Preparation method of nitrogen-doped cerium dioxide catalytic material loaded with high-dispersity Pd

Abstract

The invention discloses a preparation method of a nitrogen-doped cerium dioxide catalytic material loaded with high-dispersity Pd, which comprises the following steps: by taking nitrogen-doped cerium dioxide as a base material, carrying out optical excitation activation, and loading Pd < 2 + > at a nitrogen-doped site, thereby obtaining the nitrogen-doped cerium dioxide catalytic material loaded with high-dispersity Pd. The method is simple and easy to implement industrially, and the prepared catalytic material is excellent in performance and stable in chemical property.

Description

Technical Field

[0001] This invention relates to a method for preparing cerium dioxide catalytic materials, and more particularly to a method for preparing nitrogen-doped cerium dioxide catalytic materials loaded with highly dispersed Pd. Background Technology

[0002] Humans are constantly exploring clean energy sources to replace non-renewable energy sources such as fossil fuels. Clean energy should possess characteristics such as being renewable, environmentally friendly, and producing no harmful substances after combustion. Photocatalytic water splitting for hydrogen production is an effective and green method for preparing H2. The reaction process, which converts solar energy into hydrogen energy, consumes no non-renewable energy and produces no pollutants, making it a key research area. This energy conversion requires semiconductor materials as photocatalysts. Cerium dioxide, due to its excellent redox properties and non-toxicity, is a commonly used photocatalyst and has received extensive research. However, its high band gap energy (3.2 eV) and the ease with which photogenerated electron-hole pairs recombine limit the further application of cerium-based catalysts.

[0003] To improve the photogenerated charge separation and transport efficiency of cerium-based catalysts, the main methods currently employed include noble metal doping, composite semiconductors, and transition or rare earth element doping. The improvement in quantum efficiency through the addition of noble metals may be attributed to the rapid transfer of photogenerated electrons from the semiconductor to the noble metal particles, leading to effective electron-hole separation. Furthermore, loading noble metals can extend the absorption range of semiconductor catalysts in the visible light region. For example, patent CN111790383A discloses a scheme for preparing CeO2-supported Pd nanocatalysts using an in-situ reduction-bath method, which significantly enhances the photocatalytic activity of the catalyst. Literature (Chemicalengineeringjournal, 2022, 450, 137873) utilizes TiO2 as a photocatalyst; after loading palladium nanoparticles, the hydrogen production efficiency of Pd / TiO2 under visible light irradiation is increased by 14.9 times. The literature (Chinese Journal of Catalysis, 2020, 41(6), 938-950) utilizes the redox properties of cerium dioxide to load Pd nanoparticles onto the surface of cerium dioxide, forming a strong Pd-Ce metal-support interaction, thereby enhancing the stability and catalytic performance of the catalyst.

[0004] Furthermore, nitrogen atoms are similar in size to oxygen atoms and have a low ionization energy, allowing them to replace oxygen in CeO2 and produce a large amount of Ce. 3+ In its patent CN115520893B, Vol. disclosed a method for obtaining high-N-doped nano-CeO2 by impregnation with a nitrogen source solution followed by calcination under a certain atmosphere, which further improves the charge transport characteristics of CeO2.

[0005] Photo-assisted synthesis is a common method for preparing composite catalytic materials. Patent CN111215066B discloses a method for preparing a Pt / BiVO4 / Bi2O3 heterojunction supported on noble metals. This method involves loading Pt nanoparticles onto BiVO4, utilizing the decomposition of BiVO4 into Bi2O3 and V2O5 under ultraviolet irradiation to obtain Pt / BiVO4 / Bi2O3. Because this product is generated in situ, it has advantages over samples with physically mixed BiVO4 and Bi2O3, such as a larger interface area, faster photogenerated charge transport rate, and higher photoelectrocatalytic performance. A related study (Journal of Colloid and Interface Science, 2019, 552, 179-185) used two-dimensional ultrathin bismuth tungstate (Bi2WO6) nanosheets as a photocatalyst to support platinum nanoparticles. Under simulated solar irradiation conditions, the electrocatalytic oxidation activity of Pt / Bi2WO6 for methanol was 5.1 times that under dark-field conditions, demonstrating excellent methanol oxidation performance.

[0006] However, existing photo-assisted methods for preparing heterojunctions suffer from problems such as small interfacial area and insufficient contact, resulting in low photogenerated charge separation and transport efficiencies. Therefore, developing stable composite photocatalysts with good interfacial contact is of great significance. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for preparing nitrogen-doped cerium dioxide catalytic materials loaded with highly dispersed Pd. The method of this invention is simple, easy to implement industrially, and produces catalytic materials with excellent performance and stable chemical properties.

