阅读说明：本技术 一种二氧化铈纳米线的制备方法及其应用 (Preparation method and application of cerium dioxide nanowire ) 是由 赵杰 王婷 张泽星 屈妙 李昊龙 于 2021-10-11 设计创作，主要内容包括：本发明公开了一种二氧化铈纳米线的制备方法及其应用,属于材料制备和环境治理技术领域,将钼源、铈源的水溶液通过强碱性水热反应后生成氧化铈前驱体、钼源的混合物,通过水热搅拌将其均匀混合,最后在空气气氛中高温煅烧得到了二氧化铈纳米线。用钼元素对二氧化铈改性以后不仅可以改变二氧化铈的形貌,而且可以提高二氧化碳的产量,可代替贵金属来达到提高二氧化碳产量的目的,显著降低了成本。本发明方法具有操作简便、原料易得、成本低、能源消耗少等优点；稳定性良好,活性高,光热催化燃烧挥发性有机化合物的效率高。(The invention discloses a preparation method and application of cerium dioxide nanowires, belonging to the technical field of material preparation and environmental management. The molybdenum element is used for modifying cerium dioxide, so that the morphology of the cerium dioxide can be changed, the yield of carbon dioxide can be increased, the precious metal can be replaced, the purpose of increasing the yield of the carbon dioxide can be achieved, and the cost is obviously reduced. The method has the advantages of simple and convenient operation, easily obtained raw materials, low cost, low energy consumption and the like; good stability, high activity and high efficiency of photo-thermal catalytic combustion of volatile organic compounds.)

1. A preparation method of cerium dioxide nanowires is characterized by comprising the following steps:

step 1) mixing sodium hydroxide, cerium nitrate, molybdate and deionized water to obtain a mixed solution;

step 2) carrying out hydrothermal reaction on the mixed solution, cooling, washing and drying to obtain a cerium dioxide precursor;

and 3) carrying out high-temperature calcination on the cerium dioxide precursor to obtain the cerium dioxide nanowire.

2. The method of preparing cerium dioxide nanowires according to claim 1, wherein the molybdate is any one of sodium molybdate dihydrate, ammonium molybdate tetrahydrate, or cobalt molybdate; the cerium salt is cerium nitrate; the strong alkaline solution is sodium hydroxide solution.

3. The method for preparing cerium dioxide nanowires according to claim 1, wherein the mixing ratio of sodium hydroxide, cerium nitrate, molybdate and deionized water is 19.2 g: 1.74 g: (0.0187 to 0.1269) g: 80 ml.

4. The method for preparing cerium dioxide nanowires according to claim 1, wherein the hydrothermal reaction conditions are as follows: the temperature is 80-180 ℃, and the time is 12-48 h.

5. The preparation method of the cerium dioxide nanowire according to claim 1, wherein the cerium dioxide nanowire is washed to be neutral by deionized water and then dried in an oven, wherein the drying temperature is 50-80 ℃ and the drying time is 6-8 h.

6. The method for preparing cerium oxide nanowires according to claim 1, wherein the conditions of the high-temperature calcination are as follows: the temperature is 400-600 ℃, and the time is 2-6 h.

7. The cerium dioxide nanowire obtained by the preparation method according to any one of claims 1 to 6, wherein the cerium dioxide nanowire has a size of 30 to 200nm and a structure shape of a cubic fluorite structure.

8. The use of the ceria nanowires of claim 7 in the field of photo-thermal catalytic combustion of volatile organic compounds, wherein the ceria nanowires are used as a catalyst.

Technical Field

The invention belongs to the technical field of material preparation and environmental management, and relates to a preparation method and application of cerium dioxide nanowires.

Background

VOCs (volatile organic compounds) refer to various organic compounds with boiling points of 50-260 ℃ at normal temperature, can participate in the formation of ozone, photochemical smog and secondary aerogel in the atmospheric environment, are important factors for exacerbating atmospheric composite pollution, and directly influence human health and sustainable development of economy and society. In recent years, pollution control of volatile organic compounds has been highly regarded. The catalytic combustion method is considered to be one of the most effective technologies for treating VOCs due to the advantages of high removal efficiency, no secondary pollution and the like, and the research and development of efficient catalysts are the key for improving the core competitiveness of the technologies. Wherein, CeO₂Middle Ce³⁺And Ce⁴⁺The change-over between states may effect a redox cycle, whereby CeO₂The catalyst has excellent oxygen storage/release function and oxygen vacancy rapid diffusion capacity, can be used as an auxiliary agent to improve the performance of the catalyst, and can also be used as an active component or a carrier to ensure that the catalyst can keep activity under oxygen-poor and oxygen-rich conditions.

