Topotactic Reaction Research Articles

Mg-ion storage materials based on MnO2 frameworks

A wide variety of crystal structures for MNO2, so-called polymorphs, is promising for basic flameworks of cathode materials in next-generation batteries such as Mg rechargeable batteries (MRBs). In this short review, we summarize recent progress on MNO2-based cathode materials for MRBs, especially focusing on the structures of α-MnO2 and λ-MnO2 to discuss the criteria for achieving topotactic reactions during magnesiation. In contrast to adequately stable α-MnO2, spinel-structured λ-MnO2 is unstable at elevated temperatures around 150 °C; however, its stability can be significantly improved by materials design. Here we introduce as a successful example that defect spinel ZnMnO3 exhibits long-term cycle performance even at 150 °C with high potential and capacity.

Topotactic Transformation of Surface Structure Enabling Direct Regeneration of Spent Lithium-Ion Battery Cathodes.

Recycling spent lithium-ion batteries (LIBs) has become an urgent task to address the issues of resource shortage and potential environmental pollution. However, direct recycling of the spent LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode is challenging because the strong electrostatic repulsion from a transition metal octahedron in the lithium layer provided by the rock salt/spinel phase that is formed on the surface of the cycled cathode severely disrupts Li+ transport, which restrains lithium replenishment during regeneration, resulting in the regenerated cathode with inferior capacity and cycling performance. Here, we propose the topotactic transformation of the stable rock salt/spinel phase into Ni0.5Co0.2Mn0.3(OH)2 and then back to the NCM523 cathode. As a result, a topotactic relithiation reaction with low migration barriers occurs with facile Li+ transport in a channel (from one octahedral site to another, passing through a tetrahedral intermediate) with weakened electrostatic repulsion, which greatly improves lithium replenishment during regeneration. In addition, the proposed method can be extended to repair spent NCM523 black mass, spent LiNi0.6Co0.2Mn0.2O2, and spent LiCoO2 cathodes, whose electrochemical performance after regeneration is comparable to that of the commercial pristine cathodes. This work demonstrates a fast topotactic relithiation process during regeneration by modifying Li+ transport channels, providing a unique perspective on the regeneration of spent LIB cathodes.

Topotactical Route to Multiwalled Cerium Oxide Nanotubes from MWCNTs

AbstractThe development of new strategies for synthesizing 1D cerium oxide (CeO2) hollow nanostructures has attracted much attention in recent years due to the importance of their superior properties and highly anisotropic geometry. This study reports an unpublished route of fabricating novel multiwalled CeO2‐δ nanotubes (CeO2‐δ NTs) in which the entire volume of functionalized multiwalled carbon nanotubes (f‐MWCNTs) is converted into the CeO2‐δ pseudomorph through oxidation and dehydration topotactic reactions. The stable CeO2‐δ (111) planes are topotactically grown on the curved C (002) planes, preferentially exposed along the nanotube axis. In their initial condition, the novel nanotubes consist of Ce oxyhydroxide (CeO2‐x(OH)x) with residual carbon. When heating the air up to 500 °C, CeO2‐x(OH)x transforms gradually by dehydration into CeO2‐δ, while the residual carbon is oxidized. Despite compositional changes, nanotubes maintain their multiwalled structural integrity up to ≈550 °C. The CeO2‐δ NTs exhibit an unusually high presence of Ce3+ ions and surface O vacancies, contributing to a low direct band gap ranging from 2.67 to 2.32 eV compared to their NPs counterparts (3.2 eV).

Critical role of hydrogen for superconductivity in nickelates.

The newly discovered nickelate superconductors so far only exist in epitaxial thin films synthesized by a topotactic reaction with metal hydrides1. This method changes the nickelates from the perovskite to an infinite-layer structure by deintercalation of apical oxygens1-3. Such a chemical reaction may introduce hydrogen (H), influencing the physical properties of the end materials4-9. Unfortunately, H is insensitive to most characterization techniques and is difficult to detect because of its light weight. Here, in optimally Sr doped Nd0.8Sr0.2NiO2H epitaxial films, secondary-ion mass spectroscopy shows abundant H existing in the form of Nd0.8Sr0.2NiO2Hx (x ≅ 0.2-0.5). Zero resistivity is found within a very narrow H-doping window of 0.22 ≤ x ≤ 0.28, showing unequivocally the critical role of H in superconductivity. Resonant inelastic X-ray scattering demonstrates the existence of itinerant interstitial s (IIS) orbitals originating from apical oxygen deintercalation. Density functional theory calculations show that electronegative H- occupies the apical oxygen sites annihilating IIS orbitals, reducing the IIS-Ni 3d orbital hybridization. This leads the electronic structure of H-doped Nd0.8Sr0.2NiO2Hx to be more two-dimensional-like, which might be relevant for the observed superconductivity. We highlight that H is an important ingredient for superconductivity in epitaxial infinite-layer nickelates.

