CN116832837A - A spherical TiO2/BiOBr core-shell structure heterojunction material and its preparation method and application - Google Patents

Abstract

The invention discloses a spherical TiO ₂ /BiOBr core-shell structure heterojunction material and a preparation method thereof. The present invention uses silica as a template to synthesize regular TiO ₂ hollow microspheres, and then mounts flaky BiOBr on the surface of the TiO ₂ hollow microspheres through an in-situ hydrothermal method to form a flower-shaped hierarchical core-shell with strong light absorption capabilities. Structural TiO ₂ /BiOBr heterojunction materials. The TiO ₂ /BiOBr heterojunction material can take advantage of the characteristics of multiple reflections of light inside the hollow microspheres to improve its utilization of light energy when used as a catalyst to achieve efficient reduction of CO ₂ , so it has good practical applications. value.

Description

A spherical TiO2/BiOBr core-shell structure heterojunction material and its preparation method, application

Technical field

The invention relates to the technical fields of photocatalytic degradation and photocatalytic carbon dioxide reduction, specifically a spherical TiO ₂ /BiOBr core-shell structure heterojunction material and its preparation method and application.

Background technique

With the development of society, environmental problems and energy crisis are things we urgently want to solve. To meet production and living needs, we need to burn fossil energy, which will produce a large amount of CO ₂ , exacerbating the greenhouse effect and leading to global warming. As a new catalytic method, photocatalysis can make full use of solar energy, providing an important opportunity to alleviate global energy shortage and environmental pollution problems. Photocatalysts can reduce CO ₂ to produce fuels and chemicals by absorbing solar energy. They have attracted high social attention because they provide alternatives to fossil raw materials and can convert and cycle greenhouse gases on a large scale.

TiO ₂ /BiOBr has the characteristics of low cost, non-toxicity, good stability, etc., so it is widely used in the field of photocatalysis. However, due to the small specific surface area and weak light absorption capacity; the small heterojunction interface area limits the practical application of TiO ₂ /BiOBr in the field of photocatalysis.

Contents of the invention

The technical problem to be solved by the present invention is to provide a TiO ₂ /BiOBr core-shell structure heterojunction material with strong light absorption capability in view of the above-mentioned deficiencies in the prior art. This material has a larger specific surface area and heterojunction interface area, and has many reactive active sites. When used as a photocatalyst, it can improve the light absorption capacity and has a stronger ability to reduce CO ₂ .

The technical solutions adopted by the present invention to solve the above-mentioned problems are:

A flower-shaped TiO ₂ /BiOBr core-shell structure heterojunction material, with hollow TiO ₂ hollow microspheres as the main body, and BiOBr nanosheets growing on the surface of TiO ₂ hollow microspheres, forming a flower-shaped heterostructure with a core-shell structure; Wherein, the size of the TiO ₂ hollow microspheres is 300-600 nm, and the overall size of the spherical TiO ₂ /BiOBr core-shell structure heterojunction material is 400-800 nm; the TiO ₂ /BiOBr core-shell structure heterojunction material The molar ratio of Ti/Bi is (0.7~3):1.

The present invention also provides a method for preparing the above-mentioned TiO ₂ /BiOBr core-shell structure heterojunction, using silica as a template to synthesize TiO ₂ hollow microspheres, and then using an in-situ hydrothermal method to mount flaky BiOBr in the TiO ₂ hollow microspheres. On the surface of the microsphere, a hierarchical core-shell structure TiO ₂ /BiOBr hierarchical core-shell structure heterojunction material with strong light absorption capability is formed. Specific steps are as follows:

(1) Dissolve tetraethyl silicate in ethanol, deionized water and ammonia solution, stir the reaction, and prepare SiO ₂ microspheres;

(2) Disperse SiO ₂ microspheres in ethanol, then add ammonia water, and stir to obtain a dispersion; add tetrabutyl titanate to the dispersion and perform heat treatment; after the heat treatment, the solid product is separated from the resulting solution and calcined , to obtain SiO ₂ @TiO ₂ microspheres; etching the SiO ₂ @TiO ₂ microspheres with hydrofluoric acid solution to obtain TiO ₂ hollow microspheres;

(3) Soak the hollow TiO ₂ microspheres in dilute sulfuric acid, wash, dry, and disperse into ethylene glycol, then add bismuth nitrate pentahydrate, cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone ( PVP), perform a hydrothermal reaction, BiOBr nanosheets grow on the surface of TiO ₂ hollow microspheres, and evenly wrap around the surface of TiO ₂ hollow microspheres, obtaining a TiO ₂ /BiOBr core-shell structure heterojunction material.

