Piezoelectric catalytic polyvinylidene fluoride material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of new materials, in particular to a piezoelectric catalytic polyvinylidene fluoride material and a preparation method and application thereof, and the preparation method comprises the steps of obtaining nanoflower ZnO and obtaining a piezoelectric catalytic film. The nanoflower ZnO and the carbon nanotubes are used as fillers of the PVDF film, so that the contact area between the surface of a film material and target pollutants subjected to piezoelectric degradation is effectively increased, and the supply of piezoelectric charges and the charge transmission efficiency in a PVDF matrix are increased, thereby improving the capability and efficiency of degrading organic pollutants. Organic pollutants are directly degraded through piezoelectric catalysis under low-frequency water flow; meanwhile, the thin film material structure is easy to recycle and shows good cycling stability, the problem of secondary pollution generally related to inorganic piezoelectric powder is solved, the limitation of a traditional piezoelectric catalysis system is overcome, and an extensible and environment-friendly method is provided for organic pollutant degradation.

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] Piezoelectric catalysis can be used in various fields such as energy conversion, environmental governance and biomedicine. It is a technology that uses mechanical stress to deform piezoelectric materials with non-centrosymmetric crystal structures and promote the migration of carriers to the surface of the material to participate in catalysis. When non-centrosymmetric piezoelectric materials are deformed, they will generate internal dipole moments, resulting in the separation of electron-hole pairs in the material. However, different fields have different requirements for material performance. For example, in the field of environmental governance, active carriers can be used to migrate to the surface of materials to directly react with organic pollutants or interact with small molecules (hydroxyl, water molecules, oxygen molecules, etc.) that are fully present on the surface to produce free radicals with strong oxidation and mineralization capabilities. Free radicals, as the core of advanced oxidation technology, 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 system of using high-frequency ultrasound to excite piezoelectric materials in powder state; or introducing superoxidants (such as persulfate, Fe 2+ -H2O2 Fenton system), a system that uses free radicals generated by the piezoelectric principle itself to assist in activating superoxidants. However, the ultrasonic excitation method has practical limitations because it requires specialized equipment, has high energy consumption, and is generally not suitable for large-scale environmental applications. The introduction of superoxidants can increase the concentration of free radicals, thereby more effectively degrading pollutants; but this strategy also has the problem of high cost of chemical oxidants and 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 a problem to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a piezoelectric catalytic polyvinylidene fluoride material and a preparation method and application thereof to solve the above technical problems existing in the prior art, which mainly include the following three aspects: 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 the obtaining of 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 at 100° C. to 150° C. for 16 h to 30 h, washing, and drying to obtain the nanoflower ZnO; The method for obtaining the piezoelectric catalytic film comprises the following steps: uniformly dispersing the nanoflower ZnO and PVDF in a mass ratio of 1:5-20 in a solvent to form a precursor solution, defoaming, and curing to obtain the piezoelectric catalytic film.

[0006] Furthermore, the zinc salt is at least one of zinc nitrate, zinc acetate and zinc chloride.

[0007] Furthermore, the zinc ion complexing agent is at least one of sodium citrate, sodium tartrate, ethylenediaminetetraacetic acid (EDTA) and its salt polyacrylic acid.

[0008] Furthermore, the solvent is at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and N-methylpyrrolidone (NMP).

[0009] 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 a piezoelectric catalytic film.

[0010] Furthermore, the highly conductive nanomaterial is at least one of carbon nanotubes (CNTs), graphene, carbon quantum dots and MXene.

[0011] 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, then the nanoflower ZnO is added and mixed uniformly, and then PVDF is added and mixed at 65°C to 80°C.

[0012] 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 at least contains nanoflower ZnO. The nanoflower ZnO is formed by 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, 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.

[0013] Furthermore, it is prepared by the above-mentioned preparation method.

[0014] The third aspect of the present invention provides an application method of the above-mentioned piezoelectric catalytic polyvinylidene fluoride material for piezoelectric catalytic degradation of organic pollutants.

