JP2002085967A - Photocatalyst membrane and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalyst membrane having improved catalytic efficiency and a method of producing the same. SOLUTION: The photocatalyst membrane contains TiO2 as a main component and has a multilayer structure in which the distribution of the porosity is such that the porosity is <=80% at the surface of the membrane and >=10% at the inside of the membrane, and the distribution of the average pore diameter is such that the average pore diameter is <=5 μm at the surface of the membrane and >=2 nm at the inside of the membrane and which is composed of not more than 10 layers, each having a membrane thickness of >=0.2 μm. In the photocatalyst membrane, the porosity and the average pore diameter are decreased toward the inside from the surface of the membrane, the thickness of the membrane is <=5 μm, the content of the metal particles is 0.01 to 30%, an average diameter of the metal particles is <=0.1 μm and the content of zeolite is 0.1 to 50%. Further, the method of producing the photocatalyst membrane comprises adding a binder to primary particles of TiO2 having an average particle size of <=100 nm, being a raw material, to obtain a slurry, then coating the slurry onto a substrate by a slip casting method and sintering the coated film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalyst film having high photocatalytic performance and a method for producing the same, and more particularly to a photocatalyst film applicable to an environment purification type apparatus such as air purification and water purification, and a method for producing the same. It is.

[0002]

2. Description of the Related Art In recent years, photocatalysts have received attention in a wide range of fields such as air purification / deodorization, water purification / drainage treatment, antifouling, antibacterial / sterilizing, and antifogging. When light of a wavelength having energy equal to or greater than the band gap is applied to the optical semiconductor particles, electrons existing in the valence band are photoexcited and move to the conduction band, while holes in the valence band are present. Is generated. The generated electron (e ⁻ ) reacts with oxygen (O ₂ ) to generate a superoxide anion (· O ₂ ⁻ ), and the hole (h ⁺ ) reacts with water to generate a hydroxyl radical (· OH). Generate

[0003] The superoxide anion (· _{O 2} ^-)
Has a strong reducing power, and the hydroxyl radical (.OH) has a strong oxidizing power. Therefore, attempts have been made to use these compounds in various fields of environmental purification as described above.

[0004] Photocatalysts have received a great deal of attention in terms of their "environmental friendliness" because of their extremely wide application range and the direct use of sunlight or fluorescent light as an energy source. It was not powerful and quick. Therefore, improving the efficiency of the catalytic reaction is the most important issue, and many studies have been made for the purpose of improving the efficiency of the photocatalytic film.

For example, Japanese Patent Application Laid-Open No. 9-262482 discloses that Cr, V, Cu, Fe, Mg, Ag, Pd, Ni,
It describes that one or more metal ions selected from the group of Mn and Pt are contained from the surface to the inside of titanium oxide at a rate of 1 × 10 ¹⁵ ions / g-TiO ₂ or more. Specifically, a method is described in which the metal ions are accelerated to a high energy of 30 keV or more and the titanium ions are irradiated with the metal ions to dope the metal ions to the titanium oxide.

JP-A-2-107339 discloses that a photocatalytic active component is supported on a substrate having a three-dimensional structure through which a reaction gas and light can flow to form a catalyst structure. It is said that the odorous components contained in the air can be efficiently removed.

JP-A-8-103631 discloses a titania sol prepared from alkoxides of titanium and alcoholamines or polyethylene glycol or polyethylene oxide on a glass filter prepared by fusing spherical heat-resistant glass. It is described that, after coating with the additive, the product is heated and gradually heated from room temperature to a final temperature of 600 ° C. to 700 ° C., whereby the contaminants can be adsorbed and decomposed and removed.

[0008]

However, in spite of various studies as described above, in any case, the efficiency is still not sufficient, and effective measures for improving the efficiency are not yet considered. Was sought.

The present invention has been made to solve the above problems, and has as its object to obtain a photocatalyst film with further improved catalytic reaction efficiency and a method for producing the same.

[0010]

Means for Solving the Problems As a result of intensive studies on the improvement of the efficiency of the photocatalytic film, the present inventors have found that the structure of the photocatalytic film can be efficiently controlled by controlling the porosity and the pore diameter on the surface and inside. It has been found that the specific surface area and the adsorption site of the substance to be decomposed can be greatly increased, and that apparently the photocatalytic performance is dramatically improved, and a method for controlling such a photocatalytic film with good reproducibility and free control has been found. The invention has been completed.

