Preparation method of a medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst

Abstract

The present invention discloses a preparation method of a medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst, which comprises the following steps: S1, synthesizing a multi-entropy alloy precursor solution; S2, hydrothermally synthesizing Bi3O4Br nanosheets; S3, pyrolytically synthesizing CNNs nanosheets; S4, heating and refluxing to reduce and synthesize a medium-entropy alloy / CNNs composite; S5, ultrasonically compounding to synthesize a medium-entropy alloy / Bi3O4Br / CNNs ternary heterojunction composite photocatalytic material; The catalyst of the present invention does not require any noble metals to participate. The alloy has an LSPR effect, which can improve the visible light utilization rate of the catalyst. At the same time, the obtained composite material has a Z-type heterojunction structure, which improves the separation efficiency of photo-generated carriers and has a high photocatalytic removal efficiency for antibiotics in sewage.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalysts, and particularly relates to a preparation method of a medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst for photocatalytic degradation of antibiotics and organic pollutants in water bodies. Background Art

[0002] The main pollutants in wastewater are the color dyes from the textile industry and the broad-spectrum and narrow-spectrum antibiotics from the pharmaceutical industry. One way to solve the environmental crisis is to use semiconductor photocatalysis. During the photocatalysis process, the semiconductor photocatalyst absorbs energy (hv) equal to or higher than its bandgap energy (Eg), resulting in the excitation of electrons from the valence band (VB) of the semiconductor to the conduction band (CB). However, with the photoexcitation of electrons, holes are generated in the valence band, and electrons occupy the conduction band. In fact, valence band holes can capture hydroxide ions (OH - −) or water (H2O) to form extremely powerful and non-selective oxidizing hydroxyl radicals (•OH). At the same time, conduction band electrons are captured by molecular oxygen (O2) to form another important oxidant superoxide radicals (•O2 - −). Hydroxyl radicals and superoxide radicals participate in the degradation of organic pollutants into carbon dioxide, water, and inorganic ions.

[0003] Bismuth oxyhalide (BiOX, X = F, Cl, Br, I) is a good candidate material for application in the field of photocatalysis due to its unique physical and chemical properties, including optimized band structure, suitable aspect ratio, large specific surface area, active active centers, etc. As a V-VI-VII type ternary semiconductor layered material, it has shown the feasibility of photocatalysis and potential applications in optoelectronics, optical modulators, and photodetectors. Among them, Bi3O4Br has a narrow bandgap and excellent photocatalytic activity, and has been widely used in the field of photocatalysis.

[0004] Graphite-phase carbon nitride (g-C3N4) is the most stable allotrope among the carbon nitride structures. Due to its high thermal stability, chemical stability, semiconductor properties, and special optical properties, g-C3N4 has attracted the research interest of numerous scientific researchers worldwide. However, the bulk g-C3N4 obtained by the direct thermal polymerization method cannot achieve satisfactory catalytic activity. To overcome the limitations of the application of g-C3N4, many effective methods have been proposed by scientific researchers, such as morphology regulation, element doping, metal deposition, and heterostructures. Among them, constructing carbon nitride nanosheets (CNNs) is beneficial to expanding the specific surface area, improving the charge transfer efficiency, and enhancing the catalytic activity.

[0005] The reasons why metal plasma has significant photocatalytic activity are: 1) The electron conduction of metal nanoparticles can obtain radiation energy, thereby generating high-energy electrons on their surface, which is conducive to activating the oxidation of organic pollutant molecules adsorbed on their surface. 2) Metal nanoparticles have a better affinity for organic pollutant molecules than semiconductors; 3) The electron density on the surface of metal nanoparticles is much higher than that of semiconductors, which strengthens the reaction of organic pollutant molecules on the surface of metal nanoparticles. Common Au and Ag nanoparticles are often used as co-catalysts for photocatalysis, but due to their high prices, optimizing non-precious metals is one of the problems that need to be solved urgently; medium-entropy alloys containing multiple metal elements have many advantages such as excellent catalytic activity, high strength, and good corrosion resistance due to coordination and geometric effects.

