Gas diffusion layer, gas diffusion electrode, membrane electrode assembly, fuel cell, method for manufacturing a gas diffusion layer, method for manufacturing a gas diffusion electrode, and method for manufacturing a membrane electrode assembly

Abstract

A gas diffusion layer, a gas diffusion electrode, a membrane electrode assembly, a fuel cell, a method for manufacturing the gas diffusion layer, a method for manufacturing the gas diffusion electrode, and a method for manufacturing the membrane electrode assembly, each comprising a carbon fiber layer and a microporous layer provided on the carbon fiber layer, comprising an aromatic polyamide pulp, a water-dispersible resin, and a carbon-based conductive material.

Description

[Technical Field]

[0001] This disclosure relates to a gas diffusion layer, a gas diffusion electrode, a membrane electrode assembly, a fuel cell, a method for manufacturing a gas diffusion layer, a method for manufacturing a gas diffusion electrode, and a method for manufacturing a membrane electrode assembly. [Background technology]

[0002] Fuel cells are broadly classified into four types based on the type of electrolyte used: molten carbonate fuel cells (MCFCs), solid oxide fuel cells (SOFCs), phosphoric acid fuel cells (PAFCs), and polymer electrolyte fuel cells (PEFCs).

[0003] Among the above, solid polymer fuel cells include a membrane electrode assembly (MEA) in which a thin polymer electrolyte membrane is sandwiched between a gas diffusion layer (GDL) via a catalyst layer. The configuration comprising a catalyst layer and a gas diffusion layer is called a gas diffusion electrode (GDE).

[0004] The performance requirements for the gas diffusion layer have traditionally included gas diffusion performance to guide fuel gas or air into the catalyst layer and diffuse the fuel gas into the catalyst layer, water-repellent performance to discharge the generated water produced by the power generation reaction to the separator, high conductivity to extract the generated current to the outside without loss, and resistance to strongly acidic and strongly basic atmospheres caused by the generated ions.

[0005] Typically, a gas diffusion layer comprises a carbon fiber layer, such as a carbon fiber sheet, and a microporous layer (also known as a Micro Porous Layer: MPL, microporous layer, fine porous layer, or water-repellent layer) on the surface of the carbon fiber layer, from the viewpoint of uniformly diffusing fuel gas into the catalyst layer and adjusting the wettability of the membrane electrode assembly.

[0006] Conventional gas diffusion layers are formed by applying a microporous layer-forming coating solution onto a carbon fiber layer, followed by drying and sintering, thereby creating a microporous layer on top of the carbon fiber layer.

[0007] For example, Patent Document 1 describes how a gas diffusion layer with a microporous layer is manufactured by coating the surface of a carbon fiber sheet with a slurry containing a carbon-based conductive material and a fluororesin at appropriate concentrations using a spray or knife coating method. Furthermore, for example, Patent Document 2 proposes a method for producing a gas diffusion layer by dispersing a fibril-like substance consisting of a conductive carbon material, a fluororesin, and an aromatic polyamide in a solvent, forming a paper mold, hot-pressing the resulting precursor, and then firing it.

[0008] Patent document 1: Japanese Patent Application Laid-Open No. 7-220734 Patent Document 2: International Publication No. 2012-026498 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, conventional coating methods are prone to inconsistencies in the thickness and film quality of the resulting microporous layer due to technical factors. As a result, when a catalyst layer is placed on top of the gas diffusion layer to form a gas diffusion electrode, carbon fibers contained in the carbon fiber layer tend to protrude into the microporous layer, damaging the microporous layer and the catalyst layer placed on top of it, thus impairing their properties. Batteries with a gas diffusion layer in which the properties of the microporous layer and catalyst layer have been impaired tend to have reduced battery performance.

[0010] Therefore, this disclosure aims to provide a gas diffusion layer that suppresses roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer, as well as a gas diffusion electrode, a membrane electrode assembly, and a fuel cell equipped therewith. This disclosure also provides a simple method for manufacturing the gas diffusion layer. [Means for solving the problem]

[0011] The following are examples of specific means for solving the problem: <1> A carbon fiber layer, A microporous layer provided on the carbon fiber layer comprises aromatic polyamide pulp, a water-dispersible resin, and a carbon-based conductive material, A gas diffusion layer having the following characteristics. <2> The microporous layer has a maximum peak in the pore size distribution of 0.1 μm or more and 5.0 μm or less. <1> The gas diffusion layer described above. <3> The microporous layer has a tensile modulus of 300 MPa or more and 900 MPa or less. <1> The gas diffusion layer described above. <4> The aforementioned <1> ~ <3> A gas diffusion layer described in any one of the following, A catalyst layer provided on the microporous layer in the gas diffusion layer, A gas diffusion electrode having <5> Polymer electrolyte membrane, The system comprises a pair of gas diffusion electrodes that sandwich the polymer electrolyte membrane, At least one of the pair of gas diffusion electrodes is <4> A membrane electrode assembly, which is a gas diffusion electrode as described above. <6> The aforementioned <5> The membrane electrode assembly described above, Separator and, A fuel cell equipped with a fuel cell. <7> The process includes a step of forming a laminate by bonding a microporous sheet containing aromatic polyamide pulp, a water-dispersible resin, and a carbon-based conductive material with a carbon fiber sheet. A method for manufacturing a gas diffusion layer. <8> The microporous sheet has a maximum peak in the pore size distribution of 0.1 μm or more and 5.0 μm or less. <7> A method for producing a gas diffusion layer as described above. <9> The microporous sheet has a tensile modulus of 300 MPa or more and 900 MPa or less. <7> or <8> A method for producing a gas diffusion layer as described above. <10> The process further includes heating and pressing the laminate from the stacking direction in a range of 150°C to 400°C, <7> ~ <9> A method for manufacturing a gas diffusion layer as described in any one of the following. <11> The aforementioned <7> ~ <10> A step of manufacturing a gas diffusion layer by any one of the manufacturing methods described in the following: A step of providing a catalyst layer on the surface of the microporous sheet side in the manufactured gas diffusion layer; A method for manufacturing a gas diffusion electrode, comprising: <12> A step of manufacturing a gas diffusion layer by the manufacturing method according to any one of <7> to <10>; A step of providing a catalyst layer and a polymer electrolyte membrane in this order on the surface of the microporous sheet side in the manufactured gas diffusion layer; A method for manufacturing a membrane electrode assembly, comprising: <13> A method for manufacturing the membrane electrode assembly according to <12>, wherein a catalyst layer and a polymer electrolyte membrane are provided in this order on the surface of the microporous sheet side in the manufactured gas diffusion layer, and pressure bonding is performed within a range of 60°C or higher and 130°C or lower.

