Topotactic Ion-exchange Research Articles

In Situ Self‐Assembled Active and Stable Ir@MnOx/La0.7Sr0.3Cr0.9Ir0.1O3−δ Interfaces for CO2 Electrolysis

AbstractSolid oxide electrolysis cells are prospective approaches for CO2 utilization but face significant challenges due to the sluggish reaction kinetics and poor stability of the fuel electrodes. Herein, we strategically addressed the long‐standing trade‐off phenomenon between enhanced exsolution and improved structural stability via topotactic ion exchange. The surface dynamic reconstruction of the MnOx/La0.7Sr0.3Cr0.9Ir0.1O3−δ (LSCIr) catalyst was visualized at the atomic scale. Compared with the Ir@LSCIr interface, the in situ self‐assembled Ir@MnOx/LSCIr interface exhibited greater CO2 activation and easily removable carbonate intermediates, thus reached a 42 % improvement in CO2 electrolysis performance at 1.6 V. Furthermore, an improved CO2 electrolysis stability was achieved due to the uniformly wrapped MnOx shell of the Ir@MnOx/LSCIr cathode. Our approach enables a detailed understanding of the dynamic microstructure evolution at active interfaces and provides a roadmap for the rational design and evaluation of efficient metal/oxide catalysts for CO2 electrolysis.

In Situ Self-Assembled Active and Stable Ir@MnOx/La0.7Sr0.3Cr0.9Ir0.1O3-δ Interfaces for CO2 Electrolysis.

Solid oxide electrolysis cells are prospective approaches for CO2 utilization but face significant challenges due to the sluggish reaction kinetics and poor stability of the fuel electrodes. Herein, we strategically addressed the long-standing trade-off phenomenon between enhanced exsolution and improved structural stability via topotactic ion exchange. The surface dynamic reconstruction of the MnOx/La0.7Sr0.3Cr0.9Ir0.1O3-δ (LSCIr) catalyst was visualized at the atomic scale. Compared with the Ir@LSCIr interface, the in situ self-assembled Ir@MnOx/LSCIr interface exhibited greater CO2 activation and easily removable carbonate intermediates, thus reached a 42 % improvement in CO2 electrolysis performance at 1.6 V. Furthermore, an improved CO2 electrolysis stability was achieved due to the uniformly wrapped MnOx shell of the Ir@MnOx/LSCIr cathode. Our approach enables a detailed understanding of the dynamic microstructure evolution at active interfaces and provides a roadmap for the rational design and evaluation of efficient metal/oxide catalysts for CO2 electrolysis.

Designing Topotactic Ion-Exchange Reactions in Solid-State Oxides Through First-Principles Calculations

Designing Topotactic Ion-Exchange Reactions in Solid-State Oxides Through First-Principles Calculations

Simple to Quadruple Perovskite Transformation by Coordination Switching upon Solid-State Ion Exchange of NaNbO3.

Topotactic ion exchange is ubiquitous in the preparation of many metastable solids with layered structures. In recent times, the scope of chimie-douce ion exchange has been extended to quasi-2D and -3D structures including nanocrystals. The low-temperature solid-state exchange is yet another unique synthetic tool to access preconceived structures for the rational design of solids. Although rational synthesis using inorganic synthons is rare, few examples exist among inorganic solids with layered structures. Herein, we extend the scope further by transforming a simple perovskite (ABO3) into a high-pressure quadruple (AA'3B4O12) perovskite. The transformation is achieved at moderate temperatures and ambient pressure via a solid-state metathesis reaction, wherein the transition metal adopts a new A-cation coordination upon exchange. Such coordination switching upon ion exchange will open up possibilities for functionality-driven structural transformations and the rational design of new solids.

Mercaptoalkyl Groups Anchored on the Layer Surface of New α‐Zirconium Phosphate Phosphonates for the Stabilization of Gold Nanoparticles

AbstractLayered zirconium phosphate mercaptoalkylphosphonates, with general composition Zr(O3POH)2‐x(O3P(CH2)11SH)x, where x=0.4–1.4, are prepared according to two procedures: direct reaction between a zirconyl salt and a mixture of phosphoric/phosphonic acid in propanol, or topotactic ion exchange reaction of phosphate groups of nanocrystalline α‐Zr(O3POH)2 with mercaptoundecylphosphonate groups. FT‐IR analysis and XPS proves the presence of the mercapto groups and, according to X‐Ray diffraction analysis, they result randomly distributed on the layer surface. The solids are used as supports for gold nanoparticles synthesized according to three different methods: reaction of HAuCl4 with NaBH4, added after 24 hours (Procedure A), or concomitantly (Procedure B) to the addition of the Au(III) salt to the solid suspension, or by mixing the solid suspension with a colloidal dispersion of gold nanoparticles prepared according to the Turkevich method (Procedure C). The best results were obtained with Procedure B, that provided composites with gold nanoparticles having an average size of (6±2) nm.

