Layered Hydroxides Research Articles

Sonochemical synthesis, characterization and investigation of the electrochemical hydrogen storage properties of Ho3Fe5O12/Mg2Al(OH)7 nanocomposites

It has been noted that hydrogen has attracted extensive consideration in the field of new energy, resulting in a wide range of studies concerning hydrogen production, storage, and use. As part of this research, mixed metal oxide materials with double layer hydroxides are primarily studied for their hydrogen storage capacity. In terms of hydrogen storage capacity, the sonochemically synthesized Ho3Fe5O12/Mg2Al(OH)7 nanocomposites (HF/MgAl(OH)) with different ratios of Ho3Fe5O12 to Mg2Al(OH)7 were compared with pristine LDH of Mg2Al(OH)7. It has been demonstrated that the capacity of Ho3Fe5O12/Mg2Al(OH)7 nanocomposites (422 mAhg−1) with a 1:1 ratio of Ho3Fe5O12 to Mg2Al(OH)7 is significantly higher than pristine LDH (213 mAhg−1).

Effect of Surface Strain to Hydroxide Layer Formation on High-Pressure Die Casting Magnesium Alloy

Magnesium hydroxide layer improve corrosion resistance of magnesium alloys. Nonuniform strain on magnesium alloys surface was reported that affected to layer formation and corrosion resistance properties. Hydroxide layer formed to high pressure die cast ASTM AZ91D magnesium alloy, then investigated to correlation between hydroxide layer formation and residual stress and strain distribution on alloy surface which were measured by X-ray. Strain distribution was evaluated by full width half maximum (FWHM) value. Formed hydroxide layer was well compatible with FWHM distribution in as cast specimen. Heat treated for homogenization was carried out to inspection for correlation FWHM. FWHM was significantly lowering by heat treatment. Hydroxide layer tends to thin where FWHM value was low, therefore correlation between nonuniform strain and hydroxide layer formation was found out.

СОРБЦИОННАЯ СПОСОБНОСТЬ СЛОИСТЫХ ДВОЙНЫХ ГИДРОКСИДОВ Mg-Al ПО ОТНОШЕНИЮ К ИОНАМ Co (II), Cu (II), Sr (II) и Cs (I)

Mg-Al layered double hydroxides with a hydrotalcite structure have been synthesized. The sorption properties of the synthesized sample with respect to non-ferrous metal ions — Co2+, Cu2+, Sr2+ and Cs+ are investigated. The capacities of the adsorption monolayer of the Mg-Al layered hydroxide sample were calculated, amounting to 2.13, 2.21, 1.88 and 3.48 mmol/g with respect to Co(II), Cu(II), Sr(II) and Cs(I) ions, respectively. It is shown that the sorption process is described by a pseudo-second-order kinetic model and proceeds in a mixed diffusion mode.

Effect of surface preparation by high-temperature hydrogen annealing on the passivation of Ni-20 at.% Cr alloy in sulfuric acid

The effect of high-temperature annealing under hydrogen gas (H2) surface preparation on a binary polycrystalline Ni-20 at.% Cr alloy was investigated in comparison with conventional mechanical grinding surface preparation. Duplex surface films with inner Cr(III) oxide and outer Ni(II) and Cr(III) hydroxide layers natively formed before and after H2 annealing were characterized by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. A thinner and less homogeneous inner barrier layer formed after H2 annealing caused an oxidation peak at the active/passive transition in the linear sweep voltammetry measurement in a 0.5 M H2SO4 solution. Despite this high oxidation peak, passivation of the H2 annealed surface resulted in the formation of a more corrosion resistant inner layer than on the mechanically ground surface, as demonstrated by electrochemical impedance spectroscopy. The corrosion resistant passive film formation of the H2 annealed surface is attributed to the increased Cr enrichment of the inner layer caused by the selective Ni dissolution providing corrosion resistance to the initially weakly protected sites of the natively formed surface film.

