JP6628271B1 - Photocatalyst particles, method for producing the same, material containing the particles, and product containing the material - Google Patents

Abstract

The present invention relates to photocatalyst particles containing titanium dioxide, phosphorus, silver, silver oxide, and silver phosphate, a method for producing the same, a material containing the photocatalyst particles, and a product containing the material.

Description

  The present invention relates to photocatalyst particles and a method for producing the same, a material containing the particles, and a product containing the material.

In recent years, the photocatalytic action of titanium dioxide (TiO ₂ ) has attracted much attention in the field of water and air purification (for example, see Non-Patent Documents 1 and 2). However, problems such as fast recombination of electron-hole pairs, no redox reaction (photocatalytic reaction) due to visible light, and extremely troublesome separation of titanium dioxide nanoparticles have caused the practical use of titanium dioxide. (See, for example, Non-Patent Documents 3 to 5). In particular, the conventional titanium dioxide-based photocatalyst shows a redox reaction when irradiated with ultraviolet light, but does not show a redox reaction when irradiated with visible light, and thus did not show sufficient photocatalytic activity with sunlight alone. Therefore, using a conventional photocatalyst has a problem that a light source for irradiating the photocatalyst with ultraviolet light is required.

  Patent Document 1 discloses a photocatalyst comprising titanium dioxide nanoparticles containing metallic silver and silver phosphate. The photocatalyst disclosed in this document exhibits photocatalytic activity by visible light.

JP-A-2006-59878

A. Fujishima et.al., Nature 238 (1972) 37-38. A. Mills, S.L. et al., Journal of Photochemistry and Photobiology A: Chemistry 108 (1997) 1-35. J. Wang et al., J. Colloid Interface Sci. 320 (1) (2008) 202-209. Chen Shifu et al., Journal of Hazardous Materials 155 (2008) 320-326. M.M.Viana et al., Applied Surface Science 265 (2013) 130-136.

  The photocatalyst disclosed in Patent Document 1 prepares a sol-gel solution by adding a solution containing silver nitrate, phosphoric acid, and nitric acid to an aqueous solution of tetrabutyl titanate and stirring the solution, drying the solution, and further firing. It is prepared by performing a binding treatment (hereinafter, the method for producing the photocatalyst is also referred to as a “sol-gel method”). The photocatalyst produced by the sol-gel method exhibits photocatalytic activity by visible light, and further improvement in catalytic activity is desired.

  Accordingly, an object of the present invention is to provide a catalyst that exhibits excellent photocatalytic activity by visible light.

  Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies and as a result, in the sol-gel method of Patent Document 1, performing a solvothermal reaction instead of a sintering process, thereby producing the sol-gel method by the method of Patent Document 1. The present inventors have found that higher photocatalytic activity can be obtained as compared with the photocatalyst particles thus obtained, and have reached the present invention.

One or more embodiments of the present invention include the following <1> to <14>.
<1>
Photocatalytic particles comprising titanium dioxide , silver, silver oxide and silver phosphate,
A specific surface area of 150 to 400 m ² / g,
Photocatalytic particles.
<2>
The ratio of titanium to all elements in the photocatalyst particles is 20 mol% to 30 mol%,
The ratio of oxygen to all elements in the photocatalyst particles is 60 mol% to 80 mol%,
The ratio of silver to all elements in the photocatalyst particles is 0.2 mol% to 0.9 mol%,
The ratio of phosphorus to all elements in the photocatalyst particles is 0.2 mol% to 0.6 mol%,
The photocatalyst particles according to <1>, wherein the total amount of titanium, oxygen, silver, and phosphorus is 100 mol%.
<3>
The photocatalyst particles according to <1> or <2>, wherein the crystal size is 2.0 to 4.0 nm.
<4>
Photocatalytic particles comprising titanium dioxide , silver, silver oxide and silver phosphate,
The ratio of titanium to all elements in the photocatalyst particles is 20 mol% to 30 mol%,
The ratio of oxygen to all elements in the photocatalyst particles is 60 mol% to 80 mol%,
The ratio of silver to all elements in the photocatalyst particles is 0.2 mol% to 0.9 mol%,
The ratio of phosphorus to all elements in the photocatalyst particles is 0.2 mol% to 0.6 mol%,
The total amount of titanium, oxygen, silver and phosphorus is 100 mol%,
Photocatalytic particles.
<5>
The photocatalyst particles according to <4>, wherein the crystal size is 2.0 to 4.0 nm.
<6>
Photocatalytic particles comprising titanium dioxide , silver, silver oxide and silver phosphate,
The crystal size is 2.0 to 4.0 nm;
Photocatalytic particles.
<7>
The photocatalyst particles according to any one of <1> to <6>, having a band gap energy of 2.4 eV to 3.2 eV.
<8>
The amount of silver leaking into water after stirring a 0.5 g / L aqueous suspension of the photocatalyst particles in a dark place at 37 ° C. for 12 hours is less than 0.100 mg / L. The photocatalyst particles according to any one of <7>.
<9>
The method for producing photocatalyst particles according to any one of <1> to <8>, comprising the following steps:
(1) An alkyl titanate represented by Ti (OR) ₄ (where R = C _n H _{2n + 1} and n = 2 to 8), silver nitrate, silver phosphate and nitric acid are mixed in a solvent And (2) performing a solvothermal reaction on the sol-gel solution prepared in the step (1).
<10>
The method according to <9>, wherein the solvent in step (1) is ethanol.
<11>
The method according to <9> or <10>, wherein the solvothermal reaction is performed at more than 100 ° C and less than 140 ° C for more than 1.0 hour and less than 4.0 hours.
<12>
The method according to any one of <9> to <11>, wherein the solvothermal reaction is performed at 110 ° C to 130 ° C for 1.5 to 3.5 hours.
<13>
A material comprising the photocatalyst particles according to any one of <1> to <8>.
<14>
A product comprising the material according to <13>.

  The photocatalyst particles of the present invention exhibit excellent photocatalytic activity by visible light.

