Flower-like Layered Double Hydroxides Research Articles

Preparation of Flower-Like Layered Double Hydroxides Supercapacitor Cathode Based on Biomineralization Strategy

Preparation of Flower-Like Layered Double Hydroxides Supercapacitor Cathode Based on Biomineralization Strategy

Flower-Like Layered Double Hydroxides for the Adsorption of Azocarmine G: Kinetic, Isotherm, and Thermodynamic Studies

Flower-Like Layered Double Hydroxides for the Adsorption of Azocarmine G: Kinetic, Isotherm, and Thermodynamic Studies

The excellent microwave absorption properties of the composite structure of 3D flower-like layered double hydroxide derivatives and multi-walled carbon nanotubes

The control of electromagnetic pollution and military affairs both heavily rely on the absorption and attenuation of electromagnetic waves. NiO/Co3O4 obtained by pyrolysis of NiCo-layered double hydroxides retained the structural framework of the precursor and introduced a porous structure in the pyrolysis process, which effectively enhanced the multiple reflections and scattering of electromagnetic waves. Furtherly, multi-walled carbon nanotubes were embedded into bimetallic oxides to create a conductive network and introduce polarization groups, resulting in a reflection loss of −56.90 dB and an absorption bandwidth of 6.19 GHz. Compared to traditional metal oxides, the NiO/Co3O4-MWCNT composite greatly improved the wave absorption effect. Such a new structure provided a new idea for the application of LDH in the field of wave absorption.

Facile synthesis of interlaced flower-like layered double hydroxides grown on porous CoMoP as a highly efficient electrocatalyst for hydrogen evolution reaction

Rational morphology design and electronic structure modulation of efficient and durable electrocatalyst for hydrogen evolution reaction (HER) are urgent and challenging tasks to solve the large overpotential problems currently required. Herein, this study investigated the effect of dual electrodeposition and doping on the HER performance of electrocatalysts. Highly porous cobalt molybdenum phosphate (CoMoP) was used as a support for three different layered double hydroxides (LDHs)including cobalt nickel (CoNi), nickel iron (NiFe), and cobalt iron (CoFe). CoFe-LDH/CoMoP electrodeposited on nickel foam (NF) only need 22.5 mV overpotential to reach current response of 30 mA cm−2. To be used as a HER electrocatalyst, however, NiFe-LDH/CoMoP/NF (383 mV) and CoNi-LDH/CoMoP/NF (117 mV) require much higher overpotential than that of CoFe-LDH/CoMoP/NF. The newly developed porous CoFe-LDH/CoMoP/NF works well as an active HER electrocatalyst in the alkaline medium with a low overpotential. In the analysis of the second electrodeposition effect on HER performance of the three developed LDHs, the second electrodeposited CoFe-LDH/CoMoP/NF electrocatalyst showed greatly decreased Tafel slope and overpotential at a constant time as compared to the first electrodeposition. Considering their superior HER performance and keeping good stability even after 19 h, the developed electrocatalysts could be an excellent replacement for non-noble-metal HER catalysts.

Simultaneous Electrochemical Determination of Catechol and Hydroquinone Using a Flower-Like Ni-Al Layered Double Hydroxide/Carbon Black Nanocomposite-Modified Electrode

We have developed a Ni-Al layered double hydroxide (LDH) and carbon black (CB) composite for the selective electrochemical detection of hydroquinone (HQ) and catechol (CT). LDH exhibits multiple active sites and high adsorption capacity for phenolic substances. CB demonstrates high conductivity and electrocatalytic capacity. The crystal structure was characterized by X-ray diffraction, establishing the successful synthesis of flower-like LDH, and the successful combination of LDH and CB. Fourier-transform infrared spectroscopy confirmed that the LDH surface contained sufficient hydroxyl groups to adsorb CT and HQ. The morphology of LDH/CB was characterized by scanning electron microscopy, and the composition and valence confirmed by X-ray photoelectron spectroscopy. The LDH/CB sensor delivered excellent performance in terms of sensing HQ and CT, with a wide detection range (0.1–150 μM) and detection limits of 0.011 and 0.0091 μM (DL = 3.3σ/S), respectively. The excellent performance of this sensor makes it a reliable choice for detecting HQ and CT in water.

Block Copolymer Self-Assembly Guided Synthesis of Mesoporous Carbons with In-Plane Holey Pores for Efficient Oxygen Reduction Reaction.