Advantages of the Invention

[0012] According to the present disclosure, there are provided a gas diffusion layer, a gas diffusion electrode, a membrane electrode assembly, and a fuel cell in which roughening of a microporous layer or a catalyst layer due to protrusion of carbon fibers contained in a carbon fiber layer is suppressed. Further, according to the present disclosure, a simple manufacturing method of a gas diffusion layer is also provided.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of a membrane electrode assembly according to the present disclosure. [Figure 2] FIG. 2 is a pore distribution diagram when [dV / d(log d) (cc / g)] of the microporous layer in the gas diffusion layer of Example 1 is taken as the vertical axis and the pore diameter (μm) of the microporous layer is taken as the horizontal axis. [Figure 3] FIG. 3 is a cross-sectional photograph in the stacking direction of the gas diffusion layer of Example 1 observed by a scanning electron microscope.

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments which are an example of the present disclosure will be described. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the invention. In numerical ranges described stepwise within this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described within this specification, the upper or lower limit of that range may be replaced with the values ​​shown in the examples.

[0015] Each component may contain multiple types of the relevant substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, unless otherwise specified, it refers to the total amount of those multiple substances present in the composition.

[0016] When describing embodiments with reference to the drawings, components having substantially the same function will be given the same reference numeral throughout the drawings, and redundant explanations may be omitted.

[0017] <Methods for measuring various physical properties> The measurement methods used in this specification are as follows: The method for measuring the thickness of the microporous layer is as follows: The thickness of the microporous layer was measured at 10 cm intervals at five arbitrary points using a thickness gauge (manufactured by Ono Sokki), and the arithmetic mean of these measurements was taken as the thickness of the microporous sheet.

[0018] The method for measuring the water contact angle of a microporous layer is as follows. Water is dropped onto a microporous layer, and the contact angle is measured using a contact angle meter (KYOWA DMo-502) at 20°C to 25°C and 65% RH.

[0019] The method for measuring the pore size distribution of a microporous layer is as follows: A fully automated pore size distribution analyzer (Anton Paar PoreMaster60-GT) is used to measure the pore size distribution in a microporous layer, ranging from 0.01 μm to 100 μm. The observed maximum peak value is then defined as the maximum peak in the pore size distribution, with the vertical axis being [dV / d(logd)(cc / g)] and the horizontal axis being pore size (μm).

[0020] The method for measuring the tensile modulus of a microporous layer is as follows. A 13 cm sample was obtained by collecting a microporous layer from the gas diffusion layer to be measured. Using a Tensilon (Orientec RTC-1310A), the breaking strength and elongation at break were measured under the conditions of a chuck distance of 10 cm, a tensile speed of 50 mm / min, 20°C to 25°C, and 65% RH, and the tensile modulus was calculated.

[0021] The laminated structure of the laminate and the state of each layer can be confirmed by cutting the gas diffusion layer along the lamination direction and observing the cross-section with a scanning electron microscope (SU3500, Hitachi, Ltd.).

[0022] The carbon fibers, carbon milled fibers, and carbon nanofibers described herein may consist of multiple fibers having different average fiber diameters. The carbon fibers, carbon milled fibers, and carbon nanofibers described herein may consist of multiple fibers having different average fiber lengths. The carbon fibers, carbon milled fibers, and carbon nanofibers described herein may consist of multiple fibers having different average fiber diameters and average fiber lengths.

[0023] <Gas diffusion layer> The gas diffusion layer according to this disclosure comprises a carbon fiber layer and a microporous layer provided on the carbon fiber layer, comprising aromatic polyamide pulp, a water-dispersible resin, and a carbon-based conductive material.

[0024] The gas diffusion layer according to this disclosure, having the above configuration, suppresses roughening of the microporous layer and catalyst layer due to the protrusion of carbon fibers contained in the carbon fiber layer. Therefore, even when a battery is equipped with the gas diffusion layer according to this disclosure, the deterioration of battery performance caused by roughening of the microporous layer and catalyst layer is also suppressed.

[0025] [Carbon fiber layer] The carbon fiber layer is not particularly limited, and any known carbon fiber layer that can be used as a diffusion layer in a gas diffusion layer can be applied.

[0026] The carbon fiber layer has a specific gravity of 1.10 g / cm³, which is desirable for effectively controlling the diffusivity of the gas diffusion layer. 3 More than 2.00g / cm 3 Preferably, it is 1.50 g / cm³. 3 More than 1.90g / cm 3 The following is more preferable:

[0027] The average fiber diameter of the fibers contained in the carbon fiber layer is not particularly limited, but from the viewpoint of suitably controlling the diffusivity of the gas diffusion layer, it is preferably 5.0 μm to 50.0 μm, and more preferably 5.0 μm to 20.0 μm.

[0028] The average fiber length of the fibers contained in the carbon fiber layer is not particularly limited, but from the viewpoint of handling, it is preferably 1.0 mm to 15.0 mm, and more preferably 2.0 mm to 10.0 mm.

[0029] The thickness of the carbon fiber layer is not particularly limited, but from the viewpoint of ease of handling, it is preferably 100 μm to 300 μm, and more preferably 120 μm to 250 μm.

[0030] [Microporous layer] The microporous layer (so-called MPL layer) contains aromatic polyamide pulp, water-dispersible resin, and carbon-based conductive material. The microporous layer may further contain other materials besides aromatic polyamide pulp, water-dispersible resin, and carbon-based conductive material.

[0031] The microporous layer is provided on top of the carbon fiber layer. The microporous layer may be provided in contact with the carbon fiber layer, or it may be provided between the microporous layer and the carbon fiber layer with another layer in between. The microporous layer may be provided on a portion of the carbon fiber layer, but it is preferable that it be provided on the entire carbon fiber layer.

