JP3046581B2 - Method for using photolysis catalyst and method for producing hydrogen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to the use of a photolysis catalyst .
A method及beauty Hydrogen production method, to a method及beauty Hydrogen production method using photolysis catalyst which acts efficiently in particular by sunlight.

[0002]

2. Description of the Related Art In recent years,
A method for producing hydrogen by photodecomposing water using a semiconductor as a photodecomposition catalyst has been found, and a method for converting light energy into chemical energy has been proposed. As described above, platinum-supported titanium oxide is known as a typical semiconductor capable of photodecomposing water into hydrogen and oxygen. However, when this catalyst is used by suspending it in water, the decomposition reaction of water is immediately stopped. This is reported to be due to the reverse reaction of hydrogen and oxygen recombination progressing on the platinum on the catalyst surface (K. Sayama, H. Arakawa, J. Chem.
Soc. Chem. Commun., 150 (1992).). As a method of suppressing this reverse reaction, it is effective to include platinum-supported titanium oxide between layers of the layered compound, and in particular, a catalyst in which titanium oxide and platinum are included between layers of the layered titanate compound is in a suspended state in water. However, it has been reported that water can be stably photodegraded for a long time (S. Uchida, Y. Yamamoto, Y. Hij
ishiro, A. Watanabe, O. Ito, T. Sato, J. Chem. So
c. Faraday Trans., 93, 3229 (1997).

However, conventional photocatalysts capable of stably photodecomposing water have a large band gap energy of 3 eV or more, and can be excited by long-wavelength light (visible light) having a wavelength of 400 nm or more. Did not. As is well known, the light (ultraviolet light) having a wavelength of 400 nm or less contained in sunlight is about 5%, and most is visible light having a wavelength of 400 nm or more. Therefore, development of a semiconductor photocatalyst which can be excited by visible light and has high utilization efficiency of sunlight has been conventionally desired.

An object of the present invention is to provide a method及beauty Hydrogen production method using photolysis catalysts having good catalyst activity and efficient in sunlight.

[0005]

Means for Solving the Problems The use of the photolysis catalyst of the present invention.
The method of use is a cation exchange containing at least one metal ion selected from vanadium, chromium, manganese, iron, cobalt, nickel, copper, molybdenum, ruthenium, silver, cadmium, and cerium in the layered titanate crystal structure. Photodecomposition catalyst composed of a layered titanate compound
It is characterized by being excited by irradiating visible light of 400 nm or more .

In the photodecomposition catalyst of the present invention, a part of the titanium atoms is replaced by these metal atoms by including the metal ions in the crystal structure of the layered titanic acid.
As a result, the band gap energy decreases, and excitation with visible light becomes possible. Therefore, a photodecomposition catalyst that works efficiently with sunlight can be obtained. In addition, by decomposing water using such a photodecomposition catalyst, water can be decomposed efficiently by sunlight and hydrogen can be produced.

In the present invention, in order to further enhance the catalytic activity, at least one metal or metal oxide selected from titanium oxide, platinum, ruthenium, rhodium, copper and nickel is assisted between the layered titanate compounds. It may be included as a catalyst. The content of such a co-catalyst is
It is appropriately selected depending on the type of the co-catalyst, the type of the layered titanate compound, and the like, but is generally preferably 0.01 to 10% by weight.

[0008] These cocatalysts may be included by mixing a plurality of types. For example, platinum, ruthenium,
At least one selected from rhodium, copper, and nickel
After the seed metal or metal oxide is included, titanium oxide may be further included between the layers. This makes it possible to obtain a photolysis catalyst in which titanium oxide supporting a promoter such as platinum is included between layers of the layered titanate compound.

The method for producing hydrogen of the present invention is characterized in that hydrogen is produced by decomposing water by irradiating visible light having a wavelength of 400 nm or more using the photodecomposition catalyst of the present invention.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. (1) Configuration of Photodecomposition Catalyst The photodecomposition catalyst of the present invention comprises a cation-exchangeable layered titanate compound (a) containing the above-mentioned metal ion in the crystal structure of layered titanate alone or a layered titanate compound ( It is a layered titanate compound in which the above cocatalyst (b) is included between the layers of a).

