JP2020059895A - Photo-excitation material, production method thereof, photochemical electrode, and photoelectrochemical reaction apparatus - Google Patents

Abstract

To provide a photo-excitation material whose characteristics are hard to decline even in repeated use, the production method thereof, a photochemical electrode using the photo-excitation material, and a photoelectrochemical reaction apparatus.SOLUTION: A photo-excitation material comprises: a photo-excitation material part including an oxynitride that absorbs light for excitation; and a co-catalyst part including a co-catalyst that is arranged in contact with the photo-excitation material part. The oxynitride preferably includes at least one of BaTaON, BaNbON, SrNbON, and LaTiON.SELECTED DRAWING: Figure 1

Description

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

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

  Artificial photosynthesis technology has been attracting attention in recent years as a method for reducing carbon dioxide in the atmosphere. Artificial photosynthesis technology is roughly classified into a bright reaction in which a photoexcited material is irradiated with visible light to generate electrons and protons, and a dark reaction in which carbon dioxide and protons are subjected to multielectron reduction to generate an organic substance.

As the photoexcitation material used in the bright reaction, it is necessary to use a material satisfying 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 a high photocurrent can be formed by the excited electrons. The fourth point is that it has excellent redox resistance in water.
An oxynitride material has been proposed as a material satisfying these conditions (for example, Patent Document 1).

JP, 2017-160524, A

It is particularly important for the photoexcitable material that it can stably generate a photocurrent even when it is irradiated with visible light several times, that is, whether the characteristics are hard to deteriorate and the reliability is high when it is applied to an artificial photosynthesis system. Is becoming.
However, when oxynitride is used as the photoexcitation material, the photocurrent decreases when the visible light irradiation is performed a plurality of times, and therefore, it cannot be said that it is sufficient in terms of reliability.

  It is an object of the present invention to provide a photoexcited material whose characteristics do not deteriorate even after repeated use, a method for producing the same, a photochemical electrode using the photoexcited material, and a photoelectrochemical reaction device.

The means for solving the above problems are as follows. That is,
In one aspect, the photoexcitation material is
A photoexcitation material portion containing an oxynitride that absorbs and excites light,
A co-catalyst site containing a co-catalyst placed in contact with the photoexcitation material site,
Have.

Further, in one aspect, the method for producing a photoexcitation material includes
A photoexcitation material portion containing an oxynitride that absorbs and excites light,
A co-catalyst site containing a co-catalyst placed in contact with the photoexcitation material site,
A method for producing a photoexcited material for producing a photoexcited material having:
Arranging the oxynitride to form a photoexcitation material site,
In a state in which the precursor of the promoter portion is disposed on at least a part of the surface of the photoexciting material portion, heating the photoexciting material portion and the precursor of the promoter portion, and forming the promoter portion,
including.

Also, in one aspect, the photochemical electrode is
A conductor,
And a photoexcitation material arranged so as to contact the conductor,
The photoexcitation material, a photoexcitation material site containing an oxynitride that absorbs and excites light, and a cocatalyst site containing a cocatalyst placed in contact with the photoexcitation material site,
Have.

Also, in one aspect, the photoelectrochemical reactor is
A counter electrode,
A photochemical electrode connected to the counter electrode via a conductive wire;
A translucent container for immersing the counter electrode and the photochemical electrode in water,
Have
The photochemical electrode has a conductor and a photoexciting material arranged in contact with the conductor,
The photoexcitation material, a photoexcitation material site containing an oxynitride that absorbs and excites light, and a cocatalyst site containing a cocatalyst placed in contact with the photoexcitation material site,
Have.

