Encapsulated Fe Nanoparticles Research Articles

An electron transfer tuning strategy for the efficient degradation of tetracycline hydrochloride by Fe-N co-doped carbon materials activated with peroxymonosulfate

In order to address the problems of metal leaching and low electron transfer efficiency, the iron (Fe) nitrogen (N) co-doped MOFs derived carbon catalysts presented a promising strategy to activate peroxymonosulfate (PMS) for water purification. In this work, using the MOF-5 as a template and iron phthalocyanine (FePc) and dicyandiamide (DCD) as a source, Fe, N co-doped carbons were prepared through milling and two-step pyrolysis. The catalytic performance and mechanism of the materials on tetracycline hydrochloride (TC) degradation in the PMS activation system (0.1Fe/N-CPMS) was systematically investigated. The results showed that the stable framework structure of MOFs-derived carbon conduced to encapsulate the Fe nanoparticles within the carbon skeleton, and then the xFe/N-C catalyst with hierarchical pore structure and good electrical conductivity was obtained, which significantly improved the TC catalytic performance. Notably, the 0.1Fe/N-C exhibited the greatest degradation performance achieving a degradation rate of 0.6315 min-1, which was approximately five times higher than that of N-C. Moreover, the degradation performance of the 0.1Fe/N-C kept the stability in various interference conditions, and still remained over 80% after three cycles test. Combine with the characterization and DFT calculation, the mechanism of the TC degradation in 0.1Fe/N-CPMS system was revealed by a non-radical process dominated by electron transfer, and the degradation efficiency was greatly improved by the synergistic effect of Fe/N on the as-prepared material. The received findings provide an electron transfer tuning strategy of Fe/N co-doped carbon nanomaterials synthesis for promoting the non-radical degradation pathways in the application of organic pollutants removal.

Magnetic carbon nanocomposites via the graphitization of glucose and their induction heating

Carbon nanocomposites containing iron-based nanoparticles are attractive materials for the catalyst supports used for magnetic (induction) heating catalysis. The metallic, soft-magnetic iron nanoparticles provide local heating of the support in an alternating magnetic field and ensure rapid magnetic separation of the nanocomposite particles from reaction suspensions. In this work, magnetic carbon nanocomposites were prepared by annealing the precursor particles consisting of iron-oxide nanoparticles dispersed in a carbohydrate matrix. The annealing was conducted at 600 °C and 750 °C in an Ar atmosphere. At both temperatures the carbothermal reduction of iron oxide to Fe/Fe3C was observed; however, at the lower temperature the rate of reduction and the growth of the nanoparticles were considerably slower. The Fe3C was formed in negligible amounts only after a prolonged period of annealing at 600 °C. A detailed structural analysis showed that the Fe/Fe3C nanoparticles catalyze the graphitization of the carbonaceous precursor material already at 600 °C, resulting in the formation of a graphitic shell that surrounds them. This shell is tight enough to prevent the areal oxidation of the encapsulated Fe nanoparticles; their magnetic properties remained unchanged even after 1 year of storage under ambient conditions. At the higher annealing temperature, the growth of the Fe/Fe3C nanoparticles caused bursting of the graphitic shell and thus partially exposed their surfaces to the atmosphere. All the nanocomposites exhibited ferromagnetic behavior in accordance with their compositions. The nanocomposite that was predominantly composed of a graphitic shell, encapsulated Fe nanoparticles and a negligible amount of Fe3C, showed the highest specific absorption rate (760 W/gFe at 274 kHz), even at a relatively low AC-field amplitude (88 mT).

The pseudo-capacitance of graphitic nanoribbons aerogel with encapsulated Fe nanoparticles

A graphitic nanoribbons (GNRs) encapsulated with Fe nanoparticles (NPs) hybrids derived from pyrrole and FeCl3 through polymerization, freeze drying and catalytic graphitization process showed excellent capacitive and cycle performance using as pseudo-capacitive material for supercapacitors (SC). The precursor of FeCl3 ingeniously served as oxidant for polymerization of pyrrole, catalyst for graphitization of polypyrrole and pseudo-capacitive material for SC successively. The obtained Fe@GNRs electrode exhibited a remarkable pseudocapacitance performance with a high specific capacitance of 526.7 F g−1 at a discharge current density of 1 A g−1. GNRs obtained by catalytic graphitization of polypyrrole under metallic Fe could effectively protect and stabilize the encapsulated Fe NPs showing ~100% capacitance retention rate after 10,000 cycles under 10 A g−1.