Immobilization of Alendronate on Zirconium Phosphate Nanoplatelets

Different amounts of sodium-alendronate (ALN) were loaded into layered zirconium phosphates of alpha and gamma type (αZP and γZP) by means of topotactic exchange reactions of phosphate with ALN. In order to extend the exchange process to the less accessible interlayer regions, ALN solutions were contacted with colloidal dispersions of the layered solids previously exfoliated in single sheets by means of intercalation reaction of propylamine (for αZP) or acetone (for γZP). The ALN loading degree was determined by liquid P-nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP), and it was reported as ALN/Zr molar ratios (Rs). The maximum R obtained for γZP was 0.34, while αZP was able to load a higher amount of ALN, reaching Rs equal to 1. The synthesized compounds were characterized by X-ray powder diffractometry, scanning electron microscopy (SEM), solid-state NMR, and infrared spectroscopy. The way the grafted organo-phosphonate groups were bonded to the layers of the host structure was suggested. The effect of ZP derivatives was assessed on cell proliferation, and the results showed that after 7 days of incubation, none of the samples showed a decrease in cell proliferation.

TiO2 mesocrystals: Immobilisation, surface fluorination and application in photocatalytic water treatment

Immobilised TiO2 mesocrystals were prepared on sanded glass substrates via a solution synthesis of immobilised precursor, followed by a thermal treatment which triggered a topotactic conversion reaction. The obtained mesocrystals possessed not only anatase nanoparticles with high surface area and co-exposed {101}/{001} facets but also large overall particle size and strong binding to the substrate inherited from the immobilised precursor. The unique structural features make the material a promising candidate as a high-efficient and separable photocatalyst. The thermal treatment parameters were also demonstrated to be crucial for adjusting the structural or surface properties and thus the photocatalytic performance of the immobilised TiO2 mesocrystals.

Morphology Control of Transition Metal Oxides by Liquid-Phase Process and Their Material Development

It is well known that the functionality of inorganic materials strongly depends on the chemical composition, morphology, particle size, crystal facet, etc., which are strongly influenced by the synthesis process. The precise control of the synthesis process is expected to lead to the discovery of new functionality and improvement of the functionality of materials. For example, in a high-temperature solid-phase reaction, it is difficult to control the morphology of nanocrystals. On the other hand, synthesizing functional materials using solution processes, such as hydrothermal and solvothermal reactions, makes it possible to control the morphology and particle size precisely. Usually, the solution process is strongly related to the dissolution reprecipitation mechanism. Therefore, the material composition can be strictly controlled and is suitable for forming fine particles with high crystallinity. In this review paper, the role of the solvent in the solution process, its effect on particle size and morphology of the transition metal oxide, and the related functional improvement will be focused. Furthermore, the direct formation of functional thin films by the solution process and the morphology control by non-oxide materials by the topotactic reaction will also be introduced.

Electrochemical Control Ionic Defects Modulation Induced Phase Transition in SrCoOx: Progress and Prospect

Transition metal oxides (TMOs), as one of the advanced materials, have been widely studied due to their unique electronic, magnetic, optical, and thermal transport properties. Among them, SrCoOx (SCOx) is known as an oxygen sponge, where the ordered one-dimensional oxygen vacancy channels in the structure can work as the pathway for hydrogen/oxygen ions migration, facilitating the modulation of oxygen stoichiometry through the topotactic redox reaction. In this way, a “multi-state” phases transition with tunable physical properties can be realized. In this review, we summarize recent research progress in the utilization of H+ and O2 ions to induce distinct phase transitions in SCOx, which result in obvious physical property changes. The ability to control the properties of SCOx over a wide range through the incorporation of ionic defects provides a promising route for the development of advanced functional devices.

Forced topochemistry of a solid-state Diels–Alder reaction by encapsulation in epoxy glue

Encapsulation of unreacted crystals with epoxy glue forced a topotactic reaction to occur topochemically until ∼89% conversion which led to more reaction details being exposed.

