Water Intercalation Research Articles

Hydrate formation at extreme conditions.

The article of Yamashita et al. [Acta Cryst. (2022), C78, 749–754] on water intercalation into the B1 structure of KCl under high pressure illustrates the ability of in situ crystal growth to by-pass kinetic barriers between phases, demonstrating the importance of this approach in phase discovery.

Temperature-resolved nanoscale hydration of a layered manganese oxide.

Water films captured in the interlayer region of birnessite (MnO2) nanosheets can play important roles in biogeochemical cycling, catalysis, energy storage, and even atmospheric water harvesting. Understanding the temperature-dependent loadings and properties of these interlayer films is crucial to comprehend birnessite reactivity when exposed to moist air and temperature gradients. Using vibrational spectroscopy we show that birnessite intercalates one water (1W) monolayer at up to ∼40 °C, but that loadings decrease by half at up to 85 °C. Our results also show that the vibrational properties of intercalated water are unaffected by temperature, implying that the hydrogen bonding network of water remains intact. Using molecular simulations, we found that the lowered water storage capacity at high temperatures cannot be explained by variations in hydrogen bond numbers or in the solvation environments of interlayer K+ ions initially present in the interlayer region. It can instead be explained by the compounded effects of larger evolved heat, as inferred from immersion energies, and by the larger temperature-driven mobility of water over that of K+ ions, which are electrostatically bound to birnessite basal oxygens. By shedding new light on the temperature-driven intercalation of water in a nanolayered mineral, this study can guide future efforts to understand the (geo)chemical reactivity of related materials in natural and technological settings.

Crystal water intercalated interlayer expanded MoS2 nanosheets as a cathode for efficient zinc-ion storage.

Zinc-ion batteries (ZIBs) have attracted tremendous interest from the scientific community in recent years due to their extreme safety, cost-effectiveness, environmental benignity and the unique properties of the Zn anode. However, more suitable cathode materials are needed to achieve their potential widespread applications. MoS2, a 2D layered material with fascinating properties, could also serve as a cathode in ZIBs but is rarely studied due to its limited interlayer spacing, poor ionic/electronic conductivity and hydrophobicity. In this work, we report a facile hydrothermal method for synthesizing crystal water-intercalated MoS2 nanosheets and their application in efficient Zn-ion storage. Morphological characterization reveals the average thickness of the nanosheets to be 15.2 nm. With a large interlayer spacing (0.79 nm), high 1T content (49.7%) and high defects, MoS2·nH2O achieves a high discharge capacity of 197 mA h g-1 at 0.1 A g-1 in an aqueous 2 M ZnSO4 electrolyte. Moreover, it exhibits modest cyclic stability with 55% capacity retention after 1000 charge/discharge cycles. Furthermore, we evaluated the charge storage kinetics of crystal water-intercalated MoS2 nanosheets and realized that the electrochemical reaction is diffusion dominated with a diffusion coefficient of 10-10 to 10-13 cm2 s-1 in a 0.3 to 1.3 V potential window. This simple and cost-effective strategy for improving the performance of ZIBs by crystal water intercalation in 2D cathode materials will pave the way for their commercial-level grid-scale applications.

Percolative proton transport in hexagonal boron nitride membranes with edge-functionalization.

Two-dimensional layered materials have been used as matrices to study the structure and dynamics of trapped water and ions. Here, we demonstrate unique features of proton transport in layered hexagonal boron nitride membranes with edge-functionalization subject to hydration. The hydration-independent interlayer spacing indicates the absence of water intercalation between the h-BN sheets. An 18-fold increase in water sorption is observed upon amine functionalization of h-BN sheet edges. A 7-orders of magnitude increase in proton conductivity is observed with less than 5% water loading attributable to edge-conduction channels. The extremely low percolation threshold and non-universal critical exponents (2.90 ≤ α ≤ 4.43), are clear signatures of transport along the functionalized edges. Anomalous thickness dependence of conductivity is observed and its plausible origin is discussed.

