JP2006095520A - Manufacturing method of heteroatom introduction-type titanium oxide photocatalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a heteroatom introduction-type titanium oxide photocatalyst having high performance as a photocatalyst in a visible light area. <P>SOLUTION: The method comprises the steps of mixing a reactive compound containing nitrogen atom to be introduced with titanium oxide, then casting ionizing radiation to partially activate the titanium oxide and the reactive compound and subsequently heating them in an oxygen-free atmosphere. The performance of the photocatalyst is highly enhanced under the visible light by this method as compared with the case without irradiation with the ionizing radiation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heteroatom-introduced titanium oxide photocatalyst exhibiting high performance under visible light.

  Conventionally, titanium oxide, particularly anatase-type titanium dioxide, has been widely used as a photocatalyst. When used as a photocatalyst, this anatase-type titanium dioxide exhibits catalytic activity in ultraviolet light, but exhibits little catalytic activity in visible light. From the viewpoint of efficient use of solar energy and from the viewpoint of using a light source other than sunlight, a photocatalyst that operates under visible light irradiation is required.

At present, a heteroatom-introduced titanium oxide photocatalyst such as nitrogen, sulfur, carbon or the like is attracting attention as a visible light operation type photocatalyst capable of operating in such a visible light region. Japanese Patent Laid-Open No. 2001-207082 (Patent Document 1) describes a method for producing a nitrogen-introduced titanium oxide photocatalyst using ammonia as a nitrogen source. This method requires heat treatment at a high temperature of 600 ° C. or higher, and the specific surface area of titanium oxide is considerably reduced to 50 m ² / g or less. Since the specific surface area reflects the amount of the titanium oxide photocatalyst that adsorbs the treatment substance, the larger the specific surface area, the larger the adsorption amount of the treatment substance and the greater the ability of the photocatalyst to decompose and remove. Therefore, it is not preferable from the viewpoint of the processing ability of the photocatalyst to reduce the specific surface area by heat treatment at a high temperature during the production of the titanium oxide photocatalyst.

  Moreover, the manufacturing method of the nitrogen introduction | transduction type titanium oxide photocatalyst described in Unexamined-Japanese-Patent No. 2002-154823 (patent document 2) which uses urea as a nitrogen source is 400 to 450 degreeC which is low temperature compared with the said ammonia treatment method. Therefore, the specific surface area is maintained.

  The method for producing a sulfur-introduced titanium oxide photocatalyst using thiourea or the like as a sulfur source described in Japanese Patent Application Laid-Open No. 2004-143032 (patent document 3) is characterized by simultaneously introducing sulfur into titanium oxide in addition to nitrogen. .

It is also known that a carbon-introduced titanium oxide photocatalyst can be produced by mixing thiourea and urea with titanium oxide and heating at a temperature of 400 to 500 ° C. (for example, “Degradation of Methylene Blue on Carbonate Species- See doped TiO ₂ Photocatacatalysts under Visible Light “Chemistry Letters Vol. 33, P. 750 (2004) (Non-patent Document 1)).

  Japanese Patent Application Laid-Open No. 2000-70728 (Patent Document 4) discloses a method of increasing photocatalytic activity by irradiating a coating containing a photocatalyst with a low energy electron beam of 20 to 80 kV. This method is intended to activate only the portion exposed on the surface of the photocatalyst coating effective only for ultraviolet light. The principle of improving photocatalytic activity is to increase the electron density by irradiating crystal defects of the photocatalyst with an electron beam to increase the photocatalytic activity.

JP2001-207082 JP 2002-154823 A JP2004-143032 JP 2000-70728 A "Degradation of Methylene Blue on Carbonate Species-doped TiO2 Photocatacatalysts under Visible Light" Chemistry Letters Vol.33, P.750 (2004)

  The heteroatom-introduced titanium oxide photocatalyst, which is the visible light responsive photocatalyst, is a substance that exhibits good photocatalytic activity in the visible light region. However, in order to use solar energy and the like more efficiently, it is desirable to further improve the performance of the visible light responsive photocatalyst such as the heteroatom-introduced titanium oxide.

  The present invention has been made in view of the above-described conventional problems, and the purpose thereof is a heteroatom-introduced titanium oxide photocatalyst having high performance as a photocatalyst in the visible light region, particularly a nitrogen-introduced titanium oxide photocatalyst and a sulfur-introduced oxidation. The object is to provide a titanium photocatalyst and a carbon-introduced titanium oxide photocatalyst.

