CN103523824A - Preparation method of nano flaky ferroelectric material for photocatalysis - Google Patents

Abstract

The invention relates to a method for preparing a nanosheet ferroelectric material for photocatalysis. According to the molecular formula of barium strontium titanate (Ba _x Sr _1-x TiO ₃ ), barium salt, strontium salt and titanium salt are configured to obtain a premix, Barium salt and strontium salt are mixed and dissolved in water according to the proportion, and NaOH is added, and titanium salt is dissolved in absolute ethanol. After the above raw materials are mixed evenly, they are kept in an autoclave at 160-200°C for 24 hours, and then cooled to room temperature in air. After filtering, washing and drying, the nano-sheet strontium barium titanate powder is prepared. Compared with the prior art, the preparation process of the present invention is simple, and the agglomeration phenomenon of the prepared nanoparticles is less; compared with the preparation of strontium barium titanate nanopowder by the traditional hydrothermal method, the present invention uses butyl titanate as the titanium source, and the prepared The sample has the characteristics of high purity and good crystallinity of the powder.

Description

A preparation method of nanosheet ferroelectric material for photocatalysis

technical field

The invention relates to the preparation technology of sheet-shaped nano-ferroelectric materials, in particular to a preparation method of nano-sheet-shaped ferroelectric materials for photocatalysis.

Background technique

With the development of science and technology, the environmental pollution caused by the industrial field, especially the textile industry, has gradually intensified, and water pollution has become an urgent problem to be solved. With the research on treatment methods, photocatalytic degradation of organic matter has gradually gained attention due to its advantages of high efficiency, low cost, and energy saving. Since the discovery in 1972 that _TiO2 can split water to produce hydrogen by relying on light energy, people have been interested in using photocatalytic technology to control water pollution. After decades of development, many semiconductor photocatalysts have been prepared.

However, there are still three defects in the current semiconductor photocatalyst: 1. Due to the large band gap of the semiconductor catalyst, its photoresponse region is in the ultraviolet region, and ultraviolet light only accounts for 4% of sunlight; Current carriers (photogenerated electrons and photogenerated holes) are prone to recombination during the transition to the surface of the catalyst, resulting in a decrease in photocatalytic efficiency; 3. Since photocatalysts are semiconductors, their conductivity is not good, resulting in the transfer of carriers to the catalyst The surface is more difficult. The application time of ferroelectric materials in the field of photocatalysis is still short, but they have attracted attention due to their unique advantages. Ferroelectric materials have spontaneous polarization below the Curie temperature, and the spontaneous polarization can be reversed by an external electric field. The spontaneous generation of ferroelectric materials is extremely beneficial to the separation of negatively charged electrons and positively charged holes generated by photocatalysis, so it is theoretically expected to improve its photocatalytic efficiency.

Among the ferroelectric materials, strontium titanate (SrTiO ₃ ) and barium titanate (BaTiO ₃ ) have good photocatalytic efficiency. The solid solution of strontium titanate (SrTiO ₃ ) and barium titanate (BaTiO ₃ ) to form barium strontium titanate (ie BST) will increase the degree of lattice distortion, so that electrons can be excited more easily to improve the photocatalytic performance. Photocatalytic applications require ferroelectric materials to be nanoparticles and well dispersed to increase the contact surface area with light and reactants. At present, the methods for synthesizing BST nanopowder mainly include sol-gel method and hydrothermal method. The agglomeration phenomenon of BST powder synthesized by sol-gel method is more serious, while the crystallinity of barium strontium titanate powder synthesized by hydrothermal method is poor. In photocatalytic applications, catalyst crystallinity has a great influence on the catalytic efficiency of photocatalysts. Therefore, it is very necessary to adopt a new synthesis process to prepare nano-BST powder with good crystallinity and good dispersibility to promote its further application in the field of photocatalysis.

Contents of the invention

The purpose of the present invention is to solve the problems of too large powder particles, too serious powder agglomeration and poor powder crystallinity in the existing technology of strontium barium titanate powder synthesis, and on this basis, combine sol-gel method and traditional water Advantages of the thermal method, using butyl titanate as a raw material to synthesize flake nano-strontium barium titanate powder by hydrothermal method.

