Membrane-electrode assembly for fuel cell and fuel cell comprising same

Abstract

The present invention relates to a membrane-electrode assembly for a fuel cell and a fuel cell comprising same and, more specifically, to a membrane-electrode assembly for a fuel cell and a fuel cell comprising same, wherein by forming a separate radical protective layer comprising fucoidan and a radical scavenger other than fucoidan between a polymer electrolyte membrane and an electrode layer, deterioration of the electrolyte membrane due to radicals can be prevented, thereby greatly improving chemical resistance.

Description

Membrane-electrode assembly for fuel cell and fuel cell including same

[0001] This invention claims the benefit of Korean Patent Application No. 10-2024-0001926, filed with the Korean Intellectual Property Office on January 5, 2024, the entire contents of which are incorporated herein by reference. The present invention relates to a membrane-electrode assembly for a fuel cell and a fuel cell comprising the same.

[0002] Polymer Electrolyte Membrane Fuel Cell (PEMFC) is a type of fuel cell that is attracting attention as a next-generation energy source. It is a fuel cell that uses a polymer membrane with hydrogen ion exchange properties as an electrolyte.

[0003] A fuel cell is a battery equipped with a power generation system that directly converts chemical reaction energy, such as the oxidation / reduction reaction of hydrogen and oxygen contained in hydrocarbon fuels such as methanol, ethanol, and natural gas, into electrical energy. Due to its high energy efficiency and environmentally friendly characteristics of low pollutant emissions, it is attracting attention as a next-generation clean energy source that can replace fossil fuels.

[0004] Fuel cells can be classified into alkaline electrolyte fuel cells and polymer electrolyte membrane fuel cells (PEMFC) depending on the state and type of electrolyte. Among them, polymer electrolyte fuel cells are attracting attention as portable, automotive, and home power sources due to their advantages such as low operating temperature below 100℃, fast start-up and response characteristics, and excellent durability.

[0005] To summarize the reactions occurring in a polymer electrolyte fuel cell, first, when fuel such as hydrogen gas is supplied to the anode, hydrogen ions (H) are produced by the oxidation reaction of hydrogen at the anode. + ) and electrons (e -) is generated. The generated hydrogen ions are transferred to the cathode through the polymer electrolyte membrane, and the generated electrons are transferred to the cathode through the external circuit. At the cathode, oxygen is supplied, and the oxygen combines with the hydrogen ions and electrons to produce water through the reduction reaction of oxygen.

[0006] Meanwhile, many technological hurdles remain to be overcome before commercializing polymer electrolyte membrane fuel cells. Essential improvements include achieving high performance, extended lifespan, and reduced production costs. The component most significantly impacting these improvements is the membrane-electrode assembly (MEA), and among these, the polymer electrolyte membrane is one of the key elements that most significantly influences the performance and price of the MEA.

[0007] Deterioration of the electrolyte membrane can be categorized into chemical / electrochemical and mechanical degradation. Chemical / electrochemical degradation occurs when radicals / hydrogen peroxide generated within the cell attack the polymer membrane, resulting in membrane deterioration. This is one of the main causes of shortened fuel cell life.

[0008] The purpose of the present invention is to provide a membrane-electrode assembly for a fuel cell in which the deterioration phenomenon caused by radicals generated during fuel cell operation is improved.

[0009] Another object of the present invention is to provide a fuel cell with improved performance including the membrane-electrode assembly.

[0010] According to a first aspect of the present invention, a membrane-electrode assembly for a fuel cell is provided, comprising: a polymer electrolyte membrane; a radical protection layer formed on at least one surface of the polymer electrolyte membrane and including a radical scavenger; and an electrode layer formed on the radical protection layer; wherein the radical scavenger includes fucoidan.

[0011] According to a second aspect of the present invention, in the first aspect, the radical scavenger may further include at least one of transition metals, ions thereof, salts thereof, oxides thereof, nitrides thereof, and complexes thereof, carotenoids, flavonoids, vitamins, and glutathione.

[0012] According to a third aspect of the present invention, in the first aspect, the fucoidan may be included in an amount of 0.2 wt% or more and 1.0 wt% or less based on the total weight of the radical protective layer including fucoidan.

[0013] According to a fourth aspect of the present invention, in the second aspect, the radical protective layer may include a first radical protective layer and a second radical protective layer, and at least one layer of the first radical protective layer and the second radical protective layer may include fucoidan.

[0014] According to a fifth aspect of the present invention, in the fourth aspect, the first radical protection layer is positioned on the polymer electrolyte membrane, the second radical protection layer is positioned on the first radical protection layer, and the content of a radical scavenger other than the fucoidan in the first radical protection layer may be higher than that in the second radical protection layer.

