The effect of electrode microstructure on cathodic polarization

Ni + yttria-stabilized zirconia (YSZ)-anode-supported cells with a thin YSZ electrolyte and Sr-doped LaMnO3 (LSM) + YSZ composite cathode were fabricated. Volume fractions of LSM and YSZ in the composite cathode were varied over a wide range. Cell performance was measured at 800degreesC with hydrogen as fuel and air as oxidant. Cathode microstructures were characterized by quantitative stereology to estimate the three phase boundary (TPB) length, porosity and the aggregate grain size of YSZ in the cathode. Measured polarization was correlated with microstructure. Experimental results are in reasonable agreement with the previously published theoretical model. The intrinsic charge transfer resistivity, p, at LSM/YSZ/air TPB was determined as similar to1.0 x 10(5)Omegacm at 800degreesC.