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Early detection of histamine in foodstuffs/beverages could be useful in preventing various diseases. In this work, we have prepared a free-standing hybrid mat based on manganese cobalt (2-methylimodazole)–metal organic frameworks (Mn-Co(2-MeIm)MOF) and carbon nanofibers (CNFs) and explored as a non-enzymatic electrochemical sensor for determining the freshness of fish and bananas based on histamine estimation. As-developed hybrid mat possesses high porosity with a large specific surface area and excellent hydrophilicity those allow easy access of analyte molecules to the redox-active metal sites of MOF. Furthermore, the multiple functional groups of the MOF matrix can act as active adsorption sites for catalysis. The Mn-Co(2-MeIm)MOF@CNF mat-modified GC electrode demonstrated excellent electrocatalytic activities toward the oxidation of histamine under acidic conditions (pH = 5.0) with a faster electron transfer kinetics and superior fouling resistance. The Co(2-MeIm)MOF@CNF/GCE sensor exhibited a wide linear range from 10 to 1500 µM with a low limit of detection (LOD) of 89.6 nM and a high sensitivity of 107.3 µA mM−1 cm−2. Importantly, as-developed Nb(BTC)MOF@CNF/GCE sensor is enabled to detect histamine in fish and banana samples stored for different periods of time, which thus indicates its practical viability as analytical histamine detector. [ABSTRACT FROM AUTHOR]

Abstract MnO 2 - and boron-incorporated polyacrylonitrile (PAN)/pitch-based carbon nanofiber (PPBMn) composites for electrochemical supercapacitors are successfully fabricated by one-step electrospinning using a combined solution of MnCl 2 , B 2 O 3, PAN, and pitch. The surface morphologies, microstructures, surface chemical states, and texture properties of the PPBMn composites are investigated and the effect of the MnCl 2 content on the electrochemical performance in aqueous electrolytes is also examined. The PPBMn composites exhibit a high specific surface area with mesoporous structure, and boron and MnO 2 functional groups as electroactive sites. Enriched boron and MnO 2 functional groups provide low internal resistance of charge diffusion by better wettability of electrolyte ions into the pores and also accommodate more charges, leading to high gravimetric capacitance and energy density, and enhanced cycling stability. Therefore, the PPBMn series exhibits superior electrochemical performance through the combined functions of their double-layer capacitance and pseudo-capacitive character through the high porosity, higher attractive force by the surface chemical activity and the wettability between the electrode and electrolyte. Highlights • Incorporation of MnO 2 into boron-enriched eCNF are fabricated by electrospinning. • PPBMn reveals a large specific surface area and electrochemically active sites. • Boron and MnO 2 groups provide better wettability of ions and accommodate more charges. • Enhanced electrochemical property is combined with double-layer and pseudo-capacitance. [ABSTRACT FROM AUTHOR]

Highlights • Low-cost photocatalytic activity under visible light of pitch-based porous CNF aided by zinc oxide. • Charge reservoir and transport of the PP-based CNFs by surface area and electrical conductivity. • PP-based CNFs act as a trapping center to separate the photoinduced e−-h+, thereby extending the visible light. Abstract To explore and develop an economical, novel, and effective photocatalyst for the degradation of methylene blue (MB) under visible-light irradiation, polyacrylonitrile (PAN)/pitch-based carbon nanofibers (CNFs) with ZnO (PPZn) are successfully produced by one-step electrospinning of PAN, pitch, and zinc acetate in dimethylformamide (DMF) solution. The charge separation rate, adsorption capacity, and visible-light harvesting effects are all enhanced by the synergistic effect of PAN/pitch-based CNFs and ZnO coupling. The resulting PPZn photocatalysts exhibit excellent removal capacity of 100% of MB within 30 min and a kinetic rate constant of 0.018 min−1 under visible light. PPZn also exhibits a consistent and stable photocatalytic performance by maintaining nearly 100% removal of 15 ppm MB over 8 regeneration cycles. The PP-based CNFs in PPZn act as a charge reservoir to afford fast transport for suppressing the e--h+ recombination and high electrical conductivity induced by the pitch, thereby expanding the visible-light response. The PP(3)Zn composites demonstrate a promising potential as a low-cost photocatalyst material offering excellent photocatalytic efficiency in the visible-light spectrum. [ABSTRACT FROM AUTHOR]

Manganese oxide (MnO 2 ) and boron dual-decorated carbon nanofibers with hierarchical micro/mesopores (PPMMABMn) were fabricated by electrospinning and subsequent thermal technique to study the effect of the MnCl 2 content on the microstructures and electrochemical properties in application as an electrode material of electrochemical capacitors (ECs). Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), mapping images, and X-ray photoelectron spectroscopy (XPS) confirm the compositions and amounts of boron and MnO 2 in the CNF composites. Furthermore, the nitrogen sorption isotherms and the Brunauer-Emmett-Teller (BET) theory reveal the co-existence of micropores and mesopores, with the latter representing more than 50% of the pore volume fraction. A high MnO 2 content and many mesopores in PPMMABMn composites contribute to the main redox pseudocapacitance of MnO 2 and low internal resistance for ion charge diffusion for good capacitive performance in KOH aqueous electrolyte in terms of large specific capacitance, great energy density and high rate capability. [ABSTRACT FROM AUTHOR]

Electrospun boron-enriched PAN/pitch-based CNF composites (PPB) are developed by combining B 2 O 3 as the boron source, and pitch and polyacrylonitrile as the carbon precursor, to introduce surface boron heteroatoms and enhance the electrical conductivity in CNF composites. PPB-10 electrodes prepared from 10 wt% B 2 O 3 added to the PAN/pitch solution exhibit a high specific capacitance of 180 Fg −1 at a discharge current density of 1 mAcm −2 and energy density of 22.0–15.8 Whkg −1 in the power density range of 400–10,000 W kg −1 in 6 M KOH aqueous electrolyte, owing to the larger amount of heteroatoms such as boron and the addition of the pitch, thereby inducing fast and reversible surface redox reactions in aqueous electrolyte. Furthermore, the highly mesoporous PPB-10 composite offers 92% capacity retention of the initial current density and a low equivalent series resistance through quick pathways for ion transport and charge diffusion. Hence, these PPB composites exhibit a very promising potential as electrode materials for supercapacitor electrodes due to boron incorporated into the carbon framework, suitable porosity, and good electrical conductivity. [ABSTRACT FROM AUTHOR]

