Composite membrane, membrane-electrode assembly comprising same, and fuel cell

Abstract

Disclosed is a composite membrane having improved chemical and mechanical durability. Provided is a composite membrane according to an aspect of the present invention comprising a polymer electrolyte membrane, and a reinforcing layer disposed on at least one surface thereof, the reinforcing layer comprising any one from the group consisting of graphene, hexagonal boron nitride (h-BN), and a combination thereof.

Description

Composite membrane, membrane-electrode assembly and fuel cell comprising the same

[0001] The present disclosure relates to a composite membrane, and more particularly, to a composite membrane, a membrane-electrode assembly including the same, and a fuel cell.

[0002] Fuel cells directly convert the chemical energy generated by fuel oxidation into electrical energy. Their high energy efficiency and environmentally friendly characteristics, coupled with minimal pollutant emissions, have drawn attention as a next-generation energy source. These fuel cells typically consist of a polymer electrolyte membrane, with an anode and cathode electrode formed on either side. This structure is called a membrane electrode assembly (MEA).

[0003] Fuel cells can be classified into alkaline electrolyte fuel cells and polymer electrolyte membrane fuel cells (PEMFC) depending on the type of electrolyte membrane. Among them, polymer electrolyte membrane fuel cells are attracting attention as portable, automotive, and home power sources due to their advantages such as low operating temperatures below 100℃, fast start-up and response characteristics, and excellent durability. A representative example of such polymer electrolyte membrane fuel cells is the hydrogen ion exchange membrane fuel cell, which uses hydrogen gas as fuel. To summarize the reactions that occur in a polymer electrolyte membrane fuel cell, first, when a fuel such as hydrogen gas is supplied to the anode electrode (anode), hydrogen ions and electrons are generated through an oxidation reaction of the hydrogen gas at the anode. The generated hydrogen ions are transferred to the cathode electrode (reduction electrode) through the polymer electrolyte membrane, and the generated electrons are transferred to the cathode electrode (reduction electrode) through an external circuit. At the reduction electrode, oxygen gas is supplied, and the oxygen gas combines with hydrogen ions and electrons to produce water through a reduction reaction.

[0004] According to one aspect of the present invention, a composite membrane is provided that improves both the mechanical and chemical durability of a membrane-electrode assembly.

[0005] According to another aspect of the present invention, a composite membrane capable of effectively dissipating heat generated during operation of a fuel cell to the outside is provided.

[0006] According to another aspect of the present invention, a composite membrane is provided that prevents degradation of fuel cell performance under high temperature and low humidity conditions.

[0007] According to another aspect of the present invention, a composite membrane capable of effectively blocking radicals and dissolved radical scavengers or catalyst ions generated during fuel cell operation is provided.

[0008] According to another aspect of the present invention, a membrane-electrode assembly comprising the composite membrane is provided.

[0009] According to another aspect of the present invention, a fuel cell including the membrane-electrode assembly is provided.

[0010] The purposes of the present invention are not limited to those mentioned above, and other unmentioned purposes and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0011] According to a first aspect of the present invention, a composite membrane is provided, comprising a polymer electrolyte membrane and a reinforcing layer disposed on at least one surface of the polymer electrolyte membrane, wherein the reinforcing layer comprises one selected from the group consisting of graphene, hexagonal boron nitride (h-BN), and combinations thereof.

[0012] According to a second aspect of the present invention, in the first aspect, the graphene may be any one selected from the group consisting of single crystal graphene, polycrystalline graphene, and combinations thereof.

[0013] According to a third aspect of the present invention, in the first or second aspect, the graphene may include single crystal graphene.

[0014] According to a fourth aspect of the present invention, in any one of the first to third aspects, the hexagonal boron nitride may be any one selected from the group consisting of single-crystal hexagonal boron nitride, polycrystalline hexagonal boron nitride, and combinations thereof.

[0015] According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the hexagonal boron nitride may include single crystal hexagonal boron nitride.

[0016] According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the thickness of the reinforcing layer may be 0.1 nm or more and 8.0 nm or less.

[0017] According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the reinforcing layer includes the graphene and the hexagonal boron nitride, and the ratio of an area where the graphene and the hexagonal boron nitride overlap may be 40% or more and 100% or less.

[0018] According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the reinforcing layer may include two or more sub-reinforcing layers.

[0019] According to a ninth aspect of the present invention, in the eighth aspect, the two or more sub-reinforcement layers may include a first layer and a second layer disposed on the first layer.

[0020] According to a tenth aspect of the present invention, a membrane-electrode assembly is provided, comprising: a composite membrane according to any one of the first to ninth aspects; an anode electrode disposed on one side of the composite membrane; and a cathode electrode disposed on the other side of the composite membrane.

[0021] According to the eleventh aspect of the present invention, in the tenth aspect, the area occupied by the reinforcing layer may be 60% or more and 150% or less of the total area of ​​one side of one of the anode electrode and the cathode electrode.

[0022] According to a twelfth aspect of the present invention, a fuel cell is provided comprising a membrane-electrode assembly according to the tenth or eleventh aspect.

[0023] The solutions to the above problems are not exhaustive and may be combined with some embodiments of the present disclosure. The various features of the present invention and their corresponding advantages and effects can be understood in more detail by referring to the detailed description below.