[0032] (Aromatic polyamide pulp) Aromatic polyamide pulp (hereinafter also referred to as "aramid pulp") is, for example, a fiber of aromatic polyamide having amide bonds in which 85 mol% or more of the amide bonds are formed by the dehydration condensation of aromatic diamine components and aromatic dicarboxylic acid components. It is preferable that the aramid pulp has fibers that are highly fibrillated. Examples of aramids include poly(p-phenylene terephthalamide), copoly(p-phenylene-3,4'-oxydiphenylene-terephthalamide), poly(metaphenylene isophthalamide), poly(p-benzuamide), poly-4,4'-diaminobenzanilide, poly(p-phenylene-2,6-naphthalicamide), copoly(p-phenylene / 4,4'-(3,3'-dimethylbiphenylene)terephthalamide, poly(orthophenylene terephthalamide), poly(p-phenylene phthalamide), and poly(metaphenylene isophthalamide).

[0033] Fibrillation refers to a method of randomly forming minute single fibers on the surface of a fiber. In this disclosure, fibrillation of aramid pulp is carried out by known methods. For example, it is carried out by adding a precipitating agent to an organic polymer solution as described in Japanese Patent Publication No. 35-11851 and Japanese Patent Publication No. 37-5752, and mixing them in a system that generates shear force. Alternatively, it can be carried out by applying mechanical shear force, such as beating, to a molded article having molecular orientation formed from an optically anisotropic polymer solution as described in Japanese Patent Publication No. 59-603, thereby randomly imparting minute single fibers.

[0034] The average fiber length of aramid pulp is not particularly limited, but from the viewpoint of high strength and high modulus of elasticity, it is preferably 0.1 mm to 10.0 mm, more preferably 0.2 mm to 5.0 mm, and even more preferably 0.3 mm to 3.0 mm.

[0035] (Water-dispersed resin) The water-dispersible resin can be contained within the microporous layer, for example, attached to the surface of the aromatic polyamide pulp, or fused to the surface of the aromatic polyamide pulp. The inclusion of this water-dispersible resin imparts water repellency to the microporous layer.

[0036] The water-dispersible resin is not particularly limited, and any known water-dispersible resin used in the gas diffusion layer may be used. The water-dispersible resin may be used alone or in combination of two or more types.

[0037] Examples of water-dispersible resins include fluororesins, water-dispersible acrylic resins, water-dispersible polyester resins, water-dispersible polystyrene resins, and water-dispersible urethane resins. Among these, it is preferable to include fluororesins as the water-dispersible resin from the viewpoint of having excellent water repellency.

[0038] Examples of fluororesins include tetrafluoroethylene resin (hereinafter sometimes referred to as "PTFE"), perfluoroalkoxy resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, tetrafluoroethylene-ethylene copolymer resin, vinylidene fluoride resin, trifluoroethylene chloride, and the like. Among the above, it is preferable that the fluororesin contains PTFE from the viewpoint of having excellent heat resistance and sliding properties.

[0039] (Carbon-based conductive material) The carbon-based conductive material only needs to be contained in the microporous layer; for example, it may be dispersed between the fibers of aromatic polyamide pulp. The inclusion of this carbon-based conductive material imparts conductivity to the microporous layer.

[0040] The carbon-based conductive material is not particularly limited, and any known carbon-based conductive material used in the gas diffusion layer may be used. The carbon-based conductive material may be used alone or in combination of two or more types.

[0041] As a carbon-based conductive material, it is preferable to use a material that has a carbon content of 94% by mass or more and a resistivity of 5 Ω·cm or less, from the viewpoint of conductive performance. Specific examples of carbon-based conductive materials include carbon fibers, carbon black, graphite particles, carbon nanotubes, carbon milled fibers, carbon nanofibers, carbon nanohorns, and graphene.

[0042] Among the above, the carbon-based conductive material preferably includes at least one selected from the group consisting of graphite particles, carbon black, carbon fibers, carbon milled fibers, and carbon nanofibers, more preferably includes at least one selected from the group consisting of carbon black, carbon fibers, carbon milled fibers, and carbon nanofibers, and even more preferably includes at least one of carbon milled fibers and carbon nanofibers. Including at least one selected from the group consisting of the above further suppresses roughening of the microporous layer and catalyst layer due to protrusions of carbon fibers contained in the carbon fiber layer.

[0043] • Graphite particles Examples of graphite particles include flaky graphite, scale-like graphite, clay-like graphite, artificial graphite, expanded graphite, expanded graphite, leaf-like graphite, nodular graphite, and spheroidal graphite. Spheroidal and flaky graphite are particularly preferred. The average particle size of the graphite particles is preferably between 0.05 μm and 300.0 μm.

[0044] • Carbon Black Examples of carbon black include acetylene black and Ketjenblack (registered trademark), which has a hollow shell structure. Ketjenblack is particularly preferred.

[0045] The average primary particle size of the carbon black is preferably, for example, 1.0 nm to 500.0 nm, more preferably 1.0 nm to 200.0 nm, and even more preferably 10.0 nm to 100.0 nm. The average secondary particle diameter of the carbon black is preferably, for example, 0.5 nm to 20.0 μm. If the average secondary particle diameter is 0.5 μm or more, further aggregation of the carbon black is suppressed when preparing the carbon black dispersion. If the average secondary particle diameter is 20.0 μm or less, the carbon-based conductive material can easily penetrate into the interior of the sheet, improving the conductivity of the sheet.

[0046] • Carbon fiber and carbon milled fiber Examples of carbon fibers and carbon milled fibers include PAN-based carbon fibers, pitch-based carbon fibers, and phenol-based carbon fibers, and among these, it is preferable to include pitch-based carbon fibers.

[0047] In this specification, "carbon milled fiber" refers to fibrous carbon fiber that has been ground into a powder (milled) form using a pulverizer or the like.

[0048] When using at least one of carbon fibers and / or carbon milled fibers, the average fiber diameter is not particularly limited, but is preferably, for example, 3 μm to 20 μm, and more preferably 5 μm to 13 μm.

[0049] The average fiber diameter is a value measured by microscopic observation. If the carbon fiber has a flattened cross-section, the arithmetic mean of the major and minor axes is used as the average fiber diameter.

[0050] When the average fiber diameter is 3 μm or more, the strength of the individual fibers is high, making it easier to improve the strength of the gas diffusion layer. When the average fiber diameter is 20 μm or less, localized lifting of the carbon fiber layer from the microporous layer is suppressed when used as a gas diffusion layer. As a result, the formation of surface irregularities caused by the lifting of the carbon fiber layer is suppressed, resulting in good surface smoothness and lower contact electrical resistance when used as a gas diffusion layer. In other words, it leads to superior battery performance.

