LDH Sheets Research Articles

Photocatalytic CO2 Reduction by Near‐Infrared‐Light (1200 nm) Irradiation and a Ruthenium‐Intercalated NiAl‐Layered Double Hydroxide

AbstractNear‐infrared light‐driven photocatalytic CO2 reduction (NIR‐CO2PR) holds tremendous promise for the production of valuable commodity chemicals and fuels. However, designing photocatalysts capable of reducing CO2 with low energy NIR photons remains challenging. Herein, a novel NIR‐driven photocatalyst comprising an anionic Ru complex intercalated between NiAl‐layered double hydroxide nanosheets (NiAl‐Ru‐LDH) is shown to deliver efficient CO2 photoreduction (0.887 μmol h−1) with CO selectivity of 84.81 % under 1200 nm illumination and excellent stability over 50 testing cycles. This remarkable performance results from the intercalated Ru complex lowering the LDH band gap (0.98 eV) via a compression‐related charge redistribution phenomenon. Furthermore, transient absorption spectroscopy data verified light‐induced electron transfer from the Ru complex towards the LDH sheets, increasing the availability of electrons to drive CO2PR. The presence of hydroxyl defects in the LDH sheets promotes the adsorption of CO2 molecules and lowers the energy barriers for NIR‐CO2PR to CO. To our knowledge, this is one of the first reports of NIR‐CO2PR at wavelengths up to 1200 nm in LDH‐based photocatalyst systems.

Photocatalytic CO2 Reduction by Near-Infrared-Light (1200 nm) Irradiation and a Ruthenium-Intercalated NiAl-Layered Double Hydroxide.

Near-infrared light-driven photocatalytic CO2 reduction (NIR-CO2PR) holds tremendous promise for the production of valuable commodity chemicals and fuels. However, designing photocatalysts capable of reducing CO2 with low energy NIR photons remains challenging. Herein, a novel NIR-driven photocatalyst comprising an anionic Ru complex intercalated between NiAl-layered double hydroxide nanosheets (NiAl-Ru-LDH) is shown to deliver efficient CO2 photoreduction (0.887 μmol h-1) with CO selectivity of 84.81 % under 1200 nm illumination and excellent stability over 50 testing cycles. This remarkable performance results from the intercalated Ru complex lowering the LDH band gap (0.98 eV) via a compression-related charge redistribution phenomenon. Furthermore, transient absorption spectroscopy data verified light-induced electron transfer from the Ru complex towards the LDH sheets, increasing the availability of electrons to drive CO2PR. The presence of hydroxyl defects in the LDH sheets promotes the adsorption of CO2 molecules and lowers the energy barriers for NIR-CO2PR to CO. To our knowledge, this is one of the first reports of NIR-CO2PR at wavelengths up to 1200 nm in LDH-based photocatalyst systems.

Investigation of Ag nanoparticles decorated Ni-Al layered double hydroxide as a gas sensor

Chemiresistive gas sensors based on LDH structure were investigated for the detection of widely used volatile organic compounds (VOCs) including methanol, ethanol, and acetone at room temperature. In order to increase the surface active sites and subsequently improve the detection sensitivity of gas molecules, the use of Ag decoration method along with the creation of porosity on the surface of LDH structures were investigated. In this method, methanol solvent was used as a hole scavenger and UV radiation as a catalyst for binding Ag to the surface of LDH sheets. The microstructure and morphology of the composites were investigated by FESEM, HRTEM, EDS, EDS mapping, XRD, and MS analysis. The investigated parameters included relative humidity, calibration curve, repeatability, selectivity, and response/recovery times. According to the obtained results, the creations of surface corrosion by methanol and decorating the structure with Ag have both affected the sensitivity of the sensors. The pure Ni-Al LDH sensor has a response value of 6.8–250 ppm of ethanol. By increasing the specific surface area and creating LDH nanosheets, the response value can be increased up to 8.52. Also, the addition of Ag NP (Ni-Al LDH decorated with Ag NP) has increased the response up to 10.89. It was also observed that the response times in different modes have the least difference. At the end, the response mechanism was investigated based on the heterojunction theory.