(A) Layered titanate compound The layered titanate compound in the present invention may be any compound as long as it can ion-exchange a cation having a layered interstitial with a cation outside the compound. Specifically, H ₂ Ti ₂ O ₅ , H ₂ Ti ₃ O ₇ , H ₂ Ti ₄ O
₉ , H ₂ La ₂ Ti ₃ O ₁₀ , HTiNbO ₅ , and alkali metal salts and alkaline earth metal salts thereof, and particularly, H ₂ Ti ₂ O ₅ , H ₂ Ti ₃ O ₇ , H ₂ Ti ₄
O ₉ is preferred.

In the photodecomposition catalyst of the present invention, the metal ion is contained in such a layered titanate compound,
It is considered that at least a part of the metal ion is replaced with a part of the titanium atom in the crystal structure of such a layered titanate compound, and the band gap energy is reduced.

The content of the metal ions is not particularly limited, but is preferably about 0.01 to 2.0 mol% of titanium sites in the crystal structure of the layered titanate compound, and more preferably. Is about 0.02 to 0.5 mol%.

(B) Promoter As described above, at least one metal or metal oxide selected from titanium oxide, platinum, ruthenium, rhodium, copper, and nickel is used as the promoter. More preferably, these metal elements are used for platinum, ruthenium, and rhodium, and their oxides are used for copper and nickel.

When the titanium oxide is included between the layers, as described above, the titanium oxide may be included between the layers of the layered titanate compound in which a promoter other than the titanium oxide is previously included. Titanium oxide may be included by reacting a titanium oxide colloid solution, or by intercalating a complex cation containing titanium and then thermally or photolytically decomposing the titanium oxide between the layers. May be generated.

As the complex cation containing titanium, for example, a cation of a titanium acyl complex ([Ti (OAc) _x
(OH) _y ] ^{Z +} ). Further, examples of the complex cation containing titanium include a cation of a complex using a carboxylic acid such as citric acid.

As described above, the amount of the cocatalyst included is preferably 0.01 to 10% by weight based on the entire photolysis catalyst. In particular, since titanium oxide itself is a semiconductor that is excited by light such as sunlight and generates electrons and holes, it can be included in a relatively large amount, and the amount of titanium oxide is 1.0% with respect to the entire photolysis catalyst. It is preferable that the inclusion is made up to 5.0% by weight. In addition, it is preferable that the cocatalyst other than titanium oxide be included in an amount of 0.05 to 0.1% by weight based on the entire photolysis catalyst.

(2) Method for Producing Photodecomposition Catalyst A method for producing the photodecomposition catalyst of the present invention will be described below with reference to examples. By mixing a metal oxide or a metal carbonate or the like as a raw material of the layered titanate compound and a metal oxide or a metal carbonate or the like as a raw material of a metal ion to be added at a predetermined molar ratio, and baking the mixture. A layered titanate compound containing the metal ion can be obtained. In the case of synthesizing potassium titanate as a layered titanate compound, for example, K ₂ CO ₃ , TiO ₂ , and a metal oxide or metal carbonate as a raw material of a metal ion to be added are mixed at a predetermined molar ratio. By baking at 800 to 1500 ° C. for 1 to 240 hours, potassium titanate containing metal ions can be synthesized. When synthesizing a titanate compound other than a potassium salt, it can be synthesized by replacing K ₂ CO ₃ with another metal oxide or metal carbonate. Moreover, you may synthesize | combine by a flux method or a hydrothermal method other than such a solid phase method. Further, when the layered titanate compound is ion-exchanged in a mineral acid, a layered titanic acid in which interlayer metal ions are ion-exchanged into hydrogen ions can be obtained.

