A nano-confined piezoelectric coupled photocatalyst, its preparation method and application

Abstract

This application provides a nano-confined piezoelectric coupled photocatalyst, its preparation method, and its application. The piezoelectric coupled photocatalyst provided in this application includes AgNbO3-Bi2Sn2O7, and the particle size of AgNbO3 and Bi2Sn2O7 is nanoscale. It can couple piezoelectric materials and semiconductor properties, combining the principles of photocatalysis and piezoelectric catalysis. This can not only improve efficiency and speed up all-weather algae suppression, but also couple natural wind energy, water wave energy, vibration, and solar energy into one, achieving the effect of energy saving and emission reduction.

Description

Technical Field

[0001] This application relates to the field of catalytic algae removal technology, and in particular to a nano-confined piezoelectric coupled photocatalyst, its preparation method, and its application. Background Technology

[0002] With the increasing eutrophication of water bodies, the ecological security crisis caused by cyanobacterial blooms is becoming increasingly severe. The explosive proliferation of algae not only leads to decreased water transparency, depletion of dissolved oxygen, and decline in biodiversity, but also releases secondary pollutants such as microcystins and anthocyanins, posing a direct threat to drinking water safety. Photocatalytic advanced oxidation is considered one of the most effective technologies for algal inactivation and organic matter degradation due to its low cost, environmental sustainability, and high efficiency. Photocatalytic algae removal utilizes the abundant solar energy present in the waters where algal blooms occur. Under daylight, photocatalysts generate highly oxidizing free radicals and other reactive oxygen species that efficiently inactivate algal cells and oxidize secondary byproducts such as algal toxins.

[0003] However, although current photocatalytic oxidation technology shows potential in algae inactivation and organic matter degradation, it is limited by low spectral utilization, low charge separation efficiency, low orbital matching degree, and susceptibility to ambient light, which seriously restricts the application efficiency of this technology in actual water treatment projects. Summary of the Invention

[0004] This application provides a nano-confined piezoelectric coupled photocatalyst, its preparation method, and its application, aiming to improve the problems of existing photocatalysts having a narrow spectral response range, low catalytic activity, and inability to catalyze throughout the entire time period.

[0005] To solve the above problems, this application provides the following technical solution:

[0006] This application proposes a nano-confined piezoelectric coupled photocatalyst comprising AgNbO3-Bi2Sn2O7, wherein the particle size of AgNbO3 and Bi2Sn2O7 is nanoscale.

[0007] Furthermore, the molar ratio of AgNbO3 to Bi2Sn2O7 in the nano-confined piezoelectric coupled photocatalyst is (1:2) to (4:1).

[0008] Furthermore, the particle size of AgNbO3 and Bi2Sn2O7 in the nano-confined piezoelectric coupled photocatalyst is 50~200 nm.

[0009] This application proposes a method for preparing a nano-confined piezoelectric coupled photocatalyst, comprising:

[0010] Provides nanoscale monomers Bi2Sn2O7;

[0011] By compositing the Bi2Sn2O7 with nanoscale AgNbO3, a piezoelectrically coupled photocatalyst was obtained.

[0012] Furthermore, in the preparation method described above, the nanoscale monomer Bi2Sn2O7 is provided by:

[0013] Bismuth nitrate and polyvinylpyridinium are added to an aqueous mannitol solution and mixed well. Then, an aqueous mannitol solution of stannate is added dropwise, and a strong base is added until the pH is 9-13 to obtain a first solution. The stannate includes at least one of sodium stannate and potassium stannate.

[0014] The first solution was heated by hydrothermal method to obtain the monomer Bi2Sn2O7.

[0015] Furthermore, in the preparation method, during the hydrothermal heating of the first solution, the heating temperature is 180~210°C and the time is 20~30 h.

[0016] Furthermore, in the preparation method, the Bi2Sn2O7 is composited with nano-sized AgNbO3, comprising:

[0017] Add NH4HF2 and Nb2O5 to deionized water and mix well. Then add Bi2Sn2O7 and Ag2O to obtain the second solution.

[0018] The second solution was heated by hydrothermal method to obtain a nano-confined piezoelectric coupled photocatalyst.

[0019] Furthermore, in the preparation method, during the hydrothermal heating of the second solution, the heating temperature is 210~230°C and the time is 30~40 h.

[0020] Furthermore, in the preparation method, during the process of adding NH4HF2 and Nb2O5 to deionized water and mixing, and then adding Bi2Sn2O7 and Ag2O, the molar ratio of Bi2Sn2O7, Nb2O5 and Ag2O is controlled to be (0.1~8):1:1.

[0021] This application also proposes an application of the above-mentioned piezoelectrically coupled photocatalyst, wherein the piezoelectrically coupled photocatalyst is used to inactivate algae.

