JPS60140668A - Gas diffusion electrode - Google Patents

Abstract

PURPOSE:To obtain a low-cost gas-diffusion electrode having a superior characteristic and a long life by pressing and fixing a catalyst layer and a diffusion layer on the surfaces of a specific porous thin tetrafluoroethylene film. CONSTITUTION:A high-extension fiber material 1 obtained by a general method for manufacturing a porous fluorine resin film has a thickness of 15mum or less, a mean hole diameter of 0.2-15mum and a porosity of 90% or more. After a catalyst layer 2 is affixed to one surface of the fiber material 1 and a diffusion layer 3 is affixed to the other surface of the fiber material 1, the thus formed body is pressed to make a gas diffusion electrode. As a result, the thickness of the film 1 is decreased and its density is increased, thereby achieving further increased water-repellency while minimally changing the gas permeability. Besides the film 1 exhibits a good conductivity despite the fact that the fiber material 1 before undergoing the above process works as an insulating material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the creation of a gas diffusion electrode, which is used in fuel cells and oxygen
The gas diffusion 1kL electrode used in batteries such as metal batteries, salt, paper waste tanks, and other fil vaporization chemical devices has been improved in terms of electrode characteristics and life span, and is low-cost and easy to manufacture. It is something.

Gas diffusion electrodes used in fuel cells are generally composed of a catalyst, a current collector, and a waterproof and breathable diffusion layer. Expanded metal, punched metal, etc. are used, and as the diffusion layer, a water-repellent fluororesin/resin porous membrane feather such as a fine fiber material of polytetrafluoroethylene resin is used. In other words, as mentioned above, only a limited number of metal materials with resistance to electrolytes and reactive gases can be used as current collectors, making them expensive.Furthermore, the porous fluororesin membrane used as the diffusion layer is not an insulator. Therefore, it is necessary to take out lead wires to the outside in order to take out or supply the generated electricity and to connect each cell, which is complicated. In order to avoid the above-mentioned disadvantages, a structure has been proposed in which the diffusion layer is made electrically conductive, and a direct electrical connection is obtained from the catalyst layer to the back surface through the diffusion layer. It has been proposed to use a porous material bound with a water-repellent binder such as a fluororesin, or to use carbon paper waterproofed with a fluororesin. However, in these cases, Since the pore size is relatively large and lacks uniformity, the water-repellent resin used as the binder must have multiple values in order to obtain sufficient waterproofness, and as a result, the tetraelectricity deteriorates. Of course, the waterproofing treatment itself as described above is also complicated.

In view of the above-mentioned circumstances, the present invention has been devised using the classification system 11 (11). The film thickness produced by the porous fluororesin film manufacturing method is 15 μm or more1
The average pore diameter is 0.2 to 15 μm, and the porosity is 90%.
Commercial stretch ratio fiber material with the above characteristics (for example, the film used in Gore-Tex bag filters)
average pore diameter 3μmS film thickness 12μm1 porosity 95%)1
The fiber material 1 may be either a fired product or an unfired product. A catalyst layer 2 is layered on one side of such a fiber material 1, and this catalyst layer 2 is made of activated carbon, graphite powder, carbon black, or a mixture thereof, or a mixture of carbon powder* and a catalyst. It is a mixture of powders bound together with a fluororesin adhesive. Furthermore, a diffusion layer 3 is layered on the other side of the fiber material 1, but since the above-mentioned specific fiber material 1 is used for this diffusion layer 3, it itself has waterproof properties and is particularly strong. Therefore, there is no need to use multiple layers of water-repellent resin, etc., as in the past.For example, carbon paper or slightly waterproof carbon paper (or carbon powder with water-repellent A1 A layer bound with fat is sufficient, and the same applies to the catalyst layer 2.

That is, when the above-mentioned porous fluororesin film 1 has a film thickness of 15 μm or less and an average pore diameter of 0.2 to 15 μm, the catalyst layer and diffusion layer 3 described above are laminated and pressurized.
As the thickness of the film 1 becomes relatively thin, the 414 structure becomes denser, and the waterproof property is further improved without substantially changing breathability.Moreover, it is preferable that the film 1 is originally used as an insulating material. It shows good 5-t (conductivity) even though it is not conductive (4I). By press-forming with the film 1, a highly water-repellent waterproof layer is formed on the extremely thin film 1, and conductivity is obtained by penetrating a certain amount of conductive powder into the porous structure. It is presumed that since the thickness becomes thinner, it exhibits a large electrical resistance.

