Oxygen evolution on titanium anodes coated with conductive metallic oxides: Kinetics and mechanism in alkaline solution

Ti/SnO2 + CuCo2O4 and Ti/RuO2 + TiO2 anodes were used to study oxygen evolution in alkaline solutions and to compare the kinetics on both electrodes. On each electrode the existence of two Tafel regions was confirmed. At low current density (ed) the Tafel slope is 39 mV decade(-1), whereas at high ed it is 120 mV decade(-1). The reaction orders with respect to the activity of OH-(a(OH-)), or the activity of water (a(w)), or a(OH-)a(w), in two Tafel regions and in dilute and concentrated alkaline solutions, respectively, were obtained. According to the obtained kinetic data, the mechanisms of oxygen evolution on these types of electrodes were proposed.