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In this study, an electrospinning method was used to produce highly conductive freestanding carbon nanofibers (CNFs). The freestanding CNFs are compatible with hierarchical growth techniques, such as hydrothermal processes, for the nanostructure engineering of supercapacitor electrodes with enhanced electrochemically active sites. Therefore, the flower-like FeMoO 4 @CNF nanosheets were investigated to improve the electrochemical performance using aqueous and neutral electrolytes (Na 2 SO 4 and K 2 SO 4). The optimized FeMoO 4 @CNF electrode exhibits areal capacitances of 252 and 220 mF·cm−2 at a high current density of 2.5 mA·cm−2 with Na 2 SO 4 and K 2 SO 4 electrolytes, respectively. The wide potential window (1.6 V) of the symmetric supercapacitor delivered maximum energy densities of 22.4 and 19.6 μWh·cm−2 at a power density of 2 mW·cm−2 for Na 2 SO 4 and K 2 SO 4 electrolytes, respectively. [ABSTRACT FROM AUTHOR]

Exploring bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which combine the features of effective electrocatalytic activity, high electrical conductivity, and superior stability, remains a significant challenge for rechargeable Zn–air batteries (ZABs). Herein, we report a material, selenium (Se)-doped CoSe2 embedded in carbon nanofibers (CNFs) (denoted as Se–CoSe2/CNFs), which was synthesized as a bifunctional electrocatalyst for ZABs via electrospinning combined with in situ growth of Zeolitic Imidazolate Framework-67 strategy, followed by carbonization and a facile selenization process. The as-synthesized Se–CoSe2/CNF electrode exhibits satisfactory electrochemical performance in an alkaline environment with a low overpotential of 325 mV at 10 mA cm−2 toward OER and a half-wave potential of 0.80 V for ORR. Remarkably, the Se–CoSe2/CNF catalyst-based ZAB shows a peak power density of 149.4 mW cm−2 and the voltage window barely changes after 180 h of cycling at 5 mA cm−2, which proves its great potential application for advanced bifunctional electrocatalysis in ZABs. [ABSTRACT FROM AUTHOR]

Sub-fluorinated carbon nanofibers (F-CNFs) can be described as a non-fluorinated core surrounded by a fluorocarbon lattice. The core ensures the electron flux in the cathode during the electrochemical discharge in the primary lithium battery, which allows a high-power density to be reached. The ball-milling in an inert gas (Ar) of these F-CNFs adds a second level of conductive sp2 carbons, i.e., a dual sub-fluorination. The opening of the structure changes, from one initially similar multi-walled carbon nanotube to small lamellar nanoparticles after milling. The power densities are improved by the dual sub-fluorination, with values of 9693 W/kg (3192 W/kg for the starting material). Moreover, the over-potential of low depth of discharge, which is typical of covalent CFx, is suppressed thanks to the ball-milling. The energy density is still high during the ball-milling, i.e., 2011 and 2006 Wh/kg for raw and milled F-CNF, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1D skin-core multilayer structure was fabricated by a facile template method. • Bicontinuous electron/ion transport during the charge/discharge process. • The large specific surface area and hollow hierarchical porous structure. • Adjusting active layers or sites can obviously improve the capacitive properties. • The maximum energy density of 8.77 Wh kg−1 at a power density of 0.25 kW kg−1. The fast transport of electrons and ions within electrodes is crucial to the final electrochemical properties. Herein, we have developed a unique ultra-long one-dimensional (1D) skin-core multilayer structure based on electrospun carbon nanofibers mainly through a facile Stöber method combined with resorcinol–formaldehyde resin, which not only achieves bicontinuous electron/ion transport during the charge/discharge process, but also provides large surface area for ion adsorption. Particularly, controlling the number of active layers as well as regulating the active sites in layer both can obviously improve capacitive properties. Benefiting from the synergistic effects of the desirable architecture, such the rational-designed skin-core structural carbon nanofibers as supercapacitor electrode can deliver a high specific capacitance up to 255 F g−1 at 0.5 A g−1, favorable rate capability with 89% capacitance retention of initial capacitance at 8 A g−1, and excellent cycling stability with nearly 93% capacity retention after 10,000 cycles at 2 A g−1. Furthermore, the as-assembled symmetric supercapacitor devices also present a maximum energy density of 8.77 Wh kg−1 at 0.25 kW kg−1 and a maximum power density of 3.70 kW kg−1 at 6.74 Wh kg−1. Such skin-core carbon nanofibers provide an effective strategy to design high-performance supercapacitor electrode for the next-generation energy storage devices. [ABSTRACT FROM AUTHOR]

Herein, MnO2 nanoflowers are electrodeposited on a self-supported and electroconductive electrode in which 2D Ti3C2Tx nanosheets are encased in carbon nanofibers (MnO2@Ti3C2Tx/CNFs). This improves the conductivity and hydrophilicity of the MnO2 composite electrode. The asymmetric supercapacitor shows a high energy density of 46.4 W h kg−1 and a power density of 4 kW kg−1. [ABSTRACT FROM AUTHOR]

Reasonable construction of high activity and low cost non-noble metal oxygen reduction reaction (ORR) catalyst is of great importance for the wide application of zinc-air batteries (ZABs). Using bimetallic MOF as a precursor combined with electrospinning, high-temperature carbonization and electrodeposition, we successfully developed a porous carbon nanofiber (Co@Fe-CNFs-1000) with bimetallic active center as an efficient catalyst for ORR. The successful construction of this special core-shell structure directly explores the synergy between different active centers. The results showed that the synthesized Co@Fe-CNFs-1000 catalyst exhibited ORR performance comparable to that of Pt/C in 0.1 mol/L KOH electrolyte, high half-wave potential (E1/2=0.81 V) and limiting current density (JL=5.4 mA-cm−2). In addition, homemade liquid ZABs with Co@Fe-CNFs-1000 as the air cathode showed excellent power density (155.8 mW·cm−2), specific capacity (780.6 mAh·gZn−1) and long-term stability (over 100 h at 2 mA·cm−2), surpassing even Pt/C-based batteries. In addition, the flexible solid-state ZABs assembled based on Co@Fe-CNFs-1000 demonstrates excellent flexibility and durability. This work provides a new idea for constructing ORR catalysts with high activity centers. [ABSTRACT FROM AUTHOR]

The exploitation of high‐performance, durable, and low‐cost oxygen reduction reaction (ORR) electrocatalysts is crucial for energy storage and convert devices. Herein, a core‐shell structured catalyst (FeNx@graphite carbon) is developed by coaxial electrospinning. The resulting nanofibers combines the distinguished activity of FeNx and the good conductivity and stability of graphite carbon. This unique core‐shell structure with potential synergistic interaction leads to high activity and outstanding stability. As an excellent cathode catalyst for the Zn‐air battery, FeNx@graphite carbon displays an outstanding open‐circuit voltage (1.592 V), a high peak power density (100 mW cm−2) and stable rechargeability (30 h), outperforming that of Pt/C assembled Zn‐air battery. Our work provides a guide to rational design for achieving both high ORR activity and good stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co/CoFeNC@N-CNF displays efficient catalytic performance for ORR, OER and HER. • The assembled mold battery can provide a power density of 292 mW cm−2. • The DFT calculations indicate that the synergistic effect between Co/CoFe bimetal. In this work, a three-dimensional (3D) multifunctional Co/CoFeNC@N-CNF electrocatalyst was first synthesized by the pyrolysis of a CoFe bimetal-centred metal-organic framework (MOF) and bacterial cellulose (BC). The initial potential and half-wave potential of Co/CoFeNC@N-CNF can reach 0.99 V and 0.8 V. Low overpotentials of 320 mV and 155 mV are purely required for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) at a current density of 10 mA cm−2, respectively. The electrochemical performance of Co/CoFeNC@N-CNF exceeds most bimetal-MOF-derived electrocatalysts reported to date. The superior electrochemical performance is mainly due to abundant active sites, high-efficiency electrochemical performance, and high electron transport efficiency. In addition, the theoretical calculation results show that the synergistic effect of the CoFe bimetal can optimize the adsorption energy for intermediates of the oxygen reduction reaction (ORR), OER and HER. Furthermore, we assembled a mold and solid Zn-air battery using the catalyst as an air cathode catalyst, demonstrating the maximum power densities of 292 mW cm−2 and 178 mW cm−2. The 3D structure electrocatalysts derived from the MOF and bacterial cellulose provide an innovative and instructive approach for the design of diverse energy nanomaterials. [ABSTRACT FROM AUTHOR]

