KR101020106B1 - Three dimensional nanostructures of hydroxy phosphate-based materials and synthesis methods thereof - Google Patents

Abstract

The present invention relates to a three-dimensional nanostructure of the phosphate-based hydroxide and a method for manufacturing the same, to provide a three-dimensional nanostructure that can decompose harmful substances as a catalyst or photocatalyst, the production of a three-dimensional nanostructure that can be produced by a simple method By providing a method, it is possible to provide a three-dimensional nanostructure that is economical, improves light absorption and surface properties, and has a large specific surface area and is chemically and physically stable.

Description

Three dimensional nanostructures of hydroxy phosphate-based materials and synthesis methods

The present invention relates to a three-dimensional nanostructure of the phosphate-based hydroxide and a method for manufacturing the same, to provide a three-dimensional nanostructure that can decompose harmful substances as a catalyst or photocatalyst, the production of a three-dimensional nanostructure that can be produced by a simple method It is about a method.

Nanotechnology is a technology that seeks to find new phenomena that do not appear in bulk size, to understand them, and to manipulate them directly.These nano technologies are cutting-edge science, including the development of next-generation memory chips and nanomachines that can be inserted into the human body. It is recognized as an essential research in the technical field. Nanostructure generally refers to an architecture in which nanoparticles, nanorods, nanoplates, etc., having sizes ranging from 1 to 100 nm are combined. It can be widely used in various fields such as catalysts, pharmaceuticals, paint industry, self-assembly materials and nonlinear optical materials. In addition, when the nanostructure is formed, the size of the nanoparticles is increased to about several hundred nm to several μm, so it is easy to handle, and it is very useful because it retains various properties that were exhibited when the nanoparticles were used. Accordingly, research on nanostructures is being actively conducted.

However, in order to prepare a nanostructure consisting of these nano-size particles are combined, complex processes such as surfactants and supports are not only necessary, but also easy to control the shape and additional washing process is inevitable. Therefore, a lot of studies on the synthesis of nanostructures have been reported, but the amount produced is about several milligrams, there are many problems to use in the actual industry.

The present invention is to provide a three-dimensional nanostructure that can be applied as a photocatalyst that can be sensitive to light including visible light, such as indoor light, sunlight can decompose environmental pollutants such as volatile organic compounds or waste water / waste water in the room.

In another aspect, the present invention is to provide a three-dimensional nanostructure manufacturing method that can be prepared in a simple process using a phosphate-based hydroxide without using a surfactant or a support.

According to a first preferred embodiment of the present invention, there is provided a method comprising: weighing and mixing a metal compound and a phosphorus compound; Adjusting the pH of the mixed compound to 3-9; And it provides a method for producing a three-dimensional nanostructure for producing a compound of the formula 1 including the step of reacting the pH controlled peha (pH).

<Equation 1>

(A _2-x A ' _x ) PO ₄ OH

Wherein A and A 'are the same or different metals selected from transition metals, and x is 0 ≦ x ≦ 2.

In the above embodiment, the transition metal may be selected from Cu, Ni, Co, Fe, Zn and Mn.

In the above embodiment, the step of reacting the compound under pH (pH) may be to react at 40 ~ 90 ℃.

As a second preferred embodiment of the present invention, it provides a three-dimensional nanostructure produced by the above production method.

As a third preferred embodiment of the present invention, it provides a three-dimensional nanostructure represented by the following formula (1).

<Equation 1>

(A _2-x A ' _x ) PO ₄ OH

Wherein A and A 'are the same or different metals selected from transition metals, and x is 0 ≦ x ≦ 2.

In the above embodiment, the transition metal may be selected from Cu, Ni, Co, Fe, Zn and Mn.

Three-dimensional nanostructures according to the embodiment may have a particle diameter of 1㎛ ~ 5㎛.

Three-dimensional nanostructure according to the embodiment may have a specific surface area of 1 ~ 100㎡ / g.

Three-dimensional nanostructure according to the embodiment may have a light absorption wavelength of 380nm or more.