Topotactic metal hydroxide decomposition to organize metal oxide nanoparticles inside electrospun fibers

For electrospinning of MgO nanoparticle-based fiber architectures, we exploit the intermediate formation of layered Mg(OH)2 nanosheets that form inside polyvinylalcohol (PVA) based fibers during nanoparticle-polymer formulation. Upon calcination, Mg(OH)2 nanosheets undergo a topotactic dehydration reaction. In conjunction with polymer removal, these sheets generate staggered MgO nanoparticle ensembles that comprise flat ribbons. With methanol as a solvent and in polyvinylpyrrolidone (PVP) fibers, the MgO nanoparticles retain their crystallinity and structure inside the electrospun fibers. After calcination, they form nanoparticle threads with a cylindrical profile and particle size gradient.

Study on Thermoelectric Property of Te Wire-Based Organic-Inorganic Hybrid Thermoelectric Composites through Electrochemical Process

Energy demand and importance are increasing with the industrial development and the development of high technology in modern society. However, the global supply of energy is facing problems such as fossil energy depletion and environmental pollution, and research and interest in alternative energy are increasing. Among them, research on thermoelectricity is being actively conducted. The thermoelectric characteristics are represented by the Seebeck coefficient, electrical conductivity, and thermal conductivity at the operating temperature. This is expressed as a thermoelectric performance index (ZT). ZT appears in proportion to the electrical conductivity and Seebeck coefficient, and inversely proportional to the thermal conductivity. Thermoelectric materials are divided into inorganic thermoelectric materials and organic thermoelectric materials, both of which have advantages and disadvantages. The inorganic thermoelectric material has high thermoelectric performance, but it is highly toxic and has low electrical conductivity. On the other hand, organic thermoelectric materials have lower performance than inorganic materials they are easy to obtain and have high electrical conductivity. In this study, organic-inorganic hybrid thermoelectric material was studied by combining the advantages of each material.In this study, Te nanowires (NWs) were synthesized at 50 Co by galvanic replacement reaction. We used Si (1 0 0) wafer as substrate of NWs. The substrate was degreased with acetone and ethanol. The solution of cadmium(1M), hydrofluoric acid (HF 51.0%, 4.5M) and tellurium dioxide (TeO2, 2mM). After the reaction, the synthesized Te NWs were washed with deionized water and IPA. The prepared Te NWs reacted with solution (silver nitrate in ethylene glycol) for topotactic reaction. After the reaction, the wires are washed several times with ethanol. The hybrid TE was fabricated by coating PEDOT:PSS on Ag-Te NWs with different ethylene glycol (EG) doping.A composite thermoelectric material was manufactured using Te (inorganic thermoelectric material) and PEDOT:PSS (organic thermoelectric material). Ag-topotactic reaction was conducted to increase the electrical conductivity of NWs. As the EG doping concentration of PEDOT increased, the electrical conductivity because the layer of PEDOT:PSS became thinner and didn’t fill the gap of NWS sufficiently. In conclusion, the Te NWs coated with PEDOT:PSS with 10% EG doping showed the best electrical conductivity and power factor. The more details will be presented. Figure 1

Synthesis, crystal structure and properties of catena-poly[[[bis-(3-methyl-pyridine-κN)nickel(II)]-di-μ-1,3-thio-cyanato] aceto-nitrile monosolvate

In the crystal structure of the title compound, {[Ni(NCS)2(C6H7N)2]·CH3CN} n , the NiII cation is octa-hedrally coordinated by two N-bonding and two S-bonding thio-cyanate anions, as well as two 3-methyl-pyridine coligands, with the thio-cyanate S atoms and the 3-methyl-pyridine N atoms in cis-positions. The metal cations are linked by pairs of thio-cyanate anions into chains that, because of the cis-cis-trans coordination, are corrugated. These chains are arranged in such a way that channels are formed in which disordered aceto-nitrile solvate mol-ecules are located. This overall structural motif is very similar to that observed in Ni(NCS)2[4-(boc-amino)-pyridine]2·CH3CN reported in the literature. At room temperature, the title compound loses its solvent mol-ecules within a few hours, leading to a crystalline phase that is structurally related to that of the pristine material. If the ansolvate is stored in an aceto-nitrile atmosphere, the solvate is formed again. Single-crystal X-ray analysis at room-temperature proves that the crystals decompose immediately, presumably because of the loss of solvent mol-ecules, and from the reciprocal space plots it is obvious that this reaction, in contrast to that in Ni(NCS)2[4-(boc-amino)-pyridine]2·CH3CN, does not proceed via a topotactic reaction.

