A comparative study of electrochemical performance of La0.5Ba0.5CoO3−δ and La0.5Ba0.5CoO3−δ–Gd0.1Ce0.9O1.95 cathodes

Cubic perovskite oxide La0.5Ba0.5CoO3−δ (LBCO) and its composite with Gd0.1Ce0.9O1.95 (GDC) electrolyte, LBCO–GDC in 1:1 weight ratio were prepared. Chemical compatibility between LBCO and GDC was studied and no serious phase reaction occurred at temperatures up to 1050 °C in air. Electrochemical performance of the cathodes was measured by Electrochemical Impedance Spectroscopy (EIS) as a function of temperature and oxygen partial pressure. Electrode reaction mechanism was analyzed based on fitting results of the EIS with proper equivalent circuit models. Comparison of the results demonstrated that introduction of the ionic conductive GDC component to the LBCO–GDC composite cathode hardly influenced gas diffusion through bulk of the cathode (low-frequency process) while greatly enhanced oxygen ionic transfer across the cathode/electrolyte interface (high-frequency process) and the electrode reaction occurring in the medium-frequency range. As a result, the LBCO–GDC composite cathode exhibited lower area-specific resistance (ASR) than the LBCO cathode, with ASR value ranging from ∼0.12 Ω cm2 at 600 °C to ∼0.01 Ω cm2 at 800 °C. These results have demonstrated that the LBCO–GDC composite (1:1 weight ratio) is highly promising as a cathode for intermediate temperature solid oxide fuel cell.

► LBCO was chemically stable with GDC electrolyte at 1050 °C in air. ► LBCO–GDC composite cathode had lower ASRs than LBCO cathode. ► GDC promoted electrode reaction and cathode/electrolyte interface charge transfer. ► GDC component hardly influenced gas diffusion through the porous cathode. ► LBCO–GDC composite cathode is promising with applications in IT-SOFCs.