JP6596886B2 - Method for producing gas diffusion layer - Google Patents

Description

  The present invention relates to a gas diffusion layer, and more particularly to a gas diffusion layer used for a polymer electrolyte fuel cell, and a method for producing the same.

  A polymer electrolyte fuel cell is an apparatus that obtains an electromotive force by electrochemically reacting a fuel gas such as hydrogen and an oxidizing gas such as oxygen. The polymer electrolyte fuel cell includes a hydrogen ion (proton). And a polymer electrolyte membrane that selectively conducts. Further, two sets of gas diffusion electrodes each having a catalyst layer mainly composed of carbon powder carrying a noble metal catalyst and a gas diffusion electrode substrate are joined to both surfaces of the polymer electrolyte membrane.

  Such a joined body composed of a polymer electrolyte membrane and two sets of gas diffusion electrodes is called a membrane-electrode assembly (MEA). Further, on both outer sides of the MEA, separators are provided in which gas flow paths for supplying fuel gas or oxidizing gas and for discharging generated gas and excess gas are formed.

  The gas diffusion electrode substrate is mainly required to have the following three functions. The first function is a function of uniformly supplying the fuel gas or the oxidizing gas to the noble metal-based catalyst in the catalyst layer from the gas flow path formed in the separator disposed outside the first function. The second function is a function of discharging water generated by the reaction in the catalyst layer. The third function is a function of conducting electrons necessary for the reaction in the catalyst layer or electrons generated by the reaction in the catalyst layer to the separator. As a base material satisfying these functions, a base material having a porous structure made of a carbonaceous material is usually used. Specifically, substrates using carbon fibers such as carbon paper, carbon fiber cloth, carbon fiber felt, etc. are generally used. These base materials are not only highly conductive due to carbon fibers, but are porous materials, and are therefore suitable materials for gas diffusion layers because of high permeability of liquids such as fuel gas and generated water.

  For the purpose of reducing the contact resistance between the porous carbon electrode substrate such as carbon paper and carbon cloth mentioned above and the electrode catalyst layer, and efficiently discharging generated water generated during power generation, carbon fine particles and water repellent A coating layer made of may be provided between the porous carbon electrode substrate and the electrode catalyst layer. Patent Document 1 discloses a gas diffusion layer provided with a water repellent layer as the coating layer.

JP 2010-129451 A

  However, the gas diffusion layer formed by this method has a remarkably high density of the coating layer compared to the gas diffusion layer base material, so that the adhesion with the electrode catalyst layer is poor, and the liquid water is efficiently removed from the system. It was difficult to discharge. Therefore, there has been a demand for a gas diffusion layer that improves the adhesion with the electrode catalyst layer and can efficiently discharge liquid water generated during power generation.

  As a result of intensive studies to solve the above problems, the present inventors have improved the adhesion with the electrode catalyst layer by providing irregularities in the coating layer, and can efficiently discharge liquid water generated during power generation. As a result, the present invention has been completed. That is, the gist of the present invention resides in the following (1) to (7).

  (1) A gas diffusion layer in which a coating layer made of carbon powder and a water repellent agent is provided on at least one surface of a porous carbon electrode substrate, and the coating has linear irregularities along the longitudinal direction of the sheet A gas diffusion layer forming a layer.

(2) The gas according to (1) above, wherein the porous carbon electrode substrate constituting the gas diffusion layer has a thickness of 50 to 250 μm, and the coating layer formed on at least one surface has a thickness of 5 to 100 μm. Diffusion layer.

  (3) Gas diffusion as described in said (1) or (2) whose ratio H / A of the average depth H of the recessed part on a coating layer with respect to the average thickness A of a coating layer is 0.01-0.3. layer.

  (4) The gas diffusion layer according to any one of (1) to (3), wherein the width of the concave portion and the convex portion on the coating layer is in the range of 0.1 to 1000 μm.

  (5) The gas diffusion layer according to any one of (1) to (4), wherein a difference between the width of the concave portion and the width of the convex portion is 0.1 to 500 μm.

(6) Coating liquid comprising carbon powder, water repellent, surfactant, and water at a speed of 1 to 10 m / min using a coating rod having a pitch of 0.1 mm to 1.5 mm and a depth of 5 to 350 μm. A method for producing a gas diffusion layer in which a coating is formed on a porous carbon electrode substrate to form a coating layer having continuous irregularities along the longitudinal direction of the sheet.

  (7) Production of the gas diffusion layer according to (6) above, wherein the coated coating liquid is solidified and dried before being flattened to form a coating layer having continuous irregularities along the longitudinal direction of the sheet. Method.

  Providing a gas diffusion layer capable of efficiently discharging liquid water generated during power generation while improving the adhesion to the electrode catalyst layer by providing irregularities in the coating layer while being a simple manufacturing method it can.

It is a scanning electron micrograph of the gas diffusion layer of this invention.

  Hereinafter, the present invention will be described in detail.

1. Method for Producing Gas Diffusion Layer The gas diffusion layer of the present invention can be produced by a production method including the following steps [1] to [4].

  Step [1]: A step of mixing and stirring a liquid composed of carbon powder, a water repellent, a surfactant, and water using a stirrer to obtain a coating liquid.

Step [2]: Using a coating rod having a pitch of 0.1 mm to 1.5 mm and a depth of 5 to 350 μm, the coating liquid is applied onto the porous carbon electrode substrate at a speed of 1 to 10 m / min, and the surface Forming a coating layer having a concave portion and a convex portion along the sheet width direction, wherein the concave portion and the convex portion are respectively continuously formed along the sheet longitudinal direction .

Step [3]: a coating layer that is solidified and dried before the coated coating solution is flattened, and has concave and convex portions along the sheet width direction on the surface, wherein the concave and convex portions are respectively Forming a coating layer continuously formed along the longitudinal direction of the sheet ;

  Step [4]: A step of heating the porous carbon electrode substrate on which the coating layer is formed to 200 to 400 ° C. to obtain a gas diffusion layer.

<Step [1]: Step of obtaining a coating solution by mixing and stirring a liquid composed of carbon powder, water repellent, surfactant and water using a stirrer>
As the carbon powder to be used, for example, graphite powder or carbon black can be used. For example, acetylene black (for example Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd.), ketjen black (for example Ketjen Black EC manufactured by Lion Co., Ltd.), furnace black (for example, Vulcan XC72 manufactured by CABOT), etc. are used as carbon black. Can be used. From the viewpoint of expressing higher conductivity, it is preferable to use carbon black.

