A piezoelectric catalytic polyvinylidene fluoride material and its preparation method and application

Abstract

The present invention relates to the field of new material technology, and in particular to a piezoelectric catalytic polyvinylidene fluoride material and its preparation method and application, including obtaining nanoflower ZnO and obtaining a piezoelectric catalytic film. By using nanoflower ZnO and carbon nanotubes as fillers for PVDF membranes, the contact area between the surface of the film material and the target pollutants for piezoelectric degradation is effectively increased, the supply of piezoelectric charges and the charge transfer efficiency within the PVDF matrix are increased, thereby improving the ability and efficiency of degrading organic pollutants. Direct piezoelectric catalysis under low-frequency water flow is achieved for organic pollutants; at the same time, the film material structure is easy to recycle and exhibits good cycle stability, solving the secondary pollution problem commonly associated with inorganic piezoelectric powders, overcoming the limitations of traditional piezoelectric catalytic systems, and providing a scalable and environmentally friendly method for the degradation of organic pollutants.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a piezoelectric catalytic polyvinylidene fluoride material and a preparation method and application thereof. Background Art

[0002] Piezocatalysis can be used in various fields, including energy conversion, environmental governance, and biomedicine. It uses mechanical stress to deform piezoelectric materials with non-centrosymmetric crystal structures, promoting the migration of charge carriers to the material's surface for catalysis. When non-centrosymmetric piezoelectric materials deform, they generate internal dipole moments, leading to the separation of electron-hole pairs within the material. However, different fields have different material performance requirements. For example, in the field of environmental governance, active charge carriers migrate to the material surface, where they can directly react with organic pollutants or interact with abundant small molecules (hydroxyl, water, oxygen, etc.) on the surface, generating free radicals with strong oxidizing and mineralizing abilities. Free radicals, as the core of advanced oxidation technologies, have been experimentally proven to be highly effective in degrading organic pollutants such as antibiotics, organic dyes, phenolic microplastics, and organochlorine / organophosphorus pesticides.

[0003] At present, in the field of environmental governance, the mainstream research on piezoelectric catalysis is still limited to the use of high-frequency ultrasound to excite piezoelectric materials in powder state; or the introduction of superoxidants (such as persulfate, Fe 2+ The oxidant-H2O2 Fenton system utilizes piezoelectrically generated free radicals to assist in the activation of superoxidants. However, ultrasonic excitation methods are limited in practical application because they require specialized equipment and consume high energy, making them generally unsuitable for large-scale environmental applications. Introducing superoxidants can increase free radical concentrations, leading to more efficient pollutant degradation. However, this strategy also presents challenges such as the high cost of chemical oxidants and the secondary pollution caused by residual inorganic byproducts (sulfate, iron ions, chloride ions, etc.).

[0004] In the process of realizing the present invention, the applicant discovered that in the process of piezoelectric catalytic degradation of organic pollutants, how to improve the utilization efficiency of low-frequency mechanical energy is also an urgent problem to be solved. Summary of the Invention

[0005] The purpose of the present invention is to provide a piezoelectric catalytic polyvinylidene fluoride material and its preparation method and application to solve the above technical problems existing in the prior art, mainly including the following three aspects:

[0006] The first aspect of the present invention provides a method for preparing a piezoelectric catalytic polyvinylidene fluoride material, comprising obtaining a nanoflower ZnO and obtaining a piezoelectric catalytic film, wherein obtaining the nanoflower ZnO comprises the following steps: dissolving a zinc salt and a zinc ion complexing agent in a mass ratio of 1.5 to 3:1 in water to form a mixed solution, adjusting the pH value of the mixed solution to 12 to 13, and then reacting the mixed solution at 100°C to 150°C for 16 hours to 30 hours, washing, and drying to obtain the nanoflower ZnO;

[0007] The method for obtaining the piezoelectric catalytic film comprises the following steps: uniformly dispersing the nanoflower ZnO and PVDF in a mass ratio of 1:5 to 20 in a solvent to form a precursor solution, defoaming, and curing to obtain the piezoelectric catalytic film.

[0008] Furthermore, the zinc salt is at least one of zinc nitrate, zinc acetate, and zinc chloride.

[0009] Furthermore, the zinc ion complexing agent is at least one of sodium citrate, sodium tartrate, ethylenediaminetetraacetic acid (EDTA) and its salt polyacrylic acid.

[0010] Furthermore, the solvent is at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and N-methylpyrrolidone (NMP).

[0011] Furthermore, the preparation of the piezoelectric catalytic film includes the following steps: uniformly dispersing the highly conductive nanomaterial, the nanoflower ZnO and PVDF in a solvent at a mass ratio of 0.05-0.15:1:5-20 to form a precursor solution, defoaming, and curing to obtain the piezoelectric catalytic film.

[0012] Furthermore, the highly conductive nanomaterial is at least one of carbon nanotubes (CNTs), graphene, carbon quantum dots and MXene.

[0013] Furthermore, when the highly conductive nanomaterial, the nanoflower ZnO and PVDF are uniformly dispersed in a solvent, the highly conductive nanomaterial is first ultrasonically dispersed in the solvent, and then the nanoflower ZnO is added and mixed uniformly, and then PVDF is added and mixed at 65° C. to 80° C.

