Preparation method and application of in-situ hydrogen peroxide production photo-fenton catalytic material

Abstract

The application discloses a preparation method of a photo-Fenton catalytic material for in-situ production of hydrogen peroxide and application thereof, and comprises the following steps: after urea and water are stirred and mixed, the mixture is transferred into a ceramic crucible with a cover, high-temperature calcination is carried out, and cooling is performed to room temperature to obtain a light yellow powder of gas shock exfoliated ultrathin g-C3N4-NPs; the obtained light yellow powder of ultrathin g-C3N4-NPs is added into a N,N-dimethylformamide (DMF) solvent, magnetic stirring is performed, and mixing is uniform to obtain a uniformly dispersed mixed solution; (NH4)2MoS4 is added into the mixed solution, mixing and stirring are uniform, the mixture is transferred into a polytetrafluoroethylene reaction kettle, high-temperature hydrothermal treatment is performed, and cooling is performed to room temperature to obtain a composite MoS2 / g-C3N4-NPs catalyst powder. The MoS2 / g-C3N4-NPs composite material provided by the application has a simple and convenient preparation process, high photo-Fenton catalytic activity, and can produce hydrogen peroxide in-situ.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic water treatment technology, specifically to a method for preparing a photo-Fenton catalytic material for in-situ hydrogen peroxide production and its application. Background Technology

[0002] Hydrogen peroxide (H2O2), as a good reducing oxidant, can non-selectively oxidize organic pollutants into H2O and CO2, with the only products being H2O and O2. Currently, the main synthesis processes for H2O2 include the anthraquinone method, the direct hydrogen-oxygen conversion method, and the electrochemical method. The anthraquinone method is complex and consumes large amounts of organic solvents and energy, and is also prone to contamination by organic solvents during H2O2 purification. The direct hydrogen-oxygen conversion method suffers from potential explosion risks due to hydrogen-oxygen contact and low hydrogen utilization. The electrochemical method mainly involves the electrolysis of sulfuric acid or sulfates. The corresponding molar amount of persulfate or persulfate generated at the cathode of the electrolytic cell is used to hydrolyze the cathode products to obtain H2O2 and the initial electrolyzed salt; however, to obtain pure H2O2, further separation and purification of the mixed products are required, resulting in high energy consumption. Therefore, developing safe, energy-saving, and environmentally friendly H2O2 synthesis technologies is of great significance.

[0003] Photocatalysis can convert H2O and O2 into H2O2 under mild reaction conditions, representing a potentially safe, green, and sustainable route for the synthesis of hydrogen peroxide. The principle involves electrons that transition to the semiconductor surface under photoexcitation, reacting with O2 and H2O adsorbed on the surface. + The reaction produces H2O2, and the corresponding holes (not recombine) react with H2O to generate... • Therefore, the conduction band (CB) and valence band (VB) positions of the photocatalyst intrinsically affect the generation of H2O2. Providing photocatalytic materials that thermodynamically meet the potential requirements for H2O oxidation (1.23 eV) and O2 reduction (-0.33 V) is a key focus of development and research. Currently, photocatalytic materials used for H2O2 synthesis mainly include metallic or non-metallic semiconductors such as TiO2, CdS, ZnO, and g-C3N4.

[0004] Chinese patent application number 202111001253 discloses a method for preparing CdS nanoribbons for H2O2 production. This patent directly obtains uniform CdS nanoribbons via a solvothermal method using an alkaline organic solvent. The change in the intrinsic band structure of the material induced by the alkalization of the CdS nanoribbons improves the H2O2 production efficiency. However, CdS is significantly toxic to bacterial cells; even at concentrations of only μM or nM in the environment, it can significantly inhibit or even kill tested bacterial cells. Therefore, the environmental toxicity of the CdS nanoribbon-based photocatalytic material described in this patent limits its large-scale application.

