JPH11302888A - Water electrolysis type ozonizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent a hydrogen gas produced on a cathode of a water electrolysis type ozonizer which electrolyzes water to produce ozone from diffusing through a solid polymer electrolytic membrane to reach an anode and to prevent the reduction of the anode metal and therefore, to prevent a decrease in the produced amt. of the ozone. produced. SOLUTION: A catalyst layer 9 is formed in a solid polymer electrolyte membrane 8 disposed between an anode 6 and a cathode 7. Water is electrolyzed on the anode 6 to produce an oxygen, ozone and hydrogen ion. The hydrogen ion reaches the cathode 7 to be changed into hydrogen which then, again diffuses through the solid polymer electrolytic membrane 8 toward the anode 6. In this process, since the oxygen and ozone diffusing from the anode 6 side react on the catalyst layer with the hydrogen diffusing from the cathode 7 side to produce water, the hydrogen produced on the cathode 7 does not reach the anode 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water electrolysis type ozonizer which uses water as a raw material and electrolyzes the water to generate ozone.

[0002]

2. Description of the Related Art For example, ozone water obtained by dissolving ozone in water is subjected to water treatment of water supply and sewerage by strong oxidizing action of ozone.
It is used for sterilization and deodorization of hotels and hospitals, and sterilization and deodorization of various foods. As a method for producing this ozone water, a water electrolysis method in which water is electrolyzed using a water electrolysis ozonizer and the obtained ozone is dissolved in water to obtain ozone water is conventionally known.

FIG. 4 shows an ozone water producing apparatus using such a conventional water electrolysis type ozonizer.
Is separated into an ozone water generation chamber 23 and a processing air supply chamber 24 by a water electrolysis type ozonizer 22 provided therein. The ozonizer 22 has an anode 25 made of lead dioxide that generates oxygen and ozone by electrolyzing water.
A solid polymer electrolyte membrane 27 serving as a hydrogen ion exchange membrane through which hydrogen ions pass is sandwiched between a hydrogen ion generated by the anode 25 and a cathode 26 that reduces the hydrogen ions to hydrogen.

As shown in FIG. 5, an ozone water generation chamber 23 facing an anode 25 of a water electrolysis type ozonizer 22 is provided.
In water the (H ₂ O) to supply, at the anode _{25, 3H 2 O → O 3} + 6H + + 6e - 2H 2 O → O 2 + 4H + + 4e - two reaction proceeds simultaneously, ozone (O ₃₎ A mixed gas of oxygen and oxygen (O ₂ ) is obtained, and this is dissolved in the water (H ₂ O) in the ozone water generation chamber 23 to obtain ozone water.

[0005]

At this time, hydrogen ions (H.sup. ⁺ ) Generated at the anode 25 as a by-product move in the solid polymer electrolyte membrane 27 to reach the cathode 26, where the hydrogen ions (H.sup. ⁺ ) ^{receipt, 6H + + 6e - → 3H} 2 (4H + + 4e - → 2
H ₂ ) produces hydrogen gas (H ₂ ). Then, the hydrogen gas (H ₂ ) diffuses through the solid polymer electrolyte membrane 27 and reaches the anode 25, where PbO ₂ + H ₂ → HPbO ₂ ⁻ + H ⁺ → PbO + H ₂
Due to the reaction of O 2, lead dioxide (P
Since the catalyst function is reduced by reducing bO ₂ ), there has been a problem that the amount of generated ozone is reduced when used for a long time. Attempts have been made to increase the thickness of the solid polymer electrolyte membrane 27 in order to reduce the influence of the diffusion of hydrogen gas. However, the solid polymer electrolyte membrane 27
When the film thickness is increased, the electric resistance increases, so that the current density decreases at the same power supply voltage and the amount of generated ozone decreases. Also, increasing the film thickness does not prevent the diffusion of hydrogen gas, but merely extends the time until the hydrogen gas diffuses and reaches the anode 25, so that the amount of ozone generated also decreases. The problem of coming up cannot be solved.

Accordingly, the present invention reliably prevents the hydrogen gas generated at the cathode from diffusing into the solid polymer electrolyte membrane and reaching the anode, thereby preventing the anode metal from being reduced,
Further, it is a technical problem to prevent the ozone generation amount from decreasing.

[0007]

In order to solve this problem, the present invention provides an anode for electrolyzing water as a raw material into ozone, oxygen and hydrogen ions, and a method for reducing hydrogen ions generated at the anode to hydrogen. In a water electrolysis type ozonizer in which a solid polymer electrolyte membrane serving as a hydrogen ion exchange membrane is sandwiched between a cathode and a cathode, oxygen and ozone diffused from the anode side and the cathode are contained in the solid polymer electrolyte membrane. The catalyst layer is characterized in that a catalyst layer that reacts with hydrogen diffused from the side and converts it into water is formed.

