A modified cellulose aerogel and a preparation method and application thereof

Abstract

The application belongs to the technical field of nano energy, and particularly relates to a modified cellulose aerogel preparation method and application. Hybrid nanosheets are synthesized through a hydrothermal reaction, then grafted to the surface of cellulose through tetraethyl orthosilicate, and finally formed into cellulose aerogel through dissolution and regeneration. The balance between low pressure drop and high filtration efficiency is achieved through mechanical interception and electrostatic induction, and strong and stable filtration performance is exhibited even under high humidity conditions. A sterilization rate of 99.9% can be achieved in 20 min, the device can accurately detect and quickly respond to 1 ppm NH3, and the response rate to 100 ppm NH3 reaches 77% in 12 seconds. Even after 7 cycles of testing-washing, the filtration performance, sterilization and ammonia gas responsiveness of the material still maintain excellent stability. The application provides a new method for developing multifunctional self-powered biomass-based wearable medical devices in extreme environments.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nano energy, and particularly relates to a modified cellulose aerogel and a preparation method and application thereof. BACKGROUND

[0002] High-concentration particulate matter (PM) and toxic gas compounds produced by combustion in fire accidents pose a serious threat to human health and life. In addition, the large surface area of particulate matter can effectively promote the long-distance and long-time transmission of viruses, bacteria and toxic substances, thereby exacerbating health risks.

[0003] Traditional air filtration equipment achieves high filtration efficiency at the cost of increased pressure drop, which greatly increases energy consumption. In addition, electronic filtration equipment often fails at high temperatures and poses safety risks such as power explosion. Therefore, self-powered air filtration equipment has become a prominent research focus. Triboelectric nanogenerators (TENGs) as high-efficiency electromechanical conversion devices in self-powered medical and health equipment show great potential. TENGs generate an induced electric field under the driving of respiration, which polarizes inhalable particulate matter and effectively adsorbs it on the material surface.

[0004] Ammonia (NH3) is different from common gases such as CO2, and is usually not present in the daily environment, so NH3 monitoring is a reliable indicator of toxic gas leakage or generation in fires. MXene is a new type of two-dimensional transition metal material, and due to its excellent electrical conductivity, high selectivity to NH3 and rich active sites, it has attracted widespread attention in self-powered sensing, energy storage and catalysis. As high-efficiency electromechanical conversion devices for self-powered air filtration, TENGs show great potential. However, the complex environment of high temperature and high humidity in fire accidents can cause charge dissipation or neutralization, thereby reducing the output performance of TENGs and affecting the stability of self-powered medical equipment based on TENGs. Due to the difficulty in recycling of petroleum-based medical equipment and the prevalence of the concept of sustainable development, the development of biomass materials has become a hot research topic. Among them, cellulose has attracted the interest of many researchers due to its wide source in nature, sustainability and degradability. However, the spinnability and hydrophilicity of cellulose are poor, which limits its development as a self-powered air filtration material. In addition, the filtration performance of petroleum-based medical and health equipment will be severely degraded after repeated use, further exacerbating the exploitation of petroleum resources. SUMMARY

[0005] In order to solve the above-mentioned technical problems, the present application provides the following technical solutions:

[0006] The application provides a preparation method of a modified cellulose aerogel, comprising the following steps:

[0007] S11: adding cellulose into a silane hydrolysis solution, heating and mixing, and dispersing the separated solid in a lithium bromide aqueous solution to obtain a mixed dispersion solution; the silane hydrolysis solution is obtained by heating and mixing tetraethyl orthosilicate, ammonia water and ethanol at 50-75 ℃ for 8-20 h;

[0008] S12: adding Ti3C2T x / ZIF-8 material into the mixed dispersion solution, mixing and then heating to react, and cooling to obtain a hydrogel; the Ti3C2T x / ZIF-8 material is obtained by mixing solution B and solution A and then reacting at room temperature (25±5 ℃) for 12-48 h;

[0009] The solution A is obtained by mixing dimethyl imidazole-containing methanol and zinc nitrate; and the solution B is obtained by adding Ti3C2T x (CAS No. 12363-89-2) into methanol containing zinc nitrate;

[0010] S13: washing the hydrogel, freeze-drying and heat-treating to obtain the modified cellulose aerogel.

