A double-defect type Bi 12 O 17 Preparation method and application of Cl2 ultrathin nanosheet photocatalyst

Abstract

This invention provides a double-defect type Bi 12 O 17 This paper describes the preparation method and application of Bi2 ultrathin nanosheet photocatalysts, belonging to the field of photocatalytic materials technology. The preparation method is as follows: Bi2 is prepared by reacting a strong base with BiCl3 under ultrasonic assistance. 12 O 17 Cl2 ultrathin nanosheet precursor; then the precursor is mixed with sodium borohydride and a sulfur source and ground to obtain the target catalyst. In Bi 12 O 17 Sulfur doping and oxygen vacancies are simultaneously introduced into Cl2 ultrathin nanosheets to construct a doped-vacancy dual-defect system. By comprehensively utilizing the synergistic enhancement effect of the dual defects, the bottleneck of single-defect modification is overcome, thereby achieving a comprehensive improvement in photocatalytic performance (light capture, charge separation, surface reaction, and stability). This invention features a simple process, low requirements for preparation conditions, and is easily achievable for mass production, demonstrating high practical value and application prospects.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation and visible light photocatalysis technology, specifically relating to a dual-defect Bi 12 O 17 Preparation method and application of Cl2 ultrathin nanosheet photocatalyst. Background Technology

[0002] Hydrogen peroxide (H2O2) is a widely used oxidant and carbon-free fuel, with applications spanning wastewater remediation, antibacterial disinfection, organic synthesis, and energy storage. With the increasing demand for sustainable energy and environmental remediation, the development of environmentally friendly hydrogen peroxide production methods has attracted widespread attention. Photocatalysis, with its ability to cleverly utilize solar radiation to promote the oxygen reduction reaction (ORR) and water oxidation reaction (WOR), has become a promising strategy for environmentally friendly hydrogen peroxide production. However, this method is still limited by low production efficiency, highlighting the urgent need to develop highly active photocatalytic materials to overcome these limitations.

[0003] In recent years, non-stoichiometric bismuth halide (Bi) x O y X z Bismuth (Bi) has become a research focus in the field of photocatalysis, and related explorations continue to deepen. These materials, with their unique layered structure, can be easily exfoliated into two-dimensional ultrathin nanosheets—possessing not only an ultra-large specific surface area and atomic-level thickness, but also rich in uncoordinated surface atoms, thus exhibiting significant advantages in efficient light harvesting, promoting electron-hole separation, and providing highly active sites. Furthermore, compared to similar materials with the same stoichiometric ratio, increasing the ratio of bismuth (Bi) to halogens (X, i.e., Cl, Br, I) not only enhances light absorption performance but also promotes charge separation and migration by strengthening the conduction band hybridization effect; simultaneously, this ratio regulation can significantly improve the photostability of the material. Among numerous Bi... x O y X z In, it has additional [Bi3O] 4.25 The intermediate layer Bi 12 O 17 Cl2 along the [Bi] layer perpendicular to the [Cl] layer 12 O 17 A permanent internal electric field (IEF) exists in the direction of ] Bi. 12 O 17 Cl2 exhibits good photocatalytic performance and selectivity in various photocatalytic reaction systems. However, Bi... 12 O 17 The rapid recombination of photogenerated electrons and holes in Cl2 remains a major barrier limiting its widespread application. Therefore, how to promote the rapid recombination of photogenerated electrons and holes in Bi2 is a key challenge. 12 O 17Effective carrier separation of Cl2 is crucial for improving its photocatalytic performance.

