Potassium-doped colonic carbon nitride as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of visible light catalysis, and relates to potassium-doped colonic carbon nitride as well as a preparation method and application thereof. The invention successfully prepares the hollow carbon nitride material with the colon-shaped structure. The unique structure not only increases the specific surface area of the material, provides more active sites and is beneficial to substance transport and contact efficiency in a photocatalytic reaction, but also is beneficial to optimization of light absorption, charge transport and diffusion kinetics due to the fact that the morphological inspiration of the material comes from an efficient tubular structure (such as intestinal microvilli) in a biological system.

Description

Technical Field

[0001] The present invention belongs to the technical field of visible light catalysis, and relates to potassium-doped colon-shaped carbon nitride and its preparation method and application. Background Art

[0002] Graphitic carbon nitride (g-C3N4), as a non-metallic, stable and low-cost material, has received extensive attention due to its excellent performance in the field of photocatalytic generation. The characteristic of this material being easy to scale up production further enhances its attractiveness and potential in industrial applications. With the growing global demand for sustainable energy solutions, g-C3N4 has shown great application prospects in the field of photocatalysis due to its unique physical and chemical properties. However, despite these advantages, the original form of g-C3N4 still has some inherent limitations that affect the exertion of its photocatalytic efficiency.

[0003] First of all, the relatively low specific surface area is a key factor restricting the photocatalytic performance of g-C3N4. A smaller specific surface area means a limited number of active sites, which directly affects the contact efficiency between the material and the reactants, thereby reducing the speed and efficiency of the photocatalytic reaction. To overcome this problem, researchers have tried various methods to increase the specific surface area of g-C3N4, such as strategies of synthesizing nanostructures and introducing pores. These improvement measures not only increase the number of active sites but also improve the light absorption efficiency of the material, providing the possibility for enhancing the photocatalytic performance.

[0004] In addition, the rapid recombination of photo-generated carriers under light irradiation is also an important reason restricting the photocatalytic efficiency of g-C3N4. When the material is irradiated with light, electron-hole pairs are excited to generate, but these carriers often recombine quickly, resulting in a reduction in the number of effective carriers that can participate in the photocatalytic reaction.

[0005] The Chinese patent document (CN109603875A) discloses a carbon nitride material and its preparation method and application. This carbon nitride material does not contain a structure that can usually enhance mass transfer and contact efficiency in terms of structure, and has a weak adsorption effect on substrates in photocatalytic applications.

[0006] The Chinese patent document (CN113145158B) discloses a exfoliated tubular carbon nitride photocatalyst and its preparation method and application. However, its preparation process involves a series of relatively complex steps, including hydrothermal treatment, washing, drying and final calcination treatment, and the performance of the prepared carbon nitride needs to be further improved. Summary of the Invention

[0007] The object of the present invention is to address the above problems existing in the prior art, and a potassium-doped colon-shaped carbon nitride is proposed, which can facilitate the separation of photo-generated carriers, thereby promoting the photocatalytic performance of the composite material.

[0008] The object of the present invention can be achieved by the following technical solutions:

[0009] A preparation method of potassium-doped colon-shaped carbon nitride, the method comprising the following steps:

[0010] S1. Uniformly grinding potassium phthalazine trione salt and a carbonitrogen source to obtain a precursor;

[0011] S2. Calcining the precursor and finally cooling to obtain colon-shaped carbon nitride.

[0012] In the above preparation method of potassium-doped colon-shaped carbon nitride, the chemical structure of the potassium phthalazine trione salt is shown as follows:

[0013]

