Preparation method of cerium dioxide-carbon nitride high-efficiency heterojunction based on defect anchoring

Abstract

The application discloses a preparation method of a defect-anchored cerium dioxide-carbon nitride high-efficiency heterojunction. 3+ The method is simple, easy to implement in industry, and high in heterojunction carrier separation efficiency and photocatalytic performance.

Description

Technical Field

[0001] This invention relates to a method for preparing a cerium dioxide-carbon nitride high-efficiency heterojunction, and more particularly to a method for preparing a cerium dioxide-carbon nitride high-efficiency heterojunction based on defect anchoring. Background Technology

[0002] Photocatalysis, as a highly efficient, environmentally friendly, and simple catalytic reaction, is widely used in wastewater treatment, hydrogen production, and bacterial disinfection. Photocatalysts are the foundation and core of photocatalytic reactions, and cerium dioxide, as a commonly used photocatalyst, has been extensively studied and reported due to its good redox properties and oxygen storage capacity. However, the development and application of cerium-based photocatalysts are limited by problems such as the large band gap and excessively rapid recombination of photogenerated electrons / holes inherent in cerium dioxide.

[0003] Constructing cerium-based composite catalysts is one of the commonly used methods to improve the performance of cerium-based catalysts. Common composite methods include sintering, molten salt method, hydrothermal method, mechanical ball milling method, in-situ growth method, and thermal calcination method. For example, patent CN109338512A discloses a method for preparing cerium oxide-alumina fibers by thermal calcination, which improves the photocatalytic performance.

[0004] Carbon nitride is a commonly used catalyst substrate material. Its defective structures, such as nitrogen and carbon vacancies, can facilitate the separation of photogenerated electron / hole pairs. Combining it with cerium dioxide can significantly improve photocatalytic performance. For example, patent CN113731394A discloses a molten salt method cerium dioxide-carbon nitride composite material, which exhibits significantly improved photocatalytic activity.

[0005] Meanwhile, photo-assisted preparation of composite materials is a commonly used method. For example, patent CN109046436A discloses a method for photo-assisted preparation of Fe2O3 quantum dot / carbon nitride photocatalysts, which improves the photocatalytic hydrogen evolution performance.

[0006] For example, patent CN111215066A discloses a photo-assisted Pt / BiVO4 / Bi2O3 catalyst with good photoelectrocatalytic oxidation performance of methanol.

[0007] However, there are currently no studies on material preparation using direct defect anchoring, and few reports on the preparation of cerium dioxide-carbon nitride composites using light-assisted methods. Therefore, this invention proposes a method of preparing high-efficiency cerium dioxide-carbon nitride heterojunctions by using light-induced defect anchoring in cerium salt solutions, providing a new approach for the preparation and production of related materials. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring. This method is simple, easy to implement industrially, and produces a heterojunction with high carrier separation efficiency and strong photocatalytic performance.

[0009] The technical solution of the present invention:

[0010] A method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring involves using a defect-rich C3N4 material as a matrix, mixing it with cerium salt, and then loading Ce at the defect sites through photoradiative excitation. 3+ Then, after calcination, a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring is obtained.

[0011] Preferably, the aforementioned method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring specifically includes the following steps:

[0012] S1. C3N4 material rich in defect states was synthesized using conventional methods;

[0013] S2. Disperse the defect-rich C3N4 material with cerium salt in water to obtain a suspension;

[0014] S3. Stir the suspension under light in a water bath, then filter and dry to obtain the precursor;

[0015] S4. The precursor is placed in a furnace and calcined to obtain a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring.

[0016] Preferably, in the aforementioned method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring, the defect type in the defect-rich C3N4 material is a carbon vacancy defect or a nitrogen vacancy defect.

[0017] Preferably, in the aforementioned method for preparing a high-efficiency heterojunction of cerium dioxide-carbon nitride based on defect anchoring, the cerium salt is one or any combination of cerium nitrate, cerium chloride, cerium sulfate, or cerium acetate.

