Nitrogen-doped ceramic graphene aerogel and preparation method thereof

Abstract

The invention relates to the technical field of graphene aerogel, and discloses nitrogen-doped ceramic graphene aerogel and a preparation method thereof. The preparation method comprises the following steps: S1, dispersing few-layer graphene oxide, polysilazane, polyethylene glycol and sodium ascorbate in water, and stirring at 70-90 DEG C to obtain uniform slurry; s2, quickly freezing the slurry, and performing freeze-drying treatment to obtain a precursor with a porous structure; and S3, heating the precursor in an inert atmosphere to 400-600 DEG C for calcination, and then raising the temperature to 900-1200 DEG C for calcination to obtain the nitrogen-doped ceramic graphene aerogel. According to the preparation method, the conductivity and the interface interaction capability of the graphene aerogel are improved, the ceramized surface has more binding sites and better structural strength, and the porous structure and the high surface area enable the graphene aerogel to have excellent performance in catalysis, adsorption, energy storage and other applications. The nitrogen-doped ceramic graphene aerogel prepared by the invention has excellent electrical conductivity, thermal conductivity and mechanical strength.

Description

Technical Field

[0001] The present application relates to the technical field of graphene aerogels, and in particular to a nitrogen-doped ceramicized graphene aerogel and a preparation method thereof. Background Art

[0002] With the continuous development of global science and technology and industry, the demand for efficient and reliable new materials is growing. In many key fields, such as energy storage, environmental purification, electronic equipment and high-temperature industry, the application of various high-performance functional materials has become the key to improving efficiency and achieving technological breakthroughs. As a new functional material, nitrogen-doped ceramic graphene aerogel has gradually become a hot spot for research and industrial applications due to its unique physical and chemical properties.

[0003] Nitrogen-doped ceramic graphene aerogel (N-CGA) combines the high conductivity of graphene with the high temperature stability of ceramics. It has excellent electrochemical activity and catalytic performance, and can maintain stability even in extreme environments, giving it significant application advantages in supercapacitors, sensors, catalyst carriers and other fields. For example, the energy storage performance of ceramic graphene aerogels was improved by introducing nitrogen doping, significantly improving its charge and discharge cycle stability and energy density in batteries and supercapacitors; nitrogen-doped 3D carbon materials derived from PAF were developed, which showed high efficiency in energy conversion and storage; nitrogen-doped porous carbon materials were synthesized through conjugated microporous polymer precursors, and these materials were successfully applied to CO 2 Capture and energy storage systems. Existing research highlights the potential of these materials to tackle greenhouse gas emissions and provide sustainable energy solutions.

[0004] Although nitrogen-doped ceramic graphene aerogels have excellent performance in theory, their practical application still faces some challenges, including complex preparation process, poor compatibility with existing systems, and low long-term stability. At present, nitrogen-doped ceramic graphene aerogels are often prepared by directional freezing method using water as solvent. However, the freezing process in this method is slow, and water is easily separated from the organic phase, resulting in low conductivity and mechanical strength of the prepared nitrogen-doped ceramic graphene aerogels, and high production costs. Summary of the invention

[0005] The present application provides a nitrogen-doped ceramic graphene aerogel and a preparation method thereof, aiming to solve the problems of complex preparation process and high production cost of existing nitrogen-doped ceramic graphene aerogel, as well as low conductivity and mechanical strength of the prepared nitrogen-doped ceramic graphene aerogel.

[0006] In order to achieve the above objectives, the present application adopts the following technical solutions.

[0007] In a first aspect of the present application, a method for preparing nitrogen-doped ceramic graphene aerogel is provided, comprising:

[0008] S1, dispersing few-layer graphene oxide, polysilazane, polyethylene glycol and sodium ascorbate in water, stirring at 70-90° C. to obtain a uniform slurry;

[0009] S2, rapidly freezing the slurry and freeze-drying it to obtain a precursor of a porous structure;

[0010] S3, heating the precursor to 400-600° C. in an inert atmosphere for calcination, and then heating to 900-1200° C. for calcination to obtain nitrogen-doped ceramic graphene aerogel.

