JP6722313B2 - Photocatalytic material - Google Patents

Description

The present invention relates to a photocatalytic material, and more particularly, to a visible light responsive photocatalytic material.

The photocatalyst material has semiconductor properties, and by irradiation with light having a band gap or more, electron-hole pairs are generated in the conduction band and the valence band. As a result, due to the redox action of electron-hole pairs, active oxygen species such as hydroxyl radicals and superoxide ions are generated on the surface of the photocatalyst material and its vicinity. The photocatalytic material is a substance having an organic substance decomposing action and a self-cleaning action due to the oxidizing power and hydrophilicity of these active oxygen species.

Among the photocatalytic materials, titanium oxide has a high photocatalytic effect and has been widely studied. However, titanium oxide has a large band gap and absorbs ultraviolet light, but does not absorb visible light. Therefore, titanium oxide exhibits photocatalytic activity under ultraviolet light, but does not exhibit activity under visible light, and therefore cannot exhibit photocatalytic effect in an indoor environment where the amount of ultraviolet rays is extremely small.

On the other hand, tungsten oxide is known as a visible light responsive photocatalyst material. However, since the lower end potential of the conduction band of tungsten oxide is more positive than the redox potential of oxygen, it is difficult for electrons excited in the conduction band to reduce oxygen. Therefore, on the contrary, electrons recombine with holes and tungsten oxide alone does not exhibit high photocatalytic activity.

Therefore, it is known that by forming an electron-withdrawing substance (co-catalyst) on the surface of the tungsten oxide particles, it can be used as a visible light responsive photocatalyst. In this visible light responsive photocatalyst, recombination of electrons excited in the conduction band and holes generated in the valence band by light irradiation is suppressed, so that the photocatalytic activity of the tungsten oxide particles is enhanced.

For example, Patent Document 1 discloses a photocatalyst in which platinum particles having a primary particle diameter of 3 nm to 20 nm are carried on the surface of tungsten oxide particles by 0.03 to 5 parts by weight per 100 parts by weight of tungsten oxide particles. Furthermore, the photocatalyst has a high photocatalytic activity because at least a part of the surface of the tungsten oxide particles is independently supported on the surface in a state where the platinum particles are in contact with each other (beaded shape).

Further, since tungsten oxide has a property of being easily dissolved in an alkaline solution, there is a possibility that the photocatalytic activity may be reduced by a basic gas such as ammonia generated in a smoking room, a toilet, or the like. Further, for example, when the wall surface coated with tungsten oxide is wiped and washed with a household basic detergent or the like, the photocatalytic activity may be similarly reduced.

Therefore, in Patent Document 2, by partially coating the tungsten oxide and the promoter supported on the surface of the tungsten oxide with titanium oxide, the photocatalytic activity is higher than that of the uncoated tungsten oxide. It is disclosed to rapidly decompose volatile aromatic compounds therein.

JP-A-2009-160566 (Published July 23, 2009) JP 2012-110831 A (Published June 14, 2012)

However, the photocatalytic activity of the conventional tungsten oxide photocatalyst is still low, and improvement of the photocatalytic activity is required.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a photocatalytic material having a higher photocatalytic activity than the conventional tungsten oxide photocatalyst.

In order to solve the above problems, the photocatalyst material according to one embodiment of the present invention is a photocatalyst material containing a core particle containing tungsten oxide, and a promoter supported on the surface of the core particle,
It is characterized by being doped with halogen.

According to one aspect of the present invention, it is possible to enhance the photocatalytic activity of the tungsten oxide-based photocatalytic material.

It is sectional drawing which shows typically the photocatalyst material which concerns on Embodiment 1 of this invention. It is sectional drawing which shows typically the photocatalyst material which concerns on Embodiment 2 of this invention. It is sectional drawing which shows typically the photocatalyst material which concerns on Embodiment 3 of this invention. It is sectional drawing which shows typically the photocatalyst material which concerns on Embodiment 4 of this invention. 3 is a graph showing the relationship between the amount of hydrochloric acid added and the decomposition rate constant in the photocatalytic material according to the present invention. FIG. 6 is a diagram showing the relationship between the added amount of hydrochloric acid and the relative chlorine concentration contained in tungsten oxide in the photocatalytic material according to the present invention.

Tungsten oxide exhibits a photocatalytic effect while having a low photocatalytic activity because the electrons excited in the conduction band generate an active oxidative species through a two-electron reduction reaction or a four-electron reduction reaction of oxygen, and the oxidative decomposition reaction of the active oxidative species. It is thought that it is caused by.

However, in order to efficiently proceed the multi-electron reduction reaction of oxygen, it is necessary to carry the electrons excited in the conduction band to the surface of the photocatalyst particles and the promoter (precious metal etc.) carried on the surface.

