Layered Double Hydroxides Research Articles

Preparation and Physicochemical Characterization of Layered Double Hydroxide MgAl‐LDHs/Celecoxib Hybrid Material

Preparation and Physicochemical Characterization of Layered Double Hydroxide MgAl‐LDHs/Celecoxib Hybrid Material

Improving the Oxygen Evolution Reaction Performance of Ternary Layered Double Hydroxides by Tuning All Three Cations’ Electronic Structures

Improving the Oxygen Evolution Reaction Performance of Ternary Layered Double Hydroxides by Tuning All Three Cations’ Electronic Structures

Fabrication and Modification of Hydrotalcite-BasedPhotocatalystsand TheirCompositesfor CO 2 Reduction: A Critical Review.

Layered double hydroxides(LDHs), whichresemble hydrotalcite, are a type ofmaterials withcationic layers and exchangeable interlayer anions. Theyhave drawn lots of curiosity as a high-temperature CO2adsorbentbecause of its quick desorption/sorption kinetics andrenewability.Due to its extensive divalent or trivalent cationic metals,high anion exchange property, memory effect, adjustable behavior, bio-friendliness, easy to prepareand relatively low cost, the LDHs-based materials are becoming increasingly popular for photocatalytic CO2reduction reaction (CO2RR). Fabricationand modificationaregood waysto move forward the advancement of LDHs-based catalysts, which will help chemistry and materials science makegreat progress.In this review we discussed structural characteristics and the methods for preparation and modification of LDHs-based photocatalysts.We also highlighted and discussed the major developments andapplications in photocatalytic CO2RR as well asthe photocatalytic mechanism. The goal of the present review is to give a broad summary of the various LDHs-basedphotocatalystsand the correspondingdesign strategies, which could motivate more excellent research works to explore this kind of CO2RR photocatalysts to further increase CO2conversion yield and selectivity.

ZnFe Layered Double Hydroxide Nanosheets Loaded with Cu Single-Atom Nanozymes with Multi-Enzyme-Like Catalytic Activities as an Effective Treatment for Bacterial Keratitis.

Bacterial keratitis (BK) is a type of corneal inflammation resulting from bacterial infection in the eye. Although nanozymes have been explored as promising materials in corneal wound healing, currently available nanozymes lack sufficient catalytic activity and the ability to penetrate bacterial biofilms, limiting their efficacy against the treatment of BK. To remedy this, ZnFe layered double hydroxide (ZnFe-LDH) nanosheets are loaded with Cu single-atom nanozymes (Cu-SAzymes) and aminated dextran (Dex-NH2), resulting in the formation of the nanozyme DT-ZnFe-LDH@Cu, which possesses peroxidase (POD)-, oxidase (OXD)-, and catalase (CAT)-like catalytic activities. This enables the nanozyme to generate reactive oxygen species (ROS), such as hydroxyl radicals (•OH), superoxide anion radical (O2 •-), and singlet oxygen (1O2) from hydrogen peroxide (H2O2), thereby killing the bacteria causing the infections. The surface Dex-NH2 enabled the DT-ZnFe-LDH@Cu to penetrate the biofilm and adsorb onto extracellular polymeric substances (EPS) produced by bacteria in the biofilm. Additionally, the DT-ZnFe-LDH@Cu successfully repaired P. aeruginosa-infected corneal injury in a BK rabbit model more effectively than commercially available tobramycin eye drops. This was enabled, in part, by the ability of DT-ZnFe-LDH@Cu to reduce inflammation by promoting the polarization of pro-inflammatory macrophages (M1) to anti-inflammatory macrophages (M2) and decrease the expression of α-smooth muscle actin (α-SMA) to promote wound healing without scar formation. This study provides an innovative concept for the treatment of BK and holds great scientific value and clinical application potential.

