Thermal Deintercalation Research Articles

Quasi-2D Bi0.775Ln0.225O1.5 (Ln = La, Pr, Nd, Sm, Eu): reversible iodine intercalation and their evaluation as the anode in the lithium-ion battery system.

Layered materials with a robust structure and reversible intercalation behavior are highly sought-after in applications involving energy conversion and storage systems, energy converting devices, supercapacitors, batteries, superconductors, photonic materials, and catalysis involving hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), solar cells and sensors. In the current study, quasi-2D rhombohedral Bi0.775Ln0.225O1.5 (Ln = La, Pr, Nd, Sm, and Eu) samples, synthesized by a solution combustion route, have been demonstrated to intercalate iodine reversibly. A solid-vapor reaction was employed to intercalate iodine at moderate temperatures, and deintercalation occurred on heating at higher temperatures. Expansion of the rhombohedral c-axis by ∼10 Å occurred, and the iodine between the interlayers existed as triiodide ions (I3-) in an unsymmetrical fashion. The amount of intercalated iodide has been determined from thermogravimetric analysis. Electron microscopic analysis confirmed these systems' intercalation and subsequent lattice expansion. In the diffuse reflectance spectra, charge transfer from the triiodide ions to the host oxide was noticed, and it caused the absorption edge to fall beyond the visible region for the intercalated samples. XPS analysis of iodine intercalated Bi0.775Pr0.225O1.5 has shown the mixed valence states for Pr and the existence of I3- along with some IO3- species. The quasi-2D structure was stable during the thermal deintercalation process. The evaluation of iodine intercalated Bi0.775Ln0.225O1.5 (Ln = La, Pr, Nd, Sm, and Eu) samples as anode material in the lithium-ion battery system has given quite promising results, exhibiting fast Li+-ion diffusion, low charge transfer resistance, good reversible capacity, capacity retention (after cycling back to 10 mA g-1), and structural stability (after long cycles).

Structural Model and De-Intercalation Kinetics of Kaolinite-Methanol-Sodium Stearate Intercalation Compound

Kaolinite-methanol-sodium stearate intercalation compound (Ka-MeOH-SS) was prepared by intercalation of kaolinite with dimethyl sulfoxide (DMSO) followed by displacing of DMSO with methanol and methanol by sodium stearate. The sample was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal analysis (thermogravimetry (TGA) and differential scanning calorimetry (DSC)) and transmission electron microscopy (TEM). The results show that the basal spacing of Ka-MeOH-SS was enlarged to 45.5-47.9 A and parts of its layers cocked and curled. Stearate ions were grafted on the methoxy groups and arrayed aslant in the interlayer space of kaolinite with an inclination angle of 47.45o to 52.17o. Sodium ions were adsorbed around the SiO4 tetrahedron and interlayer carboxylate anions, whereas some of them entered into the ditrigonal hole of tetrahedral sheets. The thermal de-intercalation of Ka-MeOH-SS includes three steps and the activation energy E is 98.3 kJ mol−1, logarithm of pre-exponential factor lg(A / s-1 is 9.71 and the mechanism function is f(α) = −ln (1 − α) and G(α) = 1 − α.

Effect of Intercalated Agents on Thermal Deintercalation of Kaolinite

A series of intercalated kaolinite with formamide, potassium acetate and acrylamide were prepared. The thermal deintercalation processes of these composites were studied using a combination of X-ray diffraction and thermal analysis technique. X-ray diffraction spectra showed acrylamide could be indirectly intercalated into kaolinite layers. The activatory energy of thermal deintercalation of acrylamide from kaolinite-potassium acetate composites was 15.60 kJ/mol, higher than that from kaolinite-formamide composites, 9.51 kJ/mol. The reason was that strong hydrogen bondings between acrylamide and potassium acetate were formed in kaolinite layers.

