JP5830386B2 - POLYMER ELECTROLYTE MEMBRANE FOR DIRECT OXIDATION FUEL CELL, ITS MANUFACTURING METHOD, AND DIRECT OXIDATION FUEL CELL SYSTEM INCLUDING THE SAME - Google Patents

Description

  The present invention relates to a polymer electrolyte membrane for a direct oxidation fuel cell, a method for producing the same, and a direct oxidation fuel cell system including the same, and more specifically, high-output is achieved by suppressing permeation of the hydrocarbon fuel to the electrolyte membrane even in a thin film state. The present invention relates to a direct oxidation fuel cell system capable of providing a battery exhibiting a density.

  A fuel cell is a power generation system that directly converts chemical reaction energy of hydrogen and an oxidant contained in a hydrocarbon-based material such as methanol, ethanol, and natural gas into electric energy.

  Typical examples of the fuel cell system include a polymer electrolyte fuel cell (PEMFC) and a direct oxidation fuel cell. When methanol is used as the fuel of the direct oxidation fuel cell, there is a direct methanol fuel cell (DMFC).

  The polymer electrolyte fuel cell is an environmentally friendly energy source that can replace fossil energy, has high power density and energy conversion efficiency, can operate at room temperature, and can be downsized and sealed, It can be widely used in fields such as pollution-free automobiles, household power generation systems, portable power supplies for mobile communication equipment, and military equipment.

  Although the polymer electrolyte fuel cell has an advantage of high energy density, it requires careful handling of hydrogen gas and reforms methane, methanol, natural gas, etc. to produce high fuel gas hydrogen. Therefore, there is a problem that requires equipment such as a fuel reformer.

  On the other hand, the direct oxidation fuel cell has a lower energy density than the polymer electrolyte fuel cell, but has a feature that it does not require a fuel reforming device because the fuel is easily handled and the operating temperature is low. Therefore, it is recognized as a system suitable for small-sized and general-purpose mobile power supplies.

  In such a fuel cell, a stack that substantially generates electricity has several to several tens of unit cells each composed of a membrane-electrode assembly (MEA) and a separator (or a bipolar plate (Bipolar Plate)). Have a laminated structure. The membrane-electrode assembly includes an anode electrode (also referred to as “fuel electrode” or “oxidation electrode”) and a cathode electrode (“air electrode”) with a polymer electrolyte membrane containing a hydrogen ion conductive polymer interposed therebetween. Or a “reduction electrode”).

  As the polymer electrolyte membrane, a perfluorosulfonic acid resin membrane made of a perfluorosulfonic acid resin (trade name: Nafion, manufactured by DuPont) having excellent conductivity, mechanical properties and chemical resistance is mainly used. . As the thickness of the perfluorosulfonic acid resin film increases, the dimensional stability and mechanical properties improve, but the film resistance that hinders ion conduction of the resin film increases, and conversely, when the thickness decreases, the resistance of the resin film decreases. However, there is a problem (called crossover) that the mechanical properties are lowered, and the gas and liquid of the unreacted fuel pass through the polymer membrane during the operation of the battery, resulting in fuel loss and the deterioration of the cell performance. is there.

  In particular, the polymer electrolyte membrane has a thickness change and a volume change of 15 to 30% depending on the temperature and the degree of hydration in the state of being thermocompression bonded to the platinum catalyst electrode, and 3 to 50% by weight of methanol fuel. In some cases, a volume change of 200% or more at maximum occurs. Such an increase in thickness due to swelling of the electrolyte membrane causes excessive stress in the gas diffusion layer that is the electrode substrate, and the dimensional change in the surface direction may cause the catalyst particles and the electrolyte membrane interface during long-term operation of the fuel cell. Induces physical degradation.

  In order to solve such problems, a resin solution such as perfluorosulfonic acid is applied to a porous polytetrafluoroethylene thin film support and dried to fill the pores (pores) of the support. This method is described in US Pat. Nos. 5,547,551 and 5,599,614. The membrane produced in this way can be thinned because of its excellent mechanical properties and dimensional stability even when the thickness is reduced to about 25 μm by the action of the polytetrafluoroethylene support. . However, when this reinforced composite membrane is applied as a polymer electrolyte membrane of a direct oxidation fuel cell using methanol as a fuel, methanol crossover occurs at a high rate through the thin film, so there is no limit to methanol fuel cells. Use is considered problematic.

US Pat. No. 5,547,551 US Pat. No. 5,599,614

  A first object of the present invention is a polymer electrolyte for a direct oxidation fuel cell, which has excellent electrochemical characteristics, thermal stability, dimensional stability and mechanical characteristics, and can reduce crossover of hydrocarbon fuel. It is to provide a membrane.

  The second object of the present invention is to provide a method for producing the polymer electrolyte membrane for a direct oxidation fuel cell.

  The third object of the present invention is to provide a membrane-electrode assembly including the polymer electrolyte membrane.

  A fourth object of the present invention is to provide a direct oxidation fuel cell including the membrane-electrode assembly.

