JPH0628163B2 - Fuel cell electrode / matrix combination - Google Patents

Description

The present invention relates to a fuel cell electrode / matrix combination.

[Conventional technology]

FIG. 2 is a sectional view showing a conventional fuel cell electrode / matrix combination disclosed in, for example, Japanese Examined Patent Publication No. 58-152, in which (1) is an electrode substrate and (2) is a catalyst layer. , (3) is a catalyst impregnated layer, and (4) is a matrix layer.

Next, the manufacturing method will be described. The electrode substrate (1) is electrically conductive and breathable. For example, by immersing a porous electrically conductive sheet such as carbon paper in a dispersion liquid of polytetrafluoroethylene (hereinafter abbreviated as PTFE) A water-repellent material is used.

The catalyst layer (2) is formed by, for example, applying a catalyst paste containing platinum fine particles on a carbon powder surface and PTFE as a binder to the electrode base material (1), for example, 3
What was heat-treated at a temperature of around 00 to 350 ° C is used. The matrix layer (4) is, for example, a catalyst layer containing a matrix paste containing silicon carbide powder and PTFE as a fixing material.
It is formed by applying to (2) and subjected to heat treatment at a temperature of about 300 to 350 ° C., for example. Catalyst layer
(2) and the matrix layer (4) are individually heat treated,
May be done at the same time.

As a method of applying the catalyst paste and the matrix paste, there are a spray method, a curtain coating method, a doctor blade method and the like. The above catalyst paste is used as an electrode substrate (1)
When applied to, the catalyst paste is soaked into the electrode base material (1) to form a catalyst impregnated layer (3),
The depth thereof changes depending on conditions such as the size of the pores of the electrode base material (1), the strength of water repellency, the viscosity of the catalyst paste, and the like. Therefore, the depth of the catalyst-impregnated layer (3) is easily influenced by the manufacturing base of the electrode base material (1) and the catalyst paste. In addition, if the size of the pore diameter and the distribution of water repellency are not uniform in one electrode base material (1), the distribution of the depth of the catalyst impregnated layer (3) will not be uniform. Furthermore, the PTFE used for the water repellent treatment of the electrode base material (1) melts when the heat treatment is performed at a temperature of around 300 to 350 ° C after the application of the catalyst paste to change the pore structure of the catalyst layer (2). Will end up.

[Problems to be solved by the invention]

Since the conventional fuel cell electrode / matrix combination is configured as described above, the catalyst paste is used as the electrode base material (1).
Since it penetrates into the inside of the electrode base material and the pores of the electrode base material (1) are filled with the catalyst powder and the binder, there is a problem that the gas diffusivity of the electrode base material (1) decreases. . In the case of the method of retaining the electrolyte inside the electrode base material such as the ribbed electrode, there is a problem that the amount of the retained electrolyte is reduced and the battery life is shortened because the pore volume is reduced. . In addition, the catalyst that has penetrated into the electrode base material (1) is not effectively used in the cell reaction, so that the catalyst utilization rate is low. Further, when an electrode base material subjected to water repellent treatment is used, there is a problem that the electrolyte such as phosphoric acid can be applied and impregnated only from the surface of the matrix layer.

The present invention has been made to solve the above problems, and can improve the gas diffusivity of the electrode base material, increase the amount of electrolyte retained in the electrode base material, and improve the catalyst utilization rate, An object is to obtain a fuel cell electrode / matrix combination capable of coating and impregnating an electrolyte such as phosphoric acid from both the catalyst layer surface and the matrix layer surface.

[Means for solving problems]

The fuel cell electrode / matrix binder according to the present invention separates the electrode base material and the catalyst layer / matrix binder, and binds the catalyst layer / matrix binder to the catalyst powder from one surface of the porous sheet. And a catalyst layer comprising a catalyst-filled layer filled with a material and a catalyst-attached layer having catalyst powder and a binder attached to the surface of the catalyst-filled layer, and a matrix skeleton material from the other surface of the porous sheet. And a matrix filling layer filled with a fixing material, and a matrix layer including a matrix attachment layer having a matrix skeleton material and a fixing material attached to the surface of the matrix filling layer.

[Action]

The fuel cell electrode / matrix combined body according to the present invention can form the catalyst layer / matrix combined body as an independent film, and can produce the electrode / matrix combined body without adversely affecting the pore structure of the electrode base material and the catalyst. It can be used for battery reaction without waste.

Example of Invention

In order to stably obtain the catalyst layer / matrix combination according to the present invention, the porous sheet preferably has a porosity of, for example, 50% or more (preferably 75% or more), for example, a thickness of 30 to 300 μm ( A carbon fiber sheet of 50 to 200 μm is preferable. The thickness of the catalyst adhesion layer is, for example, 10 to
200 μm (preferably 50 to 150 μm), the thickness of the matrix attachment layer is, for example, 30 to 300 μm (preferably 50 to 200 μm)
m) is desirable. The total thickness of the catalyst layer is, for example, 50 to 400 μm (preferably 100 to 300 μm), and the total thickness of the matrix layer is, for example, 50 to 500 μm (preferably 1 μm).
00-300 μm) is desirable.

