JP2010073586A - Electrolyte membrane-electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte membrane-electrode assembly, which by solving problems, shows stable power generation performance in operations, under conditions ranging from low humidity to high humidity, and from low temperature to high temperature, and also shows stable performance during a period of use of a fuel cell. <P>SOLUTION: The electrolyte membrane-electrode assembly has: an electrolyte membrane; a cathode gas diffusion electrode arranged on one surface of the electrolyte membrane and including a cathode catalyst layer and a cathode gas diffusion layer; and an anode gas diffusion electrode, arranged on the other surface of the electrolyte membrane and including an anode catalyst layer and an anode gas diffusion layer. In the cathode gas diffusion layer or the anode gas diffusion layer, at least two gas diffusion layer base materials, having different compression moduli, are laminated. When a gas diffusion layer base material S represents a gas diffusion layer base material, arranged adjacent to a separator out of the gas diffusion layer base materials, the gas diffusion layer base material S has the highest compression modulus and the smallest thickness. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrolyte membrane-electrode assembly. In particular, the present invention relates to an electrolyte membrane-electrode assembly obtained by improving a gas diffusion layer base material.

  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, the polymer electrolyte fuel cell is expected as a power source for electric vehicles because it operates at a relatively low temperature. The polymer electrolyte fuel cell generally has a structure in which an electrolyte membrane-electrode assembly (MEA) is sandwiched between separators. The electrolyte membrane-electrode assembly is formed by sandwiching a polymer electrolyte membrane between a pair of electrode catalyst layers and a gas diffusion layer.

In a polymer electrolyte fuel cell having an MEA as described above, an electrode reaction represented by the following reaction formula is allowed to proceed in accordance with the polarity of both electrodes (cathode and anode) sandwiching the polymer electrolyte membrane. Are getting electrical energy. First, hydrogen contained in the fuel gas supplied to the anode (fuel electrode) side is oxidized by the catalyst component to become protons and electrons (2H ₂ → 4H ⁺ + 4e ⁻ : reaction 1). Next, the generated protons pass through the solid polymer electrolyte contained in the electrode catalyst layer and the solid polymer electrolyte membrane in contact with the electrode catalyst layer, and reach the cathode (oxygen electrode) side electrode catalyst layer. In addition, the electrons generated in the anode-side electrode catalyst layer are in contact with a conductive carrier (electron-conductive carrier) constituting the electrode catalyst layer, and a gas in contact with a different side of the electrode catalyst layer from the solid polymer electrolyte membrane. The cathode side electrocatalyst layer is reached through the diffusion layer, separator and external circuit. The protons and electrons that have reached the cathode-side electrode catalyst layer react with oxygen contained in the oxidant gas supplied to the cathode side to generate water (O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O: Reaction 2). . In the fuel cell, electricity can be taken out through the above-described electrochemical reaction.

In the electrochemical reaction, hydrogen ions (H ⁺ ) (hereinafter also referred to as “protons”) generated by the reaction 1 on the anode side permeate the solid polymer electrolyte membrane in a hydrated state (H ₃ O ⁺ ). Protons that have diffused and permeated through the membrane are supplied to the reaction 2 together with oxygen and electrons that have permeated (diffused) through a gas diffusion layer (hereinafter also referred to as “GDL”) at the cathode. That is, the reaction at the anode and the cathode uses the electrode catalyst layer in close contact with the solid polymer electrolyte membrane as a reaction site, and the catalyst in the electrode catalyst layer and the solid polymer electrolyte (hereinafter also referred to as “polymer electrolyte”). Progress at the interface. Therefore, if the interface between the catalyst and the polymer electrolyte is increased and the formation of the interface is made uniform, the above reactions 1 and 2 are preferable because the reaction proceeds more smoothly and actively. As described above, attempts have been made to use the fuel cell as an automobile or stationary power source.

  However, in order to efficiently extract the electric energy generated at the fuel electrode and oxygen electrode to the outside of the fuel cell over a long period of time, it exhibits stable power generation performance at low humidification to high humidification operation, low temperature to high temperature operation, and during the fuel cell usage period There is a need to provide a fuel cell that exhibits stable performance.

Under such circumstances, a porous layer is provided on the catalyst electrode layer, and through this porous layer, the reaction gas supplied to the fuel cell is efficiently supplied to the catalyst electrode layer, whereby a gas in an electrochemical reaction is obtained. There is a technique that attempts to improve the utilization rate (Patent Document 1). Patent Document 1 aims to ensure a gas utilization rate when gas is supplied to a catalyst electrode layer through a porous layer composed of a plurality of layers provided on the catalyst electrode. The purpose is a structure in which a metal porous member and a conductive porous member are laminated. The metal porous member is laminated on the outer side and arranged as a gas supply unit, and has a structure having a higher compression modulus than that of the inner GDL. I am trying to achieve it.
JP 2007-53007 A

  However, in the above-mentioned patent document, since gas is supplied through the metal porous body, there is a problem that the pressure loss in the fuel cell operation is large and the power generation performance is low. In addition, there has been a problem that performance degradation is large due to fuel cell operating conditions and lifetime. Furthermore, it is a premise that a separator that does not constitute a gas flow path is used, and there is a problem of increasing the thickness of the second gas diffusion layer due to gas diffusibility.

  Therefore, the present invention solves the above-mentioned problems, and shows an electrolyte membrane-electrode assembly that exhibits stable power generation performance during low-humidity to high-humidification operation and low-temperature to high-temperature operation, and also exhibits stable performance during the fuel cell usage period. The purpose is to provide.

  Another object of the present invention is to provide a fuel cell in which such an electrolyte membrane-electrode assembly is sandwiched between separators.

  Still another object of the present invention is to provide a vehicle equipped with such a fuel cell.

  The present inventor has intensively studied to achieve the above object. As a result, the present inventors have found that this object can be achieved by configuring the gas diffusion layer with two or more gas diffusion substrates so that the substrate on the separator side is the hardest and thinnest.

  The electrolyte membrane-electrode assembly of the present invention exhibits stable power generation performance during low humidification to high humidification operation and low temperature to high temperature operation, and also exhibits stable performance during the fuel cell usage period.

  Hereinafter, a fuel cell having an MEA of the present invention will be described in detail as a preferred embodiment with appropriate reference to the drawings. 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.

  The present invention relates to an electrolyte membrane, a cathode gas diffusion electrode including a cathode catalyst layer and a cathode gas diffusion layer disposed on one surface of the electrolyte membrane, and an anode catalyst disposed on the other surface of the electrolyte membrane. And an anode gas diffusion electrode including an anode gas diffusion layer, wherein the cathode gas diffusion layer or the anode gas diffusion layer has at least two gas diffusion layers having different compression elastic moduli When the gas diffusion layer base material S is formed by laminating the base material and the gas diffusion layer base material S disposed adjacent to the separator in the gas diffusion layer base material is compressed, the gas diffusion layer base material S is compressed. An electrolyte membrane-electrode assembly (MEA) having the highest elastic modulus and the smallest thickness.

