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To overcome the drawback of carbon nanofibers (CNFs) such as the low energy density and low specific capacitance as electrode for supercapacitors, SiO 2 /PANI@CNFs composite was prepared by layer-by-layer (LbL) assembly technique, in which the SiO 2 served as a component for improving capacitive behavior. Polyaniline (PANI) is used as nucleation site for synthesizing SiO 2 particles as well as active material for improving capacitance. In this study, SiO 2 particles were synthesized using biosilicification process as a bioinspired, rapid, and facile synthetic route for SiO 2 particles at ambient temperature and pressure, etc. To elucidate effect of SiO 2 on the electrochemical properties, SiO 2 /PANI@CNFs samples were prepared by varying concentration ratio of tetraethyl orthosilicate (TEOS) to CNFs. It was observed that the specific surface area and the capacitance are highly dependent on the TEOS concentration. The capacitance of the composite prepared at the TEOS concentration of 0.19 mmol reaches 412 F g−1 at the current density of 1 A g−1. These results are attributed to increased specific surface area from interstitial voids between SiO 2 particles and hydrophilic nature of SiO 2 particles, which offers sufficient channels for rapid ion diffusion and leads easy accessibility to the active sites for the electrochemical reaction between electrode and aqueous electrolyte. Due to its excellent electrochemical and biocompatible properties, bioinspired SiO 2 inorganic material will promote the development of energy storage devices in biomedical and environmental electronics. [ABSTRACT FROM AUTHOR]

Supercapacitors are considered as important energy conversion and storage devices, and one‐dimensional carbon nanofibers derived from electrospinning have been widely applied for supercapacitor electrode materials. The integration of carbon and metal hydroxide materials has become particularly important in order to pursue their higher electrochemical properties. In this paper, a one‐dimensional core‐shell electrode with Ni(OH)2 as shell and carbon nanofibers as core (Ni/CNFs@Ni(OH)2) was fabricated by electrospinning, high‐temperature carbonization and hydrothermal synthesis. This electrode exhibited high energy storage performance (785 F g−1 (1 A g−1)), good coulombic efficiency and cycling stability. Furthermore, the asymmetric supercapacitor (ASC) assembled with activated carbons as negative electrode and Ni/CNFs@Ni(OH)2 as positive electrode demonstrated a good energy storage performance (62.5 F g−1 (1.6 V)). Meanwhile, this ASC displayed a significant energy density of 22.2 Wh kg−1 at 800 W kg−1 and an outstanding rate capability, indicating that Ni/CNFs@Ni(OH)2 had a high potential application value in supercapacitors. [ABSTRACT FROM AUTHOR]

Transition−metal−based materials show great promise for energy conversion and storage due to their excellent chemical properties, low cost, and excellent natural properties. In this paper, through simple strategies such as classical electrospinning, air calcination, and the one−step hydrothermal method, a large area of Ni(OH)2 nanosheets were grown on NiMoO4 nanofibers, forming NiMoO4@Ni(OH)2 nanofibers. The one−dimensional nanostructure was distributed with loose nanosheets, and this beneficial morphology made charge−transfer and diffusion more rapid, so the newly developed material showed good capacitance and conductivity. Under the most suitable experimental conditions, the optimal electrode exhibited the highest specific capacitance (1293 F/g at 1 A/g) and considerable rate capability (56.8% at 10 A/g) under typical test conditions. Most interestingly, the corresponding asymmetrical capacitors exhibited excellent electrochemical cycle stability, maintaining 77% of the original capacitance. NiMoO4@Ni(OH)2 nanofibers were verified to be simple to prepare and to have good performances as energy−storage devices within this experiment. [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]

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]

Nowadays, materials that possess high activity and natural oxygen vacancy have garnered significant attention as potential electrode materials for supercapacitors. In this study, we successfully prepared the Hf 6 Ta 2 O 17 (HTO) nanofibres (NFs) with an orthorhombic superlattice structure using the electrospinning technique and sintering process. The characterization results indicate that the HTO NFs synthesized at 750 °C show good micro nanostructures and outstanding electrochemical properties. To enhance its energy storage performance, additional oxygen vacancies (OVs) were introduced through a carbothermal treatment under an Ar atmosphere. Although longer reduction reaction times can produce more OVs, the integration of grain boundaries and the growth of grain size caused by large annealing times may limit its electrochemical performance. Therefore, the HTO NFs treated for 1 h (HTO/C-1) exhibited the maximum C s of 925 F·g−1 at 1 A·g−1 with a larger voltage window of 2.1 V. Furthermore, a symmetric supercapacitor fabricated by two reduced HTO NFs electrodes and 1 M Na 2 SO 4 solution, recorded as r-HTO NFs//r-HTO NFs. The device demonstrated excellent energy density of 73.3 Wh·kg−1 (at power density of 1050 W·kg−1) and a long cycling life (81.8% retained after 5000 cycles). These results suggest that the optimized reduction process can provide appropriate oxygen vacancies in HTO NFs, thereby effectively enhancing its performance. [Display omitted] • The Hf 6 Ta 2 O 17 (HTO) nanofibres (NFs) are synthesized by electrospinning method. • The micro nanostructures and electrochemical property of HTO NFs can be designed by controlling the synthesis temperature. • The carbothermal treatment carried under Ar atmosphere is used to improve the amount of oxygen vacancies of HTO NFs. • The HTO NFs treated of 1 h (HTO/C-1) presents excellent capacitance of 925 F·g−1 at 1 A·g−1. • The r-HTO NFs//r-HTO NFs device shows high energy density of 73.3 Wh·kg−1 at power density of 1050 W·kg−1. [ABSTRACT FROM AUTHOR]

