JPH11300215A - Photocatalytic particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalytic particle in which photocatalytic characteristics are excellent, especially in a visible light range. SOLUTION: The photocatalytic particle 1 is equipped with a titanium oxide particle 2 and at least one kind of metal selected from silver, copper, zinc and nickel or alloy 3 which covers the surface 2a of the titanium oxide particle 2 so that a part of the surface 2a of the particle 2 is exposed. The diameter of the particle 2 is <=1 μm. Photocatalytic activity of titanium oxide is developed in the especially exposed part because a part of the surface 2a of the particle 2 is exposed. Since the photocatalytic particle 1 is equipped with at least one kind of metal selected from silver, copper, zinc and nickel or alloy 3, it is easily excited by irradiation of light in a visible region and an electron and a positive hole are generated. Such a state is caused that movement or the electron and the positive hole is enabled between metal or alloy 3 and the particle 2 in the covered parts. Therefore, the electron of the positive hole generated in metal or alloy is supplied to titanium oxide. Further, since particle diameter of titanium oxide is <=1 μm, quantum size effect arises.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to photocatalytic particles having a photocatalytic action, and more particularly to photocatalytic particles used for decomposing oil attached to kitchen equipment, decomposing dirt on exterior materials, deodorizing, fixing carbon dioxide, and the like. Suitable photocatalytic particles.

[0002]

2. Description of the Related Art Conventionally, for the decomposition of oil, etc., a method of using γ-manganese oxide as a catalyst and heating the oil together therewith to promote complete combustion of the oil (thermal catalyst), or a method of using titanium oxide on a steel sheet or the like. A method using a photocatalyst, which applies oil to a support such as a filter and irradiates the support with ultraviolet rays to decompose oil, has been used. In particular, the demand for photocatalysts has been rapidly increasing in recent years because there is no need to maintain the target at a high temperature during decomposition unlike the thermal catalysts. It is also known that titanium oxide obtained by ion implantation of a transition metal such as Cr has a photocatalytic action in the visible light region. Furthermore, even with an organic polymer semiconductor that excites at a wavelength relatively close to the visible light region, a photoexcitation effect has been confirmed.

[0003]

However, the inorganic photocatalyst represented by titanium oxide as described above does not produce a catalytic action unless it is ultraviolet light, and therefore requires an ultraviolet lamp when used. Since ultraviolet rays are used, light shielding to the human body must be considered. Also, photocatalysts utilizing ion implantation have high manufacturing costs,
It was difficult to use widely in practical use. On the other hand, there is a problem that the photoexcitation effect of the organic polymer semiconductor is not strong enough to decompose oil and dirt.

Accordingly, an object of the present invention is to provide photocatalytic particles having excellent photocatalytic properties, particularly excellent photocatalytic properties in the visible light region.

[0005]

In order to achieve the above object, a photocatalytic particle 1 according to the first aspect of the present invention has a structure as shown in FIG.
And titanium oxide particles 2;
At least one metal or alloy 3 selected from silver, copper, zinc, and nickel, which covers the surface 2a of the titanium oxide particles 2 so that a part of the surface 2a is exposed;
The particle size of the titanium oxide particles 2 is 1 μm or less.

With this configuration, the titanium oxide particles 2
Of the surface 2a is exposed, the photocatalytic activity of the titanium oxide is particularly exhibited in the exposed portion, and silver, copper, zinc,
And at least one metal or alloy 3 selected from nickel and nickel, so that it is easily excited by irradiation with light of a visible light region or a shorter wavelength to generate electrons and holes, and a metal or alloy Since electrons and holes can move between the alloy 3 and the titanium oxide 2, electrons or holes generated in the metal or the alloy 3 are supplied to the titanium oxide. In addition, the particle size of titanium oxide is 1 μm
The following produces a quantum size effect.

[0007] In the photocatalytic particles, the alloy 3 may contain silver, and may further contain one or both of copper and zinc in a total amount of 10 to 50% by weight.

In such a configuration, the alloy 3 contains silver,
Further, one or both of copper and zinc are added in a total of 10 to 50.
Since it contains only% by weight, it is particularly excellent in oil decomposition characteristics.

