A rare earth metal oxide-copper oxide composite material and a method for preparing the same
By modifying the core-coating structure and preparation method, the problem of uneven mixing in rare earth metal oxide-copper oxide composite materials was solved, thereby improving catalytic activity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WEICHAI POWER CO LTD
- Filing Date
- 2024-01-25
- Publication Date
- 2026-07-10
AI Technical Summary
In the rare earth metal oxide-copper oxide composite material, the copper oxide particles and rare earth metal oxide particles are not mixed evenly, resulting in the catalytic activity not being fully realized.
A core-coating structure was adopted, with a rare earth metal oxide core and a copper oxide coating. The rare earth metal oxide-copper oxide composite material was prepared by hydrothermal treatment, centrifugation, washing, drying, calcination and sintering, and the contact area between copper oxide and rare earth metal oxide was controlled.
This significantly increased the contact area between copper oxide and rare earth metal oxides, enhanced their synergistic effect, and improved the catalytic activity of the composite material.
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Figure CN117753480B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of copper oxide composite materials technology, and in particular to a rare earth metal oxide-copper oxide composite material and its preparation method. Background Technology
[0002] Rare earth metal oxides, such as cerium oxide, are widely used in many fields as common metal oxide supports and important components of bimetallic composite modified materials. Currently, rare earth metal oxide-copper oxide composites suffer from uneven mixing of copper oxide and rare earth metal oxide particles, and the synergistic effect between copper oxide and rare earth metal oxides needs to be improved, resulting in the catalytic activity of the rare earth metal oxide-copper oxide composites not being fully realized. Summary of the Invention
[0003] This application discloses a rare earth metal oxide-copper oxide composite material and its preparation method, in order to improve the problem of uneven mixing of copper oxide particles and rare earth metal oxide particles in existing rare earth metal oxide-copper oxide composite materials.
[0004] To achieve the above objectives, this application provides the following technical solution:
[0005] In a first aspect, this application provides a rare earth metal oxide-copper oxide composite material, which includes a core and a coating layer, wherein the core includes rare earth metal oxide and the coating layer includes copper oxide.
[0006] Furthermore, the average particle size of the rare earth metal oxide-copper oxide composite material is 90-110 nm, and / or the mass ratio of copper oxide to rare earth metal oxide is 0.12-0.18:1.
[0007] Furthermore, copper oxide includes Cu 2+ and Cu 1+ Cu 1+ Molar amount of Cu 2+ and Cu 1+ The ratio of the sum of their molar amounts is 0.4-0.45:1.
[0008] Secondly, this application provides a method for preparing a rare earth metal oxide-copper oxide composite material, the method comprising the following steps: mixing a soluble salt of a rare earth metal, polyvinylpyrrolidone, a strong alkaline solution and ammonia to obtain a mixed solution; hydrothermally treating the mixed solution at 140-180℃ for 18-30 h, and obtaining rare earth metal oxide particles by centrifugation, washing, drying and calcination; mixing the rare earth metal oxide particles, polyvinylpyrrolidone, soluble copper salt and a reducing agent, bathing in a water bath at 50-70℃ for 3-5 h, and obtaining a pulverized product by centrifugation, washing, drying and pulverization; and sintering the pulverized product to obtain the rare earth metal oxide-copper oxide composite material.
[0009] Furthermore, the strong alkaline solution includes at least one of sodium hydroxide solution and potassium hydroxide solution.
[0010] Furthermore, the molar ratio of the strong alkali solution to ammonia is 1:2 to 2:1.
[0011] Furthermore, the soluble salt of the rare earth metal is selected from at least one of soluble cerium salt, soluble zirconium salt, and soluble lanthanum salt.
[0012] Furthermore, the soluble copper salt is selected from at least one of copper nitrate, copper chloride, and copper sulfate.
[0013] Furthermore, the calcination treatment is carried out at a temperature of 400-600℃ for 4-6 hours; and / or the sintering treatment is carried out at a temperature of 500-600℃ for 3-5 hours.
[0014] Furthermore, the molar ratio of copper ions in rare earth metal oxides and soluble copper salts is 1.8:1-2:1.
