JP6572665B2 - Membrane electrode assembly and fuel cell including the same - Google Patents

Description

  The present invention relates to a membrane electrode assembly and a fuel cell including 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 power sources for electric vehicles 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 polymer electrolyte fuel cell (PEFC) is expected as a power source for electric vehicles because it operates at a relatively low temperature.

  The polymer electrolyte fuel cell has a structure in which a plurality of single cells that exhibit a power generation function are stacked. This single cell includes a polymer electrolyte membrane, a membrane electrode assembly (MEA) having a pair of catalyst layers and a pair of gas diffusion layers (GDL) that are sequentially formed on both surfaces of the membrane. And MEA which each single cell has is electrically connected with MEA of an adjacent single cell through a separator. Thus, a fuel cell stack is comprised by laminating | stacking a single cell. The fuel cell stack functions as power generation means that can be used for various applications.

  Among the above-described configurations, the gas diffusion layer functions as a gas flow path for diffusing the fuel gas and the oxidizing gas (reactive gas) supplied to the membrane electrode assembly and spreading them throughout the catalyst layer.

  As a gas diffusion layer base material constituting the gas diffusion layer, for example, a porous member having conductivity and gas permeability such as carbon paper and carbon cloth is known. These typically include sharp edges that extend outward due to the nature. In particular, when the gas diffusion layer base material is molded so as to have a predetermined size, the sharp end tends to be directed outward.

  By the way, the electrolyte membrane is generally a thin film, and is easily damaged from the outside because of its thinness. Therefore, if the gas diffusion layer including the sharp end contacts the electrolyte membrane and the electrolyte membrane is damaged, a cross leak may occur. This phenomenon also occurs through the microporous layer. When the cross leak occurs, the power generation performance and fuel consumption are reduced.

  In order to solve such a problem, the following configurations are conventionally known.

  That is, an electrolyte membrane and a catalyst layer that sandwiches the electrolyte membrane from both sides, and the outer peripheral end portion of the catalyst layer is located inside the outer peripheral end portion of the electrolyte membrane, and the outer periphery of the catalyst layer is disposed. It is a structure with the membrane electrode assembly which has the convex part protruded from the surface.

  By setting it as such a structure, it is trying to suppress the pressing force which an electrolyte membrane receives from a gas diffusion layer in the outer peripheral area | region of a catalyst layer by the height of a convex part (for example, patent document 1 FIG. 8).

2010-257634

  However, in the configuration of Patent Document 1, damage to the electrolyte membrane cannot be sufficiently suppressed.

  Accordingly, an object of the present invention is to provide a novel membrane electrode assembly capable of protecting the electrolyte membrane constituting the membrane electrode assembly.

  The present inventors have intensively studied to solve the above problems. As a result, it has been found that the above problem can be solved by providing a portion formed by disposing a resin in at least a part of the outer peripheral region of the gas diffusion layer and / or a surface of at least a part of the outer peripheral region. Completed.

  The membrane / electrode assembly of the present invention has a portion formed by arranging a resin in at least a part of the outer peripheral region of the gas diffusion layer and / or at least a part of the surface of the outer peripheral region. The resin protects the electrolyte membrane from sharp edges extending outward in the gas diffusion layer. As a result, a decrease in power generation performance and a decrease in fuel consumption can be suppressed.

It is a schematic sectional drawing which shows the basic composition of the polymer electrolyte fuel cell which concerns on one Embodiment of this invention. It is a schematic sectional drawing which shows the basic composition of the membrane electrode assembly which concerns on the 1st Embodiment of this invention. It is a schematic sectional drawing which shows the basic composition of the membrane electrode assembly which concerns on the 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the basic composition of the membrane electrode assembly which concerns on the 3rd Embodiment of this invention. It is a schematic sectional drawing which shows the basic composition of the membrane electrode assembly which concerns on the 4th Embodiment of this invention. It is a schematic sectional drawing which shows the basic composition of the membrane electrode assembly which concerns on the 5th Embodiment of this invention. It is a schematic sectional drawing which shows the basic composition of the membrane electrode assembly which concerns on the 6th Embodiment of this invention. It is a figure which shows the manufacturing method of the membrane electrode assembly which concerns on one Embodiment of this invention. It is a figure which shows the manufacturing method of the membrane electrode assembly which concerns on other embodiment of this invention. It is a result of the maximum piercing stress measurement of an Example and a comparative example.

  Hereinafter, an embodiment of a fuel cell of the present invention will be described in detail with reference to the drawings as appropriate. However, the present invention is not limited only to the following embodiments. Each drawing is exaggerated for convenience of explanation, and the dimensional ratio of each component in each drawing may be different from the actual one. Further, in the case where the embodiment of the present invention is described with reference to the drawings, the same reference numerals are given to the same elements in the description of the drawings, and a duplicate description is omitted.

  In this specification, “X to Y” indicating a range means “X or more and Y or less”. Unless otherwise specified, measurement of operation and physical properties is performed under conditions of room temperature (20 to 25 ° C.) / Relative humidity 40 to 50%.

  The membrane electrode assembly of one embodiment of the present invention can be preferably applied to a fuel cell. Therefore, the present invention also provides a fuel cell including a membrane electrode assembly. Below, the form which applied the membrane electrode assembly of one Embodiment of this invention to the fuel cell is mentioned as an example, and is demonstrated.

<Fuel cell>
A fuel cell includes a membrane electrode assembly (MEA), a pair of separators including an anode side separator having a fuel gas flow path through which fuel gas flows and a cathode side separator having an oxidant gas flow path through which oxidant gas flows. Have.

  A membrane electrode assembly (MEA) according to an embodiment of the present invention includes at least a catalyst layer on both sides of an electrolyte membrane; a microporous layer, a base that forms a main body, and a sharp tip extending outward from the outer surface of the base A gas diffusion layer including a conductive gas diffusion layer substrate including an end, and in this order, at least one of the gas diffusion layers being in contact with the gas diffusion layer The catalyst layer having a larger outer peripheral area in the planar direction than the catalyst layer and the catalyst layer in contact with the gas diffusion layer is smaller in the planar direction than the electrolyte membrane, and the inside of at least a part of the outer peripheral area and // A membrane electrode assembly having a portion where a resin is disposed on at least a part of the surface of the outer peripheral region.

  With such a configuration, the resin protects the electrolyte membrane from the sharp end extending outward in the gas diffusion layer. As a result, cross leaks, and hence power generation performance and fuel consumption are prevented from being reduced. In addition, the sharp end of the substrate is prevented from penetrating the microporous layer and directly contacting the electrolyte membrane.

  First, the basic structure of a polymer electrolyte fuel cell (PEFC) 1 according to an embodiment of the present invention will be described with reference to FIG. 1, and a form having a portion where a resin is arranged will be described with reference to FIG. explain.

  As shown in FIG. 1, the PEFC 1 includes an electrolyte membrane 2 and a pair of catalyst layers (an anode catalyst layer 3a and a cathode catalyst layer 3c) that sandwich the membrane. The laminate of the electrolyte membrane 2 and the catalyst layers (3a, 3c) is further sandwiched between a pair of gas diffusion layers (GDL) (the anode gas diffusion layer 4a and the cathode gas diffusion layer 4c). Thus, the PEFC 1 constitutes the membrane electrode assembly (MEA) 10 in a state where the electrolyte membrane 2, the pair of catalyst layers (3a, 3c) and the pair of gas diffusion layers (4a, 4c) are laminated.

  Here, the anode gas diffusion layer 4a and the cathode gas diffusion layer 4c are formed by laminating a gas diffusion layer base material (4ag, 4cg) and a microporous layer (4am, 4cm). Here, a microporous layer (4am, 4cm) is provided on the catalyst layer (3a, 3c) side. That is, the PEFC 1 according to an embodiment of the present invention includes at least a catalyst layer (3a, 3c) on each side of the electrolyte membrane 2, a microporous layer (4am, 4cm), and a gas diffusion layer base material (4ag, 4cg). And a gas diffusion layer including: in this order.

