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Nickel cobalt phosphide/carbon nanofibers (NiCoP/C) with an average diameter of approximate 200 nm are prepared by electrospinning combined with calcinations. Carbon nanofibers with an average pore size of 10.77 nm as conductive skeletons support the dispersed NiCoP nanoparticles with the size ranging from 20 to 80 nm, providing abundant reactive sites and facilitating the electrochemical reactions. The specific capacitance of NiCoP/C reaches 478 F g−1 at 2 A g−1 in a 3 M KOH electrolyte, showing superior electrochemical properties compared to its counterparts. After 5000 charge/discharge cycles at 10 A g−1, 99.99 % of initial specific capacitance is retained. In addition, an asymmetric supercapacitor assembled using NiCoP/C as positive electrode and activated carbon as negative electrode exhibits an energy density of 16.72 Wh kg−1 at a high-power density of 7250 W kg−1. Furthermore, the capacitance loss of the supercapacitor is only 0.04 % after 5000 cycles at 10 A g−1, which is mainly attributed to the enhanced stability of NiCoP nanoparticles owing to the assistance of carbon nanofibers as the skeleton. The synergistic effects of NiCoP nanoparticles and carbon nanofibers result in the boosted electrochemical performances. This study demonstrates the potential application of carbon nanofibers as conductive skeletons for nanostructured electrodes. • NiCoP/C nanofibers were prepared by electrospinning without the emission of PH 3. • Carbon nanofibers acted as skeletons and conductive channels for NiCoP. • Assembled NiCoP/C//AC supercapacitor achieved 16.72 Wh kg−1 at 7250 W kg−1. [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]

Although high-rate, long-cycle energy storage devices play a crucial role in the field of energy storage, they are relatively under-reported. This work reports the preparation of fibrous porous carbons ultra-high specific surface area of 3384 m2g-1 derived from medical waste degreased cotto. As electrode material for supercapacitors, the resulted porous carbons demonstrate an ultra-high specific capacitance of 505.5 F g−1 at 0.5 A g−1 in a three-electrode system with 6 M KOH as electrolyte. Assembled symmetric supercapacitors show a specific capacitance of 403.84 F g−1 at 0.5 A g−1 and 294.95 F g−1 at 20 A g−1, with a capacity retention rate of 73.62 %, impressively retaining 82.66 % of the capacity after 300000 cycles at 10 A g−1. The average capacity loss is minimal, at 0.000557 % per cycle. The as-assembled zinc-ion hybrid capacitors (ZIHCs) demonstrate a high energy density of 69.33 Wh kg−1 at 2400 W kg−1 in 2 M ZnSO 4 electrolyte and retain 99.3 % capacity after 120000 cycles at 7 A g−1, suggesting the excellent long cycling stability. These outstanding performances demonstrate a promising solution for recycling and utilizing medical waste-degreased cotton in energy storage devices, also addressing the research gap in high-rate, long-cycle applications. • Medical decreased waste cotton is efficiently transformed into porous carbons. • Porous carbons exhibit an ultra-high specific surface area of 3384 m2g-1. • As For supercapacitors (SCs), it exhibits high capacitance of 505.5 F g−1. • After 300000 cycles, SCs maintain a high-capacity retention rate of 82.66 %. • After 120000 cycles, the ZIHCs maintain a high-capacity retention rate of 99.3 %. [ABSTRACT FROM AUTHOR]

Herein, a kind of hydroxyl and sulfonyl-containing diamine 2,2-bis[4-(3-hydroxy-4-aminophenoxy)phenyl]sulfone (BHAPS) was first synthesized and polymerized with pyromellitic dianhydride (PMDA) to obtain poly(amic acid) (PAA) solution. Then, the PAA nanofibers were fabricated by electrospinning technology, which were further thermally treated at 300 °C for imidization, 450 °C for rearrangement and a certain final temperature for carbonization to obtain carbon nanofibers (CNFs). The PAA concentration, carbonization temperature and thermal rearrangement time were separately optimized, and the HPI-CNF-20-2-800 exhibited better electrochemical properties. Next, the HPI-CNF-20-2-800 was chemically activated with KOH to enhance specific surface area. The preferred A-HPI–CNF–1/3 demonstrated a specific capacitance maximum of 335.0 F g−1 at 0.5 A g−1, with a 73 % capacitance retention at 10 A g−1. Furthermore , the SC device was symmetrically assembled with self-supporting A-HPI–CNF–1/3 membranes, which showed a maximum energy density of 10.42 Wh kg−1 at a power density of 250.0 W kg−1. In addition, the capacitance retention rate of the SC reached 99.94 % even after 50,000 charge/discharge cycles at a current density of 1 A g−1. Thus, this work reports a new precursor to prepare N, O, S co-doped active CNFs with better electrochemical performance, which will provide a reference for the preparation of co-doped self-supporting SC electrodes. • A new kind of diamine monomer containing hydroxyl and sulfonyl was synthesized. • The N, O, S co-doped activated carbon nanofibers were prepared. • The capacitive performance of self-supporting electrode was effectively boosted. [ABSTRACT FROM AUTHOR]

