A sheet-like pn heterojunction BiOBr / CoWO4 visible light photocatalytic material, its preparation method and application

Abstract

This invention belongs to the field of photocatalytic materials technology, and relates to a BiOBr / CoWO4 visible light photocatalytic degradation material, its preparation method, and its application. The BiOBr / CoWO4 visible light photocatalytic material is a BiOBr / CoWO4 visible light photocatalytic material with CoWO4 nanoparticles loaded on the surface of sheet-like BiOBr and possessing a p-n heterojunction. The p-n heterojunction formed by the BiOBr / CoWO4 visible light photocatalytic degradation material of this invention can effectively control the visible light absorption range of BiOBr, solving the problem of low carrier transport efficiency.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, and relates to a BiOBr / CoWO4 visible light photocatalytic degradation material, its preparation method and application. Background Technology

[0002] Over the past few centuries, with the depletion of fossil fuels, humanity has faced enormous energy crises and environmental problems. Semiconductor photocatalysis technology, utilizing clean and abundant solar energy for pollutant decomposition, water splitting, and carbon dioxide conversion, is considered a green and promising alternative energy source and environmental management solution. Bismuth oxybromine (BiOBr), an n-type indirect semiconductor based on bismuth halide, is widely used as a photocatalyst for carbon dioxide reduction and dye degradation. BiOBr materials possess a wide bandgap of 2.64–2.91 eV. Although BiOBr exhibits significant degradation activity under both ultraviolet and visible light, its utilization of visible light is limited, and it undergoes rapid recombination of electrons and holes. Therefore, BiOBr exhibits low photocatalytic performance under visible light, limiting its practical application in environmental remediation. Studies have reported that the performance of BiOBr can be improved through metal ion doping, noble metal deposition, and the development of semiconductor composite materials. For example, the ZnS / BiOBr photocatalyst prepared by Yan et al. achieved a tetracycline hydrochloride degradation rate of 82%; the photocatalytic activity of the Bi2S3 / BiOBr heterojunction prepared by Cui et al. was significantly higher than that of the previous generation. − -h + The reduction in recombination significantly improves the results. These methods help to adjust the band edge position and achieve charge separation, ultimately enhancing the photoactivity of BiOBr.

[0003] Cobalt tungstate (CoWO4) is a p-type semiconductor that exhibits paramagnetic behavior at room temperature. CoWO4 has a band gap of approximately 2.24 eV, making it suitable for visible light absorption. Therefore, CoWO4 has been used as a photocatalyst, electrocatalyst, and photoanode in photoelectrochemical cells. Summary of the Invention

[0004] The purpose of this invention is to provide a BiOBr / CoWO4 heterostructure photocatalyst with a pn heterojunction, its preparation method, and its applications. The pn-type heterojunction formed by the BiOBr / CoWO4 designed in this invention can effectively control the visible light absorption range of BiOBr, solving the problem of low carrier transport efficiency. Furthermore, this invention utilizes a one-step hydrothermal method to prepare the pn heterojunction BiOBr / CoWO4 photocatalytic material, which features mild reaction conditions, ease of implementation, and easy process control.

[0005] In a first aspect, the present invention provides a BiOBr / CoWO4 visible light photocatalytic material. The BiOBr / CoWO4 visible light photocatalytic material is a BiOBr / CoWO4 visible light photocatalytic material in which CoWO4 nanoparticles are loaded onto the surface of a sheet-like BiOBr, and a pn heterojunction is formed.

[0006] Combining the narrow bandgap of CoWO4 nanoparticles with the wide bandgap of BiOBr to construct BiOBr / CoWO4 heterostructures is a promising method for utilizing visible light and promoting photoinduced electron-hole pair separation, thereby enhancing photoactivity. In BiOBr / CoWO4 nanocomposites, BiOBr photocatalyst is the primary photocatalyst, while CoWO4 nanoparticles act as sensitizers for visible light absorption. Compared to the pure-phase compound, the prepared heterostructured BiOBr / CoWO4 photocatalyst exhibits better visible light response, larger specific surface area, higher charge separation efficiency, and greater photoactivity.

[0007] In an optional embodiment, the BiOBr / CoWO4 visible light photocatalyst material has a sheet-like morphology.

