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

Abstract

The application provides a kind of all-weather piezoelectric coupling photocatalyst and its preparation method and application, wherein the piezoelectric photocatalyst prepared in the application can couple piezoelectric material and semiconductor characteristics, combine the principles of photocatalysis and piezoelectric catalysis, can realize the efficiency and speed of all-weather algae inhibition, and can also couple the wind energy, water wave energy, vibration and solar energy in nature, provide a new principle and new idea for multi-way use of natural energy and energy saving and emission reduction, and play a great potential in future energy environment applications.

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. Algal explosive proliferation not only causes water transparency to decline, dissolved oxygen to be exhausted, and biodiversity to be attenuated, but also releases secondary pollutants such as microcystins and fishy algae toxins, which directly threatens drinking water safety. Photocatalytic advanced oxidation is considered to be 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 commonly existing in algal bloom growth water is used 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.

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

[0004] 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:

[0006] The present application provides a preparation method of an all-weather piezoelectric coupling photocatalyst, comprising:

[0007] providing a monomer Bi2O2S;

[0008] 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;

[0009] heating the first solution by a hydrothermal method to obtain the all-weather piezoelectric coupling photocatalyst Bi4O5I2-Bi2O2S.

[0010] Further, in the preparation method, the provision of the monomer Bi2O2S comprises:

[0011] dissolving bismuth nitrate in water, then adding a sulfur source and adding LiOH to pH≥14 to obtain a second solution;

[0012] The second solution is heated by a hydrothermal method to obtain monomer Bi2O2S.

[0013] Further, in the preparation method, the sulfur source is thiourea.

[0014] Further, in the preparation method, during the adding of the sulfur source, the molar ratio of the bismuth nitrate to the thiourea is controlled to be 1-3:1.

[0015] Further, in the preparation method, during the hydrothermal heating of the third solution, the temperature of the hydrothermal heating is 200 DEG C, and the time is 72 h.

[0016] Further, in the preparation method, during the adding of the monomer Bi2O2S and KI in sequence, the molar ratio of the bismuth nitrate, Bi2O2S and KI is controlled to be 1:(0.1-0.25):2.

[0017] Further, in the preparation method, during the hydrothermal heating of the first solution, the temperature of the hydrothermal heating is 150 DEG C, and the time is 12 h.

[0018] The application further provides an all-weather piezoelectric coupling photocatalyst prepared by the method.

[0019] The application further provides an application of the all-weather piezoelectric coupling photocatalyst.

[0020] The preparation method of the all-weather piezoelectric coupling photocatalyst provided in the application comprises the following steps: dissolving bismuth nitrate in ethylene glycol, adding monomer Bi2O2S and KI in sequence, uniformly mixing, adding a strong base to pH 7.5-9.5, and then performing hydrothermal heating to prepare the all-weather piezoelectric coupling photocatalyst Bi4O5I2-Bi2O2S. - OH -Due to the mediation of ethylene glycol, the BiOI surface has less hydroxyl 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 composed of numerous nanosheets and coated on the surface of Bi2O2S, and the thickness is less than 15 nanometers. The 3D hierarchical micro / nano structure formed by the stacking of the inner two-dimensional nanosheet structure makes Bi4O5I2 have high flexibility and 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 composite to build a heterojunction, thereby greatly promoting the transfer of photo-generated carriers and retaining its high potential, and the [Bi2O2] 2+ layer is 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 the daytime or in an environment with sufficient light, Bi4O5I2-Bi2O2S can absorb most of the ultraviolet-visible light, generate ROS to inhibit the reproduction of algae and inactivate the algal 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 transport of photo-generated carriers, and improves the photocatalytic performance; while 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 algal cells, and realize all-weather algae removal. Therefore, the piezoelectric photocatalyst provided in the embodiments of the present application can couple the piezoelectric material and semiconductor characteristics, combine the principles of photocatalysis and piezoelectric catalysis, not only can realize efficient and rapid all-weather algae inhibition, but also can couple the wind energy, water wave energy, vibration and solar energy in nature, provide a new principle and new idea for the multi-way utilization of natural energy and energy saving and emission reduction, and play a great potential in future energy and environmental applications. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the electron microscope test graph of the catalyst provided in the test example of the present application;

[0022] Figure 2 is the XRD test graph of the catalyst in the test example of the present application;

[0023] Figure 3 is the XPS test graph of the catalyst in the test example of the present application;

[0024] Figure 4 is the KPFM test graph of the catalyst in the test example of the present application;

[0025] Figure 5 is the butterfly-shaped displacement-voltage curve graph of the catalyst in the test example of the present application;

[0026] Figure 6 is the UV diffuse reflectance test and band gap diagram of the catalyst in the test example of the present application;

[0027] Figure 7 is the PL spectrum test diagram of the catalyst in the test example of the present application;

[0028] Figure 8 is the transient photocurrent response test and impedance test diagram of the catalyst in the test example of the present application;

[0029] Figure 9 is the piezoelectric photocatalytic activity test diagram of the catalyst in the test example of the present application;

[0030] Figure 10 is the cycle performance test diagram of the catalyst in the test example of the present application;

[0031] Figure 11 is the in-situ infrared spectrum test diagram of the catalyst in the embodiment of the present application;

[0032] Figure 12 is the in-situ Raman spectrum test diagram of the catalyst in the embodiment of the present application;

[0033] Figure 13 is the scanning electron microscope diagram of the algal cell morphology under different processing times;

[0034] Figure 14 is the quenching experiment test diagram of the catalyst in the test example of the present application;

[0035] Figure 15 is the energy level structure diagram of the catalyst in the test example of the present application. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and beneficial effects solved by the present application more clear and explicit, the present 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 present application and do not limit the present application.

