Evaluation of calcium codoping in double perovskite PrBaCo2O5+ as cathode material for IT-SOFCs

Layered perovskite oxides have attracted great attention in the electrochemical-energy field due to fast oxygen kinetics at low temperature and high electronic/ionic conductivity. Developing low-cost, high-performance electrocatalysts is a necessary path for the commercialization of electrochemical energy-devices. In the current research study, PrBaCo2O5+δ codoping with Ca to substitute Pr and Ba is prepared by a modified complexing sol-gel process. New perovskite oxides Pr0.9Ca0.1Ba1–xCaxCo2O5+δ (x=0–0.2, PCBCx) remained in a pure-phase tetragonal (P4/mmm) structure. PCBCx exhibit good chemical compatibility with Ce0.8Sm0.2O1.9 (SDC) after calcining at 1000 °C for 10 h. The doping of calcium ions at the Ba-site effectively improved the electrical conductivity. XPS analysis indicate that Co ions exist at +3 and +4 valence states in PCBCx samples. The thermal-expansion coefficients (TECs) of PCBCx samples decrease as the calcium ion doping concentration increasing. The polarization resistance of a PCBCx cathode on the SDC electrolyte, where x=0–0.3 at 700 °C, are 0.097, 0.076, 0.069, and 0.106 Ω cm2, respectively. The x=0.2 cathode reveals the best electrochemical performance. The maximum power densities of the PCBC2 cathode are 712, 541, and 392 mW cm–2 at 800, 750, and 700 °C, respectively. The results demonstrate an effective codoping strategy to improve conductivity, thermal stability, and electrochemical performance, and provide evidence for the great potential of prepared novel double-perovskite oxides PCBCx as solid-oxide fuel cell cathodes.