JP2000312830A - Photocatalyst composite material and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a photocatalyst composite material in which photocatalytic activity is not impaired and the activity inherent in the photocatalyst is sufficiently exhibited, and a method for producing the same. A photocatalyst composite material has a metal oxide layer (3) between a substrate (1) made of aluminum or a metal containing aluminum and a photocatalyst layer (2) for suppressing diffusion of oxygen from the photocatalyst layer toward the substrate. The metal oxide layer may be an aluminum oxide formed by subjecting a substrate to an oxidation treatment. This photocatalyst composite material is formed by applying a sol solution containing metal oxide fine particles or a solution containing a metal oxide precursor to the surface of a base material, followed by firing to form a metal oxide layer. And by forming a photocatalytic layer on the surface thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalyst composite material and a method for producing the same, and more particularly, to a photocatalytic composite material which, when irradiated with light, has a function of decomposing substances adhered to the composite material surface, deodorizing, antibacterial, decomposing harmful substances, and the like. The present invention relates to a photocatalyst composite material developed and a method for producing the same.

[0002]

2. Description of the Related Art When a semiconductor is irradiated with light, electrons having a strong reducing action and holes having a strong oxidizing action are generated on the irradiated surface. When a harmful substance or the like comes into contact with the surface of the semiconductor in such a state, the substance is decomposed by the strong oxidation-reduction action of the semiconductor.

Recently, the photocatalysis of such semiconductors has been
2. Description of the Related Art Various technologies for purifying the environment, such as decomposition and detoxification of harmful substances contained in air and water, deodorization, antifouling, and sterilization in living spaces and the like, have been vigorously developed. Titanium oxide (TiO ₂ ), which has relatively high photocatalytic activity, is excellent in safety, and is chemically stable, is the most frequently used semiconductor photocatalyst (hereinafter, simply referred to as photocatalyst) used for such purpose. Have been.

When a photocatalyst is applied to the above-mentioned environmental purification, it is generally used in a state where a photocatalyst such as titanium oxide is fixed as a thin film on the surface of a substrate made of a material such as metal, glass or ceramics. It is.

In order to fix the photocatalyst to the substrate, mainly, 1) a method in which the photocatalyst particles are applied to the substrate using a binder and then fired at a relatively low temperature of 200 ° C. or lower;
A method such as a so-called sol-gel method has been used in which a photocatalyst precursor substance is applied to a substrate and then baked at a relatively high temperature of 300 ° C. or higher.

Conventionally, when a photocatalyst is baked at a high temperature on a substrate such as a metal such as stainless steel or glass by a sol-gel method or the like, an impurity element (for example, chromium, iron, glass, etc. in stainless steel) is removed from the substrate. In some cases, sodium) diffused into the photocatalyst and reduced the photocatalytic activity. Therefore, a method of providing a barrier layer between the photocatalyst and the substrate has been adopted (for example, Japanese Patent Application Laid-Open No. 9-3101).
No. 85).

On the other hand, for aluminum-based substrates,
Since the softening point and melting point are low, most of them use a binder (for example, JP-A-9-59041 and JP-A-10-216528), and do not bake at a high temperature of 500 ° C. or more. Therefore, diffusion of the impurity element into the photocatalyst did not become a problem, but if the above-mentioned sol-gel method or the like can be applied, a photocatalytic layer having more excellent photocatalytic activity and a high strength is formed. It becomes possible. However, when a photocatalyst such as titanium oxide is fixed on the surface of an aluminum substrate by the sol-gel method, the photocatalytic activity may be lower than when the photocatalyst is fixed on quartz glass.

[0008]

The present invention relates to a photocatalyst composite material in which a photocatalyst is fixed to aluminum or a metal containing aluminum, the photocatalyst composite material exhibiting sufficient photocatalytic activity without being impaired. , And a method of manufacturing the same.

[0009]

The gist of the present invention resides in the following photocatalyst composite materials (1) and (2) and the production methods thereof (3) and (4).

(1) A photocatalyst composite material having a metal oxide layer between a photocatalytic layer and a substrate made of aluminum or a metal containing aluminum, which suppresses diffusion of oxygen from the photocatalyst layer toward the substrate.

(2) The method according to (1), wherein the base material is a metal containing aluminum as a main component, and the metal oxide layer is a layer made of aluminum oxide formed by subjecting the base material to an oxidation treatment. The photocatalyst composite material according to the above.

(3) A sol solution containing fine particles of a metal oxide is applied to the surface of the substrate, or a solution containing a precursor of the metal oxide or a solution obtained by subjecting this solution to a hydrolysis treatment is applied. The method for producing a photocatalyst composite material according to the above (1), wherein the photocatalyst layer is formed on the surface after firing to form a metal oxide layer.

(4) The photocatalyst composite material according to (2), wherein the metal oxide layer is formed by subjecting the substrate to an oxidation treatment under the conditions satisfying the following formula, and then a photocatalyst layer is formed on the surface. Production method.

