Environment-friendly carbon nitride cold cloud catalyst, preparation method and application thereof

Abstract

The application provides an environment-friendly carbon nitride cold cloud catalyst and a preparation method thereof, and belongs to the technical field of catalyst material synthesis. The raw material for preparing the catalyst comprises a nitrogen source and silver iodide. The nitrogen source is compounded with the silver iodide through a thermal polycondensation reaction to obtain a carbon nitride / silver iodide composite photocatalytic cold cloud catalyst. The carbon nitride / silver iodide composite photocatalytic cold cloud catalyst can generate photo-generated carriers through a photocatalytic reaction, and then generate surface charges, thereby producing an amplification effect on the cold cloud catalyst.

Description

Technical Field

[0001] This invention relates to the field of catalyst material synthesis technology, specifically to an environmentally friendly carbon nitride cold cloud catalyst, its preparation method, and its application. Background Technology

[0002] Cold cloud catalysis is one of the important methods of artificial rain enhancement. In the cloud, when supercooled water droplets and ice crystals coexist, the water molecules of the supercooled water droplets will continuously sublimate to the surface of the ice crystals due to the low saturated water vapor pressure of the ice crystals. This causes the ice crystals to grow larger and larger. When the ice crystals grow to a certain mass, they will fall into the warmer cloud layer due to gravity and melt into water droplets as the temperature increases, eventually forming rainfall.

[0003] Since the low-temperature conditions required for this process in nature are extremely demanding and difficult to meet in actual atmospheric conditions, the formation of ice crystals can be promoted by increasing the ice crystal content in the clouds through seeding cold cloud catalysts (artificial ice nuclei), thereby promoting rainfall.

[0004] Silver iodide, with its hexagonal structure similar to ice crystals, has excellent ice-forming nucleation properties and is often used as an artificial ice nucleus for heterogeneous nucleation of ice crystals, and is widely applied in cold cloud catalytic precipitation operations.

[0005] Currently, cold cloud catalytic precipitation mainly involves preparing silver iodide as a flaming agent and then spreading it into clouds through high-altitude combustion to achieve precipitation. However, this method still suffers from problems such as low efficiency and high cost. Furthermore, the silver iodide that falls with the rain also has a cumulative impact on the environment and ecology. Therefore, it is essential to explore new catalysts to improve the efficiency of cold cloud catalysis and reduce the amount of silver iodide used.

[0006] Photocatalysis is a technology based on the band structure characteristics of semiconductor materials. Under light irradiation, photocatalytic materials such as titanium dioxide (TiO2), zinc oxide (ZnO), iron oxide (Fe2O3), and carbon nitride (g-C3N4) absorb light energy, excite their internal electrons to an excited state, and then move within the catalyst to undergo energy level transitions, forming electron-hole pairs. Subsequently, charge transfer occurs, resulting in changes in the charge distribution on the material surface.

[0007] Recent studies on the influence of surface charge on water droplet condensation and growth have shown that the surface charge of cold cloud catalysts can significantly affect the efficiency of artificial rainmaking. However, there is currently a lack of cloud seed materials that can be designed and screened as cold cloud catalysts by controlling the surface charge of the materials. Therefore, it is highly likely that photocatalytic materials or photocatalytic materials combined with traditional silver iodide cold cloud catalysts can be synthesized through carrier control methods such as precursors, heterojunctions, and cation doping to create novel and highly efficient natural light-induced cold cloud catalysts (photocatalytic cold cloud catalysts), which are worthy of further research. Summary of the Invention

[0008] The purpose of this invention is to provide an environmentally friendly carbon nitride cold cloud catalyst, its preparation method, and its application, so as to solve at least one of the technical problems existing in the background art.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides an environmentally friendly carbon nitride cold cloud catalyst, the raw materials for which the catalyst is prepared include a nitrogen source and silver iodide; the nitrogen source and silver iodide are combined through a thermal polycondensation reaction to obtain a carbon nitride / silver iodide composite photocatalytic cold cloud catalyst; the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst can generate photogenerated carriers through a photocatalytic reaction, thereby generating surface charge and amplifying the cold cloud catalysis effect.

