JP2000051712A - Photocatalyst body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalyst body having an increased surface area of a substrate, capable of activating almost uniformly a photocatalytic function layer formed on the surface of the substrate and increasing the contact efficiency between a fluid and a photocatalytic semiconductor. SOLUTION: This photocatalyst body 1 has a substrate 2 with a plain weave wire net 3 formed from wires comprising SUS, Ti or its alloy, Cu or its alloy, Al or its alloy and a porous layer 4 formed on the surface of each of the wires by sintering metal particles made of SUS, Ti or its alloy, Cu or its alloy, Al or its alloy and forms a photocatalytic function layer 5 on the surface of the porous layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalyst for oxidatively decomposing organic compounds suspended in a gas or liquid (hereinafter referred to as a fluid).

[0002]

2. Description of the Related Art As petrochemical products increase, complex pollution of harmful organic compounds inside and outside a living environment has become a problem. As a means for solving this, there is a purification method using oxidative decomposition by a photocatalytic semiconductor.

For example, there is a method in which a photocatalytic semiconductor is carried on the surface of a gas constituting an apparatus or equipment, and the harmful organic substance is brought into contact with the photocatalytic semiconductor by placing the apparatus or equipment in a fluid in which the harmful organic substance floats. is there. In this case, in order to achieve a high photocatalytic function, it is necessary that the surface area of the photocatalytic function layer is large and that the photocatalytic semiconductor is sufficiently activated by an electromagnetic wave having an excitation wavelength.

Therefore, various proposals have conventionally been made with respect to a technique for increasing the surface area of the substrate and a technique for forming a photocatalytic layer (see, for example, JP-A-5-309267 and JP-A-8-196903). ).

[0005]

However, these methods merely increase the surface area and increase the area of the photocatalyst functional layer, but the activation rate by the electromagnetic wave of the excitation wavelength is low, or the fluid and the photocatalyst semiconductor cannot be separated. There are disadvantages such as poor contact efficiency. In addition, in order to form a device or an appliance, it is preferable that the substrate supporting the photocatalytic semiconductor can be formed by pressing such as press working, or has flexibility that can be rounded or bent. In particular, no inorganic base material has such a condition, and the range in which the photocatalyst can be used is narrow. Ti as substrate
Using a plate (Japanese Patent Laid-Open No. 8-246192) or using a wire mesh (SUS304) (Japanese Patent Laid-Open No. 8-21557)
No. 7) has been proposed, but there is a problem that a Ti plate is expensive and a simple wire mesh has a weak adhesion of a photocatalytic functional layer.

Accordingly, it is an object of the present invention to provide a photocatalyst which can increase the surface area of a substrate, activate a photocatalytic functional layer formed on the surface thereof almost uniformly, and increase the contact efficiency between a fluid and a photocatalytic semiconductor. Is to provide the body.

[0007]

According to the present invention, there is provided a stainless steel or Al, C
any one selected from u or Ti and its alloys
A plate-shaped substrate having a mesh-like member formed of a wire made of a kind of metal material and a porous layer in which particles made of the metal material are carried and sintered on the surface of the wire, and a photocatalytic function formed on the surface thereof And technical means of having a layer. In the present invention, the substrate is not limited to a flat plate, but may be a three-dimensional (cubic, ball, honeycomb, lattice, etc.) net-like body formed by combining the mesh members, and a wire rod. It is also possible to use a substrate having a porous layer in which particles made of the metal material are carried and sintered on the surface of the substrate. In the present invention, a plain woven wire mesh can be used as the mesh member as it is, but the plain woven wire mesh may be reduced. In the present invention, as the metal particles, regular particles (spherical or granular powder particles) or irregular particles (particles having sharp corners such as angular powder particles) can be used. In particular, the use of amorphous particles increases the depth of the concave portion formed on the surface of the substrate, which is effective in increasing the surface area. In the present invention, since the porous layer made of metal particles is formed on the surface of the wire constituting the mesh member or the three-dimensional mesh, the surface area of the base can be increased. In the present invention, since the porous layer is formed of metal powder, a substrate having high mechanical strength can be obtained. In the present invention, a punching metal can be used instead of the mesh member. The punching metal is not limited to a flat plate, and may be a structure in which the flat plates are three-dimensionally combined.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of a photocatalyst according to one embodiment of the present invention. In the figure, 1 is a photocatalyst, 2 is a substrate, 3
Is a wire mesh, 4 is a porous layer, and 5 is a photocatalytic function layer. FIG. 2 schematically shows the appearance of the substrate.

