JP2000299113A - Conductive sheet and electrode base material for fuel cell using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce electric resistance, improve gas permeability and improve jointing to a catalyst layer of a cell by forming the porous structure of one side layer of sheet material mainly composed of conductive material, to be coarse, and forming the porous structure of the other side layer to be dense. SOLUTION: The sheet material is formed in coarse and dense structure combining fibrous conductive material 5-10 μm in diameter and 1 mm or more in fiber length and fibrous conductive material 5-10 μm in diameter and less than 1 mm in fiber length. A conductive sheet of coarse and dense structure can be formed by forming a coarse porous structure surface of the fibrous conductive material 1 mm or more in fiber length and forming a denser porous structure surface of the fibrous conductive material less than 1 mm in fiber length. It is also desirable to form the conductive sheet of coarse and dense structure using an unwoven fabric structure sheet using carbon fiber 1-30 mm in fiber length for the coarse porous structure surface and using carbon fiber less than 1 mm in fiber length for the dense porous structure surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for applications requiring fluid permeability and conductivity, for example, electrodes.
In particular, the present invention relates to a porous conductive sheet used as an electrode substrate (current collector) in a polymer electrolyte fuel cell.

[0002]

2. Description of the Related Art Electrode substrates for fuel cells (also called current collectors)
In addition, the diffusion and permeability of substances involved in the electrode reaction are required in addition to the current collecting function. In addition, the material forming the electrode base material needs to have conductivity, gas diffusion / permeability, strength enough to withstand handling, and the like.

[0003] As an electrode substrate of such a fuel cell,
For example, JP-A-6-20710 and JP-A-7-32
Japanese Patent Application Laid-Open No. 6362/1995 and Japanese Patent Application Laid-Open No. 7-220735 discloses a device using a porous carbon plate formed by binding short carbon fibers with carbon. However, such an electrode substrate is produced by first forming an aggregate of short fibers made of carbon fibers or precursor fibers thereof, impregnating or mixing the resin with the aggregates, and then firing the aggregates. Further, when the density is low, there is also a problem that the bound carbon is apt to collapse due to the pressure during the production of the electrode or when assembled in a battery.

As a method for solving the problem of the manufacturing cost, Japanese Patent Application Laid-Open Nos. 7-105957 and 8-78
No. 97 proposes using a paper-like carbon short fiber aggregate as an electrode substrate. Such an electrode substrate,
The problem is that the electrical resistance in the thickness direction is high.

On the other hand, the fuel cell electrode substrate has a structure in which one surface is in contact with the gas flow path separator and the other surface is in contact with the catalyst layer as a structure of the fuel cell. For this reason,
The required characteristics of the fuel cell electrode base material require not only the above-described conductivity and gas permeation / diffusion properties but also good bonding with the catalyst layer. Regarding the joining with the catalyst layer, good joining is also achieved between the electrode base material and the catalyst layer because the electric resistance is low and the gas permeability is good. However, the conventional electrode substrate has a problem that, when gas permeability is improved, the electrode substrate has a rough structure in which the porosity is increased, and bonding with the catalyst layer becomes poor.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to provide low electric resistance, good gas permeability, and It is an object of the present invention to provide a porous conductive sheet having an asymmetrical structure with a dense and dense structure, which can be bonded well to a catalyst layer when used as a fuel cell electrode base material.

[0007]

SUMMARY OF THE INVENTION The present invention is a sheet-like material having a porous structure using a conductive material as a main constituent material, wherein a porous structure of a layer on one surface is rough, and The present invention relates to a conductive sheet characterized by having a dense porous structure of a layer on the surface of (1), and its use.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive sheet of the present invention is characterized in that one surface has a rough porous structure and the other surface has a dense porous structure. It is characterized by having an asymmetric porous structure by making the bulk density of the conductive material different.

Therefore, depending on the form of the conductive substance,
The method of forming the dense-dense asymmetric structure is not particularly limited.

In the conductive sheet of the present invention, the method of manufacturing the layer having the rough structure and the layer having the dense structure are not particularly limited as described above. The parameters representing the properties can be defined using porosity, bulk density, gas permeation resistance and the like.

The porosity is a percentage (%) obtained by subtracting the volume occupied by the conductive material from the total sheet volume and dividing by the total sheet volume. The porosity is large in a rough structure and small in a dense structure. In particular, when the porosity of the porous structure of the layer on the rough surface is VA (%) and the porosity of the porous structure on the layer of the dense surface is VB (%), 5 ≦ VA− V
It is preferable that B ≦ 90 as the dense structure of the present invention. In particular, when the conductive sheet of the present invention is used as an electrode base material for a polymer electrolyte fuel cell, the porosity preferably satisfies VA ≧ 90 and VB ≦ 80.

The bulk density is obtained by dividing the total weight of the sheet by the total volume of the sheet. Here, the unit is g / cm ³ .
This bulk density is small in a rough structure and large in a dense structure. In particular, when the bulk density of the porous structure of the layer having a rough surface is DA (g / cm ³ ) and the bulk density of the porous structure of the layer having a dense surface is DB (g / cm ³ ), 1 ≦ DB /
It is preferable that DA ≦ 100 as the dense structure of the present invention. More preferably, 1.1 ≦ DB / DA ≦ 20.

When calculating the above porosity and bulk density, it is necessary to obtain the total volume of the sheet. However, when the thickness of the conductive sheet changes due to pressure, the thickness at a pressure of 12.7 kPa is set to the sheet thickness. And

The gas permeation resistance is 14 cm in the thickness direction when the sheet is not pressurized by the surface pressure in the thickness direction.
Pressure loss when permeating air per second. Here, the unit is Pa. This gas permeation resistance is small in a rough structure and large in a dense structure. In particular, the gas permeation resistance of the porous structure of the layer having the rough surface is PA (Pa), and the gas permeation resistance of the porous structure of the layer having the dense surface is PB (P).
In the case of a), it is preferable that 1 ≦ PB / PA ≦ 100 as the dense / dense asymmetric porous structure of the present invention.
More preferably, 1.1 ≦ PB / PA ≦ 20.

The layer having a coarse porous structure and the layer having a dense porous structure preferably have a thickness of 1 μm to 1 mm (more preferably 5 μm to 500 μm). Also, the ratio of the thicknesses of the two (rough layer thickness (TA) / dense layer thickness (T
B)) is preferably 0.1 to 1000 (0.5 to 100).
Are more preferable, and 1-20 are still more preferable.). In addition, when mixing occurs at the interface between the two layers and the boundary is unclear, the depth from each surface to the point where the region is clear (or the depth from the center to the center of the range where the boundary is not clear). ) Is the thickness of each layer.

The conductive substance is preferably a fibrous substance. As long as the substance has a fibrous form, it is possible to form a dense-dense asymmetric structure using substances having different fiber lengths. For example, make the surface containing many short fibers a dense structure,
The surface containing many long fibers can have a rough structure.
The specific fiber length should be appropriately determined according to the diameter and elastic modulus of the fibrous substance, the application in which the conductive sheet is used, the required performance, and the like. As a fibrous conductive substance used in such a case, a carbon fiber is preferable as described below, and a PAN-based carbon fiber is particularly preferable.

Further, a fibrous conductive material having a diameter of 5 to 10 μm and a fiber length of 1 mm or more, a diameter of 5 to 10 μm and a fiber length of 1 mm
When a dense porous structure is formed by combining a fibrous conductive material having a fiber length of 1 mm or more with a fibrous conductive material having a fiber length of less than 1 mm, a coarse porous structure surface is formed with a fibrous conductive material having a fiber length of 1 mm or more. By forming the conductive sheet with a fibrous conductive substance having a size of less than 1 mm, a conductive sheet having a dense and dense structure can be formed. In such a case, it is a preferred embodiment that the fibrous conductive material is carbon fiber. In this case, there is no limitation, but the coarse porous structure surface uses a nonwoven fabric structure sheet using carbon fibers having a fiber length of 1 to 30 mm, and the dense porous structure surface uses a carbon fiber having a fiber length of less than 1 mm. It is also preferred to make a structural conductive sheet. It is also preferable to use a woven structure sheet using carbon fibers for the rough porous structure surface and to prepare a conductive sheet having a dense and dense structure using carbon fibers having a fiber length of less than 1 mm for the dense porous structure surface. Fiber length 5
A coarse structure was obtained with a 30 mm length, and the fiber length was 10 μm
It is more preferable to obtain a denser structure with a sheet having a thickness of about 1 mm to form a sheet.

When the fiber length of the conductive fibrous substance contained in the layer on the dense surface is longer than 1 mm, the conductive fiber contained in the dense surface and the conductive fiber contained in the dense surface are provided. It is not preferable because the fiber length of the particulate material is too close to obtain a substantially dense structure.

When the conductive sheet of the present invention contains a conductive fibrous substance, the parameter representing the physical property is determined by using the fiber length of the conductive fibrous substance (particularly, the ratio of the fiber length). Can be specified. One side (A
When the fiber length of the conductive fibrous substance included in the (side) is longer than the fiber length of the conductive fibrous substance included in the other side (side (B)), the side A has a coarser structure than the side B. In particular, the fiber length of the conductive fibrous substance contained in the layer having a rough surface is set to LA.
(Μm) and the fiber length of the conductive fibrous substance contained in the dense layer is LB (μm), 2 ≦ LA / L
It is preferable that B ≦ 10000 as the dense structure of the present invention. When LA / LB is less than 2, the fiber length of the conductive fibrous material contained in the rough surface and the conductive fibrous material contained in the dense surface is too close to obtain a substantially dense structure. When LA / LB is greater than 10000, the structure of the dense surface becomes too dense and the gas permeation resistance becomes large, and the gas permeation in the surface direction when used as an electrode substrate of a fuel cell. It is not preferable because the property is lowered. More preferably, 2 ≦ LA / LB ≦ 1000.

When the conductive sheet made of a fibrous conductive material has a woven structure, a knitted structure, a nonwoven structure, or the like, a sheet having a rough structure and a sheet having a dense structure are overlapped. A dense and dense structure conductive sheet can be obtained by a method such as adding a conductive substance having a short fiber length to the surface to form a dense porous structure. In a woven fabric, a knitted fabric, a nonwoven fabric, or the like, the density structure can be controlled by changing the number of fibers per unit area or the weight of fibers.

The above-mentioned nonwoven fabric sheet includes a paper-like sheet obtained by binding conductive fibers oriented in a random direction in a substantially two-dimensional plane with a polymer substance. A porous conductive sheet having a length of at least 3 mm and at least 5 times the thickness of the sheet can also be used. Here, the thickness of the sheet is JIS P81
Measure according to 18. The surface pressure during the measurement is 13 kPa. The meaning that the conductive fibers are oriented substantially in a two-dimensional plane means that the conductive fibers lie substantially to form one surface. This can prevent a short circuit between the conductive fiber and the counter electrode and breakage of the conductive fiber.

In order to increase the strength and handleability of the conductive sheet and to orient the conductive fibers in a substantially two-dimensional plane, the length of the conductive fibers is at least 3 mm, preferably 4.5 mm. More preferably, it is 6 mm or more. If it is less than 3 mm, it is difficult to maintain strength and handleability. Further, in order to orient the conductive fibers in a random direction in a substantially two-dimensional plane, the length of the conductive fibers is 5 times or more, preferably 8 times or more, more preferably 12 times or more the thickness of the conductive sheet. More than double. If it is less than 5 times, it is difficult to secure the orientation in two dimensions. The upper limit of the length of the conductive fiber is 30 mm in order to be oriented in a random direction in a substantially two-dimensional plane.
Or less, more preferably 15 mm or less, and 8 mm
The following are more preferred. If the conductive fibers are too long, poor dispersion is likely to occur, and many fibers may remain in a bundle. In such a case, the porosity of the bundle-shaped portion is low, and the thickness at the time of pressurization is large, so that high pressure is applied at the time of pressurization. Problems such as layering are likely to occur.