  In PEFC1, the MEA 10 is further sandwiched between a pair of separators (anode separator 5a and cathode separator 5c). In FIG. 1, the separators (5 a, 5 c) are illustrated so as to be positioned at both ends of the illustrated MEA 10. However, in a fuel cell stack in which a plurality of MEAs are stacked, the separator is generally used as a separator for an adjacent PEFC (not shown). In other words, in the fuel cell stack, the MEAs are sequentially stacked via the separator to form a stack. In an actual fuel cell stack, a gas seal portion (gasket) is disposed between the separators (5a, 5c) and the electrolyte membrane 2 or between the PEFC 1 and another PEFC adjacent thereto. These descriptions are omitted in FIG.

  The separators (5a, 5c) are obtained, for example, by forming a concavo-convex shape as shown in FIG. 1 by subjecting a thin plate having a thickness of 0.5 mm or less to a press treatment. The convex part seen from the MEA side of the separator (5a, 5c) is in contact with the MEA 10. Thereby, the electrical connection with MEA10 is ensured. Further, a recess (space between the separator and the MEA generated due to the concavo-convex shape of the separator) viewed from the MEA side of the separator (5a, 5c) is a gas for circulating gas during operation of the PEFC 1 Functions as a flow path. Specifically, fuel gas (for example, hydrogen) is circulated through the anode gas channel 6a of the anode separator 5a, and oxidant gas (for example, air) is circulated through the cathode gas channel 6c of the cathode separator 5c. Let

  On the other hand, the recess viewed from the side opposite to the MEA side of the separator (5a, 5c) serves as a refrigerant flow path 7 for circulating a refrigerant (for example, water) for cooling the PEFC during operation of the PEFC 1. . Further, the separator is usually provided with a manifold (not shown). This manifold functions as a connection means for connecting cells when a stack is formed. With such a configuration, the mechanical strength of the fuel cell stack can be ensured.

  In addition, in embodiment shown in FIG. 1, the separator (5a, 5c) is shape | molded by the uneven | corrugated shape. However, the separator is not limited to such a concavo-convex shape, and may be any form such as a flat plate shape and a partially concavo-convex shape as long as the functions of the gas flow path and the refrigerant flow path can be exhibited. Also good.

[Membrane electrode assembly]
FIG. 2 is a schematic sectional view showing the first embodiment of the membrane electrode assembly of the present invention.

(Gas diffusion layer)
In FIG. 2, the gas diffusion layers (4a, 4c) are composed of a gas diffusion layer base material (4ag, 4cg) and a microporous layer (4am, 4cm) disposed adjacent to the gas diffusion layer base material. The microporous layer (4am, 4cm) is disposed on the catalyst layer (3a, 3c) side.

  In the gas diffusion layer (4a, 4c) of the present embodiment, an intermediate layer may be provided between the gas diffusion layer substrate (4ag, 4cg) and the microporous layer (4am, 4cm). However, a form in which the microporous layer (4am, 4cm) is directly disposed on the gas diffusion layer substrate (4ag, 4cg) is preferable. This is because drainage can be performed efficiently without increasing the resistance of the entire gas diffusion layer (4a, 4c), and the battery characteristics are improved.

  The gas diffusion layer (4a, 4c) has a function of promoting the diffusion of the gas (fuel gas or oxidant gas) supplied through the gas flow path of the separator into the catalyst layer (3a, 3c), and an electron conduction path. As a function.

  In one embodiment of the membrane electrode assembly of the present invention, the material constituting the gas diffusion layer base material (4ag, 4cg) includes a base portion that forms the main body and a sharp tip that extends outward from the outer surface of the base portion. Including ends. More specifically, the material constituting the gas diffusion layer base material (4ag, 4cg) is, for example, a carbon woven fabric formed of carbon fibers such as carbon paper or carbon cloth, a paper-like paper body, a felt, or a non-woven fabric. Examples thereof include a sheet-like material having conductivity and porosity; and a wire mesh, a foam metal, an expanded metal, a precision press-worked plate, a metal mesh, a metal fine wire sintered body, a metal nonwoven fabric, and the like.

  Here, the “base forming the main body” in the case of carbon paper refers to a conductive porous sheet-like material formed of carbon fibers. In addition, “a sharp end extending outward from the outer surface of the base” is usually a porous sheet-like material formed of carbon fiber, and the end of the fiber faces outward. There is a protruding part, which means it. In the case of a wire mesh, the “base portion constituting the main body” refers to a porous sheet made by knitting or overlapping wire materials. In addition, the “sharp end extending outward from the outer surface of the base” is a portion of a wire mesh or the like that usually protrudes outward due to the surface of the wire constituting the wire mesh being scraped or peeled off. There is and it means.

  On the other hand, in the first embodiment of the present invention, as shown in FIG. 2, the gas diffusion layers (4a, 4c) are in contact with the catalyst diffusion layers (3a, 3c). ) It has a larger outer peripheral area in the plane direction. With such a configuration, the effective reaction area of the catalyst layers (3a, 3c) is utilized to the maximum extent. Further, the catalyst layers (3a, 3c) in contact with the gas diffusion layers (4a, 4c) are smaller in the planar direction than the electrolyte membrane 2. In other words, the electrolyte membrane 2 is larger in the planar direction than the catalyst layers (3a, 3c). Thereby, the effective reaction area of the catalyst layers (3a, 3c) is utilized to the maximum extent.

  However, in the membrane electrode assembly 10 having such a magnitude relationship, the sharp end portion extending outward of the gas diffusion layer base material (4ag, 4cg) is likely to come into contact with the electrolyte membrane 2. This is the same even if there is a microporous layer (4am, 4cm).

  The electrolyte membrane is generally a thin film, and is easily damaged from the outside because of its thinness. When the sharp end portion extending toward the outside of the gas diffusion layer base material (4ag, 4cg) is in direct contact with the electrolyte membrane 2, the electrolyte membrane 2 may be pierced, which is more likely to be damaged. . This is the same even if the microporous layer is interposed, and the microporous layer is generally a thin film. If the electrolyte membrane 2 is damaged, a cross leak may occur. When the cross leak occurs, the power generation performance and fuel consumption are reduced.

  On the other hand, in the first embodiment of the membrane electrode assembly of the present invention shown in FIG. 2, at least one of the regions in the gas diffusion layer (4a, 4c) larger in the plane direction than the catalyst layers (3a, 3c). Inside the part, there is a portion R in which resin is arranged. With such a configuration, the resin protects the electrolyte membrane 2 from a sharp portion of the gas diffusion layer base material. As a result, a decrease in power generation performance and a decrease in fuel consumption can be suppressed. More specifically, the resin covers the sharp end portion (protruding fiber in the case of carbon fiber) that extends outward, and the protruding fiber is in direct contact with the electrolyte membrane 2. Suppress. The resin also has an effect of preventing deformation of the outer peripheral region of the gas diffusion layer base material and hardening the outer peripheral region of the microporous layer. The “region larger in the planar direction than the catalyst layers (3a, 3c)” is also simply referred to as “outer peripheral region” in the present specification.

  The gas diffusion layers (4a, 4c) are generally formed by punching, cutting, or the like in the manufacturing process. In the gas diffusion layers (4a, 4c) thus formed (particularly, the outer peripheral region), a sharp member constituting the base portion that has been cut from the base portion that forms the main body remains. There is a case. Then, when the membrane / electrode assembly 10 is manufactured or when the membrane / electrode assembly 10 is used (that is, when the fuel cell is operated), the sharp member may drop out and come into contact with the electrolyte membrane 2. There is also.

  On the other hand, in one embodiment of the membrane electrode assembly of the present invention, a sharp member that is cut (or possibly cut) may be fixed to the base portion that forms the main body by the resin. it can. By doing so, it is possible to suppress such dropout and improve the reliability of the fuel cell.

