All-weather piezoelectric coupling photocatalyst as well as preparation method and application thereof

Abstract

The embodiment of the invention provides an all-weather piezoelectric coupling photocatalyst as well as a preparation method and application thereof, the piezoelectric photocatalyst prepared by the embodiment of the invention can couple the characteristics of a piezoelectric material and a semiconductor, combines the principles of photocatalysis and piezoelectric catalysis, not only can realize all-weather algal inhibition with improved efficiency and speed, but also can realize all-weather algal inhibition with improved efficiency and speed. The wind energy, the water wave energy, the vibration and the solar energy in the nature can be coupled into a whole, a new principle and a new thought are provided for multi-path utilization, energy conservation and emission reduction of natural energy, and huge potential is achieved in future energy environment application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalytic algae removal, and particularly relates to an all-weather piezoelectric coupling photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] With the aggravation of water eutrophication, the ecological safety crisis caused by cyanobacterial blooms is becoming increasingly serious. The explosive proliferation of algae not only causes the decline of water transparency, the depletion of dissolved oxygen and the decline of biodiversity, but also releases secondary pollutants such as microcystins and fishy algae toxins, which directly threaten 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. When photocatalytic algae removal is performed, solar energy, which is ubiquitous in algae bloom growth water, is used to generate highly oxidative free radicals and other active oxygen species through photocatalysts under daylight to efficiently inactivate algal cells and oxidize secondary products such as algal toxins.

[0003] However, the current photocatalytic oxidation technology has potential in terms of algae inactivation and organic matter degradation, but is severely limited in terms of application performance in actual water treatment projects due to low spectral utilization rate, low charge separation efficiency, low orbital matching degree and susceptibility to environmental light. SUMMARY

[0004] The embodiments of the present application provide an all-weather piezoelectric coupling photocatalyst and a preparation method and application thereof, aiming to improve the problem of narrow spectral response range, low catalytic reaction activity and inability to catalyze at all times of the existing photocatalyst.

[0005] To solve the above problems, the present application is realized through the following technical solutions: The present application provides a preparation method of an all-weather piezoelectric coupling photocatalyst, comprising: providing a monomer Bi2O2S; dissolving bismuth nitrate in ethylene glycol, then sequentially adding the monomer Bi2O2S and KI, mixing uniformly and adding a strong base to pH 7.5-9.5 to obtain a first solution; heating the first solution by a hydrothermal method to obtain the all-weather piezoelectric coupling photocatalyst Bi4O5I2-Bi2O2S.

[0006] Further, in the preparation method, the provision of the monomer Bi2O2S comprises: dissolving bismuth nitrate in water, then adding a sulfur source and adding LiOH to pH≥14 to obtain a second solution; heating the second solution by a hydrothermal method to obtain the monomer Bi2O2S.

[0007] Further, in the preparation method, the sulfur source is thiourea.

[0008] Further, in the preparation method, the molar ratio of bismuth nitrate to thiourea is controlled to be 1-3:1 during the addition of the sulfur source.

[0009] Further, in the preparation method, the temperature of the hydrothermal heating is 200°C and the time is 72 h during the hydrothermal heating of the third solution.

[0010] Further, in the preparation method, the molar ratio of bismuth nitrate, Bi2O2S and KI is controlled to be 1:(0.1-0.25):2 during the sequential addition of the monomer Bi2O2S and KI.

[0011] Further, in the preparation method, the temperature of the hydrothermal heating is 150°C and the time is 12 h during the hydrothermal heating of the first solution.

[0012] The application also provides an all-weather piezoelectric coupling photocatalyst prepared by the above method.

[0013] The application also provides an application of the all-weather piezoelectric coupling photocatalyst as described above, wherein the all-weather piezoelectric coupling photocatalyst is used for at least one of inactivating algae, pathogenic microorganisms and degrading pollutants, and the pollutants include at least one of phenol, bisphenol A and antibiotics.

[0014] The preparation method of the all-weather piezoelectric coupling photocatalyst provided in the application dissolves bismuth nitrate in ethylene glycol, sequentially adds the monomers Bi2O2S and KI, uniformly mixes, and then adds a strong base to a pH of 7.5-9.5 to prepare the all-weather piezoelectric coupling photocatalyst Bi4O5I2-Bi2O2S by hydrothermal heating, wherein the ethylene glycol plays the role of a coordination agent and can inhibit the hydrolysis of bismuth nitrate in the initial stage, and after the strong base is added to a pH of 7.5-9.5, the bismuth nitrate rapidly hydrolyzes to form BiOI before heating, and with the heating, OH − may gradually replace I − Due to the mediation of ethylene glycol, the BiOI surface has fewer hydroxyl groups and higher viscosity, the BiOI nanosheet rotates to form a low-energy configuration interface, and a reasonably oriented assembly is formed, therefore, the Bi4O5I2 in the formed catalyst presents a three-dimensional (3D) hierarchical micro / nano structure, which is composed of numerous nanosheets and coated on the surface of Bi2O2S, and the thickness is less than 15 nanometers, the easily formed two-dimensional nanosheet structure formed by the internal layered stacking structure makes the Bi4O5I2 have high flexibility and sensitivity to mechanical stimulation, strong strain bearing capacity, short charge transport distance and large specific surface area ratio; and the Bi2O2S also contains [Bi2O2] 2+which has a similar crystal structure to Bi4O5I2. Not only is it easy to compound with Bi4O5I2 to build a heterojunction, thereby greatly promoting the transfer of photo-generated carriers and retaining their high potential, but also the [Bi2O2] 2+ The layers are separated by a row of S 2− , so that Bi2O2S has a smaller band gap, improving its stability in the photocatalytic process; in addition, in daylight or well-lit environments, Bi4O5I2-Bi2O2S can absorb most of the ultraviolet-visible light, generating ROS to inhibit the reproduction of algae and inactivate algal cells. At the same time, the piezoelectric effect uses the mechanical vibration in the water body to generate a polarized electric field, promoting the separation and transport of photo-generated carriers and improving the photocatalytic performance. In the absence of light at night, the piezoelectric material Bi4O5I2 can use the tidal vibration mechanical energy of the water body to generate a variety of ROS to continuously inhibit the reproduction of algal cells, achieving all-weather algae removal. Therefore, the piezoelectric photocatalyst provided in the embodiments of the present application can couple the piezoelectric material and semiconductor properties, combine the principles of photocatalysis and piezoelectric catalysis, achieve all-weather algae inhibition with improved efficiency and speed, and couple wind energy, water wave energy, vibration and solar energy in nature, providing a new principle and new idea for the multi-way use of natural energy and energy saving and emission reduction, and playing a huge potential in future energy and environmental applications. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is an electron microscope test graph of the catalyst provided in the test examples of the present application; Figure 2 is an XRD test graph of the catalyst in the test examples of the present application; Figure 3 is an XPS test graph of the catalyst in the test examples of the present application; Figure 4 is a KPFM test graph of the catalyst in the test examples of the present application; Figure 5 is a butterfly-shaped displacement-voltage curve graph of the catalyst in the test examples of the present application; Figure 6 is an ultraviolet diffuse reflectance test and band gap graph of the catalyst in the test examples of the present application; Figure 7 is a PL spectrum test graph of the catalyst in the test examples of the present application; Figure 8 is a transient photocurrent response test and impedance test graph of the catalyst in the test examples of the present application; Figure 9 is a piezoelectric photocatalytic activity test graph of the catalyst in the test examples of the present application; Figure 10 is a cycle performance test graph of the catalyst in the test examples of the present application; Figure 11 is an in-situ infrared spectrum test graph of the catalyst in the embodiments of the present application; Figure 12 The in-situ Raman spectrum test chart of the catalyst in the embodiment of the application is as shown in the following figure: Figure 13 The scanning electron microscope images of the algal cell morphology under different processing durations are as shown in the following figures: Figure 14 The quenching experiment test chart of the catalyst in the test example of the application is as shown in the following figure: Figure 15 The energy level structure chart of the catalyst in the test example of the application is as shown in the following figure. DETAILED DESCRIPTION

