Investigation of the necessity to apply a (Ce, Gd)O2 interlayer between the low-temperature processed (La, Sr)CoO3 electrode film and the (Zr, Y)O2 electrolyte in solid oxide fuel cells

Gadolinia doped ceria (GDC) interlayers have been widely used to avoid resistive phase formation at the mixed ionic electronic conductor (MIEC) (La,Sr)CoO3 (LSC) air electrode/ yttria stabilized zirconia (YSZ) electrolyte interfaces. Although MIEC electrodes fabricated by low-temperature metal organic precursor methods offer the highest electrochemical performance, no studies exist on the effect of GDC interlayer on their performance. In this work, we investigated the necessity for a GDC interlayer between the low-temperature processed LSC electrode and the YSZ electrolyte. Through x-ray diffraction, scanning transmission electron microscopy/energydispersive x-ray spectroscopy and x-ray photoelectron spectroscopy analyses, we studied the impact of the GDC interlayer on i) the formation of resistive zirconate phases at the LSC/YSZ interface and ii) the overall phase and surface chemistry evolution. While no resistive zirconate phases formed in the LSC/YSZ system due to low processing temperatures, La leaching into the GDC layer altered the overall phase evolution, in addition to the resulting cation stoichiometry. This LSC/GDC/YSZ system showed a polarization resistance improved by an order of magnitude, attributable to the changes in phase composition.