A cellulose-based aerogel triboelectric material and its preparation method

Abstract

The present invention belongs to the technical field of triboelectric materials, and specifically relates to a cellulose-based aerogel triboelectric material and a preparation method thereof. The method comprises the following steps: gelling a first chitosan, adding a first crosslinking agent to react, and obtaining a first chitosan fiber; gelling a second chitosan, and then adding a second crosslinking agent after homogenization to obtain a second chitosan fiber; sequentially adding the first chitosan fiber and the second chitosan fiber to the homogenized cellulose fiber dispersion, and then sequentially adding a water-soluble metal salt and a third crosslinking agent, stirring and dispersing the mixture, performing a crosslinking reaction, and freezing to obtain a cellulose-based aerogel precursor; immersing the mixture in a solvent for solvent replacement, and obtaining a cellulose-based aerogel triboelectric material after extrusion and drying. The present invention improves the dielectric properties of cellulose-based triboelectric materials, enhances the mechanical stability and humidity adaptability of the materials, and enhances the energy efficiency of the self-powered process of the materials in a high humidity environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of triboelectric materials, and in particular relates to a cellulose-based aerogel triboelectric material and a preparation method thereof. Background Art

[0002] With the development of industries such as the Internet of Things and smart homes, the use of sensors has expanded significantly, but their widespread applicability is often limited by external power sources and complex manufacturing processes. The invention of triboelectric nanogenerators provides an effective solution for achieving self-driving sensors and simplifying manufacturing processes. Triboelectric nanogenerators, abbreviated as TENG, are convenient, sustainable, and green energy devices that convert low-frequency and irregular mechanical energy into electrical energy based on the triboelectric effect and electrostatic induction. They have the advantages of high energy conversion efficiency, high output power, a wide range of material options, high reliability, and low cost. The core component of TENG is the triboelectric material, which plays a key role in determining the output power of TENG.

[0003] In the existing technology, the commonly used triboelectric materials are petroleum-based synthetic high molecular polymers. The main advantage of this type of material is its stable properties, but the disadvantage is that it is generally non-renewable and non-biodegradable, which has an adverse impact on the environment and the overall benefits of its application.

[0004] Cellulose is one of the world's most abundant natural polysaccharides, boasting a range of advantageous properties, including renewability, biodegradability, chemical modifiability, and low cost. Cellulose surfaces contain numerous oxygen atoms with lone electron pairs. These oxygen atoms possess high electronegativity, attracting electrons from neighboring atoms. This oxygen atom forms a negative local dipole in the highest occupied molecular orbital band composed of non-bonding electrons, providing more electrons during contact charging. Therefore, cellulose is a promising environmentally friendly triboelectric cathode material. However, prior art methods for preparing triboelectric materials from cellulose have shown that due to its highly crystalline structure, many hydroxyl groups are encapsulated in hydrogen bonds, preventing them from losing electrons during contact charging. This reduces the polarity and electron-donating capacity of the cellulose molecules. The abundant hydroxyl groups in cellulose molecules readily adsorb excessive water molecules, leading to charge dissipation in high-humidity environments and reducing the surface charge density of the cellulose material. The water molecules induce an electrostatic shielding effect, resulting in surface charge dissipation and reduced power output in the friction layer. This significantly degrades the performance of cellulose-based TENGs and hinders their practical application. Prior art also suggests that the triboelectric output properties of cellulose can be enhanced by adding chitosan to the preparation of triboelectric materials from cellulose. However, since both cellulose and chitosan have the characteristics of high resistivity and low dielectric constant, there is a problem of hindering the transfer and accumulation of charges in TENG devices, resulting in low energy efficiency of the self-powered process of TENG in high humidity environment. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a cellulose-based aerogel triboelectric material and a preparation method thereof, so as to improve the dielectric properties of the cellulose-based triboelectric material, enhance the mechanical stability and wet stability of the material, and enhance the energy efficiency of the material's self-powered process in a high humidity environment.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] In one aspect, the present invention provides a method for preparing a cellulose-based aerogel triboelectric material, comprising the following steps:

[0008] Step 1: dissolving the first chitosan in the first acid solution to form a first precursor solution, stirring and adjusting the pH value to alkaline to gel, and then adding the first crosslinking agent to perform the first crosslinking reaction to obtain the first chitosan fiber.

[0009] Step 2: dissolving the second chitosan in the second acid solution to form a second precursor solution, stirring and adjusting the pH value to alkaline, gelling, and then adding the second crosslinking agent after homogenization to perform a second crosslinking reaction to obtain the second chitosan fiber.

[0010] Step 3: add the first chitosan fiber and the second chitosan fiber to the homogenized cellulose fiber dispersion in sequence, mix them evenly, then add the water-soluble metal salt and the third crosslinking agent in sequence, stir and disperse them, perform a third crosslinking reaction, and freeze after the reaction to obtain a cellulose-based aerogel precursor.

[0011] Step 4: Immerse the cellulose-based aerogel precursor in a solvent for solvent replacement, and obtain the cellulose-based aerogel triboelectric material after extrusion and drying.

[0012] It should be noted that the present invention gels a first chitosan and cross-links it with a first cross-linking agent to form an amide structure, thereby forming chitosan micron-scale fibers. A second chitosan is gelled and homogenized, and cross-linked with a second cross-linking agent to form an amide structure, thereby forming chitosan micro / nanoscale fibers. A multi-scale fiber entanglement skeleton is constructed by homogenizing cellulose fibers, chitosan micron-scale fibers, and chitosan micro / nanoscale fibers. A multi-network structure is constructed by complexing water-soluble metal salt ions to form chelate bonds, as well as chemical cross-linking and hydrogen bonding. A cellulose-based aerogel triboelectric material is then formed in the form of an aerogel through solvent exchange, rapid desolvation by extrusion, and ambient drying. This aerogel has the characteristics of low apparent density, high specific surface area, and adjustable surface chemical properties. Its porous structure helps increase the effective contact area and provides abundant active sites for water molecules in high humidity environments. The prepared cellulose-based aerogel has a large number of active sites for water molecules and a multi-network structure system for rapid adsorption and desorption of water molecules, which gives the material excellent humidity adaptability; the constructed hydrogen bond cross-linking, chemical covalent cross-linking and ion coordination multi-cross-linking network system gives the material excellent mechanical properties and wet stability; metal ions improve the dielectric properties of the material, giving the material excellent triboelectric output characteristics, forming a material system with high stability, triboelectric properties and humidity adaptability.

[0013] Furthermore, the present invention provides a method for preparing cellulose-based aerogel triboelectric materials. First, the first chitosan is dissolved in an acid solution, and the pH value is adjusted to induce regeneration, thereby causing a gelation transition. The active groups on the first cross-linking agent and the amino groups on the chitosan chain form an amide structure, thereby achieving cross-linking of the chitosan molecular chains and forming chitosan micron-sized fibers. Secondly, the second chitosan is dissolved in an acid solution, and the pH value is adjusted to induce regeneration, thereby causing a gelation transition, and further homogenization treatment can improve the rheological properties of the polymer solution, and the molecular chains are prompted to stretch and arrange along the flow direction through the action of shear force, thereby reducing the entanglement density of the molecular chains. Then, the active groups on the second cross-linking agent and the amino groups on the chitosan chain form an amide structure, thereby achieving cross-linking of the chitosan molecular chains. The cellulose fiber dispersion is homogenized to achieve multi-level dispersion, constructing cellulose fibers with a multi-scale structure. Cellulose fibers and chitosan micron-scale fibers serve as the matrix skeleton, chitosan micron-scale fibers serve as the reinforcing skeleton, and metal ions in water-soluble metal salts serve as reinforcing bridges, forming chelate bonds with the active groups in chitosan and cellulose fibers. Based on a third crosslinker, a multi-network composite aerogel is formed through a combination of chemical crosslinking, ion complexation, and hydrogen bond crosslinking. Finally, through solvent exchange, extrusion rapid desolventizing, and ambient drying, a multi-network cellulose-based aerogel triboelectric material is constructed. This aerogel has a porous structure with low apparent density and high specific surface area. The porous structure increases the effective contact area and free volume effect, while also helping to form more active sites for water molecules in high humidity environments.