The hydroxyl-functionalized poly (amic acid) (PAA) is first synthesized from 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAP) and 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and electrospun into nanofibers. Then, the PAA nanofibers are thermally imidized at 300 °C and rearranged at 450 °C, followed by an ultimate carbonization to obtain hydroxyl-functionalized polyimide (HPI) based carbon nanofibers (CNFs). When the PAA concentration and carbonization temperature are respectively optimized as 28 % and 800 °C, the obtained CNF specimen HPI(6FAP-6FDA)-28-800 exhibits a better electrochemical performance, with a specific capacitance of 226.3 F g−1 at 0.5 A g−1. Subsequently, the HPI(6FAP-6FDA)-28-800 is subjected to KOH activation treatment. When the CNF/KOH mass ratio is 1/3, the activated sample CNF(6FAP-6FDA)-1/3 displays a maximum specific capacitance of 354.0 F g−1, coupled with a high rate-performance of 75 % (10 A g−1). Furthermore, a button-type supercapacitor (SC) assembled by two pieces of self-supporting CNF(6FAP-6FDA)-1/3 membrane attains an energy density maximum of 11.39 W h kg−1 at a power density of 250 W kg−1. Under 10,000 cycles of charging-discharging, the SC demonstrates an outstanding working stability. In brief, this study reports a novel polymer precursor for the preparation of N, O co-doped active CNFs, and provides an insight into the relationship between the chemical structure, microstructure and electrochemical performance for self-supporting SC electrodes. • The N, O co-doped activated carbon nanofibers were prepared. • The o -hydroxyl polyimides containing rich –C(CF 3) 2 - structures were used as precursors. • The self-supporting electrodes exhibited superior capacitive performances. [ABSTRACT FROM AUTHOR]

Developing a simple and effective method for optimizing lignin structure is a key challenge for the application of biomass-based carbon nanofibers in energy storage and moisture-enabled electricity generation fields. In this work, an effective strategy is designed to prepare novel biomass-based carbon nanofibers. Carbon quantum dots (CQDs) are introduced as functional components into biomass-based carbon nanofibers to optimize the inherent structural defects of lignin. The introduction of CQDs effectively reduces the interaction between lignin macromolecules, thereby increasing the flexibility of lignin macromolecule chain segments. The obtained biomass-based carbon nanofibers exhibit excellent microfiber morphologies and a high degree of graphitization. The specific capacitance and energy density for biomass-based carbon nanofibers as the energy storage device reach 294.4 F/g and 28.3 W h/kg, respectively. Furthermore, the biomass-based moist-electric generator shows high power generation efficiency, the output voltage and output current of a single device reach 0.75 V and 1.8 μA, respectively. Notably, as the number of biomass-based moist-electric generators in series or parallel increases, the overall output efficiency of the device system has a linear relationship, which means that a sufficient number of biomass-based moist-electric generator devices can meet the power supply requirements of larger power systems. This work puts forward a promising strategy to prepare low-consumption, high-performance, and environmentally friendly biomass-based carbon nanofibers for the supercapacitors and moist-electric generators. [Display omitted] • The introduction of CQDs optimize the inherent structural defects of lignin. • CQDs improve the fiber morphology and graphitization degree of carbon nanofibers. • Biomass-based carbon nanofibers exhibit excellent electrochemical performance. • Biomass-based carbon nanofibers can be used for a novel moist-electric generator. • The preparation of novel biomass-based carbon nanofibers was proposed. [ABSTRACT FROM AUTHOR]

In this work, the carbon nanofibers (CNFs) are first prepared by electrospinning the poly(amic acid) (PAA) solution containing aryl imidazole and hydroxyl groups, followed by thermal imidization, rearrangement and carbonization. Then, the CNFs are further treated with KOH to obtain activated CNFs. The effects of the PAA concentration, rearrangement time, carbonation temperature and mass ratio of CNFs/KOH on the electrochemical properties are investigated. The results show that the sample HPI-CNF-20-2-800 displays the best electrochemical performance. After activation, the A-HPI–CNF–1/3 exhibits a maximum specific surface area of 1762 m2 g−1 and pore volume of 0.92 cm3 g−1, leading to a high specific capacitance of 325.0 F g−1 at 0.5 A g−1. Moreover, the specific capacitance can reach 234.6 F g−1 when the current density is 20 A g−1. Furthermore, the symmetric supercapacitor fabricated by A-HPI–CNF–1/3 shows a maximum energy density of 29.17 Wh kg−1, coupled with a power density of 500.0 W kg−1. The capacitance retention rate of the supercapacitor maintains about 99.95% after 20,000 charge-discharge cycles at 1 A g−1. Therefore, this work provides a novel rearrangeable precursor for the preparation of activated CNFs with a considerable electrochemical performance, which will be considered as excellent electrode materials for supercapacitors. [Display omitted] • A novel polyimide precursor with aryl imidazole and hydroxyl groups was synthesized. • The CNFs contained abundant N and O atoms and high specific surface areas. • The supercapacitor with activated CNFs showed a high energy density of 29.17 Wh kg−1. [ABSTRACT FROM AUTHOR]

Abstract In this article, mesoporous carbon nanofibers electrode material is reported using polymer/block copolymer blending system as the precursor. The method combines electrospinning process and high temperature carbonization. In the spinning solution, the polymer of polyacrylonitrile is used as precursor, and the block copolymer of polyacrylic acid- b -polyacrylonitrile- b -polyacrylic acid is used as pore forming additive. Abundant pores are formed due to the sacrifice of the thermoplastic chains in the block copolymers during pre-oxidation and thermal annealing process. The effect of block copolymer content in system on electrochemical performance is investigated. The obtained mesoporous carbon nanofibers display a maximum specific capacitance of 256.3 F g−1 in KOH electrolyte when the amount of the block copolymer is 0.6 g. Furthermore, symmetrical supercapacitor assembled with mesoporous carbon nanofibers exhibits a maximum specific capacitance of 22.34 F g−1 and a capacitance retention of 90% after 80, 000 cycles. Highlights • Polymer/block copolymer blending system is designed as precursor of porous carbon fiber. • Effect of block copolymer content on the electrochemical performance is investigated. • The prepared carbon fibers display a maximum specific capacitance of 256.3 F g−1 • The asymmetric supercapacitor shows a capacitance retention of 90% after 80, 000 cycles. [ABSTRACT FROM AUTHOR]