As a result of earnest studies by the present inventors, the inventors have found that the photocatalytic activity is improved by adding halogen, which is an n-type impurity, to the tungsten oxide-based photocatalytic material, and completed the present invention.

[Embodiment 1]
An embodiment of the present invention will be described based on FIG. FIG. 1 is a sectional view schematically showing a photocatalytic material 1A according to this embodiment.

As shown in FIG. 1, the photocatalyst material 1A includes a core particle 2 and a co-catalyst 3 carried on the surface of the core particle 2. Further, although not shown, the photocatalyst material 1A contains halogen as an impurity.

(Core particle 2)
In the photocatalytic material 1A, the core particles 2 are composed of tungsten oxide particles. Therefore, the photocatalyst material 1A is a visible light responsive photocatalyst material that exhibits photocatalytic activity when irradiated with visible light. Although the core particle 2 of the first embodiment is made of tungsten oxide, the present invention is not limited to this, and the core particle 2 may include at least tungsten oxide.

The particle size of the core particles 2 is not particularly limited, but is preferably 5 nm or more and 100 nm or less. If the particle size is smaller than 5 nm, aggregation tends to occur, and if it is larger than 100 nm, the photocatalytic activity decreases. The particle size of the core particles 2 here is an average particle size calculated based on the BET specific surface area. The core particles 2 may be composed of particles having a uniform particle size, or may be composed of a mixture of particles having a non-uniform particle size. That is, the spread (size) and distribution shape of the particle size distribution of the core particles 2 are not particularly limited, and a plurality of peaks of the particle size distribution may exist.

The method for producing the tungsten oxide forming the core particles 2 may be a general method, for example, a method of thermally decomposing ammonium paratungstate (APT), a method of heating a metal tungsten powder in an oxygen atmosphere, and the like. When the particle size distribution of the tungsten oxide obtained by the above method is large, the tungsten oxide having a large particle size is removed through an appropriate filter before use. Alternatively, commercially available tungsten oxide may be used.

Further, the tungsten oxide constituting the core particle 2 may be one having a photocatalytic activity upon irradiation with visible light, and examples thereof include WO ₃ , W ₂₅ O ₇₃ , W ₂₀ O ₅₈ , and W ₂₄ O _68. ..

(Co-catalyst 3)
The promoter 3 is supported on the surface of the core particle 2. The promoter 3 enhances the photocatalytic activity of the photocatalytic material 1A. The co-catalyst 3 is composed of a metal or a metal compound having an electron-withdrawing property. Examples of the metal forming the promoter 3 include copper, platinum, palladium, iron, silver, gold, nickel, ruthenium, iridium, niobium, molybdenum and the like. Examples of the metal compound forming the promoter 3 include chloride, bromide, iodide, oxide, hydroxide, sulfate, nitrate, carbonate, phosphate, organic acid salt of the metal forming the promoter 3. And so on.

The cocatalyst 3 may be formed on the surface of the core particle 2 by (1) kneading the tungsten oxide particles forming the core particle 2 and the metal particles or metal compound particles forming the cocatalyst 3, or (2) ) After adding the tungsten oxide particles constituting the core particle 2 to the solution containing the metal or the metal compound constituting the co-catalyst 3, the obtained solution is heated or the obtained solution is irradiated with light to form the core particle 2 And a method of depositing a metal or a metal compound constituting the co-catalyst 3 on the surface of the.

The amount of the metal or metal compound forming the co-catalyst 3 (that is, the amount of the co-catalyst 3 carried on the surface of the core particle 2) was 0. It is preferably from 01% by weight to 3% by weight. When the co-catalyst 3 is a metal compound, the amount of the metal compound added (the amount of the co-catalyst 3 supported) indicates the amount of metal in the metal compound. When the amount of the above metal or metal compound added is less than 0.01% by weight, the effect as the co-catalyst 3 becomes small, and high photocatalytic activity cannot be obtained. If the amount of the metal or metal compound added is more than 3% by weight, the amount of the co-catalyst 3 covering the surface of the core particle 2 will increase. As a result, the amount of light reaching the core particles 2 is reduced, and thus high photocatalytic activity cannot be obtained.

(Impurity halogen)
The photocatalyst material 1A is doped with halogen. That is, the photocatalyst material 1A contains halogen added as an n-type impurity. The halogen added as the n-type impurity may be contained in at least one of the core particle 2 and the cocatalyst 3 of the photocatalyst material 1A, and is preferably contained in the core particle 2. Further, the photocatalyst material 1A is preferably doped with at least one of chlorine, fluorine, bromine, and iodine, and more preferably doped with chlorine from the viewpoint of easy availability and handling of raw materials. ..