In the product according to the present invention, if 1Pfi# of the porous tetrafluoroethylene resin is 15 μm or more, effective conductivity cannot be obtained when pressure is applied, and air permeability tends to be impaired. If the diameter is less than 2 μm, the handleability becomes extremely poor and effective waterproofing properties cannot be obtained.

In addition, if the average pore diameter is 0.2 μm or less, effective conductivity cannot be obtained even after pressure lamination, whereas if the average pore diameter is 15 μm or more, the waterproof layer that is the object of the present invention cannot be formed. Can not do it. If the 45'RK porosity is less than 90 inches, effective conductivity cannot be obtained.

In addition, in the above-mentioned lamination and integration, it is preferable to use a surface pressure of 10 or more; below this level, integration cannot be obtained, and the above-mentioned conductivity cannot be properly obtained. In addition, when the contact pressure exceeds that made by XOCIO, the electrode as a whole has air permeability.A specific manufacturing example of the electrode according to the present invention will be described below.

Production Example 1 A fluororesin porous material containing 70% carbon black (VULCAN Two membrane bodies were produced. The physical properties of Chiko's membrane are as follows: Shiba Inu pore diameter is 0.6 μm, galley number 11 seconds, film thickness 120 μm, maximum pore diameter 08 μm1, galley number 10 seconds, film thickness 8
It is 0 μm.

These two membrane bodies were bonded together as shown in Figure 1 above through a stretched porous fluororesin fibrous material with an average pore diameter of 5 μm, a nitrogen porosity of 97%, and a film thickness of 10 μm. A laminated counterfeit film having a thickness of 80 μm was obtained by applying pressure with a roll.

Furthermore, the four sides of the structured film thus obtained were fixed and heated to 355°C.
The mixture was heated for 5 minutes to form a laminated integrally formed membrane. That is, the physical properties of the structured membrane obtained as described above are such that the Shiba Inu pore diameter is 05 μm.
m, Gurley number of 80 seconds, j film thickness of 100 μm, the amount of platinum supported was determined by moistening this film with methanol, replacing water with methanol, and further performing platinum chloride vXX liquid-liquid replacement and then reducing it. An electrode film having a weight of 0.7 wt was obtained.

That is, as shown in FIG. 2, the membrane material prepared as described above is covered with a carbon paper 11 on one side (the thinner carbon layer) and a stainless steel net 12 on the back side of the membrane material 1o. By joining the stainless steel plate 13 together, it becomes a gas diffusion electrode for the salt and decomposition tank 20 as shown in FIG. 30 wt% Na0H) between the inlet 1T and the ion father exchange membrane (e.g. Nafion 2).
27) When salt electrolysis was performed using No. 15, at a current density of 20 V and a tank temperature of 85°C, the cell voltage was 2 at the initial stage of observation.
．． 30V, and this value hardly changed even after 90 days. Needless to say, there was no leakage of water from the electricity wells, and stable operations were achieved.

Production Example 2 Carbon black containing 10 wt % of platinum catalyst (VULCANXC-7 manufactured by Cabot, USA)
2) Add polytetrafluoro dispersion to 1)
Add 10wt% in 8 minutes, knead, and then expand to form a 0.5% powder.
A catalyst layer was formed in the form of a 15 mm sheet.

Apart from the above, 4'g of the same dispersion (in addition 1
A diffusion layer having a thickness of 0.08 M was formed into a sheet by kneading and expanding the mixture.

Each sheet as described above has an average pore diameter of 3/jm and a film thickness of 1
0 μm and a stretched porous film with a porosity of 96% (after polymerization via the fat film 1, both end faces were
．． After sandwiching between 2 μm porous fluorine side membranes and pressurizing and integrating with a surface pressure of 30 υ, heat treatment was performed at 250°C for 10 minutes. 'Turtle@!' according to the present invention with a total N of 0.18 myn after peeling off the resin film! , IIa was obtained.

