A method for preparing a defective PbBiO2Br multilayer hollow nanosphere catalyst

Abstract

The application belongs to the technical field of photocatalytic materials, and provides a method for preparing a defective PbBiO2Br multilayer hollow nanosphere catalyst. The method comprises the following steps: (1) adding bismuth nitrate and lead nitrate into a nitric acid solution, and standing the solution to obtain a solution A; (2) obtaining a mixed solution B by adding brominated 1-octyl-3-methyl imidazole, water and a TX-100 emulsifier; (3) adding the mixed solution A into the mixed solution B to obtain a mixed solution C; (4) adjusting the pH of the mixed solution C to 10-10.5, and performing hydrothermal treatment, centrifugation and drying, and the obtained product is the defective PbBiO2Br multilayer hollow nanosphere catalyst after refinement. The method has the advantages of simple process, simple operation and low cost. The PbBiO2Br catalyst synthesized by the method has stable performance, high catalytic efficiency and strong selectivity, and is mainly applied to selective oxidation of organic matters.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic materials technology, and in particular to a method for preparing defective PbBiO2Br multilayer hollow nanosphere catalysts. Background Technology

[0002] In recent years, my country's various industries have developed rapidly. This rapid societal development and high consumption of fossil fuels have inevitably led to environmental and energy crises. Selective oxidation is one of the most efficient synthetic routes for high-yield organic intermediates (including aldehydes, ketones, epoxides, etc.). However, industrial production typically involves high-temperature and high-pressure conditions, which causes environmental pollution and energy consumption. Therefore, developing green and environmentally friendly catalysts for selective oxidation reactions is crucial.

[0003] Solar energy is a highly economical and clean energy source, serving as a green and pollution-free driver for selective oxidation. However, traditional photocatalysts like TiO2 suffer from several drawbacks, such as low quantum utilization efficiency and low solar energy utilization rate. This results in low conversion and selectivity in photocatalytic selective oxidation, severely limiting its practical application. Conventional solutions, such as noble metal loading, composite semiconductors, and ion doping modification, can significantly improve this situation, but these methods are complex and costly. Therefore, developing photocatalysts is a crucial step towards further advancements in selective oxidation and its application in industrial production.

[0004] PbBiO2Br is a class of bismuth-based semiconductor materials (photocatalysts) with wide applications in photocatalytic selective oxidation. PbBiO2Br possesses a suitable bandgap, effectively absorbing visible light, making it significant as a catalyst for studying efficient selective oxidation using sunlight. Seeking inexpensive, efficient, and easily synthesized photocatalytic materials is an inevitable trend for the further practical application of photocatalysis. Previous reports have mostly focused on the study of PbBiO2Br monomers. Fang et al. (Fang Yuan Xiao, RSC Advances, 2013, 3, 10687-10690) prepared novel ultrathin PbBiO2Br nanosheets using a solvothermal method; Yu et al. (Yan long Yu, Applied Surface Science 428(2018) 844-850) prepared novel single cubic nanosheet microcrystalline PbBiO2Br via hydrothermal synthesis. The PbBiO2Br nanocatalysts prepared by these processes exhibit varying morphologies, and most do not demonstrate excellent catalytic efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing defective PbBiO2Br multilayer hollow nanosphere catalysts to overcome the shortcomings of existing technologies.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing defective PbBiO2Br multilayer hollow nanosphere catalysts, comprising the following steps:

[0008] (1) Add bismuth nitrate and lead nitrate to a nitric acid solution and let the solution stand to obtain solution A;

[0009] (2) Mix 1-octyl-3-methylimidazol bromide, water and TX-100 emulsifier to obtain mixed solution B;

[0010] (3) Add mixed solution A dropwise to mixed solution B to obtain mixed solution C;

[0011] (4) Adjust the pH of the mixed solution C to 10-10.5, then centrifuge and dry it after hydrothermal treatment. The refined product is the defective PbBiO2Br multilayer hollow nanosphere catalyst.

[0012] There is no requirement for the order of steps (1) and (2).

