A CNTs / Fe3O4 / FeS2 / MoS2 composite material and its preparation method

Abstract

The present invention provides a CNTs / Fe3O4 / FeS2 / MoS2 composite material and a preparation method thereof, which relates to the technical field of microwave absorption materials. The method comprises the following steps: adding ferric chloride hexahydrate into an ethylene glycol solution and stirring to make it evenly mixed, then adding carbon nanotubes, polyethylene glycol and anhydrous sodium acetate into the mixed solution and continuing magnetic stirring; transferring the obtained solution to an autoclave for solvothermal reaction; after the obtained solution is cooled to room temperature, centrifuging to collect the sample, washing the sample with deionized water and alcohol, centrifuging the washed sample to collect it, and carrying out vacuum drying in a vacuum drying oven to obtain the CNTs / Fe3O4 material; dissolving thioacetamide and sodium molybdate in deionized water and stirring evenly, dissolving the CNTs / Fe3O4 material into the above solution for neutralization and ultrasonic treatment to make the solution uniform; carrying out hydrothermal reaction on the solution at 200 °C; centrifuging and collecting the obtained solution, washing it with deionized water and ethanol, and then drying it in a vacuum drying oven to obtain the CNTs / Fe3O4 / FeS2 / MoS2 composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorption materials, and particularly to a CNTs / Fe3O4 / FeS2 / MoS2 composite material and a preparation method thereof. Background Art

[0002] With the rapid development of 5G mobile networks and electronic devices, the problem of electromagnetic pollution has become increasingly serious. This not only threatens the health of organisms, but also interferes with the normal operation of electronic devices, and even leads to information leakage, posing a danger to national defense security. In order to alleviate the increasingly serious electromagnetic radiation hazards, seeking highly efficient microwave absorption materials in the centimeter wave band (2-18 GHz) has become a research topic worthy of attention.

[0003] Electromagnetic waves in the S band (2-4 GHz) have the characteristics of strong penetration ability, small attenuation, reliable signal transmission, and high data accuracy, and are widely used in fields such as radar, military communication, spaceborne radar, and meteorological detection. However, currently, the effective absorption frequencies of most absorbing materials are concentrated in the high-frequency band, and there are few research reports in the low-frequency band, especially in the S band. This may be because the longer the wavelength, the more difficult it is for the wave to attenuate. Therefore, it is very challenging and valuable to study a material with high-efficiency wave absorption performance in the S band. Summary of the Invention

[0004] The purpose of the present invention is to provide a CNTs / Fe3O4 / FeS2 / MoS2 composite material and a preparation method thereof to solve the technical problem that the existing absorbing materials cannot effectively absorb in the S band. The preferred technical solutions provided by the present invention can achieve the following technical effects, which will be elaborated below.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A preparation method of a CNTs / Fe3O4 / FeS2 / MoS2 composite material provided by the present invention includes the following steps:

[0007] Step S1: Add ferric chloride hexahydrate to an ethylene glycol solution, stir to mix evenly, and then add carbon nanotubes, polyethylene glycol, and sodium acetate anhydrous to the mixed solution, and continue magnetic stirring;

[0008] Step S2: Transfer the solution obtained in Step S1 to an autoclave and carry out a solvothermal reaction at 160-210 °C for 10-18 hours;

[0009] Step S3: After the solution obtained in Step S2 is cooled to room temperature, centrifuge to collect the sample. Wash the sample with deionized water and alcohol, centrifuge to collect the washed sample, and perform vacuum drying in a vacuum drying oven to obtain the CNTs / Fe3O4 material;

[0010] Step S4: Dissolve thioacetamide and sodium molybdate in deionized water and stir evenly. Dissolve the CNTs / Fe3O4 material obtained in Step S3 into the above solution and perform neutralization ultrasonic treatment to make the solution uniform;

[0011] Step S5: Hydrothermally react the solution in Step S4 at 160 - 220 °C for 12 - 24 hours;

[0012] Step S6: Centrifuge to collect the solution obtained in Step S5, wash it with deionized water and ethanol, and then dry it in a vacuum drying oven to obtain the CNTs / Fe3O4 / FeS2 / MoS2 composite material.

