Preparation method and application of composite photocatalyst for producing hydrogen peroxide in high-chlorine environment

Abstract

The invention discloses a preparation method and application of a composite photocatalyst for producing hydrogen peroxide in a high-chlorine environment, and aims to solve the problem that the photocatalytic activity of most photocatalytic materials in the high-chlorine environment is obviously inhibited, so that the hydrogen peroxide production capacity is relatively low. The preparation method comprises the following steps: 1, treating melamine at high temperature to obtain a BCN material; 2, carrying out heat treatment and ultrasonic stripping treatment on the BCN material in air to obtain a flaky OCN material; and 3, dissolving the OCN material and anthraquinone-2-carboxylic acid in a dichloromethane solution, and preparing the OCN-AQ composite photocatalytic material by using a chemical catalytic coupling method. AQ molecules in the prepared OCN-AQ composite photocatalytic material are loaded to the edge of a carbon nitride structure in a covalent bond chemical coupling mode, the photon-generated carrier separation and transmission efficiency of the composite material is remarkably improved, the composite material has more excellent photocatalytic activity, and the excellent photocatalytic hydrogen peroxide production capacity is achieved in a high-chlorine environment.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalysts, and particularly relates to a method for preparing a composite photocatalyst having excellent visible light photocatalytic performance in a high-chlorine environment, and the use of the photocatalyst to prepare hydrogen peroxide. Background Art

[0002] Hydrogen peroxide (H2O2), as a highly efficient and green oxidant, is in widespread demand in energy, environmental protection, and other fields, but its mainstream industrial production still relies on the traditional anthraquinone method. This method requires multiple hydrogenation / oxidation reactions, which are complex, energy-intensive, and subject to byproduct pollution, making it difficult to meet the needs of a low-carbon economy. How to efficiently and greenly produce hydrogen peroxide has become a hot topic today. Photocatalytic technology uses solar energy to convert water into H2O2, theoretically offering significant advantages of cleanliness and low cost. However, existing catalysts generally suffer from defects such as narrow light absorption range, high carrier recombination rate, and poor product selectivity, resulting in actual yields far below theoretical values.

[0003] Seawater accounts for 96.5% of the earth's water resources and contains rich dissolved oxygen, which can be used as a natural reaction medium to significantly reduce fresh water consumption and raw material costs. However, the high concentration of chloride ions (Cl - ), organic matter, and complex water environments can easily affect photocatalytic activity, triggering side reactions and leading to a sharp decrease in H2O2 yield and selectivity. Therefore, there is an urgent need to develop new composite photocatalysts with broad spectral response, resistance to ion interference, and high stability to overcome the technical bottleneck of hydrogen peroxide production in seawater environments. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem that the photocatalytic activity of most current photocatalytic materials is significantly inhibited in a high chlorine environment, resulting in a low hydrogen peroxide production capacity, thereby providing a method for preparing a composite photocatalyst that can efficiently produce hydrogen peroxide in a high chlorine environment.

[0005] The preparation method of the composite photocatalyst for producing hydrogen peroxide in a high chlorine environment of the present invention is achieved by the following steps:

[0006] First, melamine is placed in a crucible and treated at a temperature of 500-600°C. After cooling to room temperature, the BCN material is obtained after washing and drying.

[0007] 2. The BCN material is evenly spread in a crucible and fully exposed to the atmosphere. After standing, it is heated to 500-600 ° C and maintained for 2-3 hours. After cooling to room temperature, it is dispersed in deionized water and subjected to ultrasonic exfoliation treatment. After washing and drying, the sheet-like OCN material is obtained.

[0008] 3. Dissolve the sheet OCN material and anthraquinone-2-carboxylic acid (AQ-COOH) in a dichloromethane solution, mix well, and gradually add diisopropylethylamine, 1-hydroxybenzotriazole, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide. After ultrasonic treatment, stir and react at room temperature for 48-72 hours. After washing and drying, a composite photocatalyst (OCN-AQ composite photocatalytic material) that produces hydrogen peroxide in a high chlorine environment is obtained.

[0009] The mass ratio of anthraquinone-2-carboxylic acid, diisopropylethylamine, 1-hydroxybenzotriazole and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in step 3 is (10-20): (7-15): (8-16): (10-25).

