Binary Layered Double Hydroxides Research Articles

Multiple phase transformation of ZIF-L to LDH and Ag nanoparticles decorated on CoNi layered double hydroxides for high-performance supercapacitor and highly efficient hydrogen evolution reaction

ZIF-L-derived binary layered double hydroxide (LDH) established active catalysts have been shown to have potential as electrode materials in the development of high-performance supercapacitors (SCs) and hydrogen evaluation reactions (HER). This study uses conductive nano-silver (Ag) particles in hierarchically integrated CoNi-LDH nanosheets (NSs), which are described. The developed Ag@CoNi-LDH NSs electrode has a very high specific capacitance of 2878 F g−1 at 0.5 A g−1 and an impressive rate capability. This is due to consistent morphology, plentiful electroactive sites, homogeneous particle size, and decreased electronic/ionic impedance. The fabrication of solid-state hybrid supercapacitors (HSCs) using Ag@CoNi-LDH NSs as the positive electrode and activated carbon (AC) as the negative electrode in PVA/KOH polymer gel electrolytes has been described. The prepared supercapacitors achieve a maximum energy density of 105 Wh kg−1 at power densities of 1183 Wh kg−1, coupled with excellent initial capacitance retentions of 97 % after 20,000 cycles. Ag@CoNi-LDH NSs demonstrate effective electrocatalytic activity towards HER with an ultra-low overpotential of 26 mV at 10 mA cm−2 and the associated Tafel value of 35 mV dec−1 using 0.5 M acidic electrolyte. It is possible to attribute the extraordinary electrochemical performance to the thoughtful mixture of two electroactive materials in the future.

Efficient phosphate removal by Mg-La binary layered double hydroxides: synthesis optimization, adsorption performance, and inner mechanism.

Layered double hydroxides (LDH) hold great promise as phosphate adsorbents; however, the conventional binary LDH exhibits low adsorption rate and adsorption capacity. In this study, Mg and La were chosen as binary metals in the synthesis of Mg-La LDH to enhance phosphate efficient adsorption. Different molar ratios of Mg to La (2:1, 3:1, and 4:1) were investigated to further enhance P adsorption. The best performing Mg-La LDH, with Mg to La ratio is 4:1 (LDH-4), presented a larger adsorption capacity and faster adsorption rate than other Mg-La LDH. The maximum adsorption capacity (87.23 mg/g) and the rapid adsorption rate in the initial 25 min of LDH-4 (70 mg/(g·h)) were at least 1.6 times and 1.8 times higher than the others. The kinetics, isotherms, the effect of initial pH and co-existing anions, and the adsorption-desorption cycle experiment were studied. The batch experiment results proved that the chemisorption progress occurred on the single-layered LDH surface and the optimized LDH exhibited strong anti-interference capability. Furthermore, the structural characteristics and adsorption mechanism were further investigated by SEM, BET, FTIR, XRD, and XPS. The characterization results showed that the different metal ratios could lead to changes in the metal hydroxide layer and the main ions inside. At lower Mg/La ratios, distortion occurred in the hydroxide layer, resulting in lower crystallinity and lower performance. The characterization results also proved that the main mechanisms of phosphate adsorption are electrostatic adsorption, ion exchange, and inner-sphere complexation. The results emphasized that the Mg-La LDH was efficient in phosphate removal and could be successfully used for this purpose.

Flower-like FeCoNi ternary composite formed by interweaving nano needles for positive electrode material of supercapacitor

Ternary layered double hydroxide (LDH) are potential electrode material choices for supercapacitors (SCs) due to their various oxidation states and high theoretical specific capacitance. In this paper, FeCoNi-LDH composite with cross-braided flowers of nanoneedles has been prepared by a single-step hydrothermal method. By highlighting the structural and morphological advantages, the obtained ternary LDH shows lower resistivity in comparison with the binary LDH. As electrode material, the ternary LDH exhibits excellent electrochemical properties, such as superb specific capacitance of 2163.3 F·g−1 at 0.5 A·g−1 and good cycle retention rate of 93.8% after 5000 cycles at 20 A·g−1. Meanwhile, the assembled asymmetric flexible solid-state supercapacitor device can provide 44.8 Wh·kg−1 energy density at 807.5 W·kg−1. Moreover, two devices in series can also light up miniature light bulbs of different hues and maintain them for a long period when they are connected in series.

