JP5993768B2 - Gas production equipment - Google Patents

Description

  The present invention relates to a gas manufacturing apparatus, and more particularly to a gas manufacturing apparatus that receives light to decompose water and produce hydrogen and oxygen.

Conventionally, as one form of utilizing solar energy as renewable energy, photoelectric conversion materials used in solar cells are used, and electrons and holes obtained by photoelectric conversion are used for water decomposition reaction. Thus, hydrogen production apparatuses that produce hydrogen used in fuel cells and the like have been proposed (see, for example, Patent Documents 1 and 2).
Each of the hydrogen production apparatuses disclosed in Patent Documents 1 and 2 includes a photoelectric conversion unit or a solar cell in which two or more pn junctions that generate an electromotive force when sunlight is incident are connected in series. An electrolytic solution chamber is provided on the lower side of the photoelectric conversion unit or solar cell opposite to the light receiving surface that receives light, the electrolytic chamber is divided by an ion conductive partition or a diaphragm, and the photoelectric conversion unit or solar cell is received by receiving sunlight. It discloses that water is electrolyzed to generate hydrogen by the generated electric power.

The hydrogen production apparatus disclosed in Patent Document 1 can further adjust the direction of the light-receiving surface with respect to sunlight, so that the amount of incident light to be subjected to photoelectric conversion can be increased and the hydrogen generation efficiency is reduced. There is no such thing.
Moreover, since the hydrogen production apparatus disclosed in Patent Document 2 electrolyzes water using the electrode plates connected to the p-type and n-type semiconductors of the solar cell as an anode and a cathode, respectively, the conversion efficiency from solar energy to hydrogen It can be raised.

JP 2012-177160 A JP 2004-197167 A

By the way, in the hydrogen production apparatus disclosed in Patent Documents 1 and 2, both of the hydrogen and oxygen are obtained by electrolyzing water in the electrolytic solution chamber on the side opposite to the light receiving surface of the photoelectric conversion unit or solar cell, that is, the back surface side. The generated gas such as hydrogen or oxygen adheres to the gas generation surface of the photoelectric conversion unit gas generation electrode or the electrode plate of the solar cell, and the gas generation surface and an aqueous solution such as an electrolyte solution are present. If it stays in the gas, the contact area between the gas generating surface and the aqueous solution is lowered, and there is a problem that the efficiency of gas production such as hydrogen and oxygen is lowered.
Even if the hydrogen production apparatus disclosed in Patent Documents 1 and 2 exhibits high gas generation efficiency at the initial stage of gas generation, the gas generation surface and an aqueous solution such as an electrolyte solution are obtained over time. The amount of gas staying in between increases and the contact area between the gas generation surface and the aqueous solution further decreases, so that the efficiency of gas generation such as hydrogen and oxygen is greatly reduced, and stable gas generation cannot be performed. There was a problem.

  The object of the present invention is to solve the above-mentioned problems of the prior art and maintain high gas generation efficiency even at the initial stage of gas generation or when time has passed. An object of the present invention is to provide a gas production apparatus capable of stably producing a gas as a high-purity gas completely separated.

In order to achieve the above object, the gas production apparatus of the present invention includes an element laminate in which a plurality of elements each having a light receiving portion and formed with a semiconductor thin film having a pn junction are laminated in series. A hydrogen gas generation unit that is formed on the surface of the first element at one end of the element stack in the plurality of elements and generates hydrogen gas; and a hydrogen gas generation unit, A first electrolysis chamber for accommodating an electrolytic aqueous solution in contact with the generated hydrogen gas, and a conductive film in which a semiconductor thin film of a second element at the other end of the element stack is formed in the plurality of elements. An oxygen gas generation unit that generates oxygen gas, an electrolytic aqueous solution that includes the oxygen gas generation unit and is in contact with the oxygen gas generation unit, and a second electrolytic chamber that stores the generated oxygen gas And between the first electrolysis chamber and the second electrolysis chamber Ion permeability kicked, and have a gas impermeable membrane, the first element is comprised of a plurality of sub-elements, the plurality of sub-elements, on the second element, the second It is characterized by being discretely arranged with respect to the element .

Here, the hydrogen gas generator includes a hydrogen generation plane, the hydrogen generating surface is not preferable to be formed on the surface of the semiconductor thin film of the first element.
The plurality of subelements preferably have a smaller element area than the second element.
The oxygen gas generation unit includes an oxygen generation surface, and the oxygen generation surface is formed on the back surface of the conductive substrate. The oxygen generation surface is on the upper side along the flow direction of the electrolytic aqueous solution in the second electrolytic chamber. It is preferable to be inclined.

Moreover, it is preferable that a semiconductor thin film contains a CIGS type compound semiconductor.
Moreover, it is preferable that a semiconductor thin film contains a CZTS type compound semiconductor.
Moreover, it is preferable that the absorption wavelength edge of a semiconductor thin film is 800 nm or more.
Furthermore, it is preferable to have a hydrogen generation co-catalyst provided on the hydrogen generation surface provided in the hydrogen gas generation unit.
The hydrogen generation co- catalyst is preferably platinum.

  According to the present invention, it is possible to maintain a high gas generation efficiency even in the initial stage of gas generation or when time has elapsed, and the high purity of hydrogen and oxygen gas completely separated. It can be manufactured stably as a gas.

It is sectional drawing which shows typically an example of the gas manufacturing apparatus which concerns on one Embodiment of this invention. It is a top view of the gas manufacturing apparatus shown in FIG. It is a flowchart which shows an example of the process which manufactures the gas manufacturing apparatus shown in FIG.

