Performance of Calcium Doping in Layered Double Perovskite as Cathode Material for Solid Oxide Fuel Cells

The double perovskite oxides are widely investigated as cathode materials for solid oxide fuel cell (SOFC) due to their superior ionic electron conductivity. In this work, Pr_0.9Ca_0.1Ba_1–xCa_xCo₂O_5+δ (0≤ x≤ 0.3, PCBC) was prepared by a modified complexing sol–gel process. Based on the electrical conductivity results, Ca ion co-doping can effectively improve the conductivity of the material. The electrochemical performance results indicate that the cathode with x of 0.2 has the optimum oxygen catalytic activity, and the polarization impedance is only 0.069 Ω·cm² at 700 ℃. The oxygen vacancy formation energy, density of states, as well as O s and O p band center of PrBaCo₂O_5+δ, Pr_0.75Ca_0.25BaCo₂O_5+δ, and Pr_0.75Ca_0.25Ba_0.75Ca_0.25Co₂O_5+δ materials were calculated based on the GGA–PBE function. It is indicated that Pr-site doped with Ca can reduce the oxygen vacancy formation energy, while Ba-site doped with Ca can increase the oxygen vacancy formation energy. The calculation results of O p band center show that the strategy of Ba–site doped with Ca can effectively increase the oxygen reduction activity. The co-doping strategy of double perovskite can improve the thermal expansion, conductivity, electrochemical performance, and long-term stability of the material.