A new composite cathode for intermediate temperature solid oxide fuel cells with zirconia-based electrolytes

Improving the electrocatalytic activity of electrode materials is vitally important to achieve practically meaningful performance for intermediate temperature solid oxide fuel cells (IT-SOFCs). The present work develops a composite cathode consisting of an electronic conductor Sr-doped LaMnO3 (LSM) and an ionic conductor Y- and Ce- co-doped Bi2O3 (BYC7). BYC7 is an excellent oxide-ion conductor, exhibiting a high and stable ionic conductivity of 0.008 S cm−1 at 500 °C. The polarization resistance of LSM-BYC7 cathode in a symmetrical cell with doped ZrO2 as electrolyte varies from 5.76 at 500 °C to 0.25 Ω cm2 at 650 °C. The surface diffusion and charge transfer at the triple phase boundaries are the rate determining steps based on the dependence of polarization resistance on partial pressure of oxygen. The maximum power density of a ZrO2-based anode-supported cell with LSM-BYC7 composite cathode is 56.4, 154.6, 327.9, and 451.0 mW cm−2 at 500, 550, 600, and 650 °C respectively. AC impedance analysis reveals that the performance of IT-SOFC prepared in this study is actually limited by the anode, not by LSM-BYC7 cathode.