TiO2 NANOPARTICLES

The present invention is a TiO having a photocatalytic activity that decomposes water to generate hydrogen by irradiation with light._２Regarding nanoparticles.

Titanium dioxide (Tio)_２) Shows ultraviolet light absorption characteristics due to its wide bandgap, and has excellent adsorptivity due to desorption of oxygen on the surface, and is widely put into practical use mainly in the field of catalysts. The transfer of electrons and / or holes associated with the photocatalytic reaction is TIO_２Occurs on the surface. Therefore, in order to increase the surface area as much as possible and improve the photocatalytic reaction efficiency, powdered TiO_２Is manufactured.

On the other hand, since most of the sunlight that reaches the ground surface is visible light, for example, TiO._２Attempts have also been made to dope impurities into the bandgap to form impurity levels in the bandgap to narrow the bandgap and to form impurity-doped titanium dioxide that is photocatalytically active even in visible light.

Powdered TiO currently on the market_２There are dozens of types, and they differ in particle purity, specific surface area (particle size), crystal morphology (anatase, rutile phase), etc. depending on the production method. There are a liquid phase method and a gas phase method as general manufacturing methods.

Further, in recent years, Ti powder or a Ti-containing solution and oxygen gas as a reaction gas are supplied to a high-frequency plasma flame (about 10000K) to react with TiO._２Attempts have also been made to produce nanoparticles. Hereinafter, a conventional example using high-frequency plasma will be described.

In Patent Document 1, TiO is used by high-frequency plasma._２A method of producing particles is disclosed. Here, TiO_２The starting material for producing nanoparticles is a mixed solution of titanium trichloride liquid, ammonium persulfate as an oxidizing agent, and ammonium hydroxide as a pH adjuster. In the mixed solution, a solution containing a nitrogen element, a carbon element, etc., which is unnecessary for the original synthesis, is mixed. Therefore, if such a mixed solution is supplied to the thermal plasma, nitrogen elements, carbon elements, etc. will react together, and TiO will occur._２There is a possibility that unnecessary elements may enter, such as sneaking into the particles or replacing with oxygen.

In Patent Document 2, TIO doped with rare earth elements_２A manufacturing method using particles and thermal plasma is disclosed. According to this, the precursor supplied to the thermal plasma is a liquid containing components unnecessary for the original synthesis such as an organic solvent that stabilizes the precursor. If a precursor containing such an unnecessary component and a reaction gas are reacted in a high-temperature thermal plasma, carbon elements and the like in an organic solvent are also doped together with rare earth elements, resulting in high-purity TIO._２Particles are unlikely to be obtained. In addition, since the precursor consists of an organic solvent for stabilizing the complex, such as a complex containing a Ti element and a nitrate containing a rare earth element, it is possible to select the optimum liquid such that the precursor liquids do not chemically react with each other. The process of preparing the precursor, such as mixing them, is complicated.

According to the conventional technique of supplying a Ti-containing liquid to a plasma flame as a starting material, the influence of unnecessary atoms (nitrogen, carbon, etc.) contained in the liquid can be ignored as the generated particle size becomes smaller. It may disappear. Since the photocatalytic reaction occurs on the surface of the particles, for example, if such unnecessary atoms are precipitated on the surface, the photocatalytic reaction is less likely to occur. In Patent Documents 1 and 2, TiO_２It is not disclosed whether the particles are photocatalytically active.

Further, according to the prior art of supplying a Ti-containing liquid to the plasma flame as a starting material, the Ti-containing liquid is vaporized in the plasma generation chamber, so that, for example, a large amount of organic gas is generated. Especially in large quantities_２In the case of producing particles, a large amount of liquid is required for that amount, and it is necessary to additionally connect an exhaust system to the chamber or the like to prevent the vaporized gas from dripping into the atmosphere. Therefore, the scale of the manufacturing apparatus also increases.

In Non-Patent Document 1, TiO using high-frequency plasma_２Ultrafine particles, that is, TiO_２A method for synthesizing nanoparticles is disclosed. Here, it is disclosed that the photocatalytic property (hydrogen generation) is exhibited under simulated sunlight irradiation, but TiO_２Injecting metals and / or metal oxides into nanoparticles is not disclosed.

