Bimetal atom doped porous carbon material and application thereof in electromagnetic wave absorption

Abstract

The invention discloses a bimetallic atom doped porous carbon material and application thereof in electromagnetic wave absorption, and belongs to the technical field of preparation of electromagnetic wave absorbing materials.The preparation method of the bimetallic atom doped porous carbon material comprises the steps that under the room temperature condition, dopamine hydrochloride and sodium chloride are added into deionized water to be stirred, and a mixed solution A is obtained; adding ferrous chloride tetrahydrate and soluble metal salt into the mixed solution A, and stirring; a mixed solution is obtained; performing freezing treatment and freeze drying treatment on the mixed solution to obtain a powder sample; roasting the powder sample in an inert gas protective atmosphere at 700-800 DEG C to obtain black gray powder; the black gray powder is soaked in an acid solution for soaking treatment, then centrifugation, washing and drying are conducted, and the bimetallic atom doped porous carbon material is obtained; the bimetallic atom doped porous carbon material has the advantages of light weight, stable chemical property and small matching thickness, and also has excellent electromagnetic wave absorption performance and wide absorption bandwidth.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of electromagnetic wave absorbing materials, and particularly relates to a bimetallic atom-doped porous carbon material and its application in electromagnetic wave absorption. Background Art

[0002] At present, the wireless communication technology mainly based on 5G network has developed rapidly. The derived intelligent devices have brought great convenience to people's lives, but they have also made the social electromagnetic environment become increasingly complex. To solve the negative impacts brought by electromagnetic interference, people have focused on electromagnetic wave absorbing materials. Traditional electromagnetic wave absorbing materials cannot meet the performance requirements of "thin, light, wide, and strong" for electromagnetic wave absorbing materials at the present stage. Therefore, to solve the above-mentioned shortcomings of electromagnetic wave absorbing materials, single-atom materials have gradually come into people's view. Single-atom materials have an atomic utilization rate close to 100%, which can maximize the potential of electromagnetic wave absorbing materials. However, limited by the complete isolation of metal centers in single-atom materials, the current single-atom materials have the following technical problems: (1) The interaction between metal atoms can be ignored, which leads to a significant reduction in the electron migration ability of the single-atom material. (2) Poor dielectric properties, and isolated metal centers will damage the conductive network of the carrier. Summary of the Invention

[0003] In view of the above problems, the present invention provides a bimetallic atom-doped porous carbon material and its application in electromagnetic wave absorption. The bimetallic atom-doped porous carbon material of the present invention has the advantages of light weight, stable chemical properties, thin matching thickness, and also has excellent electromagnetic wave absorption performance and a wide absorption bandwidth.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows: A bimetallic atom-doped porous carbon material, and its preparation method includes the following steps: Step (1): At room temperature, add dopamine hydrochloride and sodium chloride to deionized water and stir evenly to obtain a mixed solution A; add ferrous chloride tetrahydrate and a soluble metal salt to the mixed solution A and stir until completely dissolved; obtain a mixed solution; In step (1), the mass ratio of dopamine hydrochloride to sodium chloride is 1:9 - 11; The mass-volume ratio of dopamine hydrochloride to deionized water is 0.5 g:90 - 110 mL; The mass ratio of dopamine hydrochloride to ferrous chloride tetrahydrate is 10:0.9 - 1.1; The total molar amount of ferrous chloride tetrahydrate and the soluble metal salt is 0.0005 - 0.0006 mol; The soluble metal salt is one of manganese nitrate tetrahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, zinc nitrate hexahydrate, and copper nitrate trihydrate; Step (2): Freeze the mixed solution and then perform freeze-drying to obtain a powder sample. Heat the powder sample to 700 - 800 °C under an inert gas protection atmosphere and calcine it at 700 - 800 °C to obtain a blackish-gray powder. In step (2), the temperature for the freezing treatment is -65 °C to -55 °C, and the time is 10 - 11 h. The temperature for the freeze-drying treatment is -65 °C to -55 °C, and the time is 24 - 26 h. The inert gas protection atmosphere is a nitrogen gas protection atmosphere. The heating rate when heating to 700 - 800 °C is 4 - 6 °C / min. The calcination time at 700 - 800 °C is 3 - 3.5 h. Step (3): Immerse the blackish-gray powder in an acid solution for soaking treatment, then perform centrifugation, washing, and drying to obtain a bimetallic atom-doped porous carbon material. In step (3), the acid solution is one of a nitric acid solution or a hydrochloric acid solution. The concentration of the acid solution is 1.9 - 2.1 mol / L. The temperature for the soaking treatment is 78 - 82 °C, and the time is 24 - 26 h. The centrifugation speed during centrifugation is 9000 - 10000 r / min, and the centrifugation time is 6 - 7 min. The temperature during drying is 78 - 82 °C, and the time is 24 - 26 h.

