Photocatalyst with implanted metal ions

[0001] The present invention relates to a photocatalyst capable of exhibiting catalytic activity even by irradiation with visible light, a method for producing the photocatalyst, and nitrogen oxidation under visible light irradiation by the photocatalyst. It relates to photocatalytic reaction methods such as decomposition reaction of substances and isomerization reaction of butene. Specifically, it applies an ion injection method that introduces metal ions by irradiating accelerated high-energy metal ions to a specific metal. It relates to a photocatalyst in which ions are introduced into titanium oxide.

[0002] [Conventional Technology] Photocatalytic reactions using titanium oxide have attracted attention as an environment-friendly process that cleanly converts light energy into chemical energy at room temperature, and applied research for environmental purification and the like is being actively conducted. In particular, research on adsorbing dyes to titanium oxide in order to use ultrafine particles to improve the photocatalytic activity of titanium oxide, addition of metals such as Pt, Ag, and Ni, and light in the visible light region (about 400 nm to 800 nm). And so on.

[0003] However, although conventional photocatalysts operate in the ultraviolet light region having a wavelength shorter than about 380 nm, it has been considered impossible to perform a steady photocatalytic reaction in the visible light region having a long wavelength. For example, examples of conventional photocatalytic reactions using titanium oxide include nitrogen oxide decomposition reactions and butene isomerization reactions, but these photocatalytic reactions proceed efficiently only under ultraviolet light irradiation. For this reason, only about 5% of ultraviolet light can be used with sunlight alone, and in order to actually cause a reaction, a light source capable of irradiating ultraviolet light such as a mercury lamp is required separately.

[0004] The present invention has been made under such circumstances, and an object of the present invention is to shift the light absorption band of titanium oxide to the visible light region, and to shift the light absorption band to the visible light region. To provide a photocatalyst that works stably even in the above, and to irradiate this photocatalyst with light from ultraviolet light to visible light in the presence of nitrogen oxides, butene, etc., the decomposition reaction of nitrogen oxides and the isomerization of butene. It is to provide a photocatalytic reaction method such as a reaction.

[Means for Solving the Problems] As a result of diligent studies to solve the above problems, the present inventors have focused on the ion implantation method used as a means for doping in the semiconductor field. After investigating the modification of the electronic state of the catalyst by ion implantation into various catalyst materials, and further examining the injection of various metal ions into titanium oxide, the effect of metal ions on the photocatalytic properties was investigated, and it was surprising. In particular, the photocatalyst obtained by introducing specific metal ions into titanium oxide causes absorption of light not only in the ultraviolet light region but also in the visible light region (about 400 nm to 800 nm), which has been impossible until now. It has been found that it exhibits activity at room temperature in various photocatalytic reactions such as decomposition of nitrogen oxides under irradiation with visible light and isomerization reaction of butene, and the present invention has been completed based on this finding.

That is, the present invention contains 1 × 10 ions of one or more metals selected from the group consisting of Cr, V, Cu, Fe, Mg, Ag, Pd, Ni, Mn and Pt.¹⁵Ion / g-Titanium oxide or more from the surface to the inside of titanium oxide<u style="single">(However, the outer surface of titanium oxide, the surface inside the pores, and the inside of the pores are excluded.)</u>It provides a photocatalyst characterized by being contained in. Further, the present invention accelerates the ion of one or more metals selected from the group consisting of Cr, V, Cu, Fe, Mg, Ag, Pd, Ni, Mn and Pt to a high energy of 30 KeV or more. The present invention provides a method for producing a photocatalyst, which comprises irradiating titanium oxide and introducing the metal ions into titanium oxide. The present invention also provides a photocatalytic reaction method characterized in that a photoreaction is carried out by irradiating visible light in the presence of the above photocatalyst. Hereinafter, the present invention will be described in detail.