Hierarchically Porous and Magnetic MgFe2O4@MgAl‐LDHs Microspheres Synthesized by a Bio‐Templating Strategy for Efficient Removal of Congo Red from Water**

AbstractLDHs (Layered double hydroxides) has broad application prospects as adsorbent. Herein, a facile bio‐template route was developed using pine pollens to fabricate a novel 3D hierarchical MgFe2O4@MgAl‐LDHs adsorbent for rapid removal of organic pollutant from water. The agglomeration of the LDH sheets was prevented and evenly distributed over the surface of MgFe2O4 which resulting in large surface area (108.660 m2 g−1). The adsorption and regeneration of the adsorbent were examined. The as‐prepared MgFe2O4@MgAl‐LDHs exhibited excellent adsorption capacity (191.20 mg g−1) for Congo Red and still remained 81.61 % (156.03 mg g−1) of the first time after regenerated 3 times with methanol. Additionally, it could be conveniently recycled via an external magnetic field. The high adsorption capacity, easy recycling, and the low‐cost and readily available biomass made MgFe2O4@MgAl‐LDHs attractive for water remediation.

Investigating the microstructures and properties of Mg‐Al LDH film‐coated Mg‐Li alloy: Effect of hydrothermal temperature

AbstractMagnesia‐alumina layered double hydroxide (Mg‐Al LDH) films grown in situ on LA43M magnesium‐lithium (Mg‐Li) alloy were synthesized utilizing the hydrothermal method. Scanning electron microscopy (SEM), energy‐dispersive spectrometry (EDS), and X‐ray diffraction (XRD) were used to characterize the surface morphologies, composition, and phase of the Mg‐Al films. The corrosion resistance of the Mg‐Al films was estimated via immersion experiment and hydrogen evolution test, and the tribological properties were investigated using tribological wear tests. The results showed that the thickness of the Mg‐Al LDH film enhanced, and the size of the LDH sheets increased as the hydrothermal temperature raised, resulting in the improvement of the corrosion and wear resistance. When the hydrothermal temperature reached 110°C, interlayer anions were loaded the most, and the film achieved the optimal thickness. The Mg‐Al LDH film had the optimum corrosion resistance and tribological properties. At this point, the weight loss of the film was 1.3560 mg·cm–2, and the average friction coefficient was .149. It demonstrated that synthesizing Mg‐Al LDH at a hydrothermal temperature of 110°C was an effective approach to improve the corrosion resistance of LA43M.

Constructing S-scheme heterojunction of carbon nitride nanorods (g-CNR) assisted trimetallic CoAlLa LDH nanosheets with electron and holes moderation for boosting photocatalytic CO2 reduction under solar energy

• Fabrication of 1D/2D g-CNR and trimetallic CoAlLa-LDH heterojunction for CO 2 reduction. • 1D g-CNR provides extra active reaction place and permits fast photogenerated charge carriers separation. • 2D/2D g-CNR/CoAlLa-LDH interface heterojunction showed S-scheme mechanism for efficient CO 2 reduction. • The photocatalytic bireforming of methane resulted in syngas (CO/H 2 ) evolution. • The enhanced visible light activity attributed to the formation of S-scheme with good stability. Well-designed template free synthesis of one dimensional (1D) graphitic carbon nitride nanorods (g-CNR) coupled with two dimensional (2D) trimetallic CoAlLa-LDH to construct 1D/2D interface heterostructures with strong electrostatic interactions between positively charged 2D LDH sheets and negatively charged 1D g-CNR has been investigated. The lanthanum doped CoAlLa-LDH with unsaturated metal centers has increased reductive sites and oxygen vacancies that led to enhanced charge separation. The 1D g-CNR provides extra active reaction sites for the photocatalytic reaction and permit fast photogenerated charge carriers separation across the interface. The coupling of g-CNR and CoAlLa-LDH with excellent properties resulted in 1D/2D interface heterojunction with S-scheme mechanism for charge carrier transfer by maintaining and effectively utilizing useful charge carriers. The 1D/2D g-CNR/CoAlLa-LDH showed remarkable photocatalytic performance for CO 2 reduction with H 2 O resulting in maximum CO and CH 4 production of 17.85 and 14.66 µmole, respectively. The photocatalytic bireforming (BRM) of methane resulted in the production of syngas (CO/H 2 ) with 12.32 and 5.96 µmole of CO and H 2 , respectively. The enhancement of photocatalytic activity is mainly due to the excellent interfacial contact of g-CNR with ternary metallic CoAlLa-LDH, thus resulting in better transfer and separation of photogenerated charge carriers due to the formation of S-scheme heterojunction. Additionally, the optimum g-CNR/CoAlLa-LDH nanocomposite acquired high photostability after consecutive experimental runs with no apparent variation. The spent catalyst showed no change in morphology, thus proving further good stability of the g-CNR/CoAlLa-LDH photocatalyst. The findings of this work would be beneficial to design template free heterojunction for photocatalytic CO 2 reduction and other solar energy application.