[0011] ZIF-8 is synthesized by in-situ polymerization to Ti3C2Tx, silane is hydrolyzed at room temperature, and then added into a solution containing cellulose and lithium bromide, the silane is grafted to the surface of cellulose, a mixed solution of cellulose is configured, and then Ti3C2Tx / ZIF-8 is grafted to the surface of cellulose through silane. In a high-temperature environment, heating is performed until the cellulose is dissolved, and then cooling to room temperature to form a cellulose hydrogel, after washing, freeze-drying is performed to obtain a cellulose aerogel. Then, heat treatment is performed to obtain a cellulose-based aerogel.

[0012] The method has the advantages of easy availability of raw materials, simple process and superior performance.

[0013] Specifically, the preparation method of the Ti3C2T x / ZIF-8 is as follows: 0.1-1 mmol of zinc nitrate (Zn(NO3)2) is added as a crystal growth seed in 20-90 mL of methanol solution containing dimethyl imidazole (2-M) (0.01-0.5 mol / L) to obtain a mixed solution A; Ti3C2T x is immersed in 20-90 mL of Zn(NO3)2 methanol (0.01-0.1 mol / L) for 0.5-6 hours to obtain a solution B, and then the mixture of solution B is mixed into the mixture of A and solution B, slightly stirred, and reacted at room temperature for 12-48 hours.

[0014] Preferably, the cellulose compound is selected from microcrystalline cellulose, nanocellulose or cellulose; and the mass ratio of the cellulose compound to the silane hydrolysis solution is 1:5-15.

[0015] Preferably, in the step S11, the temperature of the mixture of the cellulose compound and the silane hydrolysis solution is 50-70℃, and the time is 5-24 h.

[0016] Preferably, in the aqueous solution of lithium bromide, the weight ratio of lithium bromide to water is 2:1-3, and the stirring is performed at 0-15℃ for 0.5-5 h.

[0017] Preferably, in the step S11, the separation method is vacuum filtration, and the dispersion method is stirring at room temperature for 0.5-2 h, followed by ultrasonic dispersion for 0.5-2 h.

[0018] Preferably, in the mixed dispersion liquid, the mass concentration of the cellulose compound is 0.1-3%.

[0019] Preferably, in the silane hydrolysis solution, the volume ratio of tetraethyl orthosilicate, ammonia water and ethanol is 0.8-1.4:9-14:92-108.

[0020] Preferably, in the step S12, the Ti3C2T x The mass ratio of the ZIF-8 material to the cellulose compound in the mixed dispersion liquid is 0.02-0.3:0.8-1.2.

[0021] Preferably, in the step S12, the mixing method of the mixed dispersion liquid and the Ti3C2T x The mixing method of the mixed dispersion liquid and the Ti3C2T

[0022] Preferably, in the step S12, the temperature of the heating reaction is 95-140℃, and the time is 1-10 min, and the cooling time is 6-24 h.

[0023] Preferably, in the methanol containing dimethyl imidazole, the concentration of dimethyl imidazole is 0.01-0.5 mol / L.

[0024] Preferably, in the step S13, the washing method is to sequentially wash the hydrogel with water, ethanol and tert-butanol, each for 0.5-2 h, and then replace the solution and wash for 24 h.

[0025] Preferably, in the step S13, the heat treatment method is to heat the freeze-dried hydrogel at 150-200℃ for 0.5-4 h, and then heat at 220-260℃ for 0.5-4 h under a protective atmosphere.

[0026] Further, the protective atmosphere is selected from nitrogen or argon.

[0027] The application also provides a modified cellulose aerogel prepared by the preparation method.

[0028] The application also provides a triboelectric nanogenerator using the modified cellulose aerogel as a positive electrode material.

[0029] The modified cellulose aerogel can be used as a positive electrode and a negative electrode triboelectric material of a triboelectric nanogenerator, and the triboelectric nanogenerator based on the cellulose aerogel is suitable for multiple fields such as efficient air filtration, rapid sterilization, rapid response to ammonia concentration, repeated use and respiratory health monitoring.

[0030] Compared with the prior art, the technical scheme of the application has the following advantages:

[0031] (1) The application endows the cellulose aerogel with strong electron-withdrawing ability, so that the cellulose aerogel becomes a strong triboelectric positive electrode material that can replace animal hair, polyimide and nylon. After being assembled with a negative electrode material, the voltage is as high as 130 V. Due to the dual effects of physical interception and electrostatic adsorption, the filtration efficiency of PM 0.3 , PM 0.5 and PM1 is all more than 99.2%, and after 7 times of cleaning, the filtration efficiency of PM 0.3 is still more than 89%.

