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Abstract: This paper reports the fabrication and electrochemical properties of novel high-performance pseudosupercapacitor electrodes made of graphene-beaded carbon nanofibers (G/CNFs) surface-coated with nanostructured conducting polymers. The G/CNFs were produced by electrospinning the precursor graphene-beaded polymer nanofibers, followed by controlled pyrolysis. In situ polymerization in aqueous solution was utilized to coat an ultrathin layer of thorn-like polyaniline (PANI) nanorods onto the G/CNFs to form ternary PANI-coated G/CNFs (PANI-G/CNFs). The highly porous network morphology of PANI-G/CNFs exhibited a very large specific surface area, low internal resistance, and fast redox rate. Electrochemical characterization indicated that the PANI-G/CNF based pseudosupercapacitors carried a high value of specific capacitance up to 637 F g−1 at a current density of 0.15 A g−1 and still maintained the high value of specific capacitance of 478 F g−1 (only 25% decrease) even at a high current density of 6 A g−1. The pseudosupercapacitor showed a very good cycling stability of 87% after 1000 charge/discharge cycles at a very high current density of 15 A g−1. The experimental results indicated that the novel hierarchical, porous PANI-G/CNFs are a promising electrode material for use in high-performance energy storage devices. [Copyright &y& Elsevier]

Abstract: Mechanically flexible mats consisting of electrospun carbon nanofibers (ECNFs) were prepared by first electrospinning aqueous mixtures containing a natural product of alkali lignin together with polyvinyl alcohol (PVA) into composite nanofiber mats followed by stabilization in air and carbonization in an inert environment. Morphological and structural properties, as well as specific surface area, total pore volume, average pore size, and pore size distribution, of the lignin-based ECNF mats were characterized; and their electrochemical performances (i.e., capacitive behaviors) were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The lignin-based ECNF mats exhibited outstanding performance as free-standing and/or binder-free electrodes of supercapacitors. For example, the ECNFs made from the composite nanofibers with mass ratio of lignin/PVA being 70/30 (i.e., ECNFs (70/30)) had the average diameter of ∼100 nm and the Brunauer–Emmett–Teller (BET) specific surface area of ∼583 m2 g−1. The gravimetric capacitance of ECNFs (70/30) electrode in 6 M KOH aqueous electrolyte exhibited 64 F g−1 at current density of 400 mA g−1 and 50 F g−1 at 2000 mA g−1. The ECNFs (70/30) electrode also exhibited excellent cycling durability/stability, and the gravimetric capacitance merely reduced by ∼10% after 6000 cycles of charge/discharge. [Copyright &y& Elsevier]

Abstract: This paper studies the synthesis and electrochemical characterization of novel graphene-beaded carbon nanofibers (G/CNFs) as electrode material for use in supercapacitor. The porous G/CNF films were prepared by electrospinning polyacrylonitrile (PAN)/N,N-dimethylformamide (DMF) solution dispersed with oxidized graphene nanosheets, followed by carbonization at 800 °C in a tubular quartz furnace. The morphology and chemical structure of the porous G/CNF films were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The electrochemical behavior of the synthesized G/CNF films as supercapacitor electrodes was characterized by means of cyclic voltammetry (CV), galvanotactic charge/discharge, and electrochemical impedance test in a 6 m KOH aqueous electrolyte. Electrochemical measurements revealed that the maximum specific capacitance of the porous G/CNF electrodes reached up to 263.7 F g− 1 at a discharge current density 100 mA g− 1. Furthermore, the supercapacitor exhibited very good cycling stability of energy storage with the retention ratio of 86.9% after 2000 cycles. The high electrochemical performance of the G/CNF electrodes was attributed to the unique nanostructural configuration, high electrical conductivity, and large specific surface area of the graphene nanosheets. [Copyright &y& Elsevier]

Abstract: This paper reports the fabrication and mechanical properties of hybrid multi-scale epoxy composites reinforced with conventional carbon fiber (CF) fabrics surface-attached with electrospun carbon nanofiber (ECN) mats. The ECNs were prepared via thermal treatments of polyacrylonitrile copolymer nanofibers, which were produced by the electrospinning technique and collected as overlaid mats on the T300 CF fabrics. The ECN-CF fabrics/mats were used as innovative reinforcement fillers for the fabrication of hybrid multi-scale composites (with SC-15 epoxy resin) through the composite-manufacturing technique of vacuum assisted resin transfer molding. Three-point bending test and short-beam shear test were carried out to evaluate the strengthening/toughening effects of ECNs on mechanical properties of the novel composites. The results indicated that out-of-plane mechanical properties of the ECN-CF/epoxy composites were considerably higher than the control sample of traditional CF/epoxy composites. [Copyright &y& Elsevier]