SiO2 / g-c3n4 inlay type composite material and preparation method and application thereof

Abstract

The application discloses a SiO2 / g-C3N4 inlaid composite material and a preparation method and application thereof, and belongs to the technical field of photocatalysis. The SiO2 / g-C3N4 inlaid composite material is composed of SiO2 microspheres and g-C3N4; the g-C3N4 has a lamellar porous structure; and the SiO2 microspheres are inlaid in the lamella and surface of the g-C3N4 to form a close interface bonding structure. In the application, the SiO2 is in-situ grown on the pores of the g-C3N4, so that the SiO2 microspheres are inlaid in the pores of the g-C3N4 to form a SiO2 / g-C3N4 inlaid heterostructure, which can reduce the electron-hole recombination rate, improve the charge transfer rate to the material surface, thereby solving the problem that the charge is relatively slow in the process of being transferred to the material surface, and the absorbance of the SiO2 / g-C3N4 inlaid composite material is much higher than that of pure substance. In the application, the SiO2 / g-C3N4 inlaid composite material can effectively degrade RhB, methylene blue and tetracycline hydrochloride in the photocatalytic degradation of water treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of photocatalysis, and particularly relates to a SiO2 / g-C3N4 inlaid composite material, a preparation method and application thereof. BACKGROUND

[0002] The information disclosed in this Background section is for the purpose of increasing the understanding of the background of the application without admitting that such information forms prior art.

[0003] Water pollution is recognized as one of the most serious problems in the world, in order to solve this problem, many methods are taken, among which photocatalytic degradation method has been widely concerned. But there are still some problems in photocatalytic degradation of dyes, such as low photocatalytic degradation efficiency, poor stability, low sustainable utilization rate, etc. These problems are mainly caused by low absorbance of photocatalyst composite material, high electron-hole recombination rate and slow charge transfer to the surface of the material. SUMMARY

[0004] In order to solve the problems in the prior art, the present application provides a SiO2 / g-C3N4 inlaid composite material, a preparation method and application thereof. In the present application, SiO2 is grown in situ on the pores of g-C3N4, so that SiO2 nanospheres are inlaid in the pores of g-C3N4, forming a SiO2 / g-C3N4 inlaid heterostructure, which can reduce the electron-hole recombination rate and improve the charge transfer rate to the surface of the material, thereby solving the problem of slow charge transfer to the surface of the material, and the absorbance is much higher than that of pure substance.

[0005] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0006] In the first aspect, the present application provides a SiO2 / g-C3N4 inlaid composite material, which is composed of SiO2 microspheres and g-C3N4; the g-C3N4 has a lamellar porous structure; the SiO2 microspheres are inlaid in the lamellar and surface of g-C3N4, forming a close interfacial bonding structure.

[0007] The average particle size of SiO2 microspheres is 1-5 microns.

[0008] It can be understood that the "inlaid" means that part of it is buried inside the g-C3N4 layer, and part of it is exposed on the surface of g-C3N4. That is, the inlaid SiO2 is grown in situ in the pores of g-C3N4 lamellar, so that SiO2 is rooted in the pores of g-C3N4, achieving the effect of inlaying.

[0009] Preferably, the mass ratio of SiO2 and g-C3N4 is 1:(1-4), preferably 1:(2-3).

[0010] In a second aspect, the present application provides a preparation method of the SiO2 / g-C3N4 mosaic composite material, comprising the following steps:

[0011] The g-C3N4 is dispersed in an alcohol aqueous solution, and ammonia water and tetraethyl orthosilicate (TEOS) are sequentially added for stirring to obtain a mixed solution, which is centrifuged, washed, and dried to obtain a mixed material, and the mixed material is calcined at high temperature to obtain the SiO2 / g-C3N4 mosaic composite material.

[0012] In one or more embodiments, the g-C3N4 is obtained by calcining melamine as a precursor in a closed reactor at high temperature to obtain g-C3N4 with pores.

[0013] Preferably, the calcination temperature is 590-610℃, the calcination time is 3-4h, and the heating rate and the cooling rate are both 5℃ / min.