  The present invention has been made to achieve the above object, and relates to a method for producing a heteroatom-introduced titanium oxide photocatalyst using a reactive compound containing a heteroatom to be introduced as a heteroatom supply source. In particular, the present invention relates to a method for producing a nitrogen-introduced titanium oxide photocatalyst.

  The method of the present invention includes (1) mixing titanium oxide and a nitrogen compound and irradiating with ionizing radiation, and (2) heating the mixture irradiated with ionizing radiation in an oxygen-free atmosphere. Nitrogen compounds from urea, thiourea, 1,1-dimethylurea, urea compounds, cyanuric acid, hydrazine, melamine, amines, amino acids, amino acid bases, amides, azides, cyan, cyanate, cyanate, or cyanate Preferably, it is at least one selected material. The ionizing radiation is preferably α rays, β rays, γ rays, accelerated electron rays, and X rays.

  In the method of the present invention, the ionizing radiation is preferably performed in an oxygen-free atmosphere such as an ammonia gas atmosphere. The heat treatment is performed in a temperature range of 130 ° C. to 600 ° C., preferably in an ammonia atmosphere. If there is a nitrogen compound residue, it is preferably removed.

  In the present invention, in the step (1), titanium oxide is previously dried, or a mixture of titanium oxide and a reactive compound is irradiated at 80 ° C. or higher and 120 ° C. or lower before irradiation with ionizing radiation. Can be dried at temperature.

  According to the present invention, the photocatalytic performance under visible light can be improved by irradiating with ionizing radiation as compared with those not irradiating with ionizing radiation.

  In order to improve the activity of the photocatalyst, in particular, the photocatalyst of heteroatom-introduced titanium oxide, the present inventors have studied various methods for introducing a heteroatom. As a result, after being activated by irradiating ionizing radiation in an oxygen-free atmosphere after mixing titanium oxide and a reactive compound, preferably urea or thiourea, heat treatment is performed in an oxygen-free atmosphere. It has been found that the photocatalytic performance under visible light is improved as compared with the case where no radiation is irradiated.

  In particular, the present invention relates to a method capable of providing a nitrogen-introduced titanium oxide photocatalyst having a catalytic ability superior to that of the prior art by using a urea compound.

  The production method of the present invention will be described below with reference to the drawings.

  The first step of the method of the present invention (see FIG. 1) is a step of mixing a photocatalyst raw material (preferably titanium oxide) and a reactive compound and activating them by irradiating with ionizing radiation. The mixing is not particularly limited as long as the raw material of the photocatalyst and the reactive compound can be mixed uniformly. For example, a method of mixing and pulverizing titanium oxide and a reactive compound in a ball mill or a mortar, or a method of mixing titanium oxide and a reactive compound. There are methods such as mixing in a container irradiated with ionizing radiation after pulverizing with a ball mill or mortar.

  Titanium oxide, zinc oxide, tin oxide, iron oxide, tungsten oxide, silicon oxide, niobium oxide, etc. can be used as the raw material for the photocatalyst, but titanium oxide has the highest performance as a photocatalyst. is there. Therefore, in the present invention, among the photocatalyst materials, titanium oxide is most preferable as the raw material for the heteroatom-introducing photocatalyst. Therefore, in the following description, titanium oxide is described as a raw material for the photocatalyst.

  Examples of the heteroatom introduced into titanium oxide include nonmetallic atoms such as nitrogen, sulfur, and carbon, and metallic atoms such as chromium, vanadium, and iron. Among them, a photocatalyst in which nitrogen, sulfur, or carbon is introduced into titanium oxide can have high performance as a visible light responsive photocatalyst. Accordingly, a preferred embodiment of the present invention relates to a method for producing a visible light responsive photocatalyst containing nitrogen and / or sulfur and / or carbon as a hetero atom. That is, a preferred embodiment of the present invention is a method for producing a visible light responsive titanium oxide photocatalyst containing at least one heteroatom selected from nitrogen, sulfur and carbon. In particular, the present invention is directed to a visible light responsive titanium oxide photocatalyst in which a nitrogen source is introduced as a different atom.