[0005] Chinese patent application number 202211328413 discloses a method for preparing potassium thiocyanate (KSCN)-modified carbon nitride and its application in photocatalytic H2O2 production. This patent relates to a method of hydrothermally reacting dicyandiamine or melamine with potassium thiocyanate, cooling and drying the resulting white solid, and then calcining it upon cooling to obtain K2O2. + The patent describes a carbon nitride modified with cyano-CN co-doping. While the KSCN-modified carbon nitride synthesized in this patent can improve the application of photocatalytic H2O2 production, the specific chemical structure changes of the nitrogen-containing organic substrate during the hydrothermal reaction are difficult to control, resulting in unclear modification results in the catalyst material itself. In addition, the secondary catalyst substrate is an inorganic non-metallic structure with low density, making it prone to water loss and hindering solid-liquid separation in the later stages.

[0006] Existing research indicates that graphitic carbon nitride (g-C3N4), with its readily available raw materials and simple preparation method, has attracted considerable attention due to its unique Miller amine structure. In oxygen reduction reactions, g-C3N4 catalyzes the formation of peroxide intermediates from O2, facilitating the reduction of O2 molecules to H2O2 via a two-electron pathway. However, pure bulk g-C3N4 suffers from rapid recombination of photogenerated electrons and holes, and difficulty in O2 adsorption on its surface. Therefore, modification is needed to further improve its two-electron redox and photogenerated charge separation performance. Constructing heterojunctions is an effective means to address the narrow light absorption range and easy recombination of photogenerated charges in g-C3N4. g-C3N4 composite metal oxides are also a novel type of photo-Fenton catalytic material. Therefore, further exploring the practical application of g-C3N4-based composite materials in the photo-Fenton catalytic degradation of organic matter is of great significance for fully tapping the greater application potential of g-C3N4 in the field of photocatalysis. Summary of the Invention

[0007] Technical problem solved: In view of the problem that photogenerated electrons and holes are easily recombine in the photocatalysis process of non-metallic semiconductor g-C3N4 materials in the prior art, the present invention provides a method for preparing photo-Fenton catalytic materials for in-situ hydrogen peroxide production and its application.

[0008] Technical solution: A method for preparing a photo-Fenton catalytic material for in-situ hydrogen peroxide production, comprising the following steps:

[0009] Step 1: Stir and mix urea and water, transfer the mixture into a covered ceramic crucible, calcine it at high temperature in a muffle furnace and keep it at that temperature for 4 hours, then cool it to room temperature to obtain a pale yellow powder of ultrathin g-C3N4-NPs.

[0010] Step 2: Add the ultrathin g-C3N4-NPs pale yellow powder obtained in Step 1 to N,N-dimethylformamide DMF solvent, and mix evenly by magnetic stirring at 400 r / min for 30 min to obtain a uniformly dispersed mixture.

[0011] Step 3: Add (NH4)2MoS4 to the mixture in Step 2, stir at 200 r / min for 30 min, and after mixing evenly, transfer to a polytetrafluoroethylene reactor, perform high-temperature hydrothermal treatment, cool to room temperature, centrifuge, wash with water, and dry to obtain composite MoS2 / g-C3N4-NPs catalyst powder.

[0012] As a preferred embodiment of the present invention: the molar ratio of urea and water in step 1 is in the range of 1:0.5 to 1:1.5; the heating rate in the high-temperature calcination step is in the range of 5 to 10 °C / min, and the temperature range is 450 to 550 °C.

[0013] As a preferred embodiment of the present invention, the solid-liquid ratio of g-C3N4-NPs to solvent DMF in step 2 is 0.5 g: 40 mL.

[0014] As a preferred embodiment of the present invention: the solid-liquid ratio of (NH4)2MoS4 to the mixed solution in step 3 is in the range of 0.04 g : 40 mL to 0.16 g : 140 mL; the temperature range in the high-temperature hydrothermal step is 150~200 ℃, and the holding time is 8~12 h.

[0015] This application also discloses the application of the photo-Fenton catalytic material prepared by the in-situ hydrogen peroxide production method described above in the catalytic degradation of dye-containing wastewater under visible light and the evaluation of photo-Fenton catalytic performance. The composite material of MoS2 / g-C3N4-NPs, which is formed by the intercalation of a large number of interwoven sheet-like monomers, is composed of a large number of interwoven sheet-like monomers.

