Double-perovskite PrBaCo2/3Fe2/3Cu2/3O5+δ as cathode material for intermediate-temperature solid-oxide fuel cells

Double-perovskite PrBaCo2/3Fe2/3Cu2/3O5+δ (PBCFC) is synthesized by the EDTA–citrate complexing method, and investigated as a novel cathode material for CeO2-based intermediate-temperature solid-oxide fuel cells (IT-SOFCs). The PBCFC material exhibits good chemical compatibility with Ce0.8Sm0.2O1.9 (SDC) and Ce0.9Gd0.1O1.95 (GDC) electrolytes at 900 and 950 °C for 10 h, respectively. XPS analysis shows that the rare-earth and transition-metal cations in the double-perovskite PBCFC exist in two different valence states, i.e., [Pr3+/Pr4+][Ba2+][Co3+/Co4+]2/3[Fe3+/Fe4+]2/3[Cu+/Cu2+]2/3O5+δ. The electrical conductivity of the PBCFC sample reaches a maximum of 144 S cm−1 at 600 °C in air. The thermal expansion coefficient (TEC) of the PBCFC sample is 16.6 × 10−6 K−1 between 30 and 850 °C in air. The polarization resistance of the PBCFC cathode on SDC and GDC electrolytes are 0.144 and 0.038 Ω cm2 at 800 °C, respectively. The maximum power densities of a single cell with the PBCFC cathode on a 300 μm-thick GDC electrolyte are 659 and 512 mW cm−2 at 800 and 750 °C, respectively. Fe and Cu co-doped PrBaCo2O5+δ exhibits decreased TEC and improved electrochemical performance, making it a suitable cathode material for GDC electrolyte IT-SOFCs.

► A single-phase double-perovskite PrBaCo2/3Fe2/3Cu2/3O5+δ (PBCFC) is prepared by the EDTA–citrate complexing method.
► XPS analysis shows that the Pr3+/Pr4+, Co3+/Co4+, Fe3+/Fe4+, Cu+/Cu2+ and Ba2+ species coexist in the PBCFC.
► PBCFC material has a good chemical compatibility with SDC and GDC electrolytes below 900 °C and 950 °C, respectively.
► Partial substitution of Fe and Cu for Co efficiently lowers the thermal expansion coefficient of the PBCFC.
► Low polarization resistance of 0.071 Ω cm2 and high power density of 512 mW cm−2 at 750 °C are obtained on GDC electrolyte.