JPH09268395A - Electrode for electrolysis and electrolytic cell using this electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for electrolysis capable of forming a high- purity electrolyte and electrolytic gas without contg. impurities and sustaining a stable electrolytic operation for a long period of time and an electrolytic cell using this electrode. SOLUTION: This electrolytic cell is constituted by installing an anode 5 consisting of an electrode base body and an electrode material of a conductive diamond structure clad on the surface of this electrode base body into an anode chamber 3. This anode contains the electrode material of the conductive diamond structure. The electrode material has high durability and does not dissolve in the electrolyte and, therefore, the electrode has a long life and forms the high-purity electrolyte and electrolytic gas suitable for washing, etc., of semiconductor devices.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for electrolysis and an electrolytic cell using the electrode, in which an electrolyte or gas produced with a long life can contain almost no impurities. For electrolysis using an electrode material having a conductive diamond structure, and ozone generation using the electrode,
The present invention relates to an electrolytic cell used for generating acidic water and alkaline water, or for electrolysis using a corrosive electrolyte or electrolytic solution.

[0002]

2. Description of the Related Art Conventionally, attempts to produce useful various substances by electrolyzing water or an electrolytic solution in which an electrolyte is dissolved have been widely made. Due to the development of these electrolysis methods, the manufacturing process of conventional products has changed significantly. For example, organic solvents, inorganic acids such as hydrofluoric acid, sulfuric acid, hydrochloric acid and nitric acid, and oxidizing agents such as ozone water and hydrogen peroxide water have been often used for cleaning semiconductor devices and liquid crystal panels during the manufacturing process. However, these chemicals are not only dangerous when used, but organic solvents may induce environmental problems such as ozone depletion, and other inorganic acids and salts require much labor and cost for wastewater treatment. There was a problem such as hanging. Further, in devices and liquid crystal panels that have been washed with these chemicals, a large amount of so-called ultrapure water must be used to remove these chemicals.

In addition to the devices and panels described above, in the medical and food industries, a large amount of detergent must be used for sterilization and cleaning, and they must also be washed off with a large amount of water. There was a problem that became. In order to solve these problems, recently, by electrolyzing water or water containing a trace amount of hydrochloric acid, salt, or a salt such as ammonium chloride in an electrolytic cell partitioned by a diaphragm into an anode chamber and a cathode chamber, From the redox potential (OR
An aqueous solution having a high P), that is, an extremely strong oxidizing property and a slight acidity, and an aqueous solution having a low ORP, that is, a highly reducing property and a slightly basic property, are produced from the cathode chamber. It is used for cleaning of.

When a slight amount of salt is added to the electrolytic solution to carry out electrolysis, acidic water having a strong bactericidal action is obtained, and the bactericidal action of the acidic water is used in the field of food production and medical treatment.
The ORP of this acidic water is high, and it is pointed out that this high ORP is because chlorine ions in the liquid are converted into hypochlorous acid, and the hypochlorous acid may induce the formation of organic chloride. Yes, and the possibility is very low, but the possibility of secondary pollution was not complete. There is a similar possibility when the acidic water is used for cleaning semiconductor devices and liquid crystal panels. In such electrolysis, a platinum-coated titanium electrode is usually used, and its consumption rate is about 1 to 10 μg / AH. When used in an electrolyte, it is typically 1 to 10 ppb.
Some platinum will be dissolved and mixed in. An oxide electrode such as iridium oxide is also used when preparing a hypochlorous acid aqueous solution of about 100 ppm, but this also consumes about 1/10 of platinum.

This amount of dissolved metal does not pose a problem in food and medical use, but is sufficiently high in semiconductor cleaning, and its removal becomes a serious problem. The present inventors have succeeded in reducing the consumption of the electrode material to about 1/10 by using an ion exchange membrane as the solid electrolyte and adhering the electrode to the membrane for electrolysis, but still in the liquid. The problem itself is that the metal that becomes conductive when dissolved is slightly eluted. The use of ozone water is being considered to avoid these problems. Ozone is widely used as a strong oxidant in various fields such as the above-mentioned water treatment for cleaning semiconductor devices and liquid crystal panels, medical treatment and food industry. This ozone is mainly produced by an electrolysis method that can be produced at a high concentration, and ozone is produced efficiently by developing the material of the electrodes and the electrolysis conditions (S.
Stucki et al., [Journal of Electrochemical Soc., Vol.13
2, No2, p3382- (1985)], U.S. Pat.No. 4,541,98.
No. 9, Japanese Patent Publication No. 2-44908). However, even in this electrolytic ozone production, when a metal electrode is used, the metal is eluted as the electrolysis progresses, and the carbon electrode has the same drawbacks as described above that it is not suitable for long-term operation because of heavy consumption.

In order to avoid mixing of metal, the electrode may be made of a non-metal type, and carbon can be used as the non-metal. Since the carbon electrode is usually porous, it tends to be broken or dissolved as the electrolysis progresses, and when it is used as an anode, a part of it is oxidized into carbon dioxide gas, which causes rapid consumption. Even when it is used as a cathode, although it does not volatilize as carbon dioxide gas, there is a problem that bubbles of hydrogen generated are smaller than oxygen on the anode side and the destruction of the electrode easily proceeds. There is a problem that a large current cannot be passed in order to prevent the progress of the breakdown, and thus a large ORP cannot be obtained.

