Method and system for producing hydrogen peroxide

Abstract

To provide a method for efficiently producing hydrogen peroxide and an efficient hydrogen peroxide production system.SOLUTION: A method for producing hydrogen peroxide according to the present invention comprises a step of irradiating an n-type metal oxide semiconductor with light in an aqueous solution containing an organic acid salt. A system for producing hydrogen peroxide according to the present invention includes an aqueous solution containing an organic acid salt and an n-type metal oxide semiconductor, wherein the n-type metal oxide semiconductor is immersed in the aqueous solution.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for efficiently producing hydrogen peroxide and a system for efficiently producing hydrogen peroxide. [Background technology]

[0002] Hydrogen peroxide (H2O2) is not only a very strong oxidizing agent, but also acts as a reducing agent depending on the target, and is used as a disinfectant and bleach. Hydrogen peroxide is industrially produced by mixing anthrahydroquinones such as 2-ethylanthrahydroquinone and 2-amylanthrahydroquinone with oxygen in a solvent to oxidize them, extracting the resulting hydrogen peroxide from the anthraquinone with ion-exchanged water and distilling it under reduced pressure. The by-product anthraquinone can be reduced to anthrahydroquinone using a nickel or palladium catalyst and reused. However, in this method, the side chain may be oxidized when anthrahydroquinone is oxidized, and the aromatic ring may be reduced when anthrahydroquinone is reduced and reused. Therefore, a more efficient method for producing hydrogen peroxide is required.

[0003] For example, Patent Document 1 discloses a method for producing hydrogen peroxide as a by-product when an aromatic compound is oxidized to convert it into a phenol using a catalyst containing a quinolinium derivative.

[0004] Non-Patent Document 1 describes a method for producing hydrogen peroxide from water and oxygen by a photoreaction using Mo-doped BiVO4.

[0005] The present inventors have developed a method for producing hydrogen peroxide from water and oxygen by a photoreaction using Au-supported Sb(III)-doped SnO2 (Non-Patent Document 2).

[0006] Non-Patent Document 3 describes a method for producing hydrogen peroxide from water containing hydrogen carbonate ions through a photoreaction using a photoelectrode that combines BiVO4 with a WO3 underlayer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2011-189224 A [Non-patent literature]

[0008] [Non-Patent Document 1] Tian Liu et al., Nat.Commun.,2022,13,1034- [Non-Patent Document 2] Miwako Teranishi et al., Catal.Sci.Technol.,2022,16,6062- [Non-Patent Document 3] Kojiro Fuku et al.,Chem.Commun.,2016,52,5406- Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, various methods for producing hydrogen peroxide from water by photocatalytic reaction have been developed. However, the external quantum yields described in Patent Document 1 and Non-Patent Documents 1 and 2 are 5.6%, 5.8%, and 1.1%, respectively, and these methods cannot be said to be sufficiently efficient. In addition, the Faraday efficiency of Non-Patent Document 3 is about 5%, and the external quantum yield is naturally lower than this. Therefore, an object of the present invention is to provide a method for efficiently producing hydrogen peroxide and an efficient system for producing hydrogen peroxide. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems, and as a result have found that hydrogen peroxide can be efficiently produced from water by a photoreaction by using a specific catalyst and adding an organic acid salt, thereby completing the present invention. The present invention will now be described.

[0011] [1] A method for producing hydrogen peroxide, comprising: A method comprising the step of irradiating an n-type metal oxide semiconductor with light in an aqueous solution containing an organic acid salt. [2] The method according to [1] above, wherein the organic acid salt is a dicarboxylate. [3] The method according to [1], wherein the n-type metal oxide semiconductor comprises one or more n-type metal oxide semiconductors selected from the group consisting of tin oxide, titanium oxide, bismuth vanadate, and tungsten oxide. [4] The method according to [1], wherein the wavelength peak of the light is within the visible light range. [5] The method according to [1], wherein in the aqueous solution, a cathode and an anode containing the n-type metal oxide semiconductor are separated by a proton conductive membrane, and a voltage is applied between the anode and the cathode.

