Application of oxygen-doped carbon dot material as photocatalyst in photocatalytic production of hydrogen peroxide
By using oxygen-doped carbon dot materials as photocatalysts and using light energy to perform carbonyl reduction reaction in carbon dots, the problem of using precious metal catalysts in the existing H2O2 production process is solved, and efficient, green and environmentally friendly preparation of hydrogen peroxide is achieved.
Patent Information
- Application Number
- CN202411838091.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-05-02
AI Technical Summary
In the existing H2O2 production process, the hydrogenation reaction steps of the anthraquinone catalyst are complex and precious metal catalysts are required, resulting in high production costs, unfriendly environment, low reaction safety, and lack of green sustainability.
The oxygen-doped carbon dot material is used as a photocatalyst and prepared by solvothermal method. The carbonyl group in the carbon dot is reduced to hydroxyl groups by using light energy to achieve photocatalytic oxidation of water or oxygen to form hydrogen peroxide.
The process of photocatalytic preparation of hydrogen peroxide has been realized, with the advantages of simple preparation, low cost, mild reaction conditions, high stability, and fast reaction rate. It has the characteristics of green and environmental protection, and is suitable for replacing traditional processes.
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Abstract
Description
Technical Field
[0001] The invention relates to the field of photocatalytic preparation of hydrogen peroxide, and in particular to the application of oxygen-doped carbon dot materials as photocatalysts in photocatalytic production of hydrogen peroxide. Background Art
[0002] As a strong oxidant, hydrogen peroxide (H2O2) has been widely used in industrial and domestic fields, including wastewater treatment, chemical synthesis, industrial bleaching, energy storage, medical disinfection, etc., and has become a promising energy carrier in fuel cells. Since H2O2 only produces H2O and O2 after decomposition, it does not pollute the environment and is a green energy. In addition, H2O2 is a liquid fuel that can be completely soluble in water. It is easier to transport and store than traditional hydrogen energy and has higher safety. Due to its high efficiency, environmental protection, and safety, H2O2 has been selected as one of the 100 most important chemicals in the world. It is estimated that by 2027, the global market share of H2O2 will reach about 5.7 million tons, and its influence in the field of sustainable energy will become increasingly greater.
[0003] In industry, the production method of H2O2 is mainly based on the 2-ethylanthraquinone method. The production of industrial H2O2 is a four-step cycle: (i) anthraquinone catalyst hydrogenation reaction; (ii) anthraquinone oxidation and oxygen reduction process; (iii) H2O2 extraction and working liquid recycling and regeneration process; (iv) H2O2 purification, concentration, and distillation process. In the H2O2 production process, the anthraquinone catalyst hydrogenation reaction is the most core step in the whole process. The efficiency of catalytic hydrogenation directly determines the rate of O2 reduction to H2O2. In this process, nickel or precious metal palladium is required as a catalyst. H2 is introduced into the mixed reaction liquid composed of aromatic hydrocarbons and alcohols with high boiling points for catalytic hydrogenation. In this process, the carbonyl group (=O) in 2-ethylanthraquinone will be reduced and hydrogenated to hydroxyl group (-OH). Before process (ii), the catalyst in the hydrogenated working liquid needs to be separated by filtration to avoid the decomposition of H2O2 by the metal catalyst. It can be seen that this process is not only cumbersome, but also requires precious metals as catalysts, which increases production costs and is not environmentally friendly. The addition of H2 reduces the safety of the reaction process. These problems make the anthraquinone method not green and sustainable and cannot meet the development needs of today's society. Solar energy, as a clean and renewable energy source, has been favored in energy conversion applications in recent years. The technology of converting H2O or O2 into H2O2 using solar energy through photocatalytic technology is expected to become one of the ideal methods to replace traditional processes. Summary of the invention
[0004] The purpose of the present invention is to provide an application of oxygen-doped carbon dot materials as photocatalysts in photocatalytic production of hydrogen peroxide.
[0005] In order to achieve the purpose of the present invention, in a first aspect, the present invention provides the use of oxygen-doped carbon dot materials as photocatalysts in photocatalytic production of hydrogen peroxide.
[0006] The oxygen-doped carbon dot material is prepared by a bottom-up method using a small molecule compound containing an oxygen element as a precursor.