[0007] The photocatalyst of the present invention contains titanium oxide containing a specific metal ion. The metal ion introduced into titanium oxide is an ion of one or more metals selected from the group consisting of Cr, V, Cu, Fe, Mg, Ag, Pd, Ni, Mn and Pt, preferably Cr, V, Fe, Ni, Mn, particularly preferably Cr, V. The charge of the metal ion is not particularly limited, but usually exists in a monovalent state when the metal ion before injection is accelerated. After injection, metal ions are present as 1 to 5 valences in titanium oxide. These metal ions may be used alone or in combination of two or more.

[0008] The amount of metal ions introduced into titanium oxide is 1 × 10.¹⁵Ion / g-Titanium oxide or higher. The unit of the amount of metal ions introduced is the number of metal ions per 1 g of titanium oxide. The amount of metal ions introduced is 1 x 10¹⁵If it is less than ion / g-titanium oxide, the effect of absorbing light in the visible light region and exhibiting photocatalytic activity cannot be obtained. The upper limit of the amount of metal ions introduced is not particularly limited, but the amount of metal ions introduced is 1 × 10.²¹If the amount exceeds ion / g-titanium oxide, the effect of exhibiting the photocatalytic activity may not be obtained, which is not preferable. The preferable range of the amount of metal ions introduced varies depending on the type of metal ions, but is usually 1 × 10.¹⁶~5×10¹⁸The ion / g-titanium oxide range is preferred, especially 1x10.¹⁶~5×10¹⁷The ion / g-titanium oxide range is preferred.

[0009] The metal ions introduced into the base material titanium oxide may be present on the surface of titanium oxide, but it is preferable that most of the metal ions are present inside the titanium oxide, and 90% or more of the metal ions are present. It is more preferable that it is present inside the titanium oxide, more preferably 95% or more of the metal ions are present inside the titanium oxide, and particularly preferably 99% or more of the metal ions are present inside the titanium oxide. Further, the metal ion introduced into the titanium oxide preferably exists between the surface and the depth of 1000 Å, and particularly preferably exists between the surface and the depth of 300 Å. Further, it is preferable that the metal ions introduced into the titanium oxide are uniformly dispersed. The titanium oxide used as the base material is TiO.₂, SrTiO₃And so on. The crystal form of titanium oxide is not particularly limited, and anatase type, rutile type, and various other types can be used. The photocatalyst of the present invention contains titanium oxide containing the metal ions in a specific amount from the surface of titanium oxide inside, but other photocatalysts may be used in combination, or other base materials may be used. It may be contained. The shape of the photocatalyst of the present invention may be in various forms, and examples thereof include powders, particles, pellets, and membranes, and powders are preferable. The average particle size of the photocatalyst powder is not particularly limited, but is usually in the range of 1 to 1000 nm, preferably in the range of 1 to 500 nm, and particularly preferably in the range of 5 to 50 nm. The photocatalyst of the present invention may be used as it is, or a mixture of a photocatalyst and a binder may be applied to form a film, or the photocatalyst may be supported on a support such as paper.

[0010] In the method for producing a photocatalyst of the present invention, ions of one or more metals selected from the group consisting of Cr, V, Cu, Fe, Mg, Ag, Pd, Ni, Mn and Pt are 30 KeV or more. Accelerate to high energy and irradiate titanium oxide. The energy of the metal ion is 30 KeV or more, preferably in the range of 50 to 400 KeV, and particularly preferably in the range of 100 to 200 KeV. In the preferred range, the metal ion implantation can be dispersed more uniformly, and structural destruction due to the metal ions of the catalyst can be easily prevented. The preferred range of metal ion irradiation dose varies depending on the type of metal ion, but is usually 1 × 10.¹⁴~1×10¹⁹Ion / cm²The range of is preferable, especially 1 × 10¹⁶~1×10¹⁷Ion / cm²The range of is preferable. The unit of irradiation amount of metal ions is irradiation area 1 cm.²Indicates the number of metal ions per hit.

[0011] The method for introducing metal ions used to obtain the photocatalyst of the present invention is an ion implantation method used as a means for doping impurities in the semiconductor field, and uses accelerated high-energy metal ions as a semiconductor sample. The metal ions are implanted into the semiconductor by irradiating the semiconductor to modify the electronic state of the semiconductor. The ion implantation method is also used for surface modification of metal materials such as steel.