In addition to the electrodes used for the production of acidic water or alkaline water by electrolysis and the production of ozone by electrolysis described above, there are electrodes used in a corrosive atmosphere such as salt electrolysis. These electrodes, especially the anode, are so-called valve metal surfaces mainly composed of titanium, and the product name is DSE or DSA in which an electrode material containing a platinum group metal oxide such as ruthenium oxide is coated on the surface of the valve metal.
Entering the age of metal electrodes from the practical application of. This DSE was first put into practical use for electrolysis of salt, and now most of the electrodes for electrolysis of salt are replaced with the DSE in the world. In the field of high-speed industrial plating, which involves oxygen generation, the DS
Since E is stable and does not deform, it can be used with a small distance between the electrodes and has a small overvoltage, and it has little possibility of causing environmental pollution. Widely used. In addition to these uses, wastewater treatment by COD removal,
The above D also applies to the synthesis of organic or inorganic compounds by electrolytic oxidation.
SE is used.

In these applications, the DSE can achieve a remarkable improvement in electrolysis efficiency due to its characteristics, but on the contrary, it also has drawbacks due to its characteristics. That is, the DSE uses a corrosion-resistant valve metal base, and the valve metal base does not corrode many electrolytes and functions stably, but is sufficiently stable for some substances. May not be indicated. The DSE is usually produced by a thermal decomposition method, and often the electrode surface that is decomposed and adheres to the surface of the substrate does not completely cover the surface of the substrate, so that the electrolytic solution may contact the metal of the substrate through the electrode substance to cause a reaction. Therefore, the elution of the substrate cannot be suppressed sufficiently. For example, when the DSE is installed as an anode in an electrolytic bath filled with an organic compound such as methyl alcohol or ethyl alcohol and an electric field is applied, titanium as a base metal is corroded, and a phenomenon in which an electrode substance is separated occurs, It is also known that when halogens such as fluorine and bromine are included, anodic polarization is caused to cause so-called pitting corrosion and active dissolution, resulting in extremely shortened electrode life.

As a countermeasure against this, it has been partially practiced to use niobium or tantalum, which has a higher corrosion resistance than titanium, as the base metal even with the same valve metal. However, these metals are extremely expensive, difficult to process, the surface is very easily oxidized, and the surface oxide is easily separated from the metal. Therefore, DSE produced by forming an electrode substance on the surface by thermal decomposition is manufactured. However, the processing conditions are greatly limited, and the range of use is extremely limited under the present circumstances. D
SE is excellent in terms of energy saving, the overvoltage of chlorine generation is almost zero, and the overvoltage of oxygen generation is 500 mV or less. When turned upside down, chlorine and oxygen are likely to be generated, but the low electrolysis voltage means that reactivity with respect to electrolytic oxidation or decomposition reaction due to electrolysis with respect to a specific substance is weak. Actual DS
There are few examples in which E is practically used for anodization.

A part of the platinum-plated electrode is used as a countermeasure for this, but there are problems that it is extremely expensive and its life is not always sufficient. In addition to this, lead oxide electrodes, which have almost no wear and are excellent in oxidizing power, are also used depending on the conditions, but it is necessary to always be positively polarized in the electrolytic solution, and there is a problem in maintenance. It has the drawback that it does not always exhibit good durability in solution. Furthermore, there is a tin oxide electrode as a high overvoltage electrode for decomposing an organic compound, and since the electrode has an extremely high oxygen generation overvoltage, it is possible to decompose an organic compound by anodic oxidation in an aqueous solution, and particularly the decomposition of a benzene nucleus. It is reported to be suitable for. However, tin oxide itself has problems that the electrical conductivity is relatively small and a large current density cannot be obtained, and that it is difficult to set a metal as a core material because it is manufactured by a sintering method.

In recent years, diamond having conductivity has been developed. Diamond has thermal conductivity, optical transparency,
It is highly promising as a semiconductor device and an energy conversion element because it has excellent durability against high temperatures and oxidation, and in particular, its electrical conductivity can be controlled by doping. However, there is almost no report as an electrode for electrolysis. Swain et al. Reported the stability of diamond in acidic electrolyte [Journal of Electrochemical Soc., Vol.
1, 3382- (1994)], suggesting that it is far superior to other carbon materials. Fujishima et al., 5.5 eV
This paper reports on the application to the electrode for reduction reaction, focusing on the size of the band gap [Journal of Electroana
Lytical Chem., Vol. 396, 233- (1995), and Electrochemistry, Vol. 60, No. 7, 659- (1992)]. There is also a report on a humidity sensor that utilizes the surface resistance of diamond changing with humidity [Electrical Theory, Vol. 114, No. 5, 41].
3 ~, 1994]. However, there has not been reported any industrial use in a high potential region where oxygen generation or chlorine generation can occur when the current density is high.

[0012]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, does not elute the electrode substance into the electrolytic solution, and has excellent durability, and an electrode for electrolysis and an electrode for various electrolysis. It aims at providing the electrolytic cell which uses.

[0013]

The electrode for electrolysis according to the present invention is an electrode for electrolysis comprising an electrode substrate and an electrode material having a conductive diamond structure coated on the surface of the electrode substrate. Yes, the electrode substrate is made of valve metal,
An intermediate layer may be formed between the electrode substrate and the electrode material having the conductive diamond structure. The electrolytic cell of the present invention has two chambers, an anode chamber and a cathode chamber, which are partitioned by an ion exchange membrane, or an electrolytic cell having three chambers, an anode chamber, an intermediate chamber and a cathode chamber, which are accommodated in the anode chamber. At least one of the anode accommodated in the cathode chamber and the cathode housed in the cathode chamber is an electrode comprising an electrode substrate and an electrode material having a conductive diamond structure coated on the surface of the electrode substrate. An electrode base made of a valve metal, an intermediate layer containing carbide and / or silicon carbide of a valve metal coated on the surface of the electrode base, and an electrode material having a conductive diamond structure coated on the surface of the intermediate layer. You may replace it.

