Composite piezoelectric catalytic material, preparation method and application thereof, and method for degrading organic pollutants in water body

Abstract

This invention relates to the field of water pollution treatment technology, specifically to a composite piezoelectric catalytic material, its preparation method and application, and a method for degrading organic pollutants in water. The composite piezoelectric catalytic material comprises a BaTiO3 nanowire substrate and Bi2MoO6 grown in situ on the surface of the BaTiO3 nanowire substrate. A heterojunction is formed between the BaTiO3 nanowire substrate and the Bi2MoO6. Mechanical energy induces the generation of electrons and holes in the BaTiO3 nanowire substrate through the composite piezoelectric catalytic material, and the spatial separation of electrons and holes is promoted based on the heterojunction. The separated electrons and holes generate reactive oxygen species through redox reactions, thereby degrading organic pollutants. This degradation process does not require the addition of external oxidants or light to generate reactive oxygen species, improving the practicality of the composite piezoelectric catalytic material in degrading organic pollutants in water and reducing the cost of the degradation process.

Description

Technical Field

[0001] This invention relates to the field of water pollution treatment technology, specifically to a composite piezoelectric catalytic material, its preparation method and application, and a method for degrading organic pollutants in water. Background Technology

[0002] With the acceleration of industrialization and urbanization, a large number of new organic pollutants are constantly entering the aquatic environment. These pollutants have complex molecular structures and high chemical stability, making them difficult to degrade naturally in the environment. Long-term exposure to these pollutants may pose potential risks to ecosystems and human health. Therefore, developing efficient, stable, and environmentally friendly water pollutant removal technologies is of great significance. Currently used water treatment methods include biological methods, adsorption methods, and advanced oxidation technologies. Biological treatment methods have limited removal efficiency for some recalcitrant organic pollutants. Although adsorption methods are simple to operate, they can only achieve the transfer of pollutants and cannot achieve complete mineralization. Advanced oxidation technologies, such as photocatalysis, Fenton reactions, and persulfate activation systems, have certain advantages in the degradation of organic pollutants. However, these catalytic degradation processes usually require external light sources or chemical oxidants, which increases the operating costs of the catalytic degradation process and may also lead to secondary pollution problems. Summary of the Invention

[0003] To address the technical problem that existing technologies for the catalytic degradation of organic pollutants in water generally rely on light sources or chemical oxidants, resulting in high limitations in the entire catalytic degradation process, this invention provides a composite piezoelectric catalytic material, its preparation method and application, and a method for degrading organic pollutants in water.

[0004] This invention employs the following technical solution: a composite piezoelectric catalytic material comprising a BaTiO3 nanowire substrate and a Bi2MoO6 nanostructure grown in situ on the surface of the BaTiO3 nanowire substrate, wherein a heterojunction is formed between the BaTiO3 nanowire substrate and the Bi2MoO6; by mechanical energy acting on the composite piezoelectric catalytic material, electrons and holes are induced to be generated on the surface of the BaTiO3 nanowire substrate, and the spatial separation of the generated electrons and holes is promoted based on the constructed heterojunction; the separated electrons and holes generate reactive oxygen species through redox reactions, thereby degrading organic pollutants in water.

[0005] As a further improvement of the present invention, Bi2MoO6 is a nanosheet or nanoflower structure, and it is uniformly distributed on the surface of the BaTiO3 nanowire substrate.

[0006] This invention also includes a method for preparing the composite piezoelectric catalytic material as described above, comprising: dissolving Bi(NO3)3·5H2O in an organic solvent at a mass-to-volume ratio of 209 mg:40 mL to form a bismuth source solution, and adding BaTiO3 nanowires at a mass ratio of 209:100 to Bi(NO3)3·5H2O for dispersion to obtain a dispersion. Adding a Na2MoO4·2H2O solution at a mass ratio of 209:52 to Bi(NO3)3·5H2O to the dispersion and stirring to mix, thereby allowing Bi2MoO6 to grow in situ on the surface of the BaTiO3 nanowires through a hydrothermal reaction, thus obtaining the composite piezoelectric catalytic material Bi2MoO6 grown in situ on the surface of the BaTiO3 nanowire substrate.

[0007] As a further improvement of the present invention, the organic solvent is a mixture of ethylene glycol and ethanol, and the volume ratio of ethylene glycol to ethanol is 6~4:1.

[0008] As a further improvement of the present invention, the temperature of the hydrothermal reaction is 160℃~190℃, and the reaction time is 8~24h.

[0009] As a further improvement of the present invention, the preparation process of BaTiO3 nanowires is as follows: H2Ti3O7 nanowires are mixed with a barium source solution at a molar ratio of 2 to 1:1 and subjected to a hydrothermal reaction to obtain BaTiO3 nanowires.

[0010] As a further improvement of the present invention, the preparation process of H2Ti3O7 nanowires is as follows: titanium dioxide is added to sodium hydroxide solution and stirred and dispersed, and then subjected to hydrothermal reaction to obtain Na2Ti3O7 nanowires; the Na2Ti3O7 nanowires are subjected to acid exchange treatment to obtain H2Ti3O7 nanowires.

[0011] As a further improvement of the present invention, the concentration of the sodium hydroxide solution is 8~12 mol / L; the acid is hydrochloric acid, and the concentration of the hydrochloric acid is 0.2~2 mol / L.

[0012] As a further improvement of the present invention, the barium source is Ba(OH)2·8H2O.

[0013] The present invention also includes the application of the composite piezoelectric catalytic material as described above in the catalytic degradation of organic pollutants in water.

[0014] The present invention also includes a method for degrading organic pollutants in water, comprising: preparing the composite piezoelectric catalytic material as described above; adding the composite piezoelectric catalytic material to water containing organic pollutants and mixing it evenly to obtain a mixture; applying mechanical energy to the mixture and periodically measuring the concentration change of organic pollutants in the mixture; if the concentration of organic pollutants in the mixture is higher than a set threshold, extending the reaction time or continuing to add composite piezoelectric catalytic material to the mixture until the concentration of organic pollutants in the mixture is lower than the set threshold.