[0022] The piezoelectrically coupled photocatalyst provided in this application embodiment is composed of nanoscale AgNbO3 and Bi2Sn2O7 composites. Bi2Sn2O7 contains two interpenetrating metals, Bi and Sn, arranged in tetrahedral and octahedral configurations, which facilitates the separation of photogenerated charges. This not only allows for further improvement of its photocatalytic performance through defect engineering, but also demonstrates the significant piezoelectric catalytic properties of AgNbO3. Furthermore, the conduction band and valence band positions of AgNbO3 are -0.73 eV and 1.85 eV, respectively, while those of Bi2Sn2O7 are -1.29 eV and 0.71 eV, respectively. With a relatively small band gap, Bi₂Sn₂O₇ absorbs both visible and infrared spectra. Simultaneously, the band positions of AgNbO₃ and Bi₂Sn₂O₇ allow for the construction of Z-shaped heterojunctions, significantly promoting the transfer of photogenerated carriers while retaining their high potential. The nanoscale particle sizes of both AgNbO₃ and Bi₂Sn₂O₇ result in a significant nanoconfining effect during heterojunction construction, facilitating close contact between the two phases at the interface, significantly shortening the diffusion path of photogenerated carriers, enhancing electron-hole pair separation efficiency, and promoting electronic structure modulation within the confined space. This also fosters a stable built-in electric field at the interface, contributing to the enhanced photocatalytic performance of the heterojunction. The same synergistic mechanism also maintains the material's high specific surface area and abundant active sites, thereby further enhancing its reactivity. Furthermore, during the day or in environments with sufficient sunlight, AgNbO3-Bi2Sn2O7 can absorb ultraviolet, visible, and most infrared light, generating ROS to inhibit algal reproduction and inactivate algal cells. Simultaneously, the piezoelectric effect utilizes the mechanical vibration in the water to generate a polarized electric field, promoting the separation and transport of photogenerated carriers and improving photocatalytic performance. At night or in the absence of light, the piezoelectric material AgNbO3 in the AgNbO3-Bi2Sn2O7 heterojunction can utilize the tidal vibration mechanical energy of the water to generate various ROS to continuously inhibit algal cell reproduction, achieving all-weather algae removal. Therefore, the piezoelectrically coupled photocatalyst provided in this application can couple piezoelectric materials and semiconductor characteristics, combining photocatalysis and piezoelectric catalysis principles. This achieves both improved efficiency and faster all-weather algae suppression, while also coupling natural wind energy, water wave energy, vibration, and solar energy to achieve energy conservation and emission reduction. Attached Figure Description

[0023] Figure 1 This is an electron microscope image of the nano-confined piezoelectric coupled photocatalyst provided in the embodiments of this application;

[0024] Figure 2 This is an elemental distribution diagram of the nano-confined piezoelectric coupled photocatalyst provided in the embodiments of this application;

[0025] Figure 3 This is an XRD pattern of the nano-confined piezoelectric coupled photocatalyst in the embodiments of this application;

[0026] Figure 4 This is a UV diffuse reflectance test image of the piezoelectrically coupled photocatalyst in the embodiments of this application;

[0027] Figure 5 This is a piezoelectric photocatalytic activity test diagram of the piezoelectric coupled photocatalyst in the embodiments of this application;

[0028] Figure 6 This is a piezoelectric catalytic activity test diagram of the piezoelectrically coupled photocatalyst in the embodiments of this application;

[0029] Figure 7 This is a cycle performance test diagram of the piezoelectrically coupled photocatalyst in the embodiments of this application. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0031] As eutrophication intensifies, the ecological security crisis caused by algal blooms is becoming increasingly severe. Photocatalysis, with its green and energy-saving characteristics, uses sunlight to drive catalysts to generate reactive oxygen species, thereby inactivating algal cells and degrading toxins, and is considered a revolutionary solution in the field of environmental remediation.

[0032] The principle of photocatalytic algae removal is to utilize the solar energy that is commonly found in waters where algal blooms grow. A photocatalyst generates highly oxidizing free radicals and other reactive oxygen species under daylight to efficiently inactivate algal cells and oxidize secondary byproducts such as algal toxins. However, in practical algae removal applications, photocatalytic processes still face the following four technical challenges: (1) the range of absorbed and utilized spectra is too narrow; (2) the charge separation efficiency is too low; (3) the orbital matching is too low; and (4) the algae removal efficiency is greatly affected by ambient light.

[0033] To address the numerous problems associated with photocatalytic algae removal, the applicant discovered that the nanostructure of piezoelectric materials can utilize the mechanical force of water flow disturbance to generate a localized polarized electric field. Under the influence of this internal electric field, the valence band (VB) and conduction band (CB) tilt, thereby more effectively separating photoinduced electron-hole pairs generated by photocatalysis (piezoelectric photon effect). Secondly, the piezoelectric effect can bend the semiconductor energy band, increase the valence band potential, and promote electron transitions, thereby improving photon utilization. Furthermore, even when there is no energy source of light at night, the piezoelectric material can still generate a polarized electric field through the piezoelectric effect, thereby promoting the generation of highly oxidizing ROS.

