Electrochemical investigation of mixed ionic/electronic cathodes for SOFCs

Half-cells consisting of YSZ electrolyte pellets and slurry-coated cathodes were tested with a three-electrode configuration. The composite cathodes considered in this study had a fixed LSM/YSZ volume ratio equal to 1 and variable apparent surface areas, ranging from 0.05 to 0.25 cm2. Electrochemical Impedance Spectroscopy and potentiodynamic polarisations were used to evaluate the main electrochemical parameters. The results obtained with the two techniques showed a good agreement. The analysis of the electrochemical data suggests that adsorption of oxygen or ionic transport could be the key phenomena in the cathodic process. At high temperatures we noted that care needed to be taken with the cell arrangement and electronic performance of the instruments in order to obtain reliable results.