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Here, two kinds of chemical blowing agents (BAs), specifically, oxy-bis (benzene sulfonyl) hydrazide (OBSH), and azodicarbonamide (ADC) have been explored in the fabrication of carbon nanofibers for potential usage as the electrode materials in supercapacitors (SCs). The BAs are not only used as poring agents but also as heteroatom dopants. The type and the amount of BAs are significant to obtain a good porous carbon nanofiber structure and a low amount of usage provided a better nanostructure including a larger surface area (492.5 m2/g), a better total volume (0.216 cm3/g), higher level of structural disorder and defects (I D /I G , 1.02), and higher heteroatom content (5.26 at% N and 10.38 at% O) for C/OBSH-10 nanofiber. The symmetrical SC composed of C/OBSH-10 nanofiber electrode offers a specific energy of 6.2 Wh/kg at a specific power of 300 W/kg. Moreover, the cycling ability is superior (94.6 %) after 10,000 charge-discharge test and this work can be a strategy to obtain other porous carbon-based materials for energy storage applications. [Display omitted] • Chemical blowing agent (BA) provided a higher surface area (492.5 m2/g). • A higher heteroatom doping (5.26 at% N and 10.38 at% O) was obtained. • A good specific energy of 6.2 Wh/kg at 300 W/kg was achieved. [ABSTRACT FROM AUTHOR]

Antimony trioxide nanoparticles are synthesized in binder-free, self-standing, and nitrogen and sulfur as heteroatoms doped carbon nanofibers (Sb 2 O 3 -NSCFs). Two-step method including electrospinning and heat treatment is utilized to convert antimony species to nano-sized antimony nanoparticles. Structural, morphological, chemical composition, and surface area/pore size analysis of the materials are investigated using a series of analysis. The electrochemical performance of the materials is evaluated using both three- and two-electrode systems in basic electrolyte. The Sb 2 O 3 -NSCFs electrode shows a specific capacitance of 354.4 F/g at 1 A/g and the charge storage mechanism is investigated. The constructed coin-cell symmetric supercapacitor (Sb 2 O 3 -NSCF//Sb 2 O 3 -NSCF) exhibits a specific energy of 9.2 Wh/kg at 300 W/kg and also retains its capacitance of 94.4 % over 10 000 cycles. [Display omitted] • Antimony trioxide nanoparticles were synthesized in heteroatom-doped carbon nanofibers. • The Sb 2 O 3 -NSCFs electrode showed a specific capacitance of 354.4 F/g at 1 A/g. • The coin-cell symmetric supercapacitor (Sb 2 O 3 -NSCF//Sb 2 O 3 -NSCF) exhibited a good specific energy of 9.2 Wh/kg at 300 W/kg. [ABSTRACT FROM AUTHOR]

