Photocatalyst and method of manufacturing the same

The present invention relates to a photocatalyst and a method for producing the same.

Metal oxides such as titanium oxide, tin oxide, and zinc oxide are used as photocatalysts. For example, in order to improve the photocatalytic activity in the ultraviolet light region, there is a technique of supporting and fixing a copper compound on the surface of titanium oxide. Such a technique is described in Non-Patent Document 1.

On the other hand, in order to extend the wavelength of photocatalytic activity to the wavelength of visible light, there is a technique of doping ruthenium inside titanium oxide. Such a technique is described in Non-Patent Document 2. Further, for the same purpose, Patent Document 1 describes that a metal is contained inside titanium oxide by ion implantation. According to the same document, it is described that the entire absorption spectrum of titanium oxide is moved to the long wavelength side by ion implantation.

Further, claim 2 of Patent Document 2 describes that the inside and / or the surface of the photocatalyst particles contains a metal. According to this description, the inside and the surface are described as the same place where the metal is contained. Therefore, it is considered that the state of the metal is the same for the inside and the surface. Therefore, in the photocatalytic particles described in Patent Document 2, it can be said that the metal state is simply contained inside the photocatalyst particles without forming a level. Patent Document 3 states that titanium oxide is doped with a metal ion such as cerium to have a valence band potential of 3 V or higher and a band gap of 3 V between the valence band and the electron level excited from the valence band. A photocatalytic material in which a copper divalent salt and / or an iron trivalent salt is supported on the surface of the metal ion-doped titanium oxide described below is described. In Patent Document 3, the doping amount is not described in detail, and there is a description in the examples that titanium oxide powder and cerium oxide are mixed at a molar ratio of 0.995: 0.005.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 9-262482</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 7-171408</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2010-104913</text></patcit></p>

<p><nplcit num="1"><text>H. Irie et al., J. Phys. Chem. C., 113,10761-10766 (2009)</text></nplcit><nplcit num="2"><text>T. Ohno et al., Journal of Photochemistry and Photobiology A: Chemistry, 127, 107-110 (1999)</text></nplcit></p>

<p> As a result of the examination by the present inventors, in the titanium oxide described in the above document, the photocatalytic activity is low because the light absorption in the visible light wavelength region is not sufficient only by the technique of supporting the copper compound on the surface of the titanium oxide. On the other hand, it was found that the efficiency of photocatalytic activity is low because the photoexcited electrons cannot be sufficiently utilized at the reduction sites on the surface only by the technique of doping the inside of titanium oxide with ruthenium. Furthermore, as a result of studies by the present inventors, in a photocatalyst in which a specific metal is supported on titanium oxide doped with a specific element, the doping ratio (doping amount) of the element to be doped with respect to titanium oxide is higher than that of a conventionally known amount. It has been found that the photocatalytic activity is significantly improved at a very limited range of amounts.</p>

<p> The present invention includes: [1] With titanium oxide It has a metal supported on the surface of the titanium oxide and The inside of the titanium oxide is doped with at least one element selected from the group consisting of ruthenium, chromium, rhodium, iridium and manganese, and the doping amount of the element is 1.0 with respect to 1 mol of the titanium oxide. × 10^-6More than a mole 6.5 x 10^-4Less than a mole The metal is a photocatalyst comprising at least one metal selected from the group consisting of copper, iron or platinum. [2] The amount of the metal supported is 2.0 × 10 with respect to 1 mol of the titanium oxide concentration.^-5More than a mole 3.0 x 10^-2The photocatalyst according to [1], which is less than or equal to a molar amount. [3] The molar ratio of the element to the metal is 2 × 10.^-4The photocatalyst according to [1] or [2], which is 13 or more and 13 or less. [Four] The photocatalyst according to any one of [1] to [3], wherein the titanium oxide contains a rutile type. [Five] The specific surface area of the titanium oxide is 1 m.²/ g or more 100m²The photocatalyst according to any one of [1] to [4], which is less than / g. [6] The photocatalyst according to any one of [1] to [5], wherein the titanium oxide crystallite diameter is 5 nm or more and 100 nm or less. [7] The photocatalyst according to any one of [1] to [6], wherein the carbon dioxide generation rate per unit time calculated under the following conditions is 10 ppm / h or more. Conditions: The photocatalyst is used by weighing 300 mg on a glass petri dish of Φ28 mm. Using acetaldehyde as the substrate, reaction gas with an acetaldehyde concentration of 100 ppm (N adjusted to a relative humidity of 50%)₂/ O₂= Add a predetermined amount of acetaldehyde to the standard gas of 80/20 and adjust the acetaldehyde concentration to 100 ppm) Put 600 ml in a 1000 ml Tedlar bag (washed, manufactured by GL Science), leave it in the dark for 30 minutes, and then see it. Start light irradiation. For the irradiation light, a xenon light source is used, a cut filter is used, light of λ &lt;420 nm is cut, and visible light is irradiated by passing a layer of the Tedlar bag film with a digital illuminometer and adjusting the illuminance to 100,000 Lx. The amount of carbon dioxide generated 2 hours after irradiation is quantified by a gas chromatograph with a metanizer, and the amount of carbon dioxide generated is calculated using the amount of carbon dioxide generated. [8] A step of doping the inside of titanium oxide with at least one element selected from the group consisting of ruthenium, chromium, rhodium, iridium and manganese. A step of supporting at least one metal selected from the group consisting of copper, iron or platinum on the surface of the titanium oxide is included. The doping amount of the element is 1.0 × 10 with respect to 1 mol of the titanium oxide.^-6More than a mole 6.5 x 10^-4A method for producing a photocatalyst, which is less than a molar amount. [9] The photocatalyst according to [8], wherein the step of supporting the metal includes a step of mixing an element compound containing at least one element selected from the group consisting of ruthenium, chromium, rhodium, iridium and manganese with the titanium oxide. Manufacturing method. [Ten] The method for producing a photocatalyst according to [9], wherein the step of mixing the elemental compound with titanium oxide is a step of mixing using a solid phase mixing method. [11] The method for producing a photocatalyst according to any one of [8] to [10], wherein titanium oxide or amorphous titanium oxide having a crystallite diameter of 60 nm or less is used in the step of doping the element. [12] The step of doping the element is A step of mixing an elemental compound containing the element with the titanium oxide, and The method for producing a photocatalyst according to any one of [8] to [11], which comprises a step of calcining the result obtained by the step of mixing at a temperature of 500 ° C. or higher and 1100 ° C. or lower. [13] A photocatalyst obtained by the production method according to any one of [8] to [12].</p>

<p> According to the present invention, it is possible to provide a photocatalyst having excellent photocatalytic activity under visible light irradiation and a method for producing the same.</p>

