Preparation of Monodispersed Ferrous Nanoparticles Embedded Carbon Aerogels via in-situ Solid Phase Polymerization for Electrocatalytic Oxygen Reduction
The core-shell structured materials constructed by Fe/Fe3C cores and nitrogen doped carbon shells represent a type of promising non-precious oxygen reduction reaction (ORR) catalysts due to well-established active sites at the interface positions. However, the traditional liquid phase polymerization route for preparing such materials normally leads to a compact macropore-deficient structure with randomly dispersed metallic nanoparticles, being not good for mass transfer and formation of high-density dispersion of active sites. Herein, we report an “in-situ solid phase polymerization strategy” in which a frozen block containing uniformly dispersed oligomers is firstly achieved by combining a well-controlled hydrothermal reaction and a subsequent liquid nitrogen-facilitated fast solidification. During the following freeze-dry process, the oligomers in-situ polymerize into 3D highly cross-linked network in the confined space of ice block which not only effectively avoids the direct stack of polymerized intermediates, but also prevents the agglomeration of metallic nanoparticles. The finally obtained monodisperse Fe/Fe3C nanoparticles embedded nitrogen-doped carbon aerogel catalyst, in ORR, delivers an ultrahigh activity as the half-wave potential and the kinetic current density at 0.9 V reach 0.919 V and 7.83 mA cm-2 respectively in an alkaline solution. Using this route, a range of aerogel materials with improved performances for various applications may be explored.