[0008] Secondly, the present invention provides a method for preparing the BiOBr / CoWO4 visible light photocatalytic material. The preparation method includes: uniformly mixing a bismuth source and a bromine source in a solvent to obtain precursor solution A; uniformly mixing a cobalt source and a tungsten source in a solvent to obtain precursor solution B; adding precursor solution A to precursor solution B under stirring, and mixing to obtain precursor solution C; subjecting precursor solution C to a hydrothermal reaction; collecting the hydrothermal reaction product, and drying and crushing it to obtain the BiOBr / CoWO4 photocatalytic material.

[0009] In an optional embodiment, the bismuth source is one or a mixture of several of bismuth nitrate, bismuth chloride, bismuth acetate, or their hydrates; the bromine source is one or a mixture of several of potassium bromide, hydrobromic acid, and dodecyl dimethyl ammonium bromide; the cobalt source is one or a mixture of several of cobalt nitrate, cobalt chloride, cobalt sulfate, or their hydrates; and the tungsten source is one or a mixture of several of sodium tungstate, ammonium metatungstate, and ammonium tungstate.

[0010] In an optional embodiment, the molar ratio of the bismuth source to the bromine source is 1~6:1~6, preferably 1:1.

[0011] In an optional embodiment, the molar ratio of the cobalt source to the tungsten source is 1~5:1~5, preferably 1:1.

[0012] In an optional embodiment, the molar ratio of the bismuth source to the cobalt source is 1~6:1~5, preferably (1~5):1, and the molar ratio of the bismuth source to the tungsten source is 1~6:1~5, preferably (1~5):1.

[0013] In an optional embodiment, the hydrothermal reaction temperature is 120~180 ℃ and the hydrothermal reaction time is 6~12 h.

[0014] In an optional embodiment, the drying temperature is 30~60℃, the drying atmosphere is vacuum, and the drying time is 5~12 hours.

[0015] In an optional embodiment, the preparation method of the BiOBr / CoWO4 visible light photocatalyst material includes: dissolving 1-6 mmol of bismuth nitrate pentahydrate and 1-6 mmol of potassium bromide in 10-50 mL of ultrapure water, stirring to ensure complete dissolution of bismuth nitrate pentahydrate and potassium bromide, and stirring for 1-6 h to obtain precursor solution A; dissolving 1-5 mmol of cobalt nitrate hexahydrate and 1-5 mmol of sodium tungstate in 10-50 mL of ultrapure water, stirring to ensure complete dissolution of cobalt nitrate hexahydrate and sodium tungstate, and stirring for 1-6 h to obtain precursor solution B; slowly adding precursor solution A to precursor solution B while stirring, and mixing to obtain precursor solution C; transferring precursor solution C to a hydrothermal reactor, and hydrothermally heating precursor solution C at 120-180 °C for 6-12 h; after naturally cooling to room temperature, repeatedly filtering and washing with ultrapure water and anhydrous ethanol, and vacuum drying at 30-60 °C for 5-12 h. h. Grind the dried powder thoroughly with a mortar and pestle to obtain the BiOBr / CoWO4 photocatalytic material.

[0016] Thirdly, the present invention provides a BiOBr / CoWO4 visible light catalytic material, wherein the BiOBr / CoWO4 visible light catalytic material is obtained according to any one of the preparation methods described herein.

[0017] Fourthly, the present invention provides the use of BiOBr / CoWO4 visible light catalytic material in photocatalytic degradation.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The pn-type heterojunction formed by BiOBr / CoWO4 designed in this invention can effectively control the visible light absorption range of BiOBr, solve the problem of low carrier transport efficiency, and has good photocatalytic activity.

[0019] (2) The present invention utilizes a one-step hydrothermal method to prepare pn heterojunction BiOBr / CoWO4 photocatalytic materials. This preparation method is green and pollution-free, with low raw material costs, mild reaction conditions, easy implementation, and easy process control.

[0020] (3) By controlling reaction conditions such as the reaction temperature and reaction time of the precursor liquid, the present invention can obtain particle-loaded sheet-like BiOBr / CoWO4. Attached Figure Description

[0021] Figure 1The XRD pattern of BiOBr / CoWO4 prepared in Example 3.

[0022] Figure 2 The image shows the SEM pattern of BiOBr / CoWO4 prepared in Example 3.

[0023] Figure 3 The image shows an HRTEM image of the BiOBr / CoWO4 prepared in Example 3.

