Layered Double Hydroxide Nanosheets Research Articles

Core–shell heterostructure engineering of CoP nanowires coupled NiFe LDH nanosheets for highly efficient water/seawater oxidation

Searching for efficient nonprecious metal-based catalysts toward oxygen evolution reaction (OER) are of significance for seawater electrolysis. Herein, a core–shell-structured hybrid of cobalt phosphide nanowires@NiFe layered double hydroxide nanosheets grown on conductive nickel foam (CoP@NiFe LDH/NF) is prepared by a feasible approach at low temperature. The charming structure can provide numerous phosphide/hydroxide heterogenous interfaces, expose abundant active sites, and boost electron/mass transfer, synergistically enhancing catalytic OER activity. When employed as an electrocatalyst toward the OER, the resultant CoP@NiFe LDH/NF only requires a small overpotential of 287 mV to provide 300 mA/cm2 current density as well as long-time durability in 1.0 mol/L KOH seawater. The regulation of electronic states and surface reconstruction synergistically contribute to highly efficient seawater oxidation. This work provides an opportunity to construct efficient and inexpensive electrocatalysts for hydrogen production.

Study on growth behavior and properties of LDH nanosheet arrays enhanced Ni-based coatings on Mg-Li alloy

For the application of lightweight alloys, the corrosion and wear problems of magnesium-lithium (Mg-Li) alloys have always been important problems that cannot be ignored. The coupling protection of multiple technologies has gradually become a new trend. In this study, layered double hydroxides (LDH) nanosheet arrays were in-situ grown on Ni-P coating by the electroless plating technology combined with hydrothermal synthesis technology. The optimum deposition conditions (temperature-time-pH) were selected by orthogonal test. The surface morphology, structure, corrosion resistance and wear resistance of LDH/Ni composite coatings under different conditions were systematically studied by SEM, XRD, FT-IR, DSC, electrochemical and tribological tests. The growth mechanism of LDH suitable for Ni-P coating surface was proposed by analyzing the growth process of LDH nanosheet arrays. The results showed that the condition of 125 °C-12 h-13 was conducive to the growth of LDH nanosheet arrays. Compared with the Ni-P coating and the composite coating under other conditions, the LDH125°C-12h-13/Ni composite coating has the lowest self-etching current density (7.50 × 10−7 A·cm−2) and the average friction coefficient (0.35). The defect sealing effect and Cl− barrier property of LDH effectively improved the corrosion resistance of the coating. The frictional properties were improved by lubrication and heat absorption properties of LDH. In addition, it was found that the growth of LDH on the Ni-P coating surface followed the mechanism of “deposition nucleation-diffusion growth”.

Facile Synthesis of Vertical Layered Double Hydroxides Nanosheets on Co@Carbon Nanoframes as Robust Bifunctional Oxygen Electrocatalysts for Rechargeable Zn–Air Batteries

The development of efficient and low‐cost bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is imperative but remains challenging in rechargeable zinc–air batteries. Herein, a metal oxidation‐assisted approach is developed for the facile synthesis of a highly efficient bifunctional catalyst (Co@NC@LDHs) which is composed of layered double hydroxides (LDHs) nanosheets in situ vertically grown on the surface of hollow carbon nanoframes encapsulating Co nanoparticles (Co@NC). Specifically, the vertical LDHs distributing on the carbon surface ensure the maximized number of accessible active sites and the interaction between LDHs with the carbon matrix. The hierarchically structured bifunctional Co@NC@LDHs display an overpotential of 0.33 V at 10 mA cm−2 for OER and a half‐wave potential of 0.88 V for ORR. The potential gap (ΔE) of Co@NC@LDHs is calculated to be 0.68 V, outperforming the mixed Pt/C + RuO2 catalysts (ΔE = 0.77 V), manifesting its superior bifunctional electrocatalysis performance. Moreover, the Zn–air batteries based on Co@NC@LDHs electrocatalyst exhibit a high peak power density (185.2 mW cm−2) and excellent durability (5.0 mA cm−2 over 500 h). This work may provide a facile strategy for the fabrication of LDHs on carbon substrate, acting as efficient catalysts for broad energy‐related applications.

