Method for producing photocatalyst, photocatalyst, method for seawater decomposition, and method for producing composite

Abstract

To provide a method for producing a photocatalyst that enables efficient production of a photocatalyst containing Ti3+ encapsulated titanium oxide with superior catalytic activity.SOLUTION: A method for producing a photocatalyst including a pulverization step of pulverizing titanium oxide with introduced oxygen deficiency by means of a wet bead mill with added ethanol or methanol, the beads of the bead mill having a diameter of 0.03-1 mm.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for producing a photocatalyst, a photocatalyst, a method for splitting seawater, and a method for producing a composite. [Background technology]

[0002] Currently, various energy sources are used, but the reliance on thermal energy obtained by burning oil is still high. However, oil reserves are finite, and the carbon dioxide emitted when oil is burned contributes to global warming.

[0003] In this situation, hydrogen is attracting attention as a clean energy source that is expected to solve energy resource and global environmental problems. When hydrogen is burned, it only turns into water, and its use poses a small environmental burden. However, due to production efficiency and cost considerations, hydrogen is currently mainly produced from natural gas, and fossil fuels are used to generate hydrogen, which means that carbon dioxide is emitted in the hydrogen production process, making it difficult to reduce the environmental burden.

[0004] One method for extracting hydrogen using light energy is to obtain it by splitting water using a photocatalyst. Photocatalysts typically use inorganic oxide semiconductor particles. When they absorb energy above their band gap, they generate holes (+) and excited electrons (-). These contribute to oxidation and reduction reactions, respectively, enabling the production of hydrogen through water splitting. Furthermore, for practical use of photocatalysts, it is desirable to utilize sunlight, a clean, energy-saving, and highly safe light source. Sunlight that strikes the Earth's surface has its maximum radiation intensity around 500 nm, which is visible light. The energy content of the visible light region (400–750 nm) accounts for approximately 43% of all sunlight. Meanwhile, the ultraviolet region (wavelengths below 400 nm) accounts for approximately 5%. Therefore, to efficiently utilize the solar spectrum, it is desirable for photocatalysts to be able to utilize visible light.

[0005] Furthermore, water is required as a raw material for water splitting using photocatalysis, but fresh water is a precious and limited resource. Therefore, it would be extremely beneficial to use seawater, which accounts for the majority of water on Earth, as a raw material for water splitting reactions. However, splitting seawater produces by-products of chlorine-based compounds derived from the large amounts of dissolved salt, which dissolve valuable precious metals often used as co-catalysts in photocatalysts and produce harmful chlorine.

[0006] In this situation, titanium oxide, which is inexpensive and stable, has attracted attention as a photocatalyst. Titanium oxide mainly responds to ultraviolet light, but research into visible light-responsive titanium oxide is also being actively conducted. Specifically, Ti 3+ The visible light responsive titanium dioxide (hereinafter referred to as "Ti") is embedded in the titanium dioxide crystal lattice. 3+ In some cases, the use of titanium dioxide as a catalyst has been reported (Non-Patent Documents 1 to 5). 3+ is unstable and easily reacts with oxygen in air and water, but Ti 3+ In the case of encapsulated titanium oxide, Ti 3+ It is difficult to react with oxygen on the surface and is stable. 3+ Encapsulated titanium oxide is produced by mixing titanium oxide powder with a reducing precursor (such as TiCl3), or by firing or plasma treating titanium oxide powder in a hydrogen gas atmosphere. [Prior art documents] [Patent documents]

[0007] [Non-Patent Document 1] Alexandra Teleki et al. Phys. Chem. Phys., 2009,11, 3742. [Non-patent document 2] C.Di. Valentin et al. J. Phys. Chem. C, 2009, 113, 20543. [Non-patent document 3] Fan Zuo et al. J. Am. Chem. Soc. 2010, 132, 11856. [Non-patent document 4] M. Xing et al. J. Catal. 2013, 297, 236. [Non-patent document 5] Qing Zhu et al. J. Mater. Chem. A, 2014, 2, 4429. Summary of the Invention [Problem to be solved by the invention]

[0008] However, Ti 3+ In the case of manufacturing encapsulated titanium dioxide, Ti 3+ It is difficult to obtain encapsulated titanium oxide. 3+ Since the specific surface area of the encapsulated titanium oxide is insufficient and it may encapsulate impurities such as chlorine derived from the reducing precursor, further improvement in catalytic activity has been desired.