The catalyst layer is composed of catalyst powder and a binder. As the catalyst powder, one in which platinum fine particles are supported on the surface of carbon powder is used, and as the binder, polytetrafluoroethylene (PTFE) or tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter abbreviated as FEP) Fluorine resin such as is suitable.

The matrix layer is composed of a matrix skeleton material and a fixing material. As the matrix material, carbon, an inorganic compound, a metal phosphate, or the like is used. As the matrix material, inorganic compounds include powdery or fibrous zirconium oxide, silica, alumina, silica-alumina, niobium oxide, tantalum oxide, tungsten oxide,
Titanium oxide, silicon nitride, boron carbide, tungsten carbide, silicon carbide and the like are used, and silicon nitride and silicon carbide are excellent, and in the case of metal phosphate, silicon titanium, tin, aluminum, zirconium and the like are mixed with phosphoric acid. Salt, eg SiP ₂
O ₇ , ZrP ₂ O _7, etc. are suitable. PTFE or FEP as the fixing material
Fluorine resins such as are suitable, but in order to improve the retention of electrolytes such as phosphoric acid in the matrix, the fixing material, such as polyether sulfone, polyether ether ketone, polyphenylene sulfide Good results can be obtained even if a hydrophilic thermoplastic resin is contained.

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, (1) is an electrode substrate, (5) is a catalyst layer, (6) is a matrix layer, (7) is a porous sheet, the catalyst layer (5) and the matrix layer (6) are integrated. A catalyst layer / matrix combination is formed.

The catalyst layer / matrix combination is a catalyst packed layer in which the catalyst powder and the binder are filled from one surface of the porous sheet (7).
(8) and a catalyst layer on the surface of the catalyst packed layer (8), a catalyst layer (5) consisting of a catalyst adhesion layer (9) to which a binder is attached, and the porous sheet (7) Matrix skeleton material and the adhesive material from the other surface is filled with a matrix filling layer (10) and the matrix filling layer (10) on the surface of the matrix skeleton material and the adhesive material attached matrix matrix (11) and It was formed from.

Next, the manufacturing method will be described. The electrode substrate (1) is made of carbon paper having a thickness of, for example, 300 μm and a porosity of, for example, 75%.
After being immersed in the TFE dispersion liquid, it was dried and heat-treated at a temperature of, for example, 360 ° C. for water-repellent treatment.

The catalyst layer (5) was manufactured as follows. Porous Sheet (7)
A carbon paper having a thickness of, for example, 100 μm and a porosity of, for example, 80% was used. On this porous sheet (7), a catalyst powder having platinum fine particles supported on the surface of carbon powder and PT as a binder
A catalyst packed bed (8) was obtained by packing FE. Next, on the surface of the catalyst packed layer (8), a catalyst powder having exactly the same composition as the catalyst packed layer (8) and PTFE as a binder were adhered to obtain a catalyst adhering layer (9). As the catalyst powder and the binder, an aqueous paste was prepared and the porous sheet (7) was filled and adhered by a reverse roll coater method or the like. Then dry, for example
Heat treatment was performed at a temperature of 350 ° C. to complete the catalyst layer (5). The total thickness of the catalyst layer (5) is, for example, 200 μm.
The thickness of (9) was, for example, 150 μm. This catalyst layer (5) was flexible and formed an independent membrane having a self-supporting property that could be held by hand and handled.

The matrix layer (6) was manufactured as follows. The porous sheet (7) on which the catalyst layer (5) is formed is inverted, and silicon carbide powder is used as the matrix skeleton material and PT as the fixing material.
Matrix was packed with FE to obtain a matrix packed layer (10). Next, on the surface of this matrix filling layer (10) with the same composition as the matrix filling layer (10), silicon carbide powder as a matrix skeleton material, PTFE as a fixing material is attached, and a matrix adhesion layer (11). Got For the matrix material and the fixing material, prepare a porous paste by preparing an aqueous paste.
The filling and adhesion to (7) were performed by a reverse roll coater method or the like. Then, it dried and heat-processed at the temperature of 250 degreeC, for example, and completed the matrix layer (6). The total thickness of the matrix layer (6) was, for example, 200 μm, and the thickness of the matrix attachment layer (1) was, for example, 150 μm.
As a result, a catalyst layer / matrix combined body in which the catalyst layer (5) and the matrix layer (6) were integrated was obtained. This catalyst layer /
The matrix conjugate was a flexible, self-supporting, free-standing membrane that could be held and handled by hand. Electrolyte such as phosphoric acid is applied / impregnated on both surfaces of the electrode substrate (1) and the catalyst layer / matrix combination obtained by the above method, that is, the surfaces of the catalyst layer adhesion layer (9) and the matrix adhesion layer (11). Then, the battery was assembled by stacking.

