Preparation method and application of ultrathin porous carbon nitride nano-film catalyst

Abstract

The invention relates to the technical field of photocatalytic catalysts, in particular to a preparation method and application of an ultrathin porous carbon nitride nano-film catalyst, and the preparation method comprises the following steps: preparing a precursor solution, taking a certain amount of a nitrogen-containing precursor, putting the nitrogen-containing precursor into a beaker, adding deionized water, and heating, stirring and mixing for a certain time to obtain the precursor solution; preparing a carbon nitride crude product, transferring the precursor solution into a high-pressure reaction kettle for hydrothermal treatment, performing centrifugal filtration on the precursor solution subjected to hydrothermal treatment, and washing, drying and grinding a solid product after filtration to obtain the carbon nitride crude product; preparing a porous carbon nitride nano-film, calcining the carbon nitride crude product in an air atmosphere at a high temperature, and naturally cooling after calcining to obtain the ultrathin porous carbon nitride nano-film. The invention provides a preparation method and application of an ultrathin porous carbon nitride nano-film catalyst. The preparation method has the advantages that raw materials are cheap and easy to obtain, the preparation method is simple and easy to implement, and the product yield is high.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic catalysts, and in particular to a method for preparing an ultra-thin porous carbon nitride nanofilm catalyst and application thereof. Background Art

[0002] With the booming economy and explosive growth in population density, excessive discharge of antibiotics has a destructive impact on aquatic ecosystems such as oceans and lakes. Among them, tetracycline is the most representative broad-spectrum antibiotic pollutant in sewage discharge. It is not only highly toxic and difficult to degrade, but also causes the spread of antibiotic-resistant bacteria, thus having a negative impact on human health and the balance of aquatic ecosystems.

[0003] Semiconductor photocatalytic technology has shown good application prospects in wastewater treatment due to its outstanding stability, energy saving and environmental friendliness. Among them, carbon nitride has attracted widespread attention due to its strong light response characteristics, excellent physical and chemical stability and no secondary pollution. However, the carbon nitride obtained by traditional preparation methods has disadvantages such as small specific surface area, low photogenerated carrier migration rate and insufficient light absorption, which makes its photocatalytic degradation performance less than ideal. In view of the above defects, the introduction of porous structure on carbon nitride by hard template or soft template method can not only significantly increase its surface area, but also enhance its light absorption capacity. However, the hard template technology has problems such as complex process, high production cost and serious environmental pollution, while the soft template technology has shortcomings such as high residual carbon content and low predictability, which limits the further widespread application of carbon nitride. For this reason, it is urgent to explore a simple template-free preparation route to obtain high-performance carbon nitride photocatalysts. At the same time, the design of functionalized nanostructures of different sizes is considered to be an effective strategy to improve the photocatalytic degradation ability of carbon nitride, especially ultra-thin structured carbon nitride nanomaterials help to increase the photogenerated carrier migration rate and thus improve its photocatalytic performance.

[0004] Therefore, there is a need for a carbon nitride nanofilm catalyst that can improve the yield performance of a photocatalytic catalyst. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for preparing an ultra-thin porous carbon nitride nanofilm catalyst and its application, aiming to solve the problems of insufficient yield and high production cost of existing photocatalytic catalysts.

[0006] To achieve the above object, the present invention provides a method for preparing an ultra-thin porous carbon nitride nanofilm catalyst, the method comprising the following steps:

[0007] Prepare a precursor solution, take a certain amount of nitrogen-containing precursor into a beaker and add deionized water, heat and stir for a certain period of time to obtain a precursor solution;

[0008] To prepare a crude carbon nitride product, a precursor solution is transferred into a high-pressure reactor for hydrothermal treatment, the precursor solution after the hydrothermal treatment is centrifugally filtered, and after filtering, the solid product is washed, dried and ground to obtain a crude carbon nitride product;

[0009] The porous carbon nitride nanofilm is prepared by calcining the crude carbon nitride product at high temperature in an air atmosphere, and then naturally cooling the product after calcination to obtain an ultra-thin porous carbon nitride nanofilm.

[0010] Furthermore, in the step of preparing the precursor solution, taking a certain amount of nitrogen-containing precursor, putting it into a beaker and adding deionized water, heating, stirring and mixing to obtain the precursor solution, the mass of the nitrogen-containing precursor is 1 to 10 g.