[0015] The technical solution provided by this invention has the following beneficial effects: (1) The composite piezoelectric catalytic material provided in this scheme adopts the method of in-situ growth of Bi2MoO6 on the surface of BaTiO3 nanowires, so that Bi2MoO6 is uniformly loaded and forms a tight interface contact with the substrate. This structure of "in-situ growth combined with one-dimensional nanowire substrate" makes the constructed composite piezoelectric catalytic material have a higher interface contact tightness and a shorter charge migration path, which is conducive to the rapid separation and transfer of charges induced by piezoelectric potential at the interface of the composite piezoelectric catalytic material, thereby improving the catalytic efficiency of the composite piezoelectric catalytic material. Furthermore, the composite piezoelectric catalytic material provided in this scheme can be used as a catalyst for the degradation of organic pollutants in water. When the composite piezoelectric catalytic material in this scheme is applied to degrade organic pollutants in water, mechanical energy can be applied to the composite piezoelectric catalytic material, causing a piezoelectric effect to be generated under the action of mechanical energy, utilizing the polarization characteristics of BaTiO3. This results in the formation of electrons and holes on the surface of the composite piezoelectric catalytic material. At the same time, the Bi2MoO6 / BaTiO3 heterojunction structure constructed on its surface can effectively separate the generated electrons and holes, preventing them from recombinizing. This allows the generated electrons and holes to participate in the redox reaction to generate reactive oxygen species (·OH and ·O2) with oxidizing capabilities. - These free radicals can continuously attack and decompose organic pollutants in water, ultimately transforming them into harmless small molecules, thereby achieving the degradation of organic pollutants in water. This scheme induces the generation of electrons and holes on the surface of the BaTiO3 nanowire substrate through mechanical energy interaction with the composite piezoelectric catalytic material. Based on the constructed heterojunction, the generated electrons and holes are spatially separated, effectively separating them and preventing their recombination, thus improving the catalytic reaction rate and catalytic activity.

[0016] (2) The composite piezoelectric catalytic material provided in this scheme can induce the generation of active oxygen species under the action of mechanical energy to degrade organic pollutants in water. The generation of active oxygen species in this degradation process does not require the use of external oxidants or light, thereby improving the practicality of the composite piezoelectric catalytic material in the process of degrading organic pollutants in water and reducing the cost of the degradation process. Attached Figure Description

[0017] Figure 1 The present invention provides a flowchart of the preparation method of a composite piezoelectric catalytic material.

[0018] Figure 2 The XRD patterns are of the products obtained from the test examples, comparative example 1, and comparative example 2 in the performance test of this invention.

[0019] Figure 3 This is a SEM image of BaTiO3 prepared in Comparative Example 1 of the performance testing section of this invention.

[0020] Figure 4 This is a SEM image of Bi2MoO6 prepared in Comparative Example 2 of the performance testing section of this invention.

[0021] Figure 5 The image shows a SEM image of the composite piezoelectric catalytic material prepared for the test example in the performance testing section of this invention.

[0022] Figure 6 The image shows a TEM image of the composite piezoelectric catalytic material prepared as a test example in the performance testing section of this invention.

[0023] Figure 7 The image shows the surface morphology of the composite piezoelectric catalytic material used in the performance testing section of this invention, captured under a piezoelectric microscope.

[0024] Figure 8 This is the amplitude-voltage curve of the composite piezoelectric catalytic material in the performance testing section of this invention.

[0025] Figure 9 This is a phase-voltage curve of the composite piezoelectric catalytic material in the performance testing section of this invention.

[0026] Figure 10 This is a schematic diagram showing the change in the concentration percentage of different types of catalytic materials over time during the catalytic degradation of pollutant Rhodamine B in the performance test section of this invention.

[0027] Figure 11 This is a bar chart showing the removal rates of Rhodamine B by different types of catalytic materials in the performance testing section of this invention.

[0028] Figure 12This is a schematic diagram illustrating the change in the concentration of different types of pollutants over time using composite piezoelectric catalytic materials in the performance testing section of this invention.

[0029] Figure 13 This is a bar chart showing the removal rates of different types of pollutants using composite piezoelectric catalytic materials in the performance testing section of this invention.

[0030] Figure 14 This is a graph showing the degradation efficiency of the composite piezoelectric catalytic material for the catalytic degradation of pollutant Rhodamine B after four consecutive cycles in the performance testing section of this invention. Detailed Implementation

[0031] The present invention will now be further described in conjunction with specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0032] In the description of this invention, it should be noted that directional terms such as "center," "lateral," "longitudinal," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific scope of protection of this invention. The terms "first," "second," etc., in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. The terms "comprising" and "having," and any variations thereof, in the specification and claims of this invention, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or devices.

