In-situ loaded g-c3n4 biomass-derived carbon aerogel, preparation method and application thereof

Abstract

The application discloses in-situ loaded g-C3N4 biomass-derived carbon aerogel as well as a preparation method and application thereof, and comprises the following steps: corn straws are cut into small pieces, then the small pieces are soaked in deionized water, and hydrothermal carbonization is carried out to obtain corn straw-derived carbon hydrogel; the corn straw-derived carbon hydrogel is immersed in a urea solution, the concentration of the urea solution is 0.1-1.1 g / mL, solution exchange is carried out, and after the solution exchange is completed, calcination is carried out in an inert atmosphere, the calcination temperature is 400-500 DEG C, and the calcination time is 2-4 h.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of VOCs photocatalytic degradation, and particularly relates to in-situ loaded g-C3N4 biomass-derived carbon aerogel and a preparation method and application thereof. BACKGROUND

[0002] The statements herein are provided only to complement the background of the present application and are not necessarily indicative of the prior art.

[0003] Volatile organic pollutants (VOCs) are organic compounds with boiling points between 50-250℃ and existing in the form of gas at room temperature. When the concentration of VOCs exceeds a certain value, it will pose a threat to human health. The two main ways to remove VOCs are adsorption removal and catalytic degradation removal.

[0004] Although the adsorbent used in adsorption removal has obvious and rapid effects on VOCs removal, it has the disadvantages of non-renewable raw materials, toxic preparation process, and biodegradation. Moreover, after adsorption saturation, it needs to be regenerated by high-temperature desorption, otherwise, saturation desorption will cause secondary pollution.

[0005] The commonly used catalysts for catalytic degradation removal include noble metals and biological enzymes, but the catalysts are easily deactivated in the actual environment, the reaction conditions are harsh, the cost is high, and the fine powder catalyst is difficult to recover.

[0006] Photocatalytic reaction has the advantages of mild reaction conditions, complete purification, strong oxidation, and green environmental protection, but common photocatalysts are only excited by strong ultraviolet light (UVC), and excessive deep ultraviolet light irradiation is harmful to the human body, so the use of deep ultraviolet light photocatalysts has certain limitations for indoor air purification. SUMMARY

[0007] In view of the deficiencies in the prior art, the present application aims to provide an in-situ loaded g-C3N4 biomass-derived carbon aerogel and a preparation method and application thereof.

[0008] In order to achieve the above-mentioned purpose, the present application is realized by the following technical solutions:

[0009] In the first aspect, the present application provides a preparation method of in-situ loaded g-C3N4 biomass-derived carbon aerogel, comprising the following steps:

[0010] The corn straw is cut into small pieces, then soaked in deionized water, and hydrothermally carbonized to obtain corn straw-derived carbon hydrogel;

[0011] immersing the corn stalk derived carbon aerogel in a nitrogen source solution, the concentration of the nitrogen source solution being 0.1-1.1g / mL, performing solution exchange, and then calcining in an inert atmosphere, the calcination temperature being 350-650℃, and the calcination time being 0.5-4h;

[0012] The nitrogen source is urea, thiourea, melamine, cyanamide or dicyanamide.

[0013] The natural stalk surface is hydrophobic, and cannot be immersed in a urea solution, which results in low and uneven nitrogen source loading and makes it impossible to load g-C3N4 in situ. The purpose of the preferential preliminary hydrothermal carbonization is to change the biomass stalk into a biomass derived carbon aerogel. Due to the hydrophilic nature of the aerogel, it is easier to completely immerse in the nitrogen source solution, and solution exchange occurs, which makes the nitrogen source uniformly distributed in the carbon aerogel network structure, and the in-situ loading of g-C3N4 is more uniform and has a higher loading amount. The in-situ loading of g-C3N4 plays a supporting role, and well maintains the skeleton structure of the aerogel, so that the CAG structure does not shrink or collapse.

[0014] In some embodiments, the corn stalk is cut into small pieces, the height of the small pieces being 0.1-4cm, and preferably 0.5-1.5cm.

[0015] In some embodiments, the temperature of the hydrothermal carbonization is 150-300℃, and the time of the hydrothermal carbonization is 1-24h.

[0016] In some embodiments, the method further comprises the step of washing the prepared corn stalk derived carbon aerogel with ethanol and deionized water, respectively. The ethanol washing is to wash away the organic impurities in the biomass stalk after hydrothermal carbonization, and the deionized water washing is to wash away the ethanol and impurities dissolved in water.

