Membrane-electrode assembly for fuel cells and method for manufacturing same

Abstract

The present invention relates to a membrane-electrode assembly for a fuel cell and a method for manufacturing the same. More specifically, the membrane-electrode assembly for a fuel cell of the present invention includes an electrode having a high-porosity catalyst layer and a low-porosity catalyst layer, and an adhesive layer between the electrode and a polymer electrolyte membrane, thereby achieving improved durability and performance.

Description

[Technical Field]

[0001] The present invention relates to a membrane-electrode assembly for a fuel cell and a method for manufacturing the same. [Background technology]

[0002] A fuel cell is a power generation system that directly converts the chemical reaction energy between hydrogen and oxygen contained in hydrocarbon materials such as methanol, ethanol, and natural gas into electrical energy. A representative example of such a fuel cell is the polymer electrolyte membrane fuel cell (PEMFC). Due to its advantages such as a low operating temperature of less than 100°C, fast start-up and response characteristics, and excellent durability, polymer electrolyte fuel cells are attracting attention as power sources for portable, vehicular, and home use.

[0003] The membrane electrode assembly (MEA), which actually generates electricity in a fuel cell system, has a structure in which an anode electrode (also called a fuel electrode or oxidation electrode) and a cathode electrode (also called an air electrode or reduction electrode) are located on either side of an electrolyte membrane. The electrolyte is an electrically insulating but ionically conductive membrane, and protons generated at the anode pass through the membrane to be transferred to the cathode, where they combine with oxygen to produce water.

[0004] Among the manufacturing technologies for membrane-electrode assemblies, the decal method has the advantage of being easy to control the thickness and area of ​​the catalyst layer and being suitable for mass production.In addition, the decal method corresponds to the CCM (Catalyst Coated Membrane) method, which forms an electrode layer on a membrane, and has the advantage of reducing contact resistance between the membrane and catalyst layer compared to the CCG (Catalyst Coated GDL) method, which places a catalyst layer on a gas diffusion layer.

[0005] However, when a membrane-electrode assembly is manufactured using the decal method according to conventional techniques, the adhesive surface between the electrolyte membrane and the electrode interface is uneven, resulting in weak adhesion, high resistance, low output, and poor durability. Furthermore, when the assembly is joined using a high-pressure press, there are insufficient pores in the electrode, which adversely affects oxygen diffusion and water discharge from the cathode. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a membrane-electrode assembly for a fuel cell that has improved gas diffusion and moisture discharge capabilities of the electrode and excellent bonding strength between the electrode and the electrolyte membrane, a fuel cell including the same, and a method for manufacturing the same. [Means for solving the problem]

[0007] According to one aspect of the invention, there is provided a membrane-electrode assembly for a fuel cell, comprising: a polymer electrolyte membrane; a first adhesive layer on the polymer electrolyte membrane; a second adhesive layer on the first adhesive layer; a first low-porosity catalyst layer on the second adhesive layer; and a second high-porosity catalyst layer on the first low-porosity catalyst layer, wherein the first adhesive layer comprises a plasticizer and a crosslinker, and the second adhesive layer comprises an ion-conducting polymer.

[0008] According to one embodiment, the plasticizer may be at least one selected from the group consisting of (poly)alkylene glycol, dihydroxybenzene, (poly)alkylene glycol dialkyl ether, benzoquinones, dialkylene phthalate, and copolymers thereof.

[0009] According to one embodiment, the plasticizer may be at least one selected from polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, tetraethylene glycol, dihydroxybenzene, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diethyl ether, benzoquinone, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, and copolymers thereof.

[0010] According to one embodiment, the cross-linking agent may have a functional group capable of forming a hydrogen bond bridge with the ion-conducting polymer.

[0011] According to one embodiment, the cross-linking agent comprises a carbonyl group (-CO-), a hydroxyl group (-OH), a carboxyl group (-COOH), a nitro group (-NO2), and an amine group (-NR 1 R 2 ) (where R 1 and R 2 Each may independently have at least one functional group selected from the group consisting of H, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, or may be bonded to each other to form a heterocycle having 2 to 5 carbon atoms.

[0012] According to one embodiment, the crosslinking agent may be a substituted or unsubstituted benzoquinone, a substituted or unsubstituted naphthoquinone, a substituted or unsubstituted dihydroxybenzene, a substituted or unsubstituted benzenedicarboxylic acid, a substituted or unsubstituted aminophenol, a substituted or unsubstituted phenylenediamine, a substituted or unsubstituted bipyridinediamine, a substituted or unsubstituted di(aminophenyl)amine, a substituted or unsubstituted bipyrrole, or a mixture of two or more thereof.

[0013] According to one embodiment, the plasticizer and cross-linking agent may be in a weight ratio of 5:1 to 1:1.

[0014] According to one embodiment, the ion-conducting polymer may be a cation conductor having at least one proton exchange group selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphate group, an imide group, a sulfonimide group, a sulfonamide group, a sulfonyl fluoride group, and combinations thereof.

[0015] According to one embodiment, the ion-conducting polymer may be a fluorine-based cation conductor having a sulfonic acid group and / or a carboxyl group, a hydrocarbon-based cation conductor having a sulfonic acid group and / or a carboxyl group, or a mixture thereof.

[0016] According to one embodiment, the first catalyst layer and the second catalyst layer each independently include a first ion-conducting polymer and a second ion-conducting polymer, and the ion-conducting polymer of the second adhesive layer may be the same as at least one of the first ion-conducting polymer and the second ion-conducting polymer.

[0017] According to one embodiment, the first adhesive layer and the second adhesive layer may each independently have a thickness of 0.01 to 5 μm.

[0018] According to one embodiment, the highly porous second catalyst layer may have a three-dimensional network structure.

[0019] According to one embodiment, the highly porous second catalyst layer may include at least one fiber-forming polymer selected from the group consisting of polyether urethane, polyvinyl acetate (PVAc), polyvinyl acetate copolymer, polyvinyl alcohol (PVA), polyfurfuryl alcohol (PPFA), polyurethane, polyurethane copolymer such as polyether urethane, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylic copolymer, polystyrene, polystyrene copolymer, polyethylene, polyethylene glycol, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinyl acetal, polyvinyl chloride (PVC), polycaprolactone, polyvinylpyrrolidone (PVP), polyvinyl fluoride, polyvinylidene fluoride copolymer, and polyamide.