[0033] This embodiment provides a composite piezoelectric catalytic material comprising a BaTiO3 nanowire substrate and a Bi2MoO6 nanostructure grown in situ on the surface of the BaTiO3 nanowire substrate. A tightly contacted heterojunction is formed between the BaTiO3 nanowire substrate and the Bi2MoO6. The formed heterojunction generates a large number of highly active sites at the interface, thereby improving the catalytic activity of the entire composite piezoelectric catalytic material. This method employs in-situ growth of Bi2MoO6 on the surface of BaTiO3 nanowires, ensuring uniform loading of Bi2MoO6 and a tight interfacial contact with the substrate. This "in-situ growth combined with a one-dimensional nanowire substrate" structure results in a composite piezoelectric catalytic material with higher interfacial contact tightness and a shorter charge migration path, which is beneficial for the rapid separation and transfer of charges induced by piezoelectric potential at the interface of the composite piezoelectric catalytic material, thereby improving the catalytic efficiency of the composite piezoelectric catalytic material. This scheme induces the generation of electrons and holes on the surface of a BaTiO3 nanowire substrate through mechanical energy interaction with the composite piezoelectric catalytic material. The constructed heterojunction further promotes the spatial separation of these electrons and holes, effectively separating them and preventing their recombination, thereby improving the catalytic reaction rate and catalytic activity. The composite piezoelectric catalytic material provided by this scheme can be used as a catalyst for the degradation of organic pollutants in water. When applied to the degradation of organic pollutants in water, mechanical energy interacts with the composite piezoelectric catalytic material, utilizing the piezoelectric effect of BaTiO3's inherent polarization characteristics to generate electrons and holes on its surface. Simultaneously, the Bi2MoO6 / BaTiO3 heterojunction structure constructed on its surface effectively separates the generated electrons and holes, preventing their recombination. This allows the generated electrons and holes to participate in redox reactions, generating reactive oxygen species (·OH and ·O2) with oxidizing capabilities. - These free radicals can continuously attack and decompose organic pollutants in water, ultimately transforming them into harmless small molecules, thereby achieving the degradation of organic pollutants in water. Specifically: BaTiO3 is a typical piezoelectric material, which undergoes polarization and generates a piezoelectric potential under the action of mechanical energy, thereby forming electrons (electrons) on the surface of the composite piezoelectric material. - ) and holes (h +However, in a single BaTiO3 system, electrons and holes readily recombine rapidly, resulting in low efficiency in their participation in surface reactions. In this approach, a tightly packed heterojunction structure is constructed by in-situ growing Bi2MoO6 on the surface of BaTiO3 nanowires, creating a built-in electric field at the interface. This allows the heterojunction structure to effectively regulate carrier migration paths, promote spatial separation of electrons and holes, and significantly suppress their recombination process, thereby extending carrier lifetime. The separated electrons and holes can further participate in interfacial redox reactions, where electrons can reduce dissolved oxygen to generate superoxide radicals (·O2). - Holes can oxidize water or hydroxyl groups to generate hydroxyl radicals (·OH). These superoxide and hydroxyl radicals can attack the molecular structure of organic pollutants, leading to their gradual degradation and even mineralization. Furthermore, the composite piezoelectric catalytic material in this scheme forms an internal electric field based on the synergistic effect between the heterojunction interface and the piezoelectric polarization of BaTiO3 nanowires. This electric field drives electrons to spontaneously migrate from BaTiO3 to Bi2MoO6, resulting in charge redistribution and band bending at the heterojunction interface. This process effectively suppresses carrier recombination and improves charge separation efficiency. The mechanically induced piezoelectric polarization further amplifies this effect and promotes the generation of ·OH and ·O2. - The generation of reactive oxygen species plays a dominant role in the degradation process. When using the above-mentioned degradation methods to degrade organic pollutants in water, this scheme is based on the use of composite piezoelectric materials to induce the generation of reactive oxygen species under mechanical energy. This method of generating reactive oxygen species in the degradation process does not require external oxidants or light, thereby improving the practicality of composite piezoelectric catalytic materials in the degradation of organic pollutants in water and reducing the cost of the degradation process.

[0034] In this scheme, mechanical energy can be generated in any of the following ways: mechanical stirring, mechanical vibration, ultrasound, etc. These are all commonly used methods for generating mechanical energy. Using these common methods can reduce the cost of providing mechanical energy, and this universality also expands the application scenarios of the composite piezoelectric catalyst, thereby improving its practicality.

[0035] In this scheme, barium titanate (BaTiO3) is a typical lead-free ferroelectric piezoelectric material with excellent piezoelectric properties and chemical stability, attracting widespread attention in the field of piezoelectric catalysis. Bi2MoO6, as a bismuth-based semiconductor material, has a narrow band gap, good chemical stability, and good electron mobility, making it widely applicable in photocatalysis. This scheme, based on the composite piezoelectric catalytic material constructed from BaTiO3 and Bi2MoO6, enables the degradation of organic pollutants in water under conditions of no light and no oxidant. The entire degradation process is driven solely by mechanical energy, utilizing the piezoelectric effect generated by the polarization characteristics of BaTiO3 to form electrons and holes. A heterojunction is then used to promote the separation of these electrons and holes, allowing them to participate in redox reactions to generate reactive oxygen species, thus improving the efficiency of reactive oxygen species generation. Ultimately, this enhances the catalytic efficiency and effect of the composite piezoelectric catalytic material, effectively solving the problem that existing technologies for degrading organic pollutants in water typically require external light sources or chemical oxidants, increasing operating costs and causing secondary pollution.

[0036] Bi₂MoO₆ forms nanosheets or nanoflower structures, uniformly distributed on the surface of a BaTiO₃ nanowire substrate. This results in a larger specific surface area for the constructed composite piezoelectric catalytic material, exposing more surface atoms and increasing the number of active sites. Furthermore, the thinness of the nanosheets or nanoflower structures shortens the migration distance of electrons and holes, reducing ineffective recombination of charge carriers in the bulk phase. This allows the formed electrons and holes to quickly reach the surface, improving their utilization rate. In this scheme, a heterojunction is constructed based on two nanostructure materials: BaTiO₃ and Bi₂MoO₆. The resulting heterojunction, through the formation of a built-in electric field, achieves directional separation and efficient transfer of electrons and holes, effectively suppressing carrier recombination. This allows more separated electrons and holes to rapidly migrate to the surface active sites of the nanosheets / nanoflowers and participate in the catalytic reaction. The synergistic effect of the raw materials of the nanostructure, the heterojunction formed, and the piezoelectric effect generated by the polarization characteristics of BaTiO3 not only significantly improves the intrinsic activity and carrier utilization of the composite piezoelectric nanomaterial, but also enhances its catalytic selectivity by optimizing the adsorption energy and reaction pathway. At the same time, it inhibits the aggregation and corrosion of active components by means of structural support and electronic state regulation, and finally achieves a comprehensive synergistic improvement in catalytic activity, selectivity and cycle stability, providing an important idea for the design of efficient catalytic systems for organic pollutants in water.

