Ba0.5Sr0.5Fe0.8Cu0.2O3-δ (BSFCu) a cobalt-free nanostructured cathode for Intermediate Temperature – Solid Oxide Fuel Cells (IT-SOFC) has been developed with high oxygen reduction reaction (ORR) activity in the 500-700 °C range. The preparation of the nanostructured cathode is achieved by a modified gel-combustion process using ethylenediamine tetraacetic acid (EDTA) as complexation agent at pH ~10 which assures all cations but especially Ba2+ and Sr2+, to remain in solution during the gelification process without separation, and NH4NO3 as combustion promoter that ensures full and homogeneus combustion of the gel in a cheap and simple process performed in an open reaction beaker. The ashes of the combustion process are pelletized and fired at 850 °C to form the final phase. The nanopowder thus-obtained is deposited on a gadolinia-doped ceria (GDC) electrolyte by spin coating. In this article the best temperature for cathode sintering was determined that maximizes ORR activity. Cathodes sintered below 900 °C were poorly adhered to the electrolite, but at 900°C the the adherence of the cathode is ideal and the nanometric size of BSFCu particles conserved, achieving the lowest area-specific resistance (ASR) value reported for this material at 700 °C. The combination of gel-combustion preparation and low processing temperature ensures that BSFCu material deposited on GDC remains nanostructured increasing the active surface and providing the best conditions for the intrinsically high ORR activity of BSFCu to be increased. The preparation and sintering processes are determined to be of the highest importance to achieve the observed low ASR values.
Journal of Power Sources, Volume 274, 2015, Pages 318–323. Santiago Vázquez1,2, Juan Basbus3, Analía L. Soldati3, Federico Napolitano3, Adriana Serquis3, Leopoldo Suescun1,2Show Affiliations
- Cryssmat-Lab, Cátedra de Física, DETEMA, Facultad de Química, Universidad de la República, P.O. Box 1157, 11800 Montevideo, Uruguay
- Espacio Interdisciplinario, Universidad de la República, José E. Rodó 1843, 11300 Montevideo, Uruguay
- Grupo Caracterización de materiales, CAB-CNEA, Bustillo 9500, 8400 Bariloche, Argentina
In this work we studied the electrochemical performance of Ba0.5Sr0.5Fe0.8Cu0.2O3-δ(BSFCu) as cathode for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC) with Ce0.9Gd0.1O1.95 (CGO) electrolyte and the effect of the symmetric cell preparation temperature on the oxygen reduction reaction (ORR) activity. Symmetrical cells with the configuration BSFCu/CGO/BSFCu were prepared at 900 °C, 950 °C and 1000 °C to perform the electrochemical characterization in the 500–700 °C temperature range. The resultant area specific resistance (ASR) of the cells with different preparation temperatures followed the tendency: ASR900°C < ASR950°C < ASR1000°C. The symmetric cell constructed at 900 °C showed ASR values of 0.18, 0.078 and 0.035 Ω cm2 at 600, 650 and 700 °C respectively, which demonstrated superior electrochemical activities than previous reports. Additional, X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM) techniques were used to characterize the microstructure of the original and fired BSFCu materials and correlate it with the cell preparation temperature.