Further, in step (1), the volume ratio of the tetraethyl silicate to ethanol, deionized water and ammonia water is 1: (10~15): (1~2): 1; the stirring time is 2~5h .

Further, in step (2), the dispersion concentration of the SiO ₂ microspheres in ethanol is 0.5 to 2 mg/mL, the volume ratio of ammonia water to ethanol is 1: (100 to 200), and the volume ratio of butyl titanate to ethanol is The volume ratio is 1: (50~100); the heating temperature is 40~50℃, the heating time is 20~30 hours; the calcination temperature is 500~600℃, the calcination time is 1~4h; the volume concentration of the hydrofluoric acid solution is 2~5%.

Further, in step (3), the concentration of dilute sulfuric acid is 1.5~2.5mol/L, and the soaking time is 2~3h; the dispersion concentration of the hollow _TiO2 microspheres in ethylene glycol is 0.015~0.05mol/L, five Aqueous bismuth nitrate and CTAB are fed according to the molar ratio of Ti/Bi (0.7~3):1, and the molar ratio of Bi/Br: 1: (1~1.5); the concentration of PVP in ethylene glycol is 0.1~5g/ L; the hydrothermal reaction temperature is 120~180℃, and the hydrothermal time is 0.5~2h.

The TiO ₂ /BiOBr core-shell structure heterojunction material of the present invention can be used for photocatalytic carbon dioxide reduction and photocatalytic degradation.

Compared with the prior art, the beneficial effects of the present invention are as follows:

(1) The TiO ₂ /BiOBr core-shell structure heterojunction material of the present invention, BiOBr nanosheets surround the surface of the hollow spherical TiO ₂ , forming each independent flower ball, ensuring a larger contact area between BiOBr and TiO ₂ , As a result, a relatively complete heterostructure is constructed to enhance the migration rate of photogenerated carriers and achieve efficient CO ₂ reduction capabilities. Moreover, the TiO ₂ /BiOBr core-shell structure heterojunction material has a hierarchical structure and has a larger specific surface area when used as a catalyst, thereby exposing more reaction active sites and adsorption sites for CO ₂ , making it Efficient and stable reduction performance for _CO2 .

(2) The preparation method of the TiO ₂ /BiOBr core-shell structure heterojunction material provided by the present invention is to use a hard template method to prepare uniform and regular TiO ₂ hollow microspheres, and then use an in-situ hydrothermal method to prepare the hollow spherical TiO ₂ surface BiOBr nanosheets are grown to form a heterojunction material with a core-shell structure. This core-shell structure can not only enhance the multiple reflections of light inside the spherical material, but also improve its absorption capacity of visible light and obtain efficient and stable reduction performance of CO ₂ .

Description of the drawings

Figure 1 is a wide-angle diffraction XRD pattern of the TiO ₂ /BiOBr core-shell structure heterojunction material prepared in Example 1.

Figure 2 is a scanning electron microscope (SEM) image of the hollow TiO ₂ microspheres prepared in Example 1.

Figure 3 is a scanning electron microscope (SEM) image of the TiO ₂ /BiOBr core-shell structure heterojunction material prepared in Example 1.

Figure 4 is a high-angle annular dark field image (HAADF-STEM) image of the TiO ₂ /BiOBr core-shell structure heterojunction material prepared in Example 1.

Figure 5 shows the hollow TiO ₂ /BiOBr core-shell structure heterojunction materials prepared according to different Ti/Bi in Examples 1, 2 and 3 and the Bulk-TiO ₂ /BiOBr heterojunction material prepared in Comparative Example 1 under the same conditions. Comparative graph of conversion rates for _CO2 reduction to CO.

Detailed ways

In order to better understand the present invention, the content of the present invention will be further explained below in conjunction with the examples, but the present invention is not limited only to the following examples.

In the following examples, the ammonia water is commercially available ammonia water, and the concentration is 25% to 28%.