[0014] In some embodiments, the mass volume ratio of the first chitosan, the first cross-linking agent and the first acid solution is 0.5g-0.9g:0.1g-0.18g:40mL, the first acid solution is hydrochloric acid, and the concentration of hydrochloric acid is 0.05M-0.2M.

[0015] In some embodiments, the mass volume ratio of the second chitosan, the second cross-linking agent and the second acid solution is 0.05g-0.1g:0.01g-0.02g:20mL, the second acid solution is hydrochloric acid, and the concentration of hydrochloric acid is 0.05M-0.2M.

[0016] In some embodiments, the mass ratio of the cellulose fiber, the first chitosan, and the second chitosan in the cellulose fiber dispersion is 1 g: 0.5 g to 0.9 g: 0.05 g to 0.1 g.

[0017] In some embodiments, the mass ratio of cellulose fiber to soluble water-soluble metal salt in the cellulose fiber dispersion is 1g:0.04g-0.12g, and the mass ratio of cellulose fiber to the third crosslinking agent in the cellulose fiber dispersion is 1g:0.1g-0.2g.

[0018] It should be noted that the present invention, through the formulation of the technical solution of the present invention, has the characteristics of low cost, simple process and environmental protection. With the multi-scale entangled structure of cellulose fiber and chitosan micro / nanofiber as the skeleton, chemical covalent crosslinking, ionic coordination and hydrogen bond crosslinking are used, and a combination of freezing, solvent replacement, extrusion desolvation and room temperature drying strategies are used to obtain a cellulose-based aerogel triboelectric material with excellent wet structural stability, mechanical properties, humidity adaptability and high triboelectric output characteristics. Chitosan is rich in amino groups with excellent electron-donating properties, which is beneficial to improving the dielectric properties of the aerogel. The introduction of metal ions can improve the stability of the aerogel structure, reduce the crystallinity of cellulose and chitosan, further enhance the interfacial polarization effect, improve the transport characteristics of electrons and ions, increase the distance between charge centers, and increase the dipole moment of the aerogel components. The multi-crosslinked network structure facilitates the construction of channels for water molecule adsorption, transport and desorption, improving the humidity adaptability and durability of the aerogel. The porous structure, molecular entanglement structure and solution exchange process of the aerogel help to form a rough micro / nano surface, increase the effective contact area, and form a larger number of electrostatic induction sites.

[0019] In some embodiments, the water-soluble metal salt is at least one of a water-soluble copper salt, a water-soluble aluminum salt, a water-soluble magnesium salt, a water-soluble calcium salt, a water-soluble sodium salt, a water-soluble iron salt, and a water-soluble potassium salt.

[0020] It should be noted that the metal ions such as K + , Ca 2+ 、Zn 2+ 、Cu 2 + 、Al 3+ and Fe 3+ The present invention is not limited to the specific types of water-soluble copper salts, water-soluble aluminum salts, water-soluble magnesium salts, water-soluble calcium salts, water-soluble sodium salts, water-soluble iron salts or water-soluble potassium salts, as long as the metal ions such as K + , Ca 2+ 、Zn 2+ 、Cu 2+ 、Al 3+ and Fe 3+ The copper salt, aluminum salt, magnesium salt, calcium salt, sodium salt, iron salt, and potassium salt are all metal salts that are easily soluble in water, such as copper salts such as CuCl2, aluminum salts such as AlCl3, magnesium salts such as MgCl2, calcium salts such as CaCl2, iron salts such as FeCl3, potassium salts such as KCl, and sodium salts such as NaCl.

[0021] In some embodiments, the first cross-linking agent, the second cross-linking agent and the third cross-linking agent are all glycidyl ethers, and the glycidyl ether is ethylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether; the temperature of the first cross-linking reaction, the second cross-linking reaction and the third cross-linking reaction are all 50°C to 70°C, and the reaction time is all 4h to 6h.

[0022] It should be noted that during the first and second cross-linking reactions, the epoxy groups on the glycidyl ether molecules open and form amide structures with the amino groups on the chitosan chain to achieve cross-linking of the chitosan molecular chains. During the third cross-linking reaction, the epoxy groups on the glycidyl ether molecules open and undergo cross-linking reactions with the amino groups on the chitosan chain and the hydroxyl groups on the cellulose chain, respectively.

[0023] In some embodiments, the first precursor liquid is stirred at a rate of 1000 rpm to 2000 rpm, and the second precursor liquid is stirred at a rate of 500 rpm to 1000 rpm.

[0024] It should be noted that the present invention forms multi-scale fibers of chitosan fibers during the gelation transition process by means of high-speed shearing.

[0025] In some embodiments, the freezing temperature is -2°C to -10°C, the freezing time is 1 hour to 3 hours, and the solvent replacement is performed by immersing the cellulose-based aerogel precursor in anhydrous ethanol and allowing it to stand for 2 hours to 4 hours.

[0026] It should be noted that the present invention adopts a freezing method. Since hydrogen bonding plays a dominant role in low-temperature environments, the strong lateral aggregation of cellulose chains is further promoted. During the freezing process, water molecules form ice crystals, which leads to further compression of the framework and the formation of more gaps between the fibers. Through ethanol substitution and rapid desolventization, the moisture content is greatly reduced, which reduces the capillary force during the drying process and promotes the formation of physical cross-linked domains in the skeleton; then room temperature drying is carried out to finally obtain a lightweight and porous cellulose-based aerogel triboelectric material. The present invention effectively improves the shortcomings of the freeze-drying and supercritical drying methods used in the prior art for preparing biomass aerogels, such as high cost and high technical requirements, and the problem that cellulose and its derivative aerogels are generally brittle, have poor flexibility, low physical strength and small specific surface area due to low solid content, by freezing, solvent replacement and room temperature drying.

[0027] To address the existing problem of using surfactants such as sodium lauryl sulfate and octylamine to reduce water surface tension and prevent the gel structure from collapsing in dry environments, resulting in unstable aerogels and environmental and ecological hazards, the present invention utilizes a solvent exchange method in its preparation process. This method is easily scalable, relatively environmentally friendly, and facilitates industrial recycling.

[0028] In some embodiments, the cellulose fibers are one or a mixture of hardwood cellulose fibers and softwood cellulose fibers.

[0029] It should be noted that the solvent used to disperse the cellulose fibers to form a cellulose fiber dispersion is deionized water, and the concentration of the cellulose fiber dispersion is not specifically limited; only the amount of cellulose fiber used needs to be determined. After dispersing the hardwood cellulose fiber and softwood cellulose fiber raw materials in deionized water, they are homogenized using a homogenizer for 10 to 20 minutes at a speed of 11,000 to 20,000 rpm to obtain a dispersion. After the dispersion is filtered, the residue is dried to obtain the cellulose fibers. The cellulose fibers are then dispersed in deionized water to form a cellulose fiber dispersion.

[0030] In some embodiments, the pH value is adjusted to alkaline using a regulator such as NaOH, KOH, or a mixture of NH3·H2O. The regulator is prepared to form a pH adjustment solution, which is added to the first precursor solution or the second precursor solution in portions to adjust the pH value to 10.5-11.5.

[0031] In another aspect, the present invention provides a cellulose-based aerogel triboelectric material prepared using the aforementioned preparation method. This method for preparing the cellulose-based triboelectric material does not require any special equipment and significantly reduces the time required for ambient drying. For example, an aerogel measuring 50 mm × 50 mm × 25 mm can be dried in just 3 hours. The preparation process is energy-efficient, simple to operate, and easily recyclable, making it scalable. A TENG assembled from the composite aerogel triboelectric material exhibits excellent triboelectric output performance and durability, with a maximum output voltage of 205.8 V. Within a humidity range of 40% to 95% RH, the TENG exhibits excellent wet response cycling characteristics and reversibility, enabling accurate and stable detection of various biological and non-biological sound signals and recognition of electrical signals from human handwriting. This composite aerogel-based TENG has applications in voice recognition, self-powered writing boards, and identity verification. The composite aerogel exhibits excellent recyclability, durability, and biodegradability.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention provides a method for preparing a cellulose-based aerogel triboelectric material. The method comprises gelling a first chitosan and cross-linking it with a first cross-linking agent to form an amide structure, thereby forming chitosan micron-sized fibers. A second chitosan is then gelled and homogenized, and cross-linked with a second cross-linking agent to form an amide structure, thereby forming chitosan micro / nano-sized fibers. A multi-scale fiber entanglement skeleton is constructed by homogenizing the cellulose fibers, chitosan micron-sized fibers, and chitosan micro / nano-sized fibers. A multi-network structure is constructed by ion complexation with water-soluble metal salts to form chelate bonds, and chemical cross-linking and hydrogen bonding are used to form a multi-network structure. The cellulose-based aerogel triboelectric material is then subjected to solvent exchange, rapid desolvation by extrusion, and ambient drying to form an aerogel. The aerogel has the characteristics of low density, high specific surface area, and adjustable surface chemical properties and porous structure. Its porous structure helps to form additional active sites for water molecules in high humidity environments. Because the prepared cellulose-based aerogel has a large number of active sites for water molecules and a multi-network system for rapid adsorption and desorption of water molecules, the material has excellent humidity adaptability; the constructed hydrogen bond cross-linking, chemical covalent cross-linking and ion coordination multi-cross-linking network structure gives the material excellent mechanical properties and wet stability; metal ions improve the dielectric properties of the material, giving the material excellent triboelectric output characteristics, forming a material system with high stability, triboelectric properties and humidity adaptability.