In this paper, a simple approach, using interfacial self-assembly of block copolymers (BCPs) on self-sacrificial templates, for preparing mesoporous carbons with in-plane holey pores, including nitrogen atom-doped carbon nanosheets and nanoflowers (denoted as NHCSs and NHCFs), is reported. The approach employs sheet- or flower-like layered double hydroxide as the templates, P123 copolymer as the pore-directing agent, and m-phenylenediamine as the carbon source. The holey mesopores may shorten the mass transfer distance in the internal active sites of stacked nanosheets, while the 3D packing mode of nanosheets can reduce pore blockage caused by their tight stacking. Profiting from these structural advantages, acting as electrocatalysts for oxygen reduction reaction (ORR), both NHCSs and NHCFs show excellent catalytic performance better than that of carbon nanosheets without holey pores. Particularly, NHCFs exhibit a high half-wave-potential (0.82V) anda limiting current density (5.4mAcm-2 ), close to those of commercial Pt-C catalysts. This study provides valuable clues on building mesoporous materials with in-plane holey pores as well as on the effect of pore structure and stacking mode of 2D materials on their electrocatalytic ORR performance.

3D nanoflower-like layered double hydroxide modified quaternized chitosan/polyvinyl alcohol composite anion conductive membranes for fuel cells

To solve the trade-off problem among ionic conductivity, mechanical and chemical stability of anion exchange membranes (AEMs), quaternized chitosan (QCS) was first prepared and then was blended with polyvinyl alcohol (PVA) to improve mechanical strength of QCS. Afterwards, three-dimensional (3D) hierarchical flower-like layered double hydroxides (LDHs) were prepared via one-pot ethylene glycol-assisted solvothermal method, and then were incorporated into QCS/PVA blend matrix to fabricate composite AEMs. By constructing 3D hierarchical structure, the active sites of LDH nanosheets are fully exposed, thus impressive ion conductivity, alkali and fuel resistant ability of LDH nanosheets can be rationally utilized. The composite membrane displayed the maximum OH− conductivity of 25.7 mS cm-1, which was 48.6 % higher than that of the pristine membrane. Alkaline stability measurement proved that the composite membranes kept residual ionic conductivity of as high as 92 % after immersion in a 2 M KOH for 100 h. Due to the decreased methanol permeability and increased conductivity, the composite membrane with 6% LDHs content exhibited a peak power density of 73 mW cm-2 at 60 °C, whereas the pristine membrane demonstrated only 40 mW cm-2.

The coralline cobalt oxides compound of multiple valence states deriving from flower-like layered double hydroxide for efficient hydrogen generation from hydrolysis of NaBH4

Efficient hydrogen storage, transportation and generation are key-technology for future hydrogen economy. Sodium borohydride (NaBH4) stands out as promising hydrogen energy carrier with merits of high volumetric density and environmentally benign hydrolysis products. Flower-like layered double hydroxide α-Co(OH)2 with intercalation of B species was synthesized via hydrothermal crystallization method using sodium tetraphenylboron as source of B and alkaline, which makes it different from the previous supporting materials. Pure or mixed cobalt oxides with different valence states containing B (CoO/B, Co3O4/B, Co+CoO/B, CoO+Co3O4/B) were subtly prepared via controlling calcination temperature, time and atmosphere for sodium borohydride hydrolysis. Coral-like CoO+Co3O4/B displayed superior hydrogen generation rate (6478 mlH2·min−1·g−1metal) with arrhenius activation energies of 41.14 kJ/mol for NaBH4 hydrolysis in alkaline solutions compared to those reported pure precious metals. The out-standing catalytic performance of CoO+Co3O4/B may be attributed to electron transfer among cobalt oxide. DFT calculation indicates NaBH4 hydrolysis undergoes a reaction path on CoO+Co3O4 surface with lower relative energies.

Study on the efficient removal of azo dyes by heterogeneous photo-Fenton process with 3D flower-like layered double hydroxide.

As organic dyes are the main pollutants in water pollution, seeking effective removal solutions is urgent for humans and the environment. A novel environmentally friendly three-dimensional CoFe-LDHs (3D CoFe-LDHs) catalyst was synthesized by one-step hydrothermal method. Scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectra, X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller technique as well as UV-Vis diffuse reflectance spectra were used to characterize the prepared samples. The experimental results revealed that 3D CoFe-LDHs exhibited a rapid decolorization of methyl orange and Rhodamine B by heterogeneous photo-Fenton process after reaching the adsorption equilibrium, and the final decolorization efficiency reached 91.18% and 93.56%, respectively. On the contrary, the decolorizing effect of 3D CoFe-LDHs on neutral blue was relatively weak. The initial concentrations of azo dyes, pH and H2O2 concentration affected the decolorization of dyes and the catalyst maintained excellent reusability and stability after reuse over five cycles. The quenching experiments found that •OH, •O2 - and h+ were the main active substances and reaction mechanisms were further proposed. The study suggests that the synergistic effect of photocatalysis and Fenton oxidation process significantly improved the removal of azo dyes and the synthesized catalyst had potentially promising applications for difficult-to-biodegrade organic pollutants in wastewater.