[0051] The average fiber length (so-called cut length) of carbon fibers or carbon milled fibers is not particularly limited, but it is preferable to have an average fiber length of 20 mm or less. When the average fiber length is 20 mm or less, the uniform dispersion of the fibers improves, and the strength of the gas diffusion layer tends to improve.

[0052] The carbon content in carbon fibers and carbon milled fibers is preferably, for example, 94% by mass or more. A carbon content of 94% by mass or more improves the electrical conductivity of the sheet. Furthermore, even when a battery incorporating this gas diffusion layer is operated for a long period of time, the deterioration of the sheet is suppressed.

[0053] • Carbon nanofibers Carbon nanofibers may be single fibers or aggregates. The average fiber diameter of the carbon nanofibers (single fibers or aggregates) is preferably, for example, 100 nm or more and 1000 nm or less. If the average fiber diameter of carbon nanofibers is 100 nm or more, handling properties are good, and if it is 1000 nm or less, it is easier to increase the fiber density. The average fiber diameter of the carbon nanofibers is preferably 900 nm or less, more preferably 800 nm or less, even more preferably 600 nm or less, even more preferably 500 nm or less, even more preferably 450 nm or less, and even more preferably 400 nm or less. The average fiber diameter of the carbon nanofibers is preferably 110 nm or more, more preferably 120 nm or more, even more preferably 150 nm or more, and even more preferably 200 nm or more.

[0054] The average fiber length of the carbon nanofibers is preferably 1 μm or more, and more preferably 10 μm or more. If the average fiber length is 1 μm or more, it is possible to suppress a decrease in conductivity, strength, and liquid retention. Furthermore, if the average fiber length is 100 μm or less, the dispersibility of the carbon fibers is less likely to be impaired, and the carbon fibers are less likely to orient in the in-plane direction of the gas diffusion layer. As a result, it is easier to form conductive paths in the thickness direction of the gas diffusion layer. The average fiber length of carbon nanofibers is preferably 10 μm to 100 μm, and more preferably 12 μm to 80 μm, from the viewpoint of sheet strength.

[0055] Carbon nanofibers can be produced, for example, by the method disclosed in International Publication No. 2020 / 045243. Specifically, (1) A fiberization step to obtain resin composite fibers by molding a resin composition consisting of a thermoplastic resin and 30 to 150 parts by mass of mesophase pitch per 100 parts by mass of the thermoplastic resin in a molten state, thereby fiberizing the mesophase pitch. (2) A stabilization step to stabilize the resin composite fiber and obtain a resin composite stabilized fiber, (3) A thermoplastic resin removal step to obtain a stabilized fiber by removing the thermoplastic resin from the resin composite stabilizing fiber, (4) A carbonization and calcination step in which the stabilized fibers are heated in an inert atmosphere to carbonize or graphitize them to obtain a carbon fiber aggregate, A method for producing a carbon fiber aggregate containing carbon fiber is also mentioned.

[0056] (Content of various materials) The aromatic polyamide pulp content is preferably 1% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 15% by mass or less, relative to the total solid content of the microporous layer. When the aromatic polyamide pulp content is 1% by mass or more, roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers in the carbon fiber layer is further suppressed. In addition, the durability of the gas diffusion layer is improved. When the aromatic polyamide pulp content is 20% by mass or less, the relative decrease in the proportion of carbon-based conductive materials and water-dispersible resins is suppressed, thus further suppressing roughening of the microporous layer and catalyst layer due to the protrusion of carbon fibers in the carbon fiber layer. This also results in superior battery performance.

[0057] The content of the water-dispersible resin is preferably 10% by mass or more and 30% by mass or less, and more preferably 15% by mass or more and 25% by mass or less, relative to the total solid content of the microporous layer. When the water-dispersible resin content is 10% by mass or more, roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer is further suppressed. Furthermore, water repellency is improved. When the water-dispersible resin content is 30% by mass or less, the relative decrease in the proportion of aromatic polyamide pulp and carbon-based conductive materials is suppressed, thereby further suppressing roughening of the microporous layer and catalyst layer due to the protrusion of carbon fibers contained in the carbon fiber layer. In addition, the decrease in the porosity of the microporous layer due to excessive water-dispersible resin is suppressed. Furthermore, these factors result in superior battery performance.

[0058] The content of the carbon-based conductive material is preferably 50% by mass or more and 85% by mass or less, and more preferably 55% by mass or more and 80% by mass or less, relative to the total solid content of the microporous layer. When the carbon-based conductive material content is 50% by mass or more, roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer is further suppressed. Furthermore, conductivity is improved. When the carbon-based conductive material content is 85% by mass or less, the relative decrease in the proportion of aromatic polyamide pulp and water-dispersible resin is suppressed, thereby further suppressing roughening of the microporous layer and catalyst layer due to the protrusion of carbon fibers contained in the carbon fiber layer. This also results in superior battery performance.

[0059] The mass ratio of aromatic polyamide pulp to carbon-based conductive material (aromatic polyamide pulp / carbon-based conductive material) is not particularly limited, but is preferably in the range of 1 / 99 to 50 / 50, and more preferably in the range of 3 / 97 to 40 / 60. When the above mass ratio is 1 / 99 or higher, the reinforcing effect is superior due to aromatic polyamide pulp. When the above mass ratio is 50 / 50 or lower, the conductivity is superior due to carbon-based conductive material. In particular, when the carbon-based conductive material contains at least one of carbon fibers and carbon milled fibers, when the above mass ratio is above the lower limit, roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer is further suppressed.

[0060] The mass ratio of aromatic polyamide pulp to water-dispersible resin (aromatic polyamide pulp / water-dispersible resin) is not particularly limited, but is preferably in the range of 10 / 90 to 70 / 30, and more preferably in the range of 20 / 80 to 60 / 40. When the above mass ratio is 10 / 90 or higher, the reinforcing effect is superior due to aromatic polyamide pulp. On the other hand, when the above mass ratio is 70 / 30 or lower, the water-dispersible resin is superior due to water repellency.

[0061] (Other materials) The microporous layer may further contain materials other than aromatic polyamide pulp, water-dispersible resin, and carbon-based conductive material. Examples of other materials include electrode catalysts and ionomer resins.

[0062] As the electrode catalyst, catalysts used in known fuel cells such as polymer electrolyte fuel cells (PEFCs), phosphoric acid fuel cells (PAFCs), and biobatteries can be used. The type and content of the electrode catalyst can be selected according to the application of the gas diffusion layer, and examples include platinum catalysts, iridium catalysts, carbon catalysts, and enzymes.