The sluggish electron transfer at the interface of microorganisms and an electrode is a bottleneck of increasing the output power density of microbial fuel cells (MFCs). Mo-doped carbon nanofibers (Mo-CNFs) prepared with electrostatic spinning and high-temperature carbonization are used as an anode in MFCs here. Results clearly indicate that Mo2C nanoparticles uniformly anchored on carbon nanowire, and Mo-doped anodes could accelerate the electron transfer rate. The Mo-CNF ΙΙ anode delivered a maximal power density of 1287.38 mW m−2, which was twice that of the unmodified CNFs anode. This fantastic improvement mechanism is attributed to the fact that Mo doped on a unique nanofiber surface could enhance microbial colonization, electrocatalytic activity, and large reaction surface areas, which not only enable direct electron transfer, but also promote flavin-like mediated indirect electron transfer. This work provides new insights into the application of electrospinning technology in MFCs and the preparation of anode materials on a large scale. [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]

Highly graphitic porous carbon was derived from kelp biomass and prepared using KOH as the main activating agent with K2FeO4 as the assisting activated agent for supercapacitor applications. The optimum K2FeO4 mass in the total activating agent and temperature were investigated. The characterization results showed porous sheet carbon with a high specific surface area of 2868 m2 g−1 and a low ID/IG of 0.909. It delivered an excellent specific capacitance of 438 F g−1 at 0.5 A g−1. In addition, the assembled supercapacitor device reached the highest energy density of 19.9 W h kg−1 with a power density of 398 W kg−1. [ABSTRACT FROM AUTHOR]

The Indigenous bio-bed technology with electrical cells were designed to evaluate the Nitrogen removal performance and other pollutants from the river water. The designed Indigenous bio-bed technology were taken an influent levels of CODcr at 250 mg/L, NH 4 -N and, NO 3 -N concentrations at 7.5 mg/L for the experiment. The device ran for 48 h for nitrogen remediation of the river water, thus, achieving removal efficiency of 85 %, 97 %, 98 %, 95 % and 92 % for CODcr, NH 4 -N, NO 2 -N, NO 3 -N and TIN, respectively. The highest power and current density generated were 486.86 mWm−3 and 4807.02 mA/m3, respectively. The correlation of both the values of Voltage production and TIN removal performance is shown to be statistically as, R2 of 0.9861 and 0.9999 of both open and close circuit mode of operation, respectively. The dominant phylum relative abundance deduced the close circuit mode of operation: higher relative abundance than the open circuit. [Display omitted] • The removal performance of the system for COD and TIN was 85 % and 92 %, respectively. • The highest power density attained per lesser substrate concentration (250 mg/L) was 486.86 mW m−3. • The highest current density generated were 4807.02 mA m−3. • The relative abundance of proteobacteria in the carbon felt samples is shown Cathode O > Cathode C > Anode C > Anode O. • The average voltages production and bacterial community have shown a high correlation with nitrogen removal in the operation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrafine PtCo nanoparticles anchored on CNFs is fabricated by rapid heating method. • The obtained PtCo/CNFs-HHR displays outstanding ORR/OER catalytic activity. • PtCo/CNFs-HHR based ZAB exhibits a high peak power density and excellent durability. Herein, rapid heating strategy was introduced to synthesize ultrafine PtCo nanoparticles attached to carbon nanofibers (CNFs) by a high heating rate (HHR) up to about 50 °C s−1. This novel tactic is beneficial to the formation and the homogeneous distribution of ultrathin PtCo nanoparticles on CNFs. The acquired PtCo/CNFs-HHR exhibits a half-wave potential of 0.88 V for ORR, along with a low potential difference ΔE of 0.79 V. When used as the cathode catalyst of ZABs, PtCo/CNFs-HHR displays a high open circuit voltage of 1.454 V, large peak power density of 138.6 mW cm−2, and excellent charge–discharge cycle stability over 300 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • • Developed pure Si anode for enhanced LIC power density and energy density. • • Functional layers with hydrophilic groups enhance electrode adhesion. • • Functional cover suppresses volume expansion of electrode. • • Functional cover forms stable inorganic-rich SEI reducing electrode degradation. • • Achieved high energy and power density with stable cycle stability in full-cell. A lithium–ion capacitor, comprising a capacitor–type cathode and battery–type anode, exhibits high power and energy density; however, the integration of different charge storage mechanisms in one cell naturally leads to a kinetic mismatch between the two electrodes, reducing the power density and cycle stability. To solve this problem, high–capacity anode materials with thinner electrodes are required. Silicon, with its high specific capacity, is considered a promising anode material with high energy and power density; however, pure Si anodes undergo rapid capacity fading and exhibit increased internal resistance owing to volume changes during cycling. In this study, both sides of the electrode are covered with functional layers consisting of functionalized herringbone–type carbon nanofibers to protect the Si electrode from degradation. The polar functional groups on the nanofibers weakly interact with the native oxide layer of the Si surface and the carboxyl groups of the binder, ensuring stable contact between electrode materials over repeated cycles. Moreover, the conductive functional cover promotes uniform lithium ion fluxes, aiding the formation of a stable solid electrolyte interphase layer. This study investigates the effects of this strategy on pure Si electrodes by surface morphology analysis, assessment of chemical interactions, and electrochemical testing. This approach has the potential to overcome the degradation of Si electrodes and significantly improve the power and energy density of lithium–ion capacitors. [ABSTRACT FROM AUTHOR]

The synthesis of Laser-Induced Graphene (LIG) through the laser ablation process of carbon-containing materials is a rapid and scalable process which enables the production of graphene in a cost-effective manner. In recent years, metal oxide – graphene composite electrodes have gained a lot of importance due to their use in various Energy Storage Devices (ESDs). In our investigation, we manufacture composite electrodes of manganese dioxide (MnO 2) and LIG through a hydrothermal process and use it as electrodes in Flexible Supercapacitors. This method deviates from traditional procedures as it eliminates the requirement for binders in creating composite electrodes, given that MnO 2 can be directly deposited onto the LIG electrodes. The assembled all-Flexible Supercapacitor (FSC), featuring unique LIG-MnO 2 composite electrodes, showcased a remarkable areal capacitance of 66.5 mF cm−2 at 5 mV s−1 scan rate. The device also exhibited a very high areal energy density (2.3 mWh cm−2) and power density (19.7 mW cm−2) at 0.2 mA cm−2 current density. Also, 82 % capacitance retention was observed at the end of 2000 cycles and the device also exhibited a good flexibility during bending tests, as evidenced by an 80 % capacitance retention after 100 bending cycles. [ABSTRACT FROM AUTHOR]

Sodium‐ion hybrid capacitors (SIHCs) have been regarded as one of the promising energy devices thanks to its low cost and compromise between energy density and power density, yet remain a challenge towards practical levels of mass loading (>10 mg cm−2). Herein, the fabrication of a 1D core–shell structure is reported with N‐doped porous carbon encapsulating ZnV2O4 nanofibers (ZnV2O4NFs@N‐PC), which features an open framework and favorable properties for facilitating ion diffusion, mass transportation, and electron transfer, enabling it to perform impressively for sodium ions storage. A 3D printed SIHC is conceptually proposed by coupling the 3D printed ZnV2O4NFs@N‐PC anode with a 3D printed active carbon cathode, which can deliver a high energy/power density of 145.07 Wh kg−1/3677.1 W kg−1 with a durable cycling lifespan. It is demonstrated that the 3D printed SIHC, even at a high mass loading of up to 16.25 mg cm−2, can release a high areal energy/power density of 1.67 mWh cm−2/38.96 mW cm−2, outperforming most of the SIHCs developed so far. The present work sheds light on the role of the design of electrode materials and verifies the promise of 3D‐printed technology for next‐generation electrochemical energy devices. [ABSTRACT FROM AUTHOR]

