Bismuth-based ferroelectric or piezoelectric ceramic materials with photocatalytic memory effect, their preparation methods, and their applications in the field of catalysis regulation.

Abstract

This invention discloses a bismuth-based ferroelectric or piezoelectric ceramic material with photocatalytic memory effect, its preparation method, and its application in the field of catalysis regulation, belonging to the fields of inorganic non-metallic ceramic material preparation, solar energy utilization, and environmental protection technology. This ceramic material is prepared by solid-state sintering. The synthesized ceramic exhibits a significant color change under visible light irradiation, demonstrating a clear photocatalytic memory effect. Furthermore, the ceramic powder exhibiting this memory effect can effectively improve the efficiency of photocatalysis, piezoelectric catalysis, and photo-piezoelectric synergistic catalysis in degrading antibiotics in water. This not only broadens the application fields of ceramic materials but also improves degradation efficiency through the photocatalytic memory effect, providing a more efficient material for effectively solving water pollution.

Description

Technical Field

[0001] This invention relates to the fields of inorganic non-metallic ceramic material preparation, solar energy utilization and environmental protection, specifically to a bismuth-based ferroelectric or piezoelectric ceramic material with photocatalytic memory effect, its preparation method and its application in the field of catalysis regulation. Background Technology

[0002] In recent years, photocatalytic memory effect materials have been widely used in fields such as optical information storage, optical switches, and optical temperature sensors. Common photocatalytic memory effect materials include WO3, V2O5, MoO3, and TiO2. During the memory effect process, their own metal ions capture photogenerated electrons, causing them to change color. Then, the reduced metal ions undergo an oxidation reaction with oxygen, causing them to fade, which may suppress carrier recombination. Therefore, if carrier capture and subsequent surface reactions can continue to occur and reach equilibrium under photocatalytic reaction conditions, materials with photocatalytic memory effects may be suitable for photocatalytic reactions. In other words, the search for and synthesis of photocatalytic memory effect materials with the ability to suppress carrier recombination is expected to promote the development of more efficient photocatalysts.

[0003] Studies have shown that the photocatalytic memory effect is prevalent in many ferroelectric systems (such as perovskite structures (K0)). 0.5 Na 0.5 NbO3 and Na 0.5 Bi 0.5 TiO3) or bismuth layered structure (Na) 0.5 Bi 2.5 Nb2O9 and Na 0.5 Bi 4.5 Ti4O 15 (NBT) Photocatalytic memory effect exists as photochromism in most ferroelectric systems. Researchers believe that the photochromic mechanism of inorganic materials mainly originates from cations or oxygen vacancies generated by the volatilization of alkali metal ions during high-temperature sintering. Under visible light irradiation, vacancy-related defects capture light-generated charge carriers, thereby producing color centers. However, few scholars or teams have studied whether the photochromic behavior of ferroelectric materials affects their catalytic performance. Therefore, further exploring the impact of photochromic reactions on photocatalysis and piezoelectric catalysis is of great significance for the application of photochromism in ferroelectric materials. Summary of the Invention

[0004] The purpose of this invention is to provide a bismuth-based ferroelectric or piezoelectric ceramic material with photocatalytic memory effect, its preparation method, and its application in the field of catalysis regulation. This ceramic material is prepared by high-temperature solid-state sintering. Under light irradiation, the oxygen vacancies generated during high-temperature sintering cause a color change in the material, giving it a significant photocatalytic memory effect. Bismuth-based ferroelectric or piezoelectric ceramic materials with photocatalytic memory effect (such as Bi4Ti3O) 12 and Na 0.5 Bi 0.5 TiO3 exhibits a significantly better photocatalytic degradation ability for organic pollutants than Bi4Ti3O, which does not produce a photocatalytic memory effect. 12 and Na 0.5 Bi 0.5 TiO3 ceramic materials.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A bismuth-based ferroelectric or piezoelectric ceramic material with light memory effect is a bismuth-based ferroelectric ceramic material or a bismuth-based piezoelectric ceramic material with oxygen vacancies. Under light conditions, the color of the ceramic material changes, exhibiting a significant photocatalytic memory effect.

