Preparation method and application of carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material

Abstract

The present invention discloses a preparation method and application of a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material, which relates to the technical field of photocatalytic material preparation. The preparation method includes the following steps: dispersing melamine in an amine / NaCl buffer solution, adding tannic acid, collecting the powder, and calcining to obtain g-C3N4 powder; dispersing the g-C3N4 powder in deionized water, adding FeCl3·6H2O, centrifuging to obtain a precipitate, and calcining to obtain g-C3N4 / Fe2O3; adding pomelo peel powder, g-C3N4 / Fe2O3 and ZnCl2 into a three-necked flask, adding ultrapure water, stirring with an oil bath to form a dispersion, dropping an acetic acid solution into the dispersion, and pouring it into a polytetrafluoroethylene reaction kettle to obtain a pomelo peel aerogel; carbonizing the aerogel to obtain the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material. By changing the ratio of Fe2O3 to C in the aerogel, the preparation of the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material of the present invention can well match and synergistically enhance the two steps of charge generation and charge transfer, thereby significantly improving the degradation efficiency of ibuprofen.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalytic material preparation, and in particular to a preparation method and application of a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material. Background Art

[0002] The core of photocatalytic technology is its ability to use sunlight as an energy source and promote chemical reactions through specific photocatalysts, thereby achieving effective energy conversion and chemical synthesis. In the photocatalytic process, in order to achieve efficient conversion of solar energy to chemical energy, it is necessary to ensure the rapid transfer of energy and matter. This process involves two crucial steps: first, the generation of photogenerated charges, and second, the effective transfer of these charges. The efficiency of these two steps directly determines the degree of utilization of solar energy, and ultimately solar energy is converted into chemicals and stored through surface redox reactions.

[0003] In order to optimize the photocatalytic process, scientists are committed to designing and preparing new photocatalysts that can synergistically enhance the generation and transfer behavior of charges. Such catalysts are essential for realizing a variety of photocatalytic processes such as water photolysis and carbon dioxide reduction reactions. Among the many photocatalyst materials studied, graphitic carbon nitride (g-C3N4) has become a research hotspot in recent years due to its unique electronic band structure, abundant natural sources and simple preparation process. As a non-metallic organic polymer semiconductor material, g-C3N4 has a structure similar to graphene and has good chemical and thermal stability. At the same time, its band gap structure is suitable for the absorption of visible light.

[0004] However, despite its many advantages, g-C3N4 still faces some challenges in practical applications. In particular, its low charge generation efficiency and slow charge transfer rate significantly limit its application potential in the field of photocatalysis. In order to overcome these limitations, researchers have invested a lot of effort, including modifying the structure of g-C3N4 to improve its photocatalytic performance. These modification methods include strategies such as doping with other elements, constructing heterostructures, introducing nanostructures, and surface functionalization, aiming to optimize its electronic structure and enhance the separation and transfer efficiency of photogenerated charges, thereby improving the activity and stability of g-C3N4 in photocatalytic reactions. Through these studies, scientists hope to develop more efficient, economical and environmentally friendly photocatalysts to promote the application of photocatalytic technology in the fields of energy and environment.

[0005] Due to the excellent charge mobility and good compatibility with g-C3N4, researchers have introduced carbon materials into g-C3N4 to accelerate charge transfer. Charge transfer can be greatly enhanced by π-π electron superposition electric field, thereby suppressing electron-hole recombination. However, the intrinsic light absorption of carbon materials limits the effective utilization of incident light. The mismatched charge behavior of g-C3N4, namely the attenuated charge generation and enhanced charge transfer, often leads to a limited increase in available carriers, and even has a negative impact when excessive carbon is present. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation method and application of a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material to solve the problems raised in the background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material comprises the following steps:

[0009] Step 1, preparation of g-C3N4, dispersing melamine in an amine / NaCl buffer, adding tannic acid to the solution, placing the solution in a water bath and stirring; collecting the powder by centrifugation, and washing with deionized water; sealing the collected product in a crucible and calcining it to obtain g-C3N4 powder;