Study of urea intercalation into halloysite by thermoanalytical and spectroscopic techniques

Intercalation of a kaolinite-containing halloysite from Biela Hora (Slovakia) with urea was investigated by simultaneous TG–DTA, XRD, FTIR (DRIFT), and Raman spectroscopy. The process of intercalation and thermal deintercalation was followed for the as-prepared and the washed (with isopropanol) samples. The proposed structural model was supported by molecular mechanical calculations. Incorporation of the intercalate (in 5 wt%) in molten polypropylene at 200 °C resulted in the complete delamination of the mineral. It is supposed that gas formation as a result of urea decomposition between the layers prevents reorientation and restructuring of the layers.

Investigation of mechanochemically modified kaolinite surfaces by thermoanalytical and spectroscopic methods

The effect of mechanochemical activation (dry grinding), formamide intercalation, and thermal deintercalation on high- and low-defect kaolinite surfaces was studied by thermogravimetry and diffuse reflectance Fourier transform infrared spectroscopy. These investigations were completed with specific surface area and pore size distribution measurements. The surface acidity of the ground and the ground-and-intercalated kaolinites was probed with ammonia adsorption. The surface area and the pore volume as well as the amount of adsorbed ammonia increased with the rate of mechanochemical activation. At the same time the thermally deintercalated minerals showed increased surface area but decreased pore volume with the time of grinding. Adsorbed ammonia was detected as ammonium ion in the 1400–1500 cm −1 spectral range.

The combined effect of intercalated oxidant and thermal annealing on surface morphology and photo-physical properties of poly(3-octylthiophene) films

As intercalated oxidant (guest) is chemically de-intercalated stepwise from poly(3-octylthiophene) (P3OT) (host), a gradual evolution of a mat-type crystalline structure is observed. Moreover, the intercalated oxidant has marked effect on the arrangement of polymeric chains. Complete thermal de-intercalation of oxidant leads to interwoven cylindrical bundles of polymeric chains similar to corrugated-rod-type (CRT) morphology seen for thermally annealed pristine P3OT. The red shift along with increase in intensity and sharpness in UV–vis spectra and photoluminescence quenching indicate that the ripening of the self-assembling nature of pristine P3OT polymer leads to the formation of polymeric quasi-crystals when it is freed from oxidant impurity chemically or by prolonged soft-thermal annealing of oxidant intercalated polymer matrix. The present results enable the analysis of the effects of geometrical parameters characterizing the mutual host–guest complementarity as well as host–guest and guest–guest interactions on the crystal packing of intercalate.

Identification of superactive centers in thermally treated formamide-intercalated kaolinite

The thermal behavior of a formamide-intercalated mechanochemically activated (dry-ground) kaolinite was investigated by thermogravimetry–mass spectrometry (TG-MS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). After the removal of adsorbed and intercalated formamide, a third type of bonded reagent was identified in the temperature range 230–350 °C decomposing in situ to CO and NH 3. The presence of formamide decomposition products, as well as CO 2 and various carbonates identified by DRIFT spectroscopy, indicates the formation of superactive centers as a result of mechanochemical activation and heat treatment (thermal deintercalation). The structural variance of surface species decreases with the increase of grinding time. The unground mineral contains a small amount of weakly acidic and basic centers. After 3 h of grinding, the number of acidic centers increases significantly, while on further grinding the superactive centers show increased basicity. With the increase of grinding time and treatment temperature the number of bicarbonate- and bidentate-type structures decreases in favor of the carboxylate- and monodentate-type ones.

Synthesis and Characterization of Diamine Intercalation Compounds of SnS2 Single Crystals

Single crystals of SnS2 were intercalated with ethylenediamine (en) and propylenediamine (pn) by direct reaction. The resulting novel compounds were examined by different techniques including XRD, XPS, a.c. impedance, TG, and TPD measurements. The observed lattice expansion for both compounds, ca. 3.9 Å, is consistent with the location of the amine molecules at van der Waals gaps, with monolayers in the alkyl chain parallel to the sulfur layers. XPS data reveal that these complexes easily absorb moisture that binds strongly to sulfur to give hydrogen sulfide traces that were detected upon thermal deintercalation above 473 K. However, the charge transferred from the guest to the host is too small to be detected by this photoelectron technique. The en intercalate preserves the semiconductor behavior of the pristine compound, SnS2, but with two significant differences, viz. lower conductivity at low temperatures and an increased activation energy. These differences are ascribed to increased incoherent scattering of electrons resulting from the guest atoms acting as impurities and also to the lattice defects formed upon intercalation.

