KR101804627B1 - Method for manufacturing morphology controlled metal nanoparticle yolk-shell nanocomposite and its application as nanocatalyst - Google Patents

Abstract

The present invention provides a method for preparing nanoparticles comprising: a first step of preparing shape-controlled nanoparticles; A second step of coating the nanoparticles with silica to obtain a nanoparticle yoke-silica shell structure; A third step of coating a metal oxide on the nanoparticle yoke-silica shell structure to obtain a metal oxide coated nanoparticle yoke-silica shell structure; And a fourth step of removing the silica by treating the metal oxide coated nanoparticle yoke-silica shell structure with a base to obtain a nanoparticle yoke-metal oxide shell structure. Nanocomposites and their application as catalysts.

Description

METHOD AND APPARATUS FOR MANUFACTURING YOK-SHELL NANO COMPOSITE CONTAINING SHAPED-CONTROLLED METAL NANOPARTICLES Technical Field [1] The present invention relates to a method and a method for manufacturing a controlled-metal nanoparticle-controlled metal nanoparticle yolk-shell nanocomposite and its application as nanocatalyst,

The present invention relates to a method for producing a nanocomposite having a yolk-shell structure including shape-controlled metal nanoparticles, more specifically, to a nanocomposite nanocomposite having a yoke- And a method for utilizing the nanocomposite as a catalyst.

Nanoparticles are used in various fields such as engineering, optics, and medicine due to their unique optical, electrical, and chemical properties. With the development of colloid technology, it is possible to control the size and shape of metal nanoparticles. , Drug delivery, and biomedicine.

At present, the difficulty of aggregation, leaching, stability, recovery and reuse of nanoparticles makes it difficult to utilize nanoparticles.

Therefore, as a method to effectively and stably utilize the nanoparticles in order to solve such a problem, a study in which nanoparticles are immobilized on a nanocomposite having a core-shell or yokk-shell structure It went on.

Particularly, nanoparticles are applied to the catalyst field. It is known that the catalytic properties of the nanoparticles are greatly influenced by the shape and size of the nanoparticles.

However, existing methods have been difficult to maintain the initial shape of the nanoparticles because the nanoparticles have undergone shape controlled nanoparticle calcination and acid treatment during nanocomposite production. Therefore, it is difficult to maintain the nanoparticles in the core-shell, But it has limitations to utilize it as the center metal of the structure such as.

Therefore, researches have been conducted to control the formation of reaction products and by-products by controlling the activity and selectivity of the catalyst by controlling the shape and size of the nanoparticles in a nanocomposite comprising core-shell or yoke-shell structure containing nanoparticles .

KR 2015-0063002 A

In order to solve the problems of the prior art, the present invention provides a nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite nanocomposite having a shape- It is an object of the present invention to provide a method for producing a nanocomposite and a yoke-shell nanocomposite catalyst containing shape-controlled metal nanoparticles.

In order to accomplish the above object, the present invention provides a method for preparing a core nanoparticle comprising: a first step of preparing shape-controlled core nanoparticles; A second step of coating the core nanoparticles with silica to obtain a core-silica shell structure; A third step of coating a metal oxide on the core-silica shell structure to obtain a metal oxide coated core-silica shell structure; And a fourth step of removing the silica by treating the metal oxide coated core-silica shell structure with a base to obtain a nanoparticle yoke-metal oxide shell structure. The yoke-shell nanocomposite comprising shape-controlled metal nanoparticles Of the present invention.

The present invention also provides a shape controlled nanoparticle comprising a shape controlled core nanoparticle and a metal oxide shell surrounding the core nanoparticle, wherein an empty space is formed between the core nanoparticle and the metal oxide shell. The present invention provides a yoke-shell nanocomposite catalyst comprising metal nanoparticles.

The yoke-shell nanocomposite prepared according to the present invention can effectively maintain the shape and size of the core nanoparticles.

The yoke-shell nanocomposite prepared according to the present invention can stably immobilize the core nanoparticles.

The yoke-shell nanocomposite prepared according to the present invention has high recovery and reuse ratio and thus can be economically used as a catalyst.

