JP2007242378A - Gas diffusion layer for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a GDL (a gas diffusion layer) having a high gas diffusion property and capable of using in a polymer electrolyte fuel cell, and hardly producing the problem of punching through electrodes by a GDL material such as a carbon fiber. <P>SOLUTION: Porous body sintered coarse particles innumerably having relatively small diameter through holes comprising carbon particles and water repellent agent particles are connected while gaps are moderately kept to innumerably form relatively large diameter through holes. A gas diffusion layer innumerably has relatively small diameter through holes and relatively large diameter through holes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas diffusion layer (hereinafter also simply referred to as GDL) for a fuel cell, a membrane-electrode assembly (hereinafter also simply referred to as MEA) and a fuel cell using the same.

  In recent years, in response to social demands and trends against the background of energy and environmental problems, fuel cells that can operate at room temperature and obtain high output density have attracted attention as mobile power sources and stationary power sources. A fuel cell is a clean power generation system in which the product of an electrode reaction is water in principle and has almost no adverse effect on the global environment. In particular, a solid polymer fuel cell using a solid polymer electrolyte as an electrolyte operates at a relatively low temperature. Therefore, the fuel cell vehicle can be used for portable devices (for example, mobile phones, portable information terminals, portable music players, notebook type). It is expected as a power source for mobile objects in a wide range of fields, including PCs.

The GDL of such a polymer electrolyte fuel cell has a role of supplying and discharging gas to the reaction layer (electrode catalyst layer), and transferring electrons and heat. Therefore, in the GDL of the polymer electrolyte fuel cell, carbon paper or carbon cloth of about 150 μm, which is suitable for achieving such a role, is usually used (see, for example, Patent Document 1).
JP-A-60-140668

  However, the conventional carbon paper or carbon cloth material for GDL as described in Patent Document 1 is obtained by processing carbon fibers into paper or cloth. Since the diameter of the carbon fiber is about 10 μm and the fiber is hard and strong, there is a drawback that the anode (fuel electrode) and the cathode (air electrode) are short-circuited through the solid electrolyte. In addition, there is also a drawback that if the tightening pressure is increased in order to reduce the contact resistance between the GDL and a separator such as a bipolar plate, the fibers are broken because they are brittle.

  The GDL without fear of penetrating can be composed of carbon black particles and polytetrafluoroethylene (hereinafter also referred to as PTFE) particles as used in an oxygen cathode for salt electrolysis. However, when this salt electrolyzed oxygen cathode is applied as GDL, it has only average pores (pores) of about 0.1 μm, so that it has a pore size (pore size) for a polymer electrolyte fuel cell. Was too small and the gas diffusivity was too low. As a result, when such GDL is applied to a fuel cell, there is a problem that the cell performance is lowered.

  Accordingly, an object of the present invention is to provide a GDL that can be used in a polymer electrolyte fuel cell having good gas diffusibility, which is unlikely to cause a problem of penetration between electrodes due to a GDL material such as carbon fiber.

  That is, in the present invention, the porous sintered coarse particles having a myriad of relatively small-diameter through-holes composed of carbon particles and water repellent particles are connected to each other with a moderate gap therebetween. The above object is achieved by a gas diffusion layer for a fuel cell, which has an infinite number of relatively small-diameter through-holes and numerous relatively large-diameter through-holes. The

  According to the GDL of the present invention, relatively small pores (small-diameter through-holes) formed in gaps between carbon particles and / or water repellent particles in porous sintered coarse particles, and porous sintered It has relatively large holes (large diameter through holes) formed in the gaps between the coarse particles. By having two large and small holes (through holes) in this way, water can be quickly supplied and drained through relatively large holes. As for gas, countless relatively small pores (penetration) existing inside porous sintered coarse particles even when water is passing through relatively large pores (through holes) in drainage or feed water. Gas diffusion (permeation). Therefore, a structure in which the gas diffusion path (through hole) is not easily blocked by supply / drainage can be obtained. As a result, gas diffusion increases dramatically, and the performance of the fuel cell using the GDL can be significantly improved. In addition, since the porous sintered coarse particles are derived from a sintered body obtained by sintering, they are dense, extremely strong and stable, so that any pores (through holes), both large and small, are not easily crushed. ing. Therefore, the GDL of the present invention is also excellent in that the durability of the fuel cell can be greatly improved because it is not deformed over a long period of time in a high pressure state when the GDL is incorporated in a fuel cell.

  In the GDL according to the present invention, the porous sintered coarse particles having a myriad of relatively small-diameter through holes made of carbon particles and water repellent particles are connected to each other with moderate gaps. The GDL has an infinite number of through holes having a relatively small diameter and an infinite number of through holes having a relatively large diameter.

  In other words, a fuel cell gas diffusion layer configured using porous sintered coarse particles, wherein the porous sintered coarse particles are formed using carbon particles and water repellent particles. And the average pore diameter of a large number of pores formed in the gaps between the carbon particles and / or the water repellent particles is smaller than the average pore diameter of the pores formed in the gaps between the porous sintered coarse particles. It can be said that it is characterized by. Moreover, the membrane-electrode assembly (MEA) for a fuel cell according to the present invention is characterized by using the GDL of the present invention, and the fuel cell according to the present invention uses the MEA of the present invention. It is characterized by this. In the present invention, GDL is included in the constituent members of the MEA.

  In the GDL of the present invention, as described above, relatively small pores (with an average pore diameter of 0.2 μm or less) formed in the gaps between the carbon particles and / or the water repellent particles in the porous sintered coarse particles. A small-diameter through hole) and a relatively large number of relatively large pores (a relatively large through-hole having an average pore diameter of 0.5 μm or more) formed between the porous sintered coarse particles. Thereby, a relatively small small-diameter through-hole can mainly contribute to gas permeation, and a relatively large large-diameter through-hole can mainly contribute to water permeation. In addition, water can be easily supplied and drained through relatively large pores formed between the porous sintered coarse particles, and gas can be passed through both relatively small and relatively large pores. Can be easily diffused (transmitted). Therefore, in the GDL of the present invention, gas diffusion increases dramatically, so that the performance of a fuel cell using the GDL can be significantly improved. In addition, because it is composed of porous sintered coarse particles (thickness or aspect ratio is small), there is a problem of penetration between electrodes due to GDL material such as carbon fibers (thickness or aspect ratio is very large). It can also be set as the structure (structure) which is hard to produce. In addition, since the porous sintered coarse particles constituting the GDL of the present invention are manufactured under the condition that the water repellent is not fibrillated, the porous sintered coarse particles are dense, extremely strong, and stable. ) Also has a structure that is not easily crushed. Therefore, since the GDL of the present invention is not deformed for a long time in a high pressure state when the GDL is incorporated in a fuel cell, the durability of the fuel cell can be greatly improved. In addition, in GDL used for the oxygen cathode of the above-mentioned salt electrolysis, the dispersion liquid in which carbon black powder and PTFE particles are dispersed is aggregated with isopropyl alcohol to filter. At this time, PTFE particles gather together. , The basis for fibrillation is created. Solvent naphtha is added to the filtrate after drying, and shear force is applied in the kneading and rolling steps, so that PTFE is easily fibrillated. Large holes (holes) from which the solvent naphtha has been removed are crushed under heating and pressure during hot pressing. Therefore, since the average pores (pores) were only about 0.1 μm and relatively narrow pores, it was difficult to supply and drain water (product water, etc.) into the narrow pores. Narrow pores were blocked when moving water supply and drainage, and the number of pores (paths) that can be used for gas diffusion decreased, and the gas diffusivity of the entire GDL was not sufficient and it was said that the results were too low. . As a result, when such GDL is applied to a fuel cell, there is a problem that the cell performance is lowered.

  Hereinafter, fuel cells that can be used in the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view schematically showing a basic configuration (single cell configuration) of a fuel cell using a GDL having the configuration of the present invention. The present invention is not limited to this. FIG. 2A is a schematic cross-sectional view schematically showing a basic configuration of an MEA using the GDL of the present invention. FIG. 2B shows the GDL in FIG. 2A and the relatively large pores (large-diameter through holes) formed between the porous sintered coarse particles and the porous sintered coarse particles. It is the schematic which expanded and represented typically a part of. 2C shows carbon particles and water repellent particles that constitute the porous sintered coarse particles of FIG. 2B, and relatively small pores (small-diameter through-holes) formed between the carbon particles and / or the water repellent particles. It is the schematic which expanded and typically represented one porous body sintered coarse particle so that the mode of) might be understood. FIG. 2D is a schematic cross-sectional view schematically showing the basic configuration of MEA using GDL composed of a base material and a carbon particle layer (MIL) having the configuration of the present invention.

In FIG. 1, a fuel cell (single cell) 10 has an anode-side catalyst layer 12 a and a cathode-side catalyst layer 12 b facing each other on both sides of an electrolyte membrane 11. Further, the anode-side GDL 13a and the cathode-side GDL 13b are respectively arranged on both sides (outside) of the anode-side catalyst layer 12a and the cathode-side catalyst layer 12b so as to constitute the MEA 14. Anode and cathode parators 15a and 15b are arranged on both sides (outside) of the GDLs 13a and 13b. Gas flow paths (grooves) 16a and 16b are provided inside the separators 15a and 15b. Through the gas flow paths (grooves) 16a and 16b, a hydrogen-containing gas (for example, H ₂ gas) and an oxygen-containing gas (for example, Air) are passed to the catalyst layers 12a and 12b through the anode-side and cathode-side GDLs 13a and 13b. Supplied respectively. Further, in order to prevent the gas from leaking to the outside, gaskets 17 are respectively disposed between the outer peripheral region of the electrolyte membrane 11 and the separators 15a and 15b.

  Hereinafter, the GDL which is a characteristic part of the present invention and the solid polymer fuel cell using the same will be described for each component.

(1) GDL13
As shown in FIGS. 1 and 2A, by disposing the GDL 13 so as to be adjacent to the catalyst layer 12, the catalyst layer 12 and further the electrolyte membrane 11 can be uniformly moistened to express high hydrogen ion conductivity. it can. Specifically, the cathode side GDL 13b can continuously supply the oxidant gas, can smoothly perform the chemical reaction on the cathode side, and further disperse the water generated by the chemical reaction to reduce the catalytic activity. Can be prevented. In the anode side GDL 13a, the hydrogen-containing gas can be continuously supplied, and the chemical reaction on the anode side can be performed smoothly. The GDL 13 may be disposed on both the anode side and the cathode side, or may be disposed on only one side of the anode side or the cathode side. Preferably, as shown in FIGS. 1 and 2A, they are arranged on both the anode side and the cathode side.

  In the GDL 13 of the present invention, as shown in FIGS. 2B and 2C, the porous sintered coarse particles 21 are composed of the carbon sintered particles 21 and the water repellent particles 21. It is formed using the agent particles 212. Then, pores (small diameter through holes) 213 formed between the carbon particles 211 and / or the water repellent particles 212 are formed into pores (large large pores) formed between the porous sintered coarse particles 21. The diameter is smaller than 22).

  Here, the porous sintered coarse particles 21 are sintered bodies, and the water repellent particles 212 such as PTFE melt and act as a binder at the time of sintering, so that the carbon particles 211 and / or the water repellent particles 212 are bonded to each other. The structure is joined (bound) to each other. However, since no stress is applied at the time of sintering, the water-repellent particles 212 are not fibrillated and the porous sintered coarse particles 21 are formed in the form of particles. In addition, innumerable (many) voids (small-diameter through-holes) 213 are formed between the carbon particles 211 and / or the water repellent particles 212. That is, the porous sintered coarse particles 21 are sintered porous bodies having innumerable small diameter through holes 213. It is desirable that the pores (small-diameter through-holes) 213 of the porous sintered coarse particles 23 have a small pore diameter and can form a pore region having a size that is impermeable to moisture and gas permeable.