[0024] According to one aspect of the present invention, the phenomenon of hydrogen gas permeating the electrolyte membrane can be effectively prevented, and the movement of radicals within the electrolyte membrane or metal ions such as radical scavengers can be effectively prevented from being dissolved and eluted to the electrode, thereby improving the chemical durability of the membrane-electrode assembly.

[0025] According to another aspect of the present invention, a composite membrane can be provided that not only maintains the performance of a fuel cell under high temperature and low humidity conditions, but also improves mechanical durability.

[0026] In addition to the effects described above, specific effects of the present invention are described below while explaining specific details for carrying out the invention.

[0027] Figure 1 is a composite film including a reinforced layer in which graphene and hexagonal boron nitride are partially overlapped.

[0028] Figure 2 is a composite film including a reinforcing layer in which graphene and hexagonal boron nitride are completely overlapped.

[0029] Figure 3 is a cross-sectional view of a composite membrane according to one embodiment of the present invention.

[0030] Figure 4 is a cross-sectional view of a composite membrane according to another embodiment of the present invention.

[0031] FIG. 5 illustrates a membrane-electrode assembly according to one embodiment of the present invention.

[0032] Figure 6 is a schematic diagram illustrating a fuel cell according to one embodiment of the present invention.

[0033] Figure 7 is a scanning electron microscope (SEM) photograph of a composite membrane according to Example 1.

[0034] Figure 8 is a scanning electron microscope photograph of a composite membrane according to Example 3.

[0035] Figure 9 is a scanning electron microscope photograph of a composite membrane according to Example 6.

[0036] Figure 10 shows the performance evaluation results of the membrane-electrode assembly according to comparative examples and embodiments.

[0037] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0038] The terms “comprise” and / or “comprising” in this specification specify the presence of stated features, steps, numbers, operations, elements, elements and / or groups thereof, but do not exclude the presence or addition of one or more other features, steps, numbers, operations, elements, elements and / or groups thereof.

[0039] In this specification, “At least one of a, b and c” may include a, b or c alone, or a combination of two or more selected from the group consisting of a, b and c.

[0040] If multiple embodiments are described in this specification, the embodiments may be combined unless specifically stated otherwise. In this case, the effects of the present invention may be defined as including the effects derived from each embodiment and the effects resulting from the organic combination of the embodiments. For example, even if Embodiments 1 and 2 are described independently in this specification, Embodiments 1 and 2 may be organically combined, unless the context clearly indicates otherwise, and the effects of the present invention may include the effects resulting from the combination of Embodiments 1 and 2.

[0041] The numerical range indicated by the term "to" in this specification refers to a numerical range that includes the values ​​stated before and after the term as the lower and upper limits, respectively. For example, if "a" and "b" are stated in the specification, it can be understood that "a" and "b" are stated.

[0042] In the present specification, when multiple numerical values ​​are disclosed as the upper and lower limits of any numerical range, the numerical range disclosed in the present specification can be understood as any numerical range that has any one of the multiple lower limit values ​​and any one of the multiple upper limit values ​​as the lower limit value and the upper limit value, respectively. For example, when a or more, or b or more; and c or less or d or less are described, it can be understood that a or more and c or less, a or more and d or less, b or more and c or less, or b or more and d or less are described.

[0043] As used herein, terms such as "about" or "substantially" mean a reasonable amount of variation from the modified term that does not significantly alter the final result. These terms may be interpreted to include a variation of at least ±5% or at least ±10%, provided that such variation does not alter the meaning of the term and render it invalid.

[0044] In this specification, the term “layer” or film may include cases where it is formed not only on the entire area when observing the area where the layer or film exists, but also cases where it is formed on only a part of the area. For example, the surface of the layer or film may be defined to include a flat shape, a non-flat shape, and a combination thereof; or a continuous shape, a discontinuous shape, and a combination thereof. For example, when another element is formed of a layer or film directly on top of one element, the coverage of the other element on the surface of the one element may be defined to be 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, 95% or more, or 99% or more.

[0045] In this specification, “single crystal” may mean a characteristic in which the entire crystal of a crystalline material is regularly formed along a certain crystal axis.

[0046] In this specification, “polycrystalline” may mean a collection of multiple single crystals or crystal grains among crystalline materials, and may mean a property that includes at least one single crystal or crystal grain having a different crystal orientation.

[0047] For example, an XRD (X-Ray-Diffraction) analysis method can be used as a method for analyzing the single crystal and polycrystal characteristics. Specifically, the XRD analysis method can be analyzed under the analysis conditions of Cu Ka X-ray (wavelength = 0.15418 nm) as a source, continuous scan as a measurement mode, 4° / min as a scan speed, and 0.02° as a step width.

[0048] According to one aspect of the present invention, a composite membrane is provided, which comprises a polymer electrolyte membrane and a reinforcing layer disposed on at least one surface of the polymer electrolyte membrane, wherein the reinforcing layer comprises one selected from the group consisting of graphene, hexagonal boron nitride (h-BN), and combinations thereof. According to one aspect of the present invention, a two-dimensionally strong sp 2 By forming a reinforcing layer containing graphene and / or hexagonal boron nitride having a honeycomb structure in which planes arranged in a hexagonal mesh are stacked in layers and having covalent bonds, on the surface of a polymer electrolyte membrane, not only can the mechanical and chemical durability of the membrane-electrode assembly be improved simultaneously, but also the heat generated during fuel cell operation can be effectively released.

