Electrochemical performance of Ba0.8Sr0.2Co0.7Fe0.2Nb0.1O3−δ–Ce0.85Sm0.15O1.925 composite cathodes for intermediate temperature solid oxide fuel cells

Abstract

Ba1−xSrxCo0.7Fe0.2Nb0.1O3−δ (x = 0.0–0.2) are proposed as the electrodes for intermediate temperature solid oxide fuel cells (IT-SOFCs) for the first time. The minimum polarization resistance value is achieved at Ba0.8Sr0.2Co0.7Fe0.2Nb0.1O3−δ(BSCFN). In this work, BSCFN-xSDC(x = 0–40wt.%) are investigated as the cathodes for IT-SOFCs with SDC electrolyte. The structures of the cathodes are characterized by X-ray diffraction and SEM. The electrode performance of BSCFN-xSDC is measured at various temperatures and oxygen partial pressures. Comparison of the results demonstrate that introduction of ionic conductive SDC to BSCFN-xSDC composite cathode can make the oxygen reduction reaction processes from the three processes into two processes, the charge transfer process and the adsorption and dissociation of gaseous oxygen process. The charge transfer process is the major rate limiting step when oxygen partial pressure is higher than 0.05 atm. The microstructure of BSCFN-30SDC is characterized by more appropriate grain size and more adequate porosity. The area conductivity of adsorption and dissociation of gaseous oxygen process for BSCFN-30SDC is the highest. Comparison of the power density of single cell results demonstrate that BSCFN-xSDC composite cathode has higher power density than BSCFN cathode. BSCFN-30SDC electrode exhibits the highest cathode performance among BSCFN-xSDC composite cathodes.