  GDL 13 is a molded body, and when the porous sintered coarse particles 21 are heated and molded under pressure, the water repellent particles 212 on the surface of each porous sintered coarse particle 21 melt and act as a binder. The porous sintered coarse particles 21 have a structure in which they are joined (bound) to each other. Even if shear stress is applied during molding, the aggregate of water repellent particles is not formed, so the porous sintered coarse particles 21 are very strong and difficult to deform. And the clearance gap which arises between 21 porous porous sintered coarse particles 21 particle | grains forms innumerable (large number) void | hole (large diameter through-hole) 22. FIG. That is, the GDL 13 is a porous molded body having two large and small holes (small diameter through holes) 213 and holes (large diameter through holes) 22. The pores (large-diameter through-holes) 22 between the porous sintered coarse particles 21 are larger than the pores (small-diameter through-holes) 213 and form a pore region having a size that allows moisture and gas to pass therethrough. It is desirable to be able to.

  As described above, the GDL 13 of the present invention has a structure in which hard dense porous sintered coarse particles 21 are connected with an appropriate gap (large diameter through hole) 22. FIG. 3 is a scanning electron micrograph of a cut surface of GDL showing a state of continuous porous sintered coarse particles constituting the GDL of the present invention. FIG. 3A is a scanning electron micrograph of a cut surface of GDL formed by porous sintered coarse particles having an average particle diameter of 150 μm, and FIG. 3B is formed by porous sintered coarse particles having an average particle diameter of 250 μm. It is the scanning electron micrograph of the cut surface of GDL.

  In the GDL of the present invention, it is desirable that the porous sintered coarse particles have a structure in which the coarse particles adjacent to the coarse particles are in close contact with each other. As shown in FIGS. 3A and 3B, the state of mutual bonding between these porous sintered coarse particles is as follows. It is desirable to have a structure (hereinafter also referred to as a stone wall structure) joined in a stone wall shape with a gap in between. Such a stone wall structure is considered to be because the porous sintered coarse particles 21 obtained by pulverizing a hard dense sintered body are pulverized into a shape like a stone wall stone. Therefore, in the GDL of the present invention, if the porous sintered coarse particles 21 obtained by pulverizing a hard dense sintered body are pulverized so as to be rounded and spherical, a spherical porous body as shown in FIG. 2B is obtained. It is also possible to have a structure in which sintered coarse particles are joined together.

  The stone wall structure (masonry structure) is roughly divided into three types: overloading, valley stacking, and cloth stacking. Among these, in the GDL of the present invention, as shown in FIGS. 3A and 3B, the way in which the porous sintered coarse particles are connected to each other shown in the electron micrograph on the surface of the GDL is considered to be like a stone. If there is a stone wall structure (masonry structure), there is a stone wall structure (masonry structure) where there is a gap between the stones, such as an overlaid structure, a cobblestone valley structure, and a cobblestone structure. Is desirable. 4A to 4C are schematic views schematically showing a random stacking structure, a cobblestone stacking structure, and a cobblestone stacking structure model in an actual stone wall (masonry). In addition, as shown to FIGS. 4D-4H, porous sintered coarse particle | grains are this particle | grains like stratified stacking in a stone wall (masonry), turbulent layer stacking, turbulent layer stacking, quarry cloth piling, and quarry stone pileup. A structure joined in a stone wall shape so as not to have a gap in between is not included in the stone wall structure referred to in the present invention. In the present invention, it can be said that the overlaid stone wall structure of FIG. 4A is easy to make and can be easily obtained (it is also the stone wall structure actually obtained in FIGS.

  In the GDL of the present invention, the porous sintered coarse particles 21 formed using the carbon particles 211 and the water repellent particles 212 are firstly arranged between the electrodes made of a GDL material such as carbon fibers. This is because it is possible to achieve a configuration in which the problem of punching through hardly occurs. Secondly, the porous sintered coarse particles 21 obtained by sintering and finely pulverizing the carbon particles 211 and the water repellent particles 212 are dense, very strong, and stable because they are sintered bodies. The holes (through-holes) 22 and 213 can also have a structure that is not easily crushed. This is because when a GDL having such a structure is incorporated into a fuel cell, the GDL does not deform over a long period of time under a high pressure, and thus can contribute to greatly improving the durability of the fuel cell.

  Hereinafter, the porous sintered coarse particles constituting the GDL will be described.

The porous body sintered coarse particles 21 are those obtained by pulverizing a hard dense sintered body as described above, a tensile strength of 20 kgf / cm ² or more, preferably 20~40kgf / cm ^2, It is desirable that the fracture deformation rate is 20% or less, preferably 15% or less, more preferably 5 to 10%. Here, if the tensile strength of the porous sintered coarse particles 21 is 20 kgf / cm ² or more, the large-diameter holes are not crushed. The small cavities 213 and the large cavities 22 formed by connecting the particles 21 with appropriate gaps are particles that are not easily crushed even if they are heated and pressurized in the manufacturing process or in the fuel cell. Internal structures and interparticle structures can be provided. If the fracture deformation rate of the porous sintered coarse particles 21 is 20% or less, the shape stability of the post-molding sheet (GDL) is excellent and the handleability is excellent.

  The average particle diameter of the porous sintered coarse particles 21 is such that the pores (through holes) 22 generated in the gaps between the porous sintered coarse particles 21 have a desired size (specifically, a range in which moisture and gas can permeate). In other words, it may be appropriately determined so as to be 0.5 μm or more. Specifically, the average particle diameter of the porous sintered coarse particles is in the range of 1 to 500 μm, preferably 5 to 200 μm, more preferably 5 to 100 μm. Thus, the diameter and the number of distributions of relatively large through-holes (holes) can be controlled depending on the size of the porous sintered coarse particles so that the effects of the present invention can be effectively achieved. . By changing the size and the number of distributions of such relatively large through-holes, for example, the water permeability can be effectively and effectively controlled. If the average particle diameter of the porous sintered coarse particles is 1 μm or more, relatively large pores that allow liquid water to pass through can be obtained. Moreover, if the average particle diameter of the porous sintered coarse particles is 500 μm or less, film formation is facilitated.

  In addition, as described above, it is desirable that the size of the two large and small pores can improve the gas permeability. From such a viewpoint, it is relatively easy to form the carbon particles and / or the water repellent particles. The small holes (small-diameter through holes) have a large number (small number) of small-diameter through-holes having an average pore diameter of 0.2 μm or less, preferably 0.05 to 0.2 μm, more preferably 0.07 to 0.1 μm. Is desirable. On the other hand, relatively large pores formed between the porous sintered coarse particles have large-diameter through-holes having an average pore diameter of 0.5 μm or more, preferably 0.5 to 100 μm, more preferably 1 to 50 μm. It is desirable to have a large number (infinite).

  There is no particular restriction on the upper limit of the average pore diameter of the small-diameter through-holes and the average pore diameter of the large-diameter through-holes, but if it is 0.05 μm or more, gas permeation is possible, liquid water impermeability and water vapor is not It can be set as a hole area of a size that can be transmitted. In addition to the size of the hole diameter of the small-diameter through hole, the moisture permeability is a structure in which water is repelled on the entrance surface of the small-diameter through hole due to the water-repellent action of the water-repellent particles, so that it does not easily enter the small-diameter through hole It has become. For this reason, regarding the hole diameter of the small-diameter through hole, it is desirable to determine the hole diameter of the small-diameter through hole that provides optimum gas permeability in consideration of the water repellency. If the average through-hole diameter of the small-diameter through-hole is 0.2 μm or less, liquid water cannot easily enter, and it has a dense and strong particle structure and is liquid-impermeable and gas-permeable. A pore region can be formed.

  When the average pore diameter of the large-diameter through-hole is 0.5 μm or more, a pore region having a size capable of transmitting moisture and gas can be obtained. In addition, there is no particular limitation on the upper limit of the average pore diameter of the large-sized through-holes, but if it is 100 μm or less, the sheet is easy to handle and forms a pore region having a size that allows moisture and gas to pass therethrough. Gas diffusibility can be expressed.

  Moreover, the porous sintered coarse particles are prepared by (1) dispersing carbon particles and water repellent particles in water in the presence of a nonionic surfactant to prepare a carbon / water repellent particle dispersion, The carbon / water repellent particle dispersion is concentrated by using a phase separation phenomenon of a nonionic surfactant, and the phase separation and concentration is dried, heated and sintered to form a mixed sintered body, and the mixed It is desirable that the sintered body is obtained by pulverization. Or (2) preparing a carbon / water repellent particle dispersion by dispersing carbon particles and water repellent particles in water in the presence of a nonionic surfactant; It is desirable to deposit the solid content by electrodeposition, sinter the solid content to form a mixed sintered body, and pulverize the mixed sintered body. Since these details will be described with reference to the drawings in the following description of the method for producing porous sintered coarse particles, description thereof will be omitted.

  In addition, in GDL of this invention, if it is in the range which does not impair the effect of this invention other than the said porous body sintered coarse particle, other structural members may be contained in an appropriate amount. Specific examples include, but are not limited to, carbon nanotubes, spherical activated carbon, and spherical graphite.

  Next, the constituent members of the porous sintered coarse particles described above will be described focusing on carbon particles and water repellent particles.

(I) Carbon particles 211
The material (type) of the carbon particles constituting the porous sintered coarse particles 21 is a conventionally known GDL material so that conductivity (electric conductivity) and porosity can be imparted to the GDL. The same conductive carbon material used for carbon paper, carbon cloth, etc. can be used. Specifically, for example, conventional materials such as graphite and expanded graphite may be used. Of these, carbon blacks such as oil furnace black, channel black, lamp black, thermal black, and acetylene black are preferred because of their excellent electron conductivity and large specific surface area.

  The shape of the carbon particles is preferably particulate so that the anode electrode (fuel electrode) and the cathode electrode (air electrode) do not short-circuit between the electrodes as in the case of conventional carbon fibers. Specifically, the aspect ratio (aspect ratio) of the carbon particles is in the range of 1 to 3, preferably 1 to 2.

The average secondary particle size of the carbon particles is desirably one capable of forming porous sintered coarse particles having the average particle size and having the small average through-holes having the average pore size of 200 to 1000 nm, preferably 300. It is in the range of ~ 600 nm. The average primary particle size of the carbon particles is preferably 30 nm or more and the specific surface area is preferably 100 m ² / g or less.

  The particle diameter of the carbon particles can be measured by, for example, SEM (scanning electron microscope) observation, TEM (transmission electron microscope) observation, and the like (see FIG. 9A). Note that the carbon particles may include particles having different aspect ratios as described above. Accordingly, the particle size and the like referred to above are expressed by the absolute maximum length because the particle shape is not uniform. This also applies to the particle size of water repellent particles described later. Here, the absolute maximum length is the maximum length among the distances between any two points on the contour line of particles (for example, carbon particles, water repellent particles, etc.).

  The blending ratio of the carbon particles is in the range of 80 to 50% by mass, preferably 70 to 60% by mass with respect to the total amount of GDL, from the viewpoint of effectively exhibiting the above-described conductivity (electric conductivity). When the mixing ratio of the carbon particles is 50% by mass or more, good conductivity can be ensured. On the other hand, if the blending ratio of the carbon particles is 80% by mass or less, the necessary strength can be obtained by the binding action of the water repellent material.

(Ii) Water repellent particles 212
As the material (type) of the water repellent particles 212 constituting the porous sintered coarse particles 21, the GDL 13 is similar to the conventional GDL so that the water repellency can be enhanced and the flooding phenomenon can be prevented similarly to the catalyst layer 12. The same water-repellent agent as used (for example, a water-repellent material or a material having a surface subjected to water-repellent treatment) can be used. The material (type) of the water repellent particles is not particularly limited, but polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP). ) And the like, polypropylene, polyethylene and the like. Of these, fluorine-based polymer materials are preferably used because of their excellent water repellency and corrosion resistance during electrode reaction. Particularly preferably, PTFE and FEP fluorine-based polymer materials are particularly desirable because carbon particles can be bound to each other and a water-repellent surface can be formed. Furthermore, by using such a suitable water-repellent material, it is possible to provide a function of reducing electrical resistance and preventing permeation of liquid water (priority of gas passage) due to water-repellent pores (mainly relatively small pores). Is.

  The shape of the water repellent particles is preferably particulate so that the anode electrode (fuel electrode) and the cathode electrode (air electrode) do not short-circuit through the electrodes as in the case of conventional carbon fibers. . Specifically, the aspect ratio (aspect ratio) of the water repellent particles is 1 to 4, preferably 1 to 2.