T> 590t ^−0.06 Here, T: oxidation treatment temperature (K) t: treatment time (s) In the photocatalyst composite material of (1), the metal oxide layer
If the layer is made of one or more oxides of aluminum oxide, silicon oxide, zirconium oxide and magnesium oxide, the photocatalytic performance of the photocatalytic layer can be more effectively exhibited. The metal oxide layer has an oxygen deficiency ratio of 20 based on the chemical formula of the most stable structure of the oxide.
% Or less can suppress a decrease in photocatalytic performance.

As a result of repeated studies to solve the above-mentioned problems, the present inventors will form a photocatalytic layer such as titanium oxide directly on a substrate made of aluminum or a metal containing aluminum by a sol-gel method or the like. Then, during firing at a high temperature, it was found that titanium oxide was reduced (deoxygenated) by the reducing action of aluminum, and the layer formed on the base material had an oxygen-deficient structure with extremely low photocatalytic activity. Conventionally, it has been well known that when a metal oxide is in a molten state or a powder state, it is reduced by aluminum. It was not well known that the reduction effect was exerted.

This is because the energy of formation of alumina is lower than that of titanium oxide. That is, the decrease in the photocatalytic activity is caused by the diffusion of the impurity element from the base material to the photocatalyst in the case of the above-described base material made of metal such as stainless steel or glass, whereas the base made of aluminum or an aluminum-containing metal is used. In the case of a material, it is due to diffusion of oxygen from the photocatalyst based on the deoxidizing property of aluminum to the substrate.

Further, the diffusion of oxygen from the photocatalyst layer to the substrate can be performed by providing a layer made of a metal oxide for suppressing the diffusion of oxygen between the substrate made of aluminum or aluminum-containing metal and the photocatalyst layer. The present inventors have found that a photocatalyst composite material that can prevent such a phenomenon and has an excellent photocatalytic action can be provided.

The present invention has been made based on these findings.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a photocatalyst composite of the present invention and a method for producing the same will be described.

FIG. 1 is a sectional view schematically showing the structure of the photocatalyst composite of the present invention. As shown in the figure, in this photocatalyst composite, a metal oxide layer 3 for suppressing diffusion of oxygen from the photocatalyst layer 2 to the substrate 1 is provided between the substrate 1 and the photocatalyst layer 2.

(A) Substrate As the substrate, aluminum or a metal containing aluminum can be used. What is aluminum?
The term “pure aluminum” includes a very small amount of impurities that are inevitably mixed during the production. The metal containing aluminum means an aluminum alloy and various metal materials containing aluminum as an alloy element. As the aluminum alloys, alloy numbers 1000 to 7000, specified in JIS H4000, and 5
Various alloys such as N01 and 7N01 can be used. The metal material containing aluminum as an alloy element may be, for example, stainless steel, nickel, copper, titanium, or the like. The lower limit of the desirable content of aluminum in this case is 0.2% by weight.
(Hereinafter simply referred to as “%”).

However, in the photocatalyst composite material described in (2) above, aluminum or a metal containing aluminum as a main component is used. A material containing aluminum as a main component is a material containing 50% or more of aluminum. If the content of aluminum is less than 50%, it is difficult to form a metal oxide layer that effectively suppresses the diffusion of oxygen by the oxidation treatment. It is preferably at least 90%, more preferably at least 95%. More specifically, pure aluminum, alloy numbers from 1000 to 7000, and 5N
Various alloys such as 01 and 7N01 can be used.

The shape of the substrate is preferably determined according to the application. The shape may be a plate shape such as a thick plate or a thin plate, a foil shape, a spherical shape such as a bead, a net shape, a fin shape, or a complicated shape used as a product as it is. Moreover, in order to obtain a more effective photocatalytic action, the photocatalyst composite material may be formed into an arbitrary shape after it is manufactured. There is no restriction on the thickness of the substrate such as a plate. The surface of the substrate may be porous or dense.

(B) Metal Oxide Layer The metal oxide layer has a role of suppressing diffusion of oxygen from the photocatalyst layer toward the substrate.

As described above, usually, even if an attempt is made to form a photocatalyst layer such as titanium oxide on an aluminum substrate,
When firing at high temperature, the reducing action of aluminum
Oxygen diffuses from the photocatalyst such as titanium oxide to the substrate, and the photocatalyst has a large number of oxygen defects, so that the activity of the photocatalyst decreases. After the photocatalyst layer is formed on the substrate, oxygen may diffuse little by little even in a state where the photocatalyst layer is left indoors, and the activity may gradually decrease. In particular, when a photocatalyst layer is formed by a sol-gel method or the like, the firing at a relatively high temperature of 300 ° C. or more is required, so that the activity is significantly reduced. For this reason, a metal oxide layer is provided between the base material and the photocatalyst layer to prevent diffusion of oxygen, prevent the photocatalytic activity from lowering, and exhibit the original photocatalytic performance.

