Experimental and thermodynamic evaluation of La1−xSrxMnO3±δ and La1−xSrxCo1−yFeyO3−δ cathodes in Cr-containing humidified air

Chemical and structural stability of strontium doped lanthanum manganite (LSM) and lanthanum cobalt ferrite (LSCF) cathodes in Cr-containing humidified air has been studied by a combination of experimental and thermodynamic approaches. During 100 h tests performed in flowing air (3% H2O) at 1023 K, the electrochemical performance of LSM/yttria doped zirconia (YSZ)/Pt half-cells exhibited a relatively faster degradation in current (I-t) at 0.5 V applied bias than the LSCF/gadolinium-doped ceria (GDC)/Pt half-cells. Cr species from the gas phase deposited predominantly at LSM/YSZ interface while LSCF showed mainly surface deposition throughout the electrode. Raman spectra indicate SrCrO4 formation on the post tested LSCF cathode but not on the post tested LSM cathode. The polarization resistance of the LSM cathode also increased significantly compared to that of the LSCF cathode. A linear programming approach coupled with first-principles thermodynamics suggests that the stoichiometric LSM remains stable and unreacted for the whole range of experimental PCrO3 and temperature conditions whereas the formation of SrCrO4 on LSC cathode is energetically favored at 1023 K supporting the experimental findings.