  As described above, the gas diffusion layer base material in which the high elastic modulus GDL and the low elastic modulus GDL are laminated is applied as the gas diffusion layer, and the gas diffusion layer base material that is disposed adjacent to the separator is made highly elastic. The problem of the present invention can be solved by setting the rate GDL to be the thinnest. In other words, by disposing the gas diffusion layer base material S on the separator side, tenting of GDL into the gas flow path is suppressed, and by disposing the gas diffusion layer base material C on the catalyst layer side, It is possible to absorb changes in surface pressure due to dimensional changes during operation and maintain power generation performance over a long period of time.

  Since the MEA of the present invention is particularly preferably used in a polymer electrolyte fuel cell (PEFC), the polymer electrolyte fuel cell will be mainly described. The polymer electrolyte fuel cell generally has a structure in which an electrolyte membrane-electrode assembly (MEA) is sandwiched between separators. The electrolyte membrane-electrode assembly is formed by sandwiching a polymer electrolyte membrane between a pair of electrode catalyst layers and a gas diffusion layer. That is, the fuel cell of the present invention comprises an electrolyte membrane-electrode assembly (MEA) of the present invention and a pair of separators comprising a cathode-side separator and an anode-side separator that sandwich the electrolyte membrane-electrode assembly. Have. By adopting such a configuration, the fuel cell of the present invention exhibits stable power generation performance in low humidification to high humidification operation and low temperature to high temperature operation, and also exhibits stable performance during the use period of the fuel cell. Very good. In other words, the present invention can provide a fuel cell that suppresses GDL tenting into the flow path and has excellent power generation characteristics.

  FIG. 1 is a schematic cross-sectional view of a fuel cell (solid polymer fuel cell; PEFC). FIG. 1 shows a single cell of the fuel cell. The PEFC 200 shown in FIG. 1 has the MEA 100 of the present invention. In the MEA 100 of the present invention, a solid polymer electrolyte membrane 110 and a cathode gas diffusion electrode 120c including a cathode catalyst layer 122c and a cathode gas diffusion layer 124c are disposed on one surface of the solid polymer electrolyte membrane 110. The other surface of the solid polymer electrolyte membrane 110 is provided with an anode gas diffusion electrode 120a including an anode catalyst layer 122a and an anode gas diffusion layer 124a. In the present application, “electrolyte membrane-electrode assembly (MEA)” means a solid polymer electrolyte membrane 110 and a pair of gas diffusion electrodes (120c, 120a) sandwiching the solid polymer electrolyte membrane 110. It means an aggregate with. The electrolyte membrane-electrode assembly may be simply referred to as “membrane electrode assembly”.

  In the present invention, the cathode gas diffusion layer 124c or the anode gas diffusion layer 124a is formed by laminating at least two gas diffusion layer base materials having different compression elastic moduli. In the form shown in FIG. 1, each of the cathode gas diffusion layer 124c and the anode gas diffusion layer 124a is formed by laminating two gas diffusion layer base materials (124cs, 124cc, 124as, 124ac) having different compression elastic moduli. When the gas diffusion layer substrate disposed adjacent to the separator in the gas diffusion layer substrate is the gas diffusion layer substrate S (124cs, 124as), the compression elasticity of the gas diffusion layer substrate S The rate is the highest and the thickness is the thinnest. Moreover, let the gas diffusion layer base material nearest to the said catalyst layer be the gas diffusion layer base material C in the said gas diffusion layer base material. Of course, any one of the cathode gas diffusion layer 122c and the anode gas diffusion layer 124a may be formed by laminating at least two gas diffusion layer base materials having different compression elastic moduli.

  In that case, it is preferable that at least two gas diffusion layer base materials having different compression elastic moduli are laminated on the cathode gas diffusion layer 124c. The reason is as follows. That is, the gas flow rate supplied to the fuel cell on the anode side and the cathode side is different, and the flow rate on the cathode side is large. For this reason, it is necessary to make the flow path for gas flow larger on the cathode side, so the rib (described later) must be made smaller. At this time, even when the same load is applied, the surface pressure applied to the gas diffusion layer is high on the cathode side. In order to reduce the change in the surface pressure when the dimensional change occurs, it is preferable that the dimensional change of the cathode-side gas diffusion layer is flexible. Therefore, it is preferable that at least two gas diffusion layer base materials having different compression elastic modulus are laminated on the cathode gas diffusion layer 124c.

  Here, in this specification, the “compression modulus” is a value measured by the method described in the column of Examples. Although the compression characteristics of GDL will be described later, since they have nonlinear characteristics, the compression elastic modulus differs depending on which surface pressure (stress) is focused. Therefore, “the gas diffusion layer base material S has the highest compressive elastic modulus among the gas diffusion layer base materials” means that the gas diffusion layer base material is used under the same conditions (for example, “including the same surface pressure conditions”). It presupposes comparing with other gas diffusion layer base materials other than the said gas diffusion layer base material S inside. The compression modulus is the slope of the tangent of each stress point in FIG.

  The fact that at least two gas diffusion layer base materials are laminated is not particularly limited as long as the number of gas diffusion layer base materials is two or more, and three, four, or more Good. However, from the viewpoint of cost and fuel cell dimensions, it is preferably three, more preferably two. Moreover, as long as the compression elastic modulus of the gas diffusion layer base material S is the highest, the type of the gas diffusion layer base material to be laminated is not particularly limited, and the same material may be used or different materials may be used. Also good. In the case of three or more, from the viewpoint of suppressing the influence due to swelling and shrinkage of the electrolyte membrane, it is preferable that the compression elastic modulus increases in a gradient as the gas diffusion layer substrate C approaches the gas diffusion layer substrate S. There is no particular limitation on the specific compression elastic modulus ratio between the gas diffusion layer base material S and the gas diffusion layer base material C, but the tenting is sufficiently suppressed, and the change in surface pressure applied to the GDL is sufficiently suppressed, From the viewpoint of ensuring the long-term stability of the fuel cell, the ratio of the compression elastic modulus of the gas diffusion layer base material S to the compression elastic modulus of the gas diffusion layer base material C is 1.3 to 5.0, more preferably 1. .4 to 3.0. Further, the specific value is not particularly limited as long as the compression elastic modulus of the gas diffusion layer base material S is relatively highest among the gas diffusion layer base materials.

  In the present invention, the gas diffusion layer base material S (hard GDL) and the gas diffusion layer base material C (soft GDL) are used for the purpose of dealing with tenting and surface pressure fluctuation in various usage environments. .