The metal oxide constituting the metal oxide layer includes aluminum oxide, silicon oxide, zirconium oxide,
Magnesium oxide, titanium oxide, chromium oxide, copper oxide,
Iron oxide and the like can be used. If these metal oxides are contained in a weight ratio of 50% or more, an effect of inhibiting oxygen diffusion is observed, but a metal oxide layer composed of only the metal oxide is more preferable.

In order to more effectively exhibit the photocatalytic performance of the photocatalyst layer, a metal oxide containing one or more of aluminum oxide, silicon oxide, zirconium oxide and magnesium oxide as the main component is used. Is preferred. In the case of two or more kinds, they may be simply mixed or, for example, may contain at least a part of a composite oxide such as aluminosilicate.

The form of the metal oxide may be amorphous or crystalline, or a mixture thereof. The crystal form may be any. Further, it may be a hydroxide or an oxide from which most of the water of crystallization has been removed. For example, in the case of aluminum oxide, AlOOH
Or Al ₂ O ₃ . Further, as described below, the metal oxide layer is made of an oxide having an oxygen deficiency ratio of 20% or less based on the chemical formula of the most stable structure (a structure having no oxygen deficiency) of the oxide. If it is a layer, the photocatalytic performance of the photocatalytic layer formed on the metal oxide layer can be suppressed from deteriorating, and the performance can be exhibited more effectively.

When a metal oxide layer is formed on a substrate surface,
During sintering, the effects of strong oxygen and magnesium, etc. contained in the substrate, such as aluminum and magnesium, the metal oxide itself may become oxygen deficient type lacking oxygen due to insufficient supply of oxygen, When the oxygen deficiency ratio is high, even if a photocatalyst layer is formed thereon, oxygen tends to diffuse from the photocatalyst layer to the metal oxide layer, and the photocatalytic performance tends to decrease. In this case, if the oxygen deficiency ratio is 20% or less based on the chemical formula of the most stable structure of the metal oxide, even if the photocatalyst layer is formed on the metal oxide layer, ( That is, it is preferable because diffusion of oxygen (in the direction of the base material) hardly occurs and high photocatalytic activity can be maintained.

The metal oxide having an oxygen deficiency ratio of 20% or less is, for example, Al ₂ O _(3-y) (y is 0.6 or less) when the metal oxide is aluminum oxide. Is silicon oxide, zirconium oxide or magnesium oxide, SiO _{2 (2-z)} (z is 0.4
Below), ZrO _(2-v) (v is 0.4 or less), MgO
_(1-w) (w should be 0.2 or less). The oxygen deficiency ratio of these metal oxides can be determined by elemental analysis such as X-ray fluorescence or secondary ion mass spectrometry, or photoelectron spectroscopy (E
(SCA), Auger spectroscopy, and other surface analysis methods.

When the metal oxide layer is a layer made of aluminum oxide, the metal oxide layer is an aluminum oxide formed by subjecting the above-described base material containing aluminum as a main component to an oxidation treatment described later. Is also good. The aluminum oxide obtained in this manner has an extremely good adhesion to the substrate because the substrate itself is oxidized to form an oxide layer, and has no defects such as peeling or pinholes. After forming the photocatalyst layer thereon, it does not peel off even when subjected to bending.

In this case, the thickness of the aluminum oxide layer is preferably 2 nm or more so that diffusion of oxygen from the photocatalyst layer toward the substrate can be effectively prevented. Although the upper limit of the thickness is not particularly specified, if the thickness is too large, the aluminum oxide layer is likely to peel off or crack from the substrate during processing, and it is economically disadvantageous.
μm or less is preferred. More preferably, it is 2.0 nm to 5.0 μm, and still more preferably, 5.0 nm to 2.0 μm.

(C) Photocatalyst Layer The photocatalyst forming the photocatalyst layer may be a known semiconductor photocatalyst such as titanium oxide, zinc oxide, tungsten oxide, zirconium oxide, iron oxide, bismuth oxide, alone or in combination of two or more. Can be used. Further, the above-mentioned photocatalyst may be supported on a substance having no photocatalytic action, for example, a substance such as silica, alumina or zeolite.

Titanium oxide is preferred as a photocatalyst for forming a photocatalyst layer because it has a relatively high activity, is excellent in safety, and is easily available. The form of titanium oxide may be either amorphous or crystalline, or a mixture of these. In the case of crystalline, any of anatase type, rutile type, and a mixture thereof may be used.

In order to obtain a photocatalytic composite material having higher activity, it is preferable to use a titanium-based oxide containing one or more of zirconium oxide, silicon oxide and aluminum oxide. The titanium-based oxide contains zirconium, silicon, and a predetermined amount of an oxide of aluminum in titanium oxide, and the form may be a mixture of each oxide and titanium oxide. It may be one containing at least partially a composite oxide formed by the reaction of an oxide and titanium oxide. At this time, the crystal form of the base titanium oxide may be amorphous,
It may be crystalline. Also, the crystal form of the contained metal oxide or composite oxide may be either amorphous or crystalline.

