Preparation method and application of a bifunctional iron POM modified carbon-based material

Abstract

This invention discloses a method for preparing and applying bifunctional iron-POM-modified carbon-based materials, comprising: Step 1: preparation of graphitic carbon nitride; Step 2: preparation of carbon-encapsulated nickel oxide particles; Step 3: preparation of graphitic carbon nitride nanosheets supported on carbon-encapsulated nickel oxide particles; Step 4: preparation of bifunctional iron-POM-modified carbon-based materials. This invention employs an electrostatic self-assembly method to co-modify carbon-encapsulated nickel oxide particles and Fe polynuclear metal oxometalates onto the surface of graphitic carbon nitride, preparing a Fe-POM / LB-CN photocatalyst. Under simulated visible light irradiation, it can achieve in-situ production of H2O2, with the H2O2 yield reaching a certain level after 60 minutes of photocatalytic reaction. The iron sites in Fe-POM can effectively activate the decomposition of H2O2 to produce •OH. The Fe-POM / LB-CN photocatalytic system can completely degrade imidacloprid within 15 minutes, with a mineralization rate as high as 63.5%.

Description

Technical Field

[0001] This invention relates to the field of preparation of bifunctional iron POM-modified carbon-based materials, and particularly to a method for preparing and applying bifunctional iron POM-modified carbon-based materials. Background Technology

[0002] Imidacloprid (IMD) is a neonicotinoid pesticide widely used in current agricultural production. Due to long-term and unscientific use, it has accumulated in the environment, leading to residual pollution problems in soil and water bodies. Therefore, in-depth and systematic research on the remediation of this pesticide pollution in the environment is of great significance. Against this backdrop, there is an urgent need to explore efficient and economically feasible water purification technologies. Advanced oxidation processes (AOPs) generate highly reactive oxygen species (ROS), such as hydroxyl radicals (•OH) and sulfate radicals (•SO4). - ( ), showing great potential in eliminating these stubborn pollutants. Among various AOPs, the photo-Fenton reaction system based on photocatalyst-activated hydrogen peroxide (H2O2) to generate powerful ROS requires only inexhaustible oxygen and water as raw materials and renewable solar energy as energy. It can meet the needs of on-demand production and realize in-situ application, and is becoming the most promising sustainable water treatment technology.

[0003] However, existing photocatalytic generation and activation of H2O2 to degrade pollutants has several limitations that restrict its application:

[0004] First, insufficient light absorption efficiency, electron-hole recombination problems, and scarcity of active sites hinder the effective utilization of photogenerated carriers, thereby limiting the overall reaction efficiency.

[0005] Secondly, due to the low oxygen reduction reaction (ORR) and water oxidation reaction (WOR) capabilities, oxygen ventilation and the addition of sacrificial agents are usually required to assist in the generation of H2O2, which increases the implementation cost of this technology.

[0006] In addition, the insufficient production of •OH and the low selectivity of H2O2 to •OH conversion during Fenton catalysis result in the need for large amounts of chemical input and the generation of undesirable byproducts.

[0007] To this end, efforts are being made to develop high-performance photocatalysts and rational design strategies, aiming to enhance the generation and activation of H2O2, promote carrier separation, and broaden the light capture range.

[0008] Among the various photocatalysts studied, graphitic carbon nitride (g-C3N4) has become a promising candidate material for photocatalysts due to its excellent stability, tunable electronic structure, and convenient preparation process.

[0009] However, pristine g-C3N4 suffers from slow exciton dissociation and photogenerated carrier recombination, severely limiting its photocatalytic efficiency. To further improve the photocatalytic generation and activation efficiency of H2O2, an effective strategy is to deposit catalytically active species with single / bimetallic sites (such as polynuclear metal-oxygen clusters, single metal oxides, or their composite systems) onto the photocatalyst surface. These species can reduce the energy barrier of key intermediates, promote product desorption, and induce directional charge migration, thereby enhancing the generation and activation capacity of H2O2.

[0010] Therefore, in order to solve the problems of low selectivity in H2O2 generation and poor activation ability of existing H2O2, developing a high-performance photocatalyst (bifunctional iron POM modified carbon-based material) preparation method and exploring its application is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0011] In view of this, the present invention provides a method for preparing bifunctional iron POM-modified carbon-based materials and their applications.

[0012] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0013] A method for preparing bifunctional iron POM-modified carbon-based materials includes the following steps:

[0014] Step 1: Preparation of graphitic carbon nitride

[0015] The mixture of urea and melamine was spread evenly on the bottom of a quartz boat, tightly wrapped with tin foil, and then placed in a muffle furnace for calcination.

[0016] The powder obtained above was ground and placed in a quartz boat, wrapped with tin foil and punched with multiple small holes; then it was placed in a tube furnace filled with nitrogen to calcine, thus obtaining graphitic carbon nitride (CN).

[0017] Step 2: Preparation of carbon-coated nickel oxide particles

[0018] Nickel acetate hexahydrate and citric acid were dissolved in a mixture of deionized water and anhydrous ethanol and placed at the bottom of a quartz boat. The mixture was then pretreated in a forced-air drying oven to obtain a light green transparent gel. Finally, the precursor gel was calcined in a tube furnace filled with nitrogen to obtain carbon-coated nickel oxide particles NiO@C.

[0019] Step 3: Preparation of carbon-encapsulated nickel oxide particles loaded with graphitic carbon nitride nanosheets

[0020] Graphite carbon nitride and carbon-coated nickel oxide particles were dispersed in anhydrous ethanol and subjected to ultrasonic treatment. The resulting solution was dried in a forced-air drying oven. Subsequently, the resulting solid powder was mixed and ground with anhydrous ethanol to obtain carbon-coated nickel oxide particles loaded with graphite carbon nitride nanosheets NiO@C-CN.

[0021] Step 4: Preparation of bifunctional iron POM-modified carbon-based materials

[0022] K8[γ-PW 10 O 36 ·12H2O and ferrous chloride tetrahydrate were dissolved in potassium chloride aqueous solution. After vigorous stirring, hydrogen chloride solution was added to adjust the pH of the solution to 5.0. The resulting solution was heated using a heated magnetic stirrer, and then ferrous chloride tetrahydrate was added again while stirring continuously.

[0023] Subsequently, a mixture of potassium chloride and sodium chloride was added, stirred, and allowed to stand. Yellow-brown crystals precipitated, and the solid precipitate was collected by centrifugation. After washing with cold water, the precipitate was dried in a vacuum drying oven to obtain Fe polynuclear metal oxometalate Fe-POM.

[0024] Finally, NiO@C-CN and Fe-POM were dispersed in a methanol solution and subjected to ultrasonic treatment. After continuous stirring in a reflux condenser, the mixture was centrifuged and dried to obtain the bifunctional iron POM-modified carbon-based material Fe-POM / LB-CN.