Synthesis and Characterization of Poly(ethylene Oxide) Nanocomposites of Misfit Layer Chalcogenides

Nanocomposites of poly(ethylene oxide) (PEO) and (PbS)1.18(TiS2)2, a composite misfit layer sulfide were prepared by treating a lithium derivative in aqueous solutions of PEO. Under these conditions, the alkali metal intercalate readily exfoliates and rapidly reflocculates, thus trapping polymer molecules between sulfide layers. In this exfoliation and restacking process, Li+ions are partially removed. Powder X-ray, electron diffraction, and IR results are consistent with one layer of helical PEO located at all TiS2-TiS2interfaces and with empty PbS-TiS2interfaces. Thermal deintercalation of the new phase is a complex process that occurs at an unusually high temperature; this sugggests strong interactions between the polymer and the host, probably involving the alkali ions and PEO chains. Hydrogen sulfide traces were also detected. Although the XRD pattern for the decomposition product exhibits the main diffraction peaks for the host, the peaks are broad and asymmetric, which suggests that the lattice undergoes significant changes that partially collapse the structure in poorly crystalline phases.

γ-Zirconium Phosphate Rhodium Intercalation Compounds: Preparation, Chemical and Thermal Characterization

Rh 3+/H + ion exchange in γ-zirconium phosphate and in its intercalation compounds with organic diamine (2,2′-bipyridyl, 1,10-phenanthroline, and 2,9-dimethyl-1,10-phenanthroline) has been investigated. Fully exchanged rhodium-zirconium phosphate has the composition γ-Zr(PO 4)(H 0.86Rh 0.38PO 4)·2.3H 2O and an interlayer distance of 15.2 Å. The exchange of Rh 3+ in intercalation compounds leads to phases in which the molar ratio Rh 3+/diamine within the layers is about one. In some cases, a partial leaching of organic ligand during the Rh 3+/H + exchange has been observed. All the materials produced were characterized by their chemical compositions, X-ray powder diffraction patterns, and coupled TG/DTA analysis. In the presence of Rh 3+ ions, the temperature of thermal deintercalation of diamine is lower than that observed in the pure intercalation compounds.

Intercalation of n-alkylamines into misfit layer sulfides

Novel intercalation complexes of (PbS)1.18( TiS2)2 and (PbS)1.14(TaS2)2 two representative compounds of misfit layer sulfides, have been prepared by direct reaction with n-alkylamines (CnH2n+ 1 NH2)(n= 1–9). From the observed amine stoichiometry and lattice expansions, the most likely configuration for the intercalated amine molecules is one in which the latter are located at the van der Waals gap between two adjacent TS2 slabs as a monolayer with the alkyl chain oriented parallel to the layers. Thermal deintercalation of the new phases occurred at temperatures below 250 °C and in the case of Ti intercalates, H2S was released simultaneously with the amine deintercalation process. The intercalation process was confirmed to be reversible. Thus, the product obtained from the thermal treatment recovered the main features of the original host structure and, when mixed with the amine, yielded an intercalate of similar structural characteristics to those found using the original sulfide.