[0004] Defects and heteroatom doping are two key microstructural factors affecting the performance of photocatalytic materials. On the one hand, the presence of defects is a common phenomenon in the synthesis of photocatalytic nanomaterials and can effectively regulate the performance of photocatalysts. For example, oxygen vacancy defects, common in metal oxides, can optimize the conductivity and band structure of materials, thereby significantly enhancing photon absorption, exciton generation, and carrier separation processes. More importantly, oxygen vacancy defects can serve as highly active reaction sites, promoting the adsorption and activation of substrate molecules. Furthermore, the introduction of heteroatoms forms impurity energy levels in the semiconductor band gap, thereby narrowing the band gap and broadening the light absorption range. Simultaneously, heteroatom doping leads to uneven charge distribution, thereby forming an internal electric field that promotes the migration and separation of photogenerated carriers. In fact, the introduction of dopants in semiconductor doping is often accompanied by the generation of defects. Studies have shown that coupling heteroatoms with vacancy defects is an effective strategy for improving photocatalytic performance. Patents CN 115849441A and CN 116371431A disclose oxygen-vacancy-rich Bi... 12 O 17 Cl2 ultrathin nanosheets and Bi 12 O 17 The invention describes a method for preparing Cl2 ultrathin nanoribbons, and the resulting photocatalyst exhibits high photocatalytic degradation activity. However, the solvothermal method used in this patent is costly (high equipment requirements, high energy consumption), has a long production cycle, and carries high safety risks (high temperature and high pressure environment). Furthermore, the surfactants and other additives used are difficult to remove, potentially introducing impurities during the preparation process. More importantly, due to limitations of the preparation method, the obtained Bi... 12 O 17 Cl2 ultrathin nanosheets and Bi 12 O 17 Cl2 ultrathin nanoribbons contain only oxygen vacancies, exhibiting a strong tendency for vacancy migration and aggregation, resulting in poor long-term stability. More importantly, the aforementioned patents cannot fully utilize the synergistic enhancement effect of dual defects, thus limiting photocatalytic activity. Minna Guo et al. (Materials Research Bulletin, 2019, 112, 205-212) prepared an I-doped Bi nanoribbon using a simple chemical precipitation method. 12 O 17 Cl2 photocatalysts exhibit good catalytic activity for the degradation of methyl orange and phenol under visible light irradiation. However, due to limitations in their preparation method, the obtained I-doped Bi... 12 O 17Cl2 photocatalysts contain only I doping as a defect, which prevents them from fully utilizing the synergistic enhancement effect of dual defects, thus limiting their photocatalytic activity. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a double-defect type Bi. 12 O 17 Preparation method and application of Cl2 ultrathin nanosheet photocatalyst. 12 O 17 Sulfur doping and oxygen vacancy dual defects are simultaneously introduced into Cl2 ultrathin nanosheets to construct a doped-vacancy dual-defect system. By comprehensively utilizing the synergistic enhancement effect of the dual defects, the bottleneck of single-defect modification is overcome, thereby achieving a comprehensive improvement in photocatalytic performance (light capture, charge separation, surface reaction, and stability).

[0006] To achieve the above objectives, the present invention synthesizes Bi by ultrasound-assisted precipitation reaction at room temperature. 12 O 17 Using Cl2 ultrathin nanosheets as a precursor, hydrogenation and sulfur doping were performed on this basis to directly obtain the dual-defect Bi. 12 O 17 Cl2 ultrathin nanosheet photocatalyst.

[0007] This invention provides the following technical solutions:

[0008] A dual-defect type Bi 12 O 17 The preparation method of Cl2 ultrathin nanosheet photocatalyst specifically includes the following steps:

[0009] (1) Add the strong base ethanol solution dropwise to the BiCl3 ethanol solution, stir, sonicate, collect the precipitate after multiple centrifugations and washings, and then dry it to obtain BiCl3. 12 O 17 Cl2 ultrathin nanosheet precursor;

[0010] (2) The product Bi obtained in step (1) 12 O 17 Cl2 ultrathin nanosheet precursor was mixed with sodium borohydride and a sulfur-containing compound, thoroughly ground, dissolved in deionized water, and the precipitate was collected after centrifugation and washing. The precipitate was then dried to obtain dual-defect Bi. 12 O 17 Cl2 ultrathin nanosheet photocatalyst.

[0011] Preferably, the molar ratio of the strong base and BiCl3 in step (1) is 5:1 to 7:1.

[0012] Preferably, the volume ratio of anhydrous ethanol to deionized water in the ethanol solution in step (1) is 0.2:1 to 5:1.

[0013] Preferably, the volume ratio of the strong base ethanol solution and the BiCl3 ethanol solution in step (1) is 1:2 to 2:1.

[0014] Preferably, the strong base in step (1) is NaOH or KOH.

[0015] Preferably, the stirring is performed for 10 to 30 minutes in step (1).

[0016] Preferably, the ultrasonic frequency in step (1) is 20kHz~80kHz.

[0017] Preferably, the ultrasound time in step (1) is 1 to 5 hours.

