Electrochemical performance of Ba0.5Sr0.5CoxFe1−xO3−δ (x=0.2–0.8) cathode on a ScSZ electrolyte for intermediate temperature SOFCs

Autor: Chul Eui Kim, Jun Lee, Yong Ho Lim, Jong Seol Yoon, Hae Jin Hwang
Rok vydání: 2007
Předmět:
Zdroj: Journal of Power Sources. 171:79-85
ISSN: 0378-7753
DOI: 10.1016/j.jpowsour.2007.05.050
Popis: Intermediate temperature solid oxide fuel cell cathode materials (Ba, Sr)Co x Fe 1− x O 3− δ [ x = 0.2–0.8] (BSCF), were synthesized by a glycine-nitrate process (GNP) using Ba(NO 3 ) 2 , Sr(NO 3 ) 2 , Co(NO 3 ) 2 ·6H 2 O, and Fe(NO 3 ) 3 ·9H 2 O as starting materials and glycine as an oxidizer and fuel. Electrolyte-supported symmetric BSCF/GDC/ScSZ/GDC/BSCF cells consisting of porous BSCF electrodes, a GDC buffer layer, and a ScSZ electrolyte were fabricated by a screen printing technique, and the electrochemical performance of the BSCF cathode was investigated at intermediate temperatures (500–700 °C) using AC impedance spectroscopy. Crystallization behavior was found to depend on the pH value of the precursor solution. A highly acidic precursor solution increased the single phase perovskite formation temperature. In the case of using a precursor solution with pH 2, a single perovskite phase was obtained at 1000 °C. The thermal expansion coefficient of BSCF was gradually increased from 24 × 10 −6 K −1 for BSCF ( x = 0.2) to 31 × 10 −6 K −1 (400–1000 °C) for BSCF ( x = 0.8), which resulted in peeling-off of the cathode from the GDC/ScSZ electrolyte. Only the BSCF ( x = 0.2) cathode showed good adhesion to the GDC/ScSZ electrolyte and low polarization resistance. The area specific resistance (ASR) of the BSCF ( x = 0.2) cathode was 0.183 Ω cm 2 at 600 °C. The ASR of other BSCF ( x = 0.4, 0.6, and 0.8) cathodes, however, was much higher than that of BSCF ( x = 0.2).
Databáze: OpenAIRE
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