[0014] The second aspect of the present invention provides a piezoelectric catalytic polyvinylidene fluoride material, which is a PVDF film containing a filler, and the filler contains at least nanoflower ZnO. The nanoflower ZnO is formed by dissolving a zinc salt and a zinc ion complexing agent in water at a mass ratio of 1.5 to 3:1 to form a mixed solution, and then adjusting the pH value of the mixed solution to 12 to 13, and then reacting at 100°C to 150°C for 16h to 30h, washing, and drying to obtain nanoflower ZnO.

[0015] Furthermore, it is prepared by the above-mentioned preparation method.

[0016] A third aspect of the present invention provides an application method of the above-mentioned piezoelectric catalytic polyvinylidene fluoride material for performing piezoelectric catalytic degradation of organic pollutants.

[0017] Furthermore, the organic pollutant is at least one of antibiotics, organic dyes, phenolic microplastics, organochlorine pesticides, and organophosphorus pesticides;

[0018] And / or, piezoelectric catalytic degradation of organic pollutants is carried out under low-frequency water flow stirring.

[0019] Compared with the prior art, the present invention has at least the following technical effects:

[0020] The present invention adopts nanoflower ZnO as the filler of PVDF membrane, especially adopts nanoflower ZnO and CNTs as the filler of PVDF membrane, effectively improving the contact area between the surface of the film material and the target pollutants of piezoelectric degradation, increasing the supply of piezoelectric charge and the charge transfer efficiency within the PVDF matrix, thereby improving the ability and efficiency of degrading organic pollutants, and realizing direct piezoelectric catalytic degradation of organic pollutants under low-frequency water flow, without the need for high-energy ultrasonic excitation and the introduction of superoxidants, and itself has excellent catalytic activity; at the same time, the film material structure is easy to recycle and exhibits good cycle stability, solving the secondary pollution problem commonly associated with inorganic piezoelectric powders, overcoming the limitations of traditional piezoelectric catalytic systems, and providing a scalable and environmentally friendly method for the degradation of organic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a scanning electron microscope image (2 microns) of the amorphous ZnO in Comparative Example 1, the nanoflower ZnO in Example 1, the PVDF film in Test Example 1, and the nanoflower ZnO / CNTs / PVDF film prepared in Example 2 of the present invention;

[0023] Figure 2 This is a scanning electron microscope image (10 microns) of the nanoflower ZnO in Example 1 of the present invention;

[0024] Figure 3 is a scanning electron microscope image (2 microns) of amorphous ZnO in Comparative Example 1 of the present invention;

[0025] Figure 4 is a scanning electron microscope image (10 microns) of the PVDF film in Test Example 1 of the present invention;

[0026] Figure 5 is a scanning electron microscope image (10 microns) of the PVDF film in Test Example 1 of the present invention;

[0027] Figure 6 This is a scanning electron microscope image (10 microns) of the nanoflower ZnO / CNTs / PVDF film prepared in Example 2 of the present invention;

[0028] Figure 7 1 is a schematic diagram of the state of the piezoelectric catalytic degradation TC test in Test Example 1 of the present invention;

[0029] Figure 8 This is a graph showing the removal efficiency of the piezoelectric catalytic degradation TC test performed in Test Example 1 of the present invention;

[0030] Figure 9 This is a graph showing the removal efficiency of the piezoelectric catalytic cycle degradation TC test performed in Test Example 2 of the present invention;

[0031] Figure 10 This is a graph showing the removal efficiency of RhB by piezoelectric catalytic degradation in Test Example 3 of the present invention;

[0032] Figure 11 This is a graph showing the removal efficiency of the free radical inhibitors used in the test of the effect of the free radical inhibitors on the catalytic capacity in Test Example 4 of the present invention;

[0033] Figure 12 This is a graph showing the removal efficiency of a free radical inhibitor in a test of the effect of the free radical inhibitor on the catalytic ability in Test Example 5 of the present invention;

[0034] Figure 13 This is a current output diagram of the electrochemical performance test of Test Example 6 of the present invention;

[0035] Figure 14 This is an impedance diagram of the electrochemical impedance performance test of Test Example 7 of the present invention;

[0036] Figure 15 This is a top view of the PVDF modeling in Test Example 8 of the present invention;

[0037] Figure 16 This is a front view of the PVDF modeling in Test Example 8 of the present invention;

[0038] Figure 17 This is a top view of the ZnO modeling in Test Example 8 of the present invention;

[0039] Figure 18 This is a front view of the ZnO modeling in Test Example 8 of the present invention;

[0040] Figure 19Graph showing the conductivity of the material in Test Example 8 of the present invention for electrons at different energies;

[0041] Figure 20 This is a top view of PVDF adsorbing oxygen in Test Example 8 of the present invention;

[0042] Figure 21 This is a top view of oxygen adsorption on the ZnO (101) crystal plane in Test Example 8 of the present invention. DETAILED DESCRIPTION

[0043] The following description provides many different embodiments or examples for implementing different features of the present invention. The components and arrangements described in the following specific examples are only used to simplify the present invention and are only used as examples, not to limit the present invention.

