Characterization and electrochemical performances of Ba_2-xSr_xFeO_4+δ as a novel cathode material for intermediate-temperature solid oxide fuel cells

Novel cathode materials, Ba_2-xSr_xFeO_4+δ (x = 0.5, 0.6, 0.7, 0.8, 1.0), for intermediate-temperature solid oxide fuel cells on a samaria-doped ceria (SDC) electrolyte were prepared by the glycine-nitrate route and characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric (TG) analysis, electrochemical impedance spectroscopy and steady-state polarization measurement. SEM results showed that the electrode formed a good contact with the SDC electrolyte after sintering at 1000 °C for 2 h. The value of δ in Ba_1.0Sr_1.0FeO_4+δ materials was calculated from the TG results. The electrochemical impedance spectra revealed that Ba_2-xSr_xFeO_4+δ had a better electrochemical performance than that of Ln₂NiO₄ (Ln = La, Pr, Nd, Sm). In the Ba_2-xSr_xFeO_4+δ (x = 0.5, 0.6, 0.7, 0.8, 1.0) family, the composition Ba_1.0Sr_1.0FeO_4+δ exhibited the best electrochemical activity for oxygen reduction. The polarization resistance of Ba_1.0Sr_1.0FeO_4+δ on SDC electrolyte was 1.11 Ω cm² at 700 °C, which was less than half that reported for Ln₂NiO₄ at the same temperature.