[0034] Based on the above findings, in order to solve the problems of narrow spectral response range, low catalytic activity, and inability to catalyze algae removal throughout the entire time period of existing photocatalysts, this application provides a piezoelectrically coupled photocatalyst comprising AgNbO3-Bi2Sn2O7, wherein the particle size of AgNbO3 and Bi2Sn2O7 is nanoscale. That is, the piezoelectrically coupled photocatalyst provided in this application is composed of nanoscale AgNbO3 and Bi2Sn2O7.

[0035] In the piezoelectrically coupled photocatalysts provided in this application, firstly, Bi₂Sn₂O₇, as a full-spectrum photocatalyst, possesses two interpenetrating metals, Bi and Sn, arranged in tetrahedral and octahedral configurations, which facilitates the separation of photogenerated charges. Its photocatalytic performance can be further improved through defect engineering. Furthermore, AgNbO₃ exhibits significant piezoelectric catalytic performance. Secondly, the conduction band and valence band positions of AgNbO₃ are -0.73 eV and 1.85 eV, respectively, while those of Bi₂Sn₂O₇ are -1.29 eV and 0.71 eV, respectively. Bi₂Sn₂O₇ has a small band gap, allowing it to absorb visible and infrared spectra. Simultaneously, the band positions of AgNbO₃ and Bi₂Sn₂O₇ enable the construction of Z-shaped heterojunctions through their recombination. This heterostructure construction enhances carrier separation via the interfacial electric field, significantly promoting the transfer of photogenerated carriers while retaining their high potential. This improves the photocatalytic degradation performance of AgNbO₃-based photocatalysts and addresses the issue of easy recombination of photogenerated carriers generated by pure AgNbO₃ under illumination. Furthermore, the nanoscale particle sizes of both AgNbO₃ and Bi₂Sn₂O₇ result in a significant nanoconfining effect when they form a heterojunction. This facilitates close contact between the two phases at the interface, significantly shortening the diffusion path of photogenerated carriers, enhancing the electron-hole pair separation efficiency, and increasing the electrical potential within the confined space. The substructure regulation effect also promotes the formation of a stable built-in electric field at the interface, providing a synergistic mechanism for improving the photocatalytic performance of the heterojunction. It can also maintain the high specific surface area and abundant active sites of the material, thereby further enhancing the reaction activity. In addition, under daylight or sufficient light, AgNbO3-Bi2Sn2O7 can absorb ultraviolet, visible light and most infrared light, generating ROS to inhibit algal reproduction and inactivate algal cells. Furthermore, the piezoelectric effect utilizes the mechanical vibration in the water to generate a polarized electric field, promoting the separation and transport of photogenerated charge carriers and improving photocatalytic performance. At night or under no light conditions, the piezoelectric material AgNbO3 in the AgNbO3-Bi2Sn2O7 heterojunction can utilize the tidal vibration mechanical energy of the water to generate various ROS to continuously inhibit the reproduction of algal cells, achieving all-weather algae removal.

[0036] Therefore, the piezoelectric coupled photocatalyst provided in this application optimizes the composition, coordination structure, and electronic energy state of the heterojunction, thereby strengthening both the built-in electric field at the heterojunction interface and the piezoelectric polarization field, reducing carrier recombination at the interface to enhance charge separation efficiency. This not only significantly improves photocatalytic reaction activity and algae removal efficiency but also couples the characteristics of piezoelectric materials and semiconductors, combining the principles of photocatalysis and piezoelectric catalysis. This not only achieves efficient and accelerated algae suppression in all weather conditions but also integrates natural wind energy, water wave energy, vibration energy, and solar energy to achieve energy conservation and emission reduction.

[0037] Alternatively, given that the catalyst can utilize solar and mechanical energy to generate highly oxidizing reactive oxygen species, it can also be used to degrade pollutants such as phenol, bisphenol A, and antibiotics; and can also be used to inactivate pathogenic microorganisms.

[0038] Optionally, in one embodiment, the molar ratio of AgNbO3 to Bi2Sn2O7 in the above catalyst is (1:2) to (4:1), which can ensure that AgNbO3 can exert excellent photocatalytic and piezoelectric properties while using Bi2Sn2O7 to broaden the light absorption range of the material.

[0039] In practical applications, the amounts of Nb and Sn can be determined by X-ray photoelectron spectroscopy (XPS) analysis of the catalyst, thereby determining the molar ratio of AgNbO3 and Bi2Sn2O7.