The method of doping the photocatalyst material 1A with halogen is not particularly limited, and examples thereof include a method of treating the core particle 2 or the core particle 2 carrying the promoter 3 with a non-metal halide. For example, the photocatalyst material 1A can be doped with an n-type impurity by a method in which a non-metal halide is dissolved alone or in a suitable solvent, and the core particle 2 or the core particle 2 carrying the cocatalyst 3 is immersed in the solution. Can be added as halogen.

As used herein, the term “non-metal halide” refers to a compound containing no metal element and containing at least one halogen element. Further, simple halogens (chlorine, fluorine, bromine, iodine, etc.) are also included in the category of “non-metal halide”.

Examples of the non-metal halide include hydrogen halide, hydrohalic acid, ammonium halide and the like. Examples of the hydrogen halide include hydrogen chloride, hydrogen fluoride, hydrogen bromide, hydrogen iodide and the like. Hydrohalic acid is an aqueous solution of hydrogen halide, and examples thereof include hydrochloric acid (hydrochloric acid), hydrogen fluoride (hydrofluoric acid), hydrogen bromide (bromic acid), hydrogen iodide (iodic acid), and the like. To be Examples of ammonium halides include ammonium chloride, ammonium fluoride, ammonium bromide, and ammonium iodide.

As described above, the photocatalyst material 1A of the present embodiment contains the halogen added as the n-type impurity. Thereby, the photocatalytic activity of the tungsten oxide-based photocatalytic material 1A can be enhanced. The principle by which the photocatalytic activity of the photocatalytic material 1A is improved is unknown. However, it is considered that the photocatalytic activity is improved by the electric conductivity of the photocatalytic material 1A being improved by the halogen doping. That is, the photocatalyst material 1A becomes an n-type semiconductor by being doped with halogen, which is an n-type impurity. Usually, in an n-type semiconductor, electrons are excited in the conduction band from a donor at room temperature. Therefore, also in the halogen-doped photocatalytic material 1A, electrons are excited from the doped halogen (donor) to the conduction band of tungsten oxide (core particle 2). Therefore, excited electrons exist in the photocatalyst material 1A before light irradiation (irradiation of visible light). As a result, due to the presence of the electrons, the electrons excited in the conduction band after the photocatalyst material 1A is irradiated with light easily flow into the cocatalyst 3. This is considered to improve the electric conductivity of the photocatalytic material 1A and improve the photocatalytic activity. Therefore, the tungsten oxide-based photocatalyst material 1A having excellent photocatalytic activity under irradiation of visible light can be provided.

[Embodiment 2]
Another embodiment of the present invention will be described below with reference to FIG. FIG. 2 is a cross-sectional view schematically showing the photocatalytic material 1B according to this embodiment. For convenience of description, members having the same functions as those described in the first embodiment will be designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 2, the photocatalyst material 1B according to this embodiment is different from the photocatalyst material 1A of Embodiment 1 only in that the entire surfaces of the core particles 2 and the co-catalyst 3 are covered with the shell layer 4. Different.

The photocatalyst material 1B of the present embodiment is also doped with halogen as in the photocatalyst material 1A of the first embodiment. The halogen added as an n-type impurity to the photocatalyst material 1B has only to be contained in at least one of the core particle 2, the co-catalyst 3, and the shell layer 4, and is preferably contained in the core particle 2.

The shell layer 4 completely covers the entire surfaces of the core particles 2 and the promoter 3. The shell layer 4 is preferably made of titanium oxide.

When the thickness of the shell layer 4 is smaller than 1 nm, the surface of the core particle 2 and the surface of the co-catalyst 3 cannot be completely covered. When the thickness of the shell layer 4 is larger than 50 nm, the photocatalytic activity of the core particles 2 is reduced. Therefore, the thickness of the shell layer 4 is preferably 1 nm or more and 50 nm or less.

The weight ratio of the shell layer 4 to the core particles 2 is preferably 1.0 or less, and more preferably 0.01 or more and 1.0 or less. Thereby, it becomes possible to provide the photocatalyst material 1B having alkali resistance and excellent photocatalytic activity. The alkali resistance refers to the residual rate of the photocatalyst material 1B after the alkali resistance treatment. Specifically, when the weight of the photocatalyst material 1B before the alkali resistance treatment is Wa and the weight of the photocatalyst material 1A after the alkali resistance treatment is Wb, the alkali resistance is calculated by (Wa-Wb)/Wa×100. It is a value. The alkali resistance treatment can be carried out, for example, by immersing the photocatalyst material 1B in a 1 mol/L sodium hydroxide aqueous solution for 24 hours.