[0016] As a preferred embodiment of the present invention: the degradation of dye-containing wastewater is one or more of Rhodamine B, methylene blue, methyl orange, and acid red, and the application of the photo-Fenton catalytic performance evaluation specifically includes the following steps:

[0017] 1) Mix MoS2 / g-C3N4-NPs powder with an aqueous solution containing dye, and stir for 30 min in a temperature-controlled magnetic stirrer at 25 °C under dark conditions to obtain a mixed solution;

[0018] 2) Place the mixture in a simulated visible light device, add persulfate to the mixture, and after the reaction, draw up the sample with a syringe, filter it through a 0.45 μm filter membrane, and then perform subsequent detection and analysis.

[0019] As a preferred embodiment of the present invention: the amount of persulfate used in step 2) is 1.0-2.0 mM, and the amount of catalyst MoS2 / g-C3N4-NPs is 0.1-0.8 g / L.

[0020] This application also discloses the application of the MoS2 / g-C3N4-NPs composite material prepared by the in-situ photo-Fenton catalytic material preparation method for hydrogen peroxide production in situ under visible light conditions.

[0021] As a preferred embodiment of the present invention, the in-situ generation and concentration detection of hydrogen peroxide includes the following steps:

[0022] 1) Add 0.05 g of MoS2 / g-C3N4-NPs catalyst to an Erlenmeyer flask containing 100 mL of deionized water. Simultaneously turn on the magnetic stirrer and the visible light emission source (xenon lamp, λ>420 nm). After 15 min, take a sample, filter it, and use the supernatant as the test solution. Add pH 6.0 buffer solution to the test solution and mix well.

[0023] 2) Quickly add N,N-dimethyl-p-phenylenediamine solution and horseradish peroxidase solution to the mixture in step 1) above, mix well, and detect the absorbance at a wavelength of 551 nm within 40±5 s. The detection time should be consistent for each sample.

[0024] As a preferred embodiment of the present invention: the concentration of the N,N-dimethyl-p-phenylenediamine solution in step 2) is 0.1 g / 10 mL, and the concentration of horseradish peroxidase is 0.01 g / 10 mL.

[0025] Explanation of principle: The photo-Fenton MoS2 / g-C3N4-NPs catalyst material used in this invention has a flower-shaped morphology, a wide light absorption range, and high light energy utilization. The construction of heterojunction can promote the effective separation of photogenerated electrons and holes, and improve the efficiency of photocatalytic H2O2 production; at the same time, it exhibits excellent degradation efficiency of dye molecules.

[0026] Compared with the prior art, this application has the following advantages:

[0027] 1. The preparation process of the flower-shaped MoS2 / g-C3N4-NPs photo-Fenton catalytic material of the present invention is simple, the raw materials are readily available, the cost is low, and the reproducibility is strong;

[0028] 2. The ultrathin g-C3N4 prepared by the gas shock method has abundant defect structures, which can provide active sites for O2 adsorption;

[0029] 3. The heterostructure formed by MoS2 and g-C3N4 broadens the light absorption range of g-C3N4-based catalytic materials and effectively promotes the separation of photogenerated electron and hole pairs;

[0030] 4. The composite MoS2 / g-C3N4-NPs obtained in this invention exhibit excellent photocatalytic oxidation performance of organic dyes. Within 30 minutes, the removal rate of simulated wastewater containing Rhodamine B dye is increased by nearly 40% compared to unmodified carbon nitride.

[0031] 5. The composite MoS2 / g-C3N4-NPs material obtained by this invention has an H2O2 yield greater than 3000 μM / (h*g) under the premise that no gas is introduced during the reaction process, which is more than 6 times that of unmodified carbon nitride. Attached Figure Description

[0032] Figure 1 This is a scanning electron microscope (SEM) image of the MoS2 / g-C3N4-NPs described in this invention.

[0033] Figure 2 This is an EDS distribution diagram of each element in MoS2 / g-C3N4-NPs described in this invention; the upper left is the EDS distribution diagram of element N, the upper right is the EDS distribution diagram of element C, the lower left is the EDS distribution diagram of element Mo, and the lower right is the EDS distribution diagram of element S.

[0034] Figure 3 The images show the full electronic spectrum XPS diagram of MoS2 / g-C3N4-NPs and the elemental 3d and S 2p orbitals of the present invention. The upper left is the full electronic spectrum of MoS2 / g-C3N4-NPs, the upper right is the electronic spectrum of the Mo 3d orbital, and the lower part is the electronic spectrum of the S 3p orbital.