[0011] Furthermore, in the step of preparing the precursor solution, taking a certain amount of nitrogen-containing precursor into a beaker and adding deionized water, heating and stirring to obtain the precursor solution, the volume of deionized water is 30 to 180 mL, the heating temperature is 40 to 90° C., and the stirring and mixing time is 5 to 30 min.

[0012] Furthermore, in the step of preparing the crude carbon nitride product, the precursor solution is transferred into a high-pressure reactor for hydrothermal treatment, the precursor solution after the hydrothermal treatment is centrifugally filtered, and the solid product is washed, dried and ground after filtration to obtain the crude carbon nitride product, the temperature of the hydrothermal treatment is 80 to 120° C., and the time of the hydrothermal treatment is 12 to 36 hours.

[0013] Furthermore, in the step of preparing the crude carbon nitride product, the precursor solution is transferred into a high-pressure reactor for hydrothermal treatment, the precursor solution after the hydrothermal treatment is centrifugally filtered, and the solid product is washed, dried and ground after filtration to obtain the crude carbon nitride product, the drying temperature is 50-100°C, and the hydrothermal treatment time is 10-24h.

[0014] Furthermore, in the step of preparing the porous carbon nitride nanomembrane, calcining the crude carbon nitride product at high temperature in an air atmosphere, and naturally cooling it after calcination to obtain an ultrathin porous carbon nitride nanomembrane, the calcination process adopts a programmed temperature rising method and is divided into three stages, wherein the heating rate in the first stage is 2 to 5°C / min, and the temperature is raised to 80 to 150°C and then kept warm for 30 minutes to 2 hours; the heating rate in the second stage is 2 to 5°C / min, and the temperature is raised to 200 to 400°C and then kept warm for 30 minutes to 2 hours; the heating rate in the third stage is 1 to 4°C / min, and the temperature is raised to 500 to 600°C and then kept warm for 4 to 8 hours.

[0015] Furthermore, the nitrogen-containing precursor is one or more of melamine, thiourea, dicyandiamide, and urea.

[0016] The present invention also provides an ultra-thin porous carbon nitride nanofilm catalyst, wherein the ultra-thin porous carbon nitride nanofilm catalyst is prepared by the ultra-thin porous carbon nitride nanofilm preparation method described in any one of the above technical solutions.

[0017] The present invention provides a method for preparing an ultrathin porous carbon nitride nanofilm catalyst and its application. An ultrathin carbon nitride nanofilm with a porous structure is prepared by using a nitrogen-containing precursor, and a simple method for synthesizing an ultrathin porous carbon nitride nanofilm catalyst is developed by hydrothermal treatment and programmed high-temperature calcination. The present invention adopts a template-free method to directly synthesize an ultrathin porous carbon nitride nanofilm, and the synthesis process is simple and controllable; at the same time, it also has the effects of low raw material cost, abundant acquisition channels, environmental friendliness, and high efficiency in degrading tetracycline. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained according to the processes shown in these drawings without paying creative work.

[0019] Figure 1 A scanning electron microscope image of an ultra-thin porous carbon nitride nanofilm according to an embodiment of the present invention;

[0020] Figure 2 A transmission electron microscope image of an ultra-thin porous carbon nitride nanofilm according to an embodiment of the present invention;

[0021] Figure 3 is an XRD pattern of an ultra-thin porous carbon nitride nanofilm according to an embodiment of the present invention;

[0022] Figure 4 It is a graph showing the tetracycline degradation efficiency of Examples 1 and 4 of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0025] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0026] Reference Figure 1-Figure 4 The present application provides a method for preparing an ultra-thin porous carbon nitride nanofilm catalyst and its application. Specifically, the present invention also discloses embodiments 1-7 of specific applications, which are as follows:

[0027] Embodiment 1:

[0028] Place 1 g of melamine in a beaker, add 50 mL of deionized water, and stir at 85 °C for 20 min to obtain a precursor solution;

[0029] The precursor solution was poured into a high-pressure reactor, and the temperature of the high-pressure reactor was raised to 170° C. and maintained for 30 hours to perform a hydrothermal reaction on the precursor solution;

[0030] The solution after the hydrothermal reaction is centrifugally filtered, and the filter residue obtained after separation is washed multiple times. The washed filter residue is placed in an oven, heated to 60° C. and dried, and then the filter residue is ground;

[0031] The ground filter residue is placed in a crucible, and then the crucible is moved into a muffle furnace, and the sample is treated by three-stage high-temperature calcination, wherein the first stage heating rate is 3°C / min, and the temperature is increased to 100°C and then kept warm for 30 minutes, the second stage heating rate is 3°C / min, and the temperature is increased to 300°C and then kept warm for 1 hour, the third stage heating rate is 2°C / min, and the temperature is increased to 550°C and then kept warm for 4 hours. After natural cooling, the ultra-thin porous carbon nitride nanofilm catalyst of Example 1 is obtained.