[0020] According to one embodiment, the first low-porosity catalyst layer may have a porosity of 1-50% and a pore size of 10-500 nm, and the second high-porosity catalyst layer may have a porosity of 50-90% and a pore size of 500-5,000 nm.

[0021] According to one embodiment, the first low-porosity catalyst layer may have a thickness of 1 μm to 10 μm, and the second high-porosity catalyst layer may have a thickness of 1 μm to 20 μm.

[0022] According to another aspect of the present invention, there is provided a method for manufacturing a membrane-electrode assembly for a fuel cell, comprising the steps of: (a) forming a low-porosity first catalyst layer on a substrate; (b) forming a second adhesive layer containing an ion-conducting polymer on the low-porosity first catalyst layer; (c) forming a first adhesive layer containing a plasticizer and a cross-linking agent on the second adhesive layer; (d) positioning the first adhesive layer on one or both sides of a polymer electrolyte membrane so that the first adhesive layer faces the membrane, followed by bonding; (e) removing the substrate; and (f) forming a high-porosity second catalyst layer on the low-porosity first catalyst layer.

[0023] According to one embodiment, in step (b), the second adhesive layer is formed by applying a solution containing the ion-conductive polymer, and the amount of the ion-conductive polymer in the solution may be 0.5 to 60 wt % based on the total weight of the solution.

[0024] According to one embodiment, in step (c), the first adhesive layer is formed by applying a solution containing the plasticizer and the crosslinker, and the total amount of the plasticizer and the crosslinker in the solution may be 0.5 to 60 wt % based on the total weight of the solution.

[0025] According to an embodiment, in step (f), the second catalyst layer may be formed by spinning a spinning solution prepared by mixing a catalyst, an ion-conductive polymer, a fiber-forming polymer, and a solvent.

[0026] According to another aspect of the present invention, a fuel cell is provided that includes a membrane-electrode assembly. [Effects of the Invention]

[0027] The membrane-electrode assembly of the present invention can be manufactured at lower temperatures and pressures than conventional manufacturing methods that require high temperatures and pressures. This low-temperature transfer prevents deterioration of the ionomer in the electrode part and reduces deformation of the polymer electrolyte membrane and release film due to temperature and pressure, thereby improving production quality.

[0028] Furthermore, because bonding is performed at lower temperatures and pressures than conventional methods, it is possible to eliminate the problem of excessive pore loss due to densification under high temperatures and pressures. Furthermore, because the electrodes also include high-porosity catalyst layers, the membrane-electrode assembly as a whole has excellent porosity. As a result, the membrane-electrode assembly of the present invention has low mass transfer resistance. Furthermore, by combining a high-porosity catalyst layer with a low-porosity catalyst layer, charge transfer resistance can be reduced compared to a catalyst layer consisting solely of a high-porosity catalyst layer. Furthermore, while maintaining the excellent gas diffusivity and moisture discharge capabilities of the electrodes, the adhesive layer strengthens the bonding strength between the electrodes and the electrolyte membrane, improving the durability and performance of the membrane-electrode assembly. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating a membrane-electrode assembly according to one embodiment of the present invention.

[0030] [Figure 2] 1 is a schematic diagram showing the overall configuration of a fuel cell according to one embodiment of the present invention;

[0031] [Figure 3] 3 shows membrane-electrode assemblies manufactured in comparative examples and examples of the present invention, with (a) to (d) corresponding to comparative examples 1 to 4, respectively, and (e) corresponding to examples 1 and 2.

[0032] [Figure 4] 1 shows the results of a tensile test according to Experimental Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0033] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily understand and practice the present invention. However, as the present invention may be embodied in many different forms, it is not limited to the embodiments set forth herein.

[0034] In the drawings, the thickness of various layers and regions is exaggerated for clarity, and similar parts are designated by the same reference numerals throughout the specification. When a layer, film, region, plate, or other part is described as being "on" another part, this includes not only the case where it is "directly on" that other part, but also the case where there is another part between them. Conversely, when a part is described as being "directly on" that other part, it means that there is no other part between them.

[0035] As used herein, the terms "comprises" and "contains" are used to list materials, compositions, devices, and methods useful in the present invention, and are not intended to be limiting to the examples listed.

[0036] Hereinafter, a membrane-electrode assembly for a fuel cell according to one embodiment will be described with reference to FIG.

[0037] According to one aspect of the present invention, there is provided a membrane-electrode assembly 100 for a fuel cell, comprising a polymer electrolyte membrane 50, a first adhesive layer 11, 11' on the polymer electrolyte membrane 50, a second adhesive layer 12, 12' on the first adhesive layer 11, 11', a first low-porosity catalyst layer 21, 21' on the second adhesive layer 12, 12', and a second high-porosity catalyst layer 22, 22' on the first low-porosity catalyst layer 21, 21', wherein the first adhesive layer 11, 11' comprises a plasticizer and a crosslinking agent, and the second adhesive layer 12, 12' comprises an ion-conducting polymer.

[0038] The first adhesive layers 11 and 11' are layers that come into contact with the polymer electrolyte membrane 50 and contain a plasticizer and a cross-linking agent.

[0039] The plasticizer may be a plasticizer that is typically added during the production of a solid electrolyte membrane in order to control the ion transport properties and processability of the solid electrolyte, or a compound modified to include one or more functional groups that can crosslink with the polymer electrolyte or the ion-conductive polymer in the second adhesive layer.

[0040] The plasticizer may be at least one selected from aliphatic compounds and aromatic compounds having a hydroxyl end, an ether end, or an ester end. Specifically, the plasticizer may be at least one selected from the group consisting of (poly)alkylene glycols, dihydroxybenzenes, (poly)alkylene glycol dialkyl ethers, benzoquinones, dialkylene phthalates, and copolymers thereof, where the alkylene may be an alkylene having 1 to 10 carbon atoms. For example, the plasticizer may be at least one selected from polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, tetraethylene glycol, dihydroxybenzene, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diethyl ether, benzoquinone, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, and copolymers thereof.

[0041] The plasticizer may have a weight-average molecular weight of 10 to 10,000 g / mol, for example, 100 to 9,000 g / mol. If the weight-average molecular weight of the plasticizer is 10,000 g / mol or more, the hydrogen ion transfer resistance increases, which may result in a decrease in fuel cell performance.