[0007] The small molecule compound containing oxygen element can be selected from phenol, benzoquinone, benzoic acid, anthraquinone compounds, etc., and their structures are as follows: Wherein, R is any substituent at any position, and R is selected from methyl, ethyl, methoxy, amino, hydroxyl, carboxyl, cyano, halogen element substituent, and benzene ring substituent.
[0008] Furthermore, the oxygen element exists in the carbon dots in the form of carbonyl, carboxyl, aldehyde or hydroxyl groups. The carbon dots can be selected from graphene quantum dots, carbon quantum dots, carbon nanodots, carbonized polymer dots and the like.
[0009] Furthermore, the bottom-up method can be selected from hydrothermal method, solvothermal method, solvent-free method, ultrasonic method, microwave method and the like.
[0010] In a specific embodiment of the present invention, the method for preparing oxygen-doped carbon dot materials by solvothermal method includes: dissolving the precursor in a solvent, and ensuring that the precursor is completely dissolved by ultrasound; heating the mixed system to 160-220°C, keeping warm for 3-12 hours and then cooling to room temperature, transferring the reaction solution to a centrifuge tube, centrifuging, taking the supernatant and dialyzing it, and finally freeze-drying it.
[0011] The solvent may be selected from one or more of amide solvents, alcohol solvents, ketone solvents, hydrocarbon solvents and the like.
[0012] For example, the organic solvent may be selected from one or more of N,N-dimethylformamide (DMF), ethanol (EtOH), acetone, and the like.
[0013] Furthermore, the precursor can be dissolved in an organic solvent at any concentration.
[0014] Furthermore, the dialysate used for dialysis is a mixture of water and ethanol, preferably with a volume ratio of water to ethanol of 1:1.
[0015] In a second aspect, the present invention provides a method for producing hydrogen peroxide from photocatalytic oxygen molecules, using an oxygen-doped carbon dot material as a photocatalyst, dispersing the oxygen-doped carbon dot material in water, and reducing oxygen or air to hydrogen peroxide under light conditions (wherein the oxygen element in the hydrogen peroxide comes from oxygen, and the hydrogen element comes from water molecules).
[0016] In a third aspect, the present invention provides a method for photocatalytically producing hydrogen peroxide from water molecules, using oxygen-doped carbon dot materials as photocatalysts to oxidize water into oxygen or hydrogen peroxide under light conditions.
[0017] Furthermore, the illumination is one or more of xenon lamp illumination, sunlight irradiation, and LED illumination, and the wavelength of the light is 300-800 nm.
[0018] Furthermore, the intensity of the illumination is 10-1000 mW / cm 2 , the temperature is controlled at 0~100℃ during the illumination process.
[0019] In the present invention, the catalyst can be recycled.
[0020] By means of the above technical solution, the present invention has at least the following advantages and beneficial effects: The carbon dots provided by the present invention use oxygen-containing functional groups as the main active sites for hydrogen peroxide generation, and undergo oxygen reduction hydrogen peroxide generation reaction under light conditions. This type of carbon dot photocatalyst has excellent characteristics such as simple preparation, low cost, mild reaction conditions, high stability, and fast reaction rate, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is a transmission electron microscopy image of the oxygen-doped carbon dots prepared in Example 1 of the present invention.
[0022] Figure 2 XRD and Raman spectra of oxygen-doped carbon dots prepared in Example 2 of the present invention.
[0023] Figure 3 Schematic diagram of the process of preparing oxygen-doped carbon dots in Example 3 of the present invention.
[0024] Figure 4 The three-dimensional fluorescence spectrum and absorption spectrum of the oxygen-doped carbon dots prepared in Example 3 of the present invention.
[0025] Figure 5 This is an X-ray photoelectron spectrum of the oxygen-doped carbon dots prepared in Example 4 of the present invention.
[0026] Figure 6 This is the infrared spectrum of the nitrogen-doped carbon dots prepared in Example 4 of the present invention.
[0027] Figure 7 This is a graph showing the rate of producing hydrogen peroxide by the oxygen-doped carbon dots prepared in Example 1 of the present invention under different temperatures and the same light conditions. DETAILED DESCRIPTION
[0028] The present invention provides a novel photocatalyst-oxygen-doped carbon dots for application in photocatalytic H2O2 production.
[0029] Carbon dots (CDs), as a metal-free carbon-based nanomaterial, exhibit excellent photocatalytic activity. Due to its advantages of simple synthesis, low cost, green, safe, and high stability, it has a unique advantage in the field of photocatalytic H2O2 production.