[0015] According to a sixth aspect of the present invention, in the fifth aspect, the contents of fucoidan in the first radical protective layer and the second radical protective layer may be the same or different.

[0016] According to the seventh aspect of the present invention, in the fifth aspect, the radical scavenger other than fucoidan in the first radical protective layer may be included in an amount of 0.1 wt% or more and 20 wt% or less based on the total weight of the radical protective layer.

[0017] According to the eighth aspect of the present invention, in the fifth aspect, the thickness ratio of the first radical protective layer and the second radical protective layer may be 10:1 to 1:10.

[0018] According to the ninth aspect of the present invention, in the first aspect, the radical protective layer may include carbon nanofibers.

[0019] According to the tenth aspect of the present invention, in the fifth aspect, only the first radical protective layer may contain carbon nanofibers.

[0020] According to the eleventh aspect of the present invention, in the first aspect, the thickness of the radical protective layer may be 10 nm or more and 2000 nm or less.

[0021] According to the twelfth aspect of the present invention, in the first aspect, the electrode layer may include a catalyst layer formed on the surface of the electrode substrate.

[0022] According to a thirteenth aspect of the present invention, a fuel cell is provided comprising the membrane-electrode assembly for a fuel cell according to the first aspect.

[0023] Features described in one embodiment described above may be combined with other embodiments unless explicitly stated otherwise.

[0024] The radical protection layer according to the present invention can effectively block radicals flowing into a polymer electrolyte membrane, thereby improving the chemical resistance and durability of the membrane-electrode assembly, and ultimately improving the lifespan and performance of the fuel cell.

[0025] FIG. 1 is a cross-sectional view schematically showing a membrane-electrode assembly according to one embodiment of the present invention.

[0026] FIG. 2 is a cross-sectional view schematically showing a membrane-electrode assembly according to another embodiment of the present invention.

[0027] Figure 3 is a schematic diagram showing the overall configuration of a fuel cell according to one embodiment of the present invention.

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0029]

[0030] FIG. 1 is a cross-sectional view schematically showing a membrane-electrode assembly according to one embodiment of the present invention. Referring to FIG. 1, the membrane-electrode assembly (100) includes a polymer electrolyte membrane (50) and electrode layers (20, 20') respectively disposed on both sides of the polymer electrolyte membrane (50), and includes a radical protection layer (10, 10') positioned on at least one side of the polymer electrolyte membrane (50) and positioned between the electrode layers (20, 20') and the polymer electrolyte membrane (50).

[0031] Figure 1 shows one embodiment of a membrane-electrode assembly (100) in which a radical protective layer (10, 10') is formed on both sides of a polymer electrolyte membrane (50), but it can be located on only one side of the cathode side or the anode side.

[0032] One embodiment of the present invention comprises a membrane-electrode assembly for a fuel cell, comprising: a polymer electrolyte membrane (50); a radical protection layer (10, 10') formed on at least one surface of the polymer electrolyte membrane (50) and containing a radical scavenger; and an electrode layer (20, 20') formed on the radical protection layer; wherein the radical scavenger contains fucoidan.

[0033] According to one embodiment of the present invention, the polymer electrolyte membrane (50) is not particularly limited as long as it is a polymer electrolyte membrane used in a fuel cell, and the ion conductor included in the polymer electrolyte membrane may use at least one of a general hydrocarbon polymer or a fluorinated polymer. The hydrocarbon polymer may be any known hydrocarbon polymer, and may be, for example, poly(arylene ether) sulfonated derivatives (SPAEs), poly(arylene sulfide) (SPASs), polyimides (SPIs), polybenzimidazoles (PBIs), polyphenylenes (PPs), or polyetheretherketone (PEEK). In addition, the fluorinated polymer may be any known fluorinated polymer, and may be, for example, one of Nafion, Aciplex, Flemion, polyvinylidene fluoride, hexafluoropropylene, trifluoroethylene, polytetrafluoroethylene, or a copolymer thereof.

[0034] According to one embodiment of the present invention, the polymer electrolyte membrane may have a thickness of 5 ㎛ or more and 200 ㎛ or less in a non-humidified state.

[0035] According to one embodiment of the present invention, the radical protection layer (10, 10') includes a radical scavenger, thereby preventing radicals generated from the electrode layer (20, 20') from entering the polymer electrolyte membrane (50), thereby suppressing deterioration of the electrolyte membrane caused by radicals.

[0036] According to one embodiment of the present invention, the radical protection layer (10, 10') may include a radical scavenger in an interfacial adhesive layer that can be formed between the polymer electrolyte membrane (50) and the electrode layer (20, 20').

