JP7255128B2 - PHOTOEXCITATION MATERIAL AND MANUFACTURING METHOD THEREOF, PHOTOChemical ELECTRODE, AND PHOTOELECTROCHEMICAL REACTION DEVICE - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photoexcitation material, a method for producing the same, a photochemical electrode, and a photoelectrochemical reaction device.

Since global warming has been recognized, how to reduce carbon dioxide emitted into the atmosphere due to industrial activities has become an important issue.

In recent years, artificial photosynthesis technology has attracted attention as a method of reducing carbon dioxide in the atmosphere. Artificial photosynthesis technology is roughly divided into light reactions in which photoexcitation materials are irradiated with visible light to generate electrons and protons, and dark reactions in which carbon dioxide and protons undergo multi-electron reduction to generate organic substances.

As the photoexcitation material used in the light reaction, it is necessary to use a material that satisfies all of the following four conditions. The first point is that electrons can be excited by irradiation with visible light. The second point is that water can be oxidized and reduced. The third point is that the excited electrons can form a high photocurrent. Fourth, it is excellent in oxidation-reduction resistance in water.
An oxynitride material has been proposed as a material that satisfies these conditions (for example, Patent Document 1).

JP 2017-160524 A

It is particularly important for a photoexcitation material to be able to stably generate a photocurrent even when it is irradiated with visible light multiple times. It's going to be
However, when an oxynitride is used as a photoexcitation material, the photocurrent decreases when the visible light irradiation is performed multiple times. Therefore, it cannot be said that the reliability is sufficient.

An object of the present invention is to provide a photoexcitable material whose properties are unlikely to deteriorate even after repeated use, a method for producing the same, a photochemical electrode using the photoexcitable material, and a photoelectrochemical reaction device.

Means for solving the above problems are as follows. Namely
In one aspect, the photoexcitation material comprises:
a photoexcitable material portion containing an oxynitride that absorbs and excites light;
a co-catalyst site containing a co-catalyst disposed in contact with the photoexcitable material site;
have

Also, in one aspect, the method for producing a photoexcitable material comprises:
a photoexcitable material portion containing an oxynitride that absorbs and excites light;
a co-catalyst site containing a co-catalyst disposed in contact with the photoexcitable material site;
A method for producing a photoexcitation material for producing a photoexcitation material having
disposing the oxynitride to form a photoexcitable material site;
forming the promoter site by heating the photoexcitable material site and the promoter site precursor in a state where the promoter site precursor is disposed on at least a portion of the surface of the photoexcitable material site;
including.

Also, in one aspect, the photochemical electrode comprises:
a conductor;
a photoexcitable material disposed in contact with the conductor;
The photoexcitation material includes a photoexcitation material portion containing an oxynitride that is excited by absorbing light, and a cocatalyst portion containing a cocatalyst arranged in contact with the photoexcitation material portion,
have

Also, in one aspect, the photoelectrochemical reaction device comprises:
a counter electrode;
a photochemical electrode connected to the counter electrode via a lead;
a translucent container for immersing the counter electrode and the photochemical electrode in water;
has
the photochemical electrode comprises an electrical conductor and a photoexcitable material disposed in contact with the electrical conductor;
The photoexcitation material includes a photoexcitation material portion containing an oxynitride that is excited by absorbing light, and a cocatalyst portion containing a cocatalyst arranged in contact with the photoexcitation material portion,
have

ADVANTAGE OF THE INVENTION According to the photoexcitation material of this invention, the above-mentioned problems in the past can be solved, and the photoexcitation material which is hard to deteriorate in a characteristic even if it is used repeatedly can be provided.
ADVANTAGE OF THE INVENTION According to the manufacturing method of the photoexcitable material of this invention, the above-mentioned conventional problems can be solved, and the manufacturing method of the photoexcitable material which does not deteriorate easily even if it uses it repeatedly can be provided.
ADVANTAGE OF THE INVENTION According to the photochemical electrode of this invention, the above-mentioned conventional problems can be solved, and the photochemical electrode which does not deteriorate easily even if it uses it repeatedly can be provided.
INDUSTRIAL APPLICABILITY According to the photoelectrochemical reaction device of the present invention, it is possible to solve the above-mentioned conventional problems, and to provide a photoelectrochemical reaction device whose characteristics are unlikely to deteriorate even after repeated use.

