Carbon nanofiber aerogel and method for preparing the same

Abstract

The present application relates to the technical field of nanomaterials, and particularly relates to a carbon nanofiber aerogel and a preparation method thereof, and the preparation method of the carbon nanofiber aerogel comprises the following steps: freezing treatment is performed on a mixed dispersion solution obtained by mixing a bacterial cellulose dispersion solution containing inorganic ammonium salt and a polymer solution, and after freeze-drying, a bacterial cellulose aerogel is obtained; pyrolysis treatment is performed on the bacterial cellulose aerogel, and a carbon nanofiber aerogel is obtained. In the preparation process, the introduction of the polymer can produce additional carbon in the carbonization process, the connection between the carbon nanofibers is more compact, the overall structural strength of the material is enhanced, through the composite carbon network formed after the polymer carbonization, the carbon content of the aerogel is increased, and the mechanical properties of the aerogel are improved through the crosslinking and filling effects. The high-strength carbon network can better disperse stress, avoid the collapse or excessive deformation of the structure when external force is borne, so that the maximum compressive strength of the aerogel is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, and in particular to a carbon nanofiber aerogel and its preparation method. Background Technology

[0002] Carbon aerogels, as a cutting-edge material, have many advantages. They possess abundant microporous and mesoporous structures, exhibit good electrical conductivity due to their carbon-based network structure, and also have excellent mechanical properties. They can withstand certain pressure and deformation, and have good stability in high-temperature environments, showing great potential in multiple fields.

[0003] After bacterial cellulose pyrolysis, cellulose nanofibers are transformed into carbon nanofibers, forming a carbon aerogel with a three-dimensional cross-linked network structure. However, due to the limited number of cross-linking points within the carbon nanofibers after pyrolysis, its mechanical properties and stability are relatively weak. The limited number of cross-linking points may also result in a loose structure of the carbon nanofibers. Furthermore, the lack of sufficient cross-linking points also affects the electrical and thermal conductivity of carbon nanofibers, limiting their application as high-performance materials in various fields. These issues make the performance of carbon nanofibers in practical applications unsatisfactory, necessitating further research and improvement to enhance their overall performance and meet the requirements of use in various complex environments.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a carbon nanofiber aerogel and its preparation method, aiming to solve the problems of weak mechanical properties and stability, and poor electrical and thermal conductivity of existing carbon aerogels.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing carbon nanofiber aerogel, comprising the following steps:

[0008] A bacterial cellulose dispersion containing inorganic ammonium salts was mixed with a polymer solution to obtain a mixed dispersion.

[0009] The mixed dispersion was frozen and then freeze-dried to obtain bacterial cellulose aerogel.

[0010] The bacterial cellulose aerogel was subjected to pyrolysis to obtain carbon nanofiber aerogel.

[0011] The method for preparing carbon nanofiber aerogels, wherein the inorganic ammonium salt includes one or more of ammonium chloride, ammonium sulfate, and ammonium dihydrogen phosphate.

[0012] The method for preparing carbon nanofiber aerogels, wherein the inorganic ammonium salt in the bacterial cellulose dispersion contains an inorganic ammonium salt with a mass fraction of 0.5% to 80% relative to the bacterial cellulose.

[0013] The method for preparing carbon nanofiber aerogel, wherein the polymer in the polymer solution includes one or more of glucose, sodium alginate, and chitosan.

[0014] In the method for preparing the carbon nanofiber aerogel, the polymer solution has a mass fraction of 0.5% to 40% relative to bacterial cellulose.

[0015] The method for preparing carbon nanofiber aerogels, wherein the freezing treatment involves placing the mixed dispersion on a freezing stage at -20℃ to -60℃ for 10 min to 40 min.

[0016] The method for preparing carbon nanofiber aerogels includes a pyrolysis treatment temperature of 600℃ to 1400℃, a pyrolysis treatment heating rate of 2℃ / min to 10℃ / min, and a pyrolysis treatment time of 1h to 3h.

[0017] The method for preparing carbon nanofiber aerogels, wherein the pyrolysis treatment is carried out under an inert atmosphere or under vacuum conditions.

[0018] A carbon nanofiber aerogel was prepared using a method for preparing carbon nanofiber aerogels.

