WO2020022594A1 - Visible-light-active catalyst powder - Google Patents

Abstract

Provided is visible-light-active catalyst powder comprising composite particles, wherein the composite particles comprise: platinum particles; and tungsten oxide particles, wherein the tungsten oxide particles support the platinum particles, and the XPS spectrum of Pt 4f7/2, which is measured from the visible-light-active catalyst powder, has at least one normal distribution which is extracted through a Voigt function, wherein one normal distribution extracted through the Voigt function is a first normal distribution having a first peak at a binding energy of 70.8 eV to 71.2 eV, and the ratio of the integral area of the first normal distribution to the integral area of the XPS spectrum of Pt 4f7/2 is 85% or greater.

Description

Visible light active catalyst powder

A visible light active catalyst powder.

Representative photocatalyst material TiO ₂ has the advantages of excellent durability and wear resistance, a safe and nontoxic material, and low price. On the other hand, because the bandgap energy is large and can absorb only the light below the ultraviolet light, it must be used together with a separate ultraviolet supply device or used outdoors in the ultraviolet-rich environment, and there is a limit to the application indoors or under the LED.

In view of this, many studies have been conducted on a catalyst having photoactivity to visible light capable of absorbing visible light and a method of preparing the same for indoor application. However, it is difficult to find consistent trends in many case studies, particularly in the case of proven performance in real residential conditions.

One embodiment of the present invention provides a visible light active catalyst powder having improved visible light responsiveness and having improved photocatalytic performance.

In one embodiment of the present invention, the visible light active catalyst powder including the composite particles, the composite particles are platinum particles; Tungsten oxide particles, wherein the tungsten oxide particles carry the platinum particles, and the XPS spectrum for 4f _7/2 of Pt measured for the visible light active catalyst powder is at least one through the Voit function. The normal distribution of is extracted, and one normal distribution extracted through the Void function is the first normal distribution having a first peak at binding energies 70.8 eV to 71.2 eV, and integrates the XPS spectrum with respect to 4f _7/2 of Pt. Provided is a visible light active catalyst powder having a ratio of an integrated area of the first normal distribution to an area of 85% or more.

In one embodiment of the present invention, (a) preparing a slurry solution by mixing the tungsten oxide powder in the platinum precursor solution, and then irradiating the slurry solution to the first photoreaction; And (b) adding alcohol to the slurry solution, followed by light irradiation to proceed with the secondary photoreaction, and measuring 4f of Pt as measured for the visible light active catalyst powder. _The XPS spectrum for _7/2 has a first peak having at least one normal distribution extracted through the Voit function, and one normal distribution extracted through the Void function having a first peak at binding energies 70.8 eV to 71.2 eV. _Provided is a normal distribution, wherein the ratio of the integral area of the first normal distribution to the integral area of the XPS spectrum with respect to 4f _7/2 of Pt is 85% or more.

The visible light active catalyst powder can further improve visible light responsiveness, excellent photocatalytic efficiency, and economic efficiency in a manufacturing process.

1 is a schematic diagram of visible light active catalyst particles according to an embodiment of the present invention.

2 is an XPS analysis graph of 4f _7/2 of Pt measured for the visible light active catalyst powder from Example 1. FIG.

FIG. 3 is an XPS analysis graph of 4f _7/2 of Pt measured for the visible light active catalyst powder from Example 2.

4 is an XPS analysis graph of 4f _7/2 of Pt measured for the visible light active catalyst powder obtained in Comparative Example 1. FIG.

5 is an XPS analysis graph of 4f _7/2 of Pt measured for the visible light active catalyst powder obtained in Comparative Example 2. FIG.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

In one embodiment of the present invention, there is provided a visible light active catalyst powder comprising the composite particles. The composite particles are platinum particles; And tungsten oxide particles, wherein the tungsten oxide particles carry the platinum particles.

The visible light active catalyst powder may be formed as an aggregate of the composite particles.

The XPS spectrum of 4f _7/2 of Pt measured for the visible light active catalyst powder has at least one normal distribution extracted through a Voit function, and one normal distribution extracted through the Void function is 70.8 to A first normal distribution having a first peak at 71.2, and the ratio of the integral area of the first normal distribution to the integral area of the XPS spectrum with respect to 4f _7/2 of Pt may be 85% or more.