[0007] The chemical formula for the bismuth-based ferroelectric ceramic material or bismuth-based piezoelectric ceramic material with oxygen vacancies is: (Bi2O2) 2+ (A n−1 B n O 3n+1 ) 2− , where n = 1, 2 or 3, A is one or more of the elements K, Na and Bi, and B is one or more of the elements Ti, Ta and Nb.

[0008] The surface of this ceramic material has oxygen vacancies, and the oxygen defect concentration after light exposure is higher than the oxygen vacancy concentration before light exposure, and the color changes after light exposure.

[0009] The bismuth-based ferroelectric or piezoelectric ceramic material with optical memory effect is prepared by high-temperature solid-state sintering, and the preparation method includes the following steps:

[0010] (1) Ingredients: Calculate the amount of material required for the synthesis of bismuth-based ferroelectric or piezoelectric ceramic materials according to the required mass, and then calculate the required mass of raw materials according to the stoichiometric ratio of the materials;

[0011] (2) First ball milling: Place the raw materials from step (1) into an agate ball mill jar, add agate balls, add anhydrous ethanol, and place in a ball mill for 12-24 h to obtain a slurry; wherein: the weight of the agate balls added is 1.5 to 2 times the total weight of the raw materials, and the size of the agate balls is not uniform; the volume of the anhydrous ethanol added is 1 / 2 to 3 / 4 of the volume of the ball mill jar (preferably 2 / 3 of the volume of the ball mill jar);

[0012] (3) Mixing and drying: Place the slurry obtained in step (2) into a clean evaporating dish, and place the evaporating dish in a forced-air drying oven at 60-90℃ for 5-6 hours to obtain powder;

[0013] (4) Pre-firing: Place the powder obtained in step (3) in an agate mortar and grind it into fine powder. Then place it in a clean alumina crucible and pre-fire it in a muffle furnace at 850-900℃ for 3-4 hours.

[0014] (5) Secondary ball milling: The powder obtained after pre-firing in step (4) is placed in an agate mortar for grinding, and the powder is placed back into the ball mill jar for ball milling in the manner of step (2), and then dried.

[0015] (6) Sintering: The powder obtained after ball milling in step (5) is sintered in a muffle furnace at 1080-1150℃ for 2-4 h;

[0016] (7) Three ball milling: The ceramic block obtained after sintering in step (6) is further ball milled in the manner of step (2). The powder obtained after ball milling is dried at 60-90℃ to obtain the desired ceramic powder material.

[0017] In step (1) above, when preparing Bi4Ti3O 12 When preparing ceramic materials, the raw materials are BiO2 and TiO2. When preparing Na... 0.5 Bi 0.5 When making TiO3 ceramic materials, the raw materials are BiO2, TiO2, and Na2CO3.

[0018] In step (4) above, the pre-firing temperature determines whether the material can form the main crystalline phase, and in step (6) the sintering temperature determines the purity of the material.

[0019] During the high-temperature sintering process of step (6) above, the volatilization of alkali metal ions leads to the formation of oxygen vacancies on the surface of the material. Due to the generation of oxygen vacancies, the ceramic material will change color after light irradiation.

[0020] The bismuth-based ferroelectric or piezoelectric ceramic material with photocatalytic memory effect can be used as a catalyst for degrading organic pollutants in water. The application process is as follows: under light conditions, the ceramic material is first made to change color. The material that has changed color is placed in an aqueous solution containing organic pollutants. Then, under light, ultrasound, or light combined with ultrasound conditions for 10-60 minutes, the organic pollutants are degraded into carbon dioxide and water that are beneficial to the environment.

[0021] Ceramic materials that change color under light conditions exhibit better performance in catalytically degrading organic pollutants than those that do not change color before light exposure.