The photocatalyst 1 is formed on a plain woven wire mesh 3 made of austenitic stainless steel or a wire made of at least one metal material of Al, Cu, Ti and their alloys, and formed on the surface of each wire. And a photocatalytic functional layer 5 formed on the surface thereof. The plain woven wire mesh 3 is manufactured by vertically and horizontally intersecting one by one while keeping a constant interval. Depending on the combination of the number of meshes (mesh) and the wire diameter, various openings and openings are provided. Thus, a material having a ratio is obtained (see JIS G3555).
In the present invention, the mesh has a mesh of 2 to 100 meshes and a wire diameter (d).
It is preferable to use a wire mesh of 0.10 to 2.00 mm. Among these wire meshes, the gap (a) is 0.50 to 0.50.
Those having a diameter of 3.0 mm and an opening ratio (R) of 30.0 to 60.0% are more preferable. R is calculated by (a / a + d) ² × 100. SUS30 is used as the metal material forming the wire mesh.
4. Austenitic stainless steel such as SUS310 and SUS316 can be used. Also, not limited thereto, Al or its alloy (Al-Si-Mg type), Cu or its alloy, or Ti or its alloy (Ti-Mn, Ti-Cr, etc.) can be used.

In the present invention, since the mesh of this kind needs to be fine to some extent in order to be able to hold the metal fine powder on the surface, the above-mentioned plain woven wire mesh is used, or the wire mesh is uniformly formed on the surface of the wire mesh. Rolling is preferable so that a porous material having a large thickness can be formed. The rolling ratio is desirably in the range of 5 to 50%. When the rolling reduction is less than 5%, the effect is not obtained. On the other hand, when the rolling reduction exceeds 50%, the mesh is made finer than necessary, and the fluid becomes difficult to permeate. Further, the thickness of the wire mesh after the reduction is 0.5 to 3.0.
mm. It has a thickness of 0.5
If it is less than 3.0 mm, the strength is insufficient, and if it exceeds 3.0 mm, the transmission resistance becomes too large.

In the present invention, a porous layer 4 made of fine metal powder is formed on the surface of the wire mesh 3. This porous layer
A slurry obtained by mixing a metal powder having an average particle diameter of 10 to 400 μm in a solvent such as water (solid content: 60 to 80% by weight) is applied to the surface of a wire mesh, dried, and then sintered. As this metal material, SUS304, SUS310, SU
Austenitic stainless steel such as S316, Ti or its alloy (Ti-Mn-based, Ti-Cr-based, etc.), Cu or its alloy, or Al or its alloy (Al-Si-M
g). If the particle size of the metal powder is too small, the price increases (the pulverization time increases), and if it is too large, fine pores cannot be obtained.
It is preferable to use one having a thickness of 0 μm. The sintering temperature may be determined according to the material of the metal powder, but if it is too low, a sufficient sintering density is not obtained, and the strength is reduced. On the contrary, coarse pores are formed, and in the case of SUS, Ti, Cu, 800
In the case of Al, the range is preferably 300 to 400 ° C.

[0012] The porous layer 4 thus obtained is composed of 5
It preferably has a pore diameter of １０００1000 μm. If the pore diameter is too large, fine foreign substances cannot be prevented even when used for air purification, and clean air cannot be obtained. When the thickness of the porous layer is small, the strength is insufficient, and when the thickness is large, the permeation resistance increases. Therefore, the thickness of the porous layer is preferably 10 to 100 μm.