[0013] Preferably, the molar ratio of lead nitrate to bismuth nitrate in step (1) is 1:(0.9-1.1);

[0014] The concentration of nitric acid is 3.5–4.5 M;

[0015] The ratio of bismuth nitrate to nitric acid is 1 mM: 1.5–2.5 mL.

[0016] Preferably, in step (2), the ratio of 1-octyl-3-methylimidazole bromide, water and TX-100 emulsifier is 1 mM: 20-30 mL: 0.1-0.5 g.

[0017] Preferably, the molar ratio of lead nitrate to 1-octyl-3-methylimidazole bromide is 1:(0.9 to 1.1).

[0018] Preferably, in step (4), sodium hydroxide solution or ammonia water is used to adjust the pH value, with the concentration of sodium hydroxide solution being 1-3M and the concentration of ammonia water being 1-3M.

[0019] Preferably, the hydrothermal temperature in step (4) is 110–130°C and the time is 10–16 h;

[0020] The drying temperature is 115-125℃, and the time is 10-15 hours.

[0021] Preferably, the pH in step (4) is adjusted to 10.2.

[0022] Preferably, in step (4), the pH of the mixed solution C is adjusted to 10-10.5, glyoxal aqueous solution is added, and then the solution is dried by hydrothermal treatment and centrifugation.

[0023] In step (1), the volume ratio of nitric acid to glyoxal aqueous solution is 2:(0-5);

[0024] The concentration of glyoxal aqueous solution is 8.5–9 M.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention utilizes a ternary microemulsion method combined with in-situ reduction to prepare defective PbBiO2Br multilayer hollow nanospheres. This method represents the first successful synthesis of defective PbBiO2Br multilayer hollow nanospheres using this technique. The method is simple, easy to operate, and low-cost. The synthesized PbBiO2Br catalyst exhibits stable performance, high catalytic efficiency, and strong selectivity, making it primarily suitable for the selective oxidation of organic compounds. Attached Figure Description

[0027] Figure 1 The X-ray diffraction (XRD) pattern of the PbBiO2Br nanoparticles prepared in Example 1 is shown. By comparing the standard card with the diffraction peak pattern, it can be seen that the prepared PbBiO2Br nanocatalyst is pure and free of impurities.

[0028] Figure 2 The image shows a scanning electron microscope (SEM) image of the PbBiO2Br nanoparticles prepared in Example 1. It can be clearly seen from the image that the particle size of the PbBiO2Br nanocatalyst particles is about 100-150 nm.

[0029] Figure 3 The image shows a projection electron microscope (TEM) image of the PbBiO2Br nanoparticles prepared in Example 1. It can be clearly seen from the image that the PbBiO2Br nanocatalyst particles are multilayer hollow nanospheres.

[0030] Figure 4 The images show the PbBiO2Br nanospheres prepared in Example 1 and their solid UV spectra after the introduction of oxygen vacancies.

[0031] Figure 5 The table shows the effect of the PbBiO2Br nanomaterial prepared in Example 1 on the selective oxidation of benzyl alcohol to benzaldehyde. The effect is also significantly improved after introducing oxygen vacancies. Detailed Implementation

[0032] This invention provides a method for preparing defective PbBiO2Br multilayer hollow nanosphere catalysts, comprising the following steps:

[0033] (1) Add bismuth nitrate and lead nitrate to a nitric acid solution and let the solution stand to obtain solution A;

[0034] (2) Mix 1-octyl-3-methylimidazol bromide, water and TX-100 emulsifier to obtain mixed solution B;

[0035] (3) Add mixed solution A dropwise to mixed solution B to obtain mixed solution C;

[0036] (4) Adjust the pH of the mixed solution C to 10-10.5, then centrifuge and dry it after hydrothermal treatment. The refined product is the defective PbBiO2Br multilayer hollow nanosphere catalyst.

[0037] There is no requirement for the order of steps (1) and (2).

[0038] In this invention, the molar ratio of lead nitrate to bismuth nitrate in step (1) is 1:(0.9-1.1), preferably 1:1; the concentration of nitric acid is 3.5-4.5M, preferably 4-4.2M; and the ratio of bismuth nitrate to nitric acid is 1mM:1.5-2.5mL, preferably 1mM:1.8-2.3mL, and more preferably 1mM:2mL.

