Layered Double Hydroxides Research Articles

Controllable synthesis of NiCoMo-LDH with nanofloral structure assisted by monodisperse spherical silica for asymmetric supercapacitor

Traditional layered double hydroxides (LDH) have disadvantages such as small layer spacing, insufficient active sites and poor electrical conductivity, which seriously restricts their future utilization in the realm of energy storage. In this paper, a controlled synthesis strategy of tercomponent metal NiCoMo-LDH is proposed by using the structural advantages of metal-organic skeleton (MOF) templates, combining structural regulation and atom doping. On the basis of the synthesis of Ni-MOF 74, Co and Mo atoms are introduced for a small amount of doping, and the monodisperse spherical SiO2 is inserted to adjust the pore structure of NiCoMo-MOF, expand the lamellar spacing, and effectively avoid the accumulation and agglomeration of lamella. Finally, NiCoMo-LDH cathode material with loose porous and coarsely curled nanosphere structure was synthesized through the chemical reaction of OH− with SiO2 and the destruction of the skeleton structure of MOF. The specific capacitance of the material is 1423.3 F·g−1 at 0.5 A·g−1, and after 5000 cycles of charging and discharging, 80.0% of the original specific capacitance is sustained. Moreover, NiCoMo-LDH//AC ASC possesses a high energy density of 39.1 Wh·kg−1 at the power density 400 W·kg−1. Combined with density functional theory (DFT) calculation, the fact that metal doping can not only effectively improve the conductivity of electrode materials has been further proved, but also accelerate the electron/ion migration rate, which successfully reveal the synergistic enhancement mechanism of electrochemical properties of materials.

A universal approach of constructing two-dimensional transition metal phosphide heterostructures and the superior performance in (urea-rich) water electrolysis

Transition metal phosphides have consistently shown excellent performance in electrocatalytic hydrogen production, but challenges remain in the development of efficient diverse catalysts. We designed a superhydrophilic two-dimensional (2D) TMP heterostructure with generalized approach. The phosphidation of layered double hydroxides (LDHs) with controlled exfoliation yielded multiple phosphide heterostructures (Ni2P/CoP, CoP/Fe2P and Ni2P/Fe2P) of less than 5 nm, the thinnest phosphide sheet up to date. All 2D phosphide heterojunctions are superhydrophilic (θw=10°), which is more favourable for bubble desorption. Both XPS and XANES, among other characterizations, indicated the much stronger electron-donating effect of metal sites comparing with bulk analogues, resulting in the formation of highly electron-rich P sites for facilitated proton adsorption. 2D Ni2P/CoP showed superior activity (η10=46.1 mV) for hydrogen production. Interestingly, 2D Ni2P/CoP was also highly active (η50=112.1 mV) for urea oxidation. This work demonstrates a versatile method for building superhydrophilic 2D phosphides, opening up exciting opportunities for multifunctional applications.

Nanoarchitectonics with self-healing hydrogel for hierarchical porous carbons and its application in cadmium-arsenic complex pollution

A cheap and green method for porous carbons (CAC-1) with high surface area (409.41 mg/g) is constructed benefiting from self-healing properties of calcium alginate hydrogel under atmospheric drying. Layered double hydroxides modified CAC-1 (CAC-LDH-1) is applied in cadmium-arsenic complex pollution. The adsorption capacities of the CAC-LDH-1 on Cd(II) and As(V) are 331.03 mg/g and 33.48 mg/g in single system, and 79.87 mg/g and 150.59 mg/g in binary system. In binary system, the synergistic action of Cd(II) ions greatly improve the adsorption capacity and adsorption rate of As(V) ions. The adsorption process of cadmium-arsenic by CAC-LDH-1 mainly follows the second-order kinetic model and Freundlich model, and the adsorption process is endothermic and spontaneous. XPS, FTIR, XRD, SEM-EDS mapping and pore size distribution are carried out to explore the structure and adsorption mechanism of CAC-LDH-1. After treatment with 1 % CAC-LDH-1 for 30 days, the proportions of E1-Cd, F1-As, and F2-As that can be utilized by plants decrease from 46.32 % to 33.15 %, 10.08–2.15 %, and 43.06–35.23 %. Compared with CK group, Cd/As contents in the above/under-ground part of red cherry radish seedlings decrease by 31.41∼59.09 %. CAC-LDH-1 inhibits little effect on the microbial diversity of soil, but change the dominant bacterial colonies.