[0024] Figure 4 The degradation rate of 20 mg / L Rhodamine B by BiOBr / CoWO4 prepared in Example 3 was compared within 75 min. Detailed Implementation

[0025] The present invention is further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention. The following exemplarily illustrates the BiOBr / CoWO4 visible light photocatalytic material, its preparation method, and its applications.

[0026] Bismuth source and bromine source are stirred and mixed evenly in a solvent to obtain precursor solution A. The bismuth source includes, but is not limited to, bismuth nitrate, bismuth chloride, bismuth acetate, or their hydrates. The bromine source includes, but is not limited to, potassium bromide, hydrobromic acid, dodecyl dimethyl ammonium bromide, etc. The molar ratio of the bismuth source to the bromine source can be 1~6:1~6. Preferably, the molar ratio of the bismuth source to the bromine source is 1:1. As an example, but not limited to, the molar concentration of the bismuth source in precursor solution A is 1~6 mmol:10~50 mL. As an example, but not limited to, the molar concentration of the bromine source in precursor solution A is 1~6 mmol:10~50 mL. The solvent can be water. The stirring time can be adjusted as needed. For example, the stirring time is 1~3 h (e.g., 1 h).

[0027] A cobalt source and a tungsten source are stirred and mixed evenly in a solvent to obtain precursor solution B. The cobalt source includes, but is not limited to, cobalt nitrate, cobalt chloride, cobalt sulfate, or their hydrates. The tungsten source includes, but is not limited to, sodium tungstate, ammonium metatungstate, and ammonium tungstate. The molar ratio of the cobalt source to the tungsten source is 1-5:1-5. Preferably, the molar ratio of the cobalt source to the tungsten source is 1:1. As an example, but not limited to, the molar concentration of the cobalt source in precursor solution A is 1-5 mmol:10-50 mL. As an example, but not limited to, the molar concentration of the tungsten source in precursor solution A is 1-5 mmol:10-50 mL. The solvent can be water. The stirring time can be adjusted as needed. For example, the stirring time is 1-3 h (e.g., 1 h).

[0028] In an optional embodiment, the molar ratio of the bismuth source to the cobalt source can be 1~6:1~5, preferably (1~5):1. In an optional embodiment, the molar ratio of the bismuth source to the tungsten source can be 1~6:1~5, preferably (1~5):1.

[0029] While stirring, precursor solution A is slowly added to precursor solution B, and after stirring and mixing, precursor solution C is obtained.

[0030] The precursor solution C is subjected to a hydrothermal reaction. The hydrothermal reaction can be carried out in a hydrothermal reactor. The hydrothermal reaction temperature can be 120~180 ℃. The hydrothermal reaction time can be 6~12 h.

[0031] The hydrothermal reaction products were collected, dried, and crushed to obtain the BiOBr / CoWO4 visible light photocatalyst material. Drying was carried out in an electrically heated forced-air drying oven at a temperature of 30–60°C under a vacuum atmosphere for 5–12 hours.

[0032] As an optional technical solution, the preparation method of BiOBr / CoWO4 visible light photocatalyst material includes: dissolving 1-6 mmol of bismuth nitrate pentahydrate and 1-6 mmol of potassium bromide in 10-50 mL of ultrapure water, and stirring slowly to ensure complete dissolution of bismuth nitrate pentahydrate and potassium bromide, followed by stirring with a magnetic stirrer for 1 h to obtain precursor solution A. Dissolving 1-5 mmol of cobalt nitrate hexahydrate and 1-5 mmol of sodium tungstate in 10-50 mL of ultrapure water, and stirring slowly to ensure complete dissolution of cobalt nitrate hexahydrate and sodium tungstate, followed by stirring with a magnetic stirrer for 1 h to obtain precursor solution B. Adding precursor solution A slowly to precursor solution B with a magnetic stirrer to obtain precursor solution C. Adjusting the temperature of the electric heating drying oven to 160℃, transferring precursor solution C into a 100 mL hydrothermal reactor liner, sealing and tightening the lid, and reacting precursor solution C under hydrothermal conditions for 6-12 h. After the electric heating drying oven cools naturally to room temperature, the powder is repeatedly filtered and washed three times with ultrapure water and anhydrous ethanol. Then, it is vacuum dried in an electric heating drying oven at 30-60 ℃ for 5-12 hours. The dried powder is then thoroughly ground in a mortar and pestle. This powder is a BiOBr / CoWO4 photocatalytic material.