PAN/pitch-based carbon nanofiber/MnO 2 (PPMn-CNF) composites are fabricated by electrospinning to obtain a new type of electrode material for application in high-capacitance electrical double-layer capacitors (EDLCs). The energy storage capabilities of these PPMn-CNFs reveal a maximum specific capacitance of 188 Fg -1 and a maximum energy density of 20.5–15.8 Whkg −1 in the power density range of 400–10,000 Wkg -1 . Furthermore, the PPMn-CNF electrode shows good rate capability without a significant decrease at high rate. The high electrical conductivity of the pitch promotes the accessibility into the micropores and the adsorption efficiency onto the electrode surface of electrolyte ions. Therefore, the high electrical conductivity and large surface area of the PPMn-CNF composites are beneficial for the storage of charge carriers and induce a short course for charge transport, which maximizes the specific capacitance and ensures good capacitive capability. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) with controllable pore sizes are fabricated by a simple electrospinning method with the help of boron trioxide (B 2 O 3 ), and their electrochemical properties as electrodes are investigated in aqueous electrolyte. The optimized result is obtained with a B 2 O 3 concentration of 10 wt% in a spinning solution, offering a large specific surface area of 1065 m 2 /g with a mesopore volume fraction up to 35%, pore size range of 2–3 and 20–50 nm, and many heteroatoms. The CNF composite with 10 wt% B 2 O 3 concentration (PMB-10) shows a high gravimetric capacitance of 126.31 F/g with a capacitance retention of 84%, and a high energy density of 12–18 W h/kg in the power density range of 400–10,000 W/kg. Thus, the porous structures and heteroatom contents of the PMB composites can be controlled by varying the B 2 O 3 content as the pore expanding agent, as well as heteroatom generator, to optimize the electrochemical performance in an aqueous electrolyte. [ABSTRACT FROM AUTHOR]

Porous electrically conducting carbon nanofibers with MnO 2 (P-Pitch-PM-Mn) are prepared by electrospinning blended solutions of pitch, poly(methyl methacrylate) (PMMA), manganese(II) chloride (MnCl 2 ), and polyacrylonitrile (PAN) in N , N -dimethylformamide (DMF), and their electrochemical properties are investigated as supercapacitor electrodes. In these nanofiber composites, the pitch plays a key role in developing the surface area and electrical conductivity, whereas the mesopore volume fraction is increased with PMMA addition. These characteristics afford the P-Pitch-PM-Mn composite with the best electrochemical performance as a material for supercapacitor electrodes with a maximum specific capacitance of 183 F g − 1 at 1 mA cm − 2 , high energy densities of 25–20 W h kg − 1 in the power density range of 400 to 10,000 W kg − 1 , and good rate capability in aqueous solution. Thus, the combination of large specific surface area, high conductivity, and suitable mesoporosity induced by pitch and PMMA improves the electrochemical performance of the P-Pitch-PM-Mn electrodes through the effective charge accumulation at the electrode/electrolyte double-layer interfaces and rapid pathways for electrolyte transportation. [ABSTRACT FROM AUTHOR]

• Tubular nanostructured Co 3 O 4 @N-containing CNF is prepared by coaxial electrospinning. • The surface structure of PPMCoU is tuned by controlling the amount of urea. • The micro/mesopores balance aids in adsorption capacity and electron transport. • Many oxygen vacancies provide the number of active sites for the redox reactions. • N-functional groups of the carbon electrode enhance the electrical conductivity. Although N-rich electrode materials have good capacitive performance, further exploration of more efficient and straightforward methods to produce nanoporous carbon materials with a high heteroatom content remains challenging. Tubular nanostructured Co 3 O 4 @N containing carbon nanofibers (PPMCoU(10)) are fabricated by coaxial electrospinning to improve the overall electrochemical performance. The PPMCoU(10) electrode shows a high specific capacitance (193 Fg−1 at 1 mAcm−2), good rate capability (88% capacity retention at 20 mAcm−2), high energy density (24.5 Whkg−1 at 400 Wkg−1), and good cycling stability (only 8.0% loss after 10,000 cycles at 1 mAcm−2). The enhanced stored charge capacity of the PPMCoU(10) electrode is attributed to the synergy of high microporosity with a high surface area, tubular nanostructure, low crystallinity of Co 3 O 4 , many oxygen vacancies, and electrochemically active nitrogen atoms. [Display omitted] [ABSTRACT FROM AUTHOR]

Electrochemical capacitors based on hierarchical porous activated carbon nanofiber ( RuO2 / ACNF) composites are fabricated by one-step electrospinning, and then stabilized at different activation temperatures. The effect of the activation temperature on the structural properties and electrochemical behavior of the RuO2 / ACNF composites is intensively investigated in 6 M KOH electrolyte. The RuO2 / ACNF-800 composites activated at high temperature possess abundant mesopores and larger pores, which improve the electrochemical performance, especially at high charge-discharge rates. The energy storage capabilities of the RuO2 / ACNF-800 electrode prepared at high temperature are as follows: a maximum specific capacitance of 150 F/g and an energy density of 14-20 Wh/kg in the respective power density range of 400 to 10 000 W/kg in an aqueous solution. Furthermore, this electrode exhibits high-rate electrochemical performance with a specific capacitance reduction of less than 28% of the initial value at a discharge current of 20 mA/cm2. Therefore, the hierarchical porous RuO2 / ACNF composites with well-developed mesoporous structure provide low resistance for charge diffusion and a short pathway for ion transportation, yielding good capacitive behavior. [ABSTRACT FROM AUTHOR]

