A piezoelectric-photocatalytic membrane with a bilayer structure, its preparation method and application

Abstract

This invention relates to a piezoelectric-photocatalytic membrane with a bilayer structure, its preparation method, and its application, belonging to the field of photocatalysis using semiconductor nanomaterials. The bilayer structure is obtained by electrospinning a fiber membrane onto a cotton fabric substrate. The cotton fabric is subjected to a thermal reduction method to load Cu₂O nanoparticles onto its surface. The electrospun membrane is prepared by spraying a spinning solution made of PVDF / MWCNTs-OH / MoS₂ / DMF stirred at a suitable temperature under specific spinning conditions. MWCNTs-OH is embedded in the PVDF nanofibers, and MoS₂ particles are distributed on the surface of the PVDF nanofibers. The piezoelectric-photocatalytic membrane prepared by this invention has a bilayer structure, exhibits excellent visible light photocatalytic performance, and is easily recyclable.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis of semiconductor nanomaterials, and in particular to a piezoelectric-photocatalytic membrane with a bilayer structure, its preparation method and application. Background Technology

[0002] Environmental pollution poses a significant threat to human life and health, and as people's living standards improve, their demands for a healthy environment also increase. Photocatalysis technology can convert environmental pollutants into substances such as carbon dioxide, water, and inorganic salts, making it an environmentally friendly and efficient solution to environmental problems. Currently, semiconductor photocatalytic materials are widely used due to their simple preparation process, low cost, and ability to be mass-produced.

[0003] Both cuprous oxide and molybdenum disulfide have narrow band gaps, which give them a wider photoreaction range. However, the narrow band gap also leads to faster recombination of photogenerated electrons and holes, lower utilization of photogenerated carriers, and weaker redox capabilities. Furthermore, the inherent low conductivity of copper-based and molybdenum-based oxides is a key issue limiting their further applications.

[0004] Patent CN111468143A discloses a method for preparing a cuprous oxide / molybdenum disulfide composite material and its application in photocatalytic degradation of methyl orange. The method uses molybdenum disulfide nanosheets as a substrate to grow cuprous oxide material. However, both cuprous oxide and molybdenum disulfide are narrow bandgap semiconductor materials with less than ideal conductivity. Electrons are more likely to return from the excited state to the ground state, resulting in rapid recovery of photogenerated electrons and holes and low charge separation efficiency. At the same time, the presence of active sulfur in molybdenum disulfide can corrode cuprous oxide, leading to a weakening of photocatalytic ability.

[0005] Patent CN115400768A discloses the application of a heterojunction CdIn2S4 / Bi2WO6 piezoelectric-photocatalyst in the piezoelectric photodegradation of organic matter. It prepares CdIn2S4 particles and Bi2WO6 particles and then mixes and stirs them to obtain a composite catalyst. However, the mixed particles are prone to agglomeration, making it difficult for the active sites to be exposed to light, and recovery is difficult, which can easily lead to secondary pollution.

[0006] Patent CN110540430A discloses a method for preparing a piezoelectric photocatalytic film. It uses electrospinning technology to prepare photocatalytic fibers, then uses a hydrothermal method to prepare piezoelectric materials and composite them, and finally performs calcination treatment. It utilizes the internal electric field at the interface between the piezoelectric material and the photocatalyst to separate electrons and holes. However, it uses piezoelectric ceramics, which require subsequent polarization treatment to exert the piezoelectric effect. Moreover, the yield is low and the energy consumption is high.

[0007] Patent CN112121821A discloses a method for preparing a cadmium sulfide / zinc oxide composite material and its application in piezoelectric-photocatalytic removal of organic pollutants. Cadmium sulfide and zinc oxide are both n-type semiconductor materials, which easily lead to rapid recombination of photogenerated electrons and holes and have weak redox capabilities.

[0008] Patent CN103551203B discloses a method for preparing a TiO2 nanofiber photocatalyst supported on a basalt fiber cotton matrix. The method uses electrospinning to load TiO2 nanofibers on a basalt fiber cotton matrix. However, TiO2 is an n-type semiconductor material with a wide band gap, and the catalytic effect of a single photocatalyst is not ideal.