Highly Effective Electrochemical Water Splitting with Enhanced Electron Transfer between Ni2Co Layered Double Hydroxide Nanosheets Dispersed on Carbon Substrate

A reasonable design of nickel-based catalysts is key to efficient and sustainable energy conversion. For electrocatalytic materials in alkaline electrolytes, however, atomic-level control of the active sites is essential. Moreover, the well-defined surface structure contributes to a deeper understanding of the catalytic mechanism. Here, we report the loading of defective nickel–cobalt layered double hydroxide nanosheets (Ni2Co-LDH@C) after carbonization of silk. Under the precise regulation of the local coordination environment of the catalytic active site and the presence of defects, Ni2Co-LDH@C can provide an ultra-low overpotential of 164.8 mV for hydrogen evolution reactions (HERs) at 10 mA cm−2, exceeding that of commercial Pt/C catalysts. Density functional theory calculations show that Ni2Co-LDH@C optimizes the adsorption energy of the intermediate and promotes the O-O coupling of the active site in the oxygen evolution reaction. When using Ni2Co-LDH@Cs as cathodes and anodes to achieve overall water splitting, a low voltage of 1.63 V is required to achieve a current density of 10 mA cm−2. As an ideal model, Ni2Co-LDH@C has excellent water splitting properties and has the potential to develop water–alkali electrocatalysts.

Enhancing Water Oxidation Catalysis by Controlling Metal Cation Distribution in Layered Double Hydroxides

AbstractThe sluggish kinetics of the oxygen evolution reaction (OER), the limiting step of the electrochemical water splitting process, hinders the eventual commercialization of this important renewable energy strategy. Hence, the development of efficient electrocatalysts for this reaction is crucial. Multi‐metal‐based (hydr)oxides are promising OER electrocatalysts because the electronic interactions between multiple constituent metal cations can potentially enhance electrochemical performances. However, complex compositions may not always lead to positive synergistic effects. The appropriate distribution of the cations is also critical. However, the high dispersibility of cations in these hydroxides renders the control of their distribution challenging. Herein, an approach is reported to control the metal cation distribution in layered double hydroxides (LDHs) to improve their OER performances. Restacking of exfoliated NiFe and CoAl LDH nanosheets leads to electrochemical synergistic effects between different nanosheets. As far as it is known, the restacked LDH described herein exhibits the lowest overpotential (224 mV) and Tafel slope (34.26 mV dec−1) among reported powder‐type (hydr)oxide and alloy OER electrocatalysts with more than three different metal cations. Thus, a new design approach is suggested to enhance the electrochemical performances of LDHs.

Construction of Fe-substituted CoZn layered double hydroxide as an efficient electrocatalyst for the oxygen evolution reaction

BackgroundThe development of efficient electrocatalysts for water-splitting is crucial to meet future energy demands. Layered double hydroxides (LDHs) have emerged as promising electrode materials in alkaline medium owing to their superior electrocatalytic properties. MethodsIn this study, we report the synthesis of two-dimensional nanosheets of trimetallic cobalt-zinc-iron (Co1-xZnFex) LDH via a coprecipitation method as an effective catalyst for oxygen evolution reaction (OER). We investigated the electrocatalytic activity of Co1-xZnFex LDH by tuning the concentrations of Fe and Co (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5). Significant findingsThe Co1-xZnFex (x = 0.3) LDH exhibited the highest OER performance, requiring only 350 mV overpotential and showing 63 mV dec−1 Tafel slope to achieve a geometric current density of 10 mA cm−2 indicates the improved reaction kinetics. The Co0.7ZnFe0.3 LDH nanosheets had a large surface area and many active sites, as evidenced by the double layer capacitance (Cdl) slope of 28 µF cm−2 in a 1 M KOH electrolyte. Moreover, the Co0.7ZnFe0.3 LDH electrocatalysts also maintained excellent stability with a current retention of 99% over 10 h. Hence, our proposed two-dimensional nanosheets-based LDH could be a promising candidate for the development of high performance electrocatalysts for the OER.

