Evaluation of La0.4Ba0.6Fe0.8Zn0.2O3−δ + Sm0.2Ce0.8O1.9 as a potential cobalt-free composite cathode for intermediate temperature solid oxide fuel cells

The disadvantages of cobalt-based and barium-based perovskite oxides in solid oxide fuel cells are the large thermal expansion coefficients, low structure stability, and poor CO2 tolerance, although they have excellent oxygen reduction activity. To reduce the impact of these detrimental effects, cobalt-free La0.4Ba0.6Fe0.8Zn0.2O3−δ (LBFZ) was investigated as a potentially promising cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The TEC of LBFZ is 18.9 × 10−6 K−1, which is lower than other widely used cobalt-containing cathode materials. The electrode performance can be further improved by incorporating Ce0.8Sm0.2O1.9 (SDC) to form a composite. Systematic study suggests that composite cathodes containing 40 wt% SDC exhibited the best electrode performance (Rp = 0.12 Ω cm2) when they were fired at 1050 °C for 2 h, correlating to a peak power density of 839 mW cm−2 based on the single cell with the configuration NiO-YSZ/YSZ/SDC/LBFZ-SDC at 700 °C. Also, LBFZ-SDC demonstrated excellent chemical stability upon exposure to 1% CO2 at 550 °C for 100 h, and the electrochemical testing also demonstrated better CO2 tolerance than Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF). These results suggest that LBFZ and its SDC composite are promising cathode materials for IT-SOFCs.