A method for preparing CeO2 nanoparticles with controllable grain size and morphology

Abstract

This invention discloses a method for preparing CeO2 nanoparticles with controllable grain size and morphology, belonging to the field of rare earth oxide preparation technology. This method constructs solvent systems with different solvent combinations using cerium nitrate as the cerium source, polyvinylpyrrolidone as the surfactant, and deionized water and / or organic alcohols as solvents. By adjusting the solvent type and ratio, CeO2 nanoparticles of different sizes and morphologies can be obtained without calcination, achieving precise control over the size and morphology of the CeO2 nanoparticles and resulting in a highly dispersed particle distribution. This solves the problems of existing technologies, such as difficulty in achieving precise and coordinated control of CeO2 nanoparticle grain size and morphology, poor product dispersibility, and low process repeatability.

Description

Technical Field

[0001] This invention belongs to the field of rare earth oxide preparation technology, specifically relating to a method for preparing CeO2 nanoparticles with controllable grain size and morphology. Background Technology

[0002] Cerium dioxide (CeO2), as a typical rare earth oxide, is valued for its fluorite-type crystal structure and unique CeO2 content. 3+ / Ce 4+ The valence state cycling properties of CeO2 nanoparticles have demonstrated significant application value in various high-tech fields such as catalysis, precision polishing, gas sensing, and optoelectronic devices. The functional performance of a material is closely related to its microstructure, grain size, and exposed crystal faces: for example, octahedral CeO2 exhibits excellent thermal stability in high-temperature catalytic reactions due to its preferential exposure of crystal faces; spherical nanoparticles, with their uniform size and good dispersibility, can effectively reduce surface damage during sapphire substrate polishing; and porous or high specific surface area structures are beneficial for increasing the density of active sites, thereby enhancing catalytic efficiency and sensing sensitivity. Therefore, achieving precise control over the grain size and morphology of CeO2 nanoparticles has become a core technological requirement for expanding its diversified application scenarios.

[0003] Hydrothermal synthesis is widely used for CeO2 nanomaterials due to its simplicity and controllability. This method can influence the crystallization behavior and morphology evolution of the product to some extent by adjusting parameters such as precursor concentration, reaction temperature, time, and additives. However, existing techniques typically optimize only a single morphology target, lacking a universal strategy that can achieve the directional construction of various morphologies, from spherical to octahedral to truncated octahedral, by simply adjusting the solvent system within the same process framework. Furthermore, existing techniques still have significant limitations in the controllable preparation of CeO2 nanoparticles: on the one hand, traditional hydrothermal systems struggle to effectively suppress particle aggregation, resulting in poor product dispersibility and a wide particle size distribution, affecting its application in demanding scenarios such as precision polishing where particle uniformity is critical; on the other hand, existing methods lack a sufficient understanding of the correlation mechanism between solvent composition and crystal growth kinetics, failing to establish a clear mapping relationship between solvent polarity, coordination ability, and selective growth of specific crystal faces. This leads to morphology control relying heavily on trial and error, limiting process repeatability and scalability.

[0004] Based on this, the present invention proposes a method for preparing CeO2 nanoparticles with controllable grain size and morphology, in order to solve the problems of difficulty in achieving coordinated and precise control of CeO2 nanoparticle grain size and morphology, poor product dispersibility, and low process repeatability in the above-mentioned existing technologies. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing CeO2 nanoparticles with controllable grain size and morphology, which solves the problems of existing technologies that make it difficult to achieve coordinated and precise control of CeO2 nanoparticle grain size and morphology, poor product dispersibility, and low process repeatability.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing CeO2 nanoparticles with controllable grain size and morphology includes:

[0008] Step 1: Dissolve Ce(NO3)3·6H2O in a solvent, add PVP, and stir magnetically at room temperature until PVP is completely dissolved and the solution is homogeneous and transparent.

[0009] Step 2: Transfer the above solution to a high-pressure reactor, and then to a constant temperature drying oven for hydrothermal reaction;

[0010] Step 3: After the reaction is complete, allow the high-pressure reactor to cool naturally to room temperature, remove the product and centrifuge it, and wash it with anhydrous ethanol and deionized water alternately by centrifugation to remove unreacted precursors and residual impurities, retaining part of the liquid so that the precipitate is immersed in the retained liquid;

[0011] Step 4: Finally, the precipitate containing the retained liquid is placed in a constant temperature drying oven for drying, and then ground to obtain CeO2 nanoparticles;

[0012] Wherein, PVP is polyvinylpyrrolidone; the solvent is any one of deionized water, a binary mixture of butanol and deionized water, a ternary mixture of ethylene glycol, butanol and deionized water, or a ternary mixture of glycerol, butanol and deionized water.