[0034] The preparation process of the present invention is simple and can be completed using existing simple conventional equipment without the need for special equipment. The prepared cellulose-based aerogel triboelectric material has excellent mechanical properties, moisture resistance, recyclability and degradability, and is low-cost, green and biocompatible.

[0035] The present invention adopts a freezing method. Due to the dominant role of hydrogen bonds in a low-temperature environment, the strong lateral aggregation of cellulose chains is further promoted. During the freezing process, water molecules form ice crystals, which leads to further compression of the framework and the formation of more gaps between the fibers. Through ethanol substitution and rapid desolventization, the moisture content is greatly reduced, which reduces the capillary force during the drying process and promotes the formation of physical cross-linked domains in the skeleton; then environmental drying is carried out to finally obtain a lightweight and porous cellulose-based aerogel triboelectric material. This technology effectively improves the shortcomings of the existing technology for preparing biomass aerogels, which usually adopt freeze-drying and supercritical drying methods, such as high cost and high technical requirements, and improves the problem that cellulose and its derivative aerogels are usually brittle, have poor flexibility, low physical strength and small specific surface area due to low solid content. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a physical picture showing the moldability of the cellulose-based aerogel prepared in Example 1 of the present invention. Figure 1Figure i shows aerogels on flowers, Figure ii shows aerogels in various shapes, Figure iii shows aerogels in different twisted states, and Figure iv shows aerogels in different bent states.

[0037] Figure 2 These are infrared spectra of the T2-M aerogels prepared in Examples 1 to 5 of the present invention, the CS-0.5 aerogel prepared in Example 12, the CS-0.7 aerogel prepared in Example 13, and the CF / CS aerogel and CF prepared in Comparative Example 1.

[0038] Figure 3 Mg prepared in Example 3 of the present invention 2+ X-ray diffraction patterns of 2-M aerogel, CS powder, CF / CS aerogel prepared in Comparative Example 1, and CF fiber prepared in Comparative Example 2.

[0039] Figure 4 Surface scanning electron micrographs of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in comparative example 1. Figure 4 Figure a is a surface scanning electron microscope image of comparative example 1 at a size of 200 μm, Figure b is a surface scanning electron microscope image of embodiment 1 at a size of 200 μm, Figure c is a surface scanning electron microscope image of embodiment 2 at a size of 200 μm, Figure d is a surface scanning electron microscope image of embodiment 3 at a size of 200 μm, Figure e is a surface scanning electron microscope image of embodiment 4 at a size of 200 μm, Figure f is a surface scanning electron microscope image of embodiment 5 at a size of 200 μm, Figure a1 is a surface scanning electron microscope image of comparative example 1 at a size of 50 μm, Figure b1 is a surface scanning electron microscope image of embodiment 1 at a size of 50 μm, Figure c1 is a surface scanning electron microscope image of embodiment 2 at a size of 50 μm, Figure d1 is a surface scanning electron microscope image of embodiment 3 at a size of 50 μm, Figure e1 is a surface scanning electron microscope image of embodiment 4 at a size of 50 μm, and Figure f1 is a surface scanning electron microscope image of embodiment 5 at a size of 50 μm.

[0040] Figure 5 Cross-sectional scanning electron micrographs of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in comparative example 1. Figure 5Figure a is a cross-sectional scanning electron microscope image of comparative example 1 at 200 μm size, Figure b is a cross-sectional scanning electron microscope image of embodiment 1 at 200 μm size, Figure c is a cross-sectional scanning electron microscope image of embodiment 2 at 200 μm size, Figure d is a cross-sectional scanning electron microscope image of embodiment 3 at 200 μm size, Figure e is a cross-sectional scanning electron microscope image of embodiment 4 at 200 μm size, Figure f is a cross-sectional scanning electron microscope image of embodiment 5 at 200 μm size, Figure a1 is a cross-sectional scanning electron microscope image of comparative example 1 at 50 μm size, Figure b1 is a cross-sectional scanning electron microscope image of embodiment 1 at 50 μm size, Figure c1 is a cross-sectional scanning electron microscope image of embodiment 2 at 50 μm size, Figure d1 is a cross-sectional scanning electron microscope image of embodiment 3 at 50 μm size, Figure e1 is a cross-sectional scanning electron microscope image of embodiment 4 at 50 μm size, and Figure f1 is a cross-sectional scanning electron microscope image of embodiment 5 at 50 μm size.

[0041] Figure 6 Mg prepared in Example 3 of the present invention 2+ Energy dispersive X-ray spectroscopy analysis of 2-M aerogel. Figure 6 Figure a is a scanning electron microscope image selected for the surface energy dispersion X-ray spectrum analysis of Example 3, Figure b is the C element distribution diagram of Figure a, Figure c is the N element distribution diagram of Figure a, and Figure d is the Mg element distribution diagram of Figure a. Figure a1 is a scanning electron microscope image selected for the cross-sectional energy dispersion X-ray spectrum analysis of Example 3, Figure b1 is the C element distribution diagram of Figure a1, Figure c1 is the N element distribution diagram of Figure a1, and Figure d1 is the Mg element distribution diagram of Figure a1.

[0042] Figure 7 These are the compressive stress-strain and compression modulus diagrams of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in Comparative Example 1. Figure 7 Figure (a) is the compression stress-strain diagram, and Figure (b) is the compression modulus diagram.

[0043] Figure 8 Single compression cycle test diagrams and residual stress diagrams under different strains for the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in comparative example 1. Figure 8 Figure (a) is a single compression cycle test diagram under different strains, and Figure (b) is the residual stress diagram.

[0044] Figure 9 These are the before and after pictures of the wet stability test of the T2-M aerogel prepared in Example and the CF / CS aerogel prepared in Comparative Example 1. Figure 9 Figure a shows the initial state in water, Figure b shows the state after stirring and shaking in water, and Figure c shows a comparison before and after drying after continuous immersion in deionized water for 40 days.

[0045] Figure 10 This is a comparison chart of the output voltage of the TENG prepared with T6-M aerogel under different external conditions in the embodiment of the present invention. Figure 10 Figure (a) shows the output voltage under the action of 7Hz and 15N external force, Figure (b) shows the output voltage under the action of 3Hz, 5N and 7Hz, 5N external force, and Figure (c) shows the output voltage under the action of 3Hz, 5N and 3Hz, 15N external force.

[0046] Figure 11 This is a comparison chart of the output voltages of the cellulose aerogel-based TENGs prepared in Examples 3, 6, and 7 of the present invention at different thicknesses. Figure 11 Figure (a) shows the output voltage, Figure (b) shows the output performance and contact area, Figure (c) shows the thickness relationship, and Figure (d) shows the output voltage and output power density of the external load resistor.

[0047] Figure 12 For example 7Mg of the present invention 2+ Triboelectric output performance diagram of TENG prepared by 6-M aerogel under different humidity environments. Figure 12 Figure (a) is the output voltage diagram, Figure (b) is the output voltage data fitting diagram, and Figure (c) is the output current diagram.

[0048] Figure 13 For example 7Mg of the present invention 2+ Fitting diagram of the output voltage of the TENG prepared by 6-M aerogel during continuous humidity cycle test.

