated by cyclic voltammetry (CV) tests, gravimetric charge-discharge (GCD) tests, and Nyquist plots. The obtained results revealed that the HCuS@3D-CNFs exhibited greater areal capacitance (4.6 F/cm2) compared to bare HCuS (0.64 F/cm2) at a current density of 2 mA/cm2. Furthermore, HCuS@3D-CNFs retained excellent cyclic stability of 83.2% after 5000 cycles. The assembled asymmetric device (HCuS@3D-CNFs//BAC) exhibits an energy density of 0.15 mWh/cm2 with a working potential window of 1.5 V in KOH electrolyte. The obtained results demonstrate that HZnS@3D-CNF nanoarchitectonics is a potential electrode material for supercapacitor applications.

WSe2/CoSe2 nanocrystals in situ growth on three-dimensional carbon nanofibers as anode material for long-life and high-rate sodium-ion batteries

Transition metal selenides are regarded as one of the most promising anode materials because of their high theoretical specific capacity and large layer spacing. However, the unstable structural behavior and slow reaction kinetics during electrochemical reactions seriously hinder its application. Herein, a novel nanocomposite structure of WSe2/CoSe2 nanocrystals vertically grown on carbon nanofibers (WSe2/CoSe2/CNFs) was developed as anode material by electrospinning and heat treatment. In which, the self-supporting structures formed by the intersecting carbon nanofibers effectively alleviate severe volume expansion during sodiation/desodiation process, thus ensuring excellent stability. And the highly exposed CoSe2/WSe2 grown on the surface of carbon nanofibers provide abundant reaction interfaces and fast ion diffusion channels. As expected, the WSe2/CoSe2/CNFs anode shows excellent electrochemical performance, including high capacity (403.5 mAh g−1 at 0.2 A g−1), long-term cycling stability (333.5 mAh g−1 after 1800 cycles at 5 A g−1 with negligible capacity decay per cycle of only 0.0012 %) and remarkable rate performance (a reversible capacity of 312.6 mAh g−1 is achieved even at a high current density of 20 A g−1). Meanwhile, the excellent sodium storage performance of the WSe2/CoSe2/CNFs composites electrode was deeply investigated by kinetic analysis.

Three-dimensional carbon nanofiber networks encapsulated in cobalt–molybdenum metal clusters on nitrogen-doped carbon as ultra-efficient electrocatalysts for hydrogen evolution reactions

Efficient and cost-effective catalysts have been developed for the production of hydrogen via water electrolysis. In this study, we develop a strategy for the fabrication of carbon nanofiber catalysts loaded with CoMo clusters covered by a nitrogen-doped carbon network (CoMo/CN@CNFs/MEL). The surface of two-dimensional carbon fibers was coated with a nitrogen-doped carbon network via melamine pyrolysis, thereby forming three-dimensional (3D) networks. These 3D network catalysts exhibited excellent catalytic performance in the hydrogen evolution reaction with 1 M KOH, requiring an overpotential of only 148 mV to reach a current density of 10 mA cm−2 owing to synergistic effects resulting from their structure and composition. The catalytic performance of the CoMo/CN@CNFs/MEL catalysts was comparable to that of commercial Pt/C at high current densities owing to their unique structural features, including restricted Co–Mo clusters, porous nitrogen-doped carbon frameworks, continuous conducting carbon nanofibers, and carbon nitride networks. This work provides a promising approach to transition metal-based catalysts with improved stability and atom utilization efficiency.

N,S-co-doped FeCo Nanoparticles Supported on Porous Carbon Nanofibers as Efficient and Durable Oxygen Reduction Catalysts.