[0033] XRD analysis revealed that the composition of the BiOBr / CoWO4 visible light catalytic degradation material is BiOBr / CoWO4.

[0034] Based on the SEM images, the BiOBr / CoWO4 visible light catalytic degradation material exhibits a sheet-like morphology.

[0035] In an optional embodiment, the molar ratio of BiOBr to CoWO4 in the BiOBr / CoWO4 visible light catalytic degradation material is 1:(0.2~1), for example, 1:1, 1:0.6, 1:0.2, etc.

[0036] In summary, this invention utilizes a one-step hydrothermal method to synthesize BiOBr / CoWO4 photocatalytic materials. The prepared BiOBr / CoWO4 photocatalytic materials exhibit controllable structures and good visible light photocatalytic degradation performance.

[0037] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0038] Example 1

[0039] The preparation method of BiOBr / CoWO4 visible light photocatalytic degradation material includes the following steps: 5 mmol of bismuth nitrate pentahydrate and 5 mmol of potassium bromide were dissolved in 30 mL of ultrapure water. The bismuth nitrate pentahydrate and potassium bromide were slowly stirred until fully dissolved. The mixture was stirred for 1 h with a magnetic stirrer to obtain precursor solution A.

[0040] 5 mmol of cobalt nitrate hexahydrate and 5 mmol of sodium tungstate were dissolved in 30 mL of ultrapure water. The cobalt nitrate hexahydrate and sodium tungstate were fully dissolved under slow stirring. The mixture was stirred for 1 h with a magnetic stirrer to obtain precursor solution B.

[0041] With the help of a magnetic stirrer, precursor solution A is slowly added to precursor solution B and stirred to form precursor solution C.

[0042] Adjust the temperature of the electric heating drying oven to 160℃, transfer the precursor liquid C into the 100 ml hydrothermal reactor liner, seal and tighten the lid, and hydrothermally react at 160℃ for 6 h.

[0043] After the electric heating drying oven cools naturally to room temperature, the powder is repeatedly filtered and washed three times with ultrapure water and anhydrous ethanol, and then vacuum dried at 60°C for 12 hours in an electric heating drying oven. The dried powder is then thoroughly ground in a mortar and pestle. This powder is a BiOBr / CoWO4 photocatalytic material.

[0044] Example 2

[0045] The preparation method of BiOBr / CoWO4 visible light photocatalytic degradation material includes the following steps: 5 mmol of bismuth nitrate pentahydrate and 5 mmol of potassium bromide were dissolved in 30 mL of ultrapure water. The bismuth nitrate pentahydrate and potassium bromide were slowly stirred until fully dissolved. The mixture was stirred for 1 h with a magnetic stirrer to obtain precursor solution A.

[0046] 3 mmol cobalt nitrate hexahydrate and 3 mmol sodium tungstate were dissolved in 30 mL of ultrapure water. The cobalt nitrate hexahydrate and sodium tungstate were fully dissolved under slow stirring. The mixture was stirred for 1 h with a magnetic stirrer to obtain precursor solution B.

[0047] Under the stirring of a magnetic stirrer, precursor solution A is slowly added to precursor solution B and stirred until homogeneous to obtain precursor solution C.

[0048] Adjust the temperature of the electric heating drying oven to 160℃, transfer the precursor liquid C into the 100 ml hydrothermal reactor liner, seal and tighten the lid, and hydrothermally react at 160℃ for 6 h.

[0049] After the electric heating drying oven cools naturally to room temperature, the powder is repeatedly filtered and washed three times with ultrapure water and anhydrous ethanol, and then vacuum dried at 60°C for 12 hours in an electric heating drying oven. The dried powder is then thoroughly ground in a mortar and pestle. This powder is a BiOBr / CoWO4 photocatalytic material.

[0050] Example 3

[0051] The preparation method of BiOBr / CoWO4 visible light photocatalytic degradation material includes the following steps: 5 mmol of bismuth nitrate pentahydrate and 5 mmol of potassium bromide were dissolved in 30 mL of ultrapure water. The bismuth nitrate pentahydrate and potassium bromide were slowly stirred until fully dissolved. The mixture was stirred for 1 h with a magnetic stirrer to obtain precursor solution A.