Using renewable biomass precursors to develop high-performance carbon electrodes is a promising approach for the advancement of supercapacitors. This work proposes a feasible strategy to prepare self-supporting flexible porous carbon nanofibers by electrospinning and carbonizing the mixture of cuttlefish ink, polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA). The impacts of cuttlefish ink precursor on the structure, elemental composition, and capacitance properties of carbon nanofibers have been studied. Herein, the unique structural advantage of cuttlefish ink can significantly optimize the porous structure of carbon nanofibers. Due to the hierarchical porous structure, large specific surface area, hollow channels and high nitrogen content, the carbon nanofibers offer a high specific capacitance of 364.8 F g−1 at 0.5 A g−1 current density, alongside desirable rate performance and cycle life. Furthermore, the carbon nanofiber electrode performs good mechanical flexibility. The flexible solid-state supercapacitor based on this electrode exhibits 14.1 Wh kg−1 energy density at 0.4 kW kg−1 power density, and 97.8% capacitance retention after 5000 cycles. The favorable capacitive properties make this carbon nanofiber material a potential candidate for supercapacitor electrodes. [Display omitted] • Electrospun porous carbon nanofibers (CPP–CNF) were prepared from cuttlefish ink. • CPP-CNF features hierarchical pores and hollow channels. • CPP-CNF is mechanically flexible with superior capacitive performance. • The flexible supercapacitor achieves high energy density and cycling stability. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate framework-derived carbon and metal oxide composites are promising for applications in lithium-ion batteries due to their morphology and porous structure. Herein, we report freestanding carbon nanofibers grafted with amorphous ZnO where the rhombic dodecahedral morphology of the parent (ZIF8) is maintained. The impacts of ZIF8 loading temperature on particle size after pyrolysis and on the electrochemical properties of these hybrid structures for LIBs are investigated. Polyacrylonitrile nanofiber loaded with ZIF8 at 45 °C exhibits a perfect sodalite topology and optimized particle size. The carbonized freestanding composite fibers have a high specific capacity of 818 mAh·g −1 at a current density of 100 mA·g −1 after 100 cycles. This remarkable performance of ZIF8-derived ZnO is due to its loading and coordination chemistry, which facilitates flexible volume changes and continuity in electrical conductivity through a continuous carbon nanofiber. [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems (BESs) employ extracellular electron transfer from bacteria that grow at electrodes. Due to biofilm and electrode limitations, industrial-scale applications require large electrode areas, and thus inexpensive electrode materials. Here, electro-spun polyacrylonitrile (PAN) and carbon nanofiber (CNF) were manufactured. In addition, the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) was applied as a coating to these materials and to carbon cloth (CC). We tested these materials as electrodes by using physicochemical measurements, cyclic voltammetry, and bioelectrochemical growth-studies with Geobacter sulfurreducens . PAN is a nonconductive material without capacitance, but with PEDOT coating the conductivity and capacitance became sufficient to support electric current production in our BES. CNF outperformed CC in capacitance, but behaved similarly in our BES when normalized to projected surface area. With the PEDOT coating, CNF increased electric current production by 38% in our BES, while this was 64% for CC. When applied to a gold microfluidic electrode, electric current with G. sulfurreducens increased almost three-fold. PEDOT added considerable specific surface area to electrodes possessing a low surface area, but not with a high surface area such as CNF. This work demonstrates that electro-spun electrodes and PEDOT coating are a promising electrode alternative that can be readily implemented into existing BESs. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries are regarded as a promising next-generation electrical-energy-storage technology due to their low cost and high theoretical energy density. Furthermore, flexible and wearable electronics urgently requires their power sources to be mechanically robust and flexible. However, the effective progress of high-performance, flexible Li-S batteries is still hindered by the poor conductivity of sulfur cathodes and the dissolution of lithium polysulfides as well as the weak mechanical properties of sulfur cathodes. Herein, a new type of flexible porous carbon nanofiber film modified with graphene and ultrafine polar TiO 2 nanoparticles is designed as a sulfur host, in which the artful structure enabled the highly efficient dispersion of sulfur for a high capacity and a strong confinement capability of lithium polysulfides, resulting in prolonged cycle life. Thus, the cathode shows an extremely high initial specific discharge capacity of 1501 mA h g −1 at 0.1 C and an excellent rate capability of 668 mA h g −1 at 5 C as well as prolonged cycling stability. The artful design provides a facile method to fabricate high-performance, flexible sulfur cathodes for Li-S batteries. [ABSTRACT FROM AUTHOR]

A simple and fast microwave-assisted protocol to functionalize commercially available graphite felts (GFs) with carbon nanofibers (CNFs) for the application as electrode materials in redox-flow batteries (RFB) is demonstrated. As catalyst for the CNF synthesis nickel acetate is applied and ethanol serves as the carbon source. By the in-situ growth of CNFs, the active surface of the electrodes is increased by a factor of 50, which is determined by the electrochemical double layer capacities of the obtained materials. Furthermore, the morphology of the CNF-coating is investigated by scanning electron microscopy. Subsequently, the functionalized electrodes are applied in a polymer-based redox-flow battery (pRFB) using a TEMPO- and a viologen polymer as active materials. Due to the increased surface area as compared to an untreated graphite felt electrode, the current rating is improved by about 45% at 80 mA cm −2 and, furthermore, a decrease in overpotentials is observed. Thus, using this microwave-assisted synthesis approach, CNF-functionalized composite electrodes are prepared with a very simple protocol suitable for real life applications and an improvement of the overall performance of the polymer-based redox-flow battery is demonstrated. [ABSTRACT FROM AUTHOR]