[0010] Step 2, preparation of g-C3N4 / Fe2O3, re-dispersing g-C3N4 powder in deionized water to form a suspension; adding FeCl3·6H2O to the suspension and stirring for 30 minutes, centrifuging to obtain a precipitate; washing the obtained precipitate with deionized water, freeze-dried overnight, and calcined, and then ground after calcination to obtain a sample g-C3N4 / Fe2O3;

[0011] Step 3, preparation of carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material, add grapefruit peel powder, g-C3N4 / Fe2O3 and ZnCl2 into a three-necked flask, then add ultrapure water, place the three-necked flask in an oil bath, stir and reflux on a magnetic stirrer for half an hour to form a uniform dispersion of nitrogen-deficient g-C3N4 coated with grapefruit peel, cool to room temperature, add acetic acid solution dropwise to the dispersion, continue to reflux and stir for 3 hours, and then cool to form an off-white hydrogel; pour the hydrogel into a polytetrafluoroethylene reactor, take out after freezing, and further freeze-dry for 48 hours to obtain grapefruit peel aerogel; finally, put the freeze-dried aerogel into a tubular furnace, carbonize it under a high-purity nitrogen atmosphere, naturally cool to room temperature after carbonization, and take out the sample to obtain a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material.

[0012] On the basis of the above technical solution, the present invention also provides the following optional technical solution:

[0013] In an optional scheme: in step 1, the temperature of the water bath is 25°C and stirring is continued for 24 hours.

[0014] In an optional scheme: in step 1, the process conditions of calcination are: calcination at 300°C for 1 hour, calcination at 400°C for 1 hour and calcination at 550°C for 4 hours, and the heating rate is 5°C / min.

[0015] In an optional scheme: in step 2, the process conditions of calcination are: calcination at 200°C for 1 hour, calcination at 300°C for 1 hour and calcination at 400°C for 1 hour, and the heating rate is 5°C / min.

[0016] In an optional scheme: in step three, the volume percentage concentration of the acetic acid solution is 1% v / v; the hydrogel is poured into a polytetrafluoroethylene reactor, placed in a -80°C refrigerator and frozen for 2 hours before being taken out.

[0017] In an optional scheme: in step 3, the process conditions of carbonization are: carbonization at 800°C for 2 h, carbonization at 900°C for 2 h and carbonization at 1000°C for 2 h, and the heating rate is 2°C / min.

[0018] Application of the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material prepared based on the above-mentioned method for preparing the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material in the degradation of ibuprofen.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention prepares a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material to achieve efficient degradation of the organic pollutant ibuprofen in water. The photocatalytic redox reaction provides the necessary driving force for the degradation system. g-C3N4 / Fe2O3 / C is a composite photocatalytic material of Fe 3+ / polyphenol-coated melamine calcined. The optical and optoelectronic properties of g-C3N4 / Fe2O3 / C confirmed the simultaneous enhancement of charge generation and charge transfer. The excitation of the α-Fe2O3 part endowed the nanoshell with the ability to generate charges, minimizing the inefficient light absorption of the C part. At the same time, the C component promoted the transfer of electrons from the α-Fe2O3 group to g-C3N4 or from g-C3N4 to the surface of the C component, thereby suppressing the initial charge recombination of g-C3N4. By changing the ratio of α-Fe2O3 to C in the nanoshell, the charge generation and charge transfer steps can be well matched and synergistically enhanced, thereby significantly improving the degradation efficiency of ibuprofen. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron microscope image of the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material prepared by the present invention.

[0022] Figure 2 It is the X-ray diffraction pattern of the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material of the present invention.

[0023] Figure 3 The performance curve of the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material of the present invention for photocatalytic degradation of the organic pollutant ibuprofen in water. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The various embodiments listed in the present invention are only used to illustrate the present invention and are not used to limit the scope of the present invention. Any obvious modifications or changes made to the present invention do not depart from the spirit and scope of the present invention.