  As for the thickness of the gas diffusion layer substrate S, if the above is satisfied (that is, compared with other gas diffusion layer substrates other than the gas diffusion layer substrate S in the gas diffusion layer substrate, If it is the thinnest), there is no limit on the specific numerical value. From the viewpoint of sufficiently suppressing the tenting and sufficiently suppressing the change in the surface pressure applied to the GDL, the thickness of the gas diffusion layer base material S is preferably 30 to 150 μm, more preferably 40 to 130 μm. In addition, from the viewpoint of absorption of the dimensional change by the gas diffusion layer, the thickness of the gas diffusion layer base material C is preferably 70 to 300 μm, more preferably 100 to 270 μm, and still more preferably 130 to 250 μm. If the thickness of the substrate is within such a range, the balance between the mechanical strength and the diffusivity of gas, water, etc., as well as significantly acting on the swelling and shrinkage of the MEA accompanying the shrinkage of the fuel cell. Appropriately controlled. Further, the ratio of the thickness of the gas diffusion layer substrate S to the gas diffusion layer substrate C is not particularly limited, but is preferably 0.1 to 0.9, more preferably 0.2 to 0.7. In such a range, the performance as a gas diffusion layer is significantly improved. That is, when the gas diffusion layer substrate S (hard GDL) is thick, the gas diffusibility is deteriorated.

  A gas diffusion layer base material having a desired compression modulus can be prepared by, for example, purchasing a commercially available product. If a gas diffusion layer base material having a compression elastic modulus that exactly matches the desired one is not commercially available, purchase a material close to that value and control the compression elastic modulus to obtain the desired compression elastic modulus. Can be adjusted to. The method for controlling the compression elastic modulus is not particularly limited, and those skilled in the art can adjust the compression elastic modulus to a desired one by appropriately referring to or combining conventionally known knowledge. If the guideline of the concrete adjustment method is shown, it can carry out by changing a design, adjusting, and adding suitably a fabric weight, a bulk density, a porosity, and material.

  In the PEFC 200 of the present invention, the MEA 100 is sandwiched between a pair of separators including a cathode side separator 150c and an anode side separator 150a. Here, the cathode gas diffusion layer 124c side surface of the cathode side separator 150c is provided with an oxidant gas flow path 152c through which an oxidant gas flows during operation, and a coolant is provided on the opposite surface during operation. A circulating cooling channel (not shown) is provided. On the other hand, the anode gas diffusion layer 124a side surface of the anode separator 150a is provided with a fuel gas flow path 152a through which fuel gas flows during operation, and the coolant flows through the opposite surface during operation. A cooling channel (not shown) is provided. A gasket may be disposed around the PEFC 200 so as to surround the pair of gas diffusion electrodes (120c, 120a) (not shown).

  Although the specific configuration of the present invention has been described above, the reason why it is preferable to employ this configuration will be described in more detail below with reference to the mechanism of operation of the fuel cell.

  The electrode catalyst layer of the fuel cell includes a conductive carrier, catalyst particles, and an electrolyte (proton conductive electrolyte). The gas containing hydrogen supplied to the anode (fuel electrode) side reaches the catalyst layer through the gas diffusion layer disposed outside the catalyst layer, and is oxidized by the catalyst particles to generate protons and electrons. The produced protons reach the cathode (oxygen) side catalyst layer through the proton conductive electrolyte constituting the catalyst layer and the electrolyte membrane in contact with the catalyst layer. Further, the electrons generated in the anode side catalyst layer are converted into the cathode side catalyst through the conductive carrier constituting the catalyst layer, the gas diffusion layer contacting the side of the catalyst layer that is different from the electrolyte membrane, the gas separator, and the external circuit. Reach the layer. The oxygen-containing gas supplied to the cathode side reaches the catalyst layer through a gas diffusion layer disposed outside the catalyst layer as in the anode side. Protons and electrons that reach the cathode catalyst layer react with oxygen to form water. Through this reaction, the fuel cell can extract electricity to the outside.

  The gas diffusion layer of the fuel cell is configured using a base material containing at least a conductive material. The gas diffusion layer needs to provide an electron conduction path between the electrode catalyst layer and the separator, and to satisfactorily supply the gas supplied from the separator side to the electrode catalyst layer.

  In a fuel cell, a membrane electrode assembly including an electrolyte membrane, an electrode catalyst layer, and a gas diffusion layer is sandwiched between separators at a predetermined surface pressure (load). When a surface pressure is applied to the gas diffusion layer with a separator having a gas channel in the gas diffusion layer, the gas diffusion layer enters the gas channel groove. That is, tenting (invasion of the gas diffusion layer into the gas flow path) occurs, gas supply to the catalyst layer is suppressed, and good power generation performance cannot be obtained.

  In the present invention, the following configuration is adopted in order to suppress a change in surface pressure applied to the gas diffusion layer, to suppress tenting in the flow path due to a dimensional change, and to ensure gas supply to the catalyst layer. That is, a gas diffusion layer base material is used that has a high elastic modulus and a thin gas diffusion layer so as to be in contact with the separator, and a base material in which a low elastic modulus base material is laminated on the electrolyte side. By adopting such a configuration, it is possible to suppress the GDL tenting into the flow path and to provide a fuel cell having excellent power generation characteristics. That is, it is possible to provide a fuel cell having excellent power generation characteristics by suppressing GDL tenting into the flow channel.

  Next, “tenting” will be described more specifically. FIG. 2 is a diagram schematically showing the occurrence of tenting. The fuel cell is assembled by applying a predetermined load (surface pressure). Actually, the initial surface pressure varies depending on the operating conditions. That is, a constant surface pressure (initial surface pressure) has been applied since the assembly of the fuel cell was completed, and the load (surface pressure) changes from the initial surface pressure. And the load accompanying the stacking varies depending on the operating state of the fuel cell. Due to this load, a portion where the surface pressure is directly applied to the GDL (a separator and a contact portion; a rib portion) and a portion which is not directly applied (a portion which is not in contact; a flow path portion) are generated. For this reason, the amount of tenting (the amount of penetration of GDL into the flow path) varies depending on the surface pressure applied to the GDL, and the amount of tenting increases as the surface pressure increases. When the amount of tenting increases, the effective gas flow path portion becomes smaller, the gas flow is hindered, and the power generation performance deteriorates. The gas channel flow direction is from the front to the depth or from the depth to the front.

  In this specification, “tenting ratio” is used as a numerical value that objectively indicates the characteristics of the separator as a gas flow path. The tenting ratio is expressed by the following formula.