The traditional air cathode in microbial fuel cell (MFC) usually consists of catalyst layer (CL), supporting layer (SL) and conductive gas diffusion layer (GDL), the overall MFC performance is inevitably affected by the additional and expensive adhesives and conductive agents. Here, we developed an integrated air cathode in MFC without any additional SL, GDL or adhesives. The integrated air cathode was self-supporting nitrogen-doped reduced graphene oxide@carbon nanofiber (N-rGO@CNF) hybrid membranes fabricated by electrospinning with subsequent heat-treatment under ammonia atmosphere. The as-fabricated N-rGO@CNFs possessed far superior MFC performance and oxygen reduction reaction (ORR) activity to the pristine nitrogen-doped carbon nanofibers (NCNF) and commercial activated carbon (CAC). The amount of rGO embedded into CNF had prominent influence on their ORR activities and MFC performances. N-5-rGO@CNF had the lowest resistance and the maximal exchange current density, exhibiting desirable oxygen reduction performance via a four-electron pathway. The maximum power density of N-5-rGO@CNF can reach 826 mW m−2 in MFC, which is approximately 9, 2.53 and 1.82 times of pristine NCNF, CAC and Pt/C with values of 91, 327 and 454 mW m−2. The outstanding performance of the integrated air-cathodes originates from the integrality, brevity and hybrid composition of the electrospun nanofiber membrane. The appropriate embedded rGO not only improves the bulk conductivity of the rGO@CNF to promote ion adsorption, but also provides vacancies to accommodate ions, the doped nitrogen atoms facilitate O 2 adsorption and/or subsequent O–O bond breaking, thus improving the electrochemical performance of N-rGO@CNF in MFC. [Display omitted] • An integrated N-rGO@CNF air cathodes with high-efficiency were developed via electrospinning. • The integrated air cathodes showed excellent catalytic performance in Microbial Fuel Cells. • The optimal air cathode (N-5-rGO@CNF) had maximum power density of 20650 mW m−3. • N-5-rGO@CNF exhibited ideal oxygen reduction reaction via a four-electron pathway. [ABSTRACT FROM AUTHOR]

Summary: Direct methanol fuel cell (DMFC) is considered as one of the next‐generation power sources for portable electronic devices. However, the problems of structure and materials of the membrane electrode assembly (MEA) must be resolved if it is applied in flexible electronic devices. The traditional materials of MEA used in DMFC cannot bend and are easy to break. Moreover, the existence of a microporous layer increases the likelihood of separation of the gas diffusion layer (GDL) and catalytic layer. Herein, we develop a simple electrospinning method to prepare flexible titanium carbide/carbon nanofibers (TiC/CNFs) film used as GDL. TiC/CNFs film plays a GDL and a microporous layer dual role. The MEA exhibits enhancing performance and excellent flexibility. The maximum power density of flexible DMFC can reach 20.2 mW/cm2, compared with the GDL made of traditional carbon cloth (18.1 mW/cm2), the maximum power density rises by 11.6%. After 50 consecutive bends, the voltage drops less than 10%. This work would promote the flexibility of DMFC. [ABSTRACT FROM AUTHOR]

N/P dual-doped three-dimensional porous carbon was synthesized via nano-CaCO 3 template-assistant carbonization of intumescent flame retardants (IFRs) precursor. [Display omitted] Heteroatom-doped three-dimensional (3D) porous carbons possess great potential as promising electrodes for high-performance supercapacitors. Inspired by the inherent features of intumescent flame retardants (IFRs) with universal availability, rich heteroatoms and easy thermal-carbonization to form porous carbons, herein we proposed a self-assembling and template self-activation strategy to produce N/P dual-doped 3D porous carbons by nano-CaCO 3 template-assistant carbonization of IFRs. The IFRs-derived carbon exhibited large specific surface area, well-balanced hierarchical porosity, high N/P contents and interconnected 3D skeleton. Benefitting from these predominant characteristics on structure and composition, the assembled supercapacitive electrodes exhibited outstanding electrochemical performances. In three-electrode 6 M KOH system, it delivered high specific capacitances of 407 F g−1 at 0.5 A g−1, and good rate capability of 61.2% capacitance retention at 20 A g−1. In two-electrode organic EMIMBF 4 /PC system, its displayed high energy density of 62.8 Wh kg−1 at a power density of 748.4 W kg−1, meanwhile it had excellent cycling stability with 84.7% capacitance retention after 10,000 cycles. To our best knowledge, it is the first example to synthesize porous carbon from IFRs precursor. Thus, the current work paved a novel and low-cost way for the production of high-valued carbon material, and expanded its application for high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

In this work, nanorods like bimetallic Zn/Mn metal–organic-frameworks (MOFs) are proposed as the precursor for preparing MnxOy/porous carbon composite as a high-performance catalyst. The synthesis conditions, including the ratio of Zn:Mn and reaction time, are systematically investigated. The optimized sample has nanorods like morphology with a length of 200 nm and a diameter of 50 nm. Electrochemical tests show that the initial potential of the optimized MnxOy/porous carbon composite is 0.896 V(vs. reversible hydrogen electrode, RHE), the half-wave potential is 0.763 V (vs. RHE), and the kinetic current is 0.962 mA cm−2 (0.8 V). It has higher stability and selectivity than commercial Pt/C. The results reveal that the existence of Zn grain refinement occurs in MnxOy/carbon nanomaterials and increases its pore structure. The obtained material possesses a large electrochemical active area, indicating the higher exposed active sites and enhanced catalytic performance. Besides, the assembled Zn-air battery with MnxOy/porous carbon composite as cathode catalyst exhibits a power density of 0.14 W cm−2, close to that of commercial Pt/C. This work provides adequate data for further study of bimetallic MOF-derived materials as high-performance ORR catalysts. [ABSTRACT FROM AUTHOR]

Co-doped carbon nanofiber mats can be prepared by the addition of cobalt acetate to the polyacrylonitrile/DMF electrospun solution. Wastewater obtained from food industries was utilized as the anolyte as well as microorganisms as the source in single-chamber batch mode microbial fuel cells. The results indicated that the single Co-free carbon nanofiber mat was not a good anode in the used microbial fuel cells. However, the generated power can be distinctly enhanced by using double active layers of pristine carbon nanofiber mats or a single layer Co-doped carbon nanofiber mat as anodes. Typically, after 24 h batching time, the estimated generated power densities were 10, 92, and 121 mW/m2 for single, double active layers, and Co-doped carbon nanofiber anodes, respectively. For comparison, the performance of the cell was investigated using carbon cloth and carbon paper as anodes, the observed power densities were smaller than the introduced modified anodes at 58 and 62 mW/m2, respectively. Moreover, the COD removal and Columbic efficiency were calculated for the proposed anodes as well as the used commercial ones. The results further confirm the priority of using double active layer or metal-doped carbon nanofiber anodes over the commercial ones. Numerically, the calculated COD removals were 29.16 and 38.95% for carbon paper and carbon cloth while 40.53 and 45.79% COD removals were obtained with double active layer and Co-doped carbon nanofiber anodes, respectively. With a similar trend, the calculated Columbic efficiencies were 26, 42, 52, and 71% for the same sequence. [ABSTRACT FROM AUTHOR]

