Nano confinement piezoelectric coupling photocatalyst as well as preparation method and application thereof

Abstract

The embodiment of the invention provides a nano confinement piezoelectric coupling photocatalyst and a preparation method and application thereof.The piezoelectric coupling photocatalyst provided by the embodiment of the invention comprises AgNbO3-Bi2Sn2O7, the particle size of AgNbO3 and the particle size of Bi2Sn2O7 are both nanoscale, the characteristics of a piezoelectric material and a semiconductor can be coupled, photocatalysis and piezoelectric catalysis principles are combined, the photocatalytic effect is good, and the photocatalytic effect is good. Not only can all-weather algal inhibition be realized, but also natural wind energy, water wave energy, vibration and solar energy can be coupled into a whole, and the effects of energy conservation and emission reduction are achieved.

Description

Technical Field

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

[0002] As eutrophication of water bodies intensifies, the ecological security crisis caused by cyanobacterial blooms is becoming increasingly severe. The explosive growth of algae not only causes a decrease in water transparency, dissolved oxygen depletion, and a decline in biodiversity, but also releases secondary pollutants such as microcystins and anabaxins, posing a direct threat to drinking water safety. Photocatalytic advanced oxidation is considered one of the most effective technologies for algae inactivation and organic matter degradation due to its low cost, environmental sustainability, and high efficiency. Photocatalytic algae removal utilizes the solar energy commonly found in waters where algal blooms grow. Photocatalysts generate highly oxidizing free radicals and other reactive oxygen species under daylight, effectively inactivating algal cells and oxidizing secondary products 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, and susceptibility to ambient light, which seriously restricts the application efficiency of this technology in actual water treatment projects. Summary of the Invention

[0004] The embodiments of the present application provide a nano-confined piezoelectric coupled photocatalyst and its preparation method and application, aiming to improve the problems of existing photocatalysts such as narrow spectral response range, low catalytic reaction activity and inability to catalyze all the time.

[0005] In order to solve the above problems, this application is implemented through the following technical solutions: The present application proposes a nano-confined piezoelectric coupled photocatalyst, comprising AgNbO3-Bi2Sn2O7, wherein the particle sizes of AgNbO3 and Bi2Sn2O7 are both nanometer-scale.

[0006] Furthermore, the molar ratio of AgNbO3 to Bi2Sn2O7 in the nanoconfined piezoelectric coupled photocatalyst is (1:2) to (4:1).

[0007] Furthermore, the particle sizes of AgNbO3 and Bi2Sn2O7 in the nano-confined piezoelectric coupled photocatalyst are both 50~200 nm.

[0008] This application proposes a method for preparing a nano-confined piezoelectric coupled photocatalyst, comprising: Provide nano-scale monomer Bi2Sn2O7; The Bi2Sn2O7 is compounded with nano-sized AgNbO3 to obtain a piezoelectric coupled photocatalyst.

[0009] Furthermore, in the preparation method, providing the nanoscale monomer Bi2Sn2O7 includes: Bismuth nitrate and polyvinyl pyridone are added to a mannitol aqueous solution and mixed evenly, and then a mannitol aqueous solution of stannate is added dropwise, and a strong base is added to the pH value of 9 to 13 to obtain a first solution; the stannate comprises at least one of sodium stannate and potassium stannate; The first solution is hydrothermally heated to obtain monomer Bi2Sn2O7.

[0010] Furthermore, in the preparation method, during the hydrothermal heating of the first solution, the hydrothermal heating temperature is 180-210° C. and the time is 20-30 h.

[0011] Furthermore, in the preparation method, the Bi2Sn2O7 is compounded with nano-sized AgNbO3, comprising: NH4HF2 and Nb2O5 were added to deionized water and mixed, and then Bi2Sn2O7 and Ag2O were added to obtain a second solution; The second solution is hydrothermally heated to obtain a nano-confined piezoelectric coupled photocatalyst.

[0012] Furthermore, in the preparation method, during the hydrothermal heating of the second solution, the hydrothermal heating temperature is 210-230° C. and the time is 30-40 h.

[0013] Furthermore, in the preparation method, in the process of adding NH4HF2 and Nb2O5 to deionized water and mixing them uniformly, and then adding Bi2Sn2O7 and Ag2O, the molar ratio of Bi2Sn2O7, Nb2O5, and Ag2O is controlled to be (0.1~8): 1:1.

[0014] The present application also proposes an application of the above-mentioned piezoelectric coupled photocatalyst, wherein the piezoelectric coupled photocatalyst is used to inactivate algae.

