Preparation method and application of gold / bismuth oxide carbonate@trimanganese tetroxide Z-type heterojunction photocatalyst

Abstract

The application relates to a preparation method of a gold / bismuth oxide carbonate@trimanganese tetroxide Z-type heterojunction photocatalyst. The preparation method is as follows: in a neutral solution, Bi(NO3)3.5H2O and C6H8O7.H2O are used as reactants to prepare Bi2O2CO3 fiber flower balls; Au nanoparticles are loaded by using an electrostatic self-assembly method, and the Au nanoparticles are dispersed on the surface of the Bi2O2CO3 fiber flower balls to prepare an Au / Bi2O2CO3 sample; the Au / Bi2O2CO3 is dispersed into a dimethylformamide solution, and Mn(CH3COO)2.4H2O solution is dropped into the dimethylformamide solution under ultrasonic conditions to obtain an Au / Bi2O2CO3 core-shell structure sample coated with Mn3O4 nanoparticles. The three-phase photocatalyst prepared by the application has high efficient photogenerated carrier separation efficiency and strong NO oxidation capacity under visible light, has remarkable degradation activity on pollutants, and has wide application prospects in the field of photocatalysis.

Description

Technical Field

[0001] This invention relates to the field of nanophotocatalytic materials technology, and in particular to a method for preparing and applying a gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst. Background Technology

[0002] Nitrogen oxides are not only a major cause of acid rain and ozone layer depletion, but they also endanger human health. Furthermore, nitrogen oxides react chemically with various hydrocarbon compounds, producing byproducts several times more toxic than the initial products, causing extremely serious air pollution. Therefore, controlling nitrogen oxides is one of the most urgent and essential tasks in my country's air pollution control efforts.

[0003] Photocatalysis technology has attracted attention and is widely used in pollutant degradation and nitrogen oxide oxidation due to its energy-saving, environmentally friendly, non-toxic, and mild reaction conditions. Among many semiconductor photocatalysts, bismuth-based materials have advantages such as low cost and high activity. Bi₂O₂CO₃, as a novel bilayer catalyst with alternating bilayer phases and high photogenerated carrier separation efficiency, has been extensively studied. However, the wide band gap of pure Bi₂O₂CO₃ leads to lower light energy utilization and catalytic activity.

[0004] Therefore, this invention uses loaded noble metals and co-catalysts to construct a Z-type heterojunction system. In this system, the photogenerated carrier separation efficiency is high, and the visible light absorption range is expanded by changing the band gap structure, which greatly improves the catalytic activity of the photocatalyst. It can be applied to NO oxidation and the degradation of pollutant thiamethoxam. Summary of the Invention

[0005] This invention proposes a method for preparing a gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst to address the problem of low light energy utilization and catalytic activity in existing semiconductor bi-base photocatalysts, specifically pure Bi₂O₂CO₃, due to its wide band gap. The objective of this invention is to provide a method for preparing a gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst that improves the photogenerated carrier separation efficiency and significantly enhances the catalytic activity by extending the visible light absorption range through altered band gap structure. This invention also provides an application of the gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst.

[0006] The first objective of this invention is to provide a method for preparing a gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst, comprising the following steps:

[0007] Step 1: Dissolve Bi(NO3)3·5H2O in dilute nitric acid solution, then add C6H8O7·H2O, stir magnetically until the solution is clear, adjust the pH to 7, and obtain Bi2O2CO3 sample by heating in an autoclave, washing with water and ethanol, and vacuum drying.

[0008] Step 2: Mix oleylamine containing HAuCl4·4H2O with toluene solution and transfer to high pressure reactor for heating. After cooling the obtained product to room temperature, add ethanol and then centrifuge to obtain nano Au particles. Disperse them in cyclohexane by sonication and stirring to form a red dispersion. Then mix the red dispersion with 3-mercaptopropionic acid in a flask.

[0009] Step 3: Stir the mixed solution obtained in Step 2 at room temperature, centrifuge, wash the precipitate with acetone, and then disperse it in deionized water by sonication and stirring to obtain a suspension of nano Au particles. Mix Bi2O2CO3 and polyvinylpyrrolidone-K30 (PVP-K30) with the nano Au particle suspension, and obtain Au / Bi2O2CO3 sample after sonication, stirring, washing, and vacuum drying.

[0010] Step 4: Disperse the Au / Bi2O2CO3 material in dimethylformamide (DMF) solution, and then gradually add Mn(CH3COO)2·4H2O solution under ultrasonic conditions. After ultrasonication and centrifugation, a solid sample is obtained.

[0011] Step 5: Disperse the sample from Step 4 into deionized water, then seal it in an autoclave and heat it to improve the crystallinity of Mn3O4. After washing and vacuum drying, the final product is obtained.

[0012] Preferably, the heating temperature of the high-pressure reactor in step 1 is 150-200℃; the mass ratio of Bi(NO3)3·5H2O to C6H8O7·H2O is 0.73:0.21.