Regulating the microstructure and catalytic activity of metal selenides via calcination strategy for lithium-sulfur battery

Metal selenides obtain a series of advantages such as high electronic conductivity, excellent catalytic activity and facile fabrication approach, which are considered as promising catalysts in lithium sulfur (Li-S) battery. Traditional research based on metal selenides focuses on designing novel/complex microstructures or composites, however, the catalytic ability can be greatly affected by internal properties such as defect or vacancy. In this work, hollow nickel-cobalt layered double hydroxide (NiCo-LDH) is first fabricated and applied as a precursor to fabricate NiCoSe, and Se vacancy accompanied with crystal phase, microstructure and catalytic activity can be regulated by simply adjusting selenization atmosphere and temperature. Involving the application of NiCoSe in Li-S battery, the optimum fabrication parameter is perform the selenization at 600 °C under argon/5 % hydrogen, and the battery can exhibit a high discharge specific capacity of 1042.8 mAh g−1, excellent cycling performance of 500 cycles with a decay rate of 0.083 % at 1 C. This work highlights the importance of calcination process and also provides reference for further modifying the microstructure and performance of metal selenides in Li-S battery.

Effects of Mg-based admixtures on chloride diffusion in alkali-activated fly ash-slag mortars

This study evaluated the effects of various Mg-based admixtures, including magnesium oxide (MgO), layered double hydroxides (LDH), and calcined layered double hydroxides (CLDH), on the chloride resistance of alkali-activated fly ash-slag (AAFS) mortars. To this end, chloride diffusion tests were conducted on AAFS mortars containing 5 wt% MgO, Mg-Al-CO3 LDH, and CLDH. The results revealed that all Mg-based admixtures investigated in this study enhanced the chloride resistance of AAFS mortars. The inclusion of MgO led to a finer pore structure and promoted the formation of more Friedel's salt, thereby enhancing the chloride resistance performance. Although the inclusion of Mg-Al-CO3 LDH and CLDH resulted in more lager pores in the matrix, leading to slightly lower compressive strength, the overall content of Mg-Al LDH and Friedel's salt formed in the system increased, which led to an improved chloride binding capacity and enhanced chloride resistance.

Biofilm formation on MgFe-LDH@quartz sand as novel wetland substrate under varied C/N ratios for BDE-47 removal

Layered double hydroxide (LDH)-coated substrates could enhance the removal of various wastewater-born pollutants. However, research on biofilms attached to LDH-coatings and their synergistic purification effects on strongly hydrophobic persistent organic pollutants (POPs) remains limited. This study aims to investigate biofilm formation on MgFe-LDH@quartz sand and its effectiveness in removing tetrabromodiphenyl ether (BDE-47), an emerging halogenated POP in municipal wastewater. Under different C/N ratios (3, 5, and 10), BDE-47 removal rates ranged from 28.0% to 41.6% after 72 h. The optimal performance was achieved with LDH coating at C/N = 5, when substrate biofilm reached its highest extracelluar polymer substances (EPS) content, dehydrogenase activity and relative hydrophobicity. Moreover, distinct distribution patterns of EPS components’ fluorescence peaks were observed in the LDH-coating treatment using three dimensional excitation-emission matrix (3D-EEM). While substrate adsorption was the primary mechanism for BDE-47 removal, accounting for 59.6%–83.4% of the total, biofilm adsorption and degradation contributed a relatively lower amount, ranging from 11.5% to 21.4%, and were more dependent on the C/N ratio. Notably, the maximum carrying capacity of protein predicted by the logistic growth model exhibited a strong positive correlation with the total BDE-47 removal rate (R2 = 0.82, p < 0.05), highlighting the importance of biofilm extracelluar proteins.

