Ion conductor composition, polymer electrolyte membrane containing same, membrane-electrode assembly, and fuel cell

Abstract

The ionic conductor composition according to the present invention contains 100 parts by weight of an ionic conductor and 0.05 to 10 parts by weight of a saccharide compound per 100 parts by weight of the ionic conductor.

Description

[Technical Field]

[0001] The present disclosure relates to an ion conductor composition, a polymer electrolyte membrane including the same, a membrane-electrode assembly, and a fuel cell, and the ion conductor composition includes a saccharide compound having a functional group capable of interacting with water, thereby maintaining the water content in the polymer electrolyte membrane under high temperature or low humidity conditions, thereby increasing the activity of the electrolyte membrane and improving ion conductivity performance, and the polymer electrolyte membrane, membrane-electrode assembly, and fuel cell including the same. [Background technology]

[0002] Fuel cells are batteries 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 fuel materials such as methanol, ethanol, and natural gas, into electrical energy. Due to their high energy efficiency and environmentally friendly characteristics with low pollutant emissions, fuel cells are attracting attention as a next-generation clean energy source that can replace fossil energy.

[0003] Fuel cells have the advantage of being able to produce a wide range of output power thanks to their stacked structure of unit cells, and they have 4 to 10 times the energy density of small lithium batteries, making them attractive as a small and portable power source.

[0004] The stack that actually generates electricity in a fuel cell has a structure in which several to several tens of unit cells, each consisting of a membrane-electrode assembly (MEA) and a separator (also called a bipolar plate), are stacked. The membrane-electrode assembly generally has a structure in which an anode electrode (also called a fuel electrode) and a cathode electrode (also called a air electrode) are formed on either side of an electrolyte membrane.

[0005] Fuel cells can be classified into alkaline electrolyte membrane fuel cells, polymer electrolyte membrane fuel cells (PEMFC), etc. depending on the state and type of electrolyte. Among them, polymer electrolyte membrane fuel cells are gaining attention as portable, vehicular, and home power sources due to their advantages such as low operating temperature of less than 100°C, fast start-up and response characteristics, and excellent durability.

[0006] Representative examples of polymer electrolyte membrane fuel cells include proton exchange membrane fuel cells (PEMFCs), which use hydrogen gas as fuel, and direct methanol fuel cells (DMFCs), which use liquid methanol as fuel.

[0007] 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, hydrogen ions (H + ) and electrons (e - The generated hydrogen ions are transferred to the cathode electrode via the polymer electrolyte, and the generated electrons are transferred to the cathode electrode via an external circuit. Oxygen gas is supplied to the cathode electrode, and the oxygen combines with the hydrogen ions and electrons to generate water through a reduction reaction of oxygen.

[0008] However, there are still many technical hurdles to overcome before polymer electrolyte membrane fuel cells can be commercialized, and essential improvements include high performance, long lifespan, and low cost. The component that has the greatest impact on this is the membrane-electrode assembly, and the polymer electrolyte membrane is one of the key elements that has the greatest impact on the performance and cost of the MEA.

[0009] The requirements for a polymer electrolyte membrane necessary for the operation of the polymer electrolyte membrane fuel cell include high proton conductivity, chemical stability, low fuel permeability, high mechanical strength, low water content, and excellent dimensional stability. Conventional polymer electrolyte membranes tend to have difficulty in properly demonstrating high performance under certain temperature and relative humidity conditions, particularly under high temperature or low humidity conditions. Therefore, polymer electrolyte membrane fuel cells using conventional polymer electrolyte membranes are subject to limitations in their range of use.

[0010] In particular, in order to overcome the problem that polymer electrolyte membranes are difficult to exhibit high performance under high temperature or low humidity conditions, research has been ongoing into improving the ionic conductivity of polymer electrolyte membranes by introducing a hygroscopic substance into the polymer electrolyte membrane. Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention is to provide an ion conductor composition that enhances the activity of a polymer electrolyte membrane and improves its ion conductivity performance by maintaining the water content in the polymer electrolyte membrane under low-humidity or high-temperature conditions through the ion conductor composition containing a saccharide compound having a functional group capable of interacting with water (or forming hydrogen bonds).

[0012] Another object of the present invention is to provide a polymer electrolyte membrane containing the ion conductor composition.

[0013] Another object of the present invention is to provide a membrane-electrode assembly that improves the ionic conductivity of a polymer electrolyte membrane while minimizing problems caused by an interfacial difference (difference in swelling degree) between the polymer electrolyte membrane made of an ionic conductor composition containing a saccharide compound and a catalyst layer having a relatively low water content.

[0014] It is still another object of the present invention to provide a fuel cell comprising the membrane-electrode assembly.