It is difficult for green sustainable lignin-based materials to simultaneously obtain efficient electromagnetic wave absorption (EMWA) and supercapacitive energy storage (SCES), which has not yet been reported. Herein, the light-weight lignin-based carbon nanofibers (LCNFs) with proper pore size, well graphitization degree, and heteroatom doping were tailored through electrospinning and carbonization processes. Interestingly, the graphitization degree and porous structure of LCNFs could be easily adjusted by changing the activating temperature, and the higher conductivity was achieved for preparing LCNFs at higher activating temperature due to the differences in the crystal size and activating degree of LCNFs. As a result, in the field of EMWA, the LCNFs-950 exhibited the minimum reflection loss (RL) value was −41.4 dB and the absorbing frequency was 9.05 GHz at 2.5 mm thickness, which meant this absorbent could absorb and/or dissipate more than 99.9% of incident electromagnetic wave (EMW). Furthermore, the LCNFs-950 also exhibited excellent SCES ability. In two-electrode system, the optimal LCNFs-950 symmetric supercapacitor specific capacitance reached 139.4 F/g at a current density of 0.5 A/g, meanwhile, the energy density was 41.4 Wh/kg at a power density of 3500 W/Kg. These multifunctional features of LCNFs will be highly promising for the next-generation environmental remediating materials. [Display omitted] • Increasing the activating temperature was an effective strategy for preparing renewable and low-cost multifunction LCNFs. • Multifunction LCNFs in both electromagnetic wave absorption and electrochemical energy storage were fabricated. • The minimum reflection loss was −41.4 dB and the absorbing frequency was 9.05 GHz at 2.5 mm thickness. • The specific capacitance, energy density and power density were up to 139.4 F/g, 41.4 Wh/kg and 3500 W/Kg, respectively. [ABSTRACT FROM AUTHOR]

Thin carbon nanofibers (TCNFs) hanging on branched carbon nanofibers (3D TCNF/CNF) with an N-doping level up to 8.7 at% for high-performance supercapacitors are designed and synthesized. TCNF/CNF shows a 3D hierarchical porous structure, a large surface area, abundant ionic-channels, and a great number of electrochemically active sites by N-doping. Because of the multiple synergistic effects of these features, the supercapacitors (SCs) based on TCNF/CNF show a remarkably excellent electrochemical behavior with a high specific capacitance of 224 F g−1. After 50 000 cycles of charge/discharge, 92% of the initial capacitance value is retained in 1.0 M H2SO4 electrolyte. Moreover, the TCNF/CNF-based SCs show low internal resistance, leading to a high power density with a relatively high energy density. [ABSTRACT FROM AUTHOR]

Prussian blue analogs, as a pseudo-capacitor electrode materials hold great potential due to their unique framework structure, excellent electrochemical activity and high specific capacity. Herein, a versatile method for the growth of series of metal hexacyanoferrates (MHCF) on carbon nanofiber with high conductivity and flexibility was proposed. By controlling the releasing rate of metal ions through acid modulation of solution, the series of MHCF nanocubes were successfully embedded on the carbon nanofibers with super stability. Different MHCF presented various loading density. Among the MHCFs, nickel hexacyanoferrate (NiHCF) is the most easily formed with high density and uniform distribution. The obtained self-supporting NiHCF@CNF, as a representative electrode, exhibited high specific capacitance (507 F g−1, 1 A g−1) and remarkable rate performance (67% retention at 10 A g−1). Moreover, the NiHCF@CNF-based hybrid supercapacitor cell delivered a high energy density of 60 Wh kg−1 at the power density of 810 W kg−1. Meanwhile, the capacitor showed extremely high stability due to tight anchoring of NiHCF on CNFs. This work provides a simple and versatile method to produce self-supporting MHCF@CNF composites for constructing high performance supercapacitor. [Display omitted] • A versatile method to produce various MHCF@CNF is demonstrated. • The self-supporting MHCF@CNF are extremely stable with excellent flexibility. • The MHCFs particles with small size and uniform distribution promote the charge transfer. • A super high specific capacitance of 507 F g−1 (1 A g−1) is achieved on NiHCF@CNF. • NiHCF@CNF//PCNF delivers energy density of 60 Wh kg−1 at a power density of 810 W kg−1 [ABSTRACT FROM AUTHOR]

Summary: The development of efficient methods to achieve a porous activated carbon nanostructures electrode for high‐performance electrochemical double‐layer capacitor (EDLC) is urgently needed at present. In this study, biomass‐based porous hollow carbon nanofiber/nanosheet with suitable micro/mesopores was successfully prepared using a low‐cost simple approach through chemical activation at direct pyrolysis. Biomass‐based porous carbon was performed in two different chemical activation of KOH and ZnCl2. The effects of the different KOH/ZnCl2 concentrations at high‐temperature pyrolysis on the morphological structure and porosity were investigated. The synthesized activated carbon possesses micro/mesopores hollow nanofiber/nanosheet, which enhanced specific surface area from 15.163 m2 g−1 to ultrahigh specific surface area of 1041.900 m2 g−1. These behaviors exhibit a high specific capacitance of 213 F g−1 in a two‐electrode system with excellent energy and power density of 29.6 Wh kg−1 and 106.6 W kg−1 at 1 M H2SO4 aqueous electrolyte. These results provided accurate information about a feasible approach to synthesize biomass‐based porous hollow carbon nanofiber/nanosheet to boost high‐performance energy storage devices. [ABSTRACT FROM AUTHOR]

Rational design and modulation of oxygen electrocatalytic microenvironment are crucial for achieving high performance in rechargeable Zn-air batteries (RZABs). We report a high-efficiency bifunctional electrocatalyst based on S, N codoped carbon fibers confining carbon nanocapsules attached with Co 9 S 8 nanoparticles to customize the oxygen electrocatalytic microenvironment. The inner carbon nanocapsules function as a "gas buffer", while the outer fiber skeleton acts as a self-supporting structure, which jointly refine the oxygen electrocatalytic microenvironment and improve accessibility of the active sites. Such a unique nanostructure proves advantageous for O 2 adsorption/diffusion and mitigation of local pH changes during oxygen reduction reaction, and favors the release of generated O 2 and the transfer of interfacial electron during the oxygen evolution reaction as well. The constructed liquid RZABs deliver a large peak power density (280 mW cm−2) and robust cyclability (1200 h at 10 mA cm−2), and the assembled quasi-solid state flexible RZABs further indicate long-term durability. [Display omitted] • S, N codoped carbon fibers confining carbon nanocapsules attached with Co 9 S 8 NPs are constructed. • DFT confirms the curved structures can optimize the free energy of Co 9 S 8 for intermediates. • CNC/Co 9 S 8 @SNCF exhibits outstanding pH-universal ORR performance and OER activity. • The Zn-air battery shows a large peak power density (280 mW cm−2) and robust cyclability (1200 h at 10 mA cm−2). [ABSTRACT FROM AUTHOR]