The purpose of the present invention can be achieved through the following technical solutions:

A preparation method for photocatalytic nano sheet ferroelectric material, comprising the following steps:

(1) According to the molecular formula of barium strontium titanate (Ba _x Sr _1-x TiO ₃ ), the molar ratio is x: (1-x): 1 to configure barium salt, strontium salt and titanium salt to obtain a premix;

(2) Mix and dissolve the barium salt and strontium salt in water according to the proportion, then add NaOH, stir and dissolve, dissolve the titanium salt in absolute ethanol, pour the ethanol solution of the titanium salt into the above aqueous solution, and stir in the constant temperature magnetic stirrer Stir at 600r/min for 30min until completely mixed;

(3) Transfer the mixed solution into a polytetrafluoroethylene-lined autoclave, keep it warm at 160-200°C for 24 hours, cool to room temperature in the air after the reaction process, filter, wash, and dry to prepare nanosheets barium strontium titanate powder.

The range of x in step (1) is 0<x<1.

The barium salt includes BaCl ₂ , Ba(NO ₃ ) ₂ or Ba(CH ₃ COO) ₂ .

The strontium salt includes SrCl ₂ , Sr(NO ₃ ) ₂ or Sr(CH ₃ COO) ₂ .

The titanium salt is synthetic or commercially available butyl titanate ((C ₄ H ₉ O) ₄ Ti).

The reaction temperature in step (3) is preferably 160-180°C.

Compared with the prior art, the present invention combines the advantages of the sol-gel method and the traditional hydrothermal method, and uses butyl titanate as a raw material to synthesize sheet-like nano-strontium barium titanate powder using a hydrothermal method. The method synthesizes the powder The particle size is smaller, the agglomeration phenomenon is reduced, and the synthesized powder has good crystallinity and sheet-like morphology, which is expected to greatly improve its photocatalytic properties. The precursor solution in the above reaction is the Ti(C ₄ H ₉ O) ₄ in the mixed solution obtained in the above step (2) is hydrolyzed to form complex ions such as [Ti(OH) ₂ .xH ₂ O] ²⁺ , etc., and absorb Ba ^{2 +} , Sr ²⁺ , during the crystallization process, the dehydration reaction of this ion group occurs, and the precursor dehydrates quickly under high temperature and high pressure, forming a large number of crystal nuclei and growing to obtain barium strontium titanate. In the preparation of barium strontium titanate by the sol-gel method, butyl titanate is combined with barium salt and strontium salt to form a precursor, which is hydrolyzed to form a sol, and then a gel is formed, which is then calcined to form barium strontium titanate, while the traditional hydrothermal method It can provide a high temperature and high pressure environment, promote the hydrolysis of the precursor and generate a large number of crystal nuclei, and finally obtain the flaky nano powder under the conditions of controlling the experimental temperature and time.

Description of drawings

Fig. 1 is the XRD figure of the barium strontium titanate prepared in embodiment 1;

Fig. 2 is the XRD figure of the barium strontium titanate prepared in embodiment 2;

Fig. 3 is the SEM picture of the barium strontium titanate prepared in embodiment 1;

FIG. 4 is an SEM image of barium strontium titanate prepared in Example 2.

Detailed ways

The present invention will be further explained by the following examples in conjunction with the accompanying drawings, but the present invention is not limited.

The type of main equipment used in the embodiment of the present invention and the manufacturer's information are as follows: The present invention is further elaborated below through embodiment and in conjunction with accompanying drawing, but does not limit the present invention.

The model of main equipment used in each embodiment of the present invention and the information of manufacturer are as follows:

Ball mill: QM-2SP2(2L), Nanjing Nanda Instrument Factory;

Electric constant temperature blast drying oven: DHG-9240A, Shanghai Jinghong Equipment Co., Ltd.;

Solar Simulator: PLS-SXE300C, Beijing Powerline Technology Co., Ltd.;

UV-visible spectrophotometer: UV-2550, Shimadzu, Japan.

The specification of the raw material used in the embodiment of the present invention and the information of manufacturer are as follows:

Example 1

A preparation method of nanosheet ferroelectric material for photocatalysis, that is, barium strontium titanate, taking Ba _0.7 Sr _0.3 TiO ₃ as an example, calculated by molar ratio, wherein barium in barium salt: strontium in strontium salt: titanate The ratio of titanium in butyl ester: sodium hydroxide is 0.7:0.3:1:4; the barium salt used is BaCl ₂ .2H ₂ O, and the strontium salt is SrCl ₂ .2H ₂ O.

Weigh 1.7186g BaCl ₂ .2H ₂ O and 0.8039g SrCl ₂ .2H ₂ O, transfer the two materials into a conical flask, add 25ml deionized water and stir to dissolve, add 1.6667g NaOH to the above solution, stir and dissolve to form Alkaline environment.

