JP2009262049A - Photocatalytic structure and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalytic structure capable of improving the efficiency of photocatalytic reaction and its method of production. <P>SOLUTION: The photocatalytic structure includes a substrate, a titanium oxide layer formed on the substrate surface and having fixed thereto titanium oxide crystal grains, and platinum-group metal particles fixed on the surfaces of the titanium oxide crystal grains of the titanium oxide layer, and the platinum-group metal particles are not substantially present in the grain boundaries of the titanium oxide crystal grains, and in the titanium oxide layer, the average grain size of the titanium oxide crystal grains is 100 nm or smaller and the average particle size of the platinum-group metal particles is 20 nm or smaller. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photocatalyst structure having high photocatalytic performance and a method for producing the same, and more particularly to a photocatalyst structure applicable to an environmental purification apparatus such as air purification and water purification and a method for producing the same.

  Photocatalysts have a catalytic action when irradiated with light, and have recently attracted attention in a wide range of fields such as air purification / deodorization, water purification / drainage treatment, antifouling, antibacterial / sterilization, and antifogging. When photocatalyst is irradiated with light, it exhibits a strong oxidizing action and a super-water-repellent action. For example, it decomposes organic substances to purify air or develop an antifogging action.

  It is considered that the oxidation action of the photocatalyst is expressed by the following mechanism. That is, when light having a wavelength with energy equal to or greater than the band gap is given to the optical semiconductor particles, electrons existing in the valence band are photoexcited and moved to the conduction band, and holes are generated in the valence band. Generated.

The electron (e ⁻ ) in the conduction band reacts with oxygen (O ₂ ) to generate a superoxide anion (• O ₂ ⁻ ), and the hole (h ⁺ ) in the valence band reacts with water to generate a hydroxy radical ( -OH). Since the superoxide anion (.O ₂ ⁻ ) and the hydroxy radical (.OH) exhibit a strong oxidizing power, an oxidizing action occurs in the photocatalyst.

  Photocatalysts are attracting attention because they have a very wide range of applications and can be directly used as energy sources such as sunlight or light from fluorescent lamps. However, since the catalytic reaction of the photocatalyst is not so strong and rapid, it is desired to improve the efficiency of the catalytic reaction.

  Examples of conventional techniques for improving the efficiency of the photocatalytic reaction include the following.

  For example, Japanese Patent Laid-Open No. 9-262482 (Patent Document 1) discloses a photocatalyst containing one or more metal ions selected from Cr, Cu, Pd, Pt and the like in a specific ratio from the surface of titanium oxide. Is disclosed. According to this photocatalyst, since the catalytic reaction can be performed using visible light in addition to ultraviolet light, the efficiency of the photocatalyst can be improved.

  Japanese Patent Application Laid-Open No. 2-107339 (Patent Document 2) discloses a photocatalyst in which a photocatalytic active component is supported on a base material having a three-dimensional network structure. According to this photocatalyst, the efficiency of the photocatalyst is improved and the pressure loss is reduced when the photocatalyst is filled and used.

Furthermore, Japanese Patent Laid-Open No. 8-103631 (Patent Document 3) discloses a photocatalyst in which the surface of a base material formed by fusing spherical heat-resistant glass is coated with a titanium oxide film. According to this photocatalyst, since the surface area is large and incident light hits the entire titanium oxide, it is possible to efficiently adsorb or decompose and remove contaminants.
JP-A-9-262482 Japanese Patent Laid-Open No. 2-107339 Japanese Patent Laid-Open No. 8-103631

  However, the photocatalysts disclosed in Patent Documents 1 to 3 are not sufficient in the efficiency of the photocatalyst, and an improvement in the efficiency of the photocatalyst has been demanded.

  This invention is made | formed in view of the said situation, and it aims at providing the photocatalyst structure which can improve the efficiency of a photocatalytic reaction, and its manufacturing method.

  The photocatalyst structure according to the present invention solves the above-mentioned problems, a base material, a titanium oxide layer formed on the surface of the base material, to which titanium oxide crystal grains are fixed, and the titanium oxide of the titanium oxide layer. Platinum group metal grains fixed to the surface of the crystal grains, the platinum group metal grains are substantially not present at grain boundaries between the titanium oxide crystal grains, and the titanium oxide layer is an average of the titanium oxide crystal grains. The platinum group metal particles have a particle size of 100 nm or less and an average particle size of 20 nm or less.