[0013] In a preferred embodiment of the present invention, the temperature of the constant temperature drying oven is kept constant at 180 °C during the hydrothermal reaction; and the centrifugation speed of the high-speed centrifuge is 10000 r / min during centrifugal separation.

[0014] In a preferred embodiment of the present invention, when the addition ratio of Ce(NO3)3·6H2O:PVP:solvent is 0.4g:0.2g:50ml, the hydrothermal reaction time is 10h, the centrifugation time is 10min, and the drying time is 12h.

[0015] In a preferred embodiment of the present invention, when the solvent is deionized water, the prepared CeO2 nanoparticles have a spherical structure.

[0016] In a preferred embodiment of the present invention, when the solvent is a binary mixture of butanol and deionized water, the prepared CeO2 nanoparticles have an octahedral structure.

[0017] In a preferred embodiment of the present invention, in the binary mixture of butanol and deionized water, the volume ratio of butanol to deionized water is V1:V0 = 0.1-0.7:1, and as V1:V0 increases, the size of CeO2 nanoparticles first increases and then decreases.

[0018] Where V1 is the volume of butanol and V0 is the volume of deionized water.

[0019] In a preferred embodiment of the present invention, when the solvent is a ternary mixture of ethylene glycol, butanol and deionized water, the prepared CeO2 nanoparticles have a truncated octahedral structure.

[0020] In a preferred embodiment of the present invention, in the ternary mixture of ethylene glycol, butanol and deionized water, the volume ratio of ethylene glycol, butanol and deionized water is V2:V1:V0 = 0.05-0.16:0.3:1, and as the proportion of V2 increases, the crystal size of CeO2 nanoparticles tends to decrease.

[0021] Where V0 is the volume of deionized water, V1 is the volume of butanol, and V2 is the volume of ethylene glycol.

[0022] In a preferred embodiment of the present invention, when the solvent is a ternary mixture of glycerol, butanol and deionized water, the prepared CeO2 nanoparticles have a spherical structure.

[0023] In a preferred embodiment of the present invention, in the ternary mixture of glycerol, butanol and deionized water, the volume ratio of glycerol, butanol and deionized water is V3:V1:V0 = 0.03-0.08:0.3:1, and as the proportion of V3 increases, the grain size of CeO2 nanoparticles tends to decrease.

[0024] Where V0 is the volume of deionized water, V1 is the volume of butanol, and V3 is the volume of glycerol.

[0025] Compared with existing technologies, this invention provides a method for preparing CeO2 nanoparticles with controllable grain size and morphology, which has the following beneficial effects:

[0026] This invention constructs solvent systems with different solvent combinations using cerium nitrate as the cerium source, polyvinylpyrrolidone as the surfactant, and deionized water and / or organic alcohol as the solvent. By adjusting the solvent type and solvent ratio of the solvent system, CeO2 nanoparticles of different sizes and morphologies can be obtained without calcination, thus achieving precise control over the size and morphology of CeO2 nanoparticles.

[0027] This invention enables precise control over the size and morphology of CeO2 nanoparticles by simply adjusting the type and ratio of the solvent; and the CeO2 nanoparticles obtained by the method of this invention are highly dispersed, uniformly distributed, and do not agglomerate, thus meeting different application requirements.

[0028] The method of this invention is simple, the reaction conditions are relatively mild, and no calcination is required, making it easy to promote and use in industrial production. Attached Figure Description

[0029] Figure 1 These are typical XRD patterns of CeO2 prepared in different solvent systems according to the present invention.

[0030] Figure 2 This is a bar chart showing the effect of the volume ratio of butanol to deionized water on the CeO2 grain size according to the present invention.

[0031] Figure 3 This is a bar chart showing the effect of the volume ratio of ethylene glycol, butanol, and deionized water on the CeO2 grain size according to the present invention.

[0032] Figure 4 This is a bar chart showing the effect of the volume ratio of glycerol, butanol and deionized water on the CeO2 grain size in this invention.