[0049] Hereinafter, the configuration of the present invention will be described in more detail with reference to the drawings.

[0050] 1. Composite membrane

[0051] Figure 1 is a composite film including a reinforced layer in which graphene and hexagonal boron nitride are partially overlapped.

[0052] Figure 2 is a composite film including a reinforcing layer in which graphene and hexagonal boron nitride are completely overlapped.

[0053] Referring to FIGS. 1 and 2, graphene and hexagonal boron nitride may partially or fully overlap within the reinforcing layer. A method of changing the exposure amount and exposure time of a graphene precursor or a boron nitride precursor in a chemical vapor deposition method may be used as a means for controlling the overlapping ratio of the graphene and hexagonal boron nitride. For example, when the exposure amount of the graphene precursor is constant, as the exposure time of the boron nitride precursor increases, the overlapping ratio of the graphene and hexagonal boron nitride may increase. Here, the overlapping of the graphene and the hexagonal boron nitride may mean that the graphene and the hexagonal boron nitride overlap with respect to the thickness direction of the reinforcing layer. Specifically, the overlap may mean that the graphene and the hexagonal boron nitride include at least one area in which the graphene and the hexagonal boron nitride overlap with respect to the thickness direction of the reinforcing layer. Accordingly, if the graphene and the hexagonal boron nitride are in direct contact with each other, or if there is an overlapping area with respect to the thickness direction of the reinforcement layer even if the graphene and the hexagonal boron nitride are not in direct contact with each other, the graphene and the hexagonal boron nitride can be defined as overlapping with each other. Therefore, the partial overlap of the graphene and the hexagonal boron nitride can mean that the graphene and the hexagonal boron nitride overlap some area with respect to the thickness direction of the reinforcement layer, and the complete overlap of the graphene and the hexagonal boron nitride can mean that the entire area of ​​either the graphene or the hexagonal boron nitride overlaps with the other with respect to the thickness direction of the reinforcement layer. For example, whether the graphene and the hexagonal boron nitride completely overlap or partially overlap can be distinguished by measuring the difference in the ratio of the overlapping lattice planes to the non-overlapping lattice planes by any one method selected from the group consisting of energy-dispersive X-ray spectroscopy; high-resolution transmission electron microscopy, and combinations thereof.

[0054] Figure 3 is a cross-sectional view of a composite membrane according to one embodiment of the present invention.

[0055] Referring to FIG. 3, a composite membrane (50) according to the present invention includes a polymer electrolyte membrane (10) and a reinforcing layer (12) disposed on at least one surface of the polymer electrolyte membrane (10).

[0056] Specifically, the reinforcing layer (12) may include any one selected from the group consisting of graphene, hexagonal boron nitride (h-BN), and combinations thereof. The graphene and hexagonal boron nitride have a two-dimensionally strong sp 2 It has a honeycomb structure with covalent bonds and hexagonal mesh-like planes arranged in layers. Due to these structural characteristics, the graphene and hexagonal boron nitride are formed as a thin film on the surface of the polymer electrolyte membrane, thereby improving the chemical and mechanical durability of the membrane-electrode assembly and heat dissipation performance when the fuel cell is operated for a long time under high temperature and low humidity conditions.

[0057] The graphene according to the present invention may be any one selected from the group consisting of single-crystal graphene, polycrystalline graphene, and combinations thereof, and preferably may include single-crystal graphene. In particular, since single-crystal graphene, unlike polycrystalline graphene, has a characteristic in which crystal grains composed of carbon atoms are not misaligned, the effect of reducing the hydrogen crossover phenomenon in which hydrogen gas permeates the electrolyte membrane may be more excellent. For example, the graphene may be manufactured by a chemical vapor deposition (CVD) method, and specifically, may be manufactured by a method of exposing a substrate such as silicon or copper to a mixed gas containing methane and hydrogen. When the crystal orientations of the silicon or copper used as the substrate are diverse, polycrystalline graphene having multiple crystal orientations may be manufactured, and when the crystal orientation of the silicon or copper is single, single-crystal graphene may be manufactured.

[0058] The hexagonal boron nitride according to the present invention may be any one selected from the group consisting of single-crystal hexagonal boron nitride, polycrystalline hexagonal boron nitride, and combinations thereof, and preferably may include single-crystal hexagonal boron nitride. Specifically, since single-crystal hexagonal boron nitride has the characteristic that crystal grains are not misaligned, unlike polycrystalline hexagonal boron nitride, the effect of reducing hydrogen crossover, which is a phenomenon in which hydrogen gas permeates the electrolyte membrane, may be more excellent. For example, the hexagonal boron nitride may be manufactured by a chemical vapor deposition (CVD) method, and specifically, may be manufactured by a method of exposing borazine gas (B3H6N3) to a substrate such as silicon or copper. When the crystal orientations of silicon or copper used as the substrate are diverse, polycrystalline hexagonal boron nitride having multiple crystal orientations can be manufactured, and when the crystal orientation of silicon or copper is single, single-crystal hexagonal boron nitride can be manufactured.

[0059] According to one embodiment of the present invention, the reinforcing layer (12) may include a first reinforcing layer (12a), and the first reinforcing layer (12a) may be disposed only on one surface of the polymer electrolyte membrane (10).