[0008] The technical solution of the present invention:

[0009] A method for preparing a nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd involves using nitrogen-doped cerium dioxide as the matrix material, activating it through photoexcitation, and then loading Pd onto the nitrogen-doping sites. 2+ Thus, nitrogen-doped cerium dioxide catalytic materials with highly dispersed Pd loading are obtained.

[0010] Preferably, the preparation method of the aforementioned nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd includes the following specific steps:

[0011] S1. Take nitrogen-doped cerium dioxide, dissolve it in methanol solution, and obtain product A;

[0012] S2. Add palladium chloride to product A, dissolve by sonication, and stir to adsorb, to obtain product B;

[0013] S3. Irradiate product B under ultraviolet light to excite and activate nitrogen-doped sites, thereby enabling Pd2+ Loaded onto nitrogen-doped sites, C product is obtained;

[0014] S4. After removing product C, filter and dry it to obtain nitrogen-doped cerium dioxide catalyst material loaded with highly dispersed Pd.

[0015] Preferably, in the aforementioned method for preparing nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd, the concentration of nitrogen-doped cerium dioxide in product A is 0.13-10 g / L.

[0016] Preferably, in the aforementioned method for preparing nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd, the concentration of palladium chloride in product B is 0.01-1 g / L.

[0017] Preferably, in the aforementioned method for preparing nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd, the ultraviolet light source is a 300W xenon lamp, the irradiation time is 20-120 min, and the irradiation temperature is 25-60℃.

[0018] Preferably, in the aforementioned method for preparing nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd, the drying temperature in step S4 is 30-60°C.

[0019] Preferably, in the aforementioned method for preparing nitrogen-doped cerium dioxide catalytic material with highly dispersed Pd, the nitrogen-doped cerium dioxide is prepared by the following method:

[0020] S1. Cerium salt and 1,2,4,5-benzenetetracarboxylic acid are dissolved in a mixed solution of distilled water and anhydrous ethanol. After stirring and dissolving, the solution is aged for 7-10 hours. The resulting solution is filtered, dried, ground and pulverized to obtain cerium dioxide precursor.

[0021] S2. The cerium dioxide precursor is calcined in a nitrogen atmosphere to obtain nitrogen-doped cerium dioxide.

[0022] Preferably, in the aforementioned method for preparing nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd, the cerium salt is one or any combination of cerium nitrate, cerium chloride, cerium sulfate, or cerium acetate.

[0023] Preferably, in the aforementioned method for preparing nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd, the calcination temperature is 600-700℃ and the calcination time is 1-3h.

[0024] A nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd was prepared by the aforementioned method.

[0025] The beneficial effects of this invention are:

[0026] 1. This invention prepares a high-performance nitrogen-doped cerium dioxide-supported highly dispersed noble metal composite catalytic material using a photo-assisted method. Under ultraviolet irradiation, the efficient photocatalytic ability of nitrogen-doped cerium dioxide and the synergistic enhancement effect of nitrogen doping and vacancy defects on carrier separation are utilized. At the nitrogen-doped sites, noble metal ions in the solution are reduced to a metallic state and deposited around the active sites to achieve directional loading, thereby obtaining a nitrogen-doped cerium dioxide composite catalytic material supported on highly dispersed noble metal Pd. This effectively improves the hydrogenation activity, stability, and recyclability of cerium dioxide, and enhances the ability to absorb light and promote carrier separation.

[0027] 2. The cerium dioxide-based composite catalytic material of the present invention forms a structure with strong Pd-Ce metal-support interaction under low Pd loading, which enhances the stability and catalytic performance of the catalyst, while saving Pd precious metal resources and reducing the preparation cost of cerium dioxide-based composite photocatalyst.

[0028] 3. This invention prepares a high-performance nitrogen-doped cerium dioxide-supported highly dispersed noble metal composite catalytic material using a photo-assisted method. The filtrate after the preparation reaction is completed can be evaporated to recover Pd ions and reused, which can further save Pd precious metal resources. At the same time, it reduces pollution emissions and meets the relevant requirements for energy conservation and emission reduction.

[0029] 4. This invention prepares nitrogen-doped cerium dioxide-supported highly dispersed noble metal composite catalytic materials using a photo-assisted method. The preparation method is simple and easy to promote and implement industrially.