[0014] In the present invention, by introducing this potassium phthalazine trione salt, it plays a key role as a template agent in the synthesis process. It not only plays a crucial role in promoting the formation of a unique colon-shaped structure, but also realizes the precise doping of an appropriate amount of K ions at the same time. This directed self-assembly process is one of the key steps to obtain materials with a high specific surface area, an open pore structure and excellent transport properties. Compared with traditional methods, using potassium phthalazine trione salt as a template agent can more precisely control the microstructure of the final product, and thus optimize its macroscopic properties. The potassium ions (K + ) in this salt are appropriately incorporated into the lattice of the material during the synthesis process. On the one hand, this helps to adjust the electronic structure of the material and improve the separation efficiency of charge carriers; on the other hand, the presence of a certain amount of potassium ions can also improve the chemical properties of the material surface, enhance the quantity and quality of its catalytic active sites. The doping of an appropriate amount of potassium ions is particularly important for improving the photocatalytic performance of the material because it can effectively inhibit the recombination rate of photo-generated electron-hole pairs and promote the selective adsorption and conversion of target reactants.

[0015] In the above preparation method of potassium-doped colon-shaped carbon nitride, the carbonitrogen source is at least one of melamine, dicyandiamide, cyanuric acid, and urea.

[0016] In the above preparation method of potassium-doped colon-shaped carbon nitride, the carbonitrogen source is melamine and urea with a mass ratio of 1:(5 - 15).

[0017] In the above preparation method of potassium-doped colon-shaped carbon nitride, the mass ratio of the carbonitrogen source to the potassium phthalazine trione salt is (5 - 6):(0.05 - 0.15).

[0018] Too little or too much addition of the potassium salt of heptanolpyridinone of the present invention will cause the carbon nitride morphology to change and transform into an irregular aggregate morphology. Irregular aggregates often lead to a reduction in specific surface area, which directly affects the contact efficiency between the material and the reactant, reduces the photocatalytic performance, and leads to uneven pore distribution or lack of effective pore structure, which is extremely unfavorable for the diffusion and transmission of substances inside the catalyst. The low efficiency of material transmission will limit the reaction rate, making it difficult for the reactants in the photocatalytic process to effectively contact the active sites. The irregular morphology may cause an increase in internal defects or damage to the integrity of the crystal structure, which will increase the recombination probability of charge carriers and reduce the photocatalytic efficiency. The irregular morphology may affect the overall mechanical stability of the material and its structural integrity after repeated use.

[0019] In the above-mentioned method for preparing potassium-doped colonic carbon nitride, the calcination treatment is specifically heating to 550-560° C. at a heating rate of 3-8° C. / min and maintaining for 3-5 hours.

[0020] In the above method for preparing potassium-doped colonic carbon nitride, the calcination treatment is performed under an air atmosphere.

[0021] In the preparation process of potassium-doped colonic carbon nitride, calcination treatment is a crucial step, especially too high calcination temperature will lead to thermal decomposition of the material structure and a decrease in material yield. Although moderate calcination helps to form the desired crystal structure and promote the effective doping of potassium ions, too high a temperature may cause the grain growth of the material, resulting in a reduction in specific surface area, which not only reduces the number of active sites, but also reduces the material transfer efficiency in the photocatalytic reaction, thereby affecting the performance of the final product. In addition, under high temperature conditions, the material will undergo volatilization losses, especially for compounds containing light elements (such as nitrogen). High temperature may cause the volatilization of these elements, thereby reducing the actual output of the final product. In addition, too high a temperature may also cause the collapse or aggregation of the material structure, resulting in a decrease in the proportion of effective products that can be recycled.

[0022] The present invention also provides a colon-shaped carbon nitride, which is prepared by the above-mentioned preparation method.

[0023] The present invention also provides an application of the colon-shaped carbon nitride in photocatalytic degradation.

[0024] In the above application, the process includes dispersing colon-shaped carbon nitride in a bisphenol A solution, stirring the solution in a dark place, and then irradiating the solution with a xenon lamp.

[0025] In the above application, the xenon lamp power is 450-550W.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention successfully manufactures a hollow carbon nitride material with a colon-like structure. This unique structure not only increases the specific surface area of the material, provides more active sites, and is conducive to the mass transfer and contact efficiency in photocatalytic reactions, but also its morphology is inspired by the efficient tubular structures in biological systems (such as intestinal microvilli), which helps to optimize light absorption, charge transfer, and diffusion kinetics.