Inclusion of Co-Catalyst The layered titanate compound containing metal ions obtained as described above is treated with a Pt such as [Pt (NH ₃ ) ₄ ] Cl _2.
After suspending in an aqueous solution of t, Ru, Rh, Cu, and Ni compounds and allowing Pt (NH ₃ ) ₄ ²⁺ or the like to be included between the layers, the suspension is irradiated with UV light for 0.5 to 100 hours to produce Pt, Ru, Elements such as Rh are deposited between the layers. When the oxides of Ru, Cu, and Ni are included, a method of hydrolyzing or dehydrating the metal compound included between the layers can be used.

In the case where titanium oxide is included using a titanium acyl complex, a layered titanate compound containing a metal ion or a layered titanate compound containing a cocatalyst such as Pt is added to n. -After being dispersed in an organic solvent such as hexane or water, n-C ₈ H ₁₇ NH ₂ or n-C
₃ H ₇ was added an alkyl amine such as NH _2, is reacted 1 to 240 hours at a temperature below the boiling point of room temperature or higher and a solvent, the cations between the layers alkyl ammonium ion and ion exchange. The resulting alkyl ammonium ion-containing layered titanic acid _{compound, Ti (i-C 3 H} 7 O) 4 and Chitan'ashiru complex obtained by reaction of acetic acid ([Ti (OA
c) _x (OH) _y ] ^{z +} ) solution and add room temperature to 90 ° C
Reaction for 1 to 240 hours, the titanium acyl complex is included between the layers, and then UV light is irradiated for 0.5 to 50 hours,
Alternatively, heat treatment is performed at a temperature of 250 to 600 ° C. for 1 to 5 hours to obtain a photodecomposition catalyst in which titanium oxide or titanium oxide supporting a promoter such as platinum is included in a layered titanate compound.

As described above, when the titanium oxide is included, a titanium oxide colloid solution may be used instead of the titanium acyl complex solution, and the titanium oxide colloid solution may be reacted and included. The above-described production method is an example of the method for producing the photolysis catalyst of the present invention, and the photodecomposition catalyst of the present invention is not limited to the above-described production method.

The method for producing hydrogen of the present invention using the photolysis catalyst of the present invention will be described below. The aqueous solution to be subjected to photodecomposition may be pure water (meaning water containing no sacrificial reducing agent, such as an organic substance that reacts with holes, but not containing impurities), but is preferably alkaline. An aqueous solution to which a reducing compound is added, such as a compound aqueous solution, an alcohol aqueous solution, or a mixed aqueous solution thereof is used. Na ₂ S, Na ₂ S
O ₃ , Na ₂ S ₂ O ₃ , NaNO _{2 and the} like are preferable, and a mixture thereof may be used. The concentration is 0.01-1mo
1 / liter is preferred. Also, as alcohol,
Methanol, ethanol, propanol, 2-aminoethanol and the like are preferable, and a mixture thereof may be used. The concentration is preferably 0.01 to 1 mol / liter.

The photolysis catalyst of the present invention is added to the above aqueous solution. The addition amount of the photolysis catalyst is 0.5 to 50 mg / cm.
³ is preferable, and 1 to 3 mg / cm ³ is particularly preferable. By irradiating the aqueous solution to which the photolysis catalyst has been added with light as described above, water is decomposed and hydrogen is generated. The temperature of the aqueous solution is preferably about 25 to 60 ° C.

As described above, the photodecomposition catalyst of the present invention is useful as a photodecomposition catalyst for decomposing water to produce hydrogen. The photodecomposition catalyst of the present invention is suitable for such applications. It is not limited, and can be used, for example, as a catalyst for an organic substance synthesis reaction or a catalyst for a decomposition reaction of harmful substances.

The harmful substances include, for example, substances that have a bad influence on the human body and the living environment, and substances having a possibility, and include various biological oxygen-requiring substances, air pollutants, herbicides, bactericides, and insecticides. And various microorganisms such as agrochemicals, bacteria, actinomycetes, fungi, algae, molds, etc., cigarette tar, odor, pet odor, malodorous gas, human odor and the like. Examples of the environmental pollutants include organic halides, organic phosphorus compounds and other organic compounds, nitrogen compounds, sulfur compounds, cyanide compounds, chromium compounds and the like. Specific examples of the organic halogen compound include polychlorinated biphenyl, freon, trihalomethane, trichloroethylene, and tetrachloroethylene. Other than the organic halogen compounds, examples thereof include hydrocarbons such as surfactants and oils, aldehydes, mercaptans, alcohols, amines, amine acids, and proteins.
As the nitrogen compound, ammonia, nitrogen oxide (N
O _x ), sulfur oxide (SO _x ) and the like.

