JPH1128364A - Photocatalyst composite body and water purification device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalyst having a high photocatalytic activity and an abundance of adaptability and a water purification device using the photocatalyst. SOLUTION: A photocatalyst composite body 1 has a photocatalyst film 5 and an electrically-conductive film 3 provided in an adjacent relation with the photocatalyst and having transmissibility against light having wavelengths capable of activating the photocatalyst and is supported by a light-transmissive support 7. Thickness of the photocatalyst 5 is within a range of 50-500 nm. In this constitution, activity of the photocatalyst can be maintained at a high level for a long time and effective purification of water can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalyst complex for effectively using a photocatalyst used for water purification treatment, decolorization, deodorization, and the like, and to a water purification device using the photocatalyst complex.

[0002]

2. Description of the Related Art In recent years, an attempt has been made to purify water by using an inorganic compound as a photocatalyst to promote a reaction by light energy. In this purification process, a photocatalyst film is formed on a support, and the photocatalyst is put into water to be subjected to the purification process, and irradiated with light. The decomposition reaction of the organic matter in the water proceeds by the holes of the pairs of holes and electrons generated on the photocatalyst by the light irradiation.

However, in such a configuration, surplus electrons remain on the photocatalyst to suppress the progress of the decomposition reaction. Therefore, the photocatalyst does not work efficiently.

[0004] To improve this, a device in which a metal film is formed between a support and a photocatalyst film has been proposed.

[0005]

However, when the turbidity of the water to be purified is high, the reaction does not proceed sufficiently because the irradiation light is attenuated in the water and the intensity of the light reaching the photocatalyst is insufficient. There is a problem. Also, if contaminants accumulate on the surface of the photocatalyst film when the purification process is performed for a long time,
The blocking of the light delays the progress of the decomposition reaction, accelerates the coating of the photocatalyst with contaminants, and renders the photocatalyst non-functional.

[0006] The present invention has been made in view of the above problems, and has as its object to provide a photocatalyst complex that can make full use of the function of a photocatalyst and efficiently proceed a catalytic reaction for a long time. I do.

Another object of the present invention is to provide a water purification apparatus capable of efficiently performing water purification treatment using a photocatalyst.

[0008]

The photocatalyst complex of the present invention comprises a photocatalyst film containing a photocatalyst, and a photocatalyst film which is provided adjacent to the photocatalyst film and has a property of transmitting light having a wavelength at which the photocatalyst functions. And a conductive film.

The photocatalyst is titanium oxide, the conductive film contains indium oxide, and further has a platinum member interposed between the photocatalyst film and the conductive film.

The photocatalyst composite further has a light-transmitting support for supporting the photocatalyst film and the conductive film.

Further, the photocatalyst composite of the present invention is a photocatalyst composite having a photocatalyst, which has a conductive layer that is transparent to light having a wavelength at which the photocatalyst functions. Provided in contact with the conductive layer.

Further, the photocatalyst composite of the present invention has a thickness of 5
It has a photocatalytic film of 0 to 500 nm and a conductive film provided adjacent to the photocatalytic film.

Further, the photocatalyst composite of the present invention is a photocatalyst composite having a photocatalyst film and a conductive film provided adjacent to the photocatalyst film, wherein the thickness x of the photocatalyst film and the The thickness y of the film satisfies the following expressions (1) to (3).

75 ≦ x ≦ 400 (1) y ≦ x / 6 + 27.5 (2) y ≦ −7x / 50 + 96.5 (3) Further, the photocatalyst composite of the present invention comprises: A photocatalyst composite having a conductive film provided adjacent to a photocatalytic film, wherein the thickness x of the photocatalytic film and the thickness y of the conductive film are represented by the following formulas (4), (5), and (5). 6).

50 ≦ x ≦ 500 (4) y ≦ 0.2x + 30 (5) y ≦ −0.1x + 90 (6) The water purification device of the present invention is provided with a water tank for containing water and a water tank attached to the water tank. And a light source for supplying light having a wavelength at which the photocatalyst functions to the photocatalyst film of the photocatalyst composite.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the case where a photocatalyst layer is provided on a metal film, the supply of light to the photocatalyst is restricted only from one side because the metal film blocks light. This is extremely disadvantageous in configuring a processing apparatus using a photocatalyst. In addition, since the reaction efficiency of the photocatalyst depends on the amount of light reaching the photocatalyst, if the photocatalyst film provided on the metal film is thick, only the photocatalyst on the surface of the film functions and the internal photocatalyst does not function at all. Occurs. Therefore, there is a problem in efficient use of the photocatalyst.

