Calcium oxide as synergistic catalyst for oxygen reduction reaction on strontium-doped lanthanum ferrite for SOFC

Abstract

Abstract CaO is demonstrated as a synergistic electro-catalyst for oxygen reduction reaction on strontium-doped lanthanum ferrite (La0.8Sr0.2FeO3-δ, LSF) cathodes for intermediate-temperature solid oxide fuel cells based on ytrria-stabilized zirconia (YSZ) electrolytes. With 3.01wt% CaO, the interfacial polarization resistance at 750°C is reduced from 0.83 to 0.42 Ω cm2 for LSF-SDC (samaria doped ceria) composite electrodes on the YSZ electrolytes. With 3.2wt% CaO, the peak power density at 800°C is increased from 0.45 to 0.58 Wcm-2 for anode supported single cells consisting of Ni-YSZ anodes, YSZ electrolytes and LSF-SDC cathodes. The CaO particles can greatly enhance the kinetics of oxygen reduction reaction on LSF such as improving the oxygen surface exchange coefficient at 750°C from 1.9×10− 5 to 54×10− 5 cm s-1 as demonstrated by the electrochemical conductivity relaxation measurement. Specifically, CaO particles infiltrated to the LSF electrodes reduce the interfacial polarization resistance associated with the low-frequency response, which is often attributed to the surface reaction steps of the cathode reaction.