Nitrogen-doped cellulose-based carbon nano-carrier material, preparation method therefor, and use thereof

Abstract

Provided are a nitrogen-doped cellulose-based carbon nano-carrier material, a preparation method therefor, and the use thereof. The preparation method comprises the following steps: (1) pretreating a nanocellulose sol to obtain a uniformly distributed nanocellulose solution; (2) freezing the nanocellulose solution and vacuum drying same to obtain a nanocellulose aerogel; (3) pre-carbonizing the nanocellulose aerogel in an inert atmosphere, and cooling same to obtain a nanocellulose carbon aerogel; and (4) placing the nanocellulose carbon aerogel in urea powder, and performing high-temperature vapor deposition in an inert atmosphere to obtain the nitrogen-doped nanocellulose-based carbon nano-carrier material. The selected raw materials of the carbon nano-carrier material in the method are plant fibers, and have strong mechanical strength, wide sources and low costs. The prepared nitrogen-doped cellulose-based carbon nano-carrier material has good surface wettability, excellent electrical conductivity and stable properties.

Description

A nitrogen-doped cellulose-based carbon nanocarrier material, its preparation method and application Technical Field

[0001] This invention belongs to the field of nanomaterial energy storage technology, and particularly relates to a nitrogen-doped cellulose-based carbon nanocarrier material, its preparation method and application. Background Technology

[0002] Since the first reported synthesis of carbon aerogels in the 1980s, they have been widely used as nanoporous support materials in fields such as nanocatalysts, electrochemical applications, and hydrogen storage materials due to their numerous advantages, including high specific surface area, high porosity, strong corrosion resistance, a stable continuous network structure, and small pore size. Currently, the most common carbon aerogels are organic carbon aerogels, such as resorcinol-formaldehyde aerogel, melamine-formaldehyde aerogel, phenol-furfural aerogel, and polycyanate series aerogels. However, the high cost of raw materials, complex preparation processes, and long production cycles for synthesizing these organic carbon aerogels have hindered their large-scale production and application in the market.

[0003] Under this premise, more and more scholars are using inexpensive and environmentally friendly biomass materials to replace these raw materials to prepare carbon aerogels, such as bacterial cellulose and plant cellulose. However, these biomass nanocellulose materials still have some shortcomings in the field of nanoporous carrier materials: (1) The mesopore volume of biomass nanocellulose carbon aerogel materials is small, and the loaded active substances cannot be effectively utilized; (2) The surface wettability of biomass nanocellulose carbon aerogel materials is poor, and the surface charge exchange capacity is weak, resulting in poor electrochemical performance and affecting the overall application of nanocarrier materials; (3) The surface polarity of biomass nanocellulose carbon aerogel materials is poor, the diffusion resistance of electrolyte ions in the pores is large, and the stability of recycling is poor.

[0004] Therefore, seeking a nitrogen-doped cellulose-based carbon nanomaterial is of great significance for realizing the efficient utilization of active substances on the carrier. Summary of the Invention

[0005] The technical problem to be solved by this invention is that organic carbon aerogels are expensive, biomass aerogels have small loading capacity and poor charge exchange capacity. To overcome the shortcomings and defects mentioned in the background art, this invention provides a nitrogen-doped cellulose-based carbon nanocarrier material, its preparation method and application.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] A method for preparing nitrogen-doped cellulose-based carbon nanomaterials includes the following steps:

[0008] (1) Pre-treat the nanocellulose sol to obtain a uniformly distributed nanocellulose solution;

[0009] (2) Freeze the nanocellulose solution obtained in step (1) and vacuum dry it to obtain nanocellulose aerogel;

[0010] (3) The nanocellulose aerogel obtained in step (2) is pre-carbonized in an inert atmosphere and cooled to obtain nanocellulose carbon aerogel.

[0011] (4) Place the nanocellulose carbon aerogel obtained in step (3) and urea powder in a reaction vessel and perform high-temperature vapor deposition under an inert atmosphere to obtain nitrogen-doped cellulose-based carbon nanocarrier material.