A novel UV-curable composite coating with superior anti-corrosion and mechanical properties

The UV curing method is free from volatile organic compounds (VOC) and exhibits high curing efficiency. However, pore flaws and inadequate mechanical qualities after cure greatly hinder their utilization in metal anti-corrosion. Herein, layered double hydroxides (LDH) supported by molybdic acid and cerium ions were synthesized in situ on the sericite (SC) surface, enhancing the shielding, corrosion inhibition, resin compatibility, and cross-linking density of the coating. Compared with carbon steel immersed in a 3.5 wt% NaCl solution, the incorporation of SC/KH560@LDH reduced the corrosion current density (Icorr) from 2.001 × 10−5 A/cm2 to 7.883 × 10−6 A/cm2. Moreover, the low-frequency impedance of the UV-SC/KH560@LDH coating remained high at 1.939 × 1010 Ω·cm2 after 70 days of immersion in a 3.5 wt% NaCl solution. The excellent corrosion resistance of UV-SC/KH560@LDH can be attributed to the barrier properties of the filler, the chloride ion trapping, and the passivation effect. Furthermore, the UV-curable alkyd resin used in this work formed a chemical bond with the metal substrate, enhancing the mechanical properties of the coating. The adhesion strength of the UV-SC/KH560@LDH was measured at 11.50 MPa. The thickness loss (21.3 μm) of the UV-SC/KH560@LDH were minimal after 5000 cycles of wear. A new research concept for preparing the UV-SC/KH560@LDH with superior anti-corrosion and mechanical properties for carbon steel plate surfaces has been proposed to meet the demands of practical applications.

Photocatalytic degradation of tetracycline over bimetallic layered double hydroxides-MXenes heterostructures under visible light

Layered double hydroxides (LDHs) are widely used in photocatalytic degradation of antibiotic pollutants under ultraviolet (UV)-light, but their efficiency under visible light is hampered by large band gaps and layer agglomeration. Herein, we have successfully developed bimetallic NiCo LDHs-MXenes heterostructures (LDHs-MXenes) for enhanced degradation of tetracycline (TC) pollutants under visible light. As-prepared LDHs-MXenes photocatalysts (20 mg) show exceptional performance, achieving ∼ 97.4 % TC degradation efficiency (20 mg L−1, 100 mL) within just 50 min under a 300 W Xe lamp. This significant enhancement underscores the synergistic effects derived from the combination of LDHs and MXenes nanosheets.

An ultrasensitive electrochemical sensor based on NiFe-LDH-MXene and ruthenium nanoparticles composite for detection of nitrofurantoin in food samples

The excessive use of nitrofurantoin (NFT) represents a threat to ecosystems and food safety, making it necessary to develop efficient and accurate detection methods. Herein, the Ru/NiFe-LDH-MXene/SPCE electrode was successfully synthesized by one-step electrodeposition and employed to the NFT electrochemical sensing. Combining 2D MXenes with multifunctional 2D layered double hydroxides (LDHs) creates synergistic interactions within the MXene-LDH heterostructures, modifying the electrochemical performance. Furthermore, the incorporation of noble metal nanoparticles and nanoclusters can significantly enhance electrochemical performance by promoting favorable interactions at the metal-carrier interface and optimizing the rearrangement of electronic structure. Based on this, the developed Ru/NiFe-LDH-MXene/SPCE sensor demonstrates remarkable sensitivity (152.44 μA μM−1 cm−2) and an ultralow detection limit (2.2 nM). Notably, the sensor was employed for NFT detection in food samples with satisfactory recoveries, making it a promising electrochemical sensor for the detection of NFT.