The photocatalyst forming the photocatalyst layer has V, Fe, Zn, Ru,
At least one metal and / or metal compound of Rh, Pt, Ag, Pd and Cu may be contained. By including these components, the photocatalytic performance can be further enhanced, and the functions of the components themselves (for example, antibacterial properties with Zn, Ag, and Cu) can be imparted to the photocatalyst. Examples of the metal compound include metal oxides, hydroxides, oxyhydroxides, nitrates, and halogen salts.

The thickness of the photocatalyst layer is from 20 nm to 5.0 μm.
Is preferred. When the thickness is less than 20 nm, sufficient photocatalytic activity cannot be obtained, and when the thickness exceeds 5.0 μm, cracks or peeling may occur in the photocatalyst layer. When the layer thickness is in the above range, a high photocatalytic activity is exhibited, and a favorable photocatalyst composite material having few cracks and peeling can be easily produced.

(D) Method for Producing Photocatalyst Composite Material The above-mentioned photocatalyst composite material is obtained by applying a sol solution containing fine particles of metal oxide to the surface of a base material and firing it to form a metal oxide layer. It can be produced by forming a photocatalyst layer on the surface. A metal oxide layer is applied by applying a solution containing a precursor of a metal oxide to the surface of the base material, or after subjecting the solution containing the precursor to a hydrolysis treatment, and then applying and baking the solution, a so-called sol-gel method. And a method of manufacturing by forming a photocatalyst layer on the surface thereof. As a precursor of the metal oxide, for example, an organic metal or the like containing a metal constituting the oxide may be used.

First, a method for forming a metal oxide layer will be described.

When forming a metal oxide layer, a sol solution containing fine particles of a metal oxide, a solution containing a precursor of a metal oxide, or a solution obtained by subjecting the solution to hydrolysis is applied by a spin coating method. Examples of the method include coating, dip coating, spray coating, bar coating, roll coating, and spraying. Which method is adopted may be determined according to the shape of the base material in consideration of the properties of the coating solution.

The firing temperature may be determined in accordance with the properties of the coating solution, the form of the metal oxide, and the like. The upper limit is the temperature at which the substrate made of aluminum or a metal containing aluminum does not soften or melt. It is necessary to

In addition to the above method, a method such as CVD or sputtering may be used.

On the other hand, when the metal oxide layer is a layer made of aluminum oxide formed by subjecting a base material containing aluminum as a main component to an oxidation treatment, the base material is subjected to a condition satisfying the following equation. It is manufactured by forming a metal oxide layer by performing an oxidation treatment and then forming a photocatalyst layer on the surface thereof.

T> 590t ^−0.06 ... Here, T: oxidation treatment temperature (K) t: treatment time (s) The formula is derived based on the result of an oxidation treatment test of Example 4 described later. It is.

It is preferable that the oxygen partial pressure of the atmosphere at the time of performing this oxidation treatment is 40 kPa to 5 kPa. Within this range, the above equation can be applied when setting the oxidation treatment conditions, and the adjustment of the oxidation treatment atmosphere is relatively easy. When the oxygen partial pressure exceeds 40 kPa, the cost increases due to the supply of oxygen, while 5 kP
If it is lower than a, a high-temperature and long-time treatment is required to obtain a metal oxide layer having a sufficient thickness, and both are economically disadvantageous.

According to the method of forming an aluminum oxide by this oxidation treatment, the step of applying the metal oxide layer can be omitted, which is advantageous in manufacturing.

It is to be noted that a method of forming a metal oxide layer by anodizing the substrate to form an alumina film may be employed. Since the alumina film formed by anodic oxidation becomes a porous layer having a large number of fine pores of aluminum oxide, it has good adhesion to a photocatalyst layer formed thereon, and an improvement in photocatalytic activity due to an increase in surface area can be expected.

Next, a method for forming the photocatalyst layer will be described.

The photocatalyst layer is formed by dissolving a solution in which a photocatalyst precursor such as an organic metal is dissolved on the metal oxide layer formed as described above, if necessary, by partial hydrolysis or the like. It may be performed by a so-called sol-gel method after application and application, followed by baking, or by applying a suspension containing a photocatalyst precursor substance, followed by baking or a method such as CVD or sputtering. You may.

Among them, it is most preferable to use the sol-gel method of baking at a high temperature of 300 ° C. or more. This is because a photocatalyst having high photocatalytic activity and photocatalytic layer strength can be provided. When the photocatalyst is a titanium oxide-based photocatalyst, a photocatalyst excellent in transparency can be provided. In addition, a coating solution of titanium oxide generally contains an acid such as hydrochloric acid or nitric acid as a catalyst. However, if this is applied and baked at a low temperature of 300 ° C. or less, the base material is corroded because the acid remains in the photocatalyst. ,
Not only the appearance is impaired, but also the adhesion of the photocatalyst layer itself and the photocatalytic performance are reduced. In the sol-gel method in which baking is performed at a high temperature of 300 ° C. or more, since the acid volatilizes and disappears, a healthy state can be maintained for a long time.