[0013] Preferably, the heating temperature in step 2 is 50-150℃; heating time is 10-15 hours.

[0014] Preferably, in step 2, the volume ratio of oleylamine to toluene is 3:37; and the volume ratio of cyclohexane to 3-mercaptopropionic acid is 2:1.

[0015] Preferably, the mass ratio of Bi2O2CO3 to polyvinylpyrrolidone-K30 (PVP-K30) in step 3 is 3:2; the mass ratio of Au to Bi2O2CO3 is 1%-10%; and the resulting mixed solution is stirred at room temperature for 10-15 hours.

[0016] Preferably, the concentration of the Mn(CH3COO)2·4H2O solution in step 4 is 0.01-0.05 mol / L; the volume ratio of dimethylformamide to Mn(CH3COO)2·4H2O solution is 9:1.

[0017] Preferably, the mass percentage of Mn3O4 in the final solid sample described in step 4 is 5%-12%.

[0018] Preferably, the high-pressure autoclave heating temperature in step 5 is 100-150℃, and the heating treatment lasts for 4-6 hours; the vacuum drying temperature is 50-80℃, and the vacuum drying lasts for 8 hours.

[0019] The second objective of this invention is to provide an application of a gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst, which can be used for NO oxidation and degradation of the pollutant thiamethoxam.

[0020] The present invention has at least the following beneficial effects:

[0021] 1. The hierarchical structure of Bi₂O₂CO₃ fiber flowers prepared in this invention gives the catalyst more reactive sites and a larger specific surface area, increasing the contact area between the catalyst and the reactants. A three-phase Z-type heterojunction is formed by loading Au and Mn₃O₄ onto its surface. Compared to a two-phase Z-type heterojunction, the addition of nano-Au as an electron transfer medium accelerates the electron transfer rate while simultaneously generating a surface plasmon resonance effect, increasing photocurrent density, enhancing light absorption, and improving visible light utilization.

[0022] 2. The three-phase Z-type heterojunction photocatalyst prepared in this invention forms a built-in electric field due to the difference in Fermi levels when Bi2O2CO3 and Mn3O4 are in contact with Au. Under the action of the built-in electric field and the nano Au electronic medium, the migration rate of charge carriers is greatly accelerated, and electron-hole pairs are effectively separated. Compared with the traditional type II heterojunction, it enhances the redox ability of the catalyst while improving the photocatalytic performance.

[0023] 3. The catalyst prepared by this invention has a special three-phase core-shell structure, which maximizes the contact area between catalysts and greatly increases the interfacial charge transfer efficiency. At the same time, this structure covers and protects the internal Bi2O2CO3 material and nano Au particles, improving the lifespan of the photocatalyst and giving it sufficient stability and repeatability.

[0024] 4. In the preparation method provided by the present invention, nano-Au particles are loaded on the surface of Bi2O2CO3 fiber flower balls by electrostatic self-assembly, and a layer of fine Mn3O4 nanoparticles are coated on Au / Bi2O2CO3 by ultrasonic-assisted method. Finally, the crystallinity of Mn3O4 is improved by synergistic hydrothermal method. The preparation method proposed by the present invention has the advantages of low equipment requirements, mild conditions and good product performance, and has good social benefits in terms of environmental purification. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present invention and, together with the specification, serve to explain the technical solutions of the present invention.

[0026] Figure 1 The XRD patterns of different catalysts prepared in the embodiments of the present invention are shown below.

[0027] Figure 2 The image shows a TEM image of the catalyst synthesized in an embodiment of the present invention.

[0028] Figure 3 These are macroscopic and magnified SEM images of the monomer, two-phase, and three-phase catalysts in the embodiments of the present invention; (wherein: Figure 3 (a) is a macroscopic SEM image of Bi2O2CO3 obtained in Example 1; Figure 3 (b) is an enlarged SEM image of Bi2O2CO3 obtained in Example 1; Figure 3 (c) is a SEM image of Au / Bi2O2CO3 obtained in Example 4; Figure 3 (d) is a SEM image of Bi2O2CO3@Mn3O4 obtained in Example 8; Figure 3 (e) is a macroscopic SEM image of the final product Au / Bi2O2CO3@Mn3O4 from Example 8; Figure 3 (f) is an enlarged SEM image of the final product Au / Bi2O2CO3@Mn3O4 from Example 8;

[0029] Figure 4 The images show the photocatalytic oxidation of NO by various catalysts in the embodiments of the present invention.

[0030] Figure 5 The photocatalytic degradation curves of thiamethoxam by the various catalysts of this invention are shown. Detailed Implementation

[0031] To better explain the present invention, the following description, in conjunction with the accompanying drawings and embodiments, further elaborates on the content of the present invention.

[0032] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used in the following examples are commercially available unless otherwise specified.