[0037] Based on the composite piezoelectric catalytic material described above, a method for preparing the composite piezoelectric catalytic material is provided below. Please refer to [reference needed]. Figure 1 It includes the following steps: (I) Preparation of BaTiO3 nanowires (1.1) Add titanium dioxide to a NaOH solution with a mass-volume ratio of 1g:40mL~60mL and stir to disperse. Then carry out a hydrothermal reaction. After the hydrothermal reaction is completed, centrifuge to collect product one and wash it repeatedly with deionized water to obtain Na2Ti3O7 nanowires.

[0038] (1.2) The prepared Na2Ti3O7 nanowires were added to 50-200 mL of hydrochloric acid with a concentration of 0.2-2 mol / L for ion exchange, and stirred at room temperature until the pH of the system reached neutral, and product 2 was obtained. Product 2 was centrifuged and the separated solid was dried at 60 °C for 12 h to obtain H2Ti3O7 nanowires.

[0039] (1.3) H2Ti3O7 nanowires were mixed with a barium source solution at a molar ratio of 2 to 1:1 and subjected to a hydrothermal reaction to obtain product three. Product three was washed successively with deionized water and anhydrous ethanol, dried at 60°C for 12 h, and then ground to obtain BaTiO3 nanowires.

[0040] Existing methods for preparing barium titanate mainly include hydrothermal synthesis, sol-gel synthesis, and high-temperature solid-state synthesis. The sol-gel method suffers from high raw material costs, difficulty in controlling the synthesis process, and significant toxicity of the volatilized solvents and powders. The high-temperature solid-state method typically involves high-speed mixing of BaCO3 and TiO2 in a ball mill, followed by reaction in a muffle furnace at 900°C or higher. However, due to the high annealing temperature, the BaTiO3 powder exhibits significant impurity phases and poor uniformity. This proposed method, based on hydrothermal synthesis, prepares barium titanate. The raw materials are readily available, the temperature and operating environment are relatively mild, the product morphology can be controlled, the product is more uniform, and there are fewer byproducts. Furthermore, by controlling the precursor, temperature, and ratio, we can ensure that the prepared barium titanate is in a rod-like morphology.

[0041] The hydrothermal reaction conditions in step (1.1) are as follows: the hydrothermal reaction temperature is 180℃~200℃, and the hydrothermal reaction time is 18~24h. In step (1.3), the barium source solution can be Ba(OH)2·8H2O. The hydrothermal reaction conditions in step (1.3) are as follows: the hydrothermal temperature is 200℃~220℃, and the time is 2~8h.

[0042] (II) Preparation of composite piezoelectric catalytic materials (2.1) Bi(NO3)3·5H2O was dissolved in an organic solvent at a mass-volume ratio of 209 mg: 40 mL to form a bismuth source solution. Then, BaTiO3 nanowires with a mass ratio of 209: 100 to Bi(NO3)3·5H2O were added and dispersed to obtain a dispersion.

[0043] (2.2) Add Na2MoO4·2H2O solution with a mass ratio of 209:52 to Bi(NO3)3·5H2O to the dispersion and stir to mix. Through hydrothermal reaction, Bi2MoO6 is grown in situ on the surface of BaTiO3 nanowires, thus obtaining Bi2MoO6 composite piezoelectric catalyst material grown in situ on the surface of BaTiO3 nanowire substrate.

[0044] In step (2.1), the organic solvent can be a mixture of ethylene glycol and ethanol, with a volume ratio of ethylene glycol to ethanol of 6 to 4:1. The hydrothermal reaction conditions in step (2.2) are as follows: the hydrothermal reaction temperature is 160℃ to 190℃, and the reaction time is 8 to 24 hours.

[0045] The composite piezoelectric catalytic material can be prepared based on the steps described above. The entire preparation process is simple and the conditions are mild, making it suitable for large-scale preparation of composite piezoelectric catalytic materials. The prepared composite piezoelectric catalytic material can catalytically degrade organic pollutants in water under the action of mechanical energy, and the entire catalytic degradation process does not require light or continuous external oxidant.

[0046] Furthermore, this solution provides a method for degrading organic pollutants in water based on the composite piezoelectric catalytic material described above, which includes the following steps: (I) The composite piezoelectric catalytic material is prepared according to the preparation method of the composite piezoelectric catalytic material described above.

[0047] (II) Add the composite piezoelectric catalytic material to the water containing organic pollutants and mix thoroughly to obtain a mixed solution. The mass-to-volume ratio of the composite piezoelectric catalytic material to the water can be 0.1~1g:1L.

[0048] (III) Apply mechanical energy to the mixture and periodically measure the concentration change of organic pollutants in the mixture: If the concentration of organic pollutants in the mixture is higher than the set concentration threshold, extend the reaction time or continue to add composite piezoelectric catalytic material to the mixture until the concentration of organic pollutants in the mixture is lower than the set concentration threshold.

[0049] In this scheme, the concentration threshold for organic pollutants can be set to 0.0015~1 mg / L.

[0050] The above-described method for degrading organic pollutants in water can effectively and efficiently catalyze the degradation of organic pollutants in water. The entire catalytic degradation process requires no light or continuous addition of oxidants; it only requires mechanical energy acting on the composite piezoelectric material. The BaTiO3 in the composite piezoelectric material generates a piezoelectric effect based on its own polarization, forming electrons and holes on the surface of the composite piezoelectric catalytic material. Based on the constructed Bi2MoO6 / BaTiO3 heterojunction structure, the generated electrons and holes can be effectively separated to prevent their recombination. This allows the generated electrons and holes to participate in redox reactions, generating reactive oxygen species (·OH and ·O2) with oxidizing capabilities. - These free radicals can continuously attack and decompose organic pollutants in water, ultimately transforming them into harmless small molecules, thereby degrading organic pollutants in water. This degradation method is based on the synergistic effect of the piezoelectric properties of BaTiO3 and the constructed Bi2MoO6 / BaTiO3 heterojunction structure, which improves the utilization rate of electrons and holes in the composite piezoelectric catalytic material, thereby achieving the continuous and stable generation of many reactive oxygen species, and ultimately using the generated reactive oxygen species to efficiently degrade organic pollutants in water.