[0028] 2. By introducing an appropriate amount of potassium ions (K + ) through potassium phthalazinone triketone salt, the electronic energy band structure can be regulated and a local electric field can be generated, which shows great potential in promoting charge separation, thereby effectively suppressing the recombination rate of photogenerated carriers, and further improving the photocatalytic performance of the material. This provides an effective solution to the problem of rapid recombination of photogenerated carriers existing in traditional g-C3N4 materials.

[0029] 3. Through a simple one-step polymerization strategy, the present invention realizes the simultaneous potassium doping and morphology regulation under mild conditions, without complex post-treatment steps, reduces the production cost, and improves the operability of production and the possibility of large-scale production.

[0030] 4. The potassium-doped colon-like carbon nitride prepared by the present invention exhibits excellent performance in photocatalytic degradation of pollutants (such as bisphenol A solution), and the experimental results under xenon lamp irradiation verify its good photocatalytic activity. In addition, the special structure and composition of this material also show potential application value in other photocatalytic fields, such as synthesis of hydrogen peroxide, carbon dioxide reduction, etc. Description of the Drawings

[0031] Figure 1 Schematic diagram for the preparation of colon-like carbon nitride in Example 1;

[0032] Figure 2 XRD images of colon-like carbon nitride in Examples 1-3.

[0033] Figure 3 Infrared spectra of colon-like carbon nitride in Examples 1-3.

[0034] Figure 4 SEM images of colon-like carbon nitride in Example 1, a. at a long distance, b. at a close distance.

[0035] Figure 5 Transmission electron microscope (TEM) image of colon-like carbon nitride in Example 1.

[0036] Figure 6Degradation efficiency diagram of BPA by the carbon nitride materials of Examples 1-3 and Comparative Example 1. Detailed implementation manners

[0037] The following are specific examples of the present invention to further describe the technical solutions of the present invention, but the present invention is not limited to these examples.

[0038] Unless otherwise specified, the raw materials and equipment used in the present invention can be purchased from the market or are commonly used in the art. The methods in the examples, unless otherwise specified, are conventional methods in the art.

[0039] In some embodiments, the potassium salt of benzotriazolone is 1,3,4,6,7,9,9b-benzotriazolo[1,2-a]pyrimidine-2,5,8(1H,3H,6H)-trione, potassium salt (1:3), and has the following structural formula:

[0040]

[0041] Example 1:

[0042] S1. Take 5.0 g of urea, 0.5 g of melamine, and 0.1 g of the potassium salt of benzotriazolone and grind them evenly to obtain a precursor; Figure 1 S2. Place the precursor in a muffle furnace and heat it to 550 °C at a heating rate of 5 °C / min, and hold for 4 h. Finally, cool it naturally to room temperature to obtain colonic carbon nitride, denoted as 0.1KCN.

[0043]

[0044] Example 2:

[0045] S1. Take 5.0 g of urea, 0.5 g of melamine, and 0.05 g of the potassium salt of benzotriazolone and grind them evenly to obtain a precursor;

[0046] S2. Place the precursor in a muffle furnace and heat it to 550 °C at a heating rate of 5 °C / min, and hold for 4 h. Finally, cool it naturally to room temperature to obtain colonic carbon nitride, denoted as 0.05KCN.

[0047] Example 3:

[0048] S1. Take 5.0 g of urea, 0.5 g of melamine, and 0.15 g of the potassium salt of benzotriazolone and grind them evenly to obtain a precursor;

[0049] S2. Place the precursor in a muffle furnace and heat it to 550 °C at a heating rate of 5 °C / min, and hold for 4 h. Finally, cool it naturally to room temperature to obtain colonic carbon nitride, denoted as 0.15KCN.

[0050] Example 4:

[0051] S1. Take 5.0 g of urea, 0.5 g of melamine, and 0.01 g of potassium naphthyridinetrione and grind them evenly to obtain a precursor;

[0052] S2. Place the precursor in a muffle furnace and heat it to 550 °C at a heating rate of 5 °C / min, hold for 4 h, and finally cool it naturally to room temperature to obtain tubular and a small amount of colonic carbon nitride.

