Preparation method of WO3-x / BiOBr heterojunction photocatalyst and application of WO3-x / BiOBr heterojunction photocatalyst in nitrogen fixation
By constructing the WO3-x/BiOBr heterojunction photocatalyst, the problems of weak N2 adsorption activation ability and low photogenerated carrier separation efficiency of BiOBr photocatalyst during photocatalytic nitrogen fixation are solved, and the efficient photocatalytic nitrogen fixation performance is achieved, which is suitable for industrial applications.
Patent Information
- Application Number
- CN202510611612.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-13
- Publication Date
- 2025-08-12
AI Technical Summary
During the photocatalytic nitrogen fixation process, existing BiOBr photocatalysts have problems such as weak N2 adsorption activation ability and low photocarrier separation efficiency, which limits their photocatalytic performance.
The WO3-x nanowires were prepared by hydrothermal method and the solvothermal method. The WO3-x nanowires were loaded onto the surface of the BiOBr nanosheets by electrostatic self-assembly to construct a WO3-x/BiOBr heterojunction photocatalyst to promote photogenerated carrier separation and N2 mass transfer adsorption.
The photocatalytic nitrogen fixation efficiency is significantly improved, the ammonia generation rate reaches 881μmol g-1h-1, and the catalyst is stable, simple to operate and low cost, and is suitable for industrial promotion.
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Figure CN120459996A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of photocatalytic nitrogen fixation, specifically a WO 3-x Preparation method of BiOBr heterojunction photocatalyst and its application in nitrogen fixation. Background Art
[0002] Ammonia (NH3) is the second most produced chemical worldwide and plays an irreplaceable role in pillar industries such as energy and chemicals. For over a century, the development of the Haber-Bosch process has driven the progress of human society and remains the primary industrial method for producing NH3. However, the Haber-Bosch process requires high temperatures and high pressures, consuming significant amounts of energy. Furthermore, it also emits significant amounts of greenhouse gases, creating serious environmental problems. Therefore, finding a clean and efficient method for nitrogen fixation is of vital importance.
[0003] Photocatalytic nitrogen fixation, an emerging technology, has attracted widespread attention due to its mild reaction conditions, zero carbon emissions, and solar energy. BiOBr photocatalysts have been applied to photocatalytic nitrogen fixation due to their unique layered structure, tunable band gap, and susceptibility to defects, particularly oxygen vacancies. However, single, unmodified BiOBr photocatalysts often suffer from weak nitrogen (N2) adsorption and activation ability and low photogenerated carrier separation efficiency, which severely limits their photocatalytic performance. To improve the photocatalytic nitrogen fixation performance of BiOBr, developing a more rational photocatalyst preparation method is currently a hot topic. Summary of the Invention
[0004] In order to overcome the shortcomings of the prior art, the present invention proposes a WO 3-x / BiOBr heterojunction photocatalyst, hydrophobic BiOBr nanosheets were first prepared by a hydrothermal method, and WO 3-x nanowires, and then WO was assembled by electrostatic self-assembly 3-x Nanowires were loaded onto the surface of hydrophobic BiOBr nanosheets to obtain WO 3-x / BiOBr heterojunction photocatalyst. By constructing a heterojunction system, the separation of photogenerated charge carriers is significantly promoted. At the same time, the hydrophobic BiOBr nanosheets promote the mass transfer and adsorption of N2 on the catalyst surface, improving the efficiency of photocatalytic nitrogen fixation.
[0005] The second purpose of the present invention is to provide a WO with simple operation process and low cost. 3-x Preparation method of / BiOBr heterojunction photocatalyst.
[0006] The third object of the present invention is to provide a WO 3-xApplication of / BiOBr heterojunction photocatalyst in nitrogen fixation.