FIG. 1 is a schematic cross-sectional view of an example of the photoexcitation material of the present invention. FIG. 2 is a structural diagram of a film forming apparatus used for film forming by the aerosol deposition method. FIG. 3A is a diagram for explaining an example of the method for producing the photoexcitation material of the present invention. FIG. 3B is a diagram for explaining an example of the method for producing the photoexcitation material of the present invention. FIG. 3C is a diagram for explaining an example of the method for producing the photoexcitation material of the present invention. FIG. 4 is a schematic diagram of an example of the photoelectrochemical reaction device of the present invention. 5 is a diagram summarizing the photocurrent measurement results of Example 1 and Comparative Example 1. FIG.

(Photoexcitation material)
The photoexcitation material of the present invention has a photoexcitation material portion, a cocatalyst portion, and, if necessary, other portions such as a support.

The inventors of the present invention focused on an oxynitride material as a material to be used for the photoexcitation material portion. Oxynitrides are known to generate high photocurrents when used as photoexcitation materials. However, oxynitrides have the property of decreasing the photocurrent with repeated use. It is believed that this is due to elimination of nitrogen atoms in crystals of the oxynitride. For example, when SrNbO ₂ N is used as the oxynitride, the composition is SrNbO _2.03 N _0.91 after three measurements. That is, about 10% of nitrogen is desorbed.
When the oxynitride generates photocurrent, oxygen is generated and the oxygen concentration in the oxynitride increases. It is presumed that the increased oxygen expels the nitrogen in the oxynitride, thereby promoting the desorption of nitrogen.

In addition, not only oxynitrides, but also photoexcitation materials are irradiated with light, and when high-energy electrons in the photoexcitation material are excited to the conduction band by the energy of the irradiated light, the electrons escape to the valence band. Oxidative holes are generated. However, when the photoexcited material is repeatedly used, a phenomenon occurs in which the generated holes recombine with the oxygen generated by the photoexcited reaction, and the holes disappear. As a result, repeated use of the photoexcitable material causes a decrease in photocurrent.

Therefore, the present inventors have investigated a photoexcitation material whose properties are less likely to deteriorate even after repeated use. As a result, they paid attention to arranging the co-catalyst so as to be in contact with the oxynitride. By arranging the promoter in contact with the oxynitride, it is possible to suppress an increase in oxygen concentration in the oxynitride, prevent desorption of nitrogen, and prevent recombination of holes and electrons. As a result, the present inventors have found that the decrease in photocurrent can be suppressed, and have completed the present invention.

<Photoexcitation material part>
The photoexcitable material portion contains an oxynitride.
The photoexcitable material portion is preferably composed of the oxynitride itself.

<<Oxynitride>>
Oxynitrides have the property of being excited by absorbing light.
Examples of oxynitrides include BaTaO ₂ N, BaNbO ₂ N, SrNbO ₂ N, LaTiO 2 N, SrTaO ₂ N, CaNbO ₂ N, CaTaO ₂ N, LaZrO ₂ N, PrTaON _{2 ,} TaON, NbON, and GaN-ZnO. system and the like.

The shape of the photoexcitation material portion is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include a flat plate shape.
The size of the photoexcitation material portion is not particularly limited, and can be appropriately selected according to the purpose.

<Promoter site>
The cocatalyst site contains a cocatalyst.
A promoter site is disposed in contact with the photoexcitable material site.
The promoter site may or may not cover the entire surface of the photoexcitable material site, and the boundary with the photoexcitable material site may be sharp or indistinct.

<<Co-catalyst>>
Metal oxides are preferred as promoters. Examples of metal oxides include IrO ₂ , RuO ₂ , CoO ₂ and CeO ₂ .
In addition _, there is _a preferable composition combination of the co _- catalyst and the _oxynitride . ₂ is preferred.

The content of the co-catalyst is not particularly limited and can be appropriately selected according to the purpose, but is preferably 4% by mass to 6% by mass with respect to the mass of the photoexcitable material portion.

The co-catalyst site may have a metal that constitutes a metal oxide that is a co-catalyst, in addition to the co-catalyst. Such metals include, for example, Ir, Ru, Co, Ce, and the like.

The shape of the co-catalyst site is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include a flat plate shape.
The size of the co-catalyst site is not particularly limited and can be appropriately selected according to the purpose.