Hereinafter, the present invention will be described in detail. The electrode for electrolysis according to the present invention and the electrolytic cell using the electrode can be widely used for various electrolysis, and particularly, the mixing of impurities into the electrolytic solution (acidic water, alkaline water, or ozone water) or the generated gas. Electrolysis using a corrosive electrolyte solution for cleaning semiconductor devices and liquid crystal panels that are extremely disliked, and when electrolysis is performed using conventional electrodes, the electrodes are consumed in a relatively short time and cannot continue electrolysis. It can be preferably used as an application. In the present invention, an electrode material having a conductive diamond structure is used. Examples of the electrode material having the conductive diamond structure include diamond made conductive by doping impurities such as boron, phosphorus and graphite, or a composite material of diamond and amorphous boron oxide (DLN, diamond nano
o composite) and silicon carbide. Note that it is not necessary to add graphite alone to add graphite. For example, when diamond is obtained by the CVD method described later, the amount of hydrogen as an atmospheric gas is adjusted, and the temperature is slightly changed. Graphite can coexist in diamond.

This electrode material is coated on the electrode substrate in the same manner as in the prior art to form an electrode. The electrode material is preferably fine particles having a particle size of 0.01 to 1 μm, and the coating thickness on the substrate is about 1 to prevent the infiltration of the electrolytic solution into the substrate.
The thickness is preferably 0.1 to 50 μm, and particularly preferably 1 to 10 μm. When diamond is used as the electrode material, it is almost impossible to use ground natural diamond because it needs conductivity, and since it is very expensive, use synthetic diamond obtained by reducing an organic compound. Is desirable. This synthetic diamond can be synthesized by thermal CVD (chemical vapor deposition) in which an organic compound such as methyl alcohol, ethyl alcohol, or acetone, which is a carbon source, is decomposed by heating in a reducing atmosphere such as hydrogen gas.
Other methods such as physical vapor deposition (PVD) or plasma CVD may be used, but CVD with a significantly high film formation rate is possible.
It is desirable to use The heating is usually carried out by bringing the vapor of the organic compound into contact with a heated filament, and the filament temperature is preferably 1800 to 2400 ° C., although it depends on the capacity and processing speed of the apparatus. The substrate temperature reaches 750-950 ° C. It is desirable that the concentration of the organic compound gas with respect to hydrogen is 0.1 to 10% by volume, the total gas flow rate is 10 to 1000 ml / min, and the pressure is atmospheric pressure.

Since synthetic diamond as an electrode material is used by coating it on a substrate, it is desirable that the synthetic diamond produced by the reduction operation be directly attached to the surface of the electrode substrate without isolation. Since diamond alone does not have conductivity, impurities are usually mixed in the organic compound as a raw material and adhered to the substrate together with the organic compound to obtain a diamond having good conductivity. As the impurities, it is possible to use a simple substance composed of an element having a different valence from carbon or a compound containing the same, such as powdered boric acid (boron oxide) or phosphorus pentoxide. In addition to this, diborane (B ₂ H ₆ ) and phosphine (PH ₃ ) can be used as the impurities, but it is preferable to use the powdered boric acid and diphosphorus pentoxide because they have high toxicity. The content of the impurities is preferably 1 to 10000 ppm, more preferably 100 to 1000 ppm. Resistivity is 100 to 0.1 Ωcm
It can be controlled within the range.

Silicon carbide and titanium carbide having a diamond structure other than diamond are also CVs like diamond.
It can be deposited on the substrate by using D or PVD. For the deposition, it is desirable to use a plasma spraying method which can be deposited as conductive particles and whose electric conductivity is further increased by exposing to high temperature. . When the plasma spraying method is used, it is necessary to form a thicker coating than that of the CDV method in order to completely cover the base metal, and in the case of titanium carbide, the thickness is 10 to 20 μm. It may be other than. Silicon carbide has the advantages that it is inexpensive, has high conductivity, and is effective for electrolysis in a halogen-containing bath, and its coating thickness is preferably about 50 to 200 μm.

The substrate may also serve as a current collector, and its material is titanium, niobium, tantalum, silicon, carbon, nickel tungsten carbide, etc., and these are wire mesh, powder sintered body, metal fiber sintered body. Etc. are used after processing. When electrolyzing an electrolytic solution containing a corrosive component, unlike in the case of electrolyzing pure water, the electrode substance is eluted although it is slightly addressed from a microscopic point of view. Considering the stability of the substrate in this case, in the case of electrolysis of corrosive components, it is desirable to use niobium or tantalum having strong corrosion resistance as the substrate. The surface of the substrate is coated with an electrode material having a conductive diamond structure directly or through an intermediate layer, but in order to improve the adhesion between the electrode material having the intermediate layer or the conductive diamond structure and the substrate and to reduce the substantial current density. For this reason, it is preferable to roughen the surface of the substrate.When using it under high current density conditions, use a # 20 alumina grid to roughen the surface to a relatively low current density under corrosive conditions. When used under # 60 ~
It is desirable to improve the adhesion of the coating by roughening the surface with a fine alumina sand of about 120.