  Moreover, the method for producing a photocatalyst structure according to the present invention solves the above-described problems, and attaches a liquid composition containing a platinum group metal to the surface of the titanium oxide layer, and dries the liquid composition. A method of manufacturing a photocatalyst structure in which platinum group metal particles are fixed to the surface of titanium oxide crystal grains of the titanium oxide layer by heat treatment, wherein the titanium oxide layer has an average particle diameter of titanium oxide crystal grains of 100 nm or less. The platinum group metal particles have an average particle size of 20 nm or less.

  The photocatalyst structure according to the present invention has high photocatalytic reaction efficiency and can be mass-produced at low cost.

  In addition, the method for producing a photocatalyst structure according to the present invention can mass-produce a photocatalyst structure having high photocatalytic reaction efficiency at low cost.

[Photocatalyst structure]
The photocatalyst structure according to the present invention includes a base material, a titanium oxide layer formed on the surface of the base material, and platinum group metal particles fixed to the surface of the titanium oxide layer.

(Base material)
As the substrate used in the present invention, a substrate having a three-dimensional network structure is used. Examples of the base material having a three-dimensional network structure include silicate, alumina silicate glass, and the like whose main component is cordierite (Mg ₂ Al ₄ Si ₅ O ₁₈ ). Here, cordierite as a main component means that 50% by weight or more of the silicate is cordierite. The base material having a three-dimensional network structure is preferably cordierite because the titanium oxide layer is difficult to peel from the base material. A base material having a three-dimensional network structure is preferred to have an open porosity of 75% or more because the pressure loss is small.

(Titanium oxide layer)
The titanium oxide layer is formed on the surface of the substrate. The titanium oxide layer has titanium oxide crystal grains fixed to each other. The titanium oxide layer has one or more titanium oxide crystal grains in the thickness direction of the titanium oxide layer. When two or more titanium oxide crystal grains exist in the thickness direction of the titanium oxide layer, a gap may be generated between the titanium oxide crystal grains. This gap may occur at a portion where three or more titanium oxide crystal grains are in contact.

  The titanium oxide layer has an average particle diameter of titanium oxide crystal grains of 100 nm or less, preferably 6 nm to 100 nm. It is preferable that the average particle diameter of the titanium oxide crystal grains is 100 nm or less because the specific surface area of the titanium oxide crystal grains is large and the activity of the photocatalytic reaction is high.

  Here, the average particle diameter of the titanium oxide crystal grains means the average particle diameter of the titanium oxide crystal grains measured using a nitrogen gas adsorption method based on physical adsorption.

The titanium oxide layer has a relative density of 85% or more, preferably 85% to 100%, with respect to the true density of titanium oxide 4.26 g / cm ³ . It is preferable that the relative density of titanium oxide is 85% or more because the strength of the titanium oxide layer is high and the activity of the photocatalytic reaction is high. If the relative density of titanium oxide is less than 85%, the strength of the titanium oxide layer is so low that the titanium oxide layer may peel off from the substrate.

  The titanium oxide layer preferably has an average thickness of 1 μm to 300 μm because it is difficult to peel off from the substrate.

(Platinum group metal particles)
The platinum group metal particles are fixed to the surface of the titanium oxide crystal grains of the titanium oxide layer. Further, the platinum group metal grains are not substantially present at the grain boundaries between the titanium oxide crystal grains of the titanium oxide layer. In the case where a gap is generated between the titanium oxide crystal grains of the titanium oxide layer, the platinum group metal grain may be present on the surface of the titanium oxide crystal grain in the gap.

  The platinum group metal particles are made of a metal containing at least one element selected from Pt, Ru, Rh, Pd, Os, and Ir.

  Further, when the platinum group metal particle is an alloy of Pt and at least one element selected from Ru, Rh, Pd, Os, and Ir, an expensive platinum group metal is maintained while keeping the activity of the photocatalytic reaction high. Among them, the amount of expensive Pt (platinum) used is particularly economical because it is economical, and further alloying is preferable because the activity of the photocatalytic reaction is improved as compared with the case of platinum alone.

  Here, the platinum group metal particle is an alloy that the first platinum group metal particle and the platinum group metal particle other than the first platinum group metal are fixed to the surface of the titanium oxide crystal particle. Means that The first platinum group metal particles and the platinum group metal particles other than the first platinum group metal may or may not adhere to each other.

  For example, when the first platinum group metal particles are platinum particles, the platinum group metal particles other than the first platinum group metal are ruthenium particles, and these are fixed to the surface of the titanium oxide crystal grains, respectively. It is recognized that a platinum-ruthenium alloy is formed.

