JP2017160523A - Photochemical electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photochemical electrode low in resistance between an oxygen generation material and a hydrogen generation material and in addition is easy to be manufactured.SOLUTION: There is provided a photochemical electrode having a first tabular body which has an oxidation reduction potential of O/HO between an upper limit of a valence band and a lower limit of a conduction band, is constituted by an oxygen generation light excitation material excited by absorbing light and is tabular, a second tabular body which has an oxidation reduction potential of H/Hbetween an upper limit of a valence band and a lower limit of a conduction band, is constituted by a hydrogen generation light excitation material excited by absorbing light and is tabular, and a conductor electrically connecting the first tabular body and the second tabular body.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a photochemical electrode that can be used for artificial photosynthesis.

  Since the recognition of global warming, how to reduce carbon dioxide emitted into the atmosphere with industrial activities has become an important issue.

  Artificial photosynthesis technology has recently attracted attention as a method for reducing carbon dioxide in the atmosphere. In the technology of artificial photosynthesis, carbon dioxide is reduced by utilizing electrons and protons obtained by water oxidation while oxidizing water with sunlight energy. Organic compounds are obtained by reduction of carbon dioxide. For example, water is oxidized by irradiating the photoexcited material placed on the anode with sunlight in a tank containing an electrolytic solution to generate electrons and protons. Then, the generated electrons and protons are sent to a reduction catalyst placed on the cathode and reacted with carbon dioxide to generate an organic compound such as formic acid.

In an artificial photosynthesis anode, water is usually oxidized in a single-stage excitation type or a two-stage excitation type.
An example of the two-stage excitation type reaction is performed as shown in FIG. As shown in FIG. 1, the oxidative decomposition of water using a two-stage excitation type material photoexcites an oxygen generating material and a hydrogen generating material in the presence of a reproducible electron transfer agent that acts as an electron donor and an electron acceptor. Is done. The oxygen generating material and the hydrogen generating material to be used do not need to sandwich the redox potential of H ⁺ / H _{2 and} the redox potential of O ₂ / H ₂ O in the band structure as in the one-step excitation type. It only needs to have sufficient potential for one reaction. Therefore, there is a possibility that the oxygen generating material and the hydrogen generating material used for the two-step excitation type reaction can narrow the band gap and effectively use solar energy. At this time, the upper end of the valence band of the band gap of the hydrogen generating material needs to be noble than the lower end of the conduction band of the band gap of the oxygen generating material.

  However, since the resistance between the oxygen generating material and the hydrogen generating material used in the two-step excitation type reaction is generally high, there is a problem that the efficiency of reaching the hydrogen generating material with electrons generated from the oxygen generating material is low.

Therefore, a method of adjoining oxygen generating material particles and hydrogen generating material particles using a liquid solid phase method has been proposed (for example, see Patent Document 1).
However, this proposed technique has a problem that control for obtaining a predetermined structure in which oxygen-generating material particles and hydrogen-generating material particles are adjacent to each other is difficult and manufacturing is not easy.

JP2013-180245A

  It is an object of the present invention to provide a photochemical electrode that has a low resistance between an oxygen generating material and a hydrogen generating material and is easy to manufacture.

In one embodiment, the photochemical electrode is
There is a redox potential of O ₂ / H ₂ O between the upper end of the valence band and the lower end of the conduction band, and it is made of an oxygen-generating photoexcited material that absorbs and excites light, and has a plate shape. A plate-like body;
A _second plate having a plate-like shape made of a hydrogen-generating photoexcited material that has a redox potential of H ⁺ / H ₂ between the upper end of the valence band and the lower end of the conduction band and absorbs and excites light. And
A conductor that electrically connects the first plate-like body and the second plate-like body;
Have

  In one aspect, it is possible to provide a photochemical electrode that has a low resistance between the oxygen generating material and the hydrogen generating material and that can be easily manufactured.