[0009] Therefore, there is an urgent need to provide a catalyst that is not prone to aggregation, has strong photocatalytic ability, and has a short catalytic time. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides a piezoelectric-photocatalytic membrane with a bilayer structure, its preparation method, and its application. The invention first pretreats cotton fabric to enable it to load a large amount of nanomaterials. Then, cuprous oxide nanoparticles are loaded onto the surface of the cotton fabric using a thermothermal reduction method. Finally, electrospinning is performed on the fabric as a substrate to obtain a Cu2O / MoS2 / PVDF / MWCNTs-OH bilayer photocatalytic membrane, achieving excellent degradation performance.

[0011] This invention is achieved through the following technical solution:

[0012] The first objective of this invention is to provide a method for preparing a piezoelectric-photocatalytic membrane with a bilayer structure, comprising the following steps:

[0013] (1) The cotton fabric was immersed in a copper salt solution, then immersed in an alkaline solution, and a reducing agent was added to prepare a composite cuprous oxide cotton fabric by reaction; it was then used as an electrospinning substrate.

[0014] (2) Add MWCNTs-OH and MoS2 particles to the PVDF solution and stir to obtain PVDF / MWCNTs-OH / MoS2 spinning solution;

[0015] (3) Using electrospinning technology, PVDF / MWCNTs-OH / MoS2 spinning solution is sprayed onto the surface of the cotton fabric with composite cuprous oxide obtained in step (1) to prepare the piezoelectric-photocatalytic membrane with a double-layer structure.

[0016] In one embodiment of the present invention, in step (1), the cotton fabric is pretreated to obtain:

[0017] The cotton fabric is pretreated by immersing it in an alkaline solution containing urea. In this treatment, urea causes the fibers to swell, and the alkaline treatment roughens the surface of the cotton fabric, thus enabling the subsequent loading of large quantities of nanomaterials.

[0018] In one embodiment of the present invention, in step (1), the reducing agent is a reducing agent containing an aldehyde group; the concentration of the reducing agent is 0.9 mmol / L to 1.1 mmol / L.

[0019] In one embodiment of the present invention, in step (1), the molar ratio / mass ratio of copper salt to reducing agent in the copper salt solution is 100-150:9-11.

[0020] In one embodiment of the present invention, in step (2), the molecular weight of PVDF in the PVDF solution is 700,000 to 800,000.

[0021] In one embodiment of the present invention, in step (2), the mass ratio of PVDF, MWCNTs-OH and MoS2 in the PVDF solution is 390-410:5-7:1-7.

[0022] In one embodiment of the present invention, in step (2), the PVDF / MWCNTs-OH / MoS2 spinning solution is prepared by the following method: PVDF (polyvinylidene fluoride) is first added to DMF and stirred at 60°C for 1.5h to 3.5h at a stirring speed of 500r / min to prepare the PVDF spinning solution. Then, 25mg to 35mg of MWCNTs-OH is added to the solution and stirred at 500r / min at room temperature for 1h to 2h to prepare the PVDF / MWCNTs-OH spinning solution. Finally, 5mg to 35mg of MoS2 particles are added and stirred and dispersed at 500r / min at room temperature for 6h to 24h to finally obtain the PVDF / MWCNTs-OH / MoS2 spinning solution.

[0023] In one embodiment of the present invention, in step (3), the parameters of the electrospinning technology satisfy one or more of the following conditions:

[0024] The needle used for electrospinning is 21G;

[0025] The feed rate is 0.6 mL / h to 1.25 mL / h;

[0026] The voltage is 12kV to 18kV;

[0027] The collection distance is 18cm to 20cm;

[0028] The collecting device rotates at a speed of 300 r / min to 450 r / min;

[0029] The temperature is 20℃~30℃;

[0030] The humidity is 40%–50%.

[0031] In one embodiment of the present invention, in step (3), the solvent of the electrospinning solution is N,N-dimethylformamide (DMF).

[0032] The second objective of this invention is to provide a piezoelectric-photocatalytic membrane with a bilayer structure obtained by the preparation method described above.

[0033] A third objective of this invention is to provide the application of the piezoelectric-photocatalytic membrane with the bilayer structure in the degradation of pollutants, wherein the pollutants are methyl orange, methylene blue, or rhodamine B.

[0034] In one embodiment of the present invention, the degradation time is ≤30 min.