[0033] Example 1

[0034] 1.46 g Bi(NO3)3·5H2O was dissolved in 70 mL of dilute nitric acid solution, and then 0.42 g C6H8O7·H2O was added. The mixture was stirred for 10 min until the solution became clear. Under magnetic stirring, the pH of the solution was adjusted to 7 with 2 mol / L NaOH. The resulting transparent solution was transferred to a 100 mL high-pressure reactor and kept at 180 °C for 20 h. After washing three times with water and ethanol, the solution was dried under vacuum at 60 °C for 8 h to obtain the Bi2O2CO3 sample.

[0035] Test Example 1

[0036] The photocatalytic activity of the photocatalyst was determined by photocatalytic oxidation of NO in a continuous flow reactor. The initial concentration of NO gas used in the reaction was approximately 600 ppb. First, 0.2 g of the photocatalyst was dispersed in 20 mL of deionized water for 5 min. The resulting solution was transferred to a glass dish and evaporated by heating in an oven at 60 °C for 3 h. The culture dish coated with the photocatalyst film was then placed in the center of the glass reactor. The photocatalytic activity was measured by online NO oxidation. X The analyzer recorded the NO concentration at the reactor outlet. After adsorption-desorption equilibrium was reached, a 500W xenon lamp (λ≥420nm) with a cutoff filter was turned on as a visible light source to carry out the NO photocatalytic oxidation reaction, with an NO oxidation removal rate of 27.9%.

[0037] 0.025 g of the above catalyst was dispersed in a quartz test tube containing 50 mL of 10 mg / L thiamethoxam solution. After the dark reaction reached adsorption-desorption equilibrium, it was irradiated. 3 mL of the reaction solution was extracted from the reaction tube within a given irradiation time interval. After microfiltration, the concentration of thiamethoxam was determined by high performance liquid chromatography (HPLC). The degradation rate of thiamethoxam was 25.8%.

[0038] Example 2

[0039] 3 mL of oleylamine containing 0.15 mmol HAuCl4·4H2O was mixed with 37 mL of toluene solution and transferred to a 50 mL high-pressure reactor. The mixture was heated at 100 °C for 12 h. After cooling the product to room temperature, ethanol was added, and the mixture was centrifuged to obtain nano-Au particles. These particles were then dispersed in 12 mL of cyclohexane by sonication and stirring to form a red dispersion. This dispersion was then mixed with 6 mL of 3-mercaptopropionic acid in a 50 mL flask. The resulting mixture was stirred at room temperature for 12 h. After centrifugation, the precipitate was washed with acetone and then dispersed in 20 mL of deionized water by sonication and stirring to obtain a 1.5 g / L nano-Au particle suspension.

[0040] 0.3 g of Bi2O2CO3 prepared in Example 1 and 0.2 g of polyvinylpyrrolidone-K30 (PVP-K30) were mixed with 4 mL of nano Au particle suspension and 46 mL of deionized water. After sonication for 0.5 h and stirring at room temperature for 2 h, the mixture was washed three times with water and ethanol respectively and then vacuum dried at 60 °C for 8 h to obtain Au / Bi2O2CO3 sample, wherein the mass ratio of Au to Bi2O2CO3 was marked as 2%.

[0041] Test Example 2

[0042] The photocatalytic activity of the photocatalyst was determined by photocatalytic oxidation of NO in a continuous flow reactor. The initial concentration of NO gas used in the reaction was approximately 600 ppb. First, 0.2 g of the photocatalyst was dispersed in 20 mL of deionized water for 5 min. The resulting solution was transferred to a glass dish and evaporated by heating in an oven at 60 °C for 3 h. The culture dish coated with the photocatalyst film was then placed in the center of the glass reactor. The photocatalytic activity was measured by online NO oxidation. X The analyzer recorded the NO concentration at the reactor outlet. After adsorption-desorption equilibrium was reached, a 500W xenon lamp (λ≥420nm) with a cutoff filter was turned on as a visible light source to carry out the NO photocatalytic oxidation reaction, with an NO oxidation removal rate of 38.7%.

[0043] 0.025 g of the above catalyst was dispersed in a quartz test tube containing 50 mL of 10 mg / L thiamethoxam solution. After the dark reaction reached adsorption-desorption equilibrium, it was irradiated. 3 mL of the reaction solution was extracted from the reaction tube within a given irradiation time interval. After microfiltration, the concentration of thiamethoxam was determined by high performance liquid chromatography (HPLC). The degradation rate of thiamethoxam was 40.8%.

[0044] Example 3

[0045] 3 mL of oleylamine containing 0.15 mmol HAuCl4·4H2O was mixed with 37 mL of toluene solution and transferred to a 50 mL high-pressure reactor. The mixture was heated at 100 °C for 12 h. After cooling the product to room temperature, ethanol was added, and the mixture was centrifuged to obtain nano-Au particles. These particles were then dispersed in 12 mL of cyclohexane by sonication and stirring to form a red dispersion. This dispersion was then mixed with 6 mL of 3-mercaptopropionic acid in a 50 mL flask. The resulting mixture was stirred at room temperature for 12 h. After centrifugation, the precipitate was washed with acetone and then dispersed in 20 mL of deionized water by sonication and stirring to obtain a 1.5 g / L nano-Au particle suspension.