[0010] The application of the composite photocatalyst for producing hydrogen peroxide in a high-chlorine environment of the present invention is to place the composite photocatalyst in a high-chlorine environment and prepare hydrogen peroxide under visible light conditions.

[0011] The BCN prepared by the present invention has a graphite layered stacking structure and no obvious pore size. The interlayer distance of the OCN after pyrolysis and ultrasonic exfoliation is reduced, and the specific surface area is significantly increased. In addition, the chemical catalytic coupling of anthraquinone molecules (AQ) does not significantly affect the surface morphology characteristics and pore structure of the OCN.

[0012] Through experimental analysis of photocatalytic hydrogen peroxide production, the present invention shows that the OCN-AQ composite photocatalytic material has the best photocatalytic activity in a high-chlorine environment. Under the condition of 10% isopropyl alcohol (IPA) as a sacrificial agent, the H2O2 production reaches 44 mM / g within 60 minutes, which is 7.68 times that of pure BCN. The morphological and structural characteristics of the materials did not show obvious changes after the chemical catalytic coupling of OCN and AQ. The results of surface chemical property analysis showed that AQ molecules were loaded onto the edge of the carbon nitride structure through covalent chemical coupling. The results of optical property analysis showed that the band gaps of BCN, OCN and OCN-AQ composites were 2.75eV, 2.84eV and 2.81eV, respectively. The valence band spectrum results showed that their valence band positions (VB) were 1.62eV, 1.92eV and 2.27eV, respectively, and the conduction band positions (CB) were -1.27eV, -1.06eV and -0.68eV, respectively. The results of photoelectric effect analysis showed that the separation and transmission efficiency of photogenerated carriers of the composite materials were significantly enhanced after oxygen atom doping and AQ loading, and they had better photocatalytic activity.

[0013] In the OCN-AQ composite photocatalytic material prepared by this invention, AQ molecules are covalently bonded to the OCN surface. This significantly enhances the separation and transport efficiency of photogenerated charge carriers, resulting in superior photocatalytic activity. The optimal OCN-AQ composite photocatalyst prepared by this invention achieved a H₂O₂ yield of 3305 μmol / g within 60 minutes in a high-chloride environment with 10% IPA as a sacrificial agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 X-ray diffraction spectra of BCN, OCN and OCN-AQ composite photocatalytic materials prepared in Examples;

[0015] Figure 2 BCN, OCN and OCN-AQ composite photocatalytic materials prepared in the examples 13 C NMR spectrum;

[0016] Figure 3 The open circuit potential decay graphs of BCN, OCN and OCN-AQ composite photocatalytic materials prepared in the examples;

[0017] Figure 4 This is a graph showing the H2O2 photocatalytic yield of BCN, OCN and OCN-AQ composite photocatalytic materials prepared in the examples under high chlorine conditions of 10% IPA;

[0018] Figure 5 This is a graph showing the H2O2 photocatalytic yield of BCN, OCN and OCN-AQ composite photocatalytic materials prepared in the example under the condition of 10% IPA deionized water;

[0019] Figure 6 Schematic diagram of the photocatalytic mechanism of the OCN-AQ composite photocatalytic material prepared in the example in a high chlorine environment. DETAILED DESCRIPTION

[0020] Specific embodiment 1: The preparation method of the composite photocatalyst for producing hydrogen peroxide in a high chlorine environment in this embodiment is implemented according to the following steps:

[0021] First, melamine is placed in a crucible and treated at a temperature of 500-600°C. After cooling to room temperature, the BCN material is obtained after washing and drying.

[0022] 2. The BCN material is evenly spread in a crucible and fully exposed to the atmosphere. After standing, it is heated to 500-600 ° C and maintained for 2-3 hours. After cooling to room temperature, it is dispersed in deionized water and subjected to ultrasonic exfoliation treatment. After washing and drying, the sheet-like OCN material is obtained.

[0023] 3. Dissolve the sheet OCN material and anthraquinone-2-carboxylic acid (AQ-COOH) in a dichloromethane solution, mix well, and gradually add diisopropylethylamine, 1-hydroxybenzotriazole, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide. After ultrasonic treatment, stir and react at room temperature for 48-72 hours. After washing and drying, a composite photocatalyst (OCN-AQ composite photocatalytic material) that produces hydrogen peroxide in a high chlorine environment is obtained.