In-situ topotactic construction of novel rod-like Bi2S3/Bi5O7I p-n heterojunctions with highly enhanced photocatalytic activities

• Novel 3D rod-like Bi 2 S 3 /Bi 5 O 7 I p-n heterostructures with rich OVs were synthesized by an in-situ topotactic ion exchange method. • BSI RHs were composed of internal Bi 5 O 7 I nanobelts and outside networks orderly interwoven by Bi 2 S 3 nanorods. • BSI RHs exhibited a highly enhanced photocatalytic activity. • p-n heterostructure and rich OVs led to the efficient separation of photoinduced charge carriers. • ⋅O 2 − and h + played key roles in the photocatalytic process. In this work, a novel Bi 2 S 3 /Bi 5 O 7 I p-n heterojunction with three-dimensional rod-like nanostructure was successfully constructed through an in-situ topotactic ion exchange approach. A possible evolution mechanism from Bi 5 O 7 I nanobelts (NBs) into Bi 2 S 3 /Bi 5 O 7 I rod-like heterostructures (BSI RHs) was proposed, depicting the self-assembly process of internal Bi 5 O 7 I NBs and outside networks interwoven by Bi 2 S 3 nanorods (NRs), which abided by the Ostwald ripening and epitaxial growth. Owing to the formation of p-n heterojunction and rich oxygen vacancies (OVs), the visible-light absorption ability and separation of photogenerated charge carriers of BSI RHs were highly promoted, leading to greatly improved photocatalytic ability than that of Bi 2 S 3 and Bi 5 O 7 I. BSI-1 exhibited the strongest photocatalytic performance, and almost all rhodamine B (RhB) and Pseudomonas aeruginosa ( P. aeruginosa ) can be thoroughly removed within 90 min. Moreover, a possible photocatalytic mechanism of BSI RHs was proposed based on the tests of active species trapping, electron spin resonance (ESR), photoelectrochemistry (PEC), and photoluminescence (PL) combined with the density functional theory (DFT) simulated computation, validating the dominating roles of ∙O 2 − and h + during the photocatalytic process. This work is expected to motivate further efforts for developing novel heterostructures with highly efficient photocatalytic performances, which presents a promising application prospect in the fields of energy and environment. Bi 2 S 3 /Bi 5 O 7 I p-n heterojunction with three-dimensional rod-like nanostructure and highly enhanced photocatalytic activity was successfully constructed through an in-situ ion exchange approach.

Relative Kinetics of Solid-State Reactions: The Role of Architecture in Controlling Reactivity.

Countless inorganic materials are prepared via high temperature solid-state reaction of mixtures of reagents powders. Understanding and controlling the phenomena that limit these solid-state reactions is crucial to designing reactions for new materials synthesis. Here, focusing on topotactic ion-exchange between NaFeO2 and LiBr as a model reaction, we manipulate the mesoscale reaction architecture and transport pathways by changing the packing and interfacial contact between reagent particles. Through analysis of in situ synchrotron X-ray diffraction data, we identify multiple kinetic regimes that reflect transport limitations on different length scales: a fast kinetic regime in the first minutes of the reaction and a slow kinetic regime that follows. The fast kinetic regime dominates the observed reaction progress and depends on the reagent packing; this challenges the view that solid-state reactions are necessarily slow. Using a phase-field model, we simulated the reaction process and showed that particles without direct contact to the other reactant phases experience large reduction in the reaction rate, even when transport hindrance at particle-particle contacts is not considered.

