Development of the Cathode Materials for Intermediate-Temperature SOFCs Based on Proton-Conducting Electrolytes

Abstract

High-temperature proton-conducting oxide materials are of great fundamental interest due to the phenomenon of proton conductivity which appears with oxygen-ionic conductivity in a humidified atmosphere and is strongly dependent on temperature. The practical interest associated with the use of such Co-ionic electrolyte materials in solid oxide fuel cells (SOFCs) derives from the increased efficiency as a result of the higher open circuit voltage and, correspondingly, power output characteristics in comparison with those of SOFCs based on unipolar oxygen-ion conducting electrolytes. Today there is much work directed toward enhancing an SOFC’s electrochemical characteristics by developing new cathode materials that have excellent electrocatalytic activity. Thermal affinity between electrolyte and cathode materials should also be considered in order to attain both long-term stability and cycling. In this work the analysis of structural, electrical, and thermal properties of simple and layered cobaltites (GdBaCo2O5 + δ, NdBaCo2O5 + δ, Ba0.5Sr0.5CoO3–δ, Y0.8Ca0.2BaCo4O7 + δ), cobaltite-ferrites (NdBa0.5Sr0.5Co1.5Fe0.5O5 + δ, GdBaCoFeO5 + δ, Ba0.5Sr0.5Co0.8Fe0.2O3–δ, Ba0.5Sr0.5Co0.2Fe0.8O3–δ, La0.6Sr0.4Co0.2Fe0.8O3), nikelites (La2NiO4 + δ and its alkali earth element substituted derivatives) and nikelate (LaNi0.6Fe0.4O3–δ) was investigated in terms of their perspective applications in intermediate-temperature SOFCs based on proton-conducting electrolytes.