Preparation method and application of CeO2 catalysts with different morphologies

Abstract

The invention discloses a preparation method and application of CeO2 catalysts with different morphologies. The preparation method comprises the following steps: S1, pretreating to obtain a sample; s2, transferring the sample into a muffle furnace, and calcining at 400 DEG C for 4 hours at the heating rate of 2 DEG C / min; and S3, cooling and taking out to obtain CeO2 catalysts with different morphologies. According to the method, the catalysts with different morphologies including CeO2 nano particles, CeO2 nano square blocks, CeO2 nano rods and CeO2 nano hollow spheres are synthesized through the steps of pretreatment and calcination, the sizes of the catalysts are uniform, and the synthesis method is safe, convenient and high in repeatability. CeO2 catalysts with different morphologies are applied to a novel catalytic system, namely dielectric barrier discharge plasma synergistic CO2 conversion, and the reaction conversion rate and stability are good; the CeO2 nano hollow sphere synthesized by the method has a large number of oxygen vacancies, and the content of the oxygen vacancies is increased along with the proceeding of the reaction in the process of converting CO from dielectric barrier discharge plasma to CO2, so that the adsorption, activation and conversion efficiency of CO2 are obviously improved.

Description

Technical field:

[0001] The present invention belongs to the field of plasma conversion technology, and in particular relates to a preparation method and application of CeO2 catalysts with different morphologies. Background technology:

[0002] With the urgent global pursuit of sustainable energy and stringent requirements for greenhouse gas emission reduction, the development of technologies to convert greenhouse gases into hydrocarbon fuels has become a key area of research in the energy and environment fields. Plasma-assisted greenhouse gas conversion has shown great potential. However, this technology is currently limited by low conversion efficiency of target chemicals and fuels. Dielectric barrier discharge plasma is the most widely studied plasma technology. The collision of high-energy electrons generated by the plasma can directly decompose carbon dioxide into carbon monoxide and oxygen. Dielectric barrier discharge plasma can also promote conversion through synergistic effects with catalysts. Cerium is the most abundant rare earth element, and Ce-based catalysts have excellent performance. Studies have shown that CeO2 exhibits different oxygen vacancy contents and, therefore, different catalytic properties due to its different structural characteristics. Therefore, the synthesis of CeO2 catalysts containing oxygen vacancies and their application in dielectric barrier discharge plasma for CO2 conversion are important research directions. Summary of the invention:

[0003] The first object of the present invention is to provide a method for preparing CeO2 catalysts with different morphologies, exposing oxygen vacancies in cerium oxide to improve its catalytic ability.

[0004] The second object of the present invention is to provide an application of CeO2 catalyst.

[0005] The first object of the present invention is implemented by the following technical solutions:

[0006] The preparation method of CeO2 catalysts with different morphologies comprises the following steps:

[0007] S1, pre-treatment to obtain samples;

[0008] S2. The sample was transferred into a muffle furnace and calcined at 400° C. for 4 h at a heating rate of 2° C. / min.

[0009] S3. Take out after cooling to obtain CeO2 catalysts with different morphologies.

[0010] Preferably, the pre-treatment comprises the following steps:

[0011] B1. Add NaOH to deionized water and stir until dissolved to obtain Solution 1; the mass volume ratio of the NaOH to the deionized water in Solution 1 is 250-300 mg / mL;

[0012] B2. Add Ce(NO3)3·6H2O to deionized water and stir to obtain a second solution; the mass volume ratio of Ce(NO3)3·6H2O to deionized water in the second solution is 150-200 mg / mL;

[0013] B3, slowly dripping the solution 2 into the solution 1, stirring for 20-40 minutes, then pouring into the reaction kettle, and performing a solvothermal reaction at 100° C. for 24 hours;

[0014] B4. After the solvothermal reaction is completed, the mixture is cooled to room temperature, and the resulting precipitate is washed three times with deionized water and anhydrous ethanol, respectively, dried at 50-90° C. overnight, and then ground;

[0015] The CeO2 catalyst obtained in step S3 is CeO2 nanocubes.