In one embodiment, the XPS spectrum for 4f _7/2 of Pt may match the first normal distribution, in which case the first normal to the integral area of the XPS spectrum for 4f _7/2 of Pt The percentage of integrated areas of the distribution is 100%.

In one embodiment, with the first normal distribution, a second normal distribution with a second peak at 71.8 to 72.2 can be extracted from the XPS spectrum for 4f _7/2 of the Pt through the Void function, In this case, the ratio of the integral area of the first normal distribution to the integral area of the XPS spectrum with respect to 4f _7/2 of Pt may be 85% or more and less than 100%.

As a normal distribution extracted through a Void function from the XPS spectrum of 4f _7/2 of Pt, there may be another normal distribution in addition to the first normal distribution and the second normal distribution.

X-ray photoelectron spectroscopy (XPS) spectra for 4f _7/2 of Pt may be used as an XPS measuring apparatus of ESCA manufactured by Sigma Probe.

The first normal distribution and the second normal distribution are obtained by extracting through a Voit function from the XPS spectrum for 4f _7/2 of Pt, measured for the visible light active catalyst powder, for example, Voigt amplitude It can be obtained by using the R ² value to be 0.999 or more.

The composite particles are formed in a form in which nanoparticles of platinum particles are supported on a surface of the tungsten oxide particles.

The platinum particles are reduced and formed from a platinum precursor in accordance with the production method described below. For example, when the platinum precursor is H ₂ PtCl ₆ , the oxidation number of Pt is +4, and such Pt ⁴⁺ ions are reduced to form platinum particles in the composite particles. Platinum particles in the composite particles can be effectively reduced to the visible light activity when the oxidation number is zero. Platinum particles having an oxidation number of zero mean that they are supported in a metal state rather than an ion.

However, some platinum particles of the composite particles also occur when the oxidation number is +2. Platinum particles in an ionic state, such as Pt ²⁺ , produced by incomplete reduction of platinum in the manufacturing process, do not function as cocatalysts during the photocatalytic reaction of the composite particles, but rather interfere with photocatalytic reactions such as harmful gas removal Lowers the overall efficiency. That is, the platinum particles supported in the ionic state may cause a decrease in performance because they inhibit the photocatalytic reaction of the composite particles as the visible light active catalyst. In addition, when the content of the platinum particles supported in the ionic state increases, it can be seen that the expensive platinum precursor was wasted.

1 is a cross-sectional view schematically showing a composite particle 10 according to an embodiment of the present invention.

In FIG. 1, the composite particle 10 includes tungsten oxide particles 1 and platinum particles 2. For convenience, in FIG. 1, the platinum particles 2 are not distinguished according to the oxidation number, but the platinum particles when the oxidation number is not 0 or when the oxidation number is +2 are mixed with the platinum particles having the oxidation number 0. In FIG.

The composite particle 10 is a material capable of purifying air, deodorizing, and antibacterial by generating surface active oxygen such as superoxide anion or hydroxy radicals generated from energy obtained by absorbing light. For example, the superoxide anion or hydroxy radicals generated by the photoactive action of the multiparticulates can decompose harmful substances such as acetaldehyde, ammonia, formaldehyde, acetic acid, TVOC, and the like, such as Escherichia coli and Staphylococcus aureus. Antibacterial action is possible against bacteria.

Since the composite particle 10 may be activated not only by ultraviolet light but also by visible light, it may show excellent efficiency even in an indoor light source, and thus may not require a separate ultraviolet light supply device.

The composite particles have excellent visible light activity because of the high content of platinum particles having zero oxidation number in the total platinum particles. Thus, the visible light active catalyst powder increases the economics in the manufacturing process and reduces the waste of precursors.

On the other hand, the composite particles may have an advantage of improving the photocatalyst performance as the content of platinum particles having zero oxidation number is increased and increasing the complete decomposition probability of the reaction intermediate when decomposing harmful gases. In other words, when the harmful gas is decomposed by the visible light active catalyst powder, the probability that the reaction intermediate is completely decomposed into water and CO ₂ increases.

The XPS spectrum of 4f _7/2 of Pt is measured with respect to the binding energy of electrons belonging to the 4f electron shell of platinum particles contained in the visible light active catalyst powder. Since the first normal distribution has a peak at about 70.8 eV to 71.2 eV, specifically about 71.0 eV, the first normal distribution is associated with platinum particles having an oxidation number of 0, and the second normal distribution is a binding energy. Has a second peak at around 71.8 eV to 72.2 eV, specifically around 72.0 eV, and thus relates to platinum particles having an oxidation number of +2.