One-step synthesis of “nuclear-shell” structure iron-carbon nanocomposite as a persulfate activator for bisphenol A degradation

In this study, a “nuclear-shell” structure iron-carbon nanocomposite catalyst (Fe@CNs) was prepared by a one-step synthesis method using sodium alginate as a template to activate persulfate (PS) for bisphenol A (BPA) degradation. The TEM image of Fe@CNs showed that the Fe nanoparticles were encapsulated in the carbon matrix with doubly protected by both the “carbon shell” and adherent graphite structures (“carbon network”). According to the X-ray diffraction pattern and elemental composition analysis, the encapsulated Fe nanoparticles were designated as Fe3C. Catalytic results show that the Fe@CNs composite has good advanced oxidation catalytic performance and can remove 96% of BPA within 30 min. The effects of coexisting anions and water matrix on the removal of BPA and TOC were also investigated. Free radical quenching experiments confirmed that several free radicals (including OH, SO4−, O2− and 1O2) acted together to cause BPA decomposition. In addition, the catalytic activity of Fe@CNs used in the cycle experiments was mainly recovered after thermal regeneration. Based on the detected intermediates, we proposed a potential BPA degradation pathway and degradation mechanism in the Fe@CNs/PS reaction system. This is a new attempt to synthesize a “nuclear-shell” structure of Fe@CNs using sodium alginate hydrogel as a template in a facile one-step pyrolysis.

Radical assisted iron impregnation on preparing sewage sludge derived Fe/carbon as highly stable catalyst for heterogeneous Fenton reaction

Radical induced sewage sludge pretreatment has been developed to enhance sludge stabilization and dewaterability. Except for anaerobic digestion, the reutilization of the oxidized sludge residuals is still a challenging issue for wastewater treatment plant. In the view of favorable role in sludge disintegration, the pretreated sludge precursors, which was obtained by sequential radical oxidation and iron impregnation, was carbonized to prepare the carbon encapsulated Fe nanoparticles (Fe NPs), which could then behave as highly stable and active heterogeneous Fenton-like catalyst to degrade Black-T. By contrast, the carbonized products derived from direct iron impregnation were also prepared as a control method. The effect of H2O2/Fe2+ on zeta potential, particle size, morphology and texture structure of the pretreated sludge precursors and their corresponding influence on the carbonized materials were systematically evaluated. Results showed that radicals’ activation could facilitate the iron impregnation on sewage sludge by rupturing the microbial aggregate and making them more accessible to subsequent microbial fragments. Compared to direct iron impregnation, the carbonized products featured much higher iron insertion rate and the uniformly dispersed Fe NPs encapsulated into porous carbons, which in turn enables catalysts exhibiting more efficient catalytic activity in continuous heterogeneous Fenton-like degradation and resistance to metal leaching.

Nitrogen-doped carbon nanotubes with encapsulated Fe nanoparticles as efficient oxygen reduction catalyst for alkaline membrane direct ethanol fuel cells

Exploring low-cost and highly efficient non-precious metal electrocatalysts toward oxygen reduction reaction is crucial for the development of fuel cells. Herein, we report the synthesis of bamboo-like N-doped carbon nanotubes with encapsulated Fe-nanoparticles through high-temperature pyrolysis of multiple nitrogen complex consisting of benzoguanamine, cyanuric acid, and melamine. As-prepared catalyst exhibits high catalytic activity for oxygen reduction with onset potential of 1.10 V and half-wave potential of 0.93 V, as well as low H2O2 yield (<1%) in alkaline medium. The mass activity of the catalyst at 1.0 V (0.58 A g−1) can reach 43% of state-of-the-art commercial Pt/C. This catalyst also exhibits high durability and ethanol tolerance. When it was applied in alkaline membrane direct ethanol fuel cell, the peak power density could reach to 64 mW cm−2, indicating its attractive application prospect in fuel cells.