[0011] In some embodiments, the concentration of few-layer graphene oxide in the slurry is 10-20 mg / mL; the concentration of polysilazane is 2-4 mg / mL; the concentration of polyethylene glycol is 150-200 mg / mL; and the concentration of sodium ascorbate is 0.4-0.8 mg / mL.

[0012] In some embodiments, the rapid freezing comprises:

[0013] The slurry is injected into the mold, and the mold is oriented and frozen from bottom to top by liquid nitrogen. The freezing time is 10 to 15 minutes.

[0014] In some embodiments, the diameter of the mold is 3 to 10 cm.

[0015] In some embodiments, the freeze-drying treatment temperature is -70 to -80°C, the vacuum degree is <15 Pa, and the freeze-drying time is 24 to 48 hours.

[0016] In some embodiments, the calcination time at 400-600° C. in step S3 is 1-2 h; the calcination time at 900-1200° C. is 3-5 h.

[0017] In some embodiments, the few-layer graphene oxide is prepared by the following method:

[0018] Mix graphite and sulfuric acid evenly, add sodium nitrate and phosphorus pentoxide, stir at 80-100°C for 12-24h, separate and collect the solid phase, wash and shade-dry to obtain the precursor;

[0019] The precursor is dispersed in excess concentrated sulfuric acid, and potassium permanganate is slowly added thereto, stirred at -10 to 0°C, and then diluted with water, and then heated to 90°C, and hydrogen peroxide is added until the solution turns bright yellow to obtain a dispersion;

[0020] The dispersion is diluted with water, centrifuged at a speed of 5000-7000 r / min to remove multilayer graphene oxide, and then centrifuged at a speed of 10000-12000 r / min to remove impurities, and the concentrated solution obtained by centrifugation is freeze-dried to obtain few-layer graphene oxide.

[0021] In some embodiments, the mass ratio of graphite, sulfuric acid, sodium nitrate and phosphorus pentoxide is (1-2):(18-20):(1.5-2):(1.5-2);

[0022] The mass ratio of potassium permanganate to graphite is 5:1.

[0023] In a second aspect of the present application, a nitrogen-doped ceramic graphene aerogel prepared by the above preparation method is provided.

[0024] The third aspect of the present application provides applications of the nitrogen-doped ceramic graphene aerogel prepared by the above preparation method in the fields of electronic manufacturing, energy conversion and environmental protection.

[0025] Compared with the prior art, the beneficial effects of this application are:

[0026] The present application prepares a high-porosity aerogel through an improved hydrothermal reaction and freeze-drying process, removes the supporting material under high temperature conditions, and performs ceramicization treatment through thermal reduction to prepare nitrogen-doped ceramicized graphene aerogel. Among them, the improved hydrothermal reaction uses polyethylene glycol as the main solvent, which effectively prevents phase separation during the freezing process and ensures the uniformity and stability of the final aerogel; the vertically oriented structure is obtained through directional freezing, so that the aerogel has better electrical conductivity, thermal conductivity and mechanical strength; and nitrogen doping further improves the electrical conductivity and thermal conductivity of the material, providing its performance in electronic and thermal management applications. The preparation method of the present application not only improves the electrical conductivity and interface interaction ability of the graphene aerogel, but also the surface after ceramicization has more binding sites and better structural strength. Its porous structure and high surface area make it excellent in applications such as catalysis, adsorption and energy storage.

[0027] The preparation method of the present application has simple and efficient process, low production cost, good repeatability and stability, and is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1This is a physical picture of the precursor prepared by liquid nitrogen directional freezing and freeze-drying in Example 1;

[0030] Figure 2 This is a physical picture of the nitrogen-doped ceramic graphene aerogel prepared in Example 1;

[0031] Figure 3 XRD spectrum of nitrogen-doped ceramic graphene aerogel prepared in Example 1;

[0032] Figure 4 This is a SEM spectrum of the nitrogen-doped ceramic graphene aerogel prepared in Example 1;

[0033] Figure 5 This is an enlarged SEM spectrum of the nitrogen-doped ceramic graphene aerogel prepared in Example 1. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0035] In the following description of this embodiment, the terms "include", "comprising", "having" and "containing" are all open terms, meaning including but not limited to.

