Hollow spherical carbon nitride as well as preparation method and application thereof

Abstract

The invention discloses hollow spherical carbon nitride as well as a preparation method and application thereof. The carbon nitride is of a hydrangea-shaped structure with a hole in the center and a porous surface. The method comprises the following steps: 1, measuring an HF solution, putting the HF solution into a tetrafluoroethylene reaction kettle, adding Ti3AlC2, heating and stirring; 2, washing the solid powder to obtain Ti3C2; 3, dispersing Ti3C2 in DMSO (Dimethylsulfoxide) to form a dispersion liquid; 4, respectively dissolving cyanuric acid and melamine in two parts of DMSO (Dimethylsulfoxide); 5, dropwise adding the solution obtained in the step 3 into the two solutions obtained in the step 4 respectively; 6, heating the cyanuric acid mixed solution and the clarified melamine mixed solution, mixing the cyanuric acid mixed solution and the clarified melamine mixed solution under violent stirring to obtain grey white precipitate, and drying the grey white precipitate in a drying oven; 7, adding the grey white powder into a crucible, coating tin foil, and calcining in a constant-temperature furnace to finally obtain hollow spherical carbon nitride; the carbon nitride preparation method provided by the invention is simple in operation process, does not use a template, is stable in product morphology, and is convenient for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of new carbon nitride materials, and particularly to a hollow spherical carbon nitride and its preparation method and application. Background Art

[0002] With the rapid growth of the population, the pollution of water resources has become increasingly serious, and organic pollutants in water have become an important threat to human health. Traditional methods are difficult to perfectly remove organic pollutants, while photocatalytic materials show potential application prospects in the field of environmental purification. As an ideal water treatment method that uses solar energy for photocatalytic oxidation and is green and environmentally friendly, great progress has been made in research and application.

[0003] Graphitic carbon nitride (g-C 3 N 4 ) has attracted people's attention due to its stability, moderate energy band level, and easy preparation. However, the rapid electron-hole (e- / h+) recombination rate, low crystallinity, and small surface area have greatly limited its application in photocatalysis. Various modification methods can improve the photocatalytic performance of gC 3 N 4 . Among them, microstructure and morphology control is a potential approach, which can provide a larger specific surface area, improve the path of electron transfer, and other properties.

[0004] Ti 3 C 2 is a new type of two-dimensional layer structure of MXene. In the past period of time, Ti 3 C 2 has attracted the research interest of researchers in the fields of catalysts, ion batteries, energy storage, and sensors. The large specific surface area, hydrophilicity, excellent electronic conductivity, and surface groups of Ti 3 C 2 play a significant role in improving the photocatalytic efficiency, and it can be applied to improve the performance of photocatalytic hydrogen evolution, CO 2 conversion, photocatalytic degradation of pollutants, and nitrogen fixation.

[0005] Under normal conditions, the carbon nitride obtained by high-temperature thermal polycondensation using carbon and nitrogen precursors such as urea and melamine as raw materials is mostly a block material with densely packed sheets. The tight packing effect hinders the reaction active sites of the carbon nitride material. The existing g-C 3 N 4 / Ti 3 C 2 composite material has a complex operation process, requires the use of templates, and the product morphology is unstable, which is not conducive to industrial production and has a small specific surface area.

[0006] Based on this, the present invention designs a hollow spherical carbon nitride and its preparation method and application to solve the above problems. Summary of the Invention

[0007] The object of the present invention is to provide a hollow spherical carbon nitride, a preparation method thereof and an application thereof, so as to solve the problems put forward in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: A hollow spherical carbon nitride has a hydrangea-like structure with a central opening and porous surfaces.

[0009] Preferably, the color of the carbon nitride is yellowish gray.

[0010] Preferably, a preparation method of a hollow spherical carbon nitride is characterized by comprising the following steps:

[0011] Step 1: Measure HF solution and place it in a polytetrafluoroethylene reaction kettle, and then slowly add Ti 3 AlC 2 , heat it in an oil bath and continuously stir.

[0012] Step 2: After the reaction ends, wash the solid powder several times, and vacuum dry the obtained black solid powder at 50°C - 80°C to obtain Ti 3 C 2 .

[0013] Step 3: Disperse Ti 3 C 2 in DMSO, and use ultrasonic vibration to form a dispersion for standby.