As a fourth preferred embodiment, the present invention provides a photocatalyst composition comprising the three-dimensional nanostructure.

In the above embodiment, the oxidation catalyst (H ₂ O ₂ ) may be 0.1 to 5% by weight based on the three-dimensional nanostructure.

The present invention is applied as a photocatalyst capable of responding to light including visible light such as fluorescent light and solar light by improving the light absorption characteristics and surface properties can decompose environmental pollutants such as volatile organic compounds and waste water / waste water indoors Can provide a three-dimensional nanostructure.

In another aspect, the present invention can provide a three-dimensional nanostructure manufacturing method that can be produced in a simple process using a phosphate-based hydroxide without using a surfactant or a support.

The present invention relates to a three-dimensional nanostructure represented by the following formula (1).

<Equation 1>

(A _2-x A ' _x ) PO ₄ OH

Wherein A and A 'are the same or different metals selected from transition metals, and x is 0 ≦ x ≦ 2.

The transition metal is preferably selected from Cu, Ni, Co, Fe, Zn and Mn in that it enhances light absorption characteristics and adsorption characteristics.

The three-dimensional nanostructure represented by the formula (1) is a phosphate-based hydroxide, characterized in that it includes a hydroxyl group in the structure and can substitute a variety of transition metals and is a chemical and physically stable material.

In this case, the compound of Formula 1 is preferably a three-dimensional nanostructure of 1㎛ ~ 5㎛ in consideration of the high specific surface area and easy to handle the powder.

In addition, it is preferable that the specific surface area is 1 to 100 m ² / g, more preferably 20 to 100 m ² / g in view of the catalytic reaction being a surface reaction.

And the three-dimensional nanostructure of the present invention may have a light absorption wavelength of more than 380nm, in the case of the phosphate-based hydroxide which is not a three-dimensional nanostructure light absorption wavelength did not reach 380nm, but the three-dimensional nanostructure of the present invention Since the structure can absorb light of more wavelengths and can react to visible or fluorescent light to decompose harmful substances, it can be utilized in a wider range of industries.

Method for preparing a compound represented by the formula 1 can be used a liquid phase method, first weighing the metal compound and phosphorus compound as a starting material and dissolved in distilled water, respectively, and then mixed the two solutions. At this time, the metal compound and the phosphorus compound are weighed such that the molar ratio is (A + A '): P = 2: 1.

The metal compound is preferably a metal nitride or metal chloride, and as the phosphorus compound, phosphoric acid (H ₃ PO ₄ ) or ammonium phosphate ((NH ₄ ) ₂ HPO ₄ or NH ₄ H ₂ PO ₄ )) may be used.

Examples of the metal nitrides include Cu (NO ₃ ) ₂ 3H ₂ O, Ni (NO ₃ ) ₂ 6H ₂ O, Co (NO ₃ ) ₂ 6H ₂ O, Zn (NO ₃ ) _2. 6H ₂ O, Mn (NO ₃ ) ₂ .6H ₂ O, FeNO ₃ ) ₃ .9H ₂ O and the like can be used. Examples of the metal chlorides include CuCl ₂ 2H ₂ O, NiCl ₂ 6H ₂ O, and the like. , CoCl ₂ .6H ₂ O and the like can be used.

The pH of the mixed compound is adjusted to be 3-9. At this time, in order to control the shape of the three-dimensional nanostructure, it is preferable to adjust the pH (pH) using an acid or base titration solution. The titration solution may include ammonia water (NH ₄ OH), sodium hydroxide solution (NaOH), potassium hydroxide solution (KOH), nitric acid solution (HNO ₃ ) and the like.

By the above method, the compound controlled by pH (pH) is reacted at 40 to 90 ° C. for 1 to 24 hours. In this step, it is preferable to synthesize at a normal pressure and relatively low temperature, that is, 40 to 90 ° C., without using high temperature / high pressure, such as hydrothermal synthesis, to heat crystallization to obtain a large surface specific three-dimensional nanostructure. Do.

