JP3334996B2 - Reduction-suppressed cathode and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode used for electrolyzing an aqueous solution of an inorganic salt and a method for producing the same, and particularly to a method for converting hypochlorite, chlorate, perchlorate, persulfate, etc. The present invention relates to a cathode used for production by decomposition and a production method thereof.

[0002]

2. Description of the Related Art An aqueous solution of an alkali metal chloride or the like is electrolyzed to produce useful oxidizing substances such as hypochlorite, chlorate and perchlorate. In the production of oxidizing substances, it is known that the yield of oxidizing substances decreases due to side reactions, decomposition by temperature, reduction by contact with the cathode, etc. Various methods have been adopted to improve the performance. Hypochlorite is industrially produced by the chemical reaction of chlorine and alkali metal hydroxide, but it is used to sterilize water and sewage systems and to prevent biofouling of underwater structures and pipes. The hypochlorite used for is manufactured by electrolysis at the point of consumption. In the case of production by electrolysis, a relatively low-concentration salt water of a few percent is used as a raw material, a metal electrode using a noble metal or a noble metal oxide as an electrode catalyst is used as an anode, and a metal such as stainless steel or titanium is used as a cathode. Has been disassembled.

The area ratio of anode / cathode is increased for the purpose of increasing the production efficiency of hypochlorite obtained by electrolysis, preventing reduction of hypochlorite by a cathode, and preventing decomposition due to temperature rise. Method (JP-A-63-110575),
A method of increasing the liquid flow velocity (Japanese Patent Publication No. 46-4450),
There is a method (JP-A-4-74879) for improving the structure of the electrolytic cell. However, these methods do not sufficiently control the reduction of hypochlorite, and can reduce the conversion rate of sodium chloride to hypochlorite by keeping the hypochlorite concentration low. Is the mainstream.

[0004] The production of chlorate is generally carried out by electrolysis using a noble metal or a noble metal oxide and an electrode catalyst as an anode, iron or titanium or the like as a cathode, and a diaphragm without a diaphragm. In this case, as a method of reducing the reduction of the product chlorate by the cathode, it is known to add a chromate or a bichromate to the electrolytic solution. This method is effective in suppressing the reduction of chlorate at the cathode, but the addition of chromate increases the electrolysis voltage, deteriorating the power consumption, and causing harmful chromate in the product. There was a problem of mixing. As a method of increasing the chlorate yield without adding chromate, electrolysis is performed while adding an aqueous solution of alkali metal hydroxide generated in the cathode compartment to the anode compartment of the electrolytic cell partitioned by a cation exchange membrane. And a method for obtaining chlorate from the anode chamber is described in JP-A-3-199387. This method uses a salt ion exchange membrane electrolysis facility for the production of chlorate,
It is necessary to use an expensive cation exchange membrane, and there is a problem that salt water is required to have the same quality as that of the salt electrolysis by the ion exchange membrane method.

When producing perchlorate by electrolysis,
A common method is to use a chlorate aqueous solution with platinum or a platinum-iridium alloy as an anode and iron as a cathode to perform electrolysis without a diaphragm. In this case, it is known to add a chromate or a dichromate to the electrolytic solution as a method of reducing the reduction of the product perchlorate by the cathode. But,
This method also has a problem in that the addition of chromate increases the electrolysis voltage and deteriorates the power consumption unit, as in the production of chlorate, and harmful chromate is mixed into the perchlorate of the product. When a persulfate is produced by electrolysis, it is common to electrolyze a sulfate aqueous solution using platinum as an anode and lead or the like as a cathode. In this case, it is known to use an ion exchange membrane as a method for reducing the reduction of the product persulfate by the cathode. However, this method has problems such as an increase in the electrolysis voltage due to the use of the membrane and an expensive and uneconomical diaphragm.

[0006]

When hypochlorite is produced by electrolysis, it is an object of the present invention to increase the decomposition rate of sodium chloride and to efficiently obtain a solution having an effective chlorine concentration of 10,000 ppm. In the case of producing chlorate or perchlorate by electrolysis, the problem is to obtain high current efficiency without using chromate.In addition, persulfate is produced by electrolysis. In this case, it is an object to obtain high current efficiency without using a diaphragm.

[0007]

According to the present invention, there is provided a cathode for suppressing the reduction of ions occurring on an electrode surface by covering the electrode surface with an ion exchanger in an electrolytic cell for electrolyzing an aqueous solution of an inorganic salt. You. Further, the present invention provides a method for producing a reduction-suppressing cathode, wherein the method of covering the electrode surface with the ion exchanger is coating of the ion exchanger.

