Synthesis and characterization of PrBa0.5Sr0.5Co2−xNixO5+δ (x=0.1, 0.2 and 0.3) cathodes for intermediate temperature SOFCs

Strontium and nickel co-doped layerd-perovskite PrBa0.5Sr0.5Co2−xNixO5+δ (PBSCN) with various proportions of nickel (x=0.1, 0.2 and 0.3, abbreviated as PBSCN-1, PBSCN-2 and PBSCN-3, respectively) are investigated as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). The PBSCN powders are synthesized by a combined EDTA–citrate complexing sol–gel method. Then PBSCN pellets are sintered at 1100 °C for 10 h in air. The materials exhibit an orthorhombic structure with the space group of Pmmm. The electrical conductivity is determined by the van der Pauw method at the temperature range of 400–800 °C. It is shown that the electrical conductivity declines with increasing temperature for all the samples. The highest conductivity of 1590 S cm−1 for PBSCN-3 is obtained at 400 °C. The thermal expansion coefficient (TEC) decreases with the increase of Ni content. The average TEC at the temperature range of 30–900 °C decreases from 21.9×10−6 K−1 for PBSCN-1 to 19.7×10−6 K−1 for PBSCN-3. Yttria stabilized zirconia (YSZ) with thickness in 0.3 mm is used as the electrolyte in this study. Electrolyte supported fuel cells prepared by coating method are employed to study the electrochemical properties from 600 to 800 °C. The polarization resistances of PBSCN samples on YSZ electrolyte at 800 °C are 0.297, 0.314 and 0.321 Ω cm2 for PBSCN-1, PBSCN-2 and PBSCN-3, respectively. The single fuel cell with the configuration of PBSCN-1/YSZ/Pt delivers the highest power density of 120 mW cm−2 at 800 °C.