Enhanced electrochemical properties of nickel-cobalt hydroxide nanosheet by high-gravity liquid phase modification

Nickel-cobalt layered double hydroxide (Ni-Co LDH) nanosheet has a low specific capacity and poor rate capability. This study uses an anionic surfactant to modify Ni-Co LDH by the high-gravity liquid-phase method. The results reveal that the sodium dodecyl benzene sulfonate (SDBS) adsorption and intercalation can increase electrode interface area, enlarge interlayer spacing of Ni-Co LDH, accelerate the diffusion of electrolyte ions, and thus improve its specific capacity and rate capability. Compared with the stirred flow field, the high gravity further intensifies the surface adsorption and substitution intercalation of SDBS, resulting in a bigger interface area and interlayer spacing of Ni-Co LDH, which is more favorable to its specific capacity and rate capability. The specific capacity of Ni-Co LDH after high-gravity modification is 984 C g−1 (2187 F g−1, 2 A g−1), and its capacity retention rate reached 80 % (1–30 A g−1), significantly higher than that of the untreated one. Besides, an electrochemical kinetic study shows that a high gravity modification substantially enhances the ion diffusion rate. The modified materials under a high gravity field are utilized as anode materials and activated carbons (ACs) as cathode materials to construct supercapacitors. The Ni-Co LDHs//AC has a 50 Wh kg−1 energy density with well cycling stability. The paper proposes a high-gravity liquid-phase modification method to explore potential high-performance electrode materials.

Heterostructure membranes of high permeability and stability assembled from MXene and modified layered double hydroxide nanosheets

Two-dimensional (2D) MXene-based lamellar membranes play transformative roles in membrane filtration technology. Their practical use in water treatment is however hindered by several hurdles, e.g., unfavorable swelling due to weak interactions between adjacent MXene nanosheets, tortuous diffusion pathways of layered stacking, and the intrinsic aquatic oxidation-prone nature of MXene. Herein, nanoporous 2D/2D heterostructure membranes are elaborately constructed via solution-phase assembly of oppositely charged MXene and modified layered double hydroxide (MLDH) nanosheets. As a multifunctional component, positively charged holey MLDH nanosheets were first tailor-made to serve simultaneously as a binder, spacer and surface-modifier; next they were intercalated into negatively charged MXene lamella to enhance structural stability and mass transfer of membranes. As a result, the as-prepared MLDH@MXene heterostructure membranes successfully break the persistent trade-off between high permeability and selectivity while mitigating the common drawbacks in 2D MXene-based lamellar membranes, e.g., swelling issues, restacking problems, and vulnerable chemical stability. Noticeably, at an operating pressure of 4 bar and a feed solution of 100 ppm of Congo red, the heterostructure membranes enable a threefold jump in permeability (332.7 ± 20 L m-2 h-1 bar-1) when compared to the pristine MXene membrane (119.3 ± 18 L m-2 h-1 bar-1), and better operational stability without compromising the rejection.

Effect of different anion intercalations on the corrosion resistance of layered double hydroxides on the surface of LA43M

AbstractLayered double hydroxides (LDH) are widely used in the field of Mg alloy surface protection due to their interlayer anion exchangeable and physical barrier. To explore the effect of corrosion inhibitor modification on the growth and corrosion resistance of LDH coating, MgAl‐NO3−‐LDH precursor film was obtained on the surface of LA43M alloy by in situ growth method, and then MgAl‐V2O74−‐LDH, MgAl−Cl−‐LDH and MgAl‐ASP‐LDH were prepared by the ion exchange method. The morphology, composition, and corrosion resistance of the LDH film with different anion intercalation were studied systematically by scanning electron microscope, energy disperse spectroscopy, X‐ray diffractometer, Fourier‐transform infrared spectroscopy, and electrochemical tests. The results show that the modified LDH nanosheets are larger in size and uniformly tightly bonded to the substrate, and the thickness of the film is increased. Electrochemical tests and hydrogen precipitation experiments demonstrated that all four LDH films provided protection to the substrate, and the corrosion resistance of the V2O74−, Cl− and ASP‐containing films modified by corrosion inhibitors was improved compared with that of the precursor films, among which the MgAl‐V2O74−‐LDH had the best corrosion resistance.

