A molybdenum-doped carbon nitride photocatalytic material, its preparation method and application

Abstract

The present invention provides a molybdenum-doped carbon nitride photocatalytic material, a preparation method thereof, and an application thereof. The preparation method is as follows: 3-amino-1,2,4-triazole and molybdate are put into a mortar and ground, and then poured into a crucible; subsequently, it is placed in a muffle furnace and reacted at 500-560 °C for 2-3 hours, and naturally cooled to obtain a light earth-yellow powdery material C3N5 / Mo. This material has a low recombination rate of photo-generated e ‑ and h + , and has extremely strong degradation ability for organic substances such as methyl orange, methylene blue, rhodamine, and oxytetracycline under visible light.

Description

Technical Field

[0001] The present invention relates to photocatalytic materials, and specifically to a molybdenum-doped carbon nitride photocatalytic material, a preparation method thereof, and an application thereof. Background Art

[0002] The photocatalytic performance of graphitic carbon nitride (CN) has attracted increasing attention. The redox reaction generated by photo-induced holes and electrons can photocatalytically degrade pollutants, and carbon nitride is expected to be applied to the treatment of wastewater. Previously, people synthesized C3N4 using melamine. Due to its relatively wide bandgap and narrow light absorption range (λ < 450 nm), its application is limited. Subsequently, scientists discovered C3N 5。 As a novel carbon nitride photocatalyst, C3N5 has a high nitrogen content and a narrow bandgap, showing extraordinary performance in the field of photocatalysis. However, C3N5 also has inherent disadvantages such as carrier recombination and low specific surface area.

[0003] The doping strategy is a relatively direct and effective method to improve photocatalytic activity. It can directly affect the energy band structure by introducing intermediate energy levels or narrowing the bandgap, thereby enhancing visible light absorption and changing the redox potential. The empty intermediate band can accommodate photo-excited electrons from the valence band, contributing to the absorption of photons with energy lower than the bandgap. Noble metals such as Au, Pt, and Pd have been widely used as effective doping materials. However, the high cost of noble metals limits their practical applications. Practically speaking, it is imperative to develop doping materials that are rich in resources, low in cost, and non-noble metals to improve photocatalytic performance. Summary of the Invention

[0004] The main purpose of the present invention is to provide a molybdenum-doped carbon nitride material (abbreviated as C3N5 / Mo material), a preparation method thereof, and an application thereof. Using 3-amino-1,2,4-triazole as the synthesis raw material of C3N5, molybdate is doped during the reaction process, and the target product C3N5 / Mo is synthesized by "one-pot" polycondensation. The synthesis yield is high and the repeatability is strong. This material has a low recombination rate of photo-generated e - and h + and has extremely strong degradation ability for organic substances such as methyl orange, methylene blue, rhodamine, and oxytetracycline under visible light. The purpose of this invention is to use photocatalytic technology to solve the problem that organic substances in sewage treatment plants are difficult to degrade.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A molybdenum-doped carbon nitride photocatalytic material, wherein the photocatalytic material is a C3N5 / Mo material.

[0007] Preferably, the band gap of the photocatalytic material is 1.87 eV; the microstructure morphology is irregular granular; the X-ray powder diffraction data are 13.133, 16.129, 18.830, 23.540, 27.184, 29.117, 45.916 and 57.320 degrees; the infrared spectrum data are 495, 804, 1204, 1240, 1321, 1403, 1458, 1546, 1635, 3085 cm -1 .

[0008] The present invention also discloses a preparation method of the above-mentioned molybdenum-doped carbon nitride photocatalytic material, comprising the following steps:

[0009] 1) Put 3-amino-1,2,4-triazole and molybdate into a mortar according to a molar ratio of 500:1 to 600:1, grind them, and then pour them into a crucible;

[0010] 2) Place the crucible in a muffle furnace, heat it up to 500-560 °C and react for 2-3 hours to obtain the molybdenum-doped carbon nitride photocatalytic material.

[0011] The microscopic morphology of the catalyst prepared by the present invention is mainly irregular small granular, the particle size is smaller, and the particle distribution is more uniform after grinding, which greatly improves the specific surface area of the catalyst.

[0012] The reason for using 3-amino-1,2,4-triazole as a raw material in the present invention: it contains rich nitrogen elements, which makes it an ideal raw material for preparing materials with high nitrogen content such as C3N5. From a structural point of view, the distribution of nitrogen atoms in its molecular structure and other characteristics are conducive to constructing the structural framework of C3N5 through appropriate reactions. During the reaction process, it can provide a nitrogen source for the formation of C3N5 and contribute to the formation of its specific structure through atomic rearrangement, bond breaking and formation, etc.

[0013] Further, the molybdate in step 1) is sodium molybdate, potassium molybdate or ammonium molybdate.