Tribochemical insights into the carbon film formation induced by metallic species derived from layered double hydroxide nanoadditives

Layered double hydroxides (LDHs) have demonstrated excellent tribological performance in various studies. However, there remains a fundamental knowledge gap concerning the chemical composition of tribofilms across the cross-section. In this study, we seek to elucidate this question by tribologically testing various binary LDHs. It was found that five out of eight LDHs, denoted as CoAl-, CoFe-, MgAl-, NiFe-, and ZnAl-LDHs could induce hierarchical protective tribofilms due to the formation of rigid oxide layers and in situ carbon-based films. The five tribofilms helped to reduce wear loss and friction by approximately 90% and 20%, respectively. Remarkably, the Co-based tribofilms showed the best antiwear performance because of the thick carbon tribofilm formation and the strong bonding at the metallic/tribo-oxide interfaces. The formation mechanisms of the carbon tribofilm and its characteristic nature were evaluated and revealed by scanning transmission electron microscopy and electron energy loss spectroscopy. Meanwhile, the intriguing nano-scale mechanical properties, i.e., the hardness and reduced elastic modulus of different tribofilms, were well-demonstrated by nanoindentation and nanoscratch experiments. The correlation between chemical structures and mechanical properties of the tribofilms derived from LDH lubricant additives was first conducted and discussed, unveiling the tribochemical and lubrication mechanisms between the LDHs and sliding surfaces.

Recent Advances and Prospects of FeOOH-Based Electrode Materials for Supercapacitors

Supercapacitors (SCs) offer a potential replacement for traditional lithium-based batteries in energy-storage devices thanks to the increased power density and stable charge–discharge cycles, as well as negligible environmental impact. Given this, a vast array of materials has been explored for SCs devices. Among the materials, iron oxyhydroxide (FeOOH) has gained significant attention in SC devices, owing to its superior specific capacitance, stability, eco-friendliness, abundance, and affordability. However, FeOOH has certain limitations that impact its energy storage capabilities and thus implicate the need for optimizing its structural, crystal, electrical, and chemical properties. This review delves into the latest advancements in FeOOH-based materials for SCs, exploring factors that impact their electrochemical performance. To address the limitations of FeOOH’s materials, several strategies have been developed, which enhance the surface area and facilitate rapid electron transfer and ion diffusion. In this review, composite materials are also examined for their synergistic effects on supercapacitive performance. It investigates binary, ternary, and quaternary Fe-based hydroxides, as well as layered double hydroxides (LDHs). Promising results have been achieved with binder-free Fe-based binary LDH composites featuring unique architectures. Furthermore, the analysis of the asymmetric cell performance of FeOOH-based materials is discussed, demonstrating their potential exploitation for high energy-density SCs that could potentially provide an effective pathway in fabricating efficient, cost-effective, and practical energy storage systems for future exploitations in devices. This review provides up-to-date progress studies of novel FeOOH’s based electrodes for SCs applications.

Binary Layered Double Hydroxide Electrode Array Synthesized via Metal Alloy Corrosion for Oxygen Evolution Reaction

Developing highly efficient and cost-effective anodic electrodes is one of the major challenges in hydrogen evolution via water electrolysis technology. We demonstrate that the chloride corrosion can transform commercial Ni–Fe alloy (invar) into an electrode, revealing a high-efficiency oxygen evolution reaction (OER). The corroded electrode consisted of a dense vertical array of NiFe layered double hydroxide (LDH) nanosheets on the invar foil surface. We discovered that the corrosion rate difference between metallic components of the binary metal serves the growth of the NiFe LDH at the invar surface. This NiFe LDH electrode required an overpotential of 211 mV at a current density of 10 mA/cm2 in 1 M KOH, outperforming the commercial IrO2 catalyst by 47 mV. This electrode showed excellent activity against OER owing to their high intrinsic electrical conductivity of direct growth and high electrochemical surface area of NiFe LDH nanosheets. Furthermore, this electrode exhibited excellent electrochemical stability without decay in performance for 7 days at the current density of 50 mA/cm2. This study provides rationally designed electrocatalysts with high and stable catalytic activity to obtain a convenient route to the large-scale production of OER electrodes.