[0039] In this invention, the ratio of 1-octyl-3-methylimidazole bromide, water and TX-100 emulsifier in step (2) is 1 mM: 20-30 mL: 0.1-0.5 g, preferably 1 mM: 22-28 mL: 0.1-0.4 g, and more preferably 1 mM: 25-26 mL: 0.2-0.3 g.

[0040] In this invention, the molar ratio of lead nitrate to 1-octyl-3-methylimidazole bromide is 1:(0.9-1.1), preferably 1:1.

[0041] In this invention, in step (4), sodium hydroxide solution or ammonia is used to adjust the pH value. The concentration of sodium hydroxide solution is 1-3M, preferably 2-2.5M; the concentration of ammonia is 1-3M, preferably 2M.

[0042] In this invention, the hydrothermal temperature in step (4) is 110-130°C, preferably 115-125°C, and more preferably 120-122°C; the time is 10-16 hours, preferably 12-14 hours.

[0043] The drying temperature is 115–125℃, preferably 120–123℃; the drying time is 10–15 h, preferably 12–13 h.

[0044] In the preferred embodiment of the present invention, in step (4), the pH of the mixed solution C is adjusted to 10-10.5, an aqueous solution of glyoxal is added, and then the solution is dried by hydrothermal treatment and centrifugation; the addition of glyoxal can form oxygen vacancies;

[0045] In step (1), the volume ratio of nitric acid to glyoxal aqueous solution is 2:(0-5], preferably 2:1-4, and more preferably 2-3;

[0046] The concentration of the glyoxal aqueous solution is 8.5–9 M, preferably 8.7–8.8 M.

[0047] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] A method for preparing defective PbBiO2Br multilayer hollow nanosphere catalysts using a microemulsion method combined with in-situ reduction includes the following steps:

[0050] (1) Add 1 mM bismuth nitrate and 1 mM lead nitrate to 2 mL of 4 M nitric acid solution, and let the solution stand to obtain solution A;

[0051] (2) Take 1 mM 1-octyl-3-methylimidazole bromide and 0.2 g emulsifier TX-100 into a 100 mL beaker, then add 25 mL of aqueous solution and stir well to form mixed solution B;

[0052] (3) Add mixed solution A dropwise to mixed solution B while stirring. After the addition is complete, mixed solution C is formed. Adjust the pH of mixed solution C to 10.2 using a 2M sodium hydroxide solution. Put the solution into a reaction vessel and place the reaction vessel in a 120℃ oven for 12 hours.

[0053] (4) After cooling, the mixed solution is washed several times with distilled water and anhydrous ethanol, and then dried and ground in a 60°C oven to obtain PbBiO2Br hollow nanospheres.

[0054] Example 2

[0055] A method for preparing defective PbBiO2Br multilayer hollow nanosphere catalysts using a microemulsion method combined with in-situ reduction includes the following steps:

[0056] (1) Add 1 mM bismuth nitrate and 1 mM lead nitrate to 2 mL of 4 M nitric acid solution, and let the solution stand to obtain solution A;

[0057] (2) Take 1 mM 1-octyl-3-methylimidazole bromide and 0.2 g emulsifier TX-100 into a 100 mL beaker, then add 25 mL of aqueous solution and stir well to form mixed solution B;

[0058] (3) Add mixed solution A dropwise to mixed solution B while stirring. After the addition is complete, mixed solution C is formed. Adjust the pH of mixed solution C to 10.2 using 2M sodium hydroxide solution. Put it into the reaction vessel, add 100μL of glyoxal solution, and hydrothermally heat at 120℃ for 12h. Then put the reaction vessel into a 120℃ oven for 12h.

[0059] The concentration of the glyoxal aqueous solution is 8.8M.

[0060] (4) After cooling, the mixed solution is washed several times with distilled water and anhydrous ethanol, respectively, and then dried and ground in a 60°C oven to obtain PbBiO2Br hollow nanospheres with oxygen vacancies, denoted as DP-PBOP-HNSs.