The aim of this study is to explore innovative materials for the development of next-generation supercapacitor electrodes. The hypothesis is that, upon the surface-decoration with appropriate amount of MnO 2 nanowhiskers, freestanding and highly graphitic electrospun carbon nanofiber (ECNF) mats (with fiber diameters of ∼200 nm and BET specific surface areas of ∼583 m 2 g −1 ) derived from a natural product of lignin would be binder-free supercapacitor electrodes with high performance. To test the hypothesis, the ECNF mats have been prepared first; thereafter, the acquired ECNF mats have been surface-decorated with varied amounts of MnO 2 nanowhiskers to prepare three types of ECNF/MnO 2 mats. The morphological and structural properties of ECNF and ECNF/MnO 2 mats are characterized by SEM, TEM and XRD, the weight percentages of MnO 2 nanowhiskers in three ECNF/MnO 2 mats are determined by thermal gravimetric analysis; while the electrochemical performance of each mat/electrode is evaluated by cyclic voltammetry, galvanostatic charge/discharge method, and electrochemical impedance spectroscopy. This study reveals that, all of the three ECNF/MnO 2 mats/electrodes have significantly enhanced electrochemical performances compared to the ECNF mat/electrode; while the ECNF/MnO 2 (1:1) mat/electrode exhibits the highest gravimetric capacitance of 83.3 F g −1 , energy density of 84.3 W h kg −1 , and power density of 5.72 kW kg −1 . [ABSTRACT FROM AUTHOR]

There is growing interest in flexible, cost-effective, and binder-free energy storage devices to meet the special needs of modern electronic systems. Herein we report a general, scalable, eco-friendly, and cost-effective approach for the fabrication of nano-Fe 3 O 4 -anchored three-dimensional (3D) carbon nanofiber (CNFs) aerogels (Fe 3 O 4 @BC-CNFs). The preparation processes include the anchoring of Fe 2 O 3 nanoparticles on bacterial cellulose (BC) nanofibers with intrinsic 3D network structure and subsequent carbonization at different temperatures. The aerogel carbonized at 600 °C (Fe 3 O 4 @BC-CNFs-600) is highly flexible and was directly used as working electrodes in lithium-ion batteries without metal current collectors, conducting additives, or binders. The Fe 3 O 4 @BC-CNFs-600 demonstrates greatly improved electrochemical performance in comparison to the bare Fe 3 O 4 nanoparticles. In addition to its excellent flexibility, a stable capacity of 755 mAh g −1 for up to 80 cycles is also higher than most of carbon-Fe 3 O 4 hybrids. The high reversible capacity and excellent rate capability are attributed to its 3D porous network structure with well-dispersed Fe 3 O 4 nanoparticles on the surfaces of CNFs. [ABSTRACT FROM AUTHOR]

A new freestanding Fe 3 C/carbon nanofiber (CNF) film is developed using a facile one-pot electrospinning method as an interlayer for high performance lithium–sulfur (Li–S) batteries. The interlayer placed between the separator and the sulfur cathode plays many synergistic roles, offering (i) a number of macropores within the nanofiber web to facilitate ion transport and electrolyte penetration, (ii) nitrogen-containing functional groups that entrap soluble polysulfides by strong interatomic attraction, and (iii) much enhanced electron/ion transfer due to the high electrical conductivity of the CNF web. The battery delivers an excellent specific discharge capacity of 893 mA h/g after 100 cycles, maintaining 76% of its initial capacity of 1177 mA h/g. These values are among the highest for those reported recently with similar nanocarbon-based interlayers in terms of rate capability and cyclic stability. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs), among various carbonaceous candidates for electric double-layer capacitor (EDLC) electrodes, draw extensive attention because their one-dimensional architecture offers both shortened electron pathways and high ion-accessible sites. Creating porous structures on CNFs yields larger surface area and enhanced capacitive performance. Herein, porous carbon nanofibers (PCNFs) were synthesized via centrifugal spinning of polyacrylonitrile (PAN)/poly(methyl methacrylate) (PMMA) solutions combined with thermal treatment and were used as binder-free EDLC electrodes. Three precursor fibers with PAN/PMMA weight ratios of 9/1, 7/3 and 5/5 were prepared and carbonized at 700, 800, and 900 °C, respectively. The highest specific capacitance obtained was 144 F g −1 at 0.1 A g −1 with a rate capability of 74% from 0.1 to 2 A g −1 by PCNFs prepared with PAN/PMMA weight ratio of 7/3 at 900 °C. These PCNFs also showed stable cycling performance. The present work demonstrates that PCNFs are promising EDLC electrode candidate and centrifugal spinning offers a simple, cost-effective strategy to produce PCNFs. [ABSTRACT FROM AUTHOR]

