Electrochemical behavior of Ln0.6Sr0.4Co0.2Fe0.8O3−δ (Ln=Ce, Gd, Sm, Dy) materials used as cathode of IT-SOFC

The perovskite-type compounds Ln_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (Ln=Ce, Sm, Gd, Dy) used as the cathodes of intermediate temperature solid oxide fuel cell (IT-SOFC) were studied. The cells consisted of anode supported Sm-doped-ceria electrolyte bi-layer and cathode with 0.65 cm² effective area. Open-circuit voltage (OCV), V–I and P–I curves of the cells were measured over a temperature range from 400 to 800 °C, using H₂–3%H₂O as fuel and air as oxidant. Polarization potential of electrodes were measured with asymmetry three-electrode method during cell discharging. The results indicated that, Dy-SCF material cathode behaved with high catalytic activity for oxygen dissociation at low temperatures. For each cell with a particular cathode, there was a transition temperature, at which OCV of the cell reached the highest value. When temperature was higher than the transition temperature, OCV of the cell increases with decreasing temperature, whereas as temperature was lower than that, OCV decreased with lowering temperature.