JP2018003041A - Hydrogen-generating photocell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen generating photocell capable of removing bubbles attached to an electrode surface and a wall surface inside a casing without requiring dispensing with external energy.SOLUTION: The hydrogen-generating photocell 100 includes: a casing 1; a separator 2 for dividing the casing 1 into a first space 3 and a second space 4; a semiconductor photo-electrode 5 disposed inside the first space 3, and including a conductive layer 51 and a photo-semiconductor layer 52; a counter electrode 6 disposed inside the second space 4, and electrically connected to the semiconductor photo-electrode 5; an electrolytic solution 7; and a gas-storing part 8 disposed inside the first space 3, and having a gas-storing plane 8a. The casing 1 has a transparent plane 1a facing to the first space 3. The gas-storing part 8 is disposed in a region facing to a photo-semiconductor layer 52 side (referred to as a first surface) of the semiconductor photo-electrode 5. The gas-storing plane 8a directs downward in a vertical direction or diagonally downward, and includes a plane directing to a direction crossing the first surface of the semiconductor photo-electrode 5. A communication part 9 between the first region of a gas-storing plane 8a side and the second region of the opposite side of the first region is provided in the first space 3.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a photohydrogen generation cell.

  Conventionally, as a technique using a semiconductor material that functions as a photocatalyst, a technique for collecting hydrogen by collecting light by irradiating the semiconductor material with light or a technique for collecting electric energy is known (for example, (See Patent Documents 1 and 2).

  Patent Document 1 discloses a hydrogen generation module using a semiconductor photoelectrode for water splitting, wherein a silicon substrate constituting a solar cell is reused. The hydrogen generation module includes a water splitting semiconductor photoelectrode in which a photocatalyst layer is formed on one surface of a silicon substrate and a metal electrode is formed on the other surface, a counter electrode, a holding member that holds the semiconductor photoelectrode, The container is configured by a container having a substantially concave shape so as to accommodate the holding member and capable of introducing a liquid, and a transparent lid plate closing the upper end of the container. In this hydrogen generation module, the semiconductor photoelectrode is sandwiched between the container and the lid plate. Patent Document 1 describes that water or an aqueous electrolyte solution pressurized by a pump is supplied between a semiconductor photoelectrode and a lid plate. In this hydrogen generation module, the water or the electrolyte aqueous solution overflowed between the semiconductor photoelectrode and the cover plate is recovered from the drain provided in the upper part of the hydrogen generation module and reused.

  Patent Document 2 discloses a photoelectrochemical cell characterized in that gas is forced to flow from the lower part to the upper part of the cell. In the space where the semiconductor photoelectrode or counter electrode is arranged, the oxygen or hydrogen gas introduction pipe is provided in the lower part, and the oxygen or hydrogen gas discharge pipe is provided in the upper part. Oxygen or hydrogen gas circulates. As a result, oxygen and hydrogen bubbles adhering to the surface of the semiconductor photoelectrode, the counter electrode surface, and the inner wall of the casing float together with the oxygen gas and hydrogen gas introduced from the gas introduction pipe to the upper part of the space. Thereby, the bubbles adhering to the surface of the semiconductor photoelectrode, the counter electrode surface and the inner wall of the housing are quickly removed, and the water photolysis efficiency is improved.

JP 2006-104571 A JP 2012-238525 A

  The hydrogen generation module disclosed in Patent Document 1 has a configuration in which water or an aqueous electrolyte solution is supplied from the upper part of the module, and the overflowed solution is discharged from the upper part of the module. Therefore, the solution present in the gap between the semiconductor photoelectrode and the cover plate, particularly the solution present in the lower portion of the gap, does not sufficiently flow and stays. Some of the oxygen and hydrogen bubbles generated on the semiconductor photoelectrode surface and the counter electrode surface by light irradiation adhere to both the electrode surface and the lid plate surface, but the solution flow rate in the vicinity of these surfaces is insufficient. As a result, the attached bubbles continue to remain on these surfaces without being swept away by the water flow. If bubbles continue to adhere to the surfaces of both electrodes, contact between the surfaces of both electrodes and water or the aqueous electrolyte solution is hindered, so that the efficiency of photolyzing water is significantly reduced. Further, if bubbles continue to adhere to the lid plate surface, light passing through the lid plate is scattered and the amount of light reaching the semiconductor photoelectrode surface is reduced. This also contributes to a decrease in water photolysis efficiency.

  The photoelectrochemical cell disclosed in Patent Document 2 is a gas that is forcibly introduced in response to the problem of air bubble adhesion on the electrode surface and housing inner wall surface of the hydrogen generation module of Patent Document 1. It presents a solution that removes these bubbles by integrating them with the bubbles attached to the surface and the inner wall surface of the housing. However, the photoelectrochemical cell of Patent Document 2 requires a compressor, a flow rate controller, and the like in order to forcibly introduce gas. The operation of these devices requires energy input from the outside. That is, in the photoelectrochemical cell disclosed in Patent Document 2, energy loss occurs due to the introduction of these devices, and this energy loss causes a decrease in energy conversion efficiency of the entire photoelectrochemical cell. .

  Therefore, the present disclosure is a photohydrogen generation cell that collects hydrogen using a decomposition reaction of water by a photocatalyst, and removes bubbles adhering to the electrode surface and the inner wall surface of the housing without requiring external energy input. Thus, it is an object of the present invention to provide a photohydrogen generation cell capable of suppressing a decrease in the photolysis efficiency of water caused by bubbles adhering to the electrode surface and the inner wall surface of the housing.

This disclosure
A housing,
A separator that divides the internal space of the housing into a first space and a second space;
A semiconductor photoelectrode disposed in the first space and including a conductive layer and a photosemiconductor layer formed on the conductive layer;
A counter electrode disposed in the second space and electrically connected to the semiconductor photoelectrode;
An electrolyte containing water in the first space and the second space;
A gas accumulating portion having a gas accumulating surface, disposed in the first space;
A photohydrogen generation cell comprising: the housing has a light-transmitting surface facing the first space;
In the semiconductor photoelectrode, when the surface on the optical semiconductor layer side with respect to the conductive layer is a first surface and the surface opposite to the optical semiconductor layer side with respect to the conductive layer is a second surface, The gas accumulating part is disposed in a region facing the first surface of the semiconductor photoelectrode,
The gas storage surface includes a surface that is vertically downward or obliquely downward in a state where the photohydrogen generation cell is installed and that faces a direction intersecting the first surface of the semiconductor photoelectrode,
In the first space, communication between the first region on the gas storage surface side with respect to the gas storage portion and the second region on the opposite side of the gas storage surface with respect to the gas storage portion. Part is provided,
A photohydrogen generation cell is provided.

  The photohydrogen generation cell of the present disclosure removes bubbles adhering to the electrode surface and the inner wall surface of the housing without requiring external energy input, so that water caused by the air bubbles adhering to the electrode surface and the inner wall surface of the housing is removed. It is possible to suppress a decrease in the photolysis efficiency.

FIG. 1 is a schematic cross-sectional view illustrating an example of a photohydrogen generation cell according to Embodiment 1 of the present disclosure. FIG. 2 is a perspective view of the photohydrogen generation cell shown in FIG. 1 as viewed from the light transmitting surface side of the housing. FIG. 3 is a schematic diagram for explaining the relationship among the thickness of the first space, the length of the communication portion, and the width of the communication portion in the photohydrogen generation cell according to Embodiment 1 of the present disclosure. FIG. 3 is a schematic diagram for explaining the relationship among the thickness of the first space, the length of the communication portion, and the width of the communication portion in the photohydrogen generation cell according to Embodiment 1 of the present disclosure. FIG. 5 is a perspective view illustrating an example of the photohydrogen generation cell according to Embodiment 2 of the present disclosure as viewed from the light-transmitting surface side of the housing. FIG. 6 is a schematic cross-sectional view illustrating an example of a photohydrogen generation cell according to Embodiment 3 of the present disclosure.

