AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst as well as preparation method and application thereof
By constructing a ternary heterojunction photocatalyst of AgI/Bi5O7I/Bi7O9I3, the problems of high photogenerated electron-hole recombination rate and narrow light absorption range of BiOI photocatalytic materials were solved, achieving efficient degradation of tetracycline and rhodamine B and improving photocatalytic performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-04
- Publication Date
- 2026-04-14
Smart Images
Figure CN121847175A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalytic materials technology, and specifically discloses an AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst and its preparation method, as well as the application of the catalyst in the photocatalytic degradation of organic molecules including tetracycline and rhodamine B. Background Technology
[0002] With the rapid development of industrialization and urbanization in modern society, water pollution has become an environmental problem that cannot be ignored. Tetracycline is a broad-spectrum antibacterial agent that has been used clinically for anti-infective treatment for a long time. However, its molecular structure is relatively stable, and after administration, more than 70% of the active ingredient is excreted into the water environment through urine or feces. Its high hydrophilicity and low volatility make it difficult to degrade in the natural environment, and it may continue to remain in drinking water, thus posing certain harms to the human body. At the same time, antibiotics remaining in the water environment can further induce the emergence of antibiotic-resistant microorganisms, thereby inducing human diseases and threatening human health. Wastewater treatment processes have a long history and mainly include physical, biological, and chemical technologies. Among them, chemical technologies mainly convert pollutants in wastewater into small molecules such as H2O or CO2, or into non-toxic and easily degradable intermediate products, through oxidation-reduction processes. These include chlorination and advanced oxidation processes, with advanced oxidation processes including ozonation, electrochemical oxidation, and photocatalytic oxidation. Among these, photocatalysis is a highly promising advanced oxidation technology that directly utilizes light energy to degrade organic pollutants, and it has advantages such as high efficiency, environmental friendliness, and greenness. Catalysts, under photoexcitation, generate photogenerated electron-hole pairs, which then react with oxygen or water molecules in the surrounding environment to produce... O2 - , 1 O2, It contains highly reactive oxygen species such as OH, which are strong oxidizing agents, and thus efficiently degrades pollutants into smaller molecules with lower toxicity.
[0003] Bismuth oxyiodide (BiOI), a typical bismuth-based semiconductor photocatalyst, possesses a suitable bandgap (~1.8 eV) and a unique layered crystal structure, exhibiting excellent photoresponse performance in the visible light region and is widely used for the degradation of organic pollutants. However, single BiOI suffers from high photogenerated electron-hole recombination rates and poor cycling stability, limiting its actual photocatalytic degradation efficiency. Its photocatalytic performance can be significantly improved through heterostructure construction and loading modification. Heterostructure construction is a common method for modifying photocatalytic materials. Silver iodide (AgI), as a narrow bandgap semiconductor, can be combined with BiOI to suppress photogenerated carrier recombination through interfacial charge transfer effects, thereby enhancing photocatalytic activity. For example, Lv et al. used methyl orange (MO), rhodamine B (RhB), and methylene blue (MB) as target dyes, and found that the photocatalytic performance of AgI / BiOI composites was significantly improved under visible light irradiation.J. Environ. Chem. Eng. 2013, 1(3), 526-533); Cui et al. prepared an AgI / Bi5O7I composite photocatalyst by regulating iodine defects, which significantly improved the adsorption and degradation capacity of Rhodamine B ( Appl. Surf. Sci .2016, 387, 912-920).