[0009] In the photocatalytic particles as described above, claim 3
As described above, the metal or alloy 3 is preferably coated on the surface 2a of the titanium oxide particles 2 in a discontinuous film form.

In such a configuration, the metal or alloy 3
Since the surface 2a of the titanium oxide particles 2 is coated in a discontinuous film form, a part of the surface of the titanium oxide particles is exposed.

[0011] Further, as described in claim 4, claim 1
It is preferable that the metal or alloy 3 has a particle diameter of 0.1 μm or less.

Further, as described in claim 5, claim 1 is
In the photocatalytic particles according to any one of claims to 4, it is preferable that the weight ratio of the coated metal or alloy to the photocatalytic particles 1 is 1 to 20%.

In this case, since the weight ratio of the metal or alloy to the photocatalytic particles 1 is 1 to 20%, the metal or alloy film can be coated finely in a discontinuous film, for example, in the form of islands. Since sufficient electrons and holes are supplied, the composition has excellent oil and dirt decomposition properties.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged schematic view showing only one photocatalytic particle according to the present invention. Actually, a fine powder composed of such photocatalytic particles is used as a catalyst. As shown in FIG. 1, the photocatalytic particles according to the embodiment of the present invention cover a metal or alloy 3 on a surface 2a of titanium oxide 2 which is a substantially spherical base material so that a part thereof is exposed. doing.

In one embodiment of the present invention, silver, silver, or titanium oxide particles that are excited in the ultraviolet light range and exhibit oil decomposition characteristics and the like are added.
A metal or alloy containing at least one of copper, zinc and nickel as a main component is coated in a discontinuous film form (particularly in an island form) such that a part of the surface of titanium oxide is exposed.

When these metals or alloys 3 are coated on the titanium oxide particles 2, oxides are formed on the surface or the surface layer by oxygen present in the periphery, for example, in the atmosphere. At this time, the coated metal or alloy does not need to be entirely oxidized to the inside, and only the surface or the surface layer of the coating need be oxidized. Further, the entire surface area of the coating may not be oxidized, but may be only partially oxidized.

As described above, the surface oxide of the metal or alloy formed on the surface or the surface layer of the coating has semiconductor characteristics. For example, the band gap at room temperature of silver oxide (Ag ₂ O) is 1.2 eV, which is 3.2 eV of that of titanium oxide.
It is very narrow compared to eV, and is easily excited by irradiation with light having a wavelength in the visible light range or shorter to generate electrons and holes.

Here, some of the electrons and holes emitted from the silver oxide are supplied to the titanium oxide as a base material through the silver film, and the surface of the titanium oxide is exposed to visible light such as sunlight. Synergizes with electrons and holes generated by being excited by ultraviolet rays contained in the titanium oxide, thereby promoting the photocatalytic activity of titanium oxide. Furthermore, since these metals or alloys themselves have a catalytic effect of oxidizing organic substances, these two effects exert excellent effects such as oil decomposition.

That is, in the embodiment of the present invention, a part of the surface of titanium oxide is exposed, and
An active film of a metal or an alloy containing at least one of silver, copper, zinc and nickel as a main component is finely coated, and this film is made of titanium oxide and is capable of transferring electrons and holes. Coated.

In addition, since the titanium oxide as the base material is fine particles of 1 μm or less, a quantum size effect is produced. When the titanium oxide particles have such a size and the surface is coated with the above-mentioned metal or alloy in the form of islands, these electrons and holes do not undergo thermal relaxation with the lattice and become reactive. Will be high. That is, the reactivity of electrons and holes when the metal or alloy coated on the surface of the particles is excited is increased. The size of the titanium oxide particles is desirably 0.5 μm or less. When the size of the titanium oxide particles of the base material exceeds 1 μm, electrons and holes generated by excitation of oxides present on the surface layer of the metal or alloy coated on the surface disappear by lattice vibration, and the photocatalytic activity is reduced. It is difficult to develop.

The metal or alloy is coated on the surface of titanium oxide as a base material in a discontinuous film form so that a part of the surface of titanium oxide is exposed. This is because if the titanium oxide is completely covered with the metal or alloy, the photocatalytic activity of the titanium oxide does not appear.