[0013] According to a preferred embodiment, in Step S1, the mass ratio of ferric chloride hexahydrate to the carbon nanotubes is 80:1, the dosage of ethylene glycol is 50 ml - 80 ml, the mass ratio of ferric chloride hexahydrate, polyethylene glycol to sodium acetate anhydrous is 40:1:25, and the magnetic stirring time is 30 - 60 minutes.

[0014] According to a preferred embodiment, in Step S2, the temperature of the solvothermal reaction is 205 °C and the reaction time is 16 hours.

[0015] According to a preferred embodiment, in Step S3, the sample is washed with deionized water and alcohol at least three times, and the drying temperature in the vacuum drying oven is 40 - 80 °C.

[0016] According to a preferred embodiment, in Step S4, the mass ratio of thioacetamide to sodium molybdate is 2:1, and the mass percentage of CNTs / Fe3O4 is 7 wt% - 25 wt%.

[0017] According to a preferred embodiment, in Step S5, the temperature of the hydrothermal reaction is 200 °C and the reaction time is 24 hours.

[0018] According to a preferred embodiment, in Step S6, the washing times with deionized water and ethanol are at least three times, and the drying temperature in the vacuum drying oven is 40 - 80 °C.

[0019] This application also provides a CNTs / Fe3O4 / FeS2 / MoS2 composite material, and the CNTs / Fe3O4 / FeS2 / MoS2 composite material is prepared by the described preparation method.

[0020] Based on the above technical solution, the CNTs / Fe3O4 / FeS2 / MoS2 composite material of the present invention and its preparation method at least have the following technical effects:

[0021] The preparation method of this application has simple operation process, high yield and low cost of the prepared material. The CNTs / Fe3O4 / FeS2 / MoS2 composite material prepared by the preparation method of this application is a multi-component wave-absorbing material, which has a uniform distribution of carbon, iron, oxygen, molybdenum and sulfur elements. Through the synergistic effect of dielectric loss and magnetic loss, and by adjusting the dielectric constant and magnetic permeability, the material can have good impedance matching characteristics. The prepared composite material has strong absorption in the S band, and strong absorption in the Ku band can also be achieved by adjusting the thickness. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 XRD, Raman and crystal structure model diagrams of the CNTs / Fe3O4 material obtained in Example 1 and the CNTs / Fe3O4 / FeS2 / MoS2 composite material prepared in Example 3;

[0024] Figure 2 Scanning electron microscope diagrams of the CNTs / Fe3O4 prepared in Example 1 and the CNTs / Fe3O4 / FeS2 / MoS2 composite materials with different proportions of MoS2 coating prepared in Examples 2, 3 and 4, and transmission and surface distribution diagrams of the CNTs / Fe3O4 / FeS2 / MoS2 composite material prepared in Example 3;

[0025] Figure 3 Three-dimensional diagrams, contour diagrams and two-dimensional diagrams of the microwave absorption properties of the CNTs / Fe3O4 composite material prepared in Example 1 and the CNTs / Fe3O4 / FeS2 / MoS2 composite materials prepared in Examples 2, 3 and 4. Detailed Embodiments

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other implementation manners obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope protected by the present invention.

[0027] This application provides a method for preparing a CNTs / Fe3O4 / FeS2 / MoS2 composite material, and the specific steps are as follows:

[0028] Step S1: Add ferric chloride hexahydrate to 50 ml - 80 ml of ethylene glycol solution, stir to mix evenly, and then add carbon nanotubes, polyethylene glycol, and anhydrous sodium acetate to the mixed solution, and continue magnetic stirring for 30 - 60 minutes; wherein, in this step, the mass ratio of the ferric chloride hexahydrate to the carbon nanotubes is 80:1, and the mass ratio of the ferric chloride hexahydrate, the polyethylene glycol, and the anhydrous sodium acetate is 40:1:25.

[0029] Step S2: Transfer the solution obtained in Step S1 to a Teflon-lined stainless steel autoclave and carry out a solvothermal reaction at 160 - 210 °C for 10 - 18 hours. Preferably, the temperature of the solvothermal reaction is 205 °C and the reaction time is 16 hours.

