JP2009297662A - Photocatalyst, its preparing method and its application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalyst exhibiting a high photocatalytic activity with practical light sources such as a fluorescent lamp and to provide its preparing method capable of easily obtaining the photocatalyst. <P>SOLUTION: The photocatalyst is a composite formed from tungsten oxide and porous silica which possesses a BET specific surface area of 150-800 m<SP>2</SP>/g and a pore volume of 0.15-1.0 cm<SP>3</SP>/g. The method for preparing the photocatalyst comprises dispersing the tungsten oxide particles in a solvent, dissolving a material forming micell therein, and adding a silicone compound, to hydrolyse or neutralize the silicone compound, and calcining the resultant solid. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photocatalyst that exhibits high photocatalytic activity with a practical light source such as a fluorescent lamp, a method for producing the same, and a use thereof.

  When a semiconductor is irradiated with light having energy higher than the band gap, electrons in the valence band are excited to the conduction band, and holes are generated in the valence band and electrons are generated in the conduction band. These have strong oxidizing power and reducing power, respectively, and exert a redox action on the molecular species in contact with the semiconductor. Such an action is called a photocatalytic action, and by utilizing this photocatalytic action, organic substances in the atmosphere can be decomposed and removed.

  Conventionally, titanium oxide is generally used as a substance exhibiting a photocatalytic action, and photocatalysts in which titanium oxide particles are dispersed or supported on various media or carriers have been put into practical use. Furthermore, in recent years, a method for improving the photocatalytic function of a titanium oxide photocatalyst has been studied. For example, titanium oxide particles are dispersed in a synthetic medium, and a porous skeleton such as porous silica is generated therein. A composite porous body containing titanium oxide (see Patent Document 1) is proposed.

  However, a conventional photocatalyst comprising a titanium oxide photocatalyst or a titanium oxide-containing composite porous material proposed in Patent Document 1 is a good photocatalyst under irradiation of light in the ultraviolet region with a relatively short wavelength such as sunlight. Although it shows activity, there is a case where sufficient photocatalytic activity cannot be obtained in an indoor space illuminated with a practical light source that occupies most of visible light such as a fluorescent lamp.

JP-A-2005-314208

  Then, the subject of this invention is the photocatalyst which shows high photocatalytic activity with practical light sources, such as a fluorescent lamp, the manufacturing method which can obtain this photocatalyst easily, The decomposition | disassembly processing method of organic substance using this photocatalyst, Is to provide.

  The present inventors have intensively studied to solve the above problems. As a result, the conventional photocatalyst made of titanium oxide or a composite porous body containing titanium oxide did not exhibit sufficient photocatalytic activity under the irradiation of a practical light source such as a fluorescent lamp. Titanium oxide that had been used was difficult to exhibit catalytic activity unless it was light in the ultraviolet region with a short wavelength, and the visible light that occupies most of the indoor light could not be used effectively. It was considered that the contact rate with the reaction substrate to cause the photocatalytic action, in other words, the amount of the reaction substrate adsorbed to the photocatalyst was insufficient, had a combined effect. Then, the first factor is eliminated by forming a composite with porous silica using tungsten oxide instead of titanium oxide, and the BET specific surface area in the composite of tungsten oxide and porous silica and If the second factor is eliminated by designing the pore volume within a specific range, it is found that even if it is a practical light source such as a fluorescent lamp that occupies most of the visible light, high photocatalytic activity can be expressed. The invention has been completed.

That is, the present invention has the following configuration.
(1) A composite formed of tungsten oxide and porous silica, having a BET specific surface area of 150 to 800 m ² / g and a pore volume of 0.15 to 1.0 cm ³ / g. A photocatalyst body.
(2) The method for producing a photocatalyst according to (1), wherein tungsten oxide particles are dispersed in a solvent and a substance that forms micelles is dissolved, and then a silicon compound is added, and the silicon compound is added. A method for producing a photocatalyst, characterized by firing a solid obtained by hydrolysis or neutralization.
(3) A method for decomposing an organic substance in a reaction substrate by irradiating light in contact with a photocatalyst, wherein the photocatalyst described in (1) is used as the photocatalyst. Decomposition method of organic matter.

  According to the present invention, high photocatalytic activity can be exhibited by a practical light source such as a fluorescent lamp.