Further, the form of the conductive fiber is preferably a straight line in order to more completely prevent a short circuit with the counter electrode by the fiber. Here, the linear conductive fiber means that when a length L (mm) in the fiber length direction is taken in a state where the external force for bending the conductive fiber is removed, the linearity with respect to the length L The deviation Δ (mm) is measured, and Δ / L is about 0.1 or less. On the other hand, non-linear fibers have the disadvantage that they tend to be oriented in a three-dimensional direction when oriented in a random direction in a substantially two-dimensional plane.

In the preparation of the conductive sheet, the conductive fibers can be oriented in a random direction in a substantially two-dimensional plane by a wet method in which the conductive fibers are dispersed in a liquid medium to form a paper, or by air. There is a dry method in which conductive fibers are dispersed and accumulated on the inside. In order to reliably orient the conductive fibers substantially in a two-dimensional plane and to increase the strength of the conductive fibers, a wet method, particularly a so-called papermaking method, is preferable.

In the conductive sheet, in order to prevent breakage of the conductive material when pressurized and to reduce the weight loss of the conductive sheet to 3% or less, the fibers used are preferably short carbon fibers obtained by cutting carbon fibers. It is more preferable to apply tension during heat treatment, and it is more preferable to apply tension during heat treatment.

Examples of the carbon fiber include polyacrylonitrile (PAN) -based carbon fiber, phenol-based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber and the like. Among them, PAN-based carbon fibers are preferred. PAN-based carbon fibers have higher compressive strength and tensile breaking elongation than pitch-based carbon fibers, and are less likely to break. This is considered to be due to a difference in crystallization of carbon constituting carbon fibers. In order to obtain a carbon fiber that is difficult to break, the heat treatment temperature of the carbon fiber is preferably 2,500 ° C. or less, more preferably 2,000 ° C. or less.

The carbon fibers, preferably short carbon fibers, used in the conductive sheet of the present invention have the following relationships among the diameter D (μm), the tensile strength σ (MPa), and the tensile modulus E (MPa). It is good to satisfy the formula. This is because the conductive sheet made of such short carbon fibers is hard to break. That is, the shorter carbon fibers have a smaller diameter, a higher tensile strength, and a lower tensile modulus, the harder the carbon short fibers are to be broken, and the more difficult the conductive sheet is to be broken when pressurized.

Σ / (E × D) ≧ 0.5 × 10 ^-3 where the tensile strength and tensile modulus of the carbon fiber are JIS R
It is measured according to 7601. In the case of a carbon fiber having a flat cross section, the average value of the major axis and minor axis is defined as the diameter. When different types of short carbon fibers are mixed, values obtained by weighting D, σ, and E are used. Preferably, σ / (E ×
D) ≧ 1.1 × 10 ⁻³ , and more preferably σ / (E
× D) ≧ 2.4 × 10 ⁻³ .

The tensile elongation at break of short carbon fibers is preferably 0.7% or more, more preferably 1.2% or more, and further preferably 1.%, because of the strength of the conductive sheet.
8% or more. The tensile elongation at break is a value obtained by dividing the tensile strength (σ) by the tensile modulus (E).

Since breakage of the short carbon fiber occurs in various situations, the tensile strength of the short carbon fiber is preferably 500 MPa or more, more preferably 1,000 MPa or more, and more preferably 2,000 MPa or more. Is more preferred.

The conductive material may be a particulate material.
If it is a substance having a particulate form, it is possible to use a substance having a different particle diameter to form a dense-dense asymmetric structure.
For example, a surface containing many particles with small diameters has a dense structure,
A surface including many particles having a large diameter can have a rough structure.

The conductive substance may also be a mixture of a substance having a fibrous form and a substance having a particulate form. In that case, it is possible to obtain a dense and dense asymmetric structure by changing the ratio of both the fibrous material and the particulate material. The specific ratio should be appropriately determined according to the fiber length of the fibrous substance, the fiber diameter, the elastic modulus and the particle diameter and aspect ratio of the particulate matter, or the use or required performance of the conductive sheet. ,
For example, when a fibrous conductive material having a diameter of 5 to 10 μm and a fiber length of 1 mm or more is combined with a particulate conductive material having a particle diameter of 10 nm to 10 μm to form a coarse-dense structure, the coarse porous structure surface is formed by a fiber. A conductive sheet having a sparse-dense structure can be prepared by forming a dense porous structure surface with a particulate conductive material by using a conductive material having a dense structure. In such a case, it is a preferred embodiment that the fibrous conductive material is carbon fiber and the particulate conductive material is carbon powder. In this case, the rough porous structure surface is not limited, but the nonwoven fabric structure sheet using carbon fiber having a fiber length of 1 to 30 mm is used, and the dense porous structure surface is formed of carbon particles or carbon black. It is also preferred to make a sheet. It is also preferable to use a woven structure sheet using carbon fibers for the rough porous structure surface and to prepare a conductive sheet having a dense and dense structure using carbon particles or carbon black for the dense porous structure surface.

In the structural conductive sheet of the present invention, the porous structure of the layer having a rough surface has a fiber diameter of 5 μm to 5 μm.
In the case of a woven or nonwoven structure of a conductive fibrous material having a fiber length of 10 μm and a fiber length of 1 mm or more, the particle size of the conductive particulate material contained in the dense layer is 10 n.
m to 10 μm. When the particle size of the conductive particulate matter contained in the layer on the dense surface is larger than 10 μm, the conductive particles contained on the surface dense with the fiber diameter of the conductive fibrous material contained on the coarse surface It is not preferable because the particle size of the particulate matter is too close to obtain a substantially dense structure.
If it is smaller than 0 nm, the structure of the dense surface becomes too dense and the gas permeation resistance increases, and when used as an electrode base material for a fuel cell, the gas permeability in the surface direction is undesirably low.

Further, even in the case of a mixture of a fibrous conductive substance and a particulate conductive substance, a dense structure is formed by different fiber lengths, and the particulate conductive substance is uniformly present in the sheet. Sheets are also a preferred embodiment. The particulate matter at this time contributes to the improvement of the conductivity of the sheet.

In the structural conductive sheet of the present invention, a polymer material can be added in addition to the conductive material. As a result, the conductive sheet is resistant to compression and tension, and the strength and handleability are enhanced, and the conductive substance can be prevented from coming off the conductive sheet and being prevented from being oriented in the thickness direction of the conductive sheet. Particularly, when a porous conductive sheet is prepared by making conductive short fibers, a polymer substance is used as a binder. As a method of binding a polymer substance, a method of mixing a fibrous, granular, or liquid polymer substance when a conductive substance is oriented in a random direction in a substantially two-dimensional plane, There is a method of attaching a fibrous or liquid polymer substance to an aggregate in which the substance is oriented in a random direction in a substantially two-dimensional plane. The concept of a liquid includes an emulsion, a dispersion, a latex, and the like, in which fine particles of a polymer substance are dispersed in a liquid and can be handled substantially as a liquid. In order to strengthen the binding of the conductive material or lower the electric resistance of the conductive sheet, the polymer material to be bound is preferably fibrous, emulsion, dispersion or latex. In the case of a fibrous polymer substance, it is preferable to use a filament yarn to reduce the content.

Further, by changing the amount ratio of the high molecular substance binding the conductive substance, it is possible to obtain a dense and dense asymmetric structure. For example, a surface containing a large amount of a polymer substance can have a dense structure, and a surface containing a small amount of a polymer substance can have a rough structure. The form of the conductive substance in this case can be used without any particular limitation, and it may be a fibrous conductive substance, a particulate conductive substance, or a mixture thereof. .

As the high molecular substance binding the conductive substance, a high molecular substance having carbon or silicon in its main chain is preferable. For example, polyvinyl alcohol (PVA), polyvinyl acetate (vinyl acetate), polyethylene terephthalate (P
ET), polypropylene (PP), polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic resin, polyurethane and other thermoplastic resins, phenolic resin, epoxy resin, melamine resin, urea resin, alkyd resin, unsaturated polyester resin , Acrylic resin, thermosetting resin such as polyurethane resin, thermoplastic elastomer, butadiene-styrene copolymer (SBR),
Elastomers such as butadiene-acrylonitrile copolymer (NBR), rubber, cellulose, pulp and the like can be used. Using a water-repellent resin such as a fluororesin, the conductive sheet may be subjected to a water-repellent treatment simultaneously with the binding of the conductive substance.

In order to make the conductive sheet less likely to break when pressed, the polymer material binding the conductive material should be soft, and if the polymer material is in the form of fibers or particles, Is thermoplastic resin, elastomer, rubber,
Cellulose, pulp and the like are preferred. When the polymer substance is used in a liquid form, the polymer substance is a thermoplastic resin, an elastomer, a rubber, or a thermoplastic resin,
A thermosetting resin modified with a soft material such as an elastomer or a rubber is preferable. In particular, when a thermoplastic resin, an elastomer or a rubber is used, the conductive sheet is less likely to break when pressed, and is more preferable.

The high-molecular substance preferably has a compression modulus at 23 ° C. of 4,000 MPa or less, preferably 2,000 MPa.
More preferably 0 MPa or less, 1,000 MPa
It is more preferable that it is not more than a. The reason is that the high-molecular substance having a low compression modulus relieves the stress applied to the binding portion and makes it difficult to release the binding, and also relaxes the stress applied to the conductive substance to make it hard to break.

In the polymer electrolyte fuel cell, at the cathode (air electrode, oxygen electrode), water as an electrode reaction product,
Water permeates the electrolyte. At the anode (fuel electrode), the fuel is supplied humidified to prevent the polymer electrolyte membrane from drying. Since the condensation and stagnation of water and the swelling of the polymer substance due to water hinder the supply of the electrode reactant, the lower the water absorption of the polymer substance, the better. It is preferably at most 20%, more preferably at most 7%.

From such a point, when the conductive sheet is applied to the electrode, it is also a preferable embodiment to include a water-repellent polymer. In particular, polytetrafluoroethylene (PTF
E), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA)
Fluororesins such as are preferred because they have high water repellency. When the conductive sheet is used as a current collector (supply) for a fuel cell, a water-repellent treatment is indispensable, and the water-repellent polymer at that time also provides an adhesive effect between the conductive substances constituting the conductive sheet. . This is useful from the viewpoint of strength and electric resistance of the conductive sheet. PTFE, FEP, PFA
Is high in water repellency and oxidation resistance required for a fuel cell current collector, and PTFE and PFA are more preferable because they provide an effect of lowering electric resistance.

It is preferable that the content of the above-mentioned polymer substance in the conductive sheet is in the range of 0.1 to 50% by weight. In order to reduce the electric resistance of the conductive sheet, it is better that the content of the high molecular substance is small, but 0.1% by weight.
If the amount is less than the above range, the strength for handling is insufficient, and the amount of the conductive substance falling off increases. Conversely, if it exceeds 40% by weight, a problem arises in that the electric resistance of the conductive sheet increases. More preferably, it is in the range of 1 to 30% by weight.

The polymer substance added to the conductive sheet is 20
Firing at 0 ° C. or higher is also a preferred embodiment. The above-mentioned fluororesin used for the water-repellent treatment is improved in water-repellency and binding property by being heated to a melting point or higher. In addition, in the case of a polymer substance other than the fluororesin, in addition to the improvement of the binding force by firing, a decrease in electric resistance and an improvement in corrosion resistance are observed. Especially in the case of polymer materials other than fluororesin, when used as electrodes for electrochemical devices such as fuel cells,
Oxidation resistance may be poor, which may lead to a decrease in electrode performance during use. For this reason, it is preferable to use a polymer substance as a binder at the time of forming an electrode, and to bake it before using it as an electrode.