1 is a schematic diagram of a process for fabricating shape-controlled metal nanoparticle yoke-metal oxide shell nanocomposites according to an embodiment of the present invention.
Fig. 2 is a TEM photograph of the cube-shaped palladium nanoparticles prepared in the first step of Example 1. Fig.
3 is a TEM photograph of the core-shell nanocomposite prepared in the second step of Example 1. FIG.
FIGS. 4 and 5 are TEM photographs of the palladium yoke-zirconia shell nanocomposite prepared in the third and fourth steps of Example 1. FIG.
6 is a TEM photograph of the palladium yoke-titania shell nanocomposite prepared in Example 2. Fig.
FIG. 7 shows the results of nitrogen adsorption and desorption of the palladium yoke-zirconia shell nanocomposite prepared in the second and fourth steps of Example 1. FIG.
8 is an XPS result of the palladium yoke-zirconia shell nanocomposite prepared in Example 1. Fig.

Hereinafter, the present invention will be described in detail.

The method for manufacturing a yoke-shell nanocomposite including shape-controlled metal nanoparticles of the present invention comprises: a first step of preparing shape-controlled core nanoparticles; A second step of coating the core nanoparticles with silica to obtain a core-silica shell structure; A third step of coating a metal oxide on the core-silica shell structure to obtain a metal oxide coated core-silica shell structure; And a fourth step of removing the silica by treating the metal oxide coated core-silica shell structure with a base to obtain a nanoparticle yoke-metal oxide shell structure.

The nanoparticles may be selected from the group consisting of Pd, Pt, Au, Ag, Rh, Ru, Ni, Co, Cu, Metal nanoparticles of one or more kinds of alloys selected from the group consisting of molybdenum (Mo), tungsten (W), and tin (Sn).

In a preferred embodiment of the present invention, since the yoke-shell nanocomposite is used as a catalyst, palladium (Pd) having high utilization as a catalyst is preferable.

The shape of the shape-controlled nanoparticles may be a sphere; A tetrahedron, a cube, an octahedron or a dodecanhedron; A plate; Cylinder, starlike; Or flowerlike, but are not necessarily limited thereto.

The shape of the nanoparticles contained in the yoke-shell nanocomposite can be an important factor in the structure sensitive reaction. For example, when the yoke-shell nanocomposite is used as a catalyst for direct synthesis of hydrogen peroxide (H ₂ O ₂ ), it is most advantageous that the morphology of the nanoparticles contained in the yoke-shell nanocomposite is octahedral. That is, the octahedral structure is surrounded by the Pd {111} plane, and the hydrogen peroxide selectivity and yield of Pd {111} plane are higher than those of Pd {100} plane in hydrogen peroxide synthesis.

The size of the shape-controlled nanoparticles is preferably 1 nm to 30 nm, and may vary depending on the reaction to be applied. When it exceeds 30 nm, the surface area of the nanoparticles decreases, and the active sites that can act as catalysts can be reduced.

The content of the nanoparticles is preferably 0.1 to 20% by weight based on the total weight of the yoke-shell nanocomposite and may vary depending on the reaction to be applied. When it exceeds 20% by weight, the size of the nanoparticles is too large to be effective as a center metal.

The second step may include redispersing the shape-controlled nanoparticles in a solvent and then adding a silica precursor. The dispersion solvent may include at least one selected from water and ethanol.

As the silica precursor, tetramethylorthosilicate (TMOS), tetraethylorthosilicate (TEOS), tetrapropylorthosilicate (TPOS) or the like may be used, but the present invention is not limited thereto.

The third step may include a step of adding a metal oxide solution after the second step and coating the metal oxide on the nanoparticle yoke-silica shell structure.

The metal oxide may be an aluminum (Al) oxide, a titanium (Ti) oxide, a zirconium (Zr) oxide, a cerium (Ce) oxide, or a composite oxide in which two or more thereof are mixed.

The fourth step may be a step of selectively removing silica by treating the metal oxide coated nanoparticle yoke-silica shell structure obtained in the third step with a basic solution at room temperature for 30 minutes to 3 hours. Sodium hydroxide or potassium hydroxide may be used as the basic solution, but the present invention is not limited thereto.