  In addition, in one Embodiment of the membrane electrode assembly of this invention, the site | part R by which resin is arrange | positioned should just have in the inside of at least one part of the outer peripheral area | region of a gas diffusion layer (4a, 4c). Thus, for example, in a frame-shaped outer peripheral region, at least one side, two sides, or three sides have a portion R in which resin is arranged, and the other side has an outer peripheral region of the gas diffusion layer (4a, 4c). An intermediate layer may be provided so that the electrolyte membrane 2 does not come into direct contact with the electrolyte membrane 2. By adopting such a form, the manufacturability of the membrane electrode assembly is improved, and the yield is improved and the cost is reduced.

  Further, in at least a part of the outer peripheral region of the gas diffusion layer, the thickness of the resin may not coincide with the thickness of the outer peripheral region of the gas diffusion layer, and preferably 50% of the thickness of the outer peripheral region of the gas diffusion layer. % Or more, preferably 70% or more, and more preferably 90% or more. Further, the resin thickness may be partially different in at least a part of the outer peripheral region of the gas diffusion layer. At this time, it is more preferable to arrange on the microporous layer side.

  The outer peripheral region is not limited to a rectangular frame shape, and each corner may be rounded.

  Moreover, resin does not need to be arrange | positioned continuously in each edge | side. FIG. 3 is a schematic cross-sectional view in which one side of the outer peripheral region of the gas diffusion layer (4a, 4c) is cut so as to be orthogonal to the gas flow path. As shown in FIG. 3, in the outer peripheral region of the gas diffusion layers (4a, 4c), the parts R where the resin is arranged are provided discontinuously (in FIG. 3, the parts R are provided in a scattered manner). ing).

  By providing the resin discontinuously as described above, it is possible to obtain the same effect as the intended effect of the present invention while reducing the amount of the resin used.

  In addition, although the location in particular where the site | part R where resin is arrange | positioned is located is not restrict | limited, as FIG. 3 shows, the convex part (rib) of a separator (5a, 5c) is right above (it is right below depending on direction). It is good to provide. By providing in this way, improvement in the mechanical strength of the membrane electrode assembly can be expected. In addition, the gas diffusion layer can be in contact with the electrolyte membrane to protect a portion that is easily damaged, and has an effect of suppressing cross leak.

  In addition, when positioning the site | part R where resin is arrange | positioned discontinuously, about 5 to 50% or about 9 to 25% is provided with respect to each projection area difference of a gas diffusion layer and a catalyst layer, for example. Is good.

  Moreover, in 1st Embodiment of the membrane electrode assembly of this invention shown by FIG. 2, the outer peripheral edge of a catalyst layer (3a, 3c) and the inner peripheral edge of the site | part R where resin is arrange | positioned are flush. It is. As shown in FIG. 4, according to the third embodiment, the portion R where the resin is arranged may be provided toward the inside of the gas diffusion layers (4 a, 4 c). However, the portion R where the resin is provided inward may interfere with the electrode reaction. Therefore, it is preferable to position the portion R where the resin is provided so as to ensure an electrode effective area of the gas diffusion layer of 85%, 90%, or 97%.

  In the first embodiment of the membrane / electrode assembly of the present invention shown in FIG. 2, the gas diffusion layers (4a, 4c) are also provided inside at least a part of the outer peripheral region of the microporous layer (4am, 4cm). It has the site | part R where resin is arrange | positioned.

  Here, since the microporous portion is more fragile than the gas diffusion layer base material, the end portion is broken or cracked when the member is cut. As a result, there is a risk of damage due to the gas diffusion layer fibers coming into direct contact with the electrolyte membrane. In addition, even when a microporous layer is separately laminated on the base material, a portion that is not covered by the microporous layer is generated on the outer peripheral portion due to a stacking position shift or a size error, and gas is directly applied to the electrolyte membrane. There is a risk of damage due to contact of the diffusion layer fibers. On the other hand, according to the present invention, the electrolyte membrane 2 constituting the membrane electrode assembly 10 is protected from the sharp end extending outward by the resin. Thereby, even if the sharp end portion is exposed through the crack portion, the sharp end portion is suppressed from coming into direct contact with the electrolyte membrane 2. This leads to a decrease in power generation performance and a reduction in fuel consumption.

  Moreover, when producing the gas diffusion layer which has the site | part R by which resin is arrange | positioned, resin fills a crack part normally. Therefore, it is further suppressed that the sharp end directly contacts the electrolyte membrane 2, which also leads to suppression of power generation performance and fuel consumption.

  Moreover, in 1st Embodiment of the membrane electrode assembly of this invention shown by FIG. 2, the thickness of the site | part R and the thickness of a gas diffusion layer (4a, 4c) correspond. However, the thickness of the part R and the thickness of the gas diffusion layers (4a, 4c) do not have to be matched.

  In the fourth embodiment of the membrane electrode assembly of the present invention shown in FIG. 5, a portion in which resin is arranged in the surface layer region on the electrolyte membrane 2 side in the outer peripheral region of the gas diffusion layers (4 a, 4 c). R is included. In this embodiment, the surface layer region on the separator (5a, 5c) side does not have the portion R where the resin is arranged. By setting it as such a form, resin can be used efficiently and the technical effect similar to the form of FIG. 2 can be acquired.

  Here, among the outer peripheral regions of the gas diffusion layers (4a, 4c), the surface layer region on the electrolyte membrane 2 side preferably includes the outer peripheral region of the microporous layer (4am, 4 cm). Moreover, it is preferable that the surface layer area | region by the side of a microporous layer is included among the outer peripheral area | regions of a gas diffusion layer base material (4ag, 4cg). Here, the surface layer region on the microporous layer side refers to the gas diffusion layer base material (4ag, 4cg) from the surface on the microporous layer side of the gas diffusion layer base material toward the separator (5a, 5c) side. It is preferably about 15%, about 20%, or about 50% of the thickness. As this number increases, the reliability of the fuel cell improves.

  In addition, the fifth embodiment of the membrane electrode assembly of the present invention shown in FIG. 6 is a portion in which resin is also disposed on the surface on the electrolyte membrane 2 side in the outer peripheral region of the gas diffusion layers (4a, 4c). It is a form having R. By adopting such a configuration, the technical effects described above can be obtained more reliably, and a highly reliable fuel cell can be provided more reliably. There is no particular limitation on the thickness of the portion R provided with resin on the surface on the electrolyte membrane 2 side, but it is preferably thinner than the thickness of the catalyst layer 2. That is, in a preferred embodiment of the present invention, the resin disposed on at least a part of the surface of the outer peripheral region is thinner than the catalyst layer in contact with the gas diffusion layer. Thus, by making the thickness of the resin disposed on the surface thinner than the thickness of the catalyst layer, it is possible to suppress direct contact between the resin R disposed on the surface and the electrolyte membrane 2. As a result, the above-described effect can be obtained more reliably.

  As described above, in a preferred embodiment of the present invention, not only at least a part of the outer peripheral region but also at least a part of the outer peripheral region has a portion where the resin is arranged. As a result, the technical effects described above can be obtained more reliably, and a highly reliable fuel cell can be provided more reliably. Of course, you may have the site | part by which resin is arrange | positioned only at the surface of at least one part of an outer peripheral area | region.

  Moreover, in 1st Embodiment of the membrane electrode assembly of this invention shown by FIG. 2, the outer periphery edge of the gas diffusion layer (4a, 4c) and the outer periphery edge of the site | part R where resin is arrange | positioned are flush. However, it is not necessary to do so.

  The sixth embodiment of the membrane electrode assembly of the present invention shown in FIG. 7 has a portion R in which the resin is also disposed at the end portion in the outer peripheral region of the gas diffusion layer (4a, 4c). is there. That is, in a preferred embodiment of the present invention, it further has a portion where resin is arranged at least at a part of the end of the outer peripheral region.