[0009] The present invention has been made in view of the above circumstances, and provides a Ti catalyst having excellent catalytic activity. 3+ The present invention aims to provide a method for producing a photocatalyst that can efficiently produce a photocatalyst containing encapsulated titanium oxide, and a photocatalyst obtained by this method. 3+ The object of the present invention is to provide a method for splitting seawater using a photocatalyst containing encapsulated titanium oxide. 3+ Ti was produced by the same method as that for producing titanium dioxide. 3+ The present invention aims to provide a method for producing a composite in which various metals are supported by encapsulated titanium oxide. [Means for solving the problem]

[0010] In order to solve the above problems, the following methods for producing a photocatalyst, a photocatalyst, a method for splitting seawater, and a method for producing a composite are provided. [1]Ti3+ A method for producing a photocatalyst containing encapsulated titanium oxide, comprising: The method includes a pulverization step of pulverizing the titanium oxide having oxygen vacancies introduced therein by a wet bead mill to which ethanol or methanol has been added, The diameter of the beads of the bead mill is 0.03 to 1 mm. Photocatalyst manufacturing method. [2] The diameter of the beads is 0.1 to 0.5 mm. The method for producing the photocatalyst according to [1] above. [3] Adding Ni oxide or hydroxide to the bead mill; The method for producing the photocatalyst according to [1] or [2] above. [4] Ti obtained in the grinding process 3+ The method includes a step of supporting Pt on endohedral titanium oxide. The method for producing the photocatalyst according to [1] or [2] above. [5] Ni and Ti 3+ It is a composite with encapsulated titanium oxide, and has a specific surface area of 100m 2 g -1 That's all. Photocatalyst. [6] Seawater contains organic compounds and Ti 3+ and a photocatalyst containing encapsulated titanium oxide, and simultaneously irradiating the photocatalyst with ultraviolet light and visible light. Seawater decomposition method. [7] The organic compound is an alcohol, The method for decomposing seawater according to [6], wherein the amount of the alcohol added to the seawater is 0.005 to 0.5 vol %. [8] The photocatalyst is manufactured by the manufacturing method of [1]. The seawater decomposition method according to [6] or [7] above. [9]Ti 3+ A method for producing a composite of encapsulated titanium oxide and another metal compound, comprising the steps of: The method includes a pulverization step of pulverizing the titanium oxide having oxygen vacancies introduced therein by a wet bead mill to which ethanol or methanol has been added, The diameter of the beads of the bead mill is 0.03 to 1 mm, In the pulverization step, at least one of a metal oxide, a metal hydroxide, and a metal nitrate is added to the bead mill as a raw material of the other metal compound. Method for manufacturing the composite.

[10] The metal oxide, the metal hydroxide, and the metal nitrate contain at least one metal or element selected from Ni, Co, Cu, Fe, Ti, Mn, Ag, Mg, Ce, Zn, Nb, B, N, and Al; A method for producing the composite of [9] above.

[11] The diameter of the beads is 0.1 to 0.5 mm. A method for producing the complex according to [9] or

[10] . [Effects of the Invention]