[0025] Preferably, in step one, the mass ratio of urea to melamine is 1.5~2.5 g: 1.5~2.5 g;

[0026] The calcination conditions for quartz boats in a muffle furnace are: heating to 450~550℃ and holding for 3~5 hours;

[0027] The calcination conditions for quartz boats in a tube furnace are: heating to 450~550℃ and holding for 3~5 hours.

[0028] Preferably, in step two, the mass-to-volume ratio of nickel acetate hexahydrate, citric acid, deionized water, and anhydrous ethanol is 0.3~0.5 g : 0.9~1.1 g : 2~3 mL : 0.5~1.5 mL;

[0029] The pretreatment conditions for quartz boats in a forced-air drying oven are: heating to 70~80℃ and maintaining for 2~3 hours;

[0030] The calcination conditions for quartz boats in a tube furnace are: heating to 300~400℃ and holding for 7~9 hours.

[0031] Preferably, in step three, the mass-to-volume ratio of graphite carbon nitride, carbon-coated nickel oxide particles, and anhydrous ethanol is 90-110 mg: 4-6 mg: 4-6 mL, and the ultrasonic treatment time is 1-3 hours.

[0032] The drying oven is kept at 50-70℃ for 5-7 hours, and the mixing and grinding time is 50-70 minutes.

[0033] Preferably, in step four, K8[γ-PW] 10 O 36 The mass-to-volume ratio of 12H2O, ferrous chloride tetrahydrate, and potassium chloride aqueous solution was 450-550 mg: 60-100 mg: 15-25 mL. The heating conditions for the magnetic stirrer were: heating to 35-45℃ and maintaining for 1.5-2.5 hours.

[0034] Add 20-60 mg of ferrous chloride tetrahydrate again, and continue stirring with a magnetic stirrer for 1.5-2.5 hours.

[0035] Preferably, in step four, the mass ratio of potassium chloride to sodium chloride is 80-120 mg: 20-40 mg, and the magnetic stirrer continues to stir for another 20-40 minutes.

[0036] The mixed solution was left to stand at 2-6℃ for 20-28 hours, centrifuged at 6000-8000 rpm for 5-10 minutes, and then dried in a vacuum drying oven at 35-45℃ for 20-28 hours.

[0037] Preferably, in step four, the mass-to-volume ratio of NiO@C-CN, Fe-POM, and methanol solution is 120~160 mg: 15~25 mg: 15~25 mL, and the ultrasonic treatment time is 20~40 minutes.

[0038] Preferably, in step four, the reflux condenser is heated to 55-65°C and maintained for 22-26 hours, centrifuged at 6000-8000 rpm for 5-10 minutes, and the vacuum drying oven is maintained at 55-65°C for 10-14 hours.

[0039] A method for preparing bifunctional iron POM-modified carbon-based materials and their application as photocatalysts in the removal of pesticides from water.

[0040] Preferably, the application method is as follows: bifunctional iron POM modified carbon-based material is used as a photocatalyst to produce H2O2 in situ and promote its activation to degrade imidacloprid.

[0041] The present invention achieves the following technical effects compared to the prior art:

[0042] (1) In this invention, carbon-encapsulated nickel oxide (NiO@C) particles and Fe polynuclear metal oxometalate (Fe-POM) are jointly modified onto the surface of graphitic carbon nitride to prepare Fe-POM / LB-CN catalyst. The oxygen vacancies in the NiO@C inside can act as impurity energy levels to promote the separation and migration of photogenerated electron-hole pairs, thereby significantly improving photocatalytic activity.

[0043] (2) Under simulated visible light irradiation, the apparent quantum yield (AQY) of the Fe-POM / LB-CN catalyst at 420 nm is as high as 23.6%, which shows extremely high solar energy utilization capability;

[0044] (3) The Fe-POM / LB-CN photocatalytic system of the present invention exhibits strong ORR and WOR capabilities, enabling in-situ production of H2O2. The H2O2 yield reaches 22670 µmol·g after 60 minutes of photocatalytic reaction. -1 ;

[0045] (4) The iron sites in Fe-POM of the present invention can effectively activate H2O2 decomposition to produce •OH, which can be used to degrade pesticides in wastewater;

[0046] (5) The Fe-POM / LB-CN photocatalytic system of the present invention can completely degrade imidacloprid within 15 minutes, and the mineralization rate is as high as 63.5%;

[0047] (6) This invention provides a new perspective on the preparation of single / bimetallic site modified carbon-based photocatalysts and their application in the field of pesticide degradation. Attached Figure Description

[0048] Figure 1 The X-ray diffraction (XRD) pattern of the NiO@C structure;

[0049] Figure 2 Thermogravimetric analysis (TGA) of NiO@C precursor gel;

[0050] Figure 3 Transmission electron microscopy (TEM) image of NiO@C catalyst (a); High-resolution TEM (HRTEM) image (b, c);

[0051] Figure 4 Aberration-corrected high-angle dark-field annular scanning transmission electron microscope (AC-HAADF-STEM) images and corresponding TEM / energy dispersive spectroscopy (TEM-EDS) images of NiO@C catalysts;

[0052] Figure 5 XRD patterns of NiO@C-CN and g-C3N4 catalysts;

[0053] Figure 6 TEM and HRTEM images (ac) of the NiO@C-CN catalyst; HAADF-STEM image and corresponding TEM-EDS image (df);

[0054] Figure 7High-resolution X-ray photoelectron spectroscopy (XPS) of Fe 2p (a), W 4f (b) and O 1s (c) for Fe-POM catalysts;

[0055] Figure 8 Fourier transform infrared (FTIR) spectrum of Fe-POM catalyst;

[0056] Figure 9 Powder X-ray diffraction (PXRD) patterns of NiO@C-CN catalysts supported on different iron-based POMs;

[0057] Figure 10 The UV-Vis (a) spectra of the Fe-POM / LB-CN catalyst before and after electrostatic self-assembly; the UV-Vis (b) diffuse reflectance (DRS) spectra.

[0058] Figure 11 Structural characterization of the Fe-POM / LB-CN catalyst: HRTEM images (a, b); HAADF-STEM image and corresponding TEM-EDS imaging (c).

[0059] Figure 12 For FePW 11 Structural characterization of the / LB-CN catalyst: HRTEM image (a); HAADF-STEM image and corresponding TEM-EDS imaging (b); particle size distribution (c).

[0060] Figure 13 Structural characterization of the Fe4-POM / LB-CN catalyst: HRTEM image (a); HAADF-STEM image and corresponding TEM-EDS imaging (b); particle size distribution (c).

[0061] Figure 14 For Fe 17 Structural characterization of the POM / LB-CN catalyst: HRTEM image (a); HAADF-STEM image and corresponding TEM-EDS imaging (b); particle size distribution (c).