[0014] Further, the molar ratio of 3-amino-1,2,4-triazole to molybdate in step 1) is 575:1.

[0015] Further, the particle size of the sample after grinding in step 1) is mainly distributed between 0.1 and 15 microns.

[0016] Further, the reaction temperature in step 2) is 550 °C and the reaction time is 3 hours.

[0017] Further, the heating rate range in step 2) is 3-6 °C per minute.

[0018] The present invention also provides the application of the above-mentioned photocatalytic material in photocatalytic degradation of organic pollutants.

[0019] Furthermore, the organic pollutant is one or a mixture of methyl orange, methylene blue, rhodamine, oxytetracycline, and penicillin.

[0020] According to the above technical solutions, compared with the prior art, the present invention has the following excellent effects:

[0021] Due to the doping of metal molybdenum, the oxygen vacancies in the C3N5 structure increase, and at the same time, the photo-generated electrons are transferred to molybdenum, resulting in a lower recombination rate of photo-generated e - and h + . Compared with some photocatalytic materials in the prior art, the C3N5 / Mo material has a strong degradation ability for organic substances such as methyl orange, methylene blue, rhodamine, oxytetracycline, and penicillin under visible light, and has obvious performance advantages. This invention is expected to solve the problem of wastewater degradation discharged by enterprises such as sewage treatment plants, pharmaceutical companies, hospitals, large-scale slaughterhouses, and dyeing workshops. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0023] Figure 1 It is the X-ray powder diffraction pattern of the photocatalytic material prepared in Example 1 of the present invention.

[0024] Figure 2 It is the infrared spectrum of the photocatalytic material prepared in Example 1 of the present invention.

[0025] Figure 3 It is the ultraviolet diffuse reflection of the photocatalytic material prepared in Example 1 of the present invention.

[0026] Figure 4 It is the particle size distribution of the photocatalytic material prepared in Example 1 of the present invention.

[0027] Figure 5 It is the photograph of the photocatalytic material prepared in Example 1 of the present invention.

[0028] Figure 6 It is the microscopic morphology of the photocatalytic material prepared in Example 1 of the present invention.

[0029] Figure 7 It is the degradation diagram of methyl orange by the photocatalytic materials prepared in Example 1 and Comparative Example 1 of the present invention.

[0030] Figure 8 It is the degradation diagram of methylene blue by the photocatalytic materials prepared in Example 1 and Comparative Example 1 of the present invention.

[0031] Figure 9 It is the degradation diagram of rhodamine by the photocatalytic materials prepared in Example 1 and Comparative Example 1 of the present invention.

[0032] Figure 10 It is the degradation diagram of oxytetracycline by the photocatalytic materials prepared in Example 1 and Comparative Example 1 of the present invention.

[0033] Figure 11 It is the degradation diagram of penicillin by the photocatalytic materials prepared in Example 1 and Comparative Example 1 of the present invention. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Example 1

[0036] Weigh 2 grams of 3-amino-1,2,4-triazole and 0.010 grams of sodium molybdate dihydrate and put them into a mortar for grinding for three minutes, then pour them into a 30-milliliter crucible. Subsequently, put it into a muffle furnace, heat it to 550 °C within 100 minutes, and keep it at 550 °C for 3 hours, and then cool it naturally to obtain a light earthy yellow powder, denoted as C3N5 / Mo-1, with a yield of 40%.

[0037] The X-ray powder diffraction results are as Figure 1 . It can be Figure 1 seen that the peaks at 13.133 and 27.184 are the characteristic peaks of C3N5; the peaks at 16.129, 18.830, 23.540, 29.117, 45.916 and 57.320 are the characteristic peaks of the used molybdate, fully indicating the successful preparation of the sample.

[0038] Figure 2 It is the infrared spectrum diagram of the sample. Among them, the peak at 495 cm -1 is caused by the symmetric or asymmetric vibration of Mo-O-Mo; the peak at 804 cm -1 is caused by the C-N bending vibration within the triazine unit; 1635, 1546, 1458, 1403, 1321, 1240, 1204 cm -1 are caused by the stretching vibrations of C-N and C=N; 3085 cm -1The peak at [location] is caused by the N-H stretching vibration of the uncondensed amino groups.

[0039] Figure 3 This is the UV diffuse reflectance spectrum of the prepared sample. It can be seen that the band gap of this material is 1.87 eV.

[0040] Figure 4 This is the particle size distribution diagram of the ground sample. It can be seen that the particle size of the ground sample is mainly distributed between 0.1 - 15 microns, and 70% of the particle diameters are below 5 microns.

[0041] Figure 5 This is a photo of the photocatalytic material prepared in Example 1 of the present invention.

