Tungsten-Doped PrBaFe₂O_5+δ Double Perovskite as a High-Performance Electrode Material for Symmetrical Solid Oxide Fuel Cells

Double perovskite PrBaFe2O5+δ is a potential electrode material for symmetrical solid oxide fuel cells (Sym-SOFCs). This work aims to improve the Sym-SOFC performance by partially replacing Fe with W, forming a composition of (PrBa)0.95(Fe0.95W0.05)2O5+δ. Doping W keeps PrBaFe2O5+δ stability after high-temperature treatment in both air and hydrogen atmospheres, decreases the thermal expansion coefficient from 17.11 × 10–6 to 14.59 × 10–6 K–1, increases the content of oxygen species that are essential for the electrocatalytic reactions, and increases the chemical oxygen surface exchange coefficient by 121% at 800 °C. Consequently, doping W greatly improves the electrochemical performance, such as decreasing the area-specific cathode polarization resistance by 35.5% to 0.031 Ω·cm2 at 800 °C, reducing the anode polarization resistance by 17.7% to 0.123 Ω·cm2, and increasing the peak power density of Sym-SOFCs by 32.5% to 1.02 W cm–2 using humidified hydrogen as the fuel. The performance is much higher than those reported for Sym-SOFCs using PrBaFe2O5+δ doped with the other elements. Finally, the Sym-SOFCs are capable of directly using hydrocarbon fuels, providing peak power densities of 0.610, 0.624, and 0.448 W cm–2 at 800 °C for syngas, ethane, and propane, respectively.