[0053] Example 5:

[0054] S1. Take 5.0 g of urea, 0.5 g of melamine, and 0.3 g of potassium naphthyridinetrione and grind them evenly to obtain a precursor;

[0055] S2. Place the precursor in a muffle furnace and heat it to 550 °C at a heating rate of 5 °C / min, hold for 4 h, and finally cool it naturally to room temperature to obtain irregularly aggregated carbon nitride.

[0056] Example 6:

[0057] S1. Take 5.0 g of urea, 0.5 g of melamine, and 0.1 g of potassium naphthyridinetrione and grind them evenly to obtain a precursor;

[0058] S2. Place the precursor in a muffle furnace and heat it to 500 °C at a heating rate of 5 °C / min, hold for 4 h, and finally cool it naturally to room temperature to obtain non-colonic carbon nitride.

[0059] Example 6:

[0060] S1. Take 5.0 g of urea, 0.5 g of melamine, and 0.1 g of potassium naphthyridinetrione and grind them evenly to obtain a precursor;

[0061] S2. Place the precursor in a muffle furnace and heat it to 800 °C at a heating rate of 5 °C / min, hold for 4 h, and finally cool it naturally to room temperature. No product can be obtained because most of the product volatilizes at too high a temperature.

[0062] Example 7:

[0063] S1. Take 5.0 g of urea and 0.1 g of potassium naphthyridinetrione and grind them evenly to obtain a precursor;

[0064] S2. Place the precursor in a muffle furnace and heat it to 550 °C at a heating rate of 5 °C / min, hold for 4 h, and finally cool it naturally to room temperature to obtain non-colonic carbon nitride.

[0065] Example 8:

[0066] S1. Take 0.5 g of melamine and 0.1 g of potassium naphthyridinetrione and grind them evenly to obtain a precursor;

[0067] S2. Place the precursor in a muffle furnace and heat it to 550 °C at a heating rate of 5 °C / min, and hold for 4 h. Finally, cool it naturally to room temperature to obtain non-colon-shaped carbon nitride.

[0068] Comparative Example 1:

[0069] The difference from Example 1 is only that the carbon nitride is commercially available carbon nitride nanotubes, denoted as KCN.

[0070] Comparative Example 2:

[0071] The difference from Example 1 is only that the potassium phenanthroline trione in Comparative Example 1 is replaced by phenanthroline trione.

[0072] Comparative Example 3:

[0073] The difference from Example 1 is only that the potassium salt of phenanthroline trione in Comparative Example 1 is replaced by potassium chloride.

[0074] Disperse 10 mg of the carbon nitride prepared in Examples 1-3 and Comparative Examples 1-3 in 50 mL of a bisphenol A solution with an initial concentration C0 of 20 mg / L, stir in the dark for 30 min, then irradiate with a 500 W xenon lamp. Take 3 mL of the reaction solution at regular intervals, and after filtration, detect the concentration C of BPA t .

[0075] Table 1: Detection results of the bisphenol A concentration after 120 min of xenon lamp irradiation of the carbon nitride prepared in Examples 1-3 and Comparative Examples 1-3 dispersed in the bisphenol A solution compared to the initial concentration

[0076] Example <![CDATA[C t / C0 (wt%)]]> Example 1 47.6 Example 2 58 Example 3 60.2 Comparative Example 1 98.0 Comparative Example 2 70.2 Comparative Example 3 68.5

[0077] Figure 2 is the XRD image of the colon-shaped carbon nitride in Examples 1-3. It can be seen from the figure that the synthesized sample is carbon nitride, containing the (100) and (002) crystal planes.

[0078] Figure 3 is the infrared spectrum of the colon-shaped carbon nitride in Examples 1-3. It can be seen from the figure that as the amount of doped potassium phenanthroline trione increases, the peak of the cyano functional group becomes higher and higher.