[0024] The mass ratio of anthraquinone-2-carboxylic acid, diisopropylethylamine, 1-hydroxybenzotriazole and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in step 3 is (10-20): (7-15): (8-16): (10-25).

[0025] In this embodiment, the photocatalyst for efficient hydrogen peroxide production in a high chlorine environment is prepared using melamine and anthraquinone-2-carboxylic acid as raw materials through heat treatment, ultrasonic exfoliation and chemical catalytic coupling. Under visible light irradiation, the carriers on the OCN-AQ composite photocatalytic material are separated, generating photogenerated electrons (e - ) and photogenerated holes (h + ). Then the AQ at the edge of the material will quickly capture the photogenerated electrons to generate semiquinone radicals (AQ •- ), and then H + The reaction generates hydrogen anthraquinone (H2AQ). The doping of oxygen atoms redistributes the internal charge of the material, which is conducive to the generation of an internal electric field, further promoting the separation of photogenerated carriers and strengthening the material's ability to adsorb O2 in the environment. Subsequently, H2AQ at the edge reacts with the adsorbed O2 to generate H2O2 in one step and is oxidized to AQ, realizing a one-step 2-electron oxygen reduction reaction process, thereby inhibiting the 4-electron oxygen reduction process. On the other hand, h + and a large amount of Cl in the environment - or OH - The reaction produces chlorine radicals (•Cl) and hydroxyl radicals (•OH), which further reduce the carrier recombination rate and promote the continued photocatalytic reaction.

[0026] In this embodiment, the AQ molecules in the OCN-AQ composite photocatalytic material are loaded onto the edge of the carbon nitride structure by covalent chemical coupling. The photogenerated carrier separation and transmission efficiency of the composite material are significantly enhanced, and the composite material has better photocatalytic activity, achieving excellent photocatalytic hydrogen peroxide production capacity in a high-chlorine environment.

[0027] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the high temperature treatment time in step 1 is 3-5 h.

[0028] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that in step 1, the temperature is 2.5-5℃•min -1 The temperature is raised to 500-600°C at a rate of 100-200°C.

[0029] Specific embodiment 4: This embodiment differs from any one of specific embodiments 1 to 3 in that the standing time in step 2 is 3-5 h.

[0030] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that in step 2, ultrasonic peeling is performed in deionized water at an ultrasonic frequency of 20-25 kHz for 5-8 hours.

[0031] Specific embodiment 6: The difference between this embodiment and any one of specific embodiments 1 to 5 is that the washing in step 1 and step 2 is repeated washing with anhydrous ethanol and deionized water.

[0032] Specific embodiment seven: This embodiment differs from any one of specific embodiments one to six in that the mass ratio of the sheet-like OCN material to anthraquinone-2-carboxylic acid in step three is (10-15):1.

[0033] Specific embodiment eight: This embodiment differs from any one of specific embodiments one to seven in that the mass ratio of anthraquinone-2-carboxylic acid, diisopropylethylamine, 1-hydroxybenzotriazole and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in step three is (10-15): (7-10): (8-10): (10-15).

[0034] Specific embodiment 9: This embodiment differs from any one of specific embodiments 1 to 8 in that in step 3, after ultrasonic treatment for 5-10 minutes, the reaction is stirred at room temperature for 48-55 hours.

[0035] Example: The preparation method of the composite photocatalyst for efficiently producing hydrogen peroxide in a high chlorine environment in this embodiment is implemented according to the following steps:

[0036] 1. Place 15 g of melamine in a covered aluminum chloride crucible and transfer it to a muffle furnace at 3 °C·min -1 The temperature was raised to 550°C at a speed of 1000 ℃ and kept at this temperature for 4 h. After cooling to room temperature, the collected yellow block solid was repeatedly washed with anhydrous ethanol and deionized water, and then dried in a forced air drying oven at 60°C to obtain BCN material.