Novel Metastable Structures of WO3, MoO3 and W1‐xMoxO3 Obtained by the Deintercalation of Layered Amine Adducts

AbstractDeintercalation of amines from the layered amine adducts of WO3, MoO3 and W1‐xMoxO3 has been employed as a soft chemical route to produce unusual metastable structures of the oxides. After the adducts of WO3, MoO3 and W1–xMoxO3 (x = 0.25, 0.5, 0.75) with amines such as triethylamine (TEA), pyridine, n‐butylamine and n‐octylamine had been characterized, deintercalation was carried out thermally as well as by acid leaching. Thermal deintercalation yielded novel metastable structures of WO3 and MoO3 that were significantly different from the stable forms, which contain distorted metal‐oxygen octahedra. Thus, ReO3‐type cubic WO3 was obtained by the thermal deintercalation of WO3 · 0.5 TEA. Acid leaching of the amines gave metastable phases of WO3, MoO3 and W1‐xMoxO3, which were different from those obtained thermally. All the metastable phases transformed to the corresponding stable forms at higher temperatures.

Intercalation compounds of zirconium phosphates with substituted pyrazoles and imidazoles and their ac conductivity

Intercalation compounds of α-zirconium phosphate with methyl and ethyl derivatives of pyrazole and imidazole have been prepared and characterized by XRD, TG and impedance measurements. Composition data and interlayer distances ( 10.3⩽d( A ̊ )⩽11.6 ) suggest that the guests are accomodated in the interlayer region as a monolayer of molecules lying flat or slightly tilted with respect to the surface of the α-layer. The temperature of thermal de-intercalation is always much higher than the boiling point of the pure guest. The ac conductivity has been measured in a dry nitrogen atmosphere from 100°C up to a temperature within the phase stability range. The replacement of pyrazole and imidazole with the corresponding mono- or di-substituted derivatives decreases the conductivity by at least one order of magnitude and increases the activation energy; furthermore, the conductivity of the di-substituted imidazole intercalates is lower than that of the mono-substituted ones. Comparison of conductivity data and pKa values of the protonated guest shows that, the steric hindrance being the same, the conductivity increases with decreasing the basic strength of the guest. The conductivity of intercalates of γ-ZrP with imidazole and pyrazole has also been investigated.

Synthesis and study of europium-ammonia intercalation compounds of 1T-TaS 2

Ammonia and europium-ammonia intercalation compounds of 1T-TaS 2 containing ca. 0.1 Eu per mol Ta, were synthesized using the liquid ammonia technique, characterized using X-ray diffraction, magnetic susceptibility measurements, and electron paramagnetic resonance spectroscopy. These materials are found to be Eu 2+,3+ mixed-valence compounds. Thermal deintercalation of the ammonia results in an increased Eu 3+ fraction which is related to a simultaneously occuring structural transformation. The intercalation of ammonia alone occurs to a limited extent and without signification oxidation of the molecule.

Elemental distribution in CrO 3-graphite and CrO 3-Br 2-graphite

Electron probe micro analysis of the intercalation products of CrO 3 in natural graphite flakes shows that the CrO 3 species are only intercalated at the edges of the flakes. The same Cr concentration profile is observed in bromine graphite after the displacement of bromine by CrO 3. Thermal deintercalation—monitored by thermogravimetric as well as mass spectrometric measurements shows a sealing effect of the CrO 3 edge intercalation on the outgassing of bromine from the interior of the flakes.

On the intercalation and deintercalation mechanisms for ammoniated titanium disulfide

The redox mechanism associated with ammonia intercalation of TiS 2 has been clearly demonstrated, with essentially the only reaction products being (NH 4 +) y′ (NH 3) y″ TiS 2 y′ - and N 2, (NH 4 +) y′ (NH 3) y ′(NiS 2 y′ - undergoes thermal deintercalation by the sequential removal of NH 3 and “NH 4 +” at progressively higher temperatures. Only small amounts of polysulfides and H 2S were observed during intercalation and deintercalation, respectively, indicating the near quantitative nature of the above mechanisms.