[0046] 0.3 g of Bi2O2CO3 prepared in Specific Example 1 and 0.2 g of polyvinylpyrrolidone-K30 (PVP-K30) were mixed with 8 mL of nano Au particle suspension and 42 mL of deionized water. After sonication for 0.5 h and stirring at room temperature for 2 h, the mixture was washed three times with water and ethanol respectively and then vacuum dried at 60 °C for 8 h to obtain Au / Bi2O2CO3 sample, wherein the mass ratio of Au to Bi2O2CO3 was marked as 4%.

[0047] Test Example 3

[0048] The photocatalytic activity of the photocatalyst was determined by photocatalytic oxidation of NO in a continuous flow reactor. The initial concentration of NO gas used in the reaction was approximately 600 ppb. First, 0.2 g of the photocatalyst was dispersed in 20 mL of deionized water for 5 min. The resulting solution was transferred to a glass dish and evaporated by heating in an oven at 60 °C for 3 h. The culture dish coated with the photocatalyst film was then placed in the center of the glass reactor. The photocatalytic activity was measured by online NO oxidation. X The analyzer recorded the NO concentration at the reactor outlet. After adsorption-desorption equilibrium was reached, a 500W xenon lamp (λ≥420nm) with a cutoff filter was turned on as a visible light source to carry out the NO photocatalytic oxidation reaction, with an NO oxidation removal rate of 49.3%.

[0049] 0.025 g of the above catalyst was dispersed in a quartz test tube containing 50 mL of 10 mg / L thiamethoxam solution. After the dark reaction reached adsorption-desorption equilibrium, it was irradiated. 3 mL of the reaction solution was extracted from the reaction tube within a given irradiation time interval. After microfiltration, the concentration of thiamethoxam was determined by high performance liquid chromatography (HPLC). The degradation rate of thiamethoxam was 56.3%.

[0050] Example 4

[0051] 3 mL of oleylamine containing 0.15 mmol HAuCl4·4H2O was mixed with 37 mL of toluene solution and transferred to a 50 mL high-pressure reactor. The mixture was heated at 100 °C for 12 h. After cooling the product to room temperature, ethanol was added, and the mixture was centrifuged to obtain nano-Au particles. These particles were then dispersed in 12 mL of cyclohexane by sonication and stirring to form a red dispersion. This dispersion was then mixed with 6 mL of 3-mercaptopropionic acid in a 50 mL flask. The resulting mixture was stirred at room temperature for 12 h. After centrifugation, the precipitate was washed with acetone and then dispersed in 20 mL of deionized water by sonication and stirring to obtain a 1.5 g / L nano-Au particle suspension.

[0052] 0.3 g of Bi2O2CO3 prepared in Example 1 and 0.2 g of polyvinylpyrrolidone-K30 (PVP-K30) were mixed with 12 mL of nano Au particle suspension and 38 mL of deionized water. After sonication for 0.5 h and stirring at room temperature for 2 h, the mixture was washed three times with water and ethanol respectively and then vacuum dried at 60 °C for 8 h to obtain Au / Bi2O2CO3 sample, wherein the mass ratio of Au to Bi2O2CO3 was marked as 6%.

[0053] Test Example 4

[0054] The photocatalytic activity of the photocatalyst was determined by photocatalytic oxidation of NO in a continuous flow reactor. The initial concentration of NO gas used in the reaction was approximately 600 ppb. First, 0.2 g of the photocatalyst was dispersed in 20 mL of deionized water for 5 min. The resulting solution was transferred to a glass dish and evaporated by heating in an oven at 60 °C for 3 h. The culture dish coated with the photocatalyst film was then placed in the center of the glass reactor. The photocatalytic activity was measured by online NO oxidation. X The analyzer recorded the NO concentration at the reactor outlet. After adsorption-desorption equilibrium was reached, a 500W xenon lamp (λ≥420nm) with a cutoff filter was turned on as a visible light source to carry out the NO photocatalytic oxidation reaction, and the NO oxidation removal rate was 54.4%.

[0055] 0.025 g of the above catalyst was dispersed in a quartz test tube containing 50 mL of 10 mg / L thiamethoxam solution. After the dark reaction reached adsorption-desorption equilibrium, it was irradiated. 3 mL of the reaction solution was extracted from the reaction tube within a given irradiation time interval. After microfiltration, the concentration of thiamethoxam was determined by high performance liquid chromatography (HPLC). The degradation rate of thiamethoxam was 62.3%.

[0056] Example 5

[0057] 3 mL of oleylamine containing 0.15 mmol HAuCl4·4H2O was mixed with 37 mL of toluene solution and transferred to a 50 mL high-pressure reactor. The mixture was heated at 100 °C for 12 h. After cooling the product to room temperature, ethanol was added, and the mixture was centrifuged to obtain nano-Au particles. These particles were then dispersed in 12 mL of cyclohexane by sonication and stirring to form a red dispersion. This dispersion was then mixed with 6 mL of 3-mercaptopropionic acid in a 50 mL flask. The resulting mixture was stirred at room temperature for 12 h. After centrifugation, the precipitate was washed with acetone and then dispersed in 20 mL of deionized water by sonication and stirring to obtain a 1.5 g / L nano-Au particle suspension.