[0030] Step S3: After the solution obtained in Step S2 is cooled to room temperature, centrifuge to collect the sample, wash the sample with deionized water and alcohol at least three times, centrifuge and collect the washed sample, and carry out vacuum drying in a vacuum drying oven at 40 - 80 °C to obtain the CNTs / Fe3O4 material. Preferably, in the operation of centrifuging to collect the sample, the rotation speed of the centrifuge used is 13,000 revolutions per minute. In this step, the average size of the iron oxide is 120 nm, and the carbon nanotubes are embedded in the iron oxide nanospheres.

[0031] Step S4: Dissolve thioacetamide and sodium molybdate with a mass ratio of 2:1 in deionized water, stir evenly, and dissolve the CNTs / Fe3O4 material obtained in Step S3 into the above solution for neutralization and ultrasonic treatment to make the solution uniform; the mass percentage of the added CNTs / Fe3O4 is 7 wt% - 25 wt%.

[0032] Step S5: Carry out a hydrothermal reaction on the solution in Step S4 at 160 - 220 °C for 12 - 24 hours. Preferably, the temperature of the hydrothermal reaction is 200 °C and the reaction time is 24 hours. In this step, part of the iron oxide is reduced to iron disulfide during the hydrothermal reaction.

[0033] Step S6: Centrifuge and collect the solution obtained in Step S5, wash it with deionized water and ethanol at least three times, and then perform vacuum drying in a vacuum drying oven at 40 - 80 °C to obtain the CNTs / Fe3O4 / FeS2 / MoS2 composite material. Preferably, in the operation of centrifuging and collecting the sample, the rotation speed of the centrifuge used is 13,000 revolutions per minute.

[0034] Example 1

[0035] This example provides a method for preparing a CNTs / Fe3O4 wave-absorbing material, including the following steps:

[0036] S1: Add 1.6 g of ferric chloride hexahydrate to 50 mL of ethylene glycol solution, stir to mix evenly, then add 0.02 g of carbon nanotubes, 0.04 g of polyethylene glycol (molecular weight 2000), and 1.0 g of anhydrous sodium acetate to the solution, and continue magnetic stirring for one hour;

[0037] S2: Transfer the solution obtained in Step S1 to a Teflon-lined stainless steel autoclave; perform solvothermal reaction at 205 °C for 16 hours;

[0038] S3: After the solution cools to room temperature, centrifuge and collect the sample, wash the sample with deionized water and alcohol at least three times, centrifuge and collect the washed sample, and perform vacuum drying in a vacuum drying oven at 70 °C overnight to obtain the prepared CNTs / Fe3O4 material. In the operation of centrifuging and collecting the sample, the rotation speed of the centrifuge used is 13,000 revolutions per minute.

[0039] Example 2

[0040] S1: Add 1.6 g of ferric chloride hexahydrate to 50 mL of ethylene glycol solution, stir to mix evenly, then add 0.02 g of carbon nanotubes, 0.04 g of polyethylene glycol (molecular weight 2000), and 1.0 g of anhydrous sodium acetate to the solution, and continue magnetic stirring for one hour;

[0041] S2: Transfer the solution obtained in Step S1 to a Teflon-lined stainless steel autoclave; perform solvothermal reaction at 205 °C for 16 hours;

[0042] S3: After the solution cools to room temperature, centrifuge and collect the sample, wash the sample with deionized water and alcohol at least three times, centrifuge and collect the washed sample, and perform vacuum drying in a vacuum drying oven at 70 °C overnight to obtain the prepared material CNTs / Fe3O4; preferably, in the operation of centrifuging and collecting the sample, the rotation speed of the centrifuge used is 13,000 revolutions per minute;

[0043] S4: Dissolve 0.16 g of thioacetamide and 0.08 g of sodium molybdate in 20 mL of deionized water, stir evenly, dissolve 0.08 g of CNTs / Fe3O4 into the above solution and ultrasonicate to make the solution uniform;

[0044] S5: Then carry out hydrothermal reaction at 200 °C for 24 hours;

[0045] S6: Centrifuge and collect the obtained solution, wash it three times with deionized water and ethanol, and then dry it overnight in a vacuum drying oven at 70 °C to obtain a CNTs / Fe3O4 / FeS2 / MoS2 microwave absorption composite material with a specific morphology. During the operation of centrifuging and collecting the sample, the rotation speed of the centrifuge used is 13,000 revolutions per minute.