[0015] Furthermore, the organic pollutant is at least one of antibiotics, organic dyes, phenolic microplastics, organochlorine pesticides, and organophosphorus pesticides; And / or, piezoelectric catalytic degradation of organic pollutants is carried out under low-frequency water flow stirring.

[0016] Compared with the prior art, the present invention has at least the following technical effects: 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 improves the contact area between the surface of the film material and the target pollutant of piezoelectric degradation, increases the supply of piezoelectric charge and the charge transfer efficiency in the PVDF matrix, thereby improving the ability and efficiency of degrading organic pollutants, and realizing the direct degradation of organic pollutants by piezoelectric catalysis under low-frequency water flow, without the need for high-energy ultrasonic excitation and the introduction of superoxidant, and itself has excellent catalytic activity; at the same time, the film material structure is easy to recycle and exhibits good cycle stability, solves the secondary pollution problem usually associated with inorganic piezoelectric powder, overcomes the limitations of traditional piezoelectric catalytic systems, and provides a scalable and environmentally friendly method for the degradation of organic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention or the description of the prior art will be briefly introduced below. 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 creative work.

[0018] Figure 1 It is an electron microscope scanning image (2 micrometers) of the amorphous ZnO in comparative example 1 of the present invention, the nanoflower ZnO in example 1, the PVDF film in test example 1, and the nanoflower ZnO / CNTs / PVDF film prepared in example 2; Figure 2 This is an electron microscope scanning image (10 microns) of the nanoflower ZnO in Example 1 of the present invention; Figure 3 is an electron microscope scanning image (2 micrometers) of amorphous ZnO in Comparative Example 1 of the present invention; Figure 4 is an electron microscope scanning image (10 micrometers) of the PVDF film in Test Example 1 of the present invention; Figure 5is an electron microscope scanning image (10 micrometers) of the PVDF film in Test Example 1 of the present invention; Figure 6 This is an electron microscope scanning image (10 microns) of the nanoflower ZnO / CNTs / PVDF film prepared in Example 2 of the present invention; Figure 7 This is a schematic diagram of the state of the piezoelectric catalytic degradation TC test performed in Test Example 1 of the present invention; Figure 8 This is a removal efficiency diagram of the piezoelectric catalytic degradation TC test performed in Test Example 1 of the present invention; Fig. 9 This is a removal efficiency diagram of the piezoelectric catalytic cycle degradation TC test in Test Example 2 of the present invention; Fig.10 This is a graph showing the removal efficiency of piezoelectric catalytic degradation of RhB in Test Example 3 of the present invention; Fig.11 This is a removal efficiency diagram of the test example 4 of the present invention for testing the effect of free radical inhibitors on catalytic ability; Fig.12 This is a removal efficiency diagram of the test example 5 of the present invention for testing the effect of free radical inhibitors on catalytic ability; Fig.13 This is a current output diagram of the electrochemical performance test of Test Example 6 of the present invention; Fig.14 This is an impedance diagram of the electrochemical impedance performance test of Test Example 7 of the present invention; Fig.15 It is a top view of PVDF modeling in Test Example 8 of the present invention; Fig.16 It is a front view of PVDF modeling in Test Example 8 of the present invention; Fig.17 It is a top view of ZnO modeling in Test Example 8 of the present invention; Fig.18 It is a front view of ZnO modeling in Test Example 8 of the present invention; Fig.19 is a graph of the conductivity of the material in Test Example 8 of the present invention for electrons at different energies; Fig. 20 is a top view of PVDF adsorbing oxygen in Test Example 8 of the present invention; Fig.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

[0019] 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.

[0020] 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 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.

[0021] 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.

[0022] 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, good selectivity is required 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 in order to achieve more precise treatment and sensing effects.

[0023] In the field of environmental governance, piezoelectric catalysts are mainly used to treat organic wastewater and purify air. The performance requirements for piezoelectric catalysts in this field mainly include: 1. High catalytic activity: Piezoelectric catalysts need to have high catalytic activity for specific pollutants to achieve efficient degradation and treatment. 2. Stability and durability: In the process of environmental governance, piezoelectric catalysts need to withstand the test of various environmental conditions, so they need to have good stability and durability.