  Here, the “tenting amount m” refers to the maximum dimension (μm) in which the gas diffusion layer base material S has entered the gas flow channel groove, as shown in FIG. Further, the “channel depth L (μm)” is the maximum depth of the gas channel groove of the separator as shown in FIG. Here, in this specification, the “tenting ratio” is a value calculated by measuring the “tenting amount m” and the “flow path depth L” by the method described in the example column. As a characteristic of the gas flow path of the separator, the “tenting ratio” is preferably smaller, specifically preferably 10% or less, more preferably from the viewpoint of securing gas supply to the catalyst layer. It is 5% or less, more preferably 4% or less, and particularly preferably 3% or less. If it is this range, sufficient quantity of gas can be supplied to each catalyst layer.

  According to the present invention, by reducing the “tenting ratio”, the “characteristics of the separator as a gas flow path” is improved, thereby suppressing the deterioration of the “gas flow characteristics” and the power generation performance. It becomes possible to suppress the decrease.

  Here, “air permeability” is used in the present specification as a numerical value that objectively indicates the characteristics of the gas flow. Here, in this specification, “air permeability” is a value measured by the method described in the column of Examples. Of course, the lower the “air permeability”, the more preferably it is preferably 1 second or less, more preferably 0.7 seconds or less, and even more preferably 0.5 seconds or less, considering the function of gas supply.

  Furthermore, the gas diffusion layer base material S arranged adjacent to the separator needs to have the highest compression elastic modulus, but “(surface direction) elongation at break” also prevents GDL tenting into the flow path. However, the lower one is preferable from the viewpoint of providing a fuel cell that secures power generation characteristics. Specifically, the penetration of the gas diffusion layer base material into the gas flow path is not caused by the change in the surface pressure due to the dimensional change due to the change in the fuel cell operation condition and the change in the surface pressure due to the dimensional change due to the repeated operation. From the viewpoint of suppression, it is preferably 5% or less, more preferably 2.0% or less, still more preferably 0.9% or less, and particularly preferably 0.6% or less.

  In the present specification, “elongation at break” is a value measured by the method described in the column of Examples.

  The method for controlling the elongation at break is not particularly limited, and those skilled in the art can make adjustments by appropriately referring to or combining conventionally known knowledge. Specific guidelines for the adjustment method can be obtained by appropriately changing the design weight, the bulk density, the fiber electrical resistance, the degree of graphitization, the porosity, and the material.

  As described above, in fuel cell operation, operation in a low or high humidity, low temperature to high temperature environment may be forced. Under such circumstances, in a low or high humidification state, a “dimensional change” occurs due to swelling / shrinkage of the electrolyte membrane, and components (for example, a separator, etc.) constituting a fuel cell in low temperature and high temperature operation are Similarly, “dimensional change” occurs due to thermal expansion and contraction. In this specification, “difference in compression strain” is used as a value that objectively indicates this “dimensional change”.

  FIG. 3 a shows the relationship between “difference in compressive strain” applied to GDL and “surface pressure (stress)”. FIG. 3 b shows the relationship between “surface pressure” and “thickness” applied to the GDL. FIG. 3a shows general physical properties of GDL. Specifically, it can be shown by performing the measurement of FIG. 3b. For example, when GDLs having the same composition and different thicknesses are produced, the characteristics in FIG. 3b are different, but the characteristics in FIG. 3a are the same. That is, referring to FIG. 3a, the relationship between the “difference in compressive strain” and the “surface pressure (stress)” can be understood more generally.

  Here, the “difference in compressive strain” is the ratio between the “displacement” and the “initial thickness” of the GDL when a load (surface pressure) is applied to the GDL.

Can be calculated.

  As is apparent from FIG. 3b, the displacement (initial thickness−thickness of each surface pressure) (μm) varies depending on the surface pressure. Accordingly, similarly, the “compression strain difference” also changes (see FIG. 3a). Further, it can be seen that even if the “load (surface pressure)” applied to the GDL in the surface loading direction and the unloading direction is the same, the thickness (difference in compressive strain) is different. The GDL, which has a smaller difference between the compressive strain in the load direction and the compressive strain in the unloading direction at the same surface pressure, shows stable power generation performance over a long period against changes in the surface pressure generated by operating the fuel cell. That is, it is possible to provide a fuel cell that exhibits stable power generation performance over a long period of time, regardless of operating conditions and time. It becomes possible to simplify the load adjustment mechanism of the fuel cell.

  Here, as described above, the gas diffusion layer base material C is disposed in order to suppress (absorb) a change in surface pressure due to a dimensional change during operation and maintain it for a long period of time. Considering this point, it is preferable that the difference in compressive strain of the gas diffusion layer base material C is small between the surface pressure when the load of the gas diffusion layer base material C is applied and when the load is unloaded. Specifically, in the present invention, when the difference in compressive strain at the same surface pressure during load application and unloading to the gas diffusion layer base material C is 0.1 or less, This is preferable from the viewpoint of suppressing the change in the surface pressure accompanying the change and the change in the surface pressure accompanying the repeated operation. More preferably, it is 0.2 or less, More preferably, it is 0.1 or less. In the present specification, the “difference in compression strain” is a value measured by the method described in the column of Examples.

  The method for controlling the difference in compression strain is not particularly limited, and those skilled in the art can adjust to a desired difference in compression strain by appropriately referring to or combining conventionally known knowledge. If the guideline of the concrete adjustment method is shown, it can carry out by changing and adjusting a structure (paper, a nonwoven fabric, cloth), thickness direction orientation fiber ratio, fiber length, binder amount, binder ratio suitably. .

  The above is summarized in FIG. A in FIG. 4 indicates an amount correlated with tenting at a predetermined surface pressure. The range of B in FIG. 4 shows an amount that correlates with the dimensional change accompanying the lifetime (passage) from the surface pressure initially assembled in the fuel cell to the swelling and shrinkage. Moreover, the range of C in FIG. 4 shows the change of the surface pressure applied to the GDL accompanying the dimensional change.

  The present invention uses a gas diffusion layer substrate that has a high elastic modulus and a thin gas diffusion layer so as to be in contact with the separator, and a substrate in which a low elastic modulus substrate is laminated on the catalyst layer side. A sufficient amount of gas supply, small changes in surface pressure, stable power generation performance during operation, and maintenance over a long period of time.

  Hereinafter, each component will be described in detail.

[Separator]
The separators (150c, 150a) have a function of electrically connecting each cell in series when a plurality of single cells of a fuel cell such as PEFC 200 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. Therefore, as described above, each separator is 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 used without limitation.

  The thickness and size of the separator, the shape of each flow path provided, the size of the groove of each flow path (flow path depth L), etc. are not particularly limited, and are appropriately determined in consideration of the desired output characteristics of the obtained fuel cell. Can be determined. The shape of each flow path provided is preferably a concave shape, a semicircular shape, or the like.