[0058] 0.3 g of Bi2O2CO3 prepared in Example 1 and 0.2 g of polyvinylpyrrolidone-K30 (PVP-K30) were mixed with 16 mL of nano Au particle suspension and 34 mL of deionized water. After sonication for 0.5 h and stirring at room temperature for 2 h, the mixture was washed three times with water and ethanol, and then vacuum dried at 60 °C for 8 h to obtain Au / Bi2O2CO3 sample, wherein the mass ratio of Au to Bi2O2CO3 was marked as 8%.

[0059] Test Example 5

[0060] The photocatalytic activity of the photocatalyst was determined by photocatalytic oxidation of NO in a continuous flow reactor. The initial concentration of NO gas used in the reaction was approximately 600 ppb. First, 0.2 g of the photocatalyst was dispersed in 20 mL of deionized water for 5 min. The resulting solution was transferred to a glass dish and evaporated by heating in an oven at 60 °C for 3 h. The culture dish coated with the photocatalyst film was then placed in the center of the glass reactor. The photocatalytic activity was measured by online NO oxidation. X The analyzer recorded the NO concentration at the reactor outlet. After adsorption-desorption equilibrium was reached, a 500W xenon lamp (λ≥420nm) with a cutoff filter was turned on as a visible light source to carry out the NO photocatalytic oxidation reaction, with an NO oxidation removal rate of 44.9%.

[0061] 0.025 g of the above catalyst was dispersed in a quartz test tube containing 50 mL of 10 mg / L thiamethoxam solution. After the dark reaction reached adsorption-desorption equilibrium, it was irradiated. 3 mL of the reaction solution was extracted from the reaction tube within a given irradiation time interval. After microfiltration, the concentration of thiamethoxam was determined by high performance liquid chromatography (HPLC). The degradation rate of thiamethoxam was 47.9%.

[0062] Example 6

[0063] 0.3 g of the Au / Bi₂O₂CO₃ material prepared in Specific Example 4 was dispersed in 90 mL of dimethylformamide (DMF) solution. Then, under ultrasonic conditions, 10 mL of a 0.02 mol / L Mn(CH₃COO)₂·4H₂O solution was gradually added dropwise to the above solution. After ultrasonication for 5 h, a brown suspension of solid solution was obtained. The solid sample was obtained by centrifugation and then dispersed in 70 mL of deionized water. The sample was then sealed in a 100 mL autoclave and treated at 120 °C for 3 h to improve the crystallinity of Mn₃O₄. Finally, the Au / Bi₂O₂CO₃@Mn₃O₄ sample was obtained. The sample was washed three times with water and ethanol, and then vacuum dried at 60 °C for 8 h. The two-phase Bi₂O₂CO₃@Mn₃O₄ material used as a control sample was prepared under conditions without gold doping. The mass ratio of Mn₃O₄ to Au / Bi₂O₂CO₃ was marked as 5%.

[0064] Test Example 6

[0065] The photocatalytic activity of the photocatalyst was determined by photocatalytic oxidation of NO in a continuous flow reactor. The initial concentration of NO gas used in the reaction was approximately 600 ppb. First, 0.2 g of the photocatalyst was dispersed in 20 mL of deionized water for 5 min. The resulting solution was transferred to a glass dish and evaporated by heating in an oven at 60 °C for 3 h. The culture dish coated with the photocatalyst film was then placed in the center of the glass reactor. The photocatalytic activity was measured by online NO oxidation. X The analyzer recorded the NO concentration at the reactor outlet. After adsorption-desorption equilibrium was reached, a 500W xenon lamp (λ≥420nm) with a cutoff filter was turned on as a visible light source to carry out the NO photocatalytic oxidation reaction. The NO oxidation removal rate of the three-phase Au / Bi2O2CO3@Mn3O4 photocatalyst was 60.1%, and the NO oxidation removal rate of the two-phase Bi2O2CO3@Mn3O4 photocatalyst was 44.7%.

[0066] 0.025 g of the above catalyst was dispersed in a quartz test tube containing 50 mL of a 10 mg / L thiamethoxam solution. After the dark reaction reached adsorption-desorption equilibrium, it was irradiated. 3 mL of the reaction solution was extracted from the reaction tube within a given irradiation time interval. After microfiltration, the concentration of thiamethoxam was determined by high performance liquid chromatography (HPLC). The degradation rate of thiamethoxam by the three-phase Au / Bi₂O₂CO₃@Mn₃O₄ photocatalyst was 70.6%, while the degradation rate by the two-phase Bi₂O₂CO₃@Mn₃O₄ photocatalyst was 46.2%.

