Oxygen vacancy modified layered bismuth ferroelectric BaBi4TiTaO 11 Preparation methods and applications of Cl piezoelectric photocatalytic materials

Abstract

This invention discloses an oxygen vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO 11 This paper describes a method for preparing and applying Cl piezoelectric photocatalysts, which falls under the field of catalytic materials technology. The method utilizes a molten salt process instead of the traditional high-temperature solid-state method. BiOCl, Bi3TiTaO9, and BaCO3 are mixed, a molten salt medium is added, and the mixture is ground uniformly. The mixture is then calcined in air at 840 ℃~860 ℃ for 10 h~14 h. The resulting product is washed and dried to obtain BaBi4TiTaO9. 11 Cl piezoelectric photocatalyst material; then oxygen vacancies are precisely constructed on the material surface using a hydrothermal method. The present invention relates to oxygen vacancy-modified BaBi4TiTaO. 11 Cl piezoelectric photocatalysts combine good visible light response with strong piezoelectricity, showing broad application prospects in piezoelectric photocatalytic H2O2 production, waste plastic reforming, and water pollutant degradation.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, specifically to oxygen vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO. 11 Preparation methods and applications of Cl piezoelectric photocatalytic materials. Background Technology

[0002] Currently, the dual demands for environmental pollution control and the synthesis of green chemicals are driving the development of catalytic technology towards low energy consumption, high selectivity, and sustainability. Water pollution caused by industrial wastewater, microplastics, and organic pollutants is becoming increasingly prominent, while traditional treatment technologies suffer from limitations such as low efficiency, secondary pollution, and high energy consumption. While traditional photocatalysis can utilize solar energy to drive the synthesis of H2O2 and the removal of pollutants, it faces bottlenecks such as low light energy utilization, easy recombination of photogenerated carriers, and difficulty in operating under weak or no light conditions. In contrast, piezoelectric catalysis technology utilizes the piezoelectric effect to generate a polarized electric field through ultrasonic waves and water flow disturbances, providing a driving force for the separation and migration of carriers, thereby promoting subsequent surface catalytic reactions. It maintains activity even under no-light conditions, becoming a novel green technology that compensates for the shortcomings of photocatalysis. Coupled with photocatalysis, the piezoelectric polarized electric field can effectively suppress the recombination of photogenerated carriers, achieving synergistic utilization of light and mechanical energy. This not only significantly improves catalytic efficiency but also greatly expands the technology's application scenarios.

[0003] Layered bismuth-based ferroelectric semiconductors have been widely developed as high-performance piezoelectric photocatalysts in recent years due to their unique photoexcitation properties and excellent piezoelectric performance. However, the synthesis of these materials still mainly relies on traditional high-temperature solid-state methods. This method requires high temperatures, which not only easily leads to the loss of volatile elements such as Bi and Cl, but also often results in uncontrollable grain morphology, low crystallinity, and weak piezoelectric response, severely limiting further improvements in the material's catalytic performance. Although the molten salt method has potential advantages in controlling morphology and crystallinity, it is currently not widely used for the preparation of BaBi₄TiTaO. 11 The optimal process conditions for Cl (such as temperature, holding time, and salt-to-material ratio) are still unclear and require further system optimization and exploration. Furthermore, piezoelectric photocatalytic materials generally face a series of common technical bottlenecks, including insufficient surface active sites, low photogenerated carrier separation efficiency, and difficulty in effectively coupling the piezoelectric effect with the photocatalytic process. The combination of these problems results in the overall catalytic efficiency of the materials falling far short of ideal levels, making it difficult to meet the demands of practical applications for efficient, stable, and wide-range catalytic systems. Therefore, it is necessary to develop a BaBi4TiTaO material that can both optimize the molten salt process and simultaneously introduce surface oxygen vacancy modification. 11Cl catalytic materials are of great significance for overcoming existing technological bottlenecks and improving the overall performance of piezoelectric photocatalysis. Based on the above problems, this invention provides a BaBi4TiTaO catalyst prepared by an optimized molten salt method and supplemented with oxygen vacancy modification. 11 Cl piezoelectric photocatalyst materials are used to address the shortcomings of existing technologies. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by proposing an oxygen-vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO. 11 Preparation method and application of Cl piezoelectric photocatalytic materials. This invention provides oxygen vacancy-modified BaBi4TiTaO. 11 Cl piezoelectric photocatalysts, as typical layered bismuth-based ferroelectric materials, possess both good visible light response and strong piezoelectricity, showing broad application prospects in fields such as piezoelectric photocatalytic H2O2 production, waste plastic reforming, and water pollutant degradation.

[0005] In a first aspect, the present invention provides a layered bismuth-based ferroelectric BaBi4TiTaO 11 The preparation method of Cl piezoelectric photocatalytic material includes the following steps: BiOCl, Bi3TiTaO9, and BaCO3 were mixed in stoichiometric ratio, added to a molten salt medium, ground until homogeneous, and then calcined at 840 ℃~860 ℃ for 10 h~14 h in air. The resulting product was washed and dried to obtain the layered bismuth-based ferroelectric BaBi4TiTaO9. 11 Cl piezoelectric photocatalyst materials.

[0006] Furthermore, the molar ratio of BiOCl, Bi3TiTaO9, BaCO3 to the molten salt medium is 1:1:1:(5.5~6.5).

[0007] Furthermore, the molten salt medium is KCl and / or NaCl.

[0008] Further, the preparation method of BiOCl is as follows: Bismuth nitrate pentahydrate is dissolved in deionized water to form solution A, potassium chloride is dissolved in deionized water to form solution B, solution A is slowly added dropwise to solution B under magnetic stirring, and stirring is continued for 10 h to 14 h. The resulting white precipitate is centrifuged, washed with deionized water and dried to obtain BiOCl.

[0009] Furthermore, the molar ratio of bismuth nitrate pentahydrate to potassium chloride is 1:(1~1.04).