[0061] Example 3

[0062] A method for preparing defective PbBiO2Br multilayer hollow nanosphere catalysts using a microemulsion method combined with in-situ reduction includes the following steps:

[0063] (1) Add 1 mM bismuth nitrate and 1 mM lead nitrate to 2 mL of 4 M nitric acid solution, and let the solution stand to obtain solution A;

[0064] (2) Take 1 mM 1-octyl-3-methylimidazole bromide and 0.2 g emulsifier TX-100 into a 100 mL beaker, then add 25 mL of aqueous solution and stir well to form mixed solution B;

[0065] (3) Add mixed solution A dropwise to mixed solution B while stirring. After the addition is complete, mixed solution C is formed. Adjust the pH of mixed solution C to 10.2 using 2M sodium hydroxide solution. Put it into the reaction vessel, add 300μL of glyoxal solution, and hydrothermally heat at 120℃ for 12h. Then put the reaction vessel into a 120℃ oven for 12h.

[0066] The concentration of the glyoxal aqueous solution is 8.8M.

[0067] (4) After cooling, the mixed solution is washed several times with distilled water and anhydrous ethanol, and then dried and ground in a 60°C oven to obtain PbBiO2Br hollow nanospheres with oxygen vacancies, denoted as DR-PBOP-HNSs.

[0068] Example 4

[0069] A method for preparing defective PbBiO2Br multilayer hollow nanosphere catalysts using a microemulsion method combined with in-situ reduction includes the following steps:

[0070] (1) Add 1 mM bismuth nitrate and 1 mM lead nitrate to 2 mL of 4.5 M nitric acid solution, and let the solution stand to obtain solution A;

[0071] (2) Take 1 mM 1-octyl-3-methylimidazole bromide and 0.3 g emulsifier TX-100 into a 100 mL beaker, then add 25 mL of aqueous solution and stir well to form mixed solution B;

[0072] (3) Add mixed solution A dropwise to mixed solution B while stirring. After the addition is complete, mixed solution C is formed. Adjust the pH of mixed solution C to 10.5 using a 2M sodium hydroxide solution. Put the solution into a reaction vessel and place the reaction vessel in a 120℃ oven for 12 hours.

[0073] (4) After cooling, the mixed solution is washed several times with distilled water and anhydrous ethanol, and then dried and ground in a 60°C oven to obtain PbBiO2Br hollow nanospheres.

[0074] Example 5

[0075] A method for preparing defective PbBiO2Br multilayer hollow nanosphere catalysts using a microemulsion method combined with in-situ reduction includes the following steps:

[0076] (1) Add 1 mM bismuth nitrate and 1 mM lead nitrate to 2 mL of 3.5 M nitric acid solution, and let the solution stand to obtain solution A;

[0077] (2) Take 1 mM 1-octyl-3-methylimidazole bromide and 0.15 g emulsifier TX-100 into a 100 mL beaker, then add 25 mL of aqueous solution and stir well to form mixed solution B;

[0078] (3) Add mixed solution A dropwise to mixed solution B while stirring. After the addition is complete, mixed solution C is formed. Adjust the pH of mixed solution C to 10.4 using 2M sodium hydroxide solution. Put the solution into the reaction vessel and place the reaction vessel in a 120℃ oven for 12 hours.

[0079] (4) After cooling, the mixed solution is washed several times with distilled water and anhydrous ethanol, and then dried and ground in a 60°C oven to obtain PbBiO2Br hollow nanospheres.

[0080] Figure 1 The X-ray diffraction (XRD) pattern of the PbBiO2Br nanoparticles prepared in Example 1 is shown. By comparing the standard card with the diffraction peak pattern, it can be seen that the prepared PbBiO2Br nanocatalyst is pure and free of impurities.

[0081] Figure 2The image shows a scanning electron microscope (SEM) image of the PbBiO2Br nanoparticles prepared in Example 1. It can be clearly seen from the image that the particle size of the PbBiO2Br nanocatalyst particles is about 100-150 nm.

[0082] Figure 3 The image shows a projection electron microscope (TEM) image of the PbBiO2Br nanoparticles prepared in Example 1. It can be clearly seen from the image that the PbBiO2Br nanocatalyst particles are multilayer hollow nanospheres.