[0035] In one embodiment of the present invention, in step (1), the copper salt is selected from one or more of copper sulfate, copper chloride, copper nitrate and copper acetate; the reducing agent is selected from one or more of hydrazine hydrate, glucose and formaldehyde.

[0036] The alkaline solution is an aqueous solution of sodium hydroxide with a concentration of 0.15 mol / L to 0.2 mol / L.

[0037] In one embodiment of the present invention, the MWCNTs-OH is prepared by the following method:

[0038] MWCNTs were immersed in a mixed solution of concentrated nitric acid and concentrated sulfuric acid and sonicated to introduce surface defects on the MWCNTs and improve their surface activity. Then, alkali was added to the above solution until neutral. The sample was then washed, dried, and sonicated in NH3·H2O. Finally, the mixture was rinsed and dried to obtain the MWCNTs-OH.

[0039] In one embodiment of the present invention, in step (3), the dimensions of the composite cuprous oxide cotton fabric are: 23cm × 30cm, and the weight is 140g / m². 2 ~180g / m 2 The thickness is 0.2mm.

[0040] The above technical solution of the present invention has the following advantages over the prior art:

[0041] 1. In this invention, the p-Cu2O / n-MoS2 heterostructure alters the transfer pathway of photogenerated electrons and holes, significantly reducing the recombination rate of electrons and holes, which is beneficial for redox reactions and greatly improves the efficiency of organic matter degradation. PVDF, due to its inherent piezoelectric effect, can generate an internal polarized electric field. Mechanically induced spontaneous polarization and piezoelectric potential facilitate charge separation of excitons in the nanomaterial, allowing photogenerated electrons and holes to move in opposite directions under local piezoelectric potential, thereby inhibiting photogenerated electron-hole recombination and improving photocatalytic performance.

[0042] 2. The piezoelectric photocatalytic thin film prepared by the electrospinning technology of this invention has high flexibility, high specific surface area, good continuity, excellent air permeability, and simple process. It greatly exposes the active sites of the catalyst, maintains the reaction area of ​​the semiconductor material, and at the same time constructs a continuous piezoelectric field, improves the separation rate of photogenerated electrons and holes, and enhances the catalytic effect of the photocatalyst. Using electrospinning technology to directly spray the fiber film onto cotton fabric can make the double-layer structure more firmly bonded without the need for other adhesives. At the same time, the piezoelectric current can directly and continuously stimulate the semiconductor material on the cotton fabric, slowing down the binding speed of photogenerated electrons and holes.

[0043] 3. In this invention, the interlaced warp and weft structure of the cotton fabric itself allows for the easy and secure loading of a large number of cuprous oxide nanoparticles. Furthermore, electrospinning with the cuprous oxide composite cotton fabric as a substrate prevents the cuprous oxide from contacting other compounds and being corroded or denatured. In addition, forming films of cuprous oxide and molybdenum disulfide on two separate substrates minimizes their aggregation, thus improving the performance of the photocatalyst. The photocatalyst prepared by this invention is stable in water, not easily broken, and easy to recover.

[0044] 4. In this invention, multi-walled carbon nanotubes (MWCNTs) are ideal conductive materials due to their excellent electrochemical properties, high conductivity, and large specific surface area. MWCNTs can induce charge accumulation at material boundaries. Electrospinning MWCNTs combined with PVDF promotes the alignment of PVDF chains in the β-phase conformation, improves the piezoelectric properties of PVDF, and further restricts the recombination of photogenerated electrons and holes on the ground, thus improving photocatalytic efficiency. Loading with carbon nanotubes can reduce the recombination rate of photogenerated carriers and inhibit photocorrosion of the photocatalyst. The excellent electron storage capacity of carbon nanotubes makes them excellent electron acceptors; photogenerated electrons from the conduction band of the photocatalyst are transferred to the carbon nanotubes, while holes remain on the photocatalyst surface. Therefore, the recombination efficiency of photogenerated electrons and holes is delayed, significantly improving photocatalytic efficiency. Hydroxylation of MWCNTs can prepare MWCNTs with hydroxyl radicals. Hydroxyl radicals are important groups for degrading pollutants and can enhance photocatalytic effects. Attached Figure Description

[0045] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0046] Figure 1 This is a flowchart illustrating the preparation process of the piezoelectric-photocatalytic membrane with a bilayer structure in this invention.

