JP6502683B2 - Photocatalytic material - Google Patents

Description

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

  The photocatalytic material has semiconductor physical properties, and electron-hole pairs are generated in the conduction band and the valence band by irradiating light with a band gap or more. As a result, due to the redox action of the electron-hole pair, active oxygen species such as hydroxyl radical and superoxide ion are generated on the surface of the photocatalyst material and in the vicinity thereof. The photocatalytic material is a substance having an organic substance decomposition action and a self-cleaning action by the oxidizing power and hydrophilization of these active oxygen species.

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

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

  Then, it is known that it can be utilized as a visible light responsive photocatalyst by forming an electron-withdrawing substance (co-catalyst) on the surface of tungsten oxide particles. In this visible light responsive photocatalyst, since the recombination of electrons excited in the conduction band by light irradiation and holes generated in the valence band is suppressed, 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 supported on the surface of tungsten oxide particles in an amount of 0.03 to 5 parts by weight per 100 parts by weight of tungsten oxide particles. Furthermore, the photocatalytic activity of the photocatalyst is enhanced by being independently supported on the surface of at least a part of the surface of the tungsten oxide particles in a state where the platinum particles are in contact with each other (in bead shape).

  In addition, since tungsten oxide has the property of being easily dissolved in an alkaline solution, the photocatalytic activity may be reduced by a basic gas such as ammonia generated in a smoking room or a toilet. In addition, 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 lowered.

  Therefore, in Patent Document 2, since tungsten oxide and a promoter supported on the surface of tungsten oxide are partially coated with titanium oxide, they have higher photocatalytic activity than uncoated tungsten oxide, and thus the gas phase is It is disclosed that the volatile aromatic compounds in it are rapidly decomposed.

JP, 2009-160566, A (August 23, 2009 publication) Unexamined-Japanese-Patent No. 2012-110831 (June 14, 2012 publication)

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

  Then, this invention is made in view of said subject, The objective is to provide a photocatalyst material with a photocatalytic activity higher than the conventional tungsten-oxide type photocatalyst.

In order to solve the above problems, a photocatalytic material according to an aspect of the present invention is a photocatalytic material containing core particles containing tungsten oxide, and a cocatalyst supported on the surface of the core particles,
It is characterized in that halogen is doped.

  According to one aspect of the present invention, it is possible to enhance the photocatalytic activity of a tungsten oxide 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 the photocatalyst material which concerns on Embodiment 3 of this invention typically. It is sectional drawing which shows typically the photocatalyst material which concerns on Embodiment 4 of this invention. It is a graph which shows the relationship of the hydrochloric acid addition amount and decomposition rate constant in the photocatalyst material which concerns on this invention. It is the figure which showed the relationship between the hydrochloric acid addition amount and the relative chlorine concentration contained in tungsten oxide in the photocatalyst material which concerns on this invention.

  Tungsten oxide exhibits a photocatalytic effect with low photocatalytic activity because electrons excited in the conduction band generate active oxidation species through the two-electron reduction reaction or four-electron reduction reaction of oxygen, and the oxidation decomposition reaction of the active oxidation species It is thought that it may be due to

  However, in order to allow the multiple electron reduction reaction of oxygen to proceed efficiently, it is necessary to transport the electrons excited in the conduction band to the surface of the photocatalyst particle or a cocatalyst (such as a noble metal) supported on the surface.

  As a result of intensive studies by the present inventors, it was found that the photocatalytic activity is improved by incorporating a halogen which is an n-type impurity into a tungsten oxide photocatalytic material, and the present invention has been completed.

Embodiment 1
One embodiment of the present invention will be described based on FIG. FIG. 1 is a cross-sectional view schematically showing a photocatalytic material 1A according to the present embodiment.

  As shown in FIG. 1, the photocatalytic material 1 </ b> A includes a core particle 2 and a co-catalyst 3 supported on the surface of the core particle 2. Furthermore, although not shown, the photocatalytic material 1A contains halogen as an impurity.