Example 1

A method for preparing a spherical TiO ₂ /BiOBr core-shell structure heterojunction material, which mainly includes the following steps:

(1) Use a graduated cylinder to measure tetraethyl silicate, ammonia, deionized water and ethanol, mix them in a beaker, stir at room temperature for 3 hours, wash with deionized water 3 to 5 times, and dry to obtain SiO ₂ microspheres , for later use; among them, the volume ratio of tetraethyl silicate, ammonia, deionized water and ethanol is 1:1:2:15;

(2) Use an electronic balance to weigh the 0.2g SiO ₂ microspheres synthesized in step (1) and disperse them in 150 mL of ethanol to obtain a suspension;

(3) Use a graduated cylinder to measure 1 mL of ammonia water and 2 mL of tetrabutyl titanate into the suspension in step (2), heat at 45°C and stir for 24 hours. After the resulting solution is cooled to room temperature, centrifuge and dry, and use absolute ethanol and Wash with deionized water 3 to 5 times, and then dry it in a 60°C oven to obtain amorphous SiO ₂ @TiO ₂ for later use. Among them, control the volume ratio of ammonia water, tetrabutyl titanate and ethanol in the suspension to be 1:2:150.

(4) Transfer the amorphous SiO ₂ @TiO ₂ obtained in step (3) to a muffle furnace, heat at 550°C for 2 hours, and then cool to room temperature with the furnace to obtain SiO ₂ @TiO ₂ microspheres;

(5) The SiO ₂ @TiO ₂ microspheres obtained in step (4) are first etched in a hydrofluoric acid solution with a volume concentration of 5%, washed 3 to 5 times with absolute ethanol and deionized water, and then placed Dry in an oven at 60°C to obtain TiO ₂ hollow microspheres for later use.

(6) Surface-treat the TiO ₂ hollow microspheres obtained in step (5), soak them in a dilute sulfuric acid solution with a concentration of 2 mol/L for 2 hours, wash them 3 to 5 times with absolute ethanol and deionized water respectively, and then Place in a 60°C oven to dry and set aside.

(7) Weigh the TiO ₂ hollow microspheres, bismuth nitrate pentahydrate, cetyltrimethylammonium bromide and PVP obtained in step (6), dissolve them in ethylene glycol, stir for half an hour, and transfer to a 50mL reaction kettle. , heat with water for 1 hour at 160°C, cool to room temperature with the furnace, and centrifuge to obtain a crude product of TiO ₂ /BiOBr core-shell structure heterojunction material; among which, the concentration of bismuth nitrate pentahydrate in ethylene glycol is 0.02mol/L, the concentration of PVP in ethylene glycol is 0.2g/L, and the molar ratio of TiO ₂ hollow microspheres to bismuth nitrate pentahydrate and cetyltrimethylammonium bromide is 5:4:4.

(8) Wash the crude TiO ₂ /BiOBr core-shell structure heterojunction material obtained in step (7) with absolute ethanol and deionized water 3 to 5 times, and then dry it in a 60°C oven to obtain Flower ball-shaped TiO ₂ /BiOBr core-shell structure heterojunction material.

It can be seen from Figure 1 that the flower-shaped TiO ₂ /BiOBr core-shell structure heterojunction material prepared in this embodiment has a single diffraction peak of TiO ₂ and BiOBr. The peak positions in the figure correspond to the standard PDF cards TiO ₂ (JCPDS: 84-1286) and BiOBr (JCPDS: 78-0348). Among them, 2θ=25.3° corresponds to the (101) crystal plane of TiO _2. Since TiO ₂ has a relatively low mass in the sample, the diffraction peak of TiO ₂ is smaller; other 2θ=25.2°, 31.7°, 32.2° , 46.2°, 57.2°, 67.5° and 76.8° respectively correspond to the (101), (102), (110), (200), (212), (220) and (310) crystal planes of BiOBr. It can be seen from the XRD pattern that the TiO ₂ /BiOBr composite material was synthesized.

As can be seen from Figure 2, the diameter of the hollow TiO ₂ microspheres prepared in this example is basically in the range of 400 to 600 nm. Some microspheres with smaller wall thickness are broken, and the hollow structure can be seen.

As can be seen from Figure 3, the TiO ₂ /BiOBr core-shell structure heterojunction material prepared in this embodiment is in the shape of independent flower balls, and it can be seen that the BiOBr nanosheets are wrapped around the surface of the hollow TiO ₂ microspheres to form a flower ball shape. For TiO ₂ /BiOBr heterojunction materials, the overall size of each independent flower ball is basically in the range of 400 to 800nm.