A novel anode material for lithium-ion batteries, graphene-wrapped Si nanoparticles (NPs) embedded in carbon composite nanofibers (CCNFs) with G/Si, is fabricated by electrospinning and subsequent thermal treatment. In CCNFs with G/Si, Si NPs are distributed and preserved inside the CNF surface because the graphene wrapping the Si NPs help prevent agglomeration and ensure a good dispersion of Si NPs inside the CNF matrix. 20-GSP prepared from a weight ratio of 20 wt% of G/Si to polyacrylonitrile exhibits stable capacity retention and a reversible capacity of above 600 mAh g −1 up to 100 cycles. The high cycling performance and superior reversible capacity of the 20-GSP anode can be attributed to the one-dimensional nanofibrous structure with non-agglomerated Si NPs in the CNF matrix, which promotes charge transfer, maintains a stable electrical contact, and buffers the Si volume expansion. [ABSTRACT FROM AUTHOR]

Phosphorus-doped tin oxides/carbon nanofibers (P-SnO x /CNFs) composite materials are prepared via electrospinning of a mixed solution composed of polyacrylonitrile (PAN), N , N -dimethyl formamide (DMF), tin tetrachloride, ethylene glycol and phosphoric acid as well as subsequent thermal treatments. The P-SnO x /CNFs samples with tunable P-doping contents are directly used as anodes for lithium-ion batteries without any binders and conductors, exhibiting enhanced reversible capacities and cycling stabilities in comparison with pristine undoped SnO x /CNFs (0P-SnO x /CNFs). In a controlled experiment, the 0.25P-SnO x /CNFs anode with the atomic ratio of P:Sn = 0.25:1 shows the highest specific reversible capacity of 676 mA h g −1 at 200 mA g −1 after 100 cycles. Even at a higher current density of 2000 mA g −1 , it still maintains a superior specific reversible capacity of 288 mA h g −1 . The improved electrochemical performances are attributed to the P-doping effects such as inducement of a stable structural protection for tin particles, and enhancement of lithium ion diffusion coefficient and electron kinetics of electrode materials. [ABSTRACT FROM AUTHOR]

Lithium titanium oxide (Li 4 Ti 5 O 12 ) is a promising anode material, owing to its superior safety and reliability. However, the main challenge of Li 4 Ti 5 O 12 is the low material conductivity which restricts its electrochemical performance. In order to use Li 4 Ti 5 O 12 in practical sodium-ion batteries, copper-doped Li 4 Ti 5 O 12 (Li 4− x Cu x Ti 5 O 12 , x = 0, 0.05, 0.1) nanoparticles were prepared to enhance the electronic conductivity. Copper-doped Li 4 Ti 5 O 12 nanoparticles were then embedded in continuous carbon nanofibers (CNFs), which gave rise to fast electron transfer along the fiber direction. After copper-doping and CNF embedding, the resultant copper-doped Li 4 Ti 5 O 12 /CNFs achieved excellent reversible capacity (158.1 mAh g −1 ) at 30 mA g −1 , high coulombic efficiency (99.87%), and good capacity retention (91%) after 150 cycles. In addition, copper-doped Li 4 Ti 5 O 12 /CNFs also exhibited good rate capability. It is, therefore, demonstrated that copper-doped Li 4 Ti 5 O 12 /CNFs are promising anode candidate. [ABSTRACT FROM AUTHOR]