[0060] In some embodiments of the present invention, the thickness of the first reinforcing layer (12a) may be 0.1 nm or more and 8.0 nm or less. Specifically, the thickness of the first reinforcing layer (12a) may be 0.1 nm or more, 1.0 nm or more, 1.5 nm or more, or 2.0 nm or more; and 8.0 nm or less, 7.0 nm or less, 6.0 nm or less, less than 6.0 nm, 5.0 nm or less, 4.0 nm or less, 3.0 nm or less, or 2.5 nm or less. By controlling the thickness of the first reinforcing layer within the above numerical range, the ionic conductivity of the electrolyte membrane and the performance of the interfacial adhesion between the electrolyte membrane and the catalyst layer may be improved at the same time. That is, the thickness of the reinforcing layer (12) may be the same as the thickness of the first reinforcing layer (12a).

[0061] According to another embodiment of the present invention, the ratio of the area where the graphene and the hexagonal boron nitride overlap in the reinforcement layer (12) may be 40% or more and 100% or less, and specifically 50% or more and 95% or less. Specifically, the ratio of the area where the graphene and the hexagonal boron nitride overlap in the reinforcement layer (12) may be 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, or 70% or more; and 75% or less, 80% or less, 85% or less, 90% or less, 95% or less, or 100% or less. By controlling the ratio of the area where the graphene and the hexagonal boron nitride overlap within the above numerical range, the chemical and mechanical durability of the membrane-electrode assembly can be further improved. For example, the ratio of the overlapping areas of the graphene and the hexagonal boron nitride can be analyzed by measuring the difference in the ratio of overlapping and non-overlapping lattice planes by any one method selected from the group consisting of SEM, AFM (Atomic Force Microscope), energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and combinations thereof.

[0062] According to another embodiment of the present invention, the reinforcement layer (12) may include two or more sub-reinforcement layers. Specifically, each of the sub-reinforcement layers may independently include one selected from the group consisting of graphene, hexagonal boron nitride (h-BN), and combinations thereof. According to some embodiments of the present invention, each of the sub-reinforcement layers includes one selected from the group consisting of graphene, hexagonal boron nitride (h-BN), and combinations thereof, thereby minimizing the voltage loss of the membrane-electrode assembly under high temperature and low humidity conditions and partially improving the stability.

[0063] For example, the two or more sub-reinforcement layers may include a first layer and a second layer disposed on the first layer. Here, the first layer may be in contact with the polymer electrolyte membrane, and the second layer may be disposed on the first layer, and more specifically, may be disposed directly on the first layer.

[0064] In another example, the above-mentioned reinforcement layer (12) may have a single-layer structure.

[0065] In some embodiments of the present invention, the thicknesses of the first and second layers may each independently be 0.05 nm or more and 4.0 nm or less. Specifically, the thicknesses of the first and second layers may each independently be 0.05 nm or more, 0.1 nm or more, 0.5 nm or more, or 1.0 nm or more; and 1.5 nm or less, 2.0 nm or less, 2.5 nm or less, 3.0 nm or less, 3.5 nm or less, or 4.0 nm or less. In some embodiments of the present invention, by controlling the thicknesses of the first and second layers within the above numerical ranges, the interfacial adhesion between the electrolyte membrane and the catalyst layer and the ionic conductivity of the polymer electrolyte membrane can be achieved simultaneously.

[0066] In some embodiments of the present invention, the two or more sub-reinforcement layers; or the first layer and the second layer may each independently include any one selected from the group consisting of graphene, hexagonal boron nitride (h-BN), and combinations thereof. For example, the first layer may be a graphene layer and the second layer may be a hexagonal boron nitride layer, or the first layer may be a hexagonal boron nitride layer and the second layer may be a graphene layer. According to some preferred embodiments of the present invention, the first layer in contact with the polymer electrolyte membrane includes graphene, and the second layer disposed directly on the first layer includes hexagonal boron nitride, thereby minimizing the voltage loss of the membrane-electrode assembly under high temperature and low humidity conditions and partially improving the stability.

[0067] Figure 2 is a cross-sectional view of a composite membrane according to another embodiment of the present invention. Parts that are repeated in the description above are briefly described or omitted.

[0068] Referring to FIG. 2, a composite membrane (50) according to another embodiment of the present invention may include a first reinforcing layer (12a) disposed on one surface of the polymer electrolyte membrane (10) and a second reinforcing layer (12b) disposed on the other surface. The second reinforcing layer (12b) may be the same as or different from the first reinforcing layer (12a). For example, the first and second reinforcing layers (12a, 12b) may each independently include any one selected from the group consisting of graphene, hexagonal boron nitride (h-BN), and combinations thereof.

[0069] According to one embodiment of the present invention, the polymer electrolyte membrane (10) may be, for example, a conventional single membrane in the relevant technical field.

[0070] According to another embodiment of the present invention, the polymer electrolyte membrane (10) may be a reinforced composite membrane in which an ion conductor is impregnated into a porous support.

[0071] The porous support may be, for example, expanded polytetrafluoroethylene (e-PTFE) having a microstructure of polymer fibrils or a microstructure in which nodes are interconnected by fibrils. Additionally, a film having a microstructure of polymer fibrils without nodes may also be used as the porous support.

[0072] The above ion conductor may be, for example, any one selected from the group consisting of fluorine-based ionomers, hydrocarbon-based ionomers, and mixtures thereof.