This material was further coated with an aqueous dispersion of 60% polytetrafluoroethylene and 40% FEP on the surface of the diffusion layer, and then further impregnated with an aqueous dispersion of the same composition to a ZI5' carbon paper. -Press 3
The prefectural power grid was bonded by heating and pressurizing it to 0°C to create a gas diffusion device.

However, when an oxygen-hydrogen fuel cell was constructed using the electrodes tabulated as described above as an anode and a negative orange, and KUH was used as an electrolyte, the output characteristics were measured and the results are shown in Figure 3. It is stable and the results of the durability test are 1! in Figure 4. J type, discharge time 20
It was confirmed that it still had sufficient durability even after 00 hours or more.

In the case of the present invention as explained above, the film thickness is 15 μm.
Below, a catalyst layer consisting of carbon powder, a binder and a catalyst and a diffusion layer which is a tetraelectric porous layer are formed through a porous tetrafluoroethylene resin thin film with an average pore diameter of 02 to 10 μm and a porosity of 90% or more. By laminating them under pressure and integrating them, a relatively thin layer of gas diffusion electrode is formed.It also has good waterproof properties, which makes it possible to use a wider variety of materials as the diffusion layer material, resulting in lower costs. This invention has the advantages of providing a product with sufficient durability and further making it possible to downsize the entire device, making it a highly effective invention industrially.

[Brief explanation of drawings]

The drawings show the technical content of the present invention. Figure 1 is a sectional view of the gas diffusion '6L& according to the present invention, and Figure 2 shows a manufacturing example of the same when applied to an electrolytic cell. A cross-sectional explanatory diagram, FIG. 3 is a diagram of output characteristic measurement results of a manufacturing example, and FIG. 4 is a consolidated result of a durability test. In these drawings, 1 is a porous tetrafluoroethylene resin thin film, 2 is a catalyst layer, 3 is a diffusion layer, 10 is an electrode membrane material, 11 is carbon vapor, 12 is a stainless steel net,
13 is a stainless steel plate, 16 is a catholyte inlet, 1T is a catholyte inlet, and 20 is an electrolytic cell. Patent applicant Japan Gore-Tex Co., Ltd. Inventor Hiroshi Kato',,:', Company 2 The color of the procedural amendment is ゝ Showa 5 bag 12 bow 0 Commissioner of the Patent Office Kazu Wakasugi Failure 1, case display 11ij Kazu 6;” Year special l1v-application number: 241B/'7
f r. 2. Invention of the invention, i & name dregs payment #kinkaki 3. Person making the amendment Patent applicant name (name)
Month Date Dispatch 6, Contents of Amendment Subject to Amendment 1, Section ``2 Claims'' on page 1 of the specification of the present application are revised as follows. 1 The film thickness is 15 μm or less and the average pore size is 0.2 to 10 μm.
A catalyst layer consisting of a carbon powder binder and a catalyst and a diffusion layer which is a conductive porous layer are pressurized through a porous tetrafluoroethylene resin thin film having a porosity of 90% or more. A dregs diffusion electrode characterized by having a t/L layer. 2 Porous tetrafluoroethylene resin thin 11m has countless connections f1
Consists of fine fibers interconnecting 11iXl♂, so, h, etc.! 1. A gas diffusion electrode as described in scope 1 of the J permit application. , ” Procedural amendment filed on September 4th, 1920 by Kazu Wakasugi, Commissioner of the Japan Patent Office Failure 1. Indication of the incident, 1923 General Application No. 111f #7; 2. Name of the invention, Sword 1 Personality tJk 3. Relationship with the person making the amendment 9 N. Applicant Name (Name) Japan Goatenox (Shu Shikikai 1 Sat 4,
Agent dispatched on the 27th of May 1972 6. Contents of the amendment subject to amendment

Claims (1)

[Claims] 1. The film thickness is 15 μm or less and the average pore diameter is 0.2 to 10 μm.
A membrane consisting of carbon powder, a binder, and a catalyst is passed through a thin film of porous tetrafluoroethylene resin having 90% or more of voids, and then a membrane consisting of carbon powder, a binder, and a catalyst, and a diffusion layer, which is a tetraelectric porous layer, are polished horizontally under pressure. A gas diffusion electrode characterized by: 2. The gas diffusion electrode according to claim 1, wherein the porous tetrafluoroethylene resin thin film is composed of numerous nodules and micro+I41] fibers interconnecting them.