A bifunctional catalyst, its preparation method and use

Abstract

The application discloses a bifunctional catalyst and a preparation method and application thereof, relates to the technical field of catalytic materials, and comprises a carrier, single-atom Ag and nano Ag clusters dispersed on the carrier, and the catalyst obtained by loading single-atom Ag and nano Ag clusters on the surface of the carrier has the dual functions of synthesizing hydrogen peroxide and efficiently degrading tetracycline in sewage. Meanwhile, the concentration of hydroxyl radicals synthesized by the bifunctional catalyst is significantly higher than that of other catalysts, the bifunctional catalyst has higher reaction activity, can completely degrade tetracycline in sewage within 10 min, and the degradation rate is as high as 0.36 min ‑1 .

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalytic materials, in particular to a bifunctional catalyst and a preparation method and application thereof. BACKGROUND

[0002] In recent years, in the forefront research field of modern sewage treatment technology, photocatalytic oxygen reduction reaction has become an important direction with great application potential due to its unique reaction mechanism and environmental friendly characteristics, which has far-reaching significance for promoting sewage treatment technology to develop in a green and efficient direction.

[0003] In the related art, a catalyst is used to catalyze oxidation to form hydrogen peroxide, and the generated hydrogen peroxide is used to remove organic pollutants in sewage. Although hydrogen peroxide has certain redox activity, its redox activity is still low in a complex sewage environment, and it cannot degrade various types of difficult-to-degrade organic pollutants.

[0004] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present disclosure, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0005] The technical task of the present application is to solve the above problems, and provide a bifunctional catalyst and a preparation method and application thereof. The catalyst obtained by loading single atom Ag and nano Ag clusters on the surface of a carrier has the dual functions of synthesizing hydrogen peroxide and efficiently degrading tetracycline in sewage.

[0006] To achieve the above object, the present application provides the following technical solutions:

[0007] According to one aspect of the present application, a bifunctional catalyst is provided, comprising: a carrier and single atom Ag and nano Ag clusters dispersed on the carrier.

[0008] In some embodiments, the carrier is polyheptazine imide.

[0009] In some embodiments, the loading amount of Ag on the carrier is 0.5-5wt%.

[0010] According to another aspect of the present application, a preparation method of a bifunctional catalyst is also provided, comprising: adding NaBH4 to AgNO3 solution and stirring for 1 min, then adding polyheptazine imide and stirring for 3-5 h, filtering after stirring, drying the filtered solid material at 40-60°C for 6-12 h, to obtain a bifunctional catalyst with coexistence of single atom Ag and nano Ag clusters on the surface.

[0011] In some embodiments, the concentration of the AgNO3 solution is 0.05-0.5 mg / mL.

[0012] In some embodiments, the ratio of the addition amount of the AgNO3 solution, the NaBH4 and the polyheptazine imidazole is 10 ml:0.1 mg:100 mg.

[0013] In some embodiments, the preparation method of the polyheptazine imidazole comprises: uniformly mixing lithium chloride, potassium chloride and graphite phase carbon nitride in a mortar to obtain a mixture; placing the mixture into a crucible, heating the crucible to 400-600 DEG C at a heating rate of 5-10 DEG C / min in an air environment, keeping the temperature for 2-4 h, then washing with water at a temperature of 60 DEG C-80 DEG C for 2-4 h, filtering, drying the filtered solid substance at 40 DEG C-60 DEG C for 6-12 h to obtain the polyheptazine imidazole.

[0014] In some embodiments, the mass ratio of the lithium chloride, the potassium chloride and the graphite phase carbon nitride is 4.5:5.5:1.

[0015] According to another aspect of the present application, the application further provides a use of a bifunctional catalyst in the synthesis of hydrogen peroxide by photo and electro catalytic oxygen reduction and in the photocatalytic degradation of tetracycline.

[0016] In some embodiments, the photocatalytic degradation of tetracycline is photocatalytic degradation of tetracycline in wastewater.

