Improvement in stability of La0.4Ba0.6CoO3 cathode by combination with La0.6Sr0.4Co0.2Fe0.8O3 for intermediate temperature-solid oxide fuel cells

Improvement in long-term stability and cathodic activity of La0.4Ba0.6CoO3 (BLC) was studied by mixing with La0.6Sr0.4Co0.2Fe0.8O3 (LSCF). LSCF exhibits good long-term stability; however, surface activity is not high like Co-based perovskite. On the other hand, the cathodic activity of BLC is high; however, long-term stability was not so good and large degradation at initial period is observed. Combination of the two oxides shows small overpotential as well as improved long-term stability. Effects of BLC/LSCF ratio on stability and overpotential were studied and it was found that BLC–LSCF (7:3) showed the most stable and small cathodic overpotential among the examined compositions. Although the power density was still slightly decreased over 24 h at 0.5 V terminal voltage, the maximum powder density of the cell using BLC–LSCF composite oxides for cathode shows 2.5 times larger than that of the cell using LSCF cathode and 1.06 times larger than that of BLC. Degradation rate is smaller than 4 % from 5 to 24 h on this BLC–LSCF cathode at current density as high as 682 mA/cm2 after 24 h operation.