(Core particle 2)
In the photocatalyst material 1A, the core particles 2 are composed of tungsten oxide particles. Therefore, the photocatalytic material 1A is a visible light responsive photocatalytic material that exhibits photocatalytic activity by irradiation with visible light. In addition, although the core particle 2 of this Embodiment 1 is comprised from tungsten oxide, this invention is not limited to this, The core particle 2 should just contain the tungsten oxide at least.

  The particle size of the core particle 2 is not particularly limited, but is preferably 5 nm or more and 100 nm or less. When the particle size is less than 5 nm, aggregation tends to occur, and when it is more than 100 nm, photocatalytic activity is reduced. Here, the particle diameter of the core particle 2 is an average particle diameter calculated based on the BET specific surface area. The core particle 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 the distribution shape of the particle size distribution of the core particle 2 are not particularly limited, and a plurality of peaks of the particle size distribution may exist.

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

Further, the tungsten oxide constituting the core particles 2, as long as it has a photocatalytic activity by irradiation of visible light, for _example, like _{WO 3, W 25 O 73,} W 20 O 58, W 24 O 68 .

(Co-catalyst 3)
The cocatalyst 3 is supported on the surface of the core particle 2. The co-catalyst 3 enhances the photocatalytic activity of the photocatalytic material 1A. The co-catalyst 3 is composed of a metal or metal compound having an electron withdrawing property. Examples of the metal constituting the co-catalyst 3 include copper, platinum, palladium, iron, silver, gold, nickel, ruthenium, iridium, niobium, molybdenum and the like. Examples of metal compounds constituting the cocatalyst 3 include chlorides, bromides, iodides, oxides, hydroxides, sulfates, nitrates, carbonates, phosphates and organic acid salts of metals constituting the cocatalyst 3 Etc.

  As a method of forming the co-catalyst 3 on the surface of the core particle 2, (1) a method of kneading tungsten oxide particles constituting the core particle 2 and metal particles or metal compound particles constituting the co-catalyst 3, (2 ) After adding the tungsten oxide particles constituting core particle 2 to the solution containing the metal or metal compound constituting promoter 3, the solution obtained is heated or the solution obtained is irradiated with light to obtain core particle 2 The method etc. which precipitate the metal or metal compound which comprises the promoter 3 on the surface of these are mentioned.

  The addition amount of the metal or metal compound constituting the co-catalyst 3 (that is, the supported amount of the co-catalyst 3 supported on the surface of the core particle 2) is 0. 0 relative to the weight of tungsten oxide constituting the core particle 2. It is preferable that it is 01 weight% or more and 3 weight% or less. When the promoter 3 is a metal compound, the amount of the metal compound added (the amount of the supported promoter 3) indicates the amount of metal in the metal compound. If the amount of addition of the metal or the metal compound is less than 0.01% by weight, the effect as the co-catalyst 3 becomes small, and high photocatalytic activity can not be obtained. In addition, when the addition amount of the metal or the metal compound is more than 3% by weight, the amount of the promoter 3 covering the surface of the core particle 2 is increased. As a result, the amount of light reaching the core particle 2 decreases, so that high photocatalytic activity can not be obtained.

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

  The method for doping the photocatalyst material 1A with halogen is not particularly limited, and examples thereof include a method for treating the core particle 2 or the core particle 2 supporting the co-catalyst 3 with a nonmetal halide. For example, the non-metallic halide is dissolved alone or in a suitable solvent, and the core particle 2 or the core particle 2 carrying the co-catalyst 3 is immersed in the solution to n-type impurities in the photocatalytic material 1A. As halogens can be added.

  In the present specification, the term "non-metallic halide" refers to a compound that does not contain a metal element but contains at least one halogen element. Further, the category of "non-metallic halide" also includes simple halogens (chlorine, fluorine, bromine, iodine, etc.).

  Examples of the nonmetal halides include hydrogen halides, hydrohalic acids and ammonium halides. The hydrogen halide includes, for example, hydrogen chloride, hydrogen fluoride, hydrogen bromide or hydrogen iodide. The hydrohalic acid is an aqueous solution of hydrogen halide, such as hydrochloric acid (hydrochloric acid), hydrogen fluoride (hydrofluoric acid), hydrogen bromide (bromic acid), or hydrogen iodide (iodic acid). Be As the ammonium halide, for example, ammonium chloride, ammonium fluoride, ammonium bromide, ammonium iodide and the like can be mentioned.