[0030] In summary, the preparation method of nitrogen-doped cerium dioxide-supported highly dispersed noble metal composite catalytic material of the present invention has good theoretical and practical application value. The nitrogen-doped cerium dioxide-supported highly dispersed noble metal composite catalytic material obtained by this method has the advantages of excellent photocatalytic performance, stable chemical properties, green and environmentally friendly preparation process, wide applicability, simple operation, and low cost. While ensuring reproducibility and theoretical feasibility, this method also provides new ideas and theoretical support for the industrial production and application of related high-performance photocatalytic composite nanomaterials. Attached Figure Description

[0031] Appendix Figure 1 This is a comparison chart of the photocatalytic results of Example 1 and Comparative Example 1 of the present invention;

[0032] Appendix Figure 2 This is a comparison chart of the photocatalytic results of Example 1, Comparative Examples 2 and 3 of the present invention;

[0033] from Figure 1 It can be seen that after treatment with an external physical field, the photocatalytic activity of Example 1 is far superior to that of Comparative Example 1.

[0034] from Figure 2 As can be seen, compared with the traditional preparation methods used in Comparative Examples 2 and 3, Example 1 prepared by the method mentioned in this invention achieves high-efficiency degradation of high-concentration organic matter and has stronger photocatalytic activity. Detailed Implementation

[0035] 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.

[0036] Embodiments of the present invention

[0037] Example 1:

[0038] This embodiment prepares a nitrogen-doped cerium dioxide-supported highly dispersed noble metal composite catalytic material according to the following steps:

[0039] (1) Mix 0.5g of nitrogen-doped cerium dioxide with 10mL of palladium chloride solution in 50mL of methanol solution, sonicate at 50℃ for 1h, and then stir at 30℃ for 0.5h.

[0040] (2) Irradiate the suspension with a xenon lamp at 50°C (electric power of 300W, light power of 50W) for 1.5h;

[0041] (3) After filtering the reaction solution and collecting the solid, the sample powder was dried and ground at 50°C to obtain nitrogen-doped cerium dioxide supported highly dispersed noble metal composite catalyst.

[0042] Example 2:

[0043] This embodiment prepares a nitrogen-doped cerium dioxide-supported highly dispersed noble metal composite catalytic material according to the following steps:

[0044] (1) Mix 0.65g of nitrogen-doped cerium dioxide and 0.05g of palladium chloride in 5L of methanol solution, sonicate at 50℃ for 1h, and then stir at 30℃ for 0.5h.

[0045] (2) Irradiate the suspension with a xenon lamp (electric power of 300W, light power of 50W) at 25°C for 2 hours;

[0046] (3) After filtering the reaction solution and collecting the solid, the sample powder was dried and ground at 30°C to obtain nitrogen-doped cerium dioxide supported highly dispersed noble metal composite catalyst.

[0047] Example 3:

[0048] This embodiment prepares a nitrogen-doped cerium dioxide-supported highly dispersed noble metal composite catalytic material according to the following steps:

[0049] (1) Mix 0.5g of nitrogen-doped cerium dioxide and 0.05g of palladium chloride in 100ml of methanol solution, sonicate at 50℃ for 1h, and then stir at 30℃ for 0.5h.

[0050] (2) Irradiate the suspension with a xenon lamp at 60°C (electric power of 300W, light power of 50W) for 20 minutes;

[0051] (3) After filtering the reaction solution and collecting the solid, the sample powder was dried and ground at 60°C to obtain nitrogen-doped cerium dioxide supported highly dispersed noble metal composite catalyst.

[0052] Comparative Example 1:

[0053] Nitrogen-doped cerium dioxide without Pd loading

[0054] (1) Cerium acetate and 1,2,4,5-benzenetetracarboxylic acid were dissolved in a mixed solution of distilled water and anhydrous ethanol. After stirring and dissolving appropriately, the solution was aged for 9 hours. The resulting solution was filtered, dried, ground and pulverized to obtain cerium dioxide precursor.

[0055] (2) The cerium dioxide precursor was kept at 650℃ for 2 hours in a high-concentration nitrogen atmosphere to obtain nitrogen-doped cerium dioxide.

[0056] Comparative Example 2:

[0057] Polyhedral cerium dioxide prepared by hydrothermal method

[0058] (1) Dissolve 0.868g of cerium nitrate and 0.16g of NaOH in 40mL of distilled water and stir continuously for 1h;

[0059] (2) The suspension was loaded into a 50mL high-pressure reactor and hydrothermally reacted at 100℃ for 24h;

[0060] (3) After filtration, washing and drying, polyhedral cerium dioxide is obtained.