  Examples of the water repellent include a fluororesin. Examples of the fluororesin include tetrafluoroethylene-hexafluoropropylene copolymer, polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer and the like, and polytetrafluoroethylene (PTFE) is particularly preferable. PTFE may be dispersed in water with a surfactant, or a dispersion dispersed in advance may be used.

  A known surfactant can be used. Examples thereof include nonionic surfactants such as polyoxyethylene (10) octylphenyl ether (for example, Triton X-100 manufactured by ACROS ORGANICS), alkyl ether, alkylphenyl ether, and the like. From the viewpoint of handleability and decomposition temperature, it is preferable to use polyoxyethylene (10) octylphenyl ether.

  As a method for preparing a coating liquid from carbon powder, a water repellent and a surfactant, and water, a known method can be used. A carbon powder dispersion and a water repellent dispersion are respectively prepared and mixed. In order to obtain the carbon dispersion, water is mixed into the carbon powder. At this time, it is preferable to add an organic solvent or a surfactant in order to improve the wettability of the carbon powder and improve the dispersibility. Such organic solvents are preferably lower alcohols and acetone. The addition amount of the surfactant may be 0.1 wt% or more with respect to the entire coating liquid in order to increase the dispersibility of the carbon powder, and if the addition amount is too large, foaming occurs, so that 5 wt%. The following is preferable. A thickener or the like can be added according to the desired viscosity. As a device used for stirring, a general stirrer such as a disper, a homogenizer, a sand mill, a jet mill, a ball mill, a bead mill, or the like can be used. It is preferable to use a disper, a homogenizer, or the like from the viewpoint that the operation is simple and the processing time is shortened. In order to fiberize the water repellent, the stirring temperature of the coating liquid in which the carbon powder and the water repellent are dispersed is kept at 30 ° C. or higher, and the stirring speed when using a disper is at least 5000 rpm for 15 minutes or longer. It is preferable to mix and stir. The viscosity of the coating liquid is preferably in the range of 100 to 10,000 mPa · s. When the viscosity of the coating liquid is less than 100 mPa · s, it becomes difficult to provide unevenness on the coating layer. On the other hand, if the viscosity of the coating liquid is greater than 100 mPa · s, it is difficult to form a coating film.

<Step [2]: Using a coating rod having a pitch of 0.1 mm to 1.5 mm and a depth of 5 to 350 μm, the coating liquid is applied onto the porous carbon electrode substrate at a speed of 1 to 10 m / min, Step of forming a coating layer having a concave portion and a convex portion along the sheet width direction on the surface, wherein the concave portion and the convex portion are respectively continuously formed along the sheet longitudinal direction >
<< Treatment of porous carbon electrode substrate >>
In the water repellent treatment performed to impart water repellency to the porous carbon electrode substrate, a dispersion liquid in which particles of a water repellent such as a fluororesin are dispersed in a solvent is used. When water is used as the solvent, the water repellent is not dispersed in water as it is, and is thus dispersed in water with an appropriate surfactant. Further, as the dispersion, a dispersion in which a water repellent is dispersed in advance can be used.

<< Formation of coating film >>
As a coating method for forming a coating liquid for forming a coating film on a porous carbon electrode substrate, a conventionally known method can be used, for example, a bar coating method, a blade method, a screen printing method, a spray method, Examples include curtain coating and roll coating. By these methods, a uniform coating film can be formed on the porous carbon electrode substrate.

  In the present invention, it is preferable to apply a bar coating method in order to form irregularities in the coating layer.

  The thickness of the coating film is preferably 50 to 2000 μm. If the thickness of the coating film is less than 50 μm, it is difficult to obtain a film having a uniform thickness, and if it is more than 2000 μm, unintended large cracks are likely to occur in the coating layer after drying, such being undesirable. A more preferable range of the thickness of the coating film is 50 to 1000 μm.

  The coating speed is preferably in the range of 1 to 10 m / min from the viewpoint of productivity.

<< Coating rod >>
The coating rod is not limited to a wire bar that has been used conventionally, and a bar having a groove formed on the surface of a metal rod can also be used. The pitch of the coating rod is preferably 0.1 mm to 1.5 mm, and the depth is preferably in the range of 5 to 350 μm.

<Step [3]: A coating layer that is solidified and dried before the coated coating liquid is flattened, and has concave and convex portions along the sheet width direction on the surface, wherein the concave and convex portions are Step of forming a coating layer formed continuously along the longitudinal direction of the sheet >
In the present invention, it is a coating layer having a concave portion and a convex portion along the sheet width direction on the surface by solidifying and drying before the coated coating liquid is flattened, and the concave portion and the convex portion are Each of the coating layers is formed continuously along the longitudinal direction of the sheet . As a drying method, for example, a plate heater, a heating roll, a hot air dryer, an IR heater, or the like can be used. As an atmospheric temperature at the time of drying, it is preferable that it is the range of 50 to 300 degreeC, More preferably, it is 100 to 300 degreeC. When the drying temperature is lower than 50 ° C., the drying speed of the coating film is slow, and unevenness cannot be formed on the coating layer. When the drying temperature is higher than 300 ° C., the evaporation rate of the solvent is too high. Unintended large cracks are generated in the coating film, and the strength of the coating film is lowered. The drying time is preferably 0.5 minutes to 20 minutes, more preferably 0.5 to 10 minutes in consideration of productivity.

<Step [4]: Step of obtaining a gas diffusion layer by heating the porous carbon electrode substrate on which the coating layer is formed to 200 to 400 ° C.>
In the present invention, the gas diffusion layer is produced by baking the “porous carbon electrode substrate on which a coating film has been formed” in an environment of 300 to 400 ° C. after drying.

  In this firing step, first, the dispersant such as the surfactant contained in the porous carbon electrode substrate and the coating film is eliminated, and in addition, the water repellent is heated to near the melting point, thereby making the water repellent By controlling the shape by melting the agent particles, the pore structure control of the coating layer and the binding of the carbon powder are strengthened. Therefore, the temperature is preferably in the range of 300 to 400 ° C, more preferably 340 to 400 ° C. The firing time is preferably 5 to 90 minutes, more preferably 10 to 60 minutes.

<< Porous carbon electrode base material >>
By the production method of the present invention, a porous carbon electrode for a polymer electrolyte fuel cell having a low electrical resistance and good drainage can be produced from a porous carbon electrode substrate. As long as it is a porous carbon electrode substrate, the above effect can be expressed by using the technique of the present invention rather than using the conventional manufacturing technique.

  As described above, any porous carbon electrode substrate in the present invention can be used.

