阅读说明：本技术 一种高暴露{001}晶面钛铌酸铋纳米片压电催化剂及其制备方法和应用 (High-exposure {001} crystal face bismuth niobate titanate nanosheet piezoelectric catalyst and preparation method and application thereof ) 是由 崔永飞 张黄涵 王锋辉 郭鹏 于 2021-10-13 设计创作，主要内容包括：本发明公开了一种高暴露{001}晶面钛铌酸铋纳米片压电催化剂及其制备方法和应用,以Bi-(2)O-(3)、TiO-(2)、Nb-(2)O-(5)为原料,以NaCl、KCl为熔盐混合后进行球磨,将球磨后所得的粉体干燥后通过熔盐反应,得到的产物经洗涤干燥后得到高暴露{001}晶面钛铌酸铋纳米片压电催化剂Bi-(3)TiNbO-(9),并成功应用于压电催化降解罗丹明B。本发明制备得到纯度高、结晶性好、高暴露{001}晶面纳米片,高活性暴露面有利于提高光生电荷的传输与分离,提高Bi-(3)TiNbO-(9)的压电催化性能,且制备工艺简单。(The invention discloses a high-exposure {001} crystal face bismuth niobate titanate nanosheet piezoelectric catalyst, and a preparation method and application thereof, wherein Bi is used 2 O 3 、TiO 2 、Nb 2 O 5 Taking NaCl and KCl as molten salts as raw materials, mixing, performing ball milling, drying powder obtained after ball milling, performing molten salt reaction, washing and drying the obtained product to obtain the high-exposure {001} crystal face bismuth titanate niobate nanosheet piezoelectric catalyst Bi 3 TiNbO 9 And is successfully applied to the piezoelectric catalytic degradation of rhodamine B. The nanosheet with the high-purity {001} crystal face, good crystallinity and high exposure is prepared, and the high-activity exposure face is beneficial to improving the transmission and separation of photo-generated charges and improving Bi 3 TiNbO 9 The piezoelectric catalyst has good piezoelectric catalytic performance and simple preparation process.)

1. The preparation method of the high-exposure {001} crystal face bismuth niobate titanate nanosheet piezoelectric catalyst is characterized by using Bi₂O₃、TiO₂、Nb₂O₅Taking NaCl and KCl as molten salts as raw materials, mixing, performing ball milling, drying powder obtained after ball milling, performing molten salt reaction, washing and drying the obtained product to obtain the high-exposure {001} crystal face bismuth titanate niobate nanosheet piezoelectric catalyst Bi₃TiNbO₉。

2. The preparation method of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst according to claim 1, wherein the temperature of the molten salt reaction is 750-850 ℃ and the time is 1-4 h.

3. The preparation method of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst as claimed in claim 2, wherein the temperature rise speed is controlled to be 5 ℃/min in the temperature rise process of the molten salt reaction, and the temperature is reduced to 500 ℃ at the speed of 5 ℃/min in the temperature reduction process and then is reduced to room temperature along with the furnace.

4. The preparation method of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst according to claim 1, wherein the Bi is Bi₂O₃、TiO₂And Nb₂O₅In a molar ratio of 3: 2: 1.

5. the preparation method of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst according to claim 1, wherein the NaCl, the KCl and the Bi are₃TiNbO₉The molar ratio of 50: 50: 1.

6. the preparation method of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst according to claim 1, wherein the ball milling specifically comprises: adding Bi₂O₃、TiO₂、Nb₂O₅And NaCl and KCl are put into a ball milling tank, and then ball stones and absolute ethyl alcohol are added into the ball milling tank for ball milling for 4 hours.

7. The preparation method of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst according to claim 1, wherein the washing specifically comprises: washed several times with deionized water under magnetic stirring at 500 rpm.

8. The preparation method of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst according to claim 7, wherein the product is washed and then dried at 60 ℃ for 12 hours.

9. A high-exposure {001} crystal face bismuth niobate titanate nanosheet piezoelectric catalyst is characterized by being prepared by the preparation method of any one of claims 1-8.

10. The application of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst in degrading the organic dye rhodamine B as claimed in claim 9, wherein the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst is added into the organic dye rhodamine B under the drive of ultrasonic waves, so that the concentration of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst is 1mg/1ml, and the frequency of the ultrasonic waves is 40 kHz.