[0044] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0045] In the field of energy conversion, piezoelectric catalysts are mainly used to convert mechanical energy into electrical energy, or use the piezoelectric effect to drive or promote chemical reactions, such as water decomposition to produce hydrogen, CO2 reduction, etc.; therefore, the performance requirements for piezoelectric catalysts in this field mainly include: 1. High energy conversion efficiency: Piezoelectric catalysts need to efficiently use the piezoelectric effect to convert mechanical energy into electrical energy, or ultimately promote chemical reactions to improve energy conversion efficiency; 2. Good stability: Piezoelectric catalysts need to maintain good stability during long-term energy conversion to avoid performance degradation; 3. Efficient catalytic activity: For piezoelectric catalysts that promote chemical reactions, they need to have efficient catalytic activity to reduce energy consumption and improve product selectivity.

[0046] In the biomedical field, piezoelectric catalysts are mainly used in disease treatment, antibacterial treatment, organic matter degradation, biosensing, etc.; the performance requirements for piezoelectric catalysts in this field mainly include: 1. Biocompatibility: Piezoelectric catalysts need to have good biocompatibility to avoid adverse effects on human tissues; 2. Selectivity: In biomedical applications, they need to have good selectivity to avoid damage to normal cells; 3. Controllability and intelligence: With the continuous development of the biomedical field, the controllability and intelligence requirements of piezoelectric catalysts are also getting higher and higher to achieve more precise treatment and sensing effects.

[0047] In the field of environmental remediation, piezoelectric catalysts are primarily used for treating organic wastewater and purifying air. The performance requirements for piezoelectric catalysts in this field include: 1. High catalytic activity: Piezoelectric catalysts must exhibit high catalytic activity against specific pollutants to achieve efficient degradation and treatment. 2. Stability and durability: During the environmental remediation process, piezoelectric catalysts must withstand a variety of environmental conditions and therefore require excellent stability and durability.

[0048] At present, the mainstream piezoelectric catalysts used in the field of environmental governance are limited to systems that use high-energy high-frequency ultrasound and systems that additionally introduce superoxide. Both systems have cost defects. In addition, since the piezoelectric catalysts in the prior art are all inorganic powders with microscopic granular morphology, they will disperse into suspensions in the fluid during application. If no subsequent treatment is performed, secondary pollution problems will occur. To this end, based on the application of non-toxic piezoelectric materials using low-frequency water flow to achieve efficient catalysis and direct degradation of organic pollutants, the present application provides a piezoelectric catalytic polyvinylidene fluoride material, which is prepared by a method comprising the following steps: obtaining nanoflower ZnO and obtaining a piezoelectric catalytic film, wherein obtaining nanoflower ZnO comprises the following steps: dissolving a zinc salt and a zinc ion complexing agent in a mass ratio of 1.5 to 3:1 in water to form a mixed solution, adjusting the pH value of the mixed solution to 12 to 13, and then reacting at 100°C to 150°C for 16h to 30h, washing, and drying to obtain nanoflower ZnO.

[0049] The method for obtaining the piezoelectric catalytic film comprises the following steps: uniformly dispersing the nanoflower ZnO and PVDF in a mass ratio of 1:5 to 20 in a solvent to form a precursor solution, defoaming, and curing to obtain the piezoelectric catalytic film.

[0050] Specifically, the zinc salt is at least one of zinc nitrate, zinc acetate, and zinc chloride.

[0051] Specifically, the zinc ion complexing agent is at least one of sodium citrate, sodium tartrate, ethylenediaminetetraacetic acid (EDTA) and its salts, and polyacrylic acid.

[0052] Specifically, the solvent is at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and N-methylpyrrolidone (NMP).

[0053] Specifically, the preparation of the piezoelectric catalytic film includes the following steps: uniformly dispersing the highly conductive nanomaterial, the nanoflower ZnO and PVDF in a solvent at a mass ratio of 0.05-0.15:1:5-20 to form a precursor solution, defoaming, and curing to obtain the piezoelectric catalytic film.

[0054] Specifically, the highly conductive nanomaterial is at least one of carbon nanotubes (CNTs), graphene, carbon quantum dots and MXene.

[0055] Specifically, when the highly conductive nanomaterial, the nanoflower ZnO and PVDF are uniformly dispersed in a solvent, the highly conductive nanomaterial is first ultrasonically dispersed in the solvent, then the nanoflower ZnO is added and mixed uniformly, and then PVDF is added and mixed at 65°C to 80°C.

[0056] Example 1

[0057] A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps:

[0058] To obtain ZnO nanoflowers, 2g of zinc acetate and 1g of citric acid were dissolved in 60mL of distilled water. A 2.5mol / L aqueous sodium hydroxide solution was then slowly added dropwise to the solution while stirring to adjust the pH to 12.5. The mixture was vigorously stirred for 1 hour. The mixture was then transferred to a 100mL Teflon-sealed autoclave and maintained at 120°C for 24 hours. The resulting product was vacuum filtered, washed sequentially with water and ethanol, and finally dried in a vacuum oven at 45°C.

[0059] To obtain a piezoelectric catalytic film, 1.5% nanoflower ZnO by weight was placed in DMF (N,N dimethylformamide) and stirred for 1 hour. Then, 15% PVDF powder by weight was added, heated to 70°C and stirred for 3 hours to completely dissolve the PVDF to obtain a ZnO / PVDF precursor solution. The ZnO / PVDF precursor solution was placed in a vacuum for 1 hour to eliminate bubbles. Then, 2 g of the ZnO / PVDF precursor solution was poured into a 6 cm*4 cm rectangular mold. The mold was then immersed in 75% alcohol solution and ultrapure water for 1 hour to cure, thereby obtaining a nanoflower ZnO / PVDF film.

