Revisiting Mo‐Doped SrFeO3‐δ Perovskite: The Origination of Cathodic Activity and Longevity for Intermediate‐Temperature Solid Oxide Fuel Cells

Abstract The development of cathode materials for rapid and durable oxygen reduction reaction (ORR) is of great importance for intermediate‐temperature solid oxide fuel cells (IT‐SOFCs). Here, we reported a rationally designed minor acidic MoO 3 incorporated SrFeO 3‐δ ‐based perovskite oxide, SrFe 0.93 Mo 0.07 O 3‐δ instead of normally heavily doped one, with stable cubic phase, exceptional ORR activity, strong Sr segregation resistance and CO 2 tolerance as a reliable cathode for IT‐SOFCs through a combined strategy of smith acidity and average metal‐oxygen bond energy regulations. Theoretical investigation on the origin of nonstoichiometric and associated electronic structure properties shows that significant hybridization of the Fe‐3d and O‐2p state, reduced oxygen vacancies formation energy and eased bulk oxide ion diffusivity through controllable amount of Mo‐doping contribute to remarkable ORR activity. The single cell with SrFe 0.93 Mo 0.07 O 3‐δ cathode exhibits a peak power density of 0.24–1.12 W cm −2 at 600–800 °C, and excellent stability for 270 h at 700 °C. Furthermore, the single cell demonstrates excellent thermal cycling robustness and well‐integrated interfaces without any performance degradation after undergoing 20 rapid temperature fluctuations throughout 500 h. Therefore, this work embodies a combined strategy for designing active perovskite cathode and highlights the great potential for IT‐SOFCs as validated by multiple perspective considerations.