[0051] Performance testing To verify the performance of the composite piezoelectric catalytic material provided in this embodiment, the following experiments were also conducted.

[0052] Test Example: Preparation of Composite Piezoelectric Catalytic Materials The specific preparation process is as follows: Weigh 1.5 g TiO2 (P25) and add it to 60 mL of 10 mol·L⁻¹ solution. -1 The solution was stirred vigorously in NaOH solution at room temperature for 4 h to form a homogeneous dispersion. The resulting suspension was transferred to a 100 mL PPL-lined hydrothermal reactor and reacted at 180 °C for 24 h to obtain Na₂Ti₃O₇ nanowires. After the reaction, the product was collected by centrifugation and washed repeatedly with deionized water. The obtained product was then added to 0.2 mol·L⁻¹ -1 Ion exchange was performed in hydrochloric acid solution, and the mixture was stirred at room temperature until the pH of the system reached neutral. The product was then centrifuged and dried at 60 °C for 12 h to obtain H2Ti3O7 nanowires.

[0053] H₂Ti₃O₇ nanowires and Ba(OH)₂·8H₂O were added to 60 mL of deionized water at a 1:1 molar ratio and stirred thoroughly at room temperature. The mixture was then transferred to a 100 mL hydrothermal reactor and reacted at 210 °C for 4 h. After the reaction, the product was washed with deionized water and anhydrous ethanol. The product was dried at 60 °C for 12 h and then ground to obtain BaTiO₃ nanowires.

[0054] 209 mg of Bi(NO3)3·5H2O was weighed and added to 40 mL of ethylene glycol. The mixture was stirred at 800 rpm for 1 h until completely dissolved. 100 mg of BaTiO3 nanowires (Bi2MoO6 / BaTiO3 molar ratio 0.5:1) were added to the solution and dispersed thoroughly. 52 mg of Na2MoO4·2H2O and 10 mL of anhydrous ethanol were added to the system. The mixture was stirred at 200 rpm for 4 h to obtain a homogeneous suspension. The resulting suspension was transferred to a 100 mL reactor and reacted at 160 °C for 12 h. After the reaction, the product was collected by centrifugation and washed six times with ethanol. The product was dried at 60 °C for 12 h to obtain the Bi2MoO6 / BaTiO3 composite piezoelectric catalyst.

[0055] Comparative Example 1: Preparation of BaTiO3 nanowires (BTO) The specific process is as follows: Weigh 1.5 g TiO2 (P25) and add it to 60 mL of 10 mol·L⁻¹ solution. -1 The solution was stirred vigorously in NaOH solution at room temperature for 4 h to form a homogeneous dispersion. The resulting suspension was transferred to a 100 mL PPL-lined hydrothermal reactor and reacted at 180 °C for 24 h to obtain Na₂Ti₃O₇ nanowires. After the reaction, the product was collected by centrifugation and washed repeatedly with deionized water. The obtained product was then added to 0.2 mol·L⁻¹ -1 Ion exchange was performed in hydrochloric acid solution, and the mixture was stirred at room temperature until the pH of the system reached neutral. The product was then centrifuged and dried at 60 °C for 12 h to obtain H2Ti3O7 nanowires.

[0056] H₂Ti₃O₇ nanowires and Ba(OH)₂·8H₂O were added to 60 mL of deionized water at a 1:1 molar ratio and stirred thoroughly at room temperature. The mixture was then transferred to a 100 mL hydrothermal reactor and reacted at 210 °C for 4 h. After the reaction, the product was washed with deionized water and anhydrous ethanol. The product was dried at 60 °C for 12 h and then ground to obtain BaTiO₃ nanowires (BTO).

[0057] Comparative Example 2: Preparation of Bi₂MoO₆ (BMO) The specific preparation process is as follows: 970 mg of Bi(NO3)3⋅5H2O was weighed and stirred at 600 r / min for 1 h at room temperature until it was completely dissolved in 40 mL of ethylene glycol. Subsequently, 240 mg of Na2MoO4⋅2H2O and 10 mL of ethanol were added, and stirring was continued for 1 h until Na2MoO4⋅2H2O was completely dissolved. The resulting mixture was then sealed in a stainless steel reactor with a 100 mL polytetrafluoroethylene liner and reacted at 160 °C for 12 h. After the reaction was stopped, the solid was obtained by centrifugation, washed 6 times with ethanol by high-speed centrifugation, and then dried at 60 °C for 24 h. The resulting pale yellow product was obtained by grinding, which was Bi2MoO6 (abbreviated as BMO).

[0058] (a) XRD analysis (i.e., X-ray diffraction analysis) The crystal structures of the samples prepared in the test example, comparative example 1, and comparative example 2 were characterized using X-ray diffraction, and the results were obtained. Figure 2 .in, Figure 2 The XRD patterns are shown for the products obtained from the test example, Comparative Example 1, and Comparative Example 2. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Figure 2 Analysis shows that for BaTiO3, the XRD peaks at 2θ values ​​of 22.21°, 31.54°, 38.90°, 45.30°, 56.11° and 65.84° on the standard card (JCPDS No. 79-2264) can be attributed to the (100), (101), (111), (200), (112) and (202) crystals of tetragonal BaTiO3, respectively, which confirms that BaTiO3 was successfully synthesized. For Bi₂MoO₆, its diffraction peaks at 2θ values ​​of 23.52°, 28.24°, 34.48°, 46.71°, and 55.45° can be compared with the (111), (131), (220), (202), and (331) crystals of the Bi₂MoO₆ standard card (JCPDS No. 76-2388), thus confirming the successful synthesis of Bi₂MoO₆. Furthermore, both BaTiO₃ and Bi₂MoO₆ exhibit high-intensity diffraction peaks, indicating that the prepared materials have good crystallinity. For the composite piezoelectric catalyst, the XRD pattern clearly shows distinct diffraction peaks of BaTiO₃ and Bi₂MoO₆, indicating the successful combination of BaTiO₃, Bi₂MoO₆, and the composite piezoelectric material via a solvothermal method.

