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Synthesized by dripping iron acetate into the N-doped carbon film enriched with pyridinic N and followed by annealing at 800 °C, Fe–N-doped amorphous carbon (dFe–N-C) with an Fe content of 0.2 at.% showed excellent electrocatalytic activity, stability and methanol tolerance via a four-electron pathway for oxygen reduction reaction (ORR), which outperformed commercial Pt/C catalyst. More importantly, by tuning the Fe content and annealing temperature, the trace Fe in dFe–N-C was supposed to form high active FeN4 sites with pyridinic N and played an important role in the excellent electrocatalytic performance for ORR.

Transition metal is usually required for obtaining N-doped carbon (dN-C) catalysts toward oxygen reduction reaction, leading to an intense debate on whether the active sites in dN-C correlate to transition metal. Here, we report that metal-free amorphous dN-C was synthesized using simple one-step magnetron sputtering at relatively low temperature. The chemical bonding states of N atoms, which play a key role in optimizing the electrocatalytic activity, can be tuned by adjusting deposition temperature. The metal-free dN-C with high pyridinic N content exhibits high electrocatalytic activity, and its stability and methanol tolerance are much better than commercial Pt/C catalyst.