[0083] Figure 4 The image shows the PbBiO2Br nanospheres prepared in Example 1 and their solid UV spectra after the introduction of oxygen vacancies.

[0084] Comparative Example 1

[0085] Replacing the emulsifier TX-100 with polyvinylpyrrolidone (PVP) resulted in a catalyst that did not possess the hollow nanosphere morphology. This demonstrates that TX-100 is crucial for the synthesis of hollow nanospheres.

[0086] Experimental Example

[0087] PBOB is a common sheet-like PbBiO2Br catalyst, PBOB-HNSs is the catalyst obtained in Example 1, while DP-PBOP-HNSs and DR-PBOB-HNSs are modified catalysts of the catalyst obtained in Example 1.

[0088] Photocatalytic oxidation was performed using the above catalyst. A suitable concentration of benzyl alcohol was added to a quartz reaction vessel, an oxygen atmosphere was introduced, and the reaction was carried out under a 300W xenon lamp irradiation for 8 hours. The concentration of benzyl alcohol after 8 hours of reaction was detected by gas chromatography, and the conversion rate and selectivity of the catalyst were calculated to evaluate the catalytic effect. Results are as follows: Figure 5 As shown, Figure 5 In this context, "conversion" refers to the conversion rate, and "selection" refers to the selectivity. Figure 5 It is evident that, compared with ordinary sheet-like PbBiO2Br catalysts, the nano-hollow spherical catalysts obtained in this application have significant advantages in both conversion rate and selectivity.

[0089] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a defective PbBiO2Br multilayer hollow nanospheres catalyst for selective oxidation of organic matter, characterized in that, The method comprises the following steps: (1) adding bismuth nitrate and lead nitrate into a nitric acid solution, and standing the solution to obtain solution A; (2) obtaining mixed solution B by mixing 1-octyl-3-methyl imidazole bromide, water and TX-100 emulsifier; (3) adding mixed solution A into mixed solution B to obtain mixed solution C; (4) adjusting the pH value of mixed solution C to 10-10.5, and then performing hydrothermal treatment, centrifugation and drying, and the obtained product is the defective PbBiO2Br multi-layer hollow nanosphere catalyst after refinement; The sequence of step (1) and step (2) is not limited; The organic matter comprises benzyl alcohol.

2. The production method according to claim 1, characterized by, The molar ratio of lead nitrate to bismuth nitrate in step (1) is 1:(0.9-1.1). The concentration of the nitric acid solution is 3.5-4.5M. The dosage ratio of bismuth nitrate to the nitric acid solution is 1mM:1.5-2.5mL.

3. The production method according to claim 1 or 2, characterized by, The dosage ratio of 1-octyl-3-methyl imidazole bromide, water and TX-100 emulsifier in step (2) is 1mM:20-30mL:0.1-0.5g.

4. The production method according to claim 3, characterized by, The molar ratio of lead nitrate to 1-octyl-3-methyl imidazole bromide is 1:(0.9-1.1).

5. The production method according to claim 1, 2 or 4, characterized by, In step (4), the pH value is adjusted by using a sodium hydroxide solution or ammonia water, the concentration of the sodium hydroxide solution is 1-3M, and the concentration of the ammonia water is 1-3M.

6. The preparation method according to claim 5, characterized in that, In step (4), the hydrothermal temperature is 110-130℃, and the time is 10-16h. The drying temperature is 115-125℃, and the time is 10-15h.

7. The production method according to claim 1, 2, 4 or 6, characterized by, In step (4), the pH value is adjusted to 10.

2.

8. The preparation method according to claim 7, characterized in that, In step (4), the pH value of mixed solution C is adjusted to 10-10.5, and then a glyoxal aqueous solution is added, and then hydrothermal treatment, centrifugation and drying are performed; In step (1), the volume ratio of the nitric acid solution to the glyoxal aqueous solution is 2:(0-5), and the volume of the glyoxal aqueous solution is not 0. The concentration of the glyoxal aqueous solution is 8.5-9M.

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