Oxygen-enriched carbon quantum dot composite bismuth oxybromide nanosheet material, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are an oxygen-enriched carbon quantum dot composite bismuth oxybromide nanosheet material, and a preparation method therefor and the use thereof. The preparation method comprises: sequentially uniformly dissolving Bi(NO3)3·5H2O and oxygen-enriched carbon quantum dots in a mannitol solution, then adding KBr thereto, stirring the mixture, then subjecting same to a solvothermal reaction, and then subjecting same to washing, suction filtration and drying, so as to obtain an oxygen-enriched carbon quantum dot composite bismuth oxybromide nanosheet material. The preparation method of the present invention is simple, and the bismuth oxybromide nanosheet is more easily and uniformly modified with the oxygen-enriched carbon quantum dots. The oxygen-enriched carbon quantum dots provide more active sites for bismuth oxybromide, thereby overcoming the defects of monomer bismuth oxybromide having a limited visible-light response and few active sites, optimizing the electron transmission performance of monomers, enhancing the light absorption intensity of the material, effectively guiding the charge flow, accelerating the separation and transfer of photo-generated charges, and achieving efficient visible light catalytic activity.

Description

Oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material and preparation method and application Technical Field

[0001] The present invention relates to the technical field of photocatalytic materials, and in particular to an oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material, a preparation method and an application thereof. Background Art

[0002] Due to the rapid development of industry and urbanization, energy shortages and environmental pollution have had a serious impact on the development of human society. Among them, environmental pollution problems such as water pollution, air pollution and soil pollution have posed a huge threat to the natural environment on which human beings depend for survival. The problem of water pollution is particularly prominent, and how to effectively treat pollutants in water has therefore become a hot topic of concern for scientists. Common methods for treating water pollutants include biodegradation, physical filtration, adsorption, ion exchange and photocatalytic degradation. However, methods such as biodegradation, physical filtration, adsorption and ion exchange require high costs, low treatment efficiency and can cause secondary pollution.

[0003] Compared to the aforementioned treatment technologies, photocatalysis offers advantages such as low cost, ease of operation, mild reaction conditions, and no secondary pollution after treatment, making it a promising technology. Photocatalysis primarily utilizes semiconductors as photocatalysts, utilizing sustainable sunlight to activate the semiconductors and generate active species with strong oxidizing properties. These highly oxidizing active species are capable of oxidizing and decomposing organic pollutants, converting high-molecular-weight pollutants into low-molecular-weight, non-polluting substances, thereby achieving efficient pollutant removal.

[0004] Among various semiconductor photocatalyst materials, bismuth oxybromide (BiOBr) has attracted significant attention due to its suitable bandgap (approximately 2.6 eV) and stable chemical properties. In previous reports, BiOBr has been used to remove organic pollutants and antibiotics. However, BiOBr materials typically exhibit low carrier mobility and rapid carrier recombination, and their independent utilization for environmental remediation is hindered by inherent defects, requiring further optimization. BiOBr's narrow light absorption edge (approximately 435 nm) hinders its ability to maximize the conversion of solar energy into chemical energy. The scarcity of exposed active sites on the surface leads to sluggish surface reaction kinetics, severe recombination of photogenerated electron-hole pairs, and slow separation and transfer of photogenerated charge, resulting in poor activity. Therefore, an environmentally friendly and feasible co-catalyst is urgently needed to optimize BiOBr's inherent defects.

[0005] Carbon quantum dots (CQDs), as a zero-dimensional carbon nanomaterial, are excellent light-absorbing materials with conversion photoluminescence properties and can be applied to long-wavelength light response. Due to their π-conjugated structure, CQDs also show good electron transport properties between semiconductors. In addition, due to the large number of carboxyl, alcohol and amine groups on their surface, they are hydrophilic, which is beneficial for environmental remediation applications. However, the original CQDs exhibit low photosensitivity, which limits their practical application in the photocatalytic degradation of environmental pollutants. Modifying CQDs with oxygen atoms can further enhance their charge transfer and active sites. Taking these results into account, the use of oxygen-doped carbon quantum dots to modify BiOBr photocatalysts can effectively improve their photocatalytic activity towards organic pollutants. Summary of the Invention

[0006] Therefore, the purpose of the present invention is to provide an oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material, a preparation method and an application thereof, by modifying bismuth oxybromide using oxygen-rich carbon quantum dots, thereby enhancing the light absorption intensity of the material, promoting the separation and transfer of photogenerated charges, and achieving efficient visible light catalytic activity.