Since the catalytic reactivity of ceria is strongly dependent on the crystal exposure, control of its morphology is crucial. CN201911262263.9 discloses a preparation method of cerium dioxide nanosheets, wherein ethyl orthosilicate is used as a template agent, cerium nitrate is used as a source substance to obtain cerium dioxide nanosheets with uniform size, and the template agent is required to be added in the preparation process. CN202110191015.0 reports a method for preparing spherical nano-ceria material, in which cerium source is dissolved in organic solvent, then high molecular polymer is added, and the material is centrifugally washed and dried to obtain spherical nano-ceria material, the preparation process is complex, and the distribution of spherical particles is not uniform. CN201910920710.9 reports preparation of cerium dioxide nanowires, which is a paper sheet jointly modified by filter paper serving as a substrate, activating the surface of the filter paper, growing a metal organic framework material in situ, and preparing a cerium dioxide nanowire-metal organic framework heterojunction through electrodeposition, wherein the preparation process needs a substrate substance, and the preparation method has the defects of complex process, complex reaction conditions and the like. Xianjun Du produced ceria nanowires in 2012 using cerium nitrate and sodium hydroxide, but found that the nanowires were not uniformly distributed with further experimental repetitions.

Disclosure of Invention

In order to overcome the defects of nonuniform distribution and small length-diameter ratio of cerium dioxide nanowires in the prior art, the invention aims to provide a preparation method and application of cerium dioxide nanowires.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a preparation method of cerium dioxide nanowires comprises the following steps:

step 1) mixing sodium hydroxide, cerium nitrate, molybdate and deionized water to obtain a mixed solution;

step 2) carrying out hydrothermal reaction on the mixed solution, cooling, washing and drying to obtain a cerium dioxide precursor;

and 3) carrying out high-temperature calcination on the cerium dioxide precursor to obtain the cerium dioxide nanowire.

Preferably, the molybdate is any one of sodium molybdate dihydrate, ammonium molybdate tetrahydrate or cobalt molybdate; the cerium salt is cerium nitrate; the strong alkaline solution is sodium hydroxide solution

Preferably, the mixing dosage ratio of the sodium hydroxide, the cerium nitrate, the molybdate and the deionized water is 19.2 g: 1.74 g: (0.0187 to 0.1269) g: 80 ml.

Preferably, the conditions of the hydrothermal reaction are: the temperature is 80-180 ℃, and the time is 12-48 h.

Preferably, the mixture is washed to be neutral by deionized water and then dried in an oven, wherein the drying temperature is 50-80 ℃, and the drying time is 6-8 h.

Preferably, the conditions of the high-temperature calcination are: the temperature is 400-600 ℃, and the time is 2-6 h.

The cerium dioxide nanowires obtained by the preparation method have the size of 30-200nm and the structural shape of a cubic fluorite structure.

The application of the cerium dioxide nanowire in the field of photo-thermal catalytic combustion of volatile organic compounds is disclosed, and the cerium dioxide nanowire is used as a catalyst.

Compared with the prior art, the invention has the following beneficial effects:

the invention discloses a preparation method of cerium dioxide nanowires, which comprises the steps of carrying out strong alkaline hydrothermal reaction on a molybdenum source and a cerium source water solution to generate a cerium oxide precursor and molybdenum source mixture, uniformly mixing the cerium oxide precursor and the molybdenum source mixture through hydrothermal stirring, and finally calcining at high temperature in an air atmosphere to obtain the cerium dioxide nanowires. The molybdenum element is used for modifying cerium dioxide, so that the morphology of the cerium dioxide can be changed, the yield of carbon dioxide can be increased, the precious metal can be replaced, the purpose of increasing the yield of the carbon dioxide can be achieved, and the cost is obviously reduced. The method has the advantages of simple and convenient operation, easily obtained raw materials, low cost, low energy consumption and the like; good stability, high activity and high efficiency of photo-thermal catalytic combustion of volatile organic compounds.

Further, the content of molybdenum is too low, and the catalytic efficiency of the composite catalyst is low; too high a molybdenum content can cover the active sites of ceria and can also affect catalytic efficiency.

Furthermore, the molybdenum source has diversified sources, easy purchase and low cost.

Furthermore, the calcination temperature is 400-600 ℃, the calcination time is 2-6 h, and the calcination temperature and the calcination time can affect the crystal form of the cerium dioxide.

The invention also discloses cerium dioxide nanowires prepared by the preparation method, wherein the cerium dioxide nanowires are CeO with a cubic fluorite structure₂Toluene can be catalytically oxidized to carbon dioxide. In addition, the material has the characteristics of no toxicity, no harm, high temperature resistance, acid and alkali corrosion resistance, and is a photo-thermal catalytic material with good stability.