Thereafter, finally, may include the step of obtaining a powder through separation, washing and drying, the slurry obtained after the reaction can be separated using a centrifuge or by a simple precipitation, it is washed with distilled water and the like, and frozen It can be dried by drying or oven drying.

The compound prepared by the above method has a shape of a three-dimensional nanostructure, and has various shapes such as rod-shaped, nanorod-coupled chestnut-shaped, ellipsoidal, floral, and walnut-type according to a proper pH or a proper solution (FIG. 2). ).

Nanostructures prepared as described above can be applied as a photocatalyst, it can be applied to the decomposition of various harmful substances using this. For example, in the case of liquid phase decomposition such as phenol and dye, an aqueous solution containing the powder may be prepared and applied to the decomposition of harmful substances by adding light energy including various visible rays such as fluorescent lamps, halogen lamps, xenon lamps, and sunlight. Can be.

Meanwhile, the three-dimensional nanostructure of the present invention may be used alone as a photocatalyst, or may be used by further adding an oxidation catalyst. In this case, the oxidation catalyst is preferably included 0.1 to 5% by weight based on the three-dimensional nanostructure of the formula (1). If more than 5% by weight is added, it is not preferable because of the heat caused by the rapid reaction. The oxidation catalyst is not particularly limited, but hydrogen peroxide (H ₂ O ₂ ), oxygen (O ₂ ), or the like is preferably used.

In addition to the form of the aqueous solution containing the powder, a method of coating the substrate may be used. In addition, in the case of gas phase decomposition such as acetaldehyde, odorous substances, etc., it may be used including a powder form, a method of coating on a substrate, a method of coating on a reaction vessel.

In the case of the three-dimensional nanostructure manufactured by the present invention, it is not only chemically stable, there is no change before and after the catalytic reaction, and there is an advantage that it can be effectively applied to decomposition of liquid or gaseous harmful substances.

Hereinafter, examples of the present invention will be described in more detail, but the scope of the present invention is not limited to these examples.

<Examples 1-21, Comparative Examples 1-3>

The composition represented by the following formula 1 was prepared according to the composition of Table 1, Examples 1 to 11, Comparative Examples 1 to 3 is a case in which x is 0 in the following formula 1, Examples 12 to 21 is not x is 0 If it is. The preparation process and the specific surface area, light absorption characteristics, and decomposition characteristics of the prepared compound were evaluated and shown in Table 1.

<Equation 1>

(A _2-x A ' _x ) PO ₄ OH

Wherein A and A 'are the same or different metals selected from transition metals, and x is 0 ≦ x ≦ 2.

First, a metal nitride having a purity of 99.9% A as a starting material, for example, Cu (NO ₃ ) ₂ ㆍ 3H ₂ O, Ni (NO ₃ ) ₂ ㆍ 6H ₂ O, Co (NO ₃ ) ₂ ㆍ 6H ₂ O, Zn (NO ₃ ) ₂ ㆍ 6H ₂ O, Mn (NO ₃ ) ₂ ㆍ 6H ₂ O, FeNO ₃ ) _{3 ·} 9H ₂ O or metal chlorides, such as CuCl ₂ 2H ₂ O, NiCl ₂ 6H ₂ One selected from O, CoCl ₂ 6H ₂ O, and ammonium phosphate ((NH ₄ ) ₂ HPO ₄ ) or phosphoric acid (H ₃ PO ₄ ) is weighed such that (A + A '): P = 2: 1, respectively, and distilled water It was dissolved while stirring. The metal nitride or metal chloride solution is then mixed with a phosphoric acid or ammonium phosphate solution and then titrated, such as aqueous ammonia (NH ₄ OH), sodium hydroxide (NaOH), potassium hydroxide (KOH), nitric acid PH was adjusted using a solution (HNO ₃ ) and the like. The reaction was further stirred for 10 to 30 minutes and then heated to an appropriate temperature. After the reaction, the resulting slurry was separated by centrifugation or simple precipitation, washed with distilled water, and dried in a freeze dryer or an oven at 90 ° C. The completely dried powder was identified through X-ray diffraction (XRD) and electron scanning microscope (SEM) to confirm phase identification and the presence of three-dimensional nanostructures. Some of the powder SEM photographs of various compounds prepared are shown in FIG. 2.

