Preparation method of high-concentration nitrogen-doped graphene aerogel material and application thereof

Abstract

The application discloses a preparation method of high-concentration nitrogen-doped graphene aerogel material, and comprises the following steps: (1) mixing nickel oxide and an ethanol aqueous solution by high-frequency ultrasonic, adding urea into the ethanol aqueous solution containing the nickel oxide, stirring and mixing, and then rapidly freezing and freeze-drying to obtain a nickel oxide-urea mixture; (2) adding the nickel oxide-urea mixture obtained in the step (1) into a graphene oxide aqueous solution, fully mixing to obtain a graphene oxide mixture; and (3) performing hydrothermal reaction on the graphene oxide mixture obtained in the step (2), and finally performing washing and freeze-drying to obtain the high-concentration nitrogen-doped graphene aerogel material. The application has the beneficial effects of efficient nitrogen source utilization, uniform mixing and catalytic effect, an optimized mixing process and a green and efficient production process, and provides a new technical path for the preparation of efficient air purification materials.

Description

Technical Field

[0001] This invention belongs to the field of air purification material preparation technology, specifically relating to a method for preparing high-concentration nitrogen-doped graphene aerogel material and its application. Background Technology

[0002] Formaldehyde is a major indoor air pollutant, typically originating from the release of building materials, furniture, paints, and other organic products. High concentrations of formaldehyde in indoor environments can severely harm the human respiratory, nervous, and immune systems. In fact, even low concentrations of formaldehyde can have adverse effects on human health. Therefore, developing highly efficient gas adsorption materials to remove formaldehyde is crucial to minimizing its harmful effects on the human body.

[0003] Currently, commonly used formaldehyde removal methods on the market employ adsorbents such as activated carbon or bamboo charcoal bags. However, these adsorbents have significant limitations. Due to their weak chemical adsorption capacity and limited adsorption capacity, they cannot quickly adsorb formaldehyde and are prone to desorption. This not only affects the air purification effect but may also lead to secondary environmental pollution. In contrast, graphene materials show promising application prospects in formaldehyde adsorption. In particular, by doping graphene with heteroatoms such as nitrogen (N), sulfur (S), and phosphorus (P), its chemical adsorption capacity can be significantly improved, and desorption can be reduced. Among these, nitrogen atom doping has received widespread attention due to its more mature preparation process and potential for industrial application.

[0004] However, to obtain graphene materials with high nitrogen doping concentrations, many studies have used amino-containing chemicals as nitrogen sources. These substances are generally toxic and costly, making them unsuitable for large-scale production. In contrast, urea is an abundant, low-toxicity, and nitrogen-rich substance, making it an ideal nitrogen source. Although using urea as a nitrogen source allows for the loading of nitrogen atoms onto graphene, thereby improving its chemisorption capacity for formaldehyde, achieving high-concentration nitrogen doping with low urea dosages is difficult. This limits its effectiveness and economic viability in practical applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method for preparing high-concentration nitrogen-doped graphene aerogel materials.

[0006] Another object of the present invention is to provide the application of the high-concentration nitrogen-doped graphene aerogel material prepared by the above preparation method.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a high-concentration nitrogen-doped graphene aerogel material includes the following steps:

[0009] (1) Nickel oxide and ethanol aqueous solution are thoroughly mixed by high frequency ultrasound, urea is added to ethanol aqueous solution containing nickel oxide, and after stirring and mixing and rapid freezing, nickel oxide and urea mixture is obtained by freeze drying.

[0010] (2) Add the nickel oxide urea mixture obtained in step (1) to the graphene oxide aqueous solution and mix thoroughly to obtain the graphene oxide mixture.

[0011] (3) The graphene oxide mixture obtained in step (2) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain a high-concentration nitrogen-doped graphene aerogel material.

[0012] In a preferred embodiment of the present invention, in step (1), the mass ratio of urea to nickel oxide is 100-1000:1.