[0037] 2. Weigh 1.5 g of the BCN material obtained in step 1 and spread it evenly in an uncovered alumina crucible to fully contact the atmosphere. After standing for 3 h, transfer it to a muffle furnace and heat it at 3 °C·min -1The temperature was raised to 550°C and maintained for 2 h. After cooling to room temperature, the collected light yellow powder was dispersed in 500 mL of deionized water and subjected to ultrasonic exfoliation at a frequency of 20 kHz for 8 h. After repeated washing with anhydrous ethanol and deionized water, the powder was dried in a forced air drying oven at 60°C to obtain a flaky OCN material.

[0038] 3. Weigh 0.1 g of the OCN material obtained in step 2 and 10 mg of AQ-COOH and dissolve them in 50 ml of dichloromethane solution. After mixing evenly, gradually add 7.7 mg of diisopropylethylamine, 8.1 mg of 1-hydroxybenzotriazole and 11.5 mg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide. Ultrasonic treatment is performed at a frequency of 10 kHz for 5 min. The mixture is stirred at room temperature for 48 h. The collected product is repeatedly washed with dichloromethane and deionized water, and then dried in a vacuum drying oven at 80 ° C to obtain a composite photocatalyst (OCN-AQ composite photocatalytic material) that produces hydrogen peroxide in a high chlorine environment.

[0039] The OCN-AQ composite photocatalytic material obtained in this example was used to conduct a photocatalytic H2O2 production experiment. During the photocatalytic production of H2O2 by the OCN-AQ composite material, OCN-AQ was excited by visible light, and the carriers separated, generating photogenerated electrons and photogenerated holes. In this process, the photogenerated electrons were quickly captured by AQ to generate semiquinone free radicals (AQ •- ), further and environmental H + The reaction generates hydrogen anthraquinone (H2AQ), which suppresses photogenerated electron quenching and carrier recombination. The doping of oxygen atoms redistributes the charge within the material, enhancing its ability to adsorb ambient O2. H2AQ then reacts with the adsorbed O2 to generate H2O2 in a single step, which is then oxidized to AQ, completing a one-step two-electron oxygen reduction reaction. To confirm the influence of material type and water environment on photocatalytic H2O2 production, photocatalytic H2O2 production experiments were conducted using BCN, OCN, and OCN-AQ in high-chloride seawater and deionized water environments.

[0040] In a high-chloride seawater environment with 10% isopropyl alcohol (IPA) as a sacrificial agent, the photocatalytic material BCN produced only 301 μmol / g of H2O2 within 60 minutes. After heat treatment and ultrasonic exfoliation, the photocatalytic material OCN produced only 647 μmol / g of H2O2 within 60 minutes. However, the OCN-AQ composite photocatalytic material modified by chemical catalytic coupling produced 3305 μmol / g of H2O2 within 60 minutes. Furthermore, to explore the effects of different water environments, in deionized water with 10% isopropyl alcohol (IPA) as a sacrificial agent, the H2O2 production of BCN, OCN, and OCN-AQ composite photocatalysts within 60 minutes was 289, 991, and 2207 μmol / g, respectively. This indicates that the complex water quality environment in seawater significantly affects the efficiency of photocatalytic H2O2 production. Among them, the abundant chloride ions in seawater may interfere with the photocatalytic process. They will react with the generated superoxide radicals and inhibit the production of H2O2, resulting in low efficiency of BCN and OCN in producing H2O2 in a high-chlorine environment; while OCN-AQ has a one-step reaction from O2 to generate H2O2 in the photocatalytic process, realizing a one-step 2-electron oxygen reduction reaction process, effectively avoiding the interference of a large number of anions and achieving a high H2O2 yield.