Direct recycling and remanufacturing of anode scraps

With the rapid expansion of Li-ion battery production, significant amounts of electrode scraps that need to be recycled are being produced during cell manufacturing. Anode scrap that comprises critical materials such as graphite and valuable Cu should be recycled and reintegrated into the battery supply chain. This study reports a simple yet efficient water-based recovery process for delaminating anode films from Cu foils through the intercalation of water between the hydrophilic Cu foil and hydrophobic anode coating. Because of the absence of harsh chemicals, the recovered anode films and Cu foils are battery grade and free of damage in terms of physical and chemical properties. This study also demonstrates the reprocessing of those anode films into a new anode that exhibits electrochemical performance similar to that of the pristine anode. This environmentally friendly and cost-effective separation technique allows battery manufacturers to directly recycle and reuse their electrode scraps safely and effectively on-site.

Crystal structure of potassium chloride monohydrate: water intercalation into the B1 structure of KCl under high pressure.

A new hydrate form of potassium chloride, KCl·H2O, is identified for the first time by in situ single-crystal X-ray diffraction under high pressure. It has a monoclinic structure with lattice parameters of a= 5.687 (7), b= 6.3969 (3), c= 8.447 (3) Å and β= 107.08 (8)° at 2.23 (4) GPa and 295 K. The structure of this hydrate has K-Cl alignments similar to the B1 phase of anhydrous KCl, while water molecules intercalate among the ionic species. The coordination structures of the K and Cl atoms can be regarded as the intermediate states between the B1 and B2 phases of KCl. This finding provides a perspective on the structural interpretation of multicomponent materials and an additional candidate for bound water in salt-water systems under high pressure, such as inside of icy bodies.

Structural, optical, and electrical properties of proton intercalation H+/Na+ phases in nanostructured titanates induced by pH during hydrothermal synthesis

In search of a promising alternative to manufacture anodes for sodium-ion batteries, a study of the pH variation during hydrothermal synthesis of nanostructures of sodium titanate is presented. In particular, structural, optical and electrical properties of these materials are assessed when varying the pH for two different synthesis conditions. A mixture of phases was found, in agreement with ( N a , H ) 2 T i 3 O 7 ⋅ n H 2 O , and its cause is attributed to the proton( H + )/sodium( N a + ) exchange and the intercalation of structural water. Also, changes in the morphology of the structural phases were observed, for example the phase with lower interlaminal distance appears to be nanorods, instead of nanotubes. The relative weight between phases and the direct band gap can be tuned by controlling synthesis conditions, in particular pH conditions. An enhancement of new processes in the electrical response and the suppression or enhancement of some defect due to the mixture of phase is also discussed. Additionally, the changes in electrical properties over a possible operation temperature range of a potential device, between −30 °C and 50 °C is reported. It was found that the changes in impedance in the proposed temperature range are of the order of 25 % of the modulus. This work shows how the final N a + content in the sample alters its optical and electrical properties, which are determinant in its performance as an anode. • Effect of pH during the synthesis of sodium titanate nanostructure. • Mixture of phases concordant with (Na, H) 2 Ti 3 O 7 .nH 2 O. • Mixture of phases regulates optical and electrical properties. • Direct Band gap could be tuned with pH during synthesis. • Study of the electrical impedance in the operation temperature range.

Advanced Proton-Conducting Ceramics Based on Layered Perovskite BaLaInO4 for Energy Conversion Technologies and Devices.

Production of high efficiency renewable energy source for sustainable global development is an important challenge for humans. Hydrogen energy systems are one of the key elements for the development of sustainable energy future. These systems are eco-friendly and include devices such as protonic ceramic fuel cells, which require advanced proton-conducting materials. In this study, we focused on new ceramics with significantly improved target properties for hydrogen energy purposes. Neodymium-doped phase based on layered perovskite BaLaInO4 was obtained for the first time. The ability for water intercalation and proton transport was proved. It was shown that the composition BaLa0.9Nd0.1InO4 is the predominant proton conductor below 400 °C under wet air. Moreover, isovalent doping of layered perovskites AA′BO4 is the promising method for improving transport properties and obtaining novel advanced proton-conducting ceramic materials.