FIG. 1 is an explanatory diagram of a two-stage excitation type reaction. FIG. 2 is a diagram showing a band structure of a general photoexcitation material. FIG. 3 is a schematic top view of an example of the disclosed photochemical electrode. FIG. 4 is a schematic top view of another example of the disclosed photochemical electrode. FIG. 5 is a schematic diagram of an example of the AA cross section of FIG. FIG. 6 is a schematic diagram of another example of the AA cross section of FIG. 4. FIG. 7 is a schematic view of another example of the AA cross section of FIG. FIG. 8 is a schematic view of another example of the AA cross section of FIG. FIG. 9 is a schematic top view of another example of the disclosed photochemical electrode. FIG. 10 is a schematic top view of another example of the disclosed photochemical electrode. FIG. 11 is a schematic cross-sectional view of another example of the disclosed photochemical electrode. FIG. 12 is a schematic cross-sectional view of another example of the disclosed photochemical electrode. FIG. 13 is a schematic cross-sectional view of another example of the disclosed photochemical electrode. FIG. 14 is a schematic cross-sectional view of another example of the disclosed photochemical electrode. FIG. 15 is a schematic top view of the photochemical electrode of Example 1. FIG. 16 is a schematic diagram of the AA cross section of FIG. 15 in the photochemical electrode 1-A of Example 1. FIG. 17 is a schematic diagram of the AA cross section of FIG. 15 in the photochemical electrode 1-B of Example 1. FIG. FIG. 18 is a schematic cross-sectional view of the photochemical electrode of Example 2.

(Photochemical electrode)
The disclosed photochemical electrode includes a first plate-like body, a second plate-like body, and a conductor, and further includes other members as necessary.

<First plate-like body>
The first plate-like body is a plate-like body of an oxygen generation photoexcitation material.

There is no restriction | limiting in particular as a shape of the surface of a said 1st plate-shaped object, According to the objective, it can select suitably, For example, a polygon, circular, an ellipse etc. are mentioned. Examples of the polygon include a quadrangle. Examples of the quadrangle include a rectangle.
There is no restriction | limiting in particular as a magnitude | size of a said 1st plate-shaped object, According to the objective, it can select suitably.
As the area of the surface portion of the first plate-like member is not particularly limited and may be selected accordingly and examples thereof include 1 mm ² 100 mm ^2.
There is no restriction | limiting in particular as thickness of the said 1st plate-shaped object, According to the objective, it can select suitably, For example, 0.01 mm-1.0 mm etc. are mentioned.

The first plate-like body preferably has a groove in the surface portion of the first plate-like body. By doing so, the surface area is increased and the efficiency of oxidation of water to oxygen is improved.
There is no restriction | limiting in particular as a shape and a magnitude | size of the said groove | channel, According to the objective, it can select suitably.

  The photochemical electrode may have one or a plurality of the first plate-like bodies.

<< Oxygen-generating photoexcitation material >>
In the oxygen generation photoexcitation material, there is an O ₂ / H ₂ O redox potential between the upper end of the valence band (VBM) and the lower end of the conduction band (CBM).
The oxygen-generating photoexcitation material is a material that excites electrons by absorbing light in a specific range of wavelengths.

A generally known photoexcitation material has a band structure as shown in FIG.
Here, −5.73 eV (vs VAC) represents the redox potential of O ₂ / H ₂ O at the vacuum level.
−4.5 eV (vs VAC) represents the redox potential of H ⁺ / H _{2 at} the vacuum level.

Examples of the oxygen generating photoexcitation material include WO ₃ , SnO ₂ , Fe ₂ O ₃ , TiO ₂ , BiVO ₄ , SrTiO ₃ , BaTiO _{3 and the} like.

  There is no restriction | limiting in particular as a band gap of the said oxygen production | generation photoexcitation material, Although it can select suitably according to the objective, 1.8 eV-3.0 eV are preferable from the point which photoexcitation reaction is performed with visible light, 1 .8 eV to 2.5 eV is more preferable.