[0015] The objects of the present invention are not limited to the objects mentioned above, and other objects and advantages of the present invention not mentioned above can be understood from the following description and will be more clearly understood from the embodiments of the present invention. Furthermore, it will be easily understood that the objects and advantages of the present invention can be realized by the means and combinations thereof recited in the claims. [Means for solving the problem]

[0016] To achieve the above object, one embodiment of the present invention provides an ion conductor composition comprising 100 parts by weight of an ion conductor and 0.05 to 10 parts by weight of a saccharide compound relative to 100 parts by weight of the ion conductor.

[0017] In order to achieve the above object, another embodiment of the present invention provides a polymer electrolyte membrane including the ion conductor composition.

[0018] In order to achieve the above object, yet another embodiment of the present invention provides a membrane-electrode assembly including the polymer electrolyte membrane and a catalyst layer disposed on at least one surface of the polymer electrolyte membrane.

[0019] In order to achieve the above object, yet another embodiment of the present invention provides a fuel cell including the membrane-electrode assembly. [Effects of the Invention]

[0020] According to one aspect of the present invention, an ion conductor composition can be provided that maintains the water content in a polymer electrolyte membrane under low-humidity or high-temperature conditions through the use of an ion conductor composition containing a saccharide compound having a functional group capable of interacting with (or hydrogen bonding with) water, thereby increasing the activity of the polymer electrolyte membrane and improving its ion conductivity.

[0021] According to another aspect of the present invention, there is provided a polymer electrolyte membrane comprising the ion conductor composition.

[0022] According to yet another aspect of the present invention, there is provided a membrane-electrode assembly that improves the ionic conductivity of a polymer electrolyte membrane while minimizing problems caused by an interfacial difference (difference in swelling degree) between the polymer electrolyte membrane manufactured using an ionic conductor composition including a saccharide compound and a catalyst layer having a relatively low water content.

[0023] According to yet another aspect of the present invention, there is provided a fuel cell including the membrane-electrode assembly.

[0024] The specific effects of the present invention, together with the above-mentioned effects, will be described below while explaining specific details for carrying out the invention. [Brief explanation of the drawings]

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

[0026] [Figure 2] 1 is a schematic diagram showing a fuel cell according to one embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

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

[0028] One embodiment of the present invention provides an ion conductor composition comprising 100 parts by weight of an ion conductor and 0.05 to 10 parts by weight of a saccharide compound relative to the 100 parts by weight of the ion conductor. According to one aspect of the present invention, the water content within a polymer electrolyte membrane can be maintained under low-humidity or high-temperature conditions through the ion conductor composition, which includes a saccharide compound having a functional group capable of interacting with (or hydrogen bonding with) water, thereby enhancing the activity of the polymer electrolyte membrane and improving its ion conductivity. According to another aspect of the present invention, problems caused by interfacial differences (differences in swelling degree) in a catalyst layer with a relatively low water content can be minimized.

[0029] The configuration of the present invention will be described in more detail below.

[0030] The ionic conductor according to the present invention may be one selected from the group consisting of fluorine-based ionic conductors, hydrocarbon-based ionic conductors, and combinations thereof, and is preferably a hydrocarbon-based ionic conductor. Combining the hydrocarbon-based ionic conductor with a sugar compound not only further enhances ionic conductivity compared to the combination of the fluorine-based ionic conductor and the sugar compound, but also reduces the dimensional change rate of the polymer electrolyte membrane, improving dimensional stability and increasing the water content to an appropriate level under low-humidity conditions. Furthermore, due to the structural similarity between the hydrocarbon-based ionic conductor and the sugar compound, they are highly compatible, making it easier to realize the effects of the sugar. The ionic conductor may be a cation conductor having a cation exchange functional group such as a hydrogen ion, or an anion conductor having an anion exchange functional group such as a hydroxyl ion. The cation exchange functional group may be any one selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphate group, an imide group, a sulfonimide group, a sulfonamide group, a sulfonyl fluoride group, and combinations thereof, and may generally be a sulfonic acid group or a carboxyl group. For example, the fluorine-based ion conductor may be perfluorosulfonic acid (PFSA).

[0031] Examples of the cation conductor include a fluorine-based polymer containing the cation exchange functional group and fluorine in the main chain, a hydrocarbon polymer such as benzimidazole, polyamide, polyamideimide, polyimide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, polyetherimide, polyester, polyethersulfone, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyetheretherketone, polyetherketone, polyarylethersulfone, polyphosphazene, or polyphenylquinoxaline, a partially fluorinated polymer such as polystyrene-graft-ethylenetetrafluoroethylene copolymer or polystyrene-graft-polytetrafluoroethylene copolymer, sulfonimide, or a mixture thereof.