[0006] Di et al. (J. Di, J. Xia, MF Chisholm, J. Zhong, C. Chen, X. Cao, F.Dong, Z. Chi, H. Chen, YX Weng, J. Xiong, SZ Yang, H. Li, Z. Liu, S. Dai, Defect-Tailoring Mediated Electron-Hole Separation in Single-Unit-Cell Bi3O4BrNanosheets for Boosting Photocatalytic Hydrogen Evolution and NitrogenFixation[J]. Adv Mater, 31 (2019) 1807576) proposed an atomically thin structural model of Bi3O4Br with single unit-cells and high photocatalytic efficiency with surface defects. The modified Bi3O4Br is 4.9 times and 30.9 times that of bulk Bi3O4Br in photocatalytic hydrogen evolution and nitrogen fixation, respectively.

[0007] Wu et al. (S. Wu, H. Yu, S. Chen, X. Quan, Enhanced Photocatalytic H2O2 Production over Carbon Nitride by Doping and Defect Engineering[J]. ACSCatalysis, 10 (2020) 14380-14389) greatly suppressed charge recombination by alkali metal doping and the introduction of N vacancies. The synergistic effect of doping and defects led to the improvement of photocatalytic performance, with a H2O2 production rate of 10.2 mmol / h / g, which is 89.5 times that of the original C3N4.

[0008] The invention patent CN 114160165 A proposes a preparation method of a high-entropy alloy / NiIn2S4 composite catalyst. Compared with the prior art, the synthesis process is simple and easy to prepare in batches. The obtained composite material is a Z-type heterostructure, which improves the separation efficiency of photogenerated carriers and has a high catalytic efficiency for various antibiotics and organic pollutants in sewage.

[0009] The invention patent CN 11599642 A proposes a preparation method of a hammer coral-like Bi2S3 / Ni / g-C3N4 ternary composite catalyst. The presence of Bi2S3 provides an opportunity for the Ni metal to change its valence to promote the activation of PMS in the solution system to rapidly degrade organic pollutants. Moreover, due to the properties of porous and multi-active sites of this catalyst, its catalytic activity is greatly improved.

[0010] However, the solar light utilization rate and catalytic oxidation ability of the above-mentioned existing photocatalysts are not high. In addition, there is no report in the current prior art on the use of a medium-entropy alloy / Bi3O4Br / CNNs composite photocatalytic material for photocatalytic degradation of antibiotics. Summary of the Invention

[0011] The object of the present invention is to provide a preparation method of a medium-entropy alloy / Bi3O4Br / CNNs ternary composite material. The medium-entropy alloy / Bi3O4Br / CNNs composite material has excellent application effects in the photocatalytic efficient degradation of organic matter. It has high catalytic activity, a simple production process, strong stability, and is convenient for recycling and reuse. It meets the needs of industrial production and has great potential for industrial application in the field of semiconductor catalytic degradation.

[0012] The technical solution adopted by the present invention to solve its technical problems is:

[0013] A preparation method of a medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst, characterized by comprising the steps of:

[0014] S1. Weigh the metal sources and reducing agents of four metal ions, add them to solvent A, and stir well to dissolve to form a medium-entropy alloy precursor solution;

[0015] S2. Weigh and mix bismuth salt and bromine source solution, add sodium hydroxide solution, react at 150-180 °C for 6-12 h, and obtain Bi3O4Br nanosheets after post-treatment;

[0016] S3. Weigh and mix melamine, cyanuric acid and dicyandiamide, add them to solvent B, stir well to dissolve and perform ultrasonic treatment for 2-4 h, and then stir and evaporate to form a carbon nitride precursor. Pyrolyze the carbon nitride precursor and obtain CNNs nanosheets by heat treatment under a nitrogen atmosphere;

[0017] S4. Weigh the CNNs nanosheets and add them to the high-entropy alloy precursor solution prepared in S1. Perform reaction reduction using the oil bath reflux method. After completion, wash and dry to obtain the medium-entropy alloy / CNNs composite.

[0018] S5. Weigh the medium-entropy alloy / CNNs composite prepared in S4 and place it in a dispersant. Add the Bi3O4Br nanosheets prepared in S2 and perform ultrasonic compounding to obtain the medium-entropy alloy / Bi3O4Br / CNNs ternary heterostructure composite photocatalytic material.

