Novel cobalt-free perovskite PrBaFe1.9Mo0.1O5+δ as a cathode material for solid oxide fuel cells

Abstract

Fe-based perovskite PrBaFe2O5+δ is inactive toward the oxygen reduction reaction (ORR) due to the sluggish oxygen-ion transport kinetics. Herein, Mo doping is developed as a simple and effective strategy to improve the ORR activity of PrBaFe2O5+δ. Mo-doped PrBaFe1.9Mo0.1O5+δ (PBFMO) is comparatively studied with undoped PrBaFe2O5+δ (PBFO) to reveal the effect of Mo doping on its crystal structure, thermal expansion behavior, electrical and electrochemical properties. PBFMO sample has a tetragonal structure with P4/mmm space group. Pr, Fe, and Mo in PBFMO sample exist as Pr3+/Pr4+, Fe2+/Fe3+, and Mo5+/Mo6+ mixed valence states. Mo doping reduces the average thermal expansion coefficient (TEC) from 18.8 × 10−6 K−1 down to 14.5 × 10−6 K−1, which is closer to the TEC of La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte. Moreover, Mo doping results in the increment of oxygen vacancy content and thus the enhancement of electrochemical performance. The polarization resistance (Rp) is 0.092 Ω·cm2 at 800 °C for PBFMO and is reduced by 27.0% after Mo doping. The peak power density is 0.68 W·cm−2 at 800 °C for PBFMO-based single cell. These obtained results indicate Mo doped PBFMO can be a good candidate for cathode material of intermediate temperature SOFC.