[0012] This application obtains a nanocellulose carbon aerogel carrier material by high-temperature thermal decomposition of nanocellulose aerogel. Then, urea and nanocellulose carbon aerogel are reacted under high-temperature, oxygen-free conditions, and nitrogen from the urea is doped into the carbon aerogel carrier material using vapor deposition. Urea is the first artificially synthesized inorganic substance containing abundant nitrogen, playing a crucial role in improving the performance of nanocarrier materials. Because nitrogen atoms and carbon atoms have similar structures, nitrogen can effectively replace some carbon atoms in the carbon structure at high temperatures (as shown in Figure 1). Furthermore, nitrogen atoms have stronger surface charge capacity and surface polarity than carbon atoms. Simultaneously, nitrogen can increase the wettability of the carbon material and reduce the diffusion resistance of electrolyte ions in the gaps of the carbon material. On the other hand, nanocellulose aerogel has a three-dimensional network structure, and nitrogen doping can significantly improve the specific surface area and pore volume of the three-dimensional network structure formed by nanocellulose.

[0013] In the high-temperature vapor deposition process, urea, after becoming a gas, comes into uniform contact with the nanocellulose aerogel, thereby achieving nitrogen doping. However, typically, urea particles adhere to the surface of the nanocellulose aerogel, resulting in accumulation and affecting the doping effect.

[0014] Therefore, the technical solution of this application can obtain a nanoporous support material with a three-dimensional network structure, good electrochemical performance, and excellent stability.

[0015] Preferably, in step (1), the nanocellulose sol is prepared by the following method:

[0016] Biomass cellulose powder is added to concentrated sulfuric acid with a mass fraction of 35%–65%, and stirred in a water bath at 35℃–45℃ for 1.5h–3.5h to hydrolyze the cellulose powder. The cellulose solution is washed until the pH is 6.5–7, and finally, nanocellulose sol is obtained by high-pressure homogenization for 10–25 cycles.

[0017] Biomass nanocellulose typically has a diameter of around 10 μm. Compared to other types of nanocellulose, the nanocarrier materials formed by it have stronger mechanical strength and a simple preparation mechanism. Biomass nanocellulose is a natural polymer material that is inexhaustible, highly renewable, degradable, and pollution-free.

[0018] This invention uses acid hydrolysis and mechanical treatment to prepare biomass nanocellulose. The method is simple, convenient and highly controllable. The concentration of concentrated sulfuric acid used in this application is relatively low, resulting in a large aspect ratio and low crystallinity of the prepared cellulose. In this application, the cellulose sol treated with concentrated sulfuric acid is homogenized under high pressure and ultrasonically crushed to obtain wood nanocellulose, which is more uniformly dispersed and less prone to agglomeration.

[0019] Preferably, the mass solid-liquid ratio of the biomass cellulose powder and concentrated sulfuric acid is 1:10 to 1:20.

[0020] Preferably, in step (1), the pretreatment specifically includes: ultrasonically breaking down the nanocellulose sol in an ultrasonic pulverizer for 1 min to 5 min. If the ultrasonic breaking time is too short, the nanofibers in the solution cannot be uniformly dispersed; if the ultrasonic breaking time is too long, the nanocellulose structure in the solution may be destroyed, thus affecting the stability of the carbon aerogel network structure.

[0021] Preferably, in step (2), the freezing temperature is -50℃ to -70℃, and the freezing time is 6h to 12h; the vacuum drying includes two stages: low-temperature vacuum drying and room-temperature vacuum drying. The low-temperature vacuum drying temperature is -50℃ to -70℃, and the time is 6h to 12h, while the room-temperature vacuum drying time is 6h to 12h. If the temperature is too low, the drying time will be too long, wasting resources; if the temperature is too high, the structure of the nanocellulose aerogel will collapse during the drying process, affecting the specific surface area and pore size / volume.

