JP2005103496A - Photocatalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalyst having the effects to be given to various uses such as decomposition/treatment of an environmental pollutant, deodorization, stain-resistant treatment, antibacterial treatment and defogging treatment and having high activity. <P>SOLUTION: This photocatalyst is composed of an oxide complex having a bonded part of oxide semiconductors (I) and (II) each of which has a photocatalytic characteristic and in each of which the energy level of an electron at the bottom of an electrically conductive band is different from that of an electron at the top of a valence band in an energy band structure based on a vacuum level. The oxide semiconductor (I) is composed of the perovskite type oxide shown by composition formula (VI): A<SP>2+</SP>B<SP>4+</SP><SB>1-X</SB>C<SP>3+</SP><SB>X</SB>O<SB>3-δ</SB>(wherein 0≤X≤0.5; -0.1<δ<0.1; A is one or more elements selected from Sr, Ba and Ca; B is one or more elements selected from Ti and Zr; C is one or more elements selected from Y, Ga and In). The oxide semiconductor (II) is composed of rutile type titanium dioxide, anatase type titanium dioxide or a mixture of them. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to oxide semiconductors (I) having photocatalytic properties and different energy levels of electrons at the bottom of the conduction band and electrons at the top of the valence band in the energy band structure based on the vacuum level. The present invention relates to a photocatalyst composed of an oxide composite having a joint part according to II), and particularly to a photocatalyst composed of the perovskite oxide in the oxide semiconductor (I).

  In recent years, from the global environmental purification such as purification of polluted air and contaminated water to the purification of living environment such as deodorization, antifouling and antibacterial, by actively utilizing the high oxidizing power and reducing power exhibited by the photocatalyst Research and development for the practical application of photocatalysts is underway in various fields. And in many cases, it is a research of a compound having a photocatalytic action. When a co-catalyst or a carrier for promoting the reaction is used together, noble metals such as Pt and Rh, NiO, etc. Transition metal oxides have been used.

  Specifically, for example, anatase-type titanium oxide is known as the most typical oxide having a photocatalytic action, and has already been put into practical use as a deodorizing / antibacterial / antifouling material. However, the titanium oxide exhibits the performance as a photocatalyst only with respect to ultraviolet rays which are only about 4% of the sunlight. For this reason, various improvements have been attempted with the aim of increasing the functionality of titanium oxide outdoors and responsiveness in the visible light range. For example, a method of injecting electrons into titanium oxide from an excited state of an adsorbed dye produced by adsorbing a dye on titanium oxide and absorbing visible light, and chemically ionizing metal ions such as Cr, V, Mn, Fe, and Ni Various attempts have been made at home and abroad, such as an implantation method, a method of introducing oxygen defects by plasma irradiation, and a method of introducing foreign ions. However, any of these methods is difficult to uniformly disperse and has problems such as a decrease in photocatalytic activity due to recombination of electrons and holes, and a high adjustment cost.

  On the other hand, as a semiconductor photocatalyst, titanium dioxide, strontium titanate, barium titanate, sodium titanate, cadmium sulfide, zirconium dioxide, etc. are selected, and these semiconductors include platinum groups such as platinum, palladium, rhodium, ruthenium, etc. It is also known that it is effective to carry a metal as a promoter. In particular, in the presence of a photocatalyst composed of a zirconium oxide or tantalum oxide semiconductor carrying nickel oxide, ruthenium oxide or the like, it has been reported that the catalytic activity when irradiated with light is improved (see Non-Patent Document 1). . However, the photocatalyst is still photodissolved by light irradiation, and if the catalyst surface is coated to prevent this dissolution, the catalyst performance does not appear, and other problems still remain. Further, these cocatalysts do not have photocatalytic activity, and do not affect the wavelength region of light to which the compound having photocatalytic action itself responds. In addition, in the case of NiO described above, there is a problem that usage conditions are complicated, such as reduction and subsequent oxidation.

In addition, perovskite oxides have recently attracted attention as having high catalytic activity. For example, Patent Document 1 proposes LaFeO ₃ represented by the general formula A ³⁺ B ³⁺ O ₃ , SrMnOx represented by the general formula A ²⁺ B ³⁺ Ox, and the like, which are actually high. No catalytic activity has been obtained.

In addition, research on layered perovskite oxides has been actively conducted. For example, Patent Document 2 proposes a layered perovskite type ABCO ₄ , Patent Document 3 proposes a KLaCa ₂ Nb ₃ O ₁₀ -based composite oxide, and Patent Document 4 proposes KCa ₂ Nb ₃ O _10. Has been. However, these principles and production methods are complicated, and the chemical stability of the obtained oxides is also problematic, so that they have not yet been industrialized.