Comparative study of Mg/Al-LDH and Mg/Fe-LDH on adsorption and loss control of 2,4-dichlorophenoxyacetic acid

Low efficiency and high surface runoff of 2,4-dichlorophenoxyacetic acid (2,4-D) from agricultural field threaten crop yield severely. Layered double hydroxides (LDH) have shown promising adsorption properties for 2,4-D. However, the comparison of two environmentally friendly LDHs (i.e. Mg/Al-LDH vs Mg/Fe-LDH) on adsorption of 2,4-D and corresponding intrinsic mechanisms are still unclear, and the studies on the leaching control of 2,4-D by LDHs in soil environment are particularly limited. In this study, Mg/Al-LDH and Mg/Fe-LDH were selected to conduct their adsorption kinetics experiment for 2,4-D combined with the characterization technology. The results showed that the adsorption capacity of Mg/Al-LDH and Mg/Fe-LDH for 2,4-D was up to 242 mg kg−1 and 64 mg kg−1, respectively, which were negatively correlated with pH. Adsorption mechanisms of both Mg/Al-LDH and Mg/Fe-LDH for 2,4-D are dominated by chemical adsorption, including electrostatic attraction and inner sphere complexation, but no interlayer adsorption mechanism. Mg/Al-LDH contains smaller metal ion radius, which provides greater surface charge density, resulting in greater electrostatic attraction and inner sphere complexation to 2,4-D compared to Mg/Fe-LDH. The greater adsorption capacity of Mg/Al-LDH for 2,4-D was driven by the higher adsorption energy (Eads) and lower electron density, as corroborated by density functional theory (DFT) calculation. The soil column experiment further verified that Mg/Al-LDH could control the loss of 2,4-D more effectively, and the leaching amount could be significantly reduced by 61.7%, while the effect of Mg/Fe-LDH was only 24.2%. This study provides theoretical guidance for screening more potential LDH types to solve the leaching loss of 2,4-D from soil and improve its effectiveness in agricultural production.Graphical

Hierarchical MoS2@NiFeCo-Mo(doped)-Layered Double Hydroxide Heterostructures as Efficient Alkaline Water Splitting (Photo)Electro-catalysts.

Designing cost-effective electrocatalysts with fast reaction kinetics and high stability is an outstanding challenge in green hydrogen generation through overall water splitting (OWS). Layered double hydroxide (LDH) heterostructure materials are promising candidates to catalyze both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), the two OWS half-cell reactions. This work develops a facile hydrothermal route to synthesiz hierarchical heterostructure MoS2@NiFeCo-LDH and MoS2@NiFeCo-Mo(doped)-LDH electrocatalysts, which exhibit extremely good OER and HER performance as witnessed by their low IR-corrected overpotentials of 156 and 61 mV with at a current density of 10mA cm-2 under light assistance. The MoS2@NiFeCo-Mo(doped)-LDH-MoS2@NiFeCo-LDH OWS cell achieves a low cell voltage of 1.46V at 10mA cm-2 during light-assisted water electrolysis. Both materials exhibited exceptional stability under industrially relevant HER and OER conditions, maintaining a current density of 1A cm-2 with minimal alterations in their potential and performance. The experimental and computational results demonstrate that doping the LDH matrix with high-valence Mo atoms and MoS2 quantum dots improves the electrocatalytic activity by 1) enhancing electron transfer, 2) making the electrocatalyst metallic, 3) increasing the number of active sites, 4) lowering the thermodynamic overpotential, and 5) changing the OER mechanism. Overall, this work develops a facile synthesis method to design highly active and stable MoS2@NiFeCo-Mo(doped)-LDH heterostructureelectrocatalysts.

Design, Synthesis, Characterization and Catalytic Activity of Chromium Oxide Nanoparticles Immobilized on Layered Double Hydroxide as Competent Nanocatalyst

Design, Synthesis, Characterization and Catalytic Activity of Chromium Oxide Nanoparticles Immobilized on Layered Double Hydroxide as Competent Nanocatalyst

Functionalization of sawdust biochar using Mg-Fe-LDH and sodium dodecyl sulfonate enhanced its stability and immobilization capacity for Cd and Pb in contaminated water and soil