Abstract Transition metal oxides can introduce high pseudocapacitance to an electric double layer capacitor for storing more electrical charges. Their role can be more than that since they possess high dielectric constant. Here, we propose a self-sustainable bi-functional configuration by eliminating traditional separator of a metal oxide film supercapacitor that is capable of providing good energy storage performance. We take advantage of super-aligned electrospun carbon nanofibers (SA-ECNFs) as an interconnected scaffold, coupling with electrochemical deposition of α-MnO 2 layers at different currents to introduce pseudocapacitance while providing dielectric layer functioning as a separator to assemble a state-of-the-art supercapacitor. The good electrochemical performance of galvanic charge-discharge specific capacitance at 141 F g−1 and energy density at 12.5 Wh kg−1 offers the promising applications in the energy storage field. Graphical abstract Image 1 Highlights • Manganese dioxide films play bifunctions for separation and pseudocapacitance. • The dielectric property of MnO 2 is critical for the membrane-free configuration. • A mechanistic model is proposed for understanding the bi-functions. [ABSTRACT FROM AUTHOR]

Abstract Potassium-pre-intercalated δ-phase MnO 2 is uniformly grown on carbon nanofibers for the positive electrode of asymmetric supercapacitors. An electrospun CNF is chemically activated with KOH at 800 °C for the negative electrode, showing ideal capacitive behavior. The crystallinity of MnO 2 is significantly reduced by the pre-intercalation of K ions into its layered structure. This textural characteristic is beneficial to the K+ diffusion into/out the interlayer structure, leading to effective utilization of the electroactive material of K x MnO 2. This unique composite electrode provides both ideal pseudo-capacitive behavior from K x MnO 2 and excellent electric conductivity from the CNF network, exhibiting a fairly high specific capacitance value of 279 F g-1 at 1 A g−1 with ca. 82.3% capacitance retention from 1 to 32 A g−1. A flexible ASC consisting of the positive K x MnO 2 @CNF electrode, a paper separator, and the negative ACNF electrode is successfully assembled. This cell shows superior ASC performances: a high cell voltage between 0 and 2 V, excellent capacitance retention (10,000 cycles with 10% decay), and simultaneously reaching high specific energy and power of 21.1 Wh kg−1 and 9.5 kW kg−1. The charge storage behavior of this cell without bending and with a bending angle of 90° shows no apparent difference, demonstrating its potential in the next-generation flexible energy storage devices. Highlights • K-preintercalation favors the K+ diffusion into the interlayer structure of δ-MnO 2. • K-preintercalation enhances the pseudocapacitance utilization of δ-MnO 2. • K-preintercalated δ-MnO 2 is uniformly grown on CNF with ideal behavior for flexible ASCs. • This ASC shows excellent cell capacitance retention and flexibility. [ABSTRACT FROM AUTHOR]

Novel 3D Ti 3 C 2 aerogel has been first synthesized by a simple EDA-assisted self-assembly process. Its inside are channels and pores structure. The interconnected aerogel structure could efficiently restrain restacking of Ti 3 C 2 flakes. Thus, it exhibits a large specific surface area as high as 176.3 m 2 g −1 . The electrochemical performances have been measured. The Ti 3 C 2 aerogel achieves a quite high areal capacitance of 1012.5 mF cm −2 for the mass loading of 15 mg at a scan rate of 2 mV s −1 in 1 M KOH electrolyte. An asymmetric supercapacitor (ASC) has been assembled by using the Ti 3 C 2 aerogel electrode as the negative electrode and electrospinning carbon nanofiber film as the positive electrode. The device can deliver a high energy density of 120.0 μWh cm −2 and a maximum power density of 26123 μW cm −2 . A lamp panel with nineteen red light-emitting diodes has been powered by two ASCs in series. [ABSTRACT FROM AUTHOR]

Carbon nanofibers modified with carboxyl groups (CNF-COOH) possessing good wettability and high porosity are homogeneously deposited with amorphous manganese dioxide (amorphous MnO 2 ) by potentiodynamic deposition for asymmetric super-capacitors (ASCs). The potential-cycling in 1 M H 2 SO 4 successfully enhances the hydrophilicity of carbonized polymer nanofibers and facilitates the access of electrolytes within the CNF-COOH matrix. This modification favors the deposition of amorphous MnO 2 and improves its electrochemical utilization. In this composite, MnO 2 homogeneously dispersed onto CNF-COOH provides desirable pseudocapacitance and the CNF-COOH network works as the electron conductor. The composite of CNF-COOH@MnO 2 -20 shows a high specific capacitance of 415 F g −1 at 5 mV s −1 . The capacitance retention of this composite is 94% in a 10,000-cycle test. An ASC cell consisting of this composite and activated carbon as positive and negative electrodes can be reversibly charged/discharged to a cell voltage of 2.0 V in 1 M Na 2 SO 4 and 4 mM NaHCO 3 with specific energy and power of 36.7 Wh kg −1 and 354.9 W kg −1 , respectively. This ASC also shows excellent cell capacitance retention (8% decay) in the 2V, 10,000-cycle stability test, revealing superior performance. [ABSTRACT FROM AUTHOR]