The invention also discloses application of the cerium dioxide nanowire material, and in a test experiment of activity of photothermal catalytic oxidation toluene, the cerium dioxide nanowire has obviously improved reaction activity compared with cluster-shaped cerium dioxide, wherein the yield of carbon dioxide is improved by 3 times to the maximum. In addition, the scanning electron microscope image shows that the morphology of cerium dioxide is changed after molybdenum modification, so that the material can be applied to the field of photo-thermal catalysis to catalyze and oxidize volatile organic compounds.

Drawings

FIG. 1 is an XRD pattern of a cerium oxide catalyst according to the present invention, in which black vertical thin lines correspond to CeO₂The PDF card of (1);

FIG. 2 is a graph showing the comparison of the catalytic activity of catalysts with different molybdenum contents and cerium oxide prepared in examples 1 to 4 of the present invention;

FIG. 3 is a scanning electron micrograph of the ceria catalysts according to examples 1 to 4 of the present invention (a is example 3, b is example 2, c is example 1, and d is example 4).

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

example 1

A preparation method of cerium dioxide nanowires comprises the following steps:

1) dissolving 1.74g of cerous nitrate hexahydrate and 0.1269g of ammonium molybdate tetrahydrate in 40mL of distilled water together to obtain a mixed solution of the cerous nitrate and the ammonium molybdate; dissolving 19.2g of sodium hydroxide in 40mL of distilled water to obtain a sodium hydroxide solution;

2) dropwise adding a sodium hydroxide solution into a mixed solution of cerium nitrate and ammonium molybdate while continuously stirring, and continuously stirring for 30 minutes to obtain a new mixed solution;

3) the new mixed solution was transferred to a 100mL stainless steel autoclave lined with Teflon and reacted at 120 ℃ for 36 h. After the reaction is finished and the reaction product is naturally cooled, a lower precipitate is left.

4) And (3) centrifugally washing the mixture for multiple times to neutrality by using deionized water and an ethanol solution, and drying the mixture for 8 hours at the temperature of 60 ℃ to obtain the molybdenum-cerium precursor material.

5) And (3) putting the molybdenum-cerium precursor material into a muffle furnace, and calcining at the high temperature of 500 ℃ for 4h in the air atmosphere. Thus obtaining the 10% molybdenum modified cerium dioxide photocatalytic material (10% is the ratio of the theoretical molybdenum element mass to the cerium dioxide mass).

Example 2

A preparation method of cerium dioxide nanowires comprises the following steps:

1) dissolving 1.74g of cerous nitrate hexahydrate and 0.06345g of ammonium molybdate tetrahydrate in 40mL of distilled water together to obtain a mixed solution of the cerous nitrate and the ammonium molybdate; dissolving 19.2g of sodium hydroxide in 40mL of distilled water to obtain a sodium hydroxide solution;

2) dropwise adding a sodium hydroxide solution into a mixed solution of cerium nitrate and ammonium molybdate while continuously stirring, and continuously stirring for 30 minutes to obtain a new mixed solution;

3) the new mixed solution was transferred to a 100mL stainless steel autoclave lined with Teflon and reacted at 80 ℃ for 48 h. After the reaction is finished and the reaction product is naturally cooled, a lower precipitate is left.

4) And centrifugally washing the mixture for multiple times to neutrality by using deionized water and an ethanol solution, and drying the mixture for 8 hours at 50 ℃ to obtain the molybdenum-cerium precursor material.

5) And (3) putting the molybdenum-cerium precursor material into a muffle furnace, and calcining for 6h at the high temperature of 400 ℃ in the air atmosphere. Thus obtaining the 5% molybdenum modified cerium dioxide photocatalytic material (5% is the ratio of the theoretical molybdenum element mass to the cerium dioxide mass).

Example 3

A preparation method of cerium dioxide nanowires comprises the following steps:

1) dissolving 1.74g of cerous nitrate hexahydrate and 0.0187g of sodium molybdate dihydrate into 40mL of distilled water together to obtain a mixed solution of the cerous nitrate and the ammonium molybdate; dissolving 19.2g of sodium hydroxide in 40mL of distilled water to obtain a sodium hydroxide solution;

2) dropwise adding a sodium hydroxide solution into a mixed solution of cerium nitrate and sodium molybdate while continuously stirring, and continuously stirring for 30 minutes to obtain a new mixed solution;

3) the new mixed solution was transferred to a 100mL stainless steel autoclave lined with Teflon and reacted at 100 ℃ for 24 h. After the reaction is finished and the reaction product is naturally cooled, a lower precipitate is left.

4) And (3) centrifugally washing the mixture for multiple times to neutrality by using deionized water and an ethanol solution, and drying the mixture for 6 hours at 80 ℃ to obtain the molybdenum-cerium precursor material.