[0016] Preferably, the pre-treatment comprises the following steps:

[0017] C1. Add NaOH to deionized water and stir until dissolved to obtain Solution 1; the mass volume ratio of the NaOH to the deionized water in Solution 1 is 250-300 mg / mL;

[0018] C2. Add Ce(NO3)3·6H2O to deionized water and stir evenly to obtain a second solution; the mass volume ratio of the Ce(NO3)3·6H2O to the deionized water in the second solution is 150-200 mg / mL;

[0019] C3. Slowly drop the solution 2 into the solution 1, stir vigorously for 20-40 min, then pour into the reactor and carry out solvothermal reaction at 180°C for 24 h;

[0020] C4. After the solvothermal reaction is completed, the mixture is cooled to room temperature, and the resulting precipitate is washed three times with deionized water and anhydrous ethanol, respectively, dried at 50-90° C. overnight, and then ground;

[0021] The CeO2 catalyst obtained in step S3 is CeO2 nanorods.

[0022] Preferably, the pre-treatment comprises the following steps:

[0023] D1. After mixing deionized water and glacial acetic acid, add Ce(NO3)3·6H2O and stir until completely dissolved to obtain solution three; the volume ratio of the deionized water to the glacial acetic acid is 1:1; 0.5 g of Ce(NO3)3·6H2O is added to each milliliter of the mixed solution of deionized water and glacial acetic acid;

[0024] D2. Pour the solution 3 into the ethylene glycol solution, stir vigorously until transparent, then pour into a reactor and heat to obtain solution 4;

[0025] D3, centrifuging the solution 4, washing the precipitate obtained after centrifugation with deionized water and anhydrous ethanol three times respectively, drying at 50-90° C. overnight, and then grinding;

[0026] The CeO2 catalyst obtained in step S3 is CeO2 nano hollow spheres.

[0027] Preferably, in step D2, the volume ratio of the ethylene glycol solution to the solution three is 15:1; the reactor is heated at a temperature of 150-200° C. for 2-4 hours.

[0028] The second object of the present invention is implemented by the following technical solutions:

[0029] The application of CeO2 catalysts prepared by the above-mentioned preparation methods of CeO2 catalysts with different morphologies in the dielectric barrier discharge plasma synergistic CO2 conversion to CO.

[0030] Advantages of the present invention:

[0031] The present invention synthesizes CeO2 catalysts with different morphologies through pretreatment and calcination steps to screen CeO2 catalysts with high oxygen vacancy content, including CeO2 nanoparticles, CeO2 nanocubes, CeO2 nanorods and CeO2 nanohollow spheres. The size of each catalyst is uniform, and the synthesis method is safe, convenient and highly repeatable.

[0032] The application of CeO2 catalysts with different morphologies in dielectric barrier discharge plasma-assisted CO2 conversion all showed good reaction conversion rate and stability; among them, CeO2 nano-hollow spheres had a hollow mesoporous morphology and a large number of oxygen vacancies, and the plasma-assisted catalysis caused the oxygen vacancy content in the CeO2 nano-hollow spheres to gradually increase during the reaction, thereby increasing their specific surface area, which was beneficial to the activation of CO2, maintaining the stability of the catalytic reaction, and improving the conversion rate. Description of the drawings:

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 Schematic diagram of the steps for preparing CeO2 catalysts with different morphologies;

[0035] Figure 2 This is the experimental flow chart of the dielectric barrier discharge (DBD) plasma catalysis system;

[0036] Figure 3 This is a scanning electron microscope image of the CeO2-particle catalyst of Example 1;

[0037] Figure 4 This is a scanning electron microscope image of the catalyst CeO2-cube of Example 2;

[0038] Figure 5 This is a scanning electron microscope image of the catalyst CeO2-rod of Example 3;