[0062] Figure 15 For Fe-POM / LB-CN, Fe4-POM / LB-CN, Fe 17 -POM / LB-CN and FePW 11 / LB-CN catalyst photocatalytic production of H2O2 performance;

[0063] Figure 16 Early fitting curves of the kinetic constants of the photosynthetic reaction of H2O2 for NiO@C-CN catalysts supported on different iron-based POMs;

[0064] Figure 17 Full-process fitting curves of the kinetic constants of the H2O2 photosynthetic reaction for different iron-based POM-supported NiO@C-CN catalysts;

[0065] Figure 18 This is a superimposed graph of apparent quantum yield (AQY) and absorption spectra of Fe-POM / LB-CN molecules;

[0066] Figure 19 A comparative study on the photocatalytic activity of Fe-POM / LB-CN catalyst and advanced photocatalyst for H2O2;

[0067] Figure 20 Cyclic stability testing of Fe-POM / LB-CN catalyst in H2O2 production process;

[0068] Figure 21 Electrochemical impedance spectroscopy (EIS) measurements were performed on electrolytes in different solubility environments, including Fe-POM / LB-CN and FePW. 11 Testing of / LB-CN catalyst;

[0069] Figure 22 Photocurrent response testing of Fe-POM / LB-CN catalyst;

[0070] Figure 23 Mott-Schottky curves for NiO@C-CN catalysts supported on different iron-based POMs;

[0071] Figure 24 Tauc curves of NiO@C-CN catalysts supported on different iron-based POMs;

[0072] Figure 25 The corresponding band structures of NiO@C-CN catalysts supported on different iron-based POMs are shown.

[0073] Figure 26 Performance of Fe-POM / LB-CN catalyst in photocatalytic production of H2O2 under different conditions;

[0074] Figure 27 Electron paramagnetic resonance (EPR) spectra of NiO@C-CN catalysts supported on different iron-based POMs (•O2) - Signal);

[0075] Figure 28 Electron paramagnetic resonance (EPR) spectra (•OH signals) of NiO@C-CN catalysts supported on different iron-based POMs;

[0076] Figure 29 The degradation efficiency and apparent rate constant of IMD in different catalytic systems are given.

[0077] Figure 30 The values ​​represent the IMD degradation efficiency in different catalytic systems.

[0078] Figure 31 Kinetic curves of IMD degradation mediated by photocatalytic systems with different iron-based POM-supported NiO@C-CN catalysts;

[0079] Figure 32 The apparent rate constants of IMD degradation in photocatalytic systems mediated by different iron-based POM-supported NiO@C-CN catalysts;

[0080] Figure 33 TOC removal efficiency of IMD in different catalytic systems;

[0081] Figure 34 The degradation effect of Fe-POM / LB-CN photocatalytic system on IMD under different catalyst concentrations;

[0082] Figure 35 The degradation effect of Fe-POM / LB-CN photocatalytic system on IMD under different pH conditions;

[0083] Figure 36 The degradation effect of Fe-POM / LB-CN photocatalytic system on IMD at different reaction temperatures;

[0084] Figure 37 The effect of different ions on IMD removal in the Fe-POM / LB-CN photocatalytic system;

[0085] Figure 38 For the periodic degradation of IMD in the Fe-POM / LB-CN photocatalytic system (8 cycles, no catalyst replenishment required);

[0086] Figure 39 For the periodic degradation of IMD in the Fe-POM / LB-CN photocatalytic system (11 cycles, no catalyst replenishment required);

[0087] Figure 40 For the periodic degradation of IMD in the Fe-POM / LB-CN photocatalytic system (30 cycles, catalyst replenishment required);

[0088] Figure 41 The apparent rate constant is the Fe-POM / LB-CN photocatalytic system for 30 cycles of IMD degradation. Detailed Implementation

[0089] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0090] This invention discloses a method for preparing bifunctional iron POM-modified carbon-based materials and their applications, comprising the following steps:

[0091] Step 1: Preparation of graphitic carbon nitride: A mixture of urea and melamine is spread evenly on the bottom of a quartz boat and tightly wrapped with tin foil. It is then placed in a muffle furnace for calcination. The resulting powder is ground and placed in a quartz boat, wrapped with tin foil, and small holes are punched in it. It is then placed in a tube furnace filled with nitrogen for calcination. The resulting sample is called CN.

[0092] Step 2: Preparation of carbon-coated nickel oxide particles: Nickel acetate hexahydrate and citric acid were dissolved in a mixture of deionized water and anhydrous ethanol and placed at the bottom of a quartz boat. The mixture was then pretreated in a forced-air drying oven to obtain a light green transparent gel. Finally, the precursor gel was calcined in a tube furnace filled with nitrogen, and the resulting sample was named NiO@C.

[0093] Step 3: Preparation of graphitic carbon nitride nanosheets supported on carbon-coated nickel oxide particles: Graphitic carbon nitride and carbon-coated nickel oxide particles were dispersed in anhydrous ethanol and subjected to ultrasonic treatment. The resulting solution was dried in a forced-air drying oven. Subsequently, the obtained solid powder was mixed with anhydrous ethanol and ground. The resulting sample was named NiO@C-CN.

[0094] Step 4: Preparation of bifunctional iron POM-modified carbon-based materials: K8[γ-PW] 10 O 36 ·12H2O and ferrous chloride tetrahydrate were dissolved in an aqueous potassium chloride solution. After vigorous stirring, the pH of the solution was adjusted to 5.0 by adding hydrogen chloride solution. The resulting solution was heated using a heated magnetic stirrer, and ferrous chloride tetrahydrate was added again while stirring continuously. Subsequently, a mixture of potassium chloride and sodium chloride was added, stirred, and allowed to stand, resulting in the precipitation of yellow-brown crystals. The solid precipitate was collected by centrifugation, washed three times with cold water, and then dried in a vacuum drying oven. The obtained sample was named Fe-POM. Finally, NiO@C-CN and Fe-POM were dispersed in a methanol solution and sonicated. After continuous stirring in a reflux condenser, the mixture was centrifuged and dried, resulting in a sample named Fe-POM / LB-CN. Example 2:

[0095] In step one, the mass ratio of urea to melamine is 1.5~2.5 g: 1.5~2.5 g, and the rest is the same as in Example 1. Example 3:

[0096] In step one, the quartz boat is heated to 450-550°C in a muffle furnace and held for 3-5 hours. The rest is the same as in Examples 1-2. Example 4:

[0097] In step one, the quartz boat is heated to 450~550℃ in a tube furnace and held for 3~5 hours. The rest is the same as in Examples 1-3.

[0098] Example 5: In step two, the mass-to-volume ratio of nickel acetate hexahydrate, citric acid, deionized water and anhydrous ethanol is 0.3~0.5 g: 0.9~1.1 g: 2~3 mL: 0.5~1.5 mL, and the rest is the same as in Examples 1-4.