The metal powder forming the porous layer is a particle for increasing the surface area, and is a regular particle (spherical or granular powder particle) or an irregular particle (a particle having a sharp corner such as a rectangular powder particle). However, it may be scaly or flaky. When a melting means such as baking is employed for fixing to the substrate, the material is preferably the same as that of the substrate because of good compatibility. However, even if the materials are different, they can be fixed without using an appropriate binder in an appropriate amount. When the substrate and the particles for increasing the surface area are made of different kinds of materials, it is necessary to match the coefficient of linear expansion or to maintain elasticity corresponding to the linear expansion of one of the materials. It is. As the binder, inorganic glass, frit (glaze), metal powder, ordinary thermoplastic resin, or the like can be used. In order to stack the metal particles for increasing the surface area, there are other methods such as repeating spraying and dipping several times, and repeating transfer (printing) using a screen. And, in order to roughly laminate particles as the substrate side is densely separated from the substrate during lamination,
Select the degree of dispersion (density) of the particles in the spray liquid or dipping liquid or select the roughness of the screen used for printing. It is also possible to select the particle size of the particles to be laminated. Furthermore, it is also possible to select a laminated structure in a cross section. That is, a structure is used in which several screens that can be accurately positioned are used, and a vertex is provided at a position away from the base with the base being the base in the cross-sectional configuration of the laminate. Also according to this structure, the particles for increasing the surface area are consequently coarsely laminated as the substrate side is densely separated from the substrate.

The photocatalytic function layer 5 is formed by applying a sol liquid mixed with a photoconductive semiconductor such as TiO _{2 to} the surface of the substrate by spraying or dipping and drying the sol.
It can be formed by baking at a temperature of less than 500C to less than 500C. If amorphous titanium peroxide or titanium oxide is mixed in the sol in a titanium weight ratio (dry amount) of 1: 1 or 1: 5 in addition to the photocatalyst semiconductor, the photocatalyst semiconductor is produced at a relatively low temperature. The particles can be firmly supported.

Further, P is used for complementing functions such as fungicide sterilization.
t, Ag, Rh, RuO ₂ , Nb, Cu, Sn, NiO
Of zeolite, silica (silicon dioxide), alumina, zinc oxide, magnesium oxide, rutile type titanium oxide, zirconium phosphate, etc. One or more kinds of inorganic materials, various types of activated carbon, porous phenol resins and melamine resins can be mixed.

The photocatalytic function layer can be formed after the surface of the substrate is sprayed with a protective material such as an aqueous solution of titanium peroxide to perform a base treatment for forming a protective film. In each case, PTA (Oxysan Tainic Titanium
If a film is formed in advance with an acid (aqueous solution of titanium peroxide), the adhesion and ductility of the TiO ₂ sol solution are improved, so that it is easy to get wet, and a photo functional layer is uniformly and widely formed on the surface of the substrate. can do. PTA has excellent spreadability even when the substrate is made of a metal such as stainless steel, and is effective in applying the TiO ₂ sol solution widely and uniformly. Although PTA also functions as a binder, it does not include ceramics in composition, and has good compatibility with metal, so the photocatalytic functional layer formed on the surface of the substrate is separated even if the substrate flexes or vibrates. Less.

Other photocatalytic semiconductors include ZnO, SrT
iO₃, CdS, CdO, CaP, InP, In
₂O₃, CaAs, BaTiO₃, K₂NbO₃, Fe
₂O₃, Ta₂O₅, WO₃, SaO₂, Bi₂O₃,
NiO, Cu₂O, SiC, SiO ₂, MoS₂, Mo
S₃, InPb, RuO₂, CeO₂and so on. this
Titanium oxide TiO2₂(Anatase type) is inexpensive and characteristic
Is stable and harmless to the human body.
Best.

The catalytic function of the photocatalytic semiconductor is such that when the semiconductor is irradiated with an excitation wavelength (electromagnetic wave of excitation wavelength, ultraviolet region in the case of TiO ₂ ) of a band gap or more which the semiconductor such as a metal oxide has, electron splitting occurs in the semiconductor. OH on the surface
It generates active radical hydroxyl groups and active oxygen of-and O _2- and decomposes organic compounds in contact with them by oxidation or reduction. Thereby, a bad smell and oil stain can be cleaned. In addition, bacteria and viruses can be killed (sterilized) by the same function.

According to the structure of the present invention, the surface area of the photocatalytic functional layer is large, and the electromagnetic wave of the excitation wavelength irradiated from the outside easily reaches the particles deep in the photocatalytic functional layer.
The photocatalytic function layer is activated in a wide range. In addition, since the fluid passing through such a laminated structure portion is reflected on the wall of the laminated structure, or enters the concave portion and temporarily stays, there are many chances that the organic matter floating in the fluid comes into contact with the photocatalytic semiconductor. . Therefore, the photocatalyst has high performance.

