JP2010018503A - Tungsten oxide exhibiting high photocatalytic activity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide tungsten oxide which exhibits higher photocatalytic activity. <P>SOLUTION: The tungsten oxide includes: bar-shaped parts with an almost columnar shape; and knot parts in which a plurality of the bar-shaped parts are coupled at the edge parts thereof, and has a structure where the bar-shaped parts and the knot parts compose one single crystal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to tungsten oxide exhibiting high photocatalytic activity.

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 a substance showing this photocatalytic action is called a photocatalyst. By utilizing such photocatalytic action, organic substances in the atmosphere can be decomposed. In the decomposition reaction of organic substances by photocatalysts, it is thought that holes generated in the valence band directly oxidize and decompose organic substances, or holes oxidize water and active oxygen species generated from them oxidize and decompose organic substances. In addition to this, it is considered that electrons generated in the conduction band reduce oxygen, and active oxygen species generated therefrom oxidatively decompose organic matter.

Tungsten oxide is known as a substance that exhibits a photocatalytic action by visible light.

As a photocatalyst made of tungsten oxide, for example, one obtained by firing ammonium metatungstate in the air is known (see Non-Patent Document 1).

However, as tungsten oxide exhibiting a photocatalytic action, one that exhibits higher photocatalytic activity is desired.

Applied Catalysis A: General, 210,2001,181-191.

Therefore, the present inventors have intensively studied to obtain tungsten oxide exhibiting higher photocatalytic activity, and as a result, have reached the present invention.

That is, the present invention has the following configuration.
(1) It has a structure in which a columnar part and a plurality of the columnar parts are joined at the ends thereof, and the columnar part and the connecting part constitute one single crystal. Tungsten oxide.
(2) Consisting of tungsten oxide of (1) above, the cumulative pore volume when measured by the mercury intrusion method is 1 mL / g to 5 mL / g, and the average pore radius is 0.1 μm to 0.3 μm , photocatalyst BET specific surface area of ^5g / ^{m 2 ~40g} / m 2 when measured by the nitrogen adsorption method.
(3) A method for decomposing an organic substance by irradiating light in a state of contact with the photocatalyst, wherein the organic substance is decomposed using the photocatalyst described in (2) as the photocatalyst.

According to the present invention, a photocatalyst that can exhibit high photocatalytic activity can be provided.

The tungsten oxide of the present invention has a structure having a columnar part and a node part.
The columnar portion may have a columnar shape with a constant diameter, or may have a shape in which the diameter gradually increases from the intermediate portion toward both end portions. The cross-sectional shape is generally circular, but may be flat. The diameter of the columnar portion is approximately 20 nm to 100 nm, and the length is approximately 30 nm to 200 nm.

A plurality of columnar portions are joined to the node portion at their end portions. The diameter of the node is usually approximately equal to or larger than the diameter at the end of the joined rod-like portion, and is generally 30 nm to 120 nm. The plurality of rod-like portions joined at the node are usually joined to the node from directions that do not face each other.

In such a structure, the columnar portions are usually coupled to separate nodes at both ends, and there is a gap between the columnar portions. In addition, a node portion in which a plurality of columnar portions are coupled appears repeatedly.

The columnar portion and the node portion constitute one single crystal. In the tungsten oxide of the present invention, since the columnar portion and the node portion constitute one single crystal, for example, when the columnar portion and the node portion to which the columnar portion is bonded are observed with a transmission electron microscope (TEM), the columnar portion. The checkerboard pattern observed at the point is connected to the node without interruption. When the columnar part and the node part are each irradiated with an electron beam by TEM to obtain an electron beam diffraction image, a diffraction pattern having the same pattern is shown.

Part of the tungsten oxide of the present invention may have the above structure, but the whole preferably has the above structure.

The tungsten oxide of the present invention has a structure in which the columnar portions are joined at the ends thereof, and therefore has a large specific surface area, and the columnar portions and the nodes constitute one single crystal. For example, holes generated in the valence band of the columnar part and electrons generated in the conduction band easily move to the node part and further to the columnar part coupled to the node part, so that high photocatalytic activity is achieved. It is thought that it shows.