[0099] Example 6: In step two, the quartz boat is heated to 70~80℃ in a forced-air drying oven and maintained for 2~3 hours. The rest is the same as in Examples 1-5.

[0100] Example 7: In step two, the quartz boat is heated to 300~400℃ in a tube furnace and held for 7~9 hours. The rest is the same as in Examples 1-6.

[0101] Example 8: In step 3, the mass-to-volume ratio of graphite carbon nitride, carbon-coated nickel oxide particles, and anhydrous ethanol is 90-110 mg: 4-6 mg: 4-6 mL, and the ultrasonic treatment time is 1-3 hours. Other aspects are the same as in Examples 1-7.

[0102] Example 9: In step three, the drying oven is kept at 50~70℃ for 5~7 hours, and the mixing and grinding time is 50~70 minutes. The rest is the same as in Examples 1-8.

[0103] Example 10: K8[γ-PW] in step four 10 O 36 The mass-to-volume ratio of 12H2O, ferrous chloride tetrahydrate, and potassium chloride aqueous solution is 450-550 mg: 60-100 mg: 15-25 mL. The mixture is heated to 35-45°C using a magnetic stirrer and maintained for 1.5-2.5 hours. Other steps are the same as in Examples 1-9.

[0104] Example 11: The mass of ferrous chloride tetrahydrate added again in step four is 20~60 mg, and the magnetic stirrer is used to continue stirring for 1.5~2.5 hours. The rest is the same as in Examples 1-10.

[0105] Example 12: In step four, the mass ratio of potassium chloride to sodium chloride is 80~120 mg: 20~40 mg. The magnetic stirrer is used to continue stirring for 20~40 minutes. The rest is the same as in Examples 1-11.

[0106] Example 13: The mixed solution in step four was placed at 2~6℃ and allowed to stand for 20~28 hours, centrifuged at 6000~8000 rpm for 5~10 minutes, and kept in a vacuum drying oven at 35~45℃ for 20~28 hours. Other steps were the same as in Examples 1-12.

[0107] Example 14: In step four, the mass-to-volume ratio of NiO@C-CN, Fe-POM, and methanol solution is 120-160 mg: 15-25 mg: 15-25 mL, and the ultrasonic treatment time is 20-40 minutes. Other aspects are the same as in Examples 1-13.

[0108] Example 15: In step four, the reflux condenser is heated to 55~65℃ and maintained for 22~26 hours, centrifuged at 6000~8000 rpm for 5~10 minutes, and the vacuum drying oven is maintained at 55~65℃ for 10~14 hours. The rest is the same as in Examples 1-14.

[0109] Method for verifying the beneficial effects of this invention:

[0110] A method for preparing bifunctional iron POM-modified carbon-based materials includes the following steps:

[0111] Step 1: Preparation of carbon-coated nickel oxide particles: 0.4 g of nickel acetate hexahydrate and 1.0 g of citric acid were dissolved in a mixture of 2.5 mL of deionized water and 1 mL of anhydrous ethanol and placed at the bottom of a quartz boat. The mixture was then pretreated in an 80°C oven for 3 hours to obtain a light green transparent gel. Finally, the precursor gel was calcined in a tube furnace filled with nitrogen at 350°C for 8 hours. The resulting sample was named NiO@C.

[0112] Step 2: Preparation of graphitic carbon nitride nanosheets supported on carbon-coated nickel oxide particles: 100 mg of graphitic carbon nitride and 5 mg of carbon-coated nickel oxide particles were dispersed in 5 mL of anhydrous ethanol and sonicated for 2 hours. The resulting solution was dried in a forced-air drying oven at 60°C for 6 hours. Subsequently, the obtained solid powder was mixed with anhydrous ethanol and ground for 60 minutes. The resulting sample was named NiO@C-CN.

[0113] Step 3: Preparation of bifunctional iron POM-modified carbon-based materials: 500 mg K8[γ-PW] 10 O 3612H₂O and 80 mg of ferrous chloride tetrahydrate were dissolved in 20 mL of potassium chloride aqueous solution. After vigorous stirring, the pH of the solution was adjusted to 5.0 by adding hydrogen chloride solution. The resulting solution was heated to 40°C using a heated magnetic stirrer and maintained for 2 hours. Then, another 40 mg of ferrous chloride tetrahydrate was added and stirring continued for 2 hours. Subsequently, a mixture of 100 mg of potassium chloride and 30 mg of sodium chloride was added and stirring continued for 30 minutes. The mixture was placed at 4°C and allowed to stand for 24 hours, resulting in the precipitation of yellow-brown crystals. The precipitate was then centrifuged at 7000 rpm for 10 minutes and collected. After washing three times with cold water, the precipitate was dried in a vacuum drying oven at 40°C for 24 hours. The obtained sample was named Fe-POM. Finally, 140 mg of NiO@C-CN and 20 mg of Fe-POM were dispersed in 20 mL of methanol solution and sonicated for 30 minutes. The solution was then heated to 60°C in a reflux condenser and maintained for 24 hours. The resulting mixed solution was centrifuged at 7000 rpm for 10 minutes and then dried in a vacuum drying oven at 60°C for 12 hours. The resulting sample was named Fe-POM / LB-CN.

[0114] Compare with Example 1:

[0115] Mononuclear iron POM modified carbon-based materials (FePW) 11 Preparation of / LB-CN): K8[β2-PW 11 O 39 14H₂O (320 mg) was dissolved in 10 mL of deionized water at 60°C. Then, ferric nitrate nonahydrate (40.3 mg) was dissolved in 0.5 mL of deionized water, and K₈[β₂-PW₂]₃ was added dropwise. 11 O 39 The solution was then added to a 14H₂O solution. The pH of the solution was adjusted to 4.0 with acetic acid and cooled to room temperature. 0.967 g of tetrabutylammonium bromide was then added, and a precipitate was observed. The mixed solution was stirred at 25°C for three days, and the solid powder obtained by filtering the solution was named FeSiW. 11 Next, the FeSiW was processed using the same method as in Example 1. 11 FePW was prepared by electrostatic self-assembly with NiO@C-CN. 11 / LB-CN photocatalyst.

[0116] Compare with Example 2:

[0117] Preparation of tetranuclear iron POM modified carbon-based material (Fe4-POM / LB-CN): Sodium tungstate (33 g) and disodium hydrogen phosphate (1.57 g) were dissolved in 100 mL of deionized water, and the pH was adjusted to 4.0 with dilute hydrochloric acid. A solution of ferric chloride hexahydrate (5.5 g) in 50 mL of deionized water was slowly added under vigorous stirring. The resulting mixture was stirred in a 70°C water bath for 2.5 hours, hot filtered to remove any precipitate, and then a mixture of 2 g potassium chloride and 1 g sodium chloride was added and stirred for 30 minutes. The solution was then allowed to stand at 4°C for 24 hours to precipitate crystals. The precipitate was then centrifuged at 7000 rpm for 10 minutes and collected. After washing three times with cold water, the precipitate was dried in a vacuum drying oven at 40°C for 24 hours. The resulting sample was named Fe4-POM. Finally, Fe4-POM and NiO@C-CN were electrostatically self-assembled using the same method as in Example 1 to prepare Fe4-POM / LB-CN photocatalyst.