In particular, a photocatalyst composite material in which a photocatalyst layer is formed by using the above-mentioned sol-gel method on a layer made of aluminum oxide formed by subjecting the above-mentioned aluminum-based substrate to an oxidation treatment. Is an excellent composite material having excellent adhesion between the substrate and the metal oxide layer and high photocatalytic activity.

When the photocatalyst layer is formed only by titanium oxide by the sol-gel method, a titanium alkoxide such as titanium isopropoxide or titanium butoxide, titanium sulfate, titanium tetrachloride, titanium acetylacetonate is used in a solvent such as alcohol. A sol solution obtained by adding a precursor substance such as described above, adding a small amount of acid and water as needed, and performing a hydrolysis treatment may be used.

The coating method includes spin coating, dip coating, spray coating, bar coating, roll coating, spray spraying and the like. Which method is used depends on the properties of the coating solution and the shape of the substrate. What is necessary is just to determine together.

The firing temperature may be determined according to the properties of the coating solution and the form of the metal oxide, but the upper limit must be a temperature at which the base material does not soften or melt.

The photocatalyst composite material of the present invention described above exhibits a photocatalytic action when irradiated with light having an energy higher than the band gap of the photocatalyst forming the photocatalyst layer, and decomposes and removes various harmful substances and adhered substances. Demonstrates excellent effects on detoxification. The harmful substances include NO _x , SO
_x , chlorofluorocarbons, ammonia, hydrogen sulfide and other gases contained in the atmosphere, aldehydes, amines, mercaptans, alcohols, organic compounds such as BTX (benzene, toluene, xylene) and phenols, trihalomethane, trichloroethylene, In addition to organic halogen compounds such as chlorofluorocarbons, herbicides, fungicides, various pesticides such as insecticides, various biological oxygen-requesting substances such as proteins and amino acids, surfactants, and inorganic compounds such as cyanide and sulfur compounds And various heavy metal ions, as well as microorganisms such as bacteria, actinomycetes, fungi, and algae, and those substances contained in water among the above substances.

The substances adhering directly to the surface of the photocatalytic composite material include, for example, fungi such as Escherichia coli, staphylococci, green bacterium, and mold, oil, tobacco tar, fingerprints, and the like.
There are rain streaks and mud.

As light to be applied to the photocatalyst composite material, sunlight, light from a fluorescent lamp, a black light, a mercury lamp, a xenon lamp, or the like can be used. Optimal conditions such as the amount of light irradiation and the irradiation time are preferably selected depending on the amount of the substance to be processed.

[0058]

EXAMPLES (Example 1) Five types of photocatalyst composite materials of the present invention (Test Nos. 1 to 5) and two types of composite materials for comparison (Test Nos. 6 and 7) are as follows. It was manufactured under the following conditions.

Test No. 1: A commercially available high-purity aluminum plate (Nilaco: thickness 2 mm, purity 99.999%) was used as a test material (substrate), and alcohol was added to alumina fine particle sol (Nissan Chemical Industries, solid content 20% by weight). The coating solution prepared by dip coating was applied in a dip coating (pulling speed: 10
0 mm / min). Next, by drying at 100 ° C. for 30 minutes and baking at 450 ° C. for 20 minutes in an air atmosphere,
A metal oxide layer made of alumina was formed on an aluminum plate. About this aluminum base material, the depth analysis of the metal oxide layer was performed by the secondary ion mass spectrometry (SIMS), and the thickness of the alumina layer was measured. In addition, the thickness of the metal oxide layer was similarly measured about the other base material mentioned later.

Further, a photocatalyst layer (titanium oxide film) was formed on the aluminum substrate having the alumina layer formed thereon by a sol-gel method. That is, a mixture of 0.4 part of nitric acid, 1.0 part of water and 15 parts of alcohol was added dropwise to a solution of 10 parts of titanium tetrabutoxide dissolved in 15 parts of alcohol to prepare a titanium oxide sol solution, Dip-coated on a base material, dried at 110 ° C. for 30 minutes, and baked at 450 ° C. for 20 minutes in an air atmosphere to obtain a book having a metal oxide layer made of alumina between an aluminum base material and a titanium oxide photocatalyst layer. A photocatalyst composite of the invention was made.

Test No. 2: A commercially available aluminum alloy plate (A3003 specified in JIS H4000, thickness: 0.3 mm) was used as a test material (base material), immersed in a 5% aqueous sodium hydroxide solution for 2 minutes, washed with water, and subsequently washed Immersed in a 5% nitric acid solution for 2 minutes, washed with water, and dried under vacuum. The test No. was placed on the aluminum alloy substrate subjected to this pretreatment. Alumina and titanium oxide were formed as a metal oxide layer and a photocatalyst layer, respectively, by the method described in 1.