The conductive sheet of the present invention has a conductive material as a main constituent material, and is not particularly limited. The ratio of the conductive material in the conductive sheet is as follows.
Preferably 10 to 100% by weight (more preferably 50 to 100% by weight)
100% by weight). Any conductive substance capable of forming a dense and asymmetric porous conductive sheet can be used without particular limitation. Specific examples of the conductive substance include carbon, metal, and ceramics. A carbon material and a metal material are preferable in terms of conductivity, and a carbon material is preferable in view of elution resistance.

As the conductive substance used in the present invention, a carbon material is preferably used, but it is not particularly limited, and a carbon body obtained by firing an organic substance or a naturally occurring carbon body is used. Specifically, PAN-based carbon obtained from polyacrylonitrile (PAN) and its copolymer, pitch-based carbon obtained from pitch such as coal or petroleum, cellulose-based carbon obtained from cellulose, and low-molecular-weight organic substances Examples include a vapor-grown carbon body obtained from a gas. In addition, a carbon body obtained by firing polyvinyl alcohol, lignin, polyvinyl chloride, polyamide, polyimide, phenol resin, furfuryl alcohol, or the like may be used. In addition, naturally occurring natural graphite and other carbon bodies are also examples. Among these, carbon bodies satisfying the properties are appropriately selected according to the properties of the conductive sheet in which the carbon bodies are used, and they may be one kind or a mixture of two or more kinds. Among the above-mentioned carbon bodies, a PAN-based carbon body, a pitch-based carbon body, a vapor-grown carbon body, or a naturally-produced carbon body is preferable for the asymmetric dense-dense conductive sheet of the present invention.

As the PAN-based carbon material, Japanese Patent Publication No. 37-4
No. 405, JP-B-44-21175, JP-B-47-24185, JP-B-51-6244, and many other known methods. In general, in these methods, a PAN-based polymer is calcined in air at 150 to 300 ° C., and then calcined in an inert gas atmosphere at 900 to 2000 ° C. for about 5 minutes as a holding time at the ultimate temperature. A PAN-based carbon body is obtained. Here, the inert gas is a gas that does not react with the carbon material at the exemplified firing temperature, and examples thereof include nitrogen, argon, and a mixed gas thereof. Pitch-based carbon, cellulose, and the like can also be produced by using a known method and the like, and are described in, for example, "Carbon Fiber" (by Sugio Otani, Modern Editing Company). By controlling these manufacturing conditions,
A carbon material having an appropriate structure can be obtained. When the asymmetric structure conductive sheet using the carbon body of the present invention is used for a fuel cell electrode substrate, the firing temperature is from 1000 to 1500 ° C.
The asymmetric structure conductive sheet manufactured using the amorphous PAN-based carbon material obtained in the above is preferably used because the fuel cell has a high output capacity, a good life and other characteristics.

The carbon material used for the conductive material of the present invention includes
In addition to the above-mentioned PAN-based amorphous carbon material, graphite can also be used as a crystalline carbon material. Examples of such graphite include artificial graphite obtained by subjecting pitch or coke of petroleum or coal, a high-molecular compound, a low-molecular-weight organic compound, and the like to high-temperature treatment, and natural graphite produced naturally, and are particularly limited. It can be used without. Examples of the natural graphite include flaky graphite mainly produced in Madagascar and China, flaky graphite mainly produced in Sri Lanka, and earthy graphite mainly produced in Mexico and Russia. Among these graphites, natural graphite is preferably used in terms of price. Further, graphite obtained by post-processing such artificial or natural graphite can also be used. Examples of such graphite include expanded graphite.

When the conductive sheet of the present invention uses a porous conductive sheet made of conductive fibers as described above, it further contains conductive particles to suppress the reduction in thickness at the time of compression, improve the density, and improve the electric resistance. This is a preferred embodiment also from the viewpoint of reduction. As such conductive particles, carbon particles are preferable in terms of electric resistance and corrosion resistance.

In particular, it is also preferable to use a porous conductive sheet in which conductive particles having flexibility are arranged in a sheet shape as the conductive sheet. This makes it possible to provide an inexpensive conductive sheet in which components are less likely to fall off or hard to break even when a mechanical force acts thereon, have low electric resistance, and are inexpensive. In particular, the above object can be achieved by using expanded graphite particles as the conductive particles having flexibility.

Here, the expanded graphite particles are defined as graphite particles,
Graphite particles obtained by being intercalated with sulfuric acid, nitric acid, etc., and then expanded by rapid heating. Usually, the interlayer distance in the crystal structure of the expanded graphite particles is about 50 to 500 times that of the raw graphite particles.

The expanded graphite particles themselves are rich in shape deformability. This property is expressed in terms of flexibility.
This flexibility is observed due to the morphological compatibility of the expanded graphite particles with the other objects adjacent thereto. This morphological compatibility is that, when expanded graphite particles are subjected to a pressurizing action in a state where at least a part thereof overlaps, they are deformed with each other according to the pressurized state, and the particles are at least partially bonded to each other. To be observed. In addition, the morphological compatibility is based on expanded graphite particles and auxiliary materials used when they are arranged in a sheet shape while ensuring gas permeability (for example, a conventionally used flexible material such as carbon black). Non-conductive particles, or
When pressurized together with a conventionally used conductive fiber such as carbon fiber, the expanded graphite particles are observed to be deformed along the outer shape of the auxiliary material and joined to this auxiliary material. You.

In a preferred embodiment, the conductive sheet of the present invention contains other conductive particles and conductive fibers in addition to the conductive fine particles having flexibility. Since both are made of an inorganic material, a conductive sheet excellent in heat resistance, oxidation resistance, and elution resistance can be obtained. The non-flexible conductive particles may include, for example, carbon black powder, graphite powder, metal powder, ceramic powder, and the like.However, from the viewpoint of electronic conductivity and contact resistance, carbon black, graphite, and carbon Quality carbon materials are preferred. As such a carbon material, carbon black such as oil furnace black, channel black, lamp black, thermal black, and acetylene black is preferable from the viewpoint of electron conductivity and specific surface area. As the oil furnace black, Vulcan XC-72, Vulcan P, manufactured by Cabot Corporation,
Black Pearls 880, Black Pearls 1100,
Black Pearls 1300, Black Pearls 200
0, Regal 400, Ketjen Black EC manufactured by Lion Corporation, # 3150, # 3250 manufactured by Mitsubishi Chemical Corporation, and acetylene black includes Denka Black manufactured by Denki Kagaku Kogyo KK. In addition to carbon black, there are artificial graphite and carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, and furan resin. It is also possible to use carbon materials obtained by post-processing these carbon materials. Among such carbon materials, in particular, Vulcan XC-72 manufactured by Cabot Corporation, Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd., and Ketjen Black manufactured by Lion Corporation are preferably used from the viewpoint of electronic conductivity.

The particle diameter, fiber diameter, and fiber length of the conductive material used in the present invention are an average particle diameter, an average fiber diameter, and an average fiber length, respectively.
And more, 20 or more, preferably 10
It can be obtained by performing measurement on zero carbon bodies.

The electrical resistance of the conductive substance used in the present invention is appropriately required depending on the application and required performance, but generally, a lower one is preferable. In the case of a fibrous conductive material, the resistance is preferably 0.1 Ω · cm or less, and 0.01 Ω · cm or less.
cm or less is more preferable. In the case of a particulate conductive substance, it is preferably 1 Ω · cm or less, more preferably 0.1 Ω · cm or less.

The electric resistance of the conductive sheet according to the present invention is as follows.
When the porous conductive sheet is sandwiched between two glassy carbon sheets and a uniform surface pressure of 0.98 MPa is applied, the resistance is 10
0 mΩ · cm ² or less, preferably 50 mΩ · cm ²
cm 2 or less, more preferably 15 mΩ · cm ² or less.

In the measurement of the resistance, a glassy carbon plate having a smooth surface of 50 mm in width, 200 mm in length and 1.5 mm in thickness was mounted on a glassy carbon plate having a width of 50 mm, a length of 200 mm and a thickness of 0.1 m.
Two sheets of copper foil of m are stacked. This is called a test electrode. Two test electrodes are overlapped so that the glassy carbon plates face each other and are orthogonal at the center. The porous conductive sheet is cut into a circle having a diameter of 46 mm, sandwiched between overlapping portions of a glassy carbon plate, and pressed so as to have a pressure of 0.98 MPa with respect to the area of the porous conductive sheet. A terminal for current is provided at one end of the two test electrodes, and a terminal for voltage is provided at the other end. A current of 1 A flows between the two test electrodes using a current terminal. Voltage V (V) between terminals for voltage
Is measured, and the resistance R (mΩ · cm ² ) is calculated by the following equation. Here, π is a circle ratio.

R = V × 2.3 × 2.3 × π × 1000 The thickness of the conductive sheet when a uniform surface pressure of 0.98 MPa is applied in the thickness direction is preferably 0.03 to 0.3 mm. . More preferably, it is 0.05 to 0.25 mm, and still more preferably 0.07 to 0.2 mm. When the thickness is small, the strength is low. Also, when used as an electrode substrate for a fuel cell, the gas permeability in the plane direction decreases. The thicker the thickness, the higher the electrical resistance. In addition, the thickness is sandwiched between two glassy carbon plates having a uniform thickness and a smooth surface of the electrode substrate,
The pressure is applied at a uniform surface pressure of 0.98 MPa, and the pressure is determined from the difference between the upper and lower indenters when the electrode substrate is not sandwiched and when the electrode substrate is sandwiched. In measuring the interval between the indenters, the interval between the indenters is measured by a minute displacement detection device at both ends of the center point of the indenter, and the interval between the indenters is calculated as an average value of the intervals between both ends. In order to make the surface pressure uniform, one of the indenters is received by a ball seat, and the angle between the pressing surfaces of the upper and lower indenters is made variable.

The basis weight of the structural conductive sheet of the present invention is 10 to
Preferably 100 g / m ^2, more preferably 20 to 80 g / m ^2, more preferably 30 to 60 g / m ^2. The lighter the weight, the lower the strength. Also, when used as an electrode substrate for a fuel cell, the gas permeability in the plane direction decreases. If the basis weight is heavy, the electric resistance increases.

The method for producing a conductive sheet having a dense / dense structure of the present invention is not particularly limited as long as a conductive sheet having a porous structure on one side and a porous structure on the other side can be obtained. Although not required, a papermaking method such as papermaking is preferred. This papermaking method is preferable when the conductive substance is fibrous or particulate, and more preferable when the conductive substance is carbon fiber or carbon particles. When a conductive sheet is prepared by a papermaking method using carbon fiber, the carbon fiber is
It is cut into a size of about 5 μm to 5 cm, dispersed in a solvent containing a dispersant or the like, and paper is made according to the papermaking principle. In this method, in order to obtain a dense structure, a carbon fiber having a long fiber length is made in advance to prepare a sheet having a coarse structure, and a carbon fiber having a shorter fiber length is subsequently formed into a sheet having a dense structure. This enables a dense structure. In some cases, short carbon fibers may be formed first, and then long carbon fibers may be formed.