[0012] [6] An aqueous solution containing an organic acid salt and an n-type metal oxide semiconductor, The system for producing hydrogen peroxide is characterized in that the n-type metal oxide semiconductor is immersed in the aqueous solution. [7] The hydrogen peroxide production system according to [6], wherein the organic acid salt is a dicarboxylate. [8] The hydrogen peroxide production system described in [6], wherein the n-type metal oxide semiconductor comprises one or more n-type metal oxide semiconductors selected from the group consisting of tin oxide, titanium oxide, bismuth vanadate, and tungsten oxide. [9] The hydrogen peroxide production system according to [6], further comprising a light source.

[10] A cathode, an anode including the n-type metal oxide semiconductor, a proton conducting membrane, and a power source; the anode and the cathode are separated by the proton conductive membrane in an aqueous solution; The hydrogen peroxide production system according to [6], wherein the power source applies a voltage between the anode and the cathode. Effect of the Invention

[0013] According to the present invention, hydrogen peroxide can be produced in high yield and with a high external quantum yield to irradiated light. Therefore, the present invention is industrially extremely advantageous as a technology for efficiently producing useful hydrogen peroxide. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a graph showing the change in hydrogen peroxide concentration over time and the Faraday efficiency when hydrogen peroxide is produced using a photoelectrochemical cell according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The method for producing hydrogen peroxide according to the present invention includes a step of irradiating an n-type metal oxide semiconductor with light in an aqueous solution containing an organic acid salt. The system for producing hydrogen peroxide according to the present invention includes an aqueous solution containing an organic acid salt and an n-type metal oxide semiconductor, and is characterized in that the n-type metal oxide semiconductor is immersed in the aqueous solution. The present invention will be described below, but is not limited to the following specific examples.

[0016] In the present invention, the generation of hydrogen peroxide from water is significantly improved by using an aqueous solution of an organic acid salt. Although it is not entirely clear, it is believed that the organic acid salt is oxidized to a peroxide by holes in the valence band of an n-type metal oxide semiconductor excited by light irradiation, and the peroxide oxidizes water to generate hydrogen peroxide. 2R-CO2H + 2h + → RC(=O)-OOC(=O)-R + 2H + 2H2O + RC(=O)-OOC(=O)-R → H2O2+ 2R-CO2H

[0017] In the present disclosure, the organic acid salt refers to a salt of an organic compound having a carboxy group. As described above, the organic acid acts as an electron mediator to promote the reaction, and the salt of the organic acid is used from the viewpoints of water solubility and inhibition of decomposition of the generated hydrogen peroxide.

[0018] Examples of organic acids constituting the organic acid salt include monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, and benzoic acid, dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, malic acid, maleic acid, fumaric acid, and phthalic acid, and tricarboxylic acids such as citric acid and benzenetricarboxylic acid. In the case of polyvalent organic acids such as dicarboxylic acids and tricarboxylic acids, polyvalent organic acids in which carboxy groups are bonded to adjacent carbon atoms, such as 1,2-dicarboxylic acids, are preferred from the viewpoint of the stability of peroxides formed within the molecule.

[0019] As the organic acid salt, alkali metal salts such as sodium salts and potassium salts are preferred. In the case of polyvalent organic acids such as dicarboxylic acids and tricarboxylic acids, monoalkali metal salts such as alkali metal hydrogen salts and alkali metal dihydrogen salts are preferred from the viewpoint of accelerating the reaction.

[0020] The concentration of the organic acid salt in the aqueous solution may be appropriately adjusted within a range in which hydrogen peroxide is effectively generated, and may be, for example, 0.005M or more and 2M or less. If the concentration is 0.005M, the organic acid salt can function more reliably as an electron mediator. On the other hand, if the concentration is too high, the effect of the organic acid salt is saturated, so the upper limit may be, for example, 2M. The concentration is preferably 0.01M or more, more preferably 0.05M or more, and is preferably 1.5M or less or 1M or less, and more preferably 0.5M or less.