[0017] Preferably, the ethanol and deionized water are washed three times, respectively.

[0018] In some embodiments, the time of the solution exchange is 0.5-3d.

[0019] In some embodiments, the heating rate during calcination is 10-20℃ / min. A too high heating rate will result in rapid carbonization of the biomass derived carbon aerogel, which will destroy the gel framework structure and become powder, which will be blown away by N2 or other inert gases.

[0020] In a second aspect, the present application provides a biomass derived carbon aerogel loaded with g-C3N4 in situ, which is prepared by the preparation method.

[0021] In a third aspect, the present application provides the use of the biomass derived carbon aerogel loaded with g-C3N4 in situ in VOCs adsorption and photocatalysis.

[0022] The beneficial effects achieved by one or more embodiments of the present application are as follows:

[0023] The corn stalk has a porous and layered structure, and has abundant sieve tube longitudinal channels along the growth direction, and a large number of transverse micropores on the sieve tube wall, which is beneficial to gas flow. The vertical and horizontal interweaving of the stems is rich in a large number of'small compartments', which can provide more in-situ growth sites for degradation and purification materials. The urea-derived g-C3N4 has a mesoporous sheet structure and a higher specific surface area.

[0024] Due to sample solution exchange, after the exchange is completed, the sample is directly calcined without drying. The sample contains a small amount of water, and the addition of water affects the polymerization of the nitrogen source in two ways: 1. The bubble breakage in water generates a large number of pores in the generation of g-C3N4, changing the morphology; 2. The urea is subjected to low-degree polymerization, improving the yield. The g-C3N4 has a honeycomb-like and two-dimensional filamentous linear surface mixed structure, the filamentous structure is beneficial to winding on the straw carbon aerogel, and the honeycomb-like structure can reflect light multiple times, improving the light utilization efficiency.

[0025] The in-situ loaded g-C3N4 biomass-derived carbon aerogel of the present application has a simple and green preparation process, the raw materials are cheap and easy to obtain, the synthesis cost is low, the g-C3N4 is loaded on the biomass-derived carbon aerogel in a linear surface combined manner, avoiding the problems of blocking the pores of the aerogel and occupying the adsorption sites.

[0026] The biomass-derived carbon aerogel has strong adsorption performance on VOCs, and the loaded g-C3N4 occurs photocatalytic reaction under light irradiation of 365 / m (UVA waveband light, the sun contains a large amount of UVA, which is a light purple ultraviolet light, and the light is weak), which can catalytically degrade the VOCs (taking toluene as an example) adsorbed on the biomass-derived carbon aerogel, and the removal capacity of toluene can reach 1570mg / g, having a high VOCs removal capacity.

[0027] After four cycles of the test, the material has high VOCs removal activity, avoids adsorption saturation and desorption, prolongs the service life of the material, does not cause secondary pollution, and the material is in a block shape, easy to recycle.

[0028] The in-situ loaded g-C3N4 biomass-derived carbon aerogel of the present application can be used as a household adsorbent, a factory waste pollutant removal agent, and also can be used as a filter core of an air purifier, realizing indoor air purification. BRIEF DESCRIPTION OF DRAWINGS

[0029] The drawings accompanying the specification of the present application serve to provide further understanding of the present application, and the schematic embodiments of the present application and the description thereof serve to explain the present application, and do not constitute an improper limitation on the present application.

[0030] Figure 1is a preparation process flow chart of in-situ loaded g-C3N4 biomass-derived carbon aerogel in the embodiment of the present application.

[0031] Figure 2 In the figure, (a) is a SEM image of the three-dimensional network structure of the biomass corn stalks; Figure 2 (b) is a SEM image of the three-dimensional network structure of the in-situ loaded g-C3N4 biomass-derived carbon aerogel (CAG).

[0032] Figure 3 is a carbon element and nitrogen element distribution map of the in-situ loaded g-C3N4 biomass-derived carbon aerogel prepared in the embodiment 1 of the present application;

[0033] Figure 4 is a TEM image of the in-situ loaded g-C3N4 biomass-derived carbon aerogel prepared in the embodiment 1 of the present application;

[0034] Figure 5 In the figure, (a) is a N2 adsorption-desorption isotherm of CAG and g-C3N4; (b) is a pore distribution map of CAG and g-C3N4; (c) is a mercury cumulative intrusion curve of CAG; (d) is a pore size distribution curve of CAG; (e) is a contact angle of the straw and water; (f) is a contact angle of g-C3N4 and water; (g) is a contact angle of the cross-section of CAG and water; (h) is a contact angle of the longitudinal section of CAG and water.