[0059] (II) Microscopic morphology analysis (2.1) The microstructure of the products prepared in Comparative Example 1, Comparative Example 2 and Test Example was characterized by scanning electron microscopy, and the microstructures were obtained respectively. Figure 3 , Figure 4 and Figure 5 .

[0060] (2.2) The lattice structure of the heterojunction of the composite piezoelectric catalytic material was analyzed using high-resolution transmission electron microscopy (TEM), and the results were obtained. Figure 6 .

[0061] in, Figure 3 The image shows a SEM image of BaTiO3 prepared in Comparative Example 1, taken using a scanning electron microscope. Figure 4 The image shows a SEM image of Bi2MoO6 prepared in Comparative Example 2, taken under a scanning electron microscope. Figure 5 SEM image of the composite piezoelectric catalytic material prepared for the test example, taken under a scanning electron microscope. Figure 6 This is a TEM image of the heterojunction of the composite piezoelectric catalytic material obtained by high-resolution transmission electron microscopy.

[0062] Through the Figure 3 Analysis shows that, Figure 3 The synthesized product exhibits a distinct rod-like morphology, thus confirming the successful synthesis of BaTiO3 nanowires. Through analysis of... Figure 4 Analysis revealed that the product of Comparative Example 2 exhibited a three-dimensional spherical flower-like structure assembled from nanosheets under a scanning electron microscope, thus confirming the successful synthesis of Bi₂MoO₆. Further analysis... Figure 5 Analysis reveals that the microstructure of the heterojunction in the composite piezoelectric catalytic material exhibits an elliptical microsphere flower shape, which is likely due to the BaTiO3 nanowires being covered by Bi2MoO6. Further analysis... Figure 6 , Figure 6 Clear lattice fringes can be observed. According to FFT / SAED diffraction index analysis, two different lattice fringes can be observed in the same local region of the composite piezoelectric catalytic material. One type of lattice fringes has a spacing of approximately 0.284 nm, while the other type has a spacing of approximately 0.312 nm. The lattice fringes with a spacing of approximately 0.284 nm can be attributed to the (101) crystal plane of the BaTiO3 nanowires, while the lattice fringes with a spacing of approximately 0.312 nm correspond to the (131) crystal plane of Bi2MoO6. The results described above demonstrate the formation of heterojunctions in the composite piezoelectric catalytic material.

[0063] (III) Piezoelectric properties The composite piezoelectric catalytic material prepared in the test example was placed under a piezoelectric microscope, and the surface morphology, amplitude diagram, and phase diagram of the composite piezoelectric material were obtained, as shown in the figure below. Figure 7 , Figure 8 and Figure 9 The applied DC bias voltage can range from -10V to +10V.

[0064] Figure 7The image shows the surface morphology of the composite piezoelectric catalytic material. Figure 8 This is an amplitude-voltage curve of the composite piezoelectric catalytic material; Figure 9 This is the phase-voltage curve of the composite piezoelectric catalytic material. (Based on...) Figure 7 Analysis reveals that the surface of this composite piezoelectric catalytic material exhibits a nanoscale wrinkled structure. This surface morphology can enhance local stress concentration in the constructed composite piezoelectric catalytic material and may promote the generation of piezoelectric polarization. Through further analysis... Figure 8 Analysis reveals that when an electrical bias voltage is applied to the composite piezoelectric catalytic material, it exhibits a clear piezoelectric response signal, thus proving that the composite piezoelectric catalytic material of this scheme possesses piezoelectric polarization performance. Furthermore, its amplitude-voltage curve displays a typical butterfly-shaped loop, a typical characteristic of switchable piezoelectric responses in ferroelectric materials. Applying this to catalytic materials allows for the regulation of catalytic activity; for example, forward polarization promotes reduction reactions, while reverse polarization promotes oxidation reactions, thereby enabling the provision of different active oxygen species according to actual needs. Further... Figure 9 When a bias voltage is applied to the composite piezoelectric catalytic material, its phase-voltage curve shows a significant phase reversal of nearly 180°, which further confirms that the composite piezoelectric catalytic material of this scheme has reversible polarity switching.

[0065] (iv) Catalytic degradation of pollutant Rhodamine B Five different catalytic materials were prepared: Group 1 consisted of BaTiO3 nanowires prepared in Comparative Example 1; Group 2 consisted of Bi2MoO6 prepared in Comparative Example 2; Group 3 consisted of composite piezoelectric catalytic materials prepared according to the method described in the test examples, except that the molar ratio of Bi2MoO6 to BaTiO3 in Group 3 was 0.25:1; Group 4 consisted of composite piezoelectric catalytic materials prepared in the test examples; and Group 5 consisted of composite piezoelectric catalytic materials prepared according to the method described in the test examples, except that the molar ratio of Bi2MoO6 to BaTiO3 in Group 5 was 1:1.

