Hydrotalcite-based two-dimensional material and preparation method thereof

Abstract

The invention provides a hydrotalcite-based two-dimensional material and a preparation method thereof, and the preparation method comprises the following steps: S1, carrying out heat treatment on hydrotalcite at 300-600 DEG C to obtain a metal oxide; s2, dispersing a metal oxide in water to form a turbid liquid; and carrying out ultrasonic treatment on the turbid liquid in an ice bath until the turbid liquid becomes gel, and then drying to obtain the hydrotalcite-based two-dimensional material. According to the method, few-layer and single-layer two-dimensional materials can be obtained through a simple and mild preparation process.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional material preparation technology, specifically relating to a two-dimensional material based on hydrotalcite and its preparation method. Background Technology

[0002] Limited by their size and dimensionality, two-dimensional materials exhibit unique electrical, optical, magnetic, and mechanical properties distinct from bulk materials because electrons can only move freely in a low-dimensional space. They hold significant application value in semiconductor devices, catalysis, chemical engineering, optical devices, flexible electronic materials, solar cells, and sensors, making them a hot research topic worldwide in physics, chemistry, materials science, and biology. However, the controllable synthesis and large-scale preparation of two-dimensional materials remain the biggest obstacles to their development. Mechanical exfoliation, liquid-phase exfoliation, and gas-phase synthesis are currently the most commonly used methods for synthesizing two-dimensional materials. Mechanical exfoliation can rapidly obtain few-layer or even single-layer two-dimensional materials, but its large-scale production is difficult due to the bonding force between the material and the substrate. Liquid-phase exfoliation, through direct exfoliation from the solution and intercalation exfoliation by external cations, can achieve high-yield material preparation; however, its efficiency is low due to slow ion migration, and it can introduce other impurity ions that contaminate the two-dimensional material. Vapor phase growth is a bottom-up growth technique that uses methods such as chemical vapor deposition to control the thickness and size of two-dimensional materials by adjusting parameters such as growth temperature and chamber pressure. However, this technique has high manufacturing costs and complex growth processes. Therefore, there is an urgent need to develop a method for preparing two-dimensional materials that uses inexpensive raw materials, has a simple preparation process, introduces no impurity ions, and is environmentally friendly.

[0003] Layered bimetallic hydroxides ([M]) 1-x 2+ M x 3+ (OH)2] x+ [A] x / n n- Hydrotalcite (LDH), also known as hydrotalcite, is a natural mineral with a layered structure. It consists of two-dimensional lamellar structures composed of octahedrons of divalent and trivalent metal hydroxides. Excess trivalent cations give the lamellar structures a positive charge, and the interlayers are formed by CO32-. 2- Cl - NO3 - PO4 3- SO4 2-The hydrogen bond network formed by the anions and water molecules makes the layered double hydroxide as a whole exhibit electrical neutrality. The LDH layered material has wide applications in the fields of chemical industry, medicine, catalysis, etc. The performance thereof can be further optimized by various modification methods to change ions and functional groups. Firstly, the cations in the layer structure and the anions between the layers can be replaced by various metal elements or exchanged by organic / inorganic anions, so as to adsorb heavy metal elements and anion pollutants under various natural conditions such as atmosphere, water body and geology, thereby achieving efficient adsorption. Secondly, by controlling the parameters such as time, temperature and humidity of the synthesis method, the morphology, particle size and size of the LDH can be controlled, so as to realize the structure regulation of the layered oxide. Thirdly, there are a large number of hydroxyl groups on the surface and between the layers of the LDH, which can anchor inorganic / organic functional groups through intermolecular forces such as electrostatic interaction, hydrogen bond network and hydroxyl covalent connection, so as to realize the functional modification of the surface.