That is, the photocatalyst film according to claim 1 has a T
A photocatalyst film containing iO ₂ as a main component, wherein the porosity of the photocatalyst film has a distribution of 80% or less on the surface of the film and 10% or more inside the film, and the average pore diameter is on the surface of the film. It has a distribution of 5 μm or less and 2 nm or more inside the film.

According to the present invention, the photocatalyst film containing TiO ₂ as a main component has a structure in which the surface of the TiO ₂ film has a high porosity and a large pore diameter. By changing the structure of the catalyst film between the surface and the inside, the reaction area increases due to an increase in the specific surface area, and the photocatalytic efficiency improves due to an increase in the number of decomposition adsorption sites. Further, according to the present invention, since the porosity of the film surface is large and the pore diameter is large, light can efficiently pass through the inside of the TiO ₂ film. Furthermore, inside the film where light is relatively hard to transmit and photocatalytic reaction does not easily occur, the gas can be efficiently adsorbed because the porosity is low and the pore diameter is small. These synergistic effects can greatly improve the photocatalytic efficiency.

Further, the porosity of the TiO ₂ film is
% Or less, and 10% or more inside the film. However, if the porosity on the film surface exceeds 80%, desorption of TiO ₂ film particles occurs, and the porosity inside the film is 10%. If it is less, the number of sites through which light does not pass increases, the amount of adsorption sites also decreases,
This is because the reaction efficiency decreases.

In the present invention, the surface of the membrane and the interior of the membrane are used. However, the boundary between the surface and the interior is a location having a thickness of 100 nm from the surface of the catalyst film, and is closer to the surface of the catalyst film than this boundary. In this case, the surface is defined as the film surface, and when it is below the boundary, it is defined as the inside of the film.

The invention according to claim 2 is the photocatalyst film according to claim 1, wherein the porosity and the average pore diameter decrease from the film surface of the photocatalyst film toward the inside.

In the present invention, the structure in which the porosity and the average pore diameter are reduced from the film surface toward the inside of the film allows light to efficiently pass through the inside of the film and to be decomposed and adsorbed by the pores. Is to be able to be selectively adsorbed.

In the present invention, by reducing the porosity and pore diameter from the surface to the inside of the catalyst film, it becomes possible to adsorb more kinds of decomposed substances, and the decomposed substances are not specified. The photocatalytic performance in the situation is improved.

The invention according to claim 3 is the photocatalyst film according to claim 1 or 2, wherein the thickness of the photocatalyst film is 5 μm or less.

In the present invention, the thickness of the photocatalytic film is 5 μm
This is because, when the thickness exceeds 5 μm, light cannot be transmitted to the inside of the film, and the photocatalytic performance is reduced.

According to a fourth aspect of the present invention, the photocatalyst film has a multilayer structure, and each of the layers forming the multilayer structure has a thickness of 0.1 mm.
The photocatalyst film according to claim 1, wherein the thickness is 2 μm or more.

In the present invention, each layer of the catalyst film is specified to be 0.2 μm or more. However, if it is less than 0.2 μm, the production process becomes difficult and the production cost increases.

The invention according to claim 5 is the photocatalyst film according to claim 4, wherein each layer is 10 layers or less.

When the catalyst film has a multilayer structure, each layer has a thickness of 10
When the number of layers is larger than the number of layers, the manufacturing process cost is increased, but the property improvement is not so increased. For this reason, in the present invention, the number of the catalyst films is preferably 10 or less.

According to a sixth aspect of the present invention, when the metal particles have a particle diameter of 0.0
The photocatalyst film according to any one of claims 1 to 5, wherein the content is 1% or more and 30% or less, and the average particle size of the metal particles is 0.1 µm or less.