The photodecomposition catalyst of the present invention can also be used for a hydrophilicity imparting reaction. By utilizing the hydrophilicity imparting reaction, it is possible to prevent mirrors, glasses, glasses, and the like from fogging, and to prevent stains on the outer walls and the like. In addition, cancer cells can be treated using an endoscope or the like.

The photolysis catalyst of the present invention can be used in various ways. For example, the photodecomposition catalyst of the present invention may be contained in a substrate, or a coating solution containing the photodecomposition catalyst of the present invention may be applied to the surface of a substrate to form a film, or the photodecomposition catalyst of the present invention may be contained. A film to be formed can be used by laminating it on the surface of a substrate.

Examples of the substrate include porcelain, ceramic, metal, glass, plastic, wood, and composites thereof. The shape of the base material may be any shape, such as a spherical shape, a cylindrical shape, a cylindrical shape, a simple shape such as a plate-like material such as a tile, a wall material, a floor material, a sanitary ware, a wash basin,
It may be of a complicated shape such as a bathtub or a sink. Others
Curve mirrors, signs, reflectors, tunnel interior boards, tunnel lighting, exterior walls, roofs, sashes, mirrors, showcases, refrigerated and frozen showcases, show windows, signboards, glass greenhouses, vinyl houses, displays, solar cells, glasses,
It can be used for optical lenses, endoscope lenses, paints, interior members, and the like. The substrate surface may be porous or dense.

When incorporated in a base material, silicate glass, borate glass,
Phosphate-based glass and the like, and glaze frit for general ceramics and the like can be mentioned. For example, SiO ₂ —Al ₂ O ₃ —Na ₂
The photo-decomposition catalyst of the present invention is dispersed in a binder liquid composed of an O / K ₂ O frit, and the photo-decomposition catalyst is adhered to a substrate such that a part of the photo-decomposition catalyst is exposed from the binder layer. Is melted, and then cooled to solidify the binder layer, whereby a multifunctional substrate containing the photolysis catalyst of the present invention can be obtained.

The coating solution containing the photodecomposition catalyst can be obtained by mixing the photodecomposition catalyst and a coating solution binder. As the binder for the coating liquid, a binder having resistance to photodecomposition catalytic activity is desired, and examples thereof include a siloxane resin, a silicon resin, a fluororesin, and silicate glass. In order to more effectively utilize the photodecomposition catalyst mixed in the layer, a binder having a light transmitting property is more preferable. Considering that dirt is difficult to adhere, those having water repellency, such as siloxane resin and fluorine resin, are preferable.

The coating liquid can be applied by a usual method, and examples thereof include spray coating, dip coating, roll coating, and spin coating. When forming a film by coating on the surface of the base material, a layer having a photodegradation catalytic action may be formed by coating the entire surface of the base material, or may be formed by coating a part of the surface. Good. Further, the coating solution containing the photodecomposition catalyst may be applied directly to the substrate, or may be applied via a primer layer. In particular, when the base material is metallic or vitreous, the use of a primer layer is preferable from the viewpoint of improving the adhesive strength.

The film containing the photo-decomposition catalyst is sprayed on a release paper, for example, by spraying a mixture of the photo-decomposition catalyst and the binder such that a part of the photo-decomposition catalyst is exposed from the binder layer, and then cured or dried. It is obtained by peeling the pattern paper, but is not limited thereto. Next, by laminating or pasting the obtained film on a substrate, heating and melting the binder layer, and then cooling,
A multifunctional member in which a film containing a photolysis catalyst is laminated on the surface of a substrate can be obtained.

