A bismuth oxyhalide nanomaterial, a preparation method and application thereof
By preparing bismuth halide nanomaterials, and using the (101) crystal plane preferred orientation and oxygen defect structure, the problem of electron quantity and mobility in the photocatalytic nitrogen reduction process of bismuth halide nanomaterials was solved, and a highly efficient small molecule energy catalytic effect was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TAIYUAN UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2024-09-18
- Publication Date
- 2026-05-29
Smart Images
Figure CN119034766B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the fields of energy and chemical engineering, specifically to the field of small molecule energy conversion engineering, and more specifically, to a bismuth halide nanomaterial, its preparation method, and its application. Background Technology
[0002] Hydrogen energy is a renewable energy source and is widely considered a crucial component of future energy. Its unique properties and potential make it significant for energy transition and sustainable development. Hydrogen-containing molecules such as ammonia are seen as efficient intermediate media for hydrogen storage; therefore, ammonia is often presented as a new clean energy source and fuel. Currently, NH3 is mainly derived from artificial nitrogen fixation. However, due to the inertness of this molecule, fixing the abundant nitrogen on Earth is technically and economically challenging. Traditional industrial NH3 production primarily uses the Haber-Bosch process. Because N≡N has a high bond energy of 940.95 kJ / mol, this industrial production requires operation under high temperature and pressure. Furthermore, industrial NH3 production consumes approximately 2% of global energy and releases 1% of global greenhouse gases. Therefore, there is an urgent need to develop a new, cost-effective, low-energy-consumption, and environmentally friendly nitrogen reduction technology.
[0003] In recent years, photocatalysis has developed rapidly due to its advantages of being green and low-cost, and has been increasingly applied to reduce nitrogen in air and water to small-molecule energy, effectively solving the problems of low efficiency, severe pollution, and high energy consumption in traditional nitrogen reduction processes. In application, the design and development of effective semiconductor photocatalysts is a crucial first step. Bismuth oxyhalides (BiOX, X = Cl, Br, and I) are unique photocatalysts due to their specific two-dimensional (2D) structure, in which a [Bi-O] layer is sandwiched between two halogen atoms. This unique layered structure easily forms a built-in electric field, which can accelerate the transport of charge carriers from the interior to the surface. Furthermore, the multi-electron layer structure outside the Bi atom nucleus contributes to a high reduction potential in the conduction band, especially BiOCl, which promotes the entry of photogenerated electrons into the π* energy level of N2 through the outer orbitals of Bi atoms. Therefore, the separation and migration of charge carriers are key factors affecting the performance of photocatalytic nitrogen reduction.
[0004] However, actual experiments have revealed that bismuth halides currently suffer from problems such as a low number of electrons in the excited state and low carrier mobility under light conditions, which greatly affect the material's ability to catalyze nitrogen reduction. Summary of the Invention
[0005] To address the aforementioned technical problems, this application provides a bismuth halide nanomaterial and its preparation method. This bismuth halide nanomaterial exhibits significant photoresponse, numerous active sites, and high carrier separation rate and concentration under light irradiation, demonstrating excellent catalytic performance in the photocatalytic reduction of small molecule energy.
[0006] Firstly, this application provides a bismuth halide nanomaterial, which adopts the following technical solution:
[0007] A bismuth halide nanomaterial has a sheet-like structure with an average diameter of 50nm-200nm and a thickness of 15nm-30nm. The bismuth halide nanomaterial has a quadrilateral phase crystal structure, with preferred orientation growth on the (101) crystal plane. It belongs to the P4 / nmm space group with a group number of 129 and unit parameters of a×b×c=3.89×3.89×7.37 and α×β×γ=90°×90°×90°.
[0008] By adopting the above technical solution, the bismuth halide nanomaterial of this application is a bismuth halide nanomaterial with high exposure rate of (101) crystal plane. It has a high potential crystal plane with different atomic arrangements, which can effectively enrich photogenerated electrons under light, resulting in a large number of electrons in the excited state. Therefore, it has the characteristics of obvious photoresponse effect, many active sites, high carrier separation rate, high concentration and high mobility under light irradiation. In the actual photocatalytic reduction preparation of small molecule energy, it has a large adsorption capacity for small molecules represented by N2 and a good effect on catalyzing the reduction of N2 to NH3.
[0009] Preferably, the bismuth halide nanomaterial is an oxygen-deficient bismuth halide nanomaterial with an oxygen hole concentration of 66.0% and a water contact angle of 36.4°.