A hybrid of silica decorated on porous activated carbon nanofibers (ACNFs) is fabricated in the form of a web via electrospinning and an activation process as an electrode material for electrochemical capacitors in an organic electrolyte. The introduction of PhSiH 3 (PS) into the polyacrylonitrile (PAN) solution induces a porous ACNF structure containing silica nanoparticles (NPs) via the spontaneous sol-gel process of PS by steam in the subsequent physical activation process. These inorganic-organic hybrid composites of porous ACNF containing silica NPs show superior specific capacitance and energy density in electrochemical tests, along with good rate capability and excellent cycle life in an organic electrolyte, which is attributed to the combination of ACNF's high surface area and silica's hydrophilicity. The electrochemical performance decreases with increasing PS concentration, and this trend is consistent with the specific surface area results, which reveal the rapid formation of a double layer. [ABSTRACT FROM AUTHOR]

Mesopore-enriched activated carbon nanofiber mats incorporating RuO 2 (RuPM-ACNF) are prepared by a simple electrospinning method with the help of poly(methyl methacrylate) (PMMA), and their electrochemical property electrodes are investigated as a supercapacitor electrode. The microstructure of RuPM-ACNF is changed in terms of high specific surface area, narrow pore size distribution, and tunable porosity. The textural parameters affect the electrochemical properties significantly through the variation in PMMA concentration. The active sites, RuO 2 and abundant mesopore structures of RuPM-ACNF not only increase the specific capacitance but also enhance the high-rate electrochemical performance by fast electrolyte ion diffusion into the pores with increasing PMMA concentration. The RuPM-ACNF electrode also exhibits good cycling stability after 3000 charge–discharge cycles, which demonstrates the good stability, long lifetime and high degree of reversibility in repetitive charge–discharge cycling of the RuPM-ACNF electrodes. Therefore, the cooperation of large mesopores induced by PMMA and RuO 2 in the ACNF electrode materials synergistically improves the electrochemical performance because of the electric double-layer capacitance of porous ACNFs and the pseudocapacitance of RuO 2 , resulting in high rate capability, high capacitance, and long cycling life. [ABSTRACT FROM AUTHOR]

RuO 2 /activated carbon nanofiber (ACNF) composites containing graphene are prepared by a simple electrospinning method, followed by physical activated carbonation. We investigate the electrochemical properties as supercapacitor electrodes and the structural properties of these RuO 2 /ACNF materials as a function of the graphene concentration. The porous RuO 2 /ACNF composites exhibit an improved microstructure in terms of increased surface area, large mesopore volume fraction, and increased electrical conductivity with increasing graphene content. The RuO 2 /ACNFs with 3 wt% graphene are characterized as having a large specific surface area of up to 1552.2 m 2 g −1 , mesopore volume fraction up to 53%, high electrical conductivity of over 0.59 Scm −1 , gravimetric capacitance of 180.2 Fg −1 and energy density of 20.4–15.3 Whkg −1 over a power density range of 400–10,000 Wkg −1 in 6.0 M KOH electrolyte. These results suggest that RuO 2 /ACNF with graphene offers the benefits of low resistance for charge diffusion and a short pathway for ion transportation. Therefore, RuO 2 /ACNF with graphene shows good capacitive behavior when applied as an electrode material for supercapacitors in terms of high rate capability, large capacitance, and more efficient energy density. [ABSTRACT FROM AUTHOR]

One-dimensional hierarchical porous carbon nanofibers (CNFs) embedded with Co 3 O 4 nanoparticles in a hollow channel (PPMCo) are fabricated by coaxial electrospinning followed by thermal treatment. The degree to which the CNF surface is exposed to Co 3 O 4 nanoparticles was controlled by the cobalt(II) acetate concentration. The well-controlled structure of PPMCo with porous structure, heteroatoms, and amorphous Co 3 O 4 nanoparticles provided fast ion transport and large reaction surface area, resulting in effective ion migration to the active site and a high rate capacity of the electrode. Benefitting from the unique structure, the PPMCo supercapacitor electrodes displays a high specific capacitance of 188 Fg−1 at 1 mAcm−2, rate capability of 82% when the current density is increased from 1 to 20 mAcm−2, and cycling stability of 93% for 10,000 cycles. The good capacitive performance of the PPMCo electrode is attributed to the synergistic effect of the hierarchical porosity, electroactive material of Co 3 O 4 , high effective surface area, and polar effects by heteroatoms. [Display omitted] • Hierarchical porous CNF embedded with Co3O4 was prepared by coaxial electrospinning. • The degree of CNF exposed to Co3O4 was controlled by the Co(OAc)2 concentration. • The hollow core of the core part provides a fast electron transport channel. • Amorphous Co3O4 helps transport ions by reducing the charge transfer resistance. • The heteroatom functional groups on the carbon surface enhance the pseudocapacitance. [ABSTRACT FROM AUTHOR]

Nanoporous carbon nanofibers (CNFs) are produced by incorporating tetraethyl orthosilicate (TEOS) into polyacrylonitrile (PAN) via electrospinning, and their electrochemical properties are investigated as an electrode in supercapacitors. TEOS is used as a pore generator in the PAN-based precursor for the CNFs with stabilized Si-related functional structures. The microstructures (e.g., nanometer-size diameters, high specific surface areas, narrow pore size distributions, and tunable porosities) and some of the surface functionalities of the CNFs are affected by the TEOS concentration. The electrode with these characteristics demonstrates better supercapacitor performance in terms of capacitance, energy, and power efficiency, which is attributed to the synergistic effect between the double-layer capacitance and the pseudo-capacitive effect. [ABSTRACT FROM AUTHOR]

Abstract: Porous carbon nanofibers with Si O C/Si O Si group (Si/ACNF) mats are produced by incorporating tetraethyl orthosilicate (TEOS) into polyacrylonitrile (PAN) via electrospinning/activation, and their electrochemical properties as a supercapacitor electrode are investigated. The Si/ACNF exhibits a high surface area of up to 1386.91m2 g−1 as result of the ultramicropore size distributions centered at approximately 0.8nm and mesopore volume fraction up to 38%. The gravimetric capacitance of the Si/ACNF webs in an organic electrolyte is 91.95Fg−1, and the energy densities are 59.72–88.23Whkg−1 over the power density range of 1000–20,000Wkg−1. The electrochemical capacitance of a Si/ACNF electrode is closely related to the pore size distribution, surface area, and ionic accessibility of the electrode material, providing a large charge capacity and high rate capability. [Copyright &y& Elsevier]