  As the porous carbon electrode base material, it is possible to use any conductive porous material such as conductive paper, cloth, non-woven fabric made of carbon powder, carbon fiber, metal fiber, and resin as conductive fillers. Specifically, commercially available carbon paper or the like can be used, but a porous carbon electrode base material in which short carbon fibers are bound by carbon can also be used. Examples of the carbon that binds the short carbon fibers include carbon fiber precursor short fibers, resins, and the like, and there is a method of carbonizing them by treating them at a high temperature. A carbon fiber sheet can be created from short carbon fibers and short fibers as a carbon source and a resin, and a porous carbon electrode base material in which carbon short fibers are bound by carbon can be manufactured through a molding and carbonization process. . These processes are desirably manufactured continuously from the viewpoint of quality and productivity. Moreover, not only said porous carbon electrode base material but the porous carbon electrode base material which does not have a carbonization process and has low energy cost can also be used. Examples of these are porous carbon electrode bases in which fine conductive materials such as carbon fiber webs and carbon bonded with short binder fibers filled with conductive material particles are bonded with a binder such as resin. There are materials.

<<< Method for Producing Porous Carbon Electrode Base Material >>>
In manufacturing a sheet-like material, a wet method in which a short carbon fiber (A) is dispersed in a liquid medium for paper making, a dry method in which the short carbon fiber (A) is dispersed in an air, and the like is deposited. The papermaking method can be applied. A wet method is preferred.

  By dispersing the carbon fiber precursor short fiber (b) and / or the fibrillar fiber (b ′) together with the carbon fiber (A), the carbon short fiber (A) and the carbon fiber precursor short fiber (b) and / or Alternatively, the strength of the sheet-like material is improved by entanglement with the fibrillar fibers (b ′), and the binder-free material can be made substantially free.

In the present invention, a small amount of an organic polymer compound may be used as a binder. The organic polymer compound used as the binder is not particularly limited, and examples thereof include polyvinyl alcohol (PVA) and polyester or polyolefin binders that are heat-sealed. The binder may be solid or liquid such as fibers or particles. The binder content is preferably 100 g / m ² or less, more preferably 50 g / m ² or less, and particularly preferably 30 g / m ² or less. The addition method of a binder is not specifically limited.

  Hereinafter, an example of a method for producing a porous carbon electrode substrate using short carbon fibers will be described in detail. The porous carbon electrode substrate is manufactured through the following procedures (1) to (4).

Procedure (1): The process of manufacturing the papermaking body which disperse | distributed the carbon short fiber (A), the carbon fiber precursor short fiber (b), and / or the fibril-like fiber (b ').

[Short carbon fiber (A)]
The short carbon fiber (A) can be used regardless of the raw material, but is selected from polyacrylonitrile (hereinafter abbreviated as PAN) carbon fiber, pitch carbon fiber, rayon carbon fiber, and phenolic carbon fiber. It is preferable to include one or more carbon fibers, and it is more preferable to include PAN-based carbon fibers or pitch-based carbon fibers. The average diameter of the short carbon fibers (A) is preferably about 3 to 30 μm, more preferably 4 to 20 μm, and even more preferably 4 to 8 μm, from the viewpoint of surface smoothness and conductivity as a gas diffusion layer. The length of the short carbon fibers (A) is preferably 2 to 12 mm, more preferably 3 to 9 mm, from the viewpoint of dispersibility during papermaking and mechanical strength as a gas diffusion layer.

[Carbon fiber precursor short fiber (b)]
The carbon fiber precursor short fiber (b) is obtained by cutting a carbon fiber precursor fiber having a long fiber shape into an appropriate length. The fiber length of the carbon fiber precursor short fiber (b) is preferably about 2 to 20 mm from the viewpoint of dispersibility. Although the cross-sectional shape of the carbon fiber precursor short fiber (b) is not particularly limited, a high roundness is preferable from the viewpoint of mechanical strength after carbonization and production cost. The diameter of the carbon fiber precursor short fiber (b) is preferably 5 μm or less in order to suppress breakage due to shrinkage during carbonization.

  As a polymer used as such a carbon fiber precursor short fiber (b), it is preferable that the residual mass in the carbonization treatment step is 20% by mass or more. Examples of such polymers include acrylic polymers, cellulose polymers, and phenolic polymers.

  When considering the spinnability and the short carbon fibers (A) from low temperature to high temperature, the remaining mass at the time of carbonization is large, and the fiber elasticity and fiber strength when performing the entanglement treatment described below, It is preferable to use an acrylic polymer containing 50% by mass or more of acrylonitrile units. Accordingly, the carbon fiber precursor fiber (b) is preferably an acrylic fiber or an acrylic fiber (containing 50% by mass or more of acrylonitrile units).

  One type of carbon fiber precursor short fiber (b) may be used, or two or more types of carbon fiber precursor short fibers (b) having different fiber diameters and polymer types may be used.

[Fibrillar fiber (b ')]
As the fibrillar fiber (b ′), any fiber can be used regardless of whether it is a natural fiber or a synthetic fiber. For example, it includes fibrillar carbon precursor (b′-1) mainly composed of acrylic or the like to wood pulp which is a natural fiber. Among these, since it is preferable that the metal content is small, the fibrillar fiber (b ′) is preferably a synthetic fiber. More preferably, a fibrillar carbon precursor fiber (b′-1) or the like can be used. These may be used alone or in combination. Moreover, in order to improve a carbonization yield, it is preferable to use the fibrillar carbon precursor fiber (b′-1) shown below.

  The fibrillar carbon precursor fiber (b′-1) is a long-fiber, easily splittable sea-island composite fiber cut to an appropriate length, and is fibrillated by beating with a refiner, a pulper, or the like. The fibrillar carbon precursor fiber (b′-1) is produced using two or more kinds of different polymers that are dissolved in a common solvent and are incompatible, and at least one kind of polymer is carbonized. The residual mass in the process is preferably 20% by mass or more.

  Among the polymers used for the easily splittable sea-island composite fibers, those having a residual mass of 20% by mass or more in the carbonization treatment include acrylic polymers, cellulose polymers, and phenol polymers. Among them, it is preferable to use an acrylic polymer containing 50% by mass or more of an acrylonitrile unit from the viewpoint of spinnability and the remaining mass in the carbonization treatment step.

  The cross-sectional shape of the fibrillar fiber (b ′) is not particularly limited. In order to suppress dispersibility and breakage due to shrinkage at the time of carbonization, the fineness of the fibrillar fiber (b ′) is preferably 1 to 10 dtex. The average fiber length of the fibrillar fibers (b ′) is preferably 1 to 20 mm from the viewpoint of dispersibility.

