Synthesis and characterization of Mo-doped SrFeO3-δ as cathode materials for solid oxide fuel cells

This paper demonstrates the potential application of Mo-doped SrFeO3-delta perovskites as new cathode materials for solid oxide fuel cells (SOFCs). SrFe1-xMoxO3-delta (x=0, 0.05, 0.1, 0.2 and 0.25) perovskite materials have been synthesized by a microwave-assisted combustion method. By doping with Mo, the electrical conductivity of the doped SrFeO3-delta in air is reduced with increasing amounts of Mo. At 800 degrees C, the conductivity drops from about 62 to 22 S cm(-1) when the doping level is increased to 25%. According to X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR) results, a decrease in the concentration of charge carrier Fe4+ ions may account for the decrease in electrical conductivity. In contrast, the resistance to sintering and tolerance to reduction of SrFeO3-delta are improved by Mo-doping. Additionally, the thermal expansion coefficient at 800 C drops from 40.8 x 10(-6) K-1 for SrFeO3-delta to 25.7 x 10(-6) K-1 for SrFe0.8 Mo0.2O3-delta and 20.9 x 10(-6) K-1 for SrFe0.75Mo0.25O3-delta. This significant decrease in the thermal expansion coefficient makes Mo-doped SrFeO3-delta materials attractive as cathode candidates for SOFCs. Finally, a relatively low polarization resistance of 0.074 Omega cm(2) is obtained for SrFe0.8Mo0.2O3-delta at 800 degrees C in air. (C) 2011 Elsevier B.V. All rights reserved.