[0063] (Characteristics of microporous layers) The microporous layer preferably has a maximum peak in the pore size distribution of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 3.0 μm, and even more preferably 0.3 μm to 2.0 μm. When the maximum peak is between 0.1 μm and 5.0 μm, roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer is more suppressed. Furthermore, when the battery is equipped with a gas diffusion layer, the battery performance is superior.

[0064] The microporous layer preferably has a tensile modulus of 200 MPa to 900 MPa, more preferably 300 MPa to 700 MPa, and even more preferably 300 MPa to 500 MPa. When the tensile modulus of the microporous layer is 200 MPa or higher, roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer is further suppressed. Furthermore, the strength of the gas diffusion layer is superior. When the tensile modulus of the microporous layer is 900 MPa or lower, roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer is further suppressed.

[0065] The microporous layer preferably has a water contact angle of 130° to 160°, and more preferably 140° to 150°. When the water contact angle is within the above range, roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer is further suppressed.

[0066] The thickness of the microporous layer may be, for example, 170 μm or more and 250 μm or less. The thickness of the microporous layer is preferably, for example, 50 μm to 150 μm, and more preferably 50 μm to 100 μm. The thickness of the microporous layer is usually 170 μm or more, from the viewpoint of avoiding a decrease in battery performance due to carbon fibers in the carbon fiber layer protruding and roughening the microporous layer and catalyst layer. In contrast, in the gas diffusion layer according to this disclosure, even if the thickness of the microporous layer is thinner than conventional methods, between 50 μm and 150 μm, the carbon fibers in the carbon fiber layer are less likely to protrude, and roughening of the microporous layer and catalyst layer is suppressed.

[0067] [Characteristics of the gas diffusion layer] The overall thickness of the gas diffusion layer can be controlled during the manufacturing process by adjusting the basis weight of the carbon fiber layer (made of carbon fiber sheets, as described later) and the microporous layer (made of microporous sheets), as well as the temperature and pressure during hot pressing.

[0068] The applications of the gas diffusion layer according to this disclosure are not particularly limited and can be applied to known devices that use a gas diffusion layer, such as electrolysis, flow batteries, and fuel cells, but its use in fuel cells is preferred. A fuel cell equipped with the gas diffusion layer according to this disclosure has reduced catalyst layer deterioration and superior battery performance.

[0069] The method for manufacturing the gas diffusion layer according to this disclosure is not particularly limited, but it is preferable, for example, to manufacture it using the method for manufacturing the gas diffusion layer according to this disclosure described later.

[0070] <Gas Diffusion Electrode> The gas diffusion electrode according to this disclosure comprises a gas diffusion layer relating to this disclosure and a catalyst layer provided on a microporous layer in the gas diffusion layer. The gas diffusion electrode according to this disclosure suppresses roughening of the microporous layer and catalyst layer caused by the protrusion of carbon fibers contained in the carbon fiber layer. Furthermore, it also suppresses the deterioration of battery performance caused by such roughening.

[0071] The catalyst layer is not particularly limited, and known catalyst layers used in gas diffusion electrodes can be employed. Examples of catalyst layers include electrode catalysts and carbon-based conductive materials.

[0072] <Membrane electrode assembly> The membrane electrode assembly according to this disclosure comprises a polymer electrolyte membrane and a pair of gas diffusion electrodes that sandwich the polymer electrolyte membrane, wherein at least one of the pair of gas diffusion electrodes is the gas diffusion electrode according to this disclosure. According to the film electrode assembly described herein, the deterioration of battery performance caused by roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer is suppressed.

[0073] Figure 1 is a schematic cross-sectional view showing an example of the layer configuration of a membrane electrode assembly according to the present disclosure. The membrane electrode assembly 100 shown in Figure 1 comprises a polymer electrolyte membrane 10 and a pair of gas diffusion electrodes 20 that sandwich the polymer electrolyte membrane 10. As shown in Figure 1, the gas diffusion electrode 20 is a laminate in which a catalyst layer 30 and a gas diffusion layer 40 are stacked in that order from the polymer electrolyte membrane 10 side. The catalyst layer 30 contains electrode catalyst C. The gas diffusion layer 40 is a laminate in which a microporous layer 42 and a carbon fiber layer 44 are stacked in that order from the catalyst layer 30 side. One of the pair of gas diffusion electrodes 20 is the cathode electrode, and the other is the anode electrode. Hydrogen is supplied to the anode electrode, and an oxidation reaction of hydrogen occurs in the catalyst layer. Oxygen-containing air is supplied to the cathode electrode, and an oxygen reduction reaction occurs. Protons generated at the anode electrode are then conducted to the cathode electrode through the polymer electrolyte membrane 10, and in this process electrons are extracted and electricity is generated. Water is generated at the cathode electrode, and this water wets the polymer electrolyte membrane 10, increasing its proton conductivity.

[0074] In the membrane electrode assembly, at least one of the pair of gas diffusion electrodes is a gas diffusion electrode according to the present disclosure, and from the viewpoint of further suppressing the deterioration of battery performance caused by roughening of the catalyst layer on the microporous layer side, it is preferable that both of the pair of gas diffusion electrodes are gas diffusion electrodes according to the present disclosure.

[0075] The applications of the membrane electrode assembly relating to this disclosure are not particularly limited, but for example, it can be used in fuel cells and water electrolysis devices.

[0076] <Fuel cell> The fuel cell relating to this disclosure comprises a membrane electrode assembly relating to this disclosure and a separator. According to the fuel cell described herein, the deterioration of battery performance caused by roughening of the microporous layer and catalyst layer due to the protrusion of carbon fibers contained in the carbon fiber layer is suppressed.

[0077] The separator is not particularly limited, and any known separator applicable to water electrolysis devices or fuel cells can be used.

[0078] <Method for manufacturing a gas diffusion layer> The method for manufacturing a gas diffusion layer according to this disclosure includes a step of forming a laminate by bonding a microporous sheet containing aromatic polyamide pulp, a water-dispersible resin, and a carbon-based conductive material with a carbon fiber sheet (hereinafter referred to as the laminate formation step).

[0079] Conventional gas diffusion layers are formed by applying a microporous layer-forming coating solution onto a carbon fiber layer, followed by drying and sintering to create a microporous layer on top of the carbon fiber layer. However, this coating method is prone to inconsistencies in the thickness and film quality of the resulting microporous layer due to technical factors. As a result, carbon fibers contained in the carbon fiber layer may protrude from the carbon fiber layer during compression, which can easily damage the microporous layer and the catalyst layer provided on top of it.