[Manufacture of paper bodies]
The following methods can also be used for the production of paper bodies. The short carbon fibers (A) cut to a suitable length are uniformly dispersed in water, the dispersed carbon short fibers are made on a net, and the made carbon short fiber sheet is immersed in an aqueous dispersion of polyvinyl alcohol. Then, the immersed sheet is pulled up and dried. The polyvinyl alcohol serves as a binder for binding the short carbon fibers, and in a state where the short carbon fibers are dispersed, a sheet of short carbon fibers in a state where they are bound by the binder is produced. In addition, styrene-butadiene rubber, epoxy resin, or the like can be used as the binder.

  As a method for producing a paper body in which short carbon fibers (A) and carbon fiber precursor fibers (b) and / or fibrillar fibers (b ′) are dispersed, short carbon fibers (A) in a liquid medium, Wet method in which carbon fiber precursor fibers (b) and / or fibrillar fibers (b ′) are dispersed to make paper, carbon short fibers (A) in the air, carbon fiber precursor fibers (b) and / or A paper making method such as a dry method in which the fibrillar fibers (b ′) are dispersed and accumulated can be applied. However, it is preferable to use a wet method from the viewpoint of high uniformity of the paper body.

  The mixing ratio of the carbon short fiber (A), the carbon fiber precursor fiber (b) and / or the fibrillar fiber (b ′) is 100 parts by weight of the carbon short fiber (A), and the carbon fiber precursor fiber ( It is preferable to mix so that the total amount of b) and a fibrillar fiber (b ') may be 20-100 weight part. When the total amount of the carbon fiber precursor fiber (b) and the fibrillar fiber (b ′) is small, the strength of the papermaking body is lowered, and the total amount of the carbon fiber precursor fiber (b) and the fibrillar fiber (b ′) is large. And the electrical conductivity of the porous carbon electrode base material obtained as a result will become low. The ratio of the carbon fiber precursor fiber (b) to the fibrillar fiber (b ′) is 25 to 100 parts by weight of the fibrillar fiber (b ′) with respect to 100 parts by weight of the carbon fiber precursor fiber (b). It is preferable that it is contained in the ratio.

  Carbon fiber precursor fibers (b) and / or fibrillar fibers (b) are also used to help the short carbon fibers (A) open into single fibers and prevent the opened single fibers from refocusing. ´) is used. Further, if necessary, wet papermaking can be performed using a binder.

  A binder has a role as a glue which connects each component in the precursor sheet | seat containing a carbon short fiber (A) and a carbon precursor fiber (b). As the binder, polyvinyl alcohol (PVA), polyvinyl acetate, or the like can be used. In particular, polyvinyl alcohol is preferable because it has excellent binding power in the paper making process and the short carbon fibers (A) are less dropped. In the present invention, it is also possible to use the binder in a fiber shape.

  In the present invention, even if papermaking is performed without using a binder, an appropriate entanglement between the short carbon fiber (A) and the carbon fiber precursor fiber (b) and / or the fibrillar fiber (b ′) can be obtained. .

  Examples of the liquid medium in which the carbon short fibers (A) and the carbon fiber precursor fibers (b) and / or the fibrillar fibers (b ′) are dispersed include carbon precursor fibers (b) such as water and alcohol. Media that do not. Among these, it is preferable to use water from a viewpoint of productivity.

  It is preferable to use a medium such as water at a rate that the fiber concentration in the slurry in which the fiber is dispersed is about 1 to 50 g / L. If the fiber concentration in the slurry is low, the papermaking speed has to be slowed down, resulting in poor productivity, and if the fiber concentration is too high, the dispersibility of the fiber in the slurry is reduced. A lump is easily generated, and a papermaking body with large unevenness in weight per unit area is obtained.

  Examples of the method of mixing the short carbon fiber (A) and the carbon fiber precursor fiber (b) and / or the fibrillar fiber (b ′) include a method of stirring and dispersing in water and a method of directly mixing them. From the viewpoint of uniformly dispersing, a method of diffusing and dispersing in water is preferable. The strength of the papermaking body is improved by mixing the short carbon fibers (A), the carbon fiber precursor fibers (b) and / or the fibrillar fibers (b ′), and making paper to produce a papermaking body. Can do. Moreover, it can prevent that the carbon short fiber (A) peels from a precursor sheet | seat during the manufacture, and the orientation of a carbon short fiber (A) changes.

Procedure (2) The process of entanglement of the paper body is not necessarily entangled, but the carbon fiber is obtained by entanglement of the sheet-like material.

A sheet (entangled structure sheet) having an entangled structure in which (A) and carbon fiber precursor short fibers (b) and / or fibrillar fibers (b ′) are entangled three-dimensionally can be formed.

  The entanglement process can be selected as needed from the method of forming the entangled structure, and is not particularly limited. A mechanical entanglement method such as a needle punching method, a high pressure liquid injection method such as a water jet punching method, a high pressure gas injection method such as a steam jet punching method, or a combination thereof can be used. It is possible to easily suppress the breakage of the short carbon fibers (A) and the breakage of the carbon fiber precursor short fibers (b) and / or the fibrillar fibers (b ′) in the entanglement treatment step, and appropriate entanglement The high-pressure liquid injection method is preferable in that the property can be easily obtained.

  Since the tensile strength of the papermaking body is improved by the entanglement treatment step, it is not necessary to use a binder such as polyvinyl alcohol usually used in papermaking, and the tensile strength of the sheet can be maintained even in water or in a wet state.

Step (3): A step of impregnating a paper body with a resin, followed by drying and molding

〔resin〕
As the resin to be impregnated into the papermaking body, a known resin that can bind the carbon fiber of the gas diffusion layer at the stage of carbonization can be appropriately selected and used. When producing a porous carbon electrode substrate having a carbonization step, phenol resin, epoxy resin, furan resin, pitch, etc. are preferred from the viewpoint of easily remaining as a conductive substance after carbonization. In particular, a phenol resin having a high carbonization rate is particularly preferred. When producing a porous carbon electrode base material that does not have a carbonization step, it can be used regardless of whether it is a thermoplastic or thermosetting resin. From the viewpoint of increasing the water repellency of the porous carbon electrode substrate, a fluororesin is preferred. It is also effective to mix carbon powder with these resins for the purpose of further improving the conductivity of the porous carbon electrode substrate regardless of the presence or absence of the carbonization step. Carbon powder includes graphite particles such as flaky graphite, flaky graphite, earthy graphite, artificial graphite, expanded graphite, expanded graphite, flake graphite, massive graphite, spherical graphite, carbon black, fullerene, carbon And nanotubes. Although not particularly limited, graphite particles and carbon black are more preferable among the carbon powders. One or more of these may be used. ⇒Added carbon powder for Toray and Toho measures.