When assembling this battery, add it to the battery (4-10 [Kg / cm ² ]).
Since the surface pressure was applied, the electrode base material (1) and the catalyst layer / matrix combination were joined and integrated to form a fuel cell electrode / matrix combination. At this time, the electrolyte such as phosphoric acid coated and impregnated on the catalyst adhering layer (9) of the catalyst layer / matrix combination acts as an adhesive to facilitate the joining.

In the above-mentioned examples, the reverse roll coater method was used for coating and adhering the catalyst paste and the matrix paste to the porous sheet (7), but a spray method or the like can also be used. However, the reverse roll coater method is most suitable. Also, in the above examples, the electrode substrate
(1) and the catalyst layer / matrix combination were bonded and integrated by applying surface pressure to the cell during cell stack assembly to obtain a fuel cell electrode / matrix combination. May be integrated. Furthermore, in the above-mentioned examples, the electrode base material (1) is made of carbon paper that has been subjected to water repellent treatment, but it is a method of holding an electrolyte in the electrode base material (1), for example, a ribbed electrode base material. In this case, as compared with the conventional method of directly applying the catalyst paste to the electrode base material (1), there is an effect that a large amount of electrolyte such as phosphoric acid can be retained by the amount of the impregnated catalyst layer.

〔The invention's effect〕

As described above, according to the present invention, the fuel cell electrode / matrix combined body is separated from the electrode base material and the catalyst layer / matrix combined body, and the catalyst layer / matrix combined body is separated from one surface of the porous sheet. A catalyst layer composed of a catalyst filling layer filled with a catalyst powder and a binder and a catalyst adhering layer having a catalyst powder and a binder attached to the surface of the catalyst filling layer, and the other of the porous sheets. Since a matrix layer composed of a matrix filling layer in which a matrix skeleton material and a fixing material are filled from the surface and a matrix attachment layer in which a matrix skeleton material and a fixing material are attached to the surface of the matrix filling layer, the electrode is formed. The gas diffusion of the base material is good,
When configured as a battery, high output voltage, long life and stable quality can be obtained.In addition, electrolyte such as phosphoric acid can be applied and impregnated on both the catalyst layer surface and matrix layer surface, shortening the application and impregnation time. There is an effect that you can get what you can.

[Brief description of drawings]

FIG. 1 is a sectional view showing a fuel cell electrode / matrix combination according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional fuel cell electrode / matrix combination. In the figure, (1) is an electrode substrate, (5) is a catalyst layer, (6) is a matrix layer, (7) is a porous sheet, (8) is a catalyst packed layer,
(9) is a catalyst adhesion layer, (10) is a matrix filling layer, and (11) is a matrix adhesion layer. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (9)

[Claims] 1. In a fuel cell electrode / matrix combination in which an electrode base material and a catalyst layer / matrix combination are integrated, the catalyst layer / matrix combination is bonded to the catalyst powder from one surface of the porous sheet. A catalyst layer comprising a catalyst-filled layer filled with a binder and a catalyst-attached layer having catalyst powder and a binder attached to the surface of the catalyst-packed layer, and a matrix skeleton from the other surface of the porous sheet. A fuel comprising a matrix filling layer filled with a material and a fixing material, and a matrix layer including a matrix attachment layer having a matrix skeleton material and a fixing material attached to the surface of the matrix filling layer. Battery electrode / matrix combination. 2. The fuel cell electrode / matrix combination according to claim 1, wherein the porosity of the porous sheet is 50% or more. 3. The fuel cell electrode / matrix combination according to claim 1 or 2, wherein the porous sheet is a carbon fiber sheet having a thickness of 30 to 300 μm. 4. The fuel cell electrode / matrix combination according to any one of claims 1 to 3, wherein the catalyst adhesion layer has a thickness of 10 to 300 μm. 5. The thickness of the matrix adhesion layer is 30 to 300 μm.
The fuel cell electrode / matrix combination according to any one of claims 1 to 4, wherein 6. The binder according to claim 1, wherein the binder of the catalyst layer is a fluororesin such as polytetrafluoroethylene or tetrafluoroethylene-hexafluoropropylene copolymer. 5. The electrode / matrix combined body for a fuel cell according to any one of 1. 7. The fixing material for the matrix layer contains a fluororesin such as polytetrafluoroethylene or tetrafluoroethylene-hexafluoropropylene copolymer, as claimed in any one of claims 1 to 6. The fuel cell electrode / matrix combination according to any one of the items. 8. The fixing material of the matrix layer contains a hydrophilic thermoplastic resin such as polyether sulfone, polyether ether ketone, and polyphenylene sulfide, as claimed in claim 1. Through sixth
The fuel cell electrode / matrix combination according to any one of the items. 9. The skeleton material of the matrix layer is carbon,
At least 1 selected from inorganic compounds and metal phosphates
A fuel cell / matrix combination according to any one of claims 1 to 8, characterized in that it is a powder or fiber of a seed material.