[0015] The piezoelectric coupled photocatalyst provided in the embodiment of the present application is composed of a composite of nano-scale AgNbO3 and Bi2Sn2O7, wherein Bi2Sn2O7 has two interpenetrating metals Bi and Sn arranged in tetrahedral and octahedral coordination, which is conducive to the separation of photogenerated charges. Not only can its photocatalytic performance be further improved through defect engineering, but AgNbO3 also has obvious piezoelectric catalytic performance; in addition, the conduction band and valence band positions of AgNbO3 are -0.73 eV and 1.85 eV respectively, and the conduction band and valence band positions of Bi2Sn2O7 are -1.29 eV and 0.71 eV, Bi2Sn2O7 has a small band gap width and can absorb visible and infrared spectra; at the same time, the energy band positions of AgNbO3 and Bi2Sn2O7 enable them to construct a Z-type heterojunction through composite construction, thereby greatly promoting the transfer of photogenerated carriers and retaining their high potential; the particle sizes of AgNbO3 and Bi2Sn2O7 are both at the nanoscale, which makes the two have a significant nano-confinement effect when they contact to construct a heterojunction, which is conducive to the formation of close contact between the two phases at the interface, significantly shortening the diffusion path of photogenerated carriers and enhancing the separation efficiency of electron-hole pairs. The electronic structure regulation effect in the confined space also promotes the formation of a stable built-in electric field at the interface, providing assistance for the improvement of the photocatalytic performance of the heterojunction. The same synergistic mechanism can also maintain the high specific surface area and rich active sites of the material, thereby further enhancing the reaction activity; in addition, during the day or in an environment with sufficient light, AgNbO3-Bi2Sn2O7 can absorb ultraviolet light, visible light and most infrared light, generate ROS to inhibit algae reproduction and inactivate algae cells. At the same time, the piezoelectric effect uses the mechanical vibration in the water body to generate a polarized electric field, promote the separation and transmission of photogenerated carriers, and improve the photocatalytic performance; at night or under conditions without light, the piezoelectric material AgNbO3 in the AgNbO3-Bi2Sn2O7 heterojunction can use the tidal vibration mechanical energy of the water body to generate a variety of ROS to continuously inhibit the reproduction of algae cells and achieve all-weather algae removal. Therefore, the piezoelectric coupled photocatalyst provided in the embodiment of the present application can couple the piezoelectric material and semiconductor characteristics, combine the principles of photocatalysis and piezoelectric catalysis, and can not only achieve efficiency and speed-up and all-weather algae inhibition, but also couple the natural wind energy, water wave energy, vibration and solar energy into one, to achieve the effect of energy saving and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is an electron microscope test image of the nanoconfined piezoelectric coupled photocatalyst provided in an embodiment of the present application; Figure 2 This is an element distribution diagram of the nanoconfined piezoelectric coupled photocatalyst provided in an embodiment of the present application; Figure 3 This is an XRD test pattern of the nanoconfined piezoelectric coupled photocatalyst in the embodiment of the present application; Figure 4This is a UV diffuse reflection test diagram of the piezoelectric coupled photocatalyst in the embodiment of the present application; Figure 5 This is a piezoelectric photocatalytic activity test diagram of the piezoelectric coupled photocatalyst in the embodiment of the present application; Figure 6 This is a piezoelectric catalytic activity test diagram of the piezoelectric coupled photocatalyst in the embodiment of the present application; Figure 7 This is a test diagram of the cycle performance of the piezoelectric coupled photocatalyst in the embodiment of the present application. DETAILED DESCRIPTION

[0017] In order to make the technical problems, technical solutions and beneficial effects solved by this application more clearly understood, this application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0018] As eutrophication in water bodies intensifies, the ecological crisis caused by algal blooms is becoming increasingly severe. Photocatalytic technology, with its green and energy-saving properties, is considered a revolutionary solution in environmental governance. It uses sunlight to drive catalysts to produce reactive oxygen species, inactivating algal cells and degrading toxins.

[0019] The principle of photocatalytic algae removal is to utilize the sunlight energy that is prevalent in waters where algal blooms grow. Photocatalysts generate highly oxidative free radicals and other reactive oxygen species under daylight, which effectively inactivate algal cells and oxidize secondary products such as algal toxins. However, in actual algae removal applications, photocatalytic processes still face the following four technical difficulties: (1) the absorbed and utilized spectral range 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 the ambient light.