[0042] The crosslinking agent may have a functional group capable of forming hydrogen bond bridges with the ion-conductive polymer. If the amount of plasticizer is too large, the physical properties may decrease at low temperatures or the gel state may be difficult to maintain, which can be improved by adding a crosslinking agent. Therefore, it is preferable to further include a crosslinking agent that stabilizes the first adhesive layer 11, 11' containing the plasticizer at room temperature and can form hydrogen bond bridges by reacting with, for example, a carboxyl group or a sulfonic acid group of the ion-conductive polymer.

[0043] For example, the crosslinker may contain a carbonyl group (-CO-), a hydroxyl group (-OH), a carboxyl group (-COOH), a nitro group (-NO2), and an amine group (-NR 1 R 2 ) (where R 1 and R 2 Each of them can independently have at least one functional group selected from the group consisting of H, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, or can be bonded to each other to form a heterocycle having 2 to 5 carbon atoms.

[0044] The crosslinking agent may be a cyclic compound. For example, the organic compound may be an aromatic compound or an aliphatic cyclic compound, or may be a heterocyclic compound or a homocyclic compound.

[0045] According to one embodiment of the present invention, the crosslinking agent may be substituted or unsubstituted benzoquinone, substituted or unsubstituted naphthoquinone, substituted or unsubstituted dihydroxybenzene, substituted or unsubstituted benzenedicarboxylic acid, substituted or unsubstituted aminophenol, substituted or unsubstituted phenylenediamine, substituted or unsubstituted bipyridinediamine, substituted or unsubstituted di(aminophenyl)amine, substituted or unsubstituted bipyrrole, or a mixture of two or more thereof.

[0046] More specifically, the cross-linking agent may include, but is not limited to, at least one selected from the group consisting of the following compounds:

[0047] [ka]

[0048] [ka]

[0049] The thickness of the first adhesive layer 11, 11' may be 0.01 to 5 μm, specifically 0.1 to 3 μm, more specifically 0.1 to 1 μm. By setting the thickness within this range, it is possible to improve the adhesive strength between the polymer electrolyte membrane and the electrode while maintaining performance such as battery output and capacity, and mechanical properties.

[0050] The second adhesive layer 12, 12′ is a layer in contact with the catalyst layer of the electrode and contains an ion-conductive polymer, which may be an ion-conductive polymer contained in the catalyst layer of the electrode, specifically, the first catalyst layer 21, 21′ or the second catalyst layer 22, 22′.

[0051] The ion-conducting polymer may be a cation conductor having at least one proton exchange group selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphate group, an imide group, a sulfonimide group, a sulfonamide group, a sulfonyl fluoride group, and combinations thereof.

[0052] The ion-conducting polymer may be a fluorine-based cation conductor, a hydrocarbon-based cation conductor, or a mixture thereof. Specifically, the ion-conducting polymer according to an embodiment of the present invention may be a fluorine-based cation conductor having a sulfonic acid group and / or a carboxyl group, a hydrocarbon-based cation conductor having a sulfonic acid group and / or a carboxyl group, or a mixture thereof.

[0053] Examples of the fluorine-based cation conductor include Nafion, Aciplex, Flemion, polyvinylidene fluoride, hexafluoropropylene, trifluoroethylene, polytetrafluoroethylene, and copolymers thereof.

[0054] Examples of the hydrocarbon-based cation conductor include hydrocarbon-based polymers having the cation exchange group on their side chains, such as sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (SPAES), sulfonated polyetheretherketone (SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), and sulfonated polystyrene (S-PSU). polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, sulfonated polyether 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 nitrile, sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, etc.

[0055] The second adhesive layer 12, 12' may further include an antioxidant in addition to the ion-conducting polymer. The antioxidant is a particle capable of scavenging peroxides or radicals and may include at least one selected from the group consisting of transition metals, noble metals, ions thereof, salts thereof, oxides thereof, nitrides thereof, and complexes thereof. The transition metal may be one or more selected from the group consisting of cerium (Ce), manganese (Mn), tungsten (W), cobalt (Co), vanadium (V), nickel (Ni), chromium (Cr), zirconium (Zr), yttrium (Y), iridium (Ir), iron (Fe), titanium (Ti), molybdenum (Mo), lanthanum (La), and neodymium (Nd). The noble metal may be one or more selected from the group consisting of silver (Au), platinum (Pt), ruthenium (Ru), palladium (Pd), and rhodium (Rh), but is not limited thereto. The transition metal or noble metal salt may be a carbonate, acetate, chloride, fluoride, sulfate, phosphate, nitrate, tungstate, hydroxide, ammonium acetate, ammonium sulfate, or acetylacetonate. Specific examples of cerium include cerium carbonate, cerium acetate, cerium chloride, cerium acetate, cerium sulfate, diammonium cerium acetate, and tetraammonium cerium sulfate. Examples of organometallic complex salts include cerium acetylacetonate. The antioxidant may be contained in an amount of 1 to 20 parts by weight per 100 parts by weight of the ion-conductive polymer. By setting the concentration within this range, the antioxidant and the ion-conductive polymer can fully exhibit their functions.

[0056] The thickness of the second adhesive layer 12, 12' may be 0.01 to 5 μm, specifically 0.1 to 3 μm, more specifically 0.1 to 2 μm. By setting the thickness within this range, it is possible to improve the adhesive strength between the polymer electrolyte membrane and the electrode while maintaining performance such as battery output and capacity, and mechanical properties.

[0057] The second adhesive layers 12, 12' and the first adhesive layers 11, 11' may be formed in a weight ratio of 1:0.5 to 1:7, specifically 1:0.7 to 1:7, and more specifically 1:1 to 1:7, based on the weight of the solid content in each layer. By setting the weight ratio of the second adhesive layers to the first adhesive layers within this range, the adhesive strength can be sufficiently improved, while the hydrogen ion transfer resistance increases, preventing a decrease in fuel cell performance.

[0058] The first low-porosity catalyst layer 21, 21' and the second high-porosity catalyst layer 22, 22' each independently contain a first catalyst and a first ion-conducting polymer, and a second catalyst and a second ion-conducting polymer. The first catalyst and the second catalyst may be the same or different. The first ion-conducting polymer and the second ion-conducting polymer may be the same or different.

[0059] The first catalyst and the second catalyst can be any catalyst that participates in the cell reaction and can be used as a catalyst for a general fuel cell, preferably a platinum-based metal.

[0060] Platinum-based metals include platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), platinum-M alloys (where M is 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), and palladium ...Pt, Pt, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, Pd, The catalyst metal may include one selected from the group consisting of one or more selected from the group consisting of platinum (Mo), tungsten (W), lanthanum (La), and rhodium (Rh), non-platinum alloys, and combinations thereof. More preferably, a combination of two or more metals selected from the group of platinum-based catalyst metals may be used, but is not limited thereto, and any platinum-based catalyst metal that can be used in this technical field may be used without limitation.

