A-site Ba doping-induced structural reconstruction of La_0.3Sr_0.7FeO_3-δ and its performance as an electrode for SSOFCs

Symmetric solid oxide fuel cells (SSOFCs) offer advantages such as simplified manufacturing and operation; however, their performance is often constrained by insufficient oxygen vacancy concentration and sluggish oxygen ion transport in conventional electrodes. To overcome these limitations, a novel Ba-doped perovskite system, La_0.3Sr_0.7-xBa_xFeO_3-δ (LSBaF-x, x = 0.1-0.3), was developed through A-site engineering. Rietveld refinement of XRD data confirmed that LSBaF-0.2 exhibits a well-defined cubic perovskite structure, overcoming the hexagonal distortion of undoped LSF. Electrochemical performance tests revealed a significant reduction in polarization resistance (R_p) to 0.136 Ω cm² in H₂ at 800 °C, along with a decreased apparent activation energy of 0.93 eV for the oxygen reduction reaction (ORR) in air. When integrated into SSOFCs, the LSBaF-0.2 electrode achieved exceptional performance, delivering peak power densities (PPDs) of 1235 mW cm^-2 at 800 °C and 690 mW cm^-2 at 700 °C. Moreover, continuous operation for 200 h at 800 °C demonstrated excellent stability. These results highlight Ba doping as an effective strategy to stabilize cubic LSF and optimize dynamics, and LSBaF-0.2 is regarded as a highly promising electrode material for SSOFC applications.