[0019] As a further description of the above technical solution:

[0020] In the step S1, the metal sources are four of the hydrochlorides, nitrates, sulfates, and acetates of Co, Fe, Ni, and Cu, and the molar ratio of the four metal ions is 1:1:1:1, and the molar concentration of the total metal ions is 1 - 1000 mmol / L.

[0021] As a further description of the above technical solution:

[0022] In the step S1, the solvent is ethanol or ethylene glycol.

[0023] As a further description of the above technical solution:

[0024] In the step S2, the bismuth salt is an aqueous solution of 0.2 - 0.5 mol / L of one of the hydrochlorides and nitrates of Bi, and the bromine source is an aqueous solution of 0.2 - 0.5 mol / L of one of potassium bromide, sodium bromide, and dodecyltrimethylammonium bromide, and the molar ratio of the bismuth salt to the bromine source is 1:(1 - 2).

[0025] As a further description of the above technical solution:

[0026] In the step S3, the molar ratio of melamine, cyanuric acid, and dicyandiamide is 1:(1 - 2):(1 - 2).

[0027] As a further description of the above technical solution:

[0028] In the step S3, the temperature for pyrolyzing to obtain CNNs is 500 - 550 °C.

[0029] As a further description of the above technical solution:

[0030] In the step S3, the heat treatment time is 4 - 8 h.

[0031] As a further description of the above technical solution:

[0032] In the step S4, the temperature of the oil bath is 100 - 200 °C, and the reaction time is 2 - 4 h.

[0033] As a further description of the above technical solution:

[0034] In the step S5, the reaction temperature is 40 - 80 °C and the reaction time is 2 - 4 h.

[0035] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0036] 1. In the present invention, by using the method of oil bath reflux, a medium-entropy alloy with a narrow particle size range and uniform size can be prepared, and it has the advantages of fast synthesis speed and easy large-scale production;

[0037] 2. In the present invention, the medium-entropy alloy has a good LSPR effect and improves the catalytic activity of the composite material;

[0038] 3. In the present invention, by using synthesis methods such as ultrasonic waves, a tight Z-type heterojunction structure can be formed between Bi3O4Br and CNNs, which is beneficial to the separation of photo-generated carriers and improves the photocatalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic flow chart of an embodiment of the preparation method of the photocatalytic nanomaterial provided by the present invention;

[0040] Figure 2 Transmission electron microscope observation result diagram of the photocatalytic nanomaterial prepared in Example 1;

[0041] Figure 3 XRD diagram of the photocatalytic nanomaterial prepared in Example 1;

[0042] Figure 4 UV diffuse reflection spectrum diagram of the photocatalytic nanomaterial prepared in Example 1;

[0043] Figure 5 Performance diagram of visible light photocatalytic degradation of norfloxacin by the photocatalytic nanomaterial prepared in Example 1;

[0044] Figure 6 Performance diagram of photocatalytic cycle test of the photocatalytic nanomaterial prepared in Example 1. EMBODIMENTS

[0045] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention. EXAMPLES

[0046] S1. Weigh the precursor nickel chloride, copper chloride, cobalt chloride, and iron chloride according to the molar ratio of Ni:Cu:Co:Fe = 1:1:1:1, add them to the solvent ethylene glycol, and stir well to dissolve to form a medium-entropy alloy precursor solution.

[0047] S2. Weigh 1 mmol of bismuth nitrate and 1 mmol of sodium bromide solution and mix them. Add sodium hydroxide solution and react at 150 °C for 6 h. After post-treatment, Bi3O4Br nanosheets are obtained.

[0048] S3. Weigh 3.33 g of melamine, 3.33 g of cyanuric acid, and 3.33 g of dicyandiamide and mix them. Add them to the solvent ethanol, stir well to dissolve and ultrasonically treat for 4 h. Then stir and evaporate to form a carbon nitride precursor. Pyrolyze the carbon nitride precursor and perform heat treatment under a nitrogen atmosphere to obtain CNNs nanosheets.

[0049] S4. Weigh 200 mg of CNNs nanosheets and add them to the high-entropy alloy precursor solution prepared in S1. React and reduce them by the oil bath reflux method. After completion, wash and dry to obtain a medium-entropy alloy / CNNs composite.