[0073] The above fluorine-based ionomer may be, for example, any one selected from the group consisting of a fluorine-based polymer containing fluorine in the main chain, poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, a polystyrene-graft-ethylenetetrafluoroethylene copolymer, a polystyrene-graft-polytetrafluoroethylene copolymer, and mixtures thereof.

[0074] The hydrocarbon ionomers include, for example, sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (S-PEEK), sulfonated polybenzimidazole (S-PBI), sulfonated polysulfone (S-PSU), sulfonated 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,It may be any one selected from the group consisting of sulfonated polyarylene ether sulfone ketone and mixtures thereof.

[0075] 2. Membrane-electrode assembly

[0076] Figure 5 illustrates a membrane-electrode assembly according to one embodiment of the present invention. Parts that are repeated in the description above are briefly described or omitted.

[0077] Referring to FIG. 5, another embodiment of the present invention can provide a membrane-electrode assembly (100) including the composite membrane (50) and an anode electrode (20) disposed on one side of the composite membrane (50) and a cathode electrode (30) disposed on the other side of the composite membrane.

[0078] According to one embodiment of the present invention, the area occupied by the reinforcing layer may be 60% or more and 150% or less, and specifically 80% or more and 130% or less, based on the total area of ​​one side of either the anode electrode or the cathode electrode. Specifically, the area occupied by the reinforcing layer may be 60% or more, 70% or more, 80% or more, or 90% or more, and 95% or less, 100% or less, 105% or less, 110% or less, 115% or less, 120% or less, 125% or less, 130% or less, 135% or less, 140% or less, 145% or less, or 150% or less, based on the total area of ​​one side of either the anode electrode or the cathode electrode. If the area occupied by the above-mentioned reinforcing layer is less than the above-mentioned numerical range, the chemical and mechanical durability effects of the membrane-electrode assembly may not be significantly improved, and if it exceeds the above-mentioned numerical range, the problem of the interfacial adhesion between the electrolyte membrane and the catalyst layer being lowered may occur.

[0079] The anode and cathode electrodes (20, 20') above include 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 fine particles such as carbon powder or carbon black between the electrode substrate (40, 40') and the catalyst layer (30, 30') to facilitate diffusion of materials in the electrode substrate (40, 40').

[0080] The catalyst layers (30, 30') of the anode and cathode electrodes (20, 20') above include a catalyst. Any catalyst that participates in the reaction of the cell and can be used as a catalyst for a typical fuel cell can be used. Preferably, a platinum-based metal can be used. 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, a non-platinum alloy, and combinations 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 can be used without limitation. The above M may correspond to 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). Specifically, the platinum alloy may be at least one 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-Ir, and combinations thereof.In addition, at least one 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 may be used as the non-platinum alloy.

[0081] The above catalyst may be used as a catalyst itself (black) or may be used by supporting it on a carrier.

[0082] The carrier may be, for example, one selected from the group consisting of a carbon-based carrier, a porous inorganic oxide, a zeolite, and a combination thereof. The carbon-based carrier may be, for example, selected from the group consisting of 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, carbon aerogel, graphene, stabilized carbon, activated carbon, and a combination of at least one or more thereof, but is not limited thereto. The above porous inorganic oxide may correspond to at least one selected from the group consisting of, for example, zirconia, alumina, titania, silica, and ceria. The surface area of ​​the carrier may be 50 m 2 / g or more may be preferable, and the average particle diameter may be 10 to 300 nm. If the surface area of ​​the carrier is less than the above numerical range, a uniform distribution of metal nanoparticles may not be obtained.

[0083] 3. Fuel cell

[0084] Figure 6 is a schematic diagram illustrating a fuel cell according to one embodiment of the present invention.

[0085] Another embodiment of the present invention can provide a fuel cell including the membrane-electrode assembly.

[0086] Referring to FIG. 6, a fuel cell (200) according to the present invention may include a fuel supply unit (210) that supplies a mixed fuel in which fuel and water are mixed, 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 causing an electrochemical reaction between the reformed gas containing hydrogen gas supplied from the reforming unit (220) and an oxidizer, and an oxidizer supply unit (240) that supplies an oxidizer to the reforming unit (220) and the stack (230).

[0087] The above stack (230) may be equipped with a plurality of unit cells that generate electrical energy by inducing an oxidation / reduction reaction of a reforming gas containing hydrogen gas supplied from the reforming unit (220) and an oxidizing agent supplied from the oxidizing agent supply unit (240).

[0088] Each unit cell refers to a unit cell that generates electricity, and may include the membrane-electrode assembly that oxidizes / reduces oxygen in a reforming 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 reforming 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 each positioned at the outermost side of the stack are specifically referred to as end plates.

[0089] Among the above separators, the end plate may be provided with a first supply pipe (231) in the shape of a pipe for injecting reformed gas containing hydrogen gas supplied from the reforming unit (220), and a second supply pipe (232) in the shape of a pipe for injecting oxygen gas, and the other end plate may be provided with a first discharge pipe (233) for discharging reformed gas containing hydrogen gas that is ultimately unreacted and remains in a plurality of unit cells to the outside, and a second discharge pipe (234) for discharging oxidant that is ultimately unreacted and remains in the unit cells to the outside.

[0090] In the above fuel cell, the separator, fuel supply unit, and oxidizer supply unit constituting the electricity generation unit are used in a typical fuel cell, and therefore, a detailed description thereof is omitted in this specification.

[0091] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited by the following contents.