[0032] More specifically, when the cation conductor is a hydrogen ion cation conductor, the polymer may contain a cation exchange group selected from the group consisting of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group, and derivatives thereof in the side chain, and specific examples thereof include poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, defluorinated sulfurized polyether ketone, or a fluorine-based polymer including a mixture thereof.

[0033] The anion conductor is a polymer capable of transporting anions such as hydroxy ions. Anion conductors are commercially available in hydroxide or halide (generally chloride) forms, and can be used in industrial water purification, metal separation, catalytic processes, etc.

[0034] The anion conductor may generally be a polymer doped with a metal hydroxide. Specifically, metal hydroxide-doped poly(ether sulfone), polystyrene, vinyl polymer, poly(vinyl chloride), poly(vinylidene fluoride), poly(tetrafluoroethylene), poly(benzimidazole), or poly(ethylene glycol) may be used.

[0035] The hydrocarbon-based ion conductor may be 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 polyethersulfone, 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 nitrileThe polyarylene ether nitrile may be any one selected from the group consisting of sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, and mixtures thereof, although the technical concept of the present invention is not limited thereto.

[0036] The saccharide compound according to the present invention may be included in an amount of 0.05 to 10 parts by weight, preferably 0.5 to 2.0 parts by weight, and more preferably 0.5 to 1.0 parts by weight, per 100 parts by weight of the ionic conductor. If the amount of the saccharide compound is less than the above range, the water content of the polymer electrolyte membrane may be insufficient under high-temperature or low-humidity operating conditions, resulting in low hydrogen ion conductivity. If the amount of the saccharide compound is greater than the above range, the difference in swelling degree between the catalyst layer and the polymer electrolyte membrane, as described below, may become large, resulting in interface problems. The interface problems result in poor dimensional stability of the polymer electrolyte membrane.

[0037] The saccharide compound according to the present invention may be one selected from the group consisting of monosaccharides, disaccharides, polysaccharides, and combinations thereof, and specifically may be a monosaccharide.

[0038] The monosaccharide may correspond to a compound represented by the following Chemical Formula 1:

[0039] [C1]

[0040] (CH2O) n

[0041] In the above Chemical Formula 1, n may be 3 to 7, and preferably 4 to 6.

[0042] For example, the monosaccharide may be one selected from the group consisting of aldotriose, ketotriose, aldotetrose, ketotetrose, ribose, dioxyribose, fructose, glucose, galactose, aldoheptose, ketoheptose, and combinations thereof.

[0043] For example, the disaccharide may be one selected from the group consisting of sucrose, lactulose, lactose, trehalose, cellobiose, chitobiose, kojibiose, nigerose, isomaltose, β-trehalose, α,β-trehalose, sophorose, laminaribiose, gentiobiose, turanose, maltulose, isomaltulose, gentiobiulose, mannobiose, melibiose, melibiulose, rutinose, rutinulose, xylobiose, and combinations thereof.

[0044] For example, the polysaccharide may be one selected from the group consisting of starch, glycogen, cellulose, chitin, arabinoxylan, pectin, dextrin, and combinations thereof.

[0045] The solubility of the saccharide compound may be 0 to 1,000 g / L, and preferably 150 to 700 g / L, in water at 25° C. If the solubility of the saccharide compound in water is below this range, the saccharide compound may precipitate and act as resistance, while if the solubility exceeds this range, the saccharide compound may leak out of the polymer electrolyte membrane during fuel cell operation.

[0046] The sugar compound contains a functional group (hydroxy group) that can interact with water (or form hydrogen bonds), thereby maintaining the water content in the polymer electrolyte membrane under low humidity or high temperature conditions. Therefore, a high water content in the polymer electrolyte membrane under low humidity or high temperature conditions can enhance the activity of the polymer electrolyte membrane and improve its ion conductivity.

[0047] Another embodiment of the present invention provides a polymer electrolyte membrane comprising the ion conductor composition.

[0048] The polymer electrolyte membrane may be a single membrane, and the thickness of the single membrane may be, for example, 5 to 125 μm, preferably 5 to 60 μm. However, the technical concept of the present invention is not limited to the thickness of the polymer electrolyte membrane, and various thickness ranges may be applied.

[0049] According to yet another embodiment of the present invention, a polymer electrolyte membrane (or reinforced composite membrane) may further include a porous support impregnated with a dispersion containing the ion conductor composition. Existing reinforced composite membranes have superior mechanical durability compared to single membranes due to the incorporation of a porous support, but suffer from problems such as resistance, relatively low ionic conductivity, and low water content under high temperature and low humidity conditions. According to one embodiment of the present invention, impregnating a porous support with a dispersion containing the ion conductor composition not only increases ionic conductivity and water content to appropriate levels, but also improves dimensional stability.