[0004] However, due to the strong electrostatic interaction between the positively charged metal hydroxide layer and the negatively charged interlayer anions, the LDH material will spontaneously form layered crystals with a diameter of tens of microns and a thickness of several hundred nanometers during the synthesis process. The stacking of such layered crystals greatly reduces the specific surface area of the material, reduces the exposed metal hydroxide sites, and loses the intrinsic adsorption capacity of the material. On the one hand, it is difficult to dope and load metal elements, and it is difficult to change the layer charge density to adjust the electronic structure, which loses the catalytic sites and catalytic activity. On the other hand, the fixed interlayer spacing cannot be opened to replace different anions, and it is difficult to adjust the morphology and interlayer spacing. The existing growth method and production process of two-dimensional materials are suitable for graphene, boron nitride and molybdenum disulfide material systems, but it is difficult to apply to LDH material systems, and it is more difficult to synthesize single-layer LDH material on a large scale. Therefore, large-scale synthesis of few-layer or even single-layer LDH material has important significance in the fields of chemical industry, materials, catalysis, environment, medicine, etc. SUMMARY

[0005] In order to solve the problem of easy formation of layered crystal stacking in the preparation of LDH material in the prior art, the present application provides a two-dimensional material based on hydrotalcite and a preparation method thereof, which can obtain few-layer and single-layer two-dimensional material through a simple and mild preparation process.

[0006] The present application is realized by the following technical solutions: In a first aspect, the present application provides a preparation method of a two-dimensional material based on hydrotalcite, comprising: S1, heat treating hydrotalcite at 300-600 DEG C to obtain metal oxide; S2, dispersing the metal oxide in water to form a suspension; performing ultrasonic treatment on the suspension under ice bath until the suspension becomes gelatinous, and then drying to obtain the two-dimensional material based on hydrotalcite.

[0007] Preferably, in S1, the heat treatment time is 30 min to 3 h.

[0008] Preferably, in S1, the heat treatment is performed under the condition of inert gas protection.

[0009] Preferably, in S1, the chemical formula of the hydrotalcite is [M 1-x 2+ N x 3+ (OH)2] x+ [A x / n n- ]·zH2O, wherein M is one or two of Mg, Ca, Fe, Ni, Zn and Mn, N is Al, Fe, Cr or V, A is CO3 2- , Cl - , NO3 - , PO4 3- or SO4 2- .

[0010] Preferably, in S2, the ultrasonic treatment time is 2 min to 2 h.

[0011] Preferably, in S2, the ultrasonic power is 200 to 400 W.

[0012] Preferably, in S2, the mass ratio of the metal oxide to water is (4 to 6):1.

[0013] Preferably, in S2, the drying is performed by freeze drying or heating drying.

[0014] In a second aspect, the present application provides a two-dimensional material based on hydrotalcite obtained by the preparation method.

[0015] Preferably, the two-dimensional material based on hydrotalcite has a sheet thickness of 1 to 20 nm.

[0016] Compared with the prior art, the present application has the following beneficial effects: The application is based on a preparation method of two-dimensional materials of hydrotalcite, uses a natural layered mineral material, hydrotalcite, which is abundant in nature as a precursor, and through a mild and simple production process of high-temperature heat treatment + ultrasonic hydration, adjusts a suitable high-temperature heat treatment temperature to release the interlayer anions but can restore the layered structure through rehydration, and the ultrasonic hydration can maximize the conversion of disordered metal oxides into layered metal hydroxides, and the repulsion of positive charges between metal hydroxides is used to avoid the agglomeration of two-dimensional materials. The preparation method can dissociate the layered metal hydroxides with a thickness of tens to hundreds of nanometers into two-dimensional metal hydroxides with a thickness of a few layers or even a single layer, so that the specific surface area is increased by more than 10 times. The method can not only accurately control the thickness and number of layers of two-dimensional materials, but also realize large-scale synthesis of kilograms. The raw material source of the method is wide, the price is low, the process is simple and mild, and the environment is friendly. The method has the advantages of controllable thickness, adjustable structure, large-scale preparation of two-dimensional materials, becomes a new preparation method of two-dimensional materials based on hydrotalcite, and has wide commercial application value in carbon dioxide capture, catalyst carrier, heavy metal ion adsorption, harmful organic pollutant removal, lithium extraction from brine, drug molecule transport and other directions, and provides an important method for the preparation and application of two-dimensional LDH. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0018] Figure 1 It is a schematic diagram of heat treatment + ultrasonic hydration of the present application.