Further, a carbon fiber having a long fiber length is made in advance to form a sheet having a rough structure, and subsequently, a carbon fiber having a shorter fiber length—the polymer material liquid composition or the carbon particles—
By coating the polymer composition liquid composition on a sheet having a rough structure to form a sheet having a dense structure, a dense structure can be obtained. Here, the concept of liquid is as described above.
Emulsions, dispersions, latexes, and the like include those in which fine particles of a polymer substance are dispersed in a liquid and can be handled substantially as a liquid. As described above, the polymer substance is preferably a polymer substance having carbon or silicon in its main chain, such as polyvinyl alcohol (PVA), polyvinyl acetate (vinyl acetate), polyethylene terephthalate (PET), and polypropylene (PP). Thermoplastic resin such as polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, acrylic resin, polyurethane, phenol resin, epoxy resin, melamine resin, urea resin, alkyd resin, unsaturated polyester resin, acrylic resin, polyurethane resin, etc. In addition to the above thermosetting resins, thermoplastic elastomers, elastomers such as butadiene / styrene copolymer (SBR) and butadiene / acrylonitrile copolymer (NBR), rubber, cellulose, pulp and the like can be used. Using a water-repellent resin such as a fluororesin, the conductive sheet may be subjected to a water-repellent treatment simultaneously with the binding of the conductive substance.

The method of applying the carbon fiber-polymer liquid composition or the carbon particle-polymer liquid composition is selected according to the viscosity and solid content, and is not particularly limited. However, a general coating method such as a knife coater, a bar coater, a spray, a dip coater, a spin coater, a roll coater, a die coater, a curtain coater, and screen printing is used.

Further, a carbon fiber having a long fiber length is made in advance to form a sheet having a coarse structure, and then a carbon fiber dispersion liquid or a carbon particle dispersion liquid having a shorter fiber length is impregnated into the sheet having a coarse structure. By forming a sheet having a dense structure, a dense structure can be obtained. The concentration and viscosity of the dispersion liquid are appropriately selected according to the impregnating property of the carbon fiber having a short fiber length or the carbon particles into the sheet having the rough structure, and are not particularly limited. It is also a preferred embodiment that the above-mentioned polymer substance is simultaneously contained in the dispersion liquid in a state where it can be dissolved or substantially handled as a liquid in order to enhance the binding property of a sheet having a dense structure.

Further, a sheet having a rough structure and a sheet having a dense structure can be laminated to form a dense and dense continuous asymmetric structure.
Furthermore, even if the fiber length is not changed, it is also possible to make the structure coarser at first and then gradually increase the structure. For example,
Although it is not limited, after first creating a sheet with a rough structure, pressing it into a sheet with a dense structure,
This can be achieved by gradually increasing the viscosity of the dispersion when preparing a sheet having a rough structure or when making carbon fibers.

Incidentally, as in the above-mentioned dense / dense continuous asymmetric structure,
When it is difficult to distinguish between a coarse layer and a dense layer, the above-described parameters may be defined as a region between the surface and a depth of 10% of the total thickness of the conductive sheet as a coarse layer or a dense layer, respectively. .

The dense / dense conductive sheet of the present invention is not limited to a dense / dense two-layer structure, but may have a dense / dense continuous structure in which the dense / dense structure is continuously changed into three or more layers. The method of forming the dense-dense continuous structure is not particularly limited, but, for example, the fiber length of the fibrous conductive substance, the particle diameter of the particulate conductive substance, the mixing ratio thereof, etc. It can be produced by forming a denser porous structure on the denser side or a coarser porous structure on the coarser side of the dense and dense conductive sheet created by changing the above. The method for forming the porous structure is not particularly limited, and the above-described method for forming a porous structure can be used. Further, by repeating the formation of the porous structure, it is possible to produce a multilayer dense and dense conductive sheet.

The dense and dense conductive sheet of the present invention is characterized in that the conductive fibrous substance-polymer composite or the conductive particulate substance-polymer composite forming a dense porous structure has a three-dimensional network microporous structure. Is also a preferred embodiment. The conductive fibrous substance-polymer composite is a polymer composite containing a conductive fibrous substance, and the conductive particulate matter-polymer composite is a polymer composite containing a conductive particulate matter. It is a feature that these composites have a three-dimensional network microporous structure. The “three-dimensional network microporous structure” refers to a state in which these complexes have a three-dimensional network structure that is three-dimensionally connected.

When the dense porous structure has a three-dimensional network microporous structure, the microporous diameter is 0.5 to 50 μm. Preferably, it is 1 to 10 μm. The microporous diameter can be measured with a scanning electron microscope (SEM), etc.
From the photograph of the surface, 20 or more, preferably 100
It can be obtained from an average of more than 100 pieces, and can usually be measured with 100 pieces. Since the dense porous structure of the present invention when manufactured by the wet solidification method has a wide distribution of microporous diameters, it is preferable to average as many pore diameters as possible.

The porosity of the three-dimensional network microporous structure is 10
It is preferably about 95%. More preferably 50 to
90%. The porosity is a percentage obtained by subtracting the volume occupied by the conductive fibrous substance-polymer composite or the conductive particulate matter-polymer composite from the total volume of the dense porous structure, and dividing by the total volume of the dense porous structure. (%). The dense porous structure is subjected to wet solidification after being applied to a coarse porous sheet or other base material, but if it is difficult to obtain the porosity of the dense porous structure alone, The porosity of the porous sheet or other base material is determined in advance,
After determining the porosity including these substrates and the dense porous structure, it is also possible to determine the porosity of the dense porous structure alone.

Even when the dense porous structure has a three-dimensional microporous structure, the same conductive material and polymer can be used as described above. However, when creating a dense porous structure having a three-dimensional network microporous structure, it is preferable to use a wet coagulation method, which is suitable for this wet coagulation method, disperses conductive materials well, Polymers that do not degrade in an oxidizing-reducing atmosphere are preferred. Examples of such a polymer include a polymer containing a fluorine atom, and are not particularly limited. For example, polyvinyl fluoride (PVF), polyvinylidene fluoride (PVD)
F), polyhexafluoropropylene (FEP), polyperfluoroalkyl vinyl ether (PFA), etc.
Alternatively, these copolymers, copolymers of these monomer units with other monomers such as ethylene and styrene (hexafluoropropylene-vinylidene fluoride copolymer and the like), and further, blends and the like can be used.

Among them, polyvinylidene fluoride (PV
DF) or hexafluoropropylene-vinylidene fluoride copolymer is a conductive fiber having a three-dimensional network microporous structure by a wet coagulation method using an aprotic polar solvent and a coagulating solvent such as a protic polar solvent. It is a particularly preferred polymer in that a particulate matter-polymer composite or a conductive particulate matter-polymer composite can be obtained. Solvents for these polymers include N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (D
MAC), propylene carbonate (PC), dimethylimidazolidinone (DMI), and the like. Examples of the coagulating solvent include water, lower alcohols such as methanol, ethanol, and isopropanol, and esters such as ethyl acetate and butyl acetate. , Aromatic or halogenous organic solvents are used.

In the case where carbon fibers are used as the conductive material, woven fabric, knitted fabric, nonwoven fabric, etc. are preferred methods of forming the conductive sheet in addition to the above-described paper making method. In such a case, it is also a preferable production method to form a structure such as a woven fabric, a knitted fabric, or a non-woven fabric in the state of the carbon fiber precursor, and then calcinate the carbon fiber. The carbon fiber precursor is PAN
For example, polyacrylonitrile (PAN) or a flame-treated polyacrylonitrile (PAN) is used as the carbon fiber, and a molten pitch is used as the pitch carbon fiber.

In the production of the structured conductive sheet of the present invention, the method including the step of removing components other than the conductive substance in the porous conductive sheet includes a step of reducing the components other than the conductive substance contained in the porous conductive sheet. As a result, the porous conductive sheet is effective for lowering the electrical resistance and increasing heat resistance and oxidation resistance.

The dense / dense structure conductive sheet of the present invention exhibits excellent performance when used for an electrode substrate of a solid polymer (PEM) type fuel cell. The PEM fuel cell has a laminated structure in which a separator having a gas flow path, an electrode substrate, a catalyst layer, and a proton exchange membrane (polymer electrolyte) are arranged. The electrode base material is required to have a low gas permeation resistance in order to efficiently supply gas to the catalyst layer, a low electric resistance of the electrode base material, and a good bondability with good electron conduction with the catalyst layer. Have been. In order to lower the gas permeation resistance, a rough structure having a high porosity is required for the electrode substrate, and a dense structure having a low electronic resistance is required in order to improve the electron conductivity with the catalyst layer. . The dense structure of the present invention is a means for satisfying these conflicting requirements, and thereby supplies a conductive sheet having a structure suitable as an electrode substrate of a PEM fuel cell. In other words, the gas separator side has a rough porous structure, the gas from the gas separator is efficiently supplied to the catalyst layer, and the catalyst layer side has a dense porous structure.
Electron conductivity between the catalyst layer and the electrode substrate is favorably joined.

In the production of the above-mentioned PEM type fuel cell, a membrane-electrode composite (M) comprising an electrode substrate / anode catalyst layer / proton exchange membrane / cathode catalyst layer / electrode substrate integrated with each other is used.
In general, an EA (Membrane Electrode Assembly) is created, and a single cell is created by sandwiching the EA with gas separators from both sides, and a stack is created by stacking the single cells. MEA is prepared by applying a catalyst layer to an electrode substrate to form an electrode and bonding the electrode layer to a proton exchange membrane by pressure bonding, or applying a catalyst layer to the proton exchange membrane and bonding the electrode layer to the electrode substrate. Cases and the like are known. When the dense / dense structure conductive sheet of the present invention is used as a PEM fuel cell electrode base material and a catalyst layer is applied to a dense porous structure surface of the electrode base material to form an electrode, the catalyst layer coating performance is extremely high. It will be good. Various coating methods can be applied to the application of the catalyst layer, but in any case, it can be expected that the thickness distribution of the catalyst layer is small and uniform application is possible.
In particular, since the penetration of the catalyst layer coating liquid is reduced as compared with the conventional porous conductive sheet, useless coating liquid is reduced, leading to cost reduction. Further, the electron conductivity with the catalyst layer is also good, leading to excellent fuel cell performance. On the other hand, even when a catalyst layer is applied to a proton exchange membrane and bonded to a current collector, the bonding surface with the catalyst layer has a dense porous structure. It becomes possible.

The above-mentioned catalyst layer is formed of at least a catalyst or a catalyst-supporting medium (for example, a catalyst-supporting carbon is preferable. Hereinafter, the catalyst-supporting carbon will be described as an example, but the present invention is not limited to this). Having. Although not particularly limited, for example, the above-mentioned catalyst layer binds the catalyst-supporting carbon and the catalyst-supporting carbon to each other or the catalyst-supporting carbon and the electrode substrate or the catalyst-supporting carbon and the proton exchange membrane, and forms the catalyst layer. Is formed of a polymer. The catalyst contained in the catalyst-supporting carbon is not particularly limited, but a noble metal catalyst such as platinum, gold, palladium, ruthenium, and iridium is preferably used because activation overvoltage in the catalytic reaction is small. Further, two or more elements such as alloys and mixtures of these noble metal catalysts may be contained. The carbon contained in the catalyst-supporting carbon is not particularly limited, but carbon blacks such as oil furnace black, channel black, lamp black, thermal black, and acetylene black are preferable in terms of electron conductivity and the specific surface area. It is. Examples of oil furnace black include Vulcan XC-72, Vulcan P, Black Pearls 880, and Black Pearls 110 manufactured by Cabot Corporation.
0, Black Pearls 1300, Black Pearls 20
00, Regal 400, Ketchen Black EC manufactured by Lion Corporation, # 3150, # 3250 manufactured by Mitsubishi Chemical Corporation, and acetylene black includes Denka Black manufactured by Denki Kagaku Kogyo KK. Particularly, Vulcan XC-72 manufactured by Cabot Corporation is preferably used. The polymer contained in the catalyst layer is not particularly limited, but is preferably a polymer that does not deteriorate in an oxidation-reduction atmosphere in the fuel cell. Such a polymer includes a polymer containing a fluorine atom, and is not particularly limited. For example, polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polyhexafluoropropylene (F
EP), polytetrafluoroethylene, polyperfluoroalkyl vinyl ether (PFA) or the like, or a copolymer thereof, a copolymer of these monomer units with another monomer such as ethylene or styrene, or a blend is also used. be able to. As the polymer contained in the catalyst layer, a polymer having a proton exchange group is also preferable in order to improve proton conductivity in the catalyst layer. Examples of the proton exchange group contained in such a polymer include a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group, but are not particularly limited. Further, such a polymer having a proton exchange group is also selected without particular limitation, but a fluoroalkyl copolymer having a fluoroalkyl ether side chain with a proton exchange group is preferably used. For example, Nafion manufactured by DuPont is also preferable. Further, a polymer containing the above-described fluorine atom having a proton exchange group, another polymer such as ethylene or styrene, a copolymer or a blend thereof may be used.