[0007] In order to achieve the above purpose, the technical solution adopted by the present invention is a WO 3-x / BiOBr heterojunction photocatalyst, the preparation method thereof comprises the following steps:
[0008] (1) Preparation of hydrophobic BiOBr nanosheets: Bismuth nitrate pentahydrate, mannitol, and polyvinyl pyrrolidone were added to deionized water and stirred to fully dissolve to obtain a mixed solution. Then, hexadecyltrimethylammonium bromide was added to the mixed solution and stirred to obtain a uniform mixed solution. The mixed solution was then transferred to a polytetrafluoroethylene liner and heated for a hydrothermal reaction. The solid product was collected by centrifugation, washed with deionized water and ethanol multiple times, and dried to obtain hydrophobic BiOBr nanosheets.
[0009] (2) Preparation of WO 3-x Nanowires: Dissolve tungsten hexachloride in anhydrous ethanol solution and stir to fully dissolve to obtain a uniform solution. Then, transfer the solution to a polytetrafluoroethylene liner and heat it for solvent thermal reaction. Collect the solid product by centrifugation, wash it with deionized water and ethanol several times, and dry it to obtain WO 3-x Nanowires.
[0010] (3) Preparation of WO 3-x / BiOBr heterojunction photocatalyst: WO prepared in step (2) 3-x The nanowires were added to anhydrous ethanol solution and ultrasonicated to make WO 3-x The nanowires were completely dispersed, and then the hydrophobic BiOBr nanosheets prepared in step (1) were added and stirred at room temperature for electrostatic self-assembly reaction. After the reaction, the solid product was collected by centrifugation, washed with deionized water and ethanol several times, and dried to obtain WO 3-x / BiOBr heterojunction photocatalyst.
[0011] In the above scheme, in step (1), bismuth nitrate pentahydrate is 0.1-0.5 g, mannitol is 0.1-0.5 g, polyvinyl pyrrolidone is 0.1-0.3 g, hexadecyltrimethylammonium bromide is 0.2-0.6 g, and the volume of deionized water is 20-50 mL.
[0012] In the above scheme, in step (1), the stirring time is 0.5~1h and 0.5~1.5h respectively, the hydrothermal reaction temperature is 150~170℃, and the time is 3~5h.
[0013] In the above scheme, in step (2), the amount of tungsten hexachloride is 0.03-0.07 g, and the volume of anhydrous ethanol is 30-50 mL.
[0014] In the above scheme, in step (2), the stirring time is 0.5-1 h, the solvent thermal reaction temperature is 170-190° C., and the time is 10-12 h.
[0015] In the above scheme, in step (3), WO 3-x The mass ratio of BiOBr is (0.5~2):10.
[0016] In the above scheme, in step (3), the ultrasonic treatment time is 1 to 2 hours, and the stirring time is 1.5 to 2 hours.
[0017] One of the above WO 3-x Application of / BiOBr heterojunction photocatalyst in nitrogen fixation.
[0018] The beneficial effects of the present invention are:
[0019] (1) WO prepared by the present invention 3-x / BiOBr heterojunction photocatalyst overcomes the problems of weak N2 adsorption activation ability and easy recombination of photogenerated carriers in BiOBr photocatalyst.
[0020] (2) WO prepared by the present invention 3-x / BiOBr heterojunction photocatalyst has high photocatalytic nitrogen fixation performance, and the method is simple to operate, low in cost, and is expected to be used in industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 The samples BiOBr, WO prepared in Examples 1, 2 and 5 of the present invention are 3-x and 15%WO 3-x Scanning electron micrograph of / BiOBr.
[0022] Figure 2 The samples BiOBr, WO prepared in Examples 1, 2 and 5 of the present invention are 3-x and 15%WO 3-x X-ray diffraction pattern of α / BiOBr.
[0023] Figure 3 The samples BiOBr (a), WO prepared in Examples 1, 2 and 5 of the present invention 3-x (c) and 15%WO 3-x Water contact angle diagram of / BiOBr (b).
