Gas generation system

Abstract

To provide a gas generation system capable of efficiently activating a photocatalyst and continuously causing a water decomposition reaction even when sunlight with sufficient energy cannot be applied to the photocatalyst, such as at night or during bad weather.SOLUTION: A gas generation system 1 that decomposes water in contact with a photocatalyst by sunlight S and generates a mixed gas G consisting of oxygen gas and hydrogen gas, comprises: a housing 11 in which an accommodation space 12 for accommodating water and the photocatalyst is formed, the housing having a light-transmitting wall 11a that transmits the sunlight S that has reached at least a part of wall portions forming the accommodation space 12 directly or indirectly; an irradiation device 2 that emits artificial light L having a peak wavelength absorbed by the photocatalyst by supplying electric power, and applies the emitted artificial light L to the light-transmitting wall 11a; and a switch 3 that selectively switches between supply and stop of supply of electric power to the irradiation device 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to gas generating systems. [Background technology]

[0002] For example, as a technology of this type, Patent Document 1 discloses an apparatus that decomposes water to produce hydrogen gas and oxygen gas through a photocatalytic reaction. This apparatus has a light-transmitting wall that transmits sunlight from outside. In this apparatus, the sunlight passes through the light-transmitting wall, activating photocatalytic particles dispersed in water contained inside, causing a reaction that decomposes water into oxygen gas and hydrogen gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3787686 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the technology described in Patent Document 1, there are cases where the photocatalyst cannot be irradiated with sunlight with a sufficient amount of energy, such as at night or in bad weather. In such cases, the efficiency of the water splitting reaction is insufficient, and as a result, it is difficult to efficiently generate hydrogen gas.

[0005] The present invention has been made in consideration of these points, and aims to provide a gas generation system that can efficiently activate a photocatalyst and continuously cause a water decomposition reaction even when it is not possible to irradiate the photocatalyst with sunlight with a sufficient amount of energy, such as at night or during bad weather. [Means for solving the problem]

[0006] In view of the above-mentioned problems, the present invention provides a gas generation system that uses sunlight to decompose water in contact with a photocatalyst to generate a mixed gas consisting of oxygen gas and hydrogen gas. The gas generation system includes: a housing that forms a storage space for storing the water and the photocatalyst, and at least a portion of the wall that forms the storage space has a light-transmitting wall that transmits sunlight that reaches the storage space directly or indirectly; an irradiation device that, when supplied with power, emits artificial light having a peak wavelength that is absorbed by the photocatalyst and irradiates the emitted artificial light onto the light-transmitting wall; and a switch that selectively turns on and off the supply of power to the irradiation device. [Effects of the Invention]

[0007] According to the present invention, even when sunlight with a sufficient amount of energy cannot be irradiated onto the photocatalyst, such as at night or in bad weather, the water decomposition reaction can be continuously caused to occur by selectively switching the switch, and hydrogen gas can be efficiently produced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an entire gas generation system according to an embodiment of the present invention. [Figure 2] 2A and 2B are cross-sectional views of the housing and the irradiation device shown in FIG. 1. [Figure 3] FIG. 2 is a schematic diagram for explaining the principle of the laser device shown in FIG. [Figure 4] (A) is a graph showing the relationship between peak wavelength and quantum efficiency for a photocatalyst, and (B) is a graph showing the relationship between wavelength of artificial light and quantum efficiency for a light-emitting element material. [Figure 5] FIG. 10 is a schematic diagram showing another example of the configuration of the circulation system in the gas generation system according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Embodiment] Hereinafter, an embodiment of the present invention will be described in detail with reference to Figures 1 to 5. Note that the embodiment described below is one aspect of the present invention and does not limit the technical scope of the present invention.

[0010] <Configuration> FIG. 1 is a schematic diagram of the entire gas generation system 1 according to this embodiment. FIGS. 2(A) and 2(B) are cross-sectional views of the housing 11 and the irradiation device 2 shown in FIG. 1. The gas generation system 1 is a system for causing a photocatalyst to contribute to a water decomposition reaction, thereby generating a mixed gas G consisting of oxygen gas and hydrogen gas. Water that has come into contact with the photocatalyst is decomposed by sunlight S under an environment such as sunny daytime weather, generating the mixed gas G. Here, in this embodiment, the water that has come into contact with the photocatalyst is water from a dispersion liquid D in which photocatalyst particles have been dispersed.

