CN100444953C - A kind of hydrotalcite/carbon nanotube heterostructure material and preparation method thereof - Google Patents

Abstract

The invention provides a hydrotalcite/carbon nanotube heterostructure material and a preparation method thereof. In the invention, carbon nanotubes and bridging molecule L-cysteine are added to alkali solution before reaction, and then mixed salt solution containing soluble divalent metal salt and trivalent metal salt is added to prepare hydrotalcite through co-precipitation reaction. During the reaction, the -NH ₂ end of L-cysteine exists as positively charged -NH ₃ ⁺ , which is stably combined with the electronegative groups ^-COO- and ^-O- on the surface of carbon nanotubes, and its- The SH end forms a coordination bond with the metal ions on the hydrotalcite layer, so that the hydrotalcite can be assembled on the carbon nanotube through a strong interaction through the bridging effect. The preparation method adopted in the present invention not only improves the dispersibility of the hydrotalcite particles and the active center, but also has the advantages of uniformity, stability, strong binding force and adjustable assembly amount of the heterogeneous structure obtained after assembly.

Description

A kind of hydrotalcite/carbon nanotube heterostructure material and preparation method thereof

technical field

The invention belongs to the technical field of material structure preparation and assembly methods. It specifically relates to a hydrotalcite/carbon nanotube heterostructure material and a preparation method thereof. The system obtained by the method has the characteristics of stable structure, good dispersion and adjustable composition.

Background technique

Carbon nanotubes are a kind of carbon-based materials with a hollow tubular structure and a large specific surface area. Due to their unique structural characteristics and physical and chemical properties, they have broad application prospects in many fields such as adsorption, photoelectricity, hydrogen storage, energy, and catalysis. , one of the important applications is as a catalyst carrier for specific catalytic reactions to improve catalytic performance. After simple treatment and surface modification of carbon nanotubes, many functional groups such as hydroxyl groups and carboxyl groups will be connected to the outer surface of carbon nanotubes. These negatively charged groups can form with positively charged molecules or groups through electrostatic force. A relatively stable composite structure system.

Literature Q.Hong, et al.J.Mater.Chem.2001, 11,2378.B.Yoon, et al.J.Am.Chem.Soc.2005,127,17174. introduced the use of liquid phase or microemulsion Methods Metal nanoparticles (Pd, Pt, Ag, Au) with catalytic activity were assembled on the surface of carbon nanotubes. Literature X.-R.Ye, et al.J.Mater.Chem.2004, 14, 908. introduced the use of supercritical fluid method to load metal nanoparticles on carbon nanotubes. These methods require strictly controlled preparation conditions, and the resulting assembled structures are not stable.

Hydrotalcite (LDHs) is a kind of anionic layered inorganic functional materials. In the crystal structure of LDHs, metal ions are evenly distributed on the laminates in a certain way, forming a specific chemical composition and structure. Due to the uniformity and controllability of chemical composition and microstructure of LDHs, such materials are excellent precursors for the preparation of catalysts. However, due to the gradual collapse of the hydrotalcite layer and the sintering and agglomeration of the particles during the heating and calcination process, the particle dispersion is poor, the specific surface area is reduced, and the number of active centers is reduced, thereby affecting the catalytic activity. This largely limits the application of LDHs materials as catalyst precursors. In order to overcome this shortcoming, improve the dispersion of LDHs precursors and reduce the aggregation of active particles, it is necessary to assemble LDHs on an excellent catalyst support, thereby improving the dispersion of LDHs, reducing the agglomeration of calcined products, and exposing more active center to enhance its catalytic activity. Simple mixing or compounding methods will result in poor uniformity and instability of the assembled composite system structure, and the composite system will be separated from each other under the condition of external force or heating. Therefore, it is necessary to develop a special assembly method, so that the assembled composite system has the characteristics of good dispersion, uniform structure and stability. At present, there is no report on the method of assembling hydrotalcite on carbon nanotubes to obtain a composite heterostructure by using bridging molecules with functional groups.

Contents of the invention

The purpose of the present invention is to controlly assemble hydrotalcite with adjustable composition on carbon nanotubes through an effective assembly method to obtain a novel functional heterostructure material. This structure not only improves the dispersion of hydrotalcite active centers, but also has the advantages of stable structure and adjustable assembly amount after assembly.

