INVESTIGADORES
SERQUIS Adriana Cristina
congresos y reuniones científicas
Título:
Study of the oxygen reduction reaction limiting mechanisms in high performance nanostructured IT-SOFC cathodes
Autor/es:
L. BAQUÉ; L. MOGNI; A. CANEIRO; A. SERQUIS
Lugar:
Zaragoza
Reunión:
Conferencia; Fuel Cells 2010 Science & Technology; 2010
Institución organizadora:
Elsevier
Resumen:
Our previous studies [1] have shown that cathodes based on nanostructured oxides exhibit area specific resistance (ASR) values as low as 0.05 Ohm cm2 at 600 C and 0.4 Ohm cm2 at 450 C in air, which are even lower than the best known cathodes for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC) [2]. Nevertheless, it is important to investigate the steps involved in the Oxygen Reduction Reaction (ORR) for these cathodes in order to understand the origin of their high performance and to use this information in the design of IT-SOFC cathode design. La0.4Sr0.6Co0.8Fe0.2O3-delta (LSCF) powders were prepared using two chemical routes: an acetic acid-based [1,3] and an hexamethylenetetramine-based (HTMA) [1]. Two different inks were prepared with powder synthesized by each method, and then deposited onto Ce0.9Gd0.1O1.95 ceramic substrates by spin and dip-coating. The microstructure and morphology composition of the powders and films were characterized by X-ray diffraction, and scanning electron microscopy. The grain size and strain were analyzed by Rietveld method. The ORR limiting mechanisms were investigated by impedance spectroscopy measurements performed at different temperatures (400 C - 600 C), oxygen partial pressures (-3 < Log pO2 < 0) and carrier gas (Ar and He). We found that the ORR limiting mechanism is typically oxygen diffusion in the electrode bulk for low temperature (400 C) and high oxygen partial pressure (-0.7 < Log pO2 < 0), while it is oxygen gas diffusion in electrode pores for high temperature (600 C) and low partial pressure (-3 < Log pO2 < -0.7). The relation between ORR limiting mechanisms and cathode microstructure allow us to point out the relevant microstructural parameters which explain the excellent cathode performance as well as possible strategies for even further improvement of cathode ASR values. [1] L. Baqué, A. Caneiro, M. S. Moreno and A. Serquis, Electrochemistry Communications 10 (2008) 1905 [2] Z. Shao, S. Haile, Nature 431 (2004) 170. [3] Y. Xia, T. Armstrong, F. Prado, and A. Manthiram, Solid State Ionics 130 (2000) 81.