<Other parts>
Other sites include, for example, a support.
The support supports the photoexcitable material sites and the promoter sites.
The support is, for example, placed in contact with the photoexcitable material site.
Examples of the material of the support include insulators such as glass and organic resins.
The shape and size of other parts are not particularly limited and can be appropriately selected according to the purpose.

An example of the photoexcitation material of the present invention will now be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of an example of the photoexcitation material of the present invention.
The photoexcitable material 1 of FIG. 1 has a photoexcitable material portion 2 and a promoter portion 3 in contact with the photoexcitable material portion 2 . The photoexcitable material portion 2 may be supported by a support such as a glass substrate.

(Method for producing photoexcitation material)
The method for producing a photoexcitable material of the present invention is a method for producing the aforementioned photoexcitable material.
The method for producing a photoexcitable material includes a step of forming a photoexcitable material portion (hereinafter sometimes abbreviated as a “photoexcitable material portion forming step”) and a step of forming a cocatalyst portion (hereinafter, “a cocatalyst portion forming step”). may be abbreviated as) and
The method for producing a photoexcitable material further includes other steps such as a support formation step, if necessary.

<Photoexcitation material site forming step>
The photoexcitation material portion forming step is a step of disposing an oxynitride.
As the oxynitride, those described above can be used.
The photoexcitable material portion forming step is not particularly limited as long as the oxynitride can be arranged in a desired form, and can be appropriately selected according to the purpose. (hereinafter sometimes referred to as “NPD film formation”).

<<NPD film formation>>
Aerosol deposition is sometimes called nanoparticle deposition (NPD).
Nanoparticle deposition (NPD) is a method introduced in Documents 1 to 3 below.
Reference 1: Imanaka, Y.; , Amada, H.; & Kumasaka, F.; Dielectric and insulating properties of embedded capacitor for flexible electronics prepared by aerosol-type nanoparticle deposition. Jpn. J. Appl. Phys. 52, 05DA02 (2013).
Document 2: Imanaka, Y.; et al. , Nanoparticulated dense and stress-free ceramic thick film for material integration. Adv. Eng. Mater. 15, 1129-1135 (2013).
Reference 3: Imanaka, Y.; , Amada, H.; , Kumasaka, F.; , Awaji, N.L. & Kumamoto, A. , Nanoparticulate BaTiO ₃ film produced by aerosol-type nanoparticle deposition. J. Nanopart. Res. 18, 102 (2016).
In nanoparticle deposition (NPD), an aerosol in which raw material particles are dispersed in a gas is sprayed from a nozzle toward a substrate, and the aerosol collides with the substrate surface to form a film made of the raw material particles. It is a method of forming on a base material.

More specifically, the NPD is a method of producing a film made of an inorganic material as follows.
In a system that is continuously decompressed by a vacuum pump, raw material particles, which are inorganic materials, form an aerosol and are transported together with a gas stream. The conveyed raw material particles are crushed while colliding with each other in the nozzle. In the raw material particles, while maintaining the crystallinity inside the raw material particles, part of the crystal structure on the surface of the raw material particles is distorted, and the surface energy state of each raw material particle increases. When the crushed raw material particles are deposited on the substrate, the raw material particles recombine with each other due to the action (cohesive force) that stabilizes the unstable surface portions of the raw material particles in a high energy state. As a result, a dense nanoparticle aggregate structure film is obtained on the substrate at room temperature. Also, when the film is annealed, the optimum sintering temperature can be lowered to 500° C. or more because the inside of the film is composed of nanoparticles.

An example of the aerosol deposition method will now be described with reference to the drawings.
FIG. 2 is a structural diagram of an example of a film forming apparatus used for film forming by the aerosol deposition method.
The aerosol deposition film forming apparatus has an aerosol chamber 910 and a film forming chamber 920 . An aerosol chamber 910 contains fine particles 911 of a film-forming material, and is connected via a pipe 960 to a gas cylinder 930 containing a carrier gas such as He, N ₂ , or Ar. The aerosol chamber 910 and the film formation chamber 920 are connected by a pipe 941 , and a nozzle 921 is provided at the end of the pipe 941 inside the film formation chamber 920 . In the film forming chamber 920, a stage 922 is provided on the side facing the opening of the nozzle 921, and a substrate 923 on which a film is formed is placed on the stage 922. FIG. The inside of this film formation chamber 920 can be evacuated to a vacuum, and a mechanical booster pump 943 and a vacuum pump 944 are connected via a pipe 942 . The aerosol chamber 910 is connected to a pipe 942 via a pipe 945 and a valve (not shown) so that the inside of the aerosol chamber 910 can be evacuated. In addition, in the area where the aerosol chamber 910 is installed, there is a mechanism for vibrating the aerosol chamber 910 in order to prevent the particles of the material to be deposited from solidifying in the aerosol chamber 910 or to prevent the particles from being biased during the deposition. A vibrator 950 is provided.