  In other words, it is desirable that 60% or more, preferably 80% or more, particularly preferably 100% (total water repellent particles) of the water repellent particles are not fibrillated. Therefore, it can be said that the water-repellent particles (for example, PTFE) are not fibrillated means that the water-repellent particles are present in a shape with a small aspect ratio, for example, a granular shape or a layered shape. Since the water repellent particles (for example, PTFE) are not fibrillated (fibrinated) in this way, the porous sintered coarse particles and GDL structure can be strengthened, and problems such as short circuit between electrodes can be prevented. Is excellent.

  The fibrillation of the water repellent particles can be observed, for example, with a scanning electron microscope (SEM image) (see FIGS. 9A and 9B for comparison).

  The tensile strength of the water repellent particles is measured as a sintered body with 100% water repellent particles. It is desirable that the tensile strength of the water repellent particles is 10 MPa or more, preferably 10 to 30 MPa. If the tensile strength of the water repellent particles is 10 MPa or more, strong sintered coarse particles can be obtained, which is preferable. Further, the upper limit value of the tensile strength of the water repellent particles is not particularly limited.

  As the average particle diameter of the water repellent particles, those capable of forming the porous sintered coarse particles having the average particle diameter and having the small-diameter through-holes having the average pore diameter are desirably 100 to 500 nm, preferably 200. It is in the range of ˜300 nm. The particle size of the water repellent particles can be measured, for example, by SEM observation, AFM (Atomic Force Microscope) observation, or the like (see FIG. 9A). Note that the water repellent particles may include particles having different aspect ratios as described above, and the particle shape is not uniform. Therefore, the particle size is expressed by the absolute maximum length. . The absolute maximum length is as described in the particle diameter of the carbon particles.

  In addition, the mixing ratio of the carbon particles to the water repellent particles may be insufficient to obtain water repellency as expected when there are too many carbon particles. If there are too many water repellent particles, sufficient electron conductivity can be obtained. There is a fear that it is not possible. Considering these, the mixing ratio of the carbon particles and the water repellent particles in the GDL is 8: 2 to 4: 6, preferably 7: 3 to 5: 5 in terms of mass ratio. .

  Next, the average particle diameter (d1) of the carbon particles and the average particle diameter (d2) of the water repellent particles can exhibit the above-described conductivity (electric conductivity) and water repellency. In controlling the number and diameter of the generated holes, d1 / d2 is in the range of 0.5-5, preferably 1-2. When d1 / d2 exceeds 5, sufficient electron conductivity cannot be obtained. On the other hand, if d1 / d2 is less than 0.5, sufficient tensile strength cannot be obtained.

(Iii) Arbitrary constituent members constituting porous sintered coarse particles 21 The porous sintered coarse particles 21 are composed of the carbon particles and the water repellent particles. If it is in the range which does not impair, other structural members may be included. Specifically, for example, carbon nanotubes, granular activated carbon, granular graphite or the like having conductivity (electrical conductivity) may be used.

  Here, the mixing ratio of the carbon particles and the carbon nanotubes is 2 to 25 parts by mass, preferably 5 to 15 parts by mass with respect to 100 parts by mass of the carbon particles. If the compounding amount of the carbon nanotube is 2 parts by mass or more with respect to 100 parts by mass of the carbon particles, the conductivity is improved. On the other hand, if the compounding amount of the carbon nanotube is 25 parts by mass or less with respect to 100 parts by mass of the carbon particles, there is no problem such as piercing into the film and the film formability is not impaired.

  The carbon nanotubes have a length of 1 to 20 μm, preferably 5 to 15 μm. If the length is 1 μm or more, the conductivity increases, and if the length is 20 μm or less, the dispersibility is also good. When the sintered body is pulverized to obtain the porous sintered coarse particles 21, the carbon nanotubes are not sintered in a bead-like or network-like manner. Coarse particles 21 can be obtained. The tube diameter (thickness) of the carbon nanotube is 150 to 10 nm, preferably 100 to 20 nm.

(Iv) Holes (small-diameter through holes) formed in the gaps between the carbon particles and / or the water repellent particles
Since the size (average pore diameter) of the pores (small-diameter through-holes) formed in the gaps between the carbon particles and / or the water repellent particles is as already described, description thereof is omitted here.

  The number of pores (small-diameter through holes) in the porous sintered coarse particles may be any as long as good gas diffusibility can be obtained.

  In addition, the GDLs 13a and 13b in the present invention are desirably thin in order to improve the diffusibility of the fuel gas. Therefore, it may be determined as appropriate so as to obtain an MEA (fuel cell) having desired characteristics. Specifically, the thickness of each of the GDLs 13a and 13b is preferably 30 to 500 μm, and more preferably 100 to 200 μm. A GDL thickness of 30 μm or more is preferable in terms of excellent handleability and sufficient securing of a desired electrode output, and if it is 500 μm or less, necessary fuel gas can be supplied.

  Next, the GDL manufacturing method of the present invention will be described with reference to the drawings.

  FIG. 5 shows a process up to forming a mixed sintered body for porous sintered coarse particles as a representative embodiment (referred to as production method 1) of the method for producing porous sintered coarse particles used in the GDL of the present invention. It is process schematic showing the manufacturing process. FIG. 6 shows a process for producing a porous sintered coarse particle for use in the GDL of the present invention, as another typical embodiment (referred to as production method 2), until a sintered body for porous sintered coarse particle is formed. It is process schematic showing the manufacturing process of. FIG. 7 is a process schematic diagram showing a typical embodiment of a method for producing GDL using a mixed sintered body for porous body sintered coarse particles obtained by production method 1 or 2. Hereinafter, the method for producing porous sintered coarse particles and the method for producing GDL using the porous sintered coarse particles obtained thereby will be described separately.

(1) About the manufacturing method (manufacturing method 1) of porous sintered coarse particles (see FIGS. 5 and 7A-B)
As a typical embodiment of the method for producing porous sintered coarse particles used in the GDL of the present invention (referred to as production method 1), carbon particles and water repellent particles are mixed in water in the presence of a nonionic surfactant. To prepare a carbon / water repellent particle dispersion (also referred to as a carbon / water repellent particle dispersion preparation step), and the carbon / water repellent particle dispersion is phase-separated from a nonionic surfactant. Concentration using a phenomenon (also referred to as a phase separation and concentration step), and further heating and sintering the phase separation and concentration to form a mixed sintered body (also referred to as a mixed sintered body forming step), and the mixed sintering The body can be pulverized to obtain desired porous sintered coarse particles (also referred to as a pulverization step of a mixed sintered body). In the production method of the present invention (Production method 1 and further Production methods 2 to 4 described later), the shearing stress is not applied to the carbon particles and the water repellent particles (in a liquid state so as not to cause fibrillation of the water repellent particles). From the above, it can be dried and sintered (fired) above the melting point of the water repellent particles, resulting in a sintered body having a high Young's modulus, approximately the same tensile strength, brittle and difficult to compress. It has been found that if a GDL is formed by pulverizing and reinking it, the desired GDL can be obtained.

(I) Preparation process of carbon / water repellent particle dispersion (see FIGS. 5A and 5B)
In this step, carbon / water repellent particle dispersion is prepared by dispersing carbon particles and water repellent particles in water in the presence of a nonionic surfactant.

  Here, since the carbon particles and the water repellent particles are as already described, description thereof is omitted here.

  The blending amount of the carbon particles is 1 to 10% by mass, preferably 5 to 9% by mass with respect to the carbon / water repellent particle dispersion. The blending amount of the water repellent particles is 1 to 10% by mass, preferably 3 to 6% by mass with respect to the carbon / water repellent particle dispersion.

  The nonionic surfactant can be dispersed in water as a solvent, preferably uniformly dispersed in a finely divided state without agglomerating the carbon particles and water repellent particles. If it is. Specific examples of the nonionic surfactant include polyoxyethylene phenyl ether such as Triton X-100 and N-100 which is polyoxyethylene alkyl ether, but are not limited thereto. It is not something. Triton X-100 and N-100 having an appropriate cloud point are preferable from the viewpoint of phase separation. Moreover, these nonionic surfactants may be used individually by 1 type, and may use 2 or more types together.

  As the blending amount of the nonionic surfactant, the amount of the surfactant added increases or decreases in proportion to the specific surface area of carbon particles such as carbon black. Here, acetylene black AB-6 (manufactured by Deccan) is used as an example. Explained. In this case, the blending amount of the nonionic surfactant is 0.5 to 20% by mass, preferably 0.5 to 8% by mass with respect to the carbon / water repellent particle dispersion. If the blending amount of the nonionic surfactant is 0.5% by mass or more, it is dispersed well. On the other hand, if the blending amount of the nonionic surfactant is less than 0.5% by mass, carbon particles such as carbon black may not be dispersed. Moreover, if the compounding quantity of a nonionic surfactant is 20 mass% or less, it will disperse | distribute favorably, without impairing the effect of this invention.

  Further, in this step, as shown in FIG. 5A, first, carbon particles are added to water containing a nonionic surfactant, and an appropriate dispersing device such as an ultrasonic disperser, a jet mill, a bead mill or the like is used. The carbon particle dispersion 51 is prepared by dispersing to an average particle size of 300 to 600 μm. This is because carbon particles are secondarily agglomerated and agglomerated so that they can be atomized to a suitable size using a dispersing device and adsorbed on the surface to obtain a stable dispersion. It is.

  Next, as shown in FIG. 5B, a necessary amount of a commercially available water repellent particle dispersion is added to and mixed with the carbon particle dispersion obtained as described above, and excessive stress is applied using a suitable stirring device such as a stirrer. The carbon / water repellent particle dispersion 52 is prepared by gently stirring so as not to be applied. A dispersion using an optimal surfactant is stable unless excessive shear stress is applied. For example, the water repellent particles do not form aggregated fibrils by normal stirring, shaking, ultrasonic irradiation, or the like.

  Here, the reason why the water repellent particle dispersion is used is that it is impossible to disperse in water if the water repellent particles are added alone due to the water repellent action of the water repellent particles. As such a water repellent particle dispersion, those commercially available from Daikin Industries, Ltd., Asahi Glass Co., Ltd., Mitsui Fluorochemical Co., Ltd. and the like can be easily obtained.

  In the above filtration, in consideration of the secondary aggregation size of the carbon particles and the particle size in the water repellent particle dispersion, filtration is performed using a filter paper (for example, 0.2 μm filter paper) that can be sufficiently separated. To do. In this case, for example, several days are required to perform vacuum suction filtration using 0.2 μm filter paper.

(Ii) Phase separation and concentration step (see FIG. 5C)
In this step, the carbon / water repellent particle dispersion is phase-separated and concentrated. This is because the water-repellent particles become agglomerated fibrils when shear stress is applied before the carbon / water-repellent particle dispersion is solidified and sintered. This is because it is desirable. Without using a flocculant such as alcohol, water is removed from the carbon / water repellent particle dispersion. For example, solids are collected by filtration (filtering method), centrifuged, and concentrated. You can also use this method. Since the flocculant cannot be used in the filtration method, it takes a long time to filter (for example, it is difficult to obtain a filtered solid content unless filtration is performed over 2 days with a 0.2 μm filter paper). In the centrifugal separation method, the dispersion can be centrifuged at about 5000 G for 60 minutes to obtain a solid content of about 50%. A mixed sintered body can also be obtained by drying and sintering this. Here, the solid content 53 is obtained by solidification by a solidification method in which no stress is applied from the liquid state using the phase separation phenomenon of the nonionic surfactant.

The phase separation concentration method uses a phase separation phenomenon of a nonionic surfactant. When an aqueous solution containing a nonionic surfactant is heated, there is a temperature at which it becomes cloudy. This phenomenon occurs in the case of a nonionic surfactant. In the case of a nonionic surfactant, the hydrogen ion bond between a polyoxyethylene group (CH ₂ —CH ₂ —O) _n ) and a water molecule is a cloud point. Since it is cut due to thermal motion at the above temperature, the surfactant becomes difficult to dissolve. This is because nonionic surfactant molecules are insolubilized above this temperature. When the temperature of the dispersion containing the nonionic surfactant is raised, the nonionic surfactant molecules adsorbed on the surface of the dispersed particles become insoluble, so that the dispersed fine particles settle and form a concentrated phase and a dilute phase. Use separation. Thereby, it can concentrate to solid content concentration about 40% wt.

