Preparation method and application of porous nitrogen-doped graphene aerogel material in air purification materials

Abstract

The present invention belongs to the field of air purification technology and specifically discloses a method for preparing a porous nitrogen-doped graphene aerogel material. The method comprises the following steps: mixing graphite oxide and water, and subjecting the mixture to low-frequency ultrasound to obtain a graphene oxide solution; adding an alkaline substance and urea to the graphene oxide solution, adjusting the pH of the graphene oxide solution, and obtaining a graphene oxide mixed solution; and subjecting the obtained graphene oxide mixed solution to a hydrothermal reaction to obtain a porous nitrogen-doped graphene aerogel material. The present invention utilizes a one-step process to prepare the porous nitrogen-doped graphene aerogel material. The process is simple, environmentally friendly, efficient, and energy-efficient, making it suitable for large-scale industrial production and application. The preparation method can increase the specific surface area of ​​the graphene aerogel and the nitrogen atom content of the urea-doped graphene aerogel, thereby significantly improving its ability to rapidly adsorb formaldehyde in a short period of time.

Description

Technical Field

[0001] The present invention belongs to the technical field of air purification, and in particular relates to a preparation method and application of a porous nitrogen-doped graphene aerogel material. Background Art

[0002] Formaldehyde, a typical air pollutant, comes from a wide range of sources, including decoration materials, artificial furniture, textile decorations, and daily necessities. Long-term exposure to formaldehyde, especially in confined spaces where air circulation is restricted and formaldehyde concentrations are high, can cause a range of serious health problems. To reduce formaldehyde concentrations and mitigate environmental health risks, most people opt for adsorption products such as activated carbon and bamboo charcoal bags. However, these adsorption materials generally suffer from long adsorption cycles and very limited adsorption capacity, making them ineffective in rapidly absorbing formaldehyde.

[0003] In order to address the shortcomings of the above-mentioned adsorption materials, heteroatoms such as N and S are doped on the adsorption materials to form air purification materials with excellent chemical adsorption capacity, thereby achieving efficient adsorption of formaldehyde in a short time. As one of the graphene derivatives, graphene oxide not only has a significant specific surface area, but also has polar functional groups such as carboxyl, hydroxyl, and carbonyl on its surface, which is easy to chemically modify and is a suitable raw material. In addition, urea is an abundant, cost-effective, and nitrogen-rich substance. By using it as a nitrogen source to dope N atoms on graphene, its chemical adsorption capacity for formaldehyde can be improved. However, due to its low nitrogen conversion rate, most studies use PEI or EDA as a nitrogen source to dope graphene with N and adsorb formaldehyde. However, these two chemical substances are toxic and costly, and are not suitable for large-scale preparation of air purification materials.

[0004] Therefore, from the perspective of cost and environmental protection, providing an air purification material with a simple preparation process and the ability to improve the urea nitrogen conversion rate to obtain a rapid formaldehyde adsorption capability has become a technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a preparation method and application of porous nitrogen-doped graphene aerogel material.

[0006] In order to achieve the above objectives, one of the technical solutions of the present invention is: a method for preparing a porous nitrogen-doped graphene aerogel material, comprising the following steps:

[0007] (1) mixing graphite oxide and water, and obtaining a graphene oxide solution after low-frequency ultrasound;

[0008] (2) adding an alkaline substance and urea to the graphene oxide solution obtained in step (1), adjusting the pH value of the graphene oxide solution, and obtaining a graphene oxide mixed solution;

[0009] (3) subjecting the graphene oxide mixed solution obtained in step (2) to a hydrothermal reaction to obtain a porous nitrogen-doped graphene aerogel material.

[0010] In a preferred embodiment of the present invention, the mass ratio of graphite oxide to water in step (1) is (2-10): (990-998).

[0011] In a preferred embodiment of the present invention, the frequency of the low-frequency ultrasound in step (1) is 20-40 KHz, and the time of the low-frequency ultrasound is 180-360 min.

[0012] In a preferred embodiment of the present invention, the alkaline substance in step (2) is one of potassium hydroxide and sodium hydroxide.