[0037] With the aggravation of water body eutrophication, the ecological safety crisis caused by water bloom is increasingly serious. Photocatalysis technology is considered as an innovative solution in the field of environmental governance due to its green and energy-saving characteristics, which realizes algal cell inactivation and toxin degradation through the production of active oxygen species driven by sunlight.

[0038] The principle of photocatalytic algae removal is to utilize the sunlight energy commonly existing in the water area where algae blooms grow, and to generate strong oxidizing free radicals and other active oxygen species through photocatalysts under daylight to efficiently inactivate algal cells and oxidize algal toxins and other byproducts. However, in actual application of photocatalytic algae removal, the following five technical problems still exist: (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 light; and (5) the material has insufficient self-floating property.

[0039] In view of the above problems existing in photocatalytic algae removal, the applicant finds that the nanostructure of piezoelectric material can utilize the mechanical force of water flow disturbance in the 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 be tilted, 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, the 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 the piezoelectric effect, thereby generating strong oxidizing ROS.

[0040] Based on the above finding, 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, a preparation method of a full-time piezoelectric photocatalyst is provided, comprising steps 101-103:

[0041] Step 101, providing a monomer Bi2O2S;

[0042] Step 102, 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;

[0043] Step 103, heating the first solution by hydrothermal method to obtain a full-time piezoelectric coupled photocatalyst Bi4O5I2-Bi2O2S.

[0044] In the embodiments of the present application, the monomer Bi2O2S is first prepared, and then Bi4O5I2 is uniformly compounded on Bi2O2S by hydrothermal method and the like with ethylene glycol as the solvent. Thus, a piezoelectric photocatalyst capable of coupling the properties of piezoelectric material and semiconductor can be obtained, which can not only realize efficiency improvement, speed increase and full-time algae inhibition, but also can couple wind energy, water wave energy, vibration and solar energy in nature, thereby effectively solving the problems of narrow spectral response range, low catalytic reaction activity and inability to catalyze at all times of the existing photocatalyst.

[0045] wherein the ethylene glycol acts as a coordination agent, which can inhibit the hydrolysis of bismuth nitrate at the initial stage, and after adding a strong base to a pH of 7.5-9.5, the bismuth nitrate rapidly hydrolyzes to form BiOI before heating, and as the heating proceeds, the OH - may be gradually replaced by I - Due to the mediation of ethylene glycol, the BiOI surface has fewer hydroxyl groups and higher viscosity, the BiOI nanosheet rotates to find a low-energy configuration interface to form a reasonably oriented assembly, and therefore, the Bi4O5I2 in the formed catalyst presents a three-dimensional (3D) hierarchical micro / nano structure 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 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 easy to composite with Bi4O5I2 to construct a heterojunction, thereby greatly promoting the transfer of photo-generated carriers and retaining their high potential, but also the [Bi2O2] 2+ between the layers is separated by a row of S 2- , so that Bi2O2S has a smaller band gap, improving its stability in the photocatalytic process.

[0046] In the catalyst prepared by the embodiments of the present application, the Bi2O2S sheet material 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 probability of electron-hole recombination, and enhance the utilization efficiency of photo-generated carriers; and 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. 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.

[0047] In addition, Bi4O5I2 not only has obvious piezoelectric catalytic performance, but also, from the analysis of the energy band position, 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, and the band gap of Bi2O2S is smaller, which can absorb visible and infrared light, while the energy band position of Bi4O5I2 and Bi2O2S can make it form a Z-type heterojunction through combination, thereby greatly promoting the transfer of photo-generated carriers and retaining high potential.

[0048] In addition, in the daytime or in an environment with sufficient light, Bi4O5I2-Bi2O2S can absorb most of the ultraviolet-visible light, thereby generating a large number of photo-generated electrons and holes 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 on 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 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 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 properties, combine the photocatalytic and piezoelectric catalytic principles, achieve all-weather algae inhibition with improved efficiency and speed, and integrate 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.

[0049] Optionally, in an embodiment, the monomer Bi2O2S is provided, including steps 111-113:

[0050] Step 111, bismuth nitrate is dissolved in water, a sulfur source is added, and LiOH is added to pH≥14 to obtain a second solution.

[0051] In this step 111, bismuth nitrate is dispersed in deionized water, and then a sulfur source is added, wherein the sulfur source can release S 2- and Bi 3+ react to form Bi2O2S, and the addition of LiOH to pH≥14 can ensure that Bi 3+ is preferentially hydrolyzed to form [Bi2O2]² + intermediate (rather than directly precipitated as Bi(OH)3), and then Bi2O2S (containing [Bi2O2]² 2+LiOH promotes the subsequent vulcanization reaction and crystal growth, and in a high-alkali environment, promotes the decomposition of thiourea, thereby forming Bi-O-S structural units and self-assembling into Bi2O2S crystals.

[0052] 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), or the like.