  Reactive compounds containing nitrogen, sulfur or carbon include urea, thiourea, thiourea dioxide, 1,1-dimethylurea, urea compounds, cyanuric acid, hydrazine, melamine, amines, amino acids, amino acid bases, amides, azides, Examples include cyan, cyanate, cyanate, and cyanate. These compounds contain nitrogen, sulfur or carbon, and become a source of introduction of nitrogen, sulfur and carbon into titanium oxide. Among these substances, at least one kind of reactive compound can be used, but is not necessarily limited thereto. In particular, urea, thiourea, cyanuric acid, and melamine, which are easy to handle and highly reactive, are preferable from the viewpoint of toxicity, reactivity, and the like. Urea is preferred when introducing nitrogen as a heteroatom.

  The mixing ratio of the above-mentioned titanium oxide and the reactive compound may be arbitrary. For example, when urea powder is used as the nitrogen compound, urea powder is mixed with titanium oxide powder 100 at a weight ratio of 10 to less than 1000. It is desirable to do. This is because when the weight ratio is less than 10, urea is too little to introduce a sufficient amount of nitrogen into titanium oxide, and when the weight ratio is 1000 or more, the urea powder becomes excessive.

  In the present invention, the titanium oxide is preferably dried. Therefore, in the first step, a pre-dried titanium oxide catalyst is used, or the mixture of the titanium oxide and the reactive compound is heated and dried before irradiating with ionizing radiation, so that moisture adsorbed on the titanium oxide is removed. It is preferable to remove. Moisture is decomposed by ionizing radiation to generate OH radicals and the like, and, like oxygen, interferes with the reaction between nitrogen, sulfur, carbon, etc., which will be described later, and titanium oxide. In the first step, when a titanium oxide catalyst dried in advance is used, the titanium oxide may be dried by heat treatment. Moreover, what is necessary is just to heat-dry a mixture at predetermined temperature, when drying the mixture of a titanium oxide and a reactive compound. When the mixture is heated, it is necessary to heat the mixture under a temperature condition that does not cause a reaction between the titanium oxide and the reactive compound.

  The drying temperature is preferably 80 ° C. or higher and 120 ° C. or lower, more preferably 80 ° C. or higher and 100 ° C. or lower. By drying in such a temperature range, the reaction between the titanium oxide and the reactive compound can be prevented (especially in the case of urea, which is a nitrogen introduction source).

  The means for drying the titanium oxide alone or the mixture of the titanium oxide and the reactive compound is not particularly limited, and can be dried by, for example, a dryer, an oven, an electric furnace or the like.

  The dried titanium oxide alone or the mixture of titanium oxide and reactive compound is preferably sealed with moisture-free dry air, nitrogen gas, argon gas, helium gas or the like.

  Next, the titanium oxide and the reactive compound are subjected to ionizing radiation irradiation treatment.

  The ionizing radiation irradiation treatment of the above-mentioned mixture of titanium oxide and reactive compound is preferably performed in a sealed container filled with an inert gas such as nitrogen, argon or helium so that oxygen does not exist. Alternatively, urea or the like may be filled with ammonia that is generated by being decomposed by ionizing radiation. Examples of the ionizing radiation include α rays, β rays, γ rays, accelerated electron rays, X rays, and the like. Accelerated electron rays and γ rays with facilities capable of irradiation processing on a commercial scale are preferable. Further, the sealed container has a thickness that allows the ionizing radiation to pass through, and needs to be selected depending on the energy of the ionizing radiation. For example, in the case of an accelerated electron beam of about 200 keV, it is necessary to use a titanium plate having a thickness of 50 μm or less as an electron beam window. Moreover, if it is an electron beam of 2 MeV or more, since a glass bottle with a thickness of about 1 mm can be transmitted, a pressure-resistant glass bottle or the like may be used. If a material that absorbs or reflects ionizing radiation is used as a sealed container, the ionizing radiation cannot be transmitted, and therefore the mixture of titanium oxide and the reactive compound cannot be activated.