  Furthermore, it is preferable that the platinum group metal particles have a Pt content of 50 mol% or more in the alloy because the activity of the photocatalytic reaction is high.

  The platinum group metal grains are substantially formed only on the surface of the titanium oxide crystal grains of the titanium oxide layer, and are substantially not present at the grain boundaries of the titanium oxide crystal grains or inside the titanium oxide crystal grains. In the present invention, since the platinum group metal particles, which are catalytically active components, are present only on the surface of the titanium oxide crystal grains of the titanium oxide layer, which is the reaction field for the photocatalytic reaction, the photocatalytic reaction is efficiently performed and the Even if the amount of the platinum group metal used is small, the activity of the photocatalytic reaction is high.

  Generally, when titanium oxide is irradiated with ultraviolet rays, a photocatalytic reaction occurs due to the generation of electrons and holes on the surface, but these electrons and holes recombine, causing a decrease in activity. Therefore, when platinum group fine particles are supported on the surface, recombination of electrons and holes is suppressed, and a photocatalytic reaction occurs efficiently. The platinum group metal particles have an average particle size of 20 nm or less, preferably 1 nm to 20 nm. It is preferable that the average particle size of the platinum group metal particles is 20 nm or less because the activity of the photocatalytic reaction is high.

  If the average particle size of the platinum group metal particles exceeds 20 nm, the activity of the photocatalytic reaction may be lowered.

  Here, the average particle diameter of the platinum group metal particles means an average particle diameter measured by a chemical adsorption method using hydrogen.

  The platinum group metal particles are formed in an amount of 0.9 mmol% or less, preferably 0.5 mmol% to 0.9 mmol% with respect to the titanium oxide layer.

  It is preferable that the platinum group metal particles be 0.9 mmol% or less with respect to the titanium oxide layer because the activity of the photocatalytic reaction is high. Further, it is more preferable that the platinum group metal particles are 0.5 mmol% to 0.9 mmol% with respect to the titanium oxide layer because the activity of the photocatalytic reaction is higher.

  The activity of the photocatalytic reaction of the photocatalyst structure is examined by, for example, supplying ammonia-containing gas to the photocatalyst structure exposed to light, and measuring the content of ammonia in the ammonia-containing gas after flowing through the photocatalyst structure. Can do.

[Method for producing photocatalyst structure]
The photocatalyst structure according to the present invention can be produced, for example, by the following method.

  First, a titanium oxide sol is attached to the surface of the substrate. Examples of the method of attaching the titanium oxide sol to the surface of the base material include a method of impregnating the base material with the titanium oxide sol.

  The titanium oxide sol has an average particle size of usually 1 nm to 20 nm, preferably 3 nm to 10 nm.

  It is preferable that the average particle diameter of the titanium oxide sol is 1 nm to 20 nm because it is easy to form a titanium oxide layer composed of titanium oxide crystal grains having an average crystal grain diameter of 100 nm or less.

  Next, the attached titanium oxide sol is dried and heat-treated to obtain a titanium oxide layer. The heat treatment of the titanium oxide sol is performed so that the average particle diameter of the titanium oxide crystal grains in the titanium oxide layer is 100 nm or less, preferably 6 nm to 100 nm. The titanium oxide crystal grains having the above average particle diameter can be obtained, for example, by heat treatment at 350 ° C. to 700 ° C. for 2 hours to 8 hours in the air.

  The average particle diameter of the titanium oxide crystal grains can be measured using a nitrogen gas adsorption method based on physical adsorption.

  Further, a liquid composition containing a platinum group metal is attached to the surface of the titanium oxide layer. The liquid composition containing a platinum group metal is a liquid composition of at least one element selected from Pt, Ru, Rh, Pd, Os, and Ir. Specific examples of the liquid composition include chloroplatinic acid, palladium chloride, iridium oxide, rhodium acetate, tris (acetylacetonato) ruthenium, and a solution containing potassium osmate.

  The liquid composition containing a platinum group metal is adhered to the surface of the titanium oxide layer, dried, and heat-treated to fix the platinum group metal particles to the surface of the titanium oxide crystal grains of the titanium oxide layer.

  When the platinum group metal particles are made of a platinum alloy composed of two or more metals selected from Pt, Ru, Rh, Pd, Os and Ir, for example, two or more liquid compositions containing different platinum group metals are mixed. Then, a platinum alloy can be obtained by adhering to the surface of the titanium oxide layer.