[0020] In response to the above-mentioned problems with photocatalytic algae removal, the applicant discovered that the nanostructure of piezoelectric materials can utilize the mechanical force of water flow disturbance in water bodies to generate a local polarization electric field. Under the action of the internal electric field, the valence band (VB) and conduction band (CB) will tilt, thereby more effectively separating the light-induced electron-hole pairs generated by photocatalysis (piezoelectric photon effect); secondly, the piezoelectric effect can bend the semiconductor energy band, increase the valence band potential, promote electron transitions, and thus improve photon utilization; in addition, when the energy source of light is lost at night, the piezoelectric material can still generate a polarization electric field through the piezoelectric effect, thereby generating highly oxidizing ROS.

[0021] Based on the above findings, in order to solve the problems of narrow spectral response range, low catalytic reaction activity and inability to catalyze algae removal in the entire period of time in existing photocatalysts, the embodiments of the present application provide a piezoelectric coupled photocatalyst including AgNbO3-Bi2Sn2O7, and the particle sizes of AgNbO3 and Bi2Sn2O7 are both nanometer-sized, that is, the piezoelectric coupled photocatalyst provided by the embodiments of the present application is composed of a composite of AgNbO3 and Bi2Sn2O7 with nanometer-sized particles.

[0022] In the piezoelectric coupled photocatalyst provided in the embodiment of the present application, firstly, Bi2Sn2O7 as a full-spectrum photocatalyst has two interpenetrating metals Bi and Sn arranged in tetrahedral and octahedral coordination, which is conducive to the separation of photogenerated charges and can further improve its photocatalytic performance through defect engineering, and AgNbO3 has obvious piezoelectric catalytic performance; secondly, the conduction band and valence band positions of AgNbO3 are -0.73 eV and 1.85 eV respectively, and the conduction band and valence band positions of Bi2Sn2O7 are -1.29 eV and 0.71 eV, Bi2Sn2O7 has a small band gap width and can absorb visible and infrared spectra; at the same time, the energy band positions of AgNbO3 and Bi2Sn2O7 enable them to be composited to construct a Z-type heterojunction. The heterostructure construction can enhance carrier separation through the interface electric field, greatly promote the transfer of photogenerated carriers and retain their high potential, thereby improving the photocatalytic degradation performance of AgNbO3-based photocatalysts and improving the problem of easy recombination of photogenerated carriers generated by pure AgNbO3 under light; furthermore, the particle sizes of AgNbO3 and Bi2Sn2O7 are both at the nanoscale, which makes the two have a significant nano-confinement effect when they contact to construct a heterojunction, which is conducive to the formation of close contact between the two phases at the interface, significantly shortening the diffusion path of photogenerated carriers, enhancing the separation efficiency of electron-hole pairs, and the electric field in the confined space. The substructure regulation effect also promotes the formation of a stable built-in electric field at the interface, providing a synergistic enhancement mechanism for improving the photocatalytic performance of the heterojunction, and can also maintain the high specific surface area and rich active sites of the material, thereby further enhancing the reaction activity; in addition, during the day or in an environment with sufficient light, AgNbO3-Bi2Sn2O7 can absorb ultraviolet light, visible light and most infrared light, generate ROS to inhibit algae reproduction and inactivate algae cells. In addition, the piezoelectric effect uses the mechanical vibration in the water body to generate a polarization electric field, promote the separation and transmission of photogenerated carriers, and improve the photocatalytic performance; at night or in the absence of light, the piezoelectric material AgNbO3 in the AgNbO3-Bi2Sn2O7 heterojunction can use the tidal vibration mechanical energy of the water body to generate a variety of ROS to continuously inhibit the reproduction of algae cells, achieving all-weather algae removal.

[0023] Therefore, the piezoelectric coupled photocatalyst provided in the embodiment of the present application optimizes the composition, coordination structure and electronic energy state of the heterojunction, thereby strengthening the built-in electric field at the heterojunction interface and enhancing the piezoelectric polarization electric field, reducing carrier interface recombination to enhance charge separation efficiency, and significantly improving the photocatalytic reaction activity and algae removal efficiency. It also couples the properties of piezoelectric materials and semiconductors, combining the principles of photocatalysis and piezoelectric catalysis, which can not only achieve efficiency improvement and speed increase for all-weather algae inhibition, but also couple natural wind energy, water wave energy, vibration and solar energy to achieve energy conservation and emission reduction.

[0024] Alternatively, given that the catalyst can utilize solar energy and mechanical energy to generate strong oxidative reactive oxygen species, the catalyst can also be used to degrade pollutants such as phenol, bisphenol A, and antibiotics; and can also be used to inactivate pathogenic microorganisms.