After the fourth step, a nanoparticle yoke-metal oxide shell structure is obtained. At this time, the shape of the nanoparticle yoke is maintained to be the same as that of the nanoparticles of the first step.

According to another aspect of the present invention, there is provided a shape control method comprising: a shape-controlled nanoparticle yoke; and a metal oxide shell surrounding the nanoparticle yoke, wherein a void is formed between the nanoparticle yoke and the metal oxide shell. Shell nanocomposite catalyst comprising the metal nanoparticles.

The nanoparticles may be selected from the group consisting of Pd, Pt, Au, Ag, Rh, Ru, Ni, Co, Cu, Metal nanoparticles of one or more kinds of alloys selected from the group consisting of molybdenum (Mo), tungsten (W) and tin (Sn).

The shape of the shape controlled nanoparticle yoke may be a sphere; A tetrahedron, a cube, an octahedron or a dodecanhedron; A plate; Cylinder, starlike; Or flowerlike.

The size of the shape-controlled nanoparticle yoke is preferably 1 nm to 30 nm.

The content of the nanoparticles is preferably 0.1 to 20% by weight based on the total weight of the yoke-shell nanocomposite.

The metal oxide shell may include an aluminum (Al) oxide, a titanium (Ti) oxide, a zirconium (Zr) oxide, a cerium (Ce) oxide, or a composite oxide in which two or more kinds thereof are mixed.

It is preferable that the empty space is an interval of less than 1 nm and less than 300 nm formed between the core nanoparticles and the metal oxide shell. When the thickness is more than 300 nm, the shell is larger than the particles as the void increases, so that the density of the central metal per unit volume is lowered and the metal content is lowered. If the metal content is low, the overall reactor volume may increase, which is undesirable.

The yoke-shell nanocomposite catalyst prepared according to the present invention can be produced at a point of use by direct synthesis of hydrogen peroxide when applied to a hydrogen peroxide to propylene oxide process, and the manufacturing cost of the entire propylene oxide can be reduced It is advantageous. It is also applicable to structural sensitive reactions such as oxygen reduction reaction (ORR, fuel cell field), formic acid oxidation reaction, carbon monoxide oxidation reaction, benzene hydrogenation reaction and the like.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the embodiments of the present invention described below are illustrative only and the scope of the present invention is not limited to these embodiments. The scope of the present invention is indicated in the claims, and moreover, includes all changes within the meaning and range of equivalency of the claims.

Example 1: Preparation of shape controlled palladium yoke-zirconia shell (cubic Pd @ Void @ ZrO ₂ ) nanocomposite

<First Step>

Ascorbic acid, polyvinylprolidone (PVP) and potassium bromide (KBr) were dissolved in tertiary ultrapure water and stirred at 10 ° C to 100 ° C for 5 minutes using a magnetic rod. Then, a solution of disodium tetrachloropalladate (Na ₂ PdCl ₄ ) was added thereto, and the mixture was stirred at 80 ° C. for 3 hours with a magnetic rod to proceed the reaction. After the reaction, acetone was added, and the nanoparticles produced through the centrifugal separator were recovered and washed several times with tertiary ultrapure water to prepare palladium cube nanoparticles.

<Second Step>

The shape-controlled palladium cubic nanoparticles prepared in the first step were redispersed in ethanol and water and ammonia water were added. After stirring for 3 hours, a silica precursor was added, and after stirring for 24 hours, a palladium yoke-silica shell (cubic Pd @ SiO ₂ ) nanostructure produced through a centrifugal separator was recovered. The recovered nanostructures were washed several times with ethanol.

<Step 3>

The shape-controlled palladium yoke-silica shell nanostructure prepared in the second step was re-dispersed in ethanol to prepare a dispersion solution. The solution of rutensol AO5 (Lutensol AO5) was mixed with the prepared solution and stirred with a magnetic rod for 1 hour. After that, zirconium butoxide solution was added and the reaction was allowed to proceed at room temperature overnight. Then, a zirconia-coated core-shell nanocomposite (cubic Pd @ SiO ₂ @ZrO ₂ ) synthesized by centrifugal separation was recovered. The recovered material was washed with tertiary distilled water.

