JP4365167B2 - Photocatalyst composite powder and method for producing the same - Google Patents

Description

  The present invention relates to a photocatalyst composite powder that exhibits high photocatalytic activity even when irradiated with visible light, and a method for producing the same.

Photocatalytic technology having antibacterial properties, antifouling properties, deodorizing effects, and the like has attracted a great deal of attention in relation to the current social situation where environmental problems are being asked on a global scale. In particular, research and development and practical application of a technology using titanium oxide (TiO ₂ ) as a photocatalyst are progressing in a wide range of applications.
However, the region of light that can be used for the photocatalytic reaction of titanium oxide is limited to ultraviolet light, and a photocatalyst that can also be used in the visible light region is desired in order to realize effective use of energy and indoor use. .

An example of a photocatalyst that is also active in the visible light region is BiVO ₄ . BiVO ₄ has three crystal structures called Clinobisvante type, Dreyerite type, and Pucherite type. Among them, Clinobisvante type BiVO ₄ is known to have a high photocatalytic activity even in the visible light region (for example, non-visible). Patent Document 1).

Clinobisvante type BiVO ₄ is usually produced by forming, sintering, and grinding raw material powders by various methods. Such a manufacturing method requires equipment costs for carrying out heat treatment at a high temperature and great energy for heat treatment, and in order to obtain a powder by pulverizing the sintered body, There is a problem that the shape is not constant and the particle size distribution becomes wide.

As a method for producing Clinobisvante-type BiVO ₄ at room temperature without the need for heat treatment at high temperature, an aqueous solution containing Bi (NO ₃ ) ₃ and Na ₃ VO ₃ (molar ratio Bi: V = 1: 1) is mixed with a base (Na ₂ CO ₃ ) to form Dryerite type BiVO ₄ powder as a precipitate, followed by further stirring at room temperature for 46 hours to obtain a Clinobisvanite type BiVO ₄ single-phase powder (for example, non-coating) Patent Document 2).

J. et al. Am. Chem. Soc. 1999, 121, 11459-11467 Chem. Mater. 2001, 13, 4624-4628

However, in Non-Patent Document 2, the produced Clinobisvante type BiVO ₄ powder has a high secondary agglomeration property, does not sufficiently exhibit photocatalytic activity, and requires a long time for synthesis, which is disadvantageous in cost. There was a problem.

For the present invention to solve the above problems, the results of extensive studies, on the surface of porous particles composed mainly of Dreyerite type BiVO _4, the photocatalyst particles composite mainly composed of Clinobisvanite type BiVO ₄ The present inventors have found that the photocatalyst composite powder has high photocatalytic activity even in the visible light region. Further, it has been found that by adding an alkaline solution to an acidic aqueous solution containing a Bi compound and a V compound and aging, secondary aggregation is inhibited and a photocatalyst composite powder having excellent dispersibility can be obtained in a relatively short time. It was.

That is, the present invention has the following features.
1. The Dreyerite type BiVO ₄ on the surface of the porous particles mainly, with the photocatalyst fine particle mainly comprising Clinobisvanite type BiVO _4, palladium, platinum, rhodium, ruthenium, nickel, iron, copper, silver, gold and zinc group 1. Photocatalyst composite powder, wherein at least one metal selected from the above is composited. 1. The metal is silver. 2. The photocatalyst composite powder described 1. Or 2. A method for producing the described photocatalyst composite powder, comprising adding an alkaline solution to an acidic aqueous solution containing a Bi compound and a V compound, wherein the molar ratio of Bi to V is 0.1 <Bi / V <1, A solution containing a photocatalyst composite powder obtained by aging , a solution containing at least one metal salt selected from the group consisting of palladium, platinum, rhodium, ruthenium, nickel, iron, copper, silver, gold and zinc, and a reducing agent And a metal alloy on the surface of the photocatalyst composite powder by mechanical alloying at 0 ° C. to 100 ° C. 2. The metal is silver . 4. Production method of the photocatalyst composite powder described 2. The acidic aqueous solution further contains a water-soluble organic compound. Or 4. 5. Manufacturing method of photocatalyst composite powder as described in 6. 2. The concentration of the alkaline solution is adjusted so that the pH of the mixed solution does not exceed 1. To 5. 6. Production method of photocatalyst composite powder according to any one of A method for producing a photocatalyst composite powder in which photocatalyst fine particles mainly composed of Clinobisvanite type BiVO ₄ are composited on the surface of porous particles mainly composed of Dreyerite type BiVO ₄ , comprising a Bi compound and a V compound Furthermore, an alkaline solution is added to an acidic aqueous solution containing a water-soluble organic compound and the molar ratio of Bi to V is 0.1 <Bi / V <1, so that the pH of the mixed solution does not exceed 1 Method for producing photocatalyst composite powder characterized by adjusting and aging