Hydrotalcites (LDHs) are a class of anionic layered functional materials, and their chemical composition is expressed as [M ²⁺ _1-X M ³⁺ _X (OH) ₂ ] ^X+ (A ^n- ) _X/n mH ₂ O, Among them, M ²⁺ can be divalent metal cations such as Mg ²⁺ , Ni ²⁺ , Co ²⁺ , Zn ²⁺ , Fe ²⁺ , Cu ²⁺ ; M ³⁺ is Al ³⁺ , Cr ³⁺ , Ga ³⁺ , In ³⁺ , Fe ³⁺ and other trivalent metal cations; ^An- is an interlayer anion, such as CO ₃ ^2- , NO ₃ ^- , Cl ^- , OH ^- , SO ₄ ^2- , C ₆ H ₄ (COO) ₂ ^2- equal inorganic, organic ions or complex ions. LDHs are excellent precursors for the preparation of catalyst materials due to their structural uniformity and compositional tunability. In order to improve the dispersion of LDHs precursors, reduce the agglomeration of active particles and the reduction of catalytic active centers after calcination, it is necessary to use catalyst supports to controlly assemble LDHs on the supports through a specific assembly method during the preparation process to form uniform, stable A novel functional heterostructure to avoid the influence of catalytic performance due to the aggregation of LDHs particles. Aiming at this problem, the present invention proposes to introduce catalyst carrier-modified carbon nanotubes and bridging molecules with multifunctional groups in the synthesis stage of LDHs, and use L-cysteine as bridging molecules. In aqueous solution, the -NH ₂ end of L-cysteine exists in the form of -NH ₃ ⁺ , and is stably combined with the carbon nanotubes with electronegative ^-COO- and O ^- groups on the surface through electrostatic interaction; at the same time, L The -SH of -cysteine can form a stable coordination bond with the metal ions on the hydrotalcite layer, so that the synthesized LDHs molecules can be efficiently and controllably assembled on the carbon nanotube carrier by using the interaction between functional groups , forming a uniformly assembled and stable composite heterostructure.

The specific preparation method of the hydrotalcite/carbon nanotube heterostructure material is as follows:

A. Put the carbon nanotubes into the reaction vessel with a condensing device, add 10-20ml of concentrated nitric acid with a concentration of 65% per gram of carbon nanotubes, heat the solution to reflux for 3-10 hours under circulating water condensation conditions, and reflux After completion, it was cooled to room temperature for suction filtration, washed with deionized water until neutral, dried in an oven at 60°C, and the modified carbon nanotubes were collected.

The used carbon nanotubes are: multi-walled carbon nanotubes with an outer diameter of 20-100 nm and a length of 1-15 μm. Heat and reflux the raw carbon nanotubes in 65% concentrated nitric acid for 5-10 hours, so that not only can the surface of the carbon nanotubes be modified with a certain number of functional groups such as hydroxyl, carboxyl, etc., but also the residual catalyst particles in the raw materials can be removed .

B. Dissolve soluble divalent metal salts and trivalent metal salts in deionized water to prepare a mixed salt solution containing M ²⁺ and M ³⁺ , wherein the molar concentration of M ²⁺ is 0.1-1.0M, and the molar concentration of M ³⁺ The concentration is 0.05-0.5M, the molar ratio of M ²⁺ to M ³⁺ is 2-5:1, and the preferred molar ratio is 2-3:1; the acid ion in the mixed salt solution is NO ₃ ^- , Cl ^- or 1-2 of SO ₄ ^2- ; M ²⁺ is one or two of Co ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ²⁺ or Cu ²⁺ , preferably Co ^{2 +} or Ni ²⁺ , M ³⁺ is one or two of Al ³⁺ , Cr ³⁺ , Fe ³⁺ , Ga ³⁺ or In ³⁺ , preferably Al ³⁺ or Fe ³⁺ ;

Add sodium hydroxide and soluble sodium salt to deionized water to prepare a mixed alkali solution, wherein the concentration of sodium hydroxide is 0.4-2.8M, the concentration of soluble sodium salt is 0.1-1.0M; the soluble sodium salt is sodium carbonate, sodium chloride, nitric acid Either sodium or sodium sulfate;

Separately use sodium hydroxide and deionized water to prepare a sodium hydroxide supplement solution with a molar concentration of 0.4-2.8M.