  The photocatalyst of the present invention is a composite formed from tungsten oxide and porous silica. The composite mentioned here has a porous structure that is easily formed by the method for producing a photocatalyst of the present invention described later. The form of the composite in the composite is not particularly limited. For example, the form in which the porous silica covers a part or the whole of the tungsten oxide particles may be used, or the porous silica and the tungsten oxide may be used. It may be in a form where the particles are only in physical contact. Of course, the photocatalyst of the present invention may be a composite in which a plurality of composite forms are mixed.

The tungsten oxide constituting the photocatalyst of the present invention is a particulate tungsten oxide exhibiting a photocatalytic action, and for example, tungsten trioxide [WO ₃ ] particles are preferably mentioned. Tungsten trioxide particles, for example, by adding acid to an aqueous solution of tungstate to obtain tungstic acid as a precipitate and firing the resulting tungstic acid, tungstic acid, ammonium metatungstate, paratungstic acid It can be obtained by a method in which ammonium is thermally decomposed by heating.

  The content of the tungsten oxide contained in the photocatalyst of the present invention is preferably 10 to 90% by weight, more preferably 40 to 90% by weight with respect to the composite. If the content of tungsten oxide is less than 10% by weight, a sufficiently high photocatalytic activity may not be obtained. On the other hand, if the content exceeds 90% by weight, the proportion of porous silica decreases, so There is a possibility that the amount of adsorption decreases and high photocatalytic activity cannot be obtained.

  The porous silica constituting the photocatalyst body of the present invention is a porous body formed by hydrolyzing or neutralizing a silicon compound described later. Usually, simultaneously with the formation of the porous body, the compounding with tungsten oxide proceeds, and the photocatalyst body of the present invention is formed. In addition, about the formation method by hydrolysis or neutralization, it is as the description in the manufacturing method of the photocatalyst body of this invention mentioned later.

The BET specific surface area of the photocatalyst of the present invention is 150 to 800 m ² / g. When the BET specific surface area is less than 150 m ² / g, the amount of adsorption of the reaction substrate decreases, and high photocatalytic activity cannot be obtained. On the other hand, when the BET specific surface area exceeds 800 m ² / g, oxidation in the complex during production It is necessary to design the content of tungsten particles to be extremely low, and high photocatalytic activity cannot be obtained even if the amount of adsorption of the reaction substrate increases. Preferably, the lower limit of the BET specific surface area is 200 m ² / g or more, and the upper limit is 500 m ² / g or less.

The pore volume of the photocatalyst of the present invention is 0.10 to 1.0 cm ³ / g. When the pore volume is less than 0.10 cm ³ / g, the amount of adsorption of the reaction substrate decreases, and high photocatalytic activity cannot be obtained. On the other hand, when the pore volume exceeds 1.0 cm ³ / g, it is used during production. It is necessary to use a high-molecular-weight micelle-forming substance that is generally expensive as a substance that forms micelles (hereinafter also referred to as “micelle-forming substance”), and an effect that is commensurate with the cost cannot be obtained. Preferably, the lower limit of the pore volume is 0.15 cm ³ / g or more, the upper limit should preferably be equal to or less than 0.30 cm ³ / g.
In addition, the BET specific surface area and pore volume of the photocatalyst in the present invention can be measured, for example, by a nitrogen adsorption method described later in Examples.

The photocatalyst of the present invention is mainly composed of tungsten oxide and porous silica. In order to further improve the photocatalytic activity and adsorptivity, for example, Cu, Pt, Au, Pd, Ag, Fe, Nb , Ru, Ir, Rh, Co, Al, Ti, Zr, and other metal components may be included. What is necessary is just to set content of these metal components suitably in the range which does not impair the effect of this invention.
The photocatalyst of the present invention as described above can be easily obtained by the method for producing a photocatalyst of the present invention described later.

  The method for producing a photocatalyst of the present invention is obtained by dispersing tungsten oxide particles in a solvent and dissolving a micelle-forming substance, adding a silicon compound, and hydrolyzing or neutralizing the silicon compound. The solid material is fired. According to this method, since the micelle-forming substance exists as a template when the silicon compound is hydrolyzed or neutralized to form a porous silica skeleton, pores satisfying the specific dimensions described above are formed. Moreover, when the skeleton of the porous silica is formed in this way, the tungsten oxide particles are present in a state of being dispersed in the solvent. Therefore, it is possible to combine tungsten oxide with the formed porous silica. It can be done.

