A CeO2 nanotube and its preparation method and application

Abstract

The present invention discloses CeO2 nanotubes, a preparation method, and applications thereof. The method comprises the following steps: adding a cerium solution dropwise to an alkaline solution, stirring for 1±0.1 hours, subjecting the solution to a hydrothermal reaction at 100-150°C for 10-20 hours, cooling the solution, centrifuging the solution, washing the precipitate, and drying the solution to obtain powdered CeO2 nanorods with a diameter of 10-50 nm. Furthermore, 0.01-0.02 g of CeO2 nanorods are dispersed in 40 mL of water, 0.50-1.00 g of (NH4)2SO4 or 0.40-0.80 g of NH4Cl are added, and the solution is hydrothermally reacted at 100-120°C for 10-20 hours. The solution is cooled, centrifuged, and the precipitate is washed and dried to obtain powdered CeO2 nanotubes with a diameter of 40 nm±2 nm. The method is simple and easy to implement, with controllable conditions, making it suitable for large-scale production. The resulting CeO2 nanotubes are used to prepare a catalyst for CO oxidation, exhibiting excellent catalytic performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of new material development, and in particular relates to a CeO2 nanotube and a preparation method and application thereof. Background Art

[0002] Cerium dioxide (CeO2) is an inexpensive and widely used rare earth compound with N-type semiconductor properties and a unique 4f electronic structure. It exhibits excellent oxygen storage and release capacity and charge exchange capabilities, making it widely used in catalysts, sensors, dyes, batteries, and other fields. Numerous studies have shown that the morphology of a material significantly influences its performance. For example, studies have found that CeO2 with different morphologies exposes different active crystal faces, resulting in different catalytic activities. Furthermore, CeO2 nanotubes have a higher specific surface area than nanorods and are likely to have better catalytic performance. The search for simple, controllable synthesis methods has become a research hotspot in the field of materials preparation. However, further improving the catalytic performance of ceria nanomaterials remains a challenge. Summary of the Invention

[0003] In order to overcome the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a CeO2 nanotube.

[0004] Another object of the present invention is to provide a method for preparing the above-mentioned CeO2 nanotubes.

[0005] Another object of the present invention is to provide applications of the above-mentioned CeO2 nanotubes.

[0006] The present invention is achieved by a method for preparing CeO2 nanotubes, which comprises the following steps:

[0007] (1) dissolving 0.5-1.0 g of Ce(NO3)3·6H2O in 10 mL of water to obtain a cerium solution, dissolving 15-30 g of NaOH in 30 mL of water to obtain an alkaline solution, adding the cerium solution dropwise to the alkaline solution, stirring for 1±0.1 h, and hydrothermally reacting at 100-150° C. for 10-20 h. After cooling, centrifuging, washing, and drying the precipitate to obtain powdered CeO2 nanorods with a diameter of 10-50 nm;

[0008] (2) Disperse 0.01-0.02 g of the CeO2 nanorods in 40 mL of water, add 0.50-1.00 g of (NH4)2SO4 or 0.40-0.80 g of NH4Cl, and hydrothermally react at 100-120°C for 10-20 h. After cooling, centrifuge and wash and dry the precipitate to obtain powdered CeO2 nanotubes with a diameter of 40 nm ± 2 nm.

[0009] Preferably, in steps (1) and (2), the washing is performed by washing with deionized water for 3 to 5 times, and finally washing with ethanol for 1 to 2 times.

[0010] Preferably, in steps (1) and (2), the drying is performed at 50-80° C. under normal pressure or vacuum drying for 4-10 hours.

[0011] The present invention further provides CeO2 nanotubes prepared by the above method.

[0012] The present invention further provides the use of the CeO2 nanotubes as a CO oxidation catalyst.