[0061] Specifically, the platinum alloy may be selected from the group consisting of Pt-Pd, Pt-Sn, Pt-Mo, Pt-Cr, Pt-W, Pt-Ru, Pt-Ru-W, Pt-Ru-Mo, Pt-Ru-Rh-Ni, Pt-Ru-Sn-W, Pt-Co, 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, and combinations thereof, and may be used alone or in combination of two or more.

[0062] In addition, the non-platinum alloy may be selected from the group consisting of 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, and combinations thereof, and may be used alone or in combination of two or more.

[0063] Such a catalyst may be used as a catalyst black or may be supported on a carrier.

[0064] The support can be selected from carbon-based supports, porous inorganic oxides such as zirconia, alumina, titania, silica, and ceria, and zeolites. The carbon-based support may be selected from graphite, super P, carbon fiber, carbon sheet, carbon black, Ketjen Black, Denka Black, acetylene black, carbon nanotube (CNT), carbon sphere, carbon ribbon, fullerene, activated carbon, carbon nanofiber, carbon nanowire, carbon nanoball, carbon nanohorn, carbon nanocage, carbon nanoring, ordered nano- / meso-porous carbon, carbon aerogel, mesoporous carbon, graphene, stabilized carbon, activated carbon, and combinations of one or more thereof, but is not limited thereto, and any support available in the art may be used without limitation.

[0065] The catalyst may be located on the surface of the support or may permeate the interior of the support by filling the internal pores of the support.

[0066] When a metal supported on a carrier is used as a catalyst, a commercially available product may be used, or a catalyst prepared by supporting a metal on a carrier may be used. The process of supporting a metal on a carrier is well known in the art, and therefore, even if a detailed explanation is omitted in this specification, it will be easily understandable to those skilled in the art.

[0067] The first catalyst or the second catalyst may be contained in an amount of 20 to 80 wt % of the total weight of each catalyst layer. If the amount is less than 20 wt %, a decrease in activity may occur, and if the amount is more than 80 wt %, the active area may decrease due to aggregation of catalyst particles, resulting in a decrease in catalytic activity. Here, the catalyst weight may be the total weight of the carrier and the catalyst supported on the carrier.

[0068] The first catalyst or the second catalyst has a metal such as a platinum-based metal in an amount of 0.01 to 1 mg in each catalyst layer. Pt / cm 2 The first catalyst or the second catalyst can exhibit sufficient catalytic activity within the above loading range.

[0069] The first ion-conducting polymer and the second ion-conducting polymer are used for hydrogen ion transport and can also function as a binder. The ion-conducting polymers usable as the first ion-conducting polymer and the second ion-conducting polymer may be any of the ion-conducting polymers described and exemplified for the second adhesive layer, specifically, a cation conductor having at least one cation exchange group selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphate group, an imide group, a sulfonimide group, a sulfonamide group, a sulfonyl fluoride group, and combinations thereof. The ion-conducting polymers may be the same as or different from the ion-conducting polymer contained in the second adhesive layer.

[0070] The second catalyst layer 22, 22′ may further include a fiber-forming polymer in addition to the second catalyst and the second ion-conducting polymer. The fiber-forming polymer is a polymer used to form a highly porous three-dimensional web-structured frame in the second catalyst layer through a spinning process, which will be described later. Any material that can be formed into a fiber shape and does not affect the activity of the catalyst and the ion-conducting polymer may be used without limitation.

[0071] The fiber-forming polymer may be at least one selected from the group consisting of, for example, polyetherurethane, polyvinyl acetate (PVAc), polyvinyl acetate copolymer, polyvinyl alcohol (PVA), polyfurfuryl alcohol (PPFA), polyurethane, polyurethane copolymer such as polyetherurethane, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylic copolymer, polystyrene, polystyrene copolymer, polyethylene, polyethylene glycol, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinyl acetal, polyvinyl chloride (PVC), polycaprolactone, polyvinylpyrrolidone (PVP), polyvinyl fluoride, polyvinylidene fluoride copolymer, and polyamide.

[0072] According to one embodiment, the fiber-forming polymer is spun to form a hollow fiber. Since a hollow is formed inside the fiber, pores can be formed without removing all or part of the polymer, which has the advantage that heat treatment can be performed at a low temperature. Such hollow fibers can be formed by adjusting the nozzle used as the spinneret in various shapes. According to another embodiment of the invention, after forming a frame with a three-dimensional network structure, at least a portion of the fiber-forming polymer may be removed from the second catalyst layer as needed by means of heat, chemical reaction, organic solvent, etc., and pores can be formed by removing the polymer. However, since the fiber-forming polymer also functions as a binder, it is preferable to avoid removing it as much as possible.

[0073] The first catalyst layers 21, 21' may have low porosity, specifically, a porosity of 1 to 50%, more specifically, 10 to 50%, and even more specifically, 20 to 45%, and a pore size of 10 to 500 nm, more specifically, 20 to 300 nm, and even more specifically, 20 to 200 nm. If the porosity is less than 1% or the pore size is less than 10 nm, gas and moisture migration and discharge within the electrode may be hindered. If the porosity is more than 50% or the pore size is more than 500 nm, the reactive gas may not remain in the electrode for long enough, resulting in reduced battery performance.

[0074] The first catalyst layer 21, 21' may have a thickness in the range of 1 μm to 10 μm. If the thickness is less than 1 μm, the reaction area may be small, resulting in reduced activity, while if the thickness is more than 10 μm, the travel distance of ions and electrons may increase, resulting in increased resistance.

[0075] The second catalytic layer 22, 22' may be highly porous, specifically having a porosity of 50 to 90%, more specifically 60 to 80%, and a pore size of 500 to 5,000 nm, more specifically 600 to 3,000 nm. If the porosity is less than 60% or the pore size is less than 500 nm, the effects of introducing a highly porous catalytic layer, such as a reduction in mass transfer resistance, may not be fully achieved. If the porosity is more than 90% or the pore size is more than 5,000 nm, the mechanical strength of the catalytic layer may be significantly insufficient.