According to the photoexciting material of the present invention, it is possible to solve the above-mentioned problems in the related art and to provide a photoexciting material in which the characteristics are not easily deteriorated even when repeatedly used.
According to the method for producing a photoexciting material of the present invention, it is possible to solve the above-mentioned problems in the related art, and to provide a method for producing a photoexciting material in which the characteristics are not easily deteriorated even after repeated use.
According to the photochemical electrode of the present invention, it is possible to solve the above-mentioned various problems in the related art, and to provide a photochemical electrode in which characteristics are not easily deteriorated even when repeatedly used.
According to the photoelectrochemical reaction device of the present invention, it is possible to provide a photoelectrochemical reaction device which can solve the above-mentioned problems in the related art and which is difficult to deteriorate in characteristics even when repeatedly used.

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

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

The present inventors have focused on an oxynitride material as a material used for the photoexcitation material portion. Oxynitride is known to generate high photocurrent when used as a photoexcitation material. However, the oxynitride has a property that the photocurrent decreases when it is repeatedly used. This is considered to be due to the elimination of nitrogen atoms in the crystal 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, nitrogen is desorbed by about 10%.
Oxynitride generates oxygen when generating photocurrent, and the oxygen concentration in the oxynitride increases. It is speculated that this increased oxygen drives out nitrogen in the oxynitride, so that desorption of nitrogen proceeds.

  Further, not only oxynitrides, but also photoexcited materials are irradiated with light, and when high-energy electrons in the photoexcited material are excited to the conduction band by the energy of the irradiated light, electrons escape to the valence band. Oxidizing holes, which are hollow holes, are generated. However, when the photoexcited material is repeatedly used, the generated holes and the oxygen generated by the photoexcited reaction are recombined with each other to cause the disappearance of the holes. As a result, a decrease in photocurrent occurs when the photoexcitation material is repeatedly used.

  Therefore, the present inventors have studied a photoexciting material whose characteristics do not easily deteriorate even after repeated use. As a result, we focused on placing the co-catalyst in contact with the oxynitride. By disposing the co-catalyst 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, they have found that a decrease in photocurrent can be suppressed, and have completed the present invention.

<Photoexciting material site>
The photoexciting material site contains an oxynitride.
The photoexcitation material portion is preferably composed of oxynitride itself.

<< Oxynitride >>
Oxynitride has a property of absorbing and exciting light.
Examples of the oxynitride 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, etc.

The shape of the photoexcitation material site is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a flat plate shape.
The size of the photoexcitation material site is not particularly limited and can be appropriately selected depending on the purpose.

<Promoter site>
The promoter portion contains a promoter.
The promoter portion is arranged in contact with the photoexcitation material portion.
The cocatalyst site may or may not cover the entire surface of the photoexcitation material site, and the boundary with the photoexcitation material site may be clear or unclear.

<< Cocatalyst >>
As the cocatalyst, a metal oxide is preferable. Examples of the metal oxide include IrO ₂ , RuO ₂ , CoO ₂ , CeO _{2 and the} like.
There is a preferable compositional combination of the promoter and the oxynitride. For example, when SrNbO ₂ N is used as the oxynitride, the promoter is IrO ₂ , RuO ₂ , CoO ₂ , CeO ₂ . ₂ is preferred.

  The content of the co-catalyst is not particularly limited and may be appropriately selected depending on the purpose, but is preferably 4% by mass to 6% by mass with respect to the mass of the photoexcitation material site.

  In addition to the promoter, the promoter portion may have a metal that constitutes a metal oxide that is a promoter. Examples of such a metal include Ir, Ru, Co, Ce and the like.

The shape of the promoter portion is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a flat plate shape.
The size of the promoter portion is not particularly limited and can be appropriately selected depending on the purpose.

<Other parts>
Examples of other sites include a support and the like.
The support supports the photoexcitation material site and the cocatalyst site.
The support is disposed, for example, in contact with the photoexcitation material site.
Examples of the material of the support include glass, an insulator such as an organic resin, and the like.
The shape and size of other portions are not particularly limited and can be appropriately selected according to the purpose.

Here, an example of the photoexcitation material of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic sectional view of an example of the photoexciting material of the present invention.
The photoexcitation material 1 of FIG. 1 has a photoexcitation material site 2 and a cocatalyst site 3 in contact with the photoexcitation material site 2. The photoexcitation material site 2 may be supported by a support such as a glass substrate.

