Preparation method of carbon nitride nanosheet colloid and application of carbon nitride nanosheet colloid in photocatalysis
By desalting the method after calcining melamine and potassium salts, carbon nitride nanosheet colloids were successfully synthesized, solving the problems of uneven dispersion of carbon nitride and light-shielding effects in traditional methods, and achieving high-efficiency photocatalytic hydrogen production performance and the possibility of large-scale production.
Patent Information
- Application Number
- CN202510535268.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-27
- Publication Date
- 2025-06-20
AI Technical Summary
It is difficult to effectively synthesize carbon nitride nanosheet colloids in the prior art, and the carbon nitride synthesized by traditional methods has uneven dispersion and light-shielding effects, which limits its application in the fields of catalysis and photocatalysis.
The carbon nitride nanosheet colloid was obtained by mixing melamine and the two potassium salts thoroughly and calcining, followed by desalting treatment. This method exhibits excellent dispersion in water, avoiding the light shading effect.
It has achieved efficient synthesis of carbon nitride nanosheet colloids, has high photocatalytic hydrogen production performance, and can produce gram levels. It is suitable for catalysis, biomedical and thin film devices and other fields.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of material synthesis and catalysis. Specifically, it relates to a preparation method of carbon nitride nanosheet colloid and its application in photocatalysis. Background Art
[0002] Colloid is a relatively homogeneous mixture with the stability of polymer solution. Due to its characteristics of high dispersion degree and multi-phase, colloid is widely used in drug carriers, catalysis, fluorescence emission, molecular recognition, etc., showing great application prospects.
[0003] In recent years, graphitic carbon nitride semiconductor, as a metal-free material, has attracted a large number of researchers' attention due to its simple preparation, low-cost raw materials, and excellent physical and chemical stability (PMID: 18997776). The traditional synthesis methods of carbon nitride are mostly prepared from nitrogen-containing compounds, and the raw materials prepared are generally mainly materials such as melamine, thiourea, dicyandiamide, etc., and are obtained by high-temperature calcination method. However, the carbon nitride synthesized by the traditional method is a bulk material, which has disadvantages such as insoluble and uneven dispersion, seriously restricting its application in the fields of catalysis, biomedicine, etc. In addition, the bulk carbon nitride has a "light shielding" effect in the photocatalytic hydrogen evolution reaction, that is, as the concentration of the catalyst increases, the hydrogen evolution rate decreases instead, because the high-concentration catalyst will block or scatter the incident light.
[0004] So far, there are few research reports on carbon nitride colloid materials, especially the synthesis method of carbon nitride nanosheet colloid that can reach the gram level has not been reported. Some researchers use strong alkali to treat carbon nitride materials to obtain colloid (PMID: 34585790), but the conversion efficiency of this method of carbon nitride colloid is extremely low, about 1% or so. At the same time, the yield of the colloid synthesized by this method is very low, only reaching the milligram level, and there are also disadvantages such as complex preparation process and long cycle.
[0005] Therefore, it is of extremely important significance to develop a method with simple operation, green, low cost, and capable of synthesizing carbon nitride colloid in large quantities. Summary of the Invention
[0006] To overcome the above-mentioned defects and deficiencies in the prior art, the present invention provides a preparation method of carbon nitride nanosheet colloid and its application in photocatalysis. The synthesized carbon nitride nanosheet colloid has excellent dispersibility in water and can maintain a high degree of dispersion in water for a long time, solving the light shielding effect caused by the poor dispersion of carbon nitride synthesized by the traditional method, and showing more efficient photocatalytic hydrogen production performance.
[0007] The first object of the present invention is to provide a preparation method of carbon nitride nanosheet colloid.
[0008] The second object of the present invention is to provide a colloidal carbon nitride nanosheet prepared by the above-mentioned preparation method.
[0009] The third object of the present invention is to provide the application of the above-mentioned colloidal carbon nitride nanosheet in the preparation of a photocatalyst for photocatalytic hydrogen evolution.
[0010] The fourth object of the present invention is to provide the application of the above-mentioned colloidal carbon nitride nanosheet in photocatalytic hydrogen production.
[0011] The fifth object of the present invention is to provide a photocatalyst.
[0012] The sixth object of the present invention is to provide a method for photocatalytic hydrogen production.