[0017] Compared with the prior art, the application has the advantages and positive effects that: the catalyst obtained by loading single-atom Ag and nano Ag clusters on the surface of a carrier has the dual functions of synthesizing hydrogen peroxide and efficiently degrading tetracycline in wastewater.

[0018] Further, the concentration of hydroxyl radicals synthesized by the bifunctional catalyst is significantly higher than that of other catalysts, the bifunctional catalyst has higher reaction activity, can completely degrade tetracycline in wastewater within 10 min, and the degradation rate is as high as 0.36 min -1 . BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0020] Figure 1The microstructure images of the bifunctional catalyst in Example 1 of the present application are shown, wherein a is a TEM morphology image, b is a high-resolution lattice photograph, and c is a spherical aberration-corrected image;

[0021] Figure 2 The XRD patterns of the catalysts in Example 1 and Comparative Examples 1-3 of the present application are shown;

[0022] Figure 3 The synchrotron radiation patterns of the catalysts in Example 1 and Comparative Examples 2-3 of the present application are shown, wherein a is an X-ray absorption near-edge structure, and b is a fitting result in R space;

[0023] Figure 4 The XPS patterns of the catalysts in Example 1 and Comparative Examples 1-3 of the present application are shown;

[0024] Figure 5 The performance diagrams of the photocatalytic synthesis of hydrogen peroxide of the catalysts in Example 1 and Comparative Examples 1-3 of the present application are shown;

[0025] Figure 6 The performance diagrams of the photocatalytic synthesis of ·OH of the catalysts in Example 1 and Comparative Examples 1-3 of the present application are shown;

[0026] Figure 7 The performance diagrams of the photocatalytic degradation of tetracycline of the catalysts in Example 1 and Comparative Examples 1-3 of the present application are shown. DETAILED DESCRIPTION

[0027] In order to enable a clearer understanding of the above-mentioned purposes, features and advantages of the present application, the present application will be further described below in conjunction with the drawings and examples. It should be noted that the examples of the present application and the features in the examples can be combined with each other without conflict.

[0028] The present application will be further described below in conjunction with the drawings and specific examples.

[0029] Example 1: Preparation of a bifunctional catalyst coexisting surface monatomic Ag and nano Ag clusters, the specific steps are as follows:

[0030] S100, preparation of polyheptazine imide (PHI): lithium chloride, potassium chloride and graphite phase carbon nitride are uniformly mixed in a mortar, and the mass ratio of lithium chloride, potassium chloride and graphite phase carbon nitride is 4.5:5.5:1. The mixed material is placed in a crucible and heated to 550℃ at a heating rate of 5℃ / min under air, and kept for 4h. Then it is washed with 80℃ water for 2h, filtered and dried at 40℃ for 12h, and finally PHI is obtained.

[0031] S200, preparation of a bifunctional catalyst coexisting surface monatomic Ag and nano Ag clusters (PHI-Ag SA / NC ):

[0032] 0.1 mg of NaBH4 was added to 10 mL of a 0.2 mg / mL AgNO3 aqueous solution and stirred for 1 min. Then, it was mixed with 100 mg of PHI and stirred for 3 h. The mixture was then filtered and dried at 60 °C for 12 h to obtain PHI-Ag with a coexistence of Ag atoms / clusters on the surface. SA / NC catalyst.

[0033] Comparative Example 1: PHI was prepared using the method in S100 of Example 1.

[0034] Comparative Example 2: Preparation of Ag-atom-dispersed PHI catalyst PHI-Ag SA .

[0035] 100 mg of PHI obtained in Comparative Example 1 was dispersed in 100 mL of water, then mixed with a 2 mg / mL silver nitrate solution, stirred for 0.5 h, filtered, and dried at 40 °C for 12 h to finally obtain the Ag atom-dispersed PHI catalyst PHI-Ag. SA .