FIG. 1 shows the decomposition rate of rhodamine B by a photocatalytic reaction using the photocatalyst produced in Example 1. FIG. 2 shows the decomposition rate of rhodamine B by a photocatalytic reaction using the photocatalyst produced in Example 1. FIG. 3 shows the amount of hydrogen generated by the water splitting reaction using the photocatalyst produced in Example 1. FIG. 4 shows the amount of hydrogen generated by the water splitting reaction using the photocatalyst produced in Example 1. FIG. 5 shows an XRD pattern of the photocatalyst manufactured in Example 1. FIG. 6 shows an XRD pattern of the photocatalyst manufactured in Example 1. FIG. 7 shows a photograph of the appearance of the photocatalyst produced in Example 1. FIG. 8 shows a photograph of the appearance of the photocatalyst produced in Example 1. FIG. 9 shows a UV-vis spectrum of the photocatalyst produced in Example 1. FIG. 10 shows a UV-vis spectrum of the photocatalyst produced in Example 1. FIG. 11 shows a PL spectrum of the photocatalyst produced in Example 1. FIG. 12 shows a PL spectrum of the photocatalyst produced in Example 1. FIG. 13 shows an HRTEM image of photocatalyst sample 7 obtained by performing a solvothermal reaction at a temperature of 120 ° C. for 3.0 hours in Example 1. FIG. 14 shows an XPS spectrum of Sample 7. FIG. 15 shows the decomposition rate of rhodamine B by a photocatalytic reaction using Sample 7 or Sample 12 produced in Comparative Example 1. FIG. 16 shows the decomposition rate of methyl orange by the photocatalytic reaction using Sample 7 or 12. FIG. 17 shows the XRD patterns of Samples 7 and 12. FIG. 18 is an SEM image of Sample 7. FIG. 19 is an SEM image of Sample 12. FIG. 20 shows photographs of the appearance of the photocatalysts of Samples 7 and 12. FIG. 21 shows the UV-vis spectra of Samples 7 and 12. FIG. 22 shows the amount of hydrogen generated by the water splitting reaction using Samples 7 and 12. FIG. 23 shows a comparison result of band gap energies of Samples 7 and 12. FIG. 4 shows the results of evaluating antibacterial activity against E. coli. FIG. 4 shows the results of evaluating antibacterial activity against E. coli. FIG. 26 shows the evaluation results of the antibacterial activity of Sample 7 on Enterococcus faecalis. FIG. 27 is a schematic view of the device used in Example 14. FIG. 28 shows the results of evaluating the acetaldehyde decomposition activity when Sample 7 was used. FIG. 29 shows the evaluation results of the acetaldehyde decomposition activity in the case of using the composite material produced in Example 13 (supporting 10% by weight of zeolite with respect to the photocatalyst particles).

<< Photocatalyst particles >>
The photocatalyst particles of the present invention include or consist of titanium dioxide , silver , silver oxide and silver phosphate.

  The photocatalyst particles of the present invention exhibit excellent photocatalytic activity by visible light. In this specification, “visible light” means light having a wavelength of 380 nm to 780 nm. When the photocatalyst particles of the present invention are irradiated with visible light having energy equal to or greater than the band gap, electrons in the valence band are excited into the conduction band, electrons are generated in the conduction band, and holes are generated in the valence band. The electron transfer between the electrons and holes and the substance adsorbed on the surface of the photocatalyst particles causes the adsorbed substance to be oxidized or reduced and decomposed. The function of the photocatalyst particles of the present invention is referred to herein as “photocatalytic activity”. Further, as a result of the decomposition reaction of the adsorbed substance, the photocatalyst particles of the present invention can have deodorizing activity, antifouling activity, antibacterial activity, and the like. These activities are also included in the "photocatalytic activity" herein.

In one embodiment, the specific surface area of the photocatalyst particles of the present invention is 150 to 400 m ² / g. Preferably, the lower limit of the specific surface area is 160 m ² / g, 170 m ² / g, 180 m ² / g, 190 m ² / g, 200 m ² / g, 210 m ² / g, 220 m ² / g, 230 m ² / g, 240 m ² / g or 250 m ² / g, 260 m ² / g, 270 m ² / g, 280 m ² / g, the upper limit of which is 390 m ² / g, 380 m ² / g, 370 m ² / g, 360 m ² / g, It is 350 m ² / g, 340 m ² / g, 330 m ² / g, 320 m ² / g or 310 m ² / g. More preferably, the specific surface area of the photocatalyst particles of the present invention is a 150~310m ² / g or 200 to 400 m ² / g, more preferably from 250~400m ² / g. The photocatalyst particles of the present invention having a specific surface area within the above numerical range exhibit good photocatalytic activity. Generally, the larger the specific surface area, the higher the photocatalytic activity.

  In this specification, the “specific surface area” refers to a specific surface area (BET specific surface area) measured by a BET method using nitrogen gas.

In one aspect,
The ratio of titanium to all elements of the photocatalyst particles of the present invention is 20 mol% to 30 mol%;
The ratio of oxygen to all elements of the photocatalyst particles of the present invention is from 60 mol% to 80 mol%;
The ratio of silver to all elements of the photocatalyst particles of the present invention is 0.2 mol% to 0.9 mol%, preferably 0.2 mol% to 0.8 mol%, 0.2 mol% to 0.7 mol%, 0.2 mol%. % To 0.6 mol%, 0.3 mol% to 0.8 mol%, 0.3 mol% to 0.7 mol% or 0.3 mol% to 0.6 mol%;
The ratio of phosphorus to all elements of the photocatalyst particles of the present invention is 0.2 mol% to 0.6 mol%, preferably 0.2 mol% to 0.5 mol%, 0.3 mol% to 0.6 mol% or 0.3 mol%. % To 0.5 mol%;
The total amount of titanium, oxygen, silver and phosphorus in the photocatalyst particles of the present invention is 100 mol%
It is. The photocatalyst particles of the present invention having an elemental composition in the above numerical range exhibit good photocatalytic activity.