Electronic interactions and stability issues at the copper-graphene interface in air and in alkaline solution under electrochemical control

A micro-electrochemical cell is sealed with a polymer-free single-layer graphene (SLG) membrane to monitor the stability of Cu nanoparticles (NPs) attached to SLG, as well as the interfacial electronic interactions between Cu NPs and SLG both in air and in a mildly alkaline aqueous solution under electrochemical control. A combination of techniques, including in-situ Kelvin probe force microscopy (KPFM) and ex-situ electron microscopy, are applied. When Cu NPs are metallic at cathodic potentials, there is a relatively bias-independent offset in the SLG work function due to charge transfer at the Cu-SLG contact. When Cu NPs are oxidized at anodic potentials, on the other hand, the work function of SLG also depends on the applied bias in a quasi-linear fashion due to electrochemical gating, in addition to charge transfer at the CuOx-SLG contact. Furthermore, Cu NPs were found to oxidize and detach from SLG when kept under anodic potentials for a few hours, whereas they remain adhered to SLG at cathodic potentials. This is attributed to water intercalation at the CuO-SLG interface associated with the enhanced hydrophilicity of positively polarized graphene, as supported by the absence of Cu detachment following oxidation by galvanic corrosion in air.

A volatile polymer stamp for large-scale, etching-free, and ultraclean transfer and assembly of two-dimensional materials and its heterostructures

The intact transfer and assembly of two-dimensional (2D) materials and their heterostructures are critical for their integration into advanced electronic and optical devices. Herein, we report a facile technique called volatile polymer stamping (VPS) to achieve efficient transfer of 2D materials and assembly of large-scale heterojunctions with clean interfaces. The central feature of the VPS technique is the use of volatile polyphthalaldehyde (PPA) together with hydrophobic polystyrene (PS). While PS enables the direct delamination of 2D materials from hydrophilic substrates owing to water intercalation, PPA can protect 2D materials from solution attack and maintain their integrity during PS removal. Thereafter, PPA can be completely removed by thermal annealing at 180 °C. The proposed VPS technique overcomes the limitations of currently used transfer techniques, such as chemical etching during the delamination stage, solution tearing during cleaning, and contamination from polymer residues.

How the Environment Encourages the Natural Formation of Hydrated V2O5.

Herein, we report the microscopic and spectroscopic signatures of the hydrated V2O5 phase, prepared from the α-V2O5 powder, which was kept in deionized water inside an airtight glass container for approximately 2.5 years. The experimental results show an evolution of the V4+ component in V 2p3/2 core energy level spectra, and a peak corresponding to σ-OH– bond appeared in the valence band spectra in the hydrated V2O5 powder sample due to the water intercalation. Vanadium metal oxide particles were found to be self-nucleated into micro/nanorods after a long period of exposure to an extremely humid environment. The distinct features in the spectra obtained with high-resolution transmission electron microscopy, micro-Raman scattering, and X-ray photoelectron spectroscopy confirmed the presence of structural water molecules for the first time in the long-aged naturally hydrated V2O5 phase.

Tunnel cation and water structures of todorokite: Insights into metal partitioning and isotopic fractionation

Tectomanganate todorokite and phyllomanganate vernadite are the two major manganese minerals in marine ferromanganese sediments that contain large quantities of trace metals. Todorokite has a less clear metal partitioning mechanism than vernadite, mainly because the metal cation and water structures in the tunnel cavities remain poorly understood. Here, we report the composition-dependent tunnel-cation site disorder of todorokite obtained from molecular dynamics (MD) simulations. Our simulations of homocationic Ni2+-, Zn2+-, Mg2+-, Ca2+-, or Na+-todorokite revealed that tunnel cations form inner-sphere (IS) complexes with Mn octahedral surface at low hydration states, but at higher hydration states, outer-sphere (OS) complexes are the dominant cation species located at the center of the tunnel. However, K+ and Cs+ form only IS complexes regardless of the tunnel hydration state. Optimum water contents were determined based on the free energy changes associated with water intercalation into the tunnel cavities calculated as a function of water content for two heterocationic todorokite models: Mg0.5Na0.4Ca0.1Mn6O12·nH2O (Mg/Mn = 0.08, average Mn oxidation state = +3.73) and Mg1.1K0.1Ca0.1Mn6O12·nH2O (Mg/Mn = 0.18, average Mn oxidation state = +3.58). These models emulate the chemical compositions of well-characterized terrestrial and marine todorokite samples, respectively. At each optimum water content, MD simulations revealed that OS complexes are the major Mg2+ species in the former model. However, IS complexes are the major Mg2+ species in the latter model, indicating that the tunnel cation speciation of diagenetic todorokite can be influenced by the sediment pore-fluid chemistry. The atomic tunnel cation and water structures of todorokite provide a molecular basis for understanding of metal partitioning to Mn oxides and interpretation of metal stable isotopes recorded in ferromanganese nodules.