[0012] The shape of titanium oxide used in the method for producing a photocatalyst of the present invention is not particularly limited, but is preferably in the form of powder. The average particle size of the titanium oxide powder is not particularly limited, but is usually in the range of 1 to 1000 nm, preferably in the range of 1 to 500 nm, and particularly preferably in the range of 5 to 50 nm.

[0013] The photocatalyst of the present invention absorbs light not only in the ultraviolet light region but also in the visible light region (about 400 to 800 nm), which has been impossible until now. Therefore, the photocatalyst of the present invention can be used to irradiate visible light from ultraviolet light to carry out a photoreaction. The light used in the photocatalytic reaction method of the present invention is light from ultraviolet light to visible light, and may be only ultraviolet light or only visible light. Further, light having a specific wavelength of visible light may be selected from ultraviolet light and irradiated. As long as visible light is emitted from ultraviolet light, light outside this range, such as far-ultraviolet light and infrared light, may be included. The preferred range of wavelengths of ultraviolet to visible light used in the photocatalytic reaction method of the present invention is in the range of 250 to 500 nm. The irradiation intensity of ultraviolet light to visible light used in the photocatalytic reaction method of the present invention is not particularly limited and may be appropriately selected according to the type of photocatalytic reaction.

[0014] The amount of the photocatalyst used in the photocatalytic reaction method of the present invention is not particularly limited and may be appropriately selected according to the reaction system, but is usually 0.01 to 10,000 g per mole of the raw material. Examples of the photocatalytic reaction of the present invention include a method for decomposing nitrogen oxides by irradiating a photocatalyst with light from ultraviolet light to visible light in the presence of nitrogen oxide to carry out a decomposition reaction, and a method for decomposing nitrogen oxides from ultraviolet light to visible light. Examples thereof include a method for isomerization of butene, which comprises irradiating a photocatalyst with light in the presence of butene to carry out an isomerization reaction. Examples of the isomerization reaction of butene include isomerization between cis-2-butene and 1-butene, and isomerization between cis-2-butene and trans-2-butene.

[0015] Further, as another example of the photocatalytic reaction of the present invention, for example, a photoisomerization reaction of an alkene other than the above-mentioned isomerization reaction of butene, water of an alkene / alkin such as ethane or methane production from propylene and water. Photohydrogenation reaction by, photooxidation reaction of alcohol such as aldehyde / ketone formation from 2-propanol, secondary amine formation reaction from primary amine, photoamino acid synthesis such as glycine / alanine from methane / water / ammonia Reaction, CO + H₂O H₂+ CO₂Various photocatalytic reactions such as photo-water-gas shift reaction and photo-reverse water-gas shift reaction can be mentioned. From the viewpoint of inexhaustible and clean conversion and storage of solar energy, a photocatalytic reaction that uses sunlight and reduces and fixes carbon dioxide with water to lead to useful organic compounds can be mentioned. Specifically, it is a methane synthesis reaction from carbon dioxide and water, a methanol synthesis reaction, a formaldehyde synthesis reaction, and the like. Similarly, photodecomposition of water into hydrogen and oxygen using light in the visible light region uses solar energy because it uses non-depleting energy sources, inexhaustible and inexpensive raw materials, is storable, and does not pollute the environment. Is an ideal and effective way to use.

[0016] The photocatalyst of the present invention can be applied to various applications by utilizing its photocatalytic properties. For example, nitrogen oxides emitted from various combustion engines are desired to develop effective removal means because they have a direct adverse effect on the human body and can cause photochemical smog and acid rain. However, by using the photocatalyst of the present invention, these decompositions and removals are possible. That is, by applying it to the outer wall or painting of buildings, painting of roads and automobiles, window glass, etc., nitrogen oxides are decomposed and removed into nitrogen and oxygen and rendered harmless under sunlight or some kind of light source such as an electric lamp. To. Further, it becomes possible to purify water by decomposing harmful substances in water with the photocatalyst of the present invention. Examples of harmful substances in water include trihalomethanes. The photocatalytic reaction method of the present invention can be carried out at room temperature, but is not limited thereto, and can usually be carried out in the range of 0 to 200 ° C.