Effects of Layered Double Hydroxide Nanosheets with Different Cations on the Compressive Strength of Cement Composites

Effects of Layered Double Hydroxide Nanosheets with Different Cations on the Compressive Strength of Cement Composites

Surface reconstruction of NiFe layered double hydroxides by S2- corrosion for efficient oxygen evolution

Nickel-iron layered double hydroxides (NiFe LDH) are subject to surface reconstruction by the applied anodic potential in alkaline media, and the reconstructed metal hydroxyl oxides are often considered to be the actual active material for oxygen evolution reaction (OER), so how to facilitate surface reconstruction is crucial for their performance. In this paper, the surface reconstruction of NiFe LDH nanosheets was successfully induced by S2- corrosion using rapid wet chemical engineering without affecting their crystal structure and nanomorphology; Notably, the NiOOH species formed on the corroded S-NiFe LDH/NF surface participate in the OER process as active species. The electrochemical measurements show that S-NiFe LDH/NF has a low overpotential of 250 mV and a Tafel slope of 26.3 mV dec -1 at 50 mA cm−2. This work provides a simple activation strategy for the surface reconstruction of NiFe LDH, which is an important reference for the design of advanced catalysts.

Layered double hydroxide nanosheets embedded β-cyclodextrin composite membranes with enhanced chiral separation performance

The technologies for enantiomeric resolution are essential to the development of pharmaceutical industry. The membrane technology has great potential in chiral separation owing to its low cost and high throughput; however, the enantioselective of membrane is limited by the thickness of the active layer, which is closely related to the number of theoretical separation plates. In this work, the layered double hydroxides (LDH) are synthesized by hydrothermal process and then vacuum filtrated with β-cyclodextrin (β-CD) and polyvinyl alcohol (PVA) on a porous substrate to fabricate chiral selective membranes. 2D channels with increased number of separation stages are formed in the selective layer after heat post-treatment. The enantiomeric excesses value is enhanced from 10.95% to 24.32% for racemic L/D- tryptophan resolution. This work provides a new approach for designing high performance chiral separation membranes from the aspect of increasing the transport path.

Ambient Synthesis of Metal–Organic Framework-Derived Bimetallic Layered Double Hydroxide Nanosheets by the Composition Inheritance Strategy for Efficient Microwave Attenuation Applications

Ambient Synthesis of Metal–Organic Framework-Derived Bimetallic Layered Double Hydroxide Nanosheets by the Composition Inheritance Strategy for Efficient Microwave Attenuation Applications

Facile synthesis and exfoliation of micro‐sized LDH to fabricate 2D membranes towards Mg/Li separation

AbstractTwo‐dimensional (2D) membranes have demonstrated potential for molecular separation; however, their applicability for Li/Mg ion separation has been restricted by their negatively‐charged and easily‐swellable properties in water. Moreover, their practical application has been hindered by the challenge of producing significant quantities of single‐layer nanosheets. To overcome these challenges, we have developed a scalable method for synthesizing micro‐sized nitrate ZnAl layered double hydroxide (LDH) and subsequent exfoliating to yield monolayer nanosheets for the construction of 2D membranes. The sub‐nanometer channels of the LDH membrane is positively charged, which prevents the passage of magnesium ions. These channels also impede the flow of magnesium ions that are more difficult to dehydrate. As a result, the LDH membranes exhibit robust lithium–magnesium separation ability, with a separation ratio of 6 (Li/Mg). This work provides a method for producing high‐quality LDH nanosheets and validates the enormous potential of LDH membranes in the field of lithium–magnesium separation.