[0049] Figure 14 For example 7Mg of the present invention 2+ Comparison of electrical signals detected by the TENG constructed with 6-M aerogel and audio signals of different biological and non-biological sounds. Figure 14 Figure (a) is a comparison of drum sound signals, Figure (b) is a comparison of dog barking sound signals, Figure (c) is a comparison of thunder and lightning sound signals, Figure (d) is a comparison of firewood burning sound signals, and Figure (e) is a comparison of continuous piano sound signals.

[0050] Figure 15 For example 7Mg of the present invention 2+ Comparison chart of 6-M aerogel recyclability performance. Figure 15 Figure (a) shows the output voltage comparison of different aerogel-based TENGs, Figure (b) shows the output current diagram of the new and old aerogel-based TENGs, and Figure (c) shows the transfer charge diagram of the new and old aerogel-based TENGs.

[0051] Figure 16 This is a diagram showing the degradation process of the aerogels of Examples 1 to 3 of the present invention and the comparative example CF / CS aerogel. Figure 16 Figure i is the initial state diagram, ii is the state diagram after being placed in the container for 30 days, iii is the state diagram after being transferred to the natural environment for 10 days, and iv is the state diagram after being transferred to the natural environment for 30 days. DETAILED DESCRIPTION

[0052] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0053] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0054] The following is further described through specific examples.

[0055] Example 1

[0056] A method for preparing a cellulose-based aerogel triboelectric material comprises the following steps:

[0057] S1. Soak softwood pulp paper in deionized water to fully absorb and swell. Homogenize using a homogenizer at 11,000 rpm for 15 minutes to obtain a pulp dispersion. Filter the dispersion, and dry the residue to obtain cellulose fiber. Take 1 g of cellulose fiber and add it to 200 mL of deionized water, fully dispersing it to obtain a cellulose fiber dispersion.

[0058] S2. Weigh 0.9 g of chitosan and dissolve it in 40 mL of 0.1 M hydrochloric acid solution. Dissolve the chitosan fully by mechanical dissolution to form a first precursor solution. Then, add 1 M NaOH solution dropwise to adjust the pH to 11. At the same time, use mechanical stirring at 1500 rpm. Then, add 0.18 g of ethylene glycol diglycidyl ether dropwise. React at 60 ° C for 5 h to obtain a first chitosan fiber.

[0059] S3. Weigh 0.1 g of chitosan and dissolve it in 20 mL of 0.1 M hydrochloric acid solution. Dissolve the chitosan completely by mechanical dissolution to form a second precursor solution. Then, add 1 M NaOH solution to adjust the pH to 11. Use magnetic stirring at 800 rpm. Then, use a homogenizer to homogenize for 3 minutes at a speed of 11000 rpm. Then, add 0.02 g of ethylene glycol diglycidyl ether and react at 60°C for 5 hours to obtain a second chitosan fiber.

[0060] S4, mixing the cellulose fiber dispersion obtained in S1, the first chitosan fiber obtained in S2, and the second chitosan fiber obtained in S3, and after mixing evenly, adding 0.04 g of sodium chloride and 0.2 g of ethylene glycol diglycidyl ether in sequence, and stirring for 30 minutes, and then using ultrasonic dispersion for 1 hour, and then performing a third reaction at a temperature of 60° C. for a reaction time of 5 hours. After completion, placing it on a filter to drain and stand until no water droplets naturally drip, and then freezing it at a temperature of -5° C. for 2 hours to obtain a cellulose-based aerogel precursor;

[0061] S5. Immerse the cellulose-based aerogel precursor in anhydrous ethanol at 60°C, allow it to stand for 3 hours for solvent replacement, and then place it between two glass plates for extrusion. After extrusion, allow it to stand and dry to obtain a cellulose-based aerogel triboelectric material; named Na + 2-M aerogel.

[0062] Example 2

[0063] A method for preparing a cellulose-based aerogel triboelectric material, which differs from the method of Example 1 in that 0.04g of calcium chloride and 0.2g of ethylene glycol diglycidyl ether are added in sequence in S4. The obtained cellulose-based aerogel triboelectric material is named Ca 2+ 2- M aerogel.

[0064] Example 3

[0065] A preparation method of a cellulose-based aerogel triboelectric material, which differs from the preparation method of Example 1 in that 0.04g of magnesium chloride and 0.2g of ethylene glycol diglycidyl ether are added in sequence in S4. The obtained cellulose-based aerogel triboelectric material is named Mg 2+ 2-M aerogel.

[0066] Example 4

[0067] A preparation method of a cellulose-based aerogel triboelectric material, which differs from the preparation method of Example 1 in that 0.04g of ferric chloride and 0.2g of ethylene glycol diglycidyl ether are added in sequence in S4. The obtained cellulose-based aerogel triboelectric material is named Fe 3+ 2-M aerogel.

[0068] Example 5

[0069] A method for preparing a cellulose-based aerogel triboelectric material, the difference from the preparation method of Example 1 is that 0.04g aluminum chloride and 0.2g ethylene glycol diglycidyl ether are added in sequence in S4. The obtained cellulose-based aerogel triboelectric material is named Al 3+ 2-M aerogel.

[0070] Example 6

[0071] A method for preparing a cellulose-based aerogel triboelectric material is basically different from the preparation method of Example 3 in that the amount of magnesium chloride used in S4 is 0.08g. The obtained cellulose aerogel triboelectric material is named Mg 2+ 4-M aerogel.

[0072] Example 7

[0073] A method for preparing a cellulose-based aerogel triboelectric material is basically different from the preparation method of Example 3 in that the amount of magnesium chloride used in S4 is 0.12g. The obtained cellulose-based aerogel triboelectric material is named Mg 2+ 6-M aerogel.

[0074] Example 8

[0075] A preparation method of a cellulose-based aerogel triboelectric material is basically different from the preparation method of Example 1 in that the amount of sodium chloride used in S4 is 0.12g. The obtained cellulose-based aerogel triboelectric material is named Na 2+ 6-M aerogel.

[0076] Example 9

[0077] A method for preparing a cellulose-based aerogel triboelectric material is basically different from the preparation method of Example 2 in that the amount of calcium chloride used in S4 is 0.12g. The obtained cellulose-based aerogel triboelectric material is named Ca 2+ 6-M aerogel.

[0078] Example 10

[0079] A preparation method of a cellulose-based aerogel triboelectric material is basically different from the preparation method of Example 4 in that the amount of ferric chloride used in S4 is 0.12g. The obtained cellulose-based aerogel triboelectric material is named Fe 3+ 6-M aerogel.

[0080] Example 11

[0081] A method for preparing a cellulose-based aerogel triboelectric material is basically different from the preparation method of Example 5 in that the amount of aluminum chloride used in S4 is 0.12g. The obtained cellulose-based aerogel triboelectric material is named Al 3+ 6-M aerogel.

[0082] Example 12

[0083] A method for preparing a cellulose-based aerogel triboelectric material comprises the following steps:

[0084] S1. Soak softwood pulp paper in deionized water to fully absorb and swell. Homogenize the paper in a homogenizer for 15 minutes at 11,000 rpm to obtain a pulp dispersion. Filter the dispersion, and dry the residue to obtain cellulose fiber. Add 1 g of cellulose fiber to 200 ml of deionized water and fully disperse the mixture to obtain a cellulose fiber dispersion.

[0085] S2. Weigh 0.5 g of chitosan and dissolve it in 40 mL of 0.1 M hydrochloric acid solution. Dissolve the chitosan fully by mechanical dissolution to form a first precursor solution. Then, add a 1 M NaOH solution dropwise to adjust the pH to 11. Mechanical stirring is used at the same time, and the speed is controlled at 1500 rpm. Then, 0.14 g of ethylene glycol diglycidyl ether is added dropwise, and the reaction is carried out at 60° C. for 5 h to obtain a first chitosan fiber.

[0086] S3. Take 0.07g of chitosan and dissolve it in 10ml of 0.1M hydrochloric acid solution. Dissolve the chitosan completely by mechanical dissolution to form a second precursor solution. Then, add 1M NaOH solution to adjust the pH to 11. At the same time, use magnetic stirring and control the speed at 800rpm. Then use a homogenizer to homogenize for 3min at a speed of 11000rpm. Then add 0.01g of ethylene glycol diglycidyl ether and react at a temperature of 60°C for 5h to obtain a second chitosan fiber.

