Alloy vs Single-Metal Exsolution in Layered Double Perovskite PrBaMn ₂ O _5+δ Anodes for Solid Oxide Fuel Cells

Layered double perovskites offer a promising route for designing redox-stable and catalytically active SOFC anodes particularly through surface modification techniques such as controlled nanoparticle exsolution. Here, we systematically compared the single and bimetallic exsolution in PrBaMn2O5+δ (PBMO) by doping Ru (PrBaMn1.95Ru0.05O5+δ) (Ru-PBMO) and Ni-Ru (co-doped PrBaMn1.7Ni0.25Ru0.05O5+δ) (NiRu-PBMO). Structural refinement confirms dopant incorporation, with Ru-PBMO showing pronounced lattice expansion, while NiRu-PBMO exhibits a more moderate structural response. Under reduction, metallic nanoparticles exsolve, while the layered framework remains stable. In the co-doped composition NiRu-PBMO, diffraction and microscopy analysis reveals the formation of NiRu bimetallic alloy nanoparticles. X-ray photoelectron spectroscopy analysis reveals a higher concentration of surface oxygen vacancies in both Ru-PBMO and NiRu-PBMO, suggesting enhanced redox flexibility. Electrochemical testing at 800 °C shows that Ru-PBMO achieves the highest performance, with a maximum power density of 606 mW cm−2 and polarization resistance of 0.11 Ω·cm2 compared to 534 mW cm−2 and 0.15 Ω·cm2 for NiRu-PBMO and 384 mW cm−2 and 0.21 Ω·cm2 for PBMO. While Ru substitution provides the strongest improvement, the Ni-Ru system also significantly enhances performance relative to the undoped material and demonstrates the feasibility of bimetallic alloy surface engineering in PBMO. These results clarify the structural and electrochemical differences between single-metal and bimetallic strategies in layered double perovskite anodes.