  Next, the liquid composition containing the deposited platinum group metal is dried and heat-treated to obtain platinum group metal particles fixed to the surface of the titanium oxide crystal grains. The heat treatment of the liquid composition containing the platinum group metal is performed so that the average particle size of the platinum group metal particles is 20 nm or less, preferably 1 nm to 20 nm. The platinum group metal particles having the above average particle diameter can be obtained by, for example, heat treatment at 200 ° C. to 600 ° C. in the air for 0.5 hours to 4 hours.

  The average particle diameter of the platinum group metal particles can be measured using a chemical adsorption method using hydrogen.

  Through the above steps, the photocatalyst structure according to the present invention is obtained.

  Examples are shown below, but the present invention is not construed as being limited thereto.

[Example 1-1]
(Base material)
As a base material, a silicate having a three-dimensional network structure having cordierite (Mg ₂ Al ₄ Si ₅ O ₁₈ ) as a main component and an open porosity of 85% was used.

(Formation of titanium oxide film)
The substrate was impregnated with a mixture of titanium oxide sol having a concentration of 30% and a crystal grain size of 6 nm and polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., polyethylene glycol 200) and dried. Then, the photocatalyst module in which the titanium oxide film was formed on the base material was produced by heat-processing at 600 degreeC for 4 hours in air | atmosphere.

(Formation of platinum group metal particles)
The photocatalyst module on which the titanium oxide film is formed is immersed in an aqueous solution of chloroplatinic acid having a platinum equivalent concentration of 0.2 mmol%, and then heat-treated at 500 ° C. for 1 hour in the atmosphere, thereby the surface of the titanium oxide film on the substrate. A photocatalytic module in which platinum particles were formed on was prepared. The production conditions for the photocatalyst module are shown in Table 1.

  When the photocatalyst film of the obtained photocatalyst module is observed with a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDX), platinum particles are present on the surface of the titanium oxide crystal grains of the titanium oxide film. I understood.

  About the photocatalyst film | membrane of the obtained photocatalyst module, the average particle diameter of the titanium oxide crystal grain of a titanium oxide film | membrane was measured using the nitrogen gas adsorption method by physical adsorption. Moreover, about the photocatalyst film | membrane of the obtained photocatalyst module, the average particle diameter of the platinum particle was measured using the chemical adsorption method by hydrogen. Table 3 shows the measurement results.

(Measurement of ammonia decomposition efficiency)
The photocatalytic efficiency of the photocatalytic film was evaluated by measuring the decomposition efficiency of ammonia. Specifically, while the light of black light (average wavelength 370 nm, intensity 3 mW / cm ² ) is applied to the finally obtained photocatalyst module, ammonia is contained in the air at a concentration of 100 ppm, and the flow rate is 0.5 l / min. Ammonia gas was introduced from one of the photocatalyst modules. And the ammonia concentration in the exit side of the photocatalyst module opposite to the inflow side was measured.

  The measurement results of the ammonia decomposition efficiency of the photocatalyst module are shown in Table 3 and FIG.

[Example 1-2 to Example 1-3, Comparative Example 1] (Influence of grain size of titanium oxide crystal grains)
A photocatalyst was prepared in the same manner as in Example 1-1, except that the average particle diameter of the titanium oxide crystal grains of the titanium oxide film was changed as shown in Table 3 by changing the temperature and processing time of the heat treatment for forming the titanium oxide film. A module was produced. The production conditions for the photocatalyst module are shown in Table 1.

  When the photocatalyst film of the obtained photocatalyst module was observed with SEM and EDX, it was found that platinum particles were present on the surface of the titanium oxide crystal grains of the titanium oxide film.

  About the obtained photocatalyst module, it carried out similarly to Example 1-1, and measured the titanium oxide crystal grain of the titanium oxide film, the average particle diameter of platinum grain, and the decomposition efficiency of ammonia. The measurement results are shown in Table 3 and FIG.

[Comparative Example 2] (Influence of platinum group metal particles)
A photocatalyst module in which a titanium oxide film was formed on a substrate was produced in the same manner as in Example 1-1 except that platinum group metal particles were not produced. The production conditions for the photocatalyst module are shown in Table 1.

  About the obtained photocatalyst module, it carried out similarly to Example 1-1, and measured the average particle diameter of the titanium oxide crystal grain of a titanium oxide film, and the decomposition efficiency of ammonia. The measurement results are shown in Table 3 and FIG.