C. Add the mixed alkali solution prepared in step B into a stirred reactor, add modified carbon nanotubes and L-cysteine while stirring at room temperature, wherein the added carbon nanotubes and divalent metal salt The mass ratio of L-cysteine to M2+ is 0.05-0.1:1, and the molar ratio of L-cysteine to M2 ⁺ is 0.5-4:1; after being fully dissolved, the mixed salt solution prepared in step B is added dropwise to the above-mentioned reactor , and add sodium hydroxide supplement solution dropwise, and control the pH value of the solution between 7-11. After the mixed salt solution is added dropwise, the temperature is raised from room temperature to the crystallization temperature of 40-65°C, and the crystallization 2- After 20 hours, after the reaction, filter with suction, wash with deionized water until neutral, then wash with absolute ethanol for 3-5 times, and finally put the filter cake in a 60°C oven for 6-24 hours to obtain hydrotalcite/carbon Nanotube assembled heterostructure materials;

The obtained samples were characterized by XRD and transmission electron microscopy (TEM), and (003), (006) and (110) corresponding to hydrotalcites and (002) of carbon nanotubes clearly appeared on the XRD spectra of Fig. 1 and Fig. 2 Characteristic peaks (see Figure 1, Figure 2), these characteristic peaks indicate that the structure of hydrotalcite and the structure of carbon nanotubes are not destroyed after assembly. It can be observed from TEM that sheet-like hydrotalcites are assembled on the surface of carbon nanotubes, and the average grain size of hydrotalcites is 10-50 nm (see Fig. 3, Fig. 4).

The present invention has following remarkable effect:

a. Hydrotalcite can be effectively assembled on the surface of carbon nanotubes through the electrostatic interaction and coordination bonding between functional groups, and the composite system after assembly is uniform and stable.

b. By changing the amount of the bridge molecule L-cysteine, the assembly amount of hydrotalcite on the carbon nanotubes can be adjusted, so the assembly amount is adjustable.

c. The composition and structure of hydrotalcites are adjustable, and hydrotalcites with different compositions can be assembled on carbon nanotubes.

d. Assembling hydrotalcite on carbon nanotubes can improve the dispersibility of hydrotalcite particles and expose more active centers, thereby overcoming the disadvantage of reducing the number of active centers caused by particle agglomeration.

Description of drawings

Fig. 1. is the XRD spectrogram of cobalt aluminum carbonate type hydrotalcite assembled on the surface of carbon nanotube prepared in embodiment 1.

Fig. 2. is the XRD spectrogram of the nickel-aluminum nitrate-type hydrotalcite assembled on the surface of carbon nanotubes prepared in Example 2.

Fig. 3. is the TEM image of cobalt aluminum carbonate hydrotalcite assembled on the surface of carbon nanotubes prepared in Example 1 (scale length in the figure is 333nm).

Fig. 4. is the TEM image of the nickel-aluminum nitrate hydrotalcite assembled on the surface of carbon nanotubes prepared in Example 2 (the length of the scale in the figure is 67nm).

Detailed ways

Embodiment one

Take 3 g of carbon nanotubes with a length of 5-15 μm and a diameter of 40-60 nm and put them into a three-necked flask, add 100 ml of nitric acid with a concentration of 65%, heat and reflux for 6 hours, after the reflux is completed, cool to room temperature for suction filtration, and use deionized water Wash until neutral, then dry in an oven at 60° C. for 12 hours, and collect the modified carbon nanotubes.

Add 4.3655g Co(NO ₃ ) ₂ ·6H ₂ O and 1.8756g Al(NO ₃ ) ₃ ·9H ₂ O to 100ml degassed deionized water to prepare a mixed salt solution, wherein Co(NO ₃ ) ₂ ·6H ₂ The molar concentrations of O and Al(NO ₃ ) ₃ 9H ₂ O are 0.15M and 0.05M respectively, and 1.600g NaOH and 1.0599g Na ₂ CO ₃ are added to 100ml degassed deionized water to prepare a mixed alkaline solution, The molar concentrations of NaOH and _Na2CO3 are 0.4M and 0.1M respectively. Pour the mixed alkaline solution into a four- _necked flask, then add 0.5g of carbon nanotubes and 0.015mol of L-cysteine, and stir at room temperature until uniform, then slowly add the mixed salt solution dropwise, when the pH = 10.5, titrate with 0.6M NaOH replenishment solution until the mixed salt solution is titrated, then heat in a water bath at 60°C, crystallize for 6 hours, and the whole reaction process is under the condition of nitrogen gas next. After the reaction, filter with suction, wash with degassed deionized water until neutral, then wash with absolute ethanol three times, and finally put the filter cake in a vacuum oven at 60°C for 12 hours to obtain the product.

