Microwave radiated comparative growths of vanadium pentoxide nanostructures by green and chemical routes for energy storage applications

Abstract

Supercapcitors are prominent energy storage devices an account of its high-power density, long cycle life and superior rate capability. Metal oxides play an important role in energy storage devices, while vanadium pentoxide is most promising due to variable oxidation states, wide potential window, unique layer structure etc. In general, specific capacitance of a vanadium pentoxide is very low due to poor ionic diffusivity and electrical conductivity but can improve drastically by encapsulating vanadium pentoxide with metals or carbonaceous materials or by decreasing the size to nanoscale or by modifying the morphology. On the other hand, the methodologies employed play a crucial role in increasing specific capacitance of a particular compound. Here we report a microwave assisted synthesis of vanadium pentoxide nanoparticles by green and chemical synthetic approach. The prepared samples were characterized by UV–Vis spectroscopy, Fourier-Transform Infrared spectroscopy, X-ray diffraction studies, Scanning Electron Microscope and Energy Dispersive Spectroscopy. The major peak in Uv–vis spectra confirms six-fold coordination state of V+5 with square pyramidal configuration. FTIR and XRD analysis concludes orthorhombic structure of synthesized nanoparticles with crystal size ranging from 20 to 25 nm. The anions and cations of an electrolyte is also play a crucial role in determination of specific capacitance of a particular materials and is in the order of 2 M KOH > 2 M LiOH > 2 M Na2SO4 > 2 M NaOH and are in accordance with hydration sphere radius, solvated ion size, ion shape and conductivity of particular ion. On the other hand calcinations temperature and concentration of specific electrolyte play a crucial role in determination of specific capacitance of a particular materials and is as follows 6 M KOH (600 °C) > 6 M KOH (400 °C) > 2 M KOH (600 °C) > 2 M KOH (400 °C). The V2O5-green modified electrode is showing excellent electrochemical performance than V2O5-chemical modified electrodes due to less agglomeration of oxide, high percentage of vanadium over the surface leads high intercalation and de-intercalation of K+ ions from electrolyte into V2O5 lattices.