Layered perovskite LnBa0.5Sr0.5Cu2O5+δ (Ln = Pr and Nd) as cobalt-free cathode materials for solid oxide fuel cells

Cobalt-free layered perovskite LnBa0.5Sr0.5Cu2O5+δ (Ln = Pr and Nd, PBSC and NBSC) powders are prepared using combined citrate and EDTA complexing method. The performance of PBSC and NBSC cathode materials are evaluated for solid oxide fuel cells (SOFCs). Two oxidation states (Cu2+/Cu+) for Cu ions exist in LnBa0.5Sr0.5Cu2O5+δ oxides. The main valence of Pr ions in PBSC is 3+. The average thermal expansion coefficients (TECs) of PBSC and NBSC are 14.2 and 14.6 × 10−6 K−1 between 30 and 950 °C, which are similar to the TECs of La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) intermediate-temperature electrolyte. The electrical conductivity of PBSC is slightly higher than that of NBSC. At 800 °C, the polarization resistance (Rp) values of the PBSC and NBSC cathodes on the LSGM electrolyte are 0.043 and 0.057 Ω cm2, respectively. The electrolyte-supported single cells were prepared by using PBSC and NBSC as cathode, LSGM as electrolyte (300 μm thickness), Ce0.9Sm0.1O1.95 (SDC) as interlayer and Ni/SDC as anode. At 850 °C, the maximal power densities are obtained as 681 and 651 mW cm−2 for PBSC and NBSC cathodes.