<figref num="1">Cr, Mn, Ru, Rh, Ir-doped, undoped TiO₂It is a figure which shows the spectrum data in (800 ° C firing).</figref><figref num="2">Cr50ppm doped TiO₂It is a figure which shows the spectral data after carrying Cu (photocatalyst 1), after supporting Fe (photocatalyst 5), and after carrying Pt (photocatalyst 6) with reference to (800 ° C firing) (sample 1).</figref><figref num="3">Cr50ppm doped TiO₂(800 ° C firing) (Sample 1), Cu 0.1wt% supported / Cr 50ppm doped TiO₂(800 ° C firing) (photocatalyst 1), TiO₂(800 ° C firing) (Sample 19), Cu0.1 wt% supported TiO₂It is a figure which shows the spectrum data of (800 ° C firing) (photocatalyst 36).</figref><figref num="4">Visible light decomposition activity (CO₂It is a figure which shows the generation rate).</figref>

First, the photocatalyst of the present invention will be described. The photocatalyst of the present invention has titanium oxide and a metal supported on the surface of titanium oxide, and at least one selected from the group consisting of ruthenium, chromium, rhodium, iridium and manganese inside the titanium oxide. The element is doped and the metal comprises at least one metal selected from the group consisting of copper, iron or platinum.

Hereinafter, each configuration will be described. The titanium oxide according to the present invention includes various types of titanium oxide such as anatase-type titanium oxide, rutile-type titanium oxide, brookite-type titanium oxide, amorphous titanium oxide, metatitanium acid, orthotitanium acid, titanium hydroxide, titanium hydroxide-containing, and the like. Both can be used. Of these, rutile-type titanium oxide having excellent photocatalytic activity is preferable. Further, the titanium oxide according to the present invention may be a mixture containing at least rutile-type titanium oxide, and may contain a small amount of amorphous titanium oxide. Further, the titanium oxide according to the present invention includes titanium oxide whose surface is treated with a hydroxide or oxide of at least one element selected from the group consisting of silicon, aluminum, zirconium and tin, and composite oxidation. Any of titanium and the like can be used.

In the titanium oxide according to the present invention, the content of rutile-type titanium oxide is preferably 30% by weight or more, more preferably 80% by weight or more, and further preferably 90% by weight or more. By setting the content of rutile-type titanium oxide within the above range, a photocatalyst having excellent photocatalytic activity can be obtained. The content of rutile-type titanium oxide according to the present invention is determined by using an X-ray generator for Multi Flex (Cat.No.2013B303, manufactured by Rigaku Co., Ltd.), the peak position of X-ray diffraction and the area of the strongest interference line of each crystal. Calculated by calculating the ratio.

The crystallite diameter of the rutile-type titanium oxide according to the present invention is preferably in the range of 5 to 100 nm, more preferably 10 to 80 nm, and further preferably 15 to 60 nm (hereinafter, ~ is particularly in the range of 15 to 60 nm). Unless otherwise stated, it means that the upper and lower limits are included). By setting the crystallite diameter of rutile-type titanium oxide within the above range, a photocatalyst having excellent photocatalytic activity can be obtained. The crystallite diameter of rutile-type titanium oxide according to the present invention can be determined by X-ray diffraction using an X-ray generator for Multi Flex (Cat.No.2013B303, manufactured by Rigaku Co., Ltd.).

The element according to the present invention is doped inside titanium oxide. Here, doping means forming a level and containing it so as to realize a structure that absorbs visible light to a certain extent. That is, by performing heat treatment with the element according to the present invention contained inside and / or the surface thereof, the element according to the present invention is doped inside the titanium oxide to form a level. However, an absorption band different from the absorption band derived from titanium oxide can be formed. In this respect, doping is different from mere inclusion. Further, solid solution is also an aspect of doping, but is not limited to solid solution. By doping titanium oxide with a specific element in this way, it is possible to realize absorption of visible light in the photocatalyst of the present invention.

As described above, in the technique described in Patent Document 1, a metal is contained inside from the bulk surface of titanium oxide by ion implantation. As can be seen from FIG. 1 of Patent Document 1, the entire absorption spectrum of titanium oxide moves to the long wavelength side. On the other hand, in the present invention, the absorption spectrum derived from titanium oxide is unchanged, but another absorption band is formed on the long wavelength side. This absorption band is considered to be absorption derived from the level newly formed by doping with a specific element. By forming an absorption band different from the absorption band derived from titanium oxide, the absorption region of visible light can be further expanded. As a result, a wide range of visible light can be absorbed, so that a photocatalyst having excellent photocatalytic activity can be obtained.

Examples of the element according to the present invention include ruthenium, chromium, rhodium, iridium, manganese and the like. The oxides of these elements can all have a rutile-type structure (this point is described in, for example, "Helvetica Physica Acta, 1985, 58, 657-714, p611 Table 2.1"). Since these elements can have the same coordination number as titanium of rutile-type titanium oxide and are close to the ionic radius of titanium, they are easily doped into rutile-type titanium oxide and increase the amount of visible light absorbed. It is thought that it can be done. The element according to the present invention may be used alone or in combination of two or more.

The doping amount of the element according to the present invention is preferably 1.0 × 10 with respect to 1 mol of titanium oxide.^-6~6.5×10^-4Mol, more preferably 5.0 × 10^-6~5.0×10^-4It is in the range of moles. By setting the doping amount of the element according to the present invention within the above range, the photocatalytic activity can be remarkably improved. Here, as the doping amount, the value of the element to be doped in the production process of the photocatalyst of the present invention is shown.

The doping amount of the element according to the present invention is preferably 1 ppm to 1500 ppm, more preferably 5 ppm to 800 ppm, based on the weight of titanium oxide. For example, the amount of chromium doped is preferably 10 ppm or more, more preferably 20 ppm or more, based on the weight of titanium oxide. By setting the content of the element according to the present invention within the above range, the photocatalytic activity can be remarkably improved.

The metal according to the present invention is supported on the surface of titanium oxide. By supporting the specific metal in this way, the electrons excited in the conduction band can realize the reduction reaction of oxygen through the supported specific metal. It is considered that this facilitates the transfer of electrons generated by photoexcitation to the supported metal and facilitates charge separation from holes, and at the same time, promotes the reaction of electrons reducing oxygen in the air in the supported metal. .. Here, in the state where the metal is supported on the surface, the metal is supported on the outer surface of the titanium oxide, and especially when the titanium oxide has pores, the metal is supported on the outer surface and the inner surface of the titanium oxide. Means the state in which is supported. Further, the metal supported on the surface is preferably present in a state of, for example, a sulfate, a halide, a nitrate, an acetate, a hydroxide or an oxide. For example, the metal oxide may be in contact with the outer surface of at least one element-doped titanium oxide, and may even be in contact with two or more element-doped titanium oxides (in other words, element-doped titanium oxides). May be bonded via a metal oxide). The metal oxide is not particularly limited, but preferably has a crystallite diameter of, for example, 5 nm to 60 nm.

