Performance of cobalt-free perovskite La0.6Sr0.4Fe1−xNbxO3−δ cathode materials for proton-conducting IT-SOFC

A novel series of cobalt-free perovskite cathode materials La0.6Sr0.4Fe1−xNbxO3−δ (0.00 ⩽ x ⩽ 0.20) are prepared by a solid-state reaction method. The X-ray diffraction results indicate the doping limit of Nb in La0.6Sr0.4Fe1−xNbxO3−δ is at least x = 0.15. The conductivities of the cathode materials are measured as functions of temperature (300-800 °C) and oxygen partial pressure (1-10−10 atm). It is discovered that the Nb-doping for Fe-site of La0.6Sr0.4FeO3−δ distinctly improved the electrical conductivity of La0.6Sr0.4FeO3−δ; the oxides displayed a semiconductor-like conduction behavior in the temperature region. The highest conductivity is observed for La0.6Sr0.4Fe0.9Nb0.1O3−δ (LSFN10) to be 132 S cm−1 in air at 800 °C. A single cell using LSFN10 cathode and NiO-BaZr0.1Ce0.7Y0.2O3−δ (NiO-BZCY) composite anode supported BZCY electrolyte membrane (ca. 30 μm in thickness) is assembled and tested at 500-700 °C with H2 as fuel and air as oxidant. The peak power density and the interfacial polarization resistance (Rp) are 503 mW cm−2 and 0.17 Ω cm2 at 700 °C, respectively. The above results indicate that La0.6Sr0.4Fe0.9Nb0.1O3−δ is a new promising cathode material for proton-conducting IT-SOFC.