Hierarchically Porous N-Doped Carbon Nanosheet Networks with Ultrafine Encapsulated Fe 3C and Fe-N x for Oxygen Reduction Reaction in Alkaline and Acidic Media

The electrocatalytic oxygen reduction reaction (ORR) plays an important role in renewable energy storage and conversion systems such as polymer electrolyte membrane fuel cells. However, design of high-performance cathode electrocatalysts is still required to speed up the sluggish kinetics of ORR. In this work, we develop a facile strategy to synthesize a hierarchically porous N-doped carbon nanosheet network with ultrafine encapsulated Fe3C and Fe-Nx for ORR by consideration of thermodynamic (intrinsic and support effect) and kinetic (diffusion effect) parameters. The as-designed catalyst exhibits excellent ORR catalytic performance in both acidic and basic media with much positive half-wave potential and good stability, which is comparable to commercial Pt/C. The excellent ORR performance may result from highly active Fe-Nx sites and ultrafine encapsulated Fe3C, and the hierarchically porous nanosheet structure capable of accelerating mass diffusion and increasing exposure of the active site. This work may open a way for the rational design of highly active non-precious metal electrocatalysts