[0025] In one embodiment, a method for preparing a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material comprises the following steps:

[0026] Preparation of g-C3N4: Disperse 2 g of melamine in 30 mL of amine / NaCl buffer (0.133 M), and then add 5 mL of tannic acid (10 mg / mL) to the solution. Stir the solution in a water bath at 25 °C for 24 hours. Collect the powder by centrifugation and wash with deionized water. Seal the collected product in a crucible and calcine it using the following process: 300 °C / 1h, 400 °C / 1h, 550 °C / 4h, with a heating rate of 5 °C / min;

[0027] Preparation of g-C3N4 / Fe2O3: 3 g of the g-C3N4 powder obtained above was redispersed in 50 mL of deionized water. 0.1 Mmol FeCl3·6H2O (dissolved in 20 mL of deionized water) was immediately added to the suspension. The solution was stirred for 30 minutes and centrifuged to obtain a precipitate. The obtained precipitate was washed with deionized water, freeze-dried overnight, and then calcined using the following process: 200°C / 1h, 300°C / 1h, 400°C / 1h. After calcination, the sample was ground for further experiments.

[0028] Preparation of carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material: Add 2.0g of grapefruit peel powder, 5g of g-C3N4 / Fe2O3 and 0.5g of ZnCl2 to a 500mL three-necked flask, then add 200mL of ultrapure water, place the three-necked flask in an oil bath, stir and reflux on a magnetic stirrer for half an hour to form a uniform dispersion of nitrogen-deficient g-C3N4 coated with grapefruit peel. Cool to room temperature, add 2.0mL of acetic acid solution (1% v / v) to the above dispersion, continue to reflux and stir for 3h, and cool to form an off-white hydrogel. Pour the hydrogel into a 100mL polytetrafluoroethylene reactor, place it in a -80℃ refrigerator and freeze it for 2h, then take it out, and further freeze-dry it for 48h to obtain grapefruit peel aerogel. Finally, the freeze-dried aerogel was placed in a tubular furnace and carbonized in a high-purity nitrogen atmosphere at a heating rate of 2°C / min. The carbonization process was: 800°C / 2h, 900°C / 2h, 1000°C / 2h. After naturally cooling to room temperature, the sample was taken out to obtain a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material.

[0029] During the preparation process, the results of X-ray irradiation of g-C3N4, g-C3N4 / Fe2O3 and C / g-C3N4 / Fe2O3 are shown in Figure 2 shown.

[0030] Among them, there are two obvious characteristic diffraction peaks in the XRD spectrum of g-C3N4; one is located at about 13.0° at 2θ, corresponding to the (100) crystal plane. This peak represents the periodic arrangement of the triazine ring structural unit in the plane, reflecting the in-plane order of the material; the other is located at about 27.4° at 2θ, corresponding to the (002) crystal plane, which is generated by the interlayer stacking of the conjugated aromatic system, similar to the stacking of carbon atoms in graphite. For g-C3N4 / Fe2O3 material, the diffraction peaks of its Fe2O3 component are located at 24.15° (012), 30.24° (220), 33.24° (104), 35.69° (110), 40.94° (113), 43.60° (202), 49.72° (024), 54.13° (116), 57.63° (108) and 63.15° (214). The carbon aerogel (C) component of the C / C3N4 / Fe2O3 material shows a broadened diffuse peak at about 21° in the XRD spectrum, which corresponds to the (002) crystal plane diffraction of graphite-like microcrystals in the carbon material. The XRD comparison data of g-C3N4, g-C3N4 / Fe2O3 and C / g-C3N4 / Fe2O3 show that the C / g-C3N4 / Fe2O3 catalytic material was successfully synthesized, and the introduction of g-C3N4 and Fe2O3 components into g-C3N4 had no effect on its crystal structure.

[0031] Experimental determination: Ibuprofen degradation experiment

[0032] The degradation experiment of ibuprofen was carried out in a constant temperature (room temperature) shaker. First, three reaction solutions containing ibuprofen of different concentrations were prepared: 2 mg / L, 5 mg / L and 10 mg / L. 500 mg of carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material was put into three reaction bottles respectively, 10 mmol / LH2O2 was added, the shaker was started, and the degradation reaction of ibuprofen began. During the reaction, at fixed time intervals, 2 mL of suspension sample was taken into a test tube with a syringe, and 0.2 mL of isopropanol quencher was added at the same time to prevent the sample from further degradation reaction in the test tube. The supernatant was aspirated, filtered with a 0.22 μm filter membrane, and finally its concentration change was determined by high performance liquid chromatography. The test conditions were: the detection wavelength was 264 nm, the injection volume was 20 μL, the mobile phase flow rate was 1 mL / min, the column temperature was 30 ° C, and the volume content of formic acid was 0.2%. The results of the experimental determination are shown in the attached Figure 3 shown.

