Electrochemical Impedance Spectroscopy - a Tool for Solid Oxide Fuel Cells Studies

This work presents some methods for enhanced performance of Electrochemical Impedance Spectroscopy (EIS) in SOFCs studies, which brings to improved data quality and enriched information capability. The implementation of measurements in two modes - potentiostatic and galvanostatic at different amplitudes depending on the sample's resistance guarantees high quality of the measured data in a larger frequency range. The elimination of the errors produced by the parasitic components of the testing rig increases the accuracy of the electrolyte resistivity estimation. The application of the Differential Impedance Analysis technique ensures model evaluation directly from the experimental data, i.e. without the use of a preliminary working hypothesis The efficiency of the applied tools is demonstrated on EIS studies of an innovative dual membrane design of a high temperature fuel cell based on the idea for a junction between a proton conducting anode/electrolyte part and oxide ion conducting cathode/electrolyte part through a mixed H+ and O2- conducting porous ceramic membrane. In this concept, hydrogen, oxygen and water are located in three independent chambers, which avoid the gases dilution with water. The examples summarize results obtained on different materials applied in high temperature fuel cells.