[0035] Figure 6 is a solid ultraviolet test map of the in-situ loaded g-C3N4 biomass-derived carbon aerogel prepared in the embodiment 1 of the present application;

[0036] Figure 7 In the figure, (a) is a light catalytic degradation activity map of CAG to toluene; (b) is a light catalytic degradation activity map of CAG to formaldehyde; (c) is a light catalytic degradation activity map of CAG to acetone; (d) is a toluene isothermal adsorption curve of CAG; (e) is a cycle test map of CAG to adsorb and photocatalytically degrade toluene, formaldehyde and acetone.

[0037] Figure 8 In the figure, the appearance comparison map of the g-C3N4 loaded CAG (b) and the straw carbon aerogel (c) directly obtained by calcining and carbonizing the corn straw. DETAILED DESCRIPTION

[0038] It should be noted that the following detailed description is all exemplary, and is intended to provide further illustration of the present application. Unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0039] The present application will be further described below in conjunction with the embodiments. The present application will be further described below in conjunction with the embodiments.

[0040] Example 1

[0041] like Figure 1 As shown, corn stalks were cut into small pieces 1 cm high and 1.5 cm in diameter, placed in a reactor lined with 50 mL of polytetrafluoroethylene, and 10 mL of deionized water was added. The stalks were pressed down to completely immerse themselves in the deionized water. The reactor was hydrothermally heated at 180°C for 10 hours to initially carbonize and generate corn stalk-derived carbon hydrogel. After naturally cooling to room temperature, the product was removed and washed three times each with ethanol and deionized water. 5 g of urea was dissolved in 10 mL of deionized water. The corn stalk-derived carbon hydrogel was immersed in the prepared urea solution for two days of solution exchange. No drying was required. The product was then removed and placed in a quartz crucible. Under high-purity nitrogen protection, it was calcined in a tube furnace at 450°C for 3 hours at a heating rate of 15°C / m / / . After naturally cooling to room temperature, the product was removed, finally yielding fully carbonized in-situ supported g-C3N4 biomass-derived carbon aerogel (CAG).

[0042] VOCs removal performance test:

[0043] Place the CAG in a 2L quartz round-bottom flask, inject 1.14μL of VOCs (using toluene as an example), and seal with a rubber stopper. Allow 2 hours for dark adsorption. After equilibration, turn on a 365°C lamp for photocatalytic degradation testing. Starting from the dark adsorption stage, every 15 minutes, use a gas microsyringe to extract 1 mL of gas from the flask and inject it into a gas chromatograph to analyze the VOCs (using toluene as an example) content.

[0044] Cyclic stability test:

[0045] After the VOCs removal performance test, the CAG was removed from the quartz round-bottom flask, placed in a centrifuge tube, and sealed with sealing film for storage.

[0046] Clean and dry the quartz round-bottom flask, place the CAG back into the flask, inject an equal amount of VOCs (toluene as an example), seal the flask with a rubber stopper, and conduct a VOCs removal performance test. Repeat this operation to test the cyclic stability of the CAG.

[0047] from Figure 2 As can be seen from the SEM image, Figure 2 (a) The mesh of the three-dimensional network structure of biomass corn stalks is thin and smooth, with small holes visible within the mesh. Figure 2(b) The grid layer of the g-C3N4 biomass-derived carbon aerogel (CAG) three-dimensional network structure has more wrinkles, and the number of small pores in the grid increases. It is speculated that the small pores may be left after the removal of cells, proteins and other high-temperature carbonization. The grid layer is combined with the loaded g-C3N4 line surface, and there are many accumulated filamentous loadings on the three-dimensional grid sheet wall. The loadings are wrapped with the pores, and at the same time, they are also wrapped into new network structures inside the structure.

[0048] From Figure 3 The distribution of carbon and nitrogen elements shows that the loadings are g-C3N4.

[0049] From Figure 4 The TEM image also clearly shows that the g-C3N4 loaded on the biomass-derived carbon aerogel has a honeycomb-like and two-dimensional filamentous mixed structure. The relatively closed porous grid gives sufficient ammonia atmosphere during the polymerization of urea solution to form g-C3N4, which will not be directly taken away by nitrogen, and has more time to polymerize to produce g-C3N4. Therefore, g-C3N4 is retained and carried out when water vapor and ammonia are blown out of the pores, resulting in the formation of a wrapped structure. This line-surface combination increases the loading amount of g-C3N4 and reduces the shielding of the adsorption sites of the biomass-derived carbon aerogel.

