FeCl3-graphite Intercalation Compounds Research Articles

Methanol electrooxidation at NiCl2–FeCl3–graphite intercalation compound affected by ozone treatment

A graphite intercalation compound (GIC) incorporating nickel(II) and iron(III) chlorides (NiCl2–FeCl3–GIC) has been prepared, and the effect of ozone treatment on its catalytic activity towards methanol electrooxidation has been examined. The NiCl2–FeCl3–GIC was synthesized by a molten salt method, combining purified flaky graphite with the anhydrous metal chlorides. The obtained product was then modified with gaseous ozone. The crystalline structures and morphologies of the investigated compounds have been characterized by XRD and SEM/TEM techniques, respectively, and the results of these analyses have shown that ozone treatment of NiCl2–FeCl3–GIC contributes to changes in its structure and morphology. The process of methanol oxidation at both original and ozone-modified NiCl2–FeCl3–GIC electrodes has been examined in an alkaline electrolyte by means of cyclic voltammetry and a potentiostatic method. Electrochemical results have revealed that NiCl2–FeCl3–GIC exhibits activity towards the process of methanol electrooxidation. Furthermore, it has been proved that the electroactivity and durability of NiCl2–FeCl3–GIC are significantly increased following its ozone modification.

Improving the cycle stability of FeCl3-graphite intercalation compounds by polar Fe2O3 trapping in lithium-ion batteries

FeCl3-intercalated graphite intercalation compounds (GICs) with high reversible capacity and high volumetric energy density are attractive anode material alternatives of commercial graphite. However, the rapid capacity decay, which was induced by chloride dissolution and shuttling issues, hindered their practical application. To address this problem, here, we introduce flake-like Fe2O3 species with inherently polar surface on the edge of FeCl3-intercalated GICs through microwave-assisted transformation of a fraction of FeCl3 component. Theoretical simulations and physical/electrochemical studies demonstrate that the introduced Fe2O3 component can afford sufficient polar active sites for chemically bonding the soluble FeCl3 and LiCl species based on the polar—polar interaction mechanism, further inhibiting the outward diffusion of the chlorides and immobilizing them within the GIC material. In a lithium ion cell, the FeCl3-intercalated GIC with a suitable Fe2O3 content shows remarkably improved cycling stability with a high reversible capacity of 1,041 mAh·g−1 at a current density of 200 mA·g−1. Capacity retention of 91% is achieved at a high current density of 1,000 mA·g−1 over 300 cycles. This work opens up the new prospect for immobilizing chlorides by introducing inorganic species in GIC for long-cycle electrochemical batteries.

Defect-free exfoliation of graphene at ultra-high temperature

We report the effect of treatment at high temperature (2000°C) on the exfoliation of a graphene that had been prepared by amine-treatment of an FeCl3-graphite intercalation compound and by preheat-treatment at low temperature (900°C). A well expanded morphology was produced by the exfoliation, and the expansion did not lead to significant defects in the graphene sp2 sheet after heating at 2000°C. The exfoliated graphene also exhibited an enhanced capacitance. It should be noted that this heat-treatment method at ultra-high temperature provides a physical procedure for defect-free graphene exfoliation following the electrochemical performance.

Electrochemical properties of a thermally expanded magnetic graphene composite with a conductive polymer.

A magnetic graphene composite derived from stage-1 FeCl3-graphite intercalation compounds was thermally treated for up to 75 min at 400 °C or for 2 min at high temperatures up to 900 °C. These heat-treatments of the magnetic graphene composite gave rise to the cubical expansion of graphene with the enlargement of inter-graphene distances. The specific capacitance of the magnetic graphene composite increased upon heating and reached 42 F g(-1) at a scan rate of 5 mV s(-1) in 1.0 M NaCl, after being treated for 2 min at 900 °C. This value corresponds to 840% increase in the capacitance activity superior to that (5 F g(-1)) of the pristine magnetic graphene composite before heat-treatment. This capacitance enhancement can play a significant role in the increase of the surface area that reached 17.2 m(2) g(-1) during the non-defective inter-graphene exfoliation. Moreover, the magnetic graphene composite heated at 900 °C was hybridized with polyaniline by in situ polymerization of aniline to reach a specific capacitance of 253 F g(-1) at 5 mV s(-1). The current procedure of heat-treatment and hybridization with a conductive polymer can be an effective method for attaining a well-expanded magnetic graphene composite possessing an enhanced electrochemical activity with a relatively high energy density (141 W h kg(-1) in 1.0 M NaCl) and an excellent stability (99% after 9000 cycles of 20 A g(-1)).