[Action] Although the photocatalytic reaction mechanism of the photocatalyst of the present invention is not clear at present, titanium oxide obtained by an impregnation method, a co-precipitation method, an alkoxide method, etc., which are conventionally performed catalyst preparation techniques, is used. In the method of introducing a metal into the catalyst as the main component, the effect of the present invention of absorbing light in the visible light region and exhibiting photocatalytic activity is not exhibited at all. Therefore, the metal ions are homogeneous inside the photocatalyst of the present invention. It is considered that this is due to the fact that it is introduced in high dispersion. In other words, when metal ions are introduced in a homogeneous and highly dispersed manner, the electronic state of titanium oxide is perturbed and visible light can be absorbed, and this light absorption causes electrons and holes in titanium oxide. Of the electrons and holes generated by light irradiation, the electrons move to the metal sites on the surface, where the reduction reaction proceeds efficiently due to the catalytic action of the metal, so that the holes also efficiently proceed with the oxidation reaction on titanium oxide. As a result, the photocatalytic reaction is expected to proceed efficiently.

[Example] Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to these examples. In the examples, the amount of metal ions introduced into titanium oxide and the amount of injected metal ions were measured by three-dimensional SIMS (secondary electron ion mass spectrometry) and XPS (photoelectron spectroscopy).

Example 1 Using a 200 KeV ion implanter used for doping semiconductor impurities, V ions are accelerated to 150 KeV energy, and titanium oxide having an average particle size of 21 nm (manufactured by Degusa, trade name: P-). In 25), the V ion implantation amount is 7.5 × 10.¹⁵Ion / cm²And irradiated, and V ions were injected into titanium oxide. As a result of measuring the dispersed state of V ions of the photocatalyst composed of titanium oxide into which the obtained V ions were introduced by three-dimensional SIMS and XPS, the amount of V ions introduced was 7.5 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the amount of V ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with V ions prepared as described above was measured as a function of the amount of injected V ions. The obtained absorption spectrum is shown in FIG.

[0020] Example 2 A photocatalyst composed of titanium oxide injected with V ions was prepared in the same manner as in Example 1 except that the injection conditions for V ions were as follows. Acceleration energy: 150K eVV Ion irradiation dose: 1.5 × 10¹⁶Ion / cm²As a result of measuring the dispersed state of V ions of the photocatalyst composed of titanium oxide into which the obtained V ions were introduced by three-dimensional SIMS and XPS, the amount of V ions introduced was 1.5 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the amount of V ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of a photocatalyst composed of titanium oxide introduced with V ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG.

[0021] Example 3 A photocatalyst made of titanium oxide injected with V ions was prepared in the same manner as in Example 1 except that the injection conditions for V ions were as follows. Acceleration energy: 150K eVV Ion irradiation dose: 3.0 × 10¹⁶Ion / cm²As a result of measuring the dispersion state of V ions of the photocatalyst composed of titanium oxide into which the obtained V ions were introduced by three-dimensional SIMS and XPS, the amount of V ions introduced was 3.0 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the amount of V ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of a photocatalyst composed of titanium oxide introduced with V ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG.

[0022] Comparative Example 1 The ultraviolet light to visible light absorption spectrum of titanium oxide (manufactured by Degussa Co., Ltd., trade name: P-25) was measured in the same manner as in Example 1. The obtained absorption spectrum is shown in FIG. From Fig. 1, titanium oxide alone absorbed only light in the ultraviolet light region with a band cap value of about 380 nm and about 400 nm or less, and did not absorb light in the visible light region at all, but V ions were injected by the ion injection method. It can be seen that visible light absorption of 400 nm or more is occurring on the injected titanium oxide photocatalyst.