[0040] Optionally, in one embodiment, in the catalyst provided in this application, Bi2Sn2O7 covers the surface of AgNbO3; at the above molar ratio, the thickness of the covering layer formed by Bi2Sn2O7 is moderate, which is conducive to the diffusion of charge carriers to the heterojunction interface and avoids charge carrier recombination.

[0041] In particular, the molar ratio of AgNbO3 to Bi2Sn2O7 in the prepared catalyst can be controlled by adjusting the amount of Bi2Sn2O7 or AgNbO3 added to the system during the catalyst preparation process.

[0042] Optionally, in one embodiment, the particle size of AgNbO3 and Bi2Sn2O7 in the catalyst is 50~200nm, which makes the two have a more significant nanoconfining effect when they contact to form a heterojunction.

[0043] This application provides a method for preparing a nano-confined piezoelectric coupled photocatalyst, including steps 201-202:

[0044] Step 201: Provide nanoscale monomers Bi2Sn2O7;

[0045] Step 202: Composite the Bi2Sn2O7 with nano-sized AgNbO3 to obtain a nano-confined piezoelectric coupled photocatalyst.

[0046] In this embodiment, nanoscale monomer Bi2Sn2O7 is first prepared, and then Bi2Sn2O7 is uniformly composited on nanoscale AgNbO3 to obtain a piezoelectric coupled photocatalyst that can couple piezoelectric material and semiconductor properties. This can not only improve efficiency, speed up the process, and suppress algae in all weather conditions, but also couple natural wind energy, water wave energy, vibration and solar energy into one. It can effectively improve the problems of existing photocatalysts, such as narrow spectral response range, low catalytic activity and inability to catalyze at all times.

[0047] Optionally, in one embodiment, nanoscale monomer Bi2Sn2O7 is provided, including steps 111 to 112:

[0048] Step 111: Add bismuth nitrate and polyvinylpyridinone to an aqueous mannitol solution and mix well. Then add an aqueous mannitol solution of stannate dropwise and add a strong base until the pH is 9-13 to obtain the first solution. The stannate includes at least one of sodium stannate and potassium stannate.

[0049] In step 111, bismuth nitrate and polyvinylpyridinium are added to an aqueous mannitol solution and then thoroughly mixed by means of ultrasound, shaking, etc.

[0050] In step 111, the concentration of mannitol in the mannitol aqueous solution can be 0.1 M.

[0051] In step 111, bismuth nitrate can be Bi(NO3)3·5H2O, and sodium stannate crystals can be Na2SnO3·3H2O.

[0052] In step 111, Bi2Sn2O7 is adjusted to a small size by polyvinylpyridinium-assisted solvothermal method, which is easy to load on the AgNbO3 surface. At the same time, more low-coordination surface atoms are exposed and lost to form vacancies, which promotes photocatalytic carrier separation. In addition, vacancies are conducive to the formation of heterojunction with AgNbO3.

[0053] Optionally, in step 111, controlling the molar ratio of polyvinylpyridinium to bismuth nitrate and stannate to 0.3:1:1 can effectively adjust the formed Bi2Sn2O7 to a small size loaded on the AgNbO3 surface.

[0054] In step 111, when adding the mannitol aqueous solution of stannate dropwise, the mixture is thoroughly mixed by means of ultrasound, shaking, stirring, etc., to promote the reaction. For example, it can be thoroughly mixed at a stirring rate of 400 r / min.

[0055] In step 111, after adding the mannitol aqueous solution of stannate, a strong alkali solution is added to adjust the pH to 9-13, for example, one or both of the values ​​of 9, 11.5, 12, 12.5, and 13, to utilize the etching effect of the alkali to suppress the degradation of Bi due to the reactivity of mannitol. 3+ Reduction produces Bi atoms.

[0056] Optionally, the strong base mentioned above can be NaOH, KOH, etc. Optionally, the strong base solution mentioned above can be a NaOH solution with a concentration of 2 mol / L. This concentration is moderate, which can quickly adjust the pH of the system without damaging the crystal structure of the material due to excessive alkalinity.

[0057] Step 112: Heating the first solution using a hydrothermal method to obtain the monomer Bi2Sn2O7.

[0058] In step 212, the first solution is placed in a closed reaction apparatus and heated hydrothermally. This process effectively disperses the reactants and allows for uniform heating to produce a precipitate. The precipitate is then removed by centrifugation or other methods and washed with water to obtain nano-sized Bi₂Sn₂O₇. The closed reaction apparatus can be a reaction vessel, and the Bi₂Sn₂O₇ has a particle size of 50–200 nm.

[0059] Optionally, during the hydrothermal heating of the first solution, the heating temperature is within the range of one or both of 180℃, 190℃, 200℃, and 210℃, and the heating time is within the range of one or both of 20 h, 24 h, and 30 h. This is beneficial for promoting the full conversion of reactants and the purification of the crystal phase, and can effectively balance yield, purity, and product performance.