Examples of the metal according to the present invention include copper, iron, platinum, and compounds thereof (copper compound, iron compound, platinum compound) and the like. All of these metals have a standard electrode potential in the aqueous solution in the range of 0 to 1.2 V capable of reducing oxygen (in this regard, for example, "S. Higashimoto et al., Applied Catalysis A: General, 340". , 98-104 (2008) "). By using these metals, the efficiency of photocatalytic activity can be improved. The metal according to the present invention may be used alone or in combination of two or more.

The amount of the metal supported according to the present invention is preferably 2.0 × 10 in terms of metal elements with respect to 1 mol of titanium oxide.^-5~3.0×10^-2Mol, more preferably 5.0 × 10^-5~2.5×10^-2It is in the range of moles. By setting the supported amount of the metal according to the present invention to the above lower limit value or more, the efficiency of photocatalytic activity by the supported metal can be improved. On the other hand, by setting the supported amount of the metal according to the present invention to be equal to or less than the above upper limit value, it is possible to suppress the inhibition of light absorption of titanium oxide by the supported metal.

The supported amount of the metal according to the present invention is preferably 0.001 wt% to 5 wt%, more preferably 0.003 wt% to 2 wt% in terms of metal elements with respect to the weight of titanium oxide. By setting the supported amount of the metal according to the present invention within the above range, the efficiency of photocatalytic activity can be improved.

As described above, the photocatalyst of the present invention includes both a doping element and a supported metal. Moreover, in the photocatalyst of the present invention, the doping amount of the doping element is 1.0 × 10 with respect to 1 mol of titanium oxide.^-6More than a mole 6.5 x 10^-4By limiting to less than a molar amount, an improvement in photocatalytic activity not found in the prior art has been achieved. Hereinafter, inferences about the mechanism of photocatalytic activity of the photocatalyst of the present invention will be described. First, (i) by doping titanium oxide with a specific element, a new level is formed on the valence band in the band gap of titanium oxide. As a result, the amount of visible light absorbed increases and oxidation sites are formed. On the other hand, (ii) a reduction site is formed by supporting a specific metal. In this way, when visible light is irradiated, electrons are excited from the level of the specific element to the conduction band, and holes are generated at the level of the specific element. Then, at the oxidation site of the specific element, the oxidation reaction of the substrate is realized, and at the reduction site of the specific metal, the electrons excited in the conduction band realize the reduction reaction of oxygen via the supporting specific metal. Can be done. It is considered that this facilitates the transfer of electrons generated by photoexcitation to the supported metal and facilitates charge separation from holes, and at the same time, promotes the reaction of electrons reducing oxygen in the air in the supported metal. .. As a result, a visible light responsive catalyst having high catalytic efficiency is realized.

In the photocatalyst of the present invention, the molar ratio of the doped element to the supported metal (in terms of metal element) is preferably 2 × 10.^-4More than 13 and less, more preferably 2 × 10^-3More than 10 or less. By setting the molar ratio of the doping element / supporting metal within the above range, the balance between the content of the doping element and the carrying amount of the supporting metal can be improved, and the photocatalytic activity can be remarkably improved.

The specific surface area of the photocatalyst according to the present invention is preferably 1 m.²/ g or more 100m²It is less than / g, more preferably 1 m²/ g or more 85m²It is less than / g. When the specific surface area of titanium oxide according to the present invention is within the above range, good catalytic activity can be maintained. The specific surface area of the photocatalyst can be calculated by a general BET method.

In the photocatalyst of the present invention, the carbon dioxide generation rate per unit time calculated under the following conditions is preferably 10 ppm / h or more, and the upper limit is not particularly limited, but is, for example, 1000 ppm / h or less. is there. Conditions: For the carbon dioxide generation rate, 300 mg of the photocatalyst is weighed in a glass petri dish of Φ28 mm and used. Using acetaldehyde as the substrate, reaction gas with an acetaldehyde concentration of 100 ppm (N adjusted to a relative humidity of 50%)₂/ O₂= Add a predetermined amount of acetaldehyde to the standard gas of 80/20 and adjust the acetaldehyde concentration to 100 ppm). Put 600 ml in a 1000 ml Tedlar bag (washed, manufactured by GL Science), let stand in the dark for 30 minutes, and then see. Start light irradiation. The illuminance light uses a xenon light source (LA-410UV-3, light guide uses RLGB1-5L1000, manufactured by Hayashi Clock Industry Co., Ltd.), a cut filter (Y-44, manufactured by Asahi Techno Glass Co., Ltd.), and λ &lt; The 420 nm light is cut, and a digital illuminometer (IM-5, manufactured by Topcon Techno House) is used to irradiate visible light adjusted to an illuminance of 100,000 Lx through a layer of the Tedlar bag film. The amount of carbon generated is quantified with a gas chromatograph with a metanizer (GC-2014, manufactured by Shimadzu Corporation), and the amount generated is calculated. As described above, in the photocatalyst of the present invention, photocatalytic activity can be obtained by irradiation with visible light of 420 nm or more.

Next, the method for producing the photocatalyst of the present invention will be described. The method for producing a photocatalyst of the present invention involves doping the inside of titanium oxide with at least one element selected from the group consisting of ruthenium, chromium, rhodium, iridium and manganese, followed by copper on the surface of titanium oxide. Includes the step of carrying at least one metal selected from the group consisting of iron or platinum.

In the manufacturing process of the present invention, the doping step includes a step of mixing an element or a compound containing an elemental component with titanium oxide, and a step of calcining the obtained product. The doping step gives element-doped titanium oxide. Further, the supporting step includes a step of bringing the metal or a compound containing a metal component into contact with the element-doped titanium oxide. Here, as the contacting step, for example, a method of mixing a liquid and a solid or a method of mixing solids can be adopted. The resulting product may be dried. By such a supporting step, a photocatalyst containing titanium oxide containing a doping element and a supporting metal can be obtained.

First, a compound containing an element or an elemental component (hereinafter referred to as an elemental compound) is mixed with titanium oxide. Various methods can be used to mix the elements with titanium oxide. For example, a method of mixing in a solution, a method of mixing in a gas phase, or a method of mixing in a solid phase is used. Examples of the solution mixing method include (1) a method of hydrolyzing or neutralizing a titanium compound in the presence of an elemental compound and, if necessary, a crystal species, and (2) a method of hydrolyzing or neutralizing a titanium compound, and (2) titanium oxide particles in a solution of the elemental compound. (3) Add the elemental compound to the suspension of the titanium oxide particles, and then hydrolyze, neutralize, or oxidize the obtained compound. There are methods and so on.

Examples of the element used in the production method of the present invention include ruthenium, chromium, rhodium, iridium, manganese and the like. Further, as the element compound, compounds of these elements such as sulfates, halides, nitrates, acetates and oxides are preferable. Examples of elemental compounds include, for example, chromium chloride, chromium nitrate, chromium sulfate, chromium acetate, ruthenium chloride, ruthenium bromide, ruthenium iodide, ruthenium oxide (IV), rhodium acetate, rhodium chloride, rhodium bromide, iodide. Rhodium, rhodium nitrate, rhodium oxide (III), iridium chloride (III), iridium chloride (IV), iridium bromide (III), iridium bromide (IV), iridium iodide (III), iridium iodide (IV) , Iridium oxide (IV) and the like.

