Nanometer hollow microsphere photocatalytic material and preparation method and application thereof

Abstract

The application provides a kind of nano hollow microsphere photocatalytic material and its preparation method and application, [Bmim]I Except as iodine source, also as template agent, to the formation process of BiOI microsphere has played a key role. Then BiOI microsphere is calcined at 380 DEG C, makes it convert into BiOI / Bi5O7I further improves photocatalytic performance. BiOI / Bi5O7I microsphere shows more superior photocatalytic nitrogen fixation performance under visible light. In addition, BiOI microsphere shows more superior photocatalytic nitrogen fixation performance under visible light. The catalyst preparation method is simple and easy to operate, can be used for photocatalytic efficient nitrogen fixation, catalyst is easy to recycle.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis technology, and more specifically, to a hollow nanosphere photocatalytic material, its preparation method, and its application. Background Technology

[0002] Photocatalytic nitrogen fixation is a chemical reaction that uses light energy to convert nitrogen gas into ammonia, and it is an important pathway for achieving sustainable agricultural production and environmental protection. However, the traditional Haber-Bosch nitrogen fixation method requires high temperature and pressure, consumes a large amount of energy, and produces a significant amount of greenhouse gases, causing serious environmental impacts. Therefore, finding an environmentally friendly photocatalytic nitrogen fixation method is of great research value.

[0003] In recent years, with the development of semiconductor materials and nanotechnology, significant progress has been made in the research of photocatalytic nitrogen fixation. By optimizing the structure of the catalyst and reaction conditions, highly efficient and low-energy-consumption photocatalytic nitrogen fixation reactions can be achieved. Semiconductor photocatalysts can convert solar energy into chemical energy; compared to traditional industrial nitrogen fixation methods, this reaction process is greener, the reaction conditions are milder, and the reaction can be carried out in water. Furthermore, by controlling the structure of the catalyst and reaction conditions, selective adsorption and reduction of nitrogen can be achieved, thereby improving the efficiency and selectivity of photocatalytic nitrogen fixation.

[0004] However, there are still some problems in the current research on photocatalytic nitrogen fixation, such as the need to further improve the stability, selectivity and efficiency of the catalyst.

[0005] Therefore, further optimizing the catalysts and reaction conditions for photocatalytic nitrogen fixation, and improving the efficiency and selectivity of photocatalytic nitrogen fixation, is an important direction for current research on photocatalytic nitrogen fixation. Summary of the Invention

[0006] The purpose of this invention is to provide a photocatalytic material made of hollow nanospheres and its preparation method. The photocatalytic material made of hollow nanospheres is successfully prepared by means of ionic liquid assistance. The preparation method is simple and efficient.

[0007] Another objective of this invention is to provide an application of a hollow nanosphere photocatalytic material for photocatalytic nitrogen fixation.

[0008] The specific technical solution of this invention is as follows:

[0009] This invention provides a method for preparing a hollow nanosphere photocatalytic material, comprising the following steps:

[0010] 1) Mix the Bi source in a solvent to obtain solution A; dissolve the ionic liquid [Bmim]I in anhydrous ethanol to obtain solution B;

[0011] 2) Under stirring conditions, solution B is added to solution A and stirred to mix. The resulting mixed solution undergoes a hydrothermal reaction.

[0012] 3) The product from step 2) is calcined to obtain BiOI / Bi5O7I hollow nanosphere photocatalytic material.

[0013] In step 1), the ratio of Bi source to solvent in solution A is 0.05-0.15 mol / L, preferably 0.10 mol / L;

[0014] In step 1), the solvent used in solution A is a mixture of deionized water and acetic acid; the volume ratio of the deionized water to acetic acid is 1.5-5:1, preferably 4:1.

[0015] The Bi source mentioned in step 1) is selected from Bi(NO3)3·5H2O;

[0016] In step 1), the ratio of ionic liquid [Bmim]I to anhydrous ethanol in solution B is 0.1-0.3 mol / L, preferably 0.2 mol / L.

[0017] In step 1), the molar ratio of the Bi source to the ionic liquid [Bmim]I is 1:1-1.1; preferably 1:1.

[0018] Step 1) Use solutions A and B within 10 minutes of preparation;

[0019] In step 2), solution B is added to solution A by dropping, with a dropping rate of 4.5-5.5 mL / min, preferably 5 mL / min.

