Photocatalyst decomposition system

Abstract

To provide a photocatalyst decomposition apparatus that can supply a liquid phase containing a substance to be decomposed by a photocatalyst and that can perform decomposition of the substance more efficiently than in the conventional art.SOLUTION: A photocatalyst decomposition system according to the invention includes: a gas phase generation apparatus configured to convert a liquid phase containing a decomposition object into a gas phase; and a photocatalyst member configured to come into contact with the gas phase to decompose the decomposition object by light from a light source. The photocatalyst member includes a base material formed of a porous material and a photocatalyst layer provided on the surface of the base material.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a photocatalytic decomposition system. [Background technology]

[0002] The technology of splitting water using sunlight to produce hydrogen with high efficiency is an inexpensive, storable energy carrier production technology that does not emit CO2, and is expected to be applied in renewable energy and environmental businesses, such as hydrogen power generation and hydrogen vehicles that achieve a shift away from fossil fuels.

[0003] Furthermore, if photocatalytic technology that breaks down chemical substances with a large environmental impact develops and can utilize sunlight with high efficiency, it will be possible to reduce not only water but also CO2, methane, and NOx discharged into the atmosphere. x Alternatively, it can be used to decompose nitrates that flow from the soil into water sources and produce useful materials. Reducing CO2 and methane emissions can help prevent global warming, and reducing NO x Nitrates that flow from soil into water sources contribute to biodiversity through water and the atmosphere. These can be converted not only into valuable substances such as alcohol and formic acid, but also into other valuable substances such as alcohol and formic acid. This is expected to lead to the development of an industry with a circular PF based on artificial photosynthesis as a material production system.

[0004] An example of such a technique is Patent Document 1. Patent Document 1 discloses a water photolysis device having a casing 1 with a light-transmitting window 12 that transmits sunlight L, and a photolysis layer 5 provided on the casing 1. This photolysis device is placed in a floating state on a water layer 9, and water vapor is evaporated from the water layer 9 by irradiation with sunlight L, and this water vapor is introduced into the photolysis layer 5, and in the photolysis layer 5, photocatalyst particles 52 are excited by sunlight L, and the introduced water vapor is converted into water. Basic and oxygen do The configuration of Patent Document 1 is said to provide a water photolysis device that can efficiently obtain hydrogen and oxygen by suppressing the reverse reaction, and can also effectively utilize solar energy to promote the photolysis of water. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2004 / 085306 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventionally, in devices that use photocatalysts to decompose liquid phases, the photocatalyst is placed in water in the form of a powder or thin film and then irradiated with light to decompose water. The decomposed gas is generated as bubbles on the surface of the photocatalyst, and a certain amount is desorbed into the water and collected, but some parts of the photocatalyst surface are covered with the generated bubbles. This reduces the contact area between the catalyst and water, causing the reaction rate to saturate and decrease, and there was a challenge in eliminating this and maintaining a high reaction rate.

[0007] As mentioned above, in the liquid phase, the reaction rate is saturated due to bubbles, etc. decrease Therefore, it is important to improve the efficiency of the reaction by placing the photocatalyst in the gas phase, suppressing the generation of bubbles, and increasing the contact surface area between the gas phase and the photocatalyst. In the above-mentioned Patent Document 1, the photocatalyst is supported in a powder form dispersed in a porous material, but it is difficult to form electrical continuity, and it is difficult to improve the efficiency of the reaction using electrodes, etc.

[0008] In view of the above circumstances, an object of the present invention is to provide a photocatalytic decomposition system that can supply a gas phase containing a substance to be decomposed by a photocatalyst and decompose the substance more efficiently than ever before. [Means for solving the problem]

[0009] One aspect of the present invention for solving the above problems is a photocatalytic decomposition system comprising a gas phase generating device that converts a liquid phase containing a substance to be decomposed into a gas phase, and a photocatalytic member that comes into contact with the gas phase and decomposes the substance to be decomposed using light from a light source to generate a gas phase, wherein the photocatalytic member has a substrate made of a porous material and a photocatalytic layer provided on the surface of the substrate.

[0010] More specific configurations of the present invention are described in the claims. Effect of the Invention

[0011] According to the present invention, it is possible to provide a photocatalytic decomposition system that can supply a gas phase containing a substance to be decomposed by a photocatalyst and decompose the substance more efficiently than ever before.