The characteristic peaks of (003), (006) and (110), (113) of hydrotalcite and the diffraction peak of carbon nanotubes (002) can be observed through the XRD spectrum of Fig. 1, calculated by the Scherrer equation at (003 ) direction grain size is 19nm, (110) direction grain size is 27nm. It can be observed that hydrotalcite grains are uniformly assembled on carbon nanotubes through the transmission electron microscope photo in Fig. 3, indicating that the obtained structure is a hydrotalcite/carbon nanotube heterostructure.

Embodiment two

Put 3 g of carbon nanotubes with a length of 5-15 μm and a diameter of 20-40 nm into a three-necked flask, add 100 ml of nitric acid with a concentration of 65%, heat and reflux for 8 hours, after the reflux is completed, cool to room temperature for suction filtration, and use deionized Wash with water until neutral, and then dry in an oven at 60° C. for 12 hours to collect the modified carbon nanotubes.

Add 9.3056g Ni(NO ₃ ) ₂ ·6H ₂ O and 6.0021g Al(NO ₃ ) ₃ ·9H ₂ O to 80ml degassed deionized water to prepare mixed salt solution, wherein Ni(NO ₃ ) ₂ ·6H ₂ The molar concentrations of O and Al(NO ₃ ) ₃ 9H ₂ O are 0.4M and 0.2M respectively. In addition, 3.840g NaOH and 2.7197g NaNO ₃ are added to 80ml degassed deionized water to prepare a mixed alkaline solution, in which NaOH and NaNO ₃ molar concentrations are 1.2M and 0.4M respectively, pour the mixed alkaline solution into a four-necked flask, add 1g of carbon nanotubes and 0.03mol of L-cysteine, stir at room temperature until uniform, and then slowly Add the mixed salt solution dropwise, and when the pH=10, titrate with 1.6M NaOH replenishment solution until the mixed salt solution is titrated, then heat in a water bath at 60°C, and crystallize for 6 hours. The whole reaction process is carried out under the condition of nitrogen gas. After the reaction, filter with suction, wash with degassed deionized water until neutral, then wash with absolute ethanol for 4 times, and finally put the filter cake in a vacuum oven at 60°C for 15 hours to obtain the product.

The characteristic peaks of (003), (006) and (110), (113) of hydrotalcite and the diffraction peak of carbon nanotubes (002) can be observed through the XRD spectrum of Fig. 2, calculated by the Scherrer equation at (003 ) direction grain size is 8nm, (110) direction grain size is 17nm. It can be observed that hydrotalcite grains are uniformly assembled on carbon nanotubes through the transmission electron microscope photo in Fig. 4, indicating that the obtained structure is a hydrotalcite/carbon nanotube heterostructure.

Embodiment three

Put 2 g of carbon nanotubes with a length of 5-15 μm and a diameter of 20-40 nm into a three-neck flask, add 80 ml of nitric acid with a concentration of 65%, heat and reflux for 5 hours, after the reflux is completed, cool to room temperature for suction filtration, and use deionized Wash with water until neutral, and then dry in an oven at 60° C. for 12 hours to collect the modified carbon nanotubes.

Add 14.2620g NiCl ₂ 6H ₂ O and 5.4060g FeCl ₃ 9H ₂ O to 100ml degassed deionized water to prepare a mixed salt solution, wherein the molar concentrations of NiCl ₂ 6H ₂ O and FeCl ₃ 9H ₂ O are respectively For 0.6M and 0.2M, add 6.4000g NaOH and 2.3376g NaCl to 100ml degassed deionized water to prepare a mixed alkaline solution, wherein the molar concentrations of NaOH and NaCl are 1.6M and 0.4M respectively, and the mixed alkaline solution Pour the solution into a four-neck flask, add 0.8g of carbon nanotubes and 0.06mol of L-cysteine, stir at room temperature until uniform, then slowly add the mixed salt solution dropwise, when the pH=8, supplement with 2M NaOH The solution was titrated until the titration of the mixed salt solution was completed, then heated in a water bath at 65°C, and crystallized for 8 hours. The whole reaction process was carried out under the condition of nitrogen gas. After the reaction, filter with suction, wash with degassed deionized water until neutral, then wash with absolute ethanol for 3 times, and finally put the filter cake in a vacuum oven at 60°C for 18 hours to obtain the product.