[0080] According to this disclosure, a gas diffusion layer, which is a laminate, is obtained by a simple operation of bonding a microporous sheet and a carbon fiber sheet. Therefore, unevenness in the thickness and film quality of the microporous layer obtained due to technical factors is suppressed. As a result, carbon fibers contained in the carbon fiber layer protrude from the carbon fiber layer during compression or other processes, and roughening of the microporous layer and the catalyst layer provided on top of the microporous layer is suppressed. Furthermore, a decrease in battery performance caused by roughening of the microporous layer and catalyst layer is suppressed.

[0081] [Laminate formation process] In the laminate formation process, a microporous sheet containing aromatic polyamide pulp, a water-dispersible resin, and a carbon-based conductive material is bonded to a carbon fiber sheet to form a laminate.

[0082] The microporous sheet may be a commercially available product or may be manufactured, as long as it contains aromatic polyamide pulp, a water-dispersible resin, and a carbon-based conductive material, and is water-repellent.

[0083] The method for producing the microporous sheet is not particularly limited, and known methods for producing microporous layers can be applied. When producing a microporous sheet, for example, a slurry for forming a microporous sheet may be paper-formed to obtain a precursor for the microporous sheet, and the microporous sheet may be produced by calcining the precursor.

[0084] As for the aromatic polyamide pulp, water-dispersible resin, and carbon-based conductive material in the microporous sheet, those similar to the aromatic polyamide pulp, water-dispersible resin, and carbon-based conductive material exemplified in the gas diffusion layer according to this disclosure are preferred, from the viewpoint of more effectively suppressing roughness on the microporous sheet side of the catalyst layer.

[0085] As for the carbon fiber sheet, from the viewpoint of more effectively suppressing the protrusion of carbon fibers contained in the carbon fiber sheet and the resulting roughening of the microporous sheet or catalyst layer, a carbon fiber sheet similar to the one exemplified in the gas diffusion layer according to this disclosure is preferred.

[0086] The microporous sheet preferably has a peak diameter in its pore size distribution of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 3.0 μm, and even more preferably 0.3 μm to 2.0 μm. When the maximum peak is between 0.1 μm and 5.0 μm, the roughening of the microporous sheet and catalyst layer due to the protrusion of carbon fibers contained in the carbon fiber sheet is more suppressed. Furthermore, when a battery with a gas diffusion layer is used, the battery performance is superior.

[0087] The microporous sheet preferably has a tensile modulus of 200 MPa to 900 MPa, more preferably 300 MPa to 700 MPa, and even more preferably 300 MPa to 500 MPa. When the tensile modulus of the microporous sheet is 200 MPa or higher, roughening of the microporous sheet and catalyst layer due to the protrusion of carbon fibers contained in the carbon fiber sheet is further suppressed. Furthermore, the strength of the gas diffusion layer is superior. When the tensile modulus of the microporous sheet is 900 MPa or lower, roughening of the microporous sheet and catalyst layer due to the protrusion of carbon fibers contained in the carbon fiber sheet is further suppressed.

[0088] In the laminate formation process, it is preferable to heat the carbon fiber sheet and the microporous sheet when bonding them together, from the viewpoint of further improving the adhesion between the carbon fiber sheet and the microporous sheet. The heating temperature in the laminate formation process is not particularly limited and can be appropriately designed depending on the material of the carbon fiber sheet and the microporous sheet. The pressurizing temperature is preferably in the range of 100°C to 400°C, more preferably in the range of 150°C to 400°C, and even more preferably in the range of 150°C to 250°C.

[0089] In the laminate formation process, it is preferable to apply pressure when bonding the carbon fiber sheet and the microporous sheet together, from the viewpoint of further improving the adhesion between the carbon fiber sheet and the microporous sheet. The pressurizing pressure in the laminate formation process is not particularly limited and can be appropriately designed according to the materials of the carbon fiber sheet and the microporous sheet. As an example of pressurizing pressure (surface pressure), 10 kgf / cm² is used, from the viewpoint of further reducing the damage caused by carbon fibers in the carbon fiber sheet to the catalyst layer. 2 More than 60kgf / cm 2 Preferably, it is 20 kgf / cm² 2 More than 50kgf / cm 2 The following is more preferable:

[0090] The laminate formation process preferably further includes a step of heating and pressing the laminate from the lamination direction, from the viewpoint of further improving the adhesion between the carbon fiber sheet and the microporous sheet, and more preferably further includes a step of heating and pressing in a range of 150°C to 400°C (more preferably a range of 150°C to 300°C, and particularly preferably a range of 150°C to 250°C).

[0091] The method for bonding the carbon fiber sheet and the microporous sheet is not particularly limited, and known methods can be applied. From the viewpoint of preventing slippage between layers and achieving superior adhesion, the bonding method is preferably a calendering method.

[0092] In one embodiment, the laminate formation process may involve bonding a carbon fiber sheet and a microporous sheet using a laminate calender and then pressing the two together to form a laminate. In this case, the roll speed is preferably 1 m / min to 10 m / min, for example, from the viewpoint of preventing misalignment during bonding.

[0093] [Sintering process] The method for manufacturing a gas diffusion layer according to this disclosure may further include a sintering step. In the sintering step, the laminate obtained in the laminate formation step is heated and sintered. Including the sintering step results in superior water repellency, which in turn leads to superior battery performance.

[0094] The sintering method is not particularly limited, and known sintering methods for sintering gas diffusion layers can be applied.

[0095] The sintering temperature is not particularly limited and can be appropriately designed depending on the material of the carbon fiber sheet and the microporous sheet, but it may be, for example, 300°C to 500°C.

[0096] The sintering time is not particularly limited and can be appropriately designed depending on the material of the carbon fiber sheet and the microporous sheet, but for example, it may be in the range of 30 minutes to 5 hours or in the range of 30 minutes to 2 hours.

[0097] [Other processes] The method for manufacturing a gas diffusion layer according to this disclosure may further include other steps besides the laminate formation step and the sintering step. Examples of other steps include a crimping step for pressing the laminates together; a processing step for machining such as cutting; and a packaging step for packaging the obtained gas diffusion layer. Each step may be performed simultaneously with the laminate formation step or separately.