[0039] Figure 6 TEM image of the CeO2-sphere catalyst of Example 4;

[0040] Figure 7 (a) N2 adsorption-desorption isotherm and (b) pore size distribution and element distribution of the catalyst in Example 5;

[0041] Figure 8 The XRD patterns of the catalyst before and after the reaction (marked as -after in the figure) in Example 5 are shown;

[0042] Figure 9 The scanning electron micrographs of the catalyst CeO2-sphere before and after the reaction in Example 5 are shown;

[0043] Figure 10 The electron paramagnetic resonance images of CeO2-sphere at different reaction times in Example 5 are shown;

[0044] Figure 11 The Raman spectra of CeO2-sphere at different reaction times in Example 5 are shown;

[0045] Figure 12 Zeta potential diagram of CeO2-sphere at different reaction times in Example 5;

[0046] Figure 13 is the conversion rate within 30 min of the reaction of the catalyst in Example 5;

[0047] Figure 14 is the CO generation rate of the catalyst in Example 5. Specific implementation method:

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0049] Preparation methods of CeO2 catalysts with different morphologies, such as Figure 1 As shown, the following steps are included:

[0050] S1, pre-treatment to obtain samples;

[0051] S2. The sample was transferred into a muffle furnace and calcined at 400 °C for 4 h with a heating rate of 2 °C / min.

[0052] S3. Take out after cooling to obtain CeO2 catalysts with different morphologies.

[0053] In a specific embodiment:

[0054] The pretreatment includes: A1, drying and then grinding Ce(NO3)3·6H2O.

[0055] The prepared CeO2 catalyst is CeO2 nanoparticles.

[0056] In a specific embodiment:

[0057] Pre-treatment includes the following steps:

[0058] B1. Add NaOH to deionized water and stir until dissolved to obtain Solution 1; the mass volume ratio of NaOH to deionized water in Solution 1 is 250-300 mg / mL;

[0059] B2. Add Ce(NO3)3·6H2O to deionized water and stir to obtain Solution 2; the mass volume ratio of Ce(NO3)3·6H2O to deionized water in Solution 2 is 150-200 mg / mL;

[0060] B3. Slowly drop solution 2 into solution 1, stir vigorously for 20-40 min, then pour into the reactor and carry out solvothermal reaction at 100°C for 24 h;

[0061] B4. After the solvothermal reaction is completed, cool to room temperature, wash the obtained precipitate with deionized water and anhydrous ethanol three times respectively, dry it at 50-90°C overnight, and then grind it.

[0062] The prepared CeO2 catalyst is CeO2 nanocubes.

[0063] In a specific embodiment:

[0064] Pre-treatment includes the following steps:

[0065] C1. Add NaOH to deionized water and stir until dissolved to obtain Solution 1; the mass volume ratio of NaOH to deionized water in Solution 1 is 250-300 mg / mL;

[0066] C2. Add Ce(NO3)3·6H2O to deionized water and stir to obtain solution 2;

[0067] C3. Slowly drop solution 2 into solution 1, stir vigorously for 20-40 minutes, then pour into the reactor and carry out solvothermal reaction at 180°C for 24 hours;

[0068] C4. After the solvothermal reaction is completed, the mixture is cooled to room temperature, and the obtained precipitate is washed three times with deionized water and anhydrous ethanol respectively, dried at 50-90°C overnight, and then ground.

[0069] The prepared CeO2 catalyst is CeO2 nanorods.

[0070] In a specific embodiment:

[0071] Pre-treatment includes the following steps:

[0072] D1. After mixing deionized water and glacial acetic acid, add Ce(NO3)3·6H2O and stir until completely dissolved to obtain Solution 3; the volume ratio of deionized water to glacial acetic acid is 1:1; add 0.5 g of Ce(NO3)3·6H2O per milliliter of the mixed solution of deionized water and glacial acetic acid.