Abstract: Organic-inorganic hybrid composite carbon nanofibers (CCNFs) are prepared by one-step electrospinning and subsequent thermal treatment using polyphenylsilane (PPS) as an inorganic precursor. We investigate the structural properties and electrochemical behavior of these CCNF materials when applied as supercapacitor electrodes as a function of the carbonization temperature ranging from 800 to 1000°C. The introduction of PPS induces thermal stability for the organic-inorganic hybrid CCNFs via the incorporation of a porous structure with stabilized functional structures such as silicon oxynitride (SiOxNy) and silicon oxycarbide (SiOxCy). This phenomenon is attributed to the synergistic effect of both the double-layer capacitance and the pseudo-capacitive effect induced by the porous carbon layer and the some surface functionalities), thereby providing high charge capacity, power and energy density. [Copyright &y& Elsevier]

Abstract: Carbon nanofibers (CNFs) containing boron and nitrogen are prepared from polyacrylonitrile and boron trioxide (B2O3) by using simple electrospinning. The B2O3 introduction into a PAN solution causes a porous structure with stabilized [O]BN functional groups to develop in the processes of stabilization and carbonization. The pore structure and the functional groups such as B atoms and [O]BN introduce synergistic effects by not only increasing the power density but also the energy density, as shown by the results. The energy storage capabilities of the electrode prepared from 20wt% B2O3 added to the PAN solution are as follows: a capacitance of 184.0Fg−1 and an energy density of 18.7–25.2Whkg−1 in the respective power density range of 400–10,000Wkg−1 in 6M KOH electrolyte. Hence, these CNFs exhibit a very promising potential as electrode materials for electrical double-layer capacitors due to their unique microstructure and proper proportion of heteroatoms. [Copyright &y& Elsevier]

Abstract: The vanadium pentoxide (V2O5)/carbon nanofiber composites (CNFCs) were prepared from polyacrylonitrile/V2O5 in N,N-dimethylformamide by a simple electrospinning method, and their electrochemical properties as supercapacitor electrodes were investigated. Different loadings of V2O5, the microstructures of the CNFCs (e.g., nanometer-size diameters, high specific surface areas, narrow pore size distributions, and tunable porosities) were changed, and the textural parameters significantly affected the electrochemical properties of the composites. The CNFC capacitors delivered the high specific capacitances of 150.0Fg−1 for the CNFCs in an aqueous, with promising energy densities of 18.8Whkg−1, over a power density range of 400–20,000Wkg−1. The CNFCs simultaneously exhibited excellent capacity retention. [Copyright &y& Elsevier]

Abstract: The polar group SiOC introduction was made into the carbon nanofibers, and the resulting carbon nanofiber composite (CNFC) electrodes were evaluated as an electrochemical capacitor. Simple thermal treatment of the electrospun nanofibers from the blend solution of tetraethyl orthosilicate and graphene with polyacrylonitrile introduced suitable micropores to accommodate many ions without a pore creation step such as oxidative activation. The supercapacitor electrode prepared with 3wt% graphene showed high specific capacitance of 144.80Fg−1, energy density of 18.49–10.83Whkg−1 in the respective range of 400–30,000Wkg−1 in 6M KOH aqueous solution. The specific capacitance and energy density were 2 and 3 times higher, respectively, in comparison with pristine CNF. [Copyright &y& Elsevier]

Abstract: Polyacrylonitrile/poly(methyl methacrylate) (PMMA) fibers containing graphene are prepared by the electrospinning method, and hierarchical porous carbon nanofibers (CNFs) are obtained after subsequent heat treatment. The hierarchical porous CNFs have an improved structure and properties because of the increased surface area, unique nanotexture and increased electrical conductivity due to the dispersion of graphene. The carbonized fiber exhibits a high surface area (over 500m2 g−1) as result of the narrow ultramicro- and mesopore size distributions (centered at approximately 0.7 and 3.7nm, respectively), and a broad mesopore size distribution ranging from 10 to 50nm. The hierarchical pore structures are introduced by the evolution of small gas molecules during the decomposition of the PMMA during heat treatment. The highest specific capacitance of the CNFs is 128Fg−1, and the energy densities are 16.0–21.4Whkg−1 in an aqueous solution and 75.0–58.2Whkg−1 in an organic electrolyte over a power density range of 400–20,000Wkg−1. Under constant current charging/discharging at 1mAcm−2 for 100 cycles, the stability of the CNFs in a 6M KOH aqueous electrolyte decreases by ∼17% compared with the initial specific capacitance value. [Copyright &y& Elsevier]

Abstract: Graphene/carbon composite nanofibers (CCNFs) with attached TiO2 nanoparticles (TiO2–CCNF) were prepared, and their photocatalytic degradation ability under visible light irradiation was assessed. They were characterized using scanning and transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and ultraviolet–visible diffuse spectroscopy. The results suggest that the presence of graphene embedded in the composite fibers prevents TiO2 particle agglomeration and aids the uniform dispersion of TiO2 on the fibers. In the photodegradation of methylene blue, a significant increase in the reaction rate was observed with TiO2–CCNF materials under visible light. This increase is due to the high migration efficiency of photoinduced electrons and the inhibition of charge–carrier recombination due to the electronic interaction between TiO2 and graphene. The TiO2–CCNF materials could be used for multiple degradation cycles without a decrease in photocatalytic activity. [Copyright &y& Elsevier]

Abstract: Silica/carbon nanofiber (CNF) composites have been successfully prepared by a graphene /polyacrylonitrile (PAN) solution containing tetraethoxysilane (TEOS) using electrospinning, followed by stabilization and carbonization. The graphene directly accelerates the formation and growth of nanosized silica particles on the fiber surface. The silica/CNF composites are characterized by SEM, TGA, FTIR spectra, a 29Si MAS-NMR spectrum, and the crystallite parameters. This technology can be applied to prepare homogeneously dispersed nanosized metal-oxide particles on CNF composites. [Copyright &y& Elsevier]