[0013] In a preferred embodiment of the present invention, in step (2), the mass ratio of the alkaline substance to the graphite oxide is (0.3-2):1, and the mass ratio of urea to the graphite oxide is (1-50):1.

[0014] In a preferred embodiment of the present invention, the pH value in step (2) is adjusted by HCl with a concentration of 1M.

[0015] In a preferred embodiment of the present invention, the pH value of the graphene oxide mixed solution in step (2) is 1-9.

[0016] In a preferred embodiment of the present invention, the temperature of the hydrothermal reaction in step (3) is 160-200° C., and the reaction time is 6-24 h.

[0017] In a preferred embodiment of the present invention, the step (3) further comprises washing and freeze-drying after the hydrothermal reaction is completed.

[0018] More preferably, the freeze-drying time is 24-72 hours.

[0019] In order to achieve the above objectives, the second technical solution of the present invention is: a porous nitrogen-doped graphene aerogel material prepared by the above preparation method.

[0020] In order to achieve the above objectives, the third technical solution of the present invention is: application of the porous nitrogen-doped graphene aerogel material prepared by the above preparation method in air purification materials.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention adds an alkaline substance during the hydrothermal process, which can activate and form pores in graphite oxide at a relatively mild temperature, thereby increasing the total specific surface area and micropore area of ​​the graphene aerogel, as well as the active sites on the surface that react with the nitrogen source. This improves the formaldehyde adsorption capacity of the porous nitrogen-doped graphene aerogel material through both physical adsorption and chemical adsorption. Compared with the current method of preparing porous materials using alkaline substances as activators at high temperatures, the energy consumption in the preparation process can be significantly reduced.

[0023] 2. The urea used in the present invention is a nitrogen-rich substance with abundant content, high cost-effectiveness, and can, under the activation effect of alkaline substances on the raw materials, improve the nitrogen conversion rate of urea to a certain extent, thereby broadening the application of urea as a nitrogen source in the preparation of air purification materials;

[0024] 3. The present invention adopts a one-step method to prepare porous nitrogen-doped graphene aerogel materials. The process is simple and easy to implement, green and efficient, with low energy consumption, and is suitable for industrial large-scale production and application;

[0025] 4. The preparation method of the present invention can increase the specific surface area of ​​the graphene aerogel and the nitrogen atom content of urea-doped graphene aerogel, thereby significantly improving its short-term rapid adsorption capacity for formaldehyde. Compared with the nitrogen-doped graphene aerogel prepared without adding alkaline substances, the nitrogen content of the porous nitrogen-doped graphene aerogel material is increased by more than 30%, and its adsorption effect on formaldehyde within 10 minutes is improved by more than 40%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below with reference to the accompanying drawings and examples.

[0027] Figure 1 The total specific surface area and micropore area data of the porous nitrogen-doped graphene aerogel materials prepared in Example 2 of the present invention and Comparative Example 2. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is described in more detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0029] The present invention provides a method for preparing a porous nitrogen-doped graphene aerogel material, comprising the following steps:

[0030] (1) mixing graphite oxide and water, and obtaining a graphene oxide solution after low-frequency ultrasound;

[0031] (2) adding an alkaline substance and urea to the graphene oxide solution obtained in step (1), adjusting the pH value of the graphene oxide solution, and obtaining a graphene oxide mixed solution;

[0032] (3) subjecting the graphene oxide mixed solution obtained in step (2) to a hydrothermal reaction to obtain a porous nitrogen-doped graphene aerogel material.

[0033] The water in step (1) is preferably deionized water.

[0034] The mass ratio of graphite oxide to water in step (1) is preferably (2-10): (990-998), more preferably (3-9): (991-997), further preferably (4-8): (992-996), and most preferably (5-7): (993-995). The low-frequency ultrasound frequency is 20-40 kHz, more preferably 25-40 kHz, further preferably 30-40 kHz, and the low-frequency ultrasound time is 180-360 min, more preferably 210-330 min, further preferably 240-300 min. The present invention can ensure that a graphene oxide solution is obtained by controlling the mass ratio of graphite oxide to water and the frequency and time of the low-frequency ultrasound.

