Water decomposition device

Abstract

To provide a water decomposition device with a photocatalyst used therein which has high light utilization efficiency.SOLUTION: A water decomposition device which produces hydrogen and oxygen from water with light includes: a photocatalyst for hydrogen production; a photocatalyst for oxygen production; and a spectroscopic member on which light including a plurality of wavelengths is incident. The spectroscopic member disperses the incident light, causes a first light group composed of light having wavelengths of a first wavelength range to be incident on the photocatalyst for the hydrogen production, and causes a second light group composed of light having wavelengths of a second wavelength range being one different from the first wavelength range to be incident on the photocatalyst for the oxygen production.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water splitting apparatus. [Background technology]

[0002] In recent years, hydrogen has been attracting attention as an environmentally friendly new energy source, and various hydrogen production methods have been investigated. One of the hydrogen production methods is water decomposition using a photocatalyst. Patent Document 1 discloses a water decomposition device using a photocatalyst. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-139749 Summary of the Invention [Problem to be solved by the invention]

[0004] From the viewpoint of energy efficiency, it is desirable to use sunlight as the light for initiating the photocatalytic reaction. However, the sunlight utilization efficiency of water splitting photocatalysts is low, and there is a need to improve the light utilization efficiency of water splitting devices.

[0005] An object of the present invention is to provide a water splitting device that uses a photocatalyst and has high light utilization efficiency. [Means for solving the problem]

[0006] A water splitting apparatus according to one embodiment of the present invention is a water splitting apparatus that generates hydrogen and oxygen from water using light, A photocatalyst for generating hydrogen; a photocatalyst for generating oxygen; a spectroscopic member onto which light containing a plurality of wavelengths is incident, The spectroscopic member disperses incident light, A first light group consisting of light having a wavelength in a first wavelength band is incident on the photocatalyst for generating hydrogen, A second light group consisting of light having wavelengths in a second wavelength band that is different from the first wavelength band is made incident on the oxygen generating photocatalyst. [Effects of the Invention]

[0007] According to the present invention, a water splitting device using a photocatalyst and having high light utilization efficiency can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing the configuration of a water splitting apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a water splitting apparatus according to a second embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram showing the configuration of a water splitting apparatus according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a schematic diagram showing the configuration of a water decomposition apparatus according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions of each component and the refraction of light in the drawings have been appropriately distorted or exaggerated for the purpose of explanation, and may differ from the actual form.

[0010] [First embodiment] FIG. 1 is a schematic diagram showing a water splitting apparatus 1 according to a first embodiment of the present invention. The water splitting apparatus 1 includes a light collector 10, a prism 20, a casing 30, a photocatalyst 40, and a water supply unit 50. FIG. 1 also shows incident light L1 entering the light collector 10 of the water splitting apparatus 1 from the outside, a light beam L2 formed by collecting the incident light L1 by the light collector 10, and a light group L3 formed by separating the light beam L2 by the prism 20. The incident light L1 is light containing at least a plurality of wavelengths and may be white light such as sunlight.

[0011] The light collecting device 10 collects incident light L1 from the outside, converts it into a light beam L2 traveling in the same direction, and emits it to the prism 20. The specific configuration of the light collecting device 10 is not particularly limited, and it may be, for example, a collecting lens or a collecting mirror.

[0012] The prism 20 is a component that separates the light beam L2 emitted from the light collecting device 10 into light beams of different wavelengths and outputs the separated beams as light beams traveling in different directions. The prism 20 is an example of a spectroscopic component of the present invention. The light beam L2 incident on the prism 20 contains light beams of multiple wavelengths, and as shown in FIG. 1, the separated beams are emitted along different paths for each wavelength. In particular, when the incident light L1 is continuous light exhibiting a continuous wavelength spectrum, the light emitted from the prism 20 becomes a group of multiple light beams traveling in different directions for each wavelength. While FIG. 1 shows only the paths of the light beam L3a with the longest wavelength, the light beam L3c with the shortest wavelength, and the light beam L3b with an intermediate wavelength among the light beams separated and emitted by the prism 20, if the incident light L1 is continuous light, there will be a continuous series of light beams of different wavelengths between the light beams L3a and L3c. As also shown in Figure 1, in the following explanation, the collection of light emitted from prism 20 having wavelengths in the range of greater than or equal to the wavelength of light ray L3b and less than or equal to the wavelength of light ray L3a is defined as the first light group LG1, and the collection of light having wavelengths in the range of greater than or equal to the wavelength of light ray L3c and less than or equal to the wavelength of light ray L3b is defined as the second light group LG2.