[0010] Further, the preparation method of Bi3TiTaO9 is as follows: Bi2O3, Ta2O5 and TiO2 are added to a ball mill jar and ball milled with anhydrous ethanol as the medium. The resulting mixed slurry is dried and ground, then calcined in air at 680 ℃~720 ℃ for 8 h~12 h. After cooling, it is washed with deionized water and dried to obtain Bi3TiTaO9.

[0011] Furthermore, the molar ratio of Bi2O3, Ta2O5 and TiO2 is (3~3.02):1:2.

[0012] A second aspect of the present invention provides an oxygen vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO 11 The preparation method of Cl piezoelectric photocatalyst material, using the above-mentioned layered bismuth-based ferroelectric BaBi4TiTaO 11 Cl piezoelectric photocatalyst material was dispersed in water, and glyoxal aqueous solution was added. The mixture was heated at 110 ℃~130 ℃ for 11 h~13 h. The resulting product was washed successively with ethanol and deionized water to obtain the oxygen vacancy modified layered bismuth-based ferroelectric BaBi4TiTaO. 11 Cl piezoelectric photocatalyst materials.

[0013] Furthermore, the reaction between glyoxal and the layered bismuth-based ferroelectric BaBi4TiTaO is controlled. 11 The mass ratio of Cl piezoelectric photocatalyst material is (3.0~4.6):1.

[0014] In a third aspect, the present invention provides the above-described layered bismuth-based ferroelectric BaBi4TiTaO. 11 Cl piezoelectric photocatalyst or the above-mentioned oxygen vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO 11 The application of Cl piezoelectric photocatalytic materials in piezoelectric photocatalysis, wherein the application is at least one of the following (1)-(3): (1) Application in piezoelectric photocatalysis for hydrogen peroxide production; (2) Applications in piezoelectric photocatalytic reforming of plastics; (3) Application in piezoelectric photocatalytic degradation of organic pollutants.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention uses the molten salt method to prepare layered bismuth-based ferroelectric BaBi4TiTaO 11Cl piezoelectric photocatalysts effectively overcome the shortcomings of traditional high-temperature solid-state methods, such as the easy volatilization of Bi and Cl elements, the formation of impurity phases, and the uncontrollable morphology and grain size. The prepared materials have high crystallinity, regular layered morphology, and stable structure. Moreover, the preparation process is mild, simple to operate, and does not require precious metals or complex equipment, showing good prospects for industrial application and large-scale production potential.

[0016] (2) By optimizing the synthesis temperature, the present invention determines a synthesis temperature of 840 ℃~860 ℃, so that the crystallinity, piezoelectric response and light absorption capacity of the material are optimally matched, effectively solving the technical problem that the existing preparation process conditions are unclear and the material properties are difficult to effectively control.

[0017] (3) This invention effectively modulates the electronic structure and surface chemical properties of the material through oxygen vacancy defect modification, significantly increases the surface catalytic active sites, broadens the visible light absorption range, enhances the piezoelectric polarization effect, and greatly suppresses the recombination of photogenerated carriers, effectively solving the problem of BaBi4TiTaO 11 Cl materials suffer from core problems such as weak photocatalytic activity, low carrier separation efficiency, and low catalytic efficiency.

[0018] (4) The oxygen vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO prepared in this invention 11 Cl piezoelectric photocatalysts can simultaneously achieve efficient utilization of light energy and environmental mechanical energy in a piezoelectric-photosynergistic system. In applications such as the green synthesis of hydrogen peroxide via piezoelectric photocatalysis, the preparation of high-value-added industrial raw materials from plastic reforming, and the degradation of organic pollutants in water bodies, this material exhibits excellent catalytic activity and stability, providing a novel, efficient, stable, and low-cost catalytic material and technological pathway for environmental remediation and the synthesis of green chemicals. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in the embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0020] Figure 1 The XRD patterns are those of Examples 1-2 and Comparative Examples 1-5 of the present invention.

[0021] Figure 2 The images shown are SEM images of Embodiment 1 and Comparative Examples 1-3 of the present invention.

[0022] Figure 3 The images shown are SEM images of Embodiment 2 and Comparative Examples 4-5 of the present invention.

[0023] Figure 4The bar charts show the H2O2 production performance of Example 1 and Comparative Examples 1-3 of this invention; wherein, Figure 4 a represents photocatalysis. Figure 4 b represents piezoelectric catalysis. Figure 4 c represents piezoelectric photocatalysis.

[0024] Figure 5 The bar charts show the H2O2 production performance of Examples 1-2 and Comparative Examples 4-5 of this invention; wherein, Figure 5 a represents photocatalysis. Figure 5 b represents piezoelectric catalysis. Figure 5 c represents piezoelectric photocatalysis.

[0025] Figure 6 a is a bar chart showing the performance of piezoelectric photocatalytic reforming of waste plastics into high-value-added products in Examples 1 and 2 of the present invention; Figure 6 b is the concentration change over time of Rhodamine B in piezoelectric photocatalytic degradation in Examples 1 and 2. Detailed Implementation

[0026] To better understand the above technical solutions, the technical solutions of the embodiments of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0027] In a first aspect of the present invention, a layered bismuth-based ferroelectric BaBi4TiTaO 11 The preparation method of Cl piezoelectric photocatalytic material includes the following steps: BiOCl, Bi3TiTaO9, and BaCO3 were mixed in stoichiometric ratio, added to a molten salt medium, ground until homogeneous, and then calcined at 840 ℃~860 ℃ for 10 h~14 h in air. The resulting product was washed and dried to obtain layered bismuth-based ferroelectric BaBi4TiTaO9. 11 Cl piezoelectric photocatalyst materials.

[0028] In this embodiment of the invention, layered bismuth-based ferroelectric BaBi4TiTaO is prepared using the molten salt method. 11 Cl piezoelectric photocatalysts effectively overcome the shortcomings of traditional high-temperature solid-state methods, such as the easy volatilization of Bi and Cl elements, the formation of impurity phases, and the uncontrollable morphology and grain size. The prepared materials have high crystallinity, regular layered morphology, and stable structure. Moreover, the preparation process is mild, simple to operate, and does not require precious metals or complex equipment, showing good prospects for industrial application and large-scale production potential.