[0041] Figure 1 The X-ray diffraction spectra show that BCN, OCN and OCN-AQ composite photocatalytic materials all have a significant graphite-like carbon nitride stacking structure. The interlayer distance of the OCN material is reduced after heat treatment and ultrasonic exfoliation, and the AQ chemical catalytic coupling does not affect the crystal structure of the material. Figure 2 of 13 The C nuclear magnetic resonance spectra show that BCN, OCN and OCN-AQ composite photocatalytic materials all display characteristic peaks in the carbon nitride structure at 164 and 156 ppm, among which the new peak of OCN-AQ at 134 ppm represents the successful coupling of AQ. Figure 3 The open circuit potential decay diagram shows the open circuit potential decay changes of BCN, OCN and OCN-AQ composite photocatalytic materials at the moment of visible light irradiation. Among them, the photovoltage generated by OCN-AQ is 4.5 times that of BCN, reflecting that the composite photocatalytic material doped with oxygen atoms and loaded with AQ has a larger internal electric field. Figure 4 and Figure 5 The H2O2 photocatalytic yield curves of BCN, OCN and OCN-AQ composite photocatalytic materials under different environments show that OCN-AQ composite materials can not only significantly improve the photocatalytic activity, but also synergize with a large number of ions in high chlorine to promote the photocatalytic H2O2 production process. Figure 6 It can be seen that the photocatalytic process of producing H2O2 is achieved through a one-step 2-electron oxygen reduction reaction process.

Claims

1. A method for preparing a composite photocatalyst for producing hydrogen peroxide in a high chlorine environment, characterized in that The preparation method is achieved by the following steps: First, melamine is placed in a crucible and treated at a temperature of 500-600°C. After cooling to room temperature, the BCN material is obtained after washing and drying.

2. The BCN material is evenly spread in a crucible and fully exposed to the atmosphere. After standing, it is heated to 500-600 ° C and maintained for 2-3 hours. After cooling to room temperature, it is dispersed in deionized water and subjected to ultrasonic exfoliation treatment. After washing and drying, the sheet-like OCN material is obtained. Third, the sheet-like OCN material and anthraquinone-2-carboxylic acid were dissolved in a dichloromethane solution and mixed evenly. Diisopropylethylamine, 1-hydroxybenzotriazole, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide were gradually added. After ultrasonic treatment, the mixture was stirred at room temperature for 48-72 hours. After washing and drying, a composite photocatalyst for producing hydrogen peroxide in a high chlorine environment was obtained. The mass ratio of anthraquinone-2-carboxylic acid, diisopropylethylamine, 1-hydroxybenzotriazole and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in step 3 is (10-20): (7-15): (8-16): (10-25).

2. The method for preparing a composite photocatalyst for producing hydrogen peroxide in a high chlorine environment according to claim 1, characterized in that The high temperature treatment time in step 1 is 3-5 h.

3. The method for preparing a composite photocatalyst for producing hydrogen peroxide in a high chlorine environment according to claim 1, characterized in that In step 1, the temperature was set at 2.5-5℃·min -1 The temperature is raised to 500-600°C at a rate of 100-200°C.

4. The method for preparing a composite photocatalyst for producing hydrogen peroxide in a high chlorine environment according to claim 1, characterized in that The standing time in step 2 is 3-5 h.

5. The method for preparing a composite photocatalyst for producing hydrogen peroxide in a high chlorine environment according to claim 1, characterized in that In step 2, ultrasonic stripping is performed in deionized water at an ultrasonic frequency of 20-25 kHz for 5-8 h.

6. The method for preparing a composite photocatalyst for producing hydrogen peroxide in a high chlorine environment according to claim 1, characterized in that The washing in step 1 and step 2 is repeated washing with anhydrous ethanol and deionized water.

7. The method for preparing a composite photocatalyst for producing hydrogen peroxide in a high chlorine environment according to claim 1, characterized in that In step 3, the mass ratio of the flaky OCN material to anthraquinone-2-carboxylic acid is (10-15):

1.

8. The method for preparing a composite photocatalyst for producing hydrogen peroxide in a high chlorine environment according to claim 1, characterized in that In step 3, the mass ratio of anthraquinone-2-carboxylic acid, diisopropylethylamine, 1-hydroxybenzotriazole and 1-ethyl-(3-dimethylaminopropyl)carbodiimide is (10-15):(7-10):(8-10):(10-15).

9. The method for preparing a composite photocatalyst for producing hydrogen peroxide in a high chlorine environment according to claim 1, characterized in that In step 3, after ultrasonic treatment for 5-10 min, the reaction was stirred at room temperature for 48-55 h.

10. Use of the composite photocatalyst for producing hydrogen peroxide in a high chlorine environment prepared as claimed in claim 1, characterized in that The composite photocatalyst is placed in a high-chlorine environment and hydrogen peroxide is prepared under visible light conditions.

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