In the present invention, the photocatalyst film contains metal particles.
The electrons generated by the catalytic reaction
To separate the oxidation-reduction sites,
Of the photocatalyst efficiency can be improved. In the present invention, metal
The content of the particles was defined as 0.01% or more and 30% or less.
Is less than 0.01%,
The efficiency improvement by separation is small, and the content exceeds 30%
, Relatively TiO ₂The overall efficiency is reduced
It is because it falls. In addition, especially as metal particles,
When applied to air purification and water purification, chemical stability and
From this point, Pt, Au, Ag, Ru, Rh, Pd, O
It is preferable to contain metal particles such as s and Ir.

In addition, a metal phosphate may be added to the photocatalyst film.
It is good to make it contain in the range of 1% or more and 50% or less. If the content is less than 0.1%, a sufficient amount cannot be adsorbed, so that the efficiency of the photocatalytic reaction is poor. If the content exceeds 50%, T
This is because the amount of iO ₂ is relatively reduced and the photocatalytic efficiency is reduced.

On the surface of the film which is well exposed to light, the decomposition reaction mainly occurs due to the photocatalyst, and when the film is hardly exposed to light, the photocatalytic efficiency of the entire film is improved by adsorbing. It is advisable to change the phosphate content. Specifically, the content of the metal phosphate is 0.1% or more on the film surface and 50% in the film.
% Or less. Phosphate content of 0.1 at the membrane surface.
If it is less than 1%, the amount of adsorption on the membrane surface is too small to lower the photocatalytic efficiency, and if the phosphate content exceeds 50% inside the membrane, the decomposition efficiency inside the membrane is too low and the photocatalytic efficiency becomes too low. This is because the efficiency is reduced.

The invention according to claim 7 is characterized in that the zeolite is
The photocatalyst film according to any one of claims 1 to 6, wherein the content is 0.1% or more and 50% or less.

In the present invention, the content of zeolite contained in the photocatalyst membrane is specified to be 0.1% or more and 50% or less. If the content is less than 0.1%, a sufficient amount cannot be adsorbed and the photocatalyst cannot be adsorbed. ineffective. On the other hand, if the content exceeds 50%, the amount of TiO ₂ relatively decreases, and the photocatalytic efficiency decreases.

As for the content of zeolite, as in the case of the above-mentioned metal particles, the decomposition reaction is mainly caused by the photocatalyst on the membrane surface to which light is well irradiated, and the adsorption is caused inside the membrane where light is relatively hard to hit. In this way, in order to improve the reaction efficiency of the whole membrane, it is preferable to change the zeolite content on the surface and inside the photocatalyst membrane. Specifically, the zeolite content was 0.1% on the membrane surface.
As described above, the content is preferably set to 50% or less inside the film. If the content is less than 0.1% on the membrane surface, the amount of adsorption on the membrane surface is too small and the photocatalytic efficiency decreases, and if the zeolite content is more than 50% inside the membrane, the decomposition efficiency inside the membrane decreases. This is because the photocatalytic efficiency decreases.

The method for manufacturing a photocatalyst film according to claim 8 is characterized in that
A binder is added to a raw material containing iO ₂ as a main component to prepare a slurry. The slurry is applied on a substrate by a slip casting method, and then sintered.

According to the present invention, since the photocatalytic film is coated using the slip casting method, the porosity and pore size distribution on the surface and inside of the photocatalytic film can be easily controlled. Therefore, the photocatalyst film is continuously
Since it can be manufactured by a simple method, the manufacturing cost can be reduced.

Further, if the photocatalyst film is fired many times, the manufacturing cost increases. However, according to the present invention, the photocatalyst film can be manufactured by one firing, so that the manufacturing cost can be reduced. Also, by shortening the total firing time, TiO 2
₂ can be suppressed and a decrease in photocatalytic efficiency can be prevented.

On the other hand, when sintering is performed by firing many times, the porosity and pore diameter of each layer can be easily controlled by coating each layer at a different firing temperature. In the case of firing many times, if the firing temperature is higher than 600 ° C., the sintering of TiO ₂ is promoted, and the specific surface area is reduced, so that the photocatalytic efficiency is lowered. good.

Further, the density of each layer before firing can be controlled by adding an organic binder component to the TiO ₂ slurry and changing the addition concentration in each layer. For this reason,
By adjusting the concentration of the organic binder component, it is not necessary to repeat the firing many times.

When a binder is added, the binder component concentration is preferably set to 70% or less. 70% concentration
If the ratio exceeds 2,000, the distance between the TiO ₂ particles is too large, and the substantial strength is reduced. Also, the binder cost becomes high and the production cost rises.