Further, as the titanium compound, for example, titanium chloride, an organic titanium compound, titanyl sulfate, titanium sulfate and the like can be used. Preferably, titanium chloride can be used.

In the mixing method of (1) above, a titanium compound to which an element compound is added in advance is used, which is hydrolyzed or neutralized, and a monobasic acid such as nitric acid or hydrochloric acid is added to the obtained product to deflocculate. Alternatively, it may be hydrolyzed under pressure.

Further, the hydrolysis of the titanium compound is preferably carried out at a boiling point temperature or lower of the aqueous solution of the titanium compound. Examples of the base used for neutralization include various bases such as sodium hydroxide, potassium hydroxide, ammonium carbonate, ammonia, and amines.

In the mixing method of (2) and (3) above, titanium oxide particles can be obtained by various known methods. Examples of the method for obtaining titanium oxide particles include (i) a method of hydrolyzing a titanium compound such as titanium chloride, an organic titanium compound, titanyl sulfate, and titanium sulfate, if necessary, in the presence of a crystal species, (ii). A method of adding an alkali to the above titanium compound in the presence of a crystal species as necessary to neutralize it, (iii) a method of vapor-phase oxidizing titanium chloride, an organic titanium compound, etc., (iv) (i) ~ There are a method of calcining the titanium oxide obtained in (iii), or a method of hydrothermally treating a titanium oxide suspension by adding an acid or an alkali as needed. Further, in the mixing method of (2) and (3) above, water, an aqueous nitric acid solution, an aqueous hydrochloric acid solution, an aqueous sulfuric acid solution or an aqueous ammonia solution may be used as the solution or suspension, and an organic solvent such as ethanol or isopropyl alcohol may be used. May be used. Preferably, water can be used.

In the crystal of the titanium oxide particles, the crystallite diameter determined by X-ray diffraction is preferably 60 nm or less. By setting the crystallite diameter to 60 nm or less, the photocatalytic activity of the finally obtained photocatalyst of the present invention can be improved. By making the crystal particles of titanium oxide having a predetermined diameter or less, it is considered that the element can be uniformly doped inside the titanium oxide crystal in the next firing step. Further, as the titanium oxide particles, amorphous titanium oxide particles may be used.

Further, the element-containing titanium oxide obtained in the mixing step is separated, washed, dried and pulverized, if necessary. Separation can be performed by a method such as ordinary filtration or a gradient method. Drying can be performed at any temperature and pressure, but for example, a temperature of room temperature (20 ° C) to 200 ° C, normal pressure or reduced pressure is suitable.

Further, in the production method of the present invention, conditions such as the concentration and addition rate of elemental compounds, titanium compounds, acids and alkalis, the temperature of hydrolysis reaction and neutralization reaction, and the concentration of titanium oxide in the dispersion liquid are particularly important. There is no limit and it can be set as appropriate.

In the titanium oxide containing the element prepared in this manner, it is considered that the element compound is supported on the surface of the titanium oxide particle or the mixture of the element compound and the titanium oxide at this preparation stage. ..

On the other hand, as a gas phase mixing method, there is a method in which chloride of the above element is added to titanium chloride and this is subjected to high temperature gas phase oxidation. In addition, an inorganic compound or a metal organic compound is vaporized by a chemical vapor deposition (CVD) method, and an element or an element or a metal organic compound is formed inside the titanium oxide crystal by a chemical reaction in the gas phase or at the gas phase / substrate interface. It is also possible to produce titanium oxide containing an elemental compound. On the other hand, as a solid phase mixing method, there is a method in which a compound of the above element is added to titanium oxide and mixed in a mortar, a blender or a jet mill.

Subsequently, titanium oxide containing the element is fired. The element-containing titanium oxide may contain water, an acid such as nitric acid, hydrochloric acid and sulfuric acid, an alkali such as ammonia and an organic solvent such as ethanol and isopropyl alcohol. The firing temperature is, for example, 500 ° C to 1100 ° C, preferably 550 ° C to 1100 ° C, more preferably 600 ° C to 1000 ° C, and most preferably 650 ° C to 900 ° C. Is. The photocatalytic activity can be increased by setting the firing temperature to 500 ° C. or higher. It is considered that this is a result of sufficient doping of the element inside the titanium oxide crystal and an increase in visible light absorption of the photocatalyst. On the other hand, the photocatalytic activity can be increased by setting the firing temperature to 1100 ° C or lower. It is considered that this is because the crystal particle size of titanium oxide becomes too large and the surface area of the photocatalyst can be suppressed from becoming small. The temperature rising condition in firing is not particularly limited, but the temperature may be raised from room temperature (20 ° C) to a temperature range of 500 ° C to 1100 ° C, for example, between 1h and 40h. Examples of the firing atmosphere include a hydrogen atmosphere diluted with an inert gas such as air, oxygen, water vapor, nitrogen, argon, helium, vacuum, and nitrogen. Preferably, the photocatalytic activity can be increased by firing in an air or oxygen atmosphere. It is considered that this is because the oxygen defect of titanium oxide is reduced.

Further, the titanium oxide powder obtained by the vapor phase mixing method may be further fired under the above-mentioned firing conditions, if necessary, in order to optimize the content of the element inside the titanium oxide crystal.

As described above, element-doped titanium oxide can be obtained. Subsequently, at least one kind of a metal or a compound containing a metal component (hereinafter referred to as a metal compound) is supported on the surface of titanium oxide containing the doping element. As the supporting method, various methods can be used. As an example, a method of immersing element-doped titanium oxide particles or a support holding the element-doped titanium oxide particles in a solution of a metal compound, a suspension of element-doped titanium compound particles, or this titanium. There is a method of adding a metal compound to a liquid containing a support holding compound particles to adjust the pH of the solution. These techniques are preferably applied, for example, to metal compounds such as sulfates, halides, nitrates, acetates or hydroxides. As the mixing method, various methods can be used. As an example, a method of mixing element-doped titanium oxide particles and a metal compound in a dairy pot (in particular, a method of mixing solids without using a liquid such as water may be used), element-doped. There is a method of stirring the titanium oxide particles and the metal compound in water, evaporating and drying the water, and mixing them. These methods are preferably applied, for example, to metal compounds that are oxides.