[0013] The casing 30 is a housing for accommodating the photocatalyst 40 and water therein. Water is supplied to the inside of the casing 30 from a water supply unit 50 through a supply pipe 51. The water supply unit 50 is, for example, a pump. FIG. 1 shows the inside of the casing 30 filled with water W. As shown in FIG. 1, the casing 30 has a light-transmitting window 31, and light emitted from the prism 20 passes through the light-transmitting window 31 and is introduced into the inside of the casing 30.

[0014] The material that constitutes the casing 30 is not particularly limited. The light-transmitting window 31 is made of a material that transmits light of a wavelength that activates the photocatalyst 40, such as glass or resin. In this specification, "transmitting light" means that the transmittance when light is incident perpendicularly is 70% or more. The transmittance may be 80% or more, or may be 90% or more.

[0015] The photocatalyst 40 is a photocatalyst for decomposing water to generate hydrogen and oxygen, and includes a hydrogen generating photocatalyst 40a and an oxygen generating photocatalyst 40b. The hydrogen generating photocatalyst 40a is a photocatalyst that is activated by light to generate hydrogen from water. The oxygen generating photocatalyst 40b is a photocatalyst that is activated by light to generate oxygen from water. In this embodiment, the hydrogen generating photocatalyst 40a and the oxygen generating photocatalyst 40b are each sheet-shaped and arranged side by side in parallel inside the casing 30. The hydrogen generating photocatalyst 40a and the oxygen generating photocatalyst 40b are connected via electrodes (not shown), allowing electrons to move between the hydrogen generating photocatalyst 40a and the oxygen generating photocatalyst 40b.

[0016] The hydrogen generating photocatalyst 40a and the oxygen generating photocatalyst 40b can be made of known materials and are not particularly limited. However, a combination of materials that are activated by light in different wavelength bands is preferred. When the hydrogen generating photocatalyst 40a and the oxygen generating photocatalyst 40b are made of materials that are activated by light in different wavelength bands, incident light containing light of multiple wavelengths, such as sunlight, can be efficiently used for the water splitting reaction. It is preferred that at least one of the hydrogen generating photocatalyst 40a and the oxygen generating photocatalyst 40b be activated by visible light, and it is more preferred that both be activated by visible light. An example of a specific combination of catalytic materials is a combination of CuGaS2 as the hydrogen generating photocatalyst 40a and BiVO4 as the oxygen generating photocatalyst 40b. Each of the hydrogen generating photocatalyst 40a and the oxygen generating photocatalyst 40b may be a mixture of two or more catalytic materials or may include an appropriate co-catalyst.

[0017] 1, light emitted from the prism 20 and transmitted through the light-transmitting window 31 of the casing 30 reaches the photocatalyst 40 disposed inside the casing 30. In this embodiment, as shown in FIG. 1, the first light group LG1 is incident on the hydrogen generating photocatalyst 40a, and the second light group LG2 is incident on the oxygen generating photocatalyst 40b. When light is incident on the contact surface between the photocatalyst 40 and the water W in this manner, water decomposition occurs, and hydrogen and oxygen are generated at the contact surface between each photocatalyst and the water W.

[0018] The hydrogen and oxygen generated inside the casing 30 by the decomposition of water are exhausted from the casing 30, for example, through an exhaust pipe (not shown), separated into hydrogen and oxygen through a gas separator (not shown), and stored in a storage tank (not shown). The oxygen may be released into the atmosphere.

[0019] The reaction using two types of photocatalysts, a hydrogen generating photocatalyst and an oxygen generating photocatalyst, as used in this embodiment is a two-step excitation type water splitting reaction. In implementing a two-step excitation type water splitting reaction, for example, a configuration has been proposed in which the hydrogen generating photocatalyst and the oxygen generating photocatalyst are arranged in series with respect to the incident light, and the oxygen generating photocatalyst is activated by light that has passed through the hydrogen generating photocatalyst. However, in this configuration, the hydrogen generating photocatalyst must be made of a material that is capable of transmitting light of a wavelength that activates the oxygen generating photocatalyst, which limits the options for catalyst materials that can be used.