Accordingly, in order to solve the above problems, the present inventors conducted extensive research on the performance of the photocatalyst, and as a result, the composition formula (III) A _2-X B _{2 + X} O _8-2 δ is represented by a plurality of values. A composition formula (IV) A _2-X B _{2 + X} O _{7+ (X / 2) + Y in which} A ions and B ions, each of which can take a number, are regularly arranged (however, −0.4 <X <+0. 6 and a pyrochlore-related structural oxide in which oxygen ions are inserted into at least one of an oxygen deficient position or an interstitial position as seen from a fluorite structure of a pyrochlore oxide of −0.2 <Y <+0.2) When particles such as titanium oxide, zinc oxide, tin oxide, zirconium oxide or strontium titanate, which have been reported in the past, have been reported to adhere to and bonded to each other, conduction in the energy band structure based on the vacuum level is reported. The energy levels of the electrons at the bottom and the top of the valence band are Due to the difference between each semiconductor (ie, pyrochlore-related structural oxide and titanium oxide, zinc oxide, tin oxide, zirconium oxide, strontium titanate, etc.), electrons and holes are unidirectional through the junction. The electrons and holes are spatially separated and recombination of electrons and holes can be suppressed, and the molecules and ions involved in the photocatalytic reaction are easily adsorbed by the pyrochlore-related structural oxide. In addition, since the reaction positions of the photocatalytic reaction involving these electrons and holes can be spatially separated, it has been found that the photocatalyst having high catalytic activity is obtained by these synergistic actions.

  In addition, as a result of further studies on the photocatalytic action and the flow of electrons and holes in the junction, it is confirmed that the light energy in the visible light range is effectively used, and further the energy of electrons and holes contributing to the reaction. Is an ideal state for photocatalytic properties of the above-mentioned semiconductor oxide (that is, an oxide complex comprising a pyrochlore-related structure oxide and titanium oxide, zinc oxide, tin oxide, zirconium oxide, strontium titanate, etc.) I came to find out what happened at the joint.

Furthermore, these photocatalytic properties are characterized by the above-described pyrochlore-related structural oxide represented by the composition formula (III) A _2-X B _{2 + X} O _8-2 δ and titanium oxide, zinc oxide, tin oxide, zirconium oxide or titanium. Not only oxide composites such as strontium oxide, but also oxide semiconductors with different energy levels of electrons at the bottom of the conduction band and electrons at the top of the valence band in the energy band structure based on the vacuum level (I ) And (II) have also been found to function similarly in oxide composites having joints.

  In addition, in the energy band structure based on the vacuum level, there are two kinds of compound semiconductors in which the energy level of the electrons at the bottom of the conduction band and the energy level of the electrons at the top of the valence band are different, one of which has a relatively high photocatalytic action. There has been no research on synergistically improving photocatalytic performance by compounding a compound semiconductor that is weak and has a good photocatalytic activity at a lower wavelength. No research has been conducted on the preparation of high-performance photocatalysts by utilizing the flow of water.

Based on this technical discovery, the inventors have determined that the energy level of the electrons at the bottom of the conduction band and the energy level of the electrons at the top of the valence band in the energy band structure having photocatalytic properties and being based on the vacuum level. Have already proposed photocatalysts composed of oxide composites having junctions of different oxide semiconductors (I) and (II), and the oxide semiconductor (I) is composed of a pyrochlore-related structural oxide, A photocatalyst composed of any one of titanium oxide, zinc oxide, tin oxide, zirconium oxide, and strontium titanate in which the oxide semiconductor (II) is a rutile type, anatase type, or a mixture of these two types, and the above oxide The semiconductor (I) is composed of a perovskite oxide, and the oxide semiconductor (II) is a rutile type or anatase type or Two types mixed titanium oxide or the like is, zinc oxide, tin oxide, zirconium oxide, has already proposed and constructed photocatalytic either strontium titanate (see Patent Document 5).
K. Sayama, H. Arakawa; J. Photochem. And Photobio. A: Chem., 77, 243 (1994) Japanese Patent Laid-Open No. 7-24329 Japanese Patent Laid-Open No. 10-244164 JP-A-8-196912 Japanese Patent Laid-Open No. 11-139826 JP 2003-117407 A

  The present invention further develops the invention described in Patent Document 5 described above, expands the types of constituent elements of the photocatalyst in which the oxide semiconductor (I) is composed of a perovskite oxide, and is described in Patent Document 5. An object of the present invention is to provide a photocatalyst having the same photocatalytic properties as those of the present invention.