[0014] Step 4: Dissolve cyanuric acid and melamine in two portions of DMSO respectively, and perform ultrasonic vibration treatment and heating until the solids are completely dissolved.

[0015] Step 5: Add 0.5 mL - 1 mL of the solution in Step 3 to each of the two solutions in Step 4.

[0016] Step 6: Heat the black cyanuric acid mixture and the clear melamine mixture in an oil bath to 80°C - 100°C, then mix the two under vigorous stirring, and then stir at room temperature for 15 min - 60 min to carry out the reaction; wash the obtained off-white precipitate thoroughly with ethanol and dry it completely in a vacuum oven.

[0017] Step 7: Add the dried off-white powder to a crucible and wrap it with tin foil, then calcine it in a constant temperature furnace at 520°C at a heating rate of 2°C / min - 3°C / min for 2 h - 6 h, and the finally obtained yellowish gray powder material is the hollow spherical carbon nitride.

[0018] Preferably, in Step 1, measure 10 mL of HF solution and place it in a polytetrafluoroethylene reaction kettle, and then slowly add 1 g of Ti 3 AlC2 , heat it in an oil bath, and place the reaction system at 60 °C and stir continuously for 24 h.

[0019] Preferably, in step 2, wash the solid powder several times with deionized water and absolute ethanol, and vacuum-dry the obtained black solid powder at 50 °C - 80 °C for 24 h to obtain Ti 3 C 2 .

[0020] Preferably, in step 3, disperse 20 mg of Ti 3 C 2 in 20 mL of DMSO and ultrasonicate for 30 min to form a dispersion for standby.

[0021] Preferably, in step 4, dissolve 0.5 g of cyanuric acid and 0.5 g of melamine in 10 mL and 20 mL of DMSO respectively.

[0022] An application of hollow spherical carbon nitride, characterized in that: the photocatalytic application of hollow spherical carbon nitride, and the photocatalytic application refers to the catalytic degradation of tetracycline under visible light.

[0023] Compared with the prior art, the beneficial effects of the present invention are: the present invention successfully prepares spherical hollow g-C 3 N 4 / Ti 3 C 2 composite material without the need to additionally add a templating agent. Compared with the prior art, the hollow spherical carbon nitride microstructural catalyst and its preparation method provided by the present invention have a simple operation process, do not use a template, the product morphology is stable, and it is convenient for industrial production. The increased specific surface area provides rich active sites for redox reactions. The hollow structure promotes the reflection and refraction of light in the material, thereby enhancing the absorption and utilization of light, and the material has high degradation performance and good stability.

[0024] Of course, it is not necessary for any product implementing the present invention to simultaneously achieve all the above-mentioned advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 Scanning electron microscope image of ordinary carbon nitride microspheres obtained in Example 4;

[0027] Figure 2The transmission electron microscope of the hollow spherical carbon nitride prepared in Example 1 of the present invention;

[0028] Figure 3 The XRD pattern of the catalyst prepared in the present invention;

[0029] Figure 4 The schematic diagram of the activity evaluation of the catalyst prepared in the present invention for the degradation of tetracycline;

[0030] Figure 5 The schematic diagram of the stability evaluation of the hollow spherical carbon nitride photocatalyst prepared in Example 1. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Example 1:

[0033] Step 1: Measure 10 mL of HF solution and place it in a tetrafluoroethylene reaction kettle, then slowly add 1 g of Ti 3 AlC 2 , heat it in an oil bath, and place the reaction system at 60 °C and stir continuously for 24 h.

[0034] Step 2: After the reaction is completed, wash it several times with deionized water and absolute ethanol, and vacuum dry the obtained black solid powder at 60 °C for 24 h to obtain Ti 3 C 2 .

[0035] Step 3: Disperse 20 mg of Ti 3 C 2 in 20 mL of DMSO and ultrasonicate for 30 min to form a dispersion for standby.

[0036] Step 4: Dissolve 0.5 g of cyanuric acid and 0.5 g of melamine in 10 mL and 20 mL of DMSO respectively, and ultrasonicate and heat until the solids are completely dissolved.

[0037] Step 5: Add 10 mL of the solution in Step 3 to each of the two solutions in Step 4;

[0038] Step 6: After heating the black cyanuric acid mixture and the clarified melamine mixture in an oil bath to 100 °C, mix the two under vigorous stirring, and then stir at room temperature for 30 minutes for reaction. Wash the obtained off-white precipitate thoroughly with ethanol and dry it completely in a vacuum oven.