[0033] Figure 5 Typical SEM images of CeO2 nanoparticles prepared under different solvent systems according to the present invention.

[0034] Figure 6 This is a comparison of the effect of the volume ratio of butanol to deionized water on the SEM morphology of CeO2 nanoparticles in the butanol-deionized water solvent system of this invention.

[0035] Figure 7 This is a comparison of the effects of the volume ratio of ethylene glycol, butanol and deionized water on the SEM morphology of CeO2 nanoparticles in the ethylene glycol-butanol-deionized water solvent system of this invention.

[0036] Figure 8 This is a comparison of the effects of the volume ratio of glycerol, butanol and deionized water on the SEM morphology of CeO2 nanoparticles in the glycerol-butanol-deionized water solvent system of this invention.

[0037] Figure 9 This is a comparison of the effects of the glycerol-butanol-deionized water solvent system of the present invention without the addition of PVP on the SEM morphology of CeO2 nanoparticles.

[0038] Figure 10 This is a SEM image of CeO2 nanoparticles during direct drying of centrifuged precipitates in the butanol-deionized water solvent system of this invention.

[0039] Among them: Figure 5 In the figure, Figure a shows a typical SEM image of CeO2 nanoparticles prepared in a deionized water system; Figure b shows a typical SEM image of CeO2 nanoparticles prepared in a butanol-deionized water system; Figure c shows a typical SEM image of CeO2 nanoparticles prepared in an ethylene glycol-butanol-deionized water system; and Figure d shows a typical SEM image of CeO2 nanoparticles prepared in a glycerol-butanol-deionized water system.

[0040] exist Figure 6 In the above figures, Figure a shows the SEM morphology of CeO2 nanoparticles in a butanol-deionized water solvent system with a volume ratio of butanol to deionized water of V1:V0 of 0:1; Figure b shows the SEM morphology of CeO2 nanoparticles in a butanol-deionized water solvent system with a volume ratio of butanol to deionized water of V1:V0 of 0.1:1; Figure c shows the SEM morphology of CeO2 nanoparticles in a butanol-deionized water solvent system with a volume ratio of butanol to deionized water of V1:V0 of 0.3:1; Figure d shows the SEM morphology of CeO2 nanoparticles in a butanol-deionized water solvent system with a volume ratio of butanol to deionized water of V1:V0 of 0.5:1; and Figure e shows the SEM morphology of CeO2 nanoparticles in a butanol-deionized water solvent system with a volume ratio of butanol to deionized water of V1:V0 of 0.7:1.

[0041] exist Figure 7 In the figure, Figure a shows the SEM morphology of CeO2 nanoparticles in the ethylene glycol-butanol-deionized water solvent system when the volume ratio of ethylene glycol, butanol, and deionized water (V2:V1:V0) is 0:0.3:1; Figure b shows the SEM morphology of CeO2 nanoparticles in the ethylene glycol-butanol-deionized water solvent system when the volume ratio of ethylene glycol, butanol, and deionized water (V2:V1:V0) is 0.05:0.3:1; Figure c shows the SEM morphology of CeO2 nanoparticles in the ethylene glycol-butanol-deionized water solvent system when the volume ratio of ethylene glycol, butanol, and deionized water (V2:V1:V0) is 0.1:0.3:1; and Figure d shows the SEM morphology of CeO2 nanoparticles in the ethylene glycol-butanol-deionized water solvent system when the volume ratio of ethylene glycol, butanol, and deionized water (V2:V1:V0) is 0.16:0.3:1.

[0042] exist Figure 8In the figure, Figure a shows the SEM morphology of CeO2 nanoparticles in the glycerol-butanol-deionized water solvent system when the volume ratio of glycerol, butanol, and deionized water (V3:V1:V0) is 0:0.3:1; Figure b shows the SEM morphology of CeO2 nanoparticles in the glycerol-butanol-deionized water solvent system when the volume ratio of glycerol, butanol, and deionized water (V3:V1:V0) is 0.03:0.3:1; Figure c shows the SEM morphology of CeO2 nanoparticles in the glycerol-butanol-deionized water solvent system when the volume ratio of glycerol, butanol, and deionized water (V3:V1:V0) is 0.05:0.3:1; and Figure d shows the SEM morphology of CeO2 nanoparticles in the glycerol-butanol-deionized water solvent system when the volume ratio of glycerol, butanol, and deionized water (V3:V1:V0) is 0.08:0.3:1.