The above-mentioned problem is solved by using a film having both light transmittance and electron conductivity. More specifically, as shown in FIG.
Has a light-transmitting conductive film 3 and a photocatalytic film 5 provided thereon, and these are formed on a transparent support 7 in order to obtain mechanical strength. A lead wire 9 is connected to the conductive film 3, and the lead wire 9 is connected to ground or an external circuit (not shown). Due to the light transmittance of the conductive film 3 and the support 7, not only the direction from the photocatalyst film 5 side shown by the arrow A in the figure but also the arrow B
Light irradiation is also possible in the direction from the conductive film 3 side indicated by. The holes generated from the photocatalyst excited by the light irradiation are used for the progress of a processing reaction such as a decomposition reaction of contaminants. Therefore, the processing reaction proceeds by irradiating light to irradiate the photocatalyst with an object to be processed using holes (for example, water to be purified) in contact with the photocatalyst film 5, and The generated electrons move to the conductive film 3 and are removed to the outside of the composite 1 via the lead wire 9. As a result, the reaction progress is not hindered by the surplus electrons remaining in the photocatalyst film 5. Further, in the purification treatment of water or the like with high turbidity, the decomposition reaction of the contaminant can be promoted by light irradiation from the directions of arrows A and B.

FIG. 2 shows an example of a water purification apparatus using the photocatalyst complex 1 having the structure shown in FIG. This water purification device 11
A water tank 13 containing water to be treated, a photocatalyst complex 15 installed in the water tank 13, and a light source 17 for exciting the photocatalyst are provided. The photocatalyst complex 15 has a transparent support 19 formed in a cylindrical shape so as to surround the light source 17.
A light-transmitting conductive film 21 laminated on the outer periphery of the support 19; and a photocatalytic film 23 laminated on the outer periphery of the conductive film 21.
And a lead wire 25 is connected to the upper end of the conductive film 21. The water to be treated is supplied to the water tank 13 from a water supply pipe 27 provided in the water tank 13, and the treated water is discharged from a drain pipe 29. The bottom of the water tank 13 is connected to a discharge pipe 31 for removing precipitates and the like from the water tank 13.

When light is irradiated from the inside of the photocatalyst complex 15 using the light source 17, the photocatalyst is excited to decompose contaminants contained in the water supplied to the water tank 13 and kill microorganisms around the photocatalyst complex 15. Progresses.

The water purifier of FIG. 2 can be variously modified as required. For example, the photocatalyst complex 15 may be mounted on the light source 17, or a light-transmitting conductive film and a photocatalytic film may be directly laminated on the light source using the outer peripheral portion of the light source as a support. Further, the water tank 13 may be made of a transparent material, and a light source may be provided outside the water tank 13. Alternatively, a light-transmitting conductive film and a photocatalytic film may be laminated on the inner surface of the water tank 13 made of a transparent material, and light irradiation may be performed from outside the water tank.

The photocatalyst composite having the above configuration can be manufactured using the following materials. First, the photocatalyst film may be a layer of a substance having photocatalytic properties, and examples thereof include oxides such as titanium oxide, tin oxide, zirconium oxide, tungsten oxide, iron oxide, zinc oxide, and strontium titanate. In particular, titanium oxide is an excellent photocatalyst that exhibits strong oxidizing power by absorbing the energy of photons by irradiation with ultraviolet rays. The formation of the photocatalytic film from such a material can be performed by either a gas phase method or a liquid phase method. Examples of the gas phase method include a vacuum deposition method and a CVD method. Method, ion coating method, liquid phase deposition method, sol-gel method and the like. A photocatalyst capable of utilizing sunlight by implanting chromium ions into titanium oxide can also be used.

The light-transmitting conductive film may be a film of a substance having conductivity without significantly impeding the transmission of light having a wavelength for exciting the photocatalyst, and has a catalytic activity in an ultraviolet region such as titanium oxide. When a photocatalyst having the same is used, a conductive material which transmits ultraviolet light is formed. Examples of the light-transmitting conductive material include ITO (a mixture of indium oxide and tin oxide) and ATO (a mixture of antimony oxide and tin oxide). In particular, ITO has high transparency and good electron conductivity. A film made of such a material is obtained by laminating on a support using a film forming method such as a vacuum evaporation method. Alternatively, a powder made of such a material can be fixed on a support using a binder. As the binder, a material that becomes a transparent material such as glass by firing is used. A material in which a light transmitting material such as barium sulfate is coated with ITO or ATO can be used as the conductive film.

The support may be any material that does not significantly hinder the transmission of light having a wavelength that excites the photocatalyst. For example, a material containing silicon oxide, boron oxide, sodium oxide, potassium oxide, aluminum oxide, zirconium oxide, calcium carbonate, or the like as a constituent component may be used. However, in the case where a baking treatment is required in the step of forming the photocatalyst film and the support is also heated at the same time, the material must have heat resistance enough to withstand the baking treatment. When the light source is a low-pressure mercury lamp, it is preferable to use quartz glass as the material of the support, and when the light source is sunlight or black light, hard glass or the like can be suitably used.

