Prediction method of surface charge density of triboelectric nanogenerator based on modified chitosan material

Abstract

The present invention belongs to the field of nanoenergy and provides a method for predicting the surface charge density of a triboelectric nanogenerator based on a modified chitosan material. The method comprises the following steps: S1, preparing the modified chitosan; S2, testing and quantitatively characterizing the triboelectric polarity of the modified chitosan; S3, obtaining the surface potential energy and saturation charge density of the modified chitosan and its paired material; and S4, constructing a surface charge density prediction model for a triboelectric nanogenerator based on the modified chitosan material. The present invention can directly calculate the surface charge density of a triboelectric nanogenerator based on the modified chitosan material based on the degree of modification of the modified chitosan material, providing a solid theoretical basis for further research into the application of chitosan in the field of triboelectricity.

Description

Technical Field

[0001] The present application relates to the field of nano energy, and in particular to a method for predicting the surface charge density of a triboelectric nanogenerator based on modified chitosan material. Background Art

[0002] Triboelectric nanogenerators (TENGs) are a promising solution for converting mechanical energy into electrical energy, providing a self-sustaining power source for the development of electronic technologies. Material selection is crucial for improving TENG performance. Materials are arranged in a triboelectric series based on their propensity to gain or lose electrons, and this behavior is significantly influenced by the electron affinity of surface functional groups. In the field of implantable medical devices, the lack of materials with negative triboelectric polarity makes it difficult to develop effective, high-performance bio-TENGs designed entirely from biomaterials. Therefore, it is necessary to modify and design existing biomaterials to develop high-performance negative-polarity biomaterials. Simultaneously, models are being developed to optimize and predict the triboelectric properties of these materials.

[0003] Chitosan, a biopolymer derived from chitin, has become a promising triboelectric material due to its biocompatibility, degradability, and natural abundance. In previous triboelectric research, chitosan has been used exclusively as a positive triboelectric material. While numerous efforts have been made to improve its triboelectric output performance, including progress in physical doping and ion intercalation, the mechanisms of chitosan triboelectric polarity modification and related predictive models have been understudied. Designing surface functional groups and molecular structure can increase charge density and even alter triboelectric polarity. Chitosan contains numerous amino and hydroxyl groups, which contribute significantly to its electron-donating capacity and are potential sites for chemical modification. This suggests that surface chemical modification has the potential to alter triboelectric charge behavior and improve the degree of modification. Therefore, predicting the surface charge density of triboelectric nanogenerators using modified chitosan materials would be crucial for optimizing the triboelectric polarity and enhancing their electrical output performance. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, the present invention aims to propose a method for predicting the surface charge density of a triboelectric nanogenerator based on modified chitosan materials. Chitosan is modified with polyphenols to achieve a triboelectric polarity shift. Microscopic characterization techniques are then used to quantify key parameters, and a surface charge density prediction model for a triboelectric nanogenerator based on modified chitosan materials is constructed. The research encompasses chitosan modification, triboelectric polarity testing and quantitative characterization, and predictive model construction. This involves modifying different forms of chitosan with specific polyphenols, testing triboelectric nanogenerators with commonly used triboelectric materials, and using multiple techniques to acquire data, construct models, and verify and optimize them. This research can fill a gap in chitosan-related research, facilitate the development of high-performance bio-TENGs, and promote their application in biomedical fields. It can also pave the way for the research and development of novel bio-triboelectric materials, and is of great significance to the development of TENGs and biomaterials science.

[0005] To solve the above problems, the present invention provides a method for predicting the surface charge density of a triboelectric nanogenerator based on modified chitosan material, which comprises the following steps:

[0006] S1. Preparation of modified chitosan:

[0007] Polyphenol is used as a modification material to chemically modify chitosan to obtain modified chitosan.

[0008] S2. Triboelectric polarity testing and quantitative characterization of modified chitosan:

[0009] The modified chitosan is brought into contact with different materials in a known triboelectric series to generate an electrical signal, and the relative positive and negative values ​​of the electrical signal and the saturation charge density are obtained. The position of the modified chitosan in the known triboelectric series is determined based on the relative positive and negative values ​​of the electrical signal;

[0010] S3. Obtain the surface potential energy and saturated charge density of the modified chitosan and the paired material:

[0011] A triboelectric nanogenerator is composed of modified chitosan and a pairing material, and the surface potential energy of the pairing material, the surface potential energy of the modified chitosan, and the saturated charge density of the triboelectric nanogenerator during the contact and separation process are obtained respectively.