[0036] Comparative Example 3: Preparation of Ag-clustered PHI catalyst PHI-Ag NC。

[0037] 50 μL of polyethyleneimine was added to 1 mL of a 2 mg / mL silver nitrate solution and stirred. Then, 5 μL of formaldehyde solution was added and stirred overnight to obtain an Ag cluster solution. 100 mg of PHI obtained in Comparative Example 1 was dispersed in 100 mL of water, and the Ag cluster solution was added and stirred for 3 h. The mixture was then filtered and dried at 40 °C for 6–12 h to finally obtain the Ag cluster-dispersed PHI catalyst PHI-Ag. NC .

[0038] Figure 1 The image shows the microstructure of the bifunctional catalyst in Example 1 of this application, where a is a TEM image, b is a high-resolution lattice photograph, and c is an aberration-corrected image. Figure 1 As shown, lattice fringes can be clearly seen through TEM morphology images and high-resolution lattice photographs, indicating that the catalyst has been successfully synthesized. Through aberration-corrected images, it can be clearly observed that Ag clusters and single-atom Ag have been successfully loaded onto the PHI surface. The yellow dashed lines accurately circle the positions of Ag clusters, while the red solid lines circle the locations of single-atom Ag.

[0039] Figure 2 The XRD patterns of the catalysts in Example 1 and Comparative Examples 1-3 of this application are shown. Figure 2As shown, the characteristic peaks at 8° and 27° correspond to the (100) and (002) crystal planes of PHI, respectively, which further demonstrates the successful preparation of PHI. However, after loading Ag clusters and single-atom Ag, the XRD pattern of the catalyst did not change significantly, which means that the crystal structure of PHI was not substantially affected by the loading process.

[0040] Figure 3 The synchrotron radiation spectra of the catalysts in Example 1 and Comparative Examples 2-3 of this application are shown, where a is the X-ray absorption near-edge structure and b is the fitting result in R-space. Figure 3 As shown, single-atom Ag has been successfully loaded onto PHI-Ag. SA Meanwhile, Ag clusters have also been successfully loaded onto PHI-Ag. NC superior.

[0041] Figure 4 The XPS spectra of the catalysts in Example 1 and Comparative Examples 1-3 of this application are shown. Figure 4 As shown, an Ag signal peak was detected at 370 nm, proving that Ag has been successfully loaded onto the PHI surface.

[0042] The catalysts obtained in Example 1 and Comparative Examples 1-3 were tested for photocatalytic hydrogen peroxide synthesis. Specifically, 25 mg of catalyst was dispersed in 50 ml of water, 5 ml of isopropanol was added, and the mixture was ultrasonically dispersed. Oxygen was then introduced, and the reaction was carried out under a 300 W xenon lamp for 10 min. Every 2 min, 1 mL of the reaction solution was added to 1 mL of 0.4 M KI solution and 1 mL of 0.1 M potassium hydrogen phthalate solution. After standing for 20 min, the change in absorbance of the mixture was detected at 350 nm using a spectrophotometer to test the photocatalytic oxygen reduction synthesis of hydrogen peroxide.

[0043] Figure 5 The diagram shows the photosynthetic hydrogen peroxide performance of the catalysts in Example 1 and Comparative Examples 1-3 of this application. Figure 5 As shown, PHI-Ag NC The catalyst's ability to synthesize hydrogen peroxide is significantly higher than other catalysts, with a hydrogen peroxide yield as high as 550 μM, meaning that PHI-Ag... NC The catalyst significantly promoted the synthesis of hydrogen peroxide.

[0044] The catalysts obtained in Example 1 and Comparative Examples 1-3 were subjected to photosynthetic hydroxyl radical (·OH) concentration tests. Specifically, 25 mg of catalyst was dispersed in 50 ml of 0.1 mM terephthalic acid solution. After ultrasonic dispersion, the reaction was carried out under 300 W xenon lamp illumination. The concentration of terephthalic acid was detected by liquid chromatography to test the photocatalytic synthesis ·OH concentration.

[0045] Figure 6 The diagram shows the photosynthesis ·OH performance of the catalysts in Example 1 and Comparative Examples 1-3 of this application. Figure 6 As shown, PHI-Ag SA / NC The concentration of ·OH in the photosynthesis catalyst PHI-Ag was significantly higher than that in other catalysts. SA Catalysts are secondary, PHI-Ag NC The catalyst is relatively poor, meaning that successful loading of Ag clusters can significantly improve the catalyst's ability to photosynthesize ·OH.