(Invited) High Performance Fe/N/C-Based ORR Electrocatalyst and Its Application in Alkaline Fuel Cell

Fe/N/C is a promising electrocatalyst for oxygen reduction reaction (ORR). This type catalyst can perform in both acidic and alkaline media. In acidic media, the active sites of Fe/N/C can be corroded; however, in alkaline media, Fe/N/C can exhibit high stability. Therefore, it is promising to explore the applications of Fe/N/C catalyst in alkaline fuel cell. Herein, we will talk about our recent advances in preparation of Fe/N/C catalysts and the application of them in alkaline fuel cells: (1) By using 2-aminothiazole, a molecule containing both N and S atoms, we prepared S co-doped Fe/N/C catalyst with graphene nanosheets. In alkaline solution, this catalyst exhibited high ORR activity with half-wave potential of 0.926 V and mass activity of 0.56 A g-1 @ 1.0 V. Furthermore, the catalyst displayed excellent durability, and only lost 9% of initial activity after 100 h of durability test at 0.80 V. In alkaline anion exchange membrane fuel cell (AEMFC) test, the peak power density could reach 164 mW cm−2. (2) We used the unzipped carbon nanotubes as carbon support and melamine as nitrogen source, and prepared a Fe/N/C catalyst with high ORR activity in alkaline media. The edge sites of unzipped carbon nanotubes play a key role for high catalyst activity. (3) we explored a series of nitrogen source including binary polymer of melamine-terethalaldehyde, ternary polymer of cynuric acid, 2, 4-diamino-6-phenyl-1, 3, 5-triazine, and melamine. N-doped carbon nanotubes with encapsulated Fe nanoparticles were prepared. The catalyst exhibited considerably high ORR activity in alkaline solution. We further tested its performance in alkaline membrane direct ethanol fuel cell, and the peak power density was about 64 mW cm-2. These results demonstrated that Fe/N/C is a promising candidate for ORR electrocatalyst in alkaline fuel cell.

Fabrication of carbon layer coated FE-nanoparticles using an electron beam irradiation

Abstract A novel synthesis of carbon encapsulated Fe nanoparticles was developed in this study. Fe chloride (III) and polyacrylonitrile (PAN) were used as precursors. The crosslinking of PAN molecules and the nucleation of Fe nanoparticles were controlled by the electron beam irradiation dose. Stabilization and carbonization processes were carried out using a vacuum furnace at 275 °C and 1000 °C, respectively. Micro structures were evaluated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fe nanoparticles were formed with diameters of 100 nm, and the Fe nanoparticles were encapsulated by carbon layers. As the electron beam irradiation dose increased, it was observed that the particle sizes decreased.

Surface modified Fe/silica floating magnetic materials for efficient oil removal

AbstractBACKGROUNDRemediation of oil spillage accidents requires efficient and low cost floating absorbents to remove small amounts of contaminant oil. In this work, a highly hydrophobic floating magnetic macroporous structure based on silica encapsulated Fe nanoparticles was prepared and used for oil absorption from water.RESULTSThe magnetic macroporous materials were prepared by silica encapsulation of iron oxide/hydroxide nanoparticles followed by a thermal treatment with H2. Mössbauer, XRD, SEM/TEM, CHN, IR, TG/DTA and contact angle analyses showed that the Fe oxides nanoparticles are reduced by H2 to form Feo cores protected by silica which sinters to form a macroporous network. The surface reaction with octadecyltrimethoxysilane (Si(CH3O)3C18H37) was used to produce highly hydrophobic materials.CONCLUSIONSThe materials obtained showed very high oil absorption capacities for different model contaminants, i.e. petroleum, soy bean oil, diesel, gasoline and xylene removal. The results are discussed in terms of a macroporous structure with strong capillarity combined with a very hydrophobic surface. © 2015 Society of Chemical Industry

Aerosol-Processed Thermosensitive Nanocomposites for Controlled Drug Release.

In this study, an ambient-spark-produced iron (Fe)-nanoparticle-laden nitrogen gas was mixed with an atomized solution of N-isopropylacrylamide (NIPAM)-polydimethylsiloxane (PDMS). The Fe nanoparticles reacted with NIPAM-PDMS in the atomized droplets to form encapsulated Fe nanoparticles, i.e., Fe@NIPAM-PDMS nanocomposites, whose size distribution was unimodal (showing only a NIPAM-PDMS-like distribution, with the Fe distribution eliminated). By varying processing temperatures, it was possible to obtain Fe@NIPAM-PDMS nanocomposites with different sizes and morphologies. This is further attributed to the quantitative incorporation of Fe nanoparticles into atomized NIPAM-PDMS-doxorubicin (DOX) droplets. The Fe@NIPAM-PDMS-DOX nanocomposites released different amounts of DOX under a magnetothermal effect, which produced different levels of cytotoxic effects on the targeted HeLa cells. The thermosensitivity makes these nanocomposites an ideal candidate for important applications such as controlled drug delivery.

