Oxygen Reduction Kinetics and Transport Properties of (Ba,Sr)(Co,Fe)O3-δ and Related SOFC Cathode Materials

Abstract

Oxygen surface reduction kinetics is studied with the help of impedance spectra measured on dense thin film microelectrodes of (Ba1-xSrx)(Co1-yFey)O3-δ (BSCF) and related SOFC cathode materials. Effective oxygen exchange rate constants kq, calculated from area-specific surface resistances Rs extracted from the impedance spectra, increase in the sequence of LSM (La1-xSrxMnO3+/-δ), LSCF (La1-xSrxCo1-yFeyO3-δ) and BSCF. The influence of bulk properties, such as electronic conductivity and Goldschmidt tolerance factor, on kq is investigated to supply information for identifying the rate-determining step. Possible roles of oxygen vacancies in the oxygen surface incorporation reaction are discussed.