[0016] In order to make the technical problems, technical solutions and beneficial effects solved by the application clearer and more apparent, the application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.

[0017] With the aggravation of water body eutrophication, the ecological safety crisis caused by water bloom is increasingly serious. The photocatalytic technology is regarded as an innovative solution in the field of environmental governance due to its green and energy-saving characteristics, which realizes the inactivation of algal cells and the degradation of toxins through the generation of active oxygen species by sunlight-driven catalysts.

[0018] The principle of photocatalytic algae removal is to utilize the sunlight energy commonly existing in algal bloom growth water area, to efficiently inactivate algal cells and oxidize algal toxins and other secondary products through the generation of strong oxidizing free radicals and other active oxygen species by photocatalysts under daylight illumination. However, photocatalytic process still faces the following five technical problems in actual algae removal applications: (1) the spectral range absorbed and utilized is too narrow; (2) the charge separation efficiency is too low; (3) the orbital matching degree is too low; (4) the reaction is greatly affected by environmental illumination; (5) the material lacks self-floating property.

[0019] In view of the above problems existing in photocatalytic algae removal, the applicant found that the nanostructure of piezoelectric material can utilize the mechanical force of water flow disturbance in water body to generate a local polarization electric field. Under the action of the internal electric field, the valence band (VB) and the conduction band (CB) will tilt, and the photo-generated carriers can accelerate the transition to the surface of the catalyst. Thus, the photo-induced electron-hole pairs generated by photocatalysis can be effectively separated (piezophotonic effect); secondly, piezoelectric effect can make the semiconductor band bend, increase the valence band potential, and promote the transition of electrons, thereby improving the photon utilization rate; in addition, when the energy source is lost due to the absence of light at night, the piezoelectric material can still generate a polarization electric field through piezoelectric effect, thereby generating strong oxidizing ROS.

[0020] Based on the above findings, in order to solve the problems of narrow spectral response range, low catalytic reaction activity and inability to catalyze and remove algae at all times of the existing photocatalyst, the embodiment of the application provides a preparation method of an all-weather piezoelectric photocatalyst, comprising steps 101-103: Step 101, providing a monomer Bi2O2S; Step 102, dissolving bismuth nitrate in ethylene glycol, then adding the monomer Bi2O2S and KI in sequence, mixing uniformly and adding a strong base to pH 7.5-9.5 to obtain a first solution; Step 103, heating the first solution by a hydrothermal method to obtain an all-weather piezoelectric coupling photocatalyst Bi4O5I2-Bi2O2S.

[0021] In the embodiments of the present application, the monomer Bi2O2S is first prepared, and then Bi4O5I2 is uniformly compounded on Bi2O2S by a hydrothermal method or the like with ethylene glycol as a solvent, so that a piezoelectric photocatalyst capable of coupling piezoelectric material and semiconductor characteristics can be obtained, which can not only realize efficiency improvement, speed increase and all-weather algae inhibition, but also can couple wind energy, water wave energy, vibration and solar energy in nature, so as to effectively improve the problems of narrow spectral response range, low catalytic reaction activity and inability to catalyze at all times of the existing photocatalyst.

[0022] Among them, ethylene glycol plays the role of a complexing agent, which can inhibit the hydrolysis of bismuth nitrate at the initial stage, and after adding a strong base to pH 7.5-9.5, bismuth nitrate rapidly hydrolyzes to form BiOI before heating, and with the heating, OH − may gradually replace I − Due to the mediation of ethylene glycol, the surface hydroxyl group of BiOI is less and the viscosity is high, the BiOI nanosheet rotates to find a low-energy configuration interface to form a reasonably oriented assembly, therefore, the Bi4O5I2 in the formed catalyst presents a three-dimensional (3D) hierarchical micro / nano structure, which is composed of numerous nanosheets and coated on the surface of Bi2O2S, and the thickness is less than 15 nanometers, the three-dimensional (3D) hierarchical micro / nano structure formed by the inner two-dimensional nanosheet makes Bi4O5I2 have high flexibility, sensitivity to mechanical stimulation, strong strain bearing capacity, short charge transport distance and large specific surface area ratio; and Bi2O2S also contains [Bi2O2] 2+ , which has a similar crystal structure to Bi4O5I2, not only easy to compound with Bi4O5I2 to construct a heterojunction, thereby greatly promoting the transfer of photo-generated carriers and retaining high potential, but also the [Bi2O2] 2+ layer between the sheets is separated by a row of S 2− , so that Bi2O2S has a smaller band gap, improving its stability in the photocatalytic process.

[0023] The Bi2O2S flaky material in the catalyst prepared by the embodiment of the application has a short thickness dimension, which can shorten the distance of photo-generated carriers migrating from the bulk phase to the surface, significantly reduce the recombination probability of electrons and holes, and enhance the utilization efficiency of photo-generated carriers; the three-dimensional (3D) hierarchical micro / nano structure makes Bi4O5I2 have high flexibility and sensitivity to mechanical stimulation, strong ability to withstand huge strain, short charge transport distance, and large specific surface area ratio, which is beneficial to mechanical induction piezophotocatalytic purification of water bodies. Among them, the special layered structure of Bi4O5I2 containing [Bi2O2] 2+ is stacked by [Bi2O2] 2+ layer and double halogen atom layer, which is beneficial to the separation and transfer of photo-generated carriers, thereby enhancing the photocatalytic activity. In addition, Bi4O5I2 has an asymmetric crystal structure with a monoclinic space group P2 series, which endows them with attractive piezoelectric properties, i.e. the potential of converting mechanical energy into chemical energy through piezocatalysis.