[0020] In step 2), add solution B to solution A and stir for 30 minutes;

[0021] In step 2), the hydrothermal reaction is carried out in a hydrothermal synthesis reactor;

[0022] The hydrothermal reaction conditions are: 140-150℃, heating reaction for 2.5-3.5 hours; preferably, 145℃, heating reaction for 3 hours.

[0023] In step 2), after the reaction vessel has cooled to room temperature, the reaction solution is centrifuged, washed three times with 50% ethanol, and dried at 60°C for 24 hours.

[0024] The roasting described in step 3) is carried out in a muffle furnace at 340-400°C for 100-130 min; preferably, it is roasted at 380°C for 120 min.

[0025] The present invention provides a photocatalytic material of hollow nanospheres, which is prepared by the above method. It is a flower-shaped material composed of nanosheets with hollow microspheres inside. The nanosheets are 200-400 nm in size and the hollow nanospheres are 12-16 μm in size.

[0026] This invention provides an application of a hollow nanosphere photocatalytic material for photocatalytic nitrogen fixation.

[0027] This invention successfully prepared BiOI microspheres using an ionic liquid-assisted method. The structure and morphology of the material were studied in detail using characterization techniques including XRD, XPS, FT-IR, SEM, and BET. Controlled experimental results showed that the formation of the microspheres was mainly determined by oriented self-assembly and an inside-out Ostwald ripening growth mechanism, in which [Bmim]I, besides acting as an iodine source, also played a crucial role as a template agent in the formation process of BiOI microspheres. The BiOI microspheres were then calcined at 340-400℃ to transform them into BiOI / Bi5O7I, further enhancing their photocatalytic performance. BiOI / Bi5O7I microspheres exhibited superior photocatalytic nitrogen fixation performance compared to BiOI microspheres under visible light. Furthermore, BiOI microspheres showed superior photocatalytic nitrogen fixation performance compared to BiOI nanosheets under visible light. Further research revealed that the enhanced photocatalytic performance of BiOI microspheres was mainly attributed to their smaller bandwidth, larger specific surface area, and higher charge separation efficiency. These results offer new possibilities for the application of BiOI microspheres in the environmental protection field. The catalyst preparation method is simple and easy to operate, can be used for efficient photocatalytic nitrogen fixation, and the catalyst is easy to recycle.

[0028] Compared with existing technologies, this invention presents a novel BiOI microsphere photocatalytic nitrogen fixation technology that uses light energy to convert nitrogen gas into ammonia, offering advantages such as environmental friendliness, high efficiency, and economy. This photocatalytic nitrogen fixation technology can effectively reduce nitrogen oxide emissions, minimizing environmental pollution. It can also improve nitrogen fertilizer utilization rates in crops, increasing crop yield and quality, while reducing nitrogen fertilizer usage and conserving resources. Furthermore, it can achieve nitrogen fertilizer self-sufficiency, reducing dependence on external resources. Therefore, this photocatalytic nitrogen fixation technology has broad application prospects and significant social implications. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 Here is a SEM image of the BiOI / Bi5O7I hollow microsphere product prepared according to the present invention;

[0031] Figure 2 This is a TEM image of the BiOI / Bi5O7I hollow microsphere product prepared according to the present invention;

[0032] Figure 3 These are the XRD patterns of the BiOI hollow microspheres prepared by this invention and the BiOI nanosheets prepared using potassium iodide as the iodine source.

[0033] Figure 4 The images show the XRD patterns of the BiOI / Bi5O7I hollow microspheres prepared according to this invention, and the products at different calcination temperatures of 340, 360, 380, and 400°C.

[0034] Figure 5 These are FT-IR images of the BiOI hollow microsphere product prepared by this invention and the BiOI nanosheet product prepared using potassium iodide as the iodine source.

[0035] Figure 6 These are the UV-Vis diffuse reflectance images of the BiOI hollow microsphere product prepared by this invention and the BiOI nanosheet product prepared using potassium iodide as the iodine source.

[0036] Figure 7 This is a BET diagram of the BiOI hollow microsphere product prepared by this invention and the BiOI nanosheet product prepared using potassium iodide as the iodine source.

[0037] Figure 8 These are photocurrent diagrams of the BiOI hollow microsphere product prepared by this invention and the BiOI nanosheet product prepared using potassium iodide as the iodine source.

[0038] Figure 9 These are the electrochemical impedance spectroscopy diagrams of the BiOI hollow microsphere product prepared by this invention and the BiOI nanosheet product prepared using potassium iodide as the iodine source.