That is, since the XPS spectrum of 4t _7/2 of Pt is shown as a result of including not only platinum particles having zero oxidation number but also platinum particles having different oxidation numbers, the first normal distribution and the second normal distribution are extracted. Thus, the content ratio of platinum particles having an oxidation number of 0 and platinum particles having an oxidation number of +2 can be known.

A mass ratio of platinum particles having an oxidation number of 0 and platinum particles having an oxidation number of +2 is obtained in comparison with the integration area of the first normal distribution and the integration area of the second normal distribution. In the visible light active catalyst powder, the ratio of the integral area of the first normal distribution is 85% or more, specifically, 90% to 100% in the sum of the integral areas of the first normal distribution and the integral area of the second normal distribution. Can be

Almost all platinum particles in the visible light active catalyst powder are formed of platinum particles having an oxidation number of 0, and the XPS spectrum of 4f _7/2 of Pt may itself be the first normal distribution, in which case, the The ratio of the integral area of the first normal distribution to the integral area of the XPS spectrum with respect to 4f _7/2 of Pt is 100% (see the case of Example 1 described later).

In addition to the first normal distribution and the second normal distribution, a normal distribution of platinum having another oxidation number may be further extracted from the normal distribution extracted from the XPS spectrum of the 4f _7/2 of Pt through the Voit function. . However, the higher the content of platinum particles having zero oxidation number, the better the photocatalytic performance, and therefore, there is no normal distribution for platinum particles having different oxidation numbers, or the integral area thereof is relatively small.

The first normal distribution and the second normal distribution are obtained with an R ² value of 0.999 or more, and have excellent accuracy of normal fitting.

The tungsten oxide particles 1 may be formed as spherical, plate or needle shaped particles by, for example, a sol-gel method or a hydrothermal method as a carrier, but the shape thereof is not limited.

The tungsten oxide particles 1 are excellent in visible light activity performance.

The platinum particles 2 may be supported on the porous metal oxide by photodeposition, but are not limited thereto.

The platinum particles 2 act as cocatalysts to facilitate separation of electrons and holes from energy obtained by absorbing light.

The average diameter of the tungsten oxide particles 1 used in the production of the composite particles 10 may be calculated by electron microscopic measurements such as SEM image analysis, for example, the average diameter is about 30 nanometers (nm) to It may be used that is about 500 nanometers (nm). If the average diameter of the tungsten oxide particles (1) is too large exceeding the above range, it is impossible to form a stable coating liquid when the visible light active catalyst powder is dispersed in a solvent, and at the time of manufacturing a filter using the visible light active catalyst powder It may not be suitable for the process of coating the visible light active catalyst powder. If the diameter of the tungsten oxide particles 1 is too small below the range, the platinum particles 2 may be difficult to be stably supported.

The average particle diameter of the composite particle 10 is about 1 micrometer (μm) or less, specifically, about 0.2 micrometers to about 1 micrometer, for example, about 0.4 micrometers to about 0.5 micrometers. The average particle diameter of the composite particle 10 may be obtained by measuring a water dispersion of about 4 wt% of a visible light active catalyst using a particle size analyzer (Beckman, LS 13 320). In addition, the maximum particle diameter of the visible light active catalyst particles 10 is about 10 micrometers or less.

The visible light active catalyst particles 10 may include about 100 parts by weight of the tungsten oxide particles 1 and about 0.01 to about 5 parts by weight of the platinum particles 2. By adjusting their content in the weight ratio within the above range, while the tungsten oxide particles 1 sufficiently generate electrons and holes by visible light, the platinum particles 2 sufficiently prevent the recombination of the electrons and holes generated by the photocatalyst activity. The efficiency can be improved effectively.

When the content of the tungsten oxide particles (1) exceeds the content range can easily recombine electrons and electrons generated by the visible light, it is difficult to separate them does not exhibit sufficient photocatalytic activity, less than the content range In this case, the number of electrons transferred from the tungsten oxide particles 1 may not be sufficiently secured, and thus the photocatalytic activity may be reduced, and the exposure area of the tungsten oxide particles 1 to light may be reduced, thereby degrading the photocatalytic performance. .