Finding high-performance, low-cost, efficient catalysts for oxygen reduction reactions (ORR) is essential for sustainable energy conversion systems. Herein, highly efficient and durable iron (Fe) and cobalt (Co)-supported nitrogen (N) and sulfur (S) co-doped three-dimensional carbon nanofibers (FeCo-N, S@CNFs) were synthesized via electrospinning followed by carbonization. The as-prepared FeCo-N,S@CNFs served as efficient ORR catalysts in alkaline 0.1 m KOH solutions that were N2 and O2 -saturated. The experimental results revealed that FeCo-N,S@CNFs were highly active ORR catalysts with defect-rich active pyridinic N and pyrrolic N and metal bonds to N and S atom sites, which enhanced the ORR activity. FeCo-N,S@CNFs exhibited a high onset potential (Eonset =0.89 V) and half-wave potential (E1/2 =0.85 V), similar to the electrocatalytic activity of commercial Pt/C. Additionally, the durability of the as-prepared FeCo-N,S@CNFs catalysts was maintained for 14 h with long-term stability and high tolerance to methanol stability, accounting for their excellent catalytic ability. Furthermore, Co-N@CNFs, Fe-N@CNFs, and varying Fe and Co ratios were compared with those of FeCo-N,S@CNFs. Synergistic interactions between metals and heteroatoms were believed to play a significant role in enhancing the ORR activity. Owing to their excellent catalytic reduction ability, the as-prepared FeCo-N,S@CNFs can be widely used in battery-based systems and replace commercial Pt/C in fuel cell applications.

NiCoO2 and polypyrrole decorated three-dimensional carbon nanofiber network with coaxial cable-like structure for high-performance supercapacitors

Designing optimized nano-sized architecture is a promising approach to prepare high-performance electrode materials for supercapacitors. In this work, a hierarchical multi-shelled structure has been successfully synthesized, which consists of a 3D carbon nanofiber network as a supporting scaffold prepared by carbonization of aramid nanofiber aerogel, an intermediate polypyrrole (PPy) bonding layer and a NiCoO2 outer shell, just like a coaxial cable in the structure. The intermediate PPy layer facilitates the uniform deposition of NiCoO2 by providing more anchor sites, and enhances the electrical contact between carbon nanofiber network and NiCoO2 shell due to its high conductivity and good compatibility with two different substances. The synergistic effect of the hierarchical configuration endows the electrode material with a high specific capacitance of 1037 F g−1at 1 A g−1and excellent cycling stability (∼89% of initial capacitance after 7000 cycles). Moreover, an asymmetric supercapacitor based on the composite and activated carbon achieves a high energy density of 37.7 Wh kg−1 at a power density of 465 W kg−1 in 1.65 V. This work may provide a feasible strategy to design high-performance hybrid electrodes for energy storage devices.

Interface engineering of MIL-88 derived MnFe-LDH and MnFe2O3 on three-dimensional carbon nanofibers for the efficient adsorption of Cr(VI), Pb(II), and As(III) ions

On account of their high adsorption capacity towards toxic oxyanions/cations, metal oxides and hydroxides have received considerable attention. Herein, an iron-manganese layered double hydroxide (MnFe-LDH) was developed on the surface of MnFe2O3 anchored three-dimensional porous carbon nanofibers (MnFe-LDH/MnFe2O3@3DNF) by a subsequent hydrothermal process. The MnFe-LDH was derived from MIL-88. The prepared MnFe-LDH/MnFe2O3@3DNF effectively reduces the concentration of Cr(VI), Pb(II), and As(III) in an aqueous solution, meeting the drinking water standards prescribed by the World Health Organization. The adsorption isotherms of Cr(VI), Pb(II), and As(III) ions onto MnFe-LDH/MnFe2O3@3DNF were described by the Langmuir, Freundlich, and Sips models. The Sips adsorption isotherm model indicates the maximum sorption capacities of the MnFe-LDH/MnFe2O3@3DNF toward Cr(VI), Pb(II), and As(III) adsorptions are 564.88 mg g−1, 591.80 mg g−1, and 504.54 mg g−1, respectively, at room temperature. Kinetic studies revealed that the adsorption process is pseudo-second-order. The XPS, FESEM EDX, and FTIR studies indicated that the adsorption mechanism was mainly dominated by isomorphic substitution, precipitation, surface complexation, and electrostatic attraction. Importantly, the as-prepared MnFe-LDH/MnFe2O3@3DNF can be repeatedly used several times without significant degradation of the adsorption performance or the generation of secondary pollutants. The findings highlight the potential application of MnFe-LDH/MnFe2O3@3DNF for the decontamination of heavy metals by the virtue of its admirable adsorption performances.