[0039] Step 7: Add the off-white powder into a crucible and wrap it with tin foil, then calcine it in a constant-temperature furnace at 520 °C at a heating rate of 2.5 °C / min for 4 hours. The finally obtained yellowish-gray powder material is hollow spherical carbon nitride, named SCN-10.

[0040] Example 2:

[0041] The difference from Example 1 is that in Step 5, 1 mL of the solution from Step 3 is added dropwise to each of the two solutions in Step 4. Others are the same as in Example 1, and the obtained hollow spherical carbon nitride is named SCN-1.

[0042] Example 3:

[0043] The difference from Example 1 is that in Step 5, 20 mL of the solution from Step 3 is added dropwise to each of the two solutions in Step 4. Others are the same as in Example 1, and the obtained hollow spherical carbon nitride is named SCN-20.

[0044] Example 4:

[0045] Step 1: Dissolve 0.5 g of cyanuric acid and 0.5 g of melamine in 10 mL and 20 mL of DMSO respectively, and perform ultrasonic treatment and heating until the solids are completely dissolved.

[0046] Step 2: After heating the clarified solutions in Step 1 in an oil bath to 100 °C, mix the two under vigorous stirring, and then stir at room temperature for 30 minutes for reaction. Wash the obtained white precipitate thoroughly with ethanol and dry it completely in a vacuum oven.

[0047] Step 3: Add the white powder into a crucible and wrap it with tin foil, then calcine it in a constant-temperature furnace at 520 °C at a heating rate of 2.5 °C / min for 4 hours. The finally obtained yellowish-gray powder material is hollow spherical carbon nitride, named SCN.

[0048] Comparative Example 1:

[0049] Step 1: Mix 6 g of melamine and 2 g of urea and grind them finely, then place them in a 25 mL covered crucible, and then put them into a muffle furnace for high-temperature calcination. The calcination is carried out with a programmed temperature rise, rising to 550 °C at a rate of 5 °C / min and calcining at a constant temperature for 4 h, and then naturally cooling and grinding finely after cooling.

[0050] Step 2: Place it in a 25 mL covered crucible, put it into a muffle furnace, heat it to 550 °C at a rate of 10 °C / min, calcine it at a constant temperature for 2 h, and obtain light yellow g-C 3 N 4 The powder is named CN, bagged and reserved for use.

[0051] The following examples are used in the present invention to verify that the hollow spherical carbon nitride photocatalyst has improved visible light efficiency:

[0052] The scanning electron microscope image of the ordinary carbon nitride microspheres obtained through Example 4 is as Figure 1 shown. It can be seen from the figure that SCN with a hollow and uniform spherical porous structure morphology is obtained. The diameter of the sphere is 5 - 10 μm, the surface is in a rosette shape, and it is composed of ultrathin g-C 3 N 4 nanosheets with a thickness of 50 - 200 nm and unevenly distributed micropores.

[0053] The transmission electron microscope image of the hollow spherical carbon nitride prepared through Example 1 is as Figure 2 shown. It can be seen from Figure 2 that there are obvious pores, indicating the existence of a central opening, and the overall morphology is regular, presenting a spherical structure; black flakes are loaded on the surface of the sphere. Through high-resolution TEM images, obvious lattice fringes with spacings of 0.263 nm and 0.322 nm are found, which correspond to the (0110) plane and (002) crystal plane of Ti 3 C 2 . In addition, anatase TiO 2 can be identified by its corresponding crystal plane distance of 0.35 nm.

[0054] The XRD patterns of the carbon nitrides prepared through Example 1, Example 2, Example 3, Example 4, and Comparative Example 1 are as Figure 3 shown. It can be seen from the figure that diffraction peaks attributed to the (100) and (002) crystal planes of CN appear for the catalysts prepared in different examples, and with the increase in the addition amount of Ti3C2, characteristic peaks of Ti 3 C 2 and TiO 2 appear. It is confirmed that the ternary hybrid has been successfully constructed.

[0055] In order to verify the activity of the hollow spherical carbon nitride obtained in Example 1 as a photocatalytic material, the following tests were carried out.

