Preparation method of cyano-rich red carbon nitride with improved specific surface area

Abstract

The invention relates to a preparation method of cyano-rich red carbon nitride with an improved specific surface area, which comprises the following steps: grinding and uniformly mixing banded melamine and ammonium salt, and roasting in an air atmosphere to obtain a banded carbon nitride intermediate; and putting the obtained strip-shaped carbon nitride intermediate into a quartz tube, putting the quartz tube into a tubular furnace, and roasting in an oxygen-free environment to obtain the cyano-rich red carbon nitride with the high specific surface area. The cyano-rich red carbon nitride product prepared by the preparation method for improving the specific surface area of the cyano-rich red carbon nitride has a peak at 2175 cm <-1 >; the color of the product is red; the specific surface area of the product can reach 101.9 m < 2 > / g. According to the prepared cyano-rich red carbon nitride, the specific surface area is increased, meanwhile, the light absorption performance of a near-infrared region is remarkably improved, and the application range of the cyano-rich red carbon nitride in different wavelength ranges is expanded. The photocatalyst has high photocatalytic hydrogen peroxide generation rate and bactericidal activity, and has great application value in the fields of energy, environment and the like.

Description

Technical Field

[0001] The invention relates to a method for preparing cyano-rich red carbon nitride with increased specific surface area, in particular to a method for preparing cyano-rich red carbon nitride with high specific surface area by an oxygen-free roasting method, and belongs to the technical field of nano material preparation and photocatalysis. Background Art

[0002] Photocatalytic technology can effectively alleviate energy crisis and environmental pollution through reactions such as reducing oxygen to produce hydrogen peroxide, splitting water to produce hydrogen, and generating free radicals for sterilization, showing great potential application value. As an organic semiconductor photocatalyst, carbon nitride has the advantages of easy preparation, non-toxicity, and high stability, and has broad application prospects in the field of photocatalytic technology. However, a series of inherent defects of bulk carbon nitride, such as low specific surface area, poor crystallinity, weak light absorption ability, and rapid photogenerated charge recombination efficiency, restrict its photocatalytic activity.

[0003] It has been reported in the literature that constructing cyanide groups on the molecular structure of carbon nitride can improve the efficiency of photogenerated charge separation and increase light absorption to enhance the photocatalytic performance of carbon nitride. Typical methods include metal salt-assisted method and sodium borohydride-assisted method. For example, Zhang Guoqiang et al. (ACS Catalysis, 2021, 11, 6995-7005) used bulk carbon nitride and potassium chloride as raw materials and calcined them at 600°C for 4 hours to obtain highly crystalline carbon nitride containing cyanide, with a specific surface area of ​​9.4 m 2 / g, which increases its photocatalytic hydrogen production rate by 21 times compared with bulk carbon nitride. In addition, Zhao Daming et al. (Advanced Materials, 2019, 1903545) 2 / g) and sodium borohydride were calcined in an inert atmosphere for 1h to successfully prepare boron-doped cyanide-containing carbon nitride with a specific surface area of ​​35.0 m 2 / g, which increases its photocatalytic oxygen production rate by about 2 times compared with bulk carbon nitride.

[0004] In the above-mentioned preparation methods, the preparation process is complicated, and the prepared cyanide-containing carbon nitride has problems such as poor photocatalytic stability, small specific surface area, low cyanide content and weak light absorption ability. Therefore, it is urgent to seek a method with simple preparation process, low cost and easy industrial production to obtain cyanide-rich carbon nitride with high photocatalytic efficiency. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for preparing cyanide-rich red carbon nitride with high specific surface area, wherein the method prepares cyanide-rich red carbon nitride with high specific surface area ([C6N7(NH2)(NH)] n), simple operation, low cost, high yield, easy industrial application, and can significantly improve the photocatalytic hydrogen peroxide production and antibacterial efficiency of the material.

[0006] The technical solution of the present invention is as follows:

[0007] The invention discloses a preparation method of cyano-rich red carbon nitride with improved specific surface area. The method comprises the following steps: grinding and mixing ribbon-shaped melamine and ammonium salt evenly, and then calcining the mixture in an air atmosphere to obtain a ribbon-shaped carbon nitride intermediate; placing the obtained ribbon-shaped carbon nitride intermediate in a quartz tube, and then placing the obtained ribbon-shaped carbon nitride intermediate in a tube furnace and calcining the obtained ribbon-shaped carbon nitride in an oxygen-free environment to obtain cyano-rich red carbon nitride with high specific surface area.