Ni0.85Se@CoFe LDH heterostructure nanosheet arrays on Ni foam as efficient electrocatalysts for enhanced oxygen evolution

Exploring high-efficient, earth-abundant and stable electrocatalyst for oxygen evolution reaction (OER) is of vital importance for large-scale implementation of energy converting and storing. Thus, we fabricated a free-standing hierarchical heterostructure electrode of Ni0.85Se@CoFe LDH/NF via a rational combination of hydrothermal, selenization and electrodeposition process, among which the ultrathin CoFe LDH nanosheets intimately assembled onto the vertical aligned Ni0.85Se nanosheets supported on Ni foam. The constructed core-shell nanosheet arrays hold the plentiful hetero-interfaces and intimate interactions through metal-oxygen bonds between two individuals, which guarantee the fast OER kinetic processes. Additionally, CoFe LDH with crystalline/amorphous hybrid structure favors providing more reaction sites. Remarkably, the optimal Ni0.85Se@CoFe LDH/NF binary composites possess outstanding OER activity with a low overpotential of ∼223 and 280 mV at 10 mA cm−2 and 100 mA cm−2 in alkaline solution as well as good durability. This research offers an alternative approach for improving electrocatalytic water splitting through constructing 3D hierarchical heterostructures.

The space-charge region at NiFe-MOF⊆LDH p-n junction by self-sacrificing LDH to boost oxygen evolution tandem with in-situ electro-Fenton

The rational design of p-n heterojunction was highly desirable to optimize charge distribution at space-charge region, tailoring the adsorption free energy of intermediate matters, and to boost the oxygen evolution reaction (OER) and in situ electro-Fenton (EF) reaction. Herein, a self-sacrificing strategy has been employed to construct the NiFe-MOF⊆LDH nanosheet arrays on carbon cloth (CC), directly using NiFe-LDH as template. NiFe-MOF⊆LDH exhibited outperformed OER activity with a lower overpotential of 196 mV and smaller Tafel slope of 48 mV dec-1(η10). The conferred higher valence state for Ni3+ and the more carrier density to absorb more OH– ions confirmed by in-situ Raman and density functional theory (DFT) calculation endowed the excellent OER activity, which was expected to endow the self-oxygenation to support the following EF in this system without additional O2. An electrochemical flow reactor was designed for anodic OER and cathodic EF only at low voltage of 1.6 V. Typically, the in-situ H2O2 yield rate could achieve 27.4 mmol/h at cathodic ORR reaction, which was further activated by Fe2+/Fe3+ cycling for the heterogeneous Fenton reaction. This tandem reactor could remove 96% of ibuprofen (IBF) within 120 min with long-term cycle use. In a word, coupling the OER with EF in a flow reactor has possible application in the fields of sustainable energy and environmental remediation.

Design of mechanical-robust phosphorescence materials through covalent click reaction

It remains a great challenge to engineer materials with strong and stable interactions for the simultaneously mechanical-robust and room temperature phosphorescence-efficient materials. In this work, we demonstrate a covalent cross-linking strategy to engineer mechanical-robust room temperature phosphorescence materials through the B–O click reaction between chromophores, polyvinyl alcohol matrix and inorganic layered double hydroxide nanosheets. Through the covalent cross-linkage between the organic polyvinyl alcohol and inorganic layered double hydroxide, a polymeric composite with ultralong lifetime up to 1.45 s is acquired based on the inhibited non-radiative transition of chromophores. Simultaneously, decent mechanical strength of 97.9 MPa can be realized for the composite materials due to the dissipated loading stress through the covalent-bond-accommodated interfacial interaction. These cross-linked composites also exhibit flexibility, processability, scalability and phosphorescence responses towards the mechanical deformation. It is anticipated that the proposed covalent click reaction could provide a platform for the design and modulation of composites with multi-functionality and long-term durability.