Figure 4 is a high-angle annular dark field image (HAADF-STEM) of the TiO ₂ /BiOBr core-shell structure heterojunction material prepared in this embodiment. The results show that it is a hollow core-shell heterostructure, consisting of BiOBr nanosheets stacked on TiO _2. A flower-shaped TiO ₂ /BiOBr core-shell structure heterojunction material is formed on the surface of the hollow microsphere.

CO ₂ reduction was used as a model reaction to examine the photocatalytic performance of the flower-shaped TiO ₂ /BiOBr core-shell structure heterojunction material prepared in Example 1. The specific process is as follows:

Weigh 0.05g of the TiO ₂ /BiOBr catalyst prepared in this example and put it into the reaction tank. Pour CO ₂ and H ₂ into the reaction tank with a volume ratio of 1:4, and continue to ventilate it for 30 minutes to ensure that it is discharged from the reaction tank. After the ventilation is completed, the reaction tank is sealed; turn on the light source, use a full-spectrum light source for irradiation, extract 1 mL of gas from the reaction tank every half an hour, and use chromatography to detect the gas type and content of each substance. After 3 hours of illumination, it was measured that CO ₂ was converted into CO, and the CO production rate was 15.84 μmol·h ^-1 ·g ^-1 , indicating good CO conversion performance. Compared with the bulk TiO ₂ /BiOBr composite sample without adding SiO ₂ microspheres in Comparative Example 1, the catalytic performance of Example 1 is 2.2 times that of Comparative Example 1. Therefore, the TiO ₂ /BiOBr core-shell structure heterojunction material prepared by the present invention can enhance the multiple reflections of light inside the spherical material, improve its absorption capacity of visible light, expand the specific surface area, and increase the contact area with the reactants. This can improve its efficient and stable reduction performance of CO ₂ .

Comparative example 1

Comparative Example 1 uses Bulk-TiO ₂ /BiOBr material, and the specific preparation process is as follows:

(1) Use a graduated cylinder to measure 1 mL of ammonia, 2 mL of tetrabutyl titanate and ethanol, heat at 45°C and stir for 24 hours, cool to room temperature, wash with absolute ethanol and deionized water 3 to 5 times, and then place in a 60°C oven Dry in medium to obtain amorphous massive TiO ₂ particles for later use; among them, control the volume ratio of ammonia water, tetrabutyl titanate and ethanol to 1:2:150.

(2) Transfer the amorphous bulk TiO ₂ obtained in step (1) to a muffle furnace and heat it at 550°C for 2 hours, and then cool to room temperature with the furnace to obtain bulk TiO ₂ ;

(3) Surface-treat the massive TiO ₂ obtained in step (2), soak it in a dilute sulfuric acid solution with a concentration of 2 mol/L for 2 hours, wash it 3 to 5 times with absolute ethanol and deionized water, and then place it in the Dry in an oven at 60°C and set aside.

(4) Weigh the massive TiO ₂ particles obtained in step (3), bismuth nitrate pentahydrate, cetyltrimethylammonium bromide and PVP and dissolve them in 25 mL ethylene glycol, stir for 30 min, and transfer to a 50 mL reaction kettle In the process, water heat for 1 hour at 160°C, and then cool to room temperature in the furnace to obtain Bulk-TiO ₂ /BiOBr crude product; the concentration of bismuth nitrate pentahydrate in ethylene glycol is 0.02mol/L, and the concentration of PVP is 0.2g/L, control the molar ratio of Bulk-TiO ₂ , bismuth nitrate pentahydrate and cetyltrimethylammonium bromide to 5:4:4.

(5) Wash the crude Bulk-TiO ₂ /BiOBr product obtained in step (4) with absolute ethanol and deionized water 3 to 5 times, and then dry it in a 60°C oven to obtain Bulk-TiO ₂ / BiOBr composites.