The intermediate layer is for more firmly bonding the substrate and the electrode material having the conductive diamond structure, and the intermediate layer has an affinity for both the substrate metal and the electrode material having the conductive diamond structure. Is desirable,
Its thickness is about 1 to 10 μm. For example, when the base metal is titanium, if titanium carbide is used as the intermediate layer, the titanium of the base metal and the titanium carbide of the intermediate layer show affinity, and since the titanium carbide and diamond have a common element of carbon, Since the titanium carbide has a diamond structure, the affinity between the intermediate layer and the electrode material having a conductive diamond structure is further improved, giving a strong bonding force and excellent durability. In order to improve the conductivity of titanium carbide, it is also possible to immerse the titanium carbide powder in a boric acid aqueous solution in advance to form a coating film of boric acid on the surface and then perform plasma spraying. It is incorporated into the titanium carbide structure to improve conductivity.

The electrode thus produced has a high electrode potential and excellent durability and can be used as either an anode or a cathode. For example, the cleaning liquid is acidic water produced in the anode chamber. Since it is desirable to be present, it is particularly preferable to use it as an anode. When this electrode is used as an anode, if an oxygen reduction electrode is used as the counter cathode, the generation of hydrogen generated by a normal cathode reaction is suppressed, and therefore the generated hydrogen does not diffuse to the anode chamber side. When incorporating such an electrode into an electrolytic cell, an ion exchange membrane is used to divide the electrolytic cell into two chambers, an anode chamber and a cathode chamber, or three chambers, an anode chamber, an intermediate chamber and a cathode chamber. It is installed in at least one of the anode chamber and the cathode chamber. The ion exchange membrane may use either a fluororesin type or a hydrocarbon resin type, but the former is preferable from the viewpoint of corrosion resistance. The ion exchange membrane has a function of preventing each ion generated at the anode and the cathode from being consumed at the counter electrode, and has a function of promptly promoting electrolysis when the conductivity of the liquid is low.

When the electrode is used as a gas electrode in a two-chamber electrolytic cell, a cathode chamber may be provided between the ion exchange membrane and the cathode, and an anode chamber may be provided between the anode and the ion exchange membrane. Good, but when the liquid conductivity is low, the cell voltage rises, the cell structure becomes complicated, and gas-liquid separation at each electrode is required. Therefore, the structure in which the electrode is bonded to the ion exchange membrane is adopted. Is most desirable. In this case, the anode chamber is substantially a gas chamber, while the cathode chamber is in a gas-liquid mixed state. The material of the electrolytic cell varies depending on the electrolytic solution used, the gas to be produced, etc., but from the viewpoint of durability and stability, the glass lining material, carbon, a high corrosion resistant intermediate layer, stainless steel and P
It is preferable to use TFE resin or the like. When it is desirable to bring the electrode and the ion exchange membrane into close contact with each other, they may be mechanically coupled in advance, or pressure may be applied during electrolysis. The pressure at this time is preferably 0.1 to 30 kgf / cm ² .

The electrolysis conditions vary depending on the electrolytic solution used, but it is preferable that the temperature is 5 to 40 ° C. and the current density is 1 to 500 A / dm ² . The electrode for electrolysis according to the present invention and the electrolytic cell using the electrode can be applied to a wide range of applications including production of acidic water and alkaline water, production of ozone water, electrolysis of corrosive electrolytic solution, and the like, as described above. When water is electrolyzed by adding chlorine to the anode chamber, hypochlorous acid is generated in the anode chamber, and the hypochlorous acid makes the liquid acidic and acidic water is generated. On the other hand, in the cathode chamber, weak alkaline water is generated by ordinary water electrolysis. When the above-mentioned conductive diamond structure electrode material is used as the anode material in this electrolysis, the electrode material does not elute even if electrolysis is continued for a long period of time, and therefore the obtained acidic water has no metal contamination and is of extremely high purity. Acidic water is obtained, and this acidic water is optimal as water for cleaning semiconductor devices.

When pure water is supplied to the anode chamber for electrolysis,
Ozone is produced according to the formula. 3H ₂ 0 → O ₃ + 6H ⁺ + 6e When the electrode material having the conductive diamond structure is used as the anode material also in the case of ozone generation, the electrode material does not mix with ozone to be produced, and the purity is very high. Ozone gas and ozone water can be obtained. Further, industrial electrolysis may require electrolysis of an electrolytic solution containing corrosive components such as fluorine, bromine and iodine. If a conventional DSE is used for electrolysis of an electrolytic solution containing such a corrosive component, it will not cause much trouble if it is a short-term electrolysis, but if it is a long-term electrolysis, the DSE is consumed and stable electrolysis is continued. become unable. On the other hand, in the electrode for electrolysis of the present invention, since the electrode material having the conductive diamond structure is used, the durability in the electrolytic solution having the corrosive component is much larger than that of DSE, and the long-term stability is stable. It enables the electrolysis operation.

Next, an electrode for electrolysis according to the present invention and an electrolytic cell using the electrode will be illustrated with reference to the accompanying drawings. FIG.
Is a schematic vertical sectional view showing an example of a two-chamber electrolytic cell according to the present invention, FIG. 2 is a schematic vertical sectional view showing an example of a three-chamber electrolytic cell, and FIG. 3 is an example of another two-chamber electrolytic cell. It is a schematic longitudinal cross-sectional view shown. In FIG. 1, a two-chamber type electrolytic cell 1 is divided into an anode chamber 3 and a cathode chamber 4 by an ion exchange membrane 2, and an anode 5 made of an electrode material having a conductive diamond structure is disposed on the side of the anode chamber 3 of the ion exchange membrane 2. However, the porous cathode 6 made of, for example, a metal mesh is in close contact with the cathode chamber 4 side. A pure water or salt solution supply port 7 and an acidic water outlet 8 are provided on the bottom and top of the anode chamber 3, and a pure water supply port 9 and an alkaline water outlet 10 are provided on the bottom and top of the cathode chamber 4. ing. Note that 11 is a packing between the ion exchange membrane 2 and the peripheral portion.

