Ionic conduction mechanism of a nanostructured BCY electrolyte for low-temperature SOFC

Abstract A solid oxide fuel cell with 1.2 mm thick nanocrystalline BCY (BaCe0.9Y0.1O3) electrolyte was prepared by the copressing method, and its electrochemical performance was tested in H2/air conditions. The maximum power density of the nanocrystalline electrolyte cell prepared with BCY powders calcined at 1000 °C and operated at 550 °C in H2 is 405.2 mW cm−2. The carriers of nanocrystalline BCY electrolyte were studied by using double-layer electrolyte cells with pure oxygen ion conductor GDC (Gd0.1Ce0.9O2) and proton conductor SCY (SrCe0.95Y0.05O3), sintered at high temperatures as proton and oxygen ion filters. It is found that nanocrystalline BCY is a mixed conductor of oxygen ions and protons. The results of hydrogen and oxygen concentration cells show that the transference number of oxygen ions in the nanocrystalline BCY prepared in this study is higher than that of protons. XPS and HRTEM results of BCY particles before and after performance testing showed that an amorphous layer containing a high concentration of oxygen vacancies and suspected carbonate was formed on the surface of BCY particles after fuel cell performance testing. We believe that the amorphous layer should be a high-speed ion conduction channel for nanocrystalline BCY electrolyte during performance testing.