[0014] In one or more embodiments, in the alcohol aqueous solution, the alcohol is ethanol, methanol, isopropanol, or butanol, preferably ethanol, and the volume ratio of alcohol to water is (6-8):1.

[0015] In one or more embodiments, the feeding ratio of g-C3N4, the alcohol aqueous solution, ammonia water, and tetraethyl orthosilicate (TEOS) is (1-4g):(70-90mL):(2-4mL):(3-4mL), preferably (1-4g):80mL:3mL:3.5mL.

[0016] In one or more embodiments, the dispersion is performed by ultrasonic dispersion, and the ultrasonic time is 5-20min.

[0017] In one or more embodiments, after the addition of ammonia water, the stirring is performed at room temperature for 5-20min; and after the addition of tetraethyl orthosilicate (TEOS), the stirring is performed at room temperature for 6-10h.

[0018] In one or more embodiments, the centrifugal speed is 5000-8000r / min, and the centrifugal time is 3-6min.

[0019] In one or more embodiments, the washing is performed by washing with water for multiple times.

[0020] In one or more embodiments, the drying temperature is 100-125℃, and the drying time is 3-6h.

[0021] In one or more embodiments, the calcination temperature is 500-600℃, the calcination time is 0.5-1.5h, the heating rate is 3-6℃ / min, and preferably 5℃ / min.

[0022] In a third aspect, the present application provides an application of the above-mentioned SiO2 / g-C3N4 inlaid composite material in photocatalytic degradation of water treatment.

[0023] Preferably, the water treatment is degradation of water containing dyes and / or antibiotics.

[0024] Preferably, the dye includes one or more of methylene blue, rhodamine B or methyl orange.

[0025] Preferably, the antibiotic includes one or more of tetracycline hydrochloride, oxytetracycline, doxycycline and chlortetracycline.

[0026] In a fourth aspect, the present application provides a method for photocatalytic degradation of water treatment, comprising the following steps:

[0027] The above-mentioned SiO2 / g-C3N4 inlaid composite material is used as a photocatalyst and added to the water to be treated, and photocatalytic degradation is carried out under the irradiation of visible light.

[0028] The water to be treated is water containing dyes and / or antibiotics.

[0029] One or some of the above technical solutions have the following advantages or beneficial effects:

[0030] (1) The present application provides a SiO2 / g-C3N4 inlaid composite material, which grows SiO2 in situ in the pores of g-C3N4, so that SiO2 nanospheres are inlaid in the pores of g-C3N4, forming a SiO2 / g-C3N4 inlaid heterostructure, which can reduce the electron-hole recombination rate, improve the charge transfer rate to the material surface and improve the light absorbance of the composite material, solving the problems of low light absorbance of the photocatalyst composite material, high electron-hole recombination rate and slow charge transfer to the material surface.

[0031] (2) The SiO2 / g-C3N4 inlaid composite material provided by the present application can effectively degrade dyes and / or antibiotics (such as RhB, methylene blue and tetracycline hydrochloride) in photocatalytic degradation of water treatment. In the photocatalytic degradation of RhB, 94% was degraded in 15 min; in the photocatalytic degradation of methylene blue and tetracycline hydrochloride, the degradation effects of the two reached 90% and 85% respectively in about 180 min. Obviously, the SiO2 / g-C3N4 inlaid composite material as a photocatalyst can effectively improve the degradation efficiency of pollutants, which is conducive to the treatment of water pollution.

[0032] (3) The application provides a novel morphology structure of SiO2 / g-C3N4 composite material, the composite material achieves an inlaying effect through a specific synthesis method, and SiO2 and g-C3N4 are combined very closely at an interface, thereby facilitating the transfer of interface electrons. BRIEF DESCRIPTION OF DRAWINGS

[0033] The drawings accompanying the specification of the application form a part of the specification and serve to further illustrate the application, the illustrative embodiments thereof, and the description thereof, and do not limit the application.