[0043] exist Figure 9 In the figure, Figure a shows the SEM morphology of CeO2 nanoparticles in the glycerol-butanol-deionized water solvent system without PVP at a magnification of 5 kx; Figure b shows the SEM morphology of CeO2 nanoparticles in the glycerol-butanol-deionized water solvent system without PVP at a magnification of 20 kx; and Figure c shows the SEM morphology of CeO2 nanoparticles in the glycerol-butanol-deionized water solvent system without PVP at a magnification of 50 kx. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Please see Figures 1-10 The present invention provides a technical solution:

[0046] A method for preparing CeO2 nanoparticles with controllable grain size and morphology is disclosed. This method constructs solvent systems with different solvent combinations using cerium nitrate as the cerium source, polyvinylpyrrolidone (PVP) as the surfactant (structure directing agent), and deionized water and / or organic alcohols as solvents. By adjusting the solvent type and solvent ratio of the solvent system, CeO2 nanoparticles of different sizes and morphologies can be obtained without calcination. This method achieves precise control over the size and morphology of CeO2 nanoparticles, and the obtained CeO2 nanoparticles are highly dispersed, uniformly distributed, and do not agglomerate, thus meeting different application requirements.

[0047] The specific preparation process of the CeO2 nanoparticles includes:

[0048] Step 1: Dissolve cerium nitrate hexahydrate (Ce(NO3)3·6H2O) in a solvent, add a certain mass of PVP, and stir magnetically at room temperature until the PVP is completely dissolved and the solution is homogeneous and transparent.

[0049] The solvent is any one of deionized water, a binary mixture of butanol and deionized water, a ternary mixture of ethylene glycol, butanol and deionized water, or a ternary mixture of glycerol, butanol and deionized water; wherein: the volume of deionized water is V0, the volume of butanol is V1, the volume of ethylene glycol is V2, and the volume of glycerol is V3.

[0050] Step 2: Transfer the above solution to a high-pressure reactor and then place it in a constant temperature drying oven for hydrothermal reaction;

[0051] Step 3: After the reaction is complete, allow the high-pressure reactor to cool naturally to room temperature, remove the product and centrifuge it using a high-speed centrifuge. Wash it with anhydrous ethanol and deionized water alternately by centrifugation to remove unreacted precursors and residual impurities. Discard most of the liquid and retain some liquid so that the precipitate is submerged in the retained liquid.

[0052] Step 4: Finally, place the precipitate containing the retained liquid in a constant temperature drying oven to dry it, and then grind it to obtain CeO2 nanoparticles.

[0053] Example 1: Preparation of CeO2 nanoparticles in a deionized water system; including:

[0054] 0.4 g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) was dissolved in 50 ml of deionized water. 0.2 g of PVP was added, and the mixture was magnetically stirred at room temperature until the PVP was completely dissolved and the solution was homogeneous and transparent. The solution was transferred to a high-pressure reactor, which was then transferred to a 180 °C constant-temperature drying oven for hydrothermal reaction for 10 h. After the reaction, the high-pressure reactor was allowed to cool naturally to room temperature. The product was then centrifuged at 10000 r / min for 10 min using a high-speed centrifuge. The product was washed alternately with anhydrous ethanol and deionized water by centrifugation to remove unreacted precursors and residual impurities. Most of the liquid was discarded, leaving a portion to submerge the precipitate. Finally, the precipitate containing the retained liquid was dried in a constant-temperature drying oven for 12 h. After grinding, CeO2 nanoparticles were obtained. The CeO2 nanoparticles prepared in the deionized water system were as follows: Figure 5 The spherical structure shown in Figure a.

[0055] Example 2: Preparation of CeO2 nanoparticles in a butanol-deionized water system; including:

[0056] Weigh 0.4 g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and dissolve it in 50 ml of a binary mixture of butanol and deionized water. Add 0.2 g of PVP and stir magnetically at room temperature until the PVP is completely dissolved and the solution is homogeneous and transparent. Transfer the solution to a high-pressure reactor and then transfer the reactor to a 180 °C constant temperature drying oven for hydrothermal reaction for 10 h. After the reaction is complete, allow the high-pressure reactor to cool naturally to room temperature. Remove the product and centrifuge it at 10000 r / min for 10 min. Wash it alternately with anhydrous ethanol and deionized water by centrifugation to remove unreacted precursors and residual impurities. Discard most of the liquid, retaining a portion so that the precipitate is submerged in the retained liquid. Finally, place the precipitate containing the retained liquid in a constant temperature drying oven and dry it for 12 h. After grinding, CeO2 nanoparticles can be obtained.

