Boosting the ORR performance of Fe-N/C catalyst via increasing the density and modifying the electronic structure of Fe-NX active sites

Due to the existence of highly active Fe-NX coordination moieties, iron-nitrogen/carbon (Fe-N/C) materials have been considered as potential electrocatalysts toward oxygen reduction reaction (ORR). Increasing the density of Fe-NX sites is supposed to be a useful strategy to enhance the ORR performance of Fe-N/C catalysts. Herein, we report a stepwise synthesis strategy to construct Fe-N/C catalyst possessing a high ratio of mesopores and a high concentration of accessible Fe-NX active sites. Integrated with the properties of composition and morphology, the synthesized catalyst, Fe-N/C‑meso-evap, achieves remarkable ORR activity with a half potential of 0.835 V and a kinetic current density of 31.02 mA cm−2 at 0.8 V in 0.1 M HClO4. This work provides new insight for designing single-atom catalysts towards ORR.