Electrochemical performance of highly active ceramic symmetrical electrode La0.3Sr0.7Ti0.3Fe0.7O3-δ-CeO2 for reversible solid oxide cells

The electrolyte supported cells with the La0.3Sr0.7Ti0.3Fe0.7O3-δ (LSTF0.7)-CeO2|ScSZ (scandia-stabilized zirconia)|La0.3Sr0.7Ti0.3Fe0.7O3-δ-CeO2 symmetrical configuration are fabricated by infiltration method and investigated as reversible solid oxide cells (RSOCs) at different CO/CO2 ratios. A well-deposited microstructure is observed in the infiltrated electrode. From the I-V curves, the maximum current density of 1.90 A cm−2 at 2.0 V is obtained for CO: CO2 ratio of 1: 1 for CO2 electrolysis at 850 °C, while the corresponding power density under the same conditions is 357 mW cm−2 in fuel cell mode. Electrochemical impedance spectroscopy (EIS) is conducted for better understanding the electrode catalytic mechanism. The whole symmetrical cell achieves the polarization resistance (Rp) values of 0.284 and 0.203 Ω cm2 at 850 °C under open circuit and at 1.4 V, respectively. Under reversible operation (cyclic voltammetry) at 800 °C, no distinct degradation is found in the cell with the infiltrated LSTF0.7 symmetrical electrodes. The long-term stability at 1.2-2.0 V characterized by potentiostatic measurement indicates that the prepared LSTF0.7-CeO2 composite electrode is comparatively stable at low voltages while a degradation behavior is observed at high voltages. These results illustrate that the LSFT0.7-CeO2 composite is a promising active ceramic electrode for symmetrical RSOCs.