[0015] The beneficial effects of adopting the technical solution of this application are as follows:
[0016] The rare earth metal oxide-copper oxide composite material provided in this application includes a rare earth metal oxide layer and copper oxide particles disposed on the surface of the rare earth element oxide layer, a core and a coating layer. The core includes rare earth metal oxide, and the coating layer includes copper oxide. The copper oxide coating on the surface of the rare earth metal oxide can significantly increase the contact area between the two, thereby enhancing the synergistic effect of copper oxide and rare earth metal oxide. The number of active sites at the copper-rare earth metal interface increases, thereby effectively improving the catalytic activity of the rare earth metal oxide-copper oxide composite material. Attached Figure Description
[0017] Figure 1 This is a low-magnification SEM image of CeO2-NSs in Example 1 of this application;
[0018] Figure 2This is a high-magnification SEM image of CeO2-NSs in Example 1 of this application;
[0019] Figure 3 This is a TEM image of CeO2-NSs in Example 1 of this application;
[0020] Figure 4 This is an HRTEM image of CeO2-NSs in Embodiment 1 of this application;
[0021] Figure 5 This is a low-magnification SEM image of Cu / CeO2 NSs in Example 1 of this application;
[0022] Figure 6 This is a high-magnification SEM image of Cu / CeO2 NSs in Example 1 of this application;
[0023] Figure 7 This is a low-magnification TEM image of Cu / CeO2 NSs in Example 1 of this application;
[0024] Figure 8 This is a high-magnification TEM image of Cu / CeO2 NSs in Example 1 of this application;
[0025] Figure 9 This is an HRTEM image of Cu / CeO2 NSs in Example 1 of this application;
[0026] Figure 10 This is a SAED image of Cu / CeO2 NSs in Example 1 of this application;
[0027] Figure 11 This is an EDS mapping diagram of Cu / CeO2 NSs in Example 1 of this application;
[0028] Figure 12 This is a SEM image of P-CeO2 in Comparative Example 1 of this application;
[0029] Figure 13 This is a TEM image of P-CeO2 in Comparative Example 1 of this application. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0031] The application scenarios described in this application are for the purpose of more clearly illustrating the technical solutions of this application, and do not constitute a limitation on the technical solutions provided in this application. Those skilled in the art will understand that with the emergence of new application scenarios, the technical solutions provided in this application are also applicable to similar technical problems. In the description of this application, unless otherwise stated, "multiple" means two or more.
[0032] When preparing rare earth metal oxide-copper oxide composite materials, it is difficult for copper oxide to be uniformly dispersed or doped on the surface of cerium oxide rare earth metal oxide, resulting in insufficient catalytic performance or low catalyst stability.
[0033] In view of this, this application provides a rare earth metal oxide-copper oxide composite material, which includes a core and a coating layer. The core includes rare earth metal oxides and the coating layer includes copper oxide.
[0034] In this process, copper oxide coating the surface of rare earth metal oxides can significantly increase the contact area between the two, thereby enhancing the synergistic effect of copper oxide and rare earth metal oxides, and thus improving the catalytic activity of rare earth metal oxide-copper oxide composite materials.
[0035] It should be noted that the particle shape of rare earth metal oxide-copper oxide composite material can be spherical, near-spherical, or other shapes.
[0036] In some embodiments of this application, the average particle size of the rare earth metal oxide-copper oxide composite material is 90-110 nm. Examples of the average particle size of the rare earth metal oxide-copper oxide composite material are 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, or any other value among 80-110 nm.
[0037] In some embodiments of this application, the average particle size of the copper oxide particles is 80-120 nm. Examples of the average particle size of the copper oxide particles are 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, or any other value among 80-120 nm.
[0038] In some embodiments of this application, the mass ratio of copper oxide to rare earth metal oxide is 0.12-0.18:1, and examples of the mass ratio of copper oxide to rare earth metal oxide are 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1 or 0.18:1.
[0039] In some embodiments of this application, copper oxide includes Cu 2+ and Cu 1+ Cu 1+Molar amount of Cu 2+ and Cu 1+ The ratio of the sum of the molar amounts of Cu and Cu is 0.4-0.45:1, which helps to improve the catalytic performance and structural stability of the copper oxide material supported by this rare earth element oxide. 1+ Molar amount of Cu 2+ and Cu 1+ Examples of ratios of the sum of molar amounts are 0.40:1, 0.41:1, 0.42:1, 0.43:1, 0.44:1, or 0.45:1.