[0092] [Manufacturing Example 1: Manufacturing of a polymer electrolyte membrane or composite membrane]

[0093] <Comparative Example 1: Commercial Polymer Electrolyte Membrane>

[0094] After applying a commercial Nafion dispersion solution (solid content: 20 wt%) to a glass substrate, the applied Nafion dispersion solution was dried at 70°C for 12 hours to manufacture a commercial polymer electrolyte membrane having a thickness of 15 μm.

[0095] <Example 1: Composite membrane with a single crystal graphene layer disposed on the surface>

[0096] A single-crystal copper (111) substrate was placed in a furnace under 0.5 Torr and heat-treated at 1,050°C for 2 hours while flowing a mixed gas of 30 sccm H2 / 370 sccm Ar, to manufacture a single-crystal copper substrate. A single-crystal graphene layer (thickness: 2 nm) was formed on the surface of the single-crystal copper substrate using chemical vapor deposition (CVD) by additionally exposing a graphene precursor containing CH4 at 0.75 sccm for 30 minutes under the same conditions in which the single-crystal copper substrate was manufactured. The single-crystal copper substrate on which the single-crystal graphene layer was formed and a polydimethylsiloxane substrate (PDMS substrate) were bonded, and then the copper substrate was removed. Thereafter, the resultant product from which the copper substrate was removed was transferred to both sides of a polymer electrolyte membrane manufactured by the method according to Comparative Example 1 to form a composite membrane.

[0097] <Example 2-1: Composite membrane with polycrystalline graphene layer arranged on the surface>

[0098] Except for the process of manufacturing the single-crystal copper substrate, a polycrystalline graphene layer (thickness: 2 nm) was formed on the surface of a polycrystalline copper substrate using the same process as Example 1. After bonding the polycrystalline copper substrate with the polycrystalline graphene layer formed thereon to a PDMS substrate (polydimethylsiloxane substrate), the polycrystalline copper substrate was removed. Thereafter, the resultant product from which the copper substrate was removed was transferred to both sides of a polymer electrolyte membrane manufactured by the method according to Comparative Example 1 to form a composite membrane.

[0099] <Example 2-2: Composite membrane with a thick polycrystalline graphene layer disposed on the surface>

[0100] A composite membrane was manufactured using the same method as in Example 2-1, but a chemical vapor deposition (CVD) process was performed in which the polycrystalline copper substrate was additionally exposed to a graphene precursor containing CH4 at 1.00 sccm for 40 minutes, thereby forming a polycrystalline graphene layer (thickness: 6 nm) on the surface of the polycrystalline copper substrate. After the polycrystalline copper substrate on which the polycrystalline graphene layer was formed was bonded to a polydimethylsiloxane substrate (PDMS substrate), the polycrystalline copper substrate was removed. Thereafter, the resultant from which the polycrystalline copper substrate was removed was transferred to both sides of a polymer electrolyte membrane manufactured by the method according to Comparative Example 1, thereby forming a composite membrane.

[0101] <Example 3: Composite film with a single-crystal hexagonal boron nitride layer disposed on the surface>

[0102] A composite membrane was manufactured in the same manner as in Example 1, but under the same conditions as the single-crystal copper substrate was manufactured, a chemical vapor deposition (CVD) method was used to additionally expose a boron nitride precursor containing ammonia borane or borazine (B3H6N3) at 0.5 sccm for 30 minutes to form a single-crystal hexagonal boron nitride layer (thickness: 2 nm) on the surface of the single-crystal copper substrate. The copper substrate on which the single-crystal hexagonal boron nitride layer was formed and a polydimethylsiloxane substrate (PDMS substrate) were bonded, and then the copper substrate was removed. Thereafter, the resultant with the copper substrate removed was transferred to both sides of a polymer electrolyte membrane manufactured by the method according to Comparative Example 1 to form a composite membrane.

[0103] <Example 4-1: Composite film with a polycrystalline hexagonal boron nitride layer disposed on the surface>

[0104] A polycrystalline hexagonal boron nitride layer (thickness: 2 nm) was formed on the surface of a polycrystalline copper substrate in the same manner as in Example 3, except for the process of manufacturing the single-crystal copper substrate. The copper substrate on which the polycrystalline hexagonal boron nitride layer was formed was bonded to a PDMS substrate (polydimethylsiloxane substrate), and then the copper substrate was removed. Thereafter, the resultant product from which the copper substrate was removed was transferred to both sides of a polymer electrolyte membrane manufactured by the method according to Comparative Example 1 to form a composite membrane.

[0105] <Example 4-2: Composite film with a thick polycrystalline hexagonal boron nitride layer disposed on the surface>

[0106] A composite membrane was manufactured in the same manner as in Example 3, but instead of the single-crystal copper substrate, a polycrystalline copper substrate was exposed to a boron nitride precursor containing ammonia borane or borazine (B3H6N3) at 0.8 sccm for 40 minutes using chemical vapor deposition (CVD), thereby forming a polycrystalline graphene layer (thickness: 6 nm) on the surface of the polycrystalline copper substrate. After the polycrystalline copper substrate on which the polycrystalline graphene layer was formed was bonded to a polydimethylsiloxane substrate (PDMS substrate), the polycrystalline copper substrate was removed. Thereafter, the resultant from which the polycrystalline copper substrate was removed was transferred to both sides of a polymer electrolyte membrane manufactured by the method according to Comparative Example 1, thereby forming a composite membrane.