[0013] The present invention overcomes the shortcomings of the prior art and provides CeO2 nanotubes, a preparation method, and applications thereof. CeO2 nanorods of varying diameters are controllably synthesized by adjusting reaction conditions. The corresponding CeO2 nanotubes are then obtained by simply corroding the rod core with a weak acid. The technical principle is as follows: the prepared CeO2 rods are first converted from Ce(OH)3, then oxidized in water with a trace amount of O2 to form CeO2 and CeO2·nH2O. Because the walls of the CeO2 rods are incompletely crystallized and the cores are even less crystallized, they contain a high concentration of the binary solid compound CeO2·nH2O, which readily dissolves and corrodes in an acidic environment, gradually forming hollow CeO2 tubes. Experiments have shown that fresh CeO2 rods, not yet fully crystallized, are more susceptible to corrosion and conversion into nanotubes.

[0014] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects:

[0015] (1) The present invention can prepare CeO2 rods of different diameters by a simple hydrothermal method, and then obtain CeO2 nanotubes of corresponding sizes by simply corroding the rod core with weak acid. This preparation method is simple and easy to implement, with controllable conditions, and is suitable for large-scale production.

[0016] (2) In the CO oxidation experiment, the catalytic performance of the CeO2 nanotubes of the present invention as a catalyst is significantly better than that of CeO2 nanorods and nanoparticles. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 2 are electron microscope observation images of the embodiments of the present invention; wherein, Figure A is CeO2 nanorods, and Figure B is CeO2 nanotubes;

[0018] Figure 2 is the XRD characterization result of CeO2 nanorods in the embodiment of the present invention;

[0019] Figure 3 is the XRD characterization result of CeO2 nanotubes in the embodiment of the present invention;

[0020] Figure 4This is a comparison chart of the conversion rates of CO oxidation catalyzed by CeO2 nanotubes, CeO2 nanorods and CeO2 nanoparticles in the application examples of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] Example 1

[0023] (1) 0.8 g of Ce(NO3)3·6H2O was dissolved in 10 mL of water to obtain a cerium solution, and 25 g of NaOH was dissolved in 30 mL of water to obtain an alkaline solution. The cerium solution was added dropwise to the alkaline solution, stirred for 1 hour, and then poured into an autoclave. The mixture was hydrothermaled in an oven at 130°C for 15 hours, cooled, and centrifuged. The mixture was washed with deionized water for 4 times and finally washed with ethanol for 2 times. The mixture was dried at 65°C under normal pressure or vacuum dried for 6 hours to obtain powdered CeO2 nanorods.

[0024] The obtained powder was observed by electron microscope. Figure 1 As shown in A, Figure 1 As can be seen from A, CeO2 nanorods are solid rods with a diameter of about 40nm and a length of 100 to 1000nm. The obtained powder was characterized by XRD, and the results are as follows Figure 2 As shown, Figure 2 This is the XRD pattern of CeO2 nanorods (diameter about 40nm).

[0025] (2) 0.01 g of dried CeO2 nanorod powder was placed in 40 mL of water, 0.80 g of (NH4)2SO4 or 0.60 g of NH4Cl was added, and the mixture was hydroheated at 110°C for 15 h. After cooling, the mixture was centrifuged, and the precipitate was washed and dried to obtain powdered CeO2 nanotubes 1.

[0026] The obtained CeO2 nanotubes 1 were observed by electron microscope. Figure 1 As shown in B, Figure 1 B shows that CeO2 nanotubes 1 are hollow with a diameter of about 40nm. XRD characterization of the obtained CeO2 nanotubes 1 is performed. Figure 3 contrast Figure 2 The diffraction peak intensity is higher, indicating that the obtained CeO2 nanotubes 1 are better crystallized. Figure 3 As shown, Figure 3 This is the XRD pattern of CeO2 nanotube 1 (diameter about 40nm).

[0027] Example 2

[0028] (1) 0.5 g of Ce(NO3)3·6H2O was dissolved in 10 mL of water to obtain a cerium solution, and 30 g of NaOH was dissolved in 30 mL of water to obtain an alkaline solution. The cerium solution was added dropwise to the alkaline solution, stirred for 1±0.1 h, and then poured into an autoclave. The mixture was hydrothermaled in an oven at 150°C for 10 h, cooled, and centrifuged. The mixture was washed with deionized water 5 times and finally washed with ethanol once. The mixture was dried at 80°C under normal pressure or vacuum dried for 10 h to obtain powdered CeO2 nanorods.