In the case of liquid phase decomposition using light, 0.3 g of the three-dimensional nanostructure powder was weighed and placed in a 100 ml solution of Methylene blue (MB) (47.8 μmol) in a quartz glass vessel (120 ml), followed by darkness to obtain adsorption / desorption equilibrium. Stir for about 30 minutes. Then, the light was irradiated using a 300-watt xenon lamp unit (Max302, Ashahi, Japan) equipped with a 420 nm UV cut-off filter, sampled at regular intervals, and the powder remaining in the solution by centrifugation or filtering. After removal, the degree of degradation was measured by UV-vis spectroscopy.

In addition, when 0.3% by weight of 30% hydrogen peroxide (H ₂ O ₂ ) was added to the nanostructure immediately before irradiation with light in the decomposition reaction using the photocatalyst, the decomposition efficiency increased rapidly. This is because the composition decomposes hydrogen peroxide to produce oxygen (O ₂ ) and water (H ₂ O) as a catalyst, and the hydroxy radicals (OH ·) produced in this process promote the decomposition reaction.

Example A _2-x A ' _X PO ₄ OH pH shape Light absorption
Wavelength (nm) Specific surface area
(m ² / g) Without hydrogen peroxide Hydrogen peroxide
When added (0.3 wt%) x A A ' MB degradation efficiency after 3 hours (%) MB degradation efficiency after 3 hours (%) Example 1 0 Cu - 4 Chestnut type 395,650 3.2 75 89 Example 2 - 5 Ellipsoid type 410,650 17.0 80 90 Example 3 - 7 Walnut 530 37.0 98 100 Example 4 0 Co - 4 Chestnut type 430,670 4.2 35 50 Example 5 - 5 Flower 460,670 8.1 44 53 Example 6 - 7 Walnut 462,678 30.2 90 98 Example 7 0 Ni - 4 Nano rod type 370,560 2.2 22 43 Example 8 - 5 Ellipsoid type 380,560 3.1 40 52 Example 9 - 8 Walnut 400,560 24.3 80 90 Example 10 0 Zn - 7 Flower 380 4.3 60 65 Example 11 0 Mn - 7 Flower 420, 630 2.5 20 30 Example 12 0.1 Cu Ni 7 Walnut 560 35.0 97 100 Example 13 Co 7 530 28.5 99 100 Example 14 Zn 7 500 25.2 95 100 Example 15 Fe 7 545,695 39.3 99 100 Example 16 0.3 Cu Ni 7 Walnut 565 32.1 80 91 Example 17 Co 7 520 27.2 75 85 Example 18 Fe 7 540,690 38.5 99 100 Example 19 0.5 Cu Ni 7 Walnut 565 33.0 80 85 Example 20 Co 7 500 27.1 70 75 Example 21 Zn 7 500,690 33.5 94 95 Comparative Example 1 0 Cu - 2.5 Micro Rod Type 370 0.8 10 25 Comparative Example 2 0 Co - 2.5 Micro Rod Type 410,670 1.8 15 30 Comparative Example 3 0 Ni - 2.5 Micro Rod Type 380,560 1.0 20 30

As can be seen in Table 1, in the case of Comparative Examples 1 to 3 with a peh 2.5, a long rod-shaped structure was obtained instead of a nanostructure, and as the pehs increased, rounded nanoparticles (20-50 nm) were formed by agglomeration. Walnut- or flower-shaped nanostructures were obtained. In addition, nanostructures made under high pH absorbed more visible light. As can be seen from Comparative Examples 1 to 3, in the case of non-nanostructures, the specific surface area is very low and the light absorption characteristics are not good. This shows that the decomposition efficiency is very low. Cu ₂ PO ₄ OH had the best decomposition effect. Among them, the walnut-shaped nanostructure manufactured in Peha 7 showed the highest specific surface area and light absorption characteristics, resulting in the highest decomposition efficiency.