  In one embodiment, the photocatalyst particles of the present invention have a crystal size of 2.0 to 4.0 nm. Preferably, the lower limit of the crystal size of the photocatalyst particles of the present invention is 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm or 2.5 nm, and the upper limit is 3.9 nm, 3.8 nm, 3.7 nm. , 3.6 nm, 3.5 nm, 3.4 nm, or 3.3 nm. The photocatalyst particles of the present invention having a crystal size in the above numerical range show good photocatalytic activity.

In the present invention, the “crystal size” of the photocatalyst particles is a value calculated from the X-ray diffraction (XRD) pattern of the photocatalyst particles by the following Scherrer equation.
[Where,
τ is the crystal size,
K is a shape factor,
λ is the X-ray wavelength,
β is the full width at half maximum of the peak (FWHM, but in radians),
θ is the Bragg angle. ]
The crystal size of the photocatalyst particles of the present invention is a value calculated from the peak at 2θ = 25.28 ° ± 0.2 °, where K = 0.9.

The band gap energy of the photocatalyst particles of the present invention is preferably from 2.4 eV to 3.2 eV, more preferably the lower limit is 2.5 eV, 2.6 eV, 2.7 eV or 2.8 eV, and The upper limit is 3.1 eV or 3.0 eV. More preferably, the bandgap energy of the photocatalyst particles of the present invention is from 2.6 eV to 3.1 eV or from 2.7 eV to 3.2 eV. In the present invention, the band gap energy can be calculated using the following formula according to the measurement result of the ultraviolet-visible absorption spectrum (UV-vis spectrum).
[Where,
h Planck's constant,
c is the speed of light,
λ is the wavelength,
n = 1,
α is the absorbance,
K is a constant,
Eg is the band gap energy. ]

  The photocatalyst particles of the present invention preferably have a leakage amount of silver of 0.100 mg after stirring a 0.5 g / L aqueous suspension of the photocatalyst particles in a dark place at 37 ° C. for 12 hours. / L, more preferably 0.095 mg / L or less, and still more preferably 0.090 mg / L or less.

<< Production method of photocatalyst particles >>
The method for producing photocatalyst particles of the present invention includes the following steps:
(1) an alkyl titanate represented by Ti (OR) ₄ (where R = C _n H _{2n + 1} , n = 2 to 8, and preferably n = 2 to 6), silver nitrate, Preparing a sol-gel solution by mixing silver phosphate and nitric acid in a solvent; and (2) performing a solvothermal reaction on the sol-gel solution prepared in the step (1).

  In the step (1), the alkyl titanate used as a titanium dioxide source is not particularly limited as long as a sol-gel solution can be prepared, and examples thereof include tetrapropyl titanate, tetraisopropyl titanate, and tetrabutyl titanate. Preferred is tetrabutyl titanate.

  The solvent used in the step (1) is not particularly limited as long as a sol-gel solution can be prepared, and includes, for example, water, alcohol (eg, methanol, ethanol, propanol, isopropanol) or a mixed solvent thereof. Ethanol is preferred. It is preferable to use 2000 to 3000 mL of the solvent with respect to 1 mol of the alkyl titanate used in the step (1).

  In step (1), silver nitrate and silver phosphate are used as dopants, and nitric acid is used as a dispersant.

In step (1),
The molar ratio of silver nitrate to alkyl titanate is preferably from 1: 0.025 to 1: 0.2, more preferably from 0.05 to 0.1;
The molar ratio of silver phosphate to alkyl titanate is preferably from 1: 0.008 to 1: 0.067, more preferably from 0.017 to 0.033;
The molar ratio of nitric acid to alkyl titanate is preferably from 1: 0.1 to 1: 1 and more preferably from 0.4 to 0.7.

  Step (1) is preferably performed at 0 ° C to 60 ° C, more preferably at 20 ° C to 40 ° C.

  As used herein, “solvothermal reaction” refers to a reaction performed using a high-temperature and high-pressure solvent. The solvothermal reaction is performed in a pressure vessel such as an autoclave. When the solvent is water, it is called "hydrothermal reaction".

  By using the solvothermal reaction, it is possible to suppress the decomposition of silver oxide and silver phosphate to generate an excessive amount of metallic silver. Further, the structure of the photocatalyst can be shifted to an appropriate state.

  The pressure in the reaction vessel in the solvothermal reaction in the step (2) is preferably 0.10 to 1.00 Mpa, more preferably 0.40 to 0.60 Mpa.

  The temperature in the reaction vessel in the solvothermal reaction in the step (2) is preferably more than 100 ° C. and less than 140 ° C. from the viewpoint of obtaining a photocatalyst having good activity and suppressing the leakage of silver during water washing. is there. More preferably, it is more than 100 ° C. and 130 ° C. or less, 110 ° C. or more and less than 140 ° C., or 110 ° C. or more and 130 ° C. or less.

  The reaction time of the solvothermal reaction in the step (2) is preferably more than 1.0 hour and 4.0 hours from the viewpoint of obtaining a photocatalyst having good activity and suppressing the leakage of silver during washing with water. Is less than. More preferably, it is more than 1.0 hour and 3.5 hours or less, 1.5 hours or more and less than 4 hours, or 1.5 hours or more and 3.5 hours or less, and still more preferably 1.5 hours or more and 3.5 hours or less. Less than an hour.

  Preferably, the method further includes a step of removing the solvent after the step (2) and drying the photocatalyst.