Free-standing carbon nanofiber networks

We report a facile approach to the fabrication of free-standing three-dimensional carbon nanofiber (CNF) networks, by loading copper nitrates on aluminum (Al) foils, performing chemical vapour deposition (CVD), and finally etching away Al foils via sodium hydroxide. During CVD, copper-nitrate-derived copper nanoparticles catalyze growth of CNF networks on Al foils, and the CNF networks are then liberated after removal of Al foils. The resultant free-standing CNF networks exhibit porous, hydrophobic, lightweight, and highly flexible properties, and the combination of these properties enables CNF networks to absorb various oils with high absorption capacity and excellent recyclability. This work may benefit the rational design of advanced absorbents for applications in cleanup of oil spillage.

Engineering bacteria for high-performance three-dimensional carbon nanofiber aerogel

Compared with carbon nanotube (CNT) and graphene (GE) aerogels, the synthesis of three-dimensional (3D) carbon nanofiber (CNF) aerogels that are highly compressible, resilient under cyclic strains, and creep and fatigue resistant remains extremely challenging. Herein, a revolutionary green and scalable biosynthesis is presented, by which a novel 3D CNF aerogel derived from natural bacterial cellulose (BC) decorated with its mother bacteria is created. The as-prepared CNF aerogel possesses excellent mechanical resilience, ultra-low energy loss coefficient, and outstanding cycling stability, which are by far among the best performances for CNT and GE aerogels reported thus far. Furthermore, the CNF aerogel exhibits excellent creep and fatigue resistance and sensitive electrical conductivity change upon compression. Surprisingly, the as-prepared 3D CNF aerogel exhibits superhydrophilicity. These superb properties are attributed to the existing carbonized bacteria in the carbonized BC matrix that serve as crosslinks to strengthen the aerogel and buffers to store deformation energy. This study presents a breakthrough method for the construction of superb and cost-effective 3D CNF aerogel from natural biomass material.

Interface Engineering of MIL-88 Derived MnFe-LDH and MnFe <sub>2</sub>O <sub>3</sub> on Three-Dimensional Carbon Nanofibers for the Efficient Adsorption of Cr(VI), Pb(II), and As(III) Ions

Interface Engineering of MIL-88 Derived MnFe-LDH and MnFe <sub>2</sub>O <sub>3</sub> on Three-Dimensional Carbon Nanofibers for the Efficient Adsorption of Cr(VI), Pb(II), and As(III) Ions

An electrochemically reduced ultra-high mass loading three-dimensional carbon nanofiber network: a high energy density symmetric supercapacitor with a reproducible and stable cell voltage of 2.0 V.

Commercial supercapacitors need a high mass loading of more than 10 mg cm-2 and a high working potential window to resolve the low energy density concern. Herein, we have demonstrated a thick, ultrahigh mass loading (35 mg cm-2) and wide cell voltage electrochemically reduced layer-by-layer three-dimensional carbon nanofiber network (LBL 3D-CNF) electrode via electrospinning, sodium borohydride treatment, carbonization, and electro-reduction techniques. During the electro-reduction technique, Na+ is adsorbed onto the various defect sites of LBL 3D-CNFs, which properly inhibits the formation of the intermediate HER (hydrogen evolution reaction) product, leading to a wide cell voltage, whereas the LBL 3D-CNF network evokes an opportunity for storing a greater number of charges, resulting in excellent electrochemical performances. A symmetric supercapacitor with a reproducible and stable cell voltage of 2.0 V is constructed and demonstrated. The as-constructed device can deliver an areal energy output of 1922 μW h cm-2 at a power density of 3979 W kg-1 equal to a gravimetric energy density of 27 W h kg-1, and an outstanding cyclic durability of 97.4% after 20 000 GCD cycles. These record-breaking performances would make our device one of the most promising candidates from an industrial point of view.