[0011] The gas generation system 1 includes a gas generation device 10 having a housing 11 and an irradiation device 2. The gas generation system 1 further includes the irradiation device 2, a switch 3, a pyranometer 4, and a control device 5. The gas generation system 1 also includes a solar cell 71 and a storage battery 72. The gas generation device 10 includes a housing 11, within which a storage space 12 for storing a dispersion liquid D is formed. The housing 11 includes a light-transmitting wall 11a serving as a top plate, a reflecting plate 11b serving as a bottom plate, and a side wall 11c. The side wall 11c rises from the periphery of the reflecting plate 11b. The light-transmitting wall 11a covers the upper opening of the side wall 11c. Thus, the housing 11 defines a storage space 12 surrounded by the light-transmitting wall 11a, the reflecting plate 11b, and the side wall 11c. The light-transmitting wall 11a transmits sunlight S that reaches the housing 11 directly or indirectly toward the storage space 12. In this embodiment, the light-transmitting wall 11a is only the top panel, but for example, the side wall 11c may also function as a light-transmitting wall through which the sunlight S passes. Here, "directly reaching sunlight S" refers to light that is directly irradiated by sunlight S. On the other hand, "indirectly reaching sunlight" refers to light that is obtained by converting sunlight S into laser light having a specific wavelength using a laser device 8, which will be described later with reference to FIG. 3, and then causing the laser light to reach the light-transmitting wall 11a. The reflector 11b reflects the sunlight S that has passed through the light-transmitting wall 11a. This prevents the sunlight S from leaking outside the storage space 12 and makes it easier for the sunlight S to be irradiated onto the photocatalyst in the dispersion liquid D.

[0012] A gas exhaust pipe 14 that exhausts the mixed gas G generated in the storage space 12 is connected to the housing 11. The gas exhaust pipe 14 is connected to the housing 11 so as to penetrate the light-transmitting wall 11a. This allows the gas flow path of the gas exhaust pipe 14 to communicate with the storage space 12, so that the mixed gas G generated in the storage space 12 can be exhausted from the storage space 12 to the outside of the storage space 12 via the gas exhaust pipe 14. The end of the gas exhaust pipe 14 on the side from which the mixed gas G is exhausted may be connected to a separator (not shown) that can separate at least one of oxygen gas and hydrogen gas from the mixed gas G.

[0013] The gas generation system 1 further includes a circulation system 6 that circulates the dispersion D contained in the storage space 12. In this embodiment, the circulation system 6 is a system that resupplies the dispersion D discharged from the discharge port 13b to the storage space 12 from the supply port 13a via the tank 61 and the liquid feed pump 62. This allows the dispersion D to circulate in the storage space 12, thereby preventing the photocatalyst in the dispersion D from accumulating in the storage space 12. In particular, the supply pipe 13A having the supply port 13a is connected to a higher position in the housing 11 than the discharge pipe 13B having the discharge port 13b. This allows the photocatalyst that has settled at the bottom of the storage space 12 to be efficiently circulated through the circulation system 6. Note that if the dispersion D does not contain a photocatalyst and a photocatalytic sheet is retained in the storage space 12, only water may be circulated instead of the dispersion D.

[0014] The storage battery 72 stores the electric energy generated by the solar cell 71, and the electric energy stored in the storage battery 72 is supplied to the irradiation device 2 via the switch 3. In this embodiment, the electric energy is supplied from the storage battery 72 to the irradiation device 2, but for example, a commercial power source or the like may be used instead of the storage battery 72.

[0015] As shown in FIG. 1, the irradiation device 2 has a plurality of (e.g., eight) light-emitting elements 20 that are an irradiation source of artificial light L. The plurality of light-emitting elements 20 are composed of a plurality of electrically connected element groups, and each element group is connected in parallel (see the dashed lines in FIG. 1). The light-emitting elements 20 (20A, 20B: see FIG. 2(A)) that make up each element group are connected in series and emit artificial light L (L1, L2: see FIG. 2(B)) of different wavelengths. By including the irradiation device 2 in the gas generation system 1, the irradiation device 2 can irradiate the photocatalyst in the accommodation space 12 with artificial light L even in an environment where sufficient energy of sunlight S cannot be obtained, such as at night or in bad weather.