Tailoring the Composition of Ternary Layered Double Hydroxides for Supercapacitors and Electrocatalysis

Layered double hydroxides (LDHs) have attracted great consideration in electrochemical systems such as supercapacitors and water splitting due to their layered structures, flexible interlayer distances, and tunable elemental compositions. Recently, ternary LDHs have been considered as efficient materials for energy-related applications due to their superior performance as compared to binary LDHs. To optimize the composition of ternary LDHs for electrochemical applications, herein, Co-, Ni-, and Fe-based ternary LDHs (CNFLs) at different molar ratios are prepared by a facile electrodeposition method. Among them, a sample with a higher concentration of Ni (Ni-rich CNFL) exhibits a maximal specific capacity of 467 C g–¹ at the sweep rate of 5 mV s–¹ with a capacity retention of 81% after 2000 cycles. In the case of electrocatalytic activity, the Ni-rich CNFL shows an appreciable overpotential of 139 mV to reach the current density of 10 mA cm–² along with the smallest Tafel slope (46 mV dec–¹). The Ni-rich CNFL shows excellent electrocatalytic stability over 8 h of stable operation. This enhanced performance of Ni-rich CNFL is attributed to the synergic effect of Co, Ni, and Fe hydroxides and the anticipated growth of more Coᴵⱽ active sites with the higher surface area. Thus, CoNiFe LDH with a high concentration of Ni acts as a potential electrode material for electrochemical applications.

Environmental-friendly preparation of Ni–Co layered double hydroxide (LDH) hierarchical nanoarrays for efficient removing uranium (VI)

With the wide application of nuclear energy and the rapid development of mining, a great quantity of uranium (U(VI)) containing wastewater is inevitably generated. In this work, a facile environmental-friendly coprecipitation method was proposed for the green synthesis of binary layered double hydroxides (Ni–Co LDHW-7), which could be used to efficiently adsorb U(VI) from wastewater. Pseudo-second-order kinetic model and Dubinin-Radushkevich model fitted well with the adsorption of U(VI) on Ni–Co LDHW-7, the maximum adsorption capacity of U(VI) on Ni–Co LDHW-7 was 201.09 mg/g calculated by the Langmuir model. Adsorption equilibrium reached after 30 min, which is a spontaneous and endothermic process. Fourier Transform Infrared Spectrometer (FTIR) and X-ray Photoelectron Spectroscopy (XPS) measurements manifested that the favorable U(VI) extraction on Ni–Co LDHW-7 is mainly ascribed to inner-layer surface electrostatic interaction and complexation, which is dominated by abundant oxygen-containing M-OH and interlayer OH− ions. Briefly, this work provides a facial and environmental-friendly Ni–Co LDHW-7 for removing U(VI) in actual uranium-containing wastewater.

Adsorptive removal of antibiotics from water over natural and modified adsorbents.

Various adsorbents including agricultural waste-based adsorbents, nanomaterials and layered double hydroxides have been reviewed for removal of antibiotics from water due to their unique properties. The adsorption mechanism is governed mostly by the affinity of a pollutant to adsorbent materials. However, the main adsorption mechanisms defined in this study for removal of antibiotics are the electrostatic attraction, π-π interaction and hydrogen bonding. The study highlighted the contribution of modification in the adsorption capacity of antibiotics. Some of the most important adsorbents discussed in this review are graphene-based adsorbents, binary layered double hydroxides and magnetic nanoparticles as well as the antibiotics sulfamethoxazole, tetracycline and metronidazole. The key factors for the selection of the suitable materials are the structure, characteristics and other physicochemical parameters such as pH and temperature. However, the most crucial factor is the adsorption capacity. Some of the adsorption kinetics models and isotherms for antibiotic sorption are also highlighted in this study. In addition, the review summarizes the future prospects and recent challenges faced with the adsorption techniques for removal of antibiotics from wastewater. This review will help readers understand the current trend in the adsorptive removal of antibiotics from water.

