Excellent Electrochemical Performance of La_0.3Sr_0.7Fe_0.9Ti_0.1O_3-δ as a Symmetric Electrode for Solid Oxide Cells

Solid oxide cells (SOCs) can switch between fuel cell and electrolysis cell modes, which alleviate environmental and energy problems. In this study, the La_0.3Sr_0.7Fe_0.9Ti_0.1O_3-δ (LSFTi 91) perovskite is innovatively used as a symmetric electrode for solid oxide electrolysis cells (SOECs) and solid oxide fuel cells (SOFCs). LSFTi 91 exhibits a pure perovskite phase in both oxidizing and reducing atmospheres, and the maximum conductivity in air and 5% H₂/Ar is 150 and 1.1 S cm^-1, respectively, which meets the requirement of the symmetric electrode. The polarization resistance (R_p) at 1.5 V is as low as 0.09 Ω cm² in the SOEC mode due to the excellent CO₂ adsorption capacity. The current density can reach 1.9 A cm^-2 at 1.5 V and 800 °C, which is the highest electrolytic performance in the reported single-phase electrodes. LSFTi 91 also exhibits eminent oxygen reduction reaction and hydrogen oxidation reaction (ORR and HOR) activities, with R_p of 0.022 and 0.15 Ω cm² in air and wet H₂, respectively. The peak power density of SOFC could reach 847 mW cm^-2 at 800 °C. In addition, good reversibility is confirmed in the cyclic operation of SOFC and SOEC.