  The photocatalyst composite powder of the present invention exhibits high photocatalytic activity even in the visible light region, and can be produced in a short time, which is advantageous in terms of cost, non-polluting, and has a beautiful yellow color. In addition, since it is a porous particle, it exhibits excellent adsorption and resolution of harmful gases and has better photocatalytic ability.

  Hereinafter, the present invention will be described in detail based on the best mode for carrying out the invention.

(Photocatalyst composite powder)
Photocatalytic composite powder of the present invention, the surface of porous particles composed mainly of Dreyerite type BiVO _4, the photocatalyst fine particle mainly comprising Clinobisvanite type BiVO ₄ is characterized in that it is complexed.
Since the photocatalyst composite powder of the present invention exhibits high photocatalytic activity not only in the ultraviolet light region but also in the visible light region, it can be used indoors and in tunnels. Further, since porous particles mainly containing Dreyerite type BiVO ₄ are used, it is excellent in the adsorption and decomposition of harmful gases and has a more excellent photocatalytic ability.

Further, the Clinobisvante-type BiVO ₄ of the present invention is not particularly limited as long as it is complexed on the surface of the porous particles, and may be present only on a part of the particle surface or may be present on the entire particle surface. Further, if Clinobisvante-type BiVO ₄ is present on the particle surface, it may be present inside the particle.

  Such a photocatalyst composite powder desirably has a particle size of 0.01 to 100 μm (preferably 0.1 to 10 μm). By being in such a range, when used for a support such as a paint or fiber, the coloring power and the hiding power are large and are easily dispersed.

  Furthermore, since the photocatalyst composite powder of the present invention has a beautiful yellow color, it can also be used as a photocatalyst pigment suitable for use in members that require aesthetics such as indoors.

(Porous particles)
Since the porous particles of the present invention are porous, they are excellent in adsorption and decomposition of harmful gases, and a photocatalyst composite powder having excellent photocatalytic ability can be obtained by complexing photocatalyst fine particles described later. .
Such porous particles are mainly composed of Dreyerite type BiVO _4, Clinobisvanite type BiVO _4, in addition to Mg of Pucherite type _{BiVO 4, Ca, Sr, Ba} , Ti, Mn, Fe, Co, Ni , Cu, Zn, Y, Zr, Mo, Al, Si, Ga, Ge, and other metal elements and compounds thereof may be contained to such an extent that the effects of the present invention are not impaired.

  The particle shape, particle diameter, particle diameter distribution and the like of the porous particles can be appropriately set depending on the application. As the particle shape of the porous particles, spherical porous particles are preferable because they are advantageous for adsorption and decomposition of harmful gases. The particle diameter of the porous particles is desirably 0.01 to 100 μm (preferably 0.1 to 10 μm). By being in such a range, when used for a support such as paint or fiber, the coloring power and the hiding power are large, and it is easy to disperse, which is advantageous.

(Photocatalyst fine particles)
Since the photocatalyst fine particles used in the present invention are mainly composed of Clinobisvante type BiVO ₄ , they can sufficiently have excellent photocatalytic ability even in the visible light region.
Such photocatalyst fine particles is as a main component Clinobisvanite type BiVO _4, Dreyerite type BiVO _4, in addition to Mg of Pucherite type _{BiVO 4, Ca, Sr, Ba} , Ti, Mn, Fe, Co, Ni , Cu, Zn, Y, Zr, Mo, Al, Si, Ga, Ge, and other metal elements and compounds thereof may be contained to such an extent that the effects of the present invention are not impaired. The particle shape, particle size, particle size distribution, etc. of the photocatalyst fine particles can be set as appropriate.