[0008] The ammonium salt is one or a combination of two or more of ammonium chloride, ammonium bromide, ammonium sulfate, ammonium nitrate or ammonium bicarbonate.

[0009] The ammonium salt is ammonium bromide or ammonium chloride.

[0010] The mass ratio of the strip-shaped melamine to the ammonium salt is 1:0.5-5.

[0011] The roasting temperature of the strip-shaped melamine and ammonium salt mixture is 350-520°C.

[0012] The roasting time of the strip-shaped melamine and ammonium salt mixture is 2 to 8 hours.

[0013] The heating rate of the strip-shaped melamine and ammonium salt mixture is 1-10°C / min.

[0014] The oxygen-free environment is an argon atmosphere, a nitrogen atmosphere, a carbon dioxide atmosphere, a hydrogen atmosphere or a vacuum atmosphere.

[0015] The calcination temperature of the ribbon-shaped carbon nitride intermediate is 600-700° C. and the calcination time is 0.5-6 hours.

[0016] The cyanide-rich red carbon nitride product prepared by the method for preparing the cyanide-rich red carbon nitride with increased specific surface area has a surface area of ​​2175 cm -1 There is a peak at the bottom; the product is red in color; the specific surface area of ​​the product can reach 101.9m 2 / g.

[0017] In the method for preparing cyano-rich red carbon nitride with increased specific surface area of ​​the present invention, it is further preferred that the ammonium salt is ammonium bromide;

[0018] A further preferred mass ratio of the strip-shaped melamine to the ammonium salt is 1:1.

[0019] According to the present invention, the grinding is to fully mix the raw materials, so there is no special requirement for the grinding time, preferably 5 minutes.

[0020] The calcination temperature of the ribbon-shaped melamine and ammonium salt mixture is more preferably 500°C.

[0021] The roasting time of the strip-shaped melamine and ammonium salt mixture is more preferably 3 hours.

[0022] The heating rate of the strip-shaped melamine and ammonium salt mixture is more preferably 2° C. / min.

[0023] The oxygen-free environment is further preferably a vacuum atmosphere.

[0024] The calcination temperature of the ribbon-shaped carbon nitride intermediate is more preferably 650°C.

[0025] The calcination time of the ribbon-shaped carbon nitride intermediate is more preferably 1 hour.

[0026] The product obtained by the present invention is tested by infrared spectrum, optical photographs and N2 adsorption-desorption isotherm curve, which proves that a red carbon nitride with high specific surface area and rich in cyanide is obtained. Figure 1 The obtained product is shown in Figure 2175 cm-1 compared to bulk carbon nitride. -1 There is an obvious peak at , indicating that a large amount of cyano groups are produced; Figure 4 It can be seen that the color of the obtained product changes to red compared to the yellow bulk carbon nitride; Figure 6 It can be seen that the specific surface area of ​​the obtained product (101.9m 2 / g) compared with bulk carbon nitride (9.3m 2 / g) increased by about 11 times.

[0027] The technical features of the present invention are as follows:

[0028] 1. The present invention finds that the mixing ratio of the strip melamine and the ammonium salt described in the step is critical. When the amount of ammonium salt used is small, the fusion of the strip melamine in the subsequent roasting process cannot be suppressed; when the amount of ammonium salt is too much, it is wasted. Therefore, the mass ratio of the strip melamine and the ammonium salt needs to be strictly controlled.

[0029] 2. The present invention finds that the heating rate of the precursor mixture described in the step is particularly important. When the heating rate is too high, the band-shaped melamine will fuse quickly, and the intermediate structure obtained will be difficult to obtain a band-shaped structure, which is not conducive to obtaining carbon nitride with a high specific surface area; when the heating rate is too low, the heating time is too long, which will increase energy consumption. Therefore, it is necessary to strictly control the heating rate of the precursor mixture.

[0030] 3. The present invention has found that cyano groups can only be generated in an oxygen-free environment as described in the step. If oxygen is present, cyano structures cannot be generated in carbon nitride. Therefore, the calcination atmosphere of the carbon nitride intermediate in the step needs to be strictly controlled.

[0031] 4. The present invention finds that when the roasting temperature in the step is too low, cyanide-rich red carbon nitride cannot be produced. When the temperature is too high, the carbon nitride is easily decomposed, reducing the yield. Therefore, it is necessary to strictly control the roasting temperature of the carbon nitride intermediate in the step.