[0050] The porous support may be one selected from the group consisting of a fluorine-based porous support, a hydrocarbon-based porous support, and a combination thereof.

[0051] The fluorine-based porous support according to one embodiment of the present invention may include a highly fluorinated polymer, preferably a perfluorinated polymer, having excellent resistance to thermal and chemical decomposition, such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene and CF₂=CFC. n F 2n+1 (n is a real number between 1 and 5) or CF2 = CFO-(CF2CF(CF3)O) m C n F 2n+1 (m is a real number of 0 to 15, and n is a real number of 1 to 15).

[0052] According to another embodiment of the present invention, the fluorine-based porous support may be expanded polytetrafluoroethylene (e-PTFE) having a microstructure of polymer fibrils or a microstructure in which nodes are connected to each other by fibrils. Also, a film having a microstructure of polymer fibrils without nodes may be used as the porous support.

[0053] According to yet another embodiment of the present invention, a fluorine-based porous support may include a perfluorinated polymer. The fluorine-based porous support may be obtained by extruding dispersion-polymerized PTFE into a tape in the presence of a lubricant and stretching the resulting material to form a porous support that is more porous and stronger.

[0054] The amorphous content of PTFE can also be increased by heat-treating the e-PTFE at a temperature exceeding the melting point of PTFE (approximately 342°C). The e-PTFE film produced by the above method can have micropores with various diameters and porosity. The e-PTFE film produced by the above method can have at least 35% micropores, and the diameter of the micropores can be approximately 0.01 to 1 μm.

[0055] The hydrocarbon-based porous support according to one embodiment of the present invention may be a nonwoven fibrous web composed of a plurality of randomly oriented fibers. The nonwoven fibrous web refers to a sheet having a structure of individual fibers or filaments that are interlaid but not in the same manner as a woven fabric. The nonwoven fibrous web may be manufactured by any one method selected from the group consisting of carding, garneting, air-laying, wet-laying, meltblowing, spunbonding, and stitchbonding.

[0056] The fibers may comprise one or more polymeric materials. Generally, any fiber-forming polymeric material may be used. Specifically, hydrocarbon-based fiber-forming polymeric materials may be used. For example, the fiber-forming polymeric material may be any one selected from the group consisting of polyolefins (e.g., polybutylene, polypropylene, and polyethylene), polyesters (e.g., polyethylene terephthalate and polybutylene terephthalate), polyamides (nylon-6 and nylon-6,6), polyurethane, polybutene, polylactic acid, polyvinyl alcohol, polyphenylene sulfide, polysulfone, fluid crystalline polymers, polyethylene-co-vinyl acetate, polyacrylonitrile, cyclic polyolefins, polyoxymethylene, polyolefin-based thermoplastic elastomers, and combinations thereof. However, the technical concept of the present invention is not limited thereto.

[0057] A hydrocarbon-based porous support according to an embodiment of the present invention may include a nanoweb in which nanofibers are accumulated in the form of a nonwoven fabric having a plurality of pores.

[0058] The nanofibers are preferably made of hydrocarbon-based polymers that exhibit excellent chemical resistance, are hydrophobic, and are not susceptible to deformation due to moisture in a humid environment. Specifically, the hydrocarbon-based polymer may be selected from the group consisting of nylon, polyimide, polyaramid, polyetherimide, polyacrylonitrile, polyaniline, polyethylene oxide, polyethylene naphthalate, polybutylene terephthalate, styrene butadiene rubber, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyvinylidene fluoride, polyvinyl butylene, polyurethane, polybenzoxazole, polybenzimidazole, polyamide imide, polyethylene terephthalate, polyphenylene sulfide, polyethylene, polypropylene, copolymers thereof, and mixtures thereof. Among these, polyimide is preferably used because of its excellent heat resistance, chemical resistance, and dimensional stability.

[0059] The nanoweb is an aggregate of randomly arranged nanofibers produced by electrospray irradiation, and preferably has an average diameter of 40 to 5,000 nm, calculated from the average of 50 fiber diameters measured using a scanning electron microscope (JSM6700F, JEOL), taking into account the porosity and thickness of the nanoweb.

[0060] If the average diameter of the nanofibers is less than the above range, the mechanical strength of the porous support may be reduced, and if the average diameter of the nanofibers is greater than the above range, the porosity may be significantly reduced and the thickness may be increased.

[0061] The thickness of the nonwoven fibrous web may be 10 to 50 μm, specifically 15 to 43 μm. If the thickness of the nonwoven fibrous web is less than this range, the mechanical strength may be reduced, and if it exceeds this range, the resistance loss may increase, and the weight and integration may be reduced.