A photohydrogen generation cell according to the first aspect of the present disclosure is provided.
A housing,
A separator that divides the internal space of the housing into a first space and a second space;
A semiconductor photoelectrode disposed in the first space and including a conductive layer and a photosemiconductor layer formed on the conductive layer;
A counter electrode disposed in the second space and electrically connected to the semiconductor photoelectrode;
An electrolyte containing water in the first space and the second space;
A gas accumulating portion having a gas accumulating surface, disposed in the first space;
A photohydrogen generation cell comprising: the housing has a light-transmitting surface facing the first space;
In the semiconductor photoelectrode, when the surface on the optical semiconductor layer side with respect to the conductive layer is a first surface and the surface opposite to the optical semiconductor layer side with respect to the conductive layer is a second surface, The gas accumulating part is disposed in a region facing the first surface of the semiconductor photoelectrode,
The gas storage surface includes a surface that is vertically downward or obliquely downward in a state where the photohydrogen generation cell is installed and that faces a direction intersecting the first surface of the semiconductor photoelectrode,
In the first space, communication between the first region on the gas storage surface side with respect to the gas storage portion and the second region on the opposite side of the gas storage surface with respect to the gas storage portion. Is provided.

  In the conventional photohydrogen generation cell, some of the oxygen bubbles generated by light irradiation adhere to the surface of the semiconductor photoelectrode. The adhering bubbles obstruct the contact between the surface of the semiconductor photoelectrode and the electrolytic solution, thereby reducing the efficiency of the water oxidation reaction that occurs on the electrode surface. In addition, some of the generated bubbles also adhere to the surface inside the housing of the light transmitting surface of the housing. As a result, the irradiation light is scattered by the translucent surface 1a of the housing, and the amount of light reaching the semiconductor photoelectrode is reduced. This also contributes to reducing the efficiency of the water splitting reaction of the photohydrogen generation cell. As described in the “Background Art” section, as a method for improving the efficiency reduction due to the bubble adhesion, a technique for circulating the electrolyte in the photohydrogen generation cell has already been proposed (Patent Document 1). In this technique, when the electrolytic solution has a flow rate in the photohydrogen generation cell, large ones of bubbles adhering to both electrode surfaces and the inner wall of the housing are washed away by the electrolytic solution and removed. However, the microbubbles remain on both electrode surfaces and the inner wall of the housing and are difficult to remove. This is because oxygen, which is a component of bubbles, is hydrophobic. Hydrophobic bubbles have a higher affinity with the surface of the semiconductor photoelectrode electrode and the inner wall of the case than the electrolyte solution, and the area where the bubbles are in contact with the surface of the semiconductor photoelectrode and the inner wall of the case is larger. The larger the value, the greater the bubble adhesion. On the other hand, since bubbles exist in the electrolyte solution having a flow velocity, the bubbles are subjected to buoyancy and force that the electrolyte solution pushes away. At this time, if (adhesion force)> (buoyancy + pushing force), the bubbles continue to stay, and if (adhesion force) <(buoyancy + pushing force), the bubbles are removed. Considering the area where the bubble is in contact with both electrode surfaces and the inner wall of the housing per unit volume of the bubble, the smaller the bubble, the larger the area. That is, since the effect of the adhesive force is greater as the microbubbles, it tends to remain attached. Further, Patent Document 2 described in the “Background Art” column proposes a method for removing attached bubbles by forced and intermittent gas introduction. Since the huge oxygen bubbles introduced into the space in the photohydrogen generation cell that encloses the semiconductor photoelectrode are hydrophobic, the microbubbles attached to the surface of the semiconductor photoelectrode, the counter electrode surface, and the inner wall of the housing while rising according to buoyancy Integrate. The huge bubbles that are integrated are (adhesive force) <(buoyancy) for the above-mentioned reason, so they rise in the space without adhering anywhere, and as a result, the fine bubbles adhering to the surface of the semiconductor photoelectrode and the inner wall of the housing Is completely and efficiently removed. However, gas introduction by external energy input is indispensable for this removal method. In view of the energy conversion efficiency of the entire photohydrogen generation cell, it is desirable that energy for gas introduction is unnecessary.

  In contrast to the conventional photohydrogen generation cell, in the photohydrogen generation cell according to the first aspect of the present disclosure, small bubbles generated on the surface of the optical semiconductor layer in the first region in the first space Accumulated on the gas accumulation surface. The amount of gas accumulated on the gas accumulation surface increases with time. The accumulated gas levitation force in the balance of the three forces of the buoyant force of the accumulated gas, the gravity applied to the electrolyte solution above the communicating portion, and the surface tension of the electrolyte solution in the vicinity of the communicating portion. When the gas becomes dominant, the accumulated gas rises through the communication portion. At this time, the bubble size of the gas that floats through the communicating portion is significantly larger than the bubble size immediately after being generated on the first surface of the semiconductor photoelectrode. Therefore, the first surface of the semiconductor photoelectrode in the second region of the first space that is above the gas storage unit, and the housing in the second region of the first space that is above the gas storage unit The bubbles adhering to the inner wall of the cell are removed by being integrated with the floating gas, and rise to the top of the cell. Thereby, loss factors of water splitting reaction efficiency such as contact inhibition between the first surface of the semiconductor photoelectrode and the electrolytic solution due to bubbles and scattering of light irradiated from the translucent surface of the housing are removed. Thus, the photohydrogen generation cell according to the first aspect of the present disclosure removes bubbles attached to the electrode surface and the inner wall surface of the electrode without requiring external energy input, and It is possible to suppress a decrease in water photolysis efficiency caused by bubbles adhering to the wall surface.

  In the second aspect, for example, the photohydrogen generation cell according to the first aspect includes a plurality of the first regions in the first space along the horizontal direction in a state where the photohydrogen generation cell is installed. It may further include a partition plate that is divided into two spaces, and a part of the periphery of the partition plate may be in contact with the gas accumulation surface.

  According to the photohydrogen generation cell according to the second aspect, bubbles attached to the electrode surface and the inner wall surface of the casing can be removed uniformly over the entire electrode surface and the inner wall of the casing. It is possible to effectively suppress a decrease in water photolysis efficiency caused by bubbles adhering to the body wall surface.

  In the third aspect, for example, the photohydrogen generation cell according to the second aspect includes a plurality of the partition plates, and the spacing between the partition plates adjacent to each other may be within a range of 1 to 20 cm.

  In the photohydrogen generation cell according to the third aspect, the partition plates are provided so that the surface spacing of the partition plates adjacent to each other is in the above range. Bubbles can be released from any part of the part with a frequency sufficient for removing bubbles. As a result, air bubbles adhering to the electrode surface and the inner wall surface of the housing can be removed uniformly over the entire electrode surface and inner wall of the housing, so that water caused by air bubbles adhering to the electrode surface and the inner wall surface of the housing can be removed. The degradation of the photodecomposition efficiency can be effectively suppressed.