[0013] The present invention claims the following: A preparation method of a colloidal carbon nitride nanosheet, wherein the preparation method is to fully mix melamine and two potassium salts and then perform calcination, and after the calcination is completed, desalination is carried out to obtain the colloidal carbon nitride nanosheet; The potassium salts include potassium chloride and potassium carbonate; The molar ratio of melamine, potassium chloride and potassium carbonate is 20-25:92-94:6-8.
[0014] Preferably, the molar ratio of melamine to potassium salts is 20-25:100.
[0015] Preferably, the molar ratio of melamine, potassium chloride and potassium carbonate is 23.786:92-94:6-8.
[0016] Preferably, the mass of melamine is more than 3 g.
[0017] Preferably, the calcination is carried out in an air atmosphere.
[0018] Preferably, the temperature of the calcination is 545-555 °C.
[0019] More preferably, the temperature of the calcination is 550 °C.
[0020] Preferably, the time of the calcination is 2.5-3.5 h.
[0021] More preferably, the time of the calcination is 3 h.
[0022] Preferably, the method of desalination is dialysis.
[0023] A colloidal carbon nitride nanosheet prepared by any of the above-mentioned preparation methods.
[0024] The application of the above-mentioned colloidal carbon nitride nanosheet in the preparation of a photocatalyst for photocatalytic hydrogen evolution.
[0025] Application of the above-mentioned carbon nitride nanosheet colloid in photocatalytic hydrogen production.
[0026] A photocatalyst containing the above-mentioned carbon nitride nanosheet colloid.
[0027] A method for photocatalytic hydrogen production, adding the above-mentioned carbon nitride nanosheet colloid.
[0028] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a preparation method of a carbon nitride nanosheet colloid and its application in photocatalysis. The carbon nitride nanosheet colloid prepared by the present invention has characteristics such as planar cross and super large size, has excellent dispersibility in aqueous solution, can maintain a high degree of dispersion in aqueous solution for a long time, significantly avoids the influence of the light shielding effect generated by a high-concentration photocatalyst on the catalytic activity during the photocatalytic process, and avoids the decrease in the hydrogen evolution rate caused by the light shielding effect, and shows high photocatalytic water splitting hydrogen production performance.
[0029] The raw materials of the carbon nitride nanosheet colloid of the present invention are cheap and easily available, the preparation method is simple, and the conversion efficiency of carbon nitride into colloid is relatively high, reaching 20-30%, and the output can even reach the gram level, and can be mass-produced, and has broad application prospects in the fields of catalysis, biomedicine and thin film devices, etc. Description of the Drawings
[0030] Figure 1 The carbon nitride nanosheet colloid prepared in Example 2.
[0031] Figure 2 The X-ray powder diffraction (XRD) pattern of the carbon nitride nanosheet colloid prepared in Example 2.
[0032] Figure 3 The Fourier transform infrared spectrum (FT-IR) pattern of the carbon nitride nanosheet colloid prepared in Example 2.
[0033] Figure 4 The contact angle experiment diagram; a: traditional bulk carbon nitride, b: the carbon nitride nanosheet colloid prepared in Example 2.
[0034] Figure 5 The Tyndall phenomenon diagram of the carbon nitride nanosheet colloid prepared in Example 2.
[0035] Figure 6 The scanning electron microscope (SEM) image of the carbon nitride nanosheet colloid prepared in Example 2.
[0036] Figure 7 The scanning electron microscope (SEM) image of the carbon nitride nanosheet colloid prepared in Example 3.
[0037] Figure 8 Transmission electron microscopy (TEM) image of the carbon nitride nanosheet colloid prepared in Example 2.
[0038] Figure 9 Photocatalytic water splitting hydrogen production activity diagram of the carbon nitride nanosheet colloid prepared in Example 2; a: carbon nitride nanosheet colloid, b: bulk carbon nitride. Detailed implementation manners
[0039] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.
[0040] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.
[0041] Example 1 Preparation method of a carbon nitride nanosheet colloid I. Experimental method Weigh 3 g (23.786 mmol) of melamine, 94 mmol of potassium chloride, and 6 mmol of potassium carbonate, and grind and mix them evenly in a mortar. Place the evenly mixed powder in an alumina crucible and calcine it in an air furnace at 550 °C for 3 h. After natural cooling, a carbon nitride-salt mixture is obtained, and it is stirred and dispersed with water. The salt is removed by dialysis, and water is removed by freeze-drying to obtain a carbon nitride nanosheet colloid, which has a cotton-like appearance and a yield of 336 mg.