[0032] Embodiment 2:

[0033] Place 1 g of melamine in a beaker, add 50 mL of deionized water, and stir at 85 °C for 20 min to obtain a precursor solution;

[0034] The precursor solution is placed in an oven, heated to 60°C, and dried to obtain a filter residue, which is then ground;

[0035] The ground filter residue is placed in a crucible, and then the crucible is moved into a muffle furnace, and the sample is treated by three-stage high-temperature calcination, wherein the heating rate of the first stage is 3°C / min, and the temperature is increased to 100°C and then kept warm for 30 minutes, the heating rate of the second stage is 3°C / min, and the temperature is increased to 300°C and then kept warm for 1 hour, the heating rate of the third stage is 2°C / min, and the temperature is increased to 550°C and then kept warm for 4 hours. After natural cooling, the ultra-thin porous carbon nitride nanofilm catalyst of Example 2 is obtained.

[0036] Embodiment 3:

[0037] Place 1 g of melamine in a beaker, add 50 mL of deionized water, and stir at 85 °C for 20 min to obtain a precursor solution;

[0038] The precursor solution was poured into a high-pressure reactor, and the temperature of the high-pressure reactor was raised to 170° C. and maintained for 30 hours to perform a hydrothermal reaction on the precursor solution;

[0039] The solution after the hydrothermal reaction is centrifugally filtered, and the filter residue obtained after separation is washed multiple times. The washed filter residue is placed in an oven, heated to 60° C. and dried, and then the filter residue is ground;

[0040] The ground filter residue was placed in a crucible, and then the crucible was moved into a muffle furnace. The sample was treated by one-stage high-temperature calcination, wherein the heating rate was 2°C / min, and the temperature was raised to 550°C and kept for 4 hours. After natural cooling, the ultrathin porous carbon nitride nanofilm catalyst of Example 3 was obtained.

[0041] Embodiment 4:

[0042] Take 1g of melamine and place it in a crucible, place the crucible in a muffle furnace, and treat the sample by one-stage high-temperature calcination. The heating rate of the muffle furnace is 2°C / min. After heating to 550°C, keep warm for 4h, and obtain the ultra-thin porous carbon nitride nanofilm catalyst of Example 4 after natural cooling.

[0043] Embodiment 5:

[0044] Place 1 g of thiourea in a beaker, add 50 mL of deionized water, and stir at 85 °C for 20 min to obtain a precursor solution;

[0045] The precursor solution was poured into a high-pressure reactor, and the temperature of the high-pressure reactor was raised to 170° C. and maintained for 30 hours to perform a hydrothermal reaction on the precursor solution;

[0046] The solution after the hydrothermal reaction is centrifugally filtered, and the filter residue obtained after separation is washed multiple times. The washed filter residue is placed in an oven, heated to 60° C. and dried, and then the filter residue is ground;

[0047] The ground filter residue is placed in a crucible, and then the crucible is moved into a muffle furnace, and the sample is treated by three-stage high-temperature calcination, wherein the first stage heating rate is 3°C / min, and the temperature is increased to 100°C and then kept warm for 30 minutes, the second stage heating rate is 3°C / min, and the temperature is increased to 300°C and then kept warm for 1 hour, the third stage heating rate is 2°C / min, and the temperature is increased to 550°C and then kept warm for 4 hours. After natural cooling, the ultra-thin porous carbon nitride nanofilm catalyst of Example 5 is obtained.