Here, the discontinuous film form includes various forms such as island form, linear form, streak form, and dot form. The island-like coating is a state in which a metal or an alloy is coated with one or more discontinuous films on titanium oxide particles. When coated in the form of a discontinuous film, the coverage (area of titanium oxide particles coated with metal or alloy / surface area of titanium oxide)
Is desirably in the range of 20 to 50%.

Further, from the viewpoint of the discontinuous film, when the surface of the titanium oxide particles is coated so that a part of the surface of the titanium oxide particles is exposed, the coating shape of the metal or alloy is as follows:
As described above, in addition to the island shape, various shapes such as a line shape, a streak shape, and a dot shape may be used. Further, the effect is obtained if the number of the discontinuous films is one or more. However, considering that the irradiation direction of light is not isotropic in practice, as shown in FIG. It is desirable to be covered with two or more discontinuous films (FIG. 1 shows a case where five islands are formed along a great circle of substantially spherical titanium oxide particles). .

In order to receive the supply of the electrons and holes, the titanium oxide and the metal or alloy are electrically joined. In the case of a so-called mixture of the two and electrical bonding cannot be expected, the effect as in the present invention is hardly exhibited.

In such an island-shaped coating, for example, the coating amount of the metal or alloy on the titanium oxide particles is in the range of 1 to 20% by weight (weight ratio) of the formed photocatalytic particles. In this range, a discontinuous film-like coating is achieved, and sufficient electrons and holes are supplied to the titanium oxide.

Further, contamination of impurities during coating is minimized. In this case, the electric connection is strengthened. Further, from the viewpoint of alloy coating, as a coating method, physical vapor deposition such as vacuum vapor deposition or sputtering performed in vacuum or under reduced pressure is performed.

The amount of the metal or alloy coated on the titanium oxide particles is determined from the viewpoint that the titanium oxide particles are coated so that a part of the surface is exposed, that is, typically, the particles are finely coated in an island shape. From the range of 1 to 20% by weight. If the amount is less than 1% by weight, the effect of metal or alloy coating may not be exhibited. If the amount is more than 20% by weight, titanium oxide particles or agglomerates thereof may be completely covered by the surface-coated metal or alloy and photocatalytic activity may be lost. is there.
In addition, an increase in cost during coating is also a problem.

Further, the metal or alloy coated on the surface in the form of a discontinuous film (typically an island) achieved by the above-mentioned coating amount preferably has a particle size of 0.1 μm or less.
This is because the surface area is increased by finer particles to increase the catalytic activity of oxidizing organic substances, and electrons and holes are easily transported by the quantum size effect.

On the other hand, the titanium oxide to be coated is preferably an anatase type from the viewpoint of photocatalytic activity, and its shape is not particularly limited. In the case of remarkable aggregation, use after pulverization.

As described above, titanium oxide particles having a particle size of 1 μm or less, which are formed by coating at least one metal or alloy of silver, copper, zinc and nickel in a discontinuous film form in the range of 1 to 20% by weight, In addition to improving the effect of decomposing organic substances such as oil in the conventional ultraviolet wavelength range, it can also decompose oil and dirt even in long wavelength light in the visible light range. The application is extremely large.

As described above, the titanium oxide powder having a strong photocatalytic effect is coated with a predetermined amount of a metal or an alloy containing at least one of silver, copper, zinc and nickel as a main component to obtain a conventional ultraviolet wavelength region. In addition to increasing the photocatalytic activity, the photocatalytic activity can be exhibited even on the longer wavelength side than that region.

As a method for coating the above-mentioned metal or alloy on the titanium oxide particles so that a part of the surface of the titanium oxide particles is exposed, that is, in a discontinuous film form, for example, an island form, an electroless plating method is used. And a physical vapor deposition method. In particular, it is desirable to use the sputtering method disclosed in the applicant's earlier application (Japanese Patent Application Laid-Open No. 2-153068). According to this method,
The titanium oxide powder can be efficiently coated with a metal or alloy in a discontinuous film form with little contamination of impurities and no generation of waste liquid.