[0062] The nonwoven fibrous web has a basic weight of 5 to 30 mg / cm 2 If the basis weight of the nonwoven fibrous web is less than the above range, visible pores may be formed, making it difficult to function as a porous support, whereas if the basis weight exceeds the above range, the web may be manufactured in the form of paper or fabric with almost no pores.

[0063] The porosity can be calculated as the ratio of the air volume in the porous support to the total volume of the porous support according to the following mathematical formula 1. Here, the total volume is calculated by preparing a rectangular sample and measuring its width, length, and thickness, and the air volume can be obtained by measuring the mass of the sample and then subtracting the polymer volume, which is calculated back from the density, from the total volume.

[0064] [Mathematical formula 1]

[0065] Porosity (%) = (air volume in the porous support / total volume of the porous support) × 100

[0066] The porosity of the porous support according to the present invention may be 30 to 90%, and preferably 50 to 85%. If the porosity of the porous support is below this range, the impregnation of the ionic conductor may be reduced, and if it exceeds this range, the dimensional stability may be reduced, which may hinder smooth subsequent processes.

[0067] Yet another embodiment of the present invention may provide a membrane-electrode assembly comprising the polymer electrolyte membrane and a catalyst layer disposed on at least one surface of the polymer electrolyte membrane.

[0068] The configuration of the present invention will be described in detail below with reference to the drawings.

[0069] FIG. 1 is a cross-sectional view showing a membrane-electrode assembly according to one embodiment of the present invention.

[0070] As shown in FIG. 1, the membrane-electrode assembly 100 according to the present invention includes the polymer electrolyte membrane 50 and the fuel cell electrodes 20 and 20 ′ disposed on both sides of the polymer electrolyte membrane 50 , respectively.

[0071] The electrodes 20, 20′ include electrode substrates 40, 40′ and catalyst layers 30, 30′ formed on the surfaces of the electrode substrates 40, 40′. A microporous layer (not shown) containing conductive fine particles such as carbon powder or carbon black may be further provided between the electrode substrates 40, 40′ and the catalyst layers 30, 30′ to facilitate material diffusion in the electrode substrates 40, 40′.

[0072] In the membrane-electrode assembly 100, the electrode 20 disposed on one side of the polymer electrolyte membrane 50 and causing an oxidation reaction to generate hydrogen ions and electrons from the fuel transferred to the catalyst layer 30 via the electrode substrate 40 is called an anode.

[0073] The electrode 20′ disposed on the other side of the polymer electrolyte membrane 50 and causing a reduction reaction to generate water from protons supplied through the polymer electrolyte membrane 50 and an oxidant transferred to the catalyst layer 30′ via the electrode substrate 40′ is called a cathode electrode.

[0074] The catalyst layers 30, 30' of the anode and cathode electrodes 20, 20' contain a catalyst. The catalyst participates in the cell reaction and can be any catalyst that is generally usable as a catalyst for fuel cells. Preferably, a platinum-based metal can be used.

[0075] The platinum-based metal may include one selected from the group consisting of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), platinum-M alloys, non-platinum alloys, and combinations thereof. More preferably, a combination of two or more metals selected from the platinum-based catalytic metal group may be used. However, the platinum-based catalytic metal is not limited thereto, and any platinum-based catalytic metal that can be used in the present technical field may be used without limitation.

[0076] The M may be 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 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.

[0077] Furthermore, the non-platinum alloy may be selected from the group consisting of Ir-Fe, Ir-Ru, Ir-Os, Co-Fe, Co-Ru, Co-Os, Rh-Fe, Rh-Ru, Rh-Os, Ir-Ru-Fe, Ir-Ru-Os, Rh-Ru-Fe, Rh-Ru-Os, and combinations thereof, and may be used alone or in combination of two or more.

[0078] The catalyst may be used as a catalyst itself (black) or may be supported on a carrier.

[0079] According to the present invention, it is possible to provide a membrane-electrode assembly that improves the ionic conductivity of a polymer electrolyte membrane while minimizing problems caused by an interfacial difference (difference in swelling degree) between a polymer electrolyte membrane made of an ionic conductor composition containing a saccharide compound and a catalyst layer having a relatively low water content.

[0080] FIG. 2 is a schematic diagram showing a fuel cell according to one embodiment of the present invention.

[0081] An embodiment of the present invention can provide a fuel cell including the membrane-electrode assembly.

[0082] As shown in FIG. 2, a fuel cell 200 according to the present invention may include a fuel supply unit 210 that supplies a mixed fuel obtained by mixing fuel and water, a reforming unit 220 that reforms the mixed fuel to generate a reformed gas containing hydrogen gas, a stack 230 that generates electrical energy by electrochemically reacting the reformed gas containing hydrogen gas supplied from the reforming unit 220 with an oxidant, and an oxidant supply unit 240 that supplies an oxidant to the reforming unit 220 and the stack 230.