When the shell layer 4 is a titanium oxide layer, the method of coating the core particles 2 on which the cocatalyst 3 is formed with the shell layer 4 is performed by oxidizing the core particles 2 on which the cocatalyst 3 is formed in a solution in which the core particles 2 are dispersed. A method of growing a titanium oxide layer on the surface of the tungsten oxide particles that are the core particles 2 and the surface of the co-catalyst 3 formed on the surface of the tungsten oxide particles by adding a solution containing a titanium precursor (so-called solution Law). In such a solution method, the titanium oxide precursor is uniformly formed while gradually growing as a titanium oxide layer on the surfaces of the core particles 2 and the co-catalyst 3 in the solution after the addition of the solution containing the titanium oxide precursor. To go. At this time, the formed titanium oxide layer may be amorphous.

As the titanium oxide precursor, alkoxides such as titanium tetraisopropoxide, complexes such as titanium acetylacetonate and titanium lactate, and titanium aqueous solutions such as titanium chloride aqueous solution and titanium sulfate aqueous solution are used.

In addition, in Patent Document 1, a method of depositing a titanium oxide layer on the surface of the tungsten oxide particles by adding tungsten oxide particles to a solution containing a titanium oxide precursor and volatilizing a solvent in the solution (so-called impregnation method) Is listed. However, in the impregnation method, since the titanium oxide precursor is attached to the surface of the core particle and then heated to form the titanium oxide layer, the titanium oxide layer is not uniformly formed, and the surface of the core particle and the core particle are not formed. The surface of the supported cocatalyst cannot be completely covered by the titanium oxide layer.

When the shell layer 4 is a titanium oxide layer, it is preferably made of crystalline titanium oxide obtained by heat treatment after formation. This is because the crystalline titanium oxide densifies the shell layer 4 more than the amorphous titanium oxide. As a result, the photocatalyst material 1B having the shell layer 4 made of crystalline titanium oxide has higher alkali resistance than the photocatalyst material having the shell layer 4 made of amorphous titanium oxide.

As the crystalline titanium oxide forming the shell layer 4, one of anatase type and rutile type, or a mixture thereof is suitable. Anatase type titanium oxide is obtained by heating in air at a temperature of 400° C. or higher. On the other hand, rutile-type titanium oxide is obtained by heating at a temperature of 900° C. or higher. However, even if the temperature is lower than the above temperature, anatase-type or rutile-type titanium oxide may be partially formed depending on the production conditions.

As described above, the photocatalyst material 1B of the present embodiment is provided with the shell layer 4 that covers the entire surfaces of the core particles 2 and the cocatalyst 3, in addition to the configuration of the photocatalyst material 1A. Thus, in addition to the effect of the photocatalyst material 1A, it is possible to provide the tungsten oxide-based photocatalyst material 1B having higher alkali resistance than the conventional photocatalyst material in which the surface of the tungsten oxide is not covered with titanium oxide. It will be possible.

Further, when the shell layer 4 is a titanium oxide layer, it becomes possible to provide the photocatalytic material 1B which exhibits photocatalytic activity even by irradiation with ultraviolet light.

[Embodiment 3]
Next, still another embodiment of the present invention will be described based on FIG. FIG. 3 is a sectional view schematically showing the photocatalytic material 1C according to the present embodiment. Note that, as in the case of the second embodiment, for convenience of description, members having the same functions as the members described in the first and second embodiments are denoted by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 3, the photocatalyst material 1C according to the present embodiment is different from the photocatalyst material 1A of the first embodiment in that a core particle 2a is provided instead of the core particle 2. Also in the photocatalyst material 1C of the present embodiment, halogen is doped as in the photocatalyst materials 1A and 1B of the first and second embodiments. The halogen added as an n-type impurity to the photocatalyst material 1C may be contained in at least one of the core particles 2a and the co-catalyst 3, and is preferably contained in the core particles 2a.

The core particle 2a is composed of a composite of tungsten oxide and a metal oxide. The metal oxides forming the composite are titanium oxide, iron oxide, zinc oxide, copper oxide, platinum oxide, palladium oxide, silver oxide, gold oxide, nickel oxide, ruthenium oxide, iridium oxide, niobium oxide, and molybdenum oxide. Mention may be made of one or more oxides selected from the group consisting of: This metal oxide is preferably one that absorbs light in a wavelength range different from that of tungsten oxide, and is one or more oxides selected from the group consisting of titanium oxide, iron oxide, and zinc oxide. Is more preferable. That is, the core particle 2a may contain one kind of metal oxide or a plurality of kinds of metal oxides other than tungsten oxide.

The particle size of the core particles 2a is preferably 5 nm or more and 100 nm or less, like the particle size of the core particles 2 in the photocatalyst material 1A of the first embodiment. If the particle size is smaller than 5 nm, aggregation tends to occur, and if it is larger than 100 nm, the photocatalytic activity decreases.

The metal oxide forming the core particles 2a of the composite is preferably more than 0.01% by weight and less than 100% by weight with respect to tungsten oxide. If it is less than 0.01% by weight, the mixing effect of the metal oxide is not exhibited, and if it is more than 100% by weight, the mixing effect of the tungsten oxide is not exhibited.