[0060] Example 2

[0061] A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps:

[0062] To obtain ZnO nanoflowers, 2g of zinc acetate and 1g of citric acid were dissolved in 60mL of distilled water. A 2.5mol / L aqueous sodium hydroxide solution was then slowly added dropwise to the solution while stirring to adjust the pH to 12.5. The mixture was vigorously stirred for 1 hour. The mixture was then transferred to a 100mL Teflon-sealed autoclave and maintained at 120°C for 24 hours. The resulting product was vacuum filtered, washed sequentially with water and ethanol, and finally dried in a vacuum oven at 45°C.

[0063] To obtain a piezoelectric catalytic film, 0.15% CNTs by weight were placed in DMF (N,N dimethylformamide) and ultrasonically dispersed at 90W for 1 hour. Then, 1.5% nanoflower ZnO by weight was added and stirred for 1 hour. Finally, 15% PVDF powder by weight was added, heated to 70°C and stirred for 3 hours to completely dissolve the PVDF to obtain a ZnO / CNTs / PVDF precursor solution. The ZnO / CNTs / PVDF precursor solution was placed in a vacuum for 1 hour to eliminate bubbles. Then, 2 g of the ZnO / CNTs / PVDF precursor solution was poured into a 6 cm*4 cm rectangular mold. The mold was then immersed in 75% alcohol solution and ultrapure water for 1 hour to cure, thereby obtaining a nanoflower ZnO / CNTs / PVDF film.

[0064] Example 3

[0065] A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps:

[0066] To obtain nanoflower ZnO, 3g of zinc nitrate and zinc chloride and 1g of sodium tartrate were dissolved in 60mL of distilled water. A 2.5mol / L aqueous sodium hydroxide solution was then slowly added dropwise to the solution while stirring to adjust the pH to 12. The solution was stirred vigorously for 1 hour. The mixture was then transferred to a 100mL Teflon-sealed autoclave and maintained at 150°C for 16 hours. The resulting product was vacuum filtered, washed sequentially with water and ethanol, and finally dried in a vacuum oven at 45°C.

[0067] To obtain a piezoelectric catalytic film, 2% by weight of nanoflower ZnO was placed in DMF (N,N-dimethylformamide) and stirred for 1 hour. Then, 10% by weight of PVDF powder was added, and the mixture was heated to 70°C and stirred for 3 hours to completely dissolve the PVDF to obtain a ZnO / PVDF precursor solution. The ZnO / PVDF precursor solution was placed in a vacuum for 1 hour to eliminate bubbles. Then, 2 g of the ZnO / PVDF precursor solution was poured into a 6 cm*4 cm rectangular mold. The mold was then immersed in a 75% alcohol solution and then in ultrapure water for 1 hour to cure, thereby obtaining a ZnO / PVDF film.

[0068] Example 4

[0069] A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps:

[0070] To obtain nanoflower ZnO, 1.5 g of zinc nitrate and zinc chloride and 1 g of sodium citrate were dissolved in 60 mL of distilled water. A 2.5 mol / L aqueous sodium hydroxide solution was then slowly added dropwise to the solution while stirring to adjust the pH to 13. The mixture was vigorously stirred for 1 hour. The mixture was then transferred to a 100 mL Teflon-sealed autoclave and maintained at 100°C for 30 hours. The resulting product was vacuum filtered, washed sequentially with water and ethanol, and finally dried in a vacuum oven at 45°C.

[0071] To obtain a piezoelectric catalytic film, 1% by weight of nanoflower ZnO was placed in DMF (N,N-dimethylformamide) and stirred for 1 hour. Then, 20% by weight of PVDF powder was added, and the mixture was heated to 70°C and stirred for 3 hours to completely dissolve the PVDF to obtain a ZnO / PVDF precursor solution. The ZnO / PVDF precursor solution was placed in a vacuum for 1 hour to eliminate bubbles. Then, 2 g of the ZnO / PVDF precursor solution was poured into a 6 cm*4 cm rectangular mold. The mold was then immersed in a 75% alcohol solution and then in ultrapure water for 1 hour to cure, thereby obtaining a ZnO / PVDF film.

[0072] Example 5

[0073] A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps:

[0074] To obtain nanoflower ZnO, 2g of zinc acetate, 1.1g of sodium citrate, and EDTA were dissolved in 60mL of distilled water. A 2.5mol / L aqueous sodium hydroxide solution was slowly added dropwise to the solution while stirring to adjust the pH to 12.5. The solution was stirred vigorously for 1 hour. The mixture was then transferred to a 100mL Teflon-sealed autoclave and maintained at 125°C for 24 hours. The resulting product was vacuum filtered, washed sequentially with water and ethanol, and finally dried in a vacuum oven at 45°C.

[0075] To obtain a piezoelectric catalytic film, 0.05% CNTs by weight were placed in DMF (N,N dimethylformamide) and ultrasonically dispersed at 90W for 1 hour. Then, 1% nanoflower ZnO by weight was added and stirred for 1 hour. Finally, 20% PVDF powder by weight was added, heated to 70°C and stirred for 3 hours to completely dissolve the PVDF to obtain a ZnO / CNTs / PVDF precursor solution. The ZnO / CNTs / PVDF precursor solution was placed in a vacuum for 1 hour to eliminate bubbles. Then, 2g of the ZnO / CNTs / PVDF precursor solution was poured into a 6cm*4cm rectangular mold. The mold was then immersed in 75% alcohol solution and ultrapure water for 1 hour to cure, thereby obtaining a nanoflower ZnO / CNTs / PVDF film.

