Oxygen evolution on aged IrO x /Ti electrodes in alkaline solutions

O₂ evolution from 1 mol dm⁻¹ NaOH aqueous solution was studied on IrO _x /Ti electrodes already used for more than 3 years (aged). IrO _x was prepared by thermal decomposition of the chloride in the temperature range from 330 to 500 °C. Half of the electrodes were stored in air between experiments, the other half in water. The state of the electrode surface was monitored by recording voltammetric curves in a potential region prior to O₂ evolution before and after each group of experiments. O₂ evolution was studied by measuring quasistationary current–potential curves. Tafel slopes were derived using two different approaches. The reaction order with respect to OH⁻ was also determined and found to be fractional. Results show that the reaction mechanism does not depend on either the calcination temperature or the storage conditions. However, stability appears to be higher for electrodes calcined at higher temperatures and stored in air. Dedicated to Professor Algirdas Vaškelis on the occasion of his 70th birthday.