[0087] S4. Mix the cellulose fiber dispersion obtained in S1, the first chitosan fiber obtained in S2, and the second chitosan fiber obtained in S3. After uniform mixing, add 0.04g of magnesium chloride and 0.2g of ethylene glycol diglycidyl ether in sequence, stir for 30 minutes, and then disperse using ultrasound for 1 hour. Then, perform a third reaction at 60°C for 5 hours. After completion, place the mixture on a filter to drain and let it stand until no water droplets naturally drip. Then, freeze it at -5°C for 2 hours to obtain a cellulose-based aerogel precursor.

[0088] S5. Immerse the cellulose-based aerogel precursor in anhydrous ethanol at 60°C, allow it to stand for 3 hours for solvent replacement, and then squeeze it between two glass plates. After squeezing, allow it to stand and dry to obtain a cellulose-based aerogel triboelectric material, designated CS-0.5 aerogel.

[0089] Example 13

[0090] A method for preparing a cellulose-based aerogel triboelectric material differs from the preparation method of Example 12 in that:

[0091] In S2, 0.7 g of chitosan was weighed and dissolved in 40 ml of 0.1 M hydrochloric acid solution, and the amount of ethylene glycol diglycidyl ether used was 0.1 g.

[0092] In S3, 0.05 g of chitosan was weighed and dissolved in 10 ml of 0.1 M hydrochloric acid solution, and the amount of ethylene glycol diglycidyl ether used was 0.015 g.

[0093] The obtained cellulose-based aerogel triboelectric material was named CS-0.7 aerogel.

[0094] Comparative Example 1

[0095] A method for preparing a cellulose-based aerogel triboelectric material is different from the preparation method of Example 1 in that only 0.2 g of ethylene glycol diglycidyl ether is used in S4.

[0096] The obtained cellulose-based aerogel triboelectric material was named CF / CS aerogel.

[0097] Comparative Example 2

[0098] A method for preparing cellulose fibers comprises the following steps:

[0099] The softwood pulp paper was soaked in deionized water to fully absorb water and swell, and homogenized using a homogenizer for 15 minutes at a speed of 11,000 rpm to obtain a pulp dispersion. After the dispersion was filtered, the residue was dried to obtain cellulose fiber; named CF fiber.

[0100] The cellulose-based aerogels prepared in Examples 1 to 5, Comparative Example 1, and the cellulose fiber structure prepared in Comparative Example 2 were tested. Examples 1 to 5 are collectively referred to as T2-M aerogels, where T refers to the metal ion. The results are as follows:

[0101] Figure 1 This is a physical picture showing the moldability of the cellulose-based aerogel prepared in Example 1 of the present invention. Figure 1 Figure i shows aerogels on flowers, figure ii shows aerogels in various shapes, figure iii shows aerogels in different twisted states, and figure iv shows aerogels in different bent states. Figure 1 As shown in Figure 2, the prepared aerogel is light in weight and has an apparent density of 0.066 g / cm 3 , with good moldability. Aerogels can be bent and twisted, showing good flexibility.

[0102] Figure 2 The infrared spectra of T2-M aerogel prepared in Examples 1 to 5 of the present invention, CS-0.5 aerogel prepared in Example 12, CS-0.7 aerogel prepared in Example 13, CF / CS aerogel and CF prepared in Comparative Example 1 are shown. Figure 2 As shown, for CF, at 3200 cm -1 ~3500cm -1 The broad absorption band in the range of 2900 cm -1 The peaks near 1030 cm are caused by the stretching vibration of OH and -CH-. -1 、897cm -1 and 1156cm -1 The absorption peaks at 3200 cm in CF / CS aerogel represent the stretching vibration of COC, β-glycosidic bond and pyranose ring skeleton vibration, which are characteristic peaks unique to the cellulose macromolecular structure. -1 The absorption band near 2900cm becomes wider and the intensity decreases. -1 The increase in the peak width near 1646 cm is due to the introduction of -NH2 in chitosan and the cross-linking of ethylene glycol diglycidyl ether with the two components; -1 The peak intensity near 1584 cm -1 New peaks appeared at 1065cm-1, which were caused by the stretching vibration of C=O in -NHCO and the bending of NH in -NH2. -1 ~1024cm -1 The characteristic peak at 1646 cm is wider and more prominent, indicating that the added cross-linker ethylene glycol diglycidyl ether has a cross-linking reaction with CF and chitosan. -1 The peak at 1584 cm -1 The peak of Na + In 2-M aerogel triboelectric materials, Na + The complexation with -OH and -NH2 reduces the groups that can form hydrogen bonds, so at 3200cm -1 ~3500cm -1 The absorption band intensity weakens within this range. 2+ 2-M, Fe 3+ 2-M and Al 3+ 2-M aerogel, 3200 cm-1 ~3500cm -1 The absorption band intensity increases within the range of 1.5 to 2.5, which is due to the stronger binding ability of divalent and trivalent metal ions with cellulose, which improves the dispersion of cellulose in the solution and increases the distance between molecular chains, resulting in more active groups exposed. The characteristic peak positions of CS-0.5 and CS-0.7 are similar to those of Mg 2+ The characteristic peak positions of 2-M aerogel are basically consistent, but the peak intensities vary significantly. This is due to the changes in the relative proportions of the components, which cause changes in the proportions of hydrogen bonding, covalent cross-linking, and ion complexation.

[0103] Figure 3 Mg prepared in Example 3 of the present invention 2+ X-ray diffraction patterns of 2-M aerogel, CS powder, CF / CS aerogel prepared in Comparative Example 1, and CF fiber prepared in Comparative Example 2. Figure 3 As shown, the X-ray diffraction patterns of CS powder, CF fiber, CF / CS aerogel and Mg 2+ The evolution of the crystal structure of 2-M aerogel. First, the X-ray diffraction patterns of chitosan powder and chitosan fiber show similar diffraction peaks at 10.5° and 20°, but the diffraction peak intensity of chitosan fiber is significantly reduced; the X-ray diffraction pattern of CF fiber shows typical cellulose I phase diffraction peaks at 16.5° and 22.5°. 2+ All diffraction peaks of CF and CS can be observed in 2-M aerogel, but the peak intensities are reduced, indicating that the crystallinity of CF and CS in the composite aerogel is reduced, which is conducive to the formation and stabilization of the multi-cross-linked network structure.

[0104] Figure 4 Surface scanning electron micrographs of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in comparative example 1. Figure 4Figure a is a surface scanning electron microscope image of comparative example 1 at a size of 200 μm, Figure b is a surface scanning electron microscope image of embodiment 1 at a size of 200 μm, Figure c is a surface scanning electron microscope image of embodiment 2 at a size of 200 μm, Figure d is a surface scanning electron microscope image of embodiment 3 at a size of 200 μm, Figure e is a surface scanning electron microscope image of embodiment 4 at a size of 200 μm, Figure f is a surface scanning electron microscope image of embodiment 5 at a size of 200 μm, Figure a1 is a surface scanning electron microscope image of comparative example 1 at a size of 50 μm, Figure b1 is a surface scanning electron microscope image of embodiment 1 at a size of 50 μm, Figure c1 is a surface scanning electron microscope image of embodiment 2 at a size of 50 μm, Figure d1 is a surface scanning electron microscope image of embodiment 3 at a size of 50 μm, Figure e1 is a surface scanning electron microscope image of embodiment 4 at a size of 50 μm, and Figure f1 is a surface scanning electron microscope image of embodiment 5 at a size of 50 μm. Figure 4 As shown in the figure, the fibers on the surface of CF / CS aerogel are loosely distributed, some fibers are agglomerated, and the pores are large; + A large number of fibers appeared on the surface of 2-M aerogel triboelectric material; Ca 2+ In the 2-M aerogel triboelectric material, the fibers are arranged more closely and a small amount of fiber aggregation occurs; in the Mg 2+ 2-M, Fe 3+ 2-M、Al 3+ A large number of fibers can be observed in the 2-M aerogel triboelectric material, the degree of fiber adhesion is reduced, and the stacking between fibers is relatively dense.