A multilayered carbon nanosphere (CNS)/manganese oxide (MnO 2 ) nanofilm is fabricated by a newly developed layer-by-layer (LBL)–post-infiltration approach. The multilayered architecture effectively shortens the length over which ions diffuse, and the nanoscaled carbon/MnO 2 interface provides an interconnected pathway for electron conduction. MnO 2 acts not only as the redox center for charge storage, but also as the spacer between the LBL-assembled multilayers for more rapid electrolyte transport. A specific capacitance (based on MnO 2 ) of 1134.0 F g −1 is achieved at a loading of 5.22 μg cm −2 in a neutral electrolyte. This strategy provides a promising approach for fabricating high-power and high-energy electrochemical capacitors with precise control of electrode thickness on geometric device surfaces. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC), a typical biomass prepared from the microbial fermentation process, has been proved that it can be an ideal platform for design of three-dimensional (3D) multifunctional nanomaterials in energy storage and conversion field. Here we developed a simple and general silica-assisted strategy for fabrication of interconnected 3D meso-microporous carbon nanofiber networks by confine nanospace pyrolysis of sustainable BC, which can be used as binder-free electrodes for high-performance supercapacitors. The synthesized carbon nanofibers exhibited the features of interconnected 3D networks architecture, large surface area (624 m 2 g −1 ), mesopores-dominated hierarchical porosity, and high graphitization degree. The as-prepared electrode (CN-BC) displayed a maximum specific capacitance of 302 F g −1 at a current density of 0.5 A g −1 , high-rate capability and good cyclicity in 6 M KOH electrolyte. This work, together with cost-effective preparation strategy to make high-value utilization of cheap biomass, should have significant implications in the green and mass-producible energy storage. [ABSTRACT FROM AUTHOR]

In this article, vanadium nitride quantum dot/nitrogen-doped microporous carbon nanofibers (VNQD/CNF) is developed by a method of combination of electrostatic spinning and high-temperature calcination under the atmosphere of NH 3 : N 2 = 3: 2 for high performance supercapacitors. VNQD dispersing into CNF, enrichment of N atom doped in carbon bulk, and abundant porous structure not only prevent the growth and aggregation of VN nanoparticles, improve electrical conductivity, wettability, and stability of the electrode materials, but also enhance fast migration of electrolyte ions during the electrochemical process. Thus, VNQD/CNF exhibits a high specific capacitance of 406.5 F g −1 at 0.5 A g −1 and a good rate capability with a capacitance retention of 75.1% at 5.0 A g −1 . Additionally, VNQD/CNF as a negative electrode are combined with Ni(OH) 2 as a positive electrode to fabricate the hybrid supercapacitor of VNQD/CNF//Ni(OH) 2 . Remarkably, at a power density of 774.6 W kg −1 , the supercapacitor device delivers an ultrahigh energy density of 31.2 Wh kg −1 . [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]

The development of portable electronics strongly requires flexible, lightweight, and inexpensive energy-storage devices with high power density, long cycling stability, and high reliability. In this work, we prepare a flexible solid-state electrochemical capacitor using cross-linked hierarchical porous carbon network as electrode material via electrospinning and carbonization process. This device can reversibly deliver a maximum energy density of 10.18 W h/kg with excellent cycling stability which achieves 95% capacitance retention after 20000 charge/discharge cycles. Moreover, it also demonstrates outstanding mechanical flexibility and excellent capacitance retention even when the device is repeatedly bended 10000 cycles under 90°. All of these results suggest its promising perspective in flexible energy storage device. [ABSTRACT FROM AUTHOR]

Nanostructured nickel-cobalt binary hydroxide (NiCo BH) is widely investigated as supercapacitor electrode material. However, the aggregation and poor electrical conductivity of NiCo BH limit its practical application as a supercapacitor. In this work, a flexible free-standing hierarchical porous composite composed of NiCo BH nanosheets and titanium carbide-carbon nanofiber (NiCo BH@TiC/CNF) is fabricated through electrospinning and microwave assisted method. The as-prepared composites exhibit desirable electrochemical performances, including high specific capacitance, cycling stability, and rate capability. In particular, the NiCo BH41@TiC/CNF composite electrode exhibits a maximum specific capacitance of 2224 F g −1 at the current density of 0.5 A g −1 and excellent cyclic stability of 91% capacity retention after 3000 cycles at 5.0 A g −1 . To expand its practical application, an asymmetric supercapacitor (ASC) is fabricated using the NiCo BH41@TiC/CNF composite as the positive electrode and active carbon as the negative electrode. The ASC exhibits a prominent energy density of 55.93 Wh kg −1 and a high power density of 18,300 W kg −1 at 5.0 A g −1 . The superior electrochemical property is attributed to the uniform dispersion of NiCo BH nanosheets on the TiC/CNF felt matrix. The TiC/CNF felt with uniformed TiC nanoparticles makes the fiber surface more suitable for growing NiCo BH nanosheets and simultaneously enhances the conductivity of electrode. [ABSTRACT FROM AUTHOR]

A facile and one-step method is demonstrated to prepare carbon nanofibers (CNFs)-bridged porous carbon nanosheets (PCNs) through carbonization of the mixture of bacterial cellulose and potassium citrate. The CNFs bridge PCNs to form integrated porous carbon architecture with high specific surface area of 1037 m 2 g −1 , much higher than those of pure PCNs (381 m 2 g −1 ) and CNFs (510 m 2 g −1 ). As a consequence, the PCN/CNF composite displays high specific capacitance of 261 F g −1 , excellent rate capability and outstanding cycling stability (97.6% of capacitance retention after 10000 cycles). Moreover, the assembled symmetric supercapacitor with PCN/CNF electrodes delivers an ultrahigh energy density of 20.4 Wh kg −1 and outstanding cycling life (94.8% capacitance retention after 10000 cycles) in an aqueous electrolyte. [ABSTRACT FROM AUTHOR]

