A Stable and Efficient Cathode for Fluorine-Containing Proton-Conducting Solid Oxide Fuel Cells

Substitution of anions such as F^- and Cl^- can effectively improve the stability of proton-conducting electrolytes at no expense to proton conduction. However, during operation, F^- and Cl^- in electrolytes can transfer to the cathodes, which reduces the stability of the electrolytes. In this work, F^- -doped Ba_0.5 Sr_0.5 Co_0.8 Fe_0.2 O_3-δ [Ba_0.5 Sr_0.5 Co_0.8 Fe_0.2 O_2.9-δ F_0.1 (F-BSCF)] was prepared as a potential cathode for proton-conducting solid oxide fuel cells with BaCe_0.8 Sm_0.2 F_0.1 O_2.85 electrolyte. The incorporation of F^- in the cathode depressed F^- diffusion from the electrolyte and improved the stability of button cells. Temperature-changing X-ray photoelectron spectroscopy and electronic conductivity relaxation results demonstrated that the incorporation of F^- enhanced the oxygen incorporation kinetics at intermediate temperatures and improved the cathode catalytic performance. Moreover, a button cell prepared with this novel cathode was stable for 270 h at a current density of 300 mA cm^-2 and 700 °C, which was much superior than those containing a BSCF cathode.