<<< Materials containing photocatalyst particles and products containing the materials >>
One embodiment of the present invention relates to a material including the photocatalyst particles of the present invention. The material is not particularly limited, and examples thereof include materials formed of various materials such as metal, tile, enamel, cement, concrete, glass, plastic, fiber, wood, paper, leather, and ceramic. As the shape, various shapes such as a plate, a corrugated plate, a honeycomb, a sphere, and a curved surface can be used. In one embodiment, the photocatalyst particles of the present invention are immobilized on a material surface. The immobilization method is not particularly limited, and a method known to those skilled in the art can be applied. For example, the method can be carried out by applying or spraying a coating liquid containing a photocatalyst and a binder on the surface of the base material, followed by drying and, if necessary, heating. As the binder, for example, an inorganic resin and an organic resin can be used, and a binder that is not easily decomposed by a photocatalytic reaction, such as a binder such as cement, concrete, gypsum, a silicate compound, silica, a silicon compound, a silicone resin, or a fluororesin is used. preferable. In another embodiment, the photocatalyst particles of the present invention may be kneaded into a substrate and used. By kneading, the photocatalyst particles of the present invention can be stably held on the substrate, and the effect of the photocatalyst particles of the present invention can be maintained for a longer period.

One embodiment of a material comprising photocatalyst particles is a composite material comprising the photocatalyst particles of the present invention and a carrier, wherein the photocatalyst particles are supported on a carrier. The carrier can be used, for example, to make the photocatalyst particles have a size suitable for their practical use. By using a carrier, for example, it is possible to increase the light absorption efficiency and to improve the activity of the photocatalyst particles. In particular, when zeolite is used as the carrier, the adsorptivity of the composite material is increased, and the reaction activity can be improved. Although the carrier used in such a composite material is not particularly limited, for example, SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ , Fe ₂ O ₃ , B ₂ O ₃ , CaO, ZnO, BaO, ThO ₂ and mixtures thereof, such as silica - alumina, zeolite, ferrite or the like can be mentioned. Further, glass, ceramic, plastic, and the like can also be used as the carrier.
In the composite material, the amount of the photocatalyst particles of the present invention carried on the carrier is not particularly limited, and the lower limit is, for example, 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 10% by weight. , 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt% Wt%, 80 wt%, 85 wt%, 90 wt% or 95 wt%, with the upper limit being 99 wt%, 95 wt%, 90 wt%, 85 wt%, 80 wt%, 75 wt%, 70 wt%. Wt%, 65 wt%, 60 wt%, 55 wt%, 50 wt%, 45 wt%, 40 wt%, 35 wt%, 30 wt%, 25 wt%, 20 wt%, 15 wt% or 10 wt% It is. Preferably, the loading of the photocatalyst particles of the present invention on the carrier is 1 to 99% by weight, 2 to 50% by weight, 2 to 25% by weight, and 3 to 10% by weight.
The method for producing the composite material can be performed according to any known method.

  For example, the material containing the photocatalyst particles of the present invention and the carrier may be used during the step (1), between the steps (1) and (2), during the step (3), Alternatively, it can be carried out by adding and dropping the carrier at least at one point after the step (3). Preferably, a carrier is added during step (1) or between step (1) and step (2). The method for adding the carrier is not particularly limited, and examples thereof include a method of adding the entire amount at once, and a method of adding the carrier in plural times. The amounts of the reagents used and the reaction conditions are the same as in the above-described method for producing the photocatalyst particles of the present invention. The amount of the carrier to be added is the same as the amount of the photocatalyst particles of the present invention carried on the carrier described above. For example, 1 to 99% by weight, 2 to 50% by weight, 25% by weight, or 3 to 10% by weight.

  One aspect of the present invention pertains to an article of manufacture comprising a material comprising the photocatalytic particles of the present invention. The products are not particularly limited, but include, for example, toilets, wash basins, mirrors, bathrooms (walls, ceilings, floors, etc.), building materials (indoor walls, ceiling materials, floors, exterior walls), interior goods (curtains, carpets, tables, chairs) , Sofas, shelves, beds, bedding, etc.), glass, sashes, handrails, doors, knobs, clothes, household appliances, stationery (eg, book covers), abacus, musical instruments, sports equipment (eg, kendo equipment), toys, etc. Can be

  All documents mentioned herein are incorporated herein by reference in their entirety.

  The embodiments of the present invention described below are for illustrative purposes only, and do not limit the technical scope of the present invention. The technical scope of the present invention is limited only by the claims. Modifications of the present invention, for example, additions, deletions, and substitutions of constituent elements of the present invention, can be made on condition that they do not depart from the gist of the present invention.

<Reagent>
The reagents used in the present Examples and Comparative Examples are all manufactured by Wako Pure Chemical Industries.

Example 1
Production of Photocatalyst Particles Using Solvothermal Reaction Tetrabutyl titanate (6 mL) was dissolved in ethanol (46 mL) and stirred at 25 to 40 ° C. for 30 minutes to prepare solution A. Further, a solution B was prepared by dissolving silver nitrate (0.1418 g) and silver phosphate (0.1165 g) in 1 mol / l nitric acid (11 ml). The solution B was added dropwise to the solution A while stirring the solution A at 25 to 40 ° C. Thereafter, the mixture was stirred at 25 to 40 ° C. for about 19 hours. Thereafter, the solution was transferred to a solvothermal reaction vessel (product name: hydrothermal reactor; manufactured by Shanghai Yikai Instrument Equipment Co., Ltd.), and heated in an oven at 100, 110, 120, 130, or 140 ° C for 1 hour. Heat for 2, 3 or 4 hours. The pressure in the reaction vessel during the solvothermal reaction was 0.31 to 0.90 MPa. The heat treatment was performed without stirring the reaction solution in the container. After the heat treatment, the supernatant was removed to obtain a colloidal substance. The colloidal substance was transferred to a 50 ml centrifuge tube, an appropriate amount of 70% ethanol was added, and the mixture was centrifuged at 8900 / min for 5 minutes, and the supernatant was removed. This operation was repeated three times. Thereafter, the solid was dried at 60 ° C. for 12 hours to obtain a solid. The solid was pulverized to produce a photocatalyst particle sample. The manufactured sample and its manufacturing conditions are shown below.

