Morphological, chemical, and electrochemical properties of Ti/(TiO2+IrO2) electrodes

Electrodes of general composition IrxTi(1-x)O-2 with 0.2 less than or equal to x less than or equal to 1.0 were prepared on a Ti support by calcination of the chlorides at 450 degrees C. Ex situ and in situ characterization included the use of techniques such as scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). EDX showed a surface enrichment with Ti. The voltammetric charge was found to go through a maximum at 60% IrO2. O-2 evolution was studied in 1.0 mol dm(-3) HClO4 by determining Tafel slopes and impedance parameters. Tafel slopes were found to vary between 40 and 60 mV depending on the overpotential range and the oxide composition. Solution and film resistance, film and double layer capacitance, and charge transfer resistance were determined as a function of potential and oxide composition. A reaction mechanism has been proposed. Separation of geometric and electronic effects has been attempted.