Composite hydrophobic fiber membrane based on friction nano-generator and preparation method of composite hydrophobic fiber membrane

Abstract

The invention discloses a composite hydrophobic fiber membrane based on a friction nano-generator and a preparation method of the composite hydrophobic fiber membrane. The composite hydrophobic fiber membrane is composed of a polyvinylidene fluoride nanofiber membrane, boracite particles, hydrophobic nanoparticles and polyvinylidene fluoride microspheres. The boracite particles are embedded in fibers of the polyvinylidene fluoride nanofiber membrane, and the hydrophobic nanoparticles are uniformly attached to the polyvinylidene fluoride microspheres and the polyvinylidene fluoride nanofiber; the hydrophobic nano particles are titanium dioxide nano particles or zirconium dioxide nano particles. The preparation method comprises the following steps: dispersing boracite powder and polyvinylidene fluoride powder into N, N-dimethylformamide to prepare an electrostatic spinning solution; the preparation method comprises the following steps: dispersing hydrophobic nanoparticles and polyvinylidene fluoride powder into N, N-dimethylformamide to prepare an electrostatic spraying solution; the composite hydrophobic fiber membrane is prepared through synchronous electrostatic spinning and electrostatic spraying. The problem that a modified polyvinylidene fluoride fiber membrane friction nanometer generator is low in output electrical performance in a high-humidity environment can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of triboelectric materials, in particular to a composite hydrophobic fiber membrane based on a triboelectric nanogenerator and a preparation method thereof. Background Art

[0002] Triboelectric nanogenerators (TENGs) utilize the principles of triboelectric charging and electrostatic induction to generate current. This can, to a certain extent, address the challenges of traditional power sources. Consequently, in recent years, TENGs have shown promising application prospects in wearable devices, the Internet of Things, medical monitoring, and ocean energy harvesting. The TENG's operating principle is based on contact electrification and electrostatic induction. The friction layer structure is the core of the TENG, so the dielectric materials attached to this layer play a crucial role in the TENG, directly affecting its performance, including charge generation, storage, and transmission. Common dielectric materials include polyamide, aluminum, brass, polyurethane, and polytetrafluoroethylene.

[0003] Compared to other dielectric materials, polyvinylidene fluoride (PVDF) has been extensively studied as a substrate for TENGs due to its high dielectric constant, high chemical stability, easy processing and molding, and good environmental adaptability. PVDF has four crystalline phases (α, β, σ, and γ), with the α phase being the most common, and the β phase possessing the highest electrical properties. The β phase typically forms under specific processing conditions, such as low-temperature solution crystallization, mechanical stretching, and high-voltage electric field polarization. A more economical and convenient method involves stretching the polymer chains through electrospinning, causing the α phase to crystallize into the β phase. However, the β phase content of PVDF crystallized simply by optimizing the solvent and spinning parameters is insufficient for practical applications. Therefore, to increase the β phase during electrospinning, the introduction of nanofillers offers a new approach to improving the electrical properties of PVDF-based TENGs. Nanofillers such as graphene, nano-Ag, BaTiO3 nanoparticles, and other nanofillers can be uniformly dispersed in a PVDF solution and then fabricated into thin films using electrospinning, effectively increasing the β phase content. However, the addition of nanofillers increases the concentration of the PVDF spinning solution. When added in large quantities, the nanofillers tend to agglomerate, increasing the diameter of the fiber and reducing the crystallization of the β phase. This requires the discovery of a new nanofiller that can achieve a high β phase content with a small addition.

[0004] Existing technologies use tourmaline and silica as fillers for polyvinylidene fluoride and electrospinning to prepare the friction layer of triboelectric nanogenerators. This allows for the production of films with a high β-phase content without filler agglomeration. These films exhibit high electrical output and excellent mechanical properties in high-humidity environments. However, tourmaline has a high surface polarity, which can lead to functional attenuation, resulting in unstable charge. Humidity or water contact can weaken tourmaline's electrode effect. Tourmaline's strong hydrophilicity requires surface modifiers to reduce its surface energy. Furthermore, due to its high specific surface area and the polarity of its surface hydroxyl (-OH) groups, silica particles are prone to forming aggregates in the PVDF matrix due to van der Waals forces or electrostatic interactions, resulting in uneven fiber morphology or localized breakage. Therefore, further improvements are needed to improve the electrical output performance of PVDF fiber membranes while maintaining good stability in high-humidity environments. Summary of the Invention

[0005] To this end, the technical problem to be solved by the present invention is to provide a composite hydrophobic fiber membrane based on a friction nanogenerator and a preparation method thereof, so as to solve the technical problem that the output electrical performance of the existing modified polyvinylidene fluoride fiber membrane is not high when used in the friction layer of the friction nanogenerator in a high humidity environment.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A composite hydrophobic fiber membrane based on a friction nanogenerator is composed of a polyvinylidene fluoride nanofiber membrane, borate particles, hydrophobic nanoparticles and polyvinylidene fluoride microspheres; the borate particles are embedded in the fiber filaments of the polyvinylidene fluoride nanofiber membrane, the polyvinylidene fluoride microspheres are attached to the fiber filaments of the polyvinylidene fluoride nanofiber membrane, a portion of the hydrophobic nanoparticles are evenly attached to the polyvinylidene fluoride microspheres, and another portion of the hydrophobic nanoparticles are evenly attached to the fiber filaments of the polyvinylidene fluoride nanofiber membrane; the hydrophobic nanoparticles are titanium dioxide nanoparticles or zirconium dioxide nanoparticles.

[0008] The composite hydrophobic fiber membrane based on the friction nanogenerator has a thickness of 80 to 120 μm and a fiber diameter of 160 to 170 nm (the fiber diameter directly affects the specific surface area and porosity of the composite hydrophobic fiber membrane. The present invention controls the fiber diameter within the range of 160 to 170 nm. This uniform diameter and relatively fine fiber can form a grid structure with a relatively high porosity, which increases the specific surface area of ​​the composite membrane while also increasing the surface roughness, thereby effectively improving its charge capture ability). The particle size of the borate particles is 1 The diameter of the hydrophobic nanoparticles is 80-150 nm, and the diameter of the polyvinylidene fluoride microspheres is 0.5-5 μm. By controlling the particle diameters of the boron particles, hydrophobic nanoparticles and polyvinylidene fluoride microspheres on the polyvinylidene fluoride nanofiber membrane of a specific thickness within the above range, the adhesion between the polyvinylidene fluoride nanofibers can be effectively avoided, ensuring that the polyvinylidene fluoride nanofibers maintain a uniform filamentous structure, and the polyvinylidene fluoride microspheres can effectively support the polyvinylidene fluoride nanofibers to form a stable skeleton structure, which is beneficial to the charge transfer between the polyvinylidene fluoride nanofibers. The mass of the borate particles is 0.5-3.0 wt% (preferably 1.0-2.5 wt%) of the mass of the polyvinylidene fluoride fiber membrane, the mass of the hydrophobic nanoparticles is 0.2-1.0 wt% of the mass of the polyvinylidene fluoride microspheres, and the polyvinylidene fluoride microspheres are 10-20 wt% of the mass of the polyvinylidene fluoride fiber membrane; the mass ratio of the hydrophobic nanoparticles attached to the polyvinylidene fluoride microspheres to the hydrophobic nanoparticles attached to the fiber filaments of the polyvinylidene fluoride nanofiber membrane is (10-20):1; when the hydrophobic nanoparticles attached to the polyvinylidene fluoride microspheres are When the proportion of hydrophobic nanoparticles is within the above range, it can ensure that the polyvinylidene fluoride microspheres and hydrophobic nanoparticles form a secondary structure with hydrophobic properties on the surface of the composite hydrophobic fiber membrane, so that the composite hydrophobic fiber membrane maintains excellent power generation performance in a high humidity environment; the remaining hydrophobic nanoparticles are attached to the fiber filaments, which can give the fiber membrane surface a certain self-cleaning function (the photocatalytic effect of titanium dioxide or zirconium dioxide can degrade pollutants such as proteins and oxides adsorbed on the surface of the composite fiber membrane in a humid environment), which is conducive to further improving the stability of the power generation performance of the composite hydrophobic fiber membrane in a high humidity environment.

