Electrospun Carbon Nanofibers Loaded with Atomic FeNx/Fe2O3 Active Sites for Efficient Oxygen Reduction Reaction in Both Acidic and Alkaline Media

Abstract Renewable energy storage systems based on oxygen reduction reaction (ORR) call for high‐performance, durable, and low‐cost electrocatalysts. However, practical applications of ORR catalysts available today are hampered by the inability to load accessible catalytic sites efficiently. Herein, a novel and efficient ORR electrocatalyst (Fe 2 O 3 /FeN x @CNF) with atomic FeN x sites and neighboring Fe 2 O 3 nanoparticles embedded in interconnected carbon nanofibers prepared via electrospinning is reported. Detailed material characterizations confirm that the as‐prepared catalysts possess a well‐defined fibrous structure with hierarchical pores, large specific surface area, and uniformly distributed Fe 2 O 3 /FeN x active sites. Further, it exhibits excellent ORR performance with high onset potential, half‐wave potential, and current density in both alkaline and acidic media. And these electrocatalysts show excellent long‐term performance and tolerance to methanol, exceeding the properties of commercial platinum catalysts. Additionally, the Fe 2 O 3 /FeN x @CNF electrocatalyst prepared in this study exhibits high discharge voltage, excellent power density, and cycling durability in Zn–air batteries. Notably, the detailed analyses demonstrate the co‐existence of Fe 2 O 3 nanoparticles and FeN x active sites boost the ORR catalytic activity of the hybrid catalyst. These new findings, particularly the enhancement of intrinsic activity of FeN x sites brought about by Fe 2 O 3 nanoparticles, provide insights into the rational design of hybrid single‐atom ORR electrocatalysts.