Hydrogen gas production apparatus using photocatalyst

Abstract

To provide a hydrogen gas production apparatus using a photocatalyst that maximizes the amount of hydrogen gas generated per unit of irradiated light while making the configuration of the apparatus as compact as possible.SOLUTION: The hydrogen gas production apparatus comprises: a box-shaped container portion having a rectangular cross section that accommodates water in which photocatalyst bodies such as photocatalyst particles that cause a decomposition reaction to decompose water into hydrogen and oxygen when irradiated with light are dispersed or arranged; and a plurality of light-emitting elements arranged along both opposing side surfaces of the box-shaped container portion, wherein the apparatus is configured so that light emitted by the plurality of light-emitting elements from both opposing side surfaces of the box-shaped container portion is applied to the water in the box-shaped container portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen gas production device, and more particularly to a device that produces hydrogen gas by a water decomposition reaction using a photocatalyst. [Background technology]

[0002] Hydrogen gas, which is expected to be used as a clean next-generation fuel that does not produce carbon dioxide when burned, can be produced by a water splitting reaction using light energy with a photocatalyst. Therefore, various technologies for producing hydrogen gas using a photocatalyst have been proposed. For example, Patent Document 1 discloses a method for operating a photocatalytic module that has a co-catalyst-supported water splitting catalyst that splits water using light, and generates hydrogen and / or oxygen by supplying water to the water splitting catalyst. When the activity of the photocatalyst decreases, a liquid of a metal-containing compound, which is a co-catalyst precursor, is present in the module and a photocatalytic co-catalyst is precipitated on the photocatalyst by light irradiation. Patent Document 2 discloses a hydrogen generation device in which the surface of a glass substrate is provided with multiple minute semicircular grooves, the inner surfaces of which are coated with a titanium dioxide film, and the glass substrate is irradiated with light from a light irradiation device while water is flowing through the semicircular grooves, causing a photochemical reaction that separates the water into hydrogen and oxygen, and the hydrogen is recovered through a hydrogen-permeable membrane. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2023-106958 [Patent Document 2] Patent Publication No. 2004-35356 [Patent Document 3] Patent Publication No. 2023-094488 Summary of the Invention [Problem to be solved by the invention]

[0004] When constructing a hydrogen gas production device using a photocatalyst as described above, using a light-emitting element such as an LED as the light source for irradiating the water to be decomposed into hydrogen and oxygen is advantageous in that the device can be installed anywhere (without having to worry about sunlight). Furthermore, since the water decomposition reaction caused by light occurs on the surface of the photocatalyst, by uniformly dispersing a particulate photocatalyst in the water irradiated with light, forming it on a sheet-like member, or applying or covering it on a sheet-like member, more water molecules can come into contact with the irradiated photocatalyst surface, which is expected to induce more water decomposition reactions per unit of irradiated light and produce more hydrogen gas. In this case, it would be even more advantageous to construct the device as compact as possible.

[0005] Thus, a main object of the present invention is to maximize the amount of hydrogen gas produced per irradiated light amount in a hydrogen gas production device using a photocatalyst while making the structure as compact as possible. [Means for solving the problem]

[0006] According to one aspect of the present invention, the above problem is solved by a hydrogen gas production apparatus, a substantially rectangular box-shaped container portion containing water in which a photocatalyst body having a photocatalytic substance dispersed or disposed therein, the photocatalyst substance having a photocatalytic substance that initiates a decomposition reaction that decomposes water into hydrogen and oxygen when irradiated with light; a plurality of light-emitting elements arranged along both opposing side surfaces of the box-shaped container portion and outside the both side surfaces; Including, This is achieved by an apparatus configured so that light emitted from the plurality of light-emitting elements is irradiated onto the water in the box-shaped container from both of the opposing side surfaces of the box-shaped container.

[0007] In the above configuration, the "photocatalyst body having a photocatalytic substance" may be any type of photocatalytic substance that, when irradiated with light, initiates a decomposition reaction that decomposes water molecules into hydrogen and oxygen, as described in the embodiment section below. The "photocatalyst body" may be particles dispersed in water, or a sheet-like member formed of the photocatalytic substance itself, or a sheet-like member on which the photocatalytic substance is fixed and placed at any position in the water, or both. The "box-shaped container" may be a container with a substantially rectangular cross section, the side adjacent to the light-emitting element being made of a material that transmits light emitted by the light-emitting element. The "light-emitting element" may typically be any light-emitting element, such as a light-emitting diode, that uses electric power to emit light of a wavelength that can excite electrons to initiate a decomposition reaction that decomposes water molecules into hydrogen and oxygen in the photocatalyst.