[0011] Secondly, the present invention provides a method for preparing an environmentally friendly carbon nitride cold cloud catalyst as described in the first aspect, comprising: weighing a nitrogen source compound and silver iodide according to a ratio, drying them, grinding them into fine powders, and then mixing them thoroughly; placing the mixed powders in a high-temperature reaction furnace, and after a process of heating-constant temperature-cooling, removing the product, grinding it into fine powders, ultrasonically treating it for a period of time, removing the precipitate, and drying it after washing and filtering to obtain a carbon nitride / silver iodide composite photocatalytic cold cloud catalyst.

[0012] As a further limitation of the second aspect of the present invention, the nitrogen source compound is one or more of melamine, dicyandiamide, monocyanamide, urea or thiourea.

[0013] As a further limitation of the second aspect of the present invention, the drying temperature of the nitrogen source compound is 20–80°C.

[0014] As a further limitation of the second aspect of the present invention, the drying temperature of the silver iodide is 20 to 60°C.

[0015] As a further limitation of the second aspect of the present invention, the mass ratio of the nitrogen source compound to silver iodide is (1-200):1.

[0016] As a further limitation of the second aspect of the present invention, the reaction temperature in the high-temperature reactor is 300 to 800°C.

[0017] Thirdly, the present invention provides an application of the environmentally friendly carbon nitride cold cloud catalyst as described in the first aspect in cold cloud catalytic artificial rainmaking.

[0018] The beneficial effects of this invention are as follows: By combining photocatalysis with cold cloud catalysis and employing a thermal condensation method, the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst exhibits significantly improved ice nucleation performance compared to traditional silver iodide. Compared to traditional silver iodide cold cloud catalysts, it reduces the amount of silver iodide used, resulting in lower costs and effectively reducing the cumulative environmental impact of traditional silver iodide. Furthermore, the preparation method is simple, the process is straightforward, the materials are readily available, and it is suitable for mass production.

[0019] The advantages of additional aspects of the invention will be set forth more clearly in the following description or will be learned by practice of the invention. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The XRD diffraction patterns of the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst prepared in the embodiments of the present invention, as well as those of traditional silver iodide and pure carbon nitride.

[0022] Figure 2 The images show SEM and TEM images of the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst prepared in the embodiments of the present invention, as well as traditional silver iodide and pure carbon nitride.

[0023] Figure 3 The image shows a comparison of the ice core concentration spectra of the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst prepared in the embodiments of the present invention, as well as those of traditional silver iodide and pure carbon nitride.

[0024] Figure 4 This is a comparison of the ice core concentration spectra of the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst prepared in the embodiments of the present invention under high color temperature and low color temperature conditions. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as here.

[0028] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or groups thereof.

[0029] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0030] To facilitate understanding of the present invention, the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. However, the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0031] Those skilled in the art should understand that the accompanying drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily essential for implementing the present invention.

[0032] Example 1

[0033] This embodiment provides an environmentally friendly carbon nitride cold cloud catalyst. The raw materials for preparing this catalyst include one or more combinations of melamine, dicyandiamide, monocyanamide, urea, or thiourea, and traditional silver iodide. The nitrogen source and silver iodide are combined via a thermal polycondensation reaction to obtain a carbon nitride / silver iodide composite photocatalytic cold cloud catalyst. While possessing basic cold cloud catalytic performance, it can generate photogenerated charge carriers through a photocatalytic reaction, thereby generating surface charges and amplifying the cold cloud catalytic effect. The preparation of the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst using a thermal polycondensation method is simple, rapid, and inexpensive.

[0034] The preparation steps of the above-mentioned carbon nitride / silver iodide composite photocatalytic cold cloud catalyst are as follows:

[0035] Step 1: Weigh the nitrogen source compound, place it in a vacuum drying oven to dry for a period of time, and then take it out and grind it into a fine powder for later use.

[0036] Step 2: Weigh the silver iodide sample, place it in a vacuum drying oven to dry for a period of time, and then take it out and grind it into a fine powder for later use.

[0037] Step 3: Thoroughly mix the nitrogen source compound ground in Step 1 with the silver iodide powder ground in Step 2, and continue grinding until uniform for later use.