[0024] In addition, Bi4O5I2 not only has obvious piezocatalytic performance, but also from the analysis of the energy band position, the conduction band and the valence band position of Bi4O5I2 are-1.13 eV and 0.97 eV, respectively, and the conduction band and the valence band position of Bi2O2S are 0.06 eV and 1.17 eV, respectively. The band gap of Bi2O2S is smaller, which can absorb visible and infrared light spectrum, while the energy band position of Bi4O5I2 and Bi2O2S makes it possible to construct a Z-type heterojunction through recombination, thereby greatly promoting the transfer of photo-generated carriers and retaining their high potential.

[0025] In addition, in the daytime or in an environment with sufficient light, Bi4O5I2-Bi2O2S can absorb most of the ultraviolet-visible light, so that a large number of photo-generated electrons and holes are generated in Bi4O5I2 and Bi2O2S, and the electrons on the conduction band of Bi2O2S further move to the valence band of Bi4O5I2, thereby inhibiting the rapid recombination of carriers and promoting the activation of O2 and persulfate by the photo-generated electrons on the conduction band of Bi4O5I2 to generate ROS to inhibit the reproduction of algae and inactivate the algae cells; the holes on the valence band of Bi2O2S have strong oxidizing properties and can oxidize and destroy the structure of the algae cells. At the same time, the piezoelectric effect utilizes the mechanical vibration in the water body to generate a polarization electric field, promotes the separation and transmission of the photo-generated carriers, and improves the photocatalytic performance; and under the condition of night or no light, the piezoelectric material Bi4O5I2 can utilize the tidal vibration mechanical energy of the water body to generate various ROS to continuously inhibit the reproduction of the algae cells, thereby achieving all-weather algae removal. Therefore, the piezoelectric photocatalyst provided in the embodiments can couple the piezoelectric material and the semiconductor properties, combine the photocatalysis and piezoelectric catalysis principles, achieve all-weather algae inhibition with improved efficiency and speed, and couple the wind energy, water wave energy, vibration and solar energy in nature, thereby providing a new principle and new idea for the multi-way utilization of natural energy and energy saving and emission reduction, and playing a great potential in future energy and environmental applications.

[0026] Optionally, in an embodiment, the monomer Bi2O2S is provided, including steps 111-113: Step 111, dissolve bismuth nitrate in water, then add a sulfur source, and add LiOH to pH≥14 to obtain a second solution.

[0027] In this step 111, the bismuth nitrate is dispersed in deionized water, and then a sulfur source is added, wherein the sulfur source can release S 2- with Bi 3+ to generate Bi2O2S, and the addition of LiOH to pH≥14 can ensure that Bi 3 ⁺ preferentially hydrolyzes to generate [Bi2O2]² + intermediate (rather than directly precipitating as Bi(OH)3), and then Bi2O2S (containing [Bi2O2] 2+ layer) is formed; LiOH promotes the subsequent sulfuration reaction and crystal growth, and in a high-alkaline environment, promotes the decomposition of thiourea, and then forms Bi-O-S structural units and self-assembles into Bi2O2S crystals.

[0028] Specifically, the bismuth nitrate can be Bi(NO3)3·5H2O, and the sulfur source can be thiourea (SC(NH2)2), thioacetamide (CH3CSNH2), sodium thioacetamide (NaCH3CSNH2), sodium sulfide (Na2S), ammonium sulfide ((NH4)2S), L-cysteine (HSCH2CH(NH2)COOH), etc.

[0029] Optionally, in the process of adding the sulfur source, the molar ratio of bismuth nitrate to thiourea is controlled to be 1-3:1 to ensure that the sulfur source is in excess of the complexation of Bi 3+ . The molar ratio of bismuth nitrate to thiourea can be one of 1:1, 2:1, 3:1 or a range value of any two thereof, which can effectively inhibit the generation of impurities.

[0030] Step 112, hydrothermal heating of the second solution to obtain monomer Bi2O2S.

[0031] In this step 112, the second solution is placed in a closed reaction device for hydrothermal heating, which can fully disperse the reaction substances and uniformly heat to react to obtain a precipitate. The precipitate is removed by centrifugation and the like and then washed to obtain the monomer Bi2O2S. The above-mentioned closed reaction device can be a polytetrafluoroethylene autoclave.

[0032] Optionally, in the process of hydrothermal heating of the second solution, the temperature of the hydrothermal heating is 200°C and the time is 72 h, which is conducive to promoting the full conversion of the reactants and the purification of the crystal phase, and can effectively balance the yield, purity and product performance.

[0033] Optionally, in an embodiment, in the above-mentioned step 102, the material bismuth nitrate is added to ethylene glycol, and then fully mixed into a suspension by ultrasonic, shaking and the like.

[0034] In this step 102, the bismuth nitrate can be Bi(NO3)3·5H2O.

[0035] In this step 102, in the process of sequentially adding the monomer Bi2O2S and KI, the molar ratio of bismuth nitrate, Bi2O2S and KI is controlled to be 1:(0.1-0.25):2, so that I and Bi2O2S form an accurate ratio, effectively guiding the directional growth of Bi4O5I2 into nanosheets and avoiding the initiation of particle agglomeration. The molar ratio of Bi4O5I2 to Bi2O2S in the formed catalyst is 4:1-8:1.

[0036] In this step 102, after sequentially adding the monomer Bi2O2S and KI, fully mix by ultrasonic, shaking and the like, then add a strong base such as NaOH solution, KOH to adjust the pH to 7.5-9.5, for example, one of 7.5, 8, 8.5, 9, 9.5 or a range value of any two thereof, to ensure the purity and morphology of the material and avoid agglomeration or fracture. Optionally, the strong base is a NaOH solution with a concentration of 1 mol / L, which is a moderate concentration that can quickly adjust the pH of the system without damaging the crystal structure of the material due to too strong alkalinity.

[0037] In step 103, the second solution is placed in a closed reaction device for hydrothermal heating, which can fully disperse the reactants and uniformly heat the reactants to obtain a precipitate, and then the precipitate is taken out by centrifugation and the like, and then washed with ethanol and water, so as to obtain a piezoelectric photocatalyst with Bi4O5I2-Bi2O2S composite. The above-mentioned closed reaction device can be a polytetrafluoroethylene autoclave.

