Oxygen reduction reaction on neighboring Fe–N4 and quaternary-N sites of pyrolized Fe/N/C catalyst
We study the interaction between the TM–Nx and metal-free active sites of a pyrolized TM/N/C catalyst and its effect on their ORR activities. We particularly choose a Fe–N4–edge-graphene and a quaternary-N-doped zigzag edge as representatives of TM–Nx and the metal-free active sites, respectively. We find that the interaction of the Fe–N4 and quaternary-N-doped sites at the zigzag edge of graphene enhances the ORR free energy profile at the quaternary-N-doped site. However, the ORR free energy profile at the Fe–N4 site is not affected by this interaction.