[0008] The device of the present invention is configured such that water containing dispersed or disposed photocatalysts is contained in a box-shaped container, and light-emitting elements arranged on both sides of the container irradiate the water with light that triggers a water splitting reaction. This configuration uses electrically powered light-emitting elements as the light source, which, unlike devices configured to irradiate water with sunlight, allows the device to be installed anywhere. The box-shaped configuration allows for compact storage or placement. Photocatalyst particles are dispersed in the water, or a sheet-like photocatalyst is arranged, and light is irradiated from both opposing sides of the box-shaped container. This allows more water molecules to come into contact with the irradiated photocatalyst, which is expected to result in greater hydrogen gas generation. The light-emitting elements may be uniformly arranged on the side of the box-shaped container in the area where water is present (light-emitting elements need not be arranged on the side of the area where water is not present).

[0009] As described above, the device of the present invention has a box-like shape, allowing multiple box-shaped container sections to be easily stacked and arranged with almost no gaps. Therefore, the device of the present invention is advantageous in that multiple box-shaped container sections can be easily stored or arranged compactly. In this regard, when multiple box-shaped container sections are stacked in a direction perpendicular to the side surfaces on which the multiple light-emitting elements are arranged, the multiple light-emitting elements may be arranged on both sides of a common support member between the opposing side surfaces of adjacent box-shaped container sections so as to emit light toward each side surface. In other words, since the multiple light-emitting elements arranged between adjacent box-shaped container sections are arranged on a common support member, the area occupied by the device can be made smaller and the number of parts can be reduced, which is advantageous. The support member may also be configured to have a function of cooling the multiple light-emitting elements, which allows the cooling structure for the multiple light-emitting elements used for each adjacent box-shaped container section to be shared, which is advantageous in that the area occupied by the device can be made smaller and the number of parts can be reduced.

[0010] In the above-described configuration of the present invention, preferably, the plurality of light-emitting elements may be arranged inside the box-shaped container portion so that the irradiation areas or light paths of the light emitted by the plurality of light-emitting elements from both opposing side surfaces do not overlap with each other. The amount of hydrogen gas generated increases with the intensity of light irradiated onto the photocatalyst in water, but as described in Patent Document 3, it has been found that the amount of hydrogen gas generated per unit amount of incident light (photocatalytic efficiency) decreases with increasing light intensity. In other words, in terms of energy efficiency, lower light intensity is advantageous. Therefore, as described above, preferably, the irradiation areas of the light emitted by the plurality of light-emitting elements may not overlap with each other inside the box-shaped container portion, thereby preventing unnecessary increases in the light intensity of the irradiated light.

[0011] Furthermore, in the above-described configuration of the device of the present invention, the portion of the side surface of the box-shaped container facing the light-emitting element may preferably be spherically recessed toward the inside of the container. Light emitted from the light-emitting element is typically a diffused light beam that travels uniformly in a radial direction centered on the light-emitting element. Therefore, if the portion of the side surface of the box-shaped container facing the light-emitting element is spherically recessed toward the inside of the container, as described above, the angle of incidence of the light beam when it enters the side surface of the box-shaped container can be minimized. This reduces the reflectance of the light beam at the side surface of the box-shaped container (light from light-emitting diodes, which are typically used as light-emitting elements, can usually be considered to be nearly unpolarized). This allows the light from the light-emitting element to be introduced more efficiently into the container, thereby improving the energy efficiency of hydrogen gas production. More preferably, the spherical recess at the side surface of the box-shaped container facing the light-emitting element may be formed along a spherical surface centered on the light-emitting element. This makes the angle of incidence of the light beam from the light-emitting element at the part of the side of the box-shaped container facing the light-emitting element almost 0°, and when the light is unpolarized, it is possible to minimize the reflectance of the light beam, thereby improving energy efficiency. [Effects of the Invention]

[0012] Thus, in the device of the present invention, the container for storing water in which photocatalysts are dispersed or placed is shaped like a roughly rectangular box, and light-emitting elements are arranged on the outside of both sides of the container to irradiate light onto the photocatalysts.This allows light to be irradiated almost evenly onto the photocatalysts in the water, making it possible to maximize the amount of hydrogen gas produced per amount of irradiated light, and also makes it possible to store or place the device compactly in any location.