[0035] The pH value in step (2) is adjusted by HCl with a concentration of 1M.

[0036] The alkaline substance in step (2) is preferably one of potassium hydroxide and sodium hydroxide, and the mass ratio of the alkaline substance to graphite oxide is preferably (0.3-2):1, more preferably (0.5-1.5):1, and further preferably (0.8-1):1.

[0037] The preparation ratio of urea to graphite oxide in step (2) is preferably (1-50):1, more preferably (5-45):1, and further preferably (10-40):1.

[0038] The pH value of the graphene oxide mixed solution in step (2) is preferably 1-9, more preferably 3-7, and further preferably 3-5.

[0039] After obtaining the graphene oxide mixed solution, the present invention performs a hydrothermal reaction on the graphene oxide mixed solution to obtain porous nitrogen-doped graphene aerogel.

[0040] The temperature of the hydrothermal reaction in step (3) is preferably 160-200°C, more preferably 160-190°C, and even more preferably 160-180°C. The hydrothermal reaction time is preferably 6-24 hours, more preferably 10-20 hours, and even more preferably 12-16 hours. By controlling the temperature and time of the hydrothermal reaction, the present invention can ensure that urea is thermally decomposed to produce ammonia, and can also produce a complete aerogel structure.

[0041] In the present invention, after the hydrothermal reaction in step (3) is completed, washing and freeze-drying are further performed. The present invention has no particular limitation on the specific operation of the washing, and any washing method well known to those skilled in the art can be used to remove excess urea.

[0042] The freeze-drying time is preferably 24-72 hours, more preferably 30-60 hours, and further preferably 36-48 hours.

[0043] The present invention also provides a porous nitrogen-doped graphene aerogel material prepared by the preparation method described in the above technical solution.

[0044] The present invention also provides the use of porous nitrogen-doped graphene aerogel materials in air purification materials.

[0045] The present invention does not specifically limit the specific manner of applying the porous nitrogen-doped graphene aerogel material in air purification materials, and it can be determined based on the technical common sense of those skilled in the art.

[0046] Example 1

[0047] A porous nitrogen-doped graphene aerogel material is prepared by the following method, comprising the following steps:

[0048] (1) mixing graphite oxide and water, and subjecting them to low-frequency ultrasound to obtain a graphene oxide solution; the mass ratio of the graphite oxide to water is 2:998; the low-frequency ultrasound frequency is 30 kHz, and the low-frequency ultrasound time is 180 min;

[0049] (2) adding an alkaline substance and urea to the graphene oxide solution obtained in step (1), adjusting the pH value of the graphene oxide solution with 1M HCl, and fully mixing to obtain a graphene oxide mixed solution; the alkaline substance is potassium hydroxide; the mass ratio of the potassium hydroxide to the graphite oxide is 0.3:1, the mass ratio of the urea to the graphite oxide is 1:1, and the pH value of the graphene oxide mixed solution is 1;

[0050] (3) subjecting the graphene oxide mixed solution obtained in step (2) to a hydrothermal reaction, and finally washing and freeze-drying to obtain a porous nitrogen-doped graphene aerogel material; the temperature of the hydrothermal reaction is 160° C., the time of the hydrothermal reaction is 24 hours, and the time of the freeze-drying is 24 hours.

[0051] Example 2

[0052] A porous nitrogen-doped graphene aerogel material is prepared by the following method, comprising the following steps:

[0053] (1) mixing graphite oxide and water, and subjecting them to low-frequency ultrasound to obtain a graphene oxide solution; the mass ratio of the graphite oxide to water is 5:995; the low-frequency ultrasound frequency is 40 kHz, and the low-frequency ultrasound time is 300 min;

[0054] (2) adding an alkaline substance and urea to the graphene oxide solution obtained in step (1), adjusting the pH value of the graphene oxide solution with 1M HCl, and fully mixing to obtain a graphene oxide mixed solution; the alkaline substance is potassium hydroxide; the mass ratio of the potassium hydroxide to the graphite oxide is 0.8:1, the mass ratio of the urea to the graphite oxide is 10:1, and the pH value of the graphene oxide mixed solution is 3.

