Tuning the Phase Transition of SrFeO 3-δ by Mn toward Enhanced Catalytic Activity and CO 2 Resistance for the Oxygen Reduction Reaction.

Developing high-performance cathodes with sufficient stability against CO 2 rooting in ambient atmosphere is crucial to realizing the practical application of solid-oxide fuel cells. Herein, the Mn dopant is investigated to regulate the phase structure and cathode performance of SrFeO 3-δ perovskites through partially replacing the B-site Fe. Compared with parent SrFeO 3-δ , Mn-doped materials, SrFe 1- x Mn x O 3-δ ( x = 0.05 and 0.1), show stabilized cubic perovskites at room temperature. Meanwhile, doping Mn accelerates the oxygen reduction reaction process, showing a reduced polarization resistance of 0.155 Ω·cm 2 at 700 °C for SrFe 0.95 Mn 0.05 O 3-δ , which is less than 30% of SrFeO 3-δ . In addition, the Mn dopant improves the chemical oxygen surface exchange and bulk diffusion coefficients. Furthermore, Mn enhances the tolerance toward CO 2 corrosion in various CO 2 atmospheres. Density functional theory calculations also reveal that Mn can strengthen the structural stability and increase the activity for the oxygen reduction reaction.