[0021] In the present invention, although the detailed reaction mechanism is not necessarily clear, water is oxidized to generate hydrogen peroxide by exciting the n-type metal oxide with light irradiation. An n-type metal oxide semiconductor is a metal oxide semiconductor in which free electrons are mainly used as carriers to carry electric charges.

[0022] Examples of n-type metal oxide semiconductors include one or more n-type metal oxide semiconductors selected from the group consisting of tin oxide, titanium oxide, bismuth vanadate, and tungsten oxide. When two or more n-type metal oxide semiconductors are used, they may be physically mixed, or may be mixed and then co-fired.

[0023] The n-type metal oxide semiconductor may be doped with a metal having a valence greater than that of the metal ions constituting the main crystal, such as Sb(V), V(V), Nb(V), Ta(V), Mo(VI), and W(VI).

[0024] The band gap of the n-type metal oxide semiconductor is preferably 3.5 eV or less. If the band gap is 3.5 eV or less, the n-type metal oxide semiconductor is excited even by relatively low energy such as visible light, and the generated hydrogen peroxide is less likely to be further oxidized, reduced or decomposed. The band gap is the difference in energy from the top of the valence band to the bottom of the conduction band of a semiconductor, and refers to the width of the region in which electrons cannot exist. The band gap is more preferably 3.4 eV or less or 3.2 eV or less, and even more preferably 3 eV or less. The lower limit of the band gap is not particularly limited, but for example, 1.5 eV or more is preferable, and 2 eV or more is more preferable. The method for measuring the band gap is not particularly limited, but for example, the diffuse reflectance of the powder of the n-type metal oxide semiconductor is measured using an ultraviolet-visible spectrophotometer equipped with an integrating sphere, and the band gap can be calculated by converting it into an absorption spectrum using the Kubelka-Munk function.

[0025] The specific surface area of ​​an n-type metal oxide semiconductor is 1 m 2 / g or more, 70m 2 / g or less. 2 If the specific surface area is 70 m / g or more, the contact area with water is sufficiently large, so the reaction can proceed more efficiently. 2If the specific surface area is less than 3 m / g, the n-type metal oxide semiconductor will not become excessively small, and ease of handling can be ensured. 2 / g or more is more preferable, and 5m 2 / g or more is more preferable, and 25m 2 / g or less is more preferable, and 10m 2 / g or less is even more preferable.

[0026] The size of the n-type metal oxide semiconductor is preferably 100 nm or more and 500 nm or less. If the size of the n-type metal oxide semiconductor is 500 nm or less, the contact area with water is large, and the reaction can proceed more efficiently. On the other hand, if the size of the n-type metal oxide semiconductor is 100 nm or more, the size of the crystallites constituting the particles is also sufficiently large, and the reaction can proceed more efficiently. The size of the n-type metal oxide semiconductor can be determined, for example, by magnifying and observing the n-type metal oxide semiconductor with an electron microscope, measuring the longest diameter and the shortest diameter of the crystals that can be observed as a whole within a field of view of 1 to 100 μm × 1 to 100 μm, and taking the average of the measured diameters.

[0027] The n-type metal oxide semiconductor may support precious metal particles. By using an n-type metal oxide semiconductor supporting precious metal particles, protons (H + ) may further produce hydrogen peroxide according to the following formula: In this case, it is preferable to blow an oxygen-containing gas such as air into the aqueous solution. O2+ 2H + + 2e - → H2O2

[0028] Noble metals include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os), with gold, silver, platinum, and palladium being preferred, and gold being preferred.