In the mixture of the tungsten oxide and the metal oxide forming the core particle 2a, the metal oxide can absorb a wavelength of light different from that of tungsten oxide. Specifically, the absorption edge of tungsten oxide is around 460 nm. Therefore, when the metal oxide is titanium oxide or the like, it becomes possible to provide the photocatalytic material 1C that exhibits photocatalytic activity even when irradiated with ultraviolet light. On the other hand, when the metal oxide is copper oxide or the like, the absorption edge is around 620 nm, which is longer than the wavelength range of tungsten oxide. Therefore, the core particle 2a can absorb light in a longer wavelength range than the core particle 2 composed of a simple substance of tungsten oxide. Therefore, it becomes possible to improve the photocatalytic activity of the photocatalytic material 1C during irradiation of visible light.

As a method for producing a composite of tungsten oxide and a metal oxide other than tungsten oxide, a method of kneading the tungsten oxide particles and the metal oxide particles, or adding the tungsten oxide particles to the metal oxide precursor solution, Examples include a method of volatilizing the solvent in the solution.

The photocatalyst material 1C is obtained by forming the co-catalyst 3 on the manufactured core particles 2a by the method described in the first embodiment.

As described above, the photocatalyst material 1C of the present embodiment includes the core particles 2a different from the photocatalyst material 1A, and the core particles 2a are made of metal oxide other than tungsten oxide in addition to tungsten oxide. Thereby, in addition to the effect exhibited by the photocatalytic material 1A, it is possible to absorb light in a wider wavelength range. Therefore, it becomes possible to provide the photocatalyst material 1C having a wavelength different from that of the photocatalyst materials 1A and 1B of the first and second embodiments and exhibiting photocatalytic activity.

[Embodiment 4]
Another embodiment of the present invention will be described below with reference to FIG. FIG. 4 is a cross-sectional view schematically showing the photocatalytic material 1D according to this embodiment. For convenience of description, members having the same functions as those described in Embodiments 1 to 3 will be designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 4, the photocatalyst material 1D according to the present embodiment is different from the photocatalyst material 1C according to the third embodiment only in that the entire surfaces of the core particles 2a and the cocatalyst 3 are covered with the shell layer 4. Different.

Also in the photocatalyst material 1D of the present embodiment, halogen is doped as in the photocatalyst materials 1A, 1B and 1C of the first to third embodiments. The halogen added as an n-type impurity to the photocatalyst material 1D may be contained in at least one of the core particle 2a, the cocatalyst 3, and the shell layer 4, and is preferably contained in the core particle 2.

Similar to the photocatalyst material 1B of the second embodiment, the shell layer 4 completely covers the entire surfaces of the core particles 2a and the co-catalyst 3. The shell layer 4 is preferably made of titanium oxide.

As described above, the photocatalyst material 1D of the present embodiment includes the shell layer 4 that covers the entire surfaces of the core particles 2a and the cocatalyst 3 in addition to the configuration of the photocatalyst material 1C. As a result, in addition to the effect of the photocatalyst material 1C, it is possible to provide the tungsten oxide-based photocatalyst material 1D having higher alkali resistance than the conventional photocatalyst material in which the tungsten oxide surface has a portion not covered with titanium oxide. It will be possible.

In addition, when the shell layer 4 is a titanium oxide layer, it becomes possible to provide the photocatalytic material 1D that exhibits photocatalytic activity even by irradiation with ultraviolet light.

[Summary]
Photocatalyst materials 1A to 1D according to Aspect 1 of the present invention are the photocatalyst materials 1A to 1D including core particles 2 and 2a containing tungsten oxide and a co-catalyst 3 carried on the surfaces of the core particles 2 and 2a. It is characterized by being doped with halogen.

According to the above invention, the halogen added as the n-type impurity is contained. Thereby, the photocatalytic activity of the tungsten oxide-based photocatalytic material 1A can be enhanced.

In the photocatalyst materials 1A to 1D according to aspect 2 of the present invention, in the aspect 1, the core particles 2 and 2a are composed of tungsten oxide particles, or the tungsten oxide particles and a metal oxide other than tungsten oxide. It may be composed of a complex with.

According to the above invention, when the core particles 2 are made of tungsten oxide particles, the composition of the photocatalytic material can be simplified. On the other hand, when the core particles are formed of a composite of tungsten oxide and metal oxide, the metal oxide absorbs light having a wavelength different from that of tungsten oxide. Therefore, it is possible to absorb light in a wider range of wavelengths and exert a photocatalytic action.

The photocatalyst materials 1B and 1D according to the third aspect of the present invention preferably include the shell layer 4 that covers the entire surfaces of the core particles 2 and 2a and the cocatalyst 3 in the first or second aspect.

