Electrochemical Performance of SrFeO_3−δ for Application as a Symmetric Electrode in Solid Oxide Fuel Cells

SrFeO 3−δ has been earlier reported to exhibit a large area-specific resistance even though it possesses high mixed ionic–electronic conductivity both in oxidizing and reducing conditions. The present study clarifies this aspect and investigates the defect chemistry and electrochemical performance correlations in SrFeO 3− δ for the possible use as a symmetric electrode in solid oxide fuel cells. A conventional solid-state reaction method is adopted for powder synthesis. Structural characterization indicates an orthorhombic perovskite phase formation with a δ of 0.21. High dc electrical conductivities of ∼114.9 and 0.26 S·cm –1 are observed at 800 °C in air and reducing conditions, respectively. The area-specific resistance (ASR) for the SrFeO 3− δ electrode is measured in a symmetrical half-cell configuration under various gas environments. At 800 °C, SrFeO 3− δ offered low ASRs of 0.082, 0.055, and 0.122 Ω·cm 2 in air, oxygen, and 3% H 2 O/H 2, respectively. Although the ASR possesses excellent temporal stability in an oxidizing atmosphere, it increases to 0.42 Ω·cm 2 after 100 h in reducing conditions owing to the brownmillerite phase formation. The redox cycling performance is also affected with the ASR rising from 0.13 to 0.24 Ω·cm 2 at 800 °C in 3% H 2 O/H 2 after 20 cycles. A maximum power density of 202 mW·cm −2 is achieved from the electrolyte-supported symmetric single cell based on the SrFeO 3− δ electrodes at 800 °C. The results demonstrate the viability of using a SrFeO 3− δ -based electrode for symmetrical solid oxide fuel cells.