Composite cathode La0.15Bi0.85O1.5-Ag for intermediate-temperature solid oxide fuel cells

Composites consisting of silver and lanthanum stabilized bismuth oxide (La0.15Bi0.85O1.5) were investigated as cathodes for intermediate-temperature solid oxide fuel cells with doped ceria as electrolyte. No stable phases were formed via reaction between La0.15Bi0.85O1.5 and Ag. The microstructure of the interfaces between composite cathodes and Ce0.8Sm0.2O1.5 electrolytes was studied by scanning electron microscopy after sintering at various temperatures. Impedance spectroscopy measurements revealed that the performance of cathode fired at 700 degrees C was the best. When the optimum fraction of Ag was 50 vol.%, polarization resistance values for the LSB-Ag50 cathode were as low as 0.14 Omega cm(2) at 700 degrees C and 0.18 Omega cm 2 at 650 degrees C. The steady-state polarization investigations on LSB and LSB-Ag50 cathodes were performed using typical three-electrode test cells in air. The results showed that the LSB-Ag50 composite cathode exhibited a lower overpotential and higher exchange current density than LSB, which indicated the electrochemical performance of LSB-Ag50 for the oxygen reduction reaction was superior to the LSB. (C) 2007 Elsevier B.V. All rights reserved.