Novel mixed H+/e−/O2− conducting cathode material PrBa0.9K0.1Fe1.9Zn0.1O5+δ for proton-conducting solid oxide fuel cells

Abstract

Double perovskite material PrBa_0.9K_0.1Fe_1.9Zn_0.1O_5+δ (PBKFZ) has been designed using the first-principle calculations and synthesized as a new cathode for proton-conducting solid oxide fuel cells. The influence of K-doping on the crystal structure, structure stability, thermal expansion behavior, electronic conductivity, proton uptake, and electrochemical performance has been investigated. PBKFZ presents the P4/mmm space group, and its thermal expansion coefficient is 16.110⁻⁶ K⁻¹. The oxygen vacancy concentrations and proton uptake capacity of PrBaFe_1.9Zn_0.1O_5+δ (PBFZ) in wet air (5% H₂O) are significantly improved with K doping. The single cell with the PBKFZ cathode shows an excellent electrochemical performance with a peak power density of 1.4 W cm⁻² and polarization resistance of 0.06 Ω cm² at 700 °C, which is significantly higher than that of the cell using the pristine PBFZ cathode. This study provides a new and rational strategy to design a high-performance cathode for proton-conducting SOFCs.