Membrane-electrode assembly and fuel cell including same

Abstract

A membrane-electrode assembly that simultaneously improves durability and performance is provided. One embodiment of the present invention provides a membrane-electrode assembly that includes a polymer electrolyte membrane, a first catalyst layer disposed on at least one side of the polymer electrolyte membrane, and a second catalyst layer disposed on the polymer electrolyte membrane, the first catalyst layer being interposed between the polymer electrolyte membrane and the second catalyst layer, and the first catalyst layer comprising plate-shaped mesoporous carbon.

Description

[Technical Field]

[0001] The present invention relates to a membrane-electrode assembly and a fuel cell including the same, and more particularly to a membrane-electrode assembly and a fuel cell including the same that simultaneously improve performance and durability. [Background technology]

[0002] Fuel cells are cells that directly convert chemical energy generated by the oxidation of fuel into electrical energy, and are attracting attention as a next-generation energy source due to their high energy efficiency and environmentally friendly characteristics such as low pollutant emissions.Fuel cells generally have a structure in which an anode and a cathode are formed on either side of a polymer electrolyte membrane, and this structure is called a membrane electrode assembly (MEA).

[0003] Fuel cells can be classified into alkaline electrolyte fuel cells, polymer electrolyte membrane fuel cells (PEMFC), etc. depending on the type of electrolyte membrane. Among them, polymer electrolyte membrane fuel cells are attracting attention as a power source for portable, vehicular, and home use due to their advantages such as a low operating temperature of less than 100°C, fast start-up and response characteristics, and excellent durability.

[0004] A typical example of such a polymer electrolyte membrane fuel cell is a proton exchange membrane fuel cell (PEMFC), which uses hydrogen gas as fuel.

[0005] To summarize the reactions that occur in a polymer electrolyte membrane fuel cell, first, when fuel such as hydrogen gas is supplied to the oxidizing electrode (or anode), hydrogen ions and electrons are generated through an oxidation reaction at the oxidizing electrode. The generated hydrogen ions are transferred to the reducing electrode through the polymer electrolyte membrane, and the generated electrons are transferred to the reducing electrode (or cathode) through an external circuit. Oxygen gas is supplied to the reducing electrode, and the oxygen gas combines with the hydrogen ions and electrons to generate water through a reduction reaction.

[0006] Conventional catalysts have a structure in which platinum nanoparticles are supported on carbon, but they are expensive, and the carbon support easily deteriorates under fuel cell operating conditions, so the development of new electrode materials is needed. Electrode catalyst materials generally consist of platinum-based metal catalyst particles and a catalyst support, and improvements to the catalyst support alone can significantly improve fuel cell performance. Therefore, research is being continuously conducted to improve the performance of catalyst supports. Summary of the Invention [Problem to be solved by the invention]

[0007] It is an object of the present invention to provide a membrane-electrode assembly that has both improved performance and durability.

[0008] Another object of the present invention is to provide a membrane-electrode assembly having nanopore-shaped material and ion-transfer pathways perpendicular to the surface of the polymer electrolyte membrane, thereby improving ion conductivity and performance.

[0009] Another object of the present invention is to provide a membrane-electrode assembly including a catalyst layer that maintains a stable form of ion transport pathways even during operation of the fuel cell and has improved durability.

[0010] Another object of the present invention is to provide a fuel cell comprising said membrane-electrode assembly.

[0011] The objects of the present invention are not limited to the objects mentioned above, and other unmentioned objects and advantages of the present invention can be understood from the following description and will be more clearly understood by examples of the present invention. Furthermore, it will be easily understood that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims. [Means for solving the problem]

[0012] To achieve the above object, a first aspect of the present invention provides a membrane-electrode assembly including a polymer electrolyte membrane, a first catalyst layer disposed on at least one side of the polymer electrolyte membrane, and a second catalyst layer disposed on the polymer electrolyte membrane, the first catalyst layer being interposed between the polymer electrolyte membrane and the second catalyst layer, and the first catalyst layer comprising platelet mesoporous carbon.

[0013] According to a second aspect of the present invention, in the first aspect, the surface and pores of the plate-like mesoporous carbon may be coated with an ionomer layer.

[0014] According to a third aspect of the present invention, in the second aspect, the ionomer layer includes a first ionomer, and the equivalent weight (EW) of the first ionomer can be 600-1200.

[0015] According to a fourth aspect of the present invention, in the third aspect, the first ionomer may be any one selected from the group consisting of a fluorine-based ionomer, a hydrocarbon-based ionomer, and a mixture thereof.

[0016] According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the plate-like mesoporous carbon may have a form in which nanofibers or nanotubes are aligned, and pores contained in the nanofibers or nanotubes may extend perpendicular to the surface of the polymer electrolyte membrane.

[0017] According to a sixth aspect of the present invention, in the fifth aspect, the nanofibers and nanotubes may each independently have a height of 50 to 600 nm.

[0018] According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the area occupied by the first catalyst layer may be 10 to 70% based on the total area of ​​one side of the polymer electrolyte membrane.

[0019] According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the thickness of the second catalyst layer may be the same as or different from the thickness of the first catalyst layer.

[0020] According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the thickness of the second catalyst layer can be greater than the thickness of the first catalyst layer.

