A highly operating stability, oxygen reduction reaction active and CO2/Cr tolerance perovskite cathode for solid oxide fuel cells

Abstract

Layered perovskite-related GdBaFe2O5+δ (GBF) and GdBaFeCoO5+δ (GBFC) oxides are systematically studied as advanced air electrodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The characterizations of the samples are gauged with the assistance of a variety of techniques, involving X-ray diffractometer (XRD), O2-temperature programmed desorption (O2-TPD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Fourier transform infrared spectrometry (FT-IR). Results of XRD demonstrate that GBFC has the exact same crystal structure as that of GBF, which displays slight lattice shrinkage. Substitution of Co for Fe increases the TEC from 9.87 × 10−6 K−1 and 16.6 × 10−6 K−1 at 150–700 °C. GBFC shows the highest conductivity of 500 S cm−1 at 520 °C, which complies with the requirement for the cathode of the fuel cell. The polarization resistance (Rp) values of GBF and GBFC are 0.33 Ω cm2 and 0.07 Ω cm2 at 650 °C, respectively. Moreover, a single cell based on Sm0.8Ce0.2O1.9 (SDC) electrolyte-supported is indicative of a peak power density of 0.28 W cm−2 for GBFC cathode at 700 °C. This single cell also exhibits a superior operational stability utilizing dry hydrogen fuel at 600 °C during the tested 220 h. Electrochemical impedance spectroscopy (EIS) and relaxation time distribution (DRT) results are suggestive of the slowly decreasing oxygen reduction kinetics of GBFC cathode with the introduction of CO2 or gaseous Cr species, which may be connected with the formation of carbonate or Cr depositions. Compared to classic materials, GBFC cathode shows very good electrochemical stability and CO2/Cr tolerance.