The increased contamination of potentially toxic element (PTE) has posed remarkable ecological risks to environment. Application of functionalized biochar for the remediation of PTE contaminated water and soils are of great concern, and effective strategies are urgently needed to enhance the removal capacity of biochar for PTE. As a novel surface modification technology, the effect of layered double hydroxides (LDH) and sodium dodecyl sulfonate (SDS) on the remediation capacity of biochar for PTE polluted soils and water remains unclear. Sawdust biochar (SB) was coated with Mg and Fe to synthesize the Mg-Fe-LDH functionalized biochar (MFB); thereafter, the MFB was mixed with SDS solution to synthesize the organic-Mg-Fe-LDH biochar (MSB). The potential of SB, MFB, and MSB for remediation of Cd and Pb contaminated soil and water was evaluated in terms of adsorption capacity, immobilization efficiency, and stability. Loading of Mg-Fe-LDH into SB, along with SDS treatment created a regular micro-nano hierarchical structure and enhanced the surface roughness, aromaticity, and hydrophobicity of MSB as compared to SB. MSB exhibited a significantly higher maximum adsorption capacity (mg g−1) for water Pb (405.2) and Cd (673.0) than MFB (335.9 for Pb and 209.0 for Cd) and SB (178.2 for Pb and 186.1 for Cd). MSB altered the soluble fraction of Cd/Pb to the residual fraction and thus significantly decreased their mobilization in soil. The higher removal/immobilization efficiency of MSB could be attributed to its alkalinity, and the enhanced synergistic interactions including surface precipitation, ion exchange, complexation, and hydrogen bonding. The resistance to carbon loss by H2O2, thermal recalcitrance index R50, and degree of graphitization in MSB were significantly improved compared to SB, indicating a more stable carbon fraction sequestered in MSB following aging in soil. These results indicate that MSB could be used for remediation of Cd and Pb contaminated soil and water.Graphical

Elaborate Designed Three-Dimensional Hierarchical Conductive MOF/LDH/CF Nanoarchitectures for Superior Capacitive Deionization.

Rational exploration of cost-effective, durable, and high-performance electrode materialsis imperative for advancing the progress of capacitive deionization (CDI). The integration of multicomponent layered double hydroxides (LDHs) with conjugated conductive metal-organic frameworks (c-MOFs) to fabricate bifunctional heterostructureelectrode materials is considered a promising strategy. Herein,the fabrication of hierarchical conductive MOF/LDH/CF nanoarchitectures (M-CAT/LDH/CF) as CDI anodes via a controllable grafted-growth strategyis reported.In this assembly, carbon fiber (CF) provides exceptional electrical conductivity facilitating rapid ion transfer and acts as a sturdy foundation for even distribution of NiCoCu-LDH nanosheets. Moreover, the well-ordered NiCoCu-LDH further acts as interior templates to create an interface by embedding c-MOFs and aligning two crystal lattice systems, facilitating the graft growth of c-MOFs/LDH heterostructures along the LDH nanosheet arrays on CF, leading to accelerated ion diffusion kinetics.Density functional theory (DFT) confirms enhanced interfacial charge transfer between NiCoCu-LDH and M-CAT, leading to improved ion transfer and smoother Cl- shuttle.Accordingly, the asymmetrical M-CAT/LDH/CFcell exhibits superior specific capacitance, salt adsorption capacity, rapid rate, and cyclic stability.This work offers valuable insights for designing heterostructure electrode materials based on three-dimensional interconnected networks, contributing to further advancements in CDI technology.

Effective treatment of thioantimonates-bearing waters by nanocrystalline iowaite, an iron-based layered double hydroxide.

