Freestanding 1D Hierarchical Porous Fe‐N‐Doped Carbon Nanofibers as Efficient Oxygen Reduction Catalysts for Zn–Air Batteries

Abstract

High‐performance nonprecious metal‐doped 1D carbon catalysts for oxygen reduction reactions (ORR) are viable candidates in lieu of platinum‐based catalysts. Hierarchical porous Fe‐N‐doped carbon nanofibers (Fe‐NHCFs) are fabricated via carbonization of MOF nanofibers with a specific surface area of 294 m2 g−1 and inherent hierarchical porosity. Benefiting from the Fe‐N doping‐induced active sites, unique hierarchical porosity, and 1D honeycomb conductive networks to facilitate electron transfer, the freestanding Fe‐NHCFs confer a current density (5.2 mA cm−2) at 0.70 V (vs reversible hydrogen electrode), comparable with the commercial 20 wt% Pt/C (5 mA cm−2) in alkaline medium. Especially, the parallel characteristics with Pt/C is acquired in an assembled Zn–air battery, which deliver a discharge current density of 90 mA cm−2 and an output peak power density of 61 mW cm−2. This simple synthesis strategy would leverage a new geometry for tailored utility of active sites for ORR in a 1D carbon framework.

Pearl Necklace Fibrous Carbon Sharing Fe–N/Fe–P Dual Active Sites as Efficient Oxygen Reduction Catalyst in Broad Media and for Liquid/Solid‐State Rechargeable Zn–Air Battery

“…As shown in Figure , pearl necklace fiber (Zn/Fe ZIF–polyacrylonitrile [PAN]) was first fabricated via coelectrospinning, followed by carbonization–phosphidation to give rise to Fe–P/NHCF. Zn/Fe ZIF nanocrystals showed dodecahedral shape with the size of around 200 nm (Figure a) . Due to the precise optimization of ZIF/PAN ratio, solution viscosity, and electrospinning conditions, ZIF nanocrystals were uniformly distributed in the fibrous strings, portraying the necklace structure (Figure b and Figure S1e, Supporting Information) .…”

“…In contrast, NCF was obtained following the same procedure except for the absence of ZIF. For synthesizing Fe–P/NHCF or N/PHCF, 1.0 g of sodium hypophosphite monohydrate was put at the upstream site while 100 mg of Fe–NHCF or NHCF at the downstream in the tubular furnace, which were heated at 300 °C for 2 h under flowing argon …”

Recent Advances on Electrospun Nanomaterials for Zinc–Air Batteries

“…[ 90 ] The metal‐organic framework (MOF) materials can be used as another ideal precursors to prepare the air catalysts with abundant M–N–C active sites. [ 91–97 ] For example, the ZIF‐67 derived Co/N–C particles on the PAN‐based carbon nanofibers (C‐PAN@ZIF‐67) with gems‐on‐string structure and more Co–N–C active sites exposure, which exhibit a long‐term stability of 965 h ( j = 10 mA cm −2 , 10 min per cycle) (Figure 8d). [ 98 ] Similarly, bimetallic Zn/Co–ZIF was used to synthesize the CNF@Zn/CoNC.…”

Development and Applications of MOFs Derivative One-Dimensional Nanofibers via Electrospinning: A Mini-Review

“…The Co/CoO X -N-C exhibited excellent discharge specific capacity (610 mAh g −1 ) and discharge voltage, which are comparable to 20 wt % Pt/C and RuO 2 . Moreover, Wu et al have reported that hierarchical porous Fe-N-doped carbon nanofibers (Fe-NHCFs) can be fabricated via carbonization of MOF nanofibers [98]. Fe-N doping induces a large number of active sites to enhance the electrocatalytic activity of materials.…”