[0038] Step 4: Evenly spread the ground nitrogen source compound / silver iodide powder into a crucible, then place it in a high-temperature reaction furnace. After heating, maintaining a constant temperature, and cooling, remove the product and grind it into a fine powder for later use.

[0039] Step 5: After mechanically grinding the powdered product from Step 4, sonicate it for a period of time, remove the precipitate, wash and filter it, and then dry it in a vacuum drying oven for a period of time. Remove the powder to obtain the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst.

[0040] In step 1, the nitrogen source compound is selected from at least one of melamine, dicyandiamide, monocyanamide, urea, and thiourea, and includes, but is not limited to, melamine, dicyandiamide, monocyanamide, urea, and thiourea; the drying temperature of the nitrogen source compound is 20-80°C, and the drying time is 5 minutes to 4 hours.

[0041] In step 2, the silver iodide is either purchased directly or synthesized using a chemical wet process; the drying temperature of the silver iodide is 20–60°C, and the drying time is 5 minutes to 12 hours.

[0042] In step 4, the mass ratio of the nitrogen source compound to silver iodide is (1-200):1; the high-temperature reactor includes, but is not limited to, commonly used industrial furnaces such as muffle furnaces and tube furnaces; the reaction temperature in the high-temperature reactor is 300-800℃, the heating time is 10 minutes to 8 hours, the constant temperature duration is 30 minutes to 8 hours, and it is naturally cooled to room temperature.

[0043] In step 5, the mechanical grinding equipment includes, but is not limited to, common industrial grinding machines such as ball mills, sand mills, air jet mills, and vibratory mills; the ultrasonic treatment time is 20 minutes to 6 hours; the cleaning agent includes, but is not limited to, commonly used liquid stripping agents such as ultrapure water, deionized water, and anhydrous ethanol; the drying temperature after cleaning is 20 to 60°C, and the drying time is 5 minutes to 24 hours; finally, the obtained powdered carbon nitride / silver iodide composite photocatalytic cold cloud catalyst is placed in a light-proof container and stored in a cool and dry environment.

[0044] Example 2

[0045] In this Example 2, a method for preparing a carbon nitride / silver iodide composite photocatalytic cold cloud catalyst is provided, which includes the following steps:

[0046] Weigh 5g of nitrogen source sample and place it in a vacuum drying oven. Dry it at 50℃ for 30 minutes, then remove and grind it into a fine powder for later use. Weigh 500mg of purchased silver iodide reagent and place it in a vacuum drying oven. Dry it at 40℃ for 5 minutes, then remove and grind it into a fine powder for later use. Mix the two powders thoroughly and continue grinding until homogeneous. Spread the ground powder evenly in a covered alumina crucible. Using a tube furnace under argon protection, slowly heat the mixture to 625℃ at 10℃ per minute, then maintain the temperature for 2 hours. After naturally cooling to room temperature, the resulting blocky product is the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst. Grind the product into a uniform, fine powder for later use.

[0047] The above product was placed in the ball mill jar of a ball mill, and ethanol was added until it covered the powder inside the jar. The ball mill was then started and run for 12 hours. The turbid product was then removed, placed in a disc container and dried for 12 hours. The powder was then taken out for later use.

[0048] Take deionized water, cover and mix the powder obtained in the above steps to make a mixture, then sonicate for 4 hours and remove the precipitate. Then wash and filter with deionized water and anhydrous ethanol alternately for 10 minutes each time, repeating 5 times. Then place the obtained product in a vacuum drying oven and dry at 50°C for 10 hours. The obtained powder is the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst.

[0049] like Figure 1 The XRD diffraction patterns of the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst prepared in this embodiment, as well as those of traditional silver iodide and pure carbon nitride, are shown. As can be seen from the patterns, both carbon nitride and silver iodide have obvious characteristic peaks. The carbon nitride / silver iodide composite photocatalytic cold cloud catalyst prepared by thermal polycondensation reaction has the peaks of both. The characteristic peak of carbon nitride shifts slightly to the higher angle direction, which indicates that carbon nitride undergoes cell shrinkage and lattice expansion after being combined with silver iodide. This means that although the interatomic distance in the composite lattice increases, the overall crystal structure becomes more compact or ordered to some extent.