  In the fourth aspect, for example, in the photohydrogen generation cell according to the second or third aspect, the partition plate has a main surface of the partition plate substantially perpendicular to the light-transmitting surface of the housing. It may be provided in the direction. Here, “substantially perpendicular” in this specification means an angle of 60 ° to 90 °, and “substantially parallel” means an angle of 0 ° to 30 °.

  In the photohydrogen generation cell according to the fourth aspect, since the partition plate is arranged as described above, the bubbles attached to the electrode surface and the inner wall surface of the casing are removed over the entire electrode surface and the inner wall of the casing. The first area can be divided into appropriate spaces so that the process can be performed uniformly.

  In the fifth aspect, for example, in the photohydrogen generation cell according to any one of the second to fourth aspects, the partition plate has a main surface of the partition plate, and the photohydrogen generation cell is installed. It may be provided in a direction substantially parallel to the vertical direction.

  In the photohydrogen generation cell according to the fifth aspect, since the partition plate is arranged as described above, it is possible to remove bubbles adhering to the electrode surface and the inner wall surface of the casing over the entire electrode surface and inner wall of the casing. The first area can be divided into appropriate spaces so that the process can be performed uniformly.

  In the sixth aspect, for example, in the photohydrogen generation cell according to any one of the first to fifth aspects, the casing has a thin rectangular shape, and the photohydrogen generation cell is installed. In this state, the length of the vertical side of the casing in the height direction may be longer than the length of the horizontal side in the width direction.

  The photohydrogen generation cell according to the sixth aspect is configured to be vertically long with the photohydrogen generation cell installed. Thereby, the path | route of the bubble discharged | emitted via a communicating part from a gas storage part and rising a 2nd area | region becomes long. As a result, the effect of removing the bubbles adhering to the electrode surface and the inner wall of the housing by the bubbles rising in the second region is enhanced.

  In the seventh aspect, for example, in the photohydrogen generation cell according to any one of the first to sixth aspects, the semiconductor photoelectrode is configured such that the first surface faces the light-transmitting surface of the housing. It may be arranged in the direction.

  In the photohydrogen generation cell according to the seventh aspect, since buoyancy is applied to the bubbles generated on the first surface of the semiconductor photoelectrode in the direction in which the bubbles are detached from the first surface, the bubbles are formed on the first surface. By adhering, the probability that the contact between the first surface and the electrolytic solution is inhibited can be reduced.

  In an eighth aspect, for example, in the photohydrogen generation cell according to the seventh aspect, the communication part includes a gap between the gas storage part and the first surface of the semiconductor photoelectrode, the gas storage part, It may be at least one selected from a gap between the casing and the translucent surface and a through-hole provided in the gas storage unit.

  In the photohydrogen generation cell according to the eighth aspect, since the communicating portion is formed as described above, it is possible to effectively remove bubbles adhering to the electrode surface and the housing inner wall surface.

  In a ninth aspect, for example, in the photohydrogen generation cell according to the eighth aspect, the communication part may be a gap between the gas storage part and the first surface of the semiconductor photoelectrode.

  In the photohydrogen generation cell according to the ninth aspect, since the communicating portion is formed as described above, it is possible to effectively remove bubbles adhering to the electrode surface and the housing inner wall surface.

  In a tenth aspect, for example, in the photohydrogen generation cell according to any one of the first to sixth aspects, the conductive layer has a light-transmitting property, and the semiconductor photoelectrode has the second surface. May be arranged in a direction facing the translucent surface of the housing.

  In the photohydrogen generation cell according to the tenth aspect, the irradiation light reaches the photo-semiconductor layer of the semiconductor photoelectrode before reaching the bubbles generated on the first surface of the semiconductor photoelectrode. Can be reduced.

  In an eleventh aspect, for example, in the photohydrogen generation cell according to the tenth aspect, the communication part includes a gap between the gas storage part and the separator, and the gas storage part and the semiconductor photoelectrode It may be at least one selected from a gap between the surface and a through hole provided in the gas accumulating portion.

  In the photohydrogen generation cell according to the eleventh aspect, since the communicating portion is formed as described above, it is possible to effectively remove bubbles attached to the electrode surface, the inner wall surface of the housing, and the separator. .

  In a twelfth aspect, for example, in the photohydrogen generation cell according to the eleventh aspect, the communication part may be a gap between the gas storage part and the separator.

  In the photohydrogen generation cell according to the twelfth aspect, since the communicating portion is formed as described above, it is possible to effectively remove bubbles attached to the electrode surface, the inner wall surface of the housing, and the separator. .

In the thirteenth aspect, for example, in the photohydrogen generation cell according to any one of the first to twelfth aspects, in the horizontal plane in a state where the photohydrogen generation cell is installed, the translucent surface 1a The shortest distance between the separator and the separator is the thickness A of the first space, the maximum length of the communicating portion in a direction parallel to the direction of the thickness A is the length B of the communicating portion, and the thickness When the maximum width of the communication part in the direction perpendicular to the direction A is the width W of the communication part, the thickness A of the first space, the length B of the communication part, and the width W of the communication part However, the relationship of 0.17 × A ² /W≦B≦A−0.17×A ² / W may be satisfied.

  In the photohydrogen generation cell according to the thirteenth aspect, the first space and the communication portion are provided so as to satisfy the above relationship, thereby removing bubbles attached to the electrode surface, the inner wall surface of the housing, and the separator. Can be carried out effectively.

  In a fourteenth aspect, for example, in the photohydrogen generation cell according to any one of the first to thirteenth aspects, the gas accumulation unit is configured to have the first hydrogen gas in a state where the photohydrogen generation cell is installed. You may arrange | position in the area | region below the center of the perpendicular direction of space.

  According to the photohydrogen generation cell according to the fourteenth aspect, since the gas storage unit is arranged as described above, the bubbles released from the gas storage unit through the communication unit and rising in the second region The route becomes longer. As a result, the effect of removing the bubbles adhering to the electrode surface and the inner wall of the housing by the bubbles rising in the second region is enhanced.

  Hereinafter, embodiments of the photohydrogen generation cell of the present disclosure will be described in detail with reference to the drawings. The following embodiment is an example, and the present disclosure is not limited to the following embodiment. Moreover, in the following embodiment, the same code | symbol may be attached | subjected to the same member and the overlapping description may be abbreviate | omitted.

(Embodiment 1)
The photohydrogen generation cell of Embodiment 1 is demonstrated using FIG.1 and FIG.2. FIG. 1 is a schematic cross-sectional view showing a configuration example of the photohydrogen generation cell of the present embodiment. FIG. 2 is a perspective view of the photohydrogen generation cell shown in FIG. 1 as viewed from the light-transmitting surface side of the housing, that is, the configuration of the first space side of the photohydrogen generation cell.

  A photohydrogen generation cell 100 shown in FIGS. 1 and 2 includes a housing 1, a separator 2 that divides an internal space of the housing 1 into a first space 3 and a second space 4, and a first space 3. The semiconductor photoelectrode 5 disposed, the counter electrode 6 disposed in the second space, the electrolytic solution 7 containing water in the first space 3 and the second space 4, and the first space 3 The gas storage part 8 arrange | positioned in this. The semiconductor photoelectrode 5 and the counter electrode 6 are electrically connected to each other by an electrical connection portion 10. The photohydrogen generation cell 100 further includes a gas outlet 11 that penetrates the housing 1 and communicates with the inside of the first space 3, and penetrates the housing 1 and enters the inside of the second space 4. A gas outlet 12 communicating therewith is provided.

  Next, each configuration of the photohydrogen generation cell 100 will be specifically described.