[0005] Application of the aforementioned bimetallic atom-doped porous carbon material in electromagnetic wave absorption.

[0006] Compared with the prior art, the present invention has the following technical effects: (1) For the bimetallic atom-doped porous carbon material of the present invention, during preparation, a second-phase metal atom is introduced into the single-atom material, which destroys the electron symmetry configuration of the single-atom material, thereby enhancing the polarization loss ability of the material. At the same time, the introduction of the second-phase metal component can achieve electron migration between bimetallic atoms through long-range interactions, thereby changing the isolated sites of the single-atom material. A porous carrier is also used, and the cavities formed by the porous carrier can significantly improve the impedance matching characteristics of the bimetallic atom-doped porous carbon material. Moreover, this preparation method has high stability, strong controllability, simple steps, and inexpensive and easily available raw materials, which is conducive to large-scale production. The prepared bimetallic atom-doped porous carbon material can meet the requirements of "thin, light, wide, and strong" and has broad application prospects.

[0007] (2) The specific surface area of the bimetallic atom-doped porous carbon material of the present invention is high, and the specific surface area can reach 560 - 612 m 2•g -1 。

[0008] (3) The dual-metal atom-doped porous carbon material of the present invention has excellent properties of broadband, strong reflection loss, and matching thickness, meeting the requirements of new electromagnetic wave absorption materials. The dual-metal atom-doped porous carbon material of the present invention is filled in paraffin at a low filling ratio to obtain a composite material. The filling ratio is controlled to be 4 wt%, and the effective absorption bandwidth of the obtained composite material can reach 4.16 - 5.44 GHz at a matching thickness of 2.1 - 3.4 mm, and the minimum reflection loss can reach -57.96 dB to -38.50 dB. Description of the Drawings

[0009] The drawings forming a part of this application are used to further deepen the understanding of this application. The schematic embodiments and descriptions of this application are used to explain this application and do not constitute an improper limitation to this application. In the drawings: Figure 1 is the X-ray diffraction pattern of the dual-metal atom-doped porous carbon material obtained in Example 1; Figure 2 is the scanning electron microscope image of the carrier obtained in Example 1; Figure 3 is the scanning electron microscope image of the dual-metal atom-doped porous carbon material obtained in Example 1; Figure 4 is the distribution diagram of the real part ε’ of the dielectric loss of the dual-metal atom-doped porous carbon material obtained in Example 3; Figure 5 is the distribution diagram of the imaginary part ε” of the dielectric loss of the dual-metal atom-doped porous carbon material obtained in Example 3; Figure 6 is the distribution diagram of the real part μ’ of the magnetic loss of the dual-metal atom-doped porous carbon material obtained in Example 3; Figure 7 is the distribution diagram of the imaginary part μ” of the magnetic loss of the dual-metal atom-doped porous carbon material obtained in Example 3; Figure 8 is the distribution diagram of the dielectric loss tangent angle of the dual-metal atom-doped porous carbon material obtained in Example 3; Figure 9 is the distribution diagram of the magnetic loss tangent angle of the dual-metal atom-doped porous carbon material obtained in Example 3; Figure 10 is the three-dimensional diagram of the reflection loss of the dual-metal atom-doped porous carbon material obtained in Example 3 varying with frequency at different thicknesses; Figure 11 is the projection diagram of the reflection loss of the dual-metal atom-doped porous carbon material obtained in Example 3 varying with frequency at different thicknesses; Figure 12SEM image of the bimetallic atom-doped porous carbon material obtained in Comparative Example 4; wherein, Figure 12 (a) and Figure 12 (b) are SEM images of two test samples taken from the bimetallic atom-doped porous carbon material obtained in Comparative Example 4 respectively; Figure 13 SEM image of the bimetallic atom-doped porous carbon material prepared in Comparative Example 6; wherein, Figure 13 (a) and Figure 13 (b) are SEM images of two test samples taken from the bimetallic atom-doped porous carbon material obtained in Comparative Example 6 respectively. Detailed implementation manners

[0010] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation to the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0011] It should be understood that the terms described in the present invention are only for describing particular implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed.

