Hydrogen production device

Abstract

To provide a hydrogen production device in which the total light utilization efficiency is made higher than before by efficiently utilizing a wide range of wavelength components from ultraviolet light of sunlight to infrared light including visible light.SOLUTION: A hydrogen production device that has a photocatalyst and generates hydrogen from water comprises a wavelength separation unit that separates sunlight into wavelengths, an infrared light conversion unit that converts infrared light separated by the wavelength separation unit into visible light, and an ultraviolet light conversion unit that converts ultraviolet light separated by the wavelength separation unit into visible light.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a hydrogen production apparatus that decomposes water with light to produce hydrogen gas.

Background Art

[0002] Techniques for decomposing water with sunlight typified by photocatalysts to efficiently produce hydrogen are expected to be applied as renewable energy businesses and environmental businesses for realizing environmental and social infrastructure such as hydrogen power generation and hydrogen vehicles that realize hydrogen production without CO2 emissions, as inexpensive and storable energy carrier production techniques.

[0003] In addition, if technologies for highly efficiently utilizing sunlight develop, it is expected to spread to peripheral industries such as material production systems because it can be applied to the production of useful materials by applying photocatalysts that decompose chemical substances with a large environmental impact.

[0004] As a technique related to decomposing water with sunlight to produce hydrogen, Patent Document 1 describes a junction-type Z-scheme catalyst having high activity with respect to the complete decomposition reaction of water, and a method for producing hydrogen using such a catalyst. is described.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] As a high-efficiency utilization technology for solar energy required when water is decomposed by sunlight to produce hydrogen, the frequency range of irradiation light that activates the photocatalytic reaction has been developed from materials that are active in the conventional ultraviolet region (NaTaO3: 280 nm, TiO2: around 400 nm) to materials that have an active region in the visible light region (400 - 700 nm) where the light intensity of the solar spectrum is stronger.

[0007] However, the spectrum of sunlight extends not only to ultraviolet light but also significantly to infrared light, and the energy of these has not been utilized. Furthermore, infrared light of 1000 nm or more has less energy than 1.23 V required for water decomposition, so it cannot be used for water decomposition as it is. Thus, in a hydrogen production device having a photocatalyst, the light utilization efficiency could not be improved.

[0008] Even in Patent Document 1, there is no mention of effectively using light in a wide wavelength range from ultraviolet to infrared light of sunlight.

[0009] The present invention solves the above-described problems of the prior art, efficiently utilizes a wide range of wavelength components from ultraviolet to visible light including infrared light of sunlight, and provides a hydrogen production device with a higher total light utilization efficiency than before.

Means for Solving the Problems

[0010] To solve the above problems, in the present invention, having a wavelength conversion layer that converts ultraviolet light to visible light in a part thereof A hydrogen production device having a photocatalyst that generates hydrogen from water is configured with a wavelength separation unit that separates sunlight by wavelength, an infrared light conversion unit that converts the infrared light separated by this wavelength separation unit into visible light, and the visible light and ultraviolet light are incident, and a monochromator that emits the visible light and the ultraviolet light at different angles and is provided, and the ultraviolet light emitted from the monochromator is incident on the wavelength conversion layer of the photocatalyst, and the visible light emitted from the monochromator is incident on a part of the photocatalyst other than the wavelength conversion layer configured.

[0011] Also, to solve the above problems, in the present invention, a hydrogen production device includes a photocatalyst that generates hydrogen gas from water by irradiating light, a pipe through which water flows inside, a wavelength separation unit that separates sunlight by wavelength, anda monochromator that generates diffracted light according to the wavelength of the input light, A first optical system that condenses and irradiates visible light obtained by wavelength-separating sunlight in this wavelength separation unit onto a photocatalyst, a second optical system that converts ultraviolet light obtained by wavelength-separating sunlight in the wavelength separation unit into visible light, condenses it, and irradiates it onto the photocatalyst, and a third optical system that converts infrared light obtained by wavelength-separating sunlight in the wavelength separation unit into visible light, condenses it, and irradiates it onto the photocatalyst are provided. , the photocatalyst has a wavelength conversion layer that converts ultraviolet light to visible light in a part thereof, the first optical system causes the visible light obtained by wavelength separation of the sunlight to be incident on a part of the photocatalyst different from the wavelength conversion layer by the monochromator, and the second optical system causes the ultraviolet light obtained by wavelength separation of the sunlight to be incident on the wavelength conversion layer of the photocatalyst by the monochromator It was configured.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a hydrogen production apparatus that highly efficiently utilizes wavelength components in a wide range from ultraviolet light to visible light including infrared light in sunlight, and increases the total light utilization efficiency compared to the conventional case.

Brief Description of the Drawings

[0014]

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Mode for Carrying Out the Invention

[0015] The present invention relates to a hydrogen production apparatus that can efficiently separate and purify hydrogen from water by adopting a configuration that solves the problem when fusing an optical system that efficiently converts the wavelength spectrum of sunlight into the active range of a photocatalyst and condenses it on the photocatalyst with various functions.