[0022] The design mechanism of this invention is as follows:

[0023] In this invention, during the preparation of ceramic powder using a high-temperature solid-state sintering method, the high temperature causes alkali metal ions in the ceramic material to volatilize, thereby forming cation or oxygen defects. Under visible light irradiation, these defects capture photogenerated charge carriers and form color centers on the material surface, thus generating a photocatalytic memory effect. Therefore, ceramic materials exhibiting this photocatalytic memory effect can effectively promote the separation of photogenerated charge carriers, and the defect concentration in these materials is further increased, thereby improving charge separation efficiency. This further contributes to improving the performance of photocatalytic, piezoelectric, and photo-piezoelectric synergistic catalytic degradation of organic pollutants.

[0024] The advantages of this invention are:

[0025] 1. This invention utilizes a relatively simple high-temperature solid-state sintering method to prepare bismuth-based ferroelectric or piezoelectric ceramic materials with photocatalytic memory effect. The samples prepared by this method are low in cost, have long stability, are beneficial for long-term photocatalytic reactions, and exhibit stable performance in practical applications.

[0026] 2. The bismuth-based ferroelectric or piezoelectric ceramic materials prepared by solid-state sintering in this invention not only possess inherent defects, but also exhibit an increased defect concentration after photocatalytic memory effect. By utilizing the generated new defects as accelerated charge separation centers, the charge separation efficiency is improved, thereby enhancing the performance of the ceramic powder in degrading organic pollutants.

[0027] 3. The bismuth-based ferroelectric or piezoelectric ceramic materials prepared in this invention exhibit better performance in photocatalytic, piezoelectric, and photo-piezoelectric synergistic catalytic degradation of organic pollutants after light irradiation than the samples before light irradiation. Attached Figure Description

[0028] Figure 1 Bi4Ti3O prepared in Example 1 12 and Na 0.5 Bi 0.5 X-ray diffraction pattern of TiO3 ceramic powder; where: (a) Bi4Ti3O12 (b) Na 0.5 Bi 0.5 TiO3.

[0029] Figure 2 Bi4Ti3O in Example 1 12 and Na 0.5 Bi 0.5 TEM image of TiO3 ceramic powder; where: (a) Bi4Ti3O 12 (b) Na 0.5 Bi 0.5 TiO3.

[0030] Figure 3 Bi4Ti3O3 after exposure to light and after exposure to light in Comparative Example 1 and Example 2 12 and Na 0.5 Bi 0.5 Comparative figures of TiO3 photocatalytic degradation of tetracycline hydrochloride; where: (a) Comparative Example 1; (b) Example 2.

[0031] Figure 4 Bi4Ti3O3 after exposure to light and after exposure to light in Comparative Example 1 and Example 2 12 and Na 0.5 Bi 0.5 Comparative figures of TiO3 piezoelectric catalytic degradation of tetracycline hydrochloride; where: (a) Comparative Example 1; (b) Example 2.

[0032] Figure 5 Bi4Ti3O3 after exposure to light and after exposure to light in Comparative Example 1 and Example 2 12 and Na 0.5 Bi 0.5 Comparative figures of TiO3 photo-pressure synergistic catalytic degradation of tetracycline hydrochloride; where: (a) Comparative Example 1; (b) Example 2. Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] This invention provides a bismuth-based ferroelectric or piezoelectric ceramic material with photocatalytic memory effect, prepared by high-temperature solid-state sintering. Under light irradiation, the ceramic material undergoes discoloration and the oxygen vacancy defects on its surface increase significantly, thereby improving its photocatalytic, piezoelectric, and photo-piezoelectric synergistic catalytic degradation performance of tetracycline hydrochloride.

[0035] The aforementioned bismuth-based ferroelectric or piezoelectric ceramic materials with photocatalytic memory effect (such as Bi4Ti3O) 12 and Na 0.5 Bi 0.5The memory effect of TiO3 refers to the fact that ceramic materials can accumulate photogenerated electrons on their surface under light conditions, and can still release and generate active groups (photogenerated electrons) after the light is turned off.