[0018] Preferably, in step (2) Bi 12 O 17 The mass ratio of Cl2 ultrathin nanosheet precursor to sodium borohydride and sulfur-containing compound is (10~30):(0.5~5.0):(0.5~5.0).

[0019] Preferably, the sulfur-containing compound in step (2) is thiourea or thioacetamide.

[0020] Preferably, the grinding method in step (2) is manual grinding or mechanical grinding.

[0021] Preferably, the grinding time in step (2) is 10 to 120 minutes.

[0022] Preferably, the washing in steps (1) and (2) is performed using deionized water and anhydrous ethanol.

[0023] This invention also provides a double-defect type Bi prepared by the above-described method. 12 O 17 Cl2 ultrathin nanosheet photocatalyst.

[0024] The present invention also provides the aforementioned double-defect type Bi 12 O 17 The application of Cl2 ultrathin nanosheet photocatalysts for the visible light catalytic synthesis of hydrogen peroxide in pure water.

[0025] Preferably, the application method is as follows: an appropriate amount of photocatalyst is dispersed in oxygen-saturated deionized water, and hydrogen peroxide is synthesized using a 300 W xenon lamp equipped with a 420 nm cutoff filter as the light source. The hydrogen peroxide concentration is detected by the DPD method.

[0026] The present invention also provides the aforementioned double-defect type Bi 12 O 17 The application of Cl2 ultrathin nanosheet photocatalysts for visible light-catalyzed self-Fenton degradation of organic pollutants in water.

[0027] Preferably, the organic pollutants include ciprofloxacin, tetracycline hydrochloride, norfloxacin, and rhodamine B.

[0028] In this application, the ratio of strong base to BiCl3, or Bi 12 O 17 The photocatalytic activity for hydrogen peroxide synthesis and degradation of organic pollutants varies depending on the ratio of the Cl2 ultrathin nanosheet precursor to sodium borohydride and sulfur-containing compounds. More preferably, the molar ratio of the strong base to BiCl3 is 6.5:1, and Bi... 12 O 17 When the mass ratio of Cl2 ultrathin nanosheet precursor to sodium borohydride and sulfur-containing compound is 15:1:1, a double-defect Bi is obtained. 12 O 17 Cl2 ultrathin nanosheet photocatalysts exhibit the best photocatalytic activity.

[0029] Compared with the prior art, the significant advantages of the present invention are:

[0030] The photocatalyst described in this invention differs from existing Bi photocatalysts in terms of structure, preparation method, and catalytic performance. 12 O 17 Cl2-based photocatalysts are significantly different.

[0031] (1) The present invention synthesizes sulfur-doped and oxygen-vacancy dual-defect Bi using a simple grinding method at room temperature. 12 O 17 Cl2 ultrathin nanosheet photocatalysts are inexpensive and readily available in terms of equipment and raw materials, have simple processing operations, low requirements for preparation conditions, and are easy to mass-produce.

[0032] (2) The catalyst prepared by the present invention has an ultrathin nanosheet structure, which ensures that the catalyst has a high specific surface area, provides more active sites, and shortens the distance of bulk phase migration of photogenerated carriers, effectively improving the separation efficiency of photogenerated carriers.

[0033] (3) The catalyst prepared by the present invention has both sulfur doping and oxygen vacancy defects. The introduction of dual defects enables more precise band structure control and synergistic optimization of surface reactive sites, so that the catalyst has higher visible light absorption and utilization efficiency and significantly improved photogenerated carrier separation and migration efficiency.

[0034] (4) The photocatalyst described in this invention can be applied to the visible light catalytic synthesis of hydrogen peroxide in pure water and the visible light catalytic self-Fenton degradation of organic pollutants in water.

[0035] (5) The photocatalyst described in this invention has excellent photocatalytic performance and can be reused, and has high use value and application prospects. Attached Figure Description

[0036] Figure 1 The left image is an AFM morphology diagram of the photocatalyst obtained in Example 1 of the present invention, and the right image is an AFM thickness measurement diagram of the photocatalyst obtained in Example 1 of the present invention.

[0037] Figure 2 The XRD patterns are of the photocatalysts obtained in Example 1 and Comparative Examples 1-3 of this invention.

[0038] Figure 3 The EPR diagrams are of the photocatalysts obtained in Example 1 and Comparative Examples 1 and 3 of this invention.