Comparative Example 1
Production of Photocatalyst Particles by Sol-Gel Reaction Photocatalyst particles were produced according to the method described in Patent Document 1. Tetrabutyl titanate (6 mL) was dissolved in ethanol (46 mL) and stirred at 25 to 40 ° C. for 30 minutes to prepare solution A. Further, a solution B was prepared by dissolving silver nitrate (0.1418 g) and silver phosphate (0.1165 g) in 1 mol / l nitric acid (11 ml). The solution B was added dropwise to the solution A while stirring the solution A at 25 to 40 ° C. Thereafter, the mixture was stirred at 25 to 40 ° C. for about 19 hours. Thereafter, the solution was transferred to a crucible (product name: evaporating dish, manufactured by As One Corporation) and dried at 105 ° C. for 18 hours. Then, it was sintered at 400 ° C. for 2 hours in a muffle furnace (product name: Fine tabletop electric furnace, manufactured by Tokyo Glass Instruments Co., Ltd.) at 400 ° C. to obtain a solid. The solid was polished to produce a photocatalyst particle sample (referred to as “sample 12”).

Example 2
Evaluation of Decomposition Rate of Rhodamine B (RhB) A photocatalyst particle sample (each of which was prepared in Example 1) was placed in a transparent container (product name: 100 ml beaker, manufactured by HARIO Corporation) containing a 2 mg / L aqueous solution of Rhodamine B (50 mL). 0.05 g) was added. Simulated sunlight (XC-100, SERIC., Ltd., irradiation intensity 510 W / m ² ) was irradiated from outside the container while stirring the mixture. After 30 minutes, the photocatalyst powder was quickly separated from the mixture by centrifugation (10,000 rpm), and the absorbance of the obtained clarified solution was analyzed by a spectrophotometer (UV-1600, Shimadzu Corporation). The absorbance of the Rhodamine B solution was measured at a wavelength of 554 nm corresponding to the maximum absorption wavelength of Rhodamine B.

  FIGS. 1 and 2 show the decomposition rate of rhodamine B when each sample was used. It was found that the activity of the photocatalyst was significantly affected by the temperature and time of the solvothermal reaction.

  FIG. 1 shows the evaluation results of the catalytic activity depending on the temperature of the solvothermal reaction. The reaction time is 3.0 hours in each case. When sample 7 (solvothermal reaction temperature: 120 ° C.) was used, the decomposition rate of rhodamine B was the highest and was 100%. When Sample 1 (reaction temperature 100 ° C.), Sample 2 (reaction temperature 110 ° C.), Sample 10 (reaction temperature 130 ° C.), and Sample 11 (reaction temperature 140 ° C.) were used, the decomposition rate of rhodamine B was 53. 7%, 56.1%, 72.8% and 46.4%.

  FIG. 2 shows the evaluation results of the catalytic activity depending on the time of the solvothermal reaction. The reaction temperature is 120 ° C. in all cases. When sample 7 (reaction time: 3.0 hours) was used, the decomposition rate of rhodamine B was the highest and was 100%. Sample 3 (reaction time 1.0 hour), Sample 4 (reaction time 1.5 hours), Sample 5 (reaction time 2.0 hours), Sample 6 (reaction time 2.5 hours), Sample 8 (reaction time 3 .5 hours) and Sample 9 (reaction time 4.0 hours), the decomposition rates of rhodamine B were 79.4%, 84.2%, 94.7%, 95.7% and 95.7%, respectively. 2% and 31.7%.

Example 3
Evaluation of Water Splitting Reaction In a transparent reaction vessel (product name: screw mouth bottle, manufactured by Shibata Scientific Co., Ltd.) having a lid with a vent for collecting gas in the vessel, a photocatalyst sample (0.15 g) was used. A 5% aqueous methanol solution (150 mL) was mixed. Thereafter, pseudo sunlight (XC-100, SERIC., Ltd., irradiation intensity 510 W / m ² ) was irradiated from outside the reaction vessel for 3 hours. After 30 minutes, the gas in the container is collected, and the hydrogen concentration in the gas is measured by gas chromatography (GC-8A, Shimadzu Corporation) equipped with a thermal conductivity detector (100 ° C) and a Polapack Q column (83 ° C). did. The results are shown in FIGS.

  FIG. 3 shows the evaluation results of the catalytic activity depending on the temperature of the solvothermal reaction. The reaction time of each of the solvothermal reactions is 3.0 hours. When the sample 7 (solvothermal reaction temperature: 120 ° C.) was used, the highest amount of hydrogen was produced (132.6 μmol / L). The amounts of hydrogen generated when Sample 1 (solvothermal reaction temperature: 100 ° C.) and Sample 11 (solvothermal reaction temperature: 140 ° C.) were used were 26.7 μmol / L and 33.3 μmol / L, respectively.

  FIG. 4 shows the results of evaluating the catalytic activity depending on the reaction time of the solvothermal reaction. The reaction temperature of each of the solvothermal reactions is 120 ° C. When the sample 7 (solvothermal reaction time: 3.0 hours) was used, the highest amount of hydrogen was produced (132.6 μmol / L). The amount of hydrogen generated when using sample 3 (solvothermal reaction time 1.0 hour), sample 5 (solvothermal reaction time 2.0 hours), and sample 9 (solvothermal reaction time 4.0 hours) was 18. They were 3 μmol / L, 80.6 μmol / L, and 40.9 μmol / L.

Example 4
Evaluation of XRD pattern The X-ray diffraction (XRD) pattern of the sample manufactured in Example 1 was evaluated. The XRD pattern was measured with an X-ray diffractometer (Ultima III Rint-2000 X-ray diffractometer, Rigaku) using Cu-Kα rays (λ = 1.54178 °). The results are shown in FIGS. In each sample, a peak specific to anatase type titanium dioxide was observed. Particularly, in Sample 7 (solvothermal reaction temperature: 120 ° C., solvothermal reaction time: 3.0 hours), a peak specific to anatase-type titanium dioxide was strongly confirmed. Anatase crystal structures are known to have higher photocatalytic activity than rutile-type crystal structures.

