Study on the electrochemical behavior of vanadium nitride as a promising supercapacitor material

Vanadium nitride (VN) powder was synthesized by calcining V2O5 xerogel in a furnace under an anhydrous NH3 atmosphere at 400 degrees C. The structure and surface morphology of the obtained VN powder were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The supercapacitive behavior of VN in 1M KOH electrolyte was studied by means of cyclic voltammetry (CV), constant current charge-discharge cycling (CD) and electrochemical impedance spectroscopy (EIS). The XRD result indicates that the obtained VN belongs to the cubic crystal system (Fm3m [225]) with unit-cell parameter 4.15 angstrom. SEM images show the homogeneous surface of the obtained VN. The CV diagrams illustrate the existence of fast and reversible redox reactions on the surface of VN electrode. The specific capacitance of VN is 161 Fg(-1) at 30 mV s(-1). Furthermore, the specific capacitance remains 70% of the original value when the scan rate increases from 30 to 300 mV s-1. CD experiments show that VN is suitable for CD at high current density, and the slow and irreversible faradic reactions exist during the charge-discharge process of the VN electrode. The experimental results indicate that VN is a promising electrode material for electrochemical supercapacitors. (C) 2008 Elsevier Ltd. All rights reserved.