[0060] Optionally, in one embodiment, Bi2Sn2O7 is composited with nano-sized AgNbO3, including steps 211 to 212:

[0061] Step 211: Add NH4HF2 and Nb2O5 to deionized water and mix well. Then add Bi2Sn2O7 and Ag2O to obtain the second solution.

[0062] In step 211, materials NH4HF2 and Nb2O5 are added to deionized water, followed by Bi2Sn2O7 and Ag2O. The mixture is then thoroughly mixed by means of ultrasound, shaking, etc., to obtain a second solution.

[0063] In step 211, during the hydrothermal synthesis of AgNbO3, NH4HF2 not only serves as a source of fluoride ions, effectively promoting the dissolution of Nb2O5 and the complexation transformation of Nb species, but also regulates the acid-base environment of the reaction system by releasing NH4⁺ and HF, which is conducive to the formation of [NbO(OH)6]. 3⁻ Intermediates and promote the generation of the target phase.

[0064] Step 212: The second solution is heated by hydrothermal method to obtain a nano-confined piezoelectric coupled photocatalyst.

[0065] In step 212, the second solution is placed in a closed reaction device and heated by hydrothermal method, which can fully disperse the reactants and allow them to react uniformly to obtain a precipitate. The precipitate is then removed by centrifugation and washed with water to obtain a nano-confined piezoelectric photocatalyst composed of AgNbO3 and Bi2Sn2O7.

[0066] In step 212, the hydrothermal synthesis mechanism of AgNbO3 is as follows:

[0067] Nb2O5+ 6NH4HF2→ 2(NH4)3NbOF6+ 3H2O;

[0068] (NH4)3NbOF6+ 6H2O → [NbO(OH)6] 3 ⁻ + 3NH4HF2+ 3H + ;

[0069] Ag + + [NbO(OH)6] 3 ⁻ + 2H + → AgNbO3 + 4H2O;

[0070] The aforementioned closed reaction equipment can be a reaction vessel.

[0071] Optionally, during the hydrothermal heating of the second solution, the heating temperature is 210~230℃ and the time is 30~40 h, which can effectively promote Nb 5 ⁺ The formation of soluble complexes with the assistance of fluoride ions facilitates the construction of crystal structures, which helps to achieve full phase transformation and orderly crystal growth, suppresses the formation of by-products, and improves the crystallinity and structural stability of the products, thereby obtaining AgNbO3 materials with better performance.

[0072] Optionally, during the hydrothermal heating of the second solution, the heating temperature can be within the range of 210℃, 220℃, 230℃ or any two of these values, and the heating time can be within the range of 30 h, 32 h, 36 h, 40 h or any two of these values. This is beneficial for promoting the full conversion of reactants and the purification of the crystal phase, and can effectively balance yield, purity and product performance.

[0073] Optionally, during the process of adding NH4HF2 and Nb2O5 to deionized water and mixing, and then adding Bi2Sn2O7 and Ag2O, the molar ratio of Bi2Sn2O7, Nb2O5 and Ag2O is controlled to be (0.1~8):1:1, so that the thickness of the capping layer formed by Bi2Sn2O7 on the AgNbO3 surface is moderate, which is conducive to the diffusion of charge carriers to the heterojunction interface and avoids charge carrier recombination.

[0074] In step 212, after the hydrothermal reaction, the monomer BiOBr is obtained by washing with deionized water, filtering to collect the filter residue, and then drying it. Optionally, the filter residue can be dried under vacuum at a temperature of 60°C for 10 hours.

[0075] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0076] The present invention will now be described in detail through test examples.

[0077] Test Example 1

[0078] (1) 1 mmol Bi(NO3)3·5H2O and 0.3 mmol polyvinylpyridinone were added to 15 mL mannitol (0.1 M) and ultrasonically dispersed to obtain solution A; 1 mmol Na2SnO3·3H2O was dissolved in 5 mL mannitol to obtain solution B. Under strong stirring, solution B was slowly added dropwise to solution A with a dropper and stirred for 30 min. Then, the pH was adjusted to 12 with NaOH (2 M) and stirred for another 30 min. The solution was then placed in a 100 mL reaction vessel and heated at 200 °C for 24 h. After the reaction vessel cooled to room temperature, it was cleaned and dried to obtain monomer Bi2Sn2O7.

[0079] (2) Add 3 mmol of NH4HF2 and 1 mmol of Nb2O5 to 70 mL of deionized water, then add 1 mmol of monomer Bi2Sn2O7 and 1 mmol of Ag2O. Stir at room temperature for 30 min, then transfer the mixed suspension to a 100 mL high-pressure reactor and heat at 220 °C for 32 h. After cooling to room temperature, wash three times with deionized water and dry under vacuum at 80 °C to obtain the product AgNbO3-Bi2Sn2O7 (2:1) nano-confined piezoelectric photocatalyst.