Technical Field

The invention relates to the technical field of catalytic materials, and particularly relates to a high-exposure {001} crystal face bismuth niobate titanate nanosheet piezoelectric catalyst, a preparation method thereof and application of the piezoelectric catalyst in degrading an organic dye rhodamine B.

Background

With the rapid development of modern industry, the problem of water pollution caused by industrial wastewater discharge is becoming more and more serious, especially the industrial wastewater discharge industry in China is centralized and belongs to the industry with heavy water pollution, and wastewater in the industries of papermaking, metallurgy, leather, pharmacy, textile and the like contains water pollutants with various components. Among them, the colored dye accounts for a large proportion, while rhodamine B is an organic dye with wide application, and effective treatment and degradation of the dye are still one of the problems to be solved.

At present, the treatment technology of the organic dye mainly comprises physical adsorption, chemical oxidation, biological classification and the like. Compared with the prior art, the piezoelectric catalysis technology can utilize the piezoelectric material to generate electrons, holes and active free radicals under the drive of sound waves, effectively finish water cracking, organic matter degradation and the like, and has the advantages of mild operation conditions, no toxicity, no harm, economy, high efficiency, difficulty in causing no secondary pollution and the like. The technology can fully utilize mechanical vibration widely existing in nature, such as sound, water wave and the like, and realize energy conversion. Meanwhile, the piezoelectric catalysis technology overcomes the defects that the photocatalysis technology is easily irradiated by sunlight and is limited by weather and daytime, and the like, and is expected to become a new technology for realizing efficient green degradation of organic dyes in the future.

With the ZnO and BaTiO reported at present₃Bismuth titanium niobate (Bi) is comparable to that of the piezoelectric catalytic material₃TiNbO₉) The bismuth-layered ferroelectric material belongs to the Olives system, and the typical bismuth-layered structure and ferroelectric built-in electric field of the bismuth-layered ferroelectric material can effectively drive the catalytic reaction. In addition, because of the properties of good fatigue property, small leakage current, higher Curie temperature, low dielectric constant, high resistivity, low sintering temperature and the like, Bi₃TiNbO₉Are also commonly used as high temperature piezoelectric materials. Take the above into considerationTwo points, Bi₃TiNbO₉Is expected to show strong application prospect in the field of piezoelectric catalysis.

At present, researchers have prepared Bi with different shapes and different particle sizes by methods such as a solid-phase reaction method, a sol-gel method and the like₃TiNbO₉And (3) sampling. It has been found that for a typical bismuth layer structure, the {001} crystal face thereof is an active face, and thus Bi highly exposing the {001} crystal face is obtained₃TiNbO₉The nano-sheet is an effective way for further improving the catalytic efficiency. Currently prepared Bi exposing specific crystal faces₃TiNbO₉The two-step molten salt method adopted by the nanosheets needs dangerous drugs such as nitric acid, strong ammonia water and the like to prepare precursors, and the preparation process has dangerous factors, is complicated in steps and is not suitable for large-scale production.

Disclosure of Invention

The invention aims to provide a high-exposure {001} crystal face bismuth niobate titanate nanosheet piezoelectric catalyst, and a preparation method and application thereof. The nanosheet with the high-purity {001} crystal face, good crystallinity and high exposure is prepared, and the high-activity exposure face is beneficial to improving the transmission and separation of photo-generated charges, so that the Bi is improved₃TiNbO₉The material has the piezoelectric catalysis performance, is successfully applied to degrading the organic dye rhodamine B, and has simple preparation process.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of a high-exposure {001} crystal face bismuth niobate titanate nanosheet piezoelectric catalyst uses Bi₂O₃、TiO₂、Nb₂O₅Taking NaCl and KCl as molten salts as raw materials, mixing, performing ball milling, drying powder obtained after ball milling, performing molten salt reaction, washing and drying the obtained product to obtain the high-exposure {001} crystal face bismuth titanate niobate nanosheet piezoelectric catalyst Bi₃TiNbO₉。

Further, the temperature of the molten salt reaction is 750-850 ℃, and the time is 1-4 h.

Further, the temperature rise speed is controlled to be 5 ℃/min in the temperature rise process of the molten salt reaction, and the temperature is reduced to 500 ℃ at the speed of 5 ℃/min in the temperature reduction process and then is reduced to room temperature along with the furnace.