[gasket]
The gasket is disposed around the PEFC 200 so as to surround the pair of gas diffusion electrodes (120c, 120a), and has a function of preventing the gas supplied to the catalyst layer from leaking to the outside.

  The material constituting the gasket is not particularly limited, but rubber materials such as fluoro rubber, silicon rubber, ethylene propylene rubber (EPDM), polyisobutylene rubber, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), Examples thereof include fluorine-based polymer materials such as polyhexafluoropropylene and tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and thermoplastic resins such as polyolefin and polyester. Also, the thickness of the gasket is not particularly limited, and can be appropriately determined in consideration of the desired output characteristics of the fuel cell, characteristics of the constituent materials, and the like.

[Electrolyte membrane]
The electrolyte membrane of the present invention is particularly preferably a solid polymer electrolyte membrane. Therefore, the electrolyte membrane will be described focusing on the solid polymer electrolyte membrane.

  The solid polymer electrolyte membrane 110 is composed of a proton conductive electrolyte solid polymer electrolyte (hereinafter also simply referred to as “ionomer”). The ionomer has a function of selectively allowing protons generated in the anode catalyst layer 122a during PEFC operation to permeate the cathode catalyst layer 122c along the film thickness direction. The solid polymer electrolyte membrane 110 also has a function as a partition for preventing the fuel gas supplied to the anode side and the oxidant gas supplied to the cathode side from being mixed.

  The specific configuration of the solid polymer electrolyte membrane 110 is not particularly limited, and a conventionally known ionomer membrane can be appropriately employed in the technical field of fuel cells. The solid polymer electrolyte membrane 110 is roughly classified into a fluorine-based solid polymer electrolyte membrane and a hydrocarbon-based solid polymer electrolyte membrane according to the type of ionomer that is a constituent material.

  Examples of the fluorine-based solid polymer electrolyte include perfluorocarbon sulfonic acids 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. Polymer, perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride-perfluorocarbon sulfonic acid polymer Etc. From the viewpoint of power generation performance such as heat resistance and chemical stability, these fluorine-based solid polymer electrolyte membranes are preferably used, particularly preferably composed of a perfluorocarbon sulfonic acid polymer (perfluorosulfonic acid polymer). A fluorine-based solid polymer electrolyte membrane is used.

  Examples of the hydrocarbon solid polymer electrolyte include sulfonated polyethersulfone (S-PES), sulfonated polyaryletherketone, sulfonated polybenzimidazole alkyl, phosphonated polybenzimidazole alkyl, sulfonated polystyrene, and sulfonated. Examples include polyetheretherketone (S-PEEK) and sulfonated polyphenylene (S-PPP). These hydrocarbon-based solid polymer electrolyte membranes are preferably used from the viewpoint of production such that the raw materials are inexpensive, the production process is simple, and the material selectivity is high. 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.

  Materials other than the ionomer constituting the solid polymer electrolyte membrane described above may be used as the ionomer. As such materials, for example, liquids, solids, and gel materials having high proton conductivity can be used, and solid acids such as phosphoric acid, sulfuric acid, antimonic acid, stannic acid, and heteropoly acid, phosphoric acid, and the like. Hydrocarbon polymer compound doped with a non-organic acid, organic / inorganic hybrid polymer partially substituted with proton conductive functional group, gel impregnated with phosphoric acid solution or sulfuric acid solution in polymer matrix An example is a proton conductive material.

  The thickness of the solid polymer electrolyte membrane 110 is appropriately determined in consideration of the characteristics of the MEA 100 and PEFC, and is not particularly limited. However, the thickness of the solid polymer electrolyte membrane 110 is preferably 5 to 300 μm, more preferably 10 to 200 μm, still more preferably 15 to 150 μm, and particularly preferably 15 to 30 μm. When the thickness is within such a range, the balance between strength during film formation, durability during use, and output characteristics during use can be appropriately controlled.

[Cathode gas diffusion electrode]
The cathode gas diffusion electrode 120c includes a cathode catalyst layer 122c and a cathode gas diffusion layer 124c.

  The cathode catalyst layer 122c is a layer containing an electrode catalyst on which a catalyst component is supported and an ionomer.

In the cathode catalyst layer 122c, the electrode catalyst is mainly composed of protons (H ⁺ ) via the solid polymer electrolyte membrane 110, electrons (e ⁻ ) via the external circuit, and oxygen (O ₂ ) derived from the oxidant gas. It has a function of promoting a reaction for generating water (that is, a reduction reaction of oxygen).

  Simply speaking, the electrode catalyst has a structure in which a catalyst component such as platinum is supported on the surface of a conductive carrier made of carbon or the like.

  The electroconductive carrier constituting the electrode catalyst may be any one having a specific surface area sufficient to support the catalyst component in a desired dispersed state and sufficient electron conductivity. In the composition of the conductive carrier (electron conductive carrier), the main component is preferably carbon. Specific examples of the material for the conductive carrier include carbon black, activated carbon, coke, natural graphite, and artificial graphite. “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. Note that “substantially consisting of carbon atoms” means that contamination of about 2 to 3 mass% or less of impurities can be allowed.

The BET specific surface area of the conductive carrier is not particularly limited as long as it is a specific surface area sufficient to carry the catalyst component in a highly dispersed manner, but is preferably 100 to 1500 m ² / g, more preferably 200 to 1000 m. ² / g. When the specific surface area of the conductive support is in such a range, the balance between the dispersibility of the catalyst component on the conductive support and the effective utilization rate of the catalyst component can be appropriately controlled.

  Although there is no restriction | limiting in particular also about the average particle diameter of an electroconductive support | carrier, Usually, it is 5-200 nm, Preferably it is about 10-100 nm. In addition, as a value of “average particle diameter of the conductive carrier”, a value calculated by a primary particle diameter measurement method using a transmission electron microscope (TEM) is adopted.

  The catalyst component supported on the conductive carrier is not particularly limited as long as it has a function of catalytically promoting the oxygen reduction reaction described above, and a conventionally known catalyst component can be appropriately used. Specific examples of the catalyst component include platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, and alloys thereof. Etc. Among these, the catalyst component preferably contains at least platinum from the viewpoint of excellent catalytic activity, poisoning resistance to carbon monoxide and the like, and heat resistance. In this case, the shape as the catalyst component is not particularly limited, and for example, a particulate shape is preferable. The composition of the alloy in the case of using an alloy as the catalyst component in the cathode catalyst layer 122c varies depending on the type of metal to be alloyed and the like, and can be appropriately selected by those skilled in the art, but is preferably about 30 to 90 atomic% platinum. The other metal to be converted is about 10 to 70 atomic%. Note that an “alloy” is a general 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 used in the present application. Here, the alloy composition can be specified by using an ICP emission analysis method.