Below, the gas manufacturing apparatus concerning the present invention is explained in detail based on the suitable embodiment shown in an accompanying drawing.
The present invention uses a pn junction semiconductor thin film used in solar cells or the like as an electrode for decomposing water. For example, in one element composed of a pn junction-semiconductor thin film, a conductive film, and a support substrate, water is photolyzed. Since the electromotive force is not higher than the electrolysis start voltage of water, the electromotive force is increased by connecting multiple elements in series, and the sum of electromotive forces of the multiple elements is the electrolysis start voltage of water By doing so, hydrogen is generated from the light receiving surface side of the element by the photolysis reaction of water, and oxygen is generated from the side opposite to the light receiving surface, so that hydrogen and oxygen generated by water decomposition are generated. Is a device for producing hydrogen and oxygen with high purity. As a method of connecting the elements, it is preferable that the elements to be stacked are composed of a plurality of subelements having a small element area on the elements having a large element area, and these subelements are stacked in a discrete manner.

First, the characteristics of the gas production apparatus according to the present invention with respect to the conventional apparatus will be described.
As described above, in the prior art, the surface of the electrode for electrolysis that generates gas (gas generation surface) is all provided on the back side of the photoelectric conversion unit opposite to the light receiving surface that receives sunlight. The feature of the present invention is that the hydrogen generating surface is provided on the same side as the light receiving surface that receives sunlight. Thus, by arranging the hydrogen generation surface on the light receiving surface side, high gas generation efficiency can be maintained regardless of the passage of time, and hydrogen and oxygen gas can be stably manufactured. The desired effect is obtained.

FIG. 1 is a cross-sectional view schematically showing an example of a gas production apparatus according to an embodiment of the present invention, and FIG. 2 is a top view of the gas production apparatus shown in FIG.
First, as shown in these drawings, the gas production apparatus 10 includes an element laminated body 12 in which a plurality of elements semiconductor thin film is formed is Ru are stacked in series in the vertical having a pn junction, the upper and lower ends of the element stack 12 The hydrogen gas generation unit 14a and the oxygen gas generation unit 14b, the electrolytic aqueous solution AQ that is in contact with the two gas generation units 14a and 14b, and the gas generation units 14a and 14b, respectively, are provided at the open ends of the elements. A container 18 that constitutes an electrolysis chamber 16 that accommodates hydrogen and oxygen gas, and a diaphragm 20 that partitions the electrolysis chamber 16 into two electrolysis chambers 16a and 16b each including one of the gas generation units 14a and 14b, respectively. Have

Element laminate 12, the water receiving light such as sunlight from the light-receiving surface is decomposed by photolysis reaction, intended to produce hydrogen and oxygen, a plurality (shown example stacked vertically in the drawing in having a pn junction element 22 and 2 4 for two). The number of pn junction elements connected in series will be described below as two representative examples. However, if the sum of electromotive forces of a plurality of pn junction elements is equal to or higher than the electrolysis start voltage of water, Of course, the number is not limited to two and may be any number.
The pn junction elements 22 and 24 are photoelectric conversion elements having a stacked structure having the same configuration as that of a solar battery cell used as a solar battery. The pn junction elements 22 and 24 receive light such as sunlight from a light receiving surface, and perform photoelectric conversion to generate electrons. And holes are generated, and the generated electrons and holes are sent to the gas generators 14a and 14b, respectively.

The pn junction element 22 on the substrate side of the element stack 12, that is, the lower side in the figure, is an oxygen generation element that generates oxygen, and is laminated in order from the lower side to the upper side in the figure. A conversion layer 28 and a buffer layer 30 are provided, and a transparent conductive film 32 serving as an upper electrode is provided on the buffer layer 30.
On the other hand, the pn junction element 24 on the light-receiving surface side of the element stack 12, that is, the upper side in the drawing is a hydrogen generation element that generates hydrogen, and includes a plurality (9 in the illustrated example) of small pn junction elements 24 a. Nine small-sized pn junction elements (hereinafter also referred to as sub-elements) 24a are discretely formed on the pn junction element 22, specifically on the transparent conductive film 32. That is, it is arranged so as to be scattered in an island shape. In the pn junction element 24 (24a), a transparent conductive film 32, a photoelectric conversion layer 28, a buffer layer 30, and a transparent protective film 34 are stacked in this order from the lower pn junction element 22 to the upper side in the figure. On the membrane 34, the islands are formed in which promoters 36 for generating hydrogen are scattered.

Here, since the transparent conductive film 32 functions as a lower electrode in the pn junction element 24 (24a) and functions as an upper electrode in the pn junction element 22, both of the pn junction elements 22 and 24 (24a) are used. It can be said that it functions as an electrode common to the element. Since the transparent protective film 34 constitutes the upper electrode of the pn junction element 24 (24a), a transparent conductive protective film is used.
Therefore, it can be said that the pn junction element 24 (24 a) includes the transparent conductive film 32, the photoelectric conversion layer 28, the buffer layer 30, the transparent protective film 34, and the hydrogen generation promoter 36.
By the way, since the subelements 24a are arranged on the transparent conductive film 32 so as to be scattered discretely, that is, in an island shape, the transparent conductive film 32 is placed in the electrolytic chamber where the subelements 24a are not arranged. It will be exposed to 16a, will contact the electrolytic aqueous solution AQ, and will short-circuit. Further, the side surface of the pn junction element 24 (24a), that is, the side surface of the stacked body of the photoelectric conversion layer 28, the buffer layer 30, and the transparent protective film 34 is also exposed to the electrolysis chamber 16a, contacts the electrolytic aqueous solution AQ, and is short-circuited. It will be.
For this reason, the transparent conductive film 32 exposed to the electrolysis chamber 16a and the side surfaces of the pn junction element 24 (24a) are preferably covered with the transparent insulating film 37.