[0011] According to the method for producing a photocatalyst of the present invention, Ti having excellent catalytic activity can be obtained. 3+ A photocatalyst containing encapsulated titanium oxide can be efficiently obtained. The photocatalyst of the present invention has excellent catalytic activity and can decompose seawater using sunlight. According to the seawater decomposition method of the present invention, seawater can be efficiently decomposed using sunlight. According to the method for producing a composite of the present invention, Ti 3+ It is possible to obtain a composite in which various metals are supported by the encapsulated titanium oxide. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram comparing the absorption spectra of Examples 1 to 4, untreated TiO2, and TiO2 after reduction firing and before bead mill pulverization. [Figure 2] FIG. 1 is a diagram showing the band structure of Ti3+-encapsulated titanium oxide. [Figure 3] FIG. 2 is a schematic diagram showing the state of particles during bead mill pulverization. [Figure 4] FIG. 1 is a schematic diagram showing the configuration of a test device for measuring the rate of hydrogen generation by a photocatalyst. [Figure 5] FIG. 1 shows the results of evaluating the photocatalytic activity of Examples 1-4, Reference Example 1, untreated titanium oxide (TiO2), and titanium oxide (TiO2) after reduction treatment. [Figure 6] FIG. 1 shows the results of investigating the effect of the type of light (ultraviolet light + visible light, ultraviolet light only, visible light only) on hydrogen generation capacity when the sample of Example 1 is used (containing 20% ethanol). [Figure 7] FIG. 1 shows the results of comparing the hydrogen generation rate of Ti3+-encapsulated titanium oxide of Example 1 with that of composites of Ti3+-encapsulated titanium oxide and various metal compounds (Example 5, Reference Examples 2-5). [Figure 8] This figure shows the change in the hydrogen production rate over time when the photocatalyst of Example 5 (Ni oxide composite-type Ti3+-encapsulated titanium oxide) was added to pure water, light irradiation was started, a small amount of ethanol water (0.005 vol%) was added during the process, and then saline solution (adjusted so that the final concentration in the entire system was about 2%) was added. [Figure 9] FIG. 10 is a graph showing the results of a long-term decomposition reaction carried out on seawater from Tokyo Bay using the photocatalyst of Example 5. [Figure 10] (A) and (B) show the change in the hydrogen production rate over time when the Ti3+-encapsulated titanium oxide (catalyst) from Example 1 was added to pure water and irradiated with light, a small amount of ethanol water ((A): 0.05 vol% or (B): 0.005 vol%) was added during the process, and then an aqueous platinum chloride solution was added with the concentration and amount adjusted to 0.5 wt% of the initial catalyst amount to support Pt on the catalyst by photoprecipitation, and then saline solution (adjusted so that the final concentration in the entire system was about 3%) was added during the process. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the photocatalyst manufacturing method, the photocatalyst, the seawater splitting method, and the composite manufacturing method of the present invention will be described.

[0014] (Photocatalyst manufacturing method and photocatalyst) The method for producing a photocatalyst of the present invention includes a pulverization step in which titanium oxide into which oxygen vacancies have been introduced is pulverized by a wet bead mill to which ethanol or methanol has been added.

[0015] As the raw material titanium oxide, for example, commercially available powdered titanium oxide can be used appropriately. The method for introducing oxygen vacancies into titanium oxide is not particularly limited, but examples include known methods such as vacuum heating, hydrogen plasma treatment, rare gas element plasma treatment, and rare gas element ion implantation. In addition, oxygen vacancies in titanium oxide can also be confirmed using, for example, X-ray photoelectron spectroscopy (XPS).

[0016] A commercially available bead mill can be used as appropriate. The type of beads placed in the grinding chamber (vessel) of the bead mill is not particularly limited, but examples include zirconia beads, glass beads, alumina beads, zirconia-silica ceramic beads, and silicon nitride beads. Among these, zirconia beads are preferred.

[0017] The diameter of the beads in the bead mill is 0.03 to 1 mm. When the diameter of the beads is in this range, Ti with a large specific surface area can be efficiently milled. 3+ Specifically, the TiO2 obtained by the photocatalyst manufacturing method of the present invention can be obtained. 3+ The lower limit of the specific surface area of encapsulated titanium oxide is 90m 2 g -1 It is preferable that it is more than 200m 2 g -1 It is more preferable that the value is equal to or greater than Ti 3+ The upper limit of the specific surface area of encapsulated titanium dioxide is 500m 2 g -1 This is the Ti 3+ The encapsulated titanium oxide has excellent catalytic activity as a photocatalyst.

