Experimental study and first-principles calculation of enhanced electrochemical properties of Bi0.7Sr0.3FeO3-δ (BSFO) – La0.8Sr0.2MnO3-δ (LSM) composite cathodes for intermediate-temperature solid oxide fuel cells

Abstract

In order to enhance the electrochemical performance of cobalt-free Bi0.7Sr0.3FeO3-δ (BSFO) cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs), a composite cathode consisting of BSFO and La0.8Sr0.2MnO3-δ (LSM) is developed. The optimized polarization resistance of the composite cathode (0.11 Ω cm2 at 800 °C) is found to be only 61 % that of pure BSFO (0.18 Ω cm2 at 800 °C), indicating a significant improvement in performance. The first-principles calculation indicates that the enhanced electrochemical performance is mainly due to the domain of low oxygen vacancy formation energies of BSFO-LSM-L interfaces (Evac, −3.63 eV) and LSM (Evac, −3.11 eV). The anode-supported single cell of NiO-SDC/SDC/BSFO－LSM shows a peak power density of 825.83 mW cm−2 at 800 °C using wet H2 (∼3 vol% H2O) as fuels and ambient air as oxidants. In addition, the single cell exhibits a good stability at the electric current density 400 mA cm−2 for 50 h measured at 650 °C.