Electrical conductivity and air stability of FeCl3, CuCl2, MoCl5, and SbCl5 graphite intercalation compounds prepared from flexible graphite sheets

In this study, four graphite intercalation compounds (GICs) of metal chlorides, such as FeCl3, CuCl2, MoCl5, and SbCl5, were synthesized from two graphite sheets, and their electrical conductivity and air stability were accurately measured under standardized experimental conditions. After the exposure of these GICs to air, changes in their electrical conductivities and structures were recorded as a function of time. Three decomposition modes were observed. CuCl2-GICs did not decompose, and MoCl5-GICs prepared from a graphite sheet manufactured from a polyimide film (PGS) were also highly stable in air; on the other hand, immediate, extensive degradation was observed for FeCl3-GICs, while the SbCl5-GICs transformed to higher-stage (diluted) compounds. Thus, the air stability of these GICs varied with the metal chloride and host graphite used; however, their electrical conductivities prior to decomposition varied only with respect to the host graphite. Among the highly air stable, conductive compounds prepared herein, the MoCl5-GICs prepared from PGS demonstrate the highest potential for practical applications. This study reveals that highly conductive, air stable metal chlorides GICs can be synthesized.

Nondestructive Production of Magnetic Graphene Towards Energy Applications

Graphene can be prepared from a graphite intercalation compound (GIC)1 with acceptor-type intercalator, FeCl3.2 When the FeCl3–GIC is treated with primary amines at 90 °C for 6 h, the GIC expands to a few layers.3 The expansion is further facilitated, as the alkyl chain of primary amines becomes longer, while tertiary amines cannot penetrate inside the GIC because of their structural steric hindrance. The primary amine adsorbed in the GIC is oriented to form a bilayer by an indirect reactions among FeCl3–graphene–amine, and this process plays an important role in the expansion of the GIC, in contrast to the reaction of primary amines with donor-type GICs.4 Then the expanded-GIC is sonicated to exfoliate the graphene sheets. The obtained material exhibited a superparamagnetic property due to the remaining iron compounds. This approach using FeCl3–GIC and primary amine is preferable for the mass production of graphene because of the mild reaction conditions and the short treatment time for exfoliation from the chemically stable FeCl3–GIC. Moreover, the magnetization of graphene nano-composites could be useful for magnetic-recovery processes, electromagnetic heating, and the other electrochemical applications

Interaction of FeCl3-intercalated graphite with intercalants of different strengths

This paper examines reactions of stage I and II FeCl3-graphite intercalation compounds (GICs) with intercalants of different strengths: nitric acid and tetrahydrofuran (THF). The reaction of GIC-FeCl3 with nitric acid, a strong intercalant, leads to HNO3 substitution for the FeCl3 in the interlayer spaces of the graphite and formation of a stage II GICs with HNO3. THF, a weak intercalant, does not form any compounds with a stage I or II GIC with FeCl3; instead, it diffuses to intercrystalline regions of the graphite host. Flash heating of the synthesized GICs in air leads to the formation of exfoliated graphite (EG) containing α-Fe2O3 particles, which has low bulk density, down to 6.5 g/L, and high ferric oxide content, up to 33 wt %. Reduction in flowing hydrogen at 600°C leads to the formation of EG with up to 23 wt % α-Fe particles supported on it and with a saturation magnetization of 50 emu/g.

Massive-exfoliation of magnetic graphene from acceptor-type GIC by long-chain alkyl amine

Graphene can be prepared from a graphite intercalation compound (GIC) with acceptor-type intercalator, FeCl3. When the FeCl3–GIC is treated with primary amines at 90 °C for 6 h, the GIC expands to a few layers. The expansion is further facilitated, as the alkyl chain of primary amines becomes longer, while tertiary amines cannot penetrate inside the GIC because of their structural steric hindrance. The primary amine adsorbed in the GIC is oriented to form a bilayer by an indirect reactions among FeCl3–graphene–amine, and this process plays an important role in the expansion of the GIC, in contrast to the reaction of primary amines with donor-type GICs. Then the expanded-GIC is sonicated to exfoliate the graphene sheets. The obtained material exhibited a superparamagnetic property due to the remaining iron compounds. This approach using FeCl3–GIC and primary amine is preferable for the mass production of graphene because of the mild reaction conditions and the short treatment time for exfoliation from the chemically stable FeCl3–GIC. Moreover, the magnetization of graphene nano-composites could be useful for magnetic-recovery processes, electromagnetic heating, and the other applications.