[0022] Preferably, in step (3), the pre-carbonization treatment temperature is 700℃~900℃, and the time is 60min~120min. Pre-carbonization carbonizes nanocellulose into carbon materials. If the pre-carbonization temperature is too low, the degree of carbonization of nanocellulose is insufficient, affecting the overall performance of the carrier material; if the temperature is too high, the nanocellulose carbon aerogel will graphitize, and the network structure is prone to collapse. The pre-carbonization treatment is to ensure that the urea and carbon aerogel react fully in the subsequent high-temperature vapor deposition treatment. Urea reacts more easily with the surface of carbon at high temperatures. Without the pre-carbonization treatment, urea cannot fully contact the nanocellulose aerogel, resulting in poor nitrogen doping effect.

[0023] Preferably, in step (4), the mass of the nanocellulose carbon aerogel is 1g to 2g, the mass of the urea powder is 1g to 5g, and the urea powder is placed at the bottom layer of the nanocellulose aerogel. Placing the urea at the bottom layer of the nanocellulose aerogel is more conducive to the contact between the urea volatilized during the heating process and the nanocellulose aerogel, resulting in better doping.

[0024] Within this quality range, nitrogen from urea can be well incorporated into carbon aerogel materials, resulting in a carrier material with excellent stability and good loading capacity. If the urea quality is too low, there will be too little nitrogen incorporated into the carbon aerogel, failing to improve the overall performance of the carrier material; if the urea quality is too high, the nitrogen incorporated into the carbon aerogel will reach saturation, leading to resource waste.

[0025] Preferably, the high-temperature vapor deposition temperature in step (4) is 800-1000℃; the high-temperature vapor deposition time is 2-4h.

[0026] Under the same technical concept, this application also provides a nitrogen-doped cellulose-based carbon nanocarrier material, which is prepared by the above-described preparation method. The nitrogen-doped cellulose-based carbon nanocarrier material exhibits a porous three-dimensional network structure with a density of 22-26 mg / m³. 2 Specific surface area is 800-850 m² 2 / g, pore volume is 0.45-0.55cm³ 3 / g, with a pore size of 1nm to 100nm.

[0027] The method for preparing nitrogen-doped cellulose-based carbon nanomaterials according to the present invention yields a three-dimensional network structure carrier material with high porosity, high porosity, and excellent stability. In this three-dimensional network structure carrier material, mesopores constitute the majority of the porous structure, allowing the active material to adhere better and in greater quantities to the mesopores compared to micropores and macropores.

[0028] Under the same technical concept, this application also provides an application of nitrogen-doped cellulose-based carbon nanomaterials as carriers, which are used in electric double-layer supercapacitors. The electric double-layer supercapacitors assembled with the nitrogen-doped cellulose-based carbon nanomaterials have a specific capacitance of 230-280 F / g at a current density of 1 A / g, and retain 93-96% of the initial specific capacitance after 10,000 charge-discharge cycles.

[0029] The materials in this application can be used in the fields of energy storage materials or catalysts. As a nanocarrier material, nitrogen-doped cellulose-based carbon nanocarrier material itself has good electrochemical performance. Therefore, after the material is ground, slurry prepared, electrode coated, and capacitor assembled, a supercapacitor can be obtained.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) The carbon nanocarrier material selected in this invention is nanocellulose, which has strong mechanical strength, is widely available, and has low cost, and is in line with the green and sustainable development strategy.

[0032] (2) The nitrogen-doped cellulose-based carbon nanocarrier material prepared by the present invention has good surface wettability and can fully contact the electrolyte, thereby reducing the diffusion resistance of electrolyte ions in the carbon aerogel carrier material, which effectively improves the surface polarity and surface charge exchange capacity of the nanocarrier material, and has excellent conductivity and stability.

