JP7631069B2 - Gas diffusion electrode electrolysis two-chamber method for sodium chloride electrolysis and its applications - Google Patents

Description

The present invention relates to an electrolytic cell for two-chamber gas diffusion electrode salt electrolysis and its utilization technology.

Sodium hydroxide and chlorine have traditionally been produced by electrolyzing salt water using an ion exchange membrane and a metal electrode as the cathode. However, because electrolysis of salt water requires a large amount of electricity, in recent years, methods of reducing oxygen using a gas diffusion electrode as the cathode have been investigated in the hope of achieving significant energy savings.

In methods for reducing oxygen using gas diffusion electrodes, in addition to the three-chamber method in which the electrolytic cell is divided into three chambers, an anode chamber, a cathode liquid chamber, and a cathode gas chamber, a two-chamber method has been developed in which the anode, ion exchange membrane, and gas diffusion electrode are tightly attached to each other, essentially eliminating the cathode liquid chamber and dividing the electrolytic cell into two chambers, an anode chamber and a cathode gas chamber.

For example, Patent Document 1 describes a two-chamber electrolytic cell that is partitioned into an anode chamber and a cathode chamber by an ion exchange membrane, has an anode installed in the anode chamber, and a liquid retaining layer and a gas diffusion electrode installed in the cathode chamber, and electrolysis is performed by supplying saline solution to the anode chamber and an oxygen-containing gas to the cathode chamber, with a liquid retaining layer having a predetermined liquid retention amount per unit volume of the liquid retaining layer between the ion exchange membrane and the gas diffusion electrode.

Patent Document 2 also discloses a gas diffusion electrode in which a catalyst layer containing a hydrophilic catalyst and a hydrophobic binder is supported on an electrode substrate, the electrode substrate being made of a carbon material selected from carbon cloth, carbon paper, carbon foam, and carbon sintered body, and a salt electrolysis cell using the gas diffusion electrode.

International Publication No. 2012/008060 JP 2006-219694 A

However, in the techniques described in Patent Documents 1 and 2, it is necessary to install a liquid retaining layer or a hydrophilic layer between the ion exchange membrane and the gas diffusion electrode, and there is room for improvement in terms of ease of assembly of the electrolytic cell. Furthermore, Patent Document 2 does not describe the installation direction of the gas diffusion electrode in the salt electrolytic cell.

One aspect of the present invention was made in consideration of the above problems, and aims to provide an electrolytic cell for gas diffusion electrode salt electrolysis using two chambers that is easy to assemble, and a technology for using the same.

As a result of intensive research to solve the above problems, the present inventors have found that, whereas conventionally, a gas diffusion cathode is formed by applying a reactive layer to a substrate made of a carbon material, and then a liquid retaining layer or a hydrophilic layer is separately attached to the ion exchange membrane side, by forming a reactive layer on one side (the side opposite to the ion exchange membrane side) of a hydrophilic and conductive electrode support layer, an electrolytic cell for a two-chamber gas diffusion electrode salt electrolysis method having good performance can be obtained without providing a liquid retaining layer or a hydrophilic membrane, and that such an electrolytic cell is easy to assemble because it does not require the provision of a liquid retaining layer or a hydrophilic membrane, and have thus completed the present invention. That is, one embodiment of the present invention includes the following aspects.
<1> An electrolytic cell for a two-chamber method for gas diffusion electrode saline electrolysis, which is partitioned into an anode chamber and a cathode chamber by an ion exchange membrane, an anode electrode is installed in the anode chamber, a cathode electrode is installed in the cathode chamber, and electrolysis is performed by supplying saline solution to the anode chamber and an oxygen-containing gas to the cathode chamber, respectively, wherein the cathode electrode is a gas diffusion electrode consisting of only two layers: a hydrophilic and conductive electrode support layer and a conductive reaction layer which is disposed on one surface side of the electrode support layer and contains a hydrophilic catalyst and a hydrophobic resin, and within the cathode chamber, the electrode support layer of the gas diffusion electrode is disposed so as to be in contact with the ion exchange membrane on a surface opposite to the surface on which the reaction layer is disposed.
<2> The electrolytic cell according to <1>, wherein the electrode backing layer has a liquid retention amount per unit volume of the electrode backing layer of 0.10 g-H ₂ O/cm ³ to 0.80 g-H ₂ O/cm ³ .
<3> The electrolytic cell according to <1> or <2>, wherein the electrode support layer is formed of at least one selected from the group consisting of carbon, zirconium oxide, ceramics, polytetrafluoroethylene, a copolymer of tetrafluoroethylene and hexafluoropropylene, an aramid resin, a polyimide resin, a polyvinyl chloride resin, nickel, stainless steel, silver, and gold.
<4> The electrolytic cell according to any one of <1> to <3>, wherein a hydrophobic resin layer is disposed so as to be in contact with the surface of the gas diffusion electrode on which the reaction layer is disposed.
<5> A method for producing chlorine gas, comprising a step of electrolyzing saline solution using the electrolytic cell according to any one of <1> to <4> above.
<6> A method for producing sodium hydroxide, comprising a step of electrolyzing saline solution using the electrolytic cell according to any one of <1> to <4> above.

One embodiment of the present invention has the effect of providing an electrolytic cell that is easy to assemble.

FIG. 1 is a diagram showing a schematic structure of an electrolytic cell for a two-chamber gas diffusion electrode sodium chloride electrolysis method according to one embodiment of the present invention.

The embodiments of the present invention are described in detail below. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more (including A and larger than A) and B or less (including B and smaller than B)."

<1. Electrolytic cell for gas diffusion electrode salt electrolysis using two-chamber method>
An electrolytic cell for two-compartment gas diffusion electrode salt electrolysis according to one embodiment of the present invention is partitioned into an anode chamber and a cathode chamber by an ion exchange membrane, an anode electrode is installed in the anode chamber, a cathode electrode is installed in the cathode chamber, and electrolysis is performed by supplying saline solution to the anode chamber and an oxygen-containing gas to the cathode chamber, respectively, in which the cathode electrode is a gas diffusion electrode consisting of only two layers, a hydrophilic and conductive electrode support layer, and a conductive reaction layer that is disposed on one surface of the electrode support layer and contains a hydrophilic catalyst and a hydrophobic resin, and in which the electrode support layer of the gas diffusion electrode is disposed in the cathode chamber so as to contact the ion exchange membrane on the surface opposite to the surface on which the reaction layer is disposed. Hereinafter, one embodiment of the present invention will be described in detail.

As shown in FIG. 1, an electrolytic cell 1 for a two-chamber gas diffusion electrode salt electrolysis method according to one embodiment of the present invention is composed of an ion exchange membrane 2, an anode chamber 3, a cathode chamber 4, an anode electrode 5, a gas diffusion electrode (cathode electrode) 7, a cushioning material 8, a cathode chamber back plate (cathode terminal) 9, an anode gasket 10, a cathode gasket 11, an anolyte inlet 12, an anolyte and gas outlet 13, an oxygen-containing gas inlet 14, and a sodium hydroxide aqueous solution outlet 15.

The electrolytic cell 1 is divided into an anode chamber 3 and a cathode chamber 4 by an ion exchange membrane 2. An anode electrode 5 is disposed on the anode chamber 3 side of the ion exchange membrane 2. A gas diffusion electrode 7, a cushion material 8, and a cathode chamber back plate (cathode terminal) 9 are disposed in this order on the cathode chamber 4 side of the ion exchange membrane 2. The gas diffusion electrode 7 is composed of an electrode support layer 6a and a reaction layer 6b. The direct current is finally discharged by the cushion material 8. The anode gasket 10 is used to fix the anode electrode 5, and the cathode gasket 11 is used to fix the gas diffusion electrode 7 to the electrolytic cell 1.

An anolyte (saline) inlet 12 is formed near the bottom of the anode chamber 3. An anolyte (unreacted saline) and (chlorine) gas outlet 13 is formed on the upper wall side of the anode chamber 3. An oxygen-containing gas inlet 14 is formed on the side wall near the top of the cathode chamber 4, and an aqueous sodium hydroxide solution outlet 15 is formed on the side wall near the bottom of the cathode chamber 4. The aqueous sodium hydroxide solution outlet 15 also functions as an outlet for excess oxygen gas.

Anode fluid (saline solution) is supplied to the anode chamber 3 of the electrolytic cell 1 through the anode fluid inlet 12, and oxygen-containing gas (e.g., oxygen gas or air) is supplied to the cathode chamber 4 through the oxygen-containing gas inlet 14. The electrolytic cell 1 operates when electricity is applied between the two electrodes.

In the above-mentioned Patent Document 1, a "liquid retention layer" is disposed between the gas diffusion electrode and the ion exchange membrane 2, and in Patent Document 2, a "hydrophilic layer" is disposed between the gas diffusion electrode and the ion exchange membrane. In contrast, in one embodiment of the present invention, the gas diffusion electrode 7 does not need to have a separate liquid retention layer or hydrophilic layer on the ion exchange membrane side, and is composed of only two layers: an electrode support layer 6a with a liquid retention function (function as a hydrophilic layer) and a reaction layer 6b with a reaction function. With this configuration, there is no need to form a separate liquid retention layer (hydrophilic layer) between the gas diffusion electrode 7 and the ion exchange membrane 2, making assembly easier.

In one embodiment of the present invention, the electrode support layer 6a of the gas diffusion electrode 7 contacts the ion exchange membrane 2 on the side opposite to the side on which the reaction layer 6b is formed. In other words, in the cathode chamber 4, the gas diffusion electrode 7 has a two-layer structure of the electrode support layer 6a and the reaction layer 6b, and the ion exchange membrane 2, the electrode support layer 6a, and the reaction layer 6b are arranged in this order. This configuration has the advantage that, compared to a configuration in which the ion exchange membrane 2 and the reaction layer 6b are in contact, the resistance between the anode and the cathode can be reduced a predetermined time after electrolysis is started by supplying a current to the electrolytic cell 1. This is thought to be because the electrode support layer 6a is liquid-retentive or hydrophilic.

The cathodic reaction at the gas diffusion electrode is a reaction that produces only hydroxide ions from water and oxygen. The water that contributes to the reaction is desirably present on the electrolytic surface interface between the ion exchange membrane 2 and the gas diffusion electrode 7 in a sufficient amount and uniform concentration to react, since the anolyte (unreacted saline) passes through the ion exchange membrane 2 and is supplied to the gas diffusion electrode 7. With this configuration, a sufficient amount and uniform concentration of water can be present in the electrode support layer 6a, so the increase in resistance caused by one-sided current concentrated in one part or uneven water concentration distribution can be reduced. In other words, if the ion exchange membrane 2, reaction layer 6b, and electrode support layer 6a are arranged in this order, it is difficult to maintain a sufficient amount of water at a uniform concentration on the interface between the ion exchange membrane 2 and the gas diffusion electrode 7, which is thought to lead to an increase in resistance.

In addition, the gas diffusion electrode 7 of one embodiment of the present invention has the advantage that the resistance between the anode and cathode can be reduced a predetermined time after current is supplied to the electrolytic cell 1 to start electrolysis, compared to when a liquid retention layer or hydrophilic layer is separately formed between the gas diffusion electrode 7 and the ion exchange membrane 2. This is thought to be because a sufficient amount of water for reaction and a uniform concentration can be present on the electrolysis surface interface between the ion exchange membrane 2 and the gas diffusion electrode 7.

In addition, when a liquid retention layer is provided, it is believed that, compared to this configuration, additional contact resistance between the liquid retention layer and the gas diffusion electrode and resistance of the electrode support layer itself will occur, leading to an increase in resistance.

The electrode support layer 6a is hydrophilic and conductive, and functions as a support on which the reaction layer 6b is formed. The electrode support layer 6a also functions as a hydrophilic layer (liquid retention layer). The electrode support layer 6a is not particularly limited as long as it is a material that is generally used as a support for a gas diffusion electrode, but it is preferable that the electrode support layer 6a has the ability to retain liquid, particularly the aqueous sodium hydroxide solution that is generated. In addition, the electrode support layer 6a preferably has chemical and physical resistance to sodium hydroxide. By chemical resistance, we mean a material that is resistant to high alkali, and by physical resistance, we mean a material that has appropriate strength against the load applied to the electrolytic cell.

The electrode supporting layer 6a preferably has a good liquid retention function. For example, the liquid retention function is preferably such that the liquid retention amount per unit volume of the electrode supporting layer is 0.10 g-H ₂ O/cm ³ to 0.80 g-H ₂ O/cm ³ , more preferably 0.15 g-H ₂ O/cm ³ to 0.70 g-H ₂ O/cm ³ , and even more preferably 0.20 g-H ₂ O/cm ³ to 0.60 g-H ₂ O/cm ^3. The liquid retention amount of the electrode supporting layer in this specification is defined as B-A, where A is the weight of the electrode supporting layer when it is immersed in an aqueous solution of sodium hydroxide having a concentration of 34.5% by weight for one day, washed with water to completely remove the aqueous sodium hydroxide solution, and completely dried, and B is the weight of the completely dried electrode supporting layer when it is immersed in pure water for one hour and then taken out. The liquid retention per unit volume is defined as the value obtained by dividing the liquid retention by the volume of the electrode backing layer used to measure the liquid retention. Measurements were also made in the examples using the same definition.

The electrode support layer 6a is preferably formed from at least one selected from the group consisting of carbon, zirconium oxide, ceramics, polytetrafluoroethylene, copolymers of tetrafluoroethylene and hexafluoropropylene, aramid resin, polyimide resin, polyvinyl chloride resin, nickel, stainless steel, silver, and gold. Among these, a porous carbon-based substrate is a preferred example. Examples of the porous carbon-based substrate that can be used include cloth, sintered fiber, and foam made of carbon materials. Among these, either cloth or sintered fiber is preferred from the perspective of size and ease of mass production, and commercially available carbon cloth and sintered fiber such as carbon paper can be used.

The electrode support layer 6a must be permeable to oxygen and the generated sodium hydroxide, so it is preferable that it has sufficient conductivity as well as moderate porosity, with a pore size of 0.001 to 1 mm and a porosity of 30 to 95%. In addition, taking into consideration the mechanical strength, such as tensile strength, and the permeation distance of oxygen and the generated sodium hydroxide, the thickness of the electrode support layer 6a is preferably in the range of 0.1 to 1 mm.

The reaction layer 6b is disposed on one side of the surface of the electrode support layer 6a and is a conductive reaction layer that contains a hydrophilic catalyst and a hydrophobic resin.

The hydrophilic catalyst used in the reaction layer 6b is at least one of silver, platinum, and palladium, which are electrochemically stable in high-temperature and high-concentration alkali, and can be a single metal or an alloy of these metals. In terms of cost, it is preferable to use a single metal of silver, or a silver-palladium alloy or a silver-platinum alloy in which a small amount of palladium or platinum is added to silver. These hydrophilic catalysts can be commercially available particulate catalysts, but are not limited to this, and may be used after synthesis according to a known method. For example, particulate catalysts synthesized by a wet method in which a reducing agent is mixed with silver nitrate, or an aqueous solution of silver nitrate and palladium nitrate, or an aqueous solution of silver nitrate and dinitrodiammine platinum nitrate, or a dry method such as deposition or sputtering can also be used. The particle size of the hydrophilic catalyst can be 0.001 to 50 μm, and more preferably 0.001 to 1 μm.

The hydrophobic resin used in the reaction layer 6b functions as a binder for the hydrophilic catalyst. For example, a fluororesin that is chemically stable in high-temperature and high-concentration alkali can be used. Specifically, powders or aqueous suspensions of polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), etc. can be suitably used. The hydrophobic resin contributes to good electrolysis performance by imparting sufficient gas permeability to the electrode and preventing excessive wetting of the electrode by the generated sodium hydroxide, and the particle size range of the hydrophobic resin is preferably 0.005 to 10 μm.

In addition to the hydrophilic catalyst and hydrophobic resin, the reaction layer 6b can also contain a carbon material. Examples of carbon materials include carbon powder, graphite, graphene, carbon nanotubes, fullerenes, diamond, etc. The inclusion of a carbon material has the advantage of improving the electrical conductivity and hydrophilicity.

The method for forming the reaction layer 6b on the electrode support layer 6a can be suitably any conventionally known method, and is not particularly limited. For example, a slurry or resin mixture obtained by mixing, stirring, and degassing a hydrophilic catalyst and a hydrophobic resin can be applied to the electrode support layer 6a and dried to form the reaction layer 6b on one side of the electrode support layer 6a. The application of the slurry or resin mixture can be performed manually using a brush, paint brush, or scraper, or can be performed using a coater, spray dryer, or the like.

It is also preferable that a hydrophobic resin layer (not shown) is further arranged so as to be in contact with the surface on which the reaction layer 6b of the gas diffusion electrode 7 is arranged. In other words, it is preferable that the ion exchange membrane 2, the electrode support layer 6, the reaction layer 6b, and the hydrophobic resin layer are arranged in this order in the cathode chamber 4. The hydrophobic resin layer can be formed, for example, by coating the surface on which the reaction layer 6b of the gas diffusion electrode 7 is formed with a hydrophobic resin. With this configuration, the contact resistance of the gas diffusion electrode 7 can be further reduced. Note that the above-mentioned hydrophobic resins can be preferably used as the hydrophobic resin.

As the ion exchange membrane 2, a typical ion exchange membrane for a two-chamber gas diffusion electrode salt electrolysis method can be used, and is not particularly limited, but a fluororesin-based cation exchange membrane is preferred from the standpoint of corrosion resistance.

The anode electrode 5 can be suitably an insoluble anode for a typical gas diffusion electrode two-chamber salt electrolysis method, and although not particularly limited, an example is an insoluble titanium electrode called DSA.

The cushion material 8 is for bringing the gas diffusion electrode 7 into close contact with the ion exchange membrane 2. It is preferable to store the cushion material 8 in a compressed state to generate a reaction force in the cushion material 8, and to use this reaction force to bring the gas diffusion electrode 7 into close contact with the ion exchange membrane 2. In the two-chamber method, the ion exchange membrane 2 is the boundary between the anode chamber 3 and the cathode chamber 4, and liquid pressure from the saline solution acts on the anode chamber 3, and gas pressure acts on the cathode chamber 4. The reaction force of the cushion material 8 is designed according to the differential pressure between this liquid pressure and gas pressure, but since the liquid pressure is greater the deeper the saline solution is, the reaction force of the cushion material 8 is made greater in the lower part of the cathode chamber 4 than in the upper part, so that the pressure applied to the ion exchange membrane 2 and the anode electrode 5 can be equalized.

As the cushioning material 8, it is possible to use a coil material or a wave-processed mat material. Since the coil has elasticity in the diameter direction and generates a reaction force in this direction, the coil axis can be arranged parallel to the back plate of the cathode gas chamber. By adjusting the wire diameter, coil system, and laying density of the coil material, it is possible to make the reaction force of the cushioning material greater at the bottom than at the top. In addition, the wave-processed mat material can be made of a demister mesh made of knitted metal wires that has been wave-processed. By adjusting the wire diameter, number of wires to be bundled, and number of layers of the mat material, it is possible to make the reaction force of the cushioning material greater at the bottom than at the top.

It is also preferable that the salt water supplied to the anode chamber 3 is strictly purified. Calcium, magnesium ions, etc. are preferably removed to the 10 ppb level using a chelating resin.

The oxygen-containing gas supplied to the cathode chamber 4 is preferably humidified. Examples of humidification methods include a method of humidifying the oxygen-containing gas supplied to the electrolytic cell 1 by spraying water on it, and a method of humidifying the oxygen-containing gas by blowing it into water.

Between the ion exchange membrane 2 and the cathode chamber 4, sodium hydroxide dissolves in the permeating water passing through the ion exchange membrane 2 from the anode chamber 3 to become an aqueous sodium hydroxide solution. The resulting aqueous sodium hydroxide solution diffuses through the electrode support layer 6a of the gas diffusion electrode 7, and falls due to gravity, reaching the lower end of the electrode support layer 6a and flowing down as droplets to the bottom of the cathode chamber 4, where it is taken out of the electrolytic cell 1 from the aqueous sodium hydroxide solution outlet 15 together with gas containing excess oxygen.

As electrolysis conditions for the electrolytic cell 1, a current density of 1 to 10 kA/ ^m2 is preferable, and the temperatures of the anode chamber 3 and the cathode chamber 4 during electrolysis are not particularly limited, and may be any temperature that is normally used. For example, it is preferable to set the temperature in a range according to the current density in order to maximize the performance of the ion exchange membrane 2. The temperature range may be appropriately set according to the type of the ion exchange membrane 2, and for example, when the current density is 1.0 kA/ ^m2 or more and less than 2.0 kA/ ^m2 , 68 to 82°C is preferable, when the current density is 2.0 kA/m2 or more and less than 3.0 kA/ ^m2 , 77 to 85°C is preferable, and when the current density is 3.0 kA/ ^m2 or ^more , 80 to 90°C is preferable.

2. Methods for producing chlorine gas and sodium hydroxide
Moreover, one embodiment of the present invention may include a method for producing chlorine gas, which includes a step of electrolyzing saline water (producing chlorine gas by electrolyzing saline water) using the above-mentioned electrolytic cell 1. Moreover, one embodiment of the present invention may include a method for producing sodium hydroxide, which includes a step of electrolyzing saline water (producing sodium hydroxide by electrolyzing saline water) using the above-mentioned electrolytic cell 1.

When salt water is supplied to the anode chamber 3 of the electrolytic cell 1 and oxygen is supplied to the cathode chamber 4 while a current is passed between the anode electrode 5 and the gas diffusion electrode 7, sodium hydroxide is produced on the surface of the ion exchange membrane 2 on the cathode chamber 4 side on the cathode chamber 4 side, and this sodium hydroxide permeates the gas diffusion electrode 7 as an aqueous solution.

In this way, the sodium hydroxide that has passed through the gas diffusion electrode 7 is collected at the bottom of the cathode chamber 4 and is taken out from the sodium hydroxide aqueous solution outlet 15 together with unreacted oxygen. Meanwhile, the chlorine gas produced on the surface of the anode electrode 5 is collected at the top of the anode chamber 3 and is taken out from the anolyte and gas outlet 13.

According to the method for producing chlorine gas or sodium hydroxide according to one embodiment of the present invention, chlorine gas or sodium hydroxide can be easily obtained.

Below, one embodiment of the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these. One embodiment of the present invention can be practiced with appropriate modifications within the scope that can conform to the purpose described above or below, and all of these modifications are included in the technical scope of the present invention. In the following examples and comparative examples, "parts" and "%" mean parts by weight or % by weight.

Example 1
<Preparation of gas diffusion electrode (cathode)>
As a suspension for forming a reaction layer, 2.4 g of silver powder (Silcoat, manufactured by Fukuda Metal Foil Industries Co., Ltd.), 0.8 g of a polytetrafluoroethylene aqueous suspension (31JR, manufactured by Mitsui Fluorochemical Co., Ltd.), and 0.06 g of sodium carboxymethylcellulose (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed at 2000 rpm for 5 minutes using a stirrer equipped with a defoaming function, and then degassed at 2200 rpm for 5 minutes.

The obtained suspension was applied with a brush to one side of a carbon cloth (manufactured by AvCarb Material Solutions, 1071HCB, length 9 cm × width 9 cm × thickness 0.4 mm) serving as an electrode backing layer, in an area of 6 cm width × 5.6 ^cm length, so as to give a coating of 250 g/m2, and dried in a hot air dryer at 120°C for 1 hour to form a reaction layer, thereby producing a gas diffusion electrode serving as a cathode electrode. The carbon cloth used as the electrode backing layer had a liquid retention capacity per unit volume of 0.40- _H2O / ^cm3 .

<Preparation of electrolytic cell>
The electrolytic cell was prepared in the configuration shown in Figure 1. In the electrolytic cell (0.336 dm2 electrolytic cell manufactured by Chlorine Engineers Co., Ltd.), DSE (registered trademark) manufactured by Permelec Electrodes Co., Ltd. was used as the anode electrode, and A1001 manufactured by Asahi Kasei Corporation was used as the ion exchange membrane.

The electrolytic cell was constructed by sandwiching the ion exchange membrane positioned vertically and pressing the anode electrode in the direction of the ion exchange membrane in the anode chamber, and then using a cushioning material to closely attach the gas diffusion electrode in the cathode chamber so that the carbon cloth was in contact with the ion exchange membrane on the side opposite the side on which the reaction layer was placed.

<Chlorine electrolysis experiment>
In the salt electrolysis experiment, saturated saline solution at 80°C was supplied to the anode chamber from the anolyte inlet, and PSA concentrated oxygen (93 % by volume ) was supplied to the cathode chamber from the oxygen-containing gas inlet. After confirming that saturated saline solution and oxygen were supplied to the anode chamber and cathode chamber, respectively, a current of 10 A (current density 3 kA/ ^m2 ) was supplied to both the anode electrode and the gas diffusion electrode. After the current was supplied, electrolysis was performed while controlling the temperatures of the anolyte and the gas outlet at 80°C and the concentration of the generated aqueous sodium hydroxide solution at 35%.

The resistance between the anode electrode and the gas diffusion electrode was monitored and measured using a current interrupter method with a pulse generator and an oscilloscope.

In the electrolytic cell of this configuration, the resistance between the anode and cathode on the fourth day after current was supplied and electrolysis was started was 0.31 V. In addition, since there was no need to provide a separate hydrophilic layer between the ion exchange membrane and the gas diffusion electrode, assembly was easy.

Example 2
An electrolytic cell having the same configuration as in Example 1 was prepared, except that a polytetrafluoroethylene aqueous suspension (31JR, manufactured by Mitsui Fluorochemical Co., Ltd.) was further applied to the surface side of the reaction layer of the gas diffusion electrode to an extent that did not cause unevenness, thereby forming a hydrophobic resin layer. Electrolysis was performed under the same conditions as in Example 1.

In the electrolytic cell of this configuration, the resistance between the anode and cathode on the fourth day after current was supplied and electrolysis was started was 0.30 V. It is believed that the contact resistance of the electrodes was alleviated by forming a hydrophobic resin layer, and the resistance between the anode and cathode was further suppressed compared to Example 1. Also, as in Example 1, there was no need to provide a separate hydrophilic layer between the ion exchange membrane and the gas diffusion electrode, so assembly was easy.

Example 3
An electrolytic cell having the same configuration as in Example 1 was prepared, and electrolysis was performed under the same conditions, except that 0.0024 g of carbon powder (manufactured by Denki Kagaku Kogyo Co., Ltd., AB-11) and 0.0024 g of carbon powder (manufactured by Denki Kagaku Kogyo Co., Ltd., AB-6) were added to the suspension forming the reaction layer.

In the electrolytic cell of this configuration, the resistance between the anode and cathode on the fourth day after current was supplied and electrolysis was started was 0.31 V. Also, as in Examples 1 and 2, there was no need to provide a separate hydrophilic layer between the ion exchange membrane and the gas diffusion electrode, so assembly was easy.

(Comparative Example 1)
An electrolytic cell having the same configuration as in Example 1 was prepared, except that the carbon cloth of the gas diffusion electrode was fixed in close contact with the ion exchange membrane on the side where the reaction layer was disposed, in the cathode chamber, and electrolysis was performed under the same conditions.

In this electrolytic cell, the resistance between the anode and cathode deteriorated to 0.70 V four days after current was supplied and electrolysis began.

(Comparative Example 2)
An electrolytic cell was prepared in the same manner as in Example 1, and electrolysis was performed under the same conditions, except that a carbon cloth substrate two-chamber GDE manufactured by Permelec Electrodes Co., Ltd. was used as the gas diffusion electrode for the cathode, and further, a hydrophilic carbon cloth manufactured by Permelec Electrodes Co., Ltd. was disposed between the gas diffusion electrode and the ion exchange membrane.

In an electrolytic cell of this configuration, the resistance between the anode and cathode was 0.38 V four days after current was supplied and electrolysis was started.

On the other hand, in the electrolytic cell of this configuration, a hydrophilic layer of carbon cloth was placed between the gas diffusion electrode and the ion exchange membrane, so the number of parts increased and the ease of assembly was inferior to that of Example 1.

Comparative Example 2 is believed to have increased resistance due to the presence of additional contact resistance between the hydrophilic layer and the gas diffusion electrode and the resistance of the hydrophilic layer itself compared to Examples 1 to 3.

1 Electrolytic cell 2 Ion exchange membrane 3 Anode chamber 4 Cathode chamber 5 Anode electrode 6a Electrode support layer 6b Reaction layer 7 Gas diffusion electrode (cathode electrode)
8 Cushioning material 9 Cathode chamber back plate (cathode terminal)
10 Anode gasket 11 Cathode gasket 12 Anolyte inlet 13 Anolyte and gas outlet 14 Oxygen-containing gas inlet 15 Sodium hydroxide aqueous solution outlet

Claims (4)

An electrolytic cell for a two-chamber method for gas diffusion electrode salt electrolysis, which is partitioned into an anode chamber and a cathode chamber by an ion exchange membrane, an anode electrode is installed in the anode chamber, a cathode electrode is installed in the cathode chamber, and electrolysis is performed by supplying saline solution to the anode chamber and an oxygen-containing gas to the cathode chamber,
The cathode electrode is
a hydrophilic and conductive electrode backing layer;
(a) a gas diffusion electrode consisting of only two layers, i.e., a conductive reaction layer disposed on one side of the surface of the electrode support layer and containing a hydrophilic catalyst and a hydrophobic resin ; or
(b) A gas diffusion electrode consisting of only three layers: a conductive reaction layer that is disposed on one side of the surface of the electrode support layer and contains a hydrophilic catalyst and a hydrophobic resin; and a hydrophobic resin layer, the hydrophobic resin layer being disposed so as to be in contact with the surface of the gas diffusion electrode on which the reaction layer is disposed ;
The cathode electrode is electrically conductive;
the electrode backing layer has a liquid retention capacity per unit volume of the electrode backing layer of 0.10 g-H ₂ O/cm ³ to 0.80 g-H ₂ O/cm ³ ;
In the cathode chamber, the electrode support layer of the gas diffusion electrode is disposed so as to be in contact with the ion exchange membrane on a surface opposite to a surface on which the reaction layer is disposed.
An electrolytic cell using the two-chamber gas diffusion electrode salt electrolysis method. 2. The electrolytic cell according to claim 1, wherein the electrode supporting layer is formed from at least one selected from the group consisting of carbon, zirconium oxide, ceramics, polytetrafluoroethylene, a copolymer of tetrafluoroethylene and hexafluoropropylene, aramid resin, polyimide resin, polyvinyl chloride resin, nickel, stainless steel, silver, and gold. A method for producing chlorine gas, comprising a step of electrolyzing salt water using the electrolytic cell according to claim 1 or 2 . A method for producing sodium hydroxide, comprising a step of electrolyzing salt water using the electrolytic cell according to claim 1 or 2 .

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