[0039] Figure 4 XPS images of the photocatalysts obtained in Example 1 and Comparative Example 3 of this invention;

[0040] Figure 5 The UV-Vis diffuse reflectance diagrams of the photocatalysts obtained in Example 1 and Comparative Examples 1-3 of this invention are shown.

[0041] Figure 6 The diagram shows the effect of the photocatalysts obtained in Example 1 and Comparative Examples 1-4 of this invention in the synthesis of hydrogen peroxide.

[0042] Figure 7 (A) is a visible light photocatalytic degradation effect of the photocatalysts obtained in Example 1 and Comparative Examples 1-4 of the present invention on ciprofloxacin; (B) is a visible light photocatalytic degradation effect of the photocatalysts obtained in Example 1 and Comparative Examples 1-4 of the present invention on tetracycline hydrochloride; (C) is a visible light photocatalytic degradation effect of the photocatalysts obtained in Example 1 and Comparative Examples 1-4 of the present invention on norfloxacin; and (D) is a visible light photocatalytic degradation effect of the photocatalysts obtained in Example 1 and Comparative Examples 1-4 of the present invention on rhodamine B.

[0043] Figure 8 The left-middle figure is an evaluation diagram of the activity and stability of the photocatalyst obtained in Example 1 of the present invention in the photocatalytic production of hydrogen peroxide, and the right-middle figure is an evaluation diagram of the activity and stability of the photocatalyst obtained in Example 1 of the present invention in the photocatalytic degradation of ciprofloxacin. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0045] Example 1

[0046] A dual-defect type Bi 12 O 17 The preparation method of Cl2 ultrathin nanosheet photocatalyst includes the following steps:

[0047] (1) Dissolve NaOH and BiCl3 in 25 mL of ethanol solution (anhydrous ethanol and deionized water volume ratio of 1:1) at a molar ratio of 6.5:1. Add the NaOH ethanol solution dropwise to the BiCl3 ethanol solution. After stirring for 20 minutes, sonicate the mixture for 4 hours using an ultrasonic machine at a frequency of 40 kHz. Wash the obtained products multiple times with deionized water and anhydrous ethanol, centrifuge to collect the precipitate, and dry it to obtain BiCl3. 12 O 17 Cl2 ultrathin nanosheet precursor, labeled UBOC.

[0048] (2) Mix 150 mg of UBOC obtained in step (1) with 10 mg of thiourea and 10 mg of sodium borohydride, grind thoroughly in an agate mortar for 60 minutes, dissolve the resulting mixture in 200 mL of deionized water, centrifuge, wash the product multiple times with deionized water and anhydrous ethanol, centrifuge to collect the precipitate, and dry to obtain the double-defect Bi 12 O 17 Cl2 ultrathin nanosheet photocatalyst, labeled SUBOC-OV.

[0049] Example 2

[0050] A dual-defect type Bi 12 O 17 The preparation method of Cl2 ultrathin nanosheet photocatalyst includes the following steps:

[0051] (1) Dissolve KOH and BiCl3 in 25 mL of ethanol solution (anhydrous ethanol and deionized water volume ratio of 0.2:1) at a molar ratio of 5:1. Add 10 mL of NaOH ethanol solution dropwise to 25 mL of BiCl3 ethanol solution. After stirring for 10 minutes, sonicate the solution for 5 hours using an ultrasonic machine at a frequency of 20 kHz. Wash the obtained product multiple times with deionized water and anhydrous ethanol, centrifuge to collect the precipitate, and dry it to obtain BiCl3. 12 O 17 Cl2 ultrathin nanosheet precursor, labeled UBOC.

[0052] (2) Mix 300 mg of UBOC obtained in step (1) with 50 mg of thiourea and 50 mg of sodium borohydride, grind thoroughly in an agate mortar for 120 minutes, dissolve the resulting mixture in 200 mL of deionized water, centrifuge, wash the product multiple times with deionized water and anhydrous ethanol, centrifuge to collect the precipitate, and dry to obtain the double-defect Bi 12 O17 Cl2 ultrathin nanosheet photocatalyst, labeled SUBOC-OV.