In FIG. 2, the three-chamber electrolytic cell 21 is divided into an anode chamber 23 and an intermediate chamber 24 by a cation exchange membrane 22 and a intermediate chamber 24 and a cathode chamber 26 by a cation exchange membrane 25. . An anode 27 made of an electrode material having a conductive diamond structure is adhered to the anode chamber 23 side of the cation exchange membrane 22, and a porous cathode 28 is adhered to the cathode chamber 26 side of the cation exchange membrane 25. . Pure water supply ports are provided on the bottom surface and the top surface of the anode chamber 23.
29 and an acidic water outlet 30, a salt solution supply port 31 such as ammonium chloride and a salt solution outlet on the bottom surface and the upper surface of the intermediate chamber 24.
On the bottom surface and the upper surface of the cathode chamber 26, a pure water supply port 33 and an alkaline water outlet 34 are installed, respectively. Reference numeral 35 is a packing between the ion exchange membranes 22 and 25 and the peripheral portion.

In FIG. 3, a two-chamber type electrolytic cell 41 is divided into an anode chamber 44 and a cathode chamber 45 by an ion exchange membrane 43 installed in a small-diameter connecting portion 42, and the ion exchange is performed in the anode chamber 44. An anode 46 made of an electrode material having a conductive diamond structure is suspended from the membrane 43, and a porous cathode 47 made of, for example, a metal mesh is also suspended from the ion exchange membrane on the cathode chamber 45 side. ing. Formed gas outlets 48, 49 are provided on the upper surfaces of the anode chamber 44 and the cathode chamber 45, respectively.

In both of the electrolytic cells 1 and 21 shown in FIGS. 1 and 2, pure water or a salt solution supply port 7 or a salt solution supply port 31 is used to supply pure water or a salt solution such as an ammonium chloride aqueous solution or sulfuric acid. When electricity is applied between the electrodes 5, 6 and 27, 28, acidic water is produced in the anode chamber, alkaline water is produced in the cathode chamber, and at least in the anode chamber, there is no elution of the diamond, so that it is produced without containing a metal component. In addition, in the electrolytic cell 41 of FIG.
By filling the inside of the cathode chamber 45 with the electrolytic solution and energizing the electrodes 46 and 47, a predetermined product gas is generated. Also in this case, since at least one of the electrodes has an electrode material having a conductive diamond structure and the diamond is not eluted, an electrolytic solution or gas containing no impurities can be obtained.

[0028]

EXAMPLES Next, examples of the electrode for electrolysis according to the present invention and the electrolytic cell using the electrode will be described, but the examples do not limit the present invention.

[0029]

Example 1 2 mm thick porous graphite plate (base)
And a device for producing a conductive diamond structure by the thermal CVD method shown in FIG. 4 using ethyl alcohol as a raw material.
51 was used to form a diamond layer thin film having a thickness of 10 μm (electrode area: 1 cm ² ). In other words, while keeping the pressure in the chamber constant, the vapor of ethyl alcohol, which is the reaction material gas in which a trace amount of powdered boric acid (boron oxide), which is an impurity for imparting conductivity, is dissolved, and the atmosphere is kept reducing. Hydrogen gas for selectively forming only diamond was introduced through the reaction raw material gas raw material introduction port 52 and the hydrogen gas introduction port 53 by the following processes. The introduced steam is decomposed by the heated tungsten filament 54, and the substrate 57 is placed on the molybdenum cover 56 on the substrate holder 55 directly below the filament 54 (interval 3 cm).
Diamond, which is a decomposition product of the ethyl alcohol, was deposited on the surface. In addition, the temperature of the substrate is 700
Maintained at ~ 750 ° C.

The diamond layer was evaluated by electron microscopy and Raman spectroscopy. The surface of the diamond layer was polycrystalline, but no change in morphology due to the addition of impurities was observed. The lattice spacing calculated by electron diffraction was almost the same as the value reported by JCPDS card Diamond. In Raman spectroscopic analysis, a sharp peak of diamond around 1332 cm ^-1, although those Matahi amorphous was observed near 1550 cm ^-1, the latter peak intensity was minimal.
It was confirmed by the above analysis that the thin film formed had polycrystalline diamond.

The cation-exchange membrane Nafion 117 (manufactured by DuPont) was adhered to one side of the porous carbon plate with the diamond thus prepared as an anode, and one side of the cation-exchange membrane Nafion 350 (manufactured by DuPont). Then, a nickel porous cathode supporting a ruthenium oxide catalyst was adhered, and both cation exchange membranes were placed in the electrolytic cell so that the distance between the membranes was 3 mm with the anode and the cathode facing outward. The intermediate chamber formed between both cation exchange membranes was filled with Nafion resin particles (NR50), and both cation exchange membranes were clamped from the outside to form an electrolytic cell as shown in FIG. Pure water at 1 cc / min in the anode chamber and pure water in the intermediate chamber
Electrolysis was performed at a temperature of 20 ° C. and a current of 1 A while supplying pure water to the cathode chamber at 10 cc / min and 3 cc / min. The cell voltage was 9.5 V, and the ozone concentration was 0.5 mg / min from the anode chamber outlet.
In liters, acidic water with an ORP of 1000 mV was obtained.