  From the results of Examples 1-1 to 1-3, Comparative Example 1 and Comparative Example 2 in which the average particle diameter of the titanium oxide crystal grains was changed, the average particle diameter of the titanium oxide crystal grains was as shown in FIG. In the case of 120 nm, the ammonia concentration on the outlet side exceeds 50 ppm and the photocatalytic efficiency is lowered. However, when the average particle diameter of the titanium oxide crystal grains is 95 nm or less, the ammonia concentration on the outlet side is lower than 30 ppm and the photocatalytic efficiency is low. It was found to be good.

[Example 2-1 to Example 2-2, Comparative Example 3] (Effect of particle size of platinum particles)
The photocatalyst module was prepared in the same manner as in Example 2 except that the average particle diameter of the platinum group metal particles was changed as shown in Table 3 by changing the heat treatment temperature and the treatment time for forming the platinum group metal particles. Produced. The production conditions for the photocatalyst module are shown in Table 1.

  When the photocatalyst film of the obtained photocatalyst module was observed with SEM and EDX, it was found that platinum particles were present on the surface of the titanium oxide crystal grains of the titanium oxide film.

  About the obtained photocatalyst module, it carried out similarly to Example 1-1, and measured the titanium oxide crystal grain of the titanium oxide film, the average particle diameter of platinum grain, and the decomposition efficiency of ammonia. The measurement results are shown in Table 3 and FIG.

  From the results of Example 2-1 to Example 2-2 and Comparative Example 3 in which the average particle diameter of the platinum particles was changed, as shown in FIG. 2, when the average particle diameter of the platinum particles was 22 nm, the outlet However, when the average particle size was 19 nm or less, the ammonia concentration at the outlet was lower than 30 ppm and the photocatalytic efficiency was good.

[Comparative Example 4] (Effect of platinum phase existing site)
(Preparation of a liquid composition for preparing a photocatalytic film)
A liquid composition for preparing a photocatalyst film was prepared by mixing a titanium oxide sol having a concentration of 30% and a crystal grain size of 6 nm with polyethylene glycol with a chloroplatinic acid aqueous solution having a platinum equivalent concentration of 0.2 mmol%.

(Production of photocatalytic film)
A base material similar to that of Example 1-1 was impregnated with the liquid composition for producing a photocatalyst film and dried. Then, the photocatalyst module by which the photocatalyst film | membrane containing a titanium oxide and platinum was formed on the base material was produced by heat-processing at 500 degreeC for 1 hour in air | atmosphere. The production conditions for the photocatalyst module are shown in Table 1.

  When the photocatalyst film of the obtained photocatalyst module was observed by SEM and EDX, it was found that platinum particles were present at the surface of the titanium oxide crystal grains of the titanium oxide film and at the grain boundaries between the titanium oxide crystal grains.

  About the obtained photocatalyst module, it carried out similarly to Example 1-1, and measured the titanium oxide crystal grain of the titanium oxide film, the average particle diameter of platinum grain, and the decomposition efficiency of ammonia. The measurement results are shown in Table 3 and FIG. FIG. 3 also shows the measurement results of Example 1-1.

  From the results of Comparative Example 4 and Example 1-1 in which the presence or absence of the platinum phase is changed at the grain boundaries of the titanium oxide crystal grains, as shown in FIG. 3, when platinum is present at the titanium oxide crystal grain boundaries It was found that the ammonia concentration on the outlet side was 50 ppm or more and the photocatalytic efficiency was lowered.

[Example 3-1 to Example 3-4] (Influence of the density of the titanium oxide layer)
A photocatalyst module was produced in the same manner as in Example 1-1 except that the amount of polyethylene glycol added to the titanium oxide sol having a concentration of 30% and a crystal grain size of 6 nm was changed.

  It was set as Example 3-1 to Example 3-4. As for the addition amount of polyethylene glycol, the relative density of the titanium oxide film is a predetermined amount (83% (Example 3-1), 86% (Example 3-2), 91% (Example 3-3), 97% ( Example 3-4)) was adjusted. The production conditions for the photocatalyst module are shown in Table 1.

  When the photocatalyst film of the obtained photocatalyst module was observed with SEM and EDX, it was found that platinum particles were present on the surface of the titanium oxide crystal grains of the titanium oxide film.