  The solvent used in the method for producing a photocatalyst of the present invention is not particularly limited as long as it dissolves the micelle-forming substance and can function as a template for the pores of the photocatalyst. It is preferable to use it. The solvent can be preheated in order to enhance the solubility of the micelle-forming substance.

The tungsten oxide particles used in the method for producing a photocatalyst of the present invention may be particles made of the above-described tungsten oxide. The BET specific surface area of the tungsten oxide particles is not particularly limited, but is preferably 20 to 80 m ² / g. Moreover, the particle diameter of the tungsten oxide particles when dispersed in the solvent is not particularly limited, but the dispersed particle diameter is usually 50 to 200 nm, preferably 80 to 130 nm.
What is necessary is just to set the usage-amount of the said tungsten oxide particle suitably so that content of tungsten oxide in the photocatalyst body finally obtained may become the said range.

The micelle-forming substance used in the method for producing the photocatalyst of the present invention functions as a template when forming micelles in a solvent and forming porous silica. For example, hexadecyltrimethylammonium bromide, chloride Non-ionic interfaces having alkylammonium salts such as hexadecyltrimethylammonium, block copolymers such as poly (ethylene glycol) -poly (propylene glycol) -poly (ethylene glycol) copolymers, and polyoxyethylene-alkyl groups in the skeleton An active agent etc. are mentioned. Among these, block copolymers such as poly (ethylene glycol) -poly (propylene glycol) -poly (ethylene glycol) copolymer are preferably used from the viewpoint of the production process such as cost and foam suppression.
The amount of the micelle-forming substance used may be appropriately set so that the pores of the finally obtained photocatalyst body have desired dimensions. For example, the amount of the micelle-forming substance is based on the oxide equivalent (SiO ₂ ) weight of the silicon compound. The weight ratio is preferably 0.2 to 3 times.

  In preparing a dispersion liquid in which the tungsten oxide particles are dispersed in the solvent and the micelle-forming substance is dissolved (hereinafter also referred to as “micelle-forming substance-containing tungsten oxide particle dispersion liquid”), tungsten oxide is prepared. There are no particular restrictions on the order or method of adding the micelle-forming substances. For example, a dispersion in which tungsten oxide particles are dispersed in a solvent is prepared, and the micelle-forming substance is added and dissolved in the dispersion as it is, or a solution in which the micelle-forming substance is previously dissolved in the solvent is added. Alternatively, a solution in which a micelle-forming substance is dissolved in a solvent is prepared in advance, and tungsten oxide particles are added to the solution in the form of particles (in powder form) and dispersed. May be.

  In addition, an acid or a base may be appropriately added to the micelle-forming substance-containing tungsten oxide particle dispersion for the purpose of promoting or controlling a hydrolysis reaction or a neutralization reaction before adding a silicon compound described later. it can. Examples of the acid used here include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, oxalic acid, acetic acid, formic acid and the like, and examples of the base include ammonia, urea, lithium hydroxide, sodium hydroxide, potassium hydroxide, Examples thereof include cesium hydroxide.

Examples of the silicon compound used in the method for producing a photocatalyst of the present invention include ethyl silicate, methyl silicate, sodium silicate, water glass and the like. Among these, sodium silicate and water glass are preferably used from the viewpoint of cost.
What is necessary is just to set the usage-amount of the said silicon compound suitably so that content of tungsten oxide in the photocatalyst body finally obtained may become the said range.

  The hydrolysis reaction or neutralization reaction of the silicon compound can also proceed by adding the silicon compound to the micelle-forming substance-containing tungsten oxide particle dispersion and stirring at room temperature. It is preferable to heat. By heating, formation of a silica skeleton can be promoted, and porous silica can be easily obtained. In the case of heating, it is usually carried out in a temperature range of 40 ° C. to a supercritical state, but from the viewpoint of cost, it is preferably carried out below the boiling point of the solvent.