  For example, a dispersion liquid (solid content 13% wt) containing 4% Triton X-100 (nonionic surfactant) is placed in a glass bottle and left in a water bath at 70.0 ° C. for 24 hours. The dispersion is separated with a low concentration at the top and a high concentration at the bottom. By removing the upper liquid, a concentrated liquid having a solid content of 44.6% can be obtained. In this case, the solids yield is 99%, and the phase separation concentration method can be concentrated very efficiently in a short time compared to the above filtration method and the like. By drying this, solid content can be easily obtained.

(Iii) Process for forming a mixed sintered body (see FIGS. 5D and 5E)
In this step, the mixed and sintered body is formed by further heating and sintering the phase-separated and concentrated product (solid content).

  In this step, as shown in FIG. 5D, the phase-separated and concentrated solid content 53 is applied to a suitable base material 54, etc., dried as necessary, and heated and fired to form a mixed sintered body 55. To do. By peeling this from the base material 54, a dense film 56 of the mixed sintered body 55 can be obtained as shown in FIG. 5E.

  Here, the base material 54 may be any material that is thermally and chemically stable in the drying and firing stages. For example, an Al foil, a glass plate, a Kapton sheet, a titanium foil, or the like can be used. Preferably, a material excellent in peelability is desirable so that the mixed sintered body 55 can be easily peeled from the base material 54, and for example, an Al foil or the like can be suitably used.

  Even in the drying step, it is desirable to set the drying conditions so as not to cause fibrillation of the water repellent particles without applying shear stress. From this point of view, the drying conditions may be about 70 to 120 ° C. for about 1 to 5 hours. The heating rate up to the drying temperature is 10 to 100 ° C./min, preferably 20 to 50 ° C./min. Even in the drying stage, it is desirable that the drying conditions be such that no shear stress is applied and the water repellent particles are not fibrillated.

  Next, as the firing condition, the mixed sintered body 55 is fired for 0.5 to 3 hours in a temperature range higher than the melting point of the water repellent particles, preferably 5 to 50 ° C. higher than the melting point of the water repellent particles. can get. In addition, it is desirable that the rate of temperature rise to the firing temperature is 10 to 200 ° C./min, preferably 50 to 150 ° C./min.

  The thickness of the mixed sintered body 55 is desirably adjusted to about 0.2 to 5 mm, preferably about 0.5 to 2 mm from the viewpoint of productivity.

By peeling the mixed sintered body 55 from the base material 54, a dense film 56 of the mixed sintered body 55 can be obtained as shown in FIG. 5E. Physical properties of dense film (sheet) 56 of the mixed sintered body 55, as described above, a tensile strength of 20 kgf / cm ² or more, preferably 20~40kgf / cm ^2, breaking deformation rate of 20% or less Preferably, it is 10% or less. Thus, if the carbon particles and the water repellent particles are dried and sintered at a temperature equal to or higher than the melting point of the water repellent particles without applying shear stress (without causing fibrillation of the water repellent particles), the Young's modulus is increased. It is possible to obtain a dense and strong sintered body that has high tensile strength and is brittle and is not easily deformed by compression. As will be described later, by pulverizing into porous sintered coarse particles, and re-inking the particles to form a film, it is possible to obtain a GDL in which the particles are connected with a moderate gap. . That is, in the GDL formed by connecting very strong and dense porous sintered coarse particles, through-holes of an appropriate size are formed between the porous sintered coarse particles. Since the porous sintered coarse particles, which are sintered bodies, are very strong and stable, the through-holes are crushed because the water repellent particles are not fibrillated even under pressure conditions for a long time in the battery stack. Absent. Therefore, excellent gas diffusibility can be stably maintained for a long period of time.

  At the stage of peeling the mixed sintered body 55 from the base material 54, the sintered body is already a hard sintered body, and the water repellent particles do not cause fibrillation even if a certain amount of shear stress is applied. The mixed sintered body 55 may be peeled off. This is because, in the next step, the dense film 56 of the mixed sintered body 55 is pulverized, so there is no problem even if the same degree of shear stress is applied.

(Iv) Micronization process of mixed sintered body (see FIGS. 7A and 7B)
In this step, the mixed sintered body 55 is pulverized to obtain desired porous sintered coarse particles.

  In this step, as shown in FIGS. 7A and 7B, the dense film 71 (the dense film 56 of the mixed sintered body 55 in FIG. 5E) of the mixed sintered body obtained by the manufacturing method 1 is applied to an appropriate pulverizing apparatus. For example, finely pulverized using a mixer, etc., classified using an appropriate classifier such as a sieve, a classifier, etc., and a porous body having a desired size (classified to a certain particle size or less here) Sintered coarse particles 72 can be obtained. When pulverizing, the mixed sintered body is preferably cooled with liquid nitrogen or the like.

(2) About the manufacturing method (production method 2) of porous body sintered coarse particles (see FIGS. 6 and 7A-B)
As a typical embodiment of the method for producing porous sintered coarse particles used in the GDL of the present invention (referred to as production method 2), carbon particles and water repellent particles are mixed in water in the presence of a nonionic surfactant. To prepare a carbon / water repellent particle dispersion (also referred to as a carbon / water repellent particle dispersion preparation step), and electrodeposit the carbon / water repellent particle dispersion to precipitate a solid content. (Also referred to as an electrodeposition process), further, the solid content is sintered to form a mixed sintered body (also referred to as a mixed sintered body forming process), and the mixed sintered body is pulverized to form a desired porous body. Coarse coarse particles are obtained (also referred to as a pulverization step of the mixed sintered body).

(I) Preparation process of carbon / water repellent particle dispersion (see FIGS. 6A and 6B)
In this step, carbon / water repellent particle dispersion is prepared by dispersing carbon particles and water repellent particles in water in the presence of a nonionic surfactant.

  This step is the same as the preparation step of the carbon / water repellent particle dispersion liquid of production method 1, and instead of the description of production method 1 in FIGS. 5A and 5B, production method 2 uses FIGS. 6A and 6B. That is, the carbon particle dispersion 51 of FIG. 5A is the carbon particle dispersion 61 in FIG. 6A, the carbon / water repellent particle dispersion 52 of FIG. 5B is the carbon / water repellent particle dispersion 62 in 6B. However, there is nothing practically different.

(Ii) Electrodeposition process (see FIG. 6C)
In this step, the carbon / water repellent particle dispersion is electrodeposited to deposit a solid content. Also in this production method, as in production method 1, if a shear stress is applied before the carbon / water repellent particle dispersion is solidified and sintered, the water repellent particles are aggregated into fibrils, so stress is applied from the liquid state. It is because it is desirable to solidify by the solidification method which is not.

  Therefore, in this step, the carbon / water repellent particle dispersion liquid is subjected to a suitable electrodeposition method, for example, a method in which the solid content is deposited on the anode 64 by electrophoretic electrodeposition, as shown in FIG. Is solidified by a solidification method in which no electrode is added to obtain an electrodeposited solid content 65.

  This production method 2 is superior in that the solid content can be collected in a relatively short time as compared to the case of collecting the solid content by filtration as in production method 1.

(Iii) Process for forming a mixed sintered body (see FIGS. 6D and E)
In this step, the solid content is further sintered to form a mixed sintered body.

  This step is basically the same as the step of forming the mixed sintered body of production method 1, and as shown in FIG. 6D, the solid content 65 is dried as necessary, as shown in FIG. 6E. After peeling from the electrophoretic electrodeposition anode (electrode substrate) 64, firing is performed to obtain a dense film 66 of a mixed sintered body.

  Here, it is desirable that the electrode base material (electrophoretic electrode-deposited anode) 64 be stable without being electrochemically dissolved. For example, a platinum plate, a platinum-coated titanium plate, an iridium-coated titanium plate, or the like can be used. . Since the electrode (electrophoretic electrodeposition cathode) 63 used in the above process does not need to have any particular characteristics in the drying stage like the electrode (electrophoresis electrodeposition anode) 64, various conventionally known electrode materials may be used. it can. For example, a nickel mesh can be used. The following drying, sintering, and pulverization steps are the same as described above, and thus are omitted.

(3) GDL production method (production method 3) using porous sintered coarse particles obtained by production methods 1 and 2 As a representative embodiment (referred to as production method 3) of the GDL production method of the present invention, The porous sintered coarse particles obtained by the above production method 1 or 2 are dispersed in a solvent to form a porous sintered coarse particle dispersion (also referred to as an adjustment step of the porous sintered coarse particle dispersion). The porous sintered coarse particle dispersion is applied to a base material, dried and hot pressed to form a film, and separated from the base material to obtain GDL (GDL film forming step). This manufacturing method is excellent in that a GDL having a thickness unevenness of about 10 to 200 μm can be formed.

(I) Adjustment process of porous sintered coarse particle dispersion (also referred to as reinking process; see FIG. 7C)
In this step, the porous sintered coarse particles obtained by the above production method 1 or 2 are dispersed in a solvent to form a porous sintered coarse particle dispersion (reinking).

Here, the solvent is not particularly limited as long as it can disperse, preferably uniformly and uniformly disperse the porous sintered coarse particles obtained by the above production method 1 or 2. . Examples of the solvent include solvent naphtha; alkane hydrocarbons such as decane and dodecane (C _n H _{2n + 2,} where n = 10 to 16); Moreover, these solvents may be used alone or in combination of two or more. Preferably, the porous sintered coarse particles having high water repellency can be easily dispersed, and therefore, selected from the group consisting of alkane hydrocarbons (C _n H _{2n + 2} ; where n = 10 to 16) and solvents containing them. Such at least one solvent is desirable. Specific examples include decane and / or dodecane.

  In addition, in the porous sintered coarse particle dispersion, various additives such as a pore-forming agent may be appropriately used in an appropriate amount as long as the effects of the present invention are not impaired.

  The pore former is gasified by hot pressing in the next step and used for the purpose of controlling the diameter and number of pores (large-diameter through holes) formed between porous sintered coarse particles inside the GDL film. It is what In particular, relatively large pores (large-diameter through-holes) having a uniform pore size can be made relatively easily by making the addition amount and particle size of the pore-forming agent uniform. This is excellent in that the hole diameter and distribution as designed can be obtained.

  The pore-forming agent is not particularly limited, and for example, salt particles such as NaCl and metal particles such as copper and zinc can be used. However, the present invention is not limited to these. Moreover, these pore formers may be used individually by 1 type, and may use 2 or more types together. In the case of using metal particles for the pore-forming agent, for example, when hot pressing is performed in the next step, the metal particles are taken out from the GDL by using an external magnetic force action or the like, thereby forming a GDL film. You may make it control the diameter and number of the void | hole (large diameter through-hole) formed between internal porous body sintered coarse particles.

  What is necessary is just to adjust suitably the magnitude | size of the said pore making material so that the hole diameter of the target large diameter through-hole may be obtained, and it is the range of 1-50 micrometers, Preferably it is 5-30 micrometers.

  The amount of the pore former is 5 to 25% by mass, preferably 10 to 20% by mass with respect to the porous sintered coarse particle dispersion (including the pore former). When the compounding amount of the pore former exceeds 25% by mass, the strength decreases and the specific resistance increases. On the other hand, when the amount of the pore-forming agent is less than 5% by mass, the effect is small.

  In this step, as shown in FIG. 6C, first, porous sintered coarse particles 72 (see FIG. 7B) are added to the solvent, and additives such as a pore-forming agent are added as necessary, and appropriate stirring is performed. The porous body sintered coarse particle dispersion (reink) 73 is prepared by mixing with an apparatus.

  It should be noted that additives such as a pore-forming agent are particularly limited, for example, the porous sintered coarse particles 72 may be added and dispersed after being added to a solvent in advance and mixed and dispersed (while stirring). It is not a thing.

(Ii) GDL film forming process (see FIGS. 7D and 7E)
In this step, the porous sintered coarse particle dispersion is applied to a substrate, dried, hot-pressed to form a film, and separated from the substrate to obtain GDL.