[0036] The bismuth-based ferroelectric or piezoelectric ceramic materials (such as Bi4Ti3O) prepared by this invention 12 and Na 0.5 Bi 0.5 Bismuth-based ferroelectric or piezoelectric ceramic materials (such as Bi4Ti3O4) are used as catalysts for the photocatalytic, piezoelectric, and photo-piezoelectric synergistic degradation of tetracycline hydrochloride. The application process of this photocatalyst involves applying a light-sensitive, color-changing bismuth-based ferroelectric or piezoelectric ceramic material (such as Bi4Ti3O4) to the photocatalyst. 12 Or Na 0.5 Bi 0.5 TiO3 was placed in an aqueous solution containing tetracycline hydrochloride and subjected to light, ultrasound, or both light and ultrasound for 2-24 hours to degrade the tetracycline hydrochloride into carbon dioxide and water. Example

[0037] In this embodiment, Bi4Ti3O with oxygen vacancies was prepared. 12 and Na 0.5 Bi 0.5 The specific process for producing TiO3 ceramic powder is as follows:

[0038] (1) Ingredients: According to the required Bi4Ti3O 12 and Na 0.5 Bi 0.5 The mass of TiO3 is used to calculate the required amount of material for synthesis. Then, based on the stoichiometric ratio of the materials, the required mass of raw materials is calculated, where: Bi4Ti3O 12 The raw materials are BiO2 and TiO2, Na 0.5 Bi 0.5 The raw materials for TiO3 are BiO2, TiO2 and Na2CO3.

[0039] (2) First ball milling: Place the raw material mentioned in step (1) into an agate ball milling jar, add agate balls of different sizes that are 1.5 to 2 times the total mass of the raw material, add anhydrous ethanol that is 2 / 3 the volume of the ball milling jar, and put it into a ball mill for 20 hours.

[0040] (3) Mixing and drying: Place the slurry obtained in step (2) into a clean evaporating dish, and then place the evaporating dish in a forced-air drying oven at 80°C for 5 hours.

[0041] (4) Pre-firing: Place the powder obtained in step (3) into an agate mortar and grind it into fine powder. Then place it in a clean alumina crucible and pre-fire it in a muffle furnace at 880°C for 3.5 hours.

[0042] (5) Secondary ball milling: The powder obtained in step (4) is placed in an agate mortar for grinding, and the powder is placed back into the ball mill jar for ball milling in the manner of step (2). After ball milling, the material is discharged and dried.

[0043] (6) Sintering: The powder obtained in step (5) is sintered in a muffle furnace at 1100°C for 2.5 h.

[0044] (7) Three-stage ball milling: The ceramic block obtained in step (6) is further ball milled according to step (2), and then dried at the temperature of step (3) to obtain the desired ceramic powder material.

[0045] Figure 1 (a) and Figure 1 (b) Bi4Ti3O obtained in step (7) of this embodiment. 12 and Na 0.5 Bi 0.5 XRD patterns of TiO3 ceramic powder before and after light irradiation. This shows the difference in Bi4Ti3O before and after light irradiation. 12 and Na 0.5 Bi 0.5 TiO3 ceramic powder was reacted with hexagonal Bi4Ti3O3. 12 (JCPDS card number 89-7500) and cubic Na 0.5 Bi 0.5 TiO3 (JCPDS card number 89-3109) showed a good match, with no obvious impurities, indicating that the synthesized Bi4Ti3O 12 and Na 0.5 Bi 0.5 TiO3 ceramic powder has high purity.

[0046] Figure 2 (a) and Figure 2 (b) Bi4Ti3O prepared in step (7) of this embodiment. 12 and Na 0.5 Bi 0.5 TEM image of TiO3 ceramic powder. It can be seen that the prepared Bi4Ti3O 12 and Na 0.5 Bi 0.5 TiO3 ceramic powder is an irregular block.