[0080] Test Examples 2-4

[0081] The difference between Test Examples 2-4 and Test Example 1 is that in step (2), the amount of Bi2Sn2O7 added was adjusted to 0.5 mmol, 2 mmol, and 4 mmol, respectively, to obtain the product catalysts AgNbO3-Bi2Sn2O7 (4:1), AgNbO3-Bi2Sn2O7 (1:1), and AgNbO3-Bi2Sn2O7 (1:2).

[0082] Test Example 5

[0083] 1 mmol Bi(NO3)3·5H2O and 0.3 mmol polyvinylpyridinium were added to 15 mL mannitol (0.1 M) and ultrasonically dispersed to obtain solution A. 1 mmol Na2SnO3·3H2O was dissolved in 5 mL mannitol to obtain solution B. Under vigorous stirring, solution B was slowly added dropwise to solution A and stirred for 30 min. The pH was then adjusted to 12 with NaOH (2 M) and stirred for another 30 min. The solution was then placed in a 100 mL reaction vessel and heated at 200 °C for 24 h. After the reaction vessel cooled to room temperature, it was cleaned and dried to obtain the product monomer Bi2Sn2O7.

[0084] Test Example 6

[0085] Add 3 mmol of NH4HF2 and 1 mmol of Nb2O5 to 70 mL of deionized water, then add 1 mmol of Ag2O. Stir at room temperature for 30 min, then transfer the mixed suspension to a 100 mL high-pressure reactor and heat at 220 °C for 32 h. After cooling to room temperature, wash three times with deionized water and dry under vacuum at 80 °C to obtain the product nano-sized AgNbO3.

[0086] The Bi₂Sn₂O₇ prepared in Test Example 5, the AgNbO₃ prepared in Test Example 6, and the catalyst AgNbO₃-Bi₂Sn₂O₇ (2:1) prepared in Test Example 1 were subjected to scanning electron microscopy (SEM) tests, and the results are as follows: Figure 1 As shown in (a), (b), and (c). From Figure 1 It can be seen that Bi2Sn2O7 has a bulk nanostructure, while AgNbO3 has a flat bulk structure. AgNbO3-Bi2Sn2O7 (2:1) has both a small particle bulk nanostructure and a flat bulk structure, which indicates that Bi2Sn2O7 and AgNbO3 have been successfully composited.

[0087] The elemental distribution of the catalyst AgNbO3-Bi2Sn2O7 (2:1) prepared in Test Example 1 was tested, and the results are as follows: Figure 2 As shown. By Figure 2It can be seen that Bi₂Sn₂O₇ exhibits a bulk nanostructure, while AgNbO₃ has a flat, bulk structure. Ag, Nb, and O... 、 Bi 、 The uniform distribution of elements such as Sn further proves the successful preparation and composite of Bi2Sn2O7 and AgNbO3.

[0088] The Bi₂Sn₂O₇ product prepared in Test Example 5, the AgNbO₃ product prepared in Test Example 6, and the AgNbO₃-Bi₂Sn₂O₇ (2:1) catalyst product prepared in Test Example 1 were subjected to X-ray diffractometer (XRD) tests. The tests were conducted using a PANalytical Aeris benchtop diffractometer, with the following conditions set: scanning range 5–90°, scanning rate 2° / min. The obtained spectra were then compared with a standard card library. The results are as follows: Figure 3 As shown.

[0089] Depend on Figure 3 As can be seen, the XRD peaks of Bi2Sn2O7 are consistent with those of the standard card (PDF#432-6954), indicating that Bi2Sn2O7 was successfully prepared; the peak positions of AgNbO3 are consistent with those of the standard card (PDF#052-0405), indicating that AgNbO3 has a good crystal structure; AgNbO3-Bi2Sn2O7 (2:1) clearly shows the characteristic peaks of Bi2Sn2O7 and AgNbO3, indicating that Bi2Sn2O7 and AgNbO3 were successfully composited.

[0090] The Bi₂Sn₂O₇ product prepared in Test Example 5, the AgNbO₃ product prepared in Test Example 6, and the AgNbO₃-Bi₂Sn₂O₇ (2:1) catalyst prepared in Test Example 1 were subjected to diffuse reflectance spectroscopy (DRS) measurements. The measurements were performed using a PerkinElmer Lambda 1050 N / W spectrometer, with a scanning wavelength range of 200–2500 nm. The obtained diffuse reflectance spectra and band gaps are shown below. Figure 4 As shown.