[0032] The beneficial effects of the present invention are as follows:

[0033] 1. The strategy of obtaining cyano-rich carbon nitride directly in an oxygen-free environment solves the shortcomings of low cyano content, difficulty in removing unreacted metal salts after obtaining the sample, and poor sample stability compared to the traditional metal salt-assisted method. Compared with sodium borohydride, which is prone to explosion, the preparation process of the present invention is simple and safe, low in cost, and easy to achieve industrial mass production.

[0034] 2. The cyano-rich carbon nitride prepared by the present invention increases the specific surface area and significantly improves the light absorption performance in the near-infrared region, thereby expanding its application range in different wavelength ranges. The cyano-rich carbon nitride prepared by the present invention has a large number of mesopores, exposing more edge active sites.

[0035] 3. The high specific surface area cyanide-rich red carbon nitride prepared by the present invention has a high photocatalytic hydrogen peroxide production rate and bactericidal activity, and has great application value in the fields of energy and environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is the infrared spectra of the carbon nitride prepared in Example 1 and Comparative Example 1, wherein the ordinate is the transmittance and the abscissa is the wave number.

[0037] Figure 2 The X-ray diffraction spectra of the carbon nitride prepared in Example 1 and Comparative Example 1 are shown in FIG. 1 , wherein the ordinate is the diffraction intensity and the abscissa is the diffraction angle (2θ).

[0038] Figure 3 1 and 2 are scanning electron microscope (SEM) photos of the carbon nitride prepared in Example 1 and Comparative Example 1, wherein a is the SEM photo of the carbon nitride prepared in Comparative Example 1; b is the SEM photo of the carbon nitride prepared in Example 1.

[0039] Figure 4 These are optical photographs of carbon nitride prepared in Example 1 and Comparative Example 1, wherein a is an optical photograph of carbon nitride prepared in Comparative Example 1; and b is an optical photograph of carbon nitride prepared in Example 1.

[0040] Figure 5 Solid UV-visible diffuse reflectance spectra of carbon nitride prepared in Example 1 and Comparative Example 1.

[0041] Figure 6 N2 adsorption-desorption isotherms of carbon nitride prepared in Example 1 and Comparative Example 1.

[0042] Figure 7 Visible light photocatalytic hydrogen peroxide production curve of carbon nitride prepared in Example 1 and Comparative Example 1.

[0043] Figure 8 These are photos of the photocatalytic activity of carbon nitride prepared in Example 1 and Comparative Example 1 against Staphylococcus aureus. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0045] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0046] Example 1

[0047] A method for preparing high specific surface area cyanide-rich red carbon nitride comprises the following steps: grinding ribbon-shaped melamine and ammonium bromide in a mass ratio of 1:1, placing them in a muffle furnace, and roasting them at 500°C for 3 hours at a heating rate of 2°C / min to obtain a ribbon-shaped carbon nitride intermediate. The obtained ribbon-shaped carbon nitride intermediate is then placed in a tubular furnace, evacuated, and roasted at 650°C for 1 hour at a vacuum pressure of -0.1MPa to obtain high specific surface area cyanide-rich red carbon nitride.

[0048] Example 2

[0049] A method for preparing high specific surface area cyanide-rich red carbon nitride comprises the following steps: grinding ribbon melamine and ammonium bromide in a mass ratio of 1:0.5, placing them in a muffle furnace, and roasting them at 520°C for 2 hours at a heating rate of 10°C / min to obtain a ribbon carbon nitride intermediate. The obtained ribbon carbon nitride intermediate is then placed in a tubular furnace and roasted at 600°C for 6 hours under an argon atmosphere to obtain a high specific surface area cyanide-rich red carbon nitride.

[0050] Example 3

[0051] A method for preparing high specific surface area cyano-rich red carbon nitride comprises the following steps: grinding ribbon-shaped melamine and ammonium bromide in a mass ratio of 1:5, placing them in a muffle furnace, and roasting them at 350°C for 8 hours at a heating rate of 1°C / min to obtain a ribbon-shaped carbon nitride intermediate. The obtained ribbon-shaped carbon nitride intermediate is then placed in a tubular furnace and roasted at 700°C for 0.5 hours in a nitrogen atmosphere to obtain a high specific surface area cyano-rich red carbon nitride.

[0052] Comparative Example

[0053] Traditional bulk carbon nitride was prepared according to the preparation method described in Advanced Functional Materials, 2022, 32, 2205119.