[0029] The amount of precious metal particles supported on the n-type metal oxide semiconductor may be adjusted as appropriate within the range in which the reaction proceeds well, and may be, for example, 0.1 μg / g or more and 500 μg / g or less in terms of the μg ratio of precious metal to 1 g of the carrier portion other than the precious metal in the n-type metal oxide semiconductor. The ratio is preferably 0.5 μg / g or more, more preferably 1 μg / g or more or 2 μg / g or more, and is preferably 250 μg / g or less, and more preferably 100 μg / g or less or 50 μg / g or less.

[0030] The particle size of the precious metal particles may be adjusted as appropriate, but for example, the length of the minor axis of the precious metal particles is preferably 2 nm or more and 200 nm or less.

[0031] The n-type metal oxide semiconductor carrying the noble metal particles can be manufactured by a conventional method. For example, first, the raw semiconductor particles are heat-treated. The size of the raw semiconductor particles may be appropriately adjusted according to the desired size of the target catalyst. The heat treatment temperature of the raw semiconductor particles is also appropriately adjusted. For example, it can be said that the higher the heat treatment temperature, the more the crystallites grow and the higher the activity. However, if the temperature is excessively high, the specific surface area becomes smaller and the activity may decrease. For example, it is preferable to heat treat at 300°C or higher and 700°C or lower for 30 minutes or more and 10 hours or less. Next, the heat-treated raw semiconductor particles may be added to a solution containing a noble metal element, such as an aqueous solution of a salt of a noble metal acid, and impregnated and supported. Examples of the salt of a noble metal acid include chlorides such as chloroauric acid. In this case, if urea is present, NH4OH is generated in the system as a precipitant from around 70°C, promoting the precipitation of the noble metal particles. After the precious metal particles are sufficiently supported on the surface of the semiconductor particles, the catalyst particles are separated from the reaction solution by centrifugation, filtration, etc., and then thoroughly washed with water, etc., and then dried. Furthermore, the catalyst particles may be heat-treated at 300° C. or higher and 700° C. or lower for 1 hour or longer and 10 hours or shorter.

[0032] The amount of the n-type metal oxide semiconductor used may be adjusted as appropriate within a range in which hydrogen peroxide can be satisfactorily produced from water, but for example, when dispersing the n-type metal oxide semiconductor in an aqueous solution, the n-type metal oxide semiconductor can be dispersed in the aqueous solution at 0.1 mg / mL or more and 10 mg / mL or less. The proportion is preferably 0.2 mg / mL or more, more preferably 0.5 mg / mL or more, and preferably 5 mg / mL or less, more preferably 2 mg / mL or less.

[0033] Alternatively, the anode electrode may be fabricated by depositing an n-type metal oxide semiconductor on an anode current collector, or by mixing the n-type metal oxide semiconductor with a binder and a solvent to prepare a slurry, applying the slurry onto the anode current collector, and then drying the slurry. Examples of the anode current collector include an indium tin oxide (ITO) film and a fluorine-doped tin oxide (FTO) film.

[0034] In the present invention, the n-type metal oxide semiconductor is irradiated with light in an aqueous solution containing an organic acid salt. The manner of irradiating with light is not particularly limited, but for example, as described above, n-type metal oxide semiconductor particles may be dispersed in an aqueous solution containing an organic acid salt and then irradiated with light, or the aqueous solution containing an organic acid salt may be partitioned with an ion exchange membrane, and an anode electrode and a cathode electrode containing an n-type metal oxide semiconductor may be immersed in each compartment before irradiating with light.

