Atomically Dispersed Fe-N 3 C Sites Induce Asymmetric Electron Structures to Afford Superior Oxygen Reduction Activity.

Introducing heteroatoms into atomically dispersed Fe-N 4 sites with symmetric electron distribution can adjust the imperfect oxygenated adsorption-activation and promote oxygen reduction reaction (ORR) activity. However, the relevant design synthesis and deeply understanding the electrocatalytic mechanism of such an asymmetric structure by introducing Fe-C coordination remains challenging. Herein, the structural stability of Fe-N x C y (x = 0 ≈ 4, y = 4-x) is first theoretically predicted and indicates that the energy of Fe-N 4 in the two most stable structures is greater than that of Fe-N 3 C. Subsequently, Fe-N 4 and Fe-N 3 C configurations are controlled synthesized by adjusting pyrolytic temperature. The Fe-N 3 C-based electrocatalyst displays a boosted ORR activity with a half-wave potential of 0.91 V and superior long-term stability, outperforming Fe-N 4 , Pt/C, and state-of-the-art noble metal-free electrocatalysts. Density functional theory calculations unveil that Fe-N 3 C is much more favorable for electron delocalization than Fe-N 4 . Furthermore, the residual Zn atom derived from ZIF-8 would give its d-orbit electron to the Fe atom, so the synergy between Fe-N 3 C and Zn-N 4 makes an enhanced ORR activity.