Fe/Co Containing N‐Doped Hierarchical Porous Carbon Microcuboids and Microcylinders as Efficient Catalysts for Oxygen Reduction Reaction

Abstract

AbstractTransition metal‐nitrogen‐carbon (M−N−C) materials have received extensive attention as promising catalysts for oxygen reduction reaction (ORR). The surface morphology and the pore structure of the carbon supports have important effects on the ORR activity. Herein, metal‐organic complexes were prepared via a simple NaOH‐mediated method by the organometallic reaction of Fe3+/Co2+ ions and benzimidazole in the presence of polyvinylpyrrolidone. Metal‐organic complexes with either cuboid or cylindrical morphologies were obtained by modulating the initial ratio of Fe3+/Co2+. FeCo containing N‐doped carbon catalysts (FexCoy−N−C) decorated with FexCoy nanoparticles were then fabricated by a direct carbonization of the metal‐organic complexes. FexCoy−N−C catalysts have hierarchical micro‐/mesoporous structure and retain the morphologies of microcuboids and microcylinders of the metal‐organic complexes precursors. The Fe1Co7−N−C exhibits promising catalytic activity with an onset potential of 0.967 V, a half‐wave potential of 0.816 V, and a limiting current density of 4.86 mA cm−2 in 0.1 M KOH. The ORR catalytic activity should be attributed to the FeCo−Nx active sites and the encapsulated FeCo alloy nanoparticles activating the surrounding N‐doped carbon layers.