[0076] Example 6

[0077] A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps:

[0078] To obtain nanoflower ZnO, 2g of zinc chloride, 1g of citric acid, and ethylenediaminetetraacetic acid were dissolved in 60mL of distilled water. A 2.5mol / L aqueous sodium hydroxide solution was then slowly added dropwise to the solution while stirring to adjust the pH to 12.5. The solution was stirred vigorously for 1 hour. The mixture was then transferred to a 100mL Teflon-sealed autoclave and maintained at 120°C for 24 hours. The resulting product was vacuum filtered, washed sequentially with water and ethanol, and finally dried in a vacuum oven at 45°C.

[0079] Obtaining piezoelectric catalytic film: Place 0.15% nanographene by weight in dimethyl sulfoxide (DMSO) and ultrasonically disperse it at 90W for 1 hour, then add 1% nanoflower ZnO by weight and stir for 1 hour, and finally add 5% PVDF powder by weight, heat to 70°C and stir for 3 hours to completely dissolve PVDF to obtain ZnO / graphene / PVDF precursor solution, place the ZnO / graphene / PVDF precursor solution in a vacuum for 1 hour to eliminate bubbles, pour 2g of ZnO / graphene / PVDF precursor solution into a 6cm*4cm rectangular mold, and then soak the mold in 75% alcohol solution and ultrapure water in turn for 1 hour to cure, to obtain nanoflower ZnO / graphene / PVDF film.

[0080] Comparative Example 1

[0081] A method for preparing a polyvinylidene fluoride film, which differs from Example 1 in that amorphous ZnO is used instead of nanoflower ZnO for preparation. The amorphous ZnO is prepared by the following method: dissolving 2 g of zinc acetate in distilled water (60 mL), then slowly adding a 2.5 mol / L sodium hydroxide aqueous solution dropwise to the solution under stirring to adjust the pH to 12.5 and vigorously stirring for 1 hour, then transferring the mixture to a 100 mL Teflon-sealed autoclave and maintaining it at 120° C. for 24 hours; vacuum filtering the resulting product, washing it sequentially with water and ethanol, and finally drying it in a vacuum oven at 45° C. to obtain amorphous ZnO.

[0082] Then, the amorphous ZnO / PVDF film was prepared by obtaining the piezoelectric catalytic film process.

[0083] Comparative Example 2

[0084] A method for preparing a polyvinylidene fluoride film, which differs from Example 2 in that amorphous ZnO is used instead of nanoflower ZnO for preparation. The amorphous ZnO is prepared by the following method: dissolving 2 g of zinc acetate in distilled water (60 mL), then slowly adding a 2.5 mol / L sodium hydroxide aqueous solution to the solution while stirring to adjust the pH to 12.5 and vigorously stirring for 1 hour, then transferring the mixture to a 100 mL Teflon-sealed autoclave and maintaining it at 120° C. for 24 hours; vacuum filtering the resulting product, washing it sequentially with water and ethanol, and finally drying it in a vacuum oven at 45° C. to obtain amorphous ZnO.

[0085] Then, the amorphous ZnO / CNTs / PVDF film was prepared by obtaining the piezoelectric catalytic film process.

[0086] Test Example 1

[0087] The films prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2, as well as the PVDF film, were subjected to a piezoelectric catalytic degradation test of TC (tetracycline hydrochloride). The test conditions were as follows: the upper end of the film was clamped and immersed in 100 mL of a 5 mg / L TC solution, and magnetically stirred at 450 rpm for 60 min in a 250 mL beaker with a diameter of 87 mm. Figure 7 During the process, 1.5 mL of solution was collected at regular intervals and analyzed by UV-visible spectrometer (Unico, UV 4820). The removal efficiency was quantified by the standard curve corresponding to the maximum absorbance. The test results are shown in Figure 8 As shown, C0 represents the initial concentration of TC and C represents the concentration of TC during the test.

[0088] according to Figure 8 , it can be seen that under the same conditions, the addition of ZnO greatly improved the catalytic ability of the system. Among them, nanoflower ZnO promoted better catalytic efficiency than amorphous ZnO. The TC removal rates of nanoflower ZnO / PVDF film and amorphous ZnO / PVDF film within 60 minutes were 77.4% and 72.1%, respectively. The introduction of CNTs further improved the piezoelectric performance. The TC removal rate of amorphous ZnO / CNTs / PVDF film was 78.9%. Nanoflower ZnO / CNTs / PVDF film showed the best catalytic ability, completing 85.7% TC removal within 60 minutes.

[0089] It should be noted that the PVDF film is prepared by placing 15% by weight of PVDF powder in DMF (N,N dimethylformamide), heating to 70°C and stirring for 3 hours to completely dissolve the PVDF to obtain a PVDF precursor solution. After the PVDF precursor solution is placed in a vacuum for 1 hour to eliminate bubbles, 2 g of the PVDF precursor solution is poured into a 6 cm*4 cm rectangular mold, and then the mold is immersed in a 75% alcohol solution and ultrapure water in turn for curing for 1 hour to obtain a PVDF film.