[0025] Optionally, in one embodiment, the molar ratio of AgNbO3 to Bi2Sn2O7 in the above-mentioned catalyst is (1:2) to (4:1), which can ensure that AgNbO3 exerts excellent photocatalytic and piezoelectric properties while utilizing Bi2Sn2O7 to broaden the light absorption range of the material.

[0026] In practical applications, the amount of Nb and Sn can be determined by X-ray photoelectron spectroscopy (XPS) analysis of the catalyst, and then the molar ratio of AgNbO3 and Bi2Sn2O7 can be determined.

[0027] Optionally, in one embodiment, in the catalyst provided in the examples of the present application, Bi2Sn2O7 is covered on 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 carriers to the heterojunction interface and avoids carrier recombination.

[0028] In the process of preparing the catalyst, the amount of Bi2Sn2O7 or AgNbO3 added to the system can be adjusted to control the molar ratio of AgNbO3 to Bi2Sn2O7 in the prepared catalyst.

[0029] Optionally, in one embodiment, the particle sizes of AgNbO3 and Bi2Sn2O7 in the catalyst are both 50-200 nm, so that the two have a more significant nano-confinement effect when they come into contact to construct a heterojunction.

[0030] The present embodiment provides a method for preparing a nanoconfined piezoelectric coupled photocatalyst, comprising steps 201 and 202: Step 201: providing nano-scale monomer Bi2Sn2O7; Step 202: Compound the Bi2Sn2O7 with nano-sized AgNbO3 to obtain a nano-confined piezoelectric coupled photocatalyst.

[0031] In the embodiment of the present application, nano-scale monomer Bi2Sn2O7 is first prepared, and then Bi2Sn2O7 is uniformly compounded with nano-scale AgNbO3 to obtain a piezoelectric coupled photocatalyst that can couple the piezoelectric material and semiconductor properties. It can not only achieve efficiency improvement, speed increase, and all-weather algae inhibition, but also couple natural wind energy, water wave energy, vibration and solar energy into one, and can effectively improve the problems of existing photocatalysts such as narrow spectral response range, low catalytic reaction activity and inability to catalyze all the time.

[0032] Alternatively, in one embodiment, providing a nano-sized monomer Bi2Sn2O7 includes steps 111 to 112: Step 111: add bismuth nitrate and polyvinyl pyridone to a mannitol aqueous solution and mix evenly, then dropwise add a mannitol aqueous solution of stannate, and add a strong base until the pH is 9-13 to obtain a first solution; the stannate includes at least one of sodium stannate and potassium stannate.

[0033] In step 111, bismuth nitrate and polyvinyl pyridone are added to the mannitol aqueous solution, and then the mixture is fully mixed by ultrasonication, shaking, or the like.

[0034] In step 111, the concentration of mannitol in the mannitol aqueous solution can be 0.1 M.

[0035] In step 111, the bismuth nitrate may be Bi(NO 3 ) 3 ·5H 2 O, and the sodium stannate crystal may be Na 2 SnO 3 ·3H 2 O.

[0036] In step 111, Bi2Sn2O7 is adjusted to a small size through a polyvinylpyridone-assisted solvothermal method to be easily loaded on the AgNbO3 surface, while more low-coordinated surface atoms are exposed and lost to form vacancies, thereby promoting photocatalytic carrier separation; in addition, vacancies are conducive to forming a heterojunction with AgNbO3.

[0037] Optionally, in step 111, the molar ratio of polyvinyl pyridone to bismuth nitrate and stannate is controlled to be 0.3:1:1, so that the formed Bi2Sn2O7 can be effectively adjusted to a micro size and loaded on the AgNbO3 surface.

[0038] In step 111, when the mannitol aqueous solution of stannate is added dropwise, it is fully mixed by ultrasound, shaking, stirring, etc. to promote the reaction. For example, it can be fully mixed at a stirring rate of 400 r / min.

[0039] In step 111, after adding the mannitol aqueous solution of stannate, the pH value is adjusted to 9-13, for example, one or two values ​​in the range of 9, 11.5, 12, 12.5, 13, so as to utilize the etching effect of the base to inhibit the Bi from being etched by the reactivity of mannitol. 3+ Reduction produces Bi atoms.

[0040] Alternatively, the strong base may be NaOH, KOH, etc. Alternatively, the strong base solution may be a 2 mol / L NaOH solution, which is a moderate concentration that can quickly adjust the pH of the system without damaging the crystal structure of the material due to excessive alkalinity.

[0041] Step 112: hydrothermally heat the first solution to obtain monomer Bi2Sn2O7.