[0057] In the binary mixture of butanol and deionized water, the total volume of butanol and deionized water is 50 ml, and the volume ratio of butanol to deionized water is V1:V0 = 0.1-0.7:1, specifically 0.1:1, 0.3:1, 0.5:1, and 0.7:1.

[0058] The effects of different butanol to deionized water volume ratios (V1:V0) on the prepared CeO2 grain size in the butanol-deionized water system were obtained as follows: Figure 2 As shown, when the volume of butanol added is 0 (i.e., it is a deionized water system), the grain size is 13.3 nm. With the increase of V1:V0, the grain size first increases and then decreases. Meanwhile, the CeO2 nanoparticles prepared in the butanol-deionized water system are as follows... Figure 5 The octahedral structure shown in Figure b.

[0059] It should be noted that this embodiment differs from Embodiment 1 in that, when dissolving cerium nitrate hexahydrate (Ce(NO3)3·6H2O), deionized water is replaced with a binary mixture of butanol and deionized water, while the other conditions are the same as in Embodiment 1.

[0060] Example 3: Preparation of CeO2 nanoparticles in an ethylene glycol-butanol-deionized water system; including:

[0061] Weigh 0.4 g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and dissolve it in 50 ml of a ternary mixture of ethylene glycol, butanol, and deionized water. Add 0.2 g of PVP and stir magnetically at room temperature until the PVP is completely dissolved and the solution is homogeneous and transparent. Transfer the solution to a high-pressure reactor and then transfer the reactor to a 180 °C constant temperature drying oven for hydrothermal reaction for 10 h. After the reaction is complete, allow the high-pressure reactor to cool naturally to room temperature. Remove the product and centrifuge it at 10000 r / min for 10 min. Wash it alternately with anhydrous ethanol and deionized water by centrifugation to remove unreacted precursors and residual impurities. Discard most of the liquid, retaining a portion so that the precipitate is submerged in the retained liquid. Finally, place the precipitate containing the retained liquid in a constant temperature drying oven and dry it for 12 h. After grinding, CeO2 nanoparticles can be obtained. In the ternary mixture of ethylene glycol, butanol and deionized water, the total volume of ethylene glycol, butanol and deionized water is 50 ml, and the volume ratio of ethylene glycol, butanol and deionized water is V2:V1:V0 = 0.05-0.16:0.3:1, specifically 0.05:0.3:1, 0.1:0.3:1, and 0.16:0.3:1.

[0062] The effects of different volume ratios (V2:V1:V0) of ethylene glycol, butanol, and deionized water on the prepared CeO2 grain size were obtained in the ethylene glycol-butanol-deionized water system. Figure 3 As shown, the grain size tends to decrease with increasing V2 ratio. Meanwhile, CeO2 nanoparticles prepared in the ethylene glycol-butanol-deionized water system were obtained as follows: Figure 5 The truncated octahedral structure shown in Figure c.

[0063] It should be noted that this embodiment differs from Embodiment 1 in that, when dissolving cerium nitrate hexahydrate (Ce(NO3)3·6H2O), deionized water is replaced with a ternary mixture of ethylene glycol, butanol, and deionized water; the other conditions are the same as in Embodiment 1.

[0064] Example 4: Preparation of CeO2 nanoparticles in a glycerol-butanol-deionized water system; including:

[0065] Weigh 0.4 g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and dissolve it in 50 ml of a ternary mixture of glycerol, butanol, and deionized water. Add 0.2 g of PVP and stir magnetically at room temperature until the PVP is completely dissolved and the solution is homogeneous and transparent. Transfer the solution to a high-pressure reactor and then transfer the reactor to a 180 °C constant temperature drying oven for hydrothermal reaction for 10 h. After the reaction is complete, allow the high-pressure reactor to cool naturally to room temperature. Remove the product and centrifuge it at 10000 r / min for 10 min. Wash it alternately with anhydrous ethanol and deionized water by centrifugation to remove unreacted precursors and residual impurities. Discard most of the liquid, retaining a portion so that the precipitate is submerged in the retained liquid. Finally, place the precipitate containing the retained liquid in a constant temperature drying oven and dry it for 12 h. After grinding, CeO2 nanoparticles can be obtained. In the ternary mixture of glycerol, butanol and deionized water, the total volume of glycerol, butanol and deionized water is 50 ml, and the volume ratio of glycerol, butanol and deionized water is V3:V1:V0 = 0.03:0.3:1, 0.05:0.3:1, and 0.08:0.3:1.

