Effect of Cation Demixing on the Electrochemical Performance of LSCFO Cathodes for SOFCs

Hydrogen along with renewable energy resources are planned to replace fossil fuels in the near future. Solid Oxide Fuel Cells (SOFCs) are an attractive solution for the transition period between both energy sources since they can operate by using not only hydrogen but also fossil fuels. Nevertheless, the commercialization of these devices is still hindered by their cost and long term degradation. Overall cell degradation depends on the degradation of its main components: anode, electrolyte and cathode.

The use of mixed conducting cathodes such as La_1-xSr_xCo_1-yFe_yO₃ (LSCFO) improves considerably the performance of the cell. However, one of the most common degradation mechanisms of LSCF reported in the literature is the segregation of Sr.

This work aims at studying the effect of Sr segregation on the electrochemical properties of LSCFO cathodes. LSCFO oxide powders were prepared by solid state reaction and deposited on Ce_1-xGd_xO₂ electrolytes by spin coating. Afterwards, these cells were heat treated at conditions that facilitate the formation of Sr segregates. The electrochemical properties of the cathodes were monitored by electrochemical impedance spectroscopy, while the microstructure was characterized by Scanning Electron Microscopy, Transmission Electron Microscopy, Energy Dispersive Spectroscopy, and X-Ray Diffraction. The relation between the Sr segregation phenomena and the changes in the electrochemical performance of the cathode is discussed.