[0019] Figure 2 It is an atomic force microscope photo comparison chart of the initial hydrotalcite and the two-dimensional material obtained by ultrasonic hydration of the initial hydrotalcite; a, e, i correspond to the initial hydrotalcite, b, f, j correspond to the two-dimensional material obtained by ultrasonic hydration of the initial hydrotalcite for 5 min, c, g, k correspond to the two-dimensional material obtained by ultrasonic hydration for 30 min, d, h, l correspond to the two-dimensional material obtained by ultrasonic hydration for 2 h; the vertical coordinates of i, j and l are the sheet thicknesses of the corresponding materials.

[0020] Figure 3 It is a transmission electron microscope photo of the two-dimensional material obtained by different ultrasonic hydration times in examples 1-3.

[0021] Figure 4The specific surface area and pore size distribution of the two-dimensional material obtained by ultrasonic hydration of the initial hydrotalcite and the initial hydrotalcite of Example 3 for 2h; a, c correspond to the initial hydrotalcite, b, d correspond to the two-dimensional material obtained by ultrasonic hydration of Example 3.

[0022] Figure 5 The transmission electron microscopy images of the two-dimensional materials obtained at different heat treatment temperatures in Examples 5-6.

[0023] Figure 6 The transmission electron microscopy images of the two-dimensional materials obtained by different solvents in Comparative Examples 1-2. DETAILED DESCRIPTION

[0024] The present application can be implemented or applied by other different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the present application.

[0025] It should be noted that the process equipment or device not specifically mentioned in the following examples is the conventional equipment or device in the art.

[0026] It should be noted that the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not a limitation on the arrangement order of each method step or a limitation on the scope of the application, and changes or adjustments of the relative relationship, without substantial changes in the technical content, are also considered as the scope of the application.

[0027] The preparation method of the two-dimensional material based on hydrotalcite of the present application comprises: S1, heat treating the hydrotalcite at 300-600°C to obtain a metal oxide; S2, dispersing the metal oxide in water to form a suspension, ultrasonically treating the suspension under ice bath until the suspension becomes gelatinous, and then drying to obtain the two-dimensional material based on hydrotalcite.

[0028] The raw material hydrotalcite is from natural mineral or artificial synthesis, has typical layered structure characteristics, and the layer plate is composed of divalent metal and trivalent metal and octahedral structure of oxygen, the doping of trivalent atom causes the layer plate to be positively charged, can attract anion inserted into the interlayer to balance the charge, form the sheet layer stacking with fixed interlayer distance, and the thickness is 20nm~200nm.

[0029] The layered hydrotalcite will occur typical phase and structure transition in the heating process, in the process from room temperature to 300 DEG C, the interlayer water in the hydrotalcite will be gradually released, and the interlayer spacing of hydrotalcite will shrink from 0.76nm to 0.68nm, in the process from 300 DEG C to 500 DEG C, the metal hydroxide in the layer plate is gradually decomposed and releases water molecules, and is converted into metal oxide, because there is divalent metal hydroxide and trivalent metal hydroxide in the layer plate, so two different decomposition peaks will appear in this temperature range, in the process of heating to 450 DEG C~500 DEG C, the interlayer anion of hydrotalcite is desorbed and released, and finally forms the metastable metal oxide, and the metastable metal oxide can occur rehydration in aqueous solution before forming stable spinel phase, and is restored to metal hydroxide again.In 600 DEG C or more, the metal oxide will occur phase transition and form stable spinel structure, and the spinel structure cannot be restored to the initial layer by the process of hydration.Therefore, the application selects the temperature interval of 300 DEG C~600 DEG C for heat treatment, and then carries out the ultrasonic hydration process.The application more preferably carries out heat treatment in the temperature interval of 400 DEG C~600 DEG C.

