Systematic evaluation of cobalt-free Ln0.5Sr0·5Fe0·8Cu0·2O3−δ (Ln = La, Pr, and Nd) as cathode materials for intermediate-temperature solid oxide fuel cells

Cobalt-free perovskites, Ln0.5Sr0·5Fe0·8Cu0·2O3−δ (Ln = La, Pr, and Nd), are systematically evaluated as the cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) using Gd0.1Ce0·9O1.95 as the electrolyte. The samples exhibit an orthorhombic perovskite structures, and their cell volumes decrease as the ionic radius of Ln decreases. Both the oxygen vacancy content and the magnitude of lattice oxygen release per formula unit increase in the temperature range from 370 °C to 850 °C as the ionic radius of Ln decreases. Ln0.5Sr0.5Fe0.8Cu0.2O3−δ is chemically and thermally compatible with the Gd0.1Ce0·9O1.95 electrolyte. In the temperature range of 600 °C-750 °C, Nd0.5Sr0·5Fe0·8Cu0·2O3−δ possesses the highest catalytic activity for the oxygen reduction reaction with area specific resistance values of 0.071 Ω cm2 and 0.141 Ω cm2 at 750 °C and 700 °C, respectively. The maximum power densities of the anode-supported single cells at 800 °C and 700 °C are 1003.7 mW cm−2 and 516.7 mW cm−2 for Pr0.5Sr0·5Fe0·8Cu0·2O3−δ and 944.5 mW cm−2 and 530.2 mW cm−2 for Nd0.5Sr0·5Fe0·8Cu0·2O3−δ, respectively. Ln0.5Sr0.5Fe0.8Cu0.2O3−δ is shown to be a promising cathode material for IT-SOFCs.