(Method for producing photoexciting material)
The method for producing a photoexcitation material of the present invention is a method for producing the above-described photoexcitation material.
The method for producing a photoexcitation material includes a step of forming a photoexcitation material site (hereinafter, may be abbreviated as “photoexcitation material site formation step”) and a step of forming a cocatalyst site (hereinafter, “cocatalyst site formation step”). May be abbreviated as).
The method for producing a photoexcitation material further includes other steps such as a support forming step, if necessary.

<Photoexcitation material site forming step>
The photoexcitation material site forming step is a step of disposing an oxynitride.
The oxynitride can use the above-mentioned thing.
The photoexcitation material site 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, but the oxynitride particles are applied by the aerosol deposition method. It is preferable to form by doing so (hereinafter, may be referred to as “NPD film formation”).

<< NPD film formation >>
Aerosol deposition is also sometimes referred to as nanoparticle deposition (NPD).
Nanoparticle deposition (NPD) is the method introduced in the following Documents 1 to 3.
Reference 1: Imanaka, Y .; , Amada, H .; & Kumasaka, F.M. Dielectric and insulting properties of embedded capacitor for flexible electronics pre-formed by aerosol-type nanodeposition. Jpn. J. Appl. Phys. 52, 05DA02 (2013).
Reference 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 .; & Kumamoto, A .; , Nanoparticulate BaTiO ₃ film produced by aerosol-type nanoparticulate deposition. J. Nanopart. Res. 18, 102 (2016).
Nanoparticle deposition (NPD) sprays an aerosol in which raw material particles are dispersed in a gas toward a base material from a nozzle to collide the aerosol with the surface of the base material to form a film 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 the system where the pressure is continuously reduced by a vacuum pump, the raw material particles, which are an inorganic material, form an aerosol together with the gas flow and are conveyed. The fed raw material particles are crushed while colliding with each other in the nozzle. In the raw material particles, while maintaining crystallinity inside the raw material particles, a 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 becomes high. When the crushed raw material particles are deposited on the substrate, the raw material particles are recombined by the action (cohesive force) of stabilizing the unstable surface area of the raw material particles in the high energy state. As a result, a film of a dense nanoparticle aggregate structure is obtained on the substrate at a room temperature level. Also, when the film is annealed, the optimum sintering can be lowered by 500 ° C. or more because the inside of the film is composed of nanoparticles.

Here, an example of the aerosol deposition method will be described with reference to the drawings.
FIG. 2 is a structural diagram of an example of a film forming apparatus used for film formation by the aerosol deposition method.
The aerosol deposition film forming apparatus has an aerosol chamber 910 and a film forming chamber 920. The aerosol chamber 910 contains fine particles 911 of a material to be formed into a film, and a gas cylinder 930 containing a carrier gas such as He, N ₂ or Ar is connected through a pipe 960. Further, the aerosol chamber 910 and the film forming chamber 920 are connected by a pipe 941, and a nozzle 921 is provided at the end of the pipe 941 inside the film forming chamber 920. In the film formation chamber 920, a stage 922 is provided on the side facing the opening of the nozzle 921, and the stage 922 is provided with a substrate 923 for film formation. The inside of the film forming 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 the pipe 942 through the pipe 945 and a valve (not shown) so that the inside of the aerosol chamber 910 can be exhausted. In addition, in the region where the aerosol chamber 910 is installed, in order to prevent the fine particles of the material to be deposited from solidifying in the aerosol chamber 910 or to prevent the particles from being biased during deposition, the aerosol chamber 910 is vibrated. A vibrator 950 is provided.

  In this film forming apparatus, when forming a film by the aerosol deposition method, 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 rolled up by the supplied carrier gas, and the fine particles of the material to be deposited are carried to the nozzle 921 in the deposition chamber 920 through the pipe 941 together with the carrier gas. . After that, fine particles of the material to be formed with the carrier gas are ejected from the nozzle 921 toward the substrate 923, and the fine particles ejected from the nozzle 921 toward the surface of the substrate 923 are deposited to form a film. .