[0030] As Figure 1As shown, after the hydrotalcite is heat-treated to form a metastable phase of metal oxide, water is added to form a suspension, and then the suspension is subjected to ultrasonic treatment by using an ultrasonic device with a power of 200W-400W; during the ultrasonic treatment, the ambient temperature is kept below 30 DEG C by using an ice bath; during the ultrasonic hydration, the metal oxide is fully contacted with water, the original layered structure is completely opened, water is fully contacted with the surface of the metal oxide, and a two-dimensional material is more easily formed; meanwhile, the energy provided by the ultrasonic treatment is more conducive to the breaking of the H-OH bond of water molecules, and the metal-oxygen ionic bond of the metastable phase is polarized by protons to form a metal hydroxide; in this process, the metal oxide can maintain atomic-level doping without phase separation to form an independent single metal oxide, so that the two-dimensional metal hydroxide still exhibits the characteristics of overall positive charge; each layer of the two-dimensional metal hydroxide has a mutual repulsive electrostatic repulsion, avoiding the problem that the two-dimensional material tends to agglomerate due to high surface free energy, so that the specific surface area of the two-dimensional material is increased by more than 10 times, greatly increasing the performance of adsorption, catalysis and loading of the material. Therefore, by using the ultrasonic hydration synthesis process, the layered structure of tens to hundreds of nanometers can be dissociated into a few-layer or even single-layer two-dimensional metal hydroxide. This method can not only accurately control the number of layers and thickness of the two-dimensional material, but also realize large-scale synthesis of kilograms.

[0031] The raw material of the method of the application has a wide source and low price, the production process is mild and simple, the production cycle is short, the production efficiency is high, the production scale is large, and the two-dimensional material does not agglomerate, the morphology, size and thickness of the synthesized two-dimensional material can be accurately controlled, the type and number of metal atoms in the layer can be adjusted to adjust the electronic structure of the material, and the surface modification of different organic and inorganic materials can be realized through the hydroxyl groups on the surface to modify the surface interface. The two-dimensional metal hydroxide can be widely used in carbon capture, chemical material production, catalyst synthesis, drug molecule carrier, adsorption of environmental heavy metal ions and organic pollutants, and has wide commercial application value.

[0032] In some embodiments of the application, in S1, the heat treatment time is 30min-3h.

[0033] In some embodiments of the application, in S1, the heat treatment is carried out under the condition of inert gas protection, which can avoid large-scale agglomeration and sintering of the layered metal oxide.

[0034] In some embodiments of the application, in S1, the chemical formula of the hydrotalcite is [M 1-x 2+ N x 3+ (OH)2] x+ [A x / n n-]·zH2O, wherein the divalent metal element M is one or two of Mg, Ca, Fe, Ni, Zn and Mn, the trivalent metal element N is Al, Fe, Cr or V, the atomic ratio of the trivalent metal element and the divalent metal element, i.e. x:(1-x), can be 1, 2, 3, 6, 10 or 20, and the electronic structure and the energy band width thereof can be accurately adjusted Figure 3 ); A is CO3 2- , Cl - , NO3 - , PO4 3- or SO4 2- . The mutual combination of the divalent metal element M and the trivalent metal element N can obtain a hydrotalcite material of almost all metal atoms in the periodic table, and thus, through the strategy of heat treatment + ultrasonic hydration, a variety of two-dimensional double metal / triple metal hydroxides can be obtained, which can not only adjust the morphology and the layer number, but also realize the adjustment of the electronic structure.

[0035] In some embodiments of the present application, in S2, the ultrasonic time is 2 min to 2 h, and more preferably 30 min to 2 h. The length of the ultrasonic time has a relatively obvious influence on the layer number and the thickness of the two-dimensional material, and with the extension of the ultrasonic time, the thickness of the obtained two-dimensional material is gradually thinned.

[0036] In some embodiments of the present application, in S2, the ultrasonic power is 200 W to 400 W, and more preferably 300 W to 400 W.

[0037] In some embodiments of the present application, in S2, the mass ratio of the metal oxide to water is (4-6):1.

[0038] In some embodiments of the present application, in S2, the drying is performed by freeze drying or heating drying.

[0039] The two-dimensional material based on hydrotalcite obtained by the preparation method described above has a layer number of single layer to dozens of layers and a thickness of several nanometers.