In the XRD patterns of Sample 9 (solvothermal reaction temperature 120 ° C., reaction time 4.0 hours) and Sample 11 (solvothermal reaction temperature 140 ° C., reaction time 3.0 hours), peaks corresponding to silver metal were observed. (38.1 ^° , 44.0 ^° , 64.6 ^° and 77.2 ^° ). This is because silver oxide and silver phosphate were decomposed by applying high temperature and high pressure conditions. Metallic silver provides more recombination sites for photogenerated electrons and holes, thus inhibiting the generation of active free radicals.

Example 5
Evaluation of UV-vis spectrum The appearance of the photocatalyst produced in Example 1 is shown in FIGS. Sample 9 (solvothermal reaction temperature 120 ° C, reaction time 4.0 hours) and Sample 11 (solvothermal reaction temperature 140 ° C, reaction time 3.0 hours) were black due to the metallic silver generated during the solvothermal reaction. Met. On the other hand, Samples 1, 3, 5, and 7 were white. In addition, the UV-vis diffuse reflectance spectrum of these samples was measured in the range of 200 to 800 nm using a UV-vis-NIR spectrophotometer (UV-3100PC Scan UV-vis-NIR spectrophotometer, Shimadzu Corporation). did. The results are shown in FIGS.

  Samples 9 and 11 had strong absorption due to metallic silver nanoparticles in the visible light region around 400 to 780 nm. Sample 7 showed higher absorption than Samples 1, 3, and 5. This suggests that Sample 7 obtains more energy by light irradiation than Samples 1, 3, and 5, and exhibits higher activity. The band gap energies of Samples 1, 3, 5, 7, 9, and 11 were 3.09 eV, 2.94 eV, 2.92 eV, 2.91 eV, 2.58 eV, and 2.64 eV, respectively.

Example 6
Evaluation of Specific Surface Area and Crystal Size The specific surface area of the photocatalyst particles produced in Example 1 was measured using a specific surface area / pore distribution measuring device SA-3100 (manufactured by BECKMAN COULTER CORPORATION). The crystal size of the photocatalyst particles was calculated from an XRD pattern measured by an X-ray diffractometer (Ultima III Rint-2000 X-ray diffractometer, Rigaku) using Cu-Kα rays (λ = 1.54178 °). The results are shown in the table below. The larger the specific surface area, the more reactive sites on the photocatalytic surface. In addition, the smaller the crystal size, the better the crystal structure and the energy conversion ability, and as a result, the higher the photocatalytic activity.

Example 7
Evaluation of photoluminescence (PL) spectrum The photoluminescence (PL) spectrum of the photocatalyst particles produced in Example 1 at an excitation wavelength of 325 nm was measured using a fluorescence spectrophotometer (FP8500, JASCO). The results are shown in FIGS. The photoluminescence intensity in FIG. 11 was in the order of Sample 7 <Sample 11 <Sample 1. Further, the photoluminescence intensities in FIG. 12 were in the order of Sample 7 <Sample 5 <Sample 9 <Sample 3. Lower photoluminescence intensities indicate lower electron-hole recombination rates and higher photocatalytic activity.

Example 8
Analysis of Constituents in Photocatalyst Particles Sample 7 was observed using a high-resolution transmission electron microscope image (HRTEM) (JEM-2100F field emission transmission electron microscope, manufactured by JEOL Ltd.). FIG. 13 shows the results. In Sample 7, silver, silver phosphate, and silver oxide were supported on the lattice surface of titanium dioxide.

The X-ray photoelectron spectroscopy (XPS) of the sample 7 was measured using an X-ray photoelectron spectroscopy analyzer (X-ray photoelectron spectroscopy system (ARXPS), manufactured by Thermo Fisher Scientific Inc.). FIG. 14 shows the results. The presence of silver , silver oxide and silver phosphate in Sample 7 was confirmed.

Example 9
Comparison between Sample 7 and Sample 12 (1) Decomposition rate of Rhodamine B Using Sample 12 produced by the sol-gel method, the decomposition rate of Rhodamine B was evaluated in the same manner as described in Example 2. . The results are shown in FIG. Sample 7 produced using the solvothermal reaction decomposed rhodamine B by 100% in 30 minutes, whereas Sample 12 produced by the sol-gel method degraded rhodamine B by 100%. It took time.

(2) Decomposition rate of methyl orange Using Samples 7 and 12, the decomposition rate of methyl orange was evaluated. Specifically, evaluation was performed in the same manner as in Example 2 except that rhodamine B was changed to 50 mL of 2 mg / L methyl orange. FIG. 16 shows the results. Sample 7 produced using the solvothermal reaction decomposed methyl orange by 95.1% in 30 minutes, while sample 12 produced by the sol-gel method produced methyl orange in 13. minutes. It was only 6% degraded.

(3) XRD Pattern The XRD pattern of Sample 12 was evaluated in the same manner as in Example 4. FIG. 17 shows the result of comparison between Sample 7 and Sample 12. The peak peculiar to the anatase type titanium dioxide was stronger and clearly observed in the sample 7 than in the sample 12.

(4) SEM image The morphology of samples 7 and 12 was observed using a scanning electron microscope (SEM) (Hitachi FE-SEM S-4800 EDX). The results are shown in FIGS.

(5) Specific Surface Area and Crystal Size The specific surface area and crystal size of Sample 12 were evaluated in the same manner as in Example 6. The results of comparison between Sample 7 and Sample 12 are shown below.

(6) Element distribution Energy dispersive X-ray analysis (EDS) was performed using an energy dispersive X-ray analyzer (Ultra High Resolution SEM (S-4800), manufactured by Hitachi Kyowa Engineering Co., Ltd.), and samples 7 and 12 were analyzed. Element distribution was measured. The results are shown below. A great difference was confirmed between the silver content and the phosphorus content.

(7) UV-vis spectrum and band gap energy FIG. 20 shows the appearance of Samples 7 and 12. Sample 12 was gray due to the effect of metallic silver. On the other hand, Sample 7 was white. Further, the UV-vis spectrum was measured in the same manner as in Example 5 using the sample 12 manufactured in Comparative Example 1. FIG. 21 shows the result of comparison between Sample 7 and Sample 12. Sample 12 had strong absorption due to silver nanoparticles in the visible light region around 400 to 800 nm. According to the result of the UV-vis spectrum, the band gap energy of Sample 12 was calculated to be 2.29 eV. This was a lower value than the band gap energy of Sample 7 (2.91 eV).