Elevated concentrations of antimony (Sb) in the environment originating from natural and anthropogenic sources are of global concern due to their high toxicity and mobility. Notably, the formation of thioantimony species (e.g. tri- and tetra-thioantimonates) enhances Sb release into aquatic systems, and they may dominate Sb species in reducing environments, such as sulfidic geothermal waters. In this study, batch sorption experiments were conducted to investigate thioantimonates removal from aqueous solution by nanocrystalline iowaite, a sorbent suitable for incorporating hazardous anions but not used for treating thioantimonates-bearing waters up to now. Based on the fits of kinetics and isotherm sorption models as well as the structural comparison of iowaite before and after its reaction with thioantimonates-bearing solutions by use of XRD and XPS analyses, both the anion exchange between thioantimonates in solution and chloride in the interlayer regions of iowaite and the inner-sphere complexation of sorbed thioantimonates with iron atoms located in iowaite layers were found to be responsible for the efficient removal of aqueous thioantimonates by iowaite. Moreover, the presence of common anions (SO42-, Cl-, and NO3-) or Sb oxyanions (antimonite and antimonate) over a wide range of concentrations had little effect on thioantimonates sorption, whereas the addition of arsenic oxyanions (arsenite and arsenate) with high concentrations exhibited a clear inhibition of thioantimonates removal. Nevertheless, iowaite is still a strong scavenger of thioantimonates under environmentally relevant conditions and therefore holds promise for future large-scale treatment of geothermal waters, anoxic groundwaters, and mining wastewaters that are potentially rich in thioantimonates.

Highly efficient and rapid removal of Congo red dye from textile wastewater using facile synthesized Mg/Ni/Al layered double hydroxide

Layered double hydroxides (LDH) are compounds with unique structures of hydroxide functional groups on their surfaces, and they have the proper arrangement of divalent and trivalent cations to adjust their unique catalytic actions. LDH was synthesized utilizing the co-precipitation technique and was thermally treated at 300 °C. The prepared compounds were chemically and structurally elucidated using FT-IR, XRD, SEM, BET, TG-DTA, and XPS characterization. We found that the thermal treatment of the prepared magnesium/nickel-LDH resulted in dehydration and dehydroxylation in its chemical structure. The crystallinity, the surface area, and the pore volume of the formed meso- and micropores were improved considerably after the thermal treatment. The efficiency of the uptake process was increased from 84 to 97% after the thermal treatment process, and the adsorption process tracked the Freundlich adsorption isotherm and pseudo-second-order kinetic model. The kinetics indicated the occurrence of three stages, and the diffusion of dye molecules into the pores was the rate-determining step. Different real water sample treatments showed the applicability of the thermally treated Mg/Ni/Al-LDH in the treatment process under optimized conditions. The presented mechanism of the uptake process using the prepared compounds comprises several interactions between the dye molecules and the thermally treated Mg/Ni/Al-LDH. The study presented the new application for Mg/Ni/Al-LDH in the as-prepared and thermally treated forms to uptake Congo-red (CR) dye from textile effluents.

Time-resolved spectroscopy uncovers deprotonation-induced reconstruction in oxygen-evolution NiFe-based (oxy)hydroxides

Transition-metal layered double hydroxides are widely utilized as electrocatalysts for the oxygen evolution reaction (OER), undergoing dynamic transformation into active oxyhydroxides during electrochemical operation. Nonetheless, our understanding of the non-equilibrium structural changes that occur during this process remains limited. In this study, utilizing in situ energy-dispersive X-ray absorption spectroscopy and machine learning analysis, we reveal the occurrence of deprotonation and elucidate the role of incorporated iron in facilitating the transition from nickel-iron layered double hydroxide (NiFe LDH) into its active oxyhydroxide. Our findings demonstrate that iron substitution promotes deprotonation process within NiFe LDH, resulting in the preferential removal of protons from the specific bridged hydroxyl group (Ni2+-OH-Fe3+) linked to edge-sharing [NiO6] and [FeO6] octahedron. This deprotonation behavior drives the formation of high-valence Ni3+δ species (0 <δ < 1), which subsequently serve as the active sites, thereby ensuring efficient oxygen evolution activity. This approach offers high-resolution insights of dynamic structural evolution, overcoming the limitations of extended acquisition times and advancing our understanding of OER mechanisms.

Induction of Nanoscale Magnetic Ordering in Non-Ferrous Layered Double Hydroxides: Stabilizing Spintronic Electrocatalysis.