[0010] By employing the above-mentioned technical solution, this application further constructed defects in bismuth halide nanomaterials, thus obtaining oxygen-deficient bismuth halide nanomaterials. This defect construction breaks the original electronic symmetry of the material structure, leading to strong electrostatic coupling near the defects. This electrostatic attraction confines excited-state electrons around the atomic defects, significantly suppressing the transition of excited-state electrons to the ground state and their recombination with valence band holes. This further increases the number of excited-state electrons, resulting in better directional carrier mobility under illumination, and consequently, enhancing the catalytic reduction effect of the bismuth halide nanomaterials.
[0011] Secondly, this application provides a method for preparing bismuth halide nanomaterials, employing the following technical solution:
[0012] A method for preparing bismuth halide nanomaterials includes the following steps:
[0013] Bismuth nitrate pentahydrate, halide salt, surfactant and water were mixed and stirred for 2.0-2.5 hours to obtain a mixed emulsion. The mixed emulsion was then subjected to hydrothermal reaction at 130-160℃ for 8 hours. After solid-liquid separation, the precipitate was washed and dried to obtain bismuth halide nanomaterials with preferred orientation of (101) crystal plane.
[0014] More specifically, the weight ratio of the bismuth nitrate pentahydrate, halide, surfactant, and water is 1:(0.125-0.150):0.5:50.
[0015] More specifically, the surfactant is polyvinylpyrrolidone.
[0016] By adopting the above technical solution, this application uses bismuth nitrate pentahydrate, halide salt and surfactant as reaction raw materials to prepare bismuth oxide halide nanomaterials with high exposure rate of (101) crystal plane through hydrothermal reaction. The preparation method has the characteristics of low cost, no pollution and simple operation, and is suitable for large-scale industrial production.
[0017] The polyvinylpyrrolidone (PVP) of this application possesses excellent solubility and physiological compatibility, being soluble in both water and most organic solvents, and exhibiting extremely low toxicity. When added to the reaction system, it adsorbs onto the surface of the material precursor, which refers to the unformed state where crystal nuclei are growing. This reduces the surface tension of the material precursor, promotes its dispersion and stability in the solvent, and exposes the high-surface-energy crystal faces, thereby obtaining the bismuth halide nanomaterial with a high exposure rate of the specific (101) crystal facet as described in this application. As is known to those skilled in the art, different surfactants achieve different effects; not all surfactants can produce the same high-exposure (101) crystal facet as described in this application. Other surfactants may expose different crystal faces. Through experimental research, the inventors of this application have discovered that adding polyvinylpyrrolidone to the reaction system can produce the bismuth halide nanomaterial with the desired crystal form as described in this application.
[0018] Preferably, the preparation method further includes the following steps:
[0019] The bismuth halide nanomaterials grown with preferred orientation on the (101) crystal plane were immersed in NaBH4 aqueous solution and stirred for 20-30 minutes. After solid-liquid separation, the precipitate was washed and dried to obtain oxygen-deficient bismuth halide nanomaterials.
[0020] More specifically, the concentration of the NaBH4 aqueous solution is 8 mmol / L-10 mmol / L.
[0021] By adopting the above technical solution, this application further reduces the prepared (101) crystal plane high exposure rate bismuth halogen oxide nanomaterials with NaBH4 aqueous solution to form defects, thereby obtaining defective bismuth halogen oxide nanomaterials with oxygen vacancies.
[0022] In this application, all mixing processes of raw materials can be achieved by means of stirring and / or ultrasonic dispersion known to those skilled in the art. All solid-liquid separation processes can be achieved by means of centrifugation and / or filtration known to those skilled in the art. All washing and precipitation processes can be carried out by any one of washing three times with deionized water, washing three times with anhydrous ethanol, or washing three times alternately with deionized water and anhydrous ethanol. All drying conditions can be: drying at a temperature of 60°C-80°C for 12 hours.
[0023] Thirdly, this application provides an application of bismuth halide nanomaterials in the photocatalytic reduction preparation of small molecule energy.
[0024] More specifically, the amount of the bismuth halide nanomaterial used is 0.5 g / L-0.8 g / L.
[0025] More specifically, under light conditions, the bismuth halide nanomaterial is applied at a dosage of 0.5 g / L to 0.8 g / L in the process of catalyzing the reduction of N2 to ammonia in air or water, or in the process of catalyzing the reduction of CO2 to formaldehyde.