[0013] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief explanation of the drawings]

[0014] [Figure 1]1(A), 1(B), and 1(C) are a schematic perspective view, a side view, and a top view of one aspect of the hydrogen gas production device according to this embodiment, and FIGS. 1(D) and 1(E) are schematic plan views of a support member that supports a light-emitting element of the hydrogen gas production device according to this embodiment. [Figure 2] 2(A) and 2(B) are a schematic perspective view and a side view of another aspect of the hydrogen gas production device according to this embodiment. [Figure 3] FIG. 3 is a cross-sectional view from above of the vessel, which schematically shows the optical paths from a plurality of light-emitting elements in the hydrogen gas production device according to this embodiment. [Figure 4] Figure 4(A) is a diagram showing the direction of light travel when the portion of the side of the container facing the light-emitting element in a hydrogen gas production device is flat, and Figure 4(B) is a diagram showing the direction of light travel when the portion of the side of the container facing the light-emitting element in a hydrogen gas production device is spherical. [Explanation of symbols]

[0015] 1...hydrogen gas production device, 2...vessel part, 3...light emitting element support member (cooling part), 4...light emitting element substrate, 5...light emitting element (LED), w...water (surface), p...photocatalyst (photocatalytic particle), T...transmitted light, R...reflected light, C...spherical depression, S...spherical surface centered on light emitting element BEST MODE FOR CARRYING OUT THE INVENTION

[0016] Basic configuration of hydrogen gas production equipment 1(A) to 1(C), in one aspect, the hydrogen gas production device 1 of this embodiment has a substantially rectangular box-shaped container 2 that stores water w in which photocatalysts p such as photocatalyst particles are dispersed or disposed, and a plurality of light-emitting elements 5 arranged on a substrate 4 on a support member 3 that is disposed along both opposing side surfaces of the container 2 so as to cover the area where the water w is present. As shown in the figures, the light-emitting elements 5 are disposed so as to emit light toward the inside of the container 2.

[0017] The container 2 may typically be a box-shaped member with dimensions of several tens of centimeters in length and width, and a depth of several centimeters to 20-odd centimeters. The surface on which the light-emitting elements 5 are arranged is made of a material (glass, quartz, resin, etc.) that transmits light from the light-emitting elements 5. Water w is contained within the container 2. A photocatalyst p is disposed or dispersed within the water. The photocatalyst p is made of any photocatalytic substance that, when irradiated with light, excites electrons and generates holes, causing a water splitting reaction, i.e., a reaction in which water molecules react with the electrons and holes to split them into hydrogen molecules and oxygen molecules. Specifically, the photocatalyst p may be particles (photocatalyst particles) made of a photocatalytic substance, a sheet-like member made of a photocatalytic substance, or a sheet-like member coated or coated with a photocatalyst. Specific examples of photocatalytic substances that can be used include Ga2O3, NaTaO3, TiO2, SrTiO3, Al-SrTiO3, Rh-SrTiO3, and Y2Ti2O5S2. The light-emitting element 5 may be any light-emitting element that emits light of a wavelength that induces a water-splitting reaction in the photocatalytic substance, and specifically may be a light source element that emits light by power, such as a light-emitting diode (LED) or a semiconductor laser. The substrate 4 supporting the light-emitting element 5 may be configured to supply power to the light-emitting element 5 in any manner.

[0018] The substrate 4 supporting the light-emitting elements 5 is disposed on a support member 3 as shown in Figs. 1(D) and (E), and preferably, the plurality of light-emitting elements 5 may be disposed on the support member 3 so that light is irradiated almost evenly onto the water in the container 2 from both sides of the container 2. The support member 3 may be configured to have a function of cooling the light-emitting elements 5 in any manner. Specifically, the support member 3 may be formed of a material with high thermal conductivity, or may have a refrigerant circulating inside.

[0019] In operation of the device of this embodiment described above, when light is irradiated from the multiple light-emitting elements 5 onto the entire water w in which the photocatalyst p is dispersed or disposed within the container 2, the water molecules are decomposed into hydrogen gas and oxygen gas and move upward in the container 2, where the generated gas is recovered and sent to a hydrogen separator (not shown), where the hydrogen gas is collected. With this configuration, light is irradiated onto the entire water w in which the photocatalyst p is dispersed or disposed within the container 2, allowing more water-splitting reactions to occur, and since the overall shape of the device is approximately rectangular and light is emitted from the light-emitting elements 5, the device has the advantage of being able to be installed or stored compactly in any location.

[0020] Multiple containers stacked together The container 2 of the device 1 of this embodiment illustrated in Fig. 1 is box-shaped, so that multiple containers 2 can be aligned with almost no wasted space, as shown in Figs. 2(A) and (B). In particular, multiple containers 2 may be stacked in a direction perpendicular to the side surface on which the light-emitting elements 5 are arranged, as shown in the figure. In this case, multiple light-emitting elements 5 are arranged facing opposite directions on the side surface of each container 2 between adjacent containers 2, and the support member 3 supporting the substrates 4 of those light-emitting elements 5 may be a single common member, as can be seen in Fig. 2(B). This is advantageous in that the overall dimensions of the device 1 become compact and the number of parts is reduced.