[0021] According to a tenth aspect of the present invention, in any one of the first to ninth aspects, the first catalyst layer may have a thickness of 50 to 2,000 nm.

[0022] According to an eleventh aspect of the present invention, there is provided a fuel cell including the membrane-electrode assembly according to any one of the first to tenth aspects.

[0023] The above-described solutions to the problems are not intended to be exhaustive, and various features of the present invention, along with their associated advantages and benefits, may be more fully understood with reference to the following specific examples. [Effects of the Invention]

[0024] According to one aspect of the present invention, a membrane-electrode assembly that simultaneously improves performance and durability can be provided. According to another aspect of the present invention, a membrane-electrode assembly that not only improves ion conductivity and performance by having nanopore-shaped materials and ion transport channels perpendicular to the surface direction of the polymer electrolyte membrane, but also maintains stable ion transport channels through pores in the plate-like mesoporous carbon even during fuel cell operation, thereby improving durability even when the fuel cell is operated for a long period of time, can be provided.

[0025] In addition to the above-mentioned effects, specific effects of the present invention will be described together with the following explanation of specific details for carrying out the invention. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic diagram showing a method for manufacturing a membrane-electrode assembly according to one embodiment of the present invention. [Figure 2a] FIG. 2a is a schematic diagram showing a method for manufacturing a membrane-electrode assembly according to another embodiment of the present invention. [Figure 2b] FIG. 2b shows the mesoporous carbon plate with the ionomer layer of FIG. 2a coated on its surface. [Figure 3] FIG. 3 is a schematic diagram showing a method for manufacturing a membrane-electrode assembly according to another embodiment of the present invention. [Figure 4a] FIG. 4a is a schematic diagram showing a method for manufacturing a membrane-electrode assembly according to another embodiment of the present invention. [Figure 4b] FIG. 4b shows the plate-shaped mesoporous carbon coated with the ionomer layer of FIG. 4a. [Figure 5] FIG. 5 is a schematic diagram illustrating a fuel cell according to an embodiment of the present invention. [Figure 6] FIG. 6 is an ultra-high resolution scanning electron microscope (UHR-SEM) image of the plate-shaped mesoporous carbon having aligned nanofibers according to Preparation Example 1-1. [Figure 7]FIG. 7 is an ultra-high resolution scanning electron microscope (UHR-SEM) image of the plate-shaped mesoporous carbon having aligned nanotubes according to Preparation Example 2-1. [Figure 8] FIG. 8 is an SEM cross-sectional image of a membrane-electrode assembly including mesoporous carbon plates with aligned nanotubes according to Example 2-2. [Figure 9] FIG. 9 shows the results of performance evaluation of the membrane-electrode assemblies manufactured according to the examples and comparative examples under conditions of 80° C., 100% RH, and normal pressure. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, each component of the present invention will be described in more detail so that a person having ordinary skill in the art to which the present invention pertains can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited by the following content.

[0028] One embodiment of the present invention provides a membrane-electrode assembly including a polymer electrolyte membrane, a first catalyst layer disposed on at least one side of the polymer electrolyte membrane, and a second catalyst layer disposed on the polymer electrolyte membrane, the first catalyst layer being interposed between the polymer electrolyte membrane and the second catalyst layer, the first catalyst layer comprising platelet mesoporous carbon. According to one embodiment of the present invention, by introducing a layer of platelet mesoporous carbon having vertical nanopores or a layer of platelet mesoporous carbon having an ionomer layer coated on the surface and pores, the membrane-electrode assembly has nanopore-shaped material and ion transport channels perpendicular to the in-plane direction of the electrolyte membrane, improving ion conductivity and performance. Furthermore, the membrane-electrode assembly maintains stable ion transport channels through the pores in the platelet mesoporous carbon during fuel cell operation, improving durability. According to another embodiment of the present invention, metal nanoparticles are supported in the pores of the plate-like mesoporous carbon, thereby improving performance by increasing catalytic activity and effectively preventing aggregation of metal nanoparticles, thereby improving catalyst durability and significantly improving the chemical durability of the catalyst layer by acting as a radical scavenger.

[0029] The configuration of the present invention will be described in more detail below with reference to FIGS. 1 to 4b. FIG. 1 is a schematic diagram showing a method for manufacturing a membrane-electrode assembly according to one embodiment of the present invention. FIG. 2a is a schematic diagram showing a method for manufacturing a membrane-electrode assembly according to another embodiment of the present invention, and FIG. 2b is the mesoporous carbon plate having an ionomer layer coated on its surface, as shown in FIG. 2a. FIG. 3 is a schematic diagram showing a method for manufacturing a membrane-electrode assembly according to another embodiment of the present invention. FIG. 4a is a schematic diagram showing a method for manufacturing a membrane-electrode assembly according to another embodiment of the present invention, and FIG. 4b is the mesoporous carbon plate having an ionomer layer coated on its surface, as shown in FIG. 4a.

[0030] 1. Membrane-electrode assembly and manufacturing method thereof 1 to 4b, a membrane-electrode assembly 100 according to the present invention includes a polymer electrolyte membrane 10. The polymer electrolyte membrane 10 may be a commercially available polymer electrolyte membrane in the art and may include, for example, an ion conductor.