[0007] One of the technical solutions of the present invention is to provide a preparation method of oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material, which comprises the following steps: Bi(NO3)3·5H2O and oxygen-rich carbon quantum dots are uniformly dissolved in a mannitol solution in sequence, KBr is added and stirred, and then a solvent thermal reaction is carried out. The material is then washed, filtered, and dried to obtain the oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material.

[0008] In an optional embodiment, the mannitol solution is prepared by mixing mannitol and water in an addition ratio of 18 mg:1 ml;

[0009] In an optional embodiment, the mass ratio of Bi(NO3)3·5H2O, KBr and oxygen-rich carbon quantum dots is 485:119:(8-16).

[0010] In an optional embodiment, the stirring rate is 4000-5000 rpm.

[0011] In an optional embodiment, the temperature of the solvent thermal reaction is 90° C. and the time is 6 hours.

[0012] In an optional embodiment, the preparation method of the oxygen-rich carbon quantum dots comprises the following steps: dissolving D-(+)-glucose in water and performing a hydrothermal reaction, followed by dialysis and freeze-drying to obtain the oxygen-rich carbon quantum dots.

[0013] In an optional embodiment, the ratio of the added amount of D-(+)-glucose and water is 1 g:10 mL.

[0014] In an optional embodiment, the temperature of the hydrothermal reaction is 160° C. and the time is 3 hours.

[0015] In an optional embodiment, the dialysis time is 72 hours.

[0016] The second technical solution of the present invention is to provide an oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material, which is prepared by any of the above-mentioned preparation methods.

[0017] The third technical solution of the present invention is to provide the application of oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet materials in the photocatalytic degradation of organic dyes or antibiotic pollutants in water.

[0018] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0019] (1) The present invention utilizes a solvothermal method to effectively modify bismuth oxybromide nanosheets with oxygen-rich carbon quantum dots. The preparation method is simple and the oxygen-rich carbon quantum dots are more likely to uniformly modify the bismuth oxybromide nanosheets. The oxygen-rich carbon quantum dots provide more active sites for bismuth oxybromide, overcoming the shortcomings of limited visible light response and fewer active sites of monomeric bismuth oxybromide, optimizing the electron transport performance of the monomer, enhancing the light absorption intensity of the material, and effectively guiding the flow of charges, accelerating the separation and transfer of photogenerated charges, thereby achieving efficient visible light catalytic activity.

[0020] (2) The composite material prepared by the present invention has an excellent removal effect on organic pollutants (organic dyes or antibiotics), has strong anti-interference ability, and can still show excellent degradation performance under different water matrix conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 shows the composition and chemical state of the elements on the surface of OCQD materials;

[0022] Figure 2 shows the morphology and crystal phase characteristics of BOB / OCQD composite materials;

[0023] FIG3 is an X-ray diffraction pattern of the BOB / OCQD composite material;

[0024] FIG4 is a UV-visible diffuse reflectance spectrum of the BOB / OCQD composite material;

[0025] FIG5 is a graph showing the photocatalytic performance of the BOB / OCQD composite material;

[0026] Figure 6 shows the test graph of the photocatalytic activity of BOB / OCQD composite materials in different environments. DETAILED DESCRIPTION

[0027] In order to help those skilled in the art better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0028] Example 1

[0029] A method for preparing an oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material comprises the following steps:

[0030] (1) Synthesis of oxygen-rich carbon quantum dots

[0031] 40 mL of a 0.1 g / mL D-(+)-glucose aqueous solution was transferred to a 50 mL hydrothermal reactor and subjected to a hydrothermal reaction at 160°C for 3 hours to obtain a dark brown solution. After cooling to room temperature, the dark brown solution was dialyzed using a 2000 Da dialysis membrane for 72 hours to remove residues, yielding a yellow-brown solution. The yellow-brown solution was then dried by freeze drying at -40°C. The collected dark brown solids were oxygen-rich carbon quantum dots, designated OCQDs.

