Abstract
Electrodes play a crucial role in determining the performance of supercapacitors and current study mainly focused on transition metal oxides/nitrides and conducting polymers that show a large pseudo-capacitance in repeated charging-discharging profiles. Among these materials, the vanadium nitride (VN) possesses a high capacitance and chemical stability and is metallic in nature. VN, however, is often made in powder form and must combine with organic binders to form an electrode. In this case, conductivity and ionic accessibility, due to existing binders, are reduced and capacitance also decreases at high scan rates. To overcome these problems, carbon nanotubes (CNTs) are introduced to create the hierarchical electrode structure (Ni/CNTs/VN), avoiding the use of binder. CNTs–free electrodes (Ni/VN) served as control group are also measured for a comparison on capacitance. The structural properties and morphologies of electrodes are characterized by X-ray diffraction (XRD), Electron Spectroscopy for Chemical Analysis (ESCA), Raman measurement, field emission scanning electron microscopy (FE-SEM), and BET surface area measurement. The electrochemical properties, including capacitance, rate capability, and cycle life, are studied by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in aqueous and organic electrolyte, respectively. This work suggests that CNTs provide an open mesoporous texture for access of electrolyte ions and electrons, and increases utility of VN, thus enhancing the capacitive performance.