[0029] Specifically, by optimizing the synthesis temperature and calcination time, the product is ensured to be fully crystallized and structurally intact, while suppressing element volatilization and impurity phase formation, regulating grain size and surface activity, thereby improving the piezoelectric photocatalytic performance of the material. A synthesis temperature of 840 ℃~860 ℃ was determined to achieve the optimal match between the material's crystallinity, piezoelectric response, and light absorption capacity. Meanwhile, controlling the calcination time to 10-14 hours ensures that all raw materials react fully while crystals grow completely, guaranteeing the regularity and uniformity of the product's layered morphology and size, providing stable structural support for the material's excellent piezoelectric photocatalytic performance. If the calcination time is too short, the raw materials will not react sufficiently, easily leaving unreacted impurities such as BiOCl, Bi3TiTaO9, and BaCO3, resulting in low product purity, increased impurity phases, incomplete crystal growth, poor crystallinity, and irregular layered structure, thus significantly reducing the material's piezoelectric response and photocatalytic activity. If the calcination time is too long, it will lead to excessive sintering and coarsening of the grains, a decrease in specific surface area, and a reduction in catalytic active sites. Furthermore, high-temperature and long-term calcination can easily cause the volatilization of Bi and Cl elements, inducing lattice defects, which not only reduces the material's piezoelectric photocatalytic performance but also increases energy consumption and preparation costs.

[0030] In some embodiments, the molar ratio of BiOCl, Bi3TiTaO9, BaCO3 to the molten salt medium is 1:1:1:(5.5~6.5).

[0031] Specifically, controlling the amount of molten salt added avoids insufficient coating, incomplete reaction, and impurity phase formation caused by insufficient addition, while avoiding grain coarsening, decreased specific surface area, and increased post-processing costs caused by excessive addition. Simultaneously, it precisely guides crystal orientation growth, resulting in a regular lamellar morphology. Strictly controlling the molar ratio of BiOCl, Bi3TiTaO9, and BaCO3 allows for the precise preparation of the target product BaBi4TiTaO9. 11 Cl is used to avoid impurities, lattice defects, and compositional imbalances caused by ratio deviations, thus ensuring high product purity. This ratio range provides a reasonable component buffer space based on theoretical stoichiometry, effectively compensating for losses caused by Bi volatilization and the collapse of layered crystal structures during high-temperature molten salt calcination. Simultaneously, it strictly avoids the introduction of excessive Bi-based impurities, which could damage the purity of the target phase, ensuring that Ba, Bi, Ti, Ta, and Cl are expressed according to the formula BaBi₄TiTaO. 11 Precise stoichiometric coordination of Cl crystals yields pure-phase products with a single crystal phase, high crystallinity, and complete structure. Furthermore, the optimal 1:1:1 stoichiometric ratio further ensures more complete and balanced reactions among components, significantly improving the consistency of components and structural uniformity between different batches of samples. This maintains high stability in the material's piezoelectric response, light absorption capacity, and carrier separation efficiency, effectively avoiding performance instability caused by fluctuations in the raw material ratio.

[0032] In some embodiments, the molten salt medium is KCl and / or NaCl. Specifically, the molten salt medium is KCl and NaCl, or KCl or NaCl, preferably KCl and NaCl. Compared to single alkali metal chlorides, the binary mixed molten salt of KCl and NaCl has the advantages of a lower melting point, a wider liquid phase temperature range, and more uniform high-temperature fluidity. It can achieve full melting at lower temperatures, providing a more stable liquid phase environment for raw material diffusion and crystal growth. Compared with other conventional molten salts (such as SrCl2), this mixed system has stronger high-temperature chemical stability, is less prone to side reactions, and is easy to remove with subsequent water washing without residual pollution. It can effectively inhibit the volatilization of Bi and Cl elements, reduce the formation of impurity phases, and avoid cation doping, thereby ensuring the purity of the product crystal phase and the regularity of the layered morphology, significantly improving the crystallinity and catalytic performance of the material. The molten salt medium can provide a uniform liquid phase reaction environment at high temperatures, significantly reducing the diffusion resistance and reaction activation energy between raw materials, making the solid phase reaction more complete and thorough, and further ensuring that the reactions of each component are more complete and balanced. The optimal stoichiometric ratio of BiOCl, Bi3TiTaO9, BaCO3, and molten salt media (KCl and NaCl) is 1:1:1:6. This ratio provides a suitable amount of molten salt, which can completely encapsulate the precursor particles, offering a continuous and uniform liquid environment for ion diffusion and crystal growth. This promotes the full reaction of each component according to its stoichiometric ratio to generate the pure phase BaBi4TiTaO9. 11 Cl; it also effectively suppresses the volatilization of Bi and Cl elements at high temperatures, ensuring the integrity of the crystal structure and the regularity of the layered morphology. If the molten salt ratio is lower than this range, the liquid phase environment is insufficient, the diffusion of raw materials is hindered, which easily leads to incomplete reaction, increased impurities, insufficient crystal growth and uneven morphology, and a significant decrease in crystallinity and catalytic performance. If the molten salt ratio is too high, it will excessively dilute the reactant concentration, prolong the reaction cycle, increase the difficulty and energy consumption cost of water washing and desalination, easily cause salt residue pollution, and easily cause abnormal coarsening of crystal grains, reducing the specific surface area and the number of catalytic active sites. The optimal molar ratio (1:1:1:6) can achieve the best match between reaction efficiency, product quality and preparation cost, significantly improve the composition consistency and structural uniformity between different batches of samples, keep the piezoelectric response and carrier separation efficiency of the material highly stable and repeatable, effectively avoid performance instability caused by fluctuations in the raw material ratio, and thus obtain high-purity and high-crystallinity target products at relatively mild temperatures.