[0050] S5. Weigh 0.08 g of the medium-entropy alloy / CNNs composite prepared in S4 and place it in absolute ethanol. Add 0.02 g of the Bi3O4Br nanosheets prepared in S2 and ultrasonically composite for 4 h to prepare a medium-entropy alloy / Bi3O4Br / CNNs ternary heterostructure composite photocatalytic material.

[0051] Perform a photocatalytic degradation performance test on the prepared medium-entropy alloy / Bi3O4Br / CNNs composite material. Example

[0052] S1. Weigh the precursor nickel sulfate, copper sulfate, cobalt sulfate, and iron sulfate according to the molar ratio of Ni:Cu:Co:Fe = 1:1:1:1, add them to the solvent ethanol, and stir well to dissolve to form a medium-entropy alloy precursor solution.

[0053] S2. Weigh 5 mmol of bismuth nitrate and 7 mmol of cetyltrimethylammonium bromide solution and mix them. Add sodium hydroxide solution and react at 180 °C for 12 h. After post-treatment, Bi3O4Br nanosheets are obtained.

[0054] S3. Weigh 3.33 g of melamine, 3.33 g of cyanuric acid, and 3.33 g of dicyandiamide and mix them. Add them to the solvent ethanol, stir well to dissolve and ultrasonically treat for 4 h. Then stir and evaporate to form a carbon nitride precursor. Pyrolyze the carbon nitride precursor and perform heat treatment under a nitrogen atmosphere to obtain CNNs nanosheets.

[0055] S4. Weigh 300 mg of CNNs nanosheets and add them to the high-entropy alloy precursor solution prepared in S1. React and reduce them by the oil bath reflux method. After completion, wash and dry to obtain the medium-entropy alloy / CNNs composite.

[0056] S5. Weigh 0.08 g of the medium-entropy alloy / CNNs composite prepared in S4 and place it in absolute ethanol. Then add 0.02 g of the Bi3O4Br nanosheets prepared in S2 and ultrasonically compound for 4 h to obtain the medium-entropy alloy / Bi3O4Br / CNNs ternary heterostructure composite photocatalytic material.

[0057] Perform a photocatalytic degradation performance test on the prepared medium-entropy alloy / Bi3O4Br / CNNs composite material. Example

[0058] S1. Weigh the precursor nickel sulfate, copper sulfate, cobalt chloride, and iron chloride according to the molar ratio of Ni:Cu:Co:Fe = 1:1:1:1, and add them to the solvent ethanol. Stir well to dissolve to form a medium-entropy alloy precursor solution.

[0059] S2. Weigh 3 mmol of bismuth nitrate and mix it with 4 mmol of cetyltrimethylammonium bromide solution. Add sodium hydroxide solution and react at 180 °C for 12 h. After post-treatment, obtain Bi3O4Br nanosheets.

[0060] S3. Weigh 3.33 g of melamine, 3.33 g of cyanuric acid, and 3.33 g of dicyandiamide and mix them. Add them to the solvent ethanol, stir well to dissolve and ultrasonically treat for 4 h. Then stir and evaporate to form a carbon nitride precursor. Pyrolyze the carbon nitride precursor and obtain CNNs nanosheets under a nitrogen atmosphere by heat treatment.

[0061] S4. Weigh 400 mg of CNNs nanosheets and add them to the high-entropy alloy precursor solution prepared in S1. React and reduce them by the oil bath reflux method. After completion, wash and dry to obtain the medium-entropy alloy / CNNs composite.

[0062] S5. Weigh 0.08 g of the medium-entropy alloy / CNNs composite prepared in S4 and place it in absolute ethanol. Then add 0.02 g of the Bi3O4Br nanosheets prepared in S2 and ultrasonically compound for 4 h to obtain the medium-entropy alloy / Bi3O4Br / CNNs ternary heterostructure composite photocatalytic material.

[0063] Perform a photocatalytic degradation performance test on the prepared medium-entropy alloy / Bi3O4Br / CNNs composite material.

[0064] Photodegradation performance test: The synthesized composite material was added to the sewage containing antibiotics. The dosage of the catalyst was 0.1 - 1 g / L. Using a 300 W xenon lamp as the light source, the ultraviolet part was filtered out with a filter, and the light source used was visible light with a wavelength greater than 420 nm. During use, the catalyst concentration can be adjusted according to specific circumstances.