[0026] Furthermore, those skilled in the art have reason to believe that using the aforementioned bismuth halide nanomaterials in other processes that can be catalytically reduced to small molecule energy, without any inventive effort, is also within the scope of this application.
[0027] In this application, the inventors use the process of catalytically reducing N2 to ammonia in water as an example, wherein the water contains an N2 source and H2 obtained from water dissociation. + A proton source with an N2 flow rate of 50-60 mL / min was used, along with a simulated Taiyuan energy source (AM 1.5G filter, 100 mW / cm²). 2 ).
[0028] In summary, this application has the following beneficial technical effects:
[0029] 1. This application obtained bismuth halide nanomaterials with preferred orientation of (101) crystal plane by crystal plane tuning. The high potential crystal plane with different atomic arrangement can effectively enrich photogenerated electrons under light, so that there are more electrons in the excited state, thus having obvious photoresponse effect, many active sites, and high carrier separation rate, high concentration and high mobility under light irradiation.
[0030] 2. This application constructs oxygen atom defects on bismuth oxyhalide nanomaterials with high exposure of (101) crystal plane, which can suppress the transition of excited state electrons to ground state and recombination with valence band holes in the material, thereby further increasing the number of electrons in the excited state and making the directional mobility of charge carriers good under illumination conditions.
[0031] 3. The bismuth oxide halide nanomaterials of this application exhibit a large adsorption capacity for small molecules, represented by N2, and a good catalytic reduction effect on N2 to NH3 in the actual photocatalytic reduction preparation of small molecule energy.
[0032] 4. The preparation method of bismuth halide nanomaterials of this application has the characteristics of low cost, no pollution and simple operation, and is suitable for large-scale industrial production. Attached Figure Description
[0033] Figure 1 These are physical images of the bismuth oxychloride nanomaterials prepared in Examples 1-4 of this application;
[0034] Figure 2(a) is a scanning electron microscope image of the bismuth oxychloride nanomaterials prepared in Examples 1-4 of this application;
[0035] Figure 2(b) is a scanning electron microscope image of the bismuth oxychloride nanomaterials prepared in Comparative Example 1;
[0036] Figure 3(a) is the X-ray diffraction pattern of the bismuth oxychloride nanomaterials prepared in Examples 1-4 of this application;
[0037] Figure 3(b) is a crystal phase analysis diagram of the bismuth oxychloride nanomaterials prepared in Examples 1-4 of this application;
[0038] Figure 4 The electron paramagnetic resonance spectra of bismuth oxychloride nanomaterials prepared in Preparation Example 2, Preparation Example 4 and Comparative Example 1 are shown.
[0039] Figure 5 These are the positron annihilation spectra of the bismuth oxychloride nanomaterials prepared in Preparation Example 4 and Comparative Example 1;
[0040] Figure 6 This is a static water contact angle diagram of the surface of bismuth oxychloride nanomaterials prepared in Preparation Example 2, Preparation Example 4 and Comparative Example 1;
[0041] Figure 7 The NH4 in the samples of Examples 1-4 and Comparative Example 1 + Concentration detection results graph;
[0042] Figure 8 It is BOC in Example 2 (101) Repeated effect diagram of photocatalytic N2 reduction;
[0043] Figure 9It is BOC in Example 4 (101) -OVs photocatalytic N2 reduction repeatability diagram;
[0044] Figure 10 The BOC prepared in Example 2 (101) Preparation Example 4 yielded BOC (101) The photocatalytic N2 reduction effect of -OVs and BOC prepared in Comparative Example 1 under outdoor sunlight. Detailed Implementation
[0045] The present application will be further described in detail below with reference to the accompanying drawings, preparation examples and embodiments.
[0046] The bismuth oxyhalide nanomaterials of this application can be any one of bismuth oxychloride nanomaterials, bismuth oxybromine nanomaterials, and bismuth oxyiodide nanomaterials. If the obtained material is bismuth oxychloride nanomaterial, the halide salt in the raw material used is potassium chloride; if the obtained material is bismuth oxybromine nanomaterial, the halide salt in the raw material used is potassium bromide; if the obtained material is bismuth oxyiodide nanomaterial, the halide salt in the raw material used is potassium iodide. In the specific embodiments of this application, the obtained material is bismuth oxychloride nanomaterial as an example for explanation.
[0047] Unless otherwise specified, all raw materials used in this application are commercially available products.