[0012] Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0013] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0014] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are only exemplary.

[0015] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0016] The present invention provides a method for preparing a bimetallic atom-doped porous carbon material. Through the freeze-drying method, using sodium chloride as a template, a lightweight porous dopamine hydrochloride precursor is prepared. Then, different kinds of metal salts are attached thereto, and then calcined. The nitrogen element in the dopamine hydrochloride precursor can anchor metal atoms, and a porous network structure of bimetallic single atoms is formed under the etching of an acid solution, thereby promoting electron migration and enhancing the dissipation of electromagnetic wave energy.

[0017] A bimetallic atom-doped porous carbon material, and its preparation method comprises the following steps: Step (1): At room temperature, add dopamine hydrochloride and sodium chloride to deionized water and stir evenly to obtain a mixed solution A; add ferrous chloride tetrahydrate and soluble metal salts to the mixed solution A, and stir until completely dissolved; obtain a mixed solution; In step (1), the mass ratio of dopamine hydrochloride to sodium chloride is 1:10; The mass-volume ratio of dopamine hydrochloride to deionized water is 0.5 g:100 mL; The mass ratio of dopamine hydrochloride to ferrous chloride tetrahydrate is 10:1; The total molar amount of ferrous chloride tetrahydrate and soluble metal salts is 0.0005 mol; The soluble metal salt is one of manganese nitrate tetrahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, zinc nitrate hexahydrate, and copper nitrate trihydrate; Step (2): Freeze the mixed solution, perform freeze-drying treatment to obtain a powder sample; heat the powder sample to 700 - 800 °C under an inert gas protection atmosphere, and calcine at 700 - 800 °C to obtain a black-gray powder; In step (2), the temperature of the freezing treatment is -60 °C, and the time is 10 h; The temperature of the freeze-drying treatment is -60 °C, and the time is 24 h; The inert gas protection atmosphere is a nitrogen gas protection atmosphere; The heating rate when heating to 700 - 800 °C is 5 °C / min; The calcination time at 700 - 800 °C is 3 h; Step (3): Immerse the black-gray powder in an acid solution for soaking treatment, and then perform centrifugation, washing, and drying to obtain a bimetallic atom-doped porous carbon material; In step (3), the acid solution is one of a nitric acid solution or a hydrochloric acid solution; The concentration of the acid solution is 2 mol / L; The temperature of the soaking treatment is 80 °C, and the time is 24 h; The centrifugation speed during centrifugation is 9000 r / min, and the centrifugation time is 6 min; The temperature during drying is 80 °C, and the time is 24 h.

[0018] The present invention also provides an application of the aforementioned bimetallic atom-doped porous carbon material in electromagnetic wave absorption.

[0019] The technical solution of the present invention will be further described below through examples.

[0020] Example 1 A bimetallic atom-doped porous carbon material, and its preparation method includes the following steps: 1. At room temperature, add 0.5 g of dopamine hydrochloride and 5 g of sodium chloride to 100 mL of deionized water and stir for 12 h to obtain a mixed solution A; add 0.05 g of ferrous chloride tetrahydrate and 0.063 g of manganese nitrate tetrahydrate to the mixed solution A, and stir for 10 minutes to completely dissolve it to obtain a mixed solution; freeze the mixed solution at -60 °C for 10 h, then put it into a freeze dryer and freeze-dry it at a cold trap temperature of -60 °C for 24 h to obtain a powder sample; put the powder sample into a tubular furnace, and heat it to 800 °C at a rate of 5 °C / min under a nitrogen protection atmosphere, and calcine it at 800 °C for 3 h to obtain a black-gray powder; 2. Immerse the black-gray powder in a nitric acid solution with a concentration of 2 mol / L, place it in an oven at 80 °C for 24 h, then use a high-speed centrifuge to centrifuge at a speed of 9000 r / min for 6 min and wash it, and dry it in an oven at 80 °C for 24 h to obtain a bimetallic atom-doped porous carbon material.

[0021] Perform X-ray diffraction analysis on the bimetallic atom-doped porous carbon material obtained in this example, and the obtained X-ray diffraction pattern is shown in Figure 1 , from Figure 1 it can be seen that the bimetallic atom-doped porous carbon material prepared in this example does contain bimetals.