Three-dimensional, free-standing, hybrid supercapacitor electrodes combining polyaniline (PANI) and porous carbon nanofibers (P-CNFs) were fabricated with the aim to integrate the benefits of both electric double layer capacitors (high power, cyclability) and pseudocapacitors (high energy density). A systematic investigation of three different electropolymerization techniques, namely, potentiodynamic, potentiostatic, and galvanostatic, for electrodeposition of PANI on freestanding carbon nanofiber mats was conducted. It was found that the galvanostatic method, where the current density is kept constant and can be easily controlled facilitates conformal and uniform coating of PANI on three-dimensional carbon nanofiber substrates. The electrochemical tests indicated that the PANI-coated P-CNFs exhibit excellent specific capacitance of 366 F g −1 (vs. 140 F g −1 for uncoated porous carbon nanofibers), 140 F cm −3 volumetric capacitance, and up to 2.3 F cm −2 areal capacitance at 100 mV s −1 scan rate. Such excellent performance is attributed to a thin and conformal coating of PANI achieved using the galvanostatic electrodeposition technique, which not only provides pseudocapacitance with high rate capability, but also retains the double-layer capacitance of the underlying P-CNFs. [ABSTRACT FROM AUTHOR]

Freestanding carbon nanotube/carbon nanofiber (CNT/CNF) composites are prepared using electrospun CNFs as skeletons in a tubular chemical vapor deposition system. The obtained CNT/CNF composites show a hierarchical structure with a high special surface area, a high conductance (1250 S cm −1 for a 10 mm × 20 mm sample), and a high flexibility. After coated with manganese dioxide (MnO 2 ) via an in-situ redox deposition for 0.5 h (∼0.33 mg), the CNT/CNF/MnO 2 electrodes show a high specific capacitance of 517 F g −1 at a scan rate of 5 mV s −1 , which is about 5.6 time higher than that CNF/MnO 2 -0.25 h ones with MnO 2 of ∼0.36 mg. Moreover, this CNT/CNF/MnO 2 electrodes show a much higher rate capability (57% at current density of 14 A g −1 ) than CNF/MnO 2 ones (24% at 14 A g −1 ), and also show a higher cycling stability (maintaining 75% of the initial capacitance at cycle number of 1000). In addition, the symmetric supercapacitor assembled using two piece CNT/CNF/MnO 2 electrodes shows their maximum energy density of 3.88 Wh kg −1 at power density of 7000 W kg −1 . The capacitance of the assembled capacitor maintains 70% after 100 bending cycles, indicating a good flexibility. These enhancements in EC performances should be due to our designed hierarchical structures. It is suggested that such freestanding flexible CNFs/CNTs/MnO 2 hierarchical composites are highly promising for high-performance flexible supercapacitors. [ABSTRACT FROM AUTHOR]

The Ni 3 S 2 nanoparticles have been successfully grown on the carbon nanofibers (CNFs) derived from bacterial cellulose via a hydrothermal method, which the as-prepared composite exhibited high specific capacitance (883 F g −1 at 2 A g −1 ), much more than CNFs (108 F g −1 at 2 A g −1 ), and good cycle stability. The asymmetric supercapacitor was designed to contain the CNFs coated Ni 3 S 2 nanoparticles (Ni 3 S 2 /CNFs) as positive electrode and CNFs as negative electrode in 2 M KOH electrolyte. Due to the synergistic effects of the two electrodes, asymmetric cell showed superior electrochemical performances. The optimized asymmetric supercapacitor gave a operating potential of 1.7 V in 2 M KOH aqueous solution, exhibiting a high specific capacitance of 56.6 F g −1 at 1 A g −1 and considerably high energy density of 25.8 Wh kg −1 at a power density of 425 W kg −1 . Meanwhile, Ni 3 S 2 /CNFs//CNFs asymmetric supercapacitor showed excellent cycling stability with 97% specific capacitance retained after 2500 cycles. [ABSTRACT FROM AUTHOR]

This paper introduces a new design route to fabricate nickel aluminum-layered double hydroxide (NiAl-LDH) nanosheets/hollow carbon nanofibers (CNFs) composite through an in situ growth method. The NiAl-LDH thin layers which grow on hollow carbon nanofibers have an average thickness of 13.6 nm. The galvanostatic charge–discharge test of the NiAl-LDH/CNFs composite yields an impressive specific capacitance of 1613 F g −1 at 1 A g −1 in 6 M KOH solution, the composite shows a remarkable specific capacitance of 1110 F g −1 even at a high current density of 10 A g −1 . Furthermore, the composite remains a specific capacitance of 1406 F g −1 after 1000 cycles at 2 A g −1 , indicating the composite has excellent high-current capacitive behavior and good cycle stability in compared to pristine NiAl-LDH. [ABSTRACT FROM AUTHOR]