According to a ninth aspect of the present invention, as a raw material, an average
TiO with a particle size of 100 nm or less ₂Using primary particles
The method for producing a photocatalyst film according to claim 8, wherein
It is.

The smaller the average particle size of TiO ₂ constituting the TiO ₂ film is, the higher the specific surface area of each particle becomes, so that adsorption and reaction of the substance to be decomposed on the surface are likely to occur, and the photocatalytic efficiency is high. If the average particle size exceeds 100 nm, the photocatalytic efficiency is reduced.
The average particle size of the primary particles of TiO ₂ was specified to be 100 nm or less.

According to a tenth aspect of the present invention, the primary particles of TiO ₂ are agglomerated to use secondary particles having an average particle diameter of 0.2 μm or less. 3. The method for producing a photocatalyst film described in 1.

In the present invention, the average particle size of the secondary particles, which are aggregates obtained by aggregating the primary particles of TiO ₂ , is 0.2 μm.
As specified below, if the average particle size exceeds 0.2 μm, a sufficient specific surface area cannot be obtained, and thus the photocatalytic performance under ultraviolet irradiation is not sufficient. Another reason is that it is difficult to uniformly coat TiO ₂ .

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to Examples 1 to 10 and Comparative Examples 1 to 10.
This will be specifically described with reference to FIG.

Example 1 (FIG. 1) In this example, first, a crystal particle diameter of 6 nm was added to water as a solvent.
Was added to prepare a titanium oxide sol having a concentration of 30%. To this titanium oxide sol, 10% of polyethylene glycol as an organic binder was added, and
0%, 40%, and 60% were added to prepare slurries, respectively.

Next, dip coating is performed on a base material having a three-dimensional network structure containing alumina as a main component and having an open porosity of 85% in order from a low-concentration slurry containing a large amount of an organic binder, and a thickness of each layer. Was set to 0.5 μm, and a TiO ₂ film composed of four layers having different densities was formed. Then, it is baked at 550 ° C. for 1 hour in the air and has a thickness of 2.0 μm including four layers.
It was obtained of the TiO ₂ film.

After the heat treatment, the cross section of the coating film was observed with a scanning electron microscope. As a result, four TiO ₂ films having different porosity were observed.

For the purpose of investigating the porosity and pore diameter of each layer of the four-layer catalyst film in Example 1, only one layer of a slurry having a different organic binder concentration was coated, and heat treatment was performed in the same manner. And the pore diameter was measured. The amount of the organic binder added was 10
%, 20%, 40%, and 60% were prepared. As a result, when 10% of the organic binder is added, the porosity and the pore diameter are 15% and 5 nm,
When the organic binder is added in an amount of 20%, 30% or 40%, the porosity and the pore diameter become 30% and 10%, respectively.
0 nm, 50%, 2 μm, 70%, 4 μm.

Accordingly, the porosity of the four-layer catalyst film produced according to this embodiment is 80% or less on the film surface and 10% or more on the inside of the film, and the porosity decreases from the surface to the inside of the catalyst film. In addition, the pore size distribution was 5 μm or less on the film surface and 2 nm or more inside the film, and thus was within the scope of the present invention.

Comparative Example 1 (FIG. 1) In this comparative example, three types of TiO ₂ films were produced. The manufacturing method is substantially the same as that of the first embodiment.

First, a TiO ₂ film was prepared by coating only one layer of a slurry in which 10% of an organic binder was added to titanium oxide sol.

Next, a catalyst film having different firing temperatures and times was prepared. Specifically, a TiO ₂ film having a porosity of almost 0% was produced by baking in air at 800 ° C. for 2 hours.

Finally, an attempt was made to increase the amount of the organic binder to produce a film having a porosity of more than 80%. However, a large amount of TiO ₂ particles fell off from the catalyst film, and a sound film was formed. I couldn't do that.