[0047] Figure 2 This is a graph showing the photocatalytic degradation rate data of A1 to A5 in this invention;

[0048] Figure 3 This is a graph showing the photocatalytic degradation rate data of B1 to B5 in this invention;

[0049] Explanation of reference numerals in the attached figures: 1 is the impregnation tank, 2 is the cotton fabric with composite cuprous oxide, 3 is the SEM image of the cotton fabric loaded with cuprous oxide, 4 is the electrospinning high-voltage wire, 5 is the electrospinning injector, 6 is the electrospinning guide tube, 7 is the piezoelectric-photocatalytic membrane with a double-layer structure, and 8 is the SEM image of the PVDF fiber membrane. Detailed Implementation

[0050] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0051] In this invention, PVDF with a molecular weight of 700,000–800,000 was purchased from Suzhou Taolian Plastics Co., Ltd.; MWCNT was purchased from Nanjing Xianfeng Nanotechnology Co., Ltd., with a diameter of 10nm–20nm, a length of 0.5μm–2μm, and a purity of 95%; DMF was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; copper sulfate, sodium molybdate, thioacetamide, hexadecyltrimethylammonium bromide, and ammonia were all purchased from Sinopharm Group. All chemical reagents were of analytical grade and required no further purification during use. The cotton fabric had a basis weight of 140g / m². 2 ~180g / m 2 It has a thickness of 0.2mm and was purchased from Jinling Textile Factory.

[0052] Example 1

[0053] This embodiment provides a method for preparing a piezoelectric-photocatalytic membrane with a bilayer structure, as detailed below:

[0054] (1) Preparation of molybdenum disulfide particles: 0.15 g thioacetamide, 0.242 g sodium molybdate, and 0.05 g hexadecyltrimethylammonium bromide were dissolved in 50 mL of deionized water and stirred at 500 r / min for 10 min to obtain a homogeneous solution. Hexadecyltrimethylammonium bromide can effectively prevent the aggregation of MoS2. The solution was then placed in a reaction vessel and treated at 200 °C for 24 h. The prepared molybdenum disulfide was centrifuged at 8000 r / min and washed with 75 vol% ethanol. Finally, the obtained molybdenum disulfide particles were dried at 60 °C for 24 h to obtain 150 mg of MoS2 particles.

[0055] (2) Pretreatment of cotton fabrics: Select a weight of 140g / m 2 A cotton fabric with a thickness of 0.2 mm was cut into pieces of 23 cm × 30 cm. The cotton fabric was then immersed in a solution containing 14 g urea, 24 g sodium hydroxide, and 462 g distilled water, and left to stand at -20°C to obtain the pretreated cotton fabric.

[0056] (3) Preparation of cotton fabric with composite cuprous oxide: The pretreated cotton fabric was immersed in 500 mL of impregnation tank 1 containing 0.1 g CuSO4 and left to stand for 30 min to allow the cotton fabric to fully adsorb Cu. 2+ Then, the cotton fabric was removed and immersed in a 0.15 mol / L NaOH solution. It was then treated in a water bath at 75°C for 72 hours to obtain Cu(OH)2. Finally, it was soaked and reduced with a 0.1 mol / L hydrazine hydrate solution to obtain a cotton fabric loaded with Cu2O. It was then washed with water and dried in a drying oven at 60°C for 2 hours to obtain a cotton fabric with composite cuprous oxide, which was used as a substrate for electrospinning.

[0057] (4) Hydroxylation treatment of WMCNTs: Immerse MWCNTs in a mixed solution of hydrochloric acid and sulfuric acid and sonicate for 48 h to introduce surface defects on MWCNTs and improve their surface activity. The mass ratio of concentrated nitric acid to concentrated sulfuric acid is 1:3. Then add NaOH to the above solution until neutral. Then wash and dry the sample, add it to NH3·H2O and sonicate for 48 h. Finally, rinse and dry the mixture to obtain MWCNTs-OH.