Helical carbon nanofibers (HCNFs) assembly structure possesses huge development prospects in sorts of applications. Here we report a facile yet versatile strategy for synthetic HCNFs assembly structures (Sn-HCNFs) from Sn-based metal-organic framework (Sn-MOF) via an ethanol flame method (EFM) in atmospheric environment. As Sn-MOF is burned in ethanol flame, HCNFs grow on the surface of Sn-MOF progressively, forming an assembly structure with SnO 2 core and HCNFs-forest shell. The process of Sn-HCNFs formation is also investigated by a series of experiments, which demonstrate that, in ethanol flame, Sn-MOF is first converted to SnO 2 , and then SnO 2 catalyzes the formation of Sn-HCNFs. Furthermore, our strategy can also be extended to the preparation of various MOFs-based HCNFs and carbon nanotubes (CNTs)/carbon nanofibers (CNFs) assembly architectures. By electrochemical tests, Sn-HCNFs as electrode materials in supercapacitors exhibit superior electrochemical performances than pure HCNFs. The supercapacitors with the Sn-HCNFs electrode can remain the energy density of 21.67 Wh kg−1 at a very high-power density of 5000 W kg−1. Our strategy provides an alternative route to acquire various HCNFs or CNTs/CNFs assembly structures conveniently and will stimulate further researches on preparation and applications of them. [Display omitted] • HCNFs assembly structure (HCAS) grows from Sn-MOF in ethanol flame facilely. • SnO 2 derived from Sn-MOF in ethanol flame acts as the catalyzer for HCAS growth. • HCAS has more excellent electrochemical performance than HCNFs in supercapacitors. • Various CNFs/CNTs assembly structures form from different MOFs in ethanol flame. [ABSTRACT FROM AUTHOR]

Recently, a new class of mixed polyanionic compounds with general formula Na 3 MPO 4 CO 3 (M = Ni, Mn, Fe, Co, Cu), discovered through high-throughput computations have attracted much attention for its secondary battery applications and safety aspects. Here, we combine electrochemical measurements with inductively coupled plasma-optical emission spectrometer (ICP-OES), energy-dispersive X-ray (EDX), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), and an ab-initio DFT approach to unravel the dynamic self-limiting surface restructuring of Na 3 NiCO 3 PO 4 in aqueous 1 M KOH/NaOH electrolyte. The etching of lattice CO 3 2-, PO 4 3- and Na serves as the key to trigger the surface reconstruction. This work establishes a fundamental understanding of the pseudocapacitance mechanism associated with surface self-reconstruction of mixed polyanionic compounds. The reconstruction-derived self-limiting dense Ni(OH) 2 layers at the surface and its oxidation to NiOOH at anodic potentials can be attributed to the observed high-performance pseudocapacitive behavior. The surface reconstructed Na 3 NiCO 3 PO 4 electrode exhibits high specific capacitance (2378.2 F g−1 at 1 A g−1). The assembled symmetric pseudocapacitor delivers a high energy density (57.2 Wh kg−1), power density (1500 W kg−1) at 1 Ag-1 and long cycle life (13000 cycles) with 100% retention. [Display omitted] • The pseudocapacitive behavior of the Na 3 NiCO 3 PO 4 is tested. • The Na 3 NiCO 3 PO 4 undergo surface self-reconstruction. • The etching of lattice CO 3 2-, PO 4 3- and Na lead to the formation of Ni(OH) 2 at the surface. • The electrode exhibits high specific capacitance 2378.2 F g−1 at 1 A g−1 • The assembled device delivers a high energy density, power density and long cycle life. [ABSTRACT FROM AUTHOR]

Abstract: An asymmetric supercapacitor (ASC) uses very thin petal-shaped MnO2 nanosheets as the positive electrode and a network of carbon nanotube-embedded polyacrylonitrile-based carbon nanofibers (CNT-CNF electrodes) as the negative electrode. It has a high specific capacitance and a high specific energy density in 0.5 M Na2SO4. An assembled MnO2//CNT-CNF ASC is operated reversibly at a high cell voltage of 2.0 V and exhibits a high specific capacitance of 93.99 F g−1 and an excellent energy density of 52.22 Wh kg−1, which is better than those of ASCs that are based on MnO2//carbon, which can be found in the literature. The MnO2//CNT-CNF ASC has superior cycling stability with 92% retention of initial specific capacitance after 2000 cycles. [Copyright &y& Elsevier]

Abstract: This study demonstrates a facile and effective approach to prepare nitrogen/phosphorus co-doped nonporous carbon nanofibers (N/P-NPCNFs) through the electrospinning of the polyacrylonitrile and phosphoric acid precursor solutions and subsequent thermal treatment. X-ray photoelectron spectroscopy analyses show that the contents of phosphorus and pyrrol-like nitrogen in N/P-NPCNFs can be tuned by controlling the amount of phosphoric acid. The maximum specific capacitance of 224.9 F g−1 is achieved at 0.5 A g−1 in 1 M H2SO4. Furthermore, the specific capacitance could still remain 155.5 F g−1 at 30 A g−1 with a high capacitance retention ratio of 70%. It is worth noting that no capacitance loss is observed over 8000 charge/discharge cycles, clearly demonstrating a robust long-term stability. The excellent electrochemical performance can be attributed to the synergetic effect of nitrogen and phosphorus functionalities. [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: We report a facile method for obtaining extremely high surface area and uniformly porous carbon nanofibers for supercapacitors. Blends of polyacrylonitrile and sacrificial Nafion at different compositions have been electrospun into non-woven nanofiber mats with diameters in the range of 200–400 nm. Electrospun nanofiber mats are then subjected to carbonization to obtain porous carbon nanofibers (CNFs) as polyacrylonitrile converts to carbon and Nafion decomposes out creating intra-fiber pores. Resultant porous CNFs exhibit specific surface area of up to 1600 m2 g−1 with a large fraction of mesopores (2–4 nm). No additional chemical or physical activation process was used. We demonstrate the tunability of the pore sizes within CNFs by varying the amount of Nafion. The non-woven fiber mats of porous CNFs are studied as free-standing electrode materials for supercapacitors eliminating the need for polymeric binding agents. Electrochemical measurements showed large specific gravimetric and volumetric capacitances of up to 210 F g−1 and 60 F cm−3 in 1 M H2SO4 at a high cyclic voltammetry scan rate of 100 mV s−1 due to the large fraction of mesopores. These materials retain 75% performance at a large current density of 20 A g−1 indicating excellent power handling capability. [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]