[0105] Figure 5 Cross-sectional scanning electron micrographs of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in comparative example 1. Figure 5 Figure a is a cross-sectional scanning electron microscope image of comparative example 1 at a size of 200 μm, Figure b is a cross-sectional scanning electron microscope image of embodiment 1 at a size of 200 μm, Figure c is a cross-sectional scanning electron microscope image of embodiment 2 at a size of 200 μm, Figure d is a cross-sectional scanning electron microscope image of embodiment 3 at a size of 200 μm, Figure e is a cross-sectional scanning electron microscope image of embodiment 4 at a size of 200 μm, Figure f is a cross-sectional scanning electron microscope image of embodiment 5 at a size of 200 μm, Figure a1 is a cross-sectional scanning electron microscope image of comparative example 1 at a size of 50 μm, Figure b1 is a cross-sectional scanning electron microscope image of embodiment 1 at a size of 50 μm, Figure c1 is a cross-sectional scanning electron microscope image of embodiment 2 at a size of 50 μm, Figure d1 is a cross-sectional scanning electron microscope image of embodiment 3 at a size of 50 μm, Figure e1 is a cross-sectional scanning electron microscope image of embodiment 4 at a size of 50 μm, and Figure f1 is a cross-sectional scanning electron microscope image of embodiment 5 at a size of 50 μm. Figure 5As shown in Figure 2, the scanning electron microscope image of the cross section of the CF / CS aerogel shows that the fibers are stacked layer by layer and in a low-order state, resulting in a limited number of pores and a wide range of pore sizes. + 2-M aerogel and Ca 2+ The 2-M aerogel lacks order and the formation of hierarchical pores is observed in some areas. 2+ 2-M aerogel, Fe 3+ 2-M aerogel and Al 3+ The 2-M aerogel triboelectric material showed obvious stratification and formed many multi-level pores. 2+ The fibers in the 2-M aerogel triboelectric material exhibit significant order, resulting in a more regular pore arrangement and a relatively complete structure. The layered stacking of the fibers is due to hydrogen bonding between them. While forming a solid aerogel skeleton, a multi-level porosity structure is also formed through a combination of strategies. Furthermore, the complexation properties of different metal ions with CF and CS are significantly different.

[0106] Figure 6 Mg prepared in Example 3 of the present invention 2+ Energy dispersive X-ray spectroscopy analysis of 2-M aerogel. Figure 6 Figure a is a scanning electron microscope image selected from the surface energy dispersion X-ray spectrum analysis of Example 3, Figure b is the C element distribution diagram of Figure a, Figure c is the N element distribution diagram of Figure a, Figure d is the Mg element distribution diagram of Figure a, Figure a1 is a scanning electron microscope image selected from the cross-sectional energy dispersion X-ray spectrum analysis of Example 3, Figure b1 is the C element distribution diagram of Figure a1, Figure c1 is the N element distribution diagram of Figure a1, and Figure d1 is the Mg element distribution diagram of Figure a1. Figure 6 As shown, Mg 2+ The presence of a large amount of N and Mg elements in the skeleton and pore walls of 2-M aerogel further proves that multi-level cross-linking occurs.

[0107] Figure 7 These are the compressive stress-strain and compression modulus diagrams of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in Comparative Example 1. Figure 7 Figure (a) is the compression stress-strain diagram, and Figure (b) is the compression modulus diagram. Figure 7 As shown, under the same strain conditions, CF / CS aerogel and Ca 2+ The compressive strength of 2-M aerogel triboelectric material is high. However, the maximum compressive strain of the two is 40% and 36%, respectively, which is lower than that of other aerogel triboelectric materials. The two exhibit large compression modulus and elastic strain energy, with compression modulus of 0.29MPa and 0.17MPa, respectively, and elastic strain energy of 8.72kJ / m 3 and 40.43 kJ / m 3The CF / CS aerogel shrinks severely during the preparation process, and the shrinkage of the internal structure leads to a dense structure with the largest apparent density of 0.232 g / cm. 2+ 2-M, Na + 2-M、Mg 2+ 2-M, Fe 3+ 2-M and Al 3+ In 2-M aerogel triboelectric materials, Mg 2+ The internal structure of the 2-M aerogel triboelectric material is more ordered, with a better supporting skeleton, and exhibits better mechanical properties. Its compressive stress is 0.37 MPa, and the maximum compression modulus at 50% strain is 0.14 MPa.

[0108] Figure 8 The single compression cycle test graph and residual stress graph of the T2-M aerogel prepared in the embodiment of the present invention and the CF / CS aerogel prepared in comparative example 1 under different strains are shown. Figure 8 Figure (a) is a single compression cycle test diagram under different strains, and Figure (b) is a residual stress diagram. Figure 8 As shown, compression tests were performed on the aerogel samples of Examples 1 to 5 and Comparative Example 1 under different compression strains of 10% to 50%. When performing the compression external force loading-unloading test, all aerogels showed insufficient compression recovery performance. However, for CF / CS aerogel, when the strain conditions were preset to 10% and 20%, the hysteresis loop of the aerogel increased slowly, while at 30% and 40% strain, the hysteresis loop of the aerogel increased significantly. At 40% strain, the residual strain energy reached 27.44%. When the strain setting was further increased, the deformation and rebound of the aerogel could no longer meet the requirements of the test instrument, and thus the hysteresis loop under a larger strain setting could not be obtained. Combined with the surface and cross-sectional SEM results of CF / CS aerogel, it can be seen that there are a large number of large pores and voids inside the aerogel, the interaction between fibers is weak, and the compression resistance of the aerogel is limited, which indicates that its elasticity is poor. Under the same compression strain conditions, the residual strain of the aerogel after the introduction of metal ions is less than that of the CF / CS aerogel. Ca 2+ Under low strain settings of 10% and 20%, the residual strain value of 2-M aerogel is basically close to that of aerogels with other metal ions added, and it shows better resilience than CS / CF aerogel. That is to say, it has better elasticity at small strain. When the strain increases to 30% or even higher, its hysteresis loop increases significantly, and the compressive strength of the aerogel increases sharply, indicating that the aerogel structure may be greatly densified at this time, and its resilience becomes worse. The hysteresis loops of the other ion complex aerogels increase significantly when the strain is greater than 30%. However, Al 3+The hysteresis loop of 2-M aerogel changes relatively slowly as a whole, remains relatively stable, and has low residual strain, indicating that within the strain range of 10%-50%, the permanent deformation of the aerogel is relatively small and the aerogel has good resilience. 2+ At low strain, the 2-M aerogel exhibited a minimum residual strain of 5.22% at a 10% compressive strain, demonstrating optimal resilience under low strain conditions. This is due to the combined effects of the varying forces acting on the micro / nanofiber molecular chains by different ions and the aerogel's microscopic hierarchical pore structure.

[0109] The cellulose-based aerogels prepared in Examples 1 to 5 and Comparative Example 1 were subjected to a wet stability test, comprising the following steps:

[0110] Take CF / CS aerogel and Na + 2-M aerogel, Ca 2+ 2-M aerogel, Mg 2+ 2-M aerogel, Fe 3+ 2-M aerogel and Al 3+ The 2-M aerogel was cut into samples of 15mm×15mm×4mm, immersed in water, and photographed to record its initial state; then, it was magnetically stirred for 30 minutes and manually shaken in the same manner for 2 minutes, and the dispersion of each sample in water was observed and photographed; after 30 days, each sample was manually shaken in the same manner for 2 minutes, and the dispersion of the sample was photographed to record.

[0111] Figure 9 These are the before and after pictures of the wet stability test of the T2-M aerogel prepared in Example and the CF / CS aerogel prepared in Comparative Example 1. Figure 9 Figure a shows the initial state in water, Figure b shows the state after stirring and shaking in water, and Figure c shows the comparison before and after drying after continuous immersion in deionized water for 40 days. Figure 9 As shown, after the sample completely absorbed water, it was mechanically stirred and shaken in the same way and the CF / CS and Na + The 2-M aerogel triboelectric material showed obvious stratification and eventually dissociated, losing its initial complete structure. 2+ 2-M、Mg 2+ 2-M, Fe 3+ 2-M and Al 3+ The 2-M aerogel triboelectric material absorbs water and swells while maintaining its intact structure, with no significant change compared to its initial state. This phenomenon is due to the fact that the interlayer force in the CF / CS aerogel is insufficient to resist the shearing effect of water and vortex, resulting in dissociation. Metal ion complexation can enhance the force, but the complexation ability of metal ions varies. In Na + In 2-M aerogel, Na+ The binding energy with CF and CS is low, so in water, water molecules can easily destroy the complexation between alkali metals and molecular chains, making the aerogel exhibit poor water stability. 2+ Mg 2+ 、Fe 3+ 、Al 3+ The T2-M aerogel triboelectric material was immersed in deionized water for 40 days and then mechanically stirred for 30 minutes. 2+ Mg 2+ 、Fe 3+ 、Al 3+ The aerogel triboelectric materials showed no dissociation, and their structure remained consistent with their initial state. When the samples were removed from the deionized water and dried in a drying oven, the aerogel triboelectric materials were structurally intact and essentially the same size as their initial state.