The band gap can be calculated using, for example, a spectrophotometer (V-650, manufactured by JASCO Corporation).
First, the reflectance R (%) is measured for each wavelength λ to obtain a diffuse reflection spectrum. The scanning speed during measurement is 200 nm / min.
Next, the Kubelka-Munk function F (R) is calculated using the Kubelka-Munk equation for the diffuse reflectance spectrum obtained from the reflectance measurement. A relational expression between the reflectance R (%) and the Kubelka-Munk function F (R) is represented by the following expression.
F (R) = (1-R) ² / (2R)
When obtaining the band gap, there is a relational expression proposed by Tauc, Davis, Mott et al.
(Hνα) ^{(1 / n)} = A (hν−Eg) (1)
h: Planck's constant ν: Frequency α: Absorption coefficient Eg: Band gap A: Proportional constant n: Value determined by the type of transition of the sample Direct allowable transition n = 1/2
Indirect permissible transition n = 2
When the extinction coefficient α is replaced with the Kubelka-Munc function F (R), the above equation (1) is as follows.
(HνF (R)) ^{(1 / n)} = A (hν−Eg)
Note that there is a relationship of hν = 1239.7 / λ between hν (eV) and the wavelength λ (nm).
From the above results, create a graph with the horizontal axis hν and the vertical axis (hνF (R)) ² (direct permissible transition) or (hνF (R)) ^(1/2) (indirect permissible transition). When a tangent is drawn at the inflection point in the graph, the intersection of the horizontal axis and the tangent becomes a band gap.

  There is no restriction | limiting in particular as a preparation method of a said 1st plate-shaped object, According to the objective, it can select suitably, For example, a physical vapor deposition method, a chemical vapor deposition method, etc. are mentioned. Examples of the physical vapor deposition include vacuum vapor deposition and sputtering.

<Second plate-like body>
The second plate-like body is a plate-like body of a hydrogen generation photoexcitation material.

There is no restriction | limiting in particular as a shape of the surface of a said 2nd plate-shaped object, According to the objective, it can select suitably, For example, a polygon, circular, an ellipse etc. are mentioned. Examples of the polygon include a quadrangle. Examples of the quadrangle include a rectangle.
There is no restriction | limiting in particular as a magnitude | size of a said 2nd plate-shaped object, According to the objective, it can select suitably.
As the area of the surface portion of the second plate-like member is not particularly limited and may be selected accordingly and examples thereof include 1 mm ² 100 mm ^2.
There is no restriction | limiting in particular as thickness of the said 2nd plate-shaped object, According to the objective, it can select suitably, For example, 0.01 mm-1.0 mm etc. are mentioned.

The second plate-like body preferably has a groove in the surface portion of the second plate-like body. By doing so, the surface area is increased and the efficiency of the reduction of protons (H ⁺ ) to hydrogen is improved.
There is no restriction | limiting in particular as a shape and a magnitude | size of the said groove | channel, According to the objective, it can select suitably.

  The photochemical electrode may have one or a plurality of the second plate-like bodies.

<< Hydrogen generation photoexcitation material >>
In the hydrogen generation photoexcitation material, there is a redox potential of H ⁺ / H ₂ between the upper end of the valence band and the lower end of the conduction band.
The hydrogen generation photoexcitation material is a material that absorbs light in a specific range of wavelengths and excites electrons.
In order to achieve two-stage excitation, it is necessary that the upper end of the valence band of the hydrogen generation photoexcitation material is noble than the lower end of the conduction band of the oxygen generation photoexcitation material.

Examples of the hydrogen generation photoexcitation material include GaP, CdSe, CdS, and CuAlO ₂ .

  There is no restriction | limiting in particular as a band gap of the said hydrogen production | generation photoexcitation material, Although it can select suitably according to the objective, 1.8 eV-3.0 eV are preferable from the point that photoexcitation reaction is performed with visible light, 1 .8 eV to 2.5 eV is more preferable.

  There is no restriction | limiting in particular as a preparation method of a said 2nd plate-shaped object, According to the objective, it can select suitably, For example, a physical vapor deposition method, a chemical vapor deposition method, etc. are mentioned. Examples of the physical vapor deposition include vacuum vapor deposition and sputtering.

<Conductor>
The conductor electrically connects the first plate-like body and the second plate-like body.

