Interlayer AlN3 monatomic site anchored carbon nitride nanotube photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses an interlayer AlN3 monatomic site anchored carbon nitride nanotube photocatalyst as well as a preparation method and application thereof, and belongs to the field of photocatalysis. The preparation method of the photocatalyst for catalyzing water and oxygen to be converted into hydrogen peroxide comprises the following steps: (1) by taking melamine, soluble aluminum salt and a metal chelating agent as raw materials, carrying out supramolecular self-assembly reaction by adopting a hydrothermal method to generate a carbon nitride nanorod precursor; and (2) roasting the carbon nitride nanorod precursor to obtain the photocatalyst. According to the photocatalyst prepared by the method disclosed by the invention, Al atoms are connected between carbon nitride layers, so that the transfer distance of carriers from the inside to the outside can be shortened, and the carrier separation efficiency is improved; the valence band position of the photocatalyst is high, and holes in the valence band have enough energy to directly oxidize water, so that the catalytic performance is greatly improved.

Description

Technical Field

[0001] The invention relates to the field of photocatalysis, and in particular to an interlayer AlN3 single-atom anchored carbon nitride nanotube photocatalyst and a preparation method and application thereof. Background Art

[0002] The development and utilization of clean energy is an important measure to achieve the strategic goal of "carbon peak and carbon neutrality". As a new energy source with high energy density, hydrogen peroxide is a promising clean fuel for new energy vehicles and rockets, and is gradually attracting people's attention. At present, the anthraquinone method used in industrial preparation will lead to problems such as high energy consumption and high pollution. Therefore, the development of new green production technologies is imminent. The photocatalytic water / oxygen conversion to hydrogen peroxide technology only requires the use of light energy, water and oxygen, mainly including two-step reactions of water oxidation to provide protons and oxygen two-electron reduction to hydrogen peroxide. The whole process can achieve zero carbon emissions, which will effectively help achieve "carbon peak and carbon neutrality". However, severe carrier recombination, slow water oxidation kinetics, and low selectivity of oxygen reduction are the main bottlenecks in the application of this technology. The development and utilization of new photocatalysts to achieve efficient oxidation of water and highly selective reduction of oxygen are the key to breaking through this bottleneck.

[0003] Carbon nitride materials have the advantages of simple synthesis and wide sources of raw materials. At the same time, their suitable energy band structure enables them to achieve water oxidation and oxygen reduction reactions at the same time in theory, and are widely used in the research of synthesizing hydrogen peroxide. The main body of carbon nitride is a bulk powder material. When the carriers migrate from the interior to the surface active sites, the long migration distance can cause serious recombination of photogenerated carriers. In addition, it has poor visible light absorption ability, weak activation ability for water / oxygen, and other problems, and urgently needs to be modified.

[0004] Single-atom catalysts are catalytic materials prepared by anchoring metal elements in the catalyst in the form of single atoms. They have the advantages of precise coordination structure and excellent catalytic performance. Among them, single-atom catalysts prepared with metal elements filled with full d bands can avoid the formation of carrier recombination centers after the introduction of heteroatoms, and on the other hand, the electronic properties of the catalyst carrier can be adjusted to improve its catalytic performance. Therefore, using carbon nitride as a carrier to design and construct a metal single atom anchored carbon nitride photocatalyst will not only effectively improve the carrier separation efficiency of carbon nitride, but also significantly improve the catalytic performance of carbon nitride, which is of great significance for the development of new high-performance photocatalysts.