Each of the above TiO _{2 of} Example 1 and Comparative Example 1
The membrane was evaluated for photocatalytic efficiency. The photocatalytic efficiency was evaluated by measuring the decomposition efficiency of ammonia,
Specifically, a base material having an open porosity of 85% and having a three-dimensional network structure mainly composed of alumina carrying TiO ₂ and black light (average wavelength 370 nm, intensity 3 mW / cm)
² ) While applying light, adjust the ammonia concentration to 100 ppm.
Ammonia gas at a flow rate of 0.5 l / min was introduced from one of the substrates. Then, the ammonia concentration at the outlet side opposite to the inflow side was measured. This result is shown in FIG.
Shown in

As shown in FIG. 1, the ammonia concentration at the outlet side was 60% when the titanium oxide film with the added amount of the organic binder was 10% and when the porosity was 0%. %, And the ammonia decomposition efficiency was poor. On the other hand, by setting the porosity and the pore diameter of the catalyst film within the range of the present invention, the ammonia concentration on the outlet side is almost 0%, the ammonia decomposition efficiency is good, and the photocatalytic performance is excellent. It has been found.

Example 2 (FIG. 2) In this example, the primary particle size of TiO ₂ constituting the photocatalyst film was investigated, and the crystal particle size was determined using the same method as in Example 1. A 6 nm titanium oxide sol was used.

Comparative Example 2 (FIG. 2) In this comparative example, a titanium oxide powder having an average particle diameter of 0.2 μm was used instead of the titanium oxide sol having a particle diameter of 6 nm of Example 2, and TiO having a large primary particle diameter was used. _Two polycrystalline spherical particles are formed on the surface of an alumina sintered body.

The decomposition performance of ammonia gas in Example 2 and Comparative Example 2 was evaluated under the same evaluation conditions as in Example 1. The result is shown in FIG.

As shown in FIG. 2, in Example 2, the ammonia concentration on the outlet side was almost 0% and the ammonia decomposition efficiency was excellent, but in Comparative Example 2, the average particle diameter of the primary particles was Since a large one exceeding 100 nm within the range of the present invention was applied, a sufficient specific surface area could not be obtained, and ammonia decomposition efficiency was lowered.

Example 3 (FIG. 3) In this example, the particle diameter of secondary particles obtained by aggregating primary particles of titanium oxide was investigated.

The pH was adjusted by adding hydrochloric acid to the titanium oxide sol having a particle diameter of 6 nm in Example 1 to change the degree of aggregation of the secondary particles, and the particle diameters of the secondary particles were 0.05 μm, 0.10 μm,
It was set to 0.20 μm. Other conditions were the same as in Example 1.

Comparative Example 3 (FIG. 3) In this comparative example, as in Example 3, hydrochloric acid was added to the titanium oxide sol, the particle size of the secondary particles was set to 0.40 μm, the degree of aggregation was increased, and alumina sintering was performed. A TiO ₂ multilayer film is formed on the body surface.

The decomposition performance of ammonia gas in Example 3 and Comparative Example 3 was evaluated under the same conditions as in Example 1. The result is shown in FIG.

As shown in FIG.
In Example 3 in which the concentration was 02 μm or less, the ammonia concentration on the outlet side was almost 0%, and the decomposition efficiency of ammonia was excellent. However, in Comparative Example 3 in which the particle size of the secondary particles exceeded 0.02 μm, A sufficient specific surface area was not obtained, and the ammonia decomposition efficiency was reduced.

Embodiment 4 (FIGS. 4 and 5) In this embodiment, a method similar to that of Embodiment 1
TiO ₂ films having different porosity and pore diameter of the layers were formed. When the TiO ₂ film is formed, the thickness of each layer of the TiO ₂ film is set to 0.2 μm, 0.
It was changed to 4 μm and 1.0 μm.

Further, by changing the thickness of each layer of the TiO ₂ film,
A TiO ₂ film having a total thickness of 1 μm, 2 μm, 3 μm, and 5 μm was produced.

Comparative Example 4 (FIGS. 4 and 5) In this comparative example, the thickness of each layer of the TiO ₂ film was set to 0.1 μm by changing the coating time of Example 4.

By changing the thickness of each layer of the TiO ₂ film,
A TiO ₂ film having a total thickness of 7 μm was formed.

With respect to Example 4 and Comparative Example 4, the decomposition performance of ammonia gas was evaluated. The conditions are the same as in Example 1, and the results are shown in FIGS.