According to the above invention, it becomes possible to provide the tungsten oxide-based photocatalyst materials 1B and 1D having higher alkali resistance than the conventional photocatalyst material in which the surface of the tungsten oxide not covered with titanium oxide exists.

In the photocatalyst materials 1B and 1D according to aspect 4 of the present invention, in the aspect 3, the shell layer 4 is preferably made of titanium oxide.

According to the above invention, since the shell layer 4 is a titanium oxide layer, it is possible to provide the photocatalytic materials 1B and 1D that exhibit photocatalytic activity even when irradiated with ultraviolet light.

In the photocatalyst materials 1A to 1D according to aspect 5 of the present invention, in the aspects 1 to 4, the doped halogen may be chlorine.

According to the above invention, since the doped halogen is chlorine, it is possible to provide a photocatalytic material in which the raw material is easily available and easy to handle.

The present invention is not limited to the above-described embodiments, but various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in the different embodiments Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

(Experimental example 1)
After dispersing 135 g of commercially available tungsten oxide (Kishida Chemical Co., Ltd., 99.9%) in 1215 g of ion-exchanged water, it was pulverized and dispersed using a bead mill (Nippon Coke Industry, MSC50) to disperse the tungsten oxide particles. A liquid was obtained. The operating conditions of the bead mill were a bead diameter of φ0.1 mm (Nikkato), a peripheral speed of 10 m/s, and a treatment time of 360 minutes.

Subsequently, hexachloroplatinum (VI) hexahydrate was added to the obtained dispersion liquid of tungsten oxide particles so that the ratio of the weight of platinum alone to the weight of the tungsten oxide particles was 0.025% by weight. The product (Kishida Chemical Co., Ltd., 98.5%) was dissolved. Then, the dispersion liquid is heated at 100° C. to evaporate the water content, and then baked at 400° C. for 30 minutes, so that tungsten oxide particles (core) having 0.025 wt% platinum (co-catalyst) supported thereon are carried out. Particles).

An aqueous solution obtained by diluting the obtained tungsten oxide particles supporting platinum with 2.5 mL of hydrochloric acid (Kishida chemistry, 35.0%) and 5 mL of ion-exchanged water per 1 g of tungsten oxide particles supporting platinum (hydrochloric acid : After being immersed in ion-exchanged water volume ratio=1:2), the water was evaporated by heating at 100° C. As a result, a photocatalyst material was obtained in which the tungsten oxide particles supporting platinum were doped with chlorine as halogen.

Next, the photocatalytic activity (decomposition rate constant) was measured using the following method in order to evaluate the photocatalytic activity of the obtained photocatalytic material by irradiation of visible light with environmental pollutants. First, 1.3 g of the obtained photocatalyst material was placed in a petri dish, the petri dish was placed in a 5 L gas bag, and acetaldehyde was further introduced into the gas bag so that the concentration thereof was 500 ppm. Then, the gas bag was irradiated with a blue LED (wavelength 450 nm, irradiation intensity of 7 mW/cm ² on the photocatalyst material), and the change with time of the residual amount of acetaldehyde was measured by a gas detector tube. The logarithmic display of the measured residual amount of acetaldehyde was taken on the vertical axis and the elapsed time was taken on the horizontal axis, the magnitude of the gradient in the graph was calculated, and the value was defined as the decomposition rate constant. Based on the value of the decomposition rate constant, the gas decomposition performance, that is, the photocatalytic activity of the photocatalytic material was evaluated.

The decomposition rate constant of the photocatalyst material obtained in Experimental Example 1 was 3.84 [/h].

(Experimental example 2)
1 g of tungsten oxide particles supporting platinum was immersed in an aqueous solution (hydrochloric acid:ion exchanged water volume ratio=1:20) diluted with 0.25 mL of hydrochloric acid and 5 mL of ion exchanged water, except that In the same manner as in Experimental Example 1, tungsten oxide particles supporting platinum were doped with chlorine as halogen to obtain a photocatalyst material.

Next, the measurement and evaluation of the photocatalytic activity (decomposition rate constant) of the obtained photocatalytic material by irradiating the environmental pollutants with visible light were also performed by the same method as in Experimental Example 1. As a result, the obtained decomposition rate constant was 3.07 [/h].

(Experimental example 3)
1 g of platinum-supported tungsten oxide particles was immersed in an aqueous solution (hydrochloric acid:ion-exchanged water volume ratio=1:4) diluted with 1.25 mL of hydrochloric acid and 5 mL of ion-exchanged water. In the same manner as in Experimental Example 1, tungsten oxide particles supporting platinum were doped with chlorine as halogen to obtain a photocatalyst material.

Next, the measurement and evaluation of the photocatalytic activity (decomposition rate constant) of the obtained photocatalyst material by irradiating the environmental pollutants with visible light were performed in the same manner as in Experimental Example 1. As a result, the obtained decomposition rate constant was 3.33 [/h].

