Iron-nitrogen dual-doped three-dimensional mesoporous carbons for high-activity electrocatalytic oxygen reduction

To improve the efficiency of oxygen reduction reaction (ORR) on non-precious metal electrocatalyst, designing three-dimensional porous catalysts with abundant exposed active sites, accessible catalytic surface and excellent stability are of significant interest. Herein, we prepared Fe/N co-doped mesoporous carbons (FeNMCs) via a facile aggregation of renewable biomass flour, dicyanamide, colloidal silica and anhydrous ferric chloride, followed by carbonizing at 900 °C in N₂ atmosphere. The optimal catalyst (FeNMC-2) possesses interconnected uniform mesopores of ∼12.9 nm, large surface area of 769.5 m² g⁻¹, high nitrogen-doping level and atomically dispersed Fe-N_x active species. The developed porous texture is advantageous for not only promoting the formation of Fe-N coordinated functional species and the accessibility of catalytic sites, but also facilitating the transport of reactants and products during the ORR process. For the ORR, the optimized FeNMC-2 displays excellent electrocatalytic performance, which even outperforms commercial Pt/C. Furthermore, the control experiments verify that the high ORR activity should be ascribed to uniformly dispersed Fe-N_x sites within the framework of 3D porous carbons. The present strategy can be extended to design and prepare other metal, N-co-doped porous carbons with great potentials in energy conversion and storage.