[0038] Optionally, in the process of hydrothermal heating of the third solution, the temperature of the hydrothermal heating is 150°C, and the time is 12 h, which is beneficial to promote the full conversion of the reactants and the purification of the crystal phase, and can effectively balance the yield, purity and product performance.

[0039] The embodiment of the present application also provides a piezoelectric coupling photocatalyst prepared by the above-mentioned method.

[0040] The piezoelectric photocatalyst provided by the embodiment of the present application is composed of Bi4O5I2 and Bi2O2S.

[0041] Bi4O5I2 presents a three-dimensional (3D) hierarchical micro / nano structure, is composed of a large number of nanosheets and is coated on the surface of Bi2O2S, and the thickness is less than 15 nanometers. The two-dimensional nanosheet structure formed by the inner layer stack structure makes Bi4O5I2 have high flexibility, sensitivity to mechanical stimulation, strong strain bearing capacity, short charge transport distance and large specific surface area ratio; and Bi2O2S also contains [Bi2O2] 2+ , which has a similar crystal structure to Bi4O5I2. Not only is it easy to composite to build a heterojunction, thereby greatly promoting the transfer of photo-generated carriers and retaining high potential, but also [Bi2O2] 2+ The layers are separated by a row of S 2− , so that Bi2O2S has a smaller band gap, improves the stability in the photocatalytic process, and makes Bi4O5I2 and Bi2O2S have excellent photocatalytic performance.

[0042] In addition, Bi4O5I2 not only has obvious piezoelectric catalytic performance, but also from the energy band position analysis, the conduction band and the valence band of Bi4O5I2 are-1.13 eV and 0.97 eV, respectively, and the conduction band and the valence band of Bi2O2S are 0.06 eV and 1.17 eV, respectively. Bi2O2S has a smaller band gap and can absorb visible and infrared light spectrum, and the energy band position of Bi4O5I2 and Bi2O2S can build a Z-type heterojunction through composite, thereby greatly promoting the transfer of photo-generated carriers and retaining high potential.

[0043] In addition, in the daytime or in an environment with sufficient light, Bi4O5I2-Bi2O2S can absorb most of the ultraviolet-visible light to generate ROS to inhibit the reproduction of algae, and at the same time, the piezoelectric effect utilizes the mechanical vibration in the water body to generate a polarization electric field to promote the separation and transport of photogenerated carriers, thereby improving the photocatalytic performance; and in the night or in the absence of light, the piezoelectric material Bi4O5I2 can utilize the tidal vibration mechanical energy of the water body to generate various ROS to continuously inhibit the reproduction of algae cells, thereby achieving all-weather algae removal. Therefore, the piezoelectric photocatalyst provided in the embodiments of the present application can couple the piezoelectric material and the semiconductor characteristics, combine the photocatalysis and piezoelectric catalysis principles, achieve all-weather algae removal with improved efficiency and speed, and couple the wind energy, water wave energy, vibration and solar energy in nature, thereby providing a new principle and new idea for multi-path utilization of natural energy and energy saving and emission reduction, and playing a great potential in future energy and environmental applications.

[0044] Therefore, the catalyst provided in the embodiments of the present application can couple the piezoelectric material and the semiconductor characteristics, combine the photocatalysis and piezoelectric catalysis principles, and preferably use Bi2O2S with a wide visible light absorption range and Bi4O5I2 with visible light absorption and piezoelectric performance; the two are successfully compounded by a simple method, thereby preparing the piezoelectric photocatalyst algae removal material Bi4O5I2-Bi2O2S, utilizing the built-in electric field and piezoelectric polarization electric field in the heterojunction to promote the separation of carriers, thereby achieving efficient algae removal under light; utilizing the Bi sites in Bi4O5I2-Bi2O2S to efficiently activate PMS, thereby continuously removing algae at night without light, thereby achieving all-weather green energy-saving algae removal.

[0045] Alternatively, in an embodiment, the molar ratio of Bi4O5I2 to Bi2O2S in the above-mentioned catalyst is 4:1-8:1, which can ensure that Bi4O5I2 has excellent photocatalytic and piezoelectric properties, and utilize Bi2O2S to broaden the light absorption range of the material.

[0046] Alternatively, in an embodiment, the molar ratio of Bi4O5I2 to Bi2O2S in the above-mentioned catalyst is 6:1, which has particularly excellent comprehensive performance.

[0047] In the preparation process of the catalyst, the amount of Bi2O2S or Bi4O5I2 added in the system can be adjusted to control the molar ratio of Bi4O5I2 to Bi2O2S in the prepared catalyst.

[0048] The embodiments of the present application also provide an application of the all-weather piezoelectric coupling photocatalyst as described above, wherein the all-weather piezoelectric coupling photocatalyst is used for at least one of inactivating algae, pathogenic microorganisms and degrading pollutants, and the pollutants include at least one of phenol, bisphenol A and antibiotics.

[0049] In order to make the invention purposes, technical solutions and beneficial effects of the present application clearer, the present application will be further described below in conjunction with examples. It should be understood that these examples are only used to illustrate the present application and not used to limit the scope of the present application.

[0050] The present application will be described in detail below through examples.

[0051] Test Example 1 4 mmol of Bi(NO3)3·5H2O was uniformly dispersed in 60 mL of deionized water, 2 mmol of SC(NH2)2 was added, and 0.286 mol of LiOH·H2O was dissolved in the suspension. After stirring for 60 min, the suspension was placed in a 100 mL autoclave and heated at 200℃ for 72 h. After the autoclave cooled to room temperature, the suspension was filtered, washed and freeze-dried to obtain the product Bi2O2S powder.

[0052] Test Example 2 3 mmol of Bi(NO3)3·5H2O was dissolved in 30 mL of ethylene glycol using an ultrasonic shaker to form a suspension. 6 mmol of KI was added to the suspension, and after stirring for 30 min, 2 mol / L NaOH solution was used to control the pH value to 8.5. The obtained suspension was poured into a 100 mL autoclave and kept at 150℃ for 12 h. After the autoclave cooled to room temperature, the suspension was filtered, washed and freeze-dried to obtain the product catalyst Bi4O5I2. −1 NaOH solution was used to control the pH value to 8.5. The obtained suspension was poured into a 100 mL autoclave and kept at 150℃ for 12 h. After the autoclave cooled to room temperature, the suspension was filtered, washed and freeze-dried to obtain the product catalyst Bi4O5I2.