[0053] Optionally, during the addition of the sulfur source, the molar ratio of the bismuth nitrate to the thiourea is controlled to be 1-3:1 to ensure that the sulfur source is in excess of the Bi 3+ complexation. The molar ratio of the bismuth nitrate to the thiourea can be one of 1:1, 2:1, and 3:1 or a range value of any two thereof, which can effectively inhibit the generation of impurities.

[0054] In step 112, the second solution is heated by a hydrothermal method to obtain monomer Bi2O2S.

[0055] In this step 112, the second solution is placed in a closed reaction device for hydrothermal heating, which can fully disperse the reaction materials and uniformly heat them to react to obtain a precipitate. The precipitate is removed by centrifugation and then washed to obtain the monomer Bi2O2S. The above-mentioned closed reaction device can be a polytetrafluoroethylene autoclave.

[0056] Optionally, during the 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 reaction materials and the purification of the crystal phase, and can effectively balance the yield, purity, and product performance.

[0057] 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 or the like.

[0058] In this step 102, the bismuth nitrate can be Bi(NO3)3·5H2O.

[0059] In this step 102, during the sequential addition of the monomer Bi2O2S and KI, the molar ratio of the bismuth nitrate, Bi2O2S, and KI is controlled to be 1:(0.1-0.25):2, so that I and Bi2O2S are accurately proportioned, 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.

[0060] In step 102, after the monomers Bi2O2S and KI are sequentially added, the mixture is fully mixed by ultrasonic, shaking or the like, and then a strong base such as NaOH solution or KOH is added dropwise 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 breakage. Alternatively, 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 excessive alkalinity.

[0061] In step 103, the second solution is placed in a sealed reaction device for hydrothermal heating, which can fully disperse the reaction materials and uniformly heat them to obtain a precipitate. The precipitate is then taken out by centrifugation and washed with ethanol and water to obtain a piezoelectric photocatalyst with Bi4O5I2-Bi2O2S composite. The above-mentioned sealed reaction device can be a polytetrafluoroethylene autoclave.

[0062] Alternatively, during the hydrothermal heating of the third solution, the hydrothermal heating temperature is 150°C and the time is 12 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.

[0063] The present application also provides a kind of all-weather piezoelectric coupling photocatalyst, which is prepared by the above method.

[0064] The piezoelectric photocatalyst provided by the present application is composed of Bi4O5I2 and Bi2O2S composite.

[0065] Bi4O5I2 presents a three-dimensional (3D) hierarchical micro / nano structure, which is composed of numerous nanosheets and coated on the surface of Bi2O2S, with a thickness of less than 15 nanometers. The two-dimensional nanosheet structure formed by the internal layered stacking structure makes Bi4O5I2 have high flexibility, sensitivity to mechanical stimulation, strong strain bearing capacity, short charge transport distance and large specific surface area. 2+ The crystal structure of Bi2O2S is similar to that of Bi4O5I2, which not only facilitates the formation of heterojunction between the two, thereby greatly promoting the transfer of photo-generated carriers and retaining their high potential, but also makes Bi2O2S have a smaller band gap, thereby improving its stability in the photocatalytic process, so that both Bi4O5I2 and Bi2O2S have excellent photocatalytic performance. 2+ The layers are separated by a row of S 2- , making Bi2O2S have a smaller band gap and improving its stability in the photocatalytic process, so that both Bi4O5I2 and Bi2O2S have excellent photocatalytic performance.

[0066] In addition, Bi4O5I2 not only has obvious piezoelectric catalytic performance, but also, from the analysis of the energy band position, 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, and the band gap of Bi2O2S is smaller, which can absorb visible and infrared light, while the energy band position of Bi4O5I2 and Bi2O2S can make them construct Z-type heterojunction through combination, thereby greatly promoting the transfer of photo-generated carriers and retaining high potential.

[0067] 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, 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 transmission of photo-generated carriers, thereby improving the photocatalytic performance; and in the night or in the condition without 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 realizing 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 photocatalytic and piezoelectric catalytic principles, realize all-weather algae removal with high 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.

[0068] Therefore, the catalyst provided in the embodiments of the present application can couple the piezoelectric material and the semiconductor characteristics, combine the photocatalytic and piezoelectric catalytic 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 combined through a simple method, thereby preparing the piezoelectric photocatalytic algae removal material Bi4O5I2-Bi2O2S, utilizing the built-in electric field and the piezoelectric polarization electric field in the heterojunction to promote the separation of carriers, thereby realizing 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 realizing all-weather green energy-saving algae removal.

[0069] Optionally, in an embodiment, the molar ratio of Bi4O5I2 to Bi2O2S in the catalyst is 4:1-8:1, which can ensure that Bi4O5I2 has excellent photocatalytic and piezoelectric performance, and utilize Bi2O2S to widen the light absorption range of the material.

[0070] Optionally, in an embodiment, the molar ratio of Bi4O5I2 to Bi2O2S in the catalyst is 6:1, which has particularly excellent comprehensive performance.

[0071] In particular, the molar ratio of Bi4O5I2 to Bi2O2S in the prepared catalyst can be controlled by adjusting the amount of Bi2O2S or Bi4O5I2 added to the system during the catalyst preparation process.