[0037] The radical scavenger of the present invention basically comprises fucoidan, and may additionally comprise a radical scavenger such as an inorganic compound other than fucoidan. Fucoidan can be extracted from seaweed and is a sulfated heteropolysaccharide having a skeleton mainly composed of L-fucose in α-1,2 or α-1,3 bonds. Fucoidan can act as a radical scavenger due to its antioxidant action, and also has hydrogen ion conductivity due to its sulfate group content.

[0038] According to one embodiment of the present invention, the fucoidan is not only preferably distributed uniformly throughout the radical protection layer (10, 10') to improve hydrogen ion conductivity, but also can effectively block radicals from entering the electrolyte membrane.

[0039] According to one embodiment of the present invention, the radical protection layer (10, 10') preferably additionally includes an antioxidant other than fucoidan as a radical scavenger, and the additional radical scavenger may be at least one selected from the group consisting of transition metals (e.g., cerium (Ce), manganese (Mn), etc.), ions thereof, salts thereof, oxides thereof, nitrides thereof, complexes thereof, carotenoids (e.g., lutein, lycopene, carotene, etc.), flavonoids (e.g., catechin, anthocyanin, etc.), vitamins (e.g., ascorbic acid, tocopherol, etc.), and glutathione. Preferably, CeZrO2 may be further included.

[0040] According to one embodiment of the present invention, the content of the fucoidan may be 0.2 wt% or more and 1.0 wt% or less based on the total weight of the radical protective layer containing the fucoidan. If the content exceeds the above range, cell performance may deteriorate, and if the content falls below the above range, the radical removal effect may be reduced, resulting in a minimal durability improvement effect. By controlling the content of the fucoidan within the above-described range, the chemical resistance and durability of the membrane-electrode assembly can be improved, and ultimately, the lifespan and performance of the fuel cell can be improved.

[0041] According to one embodiment of the present invention, the radical protection layer (10, 10') may be formed as a single layer, but may be formed as a laminate of two or more layers.

[0042] According to one embodiment of the present invention, the radical protection layer (10) includes a first radical protection layer (11) and a second radical protection layer (12), and at least one of the first radical protection layer (11) and the second radical protection layer (12) may include fucoidan.

[0043] Referring to FIG. 2, FIG. 2 briefly illustrates an embodiment in which radical protective layers (10, 10') are formed on both sides of a polymer electrolyte membrane (50), and each radical protective layer (10, 10') is formed by a laminated structure of a first radical protective layer (11, 11') and a second radical protective layer (12, 12').

[0044] According to one embodiment of the present invention, the first radical protection layer (11, 11') and the second radical protection layer (12, 12') may each independently include fucoidan or fucoidan and an additional radical scavenger. As a specific example, the first radical protection layer (11, 11') in contact with the polymer electrolyte membrane (50) may have CeZrO2 added thereto, and the second radical protection layer (12, 12') may include only fucoidan as a radical scavenger.

[0045] According to one embodiment of the present invention, the first radical protection layer (11) is positioned on the polymer electrolyte membrane (50), and the second radical protection layer (12) is positioned on the first radical protection layer (11), and the content of a radical scavenger excluding the fucoidan in the first radical protection layer (11) may be higher than that in the second radical protection layer (12). Specifically, the first radical protection layer (11) may include CeZrO2.

[0046] The first radical protection layer (11) and the second radical protection layer (12) may have different densities of radical scavengers excluding fucoidan, and when the first radical protection layer (11) is positioned on the electrolyte membrane (50) side and the second radical protection layer (12) is positioned on the electrode layer (20) side as shown in FIG. 2, it is preferable that the density of radical scavengers excluding fucoidan in the first radical protection layer (11) is higher than that in the second radical protection layer (12). Fucoidan has proton conductivity, but radical scavengers excluding fucoidan generally have significantly lower or no proton conductivity, and therefore, in order to improve proton conductivity, it is necessary to adjust the content of radical scavengers excluding fucoidan. Therefore, it is preferable to first remove radicals in the second radical protection layer (12) having a relatively low density of radical scavengers other than fucoidan, and then remove radicals together with radical scavengers other than fucoidan in the first radical protection layer (11) in consideration of both hydrogen ion conductivity and radical removal rate.

[0047] According to one embodiment of the present invention, the contents of fucoidan in the first radical protection layer (11) and the second radical protection layer (12) may be the same or different from each other.

[0048] According to one embodiment of the present invention, in the first radical protective layer, a radical scavenger other than fucoidan may be included in an amount of 0.1 wt% or more and 20 wt% or less based on the total weight of the radical protective layer. Specifically, in the first radical protection layer, the radical scavenger other than fucoidan may be in an amount of 0.2 wt% to 19 wt%, 0.3 wt% to 18 wt%, 0.4 wt% to 17 wt%, 0.5 wt% to 16 wt%, 0.6 wt% to 15 wt%, 0.7 wt% to 14 wt%, 0.7 wt% to 13 wt%, 0.8 wt% to 12 wt%, 0.9 wt% to 11 wt%, 1 wt% to 10 wt%, 2 wt% to 9 wt%, 3 wt% to 8 wt%, 4 wt% to 7 wt%, or 5 wt% to 6 wt%, based on the total weight of the radical protection layer. If the amount exceeds the above range, cell performance may be deteriorated, and if the amount falls short of the above range, radical scavenging ability may be reduced.