[0050] The pore structure of CAG and g-C3N4 was characterized by Figure 5 (a-d) can prove that the loading of g-C3N4 on CAG increases its specific surface area, which can increase the contact area with VOCs and expose more active sites. CAG has a wide pore size distribution, which is beneficial to capturing VOCs of different particle sizes in air pollution purification. Contact angle test Figure 5 (e-h) shows that the introduction of g-C3N4 changes the hydrophilic and hydrophobic properties of the material, and the contact angle between the horizontal interface of the material and water is 77.5°, which is more hydrophilic and beneficial to the adsorption of hydrophilic pollutants. The contact angle between the vertical interface and water can reach 107.7°, which is more hydrophobic and beneficial to the adsorption of hydrophobic pollutants.

[0051] As Figure 6 Solid UV test (such as Figure 6 ) found that CAG had absorption in the full wave band.

[0052] Performance advantages:

[0053] According to the characteristics of CAG, the removal performance tests of VOCs with different molecular sizes and different hydrophilic and hydrophobic properties (such as toluene, formaldehyde, and acetone) were carried out. As Figure 7(a-c) The test results show that CAG exhibits excellent adsorption and photocatalytic degradation activity for toluene, formaldehyde, and acetone. Therefore, CAG exhibits good removal activity for hydrophilic and hydrophobic VOCs and VOCs with different molecular sizes. From the results of Figure 7 (d) The toluene isothermal adsorption curve shows that the maximum adsorption capacity of CAG for toluene is 1570 mg / g, and CAG has high toluene adsorption capacity. The cyclic test shows that Figure 7 (e) After four times, there is still high VOCs removal activity. Therefore, CAG can be used as an excellent air purification material to remove VOCs efficiently without desorption of saturation, thereby avoiding secondary pollution.

[0054] The in-situ loading of g-C3N4 plays a supporting role and well maintains the skeleton structure of the aerogel, so that the structure of CAG does not shrink or collapse, as shown in Figure 8

[0055] Example 2

[0056] The corn straw was cut into small pieces with a height of 1 cm and a diameter of 1.5 cm, and was placed in a reaction kettle containing 50 mL of a polytetrafluoroethylene liner. 10 mL of deionized water was added, and the straw was pressed to be fully immersed in the deionized water. Hydrothermal treatment was performed at 180°C for 24 hours to generate corn straw-derived carbon hydrogel. The product was naturally cooled to room temperature, and was washed with ethanol and deionized water three times, respectively. 5 g of urea was dissolved in 10 mL of deionized water, and the corn straw-derived carbon hydrogel was immersed in the prepared urea solution for solution exchange for two days. Without drying, the product was taken out and placed in a quartz crucible, and was calcined in a tube furnace under high-purity nitrogen protection at 450°C for 3 hours at a heating rate of 15°C / min. The product was naturally cooled to room temperature and was taken out, and a completely carbonized biomass-derived carbon aerogel with in-situ loading of g-C3N4 was obtained.

[0057] Example 3

[0058] The corn straw was cut into small pieces with a height of 1 cm and a diameter of 1.5 cm, and was placed in a reaction kettle containing 50 mL of a polytetrafluoroethylene liner. 10 mL of deionized water was added, and the straw was pressed to be fully immersed in the deionized water. Hydrothermal treatment was performed at 180°C for 10 hours to generate corn straw-derived carbon hydrogel. The product was naturally cooled to room temperature, and was washed with ethanol and deionized water three times, respectively. 10 g of urea was dissolved in 10 mL of deionized water, and the corn straw-derived carbon hydrogel was immersed in the prepared urea solution for solution exchange for two days. Without drying, the product was taken out and placed in a quartz crucible, and was calcined in a tube furnace under high-purity nitrogen protection at 450°C for 3 hours at a heating rate of 15°C / min. The product was naturally cooled to room temperature and was taken out, and a completely carbonized biomass-derived carbon aerogel with in-situ loading of g-C3N4 was obtained.

