Electrode/Electrolyte Interphase Studies of Ceria Based Electrolytes for IT-SOFCs

Solid oxide fuel cells (SOFCs) have emerged as an efficient and environmental friendly tecnology to convert directly hydrogen and fosil fuels into electric energy.  Usually these devices use ytria based electrolytes, requiring operation temperatures around 1000ºC.  These high temperatures challenge the long term stability and induce rapid degradation of the cell. Ceria based oxides are interesting alternatives because they present higher conductivities at lower operation temperatures. However, these materials require sinterization temperatures in the 1300-1600ºC range to achieve complete densification, which produces very large grain sizes and poor mechanical properties. The addition of transition metals oxides is effective in improving the densification and thus, lowering the sinterization temperatures.  In this work we studied Ce_0.8(Gd,Nd)_0.2O₂ with and without Co doping synthesized by a molten salt route [1], which allows obtaining smaller grain sizes at lower temperatures, improving microstructural properties. The synthesis methodology is fast, simple and cheap and combines a metathesis or displacement reaction and a low-temperature molten salt flux.

A (La,Sr)(Co,Fe)O₃ nanostructured electrode with high electrochemical performance [2,3] was deposited by spin coating techniques on electrolyte pellets. The assemblies were studied by Electrochemical Impedance Spectroscopy, X-Ray Diffraction and Transmission and Scanning Electron Microscopy. The correlation between the electrochemical behavior within the 300-600ºC range, and the bulk and interfacial characteristics will be discussed.

[1] Mendoza-Mendoza E., Padmasree K., Montemayor S. and Fuentes A., J Mater Sci 47 (2012) 6076-6085.

[2] Baqué L, Caneiro A, Moreno MS, Serquis A., Electrochem Commun 10 (2008) 1905-1908.

[3] Soldati A.,  Baqué L.,  Troiani H.,  Cotaro C., Schreiber A., Caneiro A, Serquis A. Int J Hyd Energy 36 ( 2011) 9180-9188.