[0053] Example 3

[0054] A dual-defect type Bi 12 O 17 The preparation method of Cl2 ultrathin nanosheet photocatalyst includes the following steps:

[0055] (1) Dissolve NaOH and BiCl3 in 25 mL of ethanol solution (anhydrous ethanol and deionized water volume ratio of 5:1) at a molar ratio of 7:1. Add 20 mL of NaOH ethanol solution dropwise to 10 mL of BiCl3 ethanol solution. After stirring for 30 minutes, sonicate the solution with an ultrasonic machine at a frequency of 80 kHz for 1 hour. Wash the product with deionized water and anhydrous ethanol several times. Collect the precipitate by centrifugation and dry it to obtain BiCl3. 12 O 17 Cl2 ultrathin nanosheet precursor, labeled UBOC.

[0056] (2) Mix 100 mg of UBOC obtained in step (1) with 5 mg of thioacetamide and 5 mg of sodium borohydride, and grind thoroughly in a mechanical grinder for 10 minutes. Dissolve the resulting mixture in 200 mL of deionized water, centrifuge, and wash the product multiple times with deionized water and anhydrous ethanol, respectively. Collect the precipitate by centrifugation and dry it to obtain the double-defect Bi. 12 O 17 Cl2 ultrathin nanosheet photocatalyst, labeled SUBOC-OV.

[0057] Comparative Example 1

[0058] In contrast, the difference between this comparative example and Example 1 is that only oxygen vacancy defects are introduced in this comparative example, resulting in the preparation of Bi with abundant oxygen vacancy sites. 12 O 17 Cl2 ultrathin nanosheet photocatalyst, comprising the following steps:

[0059] 150 mg of UBOC obtained in step (1) of Example 1 was mixed with 20 mg of sodium borohydride and ground thoroughly in an agate mortar for 60 minutes. The resulting mixture was dissolved in 200 mL of deionized water, centrifuged, and the product was washed multiple times with deionized water and anhydrous ethanol, respectively. The precipitate was collected by centrifugation and dried to obtain the double-defect Bi. 12 O 17 Cl2 ultrathin nanosheet photocatalyst, labeled UBOC-OV.

[0060] Comparative Example 2

[0061] In contrast, the difference between this comparative example and Example 1 is that only sulfur doping defects are introduced in this comparative example to prepare sulfur-doped Bi. 12 O 17 Cl2 ultrathin nanosheet photocatalyst, comprising the following steps:

[0062] 150 mg of UBOC obtained in step (1) of Example 1 was mixed with 20 mg of thiourea and ground thoroughly in an agate mortar for 60 minutes. The resulting mixture was dissolved in 200 mL of deionized water, centrifuged, and the product was washed multiple times with deionized water and anhydrous ethanol. The precipitate was collected by centrifugation and dried to obtain the double-defect Bi 12 O 17 Cl2 ultrathin nanosheet photocatalyst, labeled SUBOC.

[0063] Comparative Example 3

[0064] In contrast, this comparative example differs from Example 1 in that sulfur doping and oxygen vacancy defects are not introduced in this comparative example, and the resulting polished Bi 12 O 17 Cl2 ultrathin nanosheet photocatalyst, comprising the following steps:

[0065] The UBOC 150 mg obtained in step (1) of Example 1 was thoroughly ground in an agate mortar for 60 minutes. The resulting mixture was dissolved in 200 mL of deionized water, centrifuged, and the product was washed multiple times with deionized water and anhydrous ethanol, respectively. The precipitate was collected by centrifugation and dried to obtain the double-defect Bi. 12 O 17 Cl2 ultrathin nanosheet photocatalyst, labeled MUBOC.

[0066] Comparative Example 4

[0067] In comparison, the difference between this comparative example and Example 1 is that in this comparative example, the block Bi... 12 O 17 By simultaneously introducing sulfur doping and oxygen vacancy defects into Cl2, a dual-defect bulk Bi was prepared. 12 O 17 Cl2 photocatalyst, comprising the following steps:

[0068] (1) Dissolve 1.94 g of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) powder and 0.24 g of sodium chloride (NaCl) powder in 80 mL of deionized water containing 4 mL of concentrated nitric acid. After magnetic stirring for 30 minutes, transfer the mixture to a 100 mL polytetrafluoroethylene-lined reactor and react at 140 °C for 24 hours. After the synthesis reaction is complete, collect the precipitate by centrifugation and wash it several times with deionized water and anhydrous ethanol. Finally, dry the precipitate to obtain the bismuth oxychloride (BiOCl) precursor.