[Impregnation method]
As a method for impregnating the thermosetting resin, a known method can be used. For example, a dip method, a kiss coat method, a spray method, a curtain coat method, or the like can be used. In particular, from the viewpoint of production cost, it is preferable to use a spray method or a curtain coat method.

[Drying and forming process]
A known technique can be used as a drying method. For example, a drum drying method in which a heated roll is brought into contact with the heated roll or a drying method using hot air can be used. From the standpoint of maintenance, drying by a non-contact method is preferable. The drying temperature is preferably 60 to 110 ° C., more preferably 70 to 100 ° C., at which the resin does not cure.

  The process of molding the paper body after resin impregnation and drying is important. When manufacturing the porous carbon electrode base material which has a carbonization process, the carbon short fiber (A) in a precursor sheet | seat is thereby made into carbon fiber precursor short fiber (b) and / or fibril-like carbon precursor fiber ( By fusing in b′-1) and curing the thermosetting resin, a strong conductive path of the carbonized porous carbon electrode substrate is formed. When manufacturing a porous carbon electrode base material that does not have a carbonization process, the product dimensions are determined by the molding process, so the molten state of the fibrillated carbon precursor fiber (b′-1) and the resin is controlled. There must be. By performing heat treatment in an atmosphere of 200 to 400 ° C. after the molding, the manufacturing process of the carbonization step is completed.

  Any technique can be applied as long as the papermaking body can be uniformly heated and pressed. For example, a method in which a smooth rigid plate is applied to both sides of the paper body and hot-pressed, a continuous roll press apparatus, and a continuous belt press apparatus are used.

  In order to effectively smooth the surface of the precursor sheet, the heating temperature in the hot pressing is preferably less than 200 ° C, more preferably 120 to 190 ° C.

  Although the molding pressure is not particularly limited, when the content ratio of the carbon fiber precursor short fibers (b) and / or the fibrillar fibers (b ′) in the papermaking body is large, the sheet Y can be easily formed even if the molding pressure is low. The surface can be smoothed. If the press pressure is increased more than necessary at this time, there may be a problem that the short carbon fibers (A) are destroyed during the heat-pressure molding, a problem that the structure of the porous carbon electrode base material is too dense, or the like. There is. The molding pressure is preferably about 20 kPa to 10 MPa.

  The time for heat and pressure molding can be, for example, 30 seconds to 10 minutes. When the paper body is sandwiched between two rigid plates or heated and pressed with a continuous roll press or continuous belt press, carbon fiber precursor short fibers (b) and / or fibrils are applied to the rigid plate or roll or belt. It is preferable to apply a release agent in advance so that the carbon-like carbon precursor fibers (b ′) do not adhere, or to sandwich the release paper between the papermaking body and the rigid plate or roll or belt.

Procedure (4): The process of carbonizing the precursor sheet | seat obtained by the said procedure (3) at 2000-3000 degreeC in nitrogen atmosphere, and manufacturing a porous carbonaceous electrode base material .

[Carbonization]
The carbonization treatment carbonizes the carbon fiber precursor short fibers (b) and / or the fibrillar carbon precursor fibers (b ′) and the thermosetting resin in the precursor sheet. The carbonization treatment is preferably performed in an inert gas in order to increase the conductivity of the porous carbon electrode substrate. The carbonization treatment is usually performed at a temperature of 1000 ° C. or higher. The carbonization temperature range is preferably 1000 to 3000 ° C, more preferably 1000 to 2200 ° C. The carbonization treatment time is, for example, about 10 minutes to 1 hour. Moreover, the pretreatment by baking in an inert atmosphere of about 300 to 800 ° C. can be performed before the carbonization treatment.

  When carbonizing the continuously manufactured precursor sheet, it is preferable to perform the carbonizing process continuously over the entire length of the precursor sheet from the viewpoint of reducing the manufacturing cost. If the porous carbon electrode base material is long, the handling property is high, the productivity of the porous carbon electrode base material is high, and the subsequent production of the membrane-electrode assembly (MEA) can also be performed continuously. Therefore, the manufacturing cost of the fuel cell can be reduced. Moreover, it is preferable to wind up the manufactured porous carbon electrode base material continuously from a viewpoint of productivity and reduction of manufacturing cost of a porous carbon electrode base material or a fuel cell.

  A porous carbon electrode substrate can be obtained through the procedure described above. Procedure (2) and procedure (3) can be omitted.

[Method for producing porous carbon electrode base material without carbonization step]
By omitting the carbonization step, the energy cost can be greatly reduced as compared with the case of performing carbonization. In order to suppress a decrease in conductivity due to omission of the carbonization step, it is necessary to introduce a further conductive material. The above-described method for adding and fixing the conductive material to the paper body in which short carbon fibers are dispersed, and preparing a slurry comprising the conductive material and a binder resin, forming them, and then heat-treating them to make the porous body There is a method for producing a carbon electrode substrate. If it is the former method, according to the manufacturing method of the porous carbon electrode base material which has the carbonization process mentioned above, a conductive substance is added in the way of impregnating a paper body with resin, and it press-molds after that. The porous carbon electrode base material can be manufactured by fixing with the above. Also in the latter production method, in the same manner as the slurry preparation method in producing the paper body, a single or a plurality of conductive materials are selected, and a slurry is prepared by mixing in a solution with a binder material, A porous carbon electrode substrate can be produced by performing drying and heat treatment after film formation using a known coating technique. In addition, the conductive material to be used for these is not particularly limited. For example, in the case of carbon fiber, polyacrylonitrile-based (PAN-based) carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, others, carbon black, A carbon nanotube etc. can be used suitably. The kind to be used is not limited, and may be used alone or a plurality may be selected and used. As the binder for fixing the conductive substance, a resin can be used. As the resin, a fluorine-based or silicon-based resin having water repellency is preferable. In preparing the slurry, water, acetone, ethanol, methanol, or the like can be appropriately used as a solvent for the slurry, but water is used as the solvent from the viewpoint of reducing environmental burden and cost of manufacturing equipment. Is most preferred. Further, additives such as a surfactant and a sticking agent may be appropriately used to improve the dispersibility of the conductive substance and the binder substance in the slurry.

2. Gas diffusion layer The porous carbon electrode obtained by the production method of the present invention is a water repellent fiberized with carbon powder on at least one surface of a porous carbon electrode base material in which short carbon fibers are bound by carbon. It is a gas diffusion layer in which a coating layer made of an agent is formed.

<Gas diffusion layer in which a coating layer made of carbon powder and fiberized water repellent is formed on at least one surface of a porous carbon electrode substrate>
In the present invention, “a layer in which a coating layer made of carbon powder and a water repellent agent is formed on at least one surface of a porous carbon electrode substrate” is referred to as a “gas diffusion layer”. The gas diffusion layer of the present invention is useful as a gas diffusion layer for a polymer electrolyte fuel cell.