[0046] Example 3

[0047] This Example 3 provides a preparation method of a CNTs / Fe3O4 / FeS2 / MoS2 strong absorption microwave absorption material, including the following steps:

[0048] S1: Add 1.605 g of ferric chloride hexahydrate to 50 mL of ethylene glycol solution, stir to make it mix evenly, then add 0.02 g of carbon nanotubes, 0.04 g of polyethylene glycol (molecular weight 2000) and 1.0 g of anhydrous sodium acetate to the solution, and continue magnetic stirring for one hour;

[0049] S2: Transfer the solution obtained in step S1 to a Teflon-lined stainless steel autoclave; carry out solvothermal reaction at 205 °C for 16 hours;

[0050] S3: After the solution is cooled to room temperature, centrifuge and collect the sample, wash the sample with deionized water and alcohol at least three times, centrifuge and collect the washed sample, and vacuum dry it overnight at 70 °C in a vacuum drying oven. The prepared material is CNTs / Fe3O4; during the operation of centrifuging and collecting the sample, the rotation speed of the centrifuge used is 13,000 revolutions per minute;

[0051] S4: Dissolve 0.32 g of thioacetamide and 0.16 g of sodium molybdate in 20 mL of deionized water, stir evenly, dissolve 0.08 g of CNTs / Fe3O4 into the above solution and ultrasonicate to make the solution uniform;

[0052] S5: Then carry out hydrothermal reaction at 200 °C for 24 hours;

[0053] S6: Centrifuge and collect the obtained solution, wash it three times with deionized water and ethanol, and then dry it overnight in a vacuum drying oven at 70 °C to obtain a CNTs / Fe3O4 / FeS2 / MoS2 microwave absorption composite material with a specific morphology. During the operation of centrifuging and collecting the sample, the rotation speed of the centrifuge used is 13,000 revolutions per minute.

[0054] Example 4

[0055] Example 4 provides a method for preparing a CNTs / Fe3O4 / FeS2 / MoS2 strong absorption wave-absorbing composite material, comprising the following steps:

[0056] S1: Add 1.6 g of ferric chloride hexahydrate to 50 mL of ethylene glycol solution, stir to mix evenly, then add 0.02 g of carbon nanotubes, 0.04 g of polyethylene glycol (molecular weight 2000), and 1.0 g of anhydrous sodium acetate to the solution, and continue magnetic stirring for one hour;

[0057] S2: Transfer the solution obtained in step S1 to a Teflon-lined stainless steel autoclave; carry out solvothermal reaction at 205 °C for 16 hours;

[0058] S3: After the solution is cooled to room temperature, centrifuge to collect the sample, and wash the sample with deionized water and alcohol at least three times. Centrifuge to collect the washed sample and vacuum dry it overnight at 70 °C in a vacuum drying oven. The prepared material is CNTs / Fe3O4; in the operation of centrifuging to collect the sample, the rotation speed of the centrifuge used is 13,000 revolutions per minute;

[0059] S4: Dissolve 0.64 g of thioacetamide and 0.32 g of sodium molybdate in 20 mL of deionized water, stir evenly, and dissolve 0.08 g of CNTs / Fe3O4 into the above solution and ultrasonically homogenize the solution;

[0060] S5: Then carry out hydrothermal reaction at 200 °C for 24 hours;

[0061] S6: Centrifuge to collect the obtained solution, wash it three times with deionized water and ethanol, and then dry it overnight in a vacuum drying oven at 70 °C to obtain a CNTs / Fe3O4 / FeS2 / MoS2 wave-absorbing composite material with a specific morphology. In the operation of centrifuging to collect the sample, the rotation speed of the centrifuge used is 13,000 revolutions per minute.

[0062] Example 5

[0063] S1: Heat and mix the products prepared in Example 1, Example 2, Example 3, and Example 4 with paraffin according to a mass ratio of 2:3 until evenly mixed;

[0064] S2: Press the above mixture into a cylindrical composite material with a tunable layer thickness (d) (Φout = 7.00 mm, Φin = 3.04 mm).