  The material of the conductor is not particularly limited as long as it has conductivity, and can be appropriately selected according to the purpose. For example, silver (Ag), gold (Au), copper (Cu), platinum (Pt ), Palladium (Pd), tungsten (W), nickel (Ni), tantalum (Ta), bismuth (Bi), lead (Pb), indium (In), tin (Sn), zinc (Zn), titanium (Ti ), Aluminum (Al), or an alloy made of two or more metal species selected from these. Further, it may be a nanocarbon material such as carbon nanotube or graphene.

The material of the conductor is preferably a transparent conductive material. Examples of the transparent conductive material include tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), zinc oxide, indium oxide (In ₂ O ₃ ), and aluminum-doped zinc oxide (AZO). ), Metal oxides such as gallium-doped zinc oxide (GZO), tin oxide, zinc oxide-tin oxide system, indium oxide-tin oxide system, and zinc oxide-indium oxide-magnesium oxide system. Among these, fluorine-doped tin oxide (FTO) is preferable in terms of particularly high conductivity and translucency.

There is no restriction | limiting in particular as a shape of the said conductor, According to the objective, it can select suitably, A plate-like body, a thread-like body, etc. are mentioned.
There is no restriction | limiting in particular as a magnitude | size of the said conductor, According to the objective, it can select suitably.

Here, an example of the disclosed photochemical electrode will be described with reference to the drawings.
FIG. 3 is a schematic top view of an example of the disclosed photochemical electrode.
The photochemical electrode in FIG. 3 includes a plurality of first plate-like bodies 1, a plurality of second plate-like bodies 2, and a plurality of conductors 3. One first plate-like body 1 and one second plate-like body 2 are electrically connected by one conductor 3. In the photochemical electrode of FIG. 3, the plurality of first plate-like bodies 1 are further electrically connected to each other by the second conductor 4A. Further, the plurality of second plate-like bodies 2 are electrically connected by a third conductor 4B.
The first plate 1 is made of an oxygen generation photoexcitation material.
The second plate-like body 2 is made of a hydrogen generation photoexcitation material.

When light is irradiated to the photochemical electrode of FIG. 3, electrons (e ⁻ ) and holes (h ⁺ ) are generated in the oxygen generation photoexcitation material of the first plate 1. The holes oxidize the surrounding water and generate oxygen. At that time, electrons are generated. The oxidation of water is represented by the following formula (1).
H ₂ O + 2h ⁺ → 2H ⁺ + 1 / 2O ₂ Formula (1)
The generated electrons are supplied to the second plate-like body 2 through the conductor 3.
In the hydrogen generation photoexcitation material of the second plate-like body 2, when irradiated with light, electrons (e ⁻ ) and holes (h ⁺ ) are generated. The generated electrons reduce protons (H ⁺ ) to H ₂ . The reduction of proton is represented by the following formula (2). On the other hand, the holes disappear together with the electrons supplied to the second plate 2 via the conductor 3 (recombination).
H ⁺ + e ⁻ → 1 / 2H ₂ Formula (2)
When formula (1) and formula (2) are put together, the following formula (3) is obtained, and the phenomenon of formula (3) is observed in the entire photochemical electrode. That is, water decomposes to produce hydrogen and oxygen.
H ₂ O → H ₂ + 1 / 2O ₂ Formula (3)

  Here, normally, the resistance between the oxygen generation photoexcitation material and the hydrogen generation photoexcitation material is high. However, in the disclosed photochemical electrode, the resistance between the oxygen generation photoexcitation material and the hydrogen generation photoexcitation material can be reduced by connecting the oxygen generation photoexcitation material and the hydrogen generation photoexcitation material via a conductor. . Moreover, the oxygen generation photoexcitation material and the hydrogen generation photoexcitation material are each configured by a plate-like body. The plate-like body can be easily produced by a method such as physical vapor deposition or chemical vapor deposition, and can be easily connected to a conductor. Therefore, the disclosed photochemical electrode can easily form such a structure, and the control for obtaining the structure is also simple.

  Note that the presence of the second conductor 4A and the third conductor 4B makes it possible to collect the photocurrent generated in each portion in one place.

