Hierarchically Meso-Macroporous N-Doped Carbon Embedded with CoFe-Based Composite for the Oxygen Reduction Reaction

Remarkable oxygen reduction reaction (ORR) electrocatalysts have been prepared by assembling bimetallic CoFe nanoparticles on hierarchically meso-macroporous N-doped carbon nanospheres. Metal–nitrogen–carbon catalysts are emerging as promising alternatives to Pt/C for ORR; however, their performance is limited by the low density and accessibility of active metal sites. The present hierarchically structured meso-macroporous N-doped carbon provides abundant exposed sites for active metal species. The bimetallic CoFe nanoparticles, in turn, significantly increase the total density of active catalytic sites for ORR. Consequently, the optimized CoFe nanoparticles embedded in meso-macroporous N-doped carbon (CoFe@MesoMacroNC) deliver superior ORR activities in both alkali and acidic media, achieving half-wave potentials of 0.943 V vs RHE and 0.811 V vs RHE, respectively. In addition, when CoFe@MesoMacroNC is used in a Zn–air battery, it shows a higher power density of 155 mW cm–2 as compared with that of commercial Pt/C (137 mW cm–2) as well as better stability.