[0024] 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; and because the piezoelectric catalysts in the prior art are all inorganic powders with microscopic particle morphology, they will be dispersed into suspensions in the fluid during the application process. If no subsequent treatment is performed, it will also cause secondary pollution problems. 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: including obtaining nanoflower ZnO and obtaining a piezoelectric catalytic film, wherein obtaining nanoflower ZnO includes the following steps: dissolving a zinc salt and a zinc ion complexing agent with a mass ratio of 1.5 to 3:1 in water 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; The method for obtaining the piezoelectric catalytic film comprises the following steps: uniformly dispersing the nanoflower ZnO and PVDF in a mass ratio of 1:5-20 in a solvent to form a precursor solution, defoaming, and curing to obtain the piezoelectric catalytic film.

[0025] Specifically, the zinc salt is at least one of zinc nitrate, zinc acetate and zinc chloride.

[0026] Specifically, the zinc ion complexing agent is at least one of sodium citrate, sodium tartrate, ethylenediaminetetraacetic acid (EDTA) and its salts, and polyacrylic acid.

[0027] Specifically, the solvent is at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and N-methylpyrrolidone (NMP).

[0028] 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 a piezoelectric catalytic film.

[0029] Specifically, the highly conductive nanomaterial is at least one of carbon nanotubes (CNTs), graphene, carbon quantum dots and MXene.

[0030] 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.

[0031] Example 1 A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps: Obtaining nanoflower ZnO: Dissolve 2g zinc acetate and 1g citric acid in distilled water (60mL), then slowly drip 2.5mol / L sodium hydroxide aqueous solution into the solution under stirring to adjust the pH to 12.5 and stir vigorously for 1 hour, then transfer the mixture to a 100mL Teflon-sealed autoclave and keep it at 120°C for 24 hours. The obtained product was vacuum filtered and washed with water and ethanol in turn, and finally dried in a vacuum oven at 45°C.

[0032] To obtain a piezoelectric catalytic film: 1.5% by weight of nanoflower ZnO was placed in DMF (N, N dimethylformamide) and stirred for 1 hour, and then 15% by weight of PVDF powder was added, heated to 70°C and stirred for 3 hours to completely dissolve PVDF to obtain a ZnO / PVDF precursor solution. The ZnO / PVDF precursor solution was placed in a vacuum for 1 hour to eliminate bubbles, and 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 ultrapure water for curing for 1 hour to obtain a nanoflower ZnO / PVDF film.

[0033] Example 2 A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps: Obtaining nanoflower ZnO: Dissolve 2g zinc acetate and 1g citric acid in distilled water (60mL), then slowly drip 2.5mol / L sodium hydroxide aqueous solution into the solution under stirring to adjust the pH to 12.5 and stir vigorously for 1 hour, then transfer the mixture to a 100mL Teflon-sealed autoclave and keep it at 120°C for 24 hours. The obtained product was vacuum filtered and washed with water and ethanol in turn, and finally dried in a vacuum oven at 45°C.

[0034] To obtain a piezoelectric catalytic film: 0.15% by weight of CNTs was placed in DMF (N, N dimethylformamide) and ultrasonically dispersed at 90 W for 1 hour, and then 1.5% by weight of nanoflower ZnO was added and stirred for 1 hour, and finally 15% by weight of PVDF powder was added, heated to 70°C and stirred for 3 hours to completely dissolve PVDF to obtain a ZnO / CNTs / PVDF precursor solution, and the ZnO / CNTs / PVDF precursor solution was placed in a vacuum for 1 hour to eliminate bubbles, and then 2 g of the ZnO / CNTs / PVDF precursor solution was poured into a 6 cm*4 cm rectangular mold, and then the mold was immersed in a 75% alcohol solution and ultrapure water for curing for 1 hour to obtain a nanoflower ZnO / CNTs / PVDF film.