[0009] A method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator comprises the following steps:

[0010] Step (1), ultrasonically dispersing borate powder in N,N-dimethylformamide to obtain a borate dispersion; adding a first polyvinylidene fluoride powder to the borate dispersion, heating and stirring until the first polyvinylidene fluoride is completely dissolved, to obtain an electrospinning solution;

[0011] Step (2), ultrasonically dispersing hydrophobic nanoparticles into N,N-dimethylformamide to obtain a hydrophobic nanoparticle dispersion, wherein the hydrophobic nanoparticles are titanium dioxide nanoparticles or zirconium dioxide nanoparticles; adding a second polyvinylidene fluoride powder to the hydrophobic nanoparticle dispersion, heating and stirring until the second polyvinylidene fluoride is completely dissolved, to obtain an electrostatic spray liquid;

[0012] Step (3), placing the electrospinning solution and the electrostatic spray solution in an electrospinning device to simultaneously perform electrospinning and electrostatic spraying, and collecting the electrostatic jet product;

[0013] Step (4): drying the electrostatic jet products collected on the collector. After the drying process is completed, the composite hydrophobic fiber membrane based on the friction nanogenerator is obtained.

[0014] The preparation method of the composite hydrophobic fiber membrane based on the triboelectric nanogenerator is as follows: in step (1), the particle size of the boracic powder is 100-200 nm, the mass of the boracic powder in the electrospinning solution is 0.5-3.0 wt% of the mass of the first polyvinylidene fluoride, and the ultrasonic dispersion condition is: ultrasonic dispersion at a frequency of 30-60 kHz for 1.5-3 hours at room temperature. If the particle size of the boracic powder used is too large, the electric field force will be insufficient to pull the fiber filaments during the electrospinning process, and part of the boracic powder will also precipitate at the bottom of the container due to the large particle size during the spinning process, resulting in uneven distribution of boracic particles in the formed fiber filaments; if the mass ratio of the boracic powder to the first polyvinylidene fluoride in the electrospinning solution is too large, the electrospinning solution will be subjected to uneven electric field force during the electrospinning process, forming fiber filaments of different shapes, or the fiber filaments will easily adhere; if the amount of boracic powder in the electrospinning solution is too small, the improvement effect of boracic powder on the first polyvinylidene fluoride fiber membrane will not be obvious.

[0015] In the preparation method of the composite hydrophobic fiber membrane based on the above-mentioned friction nanogenerator, in step (1), the average relative molecular mass of the first polyvinylidene fluoride powder is 500,000 to 600,000, the mass fraction of the first polyvinylidene fluoride in the electrospinning solution is 15 to 20 wt%, and the heating and stirring conditions are: stirring at a temperature of 65 to 80°C and a stirring speed of 350 to 500 rpm for 2 to 5 hours; the first polyvinylidene fluoride powder with the above-mentioned molecular weight is used and its mass fraction is controlled within 15 to 20 wt%, and the viscosity of the obtained electrospinning solution is moderate, which is conducive to electrospinning to form uniform and stable nanofiber filaments. The present invention controls the particle size and amount of the boracic acid powder in the electrospinning solution, and the relative molecular mass and mass fraction of the first polyvinylidene fluoride powder, so that the first polyvinylidene fluoride is dissolved in N,N-dimethylformamide to form an electrospinning solution with moderate viscosity, and the boracic acid powder can be evenly and stably distributed in the electrospinning solution, which is not only beneficial for spinning to obtain polyvinylidene fluoride nanofibers with uniform thickness, but also beneficial for the boracic acid powder to be evenly coated on the polyvinylidene fluoride nanofibers during the electrospinning process, thereby facilitating its effective role in improving the electrical properties of the composite fiber membrane during the friction power generation process.

[0016] The above-mentioned preparation method of the composite hydrophobic fiber membrane based on the friction nanogenerator, in step (2), the particle size of the hydrophobic nanoparticles is 80-150nm, and the mass of the hydrophobic nanoparticles in the electrostatic spray liquid is 0.2-1.0wt% of the mass of the second polyvinylidene fluoride; if the particle size of the hydrophobic nanoparticles is greater than 150nm or the amount thereof in the electrostatic spray liquid is too much, it will cause the hydrophobic nanoparticles to be difficult to adhere to the polyvinylidene fluoride microspheres formed by the electrostatic spray, or the hydrophobic nanoparticles to adhere too much to the polyvinylidene fluoride nanofiber filaments, thereby causing adhesion between the polyvinylidene fluoride nanofiber filaments; if the particle size of the hydrophobic nanoparticles is less than 80nm or the amount thereof in the electrostatic spray liquid is too small, it is difficult for it to form an effective hydrophobic structure on the polyvinylidene fluoride nanofiber membrane), and the conditions for ultrasonic dispersion are: ultrasonic dispersion at a frequency of 40-60kHz at room temperature for 60-90min.

[0017] In the above-mentioned method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator, in step (2), the average relative molecular mass of the second polyvinylidene fluoride powder is 400,000 to 450,000, the mass fraction of the second polyvinylidene fluoride in the electrostatic spray liquid is 4 to 10 wt%, and the heating and stirring conditions are: stirring at a temperature of 65 to 80°C and a stirring speed of 350 to 500 rpm for 2 to 3 hours. The present invention controls the particle size and amount of the hydrophobic nanoparticles in the electrostatic spray liquid, the average relative molecular mass and mass fraction of the second polyvinylidene fluoride powder used, so that it can spray under the electric field conditions of the present invention to form polyvinylidene fluoride microspheres with moderate and uniform particle size (diameter concentrated in the range of 2 to 4 μm), and can ensure that the vast majority of the hydrophobic nanoparticles can adhere to the polyvinylidene fluoride microspheres.

[0018] In the above-mentioned method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator, in step (3), the electrospinning equipment is an electrospinning machine capable of realizing electrospinning and electrostatic spraying; when electrospinning and electrostatic spraying are performed simultaneously: the voltage of the high-voltage electrostatic field is 18 to 20 kV (if the voltage of the high-voltage electrostatic field is too large, the fiber filaments formed will be uneven in morphology due to excessive electric field force; if the voltage of the high-voltage electrostatic field is too small, the electric field force will be insufficient to pull the fiber filaments, resulting in uneven fiber filaments), and the propulsion rates of the electrospinning solution and the electrostatic spray solution are the same, both of which are 1.0 to 1.2 mL·h -1 The distance between the tip of the injection nozzle and the aluminum foil collector is 15 to 18 cm (if the distance is too short, the solvent in the electrospinning solution and the electrostatic spray will not evaporate completely, resulting in fiber adhesion; if the distance is too long, the fiber collection will not be concentrated), the temperature is controlled in the range of 30 to 45 ° C, and the relative humidity is controlled in the range of 40 to 50% (too low temperature or too high humidity will lead to incomplete solvent evaporation and fiber adhesion; too high temperature or too low humidity will make the fiber brittle and affect its mechanical properties); by controlling the electrospinning solution and electrostatic spray solution The dosage ratio is such that in the final composite hydrophobic fiber membrane, the mass of the polyvinylidene fluoride microspheres is 10 to 20 wt% of the mass of the polyvinylidene fluoride fiber membrane; if the amount of electrospinning solution is too large, the hydrophobic structure formed by the hydrophobic nanoparticles and the polyvinylidene fluoride microspheres will be relatively small, thereby affecting the hydrophobic properties of the composite hydrophobic fiber membrane; if the amount of electrostatic spray liquid is too large, the polyvinylidene fluoride microspheres will be too densely distributed on the polyvinylidene fluoride nanofiber filaments, thereby causing the polyvinylidene fluoride nanofiber filaments to adhere, thereby causing the electrical properties of the prepared composite hydrophobic fiber membrane to deteriorate.