In the sputtering method used here, for example, first, a fine powder of titanium oxide is subjected to a fluid jet mill treatment in an inert atmosphere to be dispersed into primary particles. The fine powder obtained by the dispersion treatment is heat-treated under reduced pressure in an inert atmosphere. The fine powder subjected to the heat treatment under reduced pressure was charged into a rotating container containing a sputtering source (silver, copper, zinc or nickel or an alloy thereof), and the container was rotated to form a fluidized bed of the fine powder, and the container was rotated. Sputtered on the flowing fine powder in the state. Thus, the surface of the titanium oxide particles is coated with the metal or alloy of the sputtering source.

[0034]

Example 1 A titanium oxide powder having an average particle size of 0.5 μm was coated with a metal or an alloy at a predetermined coating amount. To 1 g of this powder, 0.1 g of salad oil was added and mixed, and the mixture was placed in a glass petri dish having a diameter of 7 cm as an object to be irradiated, and allowed to stand in a closed box. And with a 400W high pressure mercury lamp (ultraviolet)
Light was irradiated from a position 250 mm away from the petri dish for 7 hours. The temperature of the object to be irradiated during this irradiation was about 120 ° C.

Under these conditions, the photocatalytic properties relating to oil decomposition were evaluated by weight loss after irradiation. The result is shown in FIG.
This is shown in the table of FIG. In the evaluation, only titanium oxide having the same particle size as the comparative material was oil-decomposed by the same method, and a material whose weight loss in this example exceeded 1.2 times the weight loss was particularly excellent in oil decomposition characteristics. ◎, and the case of 1.2 times or less and more than 1.0 time indicates that the oil decomposition property is excellent.
Was evaluated as poor when the oil decomposition property was not improved from 1.0 times or more to more than 0.8 times, and x when the property was deteriorated when 0.8 times or less.

From these results, it can be seen that the material used in this example is superior to titanium oxide alone in oil decomposition properties under ultraviolet irradiation. In addition, it can be seen from this example that a material using an alloy containing 10 to 50% by weight of copper or zinc in silver as a surface coating layer has particularly excellent characteristics.

Example 2 The same evaluation as in Example 1 was carried out using a 200 W incandescent lamp capable of irradiating the same powder as in Example 1 with light having a wavelength in the range from infrared light to visible light. The results are shown in the tables of FIGS.

From these results, it can be seen that the material used in the present example is superior in oil decomposition characteristics to the material in the infrared to visible light range as compared with the material containing only titanium oxide.
In addition, it can be seen from this example that a material using an alloy containing 10 to 50% by weight of copper or zinc in silver as a surface coating layer has particularly excellent characteristics.

Example 3 An alloy of Ag50 Zn50 (subscripts indicate% by weight) was applied to titanium oxide particles having various average particle diameters by a sputtering method to make about 5% by weight based on the total weight of the completed photocatalytic particles. As described above. At this time, oil decomposition characteristics were examined by the same evaluation method as in Example 1. FIG. 6 shows the result. According to this result, the particle size of titanium oxide was about 1.3 μm.
m, the evaluation is x, and the particle size is about 1.15 μm, the evaluation is Δ, whereas the particle size is about 1 μm, about 0.7 μm
Is evaluated as ○, and further, when the particle size is about 0.5 μm, about 0.25 μm, and about 0.1 μm, the evaluation is ◎.

From these results, it was found that the particle diameter of 1 μm in this example was 1 μm.
It can be seen that oil decomposition characteristics are excellent with titanium oxide of m or less (indicated by A in FIG. 6). It can also be seen that the characteristics are particularly excellent at a particle size of 0.5 μm or less.

Example 4 Various weight percentages of Ag 50 Cu 50 (subscripts are weight percentages) were applied to titanium oxide particles having an average particle diameter of 0.3 μm by sputtering.
Alloy was coated. At this time, the oil decomposition characteristics due to the difference in the coating amount were evaluated by the same method as in Example 1. The result is shown in FIG.
Shown in In FIG. 7, the horizontal axis is abbreviated for the sake of shortening. According to this result, the weight% of the coating amount of the alloy
However, the evaluation was “×” at about 20.7%, while the weight% of the coating amount of the alloy was about 20%, about 15.7%, about 15%.
%, The evaluation is ○, and further, about 10%, about 5%, and about 3%, the evaluation is ◎. Next, the weight% of the coating amount of the alloy is about 1%
In this case, the evaluation is ○, and at about 0.5%, the evaluation is △.