[0059] ​Example 4

[0060] The corn stalks were cut into small pieces with a height of 1 cm and a diameter of 1.5 cm, and were placed in a reaction kettle containing 50 mL of a polytetrafluoroethylene liner. 10 mL of deionized water was added, and the stalks were pressed to ensure that they were completely immersed in the deionized water. The stalks were hydrothermally treated at 200°C for 20 hours to produce a corn stalk-derived carbon hydrogel. The product was allowed to cool to room temperature naturally, and was removed. The product was washed three times with ethanol and deionized water, respectively. 5 g of urea was dissolved in 10 mL of deionized water, and the corn stalk-derived carbon hydrogel was immersed in the prepared urea solution for solution exchange for one day. The product was removed and placed in a quartz crucible, and was calcined in a tube furnace at 450°C for 3 hours under the protection of high-purity nitrogen. The heating rate was 20°C / min. The product was removed after it had cooled to room temperature naturally, and a completely carbonized biomass-derived carbon aerogel loaded with g-C3N4 in situ was obtained.

[0061] Example 5

[0062] The corn stalks were cut into small pieces with a height of 1 cm and a diameter of 1.5 cm, and were placed in a reaction kettle containing 50 mL of a polytetrafluoroethylene liner. 10 mL of deionized water was added, and the stalks were pressed to ensure that they were completely immersed in the deionized water. The stalks were hydrothermally treated at 280°C for 15 hours to produce a corn stalk-derived carbon hydrogel. The product was allowed to cool to room temperature naturally, and was removed. The product was washed three times with ethanol and deionized water, respectively. 5 g of urea was dissolved in 10 mL of deionized water, and the corn stalk-derived carbon hydrogel was immersed in the prepared urea solution for solution exchange for two days. The product was removed and placed in a quartz crucible, and was calcined in a tube furnace at 550°C for 2 hours under the protection of high-purity nitrogen. The heating rate was 15°C / min. The product was removed after it had cooled to room temperature naturally, and a completely carbonized biomass-derived carbon aerogel loaded with g-C3N4 in situ was obtained.

[0063] Example 6

[0064] The corn stalks were cut into small pieces with a height of 1 cm and a diameter of 1.5 cm, and were placed in a reaction kettle containing 50 mL of a polytetrafluoroethylene liner. 10 mL of deionized water was added, and the stalks were pressed to ensure that they were completely immersed in the deionized water. The stalks were hydrothermally treated at 250°C for 15 hours to produce a corn stalk-derived carbon hydrogel. The product was allowed to cool to room temperature naturally, and was removed. The product was washed three times with ethanol and deionized water, respectively. 5 g of melamine was dissolved in 10 mL of deionized water, and the corn stalk-derived carbon hydrogel was immersed in the prepared urea solution for solution exchange for two days. The product was removed and placed in a quartz crucible, and was calcined in a tube furnace at 600°C for 3 hours under the protection of high-purity nitrogen. The heating rate was 15°C / min. The product was removed after it had cooled to room temperature naturally, and a completely carbonized biomass-derived carbon aerogel loaded with g-C3N4 in situ was obtained.

[0065] Example 7

[0066] The corn stalks were cut into small pieces with a height of 1 cm and a diameter of 1.5 cm, and were placed in a reaction kettle containing 50 mL of a polytetrafluoroethylene liner. 10 mL of deionized water was added, and the stalks were pressed to completely immerse them in the deionized water. Hydrothermal treatment was performed at 150°C for 20 hours to generate corn stalk-derived carbon hydrogel. The product was naturally cooled to room temperature, and was washed with ethanol and deionized water three times each. 5 g of urea was dissolved in 10 mL of deionized water, and the corn stalk-derived carbon hydrogel was immersed in the prepared urea solution for solution exchange for two days. Without drying, the product was taken out and placed in a quartz crucible, and was calcined in a tube furnace under high-purity nitrogen protection at 550°C for 3 hours at a heating rate of 15°C / min. After natural cooling to room temperature, the product was taken out, and a completely carbonized in-situ loaded g-C3N4 biomass-derived carbon aerogel was obtained.

[0067] Example 8

[0068] The corn stalks were cut into small pieces with a height of 1 cm and a diameter of 1.5 cm, and were placed in a reaction kettle containing 50 mL of a polytetrafluoroethylene liner. 10 mL of deionized water was added, and the stalks were pressed to completely immerse them in the deionized water. Hydrothermal treatment was performed at 300°C for 10 hours to generate corn stalk-derived carbon hydrogel. The product was naturally cooled to room temperature, and was washed with ethanol and deionized water three times each. 5 g of urea was dissolved in 10 mL of deionized water, and the corn stalk-derived carbon hydrogel was immersed in the prepared urea solution for solution exchange for two days. Without drying, the product was taken out and placed in a quartz crucible, and was calcined in a tube furnace under high-purity nitrogen protection at 350°C for 4 hours at a heating rate of 20°C / min. After natural cooling to room temperature, the product was taken out, and a completely carbonized in-situ loaded g-C3N4 biomass-derived carbon aerogel was obtained.