The transfer of surplus electrons from the photocatalyst film 5 of the photocatalyst composite 1 of FIG. 1 to the conductive film 3 is facilitated by disposing a metal material so as to be in contact with both films. For details,
As in the photocatalyst complex 33 shown in FIG. 3, metal members 35 are provided between the conductive film 3 and the photocatalyst film 5 so as to be in contact with both films. The metal member 35 is for separating electrons by improving the conductivity between the conductive film 3 and the photocatalytic film 5. It is not necessary to connect at least the metal members 35 to form an electron conduction path. Metal member 3
As the shape of 5, for example, a spherical shape, a whisker shape, or a rod shape can be used. The metal member 35 preferably has a large contact area with both films and does not hinder light transmission.
As such a configuration, for example, a whisker-like configuration arranged so as to extend perpendicular to the junction interface between the two films can be given. Examples of the metal member include granular materials such as platinum, gold, silver, copper, palladium, ruthenium, rhodium, nickel, manganese, and cobalt. Among them, platinum has an excellent electron separation function.

FIG. 4 shows an example of a water purification device using the photocatalyst complex 33 of FIG. The water purifier 37 is provided with a photocatalyst complex 33 at the bottom of a water tank 39 formed of a light-transmitting material. By irradiating light from above or below the water tank 39, light is emitted from the photocatalyst complex 33. Support 7
Then, the reaction reaches the photocatalyst film 5 via the conductive film 3 and the decomposition reaction of the contaminants contained in the water above the photocatalyst complex 33 proceeds. The electrons generated in the photocatalytic film 5 move to the conductive film 3 through the metal member 35. The conductive film 3 is connected to ground or a circuit outside the water purification device 37 via a lead wire (not shown).

When, for example, an aqueous formic acid solution is treated using the water purifier 37 as shown in FIG. 4, the concentration of formic acid decreases with the irradiation time as shown by the line a in FIG. When a photocatalyst composite that does not constitute the conductive film 3 is used, excess electrons cannot move from the photocatalyst film 5 and the metal member 35 to the outside. (For details, see Example 1 and Comparative Example 1
See).

The boundary between the photocatalyst film and the conductive film in the photocatalyst composite does not need to be strict. In other words,
A layer having a concentration gradient such that the concentration continuously changes in the laminating direction between the photocatalyst and the conductive material may be used.
For example, as in the photocatalyst complex 41 of FIG. 6, light-transmissive conductive material particles 45 near the light-transmissive support 43.
A layer 49 having a concentration gradient such that the amount of the photocatalyst particles 47 increases with increasing distance from the support 43 may be formed on the support 43. The reaction by the irradiated light proceeds on the surface of the layer 49 by the photocatalyst particles 47, and the surplus electrons are transferred from the photocatalyst particles 47 to the conductive material particles 45, and move through the conductive material particles 45 below the layer 49 to lead. The line (not shown) is removed out of the layer 49. Therefore, by such a concentration gradient, the layer 4
9 acts substantially the same as the photocatalytic film and the conductive film described above.

In a further modification, a layer in which photocatalyst particles and conductive material particles are arbitrarily mixed may be used as long as the layer can transfer electrons between the conductive material particles. Since the conductive material particles are light-transmitting, the photocatalyst particles can receive irradiation light from both sides of the support.

FIG. 7 shows an example in which the conductive material particles are whisker-shaped. The photocatalyst composite 51 is made of whisker-shaped transparent conductive material particles 5 on a light-transmitting support 53.
5 and a layer 59 containing photocatalyst particles 57 are stacked. When the whisker-shaped conductive material particles are used, the reduction in the light transmittance of the layer when the layer is formed so as to obtain the conductivity between the particles can be smaller than when the spherical particles are used. Therefore, the photocatalyst particles 57 are easily photoexcited, and many photocatalyst particles 57 can be stacked. Instead of the whisker-like particles, a light-transmissive conductive material may be formed into a net-like long fiber, and a photocatalyst may be laminated thereon.

FIG. 8 shows an example of an application for reducing the resistance of electrons through a conductive material. In the figure, (a) is a diagram microscopically illustrating particles forming a layer, and (b) is a diagram conceptually illustrating a layer.

In this embodiment, the photocatalyst composite 61
Material particles 65 and photocatalyst particles 6 on a support 63
In the layer 69 containing 7, the thickness of the portion 65 ′ containing a large amount of the conductive material particles 65 decreases as the distance from the lead 71 to be connected decreases, and the portion 6 containing a large amount of the photocatalyst particles 67 decreases
7 'is inclined with respect to the support 63. As described above, the substantial boundary between the conductive material and the photocatalyst (indicated by a dotted line in FIG. 2B) is inclined, and the thickness of the conductive film is different.
The movement of the electrons from the photocatalyst to the lead wire becomes smooth, and the resistance decreases.