Example 4 Using a 200 KeV ion implanter used for doping semiconductor impurities, Cr ions are accelerated to 150 KeV energy, and titanium oxide having an average particle size of 21 nm (manufactured by Degusa, trade name: P-). In 25), the Cr ion implantation amount is 1 × 10.¹⁶Ion / cm²And irradiated, Cr ion was injected into titanium oxide. As a result of measuring the dispersion state of Cr ions of the photocatalyst composed of titanium oxide into which the obtained Cr ions were introduced by three-dimensional SIMS and XPS, the amount of Cr ions introduced was 1 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the amount of Cr ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Cr ions prepared as described above was measured as a function of the amount of introduced Cr ions. The obtained absorption spectrum is shown in FIG.

[0024] Example 5 A photocatalyst composed of titanium oxide injected with Cr ions was prepared in the same manner as in Example 4 except that the injection conditions for Cr ions were as follows. Acceleration energy: 150K eVCr Ion irradiation dose: 1.5 × 10¹⁶Ion / cm²As a result of measuring the dispersion state of Cr ions of the photocatalyst composed of titanium oxide into which the obtained Cr ions were introduced by three-dimensional SIMS and XPS, the amount of Cr ions introduced was 1.5 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the amount of Cr ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Cr ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG.

[0025] Example 6 A photocatalyst composed of titanium oxide injected with Cr ions was prepared in the same manner as in Example 4 except that the injection conditions for Cr ions were as follows. Acceleration energy: 150K eVCr Ion irradiation dose: 12 × 10¹⁶Ion / cm²As a result of measuring the dispersion state of Cr ions of the photocatalyst composed of titanium oxide into which the obtained Cr ions were introduced by three-dimensional SIMS and XPS, the amount of Cr ions introduced was 12 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the amount of Cr ions introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Cr ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG. From FIG. 2, as in Comparative Example 1, titanium oxide alone absorbed only light in the ultraviolet light region with a band gap value of about 380 nm and about 400 nm or less, and did not absorb light in the visible light region at all. It can be seen that visible light absorption of 400 nm or more occurs on the titanium oxide photocatalyst in which ions are injected by the ion injection method. As described above, it has been clarified that the titanium oxide containing a specific metal ion of the present invention exhibits an optical property that has not been considered in the past, that is, it absorbs light in the visible light region.

Example 7 Using a 200 KeV ion implanter used for doping impurities into a semiconductor, Fe ions are accelerated to 150 KeV energy, and titanium oxide having an average particle size of 21 nm (manufactured by Degusa, trade name: P). -25), Fe ion implantation amount is 7.5 × 10¹⁵Ion / cm²And irradiated, Fe ions were injected into titanium oxide. As a result of measuring the dispersion state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 7.5 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface.

[0027] Example 8 A photocatalyst composed of titanium oxide injected with Fe ions was prepared in the same manner as in Example 7 except that the injection conditions for Fe ions were as follows. Acceleration energy: 150 KeVFe ion irradiation dose: 1.5 × 10¹⁶Ion / cm²As a result of measuring the dispersion state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 1.5 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface.

[0028] Example 9 A photocatalyst composed of titanium oxide injected with Fe ions was prepared in the same manner as in Example 7 except that the injection conditions for Fe ions were as follows. Acceleration energy: 150 KeVFe ion irradiation dose: 3.0 × 10¹⁶Ion / cm²As a result of measuring the dispersion state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 3.0 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface.

Example 10 Using a 200 KeV ion implanter used for doping semiconductor impurities, Fe ions are accelerated to 150 KeV energy, and titanium oxide having an average particle size of 21 nm (manufactured by Degusa, trade name: P-). In 25), the Fe ion implantation amount was 2.2 × 10.¹⁵Ion / cm²And irradiated, Fe ions were injected into titanium oxide. As a result of measuring the dispersion state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 2.2 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Fe ions prepared as described above was measured as a function of the amount of injected Fe ions. The obtained absorption spectrum is shown in FIG.

[0030] Example 11 A photocatalyst composed of titanium oxide injected with Fe ions was prepared in the same manner as in Example 10 except that the injection conditions for Fe ions were as follows. Acceleration energy: 150 KeVFe ion irradiation dose: 6.6 × 10¹⁵Ion / cm²As a result of measuring the dispersion state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 6.6 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Fe ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG.

