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SrCo0.85Fe0.15O2.62 – Oxygen Deficient “314-type” Perovskite; a Highly Efficient Cathode for Solid Oxide Fuel Cells


Structure, electrical conductivity and electrochemical performance for a new oxygen deficient perovskite material with composition SrCo0.85Fe0.15O2.62 is explored here. It crystallizes in a “314-type” oxygen-vacancy ordered structure (Space Group: I4/mmm) with 2ap × 2ap × 4ap unit cell, and contains alternate oxygen replete [Co2/Fe2-O] and oxygen deficient [Co1/Fe1-O] planes along c-direction. Room temperature Mössbauer spectroscopy and room temperature neutron powder diffraction confirm the presence of mixed valence states (3+ and 4+) for both Fe and Co. Polaronic behavior in the electrical conductivity is observed below 400 °C, and attributed to the presence of Co4+ and Fe3+ cations in the structure. The electrical conductivity at 600 °C is high enough (∼200 S cm−1) to act as a cathode material. At the same time, the polarization resistance measurements show an excellent value of 0.1 Ω cm2 at 600 °C. These results suggest that at 600 °C, this material is a mixed oxide-ion and electronic conductor exhibiting excellent activity for the oxygen reduction reaction, making it a promising cathode material for an intermediate temperature solid oxide fuel cell.