[0032] (2) Synthesis of composite materials

[0033] 6 mg of OCQD was uniformly dissolved in 40 mL of 0.1 mol / L mannitol and stirred at 4500 rpm for 30 min to prepare solution A; 242.5 mg of Bi(NO3)3·5H2O was uniformly dissolved in 20 mL of 0.1 mol / L mannitol and stirred at 4500 rpm for 30 min to prepare solution B; solution B was slowly dripped into solution A and stirred at 4500 rpm for 30 min to prepare solution C; 59.5 mg of KBr was uniformly dissolved in 10 ml of 0.1 mol / L mannitol and stirred at 4500 rpm for 30 min to prepare solution D; solution D was slowly dripped into solution C and stirred at 4500 rpm for 30 min. After the solutions were evenly mixed, they were placed in an oil bath at 90°C for 6 h. After the reaction, the product was cooled to room temperature, washed with deionized water, and vacuum dried at 70°C for 24 h to obtain an oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material, named BOB / OCQD-6.

[0034] Example 2

[0035] The synthesis of oxygen-rich carbon quantum dots is the same as that in Example 1, except for the synthesis of the composite material. The synthesis of the composite material includes the following steps:

[0036] 4 mg of OCQD was uniformly dissolved in 40 mL of 0.1 mol / L mannitol and stirred at 4500 rpm for 30 min to prepare solution A; 242.5 mg of Bi(NO3)3·5H2O was uniformly dissolved in 20 mL of 0.1 mol / L mannitol and stirred at 4500 rpm for 30 min to prepare solution B; solution B was slowly dripped into solution A and stirred at 4500 rpm for 30 min to prepare solution C; 59.5 mg of KBr was uniformly dissolved in 10 ml of 0.1 mol / L mannitol and stirred at 4500 rpm for 30 min to prepare solution D; solution D was slowly dripped into solution C and stirred at 4500 rpm for 30 min. After the solutions were evenly mixed, they were placed in an oil bath at 90°C for 6 h. After the reaction, the product was cooled to room temperature, washed with deionized water, and vacuum dried at 70°C for 24 h to obtain an oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material, named BOB / OCQD-4.

[0037] Example 3

[0038] The synthesis of oxygen-rich carbon quantum dots is the same as that in Example 1, except for the synthesis of the composite material. The synthesis of the composite material includes the following steps:

[0039] 8 mg of OCQD was uniformly dissolved in 40 mL of 0.1 mol / L mannitol and stirred at 4500 rpm for 30 min to prepare solution A; 242.5 mg of Bi(NO3)3·5H2O was uniformly dissolved in 20 mL of 0.1 mol / L mannitol and stirred at 4500 rpm for 30 min to prepare solution B; solution B was slowly dripped into solution A and stirred at 4500 rpm for 30 min to prepare solution C; 59.5 mg of KBr was uniformly dissolved in 10 ml of 0.1 mol / L mannitol and stirred at 4500 rpm for 30 min to prepare solution D; solution D was slowly dripped into solution C and stirred at 4500 rpm for 30 min. After the solutions were evenly mixed, they were placed in an oil bath at 90°C for 6 h. After the reaction, the product was cooled to room temperature, washed with deionized water, and vacuum dried at 70°C for 24 h to obtain oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet material, named BOB / OCQD-8.

[0040] Comparative Example

[0041] This comparative example provides a method for preparing bismuth oxybromide nanosheets, comprising the following steps:

[0042] Solution A was prepared by dissolving 242.5 mg of Bi(NO₃)₃·5H₂O in 20 mL of 0.1 mol / L mannitol and stirring at 4500 rpm for 30 minutes. Solution B was prepared by dissolving 59.5 mg of KBr in 10 mL of 0.1 mol / L mannitol and stirring at 4500 rpm for 30 minutes. Solution B was then slowly added dropwise to Solution A with stirring at 4500 rpm for 30 minutes. After the mixture was thoroughly mixed, the mixture was placed in an oil bath at 90°C for 6 hours. After completion of the reaction, the resulting product was cooled to room temperature, washed with deionized water, and vacuum-dried at 70°C for 24 hours to obtain bismuth oxybromide nanosheets, designated BOB.