  The shape and size of the catalyst component are not particularly limited, and the same shape and size as those of conventionally known catalyst components can be adopted as appropriate, but the shape of the catalyst component is preferably granular. And the average particle diameter of a catalyst particle becomes like this. Preferably it is 1-30 nm, More preferably, it is 1.5-20 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. In the present invention, the value of the “average particle diameter of the catalyst particles” is the particle diameter of the catalyst component determined from the crystallite diameter determined from the half-value width of the diffraction peak of the catalyst component in X-ray diffraction or the transmission electron microscope image. It can be calculated as an average value of diameters.

  The ratio of the content of the conductive support and the catalyst component in the electrode catalyst is not particularly limited. However, the content (supported amount) of the catalyst component is preferably 10 to 150% by mass, more preferably 25 to 120% by mass, and further preferably 40 to 100% based on 100% by mass of the conductive carrier. % By mass. When the content of the catalyst component is 10% by mass or more, the catalyst-producing ability of the electrode catalyst is sufficiently exerted, which can contribute to the improvement of the power generation performance of PEFC100. On the other hand, the catalyst component content of 150% by mass or less is preferable because aggregation of the catalyst components on the surface of the conductive support is suppressed and the catalyst components are highly dispersed and supported. In addition, as a value of the ratio of content mentioned above, the value measured by ICP emission spectrometry shall be employ | adopted.

  The cathode catalyst layer 122c further includes an ionomer in addition to the electrode catalyst described above. The specific form of the ionomer contained in the cathode catalyst layer 122c is not particularly limited, and conventionally known knowledge can be appropriately referred to in the technical field of fuel cells. For example, as the ionomer included in the cathode catalyst layer 122c, the ionomer that constitutes the above-described solid polymer electrolyte membrane 110 can be similarly used. Therefore, details of the specific form of the ionomer are omitted here. In addition, the ionomer contained in the cathode catalyst layer 122c may be one kind alone, or two or more kinds.

  The ion exchange capacity of the ionomer contained in the cathode catalyst layer 122c is preferably 0.9 to 1.5 mmol / g, and preferably 1.1 to 1.5 mmol / g, from the viewpoint of excellent ion conductivity. Is more preferable.

  The “ion exchange capacity” of an ionomer means the number of moles of sulfonic acid groups per unit dry mass of the ionomer. The value of “ion exchange capacity” can be calculated by removing the dispersion medium of the ionomer dispersion by heat drying or the like to obtain a solid polymer electrolyte, and performing neutralization titration.

  There is no particular limitation on the ionomer content in the cathode catalyst layer 122c. However, the ratio of the ionomer content to the conductive carrier content in the cathode catalyst layer 122c (ionomer / conductive carrier mass ratio) is preferably 0.5 to 2.0, more preferably 0.7. It is -1.5, More preferably, it is 0.9-1.3. The mass ratio of ionomer / conductive carrier is preferably 0.9 or more from the viewpoint of suppressing the internal resistance of the electrolyte membrane-electrode assembly. On the other hand, an ionomer / conductive carrier mass ratio of 2.0 or less is preferable from the viewpoint of suppressing flooding.

  The cathode gas diffusion layer 124c is disposed on the surface of the cathode catalyst layer 122c described above facing the solid polymer electrolyte membrane 110. As described above, the cathode gas diffusion layer 122c can be formed by laminating at least two gas diffusion layer base materials having different compression elastic moduli. Among the gas diffusion layer substrates, the gas diffusion layer substrate closest to the catalyst layer is the gas diffusion layer substrate C (124 cc), and the gas diffusion layer substrate disposed adjacent to the separator is the gas diffusion layer substrate. Material S (124cs). And the compression elastic modulus of the said gas diffusion layer base material S (124cs) is the highest in a gas diffusion layer base material, and thickness is the thinnest.

  The cathode gas diffusion layer 124c has a function of promoting the diffusion of the oxidant gas supplied through a gas flow path of the separator described later to the cathode catalyst layer 122c and a function as an electron conduction path.

  When the base material of the cathode gas diffusion layer 124c is formed by laminating at least two gas diffusion layer base materials having different compression elastic moduli, the compression elastic modulus of the gas diffusion layer base material S is relatively high in the gas diffusion layer base material. If it is the highest, it will not specifically limit, A conventionally well-known knowledge can be referred suitably. Examples of the base material of the cathode gas diffusion layer 124c include conductive and porous sheets such as stainless fiber paper, carbon paper, carbon woven fabric, non-woven fabric, other metallic paper-like paper bodies, felt, and non-woven fabric. Material. Here, as a specific example of a combination of two gas diffusion layer base materials having different compressive elastic moduli, as gas diffusion layer base material S: gas diffusion layer base material C, stainless fiber paper: stainless fiber paper, Carbon paper: carbon non-woven fabric, carbon paper: carbon paper, metal papermaking body: carbon paper, metal papermaking body: carbon non-woven fabric, etc., and those subjected to surface treatment. Among these, from the viewpoint of improving power generation performance, stainless steel paper: stainless steel paper is preferable in terms of reducing electric resistance. From the viewpoint of cost, carbon paper: carbon non-woven fabric is preferred in terms of versatility and workability.

  Further, specific examples of combinations of three gas diffusion layer base materials having different compressive elastic moduli include: gas diffusion layer base material S: gas diffusion layer base material X: gas diffusion layer base material C; : Carbon paper: Carbon non-woven fabric, Carbon paper: Carbon non-woven fabric: Carbon paper, Carbon paper: Carbon cloth: Carbon non-woven fabric, Stainless steel paper: Carbon non-woven fabric: Carbon paper, etc. Among them, from the viewpoint of durability, stainless steel paper: carbon paper: carbon non-woven fabric, carbon paper: carbon non-woven fabric: carbon paper is preferable from the viewpoint of reducing surface pressure fluctuation accompanying dimensional change. In the case of a combination of three gas diffusion layer base materials having different compressive elastic moduli, there are effects such as an increase in allowable dimensional change and further simplification of the load adjusting mechanism.

  The cathode gas diffusion layer 124c may be subjected to water repellent treatment and hydrophilic treatment as appropriate in accordance with desired operating conditions, output characteristics, constituent material characteristics, and the like of the fuel cell.

  The cathode gas diffusion electrode 120c may further include other members (layers) as necessary. For example, in order to promote the discharge of excess moisture present in the cathode catalyst layer 122c and suppress the occurrence of the flooding phenomenon, the cathode gas diffusion layer 124c has a cathode microporous layer 140c containing carbon particles as a base catalyst layer. You may have on the side.

  Such carbon particles are not particularly limited, and conventionally known materials such as carbon black, graphite, and expanded graphite can be appropriately employed as the electron conductive substance. Among them, carbon black such as oil furnace black, channel black, lamp black, thermal black, acetylene black and the like can be preferably used because of excellent electron conductivity and a 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.