  As described above, the photocatalytic material 1A of the present embodiment contains a halogen added as an 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 electrical conductivity of the photocatalytic material 1A being improved by the halogen doping. That is, the photocatalytic material 1A is an n-type semiconductor by being doped with a halogen which is an n-type impurity. In general, in an n-type semiconductor, electrons are excited from the donor to the conduction band at about room temperature. For this reason, 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). For this reason, in the photocatalytic material 1A, excited electrons are present before light irradiation (irradiation of visible light). As a result, the presence of the electrons makes it easier for the electrons excited in the conduction band to flow to the cocatalyst 3 after the light is applied to the photocatalytic material 1A. Thereby, it is considered that the electrical conductivity of the photocatalytic material 1A is improved and the photocatalytic activity is improved. Therefore, the tungsten oxide based photocatalytic material 1A having excellent photocatalytic activity under visible light irradiation can be provided.

Second Embodiment
Another embodiment of the present invention is described below with reference to FIG. FIG. 2 is a cross-sectional view schematically showing a photocatalytic material 1B according to the present embodiment. In addition, about the member which has the same function as the member demonstrated in the said Embodiment 1 for convenience of explanation, the same code | symbol is appended and the description is abbreviate | omitted.

  As shown in FIG. 2, the photocatalytic material 1B according to the present embodiment is different from the photocatalytic material 1A of the first embodiment only in that the entire surface of the core particle 2 and the promoter 3 is covered with the shell layer 4. It is different.

  Also in the photocatalytic material 1B of the present embodiment, similarly to the photocatalytic material 1A of the first embodiment, halogen is doped. The halogen added to the photocatalytic material 1 B as an n-type impurity may 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 surface of the core particle 2 and the cocatalyst 3. The shell layer 4 is preferably made of titanium oxide.

  When the thickness is less than 1 nm, the shell layer 4 can not completely cover the surface of the core particle 2 and the surface of the promoter 3. In addition, when the thickness of the shell layer 4 is greater than 50 nm, the photocatalytic activity of the core particle 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 particle 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 which has alkali resistance and is excellent in photocatalytic activity. In addition, alkali resistance shows the residual ratio of photocatalyst material 1B after implementing 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 particle 2 on which the cocatalyst 3 is formed with the shell layer 4 involves oxidation in a solution in which the core particle 2 on which the cocatalyst 3 is formed is dispersed. A method (so-called solution) of growing a titanium oxide layer on the surface of tungsten oxide particles as core particles 2 and on the surface of cocatalyst 3 formed on the surface of tungsten oxide particles by adding a solution containing a titanium precursor Law). In such a solution method, a titanium oxide precursor is uniformly formed on the surface of core particle 2 and cocatalyst 3 as a titanium oxide layer while being gradually grown 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.

  Patent Document 1 discloses a method of depositing a titanium oxide layer on the surface of tungsten oxide particles by adding tungsten oxide particles to a solution containing a titanium oxide precursor and evaporating the solvent in the solution (so-called impregnation method). Is described. However, in the impregnation method, the titanium oxide precursor is attached to the surface of the core particle and then heated to form the titanium oxide layer, so the titanium oxide layer is not uniformly formed, and the core particle surface and core particles are formed. The surface of the supported cocatalyst can not 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 crystalline titanium oxide densifies the shell layer 4 rather than non-crystalline titanium oxide. Thus, the photocatalyst material 1B having the shell layer 4 composed of crystalline titanium oxide has higher alkali resistance than the photocatalyst material having the shell layer 4 composed of non-crystalline titanium oxide.

  As crystalline titanium oxide which comprises the shell layer 4, any one of anatase type, rutile type, or these mixtures are suitable. The 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, depending on the production conditions, titanium oxides of anatase type and rutile type may be partially formed even if the temperature is not higher than the above temperature.