Phosphate functionalized layered double hydroxides (phos-LDH) for ultrafast and efficient U(VI) uptake from polluted solutions

Elimination of U(VI) from polluted solutions is important for human health and environmental safety. In this work, a relatively low-cost 3D flower-like phosphate-functionalized layered double hydroxides (phos-LDH) was fabricated by a one-pot hydrothermal method. The prepared phos-LDH inherited the structure of 3D flower-like layered double hydroxides (LDH), and had a higher specific surface area (∼203.4 m2⋅g−1) than that of LDH. The kinetic process indicated that U(VI) adsorption onto phos-LDH achieved equilibrium within 15 min and obeyed general order model. The adsorption isotherms of phos-LDH illustrated that the U(VI) adsorption obeyed Langmuir model, the adsorption capability of phos-LDH can reach 923.1 mg⋅g−1 at 298 K. The U(VI) adsorption was a spontaneous and endothermic process according to the thermodynamic data. There was the electrostatic attraction between U(VI) and phos-LDH at pH = 5.0. FTIR and XPS analyses educed that the hydroxyl and phosphate groups played a very useful role for the complexation between U(VI) and phos-LDH. In addition, the excellent selective adsorption capability for U(VI) in competitive cation and anion solutions further confirmed the practical application of phos-LDH in real wastewater treatment.

Persistent organic pollutants removal via hierarchical flower-like layered double hydroxide: Adsorption behaviors and mechanism investigation

Nanostructured hierarchical flower-like MgAl layered double hydroxide (HMA-LDH) was synthesized via the one-pot soft-template method and employed for the adsorption of persistent organic pollutants: anionic methyl orange (MO) and non-ionic naphthalene (NAP). The adsorption performance and mechanism comparison of MO and NAP were investigated via adsorption kinetics, isotherms, thermodynamics, and microstructural characterization. The maximum adsorption capacity of MO and NAP could reach 380.2 and 43.7 mg·g−1 at 298 K, respectively. The kinetic studies illustrated that the adsorption equilibria reached in 2 and 1 h for MO and NAP, respectively. The adsorption isotherms indicated that HMA-LDH fitted the Langmuir model toward MO removal, while partition model for NAP. The comparative mechanism between MO and NAP were determined by X-ray diffraction (XRD), Fourier transform spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Anion exchange dominated the MO adsorption, whereas partition was deemed as the predominated mechanism for NAP. Furthermore, the recycle performance stated that HMA-LDH could be reused in five cycles in MO adsorption, while failed after two cycles for NAP. This study provided a theoretical foundation for the practical application of hierarchical flower-like LDH in the adsorption of persistent organic pollutants in the aquatic environment.

Preparation of LDH-modified cotton fabric based carbon aerogel as a highly efficient adsorbent for tellurium recovery

As a rare element with special properties, tellurium (Te) is an important resource that has been widely used in many fields. In this paper, a novel renewable cotton fabric based Zn–Al layered double hydroxide (LDH) functionalized carbon aerogel (ZALCA) was successfully prepared by a facile freeze-drying, carbonization and in situ growth method, which can be used for tellurium adsorption. The scanning electron microscopy results showed that the flowerlike LDH nano-sheets are growing evenly on the surface of carbon aerogel and each LDH nano-sheet has a similar shape and size. The nitrogen sorption analysis confirmed that mesoporous ZALCA has the pores centered at about 3–5 nm and Brunauer–Emmett–Teller surface area of 186.38 m2/g. Adsorption experiment results show that the ZALCA has excellent adsorption properties for tellurium ions in tellurium-containing solutions, and the maximum adsorption capacity is 132 mg/g. After recycling 10 times, the ZALCA still displayed high tellurium absorption property implies that the ZALCA has outstanding reusability performance. Therefore, the preparation of ZALCA as a tellurium adsorbent from low-cost cotton has great application potential in the recovery of tellurium.

Enhanced Heck reaction on flower-like Co(Mg or Ni)Al layered double hydroxide supported ultrafine PdCo alloy nanocluster catalysts: the promotional effect of Co.

