Synthesis and characterization of Mo-doped SrFeO 3− δ as cathode materials for solid oxide fuel cells

Abstract

This paper demonstrates the potential application of Mo-doped SrFeO 3− δ perovskites as new cathode materials for solid oxide fuel cells (SOFCs). SrFe 1− x Mo x O 3− δ ( 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 SrFeO 3− δ in air is reduced with increasing amounts of Mo. At 800 °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 Fe 4+ ions may account for the decrease in electrical conductivity. In contrast, the resistance to sintering and tolerance to reduction of SrFeO 3− δ are improved by Mo-doping. Additionally, the thermal expansion coefficient at 800 °C drops from 40.8 × 10 −6 K −1 for SrFeO 3− δ to 25.7 × 10 −6 K −1 for SrFe 0.8Mo 0.2O 3− δ and 20.9 × 10 −6 K −1 for SrFe 0.75Mo 0.25O 3− δ . This significant decrease in the thermal expansion coefficient makes Mo-doped SrFeO 3− δ materials attractive as cathode candidates for SOFCs. Finally, a relatively low polarization resistance of 0.074 Ω cm 2 is obtained for SrFe 0.8Mo 0.2O 3− δ at 800 °C in air.