  In this step, as shown in FIG. 7D, the porous sintered coarse particle dispersion 73 is applied to an appropriate base material 74 by an appropriate method, dried, and hot pressed to form a GDL 75 film. By separating (separating the substrate) from the substrate 74 by an appropriate method, a GDL film (sheet) 76 can be obtained as shown in FIG. 7E.

  Here, the base material 74 may be any material that is thermally, mechanically, and chemically stable in the drying and hot pressing stages. For example, an Al foil, a crow plate, a stainless steel plate, or the like can be used. Preferably, a material excellent in peelability is desirable so that it is easy to peel the GDL 75 from the substrate 74, and for example, an Al foil or the like can be suitably used.

  Here, the method for applying the porous sintered coarse particle dispersion 73 to the substrate 74 is not particularly limited, and various conventionally known application methods can be used. Specifically, it can apply | coat using a die-coater etc., for example. In this application stage, since the repellency of the water repellent particles does not occur because it has already been baked, an optimum application method may be applied without paying particular attention to shear stress and the like. Therefore, application methods such as spraying can also be used.

  As said drying conditions, what is necessary is just about 1 to 6 hours at 50-150 degreeC. The heating rate up to the drying temperature is 10 to 100 ° C./min, preferably 20 to 50 ° C./min. In the final drying stage, since the fibrillation of the water repellent particles does not occur because it is already after firing, an optimal drying method may be applied without paying particular attention to shear stress and the like. Accordingly, vacuum drying or vacuum drying can be used.

The hot pressing conditions, than the melting point of the water repellent particles, preferably at 5 to 50 ° C. higher heating temperatures than the melting point of the water repellent particles, pressure 20 kg / cm ² or more, preferably 10 to 50 kg / cm ^2, 5 GDL75 can be formed by hot pressing for 2 seconds to 5 minutes, preferably 30 seconds to 2 minutes.

  Further, the thickness of the GDL 75 is as already described.

  By peeling the GDL 75 from the base material 74, a GDL (dense) film 76 can be obtained as shown in FIG. 7E. Thus, the obtained GDL film 76 has relatively small through-holes (average pore diameter of 0.2 μm or less, present in hard dense particles (porous sintered coarse particles) as shown in FIG. Preferably 0.1 μm or less) and relatively large through-holes (average pore diameter of 0.5 μm or more, preferably 5 μm or more) existing between the particles. The relatively large-diameter through-hole existing in As described above, the water repellent particles are prevented from being subjected to shear stress before firing even for relatively small diameter through-holes present in hard dense particles (porous sintered coarse particles). Therefore, even if hot pressing is performed, a relatively small diameter through hole remains uncrushed. Therefore, the GDL film 76 has excellent water permeability and gas diffusibility like the existing GDL such as carbon cloth, and further includes carbon fibers and further filled water repellent particles. Therefore, even under pressure conditions for a long time in the battery stack, there is no short circuit due to penetration between electrodes due to carbon fibers and no collapse of large-diameter through-holes due to fillylation of water repellent, and excellent gas diffusibility Can be held stably for a long period of time.

That is, as a physical property of the obtained GDL film 76, since there are vacancies having a large gas permeability (relatively large through-holes existing between particles), a roll using the same carbon particles and water repellent particles is used. 10 times or more, preferably 20 to 50 times the GDL produced by the method. The tensile strength of the GDL film 76 is 20 kgf / cm ² or more, preferably 20 to 40 kgf / cm ² , and the specific resistance is 0.25 Ωcm or less, preferably 0.2 Ωcm or less.

(4) GDL production method (production method 4) using porous sintered coarse particles obtained by production methods 1 and 2 Another representative embodiment of the GDL production method of the present invention (referred to as production method 4) As described above, GDL is obtained by filling the hot-pressed porous body sintered coarse particles obtained by the above production method 1 or production method 2 into a mold (GDL production step). This manufacturing method is excellent in that it can produce a GDL with a small number of manufacturing steps and a small thickness unevenness of about 10 to 200 μm. Moreover, since the manufacturing method 3 does not use a solvent, it is excellent in that environmental measures such as solvent recovery equipment are easy.

(I) GDL production process In this production method 4, GDL is obtained by filling the porous sintered coarse particles obtained by the above production method 1 or production method 2 into a mold and hot pressing (not shown). ).

  In this production method, porous sintered coarse particles having a certain particle size or less, for example, 150 μm or less (average particle size of about 120 μm) classified by the production method 1 or 2, and, if necessary, various kinds of pore forming agents, etc. Appropriate amounts of additives are appropriately added and uniformly mixed, placed in a suitable mold (jig), and hot-pressed to produce GDL.

  Additives such as the pore former are the same as in Production Method 3.

  Moreover, as a suitable metal mold | die (jig), it does not restrict | limit in particular, A conventionally well-known hot press metal mold | die can be utilized.

The hot pressing conditions, than the melting point of the water repellent particles, preferably at 5 to 20 ° C. higher heating temperatures than the melting point of the water repellent particles, pressure 10 kg / cm ² or more, preferably 20~150kg / cm ^2, 0 GDL can be produced by hot pressing for 5 to 3 minutes, preferably 1 to 2 minutes.

  Further, the configuration and thickness of the GDL are as already described.

  Further, the physical properties of GDL are the same as described in Production Method 3.

  In addition, in the said manufacturing methods 3 and 4 of GDL of this invention, the void | hole formed between porous body sintered coarse particles in a hot press using the imprint technique, especially the nanoimprint technique suitable for this invention. The diameter and number may be controlled. That is, by forming an uneven pattern corresponding to the desired large-diameter through-holes (hole diameter and number and arrangement of large-diameter through-holes) on a mold or mold used for hot-melt by imprint technology, By pressing and transferring the desired pattern to the GDL film, the diameter and number of pores formed between the porous sintered coarse particles can be controlled.

  The above is the description regarding the GDL of the present invention. However, in the present invention, as shown in FIG. 2D, the GDLs 13a and 13b may have a two-layer structure including base materials 13-2a and 13-2b and carbon particle layers (hereinafter also simply referred to as MIL) 131a and 131b. Good. In this case, normally, the MIL 131a and 131b made of an aggregate of carbon particles containing a water repellent agent are provided on the base materials 132a and 132b of sheet-like material having conductivity and porosity. In the present invention, the above-described configuration of the GDLs 13a and 13b according to the present invention may be applied to any of the base materials 132a and 132b and the MILs 131a and 131b. However, the present invention is preferably applied to the MILs 131a and 131b as shown in (a) below. It is desirable to apply a configuration (see FIGS. 2B and 2C) having two holes (through holes) of the GDL of the invention. Even when the GDL is divided into two layers of the base material and the MIL, the effects of the present invention can be sufficiently achieved. Particularly in the following (a), it has been difficult to produce a thin and high-precision MIL, and the conventional MIL is composed of carbon black particles and PTFE particles as described in the prior art. However, it has the same problem as described in the prior art. In the present invention, a thin and high-accuracy MIL can be obtained by applying the above-described configuration having two large and small holes (through holes) of the GDL of the present invention (see FIGS. 2B and 2C) to the configuration of the MIL 131a and 131b. It can be created, and can solve the same problems as described in the prior art.

  That is, when GDL is divided into two layers of a base material and a MIL, (a) an existing base material + MIL having the GDL configuration of the present invention, or (b) a base having the GDL configuration of the present invention. Any combination of material + existing MIL may be used. When the GDL of the present invention is configured on both the base material and the MIL, it may be applied as one GDL without being divided into two, as already described above as the GDL according to the present invention. is there.

  The existing base material in the above (a) is not particularly limited, and known materials can be used in the same manner. For example, the conductive material such as a carbon woven fabric, a paper-like paper body, a felt, and a non-woven fabric can be used. The thing etc. which use the sheet-like material which has porosity as a base material are mentioned. The thicknesses of the base materials 132a and 132b may be appropriately determined in consideration of the overall characteristics of the GDLs 13a and 13b to which MIL 131a and 131b are added, respectively, but are desirably 50 to 500 μm, preferably 100 to 200 μm. . If the thickness is less than 50 μm, sufficient mechanical strength or the like may not be obtained, and if it exceeds 500 μm, the distance through which gas or water permeates is undesirably increased.

  The base materials 132a and 132b preferably contain a water repellent for the purpose of further improving water repellency and preventing flooding. Although it does not specifically limit as said water repellent, Fluorine-type, such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), etc. Examples thereof include polymer materials, polypropylene, and polyethylene.

  Regarding the MILs 131a and 131b in (a) above, the configuration of the GDLs 13a and 13b of the present invention described above can be applied, and thus the description thereof is omitted here.

  However, the thicknesses of the MILs 131a and 131b in (a) may be appropriately determined in consideration of the overall characteristics of the GDLs 13a and 13b including the existing base materials 132a and 132b, respectively. May be 20 to 50 μm. If the thickness is less than 10 μm, handling properties may be difficult, and sufficient mechanical strength may not be obtained. If the thickness exceeds 100 μm, the distance through which gas or water permeates is undesirably increased. .

  Next, regarding the MIL 131a and 131b in (b) above, the configuration of the GDLs 13a and 13b of the present invention described above can be applied, and thus description thereof is omitted here.

  As the existing MILs 131a and 131b in (b), an existing MIL 131a and 131b made of an aggregate of carbon particles containing a water repellent agent on a substrate to which the GDL configuration of the present invention is applied in order to further improve the water repellency. MIL may be used.

  The carbon particles used in the MIL 131a and 131b in (b) are not particularly limited, and may be conventional ones such as carbon black, graphite, and expanded graphite. Of these, carbon blacks such as oil furnace black, channel black, lamp black, thermal black, and acetylene black are preferred because of their excellent electron conductivity and large specific surface area. The average particle diameter of the carbon particles is preferably about 10 to 100 nm. Thereby, while being able to obtain the high drainage property by capillary force, it becomes possible to improve contact property with a catalyst layer.

  Examples of the water repellent used in the MIL 131a and 131b in (b) above include the same water repellent as that used in the existing base materials 132a and 132b in (a). Of these, fluorine-based polymer materials are preferably used because of their excellent water repellency and corrosion resistance during electrode reaction.

  The mixing ratio of the carbon particles to the water repellent in the MIL 131a, 131b of (b) above may not be able to provide water repellency as expected when there are too many carbon particles. There is a risk that electron conductivity may not be obtained. Considering these, the mixing ratio of the carbon particles and the water repellent in the MIL is preferably about 90:10 to 40:60 in mass ratio.

  The thicknesses of the MILs 131a and 131b in (b) may be appropriately determined in consideration of the water repellency of the entire GDL including the base material to which the GDLs 13a and 13b of the present invention are applied.

  In the above (a) and (b), when a GDL substrate or MIL contains a water repellent, a general water repellent treatment method may be used. For example, after immersing the base material used for GDL in the dispersion liquid of a water repellent, the method of heat-drying in oven etc. is mentioned.

  In the GDL of the above (a) or (b), when MIL is formed on a transfer mount, carbon particles, a water repellent, etc. are used such as water, perfluorobenzene, dichloropentafluoropropane, methanol, ethanol, etc. A slurry is prepared by dispersing it in a solvent such as an alcohol solvent, and the slurry is applied on a transfer mount and dried, or the slurry is dried once and pulverized to form a powder, which is then used as the substrate. What is necessary is just to use the method of apply | coating on the top. Then, it is preferable to heat-process at about 250-400 degreeC using a muffle furnace or a baking furnace.

(2) Electrolyte membrane 11
The electrolyte membrane 11 that can be used in the MEA of the present invention and a fuel cell using the MEA only needs to have high proton conductivity. Examples of the membrane having high proton conductivity include a polymer or copolymer of a monomer having an ion exchange group such as —SO ₃ H group; or a polymer of a monomer having an ion exchange group and another monomer. A film made of a material can be used. Specific examples of the material of the electrolyte membrane 11 include an electrolyte having a fluorinated resin in which all or part of the polymer skeleton is fluorinated and having an ion exchange group, or an aromatic that does not contain fluorine in the polymer skeleton. An electrolyte having an ion exchange group, which is a group hydrocarbon resin.