[0055] (3) subjecting the graphene oxide mixture obtained in step (2) to a hydrothermal reaction, and finally washing and freeze-drying to obtain a porous nitrogen-doped graphene aerogel material. The hydrothermal reaction temperature is 160° C., the hydrothermal reaction time is 12 hours, and the freeze-drying time is 48 hours.

[0056] Example 3

[0057] A porous nitrogen-doped graphene aerogel material is prepared by the following method, comprising the following steps:

[0058] (1) mixing graphite oxide and water, and subjecting them to low-frequency ultrasound to obtain a graphene oxide solution; the mass ratio of the graphite oxide to water is 5:995; the low-frequency ultrasound frequency is 25 kHz, and the low-frequency ultrasound time is 240 min;

[0059] (2) adding an alkaline substance and urea to the graphene oxide solution obtained in step (1), adjusting the pH value of the graphene oxide solution with 1M HCl, and fully mixing to obtain a graphene oxide mixed solution; the alkaline substance is sodium hydroxide; the mass ratio of the sodium hydroxide to the graphite oxide is 1:1, the mass ratio of the urea to the graphite oxide is 20:1, and the pH value of the graphene oxide mixed solution is 5.

[0060] (3) subjecting the graphene oxide mixture obtained in step (2) to a hydrothermal reaction, and finally washing and freeze-drying to obtain a porous nitrogen-doped graphene aerogel material. The hydrothermal reaction temperature is 200° C., the hydrothermal reaction time is 12 hours, and the freeze-drying time is 36 hours.

[0061] Example 4

[0062] A porous nitrogen-doped graphene aerogel material is prepared by the following method, comprising the following steps:

[0063] (1) mixing graphite oxide and water, and subjecting them to low-frequency ultrasound to obtain a graphene oxide solution; the mass ratio of the graphite oxide to water is 7:993; the low-frequency ultrasound frequency is 30 kHz, and the low-frequency ultrasound time is 360 min;

[0064] (2) adding an alkaline substance and urea to the graphene oxide solution obtained in step (1), adjusting the pH value of the graphene oxide solution with 1M HCl, and fully mixing to obtain a graphene oxide mixed solution; the alkaline substance is sodium hydroxide; the mass ratio of the sodium hydroxide to the graphite oxide is 1.5:1, the mass ratio of the urea to the graphite oxide is 40:1, and the pH value of the graphene oxide mixed solution is 9.

[0065] (3) subjecting the graphene oxide mixture obtained in step (2) to a hydrothermal reaction, and finally washing and freeze-drying to obtain a porous nitrogen-doped graphene aerogel material. The hydrothermal reaction temperature is 180° C., the hydrothermal reaction time is 18 hours, and the freeze-drying time is 48 hours.

[0066] Example 5

[0067] A porous nitrogen-doped graphene aerogel material is prepared by the following method, comprising the following steps:

[0068] (1) mixing graphite oxide and water, and subjecting them to low-frequency ultrasound to obtain a graphene oxide solution; the mass ratio of the graphite oxide to water is 10:990; the low-frequency ultrasound frequency is 20 kHz, and the low-frequency ultrasound time is 240 min;

[0069] (2) adding an alkaline substance and urea to the graphene oxide solution obtained in step (1), adjusting the pH value of the graphene oxide solution with 1M HCl, and fully mixing to obtain a graphene oxide mixed solution; the alkaline substance is sodium hydroxide; the mass ratio of the sodium hydroxide to the graphite oxide is 2:1, the mass ratio of the urea to the graphite oxide is 50:1, and the pH value of the graphene oxide mixed solution is 7.

[0070] (3) subjecting the graphene oxide mixture obtained in step (2) to a hydrothermal reaction, and finally washing and freeze-drying to obtain a porous nitrogen-doped graphene aerogel material. The hydrothermal reaction temperature is 200° C., the hydrothermal reaction time is 6 hours, and the freeze-drying time is 72 hours.

[0071] Comparative Example 1

[0072] A porous nitrogen-doped graphene aerogel material is prepared by the same method as in Example 1, except that only urea is added in step (2) without adding alkaline substances.