In the present invention, the surface of porous particles composed mainly of Dreyerite type BiVO _4, it is preferable that the metal is complexed with the photocatalyst fine particle mainly comprising Clinobisvanite type BiVO _4.
By compounding metals, harmful substances can be decomposed with high efficiency, and the effects of environmental purification such as water purification, deodorization and purification of air pollution, and photocatalytic effects such as antibacterial effects can be improved. This effect is considered to be obtained because it becomes difficult for recombination of electrons and holes to occur due to the movement of electrons to metal among the electrons and holes generated from the photocatalyst irradiated with light.

Examples of the metal include palladium, platinum, rhodium, ruthenium, iron, nickel, copper, silver, gold, and zinc, and one or more of these can be used in combination. In the present invention, palladium, platinum, copper, silver, and gold are particularly preferable, and platinum, silver, and gold are more preferable.
The average particle size of the metal is preferably smaller than the average particle size of the photocatalyst composite powder. Although the average particle diameter of a metal is not specifically limited, Usually, 0.005-0.25 micrometer, Furthermore, it is preferable that it is 0.01-0.2 micrometer.
The composite amount of the metal is not particularly limited, but is preferably 0.01 to 10 wt%, more preferably 0.1 to 9.0 wt% with respect to the total amount of the photocatalyst composite powder. When the composite amount of the metal is smaller than this range, it is difficult to improve the photocatalytic effect. When the weight of the metal is larger than this range, the photocatalytic effect may be lowered because the light irradiation to the photocatalyst particles is inhibited by the metal.

(Method for producing photocatalyst composite powder)
Method for producing a photocatalyst composite powder of the present invention, the surface of porous particles composed mainly of Dreyerite type BiVO _4, Clinobisvanite type BiVO ₄ can produce the powder photocatalyst fine particles are complexed mainly composed of Although there is no particular limitation as long as it is present, for example, a method obtained by aging by adding an alkaline solution to an acidic aqueous solution containing a Bi compound and a V compound is preferable. Such a method is advantageous in terms of cost because it can be produced in a short time, and a photocatalyst composite powder having a uniform particle shape and particle diameter can also be obtained.
Moreover, the photocatalyst fine particles can be efficiently dispersed and arranged on the surface of the porous particles, and a photocatalyst composite powder having excellent photocatalytic ability can be obtained.

The acidic aqueous solution containing the Bi compound and V compound used in the present invention can be prepared by dissolving the Bi compound and V compound in nitric acid or acetic acid. The acidic aqueous solution is preferably pH 1 or less, more preferably pH 0.5 or less, and more preferably pH 0 or less.
As the molar ratio of Bi / V in the acidic aqueous solution, it is desirable that the molar ratio of Bi and V is 0.1 <Bi / V <1 (preferably 0.2 <Bi / V <0.9). By using an aqueous solution having such a molar ratio, a product containing Clinobisvante type BiVO ₄ and Dryerite type BiVO ₄ can be produced. When the Bi / V ratio in the water solubility is smaller than such a range, products other than BiVO ₄ are produced. Therefore, Clinobisvante-type BiVO ₄ and Dryerite-type BiVO ₄ which are the objects of the present invention are the main components. The product to be produced cannot be produced efficiently. When the Bi / V ratio in water solubility is larger than this range, the Clinobisvante type BiVO ₄ phase (Bi / V = 1) or the Dryerite type BiVO ₄ (Bi / V> 1) single phase is stable. Thus, it is not possible to obtain a product composed of Clinobisvante type BiVO ₄ and Dryerite type BiVO ₄ as the object of the present invention.

  Examples of the Bi compound include bismuth hydroxide, bismuth nitrate, bismuth nitrate pentapentahydrate, basic bismuth nitrate, bismuth carbonate, basic bismuth carbonate, bismuth oxide, bismuth sulfate, basic bismuth sulfate, bismuth chloride, and citrate. Examples thereof include bismuth acid bismuth, bismuth oxychloride, bismuth iodide, bismuth, bismuth 2-ethylhexanoate, bismuth naphthenate, and bismuth disalicylate. In particular, bismuth nitrate and bismuth oxide can be preferably used.

  Examples of the V compound include vanadium chloride, vanadium oxide, vanadium sulfate, vanadium oxalate, vanadium oxide acetyl acetate, sodium metavanadate, sodium orthovanadate and the like, sodium vanadate, potassium vanadate, ammonium vanadate, and the like. In particular, sodium metavanadate, sodium orthovanadate, potassium vanadate, and ammonium vanadate can be suitably used.