[0005] At present, the methods for improving the performance of carbon nitride catalysts in producing hydrogen peroxide include introducing heteroatoms such as S into the skeleton of carbon nitride materials, constructing a black phosphorus / carbon nitride heterojunction structure, etc. The method for introducing S heteroatoms is to replace the original N position in the carbon nitride skeleton with S. The introduced S only replaces the original position of the carbon nitride N, and the efficiency of carrier transmission from the inside across the layer is low. The method for constructing a heterojunction is to use ultrasonic treatment to increase the distance between the layers of the carbon nitride layered stacking material, and then introduce another layered material such as black phosphorus between the carbon nitride layers to make them tightly combined. Carbon nitride and black phosphorus are combined together to form a new catalyst with a heterojunction structure. The synthesis process of this method is complicated, and there is no chemical bond connection between the two in this heterojunction structure, and carriers are easily compounded when they are transmitted between black phosphorus and carbon nitride. The materials prepared by the above two methods are all block powders, which is not conducive to the transmission of carriers from the inside to the surface. The holes in their valence bands do not have enough energy to oxidize water, and the catalytic performance of photocatalytic water oxygen conversion into hydrogen peroxide is difficult to improve. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a sandwich AlN3 single atom anchored carbon nitride nanotube photocatalyst and a preparation method and application thereof; the photocatalyst prepared by the method of the present invention has Al atoms connected between carbon nitride layers, which can shorten the distance for carriers to be transmitted from the inside to the outside and improve the carrier separation efficiency; the valence band position of the photocatalyst becomes higher, and the holes on the valence band have sufficient energy to directly oxidize water, which greatly improves the catalytic performance of the catalyst in photocatalyzing water and oxygen into hydrogen peroxide.

[0007] The present invention first provides a method for preparing a photocatalyst, comprising the following steps:

[0008] (1) Using melamine, soluble aluminum salt and metal chelating agent as raw materials, a hydrothermal method is used to generate a carbon nitride nanorod precursor by a supramolecular self-assembly reaction;

[0009] (2) calcining the carbon nitride nanorod precursor to obtain the photocatalyst.

[0010] In the above preparation method, the soluble aluminum salt is at least one of aluminum nitrate, aluminum chloride and aluminum sulfate;

[0011] The metal chelating agent is at least one of ethylenediaminetetraacetic acid, aminotriacetic acid, diethylenetriaminepentaacetic acid, citric acid, tartaric acid and gluconic acid;

[0012] The molar ratio of the melamine, the soluble aluminum salt and the metal chelating agent is 12:0.04-0.20:0.01-0.3; specifically, it can be 12:0.06-0.18:0.12 or 12:0.12:0.12.

[0013] In the above-mentioned preparation method, the reaction temperature of the hydrothermal method is 140-180°C; specifically, it can be 180°C;

[0014] The reaction time of the hydrothermal method is 16 to 36 hours, and can be specifically 24 hours.

[0015] In the above-mentioned preparation method, the calcination is carried out in an inert atmosphere; specifically, it can be an argon atmosphere;

[0016] The calcination temperature is 400-600°C, and can be 500°C.

[0017] The calcination time is 1 to 3 hours, specifically 1.5 hours;

[0018] The heating rate of the calcination is 1-10°C / min -1 ;Specifically, it can be 5℃ / min -1 .

[0019] In the above-mentioned preparation method, the specific method of step (1) is as follows: melamine, soluble aluminum salt and metal chelating agent are dissolved in water, and then heated to react, and the resulting precipitate is a carbon nitride nanorod precursor.

[0020] In the above preparation method, the ratio of the volume of water to the molar number of melamine is 80 mL:0.1-12 mmol; specifically, it can be 80 mL:12 mmol.

[0021] In the above preparation method, the specific method of step (1) is as follows: dissolve melamine, soluble aluminum salt and metal chelating agent in water, stir at 80°C to 100°C for 1h to 5h, and then transfer it to a reaction kettle and heat it for reaction.

[0022] In the above-mentioned preparation method, in step (1), after the hydrothermal reaction, there is a step of collecting the precipitate, washing it with water and freeze-drying it.

[0023] The invention also provides a photocatalyst prepared by the above preparation method.

[0024] The application of the above photocatalyst in catalyzing the conversion of water and oxygen into hydrogen peroxide also falls within the protection scope of the present invention. Finally, the present invention provides a method for synthesizing hydrogen peroxide, comprising the following steps: mixing water and the above photocatalyst and reacting them in an oxygen atmosphere.

[0025] The reaction is carried out under light conditions.

