A method for increasing oxygen vacancies in BiOBr photocatalytic materials

Abstract

The present invention discloses a method for increasing oxygen vacancies in BiOBr photocatalytic materials, comprising the following steps: dissolving a bromine salt and lignin in a tert-butyl alcohol solution to obtain a dispersion, then adding a bismuth salt to the dispersion and mixing evenly to obtain a reaction solution; placing the reaction solution at a temperature of 150 to 170° C. for reaction, and separating the obtained product, which is a BiOBr photocatalytic material with oxygen vacancies. The present invention selects lignin and tert-butyl alcohol as modification reagents, wherein: lignin has abundant functional groups, can be used as a surface modifier of the catalyst to regulate the growth of the catalyst, and can also be used as a reducing agent to promote the generation of oxygen vacancies; the addition of tert-butyl alcohol has a synergistic promoting effect with lignin, further promoting the formation of oxygen vacancies in the catalyst. The method of the present invention can increase the oxygen vacancy content of the BiOBr photocatalytic material, thereby improving its photocatalytic performance.

Description

Technical Field

[0001] The invention relates to the field of photocatalysis, and in particular to a method for increasing oxygen vacancies in BiOBr photocatalytic materials. Background Art

[0002] A healthy environment is necessary for the survival of the entire biota, but hazardous substances discharged by industries have caused serious harm to human survival. Many non-biodegradable organic pollutants such as organic dyes, phenolic derivatives, pesticides, antibiotics, etc. are the main factors that pollute the environment and water. Among them, organic dyes are highly toxic to organisms due to their carcinogenic and mutagenic properties. In order to remove these pollutants from the environment and water, people have made many efforts to develop economical, environmentally friendly and efficient technologies, among which photocatalytic processes are the most effective economic technologies to achieve the treatment goals. In the past few decades, a large number of photocatalysts have been explored and analyzed for the removal of organic pollutants.

[0003] Bismuth oxybromide (BiOBr) has a unique layered structure (BiOBr is composed of [Bi2O2] plates and dihalogen atom plates intersecting each other), good visible light response, and high separation efficiency of photogenerated electrons and holes, which makes BiOBr materials widely used in the degradation of dyes, various phenols, water pollutants, and many antibiotics. However, pure BiOBr catalysts are not enough in practical applications. They have poor absorption of visible light, too large energy band gap, cannot produce enough photogenerated carriers, have low quantum efficiency, and small specific surface area. These shortcomings weaken the catalytic degradation performance. Defect engineering is widely used in catalyst modification, among which oxygen vacancies are the most common and easiest to form in crystals. Oxygen vacancies can effectively expand the catalyst's absorption capacity for visible light, enhance the separation efficiency of photogenerated electrons and holes, and thus improve the photocatalytic efficiency of the catalyst. How to promote the formation of oxygen vacancies in bismuth oxybromide to improve its photocatalytic performance is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to provide a method for increasing oxygen vacancies in BiOBr photocatalytic materials to solve the problems in the prior art.

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

[0006] A method for increasing oxygen vacancies in BiOBr photocatalytic materials comprises the following steps:

[0007] The bromine salt and lignin are dissolved in a tert-butyl alcohol solution to obtain a dispersion, and then the bismuth salt is added to the dispersion and mixed evenly to obtain a reaction solution; the reaction solution is placed at a temperature of 150 to 170° C. to react for 10 to 20 hours, and the separated product is a BiOBr photocatalytic material with oxygen vacancies.

[0008] Preferably, the tert-butanol solution is a mixed solution of tert-butanol and water; the volume ratio of the tert-butanol to water is 4:1.

[0009] Preferably, the bismuth salt is bismuth nitrate, bismuth sulfate or bismuth chloride.

[0010] Preferably, the bromide salt is potassium bromide or sodium bromide.

[0011] Preferably, the lignin is alkali lignin or lignin sulfonate.

[0012] The beneficial effects of the present invention are:

[0013] The present invention selects lignin and tert-butyl alcohol as modification agents, wherein: lignin has abundant functional groups, can be used as a surface modifier of the catalyst to regulate the growth of the catalyst, and can also be used as a reducing agent to promote the generation of oxygen vacancies; the addition of tert-butyl alcohol has a synergistic effect with lignin, further promoting the formation of oxygen vacancies in the catalyst. The method of the present invention can increase the oxygen vacancy content of the BiOBr photocatalytic material, thereby improving its photocatalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 XRD patterns of the three substances B0, BE0 and BT;

[0015] Figure 2 The EPR diagrams of the three substances B0, BE0 and BT;

[0016] Figure 3 These are the UV-vis diagrams of the three substances B0, BE0, and BT. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0018] In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional means in the prior art in the field, and therefore, they are not described in detail; the raw materials and reagents used in the following embodiments are all commercially available products and can be purchased.