[0053] Test Example 3 (1) 4 mmol of Bi(NO3)3·5H2O was uniformly dispersed in 60 mL of deionized water, 2 mmol of SC(NH2)2 was added, and 0.286 mol of LiOH·H2O was dissolved in the suspension. After stirring for 60 min, the suspension was placed in a 100 mL autoclave and heated at 200℃ for 72 h. After the autoclave cooled to room temperature, the suspension was filtered, washed and freeze-dried to obtain Bi2O2S powder; (2) 3 mmol of Bi(NO3)3·5H2O was dissolved in 30 mL of ethylene glycol using an ultrasonic shaker to form a suspension. 0.5 mmol of Bi2O2S was added to the suspension and ultrasonically shaken for 0.5 h, 6 mmol of KI was added, and after stirring for 30 min, 2 mol / L NaOH solution was used to control the pH value to 8.5. The obtained suspension was poured into a 100 mL autoclave and kept at 150℃ for 12 h. After the autoclave cooled to room temperature, the suspension was filtered, washed and freeze-dried to obtain the product catalyst Bi4O5I2. −1NaOH solution was used to control the pH value at 8.5, and the obtained suspension was poured into a 100 mL high-pressure reactor, which was kept at 150℃ for 12 h; after the high-pressure reactor was cooled to room temperature, the suspension was filtered, washed and freeze-dried to obtain the product catalyst Bi4O5I2-Bi2O2S (6:1).

[0054] Test Examples 4-7 Test Examples 4-7 differ from Test Example 3 in that in step (2), the amount of Bi2O2S added is adjusted to 0.75 mmol, 0.6 mmol, 0.42 mmol and 0.375 mmol, respectively, to obtain the product catalysts Bi4O5I2-Bi2O2S (4:1), Bi4O5I2-Bi2O2S (5:1), Bi4O5I2-Bi2O2S (7:1) and Bi4O5I2-Bi2O2S (8:1), respectively.

[0055] The products prepared in Test Examples 1 and 2 and the catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3 were subjected to scanning electron microscopy tests, and the results are shown in Figs. Figure 1 (a), (b) and (c), respectively, and the catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 2 was subjected to transmission electron microscopy test, and the result is shown in Fig. Figure 1 (d). As can be seen from Figs. Figure 1 (a), (b) and (c), Bi4O5I2 exhibits a three-dimensional (3D) hierarchical micro / nano structure composed of numerous nanosheets (with a thickness of less than 15 nm), and Bi2O2S exhibits a block shape (about 7 um long); in the catalyst Bi4O5I2-Bi2O2S (6:1), Bi4O5I2 coats Bi2O2S, and the two monomers are distributed in a mutually inlaid manner in the material.

[0056] The products prepared in Test Examples 1 and 2 and the catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3 were subjected to XRD tests, and the results are shown in Fig. Figure 2 As can be seen from Fig.

[0057] The products prepared in Test Examples 1 and 2 and the catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3 were subjected to XPS tests, and the results are shown in Figs.Figure 3 The XPS spectra of (a)~(d) are shown.

[0058] wherein, Figure 3 In (a), the S 2p corresponding XPS spectrum, the S 2p peaks at 164.5 eV and 164.3 eV are respectively attributed to Bi2O2S and Bi4O5I2-Bi2O2S (6:1) in S 2- The shift of the S 2p peak of the component compared with that of Bi2O2S and Bi4O5I2-Bi2O2S (6:1) indicates that the electronic environment of S has changed; Figure 3 In (b), the O 1s corresponding XPS spectrum, the O 1s peaks at 529.9 eV, 530.8 eV and 532.6 eV are respectively attributed to the Bi-O bond, oxygen vacancy and O-H bond of Bi4O5I2-Bi2O2S (6:1); it can be seen that the O 1s peak of Bi4O5I2-Bi2O2S (6:1) has shifted compared with that of the single component material, indicating that Bi4O5I2 and Bi2O2S are successfully compounded, and thus the chemical environment of oxygen is affected; Figure 3 In (c), the I 3d corresponding XPS spectrum, the I 3d5 / 2 and I 3d3 / 2 peaks of Bi4O5I2-Bi2O2S (6:1) are respectively at 619.1 eV and 630.5 eV, while the corresponding peaks of Bi4O5I2 are at 618.9 eV and 630.4 eV, which is due to the compounding of Bi4O5I2 and Bi2O2S; Figure 3 In (d), the Bi 4f corresponding XPS spectrum, the Bi 4f7 / 2 and Bi 4f5 / 2 peaks of Bi4O5I2-Bi2O2S (6:1) are at 159.1 eV and 164.4 eV, which have shifted compared with those of Bi2O2S (159.2 eV and 164.5 eV) and Bi4O5I2 (158.9 eV and 164.2 eV); It can be seen that in the Bi4O5I2-Bi2O2S (6:1) sample, the corresponding peaks exhibit a certain degree of binding energy shift compared to the monomer, indicating that electronic interaction occurs between Bi4O5I2 and Bi2O2S, and that the two successfully recombine. Furthermore, a comparison of the positions of the S 2p, O 1s, and Bi 4f peaks in the monomer Bi2O2S and the heterojunction Bi4O5I2-Bi2O2S (6:1) reveals a shift in the binding energy toward a lower level after recombination; a comparison of the positions of the I 3d, O 1s, and Bi 4f peaks in the monomer Bi4O5I2 and the heterojunction Bi4O5I2-Bi2O2S (6:1) reveals a shift in the binding energy toward a higher level after recombination. This indicates that the built-in electric field is directed from Bi4O5I2 to Bi2O2S, and that the photogenerated electrons migrate from Bi2O2S to Bi4O5I2.

[0059] The Bi4O5I2 prepared in Test Example 1 was subjected to KPFM test, and its morphology, amplitude and phase diagrams are shown in the following table. Figure 4 As shown in (a) to (c), the butterfly displacement-voltage curve is as follows Figure 5 shown.

[0060] Among them, the image contrast between the morphology image, amplitude image and phase image is obvious, indicating that Bi4O5I2 is a piezoelectric material; at the same time, combined with Figure 5 The typical butterfly-shaped displacement-voltage curve further demonstrates the material's piezoelectric properties. Calculating the slope of the displacement-voltage curve determined the sample's maximum effective piezoelectric coefficient, d33, to be 70 pm / V. In summary, the prepared Bi4O5I2 is a piezoelectric material with excellent piezoelectric properties.

[0061] The catalysts prepared in Examples 1 and 2 were subjected to UV diffuse reflectance test. The UV diffuse reflectance spectra and band gaps were as follows: Figure 6 The catalyst band gap is calculated based on the UV diffuse reflectance spectrum according to the following formula: αhν = A(E g -hν) n / 2 , where α, h, ν, A and E g are the absorption coefficient, Planck constant, incident light frequency, constant, and bandgap width, respectively. In this equation, for direct bandgap semiconductors, n is equal to 1. Figure 6 It can be seen that the absorption edges of Bi4O5I2-Bi2O2S (6:1), Bi4O5I2, and Bi2O2S are approximately 600 nm, 520 nm, and 980 nm, respectively. These results indicate that the addition of Bi2O2S significantly broadens the absorption spectrum of the material, significantly improving the visible light capture efficiency.