Structurally stable ultrathin 1T-2H MoS2 heterostructures coaxially aligned on carbon nanofibers toward superhigh-energy-density supercapacitor and enhanced electrocatalysis

Metallic 1T MoS2 is a promising anode candidate for supercapacitors due to its intrinsically excellent electrical conductivity and high electrochemical activity. However, it is quite unstable and hard to be massively synthesized through common methods. Herein, structurally stable ultrathin (1–3 layers) in-plane 1T-2H MoS2 heterostructures have been rationally modulated and coaxially aligned on three-dimensional carbon nanofibers (MoS2/CF) through a facile hydrothermal approach for supercapacitors and electrocatalysis. Benefiting from the unique heterostructure, the MoS2/CF composite shows amazing stability with no obvious change after being stored in air for over 36 months. In addition, it presents high specific capacitance of 310 F g−1 and remarkable rate capability of 78% at 100 mV s−1. The fabricated asymmetric supercapacitor delivers an impressive energy density of 81.4 Wh kg−‍‍‍‍‍1 in 1 M Na2SO4 solution attributed to the high specific capacitance and large operating voltage range of 2 V. Moreover, the MoS2/CF composite also demonstrates enhanced electrocatalytic activity for hydrogen evolution reaction with a low overpotential of 194 mV at 10 mA cm−2. The work may promote the developments of high-performance bifunctional energy conversion and storage systems in future.

Electrochemical Sensor Based on Electrospun Three-Dimensional Carbon Nanofibers to Determine Trace Levels of Cu(II)

In this study, a three-dimensional carbon nanofiber network was formed by first electrospinning a mixed solution of montmorillonite (MMT) and polyacrylonitrile (PAN), and then carbonizing the composite nanofiber and etching it with hydrofluoric acid. The form and morphology of the nanofibers were analysized by scanning electron microscopy (SEM), Raman microspectroscopy (Raman), and X-ray photoelectron spectroscopy (XPS). The sensor fabricated on three-dimensional carbon nanofiber showed a good linear response (y = 0.076x – 0.110, R2 = 0.999, and y = 0.193x – 1.770, R2 = 0.998), high stability and selectivity, and a low detection limit (0.4 μg · L–1) for Cu(II) as measured using differential pulse voltammetry under the optimal conditions, and the method mentioned above was also used to analyze Cu(II) in real tap water samples, which had good recoveries.

Electrochemiluminescence Sensor Based on Electrospun Three-Dimensional Carbon Nanofibers for the Detection of Difenidol Hydrochloride.

The detection of difenidol hydrochloride, which is a drug that is widely used for treating the nausea and vomiting symptoms caused by certain diseases, has been increasingly involved in cases of suicide via overdosing and of drug poisoning in children. A novel electrochemiluminescence (ECL) sensor for the simple and effective detection of difenidol hydrochloride was fabricated by modifying a glassy carbon electrode with three-dimensional carbon nanofibers (3D-CNFs). The 3D-CNFs were synthesized by electrospinning a mixture of montmorillonite (MMT) and polyacrylonitrile, carbonizing the electrospun product, and etching it with hydrofluoric acid. The form and structure of the 3D-CNFs was analyzed via scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman microspectroscopy. According to the experimental results obtained using the modified electrodes, a good linear relationship was found between peak intensity and difenidol concentration (y = 868.14x − 61.04, R2 = 0.999), with a relatively low detection limit (8.64 × 10−10 mol·L−1 (S/N = 3)). In addition, our approach exhibited good recovery values ranging from 98.99% to 102.28%. The proposed novel ECL sensor has wide application prospects for the detection of difenidol hydrochloride.

Flexible free-standing SnS2/carbon nanofibers anode for high performance sodium-ion batteries

To solve the problems of insufficient conductivity and volume expansion of SnS2 during cycling when applied as anode for sodium-ion batteries (SIBs), we designed flexible and self-standing SnS2/carbon nanofibers (SnS2/CNFs) film by electrospinning technology and post sulfuration, in which the ultrafine SnS2 nanoparticles (∼5 nm) are preganated in the carbon nanofibers. The three-dimensional carbon nanofibers serve as flexible scaffold with high electrical conductivity to buffer the aggregation and pulverization of SnS2 particles. The obtained flexible SnS2/CNFs film can be directly used as anode for SIBs without adding binder and carbon additive, and exhibits excellent electrochemical performance. The SnS2/CNFs delivers a high capacity of 570.8 mAh g−1 at 0.2 A g−1. Even at a high rate of 5 A g−1, a high capacity of 247.1 mAh g−1 is still achieved. It also maintains 378.9 mAh g−1 after 100 cycles at 0.5 A g−1.