The photocatalyst of the present invention is made of such tungsten oxide, and has a cumulative pore volume of 1 to 5 mL / g as measured by mercury porosimetry. If the pore volume is less than 1 mL / g, the amount of adsorption of the reaction substrate will be reduced, and high photocatalytic activity will not be obtained. On the other hand, if it exceeds 5 mL / g, the substance that forms pores used during production In general, it is necessary to use a large amount of spherical organic particles, which are generally expensive, and an effect sufficient to meet the cost cannot be obtained. Preferably, the lower limit of the pore volume is 1.5 mL / g or more, and the upper limit is 3 mL / g or less.

This photocatalyst has an average pore radius of 0.1 to 0.3 μm as measured by mercury porosimetry. When the average pore radius is less than 0.1 μm, the amount of the reaction substrate adsorbed decreases, and high photocatalytic activity cannot be obtained. On the other hand, when the average pore radius exceeds 0.3 μm, the porous structure of the tungsten oxide particles collapses and high photocatalytic activity cannot be obtained. Preferably, the lower limit of the average pore diameter is 0.12 μm or more, and the upper limit is 0.25 μm or less.

Furthermore, the BET specific surface area of the tungsten oxide particles of the present invention is 5 to 40 m ² / g. If the BET specific surface area is less than 5 m ² / g, the amount of adsorption of the reaction substrate will be reduced, and high photocatalytic activity will not be obtained. On the other hand, if it exceeds 40 m ² / g, the tungsten oxide particle size will be reduced. Therefore, the crystallinity is lowered, so that high photocatalytic activity cannot be obtained. Preferably, the lower limit of the BET specific surface area is 8 m ² / g or more, and the upper limit is 25 m ² / g or less. In addition, the BET specific surface area of the tungsten oxide particles in the present invention can be measured by a nitrogen adsorption method.

The photocatalyst of the present invention can be produced by a method in which organic particles are impregnated with a solution in which a tungsten oxide precursor compound is dissolved and then baked. The organic particles may be used in a dried state or in a colloidal form moistened with water to some extent. Moreover, before baking, the solid substance isolate | separated from the solvent can also be dried in the range of room temperature-200 degreeC.

As a precursor compound of tungsten oxide, ammonium metatungstate, ammonium paratungstate, tungstic acid (H ₂ WO ₄ ), tungsten chloride, tungsten alkoxide, or the like can be used. Among these, it is preferable to use ammonium metatungstate because it is easily dissolved in water.

In the method for producing tungsten oxide particles of the present invention, organic particles having a particle size of 220 nm to 600 nm are used. As the organic particles, polymethyl methacrylate, polycarbonate, polystyrene, polyester, polyimide, epoxy resin, walnuts and the like can be used. Among these, polymethyl methacrylate is preferably used.

The solvent used in the method for producing tungsten oxide particles of the present invention is not particularly limited as long as it dissolves the precursor compound of tungsten oxide and does not dissolve the organic particles, but water, methanol, ethanol, propanol, etc. The alcohol is preferably used.

In the production method of the present invention, the organic particles are removed by baking. Usually, it can carry out using baking apparatuses, such as an airflow baking furnace, a tunnel furnace, and a rotary furnace. The firing temperature may be appropriately set within the range of usually 400 ° C. or higher, preferably 430 ° C. or higher, and usually 850 ° C. or lower, preferably 800 ° C. or lower. The firing time may be appropriately set according to the firing temperature, the type of firing apparatus, etc., but is usually 10 minutes or longer, preferably 30 minutes or longer, and within 30 hours, preferably within 10 hours. is there. Firing is performed in an atmosphere containing a sufficient amount of oxygen to burn off organic particles.

You may grind | pulverize the tungsten oxide obtained by the manufacturing method of this invention. 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.

The tungsten oxide of the present invention may contain a metal component. In this case, the metal component may be added at any stage in the method for producing tungsten oxide of the present invention. For example, a precursor metal compound of tungsten oxide may be loaded with a desired metal component in advance, or after firing to obtain tungsten oxide, it is subsequently placed in an aqueous solution in which the compound containing the desired metal component is dissolved. It may be impregnated and supported and dried at room temperature to 200 ° C, preferably 60 to 150 ° C. When supporting the metal component on tungsten oxide, if necessary, the tungsten oxide and the precursor of the metal component are dispersed in water containing methanol and the like, and then irradiated with ultraviolet light or visible light. Components can also be supported.
By performing light irradiation, the precursor can be converted into a metal component. When light having a wavelength capable of photoexcitation of tungsten oxide is irradiated, the precursor is reduced by the electrons generated by photoexcitation and supported on the surface of the tungsten oxide particle as a metal.