<p><patcit num="1"><text>JP-A-2007-230809</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 2006-347826</text></patcit></p>

<p><nplcit num="1"><text>Journal of the Japan Institute of Metals, Vol. 63, No. 1 (1994) 74-81.</text></nplcit></p>

<p> The present invention has a photocatalytic activity and is a metal and / or a metal oxide MxOy (M = Ni, Cr, Pt, Rh, Ru, Cu, x = 1, 2) which is an auxiliary element for highly activating the photocatalytic function. , 3 ..., y = 0, 1, 2, ...) Injected TiO_２Provide nanoparticles.</p>

<p> The metal and / or metal oxide MxOy (M = Ni, Cr, Pt, Rh, Ru, Cu, x = 1,2,3 ..., Y = 0,1,2 ...) Of the present invention. Infused TiO_２The nanoparticles include a step of mixing Ti powder and metal M (M = Ni, Cr, Pt, Rh, Ru, Cu) powder, a step of generating thermal plasma, and an inert gas for the thermal plasma. It is produced by a step of supplying the mixed titanium powder and metal powder as a carrier gas and supplying oxygen gas.</p><p> TiO of the present invention_２The nanoparticles have photocatalytic activity and are metals and / or metal oxides MxOy (M = Ni, Cr, Pt, Rh, Ru, Cu, x = 1, 2, 2, which are auxiliary elements that activate the photocatalytic function. 3 ..., Y = 0, 1, 2, ...) Is injected.</p>

<p> TiO according to the present invention_２According to nanoparticles, photocatalytic activity (hydrogen generation) is improved.</p>

<figref num="1">FIG. 1 is a schematic view of a high frequency plasma apparatus used in Examples 1 to 3.</figref><figref num="2">FIG. 2 shows a TiO containing Ni and Ni oxide produced by the production method according to Example 1._２It is a graph which shows the relationship between the ICP amount (Ni injection amount) of a nanoparticle, and the compounding amount of a starting Ni powder material.</figref><figref num="3">FIG. 3 shows a TiO containing Ni and Ni oxide produced by the production method according to Example 1._２It is a graph which shows the ratio of the anatase phase with respect to the Ni compounding amount of nanoparticles.</figref><figref num="4">FIG. 4 shows a TiO containing Ni and Ni oxide produced by the production method according to Example 1._２It is a graph which shows the light absorption property of a nanoparticle.</figref><figref num="5">FIG. 5 shows a TiO containing Ni and Ni oxide produced by the production method according to Example 1._２It is a graph which shows the photocatalytic property of a nanoparticle.</figref><figref num="6">FIG. 6 shows a TiO containing Cr and Cr oxide produced by the production method according to Example 2._２It is a graph which shows the relationship between the ICP amount (Cr injection amount) of a nanoparticle, and the compounding amount of a starting Cr powder material.</figref><figref num="7">FIG. 7 shows a TiO containing Cr and Cr oxide produced by the production method according to Example 2._２It is a graph which shows the ratio of the anatase phase with respect to the Cr compounding amount of nanoparticles.</figref><figref num="8">FIG. 8 shows a TiO containing Cr and Cr oxide produced by the production method according to Example 2._２It is a graph which shows the photocatalytic property of a nanoparticle.</figref><figref num="9">FIG. 9 shows a TIO containing Pt and Pt oxide produced by the production method according to Example 3._２It is a graph which shows the ratio of the anatase phase with respect to the Pt compounding amount of nanoparticles.</figref><figref num="10">FIG. 10 shows a TIO containing Pt and Pt oxide produced by the production method according to Example 3._２It is a graph which shows the photocatalytic property of a nanoparticle.</figref>

The present invention is a TiO that decomposes water to generate hydrogen by irradiation with light._２It is a nanoparticle, which is formed by injecting an auxiliary element that activates its photocatalytic function.

The injection was performed by the thermal plasma method as shown in the examples.

As the auxiliary element, various kinds are possible, but a metal element such as Ni, Cr, Pt, Cu, Rh or Ru and / or an oxide MxOy thereof (M = metal element, x = 1 or more integer, It is desirable that y = 0 or an integer of 1 or more).

Examples of the present invention will be described below. In Example 1, TiO injected with Ni and Ni oxide._２Nanoparticles and their production method, in Example 2, Cr and Cr oxide-injected TiO_２Nanoparticles and methods for producing them, in Example 3, Pt and Pt oxide-injected TiO_２The nanoparticles and the method for producing the nanoparticles will be described with reference to the accompanying drawings.