The specific surface area of the tungsten oxide particles 1 may be about 50 m 2 / g to about 500 m 2 / g. By having a high specific surface area within the above range can be effectively exposed to a light source such as visible light while forming a porosity at an appropriate level to sufficiently support the platinum particles (2).

Hereinafter, a method of preparing visible light active catalyst powder according to one embodiment of the present invention will be described in detail.

The method for preparing the visible light active catalyst powder is performed by sequentially performing the following steps (a) to (c).

(a) A tungsten oxide powder is mixed with a platinum precursor solution to prepare a slurry solution, and then the slurry solution is irradiated with light to undergo a first photoreaction.

(b) After alcohol is added to the slurry solution, light irradiation is carried out to proceed with the secondary photoreaction.

In the step (a), tungsten oxide powder is prepared by grinding to a level of micro units or less in order to maximize the reaction area.

The platinum precursor compound for preparing the platinum precursor solution may be a material that can be reduced to platinum by electrons excited by light irradiation, and salt compounds dissolved in an aqueous solution may be used without limitation. Specifically, PtCl ₂ , PtCl ₄ , PtBr ₂ , H ₂ PtCl ₆ , K ₂ (PtCl ₄ ), Pt (NH ₃ ) ₄ Cl ₂ , Pt (NH ₃ ) ₄ (OH) ₂ , Pt (NH ₃ ) ₄ (NO ₃ ) ₂ And Pt (NH ₃ ) ₂ (NO ₂ ) ₂ , H ₂ Pt (OH) ₆ , Na ₂ Pt (OH) ₆ , and K ₂ Pt (OH) ₆ .

For example, the concentration of the platinum precursor solution may be adjusted by the relative content with respect to the tungsten oxide powder so that the content of platinum to 100 parts by weight of tungsten oxide particles is about 0.01 parts by weight to about 5 parts by weight.

Platinum ions separated from the platinum precursor during the first photoreaction of step (a) are attached to the surface of the tungsten oxide particles, and platinum ions attached to the surface of the tungsten oxide particle during the secondary photoreaction of step (b) It is understood that the reaction to be reduced occurs mainly.

In order for the final visible light active catalyst powder to show the XPS analysis results for 4f _7/2 of Pt described above, the proportion of platinum particles completely reduced to zero oxidation number is higher than that of platinum particles having oxidation number.

To this end, the visible light active catalyst powder of the present invention can be obtained by adjusting various process conditions. Hereinafter, specific process conditions for synthesizing the above-described visible light active catalyst powder of the present invention will be described.

First, the ratio of the time for performing the first photoreaction (first photoreaction time) and the time for proceeding the second photoreaction (secondary photoreaction time) may be adjusted.

It is understood that the secondary photoreaction does not significantly affect the final formation rate of the platinum particles of the oxidation number 0 because the second photoreaction proceeds at a very high speed. Good adhesion will affect the final formation rate of the platinum particles with zero oxidation number.

Therefore, it is important to proceed with the primary photoreaction for a sufficient time so that the reaction can proceed sufficiently.

For example, the first photoreaction may be performed for 4 hours to 24 hours.

For example, the secondary photoreaction may be performed for 2 hours to 6 hours.

In one embodiment, the first photoreaction time is longer than the second photoreaction time, specifically, the ratio of the first photoreaction time to the second photoreaction time may be 2: 1 to 12: 1.

In addition, it is important to sufficiently stir the slurry solution when performing each photoreaction of step (a) and (b) by the light irradiation.

For example, an inert gas such as nitrogen may be injected into the slurry solution to allow the slurry solution to be stirred during the photoreaction.

Depending on the injection flow rate and the injection method and location of the inert gas may help to progress the photoreaction well. For example, the flow rate of the inert gas injected into the slurry solution may be 5 L / min to 30 L / min.

In one embodiment, nitrogen may be used as the inert gas. When the slurry solution is agitated by using nitrogen gas, the stirring solution is superior to mechanical stirring, and the secondary effect of removing oxygen in the slurry solution may be obtained.

In the step (a), when preparing the slurry solution, the concentration of tungsten oxide powder may be 1 to 10 wt%.

In the step (b), the addition ratio of the alcohol may be 1 to 30 wt% of the slurry solution.

In exemplary embodiments, the viscosity of the slurry solution may be about 5.0 cP to about 8.0 cP at 25 ° C. The viscosity of the slurry solution can be measured using a Brookfield viscometer (Spindle No. 61, speed: 200 rpm, measurement time: 30 seconds).