FIG. 4 is a schematic top view of another example of the disclosed photochemical electrode.
In the photochemical electrode of FIG. 4, the structure shown in FIG. 3 is arranged on one surface of the substrate 5.
In the photochemical electrode of FIG. 4, the first plate 1, the second plate 2, the conductor 3, the second conductor 4 </ b> A, and the third conductor 4 </ b> B are independently provided on the substrate 5. It can be easily produced by combining physical vapor deposition and photolithography. In addition, the conductor 3, the 2nd conductor 4A, and the 3rd conductor 4B can also be produced simultaneously, when it is the same material.

FIG. 5 is a schematic diagram of an example of the AA cross section of FIG.
In the schematic diagram of FIG. 5, the first plate 1 is disposed on the substrate 5 in contact with the substrate 5. In this example, although not shown, the conductor 3 and the second plate-like body 2 are also arranged in contact with the substrate 5.

FIG. 6 is a schematic diagram of another example of the AA cross section of FIG. 4.
In the schematic diagram of FIG. 6, the first plate-like body 1 is arranged on the substrate 5 via the conductor 3. In this example, although not shown, the second plate-like body 2 is also disposed on the substrate 5 via the conductor 3.

FIG. 7 is a schematic view of another example of the AA cross section of FIG.
In the schematic diagram of FIG. 7, the fourth conductor 6 is formed on the substrate 5, and the first plate-like body 5 is in contact with the fourth conductor 6 on the fourth conductor 6. Are arranged. Although not shown in this example, the conductor 3 and the second plate-like body 2 are also arranged in contact with the fourth conductor 6.

FIG. 8 is a schematic view of another example of the AA cross section of FIG.
In the schematic diagram of FIG. 8, the first plate 1 is disposed on the substrate 5 in contact with the substrate 5. In this example, although not shown, the conductor 3 and the second plate-like body 2 are also arranged in contact with the substrate 5. Further, a groove is formed on the surface of the first plate-like body 1. In this example, although not shown, a groove is also formed on the surface of the second plate-like body 2. Since the groove is formed on the surface of the first plate-like body 1, the surface area is increased and the efficiency of oxidation of water into oxygen is improved. Since the groove is formed on the surface of the second plate-like body 2, the surface area is increased, and the efficiency of proton reduction to hydrogen is improved.

FIG. 9 is a schematic top view of another example of the disclosed photochemical electrode.
In the photochemical electrode of FIG. 9, the photocurrent density of the oxygen-generating photoexcitation material constituting the first plate 1 is smaller than the photocurrent density of the hydrogen-generating photoexcitation material constituting the second plate 2.
Here, in the disclosed photochemical electrode, of the photoelectric effect in the first plate 1 and the photoelectric effect in the second plate 2, the smaller the photocurrent, the rate-limiting reaction of the formula (3). To do.
Therefore, in the photochemical electrode of FIG. 9, the area of the surface of the first plate 1 is larger than the area of the surface of the second plate 2. By doing so, the reaction of the formula (3) (that is, decomposition of water and generation of oxygen and hydrogen) can be performed efficiently.

FIG. 10 is a schematic top view of another example of the disclosed photochemical electrode.
In the photochemical electrode of FIG. 10, the photocurrent density of the hydrogen generation photoexcitation material constituting the second plate 2 is smaller than the photocurrent density of the oxygen generation photoexcitation material constituting the first plate 1.
Therefore, in the photochemical electrode of FIG. 10, the area of the surface of the second plate-like body 2 is made larger than the area of the surface of the first plate-like body 1. By doing so, the reaction of the formula (3) (that is, decomposition of water and generation of oxygen and hydrogen) can be performed efficiently.

FIG. 11 is a schematic cross-sectional view of another example of the disclosed photochemical electrode.
In the photochemical electrode of FIG. 11, a first plate-like body 1, a plate-like conductor 3, and a second plate-like body 2 are laminated on a substrate 5 in this order. The first plate-like body 1 and the second plate-like body 2 are electrically connected via a conductor 3.