The functions of the photocatalyst can be synergistically improved by appropriately combining the above-described embodiments as needed. The metal member as shown in FIG.
May be buried in the layer 69.

When the photocatalytic film provided on the conductive film is irradiated with light, for example, when the photocatalytic film is extremely thick,
It is conceivable that the irradiation light does not reach deep inside the photocatalytic film and acts only on the surface of the photocatalytic film. In such a case, if the electrons generated near the surface of the photocatalytic film do not cross the thick film and reach the conductive film, the electron removing ability of the conductive film does not work effectively. That is, it is conceivable that a problem of electron transmission resistance occurs depending on the thickness of the photocatalytic film. Also, even if light is acting on the entire photocatalytic film, a large distance between a portion where the reaction proceeds by photoexcitation and a portion where surplus electrons are transferred to the conductive film also causes a problem of electron transfer resistance. Will be. Therefore, it is expected that the thickness of the photocatalyst film is a factor that affects the catalytic ability of the entire photocatalyst composite. Hereinafter, the thickness of the photocatalyst film will be described.

Consider a photocatalyst complex 73 as shown in FIG. The photocatalyst composite 73 is made of a transparent support 75.
A metal film 77 and a photocatalytic film 79 having a catalytic function for ultraviolet rays are formed thereon. The metal film 77 has a thickness sufficient to completely block ultraviolet rays from below, and is grounded by a lead wire (not shown). The photocatalyst complex 73 is put into an aqueous tartaric acid solution, and while the tartaric acid aqueous solution is allowed to flow in the direction of arrow C, ultraviolet light is irradiated for a certain time from the direction of arrow A, and then the concentration of the aqueous tartaric acid is measured to calculate the decomposition rate of tartaric acid. (For details, see Example 2 and Comparative Example 2 described later). This operation is repeated for the photocatalyst films 79 having different thicknesses, and the relationship between the photocatalyst film thickness and the decomposition rate is obtained, as shown by the line c in the graph of FIG. The same operation is performed by using the metal film 77.
When the photocatalyst composite without the above was used, the result is as shown by the line d in the graph of FIG.

When there is no metal film (line d), the decomposition rate increases as the thickness of the photocatalytic film increases, but the maximum value (N1)
When it reaches about 500 nm or more, it hardly increases. On the other hand, in the case of having a metal film (line c), the decomposition rate sharply increases with an increase in the thickness of the photocatalytic film, but gradually decreases at around 200 nm, and gradually approaches N1 at around 500 nm. The difference from the case without the metal film (line d) is due to the effect that excess electrons are removed by the metal film and the progress of the reaction is not inhibited by the remaining electrons. As can be understood from the graph of FIG. 10, for light irradiation from one direction, the effect of removing surplus electrons in the conductive film in contact with the photocatalytic film is obtained only when the thickness of the photocatalytic film is about 500 nm or less. It can be seen that the time is limited. At this time, the reason why the decomposition rate exceeding the maximum value N1 due to the catalyst film alone is exceeded when the thickness of the photocatalytic film is about 50%.
It is a time of ５００500 nm.

The correlation as shown in FIG.
It is considered that the present invention can be approximately applied to a case where a fiber aggregate 81 composed of a plurality of photocatalyst composites as shown in 1 (a) and (b) is used. The fiber assembly 81 is composed of a plurality of photocatalyst composites 83, and each photocatalyst composite 83 has a metal core fiber 85 and a photocatalyst film 87 covering the core fiber 85. The electrons generated in the photocatalytic film 87 by the light irradiated from the surroundings reach the terminal through the core fiber 85. The end of the core fiber 85 is connected to ground or a circuit by a lead wire or the like. Even if the core fiber 85 is made of a light-transmitting conductive material, the effect of light transmitted from the back surface (inside) of the catalyst film is expected to be small. It is considered possible.

Consider a case where the photocatalyst composite 73 shown in FIG. 9 is irradiated with ultraviolet rays from the direction of arrow B, that is, from the support 75 side, as shown in FIG. However, in this case, the metal film 7
Reference numeral 7 denotes a thickness through which ultraviolet rays can be transmitted to some extent. The tartaric acid aqueous solution is treated in the same manner as described above using the photocatalyst complex 73 under the conditions shown in FIG. 2, and the decomposition rate of tartaric acid is calculated, as shown by the line e in the graph of FIG. When the same operation is performed on the photocatalyst composite without the metal film 77, the result is as shown by the line f in the graph of FIG. 13 (for details, see Example 3-1 and Comparative Example 3 described later).