The coating layer may be formed on one surface or both surfaces of the porous carbon electrode substrate. When forming the coating layer only on one surface of the porous carbon electrode substrate, from the viewpoint of reducing the contact resistance between the catalyst layer and the porous carbon electrode substrate, the catalyst layer in the polymer electrolyte fuel cell It is preferable to provide a coating layer on the surface of the porous carbon electrode substrate on the contact side.

  As the carbon powder used for the coating layer, for example, graphite powder or carbon black can be used. For example, acetylene black (for example, Denka black manufactured by Denki Kagaku Kogyo Co., Ltd.), ketjen black (for example, Ketjen Black EC manufactured by Lion Corporation), furnace black (for example, Vulcan XC72 manufactured by CABOT) and the like can be used. . The proportion of the carbon powder used is preferably such that the concentration when the carbon powder is dispersed in a solvent is 5 to 30%.

  Examples of the water repellent include fluororesins and silicon resins, which can be used by dispersing them in a solvent such as water. A fluororesin is particularly preferred because of its high water repellency. Examples of the fluororesin include tetrafluoroethylene-hexafluoropropylene copolymer, polytetrafluoroethylene (PTFE), and tetrafluoroethylene-ethylene copolymer, and PTFE is particularly preferable. The ratio of the water repellent used is preferably such that the concentration when the water repellent is dispersed in the solvent is 5 to 60%. In the present invention, in order to fiberize the water repellent, PTFE produced by emulsion polymerization is preferable, and among these, the use of a dispersion type is preferable.

  Water or an organic solvent can be used as a solvent for dispersing the carbon powder and the water repellent. From the viewpoint of the risk of organic solvents, cost, and environmental load, it is preferable to use water. When an organic solvent is used, it is preferable to use a lower alcohol, acetone or the like that is a solvent that can be mixed with water. As a ratio of using these organic solvents, it is preferable to use them at a ratio of 0.5 to 2 with respect to water 1.

  The coating layer composed of carbon powder and a water repellent is a combination of carbon powder and a water repellent that is a binder. In other words, carbon powder is taken into the network formed by the water repellent and has a fine network structure. When forming the coating layer, since a part of the composition penetrates into the porous carbon electrode substrate, it is difficult to define a clear boundary line between the coating layer and the porous carbon electrode substrate. The coating layer composition defines only the portion of the coating layer composition that does not penetrate into the porous carbon electrode substrate, that is, the layer composed only of carbon powder and a water repellent. Since the coating layer of the present invention contains a fiberized water repellent, the above-mentioned network structure becomes stronger and not only the strength of the coating layer is improved, but also the fibrous water repellent and the porous carbon electrode. As a result of the entanglement with the base material, the adhesion between the coating layer and the porous carbon electrode base material is improved, and a gas diffusion layer for a polymer electrolyte fuel cell having a high peel strength of the coating layer is obtained. The gas diffusion layer of the present invention has a coating layer composed of carbon powder and a water repellent agent on one of the surfaces of the porous carbon electrode substrate. The coating layer may be provided on both sides, but single-sided coating is preferable because productivity decreases due to an increase in the process, and gas diffusibility and drainage may be reduced by having a coating layer on both sides. . The surface on which the coating layer is formed may be either, but in order to form a strong coating layer, a surface having a certain degree of surface roughness is preferable. However, what formed the gas flow path in one surface of a porous carbon electrode base material is not this limitation, and it is preferable to form in the other smooth surface.

<A gas diffusion layer in which a coating layer made of carbon powder and a water repellent agent is provided on at least one surface of a porous carbon electrode substrate, and the coating layer has a recess and a surface along the sheet width direction. Gas diffusion layer having a convex part, and each of the concave part and the convex part being continuously formed along the sheet longitudinal direction >
The irregularities here, refers to a heterogeneous form of thickness definitive in the coating layer. This unevenness can be formed by adjusting the form of the rod used for coating and the drying speed of the coating film. It is preferable to adjust the ratio H / A of the average depth H of the recesses on the coating layer to the average thickness A of the coating layer to be 0.01 to 0.3. Here, when the ratio H / A is smaller than 0.01, the effect due to the unevenness is not exhibited. On the other hand, when H / A is larger than 0.3, the strength of the coating layer is lowered. About the width | variety of the recessed part and convex part on a coating layer, it is preferable to exist in the range of 0.1-1000 micrometers, respectively. The concave portion here refers to a portion having a thickness smaller than the average thickness, and the convex portion refers to a portion having a thickness larger than the average thickness.

  When the width of each portion (recessed portion and raised portion) is smaller than 0.1 μm, the effect of improving drainage due to the unevenness is reduced. Moreover, when it becomes larger than 1000 micrometers, contact resistance with an electrode catalyst layer will become large. Moreover, it is preferable that the difference of the width | variety of the said recessed part and the width | variety of a convex part is 0.1-500 micrometers. These irregularities are preferably formed continuously along the sheet flow direction.

<Average thickness of gas diffusion layer>
The thickness of the gas diffusion layer is preferably in the range of 55 to 350 μm in order to express good electrical conductivity and drainage. If it is 55 μm or more, handling is possible, and if it is 350 μm or less, good electrical conductivity is obtained. A more preferable thickness is in the range of 100 to 250 μm. The thickness of the porous carbon electrode base material constituting the gas diffusion layer is preferably 50 to 250 μm, and the average thickness of the coating layer formed on at least one surface is preferably 5 to 100 μm. If the thickness of the porous carbon electrode substrate is smaller than 50 μm, it is difficult to convey and it is difficult to provide a coating layer. Further, when the thickness of the porous carbon electrode base material is larger than 350 μm, the handleability is improved, but the electric resistance is increased, so that the power generation performance is lowered. If the thickness of the coating layer is less than 5 μm, the short carbon fibers constituting the porous carbon electrode substrate may break through the coating layer and reach the catalyst layer or the electrolyte membrane, which is not preferable. When the thickness is more than 100 μm, the electronic resistance due to the coating layer is increased, and the power generation performance is deteriorated.

  Various physical property values were measured using the following methods.

<Calculation of porous carbon electrode substrate and coating layer thickness>
From the produced porous carbon electrode substrate and the gas diffusion layer, 10 3 × 3 cm square test pieces were randomly taken out, and each thickness was measured with a micrometer at 5 points for each sample to obtain an average thickness. The thickness of the coating layer was calculated by subtracting the average thickness of the porous carbon electrode substrate from the average thickness of the gas diffusion layer.