[0118] Compare with Example 3:

[0119] Heptadecyl iron POM modified carbon-based materials (Fe 17 Preparation of ferric chloride hexahydrate (171 mg) sample: Dissolve the sample in 20 mL of deionized water and add Na 12 [A-αPW9O 34 0.5 g of nH₂O was added to the above mixture after stirring for 15 minutes. Furan dicarboxylic acid (42 mg) was then added. After stirring for 10 minutes, 0.9 mL of sodium hydroxide solution (1 M) was added dropwise, resulting in a turbid solution with a pH of approximately 8. The mixture was then heated at 80°C for 30 minutes. After cooling to room temperature, any insoluble substances were removed by centrifugation at 7000 rpm for 10 minutes. Finally, a mixture of 25 mg ammonium chloride and 10 mg sodium chloride was added, and the resulting mixture was allowed to stand at 4°C for 48 hours, resulting in the precipitation of deep red crystals. The solid precipitate was then collected by centrifugation at 7000 rpm for 10 minutes, washed three times with an ethanol-water mixture (1:1), and dried in a vacuum drying oven at 40°C for 24 hours. The resulting sample was named Fe. 17 -POM. Finally, Fe was processed using the same method as in Example 1. 17 -POM and NiO@C-CN were electrostatically self-assembled to prepare Fe 17 -POM / LB-CN photocatalyst.

[0120] According to X-ray diffraction (XRD) patterns ( Figure 1Clear diffraction peaks corresponding to the C (200) crystal plane and the NiO lattice structure (JCPDS No. 47-1049) were observed, indicating that NiO@C nanoparticles were formed by the decomposition of citric acid (carbon source) at 350°C. The NiO lattice diffraction patterns all belonged to the cubic crystal space group Fm-3m (225), indicating a significant phase transition in the NiO lattice at 350°C, further confirming the formation of NiO@C nanoparticles. Thermogravimetric analysis (TGA) of the precursor gel further confirmed the relationship between the phase transition and temperature. Figure 2 As shown, the 15.32% weight loss of the Ni-based gel precursor below 180°C is mainly attributed to the evaporation of water and ethanol molecules. Subsequently, in the temperature range of 180–310°C, the organic ligands underwent significant decomposition, resulting in a weight loss of up to 54.57%, while Ni… 2+ Transformation into NiO and defect-state Ni 3+ Based on the results obtained from TGA, 350°C was chosen as the carbonization temperature to obtain NiO@C nanoparticles.

[0121] Transmission electron microscopy (TEM) images of NiO@C ( Figure 3 (a) revealed the presence of tightly embedded 5 nm NiO within the carbon nanocages, establishing covalent connections between the carbon layers and producing a garnet-like protruding structure. This was based on high-resolution TEM (HRTEM) images ( Figure 3 The results (b, c) show that the scattering region (white dashed circular area) representing point defects in NiO@C indicates that the lattice defects are caused by the Jahn-Teller effect due to high temperature and oxygen-deficient atmosphere. Figure 3 As shown in (c), the lattice spacing on the carbon layer surface is 0.208 nm, corresponding to the NiO (200) crystal plane. Next, the atomic lattice distribution in NiO@C was observed using aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and corresponding TEM / energy-dispersive spectroscopy (TEM-EDS). Figure 4 As shown, Ni and O elements are uniformly distributed in the central region of the sample, while C elements are uniformly distributed in the outer edge region. These results indicate that NiO@C is composed of a carbon outer layer structure and a NiO / C binary interface. Figure 5 The XRD patterns shown indicate that, compared to graphitic carbon nitride (g-C3N4), the surface of the NiO@C-CN catalyst exhibits a distinct Ni characteristic peak, demonstrating the successful preparation of the NiO@C-CN catalyst. Figure 6The images show HRTEM, HAADF-STEM, and TEM-EDS imaging of the NiO@C-CN catalyst, revealing tightly bonded and uniformly dispersed 5.0 wt% NiO@C nanoparticles on the g-C3N4 surface. Figure 6 (f) TEM-EDS imaging shows the point-like distribution of O and Ni elements among C and N elements, indicating that these materials are well distributed and have an efficient synergistic effect.

[0122] Next, to confirm the valence state and microenvironment of the Fe-POM metal sites, X-ray photoelectron spectroscopy (XPS) analysis was performed on Fe-POM. The high-resolution XPS spectrum of Fe 2p was obtained by peak fitting, as shown below. Figure 7 As shown in (a), Fe 2p 3 / 2 The deconvolution peaks at 714.0 eV and 712.1 eV, Fe 2p 1 / 2 The deconvolution peaks at 726.9 eV and 724.5 eV, and the satellite peaks at 732.5 eV and 718.9 eV, confirm the presence of Fe. 3+ The existence of. For example... Figure 7 As shown in (b), W 4f at 35.4 eV and 37.6 eV 7 / 2 and W 4f 5 / 2 The bimodal pattern indicates the presence of typical W 6+ Species. Deconvolution map of the O 1s spectrum ( Figure 7 (c) Four peaks can be observed at binding energies of 530.6 eV, 531.1 eV, 531.5 eV, and 532.1 eV. The diffraction peaks at 530.6 eV and 531.1 eV correspond to W=O and WOW bonds, respectively. The diffraction peaks at 531.5 eV and 532.1 eV correspond to lattice oxygen Fe-OW in Fe-POM and crystalline H2O, respectively. The Fourier transform infrared (FT-IR) spectrum of Fe-POM... Figure 8 In ), 1056, 947, 764 and 580 cm -1 The characteristic peaks at these locations correspond to... v s (WO d ), v s (PO), v s (WO c -W) and v s (Fe-O) vibration.