High mixing enhancement for continuous uniformity Li/Al-LDHs in lithium extraction from low grade salt lakes

The enhancement of lithium extraction from low grade salt lake through the development of advanced adsorbents has become a primary focus in current research. A new method was developed in this work for the continuous fabrication of ultra-highly uniform lithium-aluminum layered double hydroxides (H-LDHs), used as lithium adsorbents, through a high mixing reactor. These H-LDHs featured a more consistent particle size distribution, which facilitated an enhanced vibrational density. This not only significantly increased the powder content in granules but also improved lithium adsorption efficiency. Computational fluid dynamics (CFD) modeling showed that the reactor reached peak mixing efficiency with a minimal gap size of 1 mm. The analysis further indicated that a Reynolds number of 75 led to enhanced mixing effects and stronger flow dynamics. Experiments with Qarhan salt lake brine demonstrated that the H-LDHs powders reached a lithium adsorption capacity of up to 7.27 mg/g, while the volumetric adsorption capacity of these H-LDHs granules exceeded that of traditional granules by 1.179 times. Subsequent desorption and cycling experiments verified the material’s enduring lithium adsorption efficacy and structural integrity, underscoring its considerable potential for industrial use.

Thin-film composite (TFC) membranes incorporated with hydrophilic additives and layered double hydroxides (LDHs) for effective brackish water (BW) desalination

To overcome the limited water permeability of thin-film nanocomposite (TFN) membranes for brackish water reverse osmosis (BWRO) processes, we have incorporated a few amine or hydroxyl group terminated hydrophilic additives during interfacial polymerization when fabricating RO membranes and found that the membrane comprising 1 wt% 2-(2-hydroxyethyl)pyridine (2-(2-pyridyl)ethylahydroxide, PEH) has the best BWRO performance. The membrane was subsequently infiltrated with layered double hydroxide (LDH) nanoparticles by a post ethanol activation and could deliver a water permeability of 4.18 LMH bar−1 which is 100 % more than the control membrane without much compromising the salt rejection. The newly developed process not only incorporates nanofillers with the advantages of simplicity and decoupling from the interfacial polymerization process, but also endows the TFN membranes with enhanced separation performance. The study may provide useful insights to incorporate nanofillers by the solvent activation approach for the fabrication of TFN membranes.

Controllable Metal–Organic Framework‐Derived NiCo‐Layered Double Hydroxide Nanosheets on Vertical Graphene as Mott–Schottky Heterostructure for High‐Performance Hybrid Supercapacitor

Layered double hydroxide (LDH) is considered a highly promising electrode material for supercapacitors (SCs) due to its high theoretical specific capacitance. However, LDH powders often suffer from poor electrical conductivity, structure pulverization, slow charge transport, and insufficient active sites. Herein, a self‐supporting electrode with a Mott–Schottky heterostructure has been designed for high‐performance SCs. The electrode consists of low crystallinity NiCo‐LDH nanosheets and vertical graphene (VG) directly grown on carbon cloth. The LDH was converted from a metal–organic framework (MOF) by the sol–gel method. This self‐supporting electrode provides fast charge transfer, reducing the pulverization effect and energy barrier. The Mott–Schottky heterostructure of LDH@VG regulates electron density and enhances electron transfer, as confirmed by density functional theory calculation. The optimized LDH@VG heterostructure electrode exhibits an excellent areal capacitance of 5513.8 mF cm−2 and rate capability of 82.1%. Furthermore, the fabricated hybrid SC demonstrates excellent energy density of 404.8 μWh cm−2 at 1.6 mW cm−2 and a remarkable cycling life, with a capacitance of 92.0% after 10 000 cycles. This work not only provides a simple dip‐coating and MOF conversion method to synthesize heterojunction‐based electrodes, but also broadens the horizon for designing advanced electrode materials for SCs.

Tailored Engineering of Layered Double Hydroxide Catalysts for Biomass Valorization: A Way Towards Waste to Wealth.

