A FIB-TEM study on evolution of passive film during deactivation processes of Ti/IrO2-Ta2O5 electrode

Ti/IrO2-Ta2O5 electrode is widely used in the electrochemical industry with oxygen evolution, however, the knowledge is still limited about the passive film structure and its variation in the processes of deactivation. In this work, the evolution of passive film under the catalytic coating during accelerated life test has been studied using FIB-TEM and other methods. The results show that the as-prepared electrode with thermal decomposition has a thin interlayer mainly composed of amorphous Ti oxides and rutile TiO2 doped with IrO2 crystallites. The Ti oxide interlayer grows further on the Ti substrate during the electrolysis with a thicker passive film formed at location with less protection from the top coating. It is the mechanical breakdown of the passive film with development of numerous cracks and voids that causes the cell voltage rise abruptly, resulting in the final deactivation.