The high-frequency plasma apparatus 1 used in the manufacturing methods of Examples 1 to 3 will be described with reference to FIG. FIG. 1 is a schematic view of the reaction chamber 2 of the high frequency plasma apparatus 1. A high-frequency plasma torch 4 that generates thermal plasma 3 inside is installed in the upper part of the reaction chamber 2. A plasma gas introduction unit 5 for introducing plasma gas into the high-frequency plasma torch is provided above the high-frequency plasma torch 4, and an RF coil 6 for converting the plasma gas introduced into the torch into plasma is provided outside. ing. A powder introduction nozzle 7 for introducing powder, which is a synthetic raw material, together with a carrier gas is provided on the upper part of the plasma torch. A counter nozzle 8 for introducing the reaction gas facing the central axis of the high-frequency plasma torch is installed in the lower part of the reaction chamber. On the lower side of the reaction chamber, a discharge port 9 for discharging the plasma gas, the reaction gas, and the carrier gas introduced into the reaction chamber is provided via the filter 10. The generated particles are sucked by a discharge pump or the like connected to the discharge pipe 11 of the discharge port 9 and collected by the filter 10. The high-frequency plasma apparatus of FIG. 1 is an example, and the present invention is not limited to this.

<p>TiO injected with Ni and Ni oxide_２Nanoparticles The manufacturing method according to the first embodiment is as follows. Steps of mixing the starting powder raw materials and 2. Steps to generate thermal plasma and 3. It comprises the step of feeding the mixed starting powder raw material together with the reaction gas to the thermal plasma.</p><p> 1. 1. Powder mixing step In this experiment, metal Ti powder having a purity of 99.9% or more (particle size size: 38 μm) and metal Ni powder having a purity of 99.9% or more (particle size size: 45 μm), which are raw materials for starting powder, were prepared.</p><p> Each mixed powder sample 1 (Ni powder blending amount 0.0 wt%), sample 2 (Ni blended amount powder 0.2 wt%), and sample 3 (Ni powder blended amount) in which the above Ti powder and Ni powder are blended in a predetermined ratio 2 wt%), sample 4 (Ni powder compounding amount 5 wt%), and sample 5 (Ni powder compounding amount 10 wt%) were separately mixed in a ball mill for several hours. This is to uniformly disperse the Ti powder and the Ni powder.</p><p> In the modified example, in order to remove the water content in the mixed powder, it may be dried at a temperature of, for example, 120 ° C. for several hours.</p><p> 2. Plasma generation step In the plasma generation step, thermal plasma was generated by the high-frequency plasma torch 4 shown in FIG. In this experiment, the plasma output was set to 5.5KV, 3.4A (19KW).</p><p> 3. 3. Mixed powder supply step For the thermal plasma generated at a predetermined output, the Ti and Ni mixed powder mixed in the powder mixing step is supplied from the raw material supply nozzle installed on the upper part of the plasma torch, for example, at a supply amount of 0.2-4 g / min. Was set to, and Ar gas was used as the carrier gas and supplied to the thermal plasma from the powder introduction nozzle 7 shown in FIG. At the same time, a mixed gas of an oxygen gas having a flow rate set to, for example, 2 L / min and an Ar gas having a flow rate set to, for example, 2 L / min is used as a reaction gas and ejected from the counter nozzle 8 in FIG. 1 below the generated thermal plasma. It was.</p><p> TiO injected with Ni and Ni oxide produced thereby_２The particles were collected by a filter 10 provided in front of the gas outlet provided at the bottom of the reaction chamber 2.</p><p> Next, TiO injected with Ni and Ni oxide obtained by the above-mentioned production method._２The basic characteristics of particles will be described. TiO injected with Ni and Ni oxide_２The photocatalytic properties of the particles will be described later.</p><p> TiO injected with Ni and Ni oxides using an energy dispersive X-ray analyzer (JED-2300T)_２Grain shape and elemental analysis were performed on the particles. From the obtained STEM image (not shown), it was confirmed that the size of the produced particles was 10 to 500 nm, and the shape was almost spherical. Also, the Ni atom is TIO._２It is not locally present in some of the nanoparticles and is not deposited only on the surface, but is TIO._２It was confirmed that they were dispersed in the nanoparticles.</p><p> The bonding state with Ti atom, Ni atom, and oxygen atom was investigated by X-ray photoemission spectroscopy (XPS) and the like. Ti atom binds to oxygen from the XPS spelling peak position of the inner core level, etc. and TiO_２It was confirmed that the Ni atom exists as a Ni metal and is combined with oxygen to exist as a Ni oxide. From these results, the nanoparticles produced by the above production method are TIO._２It was found that the nanoparticles exist in a state where Ni and Ni oxides are dispersed in the nanoparticles. That is, it was confirmed that it was a solid solution.