[0012] S4. Construction of a surface charge density prediction model for triboelectric nanogenerators based on modified chitosan materials:

[0013] The surface charge density prediction model of the triboelectric nanogenerator based on modified chitosan material is:

[0014] σ c =a(V1-V2) 2 -b(V1-V2)-c

[0015] C p =f(V2)

[0016] Where: σ c is the surface charge density of the triboelectric nanogenerator; V1 is the surface potential energy of the paired material; V2 is the surface potential energy of the modified chitosan; a, b and c are the fitting parameters corresponding to different paired materials; C p is the polyphenol concentration; f is the functional relationship between the polyphenol concentration and the surface potential energy of the modified chitosan;

[0017] According to the surface charge density prediction model of the friction nanogenerator based on modified chitosan material, when the pairing materials are determined, the surface charge density of the friction nanogenerator can be directly determined according to the polyphenol concentration; thereby guiding the optimization of the friction electric polarity of the modified chitosan and improving the electrical output performance of the friction nanogenerator.

[0018] Preferably, step S1 specifically includes:

[0019] S11, prepare polyphenol solution: dissolve polyphenol in solvent to form polyphenol concentration C p The solution, the C p The value range is (0%, 50%]; the solvent is a mixture of one or more of deionized water, ethanol, acetone and tetrachloromethane;

[0020] S12, preparing a chitosan solution: dissolving chitosan in an acid solvent and cleaning it to remove impurities and pollutants to obtain a chitosan solution; the acid solvent is a mixture of one or more of acetic acid, hydrochloric acid, nitric acid and phosphoric acid;

[0021] S13, mixing the chitosan solution of S12 with the polyphenol solution of S11, and then placing the mixture in a mold for drying to obtain modified chitosan.

[0022] Preferably, the materials in the known triboelectric sequence in step S2 include but are not limited to polyamide, thermoplastic polyurethane, polypropylene, polyethylene terephthalate, polydimethylsiloxane, polytetrafluoroethylene and polyperfluoroethylene propylene.

[0023] Preferably, step S3 specifically includes the following sub-steps:

[0024] S31, forming a triboelectric nanogenerator by combining modified chitosan and a matching material, wherein the triboelectric nanogenerator is in a contact-separation mode;

[0025] S32, measuring the charge signal of the contact and separation process using an electrometer, and obtaining the saturation charge density of the triboelectric nanogenerator through the signal amplitude;

[0026] S33. The surface potential energy of the modified chitosan material and the surface potential energy of the paired material during the contact separation process were measured using a scanning Kelvin probe microscope.

[0027] Preferably, step S4 specifically includes the following sub-steps:

[0028] S41. Based on the surface potential energy, a surface charge density prediction model of the triboelectric nanogenerator in step S3 is constructed, and its expression σ c for:

[0029] σ c =a(V1-V2) 2 -b(V1-V2)-c (1)

[0030] Where: σ cis the surface charge density of the triboelectric nanogenerator; V1 is the surface potential energy of the paired material; V2 is the surface potential energy of the modified chitosan; a, b and c are the fitting parameters corresponding to different paired materials;

[0031] S42, due to the surface charge density σ c It cannot be directly measured and obtained, the saturation charge density σ must be measured first I , and then calculated through the expression, the expression is:

[0032]

[0033] Where: z is the separation distance between the paired material and the modified chitosan; d1 and d2 are the thicknesses of the paired material and the modified chitosan, respectively; ε0 is the dielectric constant of air; ε1 and ε2 are the dielectric constants of the paired material and the modified chitosan, respectively;

[0034] S43. The surface potential energy of modified chitosan is related to the degree of modification, which in turn corresponds to the polyphenol concentration. Therefore, a surface potential energy model of modified chitosan material is established based on the polyphenol concentration:

[0035] V2=f(C p ), (3)

[0036] Where: C p is the polyphenol concentration;

[0037] S44. According to formulas (1) and (3), a surface charge density prediction model of the friction nanogenerator based on modified chitosan is obtained. When different pairing materials are used to form a friction nanogenerator with the modified chitosan material, a surface charge density prediction model of the friction nanogenerator based on the modified chitosan material with different fitting parameters is obtained. The surface charge density prediction model of the friction nanogenerator based on modified chitosan using different pairing materials can directly obtain the surface charge density of the friction nanogenerator according to the polyphenol concentration, thereby guiding the optimization of the friction electric polarity of the modified chitosan and improving the electrical output performance of the friction nanogenerator.