[0033] (3) The preparation scheme of the present invention first processes biomass nanocellulose, and then completes nitrogen doping at the same time by preparing nanocellulose-based carbon nanocarrier material through steps such as aerogel preparation, pre-carbonization, and high-temperature vapor deposition. The method is simple and convenient to operate and has strong controllability. It increases the wettability of carbon material, reduces the diffusion resistance of electrolyte ions in the gaps of carbon material, and significantly improves the specific surface area and pore volume of the three-dimensional network structure formed by nanocellulose. The preparation scheme has low energy consumption and good effect. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 is a schematic diagram of the mechanism of the nitrogen-doped modified nanocellulose aerogel of the present invention;

[0036] Figure 2 is an electron microscope image of the microstructure of the nitrogen-doped cellulose-based carbon nanocarrier material obtained in Example 1 of the present invention;

[0037] Figure 3 shows the cyclic voltammetry test results of the nitrogen-doped cellulose-based carbon nanocarrier material obtained in Example 2 of the present invention.

[0038] Figure 4 shows the cycle stability test results of the nitrogen-doped cellulose-based carbon nanocarrier material obtained in Example 3 of the present invention.

[0039] Figure 5 shows the cyclic voltammetry test curves of the materials of the comparative example and Example 1 of the present invention at a scan rate of 50 mV / s. Detailed Implementation

[0040] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0041] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0042] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0043] Example 1:

[0044] An embodiment of the preparation method of the nitrogen-doped cellulose-based carbon nanocarrier material of the present invention, wherein the specific preparation steps of the nitrogen-doped cellulose-based carbon nanocarrier material are as follows:

[0045] Step 1: Add 5g of lignocellulose powder to 50g of concentrated sulfuric acid with a mass fraction of 48%, stir in a 35℃ water bath for 3.5h to hydrolyze the lignocellulose, then wash the lignocellulose solution with ultrapure water until the pH is 6.7, and finally obtain uniformly dispersed nanocellulose sol by high pressure homogenization for 20 cycles.

[0046] Step 2: The nanocellulose sol is ultrasonically broken up in an ultrasonic pulverizer for 1 minute to obtain a uniformly distributed nanocellulose solution.

[0047] Step 3: Inject the nanocellulose solution obtained in step 2 into the mold, place it in a freeze dryer and freeze for 12 hours at a freezing temperature of -50℃, then vacuum dry at -50℃ for 10 hours, and finally vacuum dry at room temperature of 25℃ for 12 hours. Demold to obtain nanocellulose aerogel.

[0048] Step 4: The nanocellulose aerogel obtained in step 3 is pre-carbonized in a tube furnace for 60 minutes at a temperature of 700°C under nitrogen protection. After carbonization, it is cooled to obtain nanocellulose carbon aerogel.

[0049] Step 5: Place 1g of nanocellulose carbon aerogel and 1g of urea obtained from the pre-carbonization in step 4 into a container and place it in a tube furnace, with urea at the bottom of the nanocellulose carbon aerogel. Nitrogen gas is introduced for high-temperature vapor deposition treatment. The high-temperature vapor deposition temperature is 900℃ and the high-temperature vapor deposition time is 3h. After the high-temperature vapor deposition is completed, nitrogen-doped cellulose-based carbon nanocarrier material can be obtained.

[0050] The nitrogen-doped cellulose-based carbon nanocarrier material has a density of 24.67 mg / m³. 2Its specific surface area was determined to be 831.03 m² after nitrogen adsorption-desorption testing. 2 / g, pore volume is 0.508cm³ 3 Based on the BJH (Barrett-Joiner-Halenda) model, its average pore size can be calculated to be 14 nm.

[0051] The electron microscope image of the obtained nitrogen-doped cellulose-based carbon nanocarrier material is shown in Figure 2.

