Improving electrochemical performance of lanthanum strontium ferrite by decorating instead of doping cobaltite

Cobalt oxide is usually used as a dopant to improve the catalytic activity of Mn and Fe based perovskites such as lanthanum strontium ferrite (LSF) for solid oxide fuel cells. This work presents the catalytic improvement by decorating LSF surface with cobalt oxide, Co₃O₄, using infiltration technique. X-ray diffraction and high resolution electron microscopy analysis indicate that Co₃O₄ is chemically compatible with LSF at the intermediate-temperature range for solid oxide fuel cells. Electrochemical impedance spectrum demonstrates substantial reduction in interfacial polarization resistance, from 0.22 to 0.083 Ωcm² at 700 °C when 5.84 wt. % Co₃O₄ is infiltrated into the bare LSF electrodes. Further analysing the impedance spectrum with distribution of relaxation time calculation suggests that the performance improvement is associated with the charge-transfer processes of the surface reaction. Meanwhile, the electrochemical conductivity relaxation measurement shows that Co₃O₄ particles can improve the surface reaction kinetics, increasing the oxygen surface exchange coefficient by a factor of about 5 at 700 °C. In addition, Co₃O₄ particles can increase the peak power density of the single cells from 0.865 Wcm⁻² to 1.3 Wcm⁻² at 800 °C with LSF based cathodes. The results clearly demonstrate an alternative mean to use cobalt oxide in improving the catalytic performance of Mn and Fe based perovskites.