[0067] Example 7

[0068] 0.3 g of the Au / Bi₂O₂CO₃ material prepared in Specific Example 4 was dispersed in 90 mL of dimethylformamide (DMF) solution. Then, under ultrasonic conditions, 10 mL of a 0.028 mol / L Mn(CH₃COO)₂·4H₂O solution was gradually added dropwise to the above solution. After ultrasonication for 5 h, a brown suspension of solid solution was obtained. The solid sample was obtained by centrifugation and then dispersed in 70 mL of deionized water. The sample was then sealed in a 100 mL autoclave and treated at 120 °C for 3 h to improve the crystallinity of Mn₃O₄. Finally, the Au / Bi₂O₂CO₃@Mn₃O₄ sample was obtained. The sample was washed three times with water and ethanol, and then vacuum dried at 60 °C for 8 h. The two-phase Bi₂O₂CO₃@Mn₃O₄ material used as a comparison sample was prepared under conditions without gold doping. The mass ratio of Mn₃O₄ to Au / Bi₂O₂CO₃ was marked as 7%.

[0069] Test Example 7

[0070] The photocatalytic activity of the photocatalyst was determined by photocatalytic oxidation of NO in a continuous flow reactor. The initial concentration of NO gas used in the reaction was approximately 600 ppb. First, 0.2 g of the photocatalyst was dispersed in 20 mL of deionized water for 5 min. The resulting solution was transferred to a glass dish and evaporated by heating in an oven at 60 °C for 3 h. The culture dish coated with the photocatalyst film was then placed in the center of the glass reactor. The photocatalytic activity was measured by online NO oxidation. X The analyzer recorded the NO concentration at the reactor outlet. After adsorption-desorption equilibrium was reached, a 500W xenon lamp (λ≥420nm) with a cutoff filter was turned on as a visible light source to carry out the NO photocatalytic oxidation reaction, with an NO oxidation removal rate of 69.8%.

[0071] 0.025 g of the above catalyst was dispersed in a quartz test tube containing 50 mL of 10 mg / L thiamethoxam solution. After the dark reaction reached adsorption-desorption equilibrium, it was irradiated. 3 mL of the reaction solution was extracted from the reaction tube within a given irradiation time interval. After microfiltration, the concentration of thiamethoxam was determined by high performance liquid chromatography (HPLC). The degradation rate of thiamethoxam was 85.9%.

[0072] Example 8

[0073] 0.3 g of the Au / Bi₂O₂CO₃ material prepared in Example 4 was dispersed in 90 mL of dimethylformamide (DMF) solution. Then, under ultrasonic conditions, 10 mL of a 0.035 mol / L Mn(CH₃COO)₂·4H₂O solution was gradually added dropwise to the above solution. After ultrasonication for 5 h, a brown suspension of solid solution was obtained. The solid sample was obtained by centrifugation and then dispersed in 70 mL of deionized water. The sample was then sealed in a 100 mL autoclave and treated at 120 °C for 3 h to improve the crystallinity of Mn₃O₄. Finally, the Au / Bi₂O₂CO₃@Mn₃O₄ sample was obtained. The sample was washed three times with water and ethanol, and then vacuum dried at 60 °C for 8 h. The two-phase Bi₂O₂CO₃@Mn₃O₄ material used as a control sample was prepared without gold doping. The mass ratio of Mn₃O₄ to Au / Bi₂O₂CO₃ was labeled as 9%.

[0074] Test Example 8

[0075] The photocatalytic activity of the photocatalyst was determined by photocatalytic oxidation of NO in a continuous flow reactor. The initial concentration of NO gas used in the reaction was approximately 600 ppb. First, 0.2 g of the photocatalyst was dispersed in 20 mL of deionized water for 5 min. The resulting solution was transferred to a glass dish and evaporated by heating in an oven at 60 °C for 3 h. The culture dish coated with the photocatalyst film was then placed in the center of the glass reactor. The photocatalytic activity was measured by online NO oxidation. X The analyzer recorded the NO concentration at the reactor outlet. After adsorption-desorption equilibrium was reached, a 500W xenon lamp (λ≥420nm) with a cutoff filter was turned on as a visible light source to carry out the NO photocatalytic oxidation reaction, and the NO oxidation removal rate was 73.2%.

[0076] 0.025 g of the above catalyst was dispersed in a quartz test tube containing 50 mL of 10 mg / L thiamethoxam solution. After the dark reaction reached adsorption-desorption equilibrium, it was irradiated. 3 mL of the reaction solution was extracted from the reaction tube within a given irradiation time interval. After microfiltration, the concentration of thiamethoxam was determined by high performance liquid chromatography (HPLC). The degradation rate of thiamethoxam was 95.6%.