[0052] Example 2:

[0053] An embodiment of the preparation method of the nitrogen-doped cellulose-based carbon nanocarrier material of the present invention. The specific preparation steps of the nitrogen-doped cellulose-based carbon nanocarrier material are as follows:

[0054] Step 1: Add 5g of lignocellulose powder to 75g of 40% concentrated sulfuric acid and stir in a 40℃ water bath for 2.5h to hydrolyze the cellulose. Then wash the cellulose solution with ultrapure water until the pH is 6.5. Finally, obtain a uniformly dispersed nanocellulose sol by high-pressure homogenization for 25 cycles.

[0055] Step 2: The nanocellulose sol is ultrasonically broken up in an ultrasonic pulverizer for 3 minutes to obtain a uniformly distributed nanocellulose solution.

[0056] Step 3: Inject the nanocellulose solution obtained in step 2 into the mold, freeze it in a freeze dryer for 9 hours at a freezing temperature of -60℃, then vacuum dry it at -60℃ for 9 hours, and finally vacuum dry it at room temperature for 12 hours. Demold to obtain nanocellulose aerogel.

[0057] Step 4: The nanocellulose aerogel obtained in step 3 is pre-carbonized in a tube furnace for 90 minutes at 750°C under nitrogen protection. After carbonization, it is cooled to obtain nanocellulose carbon aerogel.

[0058] Step 5: Place 1.5g of nanocellulose carbon aerogel obtained from the pre-carbonization in step 4 and 3g of urea in a container and place it in a tube furnace, with urea at the bottom of the nanocellulose carbon aerogel. Nitrogen gas is introduced for high-temperature vapor deposition treatment. The high-temperature vapor deposition temperature is 1000℃ and the high-temperature vapor deposition time is 2h. After the high-temperature vapor deposition is completed, nitrogen-doped cellulose-based carbon nanocarrier material can be obtained.

[0059] First, nitrogen-doped cellulose-based carbon nanomaterials, PVDF, and acetylene black were mixed in a mass ratio of 8:1:1 and ground until homogeneous. This mixture was then coated onto 1*1 nickel foam and pressed to form an electrode material. The active material loading on the electrode material was approximately 2.5 mg. A three-electrode testing system was then used to test the electrode material, obtaining cyclic voltammetry curves at different current densities.

[0060] Figure 3 shows the cyclic voltammetry test results of the obtained nitrogen-doped cellulose-based carbon nanocarrier material under different current densities. After 10,000 charge-discharge cycles, it still retains 94.5% of the initial specific capacitance.

[0061] Example 3:

[0062] An embodiment of the preparation method of the nitrogen-doped cellulose-based carbon nanocarrier material of the present invention. The specific preparation steps of the nitrogen-doped cellulose-based carbon nanocarrier material are as follows:

[0063] Step 1: Add 5g of lignocellulose powder to 100g of 60% concentrated sulfuric acid and stir in a 45℃ water bath for 1.5h to hydrolyze the cellulose. Then wash the cellulose solution with ultrapure water until the pH is 6.8. Finally, obtain a uniformly dispersed nanocellulose sol by high-pressure homogenization for 15 cycles.

[0064] Step 2: The nanocellulose sol is ultrasonically broken up in an ultrasonic pulverizer for 5 minutes to obtain a uniformly distributed nanocellulose solution.

[0065] Step 3: Inject the nanocellulose solution obtained in step 2 into the mold, freeze it in a freeze dryer for 6 hours at a freezing temperature of -70℃, then vacuum dry it at -70℃ for 12 hours, and finally vacuum dry it at room temperature for 9 hours. Demold to obtain nanocellulose aerogel.

[0066] Step 4: The nanocellulose aerogel obtained in step 3 is pre-carbonized in a tube furnace for 120 minutes at a temperature of 700°C under nitrogen protection. After carbonization, it is cooled to obtain nanocellulose carbon aerogel.

[0067] Step 5: Place 2g of nanocellulose carbon aerogel and 5g of urea obtained from the pre-carbonization in step 4 into a container and place it in a tube furnace, with the urea at the bottom of the nanocellulose carbon aerogel. Introduce nitrogen gas for high-temperature thermal decomposition treatment. The carbonization temperature is 1000℃ and the carbonization time is 3h. After carbonization, nitrogen-doped cellulose-based carbon nanocarrier material can be obtained.

