Barium- and strontium-enriched (Ba0.5Sr0.5)1+xCo0.8Fe0.2O3−δ oxides as high-performance cathodes for intermediate-temperature solid-oxide fuel cells

(Ba(0.5)Sr(0.5))(1+x)Co(0.8)Fe(0.2)O(3-delta), or BSCF(I + x), (0 <= x <= 0.3) oxides were synthesized and investigated as cathodes for intermediate-temperature solid-oxide fuel cells. The A-site cation excess in BSCF(I + x) resulted in a lattice expansion and the creation of more active sites for oxygen reduction reaction due to the lowered valence states of the B-site ions and the increased oxygen vacancy concentration, which improved the oxygen adsorption process. On the other hand, the A-site excess could also result in higher resistances for oxygen adsorption (due to the formation of BaO and/or SrO impurities), and oxygen-ion transfer (by facilitating the solid-phase reaction between the cathode and the electrolyte). By taking all these factors into account, we found BSCF1.03 to be the optimal composition, which lead to a peak power density of 1026.2 +/- 12.7 mW cm(-2) at 650 degrees C for a single cell. (c) 2008 ACta Materialia Inc. Published by Elsevier Ltd. All rights reserved.