Inducing magnetic ordering in a non-ferrous layered double hydroxides (LDHs) instigates higher spin polarization, which leads to enhanced efficiency during oxygen evolution reaction (OER). In nano-sized magnetic materials, the concept of elongated grains drives domain alignment under the application of an external magnetic field. Hence, near the solid electrode interface, modified magnetohydrodynamics (MHD) positively impacts the electrocatalytic ability of non-ferrous nanocatalysts. Consequently, significant improvement in the water-splitting kinetics can be obtained by using even low magnetic fields. At 100 Gauss, 20% and 10% decrement in the overpotential is reported for OER and hydrogen evolution reaction (HER), respectively. Density functional theory (DFT) calculations are also presented to explain the thermodynamics of the HER/OER processes. It is established that the Gibbs energy of the process can reduce the exchange energy barrier by using dopant like cobalt. The additional cobalt metal active site have the highest probability for adsorption of reactive intermediates during HER and OER, which results in higher efficiencies.

Spray-Induced Gene Silencing (SIGS): Nanocarrier-Mediated dsRNA Delivery Improves RNAi Efficiency in the Management of Lettuce Gray Mold Caused by Botrytis cinerea

The plant pathogenic fungus Botrytis cinerea causes significant losses in agricultural production and it is rather difficult to control due to its broad host range and environmental persistence. The management of gray mold disease is still mainly based on the use of chemicals, which could have harmful effects not only due to impacts on the environment and human health, but also because they favor the development of fungicide-resistant strains. In this scenario, the strategy of RNA interference (RNAi) is being widely considered, and Spray-Induced Gene Silencing (SIGS) is gaining interest as a versatile, sustainable, effective, and environmentally friendly alternative to the use of chemicals in the protection of crops. The SIGS approach was evaluated to control B. cinerea infection on lettuce plants. In vitro-synthesized dsRNA molecules (BcBmp1-, BcBmp3-, and BcPls1-dsRNAs) were used naked, or complexed to small layered double hydroxide (sLDH) clay nanosheets. Therefore, treatments were applied by pressure spraying whole lettuce plants lately inoculated with B. cinerea. All sprayed dsRNAs proved effective in reducing disease symptoms with a notable reduction compared to controls. The effectiveness of SIGS in reducing disease caused by B. cinerea was high overall and increased significantly with the use of sLDH clay nanosheets. The sLDH clay nanosheet–dsRNA complexes showed better plant protection over time compared to the use of naked dsRNA and this was particularly evident at 27 days post-inoculation. RNAi-based biocontrol could be an excellent alternative to chemical fungicides, and several RNAi-based products are expected to be approved soon, although they will face several challenges before reaching the market.

Regulating Intermediate Adsorption and Promoting Charge Transfer of CoCr-LDHs by Ce Doping for Enhancing Electrooxidation of 5-Hydroxymethylfurfural.

Electrochemical oxidation of 5-hydroxymethylfurfural (HMFOR) to generate high-value chemicals under mild conditions acts as an energy-saving and sustainable strategy. However, it is still challenging to develop electrocatalysts with high efficiency and good durability. Here, nickel foam (NF) supported CoCrCe(7.5%)-LDH (layered double hydroxides) by doping Ce into CoCr-LDH show high 5-hydroxymethylfurfural (HMF)conversion (99%), 2,5-furandicarboxylic acid (FDCA) yield (99%), and Faraday efficiency (100%) at 1.4 VRHE. The CoCrCe(7.5%)-LDH also exhibits remarkable stability with 97% conversion of HMF after 10 cycles. The X-ray absorption near-edge spectroscopy (XANES) and theoretical calculation show that Ce doping into CoCr-LDH is beneficial to the formation of high-valance Co and significantly facilitates the electron transfer, regulates the adsorption behavior of intermediates, reduces the Gibbs free energy barrier and accelerates the reaction rate. This work promotes the use of rare earth elements as electrocatalysts to promote the oxidation of HMF.