<Promoter site forming step>
The co-catalyst site forming step has a step of heating the photo-exciting material site and the precursor of the co-catalyst site in a state where the precursor of the co-catalyst site is provided on at least a part of the surface of the photo-exciting material site.
The method of arranging the precursor of the co-catalyst site is not particularly limited and may be appropriately selected depending on the purpose, and examples thereof include the above-mentioned NPD and sputter deposition.

The heating of the photoexcitation material site and the precursor of the cocatalyst site is also called annealing, and is performed for grain growth of the oxynitride contained in the photoexcitation material site. During annealing, a part of oxygen in the oxynitride is transferred to the cocatalyst precursor, and at least a part of the cocatalyst precursor is oxidized to form a cocatalyst site.
The co-catalyst site may be in a state where the co-catalyst and the 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 promoter precursor is oxidized, and can be appropriately selected depending on the purpose, for example, 400 ° C to 700 ° C. The temperature may be 500 ° C. to 650 ° C.
The heating time is appropriately selected depending on the intended purpose without any limitation, provided that it is a time such that at least a portion of the promoter precursor is oxidized. For example, 5 minutes to 10 hours can be used. It may be 10 minutes to 1 hour.

<< Cocatalyst precursor >>
The co-catalyst precursor is not particularly limited as long as it receives oxygen desorbed from the oxynitride and can exert the function as a co-catalyst, and can be appropriately selected according to the purpose, for example, a metal oxide that is a co-catalyst. The metal that constitutes Examples of such a metal include Ir, Ru, Co, Ce and the like.

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

(Photochemical electrode)
The photochemical electrode of the present invention has at least a conductor and a photoexcitation material, and further has other members such as a support, if necessary.
The photoexcitation material is the above-mentioned 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 the material of the conductor include metals, alloys, metal oxides and the like.
Examples of metals include platinum (Pt), palladium (Pd), gold (Au), silver (Ag), copper (Cu), tungsten (W), nickel (Ni), tantalum (Ta), bismuth (Bi), and lead. Examples thereof include (Pb), indium (In), tin (Sn), zinc (Zn), titanium (Ti), and aluminum (Al).
Examples of the alloy include alloys composed of two or more kinds of metals listed above as examples of the metals.
Examples of the metal oxide 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). , 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 range of 10 ² Ωcm or less in volume resistivity.

The shape of the conductor is not particularly limited and may be appropriately selected depending on the intended purpose, and 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 vapor deposition film and the like. The vapor deposition film is formed by, for example, a physical vapor deposition method or a chemical vapor deposition method. Examples of the physical vapor deposition method include a vacuum vapor deposition method and a sputtering method.

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

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

An example of the photoelectrochemical reaction device will be described with reference to FIG.
The photoelectrochemical reaction device includes a photochemical electrode 10 which is an anode, a counter electrode 15 which is a cathode, a conductive wire 16 which connects the photochemical electrode 10 and the counter electrode 15, and a translucency which houses the photochemical electrode 10 and the counter electrode 15. And a container 17. Water 18 is contained in the translucent container 17, and the photochemical electrode 10 and the counter electrode 15 are immersed in the water 18.
As the counter electrode 15, for example, a Pt metal electrode having a high catalytic activity for hydrogen generation is used.

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

When the photochemical electrode 10 is irradiated with irradiation light 19, electrons in the valence band are excited in the photoexcitation material 13 of the photochemical electrode 10 to transit to the conduction band and holes are formed in the valence band. . The electrons excited by the irradiation light 19 are directed toward the conductor 12, and the holes are directed toward the surface. Then, on the surface of the photoexcitation material 13, when OH ⁻ ions are present in the 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, when H ⁺ ions exist in water, a reduction reaction occurs due to the electrons and hydrogen H ₂ is generated.
Here, the presence of the co-catalyst 14 contained in the photo-catalyst site in the photo-excitation material 13 promotes photo-excitation of the photo-excitation material 13 and increases the photocurrent, resulting in higher light utilization efficiency.