[0062] Photoluminescence (PL) analysis is based on the characteristic that carrier recombination will generate fluorescence. By measuring the fluorescence emission intensity of the material under light excitation, the charge separation efficiency and recombination kinetics behavior can be quantitatively characterized. Specifically, the steady-state PL spectrum intensity is negatively correlated with the non-radiative recombination probability of electron-hole pairs, while time-resolved PL (TRPL) is used to analyze the migration efficiency of carriers through the fluorescence lifetime decay curve. In this study, a full-function steady-state / transient fluorescence spectrum system was used. The test conditions were set as follows: excitation wavelength 360 nm (xenon lamp light source, bandwidth 5 nm), emission spectrum scanning range 380-900 nm (step 1 nm, integration time 0.5 s), transient test using time-correlated single photon counting (TCSPC) mode, excitation wavelength 375 nm, and the average fluorescence lifetime (τ ave ).

[0063] The products prepared in Test Examples 1 and 2 and the catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3 were subjected to PL spectrum tests, and the results are shown in FIGS. Figure 7 , respectively. The PL intensity can reflect the charge recombination process of photo-induced e - and h + , and the lower the PL intensity, the higher the electron-hole pair separation efficiency.

[0064] As can be seen from FIG. Figure 7 (a), the emission peak intensity of Bi4O5I2-Bi2O2S (6:1) is lower than that of the monomer material. Therefore, the lower fluorescence intensity of Bi4O5I2-Bi2O2S (6:1) indicates that it has a good carrier separation efficiency, which shows that the recombination of photo-generated electron-hole pairs is effectively inhibited after the material is modified. In addition, the shorter the fluorescence lifetime, the better the carrier separation efficiency. In the time-resolved PL spectrum, the fluorescence lifetime of Bi4O5I2-Bi2O2S (6:1), Bi4O5I2 and Bi2O2S is 7.29, 10.72 and 41.54 ns, respectively, which indicates that Bi4O5I2-Bi2O2S (6:1) has a better carrier separation effect compared with the monomer material.

[0065] The products prepared in Test Examples 1 and 2 and the catalysts Bi4O5I2, Bi2O2S and Bi4O5I2-Bi2O2S (6:1) prepared in Test Examples 3-7 were subjected to transient photocurrent response tests and impedance tests, and the results are shown in FIGS. Figure 8 (a)-(b), respectively.

[0066] The test method is as follows: Nafion solution (5.0 wt%, 0.1 mL) and catalyst (10 mg) are mixed with ethanol (1 mL) and ultrasonically dispersed for 3 h to obtain a suspension solution. 20 μL of the suspension solution is dropped on the surface of conductive glass, and the electrode sheet is dried at 60°C for 8 h. An electrochemical workstation (Chenhua CHI660E, Shanghai) equipped with a conventional three-electrode configuration is used for photoelectric current experiment and impedance test, a 300 W xenon lamp is used as a light source, and a 0.1 M Na2SO4 solution is used as an electrolyte.

[0067] It can be seen from Figure 8 (a) that the catalyst Bi4O5I2-Bi2O2S (6:1) has a stronger photocurrent response, which indicates that the composite material can improve the utilization rate of photons and inhibit the recombination of photo-generated carriers; and in addition, Figure 8 (b), it can be seen that the impedance of the catalyst Bi4O5I2-Bi2O2S (6:1) is the lowest, indicating that the built-in electric field formed by the composite of Bi4O5I2 and Bi2O2S can promote charge transfer.

[0068] The piezophotocatalytic activity of the catalyst prepared in each example is tested, and the results are shown in Figure 9 , and the specific test method is as follows: The catalyst prepared in each example is placed in a piezophotocatalytic reaction device to degrade Microcystis aeruginosa, and in the process of photocatalytic reaction, an LED lamp is used as a light source, 40 mL of algal suspension is used, the reactor is placed with / without catalyst (0.5 g / L), the light source (20 W / m 2 ) is turned on / off, the reactor is placed under / without ultrasound, and persulfate is added / not added.

[0069] According to the different reaction conditions in the above experiments: placing catalyst (Bi4O5I2, Bi2O2S or Bi4O5I2-Bi2O2S), turning on / off the light source (Vis), with / without ultrasound (US), adding / not adding 0.01 The reaction conditions of 1 mmol / L peroxymonosulfate (PMS) can obtain the following reaction systems: peroxymonosulfate (PMS) system; ultrasound / visible light (US / Vis) system; peroxymonosulfate / ultrasound (PMS / US) system; peroxymonosulfate / visible light (PMS / Vis) system; peroxymonosulfate / ultrasound / visible light (PMS / US / Vis) system; catalyst / peroxymonosulfate (Bi4O5I2-Bi2O2S / PMS) system; catalyst / ultrasound / visible light (Bi4O5I2-Bi2O2S / US / Vis) system; catalyst / peroxymonosulfate / ultrasound (Bi4O5I2-Bi2O2S / PMS / US) system; catalyst / peroxymonosulfate / visible light (Bi4O5I2-Bi2O2S / PMS / Vis) system; catalyst / peroxymonosulfate / ultrasound / visible light (Bi4O5I2-Bi2O2S / PMS / US) system.

[0070] 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:

[0071] 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.

[0072] Depend on Figure 9As shown in (a), pure Bi2O2S has almost no algae removal effect in the US / Vis system, while pure Bi4O5I2 performs slightly better in the same system, but can only remove 75% of the algae in 4.5 h. The catalyst in Example 3 has a better piezoelectric photocatalytic algae removal effect, and under the action of ultrasound and piezoelectricity, the chlorophyll of the algae cells is significantly destroyed, and the algae cells can be basically inactivated within 4.5 h. 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 reactive oxygen species and achieving efficient inactivation of algae cells.