Formation mechanism of carbon encapsulated Fe nanoparticles in the growth of single-/double-walled carbon nanotubes

The formation of carbon encapsulated Fe nanoparticles (Fe@C), in the process of growing single-/double- walled carbon nanotubes (S/DWCNTs) from methane was investigated by quantitatively analyzing the samples at different reaction time. We found that the ratio of Fe@C to the total Fe sustainably increased after the terminated growth of S/DWCNTs. We proposed that thin graphite layers produced in the middle stage of the reaction, as a mechanical barrier, covered the surface of MgO support and prevented Fe nanoparticles from contacting carbon source for the growth of S/DWCNTs via the root growth mode. These results suggested that the synthesis of desirable S/DWCNTs and undesirable Fe@C impurities was a consecutive process, not a paralleled one as proposed in many previous works. It provided useful information for the controlled synthesis of S/DWCNTs with high purity and high selectivity.

Fe nanoparticle-functionalized multi-walled carbon nanotubes: one-pot synthesis and their applications in magnetic removal of heavy metal ions

Magnetic-functionalized multi-walled carbon nanotubes (MWCNTs) with encapsulated Fe nanoparticles have been successfully fabricated via a one-step decomposition approach using ferrocene as a single precursor at a high temperature of 950 °C. The constituents, phase, and morphology have been characterized by X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Magnetic measurements reveal the ferromagnetic nature of the material with a magnetization saturation of 82.6 emu g−1 at room temperature. Full nitrogen sorption isotherms show that the magnetic-functionalized MWCNTs have a porous structure (2.0 nm, 6.42 nm and 11.4 nm) and large surface area (295.4 m2 g−1). Owing to their wonderful intrinsic properties, these magnetic-functionalized MWCNTs exhibit excellent ability to remove heavy metal ions from aqueous solutions. For example, the removal efficiency can be up to 97% at a Cu2+ concentration of 100 mg L−1 using these magnetic-functionalized MWCNTs as adsorbents. In addition, because the Fe nanoparticles were wrapped by MWCNTs, the material can be used in acidic solution and the removal efficiency of Cu2+ can reach 90% even in a strong acid solution (pH = 1).

Characterization of carbon encapsulated Fe-nanoparticles prepared by confined arc plasma

Carbon encapsulated Fe nanoparticles were successfully prepared via confined arc plasma method. The composition, morphology, microstructure, specific surface area and particle size of the product were characterized via X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectrometry and Brunauer-Emmett-Teller N 2 adsorption. The experiment results show that the carbon encapsulated Fe nanoparticles have clear core-shell structure. The core of the particles is body centered cubic Fe, and the shell is disorder carbons. The particles are in spherical or ellipsoidal shapes. The particle size of the nanocapsules ranges from 15 to 40 nm, with the average value of about 30 nm. The particle diameter of the core is 18 nm, the thickness of the shells is 6-8 nm, and the specific surface area is 24 m 2/g.

Preparation of Carbon-Encapsulated Fe Core-Shell Nanostructures by Confined Arc Plasma

Special carbon encapsulated Fe core-shell nanoparticles with a size range of 15–40 nm were successfully prepared via confined arc plasma method. The composition, morphology, microstructure, specific surface area, particle size of the product by this process were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray energy dispersive spectrometry (XEDS) and BET N2adsorption. The experiment results shown that the carbon encapsulated Fe nanoparticles with clear core-shell structure, the core of the particles is body centered cubic (BCC) structure Fe, and the shell of the particles is disorder carbons. The particle size of the nanocapsules ranges from 15 to 40nm，with an averaged value about 30nm, the particles diameter of the core is about 16nm and the thickness of the shells is about 6-8 nm, and the specific surface area is 24 m2/g.

Magnetic Properties and Dispersion Stability of Carbon Encapsulated Fe Nano Particles

Magnetic Properties and Dispersion Stability of Carbon Encapsulated Fe Nano Particles

Structure and magnetic properties of multi-walled carbon nanotubes modified with iron

Magnetic properties of multi-walled carbon nanotubes modified with iron (MWCNT+Fe) are studied in detail in the temperature range 4.2–300K. Carbon encapsulated Fe nanoparticles were produced by chemical vapor deposition. Low-temperature SQUID magnetization measurements are supplemented by structural studies employing thermogravimetric (TG) analysis, transmission electron microscopy (TEM), x-ray diffraction spectroscopy (XRD), and scanning electron microscopy (SEM). The magnetic susceptibility of MWCNT+Fe was also studied above room temperature to provide a complete picture of its magnetic phase transitions.

