Two-Dimensional Mesoporous Carbon Doped with Fe–N Active Sites for Efficient Oxygen Reduction

Iron–nitrogen (Fe–N) sites confined within carbon are highly active to catalyze the oxygen reduction reaction (ORR). The mesoporous structure of carbon facilitates the mass transport and availability to the Fe–N sites during the ORR; however, the construction of mesoporous carbon architecture with highly exposed and accessible Fe–N active sites remains challenging. Herein, 3D-to-2D transformation of zeolitic imidazolate framework-7 (ZIF-7) was successfully achieved via convenient impregnation in ammonium ferric citrate aqueous solution. After pyrolysis, isolated Fe–N sites are generated and confined within highly mesoporous carbon without using any additional modulator or template. The optimal Fe–N catalyst exhibits excellent performance toward ORR in alkaline medium, exceeding commercial 40% Pt/C catalyst in terms of activity, stability, and methanol resistance.