[0035] As the ion exchange membrane, it is preferable to use a cation exchange membrane such as Nafion (registered trademark), particularly a proton conductive membrane, in order to selectively allow protons to pass through. As the cathode electrode material, for example, noble metals such as platinum, palladium, and ruthenium, as well as sulfides such as Mo2S and WS2, can be used. Note that the following reaction is considered to occur at the cathode electrode. 2H + + 2e - → H2

[0036] The light to be irradiated onto the n-type metal oxide semiconductor may be appropriately selected within a range that allows hydrogen peroxide to be produced well from water. For example, it is believed that the reaction will proceed more efficiently if short-wavelength, high-energy light is used. As the high-energy light, light with a peak wavelength in the range of 180 nm or more and 360 nm or less can be used. In addition, light containing UV-B with a wavelength of 280 nm or more and 315 nm or less and / or UV-C with a wavelength of 180 nm or more and 280 nm or less can be used, and light containing UV-C with a wavelength of 180 nm or more and 280 nm or less can be used, and light with a peak wavelength in these ranges can also be used.

[0037] In addition, in the present invention, safer visible light may be used. For example, light having a peak wavelength in the range of 360 nm to 830 nm may be used. The lower limit of the peak wavelength range is preferably 380 nm, more preferably 400 nm, and the upper limit is preferably 700 nm or 600 nm, more preferably 500 nm or 450 nm.

[0038] The means of light irradiation is not particularly limited as long as it can irradiate light of the above wavelength, but examples of light sources that include light in this wavelength range include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, metal halide lamps, LED lamps, etc. From the standpoint of reaction efficiency and cost, low-pressure mercury lamps and LED lamps are preferred, and LED lamps are more preferred.

[0039] The illuminance of the light can be adjusted appropriately, for example, to 0.5 mW / cm 2 More than 100mW / cm 2 It can be as follows:

[0040] The temperature when the catalyst is irradiated with light can be adjusted to, for example, 5°C or higher and 60°C or lower, or may be room temperature. The light irradiation time is not particularly limited, and the longer the light irradiation time, the more hydrogen and oxygen can be produced. When water is consumed as the reaction proceeds, water may be added intermittently or continuously.

[0041] When using an anode electrode and a cathode electrode containing an n-type metal oxide semiconductor, a voltage may be applied between the two electrodes to further promote the reaction. The voltage may be adjusted as appropriate, and for example, the potential of the anode electrode containing an n-type metal oxide semiconductor with respect to the standard hydrogen electrode potential may be adjusted to 0.1 V or more and 3 V or less.

[0042] The present invention uses an organic acid salt to remarkably improve the efficiency of hydrogen peroxide production. In particular, when an n-type metal oxide semiconductor carrying precious metal particles is used, hydrogen peroxide is believed to be generated at two locations, the valence band and the conduction band. EXAMPLES

[0043] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is possible to carry out the present invention by making appropriate modifications within the scope of the above and below-mentioned aims, and all of these modifications are included in the technical scope of the present invention.

[0044] Manufacturing Example 1: Preparation of Au / BiVO4 nanoparticles Bismuth vanadate (BiVO4) microparticles were synthesized by the following procedure. Bismuth nitrate pentahydrate (48.5 g) and ammonium vanadate (11.7 g) were dissolved in 1.3 M aqueous nitric acid solution (500 mL) and stirred at room temperature for 1 hour. Urea (50 g) was added, and the mixture was stirred at 80°C for 18 hours. The resulting precipitate was washed three times with distilled water, dried, and then calcined at 400°C for 1 hour to obtain bismuth vanadate microparticles. To prepare gold nanoparticle-supported bismuth vanadate microparticles (Au / BiVO4), a deposition precipitation method using sodium hydroxide as a neutralizing agent was used. Chloroauric acid (HAuCl4, Kanto Chemical Co., Ltd.) was dissolved in water to prepare a 2.43 mM aqueous solution (200 mL), and the pH was adjusted to 6 using a 1.0 M aqueous sodium hydroxide solution. Bismuth vanadate microparticles (20 g) were added to the resulting solution, which was then stirred at 70°C for 1 hour. The microparticles were collected by centrifugation, washed three times with distilled water, and then dried to obtain Au.3+ Bismuth vanadate nanoparticles with complex adsorption were prepared and calcined in air at 400℃ for 4 hours to obtain Au / BiVO4 nanoparticles.