[0022] Perform scanning electron microscopy analysis on the carrier used in this example. The preparation method of the carrier is as follows: 1. At room temperature, add 0.5 g of dopamine hydrochloride and 5 g of sodium chloride to 100 mL of deionized water and stir for 12 h to obtain a mixed solution; freeze the mixed solution at -60 °C for 10 h, then put it into a freeze dryer and freeze-dry it at a cold trap temperature of -60 °C for 24 h to obtain a powder sample; put the powder sample into a tubular furnace, and heat it to 800 °C at a rate of 5 °C / min under a nitrogen protection atmosphere, and calcine it at 800 °C for 3 h to obtain a calcined powder; 2. Immerse the calcined powder in a nitric acid solution with a concentration of 2 mol / L, place it in an oven at 80 °C for 24 h, then use a high-speed centrifuge to centrifuge at a speed of 9000 r / min for 6 min and wash it, and dry it in an oven at 80 °C for 24 h to obtain a support.

[0023] The scanning electron microscope image of the obtained support is shown in Figure 2 , and it can be seen from Figure 2 that the support used in the present invention has a porous structure.

[0024] Perform scanning electron microscope analysis on the bimetallic atom-doped porous carbon material obtained in this example. The obtained scanning electron microscope image is shown in Figure 3 .

[0025] It can be seen from Figure 2 and Figure 3 that both the support and the bimetallic atom-doped porous carbon material are porous structures, indicating that after loading the bimetallic atoms on the support, the porous structure of the support is not damaged.

[0026] The specific surface area of the bimetallic atom-doped porous carbon material obtained in this example is 612 m 2 •g -1 . Fill the bimetallic atom-doped porous carbon material obtained in this example into paraffin with a low filling ratio to obtain a composite material. Control the filling ratio to be 4 wt%. The effective absorption bandwidth of the obtained composite material can reach 5.36 GHz at a matching thickness of 2.3 mm; at 8.16 GHz, the minimum reflection loss can reach -57.96 dB (matching thickness 4.1 mm).

[0027] This example also provides an application of the foregoing bimetallic atom-doped porous carbon material in electromagnetic wave absorption.

[0028] Example 2 Same as Example 1, the difference is that manganese nitrate tetrahydrate in the first step of Example 1 is replaced with cobalt nitrate hexahydrate, nickel nitrate hexahydrate, zinc nitrate hexahydrate, and copper nitrate trihydrate in equal moles respectively, and the obtained samples are iron-cobalt, iron-nickel, iron-zinc, and iron-copper bimetallic atom-doped porous carbon materials, and the others are the same as Example 1.

[0029] The specific surface areas of the obtained iron-cobalt, iron-nickel, iron-zinc, and iron-copper bimetallic atom-doped porous carbon materials are between 560 - 608 m 2 •g -1 ; The iron-cobalt, iron-nickel, iron-zinc, and iron-copper bimetallic atom-doped porous carbon materials obtained in this example were filled into paraffin at a low filling ratio to obtain composite materials. The filling ratio was controlled to be 4 wt%. The composite material obtained from the iron-cobalt bimetallic atom-doped porous carbon material had an effective absorption bandwidth of up to 4.16 GHz at a matching thickness of 3.4 mm; at 4.88 GHz, the minimum reflection loss could reach -42.68 dB (matching thickness 6.0 mm); the composite material obtained from the iron-nickel bimetallic atom-doped porous carbon material had an effective absorption bandwidth of up to 4.4 GHz at a matching thickness of 2.8 mm; at 17.12 GHz, the minimum reflection loss could reach -39.78 dB (matching thickness 2.6 mm); the composite material obtained from the iron-zinc bimetallic atom-doped porous carbon material had an effective absorption bandwidth of up to 5.04 GHz at a matching thickness of 2.6 mm; at 10.96 GHz, the minimum reflection loss could reach -43.37 dB (matching thickness 3.0 mm); the composite material obtained from the iron-copper bimetallic atom-doped porous carbon material had an effective absorption bandwidth of up to 4.8 GHz at a matching thickness of 3.4 mm; at 10.00 GHz, the minimum reflection loss could reach -38.50 dB (matching thickness 2.8 mm).

[0030] Example 3 Same as Example 1, except that the calcination temperature in Step 1 of Example 1 was changed to 700 °C, and the others were kept the same as Example 1.