Although the photocatalyst constructed as described above can be used in various forms, it may be used by forming a photocatalyst functional layer on both sides of a single flat substrate. In this case, an electromagnetic wave source having an excitation wavelength is arranged along both side edges of the flat plate, and one side (front) of the flat plate is irradiated with the electromagnetic wave source of one excitation wavelength, and the other is generated by the electromagnetic wave source of the other excitation wavelength. The surface (back) can be irradiated.

In the present invention, the photocatalyst can be used as various filters because the substrate has many fine through holes. It is not just a filter as an element.For example, if you configure the inner wall of a refrigerator that is sealed like a refrigerator and use it as a filter for the gas circulating in the refrigerator, you can extract vegetables and fruits such as ethylene gas from the air in the refrigerator. It can remove harmful gases that will be abolished, and can remove unpleasant odors such as hydrogen sulfide and mercaptan. In this case, since the inner wall functions as a filter, the volume in the refrigerator is not reduced and the filter is not obstructed as compared with a case where the filter is separately provided in the refrigerator.

Further, such a photocatalyst can be provided with a cleaning function as well as a sound deadening function, a visual shielding function, and a wave canceling and defoaming function when the fluid is in a liquid phase, depending on the mode of use. The silencing is, for example, a case where a photocatalyst is used as a partition wall that separates a roadway and a human road on a road. Is introduced into the complicated internal space of the plain woven wire mesh and absorbs the transmitted energy. The visual blocking function is a function of blocking the passage of light, so that the photocatalyst can be used as a partition or the like. Furthermore, wave extinction is analogous to the absorption of sound waves. The wave of the liquid makes the contact opportunity between the organic compound floating in the liquid and the photocatalyst semiconductor uneven, but the fluid temporarily stops in the inner space of the wire net due to the wire mesh, and the contact opportunity with the photocatalyst semiconductor is almost uniform. become.

In addition, the photocatalyst of the present invention can be used for an air conditioner or an exhaust gas treatment device body or a filter, an indoor wall plate for a toilet or building, an algae-proof aquarium wall, a swimming pool wall, and the like. The photocatalyst of the present invention is not limited to a plate-shaped one, but can be formed into various shapes according to the application and the installation place. That is, in the present invention, a three-dimensional shape such as a ball shape, a honeycomb shape, or a lattice shape, which is obtained by processing the sheet-shaped photocatalyst shown in FIG. 1 into a predetermined shape or combining them, can be provided. Among them, for example, those having a honeycomb shape are particularly useful for purifying exhaust gas. FIG. 3A shows an example in which the sheet-shaped photocatalyst 1 is formed into a ball shape. FIG. 3B shows an example in which the sheet-shaped photocatalyst 1 and the corrugated photocatalyst 1 ′ are combined in a honeycomb shape. FIG. 3C shows an example in which the sheet-shaped photocatalyst 1 is fixed to the support frame 20 in multiple stages. In the case of a flat plate (flat film), one end is fixed at a predetermined position, and the other end (free end) is connected to a vibration imparting means to continuously or intermittently vibrate, so that the fluid to be processed is The chance of contact with the photocatalytic semiconductor increases. This structure is particularly useful as a wave-breaking means of a swimming pool.

[0024]

EXAMPLES Example of Production of Photocatalyst Body Four kinds of plain-woven wire meshes each made of austenitic stainless steel SUS316 were rolled at a rolling reduction of 15% or 30% to prepare wire meshes having a thickness of 2.0 to 1.0 mm. Also pure A
The plain-woven wire mesh formed by the l-line was rolled at a rolling reduction of 20% to prepare a wire mesh having a thickness of 1.5 mm. In addition, Ti alloy (PC1
30A) The plain-woven wire mesh formed by the wire was rolled at a rolling reduction of 10% to prepare a wire mesh having a thickness of 1.5 mm. Next, SUS316 powder, Cu powder, Ti powder or Al
The powder was applied and then sintered to produce a substrate of the type shown in Table 1. Water was used as a binder for sintering each metal powder.