As the polymer contained in the catalyst layer, it is also preferable to use a polymer containing a fluorine atom or a polymer containing a proton exchange group by copolymerization or blending. In particular, blending polyvinylidene fluoride, poly (hexafluoropropylene-vinylidene fluoride) copolymer, and a polymer such as Nafion, which has a fluoroalkyl ether side chain and a fluoroalkyl main chain in the proton exchange group, can improve electrode performance. It is preferable from the point.

The main components of the catalyst layer are preferably a catalyst-carrying carbon and a polymer, and their ratio should be appropriately determined according to the required electrode characteristics, and is not particularly limited. 5/95 to 95/5 by weight ratio of supported carbon / polymer is preferably used. Particularly when used as a catalyst layer for a polymer electrolyte fuel cell,
40 / 60-85 by weight of catalyst-supporting carbon / polymer
/ 15 is preferred.

In a preferred embodiment, in addition to the above-described carbon supported on the catalyst-supporting carbon, various conductive agents are added to the catalyst layer to improve electron conductivity.
Examples of such a conductive agent include, in addition to carbon black of the same type as the carbon used for the catalyst-supporting carbon, various graphite or carbonaceous carbon materials, or metals and metalloids, but are particularly limited. Not something. Examples of such a carbon material include artificial graphite and carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, and furan resin, in addition to the above-described carbon black. These carbon materials may be in the form of fibers in addition to particles. It is also possible to use carbon materials obtained by post-processing these carbon materials. The amount of the conductive material to be added is preferably 1 to 80%, more preferably 5 to 50%, as a weight ratio to the catalyst layer.

The method of adding and forming the above-mentioned catalyst layer on the electrode substrate or the proton exchange membrane is not particularly limited. The catalyst-supporting carbon and the polymer contained in the catalyst layer are kneaded into a paste, and the catalyst layer is formed on the electrode substrate or proton by a method such as brush coating, brush coating, bar coater coating, knife coater coating, screen printing, or spray coating. The catalyst layer may be directly added to or formed on an exchange membrane, or may be once formed on another substrate (transfer substrate) and then transferred to an electrode substrate or a proton exchange membrane. In this case, as a transfer substrate, a polytetrafluoroethylene (PTFE) sheet, a glass plate or a metal plate whose surface is treated with a fluorine or silicone release agent, or the like is used.

The electrode catalyst layer is also a preferred embodiment in which the catalyst-polymer composite has a three-dimensional network microporous structure. The catalyst-polymer composite is a polymer composite containing catalyst particles, and is characterized in that the composite has a three-dimensional network microporous structure. The “three-dimensional network microporous structure” refers to a state in which the catalyst-polymer composite has a three-dimensional network structure connected three-dimensionally.

When the electrode catalyst layer has a three-dimensional mesh microporous structure, the microporous diameter is 0.05 to 5 μm. Preferably, it is 0.1 to 1 μm. The microporous diameter can be measured with a scanning electron microscope (SEM), etc.
From the photograph of the surface, 20 or more, preferably 100
It can be obtained from an average of more than 100 pieces, and can usually be measured with 100 pieces. Since the catalyst layer having a microporous structure of the present invention when produced by a wet coagulation method has a wide distribution of microporous diameters, it is preferable to average as many pore diameters as possible.

The porosity of the three-dimensional network microporous structure is 10
It is preferably about 95%. More preferably 50 to
90%. The porosity is a percentage (%) obtained by subtracting the volume occupied by the catalyst-polymer composite from the total volume of the catalyst layer and dividing it by the total volume of the catalyst layer. The catalyst layer is subjected to wet coagulation after being applied to the electrode substrate, the proton exchange membrane, and other substrates, but if it is difficult to determine the porosity of the catalyst layer alone, the electrode substrate, the proton exchange membrane It is also possible to determine the porosity of the film and the other base material in advance, determine the porosity including the base material and the catalyst layer, and then determine the porosity of the catalyst layer alone.

The electrode catalyst layer is required to have a large porosity, good gas diffusivity and good discharge of generated water, and good electron conductivity and proton conductivity. In the conventional porous method, the catalyst particle diameter and the particle size of the added polymer are increased, and a void is formed by using a pore-forming agent. The contact resistance between the proton exchange resins is larger than that of the electrode catalyst layer. On the other hand, in the three-dimensional network microporous structure by the wet coagulation method, since the polymer composite containing the catalyst-supporting carbon is in a three-dimensional network, electrons and protons are easily conducted through this polymer composite, Furthermore, because of the microporous structure, gas diffusibility and generated water discharge are also good.

Even when the electrode catalyst layer has a three-dimensional microporous structure, the same materials as those used in the related art can be used for the catalyst, the electron conductor, and the ion conductor. However, when preparing an electrode catalyst layer having a three-dimensional network microporous structure, it is preferable to use a wet coagulation method, which is suitable for this wet coagulation method, disperses catalyst particles well, and performs oxidation-reduction in a fuel cell. Polymers that do not degrade in the atmosphere are preferred. Examples of such a polymer include a polymer containing a fluorine atom, and are not particularly limited. For example, polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polyhexafluoropropylene (FEP), Perfluoroalkyl vinyl ether (PFA) or the like, or a copolymer thereof, a copolymer of these monomer units with another monomer such as ethylene or styrene (a hexafluoropropylene-vinylidene fluoride copolymer or the like), and further, Blends and the like can also be used.

Among them, polyvinylidene fluoride (PV
DF) and hexafluoropropylene-vinylidene fluoride copolymer are prepared by using a non-protonic polar solvent and a wet coagulation method using a protic polar solvent as a coagulation solvent to form a catalyst-polymer having a three-dimensional network microporous structure. It is a particularly preferred polymer in that a composite is obtained. Solvents for these polymers include N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (D
MAC), propylene carbonate (PC), dimethylimidazolidinone (DMI), and the like. Examples of the coagulating solvent include water, lower alcohols such as methanol, ethanol, and isopropanol, and esters such as ethyl acetate and butyl acetate. , Aromatic or halogenous organic solvents are used.

As the polymer of the catalyst-polymer composite, in addition to the above-mentioned polymers, a polymer having a proton exchange group for improving proton conductivity is also preferable. Examples of the proton exchange group contained in such a polymer include a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group, but are not particularly limited. Further, such a polymer having a proton exchange group is also selected without particular limitation, but a polymer having a proton exchange group composed of a fluoroalkyl ether side chain and a fluoroalkyl main chain is preferably used. For example, DuPont's
Nafion and the like are also preferable. Further, a polymer containing the above-described fluorine atom having a proton exchange group, another polymer such as ethylene or styrene, a copolymer or a blend thereof may be used.

The Nafion polymer solution may be obtained by dissolving a commercially available Nafion membrane in an aprotic polar solvent, or using Nafion, a mixed solvent of water-methanol-isopropanol manufactured by Aldrich.
An on solution or a solution obtained by replacing the Nafion solution with a solvent may be used. In this case, the coagulation solvent during wet coagulation is Na
Although it should be appropriately determined depending on the solvent of the fion solution, when the solvent of the Nafion solution is an aprotic polar solvent, as the coagulating solvent, other than water, alcohols, and esters, various organic solvents and the like are used. Preferably, in the case of a mixed solvent of water-methanol-isopropanol, esters such as butyl acetate and various organic solvents are preferably used.

As the polymer used in the catalyst-polymer composite, it is also preferable to use a polymer containing a fluorine atom or a polymer containing a proton exchange group by copolymerization or blending. In particular, blending polyvinylidene fluoride, poly (hexafluoropropylene-vinylidene fluoride) copolymer, etc. with polymers such as Nafion, which has a fluoroalkyl ether side chain and a fluoroalkyl main chain in the proton exchange group, is a point of electrode performance. Is preferred.

The main components of the catalyst-polymer composite are preferably a catalyst-supporting carbon and a polymer, and the ratio thereof is not particularly limited and should be appropriately determined according to the required electrode characteristics. Is the catalyst-supporting carbon /
A ratio of 5/95 to 95/5 by weight of the polymer is preferably used. In particular, when used as an electrode catalyst layer for a polymer electrolyte fuel cell, the weight ratio of the catalyst-supporting carbon / polymer is preferably 40/60 to 85/15.

It is also a preferred embodiment to add various additives to the catalyst-polymer composite. For example, a conductive agent such as carbon for improving the electron conductivity, a polymer for improving the binding property, an additive for controlling the pore size of the three-dimensional network microporous structure, and the like, but are not particularly limited. Can be used. The addition amount of these additives is as follows:
The weight ratio to the polymer composite is preferably from 0.1 to 50%, more preferably from 1 to 20%.

As a method for producing a catalyst-polymer composite having a three-dimensional network microporous structure, a method based on a wet coagulation method is preferable. In the wet coagulation method, after the catalyst-polymer solution composition is applied, the coating layer is brought into contact with a coagulation solvent for the polymer, and coagulation precipitation of the catalyst-polymer solution composition and solvent extraction are simultaneously performed.

This catalyst-polymer solution composition is obtained by uniformly dispersing the catalyst-supporting carbon in the polymer solution.
The above-mentioned catalyst-supporting carbon and polymer are preferably used. The solvent for dissolving the polymer should be appropriately determined according to the polymer used, and is not particularly limited. It is important that the polymer solution disperse the catalyst-supporting carbon well. If the dispersion state is poor, it is not preferable because the catalyst-supporting carbon and the polymer cannot form a composite during wet coagulation.

Regarding the coating method, a coating method is selected according to the viscosity and the solid content of the catalyst-polymer solution composition.
Although not particularly limited, a knife coater,
General coating methods such as a bar coater, a spray, a dip coater, a spin coater, a roll coater, a die coater and a curtain coater are used.

On the other hand, the coagulation solvent for wet coagulation of the polymer is not particularly limited, but a solvent which is easy to coagulate and precipitate the polymer to be used and which is compatible with the solvent of the polymer solution is preferable. The method of contact with the coagulation solvent in which wet coagulation is actually performed is not particularly limited, but the base material is immersed in the coagulation solvent, only the coating layer is brought into contact with the liquid surface of the coagulation solvent, There is no particular limitation such as showering or spraying the coating layer.

The substrate on which the catalyst-polymer solution composition is applied can be applied to either the electrode substrate or the solid electrolyte and then wet-solidified. Immediately after the wet solidification, it is possible to prevent the catalyst layer from seeping into the electrode substrate, and this is a preferred embodiment from the viewpoint of improving electrode performance. In addition, after applying to a substrate (transfer substrate) other than the electrode substrate and the solid electrolyte, and then performing wet solidification to create a three-dimensional network microporous structure, the catalyst layer is applied to the electrode substrate or the solid electrolyte. May be transferred or pinched. In this case, as a transfer substrate, a polytetrafluoroethylene (PTFE) sheet, a glass plate or a metal plate whose surface is treated with a fluorine or silicone release agent, or the like is used. The above proton exchange membrane is not particularly limited,
As proton exchange groups, sulfonic acid groups, carboxylic acid groups,
Those having a phosphoric acid group or the like are preferably used for exhibiting fuel cell performance.