Also, when 0.3 wt% of hydrogen peroxide is added to the nanostructure, it can be seen that the decomposition efficiency increases rapidly.

As a result, various nanostructures of phosphate-based hydroxides were prepared by controlling the pH during the reaction using a simple process without a surfactant or a support, and evaluated their specific surface area, light absorption characteristics and decomposition characteristics. In the case of addition of small amounts of hydrogen peroxide, the decomposition efficiency increased rapidly.

On the other hand, when Ni, Co, Zn and Fe is substituted in the Cu site, it can be seen that the decomposition efficiency is excellent, and among them, the substitution amount of Ni, Co, Zn and Fe in the Cu site is 10 mol% (x ≤0.1) or less It is more preferable, and in the case of the substitution composition, the three-dimensional nanostructure can be produced at a higher temperature than the synthesis temperature otherwise. Likewise, when hydrogen peroxide was added, the decomposition efficiency increased rapidly.

In conclusion, the present invention can prepare a three-dimensional nanostructures of various shapes by adjusting the reaction temperature and the reaction under the production of phosphate-based hydroxide, it can be applied to the decomposition of environmentally harmful substances such as photocatalyst. In the case of the three-dimensional nanostructure powder prepared according to the present invention, the light absorption characteristics and the organic substance absorption characteristics were excellent, and the specific surface area was also greatly increased. In addition, nanoparticles (20 to 50nm) are combined to have a size of about 1 to 5㎛ and at the same time have a high specific surface area, which is easy to handle, and not only the manufacturing process but also the raw material powder is low in price, and its application value is large. In addition, the powder is considerably stable chemically and physically, and when used with an oxidation reaction catalyst such as hydrogen peroxide, exhibits higher decomposition efficiency. Therefore, the powder is expected to be used not only for photocatalytic reaction but also for various catalytic reactions.

1 is a process chart illustrating a method of manufacturing a three-dimensional nanostructure of the present invention;

Figure 2 is a SEM photograph of the phosphate-based hydroxides of the compounds prepared in Examples and Comparative Examples of the present invention, (a) micro-rod-shaped powder prepared at pH 2.5 ~ 2.9, (b) chestnut prepared at pH 3.0 ~ 4.0 Type three-dimensional nanostructure powder, (c) chestnut-shaped three-dimensional nanostructure powder prepared at pH 4.0-5.0, (d) ellipsoidal three-dimensional nanostructure powder prepared at pH 5.0-6.0, (e) at pH 7.0-8.0 Photo shows the prepared walnut-shaped three-dimensional nanostructure powder.

Claims (11)

Weighing and mixing the metal compound and the phosphorus compound such that the molar ratio is (A + A ′): P = 2: 1; Adjusting the pH of the mixed compound to 3-9; And To prepare a compound of the following formula 1 comprising the step of reacting the pH controlled peha (pH) controlled at 40 to 90 ℃ for 1 to 24 hours, The compound of Formula 1 is a three-dimensional nanostructure having any one shape selected from chestnut-shaped, ellipsoidal, walnut, floral, nano-rod type, the particle size of 1000 to 5000nm three-dimensional nanostructure manufacturing method. <Equation 1> (A _2-x A ' _x ) PO ₄ OH Wherein A and A 'are the same or different metals selected from transition metals, and x is 0 ≦ x ≦ 2. The method of claim 1, Transition metal is a method of producing a three-dimensional nanostructures, characterized in that selected from among Cu, Ni, Co, Fe, Zn and Mn. delete A three-dimensional nanostructure produced by the method of any one of claims 1 to 2. delete delete delete The method of claim 4, wherein Three-dimensional nanostructure, characterized in that the specific surface area is 1 ~ 100㎡ / g. The method of claim 4, wherein Light absorption wavelength is three-dimensional nanostructure, characterized in that more than 380nm. Photocatalyst composition comprising the three-dimensional nanostructure according to claim 4. The method of claim 10, A photocatalyst composition comprising 0.1 to 5% by weight of an oxidation catalyst relative to the three-dimensional nanostructure.

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