[0045] Manufacturing Example 2: Preparation of Au / a-TiO2 fine particles Anatase-type titanium oxide particles carrying gold nanoparticles (Au / a-TiO2) were prepared in the same manner as in Production Example 1, except that anatase-type titanium particles ("A-100" manufactured by Ishihara Sangyo Kaisha) were used instead of bismuth vanadate particles.

[0046] Production Example 3: Preparation of Au / WO3 fine particles A deposition precipitation method using urea as a neutralizing agent was used to prepare gold nanoparticle-supported WO3 microparticles (Au / WO3). WO3 microparticles (manufactured by Aldrich) were calcined in air at 600°C for 4 hours. Chloroauric acid (HAuCl4, manufactured by Kanto Chemical Co., Ltd.) was dissolved in water to prepare a 0.48 mM aqueous solution (600 mL), to which the calcined microparticles (5 g) were added and dispersed. Next, urea (1.73 g) was added, and the mixture was stirred at 80°C for 16 hours. The resulting precipitate was washed three times with water, vacuum dried, and then calcined in air at 400°C for 4 hours to obtain Au / WO3 microparticles.

[0047] Production Example 4: Preparation of WO3NR fine particles WO3 nanorods (WO3NR) were prepared using the following solvothermal method. Ammonium tungstate (5.0 g) was added to a mixed solution of ethanol (50 mL), distilled water (50 mL), and hydrochloric acid (20 mL), and then 30% hydrogen peroxide (14 mL) was added to completely dissolve it. This solution was placed in two 100 mL Teflon containers, sealed in a stainless steel autoclave, and heated at 160°C for 4 hours. The resulting precipitate was washed with distilled water, dried, and then calcined in air at 400°C for 4 hours to obtain WO3NR fine particles.

[0048] Example 5: Preparation of Au / WO3NR nanoparticles Gold nanoparticle-supported WO3 nanorod particles (Au / WO3NR) were prepared in the same manner as in Production Example 3, except that WO3NR was used instead of the WO3 particles.

[0049] Manufacturing Example 6: Preparation of WO3-ATO composite particles WO3-ATO composite particles were prepared using WO3 particles (Aldrich) and antimony-doped tin oxide (ATO) particles ("SN-100P" Ishihara Sangyo Kaisha, Ltd.) according to the following method: WO3 particles (200 mg) and ATO (200 mg) were placed in an agate mortar and thoroughly kneaded, then calcined in air at 500°C for 1 hour to obtain WO3-ATO composite particles.

[0050] Example 1: Photocatalytic reaction kinetics The microparticles prepared in Production Examples 1 to 6 and the existing microparticles (10 mg) were dispersed in air-saturated water (10 mL) containing a predetermined concentration of an electron mediator as required at a temperature of 0° C. to 60° C., and then irradiated with light at a predetermined wavelength. The generated hydrogen peroxide was quantified by a colorimetric method using 2,9-dimethyl-1,10-phenanthroline, and the generation rate of hydrogen peroxide was calculated.

[0051] (1) Activity evaluation of Au / BiVO4 nanoparticles The gold nanoparticle-supported bismuth vanadate microparticles (Au / BiVO4) of Production Example 1 were dispersed in air-saturated water (10 mL) containing 0.1 M potassium hydrogen phthalate as an electron mediator at 25°C. The pH of the air-saturated water was reduced to 3.9 by the addition of potassium hydrogen phthalate. -2 The catalytic performance for generating hydrogen peroxide was evaluated by irradiating the sample with ultraviolet light. The results are shown in Table 1.

[0052] (2) Activity evaluation of Au / a-TiO2 nanoparticles The gold nanoparticle-supported anatase-type titanium oxide (Au / a-TiO2) microparticles of Production Example 2 were used, and ultraviolet light with a wavelength of 365 nm (light intensity 10 mWcm2) was used. -2 The catalytic performance for producing hydrogen peroxide was evaluated in the same manner as in Example 1(1), except that the catalyst was irradiated with 1000 nm of 1000 nm light (300 nm). The results are shown in Table 1.