Hierarchically arranged γ-NiOOH/β-FeOOH layer supported on modified Molybdenum-BiVO4 thin film for oxygen evolution reaction

Due to the slow kinetics of water oxidation, severe surface charge recombination is a significant energy loss that impedes efficient photoelectrochemical performance. Constructing a scheelite bismuth vanadate (BiVO4) electrode with an oxygen evolution catalyst and doping is an effective way to increase the performance of water oxidation. Importantly, this attempt avoids any sacrificial agents and binders. Using a single-step hydrothermal-based method, a nickel-iron (oxy)hydroxide is deposited unlike conventional two-step photoelectrodeposition method onto the surface of BiVO4 doped with 2% molybdenum dopant. Through this method, the as-formed nickel-iron (oxy)hydroxide is in γ-NiOOH and β-FeOOH forms. The difficulty of transporting charge carriers-hole pairs along the BiVO4 is reduced by incorporating molybdenum. A low-cost but efficient co-catalyst, nickel-iron (oxy)hydroxide is introduced to surpass the charge recombination on BiVO4. A comparison of photocurrent density-voltage and photocurrent density-time curves with and without an oxygen evolution catalyst reveals that nickel-iron (oxy)hydroxide accelerates the anodic photocurrent of the BiVO4 from ∼1 to 5 mA cm−2 (1.23 V vs. RHE). Simultaneously, the molybdenum-doped BiVO4 layer with a small band gap and extremely good photoelectrostability and the (oxy)hydroxide layer with good conductivity provide synergetic enhancement of both stability over 12 hours and photocurrent density.

Fabrication of Layered Hydroxide Composite with Polydimethylsiloxane Hydroxy-Terminated for Epoxy Resin Flame Retardancy

Fabrication of Layered Hydroxide Composite with Polydimethylsiloxane Hydroxy-Terminated for Epoxy Resin Flame Retardancy

Room-temperature in situ fabrication of ultrathin undulating layered hydroxide salt membranes for efficient H2/CO2 separation

Two-dimensional (2D) materials have demonstrated their superiorities as molecular sieve membranes for strategic gas separations. The promotion of these 2D membranes is confronted with great challenges such as elaborate fabrication procedures and expensive raw materials. Layered hydroxide salts (LHSs) are a kind of lamellar material involving economical ingredients and are quite easy-to-fabricate. However, they have yet to be developed into gas separation membranes and their separation potential has not been investigated, despite their merits. Here, we report the successful fabrication of ultrathin Zn5(OH)8(NO3)2·2H2O membranes by using a rapid and facile in situ growth strategy at room temperature. By virtue of the few-layered membrane thickness, the obtained membranes exhibited intriguing surface undulations, which endowed the membranes with extremely tortuous interlayer channels and therefore an auspicious molecular sieving ability. Consequently, these membranes showed an optimal H2/CO2 mixture separation selectivity of 792 ± 38 and a remarkable H2 permeance of 1607 ± 99 GPU. Moreover, with a demonstration of a gentle framework dehydration, the molecular sieving capacity of the LHS membrane was further sharpened at 150 °C owing to the narrowed interlayer channels. This work introduced a low-cost 2D membrane and manifested the advantages of fabricating few-layered 2D membranes, opening a new avenue for membrane future scale-up.

Synergistic effects between acidity and the crystalline phases of thermally activated layered Zn hydroxide nitrate on the methanolysis of acidic soybean oils

