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

A novel series of cobalt-free cathode materials, NdBaFe 2− x Mn x O 5+ 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, NdBaFe 1.9 Mn 0.1 O 5+ δ (NBFM10) exhibits the highest conductivity of 114   S   cm −1 in air at 550   °C. The H 2 /air fuel cell with the NBFM10–BZCY composite cathode and NiO–BZCY composite anode as well as BaZr 0.1 Ce 0.7 Y 0.2 O 3 − 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 R p is only 0.06   Ω   cm 2 under open circuit conditions, at 700   °C.