[0029] (2) 0.01 g of dried CeO2 nanorod powder was placed in 40 mL of water, 1.00 g of (NH4)2SO4 or 0.40 g of NH4Cl was added, and the mixture was hydroheated at 100°C for 20 h. After cooling, the mixture was centrifuged, and the precipitate was washed and dried to obtain powdered CeO2 nanotubes 2.

[0030] Example 3

[0031] (1) 1.0 g of Ce(NO3)3·6H2O was dissolved in 10 mL of water to obtain a cerium solution, and 15 g of NaOH was dissolved in 30 mL of water to obtain an alkaline solution. The cerium solution was added dropwise to the alkaline solution, stirred for 1 hour, and then poured into an autoclave. The mixture was hydrothermaled in an oven at 100°C for 20 hours, cooled, and centrifuged. The mixture was washed three times with deionized water and finally washed twice with ethanol. The mixture was dried at 50°C under normal pressure or vacuum dried for 4 hours to obtain powdered CeO2 nanorods.

[0032] (2) 0.02 g of dried CeO2 nanorod powder was placed in 40 mL of water, 0.50 g of (NH4)2SO4 or 0.80 g of NH4Cl was added, and the mixture was hydroheated at 120°C for 10 h. After cooling, the mixture was centrifuged, and the precipitate was washed and dried to obtain powdered CeO2 nanotubes 3.

[0033] Comparative Example

[0034] 0.8 g of Ce(NO3)3·6H2O was dissolved in 40 mL of water to obtain a cerium solution, which was hydrothermally reacted at 120°C for 15 h. After cooling, the solution was centrifuged and the precipitate was washed and dried to obtain powdered CeO2 nanoparticles with a diameter of 10 to 100 nm.

[0035] Application Examples

[0036] In the CO catalytic oxidation reaction, catalyst activity evaluation was conducted in a fixed-bed microreactor. CeO2 nanorods, CeO2 nanotubes 1, and CeO2 nanoparticles in the comparative example were selected as catalysts, with 50 mg of each catalyst used. The reaction gas had a volume composition of 1.6% CO, 20.8% O2, and 77.6% N2. The product was separated by 13X molecular sieve (to separate O2, N2, and CO) and Propak Q (to detect CO2), and then detected by a thermal conductivity detector. The reaction temperature was controlled at 50-400°C, and the space velocity was 15,000 ml·g -1 ·h -1 .

[0037] The catalytic reaction results are as follows Figure 4 The results show that the catalytic activity of CeO2 nanotubes 1 increases significantly with increasing reaction temperature. At 300°C, the CO conversion rate of CeO2 nanotubes 1 reaches 100%, while the CO conversion rate of CeO2 nanorods is 70%, while the CO conversion rate of CeO2 nanoparticles is less than 5%. This shows that the catalytic activity of CeO2 nanotubes is higher than that of CeO2 nanorods and CeO2 nanoparticles.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements 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 nanotubes, characterized in that: The method comprises the following steps: (1) Dissolve 0.5-1.0 g of Ce(NO3)3.6H2O in 10 mL of water to obtain a cerium solution, and dissolve 15-30 g of NaOH in 30 mL of water to obtain an alkaline solution. Add the cerium solution dropwise to the alkaline solution, stir for 1±0.1 h, and hydrothermally react at 100-150°C for 10-20 h. After cooling, centrifuge, wash, and dry the precipitate to obtain powdered CeO2 nanorods with a diameter of 10-50 nm. (2) Disperse 0.01-0.02 g of the CeO2 nanorods in 40 mL of water, add 0.50-1.00 g of (NH4)2SO4 or 0.40-0.80 g of NH4Cl, and hydrothermally react at 100-120 °C for 10-20 h. After cooling, centrifuge the precipitate, wash and dry it to obtain powdered CeO2 nanotubes with a diameter of 40 nm ± 2 nm.

2. The method according to claim 1, wherein In steps (1) and (2), the washing is performed by washing with deionized water for 3 to 5 times and finally washing with ethanol for 1 to 2 times.

3. The method according to claim 1, wherein In steps (1) and (2), the drying is performed at 50-80°C under normal pressure or vacuum drying for 4-10 hours.

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