[0013] More preferably, the concentration of the ethanol-water solution is 30-70%.

[0014] More preferably, the mass ratio of nickel oxide to the aqueous ethanol solution is 5-50:9995-9950.

[0015] In a preferred embodiment of the present invention, in step (2), the mass ratio of the nickel oxide urea mixture to the graphene oxide is 1-10:1.

[0016] More preferably, the concentration of graphene oxide in the aqueous solution of graphene oxide is 0.2-1 wt.%.

[0017] In a preferred embodiment of the present invention, in step (3), the temperature of the hydrothermal reaction is 160-200°C and the time is 8-24h.

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

[0019] The application of the high-concentration nitrogen-doped graphene aerogel material prepared by the above method in the preparation of formaldehyde adsorption materials.

[0020] A formaldehyde adsorption material, the raw material of which includes high-concentration nitrogen-doped graphene aerogel material prepared by the above preparation method.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention uses urea as the nitrogen source, which has advantages such as abundant content, low cost, and high nitrogen content. Under the catalytic hydrolysis of nickel oxide, urea can generate more ammonia gas to participate in the reaction during the hydrothermal process, thereby significantly improving the nitrogen conversion rate of urea and further expanding the application scope of urea as a nitrogen source in the preparation of air purification materials.

[0023] 2. This invention first mixes urea and nickel oxide in an aqueous ethanol solution, and then prepares a mixture of urea and nickel oxide by rapid freezing. This method effectively avoids precipitation of nickel oxide during prolonged freezing, thus ensuring uniform mixing. This provides favorable conditions for the subsequent catalytic hydrolysis of urea by nickel oxide in an aqueous graphene oxide solution.

[0024] 3. The mixing treatment of urea and nickel oxide in an ethanol-water solution in this invention is necessary and beneficial, mainly based on the dispersibility of urea and nickel oxide in different solvents. Compared with directly adding nickel oxide and urea to the graphene oxide aqueous solution, the poor dispersibility of nickel oxide in water leads to insufficient contact with urea, making it difficult to achieve a good catalytic effect. While directly adding nickel oxide and urea to the graphene oxide ethanol-water solution improves the dispersibility of nickel oxide, in the hydrothermal reaction, ethanol may undergo side reactions with urea or its decomposition products at high temperatures, reducing nitrogen doping efficiency and potentially affecting the morphology and structure of graphene, which is detrimental to the doping effect.

[0025] 4. The process of this invention is simple, easy to implement, green, efficient, and energy-saving, making it suitable for large-scale industrial production and application. This preparation method can significantly increase the specific surface area of ​​graphene aerogel and increase the nitrogen atom content of urea doped in the graphene aerogel, thereby greatly improving its short-term rapid adsorption capacity for formaldehyde. Compared with nitrogen-doped graphene aerogel prepared without adding nickel oxide as a catalyst, the high-concentration nitrogen-doped graphene aerogel material obtained by this invention has a nitrogen content increased by more than 35%, and its formaldehyde adsorption effect within 10 minutes is improved by more than 60%. Attached Figure Description

[0026] Figure 1 This shows the total specific surface area and micropore area data of the high-concentration nitrogen-doped graphene aerogel material prepared in Example 5 of the present invention and the nitrogen-doped graphene aerogel material prepared in Comparative Example 5.

[0027] Figure 2 This shows the N atom content of the high-concentration nitrogen-doped graphene aerogel material prepared in Example 5 of the present invention and the nitrogen-doped graphene aerogel material prepared in Comparative Example 6. Detailed Implementation

[0028] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0029] Example 1

[0030] (1) Nickel oxide and ethanol aqueous solution were thoroughly mixed by high frequency ultrasound. Urea was added to the ethanol aqueous solution containing nickel oxide. After stirring and mixing and rapid freezing, the nickel oxide and urea mixture was obtained by freeze drying. The mass ratio of nickel oxide to ethanol aqueous solution was 5:9995. The concentration of ethanol aqueous solution was 30%. The mass ratio of urea to nickel oxide was 100:1.

