Formation of a disordered layer lattice during the intercalation of water into anhydrous vanadyl phosphate

The course of intercalation of water into ₁-VOPO₄ has been studied by thermomechanical analysis and X-ray diffraction. Neither formation of vanadyl phosphate monohydrate nor staging were observed during the intercalation. The broadening and the shift of the positions of the lines in the diffractograms have been explained by the random stacking of intercalated and nonintercalated layers in the sample.     

Volumetric method for following the rate of intercalation of liquid molecular guests into layered hosts

A new experimental method is suggested for the kinetic measurements of intercalation reactions in systems formed by a polycrystalline layered host and a liquid molecular guest. The method is based on the fact that the molecular guest decreases its molar volume on entering the space between the host layers. Hence the volume of the system in which an intercalation process takes place is measurably decreased. The time course of the intercalation process can thus be monitored by measuring the volume change of the system. The method has been used to obtain kinetic data about heterogeneous intercalations of some liquid aliphatic compounds into layered structures of anhydrous vanadyl phosphate and sulfate.     

Optimal water concentration for aqueous Li+ intercalation in vanadyl phosphate

Development of high-performance aqueous batteries is an important goal for energy sustainability owing to their environmental benignity and low fabrication costs. Although a layered vanadyl phosphate is one of the most-studied host materials for intercalation electrodes with organic electrolytes, little attention has been paid to its use in aqueous Li⁺ systems because of its excessive dissolution in water. Herein, by controlling the water concentration, we demonstrate the stable operation of a layered vanadyl phosphate electrode in an aqueous Li⁺ electrolyte. The combination of experimental analyses and density functional theory calculations reveals that reversible (de)lithiation occurs between dehydrated phases, which can only exist in an optimal water concentration.

We demonstrate aqueous Li⁺ intercalation chemistry of vanadyl phosphate in the form of monohydrates, which are only stable in an optimal water-concentration environment.     

Intercalation chemistry of layered vanadyl phosphate: a review

The intercalation chemistry of layered α_I modification of vanadyl phosphate and vanadyl phosphate dihydrate is reviewed. The focus is on neutral molecular guests and on metal cations used as guest species. The basic condition for the ability of the neutral molecules to be intercalated into vanadyl phosphate is a presence of an electron donor atom in them. The most commonly used guest compounds are those containing oxygen, nitrogen or sulfur as electron donor atoms. Regarding the molecules containing oxygen, various compounds were used as molecular guests starting from water to alcohols, ethers, aldehydes, ketones, carboxylic acids, lactones, and esters. An arrangement of the guest molecules in the interlayer space is discussed in connection with the data obtained by powder X-ray diffraction, thermogravimetry, IR and Raman spectroscopies, and solid-state NMR. In some cases, the local structure was suggested on the basis of quantum chemical calculations. Besides of those O-donor guests, also N-donor guests such as amines, nitriles and nitrogenous heterocycles and S-donor guests such as tetrathiafulvalene were intercalated into VOPO₄. Also intercalates of complexes like ferrocene were prepared. Intercalation of cations is accompanied by a reduction of vanadium(V) to vanadium(IV). In this kind of intercalation reactions, an iodide of the intercalated cation is often used as it serves both as a mild reduction agent and as a source of the intercalated species. Intercalates of alkali metals, hydronium and ammonium were prepared and characterized. In the case of lithium and sodium intercalates, a staging phenomenon was observed. These redox intercalated vanadyl phosphates undergo ion exchange reactions which are discussed from the point of the nature of cations involved in the exchange. Vanadyl phosphates in which a part of vanadium atom is replaced by other metals are also briefly reviewed.     

Ultrafast Intercalation Enabled by Strong Solvent–Host Interactions: Understanding Solvent Effect at the Atomic Level

Solvents play an essential role in many areas of chemistry and is the cornerstone of understanding reactivity in solution‐phase reactions. Solvent effects have been widely observed in intercalation reactions; however, understanding of the influence of solvents on the thermodynamics and kinetics remains largely elusive in intercalation chemistry. Now, the solvent‐dependent kinetics of ferrocene intercalation into a layered vanadyl phosphate (VOPO₄?2 H₂O) host is presented, with a special focus on primary alcohols. From methanol to 1‐hexnaol, the intercalation rate peaks in 1‐propanol (80 times faster than the slowest case in methanol). Similar kinetics of exfoliation are also found in these solvents without ferrocene. The correlation between intercalation and exfoliation is understood at atomic level by DFT calculations, which reveal the role of pre‐intercalated solvent molecules play in intralayer interactions, interlayer expansion, and layer sliding.     