In the element stack 12, when light enters the pn junction element 24 from the transparent protective film 34 side, the light passes through the transparent protective film 34 and the buffer layer 30, and an electromotive force is generated in the photoelectric conversion layer 28. For example, the movement of charges (electrons) from the transparent conductive film 32 toward the transparent protective film 34 occurs. In other words, a current (hole movement) from the transparent protective film 34 toward the transparent conductive film 32 is generated.
On the other hand, when light enters the pn junction element 22 from the transparent insulating film 37 side, the light passes through the transparent insulating film 37, the transparent conductive film 32, and the buffer layer 30, and an electromotive force is generated in the photoelectric conversion layer 28. For example, the movement of charges (electrons) from the conductive plate 26 toward the transparent conductive film 32 occurs. In other words, a current (hole movement) from the transparent conductive film 32 toward the conductive plate 26 is generated.
For this reason, in the element stack 12, the transparent protective film 34 of the upper pn junction element 24 serves as a gas generator 14 a (electrolytic cathode electrode) that generates hydrogen, and the conductive plate 26 of the lower pn junction element 22. Becomes a gas generating part 14b (electrolytic anode electrode) for generating oxygen.

The conductive plate 26 is made of, for example, Mo, and functions as a substrate that supports the element stack 12 and also functions as an oxygen generation surface that generates oxygen.
The photoelectric conversion layer 28 is made of, for example, a CIGS compound semiconductor film or a CZTS compound semiconductor film, and is formed on the conductive plate 26 in the lower pn junction element 22 and on the transparent conductive film 32 in the upper pn junction element 24. Has been.
The buffer layer 30 is made of, for example, a thin film such as CdS, and is formed on the surface of the photoelectric conversion layer 28. A pn junction is formed at this interface. Therefore, it can also be said that the photoelectric conversion layer 28 is a p-type semiconductor thin film and the buffer layer 30 is an n-type semiconductor thin film.
The photoelectric conversion layer 28 and the buffer layer 30 are used for both the lower pn junction element 22 and the upper pn junction element 24. However, at least one of the photoelectric conversion layer 28 and the buffer layer 30 includes both pn junction elements 22, 24 may be the same or different.

The transparent conductive film 32 is made of a transparent conductive film such as an IMO (Mo-added In ₂ O ₃ ) film, and is formed on the buffer layer 30. Here, in the lower pn junction element 22, the transparent conductive film 32 functions as a light receiving surface on the pn junction including the buffer layer 30 and the photoelectric conversion layer 28 and the upper pn junction element 24. The conductive film also functions as a lower electrode. That is, the transparent conductive film 32 functions as a conductive film that connects the lower pn junction element 22 and the upper pn junction element 24 in series.
The transparent protective film 34 is made of a transparent conductive film such as an ITO (Sn-added In ₂ O ₃ ) film, and is formed on the buffer layer 30 in the upper pn junction element 24. Here, the transparent protective film 34 functions as an upper electrode of the upper pn junction element 24, and thus as a light receiving surface on the pn junction including the buffer layer 30 and the photoelectric conversion layer 28, and as a hydrogen generation surface that generates hydrogen. Also works.

  The conductive plate 26 is made of, for example, a metal such as Mo, Al, Cu, Cr, W, Ni, Ta, Fe, Co, or a combination of these metals. The conductive plate 26 may have a single layer structure or a laminated structure such as a two-layer structure. In addition, since the back surface of the conductive plate 26 becomes an oxygen gas generating surface that generates oxygen and directly contacts the electrolytic aqueous solution, the conductive plate 26 is preferably a metal that is not easily oxidized. Among these, the conductive plate 26 is preferably made of Mo. The thickness of the conductive plate 26 is generally about 1000 μm, but the thickness of the conductive plate 26 is preferably 100 to 1500 μm.

The back surface of the conductive plate 26 of the pn junction element 22 becomes a gas generating part 14b (electrolytic anode electrode) that generates oxygen, and electrons are generated from hydroxide ions OH ⁻ ionized from water molecules in the aqueous electrolytic solution AQ. taken out oxygen molecules, i.e. to generate oxygen (oxygen _{^{gas) (2OH - -> H 2}} O + O 2/2 + 2e -) ones, its surface acts as an oxygen gas generating surface.
For this reason, it is preferable that the back surface of the conductive plate 26 is inclined from the upstream side to the downstream side of the flow of the electrolytic aqueous solution AQ so as not to retain the generated oxygen. The direction of inclination is not particularly limited, and when it is inclined downward toward the downstream side, the effect of peeling off the oxygen generated on the back surface of the conductive plate 26 from the surface is high, and the inclination is inclined upward toward the downstream side. If you are in, it can flow oxygen gas collects in the rear surface of the conductive plate 26 floats above the electrolytic solution a Q toward efficiently discharge port 40b together with an electrolyte solution AQ. In the illustrated example, the supply port 38b for the electrolytic aqueous solution AQ is on the right side in the drawing, and the discharge port 40b for discharging the generated oxygen together with the electrolytic aqueous solution AQ is on the left side in the drawing. The back surface of the conductive plate 26 may be inclined upward from the right side in the figure toward the left side in the figure.

By doing so, the generated oxygen can be quickly moved without staying from the back surface of the conductive plate 26 serving as the oxygen gas generation surface and discharged from the discharge port 40b together with the electrolytic aqueous solution AQ. The back surface can be kept in contact with the electrolytic aqueous solution AQ, and a photodecomposition reaction of water can be caused on the entire back surface of the conductive plate 26, so that oxygen can be generated efficiently.
In order to promote the generation of oxygen by water photolysis reaction, the rear surface of the conductive plate 26 serving as oxygen gas generating surface, the oxygen generation auxiliary catalysts such as IrO _2, CoO _x, as scattered islands You may form in a shape.