[0047] Comparative Example 1:

[0048] The photocatalytic degradation of 10 mg / L tetracycline hydrochloride was carried out using the catalytic material prepared in Example 1. The specific process is as follows:

[0049] 1. The Bi4Ti3O prepared in Example 1 was separately... 12 and Na 0.5 Bi0.5 TiO3 ceramic powder was added directly to 10 mg / L tetracycline hydrochloride without light exposure, and the mixture was adsorbed in the dark for 15-30 min to obtain the reaction solution.

[0050] 2. Irradiate the reaction solution prepared above with a xenon lamp for 30 min-120 min.

[0051] Comparative Example 2

[0052] The piezoelectric catalytic degradation of 10 mg / L tetracycline hydrochloride was performed using the catalytic material prepared in Example 1. The specific process is as follows:

[0053] 1. The Bi4Ti3O prepared in Example 1 was separately... 12 and Na 0.5 Bi 0.5 TiO3 ceramic powder was added directly to 10 mg / L tetracycline hydrochloride without light exposure, and the mixture was adsorbed in the dark for 15-30 minutes to obtain the reaction solution.

[0054] 2. The reaction solution prepared above is sonicated for 30 min-120 min.

[0055] Comparative Example 3

[0056] The photo-pressure synergistic catalytic degradation of 10 mg / L tetracycline hydrochloride was carried out using the catalytic material prepared in Example 1. The specific process is as follows:

[0057] 1. The Bi4Ti3O prepared in Example 1 was separately... 12 and Na 0.5 Bi 0.5 TiO3 ceramic powder was added directly to 10 mg / L tetracycline hydrochloride without light exposure, and the mixture was adsorbed in the dark for 15-30 minutes to obtain the reaction solution.

[0058] 2. The reaction solution prepared above is subjected to light and ultrasound simultaneously for 30 min to 120 min. Example

[0059] 1. The Bi4Ti3O prepared in Example 1 12 and Na 0.5 Bi 0.5 TiO3 ceramic powders were irradiated to induce a photocatalytic memory effect, and then added to 10 mg / L tetracycline hydrochloride for dark adsorption for 15-30 min to obtain a reaction solution.

[0060] 2. Irradiate the reaction solution prepared above with a xenon lamp for 30 min-120 min. Example

[0061] 1. The Bi4Ti3O prepared in Example 1 12 and Na 0.5 Bi 0.5 TiO3 ceramic powders were irradiated to induce a photocatalytic memory effect, and then added to 10 mg / L tetracycline hydrochloride for dark adsorption for 15-30 min to obtain a reaction solution.

[0062] 2. The reaction solution prepared above is subjected to ultrasound for 30 min-120 min. Example

[0063] 1. The Bi4Ti3O prepared in Example 1 12 and Na 0.5 Bi 0.5 TiO3 ceramic powders were irradiated to induce a photocatalytic memory effect, and then added to 10 mg / L tetracycline hydrochloride for dark adsorption for 15-30 min to obtain a reaction solution.

[0064] 2. The reaction solution prepared above is subjected to a combination of xenon lamp and ultrasound for 30-120 minutes.

[0065] Figure 3 Bi4Ti3O in Comparative Example 1 and Example 2 12 and Na 0.5 Bi 0.5 The graph shows the photocatalytic degradation performance of TiO3 ceramic powder without light exposure and after light exposure and color change, followed by photocatalytic degradation of 10 mg / L tetracycline hydrochloride. The graph shows that the degradation performance of the sample after light exposure (Example 2) is higher than that of the sample without light exposure (Comparative Example 1).

[0066] Figure 4 Bi4Ti3O in Comparative Example 2 and Example 3 12 and Na 0.5 Bi 0.5 The graph shows the performance of TiO3 ceramic powder in photocatalytic reaction without light exposure and in piezoelectric catalytic degradation of 10 mg / L tetracycline hydrochloride after light exposure and color change. The graph shows that the degradation performance of the sample after light exposure (Example 3) is higher than that of the sample without light exposure (Comparative Example 2).