[0031] Example 12 A photocatalyst composed of titanium oxide injected with Fe ions was prepared in the same manner as in Example 10 except that the injection conditions for Fe ions were as follows. Acceleration energy: 150 KeVFe ion irradiation dose: 1.3 × 10¹⁶Ion / cm²As a result of measuring the dispersion state of Fe ions of the photocatalyst composed of titanium oxide into which the obtained Fe ions were introduced by three-dimensional SIMS and XPS, the amount of Fe ions introduced was 1.3 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the Fe ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Fe ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG. From Fig. 3, with titanium oxide alone, only light absorption in the ultraviolet light region with a band cap value of about 380 nm and about 400 nm or less occurred, and no light absorption in the visible light region occurred, but Fe ions were injected by the ion injection method. It can be seen that visible light absorption of 400 nm or more is occurring on the injected titanium oxide photocatalyst.

Example 13 Using a 200 KeV ion implanter used for doping semiconductor impurities, Ni ions are accelerated to 150 KeV energy, and titanium oxide having an average particle size of 21 nm (manufactured by Degusa, trade name: P-). In 25), the Ni ion implantation amount was 2.2 × 10.¹⁵Ion / cm²And irradiated, and Ni ions were injected into titanium oxide. As a result of measuring the dispersion state of Ni ions of the photocatalyst composed of titanium oxide into which the obtained Ni ions were introduced by three-dimensional SIMS and XPS, the amount of Ni ions introduced was 2.2 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the Ni ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Ni ions prepared as described above was measured as a function of the amount of introduced Ni ions. The obtained absorption spectrum is shown in FIG.

[0033] Example 14 A photocatalyst composed of titanium oxide injected with Ni ions was prepared in the same manner as in Example 13 except that the injection conditions for Ni ions were as follows. Acceleration energy: 150 KeVNi ion irradiation dose: 6.6 × 10¹⁵Ion / cm²As a result of measuring the dispersion state of Ni ions of the photocatalyst composed of titanium oxide into which the obtained Ni ions were introduced by three-dimensional SIMS and XPS, the amount of Ni ions introduced was 6.6 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the Ni ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Ni ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG.

[0034] Example 15 A photocatalyst composed of titanium oxide injected with Ni ions was prepared in the same manner as in Example 4 except that the injection conditions for Ni ions were as follows. Acceleration energy: 150 KeVNi ion irradiation dose: 1.3 × 10¹⁶Ion / cm²As a result of measuring the dispersion state of Ni ions of the photocatalyst composed of titanium oxide into which the obtained Ni ions were introduced by three-dimensional SIMS and XPS, the amount of Ni ions introduced was 1.3 × 10.¹⁷Ion / g-TiO₂It was confirmed that 99% or more of the Ni ion introduction amount was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Ni ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG. From FIG. 4, as in Comparative Example 1, titanium oxide alone absorbed only light in the ultraviolet light region with a band gap value of about 380 nm and about 400 nm or less, and did not absorb light in the visible light region at all. It can be seen that visible light absorption of 400 nm or more occurs on the titanium oxide photocatalyst in which ions are injected by the ion injection method. As described above, it has been clarified that the titanium oxide containing a specific metal ion of the present invention exhibits an optical property that has not been considered in the past, that is, it absorbs light in the visible light region.

Example 16 Using a 200 KeV ion implanter used for doping semiconductor impurities, Mn ions are accelerated to 150 KeV energy, and titanium oxide having an average particle size of 21 nm (manufactured by Degusa, trade name: P-). In 25), set the Mn ion implantation dose to 1 × 10.¹⁵Ion / cm²And irradiated, and Mn ion was injected into titanium oxide. As a result of measuring the dispersion state of Mn ions of the photocatalyst composed of titanium oxide into which the obtained Mn ions were introduced by three-dimensional SIMS and XPS, the amount of Mn ions introduced was 1 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the amount of Mn ion introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of the photocatalyst composed of titanium oxide introduced with Mn ions prepared as described above was measured as a function of the amount of introduced Mn ions. The obtained absorption spectrum is shown in FIG.