[0016] That is, in the present invention, in a hydrogen production apparatus, a photocatalyst having an active region in the visible light region (wavelength: 400 nm to 700 nm) where the energy level of sunlight peaks (for example, TiO2, LaTiO2, TaON, Y2Ti2O5S2, Rh-doped SrTiO3, ZnRh2O4, Sm2Ti2O2S5, CuAgZnSnS4, etc.) is used to wavelength-convert the light of the wavelength component in the ultraviolet light region and the light of the wavelength component in the infrared light region of sunlight into light having a wavelength in the visible light region, and irradiate the photocatalyst together with the visible light from sunlight, thereby enabling efficient separation and purification of hydrogen from water.

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining this embodiment, those having the same function are denoted by the same reference numerals, and repeated explanations thereof are omitted in principle.

[0018] However, the present invention is not construed as being limited to the description of the embodiments shown below. It will be easily understood by those skilled in the art that the specific configuration can be changed without departing from the spirit or gist of the present invention.

Example

[0019] The hydrogen production apparatus according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 shows a plan view of the overall configuration of the hydrogen production apparatus 10 according to the first embodiment, and FIG. 2 shows a view taken in the direction of the A-A' cross section in FIG. 1.

[0020] In the configuration shown in FIGS. 1 and 2, 101 is lens A, 201 is a mirror, 301 is a wavelength separation filter, 401 is an infrared light conversion unit, 402 is lens B, 501 is an ultraviolet light conversion unit, 601 is a photocatalyst, 602 is a cocatalyst (for hydrogen), 603 is a cocatalyst (for oxygen), 604 is a substrate, 701 is a pipe on the hydrogen gas generation side, 702 is a pipe on the oxygen gas generation side, and 703 is a water / gas separation mechanism unit that separates water from hydrogen gas or oxygen gas.

[0021] The hydrogen production apparatus 10 according to the present embodiment has a symmetrical configuration in the left and right portions with respect to the central line M-M' shown in FIG. 1. In the following description, the configuration mainly on the left side of FIGS. 1 and 2 will be described, but the same applies to the configuration on the right side.

[0022] In the configuration shown in FIGS. 1 and 2, lens A: 101 is a quartz Fresnel lens having wide wavelength transmissivity. However, lens A: 101 is not limited to a quartz Fresnel lens, and may be composed of a convex lens or a lens having a non-linear surface. The sunlight incident on lens A: 101 is condensed on the surface of the mirror 201 that is installed inclined with respect to lens A: 101 with a smaller surface area than lens A:.

[0023] The mirror 201 is a concave mirror or a mirror formed with a non-linear curved surface, and reflects the sunlight condensed by lens A: 101 and condenses it on the surface of the wavelength separation filter 301. The wavelength separation filter 301 transmits infrared light and reflects visible light and ultraviolet light having a shorter wavelength than that.

[0024] The infrared light that has passed through the wavelength separation filter 301 is incident on the infrared light conversion unit 401. The infrared light conversion unit 401 is formed of a material that emits visible light with a wavelength shorter than that of the incident infrared light (for example, a surface of a photonic crystal in which a large number of square nanopyramids with a side length of about 200 nanometers and a height of about 500 nanometers made of Si or the like are arranged in parallel on a plane at intervals of 400 nanometers, a surface in which circular nanoholes with a diameter of about 500 nanometers are similarly spread, or a surface of a photonic crystal having a structure capable of changing the properties of a semiconductor by applying a voltage thereto and adjusting the wavelength of reflected light, or a fluorescent agent (light upconversion material) that emits visible light upon infrared light irradiation, etc.) formed on a substrate. That is, when infrared light is incident, visible light is generated from the infrared light conversion unit 401.

[0025] In the infrared light conversion unit 401, when it is necessary to heat the infrared light conversion unit 401 in order to generate visible light from the incident infrared light, the infrared light conversion unit 401 may be configured to include a heating means therein.

[0026] The visible light generated in the infrared light conversion unit 401 when infrared light is incident is incident on the lens B: 402. A diagram in which the region surrounded by the dotted line B in FIG. 2 is enlarged is shown in FIG. 3. The infrared light that has passed through the wavelength separation filter 301 is incident on the infrared light conversion unit 401, and the visible light generated in the infrared light conversion unit 401 is incident on the lens B: 402 and is condensed on the surface of the photocatalyst 601 and the cocatalysts (for hydrogen) 602 and cocatalysts (for oxygen) 603 formed at both ends thereof.

[0027] The infrared light conversion unit 401 is installed inclined with respect to the wavelength separation filter 301 and the lens B: 402 in order to make more of the infrared light that has passed through the wavelength separation filter 301 incident thereon and to make more of the generated visible light incident on the lens B: 402.

[0028] On the one hand, the visible light and ultraviolet light that did not pass through the wavelength separation filter 301 among the sunlight incident on the wavelength separation filter 301 are reflected by the wavelength separation filter 301 and incident on the ultraviolet light conversion unit 501. A fluorescent agent that emits fluorescence (visible light) upon ultraviolet light irradiation is applied to the surface of the substrate of the ultraviolet light conversion unit 501.