Abstract: Polyacrylonitrile (PAN)/polyphenylsilane (PPS)-based composite carbon nanofibers (CCNFs) are prepared by one-step electrospinning and subsequent thermal treatment to produce organic-inorganic hybrid CCNFs. We investigate the electrochemical behavior and structural properties of these CCNF materials as a function the PAN/PPS ratio. The CCNFs show large specific surface area, high electrical conductivity and high thermal stability. In addition, the electrochemical performance of the organic–inorganic hybrid CCNF electrode is improved by the special porous structure and the silicon oxycarbide (Si–O–C)-related structure. [Copyright &y& Elsevier]

Polyacrylonitrile/phenylsilane/cyclodextrin-derived carbon nanofiber composites (PPSCD) are prepared by one-step electrospinning using α-cyclodextrin (CD) and phenylsilane (PS) as the pore generator, because many organic molecules are easily decomposed by a self-activation process during heat treatment. We optimize the effects of different α-CD contents on the electrochemical performance of the PPSCD derived from the inclusion complex of PS/α-CD. The PPSCD electrode exhibits a high specific capacitance of 193 F g−1 at 1 mA cm−2 and a high energy density of 23.5–16.21 Wh kg−1 at power densities ranging from 400 to 10,000 W kg−1 in an aqueous solution. The superior electrochemical properties of PPSCD are favorable for ion storage and transfer due to the synergistic effects of high specific surface area and well-balanced micro/mesoporosity. Hence, PPSCD electrodes have a promising potential as a supercapacitor electrode material in the development of high performance energy storage systems. • The effects of different α-CD contents are optimized for maximizing the porosity. • Organic molecules of α-CD are easily decomposed by a self-activation process. • The superior porosity of PPSCD is favorable for ion storage and transfer. • Highly porous PPSCD(5) is applied to high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Triple-layered boron-containing carbon nanofibers (CNFs) with hollow channels (PPMPB) are fabricated via step-by-step electrospinning for high-performance freestanding supercapacitors. Polyacrylonitrile (PAN)-based CNFs in the first layer are chosen as the support layer material because of their excellent chemical stability and electrospinnability. The well-developed hollow channels provided fast ion diffusion in the second layer of PAN/poly(methyl methacrylate) (PMMA)-based CNFs. The surface boron functional groups constituting the third layer contribute to the pseudo-capacitance. The symmetric supercapacitor of the PPMPB electrodes delivers a maximum specific capacitance of 180 Fg−1 at 1 mAcm−2, a high energy density of 22.38 Whkg−1 at a power density of 400 Wkg−1, and an excellent retention rate of 96% after 10,000 cycles in aqueous solution. The excellent electrochemical performance is attributed to the unique sandwich nanostructure with a three-layer structure, in which the factors representing the electrochemical properties of each layer do not interfere with each other. Therefore, a moderate amount of boron and the high surface area of the triple-layer structured PPMPB can be fully utilized as an excellent conductive network and electroactive sites, which is expected in a high-performance supercapacitor electrode. [Display omitted] • Triple-layered boron-containing CNFs were fabricated by step-by-step electrospinning. • The CNFs in the first layer provide active adsorption sites for EDLC. • Hollow core present in the interlayer serves as an excellent conductive network. • A moderate amount of boron in the third layer is utilized as the electroactive site. • Symmetric PPMPB(20) electrode showed good rate capability and long cycle life. [ABSTRACT FROM AUTHOR]

• Porous PPSCD are fabricated by carbonization without any additional activation step. • CD and PS are used as sources of pore-forming reagents at high temperature. • Capacitive performance is well optimized by adjusting the PS concentration. • Highly porous PPS(3)CD is applied to high-performance supercapacitors. Highly porous carbon nanofiber composites (PPSCD) are prepared through one-step electrospinning using a mixture of polyacrylonitrile (PAN), phenylsilane (PS), and α-cyclodextrin (CD) in a carbonization process without any additional physical/chemical activation step. Their capacitive performance is well optimized by adjusting the PS concentration. The PS concentration of 3 wt% in a PAN and CD polymer solution provides a large specific surface area of 563 m2g−1, which is advantageous for double layer capacitance for charge storage and rapid ion transport in charge–discharge processes. The PPSCD electrode shows a maximum specific capacitance (189 Fg−1 at a current density of 1 mAcm−2) and high energy density (22–15 Whkg−1 at power densities ranging from 400 to 10,000 Wkg−1) in a 6 M KOH aqueous solution. [ABSTRACT FROM AUTHOR]

In this study, the microwave, i.e. 0.5–10 GHz, transmission characteristics of carbon nanofiber (CNF) with three different micrometer-scale thicknesses were experimentally investigated using a coplanar waveguide transmission line. In the experimental results, when the film of CNF was thick, the signal transmission level (S 21 -magnitude) was significantly lower and its phase (S 21 -phase) was shifted toward the low-frequency region. Based on the obtained S 21 -parameter (S 21 -magnitude and S 21 -phase), the electric permittivity (ε) of CNF was extracted and showed clear differences depending on the thickness, i.e., ε thin = 1.20 (0.28), ε middle = 1.84 (0.60), ε thick = 6.30 (1.15) at 0.5 GHz (7.8 GHz). From the analysis of electromagnetic fields, the microwave conductivity (σ mw) of CNF linearly increased with the increasing thickness, i.e., σ mw/thin = 0.35 (S/m), σ mw/middle = 0.58 (S/m), σ mw/thick = 0.75 (S/m), due to enhanced electromagnetic field coupling between the film of CNF and the CPW line. As a result, we demonstrated that the film of CNF has a significant attenuation effect on signal transmission in the microwave regime, depending on micrometer-scale changes in film thickness. Image 1 [ABSTRACT FROM AUTHOR]