[0056] Test Example 1: Visible light catalytic degradation activity of tetracycline

[0057] Taking tetracycline as the target pollutant, the degradation performance of the sample was tested. First, tetracycline (TC) solutions with different concentrations were prepared, and the absorbance curves were measured using an ultraviolet spectrophotometer. The standard absorbance curve was obtained through linear fitting. Then, 50 ml of a TC solution with a concentration of 20 mg / L was prepared, and 20 mg of the sample to be tested was added to the TC solution. After standing in the dark for 30 min to reach adsorption equilibrium, samples were taken and recorded. The mixed solution was placed under irradiation of a 300 W xenon lamp, and samples were taken at regular intervals. The mixed solution was extracted using a medical syringe and then filtered through a filter head. The absorbance (absorbance; A) of the filtered solution was measured using an ultraviolet spectrophotometer.

[0058] The degradation effects of the visible-light catalytic degradation of tetracycline solution prepared by Example 1, Example 2, Example 3, Example 4, and Comparative Example 1 over time are as Figure 4 shown. It can be seen from the figure that the CN, SCN, SCN-1, SCN-10, and SCN-20 prepared in Example 1 have good visible-light catalytic performance, and the degradation efficiencies of tetracycline within 20 min are 41.92%, 68.16%, 79.04%, 81.28%, and 86.1% respectively.

[0059] The SCN-10 prepared in Example 1 has the best visible-light catalytic performance, and the degradation efficiency of tetracycline within 20 min reaches 86.1%.

[0060] The schematic diagram of the evaluation of the photocatalyst stability of the hollow spherical carbon nitride SCN-10 prepared by Example 1 is as Figure 5 shown. After five degradations under the same conditions, it can still maintain a relatively high removal rate of TC, and the degradation rate is still 82.7%.

[0061] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0062] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A hollow spherical carbon nitride, characterized in that: Its shape is a hydrangea-like structure with an open hole in the center and a porous surface.

2. The hollow spherical carbon nitride according to claim 1, characterized in that: Its color is yellow-grey.

3. A method for preparing hollow spherical carbon nitride according to any one of claims 1-2, characterized in that: The following steps are involved: Step 1, measure the HF solution and put it into a tetrafluoroethylene reactor, then slowly add Ti3AlC2, heat in an oil bath and continue stirring; Step 2, after the reaction is completed, wash the solid powder several times, and vacuum dry the obtained black solid powder at 50°C-80°C to obtain Ti3C2; Step 3, dispersing Ti3C2 in DMSO and using ultrasonic vibration to form a dispersion for later use; Step 4, dissolving cyanuric acid and melamine in two portions of DMSO respectively, and subjecting the mixture to ultrasonic vibration treatment and heating until the solid is completely dissolved; Step 5, add 1 mL-20 mL of the solution of step 3 to each of the two solutions of step 4; Step 6, heating the black cyanuric acid mixture and the clarified melamine mixture in an oil bath to 80°C-100°C, mixing the two under vigorous stirring, and then stirring at room temperature for 15min-60min to react; washing the obtained off-white precipitate with ethanol, and completely drying it in a vacuum oven; Step 7: Add the dry off-white powder into a crucible and cover it with tin foil, then calcine it in a constant temperature furnace at 520°C at a heating rate of 2°C / min-3°C / min for 2h-6h to finally obtain a yellow-gray powder material, which is hollow spherical carbon nitride.

4. The method for preparing hollow spherical carbon nitride according to claim 3, characterized in that: In the step 1, 10 mL of HF solution was measured and placed in a tetrafluoroethylene reaction kettle, and then 1 g of Ti3AlC2 was slowly added, and the reaction system was heated in an oil bath and stirred at 60° C. for 24 h.

5. The method for preparing hollow spherical carbon nitride according to claim 4, characterized in that: In the step 2, the solid powder is washed several times with deionized water and anhydrous ethanol, and the obtained black solid powder is vacuum dried at 50° C.-80° C. for 24 hours to obtain Ti3C2.

6. The method for preparing hollow spherical carbon nitride according to claim 5, characterized in that: In the step 3, 20 mg of Ti3C2 is dispersed in 20 mL of DMSO and ultrasonicated for 30 min to form a dispersion for use.

7. The method for preparing hollow spherical carbon nitride according to claim 6, characterized in that: In the step 4, 0.5 g of cyanuric acid and 0.5 g of melamine are dissolved in 10 mL and 20 mL of DMSO respectively.

8. The use of a hollow spherical carbon nitride according to any one of claims 1-2, characterized in that: The photocatalytic application of hollow spherical carbon nitride refers to the catalytic degradation of tetracycline under visible light.

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