[0029] Among the visible light and ultraviolet light incident on the ultraviolet light conversion unit 501, the visible light is reflected on the surface of the ultraviolet light conversion unit 501 and the optical path is converted, and is condensed on the surfaces of the photocatalyst 601 and the cocatalysts (for hydrogen) 602 and cocatalyst (for oxygen) 603 formed at both ends thereof by the ultraviolet light conversion unit 501. On the other hand, when ultraviolet light is incident on the ultraviolet light conversion unit 501, fluorescence (visible light) is generated from the fluorescent agent applied to the surface of the substrate of the ultraviolet light conversion unit 501, and a part of it is condensed on the surfaces of the photocatalyst 601 and the cocatalysts (for hydrogen) 602 and cocatalyst (for oxygen) 603 formed at both ends thereof.

[0030] Details of the portion including the photocatalyst 601 surrounded by the dotted line C in FIG. 2 are shown in FIG. 4. The photocatalyst 601, the cocatalyst (for hydrogen) 602 formed at one end thereof, and the cocatalyst (for oxygen) 603 formed at the other end are formed on the substrate 604. The end of the photocatalyst 601 on the side where the cocatalyst (for hydrogen) 602 is formed enters, together with the substrate 604, into the hydrogen gas generation side pipe 701 through which water flows inside. On the other hand, the end of the photocatalyst 601 on the side where the cocatalyst (for oxygen) 603 is formed enters, together with the substrate 604, into the oxygen gas generation side pipe 702 through which water flows inside. In this state, a potential difference is generated between the cocatalyst (for hydrogen) 602 and the cocatalyst (for oxygen) 603.

[0031] Between the photocatalyst 601 and the substrate 604 and the hydrogen gas generation side pipe 701 and the oxygen gas generation side pipe 702, in order to prevent the water flowing through the hydrogen gas generation side pipe 701 or the oxygen gas generation side pipe 702 from leaking to the outside, it is sealed with a sealing member (not shown).

[0032] The cocatalyst is determined in combination with the photocatalyst. For example, in the case of doped SrTiO3, IrO3, BiVO4, CoO, CoOOH, etc. are used on the anode side that generates oxygen, and the photocatalyst material itself may be used on the cathode side that generates hydrogen. In the case of WO3, PO3 is used on the anode side and WO3 is used on the cathode side. In the case of TaON, NiO is used on the anode side and TaON supporting WO3 is used on the cathode side. In the case of LaTiON, LaTiO2 is used on the anode and LaTiO2 supporting Pt is used on the cathode. In the case of Y2Ti2O2S5, IrO2 is used on the anode side and Rh formed on top of Rh or Cr2O3-coated is used on the cathode side. Examples include these, and in addition to those described here, an appropriate combination shall be selected and used.

[0033] In the configuration as shown in FIG. 4, the photocatalyst 601 and the cocatalysts (for hydrogen) 602 and cocatalysts (for oxygen) 603 formed at both ends thereof are irradiated by visible light converted from infrared light among the sunlight incident on the lens A: 101 and collected by the lens B: 402, visible light converted from ultraviolet light by the ultraviolet light conversion unit 501 among the sunlight incident on the lens A: 101, and visible light reflected by the ultraviolet light conversion unit 501.

[0034] In the photocatalyst 601 irradiated with these visible lights and the cocatalysts (for hydrogen) 602 and cocatalysts (for oxygen) 603 formed at both ends thereof, water is decomposed inside the pipe 701 on the hydrogen gas generation side to generate hydrogen gas, and water is decomposed inside the pipe 702 on the oxygen gas generation side to generate oxygen gas.

[0035] The hydrogen gas generated inside the pipe 701 on the hydrogen gas generation side flows together with water, and the hydrogen gas is separated from the water in the water-gas separation mechanism unit 703, and the hydrogen gas is recovered. On the other hand, the oxygen gas generated inside the pipe 702 on the oxygen gas generation side flows together with water, and the oxygen gas is separated from the water in the water-gas separation mechanism unit 703, and the oxygen gas is recovered.

[0036] The potential on the hydrogen generation electrode side is almost zero. However, depending on the type of catalyst, the reaction may become extremely slow or stop if it is lower than the potential of water. Therefore, it includes the case of providing a mechanism for applying a weak external voltage of less than 0.5V. Also, in order to promote the reaction, it includes the case where water is made into an electrolyte solution with an additive.

[0037] According to this embodiment, among the sunlight incident on the hydrogen production apparatus 10, by converting the infrared light and ultraviolet light components that cannot activate the photocatalyst as they are and do not contribute to the generation of hydrogen gas into visible light and using them respectively, the utilization efficiency of sunlight in the hydrogen production apparatus 10 can be improved.

Example

[0038] A second embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 is a plan view showing the overall configuration of the hydrogen production apparatus 20 according to the second embodiment. Among the configurations of the hydrogen production apparatus 20 according to this embodiment, the configuration of the optical system that irradiates the photocatalyst 601 with the sunlight incident on the lens A: 101 through the lens B: 402, and the configuration of the optical system that irradiates the photocatalyst 601 with the sunlight incident on the lens A: 101 through the ultraviolet light conversion unit 501 are the same as the configuration of the hydrogen production apparatus 10 described in the first embodiment, so the description will be omitted.