A series of PdCo alloy nanocluster (NC) catalysts x-PdCor/Co(Mg or Ni)Al-LDH (x: Pd loading, r: Co/Pd molar ratio) were synthesized by immobilizing ultrafine PdCor-PVP NCs on flower-like layered double hydroxide (LDH) supports. The sizes of PdCo alloy NCs of the catalysts can be elaborately tuned in ∼1.6-3.2 nm by both Co/Pd ratios and Pd loadings, and the PdCo NCs are mainly dispersed on the edge sites of LDH nanosheets upon a flower-like morphology. The PdCo bimetallic catalysts 0.81-PdCo0.10/MgAl-LDH (2.6 ± 0.6 nm), 0.86-PdCo0.28/MgAl-LDH (2.3 ± 0.7 nm) and 0.79-PdCo0.54/MgAl-LDH (3.2 ± 0.9 nm) exhibit enhanced activity compared with the monometallic Pd catalyst for Heck coupling of iodobenzene with styrene. Particularly, 0.86-PdCo0.28/MgAl-LDH shows the highest activity, which can be attributed to its smallest PdCo0.28 alloy NCs, and the maximum electron density of the Pd0 center resulted from the electron transfer from Co and the strongest PdCo0.28 NCs - LDH synergistic effect. 0.67-PdCo0.28/CoAl-LDH shows much better activity than those of 0.64-PdCo0.28/NiAl-LDH and 0.86-PdCo0.28/MgAl-LDH. The lowest Pd loading sample 0.01-PdCo0.28/CoAl-LDH (1.6 ± 0.4 nm) shows an ultrahigh turnover frequency of 163 000 h-1 (Pd: 1.9 × 10-5 mol%), which is the highest value obtained so far. Meanwhile, the catalyst shows excellent adaptability for the substrates and can be reused for 12 runs without significant loss of activity. The present work may provide a new idea for the simple and green synthesis of ultrafine Pd-based non-noble bimetallic catalysts for varied catalytic processes.

Synthesis and adsorption properties of flower-like layered double hydroxide by a facile one-pot reaction with an eggshell membrane as assistant

In this paper, flower-like layered double hydroxides were synthesized with eggshell membrane assistant. The as-prepared samples were characterized by a series of techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermal gravity-differential thermal analysis and Nitrogen sorption/desorption. The resulting layered double hydroxides were composed of nanoplates with edge-to-face particle interactions. The specific surface area and total pore volume of the as-prepared flower-like layered double hydroxides were 160[Formula: see text]m2/g and 0.65[Formula: see text]m3/g, respectively. The adsorption capacity of flower-like layered double hydroxides to Congo Red was 258[Formula: see text]mg/g, which was higher than that of layered double hydroxides synthesized by the traditional method.

Solid phase extraction of hexavalent chromium by Mannich base polymer wrapped flower-like layered double hydroxide

ABSTRACTIn the present work, synthesis of polymer wrapped flower-like MgAl layered double hydroxide was done through condensation of 1,4 phenylenediamine and resorcinol by p-formaldehyde. The nanocomposite was characterised with X-ray diffraction analysis, fourier transform infrared spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy techniques and employed for effective adsorption of Cr(VI) from aqueous solution prior to flame atomic absorption spectrometer determination. Optimum level of effective parameters (pH, reaction time and adsorbent dosage) and their interaction was determined by response surface methodology. To investigate applicability of method for trace heavy metal adsorption, the method was employed for preconcentration of Cr(VI) in water samples. At the optimum conditions, pH = 4.5, shaking time of 15 min and adsorbent dosage of 20 mg, analytical performance of the method was evaluated and results showed that calibration curve is linear in the concentration range of 2–100 μg L−1. Moreover, limit of detection was 0.22 µg L−1 and relative standard deviation of six replicate experiments at initial concentration of 0.1 mg L−1 was 3.3%. Isotherm study showed that Freundlich model can better describe adsorption behaviour as well as the sorbent showed the adsorption capacity of 62.5 mg g−1. Moreover, thermodynamic study revealed that chromate adsorption was spontaneous and followed the endothermic path. Regeneration of sorbent was performed using 1.0 mol L−1 of NaOH solution. The sorbent was employed for Cr(VI) determination from food additives and seawater samples.