As the metal compound, for example, a copper compound, an iron compound, a platinum compound and the like can be used. For example, copper, iron or platinum sulfates, halides, nitrates, acetates, hydroxides, oxides and the like can be mentioned. Specifically, iron (II) sulfate, iron (III) sulfate, iron (II) chloride, iron (III) chloride, iron (II) bromide, iron (III) bromide, iron (II) iodide, nitrate. Iron (III), Iron (II) Acetate, Iron (III) Hydroxide, Copper (II) Sulfate, Copper (I) Chloride, Copper (II) Chloride, Copper (I) Bromide, Copper (II) Bromide, Copper iodide (I), copper iodide (II), copper nitrate (II), copper acetate (I), copper acetate (II), copper hydroxide (II), platinum chloride (II), platinum chloride (IV) , Platinum bromide (II), platinum bromide (IV), platinum iodide (II), platinum iodide (IV), hexachloroplatinum (IV) acid, hexahydroxoplatinum (IV) acid, tetrachloroplatinum (III) Acids, iron (II) oxide, iron (II, III) oxide, iron (III) oxide, copper (I) oxide, copper (II) oxide, platinum (IV) oxide and the like can be mentioned.

Further, the concentration of the element-doped titanium oxide suspension, the pH, the concentration when a metal compound such as a copper compound, an iron compound, or a platinum compound is used as an aqueous solution, and the concentration of an acid or base used for pH adjustment are appropriately set. be able to.

Examples of the acid and base used for adjusting the pH of the element-doped titanium oxide suspension include various bases such as sulfuric acid, hydrochloric acid, nitric acid, sodium hydroxide, potassium hydroxide, ammonium carbonate, ammonia, and amines. Can be mentioned.

As described above, titanium oxide containing a doping element and a supported metal is obtained as a product. The obtained product can be used as a photocatalyst of the present invention. The product may be separated, washed and dried as needed. Separation can be performed by a method such as ordinary filtration or a gradient method. Drying can be performed at any temperature and pressure, but for example, a temperature of 20 ° C., room temperature (25 ° C.) to 300 ° C., normal pressure or reduced pressure is suitable. The other drying method is not particularly limited, but for example, air drying, vacuum drying, heat drying, spray drying, and the like can be preferably used. Further, depending on the use of the photocatalyst, the drying step can be omitted.

When the photocatalyst of the present invention is actually used for a photocatalytic reaction, it is convenient to fix it on a particulate photocatalyst, if necessary, on a base material, or to mold and granulate the photocatalyst and use it as a molded product. The base material is made of various materials such as metal, tile, enamel, cement, concrete, glass, plastic, fiber, wood, and paper. As the shape of the base material, for example, various shapes such as a plate shape, a corrugated plate shape, a honeycomb shape, a spherical shape, and a curved surface shape can be used. A known method for immobilizing a photocatalyst on such a base material, for example, a method of applying or spraying a photocatalyst on the surface of the base material, drying and firing, and applying a coating liquid containing a photocatalyst and a binder to the surface of the base material. After applying or spraying on the photocatalyst, it can be dried and heated if necessary. As the binder, an inorganic resin or an organic resin can be used, and a binder that is not easily decomposed by a photocatalytic reaction, for example, a binder such as cement, concrete, gypsum, silicic acid compound, silica, silicon compound, silicone resin, fluororesin, etc. preferable. When the photocatalyst is molded and used, it can be molded into an arbitrary shape after being mixed with a binder such as clay, diatomaceous earth, organic resin, or inorganic resin, if necessary.

Further, depending on the usage environment, it can be mixed or used in combination with another photocatalyst such as an ultraviolet light-responsive photocatalyst, or mixed or used in combination with an adsorbent such as zeolite, silica or alumina.

Next, the action and effect of the photocatalyst of the present invention will be described. In the photocatalyst of the present invention, an element is doped inside the titanium oxide crystal. As a result, visible light can be absorbed. Then, a metal is supported on the surface of titanium oxide. As a result, the recombination of electrons and holes generated by visible light irradiation can be suppressed, and the photocatalytic function under visible light irradiation can be dramatically improved. Further, in the photocatalyst of the present invention, it is possible to realize a photocatalyst exhibiting excellent photocatalytic activity under visible light irradiation without using a costly technique such as ion implantation. Thereby, the photocatalyst of the present invention can be produced at low cost. Therefore, it is widely used for various purposes such as decomposition, purification, removal, and sterilization of substances that adversely affect the human body and living environment such as deodorization and sterilization using the photocatalytic function of the photocatalyst of the present invention and substances that may have such adverse effects. Can be done.

The photocatalyst of the present invention can be more specifically used for the following applications. However, the uses described are applicable examples and do not limit the present invention. For example, the photocatalyst of the present invention is used for furniture, wall materials, lighting fixtures, bathroom materials, wash basin products, kitchen products, disposable paper, automobile interior materials, other indoor materials, dental materials, and other living materials. be able to