[0035] Example 3 A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps: Obtaining nanoflower ZnO: 3g zinc nitrate and zinc chloride, and 1g sodium tartrate were dissolved in distilled water (60mL), and then 2.5mol / L sodium hydroxide aqueous solution was slowly dripped into the solution under stirring to adjust the pH to 12 and vigorously stirred for 1 hour, and then the mixture was transferred to a 100mL Teflon-sealed autoclave and kept at 150°C for 16 hours. The obtained product was vacuum filtered and washed with water and ethanol in turn, and finally dried in a vacuum oven at 45°C.

[0036] 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, heated to 70°C and stirred for 3 hours to completely dissolve PVDF to obtain a ZnO / PVDF precursor solution, and the ZnO / PVDF precursor solution was placed in a vacuum for 1 hour to eliminate bubbles, and then 2 g of the ZnO / PVDF precursor solution was poured into a 6 cm*4 cm rectangular mold, and then the mold was immersed in 75% alcohol solution and ultrapure water for curing for 1 hour to obtain a ZnO / PVDF film.

[0037] Example 4 A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps: Obtaining nanoflower ZnO: 1.5g zinc nitrate and zinc chloride, and 1g sodium citrate were dissolved in distilled water (60mL), and then 2.5mol / L sodium hydroxide aqueous solution was slowly dripped into the solution under stirring to adjust the pH to 13 and vigorously stirred for 1 hour, and then the mixture was transferred to a 100mL Teflon-sealed autoclave and kept at 100°C for 30 hours. The obtained product was vacuum filtered and washed with water and ethanol in turn, and finally dried in a vacuum oven at 45°C.

[0038] Obtaining 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, heated to 70°C and stirred for 3 hours to completely dissolve PVDF to obtain ZnO / PVDF precursor solution, and the ZnO / PVDF precursor solution was placed in a vacuum for 1 hour to eliminate bubbles, and then 2g of ZnO / PVDF precursor solution was poured into a 6cm*4cm rectangular mold, and then the mold was immersed in 75% alcohol solution and ultrapure water for curing for 1 hour to obtain ZnO / PVDF film.

[0039] Example 5 A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps: Obtaining nanoflower ZnO: 2g zinc acetate, 1.1g sodium citrate and EDTA were dissolved in distilled water (60mL), and then 2.5mol / L sodium hydroxide aqueous solution was slowly dripped into the solution under stirring to adjust the pH to 12.5 and vigorously stirred for 1 hour, and then the mixture was transferred to a 100mL Teflon-sealed autoclave and kept at 125°C for 24 hours. The obtained product was vacuum filtered and washed with water and ethanol in turn, and finally dried in a vacuum oven at 45°C.

[0040] To obtain a piezoelectric catalytic film: 0.05% by weight of CNTs was placed in DMF (N, N dimethylformamide) and ultrasonically dispersed at 90 W for 1 hour, then 1% by weight of nanoflower ZnO was added and stirred for 1 hour, and finally 20% by weight of PVDF powder was added, heated to 70°C and stirred for 3 hours to completely dissolve PVDF to obtain a ZnO / CNTs / PVDF precursor solution, and the ZnO / CNTs / PVDF precursor solution was placed in a vacuum for 1 hour to eliminate bubbles, and then 2 g of the ZnO / CNTs / PVDF precursor solution was poured into a 6 cm*4 cm rectangular mold, and then the mold was immersed in a 75% alcohol solution and ultrapure water for curing for 1 hour to obtain a nanoflower ZnO / CNTs / PVDF film.

[0041] Example 6 A method for preparing a piezoelectric catalytic polyvinylidene fluoride material comprises the following steps: Obtaining nanoflower ZnO: 2g of zinc chloride, 1g of citric acid and ethylenediaminetetraacetic acid were dissolved in distilled water (60mL), and then 2.5mol / L sodium hydroxide aqueous solution was slowly dripped into the solution under stirring to adjust the pH to 12.5 and vigorously stirred for 1 hour, and then the mixture was transferred to a 100mL Teflon-sealed autoclave and kept at 120°C for 24 hours. The obtained product was vacuum filtered and washed with water and ethanol in turn, and finally dried in a vacuum oven at 45°C.

