Praseodymium Double-site occupancy to enhance the activity and impurity tolerance of SrCo_0.9Ta_0.1O_3-δ cathode for solid oxide fuel cells

In this work, a series of novel cathode materials with the nominal stoichiometry Pr_xSr_1-xCo_0.9Ta_0.1O_3-δ (PxSCT, 0 ≤ x ≤ 0.3) are successfully prepared and investigated as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). The results show that Pr cations are simultaneously doped at the A- and B-site in the perovskite. Among the samples, P0.1SCT exhibits the lowest thermal expansion coefficient and the highest electrical conductivity. Thus, P0.1SCT cathode shows the best oxygen reduction reaction activity, achieving a low polarization resistance of 0.022Ω cm² at 700 °C. The single cell with P0.1SCT cathode reaches 941.8 mW cm⁻² at 800 °C, higher than that of the cell with SCT cathode (874.0 mW cm⁻²). More importantly, with the increase of metal–oxygen bond strength and acidity of the material, P0.1SCT cathode shows improved poisoning tolerance towards CO₂ and Cr impurities. After Cr poisoning, the current density of the cell with P0.1SCT cathode decreases from 585.7 to 509.3 mA cm⁻², more stable than that of the cell with SCT cathode (450.8 to 251.0 mA cm⁻²). The combined results demonstrate that P0.1SCT displays considerable potential as a cathode for IT-SOFCs. Our work also provides valuable guidelines for the design of highly stable cathode materials with rare earth doping.