[0039] Figure 10 These are XPS images of the BiOI hollow microsphere product prepared by this invention and the BiOI nanosheet product prepared using potassium iodide as the iodine source.

[0040] Figure 11 These are the morphology and mapping diagrams of the BiOI hollow microspheres;

[0041] Figure 12 This is the ammonia nitrogen standard curve.

[0042] Figure 13 This is a high-resolution transmission image of the BiOI / Bi5O7I hollow microsphere product prepared by this invention;

[0043] Figure 14 The diagram shows the photocatalytic nitrogen fixation performance of the BiOI hollow microspheres prepared in this invention, the BiOI nanosheets prepared with potassium iodide as the iodine source, the BiOI / Bi5O7I hollow microspheres, and the Bi5O7I hollow microspheres calcined at 420℃.

[0044] Figure 15 This is a SEM image of BiOI nanosheets. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0047] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0048] Example 1

[0049] A method for preparing a hollow nanosphere photocatalytic material includes the following steps:

[0050] 1) Solution A: 0.001 mol Bi(NO3)3·5H2O is dissolved in a solution containing 8 mL of deionized water and 2 mL of acetic acid. Solution B: 0.001 mol of ionic liquid [Bmim]I is dissolved in 5 mL of anhydrous ethanol. Solution B is added dropwise to solution A over 10 minutes with continuous stirring at a rate of 5 mL / min. The mixture is then stirred continuously for 30 minutes.

[0051] 2) Transfer the mixed solution to a 100 ml hydrothermal synthesis reactor and heat the reactor at 145 °C for 3 hours. After the reactor cools to room temperature, centrifuge the reaction solution, wash it three times with 50% ethanol, and dry it at 60 °C for 24 hours to obtain the product BiOI microspheres (BiOI hollow spheres). Its XRD pattern is shown below. Figure 3 As shown.

[0052] 3) The obtained product was calcined in a muffle furnace at 380℃ for 120 min. The final product was designated as BiOI / Bi5O7I microspheres. SEM and XRD patterns are shown below. Figure 1 , Figure 2 SEM images show that the product is a flower-shaped structure assembled from nanosheets, with a hollow center and a size of 12-16 μm. XRD patterns of the product were obtained by changing the calcination temperature to 340, 360, and 400 °C. Figure 4 In the comparison, the characteristic peak of Bi5O7I can be seen in BiOI / Bi5O7I. Figure 2 This is a transmission image obtained after the product was prepared into a solution. The preparation steps for the transmission solution are as follows: Weigh 1 mg of solid catalyst powder into a 1.5 ml centrifuge tube, add 1 ml of anhydrous ethanol to the centrifuge tube, seal the centrifuge tube tightly, and place it in an ultrasonic machine for 1 hour to ensure that the catalyst is evenly distributed in the anhydrous ethanol. Use a pipette to transfer the anhydrous ethanol after ultrasonication onto a copper grid. After drying, perform the transmission test. The transmission image shows that the morphology of the product was destroyed due to the ultrasonic preparation into a solution.

[0053] Following the same method as in Example 1, except that in step 2), the 0.001 mol of ionic liquid [Bmim]I was replaced with 0.001 mol of potassium iodide, and a hydrothermal reaction was performed under the same conditions without subsequent calcination. The product was BiOI nanosheets, and the XRD pattern is shown below. Figure 3 As shown, the morphology is as follows Figure 15 As shown, these are just nanosheets, not assembled. The comparison between BiOI microspheres and nanosheets reveals significant structural differences. Microspheres are assembled from multiple nanosheets and may differ significantly from nanosheets in shape and size, which can impact the material's properties and applications.

[0054] Following the same method as in Example 1, except that the calcination temperature was 420°C, the product was Bi5O7I microspheres.

[0055] This invention successfully prepared hollow microsphere photocatalytic materials using an ionic liquid-assisted method. The structure and morphology of the materials were studied in detail using characterization techniques such as XRD, XPS, FT-IR, SEM, and BET. Controlled experimental results showed that the formation of the microspheres was mainly determined by oriented self-assembly and an inside-out Ostwald ripening growth mechanism. [Bmim]I, in addition to acting as an iodine source, also served as a template agent, playing a crucial role in the formation process of BiOI microspheres.

[0056] The formation mechanism of the BiOI hollow microspheres in this invention is as follows:

[0057] 1) Initial formation of microsphere structure: In the reaction solution, the nanocrystals at the center of the initially formed microsphere structure are smaller than those on the outer layer, have poor crystallinity, and the resulting aggregates are not very stable.

