Electrochemical Stability of Tungsten and Tungsten Monocarbide (WC) Over Wide pH and Potential Ranges

Tungsten monocarbide (WC) is a low cost electrode material that has shown much promise in electrocatalytic applications, yet, a comprehensive study of its electrochemical stability has been absent from literature. In this work, the electrochemical stability of single phase WC and its parent metal, tungsten (W), are determined over a wide range of pH and potential values using a variety of electroanalytical techniques. Central to this study are chronopotentiometric titration measurements, which are a quick and effective way to determine the potential-pH regions of stability for these materials. Cyclic voltammetry, chronoamperometry, and linear sweep voltammetry (LSV) measurements are also presented. X-ray photoelectron spectroscopy and scanning electron microscopy verified the results of these electroanalytical measurements. Our findings show that WC exhibits trends in electrochemical stability that are similar to those of W, which have been the focus of many electrochemical studies. Notable differences in the potential limits of stability and extent of surface oxide formation on WC and W exist and may have important implications for electrochemical applications. The results of this paper should prove useful for the selection of electrolytes, electrode conditioning parameters, and device operating conditions for a wide variety of electrochemical applications using WC. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3491341] All rights reserved.