  As described above, in addition to the configuration of the photocatalytic material 1A, the photocatalytic material 1B of the present embodiment includes the shell layer 4 that covers the surface of the core particle 2 and the entire surface of the cocatalyst 3. Thereby, in addition to the effect exhibited by the photocatalytic material 1A, it is possible to provide a tungsten oxide photocatalytic material 1B having a higher alkali resistance than the conventional photocatalytic material in which there is a portion where the titanium oxide surface is not coated with titanium oxide. It becomes possible.

  Moreover, when the shell layer 4 is a titanium oxide layer, it becomes possible to provide the photocatalyst material 1B which shows a photocatalytic activity also by irradiation of an ultraviolet light.

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

  As shown in FIG. 3, the photocatalyst material 1 </ b> C according to the present embodiment is different from the photocatalyst material 1 </ b> A of the first embodiment in that core particles 2 a are provided instead of the core particles 2. Also in the photocatalyst material 1C of the present embodiment, as in the photocatalyst materials 1A and 1B of Embodiments 1 and 2, halogen is doped. The halogen added as an n-type impurity to the photocatalytic material 1C may be contained in at least one of the core particle 2a or the promoter 3, and is preferably contained in the core particle 2a.

  The core particle 2a is composed of a complex of tungsten oxide and a metal oxide. The metal oxides constituting the complex are titanium oxide, iron oxide, zinc oxide, copper oxide, platinum oxide, palladium oxide, silver oxide, silver oxide, gold oxide, nickel oxide, ruthenium oxide, ruthenium oxide, iridium oxide, niobium oxide, and molybdenum oxide. And one or more oxides selected from the group consisting of The metal oxide preferably 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 preferred. That is, the core particle 2a may contain one type of metal oxide other than tungsten oxide, or may contain plural types of metal oxides.

  The particle size of the core particle 2a is preferably 5 nm or more and 100 nm or less, similarly to the particle size of the core particle 2 in the photocatalyst material 1A of the first embodiment. When the particle size is less than 5 nm, aggregation tends to occur, and when it is more than 100 nm, photocatalytic activity is reduced.

  The metal oxide constituting the core particle 2a of the composite is desirably 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 does not appear, and if it is more than 100% by weight, the mixing effect of tungsten oxide does not appear.

  In the mixture of tungsten oxide and metal oxide constituting 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. For this reason, when the said metal oxide is a titanium oxide etc., it becomes possible to provide the photocatalyst material 1C which shows a photocatalytic activity also by irradiation of an 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 tungsten oxide. Therefore, the core particle 2a can absorb light in a longer wavelength range than the core particle 2 composed of tungsten oxide alone. For this reason, it becomes possible to improve the photocatalytic activity of the photocatalyst material 1C at the time of visible light irradiation.

  As a method of preparing a composite of tungsten oxide and a metal oxide other than tungsten oxide, a method of kneading tungsten oxide particles and metal oxide particles, or adding tungsten oxide particles to a metal oxide precursor solution, The method of volatilizing the solvent in a solution etc. are mentioned.

  By forming the co-catalyst 3 on the produced core particles 2a by the method described in Embodiment 1, the photocatalyst material 1C is obtained.

  As mentioned above, photocatalyst material 1C of this embodiment is provided with core particle 2a different from photocatalyst material 1A, and core particle 2a is constituted from metal oxides other than tungsten oxide in addition to tungsten oxide. Thereby, in addition to the effect exhibited by the photocatalytic material 1A, light of a wider wavelength range can be absorbed. Therefore, it becomes possible to provide photocatalyst material 1C in which the wavelength which shows photocatalyst activity differs from photocatalyst materials 1A and 1B of Embodiments 1 and 2.

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 a photocatalytic material 1D according to the present embodiment. In addition, about the member which has the same function as the member demonstrated in the said Embodiment 1-3 for convenience of explanation, the same code | symbol is appended and the description is abbreviate | omitted.