[0024] Figure 4 The samples BiOBr and WO prepared in Examples 1 to 6 of the present invention are 3-x and WO 3-x Comparison of nitrogen fixation activity of β-lactamase / BiOBr.
[0025] Figure 5 The sample 15% WO prepared in Example 5 of the present invention 3-x / BiOBr was recycled multiple times to test its photocatalytic nitrogen fixation performance. DETAILED DESCRIPTION
[0026] In order to clearly understand the present invention, the following specific embodiments are 3-x The preparation method and nitrogen fixation performance of the / BiOBr heterojunction photocatalyst are further explained.
[0027] A WO 3-x The preparation steps of the α / BiOBr heterojunction photocatalyst are as follows:
[0028] (1) Preparation of hydrophobic BiOBr nanosheets: 0.486 g of bismuth nitrate pentahydrate, 0.452 g of mannitol, and 0.2 g of polyvinyl pyrrolidone were added to 30 mL of deionized water and stirred for 0.7 h to obtain a mixed solution. Then, 0.364 g of hexadecyltrimethylammonium bromide was added to the mixed solution and the mixture was stirred for 1 h to obtain a uniform mixed solution. The mixed solution was transferred to a polytetrafluoroethylene-lined reaction vessel and maintained at a temperature of 160 ° C for 4 h. The solid product was collected by centrifugation, washed with deionized water and ethanol several times, and dried to obtain hydrophobic BiOBr nanosheets;
[0029] (2) WO 3-x Preparation of nanowires: 0.05 g of tungsten hexachloride was dissolved in 40 mL of anhydrous ethanol solution and stirred for 0.6 h to fully dissolve to obtain a uniform solution. The mixed solution was then transferred to a polytetrafluoroethylene-lined reaction vessel and kept at 180°C for 11 h. The solid product was collected by centrifugation, washed with deionized water and ethanol several times, and dried to obtain WO 3-x nanowires;
[0030] (3) WO 3-x Preparation of WO / BiOBr heterojunction photocatalyst: 0.3 g WO 3-x The nanowires were added to the ethanol solution and ultrasonicated for 1.5 h to make the WO 3-x The nanowires were completely dispersed. Then 2 g of hydrophobic BiOBr nanosheets were added and stirred at room temperature for 1.7 h. After the end, the solid product was collected by centrifugation and washed with deionized water and ethanol several times, and dried to obtain WO 3-x / BiOBr heterojunction photocatalyst.
[0031] Example 1
[0032] 0.486g of bismuth nitrate pentahydrate, 0.452g of mannitol, and 0.2g of polyvinylpyrrolidone were added to 30mL of deionized water and stirred for 0.7h to obtain a mixed solution. Then, 0.364g of hexadecyltrimethylammonium bromide was added to the mixture and stirred for another hour to obtain a uniform mixed solution. The mixture was transferred to a polytetrafluoroethylene-lined reaction vessel and maintained at 160°C for 4h. The solid product was collected by centrifugation, washed multiple times with deionized water and ethanol, and dried to obtain hydrophobic BiOBr nanosheets.
[0033] Example 2
[0034] 0.05 g of tungsten hexachloride was dissolved in 40 mL of anhydrous ethanol solution and stirred for 0.6 h to fully dissolve to obtain a uniform solution. The mixture was then transferred to a polytetrafluoroethylene-lined reaction vessel and kept at 180 ° C for 11 h. The solid product was collected by centrifugation, washed with deionized water and ethanol several times, and dried to obtain WO 3-x Nanowires.
[0035] Example 3
[0036] 0.1 g of WO 3-x The nanowires were added to the ethanol solution and ultrasonicated for 1.5 h to make the WO 3-x The nanowires were completely dispersed. Then 2 g of hydrophobic BiOBr nanosheets were added and stirred at room temperature for 1.7 h. After the end, the solid product was collected by centrifugation, washed with deionized water and ethanol several times, and dried to obtain 5% WO 3-x / BiOBr heterojunction photocatalyst.