Further, said Bi₂O₃、TiO₂And Nb₂O₅In a molar ratio of 3: 2: 1.

further, the NaCl, KCl and Bi₃TiNbO₉The molar ratio of 50: 50: 1.

further, the ball milling is specifically as follows: adding Bi₂O₃、TiO₂、Nb₂O₅And NaCl and KCl are put into a ball milling tank, and then ball stones and absolute ethyl alcohol are added into the ball milling tank for ball milling for 4 hours.

Further, the washing is specifically: washed several times with deionized water under magnetic stirring at 500 rpm.

Further, the product was washed and dried at 60 ℃ for 12 hours.

The high-exposure {001} crystal face bismuth niobate titanate nanosheet piezoelectric catalyst is prepared by adopting the preparation method.

The application of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst in degrading the organic dye rhodamine B is characterized in that the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst is added into the organic dye rhodamine B under the drive of ultrasonic waves, so that the concentration of the high-exposure {001} crystal face bismuth niobate nanosheet piezoelectric catalyst is 1mg/1ml, and the frequency of ultrasonic waves is 40 kHz.

Compared with the prior art, the invention has the following beneficial technical effects:

in the two-step molten salt method adopted in the prior art, dangerous medicines such as nitric acid, strong ammonia water and the like are required to be used in advance to dissolve raw materials such as niobium oxide, bismuth nitrate and the like to prepare a precursor, the invention adopts the one-step molten salt method, directly adopts titanium dioxide, bismuth oxide and niobium oxide as a titanium source, a bismuth source and a niobium source, and realizes the preparation of the high-purity and high-exposure {001} crystal face bismuth niobate nano-sheet by regulating and controlling the reaction temperature and time of molten salt, the molar ratio of the raw materials to the molten salt and the like; the use of dangerous medicines such as nitric acid, strong ammonia water and the like in the prior art is avoided, and meanwhile, titanium dioxide and bismuth oxide with lower cost are adopted to replace tetrabutyl titanate and bismuth nitrate, so that the cost can be saved, the preparation process is simple, the yield is high, and the large-scale production is facilitated. In addition, the molten salt method can effectively control the size and the shape of crystal grains, the fluidity of the molten salt medium is good, a liquid environment required by the growth of the nano material with specific orientation can be provided, the high-purity and good-crystallinity bismuth titanium niobate nanosheet piezoelectric catalyst with a high-exposure {001} crystal face can be obtained, the nanosheet has high transmission and separation efficiency and piezoelectric performance of photo-generated electrons, and under the action of ultrasound, electrons, holes and active free radicals can be effectively generated, so that organic pollutants can be effectively degraded.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 shows Bi prepared at different molten salt reaction temperatures₃TiNbO₉XRD spectrum of the powder;

FIG. 2 shows Bi obtained by reacting different molten salts at different reaction temperatures for 2h₃TiNbO₉Powder SEM (scanning electron microscope) photograph, a: 750 ℃ (5000 times); b: 750 ℃ (10000 times); c: 800 ℃ (6000 times); d: 750 ℃ (10000 times); e: 850 ℃ (5000 times); f: 850 ℃ (10000 times);

FIG. 3 shows Bi produced by different molten salt reaction times₃TiNbO₉XRD spectrum of the powder;

FIG. 4 shows Bi prepared with different molten salt reaction times at 800 deg.C₃TiNbO₉Powder SEM photograph, a: 1h multiplied by 5000; b: 1h is multiplied by 10000; c: 2h multiplied by 6000; d: 2h is multiplied by 10000; e: 3h multiplied by 6000; f: 3h is multiplied by 10000; g: 4h multiplied by 5000; h: 4h is multiplied by 10000;

FIG. 5 shows Bi prepared at a molten salt reaction temperature of 800 ℃ for a reaction time of 2h₃TiNbO₉HRTEM photograph of the powder;

FIG. 6 shows Bi prepared at a molten salt reaction temperature of 800 ℃ for a reaction time of 2h₃TiNbO₉The powder degrades the curve of rhodamine B under the action of ultrasound.