[0072] This application also proposes an application of the all-weather piezoelectric coupled photocatalyst as described above, wherein the all-weather piezoelectric coupled photocatalyst is used to inactivate algae, pathogenic microorganisms, and degrade at least one of pollutants, including at least one of phenol, bisphenol A, and antibiotics.

[0073] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0074] The present invention will be described in detail below through embodiments.

[0075] Test Example 1

[0076] Put 4 mmol Bi(NO3)3 5H₂O was evenly dispersed in 60 mL of deionized water, then 2 mmol of SC(NH₂)₂ was added, followed by 0.286 mol of LiOH. H2O was dissolved in the suspension and stirred for 60 min. The suspension was then placed in a 100 mL autoclave and heated at 200 °C for 72 h. After the autoclave cooled to room temperature, the suspension was filtered, washed, and freeze-dried to obtain the product Bi2O2S powder.

[0077] Test Example 2

[0078] A suspension was formed by dissolving 3 mmol Bi(NO3)3·5H2O in 30 mL ethylene glycol using an ultrasonic shaker. 6 mmol KI was then added to the suspension, and the mixture was stirred for 30 min. Finally, 2 mol L... -1 The pH value of the NaOH solution was controlled at 8.5. The resulting suspension was poured into a 100 mL high-pressure reactor and kept at 150 °C for 12 h. After the high-pressure reactor cooled to room temperature, the suspension was filtered, washed and freeze-dried to obtain the product catalyst Bi4O5I2.

[0079] Test Example 3

[0080] (1) Add 4 mmol Bi(NO3)3 5H₂O was evenly dispersed in 60 mL of deionized water, then 2 mmol of SC(NH₂)₂ was added, followed by 0.286 mol of LiOH. H2O was dissolved in the suspension and stirred for 60 min. The suspension was then placed in a 100 mL autoclave and heated at 200 °C for 72 h. After the autoclave cooled to room temperature, the suspension was filtered, washed, and freeze-dried to obtain Bi2O2S powder.

[0081] (2) Dissolve 3 mmol Bi(NO3)3·5H2O in 30 mL ethylene glycol to form a suspension using an ultrasonic shaker. Add 0.5 mmol Bi2O2S to the suspension and ultrasonically shake for 0.5 h. Add 6 mmol KI and stir for another 30 min. Then use 2 mol L... -1 The pH value of the NaOH solution was controlled at 8.5. The resulting suspension was poured into a 100 mL high-pressure reactor and kept at 150 °C for 12 h. After the high-pressure reactor cooled to room temperature, the suspension was filtered, washed and freeze-dried to obtain the product catalyst Bi4O5I2-Bi2O2S (6:1).

[0082] Test Examples 4-7

[0083] The difference between Test Examples 4-7 and Test Example 3 is that in step (2), the amount of Bi2O2S added was adjusted to 0.75 mmol, 0.6 mmol, 0.42 mmol, and 0.375 mmol, respectively, to obtain product catalysts Bi4O5I2-Bi2O2S (4:1), Bi4O5I2-Bi2O2S (5:1), Bi4O5I2-Bi2O2S (7:1), and Bi4O5I2-Bi2O2S (8:1).

[0084] The products prepared in Test Examples 1 and 2, as well as the catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3, were subjected to scanning electron microscopy (SEM) analysis. The results are shown below. Figure 1 As shown in (a), (b), and (c), the catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 2 was subjected to transmission electron microscopy (TEM) analysis, and the results are as follows. Figure 1 (d) From Figure 1 It can be seen that Bi4O5I2 exhibits a three-dimensional (3D) hierarchical micro / nano structure, composed of numerous nanosheets (thickness less than 15 nm), while Bi2O2S is in a blocky shape (length approximately 7 μm). In the catalyst Bi4O5I2-Bi2O2S (6:1), Bi4O5I2 coats Bi2O2S, and the two monomers are distributed in an interlocking pattern in the material.

[0085] The products prepared in Test Examples 1 and 2, as well as the catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3, were subjected to XRD tests, and the results are as follows: Figure 2As shown in FIG. 1, it can be seen that the XRD peaks of Bi4O5I2 are consistent with the standard card (PDF #97-041-2590), indicating that Bi4O5I2 is successfully prepared; the XRD peaks of Bi2O2S are consistent with the standard card (PDF #34-1493), indicating that Bi2O2S is successfully prepared; and the characteristic peaks of Bi4O5I2 and Bi2O2S are obviously observed in Bi4O5I2-Bi2O2S (6:1), which indicates that Bi4O5I2 and Bi2O2S are successfully compounded.