Carbon nanofiber (CNF)/Co 3 O 4 nanopyramid core–shell nanowires (NWs) are synthesized using an electrospinning method followed by reduction and hydrothermal treatment in order to improve the capacity, cycle stability, and high-rate capability of the electrodes in Li ion batteries (LIBs). The morphology, crystal structure, and chemical states of all samples are investigated by means of field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. For comparison, conventional CNFs, octahedral Co 3 O 4 , and Co 3 O 4 /CNF composite electrodes are prepared. LIB cells fabricate with the CNF/Co 3 O 4 nanopyramid core–shell NWs exhibit superb discharge capacity (1173 mAh g −1 at the 1st cycle), cycle stability (795 mAh g −1 at 50 cycles), high initial Coulombic efficiency (84.8%), and high-rate capability (570 mAh g −1 at a current density of 700 mA g −1 ) as compared to the conventional CNF, octahedral Co 3 O 4 , and Co 3 O 4 /CNF composite electrodes. The performance improvement is owing to the introduction of one-dimensional CNFs relative to efficient electron transport in the core region, extensive utilization of Co 3 O 4 nanopyramids with high capacity grown closely on the CNFs in the shell region, and the network structures of the electrode relative to the improvement of Li ion diffusion. [ABSTRACT FROM AUTHOR]

Abstract: One-dimensional silicon oxycarbide (SiOC)/C composite nanofibers were fabricated by electrospinning and subsequent heat treatment. Introducing carbon matrix to SiOC anode material is an efficient way to accommodate the large volume changes during cycling and also increase the amount of free carbon, which is beneficial for improving the reversible capacity. These SiOC/C composite nanofibers form free-standing conductive membranes that can be used directly as battery electrodes without adding carbon black or polymer binder. Results show that after 80 cycles, the discharge capacity of SiOC/C composite nanofiber anodes is 70% higher than that of Si/C nanofiber anodes and more than 1.5 times larger than those of commercial anodes made from graphite. It is, therefore, demonstrated that one-dimensional SiOC/C nanofibers are promising anode material with large capacities and good cycling stability. [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: Electrospun carbon nanofiber/graphene (CNF/G) composites are prepared by in situ electrospinning polymeric nanofibers with simultaneous spraying graphene oxide, followed by heat treatment. The freestanding carbon nanofiber web acts as a framework for sustaining graphene, which helps to prevent the agglomeration of graphene and to provide a high conductivity for the efficient charge transfer to the pores. The as-obtained CNF/G composite exhibits a specific capacitance of 183 F g−1, which is approximately 1.6 times higher than that of the pristine CNF. The results have demonstrated that the high performance of the CNF/G composite is due to the novel structure and the synergic effect of graphene and the carbon nanofibers. [Copyright &y& Elsevier]

Abstract: In this study, hierarchically porous carbon nanofibers (HPCNFs) containing numerous electroactive heteroatoms are prepared by controlling carbonization and chemical activation. The HPCNFs have a large surface area of 2862.1 m2 g−1, hierarchical porous structure, and 20.6 at% electroactive oxygen atoms. These HPCNFs exhibit excellent electrochemical performance, and their thermal treatment with melamine results in nitrogen-doped HPCNFs (N-HPCNFs) with 9.1 at% nitrogen and improved electrical property (1.8 × 102 Ω □−1). The electrochemical performance of N-HPCNFs is better than that of HPCNFs, displaying specific energy of 113 Wh kg−1, specific power of 105 kW kg−1, and stable cycle life of over 5000 cycles. [Copyright &y& Elsevier]

Abstract: Several graphite-based electrodes are investigated for vanadium flow battery applications. These materials are characterized both as-received and after chemical or electrochemical treatments in order to vary the content of oxygen functional groups on the electrode surface. The surface properties of the samples are investigated by X-ray photoelectron spectroscopy. Electrochemical performance is evaluated by cyclic voltammetry and electrochemical impedance spectroscopy measurements in a three electrode half-cell. The chemical treatment with HNO3 causes a cleaning of the electrode surface from adsorbed oxygen species or labile bonded functional groups in highly graphitic samples. Whereas, carbonaceous materials characterized by smaller graphitic domains or a higher degree of amorphous carbon show an increase of oxygen functional groups upon chemical and electrochemical pre-treatments. In both cases, an increase of oxygen species content on the surface above 5% causes a decrease of electrochemical performance for the redox battery determined by an increase of ohmic and charge transfer resistance. [Copyright &y& Elsevier]