Detailed Description

The present invention is described in detail below:

a preparation method of a piezoelectric catalyst of a high-exposure {001} crystal face bismuth niobate titanate nanosheet comprises the following steps:

with Bi₂O₃、TiO₂、Nb₂O₅Taking NaCl and KCl as molten salt as raw materials, wherein the mol ratio of NaCl: KCl: bi₃TiNbO₉50: 50: 1, preparing the materials. Putting the raw materials with the corresponding stoichiometric ratio into a ball milling tank, then adding a proper amount of ball stone and 50ml of absolute ethyl alcohol into the ball milling tank, carrying out ball milling for 4 hours, taking out, drying in an oven, grinding powder particles into small particles by using a mortar, and putting the small particles into a muffle furnace. During reaction, the muffle furnace is heated to the highest temperature at the speed of 5 ℃/min, the temperature is kept for 1-4 h at the temperature of 750-850 ℃, the temperature is reduced at the speed of 5 ℃/min during temperature reduction, and the temperature is reduced to the room temperature along with the furnace temperature reduction after the temperature is reduced to 500 ℃. After the temperature reduction is finished, washing is carried out by using deionized water under the condition of magnetic stirring at 500rpm, and the washing is repeated for three to four times. Adding deionized water after washing, centrifuging at 10000 rpm for 5min, dripping the supernatant into AgNO₃In the solution, if no white precipitate exists, the molten salt in the powder is cleaned, and if the white precipitate exists, the water is continuously changed for centrifugation until no white precipitate exists. Finally, the prepared Bi is dried in an oven₃TiNbO₉And (5) drying the powder.

When the piezoelectric catalyst of the bismuth niobate titanate nanosheets with the high-exposure {001} crystal faces prepared by the method is used for degrading the rhodamine B organic dye, 50mgBi is added₃TiNbO₉Added to 50ml of rhodamine B solution (concentration of 10ppm), and stirred under dark conditions for 1 hour to reach adsorption-desorption equilibrium. The reactor was then placed in an ultrasonic cleaner and covered with aluminum foil paper to ensure that the powder and solution were left in complete darkness. The piezoelectric catalytic reaction is carried out at the ultrasonic frequency of 40kHz, and the water temperature is controlled at 25 ℃ in the whole reaction process by using cooling circulating water. Taking 3ml of liquid every 20 minutes, and representing the concentration change of rhodamine B by using an ultraviolet-visible spectrophotometer after centrifugal filtration.

The present invention will be described in detail with reference to examples. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

The following detailed description is illustrative of the embodiments and is intended to provide further details of the invention. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention.

Example 1

Preparing high-exposure {001} crystal face bismuth titanate niobate Bi by adopting molten salt growth method₃TiNbO₉The nanosheet is prepared by reacting a molten salt at 750 ℃ for 2h, and specifically operating the steps as follows:

with Bi₂O₃、TiO₂、Nb₂O is taken as a raw material, NaCl and KCl are taken as molten salts, and the molar ratio of NaCl: KCl: bi₃TiNbO₉50: 50: 1, preparing the materials. Putting the raw materials with the corresponding stoichiometric ratio into a ball milling tank, then adding a proper amount of ball stone and 50ml of absolute ethyl alcohol into the ball milling tank, carrying out ball milling for 4 hours, taking out, drying in an oven, grinding powder particles into small particles by using a mortar, and putting the small particles into a muffle furnace. During reaction, the muffle furnace is heated to 750 ℃ at the speed of 5 ℃/min and is kept warm for 2h, and the muffle furnace is cooled to 500 ℃ at the speed of 5 ℃/min and then is cooled to room temperature along with the muffle furnace. After the temperature reduction is finished, the salt is washed by deionized water under the condition of magnetic stirring at 500rpm, and the steps are repeated for three to four times. Adding deionized water after washing, centrifuging at 10000 rpm for 5min, dripping the supernatant into AgNO₃In the solution, if no white precipitate exists, the molten salt in the powder is cleaned, and if the white precipitate exists, the water is continuously changed for centrifugation until no white precipitate exists. Finally, the prepared Bi is dried in an oven₃TiNbO₉Drying the powder for 12h at 60 ℃.