Similarly, in order to compare with Example 1, CO ₂ reduction was used as a model reaction to examine the photocatalytic performance of the Bulk-TiO ₂ /BiOBr composite material prepared in Comparative Example 1. The specific process is as follows:

Weigh 0.05g of the Bulk-TiO ₂ /BiOBr composite material prepared in this comparative example and put it into the reaction tank. Pour CO ₂ and H ₂ into the reaction tank with a volume ratio of 1:4, and continue to ventilate for 30 minutes to ensure Exhaust the air in the reaction tank, seal the reaction tank after ventilation, turn on the light source, use a full spectrum light source for irradiation, extract 1mL of gas from the reaction tank every half an hour, and use chromatography to detect the gas type and content of each substance. After 3 hours of illumination, it can be determined through product detection that the production rate of CO is 7.24 μmol·h ^-1 ·g ^-1 , which is significantly lower than the catalytic performance of Example 1.

Example 2

A method for preparing a spherical TiO ₂ /BiOBr core-shell structure heterojunction material, which mainly includes the following steps:

(1) Use a graduated cylinder to measure tetraethyl silicate, ammonia, deionized water and ethanol, mix them in a beaker, stir at room temperature for 3 hours, wash with deionized water 3 to 5 times, and dry to obtain SiO ₂ microspheres , for later use; among them, the volume ratio of tetraethyl silicate, ammonia, deionized water and ethanol is 1:1:2:15;

(2) Use an electronic balance to weigh the 0.2g SiO ₂ microspheres synthesized in step (1) and disperse them in 150 mL of ethanol to obtain a suspension;

(3) Use a graduated cylinder to measure 1 mL of ammonia water and 2 mL of tetrabutyl titanate into the suspension in step (2), heat at 45°C and stir for 24 hours. After the resulting solution is cooled to room temperature, centrifuge and dry, and use absolute ethanol and Wash with deionized water 3 to 5 times, and then dry it in a 60°C oven to obtain amorphous SiO ₂ @TiO ₂ for later use. Among them, control the volume ratio of ammonia water, tetrabutyl titanate and ethanol in the suspension: 1:2:150.

(4) Transfer the amorphous SiO ₂ @TiO ₂ obtained in step (3) to a muffle furnace, heat at 550°C for 2 hours, and then cool to room temperature with the furnace to obtain SiO ₂ @TiO ₂ microspheres;

(5) The SiO ₂ @TiO ₂ microspheres obtained in step (4) are first etched in a hydrofluoric acid solution with a volume concentration of 5%, washed 3 to 5 times with absolute ethanol and deionized water, and then placed Dry in an oven at 60°C to obtain TiO ₂ hollow microspheres for later use.

(6) Surface-treat the TiO ₂ hollow microspheres obtained in step (5), soak them in a dilute sulfuric acid solution with a concentration of 2 mol/L for 2 hours, wash them 3 to 5 times with absolute ethanol and deionized water respectively, and then Place in a 60°C oven to dry and set aside.

(7) Weigh the TiO ₂ hollow microspheres, bismuth nitrate pentahydrate, cetyltrimethylammonium bromide and PVP obtained in step (6), dissolve them in ethylene glycol, stir for half an hour, and transfer to a 50mL reaction kettle. , heat with water for 1 hour at 160°C, cool to room temperature with the furnace, and centrifuge to obtain a crude product of TiO ₂ /BiOBr core-shell structure heterojunction material; among which, the concentration of bismuth nitrate pentahydrate in ethylene glycol is 0.02mol/L, the concentration of PVP is 0.2g/L, and the molar ratio of TiO ₂ hollow microspheres, bismuth nitrate pentahydrate and cetyltrimethylammonium bromide is 7:4:4.

(8) Wash the crude TiO ₂ /BiOBr core-shell structure heterojunction material obtained in step (7) with absolute ethanol and deionized water 3 to 5 times, and then dry it in a 60°C oven to obtain Flower ball-shaped TiO ₂ /BiOBr core-shell structure heterojunction material.

CO ₂ reduction was used as a model reaction to examine the photocatalytic performance of the flower-shaped TiO ₂ /BiOBr core-shell structure heterojunction material prepared in Example 2. The specific process is as follows:

Weigh 0.05g of the TiO ₂ /BiOBr catalyst prepared in this example and put it into the reaction tank. Pour CO ₂ and H ₂ into the reaction tank with a volume ratio of 1:4, and continue to ventilate it for 30 minutes to ensure that it is discharged from the reaction tank. After the ventilation is completed, the reaction tank is sealed; turn on the light source, use a full-spectrum light source for irradiation, extract 1 mL of gas from the reaction tank every half an hour, and use chromatography to detect the gas type and content of each substance. After 3 hours of illumination, it can be determined through product detection that CO2 is converted into CO, and the CO production rate is 15.11 μmol·h ^-1 ·g ^-1 , and its catalytic performance is 2.1 times that of the Bulk-TiO ₂ /BiOBr synthesized in Comparative Example 1. times.

