Microstructure and Electrochemical Properties of IrO[sub 2]-Ta[sub 2]O[sub 5]-Coated Titanium Anodes

The microstructure and electrochemical properties of coated titanium anodes have been studied using scanning electron microscopy, energy dispersive X-ray analysis, and electrochemical impedance spectroscopy (EIS) polarization and accelerated life test. The morphologies of anodes consist of dried mud-cracks surrounded by compact areas with superficial agglomerates except for 10% Ir in mole ratio) anode. The composition of oxide coating is inhomogeneous with segregation in the agglomerates. EIS study indicates that 30% Ir is a critical concentration for coating to achieve metallic conductivity. The anode with 50-70% Ir is found to have not only the largest electrochemically active surface area but also the highest electrochemical activity, with 70% Ir anode also presenting the highest stability.