[0069] (2) Mix 2 mmol of BiOCl precursor powder obtained in step (1) of Comparative Example 4 with 5 mmol of commercial Bi2O3 powder, place in a muffle furnace and heat to 650 °C at a heating rate of 5 °C / min, hold at the temperature for 10 hours. After the reaction is complete, cool naturally to room temperature to obtain bulk Bi. 12 O 17 Cl2 photocatalyst, labeled BBOC.

[0070] (3) Mix 150 mg of BBOC obtained in step (2) of Comparative Example 4 with 10 mg of thiourea and 10 mg of sodium borohydride, grind thoroughly in an agate mortar for 60 minutes, dissolve the resulting mixture in 200 mL of deionized water, centrifuge, wash the product multiple times with deionized water and anhydrous ethanol, centrifuge to collect the precipitate, and dry to obtain the double-defect type bulk Bi. 12 O 17 Cl2 photocatalyst, labeled SBBOC-OV.

[0071] The catalyst synthesized according to the method in Example 1 was observed by atomic force microscopy (AFM). The results showed that the synthesized photocatalyst had an ultrathin nanosheet structure with an average thickness of approximately 1.17 nm. (See Appendix) Figure 1 .

[0072] The catalysts synthesized according to the methods of Example 1 and Comparative Examples 1-3 were analyzed by X-ray powder diffraction (XRD). The results showed that after the introduction of sulfur doping and oxygen vacancy defects, the intensity of the XRD diffraction peaks of the samples only decreased slightly, without any other significant changes, and no new diffraction peaks were detected. This indicates that the introduction of sulfur doping oxygen vacancy defects did not significantly alter the Bi content. 12 O 17 The crystal phase structure of Cl2 ultrathin nanosheets is shown in the appendix. Figure 2 .

[0073] The catalysts synthesized according to the methods of Example 1 and Comparative Examples 1 and 3 were characterized by room-temperature electron paramagnetic resonance (EPR) technology. The results showed that all samples exhibited a significant EPR signal at g=2.003, and the intensity order of the EPR signal was MUBOC < SUBOC-OV < UBOC-OV. This indicates the presence of oxygen vacancy defects in the samples, and the concentration of oxygen vacancy defects in the SUBOC-OV and UBOC-OV samples was significantly higher than that in the MUBOC sample. (See Appendix) Figure 3 .

[0074] The catalysts synthesized according to the methods of Example 1 and Comparative Example 3 were analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that the MUBOC sample did not detect a significant S 2s XPS peak corresponding to sulfur, while the SUBOC-OV sample showed a significant S 2s XPS peak at a binding energy of approximately 225 eV. This indicates that sulfur doping was successfully achieved in the SUBOC-OV sample. (See Appendix) Figure 4 .

[0075] The catalysts synthesized according to the methods of Examples 1 and Comparative Examples 1-3 were analyzed by UV-Vis diffuse reflectance spectroscopy (DRS). The results showed that both sulfur doping and the introduction of oxygen vacancy defects could enhance the performance of Bi. 12 O 17 Cl2 ultrathin nanosheets absorb visible light, and the simultaneous introduction of sulfur doping and oxygen vacancy defects can further synergistically enhance the visible light absorption capacity. (See Appendix) Figure 5 .

[0076] Five milligrams each of the catalysts synthesized according to the methods of Example 1 and Comparative Examples 1-4 were ultrasonically dispersed in 20 mL of deionized water. The system was saturated with oxygen by bubbling for 30 minutes. The system was then irradiated with a 300 W xenon lamp equipped with a 420 nm cutoff filter. The concentration of hydrogen peroxide generated was measured every half hour using the DPD method, and the average hydrogen peroxide generation rate was calculated. The results showed that the SUBOC-OV sample, which simultaneously contained sulfur doping and oxygen vacancy dual defects, exhibited the highest visible light photocatalytic activity for hydrogen peroxide synthesis, with a hydrogen peroxide generation rate of 1392.8 μmol g. -1 h -1 These figures are 49.7 times, 3.6 times, 8.9 times, and 6.8 times higher than those of MUBOC, UBOC-OV, SUBOC, and SBBOC-OV, respectively. (See appendix) Figure 6 .