[0076] The second catalytic layer 22, 22' may have a greater porosity at its surface (e.g., the surface in contact with the gas diffusion layer) than at its surface in contact with the first catalytic layer 21, 21'. For example, the second catalytic layer 22, 22' may have 30% or less of its total porosity in the region from the surface in contact with the first catalytic layer 21, 21' to a region corresponding to half the thickness of the second catalytic layer 22, 22', and 70% or more in the region corresponding to the remaining half of the thickness. This structure can be formed, for example, by adjusting the amount of fiber-forming polymer spun from the initial stage to the later stage of spinning, for example, by adjusting the spinning speed, when producing a three-dimensional network-structured frame for the second catalytic layer by electrospinning.

[0077] The second catalytic layer 22, 22' may have a thickness in the range of 1 μm to 20 μm. If the thickness is less than 1 μm, the reaction area may be small, resulting in reduced activity. If the thickness is more than 20 μm, the migration distance of ions and electrons may increase, resulting in increased resistance, specifically, charge transfer resistance. The thickness of the second catalytic layer 22, 22' may be thinner, the same as, or thicker than the thickness of the first catalytic layer 21, 21'. According to one embodiment of the present invention, the thickness of the second catalytic layer 22, 22' may be thicker than the thickness of the first catalytic layer 21, 21', thereby further reducing mass transfer resistance.

[0078] Meanwhile, a membrane-electrode assembly for a fuel cell according to the present invention can be manufactured by a method for manufacturing a membrane-electrode assembly, including the steps of: (a) forming a low-porosity first catalyst layer on a substrate; (b) forming a second adhesive layer containing an ion-conductive polymer on the low-porosity first catalyst layer; (c) forming a first adhesive layer containing a plasticizer and a crosslinker on the second adhesive layer; (d) positioning the first adhesive layer on one or both sides of a polymer electrolyte membrane so that the first adhesive layer faces the membrane, and then bonding the membrane; (e) removing the substrate; and (f) forming a high-porosity second catalyst layer on the low-porosity first catalyst layer.

[0079] According to one embodiment of the present invention, in step (a), the low-porosity first catalyst layer may be formed by any method known in the art, such as bar coating, doctor blade coating, roll-to-roll printing, screen printing, etc., and preferably by bar coating. Specific manufacturing conditions for manufacturing the first catalyst layer may be appropriately selected by those skilled in the art.

[0080] According to one embodiment of the present invention, in step (b), the second adhesive layer can be prepared by coating a solution in which the ion-conductive polymer is mixed with a solvent. The solvent can be selected from water, hydrophilic solvents, and non-aqueous polar solvents. Examples of hydrophilic solvents include alcoholic solvents such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, and butyl alcohol. Examples of non-aqueous polar solvents include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxirane, 4,4-dimethyl-1,3-dioxirane, γ-butyrolactone, and acetonitrile.

[0081] The amount of the ion-conductive polymer in the solution may be 0.5 to 60 wt %, specifically 1 to 40 wt %, more specifically 1 to 30 wt %, based on the total weight of the ion-conductive polymer solution. If the amount of the ion-conductive polymer is too large, it may be difficult to control the thickness of the adhesive layer thin, which may result in poor battery performance, so it is preferable to set the amount of the ion-conductive polymer within the above range.

[0082] The coating may be formed by any method known in the art, such as spray coating, inkjet printing, roll-to-roll printing, screen printing, etc., and is preferably formed by spray coating. Specific manufacturing conditions, such as spray atomization pressure, drying temperature, drying time, etc., may be appropriately selected by those skilled in the art.

[0083] According to one embodiment of the present invention, in step (c), the first adhesive layer can be prepared by coating a mixed solution of the plasticizer and the crosslinker, which is prepared by mixing the plasticizer and the crosslinker with a solvent. The solvent can be selected from water, a hydrophilic solvent, and a non-aqueous polar solvent, and more specifically, can be alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, and methanol, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, and tetrahydrofuran.

[0084] The total amount of the plasticizer and crosslinker in the solution may be 0.5 to 60 wt %, specifically 1 to 40 wt %, more specifically 1 to 30 wt %, based on the total weight of the mixed solution. If the amount of the plasticizer and crosslinker is excessively large, it becomes difficult to control the thickness of the adhesive layer thin, and mechanical properties may be impaired, so it is preferable to set the amount of the plasticizer and crosslinker within the above ranges.

[0085] The plasticizer and crosslinker may be mixed in a weight ratio of 5:1 to 1:1, specifically 4:1 to 2:1. By keeping the mixing weight ratio of the plasticizer and crosslinker within this range, the adhesive exhibits excellent adhesive performance while at the same time stabilizing the adhesive layer at room temperature to prevent problems such as a decrease in physical properties due to the plasticizer or instability in the layer morphology.

[0086] The coating may be formed by any method known in the art, such as spray coating, inkjet printing, roll-to-roll printing, screen printing, etc., and is preferably formed by spray coating. Specific manufacturing conditions, such as spray atomization pressure, drying temperature, drying time, etc., may be appropriately selected by those skilled in the art.

[0087] According to one embodiment of the present invention, in step (d), the bonding may be performed by roll press bonding or hot pressing. In the case of roll press bonding, the polymer electrolyte membrane and the electrode must be bonded to each other by applying high temperature and pressure within a short period of time while the polymer electrolyte membrane and the electrode are continuously moving. This requires a relatively higher process temperature and pressure than plate press bonding. However, high temperatures and pressures can cause changes in the pore structure of the electrode, deterioration of the polymer electrolyte membrane, and mechanical deformation. Therefore, it is important to perform transfer bonding at low temperatures and pressures. According to the present invention, the roll press bonding and hot pressing can be performed at lower temperatures and pressures than conventional methods. For example, the roll press bonding can be performed at a pressure of less than 4 MPa, a temperature of 140°C or less, and a moving speed of 0.1 to 3 m / min.

[0088] According to one embodiment of the present invention, in step (f), the second catalyst layer may be formed by spinning a spinning dope prepared by mixing a second catalyst, a second ion-conducting polymer, a fiber-forming polymer, and a solvent.

[0089] The spinning may be performed by any one method selected from electrospinning, melt-blown, flash spinning, and electrostatic melt-blown, and is preferably performed by electrospinning.