[0049] According to one embodiment of the present invention, the density of the radical scavenger excluding fucoidan in the second radical protection layer (12) is lower than that in the first radical protection layer (11), so the content of the radical scavenger excluding fucoidan in the second radical protection layer (12) per the same volume is lower than that in the first radical protection layer (11).

[0050] In the case of the first radical protection layer (11), if the density of the radical scavenger excluding fucoidan is high compared to the above range, the hydrogen ion conductivity may drop significantly, which may cause a problem in that the efficiency of the fuel cell may be significantly reduced. In addition, if the density of the radical scavenger excluding fucoidan is low compared to the above range, a significant amount of radicals may flow into the electrolyte membrane, which may cause a problem in suppressing deterioration of the electrolyte membrane. It is preferable that the second radical protection layer (12) have a lower density of the radical scavenger excluding fucoidan compared to the first radical protection layer (11), and in extreme cases, it may contain only fucoidan as the radical scavenger.

[0051] According to one embodiment of the present invention, the weight ratio of the radical scavenger including fucoidan included in the first radical protective layer (11) and the radical scavenger excluding fucoidan included in the second radical protective layer (12) may be 1:5 to 1:20. Specifically, the weight ratio of the radical scavenger including fucoidan included in the first radical protective layer (11) and the radical scavenger excluding fucoidan included in the second radical protective layer (12) may be 1:6 to 1:20, 1:7 to 1:20, 1:8 to 1:20, 1:9 to 1:20, 1:10 to 1:20, 1:11 to 1:20, 1:12 to 1:20, 1:13 to 1:20, 1:14 to 1:20, 1:15 to 1:20, 1:16 to 1:20, 1:17 to 1:20, 1:18 to 1:20 or 1:19 to 1:20. When the weight ratio of the radical scavenger including fucoidan included in the first radical protection layer (11) and the radical scavenger excluding fucoidan included in the second radical protection layer (12) satisfies the above-mentioned range, the deterioration phenomenon due to radicals can be improved.

[0052] According to one embodiment of the present invention, the thickness ratio of the first radical protective layer (11) and the second radical protective layer (12) may be 10:1 to 1:10. Preferably, it may be 5:1 to 1:5, more preferably, it may be 2:1 to 1:2, and may be 2:1.

[0053] According to one embodiment of the present invention, the radical protection layer (10) may include carbon nanofibers. The radical protection layer (10) may not include a separate support because it includes fucoidan in a polymer form, but may include a separate carbon support to improve durability. The carbon support may be, for example, carbon nanofibers, and specifically, may be a support formed of carbon nanosheets.

[0054] According to one embodiment of the present invention, carbon nanofibers may be included only in the first radical protection layer. Since carbon nanofibers have excellent electrical conductivity, it is preferable that they are distributed only in a part of the radical protection layer (10) rather than throughout the entirety of the radical protection layer (10), thereby blocking electricity generated in the electrode layer from being conducted to the electrolyte membrane. Specifically, it is preferable that carbon nanofibers are not included in the second radical protection layer (12) in contact with the electrode layer (20), and carbon nanofibers are included only in the first radical protection layer (11), so that the second radical protection layer (12) can also function as an insulating layer.

[0055] According to one embodiment of the present invention, the thickness of the radical protection layer may be 10 nm or more and 2000 nm or less. Specifically, the thickness of the radical protection layer may be 50 nm or more and 1800 nm or less, 60 nm or more and 1800 nm or less, 80 nm or more and 1700 nm or less, 100 nm or more and 1600 nm or less, 120 nm or more and 1600 nm or less, 140 nm or more and 1500 nm or less, 160 nm or more and 1400 nm or less, 170 nm or more and 1300 nm or less, 180 nm or more and 1200 nm or less, 190 nm or more and 1100 nm or less, or 200 nm or more and 1000 nm or less. In addition, the thickness of the cathode side and the anode side may be the same or different. If the thickness of the radical protection layer is less than the above-described range, it may be difficult to prevent radical inflow into the polymer electrolyte membrane (50) due to the thickness being too thin, and if it exceeds the above-described range, the hydrogen ion conductivity of the membrane-electrode assembly may be significantly reduced due to the radical protection layer, and the efficiency of the fuel cell may be rapidly reduced.

[0056] According to one embodiment of the present invention, the electrode layer may include a catalyst layer formed on the surface of the electrode substrate.