As shown in FIG. 4, when the TiO ₂ film exceeded 5 μm, the ammonia decomposition efficiency was lowered.

As shown in FIG. 5, when the thickness of each layer in the TiO ₂ film was 0.2 μm or more, the outlet ammonia concentration was almost 0%, but when the thickness was less than 0.2 μm. Had a reduced ammonia decomposition efficiency.

Example 5 (FIG. 6) In this example, in addition to the organic binder-added slurry of Example 1, 5%, 15%, 25%, 30%, 50%
%, 60%, and 65% of an organic binder were added, and the slurry was coated in order of decreasing concentration. Others were exactly the same as in Example 1, and a TiO ₂ multilayer coating film was formed on the surface of the alumina sintered body. In this example, the number of stacked TiO ₂ films was set to 4, 8, and 10.

Comparative Example 5 (FIG. 6) In this comparative example, the same slurry as in Example 5 was used to obtain 1
A layer of TiO ₂ film and 11 layers of TiO ₂ multilayer coating film were formed.

With respect to Example 5 and Comparative Example 5, the decomposition performance of ammonia gas was evaluated. The conditions were the same as in Example 1. Further, the manufacturing cost when a TiO ₂ film composed of one layer was formed was set to 1, and the manufacturing cost when the number of stacked layers was changed was evaluated. FIG. 6 shows the result.

As shown in FIG. 6, when the number of laminated TiO ₂ films is four or more, the ammonia decomposition efficiency is excellent, but one TiO ₂ film, that is, the inside of the film on the film surface and When a uniform slurry was used, the production cost could be reduced, but sufficient ammonia decomposition efficiency could not be obtained. Since the manufacturing cost increases as the number of stacked TiO ₂ films increases, the number of stacked TiO ₂ films is preferably 4 to 10 in consideration of both sides of the ammonia decomposition efficiency and the manufacturing cost.

Example 6 (FIG. 7) In this example, the heat treatment step was repeated four times after coating the slurry containing the organic binder of 20% of Example 1 further. The heat treatment temperature is 550 ° C. for the first time and 500 times for the second time.
A third TiO ₂ multilayer film was formed on the surface of the alumina sintered body in the same manner as in Example 1 except that the temperature was set to 400 ° C. for the third time, to 400 ° C. for the fourth time, and to control the porosity and the pore diameter of each layer.

Comparative Example 6 (FIG. 7) In this comparative example, the first heat treatment was performed at 700 ° C., and the second and subsequent heat treatments were the same as in Example 6.

As a comparative example, sintering was performed at a temperature of 550 ° C. with one heat treatment.

For Example 6 and Comparative Example 6, the decomposition performance of ammonia gas was evaluated. The evaluation conditions were the same as in Example 1. FIG. 7 shows the result.

As shown in FIG. 7, by controlling the porosity and pore diameter of each layer by four heat treatments, the decomposition efficiency of ammonia can be improved.

Example 7 (FIG. 8) In this example, a titania sol having a crystal particle diameter of 6 nm with a concentration of 30% was used, and a TiO ₂ film was adhered on a cordierite porous substrate by a slip casting method.

Incidentally, the slip casting method is to form a TiO ₂ film continuously on a substrate, and specifically, the following method.

Using a starting material having a titania crystal particle size distribution widely distributed from 1 nm to 100 nm, a concentration of 30
% Of titania sol with a binder component,
It was adjusted to about 0 cps. In this method, a cordierite porous substrate sufficiently dried in the air is immersed in the sol, water is contained on the porous substrate, and coating is performed so that only the titania particles remain on the substrate surface.

After forming a TiO ₂ film on the base material using this slip casting method, a heat treatment at 500 ° C.
A TiO ₂ film having a changed pore diameter and porosity was formed from the surface to the inside of the film.

Comparative Example 7 (FIG. 8) In this comparative example, a TiO ₂ film was formed on a cordierite porous substrate in the same manner as in Example 7 by using a spraying method instead of the slip casting method.

For Example 7 and Comparative Example 7, the decomposition performance of ammonia gas was evaluated. FIG. 8 shows the result. The evaluation conditions were the same as in Example 1.