According to the present invention, water supplied to the ozone water generation chamber is electrolyzed to oxygen, ozone, and hydrogen ions at the anode. Hydrogen ions generated at the anode pass through the solid polymer electrolyte membrane to the cathode, receive electrons at the cathode and become hydrogen gas, and part of the hydrogen diffuses through the solid polymer electrolyte membrane toward the anode. Moving. On the other hand, part of the oxygen and ozone generated at the anode is released to the outside, and part of the oxygen and ozone diffuses in the solid polymer electrolyte membrane and moves toward the cathode. At this time, a catalyst layer is formed in the solid polymer electrolyte membrane, and hydrogen that reaches the catalyst layer from the cathode side and oxygen or ozone that reaches the catalyst layer from the anode side react with each other to generate water. Therefore, it is possible to reliably prevent the hydrogen generated at the cathode from reaching the anode, so that the hydrogen does not reduce the anode metal such as lead dioxide and the amount of generated ozone is reduced. Absent. The water generated in the catalyst layer moves to a lower humidity according to the humidity gradient of the polymer electrolyte membrane.

The catalyst layer formed in the solid polymer electrolyte membrane uses a catalyst that promotes the reaction between hydrogen and oxygen. For example, one or two selected from platinum, palladium, rhodium, ruthenium and iridium are used. It is formed of the above-mentioned metal layers, or formed by supporting these metals on a catalyst carrier. The catalyst layer is arranged at right angles to the diffusion direction of these gases in order to generate water by contacting hydrogen gas and oxygen gas diffusing in the solid polymer electrolyte membrane as much as possible. Is desirable. In particular,
A solid polymer electrolyte membrane having a catalyst layer formed by applying catalyst metal particles to a predetermined thickness on one side and a solid polymer electrolyte membrane having no catalyst layer are stacked with the catalyst layer interposed therebetween and hot-pressed. After forming a catalyst layer by applying a predetermined thickness to one side of the solid polymer electrolyte membrane, applying heat and fusing it to form a catalyst layer, The solid polymer electrolyte solution may be formed by applying a predetermined thickness and heating and fusing it.

As the anode, for example, lead dioxide is used as a catalyst electrode. This lead dioxide contains α-
There are lead dioxide and β-lead dioxide, and β-lead dioxide has higher ozone generation ability due to higher activity, but is not limited thereto. The anode is formed, for example, by directly applying a powder of lead dioxide to a Nafion (trade name of DuPont) solution onto a solid polymer electrolyte membrane and drying it, or forming lead dioxide on a platinum-plated titanium mesh. It can be formed by electrodeposition or coating.

Further, the solid polymer electrolyte membrane includes Nafion (trade name of DuPont), Flemion (trade name of Asahi Glass Co., Ltd.), and Aciplex (trade name of Asahi Kasei Co., Ltd.), which are fluororesins having sulfonic acid groups. , Gore Select (trade name of Japan Gore-Tex Corporation) and the like can be used. Still further, as the cathode, a catalyst electrode in which a catalyst in which platinum black, platinum fine particles and the like are supported on the surface of a carbon particle carrier is applied to a conductive substrate such as a porous carbon sheet can be used.

[0012]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is an explanatory view showing an ozone water producing apparatus using a water electrolysis ozonizer according to the present invention, FIG. 2 is an exploded view of the water electrolysis ozonizer, FIG.
FIG. 4 is an explanatory diagram showing a chemical change in a water electrolysis type ozonizer.

The ozone water production apparatus 1 shown in FIG. 1 has an ozone water generation chamber 4 into which water is supplied through a water electrolysis type ozonizer 3 and a processing air supply chamber 5 into which outside air is introduced, via a water electrolysis type ozonizer 3. And ozone water generation room 4
The processing air supply chamber 5 is provided with an outside air inlet 5in for introducing outside air and an exhaust port 5out for discharging air from the supply chamber 5.

The water electrolysis type ozonizer 3 includes an anode 6 for electrolyzing water supplied to the ozone water generation chamber 4 into oxygen, ozone and hydrogen ions, and a cathode for reducing hydrogen ions generated by the anode 6 to hydrogen. 7, a solid polymer electrolyte membrane having an anode ion-selective permeability, which serves as a hydrogen ion exchange membrane.
And a catalyst layer 9 for converting oxygen diffused from the anode 6 side and hydrogen diffused from the cathode 7 side into water in the solid polymer electrolyte membrane 8. Is formed.