Carbon-based supercapacitors with outstanding electrochemical performances are strongly desired for the development of portable and wearable electronics. From the free radical engineering point of view, this study innovatively developed carbon/carbon gradient-structured microspheres (CCGMs) by the strategy of "third-order graduation polymerization" and "dynamic radical oxidation". Compared to conventional hybrid materials, for the first time, the gradient structure is proved to be extremely beneficial for improving the capacitive performance. Benefiting its gradient-structured advantages, the CCGMs exhibited "three-ultrahigh" performance with gravimetric, volumetric, and areal capacitances of 408.23 F g−1, 741.11 F cm−3, and 4390 μF cm−2, respectively. In addition, the assembled all-solids-state micro-supercapacitors delivered superior volumetric and areal specific capacitances (7.704 F cm−3 and 9.245 mF cm−2 at 5 μA cm−2), excellent life-span (100% after 12000 cycles), excellent volumetric and areal energy densities (1070 mWh cm−3 and 1284 μWh cm−2). This work paves a new way to develop unique carbon composites for high‐performance energy storage devices. • A third-order graduation polymerization method was developed. • The dynamic radical oxidation method was used for ultramicroporous-confined defects. • The gradient structure could improve the "three-ultrahigh" performance of carbons. [ABSTRACT FROM AUTHOR]

Achieving high specific surface area and ion accessibility in graphene-based electrodes with a high mass loading for supercapacitors poses a significant challenge because strong π-π stacking of graphene sheets often blocks the access of electrolyte ions to active sites. Herein, we report a novel protocol to prepare free-standing laminated graphene/carbon nanofiber films as high areal mass-loading electrodes through a layer-by-layer electrospinning technique. The unique laminated structure of graphene/carbon nanofiber thin films can enhance electrolyte penetration and increase transportations of ions/electrons. The symmetric supercapacitors (SCs) using the as-obtained graphene/carbon nanofiber films as electrodes reach areal specific capacitance of 1536 mF cm−2 at a current density of 1 mA cm−2. Most importantly, the areal energy density of the SCs can reach 0.22 mWh cm−2 at a power density of 1 mW cm−2 with a high areal mass loading of 24 mg cm−2. The exceptional electrochemical properties of the laminated graphene/carbon nanofiber films render them promising materials for electrodes in SCs. [Display omitted] • Laminated graphene/CNFs were prepared via layer-by-layer electrospinning. • The unique laminated structure enhances ions accessibility at high mass loading. • The assembled symmetric supercapacitor exhibits high areal specific capacitance. [ABSTRACT FROM AUTHOR]

This work demonstrated that the performance improvement of nitrogen-doped reduced graphene oxide (N-rGO) electrodes over reduced graphene oxide (rGO) electrodes for supercapacitors could be further enhanced by violet laser treatment (VLT). A specific capacitance of 30 and 145 F g−1 was obtained for rGO and N-rGO electrodes, respectively. When using N-rGO with proper VLT, a high specific capacitance of 214 F g−1 could be achieved. In addition, the percentage of capacitive retention of the N-rGO with VLT remaining 94% after 10,000 cycles with a slower self-discharge rate at 0.55 V h−1, comparing to 0.91 V h−1 for N-rGO. Systematic investigations of N-rGO with VLT were carried out by using different film characterization techniques. The surfaces of N-rGO with VLT exhibit an increase in the number of exfoliated graphene oxide sheets with more roughness when increasing the fluence of laser. It was also found that there are the decrease in oxygen/nitrogen-containing functional groups contents and the increases in graphitic carbon phase with C C sp2-hybridization with the influence of laser. These may explain the improvements of the reported charge storage ability, electrode stability, and self-discharge rate. • Nitrogen doped reduced graphene oxide (N-rGO) is prepared via hydrothermal method. • Violet laser treatment (VLT) is simple, fast, not expensive, and effective. • VLT on N-rGO (N-rGO-V5) can enhance the C sp around 48%, compared with N-rGO. • VLT can improve self-discharge or leakage current. • N-rGO-V5 shows long cycle life at least 94% after 10,000 charge-discharge cycles. [ABSTRACT FROM AUTHOR]

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 presents highly conductive carbon nanofiber/MnO2 coaxial cables in which individual electrospun carbon nanofibers are coated with an ultrathin hierarchical MnO2 layer. In the hierarchical MnO2 structure, an around 4nm thick sheath surrounds the carbon nanofiber (CNF) in a diameter of 200nm, and nano-whiskers grow radically outward from the sheath in view of the cross-section of the coaxial cables, giving a high specific surface area of MnO2. The CNFs are synthesized by electrospinning a precursor containing iron acetylacetonate (AAI). The addition of AAI not only enlarges the specific surface area of the CNF but also greatly enhances their electronic conductivity, which leads to a dramatic improvement in the specific capacitance and the rate capability of the CNF/MnO2 electrode. The AAI-CNF/MnO2 electrode shows a specific capacitance of 311Fg−1 for the whole electrode and 900Fg−1 for the MnO2 shell at a scan rate of 2mVs−1. Good cycling stability, high energy density (80.2Whkg−1) and high power density (57.7kWkg−1) are achieved. This work indicates that high electronic conductivity of the electrode material is crucial to achieving high power and energy density for pseudo-supercapacitors. [Copyright &y& Elsevier]

