B-site Cu-doped PrBa_0.5Sr_0.5Co₂O_5+δ as novel low temperature-solid oxide fuel cells cathodes with reduced thermal expansion coefficient and enhanced oxygen-ion diffusion

PrBa_0.5Sr_0.5Co₂O_5+δ (PBSC) has attracted considerable attention as a layered perovskite cathode for solid oxide fuel cells (SOFCs) due to its favorable electrochemical properties, while also holds significant potential for modification into an efficient low-temperature cathode. However, its high thermal expansion coefficient and sluggish oxygen-ion diffusion remain critical challenges for achieving stable operation of SOFCs at reduced temperatures (below 650 °C). To overcome these limitations, we employe first-principles calculations to screen the suitable B-site dopants (M = Fe, Ni, Cu) for PBSC, aiming to optimize its structural and electrochemical characteristics. Guided by these theoretical insights, a series of PrBa0_.5Sr_0.5Co_2-xCu_xO_5+δ (x = 0, 0.5, 1.0) cathode materials were synthesized and systematically investigated with respect to their phase structure, elemental valence states, thermogravimetric properties, and microstructure. Among the tested dopants, Cu substitution proves to be the most effective in enhancing the electrochemical performance of PBSCCx cathodes, owing to the rigid Cu-O coordination and suppressed Co redox that limit lattice expansion, progressive lattice contraction upon Cu incorporation, and enriched oxygen vacancies that facilitate oxygen ion transport. Consequently, the PBSCC1.0 cathode manifests a more than 24 % reduction in thermal expansion coefficient, a 29 % decrease in polarization resistance, and an 8 % drop in activation energy compared to undoped PBSC, highlighting the effectiveness of Cu doping in optimizing cathode properties. Furthermore, the single cell employing PBSCC1.0 cathode could achieve a peak power density of 0.222 W (Formula presented) cm⁻²at 650 °C, representing an evident enhancement of over 149 % compared to undoped PBSC under the identical conditions.