As shown in FIG. 8, when the spraying method of Comparative Example 7 was used, the decomposition performance of ammonia was reduced, but when the slip casting method was used, the decomposition performance of ammonia was improved. I was

Example 8 (FIG. 9) In addition to the titanium oxide sol having a particle diameter of 6 nm of Example 1, P
Except that at least one type of metal alkoxide particles such as t, Au, Ag, Ru, Rh, Pd, Os, and Ir was added, TiO 2 was added to the surface of the alumina sintered body using the same method as in Example 1. _Two multilayer films were formed.

Comparative Example 8 (FIG. 9) In this comparative example, a TiO ₂ multilayer film was formed without adding the metal alkoxide of Example 8.

The decomposition performance of ammonia gas in Example 8 and Comparative Example 8 was evaluated. The evaluation conditions were that the ammonia concentration was 200 ppm and the flow rate was 0.5.
1 / min ammonia gas was introduced from one side of the substrate, and the ammonia concentration at the outlet side opposite to the inflow side was measured. FIG. 9 shows the result.

As shown in FIG. 9, when the metal was not added, the outlet ammonia concentration was higher and the ammonia decomposition efficiency was lower than in the case of Example 8 in which the metal was added.

Example 9 (FIG. 10) In addition to the titanium oxide sol having a particle diameter of 6 nm of Example 1, zeolite was added to dip coat the titanium oxide sol on an alumina substrate. At this time, the surface of the TiO ₂ film has a thickness of 0.1 mm.
The amount of zeolite added was adjusted to 2%, 35% inside the membrane, 0.3% on the membrane surface, and 35% inside the membrane. Others were the same as Example 1.

Comparative Example 9 (FIG. 10) In this comparative example, the amount of zeolite added was adjusted to 0.2% on the membrane surface and 35% inside the membrane using the same method as in Example 9.

The decomposition performance of ammonia gas in Example 9 and Comparative Example 9 was evaluated. The evaluation conditions were the same as in Example 8. The result is shown in FIG.

As shown in FIG. 10, in the case of Example 9 in which the amount of zeolite added was 0.1% or more at the membrane surface and 50% or less inside the membrane, the ammonia decomposition efficiency was higher than that of Comparative Example 9. Was low.

Example 10 (FIG. 11) In this example, in addition to the titanium oxide sol having a particle diameter of 6 nm of Example 1, a metal phosphate was added to dip coat the titanium oxide sol on an alumina substrate. At that time, 0.2% on the film surface, 35% inside the film, or 0.3% on the film surface
% And the amount of metal phosphate added was adjusted to 35% inside the film. Others were the same as Example 1.

Comparative Example 10 (FIG. 11) In this comparative example, the same method as that of Example 10 was used, and the amount of metal phosphate added was 0.3% on the film surface and 35% inside the film. It was adjusted.

With respect to Example 10 and Comparative Example 10, the decomposition performance of ammonia gas was evaluated. The evaluation conditions were the same as in Example 8. The result is shown in FIG.

As shown in FIG. 11, the decomposition performance of ammonia gas can be improved by setting the addition amount of phosphate to 0.1% or more on the film surface and 50% or less inside the film.

[0097]

As described above, according to the photocatalyst film and the method for producing the same of the present invention, the porosity and the pore diameter are differently distributed between the film surface and the inside of the film, so that from the film surface to the inside of the film. Obtaining a photocatalyst film with significantly improved photocatalytic performance because it allows efficient transmission of light and efficient gas adsorption inside the film, enabling efficient adsorption and decomposition of decomposed substances. Can be.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention, and is a diagram illustrating a relationship between a TiO ₂ multilayered film of Example 1 and Comparative Example 1 and photocatalytic efficiency.

FIG. 2 is a diagram showing the relationship between the TiO ₂ particle diameter in the TiO ₂ film and the photocatalytic efficiency in Example 2 and Comparative Example 2.

FIG. 3 is a graph showing the relationship between the secondary particle diameter in the TiO ₂ film and the photocatalytic efficiency in Example 3 and Comparative Example 3.

FIG. 4 is a graph showing the relationship between the thickness of a TiO ₂ film and photocatalytic efficiency in Example 4 and Comparative Example 4.

FIG. 5 is a diagram showing the relationship between the thickness of each layer in the TiO ₂ film and the photocatalytic efficiency in Example 4 and Comparative Example 4.