[0019] The carbon nanofiber aerogel, wherein the density of the carbon nanofiber aerogel is 3 mg·cm³. -3 ~25mg·cm -3 .

[0020] Beneficial Effects: This invention provides a carbon nanofiber aerogel and its preparation method. The preparation method of the carbon nanofiber aerogel includes: mixing a bacterial cellulose dispersion containing inorganic ammonium salts with a polymer solution to obtain a mixed dispersion; freezing the mixed dispersion and then freeze-drying it to obtain a bacterial cellulose aerogel; and pyrolyzing the bacterial cellulose aerogel to obtain a carbon nanofiber aerogel. This invention introduces a polymer into the preparation of the carbon nanofiber aerogel. This polymer can significantly increase the crosslinking density between carbon nanofibers by forming additional physical or chemical crosslinks in the structure of the carbon nanofiber aerogel, thereby improving the structural stability of the carbon nanofiber aerogel and effectively enhancing its mechanical properties. Furthermore, the polymer chains connect the voids between the carbon nanofibers, promoting uniform stress distribution and reducing local stress concentration. In addition, the introduction of the polymer can also regulate the void structure of the aerogel, improving the thermal stability and electrical conductivity of the material. The carbon nanofiber aerogel has low density and high volume retention, providing a high specific surface area, which is beneficial for adsorption or catalytic reactions. The enhanced compressive stress improves the mechanical stability of the carbon nanofiber aerogel, making it less prone to deformation under external pressure. Furthermore, the carbon nanofiber aerogel obtained by this preparation method has a density of 3–25 mg / cm³. -3 The volume retention rate is 15-50%, and the maximum compressive strength is >9 kPa. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the process flow for a method of preparing carbon nanofiber aerogel according to the present invention.

[0022] Figure 2 This is a photograph of the carbon nanofiber aerogel obtained in Example 1.

[0023] Figure 3 The stress-strain curve of the carbon nanofiber aerogel obtained in Example 1 after 100 cycles at 60% compressive strain;

[0024] Figure 4 This is a photograph of the carbon nanofiber aerogel obtained in Example 2.

[0025] Figure 5 The stress-strain curve of the carbon nanofiber aerogel obtained in Example 2 after 100 cycles at 60% compressive strain;

[0026] Figure 6 This is a photograph of the carbon nanofiber aerogel obtained in Example 3.

[0027] Figure 7 The stress-strain curve of the carbon nanofiber aerogel obtained in Example 3 after 100 cycles at 60% compressive strain is shown. Detailed Implementation

[0028] This invention provides a carbon nanofiber aerogel and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0030] like Figure 1 As shown, this invention provides a method for preparing carbon nanofiber aerogel, comprising the following steps:

[0031] Step S10: Mix the bacterial cellulose dispersion containing inorganic ammonium salt with the polymer solution to obtain a mixed dispersion;

[0032] Step S20: Freeze the mixed dispersion and freeze-dry it to obtain bacterial cellulose aerogel;

[0033] Step S30: The bacterial cellulose aerogel is subjected to pyrolysis treatment to obtain carbon nanofiber aerogel.

[0034] In this embodiment, a polymer is introduced during the preparation of carbon nanofiber aerogels. This polymer can significantly increase the crosslinking density between carbon nanofibers by forming additional physical or chemical crosslinks within the aerogel structure, thereby improving the structural stability and effectively enhancing its mechanical properties. Furthermore, the polymer chains connect the voids between carbon nanofibers, promoting uniform stress distribution and reducing localized stress concentration. In addition, the introduction of the polymer can regulate the pore structure of the aerogel, improving the material's thermal stability and electrical conductivity. The carbon nanofiber aerogels exhibit low density and high volume retention, providing a high specific surface area, which is beneficial for adsorption or catalytic reactions. The enhanced compressive stress improves the mechanical stability of the carbon nanofiber aerogels, making them less prone to deformation under external pressure. The carbon nanofiber aerogels obtained by this preparation method have a density of 3–25 mg / cm³. -3 The volume retention rate is 15-50%, and the maximum compressive strength is >9KPa. Furthermore, this invention utilizes bacterial cellulose and common polymers as precursors, which are inexpensive and readily available, and the method is simple and easy to mass-produce.