</p><p> TiO injected with Ni and Ni oxide according to Example 1._２The effect of the method for producing nanoparticles will be described.</p><p> The manufacturing method includes a mixing step, a thermal plasma generation step, and a supply step. In the mixing step, for example, a liquid such as an organic solvent, an oxidizing agent, or a pH adjuster is not used as in the prior art. , Ti powder and Ni powder are only mixed, so that the mixed powder as a starting material can be prepared more easily. Further, since the inert Ar gas is used as the carrier gas when the Ti and Ni mixed powder is supplied to the thermal plasma, it is contained in the organic solvent, the oxidizing agent, the pH adjuster, etc. as in the prior art. Unwanted atoms (nitrogen, carbon, etc.) are TIO_２Higher purity TiO because it does not penetrate into nanoparticles_２Nanoparticles can be produced. In addition, since no liquid is used as the starting material, there is no need to additionally connect an exhaust system to prevent the vaporized gas from dripping into the atmosphere, so the manufacturing equipment is larger than the conventional technology. It does not become.</p><p> In FIG. 2, the horizontal axis is a function of the blending amount (wt%) of Ni powder, which is the starting powder raw material, with respect to Ti powder._２It is a graph which plotted the ICP (Inductively coupled plasma) amount (wt%), that is, the injection (content) amount with respect to Ti of Ni injected (contained) in a nanoparticle. The ICP amount (injection amount) of Ni injected into the produced nanoparticles with respect to Ti was obtained by ICP mass spectrometry. As shown in FIG. 2, focusing on the slope of the ICP amount (injection amount) with respect to the blending amount (wt%), the amount of Ni injected into the nanoparticles increases linearly as the Ni addition amount increases. confirmed. Furthermore, focusing on the numerical value of the ICP amount (injection amount) with respect to the compounding amount (wt%), it was confirmed that the Ni compounding amount of the starting powder raw material and the Ni injection amount contained in the produced nanoparticles are almost the same. It was. This result shows that the composition of the particles to be produced can be arbitrarily controlled to produce the particles with good reproducibility.</p><p> FIG. 3 shows TiO in the generated nanoparticles as a function of the blending amount (wt%) of Ni powder, which is the starting powder raw material._２The graph which plotted the anatase composition ratio of a component is shown. The ratio of the anatase phase was determined by the peak intensity distribution of X-ray diffraction (XRD). From FIG. 3, it can be seen that the ratio of the anatase phase decreases as the Ni content of the starting material decreases. The result is TiO in nanoparticles_２It is shown that the crystallinity of the components can be controlled.</p><p> Next, TiO injected with Ni and Ni oxide produced by the above high-frequency plasma manufacturing method._２The characteristics of nanoparticles as a photocatalyst will be described.</p><p> FIG. 4 is a diagram showing the light absorption characteristics of Samples 1, 3, 4, and 5. Ni-free TiO in the near-ultraviolet to visible light region (wavelength: 330 nm to 550 nm)_２It was confirmed that the absorption strength increased as the amount of Ni added increased. This is because the level caused by Ni is TiO due to the addition of Ni._２It is considered that it was formed in the band gap of. TiO injected with Ni and Ni oxide_２Particle bandgap is additive-free TiO_２Since the particles are narrower than the nanoparticles, it is considered that the absorption intensity is increased in the near-ultraviolet to visible light region (wavelength: 330 nm to 550 nm).</p><p> FIG. 5 shows a TiO injected with Ni and Ni oxide._２It is a figure which shows the photocatalytic action of a particle. The horizontal axis is the amount of Ni compounded, and the vertical axis is the amount of hydrogen generated. TiO injected with Ni and Ni oxide_２The amount of hydrogen produced when the particles are suspended in an aqueous methanol solution as a sacrifice and irradiated with a xenon lamp is shown. As shown in FIG. 5, especially when the Ni compounding amount is around 0.2 wt%, Ni-free TiO._２The amount of hydrogen generated was about four times that of nanoparticles. This result shows that the amount of Ni is around 0.2 wt% of TiO._２TIO with no nanoparticles_２It shows that it has the ability to reduce protons to hydrogen compared to nanoparticles.</p><p> The above contents are summarized in Table 1.</p><p><tables num="1"></tables></p>