[0033] In some embodiments, BiOCl is prepared by dissolving bismuth nitrate pentahydrate in deionized water to form solution A, dissolving potassium chloride in deionized water to form solution B, slowly adding solution A dropwise into solution B under magnetic stirring, and continuing stirring for 10 h to 14 h. The resulting white precipitate is centrifuged, washed with deionized water, and dried to obtain BiOCl.

[0034] Optionally, the molar ratio of bismuth nitrate pentahydrate to potassium chloride is 1:(1~1.04).

[0035] Specifically, this liquid-phase precipitation method for preparing BiOCl is mild and simple to operate, and the reaction can be carried out at room temperature and pressure without the need for harsh conditions such as high temperature and high pressure. By slowly adding solution A to solution B and continuously stirring for a long time, the reaction system can always be kept in a uniform dispersion state, which is conducive to the slow and uniform nucleation and growth of BiOCl crystals, thereby obtaining a BiOCl precursor with regular morphology, uniform particle size, and good crystallinity. Moreover, the post-processing of this process is simple; high-purity products can be obtained by centrifugation, washing with water, and drying. Controlling the molar ratio of bismuth pentahydrate to potassium chloride to be 1:(1~1.04), preferably controlling the molar ratio of bismuth pentahydrate to potassium chloride to be 1:1.02, can improve the purity of the product while ensuring complete reaction. This ratio uses a slight excess of chlorine source, which can ensure that bismuth ions are completely converted into BiOCl, avoiding insufficient reaction of bismuth ions due to insufficient chloride ions, and generating by-products such as basic bismuth salts, thereby ensuring that the precursor phase is single and the crystals are complete. If the proportion of potassium chloride is too low, it will cause Bi 3+ Incomplete reaction results in residual soluble bismuth salt impurities, reducing BiOCl purity and affecting subsequent reactions. Excessive potassium chloride introduces large amounts of excess chloride ions, increasing washing difficulty and potentially causing ion residue, thus impacting the final material properties. This appropriate excess range ensures complete bismuth source conversion without significantly increasing post-processing burden, yielding high-purity, highly crystalline BiOCl, which is crucial for the subsequent synthesis of layered bismuth-based ferroelectric BaBi4TiTaO. 11 Cl provides a high-quality precursor base.

[0036] In some embodiments, the preparation method of Bi3TiTaO9 is as follows: Bi2O3, Ta2O5 and TiO2 are added to a ball mill jar and ball milled with anhydrous ethanol as the medium. The resulting mixed slurry is dried and ground, then calcined in an air atmosphere at 680 ℃~720 ℃ for 8 h~12 h. After cooling, it is washed with deionized water and dried to obtain Bi3TiTaO9.

[0037] Optionally, the molar ratio of Bi2O3, Ta2O5 and TiO2 is (3~3.02):1:2.

[0038] Specifically, this preparation method uses anhydrous ethanol as the medium for ball milling, which can make Bi2O3, Ta2O5 and TiO2 highly uniformly mixed, providing a uniform precursor mixture for subsequent calcination synthesis of pure phase Bi3TiTaO9. Calcination at 680 ℃~720 ℃ in air atmosphere for 8 h~12 h results in a mild reaction temperature and moderate holding time, which can ensure that the oxides react fully and crystallize completely, while inhibiting excessive grain coarsening, thus obtaining Bi3TiTaO9 powder with high crystallinity and pure phase. Moreover, the process is simple and easy to operate, and the post-processing is convenient, making it suitable for the stable preparation of precursor materials.

[0039] Furthermore, controlling the molar ratio of Bi2O3, Ta2O5, and TiO2 to (3~3.02):1:2 provides a reasonable tolerance for the stoichiometric ratio near the theoretical ratio, balancing reaction sufficiency and product purity. If the Bi2O3 ratio is below this range, insufficient bismuth source will lead to incomplete reaction, easily generating impurities such as titanates and tantalates, resulting in impure Bi3TiTaO9 crystal phase and poor crystallinity. If the Bi2O3 ratio is above this range, excessive bismuth will be introduced, easily forming bismuth-based impurities at high temperatures and leaving unreacted bismuth oxide, reducing precursor purity. Considering the volatility of bismuth at high temperatures, this ratio range can effectively compensate for bismuth loss during calcination, ensuring the final product conforms to the stoichiometric ratio. Maintaining a fixed stoichiometric ratio of Ta2O5 and TiO2 ensures a stable crystal framework structure, resulting in a uniform and regular Bi3TiTaO9 composition, facilitating the subsequent synthesis of BaBi4TiTaO. 11 Cl provides a stable and reliable precursor. Specifically, a preferred molar ratio of 3.01:1:2 ensures a strict match between Bi, Ti, and Ta elements in the Bi3TiTaO9 crystal composition, preventing impurity phase formation or elemental segregation, and guaranteeing a stable precursor structure and uniform composition, resulting in high-purity BaBi4TiTaO9. 11 This provides a reliable foundation for the preparation of Cl materials.

[0040] A second aspect of the present invention provides an oxygen-vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO. 11 The preparation method of Cl piezoelectric photocatalyst material, using the above-mentioned layered bismuth-based ferroelectric BaBi4TiTaO 11 Cl piezoelectric photocatalyst material was dispersed in water, and glyoxal aqueous solution was added. The mixture was heated at 110 ℃~130 ℃ for 11 h~13 h. The resulting product was washed successively with ethanol and deionized water to obtain oxygen vacancy modified layered bismuth-based ferroelectric BaBi4TiTaO 11 Cl piezoelectric photocatalyst materials.

