JPH0633490B2 - Gas diffusion electrode and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a gas diffusion electrode used for a fuel cell, a secondary battery, an electrochemical reactor, an anode for plating, and a method for producing the same.

(Prior Art) Conventionally, as a gas diffusion electrode, platinum, carbon black,
There is one in which a water-repellent gas diffusion layer made of carbon black and polytetrafluoroethylene is bonded to a hydrophilic reaction layer made of polytetrafluoroethylene.

When this gas diffusion electrode is used in a fuel cell or the like, the electrolytic solution permeates the reaction layer, but does not permeate the gas diffusion layer, but only the gas generated by the reaction or the supply gas diffuses and permeates the gas diffusion layer. is there.

(Problems to be Solved by the Invention) By the way, since the gas diffusion electrode is very thin, it lacks strength, is easily warped and is easily bent, and may be deformed or cracked during handling. In particular, when the gas diffusion layer is cracked, when used in a fuel cell, etc., the electrolytic solution passes along the crack through the gas diffusion layer, so that water repellency is lost and the function as a gas diffusion electrode is lost. Is. Therefore, the gas diffusion electrode must be handled with great care, and there is a problem in that it is extremely inferior in operability and workability.

Therefore, the present invention is intended to provide a gas diffusion electrode which has improved strength, is less likely to warp and bend, and is not deformed or cracked, and a method for manufacturing the same.

(Means for Solving Problems) The gas diffusion electrode of the present invention for solving the above problems is
Hydrophilic carbon black, water repellent carbon black, and polytetrafluoroethylene are impregnated and adhered to a non-woven sheet made of heat resistant fiber such as carbon fiber, Ni fiber, stainless steel fiber, aramid fiber, boron fiber, SiC fiber, and platinum. A reaction layer having a hydrophilic part and a water repellent part, which are impregnated and adhered with a group metal or an oxide thereof or both (hereinafter simply referred to as platinum group), has a water repellent property of water repellent carbon black or polytetrafluoroethylene. The gas diffusion layers are joined together.

Further, the production method of the present invention for producing a gas diffusion electrode having such a structure is such that hydrophilic carbon black is applied to a non-woven sheet made of heat resistant fibers such as carbon fiber, Ni fiber, stainless steel fiber, aramid fiber, boron fiber and SiC fiber. , Water repellent carbon black, polytetrafluoroethylene,
Water and surfactant are mixed and impregnated, then heated to remove water and surfactant, and then gas diffusion of water-repellent carbon black and polytetrafluoroethylene is applied to this reaction layer material sheet. The layer is characterized in that the layer is thermocompression-bonded, then the reaction layer material sheet is impregnated with a platinum group compound solution, and thermally decomposed to adhere the platinum group to form a reaction layer.

Hydrophilic carbon black has an active group having an affinity for water, such as -COOH, and has a property of dispersing in water. The water-repellent carbon black has been graphitized and has an affinity for water. Use those that do not have active groups with properties and do not disperse in water as they are.

(Operation) The gas diffusion electrode of the present invention configured as described above has a core of a non-woven sheet made of a heat resistant fiber such as carbon fiber, Ni fiber, stainless steel fiber, aramid fiber, boron fiber or SiC fiber in the reaction layer. Since it has a material, it has high strength and is not easily warped, and is not easily bent, so that it is not deformed or cracked during handling. In particular, since the gas diffusion layer is not cracked, when used in a fuel cell or the like, the electrolytic solution does not pass through the gas diffusion layer and water repellency can be maintained.

(Example) An example of the gas diffusion electrode of the present invention and a method for manufacturing the same will be described with reference to the drawings. The gas diffusion electrode 1 of the present invention shown in FIG. 1 has a width of 100 mm, a length of 100 mm and a thickness of 0.1 mm in a hydrophilic reaction layer 2 having a porosity of 65%, a width of 120 mm, a length of 12 mm and a thickness of 0.5 mm. The water-repellent gas diffusion layer 3 having a porosity of 65% is joined. The reaction layer 2 comprises a non-woven sheet having a thickness of 280μ and made of 7μ carbon fiber, a water repellent carbon black having an average particle size of 420Å, a hydrophilic carbon black having an average particle size of 450Å, and a polytetrafluoroethylene having an average particle size of 0.3μ. Ethylene fluoride powder was mixed at a ratio of 5: 5: 3, impregnated and adhered thereto, and platinum was used as a catalyst with the water repellent carbon black, hydrophilic carbon black, polytetrafluoroethylene powder and 1: 5 :.
It is impregnated and adhered in a ratio of 5: 3. The gas diffusion layer 3 is formed by mixing water-repellent carbon black having an average particle diameter of 420Å and polytetrafluoroethylene powder having an average particle diameter of 0.3 µ at a ratio of 7: 3.

