Electrochemical capacitance of mesoporous tungsten oxynitride in aqueous electrolytes

Transition metal nitrides and oxynitrides are promising candidates for the application in electrodes of supercapacitors. In this manuscript characterization of tungsten oxynitride and its electrochemical properties in a range of aqueous electrolytes (1 M H2SO4, 1 M KOH, 3 M KCl, 3 M NaCl, 1 M LiCl and 1 M CaCl2) are presented. The electrochemical behavior of tungsten oxynitride depends strongly on the type of cation present in the electrolyte, and the highest capacitance value of 85 F g(-1) is measured in 1 M H2SO4. Cyclic stability in the acid, neutral and alkaline electrolytes is evaluated, and the highest stability is observed in 1 M KOH electrolyte. Possible charge-discharge mechanisms are discussed, and the contribution of a pseudocapacitive mechanism in addition to the electric double-layer formation is proposed. (C) 2012 Elsevier B.V. All rights reserved.