[0032]

Example 2 A diamond layer containing boron having a thickness of 10 μm was formed by thermal CVD on a porous metal plate composed of a titanium mesh having an electrode area of 1 cm ² and a thickness of 1 mm to form an anode. As the cathode, a graphite porous electrode similarly formed with a diamond layer was used. Tighten the whole so that the anode and the cation exchange membrane Nafion 117 are in close contact with each other,
The electrolytic cell of FIG. 1 was constructed. Electrolysis was performed at a temperature of 20 ° C. and a current of 1 A while supplying 30 g / liter of hydrochloric acid aqueous solution at 10 cc / min to the anode chamber and deionized water at 3 cc / min to the cathode chamber. V, the effective chlorine concentration from the anode chamber outlet is 0.5 mg / liter, the pH is 2.5, and the ORP
An acidic water of 1200 mV was obtained.

[0033]

Example 3 The same electrolytic cell as in Example 2 was used, 30 g / liter of hydrochloric acid aqueous solution was supplied to the anode chamber at 10 cc / min, and oxygen gas from an oxygen cylinder was supplied to the cathode chamber at 50 ml / min. When electrolysis was performed at a temperature of 20 ° C and a current of 1 A while supplying, the cell voltage was 8.5 V, the effective chlorine concentration from the anode chamber outlet was 0.5 mg / liter, the pH was 2.5, and the ORP was
An acidic water of 1200 mV was obtained. On the other hand, alkaline water containing 1 g / liter of hydrogen peroxide was obtained at a current efficiency of 5% from the outlet of the cathode chamber.

[0034]

Example 4 The electrolytic cell of FIG. 1 shown in Example 2 was constructed using the anode and cathode of Example 1. When pure water was supplied to the anode chamber at a rate of 1 cc per minute, electrolysis was performed at a temperature of 20 ° C. and a current of 1 A. The cell voltage was 8.5 V, and 5% by weight of ozone gas was obtained from the outlet of the anode chamber.

[0035]

Example 5 The same electrolytic cell as in Example 4 was constructed except that a carbon paper porous electrode supporting a platinum catalyst was used as the cathode. Pure water was supplied to the anode chamber at 1 cc / min, and oxygen gas from the oxygen cylinder was supplied to the cathode chamber at 50 ml / min, and electrolysis was performed at a temperature of 20 ° C. and a current of 1 A. It was 7.5 V, and 5% by weight of ozone gas was obtained from the outlet of the anode chamber.

[0036]

Example 6 An anode was prepared by coating the surface of a titanium plate having an electrode area of 1 cm ² and a thickness of 1 mm with a diamond layer having a thickness of 10 μm in the same manner as in Example 1. A platinum plate having the same electrode area and thickness was used as the cathode. Both electrodes were placed in a P-Rex H-type electrolytic cell filled with 100 ml of 1 M sulfuric acid shown in FIG. 3, and electrolysis was performed at a temperature of 5 ° C. and a current of 1 A. The cell voltage was 10.5 V and the anode potential was Is 5V (vs
(Mercuric sulfate reference electrode), and 8% by weight of ozone gas was obtained from the outlet of the anode chamber.

[0037]

[Embodiment 7] An electrolytic cell having the same structure as in Example 6 was used except that the material was made of Teflon (registered trademark), and 100 ml of 1M sulfuric acid and 0.01M hydrofluoric acid were placed in the electrolytic cell. When filled and electrolyzed at a temperature of 5 ° C. and a current of 1 A, the cell voltage was 11 V, the anode potential was about 6 V (vs mercuric sulfate reference electrode), and 12 wt% ozone gas was obtained from the anode chamber outlet. .

[0038]

Example 8 Titanium was used as a substrate, and its surface was blasted using a # 20 alumina grid at a pressure of 5 kg / cm ² . The surface roughness was JIS Ra = 10.2 μm.
Further, etching was performed in 20% by weight hydrochloric acid at 90 ° C. for 15 minutes. On the surface of the titanium substrate prepared in this way, a gas in which hydrogen is added to argon is used as an atmosphere gas and the pressure is adjusted.
A boron-doped diamond layer was coated by the same thermal CVD method as in Example 1 except that it was set at 10 ⁻³ torr. 60
A thickness of about 50 ppm containing about 1000 ppm boron by operating for about 50 minutes.
A μm diamond layer was coated and served as the anode.

Using the electrolysis cell of FIG. 3, the anode and the cathode composed of a platinum plate are placed in the electrolysis cell and placed in the electrolysis cell.
It was filled with 200 g / l of sulfuric acid and electrolyzed. temperature
The oxygen generation potential at 60 ° C was 2.44 V vs NHE, which was about 800 mV higher than that of iridium oxide-based DSE. To evaluate the consumption of this electrode due to continuous electrolysis, a current density of 200
Electrolysis was carried out at A / dm ² for 500 hours. Since the consumed amount could not be measured accurately by fluorescent X-ray, the amount was consumed by the gravimetric method, and as a result, it was found that the consumed amount was not observed within the measurement accuracy and was extremely stable.