[0048] Embodiment 6:

[0049] Place 1 g of dicyandiamide in a beaker, add 50 mL of deionized water, and stir at 85 °C for 20 min to obtain a precursor solution;

[0050] The precursor solution was poured into a high-pressure reactor, and the temperature of the high-pressure reactor was raised to 170° C. and maintained for 30 hours to perform a hydrothermal reaction on the precursor solution;

[0051] The solution after the hydrothermal reaction is centrifugally filtered, and the filter residue obtained after separation is washed multiple times. The washed filter residue is placed in an oven, heated to 60° C. and dried, and then the filter residue is ground;

[0052] The ground filter residue is placed in a crucible, and then the crucible is moved into a muffle furnace, and the sample is treated by three-stage high-temperature calcination, wherein the first stage heating rate is 3°C / min, and the temperature is increased to 100°C and then kept warm for 30 minutes, the second stage heating rate is 3°C / min, and the temperature is increased to 300°C and then kept warm for 1 hour, the third stage heating rate is 2°C / min, and the temperature is increased to 550°C and then kept warm for 4 hours. After natural cooling, the ultra-thin porous carbon nitride nanofilm catalyst of Example 6 is obtained.

[0053] Embodiment 7:

[0054] Place 1 g of urea in a beaker, add 50 mL of deionized water, and stir at 85 °C for 20 min to obtain a precursor solution;

[0055] The precursor solution was poured into a high-pressure reactor, and the temperature of the high-pressure reactor was raised to 170° C. and maintained for 30 hours to perform a hydrothermal reaction on the precursor solution;

[0056] The solution after the hydrothermal reaction is centrifugally filtered, and the filter residue obtained after separation is washed multiple times. The washed filter residue is placed in an oven, heated to 60° C. and dried, and then the filter residue is ground;

[0057] The ground filter residue is placed in a crucible, and then the crucible is moved into a muffle furnace. The sample is treated with a three-stage high-temperature calcination, wherein the first stage heating rate is 3°C / min, and the temperature is increased to 100°C and then kept warm for 30 minutes. The second stage heating rate is 3°C / min, and the temperature is increased to 300°C and then kept warm for 1 hour. The third stage heating rate is 2°C / min, and the temperature is increased to 550°C and then kept warm for 4 hours. After natural cooling, the ultra-thin porous carbon nitride nanofilm catalyst of Example 7 is obtained.

[0058] Based on Example 1 using the technical solution disclosed in the present invention and Example 4 using the prior art solution as the technical solution, a photocatalytic degradation test was conducted with a 350W xenon lamp (CEL-PF300-T8E, 300-780nm) and an ultra-thin porous carbon nitride nanofilm catalyst, with the degradation performance of tetracycline as the target, and the specific test steps are as follows:

[0059] S1. Weigh the catalyst of the same mass and place it in a reactor, and add 100 mL of a 20 mg / L tetracycline solution into the reactor for mixing;

[0060] S2, turn on the stirring device of the reactor, and stir for 60 minutes in a light-proof environment to reach adsorption-desorption equilibrium;

[0061] S3, start the circulating cooling water device and start the xenon lamp light source so that the light can vertically illuminate the reaction solution;

[0062] S4. After irradiation for 1 h, 50 mL of the mixed solution was drawn from the reactor and filtered with a 0.22 μm filter membrane to separate the carbon nitride nanofilm catalyst from the supernatant;

[0063] S5. Using the absorbance difference of the degradation products as the evaluation index, the absorbance at a specific wavelength (taking the optimal absorption peak of 356 nm as the specific wavelength) is measured using an ultraviolet-visible spectrophotometer, and the degradation rate of tetracycline is obtained by calculation.

[0064] The specific calculation formula of the degradation rate is:

[0065]

[0066] Where: x is the degradation rate; C 0 is the initial concentration of the solution (mg / L); C t is the concentration of the solution after t minutes of reaction (mg / L).

[0067] like Figure 4 As shown, the ultrathin porous carbon nitride nanofilm catalyst prepared in Example 1 is recorded as gC 3 N 4-M1, the ultrathin porous carbon nitride nanofilm catalyst prepared in Example 4 is recorded as gC 3 N 4 -M4, and Figure 4 In the histogram of 3 N 4 -M1 is the rectangular box on the left of the two parallel items under the same conditions in the histogram, gC 3 N 4 -M4 is the rectangular box on the right of the two items in parallel under the same conditions in the histogram.

[0068] The experimental results show that the ultra-thin porous carbon nitride nanofilm catalyst in Example 1, which adopts hydrothermal treatment and three-stage programmed temperature rising technology, has a significant performance difference in tetracycline degradation efficiency compared with the ultra-thin porous carbon nitride nanofilm catalyst in Example 4 representing the prior art. Example 1 has a significant advantage in the degradation of organic substances such as tetracycline.