[0123] For comparison, FeSiW with mononuclear iron sites was synthesized using different raw materials. 11And Fe4-POM and Fe with multinucleated iron sites 17 -POM was used as a control sample. Then, an electrostatic self-assembly strategy was employed to uniformly anchor different iron-based POMs onto NiO@C-CN nanosheets to achieve a clear, single dispersion of Fe sites. Figure 9 As shown, no signals associated with crystalline Fe-POM bulk or metal oxides were observed in the powder X-ray diffraction (PXRD) pattern, indicating uniform dispersion of different iron-based POMs on the NiO@C-CN substrate. The UV-Vis and UV-Vis diffuse reflectance spectra of Fe-POM / LB-CN are shown below. Figure 10 As shown, compared with the catalyst obtained before electrostatic self-assembly, no significant changes were observed in the light absorption range of the electrostatically self-assembled Fe-POM / LB-CN, indicating that this preparation strategy did not affect the superior light absorption capacity of Fe-POM itself. Further verification of the uniform anchoring of Fe-POM on the NiO@C-CN substrate was achieved using HRTEM and HAADF-STEM images. Figure 11 As shown in (a) and (b), a uniform distribution of Fe-POM and NiO@C nanoparticles was observed on the g-C3N4 substrate. HAADF-STEM images ( Figure 11 (c) shows that ultrafine white spots with average sizes of 1.8 nm and 4.4 nm exist on the g-C3N4 substrate, which match the sizes of individual Fe-POM clusters and NiO@C (1.55 nm and 4.38 nm), respectively. Elemental mapping images reveal Fe-POM on the g-C3N4 substrate, with corresponding Fe (green) and W (purple) bright spots matching the arrangement of W / Fe centers in the Fe-POM, further validating the integrity of the Fe-POM. Furthermore, FePW prepared using the same strategy... 11 / LB-CN, Fe4-POM / LB-CN and Fe 17 -POM / LB-CN, HRTEM, and HAADF-STEM images respectively demonstrate that FePW 11 , Fe4-POM and Fe 17 Monodispersion and integrity of POM on NiO@C-CN substrate ( Figure 12-14 Based on the above results, we constructed carbon-based materials with mono / bimetallic catalytic active sites using a simple electrostatic self-assembly strategy. This catalyst can be easily synthesized by simultaneously and uniformly dispersing POM with multinuclear Fe sites and NiO encapsulated in carbon nanocages on a photosensitive matrix, resulting in a composite photocatalyst with a precise microenvironment. Notably, the uniform distribution of Fe sites and NiO provides an ideal platform for studying structure-activity relationships.

[0124] Using pure water and oxygen as the sole input sources, the production of H2O2 through artificial photosynthesis under simulated sunlight was systematically evaluated. Figure 15 As shown, with increasing time (0–120 minutes), the production of H2O2 first gradually increases and then tends to plateau. This may be because, as the reaction proceeds, the proportion of competing processes, including chemical equilibrium shifts and H2O2 self-decomposition, becomes increasingly larger. Figure 16 and Figure 17 As shown, in the first 60 minutes of H2O2 photosynthesis, the reaction kinetics primarily follow zero-order characteristics, indicating that the rate is independent of reactant concentration. When performing zero-order kinetic modeling, early data (R...) 2 The linearity of the ≥ 0.978 (R²) is significantly better than that of the whole process fitting (R²). 2 ≤ 0.969). This difference confirms that the initial stage mainly reflects the surface reaction control mechanism. Therefore, the kinetic constants derived at 60 min were used to evaluate the intrinsic photocatalytic activity of different iron-based POM-supported NiO@C-CN catalysts. In summary, after 60 min of photocatalytic reaction, the Fe-POM / LB-CN catalyst had the highest yield (reaching 22670 μmol·g). -1 ·h -1 ), which are Fe4-POM / LB-CN (1432 μmol·g -1 ·h -1 ), Fe 17 -POM / LB-CN (699 μmol·g) -1 ·h -1 ) and FePW 11 / LB-CN (513 μmol·g) -1 ·h -1 16, 32 and 44 times that of ).

[0125] The wavelength-dependent photocatalytic performance of Fe-POM / LB-CN catalysts was quantitatively characterized by detecting the monochromatic apparent quantum yield (AQY) in the 350–700 nm spectrum. Figure 18 As shown, AQY exhibits significant resonance enhancement at 420 nm, reaching a peak value of 23.6%, which is consistent with the maximum intramolecular charge transfer (ICT) absorption value (λ) of Fe-POM / LB-CN. abs The system is directly aligned at 420 nm. Notably, it maintains a non-zero AQY (2.7%) even at 700 nm, demonstrating near-infrared photocatalytic activity. The broadband quantum efficiency enables Fe-POM / LB-CN to exhibit excellent performance in solar-driven H2O2 production. Figure 19 As shown, compared with other reported photocatalytic systems, the Fe-POM / LB-CN system exhibits the best mass activity (22670 μmol·g).-1 ·h -1 Meanwhile, the system exhibits a solar-to-chemical energy conversion (SCC) efficiency of 1.92%, maintaining a nearly linear relationship with the SCC / mass activity ratio in the literature benchmark (R0). 2 = 0.5940), confirming the comparable energy utilization of the system. Long-term stability tests are as follows: Figure 20 As shown, after 10 consecutive cycles, the Fe-POM / LB-CN catalyst still maintains high photocatalytic activity, and the H2O2 yield still reaches 20923 μmol·g. -1 ·h -1 .

[0126] The Fe-POM / LB-CN and FePW were compared under different atmospheres by electrochemical impedance spectroscopy (EIS) system. 11 Electrochemical dynamics of / LB-CN catalysts. For example... Figure 21 As shown, FePW 11 The / LB-CN catalyst exhibits predictable oxygen inertness, maintaining a stable charge transfer resistance (R0) regardless of the presence or absence of oxygen. CT = 43.1 Ω) and mass transfer resistance (R m = 4.15 kΩ). This invariance confirms that FePW 11 / LB-CN exhibits limited interfacial interaction with O2. In contrast, the Fe-POM / LB-CN catalyst displays atmospheric-responsive behavior: exposure to oxygen increases R... m Reduced by 78% (0.91 kΩ), while simultaneously increasing R CT (49.6 Ω) increased by 13.1%. R m The reduction in H2O2 yield is directly related to the enhanced O2 adsorption, indicating that the process of oxygen adsorbing onto the Fe-POM / LB-CN catalyst surface and participating in the reaction is more likely to occur, thus explaining its H2O2 yield (22670 μmol·g). -1 ·h -1 (Far higher than FePW) 11 / LB-CN catalyst (513 μmol·g) -1 ·h -1 The reason is that the photocurrent response test of the Fe-POM / LB-CN catalyst under deoxygenated (nitrogen purging) and oxygen-containing (oxygen saturated) electrolyte conditions showed that ( Figure 22 The photocurrent density increased by 1.7 times after the introduction of oxygen, which highlights the key role of adsorbed oxygen in promoting the transfer of photogenerated electrons.