Example 2

Preparation of high-purity sodium silicate by molten salt methodBismuth niobate titanate Bi with exposed {001} crystal face₃TiNbO₉The nanosheet is prepared by reacting molten salt at 800 ℃ for 2h, and specifically operating the following steps:

with Bi₂O₃、TiO₂、Nb₂O₅Taking NaCl and KCl as molten salt as raw materials, wherein the mol ratio of NaCl: KCl: bi₃TiNbO₉50: 50: 1, preparing the materials. Putting the raw materials with the corresponding stoichiometric ratio into a ball milling tank, then adding a proper amount of ball stone and 50ml of absolute ethyl alcohol into the ball milling tank, carrying out ball milling for 4 hours, taking out, drying in an oven, grinding powder particles into small particles by using a mortar, and putting the small particles into a muffle furnace. During reaction, the temperature of the muffle furnace is raised to 800 ℃ at the speed of 5 ℃/min and is kept for 2h, and the temperature is lowered to 500 ℃ at the speed of 5 ℃/min and then is lowered to room temperature along with the furnace. After the temperature reduction is finished, the salt is washed by deionized water under the condition of magnetic stirring at 500rpm, and the steps are repeated for three to four times. Adding deionized water after washing, centrifuging at 10000 rpm for 5min, dripping the supernatant into AgNO₃In the solution, if no white precipitate exists, the molten salt in the powder is cleaned, and if the white precipitate exists, the water is continuously changed for centrifugation until no white precipitate exists. Finally, the prepared Bi is dried in an oven₃TiNbO₉Drying the powder for 12h at 60 ℃.

Example 3

Preparing high-exposure {001} crystal face bismuth titanate niobate Bi by adopting molten salt growth method₃TiNbO₉The nanosheet is prepared by reacting molten salt at 850 ℃ for 2h, and specifically operating the steps as follows:

with Bi₂O₃、TiO₂、Nb₂O₅Taking NaCl and KCl as molten salt as raw materials, wherein the mol ratio of NaCl: KCl: bi₃TiNbO₉50: 50: 1, preparing the materials. Putting the raw materials with the corresponding stoichiometric ratio into a ball milling tank, then adding a proper amount of ball stone and 50ml of absolute ethyl alcohol into the ball milling tank, carrying out ball milling for 4 hours, taking out, drying in an oven, grinding powder particles into small particles by using a mortar, and putting the small particles into a muffle furnace. During the reaction, the muffle furnace is heated to 850 ℃ at the speed of 5 ℃/min and is kept warm for 2h, and the temperature is reducedThe temperature is reduced to 500 ℃ at the speed of 5 ℃/min and then is reduced to room temperature along with the furnace. After the temperature reduction is finished, the salt is washed by deionized water under the condition of magnetic stirring at 500rpm, and the steps are repeated for three to four times. Adding deionized water after washing, centrifuging at 10000 rpm for 5min, dripping the supernatant into AgNO₃In the solution, if no white precipitate exists, the molten salt in the powder is cleaned, and if the white precipitate exists, the water is continuously changed for centrifugation until no white precipitate exists. Finally, the prepared Bi is dried in an oven₃TiNbO₉Drying the powder for 12h at 60 ℃.

Example 4

Preparing high-exposure {001} crystal face bismuth titanate niobate Bi by adopting molten salt growth method₃TiNbO₉The nanosheet is prepared by reacting molten salt at 800 ℃ for 1h, and specifically operating the following steps:

with Bi₂O₃、TiO₂、Nb₂O₅Taking NaCl and KCl as molten salt as raw materials, wherein the mol ratio of NaCl: KCl: bi₃TiNbO₉50: 50: 1, preparing the materials. Putting the raw materials with the corresponding stoichiometric ratio into a ball milling tank, then adding a proper amount of ball stone and 50ml of absolute ethyl alcohol into the ball milling tank, carrying out ball milling for 4 hours, taking out, drying in an oven, grinding powder particles into small particles by using a mortar, and putting the small particles into a muffle furnace. During reaction, the temperature of the muffle furnace is raised to 800 ℃ at the speed of 5 ℃/min and is kept for 1h, and the temperature is lowered to 500 ℃ at the speed of 5 ℃/min and then is lowered to room temperature along with the furnace. After the temperature reduction is finished, the salt is washed by deionized water under the condition of magnetic stirring at 500rpm, and the steps are repeated for three to four times. Adding deionized water after washing, centrifuging at 10000 rpm for 5min, dripping the supernatant into AgNO₃In the solution, if no white precipitate exists, the molten salt in the powder is cleaned, and if the white precipitate exists, the water is continuously changed for centrifugation until no white precipitate exists. Finally, the prepared Bi is dried in an oven₃TiNbO₉Drying the powder for 12h at 60 ℃.

