Performance of Cobaltite Solid-Oxide Fuel Cell Cathodes with Different Nano/Microstructure

ADRIANA SERQUIS; LAURA BAQUÉ; NICOLÁS GRUNBAUM; MARÍA JOSÉ SANTILLÁN; JONGSIK YOON; ROY ARAUJO; XINGHANG ZHANG; HAIYAN WANG; ALBERTO CANEIRO

S. C. de Bariloche

Otro; VII Encuentro CAB sobre Superficies y Materiales nanoestructurados; 2007

CNEA

The La1-xSrxCo1-yFeyO3-d cobaltites are good candidates for solid oxide fuel cell (SOFC) cathodes because these materials present high ionic and electronic conductivity, and compatibility with Cerium Gadolinium Oxide (CGO) electrolytes allowing a lower temperature of operation [1,2]. Most of reported cobaltites films have been deposited by slurry deposition techniques such as spraying [3], painting [4], or spin coating [5]. In order to further increase SOFC performance, it is necessary to understand how the microstructure of the composites electrodes affects the performance of the system. The aim of this work is to study the microstructure and electrode resistance of porous electrodes of the same composition films, i.e. La0.4Sr0.6Co0.8Fe0.2O3-d (LSCFO), deposited by different methods and to identify the sintering conditions to obtain low cathode overpotential values. The LSCFO powders have been prepared by an acetic acid-based gel and HTMA routes to obtain nanopowders. Then, cathodes films were deposited onto CGO ceramic substrates (pressed Ce0.9Gd0.1O1.95 disks) by serigraphy, spin coating, dip-coating [6], and electrophoresis deposition technique. On the other hand, nanostructured cathode thin films with vertically-aligned nanopores (VANP) were processed using a pulsed laser deposition technique (PLD). These VANP structures enhance oxygen-gas phase diffusivity, thus improve thin film SOFC performance. La0.5Sr0.5CoO3 (LSCO) and LSCFO were deposited on various substrates (YSZ, Si and CGO) [7].       The structure, morphology and composition of the powders and films were characterized by X-ray diffraction, transmission and scanning microscopy, and energy dispersive spectroscopy, respectively. The grain size and strain of initial powders and films prepared through different routes is analyzed by Rietveld analysis. The influence of the microstructure on the transport properties (ionic and electronic conductivity) is evaluated by means of impedance spectroscopy. We found that the electrochemical properties of LSFC cathodes films strongly depend on the microstructure that is mainly determined by synthesis parameters and technique used for the deposition of the films.       I will also present the initial structural characterization of LSCFO nanotubes that may be used for obtaining highly porous nanostructured cathodes.   Acknowledgements: This work was supported by Fundación Antorchas, Universidad de Cuyo, CONICET and SECyT.   [1] Y. Teraoka et al, Mater. Res. Bull. 23, 51 (1988). [2] F. Prado et al, Sol. State Ion. 167, 147 (2004). [3] N. Grunbaum et al, Sol. State Ion. 177, 907 (2006). [4] V. Dusastre et al, Sol. State Ion. 126, 163 (1999). [5] E. P. Murray et al, Sol. State Ion. 148, 148 (2002). [6] L. Baque et al, Mat. Res. Soc. Symp. Proc. 928, GG16-03 (2006). [7] J. Yoon et al , Applied Surface Science (2007) in press.