Characteristics and microstructure of graphite encapsulated iron nanoparticles

The graphite encapsulated α-Fe particles were prepared by reduction of stage-2 and stage-3 FeCl3 graphite intercalation compounds (GICs) with metallic potassium. X-ray diffraction analysis (XRD), energy dispersive X-ray spectroscopy (EDS) investigation and transmission electron microscopy (TEM) observation show that the reduction products of stage-2 FeCl3-GICs contains more abundant α-Fe nanoparticles than those of stage-3. High-resolution TEM (HRTEM) observation reveals that the nanoparticle of α-Fe was polycrystals or twins, which was real or quasi two-dimension in shape, and whose space orientation was strictly controlled by the graphene. Based on the experiment results, a possible growth model of the graphite encapsulated α-Fe was proposed.

Synthesis and Characterization of Acceptor Type Graphite Bi-Intercalation Compounds

FeCl3-based graphite bi-intercalation compounds (GBCs) were prepared from stage 5 FeCl3-graphite intercalation compound and their formatiomechanism, stacking sequences, and lattice dynamics were studied. Bi-intercalated species were H2SO4, IBr, ICl, and SbCl5. From the stacking sequences determined by X-ray diffraction measurements, bi-intercalation processes were found to be affected by the electron affinity of bi-intercalated species. Lattice dynamics of the resultant GBCs was investigated by Raman spectroscopy. In the Raman spectra of GBCs with one bi-intercalated layer, two peaks assigned as Raman active E (2) i2g and E (2) b2g mode frequencies were obtained, and both frequencies were affected by the bi-intercalated species. Raman spectra of GBCs with two bi-intercalated species gave two E (2) b2g mode frequencies due to the double-intercalate coupling effect.

Distribution of intercalant in copper chloride and iron chloride graphite intercalation compounds

CuCl2 and FeCl3 graphite intercalation compounds were prepared by a gas phase reaction method using different carbon host materials. The effect of the microstructure of carbon host materials on the amount of intercalation and the distribution of intercalant was investigated using x-ray diffraction and electron microprobe analysis. For a fiber sample with a core region of onion skin structure in the cross section, a lower concentration of intercalant was measured in the core region. For fiber samples with an oriented-core transverse microtexture, different intercalant distributions along the long axis (oriented-core direction) and the short axis of the elliptical cross section were found.

Inelastic Nuclear Resonant Scattering of FeCl3-Graphite Intercalation Compounds

Anisotropic phonon modes of stage-1 FeCl3-graphite intercalation compounds were studied by inelastic nuclear resonant scattering. Partial phonon modes concerning Fe atoms were measured with incident x-rays either parallel or perpendicular to graphite layers. The observed spectra well show the character of the phonon density of state weighted by the projection of phonon polarization vector to the incident x-ray.

Pyrolysis of coal tar pitch mixed in the presence of a graphite intercalation compound: A kinetic study

A kinetic study has been carried out to determine the influence of the addition of first stage FeCl 3-graphite intercalation compound (GIC) to coal tar pitch (CTP) on the formation and the development of the mesophase. The mesophase formation was followed by the determination of the tetrahydrofuran insoluble fraction (THFI) of the solid residues, which were further characterized by polarized light microscopy. The presence of the Lewis acid (desorbed from the graphite layers) has a great influence during the mesophase spherule formation and development. The activation energy of the formation and the development of the mesophase (E a) is equal to 159 and 204 kJ/mol in the case of the CTP-GIC 8% mixture and the CTP respectively. This corresponds to a decrease of 22% of E a when the CTP is mixed with the GIC. The authors want to highlight the difficulties and mainly the limitations of the method used to calculate this activation energy by THFI measurements. However, we assume that the mesophase formation and growth rates are accelerated in the presence of compounds such as GIC for two reasons: the absence of QI particles on the surface of the mesophase spherules and the catalytic activity of the Lewis acid.

Electrochemical synthesis and characterization of ferric chloride-graphite intercalation compounds in aqueous solution

Electrochemical synthesis of FeCl3-graphite intercalation compounds (GICs) in aqueous solution was studied by chronoamperometric, chronopotentiometric and cyclic voltammetric methods. Using 6–10m FeCl3-aqueous solutions, FeCl3-GICs with stage 2–6 and/or mixed stage structures were synthesized by an anodic oxidation, evidenced by both X-ray diffraction patterns and Raman spectra. The chemical formula of the synthesized GICs is experimentally determined as C12nFeCl3 · mH2O, in which n denotes the stage number, and m varies from 1 to 3. A formation diagram for FeCl3-GICs is experimentally constructed in terms of electrolyte concentration and applied potential. Addition of hydrochloric acid into the FeCl3-aqueous solution extends the potential window for intercalation and promotes the oxidation. The GIC synthesized in pure aqueous solution is more stable in air than that synthesized in the solution with hydrochloric acid.