[0098] In one embodiment, the method for manufacturing a gas diffusion layer according to the present disclosure is: The manufacturing method may include a laminate formation step of forming a laminate by bonding a microporous sheet containing aromatic polyamide pulp, a water-dispersible resin, and a carbon-based conductive material with a carbon fiber sheet and then heating and pressurizing the bonded sheet, and a sintering step of sintering the laminate.

[0099] <Method for manufacturing gas diffusion electrodes> The method for manufacturing a gas diffusion electrode according to this disclosure includes the step of providing a catalyst layer on the microporous sheet side of a gas diffusion layer manufactured by the method for manufacturing a gas diffusion layer according to this disclosure.

[0100] According to this disclosure, roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer is suppressed. Therefore, the deterioration of battery performance caused by the aforementioned roughening is suppressed.

[0101] The method for forming the catalyst layer is not particularly limited, and known methods for forming catalyst layers used in gas diffusion electrodes can be applied.

[0102] <Method for manufacturing a membrane electrode assembly> The method for manufacturing a membrane electrode assembly according to this disclosure includes the steps of manufacturing a gas diffusion layer by the method for manufacturing a gas diffusion layer according to this disclosure, and providing a catalyst layer and a polymer electrolyte membrane in that order on the microporous sheet side surface of the manufactured gas diffusion layer.

[0103] According to the present disclosure, roughening of the microporous layer and the catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer in the membrane electrode assembly is suppressed. Therefore, a decrease in battery performance caused by such roughening is suppressed.

[0104] From the viewpoint of manufacturing a membrane electrode assembly more efficiently and suppressing roughening of the microporous layer and the catalyst layer, the manufacturing method according to the present disclosure preferably provides the catalyst layer and the polymer electrolyte membrane in this order on the surface on the microporous sheet side of the manufactured gas diffusion layer, and performs pressure bonding in the range of 60°C or higher and 130°C or lower (more preferably 65°C or higher and 130°C or lower, still more preferably 70°C or higher and 125°C or lower).

[0105] The method for forming the catalyst layer is not particularly limited, and a known method for forming a catalyst layer used for a gas diffusion electrode can be applied.

Example

[0106] Hereinafter, the present disclosure will be described in more detail with reference to examples, but the invention of the present disclosure is not limited to only these examples.

[0107] <Fabrication of Gas Diffusion Layer: Example 1> A microporous sheet (thickness: 69 μm, pore diameter: 0.7 μm, elastic modulus: 347 MPa) was fabricated from 10 parts by mass of aromatic polyamide pulp (pulp of Twaron (registered trademark) 1094, manufactured by Teijin Limited), 20 parts by mass of PTFE (AD911E manufactured by AGC Inc.; water-dispersed resin), 10 parts by mass of Ketjenblack (EC600JD manufactured by Lion Corporation), and 60 parts by mass of pitch-based ultra-fine carbon fibers (manufactured by Teijin Limited, average fiber length: 10 μm to 28 μm; carbon-based conductive material). Subsequently, carbon fibers (manufactured by Teijin Limited, average fiber diameter: 7 μm, specific gravity: 1.76) cut to an average fiber length of 3 mm were water-dispersed to fabricate a carbon fiber sheet (thickness: 120 μm) by wet papermaking. Then, the microporous sheet and the carbon fiber sheet were pressure-bonded in the thickness direction using a laminating calendar. At this time, the roll temperature was 200°C (shown as the calendar pressure-bonding temperature in Table and the roll pressure was 40 kgf / cm 2The roll speed was set to 2 m / min. Furthermore, the material was sintered in an oven at 400°C for 1 hour to obtain a laminate (gas diffusion layer) consisting of a microporous layer and a porous carbon fiber layer.

[0108] Figure 2 shows the pore distribution diagram of the microporous layer in the gas diffusion layer of Example 1, with the vertical axis representing [dV / d(logd)(cc / g)] and the horizontal axis representing the pore diameter (μm) of the microporous layer. As shown in Figure 2, the microporous layer of Example 1 has a maximum peak in the pore distribution within the range of 0.2 μm to 5.0 μm.

[0109] <Fabrication of a gas diffusion layer: Example 2> A gas diffusion layer was fabricated in the same manner as in Example 1, except that a microporous layer with a thickness of 64 μm, a maximum peak in the pore size distribution of 1.0 μm, and a tensile modulus of 443 MPa was used.

[0110] <Fabrication of a gas diffusion layer: Example 3> A gas diffusion layer was fabricated in the same manner as in Example 1, except that a microporous layer with the thickness, maximum peak of the pore size distribution, and tensile modulus were used, respectively, as shown in Table 1.

[0111] <Preparation of a gas diffusion layer: Comparative Example 1> 7.5 parts by mass of Ketjenblack, 2.5 parts by mass of PTFE, 7.5 parts by mass of surfactant (DT-100, manufactured by Toyo Chemical), and 82.5 parts by mass of water were mixed in a mixer. The mixture was applied to a carbon fiber layer with a die coater and dried in an oven at 100°C for 1 hour to obtain a gas diffusion layer of a laminate consisting of a microporous layer and a carbon fiber layer. In the evaluation of the protrusion of the carbon fiber layer, carbon fibers contained in the porous carbon fiber layer protruded into the microporous layer, and cracks were observed in the microporous layer.

[0112] <Fabrication of a gas diffusion layer: Example 4> A microporous sheet and a carbon fiber sheet were prepared using the method of Example 1, consisting of aromatic polyamide pulp, PTFE (water-dispersible resin), Ketjenblack, and pitch-based ultrafine carbon fibers (carbon-based conductive material). The microporous sheet was sintered in an oven at 400°C for 1 hour. The microporous sheet and the carbon fiber sheet were then pressed together in the thickness direction using a laminate calender to obtain a laminate (gas diffusion layer). The roll temperature was 200°C and the roll pressure was 40 kgf / cm². 2 The roll speed was set to 2 m / min.

[0113] <Fabrication of a gas diffusion layer: Example 5> A laminate (gas diffusion layer) was obtained in the same manner as in Example 1, except that the roll temperature of the laminate calender was set to 350°C.