[0038] Preferably, the chitosan in step S1 includes but is not limited to non-deacetylated chitin, chitosan with different degrees of deacetylation, quaternary ammonium salt chitosan and carboxymethyl chitosan.

[0039] Preferably, the polyphenols in step S1 include but are not limited to tannic acid, catechin, dopamine and anthocyanin.

[0040] Preferably, the form of the modified chitosan in step S1 includes but is not limited to film, hydrogel, aerogel and block.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The present invention can directly obtain the surface charge density of the triboelectric nanogenerator based on the modified chitosan material according to the modification degree of the modified chitosan material, effectively filling the current research gap in the modification mechanism and prediction model of triboelectric polarity of chitosan, and providing a solid theoretical basis for subsequent in-depth exploration of the application of chitosan in the field of triboelectricity.

[0043] 2. The successful development of high-performance bio-TENG has strongly promoted the widespread application of triboelectric nanogenerators in fields such as implantable devices, providing new ideas and technical means to solve the energy supply problem of equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the chemical interaction mechanism of chitosan modified with tannic acid in the present invention;

[0045] Figure 2 1 is a comparison diagram of Fourier transform infrared spectra of chitosan before and after modification in an embodiment of the present invention;

[0046] Figure 3 1 is a comparison diagram of X-ray photoelectron spectra of chitosan before and after modification in an embodiment of the present invention;

[0047] Figure 4 1 is a comparison diagram of the surface roughness of chitosan before and after modification in an embodiment of the present invention;

[0048] Figure 5 1 is a comparison diagram of X-ray diffraction of chitosan before and after modification in an embodiment of the present invention;

[0049] Figure 6 1 is a comparison chart of the mechanical properties of chitosan before and after modification in an embodiment of the present invention;

[0050] Figure 7 Schematic diagram of the structure of a triboelectric nanogenerator based on modified chitosan in an embodiment of the present invention;

[0051] Figure 8 The saturated charge density and triboelectric polarity generated by chitosan and different paired materials before and after modification in the embodiments of the present invention;

[0052] Figure 9 is the surface potential energy of the paired materials, chitosan before and after modification in the embodiment of the present invention;

[0053] Figure 10 Parameter fitting of the surface charge prediction model of tannic acid modified chitosan in the embodiment of the present invention.

[0054] Figure 11 : represents the position of modified chitosan with different modification degrees in the triboelectric series in the embodiments of the present invention.

[0055] Figure 12 Flow chart for predicting the surface charge density of the triboelectric nanogenerator based on modified chitosan material of the present invention DETAILED DESCRIPTION

[0056] A method for predicting the surface charge density of triboelectric nanogenerators based on modified chitosan materials, such as Figure 12 As shown, the following steps are included:

[0057] S1. Preparation of modified chitosan:

[0058] Polyphenol is used as a modification material to chemically modify chitosan to obtain modified chitosan. The specific steps are:

[0059] S11, prepare polyphenol solution: dissolve polyphenol in solvent to form polyphenol concentration C p The polyphenol solution, the C p The value range is (0%, 50%].

[0060] Polyphenol concentration refers to the weight ratio of polyphenol to chitosan. The polyphenol solution prepared according to the polyphenol concentration is called a polyphenol solution with a polyphenol concentration of C. p The solvent is a mixture of one or more of deionized water, ethanol, acetone and tetrachloromethane. Polyphenols include but are not limited to tannic acid, catechin, dopamine and anthocyanidin.

[0061] S12, preparing a chitosan solution: dissolving chitosan in an acid solvent and performing a cleaning process to remove impurities and contaminants to obtain a chitosan solution;

[0062] The acid solvent is a mixture of one or more of acetic acid, hydrochloric acid, nitric acid and phosphoric acid.