For example, in the first photoreaction, the intensity of light irradiation may be about 5,000 lux to about 100,000 lux, and the intensity of light irradiation in the second photoreaction may be higher than the intensity of light in the primary photoreaction. . Specifically, the intensity of the secondary light irradiation may be 1 to 10 times higher, specifically 3 to 5 times higher than the intensity of the primary light irradiation.

After the secondary light irradiation, the catalyst recovery and drying step are optionally performed by centrifugation or the like.

Hereinafter, examples and comparative examples of the present invention are described. Such following examples are merely examples of the present invention and the present invention is not limited to the following examples.

(Example)

Example 1

A solution in which 7 wt% of tungsten oxide powder was dispersed in 93 wt% of water was prepared. An average particle diameter of 1 μm tungsten oxide powder dispersion solution was mixed with a supported raw material of 10 wt% aqueous solution of platinum chloride (H ₂ PtCl ₆ ) to prepare a slurry solution such that the amount of platinum was 1 part by weight based on 100 parts by weight of tungsten oxide powder.

The viscosity of the slurry solution was 6.2 cP at 25 ° C. using a Brookfield viscometer (Spindle No. 61, speed: 200 rpm, measurement time: 30 seconds).

Subsequently, the slurry solution is introduced into a photoreactor, a gas generator is installed to be connected to the photoreactor, and during the subsequent first and second light irradiation, nitrogen generated from the gas generator is supplied to the slurry solution. The slurry solution was allowed to stir directly into the interior of the mixture by nitrogen. The introduced nitrogen had a purity of 98.00% and a flow rate of 10 L / min.

The primary light reaction was performed for 6 hours by irradiating visible light energy of 400 nm to 700 nm to the slurry solution in the photoreactor using a visible light irradiation device. Subsequently, the visible light irradiation was blocked for about 2 minutes and the proportion of methanol was added to 5 wt% in the slurry solution, and then the visible light energy was transferred to the slurry in the photoreactor using the same irradiation apparatus as the first photoreaction. The platinum particles were supported on the tungsten oxide particles by irradiating the solution for 2 hours to carry out the secondary photoreaction to prepare a visible light active photocatalyst powder.

Example 2

A visible light active photocatalyst powder was prepared in the same manner as in Example 1 except that the first photoreaction was performed for 4 hours and the second photoreaction was performed for 2 hours.

Comparative Example 1

A visible light active photocatalyst powder was prepared in the same manner as in Example 1 except that the first photoreaction was performed for 2 hours and the second photoreaction was performed for 3 hours.

Comparative Example 2

The first photoreaction is carried out for 4 hours, the second photoreaction is carried out for 2 hours, nitrogen is not injected directly into the slurry solution, but is introduced into the top of the slurry solution in the photoreactor and the slurry solution is mechanically stirred Except for the reference point, a visible light active photocatalyst powder was prepared.

evaluation

Experimental Example 1: XPS Analysis

XPS spectra of 4t _7/2 of Pt were obtained using X-ray Photoelectron Spectroscopy (ESCA, Sigma Probe) on the visible light active catalyst powders obtained in Example 1 and Comparative Examples 1-2. The XPS spectrum of 4f _7/2 of Pt obtained above was fitted by Voigt amplitude to extract a normal distribution.

2 is the result of Example 1, where curve A is the XPS spectrum for 4f _7/2 of Pt and curve B corresponds to the first normal distribution with peaks at about 70.9. R ² of the normal distribution extracted in FIG. ² is 0.99997. 2, curve A and curve B almost coincide.

3 is the result of Experimental Example 2, curve A is the XPS spectrum for 4f _7/2 of Pt, curve B corresponds to the first normal distribution having a peak at about 70.9, and curve C at peaks at about 72.0. Corresponds to the second normal distribution. R ² of the normal distribution extracted in FIG. 3 is 0.99993.

4 is the result of Comparative Example 1, where curve A is the XPS spectrum for 4f _7/2 of Pt, curve B corresponds to a first normal distribution with a peak at about 70.9, and curve C at peaks at about 72.0 Corresponds to the second normal distribution. R ² of the normal distribution extracted in FIG. 4 is 0.99991.