[0042] Bulk carbon nitride: Weigh 3 g (23.786 mmol) of melamine and place it in an alumina crucible, and calcine it at 550 °C in an air furnace for 3 h to obtain bulk carbon nitride, with a yield of 1.326 g.
[0043] Calculate the colloid conversion efficiency according to the following formula: Colloid conversion efficiency = yield of carbon nitride nanosheet colloid / yield of bulk carbon nitride × 100%; The calculated colloid conversion efficiency is 25.34%, indicating that the method of this example has a relatively high conversion efficiency for obtaining carbon nitride colloid.
[0044] Example 2 Preparation method of a carbon nitride nanosheet colloid Weigh 9 g (71.359 mmol) of melamine, 279 mmol of potassium chloride and 21 mmol of potassium carbonate, and grind and mix them evenly in a mortar. Place the evenly mixed powder in an alumina crucible and calcine it in an air furnace at 550 °C for 3 h. After natural cooling, a carbon nitride-salt mixture is obtained, and water is added and stirred to disperse it. The salt is removed by dialysis, and water is removed by freeze-drying to obtain a carbon nitride nanosheet colloid, which has a cotton-like appearance and a yield of 1.443 g ( Figure 1 ).
[0045] Bulk carbon nitride: Weigh 9 g (71.359 mmol) of melamine and place it in an alumina crucible, and calcine it at 550 °C in an air furnace for 3 h to obtain bulk carbon nitride with a yield of 5.113 g.
[0046] According to Example 1, the colloid conversion efficiency was calculated, and the calculated colloid conversion efficiency was 28.22%, indicating that the method of this example has a high conversion efficiency for obtaining carbon nitride colloid and the yield can reach the gram level.
[0047] Example 3 A method for preparing a carbon nitride nanosheet colloid Weigh 9 g (71.359 mmol) of melamine, 276 mmol of potassium chloride and 24 mmol of potassium carbonate, and grind and mix them evenly in a mortar. Place the evenly mixed powder in an alumina crucible and calcine it in an air furnace at 550 °C for 3 h. After natural cooling, a carbon nitride-salt mixture is obtained, and water is added and stirred to disperse it. The salt is removed by dialysis, and water is removed by freeze-drying to obtain a carbon nitride nanosheet colloid, which has a cotton-like appearance and a yield of 1.276 g.
[0048] Bulk carbon nitride: Weigh 9 g (71.359 mmol) of melamine and place it in an alumina crucible, and calcine it at 550 °C in an air furnace for 3 h to obtain bulk carbon nitride with a yield of 5.113 g.
[0049] According to Example 1, the colloid conversion efficiency was calculated, and the calculated colloid conversion efficiency was 24.96%, indicating that the method of this example has a high conversion efficiency for obtaining carbon nitride colloid and the yield can reach the gram level.
[0050] Example 4 X-ray powder diffraction I. Experimental method Use an X-ray powder diffractometer (X'Pert Pro, Malvern Panalytical) to perform phase characterization on the carbon nitride nanosheet colloid prepared in Example 2. Test conditions: voltage 40 kV, current 26 mA, scanning angle range 10 - 60°, scanning speed 5° / min, CuKα (λ = 0.154 nm) ray.
[0051] II. Experimental Results The X-ray powder diffraction pattern of the carbon nitride nanosheet colloid prepared in Example 2 is as Figure 2 shown. It can be found from Figure 2 that there is an obvious diffraction peak at 27.5° for the carbon nitride nanosheet colloid, which belongs to the (002) crystal plane of graphitic carbon nitride, proving that the synthesized product is a carbon nitride material.
[0052] Example 5 Fourier Transform Infrared Spectroscopy I. Experimental Method The infrared spectrum of the carbon nitride nanosheet colloid prepared in Example 2 was measured using a Nicolet 6700 Fourier transform infrared spectrometer in the United States. The number of scans was 64 times, and the range was 4000 - 500 cm -1 , with a resolution of 4.0 cm -1 .