Hereinafter, the present invention will be described in detail. The present inventors have clarified the mechanism by which the current efficiency is reduced in the electrolysis of an inorganic salt aqueous solution, and have reached the present invention based on the mechanism. When hypochlorite is produced by electrolysis, there are the following three mechanisms for reducing current efficiency. These are oxygen generation due to low salt concentration, oxidation of hypochlorite ion to chlorite ion by anode, and reduction of hypochlorite ion to chloride ion by cathode. The inventors have considered the above 3
Experiments have confirmed that the reduction of hypochlorite ion to chloride ion by the cathode, which is the third of the three mechanisms, is the main cause of the decrease in current efficiency.

When chlorate is produced by electrolysis, there are the following three mechanisms for reducing the current efficiency. They are oxygen generation by water electrolysis, reduction of hypochlorite ion to chloride ion by cathode, and reduction of chlorite ion to chloride ion. Oxygen generation by water electrolysis is an anodic reaction. Factors that determine this are salt concentration, electrolysis temperature, current density,
There is an electrolyte pH and the like, but a value that maximizes the electrolytic performance is set. As a method of suppressing the reduction of hypochlorite ion to chloride ion by the cathode and the reduction of chlorate ion to chloride ion, it is known to add chromate or dichromate to the electrolyte. I have. The mechanism of this method is that chromate and dichromate ions are reduced on the cathode surface,
A coating mainly composed of chromium hydroxide is formed, and this coating has a function of suppressing ions such as hypochlorite ion and chlorate ion from coming into contact with the cathode, and as a result, reduction to chloride ion is performed. It is believed that it can be suppressed.

When a persulfate is produced by a diaphragmless electrolysis, there are three mechanisms for reducing the current efficiency.
These are oxygen generation by water electrolysis, generation of caloic acid by hydrolysis of persulfate ions, and reduction of persulfate ions to sulfate ions at the cathode. Oxygen generation by water electrolysis is an anodic reaction, and factors that determine this include sulfate concentration, electrolytic concentration, current density, and acidity of the electrolytic solution. The value that maximizes electrolytic performance is set. The production of caloic acid by hydrolysis of persulfate ions can be suppressed by controlling the acidity of the electrolytic solution. Prevention of reduction of persulfate ions by the cathode is implemented by partitioning the electrolytic solution with a diaphragm.

The inventors have considered the following as a method for solving the above-mentioned problem. The ions are reduced by the cathode because the oxidizing ions come into contact with or come very close to the cathode.If the oxidizing ions are prevented from coming into contact with or approaching the cathode, the reduction of the oxidizing ions by the cathode will occur. It should be able to suppress. An example of suppressing the contact or approach of ions to the cathode is the addition of chromate or dichromate ions to the electrolyte, but this method has the problems already described. The present inventors arrived at the present invention as a result of various studies, considering that a substance having the same function as a chromium hydroxide-based coating should be attached to the cathode.

The present invention discloses an electrode whose surface is covered with an ion exchanger which solves the above problems. The ion exchanger referred to in the present invention refers to all organic ion exchangers and inorganic ion exchangers, and further includes a mixture of an ion exchanger and a non-ion exchanger. There are two types of ion exchangers: anion exchanger and cation exchanger.If the ion to be prevented at the cathode is an anion, it is better to use a cation exchanger to prevent reduction at the cathode. When the ion is a cation, an anion exchanger is preferably used.

Examples of the organic ion exchanger include sulfonic acid groups, a resin obtained by copolymerizing styrene and divinyllenzene,
Quaternary ammonium groups, those in which carboxylic acid groups are bonded like polymethacrylic acid or polyacrylic acid, those in which methacrylic acid and divinylbenzene are copolymerized, and those in which primary to tertiary amine exchange groups are bonded, those in cellulose Exchange groups such as a sulfoethyl group, a phosphomethyl group, a phosphoric acid group, a carboxymethyl group, a 2-hydroxypropylamino group, a triethylamino group, a polyethyleneimino group, a diethylaminoethyl group, an epichlorohydrin triethanolamine, and a p-aminobenzyl group are included. Examples thereof include fluorinated resin ion exchangers having sulfonic acid groups, carboxylic acid groups, quaternary ammonium groups, and tertiary amine exchange groups. Use of a solution, solid powder, or dispersion thereof Can be. Examples of the inorganic ion exchanger include compounds such as hydrated oxides of iron, manganese, titanium, zirconium and cerium, titanium phosphate, zirconium phosphate, zirconium molybdate and zeolite. In the present invention, the ion exchanger may be any of an organic ion exchanger alone, an inorganic ion exchanger alone, and a mixture of an organic ion exchanger and an inorganic ion exchanger. In the present invention, a coating method is employed for attaching the ion exchanger to the cathode surface. A solution or slurry of the ion exchanger is applied to the cathode, dried, and used for electrolysis.