The evolution of local structure of Mo6S8 during Li+ electrochemical storage studied by in-situ tender X-ray absorption spectroscopy

Chevrel phase Mo6S8 has attracted great interest because of its capability to accommodate different types of small cations through reversible topotactic redox reactions. However, the intercalation mechanism of Mo6S8 is still far from being fully understood owing to the complexity of the crystal structure and limitation of the probe tools. In our study, the reaction mechanism of Li ​+ ​intercalation into Mo6S8 was studied as a model by in-situ tender X-ray absorption spectroscopy (itXAS) in the viewpoint of local structure. According to the isobestic points of the 1st derivative, the discharge process is divided into five regions while the charge process is divided into four regions, where most of the regions are assigned to the two-phase transition reactions. The intensity change of the two spectroscopic features of the 1st derivative is found to be correlated, implying that the intercluster bond length directly affects the localization of the unoccupied states of the intracluster bond. The asymmetric evolution of the intensity of a’ and b’ as well as the asymmetric partition of reaction regions demonstrate the asymmetry of the reaction path in discharge and charge process. The results help to clarify the remaining debates on the phase transitions. Besides, itXAS is demonstrated to be a powerful tool to study the reaction mechanism of Mo6S8, which is complementary to NMR, XRD and so on.

Preparation of spatially uniform monolayer FeSexTe1−x (0 < x ≤ 1) by topotactic reaction

Preparation of spatially uniform monolayer FeSexTe1−x (0 < x ≤ 1) by topotactic reaction

Mechanism of olivine and glass alteration under experimental H2O-CO2 based supercritical gas: Application to modern and ancient Venus

Extreme conditions encountered in some geological contexts (deep serpentinization, interaction of Venus atmosphere with its basaltic surface, volcanic degassing) activate mechanisms and rates of silicate alteration that are poorly understood. In the present study, we investigate the mechanisms of mineral reactions in a natural geological system at high temperature, under conditions where the low solvation of cations by fluids likely promotes surface reactions such as surface diffusion and/or local recrystallization. We focus on vitreous glasses and olivine, reputed to be the most alterable phases in volcanic rocks, by reacting samples for one week in a Ni-based alloy experimental vessel. For the framework of our experimental study, we chose to apply the deep atmosphere conditions on Venus: 470 °C and 90 bar of reconstituted Venus-like gas. We also tested the effect of water (Early Venus or wet volcanic degassing) by adding water vapor at up to 320 bar total pressure. The mineral reactions affecting the samples were identified by a set of spectroscopic surface analyses of the altered samples: Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, X-ray Diffraction in grazing incidence mode, X-ray Photo electron Spectroscopy and Raman spectroscopy.Samples of obsidian and tholeiitic glasses are found to be sensitive to a threshold water pressure, depending on glass composition, below which the reaction is limited to some elemental mobility in the glass (alkali enrichment, calcium loss) leading to a possibly more stable surface layer of tens to hundreds of microns. Above this threshold water pressure (ca. 50 bar H2O for the obsidian but >250 bar H2O for the tholeiitic glass), water promotes the depolymerization of the glass and the crystallization of stable minerals. This crystalline rim is less protective that the chemically modified layer.Olivine samples react differently depending on whether the olivine is isolated or included in a basaltic rock. In the latter case only, iron coatings are formed, which are identified as hematite, suggesting that this phase is not fed by olivine itself but rather by surface diffusion from neighboring Fe-rich phases. This supports the conclusions from experimental studies and orbital observations on the short-term visibility of unaltered olivine in Venus lava flows: such a coating is enhanced when Fe-bearing minerals are in the proximity of olivine. Under high water vapor pressure, Fe-bearing talc (and not serpentine) forms by a likely topotactic reaction that also incorporates silica from the gas. This talc layer may form a protective layer, implying that serpentinization of ultramafic rocks at high temperature may not be as prevalent as one might think in a gas-dominated system like the Early Venus surface.

Lithium intercalation and deintercalation of thermally decomposed LiAl2-layered double hydroxides

Lithium aluminum layered double hydroxide (LiAl2-LDH) nanocrystals on aluminum metal substrates were synthesized to adsorb lithium in aqueous solutions and utilized to collect lithium in aqueous media. LiAl2-LDH is transformed at 300 °C into a mixture of LiCl and Li-Al-O-OH; dissolved lithium in deionized water at 25 °C reached 85% compared to the intercalated lithium content. Amorphous Li-Al-O-OH residues on the aluminum metal substrate were capable of adsorbing lithium ions back to the lithium rich LiAl2-LDH phase. Thermal treatment followed by additional lithium intercalation suggested a topotactic reaction of lithium ions between amorphous Li-Al-O-OH and LiAl2-LDH. We also proposed a facile recycling method of lithium ions by peeling off the Li-Al-O-OH layer to save the aluminum metal substrate.