Next, a method of manufacturing the gas diffusion electrode having such a structure will be described. First, as shown in FIG. 2a, a non-woven sheet 4 made of 7 μm carbon fiber having a width of 150 mm, a length of 300 mm and a thickness of 280 μm.
In addition, water repellent carbon black with an average particle size of 420Å, hydrophilic carbon black with an average particle size of 450Å, polytetrafluoroethylene powder with an average particle size of 0.3μ, water, and nonionic triton as a surfactant 5: 5: The coating solution mixed in the ratio of 3: 60: 6 is applied, then dried and heated at 280 ° C. for 3 hours to remove water and surfactant, and the reaction layer material sheet 5 shown in FIG.
Got Next, as shown in FIG. 2c, the reaction layer material sheet 5 is formed by mixing and molding water-repellent carbon black having an average particle size of 420Å and polytetrafluoroethylene powder having an average particle size of 0.3 μ at a ratio of 7: 3. A water-repellent gas diffusion layer 3 having a length of 120 mm, a length of 120 mm and a thickness of 0.5 mm is thermocompression bonded at 380 ° C. and 600 kg / cm ² for 3 seconds, and then the reaction layer material sheet 5 is coated and impregnated with a chloroplatinic acid solution. is allowed, and heated to 200 ° C. to decompose the platinum compound was reduced in a H ₂ 200 ° C. to adhere the platinum 0.56 mg / cm ^2, the reaction layer of a porosity of 65% was formed as shown in FIG. 2 d A gas diffusion electrode 1 was made.

Since the non-woven sheet of carbon paper 4 is contained as the core material in the reaction layer 2 of the gas diffusion electrode 1 of the example thus produced, the gas diffusion electrode has a high bending strength, is hard to warp, and is not easily bent. Is. Therefore, it is not deformed or cracked during handling. In particular, since the gas diffusion layer 3 is not cracked, when used in a fuel cell or the like, the electrolytic solution does not pass through the gas diffusion layer 3 and water repellency can be maintained.

The reaction layer 2 is a non-woven sheet of carbon paper 4
Since it is included as a core material, it has a high porosity of 65%, so the catalytic reaction of platinum is sufficiently performed and the catalytic performance is improved.

Incidentally, in the above embodiment, the non-woven sheet 4 serving as the core material of the reaction layer 2
Carbon fiber was used for Ni fiber, stainless steel fiber, aramid fiber, boron fiber, SiC
It may be a fiber or a mixture thereof.

However, in the gas diffusion electrode of the present invention, in order to further improve the bending strength, the carbon paver nonwoven sheet 4 is formed on the surface of the gas diffusion layer 3 on the side opposite to the reaction layer 2 as shown in FIG. For example, a reaction layer material sheet 5 having no platinum group, which is formed by impregnating and adhering carbon black and polytetrafluoroethylene powder, may be heated and pressure bonded. By doing so, since the nonwoven sheet 4 which is the core material is provided on both sides of the gas diffusion electrode, the bending strength is remarkably increased, and warpage and bending can be eliminated.

(Effects of the Invention) As can be seen from the above description, the gas diffusion electrode of the present invention has a strong strength, is less likely to warp, and is less likely to bend because the reaction layer contains the core material of the non-woven sheet, and thus is deformable in handling. No cracks or cracks. Therefore, handling of the gas diffusion electrode is facilitated, and operability and workability are improved. Moreover, when used in a fuel cell or the like, since the gas diffusion layer has no cracks, the electrolytic solution does not pass through the gas diffusion layer, and the gas diffusion layer can maintain water repellency. Further, since the non-woven sheet core material is contained in the reaction layer as described above, the porosity is increased, the catalytic reaction of the platinum group is sufficiently performed, and the catalytic performance of the reaction layer is improved.

Further, according to the method for producing a gas diffusion electrode of the present invention, the above excellent gas diffusion electrode can be easily produced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the gas diffusion electrode of the present invention, FIGS. 2a to 2d are views showing steps of the manufacturing method of the present invention for producing the gas diffusion electrode of FIG. 1, and FIG. It is sectional drawing which shows the other Example of the gas diffusion electrode of this invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location H01M 4/96 M (56) References JP-A-60-140668 (JP, A) JP-A-60 -70194 (JP, A) JP 59-177865 (JP, A) JP 60-262989 (JP, A) Actual development Sho 58-54564 (JP, U)

Claims (2)

[Claims] 1. A hydrophilic carbon black having an active group having an affinity for water on the surface of a non-woven sheet made of heat resistant fiber,
Water-repellent part and water-repellent surface formed by impregnating and adhering water-repellent carbon black or polytetrafluoroethylene, which has no active group having affinity for water, on the surface, and further impregnating and adhering platinum group metal or its oxide or both. A gas diffusion electrode in which a water-repellent gas diffusion layer composed of water-repellent carbon black and polytetrafluoroethylene, which does not have an active group having an affinity for water, is bonded to a reaction layer having a portion. 2. A hydrophilic carbon black having a water-friendly active group on the surface of a non-woven sheet of heat-resistant fibers,
A water-repellent carbon black that does not have active groups with affinity for water, polytetrafluoroethylene, water, or a surfactant mixed on the surface is applied or impregnated and then heated to give water and surface activity. After removing the agent, a gas diffusion layer composed of water repellent carbon black and polytetrafluoroethylene, which does not have an active group having an affinity for water on the surface of the reaction layer material sheet, is heated and pressure-bonded to the reaction layer material sheet. A method for producing a gas diffusion electrode, which comprises impregnating a layer material sheet with a platinum group compound solution and thermally decomposing it to deposit a platinum group metal or its oxide or both to form a reaction layer.