[0066] The effects of different volume ratios (V3:V1:V0) of glycerol, butanol, and deionized water on the prepared CeO2 grain size were obtained in the glycerol-butanol-deionized water system. Figure 4 As shown, the grain size decreases with increasing V3 ratio. The grain size was calculated using the Scherrer formula based on XRD data: D = Kλ / (β cos θ), where D is the grain size, K is the shape factor (0.9), λ is the X-ray wavelength (1.5406 Å), β is the half-width at half maximum (in radians) of the (111) crystal plane diffraction peak, and θ is the Bragg diffraction angle. Meanwhile, CeO2 nanoparticles prepared in the glycerol-butanol-deionized water system were obtained as follows... Figure 5 The spherical structure shown in Figure d.

[0067] It should be noted that this embodiment differs from Embodiment 1 in that, when dissolving cerium nitrate hexahydrate (Ce(NO3)3·6H2O), deionized water is replaced with a ternary mixture of glycerol, butanol and deionized water, while the other conditions are the same as in Embodiment 1.

[0068] Based on the structures of CeO2 nanoparticles prepared by the methods described in Examples 1-4 above, it can be seen that in the method of the present invention, different morphologies of CeO2 can be controlled by adjusting the solvent type.

[0069] Comparative Example 1: Preparation of CeO2 nanoparticles in a glycerol-deionized water system; including:

[0070] Weigh 0.4 g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and dissolve it in 50 ml of a binary mixture of glycerol and deionized water. Add 0.2 g of PVP and stir magnetically at room temperature until the PVP is completely dissolved and the solution is homogeneous and transparent. Transfer the solution to a high-pressure reactor and place it in a constant-temperature drying oven at 180 ℃ for hydrothermal reaction for 10 h. After the reaction, allow the high-pressure reactor to cool naturally to room temperature. Remove the product and centrifuge it at 10000 r / min for 10 min. Wash it alternately with anhydrous ethanol and deionized water to remove unreacted precursors and residual impurities. Discard most of the liquid, retaining a portion so that the precipitate is submerged in the retained liquid. Finally, place the precipitate containing the retained liquid in a constant-temperature drying oven and dry it for 12 h. After grinding, CeO2 nanoparticles can be obtained.

[0071] In the binary mixture of glycerol and deionized water, the total volume of glycerol and deionized water is 50 ml, and the volume ratio of glycerol to deionized water is V3:V0 = 0.03-0.08:1, specifically 0.03:1, 0.05:1, and 0.08:1.

[0072] It should be noted that this comparative example differs from Example 1 in that, when dissolving cerium nitrate hexahydrate (Ce(NO3)3·6H2O), deionized water is replaced with a binary mixture of glycerol and deionized water, while the other conditions are the same as in Example 1.

[0073] Comparative Example 2: Preparation of CeO2 nanoparticles without PVP in a glycerol-butanol-deionized water system; including:

[0074] Weigh 0.4 g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and dissolve it in 50 ml of a ternary mixture of glycerol, butanol, and deionized water. Stir magnetically at room temperature until the solution becomes homogeneous and transparent. Transfer the solution to a high-pressure reactor and place it in a constant-temperature drying oven at 180 ℃ for hydrothermal reaction for 10 h. After the reaction, allow the high-pressure reactor to cool naturally to room temperature. Remove the product and centrifuge it at 10000 r / min for 10 min. Wash it alternately with anhydrous ethanol and deionized water by centrifugation to remove unreacted precursors and residual impurities. Discard most of the liquid, retaining a portion so that the precipitate is submerged in the retained liquid. Finally, place the precipitate containing the retained liquid in a constant-temperature drying oven and dry it for 12 h. After grinding, CeO2 nanoparticles can be obtained.