  As shown in FIG. 4, the photocatalytic material 1D according to the present embodiment is different from the photocatalytic material 1C according to the third embodiment only in that the entire surface of the core particles 2a and the promoter 3 is covered with the shell layer 4. It is different.

  Also in photocatalyst material 1D of this embodiment, halogen is doped similarly to photocatalyst materials 1A, 1B, and 1C of Embodiments 1-3. The halogen added to the photocatalytic material 1 D as an n-type impurity may be contained in at least one of the core particle 2 a, 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 a and the cocatalyst 3 in the same manner as the photocatalyst material 1 B of the second embodiment. The shell layer 4 is preferably made of titanium oxide.

  As described above, in addition to the configuration of the photocatalytic material 1C, the photocatalytic material 1D of the present embodiment includes the shell layer 4 that covers the surface of the core particle 2a and the entire surface of the cocatalyst 3. Thereby, in addition to the effect exhibited by the photocatalytic material 1C, it is possible to provide a tungsten oxide photocatalytic material 1D having a higher alkali resistance than the conventional photocatalytic material in which the tungsten oxide surface has a portion not coated with titanium oxide. It becomes possible.

  Moreover, when the shell layer 4 is a titanium oxide layer, it becomes possible to provide photocatalyst material 1D which shows a photocatalytic activity also by irradiation of an ultraviolet light.

[Summary]
The 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 cocatalyst 3 supported on the surface of the core particles 2 and 2a. It is characterized in that halogen is doped.

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

  In photocatalyst materials 1A to 1D according to aspect 2 of the present invention, in the above aspect 1, the core particles 2 and 2a are made of tungsten oxide particles, or tungsten oxide particles and metal oxides other than tungsten oxide And a complex of

  According to said invention, when core particle 2 consists of tungsten oxide particles, composition of photocatalyst material can be simplified. On the other hand, when the core particle is formed of a complex of tungsten oxide and a metal oxide, the metal oxide absorbs light of a wavelength different from that of tungsten oxide. Therefore, light of a wider range of wavelengths can be absorbed to exhibit photocatalytic action.

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

  According to the above invention, it becomes possible to provide tungsten oxide based photocatalyst materials 1B and 1D having higher alkali resistance than conventional photocatalyst materials in which there is a portion where the surface of tungsten oxide is not coated with titanium oxide.

  In photocatalyst material 1B, 1D which concerns on aspect 4 of this invention, in the said aspect 3, it is preferable that the said shell layer 4 is comprised from the titanium oxide.

  According to said invention, since the shell layer 4 is a titanium oxide layer, it becomes possible to provide photocatalyst material 1B, 1D which shows a photocatalytic activity also by irradiation of an ultraviolet light.

  In the photocatalytic materials 1A to 1D according to aspect 5 of the present invention, in the above 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 which is easy to obtain the raw material and easy to handle.

  The present invention is not limited to the above-described embodiments, and 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, new technical features can be formed by combining the technical means disclosed in each embodiment.

(Experimental example 1)
After dispersing 135 g of commercially available tungsten oxide (Kinda Chemical, 99.9%) in 1215 g of ion-exchanged water, it is pulverized and dispersed using a bead mill (MSC50, Japan Coke Industry Co., Ltd.) to disperse tungsten oxide particles. I got a liquid. The operating conditions of the bead mill apparatus were a bead diameter of 0.1 mm (Nikkato), a circumferential speed of 10 m / s, and a treatment time of 360 minutes.

  Subsequently, in the obtained dispersion liquid of tungsten oxide particles, hexachloroplatinum (VI) hexahydrate is prepared so that the proportion of the weight of platinum alone with respect to the weight of the tungsten oxide particles is 0.025% by weight. The substance (Kishida Kagaku, 98.5%) was dissolved. Thereafter, the dispersion is heated at 100 ° C. to evaporate the water, and then calcined at 400 ° C. for 30 minutes to support 0.025% by weight of platinum (co-catalyst) supported tungsten oxide particles (core Particles).