[0042] Figure 6 This is the scanning electron micrograph of the prepared sample. It can be seen that after firing for a period of time, some spherical small particles are dispersed on the surface of the sample, which helps to increase the specific surface area of the sample and thus improve the catalytic efficiency.

[0043] Example 2

[0044] Weigh 2 grams of 3-amino-1,2,4-triazole and 0.005 grams of sodium molybdate dihydrate and grind them in a mortar for three minutes, then pour them into a 30 - milliliter crucible. Subsequently, place it in a muffle furnace, heat it to 550 °C within 180 minutes, and keep it at 550 °C for 3 hours, then cool it naturally to obtain a khaki powder, denoted as C3N5 / Mo-2, with a yield of 60%.

[0045] Comparative Example 1

[0046] Preparation of pure C3N5: Weigh 2 grams of 3-amino-1,2,4-triazole and grind it in a mortar for three minutes, then pour it into a 30 - milliliter crucible. Subsequently, place it in a muffle furnace, heat it to 550 °C within 180 minutes, and keep it at 550 °C for 3 hours, then cool it naturally to obtain a brownish - yellow powder, denoted as C3N5, with a yield of 60%.

[0047] Example 3

[0048] Photodegradation of methyl orange experiment: Disperse 5 milligrams of the photocatalyst powders prepared in Example 1 and Comparative Example 1 into 50 milliliters of methyl orange solution (10 milligrams / liter) respectively. The visible light source is a 300 - watt xenon lamp, 15 centimeters away from the liquid surface. Ultrasonic the solution for 0.5 hour and keep it in the dark for 0.5 hour to reach the adsorption - desorption equilibrium of methyl orange. Continuously stir the solution under magnetic stirring to keep it in a suspended state. Use a condensing pump to maintain the reaction temperature at 20 °C. React for 30 minutes, take 1 milliliter of the sample every 5 minutes, and centrifuge to remove the catalyst in the solution. Use a Varian50Bio UV - Vis spectrophotometer to record the absorbance. The results are as Figure 7 . From Figure 7It can be seen that after 20 minutes of turning on the light, compared with the pure C3N5 group, after incorporating metal Mo, the degradation effect of the catalyst on methyl orange can reach about 75%, while that of the pure C3N5 group is only about 20%. After 60 minutes of turning on the light, the degradation efficiency of C3N5 in the group incorporating metal Mo can reach about 90%, while that of the pure C3N5 group is only about 40%.

[0049] Example 4

[0050] Photodegradation of methylene blue experiment: 5 mg of the photocatalyst powders prepared in Example 1 and Comparative Example 1 were respectively dispersed into 50 mL of methylene blue solution (10 mg / L). The visible light source was a 300 w xenon lamp, 15 cm away from the liquid surface. The solution was ultrasonically treated for 0.5 h and kept in the dark for 0.5 h to reach the adsorption-desorption equilibrium of methylene blue. The solution needed to be continuously stirred under magnetic stirring to maintain a suspended state. A condensation pump was used to maintain the reaction temperature at 20 °C. The reaction lasted for 30 minutes, and 1 mL of sample was taken every 5 minutes. The catalyst in the solution was removed by centrifugation. The absorbance was recorded using a Varian50 Bio ultraviolet-visible spectrophotometer. The results are as Figure 8 . From Figure 8 It can be seen that after 20 minutes of turning on the light, compared with the pure C3N5 group, after incorporating metal Mo, the degradation effect of the catalyst on methylene blue can reach about 91%, while the degradation efficiency of the pure C3N5 group is only 70%. After 30 minutes of turning on the light, the degradation efficiency of the catalyst in the group incorporating metal Mo can reach 99%.

[0051] Example 5

[0052] Photodegradation of rhodamine experiment: 5 mg of the photocatalyst powders prepared in Example 1 and Comparative Example 1 were respectively dispersed into 50 mL of rhodamine solution (10 mg / L). The visible light source was a 300 w xenon lamp, 15 cm away from the liquid surface. The solution was ultrasonically treated for 0.5 h and kept in the dark for 0.5 h to reach the adsorption-desorption equilibrium of methylene blue. The solution needed to be continuously stirred under magnetic stirring to maintain a suspended state. A condensation pump was used to maintain the reaction temperature at 20 °C. The reaction lasted for 30 minutes, and 1 mL of sample was taken every 5 minutes. The catalyst in the solution was removed by centrifugation. The absorbance was recorded using a Varian50 Bio ultraviolet-visible spectrophotometer. The results are as Figure 9 . From Figure 9 It can be seen that after 30 minutes of being dark and static, the catalyst reached the adsorption equilibrium. After 20 minutes of turning on the light, compared with the pure C3N5 group, after incorporating metal Mo, the degradation effect of the catalyst on rhodamine can reach about 95%, which is about 4.75 times that of the pure C3N5 group.