<Step 4>

The nanocomposite (cubic Pd @ SiO ₂ @ZrO ₂ ) prepared in the third step was treated with potassium hydroxide for 30 minutes to 3 hours at room temperature to selectively dissolve only silica, Washed and dried to prepare a cubic Pd @ Void @ ZrO ₂ nanocomposite having controlled shape.

Example 2: Preparation of shape controlled palladium yoke-titania shell nanocomposite (cubic Pd @ Void @ TiO ₂ )

A cubic Pd @ Void @ TiO ₂ nanocomposite was prepared in the same manner as in Example 1 except that titanium butoxide was used instead of zirconium butoxide.

Experimental Example 1: TEM analysis

The size and shape of the palladium nanoparticles and nanocomposite prepared through the examples were confirmed through a transmission electron microscope (TEM).

In FIG. 2, the cube-shaped palladium nanoparticles prepared in the first step of Example 1 can be identified. In FIG. 3, the core-shell nanocomposite prepared in the second step of Example 1 can be identified. In FIGS. 4 and 5, the palladium yoke-zirconia shell nanocomposite prepared in the third and fourth steps of Example 1 Can be confirmed. In FIG. 6, the palladium yoke-titania shell nanocomposite prepared according to Example 2 can be identified.

Specifically, FIG. 2 shows that a cube-shaped palladium nanoparticle having a uniform size of 9 nm is produced, and that the cube is surrounded by {100} faces of fcc through an interplanar distance (0.195 nm) It can be confirmed that it is piled up.

3 and 4, it can be seen that the generated cube-shaped palladium nanoparticles are stably placed in the center of the silica and silica-zirconia shell without changing the size and shape. In FIG. 5, after selective removal of silica, Shell structure in which palladium nanoparticles in the form of zirconia shell are present in the cavities of the zirconia shell.

6 shows the structure of the yoke-shell in which the palladium nanoparticles are present in the cavities of the titania shell.

Experimental Example 2: Nitrogen adsorption / desorption analysis

The nanocomposites prepared in the second and fourth steps of Example 1 were observed through nitrogen adsorption / desorption analysis, and the results are shown in FIG.

Referring to FIG. 7, the cubic Pd @ Void @ ZrO ₂ produced in the fourth step has a nitrogen adsorption ratio as compared with the core-shell nanocomposite (cubic Pd @ SiO ₂ ) prepared in the second step. The amount of desorption increases, and it can be confirmed that it has a high specific surface area and pore size. From this, it can be confirmed that a mesoporous yoke-shell structure is formed, and it is confirmed that a more improved mass transferring ability to the yoke-shell nanocomposite can be expected in the catalytic reaction application.

&Lt; Experimental Example 3 >: XPS analysis

The palladium yoke-zirconia shell nanocomposite prepared in Example 1 was observed through XPS and the results are shown in FIG. 8, the degree of removal of PVP used in the catalyst synthesis of Example 1 can be confirmed. PVP in the particle formation can interfere with the intrinsic properties of the particles when present on the surface of the nanoparticles. In FIG. 8, it can be seen that PVP is removed because the binding energy (399.6 eV) peak of N, the constituent of PVP, have.

<Experimental Example 4> Evaluation of catalytic activity

The palladium yoke-zirconia shell nanocomposite of Example 1 was applied to a reaction for synthesizing hydrogen peroxide from oxygen and hydrogen, and the catalytic activity was evaluated. The results are shown in Table 1 below.

sample H ₂ conversion (%) H ₂ O ₂ selectivity (%) H ₂ O ₂ Productivity
(mmol ㆍ g _Pd ^-1 h ^-1 ) Pd @ void @ ZrO ₂ 5.5 14.3 19.2

- reaction medium: deionized water mixture _{(20% ethanol, 0.03 MH 3} PO 4) 150mL

* Temperature: 20 ° C; Pressure: 1 atm; Time: 2 h; Total flow rate: 50 mL / min; H ₂ / O ₂ / N ₂ ratio: 2/10/38

* Catalyst amount: 0.2 g

As shown in Table 1, when the complex of Example 1 was applied to hydrogen peroxide synthesis reaction from oxygen and hydrogen, it can be confirmed that the catalyst activity is exhibited.