[0066] The catalytic degradation process of Rhodamine B is as follows: Six 50 mL solutions of Rhodamine B with a concentration of 5 mg / L were prepared. 50 mg of each of the five different catalytic materials prepared above was added to one of the five 50 mL Rhodamine B solutions with a concentration of 5 mg / L. The remaining Rhodamine B solution was used as a blank control group without any added catalytic material. The mixture was magnetically stirred for 30 min under light-protected conditions to reach adsorption-desorption equilibrium. The system was then placed in an ultrasonic cleaner for piezoelectric catalytic reaction at a frequency of 40 kHz and a power of 100 W. The cooling water in the ultrasonic cleaner was continuously replaced during the reaction to maintain the reaction system at room temperature. A 2.5 mL sample was taken every 10 min and filtered. The concentration change of the pollutant Rhodamine B was measured using a UV-Vis spectrophotometer, and the results were obtained. Figure 10 and Figure 11 . Figure 10 This is a schematic diagram illustrating the change in the concentration percentage of Rhodamine B over time during the catalytic degradation of the pollutant using different types of catalytic materials. Figure 10 The vertical axis represents the ratio between the concentration C of Rhodamine B at a certain moment and the initial concentration C0 of Rhodamine B. Figure 11 A bar chart showing the removal rates of Rhodamine B by different catalytic materials. Figure 10 It was found that in the blank control group, ultrasonic treatment alone could not degrade Rhodamine B. This result demonstrates that the piezoelectric effect of the composite piezoelectric material is crucial for the piezoelectric catalytic reaction. An adsorption-desorption equilibrium test was conducted 30 minutes before the start of the catalytic reaction, using slow stirring to minimize interference from the piezoelectric effect induced by mechanical stirring. During the adsorption phase (i.e.... Figure 10 During the period from -30 min to 0 min, the concentration of Rhodamine B decreased slightly. Among the five samples, Bi₂MoO₆ showed the strongest adsorption capacity as the catalyst, adsorbing approximately 15.45% of Rhodamine B during this stage. In contrast, BaTiO₃ nanowires exhibited the weakest adsorption capacity. Figure 10 In the 0-60 min stage, among the five samples, the composite piezoelectric catalyst with the best catalytic degradation effect on Rhodamine B was found when the molar ratio of Bi₂MoO₆ to BaTiO₃ was 0.5:1. Let's look at... Figure 11 , Figure 11 The composite piezoelectric catalytic material exhibits a significantly higher removal rate of Rhodamine B than pure BaTiO3 and pure Bi2MoO6. Furthermore, when the molar ratio of Bi2MoO6 to BaTiO3 in the composite piezoelectric catalytic material is 0.5:1, the removal rate of Rhodamine B can reach 99.27%, with a degradation rate k of 0.07714 min. -1This data confirms that an appropriate Bi₂MoO₆ loading can achieve a balance optimization between surface adsorption and interfacial charge transfer, thereby improving the catalytic degradation performance of the constructed composite piezoelectric catalytic material. When the Bi₂MoO₆ loading is too high, it may introduce more adsorption sites; however, excessive Bi₂MoO₆ may also partially cover the active surface of the BaTiO₃ nanowires. This coverage weakens the piezoelectric contribution of the BaTiO₃ nanowires and hinders carrier migration. Notably, although Bi₂MoO₆ exhibits stronger adsorption capacity, its degradation performance is significantly lower than that of the BaTiO₃ nanowires and the composite piezoelectric catalytic material. This result indicates that the piezoelectric catalytic degradation efficiency is not solely determined by adsorption behavior. Instead, it is determined by a combination of factors, including pollutant enrichment, piezoelectric polarization, charge separation efficiency, and active species generation. The composite piezoelectric catalytic material provided in this invention significantly optimizes this result. The above results demonstrate that the Bi₂MoO₆ / BaTiO₃-based composite piezoelectric catalytic material prepared in this invention has a high ability to piezoelectrically degrade the pollutant Rhodamine B and can be used as a piezoelectric catalytic material for the piezoelectric catalytic degradation of Rhodamine B.

[0067] (V) Degradation experiments of composite piezoelectric catalytic materials for different pollutants Prepare four 50 mL portions of deionized water. Add different contaminants to each of the four portions of deionized water, with a concentration of 5 mg / L for each contaminant. The contaminant added to the first group of deionized water is Rhodamine B (RhB); the contaminant added to the second group is tetracycline (TC); the contaminant added to the third group is bisphenol A (BPA); and the contaminant added to the fourth group is 1-naphthol (1-NPh).

[0068] 50 mg of the composite piezoelectric catalyst prepared in the test sample was added to each sample of deionized water containing contaminants to obtain a mixture. The mixture was magnetically stirred for 30 min under light-protected conditions to reach adsorption-desorption equilibrium. Subsequently, each mixture was placed in an ultrasonic cleaner for piezoelectric catalytic reaction at a frequency of 40 kHz and a power of 100 W. The cooling water in the ultrasonic cleaner was continuously replaced during the reaction to maintain the reaction mixture at room temperature. A 2.5 mL sample was taken every 10 min and filtered. The concentration change of contaminants in each mixture was measured using a UV-Vis spectrophotometer, and the results were obtained. Figure 12 and Figure 13 . Figure 12 This is a schematic diagram illustrating the changes in the concentration of different types of pollutants over time using composite piezoelectric catalytic materials. Figure 12 The vertical axis represents the ratio between the concentration C of this type of pollutant at a certain moment and the initial concentration C0 of this type of pollutant. Figure 13This is a bar chart showing the removal rates of different types of pollutants using composite piezoelectric catalytic materials. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Figure 12 Analysis shows that the composite piezoelectric catalytic material provided in this scheme can catalyze the degradation of Rhodamine B, tetracycline, bisphenol A, and 1-naphthol, thus demonstrating that the composite piezoelectric catalytic material provided in this scheme has a certain degree of universality in the degradation of different organic pollutants. Let's look at... Figure 13 The composite piezoelectric catalytic material provided in this scheme exhibits the fastest degradation rate for Rhodamine B, achieving almost complete removal within 60 minutes. Tetracycline also demonstrates high removal efficiency, while the degradation rates of bisphenol A and 1-naphthol are relatively slow, although their overall removal rates are all above 80%. This difference may be related to the molecular structure of the pollutants, their inherent reactivity, and the interaction between the pollutants and the catalyst surface. Overall, these results indicate that the composite piezoelectric catalytic material provided in this scheme has good applicability in degrading different types of organic pollutants.