Layered hydroxyl salts (LHS) is a promising catalyst in the field of methanolysis (transesterification and esterification reactions) of oil feedstocks. The catalytic activity of the catalyst can be enhanced with heat treatment. The present study investigated the relationship between thermal stability of the layered Zn hydroxide nitrate (ZHN), their acid-base properties, and the catalytic conversion of oil feedstocks to methyl ester. The solid, predominantly acidic catalyst was prepared at various temperatures (70–170 °C) and tested for the acidic/basic properties using the Hammett indicators and titration method followed by functional group analysis using FTIR, crystallization using X-ray diffraction, and surface morphology using SEM. The combination of various characterization techniques gave an insight into the changes in the phases of the layered Zn hydroxide nitrate catalysts upon thermal treatment. Major phase changes occurred at temperatures somewhat above 80, and 140 °C. The catalysts were extensively studied to understand the underlying effects on the FAME yields obtained from catalytic conversion of oleic acid spiked soy bean oil (a model of an acidic oil feedstock) into methyl esters. The results of the optimization reactions reaffirmed the effect of the phase changes when the highest FAME yield was observed from two activated samples namely, Zn5_80 and Zn5_140. The optimized reactions condition of catalytic conversion of SO containing 10% OA at 5 °C/min heating rate, 3 wt % catalyst concentration, 30:1 methanol to oil molar ratio, reaction time of 100 °C for 2 h gave 92% FAME yield when Zn5_140 was used as the catalyst. The detected of the single phase of Zn5(OH)8(NO3)2 in Zn5_80, Zn5(OH)8(NO3)2 and ZnO in Zn5_140 (2-phase system), including Zn5(OH)8(NO3)2, Zn3(OH)4(NO3)2, and ZnO in Zn5_170 (3-phase system), suggested all three phases contributes to the high catalytic activity in methanolysis of the acidic oils. Both Zn5_140 and Zn5_170 gave a comparably high FAME yields based on statistical analyses. This study ascertained the synergistic effects of the high acidity (>0.4 mmol/g) and the dominant active phases of the thermally treated layered Zn hydroxide nitrate on the high catalytic activity that favours esterification of acidic oil feedstocks.

Metal Oxide Coating On Biodegradable Magnesium Alloys

Magnesium is a biodegradable metal that has potential in orthopaedics. It has several advantages over other metallic materials because it is biocompatible and degradable now being used for biomedical applications, including elimination of stress shielding effects, enhancing degradation properties and enhancing biocompatibility concern in vivo, eliminating the second surgery for implant removal. Bioabsorbable magnesium (Mg) and related alloys have been limited in their usage because of its lower corrosion resistance. Surface alteration and functionality, in addition to basic alloying, is an important technique to deal with Mg and its alloys' reduced corrosion resistance. Magnesium's rapid depreciation however is a double-edged sword because it's critical to match bone renewal to material corrosion. As a result, calcium phosphate coatings have been proposed as a way to slow down corrosion. There are various possible calcium phosphate phases and their coating methods and can give a few distinct properties to various applications. Despite magnesium's lower melting point and greater reactivity, calcium phosphate coatings require precise settings to be effective. Because of their toxicity, non-biodegradability, and much higher cost, the recently used inorganic conversion coatings are less appealing and their application is limited. Conversion coatings are a viable alternative technology that is based on a cost- effective, environmentally friendly, and biodegradable organic component. Surface chelating functional groups in these compounds allow them to link with the magnesium/surface hydroxide layer while also providing anchoring groups for the polymer topcoat. Nanoreservoirs with multilayer inhibitors for active self-healing corrosion resistance thrive in this environment. This study examines the organic conversion coatings for Mg and its alloys in depth.

In Ukrainian

In this paper it is discussed the colloidal-chemical method of synthesis of dispersed composite bentonite-ferromagnetic powders that are stable to oxidation. It is shown that for this purpose it is advisable to use acid-activated bentonite clay with a high content of clay mineral - montmorillonite. Modified bentonite is a slightly amorphized silica product that serves as a porous matrix for crystallization of goethite α-FeOOH. The formation of goethite occurs at the centers of crystallization - particles of ferrihydrite stabilized by activated bentonite (Fh) during precipitation with an ammonia solution from a ferrum(ІІІ) hydroxide FeO(OH)×nH2O colloidal solution. In the resulting composite, goethite particles are cemented in the aluminosilicate framework of activated dispersed clay as a result of the interpenetration of the structures of the double layered hydroxide and activated bentonite. Further recrystallization of goethite with the formation of mainly magnetite and possibly maghemite in the structure of activated bentonite is provided by thermal firing of composite goethite powder with the addition of metallic iron powder. The methods of IR spectroscopy, X-ray structural analysis, electron microscopy and the study of magnetic properties showed that the obtained composite powder is environmentally friendly and exhibits the properties of a soft magnetic material. Such powders are promising for use as sorbents for environmental cleaning, as well as for biomedical purposes due to their low toxicity and high value of saturation magnetization.