  This is because, in the process of forming the gas diffusion layer, the sharp end extending toward the outside of the end of the outer peripheral region may face the electrolyte membrane side, or the electrolyte may also be caused by swelling shrinkage of the fuel cell. This is because it may face the film side.

  If it is 6th Embodiment of the membrane electrode assembly of this invention shown by FIG. 7, even in such a case, the resin is extended toward the electrolyte membrane 2 from the edge part of an outer peripheral area | region. Sharp parts can be covered. As a result, the electrolyte membrane 2 can be more reliably protected, and as a result, a reduction in power generation performance and a reduction in fuel consumption can be suppressed.

  In addition, in the form having the part where the resin is arranged at the end, the thickness of the resin is not particularly limited, but it is the same as the thickness of the part where the resin is arranged on the surface shown in FIG. Can be about. By setting the thickness to this level, it is possible to more reliably prevent the resin from covering the sharp end and projecting to the electrolyte membrane 2 and directly contacting the fiber.

(resin)
There is no particular limitation on the type of resin disposed in at least a part of the outer peripheral region and / or at least a part of the surface of the outer peripheral region, and may be a conductive resin or an insulating resin. Good. In any case, the sharp end portion (protruding fiber in the case of carbon fiber) that extends toward the outside is covered, and the protruding fiber is prevented from directly contacting the electrolyte membrane 2. Note that an insulating resin can provide a more reliable fuel cell. That is, in a preferred embodiment of the present invention, the resin is an insulating resin.

  The insulating resin is not particularly limited as long as it is an insulating resin. Examples of the insulating resin include thermoplastic insulating resins such as polyolefin, polyethylene, polypropylene, polystyrene, and ABS resin; thermosetting insulating resins such as phenol resin, epoxy resin, polyurethane, alkyd resin, and desired copolymers thereof. Is mentioned. In particular, when a thermoplastic insulating resin is used, it is possible to freely move the softened thermoplastic insulating resin by heating it above the softening point of the thermoplastic insulating resin. Therefore, when the thermoplastic insulating resin is used, there is an advantage that the thermoplastic insulating resin can be fluidized and its arrangement position can be controlled to a more suitable position.

(Gas diffusion layer base material)
The thickness of the gas diffusion layer base material may be appropriately determined in consideration of the characteristics of the obtained gas diffusion layer, but is usually about 80 to 400 μm or about 100 to 300 μm. If the thickness of the substrate is a value within such a range, the balance between mechanical strength and diffusibility such as gas and water can be appropriately controlled.

  The gas diffusion layer substrate preferably contains a water repellent. The water repellent is not particularly limited, and is a fluorine-based polymer such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Conventionally known water repellents such as molecular materials, polypropylene, and polyethylene may be used. The water repellent treatment method is not particularly limited, and may be performed using a general water repellent treatment method. For example, after immersing the base material used for a gas diffusion layer in the dispersion liquid of a water repellent agent, the method of heat-drying with oven etc. is mentioned.

  The gas diffusion layer substrate may have other additives. Examples of the additive include conductive carbon, a dispersant, and a dispersion aid.

(Microporous layer)
The microporous layer is usually provided to further improve water repellency. The microporous layer is usually composed of a carbon particle layer made of an aggregate of carbon particles containing a water repellent.

  The carbon particles 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 particle size 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 for the microporous layer include the same water repellents as those used for the gas diffusion layer substrate. 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 and the water repellent in the microporous layer is preferably about 90:10 to 40:60 in terms of mass ratio. Thereby, moderate water repellency and electronic conductivity can be obtained.

  The thickness of the microporous layer may be appropriately determined in consideration of the water repellency of the obtained gas diffusion layer, but is usually about 10 to 50 μm or about 20 to 40 μm. Thus, since the microporous layer is usually a thin film, there are cases where cracks and defects occur in the outer peripheral portion by molding the microporous layer. In such a case, the sharp end of the gas diffusion base material may be easily exposed through a crack part or a defect part. On the other hand, according to the present invention, the electrolyte membrane 2 is protected from the sharp end extending outward by the resin. Thereby, even if the sharp end portion is exposed through the crack portion, the sharp end portion is prevented from coming into direct contact with the electrolyte membrane. This eventually leads to a decrease in power generation performance and a reduction in fuel consumption. The resin also has an action of filling the crack portion. Then, the direct contact as described above is more reliably suppressed.

(Catalyst layer)
The catalyst layers (the anode catalyst layer 3a and the cathode catalyst layer 3c) are layers in which the cell reaction actually proceeds. Specifically, the oxidation reaction of hydrogen proceeds in the anode catalyst layer 3a, and the reduction reaction of oxygen proceeds in the cathode catalyst layer 3c.

  The catalyst layer includes a catalyst component, a conductive catalyst carrier (conductive carrier) that supports the catalyst component, and an electrolyte. Hereinafter, a composite in which a catalyst component is supported on a catalyst carrier is also referred to as an “electrode catalyst”.

  The catalyst component used in the anode catalyst layer is not particularly limited as long as it has a catalytic action in the oxidation reaction of hydrogen, and a known catalyst can be used in the same manner. The catalyst component used in the cathode catalyst layer is not particularly limited as long as it has a catalytic action for the oxygen reduction reaction, and a known catalyst can be used in the same manner. Specifically, it can be selected from metals such as platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, and alloys thereof. .

  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. Although the composition of the alloy depends on the type of metal to be alloyed, the content of platinum is preferably 30 to 90 atomic%, and the content of the metal to be alloyed with platinum is preferably 10 to 70 atomic%. In general, an alloy is a generic term for a metal element having one or more metal elements or non-metal elements added and having metallic properties. The alloy structure consists of a eutectic alloy, which is a mixture of the component elements as separate crystals, a component element completely melted into a solid solution, and a component element composed of an intermetallic compound or a compound of a metal and a nonmetal. There is what is formed, and any may be sufficient. At this time, the catalyst component used in the anode catalyst layer and the catalyst component used in the cathode catalyst layer can be appropriately selected from the above. In the present specification, unless otherwise specified, descriptions of the catalyst components for the anode catalyst layer and the cathode catalyst layer have the same definition for both. Therefore, they are collectively referred to as “catalyst components”. However, the catalyst components of the anode catalyst layer and the cathode catalyst layer do not have to be the same, and can be appropriately selected so as to exhibit the desired action as described above.

  The shape and size of the catalyst component are not particularly limited, and the same shape and size as known catalyst components can be adopted. For example, the catalyst component may be granular, scale-like, or layered, but is preferably granular. At this time, the average particle diameter of the catalyst particles is preferably 1 to 30 nm, more preferably 1 to 10 nm, still more preferably 1 to 5 nm, and particularly preferably 2 to 4 nm. When the average particle diameter of the catalyst particles is within such a range, the balance between the catalyst utilization rate related to the effective electrode area where the electrochemical reaction proceeds and the ease of loading can be appropriately controlled. The “average particle diameter of the catalyst particles” in the present invention is the crystallite diameter determined from the half-value width of the diffraction peak of the catalyst component in X-ray diffraction, or the particle diameter of the catalyst component determined by a transmission electron microscope (TEM). It can be measured as an average value of.

  The catalyst component described above is preferably contained in the catalyst layer as an electrode catalyst supported on a conductive carrier.

  The conductive carrier functions as a carrier for supporting the above-described catalyst component and an electron conduction path involved in the transfer of electrons between the catalyst component and another member. Any conductive carrier may be used as long as it has a 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. Is preferred. Specific examples include carbon particles made of carbon black, activated carbon, coke, natural graphite, artificial graphite and the like. “The main component is carbon” means that the main component contains carbon atoms, and is a concept that includes both carbon atoms and substantially carbon atoms. 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 weight or less is allowed.

The BET specific surface area of the conductive carrier may be a specific surface area sufficient to carry the catalyst component in a highly dispersed state, but is preferably 20 to 1600 m ² / g, more preferably 80 to 1200 m ² / g. Good. When the specific surface area is in the above range, the catalyst component and the polymer electrolyte are sufficiently dispersed in the conductive support to obtain sufficient power generation performance, and the catalyst component and the polymer electrolyte can be used sufficiently effectively.