[0031] The first catalyst layer 20 according to the present invention may be disposed on at least one surface of the polymer electrolyte membrane 10. The first catalyst layer 20 may include platelet mesoporous carbon having nanopores perpendicular to the surface of the polymer electrolyte membrane. That is, the first catalyst layer 20 according to one embodiment of the present invention may be disposed on only one surface of the polymer electrolyte membrane 10, with a commercial catalyst layer disposed on the other surface opposite the one surface. The first catalyst layer 20 according to another embodiment of the present invention may be disposed on both surfaces of the polymer electrolyte membrane 10. Conventionally, metal nanoparticles (or metal catalyst particles) supported on a carbon-based support have been used as catalyst materials. However, under fuel cell operating conditions, ion transport occurs along the ionomer disposed along the outer periphery of the support, resulting in irregular formation of long or disconnected paths, resulting in low ion conductivity. According to one embodiment of the present invention, the first catalyst layer 20 contains mesopores perpendicular to the surface of the polymer electrolyte membrane. The mesoporous carbon plate with a large surface area allows for material transport through the pore channels and ion transport through the ionomer positioned in the pore channels during fuel cell operation, resulting in a relatively short and regular ion transport path. This improves ion conductivity and performance, and the framework of the mesoporous carbon plate improves the durability of the catalyst layer. Furthermore, when metal catalyst particles (or metal nanoparticles) are supported within the pores on the mesoporous carbon plate, they are not easily degraded, and the aggregation of metal nanoparticles supported on the support can be prevented even during long-term fuel cell operation. Furthermore, the catalyst supported within the pores of the mesoporous carbon adjacent to the polymer electrolyte membrane acts as a more stable radical scavenger, thereby improving durability.

[0032] The first catalyst layer 20 according to an embodiment of the present invention may include plate-like mesoporous carbon on which metal nanoparticles are not supported.

[0033] The first catalyst layer 20 according to another embodiment of the present invention may include metal nanoparticles that fill and permeate the inner pores of the plate-like mesoporous carbon 20a, 20b.

[0034] The metal nanoparticles may be, for example, a platinum-based metal or a non-platinum-based metal. The platinum-based metal may be platinum (Pt) or a platinum-based alloy (Pt-M). M may be one or more metals selected from the group consisting of palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), gold (Au), zinc (Zn), tin (Sn), molybdenum (Mo), tungsten (W), lanthanum (La), and rhodium (Rh). The platinum-based alloy (Pt-M) may be Pt-Pd, Pt-Sn, Pt-Mo, Pt-Cr, Pt-W, Pt-Ru, Pt-Ni, Pt-Co, Pt-Y, Pt-Ru-W, Pt-Ru-Ni, Pt-Ru-Mo, Pt-Ru-Rh-Ni, Pt-Ru-Sn-W, Pt-Ru-Ir-Ni, Pt-Co, Pt-Co-Mn, Pt-Co-Ni, Pt-Co-Fe, Pt-Co-Ir, Pt-Co-S, Pt-Co-P, Pt-Fe, Pt-Fe-Ir, Pt-Fe-S, Pt-Fe-P, Pt-Au-Co, Pt-Au-Fe, Pt-Au-Ni, Pt-Ni, Pt-Ni-Ir, Pt-Cr, Pt-Cr-Ir, or a mixture of two or more thereof. The non-platinum based metal may be at least one selected from the group consisting of palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), and a non-platinum based alloy. The non-platinum based alloy may be Ir-Fe, Ir-Ru, Ir-Os, Co-Fe, Co-Ru, Co-Os, Rh-Fe, Rh-Ru, Rh-Os, Ir-Ru-Fe, Ir-Ru-Os, Rh-Ru-Fe, Rh-Ru-Os, Fe-N, Fe-P, Co-N, or a mixture of two or more thereof.

[0035] The second catalyst layer 30 according to the present invention may be disposed on the polymer electrolyte membrane 10. Specifically, the first catalyst layer 20 may be interposed between the polymer electrolyte membrane 10 and the second catalyst layer 30. That is, a portion of the second catalyst layer 30 according to an embodiment of the present invention may be disposed directly on the polymer electrolyte membrane 10, and another portion of the second catalyst layer 30 may be disposed directly on the first catalyst layer 20. According to an embodiment of the present invention, the second catalyst layer 30 may improve the chemical and / or mechanical durability of the membrane-electrode assembly by interacting with the first catalyst layer 20.

[0036] As shown in FIGS. 2b and 4b, according to one embodiment of the present invention, an ionomer layer IL may be coated on the surfaces and pores of the mesoporous carbon plates 20a and 20b. According to one embodiment of the present invention, coating the surfaces and pores of the mesoporous carbon plates 20a and 20b with the ionomer layer IL not only increases ion conductivity through a short ion transport path but also improves interfacial adhesion between the polymer electrolyte membrane and the electrode, thereby improving the durability of the membrane-electrode assembly. The thickness of the ionomer layer IL may be 1 to 7 nm (nanometers), specifically 1.5 to 6 nm (nanometers), and more specifically 2 to 5 nm (nanometers). If the thickness of the ionomer layer is less than the above range, ion conductivity may be reduced. If the thickness exceeds the above range, mass transport may be hindered, and secondary ion transport paths other than the pores may be created, resulting in reduced performance.