Air exposure improving hydrogen desorption behavior of Mg–Ni-based hydrides

It is well established that H2O and O2 have an inauspicious influence on hydrogen reactivity of hydrogen storage alloys. In this work, an unexpected improvement of the desorption behavior was discovered by just exposing the magnesium rich Mg–Ni hydrides into the air for a certain period. Upon an exposure duration of 4 months, the dehydrogenation peak and onset temperature were sharply lowered by 150 °C and 130 °C. Furthermore, the air-exposed sample could quickly absorb 3.08 wt% H2 and desorb 2.81 wt% H2 within 400 s at 300 °C. Besides the refinement of the powders due to the spontaneous hydrolysis reaction, the in-situ formed magnesium hydroxide layer and Ni are thought to be responsible for the remarkable improvement. This work gives interesting insights that the self-generating surface passivation is not necessarily harmful in the solid-state hydrogen storage area, especially for the cases where active sites of catalysis are present.

Rational Synthesis of Core-Shell-Structured Nickel Sulfide-Based Nanostructures for Efficient Seawater Electrolysis.

Versatile electrocatalysis at higher current densities for natural seawater splitting to produce hydrogen demands active and robust catalysts to overcome the severe chloride corrosion, competing chlorine evolution, and catalyst poisoning. Hereto, the core-shell-structured heterostructures composed of amorphous NiFe hydroxide layer capped Ni3 S2 nanopyramids which are directly grown on nickel foam skeleton (NiS@LDH/NF) are rationally prepared to regulate cooperatively electronic structure and mass transport for boosting oxygen evolution reaction (OER) performance at larger current densities. The prepared NiS@LDH/NF delivers the anodic current density of 1000mA cm-2 at the overpotential of 341mV in 1.0m KOH seawater. The feasible surface reconstruction of Ni3 S2 -FeNi LDH interfaces improves the chemical stability and corrosion resistance, ensuring the robust electrocatalytic activity in seawater electrolytes for continuous and stable oxygen evolution without any hypochlorite production. Meanwhile, the designed Ni3 S2 nanopyramids coated with FeNi2 P layer (NiS@FeNiP/NF) still exhibit the improved hydrogen evolution reaction (HER) activity in 1.0m KOH seawater. Furthermore, the NiS@FeNiP/NF||NiS@LDH/NF pair requires cell voltage of 1.636V to attain 100mA cm-2 with a 100% Faradaic efficiency, exhibiting tremendous potential for hydrogen production from seawater.

Investigating the evolution of surface physico-chemistry in arsenide minerals during flotation process: A study of skutterudite, gersdorffite, and nickeline

Skutterudite ((Co,Ni,Fe)As3), gersdorffite (NiAsS), and nickeline (NiAs) are some common arsenic- and nickel-bearing minerals often encountered worldwide in mine ores and mine wastes. These arsenides can be the source of arsenic- and nickel-contaminated neutral drainage (CND) when subjected to atmospheric conditions. Environmental desulphurization by froth flotation is a promising technique used to prevent this contamination. This study fills a knowledge gap in the evolution of the surface physicochemistry of these arsenides under different conditions, in order to determine the best conditions for flotation and successful environmental desulfurization. This work evaluates the impact of grinding, air-oxidation (aging), and conditioning on the mineral surfaces, as well as their interaction with potassium amyl xanthate (PAX) as a flotation collector. The effect of activation by copper sulphate (CuSO4) was also examined. The adsorption of PAX was analyzed by ultraviolet–visible (UV–Vis) spectrophotometry and zeta potential measurements, and the surface was characterized using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) allowing the speciation of the oxidation layer across the different mineral surfaces. Dry grinding and aging of the minerals produces thin heterogenous oxide and hydroxide layers that are mainly enriched in arsenic oxides, especially in the form of arsenate (as an oxidation product of arsenite), and arsenic, cobalt, and nickel sulphates and hydroxides. Arsenides conditioning under alkaline conditions enhances the oxidation effect on the mineral surfaces compared to natural conditions. Copper sulfate activation was found to be effective on the arsenides and improves the adsorption of xanthate on the oxidized arsenide surfaces, especially under alkaline conditions. The results of this study provide a better understanding of the surface chemistry of these minerals before and after collector adsorption, which should impact their flotation behavior.