  When ionizing radiation is irradiated to a mixture of titanium oxide and a reactive compound, it is considered that the titanium oxide is partially activated by the elimination of lattice oxygen. After the lattice oxygen is released, it becomes a lattice defect, which is presumed to provide a place for foreign atoms such as nitrogen, sulfur, and carbon to enter during the heat treatment. Nitrogen compounds are considered to be partially cleaved by chemical bonds by irradiation with ionizing radiation to form active species such as radicals. Most of them are considered to be the original compounds and similar compounds even after recombination, but some active species such as radicals react with titanium oxide to react with nitrogen-titanium, sulfur-titanium, carbon-titanium, nitrogen- It is considered that a bond of oxygen, sulfur-oxygen, carbon-oxygen, etc. is formed. At this time, nitrogen, sulfur and carbon become a part of the titanium oxide crystal, and in the subsequent heat treatment, different atoms are easily introduced into the titanium oxide crystal, and more foreign atoms are introduced than in the normal heat treatment. It is thought. The activation of the reactive compound with ionizing radiation is presumed from the generation of ammonia after irradiation with ionizing radiation using urea as the reactive compound. Here, when oxygen or moisture is present, it is considered that lattice defects formed after oxygen is released from titanium oxide disappear by oxidation again. Oxygen and moisture are activated by ionizing radiation to become ozone and OH radicals and show strong oxidizing power. Therefore, when irradiating with ionizing radiation, it is desirable that oxygen and moisture do not exist. However, since the reactive compound also reacts with oxygen and moisture, if the reactive compound is present in an amount greater than the equivalent amount required for the reaction compared to oxygen or moisture, an oxygen defect in titanium oxide is formed. Reacts with heteroatom to react with titanium oxide.

  The formation of lattice defects in titanium oxide by ionizing radiation and the formation of active species such as radicals of reactive compounds are considered to contribute to the improvement of the photocatalytic performance under visible light.

  The second step of the method of the present invention is a step of heat-treating the activated mixture in an oxygen-free atmosphere. (See FIG. 1). The heat treatment is performed using means capable of heating the mixture to a predetermined temperature, but this means is not particularly limited. For example, there are a method of treating in an oxygen-free atmosphere firing furnace, a method of treating the inside of the tubular furnace in an oxygen-free state, and heating by an electric heater or a burner from the outside.

  Moreover, when heating the said mixture, what is necessary is just an oxygen-free atmosphere, and the kind of atmosphere in particular is not limited. For example, when urea is used as the reactive compound, nitrogen gas, argon gas, ammonia gas and the like are suitable.

  Although it is necessary to transfer the above-mentioned mixture from the sealed container to the heat treatment apparatus after ionizing radiation irradiation, it is not particularly necessary to worry about the presence of oxygen and moisture. That is, there is no particular problem even if the sealed container is opened in the atmosphere and the mixture is exposed to oxygen and water vapor and then refilled into a heat treatment apparatus. The mixture described above is preferably replaced with a gas not containing oxygen after being refilled in a heat treatment apparatus to make an oxygen-free atmosphere. Moreover, you may add a reactive compound to the mixture mentioned above before transferring to a heat processing apparatus. This is because a part of the reactive compound is decomposed by irradiation with ionizing radiation, so that the decomposed portion is replenished. In particular, when a strong dose of ionizing radiation is irradiated, since the decomposition of the reactive compound is remarkable, it is preferable to add the reactive compound before the heat treatment. The reactive compound added before the heat treatment is preferably a reactive compound mixed before ionizing radiation irradiation, but another type of reactive compound may be added.

  In the heat-treated mixture, a substance obtained by thermally decomposing a heteroatom introduction source (for example, a reactive compound such as urea) remains, and it is necessary to sufficiently remove this. For example, when the reactive compound is urea, the heat-treated mixture is washed with water to remove impurities. Further, the washed mixture is dried.

  In the embodiment described above, the case where both the titanium oxide and the predetermined nitrogen compound are in the form of powder has been described. However, the present invention is not necessarily limited thereto. For example, a liquid nitrogen compound may be applied to thin film titanium oxide, irradiated with ionizing radiation, and then heated to react.

  Specific examples of the above-described embodiment will be described below as examples.

Example 1
Anatase-type titanium dioxide powder and urea powder previously dried at 100 ° C. were mixed at a weight ratio of 100 to 100, and sealed in a vial replaced with nitrogen gas. The vial was irradiated with an acceleration electron beam of 10 MeV for about 600 kGy. Thereafter, the mixture was taken out and heat-treated at 450 ° C. for 2 hours in ammonia gas. The powder turned orange. The change in color is due to the introduction of nitrogen into the titanium oxide. The powder obtained by this treatment was washed with water and dried.