[0112] The self-powered performance of the cellulose-based aerogels prepared in Examples 7 to 11 and Comparative Example 1 was tested. The cellulose-based aerogels prepared in Examples 7 to 11 were designated T6-M. The T6-M cellulose-based aerogel and perfluoroethylene propylene copolymer film served as the triboelectric positive and negative electrodes, respectively. Two copper sheets were attached to the T6-M aerogel and commercial FEP film as back electrodes and connected to an external circuit. An EVA sponge was used as a separator to separate the two electrodes. The resulting TENG was assembled in contact-separation mode, and its electrical output was measured to evaluate the triboelectric performance of the T6-M aerogel. For comparison purposes, a CF / CS aerogel-based TENG was also assembled using the same method.

[0113] Figure 10 This is a comparison chart of the output voltage of the TENG prepared with T6-M aerogel under different external conditions in the embodiment of the present invention. Figure 10 Figure (a) shows the output voltage at 7Hz and 15N external force, Figure (b) shows the output voltage at 3Hz, 5N and 7Hz, 5N external force, and Figure (c) shows the output voltage at 3Hz, 5N and 3Hz, 15N external force. Figure 10 As shown in Figure (a), under the conditions of action frequency of 7 Hz and action force of 15 N, CF / CS aerogel-based TENG, Na + 6-M aerogel-based TENG, Ca 2 + 6-M aerogel-based TENG, Mg 2+ 6-M aerogel-based TENG, Fe 3+ 6-M aerogel-based TENG and Al 3+The output voltages of the 6-M aerogel-based TENG are 78.9 V, 116.6 V, 73.3 V, 205.1 V, 184.1 V, and 118.5 V, respectively. 2+ The output voltage of 6-M aerogel-based TENG is 7.6% lower than that of CF / CS aerogel-based TENG, while the output voltage of Mg 2+ The output voltage of 6-M aerogel-based TENG is the highest, which is 259.9% higher than that of the 6-M aerogel-based TENG, showing excellent electrical output performance. Under different forces and frequencies, the output voltage enhancement effect of different metal ions on TENG devices is as follows: Ca 2+ <Na + <Al 3+ <Fe 3+ <Mg 2+ .like Figure 10 As shown in Figures (b) and (c), the output voltage of TENG increases significantly with the increase of action frequency and action force. There are induced charges on the contact surface of the aerogel and the interface of the structural network. In this composite aerogel, CS is rich in amino groups with excellent electron-donating properties and a large number of hydroxyl groups, which are beneficial to enhancing the dielectric properties of the composite aerogel. The high specific surface area of ​​the aerogel enables more electrostatic induction formation sites. Molecular entanglement and liquid phase exchange cause the aerogel to form a rough micro / nano surface, further increasing the effective contact area. After the introduction of metal ions, the crystallinity of CS and CF decreases, further enhancing the interfacial polarization effect, and complexing with molecular chains to form nanopores, providing a stable charge migration path for the free movement of electrons, thereby improving the transmission performance of electrons and ions. The distance between the charge centers is enlarged by hybridization of ions with CF and CS molecules, causing electrons to deviate from CF molecules and CS molecules, increasing the dipole moment. Na + There are a lot of fiber adhesions on the surface of 6-M aerogel, and there are relatively few surface pores. 2+ The structure of 6-M aerogel is relatively dense, but the compressive performance of aerogel is poor, and the resilience of both is low, which is not conducive to charge accumulation. 2+ 、Fe 3+ and Al 3+ In the aerogel, metal ions form a stable multi-network complex multi-level porous structure with CF and CS. 2+ A relatively complete ordered multi-level pore structure is formed inside the 6-M aerogel, which has a dense structure and good resilience. It can produce greater deformation during operation, resulting in an increase in the potential difference between the upper and lower electrodes when released, generating more additional triboelectric charges and enhancing the electrostatic effect.

[0114] Figure 11 This is a comparison chart of the output voltages of the cellulose aerogel-based TENGs prepared in Examples 3, 6, and 7 of the present invention at different thicknesses. Figure 11 Figure (a) shows the output voltage, Figure (b) shows the output performance and contact area, Figure (c) shows the thickness relationship, and Figure (d) shows the output voltage and output power density of the external load resistor. Figure 11 As shown in Figure (a), the more metal ions in the aerogel, the stronger the surface polarity, thereby improving the output performance of TENG. Figure 11 As shown in Figure (b), the output voltage of the TENG device increases proportionally with the effective contact area. In addition, the thickness of the aerogel also affects the output performance of the TENG, such as Figure 11 As shown in Figure (c), when Mg 2+ When the thickness of 6-M aerogel is 2mm, 3mm, 4mm and 5mm, the output voltage of TENG is 97.9V, 117.7V, 205.8V and 171.9V respectively. When the thickness of aerogel is 4mm, the output voltage of TENG is the highest. When the thickness of aerogel is 2mm, the specific surface area is relatively small, the number of active sites is limited, the electrode charge accumulation is small, and the output performance of TENG is relatively weak. As the thickness of aerogel increases, the specific surface area of ​​aerogel also increases, which is conducive to the generation of additional charge through electrostatic storage and electrostatic induction. However, when the thickness exceeds 4mm, since the further stacked aerogel structure is far away from the contact active interface, the accumulated induced charge density is low, the deformation amplitude of the aerogel structure is reduced, and the charge transfer is hindered, resulting in a decrease in the output performance of TENG. In summary, based on Mg 2+ The TENG of 6-M aerogel has the best triboelectric output performance. When the operating frequency is 7Hz, the external force is 15N, the contact area is 5cm×5cm, and the thickness is 4mm, the electrical output performance of TENG is the best, and the output voltage reaches 205.8V. In order to explore its output performance in the actual circuit of the external load, the Mg 2+ 6-M aerogel-based TENG connected to different resistance values ​​(10 4 Ω~10 7 Ω) resistor to test its output voltage and power. Figure 11 As shown in Figure (d), as the load resistance increases, the output voltage increases with the resistance. 2 / (RS), where U, R, and S are the output voltage, the resistance of the external resistor, and the contact area of ​​the friction electrode, respectively) shows a trend of first increasing and then decreasing. 7 The maximum power density at Ω is 581.16mW / m 2 After 5000 cycles, Mg 2+ The 6-M aerogel-based TENG still has stable electrical output performance, and as the test time increases, the output voltage of the TENG increases from the initial 169.1 V and remains at 202.8 V.

[0115] Mg 5cm×5cm 2+ 6-M aerogel was used as the triboelectric positive electrode material, and FEP was used as the negative electrode material to assemble TENG. The triboelectric output performance under different humidity environments was tested at an operating frequency of 1 Hz and a force of 20 N.

[0116] Figure 12 For example 7Mg of the present invention 2+ Triboelectric output performance diagram of TENG prepared by 6-M aerogel under different humidity environments. Figure 12 (a) is the output voltage diagram, (b) is the output voltage data fitting diagram, and (c) is the output current diagram. Figure 12 As shown in Figure (a), when the humidity changes from 40%RH to 70%RH, the output voltage of TENG decreases slightly, from 165.9V to 148.2V, while when the humidity increases from 70%RH to 90%RH, the output voltage decreases more significantly, from 148.2V to 73.9V. Figure 12 As shown in Figure (b), the linear fitting of the output voltage and relative humidity changes is R1 2 and R2 2 They can reach 0.972 and 0.998 respectively. This is because although free water has a dissipative effect on charge, the accumulation of water molecules will form a "water bridge", thereby increasing the electron capacity. Under low humidity conditions, a large number of water molecules will be adsorbed on the surface to form a gas-liquid interface, thereby reducing the dissipation of charge by free water molecules. At the same time, the diffusion of water molecules into the interior of the aerogel can effectively improve the ability of the electron donor, which is beneficial to charge transfer, thereby inhibiting the dissipative effect of free water to a certain extent, and the voltage output of the aerogel decreases less. However, with the continuous increase in humidity, especially when the ambient humidity reaches above 80% RH, the excess free water molecules on the surface and inside of the aerogel will lead to increased charge dissipation and enhanced electrostatic shielding effect, thereby significantly reducing the voltage output of TENG, which is consistent with the above. Figure 12 The pattern of TENG output current changing with humidity is consistent with that in Figure (c).