[0037] Specifically, the ionomer layer IL may include a first ionomer, and the equivalent weight (EW) of the first ionomer may be 600 to 1200. When the equivalent weight of the first ionomer is within this range, the interfacial adhesion between the polymer electrolyte membrane and the electrode may be improved, and both the ion conductivity performance and the catalyst durability performance may be improved.

[0038] The first ionomer may be any one selected from the group consisting of fluorine-based ionomers, hydrocarbon-based ionomers, and mixtures thereof.

[0039] The fluorine-based ionomer is, for example, a fluorine-based polymer containing fluorine in the main chain, and may be any one selected from the group consisting of poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, polystyrene-graft-ethylene-tetrafluoroethylene copolymer, polystyrene-graft-polytetrafluoroethylene copolymer, and mixtures thereof.

[0040] Examples of the hydrocarbon ionomer include sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, and sulfonated polyethersulfone. sulfone, sulfonated polyether ketone, sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrileThe polyarylene ether nitrile may be any one selected from the group consisting of sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, and mixtures thereof.

[0041] To coat the surface of the plate-like mesoporous carbon with an ionomer layer IL, a method using a homogenous mixer, high-pressure disperser, or a resonant acoustic mixer (RAM) can be used. Specifically, the coating method involves homogenizing a suspension in which a polymer solution containing the first ionomer and the plate-like mesoporous carbon are mixed in a weight ratio of 1:0.3 to 1:3 using a homogenous mixer at room temperature, drying the mixture at 60 to 100°C for 3 to 12 hours, and then heat-treating the mixture at 110 to 150°C for 30 to 100 minutes. However, the technical concept of the present invention is not limited thereto, and various methods for coating the surface of the plate-like mesoporous carbon with an ionomer layer can be used.

[0042] 1 to 4b, in the plate-shaped mesoporous carbon according to the present invention, the pores contained in the nanofibers or nanotubes may extend perpendicular to the surface of the polymer electrolyte membrane. The nanofibers and nanotubes may each independently have a height of 50 to 600 nm (nanometers). When the heights of the nanofibers and nanotubes are within the above ranges, the durability and performance of the membrane-electrode assembly can be improved by improving ionic conductivity.

[0043] Specifically, the plate-shaped mesoporous carbon 20a having aligned nanofibers may have nanopores of 2 to 20 nm (nanometers), and the plate-shaped mesoporous carbon 20b having aligned nanotubes may have mesopores of 2 to 30 nm (nanometers). The width or length of the plate-shaped mesoporous carbon having aligned nanofibers and nanotubes may be independently 100 to 1,500 nm (nanometers), specifically 200 to 1,200 nm (nanometers), more specifically 300 to 1,000 nm (nanometers).

[0044] The area occupied by the first catalyst layer 20 according to the present invention may be 10 to 70%, specifically 20 to 60%, and more specifically 30 to 50%, based on the total area of ​​one side of the polymer electrolyte membrane 10. If the area occupied by the first catalyst layer 20 is less than this range, the durability of the catalyst layer may not be sufficiently improved, and if it exceeds this range, the first catalyst layer may act as a blocking layer, which may cause a problem that the second catalyst layer is easily separated.

[0045] The second catalyst layer 30 according to the present invention may include a support and metal nanoparticles supported on the support. The support may be, for example, one selected from the group consisting of a carbon-based support, a porous inorganic oxide, a zeolite, and a combination thereof. The carbon-based support may be, for example, graphite, Super P, carbon fiber, a carbon sheet, carbon black, Ketjen black, Denka black, acetylene black, carbon nanotubes (CNTs), carbon spheres, carbon ribbons, fullerenes, activated carbon, carbon nanofibers, carbon nanowires, carbon nanoballs, carbon nanohorns, carbon nanocages, carbon nanorings, carbon aerogels, graphene, stabilized carbon, activated carbon, and combinations of at least one of these, but is not limited thereto. The porous inorganic oxide may be at least one selected from the group consisting of zirconia, alumina, titania, silica, and ceria. The surface area of ​​the support is 50 m 2 / g or more, and the average particle size may be 10 to 300 nm (nanometers). If the surface area of ​​the carrier is less than the above range, it may be difficult to obtain a uniform distribution of the metal nanoparticles.

[0046] The thickness of the second catalyst layer 30 according to the present invention may be the same as or different from the thickness of the first catalyst layer 20. This is because, when the first catalyst layers 20 are randomly distributed on one surface of the polymer electrolyte membrane 10, some of the second catalyst layers 30 may fill the empty spaces between the first catalyst layers 20, and other parts of the second catalyst layers 30 may be formed directly on the first catalyst layers 20.

[0047] According to another embodiment of the present invention, the thickness of the second catalytic layer 30 may be greater than the thickness of the first catalytic layer 20. Thus, the second catalytic layer 30 is formed not only in the spaces defined by the first catalytic layer 20 but also directly on the first catalytic layer, thereby improving the durability of the membrane-electrode assembly. The thickness of the first catalytic layer may be 50 to 2,000 nm (nanometers), specifically 200 to 1,600 nm (nanometers), and more specifically 400 to 1,200 nm (nanometers). When the thickness of the first catalytic layer 20 is within this range, the durability and performance of the membrane-electrode assembly can be simultaneously improved.