[0004] Compared to typical binary heterojunctions, ternary heterojunctions, while forming more complex band structures, also provide additional charge transfer channels, exhibiting higher charge separation efficiency. This significantly broadens the light absorption range and enhances photocatalytic performance. For example, Li et al. successfully prepared ZnO-BiOI-AgI composite materials using a sedimentation-precipitation method. The formation of this ternary heterojunction structure extended the visible light absorption range to 550 nm and reduced the recombination rate of photogenerated electron-hole pairs. However, the recombination of the three different components made the preparation process more complex. Mater. Adv. 2025, 6, 7332). Currently, there are few reports on the ternary heterojunction structure formed by BiOI and AgI composites, and the mechanism research is not in-depth. Therefore, constructing a ternary heterojunction photocatalytic material to increase the photogenerated electron-hole separation rate, broaden the light absorption range, and solve the problem of insufficient photocatalytic performance of single materials is expected to achieve efficient and rapid degradation of tetracycline antibiotics, which will have important technical significance. In addition, iodine-deficient BiOI photocatalysts were prepared by high-temperature one-step calcination. The iodine vacancies in them act as hole traps, which can effectively delay the recombination of photogenerated electron-hole pairs. Yu et al. designed a BiOI@Bi5O7I composite material to achieve efficient photocatalytic conversion of CO2 to CO. Its catalytic performance is about 6.6 times and 15.3 times higher than that of BiOI and Bi5O7I materials alone, respectively. Chem. Eng. J. (2024, 481, 148350). Therefore, combining iodine-deficient BiOI with ternary heterostructures may be an effective approach to improve photocatalytic performance. Summary of the Invention
[0005] One objective of this invention is to address the problems of complex preparation processes and poor photocatalytic performance in existing photocatalytic materials, and to provide a simple and efficient method for preparing an AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst. This method uses hydrothermally synthesized BiOI as a precursor, which is calcined to obtain a Bi5O7I / Bi7O9I3 binary heterojunction. AgI is then loaded using photodeposition to construct the ternary heterostructure. This material overcomes the problems of narrow light absorption range and high carrier recombination rate of traditional BiOI, significantly broadening the light response range and improving charge separation efficiency. It exhibits high catalytic activity and good stability in the degradation of organic compounds such as tetracycline and rhodamine B in pharmaceutical wastewater, showing promising application prospects.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing an AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst, comprising the following steps: dispersing Bi5O7I / Bi7O9I3 binary heterojunction composite powder in water and stirring evenly to obtain a Bi5O7I / Bi7O9I3 dispersion; dispersing AgNO3 in water and stirring evenly to obtain an AgNO3 solution; slowly adding the AgNO3 solution to the Bi5O7I / Bi7O9I3 dispersion and stirring continuously; after a dark reaction, turning on a xenon lamp for a photo-reaction; washing and drying the product to obtain a heterojunction powder composed of Bi7O9I3, Bi5O7I, and AgI, which is the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst.
[0007] Further improvements to the preparation method of AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalysts: Preferably, the mass ratio of Bi5O7I / Bi7O9I3 binary heterojunction composite powder to AgNO3 is (5.6~19):1, wherein the concentration of AgNO3 solution is 0.1~0.12 mol / L.
[0008] Preferably, the dark reaction time is 0.5–1 h, and the light reaction time is 0.5–1 h; the product of the light reaction is washed multiple times with ultrapure water and anhydrous ethanol, and then dried at 60–70 °C for 10–12 h.
[0009] Preferably, the preparation method of the Bi5O7I / Bi7O9I3 binary heterojunction composite powder is as follows: S1. Preparation of BiOI powder: Bi(NO3)3·5H2O was dissolved in ethylene glycol to obtain solution A; KI was dissolved in water to obtain solution B; wherein the molar ratio of Bi(NO3)3·5H2O in solution A to KI in solution B was 1:(0.9~1); solution B was slowly added to solution A, stirred evenly, and then transferred to a high-pressure reactor. The mixture was subjected to hydrothermal reaction at 150~160 ℃ for 10~12 h. After cooling, the mixture was washed and dried to obtain BiOI powder. Preparation of S2 and Bi5O7I / Bi7O9I3: BiOI powder was placed in a muffle furnace and calcined in air at 400-500 °C for 2.9-3 h to obtain Bi5O7I / Bi7O9I3 binary heterojunction composite powder.
[0010] Preferably, in solution A, the concentration of Bi(NO3)3·5H2O is 0.098–0.123 mol / L; and in solution B, the concentration of KI is 0.08–0.100 mol / L.
[0011] Preferably, solution B is slowly added to solution A and then stirred for 0.5–1 h; the product of the hydrothermal reaction is washed multiple times with ultrapure water and anhydrous ethanol, and then dried at 60–70 °C for 10–12 h.
[0012] The second objective of this invention is to provide an AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst prepared by any one of the above-mentioned methods.
[0013] The third objective of this invention is to provide an application of the above-mentioned AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst in the catalytic degradation of organic molecules, comprising the following steps: adding the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst to a solution containing tetracycline or rhodamine B, stirring thoroughly, and after a dark reaction, turning on a xenon lamp for a photo-irradiation reaction.
[0014] Further improvements to the application of the aforementioned AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst in the catalytic degradation of organic molecules: Preferably, in the solution containing tetracycline or rhodamine B, the concentration of tetracycline or rhodamine B is 20–40 mg / L, and the dosage of AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst is 0.1–0.15 g / L.
[0015] Preferably, the dark reaction time is 0.5 to 1 hour, and the light reaction time is 1 to 2 hours.