From these results, it was found that the coating amount in this embodiment was 1 to
At 20% by weight (the range indicated by B in FIG. 7), it can be seen that the oil decomposition characteristics are excellent. It can also be seen that the characteristics are particularly good when the coating amount is 3 to 10% by weight.

Example 5 An alloy of Ag50Cu30Zn20 (subscript:% by weight) was applied to titanium oxide particles having an average particle size of 1 μm by sputtering.
Wt% coating, which was heat treated in vacuum at a temperature of 600 ° C. for various times. The melting point of this alloy is about 800 ° C. At this time, the size of the surface coating alloy was observed, and the relationship between the particle size and the oil decomposition characteristics was evaluated in the same manner as in Example 1.
FIG. 8 shows the result. The horizontal axis in FIG. 8 is a logarithmic scale. According to this result, the particle size of the alloy was about 0.3 μm and the evaluation was ○, whereas the particle size of the alloy was about 0.1 μm,
The evaluation is ◎ at about 0.035 μm and about 0.016 μm.

From these results, it can be seen that when the particle diameter of the surface alloy particles is 0.1 μm or less (in the range indicated by C in FIG. 8), particularly good oil decomposition characteristics are obtained.

As described above, according to the embodiment of the present invention, the characteristics of the titanium oxide photocatalyst can be improved.
In particular, oil decomposition characteristics in the visible light region can be significantly improved. These photocatalytic particles can be applied to cooking utensils and kitchen utensils having self-cleaning properties, as well as exterior and interior building materials, and greatly contribute to industrialization. Further, the photocatalyst material according to the present invention can be used not only in oil decomposition but also in various fields such as decomposition of nitrogen oxides and sulfur oxides, decomposition of organic dirt, antibacterial and carbon dioxide fixation.

[0046]

As described above, according to the present invention, silver, which covers the surface of titanium oxide particles so as to expose a part of the surface of the titanium oxide particles to be excited in the ultraviolet region,
It comprises at least one metal or alloy selected from copper, zinc, and nickel, and the titanium oxide particles have a particle size of 1 μm or less, so that they have excellent photocatalytic properties, particularly excellent photocatalytic properties in the visible light region. It is possible to provide photocatalytic particles.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic view of a particle which is an example of the photocatalytic particle of the present invention.

FIG. 2 is a view showing a table in which evaluation results of Example 1 are summarized.

FIG. 3 is a diagram showing a continuation of the table of FIG. 2;

FIG. 4 is a diagram showing a table summarizing evaluation results of Example 2.

FIG. 5 is a diagram showing a continuation of the table of FIG. 4;

FIG. 6 is a diagram summarizing evaluation results of Example 3.

FIG. 7 is a diagram summarizing evaluation results of Example 4.

FIG. 8 is a diagram summarizing the evaluation results of Example 5.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photocatalytic particle 2 Titanium oxide particle 2a Surface of titanium oxide particle 3 Coating of silver, copper, zinc, nickel

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01J 23/755 B01J 23/80 Z 23/80 23/89 Z 23/835 C09K 3/00 U 23/89 112Z C09K 3/00 A47J 36/02 A 112 C08J 11/10 CFJ // A47J 36/02 B01J 23/74 321Z C08J 11/10 CFJ 23/82 Z C08L 91:00

Claims (5)

[Claims] 1. A titanium oxide particle; and at least one kind selected from silver, copper, zinc, and nickel, which coats the surface of the titanium oxide particle so that a part of the surface of the titanium oxide particle is exposed. A metal or alloy; a particle diameter of the titanium oxide particles is 1 μm or less; photocatalytic particles. 2. Photocatalytic particles according to claim 1, wherein the alloy comprises silver and further comprises one or both of copper and zinc in a total amount of 10 to 50% by weight. 3. The photocatalytic particle according to claim 1, wherein the metal or the alloy is coated on the surface of the titanium oxide particle in a discontinuous film form. 4. The metal or alloy has a particle size of 0.1 μm.
The photocatalytic particle according to any one of claims 1 to 3, wherein: 5. The photocatalytic property according to claim 1, wherein a weight ratio of the coated metal or alloy to the photocatalytic particles is 1 to 20%. particle.