[0025]

[Table 1]

Next, as the photocatalytic functional material, an aqueous solution of an amorphous titanium oxide (0.84 w%): an aqueous solution of anatase titanium oxide (0.84 w%): an aqueous solution of colloidal silica (0.84 w%) is 3: 7: 0. 0.7 g / 25 cm ² (wet state) on the surface of each substrate
Spray. After drying at room temperature, heat drying (3
(00 ° C. × 1 hr) to obtain a photocatalyst.

(Example 2) As an adsorption / photocatalyst functional material,
Amorphous titanium oxide aqueous solution (0.84%): anatase type titanium oxide aqueous solution (0.84%): colloidal silica aqueous solution (0.84%): coconut shell activated carbon (in terms of other aqueous solution weight) 3: 3: 0 1: mixed at a ratio of 0.3 and 0.6 g / 25 cm ^{2 on} the surface of each substrate of Example 1.
(Wet state). The whole was dried by heating (300 ° C. × 1 hr) to obtain a photocatalyst.

(Evaluation) Each of the above fourteen photocatalysts was placed in a glass tube, and the environment was conditioned with air containing 50 ppm of ethylene gas by a xenon lamp of 300 W.
Irradiation with UV light of 00 nm confirmed that the concentration of ethylene gas could be reduced to 5 ppm or less within 1 hour after irradiation with any of the photocatalysts.

FIG. 4 shows a photocatalyst device 9 in which a photocatalyst 1 formed in a flat plate is fitted into a frame 7 and a fluorescent lamp 8 as an electromagnetic wave supply source of an excitation wavelength is integrally incorporated. The photocatalyst 1 is the one shown in Example 1, and the frame 7 is formed in a rectangular shape with stainless steel. The frame members forming the vertical frames on both sides have a space for accommodating the fluorescent lamp 8.
Therefore, when the frame 7 is viewed from above, it becomes a long rectangle corresponding to the cross-sectional shape, but the flat photocatalyst 1 is arranged along the diagonal line. According to this structure, one surface (front) of the photocatalyst 1 is illuminated by one fluorescent lamp 8 and
The other surface (back surface) is irradiated by the other fluorescent lamp 8 to activate the photocatalytic function layer on each surface. Ultraviolet light from the fluorescent lamp 8 is applied to the surface of the photocatalyst 1 from one side, but the surface of the photocatalyst 1 is reflected by the uneven surface of the metal non-woven fabric, and the ultraviolet light is also applied to the shadowed portion when viewed from the fluorescent lamp side. As a result, the front surface of the photocatalytic functional layer on the photocatalyst body is almost activated, and an efficient photocatalytic function is exhibited. This photocatalyst device 9
Because of its air permeability, it can be used not only as a filter, but also as a partition that also serves as an indoor air purification device.

FIG. 5 is a sectional view of the low-temperature storage room 10 for storing vegetables and the like. The low-temperature storage chamber 10 is sealed by a door (not shown). The flat photocatalyst 1 shown in Example 1 is attached to the inside of a box-shaped outer wall 11 with a space 12 between them. ing. A flat reflecting plate 13 and a fluorescent lamp 8 as an ultraviolet light supply source are arranged on both sides of the flat reflecting plate 13 in a diagonal arrangement at the interval 12 of the ceiling portion. As shown in FIG. 6 (a), the plate-type reflector 13 has reflecting pieces 14 formed on both sides to reflect ultraviolet rays from the fluorescent lamps 8 on both sides in the same direction, that is, in the direction of the photocatalyst 1 on the ceiling.
In the case where the photocatalytic functional layers are present on both sides of the panel as in the case of the central partition wall, as shown in FIG.
8 is used. The reflection layer 18 is formed by, for example, laminating SUS particles baked on both surfaces of a stainless steel plate 19. The particles are densely arranged with a small diameter on the steel plate 19 side and densely on the side remote from the substrate, with a large diameter on the steel plate 19 side.
An elliptical reflection plate 16 having a mirror surface on the inner side and a fluorescent lamp 8 as an ultraviolet ray supply source are arranged inside the center of the reflector 15 at the wall interval 15. Each of the spaces 13 and 15 communicates with ducts 17 on both sides of the ceiling, and the internal air of the storage room 10 is circulated through the photocatalyst 1 which is an inner wall by a circulation pump. Then, when passing through the photocatalyst 1, organic compounds that are inconvenient for storing vegetables, such as ether and odor, which are suspended in the air, are decomposed by oxidation and reduction. The photocatalyst 1 as the inner wall is
In the case where the base 2 has moldability as in the embodiment, the container 2 can be formed into a container at once by press working instead of combining flat plates. When peeling of the photocatalytic function layer becomes a problem, the photocatalytic function layer may be formed after pressing the substrate 2.