[0031] The specific surface area of the bimetallic atom-doped porous carbon material obtained in this example was 605 m 2 •g -1 , and the bimetallic atom-doped porous carbon material obtained in this example was filled into paraffin at a low filling ratio to obtain a composite material. The filling ratio was controlled to be 4 wt%. The obtained composite material had an effective absorption bandwidth of up to 4.8 GHz at a matching thickness of 2.1 mm; at 8.40 GHz, the minimum reflection loss could reach -41.33 dB (matching thickness 3.4 mm).

[0032] The distribution diagram of the real part ε’ of the dielectric loss of the bimetallic atom-doped porous carbon material obtained in this example is shown in Figure 4 , the distribution diagram of the imaginary part ε” of the dielectric loss is shown in Figure 5 , the distribution diagram of the real part μ’ of the magnetic loss is shown in Figure 6 , and the distribution diagram of the imaginary part μ” of the magnetic loss is shown in Figure 7 .

[0033] The distribution diagram of the tangent angle of the dielectric loss of the bimetallic atom-doped porous carbon material obtained in this example is shown in Figure 8 , and the distribution diagram of the tangent angle of the magnetic loss is shown in Figure 9 .

[0034] The three-dimensional diagram of the reflection loss of the bimetallic atom-doped porous carbon material obtained in this example as a function of frequency at different thicknesses is shown in Figure 10 , when RL ≤ -10 dB, it is called effective wave absorption. The smaller the RL value, the better the wave absorption performance of the material.

[0035] The projection diagram of the reflection loss of the bimetallic atom-doped porous carbon material obtained in this example as a function of frequency at different thicknesses is shown in Figure 11 .

[0036] Example 4 Same as Example 1, the difference is that the nitric acid solution in the second step of Example 1 is replaced with a hydrochloric acid solution of the same molar concentration, and the others are the same as Example 1.

[0037] The specific surface area of the bimetallic atom-doped porous carbon material obtained in this example is 606 m 2 •g -1 . The bimetallic atom-doped porous carbon material obtained in this example is filled in paraffin at a low filling ratio to obtain a composite material. The filling ratio is controlled to be 4 wt%. The effective absorption bandwidth of the obtained composite material can reach 5.44 GHz at a matching thickness of 2.5 mm; at 8.08 GHz, the minimum reflection loss can reach -55.46 dB (matching thickness 3.8 mm).

[0038] Comparative Example 1 Same as Example 1, the difference is that the concentration of the nitric acid solution in the second step of Example 1 is increased to 3 mol / L, and the others are the same as Example 1.

[0039] The specific surface area of the bimetallic atom-doped porous carbon material obtained in this comparative example is 453 m 2 •g -1 , and the specific surface area is significantly reduced. It shows that too high nitric acid concentration will greatly damage the structure of the obtained bimetallic atom-doped porous carbon material and reduce the specific surface area of the obtained bimetallic atom-doped porous carbon material, indicating that a nitric acid solution with a concentration of 3 mol / L cannot be used.

[0040] Comparative Example 2 Same as Example 1, the difference is that the mass ratio of dopamine hydrochloride to sodium chloride in the first step of Example 1 is adjusted to 1:20, that is, the addition amount of dopamine hydrochloride is 0.5 g and the addition amount of sodium chloride is 10 g.

[0041] It is found that the structure of the bimetallic atom-doped porous carbon material obtained in this comparative example is damaged, and its specific surface area is reduced to 157 m 2 •g -1The bimetallic atom-doped porous carbon material obtained in this comparative example was filled into paraffin at a low filling ratio to obtain a composite material. The filling ratio was controlled to be 4 wt%, and the effective absorption bandwidth of the obtained composite material could reach 4 GHz at a matching thickness of 6.0 mm; at 6.88 GHz, the minimum reflection loss could reach -22.35 dB (matching thickness 5.7 mm).

[0042] Comparative Example 3 Same as Example 1, except that the freeze-drying time in the freeze dryer in Step 1 of Example 1 was changed to 12 h. It was found that the freeze-drying time was too short, resulting in incomplete volatilization of water in the material and damage to the structure. The specific surface area of the bimetallic atom-doped porous carbon material obtained in this comparative example was reduced to 214 m 2 •g -1 。The bimetallic atom-doped porous carbon material obtained in this comparative example was filled into paraffin at a low filling ratio to obtain a composite material. The filling ratio was controlled to be 4 wt%, and the effective absorption bandwidth of the obtained composite material could reach 4.08 GHz at a matching thickness of 1.7 mm; at 18.00 GHz, the minimum reflection loss could reach -13.60 dB (matching thickness 1.4 mm).