The characteristic peaks of (003), (006) and (110), (113) of hydrotalcite and the diffraction peak of carbon nanotubes (002) were observed by XRD, and the crystal grains can be calculated in the (003) direction by Scherrer equation The size of is 15nm, and the size in the (110) direction is 29nm. It can be observed by transmission electron microscopy that hydrotalcite grains are evenly assembled on carbon nanotubes, indicating that the prepared structure is a hydrotalcite/carbon nanotube heterostructure.

Embodiment four

Put 5g of carbon nanotubes with a length of 5-15μm and a diameter of 40-60nm into a three-necked flask, add 100ml of nitric acid with a concentration of 65%, and heat to reflux for 6h. After the reflux is completed, cool to room temperature for suction filtration, and deionized Wash with water until neutral, and then dry in an oven at 60° C. for 12 hours to collect the modified carbon nanotubes.

Add 6.9847g Co(NO ₃ ) ₂ 6H ₂ O, 2.0512g Mg(NO ₃ ) ₂ 6H ₂ O and 6.0021g Al(NO ₃ ) ₃ 9H ₂ O to 80ml degassed deionized water to prepare and mix Salt solution, wherein the molar concentrations of Co(NO3) ₂ 6H ₂ O, Mg(NO ₃ ) ₂ 6H ₂ O and Al(NO ₃ ) ₃ 9H ₂ O are 0.3M, 0.1M, 0.2M respectively, and in addition _3. Add 8400gNaOH and 2.7197gNaNO3 to 80ml degassed deionized water to prepare a mixed alkaline solution, wherein the molar concentrations of NaOH and _NaNO3 are 1.2M and 0.4M respectively, and pour the mixed alkaline solution into a four-necked bottle Add 0.5g of carbon nanotubes and 0.03mol of L-cysteine, stir at room temperature until uniform, then slowly add the mixed salt solution dropwise, when the pH=10.5, titrate with 1.5M NaOH replenishment solution until the mixed salt solution is titrated , and then heated in a water bath at 50°C for crystallization for 16 hours. The entire reaction process was carried out under the condition of nitrogen gas. After the reaction, filter with suction, wash with degassed deionized water until neutral, then wash with absolute ethanol for 3 times, and finally put the filter cake in a vacuum oven at 60°C for 18 hours to obtain the product.

The (003), (006) and (110), (113) characteristic peaks of hydrotalcite and the (002) diffraction peak of carbon nanotubes can be detected by XRD, and the crystal grains are calculated in the (003) direction by the Scherrer equation The size is 18 nm, and the size in the (110) direction is 34 nm. It can be observed by transmission electron microscopy that hydrotalcite grains are evenly assembled on carbon nanotubes, indicating that the prepared structure is a hydrotalcite/carbon nanotube heterostructure.

Embodiment five

Put 3 g of carbon nanotubes with a length of 1 to 2 μm and a diameter of 60 to 100 nm into a three-necked flask, add 100 ml of nitric acid with a concentration of 65%, and heat to reflux for 6 hours. After the reflux is completed, cool to room temperature for suction filtration, and deionized Wash with water until neutral, and then dry in an oven at 60° C. for 12 hours to collect the modified carbon nanotubes.

Add 11.6412g Co(NO ₃ ) ₂ 6H ₂ O, 5.6269g Al(NO ₃ ) ₃ 9H ₂ O and 8.4302g Fe ₂ (SO ₄ ) ₃ 9H ₂ O to 100ml degassed deionized water to prepare Mixed salt solution, in which the molar concentrations of Co(NO ₃ ) ₂ ·6H ₂ O, Al(NO ₃ ) ₃ ·9H ₂ O and Fe ₂ (SO ₄ ) ₃ ·9H ₂ O are 0.4M, 0.15M, 0.15M, respectively M, in addition, add 5.6000g NaOH and _{8.5212gNa2SO4} to 100ml degassed deionized water to prepare a mixed alkaline solution, wherein the molar concentrations _of NaOH and _Na2SO4 are 1.4M and 0.6M respectively, and _the mixed alkaline solution Pour it into a four-neck flask, add 0.8g of carbon nanotubes and 0.04mol of L-cysteine, stir at room temperature until uniform, then slowly add the mixed salt solution dropwise, when the pH=9.5, supplement with 1.5M NaOH The solution was titrated until the titration of the mixed salt solution was completed, then heated in a water bath at 60°C, and crystallized for 8 hours. The whole reaction process was carried out under the condition of nitrogen gas. After the reaction, filter with suction, wash with degassed deionized water until neutral, then wash with absolute ethanol 4 times, and finally put the filter cake in a vacuum oven at 60°C for 12 hours to obtain the product.