[0048] <Preparation Example 1>
[0049] A method for preparing bismuth oxychloride nanomaterials includes the following steps:
[0050] 0.5 g of polyvinylpyrrolidone was added to 50 g of deionized water and stirred slowly. Then, 1 g of bismuth nitrate pentahydrate and 0.125 g of potassium chloride were added and stirred for 2.0 hours to obtain a mixed emulsion. The mixed emulsion was then subjected to hydrothermal reaction at 130 °C for 8 hours. After cooling to room temperature, the product was centrifuged and washed three times alternately with deionized water and anhydrous ethanol. Then, it was dried at 60 °C for 12 hours to obtain bismuth oxychloride nanomaterials with high exposure of the (101) crystal plane, abbreviated as BOC. (101) .
[0051] <Preparation Example 2>
[0052] A method for preparing bismuth oxychloride nanomaterials includes the following steps:
[0053] 0.5 g of polyvinylpyrrolidone was added to 50 g of deionized water and stirred slowly. Then, 1 g of bismuth nitrate pentahydrate and 0.150 g of potassium chloride were added and stirred for 2.5 hours to obtain a mixed emulsion. The mixed emulsion was then subjected to hydrothermal reaction at 160 °C for 8 hours. After cooling to room temperature, the product was centrifuged and washed three times alternately with deionized water and anhydrous ethanol. Then, it was dried at 80 °C for 12 hours to obtain bismuth oxychloride nanomaterials with high exposure of the (101) crystal plane, abbreviated as BOC. (101) .
[0054] <Preparation Example 3>
[0055] A method for preparing bismuth oxychloride nanomaterials differs from Preparation Example 2 in that: bismuth oxychloride nanomaterials with high exposure of the (101) crystal plane are immersed in an 8 mmol / L NaBH4 aqueous solution and stirred for 20 minutes. After cooling to room temperature, the product is centrifuged and washed three times alternately with deionized water and anhydrous ethanol. Then, it is dried at 60°C for 12 hours to obtain oxygen-deficient bismuth oxychloride nanomaterials, abbreviated as BOC. (101) -OVs.
[0056] <Preparation Example 4>
[0057] A method for preparing bismuth oxychloride nanomaterials differs from Preparation Example 2 in that: bismuth oxychloride nanomaterials with high exposure of the (101) crystal plane are immersed in a NaBH4 aqueous solution with a concentration of 10 mmol / L and stirred for 30 minutes. After cooling to room temperature, the product is centrifuged and washed three times alternately with deionized water and anhydrous ethanol. Then, it is dried at 80°C for 12 hours to obtain oxygen-deficient bismuth oxychloride nanomaterials, abbreviated as BOC. (101) -OVs.
[0058] <Example 1>
[0059] A method for photocatalytic reduction of N2 to prepare NH3 includes the following steps:
[0060] A quartz glass reactor (150 mL) was used as the reactor, and a xenon lamp (MICROSOLAR 300, Beijing Pofilai Technology Co., Ltd.) was used as the simulated solar light source (AM 1.5G filter, 100 mW / cm²). 2 The reactor is placed vertically 10cm above the reactor, and circulating water is introduced to maintain a reaction temperature environment of 25℃.
[0061] 50 mg of the BOC prepared in Example 1 was dissolved in deionized water. (101) Wash four times to remove NH4 adsorbed on the material surface. +The N2 was then dispersed in a quartz glass reactor containing 100 mL of deionized water and sealed with a high-transparency quartz sheet. Under a stirring speed of 300 r / min, N2 was injected into the reactor at a continuous gas flow rate of 50 mL / min. The reactor was first kept in darkness for 60 min for dark chamber adsorption, and then the photocatalytic reaction lamp was turned on for 60 min.
[0062] <Example 2>
[0063] A method for photocatalytic reduction of N2 to prepare NH3 includes the following steps:
[0064] A quartz glass reactor (150 mL) was used as the reactor, and a xenon lamp (MICROSOLAR 300, Beijing Pofilai Technology Co., Ltd.) was used as the simulated solar light source (AM 1.5G filter, 100 mW / cm²). 2 The reactor is placed vertically 10cm above the reactor, and circulating water is introduced to maintain a reaction temperature environment of 25℃.