[0057] Referring to FIG. 2, the electrode (20, 20') includes an electrode substrate (40, 40') and a catalyst layer (30, 30') formed on the surface of the electrode substrate (40, 40'), and may further include a microporous layer (not shown) including conductive microparticles such as carbon powder or carbon black to facilitate diffusion of a substance in the electrode substrate (40, 40') between the electrode substrate (40, 40') and the catalyst layer (30, 30').

[0058] In the membrane-electrode assembly (100), an electrode (20) disposed on one side of a polymer electrolyte membrane (50) and causing an oxidation reaction to generate hydrogen ions and electrons from fuel transferred to a catalyst layer (30) through the electrode substrate (40) is called an anode electrode, and an electrode (20') disposed on the other side of the polymer electrolyte membrane (50) and causing a reduction reaction to generate water from hydrogen ions supplied through the polymer electrolyte membrane (50) and an oxidant transferred to a catalyst layer (30') through the electrode substrate (40') is called a cathode electrode.

[0059] The catalyst layers (30, 30') of the anode and cathode electrodes (20, 20') contain a catalyst. Any catalyst that participates in the cell reaction and can be used as a catalyst for a typical fuel cell can be used. Preferably, a platinum-based metal can be used.

[0060] The platinum-based metal may include one selected from the group consisting of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), a platinum-M alloy (wherein M is at least one 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)), a non-platinum alloy, and a combination thereof, and more preferably, a combination of two or more metals selected from the platinum-based catalyst metal group may be used, but is not limited thereto, and any platinum-based catalyst metal usable in the present technical field may be used without limitation. there is.

[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 thereof.

[0062] In addition, the non-platinum alloy may be used alone or in combination of two or more 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.

[0063] These catalysts can be used as catalysts themselves or supported on a carrier.

[0064] The above carrier may be selected from carbon-based carriers, porous inorganic oxides such as zirconia, alumina, titania, silica, and ceria, and zeolites. The above carbon-based carrier 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 carrier usable in the present technical field may be used without limitation.

[0065] The above catalyst particles may be positioned on the surface of the carrier, or may penetrate into the carrier while filling the internal pores of the carrier.

[0066] When using the precious metal supported on the above-mentioned carrier as a catalyst, a commercially available catalyst can be used, or a catalyst manufactured by supporting the precious metal on the carrier can be used. The process of supporting the precious metal on the above-mentioned carrier is widely known in the art, and thus, a detailed description thereof is omitted herein, but it is readily understood by those working in the art.

[0067] The above catalyst particles may be contained in an amount of 20 wt% or more and 80 wt% or less relative to the total weight of the catalyst electrode (30, 30'). If contained in an amount less than 20 wt%, there may be a problem of reduced activity, and if contained in an amount exceeding 80 wt%, the active area may be reduced due to agglomeration of the catalyst particles, which may conversely reduce the catalytic activity.

[0068] In addition, the catalyst electrode (30, 30') may include a binder to improve the adhesiveness of the catalyst electrode (30, 30') and to transfer hydrogen ions. It is preferable to use an ion conductor having ion conductivity as the binder, and since the description of the ion conductor is the same as that described above, a repeated description is omitted.

[0069] However, the ion conductor can be used as a single substance or in the form of a mixture, and can also be optionally used together with a non-conductive compound for the purpose of further improving adhesion to the polymer electrolyte membrane (50). It is preferable to adjust the amount used to suit the intended use.

[0070] As the above non-conductive compound, at least one selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene (ETFE), ethylene chlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), dodecylbenzenesulfonic acid, and sorbitol may be used.

[0071] The above binder may be included in an amount of 20 wt% or more and 80 wt% or less based on the total weight of the catalyst electrode (30, 30'). If the content of the binder is less than 20 wt%, the generated ions may not be properly transmitted, and if it exceeds 80 wt%, the pores may be insufficient, making it difficult to supply hydrogen or oxygen (air) and reducing the active area for reaction.

[0072] As the electrode substrate (40, 40'), a porous conductive substrate may be used to ensure a smooth supply of hydrogen or oxygen. Representative examples thereof include, but are not limited to, carbon paper, carbon cloth, carbon felt, or metal cloth (a porous film composed of a fibrous metal cloth or a cloth formed of polymer fibers on which a metal film is formed on the surface). In addition, it is preferable to use a fluorine-based resin that has been water-repellent treated as the electrode substrate (40, 40') to prevent the reactant diffusion efficiency from being reduced by water generated during operation of the fuel cell. The fluorine-based resin may be polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, fluorinated ethylene propylene, polychlorotrifluoroethylene, or a copolymer thereof.