Since a solid is present in the reaction product obtained by the hydrolysis or neutralization reaction, the solid is separated from the reaction product by solid-liquid separation, and then subjected to calcination, whereby the photocatalyst of the present invention. Is obtained.
There is no particular limitation on the method for solid-liquid separation of the solid from the reaction product obtained by the hydrolysis reaction or neutralization reaction, and a known method may be adopted as appropriate.
There are no particular limitations on the conditions for firing the solid produced by the hydrolysis reaction or neutralization reaction. For example, the firing temperature is usually 350 ° C. or higher, preferably 450 ° C. or higher, and usually 700 ° C. Hereinafter, it may be set as appropriate within a range of preferably 600 ° C. or less. Moreover, what is necessary is just to set baking time suitably in the range of 1 to 24 hours normally.

  The solid produced by the hydrolysis reaction or neutralization reaction may be subjected to pulverization, if necessary, after solid-liquid separation. This pulverization may be performed before firing or after firing. The pulverization performed here may be dry pulverization that pulverizes in a dry state without adding a liquid such as water, or may be wet pulverization that pulverizes in a wet state by adding a liquid such as water. For pulverization by dry pulverization, for example, a ball mill such as a rolling mill, a vibration ball mill, and a planetary mill, a high-speed rotary pulverizer such as a pin mill, a pulverizer such as a medium agitation mill, and a jet mill can be used. For pulverization by wet pulverization, for example, a pulverizer such as a ball mill, a high-speed rotary pulverizer, a medium stirring mill, and the like can be used.

  In the method for producing a photocatalyst body of the present invention, a treatment for removing a micelle-forming substance can be performed as necessary. Specifically, the removal of the micelle-forming substance may be performed by extracting the micelle-forming substance with an appropriate solvent after the hydrolysis reaction or neutralization reaction, or after separating the solid matter. The solvent may be removed by washing and drying in the range of room temperature to 150 ° C., and then the baking may be performed. At this time, it is needless to say that drying and baking may be continuously performed.

  As described above, the photocatalyst of the present invention can contain a metal component in addition to the main components of tungsten oxide and porous silica. In that case, the metal component is included in the method for producing the photocatalyst of the present invention. It may be added at any stage. For example, a desired metal component may be supported on tungsten oxide particles in advance, or after calcining to obtain a photocatalyst body, it is subsequently impregnated in an aqueous solution in which a compound containing the desired metal component is dissolved. You may make it carry and dry at room temperature-300 degreeC, Preferably it is 60-150 degreeC. Moreover, when carrying | supporting a metal component on a photocatalyst body, a metal component can also be carry | supported by irradiating an ultraviolet light and visible light as needed.

  The organic substance decomposition treatment method of the present invention is a method of decomposing organic substances in a reaction substrate by irradiating light in a state of contact with the photocatalyst of the present invention. According to this, even if the light to irradiate is light of a practical light source such as a fluorescent lamp in which the majority of visible light is used, harmful organic substances contained in the reaction substrate are effectively used for photocatalysis. Can be decomposed and removed (for example, wastewater treatment, sterilization / deodorization treatment, etc.). The photocatalyst of the present invention is formed in the reaction substrate by, for example, a method of forming a photocatalyst film by applying it as a dispersion on the surface of a substrate (for example, glass, plastic, metal, ceramic, concrete, etc.). What is necessary is just to contact with the organic substance.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
In addition, about the measurement of each physical property of the photocatalyst body obtained by the Example and the comparative example, and the evaluation of the photocatalytic activity were performed with the following method.

<BET specific surface area, pore volume>
Using an automatic specific surface area / pore distribution measuring device (“BELSORP-mini” manufactured by Japan BEL), the adsorption isotherm by nitrogen is measured by the nitrogen adsorption method, the BET specific surface area is calculated by the BET multipoint method, and the BJH method Was used to calculate the pore volume on the adsorption side of the adsorption isotherm.
The measurement of the adsorption isotherm was performed under the conditions that the sample (photocatalyst) was pretreated by vacuum degassing at 150 ° C. for 3 hours, then nitrogen was used as the adsorbate, the adsorption temperature was 77K, and the adsorbate cross section was 0.162 nm ² . This was done using the constant volume method below.

<Crystal structure>
The X-ray diffraction spectrum of the sample was measured using an X-ray diffractometer (“RINT2000 / PC” manufactured by Rigaku Corporation), and the crystal structure of the main component was determined from the spectrum.