[0046] The catalysts obtained in Example 1 and Comparative Examples 1-3 were tested for photocatalytic degradation of tetracycline. Specifically, 25 mg of catalyst was dispersed in 50 ml of 20 ppm tetracycline solution, and after being ultrasonically dispersed evenly, the reaction was carried out under 300 W xenon lamp illumination. The concentration of tetracycline was detected by liquid chromatography to test the photocatalytic degradation performance of tetracycline.

[0047] Figure 7 The diagram shows the photocatalytic degradation performance of tetracycline by the catalysts in Example 1 and Comparative Examples 1-3 of this application. Figure 7 As shown, PHI-Ag SA / NC The catalyst can completely degrade tetracycline within 10 minutes, with a degradation rate as high as 0.36 minutes. -1 This is because hydroxyl radicals are one of the important reactive species in the photocatalytic degradation of organic matter, PHI-Ag SA / NC The catalyst can photosynthesize more ·OH, thus having higher reactivity. At the same time, hydrogen peroxide and ·OH can work together on organic matter to achieve more efficient degradation.

[0048] It should be noted that the catalyst in this embodiment can be selected according to different actual application scenarios. For example, in application scenarios where the main goal is to synthesize hydrogen peroxide, a catalyst with only single-atom Ag loaded on its surface can be selected. However, in application scenarios where the main goal is to treat wastewater, a catalyst that simultaneously loads single-atom Ag and Ag clusters can be used to meet the actual needs. This ensures that the best application effect can be achieved by reasonably selecting the catalyst in different application scenarios.

[0049] Through the above specific embodiments, those skilled in the art can easily implement this application. However, it should be understood that this application is not limited to the specific embodiments described above. Based on the disclosed embodiments, those skilled in the art can arbitrarily combine different technical features to achieve different technical solutions.

Claims

1. A bifunctional catalyst, characterized in that, include: The support and single-atom Ag and nano-Ag clusters dispersed on the support, wherein the support is polyheptaquinone imide and the loading of Ag on the support is 0.5~5wt%; the bifunctional catalyst is a catalyst for photocatalytic oxygen reduction to synthesize hydrogen peroxide and for photocatalytic degradation of tetracycline. A method for preparing a bifunctional catalyst includes: adding NaBH4 to an AgNO3 solution and stirring for 1 min, then adding polyheptaquinone imide and stirring for 3-5 h, filtering after stirring, and drying the filtered solid at 40℃-60℃ for 6-12 h to obtain a bifunctional catalyst in which surface single-atom Ag and nano Ag clusters coexist; the concentration of the AgNO3 solution is 0.05-0.5 mg / mL; the ratio of the added AgNO3 solution, NaBH4 and polyheptaquinone imide is 10 mL: 0.1 mg: 100 mg.

2. The bifunctional catalyst according to claim 1, characterized in that, The preparation method of the polyheptaquinone imide includes: Lithium chloride, potassium chloride, and graphitic carbon nitride are mixed evenly in a mortar to obtain a mixture. The mixture is placed in a crucible, and the crucible is heated to 400-600°C in air at a heating rate of 5-10°C / min and held for 2-4 hours. Then, it is washed with water at 60-80°C for 2-4 hours, filtered, and the filtered solid is dried at 40-60°C for 6-12 hours to obtain the polyheptaquinone imide.

3. The bifunctional catalyst according to claim 2, characterized in that, The mass ratio of the lithium chloride, potassium chloride, and graphitic carbon nitride is 4.5:5.5:

1.

4. The application of the bifunctional catalyst according to any one of claims 1-3 in the photocatalytic oxygen reduction synthesis of hydrogen peroxide and in the photocatalytic degradation of tetracycline.

5. The application according to claim 4, characterized in that, The photocatalytic degradation of tetracycline refers to the photocatalytic degradation of tetracycline in wastewater.

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