[0012] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0013] [Figure 1] Schematic diagram of porous material [Diagram 2] Schematic diagram of a photocatalytic member provided in the photocatalytic decomposition device of the present invention. [Diagram 3] FIG. 1 is a schematic diagram showing a photocatalytic decomposition system according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a schematic diagram showing a photocatalytic decomposition system according to a second embodiment of the present invention. [Diagram 5] FIG. 1 is a schematic diagram showing a photocatalytic decomposition system according to a third embodiment. [Figure 6] FIG. 1 is a schematic diagram showing a photocatalytic decomposition system according to Example 4. [Figure 7] FIG. 1 is a schematic diagram showing a photocatalytic decomposition system according to Example 5. [Figure 8] FIG. 1 is a schematic diagram showing a photocatalytic decomposition system according to Example 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The configuration of the present invention will be described in detail below with reference to the drawings.

[0015] As described above, the photocatalytic decomposition system of the present invention comprises a gas phase generating device that converts a liquid phase containing a substance to be decomposed into a gas phase, and a photocatalytic member that comes into contact with the gas phase and generates a gas phase by decomposing the substance to be decomposed by light from a light source. The photocatalytic member comprises a base material made of a porous material and a photocatalytic layer provided on the surface of the base material. First, the photocatalytic member will be described. FIG. 1 is a schematic diagram of a porous material, and FIG. 2 is a schematic diagram of a photocatalytic member provided in the photocatalytic decomposition system of the present invention. The porous material 100 shown in FIG. 1 is a nanoporous material having pores 102 of several μm to several tens of μm in a base material 101. As shown in FIG. 2, the photocatalytic member 200 of the present invention has a photocatalytic layer 201 provided on the surface of the nanoporous material shown in FIG. 1. In the present invention, Akira By using such a photocatalytic member 200, a gaseous or vaporous substance is converted into another gas or substance by a photocatalytic reaction with light from a light source. to make .

[0016] The photocatalytic decomposition system of the present invention converts a liquid phase containing a substance to be decomposed into a gas phase (vapor), and decomposes the substance by contacting the gas phase with a photocatalytic member. By providing the photocatalytic layer 201 on the substrate 101 made of a porous material as described above, the surface area of ​​the photocatalytic reaction portion is increased, and the generated gas phase escapes without remaining in the photocatalytic reaction portion. This prevents the surface of the photocatalytic layer 201 from being covered with air bubbles, which occurs when the liquid phase is contacted with the photocatalytic member, and prevents a decrease in the contact area between the gas phase and the photocatalytic layer 201.

[0017] The photocatalytic member provided in the photocatalytic decomposition system of the present invention is capable of decomposing not only gas phase but also liquid phase.

[0018] The substrate 101 is preferably a material that transmits at least visible or ultraviolet wavelengths and has a three-dimensional block structure with a porous or mesh-like fibrous material as a skeleton. The material of the substrate 101 preferably contains SiO2, Al2O3, TiO2, MgO, ZnO, CaCO3, CaO, CNT (transparent carbon nanotube), or SnO.

[0019] The photocatalyst layer 201 is not particularly limited, but for example, at least one of the substances described in the following (1) to (4) can be preferably used, and these may be combined.

[0020] (1) Rh or black phosphorus doped BiVO4, BiVO4, (2) SrTiO3, SrTiO3 doped with Rh, Ir, La, or Al, (3) La-doped LaON, TiO2, GaP, SnNb2O6, NaTaO3, NaTaO3, (4)TaON, LaTiO2N, TaON, Ta3N5, SrTa2ON, LaTa2ON, ZnRh2O4, Sm2Ti2O5S2, Y2Ti2O2S5, g-C3N4, Ga3N4, Cu 0.25 Ag 0.25 In 0.25 ZnS2, CuAgZnSnS4 Particles of a co-catalyst material that promotes a photocatalytic reaction may be supported on at least a portion of the photocatalyst layer 201, or a thin film of the co-catalyst material may be provided. The co-catalyst material is not particularly limited, but may be WO3, Rh / Cr2O3, Ag, Rh / SrTiO3, Pt, CoO, Co3O4, IrO2, PtO2, phosphorus, NiO, RuO2, AgSbO3, or ZnRhO x can be preferably used.