[0042] Obtaining piezoelectric catalytic film: Place 0.15% by weight of nanographene in dimethyl sulfoxide (DMSO) and disperse it ultrasonically at 90W for 1 hour, then add 1% by weight of nanoflower ZnO and stir for 1 hour, finally add 5% by weight of PVDF powder, 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 for curing for 1 hour to obtain a nanoflower ZnO / graphene / PVDF film.

[0043] Comparative Example 1 A method for preparing a polyvinylidene fluoride film, which is different from Example 1, in that amorphous ZnO is used to replace nanoflower ZnO for preparation, and the amorphous ZnO is prepared by the following method: 2g of zinc acetate is dissolved in distilled water (60mL), and then 2.5mol / L of sodium hydroxide aqueous solution is slowly dripped into the solution under stirring to adjust the pH to 12.5 and vigorously stirred for 1 hour, and then the mixture is transferred to a 100mL Teflon-sealed autoclave and kept at 120°C for 24 hours; the obtained product is vacuum filtered and washed with water and ethanol in turn, and finally dried in a vacuum oven at 45°C to obtain amorphous ZnO.

[0044] Then, the amorphous ZnO / PVDF film was obtained by obtaining the piezoelectric catalytic film process.

[0045] Comparative Example 2 A method for preparing a polyvinylidene fluoride film, which is different from Example 2, in that amorphous ZnO is used to replace nanoflower ZnO for preparation, and the amorphous ZnO is prepared by the following method: 2g of zinc acetate is dissolved in distilled water (60mL), and then 2.5mol / L of sodium hydroxide aqueous solution is slowly dripped into the solution under stirring to adjust the pH to 12.5 and vigorously stirred for 1 hour, and then the mixture is transferred to a 100mL Teflon-sealed autoclave and kept at 120°C for 24 hours; the obtained product is vacuum filtered and washed with water and ethanol in turn, and finally dried in a vacuum oven at 45°C to obtain amorphous ZnO.

[0046] Then, the amorphous ZnO / CNTs / PVDF film was obtained by obtaining the piezoelectric catalytic film process.

[0047] Test Example 1 The films prepared in Example 1, Example 2, Comparative Example 1, Comparative Example 2, and 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, immersed in 100 mL of a 5 mg / L TC solution, and magnetically stirred at a speed of 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.

[0048] according to Figure 8It can be seen that under the same conditions, the addition of ZnO greatly improves the catalytic ability of the system. Among them, nanoflower ZnO has a better catalytic efficiency than amorphous ZnO. The TC removal rates of nanoflower ZnO / PVDF film and amorphous ZnO / PVDF film within 60 minutes are 77.4% and 72.1%, respectively; the introduction of CNTs further improves the piezoelectric performance, and the TC removal rate of amorphous ZnO / CNTs / PVDF film is 78.9%. Nanoflower ZnO / CNTs / PVDF film shows the best catalytic ability, completing 85.7% TC removal within 60 minutes.

[0049] It should be noted that the PVDF film is prepared by placing PVDF powder with a mass specific gravity of 15% 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, placing the PVDF precursor solution in a vacuum for 1 hour to eliminate bubbles, pouring 2 g of the PVDF precursor solution into a 6 cm*4 cm rectangular mold, and then immersing the mold in a 75% alcohol solution and ultrapure water for curing for 1 hour to obtain a PVDF film.

[0050] 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 microscope scanning, and the results are as follows: Figure 1~Figure 3 As shown in the figure, it can be seen that the growth law 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 a highly porous surface. The porous structure is composed of spherical PVDF cross-linked fibers with exposed nanoflower ZnO 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 charges 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 degradation of organic pollutants by piezoelectric catalysis under low-frequency water flow.

[0051] Test Example 2 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 as follows: Fig. 9As 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.

[0052] Test Example 3 The nanoflower ZnO / CNTs / PVDF film prepared in Example 2 was subjected to a piezoelectric catalytic degradation test of the representative dyes RhB (rhodamine B) and MB (methylene blue), and 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 doped with 5 mg / L of RhB, and the second group was doped with 5 mg / L of MB. The test results are shown in Figure 2. Fig.10 As 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.