Test No. 3: Test No. Using an aluminum alloy plate (A3003, same as above, thickness 0.3 mm) pretreated by the method described in 2 as a test material (substrate), an oxygen partial pressure of 20
An oxidation treatment was performed at 200 ° C. for 180 minutes in a gaseous atmosphere of KPa to form an alumina layer on the substrate surface. Test No. was applied to the substrate on which the alumina layer was formed. A titanium oxide photocatalyst layer was formed by the method described in 1.

Test No. 4: Test No. Using an aluminum alloy plate (A3003, same as above, thickness: 0.3 mm) pretreated by the method described in 2 as a test material (base material), a solution in which 5 parts of magnesium nitrate hexahydrate was dissolved in 100 parts of water was used. Dip coating was performed (pulling speed 50 mm / min). Next, after drying at 100 ° C. for 30 minutes,
By firing at 00 ° C. for 1 hour, a metal oxide layer composed of magnesium oxide was formed on the aluminum alloy substrate. Subsequently, Test No. was applied to the substrate on which the metal oxide layer was formed. A titanium oxide photocatalyst layer was formed by the method described in 1.

Test No. 5: Test No. Test No. 1 was carried out using the commercially available high-purity aluminum plate used in Example 1 as a test material (substrate), and adding 0.4 parts of zirconium isopropoxide to 10 parts of titanium tetrabutoxide. A photocatalytic sol solution was prepared in the same manner as described in 1. Using this sol solution, test no. An alumina layer was formed on the substrate surface by the method described in 1, and a titanium oxide photocatalyst layer containing zirconium oxide was further formed thereon.

Test No. 6: Test No. The commercially available high-purity aluminum plate used in Test No. 1 was used as a test material (base material) without forming an alumina layer. A photocatalyst composite material in which a photocatalyst layer was directly formed on an aluminum substrate was produced in the same manner as described in 1.

Test No. 7: Test No. The commercially available aluminum alloy plate used in Test No. 2 was used as a test material (base material) without forming an alumina layer. A photocatalyst composite material in which a photocatalyst layer was directly formed on an aluminum alloy substrate was manufactured in the same manner as described in 2.

The photocatalyst composite material of the present invention (Test No.
Acetaldehyde decomposition tests were performed on the composite materials (Test Nos. 1 and 5) and the composite material for comparison (Test Nos. 6 and 7) to evaluate their photocatalytic performance.

The acetaldehyde decomposition test was performed as follows. That is, an evaluation sample (50 mm square) cut out from each of the above composite materials was placed in a quartz reaction cell, and connected to a closed circulation line (total internal volume of about 1.0 liter). Acetaldehyde diluted with air (about 120 pp
m) was introduced into the system, and light was irradiated from a high-pressure mercury lamp of 250 W through a UV filter (UV-31 manufactured by Toshiba) while circulating. At this time, UV of the sample surface for evaluation
The intensity was 0.4 mW / cm ² . The concentration was determined using a gas chromatograph. The photocatalytic performance was evaluated by the acetaldehyde removal rate after one hour.

Table 1 shows the composition (substrate, metal oxide layer and photocatalyst layer) of each composite material and the results of the photocatalytic performance evaluation test (acetaldehyde removal rate).

As shown in Table 1, all of the photocatalyst composite materials of the present invention (Test Nos. 1 to 5) exhibited a high photocatalytic performance with an acetaldehyde removal ratio of 80% or more.

On the other hand, a composite material for comparison (Test No. 6)
In (7) and (7), the removal rate of acetaldehyde was as poor as 40% or less. This is because, if the photocatalyst layer is formed without providing a metal oxide layer for suppressing diffusion of oxygen on the aluminum base material or aluminum alloy base material, diffusion of oxygen from the photocatalyst layer to the base material occurs. Is that many oxygen vacancies are generated and the photocatalytic activity is reduced.

The structure of titanium oxide is expressed as TiO _(2-x ). In the case of the comparative examples (Test Nos. 6 and 7),
The titanium oxide layer was colored, and x had a structure close to 1. On the other hand, the photocatalyst composite material of the present invention (Test No. 1 to No. 1)
In 5), the titanium oxide layer is colorless or slightly white,
x was very close to 0, and the titanium oxide structure (TiO ₂ ) used for a normal photocatalyst was maintained.

[0073]

[Table 1]

Example 2 A photocatalyst composite material of the present invention (Test No. 8 and Test No. 9) was produced under the following conditions.