[0054] The comprehensive analysis is as follows:

[0055] The infrared spectra of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 and the bulk carbon nitride prepared in the comparative example are as follows: Figure 1 As shown, from Figure 1 It can be seen that the products obtained in Example 1 and the comparative example have typical infrared absorption peaks of carbon nitride. This indicates that the obtained products have a basic carbon nitride structure. The high specific surface area cyanide-rich red carbon nitride prepared in Example 1 has an absorption peak at 2175 cm -1 There is an obvious peak at , indicating that a large amount of cyano groups are produced.

[0056] The X-ray diffraction spectra of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 and the bulk carbon nitride prepared in the comparative example are as follows: Figure 2 As shown, from Figure 2 It can be seen that the products obtained in Example 1 and the comparative example have a typical carbon nitride (002) peak. This further indicates that the obtained product has a carbon nitride structure. The (210) peak of the carbon nitride prepared in Example 1 almost disappears, and the (002) peak becomes broadened, indicating that the introduction of a large number of cyano groups seriously destroys the periodic arrangement of its basic units in the molecule.

[0057] The scanning electron microscope pictures of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 and the bulk carbon nitride prepared in the comparative example are as follows: Figure 3 As shown, the morphology of the conventional bulk carbon nitride prepared in the comparative example is as follows Figure 3 As shown in a, almost no pores are observed; the morphology of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 is as shown in Figure 3 As shown in b, a large number of mesopores are formed and thinner nanosheets are produced.

[0058] The optical photographs of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 and the bulk carbon nitride prepared in the comparative example are as follows: Figure 4 As shown by Figure 4 It can be seen that the color of bulk carbon nitride is yellow, while the color of cyanide-rich red carbon nitride prepared in an oxygen-free environment is significantly darker and becomes dark red, indicating the formation of a large number of cyanide groups.

[0059] The solid UV-visible diffuse reflectance spectra of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 and the bulk carbon nitride prepared in the comparative example are as follows: Figure 5 As shown by Figure 5It can be seen that the light absorption performance of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 is significantly enhanced, and it also has obvious absorption of infrared light after 760nm, indicating that the formation of a large number of cyanide groups increases its light absorption intensity and range.

[0060] The N2 adsorption-desorption isotherms of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 and the bulk carbon nitride prepared in the comparative example are shown in FIG. Figure 6 As shown by Figure 6 It can be seen that the carbon nitride prepared in the comparative example and Example 1 both have type IV isotherms and H3 type hysteresis loops, that is, they have mesoporous structures. The specific surface area of ​​the bulk carbon nitride prepared in the comparative example is 9.3 m 2 / g, while the specific surface area of ​​the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 is 101.9m 2 / g, indicating that the carbon nitride prepared by this method has a high specific surface area.

[0061] The high specific surface area cyanide-rich red carbon nitride prepared in Example 1 and the bulk carbon nitride prepared in the comparative example were applied to photocatalytic hydrogen peroxide production, and the specific steps were as follows:

[0062] 20 mg of carbon nitride powder was ultrasonically dispersed in 100 mL of an aqueous solution containing 10 vol% methanol, and then oxygen was introduced for 30 min to reach saturation. A 300 W xenon lamp (wavelength greater than 420 nm) was turned on to start the photocatalytic hydrogen peroxide reaction. 2 mL of the reaction solution was taken every 15 min, and the photocatalyst particles in the solution were removed with a syringe organic filter. Then, 2 mL of potassium iodide (0.1 M) and 50 μL of ammonium molybdate (0.01 M) were added to the mixed solution and stirred for 5 min to allow it to react fully. The concentration of the reaction solution was determined using a Shimadzu UV-2700 UV-visible spectrophotometer.

[0063] The visible light photocatalytic hydrogen peroxide production curves of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 and the bulk carbon nitride prepared in the comparative example are as follows: Figure 7 As shown, from Figure 7 It can be seen that the hydrogen peroxide production rate of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 is 2465 μmol g -1 h -1 The hydrogen peroxide production rate of the bulk carbon nitride prepared in the comparative example is 118 μmol g -1 h -1 The hydrogen peroxide production rate of the carbon nitride prepared in Example 1 is 20.9 times that of the comparative example.