Thermal Degradation Kinetics Analysis of Ethylene-Propylene Copolymer and EP-1-Hexene Terpolymer.

LLDPE is a less crystalline polymer with vast industrial and domestic applications. It is imperative to understand the synthesis, processing conditions, and thermal degradation mechanism of the co- as well as terpolymers. This paper reports the in-situ synthesis and thermal degradation studies of the ethylene-propylene copolymer and ethylene-propylene-1-hexene terpolymer and its nanocomposite with ZnAL LDH sheets. The 1-hexene dosing during the in-situ process influenced the product yield and immensely affected the thermal stability of the resultant polymer. One milliliter 1-hexene in-situ addition increased the product yield by 170 percent, while the temperature at 10 percent weight loss in TGA was dropped by about 60 °C. While only 0.3 weight percent ZnAL LDH addition in the terpolymer improved the thermal stability by 10 °C. A master plot technique and combined kinetics analysis (CKA) were deployed to access the thermal degradation mechanism of the synthesized polymers.

Elucidating the effect of the spacer and the luminescence mechanism of SRB hosted in a LDH interlayer

The optical properties of LDH–DS/SRB powders were optimized by adjusting the alkyl chain length of the organic spacer between adjacent LDH sheets. In-depth study of the fluorescence dynamics enabled to propose a de-excitation mechanism.

Atomic Cation-Vacancy Engineering of NiFe-Layered Double Hydroxides for Improved Activity and Stability towards the Oxygen Evolution Reaction.

NiFe-layered double hydroxides (NiFe-LDH) are among the most active catalysts developed to date for the oxygen evolution reaction (OER) in alkaline media, though their long-term OER stability remains unsatisfactory. Herein, we reveal that the stability degradation of NiFe-LDH catalysts during alkaline OER results from a decreased number of active sites and undesirable phase segregation to form NiOOH and FeOOH, with metal dissolution underpinning both of these deactivation mechanisms. Further, we demonstrate that the introduction of cation-vacancies in the basal plane of NiFe LDH is an effective approach for achieving both high catalyst activity and stability during OER. The strengthened binding energy between the metals and oxygen in the LDH sheets, together with reduced lattice distortions, both realized by the rational introduction of cation vacancies, drastically mitigate metal dissolution from NiFe-LDH under high oxidation potentials, resulting in the improved long-term OER stability. In addition, the cation vacancies (especially M3+ vacancies) accelerate the evolution of surface γ-(NiFe)OOH phases, thereby boosting the OER activity. The present study highlights that tailoring atomic cation-vacancies is an important strategy for the development of active and stable OER electrocatalysts.

Atomic Cation‐Vacancy Engineering of NiFe‐Layered Double Hydroxides for Improved Activity and Stability towards the Oxygen Evolution Reaction

AbstractNiFe‐layered double hydroxides (NiFe‐LDH) are among the most active catalysts developed to date for the oxygen evolution reaction (OER) in alkaline media, though their long‐term OER stability remains unsatisfactory. Herein, we reveal that the stability degradation of NiFe‐LDH catalysts during alkaline OER results from a decreased number of active sites and undesirable phase segregation to form NiOOH and FeOOH, with metal dissolution underpinning both of these deactivation mechanisms. Further, we demonstrate that the introduction of cation‐vacancies in the basal plane of NiFe LDH is an effective approach for achieving both high catalyst activity and stability during OER. The strengthened binding energy between the metals and oxygen in the LDH sheets, together with reduced lattice distortions, both realized by the rational introduction of cation vacancies, drastically mitigate metal dissolution from NiFe‐LDH under high oxidation potentials, resulting in the improved long‐term OER stability. In addition, the cation vacancies (especially M3+ vacancies) accelerate the evolution of surface γ‐(NiFe)OOH phases, thereby boosting the OER activity. The present study highlights that tailoring atomic cation‐vacancies is an important strategy for the development of active and stable OER electrocatalysts.