Abstract: Carbon nanofibers (CNFs) with different content of surface functional groups which are carboxyl groups (CNF–OX), carbonyl groups (CNF–CO) and hydroxyl groups (CNF–OH) and nitrogen-containing groups (CNF–ON) are synthesized, and their electrocatalytic activities toward oxygen reduction reaction (ORR) in alkaline solution are investigated. The result of X-ray photoelectron spectroscopy (XPS) characterization indicates that a higher concentration of carboxyl groups, carbonyl groups and hydroxyl groups are imported onto the CNF–OX, CNF–CO and CNF–OH, respectively. Cyclic voltammetry shows that both the oxygen- and nitrogen-containing groups can improve the electrocatalytic activity of CNFs for ORR. The CNF–ON/GC electrode, which has nitrogen-containing groups, exhibits the highest current density of ORR. Rotating disk electrode (RDE) characterization shows that the oxygen reduction on CNF–ON/GC electrode proceeds almost entirely through the four-electron reduction pathway, the CNF–OX/GC, CNF–CO/GC and CNF–OH/GC electrodes proceed a two-electron reduction pathway at low potentials (−0.2 V to −0.6 V) followed by a gradual four-electron reduction pathway at more negative potentials, while the untreated carbon nanofiber (CNF–P/GC) electrode proceeds predominantly by a two-electron reduction pathway within the whole range of potential studied. [Copyright &y& Elsevier]

Abstract: Electrospun carbon nanotubes-embedded carbon nanofibers (CNF) fabric is employed as freestanding substrates for in-situ coating MnO2 nanostructures. Birnessite-type MnO2 nanoflakes are observed to grow vertically on individual CNF, thus building hierarchical coaxial architecture. This work presents an extensive study of the effect of temperature on the pseudo-capacitive behavior of the as-prepared freestanding MnO2@CNF composites electrodes in mild Na2SO4 electrolyte. The results show that the MnO2@CNF composites exhibit excellent pseudo-capacitive behaviors at different temperatures between 0 °C and 75 °C. The specific capacitance at 1 A g−1 increases from 365 F g−1 at 0 °C to 546 F g−1 at 75 °C, whereas the coulombic efficiency decreases with the increasing temperature, especially at lower charging rate. The cycling stability of the composites strongly depends on the temperature, i.e., 95.3% at 25 °C and 82.4% at 75 °C. This study provides a fundamental understanding of the temperature-dependent capacitive properties of MnO2 in mild electrolyte, which gives an insight into the supercapacitor design for industrial applications. [Copyright &y& Elsevier]

Abstract: Carbon nanofiber (CNF) supported PdAu nanoparticles are synthesized with sodium citrate as the stabilizing agent and sodium borohydride as the reducing agent. High resolution transmission electron microscopy (HRTEM) characterization indicates that the synthesized PdAu particles are well dispersed on the CNF surface and X-ray diffraction (XRD) characterization indicates that the alloying degree of the synthesized PdAu nanoparticles can be improved by adding tetrahydrofuran to the synthesis solution. The results of electrochemical characterization indicate that the addition of Au can promote the electrocatalytic activity of Pd/C catalyst for formic acid oxidation and the CNF supported high-alloying PdAu catalyst possesses better electrocatalytic activity and stability for formic acid oxidation than either the CNF supported low-alloying PdAu catalyst or the CNF supported Pd catalyst. [Copyright &y& Elsevier]

Abstract: In this paper we report a novel lithium-sulfur cell, which is characteristic of a unique combination of carbon nanofibers–sulfur cathode and gel polymer electrolyte (GPE). In particular, the carbon nanofibers for the cathode and the poly(acrylonitrile)/poly(methyl methacrylate) (PAN/PMMA) membrane for the GPE are prepared by electrospinning technique. The GPE consists of electrospun PAN/PMMA membrane and 1 mol kg−1 lithium bis(trifluoromethylsulfonyl)imide in N-methyl-N-butylpiperidinium bis(trifluoromethanesulfonyl)imide (PPR14TFSI) and poly (ethylene glycol) dimethyl ether (PEGDME). The membrane and cell performances are investigated by scanning electron spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. It is found that the cell using the GPE based on PAN/PMMA membrane and PPR14TFSI-PEGDME (1:1) exhibits the largest discharge capacity and the best cycle durability. The discharge capacity of this cell remains at 760 mA h g−1 after 50 cycles. This new sulfur/electrolyte system combines the advantages of the carbon nanofibers that provide an effective conduction path and network-like structure, and the GPE that suppresses the dissolution of the intermediate products generated during the discharge process. The ratio of PPR14TFSI to PEGDME affects the ionic conductivity of the GPE, the stability of the sulfur electrode and the compatibility of lithium electrode with the GPE. [Copyright &y& Elsevier]