[0127] Meeting thermodynamic requirements is a prerequisite for photocatalytic H2O2 production. Surface redox reactions on photocatalysts for H2O2 production typically involve ORR and WOR processes, the reaction pathways of which depend on the energy band positions of the catalyst. Firstly, based on the Mott-Schottky curve (… Figure 23 Determine the flat band potential of NiO@C-CN catalysts supported on different iron-based POMs, Fe-POM / LB-CN, Fe4-POM / LB-CN, Fe 17 -POM / LB-CN and FePW 11 The flat band positions of / LB-CN were determined to be -1.22, -1.18, -1.14, and -1.09 V vs. Ag / AgCl. They all exhibit n-type semiconductor characteristics, therefore the CB position will be 0.2 eV negative than the flat band position. The calculated conduction band (CB) positions are -1.02 V (Fe-POM / LB-CN), -0.98 V (Fe4-POM / LB-CN), and -0.94 V (Fe... 17 -POM / LB-CN) and -0.89 V (FePW) 11 / LB-CN) vs. NHE. According to Figure 24 The band gaps of different iron-based POM-supported NiO@C-CN catalysts are shown, and the calculated CB and valence band (VB) positions are calculated to be 1.39 V (Fe-POM / LB-CN), 1.49 V (Fe4-POM / LB-CN), and 1.55 V (Fe4-POM / LB-CN), respectively. 17 -POM / LB-CN) and 1.62 V (FePW) 11 / LB-CN) vs. NHE. Band structures of NiO@C-CN catalysts supported on different iron-based POM are as follows: Figure 25 As shown in the figure. It is noteworthy that all four catalysts satisfy the WOR thermodynamic potential (1.38 V vs. NHE), with the Fe-POM / LB-CN catalyst exhibiting the most negative CB position, indicating its highest reducibility for H2O2 production via the ORR pathway. Therefore, the optimal CB / VB positions of the Fe-POM / LB-CN catalyst enable successful H2O2 production via both ORR and WOR pathways.

[0128] To further investigate the reaction pathway of the Fe-POM / LB-CN catalyst, the photocatalytic H2O2 yield was tested under different atmospheres and quenchers. Figure 26 Under air aeration conditions, the productivity of H2O2 decreased by 14.9%. Under argon (Ar) aeration conditions and with the addition of potassium bromate (KBrO3) as an electron (e) source, the productivity of H2O2 decreased. -After the addition of quenching agents, H2O2 production was partially inhibited (reduced by 61.5% and 65.4%, respectively), while the addition of methanol (MeOH) as a hole (h + After the addition of a quencher, H2O2 production was slightly inhibited (reduced by 32.8%). These results confirm that H2O2 is produced synergistically via the ORR and WOR pathways on the Fe-POM / LB-CN catalyst, with the ORR pathway accounting for a larger proportion (approximately 60%). The addition of p-benzoquinone (p-BQ) as a superoxide radical (•O2) quencher further inhibited H2O2 production. - After the addition of a quencher, the yield of H2O2 decreased by 56.7%, indicating that the indirect 2e- quenching agent... - -ORR is the main pathway for H2O2 generation on Fe-POM / LB-CN catalysts, while •O2 - It is a key intermediate in the production of H2O2. Furthermore, the effect of adding tert-butanol (TBA) as a hydroxyl radical (•OH) quencher on H2O2 yield is negligible (only decreasing by 4.3%), which further rules out the possibility of direct 2e- ... - The hypothesis of producing H₂O₂ via the ORR pathway was then established. The types of reaction intermediates were then investigated using electron paramagnetic resonance (EPR) assays. For example... Figure 27 As shown, DMPO-•O2 was found in a solution containing the Fe-POM / LB-CN catalyst under light irradiation. - However, no signal of DMPO-•OH was detected. Figure 28 This result can help explain the indirect 2e - ORR is the main pathway for H2O2 generation on Fe-POM / LB-CN catalysts.

[0129] The ability of the Fe-POM / LB-CN photocatalytic system to remove the pesticide imidacloprid (IMD) under simulated visible light was tested, verifying the system's excellent H2O2 activation characteristics and outstanding photostability. Figure 29 and Figure 30 As shown, for Fe-POM / LB-CN and FePW under different experimental conditions 11 The degradation rate and apparent rate of IMD differ significantly in the / LB-CN photocatalytic system. H2O2, vis / H2O2, and FePW 11 The / LB-CN / vis system exhibits extremely low degradation rates and apparent rates for IMD (degradation rate less than 10%). k obs ≤0.01 min -1 ), while Fe-POM / LB-CN / vis, Fe-POM / LB-CN / H2O2 and FePW 11The IMD degradation rate / apparent rate of the / LB-CN / H2O2 system at 15 minutes were 100% / 0.446 min, respectively. -1 97.7% / 0.324 min -1 and 95.6% / 0.277 min -1 The above results indicate that the Fe-POM / LB-CN system possesses excellent H2O2 production and activation capabilities, while FePW... 11 The / LB-CN system only exhibits excellent H2O2 activation ability. Furthermore, the degradation ability of IMD by photocatalytic systems mediated by different iron-based POM-supported NiO@C-CN catalysts was compared ( Figure 31 ) and apparent rate constant ( Figure 32 The degradation rate / apparent rate of IMD in the Fe-POM / LB-CN system after 15 minutes of reaction was found to be 100% / 0.446 min. -1 The concentration was significantly higher than that of Fe4-POM / LB-CN (66.6% / 0.101 min). -1 ) and Fe 17 -POM / LB-CN (37.3% / 0.039 min) -1 The Fe-POM / LB-CN system exhibits a high mineralization rate for IMD (TOC removal efficiency up to 63.5%). Figure 33 This indicates that IMD was successfully decomposed into small molecules.

[0130] The effects of catalyst concentration, pH value, and reaction temperature on the photocatalytic activity of the Fe-POM / LB-CN system were further analyzed next. Figure 34 As shown, with the catalyst concentration increasing from 0.02 g·L⁻¹... -1 Increase to 0.4 g·L -1 The IMD degradation rate showed a trend of first increasing and then decreasing, which may be due to the high catalyst concentration hindering light absorption and utilization. When the catalyst concentration was 0.2 g·L⁻¹, the degradation rate... -1 At that time, the Fe-POM / LB-CN system achieved 100% IMD degradation rate after 15 minutes of reaction. Therefore, 0.2 g·L⁻¹ -1 The optimal catalyst concentration was determined to be the best condition for subsequent experiments. For example... Figure 35 and Figure 36 By using the same IMD degradation rate index to optimize the reaction conditions, pH=7.0 and 20℃ were determined to be the optimal experimental conditions.