[0086] The products prepared in Test Examples 1 and 2 and the catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3 were respectively subjected to XPS tests, and the results are shown in FIGS. 2(a)~(d) respectively. Figure 3

[0087] Among them, Figure 3 FIG. 2(a) is an XPS diagram corresponding to S 2p, and the S 2p peaks at 164.5 eV and 164.3 eV are respectively attributed to S in Bi2O2S and Bi4O5I2-Bi2O2S (6:1) 2- The S 2p peaks of Bi4O5I2-Bi2O2S (6:1) are shifted compared with those of Bi2O2S and Bi4O5I2-Bi2O2S (6:1), indicating that the electronic environment of S has changed;

[0088] Figure 3 FIG. 2(b) is an XPS diagram corresponding to O 1s, and 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 peaks of Bi4O5I2-Bi2O2S (6:1) are shifted compared with those of single-component materials, indicating that Bi4O5I2 and Bi2O2S are successfully compounded, and therefore the chemical environment of oxygen is affected;

[0089] Figure 3 FIG. 2(c) is an XPS diagram corresponding to I 3d, and the I 3d5 / 2 and I 3d3 / 2 peaks of Bi4O5I2-Bi2O2S (6:1) are respectively present at 619.1 eV and 630.5 eV, while the corresponding peaks of Bi4O5I2 are present at 618.9 eV and 630.4 eV, which is due to the compounding of Bi4O5I2 and Bi2O2S;

[0090] Figure 3 ​The middle (d) image shows the XPS plot corresponding to Bi 4f. The Bi 4f7 / 2 and Bi 4f5 / 2 peaks of Bi4O5I2-Bi2O2S (6:1) are located at 159.1 eV and 164.4 eV, respectively, which are shifted compared to Bi2O2S (159.2 eV and 164.5 eV) and Bi4O5I2 (158.9 eV and 164.2 eV).

[0091] It can be seen that in the Bi4O5I2-Bi2O2S (6:1) sample, the corresponding peaks show a certain degree of binding energy shift compared to the monomer, indicating that electronic interaction occurred between Bi4O5I2 and Bi2O2S, i.e., they successfully recombine. Furthermore, comparing the positions of the S 2p, O 1s, and Bi 4f peaks of the monomer Bi2O2S and the heterojunction Bi4O5I2-Bi2O2S (6:1), it was found that the binding energy shifted to a lower direction after recombination; comparing the positions of the I 3d, O 1s, and Bi 4f peaks of the monomer Bi4O5I2 and the heterojunction Bi4O5I2-Bi2O2S (6:1), it was found that the binding energy shifted to a higher direction after recombination. This indicates that the built-in electric field direction is from Bi4O5I2 to Bi2O2S, i.e., the photogenerated electron migration direction is from Bi2O2S to Bi4O5I2.

[0092] The Bi4O5I2 prepared in Test Example 1 was subjected to KPFM testing, and its morphology, amplitude diagram, and phase diagram are shown below. Figure 4 As shown in (a) to (c), its butterfly-shaped displacement-voltage curves are as follows: Figure 5 As shown.

[0093] The clear comparison between the morphology, amplitude, and phase images indicates that Bi4O5I2 is a piezoelectric material; simultaneously, combined with... Figure 5 The typical butterfly-shaped displacement-voltage curve further demonstrates the piezoelectric properties of this material. The maximum effective piezoelectric coefficient d33 of the sample was determined to be 70 pm / V by calculating the slope of the displacement-voltage curve. In summary, the prepared Bi4O5I2 is a piezoelectric material with good piezoelectric properties.

[0094] The catalysts prepared in Examples 1 and 2 were subjected to ultraviolet diffuse reflectance testing. The ultraviolet diffuse reflectance spectra and band gaps are as follows: Figure 6 As shown. The catalyst band gap is calculated based on the ultraviolet diffuse reflectance spectrum using the following formula: αhν = A(E g -hν) n / 2 In the formula, α, h, ν, A and E g These represent the absorption coefficient, Planck's constant, incident light frequency, constant, and bandgap, respectively. In this equation, for a direct bandgap semiconductor, n equals 1. Figure 6It can be seen that the absorption edges of Bi4O5I2-Bi2O2S (6:1), Bi4O5I2 and Bi2O2S are about 600 nm, 520 nm and 980 nm, respectively. These results show that the composite of Bi2O2S significantly broadens the absorption spectrum of the material, making the visible light capture efficiency significantly improved.

[0095] Photoluminescence (PL) analysis is based on the characteristic that carrier recombination will produce 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 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 ).

[0096] 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 test, and the results are shown in Figure 7 , wherein 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.

[0097] As can be seen from 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 modification of the material composite. 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 shows that Bi4O5I2-Bi2O2S (6:1) has a better carrier separation effect compared with the monomer material.

[0098] The products prepared in Test Examples 1 and 2, as well as the catalysts Bi4O5I2, Bi2O2S, and Bi4O5I2-Bi2O2S (6:1) prepared in Test Examples 3-7, were subjected to transient photocurrent response and impedance tests, respectively. The results are as follows: Figure 8 As shown in (a) to (b).

[0099] The test method is as follows: Nafion solution (5.0 wt%, 0.1 mL) and catalyst (10 mg) were mixed with ethanol (1 mL) and ultrasonically dispersed for 3 h to obtain a suspension. 20 μL of the suspension was dropped onto a conductive glass surface and dried at 60 °C for 8 h to obtain an electrode sheet. Photocurrent experiments and impedance tests were performed using an electrochemical workstation (Chenhua CHI660E, Shanghai) equipped with a conventional three-electrode configuration. A 300 W xenon lamp was used as the light source, and 0.1 M Na2SO4 solution was used as the electrolyte.

[0100] pass Figure 8 As can be seen in (a), the catalyst Bi4O5I2-Bi2O2S (6:1) exhibits a stronger photocurrent response, indicating that the composite material can improve photon utilization and suppress recombination of photogenerated carriers; furthermore, Figure 8 As can be seen in (b), the catalyst Bi4O5I2-Bi2O2S (6:1) has the lowest impedance, indicating that the built-in electric field formed by the composite of Bi4O5I2 and Bi2O2S can promote charge transfer.