[0035] Figure 4 The EPR spectrum of the MoS2 / g-C3N4-NPs solid described in this invention;

[0036] Figure 5 The UV-vis-DRS diagram of the MoS2 / g-C3N4-NPs solid described in this invention;

[0037] Figure 6 The graphs show the removal effects of different catalysts on Rhodamine B described in this invention; wherein, The figures show the relationship between visible light-activated persulfate removal of Rhodamine B and time for catalysts in unmodified carbon nitride, 1, 2, 3, and 4 at a dosage of 0.5 g / L.

[0038] Figure 7 This is a graph showing the concentration of H2O2 produced by the catalyst described in Examples 1, 2, 3 and 4 of the present invention in a pure water system under visible light irradiation. Detailed Implementation

[0039] The invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] Example 1: A method for preparing a MoS2 / g-C3N4-NP photo-Fenton catalytic material for in-situ H2O2 production, comprising the following steps:

[0041] 1) Mix urea and water at a molar ratio of 1:0.5, transfer the mixture into a covered ceramic crucible, and calcine it in a muffle furnace at a heating rate of 5 °C / min to 550 °C. Hold the temperature for 4 h and then cool to room temperature to obtain a pale yellow powder of ultrathin g-C3N4-NPs.

[0042] 2) Add the ultrathin g-C3N4-NPs pale yellow powder obtained in step 1) to DMF solvent, stir magnetically and mix evenly to obtain a uniformly dispersed mixture; wherein, the solid-liquid ratio of g-C3N4-NPs powder to DMF solution is 0.5 g : 40 mL;

[0043] 3) Add (NH4)2MoS4 powder to the dispersion mixture in step 2), mix and stir evenly, transfer to a polytetrafluoroethylene reactor, and perform a high-temperature closed hydrothermal reaction at 150°C for 8 hours. After cooling to room temperature, the product is centrifuged, washed with water and dried to obtain the MoS2 / g-C3N4-NPs composite catalyst powder; wherein, the solid-liquid ratio of (NH4)2MoS4 powder to the mixture is 0.04 g:40 mL.

[0044] The catalytic material prepared above was characterized by scanning electron microscopy and EDS elemental analysis. Figure 1 It can be seen that the catalyst after hydrothermal reaction exhibits a wrinkled monomer structure with particulate nanomonomers loaded on its surface; from Figure 2 It can be seen that the four elements C, N, Mo and S are evenly distributed in the bulk phase.

[0045] Example 2, a method for preparing a MoS2 / g-C3N4-NP photo-Fenton catalytic material for in-situ H2O2 production, comprising the following steps:

[0046] 1) Mix urea and water in a molar ratio of 1:1, transfer the mixture into a covered ceramic crucible, and calcine it in a muffle furnace at a heating rate of 10 °C / min to 500 °C. Hold the temperature for 4 hours and then cool to room temperature to obtain a pale yellow powder of ultrathin g-C3N4-NPs.

[0047] 2) Add the ultrathin g-C3N4-NPs pale yellow powder obtained in step 1) to DMF solvent, stir magnetically and mix evenly to obtain a uniformly dispersed mixture; wherein, the solid-liquid ratio of g-C3N4-NPs powder to DMF solution is 0.5g:40mL;

[0048] 3) Add (NH4)2MoS4 powder to the mixture in step 2), mix and stir evenly, transfer to a polytetrafluoroethylene reactor, and perform a high-temperature closed hydrothermal reaction at 180°C for 10 hours. After cooling to room temperature, the product is centrifuged, washed with water and dried to obtain the MoS2 / g-C3N4-NPs composite catalyst powder; wherein, the solid-liquid ratio of (NH4)2MoS4 powder to the mixture is 0.08g:40mL.