[0021] The porosity (volume ratio of pores 102) of the photocatalyst member 200 is preferably 40% to 95% (40% or more and 95% or less). If the porosity is less than 40%, it becomes difficult to secure a sufficient surface area for reaction in the photocatalyst layer 201. Also, if the porosity exceeds 95%, it becomes difficult to ensure the strength of the photocatalyst member 200. The width of the pores in the substrate 101 is preferably 10 μm to 500 μm.

[0022] The surface area of ​​the pores in nanoporous materials is between 10 and 1000 m 2 / g (general value), and it is possible to create a wide variety of pore sizes and materials. (Porous glass specific gravity: 1-2 g / cm 2 ) The photocatalytic member 200 can be produced by immersing the pores 102 of the porous material that is the substrate 101 in a liquid that is a mixture of a liquid (MOD material) made of a metal organic compound made of the material of the photocatalytic layer 201, a metal complex solution or a metal-oxide colloid solution made by the sol-gel method, etc., followed by vacuum impregnation, vacuum ventilation or spin coating, and sintering to produce an object in which the inner surfaces of the pores are coated and modified with a photocatalyst. By selectively using the above methods, a variety of photocatalytic materials can be synthesized. The coating film is continuous to the internal structure, making it possible to achieve electrical conductivity from the surface. In other words, the outer surface of the photocatalyst member 200 and the surfaces of the internal pores 102 have electrical continuity. A transparent conductive thin film layer may be provided on the surface of the photocatalyst layer 201 or between the substrate 101 and the photocatalyst layer 201, and the photocatalyst layer 201 and the transparent conductive thin film layer may be electrically connected. EXAMPLES

[0023] The photocatalytic decomposition system of the present invention, which is equipped with the above-mentioned photocatalytic member, will be described in detail below. EXAMPLES

[0024] FIG. 3 is a schematic diagram showing the photocatalytic decomposition system of Example 1. As shown in FIG. of The photocatalytic decomposition system 300a is Photocatalyst member 200 was used A photocatalyst member 320 and a steam supplying device 301 for supplying steam to the photocatalyst member 320 And The photocatalytic decomposition system is of light (e.g. sunlight 310) Light supply equipment Place Therefore, the vapor is supplied to the vapor supply device 301 and the photocatalyst member 320 . The photocatalytic decomposition system 300a includes a housing that houses the photocatalytic member 320, and the housing is provided with a transparent window, a lens, or an optical path, and sunlight 310 is irradiated onto the photocatalytic member 320 through the transparent window, the lens, or the optical path. The ultraviolet to visible light 311 obtained by dispersing and concentrating sunlight 310 is transmitted through an optical fiber 313. Installed inside the enclosure light touch Medium part Material 320 Irradiate It is preferable to supply infrared light 312 obtained by dispersing and concentrating sunlight 310 to the steam supply device 301, since this allows each device to function efficiently.

[0025] In the steam supplying device 301, a liquid phase (e.g., water) 303 containing a substance to be decomposed, supplied via a liquid phase (water) supplying pipe 306, is heated by a steam generating member 304 provided in a steam generating vessel 302 using sunlight 310 to generate steam 305. The generated steam is supplied to a photocatalytic decomposition device 314 via a steam transfer pipe 307.

[0026] In the photocatalytic decomposition device 314 , the supplied steam 305 is supplied to a photocatalytic member 320 via a steam inlet portion 315 and a steam outlet portion 318 .

[0027] The photocatalytic member 320 is Proton conductive membrane By separation membrane 319 at least Two Photocatalytic materials 401, 402 Electrodes 322 and 323 are connected to each of them as a voltage application device, so that the potential can be adjusted. Gas or water vapor is supplied to each of the at least two photocatalyst members 401 and 402. In addition, a configuration may be adopted in which the potential is adjusted by the electrodes 322 and 323 to separate the substances that are produced.

[0028] The generated gases 324, 325 generated by decomposing the steam 305 by the photocatalyst member 320 are each released to the outside. For example, when the steam 305 is water, oxygen (O2), hydrogen (H2), and water vapor (H2O) are released as generated gases. Note that the decomposition target is not limited to water, and carbon dioxide (CO2), nitrogen oxide (NO x ) and methane (CH3). The gas phase generated by decomposition by the photocatalyst member 320 is collected by a collection device.

[0029] According to the photocatalytic decomposition system 300a of the present invention described above, natural energy such as sunlight can be used to convert the decomposition target contained in the liquid phase into a gas phase, and then the target can be efficiently decomposed by the photocatalyst. The photocatalytic member 320 used for decomposition by the photocatalyst has a reactive structure (porous) that is permeable to steam, so that a larger surface area can be utilized within a three-dimensional space.