Use a measuring cylinder to take 3.4ml of butyl titanate, add an appropriate amount of absolute ethanol to form an ethanol solution of butyl titanate, pour the ethanol solution into the above-mentioned Erlenmeyer flask, and stir for 30 minutes on a constant temperature magnetic stirrer at a speed of 600r/min. Then transfer the suspension into a polytetrafluoroethylene-lined autoclave, and conduct a hydrothermal reaction at 160°C for 24 hours. After the hydrothermal reaction process, air-cool to room temperature, filter, wash, and dry. The ferroelectric material barium strontium titanate Ba _0.7 Sr _0.3 TiO ₃ was obtained. The XRD pattern and SEM pattern of the prepared barium strontium titanate are shown in Figure 1 and Figure 3, respectively. As can be seen from the XRD figure, it does not contain other miscellaneous peaks in its spectrum, and each peak corresponds to the standard spectrum neatly. It can be known that Ba _0.7 Sr _0.3 TiO prepared by this method is a pure phase; as can _be seen from the SEM figure, this method The agglomeration phenomenon of the prepared powder is relatively light, and the particle size of the powder is small.

Example 2

A preparation method of nanosheet ferroelectric material for photocatalysis, that is, barium strontium titanate, taking Ba _0.7 Sr _0.3 TiO ₃ as an example, calculated by molar ratio, wherein barium in barium salt: strontium in strontium salt: titanate The ratio of titanium: sodium hydroxide in butyl ester is 0.7:0.3:1:4; the barium salt used is BaCl ₂ .2H ₂ O, and the strontium salt is SrCl ₂ .2H ₂ O.

Weigh 1.7186g BaCl ₂ .2H ₂ O and 0.8039g SrCl ₂ .2H ₂ O, transfer the two materials into a conical flask, add 25ml deionized water and stir to dissolve, add 1.6667g NaOH to the above solution, stir and dissolve to form Alkaline environment.

Use a measuring cylinder to take 3.4ml of butyl titanate, add an appropriate amount of absolute ethanol to form an ethanol solution of butyl titanate, pour the ethanol solution into the above-mentioned Erlenmeyer flask, and stir for 30 minutes on a constant temperature magnetic stirrer at a speed of 600r/min. Then transfer the suspension into a polytetrafluoroethylene-lined autoclave, and carry out hydrothermal reaction at 180°C for 24 hours. After the hydrothermal reaction process, air-cool to room temperature, filter, wash, and dry. The ferroelectric material barium strontium titanate Ba _0.7 Sr _0.3 TiO ₃ was obtained. The XRD pattern and SEM pattern of the prepared barium strontium titanate are shown in Figure 2 and Figure 4, respectively. As can be seen from the XRD figure, it does not contain other miscellaneous peaks in its spectrum, and each peak corresponds to the standard spectrum neatly. It can be known that Ba _0.7 Sr _0.3 TiO prepared by this method is a pure phase; as can _be seen from the SEM figure, this method The prepared powder particles are in the form of flakes, and the particle diameter is within 100nm.

Example 3

A preparation method of nanosheet ferroelectric material for photocatalysis, that is, barium strontium titanate, taking Ba _0.7 Sr _0.3 TiO ₃ as an example, calculated by molar ratio, wherein barium in barium salt: strontium in strontium salt: titanate The ratio of titanium in butyl ester: sodium hydroxide is 0.7:0.3:1:4; the barium salt used is Ba(NO ₃ ) ₂ , and the strontium salt is Sr(NO ₃ ) ₂ .

Weigh 1.8295g Ba(NO ₃ ) ₂ and 0.6349g Sr(NO ₃ ) ₂ , transfer the two materials into a conical flask, add 25ml deionized water and stir to dissolve, add 1.6667g NaOH to the above solution, stir and dissolve to form Alkaline environment.

Use a measuring cylinder to take 3.4ml of butyl titanate, add an appropriate amount of absolute ethanol to form an ethanol solution of butyl titanate, pour the ethanol solution into the above-mentioned Erlenmeyer flask, and stir for 30 minutes on a constant temperature magnetic stirrer at a speed of 600r/min. Then transfer the suspension into a polytetrafluoroethylene-lined autoclave, and conduct a hydrothermal reaction at 160°C for 24 hours. After the hydrothermal reaction process, air-cool to room temperature, filter, wash, and dry. The ferroelectric material barium strontium titanate Ba _0.7 Sr _0.3 TiO ₃ was obtained.