[0039] In this embodiment, the configuration of the portion including the photocatalyst 601 corresponding to the portion surrounded by the dotted line C in FIG. 2 in the first embodiment is different from that in the first embodiment. The details of the portion including the photocatalyst 601 according to this embodiment corresponding to the portion surrounded by the dotted line C in FIG. 2 in the D-D' cross-section of FIG. 5 are shown in the perspective view of FIG. 6.

[0040] In the first embodiment, the hydrogen gas generation side pipe 701 and the oxygen gas generation side pipe 702 on both sides of the photocatalyst 601 were arranged separately from each other. In contrast, in this embodiment, the hydrogen gas generation side pipe 701-1 and the oxygen gas generation side pipe 702-1 are connected at the intermediate portion 710, and the entire photocatalyst 601 is configured to be placed in water.

[0041] With such a configuration, the water flowing through the pipe 701-1 on the hydrogen gas generation side and the water flowing through the pipe 702-1 on the oxygen gas generation side will mix with each other. However, in this embodiment, by setting the interval between the intermediate portion 710 and the photocatalyst 601 below it to be narrow, the amount of water flowing through the pipes of each other mixing is reduced. Thereby, the amount of oxygen gas flowing into the side of the pipe 701-1 on the hydrogen gas generation side and the amount of hydrogen gas flowing into the side of the pipe 702-1 on the oxygen gas generation side can be made small, and the reduction in the yield of hydrogen gas and oxygen gas separated by the water / gas separation mechanism portion 703 can be made small enough to be negligible.

[0042] According to this embodiment, since the entire photocatalyst 601 is configured to be immersed in water, the configuration can be simplified because there is no need for a configuration to prevent water leakage between the photocatalyst 601 and the pipe 701 on the hydrogen gas generation side and the pipe 702 on the oxygen gas generation side as in the configuration of the first embodiment.

[0043] [Modification Example] A modification example of the second embodiment is shown in FIG. 7. The configuration shown in FIG. 7 is the same as the configuration shown in FIG. 6 in terms of the configuration on the side of the pipe 702-2 on the oxygen gas generation side and the configuration of connecting the pipe 701-2 on the hydrogen gas generation side and the pipe 702-2 on the oxygen gas generation side by the intermediate portion 710, but the internal configuration of the pipe 701-2 on the hydrogen gas generation side is different.

[0044] That is, in this modification example, inside the pipe 701-2 on the hydrogen gas generation side, the co-catalyst (for hydrogen) 602 in FIG. 6 is eliminated, and instead, a counter electrode 606 formed of Pt or the like is provided, and an ion exchange membrane 607 is installed between the counter electrode 606, the photocatalyst 601, and the substrate 604.

[0045] The ion exchange membrane 607 has the property of permeating counter ions. By partitioning between the pipe 701-2 on the hydrogen gas generation side and the pipe 702-2 on the oxygen gas generation side with this ion exchange membrane 607, oxygen and hydrogen can be separated and generated in the pipe 701-2 on the hydrogen gas generation side and the pipe 702-2 on the oxygen gas generation side.

[0046] According to this modification example, in addition to the effects described in the second embodiment, a co-catalyst (in the example of FIG. 7, the co-catalyst (for oxygen) 603) needs to be formed only on one end side of the photocatalyst 601 (in the configuration shown in FIG. 7, the side of the pipe 702-2 on the oxygen gas generation side). Therefore, compared with the configuration in which photocatalysts are formed on both ends of the photocatalyst 601 as shown in FIG. 6, the man-hour is reduced and the manufacturing method becomes simpler.

[0047] Furthermore, since the number of types of co-catalysts combined with the photocatalyst 601 is reduced from two types in the case of FIG. 6 to one type, the selection of materials for the photocatalyst 601 and the co-catalyst becomes easier.

Example

[0048] A third embodiment of the present invention will be described with reference to FIGS. 8 to 11. In the first and second embodiments, the visible light and ultraviolet light reflected by the wavelength separation filter 301 are incident on the ultraviolet light conversion unit 501, and the visible light is reflected and the ultraviolet light is converted into fluorescence. On the other hand, in this embodiment, the wavelength conversion of ultraviolet light is not performed, and a diffracted light corresponding to the wavelength is generated using a wavelength separation plate.

[0049] FIG. 8 shows a plan view of the hydrogen production apparatus 30 according to this embodiment, and FIG. 9 shows a view in the direction of the arrow of the E-E' cross section in FIG. 8.

[0050] The configuration of the hydrogen production apparatus 30 according to this embodiment is different from the configuration described in the first and second embodiments in the processing of light having a wavelength in the ultraviolet region from the visible light separated by the wavelength separation filter 301 among the sunlight incident on the lens A: 101 and reflected by the mirror 201.

[0051] Among the sunlight incident on lens A: 101 and reflected by the reflector 201, the visible light generated from the infrared light conversion unit 401 through which the infrared light transmitted through the wavelength separation filter 301 is incident irradiates the photocatalyst 601 through lens B: 402. Since the configuration of the optical system is the same as that of the hydrogen production apparatus 10 described in the first embodiment, the description thereof is omitted.