[0058] (5) Preparation of PVDF / MWCNTs-OH / MoS2 spinning solution: First, add 2.0g PVDF to 8.0g DMF and stir at 60℃ for 2.5h at a stirring speed of 500r / min to prepare PVDF spinning solution. Then, add 30mg MWCNTs-OH to the solution and stir at 500r / min at room temperature for 2h to prepare PVDF / MWCNTs-OH spinning solution. Finally, add 30mg MoS2 particles and stir at 500r / min at room temperature for 6h to finally obtain PVDF / MWCNTs-OH / MoS2 spinning solution.

[0059] (6) Preparation of a piezoelectric-photocatalytic membrane with a bilayer structure: The PVDF / MWCNTs-OH / MoS2 spinning solution was filtered through a filter screen. 7 mL of the PVDF / MWCNTs-OH / MoS2 spinning solution was then sprayed onto the surface of the resulting composite cuprous oxide cotton fabric using electrospinning technology to prepare the piezoelectric-photocatalytic membrane with the bilayer structure. The electrospinning needle was 21G, the feed rate was 1.25 mL / h, the voltage was 16 kV, the collection distance was 20 cm, the collector rotation speed was 300 r / min, the temperature was 25 °C, and the humidity was 43%.

[0060] The piezoelectric-photocatalytic membrane with a bilayer structure prepared in this embodiment was subjected to degradation tests, and its degradation capabilities for methyl orange and methylene blue were tested, as follows:

[0061] Degradation capacity test of methyl orange: The prepared piezoelectric-photocatalytic membrane with a bilayer structure was cut into 1cm×1cm pieces. 36 pieces were selected and placed in 60mL of a 10mg / L methyl orange (MO) solution. The mixture was stirred for 30min under light-protected conditions to reach adsorption-desorption equilibrium, and then 0.2mL of hydrogen peroxide solution was added. The treated MO solution was stirred under a xenon lamp (300W power, wavelength 200nm-800nm) for 30min. After every 10min of stirring, 3mL of MO solution was taken and centrifuged at 200r / min for 2min. The supernatant was collected, and the absorbance was measured using a UV spectrophotometer at the maximum absorption wavelength of 464nm. The degradation rate was calculated.

[0062] Where C t Ct represents the absorbance of the solution at time t, and C0 represents the initial absorbance of the solution.

[0063] Degradation ability test of methylene blue: The test method is similar to that for degrading methyl orange, except that the maximum absorption wavelength of methylene blue is 664 nm.

[0064] The degradation rates of methyl orange and methylene blue by the piezoelectric-photocatalytic membrane of this embodiment at different times are denoted as A1 and B1, respectively.

[0065] Example 2

[0066] The preparation and testing methods in this embodiment are similar to those in Example 1, except that:

[0067] In step (3), the mass of CuSO4 is 0.5g and the concentration of NaOH is 0.17mol / L;

[0068] In step (5), the mass of PVDF is 2.1g, the mass of DMF is 7.9g, and the stirring time is 3h at 60℃.

[0069] In step (6), the electrospinning parameters are: feed rate 0.8 mL / h, voltage 16 kV, collection distance 18 cm, collector rotation speed 380 r / min, temperature 24 ℃, and humidity 43%.

[0070] The degradation rates of methyl orange and methylene blue were denoted as A2 and B2, respectively.

[0071] Example 3

[0072] The preparation and testing methods in this embodiment are similar to those in Example 1, except that:

[0073] In step (3), the mass of CuSO4 is 0.65 g and the concentration of NaOH is 0.18 mol / L;

[0074] In step (5), the mass of MWCNTs-OH is 35 mg, the mass of MoS2 particles is 35 mg, and the stirring time after adding MoS2 particles is 12 h;

[0075] In step (6), the electrospinning parameters are: feed rate 0.85 mL / h, voltage 16 kV, collection distance 20 cm, collector rotation speed 420 r / min, temperature 28 ℃, and humidity 45%.

[0076] The degradation rates of methyl orange and methylene blue by the piezoelectric-photocatalytic membrane of this embodiment at different times are denoted as A3 and B3, respectively.

[0077] Example 4

[0078] The preparation and testing methods in this embodiment are similar to those in Example 1, except that:

[0079] In step (2), the weight of the cotton fabric is 180 g / m². 2 ;

[0080] In step (3), the mass of CuSO4 is 0.8 g and the concentration of NaOH is 0.2 mol / L;

[0081] In step (5), the mass of PVDF is 1.9g, the mass of DMF is 8.1g, the stirring time at 60℃ is 1.5h, the mass of MWCNTs-OH is 25mg, the mass of MoS2 particles is 10mg, and the stirring time after adding MoS2 particles is 24h.

