Improved Phase Stability and CO2 Poisoning Robustness of Y-Doped Ba0.5Sr0.5Co0.8Fe0.2O3−δ SOFC Cathodes at Intermediate Temperatures

Abstract

The outstanding oxygen permeability of the perovskite Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) and its applicability as a cathode in solid oxide fuel cells are remarkable, yet have been hindered by the formation of secondary phases at T < 840 °C and the subsequent degradation. The other main drawback to BSCF is related to the formation of carbonates in the presence of CO2. These degrade its excellent oxygen surface-exchange kinetics. In this work, 10% Y-doped Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF10Y) is electrochemically, microstructurally, and chemically characterized in O2- and CO2-containing atmospheres as porous cathodes in symmetrical cells with Gd-doped ceria as electrolyte. Experiments in oxygen/nitrogen gas mixtures (pO2 = 0.02–0.40 atm) at T = 600–900 °C showed high performance with a cathode specific resistance of 49.9 mΩ cm2 at 600 °C in air (pO2 = 0.21 atm), which is very comparable to 47.8 mΩ cm2 for undoped BSCF, but which deteriorates constantly under the same conditions. Moreover, adding significant amoun...