[0063] Chitosan includes, but is not limited to, non-deacetylated chitin, chitosan with different degrees of deacetylation, quaternary ammonium chitosan, or carboxymethyl chitosan.

[0064] S13, mixing the pretreated chitosan solution with the polyphenol solution, and then placing the mixture in a mold for drying to obtain a modified chitosan material.

[0065] The forms of modified chitosan include, but are not limited to, films, hydrogels, aerogels, and monoliths.

[0066] Using polyphenol solutions with different polyphenol concentrations will produce modified chitosan with different properties. This is because the reaction between polyphenols and chitosan causes changes in chitosan properties. Using different polyphenol concentrations will result in different amino group contents consumed, and therefore different polyphenol concentrations will result in different degrees of modification. The degree of modification is defined as the amino group content consumed by the modification, quantified using elemental analysis techniques. X-ray photoelectron spectroscopy can be used to characterize the changes in the chemical bonds formed by the reaction between polyphenols and chitosan, thereby obtaining the degree of modification corresponding to different polyphenol concentrations.

[0067] S2. Triboelectric polarity testing and quantitative characterization of modified chitosan

[0068] The modified chitosan obtained from S1 was placed in contact with different materials in a known triboelectric series to generate an electrical signal. The electrical signal during the contact-separation process was measured to obtain the saturated charge density. The triboelectric polarity of the chitosan was determined based on the relative positive and negative values ​​of the electrical signal. This allowed the position of the modified chitosan from S1 in the triboelectric series to be determined.

[0069] The saturation charge density can be measured using an electrometer. The specific method is as follows: the electrometer measures the charge signal of the contact and separation process, and obtains the saturation charge density through the signal amplitude, and obtains the triboelectric polarity by displaying the relative positive and negative waveforms.

[0070] The triboelectric series refers to the regular sequence of the magnitude and positive and negative charges of two different substances when they are rubbed together. Known materials in the triboelectric series include but are not limited to polyamide, thermoplastic polyurethane, polypropylene, polyethylene terephthalate, polydimethylsiloxane, polytetrafluoroethylene and polyperfluoroethylene propylene. Modified chitosan materials with different degrees of modification will have different positions in the triboelectric series, such as Figure 11 shown.

[0071] S3. Obtain the surface potential energy and saturated charge density of the modified chitosan and the paired material:

[0072] S31. According to the measured triboelectric polarity of the modified chitosan, a pairing material is selected, and a triboelectric nanogenerator is formed by the modified chitosan and the pairing material, such as Figure 7 As shown, the triboelectric nanogenerator is in contact-separation mode; the paired material is a material in the known triboelectric series;

[0073] S32. Measure the saturated charge density of the modified chitosan and the paired material during the contact separation process. The same method as in S2 can be used, that is, use an electrometer to measure the charge signal of the contact separation process, and obtain the saturated charge density through the signal amplitude; if the saturated charge density of the friction nanogenerator has been measured in step S2, it can be used here directly without measuring again.

[0074] S33. Quantify the material's potential energy using surface potential analysis techniques. In this example, the surface potential energy of the modified chitosan and the surface potential energy of the paired material during the contact-separation process was measured using a scanning Kelvin probe microscope. If the surface potential energy of the paired material or the modified chitosan is known, it can be used directly without further measurement.

[0075] S4. Construction of a surface charge density prediction model for triboelectric nanogenerators based on modified chitosan materials:

[0076] S41. Based on the surface potential energy, a surface charge density prediction model of the triboelectric nanogenerator in step S3 is constructed, and its expression σ c for:

[0077] σ c =a(V1-V2) 2 -b(V1-V2)-c (1)

[0078] Where: σ c is the surface charge density of the friction nanogenerator; V1 is the surface potential energy of the paired material; V2 is the surface potential energy of the modified chitosan; a, b and c are the fitting parameters corresponding to different paired materials; the surface charge density of the friction nanogenerator in this embodiment represents the surface charge density generated between the two materials used in the friction nanogenerator.