That is, the invention according to claim 1
Oxide semiconductors (I) and (II) that have photocatalytic properties and have different energy levels at the bottom of the conduction band and at the top of the valence band in the energy band structure based on the vacuum level. Assuming a photocatalyst composed of an oxide composite having a joint by
The oxide semiconductor (I) has the composition formula (VI) A ²⁺ B ^{4 +} _{1 -X} C ³⁺ _X O ₃ -δ (where 0 ≦ X ≦ 0.5, −0.1 <δ <0 .1, A ion is one or more elements selected from Sr, Ba, and Ca, B ion is one or more elements selected from Ti and Zr, and C is one selected from Y, Ga, and In And the oxide semiconductor (II) is composed of a rutile type, an anatase type, or a titanium oxide in which these two types are mixed. It is a feature.

The invention according to claim 2
Based on the photocatalyst according to the invention of claim 1,
5 to 50% by weight of the perovskite oxide of the oxide semiconductor (I) is contained.

According to the photocatalyst according to the inventions of claims 1 and 2,
Similar to the invention described in Patent Document 5, the oxidation levels of the electrons at the bottom of the conduction band and the energy levels of the electrons at the top of the valence band in the energy band structure based on the vacuum level are different from each other. Because it is composed of oxide composites with joints made of physical semiconductors (I) and (II), it can be used for applications such as decomposition and treatment of environmental pollutants, deodorization, antifouling, antibacterial and antifogging Have

  Hereinafter, the present invention will be described in detail.

First, the photocatalyst according to the present invention has photocatalytic properties as in the invention described in Patent Document 5, and the energy level of the electrons at the bottom of the conduction band and the electrons at the top of the valence band in the energy band structure based on the vacuum level. Assuming that the oxide semiconductors (I) and (II) are composed of oxide composites having junctions with different energy levels, the oxide semiconductor (I) has the composition formula (VI) A ²⁺ B ⁴⁺ _1-X C ³⁺ _X O _3- δ (where 0 ≦ X ≦ 0.5, −0.1 <δ <0.1, A ion is one selected from Sr, Ba, Ca) The above elements and B ions are composed of perovskite oxides represented by one or more elements selected from Ti and Zr, and C is one or more elements selected from Y, Ga and In), The oxide semiconductor (II) is a rutile type, anatase type or Is characterized in that equal two types is composed of titanium oxide mixed.

  In the perovskite type oxide constituting the oxide semiconductor (I), the reason why the δ value in the composition formula (VI) is set to −0.1 <δ <0.1 is that of the perovskite type oxide. This is because a product outside the above numerical range cannot be obtained due to manufacturing conditions.

Then, SrTiO ₃ powder is applied as the perovskite oxide of the oxide semiconductor (I) represented by the composition formula (VI) A ²⁺ B ^{4 +} _{1 -X} C ³⁺ _X O ₃ -δ, and oxidation The following has been confirmed from the test results of Example 1 and the like described below in which anatase-type titanium oxide powder was applied as the physical semiconductor (II).

  Hereinafter, the outline of the synthesis method of the photocatalyst according to Example 1, the test method of the obtained photocatalyst according to Example 1, and the like will be briefly described.

First, SrTiO ₃ powder as the oxide semiconductor (I) and anatase-type titanium oxide powder as the oxide semiconductor (II) are Z: (1-Z) [where 0 <Z <1] in weight ratio. The mixture was baked at 700 ° C. for 1 hour and pulverized in a mortar to prepare a powder (photocatalyst) according to Example 1.

  The obtained powder (photocatalyst) according to Example 1 was dispersed in a methylene blue solution, and a decolorization (bleaching) test of methylene blue by light irradiation was performed.

And it confirmed from the following test results that the photocatalytic properties of the powder (photocatalyst) according to Example 1 were greatly improved due to the appearance of the junction of different types of semiconductors (SrTiO ₃ and anatase-type titanium oxide) by the firing treatment. Has been.

That is, the color of the powder sample in the middle of bleaching (powder according to Example 1) becomes deep blue due to the oxide complex of SrTiO ₃ and anatase-type titanium oxide. Had disappeared.

  On the other hand, in the case of only anatase-type titanium oxide powder with Z = 0 (comparative example), the color of the sample was always white during and during bleaching.

Further, in the case of only Z = 1 perovskite structure oxide (SrTiO ₃ ) powder, the color of the sample was slightly bluish during bleaching, and the bluish disappeared upon completion.