Test No. 8: Commercially available aluminum mesh (material: A5056 specified in JIS H4040,
mesh42), a test material was cut out to serve as a base material. Pretreatment was performed in the same manner as in Example 2. This was immersed in a coating solution obtained by adding 3 parts of alcohol to 1 part of alumina fine particle sol (manufactured by Nissan Chemical Co., Ltd., solid content: 20% by weight). For 20 minutes, followed by baking at 450 ° C. for 20 minutes to form an alumina layer on the substrate surface. A part of the fired substrate was analyzed for the composition of alumina by Auger spectroscopy.

Subsequently, the test No. of Example 1 was applied to the substrate on which the alumina layer was formed. After applying the titanium oxide sol solution described in 1 in the same manner and drying at 110 ° C. for 20 minutes,
The resultant was baked at 450 ° C. for 20 minutes to form a titanium oxide photocatalyst layer, thereby obtaining a photocatalyst composite material.

Test No. 9: Test No. 9 The test material was cut out from the commercially available aluminum mesh used in Example 8 as a substrate, and baked at 600 ° C. for 1 hour after dipping in a coating solution of alumina fine particle sol. An alumina layer and a titanium oxide photocatalyst layer were sequentially formed on the surface of the substrate by the same method as described in 8, to obtain a photocatalyst composite material. In addition,
For a part of the fired base material, the composition of alumina was analyzed by Auger spectroscopy.

The photocatalyst composite material of the present invention (Test No.
8 and 9), a sample (60 mm
Corners) were cut out and subjected to an acetaldehyde decomposition test in the same manner as in Example 1 to evaluate its catalytic performance.

Table 2 shows the composition (substrate,
(Alumina layer and photocatalyst layer) and acetaldehyde removal rate.

The composition of the alumina layer was determined according to Test No. 8 for A
l ₂ O _2.89 , test no. In _No. 9, the content was Al ₂ O _2.14 , and the oxygen deficiency rates were 3.7% and 28.6%, respectively.

Regarding the photocatalytic performance, Test No. The photocatalyst composite material of Test No. 8 was a test no. 9 showed a higher rate of acetaldehyde removal. This means that the oxygen deficiency ratio is 20%
This is because when the value exceeds the above, diffusion of oxygen from the titanium oxide photocatalyst layer formed thereon to the alumina layer is likely to occur, and the performance of the titanium oxide photocatalyst is somewhat reduced. From this result, it can be said that the metal oxide layer is preferably a layer made of an oxide in which the oxygen deficiency ratio of the metal oxide is 20% or less. The reason why the removal rate of acetaldehyde was relatively lower than that of Example 1 was that the net was used as the base material, so that the light receiving area was smaller than that of the flat plate, and the decomposition efficiency was poor.

[0082]

[Table 2]

(Example 3) As a substrate, purity 99.99
Using a 5% sodium hydroxide aqueous solution and a 5% nitric acid aqueous solution,
Washed well. Thereafter, an oxygen partial pressure of 20 kPa (10
kPa) in the gas phase at a temperature of 350K for 10,000 seconds, 5
The oxidation treatment was performed at 00K for 100 seconds or at 700K for 1000 seconds. Note that a part of the base material after the oxidation treatment was analyzed by SIMS, and the thickness of the oxide layer formed by the above treatment was measured.

Next, a titanium oxide photocatalyst layer was formed on the surface of the substrate after the oxidation treatment by the sol-gel method described below. That is, a titanium oxide sol solution obtained by adding a small amount of nitric acid and water to an alcohol solution of titanium butoxide by a dip coating method was applied to the base material, and then held at 823 K for 30 minutes to form a titanium oxide photocatalyst layer on the surface. . The thickness of this photocatalyst layer was 150 nm.

The photocatalyst composite material produced as described above was subjected to a methylene blue decomposition test to evaluate its photocatalytic performance.

The decomposition test of methylene blue was performed as follows. That is, a photocatalytic activity evaluation sample (8 mm × 40 mm × 2 mm) was cut out from the above photocatalyst composite material to obtain a substrate, which was placed in a Pyrex reactor, and a methylene blue aqueous solution (methylene blue: 8 pp) was added thereto.
m) was added thereto, and oxygen was blown therein for 10 minutes. After closing the lid, light irradiation was performed from a 500 W ultra-high pressure mercury lamp. Methylene blue concentration was determined using a spectrophotometer at a wavelength of 530.
This was done by measuring the absorbance in nm. The photocatalytic performance was evaluated by the decomposition rate of methylene blue after 1 hour.

Table 3 shows the oxidation treatment conditions, oxygen partial pressure, alumina layer thickness, and methylene blue decomposition rate of each test material. The oxidation treatment temperature T obtained from the above equation is also shown.

As shown in Table 3, when the oxidation treatment was not performed (Test No. 10), the decomposition rate of methylene blue was extremely low. On the other hand, when an alumina layer was formed on the surface of the substrate by performing an oxidation treatment (Test Nos. 11 to 14)
In Example 2, the decomposition rate of methylene blue increased with an increase in the layer thickness. In particular, when the thickness of the alumina layer was 2 nm or more, the decomposition rate of methylene blue was high. When the alumina layer is formed on the surface of the base material by the oxidation treatment, the thickness of the alumina layer is preferably 2 nm or more.