[0107] <Example 5: Composite membrane having a reinforcing layer comprising both graphene and partially overlapping hexagonal boron nitride on the surface>

[0108] A composite film was manufactured in the same manner as in Example 3, but under the same conditions as the single-crystal copper substrate was manufactured, a single-crystal hexagonal boron nitride layer was formed by chemical vapor deposition by additionally exposing the film to a boron nitride precursor containing ammonia borane or borazine (B3H6N3) at 0.3 sccm for 15 minutes, and then, under the same conditions as the single-crystal copper substrate, the boron nitride precursor was completely removed with Ar gas. Then, a graphene precursor containing CH4 at 0.75 sccm was additionally exposed for 20 minutes, thereby forming a single-crystal hexagonal boron nitride layer partially overlapping with graphene (overlapping area ratio: 70%) and a reinforced layer (thickness: 2 nm) containing both graphene on the surface of the single-crystal copper substrate. At this time, a single-crystal copper substrate having a reinforcing layer including both the single-crystal hexagonal boron nitride layer and graphene and a PDMS substrate (polydimethylsiloxane substrate) were bonded, and then the single-crystal copper substrate was removed. Thereafter, the resultant with the single-crystal copper substrate removed was transferred to both sides of a polymer electrolyte membrane manufactured by the method according to Comparative Example 1 to form a composite membrane. As a result, in the reinforcing layer, graphene was included in the first layer (thickness: about 1 nm) in contact with the polymer electrolyte membrane, and single-crystal hexagonal boron nitride partially overlapping with the graphene was included in the second layer (thickness: about 1 nm) directly above the first layer.

[0109] <Example 6 Composite film with a reinforcing layer containing both graphene and fully overlapping hexagonal boron nitride on the surface (GR after h-BN formation)>

[0110] A composite film was manufactured in the same manner as in Example 5, but a single-crystal hexagonal boron nitride layer was formed entirely by chemical vapor deposition under the same conditions in which the single-crystal copper substrate was manufactured, by additionally exposing the film to a boron nitride precursor containing ammonia borane or borazine (B3H6N3) at 0.3 sccm for 30 minutes, and then, after the boron nitride precursor was completely removed with Ar gas under the same conditions, a graphene precursor containing CH4 at 0.75 sccm for 20 minutes was additionally exposed to form a reinforced layer (thickness: 2 nm) containing the entire single-crystal hexagonal boron nitride and graphene on the surface of the single-crystal copper substrate using chemical vapor deposition. The single-crystal copper substrate on which the entire single-crystal hexagonal boron nitride layer and graphene composite film were formed was bonded to a PDMS substrate (polydimethylsiloxane substrate), and then the single-crystal copper substrate was removed. Thereafter, the resultant product from which the single-crystal copper substrate was removed was transferred to both sides of a polymer electrolyte membrane manufactured by the method according to Comparative Example 1 to form a composite membrane. As a result, in the reinforced layer, graphene was included in the first layer (thickness: approximately 1 nm) in contact with the polymer electrolyte membrane, and single-crystal hexagonal boron nitride completely overlapping with the graphene was included in the second layer (thickness: approximately 1 nm) directly above the first layer.

[0111] <Example 7: Composite film with a reinforcing layer containing both graphene and fully overlapping hexagonal boron nitride on the surface (h-BN after GR formation)>

[0112] A composite film was manufactured in the same manner as in Example 6, except that (i) a single-crystal graphene layer was formed by chemical vapor deposition under the same conditions as the single-crystal copper substrate under which the single-crystal copper substrate was manufactured, by additionally exposing the graphene precursor containing CH4 at 0.75 sccm for 20 minutes, and (ii) a single-crystal hexagonal boron nitride layer was formed by chemical vapor deposition under the same conditions as the single-crystal copper substrate under which the single-crystal copper substrate was manufactured, by additionally exposing the graphene precursor containing CH4 at 0.75 sccm for 20 minutes, and then (iii) a single-crystal hexagonal boron nitride layer was formed by chemical vapor deposition under the same conditions as the single-crystal copper substrate under which the single-crystal copper substrate was manufactured, by additionally exposing the graphene precursor containing CH4 at 0.75 sccm for 20 minutes.

[0113] After bonding the single-crystal copper substrate on which the above-described single-crystal graphene and hexagonal boron nitride composite film was formed and the PDMS substrate (polydimethylsiloxane substrate), the single-crystal copper substrate was removed. Thereafter, the resultant with the single-crystal copper substrate removed was transferred to both sides of a polymer electrolyte membrane manufactured by the method according to Comparative Example 1 to form a composite membrane. As a result, in the reinforced layer, the first layer (thickness: approximately 1 nm) in contact with the polymer electrolyte membrane contained hexagonal boron nitride, and the second layer (thickness: approximately 1 nm) directly above the first layer contained single-crystal graphene.

[0114] [Manufacturing Example 2: Manufacturing of a Membrane-Electrode Assembly]

[0115] A membrane-electrode assembly was manufactured by directly coating an electrode slurry containing a Pt / C catalyst and a PFSA binder mixed at a weight ratio of 1:0.35 (w / w) on both sides of the composite membrane according to Manufacturing Example 1. At this time, the area occupied by each reinforcing layer of the composite membrane was adjusted to 90% of the total area of ​​one side of the electrode.