The Emerging Layered Hydroxide Plates with Record Thickness for Enhanced High-Mass-Loading Energy Storage.

The past decade has witnessed the development of layered-hydroxide-based self-supporting electrodes, but the low active mass ratio impedes its all-around energy-storage applications. Herein, the intrinsic limit of layered hydroxides is broken by engineering F-substituted β-Ni(OH)2 (Ni-F-OH) plates with a sub-micrometer thickness (over 700nm), producing a superhigh mass loading of 29.8mg cm-2 on the carbon substrate. Theoretical calculation and X-ray absorption spectroscopy analysis demonstrate that Ni-F-OH shares the β-Ni(OH)2 -like structure with slightly tuned lattice parameters. More interestingly, the synergy modulation of NH4 + and F- is found to serve as the key enabler to tailor these sub-micrometer-thickness 2D plates thanks to the modification effects on the (001) plane surface energy and local OH- concentration. Guided by this mechanism, the superstructures of bimetallic hydroxides and their derivatives are further developed, revealing they are a versatile family with great promise. The tailored ultrathick phosphide superstructure achieves a superhigh specific capacity of 7144 mC cm-2 and a superior rate capability (79% at 50mA cm-2 ). This work highlights a multiscale understanding of how exceptional structure modulation happens in low-dimensional layered materials. The as-built unique methodology and mechanisms will boost the development of advanced materials to better meet future energy demands.

A Thermodynamic Model for the Insertion Electrochemistry of Battery Cathodes

AbstractInvited for this issue's Front Cover is the group of Prof. Dr. Uwe Schröder. The cover picture shows a crystal layer of nickel hydroxide that undergoes phase separation during electrochemical ion deinsertion (oxidation) and the corresponding modelled cyclic voltammogram. Read the full text of the Research Article at 10.1002/celc.202201118.

Construction of superhydrophobic ZIF-90/Melamine sponge with highly stable puncture structure for sustainable oil spill removal from seawater

Sustainable, environmentally friendly and economically viable treatment of marine oil spills attracts a great attention. For the first time, composites with highly durable structure were prepared for continuous oil/water separation by in situ growth of zeolitic imidazole framework ZIF-90 on a porous melamine sponge (MS). First, a thin layer of metal hydroxide (Zn-LDH) was introduced on the inner wall of MS and ZIF-90 particles were loaded onto the sponge fibers by homologous induction to obtain the ZIF-90/MS composite. The thin Zn-LDH layer greatly enhanced the anchoring force of ZIF-90 on the MS skeleton to effectively avoid the crystals from piling up together. The resulting ZIF-90/MS was modified in situ with octadecylamine (ODA) to give a superhydrophobic ODA-ZIF-90/MS composite with a water contact angle (WCA) of 154o, which demonstrated great oil adsorption capacity (24–63 g/g) and excellent recoverability (98.7% absorption retention after 50 cycles). With the assistance of a pump drive, continuous separation of oil spill contaminants from actual seawater can be achieved with fluxes of 13839 g. h−1. g−1 and 13513 g. h−1. g−1 for hexane and gasoline, respectively, without any water adsorption. The highly durable ODA-ZIF-90/MS composite with puncture structure showed excellent cycling performance in oil/water separation with less than 1% ODA-ZIF-90 spillage after 50 squeeze desorption cycles. This novel integrated ODA-ZIF-90/MS composite demonstrates a promising strategy for large-scale of oil spill cleanup.