[0031] (2) The nickel oxide urea mixture obtained in step (1) is added to the graphene oxide aqueous solution and mixed thoroughly to obtain a graphene oxide mixture; the mass ratio of the nickel oxide urea mixture to the graphene oxide is 10:1; the concentration of graphene oxide in the graphene oxide aqueous solution is 0.2 wt.%.

[0032] (3) The graphene oxide mixture obtained in step (2) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain high-concentration nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature is 200℃; the hydrothermal reaction time is 8h; and the freeze-drying time is 24h.

[0033] Example 2

[0034] (1) Nickel oxide and ethanol aqueous solution were thoroughly mixed by high frequency ultrasound. Urea was added to the ethanol aqueous solution containing nickel oxide. After stirring and mixing and rapid freezing, the nickel oxide and urea mixture was obtained by freeze drying. The mass ratio of nickel oxide to ethanol aqueous solution was 10:9990. The concentration of ethanol aqueous solution was 60%. The mass ratio of urea to nickel oxide was 1000:1.

[0035] (2) The nickel oxide urea mixture obtained in step (1) is added to the graphene oxide aqueous solution and mixed thoroughly to obtain a graphene oxide mixture; the mass ratio of the nickel oxide urea mixture to the graphene oxide is 8:1; the concentration of graphene oxide in the graphene oxide aqueous solution is 0.5 wt.%.

[0036] (3) The graphene oxide mixture obtained in step (2) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain high-concentration nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature is 180℃; the hydrothermal reaction time is 16h; and the freeze-drying time is 60h.

[0037] Example 3

[0038] (1) Nickel oxide and ethanol aqueous solution were thoroughly mixed by high frequency ultrasound. Urea was added to the ethanol aqueous solution containing nickel oxide. After stirring and mixing and rapid freezing, the nickel oxide and urea mixture was obtained by freeze drying. The mass ratio of nickel oxide to ethanol aqueous solution was 20:9980. The concentration of ethanol aqueous solution was 70%. The mass ratio of urea to nickel oxide was 300:1.

[0039] (2) Add the nickel oxide urea mixture obtained in step (1) to the graphene oxide aqueous solution and mix thoroughly to obtain a graphene oxide mixture; the mass ratio of the nickel oxide urea mixture to the graphene oxide is 3:1; the concentration of graphene oxide in the graphene oxide aqueous solution is 0.8 wt.%.

[0040] (3) The graphene oxide mixture obtained in step (2) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain high-concentration nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature is 160℃; the hydrothermal reaction time is 24h; and the freeze-drying time is 36h.

[0041] Example 4

[0042] (1) Nickel oxide and ethanol aqueous solution were thoroughly mixed by high frequency ultrasound. Urea was added to the ethanol aqueous solution containing nickel oxide. After stirring and mixing and rapid freezing, the nickel oxide and urea mixture was obtained by freeze drying. The mass ratio of nickel oxide to ethanol aqueous solution was 50:9950. The concentration of ethanol aqueous solution was 40%. The mass ratio of urea to nickel oxide was 800:1.

[0043] (2) Add the nickel oxide urea mixture obtained in step (1) to the graphene oxide aqueous solution and mix thoroughly to obtain the graphene oxide mixture; the mass ratio of the nickel oxide urea mixture to the graphene oxide is 1:1; the concentration of graphene oxide in the graphene oxide aqueous solution is 1.0 wt.%.

[0044] (3) The graphene oxide mixture obtained in step (2) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain high-concentration nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature is 180℃; the hydrothermal reaction time is 12h; and the freeze-drying time is 72h.