[0053] II. Experimental Results The Fourier transform infrared spectrum of the carbon nitride nanosheet colloid prepared in Example 2 is as Figure 3 shown. There is a strong diffraction peak at 2180 cm -1 , which belongs to the strong absorption peak of terminal cyano groups. There are obvious vibration peaks in the range of 1200 - 1700 cm -1 , corresponding to the stretching vibration peaks of C, N - heterocyclic heptazine units. There is a strong diffraction peak in the range of 3400 - 3600 cm -1 , which belongs to the stretching vibration peak of hydroxyl groups, indicating that the carbon nitride nanosheet colloid contains hydroxyl hydrophilic groups.
[0054] Example 6 Contact Angle Experiment I. Experimental Method Bulk carbon nitride was prepared according to the method of Example 2. 5 mg of bulk carbon nitride and the carbon nitride nanosheet colloid prepared in Example 2 were respectively weighed and added to 5 mL of water, and ultrasonicated to disperse evenly. The obtained dispersion was all coated on a glass slide and dried in an oven at 100 °C, and then tested using a Dataphysics DCA21 contact angle meter.
[0055] II. Experimental Results The contact angle experimental results of the carbon nitride nanosheet colloid and bulk carbon nitride prepared in Example 2 are as shown in a and b in Figure 4 . The results show that the contact angle of the carbon nitride nanosheet colloid ( Figure 4 b in) is significantly smaller than that of bulk carbon nitride ( Figure 4 a in), indicating that the carbon nitride nanosheet colloid is more hydrophilic and can show high dispersion in water.
[0056] Example 7 Detection of Tyndall Effect I. Experimental Method Disperse 20 mg of the carbon nitride nanosheet colloid prepared in Example 2 in a beaker containing 20 mL of water. Use a laser pointer as the light source and adjust the position so that the light source is parallel to the beaker. After the position is adjusted, turn on the light source and observe whether there is an obvious light path in the solution in the beaker. If there is, it is a colloidal solution.
[0057] II. Experimental Results The results are as Figure 5 shown. It can be clearly seen that there is a clear light path in the colloid in the beaker, indicating that the carbon nitride nanosheet colloid prepared in Example 2 has colloidal properties.
[0058] Example 8 Electron Microscopy Characterization I. Experimental Method Scanning electron microscopy: Ultrasonically disperse the carbon nitride nanosheet colloids prepared in Example 2 and Example 3 evenly in water. Take the dispersion and drop it on a silicon wafer. After natural drying, test it with a scanning electron microscope (JSM-7610F, JEOL Ltd., Japan).
[0059] Transmission electron microscopy: Ultrasonically disperse the carbon nitride nanosheet colloid prepared in Example 2 evenly in water. Take the dispersion and drop it on a copper grid. After natural drying, test it with a JEOL-2100F / F200 transmission electron microscope from Japan.
[0060] II. Experimental Results The scanning electron microscopy results of the carbon nitride nanosheet colloid prepared in Example 2 are as Figure 6 shown. It can be seen from the figure that the morphology of the carbon nitride nanosheet colloid is formed by the accumulation of nanosheets.
[0061] The scanning electron microscopy results of the carbon nitride nanosheet colloid prepared in Example 3 are as Figure 7 shown. It can be seen from the figure that the morphology of the carbon nitride nanosheet colloid has the characteristics of cracked nanosheets, its size can reach the μm level, and the plane presents a crossed slit structure.
[0062] The transmission electron microscopy results of the carbon nitride nanosheet colloid prepared in Example 2 are as Figure 8 shown. It can be seen from the figure that the carbon nitride nanosheet colloid is in the form of nanosheets.
[0063] Example 9 Photocatalytic Water Splitting Hydrogen Production Activity I. Experimental Method 40 mg, 80 mg, 120 mg, and 160 mg of the catalyst (the carbon nitride nanosheet colloid or bulk carbon nitride prepared in Example 2) were respectively dispersed in 80 mL of a triethanolamine solution with a volume fraction of 10%. 2 wt% of Pt was in-situ photo-deposited on the carbon nitride using chloroplatinic acid as a co-catalyst, and a visible light (λ>400 nm) catalytic reaction was carried out using an upward-irradiation reactor. The amount of hydrogen gas generated by the photocatalytic reaction was measured using a gas chromatograph.
