Characterization And Optimization Of La_(0.8)sr_(0.2)sc_(0.1)mn_(0.9)o_(3-δ)-based Composite Electrodes For Intermediate-temperature Solid-oxide Fuel Cells

摘要

Composite electrodes composed of a perovskite-type La_(0.8)Sr_(0.2)Sc_(0.1)Mn_(0.9)O_(3-δ) (LSSM) and a fluorite-type scandium-stabilized zirconia (ScSZ) were prepared and evaluated as potential cathodes for intermediate-temperature solid-oxide fuel cells. Characterization was made by phase reaction, electrochemical impedance spectroscopy, step current polarization and l-V tests. The phase reaction between LSSM and ScSZ occurred at 1150℃ or higher; however, it had a minor effect on the electrode performance. The formation of a composite electrode led to an obvious improvement in both charge transfer and surface-related processes. With the increase of ScSZ content, the rate-limiting step of oxygen reduction reaction steadily changed from mainly a surface diffusion process to an electron transfer process. The optimal ScSZ content and sintering temperature of the electrode layer were found to be 20 wt.% and 1100-1150℃, respectively. Under optimal conditions, an anode-supported single cell with LSSM + ScSZ composite cathode showed high power densities of～1211 and 386mW cm~(-2) at 800 and 650℃, respectively.