The proton exchange membrane is roughly classified into a hydrocarbon type such as a styrene-divinylbenzene copolymer and a perfluoro type such as a fluoroalkyl copolymer having a fluoroalkyl ether side chain. Although it should be appropriately selected according to the fuel cell and environment, a perfluoro-based resin is preferable from the viewpoint of fuel cell life. Further, a partial fluorine film partially substituted with fluorine atoms is also preferably used. For perfluoro membrane, DuPont
Examples include Nafion, Aciplex manufactured by Asahi Kasei, Flemion manufactured by Asahi Glass, and Gore-Select manufactured by Japan Gore-Tex Co., Ltd. is there.

The proton exchange membrane is not limited to one kind of polymer, but may be a copolymer or blend polymer of two or more kinds of polymers.
A composite membrane obtained by laminating more than two kinds of membranes, a membrane obtained by reinforcing a proton exchange membrane with a nonwoven fabric, a porous film, or the like can also be used.

The conductive sheet of the present invention is a low-temperature fuel cell material used at a temperature of 300 ° C. or lower, in particular, an electrode substrate for a polymer electrolyte fuel cell which is inexpensive, has low electric resistance, and is broken by pressure. It can be suitably used as a difficult material. An electrode substrate and a catalyst layer using a porous conductive sheet,
The polymer electrolyte membrane and the polymer electrolyte membrane are arranged in layers to constitute a unit for a fuel cell, exhibiting good characteristics due to the above-described effects, and become an inexpensive fuel cell, suitable for driving a moving body such as an automobile or a ship. is there. In particular, it is suitable as a fuel cell for driving an automobile requiring low cost.

[0099]

EXAMPLES The details of the present invention will be further described below using examples.

Example 1 (1) Preparation of Conductive Sheet Having Coarse Porous Structure Short fibers of PAN-based carbon fibers cut to a length of 12 mm were dispersed in water, paper-formed on a wire mesh, and bonded with short carbon fibers. A conductive sheet A having a coarse porous structure is coated with an emulsion composed of a mixture of polyvinyl alcohol (PVA), which is a polymer substance to be attached, and polyvinyl acetate (vinyl acetate) (mixing ratio 1: 3), and dried. I got The basis weight of the obtained sheet is 2
4 g / m ² , the content of the mixture of PVA and vinyl acetate was 22%, the porosity of the sheet was 95%, and the bulk density was 0.07 g / c.
m ³ and gas permeation resistance were 4 Pa. (2) Preparation of a conductive sheet having a dense porous structure A polymer that disperses short fibers of PAN-based carbon fiber cut to a length of 0.1 mm in water, forms a paper on a wire mesh, and binds the short carbon fibers. An emulsion composed of a mixture of a substance, polyvinyl alcohol (PVA) and polyvinyl acetate (vinyl acetate) (mixing ratio 1: 3) was adhered and dried to obtain a conductive sheet B having a dense porous structure. The basis weight of the obtained sheet was 6 g / m ² , and the content of the mixture of PVA and vinyl acetate was 22%.
The porosity of the sheet is 80%, and the bulk density is 0.2 g /
cm ³ , and gas permeation resistance was 100 Pa. (3) Preparation of conductive sheet with dense and dense structure The above sheet A and sheet B are stacked and hot pressed (temperature:
120 ° C., pressure: 1.96 MPa) to obtain a conductive sheet having a dense / dense structure. The basis weight of the obtained sheet is 30 g / m
^2. The content of the mixture of PVA and vinyl acetate was 22%. A coarse-dense asymmetric porous structure in which the coarse porous structure became the A surface and the dense porous structure became the B surface. (4) Measurement of Electric Resistance and Gas Permeation Resistance of Sheet The electric resistance and gas permeation resistance of the obtained sheet were measured by the methods described above. Electric resistance is 170mΩ · c
m ² , and the gas permeation resistance was 100 Pa. (5) Evaluation of coating performance of catalyst layer A mixture of platinum-supporting carbon and a Nafion solution (manufactured by Aldrich) (solid content weight ratio: 1: 1) was coated on the surface of the obtained sheet, which is the B side, at a coating amount of 1 mg / The composition was spray-coated so as to be cm ² . The catalyst layer was uniform and had little penetration into the sheet.

Example 2 The conductive sheet having a dense / dense asymmetric structure obtained in Example 1 was heated to 800 ° C. in a nitrogen gas atmosphere to remove a mixture of PVA and vinyl acetate. The electric resistance is 25mΩ · cm ² ,
The gas permeation resistance was 40 Pa. The coating performance of the catalyst layer was also good.

Example 3 A phenol resin monomer solution was impregnated into the conductive sheet having a dense structure formed in Example 1 to form a prepreg, which was then molded,
By firing, a carbon-carbon composite (C / C) was prepared. This C / C was a conductive sheet having a porous structure having a coarse porous structure on the A side and a dense porous structure on the B side. This C
/ C has an electric resistance of 10 mΩ · cm ² and a gas permeation resistance of 1
It was 00 Pa. The coating performance of the catalyst layer was also good.

Example 4 (1) Preparation of Conductive Sheet Having Rough Porous Structure Short fibers of PAN-based carbon fibers cut to a length of 12 mm were dispersed in an aqueous solution of carboxymethyl cellulose (CMC) and formed on a wire mesh. Thus, a conductive sheet A having a coarse porous structure was obtained. The basis weight of the obtained sheet was 24 g / m ² ,
The content of CMC is 0.5%, and the porosity of the sheet is 9%.
5%, bulk density 0.07 g / cm ³ , gas permeation resistance 4
Pa. (2) Preparation of conductive sheet having dense porous structure Short fibers of PAN-based carbon fibers cut to a length of 0.1 mm
The resultant was dispersed in an aqueous MC solution and formed on a wire mesh to obtain a conductive sheet B having a dense porous structure. The obtained sheet had a basis weight of 6 g / m ² , a CMC content of 0.5%, a porosity of the sheet of 80%, a bulk density of 0.2 g / cm ³ , and a gas permeation resistance of 100 Pa. Was. (3) Preparation of conductive sheet with dense and dense structure The sheet A and the sheet B are stacked and pressed (temperature: room temperature,
Pressure: 1.96 MPa) to obtain a dense / dense structure conductive sheet. (4) Performance of Sheet The obtained sheet has a basis weight of 30 g / m ² , a CMC content of 0.5%, and a side A having a coarse porous structure and a side B having a dense porous structure. The conductive sheet was composed of The electric resistance of this sheet was 50 mΩ · cm ² , and the gas permeation resistance was 100 Pa. The same coating solution as the catalyst layer coating solution of Example 1 was applied to the B side of the dense porous structure of the sheet by the screen printing method. However, a uniform catalyst layer was obtained, the penetration was small, and the coating performance was good. Was.

Example 5 (1) Preparation of Conductive Sheet Having Rough Porous Structure In the same manner as (1) of Example 4, a conductive sheet A having a coarse porous structure was obtained. (2) Continuous preparation of a conductive sheet having a dense porous structure on a coarse sheet Short fibers of PAN-based carbon fibers cut to a length of 0.1 mm are dispersed in a CMC aqueous solution, and the above (1) Was formed on a wire mesh on which the conductive sheet A was placed and dried to prepare a conductive sheet in which a sheet A having a coarse porous structure and a sheet B having a dense porous structure were integrated. (3) Performance of Sheet The obtained sheet has a basis weight of 30 g / m ² and a CMC content of 0.5%, and has a coarse porous structure A surface and a dense porous structure B surface. The conductive sheet was composed of The electric resistance of this sheet was 50 mΩ · cm ² , and the gas permeation resistance was 100 Pa. The same coating solution as the catalyst layer coating solution of Example 1 was applied to the B side of the dense porous structure of the sheet by the screen printing method. However, a uniform catalyst layer was obtained, the penetration was small, and the coating performance was good. Was. Comparative Example 1 Short fibers of PAN-based carbon fibers cut to a length of 12 mm were dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. The obtained sheet has a basis weight of 30 g /
m ² , the content of CMC was 0.5%, the porosity was 95%, the bulk density was 0.07 g / m ² , and the conductive sheet had a rough porous structure. The electric resistance of this sheet is 50m
Ω · cm ² , and gas permeation resistance was 5 Pa. The catalyst layer was applied to this sheet by a screen printing method. However, a uniform layer could not be formed, the penetration was large, and the application performance was poor as compared with Example 5.

Comparative Example 2 Short fibers of PAN-based carbon fibers cut to a length of 0.1 mm were dispersed in an aqueous solution of carboxymethyl cellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet B having a dense porous structure. Obtained. The obtained sheet has a basis weight of 30 g /
m ² , the content of CMC was 0.5%, the porosity was 80%, the bulk density was 0.2 g / m ² , and the conductive sheet had a dense porous structure. The electric resistance of this sheet is 40mΩ
Example 5: cm ² , gas permeation resistance: 500 Pa
The gas permeation performance was poorer than that of.

Example 6 (1) Preparation of Conductive Sheet Having Rough Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Continuous preparation of a conductive sheet having a dense porous structure on a coarse sheet Short fibers of PAN-based carbon fiber cut to a length of 0.1 mm and expanded graphite powder (PF powder 4, Toyo Carbon ( Co., Ltd.
Bulk density 0.039 g / cm ³ , average particle size 300-50
0 μm) (weight ratio 1: 1) in an aqueous CMC solution,
Paper was formed on the conductive sheet A of the above (1) placed on a wire mesh and dried to prepare a structural conductive sheet in which a sheet A having a coarse porous structure and a sheet B having a dense porous structure were integrated. (3) Performance of the sheet The obtained sheet had a basis weight of 70 g / m ² (weight ratio of the coarse layer to the dense layer was 6: 1), a CMC content of 1.5%, and a coarse porosity. The conductive sheet was composed of surface A having a porous structure and surface B having a dense porous structure. The electric resistance of this sheet is 20 mΩ · cm ² , and the gas permeation resistance is 100 Pa
Met. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 7 (1) Preparation of Conductive Sheet Having Coarse Porous Structure Short fibers of PAN-based carbon fibers cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of Conductive Sheet Having Dense Porous Structure on Rough Sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and acetylene black (DENKA BLACK, manufactured by Denki Kagaku Kogyo KK) A mixture (diameter: 42 nm) of an aqueous dispersion of PFA (neoflon PFA, manufactured by Daikin Industries, Ltd.) (solids ratio by weight: 3: 1: 1) was applied to the surface of the sheet A by a screen printing method. This sheet was fired at 400 ° C. to prepare a dense / dense conductive sheet C in which a coarse porous sheet A and a dense porous structure sheet B were integrated. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The content of PFA was 2.9%, and the conductive sheet was a dense / dense structure conductive sheet composed of a surface A having a coarse porous structure and a surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. FIG. 1 shows the result of observing the surface of the side B of the dense porous structure of the sheet C with a scanning electron microscope (SEM). The same material as the coating solution for the catalyst layer of Example 1 was applied to the B side of the dense porous structure of the sheet C by a screen printing method. The applied amount was 1 mg / cm ² . FIG. 2 shows the result of SEM observation of the surface of the catalyst layer. A uniform catalyst layer was obtained, with little penetration and good coating performance. DuPont as a proton exchange membrane with this electrode substrate with a catalyst layer
An MEA was prepared using “Nafion” 112 manufactured by KK. The fuel cell performance of this MEA is determined by measuring the current-voltage (IV).
It was performed by measurement. At a cell temperature of 60 ° C. and a gas pressure of normal pressure, the limiting current (current value at the time when the fuel cell terminal voltage becomes 0 V) was 2 A / cm ² , showing excellent high-output characteristics.