[0018] Also, if the diameter of the beads in the bead mill exceeds 1 mm, a lot of Ti 3+ Although encapsulated titanium oxide is obtained, the specific surface area is small. On the other hand, if the diameter of the beads is less than 0.03 mm, Ti 3+ It is difficult to confine Ti within the crystal lattice of titanium oxide, 3+ It is difficult to obtain encapsulated titanium oxide.3+ From the viewpoint of obtaining endohedral titanium oxide, the diameter of the beads is preferably in the range of 0.1 to 0.5 mm, and more preferably 0.2 to 0.4 mm.

[0019] Ethanol or methanol is added to the grinding chamber (vessel) of the bead mill. In other words, in the method for producing a photocatalyst of the present invention, a wet bead mill to which ethanol or methanol is added is used. By adding ethanol or methanol to the bead mill, Ti, which has a large specific surface area, can be more efficiently milled than when water is added, for example. 3+ In the present invention, the "wet bead milling with added ethanol or methanol" method includes immersing titanium oxide having oxygen vacancies in ethanol or methanol, and then adding the resulting mixture together with water to the grinding chamber (vessel) of the bead mill.

[0020] More specifically, beads and a solvent (e.g., ethanol, methanol, water, or a mixture thereof) are placed in the grinding chamber (vessel) of a bead mill, and titanium oxide powder is mixed into the slurry of beads and solvent. The mixing ratio of the solvent and the amount of titanium oxide added are not particularly limited, but the amount of titanium oxide added can be, for example, in the range of approximately 0.10 wt% to 0.20 wt% based on the weight of the beads.

[0021] Furthermore, the photocatalyst manufacturing method of the present invention does not use reducing precursors, etc., which are used in conventional methods, and therefore Ti 3+ The encapsulated titanium oxide does not encapsulate impurities such as chlorine derived from the reducing precursor. Therefore, according to the method for producing a photocatalyst of the present invention, the photocatalyst (Ti 3+ This can prevent the catalytic activity of the encapsulated titanium oxide from decreasing.

[0022] The form of the photocatalyst obtained by the production method of the present invention is not particularly limited as long as it is a form that can function as a photocatalyst, and can be appropriately selected from various forms such as particulate (powder), block, plate, etc. depending on the installation form of the photocatalyst, etc. Furthermore, the photocatalyst can be used, for example, by diluting the suspension after the pulverization step as it is.

[0023] According to the method for producing a photocatalyst of the present invention, Ti having excellent catalytic activity can be obtained. 3+ A photocatalyst containing encapsulated titanium oxide can be efficiently obtained. The photocatalyst obtained by the production method of the present invention can utilize sunlight (visible light and ultraviolet light) and can also use seawater as a raw material for water splitting reactions.

[0024] In one embodiment of the photocatalyst manufacturing method of the present invention, at least one of Ni oxide, Ni hydroxide, and Ni nitrate can be added to the grinding chamber (vessel) of the bead mill together with the oxygen-deficient titanium oxide. This allows for the production of Ti with uniformly supported Ni. 3+ Encapsulated titanium oxide (Ni composite Ti 3+ It is possible to obtain Ni-composite Ti (encapsulated titanium oxide). 3+ The specific surface area of encapsulated titanium oxide is 100m 2 g -1 It is preferable that it is 150m or more. 2 g -1 More preferably, it is 200m or more. 2 g -1 More preferably, the Ni-composite Ti content is equal to or greater than 100%. 3+ The photocatalyst containing encapsulated titanium oxide is a Ti catalyst that does not support Ni. 3+ Compared to encapsulated titanium oxide, it has particularly excellent catalytic activity. Examples of Ni oxides include nickel(II) oxide, and examples of Ni hydroxides include nickel(II) hydroxide. Examples of Ni nitrates include nickel(II) nitrate.