[0090] Electrospinning is a spinning method in which a solution is charged by directly applying a positive (+) or negative (-) voltage to a spinning nozzle, and then the charged solution is extruded into an air layer through the spinning nozzle. Subsequently, the charged filaments are stretched and branched into other filaments in the air layer, producing ultrafine fibers. To form a highly porous second catalyst layer 22, 22' by electrospinning, a spinning solution is introduced into the barrel of an electrospinning device and then extruded through a spinning nozzle to which a high voltage is applied. The resulting solution is then deposited on a substrate, such as the first catalyst layer, and dried. The voltage range, extrusion speed, viscosity of the spinning solution, and distance between the tip and the substrate can be adjusted by those skilled in the art. For example, a voltage of 7 to 30 kV can be applied, and the solution extrusion speed can be 10 to 50 μl / min.

[0091] A fuel cell according to an embodiment of the present invention includes the membrane-electrode assembly and may be, for example, a fuel cell that uses hydrogen gas as fuel.

[0092] FIG. 2 is a schematic diagram showing the overall configuration of a fuel cell according to an embodiment of the present invention.

[0093] Referring to FIG. 2, the fuel cell 200 includes a fuel supply unit 210 that supplies a mixed fuel obtained by mixing fuel and water, a reforming unit 220 that reforms the mixed fuel to generate a reformed gas containing hydrogen gas, a stack 230 that generates 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 that supplies an oxidant to the reforming unit 220 and the stack 230.

[0094] The stack 230 includes a plurality of unit cells that generate electrical energy by inducing an oxidation / reduction reaction between the reformed gas containing hydrogen gas supplied from the reforming unit 220 and the oxidant supplied from the oxidant supplying unit 240.

[0095] Each unit cell refers to a unit cell that generates electricity and includes the membrane-electrode assembly that oxidizes / reduces the reformed gas containing hydrogen gas and oxygen in 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 disposed on both sides of the membrane-electrode assembly at the center. In this case, the separator plates located at the outermost positions of the stack are sometimes referred to as end plates.

[0096] The end plate of the separator is provided with a first pipe-shaped supply pipe 231 for injecting the reformed gas containing hydrogen gas supplied from the reforming section 220 and a second pipe-shaped supply pipe 232 for injecting oxygen gas, and the other end plate is provided with a first exhaust pipe 233 for discharging the reformed gas containing hydrogen gas that ultimately remains unreacted in the plurality of unit cells to the outside and a second exhaust pipe 234 for discharging the oxidant that ultimately remains unreacted in the unit cells to the outside. [Example]

[0097] Specific examples of the present invention will be presented below. However, the examples described below are merely for the purpose of specifically illustrating or explaining the present invention, and are not intended to limit the present invention. Furthermore, since the details not described here can be sufficiently inferred by those skilled in the art, a description thereof will be omitted.

[0098] [Comparative Example 1]

[0099] The Pt / carbon catalyst and Nafion were mixed to prepare a catalyst slurry for the electrode, which was then bar-coated onto a release film. The resulting material was then dried in an oven at 60°C for 4 hours to form an electrode (low-porosity catalyst layer) (anode: 0.1 mg). Pt / cm 2 , cathode: 0.4 mg Pt / cm 2) At this time, the pores in the electrodes were formed with a mean pore size of 45 nm, and the porosity was about 33%. The anode electrode thickness was about 2 μm, and the cathode thickness was 10 μm. A hydrocarbon-based (sulfonated poly(arylene ether sulfone ketone) multiblock copolymer) electrolyte membrane was placed in the middle, and the electrodes were placed on both sides. They were thermally bonded using a roll press at 180°C, 4 MPa, and a speed of 1 m / min, to obtain the membrane-electrode assembly shown in Figure 3(a).

[0100] Comparative Example 2

[0101] A 5 wt% Nafion dispersion was prepared. The electrode (low-porosity catalyst layer) prepared in Comparative Example 1 was placed on a heating plate at 120°C, and the 5 wt% Nafion dispersion was sprayed onto the electrode to form an adhesive layer containing an ion-conductive polymer. Using a roll press, thermal bonding was performed at 160°C, 3 MPa, and a speed of 1 m / min in the same manner as in Comparative Example 1, yielding a membrane-electrode assembly as shown in Figure 3(b).

[0102] Comparative Example 3

[0103] To form the first adhesive layer, a 10 wt% solution was prepared by mixing polyethylene glycol as a plasticizer and benzoquinone as a crosslinker in a weight ratio of 3:1. This solution was spray-coated on the low-porosity catalyst layer and the second adhesive layer containing the ion-conductive polymer prepared in Comparative Example 2 to form the first adhesive layer containing the plasticizer and crosslinker, with a weight ratio of the second adhesive layer to the first adhesive layer of 1:0.5. The electrode was used as a cathode and had an area of ​​25 cm. 2 The hydrocarbon electrolyte membrane was placed in the middle and thermally bonded using a roll press at 140° C., 3 MPa, and a speed of 1 M / min to obtain a membrane-electrode assembly as shown in FIG. 3(c).

[0104] Comparative Example 4

[0105] An electrode slurry was prepared by mixing a Pt catalyst, Nafion as a binder, and PVA. The electrode slurry was electrospun onto a hydrocarbon-based (sulfonated poly(arylene ether sulfone ketone) multiblock copolymer) electrolyte membrane at 5 μl / min and 13 kV to form a highly porous web-type catalyst layer (0.4 mg). Pt / cm 2 ) was formed as an electrode to obtain a membrane-electrode assembly as shown in Figure 3(d). At this time, the pores of the electrode were formed with a mean pore size of 1,200 nm, the porosity was about 68%, and the total thickness of the cathode catalyst layer (high-porosity catalyst layer) was about 20 μm.

[0106] Comparative Example 5

[0107] To form the first adhesive layer, a 5 wt% solution of benzoquinone, a crosslinking agent, was prepared and spray-coated onto the low-porosity catalyst layer and the second adhesive layer containing an ion-conductive polymer prepared in Comparative Example 2 to form a first adhesive layer containing only the crosslinking agent, with the weight ratio of the second adhesive layer to the first adhesive layer being 1:0.5. To form the second catalytic layer, electrode slurry was prepared by mixing a catalyst, Nafion as a binder, and PVA. The low-porosity catalyst layer of the cathode was 0.3 mg. Pt / cm 2 The electrode slurry was electrospun at 5 μl / min and 13 kV onto the low-porosity catalyst layer of the membrane-electrode assembly to form a highly porous web-type catalyst layer, thereby obtaining a membrane-electrode assembly as shown in FIG. 3(e). At this time, the highly porous web-type catalyst layer was 0.1 mg. Pt / cm 2 The cathode catalyst layer was formed so that the porosity of the high-porosity catalyst layer was 68%, and the mean pore size was 1,200 nm. The total thickness of the cathode catalyst layer was approximately 13 μm, with a low-porosity catalyst layer of approximately 8 μm and a high-porosity catalyst layer of 5 μm.