<p>TiO injected with Cr and Cr oxide_２Nanoparticles The production method according to the second embodiment is the same as that of the first embodiment. Steps of mixing the starting powder raw materials and 2. Steps to generate thermal plasma and 3. It comprises the step of feeding the mixed starting powder raw material together with the reaction gas to the thermal plasma.</p><p> 1. 1. Powder mixing step In this experiment, metal Ti powder having a purity of 99.9% or more (particle size size: 38 μm) and metal Cr powder having a purity of 99.9% or more (particle size size: 63 μm), which are raw materials for starting powder, were prepared.</p><p> Each mixed powder sample 1 (Cr compounding amount 0.0 wt%), sample 2 (Cr compounding amount 0.4 wt%), and sample 3 (Cr compounding amount 0.8 wt%) in which the above Ti powder and Cr powder are blended in a predetermined ratio ), Sample 4 (Cr compounding amount 2 wt%), and Sample 5 (Cr compounding amount 5 wt%) were mixed in a ball mill for several hours. This is to uniformly disperse the Ti powder and Cr powder.</p><p> In the modified example, in order to remove the water content in the mixed powder, it may be dried at a temperature of, for example, 120 ° C. for several hours.</p><p> 2. Plasma generation step In the plasma generation step, thermal plasma was generated by the high-frequency plasma torch 4 shown in FIG. In this experiment, the plasma output was set to 5.5KV, 3.4A (19KW).</p><p> 3. 3. Mixed powder supply step For the thermal plasma generated at a predetermined output, the Ti and Cr mixed powder mixed in the powder mixing step is supplied from the raw material supply nozzle installed on the upper part of the plasma torch to, for example, 0.2-4 g / min. Ar gas was set and supplied to the thermal plasma from the powder introduction nozzle 7 shown in FIG. 1 using Ar gas as the carrier gas. At the same time, a mixed gas of an oxygen gas having a flow rate set to, for example, 2 L / min and an Ar gas having a flow rate set to, for example, 2 L / min is used as a reaction gas and ejected from the counter nozzle 8 in FIG. 1 below the generated thermal plasma. It was.</p><p> The Cr and Cr oxides produced by this are injected into the TiO._２The nanoparticles were collected by a filter 10 provided in front of the gas outlet provided at the bottom of the reaction chamber 2.</p><p> Next, TIO injected with Cr and Cr oxide obtained by the above-mentioned production method._２The basic characteristics of nanoparticles will be described. TiO injected with Cr and Cr oxide_２The photocatalytic properties of the particles will be described later.</p><p> TiO injected with Cr and Cr oxides using an energy dispersive X-ray analyzer (JED-2300T)_２Grain shape and elemental analysis were performed on the nanoparticles. From the obtained STEM image (not shown), it was confirmed that the produced particle size was 10 to 500 nm and the shape was substantially spherical. Also, as in the case of Ni, the Cr atom is TIO._２It is not locally present in some of the nanoparticles and is not distributed only on the surface, but TiO_２It was confirmed that they were dispersed in the nanoparticles.</p><p> The bonding state with Ti atom, Cr atom, and oxygen atom was investigated by XPS and the like. Ti atom binds to oxygen from the XPS spelling peak position of the inner core level, etc. and TiO_２It was confirmed that the Cr atom exists as a Cr metal and is bonded to oxygen to exist as a Cr oxide. From these results, the nanoparticles produced by the above production method are TIO._２It was found that the nanoparticles exist in a state where Cr and Cr oxide are dispersed in the nanoparticles. That is, it was confirmed that the Cr element was injected.</p><p> TIO injected with Cr and Cr oxide according to Example 2._２The effect of the method for producing nanoparticles will be described.</p><p> In FIG. 6, the horizontal axis is the ICP amount (wt%) of Cr injected into the generated nanoparticles with respect to Ti, that is, as a function of the blending amount (wt%) of Cr powder, which is the starting powder raw material, with respect to Ti powder. It is a graph which plotted the injection amount. The ICP amount (injection amount) of Cr injected into the produced nanoparticles with respect to Ti was obtained by ICP mass spectrometry. As shown in FIG. 6, focusing on the slope of the ICP amount (injection amount) with respect to the blending amount (wt%), the amount of Cr injected into the nanoparticles increases linearly as the amount of Cr added increases. confirmed. This result shows that the composition of nanoparticles to be produced can be arbitrarily controlled and reproducibly produced based on the slope of the ICP amount (injection amount) with respect to the compounding amount (wt%) shown in FIG. ing.</p><p> FIG. 7 shows TIO in the generated nanoparticles as a function of the blending amount (wt%) of Cr powder, which is the starting powder raw material, with respect to Ti powder._２The graph which plotted the anatase composition ratio of a component is shown. The ratio of the anatase phase was determined by the peak intensity distribution of XRD. From FIG. 7, it can be seen that the ratio of the anatase phase decreases as the Cr content of the starting material decreases. The result is TiO in nanoparticles_２It is shown that the crystallinity of the components can be controlled.</p><p> Next, TiO injected with Cr and Cr oxide generated by the above high-frequency plasma manufacturing method._２The characteristics of nanoparticles as a photocatalyst will be described.</p><p> FIG. 8 shows a TiO injected with Cr and Cr oxide._２It is a figure which shows the photocatalytic action of a nanoparticle. The horizontal axis is TiO_２It is the injection amount (wt%) of Cr injected into the nanoparticles, and the vertical axis is the hydrogen generation amount. TiO injected with Cr and Cr oxide_２The amount of hydrogen produced when nanoparticles are suspended in an aqueous methanol solution as a sacrifice and irradiated with a xenon lamp is shown. As shown in FIG. 8, especially when the Cr injection amount is around 0.1 wt%, Cr-free TiO._２The amount of hydrogen generated was about twice that of nanoparticles. This result shows that the Cr injection amount is around 0.1 wt% of TiO._２TIO with no nanoparticles_２It shows that it has the ability to reduce protons to hydrogen compared to nanoparticles.</p><p> The above contents are summarized in Table 2.</p><p><tables num="2"></tables></p>