(Experimental example 4)
Experiments except that 1 g of platinum-supported tungsten oxide particles was immersed in an aqueous solution (hydrochloric acid:ion-exchanged water volume ratio=1:1) diluted with 5 mL of hydrochloric acid and 5 mL of ion-exchanged water By the same method as in Example 1, a photocatalyst material obtained by doping tungsten oxide particles supporting platinum with chlorine as halogen was obtained.

Next, the measurement and evaluation of the photocatalytic activity (decomposition rate constant) of the obtained photocatalytic material by irradiating the environmental pollutants with visible light were also performed by the same method as in Experimental Example 1. As a result, the obtained decomposition rate constant was 3.59 [/h].

(Comparative Example 1)
A photocatalyst material was prepared in the same manner as in Experimental Example 1 except that dipping with hydrochloric acid was not carried out to obtain a photocatalyst material composed of tungsten oxide particles supporting platinum not doped with chlorine. As a result of compositional analysis of the obtained photocatalyst material, chlorine was not detected.

Next, the measurement and evaluation of the photocatalytic activity (decomposition rate constant) of the obtained photocatalyst material by irradiating the environmental pollutants with visible light were performed in the same manner as in Experimental Example 1. As a result, the obtained decomposition rate constant was 3.24 [/h].

The measurement results in the above Experimental Examples 1 to 4 and Comparative Example 1 are summarized in the graph shown in FIG. In FIG. 5, the vertical axis is the decomposition rate constant, and the horizontal axis is the amount of hydrochloric acid added during immersion of the tungsten oxide. Further, the chlorine concentration in the photocatalyst materials obtained in Experimental Example 1, Experimental Example 4, and Comparative Example 1 was relatively measured using TOF-SIMS. The measurement results are summarized in FIG. The absolute concentration of chlorine contained in each photocatalyst material is unknown, but the photocatalyst material with 5 mL of hydrochloric acid added (Experimental Example 4) was more than that with 2.5 mL of hydrochloric acid added (Experimental Example 1). However, the relative concentration of hydrochloric acid contained in the photocatalytic material is higher. It is considered that the intensity of the relative concentration of hydrochloric acid was detected even in the photocatalyst material containing 0 mL of hydrochloric acid because of the background.

From the description of FIGS. 5 and 6, the photocatalytic activity (decomposition rate constant) of the photocatalyst material doped with chlorine (Experimental Examples 1 to 4) was improved as compared with the photocatalyst material not doped with chlorine (Comparative Example 1). You can see that Regarding the amount of hydrochloric acid added, it was found that a photocatalytic material in which the amount of hydrochloric acid added was 1.5 mL or more per 1 g of tungsten oxide particles exhibited particularly excellent photocatalytic activity. The decomposition rate constant of the photocatalyst material (Experimental Example 2) in which the added amount of hydrochloric acid is 0.25 mL is slightly lower than that of the photocatalyst material in which hydrochloric acid is not added (Comparative Example 1). It is believed that this is due to measurement variability. That is, when the amount of hydrochloric acid added is small (less than 1.25 mL), the effect of the present invention that the photocatalytic activity of the photocatalytic material is improved by doping with halogen (chlorine) is not so remarkable. If the amount of hydrochloric acid added is 1.25 mL or more, the effect of the present invention is considered to be remarkable.

(Experimental example 5)
A dispersion liquid containing tungsten oxide particles was obtained in the same manner as in Experimental Example 1. Subsequently, hexachloroplatinum (VI) hexahydrate was added to the obtained dispersion liquid of tungsten oxide particles so that the ratio of the weight of platinum alone to the weight of the tungsten oxide particles was 0.025% by weight. The product (Kishida Chemical Co., Ltd., 98.5%) was dissolved. Then, the dispersion was heated at 100° C. to evaporate the water content, and then baked at 400° C. for 30 minutes. As a result, tungsten oxide particles supporting 0.025% by weight of platinum with respect to the weight of the tungsten oxide particles were obtained.

6 g of the obtained platinum-supported tungsten oxide particles were added to 24 g of ion-exchanged water, and the above-described platinum-supported tungsten oxide particles were dispersed using a stirrer (Primix Co., Ltd. Filmix 40-40 type). I went. The operating conditions of the agitator were a peripheral speed of 40 m/s and a treatment time of 10 minutes.

Then, in order to form a shell layer composed of titanium oxide, 9 mL of the above dispersion liquid, 7 mL of titanium tetrachloride aqueous solution (Toho titanium) having a titanium concentration of 16% by weight, and 100 mL of deionized water are round-bottomed. After mixing in a flask to obtain a mixed solution, the obtained mixed solution was heated for 5 hours at a liquid temperature of 95°C using a mantle heater for a round bottom flask.