[0058] 2) Dissolution-recrystallization process: The nanocrystals in the central part of the microsphere structure continuously dissolve and diffuse to the edge of the microsphere, where recrystallization occurs, leaving voids in the center. This dissolution-recrystallization process reduces the total energy of the system, which is conducive to the formation of hollow structures.

[0059] 3) Ostwald ripening process: The newly formed solid microspheres undergo an Ostwald ripening process from the inside out, forming a hollow structure.

[0060] The FT-IR testing steps of this invention are as follows:

[0061] Sample preparation: Prepare the sample to be tested, and dry the sample and potassium bromide in an oven at 100 degrees Celsius for 24 hours. Ensure the sample is dry to avoid the influence of moisture on the test results.

[0062] Instrument calibration: The FT-IR instrument needs to be calibrated before testing to ensure stable performance.

[0063] Baseline scan: Tablets were compressed using potassium bromide. After successful tablet compression, the tablets were placed on the sample stage of the FT-IR instrument, and the background was scanned using chromatographically pure potassium bromide.

[0064] Sample Placement: Compress the sample and potassium bromide into a tablet at a ratio of approximately 1:100. After successful tablet compression, place the tablet on the sample stage of the FT-IR instrument.

[0065] Spectral range selection: Select the spectral range to be tested as needed, usually within the infrared band (4000-400cm^-1) and a specific wavenumber range.

[0066] Sample testing: Start the FT-IR instrument and begin recording the infrared spectrum of the sample. The transmitted spectrum of the sample is measured by interacting the sample with infrared radiation.

[0067] Data processing: Processing the spectral data obtained from the test, including baseline correction, peak identification, and data interpretation.

[0068] Results analysis: Based on the position and intensity of the absorption peaks of the samples, the molecular structure and functional groups of the samples were analyzed.

[0069] SEM testing steps:

[0070] Sample preparation: Prepare the powder sample to be tested. The powder sample is adhered to a conductive sample support base for observation in SEM.

[0071] Sample preparation: Surface treatment of powder samples may be performed as needed, such as coating with a thin layer of conductive metal.

[0072] Instrument preparation: Turn on the SEM instrument and perform necessary preparations, including vacuum pump evacuation, electron beam setting, and sample support base installation.

[0073] Electron beam alignment: Adjust the electron beam of the SEM to ensure that it is perpendicularly aligned with the sample surface.

[0074] Working distance setting: Adjust the working distance (the distance between the electron beam and the sample surface) to 8cm.

[0075] Sample mounting: Mount the powder sample onto the sample support base of the SEM, ensuring good contact between the sample and the base to maintain conductivity.

[0076] Vacuum treatment: When necessary, vacuum treatment is performed to reduce interference from gases in the air.

[0077] Image acquisition: Start the SEM instrument, select the required operating parameters (such as accelerating voltage, operating mode, etc.), and begin acquiring images of the sample.

[0078] Data storage: Save test results and images for subsequent analysis and reporting.

[0079] BET testing steps:

[0080] 1. Sample Preparation: Prepare the sample to be measured. Dry the sample beforehand to avoid the influence of moisture on the test results. Then weigh the sample, typically 100 mg. Place the sample into a sample tube.

[0081] 2. Sample degassing: If adsorbed impurities are present in the sample, pretreatment is required to remove them. Degas the sample tube for three hours.

[0082] 3. BET instrument preparation: Turn on the BET instrument and perform the necessary instrument preparation work.

[0083] 4. Sample loading: Load the degassed sample tube onto the BET instrument and activate the BET test method.

[0084] 6. Selection of adsorbent gas: Nitrogen (N2) is selected as the adsorbent gas in this invention, but other gases may also be used, depending on the properties of the sample.

[0085] The test results of this invention, conducted according to the above test method, are as follows:

[0086] SEM images of hollow microsphere materials ( Figure 1 This indicates that the BiOI material has a three-dimensional microspherical structure. This three-dimensional structure is formed through the tight self-assembly of nanosheets, and the microspheres are solid. The nanosheets in the central region of the microsphere are smaller than those in the edge regions.

[0087] FT-IR spectrum of hollow microsphere material in this invention ( Figure 5 The material is located at 3436 and 1622 cm. -1 The characteristic absorption peak that appears corresponds to the stretching and bending vibrations of the OH group in water. It is located at 487 cm⁻¹. -1 The absorption peak corresponds to the stretching vibration peak of Bi-O. Meanwhile, no characteristic absorption peaks of the ionic liquid were observed in the infrared spectrum, indicating that the ionic liquid can be easily removed from the material surface by washing with water and alcohol after the reaction.