[0069] (vi) Cyclic stability test of composite piezoelectric catalytic materials 50 mg of the composite piezoelectric catalytic material prepared from the test sample was placed in 50 mL of deionized water containing 5 mg / L Rhodamine B. The mixture was magnetically stirred for 30 min under light-protected conditions to reach adsorption-desorption equilibrium. The system was then placed in an ultrasonic cleaner for piezoelectric catalytic reaction at a frequency of 40 kHz and a power of 100 W. The cooling water in the ultrasonic cleaner was continuously replaced during the reaction to maintain the reaction system at room temperature. A 2.5 mL sample was taken every 10 min and filtered. The concentration change of the pollutant Rhodamine B was measured using a UV-Vis spectrophotometer for a total measurement time of 1 h. After 1 h, the composite piezoelectric catalytic material was recovered by centrifugation. The recovered composite piezoelectric catalytic material was washed multiple times with deionized water and then dried at 60 °C. The dried composite piezoelectric catalytic material was then used again to catalytically degrade Rhodamine B in a new 50 mL sample of deionized water containing 5 mg / L Rhodamine B. The catalytic degradation process was consistent with the above description. The above-mentioned composite piezoelectric catalytic material was reused four times to obtain... Figure 14 . Figure 14 This graph shows the degradation efficiency of the composite piezoelectric catalytic material in this scheme for the catalytic degradation of pollutant Rhodamine B after four consecutive cycles. Figure 14 The vertical axis represents the ratio between the concentration C of Rhodamine B at a certain moment and the initial concentration C0 of Rhodamine B. Through analysis... Figure 14Analysis shows that the degradation efficiency of the composite piezoelectric catalytic material provided by this scheme only decreased slightly after four consecutive cycles of degradation, and the final removal rate of 5 mg / L Rhodamine B remained at 97.79% in the fourth cycle. This slight performance decrease may be attributed to the residual intermediate products adhering to the catalyst surface, but the results still indicate that the composite piezoelectric catalytic material of this scheme has excellent recyclability and stability.

[0070] In summary, the composite piezoelectric catalytic material provided in this scheme, through the heterojunction formed between BaTiO3 nanowires and Bi2MoO6, exhibits excellent organic pollutant degradation performance without the addition of oxidants. Furthermore, its degradation rate for Rhodamine B reaches up to 99.27%, with a degradation rate k of 0.07714 min. -1 It is far superior to the degradation performance of pure barium titanate piezoelectric catalysis, overcomes the shortcomings of single barium titanate piezoelectric catalytic materials in piezoelectric catalysis performance, and has better application prospects.

[0071] The basic principles, main features, and advantages of this invention have been described above. Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made without departing from the spirit and scope of the invention, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection claimed by this invention is defined by the appended claims and their equivalents.

Claims

1. A composite piezoelectric catalytic material, characterized in that, It comprises a BaTiO3 nanowire substrate and a Bi2MoO6 nanostructure grown in situ on the surface of the BaTiO3 nanowire substrate, with a heterojunction formed between the BaTiO3 nanowire substrate and Bi2MoO6. Electrons and holes are induced on the surface of the composite piezoelectric catalytic material by mechanical energy interaction, and the spatial separation of the generated electrons and holes is promoted based on the constructed heterojunction. The separated electrons and holes generate reactive oxygen species through redox reactions, thereby degrading organic pollutants in water.

2. The composite piezoelectric catalytic material as described in claim 1, characterized in that, The Bi2MoO6 is a nanosheet or nanoflower structure, and it is uniformly distributed on the surface of the BaTiO3 nanowire substrate.

3. A method for preparing the composite piezoelectric catalytic material as described in claim 1 or 2, characterized in that, It includes: Bi(NO3)3·5H2O was dissolved in an organic solvent at a mass-volume ratio of 209 mg: 40 mL to form a bismuth source solution, and BaTiO3 nanowires with a mass ratio of 209:100 to Bi(NO3)3·5H2O were added and dispersed to obtain a dispersion. A Na2MoO4·2H2O solution with a mass ratio of 209:52 to Bi(NO3)3·5H2O was added to the dispersion and stirred. Bi2MoO6 was then grown in situ on the surface of BaTiO3 nanowires through a hydrothermal reaction, thus obtaining a composite piezoelectric catalytic material, Bi2MoO6, grown in situ on the surface of BaTiO3 nanowire substrate.

4. The preparation method of the composite piezoelectric catalytic material as described in claim 3, characterized in that, The organic solvent is a mixture of ethylene glycol and ethanol, wherein the volume ratio of ethylene glycol to ethanol is 6~4:1; And / or, the temperature of the hydrothermal reaction is 160℃~190℃, and the reaction time is 8~24h.

5. The method for preparing the composite piezoelectric catalytic material as described in claim 3, characterized in that, The preparation process of the BaTiO3 nanowires is as follows: H2Ti3O7 nanowires are mixed with a barium source solution at a molar ratio of 2 to 1:1 and subjected to a hydrothermal reaction to obtain the BaTiO3 nanowires.

6. The method for preparing the composite piezoelectric catalytic material as described in claim 5, characterized in that, The preparation process of the H2Ti3O7 nanowires is as follows: titanium dioxide is added to sodium hydroxide solution and stirred and dispersed, and then subjected to hydrothermal reaction to obtain Na2Ti3O7 nanowires; the Na2Ti3O7 nanowires are then subjected to acid exchange treatment to obtain H2Ti3O7 nanowires.

7. The method for preparing the composite piezoelectric catalytic material as described in claim 6, characterized in that, The concentration of the sodium hydroxide solution is 8~12 mol / L; the acid is hydrochloric acid, and the concentration of the hydrochloric acid is 0.2~2 mol / L.

8. The method for preparing the composite piezoelectric catalytic material as described in claim 5, characterized in that, The barium source is Ba(OH)2·8H2O.

9. The application of a composite piezoelectric catalytic material as described in claim 1 or 2 in the catalytic degradation of organic pollutants in water.

10. A method for degrading organic pollutants in water, characterized in that, It includes: Prepare the composite piezoelectric catalytic material as described in claim 1 or 2; The composite piezoelectric catalytic material was added to water containing organic pollutants and mixed evenly to obtain a mixed solution; Mechanical energy is applied to the mixture, and the concentration of organic pollutants in the mixture is measured periodically. If the concentration of organic pollutants in the mixture is higher than the set threshold, the reaction time is extended or composite piezoelectric catalytic material is added to the mixture until the concentration of organic pollutants in the mixture is lower than the set threshold.

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