[0048] The method for manufacturing a membrane-electrode assembly according to the present invention can use a batch or roll-to-roll decal transfer method or direct coating method to form a first catalyst layer on at least one surface of a polymer electrolyte membrane.

[0049] The polymer electrolyte membrane 10 according to another embodiment of the present invention may be a reinforced composite membrane in which a porous support is impregnated with an ion conductor. The ion conductor may include a second ionomer, which may be the same as or different from the first ionomer.

[0050] The porous support according to the present invention may be a fluorine-based support or a nanoweb support. Specifically, the fluorine-based support may be, for example, expanded polytetrafluoroethylene (e-PTFE) having a microstructure of polymer fibrils or a microstructure in which nodes are connected to each other by fibrils. Alternatively, the porous support may be a film having a microstructure of polymer fibrils without the nodes.

[0051] The fluorine-based support can include a perfluorinated polymer. The porous support can be made by extruding dispersion-polymerized PTFE into a tape in the presence of a lubricant and stretching the resulting material to create a more porous and stronger porous support. The amorphous content of the PTFE can also be increased by heat-treating the e-PTFE at a temperature above the melting point of PTFE (approximately 342°C). The e-PTFE film produced by this method can have micropores with various diameters and porosity. The e-PTFE film produced by this method can have at least 35% voids, and the diameter of the micropores can be approximately 0.01 to 1 μm (micrometer).

[0052] The nanoweb substrate according to one embodiment of the present invention may be a nonwoven fibrous web composed of a plurality of randomly oriented fibers. The nonwoven fibrous web refers to a sheet having a structure of individual fibers or filaments that are interlaid, but not in the same manner as a woven fabric. The nonwoven fibrous web may be manufactured by any one method selected from the group consisting of carding, garnetting, air-laying, wet-laying, meltblowing, spunbonding, and stitchbonding. The fibers may include one or more polymeric materials, and any commonly used fiber-forming polymeric materials may be used. Specifically, hydrocarbon-based fiber-forming polymeric materials may be used. For example, the fiber-forming polymer material may include any one selected from the group consisting of polyolefins such as polybutylene, polypropylene, and polyethylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides (nylon-6 and nylon-6,6), polyurethanes, polybutene, polylactic acid, polyvinyl alcohol, polyphenylene sulfide, polysulfone, fluid crystalline polymers, polyethylene-co-vinyl acetate, polyacrylonitrile, cyclic polyolefins, polyoxymethylene, polyolefin-based thermoplastic elastomers, and combinations thereof, although the technical concept of the present invention is not limited thereto.

[0053] The nanoweb substrate according to one embodiment of the present invention may be a substrate in which nanofibers are accumulated in the form of a nonwoven fabric containing a large number of pores. The nanofibers are preferably made of a hydrocarbon-based polymer, which exhibits excellent chemical resistance and hydrophobicity, and is therefore unlikely to deform due to moisture in a humid environment. Specifically, the hydrocarbon-based polymer may be selected from the group consisting of nylon, polyimide, polyaramid, polyetherimide, polyacrylonitrile, polyaniline, polyethylene oxide, polyethylene naphthalate, polybutylene terephthalate, styrene butadiene rubber, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyvinylidene fluoride, polyvinyl butylene, polyurethane, polybenzoxazole, polybenzimidazole, polyamideimide, polyethylene terephthalate, polyphenylene sulfide, polyethylene, polypropylene, copolymers thereof, and mixtures thereof. Among these, polyimide is preferably used because of its excellent heat resistance, chemical resistance, and dimensional stability.

[0054] The nanoweb substrate is an aggregate of nanofibers produced by electrospinning, in which the nanofibers are randomly arranged. Taking into account the porosity and thickness of the nanoweb, the nanofibers preferably have an average diameter of 40 to 5,000 nm (nanometers), calculated from the average of 50 fiber diameters measured using a scanning electron microscope (JSM6700F, JEOL). If the average diameter of the nanofibers is below this range, the mechanical strength of the porous substrate may be reduced. If the average diameter of the nanofibers exceeds this range, the porosity may be significantly reduced and the thickness may be increased.

[0055] The thickness of the nonwoven fibrous web may be 10 to 50 μm (micrometers), specifically 15 to 43 μm (micrometers). If the thickness of the nonwoven fibrous web is less than the above range, the mechanical strength may be reduced, and if the thickness exceeds the above range, the resistance loss may increase, and the lightness and integration may be reduced. The nonwoven fibrous web has a basic weight of 5 to 30 mg / cm. 2 If the basis weight of the nonwoven fibrous web is less than the above range, visible pores may be formed and the web may not function as a porous support, whereas if the basis weight exceeds the above range, the web may be manufactured in the form of paper or fabric with almost no pores.