[0026] The photocatalyst synthesized by the method of the present invention is in the form of thin-walled nanotubes, and Al atoms are connected between carbon nitride layers; the presence of Al sites provides a channel for carrier cross-layer transmission, and the thin-walled carbon nitride nanotubes can shorten the distance for carriers to be transmitted from the inside to the outside, thereby improving the carrier separation efficiency;

[0027] The photocatalyst prepared by the present invention is a carbon nitride material anchored by Al atoms, whose valence band position becomes higher, and the holes on the valence band have enough energy to directly oxidize water, which greatly improves the catalytic performance of the catalyst in photocatalyzing water and oxygen into hydrogen peroxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is an electron microscope image of the interlayer AlN3 single-atom anchored carbon nitride nanotube photocatalyst prepared in Example 1.

[0029] Figure 2 Digital photos of interlayer AlN3 single atom anchored carbon nitride nanotube photocatalyst (CNNT-Al) and carbon nitride (CN) synthesized by traditional methods.

[0030] Figure 3 This is a comparison chart of the hydrogen peroxide production performance of photocatalysts with different Al loadings.

[0031] Figure 4 This is a diagram of the bactericidal effect of hydrogen peroxide produced by the interlayer AlN3 single-atom anchored carbon nitride nanotube photocatalyst. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with specific embodiments. The given examples are only for illustrating the present invention, but not for limiting the scope of the present invention.

[0033] The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0034] The quantitative tests in the following examples were all repeated three times, and the results were averaged.

[0035] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0036] Example 1

[0037] First, 12 mmol of melamine, 0.12 mmol of EDTA (ethylenediaminetetraacetic acid) and 0.12 mmol of Al(NO3)3·9H2O were dissolved in 80 mL of deionized water and stirred at 80°C for 1 h. The resulting solution was then transferred to a 100 mL stainless steel reactor and heated at 180°C for 24 h. After the solution was cooled, the white precipitate was collected, washed three times with deionized water by centrifugation, and the product was freeze-dried. The dried white product was heated at 500°C for 1.5 h in an argon atmosphere in a tubular furnace at a heating rate of 5°C / min. -1 Finally, yellow flocculent interlayer AlN3 single atom anchored carbon nitride nanotube photocatalyst CNNT-Al was obtained. 0.12 (abbreviated as CNNT-Al).

[0038] The electron microscope image of the interlayer AlN3 single atom anchored carbon nitride nanotube photocatalyst prepared in this example is shown in Figure 1 As shown in the figure, the photocatalyst has a tubular morphology, and the carbon nitride tube length is greater than 100 μm. The carbon nitride synthesized by the traditional method has a bulk powder morphology (see Figure 1 b) in the above.

[0039] The specific method of synthesizing carbon nitride by the traditional method is as follows: 10g of melamine is heated at 550℃ in a muffle furnace for 2h, with a heating rate of 4℃min -1 .

[0040] The interlayer AlN3 single-atom anchored carbon nitride nanotube photocatalyst prepared in this example has a fluffy cotton-like morphology (see Figure 2 ), while the carbon nitride synthesized by the traditional method ( Figure 2 CN) is a bulk powder material.

[0041] The carbon nitride synthesized by traditional methods has a stacked structure at the microscopic level, which is not conducive to the transfer of carriers from the inside to the catalyst surface. With interlayer Al-anchored carbon nitride, Al is located between the carbon nitride layers, constructing a carrier transfer channel, which is conducive to the transfer of carriers from the surface to the catalyst surface.

[0042] Example 2

[0043] The preparation method is the same as that in Example 1, except that the amount of Al(NO3)3·9H2O added is different. Specifically, first, 12 mmol of melamine, 0.12 mmol of EDTA (ethylenediaminetetraacetic acid) and 0 mmol, 0.06 mmol or 0.18 mmol of Al(NO3)3·9H2O are dissolved in 80 mL of deionized water and stirred at 80°C for 1 h. The resulting solution is then transferred to a 100 mL stainless steel reactor and heated at 180°C for 24 h. After the solution is cooled, the white precipitate is collected, washed three times by centrifugation with deionized water, and the product is freeze-dried. The above-mentioned dried white product is heated at 500°C for 1.5 h in an argon atmosphere in a tubular furnace, with a heating rate of 5°C / min -1 Finally, yellow flocculent carbon nitride nanotube photocatalyst CNNT and yellow flocculent interlayer AlN3 single atom anchored carbon nitride nanotube photocatalyst CNNT-Al with different Al contents were obtained. 0.06 and CNNT-Al 0.18 .