[0073] D2. Pour Solution 3 into the ethylene glycol solution, stir vigorously until transparent, then pour into a reactor and heat to obtain Solution 4; the volume ratio of ethylene glycol solution to Solution 3 is 15:1; the reactor is heated at 150-200°C for 2-4 hours;

[0074] D3. Centrifuge Solution 4, wash the precipitate obtained after centrifugation with deionized water and anhydrous ethanol three times respectively, then dry it at 50-90°C overnight and grind it.

[0075] The prepared CeO2 catalyst is CeO2 nano hollow spheres.

[0076] Example 1

[0077] A method for preparing a CeO2 catalyst comprises steps S1-S3.

[0078] S1. Pre-processing to obtain a sample; wherein the pre-processing includes: A1. drying and then grinding Ce(NO3)3·6H2O.

[0079] S2. The sample was transferred into a muffle furnace and calcined at 400 °C for 4 h with a heating rate of 2 °C / min.

[0080] S3. Take out after cooling to obtain CeO2 catalyst.

[0081] The CeO2 catalyst prepared by the above preparation method is CeO2 nanoparticles, such as Figure 3 As shown, it is recorded as CeO2-particle.

[0082] Example 2

[0083] A method for preparing a CeO2 catalyst comprises steps S1-S3.

[0084] S1. Pre-processing to obtain a sample; wherein the pre-processing includes:

[0085] B1. Add 17.5 mL of deionized water to a beaker, add 4.8 g of NaOH, and stir until dissolved to obtain Solution 1.

[0086] B2. In another beaker, add 2.5 mL of deionized water and 434 mg of Ce(NO3)3·6H2O and stir to obtain Solution 2.

[0087] B3. At room temperature, slowly add solution 2 to solution 1, stir vigorously for 30 min, then pour into a 50 mL reactor and carry out solvothermal reaction at 100°C for 24 h.

[0088] B4. After the solvothermal reaction is completed, the mixture is cooled to room temperature, and the obtained precipitate is washed three times with deionized water and anhydrous ethanol respectively, dried at 60°C overnight, and then ground. The particle size after grinding is 80-100 nm.

[0089] S2. The sample was transferred into a muffle furnace and calcined at 400 °C for 4 h with a heating rate of 2 °C / min.

[0090] S3. Take out after cooling to obtain CeO2 catalyst.

[0091] The CeO2 catalyst prepared by the above preparation method is CeO2 nanocubes, such as Figure 4 As shown, it is recorded as CeO2-cube.

[0092] Example 3

[0093] A method for preparing a CeO2 catalyst comprises steps S1-S3.

[0094] S1. Pre-processing to obtain a sample; wherein the pre-processing includes:

[0095] C1. Add 17.5 mL of deionized water to a beaker, add 4.8 g of NaOH, and stir until dissolved to obtain Solution 1.

[0096] C2. In another beaker, add 2.5 mL of deionized water and 434 mg of Ce(NO3)3·6H2O and stir to obtain Solution 2.

[0097] C3. At room temperature, slowly add solution 2 to solution 1, stir vigorously for 30 min, then pour into a 50 mL reactor and carry out solvothermal reaction at 180°C for 24 h.

[0098] C4. After the solvothermal reaction is completed, the mixture is cooled to room temperature, and the obtained precipitate is washed three times with deionized water and anhydrous ethanol respectively, dried at 60°C overnight, and then ground. After grinding, the length is ≤100nm and the diameter is ≤10nm.

[0099] S2. The sample was transferred into a muffle furnace and calcined at 400 °C for 4 h with a heating rate of 2 °C / min.

[0100] S3. Take out after cooling to obtain CeO2 catalyst.

[0101] The CeO2 catalyst prepared by the above preparation method is CeO2 nanorods, such as Figure 5 As shown, it is recorded as CeO2-rod.

[0102] Example 4

[0103] A method for preparing a CeO2 catalyst comprises steps S1-S3.

