JP2010017677A - Manufacturing method of photocatalytic body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a photocatalytic body, capable of exhibiting a high photocatalytic activity without need for a special apparatus. <P>SOLUTION: The manufacturing method for the photocatalytic body includes the step of burning a mixture of powder of a photocatalytic body precursor compound and organic particles, each of which has a size of 50 to 200 nm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for producing a photocatalyst having high 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 semiconductor that can exhibit 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, it is also conceivable that electrons generated in the conduction band reduce oxygen, and active oxygen species generated therefrom oxidize and decompose organic matter.

As a method for producing such a photocatalyst, for example, a method of heating an aqueous solution of tungstic acid to 250 ° C. to 300 ° C. in a sealed container has been proposed (see Non-Patent Document 1). However, this method requires special equipment such as equipment that can withstand high temperatures and high pressures.

Journal of Materials Chemistry, 2001,11,3222-3227.

Therefore, the present inventors have intensively studied to provide a method for producing a photocatalyst that can exhibit high photocatalytic activity without requiring a special apparatus, and as a result, have reached the present invention.

That is, the present invention has the following configuration.
(1) A method for producing a photocatalyst, comprising firing a mixture of a photocatalyst precursor compound powder and organic particles having a particle size of 50 nm to 200 nm.

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

Examples of the photocatalyst used in the method for producing a photocatalyst of the present invention include tungsten oxide and titanium oxide. When the photocatalyst is tungsten oxide, the precursor compound of the photocatalyst, ammonium metatungstate, ammonium paratungstate, tungstic acid (H ₂ WO _4), tungsten chloride, it can be used such as tungsten alkoxides. When the photocatalyst is titanium oxide, titanium trichloride, titanium tetrachloride, titanium sulfate, titanium oxysulfate, titanium oxychloride, titanium tetraisoporopoxide, etc. can be used as the precursor compound of the photocatalyst. . Tungsten oxide is preferably used as the photocatalyst because it exhibits high photocatalytic activity under visible light irradiation.

When the photocatalyst obtained in the present invention is tungsten oxide, the primary particle diameter is 15 nm or more and 85 nm or less. When the primary particle diameter is less than 15 nm, the crystallinity of tungsten oxide becomes insufficient and high photocatalytic activity cannot be obtained. On the other hand, when it exceeds 85 nm, the amount of the reaction substrate adsorbed on the surface of tungsten oxide decreases, and high photocatalytic activity cannot be obtained. The primary particle diameter can be calculated from the BET specific surface area as described in the examples.

The crystallization rate of tungsten oxide is 50%. When the crystallization rate is less than 50%, high photocatalytic activity cannot be obtained because of insufficient crystallinity. As described in the examples, the crystallization rate is determined by the peak intensity of the plane index (002), (020), (200) plane and the standard of tungsten oxide in the pattern obtained by the X-ray diffraction measurement of tungsten oxide. It is a value (%) obtained by taking the ratio of the peak intensities of the samples and multiplying the average value of the three obtained peak intensity ratios by 100.

In the method for producing a photocatalyst of the present invention, organic particles having a particle size of 50 nm to 200 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.

In the production method of the present invention, a mixture of the photocatalyst precursor compound powder and the organic particles is baked. Such a mixture can be obtained, for example, by bringing a solution in which a photocatalyst precursor compound is dissolved in a solvent into contact with organic particles, impregnating the organic particles with the photocatalyst precursor compound, and then distilling off the solvent. The powdery photocatalyst precursor compound and the organic particles may be mixed in a powder state. After the photocatalyst precursor compound and the organic particles are dispersed in the solvent, the solvent may be distilled off.

The organic particles may be used in a dried state or in a colloidal form moistened with water to some extent. Moreover, you may dry the mixture before baking in the range of room temperature-200 degreeC.

The solvent for dispersing or dissolving the photocatalyst precursor compound is not particularly limited as long as it can disperse or dissolve the photocatalyst precursor compound and does not dissolve the organic particles, but water, methanol, ethanol, propanol It is preferable to use an alcohol such as

In the production method of the present invention, such a mixture is baked. By firing, the organic particles are burned away. 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 350 ° C. or higher, preferably 380 ° C. or higher, and usually 750 ° C. or lower, preferably 650 ° 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 photocatalyst body 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 photocatalyst 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 the photocatalyst of the present invention. For example, the precursor compound of the photocatalyst may be loaded with a desired metal component in advance, or after calcination to obtain a photocatalyst, the solution is subsequently dissolved 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 the metal component is supported on the photocatalyst, the photocatalyst and the precursor of the metal component are dispersed in water containing methanol or the like as necessary, and the metal is 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 the photocatalyst is irradiated with light having a wavelength that can be photoexcited, the precursor is reduced by the electrons generated by photoexcitation and supported on the surface of the photocatalyst particles 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 the photocatalyst. 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. 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.