• MnO 2 /CNF/Ag nanofabric electrodes are developed for flexible supercapacitors. • The brittle issue in the CNF electrode is greatly improved by an Ag incorporation. • The optimized MnO 2 /CNF/Ag electrode has a specific capacitance of 184 F/g at 1 A/g. • An energy density of 16.3 Wh/kg and a power density of 400 W/kg was achieved. • A capacitance retention rate of 87 % was demonstrated when subjected to bending. Flexible supercapacitors are gaining increasing popularity due to their potential in powering portable, wearable, and lightweight electronic devices. In this study, we have successfully developed a high-performance flexible electrode for quasi-solid-state supercapacitors by incorporating Ag into carbon nanofibers (CNF) through electrospinning, and growing MnO 2 as an active material on the electrode using an in-situ redox method. The Ag and MnO 2 co-decorated CNF electrode offers several advantages over conventional CNF electrodes, including an enlarged reaction area, higher charge storage capacity, and improved resistance to brittleness issues. Among all the quasi-solid-state supercapacitors tested, the MnO 2 -decorated electrode with an optimized Ag incorporation exhibited the highest specific capacitance of 184 F/g at a current density of 1 A/g, representing a remarkable 17-fold increase compared to the reference CNF electrode. Furthermore, the Ag and MnO 2 co-decorated electrode demonstrated an energy density of 16.3 Wh/kg and a power density of 400 W/kg at the same current density. Notably, the electrode exhibited excellent flexibility, with a capacitance retention rate of 87 % when subjected to bending with a curvature ranging from 5 to 1.25 cm. Our results suggest that the Ag and MnO 2 co-decorated CNF electrode holds great promise for flexible energy storage applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, we have successfully developed a series of low-cost, environmentally friendly, and high-performance carbon-based conductive inks with a three-dimensional micro-nano structure through a simple dispersion and ball-milling process, offering an array of desirable characteristics. Significantly, the carbon-based conductive inks remained stable even after a 30-day settling period. Furthermore, the conductive film, produced using screen printing techniques, demonstrated an impressive conductivity of 1.99 × 103 S/m. This remarkable conductivity highlights the ability of the films to consistently maintain a robust conductivity network, even when subjected to 5000 mechanical bending/releasing tests. Expanding on the success of our carbon-based conductive inks, we harnessed their potential in the production of all-solid-state flexible Micro-supercapacitors (MSCs) with an interdigital structure, utilizing screen-printing technology. The resulting MSCs exhibited outstanding performance metrics, including a notable areal energy density of 1.47 µWh cm-2 and an area power density of 0.2 mW cm-2. Moreover, these MSCs demonstrated remarkable cycle stability, retaining 96.3% of their capacitance after 20,000 cycles. Additionally, their excellent mechanical flexibility was evident as they experienced only a minor 2.98% capacitance degradation after undergoing 5000 bending/releasing cycles. These findings highlight the enormous potential of our work in facilitating the scalable production of wearable and portable electronic products. • Synthesize a high-performance aqueous carbon-based ink. • Carbon black was attached to graphite flakes to construct an effective three-dimensional micro-nano structure. • The ink was applied in the field of planar micro-supercapacitors with screen printing technology, showing good electrochemical performances and excellent mechanical flexibility. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ni-CAT/NiFe-LDH/CNFs catalyst demonstrated effective OER performance. • It has both a large surface area and significant intrinsic activity. • The catalyst was utilized to construct liquid-state and solid-state Zn-air batteries. • Optimizing the intermediate adsorption is the main factor in enhancing catalyst performance. NiFe layered double hydroxide (NiFe-LDH) is an efficient and widely available catalyst for the oxygen evolution reaction (OER), but further improvement of its OER property remains a challenge. Therefore, a conductive Ni-organic framework is triumphantly synthesized in-situ on NiFe-LDH/carbon nanofibers (Ni-CAT/NiFe-LDH/CNFs) through a hydrothermal treatment. This configuration utilizes the exposed surface area and the electron transfer pathways of Ni-CAT and CNFs, resulting in exceptional OER kinetics in alkaline conditions. A low overpotential of 370 mV at 10 mA cm−2 and a small Tafel slope of 79 mV dec−1 are achieved. The liquid-state Zn-air batteries, featuring Ni-CAT/NiFe-LDH/CNFs catalyst as an air cathode, indicate a significant peak power density of 292.1 mW cm−2 and an extended cycle durability of over 66 h. Solid-state Zn-air batteries demonstrate stable cycling at various flat/bent/flat states, showing great potential for flexible electronic device applications. According to experimental measurements and computational analysis, the in-situ growth of Ni-CAT on the NiFe-LDH matrix can optimize intermediate adsorption and alter hydrophilicity, resulting in improved performance of Zn-air batteries. [ABSTRACT FROM AUTHOR]

The increasing commercialization of flexible electronic products has sparked a rising interest in flexible wearable energy storage devices. Supercapacitors are positioned as one of the systems with the most potential due to their distinctive advantages: high power density, rapid charge and discharge rates, and long cycle life. However, electrode materials face challenges in providing excellent mechanical strength while ensuring sufficient energy density. This study presents a method for constructing a flexible composite electrode material with high capacitance and mechanical performance by electrochemically depositing high-quality manganese dioxide (MnO 2) onto the surface of a nanocellulose (CNF) and carbon nanotube (CNT) conductive film. In this electrode material, the CNF/CNT composite film serves as a flexible conductive substrate, offering excellent mechanical properties (modulus of 3.3 GPa), conductivity (55 S/cm), and numerous active sites. Furthermore, at the interface between MnO 2 and the CNF/CNT substrate, C-O-Mn bonds are formed, promoting a tight connection between the composite materials. The assembled symmetric flexible supercapacitor (FSC) demonstrates impressive performance, with an areal specific capacitance of 934 mF/cm2, an energy density of 43.10 Wh/kg, a power density of 166.67 W/kg and a long cycle life (85 % Capacitance retention after 10,000 cycles), suggesting that they hold promise for FSC applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] Highly efficient electrochemical catalysts for oxygen reduction reactions (ORRs) are urgently needed for various energy conversion and storage devices to overcome sluggish ORR kinetics. Here, N,O-codoped carbon spheres with uniform mesopores and a high specific surface area were used as supports for decorating Co 3 O 4 nanoparticles via a facile immersion route. In addition to the benefit of ions and gas mass transfer, the abundant mesopores present in the three-dimensional (3D) carbon spheres also confine and isolate the Co 3 O 4 nanoparticles growing in it, which help to provide rich Co 3 O 4 active sites. The resulting hybrid material exhibits superior ORR activity in terms of even-better half-wave potential and stability than that of commercial Pt/C (40 wt%) in 0.1 M KOH electrolyte. To verify its catalytic activity, the hybrid material was employed as the cathode catalyst in a flexible solid-state zinc-air battery, which achieves a high power density of 227 mW cm−2; this power density is much higher than that of a Pt/C catalytic zinc-air battery (133 mW cm−2) under identical conditions. The improvement in catalytic activity in both aqueous and nonaqueous electrolytes can be attributed to the abundant active sites of the entangled Co 3 O 4 nanoparticles, as well as the novel N,O-codoped carbon structure. [ABSTRACT FROM AUTHOR]

In this work, lignin-based carbon nanofibers (LCNFs) were for the first time served as substrate for in-situ electrodeposition of polyaniline (PANI) and tested as pseudocapacitor. Two LCNFs with different lignin ratios were designed to distinguish their morphology and structural properties. Next, PANI deposition mechanisms on both LCNFs were investigated and the electrochemical performance of the resulting LCNF/PANIs were evaluated. It was found although LCNF2 was composed of less uniform nanofibers due to more presence of lignin in precursor dope, it had higher tensile strength/modulus than LCNF1 (strength: 34.3MPa to 24.2 MPa; Modulus: 2.40 GPa to 1.45GPa) and was more cost-effective. Particularly, the beaded fibers on LCNF2 contributes to the deposition of PANI with higher specific mass capacitance (612.8 F g−1 to 547.0 F g−1). Upon assembling into solid-state supercapacitors, the C m of LCNF2/PANI device was determined to be 229 F g−1 and the maximum energy density was 11.13Wh kg−1 at a power density of 0.08 kW kg−1. This work showed LCNF produced from renewable and low-cost lignin could be directly used as substrate for PANI deposition. Moreover, the composition in spinning dope played an important role in determining the performances of resulting pseudocapacitors. • First attempt to electrochemically deposit polyaniline on Lignin-based carbon fibers. • LCNF/PANI electrodes showed competitive capacitance to other non-renewable carbon-based electrodes. • LCNF/PANIs derived from beaded/non-beaded LCNFs are compared and investigated. • Higher lignin content is a merit when using as pseudocapacitor electrodes. [ABSTRACT FROM AUTHOR]

