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Abstract: Microporous carbon ultrafine fibers with different diameter were prepared by electrospinning from resole-type phenolic resin, followed by heat curing and one-step carbonization, and their adsorption performance for benzene and water was evaluated. Average diameter of as-spun fibers changed from 1.1 to 0.33μm with increasing dimethylformamide content in the spinning solution, caused by more fiber divisions. The carbon ultrafine fibers with smaller diameter exhibited enhanced benzene adsorption and diminished water adsorption due to improved specific surface area, micropore volume and hydrophobicity. In addition, the relatively developed hydrophobicity of the prepared carbon ultrafine fibers resulted in much higher adsorption tendency for benzene over water, in comparison to common polyacrylonitrile-based electrospun activated carbon nanofibers. [Copyright &y& Elsevier]

Abstract: In the present study, we prepared flexible phenolic resin fabrics and corresponding porous carbon fabrics through electrospinning and successive curing and carbonization of resol/ethanol solutions. The addition of high-molecular-weight polyvinyl butyral (PVB) is essential for the stable fabrication of bead-free resol fabrics. Due to a high evaporation rate of ethanol and non-linear molecule structure of resol, the electrospun fabrics consist of entangled high aspect ratio ribbons instead of round fibers. The resol fabrics can be simply cured by heating at low temperature in air. Further carbonization at different temperatures resulted in flexible porous carbon fabrics with different specific surface area, which reached a maximum value of 855m2/g after heat treatment at 1000°C. These phenolic resin-based free-standing porous carbon fabrics would be promising in adsorption and electrochemical applications. [Copyright &y& Elsevier]

Abstract: Porous carbon nanofibers (PCNFs) were fabricated by stabilization, carbonization and activation with steam after electrospinning the polymer solution of polyacrylonitrile (PAN) in N,N-dimethylformamide (DMF). The nitrogen adsorption and desorption at 77K showed that PAN-based PCNFs are highly microporous. Removal of NO with PCNFs at room temperature was investigated. The ratio of NO removed by PCNFs is higher than 60% when the inlet NO concentration was 20ppm with 0.10g of sample, and NOx (NO+NO2) cannot be detected when the inlet NO concentration was 2ppm within 24h. The mechanism sequence is supposed to be NO adsorption, catalytic oxidation to NO2 and part reduction to N2 by PCNFs due to greater carbon surface area and a higher quantity of nitrogen species. Thus, PCNFs would be effective for purging low concentration NOx at room temperature. [Copyright &y& Elsevier]

The adsorption of polar methy-ethyl-ketone (MEK) and non-polar benzene vapors on viscose rayon-based activated carbon fiber (ACF) was investigated. The pore texture and surface composition of ACF were characterized by nitrogen adsorption at 77 K and X-ray photoelectron spectroscopy (XPS), respectively. Gas adsorption on the samples was measured by the gravimetric method and the Dubinin–Radushkevich (DR) equation was used to fit the experimental adsorption isotherms. The experimental results show that ACF with different pore texture and surface composition exhibited different adsorption and desorption behavior for polar and non-polar vapors. The effect of adsorbate polarity on the adsorption capacity at lower concentrations was more significant in the case of adsorbents with a smaller surface area. It was found that evacuation treatment greatly increased the adsorption rate. [ABSTRACT FROM AUTHOR]

Abstract: Phenolic resin-based porous carbon nanofibers (PCNFs) with large surface area and narrow pore size distribution have been successfully prepared using novolac-type phenolic resin as precursor. The high molecular weight precursor was first synthesized in this study, then was dissolved in methanol. The PCNFs were finally obtained through electrospinning the phenolic resin polymer solution followed by successive curing and carbonization without activation. The N2 adsorption/desorption isotherms reveal that the PCNFs have high specific surface area about 812m2/g, the pore size falls in the range of 0.4–0.7nm and the pore volume is 0.91cm3/g. The vapor adsorption testing demonstrated that PCNFs exhibited different adsorption performance for ethanol and water. [Copyright &y& Elsevier]

Ultrafine carbon fiber webs were prepared from oxidatively stabilized electrospun poly(acrylonitrile) fibers, followed by carbonization or by further activation with steam. Capacitive de-ionization was evaluated in the batch mode. It was found that the webs exhibited considerable electrical adsorption, which was enhanced by activation with a faster electrosorption rate and a higher electrosorption capacity. [ABSTRACT FROM AUTHOR]

