Praseodymium and gadolinium doped ceria as oxygen electrode for solid oxide cell applications

Abstract

This study analyzes the structural and electrochemical properties of praseodymium- and gadolinium-doped ceria (CPGO) samples formed by the sintering reaction of Pr₂NiO_4+δ (PNO) and Ce_0.9Gd_0.1O_2−δ (GDC). X-ray powder diffraction analysis confirmed a single-phase cubic CPGO structure as a primary phase. The cationic compositions were determined using energy dispersive spectroscopy (EDS) in a scanning transmission electron microscope (STEM), while core-loss electron energy-loss spectroscopy (EELS) was used to determine the valence of Ce and Pr. The compatibility between thermal expansion coefficients validated their integration with electrolytes at the typical Solid Oxide Cell (SOC) operation temperatures. Oxygen chemical diffusion and surface exchange coefficients were investigated using the electrical conductivity relaxation (ECR) method at intervals of partial oxygen pressures between 0.10 and 0.21 atm and 600 °C and 800 °C. Finally, the samples were tested in symmetrical cells by electrochemical impedance spectroscopy (EIS) between 700 °C and 850 °C. A polarization resistance of 0.17 Ω cm² at 850 °C was obtained for CPGO air electrodes formed by sintering a mixture of 80% by weight of GDC and 20% by weight of PNO. These findings confirm that PNO–GDC mixtures forming CPGO oxides are excellent candidates for SOC applications.