[0077] Ten mg of each of the catalysts synthesized according to the methods of Example 1 and Comparative Examples 1-4 were ultrasonically dispersed in 80 mL of a 20 mg / L ciprofloxacin solution. The system was subjected to adsorption-desorption equilibrium for 1 hour under magnetic stirring at 1000 r / min. The system was then irradiated with a 300 W xenon lamp equipped with a 420 nm cutoff filter. Samples were taken every 10 minutes, centrifuged, and the supernatant was collected. The absorbance was measured using a UV-9000S UV-Vis spectrophotometer. The results showed that the optimal SUBOC-OV photocatalyst catalyzed the degradation of 98.8% of ciprofloxacin within 40 min, while the MUBOC, UBOC-OV, SUBOC, and SBBOC-OV photocatalysts only catalyzed the degradation of 22.5%, 81.9%, 46.8%, and 70.2% of ciprofloxacin, respectively, within 40 min. (See Appendix) Figure 7 (A)

[0078] Ten mg of each of the catalysts synthesized according to the methods of Example 1 and Comparative Examples 1-4 were ultrasonically dispersed in 80 mL of a 50 mg / L tetracycline hydrochloride solution. The system was subjected to adsorption-desorption equilibrium for 1 hour under magnetic stirring at 1000 r / min. The system was then irradiated with a 300 W xenon lamp equipped with a 420 nm cutoff filter. Samples were taken every 15 minutes, centrifuged, and the supernatant was collected. The absorbance was measured using a UV-9000S UV-Vis spectrophotometer. The results showed that the optimal SUBOC-OV photocatalyst catalyzed the degradation of 99.8% of tetracycline hydrochloride within 60 min, while the MUBOC, UBOC-OV, SUBOC, and SBBOC-OV photocatalysts only catalyzed the degradation of 18.5%, 44.9%, 32.8%, and 50.2% of tetracycline hydrochloride, respectively, within 60 min. (See Appendix). Figure 7 (B)

[0079] Ten mg of each of the catalysts synthesized according to the methods of Example 1 and Comparative Examples 1-4 were ultrasonically dispersed in 80 mL of a 10 mg / L norfloxacin solution. The system was then subjected to adsorption-desorption equilibrium for 1 hour under magnetic stirring at 1000 r / min. The system was then irradiated with a 300 W xenon lamp equipped with a 420 nm cutoff filter. Samples were taken every 10 minutes, centrifuged, and the supernatant was collected. The absorbance was measured using a UV-9000S UV-Vis spectrophotometer. The results showed that the optimal SUBOC-OV photocatalyst catalyzed the degradation of 97.8% of norfloxacin within 40 min, while the MUBOC, UBOC-OV, SUBOC, and SBBOC-OV photocatalysts only catalyzed the degradation of 28.5%, 62.8%, 64.2%, and 74.9% of norfloxacin, respectively, within 40 min. (See Appendix). Figure 7 (C)

[0080] Ten mg of each of the catalysts synthesized according to the methods of Example 1 and Comparative Examples 1-4 were ultrasonically dispersed in 80 mL of a 10 mg / L Rhodamine B solution. The system was subjected to adsorption-desorption equilibrium for 1 hour under dark adsorption with magnetic stirring at 1000 r / min. The system was then irradiated with a 300 W xenon lamp equipped with a 420 nm cutoff filter. Samples were taken every 10 minutes, centrifuged, and the supernatant was collected. The absorbance was measured using a UV-9000S UV-Vis spectrophotometer. The results showed that the optimal SUBOC-OV photocatalyst catalyzed the degradation of 99.98% of Rhodamine B within 40 min, while the MUBOC, UBOC-OV, SUBOC, and SBBOC-OV photocatalysts only catalyzed the degradation of 38.5%, 91.9%, 54.8%, and 84.2% of Rhodamine B, respectively, within 40 min. (See Appendix). Figure 7 (D)

[0081] The catalyst synthesized according to the method in Example 1 was collected by centrifugation after photocatalytic hydrogen peroxide production activity evaluation. After multiple washings and drying, the collected catalyst was subjected to further activity evaluation experiments. This process was repeated for multiple rounds of recovery and activity evaluation experiments to examine the catalyst's activity and stability. The results showed that after six consecutive cycles, the reaction rate of the prepared SUBOC-OV sample for photocatalytic hydrogen peroxide production did not decrease significantly. This indicates that the prepared dual-defect Bi... 12 O 17 The Cl2 ultrathin nanosheet photocatalyst exhibits good stability; see appendix. Figure 8 Left image.