[0068] First, nitrogen-doped cellulose-based carbon nanomaterials, PVDF, and acetylene black were mixed in a mass ratio of 8:1:1 and ground until homogeneous. This mixture was then coated onto 1*1 nickel foam and pressed to form an electrode material. The active material loading on the electrode material was approximately 2.5 mg. The electrode material was assembled into a double-layer supercapacitor, and a three-electrode testing system was used to test the electrode material. The electrochemical performance stability test at a current density of 1 A / g is shown in Figure 4. Calculations showed that the specific capacitance at a current density of 1 A / g was 253.7 F / g.

[0069] Comparative Example 1:

[0070] This comparative example demonstrates a method for preparing doped cellulose-based carbon nanocarrier materials without pre-carbonization treatment.

[0071] Step 1: Add 5g of lignocellulose powder to 50g of concentrated sulfuric acid with a mass fraction of 48%, stir in a 35℃ water bath for 3.5h to hydrolyze the lignocellulose, then wash the lignocellulose solution with ultrapure water until the pH is 6.7, and finally obtain uniformly dispersed nanocellulose sol by high pressure homogenization for 20 cycles.

[0072] Step 2: The nanocellulose sol is ultrasonically broken up in an ultrasonic pulverizer for 1 minute to obtain a uniformly distributed nanocellulose solution.

[0073] Step 3: Inject the nanocellulose solution obtained in step 2 into the mold, freeze it in a freeze dryer for 12 hours at a freezing temperature of -50℃, then vacuum dry it at -50℃ for 10 hours, and finally vacuum dry it at room temperature for 12 hours. Demold to obtain nanocellulose aerogel.

[0074] Step 4: Place 1g of nanocellulose aerogel and 1g of urea obtained in step 3 into a container and place it in a tube furnace, with urea at the bottom of the nanocellulose aerogel. Nitrogen gas is introduced for high-temperature vapor deposition treatment. The high-temperature vapor deposition temperature is 1000℃ and the high-temperature vapor deposition time is 2h. After the high-temperature vapor deposition is completed, the comparative sample can be obtained.

[0075] Comparative Example 2:

[0076] This comparative example demonstrates a general method for preparing doped cellulose-based carbon nanocarrier materials by physical mixing followed by carbonization.

[0077] Step 1: Add 5g of lignocellulose powder to 50g of concentrated sulfuric acid with a mass fraction of 48%, stir in a 35℃ water bath for 3.5h to hydrolyze the lignocellulose, then wash the lignocellulose solution with ultrapure water until the pH is 6.8, and finally obtain uniformly dispersed nanocellulose sol by high pressure homogenization for 20 cycles.

[0078] Step 2: The nanocellulose sol is ultrasonically broken up in an ultrasonic pulverizer for 1 minute to obtain a uniformly distributed nanocellulose solution.

[0079] Step 3: Inject the nanocellulose solution obtained in step 2 into the mold, freeze it in a freeze dryer for 12 hours at a freezing temperature of -50℃, then vacuum dry it at -50℃ for 10 hours, and finally vacuum dry it at room temperature for 12 hours. Demold to obtain nanocellulose aerogel.

[0080] Step 4: After physically mixing 1g of nanocellulose aerogel and 1g of urea obtained in step 3, place them in a tube furnace and pass nitrogen gas through them for high-temperature thermal decomposition treatment. After carbonization, a comparative sample can be obtained.

[0081] The samples obtained from Comparative Examples 1 and 2, PVDF, and acetylene black were mixed in a mass ratio of 8:1:1 and ground until homogeneous. This mixture was then coated onto 1*1 nickel foam and pressed to form an electrode material. The active material loading on the electrode material was approximately 2.5 mg. A three-electrode testing system was then used to test the electrode material, obtaining cyclic voltammetry curves at different current densities.