Examples of the ion-exchange group is not particularly _{limited, -SO 3 H, -COOH, -PO} (OH) 2, -POH (OH), - SO 2 NHSO 2 -, - Ph (OH) (Ph represents a phenyl group A cation exchange group such as —NH ₂ , —NHR, —NRR ′, —NRR′R ″ ⁺ , —NH ₃ ^{+ and the} like (R, R ′, R ″ represent an alkyl group, cycloalkyl Anion exchange groups such as a group, an aryl group, and the like.

  Specific examples of the electrolyte having a fluorine resin and having an ion exchange group include Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), and Flemion (registered trademark, Asahi Glass). Perfluorocarbon sulfonic acid polymer, polytrifluorostyrene sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylenetetrafluoroethylene-g-styrene sulfonic acid polymer, Suitable examples include ethylene-tetrafluoroethylene copolymer, polytetrafluoroethylene-g-polystyrene sulfonic acid polymer, and polyvinylidene fluoride-g-polystyrene sulfonic acid polymer.

  Specific examples of the electrolyte that is an aromatic hydrocarbon resin and includes an ion exchange group include a polysulfone sulfonic acid polymer, a polyether ether ketone sulfonic acid polymer, a polybenzimidazole alkyl sulfonic acid polymer, Preferred examples include benzimidazole alkylphosphonic acid polymers, cross-linked polystyrene sulfonic acid polymers, polyethersulfone sulfonic acid polymers, and the like.

  Since the material of the electrolyte membrane 11 has high ion exchange ability and is excellent in chemical durability and mechanical durability, it is preferable to use an electrolyte that is the above-mentioned fluorine-based polymer and has an ion exchange group. Of these, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.) and the like can be more preferably used.

  The thickness of the electrolyte membrane 11 can be appropriately determined in consideration of the characteristics of the obtained fuel cell, but is preferably 5 to 300 μm, more preferably 10 to 200 μm, and particularly preferably 15 to 150 μm. The thickness of the electrolyte membrane is preferably 5 μm or more from the viewpoint of strength during film formation and durability during operation of the fuel cell, and is preferably 300 μm or less from the viewpoint of output characteristics during operation of the fuel cell.

  In the present invention, the constituent member containing the electrolyte component interposed between the anode and cathode electrodes of the fuel cell is referred to as an electrolyte membrane. It goes without saying that even if it is referred to as an electrolyte layer or an electrolyte, for example, it may be included in the electrolyte membrane according to the present invention in view of the purpose of use used in the battery. The same applies to the other component requirements, and the identity is not limited to the name, but the identity may be determined in light of the purpose of use.

(3) Catalyst layer 12
The anode and cathode catalyst layers 12a and 12b that can be used in the MEA of the present invention and a fuel cell using the MEA mainly include an electrode catalyst (catalyst material) in which catalyst particles are supported on a conductive carrier, and proton conductivity. And an electrolyte (also referred to as a binder or an ionomer). Hereinafter, each of these components will be described.

(I) Electrode catalyst The electrode catalyst is formed by supporting catalyst particles on a conductive carrier.

  Here, the catalyst particles used in the cathode catalyst layer are not particularly limited as long as they have a catalytic action in the oxygen reduction reaction, and known catalysts can be used in the same manner. Also, the catalyst particles used in the anode catalyst layer are not particularly limited as long as they have a catalytic action in the oxidation reaction of hydrogen, and known catalysts can be used in the same manner. Specifically, it is selected from platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum and the like, and alloys thereof. Is done. Among these, those containing at least platinum are preferably used in order to improve catalyst activity, poisoning resistance to carbon monoxide and the like, heat resistance, and the like. The composition of the alloy is preferably 30 to 90 atomic% for platinum and 10 to 70 atomic% for the metal to be alloyed, depending on the type of metal to be alloyed. The composition of the alloy when the alloy is used as a cathode catalyst varies depending on the type of metal to be alloyed and can be appropriately selected by those skilled in the art, but platinum is 30 to 90 atomic%, and other metals to be alloyed are 10 It is preferable to set it to -70 atomic%. In general, an alloy is a generic term for an element obtained by adding one or more metal elements or non-metal elements to a metal element and having metallic properties. The alloy structure consists of a eutectic alloy, which is a mixture of component elements that form separate crystals, a component element that completely dissolves into a solid solution, and a component element that is an intermetallic compound or a compound of a metal and a nonmetal. There is what is formed, and any may be used in the present application. At this time, the catalyst particles used for the cathode catalyst layer and the catalyst particles used for the anode catalyst layer can be appropriately selected from the above. In the following description, unless otherwise specified, the descriptions of the catalyst particles for the cathode catalyst layer and the anode catalyst layer have the same definition for both, and are collectively referred to as “catalyst particles”. However, the catalyst particles for the cathode catalyst layer and the anode catalyst layer do not need to be the same, and are appropriately selected so as to exhibit the desired action as described above.

  The shape and size of the catalyst particles are not particularly limited, and the same shape and size as known catalyst particles can be used, but the catalyst particles are preferably granular. At this time, the smaller the average particle diameter of the catalyst particles used in the catalyst ink, the higher the effective electrode area where the electrochemical reaction proceeds, which is preferable because the oxygen reduction activity is also high, but in practice the average particle diameter is too small. On the other hand, a phenomenon in which the oxygen reduction activity decreases is observed. Therefore, the average particle diameter of the catalyst particles contained in the catalyst ink is preferably 1 to 30 nm, more preferably 1.5 to 20 nm, still more preferably 2 to 10 nm, and particularly preferably 2 to 5 nm. It is preferably 1 nm or more from the viewpoint of easy loading, and preferably 30 nm or less from the viewpoint of catalyst utilization. The “average particle diameter of the catalyst particles” in the present invention is the average value of the particle diameter of the catalyst particles determined from the crystallite diameter or transmission electron microscope image obtained from the half width of the diffraction peak of the catalyst particles in X-ray diffraction. Can be measured.

  The conductive carrier may have any specific surface area for supporting the catalyst particles in a desired dispersed state and has sufficient electronic conductivity as a current collector. The main component is carbon. Preferably there is. Specific examples include carbon particles made of carbon black, activated carbon, coke, natural graphite, artificial graphite and the like. In the present invention, “the main component is carbon” refers to containing a carbon atom as a main component, and is a concept including both a carbon atom only and a substantially carbon atom. In some cases, elements other than carbon atoms may be included in order to improve the characteristics of the fuel cell. In addition, being substantially composed of carbon atoms means that mixing of impurities of about 2 to 3% by mass or less is allowed.

The BET specific surface area of the conductive carrier may be a specific surface area sufficient to support highly dispersed catalyst particles, but is preferably 20 to 1600 m ² / g, more preferably 80 to 1200 m ² / g. Is good. When the specific surface area is 20 m ² / g or more, the dispersibility of the catalyst particles and the polymer electrolyte in the conductive support is improved, which is excellent in that sufficient power generation performance can be obtained. On the other hand, if it is 1600 m ² / g or less, it is excellent in that a high effective utilization rate of the catalyst particles and the polymer electrolyte can be effectively maintained.

  Further, the size of the conductive carrier is not particularly limited, but from the viewpoint of controlling the ease of loading, the catalyst utilization, and the thickness of the catalyst layer within an appropriate range, the average particle size is 5 to 200 nm, The thickness is preferably about 10 to 100 nm.

  In the electrode catalyst in which catalyst particles are supported on the conductive support, the supported amount of the catalyst particles is preferably 10 to 80% by mass, more preferably 30 to 70% by mass with respect to the total amount of the electrode catalyst. Good. When the supported amount is 80% by mass or less, the excellent dispersion degree of the catalyst particles on the conductive support can be effectively maintained, and the effect of improving the power generation performance commensurate with the increase in the supported amount is effectively achieved. There is an advantage that can be expressed. Further, when the supported amount is 10% by mass or more, the catalyst activity per unit mass is excellent, and desired power generation performance corresponding to the supported amount can be obtained. Therefore, it is excellent in that the carrying amount design for ensuring the desired battery performance can be made relatively easily. The amount of catalyst particles supported can be examined by inductively coupled plasma emission spectroscopy (ICP).

  The catalyst particles can be supported on the conductive support by a known method. For example, known methods such as impregnation method, liquid phase reduction support method, evaporation to dryness method, colloid adsorption method, spray pyrolysis method, reverse micelle (microemulsion method) can be used. Alternatively, a commercially available electrode catalyst may be used.

(Ii) Electrolyte The cathode catalyst layer / anode catalyst layer (also simply referred to as “catalyst layer”) of the present invention contains an electrolyte in addition to the electrode catalyst. The electrolyte is not particularly limited, and the same polymer electrolyte as that used for the membrane can be used. The electrolyte used for the membrane and the electrolyte used for each catalyst layer may be the same or different, but from the viewpoint of improving the adhesion between each catalyst layer and the membrane, the same one is used. Is preferred. That is, the electrolyte is not particularly limited, and a known one can be used, but any member having at least high proton conductivity may be used. Electrolytes that can be used in this case are broadly classified into fluorine-based electrolytes containing fluorine atoms in all or part of the polymer skeleton and hydrocarbon-based electrolytes not containing fluorine atoms in the polymer skeleton.

  Specific examples of the fluorine electrolyte include perfluorocarbon sulfonic acids such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.). Polymer, polytrifluorostyrene sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene A preferred example is a fluoride-perfluorocarbon sulfonic acid-based polymer.

  Specific examples of the hydrocarbon electrolyte include polysulfone sulfonic acid, polyaryl ether ketone sulfonic acid, polybenzimidazole alkyl sulfonic acid, polybenzimidazole alkyl phosphonic acid, polystyrene sulfonic acid, polyether ether ketone sulfonic acid, polyphenyl. A suitable example is sulfonic acid.

  The polymer electrolyte preferably contains a fluorine atom because of its excellent heat resistance and chemical stability. Among them, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.) Fluorine electrolytes such as Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) are preferred.

  The mass ratio of the electrolyte to the catalyst carrier is preferably 0.6: 1 to 1: 1, and more preferably 0.7: 1 to 0.9: 1. When the mass ratio of the polymer electrolyte to the catalyst support mass is 0.6 times or more, it is preferable in terms of good ion conductivity in the catalyst layer, and when it is 1 times or less, gas diffusion and water in the catalyst layer This is preferable in terms of discharge.

  Each catalyst layer, particularly the surface of the catalyst carrier and the polymer electrolyte, may further contain or contain a water-repellent polymer and other various additives. By containing the water-repellent polymer, the water repellency of the resulting catalyst layer can be increased, and water generated during power generation can be quickly discharged. The mixing amount of the water-repellent polymer can be appropriately determined within a range that does not affect the function and effect of the present invention. Examples of the water-repellent polymer include polypropylene, polyethylene, PTFE, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyhexafluoropropylene, or a copolymer of these monomers (for example, tetrafluoroethylene-hexafluoro Fluorine polymer materials such as a propylene copolymer) can be used.

  Although the thickness of the catalyst layer in this invention is not specifically limited, 0.1-100 micrometers is preferable, More preferably, it is 1-20 micrometers. When the thickness of the catalyst layer is 0.1 μm or more, it is preferable in that a desired power generation amount can be obtained, and when it is 100 μm or less, it is preferable in that a high output can be maintained.

(4) Separator 15
The anode and cathode separators 15a and 15b are not particularly limited, such as carbon paper, carbon cloth, dense carbon graphite, carbon such as a carbon plate, or metal such as stainless steel, and those conventionally known are used. Can be used. The separators 15a and 15b have a function of separating air and fuel gas, and gas flow paths (grooves) 16a and 16b processed into a desired shape in order to secure the flow paths. It is desirable that it is formed, and conventionally known techniques can be used as appropriate. The thicknesses and sizes of the separators 15a and 15b and the shapes of the gas flow channel grooves 16a and 16b are not particularly limited, and may be appropriately determined in consideration of output characteristics of the obtained fuel cell.

(5) Gasket 17
The gasket 17 may be impermeable to gas, particularly oxygen or hydrogen gas, but generally, if it is configured by a single impermeable portion such as an O-ring made of a gas impermeable material. Good. Further, if necessary, a composite such as a gas seal tape with an adhesive, which is provided with an adhesive portion for adhesion with the electrolyte membrane 11 and the edges of the oxygen electrode and the fuel electrode catalyst layers 12a and 12b. It is good also as a simple structure. There are no particular limitations on the material that forms the impervious portion of the O-ring or gas seal tape as long as it is impervious to oxygen and hydrogen gas in a state where a predetermined pressure is applied after installation.