[0082] The catalyst synthesized according to the method in Example 1 was collected by centrifugation after photocatalytic degradation of ciprofloxacin. After multiple washings and drying, the collected catalyst was subjected to further activity evaluation experiments. This process was repeated for multiple rounds of recovery and activity evaluation experiments to examine the catalyst's activity and stability. The results showed that after six consecutive cycles, the visible light photocatalytic degradation activity of the prepared SUBOC-OV sample did not significantly decrease, indicating that the prepared dual-defect Bi... 12 O 17 The Cl2 ultrathin nanosheet photocatalyst exhibits good stability; see appendix. Figure 8 The image on the right.

[0083] The photocatalyst prepared in this invention possesses an ultrathin nanosheet structure, ensuring a high specific surface area, providing more active sites, and shortening the bulk phase migration distance of photogenerated carriers, effectively improving the separation efficiency of photogenerated carriers. Furthermore, the prepared catalyst simultaneously possesses both sulfur doping and oxygen vacancies; the introduction of these dual defects enables finer band structure control, synergistically optimizing surface reactive sites, resulting in higher visible light absorption and utilization efficiency and significantly improved photogenerated carrier separation and migration efficiency. Under visible light irradiation, this photocatalyst exhibits excellent photocatalytic synthesis of hydrogen peroxide and degradation of organic pollutants, and can be reused. The equipment and raw materials involved in this invention are inexpensive and readily available, the process is simple, the requirements for preparation conditions are low, and it is easy to achieve mass production, possessing high practical value and application prospects.

Claims

1. A dual-defect type Bi 12 O 17 The method for preparing Cl2 ultrathin nanosheet photocatalysts is characterized by, Includes the following steps: (1) Add the strong base ethanol solution dropwise to the BiCl3 ethanol solution, stir, sonicate, collect the precipitate after multiple centrifugations and washings, and then dry it to obtain BiCl3. 12 O 17 Cl2 ultrathin nanosheet precursor; (2) The product Bi obtained in step (1) 12 O 17 Cl2 ultrathin nanosheet precursors were mixed with sodium borohydride and a sulfur-containing compound in a mass ratio of (10~30):(0.5~5.0):(0.5~5.0), wherein the sulfur-containing compound was thiourea or thioacetamide. After thorough grinding, the mixture was dissolved in deionized water, and the precipitate was collected after centrifugation and washing, and then dried to obtain the double-defect Bi. 12 O 17 Cl2 ultrathin nanosheet photocatalyst.

2. A double-defect type Bi according to claim 1 12 O 17 The method for preparing Cl2 ultrathin nanosheet photocatalysts is characterized by, The molar ratio of the strong base and BiCl3 in step (1) is 5:1 to 7:1; the volume ratio of anhydrous ethanol to deionized water in the ethanol solution is 0.2:1 to 5:1; and the volume ratio of the ethanol solution of the strong base to the ethanol solution of BiCl3 is 1:2 to 2:

1.

3. A dual-defect type Bi according to claim 1 12 O 17 The method for preparing Cl2 ultrathin nanosheet photocatalysts is characterized by, Stir for 10-30 minutes in step (1).

4. A double-defect type Bi according to claim 1 12 O 17 The method for preparing Cl2 ultrathin nanosheet photocatalysts is characterized by, In step (1), the ultrasonic frequency is 20kHz~80kHz and the ultrasonic time is 1~5 hours.

5. A double-defect type Bi according to claim 1 12 O 17 A method for preparing Cl2 ultrathin nanosheet photocatalysts, characterized in that, In step (2), the grinding method is manual grinding or mechanical grinding, and the grinding time is 10~120 minutes.

6. A dual-defect type Bi according to claim 1 12 O 17 A method for preparing Cl2 ultrathin nanosheet photocatalysts, characterized in that, The washing described in steps (1) and (2) is performed using deionized water and anhydrous ethanol.

7. A double-defect type Bi prepared by the preparation method according to any one of claims 1-6 12 O 17 Cl2 ultrathin nanosheet photocatalyst.

8. A double-defect type Bi according to claim 7 12 O 17 Applications of Cl2 ultrathin nanosheet photocatalysts in the visible light catalytic synthesis of hydrogen peroxide in pure water or in the visible light catalytic degradation of organic pollutants in water by Fenton.

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