[0030] The present invention provides a novel photocatalyst - carbon dots for photocatalytic H2O2 production. Since the structure of carbon dots is easy to control, an anthraquinone-like structure can be constructed in the carbon dots, and the carbonyl (=O) reduction and hydrogenation reaction in the carbon dots and further oxidation to generate hydrogen peroxide also occur. Different from the industrial reduction method, the present invention uses light energy to reduce the carbonyl (=O) in the carbon dots to hydroxyl (-OH).
[0031] The carbon dots in this catalytic system are prepared from the bottom up method using oxygen-containing small molecules and biomass as precursors. The preparation process includes three parts: synthesis, purification and separation. The synthesized carbon dots have a certain graphitized structure, which leads to good light absorption ability, charge transfer ability and cycle stability.
[0032] The oxygen-doped carbon dots described in the present invention include but are not limited to graphene quantum dots, carbon quantum dots, carbon nanodots, and carbonized polymer dots. The oxygen element exists in the carbon dots in the form of carbonyl, carboxyl, aldehyde or hydroxyl groups. It constitutes the active center for the photocatalytic production of hydrogen peroxide by carbon dots. As a semiconductor material, carbon dots generate photogenerated electrons and holes under light excitation. The photogenerated electrons will be enriched around the oxygen elements in the carbon dots for oxygen reduction reaction to generate hydrogen peroxide, and the photogenerated holes will oxidize water in the graphite conjugated structure to generate hydrogen peroxide. This process does not require the addition of any sacrificial agent, the generated hydrogen peroxide is easy to separate and utilize, and the reaction conditions are mild and the process is green and safe.
[0033] The oxygen-doped carbon dots of the present invention are prepared by a bottom-up method, including but not limited to a hydrothermal method, a solvothermal method, a solvent-free method, an ultrasonic method, a microwave method and other synthetic routes.
[0034] The solvothermal synthesis steps are as follows: S1. Using oxygen-containing small molecules as precursors, placing them in a solvent, and ultrasonicating until the precursors are completely dissolved, wherein the organic solvent includes a mixed solution of one or more different solvents selected from amide solvents, alcohol solvents, ketone solvents, hydrocarbon solvents, etc., in different proportions.
[0035] For example, the organic solvent may be selected from one or more of N,N-dimethylformamide (DMF), ethanol (EtOH), acetone, and the like.
[0036] S2. The above solution is transferred into a Teflon high-pressure reactor, and then the reactor is placed in a constant temperature forced air drying oven, heated to any temperature between 160 and 220° C., and kept warm for 3 to 12 hours.
[0037] S3. After the reaction is completed, take out the reactor and place it at room temperature to allow it to cool naturally to room temperature.
[0038] S4. The reaction solution in the reactor was transferred to a centrifuge tube and centrifuged at 10,000 rpm to remove impurities such as carbon residue.
[0039] S5. Transfer the supernatant after centrifugation to a dialysis bag with a cutoff of 3500 Da and dialyze in a mixed dialysate of water and ethanol (the volume ratio of water to ethanol is 1:1) until the dialysate is colorless, clear, and has no fluorescence.
[0040] S6. The liquid retained in the dialysis bag is freeze-dried to obtain a solid powder sample of carbon dots.
[0041] The above solvent method is used to synthesize nitrogen-doped carbon dots through a series of purifications.
[0042] The oxygen-doped carbon dot material of the present invention is used as a novel photocatalyst for photocatalytic production of hydrogen peroxide. Specifically, the oxygen-doped carbon dot material is used as a multiphase catalyst to drive the reduction reaction of oxygen and the oxidation reaction of water to generate hydrogen peroxide under light conditions.
[0043] In a specific embodiment of the present invention, the generation of hydrogen peroxide is driven under light conditions, and the light is one or more of sunlight irradiation, xenon lamp light irradiation, and LED light irradiation, and the wavelength range of the light wave is 300-800 nm.
[0044] Furthermore, the intensity of the illumination is 100-3000 mW / cm 2 During the illumination process, the temperature was controlled at 0~100℃.
[0045] Furthermore, the carbon dot photocatalyst can be recycled and reused in intermittent batch reactions.
[0046] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products.