Magnetic ordering of graphite compound intercalated by FeCl 3

Magnetic ordering of a complex magnet, FeCl 3-graphite intercalation compound (GIC) is investigated by AC susceptibility χ ∗ and non-linear magnetic response M′ 3 ω . The characteristic behavior of χ ∗ and M′ 3 ω is similar to that of a spin glass in spite of the absence of intralayer frustration.

Thermodynamic properties of FeCl 3-graphite intercalation compounds by mass-spectrometric Knudsen effusion method

A mass spectrometric Knudsen effusion method has been used for the determination of thermodynamic properties of stage 1 FeCl3-graphite intercalation compound (GIC). Enthalpies of the transformation of stage 1 to stage 2 FeCl3-GIC by the vaporization of FeCl3 (g) and Fe2Cl6 (g), and enthalpy of the reduction of FeCl3 to FeCl2 in the stage 1 FeCl3-GIC have been determined to be 170.5±5.4, 188.2±5.4 and 144.5±4.9 kJ mol-1, respectively, from the equilibrium partial pressures over the GIC. Activities of FeCl3 and FeCl2 components in. the stage 1 FeCl3-GIC together with the activity coefficient of FeCl3 have been also evaluated. The activity coefficient of FeCl3 in the stage 1 FeCl3-GIC is found to be larger than that in the stage 2 FeCl3-GIC, indicating that the stage 1 FeCl3-GIC is thermodynamically less stable than the stage 2 FeCl3-GIC.

On the nature of the so-called iron-graphite

Searching for the chemical and catalytic properties of iron-graphite, we reduced stage-1 FeCl 3-graphite intercalation compounds (GIC) with K-naphthalenide/THF solutions, methyl-Li/THF solutions and hydrogen under various conditions. In addition, stage-1 K-GIC and K(THF) x -GIC were allowed to react with different iron compounds such as FeCl 3, Fe(acac) 3, Fe(AcO) 2 and Fe(CO) 2(NO) 2. The reduction of stage-1 FeCl 3-GIC by solutions resulted in graphite, three-dimensional iron platelets, iron oxides and residual FeCl 2-GIC encapsulated by carbon. In some cases, intercalation of the reducing agent was observed. The samples reduced at high temperatures with hydrogen consist of graphite and three-dimensional iron platelets on the surface of the graphite flakes with a small amount of residual FeCl 2-GIC. In contrast to the reduction of FeCl 3-GIC, the reaction of K-GIC and K(THF) x -GIC with iron compounds resulted in the formation of graphite, isotropic three-dimensional particles of metallic and oxidic iron supported on graphite, and residual K-GIC. No lamellar two-dimensional Fe-graphite structure was found in any of these samples.

X-ray diffraction and Raman scattering studies of FeCl3–SbCl5-graphite bi-intercalation compounds

X-ray diffraction (XRD) and Raman spectroscopy have been used for the study of the bi-intercalation of SbCl5 into a stage 5 FeCl3-graphite intercalation compound (GIC). The stage 5 FeCl3-GIC is prepared by an ordinary two-bulb method with the temperature of graphite at 788 K and that of FeCl3 at 573 K. The FeCl3-SbCl5-graphite bi-intercalation compound (GBC) with one SbCl5 layer is obtained when the temperature of the stage 5 FeCl3-GIC is held at 443 K and the temperature of SbCl5 at 373 K in the two-zone system. The stacking sequence of the GBC is found to be an admixture of G(FeCl3)GG(SbCl5)GGG(FeCl3)G and G(FeCl3)GGG(SbCl5)GG(FeCl3)G by XRD, where G, (FeCl3), and (SbCl5) are the graphite, FeCl3, and SbCl5 layers, respectively. The Raman spectrum of the GBC shows two peaks associated with the and modes at 1588 cm−1 and 1610 cm−1, respectively. For the temperatures of stage 5 FeCl3-GIC at 443 K and SbCl5 at 403 K in the two-zone system, the FeCl3-SbCl5-GBC with two SbCl5 layers is obtained. The stacking sequence of the GBC is determined to be an admixture of G(FeCl3)GG(SbCl5)GG(SbCl5)G(FeCl3)G and G(FeCl3)G(SbCl5)GG(SbCl5)GG(FeCl3)G In the Raman spectrum of this GBC, two peaks associated with the mode are observed at 1616 and 1624 cm−1.

96/05949 Effect of graphite or FeCl 3-graphite intercalation compounds on the mesophase development in coal tar pitch

96/05949 Effect of graphite or FeCl 3-graphite intercalation compounds on the mesophase development in coal tar pitch

96/05948 Effect of graphite of FeCl 3-graphite intercalation compounds on the mesophase development in coal tar pitch

96/05948 Effect of graphite of FeCl 3-graphite intercalation compounds on the mesophase development in coal tar pitch