[0117] Figure 13 For example 7Mg of the present invention 2+ The output voltage fitting diagram of the TENG prepared by 6-M aerogel in continuous humidity cycle test. Figure 13 As shown, by maintaining continuous contact-separation cycles and adjusting the ambient humidity from 40% RH to 95% RH, it can be observed that the output voltage of TENG decreases from 161.9 V at the beginning to 41.8 V with the increase of ambient humidity. After that, by quickly reducing the humidity to 40% RH, the output voltage of TENG increases to 162.6 V, showing good wet-responsive cycling characteristics and reversibility.

[0118] Utilize Mg 2+ 6-M aerogel constructed single-electrode mode TENG, Mg 2+ Copper electrodes and acrylic plates were placed on top of the 6-M aerogel, and then 2+ A speaker was placed beneath the 6-M aerogel, forming a single-electrode TENG. The speaker was then connected to a computer via Bluetooth. The computer played audio signals, and an electrometer recorded the TENG's electrical output signal, thereby evaluating the TENG's sound recognition properties.

[0119] Figure 14 For example 7Mg of the present invention 2+ Comparison of electrical signals detected by the TENG constructed with 6-M aerogel and audio signals of different biological and non-biological sounds. Figure 14 Figure (a) is a comparison of drumming sound signals, Figure (b) is a comparison of dog barking sound signals, Figure (c) is a comparison of thunder and lightning sound signals, Figure (d) is a comparison of firewood burning sound signals, and Figure (e) is a comparison of a continuous section of piano sound signals. Figure 14 As shown in the figure, by comparing the converted waveforms of non-biological and biological audio signals with different characteristics with the output voltage signal of the TENG, it was found that the TENG responded quickly to these sounds. In addition, the output voltage signal showed high consistency, stability, and repeatability with the audio signal.

[0120] The Mg used in the TENG was assembled and tested. 2+ The 6-M aerogel and the remaining scraps were placed normally for 30 days, then cut and mixed, deionized water was added and stirred at high speed to make the mixture uniform, and then 50% of the newly prepared CF / CS solution and 50% of the cross-linking agent and metal ions were added to re-prepare the aerogel sample, which was named Mg 2+ 6-MM O-N , assembled into a vertical contact detachable TENG.

[0121] Figure 15 For example 7Mg of the present invention 2+ Comparison chart of 6-M aerogel recyclability performance, Figure 15 Figure (a) is a comparison of the output voltages of different aerogel-based TENGs, Figure (b) is a comparison of the output currents of the new and old aerogel-based TENGs, and Figure (c) is a comparison of the transfer charges of the new and old aerogel-based TENGs. Figure 15 As shown, Mg 2+ 6-MM O-N The output voltage of the TENG constructed with aerogel is 205.5V, which is comparable to that of the TENG based on Mg 2+ The TENG of 6-M aerogel is basically the same, and the output current and transferred charge are also basically the same.

[0122] Figure 16 This is a diagram showing the degradation process of the aerogels of Examples 1 to 3 of the present invention and the comparative example CF / CS aerogel. Figure 16 Figure i is the initial state diagram, figure ii is the state diagram after being placed in the container for 30 days, figure iii is the state diagram after being transferred to the natural environment for 10 days, and figure iv is the state diagram after being transferred to the natural environment for 30 days. Figure 16 As shown, fresh soil was placed in a dry plastic container, and CF / CS, Na + 2-M、Mg 2+ 2-M and Ca 2+ 2-M aerogels were buried in dry plastic containers to observe the degradation of the gel. After 20 days, the aerogels were dry but the structure was intact. After 30 days, they became brittle. 2+ The 2-M aerogel was obviously broken. The sample was then buried directly in outdoor soil. After 10 days, the sample further shrank. 2+ The 2-M aerogel fragmented into small pieces. After 30 days of burial, all the aerogel had degraded and disappeared. This demonstrates the good recyclability, durability, and biodegradability of aerogels.

[0123] It should be noted that when numerical ranges are mentioned in the present invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints may be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0124] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a cellulose-based aerogel triboelectric material, characterized in that: The following steps are involved: Dissolving the first chitosan in the first acid solution to form a first precursor solution, stirring and adjusting the pH value to alkaline to perform gelation, and then adding a first cross-linking agent to perform a first cross-linking reaction to obtain a first chitosan micron-sized fiber; The mass volume ratio of the first chitosan, the first cross-linking agent and the first acid solution is 0.5 g to 0.9 g: 0.1 g to 0.18 g: 40 mL; The second chitosan is dissolved in the second acid solution to form a second precursor solution, stirred and adjusted to an alkaline pH value to perform gelation, and then homogenized and a second cross-linking agent is added to perform a second cross-linking reaction to obtain the second chitosan micro / nano-scale fibers; The mass volume ratio of the second chitosan, the second cross-linking agent and the second acid solution is 0.05g-0.1g:0.01g-0.02g:20mL; The first chitosan micron-sized fiber and the second chitosan micro / nano-sized fiber are sequentially added to the homogenized cellulose fiber dispersion, and after being evenly mixed, a water-soluble metal salt and a third cross-linking agent are sequentially added. After stirring and dispersing, a third cross-linking reaction is performed, and after the reaction is completed, the product is frozen to obtain a cellulose-based aerogel precursor. The cellulose-based aerogel precursor is immersed in a solvent for solvent replacement, and the cellulose-based aerogel triboelectric material is obtained after extrusion and drying; The water-soluble metal salt is at least one of a water-soluble copper salt, a water-soluble aluminum salt, a water-soluble magnesium salt, a water-soluble calcium salt, and a water-soluble iron salt; The stirring rate of the first precursor liquid is 1000 rpm to 2000 rpm, and the stirring rate of the second precursor liquid is 500 rpm to 1000 rpm; The first cross-linking agent, the second cross-linking agent and the third cross-linking agent are all glycidyl ethers.

2. The method for preparing a cellulose-based aerogel triboelectric material according to claim 1, characterized in that: The first acid solution is hydrochloric acid, and the concentration of the hydrochloric acid is 0.05M to 0.2M.

3. The method for preparing a cellulose-based aerogel triboelectric material according to claim 1, characterized in that: The second acid solution is hydrochloric acid, and the concentration of the hydrochloric acid is 0.05M to 0.2M.

4. The method for preparing a cellulose-based aerogel triboelectric material according to claim 1, characterized in that: The mass ratio of the cellulose fiber, the first chitosan micron-scale fiber and the second chitosan micro / nano-scale fiber in the cellulose fiber dispersion is 1g: 0.5g-0.9g: 0.05g-0.1g.

5. The method for preparing a cellulose-based aerogel triboelectric material according to claim 1, characterized in that: The mass ratio of the cellulose fibers to the water-soluble metal salt in the cellulose fiber dispersion is 0.04 g to 0.12 g per gram, and the mass ratio of the cellulose fibers to the third crosslinking agent in the cellulose fiber dispersion is 0.1 g to 0.2 g per gram.

6. The method for preparing a cellulose-based aerogel triboelectric material according to claim 1, characterized in that: The glycidyl ether is ethylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether; the temperatures of the first cross-linking reaction, the second cross-linking reaction and the third cross-linking reaction are all 50° C. to 70° C., and the reaction time is all 4 h to 6 h.

7. The method for preparing a cellulose-based aerogel triboelectric material according to claim 1, characterized in that: The freezing temperature is -2°C to -10°C, and the time is 1h to 3h. The solvent replacement is to immerse the cellulose-based aerogel precursor in anhydrous ethanol and let it stand for 2h to 4h.

8. A cellulose-based aerogel triboelectric material, characterized in that: The preparation method is described in any one of claims 1 to 7.

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