[0040] According to the heat treatment + ultrasonic hydration method of the present application, a large-scale heat treatment from gram to kilogram can be realized by using a large high-temperature heat treatment furnace / joule heat ultrafast high-temperature furnace and the like, and dozens of different ultrasonic hydration reaction pools can be simultaneously performed by using a large ultrasonic instrument, and the gel-like substance obtained can be quickly dried by freeze drying or oven drying to obtain a kilogram of few-layer / single-layer two-dimensional metal hydroxide.

[0041] Example 1 Aluminum magnesium hydrotalcite ([Mg4Al2(OH) 12CO3]·3H2O) was heated to 500℃ under high temperature argon protection for 3h to obtain metal oxide, then 500mg of the metal oxide was soaked in 100mL of deionized water to disperse into a uniform suspension, then ultrasonic dispersion was carried out for 5min under the ultrasonic power of 400W using ice bath ultrasonic, until the suspension became gelatinous and no longer layered, then freeze-drying was carried out to obtain a dry powder sample, i.e. two-dimensional material.

[0042] Example 2 Aluminum magnesium hydrotalcite ([Mg4Al2(OH) 12 CO3]·3H2O) was heated to 500℃ under high temperature argon protection for 3h to obtain metal oxide, then 500mg of the metal oxide was soaked in 100mL of deionized water to disperse into a uniform suspension, then ultrasonic dispersion was carried out for 30min under the ultrasonic power of 400W using ice bath ultrasonic, until the suspension became gelatinous and no longer layered, then freeze-drying was carried out to obtain a dry powder sample, i.e. two-dimensional material.

[0043] Example 3 Aluminum magnesium hydrotalcite ([Mg4Al2(OH) 12 CO3]·3H2O) was heated to 500℃ under high temperature argon protection for 3h to obtain metal oxide, then 500mg of the metal oxide was soaked in 100mL of deionized water to disperse into a uniform suspension, then ultrasonic dispersion was carried out for 2h under the ultrasonic power of 400W using ice bath ultrasonic, until the suspension became gelatinous and no longer layered, then freeze-drying was carried out to obtain a dry powder sample, i.e. two-dimensional material.

[0044] The original hydrotalcite and the hydrotalcite after ultrasonic hydration in Examples 1-3 were analyzed by atomic force microscopy, and the results are shown in Figure 2 As shown in a, e, i in Figure 2 , the original hydrotalcite had serious sheet layer stacking, with sheet layer thickness varying from 20nm to 200nm, showing obvious agglomeration phenomenon. As shown in b, f, j in Figure 2 , after heating and ultrasonic hydration for 5min, the agglomeration phenomenon of the original hydrotalcite was obviously reduced, and the sheet layer thickness was reduced to 10nm-20nm. As shown in c, g, k in Figure 2 , after heating and ultrasonic hydration for 30min, the large agglomerated sheet layers of the original hydrotalcite were almost completely dissociated into small sheet layers, which were uniformly dispersed on the substrate surface, and the sheet layer thickness was also reduced to within 10nm. After heating and ultrasonic hydration for 2h, the layered agglomerates were completely dissociated, as shown in Figure 2As shown in d, h, and l, the material is completely transformed into a two-dimensional metal hydroxide material of 1nm~2nm. The two-dimensional metal hydroxide has a typical hexagonal planar structure, and the lateral dimension can still be maintained at about 200nm, consistent with the size of the initial hydrotalcite. It can be seen that this heat treatment + ultrasonic hydration method can significantly reduce its sheet thickness, and the number and thickness of its sheets can be controlled by adjusting the ultrasonic hydration time.

[0045] The two-dimensional materials obtained at different ultrasonic hydration times in Examples 1-3 were analyzed using transmission electron microscopy, and the results are as follows: Figure 3 As shown. Figure 3 As shown in figures a and d, the hydrotalcite, after ultrasonic hydration for 5 minutes, exhibited edge peeling, forming needle-like nanosheet structures. The structure of the layered metal oxide at the center remained intact, and selected area electron diffraction revealed polycrystalline diffraction rings with different structures. Figure 3 As shown in Figures b and e, the hydrotalcite treated with ultrasound for 30 min exhibited more severe detachment at the edges, with thinner edge lamellae, while the center still contained a significant number of thicker nanosheets that had not yet completely detached. Figure 3 As shown in Figures c and f, the hydrotalcite that was ultrasonically hydrated for 2 hours was almost completely peeled off. The thickness of the two-dimensional material at the edge was close to a single layer or a few layers, and only a very small number of unpeeled lamellae remained in the middle. Selected area electron diffraction showed that the material was transformed from a polycrystalline structure with different crystal orientations to a crystal structure with the same crystal orientation. Figure 3 The results show that during ultrasonic hydration, the edge layered structure is first peeled off, and then gradually extends inward until all the layered metal hydroxides are peeled off. The thickness of the two-dimensional material is also gradually peeled off from 20 nm to a single layer or few layers of 1-2 nm.