Abstract: A carbon particle supported sulfur (C–S) composite cathode material was prepared by a chemical deposition method in an aqueous solution. The performance of the C–S cathode material with carbon particles (CP) and carbon nanofibers (CNFs) as electrical conductors and CMC+SBR as binder was evaluated in Li/S cells using cyclic voltammetry, constant current cycling, and electrochemical impedance spectroscopy. The C–S material and the electrodes were examined by scanning electron microscopy. It is found that the C–S cathode with CNFs shows improvement of not only discharge capacity but also cycling durability. It exhibits an initial discharge capacity of 1200mAhg−1, or 72% of theoretical, and retains 668mAhg−1, or 40% of the sulfur theoretical capacity after 50 cycles. The C–S electrode with CNFs has a three-dimensional network structure with regular pores, which can suppress the agglomeration of sulfur or lithium sulfide. Thus, the cell performance is improved. [Copyright &y& Elsevier]

Abstract: We report electrochemical studies of high voltage cathodes composed of lithium rich “layered-layered” material having the nominal composition Li1.2Mn0.525Ni0.175Co0.1O2, or equivalently 0.6Li[Li1/3Mn2/3]O2–0.4Li[Mn0.3Ni0.45Co0.25]O2. These aspects were investigated by cyclic voltammetry studies in conjunction with electrochemical impedance spectroscopy measurements to understand the redox reactions involving multiple transition metals and their capacity contribution at higher voltages, up to 4.9V. Further, cathodes with 1.5wt.% carbon nanofibers added to the Li1.2Mn0.525Ni0.175Co0.1O2 composite electrode showed stable reversible capacities of about 280mAhg−1 when cycled to 4.9V for more than 100 cycles, and almost a factor of two improvements in the rate performance compared to the electrode composition prepared using conventional composition (7.5% carbon black and 7.5% binder). [Copyright &y& Elsevier]

Abstract: Oxygen- and nitrogen-containing groups are successfully introduced onto the carbon nanofiber (CNF) surfaces by sonochemical treatment in mixed acids (concentrated sulfuric acid and nitric acid) and ammonia, respectively. Pt electrocatalysts supported on the acid-treated CNF (CNF-O) and ammonia-treated CNF (CNF-ON) are prepared and the effect of CNF surface functional groups on the electrocatalytic activities of supported catalysts for oxygen reduction reaction (ORR) is investigated. High resolution transmission electron microscopy reveals that Pt particles are uniformly dispersed on the two CNF supports and the CNF-ON supported Pt nanoparticles have a smaller average particle size and a more uniform particle size distribution. Cyclic voltammetric analysis shows the Pt/CNF-ON has a larger electrochemically active surface area than Pt/CNF-O. Rotating disk electrode measurements show that the Pt/CNF-ON exhibits a considerably higher electrocatalytic activity toward ORR as compared with Pt/CNF-O. It is believed that the good electrocatalytic activity of Pt/CNF-ON can be attributed to the smaller Pt particle size and more uniform particle size distribution, to the synergistic effect and the enhanced Pt–CNF-ON interaction, and to the unique structural and electronic properties of CNF-ON. [Copyright &y& Elsevier]

Abstract: Highly dispersed and active palladium/carbon nanofiber (Pd/CNF) catalyst is synthesized by NaBH4 reduction with trisodium citrate as the stabilizing agent. The obtained Pd/CNF catalyst is characterized by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The results show that the Pd nanoparticles with an average particle size of ca. 3.8nm are highly dispersed on the CNF support even with a small ratio of citrate to Pd precursor, which is believed to be due to the pH adjustment of citrate stabilized colloidal Pd nanoparticles. The cyclic voltammetry and chronoamperometry techniques show that the obtained Pd/CNF catalyst exhibits good catalytic activity and stability for the electrooxidation of formic acid. [Copyright &y& Elsevier]