In this film forming apparatus, when film formation is performed by the aerosol deposition method, the inside of the film forming chamber 920 is evacuated by the mechanical booster pump 943 and the vacuum pump 944, and then the carrier gas is introduced into the aerosol chamber 910 from the gas cylinder 930. supply. In the aerosol chamber 910, the fine particles of the material to be deposited are picked up by the supplied carrier gas, and the fine particles of the material to be deposited are transported to the nozzle 921 in the deposition chamber 920 through the pipe 941 together with the carrier gas. . Thereafter, from the nozzle 921, fine particles of the material to be deposited are ejected together with the carrier gas toward the substrate 923, and the fine particles ejected from the nozzle 921 are deposited on the surface of the substrate 923, thereby forming a film. .

<Promoter Site Forming Step>
The step of forming a promoter site includes a step of heating the photoexcitable material site and the precursor of the promoter site in a state where the precursor of the promoter site is disposed on at least a portion of the surface of the photoexcitable material site.
The method of disposing the precursor of the co-catalyst site is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include the aforementioned NPD and sputtering deposition.

The heating of the photoexcitable material portion and the precursor of the promoter portion, also called annealing, is performed for grain growth of the oxynitride contained in the photoexcitable material portion. During annealing, some of the oxygen in the oxynitride is transferred to the cocatalyst precursor and at least a portion of the cocatalyst precursor is oxidized to form cocatalyst sites.
The co-catalyst site may be in a state in which co-catalyst and co-catalyst precursor are mixed.

The heating temperature during annealing is not particularly limited as long as it is a temperature at which at least a part of the cocatalyst precursor is oxidized, and can be appropriately selected according to the purpose. or 500°C to 650°C.
The heating time is not particularly limited as long as it is a time that at least part of the cocatalyst precursor is oxidized, and can be appropriately selected according to the purpose. 10 minutes to 1 hour.

<<Cocatalyst Precursor>>
The co-catalyst precursor is not particularly limited as long as it can receive oxygen desorbed from the oxynitride and exhibit a function as a co-catalyst, and can be appropriately selected according to the purpose. A metal that constitutes Such metals include Ir, Ru, Co, Ce, and the like.

Here, the method for producing the photoexcitable material of the present invention will be described with reference to the drawings.
3A to 3C are diagrams for explaining an example of a method for producing a photoexcitation material.
First, as shown in FIG. 3A, a photoexcitable material portion 2 containing oxynitride is produced. The photoexcitable material portion 2 can be formed, for example, by an aerosol deposition method.
Subsequently, as shown in FIG. 3B, a precursor 4 of the promoter site is placed on the photoexcitable material site 2 . The precursor 4 of the co-catalyst site is, for example, a metal film that constitutes a metal oxide that is a co-catalyst, and can be formed by an aerosol deposition method.
Subsequently, the laminate shown in FIG. 3B is heated under vacuum conditions or an inert gas atmosphere. By heating, part of the oxygen in the oxynitride contained in the photoexcitable material portion 2 moves to the precursor 4 (metal film) portion of the promoter portion, and the precursor 4 (metal film) portion of the promoter portion film) is oxidized.
As a result of the oxidation of the promoter site precursor 4 (metal film), the promoter site 3 containing the metal oxide promoter is formed (FIG. 3C).

(Photochemical electrode)
The photochemical electrode of the present invention has at least a conductor and a photoexcitation material, and if necessary, other members such as a support.
The photoexcitation material is the aforementioned photoexcitation material.

<Conductor>
The conductor is not particularly limited as long as it has conductivity, and can be appropriately selected according to the purpose.

Examples of materials for the conductor include metals, alloys, and metal oxides.
Metals include platinum (Pt), palladium (Pd), gold (Au), silver (Ag), copper (Cu), tungsten (W), nickel (Ni), tantalum (Ta), bismuth (Bi), lead (Pb), indium (In), tin (Sn), zinc (Zn), titanium (Ti), aluminum (Al), and the like.
Examples of alloys include alloys composed of two or more of the metals listed above as examples of metals.
Examples of metal oxides include tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), zinc oxide, indium oxide ( _{In2O3 )} , and aluminum-doped zinc oxide (AZO). , gallium-doped zinc oxide (GZO), tin oxide, zinc oxide-tin oxide system, indium oxide-tin oxide system, zinc oxide-indium oxide-magnesium oxide system, and the like.