Examples of such metal components include metals such as Cu, Pt, Au, Pd, Ag, Fe, Nb, Ru, Ir, Rh, and Co, preferably Cu, Pt, Au, Pd, and the like. Also included are oxides and hydroxides of these metals.

The precursor of the metal component is a compound that can transition to a metal on the surface of tungsten oxide. Examples of the precursor include nitrates, sulfates, halides, organic acid salts, carbonates, and phosphates of the above metals. Specifically, for example, as a precursor of Cu, copper nitrate (Cu (NO ₃ ) ₂ ), copper sulfate (Cu (SO ₄ ) ₂ ), copper chloride (CuCl ₂ , CuCl), copper bromide (CuBr ₂ , CuBr), copper iodide (CuI), copper iodate (CuI ₂₎ O ₆ ), ammonium copper chloride (Cu (NH ₄ ) ₂ Cl ₄ ), copper oxychloride (Cu ₂ Cl (OH) ₃ ), copper acetate (CH ₃ COOCu, (CH ₃ COO) ₂ Cu), copper formate ( (HCOO) ₂ Cu), copper carbonate (CuCO ₃ ), copper oxalate (CuC ₂ O ₄ ), copper citrate (Cu ₂ C ₆ H ₄ O ₇ ), copper phosphate (CuPO ₄ ) and the like. As precursors of Pt, platinum chloride (PtCl ₂ , PtCl ₄ ), platinum bromide (PtBr ₂ , PtBr ₄ ), platinum iodide (PtI ₂ , PtI ₄ ), platinum chloride potassium (K ₂ (PtCl ₄ )) , Hexachloroplatinic acid (H ₂ PtCl ₆ ), platinum sulfite (H ₃ Pt (SO ₃ ) ₂ OH), platinum oxide (PtO ₂ ), tetraammineplatinum chloride (Pt (NH ₃ ) ₄ Cl ₂ ), tetraammineplatinum bicarbonate (C ₂ H ₁₄ N ₄ O ₆ Pt), tetraammineplatinum hydrogen phosphate (Pt (NH ₃ ) ₄ HPO ₄ ), tetraammineplatinum hydroxide (Pt (NH ₃ ) ₄ (OH) ₂ ), tetraammineplatinum nitrate (Pt (NO ₃ ) ₂ (NH ₃ ) ₄ ), tetraammineplatinum tetrachloroplatinum ((Pt (NH ₃ ) ₄ ) (PtCl ₄ )) and the like can also be mentioned. As a precursor of Au, gold chloride (AuCl), gold bromide (AuBr), gold iodide (AuI), gold hydroxide (Au (OH) ₂ ), tetrachloroauric acid (HAuCl ₄ ), tetrachlorogold Examples thereof include potassium acid (KAuCl ₄ ), potassium tetrabromoaurate (KAuBr ₄ ), and gold oxide (Au ₂ O ₃ ). Pd precursors include palladium acetate ((CH ₃ COO) ₂ Pd), palladium chloride (PdCl ₂ ), palladium bromide (PdBr ₂ ), palladium iodide (PdI ₂ ), palladium hydroxide (Pd ( OH) ₂ ), palladium nitrate (Pd (NO ₃ ) ₂ ), palladium oxide (PdO), palladium sulfate (PdSO ₄ ), potassium tetrachloropalladate (K ₂ (PdCl ₄ )), potassium tetrabromopalladate (K ₂ (PdBr ₄ )) and the like.

These metal components and their precursors are used alone or in combination of two or more.

When using such a metal component or a precursor thereof, the amount used is usually 0.005 to 0.6 parts by mass, preferably 0.005 parts by mass in terms of metal atoms with respect to 100 parts by mass of the total amount of tungsten oxide particles. 01 parts by mass to 0.4 parts by mass. When the amount used is less than 0.005 parts by mass, the photocatalytic activity is not sufficiently improved by using the metal component, and when it exceeds 0.6 parts by mass, the photocatalytic action tends to be insufficient.