Electrochemical Sensor Based on CoMgFe-Trimetallic Layered Double Hydroxides for Flubendiamide Detection in Water Samples

Abstract Flubendiamide (FBD) is a widely used insecticide in agriculture, known for its effectiveness in controlling crop pests. However, its use presents significant risks to both the environment and human health. In this study, a novel pencil graphite electrode (PGE) was successfully modified with CoMgFe trimetallic layered double hydroxides (CoMgFe-TLDHs) to achieve sensitive and selective electrochemical detection of 20% FBD, a toxic insecticide posing ecological and health concerns. The CoMgFe-TLDHs were synthesized using a simple co-precipitation method and characterized by thermogravimetric differential thermal analysis, X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. These materials were then applied to the PGE surface, significantly enhancing its electrochemical performance, as demonstrated by differential pulse voltammetry and cyclic voltammetry. Under optimized conditions, PGE/ionic liquid/CoMgFe-TLDHs electrode exhibited excellent analytical properties toward FBD determination. A calibration curve was well-established from 0.8 to 100 µM for FBD with a detection limit of 0.36 μM. The proposed sensor enabled the practical application of sensitive FBD detection in tape and river water with good recovery rates.

FeNi-LDH Coated With Orange-Peel Carbon Aerogel for Oxygen Evolution Reaction.

In this work, the waste orange-peel was used as carbon source, and the orange-peel derived carbon material can be obtained through simple pyrolysis. Then, we designed the structure of orange-peel carbon aerogel grown on iron-nickel layered double hydroxides in situ to achieve the effect of carbon coating (FeNi-LDH/CA). The oxygen evolution reaction catalytic performance of FeNi-LDH/CA is excellent, far exceeding that of commercial RuO2. In 1 M KOH, the overpotential of FeNi-LDH/CA is only 250 mV (10 mA cm-2), obviously better than that of commercial RuO2 (295 mV). FeNi-LDH/CA shows good cycling stability, and after long-term i-t testing, the performance only decays by 3 % after running at 100 mA cm-2 for 100 h. When used as an anode, the voltage of water-splitting is only 1.48 V at 10 mA cm-2. The rechargeable liquid zinc-air battery based on Pt/C-FeNi-LDH/CA catalyst has higher open-circuit voltage (1.543 V) and galvanostatic discharge capacity at 1.23 V (830 min, 10 mA cm-2). Moreover, the zinc-air battery based on Pt/C-FeNi-LDH/CA has a small charge-discharge voltage gap (0.65 V) at 10 mA cm-2, after 200 consecutive cycles (66 h), the charge-discharge voltage gap only increased by about 30 mV, indicating good cycling stability.

Thiamine Pyrophosphate-Enhanced NiFe Layered Double Hydroxide for Robust and Durable Seawater Oxidation Electrocatalysis

Thiamine Pyrophosphate-Enhanced NiFe Layered Double Hydroxide for Robust and Durable Seawater Oxidation Electrocatalysis

Enhancing CO2 Oversaturation in the Confined Water Enables Superior Gas Selectivity of 2D Membranes.

Due to the global demands on carbon neutralization, CO2 separation membranes, particularly those based on two-dimensional (2D) materials, have attracted increasing attention. However, recent works have focused on the chemical decoration of membranes to realize the selective transport, leading to the compromised stability in the presence of moisture. Herein, we develop a series of 2D capillaries based on layered double hydroxide (LDH), graphene oxide, and vermiculite to enhance the oversaturation of CO2 in the confined water for promoting the membrane permselectivity. By employing the dielectric spectroscopy as a probe to unveil oversaturation, the dissolved CO2 can be enhanced by up to ten times facilitated by water confined in the 2D capillary, particularly constructed by the LDH, endowing the uprise of CO2/N2 separation factor by 43 times. Therefore, our work opens an avenue to the future design of selective membranes by modulating the confined water beyond chemical modification.

Nanocomposites Based on Layered Double Hydroxides Loaded with Curcumin and Carbon Nitride Quantum Dots for Combined Chemotherapy and Chemodynamic Therapy of Tumors

Nanocomposites Based on Layered Double Hydroxides Loaded with Curcumin and Carbon Nitride Quantum Dots for Combined Chemotherapy and Chemodynamic Therapy of Tumors