Self-assembly Induced Metal Ionic-Polymer Derived Fe-Nx/C Nanowire as Oxygen Reduction Reaction Electrocatalyst

Abstract Metal/nitrogen co-doped carbon (M-Nx/C) materials have shown their good catalytic activity for electrochemical/chemical reactions in energy conversion devices and organics synthesis. However, the preparation of M-Nx/C materials usually involves a high-temperature pyrolysis step, it generates not only active M-Nx sites but also inactive metal-based aggregates that restrict their activity. How to prepare the M-Nx/C materials with high density of M-Nx sites and specific nanostructure remains a challenge. Herein, we report a general method of “self-assembly induced metal ionic polymer” for preparing M-Nx/C precursors, which can not only preferentially generate M-Nx sites by inhibiting metal aggregation during pyrolysis, but also produce advanced nanostructure for catalysis. Taking the preparation of Fe-Nx/C as an example, the self-assembled nanosheets of [Fe(CN)6]4-•{[C6H4-(NH3)2]2}4+ compounds are used as prefabricated materials, which effectively induce the formation of metal ionic-polymer nanowires and nanoparticles. They are applied to synthesize the Fe-Nx/C nanowires and nanoparticles with single metal atoms, respectively. The Fe-Nx/C nanowires exhibit the excellent oxygen reduction reaction activity with the half-wave potentials of 0.82 and 0.92 V under acidic and alkaline conditions, respectively. The proposed strategy can be a general method to prepare the M-Nx/C catalyst precursors with the special morphology and high thermal stability.