[0052] In the configuration shown in FIG. 9, the light having a wavelength in the ultraviolet region from the visible light reflected by the wavelength separation filter 301 is incident on the wavelength separation unit (monochromator) 502 at the diffraction angle.

[0053] An enlarged view of the portion surrounded by the dotted line F in FIG. 9 is shown in FIG. 10. The light having a wavelength in the ultraviolet region from the visible light reflected by the wavelength separation filter 301 is incident on the wavelength separation unit (monochromator) 502 and exits from the wavelength separation unit (monochromator) 502 at the diffraction angle corresponding to the wavelength and is incident on the surface of the photocatalyst 601-1. Here, the wavelength separation unit (monochromator) 502 is adjusted so that the diffracted light generated by the light incident from the wavelength separation filter 301 travels in the direction of the surface of the photocatalyst 601-1 with respect to the angles of the wavelength separation filter 301 and the surface of the photocatalyst 601-1.

[0054] The diffracted light generated by the wavelength separation unit (monochromator) 502 has a different emission angle from the wavelength separation unit (monochromator) 502 according to the wavelength. In the example of FIG. 10, light (ultraviolet light) having a relatively short wavelength is incident on the upper side of the photocatalyst 601-1, and light (visible light) having a relatively long wavelength is incident on the lower side of the photocatalyst 601-1.

[0055] Here, the photocatalyst 601-1 is formed of a material having sensitivity to visible light, similar to the photocatalyst 601 described in Examples 1 and 2. A part of it, as enlarged and shown on the right side of FIG. 10, has a wavelength conversion layer 503 made of a material that converts ultraviolet light to visible light formed in the portion where the relatively short-wavelength light (ultraviolet light) from above is incident. The ultraviolet light incident on the wavelength conversion layer 503 is converted to visible light and reaches the photocatalyst 601-1 below the wavelength conversion layer 503. On the other hand, the relatively long-wavelength light (visible light) is incident on the portion formed of a material having sensitivity to visible light on the lower side.

[0056] By configuring so that the position where light is incident on the photocatalyst 601-1 varies according to the wavelength in this way, and forming the wavelength conversion layer 503 in the portion of the surface of the photocatalyst 601-1 where ultraviolet light is incident, among the sunlight incident on the lens A:101, the ultraviolet light is irradiated onto the photocatalyst 601-1 together with visible light without wavelength conversion. Therefore, it is possible to suppress a reduction in the amount of light irradiated onto the photocatalyst 601-1 among the sunlight incident on the lens A:101. Note that, in the portion where the wavelength conversion layer 503 in FIG. 10 is formed, instead of the wavelength conversion layer 503, a layer of an ultraviolet-sensitive photocatalyst may be formed so that a photocatalytic reaction is directly generated by the ultraviolet light incident on the portion.

[0057] [Modification Example 1] As a first modification example of Example 3, an example in which the wavelength conversion layer 503 of the photocatalyst 601-1 shown in FIG. 10 is replaced with a material having sensitivity to ultraviolet light will be described.

[0058] In the configuration of the photocatalyst 601-1 enlarged and shown on the right side of FIG. 10, by replacing the portion of the wavelength conversion layer 503 where ultraviolet light is incident with a photocatalyst formed of a material having sensitivity to ultraviolet light, the ultraviolet light diffracted by the wavelength separation unit (monochromator) 502 and incident on the upper portion of the photocatalyst 601-1 can be detected as it is without wavelength conversion. On the other hand, the portion where the relatively long-wavelength light (visible light) on the lower side is incident is formed of a material having sensitivity to visible light, similar to the photocatalyst 601 described in Example 3.

[0059] In this way, by forming the surface of the photocatalyst 601-1 with a material having sensitivity corresponding to the wavelength of the incident light, among the sunlight incident on the lens A:101, ultraviolet light is irradiated onto the photocatalyst 601-1 together with visible light without wavelength conversion. Therefore, it is possible to suppress a reduction in the amount of light irradiated onto the photocatalyst 601-1 among the sunlight incident on the lens A:101.

[0060] [Modification Example 2] As a second modification example of Example 3, a plan view of the hydrogen production apparatus 40 according to this modification example is shown in FIG. 11.

[0061] The hydrogen production apparatus 40 according to this modification example has a configuration in which the photocatalyst 601-1 and its surrounding configuration in FIG. 9 of Example 3 corresponding to the G-G' cross section in FIG. 11 are connected at the intermediate portion 710 between the hydrogen gas generation side pipe 701-1 and the oxygen gas generation side pipe 702-1 in the same manner as described with reference to FIG. 6 in Example 2, and the entire photocatalyst 601-1 is placed in water.

[0062] According to this modification example, since the entire photocatalyst 601 is placed in water, the configuration can be simplified because there is no need for a configuration to prevent water leakage between the photocatalyst 601-1 and the hydrogen gas generation side pipe 701 and the oxygen gas generation side pipe 702 as in the configuration of Example 3.