[0083] The stack 230 may include a plurality of unit cells that generate electrical energy by conducting an oxidation / reduction reaction between the reformed gas containing hydrogen gas supplied from the reforming unit 220 and the oxidant supplied from the oxidant supplying unit 240.

[0084] Each unit cell refers to a unit cell that generates electricity and may include the membrane-electrode assembly that oxidizes / reduces oxygen in the reformed gas containing hydrogen gas and the oxidant, and a separator plate (also called a bipolar plate, hereinafter referred to as "separator plate") that supplies the reformed gas containing hydrogen gas and the oxidant to the membrane-electrode assembly. The separator plates are disposed on both sides of the membrane-electrode assembly. In this case, the separator plates located at the outermost sides of the stack are also referred to as end plates.

[0085] Of the separation plates, the end plate may be provided with a pipe-shaped first supply pipe 231 for injecting the reformed gas containing hydrogen gas supplied from the reforming section 220 and a pipe-shaped second supply pipe 232 for injecting oxygen gas, and the other end plate may be provided with a first exhaust pipe 233 for discharging the reformed gas containing hydrogen gas that is ultimately left unreacted in the plurality of unit cells to the outside, and a second exhaust pipe 234 for discharging the oxidant that is ultimately left unreacted in the unit cells to the outside.

[0086] In the fuel cell, the separator, fuel supply section, and oxidant supply section that constitute the electricity generating section are the same as those used in ordinary fuel cells, and therefore detailed description thereof will be omitted in this specification.

[0087] Hereinafter, the 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 to the following content.

[0088] [Production Example: Production of a Polymer Electrolyte Membrane Containing an Ion Conductor Composition]

[0089] Polymer electrolyte membranes containing the ion conductor compositions according to the Examples and Comparative Examples were prepared according to the compositions shown in Table 1. The polymer electrolyte membranes were prepared by a conventional method for preparing a polymer electrolyte membrane.

[0090] <Comparative Example 1-1>

[0091] A Nafion dispersion (D2020; DuPont, 20 wt% Nafion) was cast onto a glass plate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0092] <Comparative Example 1-2>

[0093] Glucose was added to a Nafion dispersion (D2020; DuPont, 20 wt% Nafion) in an amount of 0.01 parts by weight per 100 parts by weight of the Nafion dispersion, and the glucose-added Nafion dispersion was stirred at room temperature for 3 hours. The stirred Nafion dispersion was cast onto a glass substrate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0094] <Comparative Example 1-3>

[0095] Glucose was added to a Nafion dispersion (D2020; DuPont, 20 wt% Nafion) in an amount of 11 parts by weight per 100 parts by weight of the Nafion dispersion, and the glucose-added Nafion dispersion was stirred at room temperature for 3 hours. The stirred Nafion dispersion was cast onto a glass substrate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0096] <Comparative Example 2-1>

[0097] A dispersion of sulfonated polyarylene ether sulfone (S-PAES) with an ion exchange capacity (IEC) of 1.3 meq / g was dissolved in DMAc (dimethylacetamide) and cast onto a glass plate using a doctor blade to fabricate a single-layer polymer electrolyte membrane.

[0098] <Comparative Example 3-1>

[0099] A polymer electrolyte membrane (or reinforced composite membrane) was fabricated by impregnating PTFE (Poly-Terafluoroethylene; 80% porosity, 0.45 μm pore size, 15 μm thickness) into a Nafion dispersion (D2020; DuPont, 20 wt% Nafion) for 1 hour and then drying.

[0100] <Example 1-1>

[0101] Glucose was added to a Nafion dispersion (D2020; DuPont, 20 wt% Nafion) in an amount of 0.1 parts by weight per 100 parts by weight of the Nafion dispersion, and the glucose-added Nafion dispersion was stirred at room temperature for 3 hours. The stirred Nafion dispersion was cast onto a glass substrate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0102] <Example 1-2>

[0103] Glucose was added to a Nafion dispersion (D2020; DuPont, 20 wt% Nafion) in an amount of 0.5 parts by weight per 100 parts by weight of the Nafion dispersion, and the glucose-added Nafion dispersion was stirred at room temperature for 3 hours. The stirred Nafion dispersion was cast onto a glass substrate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0104] <Examples 1-3>

[0105] Glucose was added to a Nafion dispersion (D2020; DuPont, 20 wt% Nafion) in an amount of 1.0 part by weight per 100 parts by weight of the Nafion dispersion, and the glucose-added Nafion dispersion was stirred at room temperature for 3 hours. The stirred Nafion dispersion was cast onto a glass substrate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0106] <Examples 1-4>

