High performance BaFe1−xBixO3−δ as cobalt-free cathodes for intermediate temperature solid oxide fuel cells

Bi2O3 doped BaFeO3−δ on the B-site as a cobalt free perovskite cathode for intermediate temperature solid oxide fuel cells is evaluated. The BaFe1−xBixO3−δ (BFBx) powders are synthesized by solid state reaction. It is found that Bi2O3 doping stabilizes the BaFeO3 cubic phase. The new cathode is compatible with Gd0.1Ce0.9O1.95 even calcined at 1000 °C for 10 h. The electronic conductivity shows a transformation from semiconductor to metal conductor, and achieves its maximum value of 28.1 S cm−1 for BFB10 at 800 °C. The δ is as high as 0.408 for BFB10 determined by iodometric titration. This leads to the free volume in crystal lattice of BFB10 21.60% higher than that of BaNb0.05Fe0.95O3−δ. The area specific resistance is only 0.133 Ω cm2 for BFB10 at 750 °C and the average TEC is 26.697 × 10−6 K−1 measured from room temperature to 800 °C. The peak power density of Ni-YSZ|YSZ|GDC|BFB10 cell is 646.28 mW cm−2 at 750 °C, higher than that of single cell using LSCF as cathode. These show that BFBx perovskite oxides with cubic phase are promising cathodes for intermediate temperature solid oxide fuel cells.