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In this study, Ce 0.65 Zr 0.25 RE 0.1 O 2−δ (RE = Tb, Gd, Eu, Sm, Nd, Pr, and La) solid solutions were successfully prepared by the glycine-nitrate process and tested for CO oxidation activity. The X-ray diffraction results confirmed the formation of complete Ce 0.65 Zr 0.25 RE 0.1 O 2−δ solid solutions. The Raman spectroscopy measurements suggested the presence of oxygen vacancies due to defective structure formation and further evidenced the formation of solid solution. The high-resolution transmission electron microscopy observations showed the nanocrystalline nature of the solid solutions. From X-ray photoelectron spectroscopy analysis it was revealed that the cerium, terbium, and praseodymium are present in +3 and +4 oxidation states. The UV−vis diffuse reflectance spectroscopy indicated that the Pr 3+ ions in the Ce 0.65 Zr 0.25 Pr 0.1 O 2−δ system provoked a significant increase in the Ce 3+ fraction on the surface. H 2 temperature-programmed reduction measurements showed an enhanced surface reduction at much lower temperatures for Ce 0.65 Zr 0.25 Pr 0.1 O 2−δ sample compared to others, indicating increased oxygen mobility in these samples, which enable the enhanced oxygen diffusion at lower temperatures. Significantly high CO oxidation activity is exhibited by Ce 0.65 Zr 0.25 Pr 0.1 O 2 solid solution.

For investigating the direct applicability of highly active cobalt containing cathodes on YSZ electrolytes at a lower processing and operating temperature range (T ≤ 650 °C), we fabricated a thin film lanthanum strontium cobalt oxide (LSC) cathode on an yttria stabilised zirconia (YSZ)‐based solid oxide fuel cell (SOFC) via pulsed laser deposition (PLD). Its electrochemical performance (5.9 mW cm–2 at 0.7 V, 650 °C) was significantly inferior to that (595 mW cm–2 at 0.7 V, 650 °C) of an SOFC with a thin (t ∼ 200 nm) gadolinium doped ceria (GDC) buffer layer in between the LSC thin film cathode and the YSZ electrolyte. It implies that even though the cathode processing and cell operating temperatures were strictly controlled not to exceed 650 °C, the direct application of LSC on YSZ should be avoided. The origin of the cell performance deterioration is thoroughly studied by glancing angle X‐ray diffraction (GAXRD) and transmission electron microscopy (TEM), and the decomposition of the cathode and diffusion of La and Sr into YSZ were observed when LSC directly contacted YSZ.

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