[0077] Example 9

[0078] 0.3 g of the Au / Bi₂O₂CO₃ material prepared in Specific Example 4 was dispersed in 90 mL of dimethylformamide (DMF) solution. Then, under ultrasonic conditions, 10 mL of a 0.043 mol / L Mn(CH₃COO)₂·4H₂O solution was gradually added dropwise to the above solution. After ultrasonication for 5 h, a brown suspension of solid solution was obtained. The solid sample was obtained by centrifugation and then dispersed in 70 mL of deionized water. The sample was then sealed in a 100 mL autoclave and treated at 120 °C for 3 h to improve the crystallinity of Mn₃O₄. Finally, the Au / Bi₂O₂CO₃@Mn₃O₄ sample was obtained. The sample was washed three times with water and ethanol, and then vacuum dried at 60 °C for 8 h. The two-phase Bi₂O₂CO₃@Mn₃O₄ material used as a comparison sample was prepared under conditions without gold doping. The mass ratio of Mn₃O₄ to Au / Bi₂O₂CO₃ was marked as 11%.

[0079] Test Example 9

[0080] The photocatalytic activity of the photocatalyst was determined by photocatalytic oxidation of NO in a continuous flow reactor. The initial concentration of NO gas used in the reaction was approximately 600 ppb. First, 0.2 g of the photocatalyst was dispersed in 20 mL of deionized water for 5 min. The resulting solution was transferred to a glass dish and evaporated by heating in an oven at 60 °C for 3 h. The culture dish coated with the photocatalyst film was then placed in the center of the glass reactor. The photocatalytic activity was measured by online NO oxidation. X The analyzer recorded the NO concentration at the reactor outlet. After adsorption-desorption equilibrium was reached, a 500W xenon lamp (λ≥420nm) with a cutoff filter was turned on as a visible light source to carry out the NO photocatalytic oxidation reaction, with an NO oxidation removal rate of 65.5%.

[0081] 0.025 g of the above catalyst was dispersed in a quartz test tube containing 50 mL of 10 mg / L thiamethoxam solution. After the dark reaction reached adsorption-desorption equilibrium, it was irradiated. 3 mL of the reaction solution was extracted from the reaction tube within a given irradiation time interval. After microfiltration, the concentration of thiamethoxam was determined by high performance liquid chromatography (HPLC). The degradation rate of thiamethoxam was 80.6%.

[0082] The XRD patterns of the catalysts prepared in the above examples are as follows: Figure 1 As shown, Figure 1 The XRD patterns are, in order: Mn3O4 monomer, Au / Bi2O2CO3@Mn3O4 prepared in Example 8, Au / Bi2O2CO3 prepared in Example 4, Bi2O2CO3@Mn3O4 prepared in Example 8, and Bi2O2CO3 prepared in Example 1.

[0083] Depend on Figure 1It can be seen that the characteristic peaks of Bi2O2CO3 at approximately 24°, 30°, 33°, 47°, and 57° are all present in Au / Bi2O2CO3@Mn3O4, Au / Bi2O2CO3, and Bi2O2CO3@Mn3O4 samples. The characteristic peaks of Mn3O4 at approximately 18°, 29°, 32°, and 36° are all present in Au / Bi2O2CO3@Mn3O4 and Bi2O2CO3@Mn3O4 samples. Moreover, the crystallinity of pure Mn3O4 samples increases after treatment, and the characteristic peaks are sharper. Au has characteristic peaks at approximately 38°, 44°, 65°, and 78°, but only the characteristic peak at approximately 38° appears in Au / Bi2O2CO3@Mn3O4 and Au / Bi2O2CO3 samples. This is due to the low gold content.

[0084] Figure 2 This is a TEM image of the Au / Bi2O2CO3@Mn3O4 catalyst synthesized in Example 8 of this invention;

[0085] Figure 3 These are macroscopic and magnified SEM images of the monomer, two-phase, and three-phase catalysts in this invention; (wherein: Figure 3 (a) is a macroscopic SEM image of Bi2O2CO3 obtained in Example 1; Figure 3 (b) is an enlarged SEM image of Bi2O2CO3 obtained in Example 1; Figure 3 (c) is a SEM image of Au / Bi2O2CO3 obtained in Example 4; Figure 3 (d) is a SEM image of Bi2O2CO3@Mn3O4 obtained in Example 8; Figure 3 (e) is a macroscopic SEM image of the final product Au / Bi2O2CO3@Mn3O4 from Example 8; Figure 3 (f) is an enlarged SEM image of the final product Au / Bi2O2CO3@Mn3O4 from Example 8;

[0086] Depend on Figure 2 It can be seen that the three-phase Z-type heterojunction structure of the catalyst Au / Bi2O2CO3@Mn3O4 is clear under TEM. This heterojunction structure has a high electron-hole separation efficiency, and the addition of metal Au accelerates the migration rate of charge carriers, giving the catalyst a good redox ability.

[0087] Depend on Figure 3 (a) and Figure 3 (b) It can be seen that the pure Bi2O2CO3 sample has a uniform fibrous flower-shaped hierarchical structure with a large specific surface area, which increases the contact area between the catalyst and the reactants and provides more active sites for the reaction.

[0088] Depend on Figure 3(c) It can be seen that Au particles obtained by electrostatic self-assembly are uniformly dispersed on Bi2O2CO3 fiber flower balls, and Bi2O2CO3 materials loaded with Au particles have stronger light absorption and higher electron migration rate.