The photocatalyst made of tungsten oxide produced as described above exhibits high catalytic activity when irradiated with visible light, which occupies most of the indoor light. Therefore, harmful organic substances contained in the reaction substrate (for example, In addition, it is possible to efficiently decompose and remove malodorous substances in the atmosphere, organic solvents in water, agricultural chemicals, surfactants, and the like.

When applying the photocatalyst of the present invention to decomposition and removal of organic matter, it can be used as it is. However, if necessary, it can be mixed with various additives, made into a dispersion (coating liquid), or molded. May be used.

When the photocatalyst is mixed with various additives, it is preferable to select an additive that can further improve the adsorptivity and photocatalytic activity of the photocatalyst. Examples of such additives include amorphous silica, silica sol, water glass, silicon compounds such as organopolysiloxane, amorphous alumina, alumina sol, aluminum compounds such as aluminum hydroxide, zeolite, and kaolinite. Alkaline earth metal (hydroxide) oxides such as aluminosilicate, magnesium oxide, calcium oxide, strontium oxide, barium oxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide, calcium phosphate, molecular sieve , Activated carbon, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu, Ag, Au Zn, Cd, Ga, In, Tl, Ge, Sn, Pb, Bi, La, C Hydroxides of these metal elements, oxides of these metal elements, polycondensates of organic polysiloxane compounds, phosphates, fluoropolymers, silicone polymers, acrylic resins, polyester resins, melamine resins, urethanes Examples thereof include resins and alkyd resins. These additives may be used alone or in combination of two or more.

When the photocatalyst is used as a dispersion, the tungsten oxide obtained by the production method of the present invention may be dispersed in an organic solvent such as water or alcohol. At that time, a dispersant may be added as necessary for the purpose of improving the dispersibility of the tungsten oxide. Furthermore, a known inorganic binder or organic binder can be added as necessary for the purpose of improving the adhesion to the substrate when it is formed into a coating film. Such dispersions (coating liquids) include, for example, fluorescent lights, halogen lamps, xenon lamps, light emitting diodes, solar rays, and the like that contain a lot of visible light, such as walls, wallpaper, ceilings, window glass, tiles, and automobile interior parts. It is applied where irradiation is possible.

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 in an Example and a comparative example, and the evaluation of the photocatalytic activity, it performed with the following method.

1. Observation of the particle shape of tungsten oxide The particle shape of tungsten oxide is observed using a scanning electron microscope (SEM, JSM-7400F, manufactured by JEOL) and a transmission electron microscope (TEM, JEM-2000FX, manufactured by JEOL). I went.

2. Cumulative pore volume and average pore radius The cumulative pore volume and the average pore radius of the tungsten oxide particles were measured by mercury porosimetry with "Autopore III9420" (manufactured by MICROMERITICS).

3. BET specific surface area The BET specific surface area of the tungsten oxide particles was measured by “NOVA1200e” (manufactured by Yuasa Ionics) by the nitrogen adsorption method.

4). Particle size measurement of polymethyl methacrylate The particle size of polymethyl methacrylate was measured by “DLS-7000” (manufactured by Otsuka Electronics Co., Ltd.) by a dynamic scattering method.

5). Decomposition of acetic acid (under visible light irradiation)
On the bottom of a glass container (capacity 330 mL), 50 mg of particulate photocatalyst was spread to 15 mm × 15 mm, the inside of the glass container was filled with synthetic air, and 14.7 μmol of acetic acid was further injected. The sample was allowed to stand for 1 hour in the dark and then irradiated with visible light. Acetaldehyde was decomposed by photocatalysis, and the concentration of carbon dioxide as a complete decomposition product was quantified by gas chromatography. As the light source, a xenon lamp (300 W, manufactured by Cermax) equipped with an ultraviolet cut filter (L-42, manufactured by Asahi Techno Glass Co., Ltd.) was used.