Intercalation of Dimethyl Carbonate, Diethyl Carbonate and Ethylene Carbonate into Vanadyl Phosphate

Intercalation compounds of vanadyl phosphate with dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylene carbonate (EC) were prepared from VOPO₄·2C₂H₅OH intercalate by a molecular exchange. The intercalates prepared were characterized using powder X-ray diffraction and thermogravimetric analysis. The EC intercalate is stable at ambient conditions, whereas the DMC and DEC intercalates transform to vanadyl phosphate dihydrate. Infrared spectra indicate that carbonyl oxygens of the guest molecules are coordinated to the vanadium atoms of the host layers. The arrangement of the guest molecules in the interlayer space was proposed.     

Tetra­aqua­cobalt(II) bis­[vanadyl(IV) phosphate], [Co(H2O)4][VO(PO4)]2

The structure of [Co(H₂O)₄][VO(PO₄)]₂ is composed of [VO(PO₄)] layers and interlayer tetrahydrated Co²⁺ ions. Alternating VO₅ square pyramids and PO₄ tetrahedra share O‐atom vertices, thus forming the vanadyl phosphate layers. Two vanadyl oxo groups from neighbouring layers are coordinated to each Co atom in a trans fashion, with Co—O distances of 2.157 (4) Å, thus generating a three‐dimensional framework structure.     

高氯酸根阴离子在HOPG中嵌入行为的EC-STM研究

运用电化学扫描隧道显微镜（EC-STM）和循环伏安（CV）技术对高氯酸根阴离子ClO₄^-在高序热解石墨（HOPG）中的电化学嵌入行为进行了研究. 通过观察嵌入前后石墨台阶处高度的变化,比较了不同高度的台阶对嵌入的影响,讨论了ClO₄^-离子嵌入石墨的可行性、可逆性和嵌入速率. 研究表明,3层以上的台阶位才有可能观察到由四阶和三阶嵌入引起的台阶高度变化,4 ~ 8个原子层高度的石墨台阶可以实现ClO₄^-在台阶处较为可逆的四阶嵌入,但1 ~ 2层台阶处无法观察到嵌入引起的台阶高度变化,嵌入反应通常会伴随台阶的剥离和脱落现象. 四阶的嵌入反应较三阶可逆,二阶和一阶时,嵌入所需反应电势较高,此时氧化反应较为剧烈,嵌入反应被掩盖,很难观察到台阶高度的变化,更多的形貌变化是台面和台阶处不可逆的损坏如剥落、断层、黑坑等.     

Different techniques for determining the coating weight of phosphate layers on galvanized steel by means of FT-IR-spectrometry

The determination of the weight per unit area (“coating weight”) of phosphate layers on galvanized steel by means of FT-IR-spectrometry has been performed by three different techniques: (i) principal component regression (PCR) of absorption data, (ii) utilizing the thickness dependent wavenumber shift of a band due to a special optical surface effect observed with parallel-polarized radiation and (iii) of an interference band observed with perpendicular-polarized radiation.     

Intercalates of Vanadyl Phosphate with Dinitriles

Intercalates of vanadyl phosphate with aliphatic dinitriles (malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile and suberonitrile) were prepared and characterized by X-ray powder diffraction, thermogravimetric analysis, IR and Raman spectroscopies. The basal spacings of all the intercalates prepared are practically identical. The dinitrile content in the intercalates decreases with increasing chain length. The dinitrile molecules are anchored to the host layers by an N–V donor–acceptor bond and their aliphatic chains are parallel to the host layers. The dinitrile intercalates are generally more stable in air (at relative humidity 40–50%) than nitrile intercalates and the guest molecules are slowly replaced by the water molecules.     

Intercalation of heterocyclic compounds in α-zirconium phosphate: Imidazole,benzimidazole, histamine and histidine

The intercalation of imidazole and some organic species containing the imidazole ring, between the layers of crystalline zirconium phosphate has been investigated. Fourteen new, well-ordered intercalation compounds are obtained with the batch procedure at r.t. and/or 60°C. A mechanism of formation of the various compounds is proposed on the basis of the interaction between the guest molecules (with their dimensions and geometries) and the free PO₃OH groups available between the layers of the host. The new phases have been characterized by TG and X-ray methods.     