[0016] As shown in FIGS. 2(A) and 2(B), each element group of the light-emitting elements 20 is supported on a support 23 via a wiring board 22. The support 23 is installed above the light-transmitting wall 11a so that artificial light L emitted from the light-emitting elements 20 is irradiated toward the light-transmitting wall 11a. A drainage pipe 23a is formed in the support 23 so as to pass through the center along the longitudinal direction thereof. Cooling water W of a cooling system 21, which will be described later, passes through the drainage pipe 23a. Note that, without using the cooling system 21, heat generated from the light-emitting elements 20 may be conducted to the housing 11 by a heat-conducting material such as metal, and the dispersion liquid D may be heated via the housing 11.

[0017] The gas generation system 1 includes a cooling system 21 that cools the light-emitting elements 20 with cooling water W. The cooling system 21 is a system that passes cooling water pressurized by a pump 211 through the irradiation device 2. Heat absorbed by the cooling water W from the light-emitting elements 20 is input to the dispersion liquid D in the circulation system 6 via a heat exchanger 212. In this way, the dispersion liquid D can be heated by the exhaust heat from the light-emitting elements 20 via the cooling water W of the cooling system 21. The photocatalyst in the dispersion liquid D is heated, and the activity of the photocatalyst in the accommodation space 12 can be increased.

[0018] The gas generation system 1 may also include a solar collector 9. The solar collector 9 is a device that converts sunlight S into thermal energy, and the converted thermal energy can be pumped and circulated by a pump 911. Then, a heat exchanger 912 can perform heat exchange between the converted thermal energy and the dispersion D after being pumped from the liquid feed pump 62 of the circulation system 6. As a result, similar to the case of the cooling system 21, the dispersion D can be heated by the heat collected by the heat exchanger 912. The photocatalyst in the dispersion D is heated, and the activity of the photocatalyst in the storage space 12 can be increased. Note that in the embodiment shown in FIG. 1 , the dispersion D after being pumped from the liquid feed pump 62 is heated by the solar collector 9. However, for example, by arranging the solar collector 9 in a V-shape below the housing 11, the dispersion D in the storage space 12 may be heated by the solar collector 9 from outside the housing 11.

[0019] FIG. 3 is a schematic diagram illustrating the principle of the laser device 8 shown in FIG. 1. The laser device 8 includes a dichroic mirror 81, a resin base material 82, a high-reflection mirror 84, and an optical fiber 85. A fluorescent agent 83 is dispersed in the resin base material 82. The dichroic mirror 81 is disposed on the upper surface of the resin base material 82, and the high-reflection mirror 84 is disposed on the lower surface thereof. An optical fiber 85 is wound around the periphery of the resin base material 82. When laser light is generated, sunlight S transmitted through the dichroic mirror 81 is absorbed by any of the fluorescent agents 83, which then emit light. This emitted light is reflected by the dichroic mirror 81 and the high-reflection mirror 84 and is focused into the optical fiber 85. The focused light passes through a cladding (not shown) in the optical fiber 85 and reaches a core (not shown), where the laser medium is excited to generate laser light. This laser light reaches the light-transmitting wall 11a as indirect sunlight.

[0020] The dichroic mirror 81 may be a dielectric multilayer film made of SiO2, TiO2, or the like. The resin base material 82 may be made of a resin such as quartz glass, polycarbonate resin, PMMA, acrylic resin, silicone resin, fluorine-based resin, or urethane resin. The fluorescent agent 83 may be made of any substance that absorbs sunlight S and emits fluorescence, such as a fluorescent dye (rhodamine, lumogen, or the like) or quantum dots (PbI3, PbS, CdTe, Si, or the like). The high-reflection mirror 84 may be made of an Al film or the like. The laser medium dispersed in the core of the optical fiber 85 may be a substance such as neodymium ions or ytterbium ions, and the core may be made of glass (typically, quartz glass) doped with these ions. The cladding outside the core may be made of a glass material with a lower refractive index than the core.

[0021] In this embodiment, the gas generation system 1 is used in the modes shown in FIGS. 2(A) and 2(B) by using the control device 5 to switch the switch 3. Specifically, in the mode shown in FIG. 2(A), by opening the switch 3, the photocatalyst in the dispersion liquid D is activated by sunlight S under an environment such as daytime sunny weather. On the other hand, in the mode shown in FIG. 2(B), by closing the switch 3, the photocatalyst in the dispersion liquid D is activated by artificial light L (L1, L2) emitted from the multiple light-emitting elements 20 (20A, 20B) of the irradiation device 2 under an environment such as nighttime or bad weather.