[0032] (2) The cellulose aerogel in the application can achieve a sterilization rate of 99.9% under near-infrared light irradiation for 20 min, and after 7 times of cleaning, the sterilization rate is still more than 97%.

[0033] (3) 1ppm NH3 can be accurately detected, and the response rate to 100 ppm NH3 reaches 78% within 12 seconds, which can quickly warn of NH3 leakage.

[0034] (4) The process flow designed by the application is short, the equipment is simple, the cost is low, the electrical output performance can be significantly improved, and the application has wide application in the fields of energy collection, human health monitoring, air purification and intelligent sensing. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 are the Raman spectrum (a) and XRD diagram (b) of the material.

[0036] Figure 2 is a filtration efficiency diagram at 95% relative humidity.

[0037] Figure 3 is a sterilization rate and ammonia response stability test diagram of the modified cellulose aerogel under different irradiation times. DETAILED DESCRIPTION

[0038] The application will be further described below with reference to the drawings and specific examples so that those skilled in the art can better understand the application and implement it. The examples are not intended to limit the application. Example 1

[0039] (1) Preparation of modified cellulose aerogel

[0040] Preferably, 0.4 mmol of Zn(NO3)2 is added in advance in 40 mL of methanol solution containing 2-M (0.1 mol / L) as a seed for crystal growth to obtain a mixed solution A; Ti3C2T x Preferably, the microcrystalline cellulose is immersed in 30 mL of Zn(NO3)2 methanol (0.22 mol / L) for 1.5 hours to obtain solution B, and then the mixture of solution B is mixed with the mixture of A and solution B, slightly stirred, and reacted at room temperature for 20 hours. The silane hydrolysis solution is composed of tetraethyl orthosilicate, ammonia water and ethanol in a volume ratio of 1:10:95, and is stirred at 50°C for 10 hours. The weight ratio of anhydrous lithium bromide to water is 2:1, and the stirring is performed at 5°C for 2 hours. The microcrystalline cellulose is added to the silane hydrolysis solution, and the mass ratio of the two is 1:10, and the stirring is performed at 70°C for 20 hours. The cellulose grafted with silane is filtered out by vacuum suction, and is loaded into a pressure-resistant bottle containing a lithium bromide solution, and the cellulose accounts for 0.5% of the total weight of the solution. Stirring is performed at room temperature for 1 hour, and then ultrasonic dispersion is performed for 0.5 hours. Then Ti3C2T x / ZIF-8, Ti3C2T x / ZIF-8 is added, and the weight ratio of Ti3C2T 2 / ZIF-8 to cellulose is 0.05:1.02, stirring is performed at room temperature for 1 hour, and then ultrasonic dispersion is performed for 0.5 hours. The cellulose solution is heated to 110°C, heated for 2 minutes, then poured into a culture dish, and cooled for 12 hours to obtain a hydrogel. Then the hydrogel is washed with water, ethanol and tert-butanol in sequence, each time for 1 hour, then the solution is replaced, and washing is performed for 24 hours, and then the cellulose aerogel is obtained after freeze-drying. Then it is placed in a nitrogen or argon environment, heated at 150°C for 2 hours, and then heated at 220°C for 0.5 hours.

[0041] (2) Preparation of a triboelectric nanogenerator

[0042] The modified cellulose aerogel prepared above is used as the positive electrode of the triboelectric nanogenerator, and the negative electrode is a polyvinylidene fluoride and nano-barium titanate blended nanofiber membrane, and the size is 4π cm 2 , and then copper foils are respectively covered on the back of the two triboelectric materials, and then fixed on an acrylic plate, and wires are connected with the upper and lower electrodes. The triboelectric nanogenerator is tested for contact separation power generation, and the pressure is 10N and the frequency is 4Hz.