[0052] 1 mmol cobalt nitrate hexahydrate and 1 mmol sodium tungstate were dissolved in 30 mL of ultrapure water. The cobalt nitrate hexahydrate and sodium tungstate were fully dissolved under slow stirring. The mixture was stirred under a magnetic stirrer for 1 h to obtain precursor solution B.

[0053] Precursor solution A was slowly added to precursor solution B under magnetic stirring to obtain precursor solution C.

[0054] Adjust the temperature of the electric heating drying oven to 160℃, transfer the precursor liquid C into the 100 ml hydrothermal reactor liner, seal and tighten the lid, and hydrothermally react at 160℃ for 12 h.

[0055] After the electric heating drying oven cools naturally to room temperature, the powder is repeatedly filtered and washed three times with ultrapure water and anhydrous ethanol, and then vacuum dried at 60°C for 12 hours in an electric heating drying oven. The dried powder is then thoroughly ground in a mortar and pestle. This powder is a BiOBr / CoWO4 photocatalytic material.

[0056] Figure 1 The image shows the XRD pattern of the BiOBr / CoWO4 prepared in Example 3 of this invention. According to standard cards PDF#78-0348 and PDF#72-0479, the photocatalyst material prepared in Example 3 contains both BiOBr and CoWO4 phases. BiOBr exhibits a tetragonal phase, while CoWO4 is a monoclinic phase, and both have good crystallinity, indicating successful synthesis of the BiOBr / CoWO4 composite photocatalyst.

[0057] Figure 2 This is a SEM image of BiOBr / CoWO4 prepared under the conditions of Example 3 of this invention. The image shows that the morphology of BiOBr / CoWO4 is a sheet-like structure supported by nanoparticles, with the size of the sheet-like structure ranging from 0.5 to 1 micrometer.

[0058] Figure 3 The image shows an HRTEM image of the BiOBr / CoWO4 prepared in Example 3. The image shows that the BiOBr / CoWO4 interface exhibits a distinct pn heterojunction.

[0059] Figure 4 This image shows the performance of BiOBr / CoWO4 prepared in Example 3 of this invention in degrading Rhodamine B. A 500 W Xe lamp was used as the visible light source to evaluate the photocatalytic activity of photons and reference materials based on aqueous Rhodamine B (RhB) degradation. 50 mg of photocatalyst was suspended in 50 mL of a fixed concentration of RhB solution. After photocatalysis, 3 mL aliquots were taken at regular intervals, and the residual RhB concentration was monitored using a UV2800-A spectrophotometer. Using 50 mL of 20 mg / L Rhodamine B as the degradation target, the degradation effect of 50 mg of BiOBr / CoWO4 photocatalyst on Rhodamine B was tested within 75 min. The degradation rate was calculated using the following formula: Degradation rate = (1 - C / C0) × 100%, where C0 and C are the initial RhB concentration at any irradiation time and the RhB concentration after degradation, respectively. The BiOBr / CoWO4 prepared in this example achieved a degradation rate of 93%.

[0060] Comparative Example 1 The method is basically the same as in Example 1, except that the tungsten source is in excess. The preparation method of the visible light photocatalytic degradation material includes the following steps: 5 mmol of bismuth nitrate pentahydrate and 5 mmol of potassium bromide were dissolved in 30 mL of ultrapure water. The bismuth nitrate pentahydrate and potassium bromide were slowly stirred until fully dissolved. The mixture was stirred for 1 h with a magnetic stirrer to obtain precursor solution A.

[0061] 5 mmol cobalt nitrate hexahydrate and 6 mmol sodium tungstate were dissolved in 30 mL of ultrapure water. The cobalt nitrate hexahydrate and sodium tungstate were fully dissolved under slow stirring. The mixture was stirred for 1 h with a magnetic stirrer to obtain precursor solution B.

[0062] With the help of a magnetic stirrer, precursor solution A is slowly added to precursor solution B and stirred to form precursor solution C.

[0063] Adjust the temperature of the electric heating drying oven to 160℃, transfer the precursor liquid C into the 100 ml hydrothermal reactor liner, seal and tighten the lid, and hydrothermally react at 160℃ for 12 h.

[0064] After the electric heating drying oven cools naturally to room temperature, the powder is repeatedly filtered and washed three times with ultrapure water and anhydrous ethanol, and then vacuum dried at 60°C for 12 hours in an electric heating drying oven. The dried powder is then thoroughly ground in a mortar and pestle. This powder is a BiOBr / CoWO4 photocatalytic material.