[0075] In the ternary mixture of glycerol, butanol and deionized water, the total volume of glycerol, butanol and deionized water is 50 ml, and the volume ratio of glycerol, butanol and deionized water is V3:V1:V0 = 0.03-0.08:0.3:1, specifically 0.03:0.3:1, 0.05:0.3:1, and 0.08:0.3:1.

[0076] It should be noted that this comparative example differs from Example 4 in that PVP was not added when dissolving cerium nitrate hexahydrate (Ce(NO3)3·6H2O), while the other conditions were the same as in Example 4.

[0077] Comparative Example 3: Preparation of CeO2 nanoparticles by drying without deionized water; including:

[0078] Weigh 0.4 g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and dissolve it in 50 ml of a binary mixture of butanol and deionized water. Add 0.2 g of PVP and stir magnetically at room temperature until the PVP is completely dissolved and the solution is homogeneous and transparent. Transfer the solution to a high-pressure reactor and place it in a constant-temperature drying oven at 180℃ for hydrothermal reaction for 10 h. After the reaction is complete, allow the high-pressure reactor to cool naturally to room temperature. Remove the product and centrifuge it at 10000 r / min for 10 min. Wash it alternately with anhydrous ethanol and deionized water by centrifugation to remove unreacted precursors and residual impurities. Discard all liquids and finally place the precipitate directly in a constant-temperature drying oven to dry for 12 h. After grinding, CeO2 nanoparticles can be obtained.

[0079] It should be noted that, unlike Example 2, this comparative example does not involve drying with the retained liquid; instead, the precipitate is dried directly. All other conditions are the same as in Example 2.

[0080] The material characterization of the CeO2 nanoparticles prepared by the preparation methods described in Examples 1-4 and Comparative Examples 1-3 is as follows:

[0081] 1. XRD characterization:

[0082] Typical XRD patterns of CeO2 nanoparticles prepared in Examples 1-4 are shown below. Figure 1 As shown. 2 θThe diffraction peaks at 28.5°, 33.0°, 47.4°, 56.3°, 59.0°, 69.4°, 76.6°, and 79.0° correspond to (111), (200), (220), (311), (222), (400), (331), and (420) on the CeO2 standard card (PDF# 34-0394), respectively. The absence of other impurity peaks indicates that pure CeO2 nanoparticles were successfully prepared in Examples 1-4. However, under the conditions of Comparative Example 1, no separable precipitate was formed, therefore CeO2 particles could not be obtained.

[0083] 2. SEM characterization:

[0084] Typical SEM morphologies of CeO2 nanoparticles prepared in different solvent systems are shown below. Figure 5 As shown, the particles prepared under all conditions are highly dispersed and exhibit no aggregation. Furthermore, the CeO2 prepared in the deionized water system is nearly spherical. Figure 5 As shown in a; CeO2 prepared in the butanol-deionized water system is octahedral, such as Figure 5 As shown in b; CeO2 prepared in the ethylene glycol-butanol-deionized water system has a truncated octahedral structure, as shown in b. Figure 5 As shown in c; CeO2 prepared in the glycerol-butanol-deionized water system has a spherical structure, as shown in c. Figure 5 As shown in d. Therefore, it can be seen that embodiments 1-4 of the present invention can control the different morphologies of CeO2 by adjusting the solvent type.

[0085] 3. Effect of solvent volume ratio on SEM morphology of CeO2 nanoparticles under different solvent systems:

[0086] (1) In the butanol-deionized water system (Example 2), such as Figure 6 As shown, with the increase of the volume ratio of butanol to deionized water (V1:V0), the morphology of CeO2 nanoparticles gradually changes from spherical to octahedral.

[0087] (2) In the ethylene glycol-butanol-deionized water system (Example 3), such as Figure 7 As shown, with the increase of ethylene glycol ratio, the morphology of CeO2 nanoparticles gradually changes from octahedral to truncated octahedral.

[0088] (3) In the glycerol-butanol-deionized water system (Example 4), such as Figure 8 As shown, with the increase of glycerol ratio, the morphology of CeO2 nanoparticles gradually changes from octahedral to spherical.

[0089] (4) When the glycerol-butanol-deionized water system does not contain PVP (Comparative Example 2), such as Figure 9As shown, CeO2 nanoparticles have the morphology of multiple cluster-like aggregates, which are formed by the aggregation of numerous particles. The overall distribution is uneven, and there are obvious gaps between the aggregates, showing the aggregation morphology of multiple particle clusters.

