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_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ [Ba_0.5Sr_0.5Co_0.8Fe_0.2O_2.9−δF_0.1 (F-BSCF)] was prepared as a potential cathode for proton-conducting solid oxide fuel cells with BaCe_0.8Sm_0.2F_0.1O_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.