Abstract: Porous carbon nanofibers (CNFs) enriched with the graphitic structure were synthesized by thermal decomposition from a mixture containing polyethylene glycol and nickel chloride (catalyst). The textural and electrochemical properties of porous CNFs were systematically compared with those of commercially available multi-walled carbon nanotubes (MWCNTs). The high ratio of mesopores and large amount of open edges of porous CNFs with a higher specific surface area, very different from that of MWCNTs, are favorable for the penetration of electrolytes meanwhile the graphene layers of porous CNFs serve as a good electronic conductive medium of electrons. The electrochemical properties of porous CNFs and MWCNTs were characterized for the application of supercapacitors using cyclic voltammetry, galvanostatic charge–discharge method, and electrochemical impedance spectroscopic analyses. The porous CNFs show better capacitive performances (C S =98.4Fg−1 at 25mVs−1 and an onset frequency of behaving as a capacitor at 1.31kHz) than that of MWCNTs (C S =17.8Fg−1 and an onset frequency at 1.01kHz). This work demonstrates the promising capacitive properties of porous CNFs for the application of electrochemical supercapacitors. [Copyright &y& Elsevier]

Carbon nanofibers from electrospun polymer nanofibers have received considerable attention. However, most of the carbon nanofibers with a surface area above 1000 m2/g were reported to have a supercapacitor electrode capacitance far below 350 F g−1. Herein, we report a novel carbon nanofibrous material that has a supercapacitor electrode capacitance as high as 394 F g−1 (1.0 A g−1). We used a polymer blend of polyacrylonitrile (PAN) and novolac (NOC) as materials, to electrospin them into precursor nanofibers and subsequently carbonize the nanofibers into carbon nanofibers. The carbon nanofibers prepared had a specific surface area as high as 1468 m2 g−1 with a meso-micro pores (average pore size 2.2 nm) predominated porous structure. The carbon nanofiber electrodes after 10,000 cycles of charging and discharging at 1.0 A g−1 maintained the capacitance almost unchanged. At the optimal condition, the supercapacitor device made of the electrodes had an energy density as high as 13.6 Wh∙kg−1 (at 0.5 kW kg−1). The high capacitance value comes from the carbon nanofibers with a large surface area and a unique porous structure. The high inter-fiber interconnection contributes to high capacitance. This super-high surface area carbon may be useful for the development of high-performance supercapacitors and other energy devices. Image 1 • Carbon nanofibers are prepared from electrospun polyacrylonitrile/novolac. • They contain micro-mese pores with a surface area as high as 1468 m2 g−1. • Electrodes made from the carbon nanofibers show a capacitance of 394 F g−1. • High capacitance originates from the unique structure and large surface area. [ABSTRACT FROM AUTHOR]

Bimetallic carbides have aroused wide attention for energy-storage applications recently. In this work, one-dimensional Fe 2 MoC/CNFs (Fe 2 MoC/C nanofibers) are successfully synthesized via a facile electrospinning method for the first time. To obtain the most integrated structure between the Fe 2 MoC nanoparticles and carbon nanofibers, we explore the optimal heating rate during the carbonization treatment. Fe 2 MoC/CNFs exhibits an integrated one-dimensional structure under 800 °C with a heating rate of 5 °C/min. As revealed in the experimental results, Fe 2 MoC/CNFs possesses a high specific surface area of 196.9 m2/g, a high specific capacitance of 347.8 F/g at the current density of 1 A/g, an excellent rate capability of 91% capacitance retention from 1 A/g to 40 A/g, and shows superior cycling stability with the capacitance retention of about 85.6% and Coulombic efficiency of about 100% after 5000 cycles. An asymmetric supercapacitor coin-cell device using Fe 2 MoC/CNFs as the positive electrode displays an energy density of 14.5 Wh/kg at a power density of 300 W/kg and an outstanding cycling life of 93% retention after 5000 cycles. The impressive electrochemical performance indicates that the Fe 2 MoC/CNFs composite is a promising material for efficient supercapacitors. Image 1 • Fe 2 MoC nanofibers can be prepared via a facile electrospinning method. • Fe 2 MoC/CNFs-5 exhibits a superior rate capability and cycle stability. • ASC coin-cell device shows a promising energy and power density. [ABSTRACT FROM AUTHOR]

Persuing both high energy and power density in one supercapacitor at low cost is very challenging to date. Here, we report the fabrication of nitorgen and Sulphur co-doped graphene (GN) modified lignin/polyacrylonitrile (PAN)-based carbon nanofiber (ACNFs) from mainly the biomass of lignin following a process of electrospinning, carbonization and activation. GN is used as nitrogen/sulphur immobilization agent to successfully capture HCN, NH 3 and SO 2 released from lignin and PAN during carbonization, and thus the content of heteroatoms of N and S in ACNFs is increased. The resulting ACNF with 0.30 wt% GN content possesses the maximum specific surface area of 2439 m2 g−1. It shows a typical three-dimensional porous network structures with the highest heteroatom doping content and high degree of crystallinity. The assembled supercapacitor exhibits superior electrochemical performance with ultra-high specific capacitance of 267.32 F g−1, low equivalent series resistance of 5.67 Ω, and outstanding cycling stability of 96.7% capacitance retention after 5000 cycles of charge/discharge in a two-electrode system with 6 mol L−1 KOH as electrolyte. Most importantly, the assembled symmetric supercapacitor shows that ACNFs doping with GNs increases the energy density from 4.12 to 9.28 Wh kg−1 and at the same time with barely reduced power density. • Using GNs as an adsorbent to capture HCN, NH 3 , SO 2 released in carbonization. • Proposing the water wetting behaviour to evaluation the supercapacitor performance. • Elucidated the mechanism between heteroatom doping and electrochemical properties. [ABSTRACT FROM AUTHOR]