Fundamental investigation on layered double hydroxides derived mixed metal oxides for selective catalytic reduction of NOx by H2

Abstract Selective catalytic reduction of nitrogen oxides (NOx) to N2 by H2 (H2-SCR) does not create any secondary contaminants and can reduce NOx at relatively low temperature. To achieve this goal, an appropriate catalyst is essential. In this contribution, the performance of binary layered double hydroxides (LDHs) derived mixed metal oxides as support for Pt-based H2-SCR catalysts was investigated for the first time. New H2-SCR catalysts Pt/M3Al1Ox (M = Co, Mg, Ni, or Cu) were carefully characterized and systematically evaluated in the presence of O2 at 120–300 °C. All 0.1 Pt/M3Al1Ox catalysts exhibited high SCR activity, with a NOx conversion higher than 90% at 200–220 °C. Among them, 0.1 Pt/Mg3Al1Ox showed higher NOx conversion rate than other catalysts, while 0.1 Pt/Ni3Al1Ox showed higher N2 selectivity. The influences of GHSV, H2 and O2 feed concentration, CO2, and water vapor on the NOx conversion over 0.1 Pt/Ni3Al1Ox catalyst were also investigated. We believe that this work could provide a new option for the selection of supporting materials for H2-SCR.

Effective capture of aqueous uranium from saline lake with magnesium-based binary and ternary layered double hydroxides

Uranium in saline lake brine is a nuclear resource that attracts worldwide attention. Relatively low concentrations (about 0.2 mg L−1 to 30 mg L−1) require high affinity for the capture materials. In this paper, magnesium binary layered double hydroxides (MgAl-LDH) and its Fe-induced ternary LDH (MgAlFe-LDH) were synthesized for the extraction of simulated concentrations of U(VI) in the saline lake brine system. Batch experiments have shown that both LDHs have strong affinity towards uranium. MgAl-LDH yielded of stronger affinity in lower U(VI) concentrations (0.2 mg L−1 to 5 mg L−1), while MgAlFe-LDH was at higher U(VI) concentrations (5 mg L−1 to 30 mg L−1). For current uranium extraction, the affinities of MgAl-LDH and MgAlFe-LDH are more than twice the maximum affinity of other LDHs and LDHs-based materials. Therefore, these two LDHs are suitable for U(VI) extraction with different concentration levels in saline lakes. The capture process followed the pseudo-second-order kinetics with fast adsorption speed, and the coexisting cations have little effect on the extraction rate. Research through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed the main adsorption mechanisms are surface complexation and the interlayer carbonate coprecipitation. This work provides a potential method for U(VI) extraction while reusing the waste magnesium resources in saline lake.

Calcium chloride addition to overcome the barriers for synthesizing new Ca-Ti layered double hydroxide by mechanochemistry

In this study, a new binary Ca-Ti layered double hydroxide (LDH) has been synthesized for the first time by a two-step (dry and wet) milling of calcium hydroxide, hydrated titanium dioxide and a third phase of calcium chloride. No reactions were observed while milling calcium hydroxide and hydrated titanium dioxide unless the further addition of a third phase of calcium chloride which triggered the solid state reaction to form LDH phase. The traditional co-precipitation process failed to synthesize Ca-Ti LDH due to the barriers of the precipitation pH and ion radius differences between Ca2+ and Ti4+. The X-ray diffraction (XRD), Thermogravimetric Analysis (TGA), X-ray photoelectron spectroscopy(XPS) and Scanning electron microscopy (SEM) techniques were applied to characterize the prepared samples. The characterization results demonstrated the successful production of high crystalline Ca-Ti LDH phase. This work proved the feasibility of mechanochemistry to produce novel binary LDH which may be of help for the synthesis of other new layered materials in general.

Novel layered double hydroxide precursor derived high-Co9S8-content composite as anode for lithium-ion batteries

