Abstract: The preparation and electrocatalytic activity for oxygen evolution of the thermally prepared Ti anodes coated with    IrO₂ -Ta₂O₅ were studied. The structure and morphologies of the oxide films with different contents of IrO₂ were determined by XRD and SEM respectively. Their electrochemical properties were studied by Linear Sweep Voltammetry, Tafel Plot and Cyclic Voltammetry. The results show that iridium and tantalum can form solid solution and the mutual solubility is affected by the ratio of Ir to Ta in coating solution. With increasing IrO₂ content in the coatings, the amount of fine crystallites of IrO₂ is increased and the electrocatalytic capability of oxygen evolution is strengthened. The coating adhesion and rigidity decrease, which affects electrochemical activity of the anode when the content of IrO₂ is too high. The electrochemically active surface area is determined not only by the content of IrO₂ but also the structure and morphology of the anode coatings. It is probably due to the existence of proper quantities of inert Ta₂O₅ which results in a typical morphology of cracks and solid solution structure.

Key words: IrO₂-Ta₂O₅; electrocatalytic activity; oxygen evolution; oxide coated anode