[0079] S42, due to the surface charge density σ c It cannot be directly measured and obtained, the saturation charge density σ must be measured first I , and then calculated through the expression, the expression is:

[0080]

[0081] Where: z is the separation distance between the paired material and the modified chitosan; d1 and d2 are the thicknesses of the paired material and the modified chitosan, respectively; ε0 is the dielectric constant of air; ε1 and ε2 are the dielectric constants of the paired material and the modified chitosan, respectively;

[0082] S43. It can be seen that the surface charge density of the triboelectric nanogenerator is determined by the surface potential energy of the modified chitosan and the surface potential energy of the paired material. In the triboelectric nanogenerator, the surface potential energy of each material has a fixed value, that is, the surface potential energy of the paired material can be directly determined based on the paired material energy. The surface potential energy of the modified chitosan is related to the degree of modification, which in turn corresponds one-to-one with the polyphenol concentration. Therefore, a surface potential energy model for the modified chitosan can be established based on the polyphenol concentration:

[0083] V2=f(C p ), (3)

[0084] Where: Cp is the polyphenol concentration;

[0085] The surface potential energy model of modified chitosan can be determined by using the point drawing method or fitting method.

[0086] S44, formula (1) and (3) are combined to obtain the modification concentration and surface charge density prediction model of the modified chitosan-based tribonanogenerator.

[0087] When different pairing materials are used with modified chitosan materials to form a friction nanogenerator, a surface charge density prediction model of the friction nanogenerator based on the modified chitosan material with different fitting parameters is obtained. In actual use, the surface charge density prediction model of the friction nanogenerator based on the modified chitosan using different pairing materials can directly obtain the surface charge density of the friction nanogenerator based on the modified chitosan material with different modification degrees, without the need for complex testing, thereby guiding the optimization of the friction electric polarity of the modified chitosan and improving the electrical output performance of the friction nanogenerator.

[0088] In a specific embodiment of the present invention, chitosan is modified using tannic acid solutions of different concentrations to obtain modified chitosan films.

[0089] In the process of example verification, different contents of tannic acid, specifically tannic acid / chitosan weight ratios of 0%, 5%, 10%, 15%, and 20%, where 0%, 5%, 10%, 15%, and 20% are different polyphenol concentrations, were added to the chitosan matrix through a simple neutralization process at room temperature to obtain uniformly mixed chitosan / tannic acid composite films (CS, CT5, CT10, CT15, and CT20), where the first CT is the modified chitosan and the number after it is the polyphenol concentration after removing the percentage sign. Figure 1 As shown in Figure 2, the cross-linked network of the composite membrane is formed by hydrogen bonds and covalent bonds. Tannic acid and chitosan interact through Schiff base reaction to form imine bonds. Figure 2 CS, CT10 and CT20 films were further characterized by ATR-FTIR spectroscopy at 3250 cm -1 (NH and OH stretching), 1648 cm -1 (-NHCO- bond) and 1540cm -1 A characteristic absorption band was found at (NH bending), which is consistent with the inherent chemical structure of chitosan. In addition, the CT20 film has a peak absorption band at 1718 cm -1 There is a weak peak at 3500-3000 cm, which is the characteristic of the carbonyl (C=O) group of tannic acid. In the CT10 and CT20 films, the hydrogen bonding interaction between tannic acid and the -OH and -NH2 groups in chitosan is at 3500-3000 cm -1There is a clear expansion zone in between.

[0090] The surface amino composition of chitosan membrane was revealed by X-ray photoelectron spectroscopy (XPS) N1s spectrum (see Figure 3 ). Table 1 summarizes the relative content of consumed amino groups. The change in -NH2 content between CT membrane and CS membrane can be used as an indicator of the degree of Schiff base reaction. Figure 4 The surface morphology of the membranes was observed using atomic force microscopy (AFM), and the calculated root mean square roughness was 3.43, 9.21, and 11.86 nm, respectively. The introduction of tannic acid enhanced the surface roughness at the nanoscale through intermolecular cross-linking, resulting in increased exposure of functional groups on the membrane surface. The crystal structure of the chitosan film was characterized by X-ray diffraction (XRD), as shown in Figure 2. Figure 5 As shown. The XRD spectrum of the CS film shows that the diffraction peaks are located at 2θ = 8.5°, 11.6° (two hydrated crystal peaks) and 22.4° (amorphous diffraction peak). After the addition of tannic acid, the peak intensities at 8.5°, 11.6° and 20.0° decreased, indicating that the cross-linking between chitosan and tannic acid molecules reduced the crystallinity of the CT film. In addition, the increase in tannic acid content caused the amorphous diffraction peak of tannic acid at 25.0° in the CT film to shift slightly upward. The addition of tannic acid affects the interaction between molecules and may also affect the structural arrangement within the membrane, thereby changing the physical properties of the membrane. Figure 6 Tensile strain-stress curves of CS and CT films characterizing the mechanical properties of the materials. The CS film exhibited a tensile strength of 25.2 MPa and an elongation at break of 46.2%. In comparison, the CT10 film exhibited a significantly higher tensile strength of 55.8 MPa. However, the CT20 film exhibited the highest tensile strength but a significantly lower elongation at break of only 7.43%. This reduction in ductility is a result of the increased tannic acid content, which promotes a higher crosslinking density and thus reduces the flexibility of the chains. Therefore, the CT10 film exhibits considerable mechanical strength and flexibility, making it suitable for flexible TENGs and sensors.