[0089] Depend on Figure 3 (d) shows that Mn3O4 particles are uniformly coated on Bi2O2CO3 fiber flower balls to form a core-shell structure.

[0090] Depend on Figure 3 (e) and Figure 3 (f) It can be seen that in the Au / Bi2O2CO3@Mn3O4 three-phase sample, Au particles are uniformly distributed on the Bi2O2CO3 fiber flower ball, and the outermost layer is covered by fine Mn3O4 particles, forming a core-shell structure of Au / Bi2O2CO3@Mn3O4. Under the action of the built-in electric field and surface plasmon resonance effect, this core-shell structure has higher interfacial charge transfer efficiency and visible light absorption capacity. Moreover, due to the protection of the outer Mn3O4 nanoparticles, the catalyst has sufficient stability and service life.

[0091] The photocatalytic oxidation of NO by the catalysts prepared in this invention are as follows: Figure 4 As shown.

[0092] Depend on Figure 4 It can be seen that Au / Bi2O2CO3@Mn3O4 has the best NO photocatalytic oxidation effect among all catalyst samples, with a NO removal rate of 73.2% after 30 min under visible light.

[0093] The photocatalytic degradation curves of thiamethoxam by the catalysts prepared in this invention are as follows: Figure 5 As shown;

[0094] Depend on Figure 5 It can be seen that Au / Bi2O2CO3@Mn3O4 showed the best photocatalytic degradation effect among all catalyst samples, with a degradation rate of 95.6% after 90 minutes under visible light.

[0095] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst, characterized in that, Includes the following steps: Step 1: Dissolve Bi(NO3)3•5H2O in dilute nitric acid solution, then add C6H8O7•H2O, stir magnetically until the solution is clear, adjust the pH to 7, and obtain Bi2O2CO3 sample by heating in an autoclave, washing with water and ethanol, and vacuum drying. Step 2: Mix oleylamine containing HAuCl4•4H2O with toluene solution and transfer to high pressure reactor for heating. After cooling the obtained product to room temperature, add ethanol and then centrifuge to obtain nano Au particles. Disperse them in cyclohexane by sonication and stirring to form a red dispersion. Then mix the red dispersion with 3-mercaptopropionic acid in a flask. Step 3: Stir the mixed solution obtained in Step 2 at room temperature, centrifuge and wash the precipitate with acetone, then disperse it in deionized water by sonication and stirring to obtain a suspension of nano Au particles. Mix Bi2O2CO3 and polyvinylpyrrolidone-K30 with the nano Au particle suspension, and obtain Au / Bi2O2CO3 sample after sonication, stirring, washing and vacuum drying. Step 4: Disperse the Au / Bi2O2CO3 material in a dimethylformamide solution, and then gradually add the Mn(CH3COO)2•4H2O solution under ultrasonic conditions. After ultrasonication and centrifugation, a solid sample is obtained. Step 5: Disperse the sample from Step 4 into deionized water, then seal it in an autoclave and heat it to improve the crystallinity of Mn3O4. After washing and vacuum drying, the final product is obtained.

2. The preparation method of the gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst as described in claim 1, characterized in that, The heating temperature of the high-pressure reactor mentioned in step 1 is 150-200℃; the mass ratio of Bi(NO3)3•5H2O to C6H8O7•H2O is 0.73:0.

21.

3. The preparation method of the gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst as described in claim 1, characterized in that, The heating temperature mentioned in step 2 is 50-150℃; heating time is 10-15 hours.

4. The preparation method of the gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst as described in claim 1, characterized in that, In step 2, the volume ratio of oleylamine to toluene is 3:37; and the volume ratio of cyclohexane to 3-mercaptopropionic acid is 2:

1.

5. The preparation method of the gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst as described in claim 1, characterized in that, In step 3, the mass ratio of Bi2O2CO3 to polyvinylpyrrolidone-K30 (PVP-K30) is 3:2; the mass ratio of Au to Bi2O2CO3 is 1%-10%; and the resulting mixed solution is stirred at room temperature for 10-15 hours.

6. The preparation method of the gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst as described in claim 1, characterized in that, The concentration of the Mn(CH3COO)2•4H2O solution mentioned in step 4 is 0.01-0.05 mol / L; the volume ratio of dimethylformamide to Mn(CH3COO)2•4H2O solution is 9:

1.

7. The preparation method of the gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst as described in claim 1, characterized in that, The mass percentage of Mn3O4 in the solid sample described in step 4 is 5%-12%.

8. The preparation method of the gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst as described in claim 1, characterized in that, The high-pressure autoclave heating temperature in step 5 is 100-150℃, and the heating treatment lasts for 4-6 hours; the vacuum drying temperature is 50-80℃, and the vacuum drying lasts for 8 hours.

9. The application of the gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst prepared by the method described in claim 1 in NO oxidation.

10. The application of the gold / bismuth oxycarbonate@manganese tetroxide Z-type heterojunction photocatalyst prepared by the method described in claim 1 in the degradation of thiamethoxam.

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