[0041] Optionally, the reaction between glyoxal and layered bismuth-based ferroelectric BaBi4TiTaO is controlled. 11The mass ratio of the Cl piezoelectric photocatalyst material is (3.0~4.6):1. Preferably, the mass ratio of glyoxal to layered bismuth-based ferroelectric BaBi4TiTaO is controlled. 11 The mass ratio of the Cl piezoelectric photocatalyst material is (3.6~4.0):1. By controlling the amount of glyoxal added to form different concentrations of oxygen vacancies, the photoresponse range of the target product is effectively broadened, the light absorption capacity of the material is improved, and photogenerated carrier recombination is suppressed, while charge separation and transfer are promoted, thereby significantly improving the photoelectric effect of layered bismuth-based BaBi4TiTaO. 11 Cl piezoelectric photocatalytic materials exhibit piezoelectric-photosynergistic catalytic performance; appropriate oxygen vacancies can also optimize the number and adsorption capacity of active sites on the material surface, enhancing catalytic reaction kinetics. Controlling the reaction between glyoxal and BaBi4TiTaO 11 Within the mass ratio of Cl (3.0~4.6):1, as the glyoxal ratio increases from 1.9 to 3.8, the oxygen vacancy concentration gradually increases and approaches the optimal level, resulting in enhanced catalytic performance. However, when the ratio exceeds 3.8 and continues to increase to 5.7, excessive reduction leads to defect density and the formation of carrier recombination centers, thus weakening the catalytic performance. Controllable adjustment of the oxygen vacancy concentration can satisfy the optimal defect environment required for catalysis. When the mass ratio is around 3.8, the reduction intensity of the system is moderate, ensuring improved carrier separation efficiency and a sufficient number of catalytically active sites without causing structural instability or the formation of carrier recombination centers due to excessive defects. If the glyoxal dosage is too low, the oxygen vacancy concentration is insufficient, limiting the improvement effect on light absorption and charge separation; if the dosage is too high, excessive reduction is likely to occur, leading to dense lattice defects and damaged crystal structure, which in turn reduces piezoelectric response and catalytic stability. Therefore, the optimal combination of glyoxal and layered bismuth-based ferroelectric BaBi4TiTaO... 11 The mass ratio of Cl piezoelectric photocatalytic material is (3.78~3.82):1, which can achieve the optimal balance between oxygen vacancy concentration, structural integrity and catalytic performance, thus realizing the highest piezoelectric photocatalytic activity and cycle stability of the material.

[0042] The piezoelectric-photocatalytic synergistic catalysis principle of this invention is as follows: layered bismuth-based ferroelectric BaBi4TiTaO 11Cl piezoelectric photocatalytic materials possess a non-centrosymmetric structure, which can generate a strong piezoelectric polarization field under mechanical stress such as ultrasound and water flow. Under the coupling of light and mechanical fields, this piezoelectric polarization field can serve as a driving force, effectively driving the directional separation and migration of charge carriers, significantly suppressing electron-hole pair recombination, and allowing more charge carriers to accumulate on the material surface to participate in redox reactions. Simultaneously, the surface oxygen vacancies introduced in this embodiment can, on the one hand, modulate the material's band structure, broaden the visible light response range, enhance light absorption, and improve light energy utilization; on the other hand, oxygen vacancies can serve as additional active sites, lowering the reaction energy barrier and promoting the adsorption and activation of reactants (such as O2, plastics, and dye molecules) on the material surface, thereby accelerating the surface redox reaction kinetics. Benefiting from the combined effect of the piezoelectric-photosynergistic effect and oxygen vacancy defect engineering, the material of this invention exhibits significantly improved catalytic performance in piezoelectric photocatalysis for green H2O2 production, reforming plastics to prepare high-value-added industrial raw materials, and degrading organic pollutants (such as RhB).

[0043] A third aspect of the present invention provides the above-described layered bismuth-based ferroelectric BaBi4TiTaO. 11 Cl piezoelectric photocatalysts or oxygen vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO 11 Applications of Cl piezoelectric photocatalysts include: piezoelectric photocatalytic hydrogen peroxide production, piezoelectric photocatalytic plastic reforming, and piezoelectric photocatalytic degradation of organic pollutants. Example 1: Layered bismuth-based ferroelectric BaBi4TiTaO 11 Cl (BBTT) piezoelectric photocatalyst material and its performance testing (I) Preparation method (1) Preparation of BiOCl 9.702 g of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) was dissolved in 250 mL of deionized water at room temperature to form solution A, and 1.521 g of potassium chloride (KCl) was dissolved in 250 mL of deionized water to form solution B. Solution A was slowly added dropwise to solution B under magnetic stirring, and stirring was continued for 12 h. The resulting white precipitate was centrifuged, washed three times with deionized water, and then dried under vacuum at 60 °C for 24 h to obtain flake-like BiOCl.

[0044] (2) Preparation of Bi3TiTaO9 Bi2O3 (3.507 g), Ta2O5 (1.105 g) and TiO2 (0.399 g) in stoichiometric ratio were added to a ball mill jar and ball milled for 48 h with anhydrous ethanol as the medium. The resulting slurry was dried at 80 °C, ground, and then placed in a crucible and calcined at 700 °C in air for 10 h. After cooling, it was washed 6 times with deionized water and dried to obtain Bi3TiTaO9 powder.

[0045] (3) Preparation of BaBi4TiTaO 11 Cl The prepared BiOCl (1.302 g), Bi3TiTaO9 (5.000 g), and BaCO3 (0.987 g) were mixed in stoichiometric ratio, and KCl (1.118 g) and NaCl (0.877 g) were added as molten salt medium. After thorough grinding and homogenization, the mixture was placed in a crucible and calcined at 850 °C for 12 h in air. The mixture was then repeatedly centrifuged and washed with deionized water until the conductivity of the supernatant was close to that of pure water. Finally, it was vacuum dried at 60 °C for 12 h to obtain high-purity, highly crystalline layered bismuth-based ferroelectric BaBi4TiTaO9. 11 Cl piezoelectric photocatalyst materials.

[0046] (II) Structural morphology characterization and performance testing The piezoelectric photocatalytic performance of the prepared semiconductor materials was investigated by piezoelectric photocatalysis to produce H2O2, piezoelectric photoreforming of plastics, and piezoelectric degradation of Rhodamine B.

[0047] XRD patterns are attached. Figure 1 As shown; SEM images are attached. Figure 2 As shown; The yield of H2O2 is shown in the attached figure. Figure 4 and Figure 5 As shown; The graphs showing the degradation performance of plastic reforming and Rhodamine B are attached. Figure 6 As shown.