[0036] Example 17 A photocatalyst composed of titanium oxide injected with Mn ions was prepared in the same manner as in Example 16 except that the injection conditions for Mn ions were as follows. Acceleration energy: 150 KeVMn Ion irradiation dose: 3 × 10¹⁵Ion / cm²As a result of measuring the dispersion state of Mn ions of the photocatalyst composed of titanium oxide into which the obtained Mn ions were introduced by three-dimensional SIMS and XPS, the amount of Mn ions introduced was 3 × 10.¹⁶Ion / g-TiO₂It was confirmed that 99% or more of the amount of Mn ion introduced was almost uniformly dispersed inside the surface of titanium oxide and the depth of 200 Å from the surface. The ultraviolet light to visible light absorption spectrum of a photocatalyst composed of titanium oxide introduced with Mn ions prepared as described above was measured. The obtained absorption spectrum is shown in FIG. From FIG. 5, as in Comparative Example 1, titanium oxide alone absorbed only light in the ultraviolet light region with a band gap value of about 380 nm and about 400 nm or less, and did not absorb light in the visible light region at all, but Mn. It can be seen that visible light absorption of 400 nm or more occurs on the titanium oxide photocatalyst in which ions are injected by the ion injection method. As described above, it has been clarified that the titanium oxide containing a specific metal ion of the present invention exhibits an optical property that has not been considered in the past, that is, it absorbs light in the visible light region.

[0037] Example 18 Butene isomerization reaction 250 mg of the Cr iontophoretic titanium oxide photocatalyst prepared in Example 4 was placed in a 50 ml Pyrex glass constant volume container and sealed. After vacuum exhaust, 20 Torr cis-2-butene was introduced, and the illuminance was 2,000 μW / cm using a mercury lamp that blocked light with a wavelength of 450 nm or less with an optical filter as a light source.²The photocatalyst was irradiated with the light of cis-2-butene in the presence of cis-2-butene, and the isomerization reaction of butene was carried out at room temperature. The reaction product was collected with a microsyringe at regular intervals, and the amount of 1-butene and trans-2-butene produced with respect to the elapsed time was quantified by gas chromatography. The results are shown in Fig. 6.

[0038] Comparative Example 2 The isomerization reaction of cis-2-butene was carried out in the same manner as in Example 18 except that the titanium oxide used in Comparative Example 1 alone was used instead of the Cr iontophoretic titanium oxide photocatalyst in Example 18. went. This result is shown in Fig. 6. As is clear from FIG. 6, under visible light irradiation of about 450 nm or more, the reaction hardly proceeds with titanium oxide alone, whereas by using the Cr ion-introduced titanium oxide photocatalyst of the present invention, cis-2 It can be seen that the isomerization reaction of butene to 1-butene and trans-2-butene proceeds efficiently as a photocatalytic reaction even at room temperature.

[0039] Example 19 Decomposition reaction of nitric oxide Nitric oxide 250 mg of the Cr iontophoretic titanium oxide photocatalyst prepared in Example 4 was placed in a 50 ml Pyrex glass constant volume container and sealed. After vacuum exhaust, 20 Torr nitric oxide was introduced, and the decomposition reaction of nitric oxide was carried out at room temperature using a mercury lamp in which light having a wavelength of 450 nm or less was blocked by an optical filter as a light source. The illuminance of the light at this time is 2,000 μW / cm.²Met. The reaction product is collected in a sampling tube at regular intervals and gas chromatographed N.₂, O₂, N₂The amount of O produced was quantified with respect to the elapsed time. It was confirmed that nitric oxide decreased according to the amount of products. The results are shown in Fig. 7.

[0040] Comparative Example 3 Nitric oxide decomposition reaction was carried out in the same manner as in Example 19 except that titanium oxide alone used in Comparative Example 1 was used instead of the Cr iontophoretic titanium oxide photocatalyst in Example 19. This result is shown in Fig. 7. As is clear from FIG. 7, the reaction does not proceed with titanium oxide alone under visible light irradiation of about 450 nm or more, whereas by using the Cr ion-introduced titanium oxide photocatalyst of the present invention, nitric oxide can be obtained. It can be seen that the decomposition reaction efficiently proceeds as a photocatalytic reaction even at room temperature.