Under the conditions as shown in FIGS. 12 and 13, when the metal film 77 is not provided (line f), the decomposition rate of tartaric acid increases with an increase in the thickness of the photocatalytic film, but reaches a local maximum value (N2) at about 250 nm. , And when the thickness of the photocatalytic film reaches 500 nm, the decomposition ability is almost eliminated. This is because, because the photocatalyst film 79 is thick, the ultraviolet light does not reach the surface of the photocatalyst film where the decomposition reaction proceeds (the side opposite to the support 75), and the ultraviolet light reaches the surface of the photocatalyst where the decomposition reaction proceeds. For example, it is difficult to emit electrons to the metal film due to a large resistance to the movement of holes and electrons generated by photoexcitation due to a long distance from a portion to be exposed.
Also in the case where the metal film 7 is present (line e), the decomposition rate is maximum when the thickness of the photocatalytic film is about 200 nm, and is about 500 nm.
Nearly there is almost no decomposition capacity. About 500 photocatalyst films
When the thickness is less than nm, the decomposition rate is improved by removing the residual electrons. However, when the photocatalytic film is thick, the effect of removing the residual electrons is not exhibited. As a result, when the metal film is provided, the decomposition rate exceeds N2 when it is in the range of about 75 to 400 nm in FIG.

The same operation as described above was repeated while changing the thickness of the metal film of the photocatalyst composite of FIG. 12, and the thickness (x (nm)) of the photocatalyst film when the decomposition rate became N2 and the thickness of the metal film The thickness (y (nm)) is determined (for details, see Example 3 below).
2), the plot is as shown in FIG. 14, and the decomposition rate becomes N2 or more in the range surrounded by this plot. When this range is approximately expressed, x and y satisfying the following expressions (1) to (3) can be expressed as hatched in the figure.

[0040]

(1) y ≦ x / 6 + 27.5 (2) y ≦ −7x / 50 + 96.5 (3) The thickness y of the metal film is about 40 nm or less and It is understood that the decomposition rate is clearly N2 or more when the thickness x of the photocatalytic film is in the range of about 75 to 400 nm. Metal film thickness is 4
If the thickness exceeds 0 nm, the transmittance of light decreases, and the effect of electron transfer does not improve. Therefore, the range showing the decomposition rate of N2 or more is limited.

Consider a case where the photocatalyst composite 73 is irradiated with ultraviolet rays from both directions of arrows A and B as shown in FIG. Also in this case, the metal film 77 has a thickness through which ultraviolet rays can pass. When the tartaric acid aqueous solution is treated in the same manner as described above, and the decomposition rate of tartaric acid is calculated, a curve g in the graph of FIG. When the same operation is performed on the photocatalyst composite without the metal film 77, the result is as shown by the line h in the graph of FIG. 16 (for details, see Example 4-1 and Comparative Example 4 described later).

Under the conditions as shown in FIGS. 15 and 16, when there is no metal film 77 (line h), the decomposition rate of tartaric acid increases as the thickness of the catalyst film increases, and the gradient of the increase is higher than that in FIG. Although large, it does not increase after the decomposition rate reaches the maximum value (N3). With the metal film 77 (line g), the decomposition rate increases significantly with increasing photocatalytic film thickness, about 2
When it exceeds about 00 nm, it gradually decreases and gradually approaches N3 around 500 nm. The decomposition rate exceeding N3 is in the range from about 50 to 500 nm in FIG. These results are shown in FIGS. 10 and 13 by light irradiation from one direction.
Is generally consistent with what is expected when considering the results of

As described above, the same operation as above was repeated while changing the thickness of the metal film of the photocatalyst composite of FIG. 15, and the thickness of the photocatalyst film when the decomposition rate became N3 (x (nm)) When the thickness (y (nm)) of the metal film is determined (for details, see Example 4-2 described later), the plot becomes as shown in FIG. 17 and the decomposition rate becomes N3 or more. The area is enclosed by. When this range is approximately expressed, x and y satisfying the following equations (4) to (6) can be obtained (shown by oblique lines in the drawing).

[0044]

(2) y ≦ 0.2x + 30 (5) y ≦ −0.1x + 90 (6) The thickness y of the metal film is about 40 nm or less, and the thickness of the photocatalyst film In the range of about 50 to 500 nm, the decomposition rate is clearly N
It is understood that there are three or more. Metal film thickness 50nm
When N exceeds 3, the transmitted light is insufficient, and the effect due to the movement of electrons is not improved, so that the range showing the decomposition rate of N3 or more is limited.

The above numerical values relating to the thickness of the photocatalytic film and the metal film show the same tendency even when the material used is changed, and can be suitably applied by making some corrections. In addition, a photocatalyst composite using a light-transmitting conductive film (for example, an ITO film) other than the above-described metal film has a high light-transmitting property and is not easily affected by the thickness of the conductive film. It is preferable to set the thickness of the photocatalyst film in an appropriate range as easily considered from 12 to 17. It is set in the range of about 50 to 500 nm, more preferably in the range of about 75 to 400 nm.