Bacterial Cellulose-Based Three-Dimensional Carbon Nanofibers for the Sensitive and Selective Determination of Uric Acid

In recent years, the interest in the optimization of novel nanomaterials for electrodes preparation has received tremendous attention. This article describe about develop an electrochemical sensor for to detect the uric acid (UA). Firstly, the sensing materials of carbon nanofibers (CNFs) were prepared through an economical approach under freeze-dried, mainly for CNFs were successfully synthesized through carbonized biomass green bacterial cellulose (BC) at 800 °C. The obtained CNFs were used to modify the glassy carbon electrode (GCE), and have an excellent electrochemical response towards the UA. Under the optimized condition, the current response of UA at the CNFs/GCE increased also the peak current linearly with the UA concentration, the limitation of detection (LOD) calculated as 0.29 μM (S/N = 3), revealing the a high sensitivity and an broader analytical range of the as-prepared CNFs/GCE. Finally, the proposed electrochemical sensor can be used for detection of UA in human urine with the satisfactory result.

Constructing superior carbon-nanofiber-based composite microwave absorbers by engineering dispersion and loading of Fe3O4 nanoparticles on three-dimensional carbon nanofibers derived from bacterial cellulose

Three-dimensional (3D) carbon nanofibers (CNFs) produced from pyrolysis of bacterial cellulose (BC) were used as the substrate for anchoring Fe3O4 nanoparticles. In order to control the dispersion of Fe3O4 nanoparticles on the surfaces of BC-derived CNFs (BC-CNFs), BC-CNFs were surface-treated in HNO3 solution. The resultant BC-CNF/Fe3O4 nanocomposites possessed ultra-small and highly dispersed Fe3O4 nanoparticles and demonstrated greatly enhanced absorption over their untreated counterparts. Moreover, among all BC-CNF/Fe3O4 nanocomposites, the BC-CNF/Fe3O4 containing 52.7 wt% Fe3O4 exhibited excellent absorption performance with the minimal reflection loss (RL) of −62.1 dB at 9.12 GHz, which is the best among all relevant CNF-Fe3O4 composites reported so far.

A bifunctional electrocatalyst of PtNi nanoparticles immobilized on three-dimensional carbon nanofiber mats for efficient and stable water splitting in both acid and basic media

Inspired by the excellent activity of platinum in hydrogen evolution reaction (HER) and the good performance of Ni-based compounds in oxygen evolution reaction (OER), a bifunctional electrocatalyst PtNi carbon nanofiber (CNF) is designed and fabricated using electrospinning followed by carbonization. Ultra-small PtNi nanoparticles of several nanometers in size are densely dispersed on every CNF, along with a few larger nanoparticles with sizes of several decades of nanometers. The as-prepared catalysts can be directly used as an electrode and act as high-efficiency materials for water splitting, including HER and OER. For HER activity, the PtNi/CNFs reach 10 mA cm−2 current density at low overpotentials of 34 mV and exhibit a small Tafel slope of 31 mV dec−1 in acidic electrolytes of 0.5 M H2SO4, which is close to that of commercial Pt/C (20 wt%) electrocatalytic catalysts. In 1 M KOH solution, the PtNi/CNFs also exhibit excellent HER activity with a low overpotential of 82 mV to achieve a current density of 10 mA cm−2 and a small Tafel slope of 34 mV dec−1. Moreover, the PtNi/CNFs also show good activity for OER in alkaline electrolyte of 1 M KOH with a Tafel slope of 159 mV dec−1 and a small overpotential of 151 mV to reach a current density of 10 mA cm−2. In addition, the OER performance of the PtNi/CNFs in acid media is also favorable, with a 198 mV dec−1 Tafel slope. The decent activity of the PtNi/CNFs for water splitting originates from the synergistic effects of using Pt and Ni, large amounts of ultra-small nanoparticles densely dispersed on the CNFs, high conductivity of the support materials and interconnected three-dimensional structures of the carbon nanofiber mats.