FIG. 12 is a schematic cross-sectional view of another example of the disclosed photochemical electrode.
In the photochemical electrode of FIG. 12, the 4th conductor 6 is formed on the board | substrate 5, The 1st plate-shaped body 1, the plate-shaped conductor 3 on the 4th conductor 6, The second plate-like body 2 is laminated in this order. The plurality of second plate-like bodies 2 are electrically connected by a fifth conductor 4C.

  In the photochemical electrode of FIGS. 11 and 12, the substrate 5 is, for example, a glass substrate, and in the photochemical electrode of FIG. 12, the fourth conductor 6 and the fifth conductor 4C are transparent conductors. Light is emitted from both above and below. By doing so, both the first plate-like body 1 and the second plate-like body 2 are irradiated with light.

FIG. 13 is a schematic cross-sectional view of another example of the disclosed photochemical electrode.
In the photochemical electrode of FIG. 13, a first plate-like body 1, a plate-like conductor 3, and a second plate-like body 2 are laminated on a substrate 5 in this order.
In the photochemical electrode of FIG. 13, the photocurrent density of the oxygen-generating photoexcitation material constituting the first plate 1 is smaller than the photocurrent density of the hydrogen-generating photoexcitation material constituting the second plate 2.
Therefore, in the photochemical electrode of FIG. 13, the area of the surface of the first plate 1 is made larger than the area of the surface of the second plate 2. By doing so, the reaction of the formula (3) (that is, decomposition of water and generation of oxygen and hydrogen) can be performed efficiently.

FIG. 14 is a schematic cross-sectional view of another example of the disclosed photochemical electrode.
In the photochemical electrode of FIG. 14, the second plate-like body 2, the plate-like conductor 3, and the first plate-like body 1 are laminated on the substrate 5 in this order.
In the photochemical electrode of FIG. 14, the photocurrent density of the hydrogen generation photoexcitation material constituting the second plate 2 is smaller than the photocurrent density of the oxygen generation photoexcitation material constituting the first plate 1.
Therefore, in the photochemical electrode of FIG. 14, the area of the surface of the second plate-like body 2 is made larger than the area of the surface of the first plate-like body 1. By doing so, the reaction of the formula (3) (that is, decomposition of water and generation of oxygen and hydrogen) can be performed efficiently.

<Application example>
The photochemical electrode is useful as an anode electrode used for an anode of a carbon dioxide reduction device that performs artificial photosynthesis.
The carbon dioxide reduction device has the photochemical electrode that is an anode electrode, a proton permeable membrane, and a cathode electrode in this order, and further includes other members as necessary.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
<Production of photochemical electrode>
A photochemical electrode shown in FIG. 15 was produced using the following materials.
Substrate: glass substrate 5 on which an FTO film as the fourth conductor 6 is formed
・ Oxygen-generating photoexcitation material: WO ₃
・ Hydrogen generation photoexcitation material: GaP
-Conductor 3: Gold-Second conductor 4A: Gold-Third conductor 4B: Gold

First, a WO ₃ film is formed by sputtering on the FTO film of the glass substrate 5 on which the FTO film as the fourth conductor 6 is formed, and patterned by photolithography. Three first plate-like bodies 1 having a thickness of 10 mm and a thickness of 0.5 mm were produced in an arrangement as shown in FIG.
Subsequently, GaP is formed by sputtering on the FTO film of the glass substrate 5 on which the FTO film as the fourth conductor 6 is formed, and is patterned by photolithography to obtain a width of 2 mm and a long length. Three second plate-like bodies 2 having a thickness of 10 mm and a thickness of 0.5 mm were produced in an arrangement as shown in FIG. The distance between the first plate 1 and the second plate was 4 mm.
Subsequently, gold is deposited on the FTO film of the glass substrate 5 on which the FTO film as the fourth conductor 6 is formed by a vacuum deposition method and patterned by a photolithography method. Three conductors 3 having a length of 4 mm and a thickness of 0.004 mm, a second conductor 4A having a width of 1 mm and a thickness of 0.004 mm, and a third conductor 4B having a width of 1 mm and a thickness of 0.004 mm are illustrated. Three were prepared in the arrangement as shown in FIG. 15 to obtain a photochemical electrode 1-A. A schematic cross-sectional view of the photochemical electrode 1-A is shown in FIG.