[0030] Furthermore, by providing electrodes 322 and 323, the decomposition reaction by the photocatalyst can be controlled. EXAMPLES

[0031] Fig. 4 is a schematic diagram of a photocatalytic decomposition system 300b of Example 2. Fig. 4 mainly illustrates the configuration of a photocatalytic decomposition device 314 constituting the photocatalytic decomposition system 300b. The photocatalytic decomposition system 300b of this example differs from the photocatalytic decomposition system 300a of Example 1 in that it has a reference electrode 403. This makes it possible to control the potential of the electrodes 322 and 323. The reference electrode 403 can be made of Ag / AgCl. EXAMPLES

[0032] FIG. 5 is a schematic diagram of a photocatalytic decomposition system 300c according to a third embodiment. FIG. 5 mainly illustrates the configuration of a photocatalytic decomposition device 314 that constitutes the photocatalytic decomposition system 300c. The photocatalytic decomposition system 300c according to the third embodiment is 2 Photocatalytic decomposition system 300 b The difference from the first embodiment is that the photocatalyst member 320 is in direct contact with the vapor discharge portion 318. By adopting such a configuration, the vapor 305 can be supplied to the photocatalyst member 320 more efficiently. EXAMPLES

[0033] Fig. 6 is a schematic diagram of a photocatalytic decomposition system 300d according to a fourth embodiment. Fig. 6 mainly illustrates the configuration of a photocatalytic decomposition device 314 that constitutes the photocatalytic decomposition system 300d. The photocatalytic decomposition system 300d according to the fourth embodiment is 2 Photocatalytic decomposition system 300 b The difference from the above is that it is provided with a conductive terminal 601. With this configuration, it is possible to exchange carriers between the electrodes 322 and 323, and the photocatalytic decomposition reaction can be controlled more precisely and efficiently. EXAMPLES

[0034] Fig. 7 is a schematic diagram of a photocatalytic decomposition system 300e of Example 5. Fig. 7 mainly illustrates a photocatalytic decomposition device 314 of the photocatalytic decomposition system 300e of this example. 2 Photocatalytic decomposition system 300 bThe difference from the above is that the photocatalyst member 320 is in contact with the liquid phase 701. With this configuration, the liquid phase can be directly supplied to the photocatalyst member 320, and the liquid phase 701 can be efficiently reacted while the gas phase 305 is decomposed. EXAMPLES

[0035] Fig. 8 is a schematic diagram of a photocatalytic decomposition system 300f according to a sixth embodiment. Fig. 8 mainly illustrates a photocatalytic decomposition device 314 constituting the photocatalytic decomposition system 300f. The photocatalytic decomposition system 300f according to the sixth embodiment is 2 Photocatalytic decomposition system 300 b The difference is that Medium part Material 320 with cocatalyst pole 4 04 ,405 With this configuration, the photocatalyst member 320 can react efficiently.

[0036] As described above, it has been shown that the present invention can provide a photocatalytic decomposition device that can supply a gas phase containing a substance to be decomposed by a photocatalyst and decompose the gas phase more efficiently than conventional methods.

[0037] The present invention is not limited to the above-mentioned embodiment, but includes various modified examples. For example, the above-mentioned embodiment has been described in detail to easily explain the present invention, and is not necessarily limited to those including all of the configurations described. It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0038] 300a, 300b, 300c, 300d, 300e, 300f... photocatalytic decomposition system, 314... photocatalytic decomposition device, 401, 402... photocatalytic Medium partmaterial, 301...steam supply device, 302...steam generating vessel, 303...liquid phase, 304...steam generating member, 305...gas phase (steam), 306...liquid phase supply pipe, 307...steam transfer pipe, 308, 309...flow rate adjustment section, 310...sunlight, 311...ultraviolet to visible light, 312...infrared light, 313...optical fiber, 315...steam introduction pipe, 316...photocatalytic reaction vessel (cathode side), 317...photocatalytic reaction vessel (anode side), 318...steam release section, 319...separation membrane, 320...photocatalytic member, 321...steam + separated product gas, 322...voltage application device (anode), 323...voltage application device (cathode), 324, 325...product gas, 326...light from the end of the optical fiber, 40 3… reference electrode, 404, 405... Electrodes with promoters, 601...Continuity terminal, 701...Liquid phase.