[0082] Figure 5 shows the cyclic voltammetry curves of the materials obtained from Comparative Examples 1, 2, and 1 at a scan rate of 50 mV / s. Calculations show that the specific capacitance of Comparative Example 1 is 147.1 F / g, that of Comparative Example 2 is 100.8 F / g, and that of Example 1 is 253.7 F / g.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing nitrogen-doped cellulose-based carbon nanocarrier materials, characterized in that, Includes the following steps: (1) Pre-treat the nanocellulose sol to obtain a uniformly distributed nanocellulose solution; (2) Freeze the nanocellulose solution obtained in step (1) and vacuum dry it to obtain nanocellulose aerogel; (3) The nanocellulose aerogel obtained in step (2) is pre-carbonized in an inert atmosphere and cooled to obtain nanocellulose carbon aerogel. (4) Place the nanocellulose carbon aerogel obtained in step (3) and urea powder in a reaction vessel and perform high-temperature vapor deposition under an inert atmosphere to obtain nitrogen-doped cellulose-based carbon nanocarrier material.

2. The preparation method according to claim 1, characterized in that, In step (1), the nanocellulose sol is prepared by the following method: Biomass cellulose powder is added to concentrated sulfuric acid with a mass fraction of 35%–65%, and stirred in a water bath at 35℃–45℃ for 1.5h–3.5h to hydrolyze the cellulose powder. The cellulose solution is washed until the pH is 6.5–7, and finally, nanocellulose sol is obtained by high-pressure homogenization for 10–25 cycles.

3. The preparation method according to claim 2, characterized in that, The mass solid-liquid ratio of the biomass cellulose powder and concentrated sulfuric acid is 1:10 to 1:

20.

4. The preparation method according to claim 1, characterized in that, In step (1), the pretreatment specifically includes: ultrasonically breaking down the nanocellulose sol in an ultrasonic pulverizer for 1 min to 5 min.

5. The preparation method according to claim 1, characterized in that, In step (2), the freezing temperature is -50℃ to -70℃ and the freezing time is 6h to 12h; the vacuum drying includes two stages: low temperature vacuum drying and normal temperature vacuum drying. The low temperature vacuum drying temperature is -50℃ to -70℃ and the time is 6h to 12h, and the normal temperature vacuum drying time is 6h to 12h.

6. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the pre-carbonization treatment is 700℃~900℃ and the time is 60min~120min.

7. The preparation method according to claim 1, characterized in that, In step (4), the mass of the nanocellulose carbon aerogel is 1g to 2g, the mass of the urea powder is 1g to 5g, and the urea powder is placed at the bottom layer of the nanocellulose aerogel.

8. The preparation method according to claim 1, characterized in that, In step (4), the high-temperature vapor deposition temperature is 800-1000℃ and the high-temperature vapor deposition time is 2-4h.

9. A nitrogen-doped cellulose-based carbon nanocarrier material as described in any one of claims 1-8, characterized in that, The nitrogen-doped cellulose-based carbon nanocarrier material is prepared by the preparation method according to any one of claims 1-8, and the nitrogen-doped cellulose-based carbon nanocarrier material has a porous three-dimensional network structure with a density of 22-26 mg / m³. 2 Specific surface area is 800-850 m² 2 / g, pore volume is 0.45-0.55cm³ 3 / g, with a pore size of 1nm to 100nm.

10. The application of a nitrogen-doped cellulose-based carbon nanocarrier material as described in any one of claims 1-8, characterized in that, The nitrogen-doped cellulose-based carbon nanocarrier material is used in electric double-layer supercapacitors. The electric double-layer supercapacitor assembled with the nitrogen-doped cellulose-based carbon nanocarrier material has a specific capacitance of 230-280 F / g at a current density of 1 A / g, and retains 93-96% of the initial specific capacitance after 10,000 charge-discharge cycles.

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