<Dispersed particle size>
The particle size distribution of the sample is measured using a submicron particle size distribution measuring device (“N4Plus” manufactured by Coulter, Inc.), and the result obtained by performing the monodisperse mode analysis automatically with the software attached to this device is used as the dispersed particle size. did.

<Evaluation of photocatalytic activity>
The photocatalytic activity was evaluated by measuring the first-order rate constant in the decomposition reaction of acetaldehyde under fluorescent lamp irradiation.
First, a sample for evaluating photocatalytic activity was prepared. That is, 0.2 g of the photocatalyst was placed in a glass petri dish having an inner diameter of 60 mm, and a small amount of water was added to form a paste, and then the obtained paste was developed so as to be uniform throughout the petri dish. Subsequently, this petri dish was dried with a dryer at 110 ° C. for 1 hour to prepare a sample for photocatalytic activity evaluation. The obtained sample was initially irradiated with 16 hours of black light (ultraviolet intensity ² mW / cm ² : measured by attaching a UV receiver “UD-36” manufactured by Topcon UV intensity meter “UVR-2”) for 16 hours. It was converted.

Next, this initialized sample for photocatalytic activity evaluation was placed in a sealed glass container (diameter 8 cm, height 10 cm, capacity about 0.5 L) together with the petri dish, and then this container was filled with 20% oxygen and nitrogen. The mixture gas was filled with 80% by volume, and 13.4 μmol of acetaldehyde was further sealed therein. The decomposition reaction of acetaldehyde was performed by irradiating light from a fluorescent lamp from the outside of the container. At this time, the concentration of acetaldehyde in the container was measured over time from the start of the reaction (start of light irradiation with a fluorescent lamp) with a photoacoustic multi-gas monitor (“1312” manufactured by INNOVA). And the first-order rate constant was computed from the density | concentration of the acetaldehyde with respect to irradiation time, and this was evaluated as acetaldehyde resolution | decomposability. It can be said that the higher the first-order reaction rate constant, the higher the acetaldehyde resolution (in other words, the photocatalytic activity).
During the acetaldehyde decomposition reaction, the intensity of light near the sample surface is 470 μW / cm ² for light near the wavelength of 400 nm (the company's light receiving unit “UD-40” is attached to the UV intensity meter “UVR-2” manufactured by Topcon). The light in the vicinity of a wavelength of 360 nm was 40 μW / cm ² (measured by attaching a UV receiver “UD-36” manufactured by Topcon to a UV intensity meter “UVR-2” manufactured by Topcon). In addition, the illuminance near the sample surface was 6000 lux (measured with a Minolta illuminometer “T-10”).

(Example 1)
First, ammonium paratungstate (manufactured by Nippon Inorganic Chemical Co., Ltd.) was fired in air at 700 ° C. for 6 hours to obtain a tungsten oxide powder. 1 kg of this tungsten oxide powder was added to 4 kg of ion-exchanged water and mixed, and the resulting mixture was subjected to a dispersion treatment under the following conditions using a medium stirring type disperser (“Ultra Apex Mill UAM-1 1009” manufactured by Kotobuki Giken Co., Ltd.). As a result, a tungsten oxide particle dispersion was obtained.
Dispersion medium: 1.85 kg of zirconia beads having a diameter of 0.05 mm
Stirring speed: peripheral speed 12.6 m / sec Flow rate: 0.25 L / min Total processing time: about 60 minutes

The dispersion particle diameter of the tungsten oxide particles in the obtained tungsten oxide particle dispersion was 94 nm, and the pH of the dispersion was 2.6. A part of this dispersion was vacuum dried to obtain a solid content. As a result, the BET specific surface area of the obtained solid content was 39 m ² / g, and the solid content concentration of this dispersion was 20% by weight. It was. In addition, when the solid content in the mixture before the dispersion treatment and the solid content in the dispersion liquid after the dispersion treatment were measured and compared with each other, the crystal form was WO ₃ and both were dispersed. There was no change in crystal form due to treatment.

  Next, 4 g of a nonionic surfactant (“Brij56” manufactured by Aldrich) was dissolved in 125 g of water, and 18.39 g of the tungsten oxide particle dispersion obtained above was added and stirred. Next, 8.5 g of high-purity orthoethyl silicate (manufactured by Tama Chemical Industries) was added and stirred at room temperature for 18 hours, and then heated at 80 ° C. for 18 hours. Thereafter, the resulting solid was filtered, washed with water, dried at 80 ° C. for 12 hours, and calcined in air at 500 ° C. for 6 hours to remove organic substances, and formed from tungsten oxide and porous silica. A composite photocatalyst was obtained. The tungsten oxide content in this photocatalyst (composite) was 60% by weight.