[0033]

As described above, the bandgap energy of the conventional layered titanate compound is 3.2 to 3.5 eV and does not show sufficient photocatalytic activity under irradiation with visible light. , The band gap energy is, for example, 2.4 to 3.3 eV, and the wavelength is 375 to 550 n.
It is excited even by irradiation with visible light of m, and shows high catalytic activity for photolysis of water and the like. It is considered that this is because the band gap energy of the layered titanate compound is reduced by replacing the metal ion with the titanium atom of the layered titanate compound as described above.

Further, when a cocatalyst is included between the layers, electrons or holes generated by photoexcitation of the layered titanate compound of the host layer move to the cocatalyst, whereby charge separation effectively occurs, and electrons and holes are effectively generated. Since the recombination of holes is suppressed, the photocatalytic activity is improved. Further, the photodecomposition catalyst of the present invention hardly dissolves in an aqueous solution, and is chemically stable.

[0035]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited to the following examples.

Example 1 K ₂ CO ₃ , TiO ₂ and Fe ₂ O ₃ were mixed at a molar ratio of 1: 2.
The mixture was mixed at 25: 0.25 and calcined at 1300 ° C. for 5 hours to synthesize potassium titanate powder containing iron ions. This potassium titanate powder was dispersed in a 1 M aqueous hydrochloric acid solution at 30 ° C. for 30 minutes to obtain titanic acid containing (solid solution) 6.6% by weight of iron ions. The powder X-ray diffraction pattern and ultraviolet-visible diffuse reflection spectrum of this sample are shown in FIGS. 0.5 g of this sample was added to 0.1 M Na at 60 ° C.
_The solution was added to 500 cm ³ of a 2S aqueous solution, and a 100 W mercury lamp with visible light having a wavelength of 400 nm or more was irradiated. Photolysis of water occurred by irradiation with visible light, and hydrogen was generated. FIG. 3 shows the amount of hydrogen generated at this time.

Example 2 K ₂ CO ₃ , TiO ₂ and NiO were mixed at a molar ratio of 1: 2: 0.
5 and baked at 1300 ° C. for 5 hours to synthesize a powder of potassium titanate containing nickel ions. This potassium titanate powder was added to a 1 M aqueous hydrochloric acid solution at 30 ° C.
The mixture was dispersed for 0 minute to obtain titanic acid containing (solid solution) 7.3% by weight of nickel ions. The powder X-ray diffraction pattern and ultraviolet-visible diffuse reflection spectrum of this sample are shown in FIGS. 0.5 g of this sample was added to 0.1 M Na at 60 ° C.
_The solution was added to 500 cm ³ of a 2S aqueous solution, and a 100 W mercury lamp with visible light having a wavelength of 400 nm or more was irradiated. Photolysis of water occurred by irradiation with visible light, and hydrogen was generated. FIG. 3 shows the amount of hydrogen generated at this time.

Example 3 K ₂ CO ₃ , TiO ₂ and CuO were mixed at a molar ratio of 1: 2.4.
5: 0.05, baked at 1300 ° C. for 5 hours,
A powder of potassium titanate containing copper ions was synthesized.
This potassium titanate powder was dispersed in a 1 M aqueous hydrochloric acid solution at 30 ° C. for 30 minutes to obtain titanic acid containing (solid solution) 0.43% by weight of copper ions. The powder X-ray diffraction pattern and ultraviolet-visible diffuse reflection spectrum of this sample are shown in FIGS. 0.5 g of this sample was added to 0.1 M Na at 60 ° C.
_The solution was added to 500 cm ³ of a 2S aqueous solution, and a 100 W mercury lamp with visible light having a wavelength of 400 nm or more was irradiated. Photolysis of water occurred by irradiation with visible light, and hydrogen was generated. FIG. 3 shows the amount of hydrogen generated at this time.