In the present invention, by using an alkaline solution, a Bi compound and a V compound can be co-precipitated to produce Clinobisvante type BiVO ₄ and Dreyerite type BiVO ₄ .
At this time, the concentration of the alkaline solution is preferably adjusted so that the pH of the mixed solution does not exceed 3, more preferably 1. If the pH is higher than 3, it will be difficult to produce Clinobisvante-type BiVO ₄ .
As such an alkaline solution, for example, an aqueous solution of potassium hydroxide, sodium hydroxide, sodium carbonate, ammonia, urea is preferably used.
The mixing of the acidic aqueous solution containing the Bi compound and the V compound and the alkaline solution can be performed either batchwise or continuously. Further, if necessary, it can be carried out in a highly turbulent flow, for example, in a device equipped with a high-performance stirrer using a flow reactor or a mixing nozzle. Moreover, it can also carry out by the continuous method which adds these simultaneously, or can also carry out by the batch system which puts one kind of solution first and then adds another solution by metering.

It is desirable that the acidic aqueous solution containing the Bi compound and the V compound further contains a water-soluble organic compound. By using such a water-soluble organic compound, a major component particle shape of the porous particles composed mainly of Dreyerite type BiVO _4, particle diameter, it is possible to control the particle size distribution, further Clinobisvanite type BiVO ₄ particle shape of the photocatalyst particles, the particle diameter, it is possible to control the particle size distribution, the photocatalyst fine particle mainly comprising Clinobisvanite type BiVO ₄ on the surface of the porous particles composed mainly of Dreyerite type BiVO ₄ efficiently dispersed The arranged photocatalyst composite powder can be obtained. Moreover, the particle shape, particle diameter, and particle diameter distribution of the photocatalyst composite powder can be controlled, and a photocatalyst composite powder excellent in dispersibility can be obtained.
The water-soluble organic compound of the present invention acts on the surface of the produced Clinobisvante-type BiVO ₄ or Dreyerite-type BiVO ₄ to control particle growth, and as a result, controls the particle shape, particle size, particle size distribution, etc. It seems that there is.

  Such water-soluble organic compounds include alcohols, polyols, ketones, polyethers, esters, carboxylic acids, polycarboxylic acids, celluloses, saccharides, sulfonic acids, amino acids, amines, More specifically, aliphatic alcohols such as methanol, ethanol, propanol, butanol, pentanol and hexanol, aliphatic polyhydric alcohols such as ethylene glycol, propanediol, butanediol, glycerin, polyethylene glycol and polypropylene glycol, phenol and catechol , Aromatic alcohols such as cresol, alcohols having a heterocyclic ring such as furfuryl alcohol, ketones such as acetone, methyl ethyl ketone, acetylacetone, ethyl ether, tetrahydrofuran, dioxane, polyethylene Ethers or polyethers such as oxyalkylene ethers, ethylene oxide adducts, propylene oxide adducts, esters such as ethyl acetate, ethyl acetoacetate, glycine ethyl ester, formic acid, acetic acid, propionic acid, butanoic acid, butyric acid, oxalic acid, Carboxylic acid such as malonic acid, citric acid, tartaric acid, gluconic acid, salicylic acid, benzoic acid, acrylic acid, maleic acid, glyceric acid, eleostearic acid, polyacrylic acid, polymaleic acid, acrylic acid-maleic acid copolymer, polycarboxylic acid Or hydroxycarboxylic acids and salts thereof, carboxymethylcelluloses, monosaccharides such as glucose and galactose, polysaccharides such as sucrose, lactose, amylose, chitin, and cellulose, alkylbenzenesulfonic acid, paratoluenesulfonic acid, Sulfonic acids such as alkyl sulfonic acid, α-olefin sulfonic acid, polyoxyethylene alkyl sulfonic acid, lignin sulfonic acid and naphthalene sulfonic acid and salts thereof, amino acids such as glycine, glutamic acid, aspartic acid and alanine, monoethanolamine, diethanolamine, Examples thereof include hydroxyamines such as triethanolamine and butanolamine, trimethylaminoethylalkylamide, alkylpyridinium sulfate, alkyltrimethylammonium halide, alkylbetaine, and alkyldiethylenetriaminoacetic acid.