An Improved Humidity Sensor with GO-Mn-Doped ZnO Nanocomposite and Dimensional Orchestration of Comb Electrode for Effective Bulk Manufacturing.

The measurement and control of humidity is a major challenge that affects the sensing properties of sensors used in high-precision equipment manufacturing industries. Graphene Oxide(GO)-based materials have been extensively explored in humidity sensing applications because of their high surface area and functional groups. However, there is a lack of effective bulk-manufacturing processes for the synthesis of 2D-based nanocomposites with comb electrodes. Moreover, water intercalation within the layers of 2D materials increases recovery time. This work demonstrates the enhanced sensing characteristics of a capacitive/resistive GO-MnZnO nanocomposite humidity sensor produced using a cost-effective single-pot synthesis process. The in-plane sensing layer consistently improves sensitivity and reduces response time for a wide range of relative humidity measurements (10% to 90%). Interdigitated gold electrodes with varying numbers of fingers and spacing were fabricated using photolithography on a Si/SiO₂ for a consistent sensor device platform. The choice of nanomaterials, dimension of the sensor, and fabrication method influence the performance of the humidity sensor in a controlled environment. GO nanocomposites show significant improvement in response time (82.67 times greater at 40% RH) and sensitivity (95.7 times more at 60% RH). The response time of 4.5 s and recovery time of 21 s was significantly better for a wider range of relative humidity compared to the reduced GO-sensing layer and ZnMnO. An optimized 6 mm × 3 mm dimension sensor with a 28-fingers comb was fabricated with a metal-etching process. This is one of the most effective methods for bulk manufacturing. The performance of the sensing layer is comparable to established sensing nanomaterials that are currently used in humidity sensors, and hence can be extended for optimal bulk manufacturing with minimum electrochemical treatments.

Excellently balanced water-intercalation-type heat-storage oxide

Importance of heat storage materials has recently been increasing. Although various types of heat storage materials have been reported to date, there are few well-balanced energy storage materials in terms of long lifetime, reversibility, energy density, reasonably fast charge/discharge capability, and treatability. Here we report an interesting discovery that a commonly known substance, birnessite-type layered manganese dioxide with crystal water (δ-type K0.33MnO2 ⋅ nH2O), exhibits a water-intercalation mechanism and can be an excellently balanced heat storage material, from the above views, that can be operated in a solid state with water as a working pair. The volumetric energy density exceeds 1000 MJ m−3 (at n ~ 0.5), which is close to the ideally maximum value and the best among phase-change materials. The driving force for the water intercalation is also validated by the ab initio calculations. The proposed mechanism would provide an optimal solution for a heat-storage strategy towards low-grade waste-heat applications.

Selenous Acid in an Aromatic Framework: Insights Into a Temperature-Sensitive Internal Redox System from the Solid State.

We report on a new compound composed of a phenanthroline network in which emerging channels are alternately occupied by selenous acid (H2SeO3) and dioxane molecules. The material undergoes a variety of structural changes due to both its redox activity as well as its thermal decomposition. We investigate an internal redox system of the incorporated selenous acid and the aldehyde groups of the phenanthroline framework. The reduction process of the selenium species was further elucidated by cyclic voltammetry, while the oxidation process was also monitored by 1H NMR spectra. The thermal behavior reveals that the material can undergo a reversible, topotactic transition due to dioxane and water (de)intercalation.

