Electrochemical performance of Nd0.6Sr0.4Co0.5Fe0.5O3−δ–Ag composite cathodes in intermediate temperature solid oxide fuel cells

The electrochemical performances of Nd0.6Sr0.4Co0.5Fe0.5O3−δ–Ag composite cathodes have been investigated in intermediate temperature solid oxide fuel cells. The Nd0.6Sr0.4Co0.5Fe0.5O3−δ–Ag cathodes prepared by ball milling followed by firing at 920 °C show the maximum performance (power density: 0.15 W cm−2 at 800 °C) at 3 wt.% Ag. On the other hand, the Nd0.6Sr0.4Co0.5Fe0.5O3−δ–Ag composite cathodes with 0.1 mg cm−2 (∼0.5 wt.%) Ag that were prepared by an impregnation of Ag into Nd0.6Sr0.4Co0.5Fe0.5O3−δ followed by firing at 700 °C (but the electrolyte–Nd0.6Sr0.4Co0.5Fe0.5O3−δ assembly was prepared first by firing at 1100 °C) exhibit much better performance (power density: 0.27 W cm−2 at 800 °C) than the composite cathodes prepared by ball milling, despite a much smaller amount of Ag due to a better dispersion and an enhanced adhesion. AC impedance analysis indicates that the Ag catalysts dispersed in the porous Nd0.6Sr0.4Co0.5Fe0.5O3−δ cathode reduce the ohmic and the polarization resistances due to an increased electronic conductivity and enhanced electrocatalytic activity.