[0107] Sucrose was added to a Nafion dispersion (D2020; DuPont, 20 wt% Nafion) in an amount of 0.5 parts by weight per 100 parts by weight of the Nafion dispersion, and the sucrose-added Nafion dispersion was stirred at room temperature for 3 hours. The stirred Nafion dispersion was cast onto a glass substrate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0108] <Examples 1-5>

[0109] Maltose was added to a Nafion dispersion (D2020; DuPont, 20 wt% Nafion) in an amount of 0.5 parts by weight per 100 parts by weight of the Nafion dispersion, and the maltose-added Nafion dispersion was stirred at room temperature for 3 hours. The stirred Nafion dispersion was cast onto a glass substrate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0110] <Examples 1-6>

[0111] Starch was added to a Nafion dispersion (D2020; DuPont, 20 wt% Nafion) in an amount of 0.5 parts by weight per 100 parts by weight of the Nafion dispersion, and the starch-added Nafion dispersion was stirred at room temperature for 24 hours. The stirred Nafion dispersion was cast onto a glass substrate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0112] <Example 2-1>

[0113] Sulfonated polyarylene ether sulfone (S-PAES) with an ion exchange capacity (IEC) of 1.3 meq / g was dissolved in dimethylacetamide (DMAc) to prepare an S-PAES dispersion. 1.0 part by weight of glucose was added to 100 parts by weight of the S-PAES dispersion, and the glucose-added S-PAES dispersion was stirred at room temperature for 3 hours. The stirred S-PAES dispersion was cast onto a glass plate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0114] <Example 2-2>

[0115] Sulfonated polyarylene ether sulfone (S-PAES) with an ion exchange capacity (IEC) of 1.3 meq / g was dissolved in dimethylacetamide (DMAc) to prepare an S-PAES dispersion. 0.5 parts by weight of sucrose was added to 100 parts by weight of the S-PAES dispersion, and the S-PAES dispersion containing sucrose was stirred at room temperature for 3 hours. The stirred S-PAES dispersion was cast onto a glass plate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0116] <Example 2-3>

[0117] Sulfonated polyarylene ether sulfone (S-PAES) with an ion exchange capacity (IEC) of 1.3 meq / g was dissolved in dimethylacetamide (DMAc) to prepare an S-PAES dispersion. 0.5 parts by weight of maltose was added to 100 parts by weight of the S-PAES dispersion, and the maltose-added S-PAES dispersion was stirred at room temperature for 3 hours. The stirred S-PAES dispersion was cast onto a glass plate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0118] <Example 2-4>

[0119] Sulfonated polyarylene ether sulfone (S-PAES) with an ion exchange capacity (IEC) of 1.3 meq / g was dissolved in dimethylacetamide (DMAc) to prepare an S-PAES dispersion. 0.5 parts by weight of starch was added to 100 parts by weight of the S-PAES dispersion, and the starch-added S-PAES dispersion was stirred at room temperature for 6 hours. The stirred S-PAES dispersion was cast onto a glass plate using a doctor blade to prepare a single-layer polymer electrolyte membrane.

[0120] <Example 3-1>

[0121] Glucose was added to a Nafion dispersion (D2020; DuPont, 20 wt% Nafion) in an amount of 1.0 part by weight per 100 parts by weight of the Nafion dispersion, and the glucose-added Nafion dispersion was stirred at room temperature for 3 hours. PTFE (Poly-Terafluoroethylene; 80% porosity, 0.45 μm pore size, 15 μm thickness) was impregnated into the stirred Nafion dispersion for 1 hour and then dried to prepare a polymer electrolyte membrane (or reinforced composite membrane).

[0122] [Table 1]

[0123] [Experimental example: Ion conductivity, moisture content, and dimensional stability evaluation experiment]

[0124] The ionic conductivity, water content, and dimensional stability of the polymer electrolyte membranes prepared using the ionic conductor compositions prepared in the examples and comparative examples were measured, and the results are shown in Table 2. The respective measurement methods are as follows.

[0125] 1) Ionic conductivity (high temperature / low humidity conditions: 80°C / 50%RH)

[0126] The ionic conductivity of the polymer electrolyte membranes according to the comparative examples and examples was measured using a measuring device (Solatron-1280 Impedance / Gain-Phase analyzer) at a measurement temperature of 80° C. Specifically, the ohmic resistance or bulk resistance was measured using a four-point probe AC ​​impedance spectroscopic method, and then the ionic conductivity was calculated using the following [Equation 2].