[0043] 1. Characterization and Analysis

[0044] (1) Composition and chemical state of surface elements on oxygen-rich carbon quantum dots (OCQDs)

[0045] The composition and chemical state of the elements on the OCQD surface were analyzed using X-ray photoelectron spectroscopy. As shown in Figure 1, the C1s and O1s peaks of the OCQD appear at 284.5 eV and 532.3 eV, respectively. Based on peak area calculations, the atomic ratio of C:O is 69.1:30.9, indicating that the carbon quantum dots of the present invention are oxygen-rich.

[0046] (2) Morphology and crystal phase characteristics of BOB and BOB / OCQD-6

[0047] To verify the morphology and crystalline phase characteristics of the bismuth oxybromide nanosheets (BOB) obtained in the comparative example of the present invention and the oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material (BOB / OCQD-6) obtained in Example 1, the samples obtained in the present invention were photographed using a transmission electron microscope (JEOL JSM-2010). The results are shown in Figure 2. As shown in Figure 2, the high-magnification transmission electron microscope image of the OCQDs shows that the OCQDs are uniformly distributed.

[0048] Part a of Figure 2 provides a further magnified image of OCQD, showing its clear lattice fringes: the lattice spacing value of 0.21nm is consistent with the (100) crystal plane of graphene. In addition, the size of OCQD is about 2-5nm. Part b of Figure 2 shows that the size of BOB of the present invention is about 15nm, which is a nanosheet structure. And under the 5nm scale, the (012) crystal plane belonging to BOB can be clearly seen. Parts c and d of Figure 2 are transmission electron microscope images of BOB / OCQD-6 composite samples: under the 10nm scale, it can be clearly seen that there are a large number of OCQD loads on the surface of BOB nanosheets (part c of Figure 2). Further magnification shows that the (012) crystal plane of BOB and OCQD exist at the same time (part d of Figure 2), indicating that a strong bond is formed between OCQD and BOB, and the BOB / OCQD-6 composite material is successfully prepared.

[0049] (3) X-ray diffraction of BOB, BOB / OCQD-4, BOB / OCQD-6, and BOB / OCQD-8

[0050] As shown in Figure 3, it can be seen that the characteristic peaks of BOB prepared in the comparative example are consistent with the BiOBr X-ray diffraction standard card (JCPDS No. 73-2061). For the three composite samples (BOB / OCQD-6, BOB / OCQD-4, BOB / OCQD-8) prepared in Examples 1-3, their characteristic diffraction peaks are all consistent with the BiOBr XRD standard card (JCPDS No. 73-2061). Among them, the X-ray diffraction patterns of the three composite samples do not show significant characteristic peaks of QCQDs, indicating that OCQDs exist in the composite material in a highly dispersed form.

[0051] (IV) UV-visible diffuse reflectance spectra of BOB, OCQD, BOB / OCQD-4, BOB / OCQD-6, and BOB / OCQD-8

[0052] As shown in Figure 4, the absorption edge of BOB is observed at 440 nm. From the spectrum, it can be seen that after the introduction of OCQDs, the absorption edge of the composite material has almost no change, but its light absorption intensity has a tendency to gradually increase.

[0053] 2. Photocatalytic performance testing of pollutant degradation

[0054] The visible light photocatalytic activity of the materials prepared in this invention (BOB, BOB / OCQD-4, BOB / OCQD-6, and BOB / OCQD-8) was tested using RhB (20 mg / L) and CIP (10 mg / L) as target pollutants. The steps are as follows:

[0055] (1) 10 mg of the material was uniformly dispersed in 100 mL of the target pollutant and the photocatalytic reaction was carried out in a reaction vessel. The visible light source was a 300 W Xe lamp with a cutoff filter (λ > 400 nm).

[0056] (2) The reaction temperature was kept stable at room temperature by a circulating water system throughout the reaction. Before xenon lamp irradiation, the dark reaction (the solution was stirred in the dark) was carried out for 30 min to allow the adsorption-desorption equilibrium to be reached on the surface of the material.

[0057] (3) Turn on the Xe lamp, take 4 ml of the supernatant every 5 minutes, centrifuge at 5000 rpm for 3 minutes to separate the solid and liquid in the solution, and filter through 0.2 μm polyethersulfone to remove particles to obtain the final solution.