6). Synthesis of spherical polymethyl methacrylate having an average particle size of 260 nm 100 mL of methyl methacrylate monomer (manufactured by Wako Pure Chemicals, special grade of reagent) and 400 mL of water are placed in a 1 L four-necked round bottom flask, to which an electric stirrer and argon gas are supplied A pipette and a thermometer were attached, and the mixture was heated to about 80 ° C. while stirring in an oil bath at a stirring speed of 350 rpm. After the temperature reached equilibrium, bubbling with argon gas was performed for 30 minutes. As an initiator, 3 mL of water in which 0.38 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemicals, reagent grade 1) was dissolved was added and reacted for 2 hours. After the reaction, the four-necked flask was allowed to cool at room temperature to obtain a latex containing spherical polymethyl methacrylate having an average particle size of 260 nm.

7). Synthesis of spherical polymethyl methacrylate having an average particle size of 490 nm Methyl methacrylate monomer (manufactured by Wako Pure Chemicals, special grade of reagent) 150 mL and water 350 mL are placed in a 1 L four-necked round bottom flask, to which an electric stirrer and argon gas are supplied A pipette and a thermometer were attached, and the mixture was heated to about 70 ° C. while stirring in an oil bath at a stirring speed of 350 rpm. After the temperature reached equilibrium, bubbling with argon gas was performed for 30 minutes. As an initiator, 3 mL of water in which 0.38 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride (manufactured by Wako Pure Chemicals, reagent grade 1) was dissolved was added as an initiator and reacted for 6 hours. It was. After the reaction, the four-necked flask was allowed to cool at room temperature to obtain a latex containing spherical polymethyl methacrylate having an average particle size of 490 nm.

Example 1
100 mL of latex containing spherical polymethyl methacrylate having an average particle size of 260 nm was sedimented by centrifugation at 2500 rpm for 2 hours and naturally dried for 2 days to obtain a colloidal crystal template. After sizing into particles of 425 μm to 2 mm using a screen sieve, a mixed solution of ammonium metatungstate (50 wt% aqueous solution as WO ₃ manufactured by Nippon Inorganic Chemical Industries) and methanol (2.5 mol as tungsten oxide) / L) 7.3 mL was added and impregnated for 3 hours. Thereafter, the particles were collected by suction filtration and dried overnight at room temperature. The obtained powder was heated to 500 ° C. at 1 ° C./min in the air, and then baked at this temperature for 5 hours to remove spherical polymethyl methacrylate and to have a BET specific surface area of 16 m ² / g tungsten oxide particles were obtained.

0.5 g of the obtained tungsten oxide particles are dispersed in 50 mL of water, and an aqueous hexachloroplatinic acid solution having a concentration of 0.019 mol / L so that Pt is 0.5 parts by weight with respect to 100 parts by weight of the tungsten oxide particles ( H ₂ PtCl ₆ ) was added and irradiated with visible light for 2 hours with stirring. As the light source, a xenon lamp (300 W, manufactured by Cermax) equipped with an ultraviolet cut filter (“L-42”, manufactured by Asahi Techno Glass Co., Ltd.) was used. Thereafter, 5 mL of methanol was added to the above dispersion of tungsten oxide particles, and irradiation with visible light was performed for 2 hours in the same manner as described above while stirring. Thereafter, filtration, washing with water, and drying at 120 ° C. yielded particulate Pt-supported tungsten oxide particles.
When the Pt-supported tungsten oxide particles were measured by mercury porosimetry, the cumulative pore volume was 2.48 mL / g and the average pore radius was 0.15 μm.

Moreover, when this Pt carrying | support tungsten oxide particle was observed by SEM, it turned out that it has a porous structure as shown in FIG. Furthermore, when observed with TEM, it has the shape shown in FIG. 2, and as a result of electron beam diffraction, the same pattern is observed from 5 points (1st to 5th) out of 6 measurement spots, In addition, as shown in the TEM photograph of FIG. 3, the lattice fringes were observed without interruption at curved locations. From this, it was found that the Pt-supported tungsten oxide particles having a bowl-like shape are not a series of fine particles, but the particles themselves are composed of one single crystal.

The resulting Pt-supported tungsten oxide particles were used for the decomposition reaction of acetic acid under visible light irradiation. The production rate of carbon dioxide was 19 μmol / h.

