JPH06228781A - Gas diffusion electrode and production thereof - Google Patents

Abstract

PURPOSE:To provide a gas diffusion electrode by which water repellency of the gas diffusion layer is reinforced, dew condensation on the surface of the gas electrode is prevented, drops of water hardly remain, and the life of the electrode is prolonged, and to provide a production method. CONSTITUTION:A dendritic porous layer 4 consisting of water-repellent material is formed on a gas diffusion layer 3 of a gas diffusion electrode 1. The dendritic porous layer 4 is formed by spraying a soln. or dispersion liquid consisting of water-repellent material and solvent onto the surface of the gas diffusion layer of the gas diffusion electrode 1 kept at temp. the solvent smoothly vaporizes. The sprayed material is grown into a dendritic state and then sintered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved gas diffusion electrode used in electrolysis, batteries, electroplating, electrochemical reactors and the like, and a method for producing the same.

[0002]

2. Description of the Related Art A conventional gas diffusion electrode has a reaction layer (carrying a catalyst) in which a fine hydrophilic portion (passage) through which a liquid can permeate and a fine water repellent portion (passage) through which a gas can flow in and out are in contact with each other. In general, the reaction layer is laminated with a gas diffusion layer in which fine water-repellent portions (passages) through which gas can flow in and out are finely dispersed.

By the way, in the gas diffusion electrode, in electrolysis, batteries, electroplating, etc., the water repellency of the gas diffusion layer deteriorates with time, and dew condensation occurs on the surface of the gas diffusion layer so that water droplets accumulate. It takes a short time to reach the end and the life of the gas diffusion electrode is short. In addition, since the surface of the gas diffusion layer of this gas diffusion electrode is flat, even if it is slightly soiled, the water repellency will be reduced, dew condensation will occur more quickly, and water droplets will accumulate, which further increases the service life. Making it short.

[0004]

Therefore, the present invention can reinforce the water repellency of the gas diffusion layer, prevent dew condensation on the surface of the gas diffusion layer, prevent water droplets from accumulating, and prolong the life. A gas diffusion electrode and a method for manufacturing the same are provided.

[0005]

The gas diffusion electrode of the present invention for solving the above-mentioned problems is characterized in that a dendritic porous layer made of a water-repellent substance is formed on the surface of the gas diffusion layer. To do.

Further, in the manufacturing method of the present invention for producing this gas diffusion electrode, the solution or dispersion of the water-repellent substance and the solvent is sprayed onto the surface of the gas diffusion layer of the gas diffusion electrode which is kept at a temperature at which the solvent is rapidly evaporated. It is grown in a dendritic form and sintered to form a dendritic porous layer. For example, when polytetrafluoroethylene is used as the water repellent substance, the gas diffusion electrode is
While heating and holding at 120-160 ℃, on the surface of the gas diffusion layer,
A powder of polytetrafluoroethylene is slowly sprayed and grown in a dendritic form and then sintered at 340 ° C. to form a dendritic porous layer. In this manufacturing method, the reason why the gas diffusion electrode is heated and maintained at a temperature at which the solvent rapidly evaporates is that the surface of the gas diffusion layer is necessary for the polytetrafluoroethylene powder to grow in a dendritic form, This is because at a temperature lower than that, the surface of the gas diffusion layer does not grow like dendritic and becomes flat. The reason for sintering is to maintain the shape of the powder of polytetrafluoroethylene that has adhered and grown and to sinter.

[0007]

As described above, in the gas diffusion electrode of the present invention, since the dendritic porous layer made of the water repellent material is formed on the surface of the gas diffusion layer, the water repellency of the gas diffusion layer is reinforced and the gas diffusion layer is reinforced. Condensation on the surface of the diffusion layer is prevented, and water drops are less likely to collect. Moreover, since the surface of the gas diffusion layer has a dendritic shape, the water repellency does not deteriorate even if it is slightly soiled, so that dew condensation does not occur and water droplets do not easily accumulate. Therefore, the life of the gas diffusion electrode is extended. Further, according to the method for manufacturing the gas diffusion electrode of the present invention, the gas diffusion electrode having a long life can be easily manufactured.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the gas diffusion electrode and the method for manufacturing the same according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the gas diffusion electrode 1 of the present invention has a fine hydrophilic part (passage) through which a liquid can permeate and a water repellent part (passage) through which gas can flow in and out, and is in contact with each other. , 120 mm in height in which the reaction layer 2 having a thickness of 0.1 mm and the fine water-repellent portion (passage) that is bonded to the reaction layer 2 and allows gas to flow in and out are finely dispersed.
m, width 120 mm, thickness 0.5 mm, gas diffusion layer 3, and water repellent material formed on the surface of this diffusion layer 3, in this example, water repellent composed of polytetrafluoroethylene and carbon black 5: 5 It is composed of a dendritic porous layer 4 of material. The thickness of the dendritic porous layer 4 in the gas diffusion electrode 1 is
10 to 25 μm at the tip of the branches, 2 to the groove between the branches
18 μm.