[0104] S1. Pre-processing to obtain a sample; wherein the pre-processing includes:

[0105] D1. Add 2 mL of deionized water and 2 mL of glacial acetic acid (99.5 wt%) to a beaker, mix, then add 2 g of Ce(NO3)3·6H2O and stir until completely dissolved to obtain Solution 3.

[0106] D2. Add 60 mL of ethylene glycol solution (99.9 wt%) to another beaker, then pour Solution 3 into the beaker, stir vigorously until transparent, then pour into a 100 mL reactor and heat at 180°C for 3 h to obtain Solution 4.

[0107] D3. Centrifuge Solution 4 at 8000 rpm for 3 min. Wash the precipitate obtained after centrifugation with deionized water and anhydrous ethanol three times respectively, then dry it at 70°C overnight and grind it to a particle size of ≤100 nm.

[0108] S2. The sample was transferred into a muffle furnace and calcined at 400 °C for 4 h with a heating rate of 2 °C / min.

[0109] S3. Take out after cooling to obtain CeO2 catalyst.

[0110] The CeO2 catalyst prepared by the above preparation method is CeO2 nano hollow spheres, denoted as CeO2-spheres. Figure 6 As shown, the diameter of the CeO2-sphere is about 80 to 120 nm, and the wall thickness of the shell is about 20 to 30 nm. The CeO2-sphere shows the characteristics of a hollow porous structure and has good dispersion.

[0111] Example 5

[0112] In Examples 1-4, the morphology of the catalyst was regulated by different pretreatment steps to prepare four types of catalysts with different morphologies: CeO2 nanoparticles (CeO2-particle), CeO2 nanocubes (CeO2-cube), CeO2 nanorods (CeO2-rod) and CeO2 nanohollow spheres (CeO2-sphere).

[0113] The catalysts with different morphologies such as CeO2-particle, CeO2-cube, CeO2-rod and CeO2-sphere were filled into the plasma reactor respectively, and the dielectric barrier discharge (DBD) plasma catalytic system was used, such as Figure 2 As shown, CO2 is introduced and a plasma discharge reaction is carried out to reduce CO2 to CO. The reaction process includes four parts: a gas distribution system, a plasma generator, a plasma reaction device, and a product detection system. It can be used for the study of new low-cost and high-efficiency catalytic CO2 conversion to CO. Compared with thermal catalysis, which requires burning fossil fuels to provide the heat energy required to drive the reaction, it results in high energy costs and also leads to additional CO2 emissions, which does not meet the requirements of sustainable energy development. Although the photocatalytic and electrocatalytic methods driven by renewable energy reduce energy costs, due to the thermodynamic stability and kinetic inertness of CO2 molecules, these two technologies also have problems such as low CO2 conversion rate and poor selectivity of single target products. In view of the disadvantages of high cost, low conversion rate, and difficulty in conversion of the above-mentioned existing conversion methods, the present invention uses catalysts of different morphologies produced in collaboration with DBD plasma devices to convert CO2. Low-temperature plasma can produce highly active substances and electrons (average electron energy of 1-10eV) to excite molecules and thus destroy their chemical bonds under environmental conditions, which makes the reaction that is thermodynamically difficult to occur efficiently converted at a reasonable energy cost and improves the gas conversion rate.

[0114] The nitrogen isothermal adsorption-desorption curves of CeO2-particle, CeO2-cube, CeO2-rod and CeO2-sphere were tested, and the pore size distribution data of each were calculated. Figure 7 As shown in the figure, the pore structure of CeO2-sphere is mainly composed of small-sized mesopores of 3 to 6 nm, with the highest specific surface area, indicating that CeO2-sphere has a mesoporous structure, which is conducive to the adsorption and diffusion of CO2 on the catalyst surface.