The anode 6 includes a catalyst electrode 6a formed on the surface of the polymer electrolyte membrane 8, and a collector electrode 6b for applying a positive DC voltage to the catalyst electrode 6a. Catalyst electrode 6a
Is mixed with an aqueous solution of 5% Nafion (trade name of DuPont) at twice the weight ratio of α-lead dioxide, and the mixture is applied to one surface of a 50 μm thick Nafion membrane 8A constituting the solid polymer electrolyte membrane 8. It was applied and dried to form α-lead dioxide at a concentration of 4 mg / cm ² per unit area. Note that the collector electrode 6b is formed in a sheet shape by electroplating 1 μm thick platinum on a 50 μm thick titanium mesh sheet.

The thickness 5 constituting the solid polymer electrolyte membrane 8
On one surface of another Nafion membrane 8B having a thickness of 0 μm, a mixture of a platinum-supported carbon catalyst carrying 30% of platinum in a 5% aqueous solution of Nafion (trade name of DuPont) twice as much as the weight ratio was applied and dried. The platinum loading amount is 0.3mg
/ Cm ² , the catalyst layer 9 is formed.

The cathode 7 has a thickness of 30% in a solution obtained by diluting a 30% aqueous solution of Teflon (trade name) dispersion.
A porous conductive base material 7a made of a 0.3 mm porous carbon sheet is immersed and fused by heating at 350 ° C. to perform a water-repellent treatment. Next, a catalyst paste containing a mixture of carbon catalyst particles carrying 30% of platinum and a small amount of Teflon dispersion, a thickener, isopropyl alcohol, etc. is applied to one or both surfaces of the conductive substrate by screen printing or the like and dried. After that, the resultant was heated and fused at 350 ° C. to form a catalyst electrode having the catalyst layers 7b and 7b formed thereon, and further impregnated with a 5% Nafion aqueous solution and dried. did.

A Nafion film 8 having a collector electrode 6 b of the anode 6 and a catalyst electrode 6 a constituting the anode 6 on one side is formed.
A, and Nafion membrane 8B forming the catalyst layer 9 on one side, a cathode 7 are stacked, 160 ° C., 2 at a pressure of 50 kg / cm ²
By hot pressing for minutes, a water electrolysis type ozonizer 3 was formed. Reference numeral 10 denotes a DC power supply that supplies a predetermined DC voltage between the anode 6 and the cathode 7.

The above is an example of the configuration of the present invention, and its operation will be described below. FIG. 3 is an explanatory view schematically showing a chemical change in the water electrolysis type ozonizer 3. When a predetermined voltage is applied between the anode 6 and the cathode 7, water as a raw material is supplied to the ozone water generation chamber 4. In the anode 6, water (H ₂ O)
Is electrolyzed into oxygen (O ₂ ), ozone (O ₃ ), and hydrogen ions (H ⁺ ). Then, part of the oxygen (O ₂ ) and ozone (O ₃ ) generated by the electrolysis is released to the ozone water generation chamber 4, dissolved in the water in the generation chamber 4 to generate ozone water, and the rest is solid It diffuses in the polymer electrolyte membrane 8 toward the cathode 7.

On the other hand, hydrogen ions (H
⁺ ) Passes through the solid polymer electrolyte membrane 8, passes through the catalyst layer 9, and reaches the cathode 7, receives electrons, and combines them into hydrogen gas (H ₂ ). And
Part of the hydrogen (H ₂ ) is oxidized by oxygen (O ₂ ) contained in the outside air by the action of the catalyst supported on the cathode 7, and is released to the outside as water vapor (H ₂ O). The hydrogen (H ₂ ) that has not been completely oxidized diffuses in the solid polymer electrolyte membrane 8 toward the anode 6.

In the catalyst layer 9 formed in the solid polymer electrolyte membrane 8, oxygen (O ₂ ) and ozone (O ₃ ) diffuse from the anode 6 side, and diffuse from the cathode 7 side. Hydrogen (H ₂ ) reacts and changes to water (H ₂ O), and moves inside the solid polymer electrolyte membrane 8 toward a lower humidity. For example, when the humidity of the Nafion membrane 8B on the cathode 7 side of the solid polymer electrolyte membrane 8 is lower, water vapor (H ₂ O)
Moves to the cathode 7 side and is discharged to the processing air supply chamber 5.

In this example, when a DC voltage of 3 V was applied between the anode 6 and the cathode 7, generation of 0.1 mg / hr / cm ² of ozone was confirmed. Further, the water electrolysis type ozonizer according to the present invention having an effective membrane area of 6 cm ² was placed in a stainless steel reaction vessel 2 having a volume of 40 liters, and was continuously driven at room temperature. And the ozone concentration hardly decreased even after 12,000 hours had passed.