Fibrous carbon materials have a variety of dimensions and structures. However, these materials were earlier restricted for use as anode materials for lithium ion batteries due to their cost and performance. With the development of nanotechnology, some modified and new forms of carbon fibers have emerged, which show good performance as anode materials. This paper reviews recent domestic and foreign research progress on fibrous carbon materials as anode materials. The electrochemical performance and prospective use of graphite fibers, carbon fibers and carbon nanofibers for this purpose are summarized. Research has ranged from non-graphitized to graphitized carbon fibers, from micron to nanometer diameter, and has focused on the parameters of their preparation to the design of their microstructure. Fibrous carbon materials are likely to be important alternatives for carbon anode materials in the future based on their high capacity, high rate capability, low cost and ease of industrialization. [New Carbon Materials 2015, 30(1): 1–11] [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanofibers (CNFs)/MnO2 nanocomposites were prepared as freestanding electrodes using in situ redox deposition and electrospinning. The electrospun CNFs substrates with porosity and interconnectivity enabled the uniform incorporation of birnessite-type MnO2 deposits on each fiber, thus showing unique and conformal coaxial nanostructure. CNFs not only provided considerable specific surface area for high mass loading of MnO2 but also offered reliable electrical conductivity to ensure the full utilization of MnO2 coatings. The effect of MnO2 loading on the electrochemical performances was investigated by cyclic voltammetry (CV), impedance measurements and Galvonostatic charging/discharging technique. The results showed that an ultrathin MnO2 deposits were indispensable to achieve better electrochemical performance. The maximum specific capacitance (based on pristine MnO2) attained to 557F/g at a current density of 1A/g in 0.1M Na2SO4 electrolyte when the mass loading reached 0.33mg/cm2. This freestanding electrode also exhibited good rate capability (power density of 13.5kW/kg and energy density of 20.9Wh/kg at 30A/g) and long-term cycling stability (retaining 94% of its initial capacitance after 1500 cycles). These characteristics suggested that such freestanding CNFs/MnO2 nanocomposites are promising for high-performance supercapacitors. [Copyright &y& Elsevier]

We report a simple process to connect graphene sheets forming graphene hollow microtubes (GHMs), where the tube diameter can be adjusted in the 100–500 nm range by changing reaction conditions. We discovered that graphene sheets can be seamlessly linked to each other if C atoms are substituted for N atoms at the edges of the sheets during annealing of graphene oxide(G-O)-coated electrospun PAN carbon fibers in ammonia atmosphere. The G-O/carbon hybrid nanofibers framework served as a confining template around which graphene sheets curved to form tubular structures. The GHMs formed by this process are similar to (very) large diameter carbon nanotubes (CNTs) with relatively low curvature whose electron field-emission properties include a low turn-on voltage of 0.18 V/μm (at J = 10 μA/cm2), low threshold field of 0.35 V/μm (at J = 10 mA/cm2), and high field-emission stability. This process to produce GHMs can be scaled up to fabricate GHMs of variable diameter in bulk quantities. [ABSTRACT FROM AUTHOR]

Flax-derived flexible porous nitrogen-doped carbon fibers (PNCFs) with controllable textural structure and nitrogen content are obtained via NH 3 activation. The PNCFs-based flexible supercapacitor shows high energy and power density. • A facile approach to flexible high-performance carbon fiber sheets was disclosed. • The procedure parameters of NH 3 activation/doping of flax fabrics were investigated. • The flexible capacitor of PNCF displays an energy density of 174.7 μWh cm−2. A facile and cost-effective approach to flexible high nitrogen-containing porous carbon fiber sheets (PNCFs) was disclosed. The PNCFs were fabricated through a facile strategy of activation/doping of flax fabrics in ammonia (NH 3). The procedure parameters of NH 3 modification, such as the timing of NH 3 switching, activation temperature and duration time were systematically investigated. PNCFs with the highest specific surface area (SSA) of 1152 m2 g−1, largest pore volume of 0.502 cm3 g−1 and maximal nitrogen content of 5.56 at.% were obtained by activation via NH 3 at 900 °C for 45 min after pre-carbonization. The optimized sample PNCF-IV-900-45 with the highest SSA, developed hierarchical micro-mesoporous structure and maximal nitrogen content exhibits a large energy density of 16.4 Wh kg−1 at 100 W kg−1. The NH 3 -activated flax-derived carbon fiber sheets assembled into a flexible supercapacitor also shows preeminent electrochemical performance and the flexibility. The symmetric flexible capacitor by PNCF-IV-900-45 electrodes displays a remarkable specific energy density of 174.7 μWh cm−2 at 500 μW cm−2, which results from the hierarchical porous structure and N functionalities. The synergistic combination of the hierarchical micro-mesoporous textures, high specific surface area, N-doping and flexibility of flax-based PNCFs to the enhanced electrochemical performance in flexible supercapacitor. [ABSTRACT FROM AUTHOR]