[0069] In combination with all the above technical solutions, the present invention provides a method for preparing an ultra-thin porous carbon nitride nanofilm catalyst and its application, which includes dissolving a nitrogen-containing precursor in deionized water, then subjecting the solution to hydrothermal treatment, and finally obtaining an ultra-thin porous carbon nitride nanofilm catalyst after programmed temperature calcination in an air atmosphere. The present invention synthesizes an ultra-thin porous carbon nitride nanofilm catalyst through a template-free synthesis strategy and a hydrothermal treatment-programmed temperature calcination route. The raw materials selected by the technical method are cheap and easy to obtain, and have economic value. At the same time, the preparation method is simple and easy, the product yield is high, and it is easy to scale up production. In addition, the catalyst has good efficiency in photocatalytic degradation of tetracycline and has broad application prospects.

[0070] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing an ultrathin porous carbon nitride nanofilm, characterized in that: The following steps are involved: Prepare a precursor solution, take a certain amount of nitrogen-containing precursor into a beaker and add deionized water, heat and stir for a certain period of time to obtain a precursor solution; To prepare a crude carbon nitride product, a precursor solution is transferred into a high-pressure reactor for hydrothermal treatment, the precursor solution after the hydrothermal treatment is centrifugally filtered, and after filtering, the solid product is washed, dried and ground to obtain a crude carbon nitride product; The porous carbon nitride nanofilm is prepared by calcining the crude carbon nitride product at high temperature in an air atmosphere, and then naturally cooling the product after calcination to obtain an ultra-thin porous carbon nitride nanofilm.

2. The method for preparing an ultrathin porous carbon nitride nanofilm according to claim 1, characterized in that: In the step of preparing the precursor solution, taking a certain amount of nitrogen-containing precursor and putting it into a beaker, adding deionized water, heating, stirring and mixing to obtain the precursor solution, the mass of the nitrogen-containing precursor is 1 to 10 g.

3. The method for preparing an ultrathin porous carbon nitride nanofilm according to claim 2, characterized in that: In the step of preparing the precursor solution, a certain amount of nitrogen-containing precursor is put into a beaker and deionized water is added, and the precursor solution is obtained after heating, stirring and mixing. The volume of the deionized water is 30 to 180 mL, the heating temperature is 40 to 90° C., and the stirring and mixing time is 5 to 30 minutes.

4. The method for preparing an ultrathin porous carbon nitride nanofilm according to claim 1, characterized in that: In the step of preparing the crude carbon nitride product, the precursor solution is transferred into a high-pressure reactor for hydrothermal treatment, the precursor solution after the hydrothermal treatment is centrifugally filtered, and the solid product is washed, dried and ground after filtration to obtain the crude carbon nitride product, wherein the hydrothermal treatment temperature is 80 to 120° C. and the hydrothermal treatment time is 12 to 36 hours.

5. The method for preparing an ultra-thin porous carbon nitride nanofilm according to claim 1, characterized in that: In the step of preparing the crude carbon nitride product, the precursor solution is transferred into a high-pressure reactor for hydrothermal treatment, the precursor solution after the hydrothermal treatment is centrifugally filtered, and the solid product is washed, dried and ground after filtration to obtain the crude carbon nitride product. The drying temperature is 50-100° C. and the hydrothermal treatment time is 10-24 hours.

6. The method for preparing an ultra-thin porous carbon nitride nanofilm according to claim 1, characterized in that: In the step of preparing the porous carbon nitride nanomembrane, the crude carbon nitride product is calcined at high temperature in an air atmosphere, and naturally cooled after calcination to obtain an ultra-thin porous carbon nitride nanomembrane. The calcination process adopts a programmed temperature rising method and is divided into three stages. In the first stage, the heating rate is 2-5°C / min, and the temperature is raised to 80-150°C and then kept warm for 30min-2h; the heating rate in the second stage is 2-5°C / min, and the temperature is raised to 200-400°C and then kept warm for 30min-2h; the heating rate in the third stage is 1-4°C / min, and the temperature is raised to 500-600°C and then kept warm for 4-8h.

7. The method for preparing an ultra-thin porous carbon nitride nanofilm according to claim 1, characterized in that: The nitrogen-containing precursor is one or more of melamine, thiourea, dicyandiamide and urea.

8. An ultra-thin porous carbon nitride nanofilm catalyst, characterized in that: The ultra-thin porous carbon nitride nanofilm catalyst is prepared by the ultra-thin porous carbon nitride nanofilm preparation method according to any one of claims 1 to 6.

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