Advancing Solid Oxide Fuel Cell Performance: Enhanced Electrochemical Properties of Pr1–xCaxBaFe2O5+δ Nanofiber Cathodes via Ca Doping

The double perovskite oxide PrBaFe₂O_5+δ has great potential as a cathode material for solid oxide fuel cells (SOFCs). However, the electrochemical characteristics of Fe-based double perovskites are relatively inferior. To improve its electrochemical performance, Ca is investigated to partially replace Pr, forming Pr_1-xCa_xBaFe₂O_5+δ (PCBFx, x = 0.0-0.3) by an electrospinning technique. The PCBFx nanofibers exhibited a crystalline structure characterized by orthorhombic symmetry and space group P4/mmm. Furthermore, these PCBFx nanofibers displayed exceptional chemical compatibility with the Sm_0.2Ce_0.8O_1.95 (SDC) electrolyte when sintered at a temperature of 900 °C for 5 h. The X-ray photoelectron spectroscopy (XPS) analysis reveals a progressive increase in the Fe⁴⁺ concentration as the Ca doping level rises. The polarization resistances (R_p) of the PCBF00, PCBF01, PCBF02, and PCBF03 nanofiber cathodes were 0.103, 0.079, 0.056, and 0.048 Ω cm² at 750 °C. In the meantime, doping Ca increases the peak power density of the single cell by 46%, from 762.80 (PCBF00) to 1114.85 (PCBF03) mW cm^-2 at 750 °C. The results demonstrate that PCBF03 double perovskite nanofibers exhibit great potential as cathode materials for SOFCs.