[0033] Graphitized carbon nitride (g-C3N4) is an emerging metal-free photocatalyst due to its low band position, active properties and ease of preparation. Synergistically enhancing the charge generation and charge transfer of g-C3N4 to improve solar and chemical efficiencies remains a hot but challenging issue. Here, Fe 3+ / polyphenol coated melamine, and a nanoshell containing α-Fe2O3 and carbon aerogel was in situ formed on the surface of g-C3N4 core, thus obtaining a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalyst. The α-Fe2O3 component, as an additional photosensitizer, can provide more photogenerated electrons, while the C component provides a "highway" to promote the transfer of electrons from the α-Fe2O3 component to g-C3N4 or from g-C3N4 to the C component. Under the conditions of an initial pH value of 3.0 and an initial H2O2 concentration of 5mmol / L, the ibuprofen pollutant in the water can be completely degraded after 60min of reaction. The system shows good universality for the degradation of pharmaceutical organic pollutants, and after 4 cycles of degradation experiments, the degradation efficiency can still be maintained above 90%, indicating that the composite material has excellent catalytic stability.

[0034] The above is only a specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for preparing a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material, characterized in that: The following steps are involved: Step 1, preparation of g-C3N4, dispersing melamine in an amine / NaCl buffer, adding tannic acid to the solution, and placing the solution in a water bath and stirring; The powder was collected by centrifugation and washed with deionized water; the collected product was sealed in a crucible and calcined to obtain g-C3N4 powder; Step 2, preparation of g-C3N4 / Fe2O3, re-dispersing g-C3N4 powder in deionized water to form a suspension; adding FeCl3·6H2O to the suspension and stirring for 30 minutes, centrifuging to obtain a precipitate; washing the obtained precipitate with deionized water, freeze-dried overnight, and calcined, and then ground after calcination to obtain a sample g-C3N4 / Fe2O3; Step 3, preparation of carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material, add grapefruit peel powder, g-C3N4 / Fe2O3 and ZnCl2 into a three-necked flask, then add ultrapure water, place the three-necked flask in an oil bath, stir and reflux on a magnetic stirrer for half an hour to form a uniform dispersion of nitrogen-deficient g-C3N4 coated with grapefruit peel, cool to room temperature, add acetic acid solution dropwise to the dispersion, continue to reflux and stir for 3 hours, and then cool to form an off-white hydrogel; pour the hydrogel into a polytetrafluoroethylene reactor, take out after freezing, and then freeze-dry for 48 hours to obtain grapefruit peel aerogel; finally, put the freeze-dried aerogel into a tubular furnace, carbonize it under a high-purity nitrogen atmosphere, naturally cool to room temperature after carbonization, and take out the sample to obtain a carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material.

2. The method for preparing the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material according to claim 1, characterized in that: In step 1, the temperature of the water bath was 25° C. and stirring was continued for 24 hours.

3. The method for preparing the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material according to claim 1, characterized in that: In step 1, the calcination process conditions are: calcination at 300° C. for 1 h, calcination at 400° C. for 1 h and calcination at 550° C. for 4 h, and the heating rate is 5° C. / min.

4. The method for preparing the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material according to claim 1, characterized in that: In step 2, the calcination process conditions are: calcination at 200° C. for 1 h, calcination at 300° C. for 1 h, and calcination at 400° C. for 1 h, and the heating rate is 5° C. / min.

5. The method for preparing the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material according to claim 1, characterized in that: In step 3, the volume percentage concentration of the acetic acid solution is 1% v / v; the hydrogel is poured into a polytetrafluoroethylene reactor, placed in a -80°C refrigerator and frozen for 2 hours before being taken out.

6. The method for preparing the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material according to claim 1, characterized in that: In step 3, the carbonization process conditions are: carbonization at 800 °C for 2 h, carbonization at 900 °C for 2 h, and carbonization at 1000 °C for 2 h, and the heating rate is 2 °C / min.

7. Use of the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material prepared by the preparation method of the carbon aerogel / g-C3N4 / Fe2O3 composite photocatalytic material according to any one of claims 1 to 6 in the degradation of ibuprofen.

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