[0053] Test Example 4 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 were 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 superoxide radical ( • O2 - ) inhibitor, and the fourth group added chloroform (Chlo) as a superoxide radical ( • O2 - ) inhibitors; test results such as Fig.11 shown.

[0054] Depend on Fig.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 removed only 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 oxidation ability to degrade TC under low-frequency water flow, among which • O2 - It is the main active species for degrading TC.

[0055] Test Example 5 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 and were divided into six groups. The first group degraded 5 mg / L RhB without adding inhibitors, and the second group added 0.3 mol / L tert-butyl alcohol (TBA) as a hydroxyl radical ( • OH) inhibitor degraded 5 mg / L RhB, and the third group added 0.3 mol / L excess benzoquinone (BQ) as superoxide radical ( • O2 - ) inhibitor degraded 5 mg / L RhB; the fourth group degraded 5 mg / L MB without 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 Fig.12 shown.

[0056] Depend on Fig.12 It can be seen that for • O2 - The inhibitor BQ, nanoflower ZnO / CNTs / PVDF piezoelectric film removed 71.5% of RhB and 63.7% of MB within 60 minutes; • 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 removes 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 mainly contributes to piezoelectric degradation.

[0057] Test Example 6 The films obtained in Example 1, Example 2, Comparative Example 1, and PVDF film were subjected to comparative tests of electrochemical transient current performance. The tests were conducted in a standard three-electrode electrochemical workstation, and the piezoelectric current output was measured under low-power ultrasound at 40kHz, 10W using a constant potential polarization mode, 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 Na2SO4 solution with a concentration of 0.5mol / L. Preparation method of the working electrode: Use a glass rod to apply the precursor solution on the conductive surface of the FTO conductive glass to ensure that the effective area is 1cm 2 Then, the precursor solution was spin-coated with a 100 μm coater and dried in a vacuum oven at 45°C for 20 min before use.

[0058] The test results are as follows Fig.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 illustrates the higher utilization efficiency of the nanoflower ZnO / CNTs / PVDF film for external mechanical force.

[0059] Test Example 7 The films prepared in Example 1, Example 2, Comparative Example 1, and PVDF film were subjected to comparative tests of electrochemical impedance performance 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 method of the working electrode: Use a glass rod to apply the precursor solution on the conductive surface of the FTO conductive glass to ensure that the effective area is 1 cm 2 Then, the precursor solution was spin-coated with a 100 μm coater and dried in a vacuum oven at 45°C for 20 min before use.

[0060] The test results are as follows Fig.14 As shown in the figure, the radius of the semicircle corresponding to the high-frequency sine wave area on the left directly reflects the size of the electrochemical impedance. It can be seen from the figure that under the same conditions, the impedance of the film is PVDF film> amorphous ZnO / PVDF film> nanoflower ZnO / PVDF film> nanoflower ZnO / CNTs / PVDF film, which shows that nanoflower ZnO and CNTs as fillers of PVDF film promote the charge transfer inside the film.

[0061] Test Case 8 Taking Test Example 1 and Test Example 4 as reference, theoretical modeling and simulation were carried out on ZnO and thin film PVDF, which contributed the most to the improvement of catalytic ability, to verify the effects of adding ZnO on charge transfer efficiency and generation of superoxide radicals. • O2 - Improved efficiency, computational modeling by Figure 15~Figure 18 The Vienna ab initiosimulation package developed by the University of Vienna was used to simulate the conductivity of the material and the energy change before and after the material adsorbs oxygen molecules (adsorption energy). The data was post-processed using the VASPKIT open source program.

[0062] Specifically, the projected augmented plane wave is used to describe the wave function of the system, and the Perdew-Burke Ernzerhof functional is used to treat the exchange correlation potential. The cutoff energy of the valence electron 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 long-range force correction. For the calculation of conductivity, the relaxation time is 1 s, the Fermi level is set as 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: 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 the adsorption energy, the easier it is to adsorb.