The ion exchanger used in the present invention has ion exchange properties when used, and does not need to have ion exchange properties when applied. For example, in the case of a fluororesin-based ion exchanger, a resin to which a sulfonyl fluoride group or a carboxylic acid methyl ester group is bonded can be obtained in the polymerization step.If such a resin is used as a coating solution, it is dried and hydrolyzed. And then use for electrolysis. The solution of the ion exchanger can be produced by dissolving the organic ion exchanger in a solvent. Further, the slurry of the ion exchanger is prepared by pulverizing an organic ion exchanger or an inorganic ion exchanger into fine powder and dispersing the powder in a liquid in which an adhesion matrix is dissolved, dispersed or melted (hereinafter referred to as a coating liquid). The attachment matrix refers to a substance that adheres and fixes the ion exchanger on the surface of the cathode, and non-ion exchanger synthetic resins and organic ion exchangers can be used.

Further, in the cathode of the present invention, it is important that the performance of the cathode is not impaired even if the ion exchanger is attached to the cathode, and that the attached ion exchanger is not easily separated. That is, reduction of hydrogen ions occurs on the cathode surface,
This is a quick separation of the generated hydrogen from the cathode. In order to achieve this object, the surface of the cathode before the application of the ion exchanger is porous or rough, and the attached ion exchanger is finely divided so that hydrogen can easily pass therethrough. It is important that holes or cracks are formed. In order to make the surface of the cathode porous or rough, the surface of the cathode substrate can be roughened by sandblasting and further etched by an acid or the like. Also, in order to make the ion exchanger porous, it is necessary to increase the vaporization rate of the solvent of the coating solution, use a coating solution with a composition that causes fine cracks when drying, or elute before or during use. Mixing substances that make it porous,
Further, it can be achieved by a method of mixing a porous solid.

As a method of applying the coating solution on the cathode surface, a method of applying the coating solution with a brush, a brush, a roll, or the like, a method of spraying the coating solution, or a method of dipping the cathode in the coating solution can be adopted. The amount of the ion exchanger applied to the cathode surface depends on the type of ion exchanger, the porosity of the applied material, the concentration of the ion exchanger in the coating solution, and the concentration and type of the ion to be reduced. It is preferable to apply the solution so that the ion exchange liquid on the surface of the cathode becomes 1.0 meq / m ² or more. When the amount of the ion exchanger on the cathode surface is less than 1.0 meq / m ² , the suppression of ion reduction at the cathode is insufficient, which is not preferable. The ion exchanger and the attachment matrix used in the present invention should be selected so that they do not dissolve or deteriorate under the use conditions. I do. For example, in the electrolytic production of hypochlorite, the use of a hydrocarbon-based organic ion exchanger is not preferred, and a perfluoro-based organic ion exchanger or an inorganic ion exchanger is preferably used. As the material of the cathode used in the present invention, iron, stainless steel, nickel, lead, titanium, graphite, ferrite, titanium or tantalum coated with a noble metal or a noble metal can be used. Further, as the shape of the cathode used in the present invention, a flat plate, a perforated plate, an expanded metal, a net, a reed-shaped bar and the like can be used.

Although the concentration of the ion exchanger in the coating solution used in the present invention varies depending on the type of the ion exchanger, the amount of the ion exchanger to be coated, the coating method, etc., it cannot be said unconditionally.
It is 0.01% or more and 10% or less, more preferably 0.05% or more and 5% or less. The amount of ion exchanger in the coating solution is 0.0
If it is less than 1%, the application must be repeated 10 times or more in order to obtain the required application amount of the ion exchanger, and there is a disadvantage that the cathode processing requires too much labor, which is not preferable. When the amount of the ion exchanger in the coating solution is more than 10%, it is difficult to apply the ion exchanger more than necessary in a single application, or it becomes difficult to apply uniformly because the viscosity of the coating solution increases. The problem that large cracks enter the coating to reduce the reduction suppressing effect occurs, which is not preferable.