[0042] In step 212, the first solution is placed in a sealed reaction apparatus and hydrothermally heated to fully disperse the reactants and uniformly heat them to react and obtain a precipitate. The precipitate is then removed by centrifugation or other methods and washed with water to obtain nano-sized Bi2Sn2O7. The sealed reaction apparatus can be a reactor, and the particle size of the Bi2Sn2O7 is 50-200 nm.

[0043] Optionally, during the hydrothermal heating of the first solution, the hydrothermal heating temperature is in the range of one or any two of 180°C, 190°C, 200°C, and 210°C, and the heating time is in the range of one or any two of 20 h, 24 h, and 30 h, which is beneficial to promote the full conversion of the reactants and the purification of the crystal phase, and can effectively take into account the yield, purity and product performance.

[0044] Alternatively, in one embodiment, Bi2Sn2O7 is compounded with nano-sized AgNbO3, including steps 211 and 212: Step 211: Add NH4HF2 and Nb2O5 to deionized water and mix well, then add Bi2Sn2O7 and Ag2O to obtain a second solution.

[0045] In step 211, the materials NH4HF2 and Nb2O5 are added to deionized water, and then Bi2Sn2O7 and Ag2O are added, and then fully mixed by ultrasonication, shaking, etc. to obtain a second solution.

[0046] In step 211, during the hydrothermal synthesis of AgNbO3, NH4HF2 not only serves as a fluoride ion source, 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 formation of the target phase.

[0047] Step 212: hydrothermally heat the second solution to obtain a nano-confined piezoelectric coupled photocatalyst.

[0048] In step 212, the second solution is placed in a closed reaction device and hydrothermally heated to fully disperse the reactants and uniformly heat them to react and obtain a precipitate. The precipitate is then removed by centrifugation or the like and washed with water to obtain a nano-confined piezoelectric coupled photocatalyst containing a composite of AgNbO3 and Bi2Sn2O7.

[0049] In step 212, the hydrothermal synthesis mechanism of AgNbO3 is: Nb2O5+ 6NH4HF2→ 2(NH4)3NbOF6+ 3H2O; (NH4)3NbOF6+ 6H2O → [NbO(OH)6] 3 ⁻ + 3NH4HF2+ 3H + ; Ag + + [NbO(OH)6] 3 ⁻ + 2H + → AgNbO3+ 4H2O; Wherein, the above-mentioned closed reaction equipment can be a reactor.

[0050] Optionally, during the hydrothermal heating of the second solution, the hydrothermal heating temperature is 210-230°C and the time is 30-40 h, which can effectively promote the formation of Nb 5 ⁺The formation of soluble complexes with the assistance of fluoride ions, which in turn completes the construction of the crystal structure, helps to achieve full phase transformation and orderly crystal growth, inhibits the formation of by-products, and improves the crystallinity and structural stability of the product, thereby obtaining AgNbO3 materials with better performance.

[0051] Optionally, during the hydrothermal heating of the second solution, the hydrothermal heating temperature can be in the range of one or any two of 210° C., 220° C., and 230° C., and the heating time can be in the range of one or any two of 30 h, 32 h, 36 h, and 40 h, which is beneficial to promote the full conversion of the reactants and the purification of the crystal phase, and can effectively take into account the yield, purity and product performance.

[0052] Optionally, in 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 covering layer formed by the Bi2Sn2O7 on the surface of AgNbO3 is moderate, which is conducive to the diffusion of carriers to the heterojunction interface and avoids carrier recombination.

[0053] In step 212, after the hydrothermal reaction, the BiOBr monomer is obtained by washing with deionized water, filtering and collecting the residue, and drying it. Optionally, the residue can be vacuum dried at a temperature of 60° C. for 10 hours.

[0054] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention is further described below in conjunction with examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0055] The present invention is described in detail below through test examples.

[0056] Test Example 1 (1) 1 mmol Bi(NO3)3·5H2O and 0.3 mmol polyvinylpyridone 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 to solution A with a dropper and stirred for 30 min. 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 reactor and heated at 200°C for 24 h. After the reactor was cooled to room temperature, it was cleaned and dried to obtain monomer Bi2Sn2O7. (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, and stir at room temperature for 30 min. Then transfer the mixed suspension to a 100 mL high-pressure reactor, heat at 220 °C for 32 h, cool to room temperature, wash three times with deionized water, and dry under vacuum at 80 °C to obtain the product nano-confined piezoelectric coupled photocatalyst AgNbO3-Bi2Sn2O7 (2:1).