  The cathode microporous layer 140c may include a water repellent (conductive water repellent layer). Examples of the water repellent include fluorine-based polymer materials such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Examples include polypropylene and polyethylene. Among them, a fluorine-based polymer material (for example, polytetrafluoroethylene) can be preferably used because of excellent water repellency, corrosion resistance during electrode reaction, and the like.

[Anode gas diffusion electrode]
The anode gas diffusion electrode 120a includes an anode catalyst layer 122a and an anode gas diffusion layer 124a.

  The anode catalyst layer 122a is a layer containing an electrode catalyst on which a catalyst component is supported and an ionomer.

In the anode catalyst layer 122a, the electrode catalyst has a function of promoting a reaction in which hydrogen (H ₂ ) derived from fuel gas is converted into protons (H ⁺ ) and electrons (e ⁻ ) (that is, hydrogen oxidation reaction).

  As for the specific forms of the electrode catalyst and ionomer constituting the anode catalyst layer 122a, the forms described above in the column of the cathode catalyst layer 122c can be similarly adopted. Therefore, detailed description is omitted here. The cathode catalyst layer 122c and the anode catalyst layer 122a may have the same or different specific forms of electrode catalyst and ionomer that constitute the catalyst layer.

  In the MEA 100 of the present embodiment, the average thickness (Ya) of the anode catalyst layer 122a is preferably smaller than the average thickness (Yc) of the cathode catalyst layer 122c. When Ya is smaller than Yc, proton conductivity to the cathode catalyst layer 122c is improved. Specifically, Ya / Yc is preferably 0.1 to 0.9, and more preferably 0.2 to 0.5. In addition, the average thickness of the anode catalyst layer 122a is preferably 1.0 to 20.0 μm, and more preferably 2.0 to 5.0 μm. In addition, as a value of the thickness of the catalyst layer, a value obtained by observing a cross section of the catalyst layer with a scanning electron microscope (SEM) is adopted.

  As for a specific form of the anode gas diffusion layer 124a constituting the anode gas diffusion electrode 120a, the form described above in the column of the cathode gas diffusion layer 124c constituting the cathode gas diffusion electrode 120c can be similarly adopted. Therefore, detailed description is omitted here. In addition, the anode gas diffusion electrode 120a may further include a member (layer) such as the anode microporous layer 140a as necessary, similarly to the cathode gas diffusion electrode 120c described above.

  So far, the use of the MEA of the present invention for a fuel cell represented by PEFC has been described, but the MEA of the present invention is not limited to this application.

  In the present invention, a stack in which a plurality of MEAs are stacked and connected in series via a separator may be formed so that the fuel cell can obtain a desired voltage. The shape of the fuel cell is not particularly limited, and may be appropriately determined so that desired battery characteristics such as voltage can be obtained.

  The present invention also includes a vehicle equipped with the above-described PEFC or fuel cell stack of the present invention. The PEFC and fuel cell stack of the present invention exhibit stable power generation performance in low humidification to high humidification operation and low temperature to high temperature operation, and also show stable performance during the fuel cell usage period, and are excellent in output performance. Therefore, it is suitable for vehicle applications that require high output. Further, it can be widely applied to household fuel cells, electronic device fuel cells, and the like.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these.

<Tenting ratio>
The tenting ratio (%) is calculated by the following mathematical formula as described above.

  Tenting amount m and flow path depth L were observed with an optical microscope with a length measurement function when the gas diffusion layer base material S and the separator with a gas flow path to be used were brought into contact with each other and a load was applied. It was calculated by doing.

<Compression test (compression elastic modulus, difference in compression strain) / tensile test (elongation at break)>
The measurement was performed by measuring the applied load to the gas diffusion layer (GDL) and the displacement at that time using a commercially available device (Universal Material Tester Model 5867 manufactured by Instron).

  The measurement conditions are as follows.

  Under the above measurement conditions, the compression modulus (thickness direction), the difference in compression strain, and the elongation at break (plane direction) were measured.

<Air permeability>
Measured as a value corresponding to the degree of air resistance described in JIS (1998) P8117 Gurley tester method. Specifically, using a commercially available device (Automated Perm Porometer CFP 1200 manufactured by PMI), the pressure difference applied to both sides of the GDL and the gas flow rate flowing in the thickness direction of the GDL at that time were measured, and the value converted to Gurley was calculated. Calculated.

<Example 1>
1. Preparation of an electrode catalyst layer Carbon black (Ketjen Black manufactured by Mitsubishi Chemical Corporation BET specific surface area 800 m ² / g, average particle size 40 nm) was used as an electron conductive carrier, and this electron conductive carrier had an average particle size of 2 to 3 nm. An electrode catalyst carrying 41 wt% of platinum particles was prepared.

  The electrode catalyst, pure water, and a proton conductive electrolyte solution (Nafion solution DE520 manufactured by DuPont, electrolyte content 5 wt%) are mixed into a mass ratio of the electrocatalyst conductive support to the proton conductive electrolyte (the mass of the proton conductive electrolyte). The electrocatalyst slurry was prepared by mixing, stirring, and defoaming with a mass of / conductive support) of 0.79.

The prepared electrode catalyst slurry was applied on a Teflon sheet using a screen printing method to produce an electrode catalyst layer. At this time, catalyst slurry application conditions were adjusted so that the Pt mass per unit area was 0.4 mg / cm ² , the area of the electrode catalyst layer was 5 cm × 5 cm, and the thickness of the electrode catalyst layer was 10 μm.

2. Preparation of Gas Diffusion Layer A 200 μm thick stainless fiber paper is pre-compressed at a pressure higher than the surface pressure expected to occur in the fuel cell operating environment to a thickness of 70 μm, and the compression modulus at 1 MPa point The pressure was 60 MPa, punched out into a 7 cm square, and used as a gas diffusion layer substrate S. At this time, the breaking strain was 0.9%. In addition, a stainless fiber paper having a thickness of 500 μm was subjected to a compression treatment in the same manner as described above to obtain a thickness of 250 μm, a compression elastic modulus of 40 MPa at a point of 1 MPa, and punching into a 7 cm square, which was used as a gas diffusion layer substrate C . In addition, the difference of the compressive strain of the gas diffusion layer base material C in the load application direction and the difference of the compressive strain in the unloading direction were 0.04 when compared at the 1 MPa point.

  Subsequently, in order to perform water repellency treatment on the gas diffusion layer base material S and the gas diffusion layer base material C, each gas diffusion layer was treated with a polytetrafluoroethylene (PTFE) dispersion (Daikin Industries, Ltd., D- 1, a PTFE solution containing 60% by mass was diluted with pure water), and after dipping for 5 minutes, it was pulled up and drained. Then, it was dried in the atmosphere at 60 ° C. for 30 minutes.

