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The preparation of composite carbon nanomaterials is one of the methods for improving the electrochemical performance of carbon-based electrode materials for supercapacitors. However, traditional preparation methods are complicated and time-consuming, and the binder also leads to an increase in impedance and a decrease in specific capacitance. Therefore, in this work, we reduced Ni-Cu nanoparticles on the surface of nitrogen-doped carbon nanofibers (CNFs) by employing an electrostatic spinning method combined with pre-oxidation and annealing treatments. At the same time, Ni-Cu nanoparticles were vulcanized to Ni–Cu–S nanoparticles without destroying the structure of the CNFs. The area-specific capacitance of the CNFs/Ni–Cu–S–300 electrode reaches 1208 mF cm−2 at a current density of 1 mA cm−2, and the electrode has a good cycling stability with a capacitance retention rate of 76.5% after 5000 cycles. As a self-supporting electrode, this electrode can avoid the problem of the poor adhesion of electrode materials and the low utilization of active materials due to the inactivity of the binder and conductive agent in conventional collector electrodes, so it has excellent potential for application. [ABSTRACT FROM AUTHOR]

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]

• 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]

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