  Among these water-soluble organic compounds, water-soluble organic compounds having one or more functional groups of any one of hydroxyl group, carboxyl group and amino group are preferred, for example, aliphatic alcohols and aliphatic polyhydric alcohols. Can be mentioned. These may be used alone or in combination of two or more.

  The water-soluble organic compound is preferably contained in an acidic aqueous solution containing the Bi compound and the V compound in a range of 0.001 wt% to 10 wt% (preferably 0.01 wt% to 5 wt%). By appropriately setting the content of the water-soluble organic compound, the particle shape, particle size, particle size distribution and the like can be controlled.

In the production of the photocatalyst composite powder of the present invention, an alkali solution is added at a relatively low temperature of 10 to 100 ° C. (preferably 20 to 40 ° C.), and then aged while being kept stirring. preferable. This operation time is 0.5 to 24 hours (preferably 0.5 to 12 hours).
This operation is effective for improving the particle shape, particle diameter, particle distribution, and surface properties and crystallinity of the photocatalyst composite powder.
After aging, solid-liquid separation is performed, followed by washing and drying, whereby a powdery product can be obtained. At this time, it is preferable to sufficiently remove ions remaining in the suspension of the water-soluble organic compound and the alkali solution after precipitation, by solid-liquid separation and washing. The solution used for washing is not particularly limited, but water is preferably used.

Further, the method of compounding the metal is not particularly limited, but it is obtained by mechanically alloying the photocatalyst composite powder obtained as described above, the metal salt solution, and the reducing agent at 0 ° C. to 100 ° C. Methods and the like.
In such a method, compared to known methods such as electroless plating and physical vapor deposition, the metal can be uniformly combined on the powder surface, and less waste liquid is discharged. Can be used.

In mechanical alloying according to the present invention, a photocatalyst composite powder in which a photocatalyst is supported on a porous inorganic powder, a metal salt solution, and a reducing agent are mixed and mechanically pulverized. At the same time, the metal fine particles are uniformly dispersed on the surface of the photocatalyst composite powder by mechanical energy and then fixed, so that a photocatalyst composite powder carrying a metal can be produced. According to such a manufacturing method, since it can manufacture in a short time, it is advantageous in cost, and a metal can adhere more uniformly to the surface of porous inorganic powder, and is preferred.
Mechanical pulverization includes jet method using a jet pulverizer, pin mill, disc mill, hammer mill, hammer type using axial flow type / vortex type mill, classifier combined mill, etc., media type pulverizer such as ball mill, media stirring mill, etc. It can be performed by a mill method using a roller mill or the like.
In the present invention, it is particularly desirable to use a media-type pulverizer such as a ball mill or a media agitating mill that can continuously mix and pulverize solid raw materials in a constant space during the reaction time during which the compound is formed.
The balls and grinding media used in the ball mill and media stirring mill are not limited as long as they have appropriate hardness and specific gravity. For example, steel, glass, zirconia, agate, alumina, tungsten carbide, chrome steel, silicon nitride, plastic Those having a composition such as polyamide can be used.
In the present invention, those having a chemically stable composition such as glass, zirconia, agate and the like are particularly preferable.
Also, in order to prevent overheating of the reaction system due to frictional heat of mechanical mixing and pulverization, a certain cooling time may be inserted during the mechanical mixing and pulverization, and the air may be naturally cooled. A device may be incorporated.
Mechanical mixing and pulverization may be performed continuously or batchwise. The production time is not particularly limited, but is usually about 10 minutes to 500 minutes.

  The metal salt solution of this invention is used in order to precipitate a metal by reacting with the reducing agent mentioned later. The solute of such a metal salt solution is not particularly limited, but includes, for example, at least one metal element selected from palladium, platinum, rhodium, ruthenium, iron, nickel, copper, silver, gold, and zinc. Are preferably used, and in particular, those containing palladium, platinum, copper, silver, and gold are preferable, and those containing platinum, silver, and gold are preferable because they are stable. In the present invention, it is desirable to use at least one metal salt selected from nitrates, chlorides, acetates, sulfates, acetylacetonates, and ammine complexes of such metal elements.

