Performance and Characterization of (La, Sr)MnO₃/YSZ and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ Electrodes for Solid Oxide Electrolysis Cells

Two alternative oxygen electrodes (anodes), La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ (LSCF) and La 0.8 Sr 0.2 MnO 3−δ (lanthanum strontium manganite)/YSZ (yttria stabilized zirconia), were tested in 10Sc1CeSZ (scandia and ceria stabilized zirconia) based electrolysis cells and electrochemically evaluated. In all the samples, the impedance response at OCV is characterized by a small arc at high frequencies around 10 kHz assigned to the Ni/YSZ polarization and a larger arc at low frequencies at about 200 Hz associated with the oxygen electrode. Lower polarization resistances were found for the LSCF electrode. Good performance in electrolysis mode was measured at an operating temperature of 800 °C and using 70% H 2 O at the Ni/YSZ cathode. Area specific resistance (ASR) values of 0.93 and 0.79 Ω.cm 2 were obtained for the LSM/YSZ and the LSCF samples respectively. After operation, we have observed a ∼10% increase in the ohmic resistance for the LSM/YSZ sample. This degradation was studied by both X-ray diffraction and scanning electron microscopy. LSM/YSZ and LSCF are suggested as good candidates for oxygen electrodes in high temperature electrolysis cells. Finally, good electrochemical performance was also observed in reversible fuel cell mode.