[0082] In step (6), the electrospinning parameters are: feed rate 0.8 mL / h, voltage 18 kV, collection distance 20 cm, collector rotation speed 450 r / min, temperature 27 °C, and humidity 43%.

[0083] The degradation rates of methyl orange and methylene blue by the piezoelectric-photocatalytic membrane of this embodiment at different times are denoted as A4 and B4, respectively.

[0084] Example 5

[0085] The preparation and testing methods in this embodiment are similar to those in Example 1, except that:

[0086] In step (2), the weight of the cotton fabric is 180 g / m². 2 ;

[0087] In step (3), the mass of CuSO4 is 0.3g and the concentration of NaOH is 0.15mol / L;

[0088] In step (5), the mass of PVDF is 1.9g, the mass of DMF is 8.1g, the stirring time at 60℃ is 1.5h, the mass of MoS2 particles is 15mg, and the stirring time after adding MoS2 particles is 18h.

[0089] In step (6), the electrospinning parameters are: feed rate 0.9 mL / h, voltage 14 kV, collection distance 20 cm, collector rotation speed 380 r / min, temperature 26 ℃, and humidity 40%.

[0090] The degradation rates of methyl orange and methylene blue by the piezoelectric-photocatalytic membrane of this embodiment at different times are denoted as A5 and B5, respectively.

[0091] Comparative Example 1

[0092] The preparation and testing methods of this comparative example are similar to those of Example 1, except that:

[0093] In step (5), PVDF was replaced with PAN; its degradation rates for methyl orange and methylene blue after 30 min were 65.52% and 67.21%, respectively.

[0094] It is evident that in this comparative example, the replacement of PVDF with PAN resulted in the loss of piezoelectric effect and the absence of the driving force to prevent electron-hole recombination, leading to faster electron-hole recombination, reduced photocatalytic effect, and consequently, a decrease in the degradation rate of methyl orange and methylene blue by the prepared photocatalytic film.

[0095] Comparative Example 2

[0096] The preparation and testing methods of this comparative example are similar to those of Example 1, except that:

[0097] Without adding MWCNTS-OH in step (5), the degradation rates of methyl orange and methylene blue after 30 min were 48.32% and 51.78%, respectively.

[0098] It is evident that in this comparative example, the absence of MWCNTS-OH leads to a reduction in the β-phase content of PVDF, resulting in a weaker piezoelectric effect. Simultaneously, the electrons on the conduction band of the photocatalyst lose other acceptors, leading to accelerated photogenerated electron-hole recombination and a weakened redox capacity of the photocatalyst. Consequently, the degradation rate of methyl orange and methylene blue by the prepared photocatalytic film decreases.

[0099] Comparative Example 3

[0100] The preparation and testing methods of this comparative example are similar to those of Example 1, except that:

[0101] In step (5), PVDF was replaced with PAN and MWCNTS-OH was not added. The degradation rates of methyl orange and methylene blue after 30 min were 22.62% and 21.64%, respectively.

[0102] It is evident that in this comparative example, the replacement of PVDF with PAN and the absence of MWCNTS-OH led to an accelerated photoelectron-hole recombination rate in the photocatalyst, resulting in weaker redox capabilities and poorer photocatalytic performance. Consequently, the degradation rate of methyl orange and methylene blue in the prepared photocatalytic film decreased.

[0103] Comparative Example 4

[0104] In this comparative example, Cu2O and MoS2 were prepared separately. 60 mg of Cu2O, 40 mg of MoS2 and 100 mg of BaTiO3 were added to 100 mL of distilled water, and the pretreated cotton fabric was immersed in the aqueous solution for 2 h to fully adsorb the adsorption. Cotton fabric loaded with Cu2O, MoS2 and BaTiO3 was prepared. Its degradation rates of methyl orange and methylene blue after 30 min were 43.21% and 45.35%, respectively.

[0105] It is evident that, in this comparative example, BaTiO3 exhibits a better piezoelectric effect due to the different methods used to prepare the photocatalytic membrane. However, the agglomeration effect of the particles and their difficulty in achieving uniform distribution result in a weak effect of piezoelectricity on photocatalysis and a weak enhancement effect on photocatalysis. Consequently, the degradation rate of methyl orange and methylene blue by the prepared photocatalytic membrane is reduced.