After that, the mixed liquid after heating was centrifuged at 9000 rpm for 5 minutes to separate the powder, and then the pH of the separated liquid part was measured. As a result, it was greater than -1 and less than 0. .. Then, the mixed liquid was heated at 100° C. for 1 hour to evaporate the separated liquid and dry the separated powder. As a result, a powder of platinum-supported tungsten oxide particles coated with a shell layer made of titanium oxide was obtained.

The obtained powder was calcined in the air at 400° C. for 30 minutes to obtain a photocatalyst material composed of platinum-supported tungsten oxide particles coated with a shell layer of titanium oxide.

The composition of the photocatalyst material obtained in Experimental Example 5 was analyzed. As a result, tungsten 5.8 atom%, titanium 24.5 atom%, oxygen 68.8 atom%, chlorine 0.9 atom% were obtained. there were.

Further, the measurement and evaluation of the photocatalytic activity (decomposition rate constant) of the obtained photocatalytic material by irradiation of visible light of environmental pollutants were carried out in the same manner as in Experimental Example 1. As a result, the obtained decomposition rate constant was 3.8 [/h].

(Experimental example 6)
After the powder was separated by centrifugation, the supernatant was discarded, ion-exchanged water was added, and the powder was again separated by centrifugation to repeat the step of washing the powder three times. A photocatalyst material composed of platinum oxide-supported tungsten oxide particles coated with a titanium oxide shell was obtained in the same manner as in Experimental Example 5 except for the above. Moreover, as a result of measuring the pH of the dispersion after the final washing, the pH of the dispersion after the final washing was 3.

Since the pH value of the dispersion liquid measured in Experimental Example 6 is higher than the pH value of the dispersion liquid after the final washing measured in Experimental Example 5, the photocatalyst material of Experimental Example 6 has the same pH value. It can be seen that the amount of doped halogen (chlorine) is smaller than that of the photocatalyst material obtained in Experimental Example 5 by repeating the washing process.

The measurement and evaluation of the photocatalytic activity (decomposition rate constant) of the obtained photocatalyst material by irradiating the environmental pollutants with visible light were performed in the same manner as in Experimental Example 1. As a result, the obtained decomposition rate constant was 3.4 [/h].

(Comparative example 2)
After separating the powder using centrifugation, discard the supernatant liquid, add ion-exchanged water, and separate the powder using centrifugation again to repeat the step of washing the powder 9 times. A photocatalyst material composed of platinum-supported tungsten oxide particles coated with a shell of titanium oxide was obtained in the same manner as in Experimental Example 5, except that Moreover, as a result of measuring the pH of the dispersion after the final washing, the pH of the dispersion after the final washing was 7.

As a result of composition analysis of the obtained photocatalyst material, chlorine was not detected.

Further, the measurement and evaluation of the photocatalytic activity (decomposition rate constant) of the obtained photocatalytic material by irradiation of visible light of environmental pollutants were carried out in the same manner as in Experimental Example 1. As a result, the obtained decomposition rate constant was 2.8 [/h].

As described above, from the results of Experimental Examples 5 and 6 and Comparative Example 2, the tungsten oxide particles supporting the platinum particles were used as the core particles, and the core particles and the titanium oxide shell layer covering the entire surface of the platinum particles were used. It has been confirmed that even in the photocatalytic material in which the shell layer or the shell layer and the core particles are doped with chlorine, high photocatalytic activity is exhibited by doping the photocatalytic material with chlorine.

INDUSTRIAL APPLICABILITY The present invention exhibits high catalytic activity with respect to visible light, and thus can be used for visible light responsive photocatalytic functional products. The photocatalyst functional product is provided with a photocatalyst layer formed of the photocatalyst material of the present invention on the surface of the base material, and has a function of adsorbing environmental pollutants and decomposing and removing them with visible light. Specific examples include building materials such as ceiling materials, tiles, glass, wallpaper, wall materials, floors, interior materials for automobiles, home electric appliances such as refrigerators and air conditioners, and textile products such as clothes and curtains.

1A, 1B, 1C, 1D Photocatalytic material 2, 2a Core particle 3 Promoter 4 Shell layer

Claims (4)

In a photocatalyst material comprising a core particle containing tungsten oxide, and a cocatalyst carried on the surface of the core particle,
By halogen is contained in the upper Kisuke catalysts, halogen is doped to the core particles,
A shell layer covering the entire surface of the core particles and the promoter,
The photocatalyst material, wherein the shell layer is composed of titanium oxide. The photocatalytic material according to claim 1, wherein the core particles are doped with halogen by containing halogen derived from a non-metal halide. The core particle is composed of a tungsten oxide particle or is composed of a composite of a tungsten oxide particle and a metal oxide other than tungsten oxide. Photocatalytic material. The photocatalytic material according to claim 1, wherein the doped halogen is chlorine.

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