[0088] BET test results are as follows Figure 7 As shown, Figure 7 This indicates that BiOI microspheres have a significantly increased specific surface area compared to nanosheets. A larger specific surface area allows for the adsorption of more active species and reactants on their surface. Therefore, it can be inferred that the construction of hollow microsphere structures will be beneficial to improving their photocatalytic activity.

[0089] Figure 6 These are UV-Vis diffuse reflectance spectra of the BiOI hollow microspheres prepared in this invention and the BiOI nanosheets prepared using potassium iodide as the iodine source. The figures show that the light absorption edge of the BiOI microspheres is red-shifted towards the visible light region, indicating a wider absorption range for visible light. This helps improve the absorption efficiency of the photocatalyst for visible light, enabling it to utilize visible light more effectively for photocatalytic reactions.

[0090] Figure 8 This is a photocurrent spectrum of the BiOI hollow microsphere product prepared in this invention and the BiOI nanosheet product prepared using potassium iodide as the iodine source. During testing, the preparation involved connecting the working electrode of the electrochemical workstation to the electrode made from the material, the counter electrode to a platinum grid, and the reference electrode to a saturated calomel electrode. Electrolyte was poured in, and the system was stabilized for half an hour after the light was turned on. Linear scanning was performed: the initial potential was found, and after the electrode stabilized, the light was applied for 10 seconds, then blocked for 10 seconds. This cycle was repeated for 200 seconds. Based on... Figure 8 The BiOI microspheres exhibited higher photocurrent intensity, which indicates that the prepared BiOI microspheres exhibited higher separation efficiency of photogenerated charges.

[0091] Figure 9This document presents electrochemical impedance spectroscopy (EIS) diagrams of the BiOI hollow microspheres prepared in this invention and the BiOI nanosheets prepared using potassium iodide as the iodine source. A three-electrode system was selected, with anhydrous sodium sulfate as the electrolyte, and a CHI760E electrochemical workstation from Shanghai Chenhua Instruments Co., Ltd. was used. The working electrode underwent polishing, coating, and drying, while the electrolyte was prepared and degassed. EIS was used to further investigate charge transfer; a smaller semi-circular diameter indicates lower resistance. Compared to bulk and ultrathin materials, BiOI microspheres exhibit lower interfacial charge transfer resistance. Therefore, charge transport on BiOI microspheres is faster.

[0092] Figure 10 These are XPS images of the BiOI hollow microspheres prepared by this invention and the BiOI nanosheets prepared using potassium iodide as the iodine source. It can be seen that both products contain the three elements Bi, O, and I and have the same valence state.

[0093] Figure 13 This is a high-resolution transmission image of the BiOI / Bi5O7I hollow microspheres calcined at 380℃ prepared according to the present invention; it can be seen that the product includes BiOI and Bi5O7I.

[0094] This invention further explores the effect of different reaction times:

[0095] The reaction process was followed according to Example 1, except that solution B was added to solution A and the stirring time was changed. The results are as follows:

[0096] 0 minutes: Three-dimensional microsphere structure is formed, with smaller nanosheets in the central region of the microsphere.

[0097] 5 minutes: The nanosheets in the central region of the microsphere structure dissolve, forming a hollow structure.

[0098] 30 minutes: The hollowness increases, and the entire hollow structure is formed.

[0099] Further investigation into the effect of different ionic liquid concentrations:

[0100] The reaction process was the same as in Example 1, except that the amount of [Bmim]I was changed. Adding 2 mmol of [Bmim]I resulted in the formation of a hollow microsphere structure, but only a nanosheet structure. Adding 3 mmol of [Bmim]I resulted in the formation of a nanosheet structure with varying sizes.

[0101] Further investigation into the effect of acetic acid: Following the reaction process of Example 1, except that 5 mL of acetic acid was used: the microsphere structure was still maintained.

[0102] In summary, it can be seen that when solution B is added to solution A, the stirring time and the amount of ionic liquid added significantly affect the formation of the hollow structure.