5 is the result of Comparative Example 2, where curve A is the XPS spectrum for 4f _7/2 of Pt, curve B corresponds to the first normal distribution with peaks at about 70.9, and curve C at peaks at about 72.0. Corresponds to the second normal distribution. R ² of the normal distribution extracted in FIG. 5 is 0.99994.

2 to 5, the ratio of the integral area of the first normal distribution to the integral area of the XPS spectrum for 4f _7/2 of Pt is calculated and shown in Table 1 below.

division	% Of integral area of first normal distribution	% Of integral area of the second normal distribution
Example 1	100	-
Example 2	89	11
Comparative Example 1	67	33
Comparative Example 2	81	19

Experimental Example 2

Performance evaluation of the visible light active catalyst powders prepared in Examples 1-2 and Comparative Examples 1-2 proceeded to the gas bag evaluation described below.

A vessel containing 0.5 g of the visible light active catalyst powder was put in a gas bag, sealed, the remaining gas was drained, and 3 L of acetaldehyde 3 ppm gas was injected. The illuminance of the light source was 25,000 lux. Gas before injection and 30 minutes after injection are collected in a DNPH (2,4-dinitrophenylhydrazine) cartridge to obtain acetaldehyde concentration by high performance liquid chromatography (HPLC). By analyzing, acetaldehyde removal performance of each sample was calculated.

The evaluation results are shown in Table 2 below.

division	Acetaldehyde removal performance (%)
Example 1	92
Example 2	84
Comparative Example 1	65
Comparative Example 2	77

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of the invention.

<Code description>

1: tungsten oxide particles

2: platinum particles

10: composite particles

Claims (10)

1. It is a visible light active catalyst powder containing a composite particle,

   The composite particles are platinum particles; Tungsten oxide particles;

   The tungsten oxide particles carry the platinum particles,

   The XPS spectrum of 4f _7/2 of Pt measured for the visible light active catalyst powder is obtained by extracting at least one normal distribution through a Voit function, and one normal distribution extracted through the Void function is bound energy. A first normal distribution with a first peak at 70.8 eV to 71.2 eV,

   The ratio of the integral area of the first normal distribution to the integral area of the XPS spectrum for 4f _7/2 of Pt is 85% or more.

   Visible light active catalyst powder.
2. The method of claim 1,

   The XPS spectrum for 4f _7/2 of Pt matches the first normal distribution, or

   Along with the first normal distribution, a second normal distribution having a second peak at a binding energy of 71.8 eV to 72.2 eV is extracted through the Void function from the XPS spectrum for 4f _7/2 of the Pt.

   Visible light active catalyst powder.
3. The method of claim 1,

   The R ² value is 0.999 or more when the normal distribution is extracted through the Voit function.

   Visible light active catalyst powder.
4. The method of claim 1,

   The composite particles have a diameter of 1 micrometer or less

   Visible light active catalyst powder.
5. The method of claim 1,

   The platinum particles have a diameter of 1 nanometer to 10 nanometers

   Visible light active catalyst powder.
6. The method of claim 1,

   The amount of the platinum particles is 0.01 to 5 parts by weight based on 100 parts by weight of the tungsten oxide particles.

   Visible light active catalyst powder.
7. (a) mixing a tungsten oxide powder with a platinum precursor solution to prepare a slurry solution, and then irradiating the slurry solution with light to perform a first photoreaction; And

   (b) adding alcohol to the slurry solution, and then irradiating the light with a second photoreaction.

   It is a manufacturing method of visible light active catalyst powder,

   The XPS spectrum of 4f _7/2 of Pt measured for the visible light active catalyst powder is obtained by extracting at least one normal distribution through the Voit function, and one normal distribution extracted through the Void function. The first normal distribution has a first peak at 70.8 eV to 71.2 eV, and the ratio of the integral area of the first normal distribution to the integral area of the XPS spectrum for 4f _7/2 of the Pt is 85% or more.

   Method for producing visible light active catalyst powder.
8. The method of claim 7, wherein

   The first photoreaction is performed for 4 hours to 24 hours

   Method for producing visible light active catalyst powder.
9. The method of claim 7, wherein

   The ratio of the time for performing the first photoreaction to the time for conducting the second photoreaction is 2: 1 to 12: 1.

   Method for producing visible light active catalyst powder.
10. The method of claim 7, wherein

    The first photoreaction and the second photoreaction is carried out while stirring by injecting an inert gas into the slurry solution

    Method for producing visible light active catalyst powder.

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