[0048] Example 2: Oxygen-vacancy modified layered bismuth-based ferroelectric BaBi4TiTaO 11 Cl piezoelectric photocatalyst materials and their performance testing (I) Preparation method 2 ml of glyoxal aqueous solution (30 wt%) was added to 30 ml of aqueous solution containing 0.2 g of BBTT piezoelectric photocatalyst material prepared in Example 1 (the mass ratio of glyoxal to BBTT piezoelectric photocatalyst material was 3.8:1). The mixture was stirred for 4 h, transferred to a reaction vessel, and heated at 120 °C for 12 h. The resulting solid was washed several times with ethanol and then several times with deionized water to obtain the product, oxygen vacancy modified layered bismuth-based ferroelectric BaBi4TiTaO. 11 Cl piezoelectric photocatalyst material (BBTT-OV2 for short).

[0049] (II) Structural morphology characterization and performance testing XRD patterns are attached. Figure 1 As shown; SEM images are attached. Figure 3 As shown; The yield graph of H2O2 is attached. Figure 5 As shown; The graphs showing the degradation performance of plastic reforming and Rhodamine B are attached. Figure 6 As shown.

[0050] Comparative Example 1: Synthesis of BBTT piezoelectric photocatalyst material by high-temperature solid-state method and its performance testing (I) Preparation method (1) Preparation of BiOCl Same as Example 1.

[0051] (2) Preparation of Bi3TiTaO9 Same as Example 1.

[0052] (3) Preparation of BaBi4TiTaO 11 Cl The BiOCl (1.302 g), Bi3TiTaO9 (5.000 g), and BaCO3 (0.987 g) prepared above were mixed in stoichiometric ratio, ground thoroughly and uniformly, and placed in a crucible. The mixture was then calcined at 850 °C for 12 h in air. The resulting product was repeatedly centrifuged and washed with deionized water until the conductivity of the supernatant was close to that of pure water. Finally, it was vacuum dried at 60 °C for 12 h to obtain the BBTT piezoelectric photocatalyst material BBTT (abbreviated as SSR-850) synthesized by high-temperature solid-phase method.

[0053] (II) Structural morphology characterization and performance testing XRD patterns are attached. Figure 1 As shown; SEM images are attached. Figure 2 As shown; The yield graph of H2O2 is attached. Figure 4 As shown.

[0054] Comparative Example 2: Synthesis of BBTT piezoelectric photocatalyst material (MSS-750) by molten salt method at 750℃ and its performance testing (I) Preparation method The only difference from Example 1 is the calcination temperature: BaBi4TiTaO was prepared... 11 In Cl, it was calcined at 750 °C for 12 h in air.

[0055] (II) Structural morphology characterization and performance testing XRD patterns are attached. Figure 1 As shown; SEM images are attached. Figure 2 As shown; The yield graph of H2O2 is attached. Figure 4 As shown.

[0056] Comparative Example 3: Synthesis of BBTT piezoelectric photocatalyst material (MSS-950) by molten salt method at 950℃ and its performance testing (I) Preparation method The only difference from Example 1 is the calcination temperature: BaBi4TiTaO was prepared... 11 In Cl, it was calcined at 950 °C for 12 h in air.

[0057] (II) Structural morphology characterization and performance testing XRD patterns are attached. Figure 1 As shown; SEM images are attached. Figure 2 As shown; The yield graph of H2O2 is attached. Figure 4 As shown.

[0058] Comparative Example 4: Oxygen-vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO 11 Cl piezoelectric photocatalyst material (BBTT-OV1) and its performance testing (I) Preparation method The only difference from Example 2 is that the amount of glyoxal aqueous solution added is adjusted from 2 mL to 1 mL (the mass ratio of glyoxal to BBTT piezoelectric photocatalyst is 1.9:1), and the other operation steps are completely the same.

[0059] (II) Structural morphology characterization and performance testing XRD patterns are attached. Figure 1 As shown; SEM images are attached. Figure 3 As shown; The yield graph of H2O2 is attached. Figure 5 As shown.

[0060] Comparative Example 5: Oxygen-vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO 11 Cl piezoelectric photocatalyst (BBTT-OV3) and its performance testing (I) Preparation method The only difference from Example 2 is that the amount of glyoxal aqueous solution added is adjusted from 2 mL to 3 mL (the mass ratio of glyoxal to BBTT piezoelectric photocatalyst is 5.7:1), and the other operation steps are completely the same.

[0061] (II) Structural morphology characterization and performance testing XRD patterns are attached. Figure 1 As shown; SEM images are attached. Figure 3 As shown; The yield graph of H2O2 is attached. Figure 5 As shown.

[0062] The performance evaluation methods for the following embodiments and comparative examples are as follows: (1) Phase evaluation methods for the examples and comparative examples: X-ray diffraction (XRD): The crystal structure of the samples in the examples and comparative examples was analyzed using a Bruker D8 Advance series wide-angle X-ray diffractometer (Germany). The scanning speed was 5° / min and the scanning range was 10°~60°.

[0063] (2) Evaluation methods for the microstructure of the examples and comparative examples: Scanning electron microscopy (SEM): The prepared catalytic material was tested on a JEOL JSM-IT300 series scanning electron microscope in Japan, with an accelerating voltage of 5-20 kV.