[0114] <Fabrication of a gas diffusion layer: Example 6> A microporous sheet (thickness 87 μm, pore size 2.5 μm, elastic modulus 416 MPa) was prepared from 9 parts by mass of aromatic polyamide pulp (Teijin Limited, pulp of Twaron® 1094), 5 parts by mass of PTFE (AGC Inc., AD911E; water-dispersible resin), 30 parts by mass of Ketjenblack (Lion Corporation, EC600JD), 35 parts by mass of pitch-based ultrafine carbon fibers (Teijin Limited, average fiber length 10 μm to 28 μm; carbon-based conductive material), and 21 parts by mass of carbon fibers (Teijin Limited, average fiber diameter 7 μm, specific gravity 1.76) cut to an average fiber length of 3 mm. The sheet was then compressed and sintered with the carbon fiber sheet using the method described in Example 1 to obtain a laminate (gas diffusion layer).

[0115] <Fabrication of a membrane electrode assembly: Example 7> As described in Example 6, a microporous sheet was prepared. A membrane electrode assembly was fabricated by pressing a catalyst-equipped polymer electrolyte membrane (Fuel Cell.com) and the microporous sheet using a press machine. The pressing temperature was 80°C, the pressure was 0.5 MPa, and the pressing time was 6 minutes.

[0116] <Fabrication of a film electrode assembly: Example 8> The film electrode assembly was fabricated in the same manner as in Example 7, except that the pressing temperature was set to 120°C.

[0117] <Physical properties of gas diffusion layer and membrane electrode assembly> For each example, the thickness of the microporous layer in the gas diffusion layer, the maximum peak value of the pore size distribution, the tensile modulus, and the contact angle were measured using the measurement method described above. The results are shown in Table 1. Items marked with [-] in the table indicate that the measurement was not performed. In the table, items where the microporous sheet and carbon fiber sheet were pressed together before sintering are indicated as [After Pressing], and items where the microporous sheet and carbon fiber sheet were sintered before pressing together are indicated as [Before Pressing]. In the table, the temperature at which the polymer electrolyte membrane with the catalyst layer is pressed against the gas diffusion layer is indicated as [Press Pressing Temperature].

[0118] <Evaluation of microporous layers and membrane electrode assemblies> The gas diffusion layers prepared in Examples 1 to 5 and Comparative Example 1 were observed using a scanning electron microscope to evaluate the state of the microporous layers. For evaluation, samples with no roughness in the microporous layer were marked [OK], while samples with roughness in the microporous layer due to carbon fibers in the porous carbon fiber layer protruding into the microporous layer were marked [NG]. In addition, for the membrane electrode assemblies of Examples 7 and 8, the condition of the catalyst layer after pressing was observed using a scanning electron microscope, and samples with no roughness were marked [OK], while samples with roughness were marked [NG].

[0119] [Table 1]

[0120] Figure 3 is a cross-sectional image of the gas diffusion layer of Example 1 observed with a scanning electron microscope, showing the stacking direction. As shown in Figure 3, it can be seen that in Example 1, the gas diffusion layer is formed by the close contact of the microporous layer (upper layer) and the porous carbon fiber layer (lower layer). Furthermore, as shown in Figure 3, in the gas diffusion layer of Example 1, the carbon fibers contained in the porous carbon fiber layer do not protrude from the carbon fiber layer, and no roughness is observed in the microporous layer.

[0121] The gas diffusion layers of Example 2 and Comparative Example 1 were also examined in the same manner as the gas diffusion layer of Example 1 to check for the protrusion of carbon fibers contained in the porous carbon fiber layer into the microporous layer and the resulting roughening of the microporous layer. The results are shown in Table 1.

[0122] As shown in Table 1, the gas diffusion layer of the example was found to suppress roughening of the microporous layer and catalyst layer due to protrusion of carbon fibers contained in the carbon fiber layer, etc., compared to the gas diffusion layer of the comparative example.

[0123] The disclosure of Japanese Patent Application No. 2024-229276, filed on 25 December 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

[0124] (Explanation of symbols) 100 Membrane electrode assembly 10 Polymer electrolyte membrane 20 Gas diffusion electrode 30 Catalyst layer 40 Gas diffusion layer C Electrocatalyst 42 Microporous layer 44 Carbon fiber layer

Claims

1. A carbon fiber layer, A microporous layer provided on the carbon fiber layer comprises aromatic polyamide pulp, a water-dispersible resin, and a carbon-based conductive material, It has, The microporous layer has a maximum peak in the pore size distribution of 0.1 μm or more and 5.0 μm or less, and a tensile modulus of elasticity of 300 MPa or more and 900 MPa or less. The content of the aromatic polyamide pulp is 1% by mass or more and 20% by mass or less relative to the total solid content of the microporous layer. Gas diffusion layer.

2. The gas diffusion layer according to Claim 1, A catalyst layer provided on the microporous layer in the gas diffusion layer, A gas diffusion electrode having

3. Polymer electrolyte membrane, The system comprises a pair of gas diffusion electrodes that sandwich the polymer electrolyte membrane, A membrane electrode assembly wherein at least one of the pair of gas diffusion electrodes is the gas diffusion electrode described in claim 2.

4. A membrane electrode assembly according to claim 3, Separator and, A fuel cell equipped with a fuel cell.

5. The process includes a step of forming a laminate by bonding a microporous sheet containing aromatic polyamide pulp, a water-dispersible resin, and a carbon-based conductive material with a carbon fiber sheet. The microporous sheet has a maximum peak in the pore size distribution of 0.1 μm or more and 5.0 μm or less, and a tensile modulus of elasticity of 300 MPa or more and 900 MPa or less. The content of the aromatic polyamide pulp is 1% by mass or more and 20% by mass or less relative to the total solid content of the microporous sheet. A method for manufacturing a gas diffusion layer.

6. The method for manufacturing a gas diffusion layer according to claim 5, further comprising the step of heating and pressing the laminate in the lamination direction at a temperature of 150°C to 400°C.

7. A step of manufacturing a gas diffusion layer by the manufacturing method described in Claim 5 or Claim 6, A step of providing a catalyst layer on the microporous sheet side of the manufactured gas diffusion layer, A method for manufacturing a gas diffusion electrode, including the method described above.

8. A step of manufacturing a gas diffusion layer by the manufacturing method described in Claim 5 or Claim 6, The process involves providing a catalyst layer and a polymer electrolyte membrane in this order on the microporous sheet side of the manufactured gas diffusion layer, A method for manufacturing a membrane electrode assembly, including the following:

9. A method for manufacturing a membrane electrode assembly according to claim 8, wherein a catalyst layer and a polymer electrolyte membrane are provided in this order on the microporous sheet side of the manufactured gas diffusion layer, and the assembly is pressed together in a range of 60°C to 130°C.

Images