[0025] Furthermore, in the method for producing a photocatalyst of the present invention, Ti 3+It is also possible to include a step of supporting Pt on the endohedral titanium oxide by a known method such as photoprecipitation. 3+ The encapsulated titanium oxide has excellent catalytic activity as a photocatalyst.

[0026] (Seawater decomposition method) The seawater decomposition method of the present invention comprises adding an organic compound and Ti to seawater. 3+ The method includes a step of adding a photocatalyst containing encapsulated titanium oxide and irradiating the resulting mixture with ultraviolet light and visible light simultaneously.

[0027] Examples of the organic compound include alcohols such as ethanol and isopropyl alcohol, acetic acid, formic acid, etc. Among these, it is preferable that the organic compound contains an alcohol.

[0028] For example, the amount of alcohol added to seawater is 0.005 to 0.5 vol%, and more preferably 0.01 to 0.1 vol%. When the amount of alcohol added is within this range, the function of the chloride ions in the seawater as a sacrificial reagent is promoted, thereby facilitating seawater decomposition (hydrogen production) by the photocatalyst.

[0029] The photocatalyst used in the seawater splitting method of the present invention is Ti obtained by a conventional method (e.g., Non-Patent Documents 1-5). 3+ Although it may be an encapsulated titanium oxide, the Ti obtained by the photocatalyst manufacturing method of the present invention is 3+ It is preferable that the photocatalyst contains encapsulated titanium oxide. 3+ Complex with encapsulated titanium oxide (Ni complex Ti 3+ Inclusion-type titanium oxide), Pt-supported Ti 3+ It may be in the form of encapsulated titanium oxide or the like.

[0030] In the seawater splitting method of the present invention, ultraviolet light and visible light are irradiated simultaneously. This allows for more rapid seawater splitting (hydrogen production) by the photocatalyst than when only ultraviolet light or only visible light is irradiated. Furthermore, in the seawater splitting method of the present invention, the photocatalyst can utilize sunlight (e.g., ultraviolet light, visible light, and infrared light), which reduces the environmental impact, saves energy, and is also safe.

[0031] (Method of manufacturing the composite) The method for producing the composite of the present invention is 3+ This is a method for producing a composite of encapsulated titanium oxide and other metal compounds. Explanation of the content common to the method for producing the photocatalyst of the present invention described above will be omitted.

[0032] The method for producing the composite of the present invention includes a pulverization step of pulverizing titanium oxide having oxygen vacancies introduced therein using a bead mill to which ethanol or methanol has been added.

[0033] The diameter of the beads of the bead mill is 0.03 to 1 mm, preferably 0.1 to 0.5 mm.

[0034] In the method for producing a composite of the present invention, at least one of a metal oxide, a metal hydroxide, and a metal nitrate is added to a bead mill in the pulverization step as a raw material for other metal compounds. The metals or elements constituting the metal oxide, metal hydroxide, and metal nitrate are not particularly limited. The metal oxide, metal hydroxide, and metal nitrate preferably contain at least one metal or element selected from, for example, Ni, Co, Cu, Fe, Ti, Mn, Ag, Mg, Ce, Zn, Nb, B, N, and Al. This allows for the production of Ti 3+ It is possible to efficiently obtain a composite of encapsulated titanium oxide and metal compounds (Ni, Co, Cu, Fe, Ti, Mn, Ag, Mg, Ce, Zn, Nb, B, N, and Al). This composite contains Ti in the crystal lattice of titanium oxide. 3+ It contains these compounds and has a large specific surface area, making it suitable for use as a variety of functional materials.

[0035] Specifically, as mentioned above, Ni composite Ti 3+ Encapsulated titanium oxide can be used as a photocatalyst with excellent catalytic activity. 3+ The encapsulated titanium oxide can be used, for example, as an electrode material or a combustion catalyst.

[0036] The method for producing a photocatalyst, the photocatalyst, the method for splitting seawater, and the method for producing a composite of the present invention are not limited to the above-described embodiments. [Example]

[0037] The present invention will be described below with reference to examples, but the photocatalyst production method, photocatalyst, seawater splitting method, and composite production method of the present invention are not limited to the following examples in any way.