[0050] like Figure 2 The images shown are SEM and TEM images of the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst prepared in this embodiment, as well as traditional silver iodide and pure carbon nitride. It can be observed that after the thermal polycondensation reaction, silver iodide is dispersed in layers of carbon nitride thin layers, and is not just present on the surface of carbon nitride.

[0051] like Figure 3The figure shows a comparison of the ice nucleus concentration spectra of the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst prepared in this embodiment, as well as those of traditional silver iodide and pure carbon nitride. The horizontal axis represents the real-time temperature of the material during detection, and the vertical axis represents the ice nucleus concentration, i.e., the number of ice nuclei released per milligram of sample at each temperature sampling point. In actual cold cloud catalytic precipitation operations, the ice nucleus concentration in the low-temperature region is of greater concern. It can be noted that the ice nucleation ability of pure carbon nitride is more than two orders of magnitude worse than that of silver iodide, making it insufficient for direct application in cold cloud catalysis. However, after combining carbon nitride with silver iodide, the ice nucleus concentration released by the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst in the low-temperature region of -20 to -25°C is more than two orders of magnitude higher than that of pure silver iodide.

[0052] like Figure 4 The figure shows a comparison of the ice nucleus concentration spectra of the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst prepared in this embodiment under high color temperature (HCT, 6500K) and low color temperature (LCT, 3200K) conditions. It can be observed from the figure that, regardless of the color temperature, the ice nucleus concentration released by the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst in the -20 to -25℃ low-temperature region is at least one order of magnitude higher than that of pure silver iodide. Theoretically, when the color temperature decreases, the blue-violet light portion is weakened, meaning the material's absorption of blue-violet light decreases. Since the highest light utilization portion of carbon nitride photocatalysis is blue-violet light, from... Figure 4 It can be observed that after weakening blue-violet light, the ice nucleus concentration of the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst is significantly reduced, indicating that photocatalysis can indeed contribute to the nucleation of cold cloud catalysis.

[0053] Example 3

[0054] This Example 3 provides a carbon nitride / silver iodide composite photocatalytic cold cloud catalyst, which is prepared through the following process:

[0055] Weigh 3g of nitrogen source sample and place it in a vacuum drying oven. Dry it at 50℃ for 30 minutes, then remove and grind it into a fine powder for later use. Weigh 300mg of purchased silver iodide reagent and place it in a vacuum drying oven. Dry it at 40℃ for 5 minutes, then remove and grind it into a fine powder for later use. Mix the two powders thoroughly and continue grinding until homogeneous. Spread the ground powder evenly in a covered alumina crucible. Using a tube furnace under argon protection, slowly heat the mixture to 600℃ at 10℃ per minute, then maintain the temperature for 2 hours. After naturally cooling to room temperature, the resulting blocky product is the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst. Grind the product into a uniform, fine powder for later use.

[0056] The above product was placed in the ball mill jar of a ball mill, and ethanol was added until it covered the powder inside the jar. The ball mill was then started and run for 12 hours. The turbid product was then removed, placed in a disc container and dried for 12 hours. The powder was then taken out for later use.

[0057] Take deionized water, cover and mix the powder obtained in the above steps to make a mixture, then sonicate for 4 hours and remove the precipitate. Then wash and filter with deionized water and anhydrous ethanol alternately for 10 minutes each time, repeating 5 times. Then place the obtained product in a vacuum drying oven and dry at 50°C for 10 hours. The obtained powder is the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst.

[0058] The carbon nitride / silver iodide composite photocatalytic cold cloud catalyst obtained in this embodiment showed a two-order-of-magnitude increase in the concentration of ice nuclei released in the -20 to -25°C low-temperature region compared to pure silver iodide, approximately 86% of that in Example 2.