The obtained photocatalyst had a pore volume of 0.17 cm ³ / g and a BET specific surface area of 210 m ² / g. Moreover, when this photocatalyst was used for the decomposition reaction of acetaldehyde under fluorescent lamp irradiation and the photocatalytic activity was evaluated, the reaction rate constant was 0.0408 min ⁻¹ .

(Example 2)
In 90 g of water, 4 g of poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (manufactured by Aldrich; number average molecular weight: about 2900) was dissolved and obtained in the same manner as in Example 1. 18.39 g of a tungsten oxide particle dispersion was added and stirred. Next, an aqueous solution obtained by dissolving 11.6 g of sodium metasilicate nonahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) in 36.5 g of water was added, stirred at room temperature for 18 hours, and then heated at 80 ° C. for 18 hours. Thereafter, the resulting solid was filtered, washed with water, dried at 80 ° C. for 12 hours, and calcined in air at 500 ° C. for 6 hours to remove organic substances, and formed from tungsten oxide and porous silica. A composite photocatalyst was obtained. The tungsten oxide content in this photocatalyst (composite) was 60% by weight.

The obtained photocatalyst had a pore volume of 0.19 cm ³ / g and a BET specific surface area of 313 m ² / g. Moreover, when this photocatalyst was used to decompose acetaldehyde under fluorescent lamp irradiation and the photocatalytic activity was evaluated, the reaction rate constant was 0.0394 min ⁻¹ .

(Comparative Example 1)
A photocatalyst, which is a composite formed from tungsten oxide and porous silica, was obtained in the same manner as in Example 1 except that the nonionic surfactant was not used in Example 1. The tungsten oxide content in this photocatalyst (composite) was 60% by weight.

The obtained photocatalyst had a pore volume of 0.13 cm ³ / g and a BET specific surface area of 40 m ² / g. In addition, when this photocatalyst was used to undergo a decomposition reaction of acetaldehyde under fluorescent lamp irradiation and the photocatalytic activity was evaluated, the reaction rate constant was 0.0309 min ⁻¹ .

(Comparative Example 2)
The tungsten oxide particle dispersion obtained in the same manner as in Example 1 was vacuum dried at 70 ° C. for 12 hours to remove moisture, and then the obtained solid was calcined in air at 500 ° C. for 6 hours, A photocatalyst made of tungsten oxide was obtained.

The obtained photocatalyst had a pore volume of 0.11 cm ³ / g and a BET specific surface area of 20 m ² / g. Moreover, when this photocatalyst was used to decompose acetaldehyde under fluorescent lamp irradiation and the photocatalytic activity was evaluated, the reaction rate constant was 0.0386 min ⁻¹ .

  When Examples 1 and 2 were compared with Comparative Example 1, when a tungsten oxide-porous silica composite was produced without using a micelle-forming substance as a template, only a composite having a small BET specific surface area was obtained. It is clear that the photocatalytic activity is significantly inferior to the composite produced using the micelle-forming substance. In addition, when Examples 1 and 2 are compared with Comparative Example 2, the photocatalysts of Examples 1 and 2 contain only 60% of the photocatalyst of Comparative Example 2 but include Comparative Example 2. This indicates that the photocatalytic activity is superior to that of the photocatalyst, and it can be seen that the photocatalytic activity is improved by complexing with porous silica.

Claims (3)

A photocatalyst comprising a composite formed of tungsten oxide and porous silica, having a BET specific surface area of 150 to 800 m ² / g and a pore volume of 0.15 to 1.0 cm ³ / g body.   2. The method of producing a photocatalyst according to claim 1, wherein the tungsten oxide particles are dispersed in a solvent and a substance that forms micelles is dissolved, and then a silicon compound is added to hydrolyze or neutralize the silicon compound. A method for producing a photocatalyst body, comprising firing a solid obtained by summing.   A method for decomposing an organic substance in a reaction substrate by irradiating light in a state of contact with the photocatalyst, wherein the photocatalyst according to claim 1 is used as the photocatalyst. Method.