[0016] The advantages of this invention compared to the prior art are as follows: 1. This invention provides a method for preparing an AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalytic material. This method uses Bi(NO3)3·5H2O and KI as raw materials to prepare BiOI via a hydrothermal method. The raw materials are inexpensive and readily available, and the preparation method is simple and easy to operate. Then, an iodine-deficient phase Bi5O7I / Bi7O9I3 binary heterojunction is formed in situ in one step via calcination. The preparation process for this defect site is relatively simplified and helps improve the separation efficiency of photogenerated carriers. Furthermore, AgNO3 is mixed with the Bi5O7I / Bi7O9I3 binary heterojunction composite powder, and under room temperature and atmospheric pressure conditions, a redox reaction occurs under photoexcitation, resulting in the recombination of Ag-I chemical bonds, thereby promoting the in-situ generation of AgI on the surface. The preparation conditions used in this photodeposition method are mild, requiring no heating or pressurization, and the three phases of Bi5O7I, Bi7O9I3, and AgI can be stably combined into a whole.
[0017] 2. To address the problems of easy recombination of photogenerated electrons and holes, narrow light absorption range, and poor photocatalytic degradation performance in single-component photocatalytic materials, this invention proposes a method for degrading tetracycline and rhodamine B in water using an AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalytic material. Based on XPS, UV-vis, and PL characterization results, compared to pure AgI and BiOI, the in-situ prepared AgI / Bi5O7I / Bi7O9I3 ternary heterojunction composite material broadens the light absorption range and enhances the absorption intensity in the visible light region. Simultaneously, interfacial charge transfer exists between AgI and the defective phases of Bi5O7I and Bi7O9I3, with electrons transferring from the defective bismuth oxyiodide phase to the AgI phase. This improves the separation efficiency of photogenerated electron-hole pairs, providing more active charge carriers for the photocatalytic reaction, and also provides a more potent redox pair.
[0018] 3. The AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalytic material prepared in this invention exhibits excellent photocatalytic performance, improving the degradation efficiency of organic pollutants such as tetracycline and rhodamine B. The removal rate of rhodamine B is 82%, which is 75% higher than that of the original BiOI. The removal rate of tetracycline is 71%, which is 60% higher than that of the original BiOI. First-order reaction kinetic fitting results confirm that the kinetic constants for the degradation of tetracycline and rhodamine B are increased by 13 times and 26 times, respectively. Active species capture experiments confirm that during the photocatalytic degradation process, ·O2… - and h + It is the main biodegrading species. Attached Figure Description
[0019] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.
[0020] Figure 1 This is a degradation diagram of tetracycline removal by the AgI / Bi5O7I / Bi7O9I3 photocatalyst prepared in Examples 1, 2 and 3 of this invention.
[0021] Figure 2 The diagrams show the degradation of tetracycline by Bi7O9I3 powder (catalyst product) prepared in Comparative Example 3, Bi5O7I / Bi7O9I3 binary heterojunction composite powder (catalyst product) prepared in Comparative Example 4, and Bi5O7I powder (Bi5O7I powder) prepared in Comparative Example 5.
[0022] Figure 3The diagram shows the degradation of tetracycline by the photocatalysts AgI prepared in Comparative Example 1, BiOI prepared in Comparative Example 2, Bi7O9I3 prepared in Comparative Example 3, Bi5O7I / Bi7O9I3 prepared in Comparative Example 4, Bi5O7I prepared in Comparative Example 5, and 10% AgI / Bi5O7I / Bi7O9I3 prepared in Example 2.
[0023] Figure 4 The reaction rate constant k values are for the removal of tetracycline degradation by the photocatalysts AgI prepared in Comparative Example 1, BiOI prepared in Comparative Example 2, Bi7O9I3 prepared in Comparative Example 3, Bi5O7I / Bi7O9I3 prepared in Comparative Example 4, Bi5O7I prepared in Comparative Example 5, and 10% AgI / Bi5O7I / Bi7O9I3 prepared in Example 2.
[0024] Figure 5 The diagram shows the degradation of Rhodamine B by the photocatalysts AgI prepared in Comparative Example 1, BiOI prepared in Comparative Example 2, Bi7O9I3 prepared in Comparative Example 3, Bi5O7I / Bi7O9I3 prepared in Comparative Example 4, Bi5O7I prepared in Comparative Example 5, and 10% AgI / Bi5O7I / Bi7O9I3 prepared in Example 2.
[0025] Figure 6 The reaction rate constant k values are for the removal of Rhodamine B degradation by the photocatalysts AgI prepared in Comparative Example 1, BiOI prepared in Comparative Example 2, Bi7O9I3 prepared in Comparative Example 3, Bi5O7I / Bi7O9I3 prepared in Comparative Example 4, Bi5O7I prepared in Comparative Example 5, and 10% AgI / Bi5O7I / Bi7O9I3 prepared in Example 2.
[0026] Figure 7 The XRD patterns are of BiOI prepared in Comparative Example 2, Bi7O9I3 prepared in Comparative Example 3, Bi5O7I / Bi7O9I3 prepared in Comparative Example 4, and Bi5O7I prepared in Comparative Example 5.