Moreover, the film thickness of the titanium oxide film was measured, and the relative density of the titanium oxide film was calculated from the film thickness and the titanium oxide weight. The relative density of the titanium oxide film was determined as the relative density when the true density of titanium oxide 4.26 g / cm ³ was taken as 100%.

  About the obtained photocatalyst module, it carried out similarly to Example 1-1, and measured the titanium oxide crystal grain of the titanium oxide film, the average particle diameter of platinum grain, and the decomposition efficiency of ammonia. The measurement results are shown in Table 3 and FIG.

  From the results of Example 3-1 to Example 3-4 in which the relative density of the titanium oxide film was changed, as shown in FIG. 4, when the relative density of the titanium oxide film was in the range of 97% to 86%, It was found that the ammonia concentration at the outlet was lower than that in the case of a relative density of 83%, indicating a good photocatalytic efficiency.

[Example 4-1 to Example 4-5] (Influence of platinum concentration of chloroplatinic acid aqueous solution)
Platinum conversion concentration is 0.1 mmol% (Example 4-1), 0.2 mmol% (Example 4-2), 0.5 mmol% (Example 4-3), 0.7 mmol% (Example 4-4) ), 0.9 mmol% (Example 4-5), a photocatalyst module was produced in the same manner as in Example 1-1 except that the concentration of the chloroplatinic acid aqueous solution was changed. The production conditions for the photocatalyst module are shown in Table 1.

  When the photocatalyst film of the obtained photocatalyst module was observed with SEM and EDX, it was found that platinum particles were present on the surface of the titanium oxide crystal grains of the titanium oxide film.

  About the obtained photocatalyst module, it carried out similarly to Example 1-1, and measured the titanium oxide crystal grain of the titanium oxide film, the average particle diameter of platinum grain, and the decomposition efficiency of ammonia. The measurement results are shown in Table 3 and FIG.

  From the results of Example 4-1 to Example 4-5 in which the concentration of the chloroplatinic acid aqueous solution was changed, as shown in FIG. 5, the platinum amount of the platinum particles was 0.1 mmol% with respect to the titanium oxide of the titanium oxide film, When the concentration is 0.2 mmol%, the ammonia concentration at the outlet is lower than 25 ppm and the photocatalytic efficiency is good. However, when the concentration is 0.5 mmol%, 0.7 mmol%, and 0.9 mmol%, the ammonia concentration is even better. It was.

[Example 5-1 to Example 5-6] (Influence of platinum group metal type)
A photocatalyst module (in the same manner as in Example 1-1) except that a solution containing the following platinum group metal was used instead of the chloroplatinic acid aqueous solution having a platinum equivalent concentration of 0.2 mmol% with respect to the amount of titanium oxide in the titanium oxide sol. Examples 5-1 to 5-6) were prepared.

  That is, instead of the chloroplatinic acid aqueous solution (Example 5-1) having a platinum equivalent concentration of 0.2 mmol% in Example 1-1, tris (acetylacetonato) ruthenium having a ruthenium equivalent concentration of 0.2 mmol% (implementation) Example 5-2), rhodium acetate having a rhodium equivalent concentration of 0.2 mmol% (Example 5-3), palladium chloride having a palladium equivalent concentration of 0.2 mmol% (Example 5-4), and an osmium equivalent concentration of 0. 2 mmol% potassium osmate (Example 5-5) or iridium oxide having a iridium equivalent concentration of 0.2 mmol% (Example 5-6) was used. Table 2 shows the production conditions of the photocatalyst module.

  About the photocatalyst film | membrane of the obtained photocatalyst module, when it observed by SEM and EDX, platinum particle | grains (Example 5-1), ruthenium particle | grains (Example 5-2) on the surface of the titanium oxide crystal grain of a titanium oxide film | membrane, It was found that rhodium particles (Example 5-3), palladium particles (Example 5-4), osmium particles (Example 5-5), and iridium particles (Example 5-6) were present.

  About the obtained photocatalyst module, it carried out similarly to Example 1-1, and the titanium oxide crystal grain of a titanium oxide film, and platinum group metal grain (Platinum grain, ruthenium grain, rhodium grain, palladium grain, osmium grain, iridium grain) The average particle size and ammonia decomposition efficiency were measured. The measurement results are shown in Table 4 and FIG. FIG. 6 also shows the measurement results of Comparative Example 2.