Comparative Example 3 A sheet A having a rough porous structure was obtained in the same manner as in Example 7 (1). The obtained sheet A has a basis weight of 60 g.
/ Cm ² , and the content of CMC was 1.5%. The electric resistance of this sheet A was 20 mΩ · cm ² , and the gas permeation resistance was 20 Pa. FIG. 3 shows the result of observing the surface of the sheet A with a scanning electron microscope (SEM). Further, a catalyst layer was applied to the surface of the sheet A in the same manner as in Example 7 by a screen printing method. The application amount was 3 mg / cm ² . FIG. 4 shows the result of SEM observation of the surface of the catalyst layer. A uniform catalyst layer could not be formed, the penetration was large, and the coating performance was poor. This electrode substrate with a catalyst layer was prepared by MEA in the same manner as in Example 7, and the IV measurement was performed in a fuel cell. The limiting current was 0.5 A / cm ² , and the high output characteristics were poor compared to Example 7.

Comparative Example 4 (1) Preparation of Conductive Sheet Having Coarse Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of conductive sheet having dense porous structure on coarse sheet Acetylene black (DENKA BLACK, manufactured by Denki Kagaku Kogyo Co., Ltd., particle size 42 nm) and PFA aqueous dispersion (Neoflon PFA, Daikin Industries, Ltd.) (Manufactured by Co., Ltd.) (solid content ratio by weight: 4: 1) is applied to the surface of the sheet A by a screen printing method to form a rough porous sheet A and a dense porous structure sheet B. An integrated dense and dense structure conductive sheet C was produced. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The content of PFA was 2.9%, and the conductive sheet was a dense / dense structure conductive sheet composed of a surface A having a coarse porous structure and a surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 500 Pa. As compared with Example 7, the gas permeation performance was poor.

Example 8 (1) Preparation of a Conductive Sheet Having a Rough Porous Structure Short fibers of PAN-based carbon fibers cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of Conductive Sheet Having Dense Porous Structure on Rough Sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and acetylene black (DENKA BLACK, manufactured by Denki Kagaku Kogyo KK) A mixture (diameter: 42 nm) of an aqueous dispersion of PTFE (polyfluorocarbon PTFE, manufactured by Daikin Industries, Ltd.) (solid content weight ratio: 3: 1: 1) was applied to the surface of the sheet A by a screen printing method. 380 of this sheet
The resultant was baked at a temperature of ° C. to prepare a dense / dense structure conductive sheet C in which a coarse porous structure sheet A and a dense porous structure sheet B were integrated. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The content of PTFE was 2.9%, and the conductive sheet was a dense / dense structure conductive sheet composed of a surface A having a coarse porous structure and a surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 9 (1) Preparation of Conductive Sheet Having Coarse Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of Conductive Sheet Having Dense Porous Structure on Rough Sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and acetylene black (DENKA BLACK, manufactured by Denki Kagaku Kogyo KK) A mixture (diameter: 42 nm) of an aqueous dispersion of FEP (neoflon FEP, manufactured by Daikin Industries, Ltd.) (solids ratio by weight: 3: 1: 1) was applied to the surface of the sheet A by a screen printing method. This sheet was fired at 270 ° C. to prepare a dense / dense structure conductive sheet C in which a coarse porous sheet A and a dense porous sheet B were integrated. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The FEP content was 2.9%, and the conductive sheet was a dense / dense structure conductive sheet composed of a surface A having a coarse porous structure and a surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 10 (1) Preparation of Conductive Sheet Having Rough Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of Conductive Sheet Having Dense Porous Structure on Rough Sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and acetylene black (DENKA BLACK, manufactured by Denki Kagaku Kogyo KK) A mixture of PVDF NMP solution (solid diameter ratio: 3: 1: 1) with a sheet A
The surface was coated by a screen printing method to prepare a dense / dense structure conductive sheet C in which a coarse porous sheet A and a dense porous structure sheet B were integrated. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The PVDF content was 2.9%, and the conductive sheet was a coarse-dense structure conductive sheet composed of surface A having a coarse porous structure and surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. FIG. 5 shows the result of observing the surface of the side B of the dense porous structure of the sheet C with a scanning electron microscope (SEM).
In addition, Example 7 was applied to the B side of the dense porous structure of the sheet C.
The catalyst layer was applied by the screen printing method in the same manner as in the above. The applied amount was 1 mg / cm ² . FIG. 6 shows the result of SEM observation of the surface of the catalyst layer. A uniform catalyst layer was obtained, with little penetration and good coating performance. This electrode substrate with a catalyst layer was prepared by MEA in the same manner as in Example 7, and the IV measurement was performed in a fuel cell. The limit current is 2A /
cm ² , showing excellent high-output characteristics.

Example 11 (1) Preparation of Conductive Sheet Having Rough Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of a conductive sheet having a dense porous structure on a coarse sheet Graphite particles (MCMB-6-28, manufactured by Osaka Gas Co., Ltd.) having a particle size of 6 μm and acetylene black (DENKA BLA)
CK, manufactured by Denki Kagaku Kogyo KK, particle size 42 nm) and PFA
Aqueous dispersion (Neoflon PFA, manufactured by Daikin Industries, Ltd.)
(A solid content weight ratio of 3: 1: 1) is applied to the surface of the sheet A by a screen printing method to form a sheet A having a coarse porous structure and a sheet B having a dense porous structure. A dense and dense structure conductive sheet C was produced. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The content of PFA was 2.9%, and the conductive sheet was a dense / dense structure conductive sheet composed of a surface A having a coarse porous structure and a surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 150 Pa. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 12 (1) Preparation of Conductive Sheet Having Coarse Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) in carboxymethylcellulose (CMC) aqueous solution and paper-made on a wire mesh to obtain conductive sheet A having a coarse porous structure. (2) Preparation of a conductive sheet having a dense porous structure on a coarse sheet Graphite particles (MCMB-10-28, manufactured by Osaka Gas Co., Ltd.) having a particle size of 10 μm and acetylene black (DENKA B)
LACK, manufactured by Denki Kagaku Kogyo KK, particle size 42 nm) and P
FA aqueous dispersion (Neoflon PFA, Daikin Industries, Ltd.)
(Solid content weight ratio: 3: 1: 1) is applied to the surface of the sheet A by a screen printing method, and the sheet A having a coarse porous structure and the sheet B having a dense porous structure are integrated. A conductive sheet C having a dense and dense structure was prepared. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The content of PFA was 2.9%, and the conductive sheet was a dense / dense structure conductive sheet composed of a surface A having a coarse porous structure and a surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 13 (1) Preparation of Conductive Sheet Having Coarse Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) with polyvinyl alcohol (PV
A) Dispersion in an aqueous solution and papermaking on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of Conductive Sheet Having Dense Porous Structure on Rough Sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and acetylene black (DENKA BLACK, manufactured by Denki Kagaku Kogyo KK) A mixture (diameter: 42 nm) of an aqueous dispersion of PFA (neoflon PFA, manufactured by Daikin Industries, Ltd.) (solids weight ratio: 3: 1: 1) was applied to the surface of the sheet A by a screen printing method. Sheet A with porous structure
And a dense / dense conductive sheet C integrated with a sheet B having a dense porous structure. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio of the coarse layer to the dense layer is 6: 1) and a PVA content of 4.3.
%, The content of PFA was 2.9%, and the conductive sheet was a dense / dense structure conductive sheet composed of a surface A having a coarse porous structure and a surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 14 (1) Preparation of Conductive Sheet Having Rough Porous Structure Short fibers of PAN-based carbon fibers cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) with polyvinyl alcohol (PV
A) and a mixture of polyvinyl acetic acid (PVAc) (PVA and P
VAc (weight ratio of 1: 3) was dispersed in an aqueous solution and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of Conductive Sheet Having Dense Porous Structure on Rough Sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and acetylene black (DENKA BLACK, manufactured by Denki Kagaku Kogyo KK) A mixture (diameter: 42 nm) of an aqueous dispersion of PFA (neoflon PFA, manufactured by Daikin Industries, Ltd.) (solids weight ratio: 3: 1: 1) was applied to the surface of the sheet A by a screen printing method. Sheet A with porous structure
And a dense / dense conductive sheet C integrated with a sheet B having a dense porous structure. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio of the coarse layer to the dense layer is 6: 1) and a PVA content of 1.1.
%, The content of PVAc is 3.2%, the content of PFA is 2.9%, and the dense and dense structure conductive sheet is composed of the A surface having a coarse porous structure and the B surface having a dense porous structure. Met. The electric resistance of this sheet C is 20 mΩ · cm ² ,
The gas permeation resistance was 100 Pa. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 15 (1) Preparation of conductive sheet with coarse and dense structure Short fibers of PAN-based carbon fiber cut to a length of 30 μm, acetylene black (DENKA BLACK, manufactured by Denki Kagaku Kogyo KK, particle size 42 nm) and PFA A mixed solution (solid weight ratio: 3: 1: 1) with an aqueous dispersion (Neoflon PFA, manufactured by Daikin Industries, Ltd.) was applied to a carbon fiber fabric (ET).
EK cloth, basis weight 120 g / m ² , sheet A) is applied by screen printing to the surface of the coarse-porous structure sheet A and the dense porous structure sheet B. A sheet C was prepared. (3) Performance of Sheet The obtained sheet C has a basis weight of 130 g / m ² (weight ratio of the coarse layer to the dense layer is 12: 1) and a PFA content of 1.
5%, which was a dense / dense structure conductive sheet composed of surface A having a coarse porous structure and surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 16 (1) Preparation of Conductive Sheet Having Coarse Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of Conductive Sheet Having Dense Porous Structure on Coarse Sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and Ketjen Black (Lion Co., Ltd., particle size 30 n
m) and an aqueous dispersion of PFA (neoflon PFA, manufactured by Daikin Industries, Ltd.) (solids weight ratio 3: 1: 1)
Was applied to the surface of the sheet A by a screen printing method. This sheet was fired at 400 ° C. to prepare a dense / dense conductive sheet C in which a coarse porous sheet A and a dense porous structure sheet B were integrated. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The content of PFA was 2.9%, and the conductive sheet was a dense / dense structure conductive sheet composed of a surface A having a coarse porous structure and a surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 17 (1) Preparation of Conductive Sheet Having Rough Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) in an aqueous carboxymethylcellulose (CMC) solution and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of a conductive sheet having a dense porous structure on a coarse sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and carbon black (Vulcan XC-72, Cabo)
A liquid mixture of PFA aqueous dispersion (Neoflon PFA, manufactured by Daikin Industries, Ltd.) (solid content weight ratio: 3: 1: 1) was coated on the surface of sheet A by a screen printing method. Applied. This sheet was fired at 400 ° C. to prepare a dense / dense conductive sheet C in which a coarse porous sheet A and a dense porous structure sheet B were integrated. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The content of PFA was 2.9%, and the conductive sheet was a dense / dense structure conductive sheet composed of a surface A having a coarse porous structure and a surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 18 (1) Preparation of Conductive Sheet Having Rough Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of Conductive Sheet Having Dense Porous Structure on Rough Sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and acetylene black (DENKA BLACK, manufactured by Denki Kagaku Kogyo KK) A mixture of PVDF NMP solution (solid diameter ratio: 3: 1: 1) with a sheet A
Immediately after coating on the surface of the sample by screen printing, it was immersed in methanol to perform wet coagulation. Remove after 10 minutes 9
The resultant was dried at 0 ° C. to prepare a coarse / dense structure conductive sheet C in which a coarse porous structure sheet A and a dense porous structure sheet B were integrated. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The PVDF content was 2.9%, and the conductive sheet was a coarse-dense structure conductive sheet composed of surface A having a coarse porous structure and surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. Example 7 was applied to the B side of the dense porous structure of the sheet C.
The catalyst layer was applied by the screen printing method in the same manner as in the above. The coating amount was 1 mg / cm ² , a uniform catalyst layer was obtained, the penetration was small, and the coating performance was good. This electrode substrate with a catalyst layer was prepared by MEA in the same manner as in Example 7, and the IV measurement was performed in a fuel cell. The limit current is 2A /
cm ² , showing excellent high-output characteristics.