[0090] The amorphous ZnO in comparative example 1, the nanoflower ZnO in example 1, the PVDF film in test example 1, and the nanoflower ZnO / CNTs / PVDF film prepared in example 2 were observed by electron microscopy. The results are as follows: Figures 1 to 3 As shown in the figure, it can be seen that the growth pattern of nanoflower ZnO relative to amorphous ZnO shows a stacked structure; Figure 4 and Figure 5 As shown in Figure 2, different parts of the PVDF film have both dense surfaces and large flaky particles connected to each other; Figure 6 As shown, different parts of the nanoflower ZnO / CNTs / PVDF film all show highly porous surfaces. The porous structure is composed of spherical PVDF cross-linked fibers, and exposed nanoflower ZnO is distributed on its surface, which effectively increases the contact area between the surface of the ZnO / CNTs / PVDF piezoelectric film and the target pollutants for piezoelectric degradation, increases the supply of piezoelectric charge and the charge transfer efficiency within the PVDF matrix, thereby improving the ability and efficiency of degrading organic pollutants and achieving the goal of direct piezoelectric catalysis and degradation of organic pollutants under low-frequency water flow.

[0091] Test Example 2

[0092] The nanoflower ZnO / CNTs / PVDF film prepared in Example 2 was subjected to a cycle test for degradation of the representative antibiotic TC. The test conditions were the same as those in Test Example 1. Four cycle tests were performed. The test results are shown in FIG. Figure 9 As shown in the figure, it can be seen that the nanoflower ZnO / CNTs / PVDF film still has the ability to remove 70.5% TC within 60 min after 4 cycles.

[0093] Test Example 3

[0094] The nanoflower ZnO / CNTs / PVDF film prepared in Example 2 was subjected to a piezoelectric catalytic degradation test of representative dyes RhB (rhodamine B) and MB (methylene blue). The test conditions were the same as those in Test Example 1. The nanoflower ZnO / CNTs / PVDF film was divided into two groups. The first group was dosed with 5 mg / L of RhB, and the second group was dosed with 5 mg / L of MB. The test results are shown in Figure 2. Figure 10As shown in the figure, it can be seen that the nanoflower ZnO / CNTs / PVDF film removed 87.2% of RhB and 72.1% of MB within 60 minutes.

[0095] Test Example 4

[0096] The nanoflower ZnO / CNTs / PVDF film prepared in Example 2 was tested for the effect of free radical inhibitors on the catalytic ability of antibiotics. The test conditions were the same as those in Test Example 1 and the film was divided into four groups. The first group did not add inhibitors, and the second group added 0.3 mol / L tert-butyl alcohol (TBA) as a hydroxyl radical ( • OH) inhibitor, and the third group added excess benzoquinone (BQ) at a concentration of 0.3 mol / L as a superoxide radical ( • O2 - ) inhibitor, the fourth group added chloroform (Chlo) as a superoxide radical ( • O2 - ) inhibitors; test results such as Figure 11 shown.

[0097] Depend on Figure 11 It can be seen that for • O2 - The inhibitor BQ (inhibits the reaction rate by about 10 9 M -1 s -1） and chloroform (inhibits the reaction rate by about 10 10 M -1 s -1 ) ， The nanoflower ZnO / CNTs / PVDF piezoelectric film only removed 17.6% and 29.2% of TC in 60 min, respectively. For the inhibitor TBA of •OH (the inhibition reaction rate is about 3.8–7.6 ×10 8 M -1 s -1 ), the nanoflower ZnO / CNTs / PVDF piezoelectric film removed 68.0% of TC within 60 minutes. It can be seen that the nanoflower ZnO / CNTs / PVDF piezoelectric film mainly relies on the free radicals with high oxidative ability to degrade TC under low-frequency water flow, among which • O2 - It is the main active species for degrading TC.

[0098] Test Example 5

[0099] The nanoflower ZnO / CNTs / PVDF film prepared in Example 2 was tested for the effect of free radical inhibitors on the catalytic ability of dyes. The test conditions were the same as those in Test Example 1. The film was divided into six groups. The first group degraded 5 mg / L of RhB without adding inhibitors. The second group added 0.3 mol / L tert-butyl alcohol (TBA) as a hydroxyl radical ( • OH) inhibitor to degrade 5 mg / L RhB, and the third group added excess benzoquinone (BQ) at a concentration of 0.3 mol / L as superoxide radical ( • O2 - ) inhibitor to degrade 5 mg / L RhB; the fourth group degraded 5 mg / L MB without adding inhibitor, and the fifth group added 0.3 mol / L tert-butyl alcohol (TBA) as hydroxyl radical ( • OH) inhibitor to degrade 5 mg / L MB, and the sixth group added 0.3 mol / L excess benzoquinone (BQ) as superoxide radical ( • O2 - ) inhibitor degraded 5mg / L MB; the test results are as follows Figure 12 shown.

[0100] Depend on Figure 12 It can be seen that for • O2 - The inhibitor BQ and the nanoflower ZnO / CNTs / PVDF piezoelectric film removed 71.5% of RhB and 63.7% of MB within 60 min respectively. • The inhibitor TBA of OH, the nanoflower ZnO / CNTs / PVDF piezoelectric film removed 82.2% of RhB and 70.4% of MB in 60 minutes. It can be seen that due to the strong adsorption of dyes, the nanoflower ZnO / CNTs / PVDF piezoelectric film removed the dyes RhB and MB by the combined action of piezoelectric catalysis and physical adsorption under low-frequency water flow. • OH is the active species that plays a major role in piezoelectric degradation.