[0069] Example 9

[0070] The corn stalks were cut into small pieces with a height of 1 cm and a diameter of 1.5 cm, and were placed in a reaction kettle containing 50 mL of a polytetrafluoroethylene liner. 10 mL of deionized water was added, and the stalks were pressed to completely immerse them in the deionized water. Hydrothermal treatment was performed at 200°C for 20 hours to generate corn stalk-derived carbon hydrogel. The product was naturally cooled to room temperature, and was washed with ethanol and deionized water three times each. 5 g of urea was dissolved in 10 mL of deionized water, and the corn stalk-derived carbon hydrogel was immersed in the prepared urea solution for solution exchange for two days. The product was freeze-dried, and was taken out and placed in a quartz crucible. Calcination was performed in a tube furnace under high-purity nitrogen protection at 650°C for 0.5 hours at a heating rate of 15°C / min. After natural cooling to room temperature, the product was taken out, and a completely carbonized in-situ loaded g-C3N4 biomass-derived carbon aerogel was obtained.

[0071] Example 10

[0072] The corn stalks are cut into small pieces with a height of 1 cm and a diameter of 1.5 cm, and are placed in a reaction kettle containing 50 mL of a polytetrafluoroethylene liner, 10 mL of deionized water is added, and the stalks are pressed to immerse them in the deionized water, and hydrothermal treatment is performed at 300 DEG C for 10 hours to generate corn stalk-derived carbon aerogels through preliminary carbonization. The product is naturally cooled to room temperature, and is taken out and washed with ethanol and deionized water three times each. 5 g of urea is dissolved in 10 mL of deionized water, the corn stalk-derived carbon aerogel is immersed in the prepared urea solution, and solution exchange is performed for two days, without drying, and the product is taken out and placed in a quartz crucible, and is calcined in a tube furnace under high-purity nitrogen protection at 400 DEG C for 3 hours, with a heating rate of 15 DEG C / m / / , and is naturally cooled to room temperature and taken out, and finally, the completely carbonized in-situ loaded g-C3N4 biomass-derived carbon aerogel is obtained.

[0073] The preferred embodiments of the present application have been described above with the aid of drawings and are not intended to limit the present application, and various modifications and changes can be made by those skilled in the art to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing in-situ supported g-C3N4 biomass-derived carbon aerogel for VOCs adsorption photocatalysis, characterized in that: Includes the following steps: Corn stalks were cut into small pieces, then soaked in deionized water and hydrothermally carbonized to obtain corn stalk-derived carbohydrate gel. Corn stalk-derived carbohydrate gel was impregnated in a nitrogen source solution with a concentration of 0.1-1.1 g / mL for solution exchange. After the exchange was completed, without drying, it was taken out and placed in a quartz crucible and calcined in an inert atmosphere at a temperature of 400-500℃ for 2-4 hours. The nitrogen source is urea; The in-situ loaded g-C3N4 biomass-derived carbon aerogel has a mixed honeycomb and two-dimensional filament structure.

2. The preparation method according to claim 1, characterized in that: Cut the corn stalks into small pieces, each piece being 0.1-4cm high.

3. The preparation method according to claim 1, characterized in that: The height of the small pieces is 0.5-1.5cm.

4. The preparation method according to claim 1, characterized in that: The temperature for hydrothermal carbonization is 150-300℃, and the time for hydrothermal carbonization is 1-24h.

5. The preparation method according to claim 1, characterized in that: It also includes the step of washing the prepared corn stalk-derived carbohydrate gel with ethanol and deionized water, respectively.

6. The preparation method according to claim 5, characterized in that: Wash three times each with ethanol and deionized water.

7. The preparation method according to claim 1, characterized in that: The solution exchange time is 0.5-3 days.

8. The method for preparing in-situ supported g-C3N4 biomass-derived carbon aerogel according to claim 1, characterized in that: The heating rate during calcination is 10-20℃ / min.

9. An in-situ supported g-C3N4 biomass-derived carbon aerogel, characterized in that: Prepared by the preparation method according to any one of claims 1-8.

10. The application of the in-situ supported g-C3N4 biomass-derived carbon aerogel as described in claim 9 as a VOCs adsorption photocatalyst.

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