  The photoelectric conversion layer 28 forms a pn junction in which the photoelectric conversion layer 28 side is P-type and the buffer layer 30 side is N-type at the interface with the buffer layer 30, and the transparent insulating film 37, the transparent conductive film 32, and the buffer layer It is a layer that absorbs light that has passed through 30 and generates holes on the p side and electrons on the n side, and has a photoelectric conversion function. In the photoelectric conversion layer 28, holes generated at the pn junction are moved from the photoelectric conversion layer 28 to the conductive plate 26 side, and electrons generated at the pn junction are moved from the buffer layer 30 to the transparent conductive film 32 side. The film thickness of the photoelectric conversion layer 28 is preferably 200 to 3000 nm, particularly preferably 500 to 2000 nm.

The photoelectric conversion layer 28 is preferably a compound semiconductor-based photoelectric conversion semiconductor layer, and the main component (the main component means a component of 20% by mass or more) is not particularly limited, and high photoelectric conversion efficiency is obtained. Therefore, a chalcogen compound semiconductor, a compound semiconductor having a chalcopyrite structure, and a compound semiconductor having a defect stannite structure can be preferably used.
As a chalcogen compound (compound containing S, Se, Te),
II-VI compounds: ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, etc.
I-III-VI ₂ group _{compounds: CuInSe 2, CuGaSe 2, Cu} (In, Ga) Se 2, CuInS 2, CuGaSe 2, Cu (In, Ga) (S, Se) 2 , etc.,
Preferable examples include I-III ₃ -VI ₅ group compounds: Cull ₃ Se ₅ , CuGa ₃ Se ₅ , Cu (ln, Ga) ₃ Se _{5 and the} like.

As a compound semiconductor having a chalcopyrite structure and a defect stannite structure,
I-III-VI ₂ group _{compounds: CuInSe 2, CuGaSe 2, Cu} (In, Ga) Se 2, CuInS 2, CuGaSe 2, Cu (In, Ga) (S Se) 2 , etc.,
Preferred examples include I-III ₃ -VI ₅ group compounds: CuIn ₃ Se ₅ , CuGa ₃ Se ₅ , Cu (In, Ga) ₃ Se _{5 and the} like.
However, in the above description, (In, Ga) and (S, Se) are (In _1-x Ga _x ) and (S _1-y Se _y ) (where x = 0 to 1, y = 0, respectively). To 1).

Among these, the photoelectric conversion layer 28 is preferably composed of, for example, a CIGS compound semiconductor or a CZTS compound semiconductor having a chalcopyrite crystal structure. That is, the photoelectric conversion layer 28 is preferably composed of a CIGS layer. The CIGS layer may be composed of not only Cu (In, Ga) Se ₂ but also known materials used for CIGS systems such as CuInSe ₂ (CIS).
A method for forming the photoelectric conversion layer 28 is not particularly limited. For example, methods for forming a CIGS layer containing Cu, In, Ga, and S include 1) multi-source deposition, 2) selenization, 3) sputtering, 4) hybrid sputtering, and 5) mechanochemical process. Etc. are known.
Other CIGS layer forming methods include screen printing, proximity sublimation, MOCVD, and spray (wet film formation). For example, a fine particle film containing an Ib group element, an IIIb group element, and a VIb group element is formed on a substrate by a screen printing method (wet film forming method) or a spray method (wet film forming method), and then pyrolyzed ( At this time, a crystal having a desired composition can be obtained by performing a thermal decomposition treatment in a VIb group element atmosphere (Japanese Patent Laid-Open Nos. 9-74065, 9-74213, etc.).

In the present invention, as described above, the photoelectric conversion layer 28 is preferably composed of, for example, a CIGS compound semiconductor or a CZTS compound semiconductor having a chalcopyrite crystal structure, but the present invention is not limited thereto. First, any photoelectric conversion element may be used as long as it can form a pn junction made of an inorganic semiconductor, cause a photodecomposition reaction of water, and generate hydrogen and oxygen. For example, the photoelectric conversion element used for the photovoltaic cell which comprises a solar cell is used preferably. Such photoelectric conversion elements include CIGS thin film photoelectric conversion elements, CIS thin film photoelectric conversion elements, CZTS thin film photoelectric conversion elements, thin film silicon thin film photoelectric conversion elements, and CdTe thin film photoelectric conversion elements. Examples thereof include a conversion element, a dye-sensitized thin film photoelectric conversion element, and an organic thin film photoelectric conversion element.
The absorption wavelength of the inorganic semiconductor forming the photoelectric conversion layer 28 is not particularly limited as long as it is a wavelength range that allows photoelectric conversion. However, the wavelength range of sunlight and the like, particularly from the visible wavelength range to the infrared wavelength range. However, it is preferable that the absorption wavelength end includes 800 nm or more, that is, the infrared wavelength region. The reason for this is that more than half of the solar energy reaching the ground is contained in the ultraviolet and visible light region with a wavelength of 800 nm or less. By effectively using these energies, hydrogen energy can be used as an alternative to fossil fuels. This is because it makes sense to manufacture the device with this apparatus.

The buffer layer 30 constitutes a pn junction layer together with the photoelectric conversion layer 28, that is, forms a pn junction at the interface with the photoelectric conversion layer 28, protects the photoelectric conversion layer 28 when the transparent conductive film 32 is formed, and It is formed to transmit light incident on the film 32 to the photoelectric conversion layer 28.
For example, the buffer layer 30 is specifically made of CdS, ZnS, Zn (S, O), and / or Zn (S, O, OH), SnS, Sn (S, O), and / or Sn (S , O, OH), InS, In (S, O), and / or at least one metal element selected from the group consisting of Cd, Zn, Sn, and In, such as In (S, O, OH). It preferably contains a metal sulfide. The thickness of the buffer layer 30 is preferably 10 nm to 2 μm, and more preferably 15 to 200 nm. The buffer layer 30 is formed by, for example, a chemical bath deposition method (hereinafter referred to as CBD method).
For example, a window layer may be provided between the buffer layer 30 and the transparent conductive film 32. This window layer is composed of, for example, a ZnO layer having a thickness of about 10 nm.

