INVESTIGADORES
MOGNI Liliana Veronica
congresos y reuniones científicas
Título:
Study of the Oxygen Reduction Reaction Limiting Mechanisms in High Performance Nanostructured IT-SOFC Cathodes
Autor/es:
BAQUE L.; L. MOGNI; A. CANEIRO; A. SERQUIS
Lugar:
Zaragoza
Reunión:
Congreso; Fuel Cell 2010-Grove Conference; 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 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 on symmetrical cells 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.