[0065] 50 mg of the BOC prepared in Example 2 was dissolved in deionized water. (101) Wash four times to remove NH4 adsorbed on the material surface. + The N2 was then dispersed in a quartz glass reactor containing 100 mL of deionized water and sealed with a high-transparency quartz sheet. Under a stirring speed of 300 r / min, N2 was injected into the reactor at a continuous gas flow rate of 60 mL / min. The reactor was first kept in darkness for 60 min for dark chamber adsorption, and then the photocatalytic reaction lamp was turned on for 60 min.
[0066] <Example 3>
[0067] A method for photocatalytic reduction of N2 to prepare NH3, which differs from Example 2 in that: the BOC obtained in Preparation Example 2 is used... (101) Replace with BOC obtained in Preparation Example 3 (101) -OVs, the rest are the same as in Example 2.
[0068] <Example 4>
[0069] A method for photocatalytic reduction of N2 to prepare NH3, which differs from Example 2 in that: the BOC obtained in Preparation Example 2 is used... (101) Replace with BOC obtained in Preparation Example 4 (101) -OVs, the rest are the same as in Example 2.
[0070] <Comparative Example 1>
[0071] The difference from Example 2 is that the bismuth oxychloride nanomaterials prepared in Example 2 were replaced with ordinary bismuth oxychloride nanomaterials. These ordinary bismuth oxychloride nanomaterials were prepared using the following method:
[0072] 1g of bismuth nitrate pentahydrate and 0.150g of potassium chloride were added to 50g of water and mixed and stirred for 2.5 hours to obtain a mixed emulsion. The mixed emulsion was then subjected to hydrothermal reaction at 160℃ for 8 hours. After cooling to room temperature, the product was centrifuged and washed three times alternately with deionized water and anhydrous ethanol. Then it was dried at 80℃ for 12 hours to obtain sheet-like ordinary bismuth oxychloride nanomaterials with a side length of 1μm-5μm and a thickness of 100nm-120nm, abbreviated as BOC.
[0073] Performance Testing
[0074] 1. Morphology, phase, and crystal phase analyses were performed on the bismuth oxychloride nanomaterials prepared in Examples 1-4 and the ordinary bismuth oxychloride nanomaterials prepared in Comparative Example 1, respectively. The results are as follows: Figure 1 As shown in Figure -3.
[0075] from Figure 1 It can be seen that the materials prepared in Examples 1-4 of this application are black powders. Referring to Figure 2(a), it can be seen that the materials prepared in Examples 1-4 of this application have a sheet-like structure with an average diameter of 50 nm-200 nm and a thickness of 15 nm-30 nm. As can be seen from Figure 2(b), the material prepared in Comparative Example 1 is sheet-like with a side length of 1 μm-5 μm and a thickness of 100 nm-120 nm.
[0076] As can be seen from Figure 3(a), the series of materials prepared in Examples 1-4 of this application belong to bismuth oxychloride materials (pdf card number: 85-0861), and the crystal planes (001), (002), (101), (110), (012), (003), (112), and (200) of the material are respectively located at 12°, 23.5°, 26°, 32.8°, 33.7°, 36.5°, 41.6°, and 46.8°.
[0077] As can be seen from Figure 3(b), the bismuth oxychloride nanomaterials prepared in Examples 1-4 of this application have a simple tetragonal crystal form, with preferred orientation growth on the (101) crystal plane, belonging to the P4 / nmm space group, with a group number of 129, and unit parameters of a×b×c=3.89×3.89×7.37, α×β×γ=90°×90°×90°.
[0078] 2. The bismuth oxychloride nanomaterials (BOC) prepared in Example 2 were tested separately. (101) ), Preparation Example 4: Oxygen-deficient bismuth oxychloride nanomaterials (BOC) (101)Electron paramagnetic resonance (EPR) analysis was performed on the bismuth oxychloride nanomaterials (BOC) prepared in Comparative Example 1 and the oxygen hole concentration was precisely quantified using positron annihilation spectroscopy. Static water contact angle tests were then conducted on the three materials, and the results are shown in Table 1. Figure 4-6 As shown.
[0079] Table 1 Positron lifetime of different materials
[0080]
[0081] from Figure 4 As can be seen, the oxygen-deficient bismuth oxychloride nanomaterial prepared in Example 4 exhibits a clear oxygen hole signal with a g value of 2.003.
