The active center of N-G catalysts for ORR is confirmed to be related to the graphitic N, and the total N content in N-G catalysts is not the key factors to determine the ORR activity.

The improved ORR performance is attributed to the rich density of the Fe–Nx moieties derived from regulated coordination structures using dual-nitrogen-sources.

A C atom with a positive charge in the graphite N–C–P structure is the dominating ORR active site in N,P-HGFs.

No abstract