[0035] Specifically, the carbon nanofiber aerogel of this invention is prepared by carbonization of bacterial cellulose. Bacterial cellulose is a highly ordered nanofiber structure, and the carbonization process can transform it into carbon nanofibers. This transformation greatly reduces the density of the material while retaining the network structure of the nanofibers. However, during the carbonization process, due to the high-temperature decomposition of organic matter, the material undergoes volume shrinkage, resulting in a decrease in volume retention. During pyrolysis, inorganic salts act as a catalyst, changing the pyrolysis mode of bacterial cellulose fibers and effectively promoting the dehydration of bacterial cellulose fibers. This reduces the carbon-to-oxygen ratio in the released gaseous and liquid products, increasing the carbon residue after bacterial cellulose pyrolysis. The polymer introduced in the preparation process of this invention can generate additional carbon during carbonization, making the connections between carbon nanofibers tighter and enhancing the overall structural strength of the material. This composite carbon network formed after polymer carbonization not only increases the carbon content of the aerogel but also further improves its mechanical properties through cross-linking and filling. The high-strength carbon network can better disperse stress, preventing structural collapse or excessive deformation under external forces, thereby significantly improving the maximum compressive strength of the aerogel.

[0036] In some embodiments, the inorganic ammonium salt includes one or more of ammonium chloride, ammonium sulfate, and ammonium dihydrogen phosphate. Using the above-mentioned inorganic ammonium salt as a catalyst can effectively promote the dehydration of bacterial cellulose fibers by altering the pyrolysis mechanism and route, thereby reducing the carbon-to-oxygen ratio in the escaping gaseous and liquid products and increasing the residual carbon content after bacterial cellulose pyrolysis.

[0037] In some embodiments, the inorganic ammonium salt in the bacterial cellulose dispersion has a mass fraction of 0.5% to 80% relative to the bacterial cellulose. Controlling the mass fraction of the inorganic ammonium salt within the above range enables the polymer solution to effectively encapsulate the bacterial fibers, allowing new cross-linking points to form after carbonization, and increasing the carbon residue after the pyrolysis of the bacterial cellulose.

[0038] In a preferred embodiment, the inorganic ammonium salt in the bacterial cellulose dispersion contains 0.5% to 60% of the inorganic ammonium salt relative to the bacterial cellulose, more preferably 0.5% to 50%, and most preferably 0.5% to 40%; in some embodiments provided by the present invention, the mass fraction of the ammonium dihydrogen phosphate relative to the bacterial cellulose is preferably 17%.

[0039] In some embodiments, the inorganic ammonium salt in the bacterial cellulose dispersion contains an inorganic ammonium salt with a mass fraction of 0.8%-50% relative to the bacterial cellulose.

[0040] In some embodiments, the polymer in the polymer solution includes one or more of glucose, sodium alginate, and chitosan. The introduction of these polymers can also modulate the porosity structure of the aerogel, improving the material's thermal stability and electrical conductivity. Preferably, the polymer solution uses only deionized water as the solvent.

[0041] In some embodiments, the polymer solution has a mass fraction of 0.5% to 40% relative to bacterial cellulose. Controlling the mass fraction of the polymer solution within this range allows the polymer solution to effectively encapsulate the BC fibers, forming new crosslinking points after carbonization. Furthermore, it enables the polymer to form polymer chains within the carbon nanofiber aerogel, connecting the gaps between the carbon nanofibers, promoting uniform stress distribution, and reducing localized stress concentration.

[0042] In some embodiments, the freezing treatment involves placing the mixed dispersion on a freezing stage at -20°C to -60°C for 10 to 40 minutes. The freezing treatment causes the mixed dispersion to form ice blocks; then, freeze-drying under vacuum and low temperature conditions removes the water from the ice blocks through sublimation, resulting in a freeze-dried aerogel with a honeycomb-like porous structure.

[0043] It should be explained that the term "freezing" refers to the process of converting a dispersion of bacterial cellulose and polymer into ice; the term "freeze-drying" refers to placing these frozen ice cubes in a freeze dryer and drying them through a sublimation process under low temperature and vacuum conditions.

[0044] In a preferred embodiment, the temperature of the freezing stage is -30°C to -40°C, and the freezing time is preferably 20 min to 30 min.

[0045] In some embodiments, the freeze-drying time is 3 to 5 days, allowing the water in the ice to completely sublimate, resulting in an anhydrous honeycomb-like porous aerogel.