[0065] S3: Use the coaxial method of a vector network analyzer to test the wave-absorbing performance of the composite material.

[0066] As shown Figure 1 in FIGS. 4, Figure 1 4 are pictures obtained by characterizing the CNTs / Fe3O4 prepared in Example 1 and the CNTs / Fe3O4 / FeS2 / MoS2 composites prepared in Examples 2 to 4.

[0067] Among them:

[0068] Figure 1 are the XRD, Raman and crystal structure model diagrams of the CNTs / Fe3O4 material obtained in Example 1 and the CNTs / Fe3O4 / FeS2 / MoS2 composite material prepared in Example 3. Figure 1 (a) The figure is the XRD analysis result of the sample. The XRD pattern reveals the crystal structure of the prepared composite material, indicating that the material contains substances such as Fe3O4, MoS2, and FeS2. Figure 1 (b) The figure is a partial Raman spectrum of the sample. Raman spectroscopy analysis shows the typical D and G bands of CNTs, proving the presence of carbon nanotubes. Therefore, it can be proved that the preparation method of this application can prepare a composite material containing carbon nanotubes, Fe3O4, FeS2, and MoS2. Figure 1 (c) The figure is the crystal model of the crystal structures of Fe3O4, FeS2, and MoS2 in the CNTs / Fe3O4 / FeS2 / MoS2 composite material sample. Among them, Fe3O4 has a cubic structure with the Fd-3m space group. FeS2 has a cubic structure with the Pa-3 space group. In addition, MoS2 has a hexagonal structure with the R3m space group.

[0069] Figure 2 are the scanning electron microscope images of the CNTs / Fe3O4 prepared in Example 1 and the CNTs / Fe3O4 / FeS2 / MoS2 composite materials with different proportions of MoS2 coating prepared in Examples 2, 3, and 4, and the transmission and surface distribution diagrams of the CNTs / Fe3O4 / FeS2 / MoS2 composite material prepared in Example 3. Among them, Figure 2 (a) The figure is the scanning electron microscope image of the CNTs / Fe3O4 material in Example 1; Figure 2 (b) The figure is the scanning electron microscope image of the CNTs / Fe3O4 / FeS2 / MoS2 composite material obtained in Example 2; Figure 2 (c) The figure is the scanning electron microscope image of the CNTs / Fe3O4 / FeS2 / MoS2 composite material obtained in Example 3; Figure 2 (d) The figure is the scanning electron microscope image of the CNTs / Fe3O4 / FeS2 / MoS2 composite material obtained in Example 4. As shown Figure 2 from (a) to Figure 2(d) indicates that under high pressure and sulfidation, the Fe3O4 microspheres gradually transform into Fe3O4(FeS2) flakes. As Figure 2 b to Figure 2 d shows, MoS2 nanosheets are wrapped on the Fe3O4 / FeS2 flakes.

[0070] Figure 2 Figure (e) is the low-magnification transmission electron microscopy image of the obtained CNTs / Fe3O4 / FeS2 / MoS2 composite in Example 3; Figure 2 Figure (f) is the high-resolution transmission electron microscopy image of the obtained CNTs / Fe3O4 / FeS2 / MoS2 composite in Example 3; Figure 2 Figure (g) is the elemental distribution map of the obtained CNTs / Fe3O4 / FeS2 / MoS2 composite in Example 3. As Figure 2 shown in e, CNTs are embedded in the flaky structure.