[0027] Figure 8 The images show the XRD patterns of 10% AgI / Bi5O7I / Bi7O9I3 prepared in Example 2, AgI prepared in Comparative Example 1, and Bi5O7I / Bi7O9I3 prepared in Comparative Example 4.
[0028] Figure 9 The UV-Vis diffuse reflectance spectra of the 10% AgI / Bi5O7I / Bi7O9I3 composite material prepared in Example 2, the AgI prepared in Comparative Example 1, and the Bi5O7I / Bi7O9I3 prepared in Comparative Example 4.
[0029] Figure 10The image shows the PL plots of the 10% AgI / Bi5O7I / Bi7O9I3 composite material prepared in Example 2, the AgI prepared in Comparative Example 1, and the Bi5O7I / Bi7O9I3 prepared in Comparative Example 4.
[0030] Figure 11 These are the band gap diagrams of AgI prepared in Comparative Example 1, Bi7O9I3 prepared in Comparative Example 3, and Bi5O7I prepared in Comparative Example 5.
[0031] Figure 12 These are VB-XPS images of AgI prepared in Comparative Example 1, Bi7O9I3 prepared in Comparative Example 3, and Bi5O7I prepared in Comparative Example 5.
[0032] Figure 13 XPS images of the 10% AgI / Bi5O7I / Bi7O9I3 composite material prepared in Example 2, and AgI prepared in Comparative Example 1, BiOI prepared in Comparative Example 2, and Bi5O7I / Bi7O9I3 prepared in Comparative Example 4.
[0033] Figure 14 This is an experimental diagram of the tetracycline degradation active species capture of the 10% AgI / Bi5O7I / Bi7O9I3 composite material prepared in Example 2.
[0034] Figure 15 This is a mechanism diagram of the AgI / Bi5O7I / Bi7O9I3 prepared according to the present invention. Detailed Implementation
[0035] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.
[0036] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.
[0037] 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.
[0038] Example 1
[0039] This embodiment provides a method for preparing an AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst, comprising the following steps: S1. Dissolve 1.940 g of Bi(NO3)3·5H2O in 40 mL of ethylene glycol to obtain solution A; dissolve 0.664 g of KI in 40 mL of water to obtain solution B; wherein the molar ratio of Bi(NO3)3·5H2O in solution A to KI in solution B is 1:1; slowly add solution B to solution A, stir evenly, transfer to a high-pressure reactor, and hydrothermally react at 160 ℃ for 12 h. After cooling, wash repeatedly with ultrapure water and anhydrous ethanol, and then dry in an oven at 60 ℃ for 12 hours to obtain BiOI powder.
[0040] S2. Place BiOI powder in a muffle furnace and calcine it in air at 410 °C for 3 hours to obtain Bi5O7I / Bi7O9I3 binary heterojunction composite powder.
[0041] S3. Disperse 0.1 g of Bi5O7I / Bi7O9I3 binary heterojunction composite powder in 30 mL of water and stir until homogeneous to obtain Bi5O7I / Bi7O9I3 dispersion; take 0.310 mL of 0.1 mol / L AgNO3 solution and disperse it in Bi5O7I / Bi7O9I3 dispersion; the mass ratio of Bi5O7I / Bi7O9I3 to AgNO3 is 18.9:1; S4. Slowly add AgNO3 solution to Bi5O7I / Bi7O9I3 dispersion, stir and react in the dark for 1 hour, then turn on the xenon lamp for 1 hour of light reaction. Wash the product multiple times with ultrapure water and anhydrous ethanol, and then dry it in an oven at 60 ℃ for 12 hours to obtain a heterojunction photocatalyst composed of three phases of Bi7O9I3, Bi5O7I and AgI, denoted as 5%AgI / Bi5O7I / Bi7O9I3.
[0042] Example 2
[0043] This embodiment provides a method for preparing an AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst. The specific steps are the same as in Example 1, except that the mass ratio of Bi5O7I / Bi7O9I3 to AgNO3 is 9:1. The resulting ternary heterojunction photocatalyst is designated as 10%AgI / Bi5O7I / Bi7O9I3.
[0044] Example 3
[0045] This embodiment provides a method for preparing an AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst. The specific steps are the same as in Example 1, except that the mass ratio of Bi5O7I / Bi7O9I3 to AgNO3 is 5.6:1. The resulting ternary heterojunction photocatalyst is designated as 15%AgI / Bi5O7I / Bi7O9I3.
[0046] Comparative Example 1
[0047] This comparative example provides a method for preparing AgI, which specifically includes the following steps: 0.664 g of KI was dissolved in 30 mL of water to obtain a KI solution; 0.679 g of AgNO3 was dissolved in 30 mL of water to obtain an AgNO3 solution. The AgNO3 solution was slowly added to the KI solution and stirred evenly for 1 hour. The product was then dried at 60 °C for 12 hours to obtain AgI.