[0037] Example 4
[0038] 0.2 g of WO 3-x The nanowires were added to the ethanol solution and ultrasonicated for 1.5 h to make the WO 3-x The nanowires were completely dispersed. Then 2 g of hydrophobic BiOBr nanosheets were added and stirred at room temperature for 1.7 h. After the end, the solid product was collected by centrifugation, washed with deionized water and ethanol several times, and dried to obtain 10% WO 3-x / BiOBr heterojunction photocatalyst.
[0039] Example 5
[0040] 0.3 g of WO 3-x The nanowires were added to the ethanol solution and ultrasonicated for 1.5 h to make the WO 3-xThe nanowires were completely dispersed. Then 2 g of hydrophobic BiOBr nanosheets were added and stirred at room temperature for 1.7 h. After the end, the solid product was collected by centrifugation, washed with deionized water and ethanol several times, and dried to obtain 15% WO 3-x / BiOBr heterojunction photocatalyst.
[0041] Example 6
[0042] 0.4 g of WO 3-x The nanowires were added to the ethanol solution and ultrasonicated for 1.5 h to make the WO 3-x The nanowires were completely dispersed. Then 2 g of hydrophobic BiOBr nanosheets were added and stirred at room temperature for 1.7 h. After the end, the solid product was collected by centrifugation, washed with deionized water and ethanol several times, and dried to obtain 20% WO 3-x / BiOBr heterojunction photocatalyst.
[0043] Example 7
[0044] 50 mg of catalyst was added to a top-illuminated quartz reactor, and 60 mL of deionized water was added. High-purity nitrogen was introduced into the reactor to exclude air under light-proof conditions. A 150W xenon lamp was used to simulate sunlight. In order to prevent the reaction temperature from changing due to light, circulating cooling water was connected to the periphery of the reactor. The NH3 / NH4 + The concentration can be determined using the Nessler method. Each data was repeated three times to determine the catalytic results to ensure the accuracy of the experimental results.
[0045] WO 3-x Characterization and nitrogen fixation performance test of / BiOBr heterojunction photocatalyst
[0046] Scanning electron microscope image: Figure 1 It can be observed that WO 3-x WO has a nanowire morphology with a length of 500~1000nm. BiOBr has a nanosheet morphology with a size range of 50~100nm. When these two materials are combined, WO 3-x The nanowires are uniformly loaded on the surface of BiOBr nanosheets.
[0047] X-ray diffraction spectrum: Figure 2 The prepared heterojunction sample WO 3-x WO can be observed in / BiOBr 3-x Characteristic peaks, and the diffraction peaks of BiOBr can also be observed, indicating that WO was successfully prepared. 3-x / BiOBr heterojunction photocatalyst.
[0048] Water contact angle diagram: Figure 3 In, such as Figure 3 As shown in (a), the prepared BiOBr has a water contact angle of 129°, indicating hydrophobicity. Figure 3 (c) As shown, the prepared WO 3-x The water contact angle is 21°, which indicates hydrophilicity. Figure 3 (b) shows that when these two materials are combined, the heterojunction sample 15% WO 3-x The water contact angle of / BiOBr is 110°, which shows hydrophobicity, indicating that the hydrophobic WO was successfully prepared. 3-x / BiOBr heterojunction photocatalyst.
[0049] Nitrogen fixation performance test diagram: The photocatalytic nitrogen fixation activity of the sample prepared as shown in Figure 4 is as follows: 3-x The photocatalytic nitrogen fixation performance was improved with the increase of WO 3-x The addition promotes the separation of photogenerated electron-hole pairs. 3-x / BiOBr’s nitrogen fixation performance actually decreased, indicating that excessive WO 3-x It will cover the hydrophobic active surface of BiOBr and reduce the active sites of the catalyst. 3-x / BiOBr exhibited the best photocatalytic nitrogen fixation performance, with an ammonia production rate of 881 μmol g -1 h -1 , and the nitrogen fixation efficiency was still 849 μmol g after five cycles of testing. -1 h -1 ,like Figure 5 As shown, this confirms that WO 3-x / BiOBr heterojunction photocatalyst has excellent photostability. 3-x / BiOBr heterojunction photocatalysts have great development and application prospects in photocatalytic green ammonia synthesis.