  The housing 1 has a translucent surface 1 a that faces the first space 3. This translucent surface 1a becomes a surface (light irradiation surface) on which light of the housing 1 is irradiated. The translucent surface 1a is desirably formed of a material that has corrosion resistance and insulation with respect to the electrolytic solution 7 and transmits light in the visible light region. More preferably, the translucent surface 1a is formed of a material that transmits light including the peripheral wavelength of the visible light region in addition to the wavelength of the visible light region. Examples of the material include glass and resin. The part other than the translucent surface 1a of the housing 1 only needs to have corrosion resistance and insulation against the electrolytic solution 7, and need not have the property of transmitting light. As the material of the portion other than the light transmitting surface 1a of the housing 1, in addition to the glass and the resin described above, a metal whose surface is corrosion-resistant and insulated can be used.

  As described above, the separator 2 divides the inside of the housing 1 into the first space 3 that accommodates the semiconductor photoelectrode 5 and the second space 4 that accommodates the counter electrode 6. For example, as shown in FIG. 1, the separator 2 is preferably disposed so as to be substantially parallel to the light-transmitting surface 1 a that is the light irradiation surface of the housing 1. The separator 2 plays a role of allowing exchange of ions between the electrolytic solution 7 in the first space 3 and the electrolytic solution 7 in the second space 4. Therefore, at least a part of the separator 2 is in contact with the electrolytic solution 7 in the first space 3 and the second space 4. The separator 2 is formed of a material having a function of allowing the electrolyte in the electrolytic solution 7 to permeate and suppressing the permeation of oxygen gas and hydrogen gas in the electrolytic solution 7. Examples of the material of the separator 2 include a solid electrolyte such as a polymer solid electrolyte. Examples of the polymer solid electrolyte include ion exchange membranes such as Nafion (registered trademark). Since the separator 2 separates the oxygen generation side space and the hydrogen generation side space inside the housing, the generated oxygen and hydrogen can be separated and recovered.

  The semiconductor photoelectrode 5 includes a conductive layer 51 and an optical semiconductor layer 52 formed on the conductive layer 51. For example, as shown in FIG. 1, the semiconductor photoelectrode 5 is preferably provided in a direction in which the main surface of the conductive layer 51 is substantially parallel to the light transmitting surface 1 a that is the light irradiation surface of the housing 1. Here, in the semiconductor photoelectrode 5, the surface on the optical semiconductor layer 52 side with respect to the conductive layer 51 is defined as a first surface, and the surface opposite to the optical semiconductor layer 52 side with respect to the conductive layer 51 is defined as a second surface. To do. In the example shown in FIGS. 1 and 2, the semiconductor photoelectrode 5 includes a conductive layer 51 and an optical semiconductor layer 52. Therefore, in the example shown in FIGS. 1 and 2, the surface of the optical semiconductor layer 52 opposite to the surface in contact with the conductive layer 51 is the first surface of the semiconductor photoelectrode 5, and is in contact with the optical semiconductor layer 52 of the conductive layer 51. The surface opposite to the surface on which the light is applied becomes the second surface of the semiconductor photoelectrode 5. In the photohydrogen generation cell 100 of the present embodiment, the first surface of the semiconductor photoelectrode 5 is arranged in a direction facing the translucent surface 1 a of the housing 1.

  For the conductive layer 51, for example, a conductive substrate or a substrate on which a conductive material is formed can be used. Examples of the conductive layer 51 include a metal plate, a glass plate with indium tin oxide (ITO) formed on the surface, and a glass plate with fluorine-doped tin oxide (FTO) formed on the surface.

The optical semiconductor layer 52 is formed of an n-type semiconductor or a p-type semiconductor. If the optical semiconductor layer 52 is formed of an n-type semiconductor, oxygen is generated from the semiconductor photoelectrode 5 and hydrogen is generated from the counter electrode 6. Conversely, if the optical semiconductor layer 52 is formed of a p-type semiconductor, hydrogen is generated from the semiconductor photoelectrode 5 and oxygen is generated from the counter electrode 6. The optical semiconductor layer 52 needs to decompose water by excitation of electrons by light irradiation. Therefore, the band edge level of the conduction band is 0 V or less, which is the standard reduction potential of hydrogen ions, and the band edge level of the valence band is formed by a semiconductor having a standard oxidation potential of water of +1.23 V or more. It is preferable that Such semiconductors include titanium, zirconium, vanadium, tantalum, niobium, tungsten, iron, copper, zinc, cadmium, gallium, indium and germanium oxides, oxynitrides and nitrides, complex oxides thereof, acids Nitride and nitride, and those obtained by adding alkali metal ions or alkaline earth metal ions to these nitrides are effectively used. In addition, a film made of a material having a band edge level in the conduction band of hydrogen ions with a standard reduction potential of 0 V or less and a film made of a material having a band edge level of the valence band of water having a standard oxidation potential of +1.23 V or more The laminated films bonded to each other are also effectively used as the optical semiconductor layer 52. As an example, for example, a WO ₃ / ITO / Si laminated film is effectively used.

  The counter electrode 6 is made of a conductive material that is active in the hydrogen generation reaction when the optical semiconductor layer 52 is an n-type semiconductor and active in the oxygen generation reaction when the optical semiconductor layer 52 is a p-type semiconductor. Examples of the material for the counter electrode 6 include carbon and noble metals generally used as an electrode for water electrolysis. Specifically, carbon, platinum, platinum-supporting carbon, palladium, iridium, ruthenium, nickel, and the like can be used. The shape of the counter electrode 6 is not particularly limited, and is not particularly limited as long as the installation position is also in the second space 4. The counter electrode 6 and the inner wall of the second space 4 may be in contact with each other or may be separated from each other.

  For the electrical connection portion 10, for example, a general metal conductor can be used.

  The electrolytic solution 7 accommodated in the first space 3 and the second space 4 may be an electrolytic solution containing water, and may be acidic, neutral, or basic. . For example, electrolytes such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, sodium dihydrogen phosphate, potassium chloride, sodium chloride, potassium sulfate, sodium sulfate, sodium hydrogen carbonate, disodium hydrogen phosphate and sodium hydroxide may be used alone or Aqueous solutions dissolved by mixing are used effectively.

  Next, the gas accumulation unit 8 will be described. The gas accumulation unit 8 is disposed in a region facing the first surface of the semiconductor photoelectrode 5 in the first space 3. In addition, the gas storage unit 8 is preferably disposed in a region below the center in the vertical direction of the first space 3 in a state where the photohydrogen generation cell 100 is installed. The gas accumulation part 8 has a gas accumulation surface 8a. The gas storage surface 8 a includes a surface that is vertically downward or obliquely downward in a state where the photohydrogen generation cell 100 is installed and that faces in a direction intersecting with the first surface of the semiconductor photoelectrode 5. In addition, “the gas storage surface 8 a includes a surface facing the direction intersecting the first surface of the semiconductor photoelectrode 5” means that the gas storage surface 8 a is only a surface parallel to the first surface of the semiconductor photoelectrode 5. In other words, part or all of the gas accumulation surface 8 a is not parallel to the first surface of the semiconductor electrode 5. Note that the gas accumulating unit 8 does not completely separate the inside of the first space 3. That is, in the first space 3, the first region 3 a on the gas accumulation surface 8 a side with respect to the gas accumulation unit 8, and the second region 3 b on the opposite side of the gas accumulation surface 8 a with respect to the gas accumulation unit 8. The communication part 9 is provided.