  In addition, the size of the conductive carrier is not particularly limited, but from the viewpoint of controlling the ease of loading, catalyst utilization, and the thickness of the electrode 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 the catalyst component is supported on the conductive support, the supported amount of the catalyst component is preferably 10 to 80% by weight, more preferably 30 to 70% by weight, based on the total amount of the electrode catalyst. . When the supported amount of the catalyst component is within such a range, the balance between the degree of dispersion of the catalyst component on the catalyst support and the catalyst performance can be appropriately controlled. The amount of the catalyst component supported can be examined by inductively coupled plasma emission spectroscopy (ICP).

  The catalyst layer includes an ion conductive polymer electrolyte in addition to the electrode catalyst. The polymer electrolyte is not particularly limited, and conventionally known knowledge can be referred to as appropriate. For example, the ion exchange resin which comprises the following electrolyte layer can be added to a catalyst layer as a polymer electrolyte.

  The polymer electrolyte is not particularly limited, and conventionally known knowledge can be referred to as appropriate. Polymer electrolytes are roughly classified into fluorine-based polymer electrolytes and hydrocarbon-based polymer electrolytes depending on the type of ion exchange resin that is a constituent material. In addition, since the specific description of the fluorine-based polymer electrolyte and the hydrocarbon-based polymer electrolyte is the same as the description of the following electrolyte membrane, the description is omitted here. Among these, the polymer electrolyte preferably contains a fluorine atom because it is excellent in heat resistance, chemical stability, and the like. Particularly preferred are fluorine-based electrolytes such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), and the like.

  The content of the polymer electrolyte in the catalyst layer is not particularly limited, but the ratio of the polymer electrolyte to carbon in the electrode catalyst is preferably 0.3 to 1.6.

  The catalyst component can be supported on the conductive carrier 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.

  The method for forming the catalyst layer is not particularly limited, but preferably a method for forming the catalyst layer by applying a catalyst ink comprising the electrode catalyst, polymer electrolyte and solvent as described above to the surface of the polymer electrolyte membrane. Is mentioned. In this case, the solvent is not particularly limited, and usual solvents used for forming the catalyst layer can be used in the same manner. Specifically, lower alcohols such as water, cyclohexanol, ethanol, 1-propanol and 2-propanol can be used. Further, the amount of the solvent used is not particularly limited, and a known amount can be used. In the catalyst ink, the electrocatalyst is used in any amount as long as it can sufficiently exhibit the desired action, that is, the action of catalyzing the hydrogen oxidation reaction (anode side) and the oxygen reduction reaction (cathode side). May be. It is preferable that the electrode catalyst is present in the catalyst ink in an amount of 5 to 30% by weight, more preferably 9 to 20% by weight.

  The preparation method of the catalyst ink is not particularly limited as long as the electrode catalyst, the electrolyte and the solvent, and if necessary, the water-repellent polymer and / or the thickener are appropriately mixed. For example, a catalyst ink can be prepared by adding an electrolyte to a polar solvent, heating and stirring the mixed solution to dissolve the electrolyte in the polar solvent, and then adding an electrode catalyst thereto. Alternatively, after the electrolyte is once dispersed / suspended in a solvent, the dispersion / suspension may be mixed with an electrode catalyst to prepare a catalyst ink. In addition, a commercially available electrolyte solution (for example, DuPont Nafion solution: Nafion dispersed / suspended at a concentration of 5 wt% in 1-propanol) in which the electrolyte is previously prepared in the above other solvent is used as it is. May be used in the method.

  The catalyst ink as described above is applied on the polymer electrolyte membrane or the gas diffusion layer of the present invention to form each catalyst layer. At this time, the conditions for forming the cathode / anode catalyst layer on the polymer electrolyte membrane are not particularly limited, and can be used in the same manner as known methods or appropriately modified.

Further, the catalyst content per unit catalyst coating area (mg / cm ² ) is not particularly limited, but in view of sufficient dispersion of the catalyst on the carrier, power generation performance, etc., 0.01 to 1.0 mg / cm ² . However, when the catalyst contains platinum or a platinum-containing alloy, the platinum content per unit catalyst coating area is preferably 0.5 mg / cm ² or less. The use of expensive noble metal catalysts typified by platinum (Pt) and platinum alloys has become a high cost factor for fuel cells. Therefore, it is preferable to reduce the amount of expensive platinum used (platinum content) to the above range and reduce the cost. The lower limit is not particularly limited as long as power generation performance is obtained, and is, for example, 0.01 mg / cm ² or more. In this specification, inductively coupled plasma emission spectroscopy (ICP) is used for measurement (confirmation) of “catalyst (platinum) content per unit catalyst application area (mg / cm ² )”. A person skilled in the art can easily carry out a method of making the desired “catalyst (platinum) content per unit catalyst coating area (mg / cm ² )”, and control the ink composition (catalyst concentration) and coating amount. You can adjust the amount.

  The thickness of the catalyst layer is preferably 0.5 to 30 μm, more preferably 1 to 20 μm, and still more preferably 2 to 15 μm. In addition, the said thickness is applied to both a cathode catalyst layer and an anode catalyst layer. The thickness of the cathode catalyst layer and the anode catalyst layer may be the same or different.

(Electrolyte membrane)
The electrolyte membrane 2 has a function of selectively transmitting protons generated in the anode catalyst layer 3a during operation of the PEFC 1 to the cathode catalyst layer 3c along the film thickness direction. The electrolyte membrane 2 also has a function as a partition wall for preventing the fuel gas supplied to the anode side and the oxidant gas supplied to the cathode side from being mixed.

  The electrolyte membrane 2 is roughly classified into a fluorine-based polymer electrolyte membrane and a hydrocarbon-based polymer electrolyte membrane depending on the type of ion exchange resin that is a constituent material. Examples of ion exchange resins constituting the fluorine-based polymer electrolyte membrane include Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), and the like. Perfluorocarbon sulfonic acid polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride- Examples include perfluorocarbon sulfonic acid polymers. From the viewpoint of improving power generation performance such as heat resistance and chemical stability, these fluorine-based polymer electrolyte membranes are preferably used, and particularly preferably fluorine-based polymer electrolytes composed of perfluorocarbon sulfonic acid polymers. A membrane is used.

  Specific examples of the hydrocarbon electrolyte include sulfonated polyethersulfone (S-PES), sulfonated polyaryletherketone, sulfonated polybenzimidazole alkyl, phosphonated polybenzimidazole alkyl, sulfonated polystyrene, and sulfonated poly. Examples include ether ether ketone (S-PEEK) and sulfonated polyphenylene (S-PPP). These hydrocarbon-based polymer electrolyte membranes have manufacturing advantages such as low cost raw materials, simple manufacturing processes, and high material selectivity.

  In addition, as for the ion exchange resin mentioned above, only 1 type may be used independently and 2 or more types may be used together. Moreover, it is not restricted only to the material mentioned above, Other materials may be used.

  The thickness of the electrolyte membrane may be appropriately determined in consideration of the characteristics of the obtained fuel cell, and is not particularly limited. The thickness of the electrolyte membrane is usually about 5 to 200 μm, or about 10 to 30 μm. When the thickness of the electrolyte membrane is within such a range, the balance of strength during film formation, durability during use, and output characteristics during use can be appropriately controlled. As described above, the electrolyte membrane is generally a thin film and is easily damaged from the outside because of its thinness. Therefore, if the gas diffusion layer including the sharp end contacts the electrolyte membrane and the electrolyte membrane is damaged, a cross leak may occur. When the cross leak occurs, the power generation performance and fuel consumption are reduced.