[0048] Comparative Example 2
[0049] This comparative example provides a method for preparing BiOI powder, and the specific steps are as described in step S1 of Example 1.
[0050] Comparative Example 3
[0051] This comparative example provides a method for preparing Bi7O9I3, which specifically includes the following steps: First, BiOI powder was prepared by referring to step S1 of Example 1.
[0052] The BiOI powder was then placed in a muffle furnace and calcined in air at 400 °C for 3 hours to obtain Bi7O9I3 powder.
[0053] Comparative Example 4
[0054] This comparative example provides a method for preparing Bi5O7I / Bi7O9I3, which specifically includes the following steps: First, BiOI powder was prepared by referring to step S1 of Example 1.
[0055] The BiOI powder was then placed in a muffle furnace and calcined in air at 410 °C for 3 hours to obtain Bi5O7I / Bi7O9I3 powder.
[0056] Comparative Example 5
[0057] This comparative example provides a method for preparing Bi5O7I, which specifically includes the following steps: First, BiOI powder was prepared by referring to step S1 of Example 1.
[0058] The BiOI powder was then placed in a muffle furnace and calcined in air at 500 °C for 3 hours to obtain Bi5O7I powder.
[0059] Example 4
[0060] The application of photocatalysts in the photocatalytic degradation of the organic compound tetracycline includes the following steps: Weigh 15 mg of the 5% AgI / Bi5O7I / Bi7O9I3 powder prepared in Example 1 and add it to 100 mL of a solution containing 40 mg / L tetracycline. Stir thoroughly for 1 h in the dark to ensure uniform dispersion of the catalyst in the TC solution. To ensure the catalyst and TC adsorption-desorption equilibrium, take 4 mL samples every 15 minutes and centrifuge to collect the supernatant. Then, turn on the xenon lamp (300 W, current maintained at 15 A) for 1 h of photocatalytic reaction. Take 4 mL samples every 10 minutes, centrifuge for 10 minutes, and measure the absorbance of the supernatant using a UV-Vis spectrophotometer. Convert the absorbance to tetracycline concentration according to the standard curve. The photocatalytic degradation efficiency is calculated using the following formula: Y = 1 - C t / C0, where Y is the tetracycline degradation rate, C t C0 represents the tetracycline concentration at the sampling time point, and C0 represents the initial tetracycline concentration.
[0061] Accordingly, 15 mg each of the 10% AgI / Bi5O7I / Bi7O9I3 powder prepared in Example 2 and the 15% AgI / Bi5O7I / Bi7O9I3 powder prepared in Example 3 were weighed out and subjected to the degradation test as described above. The test results are as follows. Figure 1 As shown. From Figure 1 It can be found that after 60 minutes of light exposure, the tetracycline degradation rates of the 5%AgI / Bi5O7I / Bi7O9I3, 10%AgI / Bi5O7I / Bi7O9I3, and 15%AgI / Bi5O7I / Bi7O9I3 samples reached 67%, 71%, and 63%, respectively. This confirms that the 10%AgI / Bi5O7I / Bi7O9I3 sample has the best degradation effect, and the optimal mass ratio of Bi5O7I / Bi7O9I3 to AgNO3 is 9:1.
[0062] Accordingly, 15 mg each of the catalytic product Bi7O9I3 powder prepared in Comparative Example 3, the catalytic product Bi5O7I / Bi7O9I3 powder prepared in Comparative Example 4, and the Bi5O7I powder prepared in Comparative Example 5 were weighed out and subjected to the degradation tests described above. The test results are as follows: Figure 2 As shown. From Figure 2 It can be observed that after 60 minutes of light exposure, the degradation rates of tetracycline reached 56%, 61%, and 28%, respectively, with Bi5O7I / Bi7O9I3 showing the best degradation effect.
[0063] Accordingly, 15 mg each of the AgI prepared in Comparative Example 1, the BiOI prepared in Comparative Example 2, the Bi7O9I3 prepared in Comparative Example 3, the Bi5O7I / Bi7O9I3 prepared in Comparative Example 4, the Bi5O7I prepared in Comparative Example 5, and the 10% AgI / Bi5O7I / Bi7O9I3 catalyst prepared in Example 2 were weighed out and subjected to the degradation tests described above. The test results are as follows: Figure 3 As shown, Figure 4 The value of the reaction rate constant k is obtained by fitting first-order reaction kinetics. From... Figure 3 It can be observed that after 60 minutes of light exposure, the tetracycline degradation rates of BiOI, AgI, Bi7O9I3, Bi5O7I, Bi5O7I / Bi7O9I3, and 10% AgI / Bi5O7I / Bi7O9I3 reached 9%, 49%, 56%, 28%, 61%, and 71%, respectively. Figure 4 It can be found that the tetracycline degradation rate constant k for BiOI, AgI, Bi7O9I3, Bi5O7I, Bi5O7I / Bi7O9I3, and 10%AgI / Bi5O7I / Bi7O9I3 is 0.00149 min. -1 0.01108 min -1 0.01293 min -1 0.00549 min -1 0.01475 min -1 and 0.01965 min -1 The order of photocatalytic performance is as follows: 10%AgI / Bi5O7I / Bi7O9I3 > Bi5O7I / Bi7O9I3 > Bi7O9I3 > AgI > Bi5O7I > BiOI. Among them, the tetracycline degradation rate constant k of 10%AgI / Bi5O7I / Bi7O9I3 is 13 times that of BiOI, indicating that the ternary heterojunction structure of AgI / Bi5O7I / Bi7O9I3 can significantly improve its photocatalytic performance.