Claims

1. A gas phase generating device for converting a liquid phase containing a decomposition target into a gas phase; a photocatalyst member that comes into contact with the gas phase and decomposes the substance to be decomposed by light from a light source; The photocatalytic decomposition system is characterized in that the photocatalytic member has a base material made of a porous material and a photocatalytic layer provided on a surface of the base material.

2. 2. The photocatalytic decomposition system according to claim 1, wherein the photocatalytic member also comes into contact with the liquid phase to decompose the substance to be decomposed.

3. 3. The photocatalytic decomposition system according to claim 1, wherein the outer surface of the photocatalytic member and the surfaces of the internal pores have electrical continuity.

4. The photocatalytic decomposition system according to claim 1 or 2, characterized in that a transparent conductive thin film layer is provided on a surface of the photocatalytic layer or between the substrate and the photocatalytic layer, and the photocatalytic layer and the transparent conductive thin film layer are electrically connected.

5. 3. The photocatalytic decomposition system according to claim 1, further comprising at least one pair of electrodes in contact with the photocatalytic member, the potential of which can be adjusted by the at least one pair of electrodes.

6. The photocatalytic device has at least two of the photocatalytic members, a proton conductive membrane provided between the at least two photocatalytic members, and a pair of electrodes connected to each of the at least two photocatalytic members, The potential can be adjusted by the electrodes, 3. The photocatalytic decomposition system according to claim 1, wherein a gas or water vapor is supplied to each of the at least two photocatalytic members.

7. 6. The photocatalytic decomposition system according to claim 5, wherein the substances produced are separated by adjusting the potential with the electrodes.

8. A housing that houses the photocatalytic member, the light source is sunlight, 3. The photocatalytic decomposition system according to claim 1, wherein a transparent window, a lens or an optical path is provided in the housing, and the sunlight is irradiated onto the photocatalytic member through the transparent window, the lens or the optical path.

9. 9. The photocatalytic decomposition system according to claim 8, wherein the light concentrated outside the housing is introduced into the housing by an optical fiber and irradiated onto the photocatalytic member.

10. 3. The photocatalytic decomposition system according to claim 1, wherein the substrate transmits at least light of a visible or ultraviolet wavelength.

11. 3. The photocatalytic decomposition system according to claim 1, wherein the width of the pores in the substrate is 10 μm to 500 μm and the porosity is 40% to 95%.

12. The porous material constituting the substrate is SiO ２ , Al ２ O ３ , TiO ２ , MgO, ZnO, CaCO ３ 3. The photocatalytic decomposition system according to claim 1, further comprising: CaO, SnO, or transparent carbon nanotubes.

13. 3. The photocatalytic decomposition system according to claim 1, wherein the photocatalytic layer is at least one of the substances listed in the following (1) to (4). (1) Rh or black phosphorus doped BiVO ４ , BiVo ４ , (2) SrTiO doped with Rh, Ir, La, and Al ３ , SrTiO3, (3) La-doped LaON, TiO ２ , GaP, SnNb ２ O ６ , NaTaO ３ , NaTaO ３ , (4)TaOｮ、LaTiｯｯ ２ N、4aｯN、4a ３ 8. ５ 、″r⁴a ２ O、LaTa ２ O、Znｲh ２ 9 ４ 、″m ２ Ti ２ 9 ５ ﳳ ２ 、Y ２ Ti ２ 9 ２ 34、g-3 ３ 8. ４ 、1a ３ 8. ４ 、Cu ０．２５ Ag ０．２５ 9. ０．２５ a. ２ 、CuAgZnｳnﳳ ４

14. 3. The photocatalytic decomposition system according to claim 1, wherein particles of a promoter material are supported on at least a portion of the photocatalytic layer, or a thin film of a promoter material is provided on at least a portion of the photocatalytic layer.

15. The cocatalyst material is WO ３ , Rh / Cr ２ O ３ , Ag, Rh / SrTiO ３ , Pt, CoO, Co ３ O ４ , IrO ２ , PtO ２ , phosphorus, NiO, RuO ２ , AgSbO ３ Or ZnRhO ｘ The photocatalytic decomposition system according to claim 14,

16. 3. The photocatalytic decomposition system according to claim 1, further comprising: a light supplying device that supplies light to the photocatalytic member and the gas phase generating device; and a recovery device that recovers the gas phase generated by decomposition by the photocatalytic member.

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