[0064] The high specific surface area cyanide-rich red carbon nitride prepared in the example and the bulk carbon nitride prepared in the comparative example were applied to photocatalytic sterilization, and the specific steps were as follows:

[0065] 5 mg of carbon nitride powder was ultrasonically dispersed in 1 mL of aqueous solution for 5 min. Then 40 μL of catalyst suspension was taken and 160 μL of bacterial solution (1×10 7 CFU mL -1 ) and mixed evenly. Then the mixture was transferred to a 96-well plate and irradiated with a 300W xenon lamp (wavelength greater than 420nm) for 20 minutes. The mixed solution containing bacteria was diluted to 1×10 5 CFU mL -1 , take 10 μL and evenly spread it on the agar plate, and culture it in a 37℃ constant temperature incubator for 24 hours. Finally, take out the cultured bacteria, take pictures and count them. Use the formula, antibacterial rate = (control group colony number - experimental group colony number) / control group colony number × 100% to calculate the antibacterial rate of each group.

[0066] The photos of the photocatalytic anti-Staphylococcus aureus of the high specific surface area cyanide-rich red carbon nitride prepared in the example and the bulk carbon nitride prepared in the comparative example are shown in FIG. Figure 8 As shown, from Figure 8 It can be seen that the antibacterial efficiency of the bulk carbon nitride prepared in the comparative example is 35.30%, and the antibacterial efficiency of the high specific surface area cyanide-rich red carbon nitride prepared in Example 1 is 99.74%, proving that the high specific surface area cyanide-rich red carbon nitride has more excellent photocatalytic antibacterial performance.

[0067] The above data show that the high specific surface area cyanide-rich red carbon nitride prepared by oxygen-free calcination has higher photocatalytic activity and higher industrial application value.

[0068] Obviously, the above-mentioned embodiments of the present invention are only simple applications of oxygen-free calcination to improve the activity of photocatalysts. They are examples to clearly illustrate the breadth of the present invention, but not to limit the application fields and implementation methods of the present invention. For the specific application of each photocatalyst, other different forms of changes should be made under specific circumstances. It is not necessary and impossible to list all the implementation methods here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing cyano-rich red carbon nitride with increased specific surface area, Its characteristics are: After the ribbon-shaped melamine and ammonium salt are ground and mixed evenly, they are roasted in an air atmosphere to obtain a ribbon-shaped carbon nitride intermediate; the obtained ribbon-shaped carbon nitride intermediate is then placed in a quartz tube, and then placed in a tube furnace and roasted in an oxygen-free environment to obtain a high specific surface area cyanide-rich red carbon nitride.

2. The method for preparing cyano-rich red carbon nitride with increased specific surface area according to claim 1, Its characteristics are: The ammonium salt is one or a combination of two or more of ammonium chloride, ammonium bromide, ammonium sulfate, ammonium nitrate or ammonium bicarbonate.

3. The method for preparing cyano-rich red carbon nitride with increased specific surface area according to claim 1, Its characteristics are: The ammonium salt is ammonium bromide or ammonium chloride.

4. The method for preparing cyano-rich red carbon nitride with increased specific surface area according to claim 1, Its characteristics are: The mass ratio of the strip melamine to the ammonium salt is 1:0.5-5.

5. The method for preparing cyano-rich red carbon nitride with increased specific surface area according to claim 1, Its characteristics are: The calcination temperature of the strip-shaped melamine and ammonium salt mixture is 350-520°C.

6. The method for preparing cyano-rich red carbon nitride with increased specific surface area according to claim 1, Its characteristics are: The roasting time of the strip-shaped melamine and ammonium salt mixture is 2 to 8 hours.

7. The method for preparing cyano-rich red carbon nitride with increased specific surface area according to claim 1, Its characteristics are: The heating rate of the strip-shaped melamine and ammonium salt mixture is 1-10°C / min.

8. The method for preparing cyano-rich red carbon nitride with increased specific surface area according to claim 1, Its characteristics are: The oxygen-free environment is an argon atmosphere, a nitrogen atmosphere, a carbon dioxide atmosphere, a hydrogen atmosphere or a vacuum atmosphere.

9. The method for preparing cyano-rich red carbon nitride with increased specific surface area according to claim 1, Its characteristics are: The calcination temperature of the ribbon carbon nitride intermediate is 600-700°C; the calcination time is 0.5-6h.

10. The cyanide-rich red carbon nitride product prepared by the method for preparing the cyanide-rich red carbon nitride with increased specific surface area according to claim 1 has a surface area of ​​2175 cm -1 There is a peak at the bottom; the product is red in color; the specific surface area of ​​the product reaches 101.9m 2 / g.

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