[0049] The catalytic material prepared above was characterized by XPS, and the full XPS spectrum of the material is as follows: Figure 3-1 As shown; Figure 3-2 The peaks on the Mo 3d orbital near 232.2 eV and 229.0 eV are characteristic peaks of the 2H phase of MoS2, while the peaks at 231.4 eV and 228.1 eV are characteristic peaks of the 1T phase of MoS2. Figure 3-3 The binding energy peak at 159.9 eV in the S 2p orbital is a characteristic peak of the terminal unsaturated S atom in MoS2, while the binding energy peak near 158.5 eV is a characteristic peak of the unsaturated planar S atom. Combined with XPS spectra and peak analysis, it can be seen that the synthesized MoS2 / g-C3N4-NPs catalytic material exhibits a two-phase structure of 2H and 1T in MoS2.

[0050] Example 3, a method for preparing a MoS2 / g-C3N4-NP photo-Fenton catalyst for in-situ H2O2 production, comprising the following steps:

[0051] 1) Mix urea and water at a molar ratio of 1:1.5, transfer the mixture into a covered ceramic crucible, and calcine it in a muffle furnace at a heating rate of 10℃ / min to 450℃. Hold the temperature for 4 hours and cool to room temperature to obtain a pale yellow powder of ultrathin g-C3N4-NPs.

[0052] 2) Add the ultrathin g-C3N4-NPs pale yellow powder obtained in step 1) to DMF solvent, stir magnetically and mix evenly to obtain a uniformly dispersed mixture; wherein, the solid-liquid ratio of g-C3N4-NPs powder to DMF solution is 0.5 g : 40 mL;

[0053] 3) Add (NH4)2MoS4 powder to the mixture in step 2), mix and stir evenly, transfer to a polytetrafluoroethylene reactor, and perform a high-temperature closed hydrothermal reaction at 200°C for 12 hours. After cooling to room temperature, the product is centrifuged, washed with water and dried to obtain the MoS2 / g-C3N4-NPs composite catalyst powder; wherein, the solid-liquid ratio of (NH4)2MoS4 powder to the mixture is 0.012g:40mL.

[0054] The catalytic material prepared above was characterized by solid-state EPR. Figure 4 It can be seen that the catalytic materials in Examples 1, 2 and 3 all have strong signals under magnetic field conditions, indicating that there are unpaired electrons on the catalyst surface. These electrons can participate in the photo-Fenton catalytic reaction to achieve photodegradation of dye-containing organic matter.

[0055] Example 4: A method for preparing a MoS2 / g-C3N4-NP photo-Fenton catalytic material for in-situ H2O2 production, comprising the following steps:

[0056] 1) Mix urea and water in a molar ratio of 1:1, transfer the mixture into a covered ceramic crucible, and calcine it in a muffle furnace at a heating rate of 10℃ / min to 550℃. Hold the temperature for 4 h and cool to room temperature to obtain a pale yellow powder of ultrathin g-C3N4-NPs.

[0057] 2) Add the ultrathin g-C3N4-NPs pale yellow powder obtained in step 1) to DMF solvent, stir magnetically and mix evenly to obtain a uniformly dispersed mixture; wherein, the solid-liquid ratio of g-C3N4-NPs powder to DMF solution is 0.5 g: 40 mL;

[0058] 3) Add (NH4)2MoS4 powder to the mixture in step 2), mix and stir evenly, transfer to a polytetrafluoroethylene reactor, and perform a high-temperature closed hydrothermal reaction at 200℃ for 12 h. After cooling to room temperature, the product is centrifuged, washed with water and dried to obtain the MoS2 / g-C3N4-NPs composite catalyst powder; wherein the solid-liquid ratio of (NH4)2MoS4 powder to the mixture is 0.016 g:40 mL.

[0059] The catalytic material prepared above was characterized by UV-vis-DRS. Figure 5 The image shows the solid UV-Vis diffuse reflectance of the catalyst, and calculations show that the band gap of the catalyst material is 2.64 eV.

[0060] Example 5, a method for preparing a MoS2 / g-C3N4-NP photo-Fenton catalytic material for in-situ H2O2 production, comprising the following steps:

[0061] 1) Mix urea and water in a molar ratio of 1:1, transfer the mixture into a covered ceramic crucible, and calcine it in a muffle furnace at a heating rate of 10℃ / min to 550℃. Hold the temperature for 4 hours and then cool it to room temperature to obtain a pale yellow powder of ultrathin g-C3N4-NPs.