[0038] The following preparation method is common to Examples 1 to 5 and Comparative Examples 1 to 6.

[0039] The bead mill treatment was carried out at 1910 rpm for 3 hours. The zirconia beads were removed by filtering the milled slurry, and the remaining photocatalyst dispersion was air-dried to obtain a powder sample. 0.45 g of powder was added to 300 g of zirconia beads. The solvent was added so that the filling rate was approximately 50%.

[0040] The hydrogen production rate was calculated by adding 0.01 g of catalyst powder to 20 ml of 20% ethanol solution, irradiating it with ultraviolet and visible light, and continuously detecting the hydrogen produced under a 7 ml / min Ar flow using a micro GC. 3+ The BET specific surface area of the encapsulated titanium oxide was measured using a gas adsorption measurement device, BELSORP-max, manufactured by Microtrackbell Co., Ltd. Nitrogen was used as the adsorption gas, and measurements were performed under liquid nitrogen conditions. Prior to measurement, pretreatment was performed at 110°C for approximately 3 hours (in vacuum). Example 1 Titanium oxide, which had been previously treated for oxygen deficiency, was pulverized in a wet bead mill using 0.3 mm zirconia beads and ethanol (solvent) to obtain Ti 3+ Encapsulated titanium oxide was prepared. [Example 2] Titanium oxide, which had been previously treated for oxygen deficiency, was pulverized in a wet bead mill using zirconia beads with a diameter of 0.03 mm and ethanol (solvent) to obtain Ti 3+ Encapsulated titanium oxide was prepared. Example 3 Titanium oxide, which has been preliminarily treated for oxygen deficiency, is ground in a wet bead mill using 0.1 mm zirconia beads and ethanol (solvent) to obtain Ti 3+ Encapsulated titanium oxide was prepared. Example 4 Titanium oxide, which had been previously treated for oxygen deficiency, was pulverized in a wet bead mill using 0.5 mm zirconia beads and ethanol (solvent) to obtain Ti 3+ Encapsulated titanium oxide was prepared. Example 5 A mixture of oxygen-deficient titanium oxide and 0.5 wt% nickel oxide was milled in a wet bead mill using 0.3 mm diameter zirconia beads and ethanol (solvent) to produce a Ti-Ni oxide composite. 3+ Encapsulated titanium oxide was prepared. [Reference example 1] Titanium oxide, which has been preliminarily treated for oxygen deficiency, is ground in a wet bead mill using 0.3 mm zirconia beads and distilled water (solvent) to produce Ti 3+ An encapsulated titanium oxide was prepared. [Reference Example 2] A mixture of pre-oxidized titanium oxide and 0.5 wt% cobalt oxide was milled in a wet bead mill using 0.3 mm diameter zirconia beads and ethanol (solvent) to produce a Ti-Co oxide composite. 3+ Encapsulated titanium oxide (composite) was prepared. [Reference example 3] A mixture of pre-oxidized titanium oxide and 0.5 wt% manganese oxide was milled in a wet bead mill using 0.3 mm diameter zirconia beads and ethanol (solvent) to produce a Mn oxide composite Ti 3+ Encapsulated titanium oxide (composite) was prepared. [Reference example 4] A mixture of oxygen-deficient titanium oxide and 0.5 wt% iron oxide was milled in a wet bead mill using 0.3 mm diameter zirconia beads and ethanol (solvent) to produce a composite TiFe oxide. 3+ Encapsulated titanium oxide (composite) was prepared. [Reference example 5] Titanium oxide and 0.5 wt% titanium chloride, which had been heated in advance in a vacuum, were ground in a wet bead mill using 0.3 mm diameter zirconia beads and ethanol (solvent) to obtain a chlorine-containing Ti composite. 3+ Encapsulated titanium oxide (composite) was prepared.