FIG. 6 is a diagram showing the relationship between the number of stacked TiO ₂ films, photocatalytic efficiency, and manufacturing cost in Example 5 and Comparative Example 5.

FIG. 7 is a graph showing the relationship between the number of heat treatments, the heat treatment temperature, and the photocatalytic efficiency in Example 6 and Comparative Example 6.

FIG. 8 is a diagram showing the relationship between the TiO ₂ film coating method and the photocatalytic efficiency in Example 7 and Comparative Example 7.

FIG. 9 is a graph showing the relationship between the addition of metal particles to the TiO ₂ film and the photocatalytic efficiency in Example 8 and Comparative Example 8.

FIG. 10 shows TiO ₂ in Example 9 and Comparative Example 9.
The figure which shows the relationship between the zeolite addition amount in a film | membrane, and photocatalytic efficiency.

FIG. 11 shows Ti in Example 10 and Comparative Example 10.
Phosphate amount to O ₂ film and shows the relationship between the photocatalytic efficiency.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 20/18 B01J 23/40 M 21/06 23/48 M 23/40 27/16 M 23/48 29 / 06 M 27/16 35/02 J 29/06 B01D 53/36 E 35/02 ZABJ (72) Inventor Tsuneji Kameda 2-4 Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Pref. Toshiba Keihin Works Co., Ltd. (72) Inventor Akiko Suyama 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Inside the Toshiba Hamakawasaki Plant (72) Inventor Katsutoshi Nishida 2-4 Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Toshiba Keihin Plant (72 ) Inventor Yoshiyasu Ito 2-4, Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa F-term in Keihin Plant, Toshiba Corporation 4D006 GA01 GA41 MA08 MA22 MA24 MA31 MB01 MB04 MB14 MB19 MC03X NA39 NA46 NA62 PB7 0 4D048 AA08 AB03 BA03X BA07X BA12X BA30X BA31X BA32X BA33X BA34X BA41X BA44X BB09 EA01 4G066 AA23B AA61B BA03 BA05 BA23 BA25 CA02 DA01 DA07 FA15 FA22 FA28 4G069 AA03 AA08 BA01B33BBC BCA BC72A BC72B BC73A BC73B BC74A BC74B BC75A BC75B CA01 CA05 CA10 CA17 DA06 EA08 EB11 EB12X EB12Y EB15X EB15Y EB17X EB17Y EB18X EB18Y EC14X EC14Y EC27 EC28 FA03 FB15 FB23 FB30 FC08

Claims (10)

[Claims] 1. A photocatalytic film containing TiO ₂ as a main component, wherein the porosity of the photocatalytic film has a distribution of 80% or less on the film surface, 10% or more inside the film, and an average pore diameter. Is
A photocatalytic film having a distribution of 5 μm or less on the film surface and 2 nm or more inside the film. 2. The photocatalytic film is directed from the film surface to the inside of the film.
The photocatalyst film according to claim 1, wherein the porosity and the average pore diameter are reduced. 3. The photocatalyst film according to claim 1, wherein the thickness of the photocatalyst film is 5 μm or less. 4. The photocatalyst film according to claim 1, wherein the photocatalyst film has a multilayer structure, and each layer forming the multilayer structure has a thickness of 0.2 μm or more. 5. The photocatalyst film according to claim 4, wherein each layer has 10 or less layers. 6. The method according to claim 1, wherein the metal particles are contained in an amount of 0.01% or more and 30% or less, and the average particle diameter of the metal particles is 0.1 μm or less. Photocatalytic film. 7. The photocatalytic film according to claim 1, wherein zeolite is contained in an amount of 0.1% or more and 50% or less. 8. A photocatalytic film obtained by adding a binder to a raw material mainly composed of TiO ₂ to form a slurry, applying the slurry to a substrate by using a slip casting method, and then sintering the slurry. Manufacturing method. 9. The method according to claim 8, wherein primary particles of TiO ₂ having an average particle diameter of 100 nm or less are used as a raw material. 10. The photocatalyst film according to claim 9, wherein primary particles of TiO ₂ are aggregated to use secondary particles having an average particle size of 0.2 μm or less. Production method.