[0073] Comparative Example 2

[0074] A porous nitrogen-doped graphene aerogel material is prepared by the same method as in Example 2, except that only urea is added in step (2) without adding alkaline substances.

[0075] Comparative Example 3

[0076] A porous nitrogen-doped graphene aerogel material is prepared by the same method as in Example 3, except that only urea is added in step (2) without adding alkaline substances.

[0077] Comparative Example 4

[0078] A porous nitrogen-doped graphene aerogel material is prepared by the same method as in Example 4, except that only urea is added in step (2) without adding alkaline substances.

[0079] Comparative Example 5

[0080] A porous nitrogen-doped graphene aerogel material is prepared by the same method as in Example 5, except that only urea is added in step (2) without adding alkaline substances.

[0081] The N atom content in the porous nitrogen-doped graphene aerogels prepared in Examples 1-5 and Comparative Examples 1-5 was tested, and the results are shown in Table 1:

[0082] Table 1 N atom content in nitrogen-doped graphene aerogels prepared in Examples 1-5 and Comparative Examples 1-5

[0083]

[0084] The porous nitrogen-doped graphene aerogels prepared in Examples 1-5 and Comparative Examples 1-5 were used to adsorb formaldehyde, respectively. The conditions for adsorbing formaldehyde were exactly the same, and the adsorption time was 10 minutes. The removal effects obtained are shown in Table 2:

[0085] Table 2 Formaldehyde removal effects of porous nitrogen-doped graphene aerogels prepared in Examples 1-5 and Comparative Examples 1-5

[0086]

[0087]

[0088] As can be seen from Tables 1 and 2, the preparation method of the present invention uses an alkaline substance to activate graphite oxide, thereby improving the nitrogen conversion rate of urea and increasing the nitrogen atom content in the graphene aerogel, thereby increasing the ability of the graphene aerogel to quickly adsorb formaldehyde in a short period of time.

[0089] Figure 1The total specific surface area and micropore area data of the porous nitrogen-doped graphene aerogel material prepared in Example 2 of the present invention and the nitrogen-doped graphene aerogel prepared in Comparative Example 2. Figure 1 It can be seen that the preparation method of the present invention can form pores in graphite oxide by using alkaline substances, thereby increasing the total specific surface area and micropore area of ​​the graphene aerogel.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Application of a porous nitrogen-doped graphene aerogel material in air purification materials, characterized in that: The method for preparing the porous nitrogen-doped graphene aerogel material comprises the following steps: (1) mixing graphite oxide and water, and obtaining a graphene oxide solution after low-frequency ultrasound; (2) adding an alkaline substance and urea to the graphene oxide solution obtained in step (1), adjusting the pH value of the graphene oxide solution to 1-9, and obtaining a graphene oxide mixed solution; the alkaline substance is one of potassium hydroxide and sodium hydroxide, the mass ratio of the alkaline substance to graphite oxide is (0.3-2):1, and the mass ratio of urea to graphite oxide is (1-50):1; the alkaline substance can activate the graphite oxide, improve the nitrogen conversion rate of urea, increase the nitrogen atom content in the graphene aerogel, and thus increase the ability of the graphene aerogel to quickly adsorb formaldehyde in a short period of time; (3) subjecting the graphene oxide mixed solution obtained in step (2) to a hydrothermal reaction to obtain a porous nitrogen-doped graphene aerogel material; the temperature of the hydrothermal reaction is 160-200° C., and the reaction time is 6-24 h; after the hydrothermal reaction is completed, the material is washed and freeze-dried.

2. The use of the porous nitrogen-doped graphene aerogel material as claimed in claim 1 in an air purification material, characterized in that: The mass ratio of graphite oxide to water in step (1) is (2-10): (990-998).

3. The use of the porous nitrogen-doped graphene aerogel material as claimed in claim 1 in an air purification material, characterized in that: The frequency of the low-frequency ultrasound in step (1) is 20-40 KHz, and the duration of the low-frequency ultrasound is 180-360 min.

4. The use of the porous nitrogen-doped graphene aerogel material as claimed in claim 1 in an air purification material, characterized in that: The freeze-drying time in step (3) is 24-72 hours.

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