Example 4

A preparation method of nanosheet ferroelectric material for photocatalysis, that is, barium strontium titanate, taking Ba _0.7 Sr _0.3 TiO ₃ as an example, calculated by molar ratio, wherein barium in barium salt: strontium in strontium salt: titanate The ratio of titanium in butyl ester: sodium hydroxide is 0.7:0.3:1:4; the barium salt used is Ba(NO ₃ ) ₂ , and the strontium salt is Sr(NO ₃ ) ₂ .

Weigh 1.8295g Ba(NO ₃ ) ₂ and 0.6349g Sr(NO ₃ ) ₂ , transfer the two materials into a conical flask, add 25ml deionized water and stir to dissolve, add 1.6667g NaOH to the above solution, stir and dissolve to form Alkaline environment.

Use a measuring cylinder to take 3.4ml of butyl titanate, add an appropriate amount of absolute ethanol to form an ethanol solution of butyl titanate, pour the ethanol solution into the above-mentioned Erlenmeyer flask, and stir for 30 minutes on a constant temperature magnetic stirrer at a speed of 600r/min. Then transfer the suspension into a polytetrafluoroethylene-lined autoclave, and carry out hydrothermal reaction at 180°C for 24 hours. After the hydrothermal reaction process, air-cool to room temperature, filter, wash, and dry. The ferroelectric material barium strontium titanate Ba _0.7 Sr _0.3 TiO ₃ was obtained.

Example 5

A preparation method of nanosheet ferroelectric material for photocatalysis, that is, barium strontium titanate, taking Ba _0.3 Sr _0.7 TiO ₃ as an example, calculated by molar ratio, wherein barium in barium salt: strontium in strontium salt: titanate The ratio of titanium in butyl ester: sodium hydroxide is 0.3:0.7:1:4; the barium salt used is BaCl ₂ .2H ₂ O, and the strontium salt is SrCl ₂ .2H ₂ O.

Weigh 0.7238g BaCl ₂ .2H ₂ O and 1.8663g SrCl ₂ .2H ₂ O, transfer the two materials into a conical flask, add 25ml deionized water and stir to dissolve, add 1.6667g NaOH to the above solution, stir and dissolve to form Alkaline environment.

Use a measuring cylinder to take 3.4ml of butyl titanate, add an appropriate amount of absolute ethanol to form an ethanol solution of butyl titanate, pour the ethanol solution into the above-mentioned Erlenmeyer flask, and stir for 30 minutes on a constant temperature magnetic stirrer at a speed of 600r/min. Then transfer the suspension into a polytetrafluoroethylene-lined autoclave, and conduct a hydrothermal reaction at 160°C for 24 hours. After the hydrothermal reaction process, air-cool to room temperature, filter, wash, and dry. The ferroelectric material barium strontium titanate Ba _0.3 Sr _0.7 TiO ₃ was obtained.

Example 6

A preparation method of nanosheet ferroelectric material for photocatalysis, that is, barium strontium titanate, taking Ba _0.3 Sr _0.7 TiO ₃ as an example, calculated by molar ratio, wherein barium in barium salt: strontium in strontium salt: titanate The ratio of titanium in butyl ester: sodium hydroxide is 0.3:0.7:1:4; the barium salt used is BaCl ₂ .2H ₂ O, and the strontium salt is SrCl ₂ .2H ₂ O.

Weigh 0.7238g BaCl ₂ .2H ₂ O and 1.8663g SrCl ₂ .2H ₂ O, transfer the two materials into a conical flask, add 25ml deionized water and stir to dissolve, add 1.6667g NaOH to the above solution, stir and dissolve to form Alkaline environment.

Use a measuring cylinder to take 3.4ml of butyl titanate, add an appropriate amount of absolute ethanol to form an ethanol solution of butyl titanate, pour the ethanol solution into the above-mentioned Erlenmeyer flask, and stir for 30 minutes on a constant temperature magnetic stirrer at a speed of 600r/min. Then transfer the suspension into a polytetrafluoroethylene-lined autoclave, and carry out hydrothermal reaction at 180°C for 24 hours. After the hydrothermal reaction process, air-cool to room temperature, filter, wash, and dry. The ferroelectric material barium strontium titanate Ba _0.3 Sr _0.7 TiO ₃ was obtained.

Example 7

A preparation method of nanosheet ferroelectric material for photocatalysis, that is, barium strontium titanate, taking Ba _0.3 Sr _0.7 TiO ₃ as an example, calculated by molar ratio, wherein barium in barium salt: strontium in strontium salt: titanate The ratio of titanium in butyl ester: sodium hydroxide is 0.3:0.7:1:4; the barium salt used is Ba(NO ₃ ) ₂ , and the strontium salt is Sr(NO ₃ ) ₂ .