[0046] Specifically, the mixed dispersion is poured into a container and frozen on a freezing platform at -20 to -60°C, followed by freeze-drying to obtain bacterial cellulose aerogel. Freezing at the specified temperature ensures that the bacterial cellulose dispersion is fully frozen and maintains an ordered internal structure. Excessively high or low temperatures can cause the internal pores of the bacterial cellulose to enlarge due to the squeezing effect of crystallization during freezing. Completing the freeze-drying step within the specified time ensures that the bacterial cellulose aerogel is completely dried.

[0047] In some embodiments, the pyrolysis treatment temperature is 600℃~1400℃, the heating rate is 2℃ / min~10℃ / min, and the treatment time is 1h~3h. Under these conditions, pyrolysis can convert BC fibers into carbon nanofibers, and within this temperature range, pyrolysis can maximize the complete conversion of BC fibers into carbon nanofibers.

[0048] Specifically, the bacterial cellulose aerogel is preferably placed in a ceramic boat for pyrolysis treatment; the pyrolysis treatment is preferably carried out in a tube furnace; the heating rate of the pyrolysis treatment is preferably 3-8℃ / min, more preferably 4-6℃ / min, and most preferably 5℃ / min; the temperature of the pyrolysis treatment is preferably 800℃-1200℃; the time of the high-temperature pyrolysis is preferably 1-3h, that is, after heating to the high-temperature pyrolysis temperature, it is held at that temperature for 1-3h, more preferably 2h.

[0049] In some embodiments, after the pyrolysis treatment, a staged cooling process is employed; specifically: after the pyrolysis treatment, the temperature is preferably lowered to 400℃~600℃, more preferably to 450℃~550℃, then more preferably to 500℃, and then allowed to naturally cool to room temperature to obtain carbon nanofiber aerogel; the cooling rate is preferably 4~6℃ / min, more preferably 5℃ / min. In this embodiment, the tubular furnace is maintained at atmospheric pressure during both the pyrolysis treatment and the cooling process.

[0050] In some embodiments, the pyrolysis process is carried out under an inert atmosphere or under vacuum conditions. The inert atmosphere can be any protective atmosphere well known to those skilled in the art; in this embodiment, nitrogen or argon is preferred.

[0051] In some embodiments, the carbon nanofiber aerogel is in the form of a regular block with a length of 5-50 mm, a width of 5-50 mm, and a thickness of 5-30 mm, with the internal nanofibers interwoven to form a highly cross-linked three-dimensional network structure.

[0052] In a preferred embodiment, the bacterial cellulose aerogel has a diameter of (20-25) × (20-25) × (17-20) mm. 3 The blocky shape, while the carbon nanofiber aerogel obtained after pyrolysis in step S30 has a size of (13-18)×(13-18)×(12-15) mm. 3 It is in block form, with a volume retention rate of 15-50%.

[0053] In addition, the present invention also provides a carbon nanofiber aerogel, which is prepared using a method for preparing carbon nanofiber aerogel.

[0054] In this embodiment, the carbon nanofiber aerogel is prepared by carbonizing bacterial cellulose. Bacterial cellulose is a highly ordered nanofiber structure, and the carbonization process can transform it into carbon nanofibers. This transformation greatly reduces the density of the material while retaining the network structure of the nanofibers. However, during the carbonization process, due to the high-temperature decomposition of organic matter, the material undergoes volume shrinkage, resulting in a decrease in volume retention. During pyrolysis, inorganic salts act as a catalyst, changing the pyrolysis mode of bacterial cellulose fibers and altering the pyrolysis route. This effectively promotes the dehydration of bacterial cellulose fibers, reducing the carbon-to-oxygen ratio in the released gaseous and liquid products, and increasing the carbon residue after bacterial cellulose pyrolysis. The polymer introduced in the preparation process of this invention can generate additional carbon during carbonization, making the connections between carbon nanofibers tighter and enhancing the overall structural strength of the material. This composite carbon network formed after polymer carbonization not only increases the carbon content of the aerogel but also further improves its mechanical properties through cross-linking and filling. The high-strength carbon network can better disperse stress, preventing structural collapse or excessive deformation under external forces, thereby significantly increasing the maximum compressive strength of the aerogel.

[0055] In some embodiments, the density of the carbon nanofiber aerogel is 3 mg·cm³. -3 ~25mg·cm -3 .