[0019] The present invention controls the dosage ratio of the electrospinning solution (containing a specific amount of 100-200nm boracic powder and a first polyvinylidene fluoride with an average relative molecular mass of 600,000) and the electrostatic spray solution (containing a specific amount of 80-150nm hydrophobic nanoparticles and a second polyvinylidene fluoride with an average relative molecular mass of 400,000), the voltage of the high-voltage electrostatic field, the propulsion rate of the electrospinning solution and the electrostatic spray solution, the distance between the injection nozzle tip and the aluminum foil collector, the working temperature and humidity during the electrospinning and electrostatic spraying processes, so that the electrostatic spraying can form polyvinylidene fluoride microspheres of uniform size, the electrostatic spinning can form nanofibers with uniform thickness and small diameter, and the polyvinylidene fluoride microspheres formed by the spray can be uniformly attached to the polyvinylidene fluoride nanofibers formed by the electrospinning, and the specific proportion of hydrophobic nanoparticles in the electrostatic spray solution can be uniformly attached to the polyvinylidene fluoride nanofibers. The particles are attached to the polyvinylidene fluoride microspheres, and the remaining part is attached to the polyvinylidene fluoride nanofiber filaments formed by electrospinning, giving the composite hydrophobic fiber membrane good hydrophobic properties; under the process conditions of the present invention, the boracic acid particles in the electrospinning solution can be evenly embedded in the fiber filaments of the polyvinylidene fluoride nanofiber membrane (some boracic acid particles with larger diameters will protrude from the fiber filaments), which is beneficial to its full play in improving the power generation performance of the composite fiber membrane during the friction power generation process; at the same time, the polyvinylidene fluoride microspheres serve as a skeleton to support the uniform and finer polyvinylidene fluoride nanofiber filaments to form a network structure with a higher porosity, which increases the specific surface area of ​​the composite hydrophobic fiber membrane while also increasing its surface roughness, which is beneficial to improving the charge capture ability of the membrane, thereby further improving the power generation performance of the composite hydrophobic fiber membrane.

[0020] In the above-mentioned method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator, in step (4), the drying conditions are: 50-60°C, drying for 12-16 hours. If the drying time is too long or the drying temperature is too high, the composite hydrophobic fiber membrane will become brittle and mechanical properties will decrease. If the drying time is too short or the drying temperature is too low, the residual solvent may adhere to the surface of the fiber membrane and affect its electrical properties. The thickness of the composite hydrophobic fiber membrane obtained by the drying process is 80-120 μm. If the composite hydrophobic fiber membrane is less than 80 μm, its mechanical strength is difficult to meet the actual application requirements. If its thickness is greater than 120 μm, the charge transfer difficulty increases, affecting its electrical properties. The present invention can ensure that the prepared composite hydrophobic fiber membrane has good electrical properties under the premise that the mechanical strength meets the use requirements by controlling the drying temperature, drying time and thickness of the composite hydrophobic fiber membrane.

[0021] The preparation method of the composite hydrophobic fiber membrane based on the above-mentioned triboelectric nanogenerator, in step (1), the particle size of the borate powder is 100-200 nm, the mass of the borate powder in the electrospinning solution is 1.5wt% of the mass of the first polyvinylidene fluoride, and the ultrasonic dispersion conditions are: ultrasonic dispersion at a frequency of 40kHz for 2h at room temperature;

[0022] The average relative molecular mass of the first polyvinylidene fluoride powder is 600,000, the mass fraction of the first polyvinylidene fluoride in the electrospinning solution is 20 wt%, and the heating and stirring conditions are: at a temperature of 70°C and a stirring speed of 400 rpm for 4 hours;

[0023] In step (2), the particle size of the hydrophobic nanoparticles is 80 to 150 nm, the mass of the hydrophobic nanoparticles in the electrostatic spray liquid is 0.6 wt % of the mass of the second polyvinylidene fluoride, and the ultrasonic dispersion conditions are: ultrasonic dispersion at a frequency of 40 kHz at room temperature for 60 min;

[0024] The average relative molecular mass of the second polyvinylidene fluoride powder is 400,000, the mass fraction of the second polyvinylidene fluoride in the electrostatic spray liquid is 8 wt %, and the heating and stirring conditions are: at a temperature of 70° C. and a stirring speed of 400 rpm for 2 hours;

[0025] In step (3), the electrospinning equipment is an electrospinning machine capable of performing electrospinning and electrospinning spraying; when electrospinning and electrospinning spraying are performed simultaneously, the volume ratio of the electrospinning solution to the electrospinning spray solution is 2:1, the voltage of the high-voltage electrostatic field is 20 kV, and the propulsion rates of the electrospinning solution and the electrospinning spray solution are the same, both 1.2 mL·h -1 , the distance between the injection nozzle tip and the aluminum foil collector was 18 cm, the temperature was 40 °C, and the relative humidity was 40;

[0026] In step (4), the drying conditions are: 55° C., drying for 12 h; the thickness of the composite hydrophobic fiber membrane obtained by the drying treatment is 80 to 90 μm.

[0027] The technical solution of the present invention achieves the following beneficial technical effects:

[0028] 1. The preparation method of the composite hydrophobic fiber membrane based on the friction nanogenerator of the present invention is to electrospin and electrostatically spray a high-concentration PVDF electrospinning solution with a specific content of 100-200nm boracic particles and a low-concentration PVDF electrospinning solution with a specific content of 80-150nm hydrophobic nanoparticles (titanium dioxide or zirconium dioxide) in a specific ratio, and electrospin and electrostatically spray them simultaneously. In the electrospinning process, the 100-200nm boracic particles are embedded in the fiber filaments formed by the high-concentration high-molecular-weight PVDF electrospinning solution, and the low-concentration hydrophobic nanoparticles (titanium dioxide or zirconium dioxide) are embedded in the fiber filaments formed by the high-concentration high-molecular-weight PVDF electrospinning solution. The lower molecular weight PVDF in the PVDF electrostatic spray liquid forms micron-sized PDVF microspheres that attach to the fiber filaments formed by the high-concentration and high-molecular weight PVDF electrostatic spinning liquid, and a part of the hydrophobic nanoparticles (titanium dioxide or zirconium dioxide) attach to the micron-sized PDVF microspheres, and the other part of the hydrophobic nanoparticles (titanium dioxide or zirconium dioxide) attach to the fiber filaments formed by the high-concentration and high-molecular weight PVDF electrostatic spinning liquid, thereby forming a composite hydrophobic fiber membrane with good hydrophobicity. The composite hydrophobic fiber membrane is used for the friction layer of the friction nanogenerator, which can maintain good stability and high output electrical performance in a high-humidity environment.