[0063] Also, it may be configured as described with reference to FIG. 7 as a modification example of Example 2. By adopting the configuration shown in this FIG. 7, the man-hour is reduced and the manufacturing method becomes simpler compared to the configuration in which the co-catalysts 602 and 603 are formed at both ends of the photocatalyst 601-1 as shown in FIG. 9.

[0064] Furthermore, since the number of types of co-catalysts combined with the photocatalyst 601-1 is reduced from two types in the case of FIG. 6 to one type as shown in FIG. 7, the selection of materials for the photocatalyst 601-1 and the co-catalyst becomes easier.

Example

[0065] A fourth embodiment of the present invention will be described with reference to FIGS. 12 to 14. This embodiment is different from the configurations described in the first to third embodiments in that the visible light emitted from the infrared light conversion unit 401 is irradiated onto the photocatalyst 601 using an optical fiber.

[0066] FIG. 12 shows a plan view of the hydrogen production apparatus 50 according to this embodiment, and FIG. 13 shows a view taken along the arrow of the H-H' cross section in FIG. 12.

[0067] In the configuration of the hydrogen production apparatus 50 shown in FIGS. 12 and 13, among the sunlight incident on the lens A: 101 and reflected by the mirror 201, the light having a wavelength in the ultraviolet region from the visible light separated by the wavelength separation filter 301 is incident on the ultraviolet light conversion unit 501, and the visible light emitted from the ultraviolet light conversion unit 501 is irradiated onto the photocatalyst 601. The optical system configuration, and among the sunlight incident on the lens A: 101 and reflected by the mirror 201, the infrared light transmitted through the wavelength separation filter 301 is incident on the lens B: 402 from the infrared light conversion unit 401. Since the optical system up to this point is the same as the configuration of the hydrogen production apparatus 10 described in the first embodiment, the description thereof will be omitted.

[0068] As shown in FIG. 12, the hydrogen production apparatus 50 according to this embodiment has a different positional relationship between the lens B: 402 and the infrared light conversion unit 401 from the configurations of the first to third embodiments. The tip portion 403 of the optical fiber 404 is disposed on the side opposite to the infrared light conversion unit 401 with the lens B: 402 interposed therebetween.

[0069] As shown in the cross-sectional view of FIG. 13, in the hydrogen production apparatus 50 according to this embodiment, an optical fiber 404 is disposed between the lens B: 402 and the photocatalyst 601. In such a configuration, as shown in FIG. 14, which is an enlarged view of the portion surrounded by the dotted line I in FIG. 13, the visible light generated by the infrared light conversion unit 401 by the infrared light that has passed through the wavelength separation filter 301 and entered the infrared light conversion unit 401 enters the lens B: 402, and the visible light emitted from the lens B: 402 is condensed on the tip portion 403 of the optical fiber 404. The light condensed on this tip portion 403 is transmitted through the optical fiber 404 and emitted from the opposite end to the side of the photocatalyst 601. Actually, the optical fiber 404 branches in the middle as shown in FIG. 13 and is also emitted to the side of the other photocatalyst 601, but in FIG. 14, its display is omitted.

[0070] According to this embodiment, by adopting a configuration in which the photocatalyst 601 is irradiated with visible light using the optical fiber 404, the optical path can be set without being affected by the structure between the lens B: 402 and the photocatalyst 601, and the visible light generated by the infrared light conversion unit 401 can be surely irradiated to the photocatalyst 601.

[0071] In this embodiment as well, the hydrogen gas generation side pipe 701 and the oxygen gas generation side pipe 702 may be connected at the intermediate portion 710 in the same manner as the hydrogen gas generation side pipe 701-1 and the oxygen gas generation side pipe 702-1 described with reference to FIG. 6 in Example 2, so that the entire photocatalyst 601 is immersed in water, or may be configured as shown in FIG. 7 as described in the modified example of Example 2.

[0072] Further, the ultraviolet light conversion unit 501 may be replaced with a wavelength separation unit (monochromator) 502 as described in Example 3 and combined with a configuration in which a wavelength conversion layer 503 is formed on a part of the photocatalyst 601-1 as described with reference to FIG. 10.

Example

[0073] The fifth embodiment of the present invention will be described with reference to FIGS. 15 and 16. FIG. 15 is a plan view of the hydrogen production apparatus 60 according to the present embodiment, and FIG. 16 is a view taken along the arrow of the J-J' cross section in FIG. 15.

[0074] The hydrogen production apparatus 60 according to the present embodiment is common to the hydrogen production apparatus 10 described in Example 1 in that the lens A: 101 is used, but the optical path of the light emitted from the lens A: 101 is different from that of the hydrogen production apparatus 10 described in Example 1.

[0075] The hydrogen production apparatus 60 according to the present embodiment includes a wavelength separation mechanism (monochromator type) 202, a lens C (infrared light) 302, a lens D (visible light) 303, a lens E (ultraviolet light) 304, an infrared light conversion unit 401, a condenser lens B: 406, an ultraviolet light conversion unit 504, a condenser lens D: 505, a photocatalyst 601, a promoter (for hydrogen) 602, a promoter (for oxygen) 603, a substrate 604, a pipe 701 on the hydrogen gas generation side, and a pipe 702 on the oxygen gas generation side.