[0056] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention.

[0057] Example 1

[0058] Add 0.016 g of ammonium dihydrogen phosphate to 10 g of a bacterial cellulose dispersion (0.8% by mass), shake thoroughly until homogeneous, then add 0.37 g of a glucose solution (2.4% by mass), and shake again until homogeneous. Remove air bubbles from the dispersion using a vacuum oven. Pour the resulting dispersion into a 25 mm × 25 mm × 20 mm polytetrafluoroethylene mold and freeze on a -40 °C freezer for 30 min. After complete freezing, transfer to a freeze dryer and dry for 3 days at a cold trap temperature of -60 °C and a pressure of 0.04 mbar to obtain a bacterial cellulose / glucose mixed aerogel.

[0059] The freeze-dried bacterial cellulose / glucose mixed aerogel was placed in a ceramic boat and then placed in a tube furnace. Nitrogen gas was introduced into the tube furnace as a protective gas. The furnace was first heated to 1000℃ at a rate of 5℃ / min and held for 2 hours; then cooled to 500℃ at a rate of 5℃ / min, and finally allowed to cool naturally to room temperature, yielding a black carbon nanofiber aerogel with a volume retention of 34%. Figure 2 As shown. The dimensions of the obtained carbon nanofiber aerogel are 16 mm long × 16 mm wide × 13 mm thick. 3 Its density is 7.3 mg / cm³. 3 .

[0060] Mechanical tests were performed on the carbon nanofiber aerogel obtained in Example 1. Figure 3 The stress-strain curve of the carbon nanofiber aerogel provided in this embodiment after 100 cycles at 60% compressive strain is shown. Because the pore structure of the carbon aerogel is stable and uniformly distributed, the aerogel can still recover its original shape after 100 compression cycles, indicating that it has good compressive resilience.

[0061] Example 2

[0062] Add 0.016 g of ammonium dihydrogen phosphate to 10 g of a bacterial cellulose dispersion with a mass fraction of 0.8%, shake thoroughly until homogeneous, then add 0.175 g of a sodium alginate solution with a mass fraction of 2.4%, and shake again until homogeneous. Remove air bubbles from the dispersion using a vacuum oven. Pour the resulting dispersion into a 25 mm × 25 mm × 20 mm polytetrafluoroethylene mold and freeze on a -30 °C freezer for 25 min. After complete freezing, transfer to a freeze dryer and dry for 3 days at a cold trap temperature of -60 °C and a pressure of 0.04 mbar to obtain a bacterial cellulose / sodium alginate mixed aerogel.

[0063] The freeze-dried bacterial cellulose / sodium alginate mixed aerogel was placed in a ceramic boat and then placed in a tube furnace. Argon gas was introduced into the tube furnace as a protective gas. First, the tube furnace was heated to 1000℃ at a rate of 5℃ / min and held for 2 hours. Then, it was cooled to 500℃ at a rate of 5℃ / min and finally allowed to cool naturally to room temperature, resulting in a black carbon nanofiber aerogel with a volume retention rate of 33%. Figure 4 As shown. The dimensions of the obtained carbon nanofiber aerogel are 15 mm long × 15 mm wide × 12 mm thick. 3 Its density is 7.85 mg / cm³. 3 .

[0064] Mechanical tests were performed on the carbon nanofiber aerogel obtained in Example 1. Figure 5The stress-strain curve of the carbon nanofiber aerogel provided in this embodiment after 100 cycles at 60% compressive strain is shown. Because the pore structure of the carbon aerogel is stable and uniformly distributed, the aerogel can still recover its original shape after 100 compression cycles, indicating that it has good compressive resilience.

[0065] Example 3

[0066] Add 0.016 g of ammonium dihydrogen phosphate to 10 g of bacterial cellulose dispersion (0.8% by mass), shake thoroughly until homogeneous, then add 0.37 g of chitosan solution (2.4% by mass), and shake again until homogeneous. Remove air bubbles from the dispersion using a vacuum oven. Pour the resulting dispersion into a 15 mm × 15 mm × 15 mm polytetrafluoroethylene mold and freeze at -40 °C for 35 min. After complete freezing, transfer to a freeze dryer and dry for 3 days at a cold trap temperature of -60 °C and a pressure of 0.04 mbar to obtain a bacterial cellulose / glucose mixed aerogel.