Mesoporous CuZnAl-layered double hydroxide/graphene oxide nanohybrid as an energy storage electrode for supercapacitor application

With the purpose of the enhancement of supercapacitor behaviour, a CuZnAl-layered double hydroxide/graphene (CuZnAl-LDH/GO) nanohybrid was synthesized via facile method. The layered structures of GO and CuZnAl-LDH lead to create favourable conditions for energy storage capacity. The prepared CuZnAl/GO nanohybrid was characterized by X-ray diffraction, inductively coupled plasma optical emission spectrometry analysis, field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy, N2 adsorption/desorption analysis measurements. The electrochemical behaviour of prepared nanohybrid was evaluated by conventional cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy techniques. As a supercapacitor, the prepared CuZnAl/GO nanohybrid electrode revealed higher specific capacitance (3.87 F cm−2) than CuZnAl-LDHs (1.37 F cm−2). The CuZnAl/GO nanohybrid exhibited good stability, with high specific capacitance for over 1000 charge–discharge cycles. The obtained results can be justified by enhancing electrochemically active areas provided by layered structures of LDH and preventing effect of GO in the aggregation of LDH sheets. Moreover, the GO increase the electrical conductivity in nanohybrid. The facile synthesis and high electrochemical performance of CuZnAl/GO nanohybrid showed that this hybrid material can be suitable as an electrode material for energy storage and supercapacitor devices.

Influence of W6+ cations on the photocatalytic activity of Zn2+Al3+W6+ layered double hydroxides in the degradation of diclofenac

The photocatalytic activity of ZnAl and ZnAlW-x layered double hydroxides (where x = 1.5, 3.0 and 5.0 mol% of W6+ cations) prepared by the coprecipitation method was studied in the photo-degradation of diclofenac (DCF) in aqueous medium using UV light irradiation. The incorporation of W6+ cations within the ZnAl LDH brucite-type layer structure promotes the elimination of CO23– anions and H2O molecules from since the interlayer space as well as the decrease in the band gap energy and the retarding in the recombination rate of electron-hole pairs, giving rise to the improvement in the photocatalytic activity in the degradation of DCF in aqueous medium. Such improvement in the photocatalytic activity could be favored by the increase in the positive charge of the ZnAl LDH sheets due to the incorporation of W6+ cations, arising an increase in the attractive potential for the uptake of anionic diclofenac molecules within the inter-lamellar spacing to compensate the excess of positive charge. ZnAl LDH photoconverts 29.0% of DCF after 90 min of photoreaction. However, the photoconversion percentage of DCF increases with the molar concentration of W6+ to reach 68.0% in 40 min and 82.0% in 90 min of photoreaction respectively using either ZnAlW-1.5 or ZnAlW-3 LDHs. The kinetics studies confirmed that ZnAlW-1.5 and ZnAlW-3 LDHs are the photocatalysts with the highest activity for the elimination of DCF in aqueous medium. Total organic carbon analysis also confirmed the highest efficacy of ZnAlW-1.5 and ZnAlW-3 LDHs to mineralize diclofenac molecules in aqueous medium.

Nanoarray-structured nitrogen-doped graphite foil as the support of NiFe layered double hydroxides for enhancing oxygen evolution reaction

An ideal carbon support, nanoarray-structured nitrogen-doped graphite foil (NNGF), is facilely prepared via a nitrogen plasma procedure of commercial graphite foil (GFL). After plasma treatment, NNGF owns both the bulk layer of graphite inherited from GFL and surface layer of nanoarray-structured defect-rich N doped carbon. Nanometer-sized NiFe layered double hydroxides (NiFe LDH), as an example, are electrodeposited onto NNGF for direct utilization as an OER electrode. Due to the remained graphite layer, the composite electrode is highly conductive; owing to the strong interaction between N dopants and LDH sheets, the charge transfer is dramatically enhanced; meanwhile the diffusion of liquid reactants and gas products during electrocatalysis is also facilitated by the nanoarray structure. As expected, this hybrid NiFe LDH/NNGF electrode exhibits a low overpotential of 0.191 V at 10 mA cm−2. Such nanoarray-structured carbon material is promising to be a universal support for other active species (e.g. NiCo LDH).