[0115] X-ray diffraction analysis was performed on CeO2-particle, CeO2-cube, CeO2-rod and CeO2-sphere before and after plasma catalytic CO2 reduction reaction, such as Figure 8 As shown. It can be seen that the crystal phase of CeO2-particle, CeO2-cube, CeO2-rod and CeO2-sphere did not change significantly before and after the catalytic reaction. Figure 9 There is no obvious change in the morphology of CeO2-sphere before and after the reaction. This shows that the catalyst, especially CeO2-sphere, is stable during the plasma-assisted reaction, providing the prerequisite for the smooth progress of the catalytic reaction.

[0116] CeO2 exhibits different oxygen vacancy contents due to different structural characteristics, and thus exhibits different catalytic properties. Figure 10 As shown, the symmetrical EPR signal is concentrated at the g = 2.003 position, which is caused by the unpaired electrons at the oxygen vacancy defect site, proving the existence of the oxygen vacancy defect site. The CeO2 hollow nanospheres synthesized by the present invention have a large number of oxygen vacancies. In order to clarify the role of oxygen vacancy defects in the plasma-synergistic catalytic reaction, visible Raman spectroscopy tests were performed on CeO2-spheres treated with plasma for 0 min, 3 min, 12 min, and 30 min, respectively.

[0117] like Figure 11 As shown, the strong vibration Raman peak is located at 465 cm -1 , corresponding to the F2g vibration mode (Ce-O-Ce) of CeO2 cubic fluorite phase. Located at 597cm -1 The peak position belongs to the defect-induced D mode, which is attributed to the vibration of oxygen vacancies in the catalyst, and the peak intensity gradually becomes stronger with the delay of reaction time, indicating that the number of oxygen vacancies increases with time.

[0118] By calculating the ratio of F 2g and D mode intensities I D / I F2g , the relative concentration of surface oxygen vacancies can be determined, and the calculation results are shown in Table 12. As time goes by, I D / IF2g The value of gradually increases, showing I D / I F2g -30min>I D / I F2g -12min>I D / I F2g -3min>I D / I F2g -0min, indicating that the relative concentration of CeO2-sphere oxygen vacancies gradually increases and plays a key role in the catalytic reaction process.

[0119] Table 12 I calculated for CeO2-sphere at different reaction times D / I F2g value

[0120] Reaction time (min) 0 3 12 30 <![CDATA[I D / I F2g (×100%)]]> 3.023 3.113 3.193 3.435

[0121] Zeta potential tests were performed on CeO2-spheres treated with DBD plasma for 0 min, 3 min, 12 min, and 30 min, and the results were analyzed. Figure 12 As shown in the figure, with the increase in DBD plasma-catalyst reaction time, the zeta potential gradually increases and shifts toward the positive potential direction, indicating that the plasma introduces more oxygen vacancy defects into the CeO2-spheres. This shows that, unlike the gradual decline in performance of general catalysts, the dielectric barrier discharge plasma increases the oxygen vacancy content in the CeO2 hollow nanospheres during the reaction, thereby increasing their specific surface area. This results in a gradual increase in the CO2 conversion rate as the reaction time increases during the catalytic reaction.

[0122] like Figure 13 As shown, within the first 15 minutes of plasma-catalyzed CO2 reduction, the conversion rates of CeO2-particles and CeO2-rods increased significantly, while the conversion rate of CeO2-cubes increased within 9 minutes of the reaction. The conversion rate of CeO2-spheres rose steadily, reaching a maximum of 14.4%, and then remained stable. This suggests that the O vacancies in CeO2-spheres and the subsequent DBD-induced plasma-catalyzed O vacancies stabilize the catalytic activity.

[0123] The CO generation rates of CeO2-particle, CeO2-cube, CeO2-rod and CeO2-sphere at the highest conversion rate and 30 minutes were calculated respectively. Figure 14As shown, CeO2-spheres exhibit the highest catalytic activity at 30 minutes and are superior to the other three catalysts in terms of sustained CO release. The difference in CO generation rate between the highest conversion and 30 minutes represents the stability of the catalyst. The difference for CeO2-spheres is the smallest, consistent with the conversion trend. This indicates that CeO2-spheres with oxygen vacancies have a stronger ability to generate CO and possess the best stability of the four catalysts.