[0046] The specific surface area and pore size distribution of the initial hydrotalcite and the hydrotalcite after ultrasonic hydration for 2 hours in Example 3 were tested using a nitrogen adsorption analyzer. The results are shown in [Figure Number]. Figure 4 .like Figure 4 As shown in Figure a, the initial specific surface area of ​​the hydrotalcite is 33.12 m². 2 / g, the specific surface area of ​​the two-dimensional material obtained after ultrasonic hydration for 2 hours increased by nearly 10 times compared to the initial hydrotalcite, reaching 269.88m². 2 / g ( Figure 4 (b). The pore size of the two-dimensional material obtained after ultrasonic hydration for 2 hours also increased from 26.1 nm in the initial hydrotalcite. Figure 4 The nanometer size was reduced to 14.9nm (c). Figure 4 (d). This result demonstrates that the method of the present invention can significantly increase the specific surface area of ​​the obtained two-dimensional material while reducing the thickness of the hydrotalcite layers. Figure 4 ).

[0047] Example 5 Aluminum magnesium hydrotalcite ([Mg4Al2(OH) 12 CO3] 3H2O) was heated to 400 °C under high temperature argon protection for 3 h to obtain metal oxide, then 500 mg of the metal oxide was immersed in 100 mL of deionized water to disperse into a uniform suspension, and then ultrasonic dispersion was carried out under the ice bath ultrasonic at an ultrasonic power of 300 W for 2 min until the suspension became gelatinous and no longer stratified, and then freeze-drying was performed to obtain a dry powder sample, i.e., a two-dimensional material.

[0048] Example 6 Aluminum magnesium hydrotalcite ([Mg4Al2(OH) 12 CO3] 3H2O) was heated to 600 °C under high temperature argon protection for 3 h to obtain metal oxide, then 400 mg of the metal oxide was immersed in 100 mL of deionized water to disperse into a uniform suspension, and then ultrasonic dispersion was carried out under the ice bath ultrasonic at an ultrasonic power of 300 W for 2 min until the suspension became gelatinous and no longer stratified, and then freeze-drying was performed to obtain a dry powder sample, i.e., a two-dimensional material.

[0049] The two-dimensional materials obtained at different heat treatment temperatures in Examples 5 and 6 were analyzed by transmission electron microscopy, and the results are shown in Figure 5 When the heating temperature was 400 °C, the carbon dioxide between the hydrotalcite layers had not been completely released, and rehydration could peel off the edge layers, but a large number of central position layered structures were still not rehydrated into two-dimensional materials. When the heating temperature was 600 °C, the water molecules and carbon dioxide molecules between the hydrotalcite layers were completely released, and the layered structure was severely broken and formed many nanoscale pores on the surface of the layers.

[0050] Comparative Example 1 Aluminum magnesium hydrotalcite ([Mg4Al2(OH) 12 CO3] 3H2O) was heated to 500 °C under high temperature argon protection for 3 h to obtain metal oxide, then 500 mg of the metal oxide was immersed in 100 mL of ethanol to disperse into a uniform suspension, and then ultrasonic dispersion was carried out under the ice bath ultrasonic at an ultrasonic power of 400 W for 2 h until the suspension became gelatinous and no longer stratified, and then freeze-drying was performed to obtain a dry powder sample.

