Oxygen Evolution on Aged IrOx/Ti Electrodes. I.Acidic Solutions

Department of Physical Chemistry and Electrochemistry, University of Milan, Via Venezian 21, 20133 Milan. Italy

Manuscript received 5 January 1993

The effect of ageing and of the electrolyte anion in O² evolution on IrO_X/Ti electrodes has been studied in H₂SO_⁴ and HClO₄ solutions with IrO_X, electrodes, prepared by thermal decomposition at 300-500^°, already used for over two years under cathodic conditions. The influence of the storage conditions (water vs air) has also been investigated. Results have shown that the Tafel slope is lower in HClO₄ and that the true electrocatalytic activity increases at lower calcination temperatures. Ageing improves the electrode activity, especially for water-stored samples. A general mechanism is proposed. IrO_X, electrodes do not show serious signs of erosion under anodic load in acidic solutions.