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

Next, in order to evaluate the photocatalytic activity of the environmental pollutants of the obtained photocatalytic material by visible light irradiation, the photocatalytic activity (decomposition rate constant) was measured using the following method. First, 1.3 g of the obtained photocatalytic 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 as to have a concentration of 500 ppm. Thereafter, the gas bag was irradiated with a blue LED (wavelength 450 nm, irradiation intensity to photocatalytic material 7 mW / cm ² ), and the change with time of the remaining amount of acetaldehyde was measured with a gas detection tube. The ordinate represents the logarithmic representation of the measured residual amount of acetaldehyde, the elapsed time is on the horizontal axis, the magnitude of the gradient of the graph is calculated, and the value is 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 photocatalytic material obtained in Experimental Example 1 was 3.84 [/ h].

(Experimental example 2)
Except that 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 hydrochloric acid at a ratio of 0.25 mL and ion-exchanged water 5 mL, In the same manner as in Experimental Example 1, a platinum material-supported tungsten oxide particle was doped with chlorine as a halogen to obtain a photocatalyst material.

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

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

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

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

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

(Comparative example 1)
A photocatalytic material was prepared using the same method as in Experimental Example 1 except that immersion using hydrochloric acid was not performed, to obtain a photocatalytic material composed of platinum oxide-loaded platinum oxide particles not doped with chlorine. As a result of composition analysis of the obtained photocatalyst material, chlorine was not detected.

  Next, the measurement and evaluation of the photocatalytic activity (degradation rate constant) of the environmental pollutants of the obtained photocatalytic material by visible light irradiation were performed in the same manner as in Experimental Example 1. As a result, the degradation rate constant obtained 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 ordinate represents the decomposition rate constant, and the abscissa represents the amount of hydrochloric acid added during immersion of tungsten oxide. Moreover, the contained chlorine concentration of the photocatalyst material obtained by Experimental example 1, Experimental example 4, and the comparative example 1 was measured relatively using TOF-SIMS. The measurement results are summarized in FIG. Although the absolute concentration of chlorine contained in each photocatalytic material is unknown, the amount of hydrochloric acid added is 2.5 mL of the photocatalytic material (Experimental Example 4) compared to the photocatalytic material (Experimental Example 1) of 2.5 mL. On the other hand, the relative concentration of hydrochloric acid contained in the photocatalytic material is higher. It is considered that the intensity indicating the relative concentration of hydrochloric acid is detected even in the photocatalyst material in which the amount of hydrochloric acid added is 0 mL, because of the background.

  From the description of FIG. 5 and FIG. 6, the photocatalytic activity (decomposition rate constant) of the chlorine-doped photocatalyst material (Experimental Examples 1 to 4) is improved compared to the photocatalyst material (Comparative Example 1) not doped with chlorine. Know that In addition, regarding the addition amount of hydrochloric acid, it was found that the photocatalytic material in which the addition amount of hydrochloric acid was 1.5 mL or more with respect to 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 amount of hydrochloric acid added is 0.25 mL has a slightly lower value than that of the photocatalyst material (Comparative Example 1) in which hydrochloric acid is not added, but It is believed to be due to measurement variability. That is, when the addition amount of hydrochloric acid is a small amount (less than 1.25 mL), the effect of the present invention that the photocatalytic activity of the photocatalytic material is improved by being doped with halogen (chlorine) appears so remarkably It is considered that when the amount of hydrochloric acid added is not less than 1.25 mL, the effects of the present invention are significantly exhibited.

(Experimental example 5)
A dispersion containing tungsten oxide particles was obtained in the same manner as in Experimental Example 1. Subsequently, in the obtained dispersion liquid of tungsten oxide particles, hexachloroplatinum (VI) hexahydrate is prepared so that the proportion of the weight of platinum alone with respect to the weight of the tungsten oxide particles is 0.025% by weight. The substance (Kishida Kagaku, 98.5%) was dissolved. Thereafter, 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 oxide-supported tungsten oxide particles is added to 24 g of ion-exchanged water, and dispersion of the platinum oxide-supported tungsten oxide particles is performed using a stirrer (Plymix Co., Ltd. film mix 40-40 type) Did. The operating conditions of the stirrer were: circumferential speed: 40 m / s, treatment time: 10 minutes.