  From these results, the adsorption of methylene blue to the oxide complex (powder according to Example 1) as a sample is promoted by light irradiation, and the methylene blue is a perovskite structure that constitutes one of the oxide complexes. The oxides are more easily adsorbed, the junction with titanium oxide promotes the adsorption of methylene blue to the perovskite structure oxide, and the improvement of the photocatalytic properties by the oxide complexation and the above-mentioned adsorption phenomenon of methylene blue It was confirmed that they were deeply related.

  Here, when oxide semiconductors (I) and (II) with different energy levels of electrons at the bottom of the conduction band and electrons at the top of the valence band in the energy band structure based on the vacuum level are joined, In general, it is known that electrons and holes flow in one direction near the junction.

At this time, due to the above-described adsorption phenomenon promoted by light irradiation, the tendency of the electrons and holes flowing through the junction to be separated increases. This phenomenon depends on whether the adsorbing ion is positive or negative, and is the case where the adsorbing ion is negative, and the composition formula (VI) A ²⁺ B ^{4 +} _{1 -X} C ³⁺ _X O ₃ -δ ( However, 0 ≦ X ≦ 0.5, −0.1 <δ <0.1, A ion is one or more elements selected from Sr, Ba, and Ca, and B ion is selected from Ti and Zr. In the case of the above oxide complex composed of a perovskite oxide represented by an element of at least one species, and C is one or more elements selected from Y, Ga, and In) and anatase titanium oxide As shown in the conceptual diagram of FIG. 10A, holes flow on the surface of the junction (the side in contact with the outside world), and electrons flow through the center of the junction, and electrons and holes in the junction. Separating the flow of electrons leads to the spatial separation of electrons and holes in the whole oxide complex, and electrons excited by light And hole recombination are suppressed. As a result, since the reaction positions of the photocatalytic reaction involving electrons and holes are spatially separated, it is presumed that the photocatalyst having a significantly enhanced catalytic activity is obtained by the bonding.

Note that FIG. 10B shows an oxide composed of a perovskite oxide represented by a composition formula (VI) A ²⁺ B ^{4 +} _{1 -X} C ³⁺ _X O ₃ -δ and anatase titanium oxide. The energy band structure figure in the junction part of a composite_body | complex is shown.

Here, the perovskite oxide represented by the composition formula (VI) A ²⁺ B ^{4 +} _{1 -X} C ³⁺ _X O ₃ -δ is an ordinary solid phase method, that is, each metal component as a raw material. These oxides or salts such as carbonates and nitrates are mixed at a target composition ratio and baked, but may be synthesized by a wet method other than the solid phase method or a gas phase method.

  Hereinafter, the solid phase method will be described as an example. Oxides or carbonates such as carbonates and nitrates as raw materials are mixed so as to have a target composition ratio using a planetary ball mill or the like, and temporarily prepared at 800 to 900 ° C. Bake. After calcination, it is pulverized again and formed into an appropriate size, and then placed in a Pt crucible and fired at 1400-1500 ° C. for about 10 to 100 hours. Then, the obtained perovskite oxide fired product is pulverized into powder.

  Thereafter, as shown in the following comparative examples, the anatase-type titanium oxide powder obtained by a usual method and the weight ratio of Z: (1-Z) [where 0 <Z <1] are satisfied. Weigh and mix using a mortar or ball mill.

  The mixed sample is baked at 300 to 1200 ° C. for about 5 minutes to 1 hour to prepare an oxide composite having a heterogeneous oxide semiconductor junction (that is, the photocatalyst of the present invention). In addition, when the firing temperature is lower than 300 ° C., good bonding may not be obtained, and when it is higher than 1200 ° C., a different reaction phase may be generated and the photocatalytic characteristics of the oxide composite may be deteriorated. The above 300-1200 degreeC conditions are preferable.

  The shape of the photocatalyst according to the present invention thus prepared is preferably composed of particles having a large specific surface area so that light can be used effectively. In general, the size of each particle is 0.1 to 10 μm, 0.1 to 1 μm is preferable. In particular, the perovskite oxide of the oxide semiconductor (I) is more preferably 100 nm or less.

  Further, as a conventional means for obtaining an oxide composite powder having the above particle size, for example, by hand pulverization using a mortar, or pulverization of each oxide semiconductor using a ball mill or a planetary rotating ball mill, The obtained two kinds of powders are weighed, mixed, and fired to obtain an oxide composite having the above-mentioned bonding, and then pulverized again to obtain a final sample powder.

  Next, specific examples of the present invention will be described. However, the present invention is not limited to the following examples.