[0063] The simulation results are given by Fig.19 , Fig. 20 and Fig.21 shown. Fig.19The conductivity of the material for electrons of different energies is shown. The energy region where ZnO conductivity is zero is significantly smaller than the region where PVDF conductivity is zero, indicating that ZnO has a narrower bandgap; and in the left region (valence band region), the electronic conductivity of ZnO changes little under different energies, indicating that its electronic state distribution is wide and the electronic localization is weak. Therefore, ZnO has better electron transfer efficiency. Fig. 20 and Fig.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 is E a (-2.803eV) is much larger than the adsorption energy E of PVDF for oxygen a (-0.467eV), indicating that O2 is firmly adsorbed on ZnO, which is conducive to the transfer of electrons to oxygen and ultimately produces superoxide radicals, achieving piezoelectric catalytic degradation of organic pollutants. The simulation further verifies the claim that using nanoflower ZnO as a filler for PVDF membranes can improve the charge transfer efficiency within the matrix and the catalytic ability of the membrane itself.

[0064] Test Example 9 For piezoelectric catalysts used in environmental management, 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 flow to degrade TC in the experiment. Specifically, the mechanical energy in the process of stirring mass transfer to excite the piezoelectric film is estimated by the following formula:

[0065] Where P is the power required for stirring (cross-shaped magnetic stirring bar, W), N p is the power number, which is taken as 2.0 according to Ruston's power 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).

[0066] By calculating the power estimation, the total amount of polluted water and the degradation rate corresponding to each experiment were comprehensively considered to obtain the comprehensive energy consumption EE / O (kWh m -3 )for:

[0067] 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 tare the pollutant concentrations before and after the reaction (mg / L), k is the pseudo-first-order kinetic constant reflecting the degradation rate (min -1 ).

[0068] 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, et al., 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.

[0069] Table 1 Comprehensive energy consumption of piezoelectric catalysis

[0070] As can be seen from Table 1, the comprehensive energy consumption EE / O of the nanoflower ZnO / CNTs / PVDF film is greatly reduced while maintaining a good TC degradation rate, indicating that the nanoflower ZnO / CNTs / PVDF film has a good utilization rate of the tangential water flow under stirring. Compared with the piezoelectric pipe that relies on external high-energy pumping to generate dynamic water pressure, the nanoflower ZnO / CNTs / PVDF film has greatly reduced energy consumption, which is conducive to the application of natural water bodies and has a wider universality.

[0071] 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 protection scope 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 h to 30 h, washing, and drying to obtain the nanoflower ZnO; The method for obtaining the piezoelectric catalytic film comprises the following steps: uniformly dispersing the nanoflower ZnO and PVDF in a mass ratio of 1:5-20 in a solvent to form a precursor solution, defoaming, and curing to obtain the piezoelectric catalytic film.

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

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

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

5. The preparation method according to any one of claims 1 to 4, characterized in that The preparation of the piezoelectric catalytic film comprises 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.

6. The preparation method according to claim 5, characterized in that: The highly conductive nanomaterial is at least one of carbon nanotubes (CNTs), graphene, carbon quantum dots and MXene.

7. The preparation method according to claim 5, characterized in that: When the highly conductive nanomaterial, the nanoflower ZnO and PVDF are uniformly dispersed in the 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.

8. A piezoelectric catalytic polyvinylidene fluoride material, characterized in that: The material is a PVDF film containing a filler, wherein the filler contains at least nanoflower ZnO, and the nanoflower ZnO is prepared by 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, and then adjusting the pH value of the mixed solution to 12 to 13, and then reacting at 100° C. to 150° C. for 16 h to 30 h, washing, and drying to obtain the nanoflower ZnO.

9. A piezoelectric catalytic polyvinylidene fluoride material as claimed in claim 8, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

10. An application method of the piezoelectric catalytic polyvinylidene fluoride material as claimed in claim 8 or 9, characterized in that: Used for piezoelectric catalytic degradation of organic pollutants.

Images