Influences of metal oxides on carbon corrosion under imposed electrochemical potential conditions

Graphite electrodes, whose surface is partially covered with metal oxides, are prepared by the electrochemical deposition of MoOx, WOx, and SnO2 particles, and their corrosion behaviors under the imposed electrochemical potential conditions are investigated. Scanning electron microscopy observation shows that highly oriented pyrolytic graphites (HOPGs) modified with MoOx and WOx particles (MoOx|HOPG and WOx|HOPG) suffer from carbon corrosion and show pits formation on the surface of HOPG after an electrochemical potential cycling in a range of 0.8–1.0 V. In contrast, SnO2-modified HOPG (SnO2|HOPG) exhibits superior tolerance to electrochemical oxidation. Cyclic voltammograms show that the SnO2 modification prevents an increase in the redox currents for quinone/hydroquinone reactions and the electrochemical double layer capacitances on the HOPG electrode. These results indicate that the influence of metal oxides on carbon corrosion varies depending on the kind of metal oxides, and that SnO2 is a proper choice to protect the surface of HOPG from carbon corrosion, under electrochemical potentials.