[0036] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0037] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0038] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0039] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0040] Those skilled in the art will appreciate that the numerical ranges in the embodiments of the present application are to be construed as specifically disclosing each intermediate value between the upper and lower limits of the scope. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present application. The upper and lower limits of these smaller ranges may be independently included or excluded in the scope.

[0041] Unless otherwise specified, the technical / scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0042] In a first aspect, the present application provides a method for preparing nitrogen-doped ceramic graphene aerogel, comprising:

[0043] S1, dispersing few-layer graphene oxide, polysilazane, polyethylene glycol and sodium ascorbate in water, stirring at 70-90° C. to obtain a uniform slurry;

[0044] In the present application, a slurry is prepared by adding a few-layer graphene oxide, polysilazane and sodium ascorbate to a polyethylene glycol aqueous solution and stirring at 70 to 90 ° C for 24 to 48 hours. The slurry of the present application uses polyethylene glycol as the main solvent. The higher melting point and faster solidification rate of polyethylene glycol help prevent organic phase separation during freezing, ensure the uniformity and stability of the material, and polyethylene glycol can help polysilazane and graphene to mix evenly, and the molding effect is good. Sodium ascorbate is used to adjust the degree of self-assembly of graphene oxide, and its interaction with polysilazane can effectively improve the structural strength of the product. In the present application, it is preferred that the molecular weight of polyethylene glycol is 3500.

[0045] In the present application, the concentration of the few-layer graphene oxide in the slurry is preferably 10-20 mg / mL; the concentration of polysilazane is 2-4 mg / mL, the concentration of polyethylene glycol is 150-200 mg / mL, the concentration of sodium ascorbate is 0.4-0.8 mg / mL, the stirring temperature is preferably 80°C, and the stirring time is preferably 48h.

[0046] S2, rapidly freezing the slurry and freeze-drying it to obtain a precursor of a porous structure;

[0047] Specifically, the slurry is injected into a mold with a diameter of 3 to 10 cm, and the mold is oriented and frozen from bottom to top by liquid nitrogen for 10 to 15 minutes. Vertically oriented graphene aerogels can be prepared by oriented freezing, and the vertically oriented structure can significantly improve the electrical conductivity, thermal conductivity and structural strength of the aerogel. Polyethylene glycol, due to its higher melting point and faster solidification speed, helps prevent organic phase separation during the freezing process, ensuring the uniformity and stability of the precursor material.

[0048] Subsequently, the temperature is controlled at -70 to -80°C and a freeze-drying treatment is performed for 24 to 48 hours under the condition of a vacuum degree of less than 15 Pa to obtain a precursor of a porous structure.

[0049] S3, heating the precursor to 400-600° C. in an inert atmosphere for calcination, and then heating to 900-1200° C. for calcination to obtain nitrogen-doped ceramic graphene aerogel.

[0050] Specifically, the inert atmosphere described in the present application is an argon atmosphere. The precursor is calcined at 400-600°C for 1-2 hours to remove the polyethylene glycol therein and enhance the thermal stability of the aerogel; the precursor is then calcined at 900-1200°C for 3-5 hours to achieve ceramicization of polysilazane and combine it with graphene oxide aerogel.

[0051] In the present application, the ceramicization degree and the strength of the aerogel vary with the calcination temperature and the polysilazane doping amount. The ceramicized nitrogen-doped graphene aerogel has good structural strength and stable conductive channels, and its vertically oriented internal structure can also meet more reaction requirements and provide more reaction binding sites.

[0052] The present application prepares an aerogel with high porosity through an improved hydrothermal reaction and precise freeze drying, then removes the supporting material from the aerogel at high temperature, and realizes ceramicization through pyrolysis reduction, and finally obtains nitrogen-doped ceramicized graphene aerogel. The preparation method of the present application improves the conductivity and interface interaction ability of the graphene aerogel, and the surface after ceramicization has more binding sites and better structural strength, and the process is simple and efficient, the production cost is low, and it has good repeatability and stability, which is conducive to large-scale production. The nitrogen-doped ceramicized graphene aerogel prepared in the present application has excellent electrical conductivity, thermal conductivity and mechanical strength.

