Molecular scissor tailoring hierarchical architecture of ZIF-derived Fe/N/C catalysts for acidic oxygen reduction reaction

Abstract

Iron and nitrogen co-doped carbon (Fe/N/C) electrocatalysts have great potential to catalyze the kinetically slow oxygen reduction reaction (ORR). Unfortunately, the ORR performance of existing Fe/N/C catalysts is seriously hindered by the insufficient density and accessibility of the atomic Fe-Nx moieties. Herein, the carboxylate (OAc) molecular scissor is proposed to tailor Fe doped zeolitic-imidazolate-framework-8 (ZIF-8) at atomic scale and construct a multi-dimensional concave Fe@NC catalyst structure (Fe@MNC-OAc). This molecular scissoring strategy imparts Fe@MNC-OAc with dense accessible active sites, multidimensional mass transfer pathways, hierarchical porous structure, and entangled carbon nanotubes network. Therefore, the tailored Fe@MNC-OAc electrocatalyst exhibits excellent ORR activity in acidic media with a half-wave potential of 0.838 V, which is comparable to state-of-the-art non-precious metal catalysts. When assembled as cathode catalyst in a H2-O2 proton exchange membrane fuel cell, it delivers a peak power density of 903 mW cm−2. This work provides a new approach to tailoring the catalyst architecture and improving the accessibility of active sites.