[0106] Comparative Example 5

[0107] The preparation and testing methods of this comparative example are similar to those of Example 1, except that:

[0108] The PVDF in step (5) has a molecular weight of 400,000–500,000, which results in a thin PVDF / MWCNTs-OH / Cu2O film that is difficult to bond firmly to the substrate. During testing, the film breaks and separates from the substrate, disrupting the piezoelectric continuity and weakening its effect on the photocatalyst. Its degradation rates for methyl orange and methylene blue after 30 minutes were 71.86% and 73.19%, respectively.

[0109] Test Example 1

[0110] The degradation rates of methyl orange by the piezoelectric-photocatalytic membranes with bilayer structures prepared in Examples 1 to 5 are shown in Table 1 and [Table data would be inserted here]. Figure 2 .

[0111] Table 1. Degradation rate of methyl orange by different piezoelectric-photocatalytic membranes

[0112]

[0113] From Table 1 and Figure 2 It can be seen that the piezoelectric-photocatalytic membrane with a bilayer structure obtained by the present invention has a high photocatalytic effect, and its degradation rate of methyl orange can reach up to 99.06% after 30 minutes.

[0114] Test Example 2

[0115] The degradation rates of methylene blue by the piezoelectric-photocatalytic films with bilayer structures prepared in Examples 1 to 5 are shown in Table 2 and... Figure 3 .

[0116] Table 2 Degradation rates of methylene blue by different piezoelectric-photocatalytic membranes

[0117]

[0118] From Table 2 and Figure 3 It can be seen that the piezoelectric-photocatalytic membrane with a bilayer structure obtained by the present invention has a high photocatalytic effect, and its degradation rate of methylene blue can reach up to 98.38% after 30 minutes.

[0119] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a piezoelectric-photocatalytic membrane with a bilayer structure, characterized in that, Includes the following steps: (1) The cotton fabric was immersed in a copper salt solution, then immersed in an alkaline solution, and a reducing agent was added to prepare a composite cuprous oxide cotton fabric by reaction. (2) Add MWCNTs-OH and MoS2 particles to the PVDF solution and stir to obtain PVDF / MWCNTs-OH / MoS2 spinning solution; (3) Using electrospinning technology, PVDF / MWCNTs-OH / MoS2 spinning solution is sprayed onto the surface of the cotton fabric with composite cuprous oxide obtained in step (1) to prepare the piezoelectric-photocatalytic membrane with a double-layer structure.

2. The preparation method according to claim 1, characterized in that, In step (1), the cotton fabric is pretreated to obtain: The cotton fabric is soaked in an alkaline solution containing urea to obtain the pretreated cotton fabric.

3. The preparation method according to claim 1, characterized in that, In step (1), the reducing agent is a reducing agent containing an aldehyde group; the concentration of the reducing agent is 0.9 mmol / L to 1.1 mmol / L.

4. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of copper salt to reducing agent in the copper salt solution is 100-150:9-11.

5. The preparation method according to claim 1, characterized in that, In step (2), the molecular weight of PVDF in the PVDF solution is 700,000 to 800,000.

6. The preparation method according to claim 1, characterized in that In step (2), the mass ratio of PVDF, MWCNTs-OH and MoS2 in the PVDF solution is 390-410:5-7:1-7.

7. The preparation method according to claim 1, characterized in that, In step (3), the parameters of the electrospinning technology satisfy one or more of the following conditions: The needle used for electrospinning is 21G; The feed rate is 0.6 mL / h to 1.25 mL / h; The voltage is 12kV to 18kV; The collection distance is 18cm to 20cm; The collecting device rotates at a speed of 300 r / min to 450 r / min; The temperature is 20℃~30℃; The humidity is 40%–50%.

8. The piezoelectric-photocatalytic membrane with a bilayer structure obtained by the preparation method according to any one of claims 1 to 7.

9. The application of the piezoelectric-photocatalytic membrane with a bilayer structure as described in claim 8 in the degradation of pollutants.

10. The application according to claim 9, characterized in that, The degradation time is ≤30 min.

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