The transparent conductive film 32 has translucency. In the lower pn junction element 22, the light is taken into the photoelectric conversion layer 28 and is paired with the conductive plate 26 serving as the lower electrode, so that the photoelectric conversion layer 28. Functions as an upper electrode that moves holes and electrons generated (current flows), and also functions as a lower electrode of the upper pn junction element 24, and functions as a lower pn junction element 22 and an upper pn junction. In order to connect the element 24 in series, it functions as a transparent conductive film that is directly connected.
The transparent conductive film 32 is made of, for example, IMO (In ₂ O ₃ to which Mo is added), ZnO doped with Al, B, Ga, In, or the like, or ITO (indium tin oxide). The transparent conductive film 32 may have a single layer structure or a laminated structure such as a two-layer structure. The thickness of the transparent conductive film 32 is not particularly limited, and is preferably 0.1 to 2 μm, and more preferably 0.3 to 1 μm.
In addition, the formation method in particular of the transparent conductive film 32 is not restrict | limited, It can form by vapor phase film-forming methods, such as an electron beam vapor deposition method, a sputtering method, and CVD method, or the apply | coating method.

The transparent protective film 34 is formed on the upper surface of the buffer layer 30 in the upper pn junction element 24, has translucency, takes light into the photoelectric conversion layer 28, and serves as a lower electrode. A transparent conductive film that functions as an upper electrode that is paired with the transparent conductive film 32 to move holes and electrons generated in the photoelectric conversion layer 28 (current flows) and protects the buffer layer 30 and the photoelectric conversion layer 28. It functions as a film.
The transparent protective film 34 serves as a gas generation unit 14a (electrolysis cathode electrode) that generates hydrogen, and supplies electrons to hydrogen ions (protons) H ⁺ ionized from water molecules to generate hydrogen molecules, Hydrogen (hydrogen gas) is generated (2H ⁺ + 2e ⁻ −> H ₂ ), and the surface functions as a hydrogen gas generation surface.
The transparent protective film 34 includes, for example, a transparent conductive film 32 such as ITO (indium tin oxide), ZnO doped with Al, B, Ga, In, or IMO (Mo ₂ -added In ₂ O ₃ ). A similar transparent conductive film can be used. Similarly to the transparent conductive film 32, the transparent protective film 34 may have a single-layer structure or a laminated structure such as a two-layer structure. Further, the thickness of the transparent protective film 34 is not particularly limited, and is preferably 10 to 200 nm, and more preferably 30 to 100 nm.
The method for forming the transparent protective film 34 is not particularly limited, as is the case with the transparent conductive film 32, and is formed by a vapor deposition method such as an electron beam evaporation method, a sputtering method, or a CVD method, or a coating method. be able to.

As described above, the transparent protective film 34 functions as a hydrogen generation electrode, and its surface functions as a hydrogen gas generation surface. Therefore, the transparent protective film 34 functions as a gas generation unit 14a that generates hydrogen, and the region forms a hydrogen gas generation region.
On the surface of the transparent protective film 34, hydrogen generation promoters 36 for promoting hydrogen generation are formed in an island shape so as to be scattered.
Examples of the hydrogen generation promoter 36 include Pt (platinum), Pd (palladium), Ni (nickel), Au (gold), Ag (silver), Ru (ruthenium), Cu (copper), Co (cobalt), and Rh. (Rhodium), Ir (Iridium), Mn (Manganese), etc., simple substances, alloys combining them, and oxides thereof. Further, the size of the hydrogen generation co-catalyst 36 is not particularly limited and is preferably 1 to 100 nm.
The formation method of the hydrogen generation co-catalyst 36 is not particularly limited, and can be formed by a photo-deposition method, a sputtering method, an impregnation method, or the like.

As shown in the drawing, it is preferable to provide the hydrogen generation co-catalyst 36 on the upper surface of the transparent protective film 34. However, it may not be provided if sufficient hydrogen generation is possible.
In the illustrated example, the hydrogen generation co-catalyst 36 is scattered on the upper surface of the transparent protective film 34 formed on the upper surface of the buffer layer 30, but the present invention is not limited to this. Alternatively, the hydrogen generation co-catalyst 36 may be directly scattered on the upper surface of the buffer layer 30 without providing the transparent protective film 34.
In this case, the buffer layer 30 functions as an N-type semiconductor, functions as a hydrogen generation electrode, and its surface functions as a hydrogen gas generation surface. Therefore, the buffer layer 30 functions as a gas generation unit 14a that generates hydrogen, and the region forms a hydrogen gas generation region.

The transparent insulating film 37 has translucency and protects the pn junction elements 22 and 24. Specifically, the transparent insulating film 37 protects portions other than the hydrogen gas generating region in the electrolytic chamber 16a. It is provided so as to cover other parts. Specifically, in the transparent insulating film 37, the upper pn junction element 24 is not formed. Therefore, the surface of the transparent conductive film 32 serving as the light receiving surface of the lower pn junction element 22 and the pn junction element 24 are formed. It covers all the side surfaces of the individual sub-elements 24a.
Transparent insulating film 37, for _example, a _{SiO 2, SnO 2, Nb 2} O 5, Ta 2 O 5, Al 2 O 3, Ga 2 O 3 or the like. The thickness of the transparent insulating film 37 is not particularly limited, and is preferably 100 to 1000 nm.
The method for forming the transparent insulating film 37 is not particularly limited, and can be formed by RF sputtering, DC reactive sputtering, MOCVD, or the like.