<p> Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.</p><p>[Physical characteristic measurement method] The contents of various elements were measured using an ICP emission spectrometer (VISTA-PRO, manufactured by SII). Regarding the amount of Cr in sample 7, which had a low content and was below the detection limit of the IPC emission analysis method, the titanium oxide weight reduction rate before and after firing and the amount of reagent added when the raw material titanium oxide was calcined at 800 ° C. The value calculated from was used. The crystal type of titanium oxide and the content ratio of each crystal are determined by using an X-ray generator for Multi Flex (Cat.No.2013B303, manufactured by Rigaku) to determine the peak position of X-ray diffraction and the area of the strongest interference line of each crystal. The ratio was calculated and represented. The crystal particle size was calculated from the half width of X-ray diffraction using Scherrer's equation. The ultraviolet light to visible light absorption spectra of the samples and photocatalysts shown in Examples and Comparative Examples were measured using a spectrophotometer (UV-2550, manufactured by Shimadzu Corporation) using barium sulfate as a control.</p><p>[Evaluation of photocatalytic function] The photocatalytic functions of the samples obtained in the production examples, the examples, and the photocatalysts obtained in the comparative examples were investigated as follows. Weigh 300 mg of each sample and each photocatalyst into a glass petri dish of Φ28 mm, and apply black light to 2 mW / cm.²The petri dish was placed in a 1000 ml Tedlar bag (washed, manufactured by GL Science) after irradiation for 48 hours and pretreatment. Next, N adjusted to a humidity of 50% with ion-exchanged water.₂: O₂After performing gas replacement four times with standard gas at = 80: 20, the humidity was adjusted to 50% with ion-exchanged water.₂: O₂= 80:20 standard gas with acetaldehyde added, 600 ml of gas adjusted to 100 ppm was introduced into a 1000 ml Tedlar bag (washed, manufactured by GL Science), left in the dark for 30 minutes, and then irradiated with visible light. To start. The illuminance light uses a xenon light source (LA-410UV-3, manufactured by Hayashi Clock Industry Co., Ltd.) and a cut filter (Y-44, manufactured by Asahi Techno Glass Co., Ltd.) to cut the light of λ &lt;420 nm and digitally. A gas chromatograph with a metanizer is used to irradiate visible light with an illuminance meter (IM-5, manufactured by Topcon Techno House) through a film of a Tedlar bag and adjust the illuminance to 100,000 Lx. It was quantified by (GC-2014, manufactured by Shimadzu Corporation) and expressed as the carbon dioxide generation rate per unit time.</p><p>[Preparation of element-doped titanium oxide]</p><p> Manufacturing example 1 Put 10.0 g of titanium oxide (made by Showa Titanium: FP-6, crystal type: anatase type, crystallite diameter: 10 nm) in a 300 ml glass beaker, and chromium chloride hexahydrate (CrCl).₃ 6H₂O) An aqueous solution prepared by dissolving 2.6 mg of 2.6 mg in 20 ml of ion-exchanged water was added, and the mixture was mixed with a resin pharmaceutical spoon to form a paste. This was dried at a temperature of 120 ° C. for 5 hours, and then the dried product was pulverized in an agate mortar to obtain a titanium oxide powder containing chromium chloride. Next, 10.0 g of titanium oxide powder containing chromium chloride was placed in a 50 ml alumina crucible, covered, and then fired at a temperature of 800 ° C in an air atmosphere for 3 hours (heating rate 100 ° C / hr, temperature lowering rate). 100 ° C / hr). The calcined powder was pulverized in an agate mortar to obtain chromium-doped titanium oxide (Sample 1).</p><p> Manufacturing example 2 ~ 6 The same operation as in Production Example 1 was carried out except that the firing temperature was changed to obtain chromium-doped titanium oxide (samples 2 to 6).</p><p> Manufacturing examples 7 to 11 Chromium-doped titanium oxide (Samples 7 to 11) was obtained by performing the same operation as in Production Example 1 except that the amount of chromium hexahydrate added was changed.</p><p> Manufacturing example 12 Manganese-doped titanium oxide (Sample 12) was obtained by performing the same operation as in Production Example 1 except that 2.8 mg of manganese nitrate hexahydrate was used instead of chromium chloride hexahydrate.</p><p> Production example 13 Perform the same operation as in Production Example 1 except that 2.4 mg of ruthenium chloride n-hydrate (ruthenium content 40%) was used instead of chromium hexahydrate, and ruthenium-doped titanium oxide (sample 13) was used. Obtained.</p><p> Production example 14 The same operation as in Production Example 1 was performed except that 2.4 mg of ruthenium chloride n-hydrate (ruthenium content 40%) was used instead of chromium hexahydrate, and the firing temperature was set to 700 ° C. , Ruthenium-doped titanium oxide (Sample 14) was obtained.</p><p> Production example 15 Rhodium-doped titanium oxide (Sample 15) was obtained by performing the same operation as in Production Example 1 except that 2.8 mg of rhodium nitrate was used instead of chromium hexahydrate chloride.</p><p> Manufacturing example 16 The same operation as in Production Example 1 was carried out except that 3.2 mg of iridium chloride was used instead of chromium hexahydrate, to obtain iridium-doped titanium oxide (Sample 16).</p><p> Production example 17 A chromium-doped titanium oxide (Sample 17) was obtained by performing the same operation as in Production Example 1 except that titanium oxide (manufactured by TAYCA: MT-150A, crystal type: rutile type, crystallite diameter: 10 nm) was used.</p><p> Production example 18 Titanium oxide (manufactured by TAYCA: MT-150A, crystal type: rutile type, crystallite diameter: 10 nm) is used, and the same operation as in Production Example 1 is performed except that the firing temperature is 400 ° C. Titanium (Sample 18) was obtained.</p><p> Manufacturing example 19 Titanium oxide (Sample 19) was obtained by performing the same operation as in Production Example 1 except that chromium chloride was not added and only ion-exchanged water was added.</p><p> Production example 20 The same operation as in Production Example 1 except that titanium oxide (manufactured by TAYCA: MT-150A, crystal type: rutile type, crystallite diameter: 10 nm) is used, and only ion-exchanged water is added without adding chromium chloride. To obtain titanium oxide (Sample 20).</p><p> Production example 21 The same operation as in Production Example 1 was carried out except that 10.0 g of titanium oxide (Sample 19) obtained in Production Example 19 was used to obtain chromium-doped titanium oxide (Sample 21). Table 1 shows the preparation conditions and physical properties of the samples 1 to 21 obtained in Production Examples 1 to 21.</p><p> Production example 22 Titanium oxide (manufactured by Showa Titanium Co., Ltd .: FP-6, crystal type: anatase type, crystallite diameter: 10 nm) 10.0 g and ruthenium chloride n hydrate (RuCl)₃ NH₂O, put 2.6mg of ruthenium content (40%) in a 250ml glass mini bottle (manufactured by AS ONE Corporation), attach a SUS304 cutter (manufactured by AS ONE Corporation), and then use an Oster blender (manufactured by AS ONE Corporation) for 5 minutes. The mixture was stirred to obtain a titanium oxide powder containing ruthenium chloride. Next, 10.0 g of titanium oxide powder containing ruthenium chloride was placed in a 200 ml alumina crucible, covered, and then fired at a temperature of 750 ° C in an air atmosphere for 3 hours (heating rate 100 ° C / hr, temperature lowering rate). 100 ° C / hr). The calcined powder was pulverized in an agate mortar to obtain ruthenium-doped titanium oxide (Sample 22).