Front Cover: A Thermodynamic Model for the Insertion Electrochemistry of Battery Cathodes (ChemElectroChem 7/2023)

The Front Cover illustrates a crystal layer of nickel hydroxide that undergoes phase separation during electrochemical ion deinsertion (oxidation) and its corresponding cyclic voltammogram (CV). This phase separation phenomenon is revealed by a thermodynamic modelling of solid-solution and phase-separation reaction modes in battery cathodes. Furthermore, according to this model, the hysteresis observed during charge-discharge in the CV curves results from this phase separation which itself is a consequence of large radius changes in the crystal's central metal ion. More information can be found in the Research Article by K. Malaie, F. Scholz and U. Schröder.

Modeling of artificial neural networks for the adsorption of synthetic dyes in an aqueous solution using double layer hydroxides

Modeling of artificial neural networks for the adsorption of synthetic dyes in an aqueous solution using double layer hydroxides

Development of Dipeptide N-acetyl-L-cysteine Loaded Nanostructured Carriers Based on Inorganic Layered Hydroxides.

N-acetyl-L-cysteine (NAC), a derivative of the L-cysteine amino acid, presents antioxidant and mucolytic properties of pharmaceutical interest. This work reports the preparation of organic-inorganic nanophases aiming for the development of drug delivery systems based on NAC intercalation into layered double hydroxides (LDH) of zinc-aluminum (Zn2Al-NAC) and magnesium-aluminum (Mg2Al-NAC) compositions. A detailed characterization of the synthesized hybrid materials was performed, including X-ray diffraction (XRD) and pair distribution function (PDF) analysis, infrared and Raman spectroscopies, solid-state 13carbon and 27aluminum nuclear magnetic resonance (NMR), simultaneous thermogravimetric and differential scanning calorimetry coupled to mass spectrometry (TG/DSC-MS), scanning electron microscopy (SEM), and elemental chemical analysis to assess both chemical composition and structure of the samples. The experimental conditions allowed to isolate Zn2Al-NAC nanomaterial with good crystallinity and a loading capacity of 27.3 (m/m)%. On the other hand, NAC intercalation was not successful into Mg2Al-LDH, being oxidized instead. In vitro drug delivery kinetic studies were performed using cylindrical tablets of Zn2Al-NAC in a simulated physiological solution (extracellular matrix) to investigate the release profile. After 96 h, the tablet was analyzed by micro-Raman spectroscopy. NAC was replaced by anions such as hydrogen phosphate by a slow diffusion-controlled ion exchange process. Zn2Al-NAC fulfil basic requirements to be employed as a drug delivery system with a defined microscopic structure, appreciable loading capacity, and allowing a controlled release of NAC.

Micro/nano‐wrinkled elastomeric electrodes enabling high energy storage performance and various form factors

AbstractStretchable elastomer‐based electrodes are considered promising energy storage electrodes for next‐generation wearable/flexible electronics requiring various shape designs. However, these elastomeric electrodes suffer from the limited electrical conductivity of current collectors, low charge storage capacities, poor interfacial interactions between elastomers and conductive/active materials, and lack of shape controllability. In this study, we report hierarchically micro/nano‐wrinkle‐structured elastomeric electrodes with notably high energy storage performance and good mechanical/electrochemical stabilities, simultaneously allowing various form factors. For this study, a swelling/deswelling‐involved metal nanoparticle (NP) assembly is first performed on thiol‐functionalized polydimethylsiloxane (PDMS) elastomers, generating a micro‐wrinkled structure and a conductive seed layer for subsequent electrodeposition. After the assembly of metal NPs, the conformal electrodeposition of Ni and NiCo layered double hydroxides layers with a homogeneous nanostructure on the micro‐wrinkled PDMS induces the formation of a micro/nano‐wrinkled surface morphology with a large active surface area and high electrical conductivity. Based on this unique approach, the formed elastomeric electrodes show higher areal capacity and superior rate capability than conventional elastomeric electrodes while maintaining their electrical/electrochemical properties under external mechanical deformation. This notable mechanical/electrochemical performance can be further enhanced by using spiral‐structured PDMS (stretchability of ~500%) and porous‐structured PDMS (areal capacity of ~280 μAh cm−2).