The solvent of the metal salt solution is not limited as long as it dissolves the metal salt stably, and alcohols such as water, methanol, ethanol, n-propanol, isopropanol, ethylene glycol, ethylene glycol monomethyl ether, propylene glycol, propylene Glycol derivatives such as glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, esters, ketones, ethers, n-hexane, n-pentane, n-octane, n-nonane, n-decane N-undecane, n-dodecane, terpin oil, mineral hydrocarbons such as mineral spirits, aromatic hydrocarbons such as toluene, xylene, solvent naphtha, others, ethyl acetate, butyl acetate, methylethyl Tons, and methyl isobutyl ketone.
Furthermore, you may adjust suitably the pH of a metal salt solution in the range of 0-14 using a well-known base or acid. By adjusting the pH, a stable metal salt solution can be prepared. Examples of the base include sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium hydroxide, ammonia, urea, amines and the like. Examples of the acid include hydrochloric acid, sulfuric acid, acetic acid, nitric acid, citric acid, formic acid and the like.

The reducing agent functions to react with the metal salt solution to precipitate the metal. Examples of the reducing agent include hydrazine, formaldehyde, and polysaccharides such as glucose, and it is particularly preferable to use a polysaccharide such as glucose that is highly safe and inexpensive.
The mixing amount of the reducing agent is usually about 25 to 400 wt% with respect to the metal element.

  Examples and Comparative Examples are shown below to clarify the features of the present invention, but the present invention is not limited to these Examples.

(Example 1)
(Production of photocatalyst composite powder)
And _{Bi (NO 3) 3 · 5H} 2 O 4.7g, Na 3 VO 4 2.8g of (Bi / V = 0.75) was dissolved in 1N nitric acid 0.32 L, was added ethylene glycol 5.6 g. At this time, the pH was 1 or less. Next, 0.2 l of 1N sodium carbonate was added dropwise at 25 ° C. while stirring. At this time, the pH was 1 or less. Then, the photocatalyst composite powder was produced by continuing to stir at 25 ° C. for 12 hours and aging. Filtration and washing were followed by drying at 110 ° C. to obtain a yellow powder.
As a result of observing the obtained powder with an electron microscope (JSM-5310, manufactured by JEOL Ltd.), as shown in FIG. 1, plate crystals (average particle size: 1.2 μm) of Clinobisvante type BiVO ₄ were dried. A composite powder composited on the surface of spherical porous particles (average particle size 5.1 μm) made of type BiVO ₄ was observed.
Crystal structure of the obtained powder X-ray diffractometer (RINT-1100, Rigaku Co.) result of the analysis, the X-ray diffraction pattern shown in FIG. 4, the Dreyerite type BiVO ₄ surface, Clinobisvanite type BiVO ₄ It was confirmed that this occurred.

(Photocatalytic activity test in the visible light region)
0.5 g of the photocatalyst composite powder obtained in Example 1 was placed in a glass dish, uniformly dispersed using ethanol, and then dried at 110 ° C. for 2 hours. Next, this glass dish was hung on a glass top plate (thickness 5 mm) and fixed in the reaction vessel. There is a 1.5 cm gap between the glass top and the glass pan.
Commercially available ammonia gas and dry air were aerated, and the aeration was stopped when the ammonia concentration in the reaction vessel was stabilized at 1%. The light source was 18 W true light (fluorescent lamp that emits light having a spectrum close to that of sunlight), and was fixed on 5 cm above the glass plate. Next, an acrylic ultraviolet shielding plate (thickness 5 mm) is fixed between the 18 W trulite and the glass plate, shields light having a wavelength of 400 nm or less, and emits light having a wavelength of 400 nm or more (visible light). The photocatalyst composite powder was irradiated.
FIG. 7 shows the evaluation test results of the photocatalytic activity. As shown in FIG. 7, it was shown that the decomposition of ammonia occurred remarkably by irradiating the photocatalyst composite powder with visible light.

(Example 2)
12.0 g of the photocatalyst composite powder obtained in Example 1, 0.02 g of silver nitrate, 20.0 g of distilled water, 9.0 g of 25% aqueous ammonia, and 2.0 g of glucose were mixed, and beads made of zirconia (diameter 3 mm), Using a planetary ball mill (manufactured by Fritsch), mixing and pulverization were performed at 25 ° C. for 150 minutes at a rotation speed of 450 rpm. Thereafter, the solid-liquid separation and washing are performed, followed by drying at 100 ° C. for 2 hours, and the surface of the photocatalyst composite powder is combined with granular silver particles (average particle diameter 0.2 μm), which is slightly greenish yellow Of powder was obtained.
From the analysis of the X-ray diffraction pattern, the crystal structure of the obtained powder was confirmed to be complexed with Dreyerite-type BiVO ₄ , Clinobisvanite-type BiVO ₄ , and silver. FIG. 7 shows the evaluation results of the photocatalytic activity. As shown in FIG. 7, it was shown that the decomposition of ammonia occurred remarkably when the photocatalyst composite powder was irradiated with visible light.