[0124] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing CeO2 catalysts with different morphologies, characterized in that: It includes the following steps: S1, pre-treatment to obtain samples; S2. The sample was transferred into a muffle furnace and calcined at 400° C. for 4 h at a heating rate of 2° C. / min. S3. Take out after cooling to obtain CeO2 catalysts with different morphologies.

2. The method for preparing CeO2 catalysts with different morphologies according to claim 1, characterized in that: The pre-treatment comprises the following steps: B1. Add NaOH to deionized water and stir until dissolved to obtain Solution 1; the mass volume ratio of the NaOH to the deionized water in Solution 1 is 250-300 mg / mL; B2. Add Ce(NO3)3·6H2O to deionized water and stir to obtain a second solution; the mass volume ratio of Ce(NO3)3·6H2O to deionized water in the second solution is 150-200 mg / mL; B3, slowly dripping the solution 2 into the solution 1, stirring for 20-40 minutes, then pouring into the reaction kettle, and performing a solvothermal reaction at 100° C. for 24 hours; B4. After the solvothermal reaction is completed, the mixture is cooled to room temperature, and the resulting precipitate is washed three times with deionized water and anhydrous ethanol, respectively, dried at 50-90° C. overnight, and then ground; The CeO2 catalyst obtained in step S3 is CeO2 nanocubes.

3. The method for preparing CeO2 catalysts with different morphologies according to claim 1, characterized in that: The pre-treatment comprises the following steps: C1. Add NaOH to deionized water and stir until dissolved to obtain Solution 1; the mass volume ratio of the NaOH to the deionized water in Solution 1 is 250-300 mg / mL; C2. Add Ce(NO3)3·6H2O to deionized water and stir evenly to obtain a second solution; the mass volume ratio of the Ce(NO3)3·6H2O to the deionized water in the second solution is 150-200 mg / mL; C3. Slowly drop the solution 2 into the solution 1, stir vigorously for 20-40 min, then pour into the reactor and carry out solvothermal reaction at 180°C for 24 h; C4. After the solvothermal reaction is completed, the mixture is cooled to room temperature, and the resulting precipitate is washed three times with deionized water and anhydrous ethanol, respectively, dried at 50-90° C. overnight, and then ground; The CeO2 catalyst obtained in step S3 is CeO2 nanorods.

4. The method for preparing CeO2 catalysts with different morphologies according to claim 1, characterized in that: The pre-treatment comprises the following steps: D1. After mixing deionized water and glacial acetic acid, add Ce(NO3)3·6H2O and stir until completely dissolved to obtain solution three; the volume ratio of the deionized water to the glacial acetic acid is 1:1; 0.5 g of Ce(NO3)3·6H2O is added to each milliliter of the mixed solution of deionized water and glacial acetic acid; D2. Pour the solution 3 into the ethylene glycol solution, stir vigorously until transparent, then pour into a reactor and heat to obtain solution 4; D3, centrifuging the solution 4, washing the precipitate obtained after centrifugation with deionized water and anhydrous ethanol three times respectively, drying at 50-90° C. overnight, and then grinding; The CeO2 catalyst obtained in step S3 is CeO2 nano hollow spheres.

5. The method for preparing CeO2 catalysts with different morphologies according to claim 4, characterized in that: In step D2, the volume ratio of the ethylene glycol solution to the solution three is 15:1; the reactor is heated at a temperature of 150-200° C. for 2-4 hours.

6. Use of the CeO2 catalyst prepared by the preparation method of CeO2 catalysts with different morphologies according to any one of claims 1 to 5 in the CO conversion synergistically with CO2 in dielectric barrier discharge plasma.

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