[0056] The porous support according to the present invention may have a porosity of 30 to 90%, preferably 60 to 85%. If the porosity of the porous support is below this range, there is a possibility that the impregnation of the ion conductor may be reduced, while if the porosity exceeds this range, there is a possibility that the morphological stability may be reduced, making it difficult to carry out subsequent processes. The porosity can be calculated as the ratio of the air volume within the porous support to the total volume of the porous support according to the following Equation 1. Here, the total volume is calculated by preparing a rectangular sample and measuring its width, length, and thickness, and the air volume can be calculated by measuring the mass of the sample and then subtracting the volume of the polymer, calculated from the density, from the total volume.

[0057] [Formula 1] Porosity (%) = (air volume in the porous support / total volume of the porous support) × 100

[0058] 2.Fuel cell Another embodiment of the present invention may provide a fuel cell including the membrane-electrode assembly.

[0059] FIG. 5 is a schematic diagram illustrating a fuel cell according to an embodiment of the present invention.

[0060] Referring to FIG. 5, a fuel cell 200 according to the present invention may include a fuel supply unit 210 for supplying a mixed fuel obtained by mixing fuel and water, a reforming unit 220 for reforming the mixed fuel to generate a reformed gas containing hydrogen gas, a stack 230 for generating electrical energy by electrochemically reacting the reformed gas containing hydrogen gas supplied from the reforming unit 220 with an oxidant, and an oxidant supply unit 240 for supplying an oxidant to the reforming unit 220 and the stack 230.

[0061] The stack 230 may include a plurality of unit cells that generate electrical energy by inducing an oxidation / reduction reaction between the reformed gas, including hydrogen gas, supplied from the reforming unit 220 and the oxidant supplied from the oxidant supplying unit 240.

[0062] Each unit cell refers to a unit cell that generates electricity and includes the membrane-electrode assembly that oxidizes / reduces oxygen in the reformed gas containing hydrogen gas and the oxidant, and a separator plate (also called a bipolar plate, hereinafter referred to as "separator plate") that supplies the reformed gas containing hydrogen gas and the oxidant to the membrane-electrode assembly. The separator plates are arranged on both sides of the membrane-electrode assembly, with the membrane-electrode assembly at the center. In this case, the separator plates located at the outermost sides of the stack are sometimes referred to as end plates.

[0063] Among the separation plates, the end plate may be provided with a pipe-shaped first supply pipe 231 for injecting the reformed gas containing hydrogen gas supplied from the reforming section 220 and a pipe-shaped second supply pipe 232 for injecting oxygen gas, and the other end plate may be provided with a first exhaust pipe 233 for discharging the reformed gas containing hydrogen gas that is ultimately left unreacted in the plurality of unit cells to the outside, and a second exhaust pipe 234 for discharging the oxidant that is ultimately left unreacted in the unit cells to the outside.

[0064] In the fuel cell, the separator, fuel supply unit, and oxidant supply unit constituting the electricity generating unit are the same as those used in ordinary fuel cells, and therefore detailed description thereof will be omitted in this specification.

[0065] Hereinafter, the embodiments of the present invention will be described in detail so that a person having ordinary skill in the art to which the present invention pertains can easily carry out the present invention. However, this is merely an example, and the scope of the present invention is not limited by the following content.

[0066] [Synthesis Example 1: Synthesis of plate-like mesoporous silica] To synthesize the mesoporous silica plates used as templates, ZrOCl2·8H2O (0.32 g) and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic® P123; 2.0 g) were dissolved in 2.0 M HCl aqueous solution, followed by the addition of 4.2 g of TEOS (tetraethylorthosilicate) and hydrolysis at 35°C for 30 minutes. To the hydrolyzed mixture, 1.0 g of TMB (trimethylbenzene) was added, and hydrolysis and condensation polymerization were carried out at 35°C for 12 hours. The mixture was then hydrothermally treated at 90°C for 5 hours, filtered, dried, and calcined at 550°C for 6 hours to synthesize mesoporous silica plates.

[0067] [Synthesis Example 2: Synthesis of normal (non-plate-like) mesoporous silica] To synthesize conventional mesoporous silica used as a template, 2.0 g of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic® P123) was dissolved in 2.0 M aqueous HCl, followed by the addition of 4.2 g of TEOS (tetraethylorthosilicate). Hydrolysis and condensation polymerization were carried out at 35°C for 12 hours. The resulting mixture was then filtered, dried, and calcined at 550°C for 6 hours to synthesize non-platelet-shaped mesoporous silica.

[0068] [Production Example 1-1: Production of plate-shaped mesoporous carbon with vertically aligned nanofibers] Using 1.0 g of the plate-shaped mesoporous silica (length 700 nm, height 300 nm, mesopores 10 nm) prepared in Synthesis Example 1 as a template, 0.06 g of phenol formaldehyde resin (a polymer precursor) was filled into the mesopores, followed by polymerization at 140°C and carbonization at 1,000°C in an inert gas atmosphere. The template was then removed to produce plate-shaped mesoporous carbon with aligned nanofibers measuring 700 nm in length and 300 nm in height and mesopores of an average of 6 nm between the nanofibers.

[0069] [Preparation Example 1-2: Preparation of plate-shaped mesoporous carbon having vertically aligned nanofibers coated on the surface and pores with an ionomer layer] The plate-shaped mesoporous carbon prepared according to Preparation Example 1-1 and perfluorosulfonic acid (PFSA) with an equivalent weight of 800 were mixed homogeneously in a 1:1 ratio by weight using a high shear mixer to prepare a suspension. The suspension was dried at 90°C for 10 hours and then heat-treated at 130°C for 60 minutes to form a 3.5 nm thick ionomer layer on the surface and pores of the plate-shaped mesoporous carbon.