[0101] The catalysts prepared in each embodiment were subjected to piezoelectric photocatalytic activity testing, and the results are as follows: Figure 9 As shown, the specific testing method is as follows:

[0102] The catalyst was placed in a piezoelectric photocatalytic reactor to degrade Microcystis aeruginosa. During the photocatalytic reaction, an LED light was used as the light source, and 40 mL of algal suspension was used. The reactor was prepared with / without a catalyst (0.5 g / L), and the light source was turned on / off (20 W / m²). 2 Place the reactor under ultrasonic / non-ultrasonic conditions and add / do not add persulfate.

[0103] Based on the different reaction conditions in the above experiment: catalyst placement (Bi4O5I2, Bi2O2S, or Bi4O5I2-Bi2O2S), light source on / off (Vis), with / without ultrasound (US), addition / no addition of 0.01 The following reaction systems can be obtained under the reaction conditions of mmol / L persulfate (PMS): persulfate (PMS) system; ultrasound / visible light (US / Vis) system; persulfate / ultrasound (PMS / US) system; persulfate / visible light (PMS / Vis) system; persulfate / ultrasound / visible light (PMS / US / Vis) system; catalyst / persulfate (Bi4O5I2-Bi2O2S / PMS) system; catalyst / ultrasound / visible light (Bi4O5I2-Bi2O2S / US / Vis) system; catalyst / persulfate / ultrasound (Bi4O5I2-Bi2O2S / PMS / US) system; catalyst / persulfate / visible light (Bi4O5I2-Bi2O2S / PMS / Vis) system; catalyst / persulfate / ultrasound / visible light (Bi4O5I2-Bi2O2S / PMS / US / Vis) system.

[0104] At preset time intervals, 8 mL of reaction solution was taken to measure its chlorophyll a content. A 0.45 μm filter membrane was then placed on a filtration instrument, and 8 mL of sample was filtered. The filter membrane was placed in a test tube and frozen for 12 h. The test tube was then removed, and 8 mL of 90% acetone solution was added, along with a small amount of magnesium carbonate powder to protect the chlorophyll from damage. The sample was then disrupted using an ultrasonic cell disruptor (ultrasonic time 3 s, interval 2 s) for 3 min, and treated at 4500 r / min for 10 minutes. The supernatant was collected, and using 90% acetone as a reference, the chlorophyll a content was measured using OD0.05. 630 OD 647 OD 664 and OD 750 The formula for calculating the chlorophyll a content is shown below:

[0105]

[0106] In the formula:

[0107] OD 630 OD 647 OD 664 OD 750 V1 represents the absorbance values ​​of the sample at wavelengths of 630 nm, 647 nm, 664 nm, and 750 nm, respectively; V2 represents the sample volume in mL; V3 represents the volume of 90% acetone in mL.

[0108] The removal rate of Microcystis aeruginosa was calculated as C / C0, where C0 and C are the chlorophyll a contents at 0 and t min, respectively.

[0109] From Figure 9 As can be seen from (a), pure Bi2O2S has almost no algae removal effect under the US / Vis system, and pure Bi4O5I2 performs slightly better under the same system, but only 75% of the algae can be removed in 4.5 h. The catalyst in Example 3 has a better piezoelectric photocatalytic algae removal effect, and under the action of ultrasonic and piezoelectricity, the chlorophyll of the algae cells is significantly destroyed, and the algae cells can be basically inactivated in 4.5 h. This is because the composite material can promote the absorption of visible light, and the photo-generated electrons can be more efficiently separated under the dual action of built-in electric field and polarization electric field, thereby generating a higher concentration of active oxygen species, and realizing efficient inactivation of algae cells.

[0110] From Figure 9 As can be seen from (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 the algae cells in 2.5 h, which shows 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 performance of the Bi4O5I2-Bi2O2S (6:1) material. Under ultrasonic, the material generates a polarization electric field, promotes carrier separation, and then generates a large amount of active oxygen species, thereby realizing efficient inactivation of algae. Compared with the Bi4O5I2-Bi2O2S (6:1) / US / Vis (98% algae inactivated in 4.5 h), the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis has higher algae removal efficiency, because the Bi4O5I2-Bi2O2S (6:1) can promote the activation of PMS under the action of piezoelectricity and photocatalysis, generating active oxygen species such as ultrasonic free radicals and singlet oxygen, and promoting the removal of algae blooms. It is worth noting that the Bi4O5I2-Bi2O2S (6:1) / PMS / US system can inactivate 90% of the algae in 4.5 h, while the Bi4O5I2-Bi2O2S (6:1) / PMS system can inactivate 50% of the algae in 4.5 h, which shows that the Bi4O5I2-Bi2O2S (6:1) can generate a polarization electric field by mechanical disturbance of water flow at night without light, and generate a large amount of active oxygen species to inactivate the algae cells, that is, the Bi4O5I2-Bi2O2S (6:1) can realize all-weather inactivation of algae blooms.

[0111] In addition, from Figure 9From the middle (c), only US / Vis system, PMS / US, PMS / US / Vis system will not cause the death of algae, which shows that the catalyst prepared by optimizing the preparation method has better algae removal effect.