[0131] With optimized experimental parameters, the practical application potential of the Fe-POM / LB-CN photocatalytic system was extensively evaluated. For example... Figure 37As shown, this system under different coexisting anions (including Cl) - NO3 - SO4 2- HCO3 - CO3 2- and H2PO4 - The Fe-POM / LB-CN photocatalytic system maintained a high and consistent IMD degradation rate (always above 92%). Subsequently, the recovery performance of the Fe-POM / LB-CN photocatalytic system was evaluated under various conditions to explore the balance between catalytic activity and stability during H2O2 activation. Continuous IMD degradation experiments without catalyst replenishment showed that the Fe-POM / LB-CN photocatalytic system could sustain eight stable and efficient cycles. Figure 38 After 8 cycles, the IMD degradation rate of this system was still above 95%, and the apparent rate constant was still greater than 0.2 min. -1 Meanwhile, other cyclic experiments also reflected this pattern ( Figure 39 The IMD degradation rate of this photocatalytic system remained above 97.6% throughout 11 cycles. Based on these results, the photostability of the Fe-POM / LB-CN photocatalytic system was further evaluated under catalyst renewal conditions. Figure 40 As shown, the IMD degradation rate of this system consistently exceeded 97.1% throughout 30 consecutive cycles, and its apparent rate constant remained at a high level throughout the test period. k obs > 0.21 min -1 , Figure 41 This superior cycle performance redefines the concept of "stability" in the field of photo-Fenton-like wastewater purification, highlighting the outstanding efficacy and resilience of the Fe-POM / LB-CN photocatalytic system.

[0132] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a bifunctional iron POM-modified carbon-based material, characterized in that, Includes the following steps: Step 1: Preparation of graphitic carbon nitride The mixture of urea and melamine was spread evenly on the bottom of a quartz boat, tightly wrapped with tin foil, and then placed in a muffle furnace for calcination. The powder obtained above was ground and placed in a quartz boat, wrapped with tin foil and punched with multiple small holes; then it was placed in a tube furnace filled with nitrogen to calcine, thus obtaining graphitic carbon nitride (CN). Step 2: Preparation of carbon-coated nickel oxide particles Nickel acetate hexahydrate and citric acid were dissolved in a mixture of deionized water and anhydrous ethanol and placed at the bottom of a quartz boat. The mixture was then pretreated in a forced-air drying oven to obtain a light green transparent gel. Finally, the precursor gel was calcined in a tube furnace filled with nitrogen to obtain carbon-coated nickel oxide particles NiO@C. Step 3: Preparation of carbon-encapsulated nickel oxide particles loaded with graphitic carbon nitride nanosheets Graphite carbon nitride and carbon-coated nickel oxide particles were dispersed in anhydrous ethanol and subjected to ultrasonic treatment. The resulting solution was dried in a forced-air drying oven. Subsequently, the resulting solid powder was mixed and ground with anhydrous ethanol to obtain carbon-coated nickel oxide particles loaded with graphite carbon nitride nanosheets NiO@C-CN. Step 4: Preparation of bifunctional iron POM-modified carbon-based materials K8[γ-PW 10 O 36 ·12H2O and ferrous chloride tetrahydrate were dissolved in potassium chloride aqueous solution. After vigorous stirring, hydrogen chloride solution was added to adjust the pH of the solution to 5.

0. The resulting solution was heated using a heated magnetic stirrer, and then ferrous chloride tetrahydrate was added again while stirring continuously. Subsequently, a mixture of potassium chloride and sodium chloride was added, stirred, and allowed to stand. Yellow-brown crystals precipitated, and the solid precipitate was collected by centrifugation. After washing with cold water, the precipitate was dried in a vacuum drying oven to obtain Fe polynuclear metal oxometalate Fe-POM. Finally, NiO@C-CN and Fe-POM were dispersed in a methanol solution and subjected to ultrasonic treatment. After continuous stirring in a reflux condenser, the mixture was centrifuged and dried to obtain the bifunctional iron POM-modified carbon-based material Fe-POM / LB-CN.

2. The method for preparing a bifunctional iron POM-modified carbon-based material according to claim 1, characterized in that, In step one, the mass ratio of urea to melamine is 1.5~2.5 g: 1.5~2.5 g; The calcination conditions for quartz boats in a muffle furnace are: heating to 450~550℃ and holding for 3~5 hours; The calcination conditions for quartz boats in a tube furnace are: heating to 450~550℃ and holding for 3~5 hours.

3. The method for preparing a bifunctional iron POM-modified carbon-based material according to claim 1, characterized in that, In step two, the mass-to-volume ratio of nickel acetate hexahydrate, citric acid, deionized water, and anhydrous ethanol is 0.3~0.5 g : 0.9~1.1 g : 2~3 mL : 0.5~1.5 mL; The pretreatment conditions for quartz boats in a forced-air drying oven are: heating to 70~80℃ and maintaining for 2~3 hours; The calcination conditions for quartz boats in a tube furnace are: heating to 300~400℃ and holding for 7~9 hours.

4. The method for preparing a bifunctional iron POM-modified carbon-based material according to claim 1, characterized in that, In step three, the mass-to-volume ratio of graphite carbon nitride, carbon-coated nickel oxide particles, and anhydrous ethanol is 90-110 mg: 4-6 mg: 4-6 mL, and the ultrasonic treatment time is 1-3 hours. The drying oven is kept at 50-70℃ for 5-7 hours, and the mixing and grinding time is 50-70 minutes.

5. The method for preparing a bifunctional iron POM-modified carbon-based material according to claim 1, characterized in that, In step four, K8[γ-PW] 10 O 36 The mass-to-volume ratio of 12H2O, ferrous chloride tetrahydrate, and potassium chloride aqueous solution was 450-550 mg: 60-100 mg: 15-25 mL. The heating conditions for the magnetic stirrer were: heating to 35-45℃ and maintaining for 1.5-2.5 hours. Add 20-60 mg of ferrous chloride tetrahydrate again, and continue stirring with a magnetic stirrer for 1.5-2.5 hours.

6. A method for preparing a bifunctional iron POM-modified carbon-based material according to claim 1, characterized in that, In step four, the mass ratio of potassium chloride to sodium chloride in the mixture of potassium chloride and sodium chloride is 80~120 mg: 20~40 mg, and the mixture is stirred continuously with a magnetic stirrer for 20~40 minutes. The mixed solution was left to stand at 2-6℃ for 20-28 hours, centrifuged at 6000-8000 rpm for 5-10 minutes, and then dried in a vacuum drying oven at 35-45℃ for 20-28 hours.

7. The method for preparing a bifunctional iron POM-modified carbon-based material according to claim 1, characterized in that, In step four, the mass-to-volume ratio of NiO@C-CN, Fe-POM, and methanol solution is 120-160 mg: 15-25 mg: 15-25 mL, and the ultrasonic treatment time is 20-40 minutes.

8. The method for preparing a bifunctional iron POM-modified carbon-based material according to claim 1, characterized in that, In step four, the reflux condenser is heated to 55-65°C and maintained for 22-26 hours, centrifuged at 6000-8000 rpm for 5-10 minutes, and the vacuum drying oven is maintained at 55-65°C for 10-14 hours.

9. The application of the bifunctional iron POM-modified carbon-based material prepared by the method described in claim 1 as a photocatalyst in the field of pesticide removal from water.

10. The application according to claim 9, characterized in that, The application method is as follows: bifunctional iron POM-modified carbon-based materials are used as photocatalysts to produce H2O2 in situ and promote its activation, thereby degrading imidacloprid.

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