[0018] Preferably, in the aforementioned method for preparing the high-efficiency heterojunction of cerium dioxide-carbon nitride based on defect anchoring, the molar concentration of cerium salt in the suspension is 0.01-0.75 mol / L.

[0019] Preferably, in the aforementioned method for preparing the defect-anchored cerium dioxide-carbon nitride high-efficiency heterojunction, the mass concentration of C3N4 material rich in defect states in the suspension is 0.5-25 g / L.

[0020] Preferably, in the aforementioned method for preparing cerium dioxide-carbon nitride high-efficiency heterojunctions based on defect anchoring, the temperature of the water bath is 30-60°C.

[0021] Preferably, in the aforementioned method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring, the light source for illumination is a xenon lamp, high-intensity visible light, or ultraviolet light, with an illumination intensity of 1.00–1.12 W / cm². 2 Light exposure time: 1-8 hours.

[0022] Preferably, in the aforementioned method for preparing cerium dioxide-carbon nitride high-efficiency heterojunction based on defect anchoring, the calcination temperature is 200-500℃ and the time is 2-8h.

[0023] A high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring was prepared by the aforementioned method.

[0024] The beneficial effects of this invention are:

[0025] 1. The method of the present invention is to generate photogenerated carriers at the active defect sites of carbon nitride by light excitation, and to adsorb cerium dioxide in situ to form a metal load. Since the cerium dioxide loading sites are defect sites and active sites, the cerium dioxide load of the present invention can be theoretically constructed, thereby achieving a significant improvement in the performance of the photocatalyst and enhancing the industrial application value of related materials.

[0026] 2. After the preparation is completed, the surface of carbon nitride is still rich in defective structures such as nitrogen vacancies and carbon vacancies, which is beneficial to promote the efficient separation of photogenerated electron / hole pairs and further improve the performance of the photocatalyst.

[0027] 3. The filtrate prepared by the method of the present invention after the reaction is completed can be evaporated to recover cerium salt and reused, which can further save rare earth resources and reduce pollution emissions, in line with the relevant requirements of energy conservation and emission reduction advocated by the state.

[0028] 4. The preparation method of the present invention is simple and easy to promote and implement on an industrial scale.

[0029] In summary, the defect-anchored cerium dioxide-carbon nitride high-efficiency heterojunction preparation method of the present invention has good theoretical and production value. The high-performance composite photocatalyst obtained by this method has the advantages of excellent photocatalytic performance, green and environmentally friendly preparation process, saving rare earth resources, wide applicability, simple operation and low cost. While ensuring reproducibility and theoretical feasibility, this method also provides new preparation ideas and theoretical support for the industrial production and application of related high-performance photocatalytic composite materials. Attached Figure Description

[0030] Appendix Figure 1 This is a comparison of the photocatalytic hydrogen production rate results of Example 1 of the present invention with those of Comparative Examples 1, 2, and 3.

[0031] Appendix Figure 2 The results of the cyclic hydrogen production rate in Example 1 of the present invention;

[0032] Appendix Figure 3 The images are SEM images of (a) Example 1 and (b) Comparative Example 1 of the present invention;

[0033] Appendix Figure 4 The XPS results are for Example 1 of this invention;

[0034] Appendix Figure 5 This is an XPS image of Comparative Example 1 of the present invention;

[0035] from Figure 1 It can be seen that the photocatalytic ability of Example 1 obtained through the above preparation method is significantly improved. From Figure 2 As can be seen, Example 1 prepared by the above method exhibits good cycle performance and can be reused for industrial production. From... Figure 3 As can be seen, cerium dioxide is uniformly distributed on carbon nitride, indicating that the method proposed in this patent can effectively load cerium dioxide. Furthermore, compared to Comparative Example 1, the morphology of Example 1 of this invention remains almost unchanged, indicating that this loading method does not damage the morphology of defect states and can effectively preserve the defect state structure on carbon nitride. Figure 4 China and Figure 5 The comparison further shows that Example 1 still has abundant vacancy structures such as nitrogen vacancies and carbon vacancies. These defective state structures can effectively promote the separation of photogenerated carriers and thus improve photocatalytic performance. Detailed Implementation