</p><p> Production example 23 Silicon-treated titanium oxide whose surface is treated with silica hydrate or silica (manufactured by TAYCA: MT-100WP, crystal type: rutile type, crystallite diameter: 11 nm, TiO₂Content: 73wt%, SiO₂Content: 26wt%) 10.0g and ruthenium chloride n hydrate (RuCl)₃ NH₂O, put 2.0 mg of ruthenium content (40%) in a 250 ml glass mini bottle (manufactured by AS ONE Corporation), attach a SUS304 cutter (manufactured by AS ONE Corporation), and then use an Oster blender (manufactured by AS ONE Corporation) for 5 minutes. The mixture was stirred to obtain a silicon-treated titanium oxide powder containing ruthenium chloride. Next, 10.0 g of silicon-treated titanium oxide powder containing ruthenium chloride was placed in a 200 ml alumina crucible, covered, and then fired at a temperature of 750 ° C in an air atmosphere for 3 hours (heating rate 100 ° C / hr, The temperature decrease rate was 100 ° C / hr). The calcined powder was pulverized in an agate mortar to obtain ruthenium-doped silicon-treated titanium oxide (Sample 23). Silicon-treated titanium oxide TiO₂The content was calculated by ICP analysis.</p><p>[Preparation of photocatalyst]</p><p> Example 1 42.5 ml of ion-exchanged water and 5.0 g of chromium-containing titanium oxide (Sample 1) obtained in Production Example 1 were charged into a 100 ml four-necked flask, and after stirring for 10 minutes, a 0.1 N hydrochloric acid aqueous solution was added dropwise to adjust the pH of the solution to 4. Prepared in, then copper chloride dihydrate (CuCl)₂ 2H₂O) An aqueous solution prepared by dissolving 13.4 mg in 7.5 ml of ion-exchanged water was added dropwise, and a 0.1N sodium hydroxide aqueous solution was further added dropwise to maintain the pH of the solution at 5, and the mixture was stirred for 1 hour. After stirring for 1 hour, a 0.1N aqueous sodium hydroxide solution was added dropwise to neutralize the pH to 7, filtered, and washed with ion-exchanged water until the conductivity of the washing water became 1 mS / m or less. The obtained wet cake was dried in an air atmosphere at 110 ° C. for 12 hours and then pulverized in an agate mortar to obtain a photocatalyst (photocatalyst 1) having a copper compound on its surface. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Examples 2-4 Copper chloride dihydrate (CuCl₂ 2H₂Photocatalysts 2 to 4 were prepared in the same manner as in Example 1 except that the amount of O) added was changed. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 5 42.5 ml of ion-exchanged water and 5.0 g of chromium-containing titanium oxide (Sample 1) obtained in Production Example 1 were charged into a 100 ml four-necked flask, stirred for 10 minutes, and then a 1N hydrochloric acid aqueous solution was added dropwise to adjust the pH of the solution to 3. Prepared in. Then iron (III) chloride (FeCl)₃ 6H₂O) An aqueous solution prepared by dissolving 24.2 mg in 7.5 ml of 0.1N hydrochloric acid was added dropwise, and a 1N sodium hydroxide aqueous solution was further added dropwise to maintain the pH of the solution at 2, and the mixture was stirred for 1 hour. After stirring for 1 hour, a 1N aqueous sodium hydroxide solution was added dropwise to neutralize the pH to 7, filtered, and washed with ion-exchanged water until the conductivity of the washing water became 1 mS / m or less. The obtained wet cake was dried at 110 ° C. for 12 hours in an air atmosphere and then pulverized in an agate mortar to obtain a photocatalyst (photocatalyst 5) having an iron compound on its surface. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 6 Copper chloride dihydrate (CuCl₂ 2H₂Instead of O), chloroplatinic acid (IV) (H)₂PtCl₆ 6H₂O) Photocatalyst 6 was prepared by performing the same operation as in Example 1 except that 13.3 mg was used. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 7 The photocatalyst 7 was prepared by performing the same operation as in Example 1 except that sample 2 (900 ° C calcined sample) was used instead of sample 1. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 8 The photocatalyst 8 was prepared by performing the same operation as in Example 1 except that sample 3 (1000 ° C calcined sample) was used instead of sample 1. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 9 The photocatalyst 9 was prepared by performing the same operation as in Example 1 except that sample 4 (700 ° C calcined sample) was used instead of sample 1. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 10 The photocatalyst 10 was prepared by performing the same operation as in Example 1 except that sample 5 (600 ° C calcined sample) was used instead of sample 1. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 11 Sample 7 (Cr content 8.2 × 10) instead of sample 1^-6mol / vs. TiO₂The photocatalyst 11 was prepared by performing the same operation as in Example 1 except that the molar ratio) was used. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 12 Sample 8 (Cr content 1.6 × 10) instead of sample 1^-5mol / vs. TiO₂The photocatalyst 12 was prepared by performing the same operation as in Example 1 except that the molar ratio) was used. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 13 Sample 9 (Cr content 4.9 × 10) instead of sample 1^-5mol / vs. TiO₂The photocatalyst 13 was prepared by performing the same operation as in Example 1 except that the molar ratio) was used. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 14 Sample 10 (Cr content 1.6 × 10) instead of sample 1^-4mol / vs. TiO₂The photocatalyst 14 was prepared by performing the same operation as in Example 1 except that the molar ratio) was used. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 15 Sample 11 (Cr content 3.3 × 10) instead of sample 1^-4mol / vs. TiO₂The photocatalyst 15 was prepared by performing the same operation as in Example 1 except that the molar ratio) was used. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 16 Sample 17 (TiO) instead of sample 1₂The photocatalyst 16 was prepared by performing the same operation as in Example 1 except that the raw material brand: MT-150A) was used. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 17 The photocatalyst 17 was prepared by performing the same operation as in Example 1 except that sample 21 was used instead of sample 1. Table 2 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 18 Instead of sample 1, sample 13 (800 ° C calcined, Ru content 7.9 × 10)^-5mol / vs. TiO₂The photocatalyst 18 was prepared by performing the same operation as in Example 1 except that the molar ratio) was used. Table 3 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Examples 19-23 Instead of sample 1, sample 14 (calcined at 700 ° C, Ru content 7.9 × 10)^-5mol / vs. TiO₂Copper chloride dihydrate (CuCl) using molar ratio)₂ 2H₂Photocatalysts 19 to 23 were prepared by changing the amount of O) added and performing the same operation as in Example 1. Table 3 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Examples 24-28 Instead of sample 1, sample 14 (calcined at 700 ° C, Ru content 7.9 × 10)^-5mol / vs. TiO₂Using molar ratio), iron (III) chloride (FeCl)₃ 6H₂Photocatalysts 24 to 28 were prepared in the same manner as in Example 5 except that the amount of O) added was changed. Table 3 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Examples 29 ~ 32 Instead of sample 1, sample 14 (calcined at 700 ° C, Ru content 7.9 × 10)^-5mol / vs. TiO₂Chloroplatinic acid (IV) (H) using molar ratio)₂PtCl₆ 6H₂Photocatalysts 29 to 32 were prepared in the same manner as in Example 6 except that the amount of O) added was changed. Table 3 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 33 Sample 12 (Mn content 8.2 × 10) instead of sample 1^-5mol / vs. TiO₂The photocatalyst 33 was prepared by performing the same operation as in Example 1 except that the molar ratio) was used. Table 3 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 34 Sample 15 (Rh content 8.1 × 10) instead of sample 1^-5mol / vs. TiO₂The photocatalyst 34 was prepared by performing the same operation as in Example 1 except that the molar ratio) was used. Table 3 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 35 Sample 16 (Ir content 8.0 × 10) instead of sample 1^-5mol / vs. TiO₂The photocatalyst 35 was prepared by performing the same operation as in Example 1 except that the molar ratio) was used. Table 3 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 36 Sample 22 (Ru content 7.9 × 10) instead of sample 1^-5mol / vs. TiO₂(Mole ratio) and iron (III) chloride (FeCl)₃ 6H₂O) The photocatalyst 36 was prepared by performing the same operation as in Example 5 except that 12.1 mg was used. Table 3 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 37 Sample 23 (Ru content 7.9 × 10) instead of sample 1^-5mol / vs. TiO₂(Mole ratio), iron (III) chloride (FeCl)₃ 6H₂O) Photocatalyst 37 was prepared by performing the same operation as in Example 5 except that 9.0 mg was used. Table 3 shows the preparation conditions, physical characteristics, and activity evaluation results.