(Example 2)
Anatase-type titanium dioxide powder and urea powder were mixed at a weight ratio of 100: 100 and sealed in a vial replaced with nitrogen gas. The vial was irradiated with a 10 MeV electron beam at about 600 kGy. Then, the mixture was taken out and heat-treated at 300 ° C. for 2 hours in ammonia gas. The powder was colored pale yellow. The powder obtained by this treatment was washed with water and dried.

(Example 3)
Anatase-type titanium dioxide powder and urea powder were mixed at a weight ratio of 100: 100, dried at 80 ° C. overnight or more to remove moisture, and then sealed in a vial replaced with nitrogen gas. The vial was irradiated with an acceleration electron beam of 10 MeV for about 600 kGy. Thereafter, the mixture was taken out and heat-treated at 450 ° C. for 2 hours in ammonia gas. The powder turned orange. The change in color is due to the introduction of nitrogen into the titanium oxide. The powder obtained by this treatment was washed with water and dried.

Example 4
Anatase-type titanium dioxide powder and urea powder were mixed at a weight ratio of 100: 100, dried at 80 ° C. overnight or more to remove moisture, and then sealed in a vial replaced with nitrogen gas. The vial was irradiated with an acceleration electron beam of 10 MeV for about 600 kGy. Then, the mixture was taken out and heat-treated at 300 ° C. for 2 hours in ammonia gas. The powder was colored pale yellow. The powder obtained by this treatment was washed with water and dried.

(Example 5)
In Example 1, it carried out similarly except the irradiation amount of the acceleration electron beam having been 210 kGy. The resulting powder was orange.

(Comparative Example 1)
In Example 1, the same operation was performed except that only the heat treatment was performed without performing accelerated electron beam irradiation. The resulting powder was orange.

(Comparative Example 2)
In Example 2, the same operation was performed except that only the heat treatment was performed without accelerating electron beam irradiation. The obtained powder was light yellow.

(Comparative Example 3)
Anatase-type titanium dioxide powder and urea powder were mixed at a weight ratio of 100: 100 and packed in a quartz glass tube. While flowing nitrogen, drying was performed at 80 ° C. for 1 hour or longer to remove moisture, and then the gas was replaced with ammonia gas, followed by heat treatment at 450 ° C. for 2 hours. The powder turned orange. The powder obtained by this treatment was washed with water and dried.

(Comparative Example 4)
Anatase-type titanium dioxide powder and urea powder were mixed at a weight ratio of 100: 100 and packed in a quartz glass tube. While flowing nitrogen, drying was performed at 80 ° C. for 1 hour or more to remove moisture, and then the gas was replaced with ammonia gas, followed by heat treatment at 300 ° C. for 2 hours. The powder was colored pale yellow. The powder obtained by this treatment was washed with water and dried.

(Performance evaluation test 1)
The performance of the photocatalysts produced in Example 1, Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 was evaluated by the following method.

Photocatalyst powder was apply | coated to the glass plate, the methylene blue aqueous solution was dripped, and methylene blue was adsorb | sucked to the photocatalyst. Thereafter, visible light (1.0 mW / cm ² ) was irradiated. Since the photocatalyst oxidizes methylene blue by light irradiation and is decolorized, the decolorization rate was measured to evaluate the performance. Table 1 shows the decolorization rate, that is, the rate of decrease in absorbance of the aqueous solution per hour of light irradiation.

  As shown in Table 1, at the time of visible light irradiation, the rate of decrease in absorbance was about 1.3 times faster in Example 1 than in Comparative Example 1 and in Example 2 than in Comparative Example 2. It was. It was found that the photocatalytic performance under visible light was improved by irradiating the electron beam in this way. As shown in Table 1, Comparative Example 1 and Comparative Example 2, and Comparative Example 3 and Comparative Example 4 each had the same value, but this is a heat treatment without taking a drying time in advance. This is considered to be due to the fact that water was desorbed and removed from the titanium oxide by the process until the processing temperature was reached (water is removed before rising to 120 ° C.). Specifically, when a quartz glass tube is filled with a mixture of titanium oxide and urea and heat-treated, moisture is condensed on both ends of the quartz glass tube that is not heated, and only a small amount of water vapor exists in the heated part. It was confirmed that it was not. Accordingly, the process preferably having no moisture is an electron beam irradiation treatment process in which water vapor cannot escape in a sealed container. In the method of the present invention, titanium oxide is irradiated before irradiation with ionizing radiation in step (1). Alternatively, it is preferable to dry a mixture of titanium oxide and a reactive compound.