[0082] from Figure 5 As can be seen from Table 1, the first positron lifetime in the BOC prepared in Comparative Example 1 is 0.209 ns, while the BOC prepared in Preparation Example 4... (101) The first positron lifetime of -OVs is 0.18 ns, which is considered to be lattice voids in the material; the second positron lifetime of BOC prepared in Comparative Example 1 is 0.441 ns, and the BOC prepared in Preparation Example 4... (101) The second positron lifetime of -OVs is 0.348 ns, which is considered to be oxygen holes. At this time, the oxygen hole concentration of BOC is 40.6%. (101) The oxygen-hole concentration of -OVs was 66.0%; the third positron lifetime in the BOC prepared in Comparative Example 1 was 2.013 ns, and the BOC prepared in Preparation Example 4... (101) The third positron lifetime of -OVs is 2.008 ns. This third lifetime is the longest and is generally considered an unavoidable defect in experiments and sample preparation. Experimental data show that, by creating defects, Preparation Example 4 increased the oxygen hole concentration from the original 40.6% to 66.0%.
[0083] from Figure 6 It can be seen that the BOC prepared in Example 2 (101) The static water contact angle was 37.1°. The BOC prepared in Example 4... (101) The static water contact angle of -OVs was 36.4°, while that of BOC prepared in Comparative Example 1 was 40.6°. Experimental data indicate that the presence of oxygen vacancies is beneficial for increasing the hydrophilicity of the material; the higher the oxygen vacancy concentration, the better the hydrophilicity, thereby promoting H+ ionization. + The material dissociates from H2O molecules and bonds with N2 during the reduction process, thereby improving the catalytic effect of the material.
[0084] 3. Take 5 mL of suspension samples from Examples 1-4 and Comparative Example 1 respectively for NH4 testing. +After testing, N2 in Examples 1-4 and Comparative Example 1 was replaced with Ar, while other conditions and procedures remained unchanged, and parallel experiments were conducted. NH4 + The yield was determined using the Nessler reagent colorimetric method. Equal volumes of Nessler reagent were added to all test solutions, and the mixture was reacted at room temperature for 12 minutes, followed by UV-Vis analysis. The absorbance of each solution was measured at 420 nm using a UV-Vis spectrophotometer (UV-2600i, Shimadzu, Japan), and then analyzed by NH4+. + The standard curve for detecting NH4 in the actual test solution is obtained. + Concentration. Results as follows Figure 7 As shown.
[0085] from Figure 7 It can be seen that the NH4 content of all samples under an Ar atmosphere is... + The concentration did not increase significantly. Under an N2 atmosphere, the NH4 concentration in the sample of Comparative Example 1 was... + The concentration of NH4 in the samples of Examples 1-2 was 0.41 mg / L. + The average concentration was 2.01 mg / L. The NH4+ concentration in the samples of Examples 3-4 was... + The average concentration was 5.42 mg / L. Experimental data show that the BOC prepared in this application... (101) The catalytic reduction of N2 to NH3 is significantly better than that of BOC, and further improvements are made in BOC. (101) BOC obtained by creating oxygen vacancies (101) -OVs are more effective at catalyzing the reduction of N2 to NH3.
[0086] 4. Take 5 mL of suspension samples from Examples 2 and 4 respectively for NH4 testing. + The test was performed, and then the conditional procedures of Examples 2 and 4 were repeated 9 times each. The results are as follows. Figure 8-9 As shown.
[0087] from Figure 8 It can be seen that during the first sampling, the NH4 content in the sample was... + The concentration was 2.35 mg / L; during the second sampling, the NH4+ concentration in the sample was... + The concentration was 2.23 mg / L; during the third sampling, the NH4+ concentration in the sample was... + The concentration was 2.42 mg / L; during the fourth sampling, the NH4+ concentration in the sample was... + The concentration was 2.16 mg / L; during the fifth sampling, the NH4+ concentration in the sample was... + The concentration was 2.21 mg / L; during the sixth sampling, the NH4+ concentration in the sample was... + The concentration was 2.48 mg / L; during the seventh sampling, the NH4+ concentration in the sample was... +The concentration was 2.50 mg / L; during the eighth sampling, the NH4 content in the sample was... + The concentration was 2.34 mg / L; during the ninth sampling, the NH4+ concentration in the sample was... + The concentration was 2.20 mg / L. The experimental data showed that the BOC used in Example 2... (101) It maintains excellent catalytic ability and strong stability throughout multiple cycles of use, with fluctuations not exceeding 8% after 9 cycles.