The aim of this study is to develop the templateless fabrication of hierarchical porous carbon nanofiber (CNF)/MnO 2 composites (PMnCD) derived from polyacrylonitrile (PAN)/cyclodextrin (CD) and investigate their morphological and electrochemical properties to determine the different capabilities of inclusion complexes (ICs) formed by α-CD, β-CD and γ-CD. Among the three CD phases, the PMnCD(β) composite using β-CD exhibits a hierarchical porous structure with large specific surface area of 499 m2g-1, and total pore volume of 0.32 cm3g-1, which helps with adsorption efficiency and accumulation of hydrated molecules for double-layer formation. In addition, the numerous mesopores and nitrogen functionalities of the PMnCD(β) composite provide fast diffusion channels for electrolyte ions and higher attractive interactions with electrolyte ions through the pseudocapacitive character. As a result, the PMnCD(β) electrode has a high specific capacitance of 228 Fg-1 at 1 mAcm−2, maximum energy density of 25.3–16.0 Whkg−1 in the power density range of 400-10,000 Wkg-1, and excellent cycling stability of more than 94% after 10000 cycles in aqueous solution, thereby offering potential applications for supercapacitors. Image 1 • Hierarchical porous PMnCD is fabricated by electrospinning without a template. • β-CD stabilizes and encapsulates MnCl 2 through the good size match of β-CD and MnCl 2. • PMnCD(β) shows a large specific surface area for accumulation of ions. • Many mesopores and nitrogen groups of PMnCD(β) provide fast ion diffusion. • Hierarchical porous PMnCD(β) is applied to high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Activated carbon nanofibers ( ACNFs) containing oxygen, nitrogen, and silicon are prepared from polyacrylonitrile ( PAN) and phenylsilane ( PS) by simple electrospinning. The PS introduction into a PAN solution causes a porous structure with functional groups by spontaneous sol-gel reaction without any catalyst of PS in the physical activation process. PS-ACNF electrode shows the highest specific capacitance, 200 F/g, and the highest energy density, 25.6-119.19 W h/kg in the range of 400-10 000 W/kg in a 6 M KOH aqueous solution. Our results suggest that the porosity and functional groups of the supercapacitor electrodes have a strong impact on the enhanced electrochemical properties, resulting from an increased electroactive surface area. [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-standing Cu-Co(2-Meim)MOF@CNF mat for simultaneous detection of dopamine and tyramine. • MOF@CNF matrix possesses high surface area and numerous functionalities as adsorption sites. • Cu-Co(2-Meim)MOF@CNF/GCE exhibits superb catalytic responses to dopamine and tyramine. • High potentiality of the hybrid sensor to dopamine and tyramine in cheese and banana. Early monitoring of histamine and tyramine levels in foodstuffs could protect against several diseases. In the present study, a self-standing copper-cobalt(2-methylimidazole) MOF anchored carbon nanofiber hybrid mat (Cu-Co(2-Meim)MOF@CNF) was prepared for the simultaneous detection and quantification of dopamine and tyramine in cheese and banana samples. As-prepared Cu-Co(2-Meim)MOF@CNF hybrid mats are highly porous with a large surface area, and also possess excellent hydrophilicity, which allows the analyte molecules to easily access the redox-active metal sites of the MOF matrix and subsequently enhance the sensitivity. The functional groups within the MOF matrix can also function as active adsorption sites during electrocatalysis. At the acidic condition (pH = 5.0), the Cu-Co(2-Meim)MOF@CNF exhibited improved catalytic activity and strong electrochemical sensitivity toward dopamine (DA) and tyramine (TY) with faster electron transfer kinetics and significant fouling resistance. The oxidation reactions of dopamine and tyramine at the hybrid electrode were irreversible and diffusion-controlled. The Cu-Co(2-Meim)MOF@CNF/GCE sensor demonstrated a broad linear range from 5 to 800 µM along with a low LOD of 44.2 nM and 52.7 nM for dopamine and tyramine, respectively. The hybrid sensor exhibited excellent anti-interference properties and long-term storage stability for up to 30 days. It is noteworthy that the Cu-Co(2-Meim)MOF@CNF/GCE sensor has demonstrated the capability of detecting dopamine and tyramine in cheese and banana samples, respectively, which would be helpful for food analysis and food safety. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hollow N -rich multilayered CNFs are prepared by sequential electrospinning. • The top-layer PAN/urea-based CNF acts as charge storage and pseudocapacitance. • The interlayer PMMA-based CNFs with tubular structure promote charge transport. • The bottom layer of PAN-based CNFs with numerous micropores provides charge storage. N -rich multilayered carbon nanofibers with hollow channels (PPMPN) are fabricated to fully utilize the mesopores, micropores, and nitrogen-functional groups of carbon nanofibers (CNFs) for superior electrochemical properties. Among all composites, the PPMPN(10) exhibits high specific surface area (570 m2g−1) with mesopore volume fraction (42%) and rich surface functionalities (∼7.25at% nitrogen and ∼ 16.1at% oxygen), helping to improve electrochemical performance. The performance of the symmetric supercapacitor of the PPMPN was significantly improved in terms of its specific capacitance of 189 Fg−1 at 1 mAcm−2, good retention of 80% (when the current density is increased from 1 to 20 mAcm−2), energy density of 23.5 Whkg−1 at a power density of 400 Wkg−1, and cycling stability of 94% for 10,000 cycles. The top layer plays a role in charge storage/transport by increasing electrical conductivity due to N -functional groups. The intermediate layer with tubular 1D nanostructures enhances the diffusion of electrolyte ions even at higher current densities. The bottom layer composed of numerous micropores serves as a charge storage layer. Therefore, in the multilayer CNF, the micropores/mesopores and N -functional properties of each layer do not interfere with each other, and the advantages of the factors of each layer are maximized in the electrochemical properties. [ABSTRACT FROM AUTHOR]