[0108] Comparative Example 6

[0109] To form the first adhesive layer, a 5 wt% solution of polyethylene glycol as a plasticizer was prepared and spray-coated onto the low-porosity catalyst layer and the second adhesive layer containing an ion-conductive polymer produced in Comparative Example 2 to form a first adhesive layer containing only the plasticizer, with the weight ratio of the second adhesive layer to the first adhesive layer being 1:0.5. The remaining first and second catalyst layers were formed in the same manner as in Comparative Example 5.

[0110] Comparative Example 7

[0111] To form the first adhesive layer, polyethylene glycol as a plasticizer and benzoquinone as a crosslinker were mixed in a weight ratio of 10:1 and sprayed onto the second adhesive layer to form a first adhesive layer containing the plasticizer and crosslinker, with the weight ratio of the second adhesive layer to the first adhesive layer being 1:0.5. The remaining catalyst layers were constructed in the same manner as in Comparative Example 5.

[0112] [Comparative Example 8]

[0113] To form the first adhesive layer, polyethylene glycol as a plasticizer and benzoquinone as a crosslinker were mixed in a weight ratio of 1:10 and spray-coated onto the second adhesive layer to form a first adhesive layer containing the plasticizer and crosslinker, with the weight ratio of the second adhesive layer to the first adhesive layer being 1:0.5. The remaining catalyst layers were constructed in the same manner as in Comparative Example 5.

[0114] [Example 1]

[0115] To form the first adhesive layer, polyethylene glycol as a plasticizer and benzoquinone as a crosslinker were mixed in a weight ratio of 3:1 and sprayed onto the second adhesive layer to form a first adhesive layer containing the plasticizer and crosslinker, with the weight ratio of the second adhesive layer to the first adhesive layer being 1:0.5. The remaining catalyst layers were constructed in the same manner as in Comparative Example 5.

[0116] [Example 2]

[0117] In the same configuration as in Example 1, the low-porosity catalyst layer was 0.2 mg. Pt / cm 2 The highly porous web-type catalyst layer was formed to a thickness of 0.2 mg. Pt / cm 2 The total thickness of the cathode catalyst layer was approximately 15 μm, with a 10 μm high-porosity catalyst layer (68% porosity, 1,200 nm mean pore size) formed on a 5 μm low-porosity catalyst layer (33% porosity, 45 nm mean pore size).

[0118] [Experimental Example 1] Adhesion strength between polymer electrolyte membrane and electrode

[0119] A tensile test was conducted to test the adhesion between the polymer electrolyte membrane and the electrodes, and the results are shown in Figure 4. When the bonded membrane-electrode assembly was pulled from both sides with a constant force using a universal testing machine, it was confirmed that the polymer electrolyte membrane and the electrodes easily separated if the adhesion was poor. Even though the MEA was bonded at a very high temperature as in Comparative Example 1, the tensile test confirmed that the electrodes and the electrolyte membrane easily separated. In contrast, in Example 1, which included both the first and second adhesive layers, transfer was possible at relatively lower temperatures and pressures than conventional methods, and the adhesion was excellent.

[0120] By varying the ratio of crosslinker and plasticizer in the first adhesive layer, we found that when the adhesive layer is made with only plasticizer, it more easily imparts polymer ductility, allowing the electrolyte membrane and electrode to be bonded at very low temperatures and pressures, while the membrane electrode easily separates in a tensile test. The crosslinker strengthens the adhesive strength between the membrane and electrode, while the plasticizer creates an MEA under lower process conditions (temperature and pressure). The above trend is dependent on the ratio of crosslinker and plasticizer, and as shown in Table 1 below, a weight ratio of plasticizer to crosslinker in the first adhesive layer between 5:1 and 1:1 offers the advantages of easy manufacturing conditions and excellent adhesive strength for the membrane electrode.

[0121] [Table 1]

[0122] [Experimental Example 2] Performance evaluation of membrane-electrode assembly

[0123] The membrane-electrode assemblies of the Comparative Example and the Example were fabricated as unit cells, and output performance was evaluated. The cell temperature of the unit cell was maintained at 65°C, and hydrogen and air at 100% relative humidity were supplied to the anode and cathode, respectively, in amounts adjusted to a stoichiometry of 1.5 / 2.0. Table 2 shows the current density of 2.2 A / cm. 2 The voltage measured when a voltage is applied is shown. The higher the measured voltage, the lower the mass transfer resistance. It can be seen that Example 1, which uses a highly porous catalyst layer, exhibits lower mass transfer resistance than other structures.

[0124] [Table 2]

[0125] Table 3 shows the current density of 1.0 A / cm 2 The voltage and charge transfer resistance measured when the voltage was applied were recorded.

[0126] In Comparative Example 4, in which the electrode was formed only with a high-porosity catalyst layer, the charge transfer resistance increased due to the increased thickness and the increased distance that protons had to travel to the reaction site on the catalyst surface. In contrast, the electrode partially containing a low-porosity web exhibited a decrease in charge transfer resistance at medium currents or lower.

[0127] From Tables 2 and 3, it can be seen that the examples according to the present invention are effective in both the medium current (Table 3) and high current (Table 2) regions.

[0128] [Table 3]

[0129] Although the preferred embodiments of the present invention have been described in detail above, the above embodiments are presented as specific examples of the present invention and do not limit the present invention. The scope of the present invention also includes various modifications and improvements made by those skilled in the art using the basic concept of the present invention as defined in the claims below. [Explanation of symbols]

[0130] 100: Membrane-electrode assembly

[0131] 10, 10': Adhesive layer

[0132] 11, 11': 1st adhesive layer, 12, 12': 2nd adhesive layer

[0133] 20, 20': Catalyst layer

[0134] 21, 21': first catalyst layer, 22, 22': second catalyst layer

[0135] 50:Polymer electrolyte membrane

[0136] 200: Fuel cell

[0137] 210: fuel supply unit, 220: reformer unit

[0138] 230: stack, 231: first supply pipe

[0139] 232: 2nd supply pipe, 233: 1st discharge pipe

[0140] 234: second discharge pipe, 240: oxidizer supply section

Claims

1. a polymer electrolyte membrane; a first adhesive layer on the polymer electrolyte membrane; a second adhesive layer on the first adhesive layer; a low-porosity first catalyst layer on the second adhesive layer; a second catalyst layer having high porosity on the first catalyst layer having low porosity; A membrane-electrode assembly for a fuel cell, wherein the first adhesive layer comprises a plasticizer and a cross-linking agent, and the second adhesive layer comprises an ion-conducting polymer.