[0045] Example 5

[0046] (1) Nickel oxide and ethanol aqueous solution were thoroughly mixed by high frequency ultrasound. Urea was added to the ethanol aqueous solution containing nickel oxide. After stirring and mixing and rapid freezing, the nickel oxide and urea mixture was obtained by freeze drying. The mass ratio of nickel oxide to ethanol aqueous solution was 10:9990. The concentration of ethanol aqueous solution was 50%. The mass ratio of urea to nickel oxide was 100:1.

[0047] (2) The nickel oxide urea mixture obtained in step (1) is added to the graphene oxide aqueous solution and mixed thoroughly to obtain a graphene oxide mixture; the mass ratio of the nickel oxide urea mixture to the graphene oxide is 10:1; the concentration of graphene oxide in the graphene oxide aqueous solution is 0.5 wt.%.

[0048] (3) The graphene oxide mixture obtained in step (2) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain high-concentration nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature is 160℃; the hydrothermal reaction time is 12h; and the freeze-drying time is 48h.

[0049] Comparative Example 1

[0050] (1) Urea was added to the aqueous solution of graphene oxide and mixed thoroughly to obtain a graphene oxide mixture; the mass ratio of urea to graphene oxide was 10:1; the concentration of graphene oxide in the aqueous solution of graphene oxide was 0.2 wt.%.

[0051] (2) The graphene oxide mixture obtained in step (1) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature is 200℃; the hydrothermal reaction time is 8h; and the freeze-drying time is 24h.

[0052] Comparative Example 2

[0053] (1) Urea was added to the aqueous solution of graphene oxide and mixed thoroughly to obtain a graphene oxide mixture; the mass ratio of urea to graphene oxide was 8:1; the concentration of graphene oxide in the aqueous solution of graphene oxide was 0.5 wt.%.

[0054] (2) The graphene oxide mixture obtained in step (1) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature is 180℃; the hydrothermal reaction time is 16h; and the freeze-drying time is 60h.

[0055] Comparative Example 3

[0056] (1) Urea was added to the aqueous solution of graphene oxide and mixed thoroughly to obtain a graphene oxide mixture; the mass ratio of urea to graphene oxide was 3:1; the concentration of graphene oxide in the aqueous solution of graphene oxide was 0.8 wt.%.

[0057] (2) The graphene oxide mixture obtained in step (1) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature is 160℃; the hydrothermal reaction time is 24h; and the freeze-drying time is 36h.

[0058] Comparative Example 4

[0059] (1) Urea was added to the aqueous solution of graphene oxide and mixed thoroughly to obtain a graphene oxide mixture; the mass ratio of urea to graphene oxide was 1:1; the concentration of graphene oxide in the aqueous solution of graphene oxide was 1.0 wt.%.

[0060] (2) The graphene oxide mixture obtained in step (1) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature is 180℃; the hydrothermal reaction time is 12h; and the freeze-drying time is 72h.

[0061] Comparative Example 5

[0062] (1) Urea was added to the aqueous solution of graphene oxide and mixed thoroughly to obtain a graphene oxide mixture; the mass ratio of urea to graphene oxide was 10:1; the concentration of graphene oxide in the aqueous solution of graphene oxide was 0.5 wt.%.

[0063] (2) The graphene oxide mixture obtained in step (1) was subjected to a hydrothermal reaction, and finally washed and freeze-dried to obtain nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature was 160℃; the hydrothermal reaction time was 12h; and the freeze-drying time was 48h.

[0064] Comparative Example 6

[0065] (1) Urea and nickel oxide were added to the aqueous solution of graphene oxide and mixed thoroughly to obtain a graphene oxide mixture; the mass ratio of urea to nickel oxide was 100:1; the mass ratio of urea to graphene oxide was 10:1; the concentration of graphene oxide in the aqueous solution of graphene oxide was 0.5 wt.%.

[0066] (2) The graphene oxide mixture obtained in step (1) was subjected to a hydrothermal reaction, and finally washed and freeze-dried to obtain nitrogen-doped graphene aerogel material; the hydrothermal reaction temperature was 160℃; the hydrothermal reaction time was 12h; and the freeze-drying time was 48h.