[0040]

Example 9 The same procedure as in Example 8 was carried out except that a niobium perforated plate was used as the base metal, and the perforated plate was etched with 4% hydrofluoric acid at room temperature for 15 minutes.
A diamond layer was coated on the surface of the substrate by a thermal CVD method to form an anode. The coating thickness was about 10 μm. 2 this anode
One of the cation exchange membranes was placed in close contact with the other in the anode chamber of a three-chamber type electrolytic cell partitioned by one cation exchange membrane.
On the cathode chamber side, carbon paper as a cathode was placed in close contact with the other cation exchange membrane. The anode chamber was filled with pure water, and the intermediate chamber was filled with iodine solution. When an electric field was applied between both electrodes, oxygen gas was obtained from the anode chamber and hydrogen iodide solution was obtained from the cathode chamber. Electrolysis was continued for 1000 hours at a current density of 5 A / dm ² , but there was no change in the electrodes.

[0041]

[Comparative Example 1] When electrolysis was continued under the same conditions as in Example 9 except that a normal DSE obtained by coating ruthenium oxide on a titanium substrate was used as an anode, corrosion of the electrode was observed in about 3 hours from the start of electrolysis. It started and became unusable after 5 hours. It is considered that this is because iodine that has permeated the cation exchange membrane corroded titanium.

[0042]

Example 10 Titanium was used as the base metal, and the surface thereof was blasted using a # 18 alumina grid at a pressure of 5 kg / cm ² . The substrate was pickled in 25% sulfuric acid for 3 hours. After drying, a silicon carbide powder having an average particle size of 40 μm and an electric conductivity of 1 Ωcm was plasma-sprayed on the surface of the substrate so as to have a sprayed thickness of 50 μm to obtain an anode. Using this anode and the cathode which is a platinum plate, electrolysis was carried out in 200 g / liter of saline solution. Anode potential (chlorine generation potential) is 30
1.44 V vs NHE at A / dm ² , and iridium oxide-based D
It was about 800 mV higher than SE. However, it was found that the oxygen concentration in the generated chlorine was 0.2% or less at pH 3, and the selectivity of the reaction was extremely excellent. 200 A / dm for accelerated electrolysis test
^{After 2} hours of electrolysis for 500 hours, almost no consumption was observed.

[0043]

Example 11 The same titanium substrate surface as in Example 8 was plasma sprayed with titanium carbide powder having an average particle size of about 40 μm to a thickness of about 30.
A μm intermediate layer was formed. Example 8 was applied to the surface of this intermediate layer.
Under the same conditions as above, a diamond layer having a thickness of about 30 μm was coated to form an anode. Using this anode and the cathode, which is a platinum plate,
Temperature of 60 ℃, current density 100 A / dm ^{2 in} 3% aqueous bromic acid solution
Electrolysis was carried out at 500 ° C. After the electrolysis, the electrode was not consumed and titanium was not corroded.

[0044]

[Comparative Example 2] Example except that a normal DSE obtained by coating ruthenium oxide on a titanium substrate was used as an anode.
When electrolysis was performed under the same conditions as in 11, the current density was 5 A /
It was extremely stable at dm ² or less, but at high current densities of 20 A / dm ² or more, titanium was destroyed and current could not be energized in 3 to 5 hours.

[0045]

The present invention is, firstly, an electrolysis electrode comprising an electrode substrate and an electrode material having a conductive diamond structure coated on the surface of the electrode substrate.
When using an electrode having a conductive diamond structure electrode material for the electrolysis of an electrolytic solution containing water electrolysis or corrosive components,
Due to the durability of the diamond, the consumption of the electrode, that is, the elution of the electrode substance is almost eliminated, and the stable electrolysis operation can be continued for a long time. Further, since the elution of the electrode substance is eliminated, the anode obtained by the electrolysis operation can be obtained. Impurities resulting from the elution of the electrode substance are not mixed in the liquid, the catholyte and the generated gas, and a high-purity electrolytic solution or generated gas can be obtained.

The electrolytic solution produced by using the electrode according to the present invention, particularly the anolyte, has various requirements required as washing water which is required to keep the impurity content level of semiconductor devices and the like extremely low. It is provided and can be efficiently used as the cleaning water. Further, ozone gas or ozone water generated in the anode chamber by water electrolysis is also used as cleaning water or sterilization in various industries including cleaning of semiconductor devices. Expected to be minimal. Ozone gas or ozone water produced using the electrode for electrolysis according to the present invention also satisfies this requirement, and is expected to be widely used as cleaning water or sterilization.

The electrode material of the present invention is an electrode material having a conductive diamond structure, of which diamond is typical. However, since diamond is not normally conductive, impurities such as boron, phosphorus and graphite for imparting conductivity are added before or after the diamond is attached to the substrate. It is not necessary to add the graphite alone, and when obtaining diamond by the CVD method, a slight amount of graphite coexists in the diamond by adjusting the amount of hydrogen as an atmospheric gas or slightly changing the temperature. Can be made. Further, the electrode material having a conductive diamond structure may be composed of a composite material of diamond and amorphous silicon oxide which is a conductive material, in addition to mixing the above-mentioned impurities into the diamond.