[0065] The initial concentration of antibiotics was 5 - 50 mg / L.

[0066] After the reaction, the degradation rate was calculated as follows:

[0067] Degradation rate = [(C0 - C t ) / C0] * 100%

[0068] where C0 was the initial concentration of the organic dye, and C t was the concentration of antibiotics measured after the reaction, and the units were both mg / L.

[0069] Note: For the photodegradation performance tests of Comparative Examples 1, 2, and 3, the synthesized composite material catalyst was not added to the solution to be degraded, and other conditions were the same as those of the photodegradation performance tests of Examples 1, 2, and 3.

Claims

1. A preparation method of a NiCuCoFe medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst, characterized in that, Including the steps: S1. Weigh the metal sources of four metal ions and a reducing agent, add them to solvent A, and stir well to dissolve to form a NiCuCoFe medium-entropy alloy precursor solution; S2. Weigh a bismuth salt and a bromine source solution, mix them, add a sodium hydroxide solution, react at 150 - 180 °C for 6 - 12 h, and obtain Bi3O4Br nanosheets after post-treatment; S3. Weigh melamine, cyanuric acid, and dicyandiamide, mix them, add them to solvent B, stir well to dissolve and perform ultrasonic treatment for 2 - 4 h, then stir and evaporate to form a carbon nitride precursor, and pyrolyze the carbon nitride precursor. Under a nitrogen atmosphere, heat-treat to obtain CNNs nanosheets; S4. Weigh the CNNs nanosheets, add them to the NiCuCoFe high-entropy alloy precursor solution prepared in S1, and perform reaction reduction using an oil bath reflux method. After completion, wash and dry to obtain a NiCuCoFe medium-entropy alloy / CNNs composite; S5. Weigh the NiCuCoFe medium-entropy alloy / CNNs composite prepared in S4, place it in a dispersant, and add the Bi3O4Br nanosheets prepared in S2, and perform ultrasonic compounding to prepare a NiCuCoFe medium-entropy alloy / Bi3O4Br / CNNs ternary heterostructure composite photocatalytic material.

2. The preparation method of a NiCuCoFe medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst according to claim 1, characterized in that, In the step S1, the metal sources are four of the hydrochlorides, nitrates, sulfates, and acetates of Co, Fe, Ni, and Cu, and the molar ratio of the four metal ions is 1:1:1:1, and the molar concentration of the total metal ions is 1 - 1000 mmol / L.

3. The preparation method of a NiCuCoFe medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst according to claim 1, characterized in that, In the step S1, the solvent is ethanol or ethylene glycol.

4. The preparation method of a NiCuCoFe medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst according to claim 1, characterized in that, In the step S2, the bismuth salt is one of the hydrochlorides and nitrates of Bi, the bismuth salt solution is an aqueous solution with a concentration of 0.2 - 0.5 mol / L; the bromine source is one of potassium bromide, sodium bromide, and dodecyltrimethylammonium bromide, the bromine source solution is an aqueous solution with a concentration of 0.2 - 0.5 mol / L, and the molar ratio of the bismuth salt to the bromine source is 1:(1 - 2).

5. The preparation method of a NiCuCoFe medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst according to claim 1, characterized in that In the step S3, the molar ratio of melamine, cyanuric acid, and dicyandiamide is 1:(1 - 2):(1 - 2).

6. The preparation method of a NiCuCoFe medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst according to claim 1, wherein, In the step S3, the temperature for pyrolyzing to obtain CNNs is 500 - 550 °C.

7. A preparation method of a NiCuCoFe medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst according to claim 1, characterized in that, In the step S3, the heat-treatment time is 4 - 8 h.

8. A preparation method of a NiCuCoFe medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst according to claim 1, characterized in that, In the step S4, the temperature of the oil bath is 100 - 200 °C, and the reaction time is 2 - 4 h.

9. The preparation method of a NiCuCoFe medium-entropy alloy / Bi3O4Br / CNNs composite photocatalyst according to claim 1, characterized in that, In the step S5, the reaction temperature is 40 - 80 °C, and the reaction time is 2 - 4 h.

10. Use of any one of the photocatalytic materials according to claims 1 - 9 in the field of photocatalysis.

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