When the photocatalyst obtained in the present invention 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 photocatalyst 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 photocatalyst. 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. 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.

2. Measurement of primary particle diameter of tungsten oxide particles The primary particle diameter of tungsten oxide particles was determined from the BET specific surface area. When the value of the BET specific surface area of the powder is S (m ² / g) and the density of the particles is ρ (g / cm ³ ), the primary particle diameter d (μm) is an equation of d = 6 / (S × ρ). Calculated by However, the primary particle diameter d is a diameter when the particles are spherical. The density of the tungsten oxide particles (WO ₃ ) was 7.16 g / cm ³ .

3. 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.

4). Crystal phase, tungsten oxide crystallization rate (%):
Measurement was performed using an X-ray diffractometer (trade name “Rigaku RINT ULTIMA” or “Rigaku MiniFlex2”, manufactured by Rigaku Corporation). The X-ray diffraction spectrum of the sample was measured, and the crystal phase was determined from the spectrum. In addition, for this spectrum, peak heights I _sa , I _sb , I _sc of the interference lines derived from the surface indices (002), (020), (200) of tungsten oxide (WO ₃ ) are obtained, and these are obtained in the standard sample. Average value (((I _sa / I _ra ) + (I _sb / I _rb ) + (I _sc / I _rc )) of the ratio of the peak heights (I _ra , I _rb , I _rc ) of the interference line having the same plane index ) × 100/3) was defined as the crystallization rate (%) of tungsten oxide. Note that tungsten oxide (manufactured by High Purity Chemical) was used as a standard sample, and the tungsten oxide crystallinity was set to 100%. When the value of crystallinity exceeded 100%, it was set to 100%.

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. A xenon lamp (300 W, manufactured by Cermax) equipped with an ultraviolet cut filter (L-42, manufactured by Asahi Techno Glass) was used as the light source.

6). Synthesis of spherical polymethyl methacrylate having an average particle size of 145 nm In a 5 L glass reaction vessel, 250 parts by weight of water, 1.5 parts by weight of sodium carbonate, 4.7 parts by weight of sodium dodecylbenzenesulfonate (15 wt%), peroxodisulfuric acid 0.06 part by weight of sodium was added, and 61.5 parts by weight of methyl methacrylate was continuously added over 60 minutes at 80 ° C. with stirring in a nitrogen atmosphere, and further aged at the same temperature for 60 minutes while stirring. Thus, a polymer latex was obtained. To this hard polymer latex, an aqueous solution consisting of 12 parts by weight of water and 0.06 part by weight of sodium peroxodisulfate was added and stirred, and then 61.5 parts by weight of methyl methacrylate was continuously added at 80 ° C. for 60 minutes. And then aged for 60 minutes at the same temperature with stirring to obtain a polymer latex. Moreover, the solid content concentration in the latex determined by the gravimetric method was 31%. This polymer latex was frozen in a freezer at −20 ° C. for 24 hours and then melted to aggregate the polymer particles. This agglomerated slurry was dehydrated using a centrifuge at 1500 rpm (470 G) for 10 minutes, and the resulting polymer wet cake was dried in a vacuum dryer at 80 ° C. for 24 hours to obtain an average particle size of 145 nm. Dry particles of spherical polymethyl methacrylate were obtained.

7). Synthesis of spherical polymethyl methacrylate having an average particle size of 180 nm 1.6 g of potassium peroxodisulfate (manufactured by Katayama Chemical Co., Ltd., reagent grade) and 780 mL of water are placed in a 1 L four-necked round bottom flask. 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. 20 mL of methyl methacrylate monomer (manufactured by Wako Pure Chemicals, special grade of reagent) was dissolved therein and reacted for 45 minutes. 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 diameter of 180 nm.

8). 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
2.5mol a polymethyl methacrylate powder 6.0g of spherical particle size 145 nm, ammonium metatungstate (aqueous solution at a concentration of 50 wt% as WO _3, Nippon Inorganic Color & Chemical Co., Ltd.) as a mixed solution (tungsten oxide of methanol / L) 12.4 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 400 ° C. at 1 ° C. per minute in the air, and then baked at this temperature for 5 hours to remove spherical polymethyl methacrylate and obtain tungsten oxide particles. The tungsten oxide particles had a BET specific surface area of 30 m ² / g, from which it was found that the primary particle diameter was 28 nm. The crystallization rate of the tungsten oxide particles was 59%.