[0064] Example 5
[0065] The application of a photocatalyst in the photocatalytic degradation of the organic compound Rhodamine B includes the following steps: Weigh 15 mg of the 10% AgI / Bi5O7I / Bi7O9I3 powder prepared in Example 2 and add it to 100 mL of a Rhodamine B solution containing 40 mg / L. Stir thoroughly for 1 h in the dark to ensure the catalyst is uniformly dispersed in the TC solution. To ensure the catalyst and TC adsorption-desorption equilibrium, take 4 mL samples every 15 minutes and centrifuge to collect the supernatant. Then turn on the xenon lamp (300 W, current maintained at 15 A) for photocatalytic reaction for 1 h. Take 4 mL samples every 10 minutes, centrifuge for 10 minutes, and take the supernatant. Measure the absorbance using a UV-Vis spectrophotometer and convert it to Rhodamine B concentration according to the standard curve. The photocatalytic degradation efficiency is calculated using the following formula: Y = 1 - C t / C0, where Y is the degradation rate of Rhodamine B, C t C0 represents the concentration of Rhodamine B at the sampling time point, and C0 represents the initial concentration of Rhodamine B.
[0066] Accordingly, 15 mg each of the AgI prepared in Comparative Example 1, the BiOI prepared in Comparative Example 2, the Bi7O9I3 prepared in Comparative Example 3, the Bi5O7I / Bi7O9I3 prepared in Comparative Example 4, the Bi5O7I prepared in Comparative Example 5, and the 10% AgI / Bi5O7I / Bi7O9I3 catalyst prepared in Example 2 were weighed out and subjected to the degradation tests described above in sequence. The test results are as follows: Figure 5 As shown, Figure 6 The value of the reaction rate constant k is obtained by fitting first-order reaction kinetics. From... Figure 5 It can be observed that after 60 minutes of light exposure, the degradation rates of Rhodamine B for BiOI, AgI, Bi7O9I3, Bi5O7I, Bi5O7I / Bi7O9I3, and 10% AgI / Bi5O7I / Bi7O9I3 reached 7%, 60%, 44%, 37%, 55%, and 82%, respectively. Figure 6 It can be found that the reaction rate constant k is 0.00103 min. -1 0.0148 min -1 0.00896 min -1 0.0074 min -1 0.01244 min -1 and 0.027 min -1 The order of size is 10%AgI / Bi5O7I / Bi7O9I3 > AgI > Bi5O7I / Bi7O9I3 > Bi7O9I3 > Bi5O7I > BiOI. The degradation rate constant k of 10%AgI / Bi5O7I / Bi7O9I3 Rhodamine B is 26 times that of BiOI, further demonstrating that the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction structure prepared in this application can significantly improve its photocatalytic performance.
[0067] The catalysts prepared in the examples and comparative examples were subjected to XRD, UV-Vis diffuse reflectance, PL, XPS and capture experiments, respectively.
[0068] like Figure 7 As shown, from bottom to top, the XRD patterns of BiOI prepared in Comparative Example 2, Bi7O9I3 prepared in Comparative Example 3, Bi5O7I / Bi7O9I3 prepared in Comparative Example 4, and Bi5O7I prepared in Comparative Example 5 are as follows: The peaks in the spectra are sharp, and no peaks related to impurity species are present, confirming that the samples have high crystallinity and that no impurities were introduced during the preparation process. The peak positions of the newly prepared BiOI correspond to its standard card spectrum (BiOI, PDF#10-0445); when the calcination temperature is 400 ℃, the spectrum corresponds to the Bi7O9I3 species, consistent with the results reported in the literature. Environ. Sci. Pollut. Res. 2023, 30, 79015-79025; RCS Adv. (2018, 8, 5967-5975); After the calcination temperature reaches 410 ℃, the Bi5O7I species is clearly visible in the spectrum, corresponding to its standard card spectrum (Bi5O7I, PDF#40-0548). At this point, Bi7O9I3 and Bi5O7I species coexist. Further increasing the calcination temperature to 500 ℃, only the species peak that can be attributed to Bi5O7I exists in the spectrum. It can be seen that at a calcination temperature of 410 ℃, a two-phase complex structure with coexistence of Bi7O9I3 and Bi5O7I is formed.