(Comparative Example 1)
The same method as in Example 1 except that the amount of Bi (NO ₃ ) ₃ .5H ₂ O was 4.65 g and the amount of Na ₃ VO ₄ was 1.76 g (Bi / V = 1.00). A yellow powder having an average particle size of 2.65 μm was obtained.
As a result of observing the obtained powder with an electron microscope, only particles having a plate-like shape were observed as shown in FIG.
As shown in the X-ray diffraction pattern of FIG. 5, it was confirmed that only the Clinobisvante-type BiVO ₄ was generated in the crystal structure of the obtained powder. FIG. 7 shows the evaluation test results of photocatalytic activity.

(Comparative Example 2)
The sample was prepared in the same manner as in Example 1 except that the amount of Bi (NO ₃ ) ₃ .5H ₂ O was 6.32 g and the amount of Na ₃ VO ₄ was 2.11 g (Bi / V = 1.33). The light yellow powder having an average particle size of 5.8 μm was obtained.
As a result of observing the obtained powder with an electron microscope, only particles having a porous spherical shape were observed as shown in FIG.
As shown in the X-ray diffraction pattern of FIG. 6, only the Dryerite type BiVO ₄ was produced in the crystal structure of the obtained powder. FIG. 7 shows the evaluation test results of photocatalytic activity.

2 is an SEM image of the photocatalyst composite powder produced in Example 1. 2 is an SEM image of the photocatalyst composite powder produced in Comparative Example 1. 4 is a SEM image of the photocatalyst composite powder produced in Comparative Example 2. 2 is an X-ray diffraction pattern of the powder produced in Example 1. FIG. 2 is an X-ray diffraction pattern of a powder produced in Comparative Example 1. 3 is an X-ray diffraction pattern of a powder produced in Comparative Example 2. It is an ammonia decomposition test result by visible light irradiation.

Claims (7)

The Dreyerite type BiVO ₄ on the surface of the porous particles mainly, with the photocatalyst fine particle mainly comprising Clinobisvanite type BiVO _4, palladium, platinum, rhodium, ruthenium, nickel, iron, copper, silver, gold and zinc group A photocatalyst composite powder comprising at least one metal selected from the group consisting of The photocatalyst composite powder according to claim 1, wherein the metal is silver. A method for producing the photocatalyst composite powder according to claim 1 or 2 , comprising a Bi compound and a V compound, wherein the molar ratio of Bi to V is 0.1 <Bi / V <1. , A photocatalyst composite powder obtained by aging by adding an alkaline solution , and a metal of at least one metal selected from the group consisting of palladium, platinum, rhodium, ruthenium, nickel, iron, copper, silver, gold and zinc A method for producing a photocatalyst composite powder , comprising mixing a solution containing a salt and a reducing agent, and mechanically alloying at 0 ° C. to 100 ° C. to form a metal on the surface of the photocatalyst composite powder. The method for producing a photocatalyst composite powder according to claim 3 , wherein the metal is silver.   The method for producing a photocatalyst composite powder according to claim 3 or 4, wherein the acidic aqueous solution further contains a water-soluble organic compound. The method for producing a photocatalyst composite powder according to any one of claims 3 to 5, wherein the concentration of the alkali solution is adjusted so that the pH of the mixed solution does not exceed 1 The Dreyerite type BiVO ₄ on the surface of the porous particles mainly to a method of producing a photocatalyst composite powder of the photocatalyst fine particle mainly comprising Clinobisvanite type BiVO ₄ is complexed, Bi compound and V compound Further, an alkaline solution is added to an acidic aqueous solution containing a water-soluble organic compound and the molar ratio of Bi to V is 0.1 <Bi / V <1, so that the pH of the mixed solution does not exceed 1. Method for producing photocatalyst composite powder characterized by adjusting and aging

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