[0076] The pipe 701 on the hydrogen gas generation side and the pipe 702 on the oxygen gas generation side are connected to the water / gas separation mechanism unit 703 in the same manner as the hydrogen production apparatus 10 of Example 1 described in FIG. 1, and hydrogen gas and oxygen gas are taken out.

[0077] In the configuration shown in FIGS. 15 and 16, the sunlight incident on the lens A: 101 is condensed and irradiated on the wavelength separation mechanism 202. The sunlight condensed and irradiated on the wavelength separation mechanism 202 is emitted at an angle corresponding to the wavelength by the wavelength separation mechanism 202. In the configuration shown in FIG. 16, the infrared light with a long wavelength is emitted in the direction of the lens C (infrared light) 302, the visible light is emitted in the direction of the lens D (visible light) 303, and the ultraviolet light is emitted in the direction of the lens E (ultraviolet light) 304.

[0078] The infrared light incident on the lens C (infrared light) 302 is emitted and converged in the direction of the infrared light conversion unit 401 and enters the infrared light conversion unit 401. When the infrared light enters, visible light is generated from the infrared light conversion unit 401, and the generated visible light is emitted in the direction of the condenser lens B: 406 and condensed and irradiated on the surface of the photocatalyst 601 by the condenser lens B: 406.

[0079] The visible light incident on lens D (visible light) 303 is emitted in the direction of the photocatalyst 601, converges, and is incident on the photocatalyst 601.

[0080] The ultraviolet light incident on lens E (ultraviolet light) 304 is emitted in the direction of the ultraviolet light conversion unit 504, converges, and is incident on the ultraviolet light conversion unit 504. When the ultraviolet light is incident, visible light is generated from the ultraviolet light conversion unit 504, and the generated visible light is emitted in the direction of the condenser lens D: 505 and condensed and irradiated on the surface of the photocatalyst 601 by the condenser lens D: 505.

[0081] In the photocatalyst 601 irradiated with visible light and the cocatalysts (for hydrogen) 602 and cocatalysts (for oxygen) 603 formed at both ends thereof, water is decomposed inside the pipe 701 on the hydrogen gas generation side to generate hydrogen gas, and water is decomposed inside the pipe 702 on the oxygen gas generation side to generate oxygen gas.

[0082] The hydrogen gas generated inside the pipe 701 on the hydrogen gas generation side flows together with water, and the hydrogen gas is separated from the water in the water-gas separation mechanism unit 703 described with reference to FIG. 1 in Example 1, and the hydrogen gas is recovered. On the other hand, the oxygen gas generated inside the pipe 702 on the oxygen gas generation side flows together with water, and the oxygen gas is separated from the water in the water-gas separation mechanism unit 703, and the oxygen gas is recovered.

[0083] According to this embodiment, among the sunlight incident on the hydrogen production apparatus 10, the infrared light and ultraviolet light components that cannot activate the photocatalyst and do not contribute to the generation of hydrogen gas are converted into visible light and used respectively, so that the utilization efficiency of sunlight in the hydrogen production apparatus 10 can be improved.

[0084] In this embodiment as well, the pipe 701 on the hydrogen gas generation side and the pipe 702 on the oxygen gas generation side may be connected at the intermediate portion 710 like the pipe 701-1 on the hydrogen gas generation side and the pipe 702-1 on the oxygen gas generation side described with reference to FIG. 6 in Example 2, so that the entire photocatalyst 601 is immersed in water, or may be configured as shown in FIG. 7 as described in the modified example of Example 2.

[0085] Further, the ultraviolet light conversion unit 504 may be replaced with the wavelength separation unit (monochromator) 502 as described in Example 3, and the condenser lens D: 505 is used to condense and irradiate the region coated with the ultraviolet light sensitive photocatalyst having sensitivity to ultraviolet light on the surface of the photocatalyst 601, and may be combined with the configuration in which the wavelength conversion layer 503 is formed on a part of the photocatalyst 601 as described in FIG. 10.

[0086] Further, a configuration similar to that described in Modification 1 of Example 3 may be adopted, in which a reflecting mirror that reflects ultraviolet light is used instead of the ultraviolet light conversion unit 504, and the condenser lens D: 505 is used to condense and irradiate the region coated with the ultraviolet light sensitive photocatalyst having sensitivity to ultraviolet light on the surface of the photocatalyst 601.

[0087] In the above-described examples, an example in which water is passed through the pipes 701 or 701-1 on the hydrogen gas generation side or the pipes 702 or 702-1 on the oxygen gas generation side to generate hydrogen gas and oxygen gas has been described. However, a liquid mixture of ammonia (NH3) and water may be passed instead of water. When such a mixture is used, hydrogen gas and nitrogen gas can be separated and recovered in the water / gas separation mechanism unit 703.

[0088] Further, by flowing a liquid mixture of water and carbon dioxide instead of water, hydrogen gas can be recovered in the water / gas separation mechanism unit 703, and formic acid can be recovered as a liquid.