[0053] In the present application, the few-layer graphene oxide is prepared by the following method:

[0054] The graphite and sulfuric acid are mixed evenly, sodium nitrate and phosphorus pentoxide are added, and the mixture is stirred at 80-100° C. for 12-24 hours, and the solid phase is separated and collected by suction filtration, and dried in the shade to obtain a precursor; wherein the graphite is preferably flake graphite;

[0055] Specifically, the mass ratio of the graphite, sulfuric acid, sodium nitrate and phosphorus pentoxide is preferably (1-2):(18-20):(1.5-2):(1.5-2).

[0056] The precursor is dispersed in excess concentrated sulfuric acid, and potassium permanganate is slowly added thereto, and stirred at -10 to 0°C for 4 to 5 hours, then the temperature is raised to 30 to 40°C, water is added for dilution, and then the temperature is raised to 90°C, and hydrogen peroxide is added until the solution turns bright yellow to obtain a dispersion;

[0057] Wherein, the mass ratio of potassium permanganate to graphite is 5:1.

[0058] The dispersion is diluted with water, centrifuged at a speed of 5000-7000 r / min to remove multilayer graphene oxide, and then centrifuged at a speed of 10000-12000 r / min to remove impurities, and the concentrated solution obtained by centrifugation is freeze-dried to obtain few-layer graphene oxide.

[0059] The nitrogen-doped ceramic graphene aerogel prepared in the present application not only has excellent electrical conductivity, thermal conductivity and mechanical strength, but also has more binding sites and better structural strength. In addition, it has a porous structure and a high surface area, which enables it to perform well in applications such as catalysis, adsorption and energy storage.

[0060] The nitrogen-doped ceramic graphene aerogel of the present application can be applied to the fields of electronic manufacturing, energy conversion and environmental protection, and has important commercial prospects and application value.

[0061] The present application is further described below by way of examples. In the examples of the present application, polyethylene glycol with a molecular weight of 3500 is selected.

[0062] Example 1

[0063] This embodiment provides a nitrogen-doped ceramic graphene aerogel, and the preparation method thereof includes:

[0064] 1) Preparation of few-layer graphene oxide:

[0065] 2 g of flake graphite was mixed with 10 ml of sulfuric acid, stirred at 80° C., and then 1.7 g of sodium nitrate and 1.7 g of phosphorus pentoxide were added in sequence, and stirring was continued for 12 hours; the mixture was filtered twice and dried in the shade at room temperature for 3 hours to obtain a precursor.

[0066] Add 80ml sulfuric acid to a beaker, add the precursor, slowly add 10g potassium permanganate to the beaker at -10℃, stir for 4.5 hours, then treat in a 35℃ water bath for 4 hours, dilute it in 1000ml water, stir for 15 minutes; heat to 90℃ and add hydrogen peroxide until the solution turns bright yellow to obtain a dispersion; centrifuge the dispersion at 11000r / min for 7min, then centrifuge at 6000r / min for 5min to remove impurities, and centrifuge again at 11000r / min for 15min to obtain a concentrate. Freeze-dry the concentrate for 48 hours to obtain few-layer graphene oxide.

[0067] 2) Preparation of nitrogen-doped ceramic graphene aerogel:

[0068] Add the few-layer graphene oxide, polysilazane, polyethylene glycol and sodium ascorbate prepared in step 1 to water and shake for 5 minutes to ensure uniform mixing, wherein the concentration of the few-layer graphene oxide is 10 mg / mL, the concentration of polysilazane is 2 mg / mL, the concentration of polyethylene glycol is 150 mg / mL, and the concentration of sodium ascorbate is 0.4 mg / mL. Treat the mixture in an oil bath at 80°C for 48 hours to obtain a uniform slurry;

[0069] The slurry was poured into a polyethylene mold with a diameter of 5 cm, and the mold was directionally frozen from bottom to top using liquid nitrogen for 15 minutes. After freezing, the mold was placed in a freeze dryer, the temperature was set to -70°C, the vacuum degree was <15Pa, and the freeze drying process was performed for 48 hours to obtain a precursor of a porous structure;

[0070] The precursor was calcined at 400 °C for 2 h in an argon atmosphere, and then the temperature was increased to 1000 °C and calcined for 3 h to obtain nitrogen-doped ceramic graphene aerogel.