2. 2. The fuel cell membrane-electrode assembly according to claim 1, wherein the plasticizer is at least one selected from the group consisting of (poly)alkylene glycol, dihydroxybenzene, (poly)alkylene glycol dialkyl ether, benzoquinones, dialkylene phthalate, and copolymers thereof.

3. 3. The membrane-electrode assembly for a fuel cell according to claim 2, wherein the plasticizer is at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, tetraethylene glycol, dihydroxybenzene, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol dipropyl ether, polyethylene glycol dibutyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diethyl ether, benzoquinone, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, and copolymers thereof.

4. 2. The fuel cell membrane-electrode assembly according to claim 1, wherein the cross-linking agent has a functional group capable of forming a hydrogen bond bridge with the ion-conducting polymer.

5. The crosslinking agent may be a carbonyl group (—CO—), a hydroxyl group (—OH), a carboxyl group (—COOH), a nitro group (—NO ２ ), and amine groups (—NR １ R ２ ) (where R １ and R ２ 5. The fuel cell membrane-electrode assembly according to claim 4, wherein each of the functional groups independently has at least one functional group selected from the group consisting of H, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, or is bonded to each other to form a heterocycle having 2 to 5 carbon atoms.

6. 6. The membrane-electrode assembly for a fuel cell according to claim 5, wherein the crosslinking agent is substituted or unsubstituted benzoquinone, substituted or unsubstituted naphthoquinone, substituted or unsubstituted dihydroxybenzene, substituted or unsubstituted benzenedicarboxylic acid, substituted or unsubstituted aminophenol, substituted or unsubstituted phenylenediamine, substituted or unsubstituted bipyridinediamine, substituted or unsubstituted di(aminophenyl)amine, substituted or unsubstituted bipyrrole, or a mixture of two or more thereof.

7. 2. The fuel cell membrane-electrode assembly according to claim 1, wherein the plasticizer and the cross-linking agent are in a weight ratio of 5:1 to 1:

1.

8. 2. The fuel cell membrane-electrode assembly according to claim 1, wherein the ion-conducting polymer is a cation conductor having at least one cation exchange group selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphate group, an imide group, a sulfonimide group, a sulfonamide group, a sulfonic acid fluoride group, and combinations thereof.

9. 9. The fuel cell membrane-electrode assembly according to claim 8, wherein the ion-conducting polymer is a fluorine-based cation conductor having a sulfonic acid group and / or a carboxyl group, a hydrocarbon-based cation conductor having a sulfonic acid group and / or a carboxyl group, or a mixture thereof.

10. 2. The fuel cell membrane-electrode assembly according to claim 1, wherein the first catalyst layer and the second catalyst layer each independently comprise a first ion-conducting polymer and a second ion-conducting polymer, and the ion-conducting polymer of the second adhesive layer is the same as at least one of the first ion-conducting polymer and the second ion-conducting polymer.

11. 2. The fuel cell membrane-electrode assembly according to claim 1, wherein the first adhesive layer and the second adhesive layer each have a thickness independently of each other of 0.01 to 5 μm.

12. 2. The fuel cell membrane-electrode assembly according to claim 1, wherein the highly porous second catalyst layer has a three-dimensional network structure.

13. 2. The fuel cell membrane-electrode assembly of claim 1, wherein the highly porous second catalyst layer comprises at least one fiber-forming polymer selected from the group consisting of polyetherurethane, polyvinyl acetate (PVAc), polyvinyl acetate copolymers, polyvinyl alcohol (PVA), polyfurfuryl alcohol (PPFA), polyurethane, polyurethane copolymers such as polyetherurethane, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylic copolymers, polystyrene, polystyrene copolymers, polyethylene, polyethylene glycol, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene oxide copolymers, polypropylene oxide copolymers, polycarbonate (PC), polyvinyl acetal, polyvinyl chloride (PVC), polycaprolactone, polyvinylpyrrolidone (PVP), polyvinyl fluoride, polyvinylidene fluoride copolymers, and polyamides.

14. 2. The fuel cell membrane-electrode assembly according to claim 1, wherein the first low-porosity catalyst layer has a porosity of 1 to 50% and a pore size of 10 to 500 nm, and the second high-porosity catalyst layer has a porosity of 50 to 90% and a pore size of 500 to 5,000 nm.

15. 2. The fuel cell membrane-electrode assembly according to claim 1, wherein the first low-porosity catalyst layer has a thickness of 1 μm or more and 10 μm or less, and the second high-porosity catalyst layer has a thickness of 1 μm or more and 20 μm or less.

16. (a) forming a low-porosity first catalyst layer on a substrate; (b) forming a second adhesive layer on the low-porosity first catalyst layer, the second adhesive layer including an ion-conducting polymer; (c) forming a first adhesive layer on the second adhesive layer, the first adhesive layer including a plasticizer and a crosslinker; (d) placing the first adhesive layer on one or both surfaces of the polymer electrolyte membrane so that the first adhesive layer faces the polymer electrolyte membrane, and then bonding the first adhesive layer to the polymer electrolyte membrane; (e) removing the substrate; (f) forming a second high-porosity catalyst layer on the first low-porosity catalyst layer; A method for manufacturing a membrane-electrode assembly for a fuel cell.

17. 17. The method for manufacturing a membrane-electrode assembly for a fuel cell according to claim 16, wherein in step (b), the second adhesive layer is formed by applying a solution containing the ion-conducting polymer, and the amount of the ion-conducting polymer in the solution is 0.5 to 60 wt % based on the total weight of the solution.

18. 17. The method for manufacturing a membrane-electrode assembly for a fuel cell according to claim 16, wherein in step (c), the first adhesive layer is formed by applying a solution containing the plasticizer and the crosslinking agent, and the total amount of the plasticizer and the crosslinking agent in the solution is 0.5 to 60 wt % based on the total weight of the solution.

19. 17. The method for manufacturing a membrane-electrode assembly for a fuel cell according to claim 16, wherein in step (f), the highly porous second catalyst layer is formed by spinning a spinning solution prepared by mixing a catalyst, an ion-conducting polymer, a fiber-forming polymer, and a solvent.

20. A fuel cell comprising the membrane-electrode assembly of claim 1.

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