[0069] like Figure 8 The XRD patterns shown are of the 10% AgI / Bi5O7I / Bi7O9I3 prepared in Example 2, AgI prepared in Comparative Example 1, and Bi5O7I / Bi7O9I3 prepared in Comparative Example 4. The peaks in the patterns are sharp, and no peaks related to impurity species are observed, confirming high crystallinity of the samples and that no impurities were introduced during the preparation process. The peak positions of the AgI comparative example correspond to its standard card spectrum (PDF#09-0374). The peaks in the 10% AgI / Bi5O7I / Bi7O9I3 spectrum can be attributed to the coexistence of AgI, Bi5O7I, and Bi7O9I3, confirming the successful preparation of the AgI / Bi5O7I / Bi7O9I3 composite material of this application.
[0070] like Figure 9 The image shows the UV-Vis diffuse reflectance spectra of the 10% AgI / Bi5O7I / Bi7O9I3 composite material prepared in Example 2, the AgI prepared in Comparative Example 1, and the Bi5O7I / Bi7O9I3 prepared in Comparative Example 4. Compared with the single material, the AgI / Bi5O7I / Bi7O9I3 composite material prepared in this application broadens the light absorption range and enhances the absorption intensity in the visible light region. The higher light absorption intensity can excite more electron-hole pairs, providing more active charge carriers for the photocatalytic reaction.
[0071] like Figure 10 The figure shows the photoluminescence (PL) plots of the 10% AgI / Bi5O7I / Bi7O9I3 composite material prepared in Example 2, AgI prepared in Comparative Example 1, and Bi5O7I / Bi7O9I3 prepared in Comparative Example 4. Compared with the single material, the AgI / Bi5O7I / Bi7O9I3 composite material prepared in this application has a lower PL intensity. Since the faster the recombination rate of photogenerated electron-hole pairs, the stronger the corresponding PL intensity, it is confirmed that the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction can weaken the recombination of photogenerated electrons and holes, thereby helping to improve the photocatalytic degradation efficiency.
[0072] like Figure 11 , 12 The image shows the bandgap diagrams and VB-XPS of AgI prepared in Comparative Example 1, Bi7O9I3 prepared in Comparative Example 3, and Bi5O7I prepared in Comparative Example 5. Figure 11 For (αhν) using linear transformation 1 / 2 The curves were plotted against energy (hν), and the Eg values for AgI, Bi7O9I3, and Bi5O7I samples were determined to be 2.66, 2.28, and 2.83 eV, respectively. The VB-XPS values for AgI, Bi7O9I3, and Bi5O7I are shown below. Figure 12 As shown, the valence band positions (E) of AgI, Bi7O9I3, and Bi5O7I samples are... VB The values were 0.64 eV, 0.82 eV, and 1.31 eV, respectively, and the conduction band position (E) CB It can be obtained through formula E CB = E VB - E g The calculated E values of AgI, Bi7O9I3, and Bi5O7I are... CB The values can be calculated as -2.02 eV, -1.46 eV, and -1.52 eV, respectively. Thus, the band structure of the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction is obtained, as follows: Figure 15 As shown.
[0073] like Figure 13 The image shows XPS images of the 10% AgI / Bi5O7I / Bi7O9I3 composite material prepared in Example 2, and AgI prepared in Comparative Example 1, BiOI prepared in Comparative Example 2, and Bi5O7I / Bi7O9I3 prepared in Comparative Example 4. The image also shows the Bi4f peak (Bi4f) in AgI / Bi5O7I / Bi7O9I3. 7 / 2 159.3 eV, Bi 4f 5 / 2 The Ag 3d peak (Ag 3d) in 10% AgI / Bi5O7I / Bi7O9I3 shifts 0.9 eV to a higher binding energy (164.6 eV). 5 / 2 368.6 eV, Ag 3d 3 / 2 The binding energy of the I3d in 10% AgI / Bi5O7I / Bi7O9I3 shifts to a higher binding energy by 0.3 eV relative to pure AgI; and the I3d peak in 10% AgI / Bi5O7I / Bi7O9I3 also shows varying degrees of shift to a higher binding energy relative to the comparative example. The O1s peak splits into three peaks at 530.1 eV, 531.2 eV, and 532.5 eV, corresponding to the Bi-O bond, OH bond, and surface adsorbed oxygen, respectively.