In the manufacturing method of the present invention for producing the gas diffusion electrode 1 having such a structure, hydrophilic carbon black having an average particle diameter of 420Å, water repellent carbon black and polytetrafluoroethylene powder having an average particle diameter of 0.3 μm are 4: 4. Mix in a ratio of 3: 3, spread this mixed powder on the upper surface of the steel mold, and put it on a sheet,
Rolled to form a reaction layer 2 having a thickness of 0.5 mm, a length of 50 mm and a width of 50 mm, and water-repellent carbon black having an average particle diameter of 420Å and polytetrafluoroethylene powder having an average particle diameter of 0.3 μm in a ratio of 6: 4. And spread the mixed powder on the upper surface of the steel mold and put it into a sheet, and roll it to a thickness of 2.5 mm, length 50 mm, width 50 mm
The gas diffusion layer 3 was prepared. Then, the reaction layer 2 and the gas diffusion layer 3 are combined, rolled to about 0.7 mm, and heated and pressed at 380 ° C. to form the gas diffusion electrode 1, and then the gas diffusion electrode 1 is placed on the heating table. While maintaining the temperature at ℃, on the surface of the gas diffusion layer 3, a water-repellent substance, in this example, an average particle size of 0.3
A powder prepared by mixing polytetrafluoroethylene powder of μm and water-repellent carbon black having an average particle size of 420Å at a ratio of 5: 5 was slowly sprayed and allowed to grow into dendritic form, then at 340 ° C.
And is sintered to form the dendritic porous layer 4.
The water repellent substance may be polytetrafluoroethylene or a mixed solution of polytetrafluoroethylene and carbon fluoride.

However, in the electrolysis, the gas diffusion electrode 1 of the above embodiment was used as an anode and a cathode, and after 200 hours, the occurrence of dew condensation on the dendritic porous layer 4 on the surface of the gas diffusion layer 3 was inspected. When I did, there was nothing. Further, after 2000 hours, when the condition of the occurrence of dew condensation was similarly inspected, a slight amount of dew condensation was found in the portion of the dendritic porous layer 4 with relatively few irregularities, but it was not enough to accumulate water drops. Didn't. On the other hand, a gas diffusion electrode having no dendritic porous layer 4 on the surface of the gas diffusion layer 3 was similarly used as an anode and a cathode in the electrolysis, and after 200 hours, dew condensation occurred on the surface of the gas diffusion layer. When the condition was inspected, dew condensation was found on almost the entire surface, and water droplets had accumulated in places.

[0011]

As can be seen from the above description, in the gas diffusion electrode of the present invention, since the dendritic porous layer of the water repellent material is formed on the surface of the gas diffusion layer, the water repellency of the gas diffusion layer is reinforced. As a result, dew condensation on the surface of the gas diffusion layer is prevented, water droplets are hard to collect, and the surface of the gas diffusion layer is dendritic, so there is no decrease in water repellency even if some dirt is attached,
Therefore, the life of the gas diffusion electrode is significantly extended. Further, according to the method for producing a gas diffusion electrode of the present invention, the gas diffusion electrode having the above excellent effects can be easily produced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a gas diffusion electrode of the present invention.

[Explanation of symbols]

 1 gas diffusion electrode 2 reaction layer 3 gas diffusion layer 4 dendritic porous layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication H01M 4/86 MH 4/88 H

Claims (2)

[Claims] 1. A gas diffusion electrode, wherein a dendritic porous layer made of a water-repellent substance is formed on the surface of the gas diffusion layer in the gas diffusion electrode. 2. A solution or dispersion of a water-repellent substance and a solvent,
A method for producing a gas diffusion electrode, characterized in that the solvent is held at a temperature at which it is rapidly evaporated, and is sprayed on the surface of the gas diffusion layer of the gas diffusion electrode to grow in a dendritic form and sintered to form a dendritic porous layer. .