Differences in the electrochemical behavior of ruthenium and iridium oxide in electrocatalytic coatings of activated titanium anodes prepared by the sol-gel procedure

The electrochemical characteristics of Ti(0.6)Ir(0.4)O(2)/Ti and Ti(0.6)Ru(0.4)O(2)/Ti anodes prepared by the sol gel procedure from the corresponding oxide sols, obtained by force hydrolysis of the corresponding metal chlorides, were compared. The voltammetric properties in H(2)SO(4) solution indicate that Ti(0.6)Ir(0.4)O(2)/Ti has more pronounced pseudocapacitive characteristics, caused by proton-assisted, solid state surface redox transitions of the oxide. At potentials negative to 0.0 V(SCE), this electrode is of poor conductivity and activity, while the voltammetric behavior of the Ti(0.6)Ru(0.4)O(2)/Ti electrode is governed by proton injection/ejection into the oxide structure. The Ti(0.6)Ir(0.4)O(2)/Ti electrode had a higher electrocatalytical activity for oxygen evolution, while the investigated anodes were of similar activity for chlorine evolution. The potential dependence of the impedance characteristics showed that the Ti(0.6)Ru(0.4)O(2)/Ti electrode behaved like a capacitor over a wider potential range than the Ti(0.6)Ir(0.4)O(2)/Ti electrode, with fully-developed pseudocapacitive properties at. potentials positive to 0.60 V(SCE). However, the impedance characteristics of the Ti(0.6)Ir(0.4)O(2)/Ti electrode changed with increasing potential from resistor-like to capacitor-like behavior.