[0088] from Figure 9 It can be seen that during the first sampling, the NH4 content in the sample was... + The concentration was 5.21 mg / L; during the second sampling, the NH4+ concentration in the sample was... + The concentration was 5.27 mg / L; during the third sampling, the NH4+ concentration in the sample was... + The concentration was 5.34 mg / L; during the fourth sampling, the NH4 content in the sample was... + The concentration was 5.03 mg / L; during the fifth sampling, the NH4+ concentration in the sample was... + The concentration was 4.95 mg / L; during the sixth sampling, the NH4+ concentration in the sample was... + The concentration was 5.23 mg / L; during the seventh sampling, the NH4+ concentration in the sample was... + The concentration was 5.37 mg / L; during the eighth sampling, the NH4 content in the sample was... + The concentration was 5.05 mg / L; during the ninth sampling, the NH4 content in the sample was... + The concentration was 5.38 mg / L. The experimental data showed that the BOC used in Example 4... (101) -OVs maintain excellent catalytic ability and strong stability even during multiple cycles of use.
[0089] 5. To verify the effectiveness of the three types of bismuth oxychloride nanomaterials in catalyzing the reduction of N2 to NH3 under outdoor sunlight, the following additional experiment was conducted. 50 mg of each of the three types of bismuth oxychloride nanomaterials prepared in Example 2 was taken. (101) Preparation Example 4 yielded BOC (101) -OVs and BOC obtained in Comparative Example 1 were dispersed in three quartz reactors containing 100 mL of deionized water, respectively. The reactors were placed outdoors under sunlight, and the reaction system was stirred at a speed of 300 r / min. After 3 hours of illumination, 5 mL of suspension samples were taken from each reactor for NH4+ ionization. + Concentration was measured, and a parallel light irradiation experiment was conducted with deionized water (without any added materials) as a control group. The results are as follows: Figure 10 As shown.
[0090] from Figure 10 It can be seen that the NH4 in the control group sample + The concentration did not change significantly, and BOC was used.(101) NH4 in samples catalyzed by -OVs + The concentration increases the fastest, and NH4 + The highest concentration of NH4 was observed in the sample catalyzed by BOC. + The concentration increases at the slowest rate, and NH4 + The concentration was the lowest. Experimental data showed that, under outdoor sunlight, the BOC prepared in this application had the lowest concentration. (101) The catalytic reduction of N2 to NH3 is significantly better than that of BOC, and further improvements are made in BOC. (101) BOC obtained by creating oxygen vacancies (101) -OVs are more effective at catalyzing the reduction of N2 to NH3.
[0091] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.
Claims
1. The application of a bismuth halide nanomaterial in the photocatalytic reduction of N2 to prepare NH3, characterized in that, The preparation method of the bismuth halide nanomaterial includes the following steps: Bismuth nitrate pentahydrate, halide, surfactant and water were mixed and stirred for 2.0-2.5 hours to obtain a mixed emulsion. The mixed emulsion was then subjected to hydrothermal reaction at 130-160℃ for 8 hours. After solid-liquid separation, the precipitate was washed and dried to obtain bismuth oxide halide nanomaterials with preferred orientation of (101) crystal plane. The bismuth halide nanomaterials grown with preferred orientation of (101) crystal planes were immersed in NaBH4 aqueous solution and stirred for 20-30 minutes. After solid-liquid separation, the precipitate was washed and dried to obtain oxygen-deficient bismuth halide nanomaterials. The weight ratio of the bismuth nitrate pentahydrate, halide, surfactant, and water is 1:(0.125-0.150):0.5:50; The surfactant is polyvinylpyrrolidone; The concentration of the NaBH4 aqueous solution is 8 mmol / L-10 mmol / L; The bismuth halide nanomaterial has a sheet-like structure with an average diameter of 50nm-200nm and a thickness of 15nm-30nm. The bismuth halide nanomaterial has a quadrilateral phase crystal structure, with preferred orientation growth on the (101) crystal plane. It belongs to the P4 / nmm space group with a group number of 129 and unit parameters of a×b×c=3.89×3.89×7.37, α×β×γ=90°×90°×90°. The bismuth halide nanomaterial is an oxygen-deficient bismuth halide nanomaterial with an oxygen hole concentration of 66.0% and a water contact angle of 36.4°.
2. The application of the bismuth halide nanomaterial according to claim 1 in the photocatalytic reduction of N2 to prepare NH3, characterized in that, The amount of the bismuth halide nanomaterial used is 0.5 g / L-0.8 g / L.