  Among the materials constituting the impervious portion, examples of the material constituting the O-ring include rubber materials such as fluorine rubber, silicon rubber, ethylene propylene rubber (EPDM), polyisobutylene rubber, and polytetrafluoroethylene (PTFE). , Fluorine polymer materials such as polyvinylidene fluoride (PVDF), polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and thermoplastic resins such as polyolefin and polyester.

  On the other hand, examples of the material constituting the impermeable portion such as a gas seal tape include polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVdF). . The material constituting the adhesive part such as a gas seal tape is not particularly limited as long as it can closely adhere the electrolyte membrane 11, the oxygen electrode and the fuel electrode catalyst layers 12a and 12b, and the gasket 17, but polyolefin, Hot melt adhesives such as polypropylene and thermoplastic elastomer, acrylic adhesives, olefin adhesives such as polyester and polyolefin can be used.

  The method for forming the gasket 17 is not particularly limited, and a known method can be used. For example, after the adhesive is applied on the electrolyte membrane 11 or on the electrolyte membrane 11 while covering the edge of the catalyst layer 12 so as to have a thickness of 5 to 30 μm, the gas-impermeable material as described above is used. Can be applied so that the thickness is 10 to 200 μm, and this is cured by heating at 25 to 150 ° C. for 10 seconds to 10 minutes. Alternatively, after a gas-impermeable material is formed into a sheet shape in advance, an adhesive is applied to the impermeable film to form a gasket 17, which is then placed on the electrolyte membrane 11 or a part of the gasket 17. You may affix on the electrolyte membrane 11, covering. At this time, the thickness of the impermeable portion is not particularly limited, but is preferably 15 to 40 μm. The thickness of the adhesive part is not particularly limited, but is preferably 10 to 25 μm.

  A commercially available gasket 17 may be purchased and used. The commercial items mentioned here include ordered items or custom-made items manufactured by the manufacturer according to the specifications (size, shape, material, characteristics, etc.) on the purchaser side.

  In the fuel cell having the configuration of the MEA 14 of the present invention, the catalyst layer 12, the GDL 13, and the electrolyte membrane 11 are desirably thin to improve the diffusibility of the fuel gas. No output is obtained. Therefore, it may be determined as appropriate so as to obtain an MEA (fuel cell) having desired characteristics.

  In addition, the MEA 14 and the fuel cell of the present invention have the above-described electrode catalyst layer 12 on the inside, the GDL 13 on the outside, the solid polymer electrolyte membrane 11 is used, and the electrolyte membrane 11 is sandwiched between the electrode catalyst layers 12 from both sides. The MEA 14 can be produced by hot pressing.

  As such hot press conditions, it is desirable to set appropriate temperature and pressure. Specifically, it is desirable to heat to 130 to 200 ° C., preferably 140 to 160 ° C., and hot press at 1 MPa to 5 MPa, preferably 2 MPa to 4 MPa for 1 to 10 minutes, preferably 3 to 7 minutes. If the hot press temperature is 130 ° C. or higher (the film is softened and bonding is easy. If the hot press temperature is 200 ° C. or lower, the film can be prevented from being decomposed. Also, the hot press pressure is 1 MPa or higher. If the hot press pressure is 5 MPa or less, problems such as film perforation can be prevented, and if the hot press time is 1 minute or longer, joining is easy. In addition, if the hot press time is 10 minutes or less, it is possible to prevent defects such as film perforations, etc. The atmosphere during hot pressing is preferably an atmosphere that does not affect the MEA, such as in nitrogen. It is desirable to carry out in an atmosphere.

  In addition, the method for producing the fuel cell of the present invention is not particularly limited, and can be assembled using a conventionally known production technique.

  Hereinafter, the present invention will be specifically described based on examples.

Example 1
100 g of carbon black (average particle size of primary particles 46 nm), 960 g of pure water and 40 g of nonionic surfactant Triton X-100 are mixed, and secondary particles of carbon black particles (primary particles are mixed with a jet mill). The agglomerated granular material) was dispersed to an average particle size of 0.5 μm. A PTFE dispersion equivalent to 40% (average particle diameter of PTFE particles 250 nm, equivalent to 60 wt% PTFE particles) was added to and mixed with this carbon black dispersion to obtain a carbon black PTFE dispersion. This carbon black PTFE dispersion was placed in an electrophoretic electrodeposition tank and electrodeposition was performed to obtain an electrodeposit (thickness of electrodeposition) having a thickness of 2 mm. The obtained electrodeposit (electrodeposited solid content) was dried with a hot air dryer at 150 ° C. for 6 hours. Then, after peeling an electrodeposit from the electrode (anode) surface, it baked and sintered at 360 degreeC for 2 hours with the electrothermal sintering furnace, and obtained the film | membrane (sheet | seat) of the mixed sintered body of thickness 1.9mm ( Production method of porous sintered coarse particles (Production method 2) and FIG. 6). The physical properties of the film (sheet) of this mixed sintered body were a tensile strength of 35 kgf / cm ² , a fracture deformation rate of 5%, and a specific resistance of 0.25 Ωcm.

The mixed sintered body film (sheet) was pulverized with a mixer and classified by sieving to obtain porous sintered coarse particles having a particle size of 150 μm or less. The porous sintered coarse particles having a particle size of 150 μm or less (average particle size of 120 μm) are filled in a hot press die (jig) and hot pressed at 360 ° C. and 100 kg / cm ² for 60 seconds to obtain GDL. It was. The obtained GDL has a thickness of 0.22 mm, and innumerable pores (large-diameter through holes) of about 0.1 mm are formed in the gaps between the porous sintered coarse particles. It was confirmed by SDL observation of GDL that they had a structure in which they were joined together in a stone wall shape (see FIG. 3A). From this, even when hot-pressing the packing of hard dense porous sintered coarse particles, the water-repellent particles and carbon particles in the porous sintered coarse particles do not flow, and the porous sintered coarse particles do not flow. The porous body sintered coarse particles themselves are not deformed or crushed so as to fill the gaps between the particles, and the porous sintered coarse particles are not reduced to a small particle size. It was found that gaps (relatively large vacancies) between the sintered coarse particles and gaps (relatively small vacancies) in the porous sintered coarse particles exist (remain).

Further, the gas permeability of GDL obtained in this example was 21.3 times better than that of GDL produced by the roll method. The physical properties of the GDL of this example were a tensile strength of 19 kgf / cm ² and a specific resistance of 0.15 Ωcm.

Comparative Example 1
A carbon black PTFE dispersion was prepared in the same manner as in Example 1. The same amount of isopropyl alcohol was added to and mixed with this carbon black PTFE dispersion to aggregate PTFE, followed by filtration. The filtrated material was kneaded with dry solvent naphtha and formed into a sheet with a roll to obtain a solid content sheet having a thickness of 1 mm. The solid content sheet was dried at 150 ° C. for 6 hours by a dryer to completely evaporate the solvent naphtha, and then fired at 360 ° C. for 2 hours in an electrothermal sintering furnace to form a mixed sintered body film having a thickness of 1 mm. (Sheet) was obtained. The physical properties of the film (sheet) of the obtained mixed sintered body were a tensile strength of 6 kg / cm ² , a fracture deformation rate of 110%, and a specific resistance of 5.6 Ωcm.

The mixed sintered body film (sheet) was pulverized with a mixer and classified by sieving to obtain porous sintered coarse particles having a particle size of 150 μm or less. The porous sintered coarse particles having a particle size of 150 μm or less (average particle size of 125 μm) are filled in a hot press die (jig) and hot pressed at 360 ° C. and 100 kg / cm ² for 60 seconds to obtain GDL. It was. The obtained GDL has a thickness of 0.2 mm, and innumerable pores having an average pore diameter of 0.1 μm are formed in the porous sintered coarse particles, and the porous sintered coarse particles are in close contact with each other without gaps. It was observed by GDL pore measurement (not shown) that it had an integral structure joined by (refusion). Therefore, the PTFE layer aggregated before filtration easily flows when hot-pressed, so that the gap between the porous sintered coarse particles is blocked, and a large void is formed in the gap between the porous sintered coarse particles. It was found that does not exist (does not remain).

  Since the number of relatively large pores is 1 to 2 times the number of coarse particles, the smaller the particle size, the larger the number.

Moreover, the gas permeability of GDL obtained in this comparative example was almost the same as that of the gas diffusion layer produced by the roll method. The physical properties of the GDL of this comparative example were a tensile strength of 36 kgf / cm ² and a specific resistance of 0.28 Ωcm.

Example 2
A dense film of a mixed sintered body 55 having a thickness of 500 μm obtained by drying and firing the solid content 53 phase-separated and concentrated by the above-described method for producing coarse sintered porous particles (Production Method 1) 56 (referred to as a fired sheet) was produced (see FIG. 5).

  Specifically, the carbon black-PTFE dispersion obtained in the same manner as in the above production method 2 was not agglomerated before filtration as in Comparative Example 1, and 4% Triton X-100 (nonionic surfactant) The dispersion (containing 13% solids) was placed in a glass bottle and left in a water bath at 70.0 ° C. for 24 hours, whereupon it precipitated at the bottom. The upper liquid was removed to obtain a concentrated liquid having a solid content of 44.6%. The yield of solid content was 99%. The concentrated liquid was evaporated at 80 ° C., dried at 150 ° C. for 6 hours, and then sintered at 360 ° C. for 3 hours to obtain a mixed sintered body film (dry sintered sheet).

The physical properties of the film (dry sintered sheet) of the obtained mixed sintered body are as follows: tensile strength 23 kgf / cm ² , cutting deformation rate 4%, specific resistance 0.26 Ωcm, water pressure strength by water pressure evaluation test is 18 kgf / cm ² .

  In the water pressure resistance evaluation test, as shown in FIG. 8, a sample sheet (dry fired sheet) 81 is set on the pressure-resistant porous body 85 in the water pressure resistance test apparatus 83, and the water pressure is gradually applied to the entire upper surface side of the sheet 81. In addition, the water pressure (water pressure strength) when leaking from the sample sheet 81 was measured. The results are shown in Table 1.

Example 3
By the above-described method for producing porous sintered coarse particles (Production Method 2), the solid content 65 deposited by electrodeposition is dried and fired to form a dense film of a mixed sintered body having a thickness of 500 μm (in Table 1, an electrodeposition sheet). A sample of 66 (see FIG. 6) was produced.

  Specifically, 100 g of carbon black, 40 g of Triton X-100 as a nonionic surfactant, and 900 g of pure water were mixed, and dispersed to an average particle size of 0.5 μm by a jet mill. A 40% equivalent PTFE dispersion was added to and mixed with this carbon black dispersion to obtain a carbon black-PTFE dispersion. This carbon black-PTFE dispersion was placed in an electrophoresis electrodeposition tank to obtain an electrodeposit having a thickness of 2 mm. After drying at 150 ° C. for 4 hours, sintering was performed at 360 ° C. (where PTFE as the water repellent particle has a melting point of 327 ° C.) for 2 hours to prepare an electrodeposition sheet having a thickness of 1.6 mm.

The resulting electrodeposition properties of deposited sheets, tensile strength 36 Kgf / cm ^2, the cutting deformation of 5%, the specific resistance 0.25Omucm, bulb pressure strength by water pressure resistance evaluation test was 16 kgf / cm ^2. The water pressure resistance evaluation test was performed in the same manner as in Example 2, and the results are shown in Table 1.

Example 4
By using the porous sintered coarse particles obtained by pulverizing the dried and fired sheet obtained in the same manner as in Example 2 with a mixer and classifying with a sieve by the GDL production method (Production Method 4) described above, A sample of GDL (referred to as a re-deposition sheet in Table 1) was produced by pressing.