[0053] (3) Activity evaluation of Au / WO3 nanoparticles The catalytic performance for producing hydrogen peroxide was evaluated in the same manner as in Example 1(1), except for using the gold nanoparticle-supported WO3 fine particles (Au / WO3) of Production Example 3. The results are shown in Table 1.

[0054] (4) Activity evaluation of Au / WO3 nanoparticles The catalytic performance for producing hydrogen peroxide was evaluated in the same manner as in Example 1(3), except that the temperature was 55° C. The results are shown in Table 1.

[0055] (5) Activity evaluation of Au / WO3NR nanoparticles The catalytic performance for producing hydrogen peroxide was evaluated in the same manner as in Example 1(2), except for using the gold nanoparticle-supported WO nanorod particles (Au / WONR) of Production Example 4. The results are shown in Table 1.

[0056] (6) Activity evaluation of Au / r-TiO2 nanoparticles The catalytic performance for generating hydrogen peroxide was evaluated in the same manner as in Example 1(2), except for using the gold nanoparticle-supporting rutile-type titanium oxide fine particles (Au / r-TiO2) of Production Example 5. The results are shown in Table 1.

[0057] (7) Activity evaluation of WO3-ATO composite particles The catalytic performance for producing hydrogen peroxide was evaluated in the same manner as in Example 1(1), except for using the WO3-ATO composite fine particles of Production Example 6. The results are shown in Table 1.

[0058] (8) Activity evaluation of WO3-ATO composite particles The catalytic performance for producing hydrogen peroxide was evaluated in the same manner as in Example 1(1), except that WO3 fine particles (manufactured by Aldrich) were used. The results are shown in Table 1.

[0059] Comparative Example 1 The catalytic performance for generating hydrogen peroxide was evaluated in the same manner as in Example 1(1), except that about 4% of ethanol was added as a hole capture agent instead of potassium hydrogen phthalate. The results are shown in Table 1.

[0060] Comparative Example 2 The catalytic performance for generating hydrogen peroxide was evaluated in the same manner as in Example 1(1), except that perchloric acid was added instead of potassium hydrogen phthalate to lower the pH of the air-saturated water to 3.9. The results are shown in Table 1.

[0061] [Table 1]

[0062] As the results shown in Table 1 show, when potassium hydrogen phthalate was added to the system as an electron mediator (Example 1 (1) to (8)), hydrogen peroxide could be produced satisfactorily. On the other hand, even when ethanol was added as a hole capture agent (Comparative Example 1), only a small amount of hydrogen peroxide was generated. Therefore, it is clear that the effect of adding potassium hydrogen phthalate is not due to its action as a hole capture agent. Furthermore, even when the pH was lowered by adding perchloric acid (Comparative Example 1), only a small amount of hydrogen peroxide was produced, which shows that the effect of adding potassium hydrogen phthalate is not simply due to the fact that oxygen becomes more easily reduced as a result of the lowering of the pH.

[0063] Example 2: External quantum yield of photocatalytic reaction The external quantum yield (φ ex ) was calculated according to the following formula 1. Equation 1: φ ex (%)={2×(Number of H2O2 generated molecules / Number of incident photons)}×100 The number of incident photons at the wavelength of 420 nm of the irradiated light was measured using a light intensity meter (Js -1 ) divided by the energy of one photon (J) and multiplied by the reaction time (s). Calculated external quantum yield φ ex was 27.2%, which was far higher than the values ​​of 5.6% and 1.1% described in Patent Document 1 and the values ​​of 1.1% and 5.8% described in Non-Patent Documents 1 and 2.