Layered double hydroxides (LDH) have significant attention in recent times due to their unique characteristic properties, including layered structure, variable compositions, tunable acidity and basicity, memory effect, and their ability to transform into various kinds of catalysts, which make them desirable for various types of catalytic applications, such as electrocatalysis, photocatalysis, and thermocatalysis. In addition, the upcycling of lignocellulose biomass and its derived compounds has emerged as a promising strategy for the synthesis of valuable products and fine chemicals. The current review focuses on recent advancements in LDH-based catalysts for biomass conversion reactions. Specifically, this review highlights the structural features and advantages of LDH and LDH-derived catalysts for biomass conversion reactions, followed by a detailed summary of the different synthesis methods and different strategies used to tailor their properties. Subsequently, LDH-based catalysts for hydrogenation, oxidation, coupling, and isomerization reactions of biomass-derived molecules are critically summarized in a very detailed manner. The review concludes with a discussion on future research directions in this field which anticipates that further exploration of LDH-based catalysts and integration of cutting-edge technologies into biomass conversion reactions hold promise for addressing future energy challenges, potentially leading to a carbon-neutral or carbon-positive future.

Simple construction of molybdate anions-intercalated NiCo-based layered double hydroxides nanosheet arrays on carbon fibers for enhanced flexible fiber-shaped supercapacitors

As the energy supply devices for miniaturized, wearable, portable and intellectualized electronic products, flexible fiber-shaped supercapacitors (FSCs) have attracted great attention by virtue of their peculiar superiorities such as ultra-fast charge/discharge ability, ultra-high output power, ideal service life, outstanding mechanical flexibility, and superior compatibility with the human body. The performance enhancement of FSCs is highly dependent on the high-performance active electrode materials. In this work, a series of molybdate anions-intercalated NiCo based layered double hydroxides (NiCoMo-LDHs) have been synthesized on flexible carbon fiber (CF) by a simple electrodeposition strategy by regulating the Mo content and the growth time. It turns out that the intercalation of molybdate anions can significantly widen the interlayer spacing and reduce the crystallinity of the synthesized LDH materials. The morphological differences between the LDHs with different Ni/Co/Mo ratios are analyzed, and the morphological evolution process of the materials with the specific Ni/Co/Mo ratio of 1:3:0.2 are systematically investigated. The well-developed NiCoMo-LDH nanosheets electrode with appropriate Ni/Co/Mo ratio (NCM2–500) delivers the best electrochemical performances among all the synthesized LDHs. In particular, the synthesized NCM2–500 fiber electrode exhibits excellent specific capacitance, superior electrical conductivity and favourable cycling stability. Additionally, the assembled parallel type NCM2–500//AC FSC device using NCM2–500 and activated carbon (AC) as the cathode and anode with the assistance of PVA/KOH gel electrolyte demonstrates a brilliant specific energy of 36 Wh cm−1 at 845 W cm−1 (nearly 17 Wh kg−1 at about 400 W kg−1) and a high cycle lifespan of maintaining 103 % of the pristine capacity after 5000 cycles. This FSC device is an ideal candidate for next-generation applications due to its remarkable electrochemical properties.

Engineering MOF@LDH heterojunction with strong interfacial built-in electric field towards enhanced electrocatalytic water oxidation

Guiding the dynamic reconstruction of the oxygen evolution reaction (OER) is crucial for realizing the industrial application of hydrogen production through water electrolysis. In this study, we have intricately designed a built-in electric field (BIEF) between MIL-88B(Fe) and layered double hydroxide (LDH) with an adjusted work function difference. This design drives an asymmetric interfacial electron distribution, enhancing electron accumulation at the Fe sites within MIL-88B(Fe) and electron-deficient LDHs. Consequently, this setup promotes the surface dynamic reconstruction of LDHs into highly active oxyhydroxides, while simultaneously slowing down the rapid dissolution of Fe during OER operation. This optimization improves the adsorption/desorption of oxygen intermediates, ensuring a sustained high OER activity during long-term electrochemical operation. As expected, the optimal MIL-88B(Fe)@NiCo LDH configuration demonstrates a remarkably low overpotential of only 279 mV at 10 mA cm−2, maintaining operational stability for 70 h. This research significantly advances our understanding of the dynamic reconstruction of MOF@LDH heterojunctions and introduces a straightforward strategy for engineering BIEF to guide this process effectively.