Layered double hydroxides (LDHs), also known as brucite (Mg(OH)2)-like anionic clay compounds, are very convenient precursors with a unique flexibility of tuning component type and molar ratio toward composite nanomaterials in energy storage, such as lithium-ion batteries (LIBs). Conventional binary LDH precursors are typically converted to active/non-active transition-metal oxide composites as anode nanomaterials for LIBs, but either with the aid of additionally introducing highly conductive carbonaceous matrix, or possessing relatively high-content non-active components that greatly lower the reversible specific capacity. Herein, we demonstrate a rational design of a novel single-source precursor of dodecyl sulfonate-intercalated Co2+Co3+Al3+-layered double hydroxide (Co2+Co3+Al3+-LDH) and its conversion to high-Co9S8-content composite (Co9S8/S-doped carbon/Al2O3) as high-efficiency anode nanomaterials for LIBs. In-situ X-ray diffraction (XRD) reveals the controllable topotactic transformation via tuning calcination temperature and time. Electrochemical test shows that the composite electrode delivers a reversible capacity of 970 mA h g−1 after 200 cycles at 100 mA g−1, and in particular, a long-term cycling stability of 780 mA h g−1 after 500 cycles at 1 A g−1, manifesting highly enhanced electrochemical performances compared with the counterpart derived from a conventional binary LDH precursor. Monitoring the discharged/charged states by in-situ XRD and ex-situ Raman spectra provides a direct support to the enhancement. Our results show that the LDH precursor-based approach provides an alternative to prepare diverse transition metal sulfides for energy storage.

Peptide Formation on Layered Mineral Surfaces: The Key Role of Brucite-like Minerals on the Enhanced Formation of Alanine Dipeptides

Alkaline hydrothermal vent environments have gained much attention as potential sites for abiotic synthesis of a range of organic molecules. However the key process of peptide formation has generally been undertaken at lower pH, and using dissolved copper ions to enhance selectivity and reactivity. Here, we explore whether layered precipitate minerals, abundant at alkaline hydrothermal systems, can promote peptide bond formation for surface-bound alanine under cycles of wetting and drying. While we find low level activity in brucite and binary layered double hydroxide carbonate minerals (typically 7 %. However the performance decreased over successive wetting/drying cycles. Control experiments show that this high degree of dipeptide formation cannot be attributed to leached copper from the mineral structure. While only dipeptides are observed, the yields obtained sugg...

Flower-like Surface of Three-Metal-Component Layered Double Hydroxide Composites for Improved Antibacterial Activity of Lysozyme.

Microbes play an important function in our lives, while some pathogenic bacteria are responsible for many infectious diseases, food safety, and ecological pollution. Layered double hydroxide (LDH) is a kind of natural two-dimensional material and has been applied in many fields. Lysozyme is a green natural antibacterial agent, while the antimicrobial activity of lysozyme is not as good as antibiotics. We use a different ratio of cations to tune the morphology of LDH covered with lysozyme to enhance the antibacterial ability of lysozyme. We synthesize MgAl-LDH, ZnAl-LDH, and ZnMgAl-LDH covered with lysozyme, characterize the structure and morphology, test the antibacterial in culture media, and evaluate the biotoxicity in vitro and in vivo. The flower-like structure of ZnMgAl-LDH has a rough surface, covered with lysozyme with a perfect ring, and presents good antibaterial properties and promotes wound healing of mice. The bloom flower structure of ZnMgAl-LDH can enhance the loading rate of lysozyme; meanwhile, the rougher surface can adhere more bacteria, so lyso@ZnMgAl-LDH presents better antibacterial activity than the binary LDHs.

Hierarchically magnetic Ni–Al binary layered double hydroxides: towards tunable dual electro/magneto-stimuli performances

Ni–Al layered double hydroxides (Ni–Al LDHs) are adopted as an electrorheological (ER) material ascribed to their special layered structure, ample polarizable groups and good dispersibility. The magnetite nanoparticles (Fe3O4 NPs) are utilized as classical magnetorheological (MR) materials on account of their excellent paramagnetic property. In this work, we report the rational design of high-performance ER/MR materials by integrating the structural merits of Fe3O4 NPs onto a binary layered structure system. The obtained Fe3O4/Ni–Al LDH NCs dispersed in silicone oil displayed appealing dual ER/MR performances. The work opens a new path toward novel stimuli-responsive materials for industrial applications.

A fascinating combination of Co, Ni and Al nanomaterial for oxygen evolution reaction

Interesting combination of Co, Ni and Al have been assessed for oxygen evolution reaction (OER). Layered double hydroxide (LDH) nanosheets of NiCoAl, Co-Al oxide nanoparticles and Co-Ni oxide nanoparticles were prepared and studied for the first time as OER catalyst. Among all the subjected catalysts, the binary LDH comprise of NiCoAl showed comparatively high catalytic activity than Co-Al oxide nanoparticles and Co-Ni oxide nanoparticles. The Co-Al and Co-Ni oxide nanoparticles showed current densities of 34.6 and 24.5mAcm−2, respectively at 1V in 0.3M KOH solution. However at the same conditions, NiCoAl-LDH showed comparatively low overpotential, high current density (40.8mAcm−2) and lower Tafel slope. The low overpotential and high catalytic activity of NiCoAl-LDH stipulate the possibility to reduce the demand of precious, rare earth and expensive transition metal catalyst in electrochemical water splitting for OER.

