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- x}Sr _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- x}Sr _xFeO _{4+ δ} had a better electrochemical performance than that of Ln ₂NiO ₄ (Ln = La, Pr, Nd, Sm). In the Ba _{2- x}Sr _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 cm ² at 700 °C, which was less than half that reported for Ln ₂NiO ₄ at the same temperature.