[0112] The catalyst Bi4O5I2-Bi2O2S (6:1) prepared in Test Example 3 was subjected to a cycle performance test, and the results are shown in Figure 10 As shown in the middle (a), the catalyst was subjected to XRD test before and after the cycle performance test, and the results are shown in Figure 10 As shown in the middle (b), the specific test method is as follows:

[0113] 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 for standby; using the above standby material, a 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.

[0114] As shown in the middle (a) of 10, Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system has good cycle stability, and after 5 cycles, it can completely inactivate the algae cells within 4.5h, which shows that the material has good cycle stability and good application prospect.

[0115] As shown in the middle (b) of 10, the XRD pattern of the catalyst material before and after the reaction is almost unchanged, which further shows that the material has good cycle stability.

[0116] 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 Figure 11 As shown in the middle (a)~(c), the specific test method is as follows:

[0117] In-situ infrared spectrum test: Fourier infrared spectrometer was used to study the change of surface functional groups of the catalyst in the PMS activation process, 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 carried out in the range of 500~2500 cm-1.

[0118] As shown in the middle (a)~(c), the specific test method is as follows: Figure 11It can be seen that compared with the system without PMS, the Bi-I, Bi-O and Bi-S bonds are obviously shifted after adding PMS, and the in-situ infrared spectrum of pure Bi4O5I2 also has similar results, which shows that PMS can react with the Bi site of Bi4O5I2 and further generate free radicals, which is the key to the continuous algae removal of Bi4O5I2-Bi2O2S (6:1) at night without light.

[0119] 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 shown in Figs. Figure 12 (a)~(c) respectively, and the specific test method is as follows:

[0120] In-situ Raman test: a 532 nm laser confocal Raman spectrometer was used to study the surface chemical changes of the sample in the activation process of persulfate (PMS), specifically, 10 mg of the sample was loaded on a glass slide and pressed into a thin piece about 1 mm thick, then persulfate (PMS) solution (0.01-2 mmol / L) was dropped on the slice, and then scanned in the range of 50~1500 cm -1 .

[0121] It can be seen that compared with the system without PMS, the Bi-I, Bi-O and Bi-S bonds are obviously shifted after adding PMS, and the in-situ infrared spectrum of pure Bi4O5I2 also has similar results, which shows that PMS can react with the Bi site of Bi4O5I2 and further generate free radicals, which is the key to the continuous algae removal of Bi4O5I2-Bi2O2S (6:1) at night without light. Figure 12 The catalyst Bi4O5I2-Bi2O2S (6:1) 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 the algae removal test by PMS / US / Vis system for 1.5 h was taken as a control group, and then the algae cell morphology was observed by biological SEM, and the results are shown in Figs.

[0122] (a)~(d) respectively. Figure 13 It can be seen that compared with the system without PMS, the Bi-I, Bi-O and Bi-S bonds are obviously shifted after adding PMS, and the in-situ infrared spectrum of pure Bi4O5I2 also has similar results, which shows that PMS can react with the Bi site of Bi4O5I2 and further generate free radicals, which is the key to the continuous algae removal of Bi4O5I2-Bi2O2S (6:1) at night without light.

[0123] Figure 13 ​It can be seen that in the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system, the algal cells gradually shrivel and break down as the reaction proceeds; while in the control group PMS / US / Vis system, the algal cells remain full, which indicates that the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system can significantly damage the algal cell membrane and other components, thereby leading to the death of the algal cells.

[0124] The catalyst prepared in Test Example 1 was subjected to a quenching experiment to explore the main active oxygen species of the all-weather algae removal system under light, and the test results are shown in Figure 14 The specific test method is as follows: the experimental method is consistent with the piezoelectric photocatalytic activity test, except that different amounts of quenching agents are added to the system (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 ethylenediaminetetraacetate (1 mmol / L) is used to quench holes, L-histidine (3 mmol / L) is used to quench singlet oxygen, tert-butyl alcohol (3 mmol / L) is used to quench hydroxyl radicals, and p-benzoquinone (3 mmol / L) is used to quench superoxide radicals.

[0125] As can be seen from Figure 14 , after the addition of p-benzoquinone, the Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system (a) in Figure 14 can only remove 20% of algae (4.5 h), while the Bi4O5I2-Bi2O2S (6:1) / PMS / US system (b) in Figure 14 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%, and similarly, disodium ethylenediaminetetraacetate can also significantly inhibit the inactivation of algae blooms, and 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).

[0126] The above results show that the main active oxygen species of Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system and Bi4O5I2-Bi2O2S (6:1) / PMS / US system are superoxide radicals, singlet oxygen and holes. The reason why Bi4O5I2-Bi2O2S (6:1) / PMS / US / Vis system generates a large amount of superoxide radicals and singlet oxygen 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 electric field generated by the piezoelectricity promote the separation of carriers, further promote the generation of superoxide radicals and singlet oxygen, and accumulate a large number of h + The efficient destruction of algal cell membranes achieves efficient inactivation of algal cells; in Bi4O5I2-Bi2O2S (6:1) / PMS / US system, Bi4O5I2 can generate a polarization electric field by using mechanical energy, promote the valence band electrons to jump to the conduction band, and further generate holes in the valence band. The conduction band electrons further activate the surface-adsorbed PMS and oxygen to generate superoxide radicals and singlet oxygen.