Effect of morphological properties of layered double hydroxides on adsorption of azo dye Methyl Orange: A comparative study

The present research discussed the utilization of layered double hydroxides (LDH) materials with different morphologies as adsorbents for Methyl Orange (MO) removal from aqueous solution. The adsorption properties of LDH with flower-like morphology (f-LDH) have been investigated for azo dye, Methyl Orange (MO), and compared to conventional stone-like coprecipitated LDH phases (c-LDH). Flower-like LDH with high specific surface area of 133m2/g were synthesized by coprecipitation method in dilute alkaline solution. With relatively high specific surface areas, the as-prepared flower-like LDH, when tested as adsorbents in azo dye removal, showed excellent performance and were better than those of conventional coprecipitated LDH. The adsorption isotherms, kinetics and mechanisms for azo dye MO onto as-prepared flower-like LDH were also investigated. The high uptake capability of the as-prepared flower-like adsorbents 500.6mg of MO/g of LDH make them potentially attractive adsorbents in water purification avoiding calcination step. Hence, a low cost material will be acquired with much more benefits namely preserving energy.

High-performance hybrid supercapacitor with 3D hierarchical porous flower-like layered double hydroxide grown on nickel foam as binder-free electrode

The synthesis of layered double hydroxide (LDH) as electroactive material has been well reported; however, fabricating an LDH electrode with excellent electrochemical performance at high current density remains a challenge. In this paper, we report a 3D hierarchical porous flower-like NiAl-LDH grown on nickel foam (NF) through a liquid-phase deposition method as a high-performance binder-free electrode for energy storage. With large ion-accessible surface area as well as efficient electron and ion transport pathways, the prepared LDH-NF electrode achieves high specific capacity (1250 C g−1 at 2 A g−1 and 401 C g−1 at 50 A g−1) after 5000 cycles of activation at 20 A g−1 and high cycling stability (76.7% retention after another 5000 cycles at 50 A g−1), which is higher than those of most previously reported NiAl-LDH-based materials. Moreover, a hybrid supercapacitor with LDH-NF as the positive electrode and porous graphene nanosheet coated on NF (GNS-NF) as the negative electrode, delivers high energy density (30.2 Wh kg−1 at a power density of 800 W kg−1) and long cycle life, which outperforms the other devices reported in the literature. This study shows that the prepared LDH-NF electrode offers great potential in energy storage device applications.

Preparation and Wetting Properties of Layered Double Hydroxide Colloidal Nano/Microspheres with Tunable Flower-Like Morphologies

Layered double hydroxides (LDHs), known as a type of multifunctional anionic layered clay, typically exhibit stability and intrinsic hydrophilicity at neutral and alkaline pH. We herein report a polymer bead-templated preparation of flower-like LDH shell microspheres with the LDH platelets tuned under different aging durations and temperatures. Thickness of LDH shell walls was tuned readily by varying preparation conditions such as aging durations and temperatures. After a simple chemical surface modification using fluorine-silane molecule, the flower-like LDH nano/microspheres show the distinctly different transitions from the intrinsic hydropholicity to the superhydrophobicity at pH 2 and neutral pH. In contrast, at alkaline condition of pH 12 small flower-like spheres were formed atop of the parent microspheres, which may be argued in terms of a process of desorption of silane molecule at the alkaline condition combined with dissolution and reassembly of LDH platelets. Our finding of the superhydrophobic LDH spheres may find useful applications in chemical and biosensors against harsh acidic conditions.

Fabrication of Hierarchical Layered Double Hydroxide Framework on Aluminum Foam as a Structured Adsorbent for Water Treatment

A hierarchical Mg–Al layered double hydroxide (LDH) framework has been fabricated via the in situ crystallization technique on aluminum foam, which can be used to remove heavy metal ion Cr(VI) and anionic dye (Remazol Brilliant Blue R, denoted as RBBR) from aqueous solutions. The as-prepared LDH/Al-foam displays flowerlike LDH microspheres composed of numerous LDH nanoplatelets, which was confirmed by XRD and SEM. The sorption kinetics of hierarchical LDH framework for Cr(VI) was appropriately described by a pseudo-second-order model. Sorption isotherms of both Cr(VI) and RBBR were also studied, which can be fitted by the Langmuir model more satisfactorily than the Freundlich one. It was found that the sorption capacities (qMAX) of the LDH framework reached 27.8 mg g–1 for Cr(VI) and 212.8 mg g–1 for RBBR, respectively, much larger than those of the corresponding LDH powder sample (21 mg g–1 for Cr(VI) and 166.7 mg g–1 for RBBR). Furthermore, the hierarchical LDH framework exhibits excellent sorption–rege...