We report the microstructure, electrical and electrochemical properties of hybrid nanofibers composed of polyacrylonitrile (PAN)/lignin-derived carbon nanofibers and LaMnO3-based inorganic nanofibers for advanced applications as free-standing and binder-free electrode materials of energy storage devices. For this purpose, hybrid nanofibers are fabricated via dual-electrospinning technique and following heat-treatment at different temperatures of 700–1000 °C for simultaneous carbonization and calcination. The SEM, EDS, and XPS analyses reveal that the carbon content in the hybrid nanofibers increases with increasing the heat-treatment temperature and that La and Mn elements are dispersed uniformly over the hybrid nanofibers. The hybrid nanofibers heat-treated at 900 and 1000 °C have a high electrical conductivity of ~ 0.22 S/cm and ~ 0.35 S/cm, respectively. Accordingly, a symmetric two-electrode supercapacitor based on hybrid nanofibers heat-treated at 1000 °C is characterized to have excellent electrochemical performance such as specific capacitance of ~ 95.2 F/g at 1 A/g, power density of 667 W/kg, energy density of 17.6 Wh/kg, and capacitance retention of ~ 97% after 2000 cycles. The results denote that PAN/lignin and LaMnO3-based hybrid nanofibers can be utilized as self-supporting high-performance electrode materials for advanced energy storage devices. [ABSTRACT FROM AUTHOR]

Integrating high‐efficiency oxygen electrocatalyst directly into air electrodes is vital for zinc–air batteries to achieve higher electrochemical performance. Herein, a self‐standing membrane composed of hierarchical cobalt/nanocarbon nanofibers is fabricated by the electrospinning technique. This hybrid membrane can be directly employed as the bifunctional air electrode in zinc–air batteries and can achieve a high peak power density of 304 mW cm−2 with a long service life of 1500 h at 5 mA cm−2. Its assembled solid‐state zinc–air battery also delivers a promising power density of 176 mW cm−2 with decent flexibility. The impressive rechargeable battery performance would be attributed to the self‐standing membrane architecture integrated by oxygen electrocatalysts with abundant cobalt–nitrogen–carbon active species in the hierarchical electrode. This study may provide effective electrospinning solutions in integrating efficient electrocatalyst and electrode for energy storage and conversion technologies. [ABSTRACT FROM AUTHOR]

The N‐doped porous carbon (NPC) /carbon micro‐nanotubes (CMNT) /NixCoyOz nanosheets with rich mesopores and 1.37 wt% nitrogen doping are successfully synthesized by a pyrolysis‐ionization‐precipitation combination process, using coal‐based polyaniline and nickelocene as original materials. Therein, most of the CMNT are upright CMTs and worm‐like curved CNTs, and a few are bamboo‐like tubes or carbon nanofibers. Moreover, many flower‐like aggregates assembled by spinel NiCo2O4 nanosheets are anchored on the surface of the NPC and CMNT. The NPC/CMNT/NixCoyOz exhibits a high specific capacitance and cycling stability, attributed to the large BET specific surface area (485 m2/g), suitable BET average pore size (2.3 nm), good hydrophilicity and wettability, and synergistic effects among three components. The assembled NPC/CMNT/NixCoyOz//AC asymmetric supercapacitor also demonstres a high specific capacitance of 120 F g−1 at a current density of 1 A g−1 and a high energy density of 16.7 Wh kg−1 at a power density of 500 W kg−1. [ABSTRACT FROM AUTHOR]

Herein, this paper reports a facile method to prepare electrospun carbon nanofiber mats (ECNFMs) with high specific surface area and interconnected structure using polyacrylonitrile (PAN) as a precursor and novolac resin (NOC) as a polymer sacrificial pore‐making agent. Without additional treatment, the prepared ECNFMs have a highly porous structure because NOC decomposes in a wider temperature range than most polymer activators. The NOC content in the PAN nanofibers shows important effects on porosity. The BET specific surface area of ECNFMs reaches a maximum of 1468 m2 g−1 when the precursor nanofibers contained 30 wt% NOC (ECNFM‐3) after carbonization at 1000 °C. The supercapacitor device from ECNFM‐3 electrode and all‐solid‐state electrolyte shows excellent cycling durability and high specific capacitance: ≈99.72% capacitance retention after 10 000 charge/discharge cycles and ≈320 mF cm−2 at 0.25 mA cm−2. Furthermore, it shows a large energy density of ≈11.1 μWh cm−2 under the power density of 500 mW m−2. Activation of carbon nanofibers simply by the addition of NOC into precursor nanofibers can offer a handy way to prepare ECNFMs for high‐performance all‐solid‐state supercapacitors and other potential applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe and Co bi-metal single atoms were doped in 3D nitrogen-doped carbon nanosheets with synergetic coupling strategy. • Synergetic coupling effect between metals atoms increases their intrinsic activity. • A-FeCo@NCNs exhibits excellent ORR/OER activity and Zn-air battery performance. Single atom catalysts (SACs) with unique structure gain much interest in the field of electrocatalysis and show a broad application prospect in long-life rechargeable Zn-air batteries. However, ingenious design and preparation of bi-metal SACs is still difficult to further enhance the bifunctional electrocatalytic activity. Herein, modified zeolitic imidazolate frameworks (SiO 2 @Fe-ZIF-8/67) was facilely designed to preparation atomically dispersed Fe and Co doping 3D nitrogen-doped carbon nanosheets (A-FeCo@NCNs). The Fe or Co single atoms are identified to be coordinated with N atoms and form FeN 4 , CoN 4 or N 3 Fe-CoN 3 anchored on 3D defect carbon, which act as reactive sites for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Through synergetic coupling effect, A-FeCo@NCNs exhibits excellent electrochemical performance with ORR/OER potential gap of 0.80 V. Density functional theory (DFT) calculations further indicate the synergistic effect between Fe and Co in A-FeCo@NCNs towards the enhancing ORR activity. The as-prepared catalyst assembled Zn-air battery shows a maximum power density, and superb cycling stability, surpassing that based on commercial Pt/C + IrO 2. Results from this study may provide a facile method for precious control of dual-metal single sites doped carbon with highly activity and durability for bifunctional electrocatalysis. [ABSTRACT FROM AUTHOR]

Summary: With the increasing challenge of energy, resource, and environment, it is highly desired to develop renewable energy and corresponding efficient energy storage technologies basing on reproducible materials. Recently, using biomass and biotechnology to prepare electrode material for energy storage devices is gaining growing attention. Here, we use biomass, celery, as a material source and developed a new way to prepare highly qualified graphitized porous carbon. Besides, instead of direct carbonization, the celery is first freeze‐dried to protect the original elements and structure of biomass. Furthermore, to sculpture more nanoscale pores in the produced material, the following carbonization process is also greatly modified by investigating proper carbonization temperature and time. Therefore, the interconnected hierarchical porous structure can be formed based on the protected original pores with size of micrometers and the newly formed pores with size of nanometers. The resulted interconnected hierarchical porous carbon is used to prepare supercapacitor electrode and exhibit excellent energy storage properties. Without any extra activating or doping process, the specific capacitance of the resulted electrode reached 350.0 F g−1 at 1 A g−1, which is 5.28 times of that of directly carbonized material. And the power density reached 8.0 kW kg−1 with the energy density maintaining 16.3 Wh kg−1. [ABSTRACT FROM AUTHOR]