[0040] Based on the same inventive concept, this application provides a method for preparing a rare earth metal oxide-copper oxide composite material, which includes the following steps:
[0041] 1) Mix a soluble salt of a rare earth metal, polyvinyl pyrrolidone (PVP), a strong alkaline solution, and ammonia to obtain a mixed solution;
[0042] 2) The mixed solution was hydrothermally treated at 140-180℃ for 18-30 hours, and then centrifuged, washed, dried and calcined to obtain rare earth metal oxide particles.
[0043] 3) Mix rare earth metal oxide particles, polyvinylpyrrolidone, soluble copper salt and reducing agent, keep warm at 50-70℃ for 3-5 hours, and obtain the pulverized product after centrifugation, washing, drying and pulverizing.
[0044] 4) The pulverized product is sintered to obtain a rare earth metal oxide-copper oxide composite material.
[0045] Optionally, in step 1), when preparing the mixed solution, the soluble salt of the rare earth metal can be dissolved in the first solvent first, and then PVP, strong alkali solution and ammonia water can be added and stirred evenly. The first solvent can be ethanol or ethylene glycol.
[0046] In some embodiments of this application, the strong alkaline solution includes at least one of sodium hydroxide solution and potassium hydroxide solution.
[0047] In some embodiments of this application, the molar ratio of strong alkali solution to ammonia is 1.8:1-2:1. By adjusting the ratio of strong alkali to ammonia, the sedimentation rate of cerium hydroxide can be controlled, thereby controlling the particle size of cerium oxide.
[0048] Optionally, in step 2), the hydrothermal treatment can be performed by placing the mixed solution in a Teflon-lined stainless steel autoclave. Optionally, the washing after hydrothermal treatment can be done with water or ethanol; preferably, the product is washed at least twice with deionized water and then at least twice with ethanol. Optionally, the drying method after washing can be oven drying; preferably, the washed product is dried at 80°C for at least 12 hours.
[0049] In some embodiments of this application, the calcination temperature is 400-700°C and the time is 4-6 hours. The calcination is carried out in a tube furnace.
[0050] In some embodiments of this application, the soluble salt of the rare earth metal is selected from at least one of soluble cerium salts, soluble zirconium salts, and soluble lanthanum salts. Specifically, when the rare earth metal is selected from soluble cerium salts, the rare earth metal may be Ce(NO3)2 or CeCl3. When the rare earth metal is selected from soluble zirconium salts, the rare earth metal may be Zr(NO3)4 or ZrCl4. When the rare earth metal is selected from soluble lanthanum salts, the rare earth metal may be La(NO3)2 or LaCl3. 3)2 Or LaCl3.
[0051] In some embodiments of this application, the soluble copper salt is selected from at least one of copper nitrate, copper chloride, and copper sulfate.
[0052] Optionally, step 3) of mixing rare earth metal oxide particles, polyvinylpyrrolidone, soluble copper salt, and reducing agent includes:
[0053] Rare earth metal oxide particles are dissolved in deionized water and dispersed by ultrasonication to obtain a suspension. A reducing agent is then added to the suspension and stirred until the suspension is homogeneous. A soluble copper salt solution is then added to the suspension, and the pH is adjusted to 9-10 with a pH adjuster. Finally, the reducing agent is added and stirred until homogeneous.
[0054] The reducing agent can be ascorbic acid or sodium citrate. The pH adjuster can be sodium carbonate solution, sodium bicarbonate solution, or potassium carbonate solution.
[0055] Optionally, the washing after centrifugation in step 3) can be done with deionized water or ethanol. Preferably, the product is washed at least twice with deionized water and then at least twice with ethanol. Optionally, the drying method after washing can be baking. Preferably, the washed product is vacuum dried at 60°C for more than 10 hours.
[0056] Optionally, the solid obtained after drying can be pulverized by grinding.
[0057] Alternatively, the method of cooling after drying is natural cooling.