Sample Preparation [Preparation of SrTiO ₃ ]
(Raw material) SrCO ₃ powder (manufactured by Kojundo Chemical Laboratory Co., Ltd., purity 99.9%, ig.-loss 0.08%): 5.8284 g,
TiO ₂ powder (Rare Metallic Anatase type, purity 99.99%, ig.-loss 0.84%): 3.1774 g
Note that “ig.-loss” indicates a loss due to moisture, absorbents, and the like.
(Mixing process) 1: Each powder sample after weighing was added with ethanol using a zirconia mortar and mixed for 1.5 hours.

2: The sample after mixing was dried, placed in a zirconia pot, and ground for 40 minutes using a planetary rotating ball mill.
(Drying process) The sample after grinding | pulverization was dried at 120 degreeC for 30 minutes or more with the thermostat.
(Preliminary calcination treatment) The dried sample was put in a rhodium / platinum crucible and calcined at 1350 ° C for 10 hours in the air.
(Re-grinding / mixing / drying treatment) After calcination, the powder was re-ground in a mortar and mixed in a planetary rotating mill. Then, it dried on the same conditions as previous drying.
(Molding process) It shape | molded in the disk shape of 17 mmphi with the pressure of 265 MPa.
(Baking process) The sample after shaping | molding was put into the rhodium / platinum crucible, and it baked at 1650 degreeC in air | atmosphere for 50 hours.
(Crushing treatment) After firing, the sample powder was obtained by grinding in a zirconia mortar for 1 hour.

"Confirmation of crystal structure"
Confirmation of the crystal structure of the obtained SrTiO ₃ was carried out using an X-ray diffractometer (using CuKα ray using a graphite Kβ ray filter cover) manufactured by MAC Science.

That is, FIG. 2A shows a graph relating to the X-ray diffraction measurement result of SrTiO ₃ .

[Anatase type titanium oxide]
Commercially available TiO ₂ (manufactured by Ishihara Sangyo Co., Ltd., ST-01, purity 99.99%, ig.-loss 15.1%) was used as the anatase type titanium oxide.

The crystal structure of TiO ₂ was also confirmed using an X-ray diffractometer (using a CuKα ray using a graphite Kβ ray filter cover) manufactured by MAC Science.

That is, FIG. 4A shows a graph relating to the X-ray diffraction measurement result of TiO ₂ .

[Production of oxide composite]
(Mixing treatment) The anatase-type titanium oxide (oxide semiconductor II) and SrTiO ₃ (oxide semiconductor I) were collected at the following weight ratios, mixed in a dry manner using a zirconia mortar for 30 minutes, and then a sample powder was obtained. It was.

Titanium oxide: 0.4743 g, SrTiO ₃ : 0.0527 g (weight ratio 90:10)
(Baking process) Each sample after mixing was put into a crucible made of rhodium / platinum and baked in the atmosphere at 600 ° C. for 1 hour.
(Crushing treatment) The obtained fired product was pulverized in a dry manner for 30 minutes using a zirconia mortar to obtain a sample powder.

FIG. 4B shows a graph relating to the X-ray diffraction measurement result of the obtained TiO ₂ —SrTiO ₃ .

Sample preparation [Preparation of BaTiO ₃ ]
(Raw material) BaCO ₃ powder (manufactured by Kojundo Chemical Laboratory Co., Ltd., purity 99.99%, ig.-loss 0.04%): 7.1101 g,
TiO ₂ powder (rare metallic company anatase type purity: 99.9% ig-loss: 0.84%): 2.889 g
(Mixing process) 1: Each powder sample after weighing was added with ethanol using a zirconia mortar and mixed for 1.5 hours.

2: The sample after mixing was dried, placed in a zirconia pot, and ground for 40 minutes using a planetary rotating ball mill.
(Drying process) The sample after grinding | pulverization was dried at 120 degreeC for 30 minutes or more with the thermostat.
(Calcination process) The dried sample was put in a rhodium / platinum crucible and calcined at 1350 ° C for 10 hours in the air.
(Re-grinding / mixing / drying treatment) After calcination, the powder was re-ground in a mortar and mixed in a planetary rotating mill. Then, it dried on the same conditions as previous drying.
(Molding process) It shape | molded in the disk shape of 17 mmphi with the pressure of 265 MPa.
(Baking process) The sample after shaping | molding was put into the rhodium / platinum crucible, and it baked at 1650 degreeC in air | atmosphere for 50 hours.
(Crushing treatment) After firing, the sample powder was obtained by grinding in a zirconia mortar for 1 hour. The composition of the fired product was BaTiO ₃ .