Heteroatoms (B, N, O)-containing porous manganese oxide (MnO 2 )/carbon nanofiber (MnB-CNF) materials are prepared by one-step electrospinning method via polyacrylonitrile (PAN) and manganese(II) chloride (MnCl 2 ) in dimethylformamide (DMF) solution containing different concentrations of B 2 O 3 . The MnB-CNF electrode exhibits optimized electrochemical behavior with a high energy density of 22.6 Whkg − 1 at a power density of 400 Wkg − 1 and a specific capacitance range of 210–160 Fg − 1 in the discharge current density range of 1.0 to 20 mAcm − 2 in aqueous KOH electrolyte. The higher electrochemical performance of MnB-CNF as a result of the electrochemical double-layer capacitor (EDLC), compared to regular Mn-CNF without B-based functional groups, is attributed to well-balanced meso- and micropores affecting the easy adsorption and transport of electrolyte ions, in addition to the pseudocapacitive redox reactions from MnO 2 , N, O, and extra numerous B in alkaline electrolytes. Thus, tailoring the pore structures with proper specific surface area, pore size, and number of heteroatoms is crucial for optimizing their electrochemical properties in the combined efforts to develop EDLCs and pseudocapacitance. [ABSTRACT FROM AUTHOR]

Hierarchically structured carbon nanofiber/graphene/MnO 2 (CGMn) hybrid with oxygen and nitrogen functionalities was fabricated in the form of a web via electrospinning as an electrode material for supercapacitors. The CGMn electrode exhibited a high capacitance (225 Fg −1 at 1 mAcm −2 ), enhanced energy and power efficiency (15.8–13.6 Whkg −1 in the power density range of 197–4000 Wkg −1 ), and excellent capacitance retention (13% of the initial value at a discharge current of 20 mAcm −2 ) in a 6 M KOH aqueous electrolyte, because of the combination of the double-layer capacitance and the pseudocapacitive character associated with the surface redox-type reactions. The porosity and the number of heteroatoms of the CGMn composite were adjusted by changing the PMMA concentration and carbonization temperature. Therefore, the oxygen- and nitrogen-containing hierarchical porous CGMn hybrid prepared by a simple method is a promising candidate as an electrode material for supercapacitors. [ABSTRACT FROM AUTHOR]

Hierarchical porous MnO 2 /carbon nanofiber composites with hollow cores (MnPMCNFs) are fabricated by a simple electrospinning method using poly(methyl methacrylate) (PMMA) for electrochemical capacitor electrodes. The introduction of PMMA into the PAN solution aids the uniform dispersion of the amorphous MnO 2 particles as a stabilizer and increases the specific surface area with numerous hollow cores, thereby aiding the electrolyte diffusion from the exterior into the interior of the electrode material. Electrochemical measurements of the MnPMCNFs reveal a maximum specific capacitance of 228 Fg −1 with a capacitance retention of 88% and high energy densities of 27–18 Whkg −1 in the power density range of 400 to 10,000 Wkg −1 in aqueous KOH electrolyte. This impressive electrochemical performance of the MnPMCNF electrode highlights the importance of incorporating the MnO 2 nanostructure and hierarchical structure into the composite, owing to the synergistic contribution of the redox pseudocapacitance and the electric double layer capacitance. [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]

RuO 2 nanorod-decorated tubular carbon nanofibers(CNFs) are carefully fabricated by adjusting the recrystallization temperature for use in high-performance electrochemical capacitors. The tubular structured CNFs/RuO 2 electrodes provide a short diffusion path for the ion transport through the inner hollow channel that allowed the maximum utilization of the active sites of the amorphous RuO 2 nanomaterials at the electrode/electrolyte interface. The optimized the tubular structured CNFs/RuO 2 electrodes exhibit good rate capability with a high surface capacitance, energy density, and good long-term cycling stability of 190 Fg−1, 22 Whkg−1, and 94% after 10,000 cycles, respectively, in an aqueous solution. The asymmetric cell presents a wide and stable operating voltage window, which greatly improves the energy density stored in the asymmetric device. In addition, there is no noticeable difference in the electrochemical properties under bent states, making it a flexible energy storage device for wearable applications. Hence, flexible supercapacitors using CNFs/RuO 2 electrodes with the tubular structure show low resistance, high capacitance, good rate retention, and excellent cycle stability, making it a promising material for energy storage applications. [Display omitted] • RuO 2 nanorod-decorated tubular CNFs are prepared via the recrystallization process. • CNFs/RuO 2 electrodes exhibit good rate capability with a high capacitance, energy density, and long-term cycling stability. • CNFs/RuO 2 electrode under bent states makes it a flexible energy storagCNFs/RuO2 electrodes exhibit good rate capability with a high capacitance, energy density, and long-term cycling stability.e device for wearable applications. [ABSTRACT FROM AUTHOR]

• Sandwich-structured C/Mn/C with a triple layer were fabricated by electrospinning. • Well-preserved MnO 2 NPs in the interlayer are utilized as electroactive sites. • Hollow core present in the interlayer serves as an excellent conductive network. • Symmetric C/Mn(10)/C electrode showed high specific capacitance and long cycle life. • Asymmetric C/Mn(10)/C offers high energy density in a high potential window. Sandwich-structured carbon nanofiber/MnO 2 /carbon nanofiber composites with a triple layer are fabricated by electrospinning. The optimized sandwich-structured composite electrodes exhibit the maximum specific capacitance of 220 F/g at 1 mA/cm2, a high energy density of 24.63 Wh/kg at a power density of 400 W/kg, and an excellent retention rate of 94% after 10,000 cycles. The stable spatial distribution of MnO 2 nanoparticles between the upper and lower carbon nanofiber webs allowed full use of the well-preserved MnO 2 nanoparticles in the interlayer as electroactive sites, providing better electrochemical performance. Furthermore, the hollow core present in the interlayer serves as an excellent conducting network, providing a short ion diffusion path for both ions and electrons. In addition, the asymmetric supercapacitor shows excellent cycling behavior between 0 and 1.4 V and a large energy density of 44.3 Wh/kg at a power density of 400 W/kg, showing great potential in the development of energy storage devices with high energy density for practical applications. [ABSTRACT FROM AUTHOR]