[0071] Example 2

[0072] This embodiment provides a nitrogen-doped ceramic graphene aerogel, and the preparation method thereof includes:

[0073] 1) Preparation of few-layer graphene oxide:

[0074] 1 g of flake graphite was mixed with 10 ml of sulfuric acid, stirred at 80° C., and then 2 g of sodium nitrate and 1.5 g of phosphorus pentoxide were added in sequence, and stirring was continued for 12 hours; the mixture was filtered twice and dried in the shade at room temperature for 3 hours to obtain a precursor.

[0075] Add 80ml sulfuric acid to a beaker, add the precursor, slowly add 5g potassium permanganate to the beaker at -10℃, stir for 4.5 hours, then treat in a 35℃ water bath for 4 hours, dilute it in 1000ml water, stir for 15 minutes; heat to 90℃ and add hydrogen peroxide until the solution turns bright yellow to obtain a dispersion; centrifuge the dispersion at 11000r / min for 7min, then centrifuge at 5000r / min for 10min to remove impurities, and centrifuge again at 11000r / min for 15min to obtain a concentrate. Freeze-dry the concentrate for 48 hours to obtain few-layer graphene oxide.

[0076] 2) Preparation of nitrogen-doped ceramic graphene aerogel:

[0077] Add the few-layer graphene oxide, polysilazane, polyethylene glycol and sodium ascorbate prepared in step 1 to water and shake for 5 minutes to ensure uniform mixing, wherein the concentration of the few-layer graphene oxide is 15 mg / mL, the concentration of polysilazane is 2 mg / mL, the concentration of polyethylene glycol is 150 mg / mL, and the concentration of sodium ascorbate is 0.5 mg / mL. Treat the mixture in an oil bath at 80°C for 48 hours to obtain a uniform slurry;

[0078] The slurry was poured into a polyethylene mold with a diameter of 3 cm, and the mold was directionally frozen from bottom to top using liquid nitrogen for 10 minutes. After freezing, the mold was placed in a freeze dryer, the temperature was set to -70°C, the vacuum degree was <15Pa, and the freeze drying process was performed for 48 hours to obtain a precursor of a porous structure;

[0079] The precursor was calcined at 500 °C for 2 h in an argon atmosphere, and then the temperature was increased to 1200 °C and calcined for 4 h to obtain nitrogen-doped ceramic graphene aerogel.

[0080] Example 3

[0081] This embodiment provides a nitrogen-doped ceramic graphene aerogel, and the preparation method thereof includes:

[0082] 1) Preparation of few-layer graphene oxide:

[0083] 2 g of flake graphite was mixed with 10 ml of sulfuric acid, stirred at 80° C., and then 1.5 g of sodium nitrate and 2 g of phosphorus pentoxide were added in sequence, and stirring was continued for 12 hours; the mixture was filtered twice and dried in the shade at room temperature for 3 hours to obtain a precursor.

[0084] Add 80ml sulfuric acid to a beaker, add the precursor, slowly add 10g potassium permanganate to the beaker at -10℃, stir for 4.5 hours, then treat in a 35℃ water bath for 4 hours, dilute it in 1000ml water, stir for 15 minutes; heat to 90℃ and add hydrogen peroxide until the solution turns bright yellow to obtain a dispersion; centrifuge the dispersion at 11000r / min for 7min, then centrifuge at 7000r / min for 5min to remove impurities, and centrifuge again at 11000r / min for 15min to obtain a concentrate. Freeze-dry the concentrate for 48 hours to obtain few-layer graphene oxide.

