Mesoporous Hollow Nitrogen-Doped Carbon Nanospheres with Embedded MnFe₂O₄/Fe Hybrid Nanoparticles as Efficient Bifunctional Oxygen Electrocatalysts in Alkaline Media

Exploring sustainable and efficient electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is necessary for the development of fuel cells and metal–air batteries. Herein, we report a bimetal Fe/Mn–N–C material composed of spinel MnFe 2 O 4 /metallic Fe hybrid nanoparticles encapsulated in N-doped mesoporous hollow carbon nanospheres as an excellent bifunctional ORR/OER electrocatalyst in alkaline electrolyte. The Fe/Mn–N–C catalyst is synthesized via pyrolysis of bimetal ion-incorporated polydopamine nanospheres and shows impressive ORR electrocatalytic activity superior to Pt/C and good OER activity close to RuO 2 catalyst in alkaline environment. When tested in Zn–air battery, the Fe/Mn–N–C catalyst demonstrates excellent ultimate performance including power density, durability, and cycling. This work reports the bimetal Fe/Mn–N–C as a highly efficient bifunctional electrocatalyst and may afford useful insights into the design of sustainable transition-metal-based high-performance electrocatalysts.