[0074] like Figure 14The figure shows the active species capture results of the 10% AgI / Bi5O7I / Bi7O9I3 composite material prepared in Example 2. The addition of EDTA and BQ significantly reduced the photocatalytic performance of AgI / Bi5O7I / Bi7O9I3 in degrading tetracycline, indicating that during the photocatalytic process, ·O2 - and h + It is the main active species.
[0075] like Figure 15 The diagram shown illustrates the photocatalytic mechanism of the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction prepared according to this invention. Under simulated sunlight irradiation, photogenerated electrons migrate from the conduction bands of Bi5O7I and Bi7O9I3 to the conduction band of AgI. These migrating electrons are captured by molecular oxygen to form ·O2. - Free radicals, and O2 - Free radicals further oxidize the tetracycline adsorbed on the catalyst surface. Simultaneously, holes separated from the valence bands of Bi5O7I and Bi7O9I3 effectively oxidize the tetracycline adsorbed on the catalyst surface into smaller molecules, confirming that this ternary heterojunction facilitates the separation of photogenerated electron-hole pairs and improves photocatalytic degradation efficiency. J. Hazard. Mater. 2016, 317, 8-16; Appl. Catal. B-Environ 2019, 254, 647-658; Phys. Chem. Chem. Phys. 2016, 18(36), 24984-24993; Mater. Adv. 6(20), 7332-7354.).
[0076] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.
Claims
1. A method for preparing an AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst, characterized in that, The process includes the following steps: dispersing Bi5O7I / Bi7O9I3 binary heterojunction composite powder in water and stirring until homogeneous to obtain a Bi5O7I / Bi7O9I3 dispersion; dispersing AgNO3 in water and stirring until homogeneous to obtain an AgNO3 solution; slowly adding the AgNO3 solution to the Bi5O7I / Bi7O9I3 dispersion while continuously stirring, and after a dark reaction, turning on a xenon lamp for a photocatalytic reaction; washing and drying the product to obtain a heterojunction powder composed of Bi7O9I3, Bi5O7I, and AgI, which is the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst.
2. The preparation method of the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst according to claim 1, characterized in that, The mass ratio of Bi5O7I / Bi7O9I3 binary heterojunction composite powder to AgNO3 is (5.6~19):1, and the concentration of AgNO3 solution is 0.1~0.12 mol / L.
3. The preparation method of the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst according to claim 1 or 2, characterized in that, The dark reaction time was 0.5–1 h, and the light reaction time was 0.5–1 h. The product of the light reaction was washed multiple times with ultrapure water and anhydrous ethanol, and then dried at 60–70 °C for 10–12 h.
4. The preparation method of the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst according to claim 1, characterized in that, The preparation method of the Bi5O7I / Bi7O9I3 binary heterojunction composite powder is as follows: S1. Preparation of BiOI powder: Bi(NO3)3·5H2O was dissolved in ethylene glycol to obtain solution A; KI was dissolved in water to obtain solution B; wherein the molar ratio of Bi(NO3)3·5H2O in solution A to KI in solution B was 1:(0.9~1); solution B was slowly added to solution A, stirred evenly, and then transferred to a high-pressure reactor. The mixture was subjected to hydrothermal reaction at 150~160 ℃ for 10~12 h. After cooling, the mixture was washed and dried to obtain BiOI powder. Preparation of S2 and Bi5O7I / Bi7O9I3: BiOI powder was placed in a muffle furnace and calcined in air at 400-500 °C for 2.9-3 h to obtain Bi5O7I / Bi7O9I3 binary heterojunction composite powder.
5. The preparation method of the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst according to claim 4, characterized in that, In solution A, the concentration of Bi(NO3)3·5H2O is 0.098–0.123 mol / L; in solution B, the concentration of KI is 0.08–0.100 mol / L.
6. The preparation method of the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst according to claim 4 or 5, characterized in that, After slowly adding solution B to solution A, stir for 0.5–1 h; the product of the hydrothermal reaction is washed multiple times with ultrapure water and anhydrous ethanol, and then dried at 60–70 °C for 10–12 h.
7. An AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst prepared by the method described in any one of claims 1-6.
8. The application of the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst according to claim 7 in the catalytic degradation of organic molecules, characterized in that, The process includes the following steps: adding the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst to a solution containing tetracycline or rhodamine B, stirring thoroughly, and after a dark reaction, turning on the xenon lamp for a photo-irradiation reaction.
9. The application of the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst according to claim 8 in the catalytic degradation of organic molecules, characterized in that, In solutions containing tetracycline or rhodamine B, the concentration of tetracycline or rhodamine B is 20–40 mg / L, and the dosage of AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst is 0.1–0.15 g / L.
10. The application of the AgI / Bi5O7I / Bi7O9I3 ternary heterojunction photocatalyst according to claim 8 or 9 in the catalytic degradation of organic molecules, characterized in that, The dark reaction time is 0.5–1 h, and the light reaction time is 1–2 h.