<Measurement of unevenness>
Ten test pieces of 5 × 5 mm square per 1 m ² were prepared from the manufactured gas diffusion layer, and each test piece was subjected to an acceleration voltage of 5 kV, a spot size of 30 mm, a focal length of 15 mm, and a magnification of 1000 using a scanning electron microscope. The entire area of each sample was taken at double magnification. The size of the irregularities was detected using cross-sectional observation and image analysis software Image-Pro Plus (manufactured by Nippon Roper). The crack size of each sample was determined by an average value.

<Adhesive evaluation with electrode catalyst layer>
A par on which a catalyst layer (catalyst layer area: 25 cm ² , Pt adhesion amount: 0.3 mg / cm ² ) made of catalyst-supported carbon (catalyst: Pt, catalyst support amount: 50 mass%), water repellent, and ionomer is formed on one side. Membrane electrode bonding is performed by applying a surface pressure of 1.5 MPa at 120 ° C to the fluorosulfonic acid polymer electrolyte membrane (film thickness: 30 µm) so that the coating layer of the catalyst layer and the gas diffusion layer are in contact with each other. Formed body. This membrane electrode assembly is cut into 20 mm squares to obtain test samples. From both sides of the test sample, a universal testing machine was used to apply a test force of 2N in the direction of pulling the test sample in the thickness direction, and the adhesiveness was evaluated based on whether or not peeling occurred in the test sample. For one example, 10 test samples were prepared and tested, and when even one point was peeled, the adhesiveness was x.

<Example 1>
(Porous carbon electrode substrate)
Commercially available carbon paper, carbon cloth, or the like can be used as the porous carbon electrode substrate, but in the present invention, the porous carbon electrode substrate was manufactured from the porous carbon electrode substrate in order to obtain a smooth porous carbon electrode substrate.

  As the carbon short fiber (A), a PAN-based carbon fiber having an average fiber diameter of 7 μm and an average fiber length of 3 mm was prepared. Further, as carbon fiber precursor short fibers (b), acrylic short fibers (Mitsubishi Rayon Co., Ltd., trade name: D122) having an average fiber diameter of 4 μm and an average fiber length of 3 mm, and fibrillar fibers (b ′) , An easily split fiber acrylic sea-island composite short fiber (made by Mitsubishi Rayon Co., Ltd., trade name: Bonnell MVP-C651, made of an acrylic polymer fibrillated by beating and diacetate (cellulose acetate), Average fiber length: 3 mm) was prepared.

  A gas diffusion layer was produced by the following operations <1> to <10>.

<1> Disaggregation of carbon short fibers (A) The carbon short fibers (A) are dispersed in water so that the fiber concentration is 1% (10 g / L), disaggregated through a mixer, and disaggregated slurry fibers (SA). ).

<2> Disaggregation of carbon fiber precursor short fibers (b) The carbon fiber precursor short fibers (b) are dispersed in water so that the fiber concentration is 1% (10 g / L), and then disaggregated through a mixer. A disaggregated slurry fiber (Sb) was obtained.

<3> Disaggregation of fibrillar fibers (b ') The above split fiber acrylic sea-island composite short fibers are dispersed in water so that the fiber concentration is 1% (10 g / L), and beaten and disaggregated through a mixer. A disaggregated slurry fiber (Sb ′) was obtained.

<4> Manufacture of papermaking body The carbon short fiber (A), the carbon fiber precursor short fiber (b), and the fibrillar fiber (b ′) are in a mass ratio of 70:10:20, and the concentration of fibers in the slurry. However, the disaggregation slurry fiber (SA), the disaggregation slurry fiber (Sb), the disaggregation slurry fiber (Sb ′), and the dilution water were weighed and dispersed so as to be 1.44 g / L. For papermaking, a sheet drive unit consisting of a net drive unit and a flat net mesh made of plastic net with a width of 60cm x length of 585cm connected in a belt shape and continuously rotated, the slurry supply unit width is 48cm, the bottom of the net A processing apparatus consisting of a vacuum dehydration apparatus arranged in the above was used. A pressurized water jet treatment apparatus provided with the following three water jet nozzles was disposed downstream of the treatment apparatus.

Nozzle 1: hole diameter φ0.15mm × 501 hole
Width direction hole pitch 1mm (1001 hole / width 1m)
1 row arrangement, nozzle effective width 500mm

Nozzle 2: hole diameter φ0.15 mm × 501 hole
Width direction hole pitch 1mm (1001 hole / width 1m)
1 row arrangement, nozzle effective width 500mm

Nozzle 3: hole diameter φ0.15 mm × 1002 holes
Width direction hole pitch 1.5mm
3 rows, 5 mm pitch between rows, 500 mm nozzle effective width

  The pressurized water jet pressure is 1MPa nozzle 1, pressure 2MPa (nozzle 2), pressure 1MPa (nozzle 3), and the slurry in which the fibers are dispersed is introduced from the slurry supply unit, and after dehydration under reduced pressure, nozzle 1, nozzle 2, nozzle The papermaking body having a three-dimensional entanglement structure was obtained by passing through in the order of 3 and applying entanglement treatment. The paper body was dried at 150 ° C. for 3 minutes using a pin tenter tester (PT-2A-400 manufactured by Sakurai Dyeing Machine Co., Ltd.) to obtain a paper body. In addition, the dispersion state of the carbon short fiber (A), the carbon fiber precursor short fiber (b), and the fibrillar fiber (b ′) in the papermaking body was good, and the handling property was also good.

<5> Resin impregnation / drying The obtained paper body was impregnated with a phenol resin dispersion and dried at an ambient temperature of 100 ° C. using a hot air dryer.

<6> Pressurization and heating molding Next, both sides of this papermaking body are arranged so as to be sandwiched by paper coated with a silicone release agent, and at 190 ° C. and a belt speed of 0.2 m / min with a double belt press device. The press molding was performed.

<7> Carbonization treatment Subsequently, this precursor sheet was carbonized in a carbonization furnace in a nitrogen gas atmosphere at 2000 ° C. to obtain a porous carbon electrode substrate. The obtained porous carbon electrode substrate was smooth without warping or undulation. The thickness of the obtained porous carbon electrode base material was 155 μm.

<8> Preparation of Coating Solution 1 Denka Black (manufactured by Denki Kagaku Kogyo Co., Ltd.), ion-exchanged water, and isopropyl alcohol are mixed at a ratio of 5: 100: 80, respectively, and a homomixer MARK-II (manufactured by Primix Co., Ltd.) is used. Then, stirring was performed at 15000 rpm for 30 minutes while cooling to obtain a coating liquid 1.