[0020] In the water splitting device according to this embodiment, incident light is split into two light groups using a spectroscopic element, and each light group is incident on a photocatalyst for generating hydrogen and a photocatalyst for generating oxygen, respectively. This configuration eliminates the need to consider the transmittance of light other than the absorption wavelength of each photocatalytic material, broadens the range of catalyst options, and allows for a water splitting device with higher light utilization efficiency. In particular, photocatalytic water splitting devices using sunlight containing light in the visible wavelength range have had the problem of low light utilization efficiency, but the present invention makes it possible to realize a water splitting device with high light utilization efficiency using sunlight.

[0021] [Second embodiment] 2 is a schematic diagram showing a water splitting apparatus 2 according to a second embodiment of the present invention. The water splitting apparatus 2 has the same configuration as the water splitting apparatus 1 according to the first embodiment, except that it has a photocatalyst 240 instead of the photocatalyst 40. Hereinafter, components already described will be assigned the same reference numerals, and redundant description will be omitted.

[0022] Inside the casing 230 of the water decomposition device 2, the surface of the sheet of the hydrogen generating photocatalyst 240a and the surface of the sheet of the oxygen generating photocatalyst 240b are arranged so that they form a V-shape. This configuration allows the angle of incidence of the first light group LG1 incident on the sheet of the hydrogen generating photocatalyst 240a and the angle of incidence of the second light group LG2 incident on the sheet of the oxygen generating photocatalyst 240b to approach 0 degrees. More specifically, the angle of incidence of the first light group LG1 with respect to the sheet of the hydrogen generating photocatalyst may be between 0 degrees and 10 degrees, and the angle of incidence of the second light group LG2 with respect to the sheet of the oxygen generating photocatalyst may be between 0 degrees and 10 degrees. The first light group LG1 and the second light group LG2 may include multiple light beams with different angles of incidence. For example, "the angle of incidence of the first light group LG1 is between 0 degrees and 10 degrees" means that the angle of incidence of the light beam with the largest angle of incidence among the light beams included in the first light group LG1 is between 0 degrees and 10 degrees.

[0023] When the prism 20 is used as the light-splitting element, the first light group LG1 and the second light group LG2 are emitted in different directions. By arranging the sheets of the hydrogen generating photocatalyst 240a and the oxygen generating photocatalyst 240b at different angles according to the traveling directions of the first light group LG1 and the second light group LG2, as in this embodiment, the light utilization efficiency can be further improved.

[0024] [Third embodiment] 3 is a schematic diagram showing a water splitting device 3 according to a third embodiment of the present invention. The water splitting device 3 has the same configuration as the water splitting device 1 according to the first embodiment, except that it has a dichroic mirror 321 and a mirror 322 instead of the prism 20, and therefore a duplicated description will be omitted. Note that for convenience of illustration, the arrangement of the light-collecting device 10 is different from that of the first embodiment, but the configuration of the light-collecting device 10 may be the same as that of the first embodiment. The dichroic mirror 321 and the mirror 322 are examples of the spectroscopic component of the present invention.

[0025] As shown in Fig. 3, the light beam L2 collected and emitted by the light collecting device 10 of the water splitting apparatus 3 is incident on the dichroic mirror 321. The dichroic mirror 321 is oriented at 45 degrees with respect to the light beam L2, and reflects only light of a specific wavelength band in a direction that is 90 degrees different from the incident light, while transmitting light of other wavelength bands. In the example shown in Fig. 3, the light group reflected by the dichroic mirror 321 (first light group LG1) is incident on the hydrogen generating photocatalyst 40a. The light group transmitted through the dichroic mirror 321 (second light group LG2) is reflected by the mirror 322 and is incident on the oxygen generating photocatalyst 40b.

[0026] As in the first and second embodiments, the configuration of this embodiment using the dichroic mirror 321 also makes it possible to separate the incident light L1 into a first light group LG1 and a second light group LG2 consisting of light having different wavelength bands and to make the light incident on each photocatalyst, thereby improving light utilization efficiency. Furthermore, according to this embodiment, as in the second embodiment, the first light group LG1 and the second light group LG2 can be made to be incident on the photocatalysts approximately perpendicularly, thereby further improving light utilization efficiency.

[0027] [Fourth embodiment] Fig. 4 is a schematic diagram showing the configuration of a water splitting device 4 according to a fourth embodiment of the present invention. As shown in Fig. 4, in this embodiment, a prism 431, which is a spectroscopic element, is built into a casing 430. In other words, the light-transmitting window 31 and prism 20 of the water splitting device 1 according to the first embodiment are implemented as the prism 431 of the water splitting device 4 according to the fourth embodiment.