[0067] Figure 5 Bi4Ti3O in Comparative Example 3 and Example 4 12 and Na 0.5 Bi 0.5The graph shows the performance of TiO3 ceramic powder in photocatalytic reaction without light exposure and in photo-piezoelectric synergistic catalytic degradation of 10 mg / L tetracycline hydrochloride after light exposure and color change. The graph shows that the degradation performance of the sample after light exposure (Example 4) is higher than that of the sample without light exposure (Comparative Example 3).

Claims

1. An application of a bismuth-based ferroelectric ceramic material with photocatalytic memory effect, characterized in that: The ceramic material is a bismuth-based ferroelectric ceramic material with oxygen vacancies. Under visible light irradiation, the color of the ceramic material changes, exhibiting a significant photocatalytic memory effect. The chemical formula for the bismuth-based ferroelectric ceramic material with oxygen vacancies is Bi4Ti3O. 12 Or Na 0.5 Bi 0.5 TiO3; The surface of this ceramic material has oxygen vacancies, and the oxygen defect concentration after visible light irradiation is higher than the oxygen vacancy concentration before visible light irradiation, and the color changes after visible light irradiation. This ceramic material can be used as a catalyst for degrading organic pollutants in water. The application process is as follows: under visible light irradiation, the ceramic material is first made to change color. The material that has changed color is placed in an aqueous solution containing organic pollutants. Then, under visible light irradiation, ultrasound, or visible light irradiation combined with ultrasound for 10-60 minutes, the organic pollutants are degraded into environmentally friendly carbon dioxide and water. The organic pollutant is tetracycline hydrochloride. Ceramic materials that change color under visible light irradiation exhibit better performance in catalytically degrading organic pollutants than those that do not change color before visible light irradiation.

2. The application of the bismuth-based ferroelectric ceramic material with photocatalytic memory effect according to claim 1, characterized in that: Bismuth-based ferroelectric ceramic materials with abundant oxygen vacancies were prepared by high-temperature solid-state sintering.

3. The application of the bismuth-based ferroelectric ceramic material with photocatalytic memory effect according to claim 2, characterized in that: The method for preparing this ceramic material includes the following steps: (1) Batching: Calculate the mass of each raw material required for the synthesis of the ceramic material based on the mass of bismuth-based ferroelectric ceramic material to be prepared; (2) First ball milling: Place the raw materials from step (1) into an agate ball mill jar, add agate balls, add anhydrous ethanol, and put it into a ball mill for 12-24 h to obtain a slurry; wherein: the weight of the agate balls added is 1.5 to 2 times the total weight of the raw materials, and the size of the agate balls is not uniform; the volume of the anhydrous ethanol added is 1 / 2 to 3 / 4 of the volume of the ball mill jar; (3) Mixing and drying: Place the slurry obtained in step (2) into a clean evaporating dish, and place the evaporating dish in a forced-air drying oven at 60-90℃ for 5-6 hours to obtain powder; (4) Pre-firing: Place the powder obtained in step (3) in an agate mortar and grind it into fine powder. Then place it in a clean alumina crucible and pre-fire it in a muffle furnace at 850-900℃ for 3-4 hours. (5) Secondary ball milling: The powder obtained after pre-firing in step (4) is placed in an agate mortar for grinding, and the powder is placed back into the ball mill jar for ball milling in the manner of step (2), and then dried. (6) Sintering: The powder obtained after ball milling in step (5) is sintered in a muffle furnace at 1080-1150℃ for 2-4 h; (7) Three ball milling: The ceramic block obtained after sintering in step (6) is further ball milled in the manner of step (2). The powder obtained after ball milling is dried at 60-90℃ to obtain the desired ceramic powder material.

4. The application of the bismuth-based ferroelectric ceramic material with photocatalytic memory effect according to claim 3, characterized in that: In step (1), when preparing Bi4Ti3O 12 When preparing ceramic materials, the raw materials are BiO2 and TiO2. When preparing Na... 0.5 Bi 0.5 When making TiO3 ceramic materials, the raw materials are BiO2, TiO2, and Na2CO3.

Images