[0091] pass Figure 4 It can be seen that the absorption boundary of the prepared product catalyst AgNbO3-Bi2Sn2O7 (2:1) is about 1190 nm, indicating that the catalyst can achieve full-spectrum absorption and can effectively improve the utilization rate of solar photons.

[0092] The products prepared in each test example were subjected to piezoelectric photocatalytic activity testing, and the results are as follows: Figure 5 As shown, the specific testing method is as follows:

[0093] The catalyst was placed in a piezoelectric photocatalytic reactor to degrade Microcystis aeruginosa. During the photocatalytic reaction, an LED light was used as the light source, and 40 mL of algal suspension was used. The reactor was prepared with / without a catalyst (0.5 g / L), and the light source was turned on / off (20 W / m²). 2 The reactor is placed under ultrasonic / non-ultrasonic conditions.

[0094] Based on the different reaction conditions in the above experiments: placement (AgNbO3, Bi2Sn2O7 or AgNbO3-Bi2Sn2O7), light source on / off (Vis), with / without ultrasound (US), the following reaction systems can be obtained: ultrasound / visible light (US / Vis) system; visible light (Vis) system; catalyst / ultrasound / visible light (AgNbO3-Bi2Sn2O7 / US / Vis) system; catalyst / visible light (AgNbO3-Bi2Sn2O7 / Vis) system.

[0095] At preset time intervals, 8 mL of reaction solution was taken to measure its chlorophyll a content. A 0.45 μm filter membrane was then placed on a filtration instrument, and 8 mL of sample was filtered. The filter membrane was placed in a test tube and frozen for 12 h. The test tube was then removed, and 8 mL of 90% acetone solution was added, along with a small amount of magnesium carbonate powder to protect the chlorophyll from damage. The sample was then disrupted using an ultrasonic cell disruptor (ultrasonic time 3 s, interval 2 s) for 3 min, and treated at 4500 r / min for 10 minutes. The supernatant was collected, and using 90% acetone as a reference, the chlorophyll a content was measured using OD0.05. 630 OD 647 OD 664 and OD 750 The formula for calculating the chlorophyll a content is shown below:

[0096]

[0097] In the formula:

[0098] OD 630 OD 647 OD 664 OD 750 V1 represents the absorbance values ​​of the sample at wavelengths of 630 nm, 647 nm, 664 nm, and 750 nm, respectively; V2 represents the sample volume in mL; V3 represents the volume of 90% acetone in mL.

[0099] The removal rate of Microcystis aeruginosa was calculated as C / C0, where C0 and C are the chlorophyll a contents at 0 and t min, respectively.

[0100] Depend on Figure 5As shown in (a), the catalyst product in Test Example 1 exhibits superior piezoelectric photocatalytic algae removal efficiency. Under both ultrasonic and piezoelectric effects, it significantly destroys chlorophyll in algal cells, removing 78% of the algae within 4.5 h, far exceeding the 30% of AgNbO3 and 10% of Bi2Sn2O7. This is because the composite material promotes the absorption of visible light, and the photogenerated electrons, under the dual effects of the built-in electric field and the polarized electric field, can be separated more efficiently, thereby generating a higher concentration of reactive oxygen species and achieving efficient inactivation of algal cells. Furthermore, the AgNbO3-Bi2Sn2O7 (2:1) / US / Vis system demonstrates better algae removal performance than the AgNbO3-Bi2Sn2O7 (2:1) / Vis system. This indicates that the polarized electric field generated by the piezoelectric material AgNbO3 can promote carrier separation and improve algae removal efficiency. Figure 5 As shown in (b), neither the US / Vis system nor the Vis system caused algal death, indicating that the catalyst prepared by optimizing the experimental preparation method has a better algae removal effect.

[0101] Using 10 ppm phenol as the target pollutant, the piezoelectric degradation performance of the products prepared in Test Example 1 and Test Example 6 was investigated under ultrasonic treatment. The results are as follows: Figure 6 As shown, the test process is as follows:

[0102] The piezoelectric degradation reaction of phenol was carried out in a 100 mL quartz beaker. The reaction system was kept at a constant temperature of 25 °C by a cooling water circulation system. The quartz beaker was placed in a 200 W ultrasonic machine and protected from light. At certain time intervals, 1 mL of the reaction solution was taken and filtered through a 0.22 µm filter membrane. The filtrate was analyzed by liquid chromatography to determine the peak signal of phenol. Each experiment was designed in triplicate. The phenol degradation curve was determined by measuring the ratio of real-time concentration to initial concentration (C / C0). The concentration of phenol was detected by high performance liquid chromatography at a characteristic wavelength of 223 nm. The mobile phase was acetonitrile:water = 20:80, and the flow rate was 0.8 mL / min.