[0073] Depend on Figure 9 As shown in (b), compared with the Bi4O5I2 / PMS / US / Vis system and the Bi2O2S / PMS / US / Vis system, the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system can completely inactivate algae cells within 2.5 h, which indicates that the composite material can significantly improve the algae removal performance. Compared with the Bi4O5I2-Bi2O2S (6:1) / PMS / Vis system (100% algae inactivated in 4.5 h), the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis has better algae removal performance, which is attributed to the good piezoelectric properties of the Bi4O5I2-Bi2O2S (6:1) material. Under ultrasound, the material generates a polarization electric field, which promotes carrier separation and then generates a large number of reactive oxygen species, achieving efficient inactivation of algae. Compared with Bi4O5I2-Bi2O2S (6:1) / US / Vis (98% algae were inactivated in 4.5 h), Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis had a higher algae removal efficiency. This was because Bi4O5I2-Bi2O2S (6:1) could promote the activation of PMS under the action of piezoelectricity and photocatalysis, generate reactive oxygen species such as ultrasonic free radicals and singlet oxygen, and promote the removal of algal blooms. It is worth noting that the Bi4O5I2-Bi2O2S (6:1) / PMS / US system can inactivate 90% of algae in 4.5 h, while the Bi4O5I2-Bi2O2S (6:1) / PMS system can inactivate 50% of algae in 4.5 h. This shows that Bi4O5I2-Bi2O2S (6:1) can use the mechanical disturbance of water flow to generate a polarized electric field on a dark night to generate a large number of reactive oxygen species to inactivate algal cells, that is, Bi4O5I2-Bi2O2S (6:1) can achieve all-weather inactivation of algal blooms.

[0074] In addition, by Figure 9 As shown in (c), the US / Vis system, PMS / US, and PMS / US / Vis system alone will not cause the death of algae, which indicates that the catalyst prepared by optimizing the experimental preparation method has a better algae removal effect.

[0075] The catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3 was subjected to a cycle performance test, and the results are shown in Table 2. Figure 10 As shown in Table 2 (a), the catalyst was subjected to XRD test before and after the cycle performance test, and the results are shown in Table 2 (b). Figure 10 As shown in Table 2 (b), the specific test method is as follows: After the completion of the first degradation reaction (1st), the catalyst was separated from the solution by suction filtration, and the filtered catalyst was washed with deionized water and ethanol, and dried in a freeze dryer for 48 hours before use; using the above standby material, the second degradation reaction (2nd) was carried out, and the remaining reaction conditions were the same as the first time; after the completion of the second reaction, the above steps were repeated to carry out the third (3rd), fourth (4th) and fifth (5th) degradation experiments.

[0076] As shown in Table 10 (a), the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system has good cycle stability, and can completely inactivate the algal cells within 4.5 hours after 5 cycles, indicating that the material has good cycle stability and good application prospect.

[0077] As shown in Table 10 (b), the XRD pattern of the catalyst material before and after the reaction is almost unchanged, further indicating that the material has good cycle stability.

[0078] The catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3, the product prepared in Test Example 1 and the product prepared in Test Example 2 were subjected to in-situ infrared spectrum test before and after the addition of PMS, and the results are shown in Table 3 (a)~(c), respectively. Figure 11 As shown in Table 3 (a)~(c), the specific test method is as follows: In-situ infrared spectrum test: Fourier infrared spectrometer was used to study the changes of surface functional groups of the catalyst during the activation process of PMS, specifically, 10 mg of catalyst was added to the test table of the infrared spectrometer, PMS solution (0.01-2 mmol / L) was added dropwise, and then scanning was performed in the range of 500-2500 cm-1.

[0079] As shown in Table 3 (a)~(c), the specific test method is as follows: Figure 11 As shown in Table 3 (a)~(c), the specific test method is as follows:

[0080] The catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3, the product prepared in Test Example 1, and the product prepared in Test Example 2 were respectively subjected to in-situ Raman spectrum test before and after adding PMS, and the results are respectively shown in Figs. Figure 12 (a)-(c) of the drawings, and the specific test method is as follows: In-situ Raman test: a 532 nm laser confocal Raman spectrometer was used to study the surface chemical changes of the sample in the process of persulfate (PMS) activation. Specifically, 10 mg of the sample was loaded on a glass slide and pressed into a thin slice of about 1 mm thick, and then persulfate (PMS) solution (0.01-2 mmol / L) was dropped on the slice, and then scanning was performed in the range of 50-1500 cm -1 .

[0081] As can be seen from Figs. Figure 12 , compared with the system without PMS, after adding PMS, the Bi-S bond of Bi4O5I2-Bi2O2S (6:1) disappeared, and the Bi-I bond obviously shifted. Similar results were observed in the in-situ Raman spectrum of pure Bi4O5I2 and Bi2O2S, which indicated that PMS could react with the Bi site on Bi4O5I2-Bi2O2S and further generate free radicals, which was particularly important for Bi4O5I2-Bi2O2S to continuously remove algae at night without light.

[0082] The catalyst prepared in Test Example 3 was subjected to 0.5 h, 1 h and 1.5 h algae removal test by Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system, and 1.5 h algae removal test by PMS / US / Vis system was taken as a control group, and then the algae cell morphology was respectively observed by biological SEM, and the results are respectively shown in Figs. Figure 13 (a)-(d) of the drawings.

[0083] As can be seen from Figs. Figure 13 , in the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system, the algae cells gradually shrunk and damaged with the reaction; while in the control group PMS / US / Vis system, the algae cells remained full, which indicated that the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system could significantly damage the cell membrane of algae and further cause the damage and death of the algae cells.

[0084] The catalyst prepared in Test Example 1 was subjected to quenching experiment to explore the main active oxygen species of the all-weather algae removal system under light, and the test results are as follows: Figure 14As shown, the specific test method is as follows: the experimental method is consistent with the piezoelectric photocatalytic activity test, the difference is that different amounts of quenchers are added to the systems (Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system and Bi4O5I2-Bi2O2S (6:1) / PMS / US system) at the beginning of the reaction, and ethanol is used to quench sulfate radicals and hydroxyl radicals, disodium ethylenediaminetetraacetic acid (1 mmol / L) to quench holes, L-histidine (3 mmol / L) to quench singlet oxygen, tert-butanol (3 mmol / L) to quench hydroxyl radicals, and p-benzoquinone (3 mmol / L) to quench superoxide radicals.

[0085] Depend on Figure 14 It can be seen that after adding p-benzoquinone, the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system ( Figure 14 (a)) can only remove 20% of algae (4.5 h), while the Bi4O5I2-Bi2O2S (6:1) / PMS / US system ( Figure 14 (b) can only remove 10% of algae (4.5 h); under the quenching of L-histidine, the algae removal effect is reduced to 50% and 10%. Similarly, disodium ethylenediaminetetraacetic acid can also significantly inhibit the inactivation of algal blooms. The Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system can only inactivate 70% of algae, while the Bi4O5I2-Bi2O2S (6:1) / PMS / US system is 40% (4.5 h).