[0061] Table 1 below compares the degradation rates of 40 mg / L tetracycline solution between Example 1 of the present invention and Comparative Examples 1 and 2. It can be seen that the cerium dioxide-based composite material prepared by the external physical field-assisted method proposed in this invention can effectively achieve a significant improvement in photocatalytic ability.

[0062] Table 1 Comparison of Photocatalytic Degradation Rates

[0063] Sample Name Degradation rate / % Example 1 68.91％ Comparative Example 1 46.01％ Comparative Example 2 17.32％

[0064] Table 2 below compares the hydrogen evolution results of methanol reforming catalysis in Example 1 of the present invention with those in Comparative Examples 1 and 2. It can be seen that the cerium dioxide-based composite material prepared by the external physical field assisted method proposed in the present invention has the highest hydrogen evolution yield. Combined with Table 1 above, it can be concluded that the external physical field assisted method proposed in the present invention can not only successfully prepare cerium dioxide-based composite materials, but also effectively improve the photocatalytic performance of the material by loading noble metal Pd nanoparticles.

[0065] Table 2 Comparison of Photocatalytic Hydrogen Evolution Yields

[0066] Sample Name <![CDATA[H2 production rate / umol / g]]> Example 1 353.65 Comparative Example 1 114.52 Comparative Example 2 73.47

[0067] 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 nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd, characterized in that: Using nitrogen-doped cerium dioxide as the matrix material, Pd is loaded onto the nitrogen-doped sites after photo-activation. 2+ Thus, nitrogen-doped cerium dioxide catalytic materials with highly dispersed Pd loading are obtained.

2. The method for preparing nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd according to claim 1, characterized in that, The specific steps of the method are as follows: S1. Take nitrogen-doped cerium dioxide, dissolve it in methanol solution, and obtain product A; S2. Add palladium chloride to product A, dissolve by sonication, and stir to adsorb, to obtain product B; S3. Irradiate product B under ultraviolet light to excite and activate nitrogen-doped sites, thereby enabling Pd 2+ Loaded onto nitrogen-doped sites, C product is obtained; S4. After removing product C, filter and dry it to obtain nitrogen-doped cerium dioxide catalyst material loaded with highly dispersed Pd.

3. The method for preparing nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd according to claim 2, characterized in that: In product A, the concentration of nitrogen-doped cerium dioxide is 0.13-10 g / L.

4. The method for preparing nitrogen-doped cerium dioxide catalytic material loaded with highly dispersed Pd according to claim 2, characterized in that: In product B, the concentration of palladium chloride is 0.01-1 g / L.

5. The method for preparing nitrogen-doped cerium dioxide catalytic material with highly dispersed Pd according to claim 2, characterized in that: The ultraviolet light source is a 300W xenon lamp, with an irradiation time of 20-120 minutes and an irradiation temperature of 25-60℃.

6. The method for preparing nitrogen-doped cerium dioxide catalytic material supported on highly dispersed Pd according to claim 2, characterized in that: The drying temperature in S4 is 30-60℃.

7. The method for preparing nitrogen-doped cerium dioxide catalytic material with highly dispersed Pd according to claim 1 or 2, characterized in that, The nitrogen-doped cerium dioxide is prepared by the following method: S1. Cerium salt and 1,2,4,5-benzenetetracarboxylic acid are dissolved in a mixed solution of distilled water and anhydrous ethanol. After stirring and dissolving, the solution is aged for 7-10 hours. The resulting solution is filtered, dried, ground and pulverized to obtain cerium dioxide precursor. S2. The cerium dioxide precursor is calcined in a nitrogen atmosphere to obtain nitrogen-doped cerium dioxide.

8. The method for preparing nitrogen-doped cerium dioxide catalytic material supported on highly dispersed Pd according to claim 7, characterized in that: The cerium salt is one or any combination of cerium nitrate, cerium chloride, cerium sulfate, or cerium acetate.

9. The method for preparing nitrogen-doped cerium dioxide catalytic material supported on highly dispersed Pd according to claim 7, characterized in that: The roasting temperature is 600-700℃, and the roasting time is 1-3 hours.

10. A nitrogen-doped cerium dioxide catalytic material with highly dispersed Pd loaded, prepared by the method according to any one of claims 1-9.

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