  According to the gas accumulation part 8 provided as described above, at least a part of the oxygen (or hydrogen) gas generated in the first region 3a of the first space 3 rises due to buoyancy and the gas accumulation surface 8a. Accumulated at. When the accumulated amount exceeds a certain level, the accumulated oxygen (or hydrogen) gas overflows from the gas accumulation surface 8a. The overflowing gas passes through the communication part 9 and is released to the second region 3b above the gas accumulation part 8 in the first space 3. The small-sized oxygen (or hydrogen) bubbles generated on the first surface of the semiconductor photoelectrode 5 rise by buoyancy and are temporarily stored in the gas storage surface 8a, so that the size of the bubbles is integrated with other bubbles. Increase. The bubbles whose size has increased are discharged from the gas storage unit 8 through the communication unit 9, whereby the first surface of the semiconductor photoelectrode 5 and the inner wall of the housing located above the gas storage unit 8 (second region 3a). The small bubbles attached to the surface float together with the large bubbles released from the gas accumulation unit 8 through the communication unit 9. As described above, the photohydrogen generation cell 100 according to the present embodiment is provided with the gas accumulation unit 8, thereby removing the bubbles attached to the first surface of the semiconductor photoelectrode 5 and the inner wall of the housing with the external energy. It becomes possible to realize voluntarily without throwing in. As a result, bubbles adhering to the first surface where the gas generation reaction occurs in the semiconductor photoelectrode 5 and the inner wall of the housing are quickly removed, and the photolysis efficiency of water in the photohydrogen generation cell is improved.

  In the photohydrogen generation cell 100, the first surface of the semiconductor photoelectrode 5 is disposed so as to face the translucent surface 1 a of the housing 1. Therefore, the communication part 9 includes a gap between the gas storage part 8 and the first surface of the semiconductor photoelectrode 5, a gap between the gas storage part 8 and the light transmitting surface 1a of the housing 1, and a gas storage part. 8 may be at least one selected from the through holes provided in FIG. In the example shown in FIGS. 1 and 2, the gap between the gas accumulation part 8 and the first surface of the semiconductor photoelectrode 5 forms a communication part 9.

Since the communication part 9 should just be the structure which connects the 1st area | region 3a of the 1st space 3, and the 2nd area | region 3b, the shape and magnitude | size are not specifically limited. However, in order for the gas accumulated on the gas accumulation surface 8a to be intermittently released to the second region 3b, the size of the communicating portion 9 is preferably 1 mm to 50 mm, for example. However, the specific optimum value of the size of the communication portion 9 varies depending on the size (thickness) of the first space 3 of the housing 1 and the like. For example, in the communication part 9, the three factors of the floating force of the gas accumulated in the gas accumulation part 8, the gravity applied to the electrolyte 7 above the communication part 9, and the surface tension of the electrolyte 7 near the communication part 9 are substantially balanced. By adjusting the size of the communication part 9 as described above, intermittent release of gas from the communication part 9 is realized. For example, in the horizontal plane in a state where the photohydrogen generation cell 100 is installed, the shortest distance between the translucent surface 1a and the separator 2 is the thickness A of the first space 3, and the direction parallel to the direction of the thickness A In the case where the maximum length of the communication portion 9 in FIG. 1 is the length B of the communication portion 9 and the maximum width of the communication portion 9 in the direction perpendicular to the direction of the thickness A is the width W of the communication portion 9, the first space 3 The thickness A, the length B of the communication portion 9 and the width W of the communication portion 9 satisfy the relationship of 0.17 × A ² /W≦B≦A−0.17×A ² / W. It is desirable.

  The desirable relationship among the thickness A of the first space 3, the length B of the communication portion 9, and the width W of the communication portion 9 will be described in more detail with reference to FIGS. 3 and 4 are schematic diagrams for explaining the relationship among the thickness A of the first space 3, the length B of the communication portion 9, and the width W of the communication portion 9. Although not shown in FIGS. 3 and 4, the width W of the communication portion 9 extends in a direction perpendicular to the paper surface in FIGS. 3 and 4, that is, the width of the communication portion 9 shown in FIGS. Corresponds to depth.

As shown in FIG. 3, when the length B of the communication part 9 is small, normally only the bubbles located directly below the communication part 9 pass through the communication part 9 and rise. Therefore, when the length B of the communication portion 9 is too small, the bubble volume passing through the communication portion 9 is small, so that the rising bubbles are difficult to contact both the inner wall of the housing 1 and the surface of the semiconductor photoelectrode 5. There is a case. If it is assumed that bubbles having a depth three times (= 3A) the thickness A of the first space 3 are stored immediately below the gas storage unit 8 and the communication unit 9, the rising bubbles are stored in the housing. In order to facilitate contact with both the inner wall of the body 1 and the surface of the semiconductor photoelectrode 5, 3A × B × W (cuboid bubble volume below the communicating portion) ≧ (π / 6) A ³ (upper communicating portion) It is desirable to satisfy the relational expression (spherical bubble volume). When this relational expression is arranged, 0.17 × A ² / W ≦ B.

On the other hand, even when the length B of the communication portion 9 is large, bubbles having a depth three times (= 3A) the thickness A of the first space 3 are accumulated immediately below the gas storage portion 8 and the communication portion 9. Based on the assumption that this is done, the relationship among the thickness A of the first space 3, the length B of the communication portion 9, and the width W of the communication portion 9 will be described. As shown in FIG. 4, when the length B of the communication portion 9 is too large, the amount of bubbles that can be accumulated immediately below the gas accumulation portion 8 is small, and when this bubble rises, it rises because the bubble volume is small. In some cases, the bubbles are less likely to contact both the inner wall of the housing 1 and the surface of the semiconductor photoelectrode 5. In order for the rising bubbles to easily come into contact with both the inner wall of the housing 1 and the surface of the semiconductor photoelectrode 5, 3A × (A−B) × W (cuboid bubble volume below the gas storage portion) ≧ (π / 6) It is desirable to satisfy the relational expression of A ³ (spherical bubble volume above the communicating portion). When this relational expression is arranged, B ≦ A−0.17 × A ² / W.

  The method for installing the gas storage unit 8 inside the housing 1 is not particularly limited. The gas accumulating unit 8 may be directly fixed to the casing 1 or may be fixed to the casing 1 through some jig.

  The photohydrogen generation cell 100 is a case where the casing 1 is viewed in plan view from the translucent surface 1a in the installed state, and the direction parallel to the horizontal direction is defined as the horizontal direction, and the direction perpendicular to the horizontal direction is defined as the vertical direction. When the direction is set, it is desirable that the longitudinal length of the housing 1 (see FIG. 2) is longer than the lateral length of the housing 1 (see FIG. 2). That is, when the housing 1 has a thin rectangular shape like the photohydrogen generation cell 100 of the present embodiment, the height of the housing 1 in the height direction in the state where the photohydrogen generation cell 100 is installed. It is desirable that the length of the side is longer than the length of the horizontal side in the width direction. Thus, by being configured to be vertically long in the state in which the photohydrogen generation cell 100 is installed, bubbles released from the gas accumulation unit 8 through the communication unit 9 and rising in the second region 3b The route becomes longer. As a result, the effect of removing bubbles adhering to the first surface of the semiconductor photoelectrode 5 and the inner wall of the housing due to rising bubbles is enhanced.

  Next, the operation of the photohydrogen generation cell 100 will be described in the case where the optical semiconductor layer 52 is an n-type semiconductor.

