Search

Manifold graphene-based supercapacitor (GSC) electrodes have been extensively studied recently. Numerous studies have aimed to improve the performance of GSCs by amending the surface using various treatments or by incorporating diverse materials. However, few studies have been conducted on the treatments for the back electrodes which support the active material in the GSCs. Herein, the activation of carbon nanofibers (CNFs) back electrodes was achieved through simple thermal activation using potassium hydroxide (KOH) as an activating agent to enhance the electrochemical performance of GSC electrodes. The optimized sample exhibited a specific capacitance (C sp) of 210 F/g at 100 mV/s without adversely affecting the self-discharge behavior of the electrodes. Compared to the reference electrodes formed on the nonactivated CNFs, the C sp at high rate operations of the GSC electrodes was markedly increased by 1.6 times. Morphological, elemental, and electrochemical analyses were conducted to study the effects of KOH activation on the performance enhancement of GSC electrodes. Our results present a novel research approach for enhancing GSC performance. [Display omitted] • KOH thermal activation for carbon nanofiber back electrodes was conducted. • An optimum temperature for the activation was found to be 800 °C. • The activation increased the specific capacitance for graphene supercapacitors. • The self-discharging did not worsen, indicating the practicality of this discovery. [ABSTRACT FROM AUTHOR]

The electrospun carbon nanofibers (ECNFs) with the advantages of facile preparation method, excellent electrical conductivity and ease compounding are expected to be excellent electrode materials for supercapacitors. However, the tiny specific surface area and low specific capacitance prevent the further development of carbon nanofibers. In this work, the porous coal-based carbon nanofibers (PCCNFs-2) are fabricated via a facile dual-template method, which can be directly employed as a flexible electrode material for supercapacitors without the addition of any conductive agents and binders. As a result, the flexible self-supporting electrode (PCCNFs-2) achieves a specific capacitance of 262.0 F g−1 at a current density of 1 A g−1, excellent rate performance (81.0 % capacitance retention at a current density of 20 A g−1) and excellent cycling stability (after 10,000 cycles, 124 % capacity retention at 2 A g−1). Furthermore, the aqueous symmetrical supercapacitors (SCs) assembled with melamine foam as the storage electrolyte at an operating voltage of 1.2 V achieved an energy density of 18.5 Wh kg−1 at a power density of 150.5 W kg−1. The effective construction of this porous carbon nanofiber assures the structural integrity and achieves excellent electrochemical performance of the electrode material, which develops a new strategy for efficient utilization of porous coal-based carbon nanofibers in supercapacitors. [Display omitted] • Flexible self-supporting PCCNFs-2 electrodes were prepared via dual-template strategy. • PCCNFs-2 electrode has a capacity retention rate of 124 % after 10,000 cycles. • The symmetrical supercapacitors with PCCNFs-2 exhibits high energy density and long cycling lifespan. [ABSTRACT FROM AUTHOR]

In this study, amorphous zinc oxide incorporated with sulfur-doped carbon composite nanofiber (ZnO@S-CNF) was obtained through a facile electrospinning technique and calcination. The ZnO@S-CNF composite was characterized in detail in order to understand the structural features of the electrodes and applied for supercapacitors. As a self-supporting electrode, it achieved a high capacitance of 209 F/g at 1 A/g and sustained 158 F/g at 10 A/g. Also, an asymmetric supercapacitor (ASC) assembled by ZnO@S-CNF as the positive and carbon nanofiber as the negative electrode (−CNF//ZnO@S-CNF+) achieved a specific energy of 11.2 Wh/kg at a specific power of 900 W/kg in 0–1.8 V. The excellent electrochemical performance can be ascribed to the enhanced surface area, increased micropore volume, and heteroatom content. This study can provide a feasible way for the development of other carbon composite electrodes with remarkable performance. [Display omitted] • Modification of the electronic structure by heteroatom doping, thereby promoting the supercapacitive performance. • Increased surface area with the synergistic effect of amorphous zinc oxide and introduction of sulfur in the carbon skeleton. • ASC device with a specific energy of 11.2 Wh/kg at a specific power of 900 W/kg. [ABSTRACT FROM AUTHOR]