Chemically Treated Carbon Nanofiber Materials for Supercapacitors

Abstract

Carbon nanofibers obtained by catalytic decomposition of methane in a vibrated fluidized bed reactor were chemically treated to increase the specific capacitance of supercapacitors. The material was studied by transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform IR spectroscopy, and cyclic voltammetry. The treatment was conducted in various media (H₂SO₄, HNO₃, H₂Cr₂O₇, and HCl) at 80°C for 6 h. The chemical treatment was accompanied by a significant weight loss (14–67 wt %) and oxidation of the material. Treatment in diluted nitric acid mainly led to the transfer of surface layers of disordered carbon into solution with their removal during washing, while treatment in concentrated acid was more conducive to oxidation of the material surface. The highest specific capacitance (50.6 F g^–1 at 2 mV s^–1 in 3.5 M H₂SO₄ electrolyte) was attained when carbon nanofibers were treated with H₂Cr₂O₇.