By the way, the region of the transparent conductive film 32 in which the transparent insulating film 37 is formed and the upper pn junction element 24 is not formed serves as a light receiving surface of the lower pn junction element 22, whereas the upper pn Since each buffer layer 30 or transparent protective film 34 of the subelement 24a of the junction element 24 serves as the light receiving surface, in order to efficiently generate hydrogen and oxygen by water photolysis reaction, the upper pn junction element is used. 24, the total light receiving area of all sub-elements 24a, and the total light receiving area of the lower pn junction element 22, that is, the region of the transparent conductive film 32 where the upper pn junction element 24 is not formed. The total area needs to have a predetermined balance according to the capabilities of the pn junction elements 22 and 24, for example, the electromotive force and the generation amount of electrons and holes. For example, when the capabilities of both the pn junction elements 22 and 24 are equal, it is preferable that the total light receiving areas of both are equal.
Therefore, it is preferable to balance the total light receiving area of both the pn junction elements 22 and 24 according to the capabilities of both.
The element laminate 12 has the above configuration.

The element laminate 12 can be manufactured by the following manufacturing method, but is not limited thereto.
FIG. 3 is a flowchart illustrating an example of a process for manufacturing the gas manufacturing apparatus illustrated in FIGS. 1 and 2.
First, in step S100, for example, a Mo substrate or the like is prepared as the conductive plate 26 that functions as a support substrate.
Next, in step S102, for example, a CIGS compound semiconductor film (P-type semiconductor layer) is formed on one surface of the conductive plate 26 as a photoelectric conversion layer 28, such as a selenization / sulfurization method or a multi-source co-evaporation method. It forms by the method of.
Next, in step S104, thus on the formed photoelectric conversion layer 28, as a buffer layer 30, for example, more form CdS film (N-type semiconductor layer) in CBD (chemical bath) methods known ways, such as.
Next, in step S106, an ITO film serving as a transparent conductive layer, for example, is formed on the buffer layer 30 thus formed by a known method such as an MOCVD method or an RF sputtering method.

Next, in step S108, for example, a CIGS compound semiconductor film (P-type semiconductor layer) is formed as the photoelectric conversion layer 28 on the transparent conductive film 32 thus formed, as in step S102 described above.
Next, in Step S110, for example, a CdS film (N-type semiconductor layer) is formed as the buffer layer 30 on the photoelectric conversion layer 28 thus formed as in Step S104 described above.
Next, in step S112, for example, a ZnO film serving as a protective layer is formed on the buffer layer 30 thus formed by a known method such as an MOCVD method or an RF sputtering method.
Next, in step S114, the structure A (upper pn junction) including the photoelectric conversion layer 28 (CIGS compound semiconductor film), the buffer layer 30 (CdS film), and the transparent protective film 34 (ZnO film) thus formed is formed. The element 24) is cut by a mechanical scribing method to form a group A of discrete structures (group of sub-elements 24a).

Next, in step S116, on the structure A group thus formed, as the transparent insulating film 37, for example, a SiO2 film to be a transparent insulating layer is formed by a known method such as MOCVD, RF sputtering, DC reactive sputtering, or the like. It forms by the method of. Subsequently, the transparent insulating film 37 (SiO 2 film) formed on the upper surface portion of the structure A is selectively scraped by a known method such as a CMP method, and the sub-element 24a (structure A as the pn junction element 24) is formed. The transparent protective film 34 (ZnO film) serving as a protective layer is exposed only on the upper surface portion of ().
Finally, in step S118, for example, a Pt promoter is used as the hydrogen generation promoter 36 only on the transparent protective film 34 exposed on the upper surface of the pn junction element 24 (subelement 24a) (structure A). Is supported by a known method such as a photo-deposition method.
Thereby, the element laminated body 12 can be manufactured.

The container 18 accommodates the element stack 12, and is generated from the electrolytic aqueous solution AQ that comes into contact with the upper surface of the transparent protective film 34 of the upper pn junction element 24a constituting the gas generator 14a, and the gas generator 14a. Electrolysis in contact with the back surface of the conductive plate 26 of the upper electrolysis chamber 16a provided on the upper side of the element stack 12 and the lower pn junction element 22 constituting the gas generation unit 14b, which stores (stores) hydrogen as a gas. An electrolysis chamber 16 is configured which includes an aqueous solution AQ and a lower electrolysis chamber 16b provided on the lower side of the element stack 12 that stores (stores) oxygen, which is a gas generated from the gas generation unit 14b.
Electrolysis chamber 16b of the upper electrolysis chamber 16a and the lower side, as shown in FIG. 2, along the inner front surface of the container 18, and connected in the region surrounding the outer periphery of the element stack 12, the area to which this leads A diaphragm 20 is disposed on the surface.

Supply port 38a of the plurality for supplying electrolytic solution AQ to the electrolytic chamber 16a (3 one in shown to Example 2) is the upper right side of the right upper side (apparatus in FIG. 1 of the electrolytic chamber 16a in the container 18 a) a plurality of to recover hydrogen plurality (in shown to example 2 produced in the outlet 40a, and the electrolysis chamber 16a of the four) for discharging the electrolytic solution AQ electrolytic chamber 16a ( recovery port 42 of the shown three in to example) in FIG. 2 are both provided on the upper left side in FIG. 1 of the electrolysis chamber 16a of the container 18 (the upper left side of the device).
Supply ports 38b of the plurality for supplying electrolytic solution AQ in the electrolyte chamber 16b (2 one in shown to Example 2) is right in the lower right side (apparatus in FIG. 1 of the electrolysis chamber 16b in the container 18 the lower side), the discharge port 40b of the plurality for exhausting electrolytic solution AQ electrolysis chamber electrolysis chamber 16b together with the generated oxygen within 16b (2 one in shown to example 2) are, inside the container 18 of The electrolytic chamber 16b is provided on the lower left side surface (lower left side of the apparatus) in FIG. The oxygen discharged together with the electrolytic aqueous solution AQ from the discharge port 40b is recovered by a recovery unit (not shown).

