Preparation of nanocrystalline VN by the melamine reduction of V2O5 xerogel and its supercapacitive behavior

An organic nitridizing reagent was employed in the preparation of nanocrystalline VN at 800 degrees C under a N-2 atmosphere. The prepared VN was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and its supercapacitive behavior was studied by cyclic voltammetry (CV) in three different types of aqueous electrolyte, 0.5 M H2SO4, 2.0 M NaNO3 and 1.0 M KOH. The XRD results indicate that prepared VN has a cubic structure with space group Fm3m and a lattice parameter of 4.139 angstrom. The nanocrystalline structure of VN with a low degree of crystallinity was confirmed by TEM imaging. The presence of oxygen on the VN surface was detected by FTIR and XPS, and its molecular composition was determined to be VN1.02O0.1. The specific capacitances of nanocrystalline VN were determined to be 114, 45.7 and 273 Fg(-1) in 0.5 M H2SO4, 2.0 M NaNO3 and 1.0 M KOH, respectively. Thus, the KOH solution was considered the best aqueous electrolyte for the capacitive performance of VN. The supercapacitive mechanism and the factor that influenced the specific capacitance are also analyzed in this paper. (C) 2011 Elsevier B.V. All rights reserved.