[0064] Example 3: Photoelectrochemical cell The WO3-NRA / FTO electrode was prepared by forming a WO3 nanorod array (NRA / FTO) on a fluorine-doped tin oxide (FTO) electrode. Specifically, ammonium tungstate (2.5 g) was added to a mixed solution of ethanol (25 mL), distilled water (25 mL) and hydrochloric acid (10 mL), and then 30% hydrogen peroxide (1.4 mL) was added to completely dissolve the solution. The solution was transferred to a Teflon container and FTO glass ("TEC7" Aldrich) was immersed in it. The Teflon container was sealed in a stainless steel autoclave and heated at 160 °C for 4 hours. The obtained thin film was washed with distilled water, dried, and then calcined in air at 500 °C for 2 hours to obtain a WO3-NRA / FTO electrode. Using this, WO3-NRA / FTO (working electrode, electrode area = 4 cm 2 A two-compartment three-electrode photoelectrochemical cell was constructed, consisting of WO3-NRA / FTO (reference electrode), 0.1 M sodium perchlorate + 0.1 M potassium hydrogen phthalate (air saturated), Nafion membrane (separator), 0.1 M sodium perchlorate + 0.1 M potassium hydrogen phthalate (argon degassed), and Pt (auxiliary electrode). The photocurrent and hydrogen peroxide production were measured when the WO3-NRA / FTO electrode was irradiated with visible light at a wavelength of 420 nm while the potential of the electrode was kept at +0.8 V vs. standard hydrogen electrode potential (SHE). Furthermore, the faradaic efficiency of hydrogen peroxide production was calculated using Eq. Equation 2: Faraday efficiency (%) = {2 x (amount of H2O2 produced (mol) x F (C / mol) / amount of electricity applied (C))} x 100 In the formula, F represents the Faraday constant.

[0065] FIG. 1 shows the changes in hydrogen peroxide concentration and faradaic efficiency over time. As shown in Figure 1, upon light irradiation, the anode side was charged with approximately 330 μMh -1 Hydrogen peroxide is generated at a constant rate of about 28 μMh on the cathode side. -1 It was confirmed that hydrogen was produced. Furthermore, the Faraday efficiency remains approximately 90% regardless of time. As described above, the photoelectrochemical cell according to the present invention makes it possible to simultaneously obtain hydrogen peroxide and hydrogen from water and oxygen using visible light such as sunlight as an energy source.

Claims

1. 1. A method for producing hydrogen peroxide, comprising: A method comprising the step of irradiating an n-type metal oxide semiconductor with light in an aqueous solution containing an organic acid salt.

2. The method of claim 1 , wherein the organic acid salt is a dicarboxylate.

3. 2. The method of claim 1, wherein the n-type metal oxide semiconductor comprises one or more n-type metal oxide semiconductors selected from the group consisting of tin oxide, titanium oxide, bismuth vanadate, and tungsten oxide.

4. The method of claim 1 , wherein the wavelength peak of the light is in the visible light range.

5. The method according to claim 1 , wherein a cathode and an anode containing the n-type metal oxide semiconductor are separated by a proton conductive membrane in the aqueous solution, and a voltage is applied between the anode and the cathode.

6. An aqueous solution containing an organic acid salt and an n-type metal oxide semiconductor, The hydrogen peroxide production system is characterized in that the n-type metal oxide semiconductor is immersed in the aqueous solution.

7. The hydrogen peroxide production system according to claim 6, wherein the organic acid salt is a dicarboxylate.

8. 7. The system for producing hydrogen peroxide according to claim 6, wherein the n-type metal oxide semiconductor comprises one or more n-type metal oxide semiconductors selected from the group consisting of tin oxide, titanium oxide, bismuth vanadate, and tungsten oxide.

9. The system for producing hydrogen peroxide according to claim 6, further comprising a light source.

10. The device further comprises a cathode, an anode including the n-type metal oxide semiconductor, a proton conducting membrane, and a power source; the anode and the cathode are separated by the proton conductive membrane in an aqueous solution; 7. The hydrogen peroxide production system according to claim 6, wherein the power source applies a voltage between the anode and the cathode.

Images