• Low-cost and pore-controlled PLMn are developed via simple and inexpensive processes. • The pore structures are tailored by varying the carbonization temperature. • PLMn-900 with many mesopores shows good rate capability and cycling stability. • High surface area of PLMn-800 optimizes the adsorption efficiency of the electrolyte ions. Low-cost porous carbon nanofibers with MnO 2 are developed via simple and inexpensive processes by using lignin as an affordable carbon precursor and generator of porous structures through one-step electrospinning and carbonization without requiring any other activating agent and process. The lignin-based carbon nanofiber/MnO 2 composites carbonized at high temperature have a high mesoporosity induced by pore opening effect, and thus exhibit a high capacitance retention of 87 % and optimum cycling stability with 93 % retention due to the excellent chemical reversibility. Further, the large surface area with many micropores derived from the low carbonization temperature affords high capacitive performance with a maximum specific capacitance of 212 Fg−1 at low current density and a high energy density of 26.5 Whkg−1 at a power density of 400 Wkg−1. These eco-friendly, low-cost, and pore-controlled MnO 2 /CNF composites have been designed with optimized carbonization temperature and lignin addition to enhance their capacitive properties. [ABSTRACT FROM AUTHOR]

A new type of PAN/phenylsilane-based CNF (PPSCD) composite with inclusion complex (IC) is prepared by one-step electrospinning for high-performance electrode materials for supercapacitors. All three cyclodextrin phases (α-CD, β-CD and γ-CD) exhibit different capabilities for the formation of ICs that depend on the size/shape match and binding force between the host CD cavity and the guest molecule of phenylsilane (PS). The effect of the stronger binding and greater interaction of PS in the cavity of α-CD on the morphology and structural properties of the electrospun CNFs are investigated by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and 29Si CP-MAS NMR. The inclusion of small PS molecules is more selective in α-CD, possibly due to stronger binding and greater interaction of PS in the cavity as compared to β- and γ-CD. The PPSα-CD electrode demonstrates superior specific capacitance (173 Fg−1 at a current density of 1 mAcm−2) and high energy density (22.0–8.0 Whkg−1 at power densities ranging from 400 to 10,000 Wk−1) in an aqueous solution. Therefore, the highly conductive PPSα-CD composite provides efficient transport of electrolyte ions and low resistance for charge diffusion in the electrolyte, thereby yielding good capacitive behavior. Unlabelled Image • A new type of PPSCD with ICs is fabricated by one-step electrospinning. • The larger γ-CD is less interactive with PS, so more silica is formed. • PPSγ-CD exhibits low conductivity due to the insulating nature of the silica particles. • The inclusion of PS is more selective in α-CD due to size matching. • Highly conductive and porous PPSα-CD is applied to high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

To develop economical and high-performance supercapacitor electrodes in an aqueous electrolyte, polyacrylonitrile (PAN)/pitch/lignin-based carbon nanofibers (CNFs) with ZnO (PPL-Zn) are successfully fabricated by one-step electrospinning of PAN, pitch, lignin, and zinc acetate. The oxygen-rich lignin in the PPL-Zn electrodes induces porosity on the fiber surface by eliminating many functional groups such carboxylic, carbonyl, hydroxyl and ketone and organic moieties in the simple heat treatment without any activation agent/activation process. Moreover, the many aromatic components, high carbon content, and low glass transition temperature of lignin are excellent precursors to CNF composites. In addition to lignin, pitch is used as a precursor to CNF to reduce the cost and increase the carbon yield and electrical conductivity of the CNFs. These characteristics afford PPL-Zn(5) (5 wt% of zinc acetate relative to PAN and lignin) with good capacitive behavior for application as supercapacitor electrodes with a maximum specific capacitance of 165 Fg-1 at 1 mAcm−2 with a capacitance retention of 88%, high energy densities of 22–18 Whkg−1 in the power density range of 400 to 10,000 Wkg-1, and excellent cycling performance reduced by only ∼6% after 3000 cycles of charge/discharge due to the synergistic effect of the electrical double layer and the pseudocapacitive effect. Image 107 [ABSTRACT FROM AUTHOR]

2-(Trimethylsilyloxy)ethyl methacrylate (SMA)-derived mesoporous carbon nanofiber composite containing MnO 2 (Si-Mn-CNF) is fabricated by electrospinning method and found to be a very promising candidate for supercapacitor electrodes. Si-Mn-CNF possesses a large surface area of 707 m 2 g − 1 , high pore volume of 2.35 cm 3 g − 1 , and high mesopore fraction of 65%. Herein, SMA is used as an activating agent to develop the mesoporous structure by the thermal decomposition of SMA without activation process. As a result, Si-Mn-CNF exhibits a high specific capacitance of 200 Fg − 1 at a discharge current density of 1 mAcm − 2 and energy density of 23.72 Whkg − 1 at a power density of 400 Wkg − 1 in 6 M KOH aqueous electrolyte, due to the pseudocapacitive character associated with the surface redox-type reactions of the MnO 2 nanoparticles (NPs). Furthermore, the Si-Mn-CNF electrode retains a specific capacitance of over 85% of the initial value at a discharge current density of 20 mAcm − 2 compared with only 40% for Mn-CNF without using SMA, due to the rapid diffusion of electrolyte ions and the decrease of resistive characteristics through the developed mesoporous structures. Therefore, Si-Mn-CNF with high mesoporosity induced by SMA exhibits excellent electrochemical performance in terms of high specific capacitance and energy density, and excellent capacitance retention. [ABSTRACT FROM AUTHOR]

• Thermally stable porous Si-CNF is fabricated by electrospinning using silole. • Silole produces well-developed pores and more oxygen groups on the CNF surface. • Polar oxygen groups provide electroactive sites in the thermally stable Si-CNF. • Thermally stable porous Si-CNF is applied to high-performance supercapacitors. Silole-derived porous carbon nanofibers (Si-CNFs) with oxygen-containing functional groups are prepared by electrospinning using silole as an inorganic precursor to improve the electrode performance. Since silole is easily decomposed and causes high oxygen diffusion rates, it produces well-developed pores and more heteroatoms through spontaneous sol–gel processing of silole in the subsequent stabilization process. The presence of more polar oxygen functional groups on the surface leads to denser adsorption of the electrolyte ions on the surface, thereby improving the electrochemical capacity. The resulting Si-CNF composites deliver a high specific capacitance of 180 Fg−1 and energy density of 23.0 Whkg−1 in an aqueous electrolyte. [ABSTRACT FROM AUTHOR]