An Investigation of the Electrochemical Activity of (Ba/Sr)FeO3-y Anodes

FeOx, SrFeO3-y (SF), and Ba0.5Sr0.5FeO3-y (BSF) were studied for application as fuel oxidation catalysts in solid oxide fuel cells (SOFC) anodes. Electrodes were prepared by impregnation into porous yttria-stabilized zirconia (YSZ), with La0.3Sr0.7TiO3-y (LST) added for electronic conductivity. The electrode impedances decreased dramatically upon addition of SF and BSF and much less when only SrO or FeOx were added. Temperature Programmed Desorption (TPD) of O-2 from oxidized BSF showed O-2 desorbing between 200 degrees C and 700 degrees C, while no O-2 desorbed from Fe2O3 below 900 degrees C. The results, together with thermodynamic analysis, suggest that stabilization of Fe+4 in the perovskite lattice plays an important role in enhancing the catalytic activity of SF and BSF by providing access to a Fe3+/Fe4+ redox couple that can accept oxygen anions from the yttria-stabilized zirconia (YSZ) electrolyte. Oxygen is weakly bound to these sites facilitating its reaction with adsorbed H-2.