Weigh 0.7841g Ba(NO ₃ ) ₂ and 1.4814g Sr(NO ₃ ) ₂ , transfer the two materials into a conical flask, add 25ml deionized water and stir to dissolve, add 1.6667g NaOH to the above solution, stir and dissolve to form Alkaline environment.

Use a measuring cylinder to take 3.4ml of butyl titanate, add an appropriate amount of absolute ethanol to form an ethanol solution of butyl titanate, pour the ethanol solution into the above-mentioned Erlenmeyer flask, and stir for 30 minutes on a constant temperature magnetic stirrer at a speed of 600r/min. Then transfer the suspension into a polytetrafluoroethylene-lined autoclave, and conduct a hydrothermal reaction at 160°C for 24 hours. After the hydrothermal reaction process, air-cool to room temperature, filter, wash, and dry. The ferroelectric material barium strontium titanate Ba _0.3 Sr _0.7 TiO ₃ was obtained.

Example 8

A preparation method of nanosheet ferroelectric material for photocatalysis, that is, barium strontium titanate, taking Ba _0.3 Sr _0.7 TiO ₃ as an example, calculated by molar ratio, wherein barium in barium salt: strontium in strontium salt: titanate The ratio of titanium in butyl ester: sodium hydroxide is 0.3:0.7:1:4; the barium salt used is Ba(NO ₃ ) ₂ , and the strontium salt is Sr(NO ₃ ) ₂ .

Weigh 0.7841g Ba(NO ₃ ) ₂ and 1.4814g Sr(NO ₃ ) ₂ , transfer the two materials into a conical flask, add 25ml deionized water and stir to dissolve, add 1.6667g NaOH to the above solution, stir and dissolve to form Alkaline environment.

Use a measuring cylinder to take 3.4ml of butyl titanate, add an appropriate amount of absolute ethanol to form an ethanol solution of butyl titanate, pour the ethanol solution into the above-mentioned Erlenmeyer flask, and stir for 30 minutes on a constant temperature magnetic stirrer at a speed of 600r/min. Then transfer the suspension into a polytetrafluoroethylene-lined autoclave, and carry out hydrothermal reaction at 180°C for 24 hours. After the hydrothermal reaction process, air-cool to room temperature, filter, wash, and dry. The ferroelectric material barium strontium titanate Ba _0.3 Sr _0.7 TiO ₃ was obtained.

Claims (6)

1. A preparation method for photocatalytic nanosheet ferroelectric material, characterized in that, the method may further comprise the steps: (1) According to the molecular formula of barium strontium titanate (Ba _x Sr _1-x TiO ₃ ), the molar ratio is x: (1-x): 1 to configure barium salt, strontium salt and titanium salt to obtain a premix; (2) Mix and dissolve the barium salt and strontium salt in water according to the proportion, then add NaOH, stir and dissolve, dissolve the titanium salt in absolute ethanol, pour the ethanol solution of the titanium salt into the above aqueous solution, and stir in the constant temperature magnetic stirrer Stir at 600r/min for 30min until completely mixed; (3) Transfer the mixed liquid into a polytetrafluoroethylene-lined autoclave, and keep it warm at 160-200°C for 24 hours. After the reaction process, cool it to room temperature in the air, and then filter, wash, and dry to prepare nano Flake barium strontium titanate powder. 2 . The preparation method of a nanosheet ferroelectric material for photocatalysis according to claim 1 , wherein the range of x in step (1) is 0<x<1. 3 . 3. A method for preparing photocatalytic nanosheet ferroelectric materials according to claim 1 or 2, wherein said barium salts include BaCl ₂ , Ba(NO ₃ ) ₂ or Ba(CH ₃ COO) ₂ . 4. The preparation method of a photocatalytic nanosheet ferroelectric material according to claim 1 or 2, wherein said strontium salt comprises SrCl ₂ , Sr(NO ₃ ) ₂ or Sr(CH ₃ COO) ₂ . 5. the preparation method of a kind of photocatalytic nano sheet ferroelectric material according to claim 1 or 2, is characterized in that, described titanium salt is synthetic or commercially available butyl titanate ((C ₄ H ₉ O) ₄ Ti). 6 . The preparation method of a nanosheet ferroelectric material for photocatalysis according to claim 1 , wherein the reaction temperature in step (3) is preferably 160-180° C.

Images