[0034] Figure 1 SEM images of the SiO2 / g-C3N4 inlaying type composite material prepared in Example 2 of the application at different magnifications; wherein the magnifications of (a) and (b) are 6k and 18k respectively;

[0035] Figure 2 The morphology image of g-C3N4 prepared in Comparative Example 2 of the application; the magnification is 8k;

[0036] Figure 3 The light absorption characteristics of the ultraviolet-visible diffuse reflectance spectrum and the transient photocurrent intensity diagram of the SiO2 / g-C3N4 inlaying type composite material prepared in Example 2 of the application; wherein a is the light absorption characteristics of the ultraviolet-visible diffuse reflectance spectrum, and b is the transient photocurrent intensity diagram;

[0037] Figure 4 The degradation efficiency diagram when the RhB solution is subjected to photocatalytic degradation in Application Example 1 of the application;

[0038] Figure 5 The degradation efficiency diagram when the methylene blue and tetracycline hydrochloride solutions are subjected to photocatalytic degradation in Application Example 2 of the application. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to more clearly understand the technical solutions of the application, the technical solutions of the application will be described in detail below with specific examples.

[0040] All reagents and medicines in the application can be purchased from the market.

[0041] Example 1

[0042] 1. Preparation of g-C3N4:

[0043] 20g melamine was put into a ceramic crucible and placed into a muffle furnace, the heating rate and the cooling rate were both set to 5℃ / min, the calcination temperature was 600℃ for 3h, after the crucible was naturally cooled to room temperature, the sample was taken out to obtain g-C3N4 with pores, and the g-C3N4 was ground with a mortar and collected for standby use.

[0044] 2. Preparation of the composite material:

[0045] 1g of prepared g-C3N4 was taken into a beaker, 70mL of C2H5OH and 10mL of H2O were added into the beaker, and the beaker was placed into an ultrasonic cleaner for ultrasonic treatment for 10min, then 3mL of ammonia water was added and stirred with a magnetic stirrer at a constant temperature of 25℃ for 10min, finally 3.5mL of TEOS was added, and the stirring was continued at a constant temperature of 25℃ for 9h, finally a mixed solution was obtained. The obtained mixed solution was placed into a centrifuge, the centrifugal speed was 7000r / min, and the centrifugal time was 5min, the obtained product was washed with deionized water and repeated for 3-4 times. Then the product was placed into a 120℃ oven for continuous drying for 4h to obtain a mixed material of SiO2 / g-C3N4. Finally, the mixed material was placed in a muffle furnace for calcination at 550℃ for 1h to obtain a composite material SCN-1.

[0046] Example 2

[0047] Different from example 1, the amount of g-C3N4 added was 2g, and the obtained composite material was SCN-2.

[0048] Example 3

[0049] Different from example 1, the amount of g-C3N4 added was 3g, and the obtained composite material was SCN-3.

[0050] Example 4

[0051] Different from example 1, the amount of g-C3N4 added was 4g, and the obtained composite material was SCN-4.

[0052] Comparative Example 1

[0053] Preparation of SiO2:

[0054] Into a beaker, 70 mL of C2H5OH, 10 mL of water was added and stirred until homogeneous, then 3 mL of ammonia was added and stirred for 10 min at 25 °C using a magnetic stirrer, finally 3.5 mL of TEOS was added. The prepared solution was placed in a water bath at 25 °C and stirred for 9 h, finally the SiO2 solution was obtained. The obtained SiO2 solution was placed in a centrifuge at a speed of 7000 r / min for 5 min, the obtained product was washed with deionized water and repeated 3-4 times. The product was then placed in an oven at 120 °C for 4 h to obtain the final product 1 g of SiO2, which was ground with a mortar and collected for use. The average particle size of the SiO2 was 2 microns.

[0055] Comparative Example 2

[0056] Preparation of g-C3N4:

[0057] A certain amount of melamine was placed in a ceramic crucible and placed in a muffle furnace, the heating rate and the cooling rate were set to 5 °C / min, the calcination temperature was 600 °C for 3 h, after the crucible was naturally cooled to room temperature, the sample was taken out to obtain g-C3N4 with pores, and the g-C3N4 was ground with a mortar and collected for use.

[0058] Comparative Example 3

[0059] Different from Example 1, the order of adding TEOS and g-C3N4 was adjusted, i.e. TEOS was added first and g-C3N4 was added last. The prepared composite material could not form an inlaid type composite material, but only SiO2 could be loaded on the surface of g-C3N4.