[0036] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0037] Embodiments of the present invention

[0038] Example 1:

[0039] (1) C3N4 material rich in defect states was prepared by conventional molten salt method;

[0040] (2) 0.1 g of C3N4 material rich in defect states was dispersed with 10 mmol of cerium nitrate in 80 mL of water to obtain a suspension;

[0041] (3) The suspension was placed in a 45°C water bath under a xenon lamp (light intensity 1.00 W / cm²). 2 Exposure to light for 4 hours;

[0042] (4) After the solid is filtered, collected and dried, it is calcined in a resistance furnace at 300°C for 5 hours to obtain a high-efficiency heterojunction of cerium dioxide-carbon nitride based on defect anchoring.

[0043] Example 2:

[0044] (1) Prepare C3N4 material rich in defect states by thermal reforming;

[0045] (2) 0.3 g of C3N4 material rich in defect states was dispersed with 6 mmol of cerium acetate in 70 mL of water to obtain a suspension;

[0046] (3) The suspension was placed in a 30°C water bath under a xenon lamp (light intensity 1.00 W / cm²). 2 8 hours of light exposure;

[0047] (4) After the solid is filtered, collected and dried, it is calcined in a resistance furnace at 200°C for 9 hours to obtain a high-efficiency heterojunction of cerium dioxide-carbon nitride based on defect anchoring.

[0048] Example 3:

[0049] (1) Prepare C3N4 material rich in defect states by molten salt method;

[0050] (2) 0.08 g of C3N4 material rich in defect states was dispersed with 5 mmol of cerium sulfate in 60 mL of water to obtain a suspension;

[0051] (3) The suspension was placed in a 60°C water bath under a xenon lamp (light intensity 1.12 W / cm²). 2 Irradiation for 1 hour;

[0052] (4) After the solid is filtered, collected and dried, it is calcined in a resistance furnace at 500°C for 2 hours to obtain a high-efficiency heterojunction of cerium dioxide-carbon nitride based on defect anchoring.

[0053] Example 4:

[0054] (1) Prepare C3N4 material rich in defect states by hydrothermal method;

[0055] (2) 0.7 g of C3N4 material rich in defect states was dispersed with 20 mmol of cerium nitrate in 100 mL of water to obtain a suspension;

[0056] (3) The suspension was placed in a 50°C water bath under a xenon lamp (light intensity 1.07 W / cm²). 2 Expose to light for 5 hours;

[0057] (4) After the solid is filtered, collected and dried, it is calcined in a resistance furnace at 300°C for 4 hours to obtain a high-efficiency heterojunction of cerium dioxide-carbon nitride based on defect anchoring.

[0058] Example 5:

[0059] (1) Prepare C3N4 material rich in defect states by hydrothermal method;

[0060] (2) 0.3 g of C3N4 material rich in defect states was dispersed with 10 mmol of cerium nitrate in 80 mL of water to obtain a suspension;

[0061] (3) The suspension was placed in a 50°C water bath under a xenon lamp (light intensity 1.05 W / cm²). 2 Expose to light for 3 hours;

[0062] (4) After the solid is filtered, collected and dried, it is calcined in a resistance furnace at 300°C for 7 hours to obtain a high-efficiency heterojunction of cerium dioxide-carbon nitride based on defect anchoring.

[0063] Comparative examples of the present invention:

[0064] Comparative Example 1:

[0065] C3N4 materials rich in defect states prepared by molten salt method

[0066] (1) Mix 5g of melamine with 18g of potassium chloride-lithium chloride mixed molten salt (potassium chloride-lithium chloride molar ratio is 49:51), add 10mL of anhydrous ethanol, and grind in a corundum crucible for 10min.

[0067] (2) Transfer the mixture into a covered corundum crucible, heat it to 500°C at 5°C / min and calcine it in air for 4 hours.

[0068] (3) After cooling to room temperature in the furnace, the product is filtered and washed multiple times with deionized water and dried at 80°C for 12 hours to obtain C3N4 material rich in defect states.

