High-performance lanthanum-ferrite-based cathode for SOFC

Abstract

(La 0.6Sr 0.4) 1- x Co 0.2Fe 0.8O 3/Ce 0.9Gd 0.1O 3 (LSCF/CGO) composite cathodes were investigated for SOFC application at intermediate temperature, i.e., 500–700 °C. The LSCF/CGO cathodes have been studied on three types of tape-casted electrolyte substrates including CGO electrolyte, Yttrium-stabilized Zirconia (YSZ) electrolyte coated with a thin layer of CGO, and YSZ electrolyte. Impedance spectra were measured to determine the polarization resistance ( R p) and series resistance ( R s) on cells in a symmetric configuration. R p of 0.19 Ω cm 2 at 600 °C and 0.026 Ω cm 2 at 700 °C were obtained using LSCF/CGO cathode on CGO electrolyte. On the YSZ electrolyte with thin layer CGO coating, R p of 0.6 Ω cm 2 at 600 °C and 0.12 Ω cm 2 at 700 °C were obtained. On the YSZ electrolyte directly, R p of 1.0 Ω cm 2 at 600 °C and 0.13 Ω cm 2 at 700 °C were achieved. These results are roughly six times better than our typical LSM cathodes. Slightly higher R s was observed in the samples with LSCF/CGO cathode on the YSZ electrolyte with CGO coating due to extra contribution from the thin CGO layer and the CGO/YSZ interface. For the samples with LSCF/CGO on YSZ, the R s was the same as that of our best LSM samples, which indicates good adhesion between LSCF/CGO cathode and YSZ electrolyte. Aging experiment at 800 °C for the cathode of LSCF/CGO on YSZ electrolyte shows a degradation rate of 5×10 −4 Ω cm 2/h in R p, while the R s has no obvious change.