Structure-activity relationship in high-performance iron-based electrocatalysts for oxygen reduction reaction

•Trace N doped on carbon treated by HNO3 synergized with Fe for high performance.•Structure-activity relationship of Fe-based active sites was firstly revealed.•This Fe–Nx/C catalyst prepared by simple method shows high fuel cell performance.•It is the first time to find the GH-Diamond in these iron-based catalysts.

A sustainable Iron (Fe), Nitrogen (N) co-doped high performance Fe–Nx/C electrocatalyst for oxygen reduction reaction (ORR) is synthesized simply based on nitric acid oxidation of cheap carbon black. The obtained optimal nonprecious metal electrocatalyst shows high ORR performance in both alkaline and acidic conditions and possesses appreciable performance/price ratio due to its low cost. Furthermore, the structure-activity relationship of different active sites on Fe–Nx/C is revealed systematically: Fe–N4/2–C > Fe4–N–C > N–C >> Fe4–C ≥ C, from both experimental and theoretical points of view.