[0041] Example 20 Butene isomerization reaction 250 mg of the V-iontophoretic titanium oxide photocatalyst prepared in Example 1 was placed in a 50 ml Pyrex glass constant volume container and sealed. After vacuum exhaust, 20 Torr cis-2-butene was introduced, and the illuminance was 2,000 μW / cm using a mercury lamp that blocked light with a wavelength of 450 nm or less with an optical filter as a light source.²The photocatalyst was irradiated with the light of cis-2-butene in the presence of cis-2-butene, and the isomerization reaction of butene was carried out at room temperature. The reaction product was collected with a microsyringe at regular intervals, and the amount of 1-butene and trans-2-butene produced with respect to the elapsed time was quantified by gas chromatography. The results are shown in Fig. 8.

Comparative Example 4 The isomerization reaction of cis-2-butene was carried out in the same manner as in Example 20 except that the titanium oxide used in Comparative Example 1 alone was used instead of the V iontophoretic titanium oxide photocatalyst in Example 20. went. This result is shown in Fig. 8. As is clear from FIG. 8, the reaction does not proceed with titanium oxide alone under visible light irradiation of about 450 nm or more, whereas by using the V ion-introduced titanium oxide photocatalyst of the present invention, cis-2- It can be seen that the isomerization reaction of butene to 1-butene and trans-2-butene proceeds efficiently as a photocatalytic reaction even at room temperature.

Example 21 Decomposition Reaction of Nitric Oxide 250 mg of the V-iontophoretic titanium oxide photocatalyst prepared in Example 1 was placed in a 50 ml Pyrex glass constant volume container and sealed. After vacuum exhaust, 20 Torr nitric oxide was introduced, and the decomposition reaction of nitric oxide was carried out at room temperature using a mercury lamp in which light having a wavelength of 450 nm or less was blocked by an optical filter as a light source. The illuminance of the light at this time is 2,000 μW / cm.²Met. The reaction product is collected in a sampling tube at regular intervals and gas chromatographed N.₂, N₂The amount of O produced was quantified with respect to the elapsed time. It was confirmed that nitric oxide decreased according to the amount of products. The results are shown in Fig. 9.

[Effect of the Invention] Since the photocatalyst of the present invention absorbs light not only in the ultraviolet light region but also in the visible light region, which has been impossible until now, in the presence of the photocatalyst of the present invention. Various photoreactions can be promoted by irradiating visible light from ultraviolet light. The photocatalyst, the method for producing a photocatalyst, and the photocatalytic reaction method of the present invention are extremely epoch-making.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an ultraviolet light to visible light absorption spectrum of a photocatalyst according to an embodiment of the present invention.

FIG. 2 is an ultraviolet light to visible light absorption spectrum of a photocatalyst according to an embodiment of the present invention.

FIG. 3 is an ultraviolet light to visible light absorption spectrum of a photocatalyst according to an embodiment of the present invention.

FIG. 4 is an ultraviolet light to visible light absorption spectrum of a photocatalyst according to an embodiment of the present invention.

FIG. 5 is an ultraviolet light to visible light absorption spectrum of a photocatalyst according to an embodiment of the present invention.

FIG. 6 is a diagram quantifying the amount of 1-butene and trans-2-butene produced with respect to the elapsed time in the butene isomerization reaction method using a photocatalyst, which is an example of the present invention.

FIG. 7 shows N in a method for decomposing nitric oxide using a photocatalyst, which is an embodiment of the present invention.₂, O₂, N₂It is a figure which quantified the amount of production with respect to the elapsed time of O production.

FIG. 8 is a diagram quantifying the amount of 1-butene and trans-2-butene produced with respect to the elapsed time in the butene isomerization reaction method using a photocatalyst, which is an example of the present invention.

FIG. 9 shows N in a method for decomposing nitric oxide using a photocatalyst, which is an embodiment of the present invention.₂, N₂It is a figure which quantified the amount of production with respect to the elapsed time of O production.