<p>TIO injected with Pt and Pt oxide_２Nanoparticles The production method according to the third embodiment is the same as that of the first and second embodiments. Steps of mixing the starting powder raw materials and 2. Steps to generate thermal plasma and 3. It comprises the step of feeding the mixed starting powder raw material together with the reaction gas to the thermal plasma.</p><p> 1. 1. Powder mixing step In this experiment, metal Ti powder having a purity of 99.9% or more (particle size size: 38 μm) and platinum black powder having a purity of 97.8% or more (particle size size: 5 μm), which are raw materials for starting powder, are prepared.</p><p> Each mixed powder sample 1 (Pt compounding amount 0.0 wt%), sample 2 (Pt compounding amount 0.2 wt%), and sample 3 (Pt compounding amount 0.8 wt%) in which the above Ti powder and Pt powder are blended in a predetermined ratio. ) And sample 4 (Pt compounding amount 1.5 wt%) are separately mixed in a ball mill for several hours. This is to uniformly disperse the Ti powder and the Pt powder.</p><p> In the modified embodiment, in order to remove the water content in the mixed powder, it may be dried at a temperature of, for example, 120 ° C. for several hours.</p><p> 2. Plasma generation step In the plasma generation step, thermal plasma was generated by the high-frequency plasma torch 4 shown in FIG. In this experiment, the plasma output was set to 5.5KV, 3.4A (19KW).</p><p> 3. 3. Mixed powder supply step For the thermal plasma generated at a predetermined output, the Ti and Pt mixed powder mixed in the powder mixing step is supplied from the raw material supply nozzle installed on the upper part of the plasma torch to, for example, 0.2-4 g / min. Ar gas was set and supplied to the thermal plasma from the powder introduction nozzle 7 shown in FIG. 1 using Ar gas as the carrier gas. At the same time, a mixed gas of an oxygen gas having a flow rate set to, for example, 2 L / min and an Ar gas having a flow rate set to, for example, 2 L / min is used as a reaction gas and ejected from the counter nozzle 8 in FIG. 1 below the generated thermal plasma. It was.</p><p> TIO injected with Pt and Pt oxide produced thereby_２The nanoparticles were collected by a filter 10 provided in front of the gas outlet provided at the bottom of the reaction chamber 2.</p><p> Next, TIO injected with Pt and Pt oxide obtained by the above-mentioned production method._２The basic characteristics of nanoparticles will be described. TiO injected with Pt and Pt oxide_２The photocatalytic properties of nanoparticles will be described later.</p><p> TiO injected with Pt and Pt oxide using an energy dispersive X-ray analyzer (JED-2300T)_２Grain shape and elemental analysis were performed on the nanoparticles. From the obtained STEM image (not shown), it was confirmed that the produced particle size was 10 to 500 nm and the shape was substantially spherical. Also, as in the case of Ni and Cr, the Pt atom is TIO._２It is not locally present in some of the nanoparticles and is not distributed only on the surface, but TiO_２It was confirmed that they were dispersed in the nanoparticles.</p><p> The bonding state with Ti atom, Pt atom, and oxygen atom was investigated by XPS and the like. Ti atom binds to oxygen from the XPS spelling peak position of the inner core level, etc. and TiO_２It was confirmed that the Pt atom exists as a Pt metal and is combined with oxygen to exist as a Pt oxide. From these results, the nanoparticles produced by the above production method are TIO._２It was found that the nanoparticles were present in a state in which Pt or Pt oxide was dispersed in the nanoparticles. That is, it was confirmed that the Pt element was injected.