Well-Dispersed CoFe-Based Nanoparticles Embedded in N-Doped Mesoporous Carbon Spheres as an Efficient Electrocatalyst for Oxygen Reduction Reaction

High-loaded and well-dispersed bimetallic CoFe-based nanoparticles embedded in N-doped mesoporous carbon spheres (CoFe-NPs/NMCSs) are prepared via a self-assembly process using dopamine hydrochloride as N and C sources and polystyrene-b-poly(ethylene oxide) diblock copolymer as a soft-template. By simply modulating the amount of metal and the species added into the reaction system, NMCSs loaded with well-dispersed metal NPs composed of Co/CoFe alloy/CoN are successfully synthesized. Morphological and electrochemical analyses confirmed that the well-defined mesoporous structures of CoFe-NPs/NMCSs provide abundant exposed active sites and a fast electron transfer rate, enhancing the ORR performance. The optimized Co50Fe10-NPs/NMCSs catalyst exhibit a half-wave potential (E1/2) of 0.828 V vs RHE, comparable to commercial Pt/C (E1/2 = 0.833 V) in 0.1 M KOH. Additionally, Co50Fe10-NPs/NMCSs display superior cycling stability to Pt/C, with only an 27 mV reduction in half-wave potential compared to 38 mV for Pt/C after 5000 CV cycles.