[0073] In addition, a microporous layer may be further included to enhance the diffusion effect of reactants in the electrode substrate (40, 40'). This microporous layer may generally include a conductive powder having a small particle size, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotube, carbon nanowire, carbon nanohorn, or carbon nano ring.

[0074] The above-described microporous layer is manufactured by coating a composition including a conductive powder, a binder resin, and a solvent on the electrode substrate (40, 40'). Preferably, the binder resin may be polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, polyvinyl alcohol, cellulose acetate, or a copolymer thereof. Preferably, the solvent may be alcohol such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, tetrahydrofuran, or the like. The coating process may be, but is not limited to, a screen printing method, a spray coating method, or a coating method using a doctor blade, depending on the viscosity of the composition.

[0075] One embodiment of the present invention includes a fuel cell including a membrane-electrode assembly for a fuel cell.

[0076] Figure 3 is a schematic diagram showing the overall configuration of the fuel cell.

[0077] Referring to FIG. 3, a fuel cell (200) includes a fuel supply unit (210) that supplies a mixed fuel in which fuel and water are mixed, a reformer unit (220) that reforms the mixed fuel to generate a reformed gas containing hydrogen gas, a stack (230) that generates electrical energy by causing an electrochemical reaction between the reformed gas containing hydrogen gas supplied from the reformer unit (220) and an oxidizer, and an oxidizer supply unit (240) that supplies an oxidizer to the reformer unit (220) and the stack (230).

[0078] The stack (230) has a plurality of unit cells that generate electrical energy by inducing an oxidation / reduction reaction of a reforming gas containing hydrogen gas supplied from a reforming unit (220) and an oxidizing agent supplied from an oxidizing agent supply unit (240).

[0079] Each unit cell refers to a unit cell that generates electricity, and includes a membrane-electrode assembly that oxidizes / reduces oxygen in a reformed gas containing hydrogen gas and an oxidizing agent, and a separator (also called a bipolar plate, hereinafter referred to as a "separator") for supplying the reformed gas containing hydrogen gas and the oxidizing agent to the membrane-electrode assembly. The separator is positioned on both sides of the membrane-electrode assembly with the membrane-electrode assembly at the center. At this time, the separator plates located at the outermost sides of the stack are also specifically referred to as end plates.

[0080] Among the separators, the end plate is provided with a first supply pipe (231) in the shape of a pipe for injecting reformed gas containing hydrogen gas supplied from a reforming unit (220), and a second supply pipe (232) in the shape of a pipe for injecting oxygen gas, and the other end plate is provided with a first discharge pipe (233) for discharging reformed gas containing hydrogen gas that is ultimately unreacted and remaining in a plurality of unit cells to the outside, and a second discharge pipe (234) for discharging oxidant that is ultimately unreacted and remaining in the unit cells to the outside.

[0081] In the fuel cell, except that the membrane-electrode assembly (100) according to one embodiment of the present invention is used, the separator, fuel supply unit, and oxidant supply unit constituting the electricity generating unit are used in a typical fuel cell, and therefore, a detailed description thereof is omitted herein.

[0082] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0083] [Manufacturing Example: Manufacturing of Membrane-Electrode Assembly]

[0084] [Comparative Example 1]

[0085] A cathode electrode composition was prepared by dispersing 88 wt% of a Pt / C cathode catalyst and 12 wt% of a Nafion / H2O / 2-propanol solution as a binder using stirring and ultrasonic methods. The prepared cathode electrode composition was coated on a Teflon release film and dried to prepare a cathode electrode. At this time, the catalyst loading of the cathode electrode was about 0.40 mg / cm. 2 It was done as follows.

[0086] An anode electrode composition was prepared by dispersing 88 wt% of a Pt / C anode catalyst and 12 wt% of a Nafion / H2O / 2-propanol solution as a binder using stirring and ultrasonic methods. The prepared anode electrode composition was coated on a Teflon release film and dried to prepare an anode electrode. At this time, the catalyst loading of the anode electrode was about 0.10 mg / cm. 2 It was done as follows.

[0087] A composition for forming an interfacial adhesive layer was prepared by containing 5 wt% of fluorinated ionomer PFSA having an EW of 700 to 800 g / eq and 95 wt% of H2O / 2-propanol solution.

[0088] The composition for forming the interface adhesive layer manufactured above is applied on the manufactured electrode at about 0.12 mg / cm 2 An interfacial adhesive layer of about 800 nm in thickness was formed on the electrode surface by spray coating in an amount of .

[0089] A fluorine-based polymer electrolyte membrane of PFSA having a thickness of 15 ㎛ was interposed between the cathode and anode electrodes manufactured above, and this was subjected to a test at 160 ℃ and 20 kgf / cm 2 After compressing for 3 minutes under the conditions of heat and pressure, a membrane-electrode assembly was manufactured in which the cathode and anode electrodes were bonded to the polymer electrolyte membrane.