<Groove formation>
Subsequently, a groove having a width of 0.6 mm as shown in FIG. 17 is formed in the length direction of the surfaces of the first plate 1 and the second plate 2 of the photochemical electrode 1-A. Photochemical electrode 1-B was obtained.
The method for forming the groove is as follows.
Etching using hydrofluoric acid was performed after the mask material was disposed at a location other than the location where the groove was formed.

<Confirmation of gas generation>
The produced photochemical electrodes 1-A and 1-B were placed in a sealed environment of 20 to 25 ° C. and 30 to 70% RH, respectively. Then, from the upper surface of the photochemical electrode, pseudo-sunlight AM-1.5 (Asahi Spectroscopy, Solar Simulator, HAL-320) was irradiated at 100 mW / cm ² to examine the generation amounts of H ₂ and O ₂ . The generation of H ₂ and O ₂ was confirmed using gas chromatography (manufactured by Shimadzu Corporation, Tracera).

As a result, the generation of gas was confirmed as follows.
Photochemical electrode 1-A:
H ₂ : 3.2 μmol / m ² / h
O ₂ : 1.5 μmol / m ² / h
Photochemical electrode 1-B:
H ₂ : 3.6 μmol / m ² / h
O ₂ : 1.8 μmol / m ² / h

Gas generation can be confirmed in both photochemical electrodes 1-A and 1-B, and the oxygen-generating photoexcitation material as the first plate and the hydrogen-generating photoexcitation material as the second plate have low resistance. It was confirmed that it was connected with.
In addition, the formation of grooves in the first plate and the second plate improved the efficiency of water decomposition and oxygen and hydrogen generation.

<Current measurement>
About each of produced photochemical electrode 1-A and 1-B, the electric current which generate | occur | produces by light irradiation was measured.
The produced photochemical electrodes 1-A and 1-B were each immersed in a 1M KNO ₃ aqueous solution. And from the upper surface of the photochemical electrode, pseudo-sunlight AM-1.5 (Asahi Spectroscopy, solar simulator, HAL-320) was irradiated at 100 mW / cm ² to measure the generated current.
The current was measured using a potentiostat (manufactured by Toyo Technica, SI1280B), and a reference electrode, a working electrode, and a counter electrode were installed to evaluate the current value.

As a result, the generation of current was confirmed as follows.
Photochemical electrode 1-A (1.23V): 0.9 × 10 ⁻⁶ A
Photochemical electrode 1-B (1.23V): 2.6 × 10 ⁻⁶ A

(Example 2)
<Production of photochemical electrode>
The photochemical electrode shown in FIG. 18 was produced using the following materials.
Substrate: glass substrate 5 on which an FTO film as the fourth conductor 6 is formed
・ Oxygen-generating photoexcitation material: WO ₃
・ Hydrogen generation photoexcitation material: GaP
-Conductor 3: Gold-Fifth conductor 4C: Transparent conductive material

First, on the FTO film of the glass substrate 5 on which the FTO film as the fourth conductor 6 is formed, WO ₃ is formed by a sputtering method and patterned by a photolithography method to obtain 10 mm × 10 mm, Four first plate-like bodies 1 having a thickness of 0.005 mm were produced in an arrangement as shown in FIG.
Subsequently, a conductor 3 having a size of 4 mm × 4 mm and a thickness of 0.004 mm was formed on each of the four first plate-like bodies 1 by forming a gold film by vacuum deposition and patterning by photolithography. .
Subsequently, GaP was formed into a film by a sputtering method, and patterned by a photolithography method, thereby producing second plates 2 having a size of 4 mm × 4 mm and a thickness of 0.005 mm on the four conductors 3, respectively.
Subsequently, the transparent resin was filled in the gap, and a transparent conductive material was formed by 4 μm by a sputtering method so as to straddle between the two second plate-like bodies 2, thereby producing a fifth conductor 4 </ b> C.
Thus, a photochemical electrode was obtained.