Intercalation of cyclic ethers into vanadyl phosphate

Two cyclic ethers, tetrahydrofuran (THF) and tetrahydropyran (THP), were intercalated into vanadyl phosphate and characterized by X-ray powder diffraction, thermogravimetry, and IR and Raman spectroscopy. Both compounds contain one molecule of ether per formula unit of VOPO(4) and show high thermal stability in comparison with VOPO(4) intercalates with other organic guest molecules. Both ethers are anchored to the VOPO(4) host layers by their oxygen atoms, which are coordinated to the vanadium atoms of the host. The probable arrangement of the tetrahydropyran molecules in the host interlayer space is derived from molecular simulations by the Cerius(2) 4.5 program.     

Intercalates of Vanadyl Phosphate with Aliphatic Nitriles

Intercalates of vanadyl phosphate with aliphatic nitriles (acetonitrile, propionitrile, butyronitrile, valeronitrile and hexanenitrile) were prepared and characterized by X-ray powder diffraction, thermogravimetric analysis, IR and Raman spectroscopies. The basal spacings of all the intercalates prepared are practically identical. The nitrile intercalates (except acetonitrile) contain one nitrile molecule per formula unit. The nitrile molecules are anchored to the host layers by an N–V donor-acceptor bond and their aliphatic chains are parallel to the host layers. The acetonitrile intercalate contains two guest molecules per formula unit. Only half of them can be bonded to the vanadium atom, the second half is probably anchored by van der Waals interaction. The intercalates prepared are moisture-sensitive and the guest molecules are easily replaced by water molecules.     

超分子结构姜黄素插层镁铝水滑石的组装、结构及缓释性能

以镁铝水滑石为主体, 以中药提取物姜黄素为客体, 由共沉淀法、离子交换法和焙烧复原法三种不同方法组装得到超分子结构复合材料——姜黄素插层镁铝水滑石. 并用XRD, IR, HPLC等手段对该材料进行了表征. 结果表明, 共沉淀法和离子交换法成功组装得到两种不同结构的姜黄素插层产物, 使材料的层间距扩大为0.82～1.36 nm, 层间客体姜黄素阴离子是以平行或者单层垂直的定位方向排列于层间的. 考察了该材料在不同pH值的磷酸盐缓冲溶液中的缓释性能, 其缓释历程为客体阴离子与介质中 的离子交换过程. 该研究指出了阴离子层状材料——水滑石在中药释释剂领域的应用潜力.     

Mixed protonic-electronic conduction and dielectric response in layered vanadyl phosphate nanocomposites

The layered vanadyl phosphate, VOPO(4)2H(2)O, is employed to prepare nanosized conducting polypyrrole by redox intercalation method. Transport and dielectric properties of various compositions have been investigated by impedance technique over a temperature range of 300-120 K. Grain boundary conductivity is larger than the bulk conductivity. The conductivity reveals a discontinuity at about 212-235 K. The conductivity is predominantly ionic at high temperature and electronic at low temperature. The dielectric spectra reveal a peak in the frequency range up to 2 MHz for higher concentration of intercalated polypyrrole. The activation energy of conductivity relaxation is different from that of total conductivity derived from the impedance plot.     

Intercalation of cyclic ketones into vanadyl phosphate

Intercalation compounds of vanadyl phosphate with cyclic ketones (cyclopentanone, cyclohexanone, 4-methylcyclohexanone, and 1,4-cyclohexanedione) were prepared from corresponding propanol or ethanol intercalates by a molecular exchange. The intercalates prepared were characterized using powder X-ray diffraction and thermogravimetric analysis. The intercalates are stable in dry environment and decompose slowly in humid air. Infrared and Raman spectra indicate that carbonyl oxygens of the guest molecules are coordinated to the vanadium atoms of the host layers. The local structure and interactions in the cyclopentanone intercalate have been suggested on the basis of quantum chemical calculations.     