The photocatalyst complex described above can be used not only for the water purification treatment as described above, but also for various reaction treatments using a photocatalyst. Synthesis, decomposition, and deodorization, decolorization, sterilization, purification, etc. based on these.

[0047]

Hereinafter, the present invention will be described in more detail with reference to examples.

(Embodiment 1) The dimensions are 100 mm × 100 mm ×
On one side of a 2 mm quartz plate, 100 mm thick by vacuum evaporation
nm of ITO (tin oxide content 5 mol%) film
A lead wire was connected to the end of the O film.

Next, by masking the ITO film with a mesh, depositing platinum, and removing the mesh,
Approximately 100,000 platinum particles with a particle size of 10-100 μm
It was formed on an O film.

On this, 10 ml of a 100-fold diluted titanium dioxide sol (ST-K01, manufactured by Ishihara Sangyo Co., Ltd.) was added.
It was applied, dried at room temperature, and fired in air at 200 ° C. for 1 hour to obtain a photocatalyst composite as shown in FIG. The thickness of the titanium dioxide layer of the photocatalyst composite was 100 nm.

The photocatalyst composite was attached to a hard glass water tank to produce a water purification device as shown in FIG. 1000 ml of a 100 ppm formic acid aqueous solution is put into this water tank,
The formic acid concentration in the formic acid aqueous solution was measured while irradiating light from below the water tank using a black light. From the measurement results, the relationship between the light irradiation time and the formic acid concentration of the formic acid aqueous solution was examined. This is shown by the line a in the graph of FIG.

On the other hand, the same operation as described above was repeated except that no platinum particles were formed to form a photocatalyst complex, and a water purification device as shown in FIG. 1 was produced. The change in formic acid concentration was measured. This result is indicated by a dashed line a ′ in the graph of FIG.

As can be understood from FIG. 5, in the photocatalyst film 5 as shown in FIG. 1, surplus electrons which hinder the progress of the photocatalytic reaction are generated by photoexcitation, and the surplus electrons are removed to the outside of the photocatalyst complex. For this purpose, the conductive film 3 is provided. Here, surplus electrons are transferred from the photocatalytic film 5 to the conductive film 3 via the interface between the two films. If the transfer, in other words, the separation of electrons from the photocatalyst film 5 is promoted, surplus electrons can move to the conductive film 3 more quickly, and as a result, the catalytic performance of the photocatalyst composite is improved.

(Comparative Example 1) The same operation as in Example 1 was repeated except that the ITO film and the platinum particles were not formed to form a photocatalyst complex, thereby producing a water purification device. The change in formic acid concentration in the formic acid aqueous solution was measured. This result is shown by the broken line b in the graph of FIG.

(Embodiment 2) The dimensions are 100 mm × 100 mm ×
A gold film having a thickness of 40 nm as a metal film and a titanium oxide film having a thickness of 25 nm as a catalyst film are formed on a transparent support made of hard glass having a thickness of 2 mm by vacuum evaporation to obtain a photocatalyst composite as shown in FIG. Was. This photocatalyst complex was put into 1000 ml of a 25 ppm aqueous tartaric acid solution, and irradiated with ultraviolet rays from a direction of an arrow A for 3 hours using a UV lamp (power consumption: 6 W) while stirring so that the aqueous solution of tartaric acid flowed in a direction of an arrow C. Thereafter, the concentration of the aqueous tartaric acid solution was measured, and the decomposition rate of tartaric acid (%) [= 100 × (25 ppm-tartaric acid concentration after irradiation) /
25 ppm] was calculated.

The same operation as described above was repeated except that the thickness of the photocatalyst film was changed in the range of 20 to 550 nm to produce a photocatalyst complex, and the decomposition rate of tartaric acid was examined using a tartaric acid aqueous solution.

From the results of the above operation, the relationship between the thickness of the photocatalytic film and the decomposition rate of tartaric acid is shown by the line c in the graph of FIG.

Comparative Example 2 A photocatalyst complex was formed by repeating the same operation as in Example 2 except that no metal film was formed, and the decomposition rate of tartaric acid was examined. From the obtained results, the relationship between the thickness of the photocatalytic film and the decomposition rate of tartaric acid is shown in FIG.
Is indicated by a line d in the graph.

