A gas diffusion strategy to engineer hierarchically porous Fe–N–C electrocatalysts for high-performance cathodes of Zn–air batteries

Abstract

The currently leading oxygen reduction reaction (ORR) catalysts are non-precious metal electrocatalysts. However, porous structure engineering and accessibility of Fe–N–C sites still remain a huge challenge. Here, we developed hierarchically porous Fe–N–C catalysts for cathodes of Zn–air batteries using a gas diffusion strategy, which has dense active Fe–N_x moieties. The Fe-NCNF-120 catalyst provided high kinetic current density and mass activity towards the ORR, as well as a more positive initial potential and half-wave potential (E_onset = 1.00 V, E_1/2 = 0.90 V). According to experiments, the outstanding ORR activity can be attributed to the organized micro- and mesoporous structure, enhanced intrinsic activity of dense and accessible active sites Fe–N_x, and the facilitated mass and electron transport by 3D interconnected pores. As the cathode for Zn–air batteries, Fe-NCNF-120 demonstrated high power density, a high open-circuit voltage, and excellent stability. The combination of inherent activity with dense and accessible spots in this work opens up new possibilities for the design and synthesis of effective electrocatalysts for energy storage and conversion.