5) And (3) putting the molybdenum-cerium precursor material into a muffle furnace, and calcining for 5h at the high temperature of 500 ℃ in the air atmosphere. Thus obtaining the 1% molybdenum modified cerium dioxide photocatalytic material (1% is the ratio of the theoretical molybdenum element mass to the cerium dioxide mass).

Example 4

A preparation method of cerium dioxide nanowires comprises the following steps:

1) dissolving 1.74g of cerous nitrate hexahydrate and 0.5049g of cobalt molybdate together in 40mL of distilled water to obtain a mixed solution of cerous nitrate and ammonium molybdate; dissolving 19.2g of sodium hydroxide in 40mL of distilled water to obtain a sodium hydroxide solution;

2) dropwise adding a sodium hydroxide solution into a mixed solution of cerium nitrate and molybdenum nitrate under continuous stirring, and continuously stirring for 30 minutes to obtain a new mixed solution;

3) the new mixed solution was transferred to a 100mL stainless steel autoclave lined with Teflon and reacted at 180 ℃ for 12 h. After the reaction is finished and the reaction product is naturally cooled, a lower precipitate is left.

4) And centrifugally washing the mixture for multiple times to neutrality by using deionized water and an ethanol solution, and drying the mixture for 7 hours at 70 ℃ to obtain the molybdenum-cerium precursor material.

5) And (3) putting the molybdenum-cerium precursor material into a muffle furnace, and calcining for 2h at 600 ℃ in the air atmosphere. Thus obtaining the 20% molybdenum modified cerium dioxide photocatalytic material (20% is the ratio of the theoretical molybdenum element mass to the cerium dioxide mass).

The addition amounts of the cerium source and the molybdenum source are determined according to the following method:

wherein, the cerium source quality is self-regulated, such as 500mg, and other results are further calculated.

100mg of the sample obtained in example 1 was taken, and X-ray diffraction was carried out to obtain an XRD diffraction pattern as shown in FIG. 1. The peaks in fig. 1 are sharp, typical ceria crystals, and there is no XRD diffraction peak associated with molybdenum due to centrifugal washing. As can be seen by comparison of the peak positions in FIG. 1 with the standard card (PDF #34-0393), cubic fluorite structured ceria is present.

The activity test process comprises the following steps: 100mg of the samples of examples 1 to 4 and 100mg of cerium oxide were weighed and subjected to five experiments. The five samples were uniformly dispersed in sample tubes having a diameter of 50mm, respectively, and placed in a vacuum reaction apparatus, 40. mu.L of toluene was added to the vacuum reaction apparatus using a syringe, and then dry air was introduced to the vacuum reaction apparatus to atmospheric pressure, and then the samples were heated to 150 ℃ and irradiated with light, and the product concentration was measured by gas chromatography every 0.5h, to obtain a curve as shown in FIG. 2. As can be seen from fig. 2, the catalytic oxidation efficiency for toluene is significantly improved in the samples of examples 1 to 4 compared to unmodified cerium oxide, and example 1 is the most preferable and can be improved by up to 3 times.

The samples prepared in the embodiments 1 to 4 are taken and subjected to scanning electron microscope test characterization, and the results are shown in fig. 3, and it is seen from fig. 3 that the morphology of the material added with molybdenum is greatly changed compared with that of pure cerium dioxide, which is beneficial to the photo-thermal concerted catalytic combustion of toluene. The morphology of cerium dioxide can be changed and the yield of carbon dioxide can be improved by controlling the morphology of cerium dioxide by using molybdenum, so that the molybdenum can replace noble metals to achieve the aim of improving the yield of carbon dioxide.

In summary, the present invention relates to a uniform ceria nanowire, a method for preparing the same, and applications thereof. The preparation method comprises the following steps: and (3) hydrothermally generating a precursor of cerium oxide by using cerium nitrate hexahydrate and molybdate, and finally calcining at a high temperature in an air atmosphere to obtain the cerium oxide catalyst. The invention also comprises cerium dioxide with different morphologies and application of the cerium dioxide in the photo-thermal catalytic degradation of toluene. The linear cerium dioxide nano material prepared by the method has obvious catalytic performance on toluene at 150 ℃, and can catalyze and degrade the toluene into nontoxic and harmless carbon dioxide. The cerium oxide is modified by molybdenum element to obtain cerium dioxide nanowires, the yield of carbon dioxide can be increased, the cerium dioxide nanowires can replace noble metals to achieve the purpose of increasing the yield of carbon dioxide, and the cost is obviously reduced. The method has the advantages of simple preparation process, low cost and easily obtained raw materials.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.