Characterization of nanostructured A1-xSrxFe0.8Cu0.2O3-d perovskites (A=La, Ba) as IT-SOFC cathodes.

SUESCÚN, LEOPOLDO; VAZQUEZ, SANTIAGO; DAVYT, S; FACCIO, RICARDO; BASBUS, JUAN; NAPOLITANO, FEDERICO; SOLDATI, ANALIA L.; SERQUIS, ADRIANA C.

Campinas

Congreso; Reunión Anual de Usuarios LNLS; 2015

LNLS CNPEM

Solid Oxide Fuel Cellsoperating in the 500-800 °C temperaure range (IT-SOFCs) require the developmentof new cathode materials with high mixed ionic-electronic conductivity and goodcatalytic activity of the oxygen reduction reaction (ORR).[1] Traditional La1-xSrxMnO3-dperovskite material does not operate well at low temperatures due to the absenceof oxygen conductivity and strong reduction of ORR activity. Cobaltites Sm0.5Sr0.5CoO3-dand related compounds show excelente conducting properties and are good ORRcatalysts, but they show a large thermal expansion coefficient (TEC) and high reactivitytowards comon electrolyte materials which prevents their efficient aplicationas ITSOFC cathodes.[2] In recent years our group has been exploring thepreparation of cobaltfree, nanostructured cathode materials, with good ORRactivity based on Fe-Cu perovskites.We have designed a novelgel-combustion technique that allowed the preparation of Ba0.5Sr0.5Fe0.8Cu0.2O3-d(BSFCu) and La0.6Sr0.4Fe0.8Cu0.2O3-d (LSFCu) materials, compatible withstandard Ce0.9Gd0.1O1.95 (CGO) electrolyte and characterized its phase evolutionwith temperature, TEC, microstructure and electrochemical performance in the 500- 700 C temperature range of symmetrical cells with the configuration cathode/CGO/cathodeprepared at different temperatures. Both LSFCu and and BSFCu materials showvery promising ASR values of 0.035 and 0.15 ohm.cm^2 at 700 °C. Structural andmicrostructural characterization of the materials show that BSFCu shows a veryisotropic and homogeneous arrangement of nanoparticles 18nm wide and a cubicPm-3m structure at all studied temperatures while LSFCu shows larger particleswith average size of 41 nm (as determined by TEM) with rhombohedral R-3c spacegroup symmetry at RT, that transforms to cubic Pm-3m above 375 °C. This phasetransition is accompanied by a significant change in the TEC that suggest BSFCuis a better candidate material for IT-SOFC cathodes [3,4].