[0064] II. Experimental Results The results are as Figure 9 shown. Compared with bulk carbon nitride, the carbon nitride nanosheet colloid prepared in Example 2 exhibited higher photocatalytic water splitting hydrogen production performance. Especially, the hydrogen production activity under high-concentration catalysts was increased by 20 times. However, for bulk carbon nitride, as the concentration increased (from 1.5 mg / mL to 2.0 mg / mL), the hydrogen evolution rate decreased instead.
[0065] The above results indicate that forming a colloidal material is beneficial to eliminating the influence of the light-shielding effect generated during the catalytic process on the catalytic activity, maximizing the catalytic activity of the catalyst.
[0066] Comparative Example 1 3 g of melamine, 94 mmol of potassium chloride, and 6 mmol of potassium sulfate were weighed and ground and mixed evenly in a mortar. The evenly mixed powder was placed in an alumina crucible and calcined in an air furnace at 550 °C for 3 h. After natural cooling, a carbon nitride-salt mixture was obtained. After adding water and stirring to disperse, the product after filtration and drying was carbon nitride powder, and no colloid could be obtained.
[0067] Comparative Example 2 3 g of melamine, 94 mmol of potassium chloride, and 6 mmol of potassium acetate were weighed and ground and mixed evenly in a mortar. The evenly mixed powder was placed in an alumina crucible and calcined in an air furnace at 550 °C for 3 h. After natural cooling, a carbon nitride-salt mixture was obtained. After adding water and stirring to disperse, the product after filtration and drying was carbon nitride powder, and no colloid could be obtained.
[0068] Comparative Example 3 3 g of melamine, 94 mmol of potassium chloride, and 6 mmol of lithium carbonate were weighed and ground and mixed evenly in a mortar. The evenly mixed powder was placed in an alumina crucible and calcined in an air furnace at 550 °C for 3 h. After natural cooling, a carbon nitride-salt mixture was obtained. After adding water and stirring to disperse, the product after filtration and drying was carbon nitride powder, and no colloid could be obtained.
[0069] Comparative Example 4 Weigh 3 g of melamine and 100 mmol of potassium chloride, and grind and mix them evenly in a mortar. Place the evenly mixed powder in an alumina crucible and calcine it in an air furnace at 550 °C for 3 h. After natural cooling, a carbon nitride-salt mixture is obtained. Add water, stir and disperse it, and the product after filtration and drying is carbon nitride powder, and no colloid can be obtained.
[0070] Comparative Example 5 Weigh 3 g of melamine and 6 mmol of potassium carbonate, and grind and mix them evenly in a mortar. Place the evenly mixed powder in an alumina crucible and calcine it in an air furnace at 550 °C for 3 h. After natural cooling, a carbon nitride-salt mixture is obtained. Add water, stir and disperse it, and the product after filtration and drying is carbon nitride powder, and no colloid can be obtained.
[0071] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.
Claims
1. A method for preparing carbon nitride nanosheet colloid, characterized in that: The melamine and two potassium salts are fully mixed and then calcined, and after the calcination, the salt is removed to obtain carbon nitride nanosheet colloid; The potassium salts include potassium chloride and potassium carbonate; The molar ratio of melamine, potassium chloride and potassium carbonate is 20-25:92-94:6-8.
2. The preparation method according to claim 1, characterized in that The mass of the melamine is greater than 3 g.
3. The preparation method according to claim 1, characterized in that: The calcination is performed in an air atmosphere.
4. The preparation method according to claim 1, characterized in that The calcination temperature is 545-555° C., and the calcination time is 2.5-3.5 h.
5. The preparation method according to claim 1, characterized in that: The desalination method is dialysis.
6. Carbon nitride nanosheet colloid prepared by the preparation method according to any one of claims 1 to 5.
7. Use of the carbon nitride nanosheet colloid according to claim 6 in preparing a photocatalyst for photocatalytic hydrogen evolution.
8. Use of the carbon nitride nanosheet colloid according to claim 6 in photocatalytic hydrogen production.
9. A photocatalyst, characterized in that Contains the carbon nitride nanosheet colloid according to claim 6.
10. A method for photocatalytic hydrogen production, characterized in that: Add the carbon nitride nanosheet colloid described in claim 6.