Abstract: Two palladium/carbon nanofibers modified glassy carbon electrodes, Pd/CNFs/GC-C and Pd/CNFs/GC-E, are fabricated by the conventional powder type method and by the electrophoretic deposition in conjunction with pulse electrodeposition method, respectively. Field emission scanning electron microscopy and high resolution transmission electron microscopy reveal that Pd particles are uniformly dispersed on the two electrodes and X-ray diffraction shows the average Pd particle size of the Pd/CNFs/GC-E electrode is slightly larger than that of the Pd/CNFs/GC-C electrode. Cyclic voltammetric analysis shows that the electrocatalytic activity of Pd/CNFs/GC-E electrode is better than that of Pd/CNFs/GC-C electrode for ethanol oxidation in alkaline media, although the latter has higher Pd loading than the former. This is believed to be due to the higher utilization of Pd catalyst on Pd/CNFs/GC-E electrode than on Pd/CNFs/GC-C electrode, which is confirmed by the electrochemically active surface area measurements. In addition, chronopotentiometric analysis shows the long-term operation stability of Pd/CNFs/GC-E electrode is better than that of Pd/CNFs/GC-C electrode. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, the Nafion®-based self-humidifying composite membrane (N-SHCM) with sulfonated carbon nanofiber-supported Pt (s-Pt/CNF) catalyst, N-s-Pt/CNF, is successfully prepared using the solution-casting method. The scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) images of N-s-Pt/CNF indicate that s-Pt/CNF is well dispersed in the Nafion® matrix due to the good compatibility between Nafion® and s-Pt/CNF. Compared with those of the non-sulfonated Pt/CNF-containing N-SHCM, N-Pt/CNF, the properties of N-s-Pt/CNF, including electronic resistivity, ion-exchange capacity (IEC), water uptake, dimensional stability, and catalytic activity, significantly increase. The maximum power density of the proton exchange membrane fuel cell (PEMFC) fabricated with N-s-Pt/CNF operated at 50°C under dry H2/O2 condition is about 921mWcm−2, which is approximately 34% higher than that with N-Pt/CNF. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the support Pt catalyst was supported by a novel spherical carbon using a convenient technique. Two different preparation methods utilizing a nanocolloidal solution method without heat treatment were developed (methods 1 and 2). The scanning electron microscope (SEM) and transmission electron microscope (TEM) observations showed that the Pt nanoparticles (particle size) were supported, with higher dispersion being achieved with method 2 than method 1. The peak of the Pt metal was confirmed from the X-ray diffraction (XRD) measurement. Based on the inductively coupled plasma mass spectrometry (ICP-MS) measurements, Pt loading was 19.5wt.% in method 1 and approximately 50wt.% in method 2. The Pt specific surface area of the Pt/novel spherical carbon catalyst calculated from the cyclic voltammetry (CV) measurement result was larger than that of the commercially available Pt/Ketjen catalyst. These results indicated that the Pt nanoparticles were supported in high dispersion without heat treatment using novel spherical carbon as a carbon support. [Copyright &y& Elsevier]

Abstract: This study examines the effect of heat-treatment temperature on the electrochemical corrosion of carbon nanofibers (CNFs) in polymer electrolyte membrane (PEM) fuel cells. Corrosion is investigated by monitoring the generation of CO2 using an on-line mass spectrometer at a constant potential of 1.4V for 30min. The experimental results show that the generation of CO2 decreases with increasing heat-treatment temperature, indicating that less electrochemical carbon corrosion occurs. In particular, when the heat-treatment temperature is 2400°C, the change intensifies. X-ray photoelectron spectroscopic analysis shows that oxygen functional groups on the carbon surface decrease with increasing heat-treatment temperature. A reduction in oxygen functional groups increases the hydrophobic nature of the carbon surface, which is responsible for the increased corrosion resistance of CNFs. [Copyright &y& Elsevier]