  Then, next, in order to form a shell layer composed of titanium oxide, 9 mL of the above dispersion, 7 mL of an aqueous solution of titanium tetrachloride with a titanium concentration of 16% by weight (Toho titanium), and 100 mL of ion exchanged water After mixing in a flask to obtain a mixture, the resulting mixture was heated at a liquid temperature of 95 ° C. for 5 hours using a mantle heater for a round bottom flask.

  Thereafter, the mixed solution after heating was subjected to centrifugation at 9000 rpm for 5 minutes to separate the powder, and then the pH of the separated liquid portion was measured. As a result, it was greater than -1 and less than 0 . After that, the separated liquid was evaporated by heating the mixed solution at 100 ° C. for 1 h, and the separated powder was dried. As a result, a powder of tungsten oxide particles carrying platinum was obtained, which was coated with a shell layer of titanium oxide.

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

  Composition analysis of the photocatalytic material obtained in Experimental Example 5 revealed that 5.8 atomic% tungsten, 24.5 atomic% titanium, 68.8 atomic% oxygen, and 0.9 atomic% chlorine. there were.

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

(Experimental example 6)
After separating the powder using centrifugation, the supernatant was discarded, ion-exchanged water was added, and the process of washing the powder was repeated three times by separating the powder using centrifugation again. A photocatalytic material composed of platinum-supported tungsten oxide particles coated with a shell of titanium oxide was obtained using the same method as that of Experimental Example 5 except for using the same method as Experimental Example 5. In addition, as a result of measuring the pH of the dispersion after final washing, the pH of the dispersion after final washing was 3.

  Since the value of the pH of the dispersion measured in Experimental Example 6 is larger than the pH of the dispersion after the final washing measured in Experimental Example 5, the photocatalytic material of Experimental Example 6 is used. It can be seen that the amount of doped halogen (chlorine) is less than the photocatalytic material obtained in Experimental Example 5 by repeating the above-mentioned washing step.

  Measurement and evaluation of the photocatalytic activity (degradation rate constant) of the environmental pollutants of the obtained photocatalytic material by visible light irradiation were carried out in the same manner as in Experimental Example 1. As a result, the degradation rate constant obtained was 3.4 [/ h].

(Comparative example 2)
After separating the powder using centrifugation, the supernatant is discarded, ion-exchanged water is added, and the process of washing the powder is repeated 9 times by separating the powder using centrifugation again. A photocatalytic material composed of platinum oxide-supported tungsten oxide particles coated with a titanium oxide shell was obtained using the same method as in Experimental Example 5 except for the above. In addition, as a result of measuring the pH of the dispersion after final washing, the pH of the dispersion after final washing was 7.

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

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

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

  INDUSTRIAL APPLICABILITY The present invention exhibits high catalytic activity for visible light, so that it can be used for visible light responsive photocatalytic functional products. The photocatalytic functional product is provided with a photocatalyst layer formed of the photocatalytic material of the present invention on the surface of a substrate, and has the function of adsorbing environmental pollutants and decomposing and removing them by visible light. Specifically, building materials such as ceiling materials, tiles, glass, wallpaper, wall materials, floors and the like, interior materials for automobiles, home appliances such as refrigerators and air conditioners, and textile products such as clothes and curtains can be mentioned.

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

Claims (4)

In a photocatalytic material comprising core particles containing tungsten oxide and a cocatalyst supported on the surface of the core particles,
By containing halogen in the core particle, the core particle is doped with halogen ,
A shell layer covering the entire surface of the core particles and the cocatalyst,
The photocatalytic material , wherein the shell layer is made of titanium oxide .   The photocatalytic material according to claim 1, wherein the core particle is doped with a halogen by containing a halogen derived from a nonmetal halide.   The core particle is composed of tungsten oxide particles, or is composed of a complex of tungsten oxide particles and a metal oxide other than tungsten oxide. Photocatalytic material. The photocatalyst material according to any one of claims 1 to 3 , wherein the doped halogen is chlorine.

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