[0089]

[Table 3]

(Example 4) An aluminum alloy plate (A3003 specified in JIS H4000) was used as a base material, and pretreatment was performed by the method described in Example 3, and then a gas phase having an oxygen partial pressure of 20 kPa was used. In the inside, oxidation treatment was performed at a temperature of 300 to 700K for 20 to 700,000 seconds.

Next, a titanium oxide photocatalyst layer was formed on the surface of the substrate after the oxidation treatment in the same manner as in Example 3.

The photocatalyst composite thus produced was subjected to a decomposition test of methylene blue in the same manner as in Example 3 to evaluate its catalytic performance.

FIG. 2 shows the relationship between the oxidation treatment conditions and the photocatalytic performance. As shown in the figure, when the decomposition rate of methylene blue was 50% or more, it was determined to be good (indicated by a circle). This corresponds to an example of the present invention.

As shown in the figure, since the processing temperature was low and a sufficient alumina layer was not formed in a short time, the decomposition rate of methylene blue did not reach 20%, and sufficient photocatalytic performance was not exhibited. On the other hand, when the treatment was performed at a high temperature for a long time, the decomposition rate of methylene blue increased. The boundary is
Assuming that the processing temperature is T (K) and the processing time is t (s), T
= 590t ^-0.06 . If the oxidation treatment temperature is higher than this temperature, it is possible to form an alumina layer having a sufficient thickness on the surface of the substrate without impairing the performance of the photocatalyst.

[0095]

The photocatalyst composite material of the present invention is based on aluminum or a metal containing aluminum, and its photocatalytic activity is not impaired, and the photocatalyst inherent to the photocatalyst, that is, higher than the bandgap of the photocatalyst It is a composite material that, when irradiated with energy light, exhibits an excellent photocatalytic action against decomposition, removal, detoxification, etc. of various harmful substances and attached substances. This photocatalyst composite can be easily manufactured by the method of the present invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration of a photocatalyst composite of the present invention.

FIG. 2 is a diagram showing the relationship between the conditions for oxidation treatment of a substrate and the photocatalytic performance of a photocatalyst composite material obtained.

[Explanation of symbols]

 1: base material 2: photocatalyst layer 3: metal oxide layer

Continued on the front page (72) Inventor Haruhiko Kajimura 4-5-33 Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd. F-term (reference) 4F100 AA17C AA20C AA27C AB10A AB31A BA03 BA07 BA10A BA10B EH46 EH462 GB07 JC00 JD02C JL08B JM01C YY00B 4G069 AA03 AA08 AA11 BA01A BA01B BA02A BA04A BA04B BA05A BA05B BA06A BA06B BA18 BA37 BA48A BB04A BC25A BC35A BC60A BC66A CA01 CA10 CA11 CA17 EA07 EB14 EB11 EB11 EB11 EB11 EB11 EB14 EB11 EB15 EB11 EB11 EB11

Claims (7)

[Claims] 1. A photocatalyst composite comprising, between a photocatalyst layer and a substrate made of aluminum or a metal containing aluminum, a metal oxide layer for suppressing diffusion of oxygen from the photocatalyst layer toward the substrate. Wood. 2. The photocatalyst composite material according to claim 1, wherein the metal oxide layer is a layer composed of at least one oxide of aluminum oxide, silicon oxide, zirconium oxide and magnesium oxide. 3. The photocatalyst composite material according to claim 1, wherein the metal oxide layer is a layer made of an oxide having an oxygen deficiency ratio of 20% or less based on the chemical formula of the most stable structure of the oxide. 4. The method according to claim 1, wherein the base material is a metal containing aluminum as a main component, and the metal oxide layer is a layer made of aluminum oxide formed by subjecting the base material to an oxidation treatment. Photocatalytic composite. 5. A sol solution containing fine particles of a metal oxide is applied to the surface of a substrate, or a solution containing a precursor of a metal oxide or a solution obtained by subjecting this solution to a hydrolysis treatment is applied, followed by firing. The method for producing a photocatalyst composite material according to claim 1, wherein a photocatalyst layer is formed on a surface of the metal oxide layer after the metal oxide layer is formed. 6. The photocatalyst according to claim 4, wherein a photocatalytic layer is formed on the surface of the metal oxide layer after the substrate is subjected to an oxidation treatment under a condition satisfying the following formula. Manufacturing method of composite material. T> 590t ^-0.06 where T: oxidation temperature (K) t: processing time (s) 7. The photocatalyst layer according to claim 6, wherein a solution containing a photocatalyst precursor substance or a solution obtained by subjecting this solution to a hydrolysis treatment is applied to the surface of the metal oxide layer, followed by baking to form the photocatalyst layer. A method for producing a photocatalytic composite material.