Claims
1. A WO 3-x Preparation method of / BiOBr heterojunction photocatalyst and its application in nitrogen fixation, characterized in that The following steps are involved: (1) Preparation of hydrophobic BiOBr nanosheets: Bismuth nitrate pentahydrate, mannitol, and polyvinyl pyrrolidone were added to deionized water and stirred to fully dissolve to obtain a mixed solution. Then, hexadecyltrimethylammonium bromide was added to the mixed solution and stirred to obtain a uniform mixed solution. The mixed solution was then transferred to a polytetrafluoroethylene liner and heated for hydrothermal reaction. The solid product was collected by centrifugation, washed with deionized water and ethanol several times, and dried to obtain hydrophobic BiOBr nanosheets. (2) Preparation of WO 3-x Nanowires: Dissolve tungsten hexachloride in anhydrous ethanol solution and stir to fully dissolve to obtain a uniform solution. Then, transfer the solution to a polytetrafluoroethylene liner and heat it for solvent thermal reaction. Collect the solid product by centrifugation, wash it with deionized water and ethanol several times, and dry it to obtain WO 3-x nanowires; (3) Preparation of WO 3-x / BiOBr heterojunction photocatalyst: WO prepared in step (2) 3-x The nanowires were added to anhydrous ethanol solution and ultrasonicated to make WO 3-x The nanowires were completely dispersed, and then the hydrophobic BiOBr nanosheets prepared in step (1) were added and stirred at room temperature for electrostatic self-assembly reaction. After the reaction, the solid product was collected by centrifugation, washed with deionized water and ethanol several times, and dried to obtain WO 3-x / BiOBr heterojunction photocatalyst.
2. A WO according to claim 1 3-x A method for preparing a / BiOBr heterojunction photocatalyst, characterized in that: In the step (1), the amount of bismuth nitrate pentahydrate is 0.1-0.5 g, the amount of mannitol is 0.1-0.5 g, the amount of polyvinyl pyrrolidone is 0.1-0.3 g, the amount of hexadecyltrimethylammonium bromide is 0.2-0.6 g, and the volume of deionized water is 20-50 mL.
3. A WO according to claim 1 3-x A method for preparing a / BiOBr heterojunction photocatalyst, characterized in that: In the step (1), the stirring time is 0.5-1 h and 0.5-1.5 h respectively, the hydrothermal reaction temperature is 150-170° C., and the time is 3-5 h.
4. A WO according to claim 1 3-x A method for preparing a / BiOBr heterojunction photocatalyst, characterized in that: In step (2), the amount of tungsten hexachloride is 0.03-0.07 g, and the volume of anhydrous ethanol is 30-50 mL.
5. A WO according to claim 1 3-x A method for preparing a / BiOBr heterojunction photocatalyst, characterized in that: In the step (2), the stirring time is 0.5-1 h, the solvent thermal reaction temperature is 170-190° C., and the time is 10-12 h.
6. A WO according to claim 1 3-x A method for preparing a / BiOBr heterojunction photocatalyst, characterized in that: In the step (3), WO 3-x The mass ratio of nanowires to hydrophobic BiOBr nanosheets is (0.5~2):
10.
7. A WO according to claim 1 3-x A method for preparing a / BiOBr heterojunction photocatalyst, characterized in that: In the step (3), the ultrasonic treatment time is 1 to 2 hours, and the stirring time is 1.5 to 2 hours.
8. A WO according to claim 1 3-x Application of / BiOBr heterojunction photocatalyst in nitrogen fixation.