(Example 3-1) The dimensions were 100 mm × 100.
A 5 nm-thick gold film as a metal film and a 25 nm-thick titanium oxide film as a catalyst film were formed on a transparent support made of a hard glass of mm × 2 mm by a vacuum evaporation method to form a photocatalyst composite as shown in FIG. I got This photocatalyst complex has a concentration of 25 ppm
The tartaric acid aqueous solution was measured by irradiating the tartaric acid aqueous solution with a UV lamp (power consumption: 6 W) for 3 hours using a UV lamp (power consumption: 6 W) for 3 hours while stirring so that the tartaric acid aqueous solution flows in the arrow C direction. , Tartaric acid decomposition rate (%) [= (25 ppm-tartaric acid concentration after irradiation) / 25 pp
m] was calculated.

The same operation as described above was repeated except that the thickness of the photocatalyst film was changed in the range of 20 to 550 nm, to produce a photocatalyst composite, and the decomposition rate of tartaric acid was examined using a tartaric acid aqueous solution.

From the result of the above-mentioned operation, the relationship between the thickness of the photocatalytic film and the decomposition rate of tartaric acid is shown by a line e in the graph of FIG.

Comparative Example 3 A photocatalyst complex was formed by repeating the same operation as in Example 3-1 except that no metal film was formed, and the decomposition rate of tartaric acid was examined. From the results obtained, the relationship between the thickness of the photocatalytic film and the decomposition rate of tartaric acid is shown in FIG.
3 is indicated by a line f in the graph.

(Embodiment 3-2) The thickness of the metal film was set to 10 to 7
A photocatalyst composite was prepared by repeating the same operation as in Example 3-1 except that the range was changed to 0 nm, and decomposition of tartaric acid using a tartaric acid aqueous solution was performed on the photocatalyst composite having a metal film of each thickness. The rate was checked. Using the results, a graph similar to that of FIG. 13 of the relationship between the thickness of the photocatalytic film and the decomposition rate of tartaric acid was created.

The maximum value N2 of the decomposition rate was obtained from the result of Comparative Example 3, and the thickness of the photocatalytic film when the decomposition rate was N2 was obtained in the graph obtained above and the graph of FIG. From these results, the relationship between the thickness of the photocatalyst film and the thickness of the metal film is shown in FIG.

(Example 4-1) The dimensions were 100 mm × 100
A 5 nm-thick gold film as a metal film and a 25 nm-thick titanium oxide film as a catalyst film are formed on a transparent support made of a hard glass of mm × 2 mm by a vacuum evaporation method to form a photocatalyst composite as shown in FIG. I got This photocatalyst complex has a concentration of 25 ppm
Of tartaric acid aqueous solution, and while irradiating ultraviolet rays from both directions of arrows A and B for 3 hours using a UV lamp (power consumption 6 W) while stirring so that the tartaric acid aqueous solution flows in the direction of arrow C, the concentration of the tartaric acid aqueous solution Was measured to calculate the decomposition rate (%) of tartaric acid [= (25 ppm-tartaric acid concentration after irradiation) / 25 ppm].

A photocatalyst composite was prepared by repeating the same operation as described above except that the thickness of the photocatalyst film was changed in the range of 20 to 550 nm, and the decomposition rate of tartaric acid was examined using a tartaric acid aqueous solution.

From the results of the above-described operation, the relationship between the thickness of the photocatalytic film and the decomposition rate of tartaric acid is shown by a line g in the graph of FIG.

Comparative Example 4 A photocatalyst complex was formed by repeating the same operation as in Example 4-1 except that no metal film was formed, and the decomposition rate of tartaric acid was examined. From the results obtained, the relationship between the thickness of the photocatalytic film and the decomposition rate of tartaric acid is shown in FIG.
The graph h is indicated by a line h.

(Example 4-2) The thickness of the metal film was set to 10 to 7
A photocatalyst composite was prepared by repeating the same operation as in Example 4-1 except for changing the range up to 0 nm. For the photocatalyst composite having a metal film of each thickness, the decomposition of tartaric acid using a tartaric acid aqueous solution was performed. The rate was checked. Using the results, a graph of the relationship between the thickness of the photocatalytic film and the decomposition rate of tartaric acid as in FIG. 16 was created.

The maximum value N3 of the decomposition rate was obtained from the result of Comparative Example 4, and the thickness of the photocatalytic film when the decomposition rate was N3 was obtained in the graph obtained above and the graph of FIG. From these results, FIG. 17 shows the relationship between the thickness of the photocatalytic film and the thickness of the metal film.

[0071]

As described above, according to the present invention, the activity of the photocatalyst can be maintained at a high level for a long time, and the processes such as water purification, decolorization, and deodorization can be efficiently advanced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a photocatalyst composite according to the present invention.

FIG. 2 is a perspective view showing a configuration of a first embodiment of the water purification device according to the present invention.

FIG. 3 is a schematic configuration diagram showing a second embodiment of the photocatalyst composite according to the present invention.

FIG. 4 is a schematic configuration diagram showing a second embodiment of the water purification device according to the present invention.