[0091] In order to study the triboelectric properties of CS and CT films, a TENG (triboelectric nanogenerator) was fabricated for electrical characterization. Figure 7 Shown is a 2×2cm 2 The device structure consists of CS / CT film, triboelectric material and copper foil. Various triboelectric materials, including polyamide (PA), thermoplastic polyurethane (TPU), aluminum (Al), paper (Paper), polypropylene (PP), polyethylene terephthalate (PET), commercial polyimide (Kapton), polydimethylsiloxane (PDMS) and fluorinated ethylene propylene (FEP), are used as another triboelectric layer. Figure 8As shown, the collected transfer charge curves indicate that under contact and separation operations, the CS pair presents consistent curves with all corresponding materials. Considering the strong negative polarity of FEP and the positive polarity of chitosan in the triboelectric series reported in previous studies, it can be inferred that CS has a more positive charge behavior than PA. However, CT10 presents opposite curves when in contact with PP and PET, indicating that the polarity of CT10 is between PP and PET. Compared with CT10, CT5 exhibits less negative charge behavior and is between paper and PP. The test results of CT15 and CT20 are similar to those of CT10. It is obvious that with the addition of tannic acid, the CT film produces a significant polarity transition from positive to negative. Among them, the surface charge density of CT10 reaches 182 μC m -2 This experiment demonstrated the effectiveness of polyphenol modification in inducing triboelectric polarity transformation of chitosan.

[0092] The surface potentials of the different films were measured by Kelvin probe force microscopy (KPFM). Figure 9 The surface potentials of CS, PA, and CT5-20 are 0.273 V, 0.203 V, -0.413 V, -0.507 V, -0.516 V, and -0.533 V, respectively. The lower surface potential observed in the CT film compared to CS indicates a higher work function, indicating a preference for negative triboelectric charge. Taking the surface potential energy of PA as V1 and the surface potential energy of CS and CT as V2, the estimated parameters a = 414.1, b = 191.8, and c = -9 are calculated. The fitting results are shown in Figure 2. Figure 10 Furthermore, by matching the expression with the consumed amino groups in Table 1, a prediction model can be obtained.

[0093] Table 1 Element characterization test results (%)

[0094]

[0095]

