La0.8Sr0.2FeO3-δ as Fuel Electrode for Solid Oxide Reversible Cells Using LaGaO3-Based Oxide Electrolyte

Activity of La0.8Sr0.2FeO3 (LSF) to the fuel electrode reaction in solid oxide reversible cells (SORCs) was investigated by using La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) and Ba0.6La0.4CoO3 (BLC) as electrolyte and air electrode, respectively. In electrolysis mode (SOEC), the LSF electrode exhibited small overpotential under the atmosphere without H-2 cofeeding; the current densities reached -1.42, -0.92, and -0.36 A/cm(2) at 1.4 V at 900, 800, and 700 degrees C, respectively, and the H-2 formation rate is well agreed with that estimated by Faraday's law. On the other hand, in the SOEC-SOFC reversible mode with the gas composition of 20% steam/20%H-2/60% Ar, the maximum power densities of 0.42, 0.28, and 0.11 W/cm(2) were achieved at 900, 800, and 700 degrees C, respectively. In addition, the cyclic reversible operation was also investigated at 800 degrees C, and it was found that the cell showed high stability over 30 cycles. DC polarization measurement suggests that the exchange current density of LSF is 14 mA/cm(2) at 700 degrees C, which is almost the same as that of Ni-YSZ reported. X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM) observation after the reversible measurement suggest that LSF is highly stable under SOEC-SOFC cyclic operation conditions. Therefore, LSF is promising as the fuel electrode for SORCs, although the conductivity is not sufficiently high as an electrode.