[0070] [Production Example 2-1: Production of plate-shaped mesoporous carbon with vertically aligned nanotubes] An acid-treated template was prepared by treating 1.0 g of the plate-shaped mesoporous silica (700 nm in length, 300 nm in height, 10 nm in mesopores) prepared in Synthesis Example 1 with AlCl3. Using the acid-treated template, preparation was carried out in the same manner as in Preparation Example 1-1 to finally prepare a plate-shaped mesoporous carbon having aligned nanotubes with an average of 8 nm pores, each measuring 400 nm in width, 700 nm in length, and 300 nm in height, and having average of 6 nm mesopores between the nanotubes.

[0071] [Preparation Example 2-2: Preparation of plate-shaped mesoporous carbon having aligned nanotubes and an ionomer layer coated on the surface and pores] An ionomer layer having a thickness of 3.5 nm was formed on the surface and pores of the plate-shaped mesoporous carbon in the same manner as in Preparation Example 1-2, except that the plate-shaped mesoporous carbon prepared according to Preparation Example 2-1 was used.

[0072] [Production Example 3: Production of a catalyst in which metal catalyst particles are supported in the pores of plate-shaped mesoporous carbon] A platinum precursor was injected into the pores of the plate-shaped mesoporous carbon synthesized according to Preparation Example 1-1, and then reduced to prepare a catalyst in which 50% Pt was supported in the pores of the plate-shaped mesoporous carbon.

[0073] [Production Example 4: Production of conventional (non-plate-like) mesoporous carbon] Using 1.0 g of conventional mesoporous silica (length 700 nm, height 800 nm, mesopores 7 nm) prepared in Synthesis Example 2 as a template, a conventional mesoporous carbon having average mesopores of 5 nm in size and a length of 700 nm and a height of 800 nm was prepared in the same manner as in Preparation Example 1-1.

[0074] [Experimental Example 1: UHR-SEM image of plate-shaped mesoporous carbon according to Preparation Example 1-1] FIG. 6 is an ultra-high resolution scanning electron microscope (UHR-SEM) image of the plate-shaped mesoporous carbon having aligned nanofibers according to Preparation Example 1-1.

[0075] Referring to FIG. 6, a first catalyst layer was formed using plate-shaped mesoporous carbon having aligned nanofibers according to Preparation Example 1-1.

[0076] [Experimental Example 2: UHR-SEM image of plate-shaped mesoporous carbon according to Preparation Example 2-1] FIG. 7 is an ultra-high resolution scanning electron microscope (UHR-SEM) image of the plate-shaped mesoporous carbon having aligned nanotubes according to Preparation Example 2-1.

[0077] Referring to FIG. 7, a first catalyst layer was formed using the plate-shaped mesoporous carbon having aligned nanotubes according to Preparation Example 2-1.

[0078] [Production Example 5: Production of membrane-electrode assembly] <Example 1-1: Preparation of membrane-electrode assembly using plate-shaped mesoporous carbon according to Preparation Example 1-1> Step (a): Producing a polymer electrolyte membrane A polymer electrolyte membrane was fabricated by applying a polymer solution, which was a mixture of a solvent (water and isopropanol) in a 1:1 weight ratio and perfluorosulfonic acid, to a glass substrate using a doctor blade, gradually increasing the temperature of the applied polymer solution to 80°C, and then drying it for 4 hours.

[0079] Step (b): Forming a first catalyst layer An electrode slurry prepared by mixing the plate-shaped mesoporous carbon of Preparation Example 1-1 and a binder (EW800) in a weight ratio of 1:1.5 was randomly applied by spray or slot die method to form a first catalyst layer with a thickness of 900 nm.

[0080] Step (c): Forming a second catalyst layer Then, an electrode slurry, which was a mixture of a commercial Pt / C catalyst (Tanaka) and a binder (EW=800) in a weight ratio of 1:0.5, was directly coated onto the first side of the polymer electrolyte membrane to form a second catalyst layer with a maximum thickness of 15 μm. As a result, the second catalyst layer was formed, and the first catalyst layer was interposed between the polymer electrolyte membrane and the second catalyst layer.

[0081] <Example 1-2: Preparation of a membrane-electrode assembly using mesoporous carbon plates coated with an ionomer layer on the surface and pores according to Preparation Example 1-2> A membrane-electrode assembly was prepared in the same manner as in Example 1-1, except that the mesoporous carbon plate prepared in Preparation Example 1-2 coated with an ionomer layer was used instead of the mesoporous carbon plate prepared in Preparation Example 1-1.

[0082] <Example 2-1: Preparation of membrane-electrode assembly using plate-shaped mesoporous carbon according to Preparation Example 2-1> A membrane-electrode assembly was prepared in the same manner as in Example 1-1, except that the mesoporous carbon plate of Preparation Example 2-1 was used instead of the mesoporous carbon plate of Preparation Example 1-1.