[0062] 2) Add the ultrathin g-C3N4-NPs pale yellow powder obtained in step 1) to DMF solvent, stir magnetically and mix evenly to obtain a uniformly dispersed mixture; wherein, the solid-liquid ratio of g-C3N4-NPs powder to DMF solution is 0.5g:40mL;

[0063] 3) Add (NH4)2MoS4 powder to the mixture in step 2), mix and stir evenly, transfer to a polytetrafluoroethylene reactor, and perform a high-temperature closed hydrothermal reaction at 200°C for 12 hours. After cooling to room temperature, the product is centrifuged, washed with water and dried to obtain the MoS2 / g-C3N4-NPs composite catalyst powder; wherein, the solid-liquid ratio of (NH4)2MoS4 powder to the mixture is 0.012g:40mL.

[0064] Prepare 100 mL of a 10 mg / L Rh B solution in an Erlenmeyer flask. Add 0.05 g of the catalyst material prepared in step 3) above to the Erlenmeyer flask. Place the flask in a temperature-controlled magnetic stirrer at 25°C and stir for 30 min to reach adsorption equilibrium. Place the Erlenmeyer flask containing the mixture in a visible light emitting device, add 1.5 mM persulfate, and start the photo-Fenton catalytic reaction. At fixed time intervals, use a syringe to draw 2 mL of sample, filter through a 0.45 μm filter membrane, and determine the Rh B concentration at different sampling times using a UV-Vis spectrophotometer. Figure 6 As can be seen from the above, the photo-Fenton catalyst MoS2 / g-C3N4-NPs in Examples 1, 2, 3 and 4 all have good degradation effects on pollutant Rh B. The catalysts in Examples 2, 3 and 4 achieved a pollutant removal rate of over 80% within 45 min.

[0065] Example 6, a method for preparing a MoS2 / g-C3N4-NP photo-Fenton catalytic material for in-situ H2O2 production, comprising the following steps:

[0066] 1) Mix urea and water in a molar ratio of 1:1, transfer the mixture into a covered ceramic crucible, and calcine it in a muffle furnace at a heating rate of 10℃ / min to 550℃. Hold the temperature for 4 hours and then cool it to room temperature to obtain a pale yellow powder of ultrathin g-C3N4-NPs.

[0067] 2) Add the ultrathin g-C3N4-NPs pale yellow powder obtained in step 1) to DMF solvent, stir magnetically and mix evenly to obtain a uniformly dispersed mixture; wherein, the solid-liquid ratio of g-C3N4-NPs powder to DMF solution is 0.5g:40mL;

[0068] 3) Add (NH4)2MoS4 powder to the dispersion mixture in step 2), mix and stir evenly, transfer to a polytetrafluoroethylene reactor, and perform a high-temperature closed hydrothermal reaction at 200°C for 12 hours. After cooling to room temperature, the product is centrifuged, washed with water and dried to obtain the MoS2 / g-C3N4-NPs composite catalyst powder; wherein, the solid-liquid ratio of (NH4)2MoS4 powder to the mixture is 0.012g:40mL.

[0069] Add 0.05 g of the MoS2 / g-C3N4-NPs catalyst material prepared in Examples 1, 2, 3, and 4 above to 100 mL of an aqueous solution containing 10% EtOH (by volume). After ultrasonic dispersion for 10 min, turn on the light source (xenon lamp, λ > 420 nm). After 60 minutes, take a sample, filter, and use the supernatant as the test solution. Add a pH 6 buffer solution to the test solution, mix well, and then quickly add 0.1 g / 10 mL of N,N-dimethyl-p-phenylenediamine solution and 0.01 g / 10 mL of horseradish peroxidase solution. Shake well, and detect the absorbance at a wavelength of 551 nm within 40 ± 5 s. Record the data and convert it to the corresponding concentration. Figure 7 It can be seen that the MoS2 / g-C3N4-NPs synthesized in this invention can accumulate 3×10⁻⁶ units within 60 min. -3 H2O2 at approximately mM / g.