The characteristic peaks of (003), (006) and (110), (113) of hydrotalcite and the diffraction peak of carbon nanotubes (002) appear in the XRD spectrum of the product, and the crystal grains are calculated in the (003) direction by the Scherrer equation. The upper size is 21 nm, and the size in the (110) direction is 35 nm. It can be observed by transmission electron microscopy that hydrotalcite grains are evenly assembled on carbon nanotubes, indicating that the prepared structure is a hydrotalcite/carbon nanotube heterostructure.

Claims (5)

1. A preparation method of hydrotalcite/carbon nanotube heterostructure material, the concrete steps are as follows: A. Put the carbon nanotubes into the reaction vessel with a condensing device, add 10-20ml of concentrated nitric acid with a concentration of 65% per gram of carbon nanotubes, heat the solution to reflux for 3-10 hours under circulating water condensation conditions, and reflux After completion, wait until it is cooled to room temperature for suction filtration, wash with deionized water until neutral, put it in a 60°C oven for drying, and collect the modified carbon nanotubes; B. Dissolve soluble divalent metal salts and trivalent metal salts in deionized water to prepare a mixed salt solution containing M ²⁺ and M ³⁺ , wherein the molar concentration of M ²⁺ is 0.1-1.0M, and the molar concentration of M ³⁺ The concentration is 0.05-0.5M, the molar ratio of M ²⁺ to M ³⁺ is 2-5:1; the acid ion in the mixed salt solution is one or two of NO ₃ ^- , Cl ^- or SO ₄ ^2- ; M ²⁺ is one or two of Co ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ²⁺ , Cu ²⁺ , and M ³⁺ is Al ³⁺ , Cr ³⁺ , Fe ³⁺ , Ga ³ One or two of ⁺ , In ³⁺ ; Add sodium hydroxide and soluble sodium salt to deionized water to prepare a mixed alkali solution, wherein the concentration of sodium hydroxide is 0.4-2.8M, the concentration of soluble sodium salt is 0.1-1.0M; the soluble sodium salt is sodium carbonate, sodium chloride, nitric acid Either sodium or sodium sulfate; In addition, use sodium hydroxide and deionized water to prepare a sodium hydroxide supplement solution with a molar concentration of 0.4-2.8M; C. Add the mixed alkali solution prepared in step B into a stirred reactor, add modified carbon nanotubes and L-cysteine while stirring at room temperature, wherein the modified carbon nanotubes added and the two The mass ratio of the valent metal salt is 0.05-0.1:1, and the molar ratio of L-cysteine to M2 ⁺ is 0.5-4:1; after being fully dissolved, the mixed salt solution prepared in step B is added dropwise to the above-mentioned In the reactor, add sodium hydroxide supplement solution dropwise, control the pH value of the solution between 7-11, after the mixed salt solution is added dropwise, raise the temperature from room temperature to the crystallization temperature of 40-65°C, crystallization After 2-20 hours, filter with suction after the reaction, wash with deionized water until neutral, then wash with absolute ethanol for 3-5 times, and finally put the filter cake in a 60°C oven for 6-24 hours to obtain water A talc/carbon nanotube heterostructure material, the material is sheet-like hydrotalcite assembled on the surface of carbon nanotubes, and the average grain size of the hydrotalcite is 10-50nm. 2. the preparation method of hydrotalcite/carbon nanotube heterostructure material according to claim 1, is characterized in that, used carbon nanotube is the multi-walled carbon nanometer that external diameter is 20-100nm and length is 1-15 μ m Tube. 3. The preparation method of hydrotalcite/carbon nanotube heterostructure material according to claim 1, characterized in that the molar ratio of M ²⁺ and M ³⁺ described in step B is 2-3: 1; M ²⁺ is Co ²⁺ or Ni ²⁺ , and M ³⁺ is Al ³⁺ or Fe ³⁺ . 4. A hydrotalcite/carbon nanotube heterostructure material, characterized in that the material is prepared by the method described in claim 1, 2 or 3. 5. The hydrotalcite/carbon nanotube heterostructure material according to claim 4, characterized in that the hydrotalcite assembled on the surface of the carbon nanotube has a sheet structure with an average grain size of 10-50nm.

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