When a slurry of an ion exchanger is used as a coating solution, the particle size of the ion exchanger is 0.01 μm.
m and 10 μm or less. When the particle size of the ion exchanger is 0.
When the thickness is less than 01 μm, the tendency of the ion exchanger to agglomerate increases, and it becomes difficult to perform monodispersion, which is not preferable. On the other hand, when the particle size of the ion exchanger is larger than 10 μm, there is a problem that the ion exchanger is sparsely attached to the cathode surface, and the strength of the coating film is weak, and the film easily peels off from the cathode surface. When using a slurry of an ion exchanger as the coating liquid, the slurry is preferably mixed with a stirring device such as an ultrasonic dispersing device, a shaker, a ball mill, or the like to uniformly disperse the ion exchanger. The cathode coated with the coating solution is dried to form a film in which the ion exchanger is fixed to the adhesion matrix. The drying of the cathode is pressurized,
It can be carried out under any of normal pressure and reduced pressure conditions. In the case of drying by heating, a heating furnace, hot air blowing, infrared irradiation or the like can be used. When the coating liquid is applied a plurality of times, the coating and drying may be repeated, and when the same coating thickness is obtained, the strength of the coating increases as the number of coatings increases.

[0019]

[Function] Since a cathode coated with an ion exchanger is used, reduction of oxidizing substances at the cathode can be prevented. When hypochlorite is used for production, high current efficiency can be obtained. A solution with an effective chlorine concentration of 10,000 or more ppm can be obtained, and when producing chlorate or perchlorate, high current efficiency can be achieved without the use of chromate, and further, persulfate is produced. In this case, high current efficiency can be obtained without a diaphragm.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. Example 1 The surface of a flat titanium cathode having a length of 10 cm and a width of 10 cm was degreased after sandblasting and immersed in 5% oxalic acid under boiling for 2 hours to perform a pretreatment. A fluorine resin-based ion exchanger solution (a 5% sulfonic acid-based resin solution of Nafion (trade name, manufactured by Aldrich Chemical Co., Ltd.), equivalent weight: 1100) (hereinafter referred to as perfluorosulfonic acid resin) Was applied as it was, or a solution diluted with n-butanol was brushed at different application times, and the cathode coated with the ion exchanger was heated and dried at 130 ° C. for 5 minutes. The coating and the heating and drying were alternately performed for those that had been applied a plurality of times. In this way, the cathodes of Sample Nos. 1 to 6 were prepared in which the production conditions and the ion-exchanger attached amount were changed as shown in Table 1, and the obtained cathode was used to produce sodium hypochlorite under the following conditions. Table 1 shows the average current efficiency when the effective chlorine concentration was 10 g / l when the cathode was evaluated by the electrolysis. Table 1 shows the average current efficiency when no ion exchanger was formed.

Electrolysis method: The concentration of sodium hypochlorite was measured at regular intervals using 300 ml of electrolyte under the following conditions: Anode: titanium substrate coated with noble metal oxide Separator: none Anode-cathode Distance: 2.5 mm Electrolysis temperature: 38 ° C. Current density: 30 A / dm ² Salt concentration of raw salt water: 30 g / l Example 2 Fluororesin-based ion exchanger solution using the following inorganic ion exchanger in Example 1 And disperse it into a coating solution,
The coating was applied to the cathode in the same manner as in Example 1 to prepare the cathodes of Sample Nos. 7 to 10 shown in Table 1, and the inorganic ion exchanger was mixed with polytetrafluoroethylene (manufactured by DuPont-Mitsui Fluorochemicals) in pure water at 1/100. It was added to the solution diluted to 100 to make a coating solution, and the cathode coated with the ion exchanger was air-dried and then dried.
C. for 10 minutes to produce cathodes of Sample Nos. 11 to 14, produced sodium hypochlorite by electrolysis under the same conditions as in Example 1, and conducted the same tests. The results are shown in Table 1. Show.

Titanium hydroxide: Titanium hydroxide manufactured by Ishihara Sangyo (trade name: MC-90) Using an average particle size of 0.018 μm, 23 mg of titanium hydroxide is added to 10 ml of a fluororesin-based ion exchanger solution or polytetrafluoroethylene disperser. The solution dispersed in the John diluent was used as a coating solution.

