Comparison of Electrochemical Properties of La0.6Sr0.4FeO3-δ Thin Film Electrodes: Oxidizing vs. Reducing Conditions

Owing to its mixed ionic and electronic conductivity and high thermochemical stability, La0.6Sr0.4FeO3-delta (LSF64) is an attractive electrode material in solid oxide fuel/electrolysis cells (SOFCs/SOECs). Well defined thin film microelectrodes are used to compare the electrochemical properties of LSF64 in oxidizing and reducing conditions. The high electronic sheet resistance in hydrogen can be overcome by the use of an additional metallic current collector. With the sheet resistance being compensated, the area specific electrode resistance is similar in humidified hydrogen and oxygen containing atmospheres. Analysis of the chemical capacitance and the electrode resistance for current collectors on top and beneath the LSF64 thin film allow mechanistic conclusions on active zones and bulk defect chemistry. Cyclic gas changes between reducing and oxidizing conditions, performed on macroscopic LSF64 thin film electrodes with top current collector, reveal a strong degradation of the surface kinetics in synthetic air with very fast recovery in reducing atmosphere. Additional in-situ high-temperature powder XRD on LSF64 demonstrates the formation of small amounts of iron oxides in humidified hydrogen at elevated temperatures. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. All rights reserved.