[0070] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that those skilled in the art can make improvements and modifications to the present invention without departing from the principle of the invention, and these improvements and modifications are also within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a photo-Fenton catalytic material for in-situ hydrogen peroxide production, characterized in that, The method comprises the following steps: Step 1, urea and water are stirred and mixed, the mixed solution is moved into a ceramic crucible with a cover, high-temperature calcination and heat preservation for 4 h in a muffle furnace, and cooling to room temperature to obtain a light yellow powder of ultra-thin g-C3N4-NPs; the molar ratio of urea to water ranges from 1:0.5 to 1:1.5; the temperature rising speed in the high-temperature calcination step ranges from 5 to 10 ℃ / min, and the temperature ranges from 450 to 550 ℃; Step 2, the light yellow powder of ultra-thin g-C3N4-NPs obtained in step 1 is added into a N,N-dimethylformamide (DMF) solvent, and is uniformly mixed by magnetic stirring at 400 r / min for 30 min to obtain a uniformly dispersed mixed solution; Step 3, (NH4)2MoS4 is added into the mixed solution in step 2, and is stirred at 200 r / min for 30 min, and then is transferred into a polytetrafluoroethylene reaction kettle for high-temperature hydrothermal treatment, and is cooled to room temperature, and the product is centrifuged, washed with water and dried to obtain a MoS2 / g-C3N4-NPs composite catalyst powder; the solid-liquid ratio of (NH4)2MoS4 to the mixed solution ranges from 0.04 g:40 mL to 0.16 g:140 mL; the temperature in the high-temperature hydrothermal step ranges from 150 to 200 ℃, and the heat preservation time is 8-12 h.

2. The method for preparing the photo-Fenton catalytic material for in-situ hydrogen peroxide production according to claim 1, characterized in that, The solid-liquid ratio of g-C3N4-NPs to the solvent DMF in step 2 is 0.5 g:40 mL.

3. Application of the MoS2 / g-C3N4-NPs composite material with an independent and complete flower ball structure formed by a large number of interlaced sheet monomers in the preparation method of the in-situ hydrogen peroxide-producing photo-Fenton catalytic material in claim 1 in visible light catalytic degradation of dye-containing wastewater and photo-Fenton catalytic performance evaluation.

4. Use according to claim 3, characterized in that, The dye-containing wastewater is one or more of rhodamine B, methylene blue, methyl orange and acid red, and the application of the photo-Fenton catalytic performance evaluation specifically comprises the following steps: 1) mixing MoS2 / g-C3N4-NPs powder with a dye-containing aqueous solution, stirring in a temperature-controlled magnetic stirring device at 25 ℃ under dark conditions for 30 min to obtain a mixed solution; 2) placing the mixed solution in a simulated visible light device, adding persulfate to the mixed solution, and after reaction, using a syringe to suck the sample, filtering through a 0.45 μm filter membrane, and then performing subsequent detection and analysis.

5. Use according to claim 4, characterized in that, The amount of persulfate in step 2) is 1.0-2.0 mM, and the amount of catalyst MoS2 / g-C3N4-NPs is 0.1-0.8 g / L.

6. Application of the MoS2 / g-C3N4-NPs composite material in the preparation method of the in-situ hydrogen peroxide-producing photo-Fenton catalytic material in claim 1 in in-situ production of hydrogen peroxide under visible light.

7. Use according to claim 6, characterized in that, The in-situ production of hydrogen peroxide and concentration detection comprises the following steps: 1) MoS2 / g-C3N4-NPs catalytic material 0.05 g was added to a conical flask containing 100 mL of deionized water, and a magnetic stirrer and a visible light emitting source xenon lamp with λ>420 nm were turned on. After 15 min, the sample was taken, filtered, and the supernatant was taken as the test solution. The test solution was mixed with pH 6.0 buffer solution; 2) N,N-dimethyl-p-phenylenediamine solution and horseradish peroxidase solution were quickly added to the mixture in step 1) above, mixed uniformly, and the absorbance was detected at a wavelength of 551 nm within 40±5 s. The detection time of each sample was kept consistent.

8. Use according to claim 7, characterized in that, The concentration of the N,N-dimethyl-p-phenylenediamine solution in step 2) was 0.1 g / 10 mL, and the concentration of the horseradish peroxidase was 0.01 g / 10 mL.

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