Synthesis and study of binuclear vanadyl complexes with acyldihydrazones of salicylaldehyde and dicarboxylic acids

The binuclear vanadyl(ii) complexes [(VO)₂·2Py·2EtOH]·mH₂O with acyldihydrazones of salicylaldehyde (H₄L) and dicarboxylic acids were synthesized and studied. In these complexes, two chelate vanadyl(ii) complexes with the tridentate bicyclic ligands are linked to each other by the polymethylene bridges —(CH₂) _n — of different lengths varying from one to four units. The ESR spectra of solutions of these complexes, unlike those of analogous copper(ii) complexes, have an isotropic signal with an eight-line hyperfine structure (g = 1.972, a _V = 93·10^–4 cm^–1) typical of monomeric vanadyl complexes, which indicates that no exchange interactions occur between the paramagnetic centers through the polymethylene chain.     

Structure analysis of intercalated layer silicates: combination of molecular simulations and experiment

Na(+)-montmorillonite type Wyoming, cloisite Na(+) from Southern Clay Products, Inc., was intercalated (i) with octadecylammonium cations and subsequently intercalated with octadecylamine molecules, (ii) with dodecylamine molecules, and (iii) with octylamine molecules to determine the applicability of these intercalates for nanocomposite materials on the base of polymer/clay. The structures were determined on the basis of a combination of results from X-ray diffraction and molecular simulations. The calculated values of basal spacings are in good agreement with experimental basal spacings when experimental samples were prepared. The interlayer space of intercalated montmorillonite shows a monolayer or bilayer arrangement of alkyl chains in dependence on the concentration of the intercalation solution. The values of the total sublimation energy, interaction energy, and exfoliation energy were calculated for all investigated samples. Low values of exfoliation energies lead to better exfoliation of intercalated silicate layers and this material appears suitable for use as a precursor for polymer/clay nanocomposites. The values of exfoliation energy for the investigated samples show that montmorillonite intercalated with dodecylamine or octadecylamine molecules is suitable for exfoliation of silicate layers.     

Surfactant-assisted intercalation of crystal violet in layered γ-zirconium phosphate. Dye uptake from aqueous solutions

Batch intercalation experiments have carried out using γ-zirconium phosphate (γ-ZrP) and one of its cationic surfactant forms (γ-ZrP/SUR⁺) for removing crystal violet from aqueous solutions. The intercalation reactions have conducted along two different intervals of time (24 and 48?h). The intercalation process has followed up by X-ray diffractometry (XRD), UV–Visible and FT-IR spectrophotometries. Regarding γ-ZrP, XRD patterns show that obtained phases are impure, even after 48?h of the reaction time at a maximum dye loading of 18%. On the other side, γ-ZrP/SUR⁺ gives an impure phase after 24?h while a pure one (2.47?nm) is obtained after 48?h at a maximum dye loading of 19%. In both cases, the observed dye loading values are approximately equal to the one calculated by molecular modeling (ca. 20%). The used analysis approaches prove that dye uptake capacity is a function of the reaction time and inclination angle of the dye molecules inside the solid matrices, where the highest dye uptakes are observed with γ-ZrP and γ-ZrP/SUR⁺ after 48?h of the reaction time. This time (48?h) is long enough for the dye molecules to be sufficiently accumulated inside the interlayer regions, in such situation dye molecules are forced to stand up perpendicular to the inorganic layers. With respect to intercalation properties, the difference between γ-ZrP and γ-ZrP/SUR⁺ could be referred to the difference between their gallery heights (1.22 and 3.00?nm, respectively). The pre-intercalation of γ-ZrP with the surfactant molecules assists the inclusion and intercalation of the huge dye molecules into the interlayer region.     

Novel vanadium phosphate phases as catalysts for selective oxidation

In our effort to induce novel modifications in the structure of some important vanadium phosphate phases used as selective oxidation catalysts, it has been observed that metal ions such as Zn²⁺, Ni²⁺, Pd²⁺can be incorporated into the vanadyl hydrogen phosphate VOHPO₄0.5H₂O phase in very different ways depending upon the medium of preparation. It has been found that the metal ions are either substituted into the lattice with retention of structure of the parent compound or intercalated between the layers of a new mixed-valent phase. These new metal-incorporated phases are catalytically active and the palladium incorporated compound in particular displays shape selective catalysis for different oxidation and reduction reactions. In another approach, the preparation of VOHPO₄0.5H₂O) has been modified to give a novel crystalline phase containing mixed-valentvanadium and having NH₃ species bound to the lattice. This phase could be a potential catalyst for ammoxidation reactions. In addition, novel mesostructured vanadium phosphate phases have been prepared using a long-chain amine as the templating agent involving a ligand templating mechanism of formation.