  In the photohydrogen generation cell 100, light that has passed through the translucent surface 1 a of the housing 1 and the electrolytic solution 7 in the first space 3 enters the optical semiconductor layer 52 of the semiconductor photoelectrode 5. The optical semiconductor layer 52 absorbs light and photoexcitation of electrons occurs. In the optical semiconductor layer 52, electrons are generated in the conduction band and holes are generated in the valence band. The holes move to the first surface of the semiconductor photoelectrode 5, that is, the surface of the optical semiconductor layer 52 (the interface with the electrolytic solution 7) here, and oxidize water molecules on the first surface of the semiconductor photoelectrode 5. As a result, oxygen is generated (the following reaction formula (1)). On the other hand, electrons generated in the conduction band move to the conductive layer 51 side. The electrons that have moved to the conductive layer 51 move to the counter electrode 6 side through the electrical connection portion 10. Electrons that move inside the counter electrode 6 and reach the surface of the counter electrode 6 (interface with the electrolytic solution 7) reduce protons on the surface of the counter electrode 6, and as a result, hydrogen is generated.

4h ⁺ + 2H ₂ O → O ₂ ↑ + 4H ⁺ (1)
_{^{4e - + 4H + → 2H 2}} ↑ (2)

  Oxygen gas generated in the first space 3 is collected through a gas outlet 11 communicating with the inside of the first space 3. Hydrogen gas generated in the second space 4 is collected through a gas outlet 12 communicating with the inside of the second space 4.

  In the photohydrogen generation cell 100, small oxygen bubbles generated on the surface of the optical semiconductor layer 52 in the first region 3 a in the first space 3 are accumulated on the gas accumulation surface 8 a of the gas accumulation unit 8. The amount of oxygen gas accumulated on the gas accumulation surface 8a increases with time. Then, in the balance of the three forces of the floating force of the oxygen gas accumulated in the communication part 9, the gravity applied to the electrolyte solution 7 above the communication part 9, and the surface tension of the electrolyte solution 7 in the vicinity of the communication part 9, When the gas levitation force becomes dominant, the oxygen gas accumulated through the communication portion 9 rises. At this time, the bubble size of the oxygen gas that floats through the communication portion 9 is significantly larger than the bubble size immediately after being generated on the first surface of the semiconductor photoelectrode 5. Therefore, the first surface of the semiconductor photoelectrode 5 in the second region 3 b of the first space 3 that is above the gas storage unit 8 and the first surface 3 of the first space 3 that is above the gas storage unit 8. The oxygen bubbles adhering to the inner wall of the housing 1 in the two regions 3b are removed by being integrated with the floated oxygen gas, and float to the top of the cell. Thereby, loss factors of water splitting reaction efficiency such as contact inhibition between the first surface of the semiconductor photoelectrode 5 and the electrolyte solution 7 caused by bubbles and scattering of light irradiated from the translucent surface 1a of the housing 1 Is removed. Thereby, the efficiency of the photodecomposition reaction of water in the photohydrogen generation cell 100 is improved as compared with that of the conventional photohydrogen generation cell that does not include the gas accumulation unit 8.

  In the photohydrogen generation cell 100 of the present embodiment, when the optical semiconductor layer 52 is formed of a p-type semiconductor, oxygen and hydrogen are used in the description of the operation in the case where the optical semiconductor layer 52 is formed of the n-type semiconductor. The operation of the photohydrogen generation cell 100 can be explained by exchanging.

(Embodiment 2)
A photohydrogen generation cell according to Embodiment 2 of the present disclosure will be described with reference to FIG. FIG. 5 is a perspective view of an example of the photohydrogen generation cell according to Embodiment 2 as viewed from the light-transmitting surface side of the housing.

  The photohydrogen generation cell 200 shown in FIG. 5 has the same configuration as the photohydrogen generation cell 100 of Embodiment 1 except that the partition plate 11 is added. Therefore, only the partition plate 13 will be described here.

  The partition plate 13 divides the first region 3a in the first space 3 into a plurality of spaces (divided spaces) along the horizontal direction in a state where the photohydrogen generation cell 200 is installed. A part of the periphery of the partition plate 13 is in contact with the gas accumulation surface 8a. In the example shown in FIG. 5, since the outer shape of the partition plate 13 is rectangular, one side of the partition plate 13 is in contact with the gas accumulation surface 8a. By providing the partition plate 13 having such a configuration, the gas accumulation unit 8 spatially partitions the region where the gas is accumulated. As described in the first embodiment, the gas accumulated in the gas accumulating unit 8 floats through the communication unit 9 because the accumulated gas levitation force, gravity applied to the electrolyte 7 above the communication unit 9, In addition, in the balance of the three forces of the surface tension of the electrolyte solution 7 in the vicinity of the communication part 9, the gas levitation force becomes dominant. In the photohydrogen generation cell 200 of the present embodiment, such a gas levitation phenomenon occurs in each divided space. Therefore, by providing the partition plates 13 at appropriate intervals, the location where the gas rises in the communication portion 9 is not limited to a part, and the bubbles are sufficiently frequently removed from each communication portion 9 in the divided space. Can be released. As a result, air bubbles attached to the electrode surface and the inner wall surface of the housing can be removed uniformly over the entire electrode surface and the inner wall surface of the housing, and water caused by the air bubbles attached to the electrode surface and the inner wall surface of the housing is removed. A decrease in photolysis efficiency can be effectively suppressed.

  Although only one partition plate 13 may be used, it is desirable that a plurality of partition plates 13 be installed as shown in FIG. Thereby, since the 1st field 3a can be divided into smaller space, the removal of the bubble adhering to the electrode surface and the case inner wall surface can be performed more uniformly over the electrode surface and the whole case inner wall.

  When the partition plate 13 is not provided, or when the surface interval of the partition plate 13 is too wide, the place where the gas floats and the place where the electrolyte 7 flows down in the communication portion 9 are spatially connected. Therefore, when the gas rises from a place where the communication part 9 is located, the electrolyte 7 flows down from the communication part 9 at another place, so that the balance of the three forces is adjusted. Further progressing, there is a concern that a situation occurs in which the gas is emitted only from a limited portion of the communication portion 9 to be released. By providing the partition plates 13 at an appropriate interval, a location where the gas floats in the communication portion 9 and a location where the electrolyte solution 7 flows down are generated in one divided space, and this concern can be prevented. In this way, by providing the partition plates 13 at appropriate intervals, air bubbles can be emitted from any part of the communication portion 9 with a frequency sufficient for air bubble removal, so that they adhere to the electrode surface and the inner wall surface of the housing. The removal of the bubbles can be performed more uniformly over the electrode surface and the entire inner wall of the housing. The appropriate interval between the partition plates 13 varies depending on the size of the photohydrogen generation cell 200 and the size of the gap, but it is adjacent to each other so that the gas is likely to float from the communication portion 9 and the above-described situation of concern is unlikely to occur. It is preferable that the surface interval of the partition plate 13 to be set is, for example, 1 cm to 20 cm.

  Since the partition plate 13 should just divide | segment the 1st area | region 3a in the 1st space 3 into several space along a horizontal direction, the shape is not specifically limited. Considering the ease of division of the first region 3a in the first space 3, a rectangular partition plate 13 as shown in FIG. 5 is suitable.