[0090]

[0091] [Comparative Example 2]

[0092] A membrane-electrode assembly was manufactured in the same manner as in Comparative Example 1, except that a hydrocarbon-based polymer electrolyte membrane of PES was used instead of the fluorine-based polymer electrolyte membrane in Comparative Example 1.

[0093]

[0094] [Example 1]

[0095] A membrane-electrode assembly was manufactured in the same manner as in Comparative Example 1, except that 0.5 wt% of fucoidan was included in the composition for forming the interfacial adhesive layer.

[0096]

[0097] [Example 2]

[0098] A membrane-electrode assembly was manufactured in the same manner as in Example 1, except that a composition for forming an interfacial adhesive layer containing 5 wt% of a radical scavenger (CeZrO2) was additionally spray-coated on the electrode on which the interfacial adhesive layer was formed to form a two-layer interfacial adhesive layer. At this time, the thickness ratio of the first radical protective layer and the second radical protective layer was 2:1. (Thickness of the first radical protective layer: 600 nm, thickness of the second radical protective layer: 300 nm)

[0099]

[0100] [Example 3]

[0101] A membrane-electrode assembly was manufactured in the same manner as in Comparative Example 2, except that 0.5 wt% of fucoidan was included in the composition for forming the interfacial adhesive layer.

[0102]

[0103] [Example 4]

[0104] A membrane-electrode assembly was manufactured in the same manner as in Example 3, except that a composition for forming an interfacial adhesive layer containing 5 wt% of a radical scavenger (CeZrO2) was additionally spray-coated on the electrode on which the interfacial adhesive layer was formed to form a two-layer interfacial adhesive layer. At this time, the thickness ratio of the first radical protective layer and the second radical protective layer was 2:1.

[0105]

[0106] [Experimental Example: Comparison of Physical Properties of Membrane-Electrode Assemblies]

[0107] Electrode area is 25 cm 2 The MEA was fastened to the unit cell, and the electrical load was applied step-by-step. After stabilization, the performance of the MEA was measured at a unit cell temperature of 65℃ and humidity of 100% by controlling the flow rate, temperature, and humidity in the MEA evaluation station (SciTech Korea, Korea).

[0108] Table 1 below shows the current density (A / cm) when the cell voltage is 0.6 V. 2 ) were compared. The accelerated durability evaluation was performed using the OCV Holding method, which is an electrochemical degradation method, and the unit cell voltage was measured after a certain period of time under the conditions of unit cell temperature 90 ℃, humidity (RH) 30%, and pressure 50 kPa, and the voltage decrease rate compared to the initial OCV was calculated. Hydrogen permeability was measured by LSV (Linear sweep voltammetry), and the hydrogen permeation current was measured while changing the voltage in the range of 0.2 to 0.8 V at a scan rate of 0.5 mV / s using a Potentio stat (Bio Logics).

[0109] The LSV method supplies hydrogen and nitrogen to the anode and cathode, respectively, and measures the current value resulting from hydrogen crossover. When the voltage is increased at a constant rate (linear sweep), the permeated hydrogen undergoes an oxidation reaction on the cathode catalyst, releasing electrons. Measuring the amount of these electrons provides an indication of the amount of hydrogen that has passed through the membrane.

[0110]

[0111] Hydrogen permeability (mA / cm) 2 ) Hydrogen permeability increase rate (%) Cell voltage decrease rate (%) Comparative example 12.103937 Example 11.951313 Example 21.5224 Comparative example 20.613026 Example 30.52159 Example 40.4635

[0112] * Hydrogen permeability increase rate: Increase rate of hydrogen permeability after 400 hours of OCV holding compared to initial hydrogen permeability

[0113]

[0114] As gas permeability increases, the OCV decreases, and fuel efficiency decreases by the amount of fuel consumed that cannot participate in the electrochemical reaction. Hydrogen that has passed through the polymer membrane at the anode meets oxygen at the cathode and is converted to H2O, H2O2, HO2, etc. through the platinum catalyst or is discharged without reacting. As these reactions proceed, a mixed potential is formed along with the original reaction of oxygen at the cathode, which reduces the OCV. When hydrogen and oxygen that have penetrated the membrane meet, H2O2 or oxygen radicals are generated through the action of the platinum catalyst. These hydrogen peroxide or radicals attack the polymer of the electrolyte membrane, deteriorating the membrane and creating pinholes. These pinholes further increase the gas permeability, and accordingly, the generation rate of hydrogen peroxide and radicals is accelerated, rapidly progressing membrane deterioration. Because the permeability of the electrolyte membrane significantly affects the performance and lifespan of the PEMFC, measuring the gas permeability of the PEMFC membrane is very important. Therefore, the degree of electrolyte membrane deterioration is analyzed by measuring the above hydrogen permeability.