The crystal structure of BaTiO ₃ was also confirmed using an X-ray diffractometer (using CuKα ray using a graphite Kβ ray filter cover) manufactured by MAC Science.

That is, a graph relating to the X-ray diffraction measurement result of BaTiO ₃ is shown in FIG.

[Production of oxide composite]
Similar to Example 1, anatase-type TiO ₂ (manufactured by Ishihara Sangyo Co., Ltd., ST-01, purity 99.99%, ig.-loss 15.1%) (oxide semiconductor II) and BaTiO ₃ (oxide semiconductor I ) Was collected at the following weight ratio and mixed in a dry manner using a zirconia mortar for 30 minutes, and then a sample powder was obtained in the same manner as in Example 1.

Titanium oxide: 0.7103 g, BaTiO ₃ : 0.3825 g (weight ratio 65:35)
Titanium oxide: 0.6888 g, BaTiO ₃ : 0.1722 g (weight ratio 80:20)
Titanium oxide: 0.6300 g, BaTiO ₃ : 0.0701 g (weight ratio 90:10)

Sample Preparation [Preparation of CaTiO ₃ ]
(Raw material) CaCO ₃ powder (manufactured by High Purity Chemical Laboratory Co., Ltd., purity 99.99%, ig.-loss 0.04%): 5.5409 g,
TiO ₂ powder (Rare Metallic Anatase type purity: 99.9% ig-loss: 0.84%): 4.4591 g
CaTiO ₃ was prepared in the same manner as in Example 2 except that.

Confirmation of the crystal structure of the obtained CaTiO ₃ was also performed using an X-ray diffraction apparatus (using CuKα rays using a graphite Kβ ray filter cover) manufactured by MAC Science.

That is, a graph relating to the X-ray diffraction measurement result of CaTiO ₃ is shown in FIG.

[Production of oxide composite]
Similar to Example 1, anatase-type TiO ₂ (manufactured by Ishihara Sangyo Co., Ltd., ST-01, purity 99.99%, ig.-loss 15.1%) (oxide semiconductor II) and CaTiO ₃ (oxide semiconductor I ) Was collected at the following weight ratio and mixed in a dry manner using a zirconia mortar for 30 minutes, and then a sample powder was obtained in the same manner as in Example 1.

Titanium oxide: 0.4743 g, CaTiO ₃ : 0.0527 g (weight ratio 90:10)

Sample Preparation [Preparation of Sr (Ti _0.9 Ga _0.1 ) O ₃ ]
(Raw material) SrCO ₃ powder (manufactured by Kojundo Chemical Laboratory Co., Ltd., purity 99.99%, ig.-loss 0.04%): 6.4020 g,
TiO ₂ powder (Rare Metallic Anatase type Purity: 99.9% ig-loss: 0.84%): 3.1432 g
GaO ₂ powder (ig-loss: 0.2%, manufactured by High Purity Chemical Laboratory Co., Ltd.): 0.4546g
In addition, Sr (Ti _0.9 Ga _0.1 ) O ₃ was prepared in the same manner as in Example 2 except that the calcination treatment and the firing treatment were performed under the following conditions.
(Calcination treatment) The dried sample was put in a rhodium / platinum crucible and calcined at 1400 ° C. for 10 hours in the air.
(Baking process) The sample after shaping | molding was put into the rhodium / platinum crucible and baked at 1500 degreeC in air | atmosphere for 50 hours.

Confirmation of the crystal structure of the obtained Sr (Ti _0.9 Ga _0.1 ) O ₃ was also performed using an X-ray diffractometer (using a CuKα ray using a graphite Kβ ray filter cover) manufactured by MAC Science. That is, FIG. 3A shows a graph relating to the X-ray diffraction measurement result of Sr (Ti _0.9 Ga _0.1 ) O ₃ .

[Production of oxide composite]
Similar to Example 1, anatase-type TiO ₂ (manufactured by Ishihara Sangyo Co., Ltd., ST-01, purity 99.99%, ig.-loss 15.1%) (oxide semiconductor II) and Sr (Ti _0.9 Ga _0.1 ) O ₃ (Oxide semiconductor I) was collected at the following weight ratio, mixed in a dry manner using a zirconia mortar for 30 minutes, and then sample powder was obtained in the same manner as in Example 1.