  On the other hand, according to the configuration of the embodiment of the present invention, the gas diffusion layer has a portion formed by arranging resin on at least a part of the outer peripheral region and / or at least a part of the outer peripheral region. ing. The resin protects the electrolyte membrane from sharp edges extending outward in the gas diffusion layer. As a result, a decrease in power generation performance and a decrease in fuel consumption can be suppressed.

  In addition, in the form shown in FIGS. 2-7, those skilled in the art can apply it combining suitably. For example, the resin is disposed on the end or on the surface of the outer peripheral region of the gas diffusion layer (4a, 4c) while having the portion R on which the resin is disposed in the surface layer region on the electrolyte membrane 2 side. You may have the site | part R. FIG. As described above, the present specification discloses a mode in which the modes illustrated in FIGS.

[Production method of membrane electrode assembly]
In the present invention, a conductive gas diffusion layer including at least a catalyst layer on both sides of an electrolyte membrane; a microporous layer, a base portion constituting a main body, and a sharp end extending outward from the outer surface of the base portion And a gas diffusion layer including a base material in this order, wherein at least one of the gas diffusion layers is larger in a planar direction than the catalyst layer in contact with the gas diffusion layer. The catalyst layer that has an outer peripheral region and is in contact with the gas diffusion layer is smaller in the planar direction than the electrolyte membrane, and at least a part of the outer peripheral region and / or at least one of the outer peripheral regions. A method for producing a membrane / electrode assembly is provided, which includes a step of producing a portion in which a resin is disposed on the surface of the part.

  By setting it as such a structure, the membrane electrode assembly of a novel structure which can reduce the damage of an electrolyte membrane significantly can be manufactured.

  In one embodiment of the method for producing a membrane electrode assembly of the present invention, at least one of the gas diffusion layers has a larger outer peripheral area in the planar direction than the catalyst layer in contact with the gas diffusion layer, and the The catalyst layer in contact with the gas diffusion layer is smaller in the planar direction than the electrolyte membrane.

  In one embodiment of the method for producing a membrane / electrode assembly of the present invention, a portion in which resin is disposed in at least a part of the outer peripheral region and / or at least a surface of the outer peripheral region is provided. It has the process to produce. This will be described in more detail below.

  In a preferred embodiment of the method for producing a membrane / electrode assembly of the present invention, a gas diffusion layer base comprising a microporous layer, a base portion constituting a main body, and a sharp end extending outward from the outer surface of the base portion. A step of preparing a gas diffusion layer precursor by laminating a material; and at least a part of an outer peripheral region of the gas diffusion layer precursor and / or a surface of at least a part of the outer peripheral region. And forming the gas diffusion layer so as to be larger in the planar direction than the contacted catalyst layer after impregnation.

  First, a gas diffusion layer precursor is prepared by laminating a microporous layer and a gas diffusion layer base material including a base portion forming a main body and a sharp end extending outward from the outer surface of the base portion. The process will be described.

  The microporous layer and the gas diffusion layer base material may be stacked in any manner, but it is preferable to stack the microporous layer on the gas diffusion layer base material. For example, there are the following methods. First, a slurry is prepared by dispersing carbon particles, a water repellent and the like in a solvent. Next, the slurry is applied onto a gas diffusion layer base material including a base portion constituting a main body and a sharp end extending outward from the outer surface of the base portion, and is dried. Alternatively, the slurry is once dried and pulverized to form a powder, and this is formed on a gas diffusion layer base material including a base portion forming a main body and a sharp end extending outward from the outer surface of the base portion. Apply. Thereafter, heat treatment is performed at about 250 to 400 ° C. using a muffle furnace or a firing furnace. In the above method, the solvent used for preparing the slurry is not particularly limited. For example, water, perfluorobenzene, dichloropentafluoropropane, alcohol solvents such as methanol and ethanol can be preferably used. In this way, a “gas diffusion layer precursor” in which the resin is not yet arranged is produced. In addition, if there exists a commercial item, you may purchase and prepare a "gas diffusion layer precursor".

  Subsequently, the resin layer is impregnated with at least a part of the outer peripheral region of the gas diffusion layer precursor and / or at least a part of the surface of the outer peripheral region, and then becomes larger in a planar direction than the catalyst layer to be contacted. Thus, the step of forming the gas diffusion layer is performed.

  First, as shown in FIG. 8, in the outer peripheral region of the gas diffusion layer precursor corresponding to the gas diffusion layer precursor corresponding thereto, the outer peripheral region of the gas diffusion layer to be molded has a portion R where the resin is arranged. A resin sheet R ′ having a shape (for example, a frame shape) can be disposed. Alternatively, the portion of the gas diffusion layer precursor (4a ′, 4c ′) that becomes the gas diffusion layer is masked, and the resin liquid can be applied to a region other than the region. Here, as a coating method, a conventionally known method can be applied. For example, an applicator or a technique such as screen printing can be used.

  In the above, a resin sheet may be arranged on the gas diffusion layer base material side of the gas diffusion layer precursor, or a resin liquid may be applied. Alternatively, a resin sheet may be disposed on the microporous layer side of the gas diffusion layer precursor, or a resin liquid may be applied. However, the latter is preferable in order to suppress direct contact of the outer peripheral region of the gas diffusion layer with the electrolyte membrane.

  Then, as shown in FIG. 8, after the resin sheet R ′ is arranged on the gas diffusion layer precursor (4a ′, 4c ′), at least one of the outer peripheral regions of the gas diffusion layer precursor (4a ′, 4c ′). A resin is impregnated into the inside of the part and / or at least a part of the surface of the outer peripheral region. The method is not limited. For example, when a thermoplastic resin is used as the resin, the softened thermoplastic resin can be freely moved (impregnated) by heating to a temperature above the softening point of the thermoplastic resin. Therefore, it is possible to fluidize the thermoplastic resin and control the arrangement position to a more suitable position. Further, the resin is applied to at least a part of the outer peripheral region and / or at least a part of the outer peripheral region while applying pressure (temperature if necessary) from above the resin sheet and the applied resin. Can also be impregnated. In addition, when performing by application | coating, it can be made to impregnate the said resin in a desired position by masking beforehand the part which does not want to apply | coat.

  In addition, what is necessary is just to design suitably the magnitude | size and thickness of a resin sheet, the application quantity, and application thickness according to where and how much the part by which resin is arrange | positioned is produced. For example, as shown in FIG. 2, when it is desired to match the thickness of the outer peripheral region with the thickness of the resin, the thickness of the resin sheet, the coating amount, and the coating thickness may be set as much as necessary. If it is desired to arrange the resin inward as shown in FIG. 4, a resin sheet having a size corresponding to the resin may be prepared or the masking size may be changed. When it is desired to dispose the resin in the surface layer region as shown in FIG. 5, the thickness, coating amount, and coating thickness of the resin sheet may be changed accordingly. In addition, as shown in FIG. 6, when resin is to be arranged on the surface of the outer peripheral region, a resin sheet having a thickness corresponding to the resin may be selected, or the amount of resin applied may be increased accordingly. Alternatively, the resin sheet may be bonded only to the surface using an adhesive or the like. Further, the pressure and / or temperature may be adjusted so that the resin remains on the surface.

  Subsequently, after impregnating the resin, the gas diffusion layer is formed so as to be larger in the planar direction than the catalyst layer to be contacted. The molding method is not particularly limited, and the gas diffusion layer may be punched out so as to have a larger outer peripheral area in the plane direction than the catalyst layer in contact with the gas diffusion layer, or may be cut at least one side at a time. .

  In the present embodiment, the gas diffusion layer is formed after the resin is arranged. In the present embodiment, a sharp end extending outward from the outer surface of the base is fixed to the base by resin. Therefore, it is possible to prevent the sharp member from dropping from the base portion. In addition, since the resin is infiltrated, the resin plays the role of an adhesive, and the base material and the microporous layer are more firmly bonded, so that the microporous layer can be prevented from dropping off. In addition, since the component constituting the microporous layer is also fixed by the resin, there is an effect of suppressing the component itself from dropping off. As described above, when the gas diffusion layer is molded or after the molding, when the gas diffusion layer is handled, dropping of the microporous layer and the sharp member can be suppressed, so that a highly reliable fuel cell can be provided. It becomes possible.