[0085] 2) Preparation of nitrogen-doped ceramic graphene aerogel:

[0086] Add the few-layer graphene oxide, polysilazane, polyethylene glycol and sodium ascorbate prepared in step 1 to water and shake for 5 minutes to ensure uniform mixing, wherein the concentration of the few-layer graphene oxide is 20 mg / mL, the concentration of polysilazane is 4 mg / mL, the concentration of polyethylene glycol is 200 mg / mL, and the concentration of sodium ascorbate is 0.8 mg / mL. Treat the mixture in an oil bath at 80°C for 48 hours to obtain a uniform slurry;

[0087] The slurry was poured into a polyethylene mold with a diameter of 5 cm, and the mold was directionally frozen from bottom to top using liquid nitrogen for 15 minutes. After freezing, the mold was placed in a freeze dryer, the temperature was set to -80°C, the vacuum degree was <15Pa, and the freeze drying process was performed for 24 hours to obtain a precursor of a porous structure;

[0088] The precursor was calcined at 600 °C for 2 h in an argon atmosphere, and then the temperature was increased to 900 °C and calcined for 5 h to obtain nitrogen-doped ceramic graphene aerogel.

[0089] The precursor prepared by liquid nitrogen directional freezing and freeze-drying in Example 1 is Figure 1 As shown. Figure 1 It can be seen that the precursor exhibits uniform distribution characteristics and has obvious orientation arrangement. This uniform distribution and orientation arrangement helps to optimize the mechanical properties and structural stability of aerogel materials, and has an important influence on the performance of aerogel materials.

[0090] The actual nitrogen-doped ceramic graphene aerogel prepared in Example 1 is as follows Figure 2 As shown. Figure 2It can be seen that although the nitrogen-doped ceramic graphene aerogel obtained after calcination has a slight cracking phenomenon, its structural strength is significantly improved. The degree of cracking is closely related to the amount of sodium ascorbate and polysilazane added and the calcination time. The lower the elasticity of the material, the higher the possibility of cracking. According to the use of nitrogen-doped ceramic graphene aerogel, the raw materials and process of nitrogen-doped ceramic graphene aerogel can be adjusted in a targeted manner.

[0091] The nitrogen-doped ceramic graphene aerogel prepared in Example 1 was subjected to XRD test, and its spectrum is as follows: Figure 3 As shown. Figure 3 It can be seen that there is an obvious diffraction peak at 2θ≈26.6°, which is a characteristic peak of graphene material, corresponding to the (002) crystal plane. The existence of this peak indicates the presence of graphene structure in nitrogen-doped ceramic graphene aerogel. There is also an obvious peak at 2θ≈43.3°, corresponding to the (100) crystal plane of graphene; the diffraction peak intensity at 2θ≈26.6° is high, indicating that graphene has a high degree of crystallinity in the material. The nitrogen-doped ceramic graphene aerogel prepared in this application has obvious graphene characteristic peaks, indicating that the graphene structure is well maintained in the material. The intensities of other peaks are relatively low, but still clearly visible, showing the polycrystalline characteristics of nitrogen-doped ceramic graphene aerogel.

[0092] Ceramics treatment usually enhances the structural strength and stability of the material, which is manifested in the XRD spectrum as a sharpening of the peak shape and an increase in the peak intensity. Figure 3 The presence of multiple diffraction peaks and polycrystalline phases in the aerogel indicates that the nitrogen-doped ceramic graphene aerogel has a complex crystal structure inside, showing its high crystallinity and multiphase characteristics, verifying that nitrogen doping and ceramic treatment have an effect on the crystal structure of the material, which helps to improve the electrical conductivity, thermal conductivity and structural strength of the material.

[0093] The nitrogen-doped ceramic graphene aerogel prepared in Example 1 was tested by scanning electron microscopy, and its spectrum is as follows: Figure 4 and Figure 5 As shown, Figure 5 for Figure 4 A partial enlarged view of Figure 4 and Figure 5 It can be seen that a large number of spherical particles are evenly distributed inside the nitrogen-doped graphene aerogel, indicating that polysilazane is well distributed in the aerogel without obvious agglomeration. The uniform distribution of particles indicates that the mixing and dispersion steps in the preparation process are very effective, and this uniform distribution helps to form a uniform ceramic structure during the calcination process. Spherical particles of different sizes can be observed in the spectrum, with sizes ranging from tens of nanometers to hundreds of nanometers. This polydisperse size distribution helps to optimize the performance of the material at different scales.