Example 2
100 mL of latex containing spherical polymethyl methacrylate having an average particle size of 490 nm was sedimented by centrifugation at 2500 rpm for 2 hours and naturally dried for 2 days to obtain a colloidal crystal template. After sizing into particles of 425 μm to 2 mm using a mesh sieve, a mixed solution of ammonium metatungstate (50 wt% aqueous solution as WO3, manufactured by Nippon Inorganic Chemical Industries) and methanol (2.5 mol / wt as tungsten oxide) L) 7.3 mL was added and impregnated for 3 hours. Thereafter, the particles were collected by suction filtration and dried overnight at room temperature. The obtained powder was heated to 500 ° C. at 1 ° C./min in the air, and then baked at this temperature for 5 hours to remove spherical polymethyl methacrylate and to have a BET specific surface area of 9.2 m. ² / g tungsten oxide particles were obtained. Thereafter, Pt was supported on the tungsten oxide particles in the same manner as in Example 1 to obtain particulate Pt-supported tungsten oxide particles. When the Pt-supported tungsten oxide particles were measured by a mercury intrusion method, the cumulative pore volume was 2.05 mL / g, and the average pore radius was 0.20 μm.

Moreover, when this Pt carrying | support tungsten oxide particle was observed by SEM, it turned out that it is a porous structure as shown in FIG. Further, when observed with a TEM, the Pt-supported tungsten oxide particles have a shape as shown in FIG. 5 and the same pattern was observed from all five measurement spots as a result of electron diffraction. Thus, it was found that the particles themselves are not composed of a series of fine particles but are composed of one single crystal.

The resulting Pt-supported tungsten oxide particles were used for the decomposition reaction of acetic acid under visible light irradiation. The production rate of carbon dioxide was 8.6 μmol / h.

Comparative Example 1
Ammonium metatungstate (aqueous solution at a concentration of 50 wt% as WO _3, Nippon Inorganic Color & Chemical Co., Ltd.) dried overnight at 90 ° C., the resulting powder was ground in a mortar to obtain a dry powder. The obtained powder was heated to 500 ° C. at 1 ° C./min in the air, and then baked at this temperature for 5 hours to obtain tungsten oxide particles having a BET specific surface area of 2.0 m ² / g. . Thereafter, Pt was supported on the tungsten oxide particles in the same manner as in Example 1 to obtain particulate Pt-supported tungsten oxide particles. When the Pt-supported tungsten oxide particles were measured by a mercury intrusion method, the cumulative pore volume was 0.17 mL / g, and the average pore radius was 0.086 μm. Moreover, when this Pt carrying | support tungsten oxide particle was observed by SEM, it turned out that it does not have a porous structure as shown in FIG. Further, when observed with TEM, it had a shape as shown in FIG. 7, and as a result of electron beam diffraction, it was found to be an aggregate of fine particles.

The resulting Pt-supported tungsten oxide particles were used for the decomposition reaction of acetic acid under visible light irradiation. The production rate of carbon dioxide was 3.4 μmol / h.

2 is a SEM photograph of Pt-supported tungsten oxide particles obtained in Example 1. 2 is a TEM photograph of Pt-supported tungsten oxide particles obtained in Example 1. FIG. 2 is a TEM photograph of Pt-supported tungsten oxide particles obtained in Example 1. FIG. 4 is a SEM photograph of Pt-supported tungsten oxide particles obtained in Example 2. 4 is a TEM photograph of Pt-supported tungsten oxide particles obtained in Example 2. 4 is a SEM photograph of Pt-supported tungsten oxide particles obtained in Comparative Example 1. 4 is a TEM photograph of Pt-supported tungsten oxide particles obtained in Comparative Example 1.

Claims (3)

An oxidation comprising: a columnar part; and a node part in which a plurality of the columnar parts are joined at an end thereof, wherein the columnar part and the connecting part form a single crystal. tungsten. A tungsten adsorption method comprising the tungsten oxide of claim 1, having a cumulative pore volume of 1 mL / g to 5 mL / g when measured by a mercury intrusion method, an average pore radius of 0.1 μm to 0.3 μm, photocatalyst BET specific surface area of 5g / m ² ~40g / m ² when in measured A method for decomposing an organic substance by irradiating light in a state of contact with the photocatalyst, wherein the photocatalyst according to claim 2 is used as the photocatalyst.