(Performance evaluation test 2)
The performance of the photocatalysts produced in Example 3, Example 4, Example 5, and Comparative Example 3 was evaluated by the following method.

  10 mg of photocatalyst was added to 40 g of a 0.1 mmol / L methylene blue aqueous solution, and the mixture was stirred for 6 hours while applying 10,000 LUX light with a fluorescent lamp. The remaining methylene blue concentration was measured with a spectrophotometer. Moreover, what added 10 mg of photocatalysts to 40 g of 0.1 mmol / L methylene blue aqueous solution was preserve | saved for 6 hours in the dark place, and the part for which the methylene blue density | concentration fell was made into adsorption amount. The methylene blue decomposition rate was calculated by the following formula (1). Furthermore, using the formula (2), the methylene blue decomposition rate of the catalyst of each example was a relative value when the decomposition rate of the catalyst of Comparative Example 1 was set to 100. The results are shown in Table 2.

  As shown in Table 2, it was found that, in the visible light irradiation, the methylene blue decomposition performance was higher in the example than in the comparative example 1.

  The amount of nitrogen contained in the powders obtained in Example 3 and Comparative Example 3 was measured using a CHN analyzer NCH-900 (manufactured by Sumika Chemical Analysis Co., Ltd.), and the results shown in Table 3 were obtained.

  As shown in Table 3, it was found that more nitrogen atoms were introduced into the photocatalyst of Example 3 than to Comparative Example 3.

  From the above results, it was found that irradiation with an accelerated electron beam such as an accelerated electron beam improves the introduction amount of different atoms such as nitrogen into the photocatalyst and improves the performance of the photocatalyst under visible light. did.

  The present invention is a method for producing a heteroatom-introduced titanium oxide photocatalyst, characterized in that a reactive compound containing a heteroatom to be introduced with titanium oxide is subjected to ionizing radiation treatment and then heat-treated in an oxygen-free atmosphere. . The photocatalyst of the present invention has various fields of use similar to those of ordinary photocatalysts. For example, it can be used in fields such as deodorization, sterilization, VOC removal, and superhydrophilic films.

It is a figure for demonstrating the manufacturing method of the photocatalyst of this invention.

Claims (8)

(1) mixing titanium oxide and a nitrogen compound and irradiating with ionizing radiation;
(2) A method for producing a nitrogen-introduced titanium oxide photocatalyst excellent in photocatalytic performance under visible light, comprising a step of heat-treating a mixture irradiated with ionizing radiation in an oxygen-free atmosphere.   The nitrogen compound is urea, thiourea, 1,1-dimethylurea, urea compound, cyanuric acid, hydrazine, melamine, amine, amino acid, amino acid base, amide, azide, cyan, cyanate, cyanate, or cyanate The method for producing a nitrogen-introduced titanium oxide photocatalyst according to claim 1, wherein the material is at least one substance selected from the group consisting of:   The method for producing a nitrogen-introduced titanium oxide photocatalyst according to claim 1 or 2, wherein the ionizing radiation is α rays, β rays, γ rays, accelerated electron rays, or X rays.   The method for producing a nitrogen-introduced titanium oxide photocatalyst according to any one of claims 1 to 3, wherein the ionizing radiation is irradiated in an oxygen-free atmosphere after mixing titanium oxide and a nitrogen compound.   5. The nitrogen-introduced titanium oxide according to claim 1, wherein the residue of the nitrogen compound is removed after the heat treatment is performed in a temperature range of 130 ° C. or higher and 600 ° C. or lower. A method for producing a photocatalyst.   The method for producing a nitrogen-introduced titanium oxide photocatalyst according to any one of claims 1 to 5, wherein the ionizing radiation is irradiated in an ammonia gas atmosphere.   The method for producing a nitrogen-introduced titanium oxide photocatalyst according to any one of claims 1 to 6, wherein the heat treatment is performed in an ammonia gas atmosphere. In the step (1), titanium oxide is previously dried, or a mixture of titanium oxide and a reactive compound is dried at a temperature of 80 ° C. or higher and 120 ° C. or lower before irradiation with ionizing radiation. The method for producing a nitrogen-introduced titanium oxide photocatalyst according to any one of claims 1 to 7.

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