[0022] The switch 3 selectively switches between supplying and stopping power to the irradiation device 2 by opening and closing an electric circuit between the storage battery 72 and the irradiation device 2. Specifically, the control device 5 controls the opening and closing operation of the switch 3 through the following steps. First, the amount of energy of the sunlight S is measured using a pyranometer 4 installed in an environment where the sunlight S is irradiated. Next, the control device 5 compares the amount of energy of the sunlight S measured by the pyranometer 4 with a preset threshold. When the amount of energy of the sunlight S falls below the threshold, the energy amount is determined to be insufficient, and the control device 5 controls the switch 3 to switch to supplying power to the irradiation device 2. That is, the switch 3 controls the electric circuit to be closed. This allows the irradiation device 2 to efficiently irradiate the photocatalyst with artificial light L even under conditions such as nighttime or bad weather, and the control device 5 can easily switch to irradiation with artificial light L. Note that when the amount of energy of the sunlight S exceeds the threshold, the control device 5 switches the switch 3 to stop the supply of power to the irradiation device 2. Here, the switch 3 may be a relay (not shown) or an element, etc., as long as it has the above-described functions. Furthermore, as a means for switching the switch 3 by the control device 5, in addition to a means for switching based on the amount of energy of sunlight S, a means for switching based on time, etc. may also be applied.

[0023] Thus, by selectively switching the modes shown in FIGS. 2(A) and 2(B) by opening and closing the switch 3, a water decomposition reaction can be continuously caused in any environment. In FIG. 2(A), when the energy amount of the sunlight S measured by the pyrheliometer 4 is larger than a preset threshold value, the control device 5 controls the switch 3 to be in an open state. However, the electric circuit may be manually closed so as to use the irradiation of the sunlight S and the irradiation of the artificial light L in combination.

[0024] Here, referring to FIG. 4(A), the relationship between the peak wavelength and the quantum efficiency of the photocatalyst will be described. As shown in FIG. 4(A), the peak wavelength at which the photocatalyst absorbs light varies depending on the material of the photocatalyst. Also, the quantum efficiency varies for each photocatalyst, and the one with a shorter peak wavelength has a higher quantum efficiency. The quantum efficiency is proportional to the production efficiency of the mixed gas. Therefore, a photocatalyst that absorbs light at a low wavelength such as ultraviolet light has a higher production efficiency of the mixed gas than others.

[0025] Therefore, in the present embodiment, the peak wavelength is roughly classified into the following three wavelength ranges. Specifically, it is classified into the wavelength range of ultraviolet light including deep ultraviolet light (the wavelength range from 10 nm to 380 nm, hereinafter also referred to as the "low wavelength range"), the wavelength range of visible light (the wavelength range from 430 nm to 550 nm, hereinafter also referred to as the "medium wavelength range"), and the wavelength range of infrared light (the wavelength range from 570 nm to 770 nm, hereinafter also referred to as the "high wavelength range"). [[ID=,9]]

[0026] Examples of the material of the photocatalyst whose peak wavelength is included in the low wavelength range include Ga2O3, NaTaO3, TiO2, SrTiO3, Al-SrTiO3, as well as La2Ti2O7, BaTiO3, Na2TiO3, ZrO2, Rb4Nb6O 17 、K2Rb2Nb6O 17 、Pb 1-x K [[ID=,19]] 2x NbO6(0 < x < 1), etc. Examples of the material of the photocatalyst whose peak wavelength is included in the medium wavelength range include GaN-ZnO, Rh-SrTiO3, etc. Examples of the photocatalyst material whose peak wavelength is included in the high wavelength range include Ta3N5, LaMg 1 / 3 Ta 2 / 3O2N, BaTaO2N, Y2Ti2O5S2, as well as α-Fe2O3 and K4Nb6O 17 etc.

[0027] Here, the type of photocatalyst contained in the dispersion liquid D is not limited as long as it absorbs sunlight S and artificial light L. For example, the photocatalyst may be composed only of a material in the long wavelength region shown in FIG. 4(A). However, in this embodiment, the photocatalyst includes a first photocatalyst and a second photocatalyst. Therefore, particles of the first photocatalyst and particles of the second photocatalyst are dispersed in the dispersion liquid D.

[0028] In this embodiment, the first photocatalyst is a catalyst that absorbs light at a peak wavelength within the infrared wavelength range (long wavelength range), and the second photocatalyst is a catalyst that absorbs light in a short wavelength range (specifically, ultraviolet wavelength range) lower than the infrared peak wavelength.