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 while stirring. A xenon lamp (300 W, manufactured by Cermax) equipped with an ultraviolet cut filter (L-42, manufactured by Asahi Techno Glass) was used as the light source. 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.

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 51 μmol / h.

Example 2
Tungsten oxide particles were obtained in the same manner as in Example 1 except that firing was performed at 450 ° C. The tungsten oxide particles had a BET specific surface area of 21 m ² / g, and the primary particle diameter was found to be 40 nm. The crystallization rate of the tungsten oxide particles was 68%. 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.

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 58 μmol / h.

Example 3
Tungsten oxide particles were obtained in the same manner as in Example 1 except that firing was performed at 500 ° C. The tungsten oxide particles had a BET specific surface area of 14 m ² / g, and the primary particle diameter was found to be 60 nm. The crystallization rate of the tungsten oxide particles was 97%. 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.

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 39 μmol / h.

Example 4
100 mL of latex containing spherical polymethyl methacrylate having an average particle size of 180 nm was sedimented by centrifugation at 2500 rpm for 2 hours and naturally dried for 2 days to obtain a colloidal crystal template. Using sieve screen, 2.5 mol after sizing the particles of 425Myuemu～2mm, ammonium metatungstate (aqueous solution at a concentration of 50 wt% as WO _3, Nippon Inorganic Color & Chemical Co., Ltd.) as a mixed solution (tungsten oxide of methanol / 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 subsequently fired at this temperature for 5 hours to remove spherical polymethyl methacrylate and obtain tungsten oxide particles. The tungsten oxide particles had a BET specific surface area of 21 m ² / g, and the primary particle diameter was found to be 40 nm. The crystallization rate of the tungsten oxide particles was 89%. 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.

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 34 μmol / h.

Example 5
Tungsten oxide particles were obtained in the same manner as in Example 1 except that firing was performed at 600 ° C. The tungsten oxide particles had a BET specific surface area of 11 m ² / g, and the primary particle diameter was found to be 76 nm. The crystallization rate of the tungsten oxide particles was 100%. 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.

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 43 μmol / h.

Comparative Example 1
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. Using sieve screen, 2.5 mol after sizing the particles of 2Mm～425myuemu, ammonium metatungstate (aqueous solution at a concentration of 50 wt% as WO _3, Nippon Inorganic Color & Chemical Co., Ltd.) as a mixed solution (tungsten oxide of methanol / 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 subsequently fired at this temperature for 5 hours to remove spherical polymethyl methacrylate and obtain tungsten oxide particles. The tungsten oxide particles had a BET specific surface area of 9.2 m ² / g, and from this, it was found that the primary particle diameter was 91 nm. The crystallization rate of the tungsten oxide particles was 61%. 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.

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 2
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 400 ° C. at 1 ° C./min in the air, and then baked at this temperature for 5 hours to obtain tungsten oxide particles. The tungsten oxide particles had a BET specific surface area of 1.4 m ² / g, and from this, the primary particle diameter was found to be 599 nm. The crystallization rate of the tungsten oxide particles was 27%. 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.

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 2.8 μmol / h.

Comparative Example 3
Tungsten oxide particles were obtained in the same manner as in Comparative Example 2 except that the firing was performed at 500 ° C. The tungsten oxide particles had a BET specific surface area of 2.0 m ² / g, and the primary particle diameter was found to be 419 nm. The crystallization rate of the tungsten oxide particles was 44%. 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.

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.

Comparative Example 4
Tungsten oxide particles were obtained in the same manner as in Comparative Example 2 except that the firing was performed at 600 ° C. The tungsten oxide particles had a BET specific surface area of 1.7 m ² / g, and from this, it was found that the primary particle diameter was 493 nm. The crystallization rate of the tungsten oxide particles was 46%. 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.

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 4.7 μmol / h.

Comparative Example 5
Tungsten oxide particles were obtained in the same manner as in Comparative Example 2 except that the firing was performed at 700 ° C. The tungsten oxide particles had a BET specific surface area of 2.3 m ² / g, and the primary particle diameter was found to be 364 nm. The crystallization rate of the tungsten oxide particles was 44%. 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.

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 6.8 μmol / h.

Claims (1)

A method for producing a photocatalyst comprising calcining a mixture of a powder of a photocatalyst precursor compound and organic particles having a particle size of 50 nm to 200 nm.