[0064] (3) Evaluation method for piezoelectric photocatalytic H2O2 production performance of the examples and comparative examples: Taking the piezoelectric photocatalytic production of H2O2 by BBTT as an example, the specific process is as follows: Take 10 mg of BBTT into a three-necked quartz flask reactor, add 100 mL of deionized water to the reaction apparatus, place it in an ultrasonic cleaner, and simultaneously place it under light conditions (using a 300W xenon lamp with an AM1.5G filter, a lamp-sample distance of 20 cm, and an irradiance of 100 mW / cm²). 2 The irradiated area is 12.6 cm². 2 Under the synergistic effect of piezoelectric light and piezoelectric conditions (ultrasonic cleaner at 25±5 ℃, KQ-400DE, 40 kHz, 240 W), the reaction solution was stirred at 260 r / s. During the 60-minute reaction, 3 mL of the reaction solution was drawn every 15 minutes and immediately centrifuged to remove the catalyst. 50 μL of ammonium molybdate and 2 mL of potassium iodide were added to the solution sequentially, and after thorough mixing, the mixture was allowed to stand for 15 min to allow the sample to develop color. The maximum absorbance of the solution at 352 nm was recorded using a UV-6100 spectrophotometer. Finally, the H2O2 concentration was determined by recording the peak absorbance using a UV-Vis absorption spectrometer (Mapada UV-6100).

[0065] (4) Evaluation methods for the performance of piezoelectric photoreformed plastics in the examples and comparative examples: The piezoelectric photocatalytic reforming of waste plastics was conducted in a self-made reactor. The specific procedure was as follows: 10 mg of catalyst and 100 mg of waste plastic powder were weighed and placed in the reactor, along with 100 ml of deionized water. During the experiment, a 300 W xenon lamp was used as the light source, and a 240 W ultrasonic cleaner was used as the pressure source to maintain the reactor temperature at 25 ± 5 ℃. Gas and liquid phase samples were extracted at regular intervals during the reaction, and the concentrations of high-value-added products such as H2, CO, and acetic acid were determined using high-performance liquid chromatography and gas chromatography.

[0066] (5) Evaluation method for piezoelectric degradation performance of RhB in the examples and comparative examples: Taking the BBTT piezoelectric photodegradation of RhB as an example, the specific process is as follows: 50 ml of RhB pollutant with a concentration of 25 mg / L was added to a quartz three-necked flask, and then 10 mg of BBTT catalyst was added. The reaction system was placed in an ultrasonic cleaner with an ultrasonic power of 240W, and the stirring speed was kept at 260 r / s. Piezoelectric photodegradation was carried out under light irradiation. 3 ml of the suspension was taken and the catalyst was removed by centrifugation. The maximum absorbance value of the solution at a wavelength of 550 nm after the reaction was recorded using a UV spectrophotometer to determine the pollutant degradation status.

[0067] Analysis of results from examples and comparative examples: As attached Figure 1 As shown, in the X-ray diffraction (XRD) patterns of Examples 1-2 and Comparative Examples 2-5, all diffraction peaks correspond to the layered bismuth-based ferroelectric material BaBi4TiTaO. 11 The results show a high degree of agreement with the standard PDF card (PDF#04-026-9708) for Cl, and no obvious impurity peaks were observed. This result confirms that high-purity, highly crystalline BaBi4TiTaO can be successfully prepared using the molten salt method. 11 The Cl material was also shown to have been introduced, indicating that the introduction of surface oxygen vacancies in Examples 2, 4, and 5 did not disrupt the original crystal structure of the material. Comparison of the diffraction peak shapes of each sample revealed that Example 1 exhibited the highest diffraction peak intensity and the narrowest half-width at half-maximum (FWHM), demonstrating optimal crystallinity. In contrast, the XRD pattern of Comparative Example 1 showed an impurity peak at 29.3°, indicating that traditional high-temperature solid-state methods are prone to elemental volatilization during synthesis, making it difficult to obtain a pure phase product. The above analysis strongly confirms the significant advantages of the molten salt method used in this invention compared to traditional solid-state methods in preparing this type of material.

[0068] Through append Figure 2 and attached Figure 3The SEM morphology characterization results clearly show that different preparation methods significantly affect the microstructure of the samples. Specifically, the samples prepared by the molten salt method exhibit large-size, low-dimensional layered and lamellar structures. In contrast, the samples prepared by the high-temperature solid-state method show irregular molten structures with blurred particle boundaries and poor morphological controllability. The lamellar structures induced by the molten salt method not only have a higher specific surface area, effectively exposing more surface active sites, but also exhibit stronger stress sensitivity due to their low-dimensional structure. Under external stress, the lamellar structures can induce a stronger built-in electric field, thus providing a favorable channel for the efficient separation and migration of photogenerated carriers. Furthermore, comparing the SEM images of Example 2, Comparative Example 4, and Comparative Example 5 reveals that although these samples differ in surface oxygen vacancy concentration, their overall microstructure remains largely unchanged. This result indicates that the construction of surface oxygen vacancies mainly affects the electronic structure and surface chemical properties of the material, without significantly damaging its macroscopic or microscopic morphology.

[0069] Appendix Figure 4 The bar charts show the H2O2 yield performance of Example 1 and Comparative Examples 1-3 under different catalytic conditions. It is clear from the figures that Example 1 exhibits the best H2O2 generation activity under all three catalytic conditions: light irradiation, ultrasound, and ultrasound-light synergy. This result further confirms the dual advantages of the low-dimensional sheet structure: on the one hand, its higher specific surface area exposes more active sites, which is beneficial for improving surface reaction efficiency; on the other hand, this structure has excellent stress sensitivity, enabling it to respond more effectively to mechanical stimulation under ultrasound, thereby enhancing piezoelectric catalytic performance. It is noteworthy that although Example 1 showed the best activity under all conditions, neither Example 1 nor Comparative Examples 1-3 showed a significant synergistic enhancement effect in H2O2 yield under ultrasound-light synergy conditions, indicating that there may be a lack of an effective synergistic mechanism between the two excitation methods in this system.