[0060] Comparative Example 4

[0061] Patent CN107649177A Example 1, specifically includes the following steps:

[0062] (1) 30 g of melamine was placed in a tube furnace and calcined at 500 °C for 4 h in an air atmosphere to obtain g-C3N4.

[0063] (2) 8 mL of ethyl silicate and 40 mL of anhydrous ethanol were mixed, and 1 g of g-C3N4 prepared in the above step was added to form A mixed solution; 6 mL of 1 mol / L HNO3, 2 mL of 3% volume concentration of HF and 12 mL of anhydrous ethanol were mixed to form B mixed solution; B mixed solution was added to A mixed solution while stirring to form a sol; the sol was transferred into a reaction kettle and subjected to hydrothermal synthesis at 100 °C, after 24 h of reaction, the cooled product was separated by suction filtration, and the separated solid material was washed and dried to obtain a g-C3N4 / SiO2 photocatalyst.

[0064] The g-C3N4 / SiO2 photocatalyst obtained in the comparative example is not a mosaic composite material.

[0065] It can be seen from Figure 2 that g-C3N4 with pores is prepared in the embodiment 1 and the comparative example 2.

[0066] It can be seen from Figure 1 that the SiO2 / g-C3N4 mosaic composite material prepared in the embodiment achieves a mosaic effect, wherein the SiO2 nanospheres are densely inlaid on the surface of the g-C3N4, and it can be seen from the figure that the interface of the SiO2 and the g-C3N4 is combined very closely, thereby being beneficial to the transfer of interface electrons.

[0067] It can be seen from Figure 3 that compared with the pure substance g-C3N4 and SiO2, the light absorption characteristics of the composite material are obviously enhanced, which shows that the formed mosaic heterostructure can improve the light absorption capacity of the composite material in the ultraviolet and visible regions, and the weakening of the light absorption characteristics of the SCN-1 may be due to the fact that the proportion of the silicon dioxide is relatively large, and the silicon dioxide is accumulated on the surface of the composite material, which affects the light absorption of the composite material to a certain extent.

[0068] It can be seen from Figure 3 that compared with the pure substance g-C3N4, the transient photocurrent intensity of the composite material SCN is significantly enhanced. Among them, the transient photocurrent of the SCN-2 is obviously higher than that of other samples, which may be due to the fact that the most suitable proportion leads to a larger specific surface area and a good charge transfer property of the SiO2 nanospheres and the dense inlaying of the SiO2 nanospheres on the surface of the g-C3N4, which increases more active sites and reduces the hindrance of electron transfer and shortens the path of electron transfer, thereby inhibiting the recombination of photo-generated carriers.

[0069] Application example 1: photocatalytic degradation of RhB solution:

[0070] A 20mg / L RhB solution is configured, and 100mL of the RhB solution is taken each time to add 0.1g of a photocatalyst (including the catalysts prepared in the embodiments 1-4, the SiO2 prepared in the comparative example 1 and the g-C3N4 prepared in the comparative example 2). Based on the absorbance value corresponding to the wavelength of 554nm, the degradation result is as shown in Figure 4 It can be seen from Figure 4 that the RhB dye can be degraded by about 95% at 15min.

[0071] Application example 2: photocatalytic degradation of tetracycline hydrochloride and methylene blue:

[0072] The methylene blue solution and tetracycline hydrochloride solution were configured at 30 mg / L respectively, and 100 mL of the methylene blue solution and tetracycline hydrochloride solution were added to 0.1 g of the photocatalyst (SCN-2 prepared in Example 2) for each test. The degradation results of the methylene blue solution and tetracycline hydrochloride solution were determined based on the absorbance values at the wavelengths of 665 nm and 358 nm respectively, and the results are shown in Table 1. Figure 5 As shown in the figure, the degradation effects of the two reached 90% and 85% respectively at about 180 min.