[0043] (3) The open circuit voltage of the pure cellulose nanofiber film without adding any modified material as the positive electrode of the friction nanogenerator is 58V; the open circuit voltage of the modified cellulose-based aerogel of the present embodiment as the friction nanogenerator is 110V. It can be seen that the electrical output performance of the friction nanogenerator of the present embodiment is obviously improved. The filtration efficiency of PM 0.3 , PM 0.5 and PM1 is as high as 98.08%, 98.59%, 99.02% respectively. Even under the harsh condition of 95% RH high humidity, the filtration efficiency can be maintained above 89%. After 7 cycles of "test-washing", the filtration performance of PM 0.3 is still above 92%. The antibacterial rate of E. coli and S. aureus under near-infrared light irradiation for 20 min reaches 99.1%. The device can accurately detect 5ppm of NH3 and quickly respond, with a response rate of 72% to 100ppm of NH3 within 13 seconds. Even after 8 cycles of "test-washing", the bactericidal property and ammonia responsiveness still maintain excellent stability. By monitoring the wearer's breathing status in real time, the respiratory health status can be continuously evaluated. Example 2

[0044] (1) Preparation of modified cellulose aerogel

[0045] 0.5 mmol Zn(NO3)2 was added in advance as a seed for crystal growth in a 50 mL methanol solution containing 2-M (0.4 mol / L) to obtain a mixed solution A; Ti3C2T x was immersed in 40 mL Zn(NO3)2 methanol (0.35 mol / L) for 1.5 hours to obtain solution B, and then the mixture of solution B was mixed into the mixture of A and solution B, with slight stirring, and reacted at room temperature for 18 hours. The silane hydrolysis solution was composed of tetraethyl orthosilicate, ammonia water and ethanol in a volume ratio of 1:9:100, and stirred at 50°C for 10h. The weight ratio of anhydrous lithium bromide to water was 3:1, and stirred at 5°C for 2h. The microcrystalline cellulose was added to the silane hydrolysis solution, and the mass ratio of the two was 1:11, and stirred at 70°C for 15h. The silane-grafted cellulose was filtered out by vacuum filtration, and was loaded into a pressure-resistant bottle containing a lithium bromide solution, and the cellulose accounted for 0.4% of the total weight of the solution. Stirring at room temperature for 1h, followed by ultrasonic dispersion for 1h. Then Ti3C2T x / ZIF-8, Ti3C2T xZIF-8 and cellulose weight ratio is 0.1:1.1, stirring at room temperature for 1 h, and then ultrasonic dispersion for 0.5 h. The cellulose solution is heated to 120℃, heated for 5 min, then poured into a petri dish, and cooled for 12 h to obtain a hydrogel. Then the hydrogel is washed with water, ethanol, tert-butanol in turn, each time for 2 h, then the solution is replaced, and washed for 24 h, and then freeze-dried to obtain a cellulose aerogel. Then it is placed in a nitrogen or argon environment, heated at 180℃ for 3 h, and then heated at 240℃ for 1 h.

[0046] (2) Preparation of a triboelectric nanogenerator

[0047] The modified cellulose aerogel prepared above is used as the positive electrode of the triboelectric nanogenerator, and the polyvinylidene fluoride and nano-barium titanate blended nanofiber film is used as the negative electrode, with a size of 4π cm 2 The copper foil is covered on the back of the two triboelectric materials respectively, and then fixed on the acrylic plate respectively, and the wires are connected with the upper and lower electrodes. The contact separation power generation test of the triboelectric nanogenerator is carried out, with a pressure of 10 N and a frequency of 4 Hz.

[0048] (3) The open-circuit voltage of the triboelectric nanogenerator with pure cellulose nanofiber film without adding any modified material as the positive electrode is 58 V; the open-circuit voltage of the triboelectric nanogenerator based on the modified cellulose-based aerogel of the present embodiment is 118 V. It can be seen that the electrical output performance of the triboelectric nanogenerator of the present embodiment is obviously improved. The filtration efficiency of PM 0.3 , PM 0.5 and PM1 is as high as 98.32%, 98.96%, and 99.12% respectively. Even under the harsh condition of 95% RH high humidity, the filtration efficiency can still remain above 90.2%. After 7 cycles of “test-washing”, the filtration performance of PM 0.3 still exceeds 92.3%. The antibacterial rate of E. coli and S. aureus after 20 min of near-infrared light irradiation reaches 99.25%. The device can accurately detect 5 ppm NH3 and quickly respond, with a response rate of 74% to 100 ppm NH3 within 14 seconds. Even after 8 cycles of “test-washing”, the bactericidal property and ammonia responsiveness still maintain excellent stability. By monitoring the wearer's breathing status in real time, the respiratory health status can be continuously evaluated. Example 3