[0079] Figure 4 is the SEM image of the colon-shaped carbon nitride in Example 1, a. at a long distance, b. at a close distance; it can be seen from the figure that the morphology of the carbon nitride is a porous sac-like shape, which is connected to form a colon-like morphology.

[0080] Figure 5 is the transmission electron microscope (TEM) image of the colon-shaped carbon nitride in Example 1; it can be seen from the figure that the carbon nitride is hollow and its wall thickness is about 10 nm.

[0081] Figure 6 Degradation efficiency diagram of carbon nitride materials in Examples 1-3 and Comparative Example 1 for BPA; It can be seen from the figure that the carbon nitride in Example 1 has the highest degradation efficiency and can degrade 52.4% of BPA within 120 minutes.

[0082] In summary, in the present invention, appropriate potassium ions (K + ) can be introduced through quinazolin-4(3H)-one potassium salt to regulate the electronic energy band structure and generate a local electric field, which shows great potential in promoting charge separation, thereby effectively suppressing the recombination rate of photo-generated carriers, and further improving the photocatalytic performance of the material. This provides an effective solution to the problem of rapid recombination of photo-generated carriers existing in traditional g-C3N4 materials.

[0083] For the points not exhausted in the technical scope required to be protected by the present invention in the embodiments herein and the new technical solutions formed by the equivalent replacement of single or multiple technical features in the technical solutions of the embodiments, they are also within the scope required to be protected by the present invention; at the same time, in all the embodiments listed or not listed in the present invention, each parameter in the same embodiment only represents an example of its technical solution (i.e., a feasible solution), and there is no strict cooperation and limitation relationship between the parameters. Among them, the parameters can be replaced with each other when not violating the axiom and the requirements of the present invention, unless otherwise specifically stated.

[0084] The technical means disclosed in the present invention are not limited to the technical means disclosed above, but also include the technical solutions formed by any combination of the above technical features. The above is the specific implementation manner of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches are also regarded as the protection scope of the present invention.

[0085] The specific embodiments described herein are only examples to illustrate the spirit of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A preparation method of potassium-doped colon-shaped carbon nitride, characterized in that, The method comprises the following steps: S1. Uniformly grinding potassium phenanthroline trione and a carbon and nitrogen source to obtain a precursor; S2. Performing a calcination treatment on the precursor and finally obtaining colonic carbon nitride after cooling.

2. The preparation method of a potassium-doped colon-shaped carbon nitride according to claim 1, characterized in that, The chemical structure of the potassium phenanthroline trione is as follows:

3. The preparation method of a potassium-doped colon-shaped carbon nitride according to claim 1, characterized in that, The carbon and nitrogen source is at least one of melamine, dicyandiamide, cyanuric acid, and urea.

4. The preparation method of a potassium-doped colon-shaped carbon nitride according to claim 1 or 3, characterized in that, The carbon and nitrogen source is melamine and urea with a mass ratio of 1:(5 - 15).

5. The preparation method of a potassium-doped colon-shaped carbon nitride according to claim 1, wherein, The mass ratio of the carbon and nitrogen source to the potassium phenanthroline trione is (5 - 6):(0.05 - 0.15).

6. The preparation method of a potassium-doped colon-shaped carbon nitride according to claim 1, characterized in that, The calcination treatment is specifically heating to 550 - 560 °C at a heating rate of 3 - 8 °C / min and holding for 3 - 5 h.

7. The preparation method of a potassium-doped colon-shaped carbon nitride according to claim 1 or 6, characterized in that, The calcination treatment is carried out in an air atmosphere.

8. A colon-shaped carbon nitride, characterized in that, The colonic carbon nitride is prepared by the preparation method described in claim 1.

9. An application of the colonic carbon nitride as described in claim 8 in photocatalytic degradation.

10. The application according to claim 9, characterized in that It includes: Dispersing the colonic carbon nitride in a bisphenol A solution, performing stirring in the dark, and then irradiating with a xenon lamp.

Images