Preparation and Electrochemical Properties of Cathode Materials Ln_2- Y CuO_4+δ for Solid Oxide Fuel Cell

Ln_2- Y CuO_4+δ (Ln = Pr, Nd, Sm; x = 0, 0.025, 0.05, 0.1) cathode materials were synthesized using a sol-gel method and calcination at 1000 °C for 24 h. The phase structure, coefficient of thermal expansion (CTE), electrical conductivity, and electrochemical impedance of cathode materials were characterized. X-ray diffraction (XRD) patterns show that the cell volume of each cathode material decreases with the increase in the Y³⁺ doping amount and has good chemical compatibility with the Sm_0.2Ce_0.8O_1.9 electrolyte. The thermal expansion test shows that the increase in Y³⁺ doping reduces the average CTE of Ln₂CuO_4+δ. The conductivity test shows that Y³⁺ doping increases the conductivity of Ln₂CuO_4+δ, and Pr_1.975Y_0.025CuO_4+δ has the highest conductivity of 256 S·cm^-1 at 800 °C. The AC impedance test shows that Y³⁺ doping reduces the polarization impedance of Ln₂CuO_4+δ, and Pr_1.9Y_0.1CuO_4+δ has a minimum area-specific resistance (ASR) of 0.204 Ω·cm² at 800 °C. In conclusion, Pr_1.975Y_0.025CuO_4+δ has the best performance and is more suitable as a cathode material for a solid oxide fuel cell (SOFC).