Example 3

A method for preparing a spherical TiO ₂ /BiOBr core-shell structure heterojunction material, which mainly includes the following steps:

(1) Use a graduated cylinder to measure tetraethyl silicate, ammonia, deionized water and ethanol, mix them in a beaker, stir at room temperature for 3 hours, wash with deionized water 3 to 5 times, and dry to obtain SiO ₂ microspheres , for later use; among them, the volume ratio of tetraethyl silicate, ammonia, deionized water and ethanol is 1:1:2:15;

(2) Use an electronic balance to weigh the 0.2g SiO ₂ microspheres synthesized in step (1) and disperse them in 150 mL of ethanol to obtain a suspension;

(3) Use a graduated cylinder to measure 1 mL of ammonia water and 2 mL of tetrabutyl titanate into the suspension in step (2), heat at 45°C and stir for 24 hours. After the resulting solution is cooled to room temperature, centrifuge and dry, and use absolute ethanol and Wash with deionized water 3 to 5 times, and then dry it in a 60°C oven to obtain amorphous SiO ₂ @TiO ₂ for later use. Among them, control the volume ratio of ammonia water, tetrabutyl titanate and ethanol in the suspension to be 1:2:150.

(4) Transfer the amorphous SiO ₂ @TiO ₂ obtained in step (3) to a muffle furnace, heat at 550°C for 2 hours, and then cool to room temperature with the furnace to obtain SiO ₂ @TiO ₂ microspheres;

(5) The SiO ₂ @TiO ₂ microspheres obtained in step (4) are first etched in a hydrofluoric acid solution with a volume concentration of 5%, washed 3 to 5 times with absolute ethanol and deionized water, and then placed Dry in an oven at 60°C to obtain TiO ₂ hollow microspheres for later use.

(6) Surface-treat the TiO ₂ hollow microspheres obtained in step (5), soak them in a dilute sulfuric acid solution with a concentration of 2 mol/L for 2 hours, wash them 3 to 5 times with absolute ethanol and deionized water respectively, and then Place in a 60°C oven to dry and set aside.

(7) Weigh the TiO ₂ hollow microspheres, bismuth nitrate pentahydrate, cetyltrimethylammonium bromide and PVP obtained in step (6), dissolve them in ethylene glycol, stir for half an hour, and transfer to a 50mL reaction kettle. , heat with water for 1 hour at 160°C, cool to room temperature with the furnace, and centrifuge to obtain a crude product of TiO ₂ /BiOBr core-shell structure heterojunction material; among which, the concentration of bismuth nitrate pentahydrate in ethylene glycol is 0.02mol/L, the concentration of PVP is 0.2g/L, and the molar ratio of TiO ₂ hollow microspheres, bismuth nitrate pentahydrate and cetyltrimethylammonium bromide is 3:4:4.

(8) Wash the crude TiO ₂ /BiOBr core-shell structure heterojunction material obtained in step (7) with absolute ethanol and deionized water 3 to 5 times, and then dry it in a 60°C oven to obtain Flower ball-shaped TiO ₂ /BiOBr core-shell structure heterojunction material.

CO ₂ reduction was used as a model reaction to examine the photocatalytic performance of the flower-shaped TiO ₂ /BiOBr core-shell structure heterojunction material prepared in Example 2. The specific process is as follows:

Weigh 0.05g of the TiO ₂ /BiOBr catalyst prepared in this example and put it into the reaction tank. Pour CO ₂ and H ₂ into the reaction tank with a volume ratio of 1:4, and continue to ventilate it for 30 minutes to ensure that it is discharged from the reaction tank. After the ventilation is completed, the reaction tank is sealed; turn on the light source, use a full-spectrum light source for irradiation, extract 1 mL of gas from the reaction tank every half an hour, and use chromatography to detect the gas type and content of each substance. After 3 hours of illumination, it was determined through product detection that the production rate of CO was 13.5 μmol·h ^-1 ·g ^-1 , and its catalytic performance was 1.86 times that of the Bulk-TiO ₂ /BiOBr synthesized in Comparative Example 1.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and changes can be made without departing from the creative concept of the present invention, and these all belong to the present invention. scope of protection.