[0067] The nitrogen atom content in the high-concentration nitrogen-doped graphene aerogel materials prepared in Examples 1-5 and the nitrogen-doped graphene aerogel materials prepared in Comparative Examples 1-5 was tested, and the results are shown in Table 1:

[0068] Table 1. N atom content in samples prepared in Examples 1-5 and Comparative Examples 1-5

[0069]

[0070] The samples prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to formaldehyde adsorption under identical conditions, with an adsorption time of 10 min for each sample. The removal results are shown in Table 2.

[0071] Table 2 shows the formaldehyde removal efficiency of the samples prepared in Examples 1-5 and Comparative Examples 1-5.

[0072]

[0073]

[0074] As can be seen from Tables 1 and 2, the preparation method of the present invention uses nickel oxide as a catalyst, which can catalyze the decomposition of urea to generate more ammonia for doping reaction, thereby improving the nitrogen conversion rate of urea and increasing the N atom content in graphene aerogel, thereby increasing the ability of graphene aerogel to rapidly adsorb formaldehyde in a short period of time.

[0075] Figure 1 This displays the total specific surface area and micropore area data of the high-concentration nitrogen-doped graphene aerogel material prepared in Example 5 of the present invention and the nitrogen-doped graphene aerogel material prepared in Comparative Example 5. Figure 1 As can be seen, the preparation method of the present invention uses nickel oxide to catalyze the decomposition of urea to generate more ammonia gas. This ammonia gas can create pores in graphene oxide, thereby increasing the total specific surface area and micropore area of ​​the graphene aerogel.

[0076] Figure 2 This shows the N atom content of the high-concentration nitrogen-doped graphene aerogel material prepared in Example 5 of the present invention and the nitrogen-doped graphene aerogel material prepared in Comparative Example 6. Figure 2 It can be seen that the preparation method of the present invention, which mixes nickel oxide and urea in advance, helps to improve the catalytic effect of nickel oxide on urea in the subsequent preparation process, thereby increasing the N atom content in the graphene aerogel.

[0077] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a high-concentration nitrogen-doped graphene aerogel material, characterized in that: Includes the following steps: (1) Nickel oxide and ethanol aqueous solution are thoroughly mixed by high frequency ultrasound, urea is added to ethanol aqueous solution containing nickel oxide, and after stirring and mixing and rapid freezing, nickel oxide and urea mixture is obtained by freeze drying. (2) Add the nickel oxide urea mixture obtained in step (1) to the graphene oxide aqueous solution and mix thoroughly to obtain the graphene oxide mixture. (3) The graphene oxide mixture obtained in step (2) is subjected to hydrothermal reaction, and finally washed and freeze-dried to obtain a high-concentration nitrogen-doped graphene aerogel material.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of urea to nickel oxide is 100-1000:

1.

3. The preparation method according to claim 2, characterized in that: The concentration of the ethanol aqueous solution is 30-70%.

4. The preparation method according to claim 3, characterized in that: The mass ratio of nickel oxide to the aqueous ethanol solution is 5-50:9995-9950.

5. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of the nickel oxide urea mixture to graphene oxide is 1-10:

1.

6. The preparation method according to claim 5, characterized in that: The concentration of graphene oxide in the aqueous solution is 0.2-1 wt.%.

7. The preparation method according to any one of claims 1 to 6, characterized in that: In step (3), the temperature of the hydrothermal reaction is 160-200℃ and the time is 8-24h.

8. The preparation method according to claim 7, characterized in that: The freeze-drying time is 24-72 hours.

9. The use of the high-concentration nitrogen-doped graphene aerogel material prepared by the preparation method according to any one of claims 1 to 8 in the preparation of formaldehyde adsorption materials.

10. A formaldehyde adsorption material, characterized in that: The raw materials include high-concentration nitrogen-doped graphene aerogel materials prepared by any one of claims 1 to 8.

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