Examination of mixed ion-electron conducting cathode materials for SOFCCopyright: V.Sarda
To obtain good efficiencies for solid oxide fuel cells (SOFC) it is important to investigate and to understand the degradation processes of each component. By using chromium containing, gas leading, bipolar plates (aka interconnects) to connect several single cells to a “cell-stack”, volatile chromium species can evaporate and subsequently undergo certain reactions with the utilized cathode material. These reactions can lead to the formation of less-conductive phases that decrease the electrochemical cell efficiency.
The topic of this master thesis is the electrochemical characterization of symmetrical solid oxide fuel cells in the presence/absence of suitable chromium sources. Therefore different Cobalt and Iron containing perovskite cathode materials (LSCF, LSC, LSF; variation of the B-site stoichiometry) will be investigated. For electrochemical characterization impedance measurements are used to examine cells for different current densities at fixed temperatures, oxygen partial pressures and humidities. Additionally SEM, EDX and XRD measurements will support the analysis of chromium poisoning. The aim of this master thesis is to investigate and to understand the mechanism of chromium poisoning of different doped Cobalt and Iron containing perovskite cathodes in operating cells.