Claims (9)

1. Flower ball-shaped TiO ₂ A heterojunction material with a BiOBr core-shell structure is characterized in that the heterojunction material adopts TiO ₂ The hollow microsphere is taken as a main body, a plurality of BiOBr nano-sheets are grown on each TiO ₂ The surface of the hollow microsphere forms a heterostructure of an independent flower-ball-shaped core-shell structure.

2. The TiO according to claim 1 ₂ The BiOBr core-shell structure heterojunction material is characterized in that the TiO ₂ The size of the hollow microsphere is 300-600 nm, and the flower-sphere-shaped TiO ₂ The overall size of the heterojunction material with the BiOBr core-shell structure is 400-800 nm; the TiO ₂ The mol ratio of Ti/Bi in the BiOBr core-shell structure heterojunction material is (0.7-3): 1.

3. the TiO according to any one of claims 1 to 2 ₂ A preparation method of a heterojunction material with a BiOBr core-shell structure is characterized in that silicon dioxide is used as a template to synthesize TiO ₂ The hollow microsphere is used for carrying the BiOBr nano sheet on TiO by an in-situ hydrothermal method ₂ The surfaces of the hollow microspheres form flower-sphere-shaped TiO ₂ A BiOBr core-shell structure heterojunction material.

4. Flower ball-shaped TiO ₂ The preparation method of the BiOBr core-shell structure heterojunction material is characterized by comprising the following steps:

(1) Dissolving tetraethyl silicate in ethanol, deionized water and ammonia water, stirring and reacting to obtain SiO ₂ A microsphere;

(2) SiO is made of ₂ Dispersing the microspheres in ethanol, adding ammonia water, and stirring to obtainA dispersion; adding tetrabutyl titanate into the dispersion liquid, and performing heating treatment; the solution obtained after the heating treatment is separated to obtain a solid product and calcined to obtain SiO ₂ @TiO ₂ A microsphere; siO is made of ₂ @TiO ₂ Etching the microspheres by using hydrofluoric acid solution to obtain TiO ₂ Hollow microspheres;

(3) Hollow TiO ₂ Soaking the microspheres in dilute sulfuric acid, washing, drying, dispersing into ethylene glycol, adding bismuth nitrate pentahydrate, cetyl trimethyl ammonium bromide and polyvinylpyrrolidone, and performing hydrothermal reaction to obtain TiO ₂ A BiOBr core-shell structure heterojunction material.

5. The TiO according to claim 4 ₂ The preparation method of the BiOBr core-shell structure heterojunction material is characterized in that in the step (1), the volume ratio of the tetraethyl silicate to ethanol, deionized water and ammonia water is 1: (10-15): (1-2): 1, a step of; the stirring time is 2-5 h.

6. The TiO according to claim 4 ₂ The preparation method of the BiOBr core-shell structure heterojunction material is characterized in that in the step (2), the SiO ₂ The dispersion concentration of the microspheres in the ethanol is 0.5-2 g/L, and the volume ratio of ammonia water to ethanol is 1: (100-200), the volume ratio of butyl titanate to ethanol is 1: (50-100); the heating temperature is 40-50 ℃ and the heating time is 20-30 hours; the calcination temperature is 500-600 ℃, and the calcination time is 1-4 h; the volume concentration of the hydrofluoric acid solution is 2-5%.

7. The TiO according to claim 4 ₂ The preparation method of the BiOBr core-shell structure heterojunction material is characterized in that in the step (3), the concentration of dilute sulfuric acid is 1.5-2.5 mol/L, and the soaking time is 2-3 h; hollow TiO ₂ The dispersion concentration of the microsphere in the glycol solution is 0.015-0.05 mol/L, and the mole ratio of bismuth nitrate pentahydrate to cetyltrimethylammonium bromide is (0.7-3) according to Ti/Bi: 1, bi/Br molar ratio of 1: (1-1.5) feeding; PVP concentration in glycol is 0.1-5 g/L; the hydrothermal reaction temperature is 120-180 ℃ and the hydrothermal time is 0.5-to-ultra2h。

8. The TiO according to claim 1 ₂ Application of the/BiOBr core-shell structure heterojunction material in photocatalytic degradation.

9. The TiO according to claim 1 ₂ Application of the/BiOBr core-shell structure heterojunction material in photocatalytic carbon dioxide reduction.