An evolution of the charge carriers’ subsystem in YBa2Cu3O y single crystals upon annealing in water vapour

ABSTRACT In the present work, we have studied the influence of low-temperature annealing in water vapour on a system of charge carriers by measuring the reflectivity spectra for YBa2Cu3O y single crystals with low and high oxygen content (y = 6.2 and y = 6.9). It has been shown that lattice parameter c and charge carrier parameters of the YBa2Cu3O6.9 sample remain unchanged upon hydration at 200°C. An intercalation of water in the form of О2- and Н+ ions results only in weakening the electron–hole coupling and decrease in the number of excitons. Unlike YBa2Cu3O6.9, the crystal structure of YBa2Cu3O6.2 has more defects, which appear as a result of hydration and an incorporation of OH-groups, which is evidenced by a pronounced change in the parameter c. As a consequence, charge carriers became more localised.

Dynamics of Two Distinct Exciton Populations in Methyl-Functionalized Germanane.

Methyl-substituted germanane is an emerging material that has been proposed for novel applications in optoelectronics, photoelectrocatalysis, and biosensors. It is a two-dimensional semiconductor with a strong above-gap fluorescence associated with water intercalation. Here, we use time-resolved photoluminescence spectroscopy to understand the mechanism causing this fluorescence. We show that it originates from two distinct exciton populations. Both populations recombine exponentially, accompanied by the thermally activated transfer of exciton population from the shorter- to the longer-lived type. The two exciton populations involve different electronic levels and couple to different phonons. The longer-lived type of exciton migrates within the disordered energy landscape of localized recombination centers. These outcomes shed light on the fundamental optical and electronic properties of functionalized germanane, enabling the groundwork for future applications in optoelectronics, light harvesting, and sensing.

Tuning the photocatalytic activity of layered perovskite niobates by controlled ion exchange and hydration

Decoupling water intercalation and proton exchange, the photocatalytic activity of proton exchanged KCa2Nb3O10 and KSr2Nb3O10 can be revealed and tailored.

Water intercalation strategy to fabricate low-potential and dense grapheme film anode for high energy density K-ion batteries

Carbon materials have appealing potential as anode for Potassium ion batteries (KIBs), but achieving low-potential plateau curve and high energy density for anode materials is a primary challenge. Herein, a 3D holey reduced graphene oxide/ carbon nanotubes (L-HRGO/CNT) film was constructed via chemical etching and low- temperature drying method. The micro/mesoporous in graphene oxide (GO) sheets are created by chemical etching, which shorts ion transfer distance, and thus increases the K+ intercalation/deintercalation rate. During low-temperature drying process, the water molecules inside the GO interlayer serve as self-sacrificial spacers for extending the stacked structure and maintaining integrity, increasing capacity contributed from K+ intercalation for a low discharge voltage. And the CNTs introduced into the film via vacuum co-filtration can enhance the conductivity and mechanical strength of the film. The optimized L-HRGO/CNT film delivered a high K+ storage capacity of 307.0 mA h g−1, high-rate capability, and the capacity retention reaches 72.6% at 200 mA g−1 for 200 cycles. When assembled with the KVPO4F cathode, the reversible capacity remains 93.8 mAh g−1 after 100 cycles, and 473.0 Wh kg−1(776.9 Wh L−1) of the energy density is achieved.

Mechanism of Actuation in Nickel Hydroxide/Oxyhydroxide Photoactuators

AbstractUnderstanding novel actuating materials which respond to a variety of stimuli is key in the development of micro/nanoscale robotics. In this work, the mechanism of actuation in nickel hydroxide/oxyhydroxide actuators by the intercalation/deintercalation of water is examined. This effect is studied under the stimuli of visible light, photoactuation, and by increased environmental temperature, thermoactuation. The photoactuation is modelled using a mechanical model, and it is demonstrated that the experimentally observed intrinsic strain can be achieved with a low deintercalation of water, around 1%. This low level of water exchange is supported by structural changes observed during heating using thin film X‐ray diffraction (XRD), as well as time of flight secondary ion mass spectrometry (ToF‐SIMS) by isotopic exchange using D2O. These results show the water intercalation hypothesis is both possible and measurable. Future development must take this mechanism into account when designing materials for improved actuation performance.