[0029] 2. Compared with the tourmaline used in the background technology, boracic acid does not contain toxic elements and is more environmentally friendly. The polarity of boracic acid is stronger than that of tourmaline. Using it as a filler for polyvinylidene fluoride can significantly improve the conductivity of the electrospinning solution, thereby making the morphology of the fiber obtained by electrospinning polyvinylidene fluoride more uniform. The electrospinning solution can respond to a larger electric field force to obtain finer fiber filaments, and is conducive to the recrystallization of polyvinylidene fluoride under the action of a high-voltage electric field, thereby obtaining polyvinylidene fluoride fiber filaments with more β phases, thereby improving the composite hydrophobic fiber membrane. Electrical properties: The present invention uses boracic acid as the filler of the first polyvinylidene fluoride, and titanium dioxide or zirconium dioxide as hydrophobic nanoparticles, which are electrostatically sprayed with the second polyvinylidene fluoride to form a hydrophobic structure of hydrophobic nanoparticles + polyvinylidene fluoride microspheres, wherein the polyvinylidene fluoride microspheres can adsorb electrons, thereby supporting the polyvinylidene fluoride nanofibers to form a grid skeleton structure with high porosity (the thinner the fiber, the more conducive to the improvement of porosity). The high porosity is conducive to the adsorption of more electrons during the friction power generation process, thereby further improving the electrical properties of the composite hydrophobic fiber membrane. The present invention controls the diameter of the fiber filaments of the polyvinylidene fluoride nanofiber membrane, the diameter of the borate particles, the diameter of the hydrophobic nanoparticles, the diameter of the polyvinylidene fluoride microspheres, the amount of the borate particles, the hydrophobic nanoparticles, and the polyvinylidene fluoride microspheres in the composite hydrophobic fiber membrane, and the distribution of the hydrophobic nanoparticles, so that the composite hydrophobic fiber membrane has better hydrophobic properties, and the borate and hydrophobic nanoparticles can work together to improve the electrical properties of the composite hydrophobic fiber membrane and the stability of the electrical properties in a high-humidity environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1a SEM image of PVDF nanofiber membrane in an embodiment of the present invention;

[0031] Figure 1b SEM image of PVDF / B composite nanofiber membrane in an embodiment of the present invention (boronite doping amount is 1.5wt%);

[0032] Figure 1c SEM image of the PVDF / BT composite hydrophobic fiber membrane in an embodiment of the present invention (boranite doping amount is 1.5wt%; titanium dioxide doping amount is 0.6wt%);

[0033] Figure 1d SEM image of the PVDF / BZ composite hydrophobic fiber membrane in the embodiment of the present invention (boranite doping amount is 1.5wt%; zirconium dioxide doping amount is 0.6wt%);

[0034] Figure 2a EDS surface scan of PVDF nanofiber membrane in an embodiment of the present invention;

[0035] Figure 2b EDS surface scan of the PVDF / B composite nanofiber membrane in an embodiment of the present invention (boronite doping amount is 1.5wt%);

[0036] Figure 3a EDS surface scan of the PVDF / BT composite hydrophobic fiber membrane in an embodiment of the present invention (boranite doping amount is 1.5wt%; titanium dioxide doping amount is 0.6wt%);

[0037] Figure 3b EDS surface scan of the PVDF / BZ composite hydrophobic fiber membrane in an embodiment of the present invention (boranite doping amount is 1.5wt%; zirconium dioxide doping amount is 0.6wt%);

[0038] Figure 4 XRD patterns of the PVDF nanofiber membrane, PVDF / B composite nanofiber membrane (boranite doping amount of 1.5 wt%), PVDF / BT composite hydrophobic fiber membrane (boranite doping amount of 1.5 wt%; titanium dioxide doping amount of 0.6 wt%), and PVDF / BZ (boranite doping amount of 1.5 wt%; zirconium dioxide doping amount of 0.6 wt%) composite hydrophobic fiber membrane prepared in the examples of the present invention;

[0039] Figure 5 FTIR spectra of the PVDF nanofiber membrane, PVDF / B composite nanofiber membrane (boronite doping amount of 1.5 wt%), PVDF / BT composite hydrophobic fiber membrane (boronite doping amount of 1.5 wt%; titanium dioxide doping amount of 0.6 wt%), and PVDF / BZ (boronite doping amount of 1.5 wt%; zirconium dioxide doping amount of 0.6 wt%) prepared in the examples of the present invention;

[0040] Figure 6a Diameter distribution of micro-nanospheres in the PVDF / BT composite hydrophobic fiber membrane (boranite doping amount is 1.5 wt%; titanium dioxide doping amount is 0.6 wt%) prepared in an embodiment of the present invention;

[0041] Figure 6b Diameter distribution of micro- and nanospheres in the PVDF / BZ composite hydrophobic fiber membrane (boranite doping amount is 1.5 wt%; zirconium dioxide doping amount is 0.6 wt%) prepared in an embodiment of the present invention;

[0042] Figure 7a 、 Figure 7b and Figure 7cWhen the PVDF / B composite nanofiber membranes (boronite doping amounts of 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, and 2.5wt%) prepared in the embodiments of the present invention were used as the friction layer of TENG, the short-circuit current, transferred charge, and open-circuit voltage of TENG;

[0043] Figure 8a 、 Figure 8b and Figure 8c When the PVDF / BT composite hydrophobic fiber membranes prepared in the embodiments of the present invention (boranite doping amount of 1.5wt%; titanium dioxide doping amounts of 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, and 1.0wt%) were used as the friction layer of TENG, the short-circuit current, transferred charge, and open-circuit voltage of TENG were measured.

[0044] Figure 9a 、 Figure 9b and Figure 9c When the PVDF / BZ composite hydrophobic fiber membranes prepared in the embodiments of the present invention (boranite doping amount of 1.5wt%; zirconium dioxide doping amounts of 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, and 1.0wt%) were used as the friction layer of TENG, the short-circuit current, transferred charge, and open-circuit voltage of TENG were measured.

[0045] Figure 10 Figure 3. Dielectric constant test results of the PVDF / B composite nanofiber membrane, PVDF / B composite nanofiber membrane (boronite doping amount of 1.5 wt%), PVDF / BT composite hydrophobic fiber membrane (boronite doping amount of 1.5 wt%; titanium dioxide doping amount of 0.6 wt%), and PVDF / BZ (boronite doping amount of 1.5 wt%; zirconium dioxide doping amount of 0.6 wt%) prepared in the examples of the present invention;

[0046] Figure 11 Figure 3 shows the air permeability test results of the PVDF / B composite nanofiber membrane (boranite doping amount of 1.5 wt%), PVDF / BT composite hydrophobic fiber membrane (boranite doping amount of 1.5 wt%; titanium dioxide doping amount of 0.6 wt%), and PVDF / BZ (boranite doping amount of 1.5 wt%; zirconium dioxide doping amount of 0.6 wt%) prepared in the examples of the present invention;

[0047] Figure 12Dielectric loss test results of PVDF / B composite nanofiber membrane (boronite doping amount of 1.5wt%), PVDF / BT composite hydrophobic fiber membrane (boronite doping amount of 1.5wt%; titanium dioxide doping amount of 0.6wt%), and PVDF / BZ (boronite doping amount of 1.5wt%; zirconium dioxide doping amount of 0.6wt%) prepared in Examples of the present invention;

[0048] Figure 13 Figure 3. Charge transfer test results of the PVDF / B composite nanofiber membrane (boronite doping amount of 1.5 wt%), PVDF / BT composite hydrophobic fiber membrane (boronite doping amount of 1.5 wt%; titanium dioxide doping amount of 0.6 wt%), and PVDF / BZ (boronite doping amount of 1.5 wt%; zirconium dioxide doping amount of 0.6 wt%) prepared in the examples of the present invention under different humidity conditions.