  Subsequently, in order to form a microporous layer (carbon particle layer, conductive water-repellent layer) on the surface of the gas diffusion layer C subjected to the water-repellent treatment, carbon black (VULCAN XC-72R manufactured by CABOT) and the above The same PTFE dispersion and pure water as used in 1 were mixed and dispersed in a homogenizer for 3 hours to form a slurry. The obtained slurry was uniformly applied to one surface of the gas diffusion layer base material C which had been previously subjected to water repellent treatment, using a doctor blade method. Thereafter, similarly, after drying at 60 ° C. for 30 minutes in the atmosphere, the gas diffusion layer base material C coated with the gas diffusion layer base material S and the microporous layer is used to weld and fix the water repellent. Baked at 350 ° C. for 30 minutes. Thereafter, the gas diffusion layer base material C and the gas diffusion layer base material S coated with the microporous layer were punched into a 5 cm square. Thereby, the gas diffusion layer base material S and the gas diffusion layer base material C were laminated | stacked, and the gas diffusion layer in which the microporous layer (thickness 50 micrometers) was formed on the gas diffusion layer base material C was obtained.

3. 1. Assembly of membrane electrode assembly and single cell A Teflon sheet coated with an electrode catalyst layer is placed on both sides of an electrolyte membrane (Dafon Nafion 112, thickness 50 μm, area 10 cm × 10 cm) at 150 ° C. for 10 minutes. After hot pressing at a pressure of 0 MPa, only the Teflon sheet was peeled off to produce an electrolyte membrane with an electrode catalyst layer.

  Subsequently, the previously prepared gas diffusion layer was disposed on both sides of the electrolyte membrane with an electrode catalyst layer so as to be inside the microporous layer, thereby forming a membrane electrode assembly.

  A sealing material and a gas separator with a gas flow path are arranged on both sides of the obtained membrane electrode assembly and tightened to a predetermined surface pressure (1.0 MPa) to produce a single cell of a fuel cell as shown in FIG. did.

  As shown in FIG. 1, the fuel cell of Example 1 includes an electrolyte membrane-electrode assembly 100 and a pair of separators that include the cathode-side separator 150 c and the anode-side separator 150 a that sandwich the electrolyte membrane-electrode assembly 100. And having. The MEA 100 includes an electrolyte membrane 110 having proton conductivity, a cathode gas diffusion electrode 120a including a cathode catalyst layer 122c and a cathode gas diffusion layer 124c disposed on one surface of the electrolyte membrane 110, and the electrolyte membrane 110. And an anode gas diffusion electrode 120a including an anode catalyst layer 122c and an anode gas diffusion layer 124a, which are disposed on the other surface of the electrode. Each catalyst layer (122a, 122c) includes carbon black as an electron conductive carrier, platinum particles as catalyst particles, and a perfluorosulfonic acid electrolyte as a proton conductive electrolyte. Further, the cathode gas diffusion layer 124c and the anode gas diffusion layer 124a are constituted by two gas diffusion layer base materials (124cs, 124cc, 124ac, 124as) having different thicknesses and compression elastic moduli. In addition, conductive water repellent layers (microporous layers) (140a, 140c) are placed in contact with the catalyst layers (122a, 122c).

<Example 2>
As the gas diffusion layer base material S, carbon paper (thickness 130 μm, compressive elastic modulus at about 1 MPa point, about 25 MPa, elongation at break 0.4%) is used, and as the gas diffusion layer base material C, carbon non-woven fabric (thickness 200 μm, 1 MPa point) This was carried out in the same manner as in Example 1 except that the compression elastic modulus at 17 MPa and the difference in compression strain of 0.03) were used. The fuel cell of Example 2 has the same structure as that of Example 1.

1 is a schematic cross-sectional view of a fuel cell (solid polymer fuel cell; PEFC) of the present invention. It is the figure which represented generation | occurrence | production of tenting typically. It shows the relationship between “difference in compressive strain” applied to GDL and “surface pressure (stress)”. It shows the relationship between “surface pressure” and “thickness” applied to the GDL. It is the figure which represented notionally the surface pressure change accompanying a tenting amount and a dimensional change.

Explanation of symbols

100 membrane electrode assembly (MEA),
110 solid polymer electrolyte membrane,
120a anode gas diffusion electrode,
120c cathode gas diffusion electrode,
122a anode catalyst layer,
122c cathode catalyst layer,
124a anode gas diffusion layer,
124c cathode gas diffusion layer,
140a anode microporous layer,
140c cathode microporous layer,
150a anode side separator,
150c cathode side separator,
152a fuel gas flow path,
152c Oxidant gas flow path.

Claims (8)

An electrolyte membrane, a cathode gas diffusion electrode including a cathode catalyst layer and a cathode gas diffusion layer disposed on one surface of the electrolyte membrane, and an anode catalyst layer and an anode gas disposed on the other surface of the electrolyte membrane An electrolyte membrane-electrode assembly having an anode gas diffusion electrode including a diffusion layer,
The cathode gas diffusion layer or the anode gas diffusion layer is formed by laminating at least two gas diffusion layer substrates having different compressive elastic moduli, and the gas diffusion disposed adjacent to the separator in the gas diffusion layer substrate. An electrolyte membrane-electrode assembly in which when the layer base material is a gas diffusion layer base material S, the gas diffusion layer base material S has the highest compression elastic modulus and the smallest thickness. When the gas diffusion layer base material C is the gas diffusion layer base material closest to the catalyst layer in the gas diffusion layer base material,
The electrolyte membrane-electrode assembly according to claim 1, wherein the ratio of the compression elastic modulus of the gas diffusion layer base material S to the compression elastic modulus of the gas diffusion layer base material C is 1.3 to 5.0.   The electrolyte membrane-electrode assembly according to claim 1 or 2, wherein the ratio of the thickness of the gas diffusion layer substrate S to the gas diffusion layer substrate C is 0.1 to 0.9.   The difference of the compressive strain of the gas diffusion layer base material C at the same surface pressure during load application and unloading to the gas diffusion layer base material C is 0.2 or less. 2. The electrolyte membrane-electrode assembly according to claim 1.   The electrolyte membrane-electrode assembly according to claim 1, wherein the elongation at break of the gas diffusion layer base material S is 5% or less.   The electrolyte membrane-electrode assembly according to any one of claims 1 to 5, wherein a tenting ratio of the gas diffusion layer base material S is 10% or less and an air permeability is 1 second or less. The electrolyte membrane-electrode assembly according to any one of claims 1 to 5,
A pair of separators comprising a cathode side separator and an anode side separator sandwiching the electrolyte membrane-electrode assembly;
A fuel cell.   A vehicle equipped with the fuel cell according to claim 7 as a power source for driving a motor.

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