[0073] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A SiO2 / g-C3N4 mosaic composite material, characterized in that, It is composed of SiO2 microspheres and g-C3N4; the g-C3N4 has a layered porous structure; the SiO2 microspheres are embedded in the layers and surface of g-C3N4 to form a tight interfacial bonding structure; The preparation method of the SiO2 / g-C3N4 mosaic composite material includes the following steps: g-C3N4 was dispersed in an alcohol-water solution, and ammonia and ethyl silicate were added sequentially and stirred to obtain a mixed solution. The solution was then centrifuged, washed, and dried to obtain a mixed material. The mixed material was then calcined at high temperature to obtain a SiO2 / g-C3N4 embedded composite material.

2. The SiO2 / g-C3N4 mosaic composite material according to claim 1, characterized in that, The mass ratio of SiO2 microspheres to g-C3N4 is 1:(1~4).

3. The SiO2 / g-C3N4 mosaic composite material according to claim 2, characterized in that, The mass ratio of SiO2 microspheres to g-C3N4 is 1:(2~3).

4. A method for preparing the SiO2 / g-C3N4 mosaic composite material according to any one of claims 1 to 3, characterized in that, Includes the following steps: g-C3N4 was dispersed in an alcohol-water solution, and ammonia and ethyl silicate were added sequentially and stirred to obtain a mixed solution. The solution was then centrifuged, washed, and dried to obtain a mixed material. The mixed material was then calcined at high temperature to obtain a SiO2 / g-C3N4 embedded composite material.

5. The preparation method according to claim 4, characterized in that, The g-C3N4 is obtained by high-temperature calcination of melamine as a precursor in a closed reactor to produce a porous g-C3N4.

6. The preparation method according to claim 5, characterized in that, The calcination temperature is 590-610℃, the calcination time is 3-4h, and the heating rate and cooling rate are both 5℃ / min.

7. The preparation method according to claim 4, characterized in that, In the alcohol-water solution, the alcohol is ethanol, methanol, isopropanol, or butanol.

8. The preparation method according to claim 7, characterized in that, In the aqueous alcohol solution, the alcohol is ethanol.

9. The preparation method according to claim 4, characterized in that, The volume ratio of alcohol to water is (6-8):

1.

10. The preparation method according to claim 4, characterized in that, The feeding ratio of g-C3N4, alcohol-water solution, ammonia and ethyl silicate is (1-4g):(70-90mL):(2-4mL):(3-4mL).

11. The preparation method according to claim 10, characterized in that, The feeding ratio of g-C3N4, alcohol-water solution, ammonia and ethyl silicate is (1-4g):80mL:3mL:3.5mL.

12. The preparation method according to claim 4, characterized in that, The dispersion is performed using ultrasonic dispersion, with an ultrasonic time of 5-20 minutes.

13. The preparation method according to claim 4, characterized in that, After adding ammonia, stir at room temperature for 5-20 minutes.

14. The preparation method according to claim 4, characterized in that, After adding ethyl silicate, stir at room temperature for 6-10 hours.

15. The preparation method according to claim 4, characterized in that, The centrifugation speed is 5000-8000 r / min, and the centrifugation time is 3-6 minutes.

16. The preparation method according to claim 4, characterized in that, The drying temperature is 100-125℃, and the drying time is 3-6 hours.

17. The preparation method according to claim 4, characterized in that, The calcination temperature is 500-600℃, the calcination time is 0.5-1.5h, and the heating rate is 3-6℃ / min.

18. The application of the SiO2 / g-C3N4 mosaic composite material according to any one of claims 1 to 3 or the SiO2 / g-C3N4 mosaic composite material obtained by the preparation method according to any one of claims 4 to 17 in photocatalytic degradation of water treatment.

19. The application according to claim 18, characterized in that, The water treatment involves degrading water containing dyes and / or antibiotics.

20. The application according to claim 19, characterized in that, The dyes include one or more of methylene blue, rhodamine B, and methyl orange.

21. The application according to claim 19, characterized in that, The antibiotics include one or more of tetracycline hydrochloride, oxytetracycline, doxycycline, and chlortetracycline.

22. A method for photocatalytic degradation of water, characterized in that, Includes the following steps: The SiO2 / g-C3N4 embedded composite material according to any one of claims 1 to 3 is added to the water to be treated as a photocatalyst, and photocatalytic degradation is carried out under visible light irradiation; The water to be treated is water containing dyes and / or antibiotics.

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