• Average diameter of SU8 polymer-derived CNF is within the range of 60–140 nm. • SU8 polymer-derived pattern CNF anodes show ultra-high capacity (3450 mA h g−1). • GED and GPDs of Li/CNF cells from DFT studies are 26.96 kW h g−1 and 26.96 kW g−1. • Average, oxidation and reduction potential of CNF/LMNC cell are 4.4, 2.44 and 2.64 V. • GED and GPDs of pattern CNF/LMNC cells are 43.18 kW h kg−1 and 51.82 kW kg−1. This study provides a novel and sustainable protocol for the synthesis of SU8 polymer-based pattern, un-pattern carbon nanofibers (CNF) using an electrospinning process followed by a photolithography technique. Scanning electron microscopy (SEM) analysis of pattern, un-pattern CNFs shows that the average diameter of CNF is within the range of 60–140 nm. Transmission electron microscopy (TEM) studies disclose the average size of CNF exists within the range of 40–150 nm. The first-principle calculations predict that the gravimetric energy and power densities of Li/CNF half cells are 26.96 kW h g−1 and 26.96 kW g−1, respectively. The corresponding theoretical volumetric energy and power densities are 0.07 W h cm−3 and 0.07 W cm−3, respectively. Electrochemical analysis demonstrates the initial discharge capacities of pattern, un-pattern Li/CNF half cells at 100 mA g−1 are 3450 and 2429.8 mA h g−1, respectively. The gravimetric energy density of pattern, un-pattern Li/CNF half cells are within the range of 1800–1366.76 W h kg−1, and subsequent power densities are in the span of 519.63–434.22 kW g−1. The theoretical gravimetric energy and power densities of CNF/LiMn 0.33 Ni 0.33 Co 0.33 (LMNC) full cells are 2.9 kWh kg−1 and ∼ 2.9 kW kg−1, respectively. Their theoretical volumetric energy and power densities are 1.96 W h cm−3 and 1.96 W cm−3, respectively. Electrochemical analysis discloses that the gravimetric energy and power densities of pattern CNF/LMNC full cells are in the range of 43.18–42.4 kW h kg−1 and 51.82–50.90 kW kg−1, respectively. The gravimetric energy and power densities of un-pattern CNF/LMNC full cells are 42.07–41.59 W h kg−1 and 50.48–49.92 kW kg−1, respectively. [ABSTRACT FROM AUTHOR]

Lithium-ion supercapacitors (LICs) have received widespread interests because of their high power density, high energy and long life characteristics. The electrodes for LICs play a significant role in enhancing their performance. Therefore, it is of great significance to design and develop high-performance electrode materials for LIC through integrating various materials to make up for each other's disadvantages. Herein, a bimetallic composite nanomaterial with hierarchical structures (CoSn X /CNFM) and a porous carbon nanomaterial with high specific surface area (PCNFM) were obtained through combining electrospinning, anion exchange or alkali etching and subsequent high-temperature carbonization, respectively. The LIC assembled with the pre-lithiated CoSn X /CNFM as anode and the PCNFM as cathode exhibited a high energy density of 41.48 Wh/kg at a power density of 1500 W/kg, and still had an energy density of 28.13 Wh/kg at a high power density of 7500 W/kg, illustrating its high power density and high energy density. Thus, this paper proposes an effective method for designing and manufacturing high-performance LICs. • Nanofibers with uniformly distributed ZIF-67 NPs were prepared in batches by EMAI. • Hierarchical-structured CoSn X /CNFM was prepared by anion exchange and carbonization. • PCNFM with high specific surface area was prepared by etching and carbonization. • A LIC with pre-lithiated CoSn X /CNFM as anode and PCNFM as cathode was assembled. • The assembled LIC had high power density and high energy density. [ABSTRACT FROM AUTHOR]

SnS is an ideal material for supercapacitors because of its unique layered structure and excellent electrochemical performance, but the research of SnS based electrode materials of flexible self-supporting supercapacitors has been rarely exploited. In this study, microsphere like Co doped SnS grown on carbon nanofibers (Co-SnS@CNF) was prepared by electrospinning, hydrothermal method and annealing treatment. Co-SnS@CNF has great flexibility, high specific capacitance, excellent rate performance and cycle stability. Specifically, the specific capacitance is 750 F g−1 at the current density of 1 A g−1. The special microsphere structure with more electrochemical active sites and lower resistance of ion and charge transfer by Co doping are responsible for the superior electrochemical performances. Furthermore, when assembled Co-SnS@CNF as the symmetrical supercapacitor device, the energy density of 20.89 Wh Kg−1 and the power density of 376 W Kg−1 are achieved at the current density of 1 A g−1, while showing ultra-high cycle stability. Therefore, the Co-SnS@CNF offers excellent application potential for flexible self-supporting supercapacitors. • Revealing reasons for the high-performance of the microspherical Co-doped SnS. • The specific capacitance is 750 F g−1 at the current density of 1 A g−1. • The assembled symmetrical device exhibits the ultra-high cycle stability. [ABSTRACT FROM AUTHOR]

Hierarchical MnO 2 -based fiber-in-tube and particle-in-tube nanostructures with unique chemical compositions and gradient pores have been rationally designed and constructed using a simple self-template method for high-performance asymmetric supercapacitors, which deliver extraordinarily excellent energy density. • MnO 2 -based fiber-in-tube and particle-in-tube nanostructures are designed. • The hierarchical architectures are fabricated via a simple self-template approach. • The novel nanotubes yield superior specific capacity as supercapacitor electrodes. • The asymmetric supercapacitors deliver extraordinarily excellent energy density. Manganese dioxide (MnO 2) promises for high-performance asymmetric suprecapacitors, owing to its high theoretical capacity, abundant source, and low cost. However, insufficient practically-achievable capacity and relatively narrow voltage window in alkaline electrolyte are blocking high energy density of MnO 2 -based supercapacitors, where strategies for activating its capacitive performance and widening voltage window are the top priorities to solve the bottleneck problems. Herein, both the fiber-in-tube (NCCM-FiT) and particle-in-tube (NCCM-PiT) nanostructures coulping active NiCoO x nanoparticles and conductive carbon with MnO 2 tubes have been purposely fabricated, using the electrospun nickel cobalt oxides/carbon nanofibers (NCO/CNFs) as the self-template agents for enhanced energy density of MnO 2 -based supercapacitors. These hierarchical hollow nanotubes with gradient pores and unique compositions yield excellent capacitive properties, in terms of a competitive capacity (431.7 F g−1 or 431.7 C g−1, 0.5 A g−1), which is 2.7 times that of the MnO 2 nanotubes-based electrodes. A maximum energy density of 46.4 Wh kg−1 is obtained at the power density of 400 W kg−1 for the asymmetric device assembled with the NCCM-PiT-based positive electrode and the electrospun CNFs-based negative electrode. The remarkable energy density demonstrated by these hierarchical hollow nanotubes exemplifies a novel and effective design in electrode materials for the asymmetric supercapacitors (ASCs) with superior performance. [ABSTRACT FROM AUTHOR]

In this paper, we proposed the synthesis of CoFe nanoparticles (NPs) which have been deposited on carbon nanofibers (CNFs) with a facile electrospinning route followed by thermal reduction. The performance of obtained CNF supercapacitors are improved from 51 to 190 F/g (247 mF/cm2) at 0.5 A/g with the combination of CoFe NPs and graphitized carbon layers The device possessed an energy and power density of 6.6 Wh/kg and 125 W/kg, respectively. Furthermore, the capacitance retention can still maintain about 96.6% after 10,000 cycle test and it is worth noting that the cycling stability is ultrahigh. This research proves that bimetallic nanoparticles embedded in CNFs can elucidate new insights into the development new nanofiber electrode materials for the next generation of symmetric supercapacitors. [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]

The preparation of electrode materials with superior electrochemical performance and excellent mechanical properties are essential for the fabrication of flexible supercapacitors. However, the compatibility of the porosity and flexibility for the electrode materials remains challenging. Herein, free-standing porous coaxial carbon nanofiber (PCCNF) membranes with large specific surface area (648 m2 g−1) and suitable pore size distribution were fabricated by a facile coaxial electrospinning technique and template method. PCCNF possesses superb capacitance of 261 and 48 F g−1 (1 A g−1) in three-electrode and two-electrode system, respectively, result in remarkable energy density (48.6 ± 3 Wh kg−1) and power density (67.5 ± 1 Wh kg−1). Moreover, supercapacitor devices based on PCCNF show superb flexibility as well as excellent electrochemical and mechanical stability. PCCNF-based high performance supercapacitors may be suitable for flexible electronic energy storage devices. Porous coaxial carbon nanofibers (PCCNF) with large specific surface area, well-balanced pore size distribution, and remarkable flexibility are fabricated by a facile coaxial electrospinning technique and template method. Flexible supercapacitors fabricated with the as-prepared PCCNF display superb electrochemical and mechanical stability. This work provides exciting opportunities for the preparation and application of flexible energy storage devices. Image 1 [ABSTRACT FROM AUTHOR]