[0083] <Example 2-2: Preparation of membrane-electrode assembly using mesoporous carbon plates coated with ionomer layers on the surface and pores according to Preparation Example 2-2> A membrane-electrode assembly was prepared in the same manner as in Example 1-2, except that the mesoporous carbon plate coated with an ionomer layer prepared in Preparation Example 2-2 was used instead of the mesoporous carbon plate coated with an ionomer layer prepared in Preparation Example 1-2.

[0084] <Example 3: Preparation of a membrane-electrode assembly using a catalyst in which metal catalyst particles are supported in the pores of a plate-shaped mesoporous carbon according to Preparation Example 3> A membrane-electrode assembly was prepared in the same manner as in Example 1-1, except that the catalyst supported on the mesoporous carbon plate of Preparation Example 3 was used instead of the mesoporous carbon plate of Preparation Example 1-1.

[0085] <Comparative Example 1: Membrane-electrode assembly using conventional (non-plate-shaped) mesoporous carbon> A membrane-electrode assembly was prepared in the same manner as in Example 1-1, except that the non-plate-shaped mesoporous carbon prepared in Preparation Example 4 was used instead of the plate-shaped mesoporous carbon prepared in Preparation Example 1-1.

[0086] [Experimental Example 3: Cross-sectional SEM image of a membrane-electrode assembly including a plate-shaped mesoporous carbon layer according to Example 2-2] FIG. 8 is an SEM cross-sectional image of a membrane-electrode assembly including mesoporous carbon plates with aligned nanotubes according to Example 2-2.

[0087] Referring to FIG. 8, after forming a first catalyst layer using the plate-shaped mesoporous carbon having aligned nanotubes according to Example 2-2, a second catalyst layer was formed.

[0088] [Experimental Example 4: Performance evaluation of membrane-electrode assembly] 9 shows the results of performance evaluation of the membrane-electrode assemblies prepared according to the examples and comparative examples under conditions of 80°C, 100% RH, and atmospheric pressure. Specifically, a fuel cell evaluation station was used to evaluate the performance of the membrane-electrode assemblies.

[0089] Referring to FIG. 9, the membrane-electrode assembly manufactured according to the example showed improved performance compared to the comparative example.

[0090] [Experimental Example 5: Evaluation of mechanical durability of membrane-electrode assembly] The mechanical durability of the membrane-electrode assemblies according to the examples and comparative examples was evaluated using the mechanical durability evaluation protocol of the US Department of Energy (DOE).

[0091] -Evaluation conditions: 80°C, air / air condition, repeated 2 minutes wet and 2 minutes dry, to evaluate the mechanical durability of the membrane-electrode assembly under cycle conditions. After 20,000 cycles of wet-dry cycling, hydrogen gas crossover (H2 crossover) was measured.

[0092] [Table 1]

[0093] Referring to Table 1, when the amount of hydrogen gas was measured at the cathode, it was confirmed that the amount of hydrogen gas permeating the polymer electrolyte membrane in the Example was significantly less than that in the Comparative Example. It can be inferred that the durability of the membrane-electrode assembly is significantly improved according to an embodiment of the present invention, thereby extending the performance and lifespan of the fuel cell.

[0094] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the claims below also fall within the scope of the present invention. [Explanation of symbols]

[0095] 10:Polymer electrolyte membrane 20: 1st catalyst layer 30:Second catalyst layer 100: Membrane-electrode assembly IL: Ionomer layer

Claims

1. Polymer electrolyte membrane; a first catalyst layer disposed on at least one surface of the polymer electrolyte membrane; and a second catalyst layer disposed on the polymer electrolyte membrane; The first catalyst layer is interposed between the polymer electrolyte membrane and the second catalyst layer, The first catalyst layer is including plate-like mesoporous carbon; Membrane-electrode assembly.

2. The surface and pores of the plate-shaped mesoporous carbon are coated with an ionomer layer. The membrane-electrode assembly according to claim 1.

3. The ionomer layer is a first ionomer; The equivalent weight of the first ionomer is 600 to 1200. The membrane-electrode assembly according to claim 2.

4. The first ionomer is The ionomer is any one selected from the group consisting of a fluorine-based ionomer, a hydrocarbon-based ionomer, and a mixture thereof. The membrane-electrode assembly according to claim 3.

5. The plate-like mesoporous carbon is The nanofibers or nanotubes are aligned, Pores contained in the nanofibers or nanotubes extend perpendicular to the surface of the polymer electrolyte membrane; The membrane-electrode assembly according to claim 1.

6. the nanofibers and nanotubes each independently have a height of 50 to 600 nm; The membrane-electrode assembly according to claim 5.

7. The area occupied by the first catalyst layer is Based on the total area of ​​one side of the polymer electrolyte membrane, 10 to 70% The membrane-electrode assembly according to claim 1.

8. The thickness of the second catalyst layer is The thickness of the first catalyst layer is the same as or different from the thickness of the first catalyst layer. The membrane-electrode assembly according to claim 1.

9. The thickness of the second catalyst layer is greater than the thickness of the first catalyst layer; The membrane-electrode assembly according to claim 8.

10. The thickness of the first catalyst layer is 50 to 2,000 nm, The membrane-electrode assembly according to claim 9.

11. A fuel cell comprising the membrane-electrode assembly according to any one of claims 1 to 10.

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