Performance of cobalt-free double-perovskite NdBaFe2−xMnxO5+δ cathode materials for proton-conducting IT-SOFC

A novel series of cobalt-free cathode materials, NdBaFe2−xMnxO5+δ (0.0 ⩽ x ⩽ 0.3), are prepared by a citric acid-nitrate process. X-ray diffraction (XRD) analysis indicates that all the samples are double-perovskite phases with cubic structure. The conductivity dependence of the cathode materials on temperature (300-800 °C) and oxygen partial pressure (1-10−10 atm) is investigated. Among the tested samples, NdBaFe1.9Mn0.1O5+δ (NBFM10) exhibits the highest conductivity of 114 S cm−1 in air at 550 °C. The H2/air fuel cell with the NBFM10-BZCY composite cathode and NiO-BZCY composite anode as well as BaZr0.1Ce0.7Y0.2O3−α (BZCY) electrolyte membrane (ca. 30 μm thickness) was assembled and tested at 500-700 °C. The peak power density of the cell reaches 453 mW cm−2, and the interfacial polarization resistance Rp is only 0.06 Ω cm2 under open circuit conditions, at 700 °C.