[0058] In some embodiments of this application, the molar ratio of copper ions in rare earth metal oxides and soluble copper salts is 1.8:1-2:1.
[0059] In some embodiments of this application, the sintering temperature is 400-700℃ and the time is 3-6h. The heating rate is preferably 5℃ / min.
[0060] In some embodiments of this application, the volume ratio of the mixed solution to ascorbic acid is 9:1 to 3.6:1.
[0061] The rare earth metal oxide-copper oxide composite material and its preparation method in this application will be further described in detail below with reference to specific embodiments and comparative examples.
[0062] Example 1
[0063] This embodiment discloses a rare earth metal oxide-copper oxide composite material and its preparation method. The preparation method of the rare earth metal oxide-copper oxide composite material includes the following steps:
[0064] Step 1) Grind 2g Ce(NO3)3·6H2O into powder, dissolve it in 50mL ethylene glycol, and add 0.8g PVP and 4mol L to it. -1 20 mL of sodium hydroxide solution and 3 mol L -1 Add 1 mL of ammonia solution and stir for 30 minutes to obtain a mixed solution; sodium hydroxide solution and ammonia solution should be added simultaneously.
[0065] Step 2) Pour the mixed solution into a 100mL Teflon-lined stainless steel autoclave and heat it at 160℃ for 24h. After hydrothermal treatment, wash it multiple times with deionized water and ethanol. Then, dry the washing product at 80℃ overnight and calcine the dried material at 600℃ for 5h to obtain spherical CeO2, which is named CeO2-NSs.
[0066] Step 3) Place the cerium oxide obtained in Step 2) into a 100mL beaker, add 20mL of deionized water, and sonicate for 30min to obtain a suspension. Add 3g of PVP powder to the suspension and stir for 30min until the suspension is uniformly mixed. Add 18mL of a pre-prepared 0.043mol / L copper nitrate solution, and then adjust the pH of the solution to 9.5 with 0.5mol / L sodium carbonate solution. Stir for 1h (the solution turns light green), then add 5mL of 4mol / L ascorbic acid solution. Incubate in a 55℃ water bath for 3h. Centrifuge the obtained solution and wash the precipitate three times each with deionized water and ethanol. Vacuum dry at 60℃ for 10h. After drying, grind into powder to obtain the pulverized product.
[0067] Step 4) Calcine the pulverized product at 500℃ for 3 hours with a heating rate of 5℃ / min. After cooling, a rare earth metal oxide-copper oxide composite material is obtained, named Cu / CeO2 NSs.
[0068] Figure 1 This is a low-magnification SEM image of CeO2-NSs in Example 1 of this application. Figure 2 This is a high-magnification SEM image of CeO2-NSs in Example 1 of this application, referring to... Figure 1 and Figure 2 You can see CeO2 spherical particles that are uniform in size, evenly distributed, and have a rough surface. Figure 3 This is a TEM image of CeO2-NSs in Embodiment 1 of this application, with reference to... Figure 3 The size of CeO2 spherical particles is around 100 nm. Figure 4 The HRTEM image of CeO2-NSs in Embodiment 1 of this application is shown below. Figure 4 Clearly, crystal lattices with the same orientation can be observed. The average lattice spacing is measured to be 0.31 nm, which corresponds to the (111) crystal plane of cerium oxide. This is consistent with the XRD results of cerium oxide, indicating that the ideal spherical cerium oxide was successfully prepared in Example 1.
[0069] Figure 5 This is a low-magnification SEM image of Cu / CeO2 NSs in Example 1 of this application. Figure 6 This is a high-magnification SEM image of Cu / CeO2 NSs in Example 1 of this application. Figure 7 This is a low-magnification TEM image of Cu / CeO2 NSs in Example 1 of this application. Figure 8 This is a high-magnification TEM image of Cu / CeO2 NSs in Example 1 of this application, with reference to... Figures 5 to 8 The morphology of Cu / CeO2 NSs is not significantly different from that of CeO2 NSs, and it still retains the original size and dispersion of CeO2 NSs.
