Microstructure and electrochemical properties of IrO2-Ta2O5-coated titanium anodes

The microstructure and electrochemical properties of IrO2-Ta2O5 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 IrO2-Ta2O5 anodes consist of dried mud-cracks surrounded by compact areas with superficial agglomerates except for 10% Ir (Ir: Ta = 10: 90 in mole ratio! anode. The composition of oxide coating is inhomogeneous with IrO2 segregation in the agglomerates. EIS study indicates that 30% Ir is a critical concentration for IrO2-Ta2O5 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. (C) 2003 The Electrochemical Society.