[0047] Example 1 1.08 g of resorcinol was placed in 10 mL of ethanol solution and ultrasonicated until the resorcinol was completely dissolved.
[0048] The above solution was transferred into a 20 mL Teflon autoclave, and then the autoclave was placed in a constant temperature forced air drying oven, heated to 200°C, and kept warm for 12 hours; After the reaction is completed, the reactor is taken out and placed at room temperature to allow it to cool naturally to room temperature.
[0049] The reaction solution in the reactor was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 15 min to separate and remove impurities such as carbon residue.
[0050] The supernatant after centrifugation was transferred to a dialysis bag with a cut-off of 3500 Da and dialyzed in a mixed dialysate of water and ethanol in a ratio of 1:1 until the dialysate was colorless, clear, and non-fluorescent.
[0051] The liquid retained in the dialysis bag can be freeze-dried to obtain a solid powder sample of nitrogen-doped carbon dots.
[0052] The transmission electron microscopy image of oxygen-doped carbon dots prepared in Example 1 is shown in Figure 1 , XRD and Raman spectra are shown in Figure 2 .
[0053] Example 2 This embodiment provides a method for synthesizing oxygen-doped carbon dots, and the preparation method thereof is as follows: 1.08 g of 3,4-dihydroxybenzoic acid was placed in 20 mL of aqueous solution and ultrasonicated until p-phenylenediamine was completely dissolved.
[0054] The above solution was transferred into a 50-m open beaker, and the beaker was placed in a microwave oven for microwave reaction at a power of 800 W for 10 min. After the reaction is completed, take out the open beaker and place it at room temperature to allow it to cool naturally to room temperature.
[0055] The reaction solution in the beaker was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 15 min to separate and remove impurities such as carbon residue.
[0056] The supernatant after centrifugation was transferred to a dialysis bag with a cut-off of 3500 Da and dialyzed in a mixed dialysate of water and ethanol until the dialysate was colorless, clear, and non-fluorescent.
[0057] The liquid retained in the dialysis bag can be freeze-dried to obtain a solid powder sample of nitrogen-doped carbon dots.
[0058] Example 3 This embodiment provides a method for synthesizing oxygen-doped carbon dots, and the preparation method thereof is as follows: 1.10 g (5 mmol) of catechol and 0.08 g (0.33 mmol) of AlCl3·6H2O were mixed and ground evenly in an agate mortar for 10 min until they were mixed well.
[0059] The mixture was then transferred into a 30 mL polytetrafluoroethylene autoclave and heated in a forced air oven at 200 °C for 12 h. The autoclave was then taken out and cooled naturally to room temperature.
[0060] The obtained carbonized powder was dissolved in an ethanol solution and filtered through a 0.22 μm polyethersulfone membrane to remove insoluble particles. The filtered solution was transferred to a dialysis bag with a cutoff of 3500 Da and dialyzed in a deionized water environment for 7 days, with the deionized water replaced every 12 hours until the dialysate was colorless, clear, and non-fluorescent.
[0061] Finally, the remaining liquid in the dialysis bag was transferred to a 50 mL centrifuge tube and vacuum freeze-dried to obtain a solid powder sample doped with carbon dots.
[0062] Example 3 Schematic diagram of the process of preparing oxygen-doped carbon dots is shown in Figure 3 .
[0063] The fluorescence three-dimensional spectrum and absorption spectrum of the oxygen-doped carbon dots prepared in Example 3 are shown in FIG. Figure 4 .
[0064] Example 4 2.10 g of 2,5-dihydroxyanthraquinone was placed in 10 mL of DMF solution and sonicated until 2,3-diaminophenolazine was completely dissolved.
[0065] The above solution was transferred into a Teflon high-pressure reactor with a volume of 20 mL, and then the reactor was placed in a constant temperature forced air drying oven, heated to 220°C, and kept warm for 12 hours.
[0066] After the reaction is completed, the reactor is taken out and placed at room temperature to allow it to cool naturally to room temperature.
[0067] The reaction solution in the reactor was transferred to a centrifuge tube and centrifuged at 10,000 rpm for 15 min to separate and remove impurities such as carbon residue.
[0068] The supernatant after centrifugation was transferred to a dialysis bag with a cut-off of 3500 Da and dialyzed in a mixed dialysate of water and ethanol in a volume ratio of 1:1 until the dialysate was colorless, clear, and non-fluorescent.