[0070] Figure 9 Here is the HRTEM image of Cu / CeO2 NSs in Example 1 of this application, with reference to Figure 9 The rare earth metal oxide-copper oxide composite material shows obvious lattice fringes with different orientations, and the lattice fringes are intertwined. The measured lattice spacings are 0.25 nm and 0.31 nm, respectively. This data is consistent with the (002) crystal plane of copper oxide and the (111) crystal plane of cerium oxide, indicating that copper oxide was successfully loaded on the surface of cerium oxide spheres.
[0071] Figure 10This is the EDS mapping diagram of Cu / CeO2 NSs in Example 1 of this application, referring to... Figure 10 The results showed the presence of diffraction rings matching the (111) crystal plane of cerium oxide and diffraction rings matching the (002), (111), and (110) crystal planes of copper oxide, which verified the presence of diffraction rings. Figure 9 The analysis results further prove the successful preparation of the composite material.
[0072] Figure 11 This is an EDS mapping diagram of Cu / CeO2 NSs in Example 1 of this application, where purple represents cerium, green represents copper, and yellow represents oxygen. (Refer to...) Figure 11 The uniform distribution of copper, cerium, and oxygen on the spherical structure indicates a high degree of composite material between copper oxide and cerium oxide, forming a heterogeneous structure of copper oxide and cerium oxide.
[0073] Examples 2-9
[0074] Examples 2-9 are all rare earth metal oxide-copper oxide composite materials and their preparation methods. The specific steps can be referred to in Example 1. The difference is the difference in experimental conditions. Please refer to Table 1 for details.
[0075] Comparative Example 1
[0076] Comparative Example 1 is a rare earth metal oxide-copper oxide composite material and its preparation method. The specific steps can be referred to in Example 1, except that the preparation steps of cerium oxide (step 1) and step 2) are different. Specifically, it includes:
[0077] First, Ce(NO3)2·6H2O was ground into powder, and then heated to 450℃ in statically flowing air at a heating rate of 2℃ / min and maintained for 4h. The resulting yellow solid was ground into powder and named P-CeO2.
[0078] Figure 12 This is a SEM image of P-CeO2 in Comparative Example 1 of this application. Figure 13 The TEM image of P-CeO2 in Comparative Example 1 of this application is shown below. Figure 12 and Figure 13 The steps for preparing cerium oxide in Comparative Example 1 were different, resulting in the final composite material exhibiting a layered structure.
[0079] Comparative Examples 2-4
[0080] Comparative Examples 2-4 are all rare earth metal oxide-copper oxide composite materials and their preparation methods. The specific steps can be referred to Example 1. The difference lies in the experimental conditions, which can be found in Table 1.
[0081] The performance of the rare earth metal oxide-copper oxide composite materials in Examples 1-9 and Comparative Examples 1-6 was tested, and the test results are listed in Table 1. The test items and test methods are as follows:
[0082] Electrochemical catalytic carbon dioxide reduction testing requires an electrolytic cell, an electrochemical workstation, a computer, and gas chromatography and liquid chromatography for product detection. Gas phase product detection can be performed real-time using online equipment. For liquid phase products, a certain coulombic concentration needs to be accumulated in the electrolyte to reach the detection limit of the liquid chromatography before sampling and detection in the liquid chromatograph. An H-type electrolytic cell is used. The operating potential during the test can be converted using the following formula: E(vs.RHE)=(0.0592×pH)+E Ag / AgCl +E(vs.Ag / AgCl).
[0083] Preparation process of catalyst ink and working electrode: Weigh 5 mg of sample (the composite material in the examples or comparative examples of this application), dissolve the sample in 200 μL of isopropanol in a small centrifuge tube, then add 5 μL of 5% Nafion, and sonicate for 30 min to obtain uniform ink. Take 40 μL of uniform ink and drop it onto a cleaned glassy carbon electrode, let it air dry naturally to obtain the working electrode.
[0084] The catalyst was subjected to IT tests at different voltages. After qualitative and quantitative analysis of the gaseous products using chromatography, the Faradaic efficiency of each gaseous product was calculated using the following formula:
[0085]
[0086] Note: p is the concentration of the product, i is the current, α is the number of electrons transferred in the product, and v is the flow rate of CO2.
[0087] The formula for calculating the Faraday efficiency of liquid-phase products is as follows:
[0088] Note: e is the number of electrons transferred, n is the amount of substance of the liquid product, and Q is the total amount of electricity generated during electrolysis.