[0127] As can be seen from the above, the algae removal principle of the all-weather piezoelectric photocatalytic material Bi4O5I2-Bi2O2S provided by the embodiments of the present application is as shown in Figure 15 .

[0128] As can be seen from the above, the algae removal principle of the all-weather piezoelectric photocatalytic material Bi4O5I2-Bi2O2S provided by the embodiments of the present application is as shown in Figure 15 It can be known that under visible light irradiation, Bi4O5I2 (band gap is 2.10 eV) and Bi2O2S (band gap is 1.11 eV) can be excited to generate electrons (e - ) and holes (h + ). The Fermi level of Bi4O5I2 is 0.1 V (V vs NHE); the Fermi level of Bi2O2S is lower, which is 0.25 V (V vs NHE). After Bi4O5I2 and Bi2O2S are constructed into a heterojunction, due to the difference in energy level, 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. Furthermore, the piezoelectric material Bi4O5I2 can generate a polarization electric field by using mechanical disturbance such as water flow, promote the interface migration of electrons, inhibit the recombination of carriers, and improve the charge separation efficiency. In addition, the energy band bending under the action of piezoelectric potential can improve the valence band potential, reduce the energy required for electron transition, and thereby 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, h + accumulate in the valence band of Bi2O2S; the high-energy electrons accumulated in the conduction band of Bi4O5I2 can effectively activate PMS and O2 to generate ·O2 - and 1O2 (reactive oxygen species). The generated h + , ·O2 - and 1 O2 and other reactive oxygen species attack the algal cells, leading to the death of the algal cells

[0129] In summary, the embodiments of the present application use the characteristics of piezoelectric and photocatalytic materials and the properties of semiconductor energy bands to design and synthesize efficient and all-weather piezoelectric-photocatalytic algae removal materials by using the method of constructing heterojunctions. In the experiment, the efficiency of the composite material in removing algae and intermediate products is studied by combining light, ultrasound, stirring and other simulated actual water environment, and the surface characteristics and action mechanism of the material, the active sites of reactive oxygen species in the algae removal process, and various algae removal indicators are explored to obtain the detailed mechanism of the material in removing algae. Through material characterization, a comprehensive understanding of the physical and chemical properties, optical properties, piezoelectric properties, etc. 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.

[0130] In addition, the catalyst provided by the embodiments of the present application can couple the piezoelectric material and the semiconductor characteristics, combine the principles of photocatalysis and piezoelectric catalysis, and preferably use Bi2O2S which has a wide visible light absorption range and Bi4O5I2 which has visible light absorption and piezoelectric properties. By a simple method, the two are successfully compounded to prepare a piezoelectric photocatalytic algae removal material Bi4O5I2-Bi2O2S, which uses the built-in electric field and piezoelectric polarization electric field in the heterojunction to promote carrier separation, realizes efficient algae removal under light, and uses the high-efficiency activation of PMS by Bi sites in Bi4O5I2-Bi2O2S to continuously remove algae at night without light, thereby realizing all-weather green and energy-saving algae removal.

[0131] Term explanation

[0132] In the present application, multiple refers to two or more than two.

[0133] 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 describe a specific order or sequence.

[0134] In the present application, the term "and / or" 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: A exists alone, A and B exist together, and B exists alone. In addition, the character " / " in the present application generally represents an "or" relationship between the front and rear associated objects.

[0135] If not otherwise specified, all steps of the application can be performed in any order. For example, the method comprises steps A and B, meaning that the method can comprise steps A and B performed in sequence, or steps B and A performed in sequence. For example, the method can further comprise step C, meaning 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.

[0136] The above description is only the preferred embodiment of the present application, and is not intended to 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 by, Comprising: providing monomer Bi2O2S; dissolving bismuth nitrate in ethylene glycol, then adding monomer Bi2O2S and KI in sequence, mixing uniformly and adding strong base to pH 7.5-9.5 to obtain a first solution; in the process of adding monomer Bi2O2S and KI in sequence, the molar ratio of bismuth nitrate, Bi2O2S and KI is controlled to be 1:(0.1-0.25):2; subjecting the first solution to hydrothermal heating to obtain all-weather piezoelectric coupling photocatalyst Bi4O5I2-Bi2O2S; in the process of subjecting the first solution to hydrothermal heating, the temperature of hydrothermal heating is 150°C and the time is 12 h; providing monomer Bi2O2S comprises: dissolving bismuth nitrate in water, then adding a sulfur source and adding LiOH to pH≥14 to obtain a second solution; the sulfur source is thiourea; in the process of adding the sulfur source, the molar ratio of bismuth nitrate to thiourea is controlled to be 1-3:1; subjecting the second solution to hydrothermal heating to obtain monomer Bi2O2S; in the process of subjecting the second solution to hydrothermal heating, the temperature of hydrothermal heating is 200°C and the time is 72 h.

2. An all-weather piezoelectric coupled photocatalyst, characterized by, Prepared by the method of claim 1.

3. The use of an all-weather piezoelectric coupled photocatalyst according to claim 2, characterized in that, The all-weather piezoelectric coupling photocatalyst is used for at least one of inactivating algae, pathogenic microorganisms and degrading pollutants, the pollutants including at least one of phenol, bisphenol A and antibiotics.

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