FIG. 5 is a graph showing the results of formic acid decomposition treatment using a water purifier, in which a line a is a case where the water purifier of FIG. 4 is used, and a line a ′ is a line in which a metal member is omitted from the water purifier of FIG. , The line b indicates the case where the water purification device of FIG. 4 from which the conductive film and the metal member are omitted is used.

FIG. 6 is a schematic configuration diagram showing a third embodiment of the photocatalyst complex according to the present invention.

FIG. 7 is a schematic configuration diagram showing a fourth embodiment of the photocatalyst composite according to the present invention.

FIGS. 8A and 8B are schematic diagrams showing a fifth embodiment of the photocatalyst composite according to the present invention, wherein FIG. 8A is a diagram microscopically showing particles forming a layer, and FIG. Diagram conceptually represented.

FIG. 9 is a schematic configuration diagram showing a sixth embodiment of the photocatalyst composite according to the present invention.

FIG. 10 is a graph showing the relationship between the photocatalytic film thickness and the decomposition rate when the photocatalyst composite of FIG. 9 is used for the decomposition reaction.

FIG. 11 is a schematic configuration diagram of a fiber aggregate using a photocatalyst composite according to a seventh embodiment of the present invention (a) and a cross-sectional view of the photocatalyst composite taken along line XX (b).

FIG. 12 is an explanatory view showing a change in a light irradiation direction in the photocatalyst composite of FIG. 9;

FIG. 13 is a graph showing the relationship between the thickness of the photocatalyst film and the decomposition rate in the photocatalyst composite of FIG.

FIG. 14 shows that the photocatalytic composite of FIG.
4 is a graph showing the relationship between the thickness of the photocatalytic film and the thickness of the metal film when the value is equal to or more than the value.

FIG. 15 is an explanatory diagram showing a change in a light irradiation direction in the photocatalyst composite of FIG. 9;

FIG. 16 is a graph showing the relationship between the thickness of the photocatalyst film and the decomposition rate in the photocatalyst composite of FIG.

FIG. 17 shows that the photocatalytic composite of FIG.
4 is a graph showing the relationship between the thickness of the photocatalytic film and the thickness of the metal film when the value is equal to or more than the value.

[Explanation of symbols]

1, 15, 33, 41, 51, 61, 73 Photocatalyst complex 3, 21 Conductive film 5, 23, 79 Photocatalyst film 7, 19, 43, 53, 63, 75 Support 9, 25, 71 Lead wire 11 , 37 Water purifier 13, 39 Water tank 17 Light source 27 Water supply pipe 29 Drain pipe 31 Drain pipe 35 Metal member 45, 55, 65 Electron conductive material particles 47, 57, 67 Photocatalytic particles 49, 59, 69 layers

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshio Nakayama 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation Fuchu Plant

Claims (8)

[Claims] 1. A photocatalyst composite comprising: a photocatalyst film containing a photocatalyst; and a conductive film provided adjacent to the photocatalyst film and having a transmittance to light having a wavelength at which the photocatalyst functions. body. 2. The photocatalyst composite according to claim 1, wherein the photocatalyst is titanium oxide, the conductive film contains indium oxide, and further includes a platinum member interposed between the photocatalyst film and the conductive film. 3. The method according to claim 1, further comprising a light-transmitting support for supporting the photocatalyst film and the conductive film.
3. The photocatalyst composite according to item 1. 4. A photocatalyst complex having a photocatalyst,
A photocatalyst composite, comprising: a conductive layer having transparency to light having a wavelength at which the photocatalyst functions, wherein the photocatalyst is provided in contact with the conductive layer. 5. A photocatalyst composite comprising: a photocatalyst film having a thickness of 50 to 500 nm; and a conductive film provided adjacent to the photocatalyst film. 6. A photocatalyst composite comprising a photocatalyst film and a conductive film provided adjacent to the photocatalyst film, wherein the thickness x of the photocatalyst film and the thickness y of the conductive film are represented by the following formula: 1) A photocatalyst complex characterized by satisfying (3): 75 ≦ x ≦ 400 (1) y ≦ x / 6 + 27.5 (2) y ≦ −7x / 50 + 96 .5 (3). 7. A photocatalyst composite comprising a photocatalyst film and a conductive film provided adjacent to the photocatalyst film, wherein the thickness x of the photocatalyst film and the thickness y of the conductive film are represented by the following formula ( 4),
Photocatalyst complex characterized by satisfying (5) and (6): 50 ≦ x ≦ 500 (4) y ≦ 0.2x + 30 (5) y ≦ −0.1x + 90 ( 6). 8. The photocatalyst composite according to claim 1, wherein the photocatalyst composite is provided in the water tank, and the photocatalyst film of the photocatalyst composite is provided with light having a wavelength at which the photocatalyst functions. And a light source for supplying water to the water purifier.