FIG. 7 shows a photocatalyst 1 as a countermeasure for deodorizing a toilet.
In this example, a flat photocatalyst 1 is attached to the ceiling at intervals. Reference numeral 8 denotes a fluorescent lamp, which is a UV light source. Normally, indoor air is constantly flowing in the indoor space of the toilet by a ventilator, and a floating organic compound as a source of odor collides with the photocatalyst 1 in the airflow and is decomposed in the photocatalytic functional layer. Since the surface of the photocatalyst 1 has a layered structure having irregularities with voids, the photocatalyst 1 is easily decomposed during contact with the floating organic compound or passing through the fine pores to easily receive the photocatalytic function, and the deodorizing effect is improved.

[0032]

According to the present invention, the photocatalyst body has many voids and irregularities in the surface layer, the photocatalytic functional layer has a large area, a large oxidizing / reducing power, and the organic compound floating in the fluid and the photocatalytic function. The photocatalyst with high performance has many opportunities to contact with the layer.

[Brief description of the drawings]

FIG. 1 is a plan view of a photocatalyst according to one embodiment of the present invention.

FIG. 2 is a schematic view showing the appearance of a base.

FIGS. 3A, 3B, and 3C are perspective views each showing an example of a three-dimensional photocatalyst;

FIG. 4 is a perspective view showing a flat photocatalyst device.

FIG. 5 is a front view of the low-temperature storage box cut away.

FIGS. 6A and 6B are plan views each showing an example of a reflection plate.

FIG. 7 is a front view schematically showing a form of use in a toilet.

[Explanation of symbols]

Reference Signs List 1 photocatalyst body, 2 substrate, 3 wire mesh, 4 porous layer, 5
Photocatalytic function layer

Continued on the front page F-term (reference) 4F100 AA20 AA21 AB04A AB04B AB10A AB10B AB12A AB12B AB17A AB17B AB31A AB31B AR00C BA03 BA07 BA13 DC11A DC16A DC21A DE01B EJ48B GB90 JL08 JL08C 4G069 AA01 BAA18 BC ABA03 BC CA07 CA10 CA11 EA12 EB12Y EB15Y EB18Y EC22Y EC26 FA04 FB15 FB23 FB24 FB31 FB33 FB70

Claims (7)

[Claims] 1. Stainless steel or Al, Cu or T
a mesh member formed of a wire made of any one of metal materials selected from i and an alloy thereof, and a porous layer in which particles of the metal material are supported and sintered on the surface of the wire. A photocatalyst comprising: a flat substrate having a photocatalyst layer; and a photocatalytic functional layer formed on the surface of the flat substrate. 2. Stainless steel or Al, Cu or T
i and alloys thereof, a three-dimensional net formed by combining mesh members formed of a wire made of any one of metal materials, and particles of the metal material carried on the surface of the wire. A photocatalyst comprising: a base having a sintered porous layer; and a photocatalytic functional layer formed on the surface thereof. 3. The photocatalyst according to claim 1, wherein the mesh member is a plain woven wire mesh or a squeezed plain woven wire mesh. 4. The photocatalyst according to claim 1, wherein the metal particles are formed of regular particles. 5. The photocatalyst according to claim 1, wherein the metal particles are made of irregular particles. 6. Stainless steel or Al, Cu or T
a flat plate-shaped substrate having a punching metal made of any one of metal materials selected from i and its alloys, and a porous layer in which particles made of the metal material are supported and sintered on the surface thereof; A photocatalyst comprising: a photocatalyst functional layer formed on the surface. 7. Stainless steel or Al, Cu or T
and a structure in which a punching metal made of any one metal material selected from i and its alloys is three-dimensionally combined, and a porous body in which particles made of the metal material are supported and sintered on the surface thereof A photocatalyst comprising: a substrate having a layer; and a photocatalytic functional layer formed on a surface of the substrate.