[0049] Figure 14a 、 Figure 14b 、 Figure 14c and Figure 14d Surface images of four fiber membranes under a 200x optical microscope: a PVDF nanofiber membrane prepared according to an embodiment of the present invention, a PVDF / B composite nanofiber membrane (boranite doping amount of 1.5 wt%), a PVDF / BT composite hydrophobic fiber membrane (boranite doping amount of 1.5 wt%; titanium dioxide doping amount of 0.6 wt%), and a PVDF / BZ (boranite doping amount of 1.5 wt%; zirconium dioxide doping amount of 0.6 wt%);

[0050] Figure 15a 、 Figure 15b 、 Figure 15c and Figure 15d Graphs showing water contact angle test results for four types of fiber membranes: PVDF nanofiber membrane prepared according to an embodiment of the present invention, PVDF / B composite nanofiber membrane (boranite doping amount of 1.5 wt%), PVDF / BT composite hydrophobic fiber membrane (boranite doping amount of 1.5 wt%; titanium dioxide doping amount of 0.6 wt%), and PVDF / BZ (boranite doping amount of 1.5 wt%; zirconium dioxide doping amount of 0.6 wt%);

[0051] Figure 16 Schematic diagram of the microstructure of the PVDF / / BT composite hydrophobic fiber membrane (boronite doping content is 1.5wt%; titanium dioxide doping content is 0.6wt%);

[0052] Figure 17a Current and output power of TENG based on PVDF / BT composite hydrophobic fiber membrane (boronite doping content is 1.5wt%; titanium dioxide doping content is 0.6wt%) under different loads;

[0053] Figure 17b The current and output power of TENG based on PVDF / BZ composite hydrophobic fiber membrane (boronite doping amount is 1.5wt%; zirconium dioxide doping amount is 0.6wt%) under different loads;

[0054] Figure 18a Short-circuit current of TENG based on PVDF / BT composite hydrophobic fiber membrane (boronite doping content is 1.5wt%; titanium dioxide doping content is 0.6wt%) at 14.4k cycle;

[0055] Figure 18b Short-circuit current of TENG based on PVDF / BZ composite hydrophobic fiber membrane (boronite doping amount is 1.5wt%; zirconium dioxide doping amount is 0.6wt%) at 14.4k cycle;

[0056] Figure 19a Charging curve of TENG capacitor based on PVDF / BT composite hydrophobic fiber membrane (boronite doping content is 1.5wt%; titanium dioxide doping content is 0.6wt%);

[0057] Figure 19b Charging curve of TENG capacitor based on PVDF / BZ composite hydrophobic fiber membrane (boronite doping amount is 1.5wt%; zirconium dioxide doping amount is 0.6wt%);

[0058] Figure 20a TENG charging test circuit diagram based on PVDF / BT composite hydrophobic fiber membrane (boronite doping content is 1.5wt%; titanium dioxide doping content is 0.6wt%).

[0059] Figure 20b Circuit diagram of the TENG power supply system based on PVDF / BT composite hydrophobic fiber membrane (boranite doping amount is 1.5wt%; titanium dioxide doping amount is 0.6wt%). DETAILED DESCRIPTION

[0060] 1. Preparation of composite hydrophobic fiber membrane

[0061] (1) Preparation of electrospinning solution

[0062] A. Add 20 g of first polyvinylidene fluoride powder (PVDF, average relative molecular mass of 600,000) to N,N-dimethylformamide, and stir at 70°C and 400 rpm for 4 h until the first polyvinylidene fluoride is completely dissolved to obtain electrospinning solution A; the mass fraction of the first polyvinylidene fluoride in the electrospinning solution A is 20 wt%.

[0063] B. Add borasite powder (particle size of 100-200 nm) to 100 mL of N,N-dimethylformamide, and ultrasonically disperse it at a frequency of 40 kHz at room temperature for 2 h to obtain a borasite dispersion; add a first polyvinylidene fluoride powder (PVDF, average relative molecular mass of 600,000) to the borasite dispersion, and stir at a temperature of 70°C and a stirring speed of 400 rpm for 4 h until the first polyvinylidene fluoride is completely dissolved to obtain an electrospinning solution B; in the electrospinning solution B, the mass fraction of PVDF is 20 wt%, and the mass of the borasite powder is 1.5 wt% of the mass of PVDF.

[0064] (2) Preparation of electrostatic spray liquid

[0065] A. Add titanium dioxide powder (particle size of 80-150 nm) to 100 mL of N,N-dimethylformamide, and ultrasonically disperse it at a frequency of 40 kHz for 60 min at room temperature to obtain a titanium dioxide dispersion; add a second polyvinylidene fluoride powder (PVDF, with an average relative molecular mass of 400,000) to the titanium dioxide dispersion, and stir at a temperature of 70°C and a stirring speed of 400 rpm for 2 h until the second polyvinylidene fluoride is completely dissolved to obtain an electrostatic spray liquid A; the mass fraction of the titanium dioxide powder in the electrostatic spray liquid A is 0.6 wt%, and the mass fraction of the second polyvinylidene fluoride is 8 wt%.

[0066] B. Add zirconium dioxide powder (particle size of 80-150 nm) to 100 mL of N,N-dimethylformamide, and ultrasonically disperse it at a frequency of 40 kHz for 60 min at room temperature to obtain a titanium dioxide dispersion; add a second polyvinylidene fluoride powder (PVDF, with an average relative molecular mass of 400,000) to the titanium dioxide dispersion, and stir at a temperature of 70°C and a stirring speed of 400 rpm for 2 h until the second polyvinylidene fluoride is completely dissolved to obtain an electrostatic spray liquid B; the mass fraction of the zirconium dioxide powder in the electrostatic spray liquid B is 0.6 wt%, and the mass fraction of the second polyvinylidene fluoride is 8 wt%.

[0067] (3) Preparation of PVDF nanofiber membrane

[0068] The electrospinning solution A was placed in the syringe of the electrospinning equipment (PS-ZJ-01 electrospinning machine of Qingdao Pansi Technology) for electrospinning. The syringe pump was operated at a high voltage of 20 kV at a speed of 1.2 mL·h -1 The distance between the syringe nozzle tip and the aluminum foil collector was fixed at 18 cm; the temperature was maintained at 40°C and the relative humidity was around 40%; after continuous collection for about 5 hours, it was dried in a 55°C oven for 12 hours to obtain a PVDF nanofiber membrane with a thickness of about 80 μm.

[0069] (4) Preparation of PVDF / B composite nanofiber membrane

[0070] The electrospinning solution B was placed in the syringe of the electrospinning equipment (Beijing Yongkang Leye SS-X3 electrospinning machine) for electrospinning. The syringe pump was operated at a high voltage of 20 kV at a speed of 1.2 mL·h -1 The distance between the syringe nozzle tip and the aluminum foil collector was fixed at 18 cm; the temperature was maintained at 40°C and the relative humidity was around 40%; after continuous collection for about 5 hours, it was dried in a 55°C oven for 12 hours to obtain a PVDF / B composite nanofiber membrane with a thickness of about 80 μm.

[0071] (5) Preparation of PVDF / BT composite hydrophobic fiber membrane

[0072] Electrospinning solution B and electrospinning spray solution A were placed in the syringes of the electrospinning equipment (Beijing Yongkang Leye SS-X3 electrospinning machine) for simultaneous electrospinning and electrospinning. Electrospinning spray solution A was filled into the middle position of three 10 mL syringes, and the syringes on both sides were filled with electrospinning solution B. Under high voltage of 20 kV, the syringe pump was pumped at 1.2 mL·h -1 The distance between the syringe nozzle tip and the aluminum foil collector was fixed at 18 cm; the temperature was maintained at 40°C and the relative humidity was around 40%; after continuous collection for about 5 hours, it was dried in a 55°C oven for 12 hours to obtain a PVDF / BT composite hydrophobic fiber membrane with a thickness of about 80 μm.