  Further, according to another preferred embodiment of the method for producing a membrane electrode assembly of the present invention, the microporous layer, the base part constituting the main body, and the sharp end extending outward from the outer surface of the base part are provided. A step of preparing a gas diffusion layer precursor by laminating a gas diffusion layer base material, and the gas diffusion layer precursor is shaped to be larger in a planar direction than a catalyst layer with which the gas diffusion layer is in contact And a step of impregnating at least a part of an outer peripheral region of the molded gas diffusion layer precursor and / or a surface of at least a part of the outer peripheral region with the resin.

  In the present embodiment, the gas diffusion layer precursor is molded so as to be larger in the planar direction than the catalyst layer with which the gas diffusion layer contacts, and then the interior of at least a part of the outer peripheral region of the molded gas diffusion layer precursor and At least a part of the surface of the outer peripheral region is impregnated with the resin. This will be described below.

  The step of preparing the gas diffusion layer precursor is the same as described above.

  Subsequently, the gas diffusion layer precursor is shaped so as to be larger in the planar direction than the catalyst layer with which the gas diffusion layer contacts. The molding method is the same as described above.

  Thereafter, as shown in FIG. 9, a frame-shaped resin sheet R ′ is disposed in the outer peripheral region of the molded gas diffusion layer precursor (4 a ′, 4 c ′). Of course, as described above, a resin liquid may be applied and impregnated with the resin. The method of arranging a resin sheet, applying a resin liquid, and the method of impregnating the resin are the same as described above.

  In this embodiment, the gas diffusion layer precursor is formed in advance. If it does so, it exists in the tendency for the sharp edge part extended toward the outer side rather than the outer surface of a base to increase. However, in this embodiment, the resin covers the sharp end. Thereby, direct contact of the gas diffusion layer with the electrolyte membrane can be suppressed. As a result, when manufacturing the membrane electrode assembly or during the operation of the fuel cell, it is possible to prevent the sharp end from dropping off, and to provide a highly reliable fuel cell.

  In the embodiment shown in FIG. 9, a resin sheet that is larger in the plane direction than the gas diffusion layer precursor impregnated with resin is used. Therefore, in the outer peripheral region of the gas diffusion layer as shown in FIG. 7, it is possible to have a portion where the resin is disposed at the end portion. As described above, according to the present invention, not only the inside and the surface of the outer peripheral region of the gas diffusion layer, but also the end portion can have a portion where the resin is arranged freely.

  The membrane / electrode assembly can be produced by using or combining conventionally known methods as long as at least the catalyst layer and the gas diffusion layer of the present invention can be produced in this order on both sides of the electrolyte membrane. It can be carried out. For example, there is a method of joining a gas diffusion layer having a portion where the resin of the present invention is disposed to a catalyst layer transferred or applied to an electrolyte membrane by hot pressing and dried. Alternatively, a method of preparing two gas diffusion electrodes (GDE) by applying a catalyst layer in advance to the microporous layer surface of the gas diffusion layer and drying, and bonding the gas diffusion electrodes to both surfaces of the electrolyte membrane by hot pressing. Can be used. Application and bonding conditions such as hot pressing may be appropriately adjusted depending on the type of polymer electrolyte (perfluorosulfonic acid type or hydrocarbon type) in the electrolyte membrane or catalyst layer.

<Fuel cell>
The present invention also provides a fuel cell in which the above membrane electrode assembly or the membrane electrode assembly produced by the above production method is sandwiched between separators having gas flow paths.

  As mentioned above, it has the site | part by which resin is arrange | positioned in the inside of at least one part of the outer periphery area | region of a gas diffusion layer, and / or the surface of at least one part of the said outer periphery area | region. Therefore, the electrolyte membrane is protected from the sharp end portion extending outward in the gas diffusion layer by the resin. As a result, a decrease in power generation performance and a decrease in fuel consumption can be suppressed.

[Separator]
The separator has a function of electrically connecting each cell in series when a plurality of single cells of a fuel cell such as a polymer electrolyte fuel cell are connected in series to form a fuel cell stack. The separator also functions as a partition that separates the fuel gas, the oxidant gas, and the coolant from each other. In order to secure these flow paths, as described above, each of the separators is preferably provided with a gas flow path and a cooling flow path. As a material constituting the separator, conventionally known materials such as dense carbon graphite, carbon such as a carbon plate, and metal such as stainless steel can be appropriately employed without limitation. The thickness and size of the separator and the shape and size of each flow path provided are not particularly limited, and can be appropriately determined in consideration of the desired output characteristics of the obtained fuel cell.

  The type of the fuel cell is not particularly limited. In the above description, the polymer electrolyte fuel cell (PEFC) has been described as an example. However, in addition to the above, an alkaline fuel cell and a direct methanol fuel cell are used. And a micro fuel cell. Among them, a polymer electrolyte fuel cell is preferable because it is small in size, and can achieve high density and high output. The fuel cell is useful as a power source for stationary vehicles as well as a power source for a moving body such as a vehicle in which a mounting space is limited. Particularly, the fuel cell is particularly useful for an automobile application in which system start / stop and output fluctuation frequently occur. It can be used suitably.

  The manufacturing method of the fuel cell is not particularly limited, and conventionally known knowledge can be appropriately referred to in the field of the fuel cell.

  The fuel used when operating the fuel cell is not particularly limited. For example, hydrogen, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, secondary butanol, tertiary butanol, dimethyl ether, diethyl ether, ethylene glycol, diethylene glycol and the like can be used. Of these, hydrogen and methanol are preferably used in that high output is possible.

  Furthermore, a fuel cell stack having a structure in which a plurality of membrane electrode assemblies are stacked and connected in series via a separator may be formed so that the fuel cell can exhibit a desired voltage. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. In the following examples, the operation was performed at room temperature (25 ° C.) unless otherwise specified. Unless otherwise specified, “%” and “part” mean “% by weight” and “part by weight”, respectively.

<Example 1 (Insulating resin is disposed inside gas diffusion layer; solid insulator is melted and impregnated)>
Production of GDL (gas diffusion layer) was performed according to the following procedure.

  First, a gas diffusion layer precursor (25BC manufactured by SGL Carbon Co.) was prepared. This gas diffusion layer precursor is composed of a gas diffusion layer substrate (carbon paper, containing 5 wt% PTFE, thickness 225 μm) and a microporous layer (thickness 35 μm). Paper, with sharp edges extending outward.

  The gas diffusion layer precursor was cut into a predetermined size.

  On the other hand, an insulating resin sheet (low density polyethylene sheet) cut out to a size larger than the gas diffusion layer precursor was prepared. It was punched into dimensions smaller than the gas diffusion layer precursor (as an unnecessary part) to produce a frame-shaped insulating resin sheet.

  A frame-shaped insulating resin sheet is laminated on the microporous layer side of the cut out gas diffusion layer precursor, and hot-pressed at 150 ° C., 0.2 MPa, for 10 minutes to make the insulating resin into the gas diffusion layer precursor. Impregnation into the outer peripheral area of the body.

  In this way, a gas diffusion layer having a portion in which a resin having the same thickness as the gas diffusion layer is arranged in the outer peripheral region of the gas diffusion layer was produced.

  In Example 1, the gas diffusion layer precursor was cut out to a predetermined size in advance, but after impregnating the insulating resin inside the outer peripheral region of the gas diffusion layer precursor, the gas diffusion layer precursor was cut out to the predetermined size. It may be a diffusion layer.

<Example 2 (Insulating resin is disposed inside GDL; applying insulating resin in solution and impregnating)>
First, a gas diffusion layer precursor (25BC manufactured by SGL Carbon Co.) was prepared.

