Pseudocapacitive Characteristics of Vanadium Oxide Deposits with a Three-Dimensional Porous Structure

Abstract

A three-dimensional porous vanadium oxide was anodically deposited onto graphite substrates (denoted as VOxn H2O/G) at 0.7 V from an aqueous solution containing 25 mM VOSO4 and 5 mM H 2O2. Through annealing at temperatures up to 350°C, the thermal stability of VOx n H2O preserved its porous morphology and excellent capacitive performances in 3 M KCl (pH 2.4). X-ray photoelectron spectroscopic analysis revealed the mixed valence nature of oxy-/hydroxyl-vanadium species in which the amount of V4+ species was not significantly affected by varying the annealing temperature. A maximal specific capacitance of ca. 150-160 F g-1 measured at 250 mV s-1 was obtained for this porous VOx n H2O annealed between 150 and 250°C. Only 9-17% loss in specific capacitance was found for these VOx n H 2O when the scan rate of the cyclic voltammetry was increased from 25 to 250 mV s-1, demonstrating a typical high power property, which was never found in the VOx n H2O -based supercapacitors. © 2009 The Electrochemical Society.