Example 5

Preparing high-exposure {001} crystal face bismuth titanate niobate Bi by adopting molten salt growth method₃TiNbO₉The nanosheet is prepared by reacting molten salt at 800 ℃ for 3h, and specifically operating the following steps:

with Bi₂O₃、TiO₂、Nb₂O₅Taking NaCl and KCl as molten salt as raw materials, wherein the mol ratio of NaCl: KCl: bi₃TiNbO₉50: 50: 1, preparing the materials. Putting the raw materials with the corresponding stoichiometric ratio into a ball milling tank, then adding a proper amount of ball stone and 50ml of absolute ethyl alcohol into the ball milling tank, carrying out ball milling for 4 hours, taking out, drying in an oven, grinding powder particles into small particles by using a mortar, and putting the small particles into a muffle furnace. During reaction, the muffle furnace is heated to 800 ℃ at the speed of 5 ℃/min and is kept warm for 3h, and the muffle furnace is cooled to 500 ℃ at the speed of 5 ℃/min and then is cooled to room temperature along with the muffle furnace. After the temperature reduction is finished, the salt is washed by deionized water under the condition of magnetic stirring at 500rpm, and the steps are repeated for three to four times. Adding deionized water after washing, centrifuging at 10000 rpm for 5min, dripping the supernatant into AgNO₃In the solution, if no white precipitate exists, the molten salt in the powder is cleaned, and if the white precipitate exists, the water is continuously changed for centrifugation until no white precipitate exists. Finally, the prepared Bi is dried in an oven₃TiNbO₉Drying the powder for 12h at 60 ℃.

Example 6

Preparing high-exposure {001} crystal face bismuth titanate niobate Bi by adopting molten salt growth method₃TiNbO₉The nanosheet is prepared by reacting molten salt at 800 ℃ for 4h, and specifically operating the following steps:

with Bi₂O₃、TiO₂、Nb₂O₅Taking NaCl and KCl as molten salt as raw materials, wherein the mol ratio of NaCl: KCl: bi₃TiNbO₉50: 50: 1, preparing the materials. Putting the raw materials with the corresponding stoichiometric ratio into a ball milling tank, then adding a proper amount of ball stone and 50ml of absolute ethyl alcohol into the ball milling tank, carrying out ball milling for 4 hours, taking out, drying in an oven, grinding powder particles into small particles by using a mortar, and putting the small particles into a muffle furnace. During reaction, the muffle furnace is heated to 800 ℃ at the speed of 5 ℃/min and is kept warm for 4h, and the temperature is reduced to 500 ℃ at the speed of 5 ℃/min during temperature reductionThen cooling to room temperature along with the furnace. After the temperature reduction is finished, the salt is washed by deionized water under the condition of magnetic stirring at 500rpm, and the steps are repeated for three to four times. Adding deionized water after washing, centrifuging at 10000 rpm for 5min, dripping the supernatant into AgNO₃In the solution, if no white precipitate exists, the molten salt in the powder is cleaned, and if the white precipitate exists, the water is continuously changed for centrifugation until no white precipitate exists. Finally, the prepared Bi is dried in an oven₃TiNbO₉Drying the powder for 12h at 60 ℃.

FIG. 1 shows Bi prepared at different molten salt reaction temperatures₃TiNbO₉In the X-ray diffraction pattern of the powder, the reaction time is 2h, and the reaction temperature is 850 ℃, 800 ℃ and 750 ℃ respectively. As shown, the three strong peaks of the three samples are respectively located at the theta angles of 14.638 degrees, 16.438 degrees and 28.261 degrees, the corresponding crystal planes are respectively (115), (220/020) and (315/135), and the three strong peaks correspond to the lower standard PDF card (JCPDS: 79-1550). This indicates that the samples prepared at the three temperatures all had Bi as the main crystal phase₃TiNbO₉. Meanwhile, no other hetero peak was observed in the diffraction peak of the sample, indicating that Bi was produced₃TiNbO₉The purity of (2) is higher.