(8) Water Splitting Reaction Using Sample 12 produced in Comparative Example 1, a water splitting reaction was performed in the same manner as in the method described in Example 3. When a comparison was made between the case where sample 7 was used and the case where sample 12 was used, the oxygen generation amounts of both were almost the same (sample 7: 96.0 μmol / L; sample 12: 94.7 μmol / L). However, the amount of hydrogen produced varied greatly. The results are shown in FIG. When sample 7 was used, hydrogen was generated at 132.0 μmol / L. On the other hand, when the sample 7 was used, only 16.4 μmol / L of hydrogen was generated.

The amount of hydrogen generated when a water splitting reaction is performed using a known photocatalyst is shown below. The hydrogen generation amount of Sample 7 is extremely high as compared with a known photocatalyst.

FIG. 23 shows comparison results of band gap energies of Samples 7 and 12. Decomposition of water occurs only when the valence band (VB) of the photocatalyst is higher than 1.2 eV and the conduction band (CB) is lower than 0 eV. The fact that the amounts of generated oxygen are equal indicates that the valence bands of Samples 7 and 12 are close to each other. However, since the band gap energy of the sample 12 is very small, the end (0.51 eV) of the conduction band of the sample 12 is lower than the hydrogen generation potential of 0 eV. The photogenerated electrons generated in sample 12 cannot participate in the half-reaction to reduce H ⁺ to generate H ₂ because of its insufficient potential. On the other hand, the end (-0.11 eV) of the conduction band of the sample 7 is at a position higher than the hydrogen generation potential of 0 eV. Therefore, the photogenerated electrons generated in Sample 7 can reduce H ⁺ to generate H ₂ .

(9) Evaluation of antibacterial activity. coli (Gram-positive bacteria) was evaluated for viability. In a transparent container (product name: 25 ml glass bottle, manufactured by HARIO Corporation), water (20 mL), E.C. coli (initial concentration when testing sample 7: about 10 ⁸ cfu / mL; initial concentration when testing sample 12: about 10 ⁷ cfu / mL) and a photocatalyst sample (0.5 g / L). While stirring the reaction mixture at 25 ° C., an LED lamp (product name: LED lamp NSSW-064, manufactured by Nichia Corporation, 465-470 nm, irradiation intensity 750 W / m ² ) was irradiated from the outside of the container. At predetermined time intervals, 1 mL of the reaction mixture was collected and rapidly diluted. Thereafter, 1 mL of the diluted sample was spread evenly on a nutrient agar medium and incubated at 37 ° C. for 24 hours. Colonies on the plate were counted and the number of viable cells in each sample was determined. The results are shown in FIGS. In all cases, excellent antibacterial activity was exhibited in the presence of light.

(10) Water washing test To a container (product name: centrifuge tube (50 ml), manufactured by As One Co., Ltd.), add sample 12 and distilled water at a concentration of 0.2 g / L, and place at 24 ° C. Shake time. Thereafter, the supernatant was recovered, and the amount of the leaked silver was measured by an ICP emission spectrometer (product name: SPS3520UV-DD, manufactured by Hitachi High-Tech Science Corporation). Thereafter, distilled water was added to the container again, and the above washing cycle of shaking and collecting the supernatant was repeated three more times. The results are shown below. Even after washing four times, 1.2 mg / L of silver was leaked. The amount exceeded the water quality standard defined by WHO (<0.1 mg / L). Further, the antibacterial activity in the above (9) may be caused by silver ions leaked from the catalyst in water.

Sample 7 and distilled water were added to a container (product name: 25 ml glass bottle, manufactured by HARIO Co., Ltd.) at a concentration of 0.5 g / L, and the mixture was shaken at 37 ° C. under light-shielding conditions to wash the sample 7 with water. Was done. After 10 minutes, 20 minutes, 30 minutes, 40 minutes or 12 hours from the start of washing, the supernatant was collected, and the amount of leaked silver was measured using an ICP emission spectrometer (product name: SPS3520UV-DD, manufactured by Hitachi High-Tech Science Corporation). ). The results are shown below.

Example 10
Evaluation of antibacterial activity against Gram-negative bacteria The viability of Enterococcus faecalis, which is a genus Enterococcus genus of Gram-negative bacteria, when a photocatalytic reaction was performed using Sample 7 was evaluated. Water (20 mL), Enterococcus faecalis (initial concentration: about 10 ⁸ cfu / mL), and a photocatalyst sample (0.5 g / L) were added to a transparent container (product name: 25 ml glass bottle, manufactured by HARIO Corporation). While stirring the reaction mixture at 25 ° C., an LED lamp (product name: LED lamp NSSW-064, manufactured by Nichia Corporation, 465-470 nm, irradiation intensity 750 W / m ² ) was irradiated from the outside of the container. At predetermined time intervals, 1 mL of the reaction mixture was collected and rapidly diluted. Thereafter, 1 mL of the diluted sample was spread evenly on Enterococcosel Agar (manufactured by Becton Tickinson Japan Co., Ltd.) and incubated at 35 ° C. for 24 ± 2 hours. Colonies on the plate were counted and the number of viable cells in each sample was determined. The results are shown in FIG. In all cases, excellent antibacterial activity was exhibited in the presence of light.

Example 11
Element distribution measurement The element distributions of samples 1 to 6, 8, 9, and 11 manufactured in Example 1 were measured in the same manner as in Example 9 (6). The results are shown below.

Example 12
Measurement of Bandgap Energy The bandgap energies of the samples 1 to 6 and 8 to 11 manufactured in Example 1 were calculated in the same manner as in Example 9 (7). The results are shown below.