<9> Preparation of coating solution 2 Polytetrafluoroethylene (PTFE) dispersion is added to coating solution 1 at a rate of 0.3 to carbon black 1, and the dispersion is stirred at 5000 rpm for 15 minutes. 2 was obtained.

<10> Preparation of water-repellent treatment liquid for porous carbon electrode base material PTFE dispersion (31-JR, manufactured by Mitsui DuPont Fluorochemical) and interface are used for preparation of water-repellent treatment liquid for porous carbon electrode base material. An activator (polyoxyethylene (10) octylphenyl ether) and distilled water were used. After adjusting the solid content concentration in the water repellent treatment liquid to 1 wt% for PTFE and 2 wt% for the surfactant, water was added by adding distilled water and stirring with a disper at 1000 rpm for 10 minutes. A treatment solution was prepared.

<11> Water-repellent treatment for porous carbon electrode substrate The porous carbon electrode substrate was impregnated by being immersed in the water-repellent treatment solution. The impregnated porous carbon electrode substrate is allowed to stand on the glass surface of an applicator (manufactured by Tester Sangyo), the attached applicator bar is pressed against the porous carbon electrode substrate, and the applicator bar is conveyed at a speed of 100 mm / sec. By removing the excess water-repellent treatment liquid adhering to the porous carbon electrode base material, the porous carbon electrode base material was subjected to a water-repellent treatment by drying the porous carbon electrode base material at 60 ° C. for 30 minutes with a dryer. A carbon electrode substrate was obtained.

<12> Formation of coating layer Further, the coating liquid 2 was applied onto the porous carbon electrode substrate using a coating rod having a pitch of 0.1 mm and a depth of 10 μm at a coating speed of 1 m / min. It dried for 20 minutes using the hot air drying furnace set to 100 degreeC. Further, after drying, a gas diffusion layer having a coating layer formed by sintering at 360 ° C. for 1 hour in a sintering furnace was obtained. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 2>
A gas diffusion layer was obtained in the same manner as in Example 1 except that the depth of the coating rod used for coating was 20 μm and the coating speed was 5 m / min. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 3>
A gas diffusion layer was obtained in the same manner as in Example 1 except that the depth of the coating rod used for coating was 50 μm and the coating speed was 10 m / min. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 4>
A gas diffusion layer was obtained in the same manner as in Example 3 except that the depth of the coating rod used for coating was 100 μm. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 5>
A gas diffusion layer was obtained in the same manner as in Example 3 except that the depth of the coating rod used for coating was 300 μm. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 6>
A gas diffusion layer was obtained in the same manner as in Example 1 except that the pitch of the coating rod used for coating was 0.5 mm and the depth was 20 μm. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 7>
A gas diffusion layer was obtained in the same manner as in Example 6 except that the depth of the coating rod used for coating was 50 μm and the coating speed was 5 m / min. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 8>
A gas diffusion layer was obtained in the same manner as in Example 6 except that the depth of the coating rod used for coating was 100 μm and the coating speed was 10 m / min. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 9>
A gas diffusion layer was obtained in the same manner as in Example 8 except that the depth of the coating rod used for coating was 300 μm. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 10>
A gas diffusion layer was obtained in the same manner as in Example 1 except that the pitch of the coating rod used for coating was 1 mm and the depth was 50 μm. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 11>
A gas diffusion layer was obtained in the same manner as in Example 10 except that the depth of the coating rod used for coating was 80 μm and the coating speed was 5 m / min. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 12>
A gas diffusion layer was obtained in the same manner as in Example 10 except that the depth of the coating rod used for coating was 100 μm and the coating speed was 10 m / min. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 13>
A gas diffusion layer was obtained in the same manner as in Example 12 except that the depth of the coating rod used for coating was 300 μm. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 14>
A gas diffusion layer was obtained in the same manner as in Example 12 except that the pitch of the coating rod used for coating was 1.5 mm and the depth was 80 μm. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 15>
A gas diffusion layer was obtained in the same manner as in Example 4 except that the pitch of the coating rod used for coating was 1.5 mm. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 16>
A gas diffusion layer was obtained in the same manner as in Example 14 except that the depth of the coating rod used for coating was 200 μm. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Example 17>
A gas diffusion layer was obtained in the same manner as in Example 5 except that the pitch of the coating rod used for coating was 1.5 mm. When the thickness of the coating layer of the obtained gas diffusion layer and the information of the formed unevenness were measured, it was as shown in Table 1. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer did not arise, but the favorable result was obtained.

<Comparative Example 1>
A gas diffusion layer was obtained in the same manner as in Example 1 except that a round rod having no pitch and depth was used as the coating rod, but a uniform coating layer could not be obtained. The thickness of the coating layer could not be measured.

<Comparative example 2>
A gas diffusion layer was obtained in the same manner as in Example 2 except that a round bar having no pitch and depth was used as the coating rod, but a uniform coating layer could not be obtained. The thickness of the coating layer could not be measured.

<Comparative Example 3>
A gas diffusion layer was formed in the same manner as in Example 4 except that when the coating liquid was applied onto the porous carbon electrode substrate, coating was performed using a blade so that the thickness of the coating layer was 50 μm. Obtained. The surface of the coating layer of the obtained gas diffusion layer had no irregularities and was a smooth surface. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer generate | occur | produced in 8 points | pieces in 10 point measurement, and the tendency for adhesiveness to be weak was confirmed. The evaluation results are summarized in Table 1.

<Comparative Example 4>
A gas diffusion layer was formed in the same manner as in Example 4 except that when the coating liquid was applied onto the porous carbon electrode substrate, the coating layer was applied to a thickness of 50 μm using a slot die. Got. The surface of the coating layer of the obtained gas diffusion layer had no irregularities and was a smooth surface. Moreover, when adhesiveness evaluation with an electrode catalyst layer was implemented, the peeling between a catalyst layer and a coating layer generate | occur | produced in 6 points | pieces during 10-point measurement, and the tendency for adhesiveness to be weak was confirmed. The evaluation results are summarized in Table 1.

Claims (2)

  Porous coating liquid consisting of carbon powder, water repellent, surfactant, and water at a speed of 1 to 10 m / min using a coating rod having a pitch of 0.1 mm to 1.5 mm and a depth of 5 to 350 μm A coating layer coated on a carbon electrode substrate and having concave and convex portions along the sheet width direction on the surface, wherein the concave and convex portions are continuously formed along the longitudinal direction of the sheet, respectively. A method for producing a gas diffusion layer for forming a coating layer. The method for producing a gas diffusion layer according to claim 1 , wherein the coating liquid is solidified and dried before being flattened to form the coating layer.