[0089] Table 1
[0090]
[0091]
[0092] Comparing the data from Example 1 and Example 3, it can be seen that when the molar ratio of strong alkali to ammonia increases within a limited range (1:2-2:1), the sedimentation rate of cerium hydroxide increases, which affects the particle size of cerium oxide and thus affects the catalytic performance of the final composite material.
[0093] Comparing the data from Example 1 and Example 4, it can be seen that when the ammonia concentration is high, the sedimentation rate of cerium hydroxide is too slow, which will affect the particle size of cerium oxide and thus affect the catalytic performance of the final composite material.
[0094] Comparing the data from Example 1 and Comparative Examples 1-3, it can be seen that the sedimentation rate of cerium hydroxide is slowed down by using strong alkali and ammonia, thereby controlling the particle size of cerium oxide and thus controlling the catalytic performance of the final composite material.
[0095] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A rare earth metal oxide-copper oxide composite material, characterized in that, The system comprises a core and a coating layer, wherein the core comprises a rare earth metal oxide and the coating layer comprises copper oxide; the copper oxide comprises Cu. 2+ and Cu 1+ ; The preparation method of the rare earth metal oxide-copper oxide composite material includes the following steps: A mixed solution is obtained by mixing a soluble salt of a rare earth metal, polyvinylpyrrolidone, a strong alkaline solution, and ammonia. The mixed solution was hydrothermally treated at 140-180℃ for 18-30 hours, and then centrifuged, washed, dried and calcined to obtain rare earth metal oxide particles. The rare earth metal oxide particles, polyvinylpyrrolidone, soluble copper salt and reducing agent are mixed and kept at 50-70℃ for 3-5 hours. After centrifugation, washing, drying and pulverizing, the pulverized product is obtained. The pulverized product is sintered to obtain the rare earth metal oxide-copper oxide composite material. The soluble salts of the rare earth metals are selected from soluble cerium salts.
2. The rare earth metal oxide-copper oxide composite material according to claim 1, characterized in that, The average particle size of the rare earth metal oxide-copper oxide composite material is 90-110 nm, and / or the mass ratio of copper oxide to rare earth metal oxide is 0.12-0.18:
1.
3. The rare earth metal oxide-copper oxide composite material according to claim 1, characterized in that, Cu 1+ Molar amount of Cu 2+ and Cu 1+ The ratio of the sum of their molar amounts is 0.4-0.45:
1.
4. A method for preparing the rare earth metal oxide-copper oxide composite material as described in any one of claims 1-3, characterized in that, Includes the following steps: A mixed solution is obtained by mixing a soluble salt of a rare earth metal, polyvinylpyrrolidone, a strong alkaline solution, and ammonia. The mixed solution was hydrothermally treated at 140-180℃ for 18-30 hours, and then centrifuged, washed, dried and calcined to obtain rare earth metal oxide particles. The rare earth metal oxide particles, polyvinylpyrrolidone, soluble copper salt and reducing agent are mixed and kept at 50-70℃ for 3-5 hours. After centrifugation, washing, drying and pulverizing, the pulverized product is obtained. The pulverized product is sintered to obtain the rare earth metal oxide-copper oxide composite material. The soluble salts of the rare earth metals are selected from soluble cerium salts.
5. The preparation method according to claim 4, characterized in that, The strong alkaline solution includes at least one of sodium hydroxide solution and potassium hydroxide solution.
6. The preparation method according to claim 4, characterized in that, The molar ratio of the strong alkali solution to the ammonia water is 1:2-2:
1.
7. The preparation method according to claim 4, characterized in that, The soluble copper salt is selected from at least one of copper nitrate, copper chloride, and copper sulfate.
8. The preparation method according to claim 4, characterized in that, The calcination treatment is carried out at a temperature of 400-600℃ for 4-6 hours; and / or the sintering treatment is carried out at a temperature of 500-600℃ for 3-5 hours.
9. The preparation method according to any one of claims 4-8, characterized in that, The molar ratio of copper ions in the rare earth metal oxide and the soluble copper salt is 1.8:1-2:1.