[0041] The production methods of Examples 1 to 5 correspond to the production methods of the photocatalyst of the present invention, and the production methods of Example 5 and Reference Examples 1 to 4 correspond to the production methods of the composite of the present invention.

[0042] Figure 1 compares the absorption spectra of Examples 1 to 4, untreated TiO2, and TiO2 before bead mill pulverization after reduction and firing. Both samples exhibited absorption in the ultraviolet and in the wide visible light region from 400 to 900 nm. This is because the Ti 3+ As shown in the band structure of endohedral titanium oxide, Ti 3+ This is thought to be due to the impurity levels derived from the SiO2.

[0043] Figure 3 is a schematic diagram showing the state of particles during bead mill grinding. In the bead mill grinding process, the main process is path i (change from state A to state B), but under certain conditions, re-agglomeration occurs as shown in path ii (change from state B to state C), and this agglomeration action results in Ti 3+ It is thought that it is possible to confine Ti within the crystal lattice. As the diameter of the beads increases, path ii becomes dominant, and more Ti3+ However, the particles become larger due to the agglomeration process, and as shown in Table 1, the specific surface area decreases as the diameter of the beads increases. 3+ From the viewpoint of the inclusion amount and the specific surface area, the diameter of the beads of the bead mill is 0.03 to 1 mm, preferably 0.1 to 0.5 mm, and more preferably 0.2 to 0.4 mm.

[0044] [Table 1]

[0045] Figure 4 is a schematic diagram showing the configuration of a test device used to measure the rate at which hydrogen is generated by a photocatalyst. As shown in Figure 4, the comparison of photocatalytic hydrogen generation ability was carried out by irradiating ultraviolet and visible light, simulating sunlight, from a xenon lamp under a flow of Ar gas, and measuring the rate at which hydrogen is generated in a continuous flow system.

[0046] Figure 5 shows the results of evaluating the photocatalytic activity of Examples 1-4, Reference Example 1, untreated titanium oxide (TiO2), and titanium oxide (TiO2) after reduction treatment. As shown in Figure 5, the optimum bead diameter was 0.3 mm, and it was confirmed that the hydrogen production rate was approximately 15 times higher than that of untreated commercially available titanium oxide (ST01).

[0047] In this photocatalytic activity evaluation, light irradiation was started 30 minutes after the start of irradiation. After a time lag of 20 to 30 minutes, the hydrogen production rate became almost constant and stabilized after about an hour. The excited electrons generated by visible light were transported to the Ti crystals. 3+ It is thought that the water splitting reaction was assisted by passing through this site.

[0048] 6 shows the results of investigating the effect of the type of light (ultraviolet light + visible light, ultraviolet light only, visible light only) on the hydrogen generation capacity (containing 20% ethanol) when using the sample of Example 1. It was confirmed that irradiation with both visible light and ultraviolet light clearly had a synergistic effect, increasing the hydrogen generation rate by approximately 9 times compared to ultraviolet light alone.

[0049] FIG. 7 shows the Ti 3+ Inclusion titanium oxide and Ti 3+ FIG. 1 shows the results of comparing the hydrogen production rates of composites (Example 5, Reference Examples 2-5) in which encapsulated titanium oxide and various metal compounds are combined.

[0050] The composite of Example 5 (Ni composite Ti) in which Ni oxide was mixed during grinding with a bead mill 3+ In the case of titanium dioxide, Ti in Example 1 3+ It was confirmed that the hydrogen generation rate increased by approximately three times compared to the encapsulated titanium oxide. 3+ It was confirmed that the encapsulated titanium oxide has excellent catalytic activity as a photocatalyst.

[0051] FIG. 8 shows the results of the measurement of the photocatalyst (Ni oxide composite Ti) of Example 5 in pure water. 3+ This figure shows the change in the hydrogen production rate over time when a small amount of ethanol water (0.005 vol%) was added and light irradiation was started, and then saline solution (adjusted so that the final concentration of the entire system was about 2%) was added.

[0052] As shown in Figure 8, the rate of hydrogen production increased by about five times after adding saline compared to before adding saline, suggesting that chloride ions functioned as a sacrificial reagent.