  The installation method of the partition plate 13 is not particularly limited. For example, as shown in FIG. 5, the partition plate 13 has a main surface of the partition plate 13 that is substantially perpendicular to the translucent surface 1 a of the housing 1, and the photohydrogen generation cell 200 is installed. In the state, it is preferably provided in an orientation that is substantially parallel to the vertical direction. In other words, in the partition plate 13, the normal vector of the main surface of the partition plate 13 is approximately parallel to the horizontal direction in a state where the photohydrogen generation cell 200 is installed, and approximately perpendicular to the normal vector of the light transmitting surface 1 a. It is preferable to be provided in such a direction. By arranging the partition plate 13 in this way, the first region 3a can be removed uniformly over the electrode surface and the entire inner wall of the housing. Can be divided into respective divided spaces.

  The partition plate 13 is desirably formed of a material that has corrosion resistance and insulation properties with respect to the electrolyte solution 7 and has a function of not allowing gas to pass therethrough. Further, as in the example shown in FIG. 5, when the semiconductor photoelectrode 5 is arranged in a direction in which the first surface, that is, the surface of the optical semiconductor layer 52 faces the translucent surface 1 a of the housing 1, 13 is arranged on the light irradiation side with respect to the semiconductor photoelectrode 5. Therefore, in the case of such a configuration, in addition to the above characteristics, the material of the partition plate 13 is light in the visible light region, more preferably light including the peripheral wavelength in the visible light region in addition to the wavelength in the visible light region. It is preferable that the material is permeable. Examples of the material include glass and resin.

  Next, the operation of the photohydrogen generation cell 200 will be described. The operation of the photohydrogen generation cell 200 is the same as that of the photohydrogen generation cell 100 shown in Embodiment 1 except that the operation differs depending on the addition of the partition plate 13. Therefore, only the operation related to the partition plate 13 will be described here. Also in the present embodiment, the case where the optical semiconductor layer 52 is an n-type semiconductor will be described.

  Small oxygen bubbles generated on the surface of the optical semiconductor layer 52 in the first region 3 a in the first space 3 are accumulated on the gas accumulation surface 8 a of the gas accumulation unit 8. This accumulation of oxygen bubbles is performed in each of the divided spaces divided by the partition plate 13. The amount of oxygen gas accumulated on the gas accumulation surface 8a increases with time. Then, in the communication portion 9 in each divided space, the three forces of the floating force of the accumulated oxygen gas, the gravity applied to the electrolyte solution 7 above the communication portion 9, and the surface tension of the electrolyte solution 7 in the vicinity of the communication portion 9. In this balance, when the levitation force of oxygen gas becomes dominant, the oxygen gas accumulated through the communication portion 9 rises. The action of removing bubbles on the electrode surface and the inner wall of the housing by the oxygen gas that has floated through the communication portion 9 is the same as that of the photohydrogen generation cell 100 of the first embodiment.

  In the photohydrogen generation cell 200 according to the present embodiment, the floating of oxygen gas from the communication portion 9 occurs in each of the divided spaces, so that the entire surface of the semiconductor photoelectrode 5 and the entire inner wall vicinity of the first space 3 of the housing 1 are covered. Oxygen gas will pass uniformly. Therefore, the photohydrogen generation cell 200 can more efficiently remove the bubbles attached to the electrode surface and the inner wall of the housing as compared with the cell in which the partition plate 13 is not provided.

(Embodiment 3)
A photohydrogen generation cell according to Embodiment 3 of the present disclosure will be described with reference to FIG. FIG. 6 is a schematic cross-sectional view showing a configuration example of the photohydrogen generation cell of the present embodiment.

  The photohydrogen generation cell 300 shown in FIG. 6 differs from the photohydrogen generation cell 100 of the first embodiment in the arrangement of the semiconductor photoelectrode 5, and further changes due to the arrangement of the semiconductor photoelectrode 5 (the gas storage unit 8 and the communication unit). 9 has the same configuration as that of the photohydrogen generation cell 100 of the first embodiment except that the positional change is performed in FIG. Therefore, here, the semiconductor photoelectrode 5 and the positional features of the gas storage unit 8 and the communication unit 9 will be described.

  The semiconductor photoelectrode 5 is disposed in a direction in which the second surface (the surface opposite to the optical semiconductor layer 52 side with respect to the conductive layer 51) faces the translucent surface 1 a of the housing 1. In the example shown in FIG. 6, the semiconductor photoelectrode 5 includes a conductive layer 51 and an optical semiconductor layer 52. Therefore, in the example shown in FIG. 6, the surface of the optical semiconductor layer 52 opposite to the surface in contact with the conductive layer 51 is the first surface of the semiconductor photoelectrode 5 and is in contact with the optical semiconductor layer 52 of the conductive layer 51. The surface opposite to the surface is the second surface of the semiconductor photoelectrode 5.

  In the photohydrogen generation cell 300, light enters the semiconductor photoelectrode 5 from the conductive layer 51 side. Therefore, the conductive layer 51 has translucency. Moreover, as shown in FIG. 6, it is desirable that the second surface of the semiconductor photoelectrode 5 is directly joined to the inner surface of the light transmitting surface 1a. Since the conductive layer 51 and the translucent surface 1a are directly bonded, the electrolytic solution 5 or the like is not interposed between the translucent surface 1a and the semiconductor photoelectrode 5, and thus reaches the optical semiconductor layer 52. Light loss can be suppressed.

  The gas accumulation unit 8 is in a region below the center in the vertical direction of the first space 3 in the state where the photohydrogen generation cell 300 is installed, and the first surface of the semiconductor photoelectrode 5 It is placed in the opposite area. That is, the gas accumulating portion 8 in the present embodiment is disposed on the opposite side to the light irradiation side with respect to the semiconductor photoelectrode 5.

  The communication part 9 includes a gap between the gas accumulation part 8 and the separator 2, a gap between the gas accumulation part 8 and the first surface of the semiconductor photoelectrode 5, and a through hole provided in the gas accumulation part 8. It can be at least one selected. In the example shown in FIG. 6, the gap between the gas accumulation part 8 and the separator 2 forms the communication part 9. As in the case of the photohydrogen generation cell 100 of the first embodiment, the communication unit 9 only needs to be configured to communicate the first region 3a and the second region 3b of the first space 3, and thus has a shape and a size. The thickness is not particularly limited. A preferable shape, size, and the like of the communication unit 9 are the same as those of the photohydrogen generation cell 100 of the first embodiment.

  It is possible to further provide the partition plate 13 of the photohydrogen generation cell 200 of the second embodiment with respect to the photohydrogen generation cell 300 of the present embodiment.

  Even in the case where the semiconductor photoelectrode 5 is arranged so that the light irradiation to the optical semiconductor layer 52 of the semiconductor photoelectrode 5 is performed through the conductive layer 51 as in the photohydrogen generation cell 300, the gas storage unit 8. The same operational effects as those of the photohydrogen generation cell 100 of the first embodiment can be obtained. The operation of the photohydrogen generation cell 300 is the same as the operation of the photohydrogen generation cell 100 of Embodiment 1 except that light irradiation to the semiconductor photoelectrode 5 is performed from the conductive layer 51 side. Description is omitted.

Example 1
Example 1 of the present disclosure will be specifically described. In Example 1, a photohydrogen generation cell having the same configuration as the photohydrogen generation cell 100 shown in FIGS. 1 and 2 was used. However, unlike the example shown in FIGS. 1 and 2, the gas storage unit 8 is a casing of the light-transmitting surface 1 a so that the gas storage surface 8 a is perpendicular to the light-transmitting surface 1 a of the casing 1. It was directly joined to the inner surface.