[0049] (1) Preparation of modified cellulose aerogel

[0050] 0.6 mmol Zn(NO3)2 is added in advance in a 50 mL methanol solution containing 2-M (0.1 mol / L) as a seed for crystal growth to obtain a mixed solution A; Ti3C2T xImmerse in 30 mL of Zn(NO₃)₂ methanol (0.3 mol / L) for 1 hour to obtain Solution B. The mixture of Solution B is then added to the mixture of Solution A and Solution B, stirred briefly, and allowed to react at room temperature for 24 hours. A silane hydrolyzate consisting of tetraethyl orthosilicate, aqueous ammonia, and ethanol in a volume ratio of 1:10:100 is stirred at 55°C for 12 hours. Anhydrous lithium bromide and water are added in a weight ratio of 2:1 and stirred at 5°C for 3 hours. Microcrystalline cellulose is added to the silane hydrolyzate in a weight ratio of 1:12 and stirred at 70°C for 22 hours. The silane-grafted cellulose is removed by vacuum filtration and placed in a pressure bottle containing lithium bromide solution, with the cellulose accounting for 1% of the total weight of the solution. Stir at room temperature for 1 hour, followed by ultrasonic dispersion for 0.5 hours. Ti₃C₂T₂ is then added. x / ZIF-8, Ti3C2T x The weight ratio of ZIF-8 to cellulose was 0.03:1.1, stirred at room temperature for 1 hour, and then ultrasonically dispersed for 1 hour. The cellulose solution was heated to 115°C for 3 minutes, then poured into a Petri dish and cooled for 15 hours to obtain a hydrogel. The hydrogel was then washed with water, ethanol, and tert-butanol, sequentially for 1 hour each wash. The solution was then replaced and washed for 24 hours. The cellulose aerogel was then freeze-dried to obtain the cellulose aerogel. The aerogel was then placed in a nitrogen or argon environment and heated at 200°C for 2 hours, followed by 230°C for 1 hour.

[0051] (2) Preparation of triboelectric nanogenerator

[0052] The modified cellulose aerogel prepared above was selected as the positive electrode of the triboelectric nanogenerator, and the nanofiber membrane of polyvinylidene fluoride and nano-barium titanate was used as the negative electrode. The size of the nanofiber membrane was 4π cm. 2 The backs of the two triboelectric materials were covered with copper foil and then fixed to acrylic plates. Wires were connected to the upper and lower electrodes. The triboelectric nanogenerator was tested for contact-separation power generation with a force of 10N and a frequency of 4Hz.

[0053] (3) The open circuit voltage of the positive electrode of the triboelectric nanogenerator using pure cellulose nanofiber membrane without any modified materials is 58V; the open circuit voltage of the triboelectric nanogenerator using the modified cellulose-based aerogel of this embodiment is 125V. It can be seen that the electrical output performance of the triboelectric nanogenerator of this embodiment is significantly improved. 0.3 、PM 0.5 The filtration efficiency of PM2.5, PM3 and PM1 were higher than 98.38%, 99.03% and 99.68% respectively. Even under the harsh conditions of high humidity of 95%RH, the filtration efficiency can be maintained above 91%. After 7 cycles of "test-washing", the filtration efficiency of PM2.5 was higher than 98.38%, 99.03% and 99.68% respectively. 0.3Filtration performance remains above 92%. After 20 minutes of near-infrared light irradiation, the antibacterial rate against Escherichia coli and Staphylococcus aureus reached 99.5%. The device can accurately detect 5 ppm NH3 and respond quickly, achieving a 75% response rate to 100 ppm NH3 within 12 seconds. Even after seven cycles of "test-and-wash," the bactericidal properties and ammonia response remained extremely stable. By monitoring the wearer's respiratory status in real time, respiratory health can be continuously assessed.

[0054] Effect evaluation 1

[0055] Figure 1 The Raman spectra of all modified materials showed that the -1 、1741 cm -1 、1415 cm -1 and 1072 cm -1 The characteristic peaks of cellulose belonging to CH stretching, CO stretching, CH bending and glycosidic stretching are retained at Figure 2 a). In the Raman spectrum of cellulose / tetraethyl orthosilicate (CT), 462 cm -1 、530 cm -1 and 784 cm -1 The characteristic peaks at 154 cm-1 in cellulose / TES / MXene (CTM) and cellulose / TES / MXene / ZIF-8 (CTMZ) are attributed to O-Si-O bending vibration, Si-O-Si torsional vibration, and Si-O stretching vibration corresponding to silicon dioxide (SiO2), confirming that tetraethyl orthosilicate (TEOS) is converted into SiO2. -1 The characteristic peaks of MXene were found at 673, 1180 and 1460 cm -1 The typical characteristic peaks at and are attributed to the imidazole ring vibration, CN stretching vibration, and methyl bending vibration of ZIF-8, respectively.