[0057] Test cases 2 to 4 The difference between Test Examples 2 to 4 and Test Example 1 is that in step (2), the addition amount of Bi2Sn2O7 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), respectively.

[0058] Test Example 5 1 mmol Bi(NO3)3·5H2O and 0.3 mmol polyvinylpyridone 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. 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 reactor and heated at 200°C for 24 h. After the reactor was cooled to room temperature, it was cleaned and dried to obtain the product monomer Bi2Sn2O7.

[0059] Test Example 6 3 mmol of NH4HF2 and 1 mmol of Nb2O5 were added to 70 mL of deionized water, and then 1 mmol of Ag2O was added. The mixture was stirred at room temperature for 30 min, and then the mixed suspension was transferred to a 100 mL high-pressure reactor, heated at 220°C for 32 h, cooled to room temperature, washed three times with deionized water, and dried under vacuum at 80°C to obtain the product, nano-scale AgNbO3.

[0060] 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 tested by scanning electron microscope respectively. The results are as follows: Figure 1 As shown in (a), (b), and (c). Figure 1 It can be seen that Bi2Sn2O7 has a bulk nanostructure, while AgNbO3 has a bulk structure with a smooth surface. AgNbO3-Bi2Sn2O7 (2:1) has a small particle bulk nanostructure and a bulk structure with a smooth surface, which indicates that Bi2Sn2O7 and AgNbO3 are successfully composited.

[0061] The catalyst AgNbO3-Bi2Sn2O7 (2:1) prepared in Test Example 1 was tested for element distribution, and the results were as follows: Figure 2 As shown. Figure 2 It can be seen that Bi2Sn2O7 is a bulk nanostructure, while AgNbO3 is a bulk structure with a smooth surface.、 Bi 、 Elements such as Sn are evenly distributed, which further proves the successful preparation and composite of Bi2Sn2O7 and AgNbO3.

[0062] The product Bi2Sn2O7 prepared in Test Example 5, the product AgNbO3 prepared in Test Example 6, and the catalyst AgNbO3-Bi2Sn2O7 (2:1) prepared in Test Example 1 were subjected to X-ray diffractometer (XRD) tests respectively. The test was performed using a PANalytical Aeris desktop diffractometer. The test conditions were set as follows: scanning range 5~90°, scanning rate 2° / min, and then the obtained spectra were compared with the standard card library. The results are as follows: Figure 3 shown.

[0063] Depend on Figure 3 It can be seen that the XRD peak of Bi2Sn2O7 is consistent with the standard card (PDF#432-6954), indicating that Bi2Sn2O7 was successfully prepared; the peak position of AgNbO3 is consistent with the standard card (PDF#052-0405), indicating that AgNbO3 has a good crystal structure; the characteristic peaks of Bi2Sn2O7 and AgNbO3 are clearly observed in AgNbO3-Bi2Sn2O7 (2:1), which indicates that Bi2Sn2O7 and AgNbO3 are successfully composited.

[0064] The product Bi2Sn2O7 prepared in Test Example 5, the product AgNbO3 prepared in Test Example 6, and the catalyst AgNbO3-Bi2Sn2O7 (2:1) prepared in Test Example 1 were subjected to UV diffuse reflectance (DRS) tests. The test was performed using a Lambda 1050 N / W spectrometer from PerkinElmer, USA, with a scanning wavelength range of 200-2500 nm. The UV diffuse reflectance spectra and band gap widths obtained from the tests are shown in Figure 2. Figure 4 shown.

[0065] pass Figure 4 It can be seen that the absorption edge of the prepared product catalyst AgNbO3-Bi2Sn2O7 (2:1) is about 1190nm, indicating that the catalyst can achieve full spectrum absorption and can effectively improve the utilization rate of solar photons.

[0066] The products prepared in each test example were tested for piezoelectric photocatalytic activity, and the results were as follows: Figure 5 The specific test method is as follows: The catalyst was placed in a piezoelectric photoreaction device to perform an experiment on the degradation of Microcystis aeruginosa. During the photocatalytic reaction, an LED lamp was used as the light source. 40 mL of algae suspension was used. The reactor contained (0.5 g / L) or no catalyst. The light source was turned on / off (20 W / m 2 ), the reactor was placed under ultrasound / no ultrasound.

[0067] According to the different reaction conditions in the above experiments: placement (AgNbO3, Bi2Sn2O7 or AgNbO3-Bi2Sn2O7), turning on / off the light source (Vis), with ultrasound / 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.