[0043] Comparative Example 4 Same as Example 1, except that the drying temperature in Step 2 of Example 1 was changed to 60 °C and the drying time was changed to 12 h. Two test specimens were taken from the bimetallic atom-doped porous carbon material obtained in this comparative example and subjected to scanning electron microscope analysis respectively. The obtained scanning electron microscope images were as shown in Figure 12 (a) and Figure 12 (b). It can be seen from Figure 12 (a) and Figure 12 (b) that due to the low drying temperature and short drying time, water and other substances in the obtained bimetallic atom-doped porous carbon material were not completely removed, and some structures were damaged, and the morphology did not reach the expected effect.

[0044] Comparative Example 5 Same as Example 1, except that the centrifugation speed in Step 2 of Example 1 was changed to 6000 rpm. It was found that due to the low centrifugation speed, there was a problem that precipitation could not be effectively separated.

[0045] Comparative Example 6 Same as Example 1, except that the standing time after soaking in the nitric acid solution in Step 2 of Example 1 was changed to 12 h. Two test specimens were taken from the bimetallic atom-doped porous carbon material obtained in this comparative example and subjected to scanning electron microscope analysis respectively. The obtained scanning electron microscope images were as shown in Figure 13 (a) and Figure 13 (b). It can be seen from Figure 13 (a) and Figure 13(b) It can be seen that since the sodium chloride template in the bimetallic atom-doped porous carbon material obtained in this comparative example was not completely removed, the morphology did not reach the expected result.

[0046] The above are only preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A bimetallic atom-doped porous carbon material, characterized in that, The preparation method comprises the following steps: Step (1): At room temperature, add dopamine hydrochloride and sodium chloride into deionized water and stir evenly to obtain a mixed solution A; add ferrous chloride tetrahydrate and soluble metal salt into the mixed solution A and stir until completely dissolved; obtain a mixed solution; Step (2): Perform freezing treatment on the mixed solution, followed by freeze-drying treatment to obtain a powder sample; heat the powder sample to 700 - 800 °C under an inert gas protection atmosphere and calcine at 700 - 800 °C to obtain a black-gray powder; Step (3): Immerse the black-gray powder in an acid solution for immersion treatment, then perform centrifugation, washing, and drying to obtain a bimetallic atom-doped porous carbon material.

2. The bimetallic atom-doped porous carbon material according to claim 1, wherein In step (1), the mass ratio of dopamine hydrochloride to sodium chloride is 1:9 - 11; The mass-volume ratio of dopamine hydrochloride to deionized water is 0.5 g:90 - 110 mL; The mass ratio of dopamine hydrochloride to ferrous chloride tetrahydrate is 10:0.9 - 1.1; The total molar amount of ferrous chloride tetrahydrate and soluble metal salt is 0.0005 - 0.0006 mol.

3. The bimetallic atom-doped porous carbon material according to claim 1, wherein In step (1), the soluble metal salt is one of manganese nitrate tetrahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, zinc nitrate hexahydrate, and copper nitrate trihydrate.

4. The bimetallic atom-doped porous carbon material according to claim 1, wherein In step (2), the temperature of the freezing treatment is -65 °C to -55 °C, and the time is 10 - 11 h; The temperature of the freeze-drying treatment is -65 °C to -55 °C, and the time is 24 - 26 h.

5. The bimetallic atom-doped porous carbon material according to claim 1, wherein In step (2), the inert gas protection atmosphere is a nitrogen gas protection atmosphere; The heating rate when heating to 700 - 800 °C is 4 - 6 °C / min; The calcination time at 700 - 800 °C is 3 - 3.5 h.

6. The bimetallic atom-doped porous carbon material according to claim 1, wherein In step (3), the acid solution is one of nitric acid solution or hydrochloric acid solution.

7. The bimetallic atom-doped porous carbon material according to claim 1, wherein In step (3), the concentration of the acid solution is 1.9 - 2.1 mol / L; The temperature of the immersion treatment is 78 - 82 °C, and the time is 24 - 26 h; The centrifugation speed during centrifugation is 9000 - 10000 r / min, and the centrifugation time is 6 - 7 min; The temperature during drying is 78 - 82 °C, and the time is 24 - 26 h.

8. Application of the bimetallic atom-doped porous carbon material according to any one of claims 1 - 7 in electromagnetic wave absorption.

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