[0096] The above-described embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. It should be understood by those skilled in the art that the present invention can be applied not only to chitosan but also to materials such as cellulose, lignin, sodium alginate, and gelatin. Without departing from the spirit of the present invention, any modifications and improvements made to the technical solution of the present invention by those skilled in the art shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for predicting the surface charge density of a triboelectric nanogenerator based on modified chitosan material, characterized in that: It includes the following steps: S1. Preparation of modified chitosan: Polyphenol is used as a modification material to chemically modify chitosan to obtain modified chitosan. S2. Triboelectric polarity testing and quantitative characterization of modified chitosan: The modified chitosan is brought into contact with different materials in a known triboelectric series to generate an electrical signal, and the relative positive and negative values ​​of the electrical signal and the saturation charge density are obtained. The position of the modified chitosan in the known triboelectric series is determined based on the relative positive and negative values ​​of the electrical signal; S3. Obtain the surface potential energy and saturated charge density of the modified chitosan and the paired material: A triboelectric nanogenerator is composed of modified chitosan and a pairing material. The surface potential energy of the pairing material and the surface potential energy of the modified chitosan during the contact and separation process, as well as the saturation charge density of the triboelectric nanogenerator are obtained respectively. S4. Construction of a surface charge density prediction model for triboelectric nanogenerators based on modified chitosan materials: It includes the following sub-steps: S41. Based on the surface potential energy, a surface charge density prediction model of the triboelectric nanogenerator in step S3 is constructed, and its expression is: for: （1）； Where: is the surface charge density of the tribonanogenerator; is the surface potential energy of the paired materials; is the surface potential energy of modified chitosan; and are the fitting parameters corresponding to different paired materials; S42, due to surface charge density It cannot be directly measured, the saturation charge density must be measured first , and then calculated through the expression, the expression is: （2）； Where: is the separation distance between the paired material and the modified chitosan; and are the thicknesses of the paired materials and modified chitosan, respectively; is the dielectric constant of air; and are the dielectric constants of the paired materials and modified chitosan, respectively; S43. The surface potential energy of modified chitosan is related to the degree of modification, which in turn corresponds to the polyphenol concentration. Therefore, a surface potential energy model of modified chitosan material is established based on the polyphenol concentration: （3）； Where: is the polyphenol concentration, f() is the functional relationship between the surface potential energy of modified chitosan and the polyphenol concentration; S44. According to formulas (1) and (3), a surface charge density prediction model of the friction nanogenerator based on modified chitosan is obtained. When different pairing materials are used to form the friction nanogenerator with the modified chitosan material, a surface charge density prediction model of the friction nanogenerator based on the modified chitosan material with different fitting parameters is obtained. The surface charge density prediction model of the friction nanogenerator based on modified chitosan using different pairing materials can directly obtain the surface charge density of the friction nanogenerator according to the polyphenol concentration, thereby guiding the optimization of the friction electric polarity of the modified chitosan and improving the electrical output performance of the friction nanogenerator.

2. The method for predicting the surface charge density of a triboelectric nanogenerator based on modified chitosan material according to claim 1, characterized in that: Step S1 specifically includes: S11, prepare polyphenol solution: dissolve polyphenol in solvent to form polyphenol concentration The solution, The value range is (0%, 50%]; the solvent is a mixture of one or more of deionized water, ethanol, acetone and tetrachloromethane; S12, preparing a chitosan solution: dissolving chitosan in an acid solvent and cleaning it to remove impurities and pollutants to obtain a chitosan solution; the acid solvent is a mixture of one or more of acetic acid, hydrochloric acid, nitric acid and phosphoric acid; S13, mixing the chitosan solution of S12 with the polyphenol solution of S11, and then placing the mixture in a mold for drying to obtain modified chitosan.

3. The method for predicting the surface charge density of a triboelectric nanogenerator based on modified chitosan material according to claim 1, characterized in that: The materials in the known triboelectric sequence in step S2 include, but are not limited to, polyamide, thermoplastic polyurethane, polypropylene, polyethylene terephthalate, polydimethylsiloxane, polytetrafluoroethylene, and polyperfluoroethylene propylene.

4. The method for predicting the surface charge density of a triboelectric nanogenerator based on modified chitosan material according to claim 1, characterized in that: Step S3 specifically includes the following sub-steps: S31, forming a triboelectric nanogenerator by combining modified chitosan and a matching material, wherein the triboelectric nanogenerator is in a contact-separation mode; S32, measuring the charge signal of the contact and separation process using an electrometer, and obtaining the saturation charge density of the triboelectric nanogenerator through the signal amplitude; S33. The surface potential energy of the modified chitosan material and the surface potential energy of the paired material during the contact separation process were measured using a scanning Kelvin probe microscope.

5. The method for predicting the surface charge density of a triboelectric nanogenerator based on modified chitosan material according to claim 1, characterized in that: The chitosan in step S1 includes but is not limited to non-deacetylated chitin, chitosan with different deacetylation degrees, quaternary ammonium salt chitosan and carboxymethyl chitosan.

6. The method for predicting the surface charge density of a triboelectric nanogenerator based on modified chitosan material according to claim 1, characterized in that: The polyphenols in step S1 include, but are not limited to, tannic acid, catechin, dopamine and anthocyanin.

7. The method for predicting the surface charge density of a triboelectric nanogenerator based on modified chitosan material according to claim 1, characterized in that: The form of the modified chitosan in step S1 includes but is not limited to film, hydrogel, aerogel and block.

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