Oxygen evolution on aged IrOx/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.