[0053] Example 6

[0054] Photodegradation experiment of oxytetracycline: 5 mg of the photocatalyst powders prepared in Example 1 and Comparative Example 1 were respectively dispersed into 50 mL of oxytetracycline solution (10 mg / L). The visible light source was a 300 W xenon lamp, 15 cm away from the liquid surface. The solution was ultrasonically treated for 0.5 h and kept in the dark for 0.5 h to reach the adsorption-desorption equilibrium of methylene blue. The solution needed to be continuously stirred under magnetic stirring to maintain suspension. A condensation pump was used to maintain the reaction temperature at 20 °C. The reaction was carried out for 30 minutes, and 1 mL of sample was taken every 5 minutes. The catalyst in the solution was removed by centrifugation. The absorbance was recorded using a Varian 50 Bio ultraviolet-visible spectrophotometer. The results are as Figure 10 . It can be seen from Figure 10 that after standing in the dark for 30 minutes, the catalyst reached the adsorption equilibrium. After turning on the light for 30 minutes, the degradation effect of the C3N5 group sample on oxytetracycline was very unsatisfactory, while about 60% of oxytetracycline could be degraded after doping with metal Mo.

[0055] Example 7

[0056] Photodegradation experiment of penicillin: 5 mg of the photocatalyst powders prepared in Example 1 and Comparative Example 1 were respectively dispersed into 50 mL of penicillin solution (10 mg / L). The visible light source was a 300 W xenon lamp, 15 cm away from the liquid surface. The solution was ultrasonically treated for 0.5 h and kept in the dark for 0.5 h to reach the adsorption-desorption equilibrium of methylene blue. The solution needed to be continuously stirred under magnetic stirring to maintain suspension. A condensation pump was used to maintain the reaction temperature at 20 °C. The reaction was carried out for 30 minutes, and 1 mL of sample was taken every 5 minutes. The catalyst in the solution was removed by centrifugation. The absorbance was recorded using a Varian 50 Bio ultraviolet-visible spectrophotometer. The results are as Figure 11 . It can be seen from Figure 11 that after standing in the dark for 30 minutes, the catalyst reached the adsorption equilibrium. After turning on the light for 30 minutes, the degradation effect of the C3N5 group sample on penicillin was very unsatisfactory, only about 20%. While the degradation efficiency could reach 65% after doping with metal Mo.

[0057] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A molybdenum-doped carbon nitride photocatalytic material, characterized in that, The photocatalytic material is C3N5 / Mo material; the band gap of the photocatalytic material is 1.87 eV; the microstructure morphology is irregular granular; The preparation method of the molybdenum-doped carbon nitride photocatalytic material comprises the following steps: 1) Put 3-amino-1,2,4-triazole and molybdate into a mortar according to the molar ratio of 500:1 to 600:1, grind them, and then pour them into a crucible; 2) Place the crucible in a muffle furnace, heat it to 500-560 °C, and react for 2-3 hours to obtain the molybdenum-doped carbon nitride photocatalytic material.

2. The molybdenum-doped carbon nitride photocatalytic material according to claim 1, wherein The X-ray powder diffraction data of the photocatalytic material are 13.133°, 16.129°, 18.830°, 23.540°, 27.184°, 29.117°, 45.916° and 57.320°; the infrared spectroscopy data are 495 cm -1 , 804 cm -1 , 1204 cm -1 , 1240 cm -1 , 1321 cm -1 , 1403 cm -1 , 1458 cm -1 , 1546 cm -1 , 1635 cm -1 , 3085 cm -1 .

3. The molybdenum-doped carbon nitride photocatalytic material according to claim 1, wherein The molybdate described in step 1) is sodium molybdate, potassium molybdate or ammonium molybdate.

4. The molybdenum-doped carbon nitride photocatalytic material according to claim 1, wherein The particle size range of the material after grinding in step 1) is 1-15 microns.

5. The molybdenum-doped carbon nitride photocatalytic material according to claim 1, wherein, The molar ratio of 3-amino-1,2,4-triazole to molybdate in step 1) is 575:

1.

6. The molybdenum-doped carbon nitride photocatalytic material according to claim 1, wherein In step 2), the reaction temperature is 550 °C and the reaction time is 3 hours.

7. The molybdenum-doped carbon nitride photocatalytic material according to claim 1, characterized in that, The heating rate range in step 2) is 3-6 °C per minute.

8. The application of the molybdenum-doped carbon nitride photocatalytic material according to any one of claims 1-7 in the photocatalytic degradation of organic pollutants.

9. The application according to claim 8, wherein The organic pollutants are one or more mixtures of methyl orange, methylene blue, rhodamine, oxytetracycline, and penicillin.

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