Both the supply port 38a and the discharge port 40a can flow water in the electrolysis chamber 16a so that hydrogen generated in the transparent protective film 34 of the pn junction element 24 (group of sub elements 24a) does not stay on the surface. As described above, the transparent protective film 34 is attached so as to be slightly above the position of the transparent protective film 34. For this reason, the surface of the transparent protective film 34 can be always kept in contact with the electrolytic aqueous solution AQ, and hydrogen can be generated efficiently. Of course, the positions of the supply port 38a and the discharge port 40a become the water surface of the electrolytic aqueous solution AQ in the electrolytic chamber 16a.
On the other hand, both the supply port 38b and the discharge port 40b are attached so as to be positioned on the back surface of the conductive plate 26 that is inclined upward toward the downstream which becomes the ceiling of the electrolysis chamber 16b.
Since hydrogen is stored above the water surface of the electrolytic aqueous solution AQ in the electrolysis chamber 16a, the ceiling of the electrolysis chamber 16a is inclined upward toward the downstream and away from the water surface, similarly to the back surface of the conductive plate 26. It is configured. The recovery port 42 is attached so as to be slightly above the position of the water surface of the electrolytic aqueous solution AQ, that is, slightly above the positions of the supply port 38a and the discharge port 40a in order to efficiently recover the stored hydrogen. ing.

The number of the supply ports 38a, the discharge ports 40a, and the recovery ports 42 is not particularly limited, and any number may be used as long as the water flow can be performed so that hydrogen does not stay on the hydrogen gas generation surface, but the pn junction element 24 ( It is preferable to provide as many as necessary at a position where water can flow reliably on the surface of the sub-element 24a group).
Further, the number of the supply ports 38b and the discharge ports 40b is not particularly limited, and any number may be used as long as the water can flow so that oxygen does not stay on the oxygen gas generation surface. However, the number of the conductive plates 26 of the pn junction element 22 is not limited. It is preferable to provide as many as necessary at a position where water can flow reliably on the back surface.

The diaphragm 20 separates the hydrogen generated in the electrolysis chamber 16a and the oxygen generated in the electrolysis chamber 16b and collects them with high purity, and also increases the hydroxide ions generated by the generation of hydrogen in the electrolysis chamber 16a. (The pH also increases), and in order to allow the hydroxide ions and hydrogen ions to pass through in order to neutralize hydrogen ions (pH decreases) due to the generation of oxygen in the electrolysis chamber 16b, The chamber 16 is for separating the electrolytic chamber 16a and the electrolytic chamber 16b, and is a membrane having ion permeability and gas non-permeability.
As described above, the diaphragm 20 is disposed in a region that surrounds the outer periphery of the element stack 12 and connects the upper electrolytic chamber 16a and the lower electrolytic chamber 16b along the outer surface of the container 18 and vertically. mounted in close contact without any gap and 18 the inner front and the outer wall surface of the element stack 12. Thus, the diaphragm 20 separates the region of the electrolysis chamber 16a in contact with the upper pn junction element 24 and the region of the electrolysis chamber 16b in contact with the pn junction element 22 so that there is no gas permeation and ion permeation occurs. be able to.
The diaphragm 20 is made of, for example, an ion exchange membrane, a ceramic filter, Vycor glass, or the like. The thickness of the diaphragm 20 is not particularly limited, and is preferably 10 to 1000 μm.
The gas production apparatus of the present invention is basically configured as described above.

  As mentioned above, although the gas manufacturing apparatus of this invention was demonstrated in detail, this invention is not limited to the above-mentioned example, In the range which does not deviate from the summary of this invention, it is possible to perform various improvements and changes. Of course.

Hereinafter, the gas production apparatus of the present invention will be specifically described based on examples. The present invention is not limited to these examples.
Example 1
First, as Example 1, the gas production apparatus 10 shown in FIG. 1 having the following configuration was manufactured, and the electrolytic chamber 16 was filled with an electrolytic aqueous solution, irradiated with light, and the amounts of generated gas of hydrogen and oxygen were evaluated.
The results are shown in Table 1.
In addition, the element laminated body 12 of the gas manufacturing apparatus 10 of Example 1 was manufactured according to the manufacturing flow shown to the flowchart of FIG.

1. Structure of hydrogen generating element (pn junction element 24 (subelement 24a)) Transparent conductive film: IMO (Mo-added In ₂ O ₃ ), 1000 nm thick P-type semiconductor thin film: CIGS, 500 nm thick N-type semiconductor thin film: CdS, 50 nm thick Protective film: ITO (Sn-added In ₂ O ₃ ), 50 nm thickness Cocatalyst: Pt
2. 2. Configuration of oxygen generation element (pn junction element 22) Conductive plate: Mo, 1 mm thick P-type semiconductor thin film: CIGS, 2000 nm thick N-type semiconductor thin film: CdS, 50 nm thick Conductive plate shape Oxygen gas generating side shape: Inclined machining toward oxygen gas outflow direction (no bubbles of oxygen gas stay)
4). Form of oxygen generating element Size: 15cm x 20cm
5. Form of the hydrogen generating element Size: 1 to 3 cm on a side
Number of elements: 9 (multiple)
5. Arrangement of elements: Each element is arranged discretely. Others Diaphragm: Nafion (Ion-permeable and gas-impermeable substance)
Electrolytic aqueous solution: 0.1 M Na ₂ SO ₄ solution (pH 9.5)
Cocatalyst: Pt particles (size: ~ φ20nm)
Materials constituting the container (module): Glass Irradiation light source: AM1.5 simulated sunlight

(Comparative Example 1)
As Comparative Example 1, a gas production apparatus having the same configuration as that of Example 1 was produced except that the hydrogen production unit and the oxygen production unit were formed in the same element, and the implementation was performed on the produced gas production apparatus. In the same manner as in Example 1, light irradiation was performed to evaluate the amount of generated gas.
The results are shown in Table 1.

