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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]

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]

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]

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]

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]

Low-cost, high-performance electrodes are highly attractive for practical supercapacitor applications. MnO 2 -deposited carbon nanofiber mats (MnO 2 -CNFMs) are prepared for use as binder-free supercapacitor electrodes. MnO 2 is deposited on the mats in situ by hydrothermally decomposing aqueous KMnO 4 , leading to the formation of nanocrystals of MnO 2 . The MnO 2 -CNFM electrode produced with 38.0 μmol KMnO 4 (this electrode) shows a high specific capacitance of ~171.6 F·g −1 at a scan rate of 5 mV·s −1 . Moreover, a symmetric supercapacitor with the electrode exhibits a specific capacitance of 67.0 F·g −1 , an energy density of 6.0 Wh·kg −1 and a power density of 160 W·kg −1 at a special current of 0.1 A·g −1 . Further, the symmetric supercapacitor displays excellent cycling stability, retains approximately 99% of the capacitance after 1000 cycles. The simplicity and ease of preparation of the MnO 2 -CNFMs as well as their suitability for use in coin-type supercapacitor cells make them ideal for application in cost-effective and high-performance electrodes for supercapacitors. [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]