Experimental Example 5: ICP analysis

The cubic Pd @ Void @ ZrO ₂ nanocomposite prepared in Example 1 was subjected to the catalytic reaction, and the palladium content before and after the catalytic reaction was confirmed by ICP analysis. Table 2 shows the results.

Cubic Pd yolk - ZrO _{2 S} hell Pd content (%) Before reaction 0.9 After the reaction 0.9

As shown in Table 2, it was confirmed that the palladium yttrium-zirconia shell (cubic Pd @ Void @ ZrO ₂ ) nanocomposite of Example 1 had no change in the palladium content before and after the reaction. Thus, it has been confirmed that the method of manufacturing the yoke-shell nanocomposite including the shape-controlled metal nanoparticles of the present invention can stably fix the shape-controlled nanoparticles.

Claims (12)

A first step of preparing shape-controlled nanoparticles;
A second step of coating the nanoparticles with silica to obtain a nanoparticle yoke-silica shell structure;
A third step of coating a metal oxide on the nanoparticle yoke-silica shell structure to obtain a metal oxide coated nanoparticle yoke-silica shell structure; And
And a fourth step of removing the silica by treating the metal oxide coated nanoparticle yoke-silica shell structure with a base, followed by washing and drying to obtain a nanoparticle yoke-metal oxide shell structure,
The pores are formed in the nanoparticle yoke-metal oxide shell structure by the washing,
Wherein the shape of the nanoparticle yoke after the fourth step is the same as the shape of the nanoparticle of the first step. The method according to claim 1,
The nanoparticles may be selected from the group consisting of Pd, Pt, Au, Ag, Rh, Ru, Ni, Co, Cu, Shell nanocomposite comprising shape-controlled metal nanoparticles, characterized in that the metal nanoparticles are metal nanoparticles of one or more alloys selected from the group consisting of molybdenum (Mo), tungsten (W) and tin (Sn) &Lt; / RTI &gt; The method according to claim 1,
The shape of the shape-controlled nanoparticles may be a sphere; A tetrahedron, a cube, an octahedron or a dodecanhedron; A plate; Cylinder, starlike; Characterized in that the metal nanoparticles are shape-controlled or flower-like. The method according to claim 1,
Wherein the shape-controlled nanoparticles have a size of 1 nm to 30 nm. 2. The method of claim 1, wherein the shape-controlled nanoparticles have a size of 1 nm to 30 nm. The method according to claim 1,
Wherein the content of the nanoparticles is 0.1 to 20% by weight based on the total weight of the yoke-shell nanocomposite. The method according to claim 1,
Characterized in that the metal oxide is a composite oxide of aluminum (Al) oxide, titanium (Ti) oxide, zirconium (Zr) oxide, cerium (Ce) oxide, Shell nanocomposite comprising the particles. The method according to claim 1,
Wherein the base treatment is a step of treating potassium hydroxide at room temperature for 30 minutes to 3 hours, and the shape-controlled metal nanoparticles. As manufactured by the manufacturing method of claim 1,
Controlled nanoparticle yoke, and a metal oxide shell surrounding the nanoparticle yoke, wherein a void space is formed between the nanoparticle yoke and the metal oxide shell. A yoke-shell nanocomposite catalyst. The method of claim 8,
The shape of the shape controlled nanoparticle yoke may be a sphere; A tetrahedron, a cube, an octahedron or a dodecanhedron; A plate; Cylinder, starlike; Characterized in that the shape-controlled metal nanoparticles are water-soluble or flower-like. The method of claim 8,
Wherein the shape controlled nanoparticle yoke has a size of 1 nm to 30 nm. The method of claim 8,
Wherein the content of the nanoparticles is 0.1 to 20% by weight based on the total weight of the yoke-shell nanocomposite. The yoke-shell nanocomposite catalyst comprising the shape-controlled metal nanoparticles. The method of claim 8,
Shell nanocomposite catalyst comprising the formation-controlled metal nanoparticles, wherein the voids are spaced from the core nanoparticles to the metal oxide shell by less than 1 nm and less than 300 nm.

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