[0058] (4) The final solution was tested using a UV-visible spectrophotometer to analyze the concentration changes of the target pollutants at the maximum absorption wavelengths of 554 and 276 nm.

[0059] The test results are shown in Figure 5, where Figure 5(a) shows the photocatalytic performance of BOB, BOB / OCQD-4, BOB / OCQD-6, and BOB / OCQD-8 towards the pollutant RhB, and Figure 5(b) shows the photocatalytic performance of BOB and BOB / OCQD-6 towards the pollutant CIP.

[0060] The results show that the oxygen-rich carbon quantum dot-modified bismuth oxybromide nanosheet material of the present invention has excellent photocatalytic performance in degrading different types of pollutants, among which BOB / OCQD-6 shows the best performance among different pollutants.

[0061] 3. Performance testing of BOB / OCQD-6 in natural water

[0062] In order to evaluate the feasibility of photocatalysts in practical applications, tests were conducted by simulating different environments. First, sodium salts (NaCl, Na2SO4, NaBr, Na2CO3, NaHCO3) were added to a deionized water environment to introduce cations (Figure 6a), and chlorides (NaCl, KCl, NH4Cl, CaCl, MgCl2) were added to introduce anions (Figure 6b) to test the effect of conventional ions on the activity of the photocatalyst. Among them, the concentration of different ion solutions was 1.0 mmol / L. The results showed that BOB / OCQD-6 has excellent resistance to self-interference, and its degradation of RhB is almost unaffected by conventional ions.

[0063] In addition, the activity of RhB was tested by adjusting the pH of the deionized water environment to 1, 3, 5, 7, 9, 11 and 13 by HCl and NaOH, as shown in Figure 6c. It was found that BOB / OCQD-6 has excellent degradation performance in neutral and acidic environments, and the stronger the acidity, the more advantageous its reaction rate. However, in an alkaline environment, its activity dropped sharply, and it was almost not degraded in a strong alkaline environment (pH = 11, 13). To further explore the application of the photocatalyst, its performance was evaluated by degrading RhB in a real seawater environment. As shown in Figure 6d, the RhB blank test in real seawater still did not degrade, and the catalyst also showed good photocatalytic activity. These data indicate that BOB / OCQD-6 is a photocatalyst with practical prospects.

[0064] Although the present invention has been described using the above preferred embodiments, they are not intended to limit the scope of protection of the present invention. Any person skilled in the art who makes various changes and modifications to the above embodiments without departing from the spirit and scope of the present invention still fall within the scope of protection of the present invention.

Claims

1. A method for preparing oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet material, characterized in that: Bi(NO3)3·5H2O and oxygen-rich carbon quantum dots were uniformly dissolved in mannitol solution in sequence, and then KBr was added for stirring. Then, a solvent thermal reaction was carried out, and then the material was washed, filtered and dried to obtain oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet material.

2. The preparation method of oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet material according to claim 1, wherein the mass ratio of Bi(NO3)3·5H2O, KBr and oxygen-rich carbon quantum dots is 485:119:(8-16).

3. The method for preparing oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet material according to claim 1, characterized in that: The stirring speed is 4000-5000 rpm.

4. The method for preparing oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet material according to claim 1, characterized in that: The temperature of the solvent thermal reaction is 90° C. and the time is 6 h.

5. The method for preparing oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet material according to claim 1, characterized in that: The preparation method of the oxygen-rich carbon quantum dots comprises the following steps: D-(+)-glucose is dissolved in water and subjected to a hydrothermal reaction, followed by dialysis and freeze-drying to obtain the oxygen-rich carbon quantum dots.

6. The method for preparing oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet material according to claim 5, characterized in that: The ratio of the added amount of D-(+)-glucose to water is 1 g:10 mL.

7. The method for preparing oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet material according to claim 5, characterized in that: The temperature of the hydrothermal reaction is 160° C. and the time is 3 hours.

8. The method for preparing oxygen-rich carbon quantum dots composite bismuth oxybromide nanosheet material according to claim 5, characterized in that: The dialysis time was 72 h.

9. An oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material, prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the oxygen-rich carbon quantum dot composite bismuth oxybromide nanosheet material according to claim 9 in photocatalytic degradation of organic dyes or antibiotic pollutants in water.

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