[Example 6-1 to Example 6-20] (Type of platinum group metal alloy and influence of platinum content ratio in platinum group metal alloy)
As a liquid composition for forming a platinum group metal particle, a platinum-converted aqueous solution and tris (acetylacetonato) ruthenium were mixed, and the platinum-converted concentration was 0.2 mmol% and the ruthenium-converted concentration was 0.2 mmol%. Photocatalyst modules were produced in the same manner as in Example 1-1 except that the liquid composition was used (Examples 6-1, 6-6, 6-11, 6-16).

  Further, as a liquid composition for forming platinum group metal particles, a liquid composition having a platinum equivalent concentration of 0.2 mmol% and a rhodium equivalent concentration of 0.2 mmol% prepared by mixing a chloroplatinic acid aqueous solution and rhodium acetate. Photocatalyst modules were produced in the same manner as in Example 1-1 except that was used (Examples 6-2, 6-7, 6-12, 6-17).

  Furthermore, as a liquid composition for forming platinum group metal particles, a liquid composition having a platinum equivalent concentration of 0.2 mmol% and a palladium equivalent concentration of 0.2 mmol% prepared by mixing an aqueous chloroplatinic acid solution and palladium chloride. Photocatalyst modules were produced in the same manner as in Example 1-1 except that was used (Examples 6-3, 6-8, 6-13, 6-18).

  Further, as a liquid composition for forming platinum group metal particles, a liquid composition having a platinum equivalent concentration of 0.2 mmol% and an osmium equivalent concentration of 0.2 mmol% prepared by mixing an aqueous chloroplatinic acid solution and potassium osmate. Photocatalyst modules were produced in the same manner as in Example 1-1 except that the product was used (Examples 6-4, 6-9, 6-14, 6-19).

  Further, as a liquid composition for forming platinum group metal particles, a liquid composition having a platinum equivalent concentration of 0.2 mmol% and an iridium equivalent concentration of 0.2 mmol% prepared by mixing an aqueous chloroplatinic acid solution and iridium oxide. Photocatalyst modules were produced in the same manner as in Example 1-1 except that was used (Examples 6-5, 6-10, 6-15, 6-20).

  In Example 6-1 to Example 6-5, the molar ratio of platinum in the liquid composition to a platinum group metal other than platinum such as ruthenium was set to 4: 6.

  In Examples 6-6 to 6-10, the molar ratio of platinum in the liquid composition to a platinum group metal other than platinum such as ruthenium was set to 5: 5.

  In Examples 6-11 to 6-15, the molar ratio of platinum in the liquid composition to a platinum group metal other than platinum such as ruthenium was set to 6: 4.

  In Examples 6-16 to 6-20, the molar ratio of platinum in the liquid composition to a platinum group metal other than platinum such as ruthenium was set to 7: 3.

  Table 2 shows the production conditions of the photocatalyst module.

  When the photocatalyst film of the obtained photocatalyst module was observed by SEM and EDX, platinum particles and ruthenium particles were fixed to the surface of the titanium oxide crystal grains of the titanium oxide film (Examples 6-1, 6-6, 6). -11, 6-16), platinum particles and rhodium particles are fixed (Examples 6-2, 6-7, 6-12, 6-17), and platinum particles and palladium particles are fixed (Example 6-3). 6-8, 6-13, 6-18), platinum particles and osmium particles are fixed (Examples 6-4, 6-9, 6-14, 6-19), and platinum particles and iridium particles are fixed. (Examples 6-5, 6-10, 6-15, 6-20).

  In Example 6-1 to Example 6-5, the ratio of platinum group metal particles formed on the surface of the titanium oxide crystal grains is 40 mol%, and the ratio of platinum group metal particles other than platinum is 60 mol%. there were.

  In Examples 6-6 to 6-10, the proportion of platinum group metal particles formed on the surface of the titanium oxide crystal grains is 50 mol%, and the proportion of platinum group metal particles other than platinum is 50 mol%. there were.

  In Examples 6-11 to 6-15, the proportion of platinum group metal particles formed on the surface of the titanium oxide crystal grains is 60 mol%, and the proportion of platinum group metal particles other than platinum is 40 mol%. there were.

  In Examples 6-16 to 6-20, the ratio of platinum group metal particles formed on the surface of the titanium oxide crystal grains was 70 mol%, and the ratio of platinum group metal particles other than platinum was 30 mol%. there were.

  About the obtained photocatalyst module, it carried out similarly to Example 1-1, and the titanium oxide crystal grain of a titanium oxide film, and platinum group metal grain (Platinum grain, ruthenium grain, rhodium grain, palladium grain, osmium grain, iridium grain) The average particle size and ammonia decomposition efficiency were measured. The measurement results are shown in Table 4 and FIG.