[0094] also, Figure 4 and Figure 5 It can also be seen that the morphology of nitrogen-doped ceramicized graphene aerogel shows good bonding between particles, indicating that the material forms a stable ceramic structure during high-temperature calcination; there are microscopic pores on the surface of the particles, which helps to increase the specific surface area of ​​the material, thereby enhancing its performance in catalytic and adsorption applications. Nitrogen doping not only improves the electrical and thermal conductivity of graphene, but also introduces more reactive sites, further enhancing the versatility of the material, which can significantly improve the performance of the material in electrochemical, catalytic and sensing applications. In addition, the ceramic treatment after calcination enhances the mechanical strength and thermal stability of the material, making it more stable and durable under harsh conditions such as high temperature and high pressure. This stability is crucial for the long-term use and reliability of the material in practical applications.

[0095] Although the present application has been described in detail in general terms and in specific embodiments in this specification, it is obvious to those skilled in the art that some modifications or improvements may be made to the present application. Therefore, these modifications or improvements made without departing from the spirit of the present application are within the scope of protection claimed in the present application.

Claims

1. A method for preparing nitrogen-doped ceramic graphene aerogel, characterized in that: include: S1, dispersing the few-layer graphene oxide, polysilazane, polyethylene glycol and sodium ascorbate in water, stirring at 70-90° C. to obtain a uniform slurry; S2, rapidly freezing the slurry and freeze-drying it to obtain a precursor of a porous structure; S3, heating the precursor to 400-600° C. in an inert atmosphere for calcination, and then heating to 900-1200° C. for calcination to obtain nitrogen-doped ceramic graphene aerogel.

2. The method for preparing nitrogen-doped ceramic graphene aerogel according to claim 1, characterized in that: The concentration of the few-layer graphene oxide in the slurry is 10-20 mg / mL; the concentration of polysilazane is 2-4 mg / mL; the concentration of polyethylene glycol is 150-200 mg / mL; and the concentration of sodium ascorbate is 0.4-0.8 mg / mL.

3. The method for preparing nitrogen-doped ceramic graphene aerogel according to claim 1, characterized in that: The rapid freezing comprises: The slurry is injected into the mold, and the mold is oriented and frozen from bottom to top by liquid nitrogen, and the freezing time is 10 to 15 minutes.

4. The method for preparing nitrogen-doped ceramic graphene aerogel according to claim 3, characterized in that: The diameter of the mold is 3 to 10 cm.

5. The method for preparing nitrogen-doped ceramic graphene aerogel according to claim 1, characterized in that: The freeze-drying treatment temperature is -70 to -80°C, the vacuum degree is less than 15Pa, and the freeze-drying time is 24 to 48 hours.

6. The method for preparing nitrogen-doped ceramic graphene aerogel according to claim 1, characterized in that: In step S3, the calcination time at 400-600°C is 1-2 hours; the calcination time at 900-1200°C is 3-5 hours.

7. The method for preparing nitrogen-doped ceramic graphene aerogel according to claim 1, characterized in that: The few-layer graphene oxide is prepared by the following method: Mix graphite and sulfuric acid evenly, add sodium nitrate and phosphorus pentoxide, stir at 80-100°C for 12-24h, separate and collect the solid phase, wash and shade-dry to obtain the precursor; The precursor is dispersed in excess concentrated sulfuric acid, and potassium permanganate is slowly added thereto, stirred at -10 to 0°C, and then diluted with water, and then heated to 90°C, and hydrogen peroxide is added until the solution turns bright yellow to obtain a dispersion; The dispersion is diluted with water, centrifuged at a speed of 5000-7000 r / min to remove multilayer graphene oxide, and then centrifuged at a speed of 10000-12000 r / min to remove impurities, and the concentrated solution obtained by centrifugation is freeze-dried to obtain few-layer graphene oxide.

8. The method for preparing nitrogen-doped ceramic graphene aerogel according to claim 7, characterized in that: The mass ratio of graphite, sulfuric acid, sodium nitrate and phosphorus pentoxide is (1-2):(18-20):(1.5-2):(1.5-2); The mass ratio of potassium permanganate to graphite is 5:

1.

9. Nitrogen-doped ceramic graphene aerogel prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the nitrogen-doped ceramic graphene aerogel prepared by the preparation method according to any one of claims 1 to 8 in the fields of electronic manufacturing, energy conversion and environmental protection.

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