[0103] Preparation of nitrogen fixation standard curve:

[0104] Preparation of standard solutions: Weigh 3.819 g of NH4Cl, dry it at (100-105℃), dissolve it in deionized water, and bring the volume to 1000 mL to obtain an ammonia nitrogen standard solution with a concentration of CN = 1000 mg / L. Dilute to ammonia nitrogen concentrations of 0, 0.25, 0.5, 0.75, 1, 1.5, 2, 2.5, 3, 3.5, and 4 mg / L respectively. Test the series of ammonia nitrogen standard solutions using a UV spectrophotometer to obtain UV-Vis absorption spectra. Plot the concentration of the ammonia nitrogen standard solution and the corresponding absorbance at 420 nm as the x and y axes to obtain the ammonia nitrogen standard curve, as shown below. Figure 12 As shown.

[0105] The application of the BiOI / Bi5O7I hollow nanosphere photocatalytic material prepared in Example 1 for photocatalytic nitrogen fixation is as follows:

[0106] First, 50 mg of the hollow nanosphere photocatalyst material prepared in Example 1 was added to a quartz test tube containing 50 mL of ultrapure water. The tube was then subjected to ultrasonic vibration in the dark for 30 minutes to ensure uniform dispersion of the catalyst. The test tube was then placed in an instrument, and nitrogen gas was introduced at a constant flow rate. A dark reaction was allowed for 1 hour to reach adsorption-desorption equilibrium and solution saturation. Subsequently, a xenon lamp was turned on for illumination. After 2 hours of illumination, 3 mL of the solution was taken from the quartz tube and filtered through a 0.22 μm filter to remove any remaining solid catalyst. Then, 1 mL of potassium sodium tartrate solution and 1 mL of Nessler's reagent were added, and the solution was shaken to mix thoroughly. The mixture was allowed to stand for 12 minutes, and finally, the absorbance at 420 nm was measured using a UV spectrophotometer. Based on the absorbance and... Figure 12 The photocatalytic nitrogen fixation performance was obtained from the standard curve.

[0107] The BiOI / Bi5O7I prepared in Example 1 was replaced with the BiOI microspheres, BiOI nanosheets, and Bi5O7I prepared above, respectively. The photocatalytic nitrogen fixation performance was tested using the same method. Figure 14 As shown, compared with BiOI nanosheets and BiOI microspheres, the nitrogen fixation performance of BiOI / Bi5O7I is significantly improved.

[0108] BiOI microspheres exhibit superior photocatalytic nitrogen fixation performance compared to BiOI nanosheets under visible light.

[0109] Furthermore, the study found that the enhanced photocatalytic performance of BiOI microspheres is mainly attributed to their smaller bandwidth, larger specific surface area, and higher charge separation efficiency. These results provide new possibilities for the application of BiOI microspheres in environmental protection. The catalyst preparation method is simple and easy to operate, can be used for efficient photocatalytic nitrogen fixation, and the catalyst is easy to recycle. Calcining the BiOI microspheres at 340-400℃ to convert them into BiOI / Bi5O7I further improves the photocatalytic performance.

[0110] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. An application of a hollow nanosphere photocatalytic material, characterized in that, Used for photocatalytic nitrogen fixation; the preparation method of the nano-hollow microsphere photocatalytic material includes the following steps: 1) Mix the Bi source in a solvent to obtain solution A; dissolve the ionic liquid [Bmim]I in anhydrous ethanol to obtain solution B; 2) Under stirring conditions, solution B is added to solution A and stirred to mix. The resulting mixed solution undergoes a hydrothermal reaction. 3) The product from step 2) is calcined to obtain BiOI / Bi5O7I hollow nanosphere photocatalytic material; In step 1), the ratio of ionic liquid [Bmim]I to anhydrous ethanol in solution B is 0.1-0.3 mol: 1 L. Step 1) The molar ratio of the Bi source and the ionic liquid [Bmim]I is 1:1-1.1; The roasting described in step 3) is carried out in a muffle furnace at 340-400℃ for 100-130 minutes.

2. The application according to claim 1, characterized in that, In step 1), the ratio of Bi source to solvent in solution A is 0.05-0.15 mol: 1L.

3. The application according to claim 1 or 2, characterized in that, In step 1), the solvent used in solution A is a mixture of deionized water and acetic acid; the volume ratio of the deionized water to acetic acid is 1.5-5:

1.

4. The application according to claim 1 or 2, characterized in that, The Bi source mentioned in step 1) is selected from Bi(NO3)3·5H2O.

5. The application according to claim 1 or 2, characterized in that, In step 2), the hydrothermal reaction is carried out under the following conditions: 140-150℃, heating reaction for 2.5-3.5 hours.

Images