[0067] The freeze-dried bacterial cellulose / glucose mixed aerogel was placed in a ceramic boat and then placed in a tube furnace. The tube furnace was then evacuated and heated to 1000°C at a rate of 5°C / min and held for 2 hours. The temperature was then lowered to 500°C at a rate of 5°C / min and finally allowed to cool naturally to room temperature, yielding a black carbon nanofiber aerogel with a volume retention of 20%. Figure 6 As shown. The dimensions of the obtained carbon nanofiber aerogel are 8 mm long × 8 mm wide × 9 mm thick. 3 Its density is 9.9 mg / cm³. 3 .

[0068] Mechanical tests were performed on the carbon nanofiber aerogel obtained in Example 1. Figure 7 The stress-strain curve of the carbon nanofiber aerogel provided in this embodiment after 100 cycles at 60% compressive strain is shown. Because the pore structure of the carbon aerogel is stable and uniformly distributed, the aerogel can still recover its original shape after 100 compression cycles, indicating that it has good compressive resilience.

[0069] In summary, this invention provides a carbon nanofiber aerogel and its preparation method. The preparation method of the carbon nanofiber aerogel includes: mixing a bacterial cellulose dispersion containing inorganic ammonium salts with a polymer solution to obtain a mixed dispersion; freezing the mixed dispersion and then freeze-drying it to obtain a bacterial cellulose aerogel; and pyrolyzing the bacterial cellulose aerogel to obtain a carbon nanofiber aerogel. This invention introduces a polymer into the preparation of the carbon nanofiber aerogel, which can significantly increase the crosslinking density between carbon nanofibers by forming additional physical or chemical crosslinks in the structure of the aerogel, thereby improving the structural stability of the carbon nanofiber aerogel and effectively enhancing its mechanical properties. Furthermore, the polymer chains connect the voids between the carbon nanofibers, promoting uniform stress distribution and reducing local stress concentration. In addition, the introduction of the polymer can also regulate the void structure of the aerogel, improving the thermal stability and electrical conductivity of the material. The carbon nanofiber aerogel has low density and high volume retention, providing a high specific surface area, which is beneficial for adsorption or catalytic reactions. The increased compressive stress improves the mechanical stability of the carbon nanofiber aerogel, making it less prone to deformation under external pressure. Furthermore, the carbon nanofiber aerogel obtained by this preparation method has a density of 3–25 mg / cm³. -3 The volume retention rate is 15-50%, and the maximum compressive strength is >9 kPa.

[0070] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a carbon nanofiber aerogel, characterized by, Including the following steps: A bacterial cellulose dispersion containing inorganic ammonium salts was mixed with a polymer solution to obtain a mixed dispersion. The mixed dispersion was frozen and then freeze-dried to obtain bacterial cellulose aerogel. The bacterial cellulose aerogel was subjected to pyrolysis to obtain carbon nanofiber aerogel. The inorganic ammonium salt includes one or more of ammonium chloride, ammonium sulfate, and ammonium dihydrogen phosphate; in the bacterial cellulose dispersion containing the inorganic ammonium salt, the mass fraction of the inorganic ammonium salt relative to the bacterial cellulose is 0.5% to 40%; the polymer in the polymer solution includes one or more of glucose, sodium alginate, and chitosan; the solvent in the polymer solution is deionized water; the mass fraction of the polymer solution relative to the bacterial cellulose is 0.5% to 40%. The carbon nanofiber aerogel is in the form of regular blocks with a length of 5-50 mm, a width of 5-50 mm, and a thickness of 5-30 mm; the density of the carbon nanofiber aerogel is 3 mg·cm³. -3 ~25mg·cm -3 ; The freezing treatment involves placing the mixed dispersion on a freezing platform at -30℃ to -40℃ for 20 to 30 minutes; the pyrolysis treatment involves a temperature of 600℃ to 1400℃, a heating rate of 2℃ / min to 10℃ / min, and a duration of 1 to 3 hours; the pyrolysis treatment is carried out under an inert atmosphere or under vacuum; and the freeze-drying time is 3 to 5 days. After the pyrolysis treatment, the temperature is reduced to 500°C at a cooling rate of 5°C / min, and then allowed to naturally cool to room temperature.

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