[0056] The XRD patterns always show a characteristic broad peak at 17°, which belongs to the (021) plane of cellulose, indicating that the modification process has not changed the basic crystal structure of cellulose ( Figure 2b). CT, CTM and CTMZ showed typical peaks at 20.8° and 26.2°, which belonged to the (101) and (111) planes of SiO2, respectively, which proved the conclusion of Raman spectroscopy and Fourier transform infrared spectroscopy analysis that TEOS was finally converted into SiO2 after some processing reactions. Characteristic peaks of MXene were found, indicating the successful synthesis of the material. Weak peaks belonging to ZIF-8 were found at 40-60°, but there were no corresponding ZIF-8 functional group peaks in the Fourier transform infrared spectrum, which might be due to the masking effect of two-dimensional carbon materials on ZIF-8.

[0057] Figure 2 In Example 2, the filtration efficiency of the TENG remained above 85% even under extreme conditions of 95% RH, after 2 hours of continuous testing Figure 2 .

[0058] Figure 3 In Example 2, the antibacterial rate of CTM on E. coli reached more than 99.5% after 20 min of near-infrared light irradiation Figure 3 . In Example 3, CTMZ maintained excellent and stable responsiveness to different concentrations of ammonia gas even after 20 days of storage at room temperature Figure 3 .

[0059] Obviously, the above examples are merely examples for clarity and do not limit the embodiments. Based on the above description, those skilled in the art can make other different forms of changes or variations. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing modified cellulose aerogel, characterized in that: The steps include: S11: adding a cellulose compound to a silane hydrolyzate and heating and mixing, and dispersing the separated solid in an aqueous solution of lithium bromide to obtain a mixed dispersion; the silane hydrolyzate is obtained by heating and mixing tetraethyl orthosilicate, aqueous ammonia, and ethanol at 50-75° C. for 8-20 h; the cellulose compound is selected from microcrystalline cellulose or nanocellulose; and the mass ratio of the cellulose compound to the silane hydrolyzate is 1:5-15; S12: Add Ti3C2T to the mixed dispersion x / ZIF-8 materials, after mixing, heating and reacting, cooling to obtain hydrogel; the Ti3C2T x / ZIF-8 material is obtained by mixing solution B and solution A and reacting at room temperature for 12-48 h; in step S12, Ti3C2T x The mass ratio of the ZIF-8 material and the cellulose compound in the mixed dispersion is 0.02-0.3:0.8-1.2; the solution A is obtained by mixing methanol containing dimethylimidazole and zinc nitrate; the solution B is obtained by mixing Ti3C2T x It is obtained by adding methanol containing zinc nitrate; S13: washing the hydrogel, freeze-drying, and heat-treating to obtain the modified cellulose aerogel; in step S13, the heat treatment method is: heating the freeze-dried hydrogel at 150-200° C. for 0.5-4 h, and then heating at 220-260° C. for 0.5-4 h under a protective atmosphere.

2. The preparation method according to claim 1, wherein In step S11, the cellulose compound and the silane hydrolyzate are heated and mixed at a temperature of 50-70° C. for 5-24 hours.

3. The preparation method according to claim 1, wherein The aqueous solution of lithium bromide has a weight ratio of lithium bromide to water of 2:1-3 and is stirred at 0-15°C for 0.5-5 h.

4. The preparation method according to claim 1, wherein In the silane hydrolysis solution, the volume ratio of tetraethyl orthosilicate, ammonia water and ethanol is 0.8-1.4:9-14:92-108.

5. The preparation method according to claim 1, wherein In step S12, the heating reaction temperature is 95-140° C., the time is 1-10 min, and the cooling is 6-24 h.

6. A modified cellulose aerogel prepared by the preparation method according to any one of claims 1 to 5.

7. A triboelectric nanogenerator, characterized in that: The modified cellulose aerogel according to claim 6 is used as the positive electrode material.

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