Titanium oxide: 0.6634 g, Sr (Ti _0.9 Ga _0.1 ) O ₃ : 0.0737 g
(Weight ratio 90:10)

Sample Preparation [Preparation of Sr (Ti _0.9 Y _0.1 ) O ₃ ]
(Raw material) SrCO ₃ powder (manufactured by High Purity Chemical Laboratory, purity 99.9%, ig.-loss 0.08%): 6.3705 g,
TiO ₂ powder (Rare Metallic Anatase type, purity 99.99%, ig.-loss 0.84%): 3.1279 g
Y ₂ O ₃ powder (manufactured by High Purity Chemical Laboratory, ig-loss: 2.9%): 0.5016 g
(Mixing process) 1: Each powder sample after weighing was added with ethanol using a zirconia mortar and mixed for 1.5 hours.

2: The sample after mixing was dried, placed in a zirconia pot, and ground for 40 minutes using a planetary rotating ball mill.
(Drying process) The sample after grinding | pulverization was dried at 120 degreeC for 30 minutes or more with the thermostat.
(Preliminary calcination treatment) The dried sample was put in a rhodium / platinum crucible and calcined at 1350 ° C for 10 hours in the air.
(Re-grinding / mixing / drying treatment) After calcination, the powder was re-ground in a mortar and mixed in a planetary rotating mill. Then, it dried on the same conditions as previous drying.
(Molding process) It shape | molded in the disk shape of 17 mmphi with the pressure of 265 MPa.
(Baking process) The sample after shaping | molding was put into the rhodium / platinum crucible, and it baked at 1650 degreeC in air | atmosphere for 50 hours.
(Crushing treatment) After firing, the sample powder was obtained by grinding in a zirconia mortar for 1 hour.

Confirmation of the crystal structure of the obtained Sr (Ti _0.9 Y _0.1 ) O ₃ was also performed using an X-ray diffractometer (using a CuKα ray using a graphite Kβ ray filter cover) manufactured by MAC Science.

That is, FIG. 3B shows a graph relating to the X-ray diffraction measurement result of Sr (Ti _0.9 Y _0.1 ) O ₃ .

[Production of oxide composite]
(Mixing treatment) Anatase-type TiO ₂ (oxide semiconductor II) and Sr (Ti _0.9 Y _0.1 ) O ₃ (oxide semiconductor I) were collected at the following weight ratios, and dried for 30 minutes using a zirconia mortar. Mixed.

Titanium oxide: 1.1380 g, Sr (Ti _0.9 Y _0.1 ) O ₃ : 0.1074 g
(Weight ratio 90:10)
(Baking process) Each sample after mixing was put into a crucible made of rhodium / platinum, and was fired in the atmosphere at 700 ° C for 1 hour.
(Crushing treatment) The obtained fired product was pulverized in a dry manner for 5 minutes using a zirconia mortar to obtain a sample powder.
[Comparative example]
Anatase type TiO ₂ (ST-01 manufactured by Ishihara Sangyo Co., Ltd., purity 99.99%, ig.-loss 15.1%) (oxide semiconductor II) was used.

[Evaluation of photocatalysis]
The catalytic activity evaluation of the photocatalysts according to Examples 1 to 5 and the comparative example was performed using a photobleaching method of a methylene blue (MB) aqueous solution.

  This is a method in which a methylene blue aqueous solution and a measurement sample (photocatalysts according to Examples 1 to 5 and Comparative Examples) are placed in the same container, irradiated with light, and the degree of decomposition of methylene blue due to the photocatalytic effect is examined with a spectrophotometer.

(Preparation of methylene blue aqueous solution)
Methylene blue (Kanto Chemical Co., Ltd., reagent grade)
Ultra pure water (specific resistance 18.2 MΩcm or more)
7.48 mg of the above methylene blue was precisely weighed and the entire amount was dissolved in 1 liter of ultrapure water using a measuring flask to prepare a 2.0 × 10 ⁻⁵ mol / liter (mol · dm ⁻³ ) aqueous solution.

(Light irradiation)
A Experimental apparatus The outline of the apparatus is shown in FIG.

Light source: Bottom irradiation type 500 W Xe lamp Spectrophotometer: U4000, U4000 spectrophotometer B Sample solution 0.20 g of photocatalyst (sample) according to Examples 1 to 5 and Comparative Example was added to 100 cm ^{3 of} methylene blue aqueous solution. Each was dispersed using a tic stirrer.

  A methylene blue aqueous solution in which each sample was dispersed was collected in a quartz cell, and a transmission spectrum was measured using a spectrophotometer.

  The measured sample was returned to its original position, stirring and light irradiation were repeated, and the transmission spectrum was measured and the absorbance was determined every time.

  And the time-dependent change of the absorbance spectrum about the photocatalyst which concerns on Examples 1-3 is shown in FIGS. 5-7, respectively.