[0029] In this embodiment, the light-emitting element 20 includes a first light-emitting element 20A and a second light-emitting element 20B, each of which has a first photocatalyst and a second photocatalyst that easily absorb light. The first light-emitting element 20A and the second light-emitting element 20B emit first artificial light L1 and second artificial light L2, respectively, as the artificial light L. The first light-emitting element 20A emits light in a long wavelength range that includes the peak wavelength of the first photocatalyst. The second light-emitting element 20B emits light in a short wavelength range that includes the low peak wavelength of the second photocatalyst.

[0030] FIG. 4(B) is a graph showing the relationship between the wavelength of artificial light L and quantum efficiency for the material of the light-emitting element 20. In this embodiment, the first light-emitting element 20A emits first artificial light L1 in the infrared wavelength range. On the other hand, the second light-emitting element 20B emits second artificial light L2 in the ultraviolet wavelength range. As the material of the first light-emitting element 20A, for example, (Al x Ga 1-x ) 0.52 In 0.48 Examples of the material of the second light emitting element 20B include In. x Ga 1-x Examples include N, diamond, GaN, and AlGaN.

[0031] As shown in FIG. 4A, when the first photocatalyst in the dispersion liquid D has a peak wavelength in the infrared wavelength range, its quantum efficiency is lower than that of the second photocatalyst, which has a peak wavelength in the ultraviolet wavelength range. Therefore, when the same light intensity of the first artificial light L1 and the second artificial light L2 is applied to the same amounts of the first and second photocatalysts, the amount of mixed gas generated by the first photocatalyst is less than that generated by the second photocatalyst. Therefore, it is preferable to increase the light intensity of the first artificial light L1 of the first light-emitting element 20A compared to the light intensity of the second artificial light L2 of the second light-emitting element 20B. Specifically, the control device 5 may control the current flowing through the first light-emitting element 20A so that the current flowing through the first light-emitting element 20A is greater than that of the second light-emitting element 20B. This allows the light intensity of the first artificial light L1 to be increased without increasing the number of first light-emitting elements 20A.

[0032] In this embodiment, a first photocatalyst and a second photocatalyst with different light absorption peak wavelengths are accommodated in the accommodation space 12 in a mixed state. As shown in FIG. 2(A), when sunlight S is irradiated, the first photocatalyst, which absorbs light at the peak wavelength, is activated and can cause a water decomposition reaction. On the other hand, when sunlight S is not irradiated sufficiently, as shown in FIG. 2(B), the first photocatalyst is activated by the first artificial light L1 irradiated from the first light-emitting element 20A of the irradiation device 2. Furthermore, the second photocatalyst is activated by the second artificial light L2 irradiated from the second light-emitting element 20B. Each photocatalyst can cause a water decomposition reaction.

[0033] In addition to the first and second photocatalysts, a third catalyst that absorbs light at a peak wavelength in the middle wavelength range may be used as the photocatalyst. In this case, the irradiation device 2 may have a third element that irradiates third artificial light that is absorbed by the third catalyst.

[0034] FIG. 5 is a schematic diagram showing another example of the configuration of the circulation system 6 in the gas generation system 1 according to this embodiment. The gas generation device 10 and the irradiation device 2 are the same as those shown in FIGS. 2(A) and 2(B), and therefore detailed description thereof will be omitted. In FIG. 5, the dispersion D is composed of a first dispersion D1 containing particles of a first photocatalyst and a second dispersion D2 containing a second photocatalyst. The circulation system 6 includes a first tank 61a and a first liquid-transfer pump 62a, and a second tank 61b and a second liquid-transfer pump 62b on the flow paths of the respective dispersions D. The first dispersion D1 is contained in the first tank 61a, and the second dispersion D2 is contained in the second tank 61b.

[0035] Furthermore, the circulation system 6 has a three-way valve 63 that switches between supplying the first dispersion liquid D1 from the first tank 61a to the storage space 12 and supplying the second dispersion liquid D2 from the second tank 61b to the storage space 12. This makes it possible to selectively supply the first photocatalyst particles and the second photocatalyst particles, which have different light absorption peak wavelengths, to the storage space 12. Specifically, when sunlight S is irradiated, the control device 5 switches the three-way valve 63 to supply the first dispersion liquid D1 to the storage space 12, causing a water decomposition reaction by the first photocatalyst. On the other hand, when sunlight S is not irradiated sufficiently, the control device 5 switches the three-way valve 63 to supply the second dispersion liquid D2 to the storage space 12, causing a water decomposition reaction by the second photocatalyst. Here, the three-way valve 63 corresponds to the switching valve in the present invention, but if it is possible to switch between the supply of the first photocatalyst particles and the second photocatalyst particles to the storage space 12, for example, an on-off valve may be provided downstream of each of the first liquid supply pump 62a and the second liquid supply pump 62b, and these on-off valves may be opened and closed individually.