The anode 6 is not limited to α-lead dioxide, but may be β-lead dioxide. Further, the catalyst layer 9 is not limited to the case of using platinum, and may be formed by using one or more metals among platinum, palladium, rhodium, ruthenium, and iridium. Furthermore, if the cathode 7 is formed on the catalyst electrode, the hydrogen generated at the cathode 7 is immediately oxidized to water, so that no hydrogen is released into the processing air supply chamber 5. Therefore, a gas mixture of hydrogen and air which may cause an explosion is not generated, and there is no need to provide a separate hydrogen treatment device.

[0024]

COMPARATIVE EXAMPLE As shown in FIG.
6, a 100 μm-thick solid polymer electrolyte membrane 27 was sandwiched therebetween, and ozone was generated by a conventional water electrolysis type ozonizer 22 having no catalyst layer formed in the solid polymer electrolyte membrane 27. Initially, the amount of generated ozone and the ozone concentration in the reaction vessel 21 were the same as those of the water electrolysis ozonizer 3 according to the present invention shown in FIG. 1, but when continuously driven at room temperature, the ozone after 4000 hours had passed. The concentration dropped to less than half of the initial concentration. This indicates that the water electrolysis ozonizer 3 of the present invention has a sufficiently longer life than the conventional ozonizer 22.

[0025]

As described above, according to the present invention, the hydrogen diffused from the cathode into the solid polymer electrolyte membrane,
A catalyst layer is formed that reacts oxygen and ozone diffused from the anode into water by reacting it.Hydrogen generated at the cathode changes into water at the catalyst layer and does not reach the anode as it is. Is not reduced by hydrogen, and therefore has an excellent effect that the amount of generated ozone can be maintained in the initial drive state even when the apparatus is continuously operated for a long time.

[Brief description of the drawings]

FIG. 1 is a diagram showing an ozone water producing apparatus using a water electrolysis type ozonizer of the present invention.

FIG. 2 is an exploded view of the water electrolysis type ozonizer.

FIG. 3 is a schematic diagram showing a chemical change in a water electrolysis type ozonizer.

FIG. 4 is an explanatory view showing a conventional water electrolysis ozonizer.

FIG. 5 is a schematic diagram showing a chemical change in a conventional water electrolysis ozonizer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ozone water production apparatus 3 ... Water electrolysis-type ozonizer 6 ... Anode 6a ... Catalyst electrode 6b ... Collector electrode 7 ... Cathode 7a ... Porous conductive base material 7b ... Catalyst layer 8 solid polymer electrolyte membrane 9 catalyst layer 10 DC power supply

Continued on the front page (72) Inventor Miyuki Imaizumi 193-1-1, Hamakawashinda, Oto-cho, Ogasa-gun, Shizuoka Prefecture Inside of Optic Didi Melco Laboratory Co., Ltd. (72) Inventor Tokushi Yokomatsu Ogasa-gun, Shizuoka Prefecture 193-1 Higashicho Hamakawa Nitta Inside Optec Didi Melco Laboratory Co., Ltd. (72) Inventor Kenro Mitsuda 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation

Claims (6)

[Claims] An anode (6) for electrolyzing water as a raw material into ozone, oxygen and hydrogen ions, and a cathode (7) for reducing hydrogen ions generated at the anode (6) to hydrogen.
In a water electrolysis type ozonizer in which a solid polymer electrolyte membrane (8) serving as a hydrogen ion exchange membrane is sandwiched, oxygen and ozone diffused from the anode (6) side are provided in the solid polymer electrolyte membrane (8). A water electrolysis type ozonizer, comprising: a catalyst layer (9) for converting water diffused from the cathode (7) side into hydrogen by reacting the same with water. 2. A water electrolysis ozonizer according to claim 1, wherein said anode (6) comprises a catalyst electrode (6a) formed of α-lead dioxide or β-lead dioxide. 3. The solid polymer electrolyte membrane (8) is formed of a fluororesin having a sulfonic acid group, and the catalyst layer (9) is formed of one or more of platinum, palladium, rhodium, ruthenium and iridium. 2. The water electrolysis ozonizer according to claim 1, wherein the water electrolysis ozonizer is formed of two or more metal layers, or formed by supporting these metals on a catalyst carrier. 4. The catalyst layer (7b), wherein the cathode (7) comprises a porous conductive substrate (7a) containing one or more metals selected from platinum, palladium, rhodium, ruthenium and iridium. The water electrolysis ozonizer according to claim 1, wherein 5. The sheet, felt or cloth formed of a sintered body of carbon fiber or granular graphite, wherein the porous conductive substrate constituting the cathode (7) is formed. Water electrolysis ozonizer. 6. The water electrolysis ozonizer according to claim 1, wherein the anode (6) and the cathode (7) are connected to a DC power supply (10) for supplying a predetermined power supply voltage.