Two types of carbon nanocomposites: Graphite encapsulated iron nanoparticles and thin carbon nanotubes supported on thick carbon nanotubes, synthesized using PECVD

In this work, graphite encapsulated Fe nanoparticles and thin carbon nanotubes (CNTs) supported on the pristine CNTs, respectively, were synthesized using plasma enhanced chemical vapor deposition via efficiently controlling the flow rate of discharging CH 4 and H 2 gas. The properties of the obtained hybrid materials were characterized with superconducting quantum interference and field emission measurements. The results showed that the encapsulated Fe nanoparticles had diameters ranging from 1 to 30 nm, and this hybrid nanocomposite exhibited a ferromagnetic behavior at room temperature. Thin CNTs with an average diameter of 6 nm were attached to the surface of the prepared CNTs, which exhibited a lower turn-on field and higher emission current density than the pristine CNTs. The Fe nanoparticles either encapsulated with graphite or used as catalyst for thin CNTs growth were all originated from the pyrolysis of ferrocene.

Tuning the coercivity of Fe-filled carbon-nanotube arrays by changing the shape anisotropy of the encapsulated Fe nanoparticles

To tune the coercivity of Fe-filled carbon-nanotube (CNT) arrays, the shape anisotropy of encapsulated Fe nanoparticles (Fe-NPs) was investigated. Four Fe-filled CNT-array samples with different Fe-NP aspect ratios were prepared by catalytic pyrolysis of acetylene using ferrocene as catalyst. The coercivity of the Fe-filled CNT arrays increased from ∼300 to ∼800 Oe at room temperature when the mean aspect ratio of the encapsulated Fe-NPs changed from 1.6 to 6.0. This clear dependence of the coercivity of the Fe-filled CNT arrays on the aspect ratio of the Fe-NPs might be interpreted in terms of the Stoner–Wohlfarth model. This result indicates that changing the shape anisotropy of the encapsulated Fe-NPs is an effective method to tune the coercivity of the Fe-filled CNTs.

Structure and magnetic properties of carbon encapsulated Fe nanoparticles obtained by arc plasma and combustion synthesis

Carbon encapsulated Fe nanoparticles were obtained using two methods: arc plasma and combustion synthesis. These powders were characterized by the following methods: SQUID magnetization measurements, transmission electron microscopy (TEM) and Mössbauer spectroscopy. The last two methods showed that Fe nanoparticles, obtained by both techniques belong to metallic and/or carbide phases, and are partially encapsulated by graphitic carbon. The particles had 10–100 nm in diameter, and were covered by carbon 5–15 nm thick layers. The transmission Mössbauer spectra revealed two magnetic and two paramagnetic components. In the plasma samples the largest part of iron was contained in the carbide phase while in the combustion samples the bcc α-Fe encompassed most of iron. The combustion sample has much higher content of carbon, indicating that the Fe particles were not covered by graphite layer totally, and were dissolved in the etching process. The dominant portion of combustion samples was not vaporized, thus the iron phase solidified from the liquid. The plasma-arc samples were synthesized via dual mechanism: growth of nanocrystals from the vapor phase (carbide) and solidification of the liquid micro-droplets in the cold zone (α-Fe and γ-Fe).

Structural and chemical evolution of single-wall carbon nanotubes under atomic and molecular deuterium interaction

The interaction of atomic (D) and molecular (D 2) deuterium, as present in a (D + D 2) gas mixture, with single-wall carbon nanotubes (SWNTs) has been studied by means of a combination of scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The SWNT samples were exposed to the gas mixture, produced by thermal dissociation of D 2 on a hot W filament, its temperature, T W, being kept at 1020 and 1550 K for a deuterium pressure of 0.6 and 60 Pa, respectively. Prolonged interaction of the low-pressure (D + D 2) gas mixture produced at T W = 1020 K leads to a conglomeration of the SWNT bundles into larger diameter ropes of square and triangular cross-section, covered by nano-aggregates of graphite material. Both the coalescence of single SWNTs and a massive reconstruction of bundles of SWNTs into a “coral reef”-like structure were found to occur after prolonged exposure of SWNTs to the high-pressure (D + D 2) gas mixture produced at T W = 1550 K. This structure is formed by the encapsulated Fe nanoparticles and deuterocarbon-like species appearing as a result of the deuterium interaction with the SWNT bundles accompanied by partial erosion of the SWNT material. The XPS valence-band spectra disclose electronic features characteristic for a hydrogen-plasma modified multi-wall carbon nanotube (MWNT)-like structure as a result of an intensive (D + D 2) induced transformation of the SWNTs into the “coral reef”-like structure.