<Confirmation of gas generation>
The produced photochemical electrode was placed in a sealed environment of 20 to 25 ° C. and 30 to 70% RH. Then, from the upper and lower surfaces of the photochemical electrode, pseudo-sunlight AM-1.5 (manufactured by Asahi Spectroscope, solar simulator, HAL-320) is irradiated at 100 mW / cm ² to examine the generation amount of H ₂ and O _2. It was. The generation of H ₂ and O ₂ was confirmed using gas chromatography (manufactured by Shimadzu Corporation, Tracera).
As a result, the generation of gas was confirmed as follows.
H ₂ : 1.8 μmol / m ² / h
O ₂ : 0.8 μmol / m ² / h

<Current measurement>
About the produced photochemical electrode, the electric current which generate | occur | produces by light irradiation was measured.
Each of the produced photochemical electrodes was immersed in a 1M KNO ₃ aqueous solution. And from the upper surface and the lower surface of the photochemical electrode, pseudo sunlight AM-1.5 (Asahi Spectroscopy, solar simulator, HAL-320) was irradiated at 100 mW / cm ² to measure the generated current.
The current was measured using a potentiostat (manufactured by Toyo Technica, SI1280B), and a reference electrode, a working electrode, and a counter electrode were installed to evaluate the current value.
As a result, generation of a current of 2.2 × 10 ⁻⁶ A (1.23 V) was confirmed.

Regarding the above embodiment, the following additional notes are disclosed.
(Appendix 1)
There is a redox potential of O ₂ / H ₂ O between the upper end of the valence band and the lower end of the conduction band, and it is made of an oxygen-generating photoexcited material that absorbs and excites light, and has a plate shape. A plate-like body;
A _second plate having a plate-like shape made of a hydrogen-generating photoexcited material that has a redox potential of H ⁺ / H ₂ between the upper end of the valence band and the lower end of the conduction band and absorbs and excites light. And
A conductor that electrically connects the first plate-like body and the second plate-like body;
A photochemical electrode comprising:
(Appendix 2)
The photochemical electrode according to supplementary note 1, wherein the first plate-like body and the second plate-like body are arranged on the same plane.
(Appendix 3)
The photochemical electrode according to supplementary note 2, wherein the first plate-like body has a groove and the second plate-like body has a groove.
(Appendix 4)
The photochemical electrode according to supplementary note 1, wherein the first plate-like body and the second plate-like body are laminated with the plate-like conductor interposed therebetween.
(Appendix 5)
The photocurrent density of the oxygen-generating photoexcitation material constituting the first plate is smaller than the photocurrent density of the hydrogen-generating photoexcitation material constituting the second plate,
The area of the surface of the first plate-like body is larger than the area of the surface of the second plate-like body,
The photochemical electrode according to any one of appendices 1 to 4.
(Appendix 6)
A photocurrent density of the hydrogen generating photoexcitation material constituting the second plate is smaller than a photocurrent density of the oxygen generating photoexcitation material constituting the first plate,
The area of the surface of the second plate-like body is larger than the area of the surface of the first plate-like body,
The photochemical electrode according to any one of appendices 1 to 4.

DESCRIPTION OF SYMBOLS 1 1st plate-like body 2 2nd plate-like body 3 Conductor 4A 2nd conductor 4B 3rd conductor 4C 5th conductor 5 Substrate 6 4th conductor

Claims (3)

There is a redox potential of O ₂ / H ₂ O between the upper end of the valence band and the lower end of the conduction band, and it is made of an oxygen-generating photoexcited material that absorbs and excites light, and has a plate shape. A plate-like body;
A _second plate having a plate-like shape made of a hydrogen-generating photoexcited material that has a redox potential of H ⁺ / H ₂ between the upper end of the valence band and the lower end of the conduction band and absorbs and excites light. And
A conductor that electrically connects the first plate-like body and the second plate-like body;
A photochemical electrode comprising:   The photochemical electrode according to claim 1, wherein the first plate-like body and the second plate-like body are arranged on the same plane.   The photochemical electrode according to claim 1, wherein the first plate-like body and the second plate-like body are laminated with the plate-like conductor interposed therebetween.