[0116] [Experimental Example 1: SEM image of composite membrane according to Example 1]

[0117] Fig. 7 is a scanning electron microscope (SEM) photograph of a composite membrane according to Example 1. Referring to Fig. 7, it can be confirmed that a single-nodule graphene layer was formed on the surface of the polymer electrolyte membrane according to Example 1.

[0118] [Experimental Example 2: SEM image of composite membrane according to Example 3]

[0119] Fig. 8 is a scanning electron microscope photograph of a composite membrane according to Example 3. Referring to Fig. 8, it can be confirmed that a single-crystal hexagonal boron nitride layer was formed on the surface of the polymer electrolyte membrane according to Example 3.

[0120] [Experimental Example 3: SEM image of composite membrane according to Example 6]

[0121] Fig. 9 is a scanning electron microscope photograph of a composite membrane according to Example 6. Referring to Fig. 9, it can be confirmed that a reinforcing layer including both graphene and hexagonal boron nitride was formed on the surface of the polymer electrolyte membrane according to Example 6.

[0122] [Experimental Example 4: Performance Evaluation of a Membrane-Electrode Assembly]

[0123] Figure 10 shows the performance results of membrane-electrode assemblies according to comparative examples and examples. Specifically, fuel cell performance measurement equipment from Scitech was used to evaluate the performance of the membrane-electrode assembly. Specifically, for the membrane-electrode assembly according to Manufacturing Example 2, 80 o C, 100%RH, and normal pressure conditions were used for performance evaluation, and the results are shown in Fig. 10.

[0124] Referring to Fig. 10, the performance evaluation results showed that Examples 1 and 3, in which the composite membrane was formed in a single crystal form, exhibited excellent performance. Comparing Examples 2-1 and 2-2, it was confirmed that when the thickness of the polycrystalline graphene layer was thin, less than 6.0 nm, ion transport was effectively performed, thereby further improving the performance of the membrane-electrode assembly. Comparing Examples 4-1 and 4-2, it was confirmed that when the thickness of the polycrystalline hexagonal boron nitride layer was thin, less than 6.0 nm, ion transport was effectively performed, thereby further improving the performance of the membrane-electrode assembly.

[0125] [Experimental Example 5: Voltage Loss Evaluation of a Membrane-Electrode Assembly]

[0126] For the membrane-electrode assembly according to the above manufacturing example 2, the OCV hold method was performed for 500 hours under the conditions of 90°C, RH30%, and 50 kPa, and the voltage loss was measured, and the measured values ​​are shown in Table 1 below.

[0127] Sample voltage loss Comparative example 118.2% Example 15.2% Example 2-16.7% Example 2-25.1% Example 35.3% Example 4-17.3% Example 4-25.1% Example 54.8% Example 64.6% Example 74.8%

[0128] Referring to Table 1 above, it was confirmed that the examples had significantly lower voltage loss compared to Comparative Example 1. This suggests that the introduction of the reinforcing layer improved the chemical durability of the membrane-electrode assembly. Comparing Examples 6 and 7 in Table 1 above, it was confirmed that the voltage loss of the membrane-electrode assembly was minimized under high temperature and low humidity conditions by including graphene in the first layer and including hexagonal boron nitride in the second layer positioned directly above the first layer.

[0129] 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.

[0130] [Explanation of symbols]

[0131] 10: Polymer electrolyte membrane

[0132] 12: Reinforcement layer

[0133] 50: Composite membrane

[0134] 100: Membrane-electrode assembly

Claims

1. Polymer electrolyte membrane; and A reinforcing layer disposed on at least one surface of the polymer electrolyte membrane; The above reinforcement layer is, Containing any one selected from the group consisting of graphene, hexagonal boron nitride (h-BN), and combinations thereof. Composite membrane.

2. In paragraph 1, The above graphene, Any one selected from the group consisting of single crystal graphene, polycrystalline graphene and combinations thereof, Composite membrane.

3. In paragraph 1, The above graphene comprises single crystal graphene. Composite membrane.

4. In paragraph 1, The above hexagonal boron nitride is, One selected from the group consisting of single crystal hexagonal boron nitride, polycrystalline hexagonal boron nitride, and combinations thereof. Composite membrane.

5. In paragraph 1, The above hexagonal boron nitride comprises single crystal hexagonal boron nitride. Composite membrane.

6. In paragraph 1, The thickness of the above reinforcement layer is 0.1 nm or more and 8.0 nm or less. Composite membrane.

7. In paragraph 1, The above reinforcing layer comprises the graphene and the hexagonal boron nitride, The ratio of the area where the above graphene and the above hexagonal boron nitride overlap is 40% or more and 100% or less, Composite membrane.

8. In paragraph 1, The above reinforcement layer is, Containing two or more sub-reinforcement layers, Composite membrane.

9. In paragraph 8, The above two or more sub-reinforcement layers are: 1st floor and comprising a second layer disposed on the first layer; Composite membrane.

10. A composite membrane according to any one of clauses 1 to 9; An anode electrode disposed on one side of the above composite membrane; and a cathode electrode disposed on the other side of the composite membrane; Membrane electrode assembly.

11. In paragraph 10, The area occupied by the above reinforcement layer is A surface area of ​​one side of one of the anode electrode and the cathode electrode is 60% or more and 150% or less, Membrane electrode assembly.

12. A fuel cell comprising a membrane electrode assembly according to paragraph 10.

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