</p><p> TIO injected with Pt and Pt oxide according to Example 3._２The effect of the method for producing nanoparticles will be described.</p><p> FIG. 9 shows TIO in the generated nanoparticles as a function of the blending amount (wt%) of the Pt powder, which is the starting powder raw material, with respect to the Ti powder._２The graph which plotted the anatase composition ratio of a component is shown. The ratio of the anatase phase was determined by the peak intensity distribution of XRD. From FIG. 9, even if the Pt compounding amount (wt%) of the starting material is increased, the ratio of the anatase phase remains almost constant, and the tendency of FIG. 3 (Example 1) and FIG. 7 (Example 2) is clear. It turns out that it is different. </p><p> That is, the result of FIG. 9 shows that even if Pt is blended, TiO in the nanoparticles_２It means that it does not affect the crystallinity of the ingredients.</p><p> Next, Pt produced by the production method according to Example 3 and TiO injected with Pt oxide were injected._２The characteristics of nanoparticles as a photocatalyst will be described.</p><p> FIG. 10 shows a TIO injected with Pt and Pt oxide._２It is a figure which shows the photocatalytic action of a particle. The horizontal axis is the injection amount (wt%) of Pt as the starting powder raw material, and the vertical axis is the hydrogen generation amount. TIO injected with Pt and Pt oxide_２The amount of hydrogen produced when nanoparticles are suspended in an aqueous methanol solution as a sacrifice and irradiated with a xenon lamp is shown. As shown in FIG. 10, especially when the Pt injection amount is around 0.6 wt%, Pt-free TiO._２The amount of hydrogen generated was about 70 times that of nanoparticles. This result shows that the amount of Pt in TIO is around 0.6 wt%._２TIO with no nanoparticles_２It shows that it has the ability to reduce protons to hydrogen compared to nanoparticles.</p><p> The above contents are summarized in Table 3.</p><p><tables num="3"></tables></p><p> TiO of the present invention_２The nanoparticles have been described in Examples 1-3, but are not limited thereto within the scope of the present invention. Hereinafter, modified examples of Examples 1-3 will be described.</p><p> 1. 1. The particle size of the starting powder raw material is not limited to Examples 1-3. The particle size of the starting material may be changed.</p><p> 2. Unnecessary gas (for example, nitrogen) contained in the atmosphere is removed in advance from the reaction chamber 2 shown in FIG. 1 by a vacuum pump or the like connected to the exhaust port 9, and replaced with an inert gas such as Ar. By doing so, a higher purity metal and metal oxide are injected into the TiO._２It is possible to produce nanoparticles.</p><p> 3. 3. In Examples 1-3, TiO injected with Ni and Ni oxides, Cr and Cr oxides, and Pt and Pt oxides, respectively._２The method for producing nanoparticles has been described, but in addition, TiO infused with other auxiliary elements (for example, Rh, Ru, Cu, etc.) and their oxides._２It can also be applied to methods for producing nanoparticles. In this case, the auxiliary element powder may be mixed with the Ti powder as the starting powder material in the powder mixing step.</p><p> 4. In Examples 1-3, only one kind of each auxiliary element was mixed with Ti powder to prepare the powder, but a plurality of auxiliary elements may be mixed and used.</p>