[0044] Example 1 and the catalysts in this example were used to perform a photocatalytic water-oxygen synthesis of hydrogen peroxide reaction experiment and to compare the performance of synthesizing hydrogen peroxide. The specific experimental method is as follows: the photoreaction was carried out in a 25 mL round bottom heat-resistant glass bottle under an O2 atmosphere (1 atm). H2O (2 mL) and a catalyst (2 mg) were added to a reactor equipped with a stirring rod. The round bottom heat-resistant glass bottle reactor was illuminated with a 300 W xenon lamp (100 mW cm -2 ) for 1 h, and the temperature was maintained at 25 °C by circulating condensed water. The H2O2 produced in the reaction was determined by iodine titration.

[0045] Carbon nitride nanotubes with different Al contents exhibit different activities for producing hydrogen peroxide (see Figure 3 ), and the catalytic performance in the presence of interlayer Al is higher than that of carbon nitride synthesized by conventional methods (CN in the figure, which is prepared by the conventional method of Example 1).

[0046] Example 3

[0047] The catalyst in Example 1 and the carbon nitride synthesized by the traditional method are used to synthesize hydrogen peroxide according to the reaction conditions in Example 2, and the synthesized hydrogen peroxide is used to inactivate fungi in water. The specific experimental method is: take the commercially available Escherichia coli S17-1 (China Center for Type Culture Collection, CCTCC for short) strain and culture it with LB medium, and then dilute it with ultrapure water to 2.5k CUF / mL; take 2 portions of the above bacterial solution and 1mL respectively dissolve and disperse them in 1mL of the above synthesized hydrogen peroxide solution. After constant temperature at 25℃ for 12h, the above solutions are respectively applied to the LB medium. The above culture medium is cultured in a constant temperature box at 25℃ for 12h.

[0048] The hydrogen peroxide produced by the interlayer AlN3 single-atom anchored carbon nitride nanotube photocatalyst has 100% bactericidal performance (see Figure 4 The hydrogen peroxide produced by conventionally synthesized carbon nitride is not sufficient to kill bacteria (see Figure 4 , left figure).

Claims

1. A method for preparing a photocatalyst, comprising the following steps: (1) Using melamine, soluble aluminum salt and metal chelating agent as raw materials, a hydrothermal method is used to generate a carbon nitride nanorod precursor by a supramolecular self-assembly reaction; (2) calcining the carbon nitride nanorod precursor to obtain the photocatalyst.

2. The preparation method according to claim 1, characterized in that: The soluble aluminum salt is at least one of aluminum nitrate, aluminum chloride and aluminum sulfate; The metal chelating agent is at least one of ethylenediaminetetraacetic acid, aminotriacetic acid, diethylenetriaminepentaacetic acid, citric acid, tartaric acid and gluconic acid; The molar ratio of the melamine, the soluble aluminum salt and the metal chelating agent is 12:0.04-0.20:0.01-0.3; specifically, it can be 12:0.06-0.18:0.12 or 12:0.12:0.

12.

3. The preparation method according to claim 1 or 2, characterized in that: The reaction temperature of the hydrothermal method is 140-180°C; The reaction time of the hydrothermal method is 16 to 36 hours.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The calcination is carried out in an inert atmosphere; The calcination temperature is 400-600°C; The calcination time is 1 to 3 hours.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The specific method of step (1) is as follows: melamine, soluble aluminum salt and metal chelating agent are dissolved in water, and then heated to react, and the resulting precipitate is a carbon nitride nanorod precursor.

6. The preparation method according to claim 5, characterized in that: The ratio of the volume of water to the molar number of melamine is 80 mL: 0.1-12 mmol.

7. The photocatalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the photocatalyst according to claim 7 in catalyzing the conversion of water and oxygen into hydrogen peroxide.

9. A method for synthesizing hydrogen peroxide, comprising the steps of: mixing water and the photocatalyst according to claim 7, and reacting them in an oxygen atmosphere.

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