[0086] The above results show that the main active oxygen species in the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system and the Bi4O5I2-Bi2O2S (6:1) / PMS / US system are superoxide radicals, singlet oxygen, and holes. The Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system produces a large amount of superoxide radicals and singlet oxygen. The reason for this may be that Bi4O5I2-Bi2O2S (6:1) can efficiently absorb photons, and the valence band electrons jump to the conduction band to activate PMS and O2 to generate superoxide radicals and singlet oxygen. In addition, the built-in electric field of the heterojunction and the polarization field generated by piezoelectricity promote carrier separation, further promoting the generation of superoxide radicals and singlet oxygen, and accumulating a large amount of h in the valence band of Bi2O2S. + It can efficiently destroy the algae cell membrane and achieve efficient inactivation of algae cells. In the Bi4O5I2-Bi2O2S (6:1) / PMS / US system, Bi4O5I2 can use mechanical energy to generate a polarized electric field, promote the transition of valence band electrons to the conduction band, and then generate holes in the valence band. The conduction band electrons further activate the PMS and oxygen adsorbed on the surface to generate superoxide radicals and singlet oxygen.

[0087] In summary, the principle of the all-weather piezoelectric photocatalytic material Bi4O5I2-Bi2O2S for removing algae provided by the embodiments of the present application is as shown in Figure 15

[0088] As can be seen from Figure 15 , under visible light irradiation, Bi4O5I2 (band gap of 2.10 eV) and Bi2O2S (band gap of 1.11 eV) can be excited to produce electrons (e⁻) and holes (h⁺). The Fermi level of Bi4O5I2 is 0.1 V (V vs NHE); the Fermi level of Bi2O2S is even lower, at 0.25 V (V vs NHE). After Bi4O5I2 and Bi2O2S are constructed into a heterojunction, due to the difference in energy levels, a built-in electric field is formed, and the photo-generated electrons flow from the conduction band of Bi2O2S to the valence band of Bi4O5I2, thereby inhibiting the recombination of the internal carriers of Bi4O5I2 and Bi2O2S. In addition, the piezoelectric material Bi4O5I2 can generate a polarization electric field by mechanical disturbance such as water flow, promote the interface migration of electrons, inhibit the recombination of carriers, and improve the charge separation efficiency. Moreover, the band bending under the action of the piezoelectric potential can increase the valence band potential, reduce the energy required for electron transition, and thus improve the spectral utilization rate. Under the action of the built-in electric field generated by the heterojunction and the polarization electric field generated by the piezoelectricity, the carriers are efficiently separated, and the h + in the valence band of Bi2O2S accumulates; the high-energy electrons accumulated in the conduction band of Bi4O5I2 can effectively activate PMS and O2 to generate ·O2⁻ and 1 O2 (reactive oxygen species). The generated h + , ·O2 - , and 1 O2 and other reactive oxygen species attack the algal cells, causing the death of the algal cells In summary, the embodiments of the present application design and synthesize efficient and all-weather piezoelectric-photocatalytic algae-removal materials by using the characteristics of piezoelectric and photocatalytic materials and the properties of semiconductor energy bands, and by using the method of constructing a heterojunction. In the experiment, the efficiency of the composite material for removing algae and the intermediate products is studied in combination with light, ultrasonic waves, stirring, and other simulated actual water environment, and the surface characteristics and the action mechanism of the material, the active sites of the active oxygen species for the algae-removal effect, and various algae-removal indicators are explored to obtain the detailed mechanism of the material for removing algae. Through material characterization, a comprehensive understanding of the physical and chemical properties, optical properties, piezoelectric properties, and the like of the material is achieved, which provides new principles and new ideas for the multi-way utilization and energy saving and emission reduction in the field of photocatalysis, and plays a greater role in future energy and environmental applications.

[0089] ​In addition, the catalyst provided by the embodiment of the present application can couple piezoelectric material and semiconductor characteristics, combine photocatalysis and piezoelectric catalysis principles, and preferably Bi2O2S with a wide visible light absorption range and Bi4O5I2 with visible light absorption and piezoelectric properties; by a simple method, the two are successfully compounded to prepare the piezoelectric photocatalytic algae removal material Bi4O5I2-Bi2O2S, the built-in electric field and piezoelectric polarization electric field in the heterojunction are used to promote carrier separation, and high-efficiency algae removal under light is realized; the efficient activation of PMS by Bi sites in Bi4O5I2-Bi2O2S can continuously remove algae at night without light, thereby realizing all-weather green energy-saving algae removal.

[0090] Term explanation In the present application, multiple refers to two or more than two.

[0091] The terms "first", "second", "third", "fourth" and the like (if any) in the present application are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence.

[0092] The term "and / or" in the present application is only a description of the association relationship between the associated objects, which means that there can be three relationships, for example, A and / or B can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in the present application generally represents an "or" relationship between the front and rear associated objects.

[0093] If not specifically stated, all steps of the present application can be performed in sequence or randomly. For example, the method comprises steps A and B, which means that the method can comprise sequentially performed steps A and B, or sequentially performed steps B and A. For example, the method can also comprise step C, which means that step C can be added to the method in any order, for example, the method can comprise steps A, B and C, or steps A, C and B, or steps C, A and B, etc.

[0094] The above only describes the preferred embodiments of the present application and does not limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing an all-weather piezoelectric coupled photocatalyst, characterized in that: include: Providing monomer Bi2O2S; Dissolve bismuth nitrate in ethylene glycol, then add monomers Bi2O2S and KI in sequence, mix well, and add a strong base until the pH is 7.5-9.5 to obtain a first solution; The first solution is hydrothermally heated to obtain an all-weather piezoelectric coupled photocatalyst Bi4O5I2-Bi2O2S.

2. The preparation method according to claim 1, characterized in that The monomer Bi2O2S provided includes: Dissolve bismuth nitrate in water, add a sulfur source, and add LiOH until the pH is ≥ 14 to obtain a second solution; The second solution is hydrothermally heated to obtain monomer Bi2O2S.

3. The preparation method according to claim 2, characterized in that The sulfur source is thiourea.

4. The preparation method according to claim 3, characterized in that During the process of adding the sulfur source, the molar ratio of bismuth nitrate to thiourea is controlled to be 1-3:

1.

5. The preparation method according to claim 2, characterized in that During the hydrothermal heating of the second solution, the hydrothermal heating temperature is 200° C. and the heating time is 72 h.

6. The preparation method according to claim 1, characterized in that During the process of sequentially adding monomers Bi2O2S and KI, the molar ratio of bismuth nitrate, Bi2O2S and KI is controlled to be 1: (0.1-0.25):

2.

7. The preparation method according to claim 1, characterized in that During the hydrothermal heating of the first solution, the hydrothermal heating temperature was 150° C. and the time was 12 h.

8. An all-weather piezoelectric coupled photocatalyst, characterized in that: Prepared by the method according to any one of claims 1 to 7.

9. An application of the all-weather piezoelectric coupled photocatalyst according to claim 8, characterized in that: The all-weather 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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