La_0.3Sr_0.7Ti_0.3Fe_0.7O_3-δ-Based Electrodes for Symmetrical Solid Oxide Fuel Cells by A-Site Deficiency Manipulation

Solid oxide fuel cells (SOFC) with symmetric configuration have received widespread attention for their potential immunity toward resisting coking and sulfur poisoning. A key requirement for electrodes in the development of symmetric solid oxide fuel cells is the high electrocatalytic activity in both oxidizing and reducing atmospheres. Herein we report a facile method to improve the electrochemical performance of La0.3Sr0.7Ti0.3Fe0.7O3-δ- (LSTF-) based perovskite electrode material by introducing the deficiency in the A-site. X-ray diffraction (XRD) results demonstrated that A-site deficient LSTF exsolves a small amount of Fe0 metallic particles and layer perovskite Sr2TiO4, which exhibits high electrical conductivity in H2 atmosphere, while at the same time the exsolution is reversible. The polarization resistances (Rp) of (La0.3Sr0.7)0.95Ti0.3Fe0.7O3-δ (LSTF-5%) are 0.032 and 0.110 Ω cm2 in air and wet H2 (containing 3% H2O), respectively, at 800 °C. The power density of the electrolyte-supported SSOFCs with LSTF-5% as symmetrical electrode reaches up to 431.8 mW cm–2 at 800 °C in wet H2/air. And the LSTF-5% symmetrical cell also exhibits excellent electrochemical performance and high stability for electrochemically reducing pure CO2. Therefore, LSTF-5% perovskite can act as an excellent electrode material in a symmetrical SOFC. The results in this paper also indicate that an appropriate amount of A-site deficiency on LSTF perovskite can lead to an increase in oxygen vacancy concentration and better electrochemical performance.