Mitigation of Chromium Impurity Effects and Degradation in Solid Oxide Fuel Cells: The Roles of Reactive Transport and Thermodynamics

Abstract

The principal objectives of this project were to understand the combined role of transport and thermodynamics in chromium poisoning of solid oxide fuel cell (SOFC) cathodes. Specifically, the differences in the chromium poisoning phenomena in predominantly electronic conducting cathodes such as strontium-doped lanthanum manganite (LSM) and mixed conducting cathodes such as strontium-doped lanthanum ferrite (LSF) and lanthanum nickelate (LNO) have been experimentally elucidated. The voltage-current density curves obtained from single cells featuring these cathode materials in the presence of chromium impurity have been analyzed using a suitable electrochemical model. The results clearly show the higher chromium tolerance of LSF and LNO cathodes compared to LSM cathodes. Further, dense protective coatings of copper-manganese spinel oxide applied via electrophoretic deposition (EPD) conformally on ferritic stainless steel current collectors that simulate the interconnection in SOFC stacks have been applied to SOFCs featuring LSM cathodes. Operation over a period of ten days of SOFCs featuring bare and spinel–coated ferritic stainless steel mesh current collectors show that the coatings are highly effectiveto protect against chromium poisoning.