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

(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), reacted in an ammonia gas stream at 1,173 K (about 900 ° C.) for 100 hours, and then purified. SrNbO ₂ N powder having a mean particle size of 1 μm and 99.9% or more was obtained.

(Comparative Example 1)
<Oxynitride>
As the raw material powder, the SrNbO ₂ N powder manufactured in Manufacturing Example 1 and having an average particle size of 1 μm was used.

<Preparation of photochemical electrode>
The nanoparticle deposition (NPD) device used consists of an aerosol generation system, a deposition chamber and a vacuum system. No heat source is placed in this deposition device.
The SrNbO ₂ N powder produced in Production Example 1 was set in the container of the aerosol generating system and vibrated at 10 Hz. Then, helium having a gas pressure of 0.2 MPa and a purity of 99.9% was introduced into the container to generate an aerosol. The pressure inside the deposition chamber was controlled to less than 10 Pa using a mechanical booster and a vacuum pump. The generated aerosol was conveyed to the nozzle in the deposition chamber.
The aerosol was ejected from the nozzle, and the aerosol was made to collide with an FTO substrate (glass on which a fluorine-doped tin oxide thin film was formed) arranged 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, at room temperature, a photoexciting material site (average thickness 2 μm) made of SrNbO ₂ N was formed on the FTO substrate.

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

(Example 1)
<Preparation of photochemical electrode having photoexcited material>
The nanoparticle deposition (NPD) device used consists of an aerosol generation system, a deposition chamber and a vacuum system. No heat source is placed in this deposition device.
The SrNbO ₂ N powder produced in Production Example 1 was set in the container of the aerosol generating system and vibrated at 10 Hz. Then, helium having a gas pressure of 0.2 MPa and a purity of 99.9% was introduced into the container to generate an aerosol. The pressure inside the deposition chamber was controlled to less than 10 Pa using a mechanical booster and a vacuum pump. The generated aerosol was conveyed to the nozzle in the deposition chamber.
The aerosol was ejected from the nozzle, and the aerosol was made to collide with an FTO substrate (glass on which a fluorine-doped tin oxide thin film was formed) arranged 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, at room temperature, a photoexciting material site (average thickness 2 μm) made of SrNbO ₂ N was formed on the FTO substrate.

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

Subsequently, a nitrogen gas atmosphere (nitrogen gas concentration of 100%) in 600 ° C., and annealed for 30 minutes to form a co-catalyst by oxidizing the Ir (IrO _2), cocatalyst site containing the cocatalyst (IrO ₂₎ Was formed.
As described above, the photochemical electrode of Example 1 was obtained.

<Photocurrent measurement>
A three-pole 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 nitrogen gas was previously bubbled for 30 minutes to degas the dissolved oxygen. The potential value was corrected to the standard hydrogen electrode reference value (vs. NHE) at pH = 0 each time, and the value was shown.
Photocurrent was measured using a solar simulator (HAL-320, manufactured by Asahi Bunko Co., Ltd.) for pseudo 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.
The photocurrents of the prepared photochemical electrodes of Example 1 and Comparative Example 1 were measured three times. The measurement was repeated three times. FIG. 5 shows the values of the second and third photocurrents when the value of the first photocurrent of each of Example 1 and Comparative Example 1 was set to 1.

  The photocurrent in the case of using the photochemical electrode having the photoexcitation material of Example 1 was about 0.55 times as large as that in the first measurement at the time of the third measurement. On the other hand, the photocurrent when the photochemical electrode having the photoexciting material of Comparative Example 1 was used was about 0.25 times larger than that at the first measurement at the time of the third measurement. From these results, it became clear that the photoexcitation material of the present invention does not deteriorate in characteristics even after repeated use.

Furthermore, the following supplementary notes are disclosed.
(Appendix 1)
A photoexcitation material portion containing an oxynitride that absorbs and excites light,
A co-catalyst site containing a co-catalyst placed in contact with the photoexcitation material site,
A photoexciting material having:
(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 photoexciting material according to any one of appendices 1 to 2, wherein the cocatalyst 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 cocatalyst further contains at least one of Ir, Ru, Co, and Ce.
(Appendix 5)
A photoexcitation material portion containing an oxynitride that absorbs and excites light,
A co-catalyst site containing a co-catalyst placed in contact with the photoexcitation material site,
A method for producing a photoexcited material for producing a photoexcited material having:
Arranging the oxynitride to form a photoexcitation material site,
In a state in which the precursor of the promoter portion is disposed on at least a part of the surface of the photoexciting material portion, heating the photoexciting material portion and the precursor of the promoter portion, and forming the promoter portion,
A method for producing a photoexcitation material, comprising:
(Appendix 6)
6. The method for producing a photoexciting material according to appendix 5, wherein the photoexciting material portion is formed by applying particles of the oxynitride by an aerosol deposition method.
(Appendix 7)
A conductor,
And a photoexcitation material arranged so as to contact the conductor,
The photoexcitation material, a photoexcitation material site containing an oxynitride that absorbs and excites light, and a cocatalyst site containing a cocatalyst placed in contact with the photoexcitation material site,
A photochemical electrode comprising:
(Appendix 8)
A counter electrode,
A photochemical electrode connected to the counter electrode via a conductive wire;
A translucent container for immersing the counter electrode and the photochemical electrode in water,
Have
The photochemical electrode has a conductor and a photoexciting material arranged in contact with the conductor,
The photoexciting material has a photoexciting material site containing an oxynitride that excites by absorbing light, and a cocatalyst site containing a cocatalyst disposed in contact with the photoexciting material site. Photoelectrochemical reactor.

1 Photoexcitation Material 2 Photoexcitation Material Site 3 Promoter Site 4 Precursor Site Promoter

Claims (7)

A photoexcitation material portion containing an oxynitride that absorbs and excites light,
A co-catalyst site containing a co-catalyst placed in contact with the photoexcitation material site,
A photoexciting material having: The photoexcitation material according to claim 1, wherein the oxynitride contains at least one of BaTaO ₂ N, BaNbO ₂ N, SrNbO ₂ N, and LaTiO ₂ N. The photoexcitation material according to claim 1, wherein the cocatalyst contains at least one of IrO ₂ , RuO ₂ , CoO ₂ , and CeO ₂ . A photoexcitation material portion containing an oxynitride that absorbs and excites light,
A co-catalyst site containing a co-catalyst placed in contact with the photoexcitation material site,
A method for producing a photoexcited material for producing a photoexcited material having:
Arranging the oxynitride to form a photoexcitation material site,
In a state in which the precursor of the promoter portion is disposed on at least a part of the surface of the photoexciting material portion, heating the photoexciting material portion and the precursor of the promoter portion, and forming the promoter portion,
A method for producing a photoexcitation material, comprising:   The method for producing a photoexcitation material according to claim 4, wherein the photoexcitation material site is formed by applying particles of the oxynitride by an aerosol deposition method. A conductor,
And a photoexcitation material arranged so as to contact the conductor,
The photoexcitation material, a photoexcitation material site containing an oxynitride that absorbs and excites light, and a cocatalyst site containing a cocatalyst placed in contact with the photoexcitation material site,
A photochemical electrode comprising: A counter electrode,
A photochemical electrode connected to the counter electrode via a conductive wire;
A translucent container for immersing the counter electrode and the photochemical electrode in water,
Have
The photochemical electrode has a conductor and a photoexciting material arranged in contact with the conductor,
The photoexciting material has a photoexciting material site containing an oxynitride that excites by absorbing light, and a cocatalyst site containing a cocatalyst disposed in contact with the photoexciting material site. Photoelectrochemical reactor.