Elucidation of the layered structures of AMO solvent-washed Mg–Al layered double hydroxides using Mg- and Al K-edge XANES and EXAFS: Impacts of washing solvents on structures and catalytic esterification of benzoic acid with 2-ethylhexanol to 2-ethylhexyl benzoate

Recently, aqueous miscible organic-layered double hydroxides (AMO-LDHs) have been found to possess impressively-enhanced surface area and pore volume. Although computer simulations were adopted to understand the interaction between an AMO solvent and an LDH, their layered structures have not yet been clearly depicted. Therefore, in this work, Mg- and Al K-edge X-ray absorption spectroscopy (XAS), in association with characterization techniques such as XRD, BET, TEM, and STA-FTIR, were employed to visualize the layered structures in the atomic level of AMO-LDHs synthesized using two AMO solvents; that are, ethanol and acetone. XANES revealed that Mg (II) and Al (III) had octahedral coordination with oxygen atoms, whereas EXAFS revealed that the coordination numbers of Mg–O and Al–O bonds in the ethanol-washed LDH were distinguished from those of acetone- and water-washed LDHs. In addition, the radial distribution around cations of Mg–O–Al bonds in the layers was different from that in the conventional LDH, due to the differences in charge balance between the LDH sheets and AMO solvents. The illustrations of AMO-LDH layered structures were then constructed, in association with the information from the Molecular Dynamic simulation. As a result, the linear combination fitting based on the Mg K-edge XANES results showed that the change in phase composition of AMO-LDHs was attributed to the significantly-enhanced surface area, acid density, and base density, and consequently to the catalytic activity of AMO LDH-derived mixed oxides on the esterification of benzoic acid, a major component in chemical wastes, with 2-ethylhexanol to valuable 2-ethylhexyl benzoate.

2‐nm‐Thick NiCo LDH@NiSe Single‐Crystal Nanorods Grown on Ni Foam as Integrated Electrode with Enhanced Areal Capacity for Supercapacitors

AbstractIt remains a great challenge to simultaneously guarantee the conductivity and high areal loading of active materials for integrated electrode of supercapacitors. Herein, we designed a hierarchical structure with cores of NiSe single‐crystal nanorods and sheaths of 2‐nm‐thick NiCo thin sheets grown on nickel foam (NiCo LDH@NiSe/NF) as integrated electrode. It reaches a high areal capacity of 1131 μAh cm−2 at a current density of 5 mA cm−2, which is 2.2 times of NiSe/NF (522 μAh cm−2) and 6.0 times of NiCo LDH/NF (189 μAh cm−2), superior to most reported integrated electrodes. The enhanced areal capacity can be ascribed to the high active material loading of 6.5 mg cm−2 (twice more than other reported values) and considerable conductivity of single‐crystal NiSe nanorods of 2630 S cm−1. The fabricated hierarchical integrated electrode of NiCo LDH@NiSe/NF assembled with activated carbon shows a maximum energy density of 0.454 mWh cm−2 and a maximum power density of 80 mW cm−2. This work presents supports of single‐crystal nanorods for thin LDH sheets to fabricate high‐density hierarchical structure for integrated electrode, which improves the conductivity and structural stability of active materials especially the LDHs, resulting in excellent electrochemical performance. It offers a promising approach to engineer and fabricate advanced supercapacitors with enhanced areal capacity.

Synergistic enhancement of vinyltriethoxysilane and layered Mg–Al double hydroxide on the tracking and erosion resistance of silicone rubber

It is of great significance and challenge to efficiently improve the tracking and erosion resistance of silicone rubber along with the growing requirements in the field of outdoor high voltage insulation. In this work, we herein proposed an effective way to address this issue by incorporating vinyltriethoxysilane (ViTES) and layered Mg–Al double hydroxide (LDH) into high temperature vulcanized silicone rubber (HTVSR). ViTES/LDH notably enhanced the tracking and erosion resistance of HTVSR. With addition of 3.33 phr ViTES and 5.00 phr LDH, the anti-tracking performance of HTVSR reached the 1A 4.5 level, and the eroded mass was merely 0.3%. The results of scanning electron microscopy and equilibrium swelling showed that ViTES substantially improved the interfacial interaction between HTVSR and LDH and the crosslinking density of HTVSR, and enhanced the dispersion of LDH sheets in the HTVSR matrix. The possible synergistic suppression mechanism of ViTES/LDH on the tracking and erosion of HTVSR was further studied and demonstrated by the plasma irradiation analysis, thermogravimetry and thermogravimetry-Fourier transform infrared spectrometry. It was indicated that under the high voltage arcing discharge, LDH facilitated the formation of a dense barrier layer consisting of bimetal mixed oxides on the HTVSR surface, exerting outstanding lamellar barrier effect. The further degradation and the generation as well as development of electrical tracking were efficiently suppressed. Our findings provided a new approach to fabricate silicone rubber with excellent tracking and erosion resistance.

