Porous‐Carbon‐Confined Formation of Monodisperse Iron Nanoparticle Yolks toward Versatile Nanoreactors for Metal Extraction

Abstract

All-in-one architectures in which uniform nanoscale zero-valent iron nanoparticles are wrapped in hollow porous carbon shells are highly desirable for environmental applications such as wastewater treatment and for use as catalysts, but their preparation remains a significant challenge. Herein, a spatially confined strategy for the in situ preparation of uniform Fe @mC (mC=micro/mesoporous carbon) yolk-shell nanospheres, in which the iron nanoparticles are encapsulated in thin, porous carbon shells, is reported. The elaborately designed Fe @mC yolk-shell nanospheres were obtained by utilizing silica- and phenolic-resin-coated magnetite nanoparticle core-shell structures as templates by means of selective etching and in situ thermal reduction. The highly dispersed iron nanoparticles with superior reduction capability can effectively remove metal pollutants (e.g., Au , Ag , and Cu ), the carbon shell acts as protective cover and prevents aggregation of iron nanoparticles, and the void space in the capsules serves as a reactor for reduction and catalytic reactions.

Tailoring the Assembly of Iron Nanoparticles in Carbon Microspheres toward High-Performance Electrocatalytic Denitrification

“…One promising approach to address the aforementioned drawbacks and improve the electrocatalytic performance is utilization of the nanostructured zerovalent iron because of the low price, excellent electron-donating capability, large specific area, and high reduction capacity. − Prior to modulating the electrocatalytic capability, a critical issue needs to be solved: how to avoid the aggregation of nanostructured iron as the natural magnetic property and high surface energy hinder the surface-active sites. For this purpose, several strategies have been explored to host nanostructured iron with conductive sites, such as graphene, hollow carbon nanoshell, and porous carbon matrix. − Zhang’s group anchored the iron nanoparticles in the mesoporous carbon framework by the nanocasting approach and demonstrated the electrocatalytic denitrification capability with a maximum removal capacity of 315 mg N/g Fe and decent nitrogen selectivity of 74% …”

Boron doping-induced interconnected assembly approach for mesoporous silicon oxycarbide architecture

“…Carbon nanospheres were obtained from carbonization of resorcinol/formaldehyde (RF) resin polymer spheres, which were synthesized according to a previous report [ 50 ]. The SiO 2 @carbon core-shell nanospheres were synthesized by a one-pot sol-gel approach [ 51 ]. Typically, 6.92 mL of tetraethyl orthosilicate (TEOS) were added in a solution containing 20 mL of deionized water, 140 mL of absolute ethanol and 6 mL of aqueous ammonia.…”

Iron Nanoparticles Confined in Periodic Mesoporous Organosilicon as Nanoreactors for Efficient Nitrate Reduction

“…The uniform Fe 3 O 4 nanoparticles were prepared based on the solvothermal synthesis strategy reported previously. 31 Typically, FeCl 3 •6H 2 O (3.25 g) and trisodium citrate (1.3 g) were dissolved in ethylene glycol (100 mL) with agitation and ultrasonication at room temperature to obtain a uniform and transparent yellow solution. Subsequently, sodium acetate (NaAc, 6.0 g) was added to the above solution.…”

“…25−27 The introduction of bridged organic groups can be considered in which some Si−O−Si bonds in mesoporous silica materials are replaced by Si−R−Si bonds (R is the bridged organic group). 31 Compared with traditional organic modification, organic groups are usually anchored on the mesoporous surface, which reduces the encapsulation and diffusion of guest molecules by steric hindrance. Organic functional groups can combine with more than two silicon atoms so that they exist not only as functional groups but also as crosslinking agents in the structure of rigid hybrid organic− inorganic frameworks.…”

“…Among wide ranges of iron matrix composite design concepts reported so far, coating or embedding structures prepared by the traditional technology suffers from the problem of slow electron transfer between the catalyst and the collector. Among various ordered mesoporous materials, periodic mesoporous organosilicon (PMO) has attracted extensive attention because of its unique organic–inorganic hybrid structure and uniform covalent binding of functional groups in the pore wall at the molecular level. − The introduction of bridged organic groups can be considered in which some Si–O–Si bonds in mesoporous silica materials are replaced by Si–R–Si bonds (R is the bridged organic group) . Compared with traditional organic modification, organic groups are usually anchored on the mesoporous surface, which reduces the encapsulation and diffusion of guest molecules by steric hindrance.…”