Probing the activity of transition metal M and heteroatom N4 co-doped in vacancy fullerene (M-N4-C64, M = Fe, Co, and Ni) towards the oxygen reduction reaction by density functional theory.

Abstract

In this study, a novel type oxygen reduction reaction (ORR) electrocatalyst is explored using density functional theory (DFT); the catalyst consists of transition metal M and heteroatom N4 co-doped in vacancy fullerene (M–N4–C64, M = Fe, Co, and Ni). Mulliken charge analysis shows that the metal center is the reaction site of ORR. PDOS analysis indicates that in M–N4–C64, the interaction between Fe–N4–C64 and the adsorbate is the strongest, followed by Co–N4–C64 and Ni–N4–C64. This is consistent with the calculated adsorption energies. By analyzing and comparing the adsorption energies of ORR intermediates and activation energies and reaction energies of all elemental reactions in M–N4–C64 (M = Fe, Co, and Ni), two favorable ORR electrocatalysts, Fe–N4–C64 and Co–N4–C64, are selected. Both exhibited conduction through the more efficient 4e− reduction pathway. Moreover, PES diagrams indicate that the whole reaction energy variation in the favorable ORR pathways of Fe–N4–C64 and Co–N4–C64 is degressive, which is conducive to positive-going reactions. This study offers worthwhile information for the improvement of cathode materials for fuel cells.