Specifically, the dried and fired sheet obtained in the same manner as in Example 2 was pulverized with a mixer and classified with a sieve to obtain porous sintered coarse particles having a particle diameter of 150 μm or less. The porous sintered coarse particles having a particle size of 150 μm or less (average particle size of 120 μm) are filled in a hot press die (jig) and hot pressed at 360 ° C. and 100 kg / cm ² for 60 seconds to obtain a thickness. A 500 μm GDL (re-deposition sheet) was prepared. The obtained re-deposition sheet had innumerable through-holes having an average pore diameter of 0.1 μm (small-diameter through holes of 0.2 μm or less) and 5 μm or more (large-diameter through-holes of 1 μm or more). In addition, the re-deposition sheet remained large-diameter holes (large-diameter through holes) even after hot pressing (see FIG. 3). Further, the gas permeability of the re-deposition sheet was 20 times that of the GDL produced by the roll method because of the large diameter holes (large diameter through holes).

The physical properties of the re-formed film obtained were as follows: tensile strength 20 kgf / cm ² , specific resistance 0.26 Ωcm, and water pressure resistance according to the water pressure evaluation test was 1 kgf / cm ² or less (a value significantly different from the tensile strength) I understood it). The water pressure resistance evaluation test was performed in the same manner as in Example 2, and the results are shown in Table 1.

Example 5
The solid content obtained by phase separation and concentration was dried and fired by the above-described method for producing coarse sintered porous particles (Production Method 1) to prepare a mixed sintered compact film (see FIG. 5).

  Specifically, the carbon black-PTFE dispersion obtained in the same manner as in the above production method 2 was not agglomerated before filtration as in Comparative Example 1, and 4% Triton X-100 (nonionic surfactant) The dispersion (containing 13% solids) was placed in a glass bottle and left in a water bath at 70.0 ° C. for 24 hours, whereupon it precipitated at the bottom. The upper liquid was removed to obtain a concentrated liquid having a solid content of 42%. The 42% concentrated liquid was evaporated at 80 ° C., dried at 150 ° C., and sintered at 360 ° C. for 1 hour to obtain a dense film (structure sheet) of a mixed sintered body.

  The obtained mixed sintered body film (structure sheet) was pulverized with a mixer and classified with a sieve to obtain porous sintered coarse particles having a particle diameter of 150 μm or less. FIG. 9A shows a drawing showing an SEM image of the cross section of the porous sintered coarse particles obtained in Example 5. FIG.

  Furthermore, the pore diameter data of the film (structure sheet) of the mixed sintered body are shown in FIG. Here, in the measurement of the pore diameter data of the film (sheet) of the mixed sintered body, a contact angle of 114 °, which is a value on a smooth PTFE surface, was used. The result almost coincided with the result of mercury porosimeter. The contact angle of the sample surface is observed to be 140 ° or more, but this is an uneven effect.

Comparative Example 2
A mixed sintered body film (sheet) was prepared in the same manner as in Comparative Example 1, and this mixed sintered body film (sheet) was pulverized with a mixer and classified by sieving. Coarse coarse particles were obtained. FIG. 9B shows a drawing showing an SEM image of the cross section of the porous sintered coarse particles obtained in Comparative Example 2.

  From the SEM images of FIG. 9A of Example 5 and FIG. 9B of Comparative Example 2, it was confirmed that the porous sintered coarse particles of the present invention hardly show fibrillation of PTFE (water repellent particles). On the other hand, the porous sintered coarse particles of Comparative Example 1 produced in the same manner as the GDL used in the conventional salt electrolysis oxygen cathode may show fibrillation of PTFE (water repellent particles). It could be confirmed.

  Further, from the measurement result of the pore distribution by the water porosimeter of FIG. 10 in Example 5, the porous sintered coarse particles of the present invention have a relatively small diameter of 0.2 μm (200 nm) or less, particularly an average pore diameter of about 70 nm. It was confirmed that many holes were formed without being crushed.

It is the cross-sectional schematic which represented typically the basic structure (single cell structure) of the fuel cell using GDL of this invention. FIG. 2A is a schematic cross-sectional view schematically showing a basic configuration of an MEA using the GDL of the present invention. FIG. 2B shows the GDL in FIG. 2A and the relatively large pores (large-diameter through holes) formed between the porous sintered coarse particles and the porous sintered coarse particles. It is the schematic which expanded and represented typically a part of. 2C shows carbon particles and water repellent particles that constitute the porous sintered coarse particles of FIG. 2B, and relatively small pores (small-diameter through-holes) formed between the carbon particles and / or the water repellent particles. It is the schematic which expanded and typically represented one porous body sintered coarse particle so that the mode of) might be understood. FIG. 2D is a schematic cross-sectional view schematically showing the basic configuration of MEA using GDL composed of a base material and a carbon particle layer (MIL) having the configuration of the present invention. FIG. 3 is a photomicrograph of the surface of the GDL showing how the porous sintered coarse particles constituting the GDL of the present invention are connected. FIG. 3A is a surface photograph of GDL formed by porous sintered coarse particles having an average particle diameter of 150 μm, and FIG. 3B is a surface photograph of GDL formed by porous sintered coarse particles having an average particle diameter of 250 μm. is there. FIGS. 4A to 4C are schematic diagrams schematically showing a model of an overlaid structure, a cobblestone valley structure, and a cobblestone structure included in an actual stone wall (masonry) included in the stone wall structure referred to in the present invention. 4D to 4H schematically show a stratified stacking, a turbulent stacking, a random stratified stacking, a crushed stone piled up structure, and a crushed stone stacked structure model in an actual stone wall (masonry) that is not included in the stone wall structure referred to in the present invention. FIG. As a typical embodiment of the method for producing porous sintered coarse particles used in the GDL of the present invention (referred to as production method 1), the production process until the formation of a mixed sintered body for porous sintered coarse particles is shown. FIG. As another typical embodiment of the method for producing porous sintered coarse particles used in the GDL of the present invention (referred to as production method 2), the production process until forming a sintered body for porous sintered coarse particles is described. It is the process schematic represented. It is process schematic which represented typical embodiment of the manufacturing method of GDL using the mixed sintered compact for porous body sintered coarse particles obtained by the manufacturing method 1 or 2. It is the schematic which showed only the outline | summary of the water-pressure-resistant evaluation test apparatus used in the Example very simply. FIG. 9A is a drawing showing an SEM image of a cross section of porous sintered coarse particles obtained in Example 5. FIG. 9B is a drawing showing an SEM image of a cross section of the porous sintered coarse particles obtained in Comparative Example 2. It is drawing which shows the pore diameter data (pore distribution by a water porosimeter) of the film | membrane (structure sheet | seat) of the mixed sintered compact obtained in Example 5. FIG.

Explanation of symbols

10 Fuel cell,
11 electrolyte membrane,
12 Fuel cell electrode catalyst layer,
12a anode catalyst layer,
12b cathode catalyst layer,
13 Gas diffusion layer,
13a Anode gas diffusion layer,
13b cathode gas diffusion layer,
131a MIL of anode gas diffusion layer,
131b MIL of cathode gas diffusion layer,
132a A base material for the anode gas diffusion layer,
132b Cathode gas diffusion layer substrate;
14 MEA,
15a anode palator,
15b cathode palator,
16a Anode side gas flow path (groove),
16b Cathode side gas flow path (groove),
17 gasket,
21 porous sintered coarse particles,
211 carbon particles,
212 water repellent particles,
213 small-diameter through-holes in porous sintered coarse particles,
22 large-diameter through-holes between porous sintered coarse particles,
51, 61 carbon particle dispersion,
52, 62 carbon / water repellent particle dispersion,
53 Solid content by phase separation concentration,
54 base material,
55 Mixed sintered body,
56, 66, 71 Dense film (sheet) of mixed sintered body,
63 Electrophoretic electrodeposition cathode
64 Electrophoresis wearing anode,
65 Electrodeposited solids (electrodeposits),
72 porous sintered coarse particles,
73 Porous sintered coarse particle dispersion (reink),
74 base material,
75 GDL,
76 GDL film (sheet),
81 Sample sheet (dry fired sheet, electrodeposition sheet, re-deposition sheet)
83 Water pressure test equipment,
85 Pressure-resistant porous material.

Claims (18)

  Porous sintered coarse particles with a myriad of relatively small-diameter through-holes made of carbon particles and water repellent particles are connected to each other with a relatively large diameter, with moderate gaps. A gas diffusion layer for a fuel cell having an infinite number of relatively small-diameter through-holes and relatively large-diameter through-holes, wherein the innumerable holes are formed. A gas diffusion layer for a fuel cell configured using porous sintered coarse particles,
The porous sintered coarse particles are formed using carbon particles and water repellent particles,
The average pore diameter of a large number of pores formed in the gaps between the carbon particles and / or the water repellent particles is smaller than the average pore diameter of the pores formed in the gaps between the porous sintered coarse particles. A gas diffusion layer for a fuel cell.   3. The gas diffusion layer for a fuel cell according to claim 1, wherein the gas diffusion layer for a fuel cell has a structure in which the adjacent coarse particles closest to the porous sintered coarse particles are joined to each other. 4. The fuel cell according to claim 1, wherein the porous sintered coarse particles have a tensile strength of 20 kgf / cm ² or more and a fracture deformation rate of 20% or less. 5. Gas diffusion layer.   5. The fuel cell gas diffusion layer according to claim 1, wherein the porous sintered coarse particles have an average particle diameter of 1 to 500 μm.   An average pore size of 0 or less formed between the carbon particles and / or the water repellent particles and an average pore size of 0 or less and a relatively small through-hole formed between the porous sintered coarse particles. The gas diffusion layer for a fuel cell according to any one of claims 1 to 5, wherein the fuel cell gas diffusion layer has a large number of pores or relatively large through holes having a diameter of 5 µm or more.   The gas diffusion layer for a fuel cell according to any one of claims 1 to 6, wherein the water repellent particles have a tensile strength of 10 MPa or more.   The gas diffusion layer for a fuel cell according to any one of claims 1 to 7, wherein the water repellent particles are polytetrafluoroethylene particles.   The gas diffusion layer for a fuel cell according to any one of claims 1 to 8, wherein the water repellent particles are not fibrillated. The porous sintered coarse particles are prepared by dispersing carbon particles and water repellent particles in water in the presence of a nonionic surfactant to prepare a carbon / water repellent particle dispersion,
Concentrating the carbon / water repellent particle dispersion using a phase separation phenomenon of a nonionic surfactant,
Furthermore, the phase-separated and concentrated product is dried, heated and sintered to form a mixed sintered body,
The gas diffusion layer for a fuel cell according to any one of claims 1 to 9, wherein the gas diffusion layer is obtained by pulverizing the mixed sintered body. The porous sintered coarse particles are prepared by dispersing carbon particles and water repellent particles in water in the presence of a nonionic surfactant to prepare a carbon / water repellent particle dispersion,
Electrodeposit the carbon / water repellent particle dispersion to deposit a solid,
Sintering the solid content to form a mixed sintered body,
The gas diffusion layer for a fuel cell according to any one of claims 1 to 9, wherein the gas diffusion layer is obtained by pulverizing the mixed sintered body. The porous sintered coarse particles according to claim 10 or 11 are dispersed in a solvent to form a porous sintered coarse particle dispersion.
The porous body sintered coarse particle dispersion is applied to a base material, dried, hot-pressed to form a film, and obtained by separating from the base material. A gas diffusion layer for a fuel cell according to Item. The solvent is at least one solvent selected from the group consisting of alkane hydrocarbons (C _n H _{2n + 2} ; where n = 10 to 16) and solvents containing these. A gas diffusion layer for a fuel cell according to 1.   14. The diameter and number of pores or relatively large through-holes formed between porous sintered coarse particles with a pore former are controlled. The gas diffusion layer for fuel cells as described.   A gas diffusion layer for a fuel cell, wherein the gas diffusion layer according to any one of claims 1 to 14 is bonded to a base material of a gas diffusion layer having a thickness of 100 to 200 µm as a carbon particle layer. .   A fuel cell membrane-electrode assembly comprising the fuel cell gas diffusion layer according to any one of claims 1 to 15.   17. The fuel cell according to claim 16, wherein a catalyst layer containing an electrode catalyst and an electrolyte is provided on the surface of the gas diffusion layer for the fuel cell, and is disposed on both surfaces of the electrolyte membrane and hot pressed. Membrane-electrode assembly.   A fuel cell comprising the membrane-electrode assembly for a fuel cell according to claim 16 or 17.