Fabrication of Vanadate-Exchanged Electrodeposited Zn-Al Layered Double Hydroxide (LDH) Coating on a ZX21 Mg Alloy to Improve the Corrosion Resistance

Fabrication of Vanadate-Exchanged Electrodeposited Zn-Al Layered Double Hydroxide (LDH) Coating on a ZX21 Mg Alloy to Improve the Corrosion Resistance

Pd‐Embedded NiFe Layered Double Hydroxides for Biomass Upgrading: Precision Construction of Dual‐Functional Synergistic Sites

Pd‐Embedded NiFe Layered Double Hydroxides for Biomass Upgrading: Precision Construction of Dual‐Functional Synergistic Sites

Functional Ni/MnO2 heterostructure electrocatalysts based on self-sacrifice-induced LDHs anchored on nanofibers for microbial fuel cells

Designing cost-effective, highly active oxygen reduction catalysts for high-power-density microbial fuel cells (MFCs) is a significant challenge. To address this, this study uniformly dispersed layered double hydroxides (LDHs) on nanofiber surfaces, and subsequently utilized the self-sacrifice method of zeolite imidazole frameworks (ZIFs) to synthesize LDH/ZIF@CNFs bimetallic heterostructure with precise lattice matching. Experimental results collectively verified that LDH/ZIF@CNFs-12 exhibits an onset potential of -0.087 V, surpassing Pt/C (-0.098 V). Impressively, MFC equipped with LDH/ZIF@CNFs-12 achieves a high power density of 939.05 mW/cm2, surpassing Pt/C (859.74 mW/cm2). The excellent electrocatalytic performance of this catalyst originates from the rich active sites exposed in the LDHs core during the MOFs-assisted synthesis process, and the synergistic catalysis achieved by the formation of heterojunctions. In addition, 3D nanofibers uniformly disperse active sites and reduce large band gaps. This work unveils a new perspective for cost-effective, eco-friendly, and sustainable catalysts suitable for MFCs.

Construction of superhydrophobic composite coating on AZ31B Mg alloy for improved corrosion resistance and anti-wear property

In this study, the EP (epoxy)/L(P) (layered double hydroxides powder)-DTMS (dodecyl-trimethoxy-silane) superhydrophobic composite coating was prepared on AZ31B Magnesium (Mg) alloy surface by spin-coating and self-assembly methods. Mg-Al layered double hydroxides (LDH) powder with ion exchange ability, prepared by hydrothermal coprecipitation, was mixed with EP to construct rough surface and provide good adhesion between the coating and Mg alloy substrate. The introduction of DTMS could reduce the surface energy of coating and improve the compactness of rough surface. Due to the shielding effect of superhydrophobic surface and the ion exchange ability of LDH, it was difficult for corrosive ions (Cl-) to reach the substrate surface in 3.5 wt% NaCl solution. And the corrosion current density was decreased by 4 orders of magnitude. Because of the lubrication of DTMS and the layered structure of L(P), the composite coating had a good wear-reducing effect under the reciprocating point contact mode against with an AISI5200 steel ball. It provided a feasible idea for the construction of multifunctional superhydrophobic coatings on metal surface with self-cleaning, corrosion resistance and wear resistance, which will expand the industrial application fields of superhydrophobic coatings.

Electrochemical Effect of Interlayer Anions on Ni–Co Layered Double Hydroxides

Electrochemical Effect of Interlayer Anions on Ni–Co Layered Double Hydroxides