Spectroscopic and ESR studies of Cd 2P 2S 6 intercalated with pyridine complexes of ferric ion

Cd 2P 2S 6 crystallizes in a layered structure which is readily intercalated with a variety of Lewis bases. We have studied the intercalation reactions of this lattice with pyridine complexes of several transition metal ions and Ce 4+. In some instances (e.g. Mn 2+) the metal ion could be co-intercalated with pyridine with little or no effect on the distribution of reaction products formed within the van der Waals gap. However, certain transition metal ions had a dramatic effect on the product distribution obtained. Co-intercalation of Fe 3+, for example, results in the production of a highly colored polysulfide species within the van der Waals gap. The intercalated species were identified by mass spectroscopic analysis during thermal de-intercalation. The co-intercalated paramagnetic transition metal ions are useful as ESR spin-probes for the study of the structure and dynamics of the intercalate layer. Analysis of the ESR spectra indicate that co-intercalated Mn 2+ can enter Cd 2+ lattice vacancies at elevated temperatures.

Die thermische deintercalation von graphitintercalationsverbindungen der arsen- und antimonchloridfluoride

In the reaction of AsCl 2F 3 with graphite, intercalation compounds of stage n = 3 are produced with an identity period of I c = 1.49 nm. The stoichiometry of the compounds varies in consequence of the dissociation and dismutation reactions of AsCl 2F 3. The exfoliation of the crystals and the release of chlorine have been observed during heat treatment. The maximum thermal deintercalation is between 350 and 440°C. Only chlorine and arsenic trihalides, no pentahalides, have been detected by mass spectrometric analysis of the pyrolysis gases. Thermogravimetric investigations of SbCl mF 5-m graphite intercalation compounds as well as mass spectrometric analyses of the pyrolysis gases show that in the deintercalation of the original intercalated pentahalides, their thermal dissociation as well as dismutation by halogen exchange overlap in the course of thermal decomposition. The conversion of stage 1 SbCl 4F graphite to stage 2 and the formation of dilute stage 2 SbCl 5 graphite as well as SbCl 4F graphite take place at 80–110°C. A high concentration of the pentahalides SbCl 5 and SbCl 4F respectively and a low concentration of trihalides have been found by mass spectrometry in the gas phase at 80–110°C. This low-temperature deintercalation is assumed to be a complete or partial emptying of galleries without a structural modification of the graphite layers. The structural conversions of stages n > 2 into stages n + 1 at higher temperatures of about 200 and 300°C are explained by a Daumas-Hérold domain model. Powdered natural graphite and synthetic graphite exhibit a preferred deintercalation of halides at 80–110°C. This may be explained by a higher density of diffusion paths and a lower ratio of crystallite sizes to domain sizes with respect to graphite flakes. The thermal dissociation of the pentahalides beginning at 190–200°C overlaps with the conversion of stage 2 to stage 3. At the same time chlorine is explosively released, leading to the exfoliation of the graphite flakes. The conversions of higher stages open intercalate islands in the crystal bulk and, consequently, the concentrations of the pentahalides and their dissociation products in the gas phase increase. The conversion of stage 3 to stage 4 occurs in the temperature range of 300–350°C; stages n > 4 degrade between 400 and 430°C. SbCl 2F 3 graphite as well as AsCl 2F 3 graphite evolves only the dissociation and dismutation products of the pentahalides. With an increase of temperature, the relative concentrations of SbF 3 and AsF 3 increase with respect to those of the Cl-containing trihalides; this is a consequence of dismutation with halogen exchange. The formation of polymeric neutral or anionic Sb halide species with fluorine bridges is presumably the reason for the dismutation reactions.

Low-temperature synthesis and magnetic properties of the mixed-valence lanthanide intercalation compounds EuxTiS2 and YbxTiS2

The lanthanide (L) intercalation compounds EuxTiS2 (x=0.007,0.014, and 0.066) and YbxTiS2 (x=0.060) have been synthesized by thermal deintercalation of NH4+ and NH3 from the corresponding L-NH3 precursors at 270°C and characterized by thermogravimetric analysis, powder X-ray diffraction, and SQUID magnetometry. Both L2+ and L3+ are present in the van der Waals gap, and the deintercalation process is accompanied by the conversion of some of the L3+ to L2+. The resulting compounds contain comparable concentrations of L2+ and L3+. Magnetic exchange interactions are negligible due to the low concentrations of lanthanide cations.