[0073] (6) Preparation of PVDF / BZ composite hydrophobic fiber membrane

[0074] Electrospinning solution B and electrospinning spray solution B were placed in the syringes of the electrospinning equipment (Beijing Yongkang Leye SS-X3 electrospinning machine) for simultaneous electrospinning and electrospinning. Electrospinning spray solution B was filled into the middle position of three 10 mL syringes, and the syringes on both sides were filled with electrospinning solution B. Under high voltage of 20 kV, the syringe pump was operated at 1.2 mL·h -1 The distance between the syringe nozzle tip and the aluminum foil collector was fixed at 18 cm; the temperature was maintained at 40°C and the relative humidity was around 40%; after continuous collection for about 5 hours, it was dried in a 55°C oven for 12 hours to obtain a PVDF / BZ composite hydrophobic fiber membrane with a thickness of about 80 μm.

[0075] The same method as above was used to control the mass fraction of the first polyvinylidene fluoride in the electrospinning solution B to 20wt%, and the mass fractions of the borate powder to 0.5wt%, 1.0wt%, 2.0wt%, and 2.5wt%, respectively, to prepare PVDF / B composite nanofiber membranes with different borate doping amounts, which were recorded as 0.5B, 1.0B, 1.5B, 2.0B, and 2.5B;

[0076] Using the same method as above, the mass fraction of the second polyvinylidene fluoride in the electrostatic spray liquid A was controlled to 8wt%, and the mass fractions of titanium dioxide were 0.2wt%, 0.4wt%, 0.8wt%, and 1.0wt%, respectively, to prepare PVDF / BT composite hydrophobic fiber membranes with different titanium dioxide doping amounts, which were recorded as 0.2T, 0.4T, 0.6T, 0.8T, and 1.0T;

[0077] Using the same method as above, the mass fraction of zirconium dioxide in the electrostatic spray liquid B was controlled to 0.2wt%, 0.4wt%, 0.8wt%, and 1.0wt%, respectively, to prepare PVDF / BZ composite hydrophobic fiber membranes with different zirconium dioxide doping amounts, which were recorded as 0.2Z, 0.4Z, 0.6Z, 0.8Z, and 1.0Z.

[0078] 2. Characterization and performance evaluation of composite hydrophobic fiber membrane

[0079] (1) Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis

[0080] This example uses a FEIApreo 2S multifunctional high-resolution field emission scanning electron microscope equipped with an Oxford Instruments Ultim Max 4.0 energy dispersive spectrometer to characterize the nanofiber surface morphology of the fiber membrane and the doping status of borate powder and hydrophobic nanoparticles.

[0081] Figures 1a to 1d The SEM analysis pictures of PVDF nanofiber membrane, PVDF / B composite nanofiber membrane, PVDF / BT composite hydrophobic fiber membrane and PVDF / BZ composite hydrophobic fiber membrane prepared in this embodiment are shown in Figure 1. As can be seen from the figure, the fiber filaments of the PVDF nanofiber membrane without any doping have different morphologies and uneven fiber diameters ( Figure 1a ); After doping with boracic acid, the uniformity of the fiber morphology is significantly improved, and the fiber diameter is more uniform ( Figure 1b ); At the same time, after electrostatic spray doping with nano-titanium dioxide / zirconium dioxide, nano-microspheres were obviously attached to the fiber, supporting the fiber structure ( Figure 1c and Figure 1dThe nanofiber membrane prepared by the method of this embodiment has uniform fiber thickness, and its diameter is basically concentrated in the range of 160 to 170 nm.

[0082] Figure 2a 、 Figure 2b 、 Figure 3a and Figure 3b The EDS analysis diagrams of the PVDF nanofiber membrane, PVDF / B composite nanofiber membrane, PVDF / BT composite hydrophobic fiber membrane, and PVDF / BZ composite hydrophobic fiber membrane prepared in this example are shown. As can be seen from the figure, the presence of dopants was verified by EDS surface scanning, and it can be clearly seen that the dopants are evenly distributed in the fiber membrane.

[0083] (2) X-ray diffraction (XRD) and X-ray fluorescence (XRF) analysis

[0084] This example used a German D8 ADVANCE X-ray diffractometer. PVDF fiber films were characterized using XRD to determine the crystal structure, β-phase content, and doping status of each fiber film. The 2θ angle scan range was 10-70°. Elemental analysis of the borax powder was performed using a US ARLAdvant X Intellipower™ 3600 X-ray fluorescence spectrometer to determine the elemental content.

[0085] Figure 4 The XRD analysis diagrams of the PVDF nanofiber membrane, PVDF / B composite nanofiber membrane, PVDF / BT composite hydrophobic fiber membrane, and PVDF / BZ composite hydrophobic fiber membrane prepared in this example are shown. As can be seen from the figure, compared with the XRD results of the PVDF fiber membrane without any doping, after doping with boracite, the characteristic peaks of boracite are clearly seen in the XRD results of the PVDF / B, PVDF / BT, and PVDF / BZ fiber membranes, once again verifying that the dopant has been successfully doped into the fiber membrane. In addition, compared with the pure PVDF fiber membrane, the characteristic peaks of the β phase of PVDF in the other three doped fiber membranes are significantly increased, while the characteristic peaks of the α phase are reduced.

[0086] Table 1 shows the XRF elemental spectrum determination results of boracite, which determines its main element composition.

[0087] Table 1

[0088]

[0089] (3) Fourier transform infrared spectroscopy (FT-IR) analysis

[0090] This example uses a Nicolet IS10 Fourier transform infrared spectrometer with a scanning range of 400 cm -1 ~4000cm -1 , which is used to characterize the percentage of β phase in electrospun composite fiber membranes.

[0091] Figure 5 FTIR spectra of the PVDF nanofiber membrane, PVDF / B composite nanofiber membrane, PVDF / BT composite hydrophobic fiber membrane, and PVDF / BZ composite hydrophobic fiber membrane prepared in this example. As can be seen from the figure, the ratio of β phase to α phase in the doped fiber membrane is higher than that of the pure PVDF fiber membrane without any doping.

[0092] FT-IR absorption follows the Lambert-Beer law, and the relative fraction of the β phase in the fiber membrane can be calculated using formula (3.1.1):

[0093]

[0094] Among them: A β and K β 840cm respectively -1 The absorption peak intensity and absorption coefficient at the absorption coefficient is 6.1×10 4 cm 2 / mol,A α and K α 763cm respectively -1 The absorption peak intensity and absorption coefficient at the absorption peak are 7.7×10 4 cm 2 / mol.

[0095] According to the results of Fourier transform infrared spectroscopy analysis, the contents of β phase in PVDF nanofiber membrane, PVDF / B composite nanofiber membrane, PVDF / BT composite hydrophobic fiber membrane and PVDF / BZ composite hydrophobic fiber membrane were calculated to be 73%, 91%, 87% and 89%, respectively.

[0096] Figure 6a and Figure 6b The diameter distribution diagrams of the microspheres in the PVDF / BT composite hydrophobic fiber membrane and the PVDF / BZ composite hydrophobic fiber membrane prepared in this example are shown in FIG. As can be seen from the figure, the diameters of the nanospheres are approximately concentrated between 2 and 4 μm.

[0097] (4) Electrical performance test

[0098] The triboelectric properties of the electrospun composite fiber film were tested using a linear motor and an electrometer (using a linear reciprocating impact of 5 N to create a simple triboelectric nanogenerator (TENG) with a contact area of ​​30 x 30 mm). The power generation principle of the contact-separation TENG is based on charge transfer caused by contact electrification and electrostatic induction coupling. Under the action of an external force, the polyamide and PVDF / TM-S surfaces come into contact, triggering the triboelectric effect. Due to the different abilities of the two materials to gain or lose electrons, the polyamide surface becomes positively charged and the PVDF / TM-S surface becomes negatively charged. Currently, these two equal and opposite charges are in the same plane, resulting in no potential difference between the two electrodes. When the force applied to the TENG is removed, the two charged surfaces separate, creating a potential difference between the two electrodes. As the electrodes gradually separate, this potential difference drives electrons from the PVDF / TM-S electrode to the polyamide electrode, generating a transient current until electrostatic equilibrium is reached. When pressure is reapplied to one end of the electrode and the distance between them decreases, a potential difference reappears between the electrodes, causing electrons to flow from the polyamide-side electrode back to the PVDF / TM-S-side electrode, reducing the amount of induced charge on the electrodes. This cyclical contact and separation process causes electrons to transfer back and forth in the external circuit, forming an electric current.