The electrode material having a conductive diamond structure is
The material is not limited to diamond itself, and silicon carbide or titanium carbide having the same or similar crystal structure as diamond can also be used as the electrode material of the conductive diamond structure. The material of the electrode substrate is not particularly limited, and valve metals such as titanium, niobium, and tantalum can be used, but in the case of electrolysis of an electrolytic solution having a corrosive component, it is more expensive than inexpensive titanium, but corrosion resistance It is desirable to use niobium, tantalum, etc., which have excellent properties. The present invention is secondly
An electrode base made of a valve metal; an intermediate layer containing carbide and / or silicon carbide of a valve metal coated on the surface of the electrode base; and an electrode material having a conductive diamond structure coated on the surface of the intermediate layer. It is a featured electrode for electrolysis.
The electrode for electrolysis having this intermediate layer is advantageous when the electrolytic solution is corrosive and the electrode material is gradually consumed by electrolysis for a long period of time, and the electrolytic solution comes into contact with the substrate by the intermediate layer and To prevent elution.

Thirdly, the present invention is, in an electrolytic cell having two chambers, an anode chamber and a cathode chamber, which are partitioned by an ion exchange membrane, and at least an anode housed in the anode chamber and a cathode housed in the cathode chamber. One is an electrolyzer, which is an electrode including an electrode substrate and an electrode material having a conductive diamond structure coated on the surface of the electrode substrate. This electrolytic cell is preferably used for the production of acidic water or alkaline water, and at least one of the anode and the cathode used in the electrolytic cell has the above-mentioned conductive diamond structure electrode substance, so that it is stable. It is possible to continue the electrolysis operation for a long period of time and obtain an electrolytic solution or generated gas in which impurities resulting from elution of the electrode substance are not mixed.

The electrode of the present invention may be incorporated into an electrolytic cell having an anode chamber, an intermediate chamber and a cathode chamber to form a three-chamber type electrolytic cell. Further, the electrode having the above-mentioned intermediate layer is used as an anode and / or
Alternatively, it may be incorporated as a cathode to form an electrolytic cell, which is particularly effective for electrolysis of an electrolytic solution containing a corrosive component.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an example of a two-chamber type electrolytic cell according to the present invention.

FIG. 2 is a schematic vertical sectional view showing an example of a three-chamber type electrolytic cell.

FIG. 3 is a schematic vertical sectional view showing another example of a two-chamber type electrolytic cell.

FIG. 4 is a schematic view of an apparatus for producing a conductive diamond structure used in the examples.

[Explanation of symbols]

1 ... Electrolyzer 2 ... Ion exchange membrane 3 ... Anode chamber 4 ... Cathode chamber 5 ... Anode 6 ... Cathode 21 ... Electrolyte chamber 22 ...
・ Ion exchange membrane 23 ・ ・ ・ Anode chamber 24 ・ ・ ・ Intermediate chamber 25
... Ion exchange membrane 26 ... Cathode chamber 27 ... Anode
28 ・ ・ ・ Cathode 41 ・ ・ ・ Electrolyzer 43 ・ ・ ・ Ion exchange membrane
44 ・ ・ ・ Anode chamber 45 ・ ・ ・ Cathode chamber 46 ・ ・ ・ Anode 47 ・ ・ ・ Cathode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masashi Tanaka 1145 Ishikawa, Fujisawa City, Kanagawa B-105 (72) Inventor Shuhei Wakita 5-9-8 Tsujido Motomachi, Fujisawa City, Kanagawa Prefecture (72) Toshi Takahashi, Kanagawa 1145 Ishikawa, Fujisawa, Japan B-103

Claims (12)

[Claims] 1. An electrode for electrolysis, comprising an electrode substrate and an electrode material having a conductive diamond structure coated on the surface of the electrode substrate. 2. The electrode for electrolysis according to claim 1, wherein the electrode material having a conductive diamond structure is a diamond containing boron, phosphorus and / or graphite. 3. The electrode for electrolysis according to claim 1, wherein the electrode material having a conductive diamond structure is a composite material of diamond and a conductive material. 4. The electrode for electrolysis according to claim 3, wherein the conductive substance is amorphous silicon oxide. 5. The electrode for electrolysis according to claim 1, wherein the electrode material having a conductive diamond structure is silicon carbide and / or titanium carbide. 6. The electrode for electrolysis according to claim 1, wherein the electrode substrate is carbon or a valve metal selected from titanium, niobium and tantalum. 7. An electrode base made of a valve metal, an intermediate layer containing a carbide and / or silicon carbide of a valve metal coated on the surface of the electrode base, and an electrode material having a conductive diamond structure coated on the surface of the intermediate layer. An electrode for electrolysis, comprising: 8. In an electrolytic cell having two chambers, an anode chamber and a cathode chamber, which are partitioned by an ion exchange membrane, at least one of the anode accommodated in the anode chamber and the cathode accommodated in the cathode chamber is an electrode substrate. And an electrode material having a conductive diamond structure coated on the surface of the electrode substrate. 9. The electrolytic cell according to claim 8, which is used for producing acidic water and / or alkaline water. 10. An electrolytic cell having three compartments, an anode compartment, an intermediate compartment and a cathode compartment, which are partitioned by an ion exchange membrane, wherein at least one of the anode contained in the anode compartment and the cathode contained in the cathode compartment is An electrolytic cell comprising: an electrode base; and an electrode material having a conductive diamond structure coated on the surface of the electrode base. 11. In an electrolytic cell having two chambers, an anode chamber and a cathode chamber, which are partitioned by an ion exchange membrane, at least one of an anode housed in the anode chamber and a cathode housed in the cathode chamber is a valve metal. And an intermediate layer containing carbide and / or silicon carbide of a valve metal coated on the surface of the electrode substrate, and an electrode material having a conductive diamond structure coated on the surface of the intermediate layer. Electrolyzer to do. 12. The electrolytic cell according to claim 11, which is used for electrolysis using a corrosive electrolyte and / or electrolytic solution.