  Subsequently, Kuraray Septon (model number: SEBS8004) and toluene were mixed at a weight ratio of 1:10, and a mixing operation was performed at 80 ° C. to prepare an insulating resin solution having a solid content concentration of 9%. Septon (model number: SEBS8004) is composed of a polystyrene block and a flexible polyolefin-structured elastomer block, and is a block copolymer based on two types of diblock and triblock.

  Subsequently, after masking the portion of the gas diffusion layer precursor on the microporous layer side corresponding to the central portion of the gas diffusion layer so as not to be impregnated with the insulating resin of the solution, the applicator is used to mask the septon solution. Was applied and impregnated with resin.

  Thereafter, the masking was peeled off, and drying was performed in an oven at 80 ° C. in an air atmosphere for 15 minutes to produce a portion having a thickness similar to that of the gas diffusion layer and having a resin disposed in the outer peripheral region.

  Thereafter, the gas diffusion layer precursor was cut into a predetermined size.

  In Example 2, a gas diffusion layer was produced by applying and impregnating a solution insulating resin with an applicator. However, the outer peripheral region of the gas diffusion layer may be applied and impregnated by another method such as screen printing. Good.

<Example 3 (Insulating resin is disposed inside and on surface of gas diffusion layer; impregnated with insulating resin in solution and disposed on surface)>
The same procedure as in Example 2 was applied except that a Septon toluene solution produced in the same procedure as in Example 2 was applied from the masking surface and a Septon resin member (10 μm) was also disposed on the microporous layer of the gas diffusion layer. Thus, a gas diffusion layer was produced.

<Comparative example (no resin impregnation)>
A gas diffusion layer that was not impregnated with an insulating resin was prepared as a comparative example using 25BC manufactured by SGL Carbon.

<Maximum piercing stress evaluation method>
An evaluation sample was prepared in which a gas diffusion layer and an electrolyte membrane were laminated so as to have the following three-layer structure.

<Sample configuration for evaluation>
Example 1
Gas diffusion layer produced in Example 1—Electrolyte membrane (NRE211 manufactured by DuPont) —Comparative gas diffusion layer (25BC manufactured by SGL Carbon)
(Example 2)
Gas diffusion layer produced in Example 2—Electrolyte membrane (NRE211 manufactured by DuPont) —Comparative gas diffusion layer (25BC manufactured by SGL Carbon)
(Example 3)
Gas diffusion layer produced in Example 3—Electrolyte membrane (NRE211 made by DuPont) —Comparative gas diffusion layer (25BC made by SGL Carbon)
(Comparative example)
Comparative Example Gas Diffusion Layer (SBC Carbon 25BC) -Electrolyte Membrane (DuPont NRE211) -Comparative Example Gas Diffusion Layer (SGL Carbon 25BC)
<Maximum piercing stress measurement>
The prepared sample for evaluation and a carbon rod having a diameter of 0.5 mm were set on a material testing machine (AUTOGRAPH AG-X manufactured by Shimadzu Corporation), and the carbon rod was 1.00 mm / min from the surface of the outer peripheral region of the produced gas diffusion layer. The piercing test was conducted at a speed of. The maximum puncture stress was calculated by measuring the maximum load during the piercing test and dividing the cross-sectional area of the carbon rod. The results are shown in FIG. In addition, the carbon rod assumes the carbon fiber which comprises a gas diffusion layer base material.

  As shown in FIG. 10, the maximum piercing stress is weaker in the configuration of the comparative example than in the configuration of the example. On the other hand, in the configuration of the example, the maximum piercing stress is stronger than the configuration of the comparative example. This suggests that it is difficult to pierce the sharp member of the gas diffusion layer (that is, it is difficult to damage the electrolyte membrane).

  Therefore, in the membrane electrode assembly, the gas diffusion layer has a larger peripheral area in the plane direction than the catalyst layer in contact with the gas diffusion layer, and the catalyst layer in contact with the gas diffusion layer has Even if it is smaller in the plane direction than the electrolyte membrane, the following effects are obtained. That is, the electrolyte membrane is protected from the sharp end portion extending outward in the gas diffusion layer by the resin. This suggests that power generation performance and fuel consumption can be prevented from decreasing.

1 ... Polymer electrolyte fuel cell (PEFC),
2 ... electrolyte membrane,
3 ... Catalyst layer,
3a ... anode catalyst layer,
3c ... cathode catalyst layer,
4a ... anode gas diffusion layer,
4c ... cathode gas diffusion layer,
4ag ... anode gas diffusion layer substrate,
4cg ... cathode gas diffusion layer substrate,
4am ... Anode microporous layer,
4 cm ... cathode microporous layer,
4a '... anode gas diffusion layer precursor,
4c '... cathode gas diffusion layer precursor,
R: part where resin is arranged,
R '... resin sheet,
5a ... anode separator,
5c ... cathode separator,
6a ... anode gas flow path,
6c ... cathode gas flow path,
7: Refrigerant flow path,
10: Electrolyte membrane electrode assembly (MEA).

Claims (7)

A gas comprising at least a catalyst layer on both sides of the electrolyte membrane; a microporous layer, and a conductive gas diffusion layer base material including a base portion forming a main body and a sharp end extending outward from the outer surface of the base portion A membrane electrode assembly having a diffusion layer and in this order,
At least one of the gas diffusion layers has a larger outer peripheral area in the planar direction than the catalyst layer in contact with the gas diffusion layer, and the catalyst layer in contact with the gas diffusion layer is the electrolyte. Smaller in the plane direction than the membrane,
Wherein at least a portion of the internal and / or at least a portion of a surface of the outer peripheral region of the outer peripheral region, have a site where the resin is disposed, at least a portion of the thickness of the placed resin on the surface of the outer peripheral region The membrane electrode assembly is thinner than the catalyst layer in contact with the gas diffusion layer .   The membrane electrode assembly according to claim 1, wherein the resin is an insulating resin. The membrane electrode assembly according to claim 1 or 2 , further comprising a portion where a resin is disposed at least at a part of an end of the outer peripheral region. A gas comprising at least a catalyst layer on both sides of the electrolyte membrane; a microporous layer, and a conductive gas diffusion layer base material including a base portion forming a main body and a sharp end extending outward from the outer surface of the base portion A manufacturing method of a membrane electrode assembly having a diffusion layer in this order,
At least one of the gas diffusion layers has a larger outer peripheral area in the planar direction than the catalyst layer in contact with the gas diffusion layer, and the catalyst layer in contact with the gas diffusion layer is the electrolyte. Smaller in the plane direction than the membrane,
In at least a portion of the inside and / or at least a portion of a surface of the outer peripheral region of the outer peripheral region, have a step of preparing a site where the resin is disposed, however, at least a portion of the surface of the outer peripheral region A method for producing a membrane / electrode assembly , wherein the resin disposed is thinner than the catalyst layer in contact with the gas diffusion layer . Preparing a gas diffusion layer precursor by laminating a microporous layer and a gas diffusion layer base material including a base portion forming a main body and a sharp end extending outward from an outer surface of the base portion; and ;
The impregnation of at least a part of the outer peripheral region of the gas diffusion layer precursor and / or a surface of at least a part of the outer peripheral region with the resin so as to be larger in a planar direction than the catalyst layer to be contacted. Forming as a gas diffusion layer;
The manufacturing method of Claim 4 which has these. Preparing a gas diffusion layer precursor by laminating a microporous layer and a gas diffusion layer base material including a base portion forming a main body and a sharp end extending outward from an outer surface of the base portion; and ;
Forming the gas diffusion layer precursor so as to be larger in a planar direction than the catalyst layer with which the gas diffusion layer contacts;
Impregnating the resin with at least a part of an outer peripheral region of the molded gas diffusion layer precursor and / or a surface of at least a part of the outer peripheral region;
The manufacturing method of Claim 4 which has these. A fuel cell, wherein the membrane electrode assembly according to any one of claims 1 to 3 is sandwiched by a separator having a gas flow path.