[0101] Test Example 6

[0102] The films prepared in Example 1, Example 2, and Comparative Example 1, as well as the PVDF film, were subjected to comparative tests of electrochemical transient current performance. The tests were conducted in a standard three-electrode electrochemical workstation, using a constant potential polarization mode to measure the piezoelectric current output under low-power ultrasound at 40kHz and 10W. The working electrode was the FTO glass coated with the sample, the reference electrode was a saturated calomel electrode, the counter electrode was a platinum sheet, and the electrolyte was a Na2SO4 solution with a concentration of 0.5mol / L. Preparation of the working electrode: Use a glass rod to apply the precursor solution to the conductive surface of the FTO conductive glass, ensuring that the effective area is 1cm 2Then, the precursor solution was spin-coated using a 100 μm coater and dried in a vacuum drying oven at 45°C for 20 min before use.

[0103] The test results are as follows Figure 13 As shown in the figure, it can be seen that under the same conditions, the piezoelectric current output generated by the nanoflower ZnO / CNTs / PVDF film due to oscillation excitation is much higher than that of other systems, which shows that the nanoflower ZnO / CNTs / PVDF film has a higher utilization efficiency of external mechanical force.

[0104] Test Example 7

[0105] The films prepared in Example 1, Example 2, and Comparative Example 1, as well as the PVDF film, were subjected to comparative tests of electrochemical impedance performance. The tests were conducted in a standard three-electrode electrochemical workstation, wherein the working electrode was the FTO glass coated with the sample, the reference electrode was a saturated calomel electrode, the counter electrode was a platinum sheet, and the electrolyte was a solution of 0.1 mol / L K3[Fe(CN)6], 0.1 mol / L K4[Fe(CN)6], and 0.1 mol / L KCl. Preparation of the working electrode: Use a glass rod to apply the precursor solution to the conductive surface of the FTO conductive glass, ensuring that the effective area is 1 cm 2 Then, the precursor solution was spin-coated using a 100 μm coater and dried in a vacuum drying oven at 45°C for 20 min before use.

[0106] The test results are as follows Figure 14 As shown in the figure, the radius of the semicircle corresponding to the high-frequency sinusoidal wave region on the left directly reflects the magnitude of the electrochemical impedance. As can be seen from the figure, under the same conditions, the impedance of the films is ranked as follows: PVDF film > amorphous ZnO / PVDF film > nanoflower ZnO / PVDF film > nanoflower ZnO / CNTs / PVDF film, demonstrating the role of nanoflower ZnO and CNTs as fillers in PVDF membranes in promoting charge transport within the membrane.

[0107] Test Example 8

[0108] Taking Test Example 1 and Test Example 4 as reference, theoretical modeling and simulation were carried out on ZnO and PVDF thin film, which contributed the most to the improvement of catalytic ability, to verify the effect of adding ZnO on charge transfer efficiency and generation of superoxide radicals. • O2 - Improved efficiency, computational modeling by Figures 15 to 18 The Vienna ab initiosimulation package, developed by the University of Vienna, was used to simulate the material's electrical conductivity and the energy change before and after oxygen adsorption (adsorption energy). Data post-processing was performed using the open-source program VASPKIT.

[0109] Specifically, the system wave function is described by projected augmented plane waves, and the exchange correlation potential is treated by the Perdew-Burke Ernzerhof functional. The cutoff energy of the valence electrons is 500 eV, and its reciprocal space is composed of a spacing of 0.03 Å. -1 The gamma grid sampling is 10. -6 eV ， The force convergence criterion is 0.02 eV / Å. Grimme's DFT+D3 method is used to consider the long-range force correction. For the calculation of conductivity, the relaxation time is 1 s, the Fermi level is set to the zero energy point, and Hubbard correction is applied to zinc atoms and oxygen atoms, with correction parameters U of 10 eV and 7 eV, respectively. For the calculation of oxygen molecule adsorption, the oxygen adsorption surface of ZnO is the (101) surface of the model, and the oxygen adsorption surface of PVDF is the side where the H atom is located. In order to avoid the oxygen molecules being too close to each other, PVDF uses the 3*1 supercell of the original unit cell for adsorption. The adsorption energy E a The calculation formula is: E a =E 基底+O2 -E 基底 -E O2 , E 基底 represents the energy of ZnO (101) or PVDF, E O2 Represents the energy of oxygen, E 基底+O2 It represents the total energy of ZnO (101) or PVDF after adsorbing oxygen. The larger the negative value of adsorption energy, the easier it is to adsorb.