(Comparative Example 2)
Next, as Comparative Example 2, the gas having the same configuration as that of Example 1 except that the hydrogen generation element and the oxygen generation element have the same size (15 cm × 20 cm) and each element is configured by one. A production apparatus was produced, and the produced gas production apparatus was irradiated with light in the same manner as in Example 1 to evaluate the amount of generated gas.
The results are shown in Table 1.

Evaluation was performed as follows.
As the gas generation amount (initial), the gas generation amount immediately after light irradiation was determined.
As a gas generation amount (time), a gas generation amount after 24 hours from light irradiation was obtained.
“A” in the column of comprehensive judgment in Table 1 is a case where the gas generation amount (initial) of hydrogen gas and the gas generation amount (timed) both exceed 50 ml / min · m ² . “B” was determined on the basis of a determination criterion of less than 50 ml / min · m ² for any one of the hydrogen gas generation amount (initial) and the gas generation amount (time). In addition, the reference value of 50 ml / min · m ² or more is a numerical value converted based on a solar conversion efficiency of 1%.

As shown in Table 1, in Example 1 of the present invention, the amount of hydrogen gas generated immediately after light irradiation was 65 ml / min · m ² . Moreover, the hydrogen gas production amount after the lapse of 24 hours was 55 ml / min · m ² . The reason why the gas generation amount decreased with respect to the initial stage is that the generated hydrogen gas bubbles adhere to a part of the hydrogen generating part on the light receiving surface side, and the contact area with the solution is reduced by the bubbles. This is because the gas generation efficiency has decreased. However, by disposing the hydrogen generating elements discretely, the water introduced into the apparatus becomes a turbulent flow, and most of the bubbles can be removed.

In Comparative Example 1, the amount of hydrogen gas generated immediately after light irradiation was 0 ml / min · m ² , and gas generation could not be detected. Similarly, after 24 hours, the amount of hydrogen gas produced was 0 ml / min · m ² , and gas generation could not be detected.
In Comparative Example 2, the amount of hydrogen gas produced immediately after light irradiation was 55 ml / min · m ² . This is because the element for generating hydrogen gas covers all the elements for generating oxygen gas, the amount of light reaching the element for generating oxygen gas is reduced, and the total gas generating ability is reduced. The amount of hydrogen gas produced after the lapse of 24 hours was 30 ml / min · m ² . This is because the generated hydrogen gas bubbles cover the entire light receiving surface, and the light is scattered by the bubbles, so that the amount of incident light is reduced and the gas generation efficiency is significantly reduced.

As is clear from the above results, in Example 1 of the present invention, a high gas generation amount is exhibited even immediately after light irradiation, and a high gas generation amount can be maintained even after a lapse of time, thereby achieving stable gas generation. You can see that
On the other hand, in Comparative Example 1, it can be seen that the potential (electromotive force) required for decomposing water into hydrogen and oxygen was not obtained.
Further, in Comparative Example 2, a high gas generation amount is shown immediately after the light irradiation, but it can be seen that after a lapse of time, the gas generation amount is remarkably reduced and stable gas generation cannot be achieved.
Thus, the superiority of Example 1 of the present invention was shown.
From the above results, the effect of the present invention is clear.

DESCRIPTION OF SYMBOLS 10 Gas production apparatus 12 Element laminated body 14a, 14b Gas production | generation part 16, 16a, 16b Electrolytic chamber 18 Container 20 Diaphragm 22, 24, 24a pn junction element 26 Conductive plate 28 Photoelectric conversion layer 30 Buffer layer 32 Transparent conductive film 34 Transparent protection Membrane 36 Cocatalyst 37 Transparent insulating film

Claims (9)

An element stack in which a plurality of elements each having a light receiving portion and having a pn junction formed thereon are connected in series;
A hydrogen gas generating part that is formed on the surface of the first element at one end of the element stack of the plurality of elements and generates hydrogen gas;
An electrolytic aqueous solution that includes the hydrogen gas generation unit and is in contact with the hydrogen gas generation unit; and a first electrolytic chamber that stores the generated hydrogen gas;
Of the plurality of elements, an oxygen gas generation unit that generates oxygen gas formed on the back surface of the conductive substrate on which the semiconductor thin film of the second element at the other end of the element stack is formed. When,
An electrolytic aqueous solution that includes the oxygen gas generation unit and is in contact with the oxygen gas generation unit; and a second electrolytic chamber that stores the generated oxygen gas;
Ion permeability is provided between the second electrolytic chamber and said first electrolytic chamber, and have a gas-impermeable membrane,
The first element includes a plurality of subelements, and the plurality of subelements are discretely arranged on the second element with respect to the second element. Gas production equipment.   The gas production apparatus according to claim 1, wherein the hydrogen gas generation unit includes a hydrogen generation surface, and the hydrogen generation surface is formed on a surface of the semiconductor thin film of the first element. Wherein the plurality of sub-elements, to the second element, the gas production apparatus according to claim 1 or 2 is intended element area is small. The oxygen gas generation unit includes an oxygen generation surface, and the oxygen generation surface is formed on the back surface of the conductive substrate.
It said oxygen generating surface, gas production apparatus according to any one of claims 1 to 3 is inclined upward along the flow direction of the electrolytic solution of the second electrolytic chamber. The gas manufacturing apparatus according to any one of claims 1 to 4 , wherein the semiconductor thin film includes a CIGS compound semiconductor. Said semiconductor thin film, gas production apparatus according to any one of claims 1 to 5 including the CZTS based compound semiconductor. The absorption wavelength edge of the semiconductor thin film, gas production apparatus according to any one of claims 1 to 6 at 800nm or more. Furthermore, gas production apparatus according to any one of claims 1 to 7 having a hydrogen generating cocatalyst provided on the hydrogen generation plane in which the hydrogen gas generator is provided. The gas production apparatus according to claim 8 , wherein the hydrogen generation co- catalyst is platinum.

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