[0069] Comparative Example 2:

[0070] Cerium dioxide-carbon nitride prepared under no light irradiation

[0071] (1) Disperse 0.1g of Comparative Example 1 and 10mmol of cerium nitrate in 80mL of water to obtain a suspension;

[0072] (2) Stir the suspension at 45°C for 4 hours;

[0073] (3) After the solid is filtered, collected and dried, it is calcined in a resistance furnace at 300°C for 5 hours to obtain the cerium dioxide-carbon nitride composite material.

[0074] Comparative Example 3:

[0075] Phototreated carbon nitride substrate

[0076] (1) Disperse 0.1g of Comparative Example 1 in 80mL of water to obtain a suspension;

[0077] (2) The suspension was heated at 45°C with a xenon lamp (light intensity 1.00 W / cm²). 2 Exposure to light for 4 hours;

[0078] (3) After the solid is filtered, collected and dried, it is calcined in a resistance furnace at 300°C for 5 hours to obtain a photo-treated carbon nitride substrate.

[0079] Table 1 below compares the hydrogen production and rate of Example 1 with Comparative Examples 1, 2, and 3 after 3 hours. It can be seen that the cerium dioxide-carbon nitride composite photocatalyst obtained by the defect-anchored cerium dioxide-carbon nitride high-efficiency heterojunction preparation method proposed in this invention can effectively achieve a significant improvement in photocatalytic activity. Furthermore, comparing Example 1 with Comparative Examples 2 and 3, the performance of Example 1 is significantly improved, indicating that this performance improvement is related to the synergistic effect of light treatment and cerium dioxide loading.

[0080] Table 1 Comparison of Photocatalytic Hydrogen Production and Rate

[0081]

[0082] First-principles calculations show that carbon nitride has a certain effect on Ce under illumination. 3+ The adsorption energy is -12.042 eV. Table 2 below compares the adsorption energies of carbon nitride with one different defect. As shown in the table, under illumination, surfaces with defective structures are more likely to attract Ce. 3+ This indicates that Ce 3+ CeO2 is more likely to appear on defect-state structures; the adsorption energy of surfaces with nitrogen vacancies is higher than that of surfaces with carbon vacancies, indicating that nitrogen vacancies are more conducive to the adsorption of Ce. 3+ This leads to the formation of CeO2.

[0083] Table 2 contains one different defect affecting Ce. 3+ Adsorption Energy Comparison Table

[0084]

[0085] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring, characterized in that, Includes the following steps: S1. C3N4 material rich in defect states was synthesized using conventional methods; S2. Disperse the defect-rich C3N4 material with cerium salt in water to obtain a suspension; S3. The suspension is stirred under light in a water bath, and excited by light radiation. Defect load Ce 3+ Then filter and dry to obtain the precursor; S4. The precursor is placed in a furnace for calcination to obtain a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring; The molar concentration of cerium salt in the suspension is 0.01-0.75 mol / L; The suspension contains a C3N4 material rich in defect states at a mass concentration of 0.5-25 g / L.

2. The method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring according to claim 1, characterized in that: The defect types in the C3N4 material rich in defect states are carbon vacancy defects or nitrogen vacancy defects.

3. The method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring according to claim 1, characterized in that: The cerium salt is one or any combination of cerium nitrate, cerium chloride, cerium sulfate, or cerium acetate.

4. The method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring according to claim 1, characterized in that: The temperature of the water bath is 30-60℃.

5. The method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring according to claim 1, characterized in that: The light source is a xenon lamp, high-intensity visible light, or ultraviolet light, with a light intensity of 1.00-1.12 W / cm². 2 Light exposure time: 1-8 hours.

6. The method for preparing a high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring according to claim 1, characterized in that: The roasting temperature is 200-500℃, and the time is 2-8 hours.

7. A high-efficiency cerium dioxide-carbon nitride heterojunction based on defect anchoring prepared by the method according to any one of claims 1-6.

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