Carbon nanofiber (CNF)‐based supercapacitors have promising applications in the field of energy storage. It is desirable, but remains challenging, to develop CNF electrode materials with large specific surface area (SSA), high specific capacitance (SC), and high power density, as well as excellent cycling stability and high reliability. Herein, acrylonitrile–acrylic acid copolymer P(AN‐co‐AA) was synthesized for the preparation of nitrogen‐doped microporous CNFs. Thermal degradation of the AA segment leads to the formation of micropores that are distributed not only on the CNF surface, but also inside the material. The microporous structure and nitrogen content can be manipulated at the molecular level by adjusting the weight ratio between AN and AA, and the SSA and SC could reach as high as 1099 m2 g−1 and 156 F g−1, respectively. After KOH activation, the activated CNFs have an extremely high SSA of 2117 m2 g−1 and SC of 320 F g−1, which are among the highest values ever reported for electric double‐layer supercapacitors with an alkaline electrolyte. Furthermore, the capacitance retention, which can be maintained at 99 % even after 16 000 cyclic tests, reveals outstanding durability and repeatability. [ABSTRACT FROM AUTHOR]

Flexible supercapacitors have drawn tremendous attention resulting from the rapid development of wearable electronic devices. Herein, we develop an effective and facile two-step approach to prepare high content nitrogen, sulfur co-doped porous carbon nanofibers film as electrodes of flexible supercapacitors. Benefiting from the high specific surface area and rich nitrogen/sulfur content, nitrogen and sulfur co-doped porous carbon fibers film (N, S co-doped PCFF) electrodes exhibit a high mass specific capacitance of 307.8 F g−1, and the capacitance retains 98% of initial capacitance after 5000 cycles in a three-electrode system. The as-assembled flexible supercapacitor devices with polyvinyl alcohol/KOH gel electrolyte demonstrate a highest mass specific capacitance of single electrode of 183.9 F g-1 at the scan rate of 2 mV s-1, which is better than that of other heteroatom doping carbon materials. In addition, the energy density reaches as high as 16.35 Wh kg−1 with the power density of 147 W kg−1 and retains as 5.34 Wh kg−1 with higher power density of 2402 W kg−1. Furthermore, the flexible devices show good cycling stability, superior flexibility and stable electrochemical performance. Schematic demonstration of Nitrogen, Sulfur co-doped PCFF electrodes, and schematic structure of flexible all-solid-state supercapacitor. Image 1 [ABSTRACT FROM AUTHOR]

Cu-N-C electrocatalyst was successfully prepared with Cu-BTC and polyacrylonitrile as templates by electrospinning and in-situ growth method. The effect of various N -doped content on the electrochemical performance of the catalyst were investigated and the Cu-N-C-0.25 exhibited the best OER/ORR catalytic activities. When it was applied to the cathode of the zinc-air batteries, the power density of Cu-N-C-0.25 was 209.1 mW cm − 2 , which exceeded that of the commercial Pt/C + IrO2 hybrid catalyst (157 mW cm − 2 ). The excellent electrochemical performance may be attributed to large number of active sites and high specific surface area on Cu-N-C electrocatalyst. It will be a promising alternative to precious metal catalysts containing Pt, Ir or Ru and their oxides. A simple and convenient method (electrospinning technique and soaking technique) was used to prepare a novel Cu-N-CNFs as a bifunctional electrochemical catalyst. The morphology and structure of Cu-N-C-0.25 were studied by SEM. The results showed the conjunct effects of the 3D porous cross-linked microstructures of carbon nanofibers, copper particles, doping of N element and structural defects as catalytic active sites, so that the carbon nanofibers have higher catalytic efficiency. [ABSTRACT FROM AUTHOR]

Rational design of highly effective and low-cost oxygen reduction reaction (ORR) electrocatalysts to replace Pt-based catalysts is still a significant challenge for rechargeable zinc-air batteries. Hence, Fe, N co-doped one-dimensional carbon nanofibers with Fe 4 N species (Fe/N-CNFs) are synthesized through the electrospun technique combining with the "rapid calcination under vacuum" method. Benefitting from the one-dimensional structure obtained by the electrospun technique, the as-synthesized Fe/N-CNFs electrocatalyst with mesoporous exhibits a relatively large specific surface area of 624.12 m2 g−1. Notably, the intrinsic activity of Fe 4 N species as well as the large specific surface area can endow the resulting Fe/N-CNFs with a positive half-wave potential of 0.88 V compared with 20 wt% Pt/C (0.86 V) for ORR. The Fe/N-CNFs also exhibits better long-term stability than 20 wt% Pt/C. Furthermore, the rechargeable zinc-air battery constructed with Fe/N-CNFs as the cathode shows a high open-circuit voltage of 1.51 V, a peak power density of 135 mW cm−2 and an excellent cycle life for 55 h. The as-synthesized electrocatalyst is promising to replace the precious metal catalysts for rechargeable zinc-air batteries. Unlabelled Image • Fe, N co-doped carbon nanofibers (Fe/N-CNFs) with Fe 4 N species were synthesized. • The "rapid calcination under vacuum" was reported for the preparation of Fe/N-CNFs. • The one-dimensional structure of Fe/N-CNFs provides a large specific surface area. • The Fe/N-CNFs exhibits more excellent ORR activity than commercial 20 wt% Pt/C. • The Fe/N-CNFs endows zinc-air batteries with comparable performances to 20 wt% Pt/C. [ABSTRACT FROM AUTHOR]

Herein, we outline the fabrication of highly porous three-dimensional carbon-fiber network anchored with uniform metallic cobalt (Co) via electrospinning and subsequent post-modification approaches. First, cobalt acetate solution saturated electrospun polyacrylonitrile (PAN) nanofibrous mat was subjected to sodium borohydride (NaBH 4) solution which results in the fabrication of three dimensional (3D) hierarchical multilayer network. Restructuring of the 2D mat into multilayered sponges with metal particles entrapment is attributed to the in-situ generated hydrogen gas into the interconnected pores of the fibrous network simultaneous with reduction of cobalt salt into metallic cobalt by NaBH 4. The resulting mesh was stabilized and carbonization at inert atmosphere to obtain metallic cobalt (Co) embedded 3D carbon nanofibrous networks (Co@3D-CNFs). Physicochemical characterization and electrochemical analysis were performed. Results show carbon network was found to be expanded with bubbling like structures often embedded metallic Co nanoparticles. X-ray diffraction (XRD) pattern confirms the existence of the metallic cobalt particles on the carbon fiber networks. Furthermore, we establish a resulting composite (Co@3D-CNFs) identify the enhanced electrochemical performance having specific capacitance 762 F g−1 compared to 173 and 180 F g−1 for corresponding @3D-CNFs and 2D carbon nanofiber network with cobalt doped (Co@2D-CNFs) counterparts, respectively. The assembled Co2@3D-CNFs//NGH ASC device exhibits a high energy density 24.6 W h Kg−1 at 797 W kg−1 power density with an operating voltage of 1.6 V (vs Ag/AgCl). The device further shows good capacitance retention (90.1%) after 5000 cycles. This research shows the simple and cost-effective strategy to make metallic particles embedded 3D porous carbonaceous electrode materials which can have great potential for energy storage application. [ABSTRACT FROM AUTHOR]