[0059] Example 4

[0060] This embodiment 4 provides a carbon nitride / silver iodide composite photocatalytic cold cloud catalyst, which is prepared through the following process: 4g of nitrogen source sample is weighed, placed in a vacuum drying oven, and dried at 50°C for 30 minutes. It is then removed and ground into a fine powder for later use. Next, 800mg of purchased silver iodide is weighed, placed in a vacuum drying oven, and dried at 40°C for 5 minutes. It is then removed and ground into a fine powder for later use. The two are then thoroughly mixed together and ground until homogeneous. The ground powder is evenly spread in a covered alumina crucible, and heated slowly to 625°C at 10°C per minute under argon protection using a tube furnace. The temperature is then maintained at this level for 2 hours. After natural cooling to room temperature, the resulting blocky product is the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst. This product is then ground into a uniform and fine powder for later use.

[0061] The above product was placed in the ball mill jar of a ball mill, and ethanol was added until it covered the powder inside the jar. The ball mill was then started and run for 12 hours. The turbid product was then removed, placed in a disc container and dried for 12 hours. The powder was then taken out for later use.

[0062] Take deionized water, cover and mix the powder obtained in the above steps to make a mixture, then sonicate for 4 hours and remove the precipitate. Then wash and filter with deionized water and anhydrous ethanol alternately for 10 minutes each time, repeating 5 times. Then place the obtained product in a vacuum drying oven and dry at 50°C for 10 hours. The obtained powder is the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst.

[0063] The carbon nitride / silver iodide composite photocatalytic cold cloud catalyst obtained in this embodiment showed a two-order-of-magnitude increase in the concentration of ice nuclei released in the -20 to -25°C low-temperature region compared to pure silver iodide, approximately 61% of that in Example 2.

[0064] In summary, the method of this invention combines photocatalysis with cold cloud catalysis for the first time, synthesizing a novel environmentally friendly carbon nitride / silver iodide composite photocatalytic cold cloud catalyst via thermal polycondensation. Compared with traditional silver iodide, this composite photocatalytic cold cloud catalyst exhibits a two-order-of-magnitude improvement in ice nucleation performance. Furthermore, the method of this invention effectively reduces the amount of silver iodide used, making the cost of the cold cloud catalyst lower and effectively reducing the cumulative environmental impact of traditional silver iodide.

[0065] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solutions disclosed in the present invention, various modifications or variations that can be made by those skilled in the art without creative effort should be included within the scope of protection of the present invention.

Claims

1. An environmentally friendly carbon nitride cold cloud catalyst, characterized in that, The raw materials for preparing this catalyst include a nitrogen source material and silver iodide; the nitrogen source and silver iodide are combined through a thermal polycondensation reaction to obtain a carbon nitride / silver iodide composite photocatalytic cold cloud catalyst; the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst can generate photogenerated carriers through photocatalytic reaction, thereby generating surface charge and amplifying the cold cloud catalysis effect.

2. A method for preparing the environmentally friendly carbon nitride cold cloud catalyst as described in claim 1, characterized in that, include: Weigh the nitrogen source material and silver iodide separately according to the formula, dry them, grind them into fine powder, and then mix them thoroughly. The mixed powder was placed in a high-temperature reactor and subjected to a heating-constant-cooling process. The product was then removed, ground into a fine powder, and ultrasonically treated for a period of time. The precipitate was then removed, washed, filtered, and dried to obtain the carbon nitride / silver iodide composite photocatalytic cold cloud catalyst.

3. The preparation method of the environmentally friendly carbon nitride cold cloud catalyst according to claim 2, characterized in that: The nitrogen source compound is one or more of melamine, dicyandiamide, monocyanamide, urea, or thiourea.

4. The method for preparing the environmentally friendly carbon nitride cold cloud catalyst according to claim 2, characterized in that: The drying temperature for nitrogen source compounds is 20–80 °C.

5. The preparation method of the environmentally friendly carbon nitride cold cloud catalyst according to claim 2, characterized in that: The drying temperature of the silver iodide is 20–60°C.

6. The method for preparing the environmentally friendly carbon nitride cold cloud catalyst according to claim 2, characterized in that: The mass ratio of the nitrogen source compound to silver iodide is (1-200):

1.

7. The method for preparing the environmentally friendly carbon nitride cold cloud catalyst according to claim 2, characterized in that: The reaction temperature in the high-temperature reactor is 300–800°C.

8. The application of an environmentally friendly carbon nitride cold cloud catalyst as described in any one of claims 1 to 8 in cold cloud-catalyzed artificial rainmaking.

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