[0051] Comparative Example 2 Aluminum magnesium hydrotalcite ([Mg4Al2(OH) 12CO3]·3H2O) was heated to 500℃ under the protection of high-temperature argon for 3h to obtain metal oxide, and then 500mg of the metal oxide was immersed in 100mL of acetone to form a uniform suspension, and then ultrasonic dispersion was performed at 400W for 2h using an ice bath until the suspension became gelatinous and no longer stratified, and then freeze-drying was performed to obtain a dry powder sample.

[0052] The two-dimensional materials obtained by different solvents in Comparative Examples 1 and 2 were analyzed by transmission electron microscopy, and the results are shown in Figure 6 The results show that although the use of organic solvents such as ethanol and acetone can exfoliate a small amount of edge layered materials, it is difficult to exfoliate most of the layered structures as in the hydration of inorganic water solvents. Organic solvents lack a large number of free hydroxyl groups and cannot hydrate metal oxides to form metal hydroxides, so there is no interlayer electrostatic repulsion, making it difficult to completely exfoliate to form two-dimensional materials.

[0053] In summary, the present application uses natural minerals and their derived materials as raw materials, and through a simple and mild preparation process, few-layer and single-layer two-dimensional metal hydroxides can be obtained. This method has the following outstanding advantages: (1) The raw materials are widely available, both natural hydrotalcite mineral materials and artificially synthesized LDHs of different metal elements can be used. The cost is low, the yield is large, the types are many, and it is suitable for large-scale modification and industrial application. At the same time, the preparation process of two-dimensional materials is simple, the conditions are mild, the water used is environmentally friendly, the equipment used is mature and can be directly used without improvement, and it can be widely applied to chemical production process. (2) This method can accurately control the thickness of the two-dimensional metal hydroxide sheets, and can synthesize two-dimensional materials with different layer numbers from single-layer to dozens of layers on a large scale. The electrostatic repulsion of different valence metal hydroxides avoids the agglomeration of two-dimensional materials, ensuring the long-term stability of two-dimensional materials. (3) Different types of LDH precursors can be synthesized by using different divalent and trivalent double metal elements, and the electronic structure of two-dimensional materials such as charge density, band width and conductivity can be adjusted by doping different metal atoms.

Claims

1. A method for preparing a two-dimensional material based on hydrotalcite, characterized in that, The preparation method comprises the following steps: S1, heat treating hydrotalcite at 300-600 ℃ to obtain metal oxide; S2, dispersing the metal oxide in water to form a suspension, and performing ultrasonic treatment on the suspension under ice bath until the suspension becomes gelatinous, and then drying to obtain a hydrotalcite-based two-dimensional material.

2. The method for preparing a two-dimensional water slippage layer based hydrotalcite material according to claim 1, characterized by, In S1, the heat treatment time is 30 min-3 h.

3. The method for preparing a two-dimensional water slippage layer based hydrotalcite material according to claim 1, characterized by, In S1, the heat treatment is performed under the protection of inert gas.

4. The method for preparing a two-dimensional water slippage layer based hydrotalcite material according to claim 1, characterized by, In S1, the chemical formula of the hydrotalcite is [M 1-x 2+ N x 3+ (OH)2] x+ [A x / n n- ]·zH2O, wherein M is one or two of Mg, Ca, Fe, Ni, Zn and Mn, N is Al, Fe, Cr or V, A is CO3 2- , Cl - , NO3 - , PO4 3- or SO4 2- .

5. The method for preparing two-dimensional materials based on hydrotalcite according to claim 1, characterized in that, In S2, the ultrasonic treatment time is 2 min-2 h.

6. The method of claim 1, wherein the hydrotalcite-based two-dimensional material is prepared by the steps of: In S2, the ultrasonic power is 200-400 W.

7. The method for preparing two-dimensional materials based on hydrotalcite according to claim 1, characterized in that, In S2, the mass ratio of the metal oxide to water is (4-6):

1.

8. The method for preparing two-dimensional materials based on hydrotalcite according to claim 1, characterized in that, In S2, the drying is performed by freeze drying or heating drying.

9. A hydrotalcite-based two-dimensional material prepared by the preparation method in any one of claims 1-8.

10. The hydrotalcite-based two-dimensional material of claim 9, wherein, The sheet thickness of the hydrotalcite-based two-dimensional material is 1-20 nm.

Images