Layered Double Hydroxide Nanosheets Boosting Red Long Afterglow via Highly Efficient Energy Transfer.

Room-temperature phosphorescent (RTP) based long-afterglow materials have shown broad application prospects in smart sensors, biological imaging, photodynamic therapy, and many others. However, the fabrication of red long-afterglow materials still faces a great challenge due to the competitive relationship between RTP efficiency and lifetime. In this work, we reported a series of layered double hydroxide (LDHs) nanosheets with red long-afterglow (quantum yield up to 42.35% and lifetime up to 256.77 ms) by taking advantage of the highly efficient triplet-triplet energy transfer from green phosphorescent LDHs to the red fluorescent dye rhodamine B (RhB, as a guest molecule). Specifically, the Zn-based LDHs@RhB composite (Zn-Al-LDH-4-CBBA@RhB) presents energy transfer efficiency as high as 95.18%, and the red long-afterglow could even be excited upon white-light irradiation. Benefiting from the time-resolved afterglow, the LDHs@RhB composites exhibit great potential in the fields of anticounterfeiting and information encryption.

Layered double hydroxide nanosheets-built porous film-covered Au nanoarrays as enrichment and enhancement chips for efficient SERS detection of trace styrene

Styrene, a prevalent volatile organic compounds (VOCs), is very harmful to atmosphere and humans. Consequently, the development of efficient detection technologies for styrene is of high importance, which is still in challenge! In this work, we crafted a layered double hydroxide (LDH) porous film-coated gold nanoarray, designed to act as a surface enhanced Raman spectroscopy (SERS) chip for the efficient and portable detection of gaseous styrene. This chip features a covering layer composed of cross-linked LDH nanosheets, notable for their porous structure and high specific surface area. When the covering layer is 100–300 nm in thickness, this composite chip has significant enrichment effect and strong SERS performance to gaseous styrene with a lowest detectable concentration below 1 ppb (4.64 ×10-3 mg/m3), and can response within 10 s, showing the rapid response and high sensitivity. Additionally, the chip has strong anti-interference capabilities and maintains excellent response to styrene, even in mixed benzene-VOCs gases. The exceptional SERS performances of this chip is ascribed to its LDH covering layer-induced styrene-enrichment and structurally-enhanced SERS performances. This study provides a simple route and practical chip for the rapid and ultrasensitive SERS-based detection of gaseous styrene, which is also potentially beneficial for the detection of other gaseous VOCs.

“One stone three birds” plasma engraving strategy to boost the hydrogen evolution reaction activity of layered double hydroxides

Possessing large specific surface areas and rich metal redox sites, layered double hydroxides (LDHs) are potentially suitable oxygen evolution reaction catalysts. It is a pity that they usually show poor hydrogen evolution reaction (HER) activity on account of the limited conductivity and deficient active sites. Taking NiFe LDH nanosheets as an example, we develop a “one stone three birds” plasma engraving strategy to enhance the HER activity of NiFe LDH. The “three birds,” including the reduction of Ni2+ to Ni nanoparticles (Ni NPs), generation of more oxygen vacancies (Ov), and exfoliation of nanosheets into much thinner ones, can obviously improve the conductivity and active sites of NiFe LDH. The plasma processing can also enhance water adsorption and accelerate the Volmer step during HER. As expected, the plasma-engraved NiFe LDH (PEH) exhibits enhanced HER activity with a low overpotential of 22 mV at 10 mA cm−2 and a small Tafel slope of 38 mV dec−1 in 1 M KOH, much better than NiFe LDH (202 mV, 145 mV dec−1). By combining optical emission spectroscopy diagnosis and structural/electrochemical characterizations, the relationship among the electron excitation temperature (Texc) in plasma, the amount of Ni NPs and Ov in PEH, and the HER activity of PEH is established. Excitingly, the PEH also displays splendid HER activity in both alkaline real seawater and overall water splitting.