Comparative Example 1 K ₂ CO ₃ and TiO ₂ were mixed at a molar ratio of 1: 2.5.
Baking at 300 ° C. for 5 hours to form a layered potassium tetratitanate (K
₂ Ti ₄ O ₉ ) powder was synthesized. This layered potassium tetratitanate powder was dispersed in a 1 M aqueous hydrochloric acid solution at 30 ° C. for 30 minutes to obtain tetratitanic acid (H ₂ Ti ₄ O ₉ ). The powder X-ray line pattern and ultraviolet-visible diffuse reflection spectrum of this sample are shown in FIGS. 0.5 g of this sample is placed at 60 ° C.
Was added to 500 cm ³ of a 0.1 M Na ₂ S aqueous solution of
A visible light of 0 W mercury lamp wavelength of 400 nm or more was irradiated.
Photolysis of water did not proceed at all with visible light irradiation. FIG.
Shows the amount of hydrogen generated.

As is apparent from FIG. 1, the samples of Examples 1 to 3 all show an X-ray line pattern similar to that of the tetratitanic acid of Comparative Example 1. As is clear from FIG. 2, the tetratitanic acid of Comparative Example 1 has an upper absorption edge wavelength of 400 n.
m and is not excited by visible light having a wavelength of 400 nm or more, but the absorption edge wavelength of each of the tetratitanic acids of Examples 1 to 3 to which iron ions, nickel ions, and copper ions are added is 54
3, 538 and 530 nm, and can be excited by visible light.

As is clear from FIG. 3, Comparative Example 1
The tetratitanic acid of Examples 1 to 3 to which iron ions, nickel ions and copper ions were added, whereas the tetratitanic acid did not show photocatalytic activity under visible light irradiation at a wavelength of 400 nm or more and did not generate hydrogen. All showed photocatalytic activity upon irradiation with visible light and photolyzed water to generate hydrogen.

Example 4 The titanic acid containing 0.43% by weight of copper ion of Example 3 having the highest activity was replaced with [Pt (NH ₃ ) ₄ ] Cl ₂
Suspended in an aqueous solution (containing Pt so that the weight ratio of Pt / titanic acid = 0.01), and [Pt (NH ₃ ) ₄ ]
After the inclusion of ²⁺ , a mercury lamp of 450 W was irradiated for 1 hour to precipitate Pt between the layers. The platinum inclusion amount of this catalyst was 0.3% by weight. 0.5 g of this sample is placed at 60 ° C.
Was added to 500 cm ³ of a 0.1 M Na ₂ S aqueous solution of
A visible light of 0 W mercury lamp wavelength of 400 nm or more was irradiated.
Photolysis of water occurred by irradiation with visible light, and hydrogen was generated. FIG. 4 shows the amount of hydrogen generated at this time.

Example 5 The titanic acid containing 0.43% by weight of copper ion of Example 3 having the highest activity was dispersed in water, and the molar ratio of nC _{3 was} 20 times the titanic acid. H ₇ NH ₂ was added and 2
The reaction was performed at 5 ° C. for 4 days, and H ⁺ between layers was replaced with nC ₃ H ₇ NH.
₃ ⁺ and the ion exchange. _{Further, Ti (i-C 3 H} 7 O)
Glacial acetic acid 5 times in molar ratio was added to ₄ and stirred for 30 minutes.
After preparing a (CH ₃ CO) _x (i-C ₃ H ₇ O) _y complex, a 5-fold amount of water was added to the solution, and the mixture was stirred for 1 hour,
(CH ₃ CO) _x (OH) _y ^{Z +} was prepared. In this solution, copper ion-containing titanic acid obtained by ion-exchanging nC ₃ H ₇ NH ₃ ⁺ is suspended (layered titanic acid / Ti (CH ₃ C ₃
O) _x (OH) _y ^{Z +} molar ratio = 40), 5-15 at room temperature
0 hours to react n-C ₃ H ₇ NH ₃ ⁺ between the layers with Ti
After ion exchange with (CH ₃ CO) _x (OH) _y ^{Z +} , filtration and separation, the sample was redispersed in water, and the light of a 450 W mercury lamp was
Irradiation for 0 hour, Ti (CH ₃ CO) included between layers
_x (OH) _yZ ⁺ was photodecomposed into titanium oxide, and a photodecomposition catalyst containing titanium oxide was prepared. The titanium oxide inclusion amount of this photolysis catalyst was 26% by weight. This sample 0.
5 g of a 0.1 M Na ₂ S aqueous solution of 500 cm ^{3 at} 60 ° C.
And irradiated with 100 W mercury lamp visible light having a wavelength of 400 nm or more. Photolysis of water occurs by irradiation with visible light,
Hydrogen evolved. FIG. 4 shows the amount of hydrogen generated at this time.