Here, the conductivity means, for example, a volume resistivity in the range of 10 ² Ωcm or less.

The shape of the conductor is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a flat plate shape.
The size of the conductor is not particularly limited and can be appropriately selected according to the purpose.

Examples of the conductor include a deposited film. The deposited film is formed by, for example, physical vapor deposition, chemical vapor deposition, or the like. Examples of physical vapor deposition include vacuum deposition and sputtering.

(Photoelectrochemical reaction device)
The photoelectrochemical reaction device of the present invention has at least a counter electrode, a photochemical electrode, and a translucent container, and optionally other members.

The counter electrode is the cathode.
The photochemical electrode is the photochemical electrode of the present invention and is the anode.
The photochemical electrode is connected to the counter electrode via a wire.
A translucent container is a container for immersing a counter electrode and a photochemical electrode in water. The material of the translucent container is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include plastic, glass, quartz and the like.

An example of the photoelectrochemical reaction device will be described with reference to FIG.
The photoelectrochemical reaction device includes a photochemical electrode 10 that is an anode, a counter electrode 15 that is a cathode, a conductive wire 16 that connects the photochemical electrode 10 and the counter electrode 15, and a translucent material that accommodates the photochemical electrode 10 and the counter electrode 15. and a container 17 . The translucent container 17 contains water 18 , and the photochemical electrode 10 and the counter electrode 15 are immersed in the water 18 .
For the counter electrode 15, for example, a Pt metal electrode that exhibits high catalytic activity for generating hydrogen is used.

The irradiation light 19 that causes the photolysis reaction of water is, for example, mixed light containing ultraviolet light.

Then, when the photochemical electrode 10 is irradiated with the irradiation light 19, in the photoexcitation material 13 of the photochemical electrode 10, electrons in the valence band are excited and transition to the conduction band, and holes are formed in the valence band. . Electrons excited by the irradiation light 19 are directed toward the conductor 12, and holes are directed toward the surface. On the surface of the photoexcitation material 13, when OH ⁻ ions are present in water, the holes cause an oxidation reaction on the surface to generate oxygen O ₂ . On the other hand, the electrons move to the counter electrode 15 connected by the conducting wire 16, and on the surface of the counter electrode 15, if H ^{2 +} ions are present in water, the electrons cause a reduction reaction to generate hydrogen H ₂ .
Here, the presence of the co-catalyst 14 contained in the co-catalyst site of the photo-excitation material 13 promotes the photo-excitation of the photo-excitation material 13, resulting in an increase in photocurrent, resulting in an increase in light utilization efficiency.

The disclosed technology will be described below, but the disclosed technology is not limited to the following examples.

(Production example 1)
<Production of oxynitride (SrNbO ₂ N)>
SrCO ₃ and Nb ₂ O ₅ were mixed at SrCO ₃ :Nb ₂ O ₅ =1:1 (molar ratio) and reacted in an ammonia gas stream at 1,173 K (about 900° C.) for 100 hours to obtain a purity of A SrNbO ₂ N powder having an average particle size of 1 μm and 99.9% or more was obtained.

(Comparative example 1)
<Oxynitride>
The SrNbO ₂ N powder having an average particle size of 1 μm produced in Production Example 1 was used as the raw material powder.

<Preparation of photochemical electrode>
The nanoparticle deposition (NPD) apparatus used consists of an aerosol generation system, a deposition chamber, and a vacuum system. No heat source is provided in this deposition apparatus.
The SrNbO ₂ N powder produced in Production Example 1 was set in the container of the aerosol generation system and vibrated at 10 Hz. Then, helium with a gas pressure of 0.2 MPa and a purity of 99.9% was introduced into the container to generate an aerosol. The pressure in the deposition chamber was controlled below 10 Pa using a mechanical booster and a vacuum pump. The generated aerosol was transported to a nozzle within the deposition chamber.
The aerosol was emitted from the nozzle and made to collide with the FTO substrate (glass on which a fluorine-doped tin oxide thin film was formed) placed in the deposition chamber for 10 minutes. The gas flow velocity at that time was 50 m/sec to 100 m/sec. The gas flow velocity was calculated from the gas flow rate at the portion passing through the nozzle opening.
As a result, a photoexcitation material portion (average thickness of 2 μm) made of SrNbO ₂ N was formed on the FTO substrate at room temperature.