[0099] Figures 7a to 7c 、 Figures 8a to 8c and Figures 9a to 9c The triboelectric performance test results of three composite fiber membranes prepared in this example are shown: PVDF / B composite nanofiber membrane, PVDF / BT composite hydrophobic fiber membrane, and PVDF / BZ composite hydrophobic fiber membrane. As can be seen from the figure, the PVDF fiber membrane doped only with boracic acid has a maximum short-circuit current of 7.1μA, a transferred charge of 102nC, and an open-circuit voltage of 294V. The PVDF fiber membrane spray-doped with titanium dioxide has a maximum short-circuit current of 6.4μA, a transferred charge of 113nC, and an open-circuit voltage of 256V. The PVDF fiber membrane spray-doped with zirconium dioxide has a maximum short-circuit current of 6.1μA, a transferred charge of 117nC, and an open-circuit voltage of 252V. The electrical performance of the fiber membrane doped only with boracic acid is greatly improved. After spray-doping with titanium dioxide / zirconium dioxide, the transferred charge is increased, but the short-circuit current and open-circuit voltage are reduced.

[0100] In this example, the dielectric constant and dielectric loss of the electrospun composite fiber membrane were measured using a DZ5001 dielectric constant tester using the plate capacitance method. The air permeability of the electrospun composite fiber membrane was measured using a Ningbo Textile Instrument Factory fully automatic air permeability meter (YG461H) using the airflow method, which measures the amount of air flowing through the electrospun composite fiber membrane per unit area per unit time under a specified pressure differential.

[0101] Figure 10 、 Figure 11 and Figure 12 The dielectric constant, air permeability, and dielectric loss test results of three composite fiber membranes prepared in this example are shown: PVDF / B composite nanofiber membrane, PVDF / BT composite hydrophobic fiber membrane, and PVDF / BZ composite hydrophobic fiber membrane. As can be seen from the figure, the dielectric constant of the spray-doped titanium dioxide / zirconium dioxide-doped fiber membrane is improved, and at high frequencies, the dielectric loss of the titanium dioxide / zirconium dioxide-doped fiber membrane is significantly reduced. At the same time, the nanospheres that appear due to the spray-doped titanium dioxide / zirconium dioxide support the fiber filaments, greatly improving the air permeability of the PVDF / BT and PVDF / BZ fiber membranes.

[0102] Figure 13 The results of charge transfer tests for the three composite fiber membranes prepared in this example, namely the PVDF / B composite nanofiber membrane, the PVDF / BT composite hydrophobic fiber membrane, and the PVDF / BZ composite hydrophobic fiber membrane, under different humidity conditions, are shown. As can be seen from the figure, the charge transfer of the unspray-doped fiber membrane decreases significantly when the ambient humidity exceeds 50%, while the charge transfer of the PVDF / BT and PVDF / BZ fiber membranes only decreases significantly when the ambient humidity reaches 70%.

[0103] (4) Hydrophobicity test

[0104] The water contact angle of the electrospun composite fiber membrane was tested at room temperature. In this embodiment, a German Dataphysics OCA50 contact angle meter was used. The test results were obtained after the droplet was stabilized on the surface of the electrospun composite fiber membrane. The reported data is the average value at five different positions on the surface of the electrospun composite fiber membrane.

[0105] Figures 14a to 14d Surface images of four fiber membranes, namely, PVDF nanofiber membrane, PVDF / B composite nanofiber membrane, PVDF / BT composite hydrophobic fiber membrane, and PVDF / BZ composite hydrophobic fiber membrane, prepared according to embodiments of the present invention, under a 200x optical microscope. As can be seen from the images, compared to fiber membranes not doped with electrostatic spraying, the PVDF / BT and PVDF / BZ fiber membranes have smoother surfaces without distinct fiber filaments. This uniform and dense surface structure without visible fiber filaments reduces the contact area with water.

[0106] Figure 15a 、 Figure 15b 、 Figure 15c and Figure 15dThe water contact angle test results of four fiber membranes prepared in this example are PVDF nanofiber membrane, PVDF / B composite nanofiber membrane, PVDF / BT composite hydrophobic fiber membrane, and PVDF / BZ composite hydrophobic fiber membrane. As can be seen from the figure, the contact angles of PVDF / BT and PVDF / BZ fiber membranes are 151.7° and 152.2°, respectively, which have reached the super-hydrophobic standard (150°) and are much larger than the first two fiber membranes. This shows that after combining the electrostatic spray process to dope titanium dioxide / zirconium dioxide, the hydrophobic properties of the fiber membrane are effectively improved, thereby improving the electrical output performance of TENG in a high humidity environment.

[0107] Figure 16 Schematic diagram of the microstructure of PVDF / / BT composite hydrophobic fiber membrane (boranite doping amount is 1.5wt%; titanium dioxide doping amount is 0.6wt%). Figure 16 The medium gray balls represent borate particles, and the large white balls are PVDF microspheres with attached nano-titanium dioxide particles.

[0108] 3. Application test of PVDF / BT composite hydrophobic fiber membrane and PVDF / BZ composite hydrophobic fiber membrane in triboelectric nanogenerator

[0109] In order to verify the mechanical energy collection and electrical performance output capabilities of PVDF / BT composite hydrophobic fiber membrane and PVDF / BZ composite hydrophobic fiber membrane, independent TENGs based on PVDF / BT composite hydrophobic fiber membrane (PVDF / BZ composite hydrophobic fiber membrane) were manufactured in actual application tests. The maximum instantaneous output power density of the two TENGs under different loads can reach 455.6mW / m by mechanical collision (collision force is 5N). 2 、433.3mW / m 2 ( Figure 17a and Figure 17b The output current remains relatively stable under 14.4k cycles of collision ( Figure 18a and Figure 18b ).

[0110] To further verify the electrical output performance of the PVDF / BT and PVDF / BZ composite hydrophobic fiber membranes under real-world conditions, the experimental setup was fully exposed to air for a seven-day test period. For the first five days, the temperature and humidity of the test environment were undisturbed. Since humidity in natural environments typically remains around 50%, this is insufficient to verify the performance of these two composite hydrophobic fiber membranes in high-humidity environments. Therefore, starting on the sixth and seventh days, the ambient humidity was artificially increased. Samples of the membranes' transferred charge were taken at the same time (10:00 AM) throughout the seven days. The test results showed no significant change in the transferred charge over the first five days. However, on the sixth and seventh days, as the humidity increased to 80% and 90%, the transferred charge decreased significantly, but the output remained stable. This demonstrates that the unique structure of the PVDF / BT and PVDF / BZ composite hydrophobic fiber membranes enables effective and stable electrical signal output even in high-humidity environments.

[0111] application Figure 20a The circuit diagram in the figure is used to test the charging of capacitors with different capacities. The test results show that the TENG based on the PVDF / BT composite hydrophobic fiber membrane has reached the power supply requirement for small electrical appliances. Capacitors can be used as energy storage devices to provide long-lasting power for electrical appliances. Figure 20b The circuit diagram link successfully powered the thermometer, and under periodic impact friction, it successfully lit up 300 small LED bulbs (the power of each LED bulb is 0.04W).

[0112] TENG based on PVDF / BT composite hydrophobic fiber membrane and PVDF / BZ composite hydrophobic fiber membrane can also be used in wearable device sensing because it can adapt to high humidity environments. It can monitor people's walking signals in real time, such as signals when the arms are folded, signals when the legs move, and signals of force on the soles of shoes when walking.