[0036] The circulation system 6 may also include a third tank 61c, a third liquid pump 62c, and on-off valves 65A and 65B for switching the supply of water on and off to circulate only water. This allows the on-off valves 65A and 65B to be open to circulate only water before the three-way valve 63 switches between the supply of the first dispersion liquid D1 and the supply of the second dispersion liquid D2, and allows the water flow to remove any of the dispersion liquid D remaining in the storage space 12 before the switch. Therefore, even if the other dispersion liquid D is supplied to the storage space 12, mixing of the two dispersion liquids D can be prevented. Alternatively, one of the dispersion liquids D recovered in the third tank 61c may be returned to the first tank 61a or the second tank 61b.

[0037] The irradiation device 2 may include at least the second light-emitting element 20B. By selectively circulating the second dispersion liquid D2 and irradiating it with second artificial light L2 from the second light-emitting element 20B, the second photocatalyst in the second dispersion liquid D2 is made to contribute to the water decomposition reaction. This makes it possible to generate a larger amount of mixed gas G than when the first photocatalyst is made to contribute to the water decomposition reaction. Note that, in an environment such as a sunny day, irradiation with sunlight S can make the first photocatalyst in the first dispersion liquid D1 contribute to the water decomposition reaction. For this reason, the first dispersion liquid D1 may be selectively circulated. [Explanation of symbols]

[0038] 1: gas generation system, 10: gas generation device, 11: housing, 11a: light-transmitting wall, 11b: reflector, 11c: side wall, 12: storage space, 2: irradiation device, 20: light-emitting element, 20A: first light-emitting element, 20B: second light-emitting element, 21: cooling system, 211: pump, 3: switch, 4: pyranometer, 5: control device, 61: tank, 61a: first tank, 61b: second tank, 63: three-way valve (switching valve), S: sunlight, G: mixed gas, D: dispersion liquid, D1: first dispersion liquid, D2: second dispersion liquid

Claims

1. A gas generation system that uses sunlight to decompose water that has come into contact with a photocatalyst to generate a mixed gas consisting of oxygen gas and hydrogen gas, a housing in which a storage space for storing the water and the photocatalyst is formed, and at least a part of a wall portion forming the storage space has a translucent wall that transmits the sunlight that has directly or indirectly reached the housing; an irradiation device that emits artificial light having a peak wavelength at which the photocatalyst absorbs light by supplying electric power and irradiates the emitted artificial light onto the light-transmitting wall; a switch for selectively turning on or off the supply of power to the irradiation device.

2. a pyranometer that measures the amount of energy of the sunlight; a control device that controls the switch so as to switch on the supply of power to the irradiation device when the amount of energy becomes equal to or less than a predetermined threshold; 10. The gas generating system of claim 1, further comprising:

3. The storage space contains a dispersion liquid in which particles of the photocatalyst are dispersed in the water, the gas generation system further includes a circulation system that circulates the dispersion liquid contained in the containing space; 2. The gas generation system according to claim 1, wherein the circulation system comprises a tank that recovers the dispersion liquid from the storage space, and a pump that pressure-feeds the dispersion liquid recovered in the tank to the storage space.

4. The photocatalyst includes a first photocatalyst that absorbs light at the peak wavelength and a second photocatalyst that absorbs light at a low peak wavelength that is lower than the peak wavelength, 2. The gas generation system of claim 1, wherein the irradiation device includes a first light-emitting element that emits light within a wavelength range that includes the peak wavelength, and a second light-emitting element that emits light within a low wavelength range that includes the low peak wavelength.

5. The photocatalyst includes a first photocatalyst that absorbs light at the peak wavelength and a second photocatalyst that absorbs light at a low peak wavelength that is lower than the peak wavelength, the dispersion liquid comprises a first dispersion liquid containing particles of the first photocatalyst and a second dispersion liquid containing particles of the second photocatalyst; the tank includes a first tank containing the first dispersion liquid and a second tank containing the second dispersion liquid; the circulation system further includes a switching valve that switches between supplying the first dispersion liquid from the first tank to the storage space and supplying the second dispersion liquid from the second tank to the storage space; The gas generation system according to claim 3 , wherein the irradiation device includes at least a light-emitting element that emits light within a wavelength range that includes the low peak wavelength.

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