[0028] In this embodiment, the light beam L2 emitted from the light collecting device 10 is directly incident on the casing 430. The light beam L2 incident on the casing 430 is split into a first light group LG1 and a second light group LG2 by a prism 431 built into the casing 430. The photocatalyst 40 is arranged so that the first light group LG1 and the second light group LG2 split by the prism 431 are incident on the hydrogen generating photocatalyst 40a and the oxygen generating photocatalyst 40b, respectively.

[0029] According to this embodiment, the casing 430 has the prism 431, which is a light-splitting member, built in, eliminating the need for a separate light-transmitting window. This allows for a compact configuration, a reduced number of parts, and reduced light loss.

[0030] The present invention has been described above with reference to specific embodiments, but the present invention is not limited to these embodiments, and a person skilled in the art can combine some or all of the embodiments as appropriate.

[0031] It has been explained that the first and second light groups emitted from the spectroscopic element are composed of light having different wavelength bands, but this explanation does not exclude the possibility that light that should belong to one light group may be unintentionally mixed into the other light group due to the spectroscopic performance of the spectroscopic element, stray light, etc.

[0032] In the above embodiment, the wavelength of the light belonging to the first light group LG1 is described as being longer than the wavelength of the light belonging to the second light group LG2. However, the wavelength of the light belonging to the first light group LG1 may be shorter than the wavelength of the light belonging to the second light group LG2. Furthermore, in the above embodiment, an example was described in which the incident light was divided into two wavelength bands based on a certain reference wavelength and defined as the first light group LG1 and the second light group LG2. However, this configuration is not limited to this. For example, the incident light may be divided into three wavelength bands, and the wavelength band with the smallest wavelength and the wavelength band with the largest wavelength may be incident on the hydrogen generating photocatalyst as the first light group, and the intermediate wavelength band may be incident on the oxygen generating photocatalyst. Alternatively, the incident light may be divided into even more wavelength bands. The wavelength bands of the first light group and the second light group may be appropriately designed to match the absorption wavelength of the photocatalytic material used. [Explanation of symbols]

[0033] 1,2,3,4 Water splitting equipment 10. Light Concentrator 20,431 Prisms 30,230,430 casing 31 Light-transmitting window 40,240 Photocatalyst 40a,240a Photocatalyst for hydrogen generation 40b,240b Photocatalyst for oxygen generation 50 Water supply section 51 Supply pipe 321 Dichroic Mirror 322 Mirror L1 incident light L2 luminous flux L3a, L3b, L3c rays LG1 First Light Group LG2 second light group

Claims

1. A water splitting device that generates hydrogen and oxygen from water using light, A photocatalyst for generating hydrogen; a photocatalyst for generating oxygen; a spectroscopic member onto which light containing a plurality of wavelengths is incident, The spectroscopic member disperses incident light, A first light group consisting of light having a wavelength in a first wavelength band is incident on the photocatalyst for generating hydrogen, a water splitting apparatus, wherein a second light group consisting of light having wavelengths in a second wavelength band that is different from the first wavelength band is incident on the oxygen generating photocatalyst;

2. The hydrogen generating photocatalyst and the oxygen generating photocatalyst are each formed in a sheet shape, the incident angle of the first light group with respect to the photocatalyst sheet for hydrogen generation is 0 degrees or more and 10 degrees or less, 2. The water splitting apparatus according to claim 1, wherein the incident angle of the second light group on the oxygen generating photocatalyst sheet is between 0 degrees and 10 degrees.

3. The photocatalyst for hydrogen generation is CuGaS ２ and the oxygen generating photocatalyst is BiVO ４ The water splitting apparatus according to claim 1 or 2, wherein

4. 3. The water splitting apparatus according to claim 1, wherein the incident light is sunlight.

5. a casing that accommodates the hydrogen generating photocatalyst and the oxygen generating photocatalyst; a water supply unit that supplies water to the inside of the casing, 3. The water splitting apparatus according to claim 1, wherein the casing has a light-transmitting window that introduces the light emitted from the spectroscopic element into the interior of the casing.

6. a casing that accommodates the hydrogen generating photocatalyst and the oxygen generating photocatalyst; a water supply unit that supplies water to the inside of the casing, 3. The water splitting apparatus according to claim 1, wherein light is introduced into the casing via the spectroscopic element attached to the casing.

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