[0110] The simulation results are given by Figure 19 、 Figure 20 and Figure 21 shown. Figure 19 The material's conductivity for electrons of different energies is shown. The energy region where ZnO's conductivity is zero is significantly smaller than that of PVDF, indicating that ZnO has a narrower band gap. Furthermore, in the left region (valence band), the electronic conductivity of ZnO varies little at different energies, indicating a wider distribution of electronic states and weaker electron localization. Therefore, ZnO has better electron transfer efficiency. Figure 20 and Figure 21 Schematic diagram showing oxygen adsorption on ZnO (101) surface and PVDF and the adsorption energy E a , it can be seen that the adsorption energy of ZnO to oxygen E a (-2.803eV) is much larger than the adsorption energy E of PVDF for oxygen a The ZnO nanoparticles exhibit a peak electrochemical activity of -0.467 eV, indicating that O₂ is firmly adsorbed on the ZnO, facilitating electron transfer to oxygen and ultimately generating superoxide radicals, enabling piezoelectric catalytic degradation of organic pollutants. The simulation further validates the claim that using nanoflower ZnO as a filler in PVDF membranes improves charge transfer efficiency within the matrix and the membrane's inherent catalytic capacity.

[0111] Test Example 9

[0112] For piezoelectric catalysts used in environmental governance, the comprehensive energy consumption required for pollutant degradation (EE / O, kWh m -3 ) is an important indicator for evaluating its energy-saving and environmentally friendly application performance. The comprehensive energy consumption can be calculated by using the flow force of water to degrade TC in the experiment. Specifically, the mechanical energy during the stirring mass transfer process to excite the piezoelectric film is estimated by the following formula:

[0113]

[0114] Where P is the power required for stirring (cross-shaped magnetic stirring bar, W), N p is the power number, which is 2.0 according to Ruston's power standard table. is the density of the reaction solution, n is the stirring speed (7.5 rs -1 ), d j is the diameter of the mixing equipment (50mm).

[0115] By calculating the power estimation, considering the total amount of polluted water and degradation rate corresponding to each experiment, the comprehensive energy consumption EE / O (kWh m -3 )for:

[0116]

[0117] Where W is the energy required for the agitator to degrade once (J), V is the volume of the reaction solution (L), p is the power required for stirring (kW), C0 and C t are the pollutant concentrations before and after the reaction (mg / L), k is the pseudo-first-order kinetic constant reflecting the degradation rate (min -1 ).

[0118] The comprehensive energy consumption EE / O of the nanoflower ZnO / CNTs / PVDF film, Fe2O3@MoS2 / PVDF piezoelectric pipe (see Wang, JX, et al., Sustainable self-powered degradation of antibiotics usingFe3O4@MoS2 / PVDF modified pipe with superior piezoelectric activity: Mechanisminsight, toxicity assessment and energy consumption. APPLIED CATALYSIS B-ENVIRONMENT AND ENERGY, 2023. 331.), and ZnO / CQDs / PVDF piezoelectric pipe (see Wang, ZC, etal., A novel ZnO / CQDs / PVDF piezoelectric system for efficiently degradationof antibiotics by using water flow energy in pipeline: Performance andmechanism. NANO ENERGY, 2023. 107.) prepared in Example 2 were calculated respectively, and the results are shown in Table 1.

[0119] Table 1 Comprehensive energy consumption of piezoelectric catalysis

[0120]

[0121] As shown in Table 1, the nanoflower ZnO / CNTs / PVDF film significantly reduces its overall energy consumption (EE / O) while maintaining a good TC degradation rate. This demonstrates the nanoflower ZnO / CNTs / PVDF film's excellent utilization of the tangential water flow under stirring. Compared to piezoelectric pipes, which rely on high-energy external pumping to generate dynamic water pressure, the nanoflower ZnO / CNTs / PVDF film significantly reduces energy consumption, facilitating its application in natural water bodies and offering wider applicability.

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a piezoelectric catalytic polyvinylidene fluoride material, characterized in that: Including obtaining nanoflower ZnO and obtaining piezoelectric catalytic film, The method for obtaining the nanoflower ZnO comprises the following steps: dissolving a zinc salt and a zinc ion complexing agent in a mass ratio of 1.5 to 3:1 in water to form a mixed solution, adjusting the pH value of the mixed solution to 12 to 13, reacting the mixed solution at 100° C. to 150° C. for 16 to 30 hours, washing, and drying to obtain the nanoflower ZnO; The method for obtaining the piezoelectric catalytic film comprises the following steps: uniformly dispersing a highly conductive nanomaterial, the nanoflower ZnO, and PVDF in a solvent at a mass ratio of 0.05-0.15:1:5-20 to form a precursor solution, defoaming, and curing to obtain the piezoelectric catalytic film; the highly conductive nanomaterial is carbon nanotubes (CNTs).

2. The preparation method according to claim 1, wherein The zinc salt is at least one of zinc nitrate, zinc acetate, and zinc chloride.

3. The preparation method according to claim 1, wherein The zinc ion complexing agent is at least one of sodium citrate, sodium tartrate, ethylenediaminetetraacetic acid (EDTA) and its salts, and polyacrylic acid.

4. The preparation method according to claim 1, wherein The solvent is at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N-methylpyrrolidone (NMP).

5. The preparation method according to claim 1, wherein When the highly conductive nanomaterial, the nanoflower ZnO and PVDF are uniformly dispersed in a solvent, the highly conductive nanomaterial is first ultrasonically dispersed in the solvent, and then the nanoflower ZnO is added and mixed uniformly, and then PVDF is added and mixed at 65° C. to 80° C.

6. A piezoelectric catalytic polyvinylidene fluoride material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.

7. A method for applying the piezoelectric catalytic polyvinylidene fluoride material according to claim 6, characterized in that: Used for piezoelectric catalytic degradation of organic pollutants.

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