Cathode materials for intermediate temperature SOFCs

This work examines the electrical transport properties and electrode performance of two ceramic cathode materials (La0.84Sr0.16Co0.3Fe0.7O3 – LSCFe7 and La0.84Sr0.16Co0.7Fe0.3O3 – LSCFe3) prepared by solid state reaction from oxides and carbonates. Point-type electrodes pressed against the electrolyte material (GCO – Gd2O3 doped CeO2) were used to study the intrinsic performance of these electrode–electrolyte combinations. Pt electrodes were also used for comparison. For both ceramic cathodes a significant decrease in the cell ohmic contribution with increasing cathodic overpotentials suggests that the electrochemical reaction spreads from the triple phase boundary line to the electrode surface, a typical feature of mixed conducting electrode materials. Overall, the steady state cathodic polarization measurements performed at 800°C showed the LSCFe3 sample to be the best cathode material. LSCFe3 also had a higher conductivity than LSCFe7 (in the range 200 to 800°C), thus showing an overall highly promising performance.