Modification of Nife Layered Double Hydroxide and Photocatalytic Activity

Modifying materials by ions with multiple valence states is an effective way for enhancing their properties. NiFe layered double hydroxides (NiFe LDHs) were prepared by using a hydrothermal method. Efficient LDH photocatalyst was synthesized by the modification of NiFe LDHs with Fe(III). Electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area, photoluminescence spectroscopy, and UV-Vis diffuse reflectance spectroscopy were used to investigate the morphology, crystal structure, and optical properties of the NiFe LDHs. The photocatalytic and adsorption performances were examined in the degradation of methyl orange. NiFe LDHs exhibited higher adsorption property but lower photocatalytic activity. After modification with Fe(III), the introducing of Fe ions and recrystallization of LDHs led to the distance decreasing between NiFe LDH sheets and exhibit higher photocatalytic performance.

Fabrication of step-by-step drug release system both sensitive to magnetic field and temperature based on layered double hydroxides and PNIPAM

Fabrication of environmental sensitive and controllable drug release systems is urgently needed. In this paper, thermosensitive and magnetic response drug release systems were fabricated via layer-by-layer technique using acetylsalicylic acid (AA) intercalated ZnAl-LDH as core, poly (N-isopropylacrylamide) (PNIPAM) and AA micelles as well as small size ZnAl-LDH sheets as building blocks of the shell. By forming anionic micelles, cationic PNIPAM macromolecules were sandwiched in the LDH sheets with cationic charges which provided a novel way of fabrication of drug release systems. The characteristics of the building blocks, the fabrication process and the release behaviors of the as-prepared drug release systems were characterized in detail. Due to the micro-environmental difference of AA in the core and shell of the systems, step-by-step release behaviors were observed. Also the drug release systems showed obvious temperature and magnetic field dependent responsibility. The obtained assembly is a potential drug release system.

Highly efficient removal of Cd(II) ions by composite of GO and layered double hydroxide composite

Herein, we report a novel nanocomposite (graphene oxide/Ni-Co LDH) via a simple and effective chemical precipitation route. First, the GO nanosheets were synthesized by Marcano method, and then, Ni-Co LDH sheets were deposited on the surface of GO by chemical precipitation. The synthesized nanocomposite was characterized by field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy and x-ray diffraction measurements. The prepared nanocomposite was investigated as an adsorbent for cadmium (II) ions removal from aqueous solutions. Batch studies have been done for obtaining optimal experimental conditions for maximizing metal sorption on the nanocomposite. The nanocomposite shows highest adsorption capacity toward Cd(II) in aqueous solution (126.58 mg g−1). The influence of experimental parameters like time of contact between adsorbent and adsorbate, pH, adsorbent dosage, initial heavy metal concentration and temperature on the removal efficiency of Cd(II) ions was extensively investigated. Kinetic and isotherm parameters of adsorption of Cd(II) were also evaluated. The pH = 7 was chosen as an optimal pH for study of the Cd(II) removal from aqueous solutions. Langmuir isotherm and pseudo-second-order kinetic models were fitted well with experimental data of Cd(II) removal. The reusability of nanocomposite exhibited reasonable values. However, the current nanocomposite could be used as a new adsorbate for adsorption of Cd(II) from contaminant water sources.

Improved performance of flower-like ZnAl LDH growing on carbon nanotubes used in zinc–nickel secondary battery

In this work, a kind of flower-like ZnAl LDH/CNTs composite is fabricated by in-situ growth method. The as-prepared material is characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM),transmission electron microscopy (TEM) and nitrogen adsorption and desorption curves. The results of XRD and FTIR prove that ZnAl LDH growing on carbon nanotubes have been synthesized with the classic hexagonal flaky structure. Morphological analysis also clearly shows that ZnAl LDH grows vertically on the surface of carbon nanotubes and forms a kind of unique flower-like structure. The special structure not only enables CNTs to constitute high conductive network, enhancing the conductivity of the material to suppress its electrochemical polarization, but also provides more active sites for the uniform distribution of zinc species, which can reduce the stacking phenomenon of traditional ZnAl LDH sheets and increase its specific surface area. Moreover, ZnAl LDH/CNTs composite exhibits outstanding electrochemical performance, including stable discharge voltage platform, high specific capacity and superior cycle stability. Although 800 cycles have been achieved, the specific capacity of the electrode of ZnAl LDH/CNTs still remains 336.35 mAh g−1 at 1C current density, with a retention rate of 94.38%. This work provides a kind of novel and attractive hydrotalcite material for zinc–nickel secondary battery.