Subsequently, annealing was performed at 600° C. for 30 minutes in a nitrogen gas atmosphere (nitrogen gas concentration 100%).
As described above, a photochemical electrode of Comparative Example 1 was obtained.

(Example 1)
<Preparation of photochemical electrode having photoexcitation material>
The nanoparticle deposition (NPD) apparatus used consists of an aerosol generation system, a deposition chamber, and a vacuum system. No heat source is provided in this deposition apparatus.
The SrNbO ₂ N powder produced in Production Example 1 was set in the container of the aerosol generation system and vibrated at 10 Hz. Then, helium with a gas pressure of 0.2 MPa and a purity of 99.9% was introduced into the container to generate an aerosol. The pressure in the deposition chamber was controlled below 10 Pa using a mechanical booster and a vacuum pump. The generated aerosol was transported to a nozzle within the deposition chamber.
The aerosol was emitted from the nozzle and made to collide with the FTO substrate (glass on which a fluorine-doped tin oxide thin film was formed) placed in the deposition chamber for 10 minutes. The gas flow velocity at that time was 50 m/sec to 100 m/sec. The gas flow velocity was calculated from the gas flow rate at the portion passing through the nozzle opening.
As a result, a photoexcitation material portion (average thickness of 2 μm) made of SrNbO ₂ N was formed on the FTO substrate at room temperature.

Subsequently, an Ir film was formed using Ir (iridium), which is a precursor of the co-catalyst site, on the entire surface of one side of the photoexcitation material site using the film formation technique of nanoparticle deposition as shown in FIG. .
The Ir film was formed so as to have an amount of 5% by mass with respect to SrNbO ₂ N.
As the raw material Ir, Ir particles manufactured by Kojundo Chemical Laboratory Co., Ltd. were used.

Subsequently, annealing is performed at 600° C. for 30 minutes in a nitrogen gas atmosphere (nitrogen gas concentration 100%) to oxidize Ir to form a cocatalyst (IrO ₂ ), and a cocatalyst site containing the cocatalyst (IrO ₂ ). formed.
As described above, a photochemical electrode of Example 1 was obtained.

<Measurement of photocurrent>
A three-electrode electrochemical cell was used for the measurement. A platinum foil was used as a counter electrode, and an Ag/AgCl (saturated KCl aqueous solution) electrode was used as a reference electrode. A 0.5 M Na ₂ SO ₄ aqueous solution (pH=6.0 to 6.5) was used as the electrolytic solution, and dissolved oxygen was degassed by passing nitrogen gas for 30 minutes in advance. The potential value was corrected to the standard hydrogen electrode reference value (vs. NHE) at pH=0 each time, and the value is shown.
Photocurrent was measured using a solar simulator (HAL-320, manufactured by Asahi Spectroscopy Co., Ltd.) for simulated sunlight, and a potentiostat (SI 1280, manufactured by Solartron Co., Ltd.) for potential measurement. The illuminance of the solar simulator was 100 mW/cm ² and the bias voltage was −1 to 1.5 V with respect to the reference electrode.
Photocurrents of the photochemical electrodes prepared in Example 1 and Comparative Example 1 were measured three times. In addition, the measurement of 3 times was performed continuously. FIG. 5 shows the second and third photocurrent values of Example 1 and Comparative Example 1, where the first photocurrent value is 1. As shown in FIG.

When the photochemical electrode having the photoexcitation material of Example 1 was used, the photocurrent in the third measurement was about 0.55 times as large as in the first measurement. On the other hand, when the photochemical electrode having the photoexcitation material of Comparative Example 1 was used, the photocurrent in the third measurement was about 0.25 times as large as in the first measurement. From these results, it has become clear that the photoexcitation material of the present invention does not easily lose its properties even after repeated use.