Claims

1. A composite hydrophobic fiber membrane based on a triboelectric nanogenerator, characterized in that: The invention is composed of a polyvinylidene fluoride nanofiber membrane, boracite particles, hydrophobic nanoparticles and polyvinylidene fluoride microspheres; the boracite particles are embedded in the fiber filaments of the polyvinylidene fluoride nanofiber membrane, the polyvinylidene fluoride microspheres are attached to the fiber filaments of the polyvinylidene fluoride nanofiber membrane, a part of the hydrophobic nanoparticles are evenly attached to the polyvinylidene fluoride microspheres, and the other part of the hydrophobic nanoparticles are evenly attached to the fiber filaments of the polyvinylidene fluoride nanofiber membrane; the hydrophobic nanoparticles are titanium dioxide nanoparticles or zirconium dioxide nanoparticles.

2. The composite hydrophobic fiber membrane based on the triboelectric nanogenerator according to claim 1, characterized in that: The thickness of the polyvinylidene fluoride nanofiber membrane is 80-120 μm, and the diameter of the fiber filaments of the polyvinylidene fluoride nanofiber membrane is 160-170 nm; the particle size of the boracic microparticles is 100-200 nm, the particle size of the hydrophobic nanoparticles is 80-150 nm, and the diameter of the polyvinylidene fluoride microspheres is 0.5-5.0 μm; the mass of the boracic microparticles is 0.5-3.0 wt% of the mass of the polyvinylidene fluoride fiber membrane, the mass of the hydrophobic nanoparticles is 0.2-1.0 wt% of the mass of the polyvinylidene fluoride microspheres, and the polyvinylidene fluoride microspheres is 10-20 wt% of the mass of the polyvinylidene fluoride fiber membrane; and the mass ratio of the hydrophobic nanoparticles attached to the polyvinylidene fluoride microspheres to the hydrophobic nanoparticles attached to the fiber filaments of the polyvinylidene fluoride nanofiber membrane is (10-20):

1.

3. A method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator, characterized in that: The steps include: Step (1), ultrasonically dispersing borate powder in N,N-dimethylformamide to obtain a borate dispersion; adding a first polyvinylidene fluoride powder to the borate dispersion, heating and stirring until the first polyvinylidene fluoride is completely dissolved, to obtain an electrospinning solution; Step (2), ultrasonically dispersing hydrophobic nanoparticles into N,N-dimethylformamide to obtain a hydrophobic nanoparticle dispersion, wherein the hydrophobic nanoparticles are titanium dioxide nanoparticles or zirconium dioxide nanoparticles; adding a second polyvinylidene fluoride powder to the hydrophobic nanoparticle dispersion, heating and stirring until the second polyvinylidene fluoride is completely dissolved, to obtain an electrostatic spray liquid; Step (3), placing the electrospinning solution and the electrostatic spray solution in an electrospinning device to simultaneously perform electrospinning and electrostatic spraying, and collecting the electrostatic jet product; Step (4): drying the electrostatic jet products collected on the collector. After the drying process is completed, the composite hydrophobic fiber membrane based on the friction nanogenerator as claimed in claim 1 is obtained.

4. The method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator according to claim 3, characterized in that: In step (1), the particle size of the borate powder is 100 to 200 nm, and in the electrospinning solution: the mass of the borate powder is 0.5 to 3.0 wt % of the mass of the first polyvinylidene fluoride, and the ultrasonic dispersion conditions are: ultrasonic dispersion at a frequency of 30 to 60 kHz at room temperature for 1.5 to 3 hours.

5. The method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator according to claim 3, characterized in that: In step (1), the average relative molecular mass of the first polyvinylidene fluoride in the first polyvinylidene fluoride powder is 500,000 to 600,000, the mass fraction of the first polyvinylidene fluoride in the electrospinning solution is 15 to 20 wt%, and the heating and stirring conditions are: stirring at a temperature of 65 to 80° C. and a stirring speed of 350 to 500 rpm for 2 to 5 hours.

6. The method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator according to claim 3, characterized in that: In step (2), the particle size of the hydrophobic nanoparticles is 80 to 150 nm, and in the electrostatic spray liquid: the mass of the hydrophobic nanoparticles is 0.2 to 1.0 wt % of the mass of the second polyvinylidene fluoride, and the ultrasonic dispersion conditions are: ultrasonic dispersion at a frequency of 40 to 60 kHz at room temperature for 60 to 90 minutes.

7. The method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator according to claim 3, characterized in that: In step (2), the average relative molecular mass of the second polyvinylidene fluoride in the second polyvinylidene fluoride powder is 400,000 to 450,000, the mass fraction of the second polyvinylidene fluoride in the electrostatic spray liquid is 4 to 10 wt%, and the heating and stirring conditions are: stirring at a temperature of 65 to 80° C. and a stirring speed of 350 to 500 rpm for 2 to 3 hours.

8. The method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator according to claim 3, characterized in that: In step (3), the electrospinning equipment is an electrospinning machine capable of performing electrospinning and electrospinning spraying; when electrospinning and electrospinning spraying are performed simultaneously: the voltage of the high-voltage electrostatic field is 18 to 20 kV, and the propulsion rates of the electrospinning solution and the electrospinning spray solution are the same, both 1.0 to 1.2 mL·h -1 , the distance between the injection nozzle tip and the aluminum foil collector is 15 to 18 cm, the temperature is controlled in the range of 30 to 45°C, and the relative humidity is controlled in the range of 40 to 50%.

9. The method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator according to claim 3, characterized in that: In step (4), the drying conditions are: 50-60° C., drying for 12-16 hours; the thickness of the composite hydrophobic fiber membrane obtained by the drying treatment is 80-120 μm.

10. The method for preparing a composite hydrophobic fiber membrane based on a triboelectric nanogenerator according to claim 3, characterized in that: In step (1), the particle size of the borate powder is 100 to 200 nm, the mass fraction of the borate powder in the borate dispersion is 0.5 to 2.5 wt %, and the ultrasonic dispersion conditions are: ultrasonic dispersion at a frequency of 40 kHz for 2 h at room temperature; The average relative molecular mass of the first polyvinylidene fluoride powder is 600,000, the mass fraction of the first polyvinylidene fluoride in the electrospinning solution is 20 wt%, and the heating and stirring conditions are: at a temperature of 70°C and a stirring speed of 400 rpm for 4 hours; In step (2), the particle size of the hydrophobic nanoparticles is 80 to 150 nm, the mass fraction of the hydrophobic nanoparticles in the hydrophobic nanoparticle dispersion is 0.2 to 1.0 wt %, and the ultrasonic dispersion conditions are: ultrasonic dispersion at a frequency of 40 kHz for 60 min at room temperature; The average relative molecular mass of the second polyvinylidene fluoride powder is 400,000, the mass fraction of the second polyvinylidene fluoride in the electrostatic spray liquid is 8 wt %, and the heating and stirring conditions are: at a temperature of 70° C. and a stirring speed of 400 rpm for 2 hours; In step (3), the electrospinning equipment is an electrospinning machine capable of performing electrospinning and electrospinning spraying. When electrospinning and electrospinning spraying are performed simultaneously, the voltage of the high-voltage electrostatic field is 20 kV, and the propulsion rates of the electrospinning solution and the electrospinning spray solution are the same, both 1.2 mL·h -1 , the distance between the injection nozzle tip and the aluminum foil collector was 18 cm, the temperature was 40 °C, and the relative humidity was 40%; In step (4), the drying conditions are: 55° C., drying for 12 h; the thickness of the composite hydrophobic fiber membrane obtained by the drying treatment is 70 to 90 μm.

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