Search

Abstract: Mechanically flexible mats consisting of electrospun carbon nanofibers (ECNFs) were prepared by first electrospinning aqueous mixtures containing a natural product of alkali lignin together with polyvinyl alcohol (PVA) into composite nanofiber mats followed by stabilization in air and carbonization in an inert environment. Morphological and structural properties, as well as specific surface area, total pore volume, average pore size, and pore size distribution, of the lignin-based ECNF mats were characterized; and their electrochemical performances (i.e., capacitive behaviors) were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The lignin-based ECNF mats exhibited outstanding performance as free-standing and/or binder-free electrodes of supercapacitors. For example, the ECNFs made from the composite nanofibers with mass ratio of lignin/PVA being 70/30 (i.e., ECNFs (70/30)) had the average diameter of ∼100 nm and the Brunauer–Emmett–Teller (BET) specific surface area of ∼583 m2 g−1. The gravimetric capacitance of ECNFs (70/30) electrode in 6 M KOH aqueous electrolyte exhibited 64 F g−1 at current density of 400 mA g−1 and 50 F g−1 at 2000 mA g−1. The ECNFs (70/30) electrode also exhibited excellent cycling durability/stability, and the gravimetric capacitance merely reduced by ∼10% after 6000 cycles of charge/discharge. [Copyright &y& Elsevier]

Abstract: This paper studies the synthesis and electrochemical characterization of novel graphene-beaded carbon nanofibers (G/CNFs) as electrode material for use in supercapacitor. The porous G/CNF films were prepared by electrospinning polyacrylonitrile (PAN)/N,N-dimethylformamide (DMF) solution dispersed with oxidized graphene nanosheets, followed by carbonization at 800 °C in a tubular quartz furnace. The morphology and chemical structure of the porous G/CNF films were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The electrochemical behavior of the synthesized G/CNF films as supercapacitor electrodes was characterized by means of cyclic voltammetry (CV), galvanotactic charge/discharge, and electrochemical impedance test in a 6 m KOH aqueous electrolyte. Electrochemical measurements revealed that the maximum specific capacitance of the porous G/CNF electrodes reached up to 263.7 F g− 1 at a discharge current density 100 mA g− 1. Furthermore, the supercapacitor exhibited very good cycling stability of energy storage with the retention ratio of 86.9% after 2000 cycles. The high electrochemical performance of the G/CNF electrodes was attributed to the unique nanostructural configuration, high electrical conductivity, and large specific surface area of the graphene nanosheets. [Copyright &y& Elsevier]