Frontispiece: Renaissance of Topotactic Ion‐Exchange for Functional Solids with Close Packed Structures

Synthetic transformations of close-packed structures have witnessed a budding renaissance with the use of topotactic ion-exchange reactions. Surprising pathways to many new multifunctional and metastable solids have been discovered by leveraging the ion mobilities within their underlying sublattices. Recent research has begun elucidating many of the key synthetic variables, such as highlighted in the article frontispiece. For more information, please see the Concept article by Maggard et al. on page 19–24 https://doi.org/10.1002/chem.202200479.

Crystal Structure, Magnetic Properties and Thermal Behavior of BaFe11.9In0.1O19 Ferrite

Herein, the crystal structure, surface morphology, and magnetic and thermal properties of the BaFe11.9In0.1O19‐substituted M‐type hexaferrite are investigated. This solid solution is fabricated using “two‐step” topotactic reactions. It is determined through the X‐ray diffraction method that the crystal structure of this solid solution under normal conditions has hexagonal symmetry with P63/mmc space group (No. 194) with the unit cell parameters a = 5.8992(1) Å and c = 23.2275(7) Å. It is determined by the scanning electron microscope (SEM) researches that the average size of the grains is = 6 μm. It is determined by the vibration magnetometry that the ferrimagnet–paramagnet phase transition happens at around T C = 420 °C. Using differential scanning calorimetry (DSC), it is found that air and water molecules leave the sample surface up to 420 °C and the resulting oxygen anions appearing as a result of a solvothermal reaction fill the oxygen vacancies in the crystal structure at high temperatures up to 800 °C. The thermal transitions repeated in the high temperatures are established. The oxidation behavior of this compound is determined from thermogravimetric analysis (TGA) in a wide temperature range.

Ultralow contents of AgNbO3 fibers induced high energy storage density in ferroelectric polymer nanocomposites

Polymer dielectric films have been widely used in electronic and power systems due to their unique dielectric properties, processing properties, and excellent cost performance. Although the dielectric constant of dielectric polymers can be improved by adding high contents of ceramic fillers, this approach comes at the expense of the breakdown strength (Eb). This work is inspired by the idea that high-aspect-ratio fibers can induce a larger electric dipole moment without sacrificing too much Eb compared to zero-dimensional nanoparticles, thereby effectively improving the energy storage performance of the composites. We synthesized antiferroelectric AgNbO3 (ANO) fibers by using an in situ topotactic transition reaction which were then introduced into the polyvinylidene fluoride (PVDF) matrix for energy storage applications. The results show that the nanocomposite film with an ultralow loading of 0.4 wt. % ANO fibers achieves a high discharge energy density of 12.97 J cm−3 at 490 MV m−1. Nanocomposites based on ultralow content ANO fibers show great promise as one-dimensional antiferroelectric fillers for high energy density capacitor applications.

Inter- to intra-layer resistivity anisotropy of NdFeAs(O,H) with various hydrogen concentrations

With molecular beam epitaxy and a topotactic chemical reaction, we prepared NdFeAs(O,H) epitaxial thin films with various hydrogen concentrations on 5\ifmmode^\circ\else\textdegree\fi{} vicinal-cut MgO substrates. By measuring the resistivities along the longitudinal and transversal directions, the $ab$-plane and the $c$-axis resistivities (${\ensuremath{\rho}}_{ab}$ and ${\ensuremath{\rho}}_{c}$) were obtained. The resistivity anisotropy ${\ensuremath{\gamma}}_{\ensuremath{\rho}}\ensuremath{\equiv}{\ensuremath{\rho}}_{c}/{\ensuremath{\rho}}_{ab}$ of NdFeAs(O,H) with various hydrogen concentrations was compared with that of NdFeAs(O,F). At the H concentrations which led to superconducting transition temperatures ${T}_{\mathrm{c}}$ over 40 K, ${\ensuremath{\gamma}}_{\ensuremath{\rho}}$ recorded $\ensuremath{\sim}100--150$ at 50 K. On the other hand, a low ${\ensuremath{\gamma}}_{\ensuremath{\rho}}$ value of 9 was observed with the highest-doped sample. The exponent \ensuremath{\beta} of the $ab$-plane resistivity obtained by fitting a power-law expression ${\ensuremath{\rho}}_{ab}(T)={\ensuremath{\rho}}_{0}+A{T}^{\ensuremath{\beta}}$ to the data was close to unity down to a low temperature in the vicinity where the second antiferromagnetic phase locates, which may be related to the quantum critical point discussed at the overdoped side of the phase diagram.