  From the results of Example 6-1 to Example 6-20 in which the type of metal element and the platinum content in the platinum alloy were changed, as shown in FIG. 7, when the platinum content was 50 mol% or more, the ammonia at the outlet The concentrations were both lower than 40 ppm and the photocatalytic efficiency was good, but it was found that the photocatalytic efficiency was lowered when the platinum content was 40% or less.

[Example 7-1] (Influence of substrate type)
Further, a photocatalyst module was produced in the same manner as in Example 1-1 except that an inorganic fiber honeycomb substrate having a regular hexagonal cell cross-section was used (Example 7-1). Table 2 shows the production conditions of the photocatalyst module.

  When the photocatalyst film of the obtained photocatalyst module was observed by SEM and EDX, it was found that in Example 6-1, platinum particles were fixed to the surface of the titanium oxide crystal grains of the titanium oxide film.

  About the obtained photocatalyst module, it carried out similarly to Example 1-1, and measured the titanium oxide crystal grain of the titanium oxide film, the average particle diameter of platinum grain, and the decomposition efficiency of ammonia. The measurement results are shown in Table 4 and FIG. FIG. 8 also shows the measurement results of Example 1-1.

  From the results of Example 1-1 and Example 7-1 in which the type of base material was changed, as shown in FIG. 8, the base material having a three-dimensional network structure has an ammonia concentration of 30 ppm or less at the outlet and good photocatalytic efficiency. However, it was found that the photocatalytic efficiency was lowered in the case of the honeycomb substrate.

The graph which shows the relationship between the particle size of a titanium oxide crystal grain, and photocatalytic efficiency. The graph which shows the relationship between the particle size of a platinum grain, and photocatalytic efficiency. The graph which shows the relationship between the existing part of a platinum phase, and photocatalytic efficiency. The graph which shows the relationship between the density of a titanium oxide layer, and photocatalytic efficiency. The graph which shows the relationship between the platinum concentration of chloroplatinic acid aqueous solution, and photocatalytic efficiency. The graph which shows the relationship between the kind of single-piece | unit platinum group metal, and photocatalytic efficiency. The graph which shows the relationship between the platinum content ratio in a platinum group metal alloy, and photocatalytic efficiency. The graph which shows the relationship between the kind of base material, and photocatalytic efficiency.

Claims (9)

A substrate;
A titanium oxide layer formed on the surface of the substrate and having titanium oxide crystal grains fixed thereto;
Platinum group metal particles fixed to the surface of the titanium oxide crystal grains of the titanium oxide layer;
With
The platinum group metal grains are not substantially present at grain boundaries between the titanium oxide crystal grains,
The titanium oxide layer has an average particle diameter of titanium oxide crystal grains of 100 nm or less,
The platinum group metal particles have an average particle size of 20 nm or less. 2. The photocatalytic structure according to claim 1, wherein the titanium oxide layer has a relative density of 85% or more with respect to a true density of 4.26 g / cm ³ of titanium oxide. 2. The photocatalytic structure according to claim 1, wherein the platinum group metal particles are made of a metal containing at least one element selected from Pt, Ru, Rh, Pd, Os, and Ir. 2. The photocatalytic structure according to claim 1, wherein the platinum group metal particle is an alloy of Pt and at least one element selected from Ru, Rh, Pd, Os, and Ir. The photocatalyst structure according to claim 4, wherein the platinum group metal particles have a Pt content in the alloy of 50 mol% or more. The photocatalyst structure according to claim 1, wherein the platinum group metal particles are formed in an amount of 0.5 mmol% or less with respect to the titanium oxide layer. The photocatalyst structure according to claim 1, wherein the substrate has a three-dimensional network structure. A photocatalyst for adhering a liquid composition containing a platinum group metal to the surface of the titanium oxide layer, drying the liquid composition, and heat-treating the platinum group metal grains on the surface of the titanium oxide crystal grains of the titanium oxide layer. A method of manufacturing a structure,
The titanium oxide layer has an average particle diameter of titanium oxide crystal grains of 100 nm or less,
The method for producing a photocatalyst structure, wherein the platinum group metal particles have an average particle size of 20 nm or less. The method for producing a photocatalyst structure according to claim 8, wherein the titanium oxide layer is obtained by attaching a titanium oxide sol to a surface of a base material, drying and heat-treating the titanium oxide layer.

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