[0071] Figure 3 Figures (a-c) are the microwave absorption performance diagrams of the obtained CNTs / Fe3O4 composite in Example 1; Figures (d-f) are the microwave absorption performance diagrams of the obtained CNTs / Fe3O4 / FeS2 / MoS2 composite in Example 2; Figures (g-i) are the microwave absorption performance diagrams of the obtained CNTs / Fe3O4 / FeS2 / MoS2 composite in Example 3; Figures (j-l) are the microwave absorption performance diagrams of the obtained CNTs / Fe3O4 / FeS2 / MoS2 composite in Example 4. Figure 3 (a-c) The results show that the maximum reflection loss value of CNTs / Fe3O4 is -55.79 dB, which occurs at 2.57 GHz, the thickness d is 9.1 mm, and the maximum absorption bandwidth is 4.36 GHz (the reflection loss value is lower than -10 dB). Therefore, its practical application is severely limited due to the too thick thickness and narrow absorption bandwidth. Figure 3 (g-i) shows that the obtained CNTs / Fe3O4 / FeS2 / MoS2 composite in Example 3 exhibits the most comprehensive and best microwave absorption ability. Through Figure 3 i, it can be seen that the reflection loss is -70.06 dB at 6.2 mm, which is located in the S band (3.47 GHz), and the maximum absorption bandwidth is 5.6 GHz. And as the thickness of the composite material decreases from 6.2 mm to 1.7 mm, the strong reflection loss moves towards the ku band, realizing the tunability of its frequency.

[0072] Therefore, the preparation method of the present application prepares a multi-component CNTs / Fe3O4 / FeS2 / MoS2 composite material through a solvothermal reaction method and a subsequent hydrothermal reaction method. Through the synergistic effect of dielectric loss and magnetic loss in the material, the material not only has strong absorption in the low-frequency S band (2-4 GHz), but by reducing the thickness, it can also have strong microwave loss in the high-frequency ku band (12-18 GHz). These findings provide new insights into the research of multi-component absorbers, including enhancing the performance of microwave absorption materials in the S band, as well as adjusting and controlling the effective absorption frequency, which has potential application value in both military and civilian fields.

[0073] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A preparation method of a CNTs / Fe3O4 / FeS2 / MoS2 composite material, characterized in that, It includes the following steps: Step S1: Add 1.6 g of ferric chloride hexahydrate into 50 ml of ethylene glycol solution, stir to mix evenly, then add 0.02 g of carbon nanotubes, 0.04 g of polyethylene glycol and 1.0 g of anhydrous sodium acetate into the mixed solution, and continue magnetic stirring; Step S2: Transfer the solution obtained in Step S1 to an autoclave, and carry out solvothermal reaction at 160 - 210 °C for 10 - 18 hours; Step S3: After the solution obtained in Step S2 is cooled to room temperature, centrifuge to collect the sample, wash the sample with deionized water and alcohol, centrifuge and collect the washed sample, and carry out vacuum drying in a vacuum drying oven to obtain CNTs / Fe3O4 material; Step S4: Dissolve 0.16 g - 0.64 g of thioacetamide and 0.08 g - 0.32 g of sodium molybdate in 20 ml of deionized water. The mass ratio of thioacetamide to sodium molybdate is 2:

1. Stir evenly, and dissolve 0.08 g of the CNTs / Fe3O4 material obtained in Step S3 into the above solution for neutralization ultrasonic treatment to make the solution uniform; Step S5: Carry out hydrothermal reaction on the solution in Step S4 at 160 - 220 °C for 12 - 24 hours; Step S6: Centrifuge and collect the solution obtained in Step S5, wash it with deionized water and ethanol, and then dry it in a vacuum drying oven to obtain CNTs / Fe3O4 / FeS2 / MoS2 composite material.

2. The preparation method according to claim 1, characterized in that, In Step S1, the magnetic stirring time is 30 - 60 minutes.

3. The preparation method according to claim 1, characterized in that, In Step S2, the temperature of the solvothermal reaction is 205 °C, and the reaction time is 16 hours.

4. The preparation method according to claim 1, characterized in that, In Step S3, the number of times of washing the sample with deionized water and alcohol is at least three times, and the drying temperature in the vacuum drying oven is 40 - 80 °C.

5. The preparation method according to claim 1, characterized in that, In Step S5, the temperature of the hydrothermal reaction is 200 °C, and the reaction time is 24 hours.

6. The preparation method according to claim 1, characterized in that, In Step S6, the number of times of washing with deionized water and ethanol is at least three times, and the drying temperature in the vacuum drying oven is 40 - 80 °C.

7. A CNTs / Fe3O4 / FeS2 / MoS2 composite material, characterized in that, The CNTs / Fe3O4 / FeS2 / MoS2 composite material is prepared by the preparation method according to any one of claims 1 to 6.

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