  A glass plate (length 210 mm × width 210 mm × thickness 3 mm) was used for the translucent surface 1 a of the housing 1. A casing 1 having an inner dimension thickness of 10 mm was prepared using a resin member other than the light transmitting surface 1a. A resin sealing material is sandwiched between the glass plate and the resin member to prevent leakage of liquid and gas from the inside of the housing 1.

  As the separator 2, an ion exchange membrane (“Nafion” DuPont) that allows permeation of protons in the electrolytic solution and suppresses permeation of oxygen and hydrogen generated in the electrolytic solution was used.

  For the conductive layer 51, a metal titanium substrate (length 200 mm × width 200 mm × thickness 0.1 mm) was used. A titanium oxide film (anatase type) having a thickness of 100 nm was formed as a photosemiconductor layer 52 on a metal titanium substrate by a sputtering method.

  As the counter electrode 6, a metal titanium substrate (length 200 mm × width 200 mm × thickness 0.1 mm) on which platinum was sputtered was used.

  In the first space 3 formed by the casing 1 and the separator 2, a conductive layer 51 formed with an optical semiconductor layer 52 is formed, and a metal titanium substrate as a counter electrode 6 is formed in the second space 4, respectively. The substrate surface is arranged so as to be substantially parallel to the translucent surface 1 a of the housing 1. The conductive layer 51 and the counter electrode 6 were electrically connected by the electrical connection portion 10. As the electrolytic solution 7, a 0.25 mol / L sodium carbonate aqueous solution was used.

  For the gas accumulating portion 8, a member made of a resin, which is 10 mm long × 200 mm wide × 1-2 mm thick and has a corrugated shape at intervals of 20 mm was used. The resin member was fixed to the surface of the light transmitting surface 1a of the housing 1 on the inner side of the housing by joining to a location with a height of 50 mm from below. The communication part 9 is formed by a gap between the gas storage part 8 and the surface of the optical semiconductor layer 52, and the size thereof is about 3 mm.

  The photohydrogen generation cell 100 of the present example manufactured as described above was irradiated with light using a xenon lamp having an intensity of 300 W from the translucent surface 1a side. Along with the light irradiation, oxygen microbubbles having a diameter of about 0.3 to 0.5 mm are generated from the surface of the optical semiconductor layer 52 of the semiconductor photoelectrode 5, and the optical semiconductor layer 52 and the first space 3 of the housing 1 are formed. Adhered to the inner wall surface. Part of the generated oxygen microbubbles accumulated on the gas accumulation surface 8a of the gas accumulation unit 8 and floated intermittently from the communication unit 9. The diameter of the oxygen gas that floated was about 10 mm. Of the microbubbles attached to the optical semiconductor layer 52 and the inner wall surface of the first space 3 of the housing 1 due to the floating oxygen gas, those present on the path of the floating oxygen gas are completely removed. It was broken.

  Since the photohydrogen generation cell of the present disclosure can improve the efficiency of the hydrogen generation reaction by light irradiation, it can be suitably used as a hydrogen supply source to the fuel cell.

DESCRIPTION OF SYMBOLS 100,200,300 Photohydrogen production | generation cell 1 Housing | casing 1a Translucent surface 2 Separator 3 1st space 3a 1st area | region 3b 2nd area | region 4 2nd space 5 Semiconductor photoelectrode 51 Conductive layer 52 Optical semiconductor layer 6 Counter electrode 7 Electrolyte 8 Gas accumulating portion 8a Gas accumulating surface 9 Communication portion 10 Electrical connection portion 11, 12 Gas outlet 13 Partition plate

Claims (14)

A housing,
A separator that divides the internal space of the housing into a first space and a second space;
A semiconductor photoelectrode disposed in the first space and including a conductive layer and a photosemiconductor layer formed on the conductive layer;
A counter electrode disposed in the second space and electrically connected to the semiconductor photoelectrode;
An electrolyte containing water in the first space and the second space;
A gas accumulating portion having a gas accumulating surface, disposed in the first space;
A photohydrogen generation cell comprising: the housing has a light-transmitting surface facing the first space;
In the semiconductor photoelectrode, when the surface on the optical semiconductor layer side with respect to the conductive layer is a first surface and the surface opposite to the optical semiconductor layer side with respect to the conductive layer is a second surface, The gas accumulating part is disposed in a region facing the first surface of the semiconductor photoelectrode,
The gas storage surface includes a surface that is vertically downward or obliquely downward in a state where the photohydrogen generation cell is installed and that faces a direction intersecting the first surface of the semiconductor photoelectrode,
In the first space, communication between the first region on the gas storage surface side with respect to the gas storage portion and the second region on the opposite side of the gas storage surface with respect to the gas storage portion. Part is provided,
Photohydrogen generation cell. In the state where the photohydrogen generation cell is installed, further includes a partition plate that divides the first region in the first space into a plurality of spaces along a horizontal direction,
A part of the periphery of the partition plate is in contact with the gas accumulation surface,
The photohydrogen generation cell according to claim 1. Including a plurality of the partition plates;
The spacing between the partition plates adjacent to each other is within a range of 1 to 20 cm.
The photohydrogen generation cell according to claim 2. The partition plate is provided in a direction in which a main surface of the partition plate is substantially perpendicular to the translucent surface of the housing.
The photohydrogen production cell according to claim 2 or 3. The partition plate is provided in a direction in which a main surface of the partition plate is substantially parallel to a vertical direction in a state where the photohydrogen generation cell is installed.
The photohydrogen production cell according to any one of claims 2 to 4. The housing has a thin rectangular shape,
In the state where the photohydrogen generation cell is installed, the length of the vertical side of the casing in the height direction is longer than the length of the horizontal side in the width direction.
The photohydrogen generation cell according to any one of claims 1 to 5. The semiconductor photoelectrode is disposed in a direction in which the first surface faces the light transmitting surface of the housing.
The photohydrogen generation cell according to any one of claims 1 to 6. The communication part includes a gap between the gas storage part and the first surface of the semiconductor photoelectrode, a gap between the gas storage part and the translucent surface of the housing, and the gas storage part. Is at least one selected from through-holes provided in
The photohydrogen generation cell according to claim 7. The communication part is a gap between the gas storage part and the first surface of the semiconductor photoelectrode.
The photohydrogen generation cell according to claim 8. The conductive layer has translucency;
The semiconductor photoelectrode is arranged with the second surface facing the translucent surface of the housing,
The photohydrogen generation cell according to any one of claims 1 to 6. The communication portion includes a gap between the gas accumulation portion and the separator, a gap between the gas accumulation portion and the first surface of the semiconductor photoelectrode, and a through hole provided in the gas accumulation portion. Is at least one selected from
The photohydrogen generation cell according to claim 10. The communication part is a gap between the gas storage part and the separator.
The photohydrogen generation cell according to claim 11. In the horizontal plane in a state where the photohydrogen generation cell is installed, the shortest distance between the translucent surface and the separator is the thickness A of the first space, and in a direction parallel to the direction of the thickness A. When the maximum length of the communication portion is the length B of the communication portion, and the maximum width of the communication portion in the direction perpendicular to the direction of the thickness A is the width W of the communication portion,
The thickness A of the first space, the length B of the communicating portion, and the width W of the communicating portion satisfy a relationship of 0.17 × A ² /W≦B≦A−0.17×A ² / W. Meet,
The photohydrogen generation cell according to any one of claims 1 to 12. The gas accumulation unit is disposed in a region below the center in the vertical direction of the first space in a state where the photohydrogen generation cell is installed.
The photohydrogen generation cell according to any one of claims 1 to 13.

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