Further, the photocatalyst of Comparative Example a photocatalyst according to Example 1 to 5 (TiO ₂ anatase), respectively Figure 8 the change of absorbance maximum in the absorbance between the wavelengths 600nm~664nm respect to the elapsed time (irradiation time) As shown in FIG.

In FIG. 8 and FIG. 9, for comparison, the case where no photocatalyst is added is indicated by “◇”, and the change in absorbance of SrTiO ₃ is indicated by “◯”.

  8 and 9, the portion indicated by a solid line does not use a filter, and the light irradiation time zone in which visible light and ultraviolet light are included, and the portion indicated by an alternate long and short dash line is a UV cut filter (λ>). 420 nm transmission) is used for the time zone in which the visible light is irradiated, and the portion indicated by the broken line indicates the time zone in which the light irradiation is not performed.

[Confirmation]
(1) As can be understood from the graphs shown in FIGS. 5 to 7, it was confirmed that the absorbance spectrum intensity of methylene blue decreased with time by adding the photocatalyst according to Examples 1 to 3. The That is, it is confirmed that the photocatalysts according to Examples 1 to 3 have good photocatalytic activity.
(2) Further, as confirmed from the graphs shown in FIG. 8 and FIG. 9, in comparison with the photocatalyst (anatase type TiO ₂ ) according to the comparative example and SrTiO ₃ indicated by “◯”, In the photocatalysts according to 1 to 5, the absorbance rapidly decreases from around 1.0, and it can be seen that the time required for bleaching is extremely short. From this, it is also confirmed that the catalytic activity of the photocatalyst according to Examples 1 to 5 is superior to that of anatase TiO ₂ and SrTiO ₃ .

Structure explanatory drawing in the light irradiation experiment apparatus for performing the catalyst activity evaluation of the photocatalyst based on Examples 1-5 and a comparative example. 2A is a graph showing the X-ray diffraction measurement result of SrTiO ₃ , FIG. 2B is a graph showing the X-ray diffraction measurement result of BaTiO ₃ , and FIG. 2C is the X-ray diffraction of CaTiO _3. The graph which shows a measurement result. 3A is a graph showing the result of X-ray diffraction measurement of Sr (Ti _0.9 Ga _0.1 ) O ₃ , and FIG. 3B is a graph showing the result of X-ray diffraction measurement of Sr (Ti _0.9 Y _0.1 ) O _3. Figure. FIG. 4 (A) graph showing the results of X-ray diffraction measurement of TiO _2, FIG. 4 (B) a graph showing the X-ray diffraction measurement results of the TiO ₂ -SrTiO _3. The graph which shows the relationship between the irradiation time by an optical bleaching method, and an absorbance spectrum about the photocatalyst which concerns on Example 1. FIG. The graph which shows the relationship between the irradiation time by an optical bleaching method, and an absorbance spectrum about the photocatalyst which concerns on Example 2. FIG. The graph which shows the relationship between the irradiation time by an optical bleaching method, and an absorbance spectrum about the photocatalyst which concerns on Example 3. FIG. The graph which shows the relationship between the irradiation time by the optical bleaching method, and the light absorbency (wavelength 600nm-664nm) about Examples 1-3 and the photocatalyst which concerns on a comparative example. The graph which shows the relationship between the irradiation time by the optical bleaching method, and the light absorbency (wavelength 600nm-664nm) about Examples 4-5 and the photocatalyst which concerns on a comparative example. FIG. 10A is a conceptual explanatory view schematically showing the flow mechanism of electrons and holes through the junction of the photocatalyst according to the present invention, and FIG. 10B is the energy at the junction of the photocatalyst according to the present invention. Band structure diagram.

Claims (2)

Oxide semiconductors (I) and (II) that have photocatalytic properties and have different energy levels at the bottom of the conduction band and at the top of the valence band in the energy band structure based on the vacuum level. In the photocatalyst constituted by the oxide composite having the joint part by
The oxide semiconductor (I) has the composition formula (VI) A ²⁺ B ^{4 +} _{1 -X} C ³⁺ _X O ₃ -δ (where 0 ≦ X ≦ 0.5, −0.1 <δ <0 .1, A ion is one or more elements selected from Sr, Ba, and Ca, B ion is one or more elements selected from Ti and Zr, and C is one selected from Y, Ga, and In And the oxide semiconductor (II) is composed of a rutile type, an anatase type, or a titanium oxide in which these two types are mixed. Characteristic photocatalyst. 2. The photocatalyst according to claim 1, wherein the perovskite oxide of the oxide semiconductor (I) is contained in an amount of 5 to 50% by weight.

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