[0068] At preset intervals, 8 mL of the reaction solution was taken to measure its chlorophyll a content. A 0.45 μm filter membrane was placed on the filtration instrument, and then 8 mL of the sample was filtered. The filter membrane was placed in a test tube and frozen for 12 h. After that, the test tube was taken out and 8 mL of 90% acetone solution was added. A small amount of magnesium carbonate powder was added to protect the chlorophyll from being destroyed. The cells were disrupted by an ultrasonic cell disruptor (ultrasonication time 3 s, interval time 2 s) for 3 min, and the sample was treated at a speed of 4500 r / min for 10 min. The supernatant was taken and 90% acetone was used as a reference. The OD value was calculated. 630 ,OD 647 ,OD 664 and OD 750 Determine the content of chlorophyll a. The calculation formula is as follows:

[0069] Where: OD 630 ,OD 647 ,OD 664 ,OD 750 are the absorbance values ​​of the samples at wavelengths of 630 nm, 647 nm, 664 nm, and 750 nm, respectively; V1 is the sample volume, mL; V2 is the volume of 90% acetone, mL; The removal efficiency of Microcystis aeruginosa was calculated as C / C0, where C0 and C were the chlorophyll a contents at 0 and t min, respectively.

[0070] Depend on Figure 5As shown in (a), the product catalyst in Test Example 1 has a better piezoelectric photocatalytic algae removal effect, and the chlorophyll of the algae cells can be significantly destroyed under the action of ultrasound and piezoelectricity, and 78% of the algae can be removed within 4.5 hours, which is much higher than the 30% of AgNbO3 and 10% of Bi2Sn2O7. This is because the composite material can promote the absorption of visible light, and the photogenerated electrons can be more efficiently separated under the dual action of the built-in electric field and the polarization electric field, thereby generating a higher concentration of active oxygen species and achieving efficient inactivation of algae cells. In addition, the algae removal performance of the AgNbO3-Bi2Sn2O7 (2:1) / US / Vis system is better than that of the AgNbO3-Bi2Sn2O7 (2:1) / Vis system, which shows that the polarization electric field generated by the piezoelectric material AgNbO3 can promote carrier separation and improve the efficiency of algae removal. Figure 5 As shown in (b), neither the US / Vis system nor the Vis system alone will cause the death of algae, which indicates that the catalyst prepared by optimizing the experimental preparation method has a better algae removal effect.

[0071] With 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 the action of ultrasound. The results are as follows: Figure 6 As shown, the test process is as follows: The piezoelectric degradation reaction of phenol was carried out in a 100 mL quartz beaker. The reaction system temperature was controlled at a constant level of 25°C by a cooling water circulation system. The quartz beaker was placed in a 200 W ultrasonic machine and shielded from light. At regular intervals between reactions, 1 mL of the reaction solution was filtered through a 0.22 µm filter membrane, and the filtrate was analyzed by liquid chromatography to determine the peak signal of phenol. Each experiment was run in triplicate. The phenol degradation curve was determined by measuring the ratio of the real-time concentration to the initial concentration (C / C0). The phenol concentration was determined by high-performance liquid chromatography at a characteristic wavelength of 223 nm. The mobile phase was acetonitrile:water (20:80) at a flow rate of 0.8 mL / min.

[0072] Depend on Figure 6 It can be seen that under ultrasound, AgNbO3 and AgNbO3-Bi2Sn2O7 (2:1) can degrade 60% and 65% of phenol in 4.5 h, respectively, indicating that AgNbO3 and AgNbO3-Bi2Sn2O7 (2:1) can generate polarized electric fields under ultrasound, thereby generating active oxygen species to degrade pollutants.

[0073] The catalyst prepared in Test Example 1 was subjected to a cycle performance test, and the results were as follows: Figure 7 The specific test method is as follows: After the first degradation reaction (1 st) is completed, the catalyst is separated from the solution by filtration, and the filtered catalyst is washed with deionized water and ethanol, and then dried in a freeze dryer for 48 hours for use; the above-mentioned spare materials are used to carry out the second degradation reaction (2 st). Except for the materials, the other reaction conditions are consistent with the first one; after the second reaction is completed, the above steps are repeated to carry out the third (3 st), fourth (4 st), and fifth (5 st) degradation experiments.

[0074] Depend on Figure 7 It can be seen that the AgNbO3-Bi2Sn2O7 (2:1) / US / Vis system has good cycle stability. After 5 cycles, the algae removal effect is only reduced by 15%, indicating that the material has good cycle stability and good application prospects.