[0070] As attached Figure 5As shown, the photocatalytic activity of Examples 2, 4, and 5 was significantly enhanced after the introduction of oxygen vacancies. This fully demonstrates that the introduction of oxygen vacancies can effectively broaden the light absorption range of the material, increase the number of surface active sites, and inhibit the recombination of photogenerated carriers, thereby significantly enhancing the photocatalytic performance of the material. It is noteworthy that under both pure piezoelectric catalysis and piezoelectric-photocoupled catalysis test conditions, Example 2 exhibited the best catalytic activity, far superior to Example 1 and other comparative samples with different oxygen vacancy concentrations. This result indicates that an appropriate concentration of oxygen vacancies can not only significantly enhance the piezoelectric catalytic activity of the material, but more importantly, it endows the material with a synergistic enhancement effect of piezoelectric-photocatalysis, achieving a "1+1>2" coupled catalytic effect. In summary, the above experimental results fully demonstrate that the 850 ℃ molten salt process established in this invention is suitable for preparing high-performance BaBi4TiTaO. 11 The optimal approach for Cl piezoelectric photocatalysts; simultaneously, the oxygen vacancy modification strategy can effectively overcome the limitations of BaBi4TiTaO. 11 The inherent defects of Cl materials, such as weak visible light response and weak piezoelectric-optical coupling effect, are significantly improved by overcoming these defects.

[0071] Appendix Figure 6 The results of real-world application performance tests conducted on the aforementioned optimal performance embodiment are presented. Figure 6 a is a bar chart showing the yields of H2, CH3COOH, and CO generated in the piezoelectric photocatalytic reforming reaction of plastics in Examples 1 and 2. Figure 6 Figure b shows the degradation curves of the target pollutant RhB for the two samples. It is clear from the figure that both Example 1 and Example 2 exhibit excellent piezoelectric photocatalytic performance. Specifically, both samples can efficiently catalyze the reforming of plastics into high-value-added products, demonstrating great potential for resource utilization; simultaneously, they can also achieve rapid degradation of organic pollutants such as RhB in a short time, demonstrating good water purification capabilities. The above results fully verify that the two piezoelectric photocatalytic materials prepared in this invention have good feasibility and broad application prospects in practical application scenarios.

[0072] In summary, this invention successfully achieved the preparation of BaBi4TiTaO by establishing a controllable preparation process using molten salt at 850 °C and combining it with an oxygen vacancy modification strategy. 11 The piezoelectric photocatalytic performance of Cl materials has been significantly improved. The prepared materials exhibit excellent catalytic activity and stability in the green preparation of hydrogen peroxide, the reforming of plastics into high-value-added products, and the efficient degradation of organic pollutants in water. This method has outstanding advantages such as simple preparation process, mild reaction conditions, and no need for precious metals, showing good prospects for industrial application and promotion value.

[0073] It will be readily understood by those skilled in the art that the above-described advantageous methods can be freely combined and superimposed without conflict. The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. A layered bismuth-based ferroelectric BaBi4TiTaO 11 The method for preparing Cl piezoelectric photocatalytic materials is characterized by... Includes the following steps: BiOCl, Bi3TiTaO9, and BaCO3 were mixed in stoichiometric ratio, added to a molten salt medium, ground until homogeneous, and then calcined at 840 ℃~860 ℃ for 10 h~14 h in air. The resulting product was washed and dried to obtain the layered bismuth-based ferroelectric BaBi4TiTaO9. 11 Cl piezoelectric photocatalyst materials.

2. The preparation method according to claim 1, characterized in that, The molar ratio of BiOCl, Bi3TiTaO9, BaCO3 to the molten salt medium is 1:1:1:(5.5~6.5).

3. The preparation method according to claim 1, characterized in that, The molten salt medium is KCl and / or NaCl.

4. The preparation method according to claim 1, characterized in that, The preparation method of BiOCl is as follows: Bismuth nitrate pentahydrate was dissolved in deionized water to form solution A, and potassium chloride was dissolved in deionized water to form solution B. Solution A was slowly added dropwise to solution B under magnetic stirring, and stirring was continued for 10 h to 14 h. The resulting white precipitate was centrifuged, washed with deionized water, and dried to obtain BiOCl.

5. The preparation method according to claim 4, characterized in that, The molar ratio of bismuth nitrate pentahydrate to potassium chloride is 1:(1~1.04).

6. The preparation method according to claim 1, characterized in that, The preparation method of Bi3TiTaO9 is as follows: Bi2O3, Ta2O5 and TiO2 were added to a ball mill jar and ball milled with anhydrous ethanol as the medium. The resulting mixed slurry was dried and ground, and then calcined in air at 680 ℃~720 ℃ for 8 h~12 h. After cooling, it was washed with deionized water and dried to obtain Bi3TiTaO9.

7. The preparation method according to claim 6, characterized in that, The molar ratio of Bi2O3, Ta2O5 and TiO2 is (3~3.02):1:

2.

8. An oxygen vacancy-modified layered bismuth-based ferroelectric BaBi4TiTaO 11 The method for preparing Cl piezoelectric photocatalytic materials is characterized by... The layered bismuth-based ferroelectric BaBi4TiTaO prepared by the method according to any one of claims 1-7 11 Cl piezoelectric photocatalyst material was dispersed in water, and glyoxal aqueous solution was added. The mixture was heated at 110 ℃~130 ℃ for 11 h~13 h. The resulting product was washed successively with ethanol and deionized water to obtain the oxygen vacancy modified layered bismuth-based ferroelectric BaBi4TiTaO. 11 Cl piezoelectric photocatalyst materials.

9. The preparation method according to claim 8, characterized in that, Controlling the reaction between glyoxal and the layered bismuth-based ferroelectric BaBi4TiTaO 11 The mass ratio of Cl piezoelectric photocatalyst material is (3.0~4.6):

1.

10. The layered bismuth-based ferroelectric BaBi4TiTaO prepared by the preparation method according to any one of claims 1-7 11 Cl piezoelectric photocatalyst material or the oxygen vacancy modified layered bismuth-based ferroelectric BaBi4TiTaO prepared by the preparation method according to any one of claims 8-9 11 The application of Cl piezoelectric photocatalytic materials in piezoelectric photocatalysis is characterized by, The application is at least one of the following (1)-(3): (1) Application in piezoelectric photocatalysis for hydrogen peroxide production; (2) Applications in piezoelectric photocatalytic reforming of plastics; (3) Application in piezoelectric photocatalytic degradation of organic pollutants.

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