[0115] Comparing the above Comparative Example 1 and Example 1 using a fluorine-based polymer electrolyte membrane, in the case of Example 1 including a radical protection layer including fucoidan, the hydrogen permeability increase rate was reduced to about 3 times or less, and the cell voltage decrease rate was also reduced to about 2.8 times.

[0116] In addition, when comparing the results of Comparative Example 2 and Example 3 using a hydrocarbon-based polymer electrolyte membrane of PES, the hydrocarbon-based polymer electrolyte membrane had better deterioration prevention properties in the example including a radical protective layer including fucoidan, and specifically, in Example 3, the hydrogen permeability increase rate decreased to less than about 2 times, and the cell voltage decrease rate also decreased by about 2.9 times.

[0117] In addition, according to the results of Examples 1 and 2, when the radical protection layer including fucoidan was laminated with an additional radical protection layer, the hydrogen permeability increase rate was reduced to about 6.5 times or less and the cell voltage decrease rate was also reduced to about 3.3 times compared to the single layer case.

[0118] In addition, according to the results of Examples 3 and 4, when the radical protection layer including fucoidan was laminated with an additional radical protection layer, the hydrogen permeability increase rate was reduced to about 5 times or less compared to the single layer case, and the cell voltage decrease rate was also reduced to about 1.8 times.

[0119] 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 following claims also fall within the scope of the present invention.

[0120] [Explanation of symbols]

[0121] 10, 10': Radical protection layer

[0122] 11, 11': First radical protection layer

[0123] 12, 12': Second radical protection layer

[0124] 20, 20': Electrode layer

[0125] 30, 30': catalyst layer

[0126] 40, 40': Electrode substrate

[0127] 50: Polymer electrolyte membrane

[0128] 100: Membrane-electrode assembly

[0129] 200: Fuel cell

[0130] 210: Fuel supply section

[0131] 220: Modification Department

[0132] 230: Stack

[0133] 231: Supply Pipe 1

[0134] 232: Second supply line

[0135] 233: First discharge pipe

[0136] 234: Second discharge pipe

[0137] 240: Oxidizer supply unit

Claims

1. Polymer electrolyte membrane; A radical protection layer provided on at least one surface of the polymer electrolyte membrane and including a radical scavenger; and An electrode layer provided on the radical protective layer; A membrane-electrode assembly for a fuel cell, wherein the radical scavenger comprises fucoidan.

2. In paragraph 1, A membrane-electrode assembly for a fuel cell, wherein the radical scavenger further comprises at least one of transition metals, ions thereof, salts thereof, oxides thereof, nitrides thereof, and complexes thereof, carotenoids, flavonoids, vitamins, and glutathione.

3. A membrane-electrode assembly for a fuel cell, wherein the fucoidan is contained in an amount of 0.2 wt% or more and 1.0 wt% or less based on the total weight of the radical protective layer containing fucoidan in the first paragraph.

4. In paragraph 2, A membrane-electrode assembly for a fuel cell, wherein the radical protective layer comprises a first radical protective layer and a second radical protective layer, and at least one layer of the first radical protective layer and the second radical protective layer comprises fucoidan.

5. In paragraph 4, The first radical protective layer is located on the polymer electrolyte membrane, and the second radical protective layer is located on the first radical protective layer. A membrane-electrode assembly for a fuel cell, wherein the content of a radical scavenger other than the fucoidan in the first radical protective layer is higher than that in the second radical protective layer.

6. In paragraph 5, A membrane-electrode assembly for a fuel cell, wherein the contents of fucoidan in the first radical protective layer and the second radical protective layer are the same or different.

7. In paragraph 5, A membrane-electrode assembly for a fuel cell, wherein a radical scavenger other than fucoidan in the first radical protective layer is contained in an amount of 0.1 wt% or more and 20 wt% or less based on the total weight of the radical protective layer.

8. In paragraph 5, A membrane-electrode assembly for a fuel cell, wherein the thickness ratio of the first radical protective layer and the second radical protective layer is 10:1 to 1:

10.

9. In paragraph 1, A membrane-electrode assembly for a fuel cell, wherein the radical protective layer comprises carbon nanofibers.

10. In paragraph 5, A membrane-electrode assembly for a fuel cell, comprising carbon nanofibers only in the first radical protective layer.

11. In paragraph 1, A membrane-electrode assembly for a fuel cell, wherein the thickness of the radical protective layer is 10 nm to 2000 nm.

12. In paragraph 1, The above electrode layer is a membrane-electrode assembly for a fuel cell, which includes a catalyst layer provided on the surface of an electrode substrate.

13. A fuel cell comprising a membrane-electrode assembly for a fuel cell according to paragraph 1.

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