Zirconium hydroxide: 3 g of zirconium hydroxide (manufactured by Daiichi Kagaku Kagaku Kogyo Co., Ltd., trade name: R-2D (average particle size: 7.5 μm)) is pulverized in an agate mortar, and the pulverized product is further colloid milled (APV GAULIN). Of pure water together with 50 ml of pure water and 30 rpm at 1000 rpm.
Milled twice for each minute. The pulverized slurry was subjected to centrifugal separation to separate solid matter and moisture, and the concentrated slurry was dried at 100 ° C. by a drier until the moisture disappeared. The average particle size of the obtained zirconium hydroxide was 0.2 μm.
A coating liquid was obtained by dispersing 33 mg of this zirconium hydroxide in 10 ml of a fluororesin-based ion exchanger solution or a polytetrafluoroethylene dispersion diluent.

Cerium hydroxide: 3 g of cerium hydroxide (manufactured by Daiichi Kagaku Kagaku Kogyo Co., Ltd.) having an average particle size of 10 μm is pulverized in an agate mortar, and the pulverized product is colloid milled (APVG G).
(Aulin) together with 50 ml of pure water, and pulverized twice at a rotation speed of 1000 rpm for 30 minutes. The pulverized slurry was subjected to centrifugal separation to separate solid matter and moisture, and the concentrated slurry was dried at 100 ° C. by a drier until the moisture disappeared. The average particle size of the obtained cerium hydroxide was 0.2 μm. 44 mg of the obtained cerium hydroxide
Was dispersed in 10 ml of a fluororesin-based ion exchanger solution or a polytetrafluoroethylene dispersion diluent to obtain a coating solution.

Ferric hydroxide: Ferric chloride hexahydrate (special grade reagent, manufactured by Wako Pure Chemical Industries) was dissolved in pure water to prepare a 32% by weight solution. 4 ml of a ferric chloride solution was dropped into 250 ml of boiling pure water, and the mixture was treated under boiling for 24 hours. The cooled slurry was dried in a centrifuge at 100 ° C. until there was no more water, to obtain ferric hydroxide having an average particle size of 0.24 μm. A coating liquid was prepared by dispersing 79 mg of the obtained ferric hydroxide in 10 ml of a fluororesin-based ion exchanger or a polytetrafluoroethylene dispersion diluent.

[0026]

[Table 1]

Example 3 A perfluoro organic ion exchanger solution (functional group having sulfonic acid) was applied to the surface of a flat titanium cathode 10 cm long and 10 cm wide with a brush, and the ion exchange solution was applied to the cathode. Was placed in a heater and dried to completely evaporate the solvent.
Thus, the cathodes of Sample Nos. 15 to 20 having different amounts of ion exchanger attached as shown in Table 2 were produced, and sodium chlorate was produced by electrolysis under the following conditions using the obtained cathodes. The average current efficiency was determined from the amount of sodium chlorate produced, and the results are shown in Table 2. The average current efficiency in the case where the ion exchanger was not formed was set to the ratio of 2, and the case where the electrolysis was performed using sodium dichromate at a concentration of 4 g / l using the cathode in which the ion exchanger was not formed. The ratio 3 is shown in Table 2. Electrolysis method: 500 ml of the electrolytic solution was electrolyzed under the following conditions, and the amount of sodium chlorate generated after 3 hours was measured.

Anode: titanium substrate coated with a noble metal Separator: none Anode-cathode distance: 4.0 mm Electrolysis temperature: 80 ° C. Current density: 30 A / dm ² Composition of electrolyte: 450 g / l of NaClO ₃ , NaCl
14 g / l Electrolyte pH: 6.5 ± 0.2 Example 4 Inorganic ion exchangers were prepared in the same manner as in Example 2, and the sample numbers 21 to 28 described in Table 2 differing in the application amount of the ion exchanger.
Was prepared, sodium chlorate was produced by electrolysis under the same conditions as in Example 3, and the same test was conducted. The results are shown in Table 2.