As is apparent from FIG. 4, the photocatalytic activity of titanic acid containing copper ions is significantly improved by enclosing platinum or titanium oxide as a co-catalyst between the layers, and the hydrogen generation rate is higher than that of Example 3. It is about 10 times and about 3 times faster, respectively.

[0045]

According to the photodecomposition catalyst of the present invention, the bandgap energy can be reduced by adding a metal ion such as iron, nickel, or copper to the layered titanate compound, and the layer can be excited by visible light. An excellent photodecomposition catalyst can be obtained.

The photocatalytic activity can be further enhanced by including a co-catalyst between the layers of the layered titanate compound. According to the hydrogen production method of the present invention, water can be efficiently decomposed and hydrogen can be produced by using the photodecomposition catalyst of the present invention.

[Brief description of the drawings]

FIG. 1 is a view showing powder X-ray diffraction patterns of metal ion-containing titanic acid and layered tetratitanic acid in Examples 1 to 3 and Comparative Example 1.

FIG. 2 is a diagram showing an ultraviolet-diffuse reflection spectrum of metal ion-containing titanic acid and layered tetratitanic acid in Examples 1 to 3 and Comparative Example 1.

FIG. 3 is a graph showing hydrogen generation amounts in Examples 1 to 3 and Comparative Example 1.

FIG. 4 is a graph showing hydrogen generation amounts in Examples 3 to 5.

Continued on the front page. (72) Inventor Satoshi Uchida 1-9-7 Minami Yagiyama, Taihaku-ku, Sendai, Miyagi Prefecture Obata Heights 202 (72) Inventor Masaru Yanagisawa 2-2-22 Mukoyama, Taihaku-ku, Sendai City, Miyagi Prefecture Wakaso 105 (56) References JP-A-2-172535 (JP, A) JP-A-64-500187 (JP, A) MACHIDA, M .; et. al. "Preparation and na nostructure of pil laid layered titanates and tantalates for photocatalytic ticial materials" Stud. Surf. Sci. Caral. , 118 (Preparation of Catalysts VII), 951-958 (elsevier) Aug. 1998 (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 21/00-38/74 C01B 3/04 CA ( STN)

Claims (5)

(57) [Claims] 1. Vanadium, chromium, manganese, iron, cobalt, nickel, copper, molybdenum, ruthenium, silver,
Cadmium, and a photo-decomposition catalyst comprising a cation-exchangeable layered titanate compound containing at least one metal ion selected from cerium in the crystal structure of the layered titanic acid ,
A method for using a photolysis catalyst , which comprises irradiating visible light having a wavelength of 400 nm or more to excite the visible light . 2. A photo-decomposition catalyst comprising at least one metal or metal oxide selected from titanium oxide, platinum, ruthenium, rhodium, copper and nickel between the layers of the layered titanate compound. A method for using the photolysis catalyst according to claim 1. 3. The method according to claim ₂ , wherein the layered titanate compound is H ₂ Ti ₂
O ₅ , H ₂ Ti ₃ O ₇ , H ₂ Ti ₄ O ₉ , H ₂ La ₂ T
i ₃ O _10, HTiNbO ₅ and using the photodegradation catalyst according to claim 1 or 2, characterized in that at least one selected from the alkali metal salts and alkaline earth metal salts. 4. A method for producing hydrogen by decomposing water by irradiating visible light having a wavelength of 400 nm or more using the photodecomposition catalyst according to claim 1. Description: Hydrogen production method. 5. The hydrogen production method according to claim 4, wherein the water to be subjected to photolysis is an aqueous solution containing a reducing compound.