[0103] Depend on Figure 6 It can be seen that under ultrasound, AgNbO3 and AgNbO3-Bi2Sn2O7 (2:1) can degrade 60% and 65% of phenol, respectively, in 4.5 h, indicating that AgNbO3 and AgNbO3-Bi2Sn2O7 (2:1) can generate a polarized electric field under ultrasound, thereby generating reactive oxygen species to degrade pollutants.

[0104] The catalyst prepared in Test Example 1 was subjected to cycle performance testing, and the results are as follows: Figure 7 As shown, the specific testing method is as follows:

[0105] After the first degradation reaction (1st) is completed, the catalyst is separated from the solution by filtration, and the filtered catalyst is washed with deionized water and ethanol and dried in a freeze dryer for 48 hours for later use. The second degradation reaction (2st) is carried out using the above-mentioned spare material. Except for the material, the other reaction conditions are the same as the first one. After the second reaction is completed, the above steps are repeated to carry out the third (3st), fourth (4st), and fifth (5th) degradation experiments.

[0106] Depend on Figure 7 It can be seen that the AgNbO3-Bi2Sn2O7 (2:1) / US / Vis system has good cycling stability. After 5 cycles, the algae removal effect only decreased by 15%, indicating that the material has good cycling stability and good application prospects.

[0107] In summary, this application's embodiments, by utilizing the characteristics of piezoelectric and photocatalytic materials and the band structure properties of semiconductors, employ a heterojunction construction method to design and synthesize highly efficient, all-weather piezoelectric-photocatalytic algae removal materials. In experiments, simulating actual aquatic environments through illumination, ultrasound, and stirring, the efficiency of the composite material in algae removal and intermediate product processing was studied. The surface characteristics and mechanism of action of the material were investigated, including the active sites of reactive oxygen species involved in algae removal and various algae removal indicators, to obtain a detailed understanding of the material's algae removal mechanism. Furthermore, through material characterization, a comprehensive understanding of the material's physicochemical properties, optical properties, and piezoelectric properties was achieved.

[0108] Furthermore, the nano-confined voltage-coupled photocatalytic material AgNbO3-Bi2Sn2O7 prepared in this application optimizes the composition, coordination structure, and electronic energy state of the heterojunction by first preparing Bi2Sn2O7 and then introducing Bi2Sn2O7 into the preparation of AgNbO3. This strengthens both the built-in electric field at the heterojunction interface and the piezoelectric polarization field, reduces carrier recombination at the interface to enhance charge separation efficiency, thereby significantly improving photocatalytic reaction activity and algae removal efficiency.

[0109] Terminology Explanation

[0110] In this application, "multiple" refers to two or more.

[0111] The terms “first,” “second,” “third,” “fourth,” etc., in this application (if present) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0112] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0113] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, if the method includes steps A and B, it means that the method may include steps A and B performed sequentially, or it may include steps B and A performed sequentially. For example, if the method may also include step C, it means that step C may be added to the method in any order. For example, the method may include steps A, B, and C, or it may include steps A, C, and B, or it may include steps C, A, and B, etc.

[0114] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a nano-confined piezoelectric coupled photocatalyst, characterized in that, include: Bismuth nitrate and polyvinylpyridinone were added to an aqueous mannitol solution and mixed well. Then, an aqueous mannitol solution of stannate was added dropwise, and a strong base was added until the pH was 9-13 to obtain the first solution. The stannate includes at least one of sodium stannate and potassium stannate; The first solution was heated by hydrothermal method to obtain the monomer Bi2Sn2O7; Add NH4HF2 and Nb2O5 to deionized water and mix well. Then add Bi2Sn2O7 and Ag2O to obtain the second solution. The second solution was heated by hydrothermal method to obtain a nano-confined piezoelectric coupled photocatalyst; the molar ratio of AgNbO3 to Bi2Sn2O7 in the catalyst was (1:2) to (4:1).

2. The preparation method according to claim 1, characterized in that, The particle size of AgNbO3 and Bi2Sn2O7 in the catalyst is 50~200 nm.

3. The preparation method according to claim 1, characterized in that, During the hydrothermal heating of the first solution, the heating temperature is 180~210°C and the time is 20~30 h.

4. The preparation method according to claim 1, characterized in that, During the hydrothermal heating of the second solution, the heating temperature is 210~230°C and the time is 30~40 h.

5. The preparation method according to claim 1, characterized in that, During the process of adding NH4HF2 and Nb2O5 to deionized water and mixing them, and then adding Bi2Sn2O7 and Ag2O, the molar ratio of Bi2Sn2O7, Nb2O5 and Ag2O is controlled to be (0.1~8):1:

1.

6. An application of a nano-confined piezoelectric coupled photocatalyst prepared by the method according to any one of claims 1 to 5, characterized in that, The piezoelectrically coupled photocatalyst is used to inactivate algae, pathogenic microorganisms, and degrade at least one of pollutants, including at least one of phenol, bisphenol A, and antibiotics.

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