</p><p> Example 38 Sample 22 (Ru content 7.9 × 10^-5mol / vs. TiO₂A molar ratio of 5.0 g and copper (II) oxide (Nanopowder, manufactured by Aldrich) 25.0 mg were mixed in an alumina mortar for 30 minutes to obtain a photocatalyst (photocatalyst 38) carrying a copper compound.</p><p> Example 39 Sample 22 (Ru content 7.9 × 10^-5mol / vs. TiO₂A molar ratio of 5.0 g and iron (III) oxide (Nanopowder, manufactured by Aldrich) 25.0 mg were mixed in an alumina mortar for 30 minutes to obtain a photocatalyst (photocatalyst 39) carrying an iron compound.</p><p> Comparative Examples 1 to 7 The decomposition activity was evaluated using the samples obtained in Production Examples 1, 12, 13, 15, 16, 17, and 19 as they were. Table 4 shows the physical characteristics and activity evaluation results of the sample.</p><p> Comparative Example 8 Change to sample 1 and sample 19 (TiO₂The same operation as in Example 1 was carried out except that brand: FP-6, no doping element was used, to obtain a photocatalyst 36 in which a copper compound was supported on sample 19. Table 5 shows the results of evaluating the physical characteristics and activity of the sample.</p><p> Comparative Example 9 Sample 20 (TiO) instead of sample 1₂A photocatalyst 37 in which a copper compound was supported on a sample 20 was obtained by performing the same operation as in Example 1 except that the brand: MT-150A, without a doping element) was used. Table 5 shows the results of evaluating the physical characteristics and activity of the sample.</p><p> Comparative example 10 Change to sample 1 and sample 19 (TiO₂Brand: FP-6, no doping element) was used, and 24.2 mg of iron (III) chloride hexahydrate was used instead of copper chloride dihydrate, and the same operation as in Example 1 was performed. A photocatalyst 38 in which an iron compound was carried on Sample 19 was obtained. Table 5 shows the results of evaluating the physical characteristics and activity of the sample.</p><p> Comparative Example 11 Change to sample 1 and sample 19 (TiO₂Brand: FP-6, no doping element) was used, and 13.3 mg of chloroplatinic acid (IV) hexahydrate was used instead of copper chloride dihydrate, and the same operation as in Example 1 was performed. , A photocatalyst 39 in which a platinum compound was carried on sample 1 was obtained. Table 5 shows the results of evaluating the physical characteristics and activity of the sample.</p><p> Comparative Example 12 Sample 6 (TiO) produced by firing at 400 ° C₂Brand: FP-6, Cr content 8.2 × 10^-5mol / vs. TiO₂The same operation as in Example 1 was carried out except that the molar ratio) was used to obtain a photocatalyst 40 in which a copper compound was supported on Sample 6. Table 5 shows the results of evaluating the physical characteristics and activity of the sample.</p><p> Comparative Example 13 Sample 18 (TiO) produced by firing at 400 ° C₂Brand: MT-150A, Cr content 8.2 × 10^-5mol / vs. TiO₂The same operation as in Example 1 was carried out except that the molar ratio) was used to obtain a photocatalyst 41 in which a copper compound was supported on the sample 18. Table 4 shows the physical characteristics and activity evaluation results of the sample.</p><p> Comparative Example 14 The photocatalyst described in Patent Document 3 was prepared. Titanium oxide (manufactured by TAYCA: MT-150A, crystal type: rutile type, crystallite diameter: 10 nm) 19.99 g and cerium oxide (manufactured by Wako Pure Chemical Industries, Ltd.) 0.22 g (molar ratio 0.995: 0.005) 1 in an alumina mortar Mixing for a time gave a mixed powder of titanium oxide and cerium oxide. Next, 10.0 g of a mixed powder of titanium oxide and cerium oxide was placed in a 50 ml alumina crucible and baked for 5 hours at a temperature of 1200 ° C in an air atmosphere (heating rate 100 ° C / hr, temperature lowering rate 100 ° C / hr). did. The powder after firing was colored gray, and the desired cerium-doped titanium oxide could not be obtained. Even after re-preparation, the powder after firing was colored gray, so the firing temperature was lowered to 800 ° C. That is, a cerium-doped titanium oxide (Sample 24) was obtained by performing the same operation as above except that the firing temperature was changed to 800 ° C. The powder after firing was colored light yellow. Then, 5.0 g of this cerium-doped titanium oxide and 45.0 ml of distilled water were placed in a 100 ml four-necked flask, stirred for 10 minutes, and then copper chloride dihydrate (CuCl).₂ 2H₂O) 13.4 mg was added, heated to 90 ° C in an oil bath, and stirred for 1 hour. After stirring for 1 hour, the mixture was filtered and washed with distilled water until the conductivity of the washing water became 1 mS / m or less. The obtained wet cake was dried in an air atmosphere at 110 ° C. for 12 hours and then pulverized in an agate mortar to obtain a photocatalyst (photocatalyst 42) having a copper compound on its surface.</p><p>Comparative Example 15 Sample 19 (TiO) instead of sample 22₂A photocatalyst 43 in which a copper compound was mixed with sample 19 was obtained by performing the same operation as in Example 38 except that brand: FP-6, no doping element was used.</p><p> Comparative example 16 Sample 19 (TiO) instead of sample 22₂A photocatalyst 44 in which an iron compound was mixed with sample 19 was obtained by performing the same operation as in Example 39 except that brand: FP-6, no doping element was used.</p><p> It was found that in Examples 1 to 39 of the present invention, excellent photocatalytic activity can be obtained. On the other hand, in Comparative Examples 1 to 7 not supporting a metal, photocatalytic activity was not obtained. Further, in Comparative Examples 8 to 11, 15 and 16 in which the element was not doped, photocatalytic activity was not obtained. Further, in Comparative Example 14, the photocatalytic activity was insufficient because the doping element was Ce. Further, in Comparative Examples 12 and 13, it is considered that the photocatalytic activity could not be obtained because the firing temperature was too low and the doping of the element was insufficient.</p><p> Further, FIG. 4 shows Comparative Example 7 (TiO) from the left.₂(Rutile)), Comparative Example 8 (Cu-supported / TiO)₂(Rutile)), Comparative Example 1 (Cr-doped TiO₂), Example 1 (Cu-supported / Cr-doped TiO)₂) Represents the rate of carbon dioxide generation per unit time.</p><p><tables num="1"><img file="JP2012016697A_D0001.tif" /></tables></p><p><tables num="2"><img file="JP2012016697A_D0002.tif" /></tables></p><p><tables num="3"><img file="JP2012016697A_D0003.tif" /></tables></p><p><tables num="4"><img file="JP2012016697A_D0004.tif" /></tables></p><p><tables num="5"><img file="JP2012016697A_D0005.tif" /></tables></p><p> As a matter of course, the above-described embodiment and a plurality of modifications can be combined as long as the contents do not conflict with each other. Further, in the above-described embodiments and modifications, the structure of each part and the like have been specifically described, but the structure and the like can be changed in various ways within the range satisfying the present invention.</p><p> This application claims priority based on Japanese Patent Application No. 2010-132706 filed on June 10, 2010, and incorporates all of its disclosures herein.</p>