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

CaO is demonstrated as a synergistic electro-catalyst for oxygen reduction reaction on strontium-doped lanthanum ferrite (La 0.8 Sr 0.2 FeO 3−δ , LSF) cathodes for intermediate-temperature solid oxide fuel cells based on yttria-stabilized zirconia (YSZ) electrolytes. With 3.01 wt% CaO, the interfacial polarization resistance at 750 °C is reduced from 0.83 to 0.42 Ω cm 2 for LSF-SDC (samaria-doped ceria) composite electrodes on the YSZ electrolytes. With 3.2 wt% 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.