FIG. 2 shows Bi prepared at different molten salt reaction temperatures₃TiNbO₉SEM image of powder, a is Bi prepared by reaction at 750 ℃ for 2h₃TiNbO₉SEM images obtained at 5000 x magnification; b is Bi prepared by reaction for 2 hours at 750 DEG C₃TiNbO₉SEM images obtained at 10000 times magnification; c is Bi prepared by reaction for 2 hours at 800 DEG C₃TiNbO₉SEM image obtained at 6000 x magnification; d is Bi prepared by reaction for 2 hours at 800 DEG C₃TiNbO₉SEM images obtained at 10000 times magnification; e is Bi prepared by reaction for 2 hours at 850 DEG C₃TiNbO₉SEM images obtained at 5000 x magnification; f is Bi prepared by reaction for 2 hours at 850 DEG C₃TiNbO₉SEM images obtained at 10000 times magnification. As is apparent from the observation of SEM images, the prepared Bi₃TiNbO₉In a lamellar structure, from regularAnd stacking the nano sheets. By analyzing the particle size of the nano-sheets, the prepared nano-sheets have the size of 0.5-3 μm, and the size of the nano-sheets is increased along with the increase of the temperature of the molten salt, and the agglomeration degree is increased.

FIG. 3 shows Bi prepared by reacting at 800 ℃ molten salt temperature for different times (1-4 h)₃TiNbO₉X-ray diffraction pattern of the powder. As shown, the X-ray diffraction peaks of the four samples are consistent with PDF card (JCPDS: 79-1550), wherein three strong peaks located at angles of 14.638 DEG, 16.438 DEG and 28.261 DEG at 2 theta correspond to the (115), (220/020) and (315/135) crystal planes, respectively. Except that Bi₃TiNbO₉No diffraction peak of other hetero-phase is observed in the XRD pattern. In addition, the XED diffraction peaks of all the samples are sharp, which proves that the samples have higher crystallinity. The above results show that the preparation of high-purity Bi by the molten salt method is successful₃TiNbO₉。

FIG. 4 shows Bi prepared by reacting at 800 ℃ molten salt temperature for different times (1-4 h)₃TiNbO₉SEM images of samples show that the Bi with the flaky morphology is obtained after reaction for 1h to 4h at 800 DEG C₃TiNbO₉And (3) powder. Through comparative observation of samples under different reaction time conditions, the particle size of the powder is increased along with the extension of the reaction time, the whole powder has certain agglomeration property, and the particle size distribution range is wider.

FIG. 5 shows Bi prepared at a molten salt reaction temperature of 800 ℃ for a reaction time of 2h₃TiNbO₉HRTEM photograph of the powder shows that Bi is present₃TiNbO₉The crystal lattice fringes are in an obvious nanometer sheet shape, and the crystal lattice fringes are analyzed and observed through a high-resolution transmission electron microscope, so that the crystal lattice fringes which are perpendicular to each other and belong to (020) and (200) can be seen, and the corresponding crystal lattice distances are respectively 0.272nm and 0.270 nm. According to Bi₃TiNbO₉The prepared nanosheet has an exposed crystal face of a {001} crystal face by combining with high-resolution lattice fringe analysis.

FIG. 6 shows Bi prepared at a molten salt reaction temperature of 800 ℃ for 2h₃TiNbO₉The powder is under the action of ultrasonic waveCurve for degrading rhodamine B. As can be seen by comparing with a control group, under the action of ultrasound, Bi₃TiNbO₉The good performance of piezoelectric degradation of rhodamine B is shown, the degradation rate reaches 60 percent within 80 minutes, and the reason of the phenomenon is that Bi is used for degrading rhodamine B₃TiNbO₉The nano-sheet belongs to a piezoelectric material, and under the action of mechanical external force (ultrasonic wave), electrons and holes can be induced and generated on the surface of the nano-sheet, and the electrons and the holes can drive to produce active groups such as superoxide anion free radicals, hydroxyl free radicals and the like. The active free radicals react with rhodamine B molecules to generate small molecules, carbon dioxide and water, so that the degradation of rhodamine B is realized.

The embodiments described above are merely preferred embodiments of the present invention, and should not be considered as limitations of the present invention, and features in the embodiments and examples in the present application may be arbitrarily combined with each other without conflict. The protection scope of the present invention is defined by the claims, and includes equivalents of technical features of the claims. I.e., equivalent alterations and modifications within the scope hereof, are also intended to be within the scope of the invention.