Example 13
Production of Composite Material of Photocatalyst Particles and Zeolite Tetrabutyl titanate (6 mL) was dissolved in ethanol (46 mL) and stirred at 25 to 40 ° C. for 30 minutes to prepare solution A. Further, a solution B was prepared by dissolving silver nitrate (0.1418 g) and silver phosphate (0.1165 g) in 1 mol / l nitric acid (11 ml). The solution A, the solution B and the synthetic zeolite (A-3, powder, 75 μm) were mixed and stirred at 25 to 40 ° C. for about 19 hours. The synthetic zeolite was 0.0736 g (5% by weight based on the generated photocatalyst particles), 0.1556 g (10% by weight based on the generated photocatalyst particles), or 0.4667 g (25% based on the generated photocatalyst particles). %) Used. Thereafter, the obtained mixture was transferred to a solvothermal reaction vessel (product name: hydrothermal reactor; manufactured by Shanghai Yikai Instrument Equipment Co., Ltd.) and heated in an oven at 120 ° C for 3 hours. The pressure in the reaction vessel during the solvothermal reaction was 0.31 to 0.90 MPa. The heat treatment was performed without stirring the reaction solution in the container. After the heat treatment, the supernatant was removed to obtain a colloidal substance. The colloidal substance was transferred to a 50 ml centrifuge tube, an appropriate amount of 70% ethanol was added, and the mixture was centrifuged at 8900 / min for 5 minutes, and the supernatant was removed. This operation was repeated three times. Thereafter, the solid was dried at 60 ° C. for 12 hours to obtain a solid. The solid was pulverized to produce a composite material containing 5%, 10%, or 25% by weight of zeolite based on the photocatalyst particles.

Example 14
Evaluation of Decomposition of Acetaldehyde in Gas Phase Using the apparatus shown in FIG. 27, using the composite material of photocatalyst particles and zeolite produced in Example 13 (supporting 10% by weight of zeolite with respect to the photocatalyst particles). Tested. A visible light lamp was used as a light source.
A photocatalyst dispersion liquid (0.4 g / ultrapure water 1 mL) was spread on a glass plate (50 mm × 100 ml) and dried at 60 ° C. The obtained glass plate was placed in an apparatus, and acetaldehyde (initial concentration: 1.5 ppm) was injected into the apparatus at a flow rate of 1.0 L / min at a relative humidity of 50%. The reaction conditions were dark for 60 minutes and light irradiation conditions (visible light irradiance 40 W / m ² ) for 180 minutes. The produced CO ₂ concentration was measured by gas chromatography. The results are shown in FIGS. FIG. 28 shows the results when Sample 7 was used, and FIG. 29 shows the results when the composite material of photocatalyst particles and zeolite produced in Example 13 (supporting 10% by weight of zeolite with respect to the catalyst particles) was used. Is the result of The amount of CO ₂ generated by the decomposition of acetaldehyde was larger when the composite material was used.

  The photocatalyst particles of the present invention exhibit an excellent redox action by visible light. The photocatalyst particles can be suitably used for hydrogen production by water splitting. Further, by applying the photocatalyst particles, a sterilizing effect can be imparted to materials and products.

Claims (15)

Photocatalytic particles comprising titanium dioxide , silver, silver oxide and silver phosphate,
A specific surface area of 150 to 400 m ² / g,
Photocatalytic particles. The ratio of titanium to all elements in the photocatalyst particles is 20 mol% to 30 mol%,
The ratio of oxygen to all elements in the photocatalyst particles is 60 mol% to 80 mol%,
The ratio of silver to all elements in the photocatalyst particles is 0.2 mol% to 0.9 mol%,
The ratio of phosphorus to all elements in the photocatalyst particles is 0.2 mol% to 0.6 mol%,
The photocatalyst particles according to claim 1, wherein the total amount of titanium, oxygen, silver, and phosphorus is 100 mol%.   The photocatalyst particle according to claim 1 or 2, wherein the crystal size is 2.0 to 4.0 nm. Photocatalytic particles comprising titanium dioxide , silver, silver oxide and silver phosphate,
The ratio of titanium to all elements in the photocatalyst particles is 20 mol% to 30 mol%,
The ratio of oxygen to all elements in the photocatalyst particles is 60 mol% to 80 mol%,
The ratio of silver to all elements in the photocatalyst particles is 0.2 mol% to 0.9 mol%,
The ratio of phosphorus to all elements in the photocatalyst particles is 0.2 mol% to 0.6 mol%, and the total amount of titanium, oxygen, silver and phosphorus is 100 mol%.
Photocatalytic particles.   The photocatalyst particle according to claim 4, wherein the crystal size is 2.0 to 4.0 nm. Photocatalytic particles comprising titanium dioxide , silver, silver oxide and silver phosphate,
The crystal size is 2.0 to 4.0 nm;
Photocatalytic particles.   The photocatalyst particle according to any one of claims 1 to 6, wherein a band gap energy is 2.4 eV to 3.2 eV.   The amount of silver leaked into water after stirring a 0.5 g / L aqueous suspension of photocatalyst particles in a dark place at 37 ° C. for 12 hours is less than 0.100 mg / L. 8. The photocatalyst particles according to any one of items 7 to 7. The method for producing photocatalyst particles according to any one of claims 1 to 8, comprising the following steps:
(1) An alkyl titanate represented by Ti (OR) ₄ (where R = C _n H _{2n + 1} and n = 2 to 8), silver nitrate, silver phosphate and nitric acid are mixed in a solvent And (2) performing a solvothermal reaction on the sol-gel solution prepared in the step (1).   The method according to claim 9, wherein the solvent in step (1) is ethanol.   The method according to claim 9 or 10, wherein the solvothermal reaction is performed at a temperature of more than 100 ° C and less than 140 ° C for more than 1.0 hour and less than 4.0 hours.   The method according to any one of claims 9 to 11, wherein the solvothermal reaction is performed at 110C to 130C for 1.5 to 3.5 hours.   A material comprising the photocatalyst particles according to claim 1. Further comprising a carrier,
The material according to claim 13, wherein the photocatalyst particles are supported on a carrier.   An article of manufacture comprising the material of claim 13.