[0029]

[Table 2]

Example 5 In the same manner as in Example 1, the cathodes of Sample Nos. 29 to 34 having different amounts of the ion exchanger attached as shown in Table 3 were produced, and the obtained cathodes were used under the following conditions. Sodium chlorate was produced by electrolysis, and the average current efficiency was determined from the amount of sodium perchlorate produced. The results are shown in Table 3. In addition, the average current efficiency in the case where the ion exchanger was not formed was set to Comparative 5, and the cathode in which the ion exchanger was not formed was used.
The concentration of sodium dichromate in the electrolyte is 0.2 g /
Table 3 shows the ratio 6 when the electrolysis was carried out in addition to l. Electrolysis method: Electric current is applied for 3 hours using 500 ml of the electrolytic solution, and the amount of generated sodium perchlorate is measured.

Anode: titanium substrate coated with noble metal Diaphragm: none Anode-cathode distance: 2.0 mm Electrolysis temperature: 50 ° C. Current density: 60 A / dm ² Composition of electrolyte solution: NaClO ₃ 550 g / l, NaCl
O ₄ 550 g / l, NaF 2 g / l Example 6 Similar to Example 2, cathodes of Sample Nos. 35 to 42 described in Table 3 having different coating amounts of the ion exchanger were produced, and the same conditions as in Example 3 were used. And sodium perchlorate was produced by electrolysis, and the same test was conducted. The results are shown in Table 3.

[0032]

[Table 3]

Example 7 In the same manner as in Example 1, the cathodes of Sample Nos. 43 to 48 were prepared as shown in Table 4 with different amounts of ion exchanger attached, and the obtained cathodes were used under the following conditions. Ammonium sulfate was produced by electrolysis, and the average current efficiency was determined from the amount of produced ammonium persulfate. The results are shown in Table 4. Table 4 shows the average current efficiency as a ratio 6 when a cathode having no ion exchanger was used. In addition, a cation exchange membrane (Nafion manufactured by DuPont) was used as a diaphragm, the anolyte was the same as the electrolyte described below, and the catholyte was 150 g / l sulfuric acid and 290 g / l ammonium persulfate. Table 4 shows the current efficiency as a ratio of 7. Electrolysis method: 500 ml of the electrolytic solution was used, and electricity was supplied for 3 hours, and the amount of generated ammonium persulfate was measured.

Anode: titanium substrate coated with a noble metal Separator: none Anode-cathode distance: 2.0 mm Electrolysis temperature: 35 ° C. Current density: 60 A / dm ² Electrolyte composition: (NH ₄ ) ₂ SO ₄ 370 g / L, (N
H ₄ ) ₂ S ₂ O ₈ 210 g / l, H ₂ SO ₄ 10 g / l,
NH ₄ SCN 0.2 g / l Example 8 The cathodes of sample numbers 49 to 56 were produced in the same manner as in Example 2, and ammonium persulfate was produced by electrolysis under the same conditions as in Example 7, and the test was carried out in the same manner. And the results are shown in Table 4.

[0035]

[Table 4]

Comparative Example A polytetrafluoroethylene dispersion (manufactured by DuPont-Mitsui Fluorochemicals) was diluted 1/100 and 1/200 with pure water on the surface of a metal substrate treated in the same manner as in Example 1 once. It was applied and dried by heating at 200 ° C. for 10 minutes. The thickness of the polytetrafluoroethylene of this cathode was 4 μm and 2 μm, respectively.

An experiment was conducted to produce the prepared cathode by electrolysis of sodium hypochlorite in the same manner as in Example 1. As a result, the average current efficiency was slightly improved to 75% when the thickness of polytetrafluoroethylene was 4 μm. However, the voltage was 0.8 V higher than that of Sample No. 4, and the voltage of the sample having a polytetrafluoroethylene thickness of 2 μm was equivalent to that of Sample No. 4, but the average current was as low as 63%.

[0038]

Since the cathode of the present invention has an ion exchanger on its surface, it is possible to prevent the reduction of the generated oxidizing substance, and when producing hypochlorite, the effective chlorine concentration is 1 with high current efficiency. It is possible to obtain a solution of tens of thousands ppm, and when producing chlorate or perchlorate, it is possible to achieve high current efficiency without using chromate, and when producing persulfate, High current efficiency can be obtained without a diaphragm.

Claims (2)

(57) [Claims] 1. A reduction-suppressing cathode for suppressing reduction of an oxidizing substance at a cathode, comprising a porous or cracked ion exchanger-containing layer on the electrode surface. 2. A method for producing a reduction-suppressed cathode, wherein a coating solution containing an ion exchanger is applied to the surface of the cathode having a porous or roughened surface, and a porous or crack-containing layer of the ion exchanger is formed. A method for producing a reduction-suppressing cathode, characterized by forming: