JP2857110B2 - Alkali metal chloride aqueous solution electrolysis tank using gas diffusion electrode and electrolysis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic cell for electrolysis of an aqueous solution of an alkali metal chloride by an ion exchange membrane method using a gas diffusion electrode as an oxygen cathode, and more particularly to an improvement in oxygen supply efficiency, a reduction in voltage, and the use of air. The present invention relates to an electrolytic cell that enables use of diluted oxygen.

[0002]

2. Description of the Related Art In an alkali metal chloride aqueous solution electrolytic cell equipped with an anode, a cation exchange membrane and a gas diffusion electrode (oxygen cathode), an aqueous solution of an alkali metal chloride (hereinafter referred to as an aqueous solution of sodium chloride or saline) is diluted in an anode chamber. It is known to obtain a concentrated aqueous caustic soda solution and chlorine by supplying an aqueous caustic solution to the catholyte compartment and supplying a gas containing oxygen to the oxygen compartment and performing electrolysis. The outline of this electrolysis method is divided into an anode chamber having an anode with a cation exchange membrane and containing salt water, and a cathode section having a cathode and containing water or an aqueous solution of caustic soda. At the time of electrolysis, a cathode is used to obtain an aqueous caustic soda solution and a cathode gas is obtained by performing electrolysis using a gas diffusion electrode that performs electrolysis while supplying an oxygen-containing gas, using a porous material as a cathode. Things. Since the cathode is an oxygen gas diffusion electrode (hereinafter sometimes simply referred to as an oxygen cathode), and no hydrogen gas is generated at the cathode during electrolysis, the reaction is performed at an extremely low voltage as compared with a normal electrolysis method of the hydrogen generation type. It is also known that it is possible to make the process progress and a large energy saving effect can be expected.

Patent documents disclosing this production method include, for example, JP-A-54-97600 and JP-A-56-4747.
No. 84, No. 56-130482, No. 57-152479
No. 59-133386, No. 61-266591
No., JP-B-58-44156, 58-49639
And Japanese Patent Publication Nos. 60-9595 and 61-20634.

[0004] The electrolytic cell is divided by a cation exchange membrane into an anode chamber having an anode and a cathode section having a gas diffusion electrode.
The cathode part is further separated into a catholyte chamber and an oxygen gas chamber (also simply referred to as a “gas chamber”) by a gas diffusion electrode. In the electrolytic cell having such a configuration, the following reaction proceeds on the gas diffusion electrode (which is a cathode). 1 / 4O ₂ + 1 / 2H ₂ O + e ⁻ → OH ⁻ (1) The oxygen cathode provided in the cathode portion has a structure in which a reaction layer and a gas diffusion layer are bonded to each other, and the reaction layer also performs gas diffusion. The layer is also composed of a thin layer mainly composed of a porous conductor. The gas diffusion electrode has air permeability as a whole, mainly carbon black is used for a reaction layer on the electrolyte side of the gas diffusion electrode, and a catalyst made of a noble metal system such as platinum is supported in its fine pores. The diffusion layer on the gas supply chamber side is composed of a water-repellent porous thin layer through which gas can pass but no leakage of the electrolyte occurs. I have.

The reaction layer is in contact with an aqueous solution of caustic soda, and the gas diffusion layer is in contact with oxygen gas. Water from the aqueous caustic soda solution enters the hydrophilic phase from the reaction layer side, reacts at the interface with the hydrophobic phase, and a part of the water enters the gas diffusion layer in the form of water vapor, and the oxygen chamber (gas chamber) Pass to. Therefore, even if pure oxygen is supplied to the oxygen chamber, it becomes a mixed gas with water vapor. On the other hand, oxygen is supplied from the gas diffusion layer side, and the reaction of the formula (1) proceeds at the interface where water and oxygen meet. In the gas diffusion electrode, it is expected that it is important to sufficiently supply oxygen to the reaction layer against the flow of water vapor in order to allow the reaction to proceed efficiently at a low voltage.

[0006] The porous reaction layer and gas diffusion layer include:
Mix and mold materials such as hydrophilic carbon, water-repellent carbon, and fluororesin microparticles so that the characteristics gradually change from the hydrophilic surface in contact with the electrolyte to the water-repellent porous thin layer on the gas supply chamber side. Is becoming Therefore, the porous oxygen cathode can efficiently supply the oxygen-containing gas from the oxygen-containing gas supply side to the side in contact with the electrolyte, and the electrolyte easily penetrates into the electrode from the side in contact with the electrolyte. It diffuses but does not leak to the gas supply chamber as a liquid. Thus, in the oxygen cathode, in the presence of the sodium ion and the catalyst supplied from the side in contact with the electrolytic solution, the water is oxidized to a hydroxyl group, and caustic soda is generated. Hydrogen generated at the cathode in the conventional electrolysis of an aqueous solution of sodium chloride by an ion exchange membrane method without using an oxygen cathode is not generated by the present method using an oxygen cathode, and the electrolysis voltage can be reduced.

In the conventional gas diffusion electrode, the side in contact with the liquid portion has a hydrophilic layer having fine holes through which liquid can penetrate, and the gas supply chamber side has fine holes through which gas can penetrate without leaking liquid. And a water-repellent layer, which is formed by laminating these layers via a reinforcing material or a current collector made of a wire mesh or the like.
In a recent gas diffusion electrode oxygen cathode, the change from a hydrophilic thin layer of a catalytically active porous layer to a water-repellent layer changes stepwise, preferably continuously, in contact with the liquid part. A layer in which a hydrophilic portion (passage) having fine pores through which liquid can penetrate and a water-repellent portion (passage) having fine pores in contact with the gas portion and through which gas can enter and exit intermingle and intermingle; Water-repellent layers have been laminated. However, the method of supplying the gas to the gas diffusion electrode has not been improved, and the supply of oxygen cannot be said to be sufficient.

[0008]

As described above, in the oxygen cathode of the conventional gas diffusion electrode, the electrolyte or air is easily diffused in the porous electrode film, and particularly, the electrolyte leaks into the gas supply chamber. Improvements such as eliminating gas flow are of interest, but the uniformity of gas distribution when supplying gas from the gas supply chamber to the gas diffusion layer of the gas diffusion electrode, Changes in the current distribution in the electrode due to the loading method have not been sufficiently studied.
Further, the relationship between the property of the gas supplied to the gas diffusion electrode and the electrode overvoltage has not been sufficiently studied. For example, as in the case of supplying air from which carbon dioxide gas has been removed, oxygen is supplied in a state where oxygen is diluted with nitrogen,
When the cathodic reaction is allowed to proceed under conditions where the supply of oxygen is insufficient, the electrode overvoltage increases and a high electrolysis voltage is considered necessary. However, in the conventional electrolysis using a gas diffusion electrode, the cathodic reaction has never been performed at a practical level under the condition of insufficient oxygen supply. for that reason,
There has been no systematic study on how much the overvoltage related to the insufficient supply of oxygen is, and what measures are required to reduce the overvoltage related to the insufficient supply of oxygen.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that in order to reduce the electrode overvoltage in the cathodic reaction of oxygen, it is necessary to supply gas from the gas supply chamber to the gas diffusion layer of the gas diffusion electrode. After examining the relationship between the uniformity of gas supply, the quality of the gas and the method of applying a current to the gas diffusion electrode, it was found that the structure of the gas chamber was extremely important, and the present invention was reached. . That is, (1) an alkali metal chloride aqueous solution electrolytic cell using a gas diffusion electrode in which an anode compartment and a catholyte compartment are partitioned by an ion exchange membrane, and the catholyte compartment and the gas compartment are partitioned by a gas diffusion electrode. In the above, the short-diameter pitch is 0.5 mm or more and 5 mm that allows gas to flow three-dimensionally in the gas chamber.
An alkaline metal chloride aqueous solution electrolysis tank characterized by being filled with the following porous material. (2) The alkali chloride as described in (1) above, wherein the porous material is made of metal, and the cathode terminal and the gas diffusion electrode are electrically connected through the metal porous material. Metal aqueous solution electrolyzer. (3) All gas diffusion is performed by using the alkali metal chloride aqueous solution electrolytic cell according to (1) or (2) having a gas diffusion electrode filled with the porous material through which gas can flow in the gas chamber. An electrolysis method for an aqueous solution of an alkali metal chloride, characterized in that electrolysis is performed on the electrode surface at a flow rate of oxygen gas of 14 EN liter / m ² / min or more. Where E
Is a numerical value representing the current density flowing through the gas diffusion electrode in the unit of kA / m ² .

Hereinafter, the present invention will be described in detail. First, the gas diffusion electrode in contact with the porous material used in the electrolytic cell of the present invention will be described. In the present invention, a gas diffusion electrode suitable for use in the electrolysis of salt water has a two-layer structure of a reaction layer and a gas diffusion layer, and both layers are formed from a mixture of graphitic carbon and Teflon particles. Things. The reaction layer is mainly composed of a mixture of hydrophilic carbon fine particles and water-repellent carbon fine particles, mixed with fluororesin fine particles, and further supported on the carbon fine particles is a catalyst made of a noble metal such as platinum. The fine particles are formed into a porous plate to form a single reaction layer.

On the other hand, the gas diffusion layer is mainly composed of a mixture of fluororesin fine particles and water-repellent carbon, and these fine particles are formed into a porous plate to form a single gas diffusion layer. These reaction layer porous plate and gas diffusion layer porous plate, preferably a mesh-like support made of a conductor sandwiched between each porous plate, a layer close to the catholyte A gas diffusion electrode is formed by arranging and laminating a reaction layer formed of a hydrophilic porous plate and a gas diffusion layer formed of a hydrophobic porous plate near a gas chamber.

Further, in such a gas diffusion electrode, a high-performance reaction layer having higher performance is disclosed in, for example, JP-A-6-66142.
It has a structure in which a hydrophilic part and a hydrophobic part are mixed. In this electrode, water diffuses from the catholyte side through the hydrophilic part of the reaction layer, while oxygen diffuses from the gas chamber side through the gas diffusion layer, through the hydrophobic part of the reaction layer, and water and oxygen The reaction (1) for generating a hydroxyl group at the interface where meets occurs. The generated hydroxyl group leaves the reaction site through the hydrophilic part and diffuses into the catholyte. The surface of the gas diffusion layer may be further coated with a water-repellent resin such as Teflon in order to prevent the gas diffusion layer surface from being covered with liquid due to dew condensation and obstructing gas supply.

[0013] In the electrolysis of an aqueous solution of an alkali metal chloride using a gas diffusion electrode (oxygen cathode), the same reaction takes place at the anode as in a normal electrode. Cl ⁻ → １ ／ · Cl ₂ + e ⁻ (2) The thermodynamic energy required to promote the reactions of (1) and (2) is 0.96 V, but the other value is 0.96 V. 5 to 0.
An electric resistance of 7 V, an overvoltage of the oxygen cathode reaction of 0.7 to 0.9 V, and others were added, and a total voltage of 2.2 to 2.6 V was required.

[0014] It has not been previously known what causes such a large overvoltage of the gas diffusion electrode (oxygen cathode). The present inventors have found in the course of studying the structure of the current collector in the gas chamber of the cathode part that the structure of the oxygen passage has a significant effect on the oxygen overvoltage. Conventionally, as shown in FIG. 4, the gas chamber is provided with a wire mesh over the gas chamber, and a gas diffusion electrode is placed on the wire mesh.
As shown in FIG. 3, it was usual to form an oxygen passage as a gas chamber in the cathode portion of the electrolytic cell. When using such an oxygen chamber structure and using pure oxygen as the oxygen source, the voltage was 2.2 to 2.6 V as described above. It is preferable that air can be used as an oxygen source for the oxygen cathode reaction. However, when oxygen is diluted with an inert gas such as nitrogen, the overvoltage of the oxygen cathode further increases, and it is difficult to use air.

In the electrolytic cell of the present invention, the following means have been developed as means for reducing the oxygen overvoltage. That is, in the electrolytic cell of the present invention, the gas chamber on the gas diffusion layer side of the gas diffusion electrode is filled with a porous material through which gas can flow three-dimensionally, and the gas is supplied to the gas diffusion layer side of the gas diffusion electrode. Is supplied uniformly. In other words, the back side of the gas diffusion electrode is filled with the porous material. At this time, it is preferable that an oxygen flow of 14 EN liter / m ² / min or more can be sent to the gas diffusion layer surface of the gas diffusion electrode in the gas diffusion electrode.

Conventionally, there is an example in which a rigid gas-permeable porous body is inserted into a gas chamber of a gas diffusion electrode. However, in the prior art, the purpose of inserting the gas-permeable porous body,
The purpose is to reinforce the gas diffusion electrode in order to compensate for the disadvantage that the strength of the gas diffusion electrode is small, and to support the gas diffusion electrode from the back of the gas diffusion electrode. As shown in the figure, it is sufficient that the material has a function of partially reinforcing the material. For that purpose, the material must be rigid, and the gas permeability of the porous material may be any as long as it does not hinder the gas supply to the electrode. From such a relationship, depending on the inserted rigid gas-permeable porous body, the inflow of gas into the gas diffusion electrode may be partially prevented and the inflow of gas may be uneven. In contrast, the first condition of the porous material according to the present invention is that the porous structure of the porous material is such that the supply of gas to the gas diffusion electrode is performed uniformly and with low resistance.

The porous material capable of three-dimensionally circulating a gas filled in the gas chamber of the alkali metal chloride electrolysis cell of the present invention is not limited to an electrically conductive material, but the gas is uniformly dispersed in the gas diffusion electrode. Any material may be used as long as it can be flowed into the device, but it is preferable that the material be electrically conductive. That is, if the porous material to be filled in the gas chamber on the gas diffusion layer side of the gas diffusion electrode is made of metal, the metal porous material is in contact with the gas diffusion electrode on the entire surface. By connecting the cathode terminal to the conductive material, the porous material becomes a wide current collector, and the current distribution can be made more uniform than that of a conventionally used current collector. Furthermore, if the metal porous material and the gas diffusion electrode are joined and integrally formed, a conventional current collector is unnecessary. At this time, the current applied to the gas diffusion electrode is also uniformly applied to the entire surface of the gas diffusion electrode as compared with the current flowing when the current is applied from a terminal provided at the peripheral end of the gas diffusion electrode. can do.

FIG. 2 is a side longitudinal sectional view of a cathode portion configured to fill a gas material in a cathode portion of an electrolytic cell with a porous material through which gas can flow three-dimensionally. In FIG. 2, 1
0 is a gas diffusion electrode, 11 is a gas chamber, 12 is a porous material to be filled therein, and 15 is a cathode terminal. Note that, in the above description, the porous material is "filled" in the gas chamber, but in this case, the filling is not intended to be filled, but means that the gas chamber is provided until it comes into contact with the surface of the gas diffusion electrode. Therefore, since the object of the present invention is to uniformly supply the gas to the surface of the gas diffusion electrode, the gas should not be densely packed so as to hinder the flow of the gas, and is referred to as “insert” or “provide”. It should be understood that this may be meaningful. If the porous material is not electrically conductive, the outer frame of the cathode may be used, a separate current collector may be provided, or the cathode terminal may be electrically connected to the gas diffusion electrode.

The porous material may take various forms, and among them, a wire mesh is most preferable. Further, it may take a form such as an expanded mesh.
The gas containing oxygen flows macroscopically parallel to the gas electrode. Therefore, it is important that the porous material has air permeability in a three-dimensional direction, particularly in a direction parallel to the plane. In that sense, an excessively smoothed expanded mesh or the like has a poor gas permeability in the direction parallel to the surface when superposed, and is unsuitable as the porous material of the present invention. By the way, wire mesh itself is porous, can pass gas three-dimensionally, and also has a function as a current collector because it is made of metal. If this wire mesh is used, a current collector having a groove structure is unnecessary. As shown in FIG. 1, a wire mesh (porous material 1) is
When an electrolytic cell 1 filled with 2) was prepared, it was found that the cell voltage was lowered, and that the voltage did not increase even when air was used, and that the electrolysis could be stably continued at a low voltage.

The preferred embodiment will be described in more detail. As a wire netting, a wire netting of various weaves or an expanded mesh is suitable. With respect to the flatness, it is possible to use those that are woven and stretched, those that have been subjected to some degree of smoothing treatment by rolling, and those that are pressed and formed on a corrugated plate. Excessive smoothing is not preferred because it hinders the passage of gas in the plane direction. The pitch of the short diameter (dense direction) of the wire mesh is preferably about 0.5 to 5 mm. One sheet can be used alone, or a plurality of sheets can be used. A thickness of 0.2 mm to 2 mm can be used. When wire meshes having different pitches in the vertical and horizontal directions are stacked, it is preferable to change the directions so as not to hinder the passage of gas. In order to ensure electrical continuity, it is preferable that the overlapped wire meshes are welded to each other by spot welding or the like, and furthermore, to the gas container body. Ag plating of the wire mesh gives good results to ensure contact with the gas diffusion electrode. Further, the electrode is heated to a temperature close to the melting point of the main component PTFE,
The best contact state can be obtained by crimping and integrating with a wire mesh. In this case, the surface of the wire mesh is treated with a fluororesin in order to enhance the adhesiveness.

The thickness of the gas chamber is also important. Although the appropriate thickness varies depending on the size of the electrolytic cell, it is preferably about 0.5 mm to 3 mm for a normal-sized electrolytic cell. 0.5
mm, the pressure loss associated with the passage of gas increases,
If the thickness is larger than 0 mm, supply of oxygen to the electrode is deteriorated, and an overvoltage is increased. The gas chamber has a thickness of about 1 mm, and the structure completely filled with a wire mesh is extremely good. By using the electrolytic cell having such a configuration, the cell voltage can be reduced to 2 V or less. Further, even if air is used as the oxygen source, the rise in voltage can be suppressed to 0.1 V or less. The effects of these porous fillers are understood as follows. It is considered that oxygen in the gas chamber is diluted with water vapor and nitrogen, and a film having an extremely low oxygen concentration is formed on the surface of the gas diffusion electrode. It is considered that the presence of the filler causes the flow of the oxygen-containing gas to be turbulent, the film to be thinned, the supply of oxygen to be promoted, and the overvoltage to be reduced. Therefore, it is considered that it is more suitable to fill a passage having a larger porosity such as a wire mesh and a greater turbulence effect than a simple groove-shaped passage.

[0022]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited by these examples.

Example 1 An electrolytic cell 1 shown in FIG. 1 was assembled. The gas diffusion electrode 10 was prepared according to the description in JP-A-63-245863.
This is a two-layer electrode having a reaction layer of 100 μm and a gas diffusion layer of 400 μm. The reaction layer has a structure in which a hydrophilic portion and a water-repellent portion are entangled. The reaction layer supports platinum as a catalyst. As a porous material (wire mesh) 12 of a gas chamber (referred to as an “oxygen chamber” in this example) 11, a plate thickness of 0.2 m
m, a horizontal pitch of 2 mm, a vertical pitch of 1.5 mm, a strand of 0.2 mm and a thickness of 0.4 mm were used. The three sheets were overlapped so that their length and width were orthogonal to each other, and were spot-welded to a nickel plate on the back of the gas chamber. The total thickness of the three superposed wire nets was 1.2 mm. The gas diffusion electrode 10 was fusion bonded to the oxygen chamber / collector structure at a temperature of 350 ° C. at a pressure of 200 kg / cm ² . The porosity of the gas chamber was 65%.

The electrolytic cell 1 was constructed by stacking an anode 2 called DSA (registered trademark), a fluorine-based cation exchange membrane 6, and the above-mentioned current collector-integrated gas diffusion electrode 10. The distance between the anode 2 and the gas diffusion electrode 10 was 2 mm. The effective area of each electrode and the ion exchange membrane 6 is 10 × 10 cm ² respectively.
310 g / l of purified saline solution is heated and supplied to the anode chamber 3, and a 32% aqueous sodium hydroxide solution is heated to the catholyte chamber 7 (between the ion exchange membrane and the cathode) to obtain a solution of 200 g / l.
It was supplied at a flow rate of ml / min. A mixed gas of oxygen and nitrogen was supplied to the oxygen chamber 11 at a varied flow rate. While controlling the temperature of the entire electrolytic cell to 90 ° C., the electrolysis was performed while changing the current. Voltage between terminals at that time (voltage between anode chamber from back plate of oxygen chamber)
Is as shown in Table 1 below.

[0025]

[Table 1]

When the ohmic loss and overvoltage analysis were performed on the voltage, all the ohmic losses were 0.13 V / (kA / m ² ).
Therefore, the change in voltage shown in Table 1 is based on the change in overvoltage. The voltage when the flow rate of oxygen was changed is as shown in Table 2.

[0027]

[Table 2]

Comparative Example 1 An electrode equivalent to that of Example 1 was used as a gas diffusion electrode. The oxygen chamber having the structure shown in FIG. 4 was used as the oxygen chamber. The thickness of the oxygen chamber was 1 mm. The container material of the oxygen chamber is made of nickel. One wire netting and a gas electrode used in Example 1 were fusion-bonded in the same manner as in Example 1 and set in an oxygen chamber container. In this case, no wire mesh is provided in the oxygen chamber. The voltages for the electrolysis experiments are as shown in Table 3.

[0029]

[Table 3]

When ohmic loss and overvoltage analysis were performed on the voltage, all the ohmic losses were 0.13 V / (kA / m ² ).
The change in the voltage shown in Table 3 is based on the change in the overvoltage. Comparative Example 2 An electrode equivalent to that of Example 1 was used as a gas diffusion electrode.
The oxygen chamber having the structure shown in FIG. 3 was used as the oxygen chamber. Depth 1
A groove-shaped oxygen chamber having a width of 1 mm, a convex portion width of 1 mm, and a pitch of 15 mm was made of nickel. A gas diffusion electrode was fusion-bonded thereon in the same manner as in Example 1. The voltage of the electrolysis experiment was as shown in Table 4.

[0031]

[Table 4]

In Example 1 and Comparative Examples 1 and 2, when the electrolytic current density was 3 kA / m ² , the voltage applied between the anode and cathode terminals of the electrolytic cell was changed to the oxygen concentration in the gas supplied to the gas diffusion electrode. FIG. 5 shows the results of measurement at different concentrations. As shown in FIG. 5, when a conductive porous material is inserted into the oxygen chamber of the cathode to promote turbulence of the gas containing oxygen, the gas supply speed to the gas diffusion electrode increases, and It can be clearly seen that the voltage drops.

[0033]

According to the present invention, the gas chamber of the oxygen gas diffusion electrode is filled with a porous material capable of flowing oxygen gas three-dimensionally and having a short diameter pitch of 0.2 mm or more and 5 mm or less. By setting the flow rate to 14 EN liter / m ² / min or more on the entire gas diffusion electrode surface, even if the oxygen concentration is insufficient, for example, even under the condition of supplying decarbonated gas air, the cathode of oxygen Electrode overvoltage in the reaction can be minimized.

[Brief description of the drawings]

FIG. 1 is a sectional explanatory view of one example of an alkali metal chloride electrolytic cell of the present invention.

FIG. 2 shows one of the cathode portions of the alkali metal chloride electrolytic cell of the present invention.
FIG. 4 shows a cross-sectional explanatory view of an example.

FIG. 3 is a sectional explanatory view of one example of a cathode portion of a conventional alkali metal chloride electrolytic cell.

FIG. 4 shows a cross-sectional explanatory view of another example of the cathode portion of the conventional alkali metal chloride electrolytic cell.

FIG. 5 is a graph showing a relationship between the concentration of oxygen supplied to a gas diffusion electrode and a voltage between terminals of an anode and a cathode of an electrolytic cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolyzer 2 Anode 3 Anode chamber 4 Salt water inlet 5 Chlorine gas outlet 6 Ion exchange membrane 7 Catholyte chamber 8 Caustic soda water outlet 9 Caustic soda water inlet 10 Gas diffusion electrode 11 Gas chamber 12 Porous material 13 Oxygen inlet 14 Oxygen outlet 15 Cathode Terminal 16 Oxygen passage 17 Current collector

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C25B 1/00-15/08

Claims (3)

(57) [Claims] 1. An alkaline metal chloride aqueous solution electrolytic cell using a gas diffusion electrode in which an anode compartment and a catholyte compartment are partitioned by an ion exchange membrane, and wherein the catholyte compartment and the gas compartment are partitioned by a gas diffusion electrode. 3. The alkaline metal chloride aqueous solution electrolysis tank according to claim 1, wherein the gas chamber is filled with a porous material capable of three-dimensionally flowing gas and having a short diameter pitch of 0.5 mm or more and 5 mm or less. 2. The chloride according to claim 1, wherein the porous material is made of metal, and the cathode terminal and the gas diffusion electrode are electrically connected through the metal porous material. Alkali metal aqueous solution electrolyzer. 3. The method according to claim 1, further comprising a gas diffusion electrode filled with the porous material through which gas can flow in the gas chamber. The flow rate of oxygen gas at the surface of the diffusion electrode is 1
An electrolysis method of an aqueous solution of an alkali metal chloride, wherein electrolysis is performed under a condition of 4 EN liter / m ² / min or more. Here, E represents the current density flowing through the gas diffusion electrode in kA / m ^2.
It is a numerical value displayed in the unit of.