Fe(III)‐Based Layered Double Hydroxides Carrying Model Naproxenate Anions: Compositional and Structural Aspects

AbstractIn this work, Al cation was gradually replaced by FeIII in the composition of Layered Double Hydroxides (LDH) and systematically investigated for LDH application as drug carriers, ultimate aiming to improve their biointegration. The incorporation of FeIII into LDH layers, as well the intercalation of organic anions in the iron‐based materials, is challenging. Several studies approach the intercalation of non‐steroidal anti‐inflammatory drugs such as anionic naproxen (NAP) into Al‐LDH. Thus, NAP was applied here as a model drug for the study of compositional and structural aspects of novel FeIII‐LDH carriers envisaging to shed light on the intercalation of other carboxylate drugs into these materials. LDH of general [M2FeyAl(1‐y)(OH)6]An− compositions (MII=Mg or Zn; An−=anion of charge n) were investigated using two synthetic methods for NAP intercalation. Full X‐ray diffraction profile refinement and a crystal‐geometrical reasoning were used to strengthen the results interpretation. Unlike coprecipitation, in which probably NAP complexation with FeIII hinders LDH‐NAP self‐assembling, topotactic ion exchange demonstrated to be a potential approach.

Room-Temperature Synthesis and Stable Na-Ion Storage Performance of Two-Dimensional Mixed Lead-Bismuth Oxychloride Heterostructure

The endless pursuit on building low cost and sustainable batteries to effectively harvest renewable energy from intermittent sources is ever increasing. The research on Na-ion technology has gained significant interest due to inexpensive and broad availability of precursor materials. Until now, various Na-ion anodes have been explored including carbonaceous materials such hard carbon, alloy-based materials such as Bi, Pb, Sb and Sn based systems and conversion materials [1]. Along this line, the recent chase on two dimensional (2D) materials such as chalcogenides, MXenes and van der Waals types oxyhalide heterostructures, have become more intense due to their excellent electrical and structural properties [2]. Among them, 2D Sillén-type metal oxyhalide heterostructures (MOX), due to their unique layered structure consisting of anionic sheets interleaved with cationic layers have gain particular interest as electrode materials. BiOCl is one such candidate with fluorite-like layers, [Bi2O2]2+ intergrown with halide Cl– anions, have been studied as anode in rechargeable batteries. For instance, the 2D-(Bi1-xFex)OCl have increased insertion kinetics in Li-ion storage performances [3] in comparison with unsubstituted BiOCl, whereas 2D-(Bi1-xSbx)OCl heterostructures have shown synergetic effect of (Bi/Sb) alloys on with improved K-ion storage capacity [4]. However, in continuation, the further assessment of other mixed cationic Sillén heterostructures with the crystal structures of [BixM1-xO2]n+ (M = Na+/Ca2+/Pb2+/Fe3+/Sb3+; n = +1, +2 and +3) layers intergrown with single/double/triple halide anionic layers, remain unexplored. This is mainly challenged by their current synthesis strategies which demand high temperature, longer reaction durations, toxic chemicals, and complex reaction setup.In this work, 2D layered lead bismuth oxychloride (PbBiO2Cl) heterostructure nanosheets were synthesized by new rapid room temperature chemical precipitation route within ~45 mins. The stepwise reaction intermediates were harvested and investigated further with XRD and SEM mechanistic studies. The formation proceeds through topotactic ion exchange route from analogous PbBiO2NO3 intermediate. When employed as an anode material in Na half-cell configurations (as presented in Figure 1), this 2D heterostructure demonstrated stable sodium storage performance (~250 mAh g–1 for 250 cycles at 100 mA g–1). Surprisingly, the electrochemical profile of the 2D-PbBiO2Cl significantly differs from those of its individual counterparts Pb, Bi anodes. This was further investigated with the combined in-operando XRD and ex-situ TEM, XPS studies, which reveal a distinct (de)sodiation process of the 2D-PbBiO2Cl in comparison with reported Na-(Pb/Bi) phase diagram. Henceforth, the detailed understanding of formation process of 2D-PbBiO2Cl at room temperature using non-operando material characterizations and electrochemical studies combined with operando findings will be discussed to comprehend the reversible storage mechanism of 2D-PbBiO2Cl type heterostructures as anodes in SIBs.

Tri-α-PbO2-Type Fe–Sb Tungstate by Topotactic Ion Exchange of LiSbWO6

Tri-α-PbO₂-Type Fe–Sb Tungstate by Topotactic Ion Exchange of LiSbWO₆

Surface roughness effect on the cellular uptake of layered double hydroxide nanoparticles

Layered double hydroxide (LDH) particles with a uniform size of ~200 nm were prepared by the hydrothermal method, and fluorescein moiety was introduced into their gallery space. Through modifying synthesis routes such as ion-exchange and reconstruction, final LDH particles were obtained with a smooth and rough surface, respectively. Thanks to the topotactic ion-exchange and systematic reconstruction, the two LDH had the same particle dimension, surface charge and colloidal properties except for surface roughness. Cell viability test employing human lung adenocarcinoma epithelial cells (A549) showed that both the LDH, regardless of surface roughness showed sufficient biocompatibility up to a concentration of 200 μg/mL. According to fluorescence assisted cell sorting and confocal microscopy, we could quantitatively and qualitatively confirm that the smooth particles were more advantageous in terms of cellular uptake compared to rough particles. According to a series of biological assays with or without proteins, we could suggest that the benefit of smooth-surfaced LDH was related to their higher protein adsorption property compared to rough particles; protein adsorption was considered to enhance both colloidal stability in biological fluid and cellular interaction at the membrane.

Topotactic Ion Exchange in a Three-Dimensional Close-Packed Trirutile Structure with an Octahedral Network.

Topotactic ion exchange in open-framework solids and oxides with layered and tunnel structures has resulted in the formation of a variety of metastable functional materials that are inaccessible otherwise. These ion exchanges are primarily limited to the above structure types because of the presence of labile ions as loosely held charge-compensating cations/anions as in the framework or tunnel structures or the lability of the ions/charged motifs in interlayer galleries of layered oxides. While such topotactic exchanges are common in the above structure types, they are rare in the three-dimensional (3D) close-packed structures based solely on corner- and/or edge-connected polyhedral networks. Herein, we demonstrate divalent iron exchange in a close-packed all-octahedral-coordinated trirutile oxide. This has enabled the transformation of a near-ultraviolet-absorbing diamagnetic insulating oxide into a visible-light-active paramagnetic semiconductor. An ion exchange of this kind may open up avenues for the development of metastable functional oxides with a variety of other 3D structures and diverse properties.

Cation-swapped homogeneous nanoparticles in perovskite oxides for high\xa0power density

Exsolution has been intensively studied in the fields of energy conversion and storage as a method for the preparation of catalytically active and durable metal nanoparticles. Under typical conditions, however, only a limited number of nanoparticles can be exsolved from the host oxides. Herein, we report the preparation of catalytic nanoparticles by selective exsolution through topotactic ion exchange, where deposited Fe guest cations can be exchanged with Co host cations in PrBaMn1.7Co0.3O5+δ. Interestingly, this phenomenon spontaneously yields the host PrBaMn1.7Fe0.3O5+δ, liberating all the Co cations from the host owing to the favorable incorporation energy of Fe into the lattice of the parent host (ΔEincorporation = −0.41 eV) and the cation exchange energy (ΔEexchange = −0.34 eV). Remarkably, the increase in the number of exsolved nanoparticles leads to their improved catalytic activity as a solid oxide fuel cell electrode and in the dry reforming of methane.

A Non-Natural Wurtzite Polymorph of HgSe: A Potential 3D Topological Insulator

This article demonstrates the power of topotactic synthesis coupled with density functional theory (DFT) for accessing and exploring new phases of matter. Naturally occurring HgSe is a semimetal with a zero gap. Unlike this natural zincblende form of HgSe, our DFT investigations predict that wurtzite HgSe has both an inverted band structure and a band gap, making it a 3D topological insulator (TI). Calculated band structures of HgxCd1–xSe alloys containing strongly relativistic Hg and weakly relativistic Cd show that band gap opening is a consequence of symmetry breaking resulting from a combination of crystal anisotropy and the scalar relativistic effect of Hg electrons. The relativistic contribution of Hg is significant enough in alloys with x ≥ 0.33 for achieving 3D TI behavior at room temperature. We experimentally realize the non-natural wurtzite form by topotactic ion exchange of wurtzite CdSe nanocrystals (NCs), which yields alloy NCs in the range x = 0–0.54 whose measured band gaps follow the pred...

Conversion of Marine Structures to Calcium Phosphate Materials: Mechanisms of Conversion Using Two Different Phosphate Solutions

Marine structure, coralline materials were converted to calcium phosphate using two different phosphate solutions. The aim was to study the conversion mechanisms under acidic and basic environment at moderate conditions of temperature. Crystal growth and morphology of converted corals were characterized by XRD and SEM respectively. The results suggested that under acidic conditions (H3PO4), dissolution and precipitation control and direct the crystal formation and morphology in which transition from plate like to rod like hydroxyapatite structure was favoured. Metastable phase such as monetite formed and transformed to HAp during reaction. During the first hour of the dissolution a monetite and hydroxyapatite mixture precipitates and then the full conversion to hydroxyapatite is observed. On the other hand, under basic conditions (NH4)2HPO4, just diffusional surface conversion of the calcium carbonate structure of coralline materials to hydroxyapatite and a very small amount of tri-calcium phosphate is observed. The mechanism can be classified as the solid-state topotactic ion-exchange reaction mechanism.

Syntheses, structural variants and characterization of AInM′S4 (A=alkali metals, Tl; M′ = Ge, Sn) compounds; facile ion-exchange reactions of layered NaInSnS4 and KInSnS4 compounds

Ten AInM′S4 (A=alkali metals, Tl; M′= Ge, Sn) compounds with diverse structure types have been synthesized and characterized by single crystal and powder X-ray diffraction and a variety of spectroscopic methods. They are wide band gap semiconductors. KInGeS4(1-β), RbInGeS4(2), CsInGeS4(3-β), TlInGeS4(4-β), RbInSnS4(8-β) and CsInSnS4(9) compounds with three-dimensional BaGa2S4 structure and CsInGeS4(3-α) and TlInGeS4(4-α) compounds with a layered TlInSiS4 structure have tetrahedral [InM′S4]− frameworks. On the other hand, LiInSnS4(5) with spinel structure and NaInSnS4(6), KInSnS4(7), RbInSnS4(8-α) and TlInSnS4(10) compounds with layered structure have octahedral [InM′S4]− frameworks. NaInSnS4(6) and KInSnS4(7) compounds undergo facile topotactic ion-exchange, at room temperature, with various mono-, di- and tri-valent cations in aqueous medium to give rise to metastable layered phases.

ChemInform Abstract: Synthesis and Thermal Stability Studies of a Series of Metastable Dion—Jacobson Double‐Layered Neodymium‐Niobate Perovskites.

AbstractThe compounds (VI), (VIII), and (X) are prepared by topotactic ion exchange using (IV) as the precursor.

Quadruple-layered perovskite (CuCl)Ca2NaNb4O13

We will present the synthesis, structure and magnetic properties of a new quadruple-layered perovskite (CuCl)Ca2NaNb4O13. Through a topotactic ion-exchange reaction with CuCl2, the precursor RbCa2NaNb4O13 presumably having an incoherent octahederal tliting changes into (CuCl)Ca2NaNb4O13 with a 2ap×2ap×2cp superstructure (tetragonal; a=7.73232(5)Å, c=39.2156(4)Å). The well-defined superstructure for the ion-exchanged product should be stabilized by the inserted CuCl4O2 octahedral layers that firmly connect with neighboring perovskite layers. Magnetic studies show the absence of long-range magnetic ordering down to 2K despite strong in-plane interactions. Aleksandrov′s group theory and Rietveld refinement of synchrotron X-ray diffraction data suggest the structure to be of I4/mmm space group with in-phase tilting along the a and b axes, a two-tilt system (++0).

Two-dimensional Frustrated Antiferromagnets (MCl)LaNb2O7 (M = Mn, Co, Cr)

Magnetic susceptibility and specific heat measurements have been performed on two-dimensional spin systems (M2+Cl)LaNb2O7 (M = Mn (S = 5/2), Cr (S = 2), Co (S = 3/2)), prepared via a topotactic ion-exchange reaction. All three compounds establish antiferromagnetic order at TN = 53 K, 61 K and 52 K, respectively for M = Mn, Co, Cr. Together with TN = 78 K for M = Fe (S = 2), this result indicates that the TN is not simply scaled by the magnitude of spin. In particular, the presence of strong spin-orbit interactions is suggested for (CoCl)LaNb2O7.

First single-crystal synthesis and low-temperature structural determination of the quasi-2D quantum spin compound (CuCl)LaNb2O7

We provide a full description of the first single-crystal synthesis of the low-dimensional quantum spin compound (CuCl)LaNb(2)O(7) through the low-temperature topotactic ion exchange route. Very fast diffusion of ion-exchanged CuCl and Cs ions is observed. In addition, thorough structure determination at very low temperature is outlined following use of single-crystal X-ray diffraction and powder neutron diffraction, taking advantage of the better sensitivity of the latter method for describing O and Cl atoms. State-of-the-art calculations (Maximum Entropy Method) are used for visualising the fine structural features of this unusual pseudo-tetragonal superstructure. Our study unambiguously throws light on the long-standing controversy concerning the crystal structure of this compound, and allows for a relevant description of its magnetic properties. Incidentally, it is demonstrated that the low-temperature structural model tentatively proposed very recently by Tsirlin et al. (Phys. Rev. B, 2010, 82, 054107), according to powder synchrotron X-ray diffraction, is correct.