[0089] The invention made by the present inventor has been specifically described based on the examples. However, it goes without saying that the present invention is not limited to the above-described examples, and various modifications can be made without departing from the gist thereof. For example, the above-described examples have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. In addition, for a part of the configuration of each example, addition, deletion, or replacement with other configurations is possible.

Explanation of Reference Numerals

[0090] 10, 20, 30, 40, 50, 60 Hydrogen Production Equipment 101 Lens A 201 Mirror 202 Wavelength Separation Mechanism 301 Wavelength Separation Filter 302 Lens C (Infrared Light) 303 Lens D (Visible Light) 304 Lens E (Ultraviolet Light) 401 Infrared Light Conversion Unit 402 Lens B 404 Optical Fiber 406 Condensing Lens B 501, 504 Ultraviolet Light Conversion Unit 503 Wavelength Conversion Layer 502 Wavelength Separation Unit (Monochromator) 505 Condensing Lens D 601 Photocatalyst 602 Promoter (for Hydrogen) 603 Promoter (for Oxygen) 701, 701-1 Hydrogen Gas Generation Side Pipe 702, 702-1 Oxygen Gas Generation Side Pipe 703 Water-Gas Separation Mechanism Unit 710 Intermediate Part

Claims

Claim 1. A hydrogen production apparatus having a photocatalyst having a wavelength conversion layer for converting a part of ultraviolet light into visible light, wherein in the hydrogen production apparatus for generating hydrogen from water, a wavelength separation unit that separates sunlight by wavelength; an infrared light conversion unit that converts the infrared light separated by the wavelength separation unit into visible light; a monochromator into which the visible light and ultraviolet light separated by the wavelength separation unit are incident and which emits the visible light and the ultraviolet light at different angles; characterized by comprising: the ultraviolet light emitted from the monochromator is incident on the wavelength conversion layer of the photocatalyst, and the visible light emitted from the monochromator is incident on a portion of the photocatalyst other than the wavelength conversion layer. Hydrogen production apparatus. Claim 2 The hydrogen production apparatus according to claim 1, wherein the wavelength separation unit transmits infrared light among the sunlight and reflects visible light and ultraviolet light. Hydrogen production apparatus. Claim 3 The hydrogen production apparatus according to claim 2, wherein the wavelength conversion layer of the photocatalyst is replaced with a photocatalyst formed of a material having sensitivity to ultraviolet light. Hydrogen production apparatus. Claim 4 A photocatalyst that generates hydrogen gas from water by irradiating light; a pipe through which water flows inside; a wavelength separation unit that separates sunlight by wavelength; a monochromator that generates diffracted light according to the wavelength of incident light; a first optical system that condenses and irradiates the visible light obtained by wavelength-separating sunlight by the wavelength separation unit onto the photocatalyst; a second optical system that converts the ultraviolet light obtained by wavelength-separating sunlight by the wavelength separation unit into visible light, condenses it, and irradiates it onto the photocatalyst; a third optical system that converts the infrared light obtained by wavelength-separating sunlight by the wavelength separation unit into visible light, condenses it, and irradiates it onto the photocatalyst characterized by comprising: the photocatalyst has a wavelength conversion layer for converting a part of ultraviolet light into visible light in a part thereof; the first optical system causes the visible light obtained by wavelength-separating the sunlight to be incident on a portion of the photocatalyst different from the wavelength conversion layer by the monochromator; the second optical system causes the ultraviolet light obtained by wavelength-separating the sunlight to be incident on the wavelength conversion layer of the photocatalyst by the monochromator; Hydrogen production apparatus characterized by the above. Claim 5. The hydrogen production apparatus according to claim 4, wherein the wavelength conversion layer of the photocatalyst is replaced with a photocatalyst formed of a material having sensitivity to ultraviolet light. Hydrogen production apparatus. Claim 6. The hydrogen production apparatus according to claim 5, It further has a first pipe through which water flows internally and a second pipe through which water flows internally. A co-catalyst for hydrogen gas is formed on a part of the photocatalyst, and a co-catalyst for oxygen gas is formed on another part of the photocatalyst. The photocatalyst on the side where the co-catalyst for hydrogen gas is formed is disposed inside the first pipe, and the photocatalyst on the side where the co-catalyst for oxygen gas is formed is disposed inside the second pipe. A hydrogen production apparatus characterized by this.

7. The hydrogen production apparatus according to claim 6, The hydrogen production apparatus characterized in that the photocatalyst is disposed inside the pipe.

8. The hydrogen production apparatus according to claim 7, The hydrogen production apparatus characterized in that a co-catalyst for hydrogen gas is formed on a part of the photocatalyst disposed inside the pipe, and a co-catalyst for oxygen gas is formed on another part of the photocatalyst.

9. The hydrogen production apparatus according to claim 7, The hydrogen production apparatus characterized in that a co-catalyst for hydrogen gas is formed on a part of the photocatalyst disposed inside the pipe, a counter electrode is disposed at a position separated from the photocatalyst inside the pipe, and the space between the photocatalyst and the counter electrode inside the pipe is partitioned by an ion exchange membrane.

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