[0019] Comparative Example 1

[0020] 4mmol KBr was added into 50ml distilled water and stirred evenly to obtain a dispersion; then Bi(NO3)3·5H2O was added into the dispersion and mixed evenly to obtain a reaction solution; the reaction solution was poured into a 100mL stainless steel hydrothermal autoclave lined with polytetrafluoroethylene, and placed in an oven and heated at 160°C for 12h to complete the reaction; after the reaction was completed, the obtained product was separated, washed and dried in sequence, and the obtained product was separated and marked as B0.

[0021] Comparative Example 2

[0022] 4mmol KBr and 0.0244g alkali lignin were added to 50ml distilled water and stirred evenly to obtain a dispersion; then Bi(NO3)3·5H2O was added to the dispersion and mixed evenly to obtain a reaction solution; the reaction solution was poured into a 100mL stainless steel hydrothermal autoclave lined with polytetrafluoroethylene, placed in an oven and heated at 160°C for 12h to complete the reaction; after the reaction was completed, the obtained product was separated, washed and dried in sequence, and the obtained product was separated and marked as BE0.

[0023] Example 3

[0024] 10 ml of distilled water and 40 ml of tert-butanol were mixed to obtain a tert-butanol solution; 4 mmol of KBr and 0.0244 g of alkali lignin were added to 50 ml of the tert-butanol solution and stirred evenly to obtain a dispersion; Bi(NO3)3·5H2O was then added to the dispersion and mixed evenly to obtain a reaction solution; the reaction solution was poured into a 100 mL stainless steel hydrothermal autoclave lined with polytetrafluoroethylene, placed in an oven and heated at 160°C for 12 hours to react; after the reaction was completed, the obtained product was separated, washed, and dried in sequence, and the obtained product was separated and marked as BT.

[0025] XRD characterization of B0, BE0, and BT was performed, and the results are as follows Figure 1 As shown. All samples show similar diffraction peaks in the X-ray spectrum without other impurity peaks, indicating that all samples are high-purity crystals. The BiOBr synthesized by the reaction of the present invention matches the tetragonal crystal JCPDF No.85-0862. The typical diffraction peaks at 2θ values ​​of 10.9°, 25.2°, 31.7°, and 32.3° correspond to the (001), (101), (102), and (110) planes, respectively. Compared with B0, BE0 added lignin during the preparation process, and BT added lignin and tert-butyl alcohol during the preparation process. It can be seen that the peak intensity ratio of the (102) crystal plane to the (110) crystal plane of BE0 and BT has changed significantly, which may be due to the formation of oxygen vacancies affecting the growth of the (102) crystal plane.

[0026] like Figure 2As shown in Figure 1, B0, BE0, and BT all exhibit a characteristic single Lorentzian line centered at g = 2.003, which is caused by unpaired electrons captured by oxygen vacancies. The number of oxygen vacancies is proportional to the relative intensity of the EPR signal peak. Figure 2 It can be seen that the relative intensity of the EPR peak is approximately BT>BE0>B0, indicating that lignin and tert-butyl alcohol are conducive to the generation of oxygen vacancies.

[0027] Figure 3 The UV-vis absorption curves of B0, BE0, and BT are shown. The absorption intensity is about BT>BE0>B0. Compared with B0, the absorption capacity of BE0 and BT to visible light has been enhanced, indicating that lignin and tert-butyl alcohol can improve the enrichment capacity of the catalyst to visible light, the absorbed energy becomes larger, the catalyst can produce more photogenerated carriers, and the photocatalytic ability is improved.

[0028] In summary, the method provided by the present invention can increase the oxygen vacancies of the BiOBr photocatalyst, thereby accelerating the separation of photogenerated electrons and holes in the BiOBr photocatalyst and enhancing the photocatalytic reaction performance.

[0029] Obviously, the described embodiments are only some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for increasing oxygen vacancies in BiOBr photocatalytic materials, characterized in that: The following steps are involved: The bromine salt and lignin are dissolved in a tert-butyl alcohol solution to obtain a dispersion, and then the bismuth salt is added to the dispersion and mixed evenly to obtain a reaction solution; the reaction solution is placed at a temperature of 150 to 170° C. to react, and the separated product is a BiOBr photocatalytic material with oxygen vacancies; The reaction time is 10 to 20 hours; The tert-butanol solution is a mixed solution of tert-butanol and water; the volume ratio of the tert-butanol to water is 4:

1.

2. The method for increasing oxygen vacancies in BiOBr photocatalytic materials according to claim 1, characterized in that: The bismuth salt is bismuth nitrate, bismuth sulfate or bismuth chloride.

3. The method for increasing oxygen vacancies in BiOBr photocatalytic materials according to claim 1, characterized in that: The bromine salt is potassium bromide or sodium bromide.

4. The method for increasing oxygen vacancies in BiOBr photocatalytic materials according to claim 1, characterized in that: The lignin is alkali lignin or lignin sulfonate.

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