[0075] In summary, the present invention utilizes the characteristics of piezoelectric and photocatalytic materials and the energy band properties of semiconductors to construct a heterojunction to design and synthesize a highly efficient, all-weather piezoelectric-photocatalytic algae removal material. In the experiment, the algae removal efficiency of the composite material and its intermediate products was studied by combining illumination, ultrasound, and stirring to simulate actual water environments. The surface characteristics and mechanism of action of the material, the active sites of the reactive oxygen species involved in the algae removal, and various algae removal indicators were explored to obtain a detailed understanding of the material's algae removal mechanism. Material characterization was then conducted to achieve a comprehensive understanding of the material's physicochemical properties, optical properties, and piezoelectric properties.

[0076] In addition, the nano-confined voltage-electrically coupled photocatalytic material AgNbO3-Bi2Sn2O7 prepared in this application can optimize the composition, coordination structure and electronic energy state of the heterojunction by first preparing Bi2Sn2O7 and then introducing Bi2Sn2O7 into the preparation of AgNbO3, thereby strengthening the built-in electric field at the heterojunction interface and enhancing the piezoelectric polarization electric field, reducing carrier interface recombination to enhance charge separation efficiency, thereby significantly improving the photocatalytic reaction activity and significantly improving the algae removal efficiency.

[0077] Terminology In this application, a plurality refers to two or more.

[0078] In this application, the terms "first," "second," "third," "fourth," etc. (if any) are used to distinguish similar objects and are not necessarily used to describe a particular sequential order.

[0079] The term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects are in an "or" relationship.

[0080] Unless otherwise specified, all steps of this application may be performed sequentially or randomly. For example, "the method includes steps A and B" means that the method may include steps A and B performed sequentially, or may include steps B and A performed sequentially. For example, "the method may also include step C" 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 steps A, C, and B, or steps C, A, and B, etc.

[0081] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A nanoconfined piezoelectric coupled photocatalyst, characterized in that: It includes AgNbO3-Bi2Sn2O7, and the particle sizes of AgNbO3 and Bi2Sn2O7 are both nanometer-level.

2. The nanoconfined piezoelectric coupled photocatalyst according to claim 1, characterized in that: The molar ratio of AgNbO3 to Bi2Sn2O7 in the catalyst is (1:2) to (4:1).

3. The nanoconfined piezoelectric coupled photocatalyst according to claim 1, characterized in that: The particle sizes of AgNbO3 and Bi2Sn2O7 in the catalyst are both 50~200 nm.

4. A method for preparing a nano-confined piezoelectric coupled photocatalyst, characterized in that: include: Provide nano-scale monomer Bi2Sn2O7; The Bi2Sn2O7 is compounded with nano-scale AgNbO3 to obtain a nano-confined piezoelectric coupled photocatalyst.

5. The preparation method according to claim 4, characterized in that The nano-sized monomer Bi2Sn2O7 provided includes: Bismuth nitrate and polyvinyl pyridone are added to a mannitol aqueous solution and mixed evenly, and then a mannitol aqueous solution of stannate is added dropwise, and a strong base is added to the pH value of 9 to 13 to obtain a first solution; the stannate comprises at least one of sodium stannate and potassium stannate; The first solution is hydrothermally heated to obtain monomer Bi2Sn2O7.

6. The preparation method according to claim 5, characterized in that During the hydrothermal heating of the first solution, the hydrothermal heating temperature is 180-210° C. and the time is 20-30 h.

7. The preparation method according to claim 4, characterized in that The Bi2Sn2O7 is compounded with nano-sized AgNbO3, comprising: NH4HF2 and Nb2O5 were added to deionized water and mixed, and then Bi2Sn2O7 and Ag2O were added to obtain a second solution; The second solution is hydrothermally heated to obtain a nano-confined piezoelectric coupled photocatalyst.

8. The preparation method according to claim 7, characterized in that During the hydrothermal heating of the second solution, the hydrothermal heating temperature is 210-230° C. and the time is 30-40 h.

9. The preparation method according to claim 7, characterized in that In the process of adding NH4HF2 and Nb2O5 into deionized water and mixing them uniformly, and then adding Bi2Sn2O7 and Ag2O, the molar ratio of Bi2Sn2O7, Nb2O5, and Ag2O is controlled to be (0.1~8): 1:

1.

10. A use of the nanoconfined piezoelectric coupled photocatalyst according to any one of claims 1 to 3, characterized in that: The piezoelectric coupled photocatalyst is used to inactivate at least one of algae, pathogenic microorganisms, and degrade pollutants, wherein the pollutants include at least one of phenol, bisphenol A, and antibiotics.

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