[0127] [Mathematical formula 2]

[0128]

number

[0129] In the above mathematical formula 2, σ is the ionic conductivity (S / cm), R is the ohmic resistance of the electrolyte membrane (Ω), L is the distance between the electrodes (cm), and S is the area in the electrolyte through which a certain current flows (cm 2 ) applies.

[0130] 2) Moisture content

[0131] The polymer electrolyte membranes according to the comparative examples and examples were washed multiple times with deionized water, and the washed polymer electrolyte membranes were dried in a vacuum oven at 120° C. for 24 hours, and then weighed (W dry The same membrane was then immersed in deionized water for 24 hours, removed, and reweighed (W wet The water absorption rate was calculated using the following mathematical formula 3.

[0132] [Mathematical formula 3]

[0133]

number

[0134] 3) Low humidity moisture content

[0135] The polymer electrolyte membranes according to the comparative examples and examples were washed multiple times with deionized water, and the washed polymer electrolyte membranes were dried in a vacuum oven at 120° C. for 24 hours, and then weighed (W dry Next, the same film was placed on a balance inside a chamber at 25°C and 50% relative humidity, and left for 24 hours, after which its weight was measured (W wet ), and the water absorption rate was calculated using the mathematical formula 3.

[0136] 4) Dimensional stability

[0137] The dimensional stability of the polymer electrolyte membranes according to the comparative examples and examples was measured in the same manner as the water absorption rate measurement method, but instead of measuring the weight, the volume change of the polymer electrolyte membrane was measured, and then the dimensional stability (or dimensional change rate) was calculated using the following Equation 4.

[0138] [Mathematical formula 4]

[0139]

number

[0140] [Table 2]

Claims

1. 100 parts by weight of an ionic conductor; An ionic conductor composition comprising 0.05 to 10 parts by weight of a saccharide compound relative to 100 parts by weight of the ionic conductor, The saccharide compound is one selected from the group consisting of monosaccharides, disaccharides, polysaccharides, and combinations thereof; The polysaccharide is One selected from the group consisting of starch, glycogen, cellulose, chitin, arabinoxylan, pectin, dextrin, and combinations thereof; Ion conductor composition.

2. The ionic conductor composition according to claim 1 , wherein the monosaccharide is a compound represented by the following chemical formula 1: [Chemical formula 1] (CH ２ O) ｎ In the above formula 1, n is 3 to 7.

3. The monosaccharide is 2. The ionic conductor composition according to claim 1, which is one selected from the group consisting of aldotriose, ketotriose, aldotetrose, ketotetrose, ribose, dioxyribose, fructose, glucose, galactose, aldoheptose, ketoheptose, and combinations thereof.

4. The disaccharide is 2. The ionic conductor composition according to claim 1, which is one selected from the group consisting of sucrose, lactulose, lactose, trehalose, cellobiose, chitobiose, kojibiose, nigerose, maltose, isomaltose, β-trehalose, α,β-trehalose, sophorose, laminaribiose, gentiobiose, turanose, maltulose, isomaltulose, gentiobiulose, mannobiose, melibiose, melibiulose, rutinose, rutinulose, xylobiose, and combinations thereof.

5. The ionic conductor is 2. The ionic conductor composition according to claim 1, which is one selected from the group consisting of fluorine-based ionic conductors, hydrocarbon-based ionic conductors, and combinations thereof.

6. The hydrocarbon-based ionic conductor is 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 (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene (S-PSU), sulfonated polyphenylene sulfonate (S-PSU), sulfonated polyphenylene ether ketone (S-PEEK), sulfonated polyphenylene ether ketone (S-PEEK), sulfonated polyphenylene ether ketone (S-PEEK), sulfonated polyphenylene ether ketone (S-PBI ... 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 nitrile6. The ionic conductor composition according to claim 5, wherein the ionic conductor is any one selected from the group consisting of polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, and mixtures thereof.

7. The fluorine-based ion conductor is 6. The ionic conductor composition according to claim 5, which is perfluorosulfonic acid (PFSA).

8. 2. The ionic conductor composition according to claim 1, wherein the solubility of the saccharide compound is 0 to 1000 g / L in water at 25°C.

9. A polymer electrolyte membrane comprising the ion conductor composition of claim 1.

10. The polymer electrolyte membrane is The polymer electrolyte membrane according to claim 9 , further comprising a porous support impregnated with a dispersion containing the ion conductor composition.

11. The porous support includes:

11. The polymer electrolyte membrane according to claim 10, which is one selected from the group consisting of a fluorine-based porous support, a hydrocarbon-based porous support, and a combination thereof.

12. The polymer electrolyte membrane according to claim 9 ; a catalyst layer disposed on at least one surface of the polymer electrolyte membrane; A membrane-electrode assembly comprising:

13. A fuel cell comprising the membrane-electrode assembly according to claim 12.

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