[0021] Irradiation area of ​​light from the light emitting element inside the container As mentioned in the "Summary of the Invention," it has been found that the amount of hydrogen gas generated by the photocatalytic water decomposition reaction increases with increasing irradiated light intensity, but the amount of hydrogen gas generated per unit irradiated light dose decreases with increasing irradiated light intensity (Patent Document 3). Therefore, the lower the irradiated light intensity, the higher the energy efficiency in generating a unit amount of hydrogen gas. As the irradiated light intensity increases, the rate of increase in the amount of hydrogen gas generated decreases. Therefore, it is preferable that the irradiated light intensity within the container 2 not be unnecessarily high. Therefore, in this embodiment, the arrangement of the light-emitting elements 5 within the container 2 may be adjusted so that the irradiated areas L of each element 5 do not overlap, as shown schematically in FIG. 3. This prevents the formation of areas where the light intensity is higher than the intensity of the light emitted by each element 5, thereby preventing a decrease in energy efficiency (due to overlapping irradiated areas).

[0022] Reduction of reflected light on the side of the container When the light-emitting element 5, which emits light using electricity, is placed outside the side surface of the container 2, the refractive index of the surroundings of the light-emitting element 5 (usually an air layer) differs from the refractive index of the interior of the side surface of the container 2 (usually glass, quartz, or transparent resin). Therefore, when the light emitted from the light-emitting element 5 travels into the side surface of the container 2, part of the light is reflected, and this reflected light does not contribute to the water decomposition reaction, resulting in a corresponding waste of light energy. Therefore, in the device of this embodiment, a configuration may be provided to reduce as much as possible the reflection of the light from the light-emitting element 5 when it travels into the side surface of the container 2, in order to more effectively utilize the light energy from the light-emitting element 5 in the water decomposition reaction.

[0023] Specifically, the light emitted from the light-emitting element 5 is typically unpolarized. In this case, if the side surface of the container 2 is flat, as shown in FIG. 3(A), the farther the position at which the light from the light-emitting element 5 enters the side surface of the container 2 is from the light-emitting element 5, the greater the incident angle θ, and the greater the reflectance (the greater the amount of reflected light R). Therefore, in this embodiment, in order to reduce the incident angle θ at which the light from the light-emitting element 5 enters the side surface of the container 2 as much as possible and thereby reduce the reflectance, the portion of the side surface of the container 2 facing the light-emitting element 5 may be formed into a spherically recessed shape C toward the inside of the container 2, as schematically shown in FIG. 3(B). This reduces the incident angle at which the light from the light-emitting element 5 enters the spherically recessed side surface of the container 2, increasing the amount of transmitted light T and allowing a greater amount of light to be introduced into the container 2. More preferably, the spherical depressions C on the side surface of the container 2 may be formed along a spherical surface S centered on each light-emitting element 5. In this case, the angle of incidence of light from the light-emitting elements 5 on the side surface of the container 2 is substantially 0° in all light propagation directions, and when the light is unpolarized, the transmittance can be maximized, allowing even more light from the light-emitting elements 5 to be introduced into the container 2.

[0024] Thus, in this embodiment, the container portion for storing water in which photocatalysts such as photocatalyst particles are dispersed or arranged is formed into an approximately rectangular box shape, and the light-emitting elements are arranged so that light is irradiated almost evenly onto the water stored in the container portion, making it possible to maximize the amount of hydrogen gas produced per amount of irradiated light, and also making it possible to store or place the device compactly in any location.

[0025] The above description has been made in relation to the embodiments of the present invention, but it will be apparent that many modifications and changes will be readily apparent to those skilled in the art, and the present invention is not limited to the above-described exemplary embodiments, but can be applied to various devices without departing from the concept of the present invention.

Claims

1. A hydrogen gas production apparatus, a substantially rectangular box-shaped container portion containing water in which a photocatalyst body having a photocatalytic substance dispersed or disposed therein, the photocatalyst substance having a photocatalytic substance that initiates a decomposition reaction that decomposes water into hydrogen and oxygen when irradiated with light; a plurality of light-emitting elements arranged along both opposing side surfaces of the box-shaped container portion and outside the both side surfaces; Including, An apparatus configured so that light emitted from the plurality of light-emitting elements is irradiated onto the water in the box-shaped container from both opposing side surfaces of the box-shaped container.

2. 2. The device of claim 1, wherein a plurality of the box-shaped container sections are stacked in a direction perpendicular to the side on which the plurality of light-emitting elements are arranged, and the plurality of light-emitting elements are arranged on both sides of a common support member so as to emit light toward each of the opposing sides of adjacent box-shaped container sections.

3. 2. The device according to claim 1, wherein the support member functions to cool the plurality of light emitting elements.

4. 2. The device according to claim 1, wherein the plurality of light-emitting elements are arranged inside the box-shaped container portion so that the irradiation areas of the light emitted by the plurality of light-emitting elements from both of the opposing side surfaces do not overlap each other.

5. 5. The device according to claim 1, wherein a portion of the side surface of the box-shaped container that faces the light emitting element is recessed in a spherical shape toward the inside of the container.

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