• Hierarchical porous carbon (HPC) is obtained with three-dimensional (3D) structure. • The HPC with highly fluffy 3D continuous network is found as an ideal support. • HPC-supported MnO 2 nanofibers composite is achieved as a supercapacitor material. • The as-prepared MnO 2 @HPC composite has 3D interpenetrating network structure. • The MnO 2 @HPC composite presents excellent electrochemical performance. For improving the conductivity of porous carbon and the utilizations of its pore structures, a hierarchical porous carbon (HPC) had been developed with highly fluffy three-dimensional (3D) continuous network structure. Using the HPC as a support, a novel MnO 2 @HPC composite with 3D interpenetrating network structure was prepared as electrode material of supercapacitor via simple hydrothermal method. When the hydrothermal reaction temperature was 100°C, the MnO 2 nanofibers (∼5 nm) were uniformly grown on and within the fluffy 3D porous network of the HPC, forming a composite with interpenetrating network structure. The as-prepared composite (MnO 2 @HPC-100) exhibited the characteristics of both electric double-layer capacitance and pseudo-capacitance, which had a high specific capacity of 368 F g−1 at a current density of 0.5 A g−1 and 186 F g−1 at 10 A g−1 (50.5% retention). In addition, the asymmetric supercapacitor device was assembled with a relatively high energy density of 88.2 Wh Kg−1 at a power density of 162 W Kg−1. The device had a high capacity retention rate of 95% after 10000 cycles, and the coulomb efficiency was stable at 99.7%, showing the excellent stability of the composite. Therefore, the MnO 2 @HPC-100 composite has great application prospects in energy storage. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • L-BCNF-x were prepared from the combination of MP and C 6 H 6 O via electrospinning process. • The performance of L-BCNF-4 was attributed to its large surface area 508.73 m2/g.. • Device exhibits high energy density of 13.3 Wh/kg at a specific power of 1741 W/kg. Supercapacitors are high power density energy storage systems with a fast charge, low-rate discharge, and excellent cycle stability. Herein, optimized method was reported to produce liquefied bio-carbon nanofibers (l -BCNF-x). This technique is based on the heating of combined mangosteen peels (MP) with monohydroxybenzene (C 6 H 6 O) in an oil bath, followed by electrospinning and carbonization under 700 °C for 1 h. After characterization, results showed that well-structured micro/mesoporous structures make the prepared l -BCNF-x with well-defined amorphous shapes. However, following the mingling of liquefied bio-carbon (LC) and (polyacrylonitrile) PAN at various mass ratios, the prepared l -BCNF-4 (6:4 mass ratio) holds an excellent electrochemical performance for supercapacitors with a specific capacitance of 365.5 F/g at 0.5 A/g and retention rate of 97.7% after 10,000 cycles. More significantly, the device exhibits a high energy density of 18 Wh/kg at a power density of 348.9 W/kg at 1 A/g current density. The performance of l -BCNF-4 was assigned to its large surface area (508.73 m2/g) which shortens the ion diffusion paths and rapid migration of electrons. Our experimental ensues prove that due to the simplicity and cost-effectiveness through the less use of PAN of the optimized introduced method, l -BCNF-x reveals promising future green energy production applications. [ABSTRACT FROM AUTHOR]

In the field of advanced energy storage, nanostructured Polyaniline (PANI) based materials hold a special place. Extensive studies have been done on the application of PANI in supercapacitors, however, the structure–property relationship of these materials is still not understood. This paper presents a detailed characterization of the novel sodium phytate doped 3D PANI nanofibers anchored on different types of carbon paper for application in supercapacitors. An excellent relationship between the structures and properties of the synthesized samples was found. Remarkable energy storage characteristics with low values of solution, charge transfer and polarization resistance and a specific capacitance of 1106.9 ± 1.5 F g−1 and 779 ± 2.6 F g−1 at current density 0.5 and 10 Ag−1, respectively, was achieved at optimized conditions. The symmetric supercapacitor assembly showed significant enhancement in both energy density and power density. It delivered an energy density of 95 Wh kg−1 at a power of 846 W kg−1. At a high-power density of 16.9 kW kg−1, the energy density can still be kept at 13 Wh kg−1. Cyclic stability was also checked for 1000 cycles at a current density of 10 Ag−1 having excellent retention, i.e., 96%. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanofibers (NCNFs) are important electrode materials that have received tremendous attention in terms of their capacity to store energy. At present, it is still desirable to fabricate high-performance NCNFs for supercapacitors. Here, for the first time, polyacrylonitrile@branched polyethylenimine (PAN@bPEI) composite nanofibers are proposed as precursors to prepare freestanding NCNFs, which can then be used directly in flexible supercapacitors. The single electrode based on the resultant NCNFs with unique chemical composition exhibits electrochemical properties that are superior to those of the polyacrylonitrile-derived CNFs electrode. In addition, a quasi-solid-state symmetric supercapacitor assembled without the use of any adhesive or conductive agent also shows a comparable energy density, favorable cycling durability, and mechanical stability, indicating that bPEI is an effective nitrogen source with which to construct nitrogen-doped carbon fibers for energy storage applications. • The freestanding nitrogen-doped carbon nanofibers (NCNFs) were prepared. • Polyacrylonitrile@branched polyethylenimine nanofibers are proposed as precursors. • The obtained NCNFs exhibited excellent supercapacitive performance and flexibility. [ABSTRACT FROM AUTHOR]