[0053] FIG. 9 shows the results of a long-term decomposition reaction carried out on seawater from Tokyo Bay using the photocatalyst of Example 5.

[0054] Using the photocatalyst of Example 5, a small amount of ethanol water (0.02 vol%) was added before the reaction, and then the reaction was carried out under irradiation with ultraviolet light and visible light in a flow of Ar. It was confirmed that the decomposition reaction (hydrogen production reaction) continued stably.

[0055] FIG. 10 shows the Ti of Example 1 in pure water. 3+ This figure shows the change in hydrogen production rate over time when encapsulated titanium oxide (catalyst) is added and light irradiation is initiated, a small amount of ethanol water (0.05 vol% or 0.005 vol%) is added during the process, and then a platinum chloride aqueous solution whose concentration and amount are adjusted to 0.5 wt% of the initial catalyst amount is added to support Pt on the catalyst using the photoprecipitation method, and then salt water (adjusted so that the final concentration in the entire system is about 3%) is added during the process.

[0056] As shown in Figure 10(A), when 0.05 vol% ethanol water was added, the hydrogen production rate increased by about 1.5 times after the addition of saline compared to before the addition of saline, suggesting that this promotes the function of chloride ions as a sacrificial reagent. As shown in Figure 10(B), when 0.005 vol% ethanol water was added, the hydrogen production rate increased by about 3 times after the addition of saline compared to before the addition of saline, suggesting that this promotes the function of chloride ions as a sacrificial reagent. It was shown that the hydrogen production rate increased with increasing amounts of ethanol, but the rate of increase in the hydrogen production rate after the addition of saline decreased.

Claims

1. Ti ３＋ A method for producing a photocatalyst containing encapsulated titanium oxide, comprising: The method includes a pulverization step of pulverizing the titanium oxide having oxygen vacancies introduced therein by a wet bead mill to which ethanol or methanol has been added, The diameter of the beads of the bead mill is 0.03 to 1 mm. Photocatalyst manufacturing method.

2. The diameter of the beads is 0.1 to 0.5 mm. The method for producing the photocatalyst according to claim 1.

3. Adding at least one of an oxide, hydroxide, and nitrate of Ni to the bead mill; The method for producing the photocatalyst according to claim 1.

4. Ti obtained by the grinding process ３＋ The method includes a step of supporting Pt on endohedral titanium oxide. The method for producing the photocatalyst according to claim 1.

5. Ni and Ti ３＋ It is a composite with encapsulated titanium oxide, and has a specific surface area of 100m ２ g －１ That's all. Photocatalyst.

6. Seawater contains organic compounds and Ti ３＋ and a photocatalyst containing encapsulated titanium oxide, and simultaneously irradiating the photocatalyst with ultraviolet light and visible light. Seawater decomposition method.

7. the organic compound is an alcohol, The amount of alcohol added to the seawater is 0.005 to 0.5 vol%. The seawater decomposition method according to claim 6.

8. The photocatalyst is manufactured by the manufacturing method of claim 1. The seawater decomposition method according to claim 6.

9. Ti ３＋ A method for producing a composite of encapsulated titanium oxide and another metal compound, comprising the steps of: The method includes a pulverization step of pulverizing the titanium oxide having oxygen vacancies introduced therein by a wet bead mill to which ethanol or methanol has been added, The diameter of the beads of the bead mill is 0.03 to 1 mm, In the pulverization step, at least one of a metal oxide, a metal hydroxide, and a metal nitrate is added to the bead mill as a raw material of the other metal compound. Method for manufacturing the composite.

10. The metal oxide, the metal hydroxide, and the metal nitrate contain at least one metal or element selected from Ni, Co, Cu, Fe, Ti, Mn, Ag, Mg, Ce, Zn, Nb, B, N, and Al. A method for producing the composite of claim 9.

11. The diameter of the beads is 0.1 to 0.5 mm. A method for producing the composite of claim 9.

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