[0090] (5) In Comparative Example 3, the centrifuged precipitate was dried by direct drying. The SEM morphology of the prepared CeO2 particles is as follows: Figure 10 As shown, the particle clusters are quite severe and uneven.

[0091] Therefore, based on the above results, it can be seen that the method described in this invention can achieve precise control over the size and morphology of CeO2 nanoparticles by simply adjusting the type and ratio of the solvent. The particles are uniformly distributed and do not agglomerate, meeting different application requirements. Moreover, the process is simple, the reaction conditions are relatively mild, and calcination is not required.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing CeO2 nanoparticles with controllable grain size and morphology, comprising: Step 1: Dissolve Ce(NO3)3·6H2O in a solvent, add PVP, and stir magnetically at room temperature until PVP is completely dissolved and the solution is homogeneous and transparent. Step 2: First, transfer the above solution to a high-pressure reactor, and then transfer the high-pressure reactor to a constant temperature drying oven for hydrothermal reaction; Step 3: After the reaction is complete, allow the high-pressure reactor to cool naturally to room temperature, remove the product and centrifuge it, and wash it with anhydrous ethanol and deionized water alternately by centrifugation to remove unreacted precursors and residual impurities, retaining part of the liquid so that the precipitate is immersed in the retained liquid; Step 4: Place the precipitate containing the retained liquid in a constant temperature drying oven to dry it, and then grind it to obtain CeO2 nanoparticles; Wherein, PVP is polyvinylpyrrolidone; the solvent is any one of deionized water, a binary mixture of butanol and deionized water, a ternary mixture of ethylene glycol, butanol and deionized water, or a ternary mixture of glycerol, butanol and deionized water. By adjusting the solvent type and ratio of the solvent system, CeO2 nanoparticles of different sizes and morphologies were obtained without calcination. Specifically, CeO2 nanoparticles with a spherical structure were prepared when the solvent was deionized water, CeO2 nanoparticles with an octahedral structure were prepared when the solvent was a binary mixture of butanol and deionized water, CeO2 nanoparticles with a truncated octahedral structure were prepared when the solvent was a ternary mixture of ethylene glycol, butanol and deionized water, and CeO2 nanoparticles with a spherical structure were prepared when the solvent was a ternary mixture of glycerol, butanol and deionized water.

2. The method for preparing CeO2 nanoparticles with controllable grain size and morphology as described in claim 1, characterized in that: The temperature of the constant temperature drying oven was kept constant at 180 ℃ during the hydrothermal reaction; the centrifugation speed of the high-speed centrifuge was 10000 r / min during centrifugal separation.

3. The method for preparing CeO2 nanoparticles with controllable grain size and morphology as described in claim 2, characterized in that: When the ratio of Ce(NO3)3·6H2O:PVP:solvent is 0.4g:0.2g:50ml, the hydrothermal reaction time is 10h, the centrifugation time is 10min, and the drying time is 12h.

4. The method for preparing CeO2 nanoparticles with controllable grain size and morphology as described in claim 1, characterized in that: In the binary mixture of butanol and deionized water, the volume ratio of butanol to deionized water is V1:V0 = 0.1-0.7:1, and as V1:V0 increases, the grain size of CeO2 nanoparticles shows a trend of first increasing and then decreasing. Where V1 is the volume of butanol and V0 is the volume of deionized water.

5. The method for preparing CeO2 nanoparticles with controllable grain size and morphology as described in claim 1, characterized in that: In the ternary mixture of ethylene glycol, butanol and deionized water, the volume ratio of ethylene glycol, butanol and deionized water is V2:V1:V0 = 0.05-0.16:0.3:1, and the grain size of CeO2 nanoparticles tends to decrease as the proportion of V2 increases.

6. The method for preparing CeO2 nanoparticles with controllable grain size and morphology as described in claim 1, characterized in that: In the ternary mixture of glycerol, butanol and deionized water, the volume ratio of glycerol, butanol and deionized water is V3:V1:V0 = 0.03-0.08:0.3:1, and the grain size of CeO2 nanoparticles tends to decrease as the proportion of V3 increases. Where V0 is the volume of deionized water, V1 is the volume of butanol, and V3 is the volume of glycerol.

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