Further, the following notes are disclosed.
(Appendix 1)
a photoexcitable material portion containing an oxynitride that absorbs and excites light;
a co-catalyst site containing a co-catalyst disposed in contact with the photoexcitable material site;
A photoexcitation material characterized by comprising:
(Appendix 2)
The photoexcitation material according to appendix 1, wherein the oxynitride contains at least one of BaTaO ₂ N, BaNbO ₂ N, SrNbO ₂ N, and LaTiO ₂ N.
(Appendix 3)
3. The photoexcitation material according to any one of Appendices 1 to 2, wherein the promoter contains at least one of IrO ₂ , RuO ₂ , CoO ₂ and CeO ₂ .
(Appendix 4)
4. The photoexcitation material according to any one of Appendices 1 to 3, wherein the promoter further contains at least one of Ir, Ru, Co, and Ce.
(Appendix 5)
a photoexcitable material portion containing an oxynitride that absorbs and excites light;
a co-catalyst site containing a co-catalyst disposed in contact with the photoexcitable material site;
A method for producing a photoexcitation material for producing a photoexcitation material having
disposing the oxynitride to form a photoexcitable material site;
forming the promoter site by heating the photoexcitable material site and the promoter site precursor in a state where the promoter site precursor is disposed on at least a portion of the surface of the photoexcitable material site;
A method for producing a photoexcitation material, comprising:
(Appendix 6)
6. The method for producing a photoexcitable material according to appendix 5, wherein the photoexcitable material portion is formed by applying particles of the oxynitride by an aerosol deposition method.
(Appendix 7)
a conductor;
a photoexcitable material disposed in contact with the conductor;
The photoexcitation material includes a photoexcitation material portion containing an oxynitride that is excited by absorbing light, and a cocatalyst portion containing a cocatalyst arranged in contact with the photoexcitation material portion,
A photochemical electrode characterized by comprising:
(Appendix 8)
a counter electrode;
a photochemical electrode connected to the counter electrode via a lead;
a translucent container for immersing the counter electrode and the photochemical electrode in water;
has
the photochemical electrode comprises an electrical conductor and a photoexcitable material disposed in contact with the electrical conductor;
The photoexcitation material has a photoexcitation material portion containing an oxynitride that is excited by absorbing light, and a cocatalyst portion containing a cocatalyst disposed in contact with the photoexcitation material portion. Photoelectrochemical reactor.

REFERENCE SIGNS LIST 1 photoexcitable material 2 photoexcitable material site 3 promoter site 4 promoter site precursor

Claims (6)

a photoexcitation material portion containing SrNbO ₂ N as an oxynitride that absorbs and excites light;
a co-catalyst site containing a co-catalyst disposed in contact with the photoexcitable material site;
has
A photoexcitation material, wherein the co-catalyst contains at least one of IrO ₂ , RuO ₂ , CoO ₂ and CeO ₂ . The photoexcitable material according to claim 1, wherein the promoter is _IrO2 . a photoexcitation material portion containing SrNbO ₂ N as an oxynitride that absorbs and excites light;
a co-catalyst site containing a co-catalyst disposed in contact with the photoexcitable material site;
A method for producing a photoexcitation material for producing a photoexcitation material having
disposing the oxynitride to form a photoexcitable material site;
forming the promoter site by heating the photoexcitable material site and the promoter site precursor in a state where the promoter site precursor is disposed on at least a portion of the surface of the photoexcitable material site;
including
A method for producing a photoexcitation material, wherein the co-catalyst contains at least one of IrO ₂ , RuO ₂ , CoO ₂ and CeO ₂ . 4. The method for producing a photoexcitation material according to claim 3, wherein the photoexcitation material portion is formed by applying particles of the oxynitride by an aerosol deposition method. a conductor;
a photoexcitable material disposed in contact with the conductor;
A photoexcitation material portion containing SrNbO ₂ N as an oxynitride that is excited by light absorption, and IrO ₂ , RuO ₂ , CoO ₂ , and CeO arranged in contact with the photoexcitation material portion. a promoter site containing a promoter containing at least one of ₂ ;
A photochemical electrode characterized by comprising: a counter electrode;
a photochemical electrode connected to the counter electrode via a lead;
a translucent container for immersing the counter electrode and the photochemical electrode in water;
has
the photochemical electrode comprises an electrical conductor and a photoexcitable material disposed in contact with the electrical conductor;
A photoexcitation material portion containing SrNbO ₂ N as an oxynitride that is excited by light absorption, and IrO ₂ , RuO ₂ , CoO ₂ , and CeO arranged in contact with the photoexcitation material portion. and a cocatalyst site containing a cocatalyst containing at least one of ( ₂₎ .

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