[0069] The liquid retained in the dialysis bag can be freeze-dried to obtain a solid powder sample of oxygen-doped carbon dots.
[0070] The X-ray photoelectron spectrum of the oxygen-doped carbon dots prepared in Example 4 is shown in Figure 5 .
[0071] The infrared spectrum of the nitrogen-doped carbon dots prepared in Example 4 is shown in Figure 6 .
[0072] Example 5 10 mg of the oxygen-doped carbon dots prepared in Example 1 was placed in 50 mL of deionized water and ultrasonicated until the carbon dots were evenly dispersed.
[0073] The aqueous dispersion of carbon dots was transferred to a quartz glass photoreactor and a flow rate of 80-100 mL min was passed under the liquid surface. -1 Oxygen was continuously introduced at a flow rate of 30 min.
[0074] The light intensity is 100 mW cm -2 A 100 W xenon lamp equipped with a 400 nm filter was used as the light source to continuously illuminate the reaction system in the photoreactor. Oxygen was continuously introduced during the illumination process, and the reaction temperature was controlled at 25 ℃, 50 ℃, and 80 ℃.
[0075] The H2O2 concentration in the aqueous solution was tested at different reaction time points.
[0076] When the H2O2 concentration in the water phase reaches the required level, turn off the oxygen and light source. Separate the carbon dots by centrifugation or filtration. Then add new deionized water to produce the next batch of H2O2.
[0077] The rate of production of hydrogen peroxide by oxygen-doped carbon dots prepared in Example 1 under light conditions is shown in Figure 7 .
[0078] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.
Claims
1. Application of oxygen-doped carbon dots as photocatalysts in photocatalytic production of hydrogen peroxide; The oxygen-doped carbon dot material is prepared by a bottom-up method using a small molecule compound containing an oxygen element as a precursor; The small molecule compound containing oxygen element is selected from phenol, benzoquinone, benzoic acid, anthraquinone compounds, and their structures are as follows: in, R is any substituent at any position, and R is selected from methyl, ethyl, methoxy, amino, hydroxyl, carboxyl, cyano, halogen element substituent, and benzene ring substituent.
2. The use according to claim 1, characterized in that: The oxygen element exists in the carbon dots in the form of carbonyl, carboxyl, aldehyde or hydroxyl groups; The carbon dots are selected from graphene quantum dots, carbon quantum dots, carbon nanodots, and carbonized polymer dots.
3. The use according to claim 1, characterized in that: The bottom-up method is selected from hydrothermal method, solvothermal method, solvent-free method, ultrasonic method and microwave method.
4. The use according to claim 3, characterized in that: The method for preparing oxygen-doped carbon dot materials by solvothermal method comprises: dissolving the precursor in a solvent, and ensuring that the precursor is completely dissolved by ultrasound; heating the mixed system to 160-220° C., keeping the temperature for 3-12 hours, and then cooling to room temperature, transferring the reaction solution to a centrifuge tube, centrifuging, taking the supernatant and dialyzing it, and finally freeze-drying it to obtain the obtained product; The solvent is selected from one or more of amide solvents, alcohol solvents, ketone solvents, and hydrocarbon solvents; The dialysate used for dialysis is a mixture of water and ethanol, preferably with a volume ratio of water to ethanol of 1:
1.
5. A method for producing hydrogen peroxide by photocatalytic oxygen molecules, characterized in that: Using oxygen-doped carbon dot materials as photocatalysts, dispersing the oxygen-doped carbon dot materials in water, and reducing oxygen or air to hydrogen peroxide under light conditions; The oxygen-doped carbon dot material is the same as that described in any one of claims 1-4.
6. A method for photocatalytically producing hydrogen peroxide from water molecules, characterized in that: Using oxygen-doped carbon dots as photocatalysts, water is oxidized into oxygen or hydrogen peroxide under light conditions; The oxygen-doped carbon dot material is the same as that described in any one of claims 1-4.
7. The method according to claim 5 or 6, characterized in that: The illumination is one or more of xenon lamp illumination, sunlight irradiation, and LED illumination, and the wavelength of the light wave is 300-800 nm.
8. The method according to claim 7, characterized in that The intensity of the light is 10-1000 mW / cm 2 , the temperature is controlled at 0~100℃ during the illumination process.
9. The method according to claim 5 or 6, characterized in that: The photocatalyst can be recycled.