Example 19 (1) Preparation of Conductive Sheet Having Coarse Porous Structure Short fibers of PAN-based carbon fiber cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd.) Bulk density 0.039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A having a coarse porous structure. (2) Preparation of Conductive Sheet Having Dense Porous Structure on Rough Sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and acetylene black (DENKA BLACK, manufactured by Denki Kagaku Kogyo KK) A mixture (diameter: 42 nm) of an aqueous dispersion of PFA (neoflon PFA, manufactured by Daikin Industries, Ltd.) (solids ratio by weight: 3: 1: 1) was applied to the surface of the sheet A by a screen printing method. This sheet was fired at 400 ° C. to prepare a dense / dense conductive sheet C in which a coarse porous sheet A and a dense porous structure sheet B were integrated. (3) Performance of Sheet The obtained sheet C has a basis weight of 70 g / m ² (weight ratio between the coarse layer and the dense layer is 6: 1) and a CMC content of 1.3.
%, The content of PFA was 2.9%, and the conductive sheet was a dense / dense structure conductive sheet composed of a surface A having a coarse porous structure and a surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. A mixture of platinum-supported carbon and a Nafion solution (manufactured by Aldrich) (solid content ratio by weight: 1: 1) was applied by screen printing onto the surface of sheet B, which was originally a sheet of the obtained sheet. Immersion. After immersion for 10 minutes, it was dried at 90 ° C. The obtained electrode catalyst layer had a coating amount of platinum of 0.5 mg / cm ² , had a three-dimensional mesh-like microporous structure, and was able to form a catalyst layer with little penetration into the sheet. This electrode substrate with a catalyst layer was prepared by MEA in the same manner as in Example 7, and the IV measurement was performed in a fuel cell. The limiting current was 2 A / cm ² , showing excellent high output characteristics.

Example 20 (1) Preparation of a conductive sheet having a dense / dense structure Graphite particles (MCMB-6-28, manufactured by Osaka Gas Co., Ltd.) having a particle size of 6 μm and acetylene black (DENKA BLA)
CK, manufactured by Denki Kagaku Kogyo KK, particle size 42 nm) and PFA
Aqueous dispersion (Neoflon PFA, manufactured by Daikin Industries, Ltd.)
(A solid content weight ratio of 3: 1: 1) is applied to the surface of a carbon fiber fabric (E-TEK cloth, basis weight 120 g / m ² , sheet A) by a screen printing method,
Sheet A with coarse porous structure and Sheet B with dense porous structure
Was prepared as a united structure conductive sheet C. (3) Performance of Sheet The obtained sheet C has a basis weight of 130 g / m ² (weight ratio of the coarse layer to the dense layer is 12: 1) and a PFA content of 1.
5%, which was a dense / dense structure conductive sheet composed of surface A having a coarse porous structure and surface B having a dense porous structure. The electric resistance of this sheet C was 20 mΩ · cm ² , and the gas permeation resistance was 100 Pa. A catalyst layer was applied to the dense porous structure B side of the sheet by screen printing, but the catalyst layer was obtained uniformly, with little penetration and good application performance.

Example 21 (1) Preparation of a conductive sheet having a dense and asymmetrical asymmetric structure Short fibers of PAN-based carbon fiber cut to a length of 20 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd. 039 g / cm ³ , average particle size 300-500
μm) (weight ratio 1: 1) was dispersed in an aqueous solution of carboxymethylcellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet A.

Separately, short fibers of PAN-based carbon fibers cut to a length of 12 mm and expanded graphite powder (PF Powder 4, manufactured by Toyo Carbon Co., Ltd., bulk density 0.039 g / cm ³ , average particle diameter 300 to 500 μm) (Weight ratio: 1: 1) was dispersed in an aqueous solution of carboxymethyl cellulose (CMC) and paper-made on a wire mesh to obtain a conductive sheet B.

The sheet A and the sheet B are stacked and hot-pressed (temperature: 120 ° C., pressure: 1.96 MPa),
A conductive sheet C having a dense and dense structure was obtained. The coarse porous structure was the A-plane and the dense porous structure was the B-plane.
The obtained sheet C had a basis weight of 60 g / m 2, a weight ratio of the coarse layer to the dense layer of 1: 1, and a CMC content of 1.5%. (2) Preparation of a conductive sheet having a denser porous structure on a dense / dense asymmetric structure conductive sheet Short fibers of PAN-based carbon fiber cut to a length of 30 μm and acetylene black (DENKA BLACK, Denki Kagaku Kogyo Co., Ltd.) A liquid mixture (solid weight ratio: 3: 1: 1) of an aqueous dispersion of PFA (neoflon PFA, manufactured by Daikin Industries, Ltd.) and a PFA aqueous dispersion (diameter: 42 nm) is screened on the side of the side of the sheet C on the B side. It was applied by a printing method. 4 this sheet
The resultant was fired at 00 ° C. to prepare a dense / dense asymmetric continuous porous structure conductive sheet D having the roughest surface on the side of the surface A. (3) Sheet Performance The obtained sheet D had a basis weight of 70 g / m ² , a CMC content of 1.3%, and a PFA content of 2.9%.
Originally, it was a dense / dense continuous asymmetric porous structure conductive sheet having the coarsest side on the A side. The electric resistance of this sheet D is 20
mΩ · cm ² and gas permeation resistance were 100 Pa. A catalyst layer was applied to the surface of the sheet D having the most dense porous structure by a screen printing method. The catalyst layer was uniformly obtained, and the coating was excellent in coating performance with little penetration.

[0126]

The structural conductive sheet of the present invention has good gas permeability and low electric resistance. In particular, when used as a polymer electrolyte fuel cell electrode base material, gas permeability is good and bonding with the catalyst layer is good, so that excellent fuel cell performance can be exhibited and the amount of catalyst can be reduced. Become cheap.

[Brief description of the drawings]

FIG. 1 is a SEM photograph of a dense side surface of an example of the present invention.

FIG. 2 is a SEM photograph of a catalyst layer surface according to an example of the present invention.

FIG. 3 is a SEM photograph of a rough sheet surface of a comparative example.

FIG. 4 is a SEM photograph of a catalyst layer surface of a comparative example.

FIG. 5 is a SEM photograph of a dense side surface of another embodiment of the present invention.

FIG. 6 is an SEM photograph of a catalyst layer surface according to another example of the present invention.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 8/02 H01M 8/02 E 8/10 8/10 F term (Reference) 5G307 AA08 CA01 CB02 5H018 AA06 AS01 DD05 DD06 DD08 DD10 EE02 EE03 EE04 EE05 EE06 EE08 EE10 EE11 EE17 HH00 HH01 HH03 HH04 HH05 HH09 5H026 AA06 CC03 CX02 CX03 CX04 EE02 EE05 EE06 EE08 EE11 EE18 HH01 HH03H04

Claims (24)

[Claims] 1. A sheet-like material mainly made of a conductive substance and having a porous structure, wherein a porous structure of a layer on one side is coarse and a porous structure of a layer on the other side is provided. A conductive sheet, characterized by being dense. 2. The porosity of the porous structure of the layer having a rough surface is represented by V
2. The conductive sheet according to claim 1, wherein, when A (%) and VB (%) are the porosity of the porous structure of the layer on the dense surface, 5 ≦ VA−VB ≦ 90. 3. The bulk density of the porous structure of the layer having a rough surface
When A (g / cm ³ ) and the bulk density of the porous structure of the dense layer are DB (g / cm ³ ), 1 <DB / D
The conductive sheet according to claim 1, wherein A ≦ 100. 4. When the pressure loss when air of 14 cm / sec is permeated is defined as gas permeation resistance, the gas permeation resistance of the porous structure of the layer having a rough surface is defined as PA (Pa), and the density is high. The conductive sheet according to any one of claims 1 to 3, wherein when the gas transmission resistance of the porous structure of the surface layer is PB (Pa), 1 <PB / PA ≤ 100. 5. The method according to claim 1, wherein the conductive substance is a fibrous substance.
5. The conductive sheet according to any one of items 4 to 4. 6. The conductive sheet according to claim 5, wherein the fibrous substance is a combination of conductive substances having different fiber lengths. 7. The fiber length of the conductive fibrous substance contained in the layer of the rough surface is set to LA (μm), and the fiber length of the conductive fibrous substance contained in the layer of the dense surface is set to LB (μm). The conductive sheet according to claim 5, wherein 2 ≦ LA / LB ≦ 10000. 8. The porous structure of the layer having a rough surface comprises a woven or nonwoven structure of a conductive fibrous substance having a fiber diameter of 5 to 10 μm and a fiber length of 1 mm or more. The conductive sheet according to any one of claims 5 to 7, wherein the conductive fibrous substance contained in the layer has a fiber length of less than 1 mm. 9. The method according to claim 1, wherein the conductive material is a particulate material.
5. The conductive sheet according to any one of items 4 to 4. 10. The conductive sheet according to claim 9, wherein the particulate matter is a combination of conductive substances having different particle diameters. 11. The conductive sheet according to claim 1, wherein the conductive substance is composed of a mixture of fibrous and particulate. 12. The porous structure of the layer having a rough surface is a woven or nonwoven structure of a conductive fibrous substance having a fiber diameter of 5 to 10 μm and a fiber length of 1 mm or more. The particle size of the conductive particulate matter contained in the layer is 10 nm
The conductive sheet according to claim 11, which has a thickness of from 10 to 10 m. 13. The layer on one side and the layer on the other side are as follows:
The conductive sheet according to claim 11, wherein the conductive sheet has a difference of any one of A to C. A. Difference in weight ratio or volume ratio between conductive fibrous substance and conductive particulate matter B. Difference in fiber length of fiber C. Difference in particle diameter of particle 14. The conductive sheet according to claim 1, wherein the conductive substance is a conductive substance containing a carbon body as a main component. 15. The conductive sheet according to claim 14, wherein the carbon body comprises at least one selected from the group consisting of a fired body made of polyacrylonitrile, a fired body made of pitch, carbon black, graphite and expanded graphite. 16. The conductive sheet according to any one of claims 1 to 15, wherein the conductive material is mainly composed of one selected from a metal, a metalloid, a compound thereof, and a mixture thereof. 17. The method according to claim 17, wherein the metal is stainless steel, titanium,
17. The conductive sheet according to claim 16, wherein one or more metals selected from chromium, nickel, molybdenum, ruthenium, rhodium, tantalum, iridium, platinum, and gold, and alloys of the metals, and those selected from these compounds are essential components. 18. The conductive sheet according to claim 1, wherein the conductive material is a mixture of a carbon body and a metal or metalloid. 19. An electrode substrate comprising the conductive sheet according to claim 1, wherein a rough surface of the conductive sheet is provided on a gas flow path side of the electrode substrate. An electrode substrate for a fuel cell, wherein the dense surface of the sheet is the catalyst layer side of the electrode substrate. 20. An electrode comprising the electrode substrate according to claim 19 and an electrode catalyst layer. 21. A membrane-electrode composite comprising the electrode substrate according to claim 19, an electrode catalyst layer, and a solid electrolyte membrane. 22. A fuel cell using the electrode substrate according to claim 19. 23. A polymer electrolyte fuel cell using the electrode substrate according to claim 19. 24. A vehicle equipped with the fuel cell according to claim 22 or 23, and using a motor using the fuel cell as a power supply as a driving means.