[0065] In this comparative example, due to an excess of tungsten source, the resulting product contained bismuth tungstate impurities.

Claims

1. A BiOBr / CoWO4 visible light photocatalytic material, characterized in that, The BiOBr / CoWO4 visible light catalytic material is a BiOBr / CoWO4 visible light catalytic material with CoWO4 nanoparticles loaded on the surface of sheet-like BiOBr and having a pn heterojunction.

2. A method for preparing BiOBr / CoWO4 visible light photocatalytic material, characterized in that, The preparation method includes: mixing a bismuth source and a bromine source uniformly in a solvent to obtain precursor solution A; mixing a cobalt source and a tungsten source uniformly in a solvent to obtain precursor solution B; adding precursor solution A to precursor solution B under stirring, and mixing to obtain precursor solution C; subjecting precursor solution C to a hydrothermal reaction; collecting the hydrothermal reaction product, and drying and crushing it to obtain BiOBr / CoWO4 visible light photocatalyst material.

3. The method for preparing the BiOBr / CoWO4 visible light photocatalyst material according to claim 2, characterized in that, The bismuth source is one or a mixture of several of bismuth nitrate, bismuth chloride, bismuth acetate, or their hydrates; the bromine source is one or a mixture of several of potassium bromide, hydrobromic acid, and dodecyl dimethyl ammonium bromide; the cobalt source is one or a mixture of several of cobalt nitrate, cobalt chloride, cobalt sulfate, or their hydrates; and the tungsten source is one or a mixture of several of sodium tungstate, ammonium metatungstate, and ammonium tungstate.

4. The method for preparing the BiOBr / CoWO4 visible light photocatalyst material according to claim 2 or 3, characterized in that, The molar ratio of the bismuth source to the bromine source is 1~6:1~6, preferably 1:

1.

5. The method for preparing the BiOBr / CoWO4 visible light photocatalyst material according to any one of claims 2 to 4, characterized in that, The molar ratio of the cobalt source to the tungsten source is 1~5:1~5, preferably 1:

1.

6. The method for preparing the BiOBr / CoWO4 visible light photocatalyst material according to any one of claims 2 to 5, characterized in that, The molar ratio of the bismuth source to the cobalt source is 1~6:1~5, preferably (1~5):1, and the molar ratio of the bismuth source to the tungsten source is 1~6:1~5, preferably (1~5):

1.

7. A method for preparing the BiOBr / CoWO4 visible light photocatalyst material according to any one of claims 2 to 6, characterized in that, The hydrothermal reaction temperature is 120~180 ℃, and the hydrothermal reaction time is 6~12 h.

8. A method for preparing the BiOBr / CoWO4 visible light photocatalyst material according to any one of claims 2 to 7, characterized in that, The preparation method of BiOBr / CoWO4 visible light photocatalyst material includes: dissolving 1-6 mmol of bismuth nitrate pentahydrate and 1-6 mmol of potassium bromide in 10-50 mL of ultrapure water, stirring until the bismuth nitrate pentahydrate and potassium bromide are fully dissolved, and stirring for 1-3 h to obtain precursor solution A; dissolving 1-5 mmol of cobalt nitrate hexahydrate and 1-5 mmol of sodium tungstate in 10-50 mL of ultrapure water, stirring slowly until the cobalt nitrate hexahydrate and sodium tungstate are fully dissolved, and stirring for 1-3 h to obtain precursor solution B; slowly adding precursor solution A to precursor solution B while stirring, and mixing to obtain precursor solution C; transferring precursor solution C to a hydrothermal reactor, and hydrothermally reacting precursor solution C at 120-180 °C for 6-12 h; after naturally cooling to room temperature, repeatedly filtering and washing with ultrapure water and anhydrous ethanol, and vacuum drying at 30-60 °C for 5-12 h. h. Grind the dried powder thoroughly with a mortar and pestle to obtain the BiOBr / CoWO4 visible light catalytic material.

9. A BiOBr / CoWO4 visible light photocatalytic material, characterized in that, The BiOBr / CoWO4 visible light catalytic material is obtained by the preparation method according to any one of claims 2 to 8.

10. The application of the BiOBr / CoWO4 visible light photocatalytic material according to claim 1 or 9 in photocatalytic degradation.

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