Epoxidation of styrene with molecular oxygen over binary layered double hydroxide catalysts

Binary layered double hydroxides (LDHs) of Mg–Al and Co–Al having varied cation molar ratio were studied for the catalytic epoxidation of styrene with molecular O 2 as an oxidant and DMF as a solvent. The effect of various reaction variables, reconstruction and reuse of LDH samples on the catalytic activity was evaluated. The cation molar ratio of LDH as well as concentration of DMF significantly affected the catalytic activity. The highest styrene conversion was observed with LDH having cation molar ratio (Mg/Co:Al) of 3:1. Mg–Al LDH showed highest styrene conversion of 85% with 80% styrene oxide selectivity and Co–Al LDH sample exhibited highest styrene conversion of 97% with 83% oxide selectivity at 100 °C after 4 h.

Density functional theory study on the influence of cation ratio on the host layer structure of Zn/Al double hydroxides

A density functional theory (DFT) study has been carried out for [Zn n−1 Al(OH 2) n+6 (OH) 2 n−2 ] 3+ ( n = 3–6) and [Zn n−1 Al(OH 2) 2 n−2 (OH) 2 n−2 ] 3+ ( n = 7) clusters, which include the basic structural information of the brucite-like lattice structure of Zn/Al layered double hydroxides (LDHs) with Zn/Al molar ratio ( R) in the range 2–6, in order to understand the effect of the Zn/Al ratio on the structure and stability of binary Zn/Al LDHs. Based on systematic calculations of the geometric parameters and formation energies of the cluster models, it was found that it is possible for Zn 2+ and Al 3+ cations to replace Mg 2+ isomorphously in the brucite-like structure with different R values, resulting in differences in microstructure of the clusters and unit cell parameter a of the Zn/Al LDHs. Analysis of the geometry and bonding around the trivalent Al 3+ or divalent Zn 2+ cations reveals that Al 3+ plays a more significant role than Zn 2+ in determining the microstructure properties, formation and bonding stability of the corresponding Zn R Al clusters when R < 5, while the influence of Zn 2+ becomes the dominant factor in the case of R ≥ 5. These findings are in good agreement with experiments. This work provides a detailed electronic-level understanding of how the composition of cations affects the microstructure and stability of Zn-containing binary LDH layers.

Theoretical Study on the Structural Properties and Relative Stability of M(II)−Al Layered Double Hydroxides Based on a Cluster Model

The [M2Al(OH2)9(OH)4]3+ clusters (M = divalent cation Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, or Cd2+), which include the basic information of layered double hydroxides (LDHs) lattice structure with the most economical size, have been investigated by density functional theory (DFT) to shed light on the structural properties and relative stability of M(II)-Al binary LDHs layers with a M2+/Al3+ ratio of 2. The geometric parameters (bond distance and bond angle), natural bond orbitals (NBO), stretching vibration frequencies of three-centered bridging OH groups (nu(O3-H)), as well as binding energy of the cluster model were systematically studied. It was found that the geometries and the nu(O3-H) frequency for the calculated clusters are remarkably influenced by the electronic structure of the divalent cations, such as valence electronic configuration, natural bond orbitals, natural charge transfer, and bond order. The calculated binding energies are in good agreement with the relative stability of the experimental results for the corresponding LDHs. The calculation results reveal that the 2Ni-Al cluster shows the highest stability among the open-shelled cation-containing clusters, while the stability of the 2Cu-Al cluster is the weakest; the 2Mg-Al and 2Zn-Al clusters are the most stable ones among the closed-shelled cation-containing clusters. These findings are in high accordance with the experimental results. Therefore, this work provides a detailed understanding of how the electronic structure of cations plays a more significant role in the structural properties and relative stability of the corresponding LDHs layers rather than ionic size.