  In order to achieve the first object of the present invention, a porous polymer support having a plurality of pores and a polymer support formed on the porous polymer support are dispersed in the cation exchange resin and the cation exchange resin. Provided is a polymer electrolyte membrane for a direct oxidation fuel cell including a hydrocarbon fuel diffusion preventing layer containing an inorganic additive.

  It is preferable that the inorganic additive is present as a nanometer-scale thin film in the cation exchange resin.

Examples of the inorganic additive include silica, alumina, zeolite, barium titanate, ceramic, inorganic silicate, zirconium hydrogen phosphate, α-Zr (O _a1 PCH _a2 OH) _a (O _b1 PC _b2 H _b4 SO _b5 H) _b. nH ₂ O (where a1, a2, a, b1, b2, b4, b5 and b are the same or independently an integer from 0 to 14 and n is an integer from 0 to 50), ν _{-Zr (PO a1) (H a2} PO a3) a (HO b1 PC b2 H b3 SO b4 H) b · nH 2 O ( where, a1, a2, a3, a , b1, b2, b3, b4 and b are the same or independently integers of 0 to 14 to each other, n is an integer from 0 to _{50), Zr (O a1 PC} a2 H a3) a Y b ( where, a , A2, a3, a and b are the same or independently selected from an integer of 0 to 14 to each _{other), Zr (O a1 PCH a2} OH) a Y b · nH 2 O ( where, a1, a2, a And b are the same or independently an integer of 0 to 14, and n is an integer of 0 to 50), α-Zr (O _a1 PC _{a2 Ha a3} SO _a4 H) _a · nH ₂ O (here A1, a2, a3, a4 and a are the same or independently an integer from 0 to 14, and n is an integer from 0 to 50), α-Zr (O _a1 POH) · H ₂ O (where a1 is an integer from 0 to 14), (P ₂ O ₅ ) _a (ZrO ₂ ) _b (where a and b are the same or independently an integer from 0 to 14) It is) composed of glass and _{P 2 O} 5 -ZrO 2 -SiO 2 glass One or more mixtures selected from the group are preferred, and inorganic silicates are most preferred.

  Examples of the silicate include plate-like layered talc, montmorillonite (MMT), fluorohectorite, kaolinite, vermiculite, and vermiculite. Illite, mica, or brittle mica is preferred. The silicate is preferably dispersed in the cation exchange resin as a nanometer-class thin film, and a polymer chain penetrates into the dispersed plate-like silicate in an intercalation manner to peel the silicate thinly. .

  The layered particles of the inorganic silicate have a small thickness with respect to the long axis length and preferably have an aspect ratio of 1/30 to 1/1000. The long axis length of the inorganic silicate is 0.05 to 0. .5 μm is preferred. When the inorganic silicate is peeled in the cation exchange resin, the silicate interlayer distance is preferably at least 3 nm.

  The silicate interlayer distance indicates the interlayer distance when the polymer chains are infiltrated between the silicate plate-like layers and the layers are separated from each other. The minimum distance is 3 nm, and the polymer chains are sequentially infiltrated with the layers. Since the silicate layer and the like are dispersed in an indefinite shape as the distance between the layers gradually increases, it is not appropriate to define the distance between the layers, and thus the distance between them cannot be measured. Therefore, the minimum distance between the layers is 3 nm, and the maximum value is meaningless.

  The thickness of the polymer electrolyte membrane is preferably 5 to 100 μm.

  At the same time, the thickness of the polymer support is preferably 10 to 15 μm, and the hydrocarbon fuel diffusion prevention layer is preferably 2 to 10 μm.

  In order to achieve the second object, the present invention provides a cation exchange resin liquid produced by dissolving a cation exchange resin having a cation exchange group in the side chain in a first organic solvent, and a solid or liquid form. There are provided a method for producing a polymer electrolyte membrane comprising the steps of: obtaining a mixed solution by mixing the inorganic additives, and coating the mixed solution on a porous polymer support to form a polymer membrane. .

  According to a preferred embodiment of the present invention, the first organic solvent is N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMA), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), Acetone, methyl ethyl ketone (MEK), tetramethyl urea, trimethyl phosphate, butyrolactone, isophorone, carbitol acetate, methyl isobutyl ketone, N-butyl acetate, cyclohexanone, diacetone alcohol, diisobutyl ketone, ethyl acetoacetate, glycol ether, propylene carbonate, Ethylene carbonate, dimethyl carbonate, diethyl carbonate, or a mixture thereof is preferable.

  The mixing ratio of the inorganic additive in the mixed solution is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the cation exchange resin solution.

  In order to achieve the third object, the present invention provides a membrane-electrode assembly for a fuel cell manufactured using the polymer electrolyte membrane according to the present invention.

  In order to achieve the fourth object, the present invention provides a fuel cell including the membrane-electrode assembly.

  The polymer electrolyte membrane for a direct oxidation fuel cell according to the present invention is manufactured by infiltrating a pore of a porous polymer support with a mixed solution of a cation exchange resin and an inorganic additive. This effectively closes the pores of the porous support, and the silicate additive having a layered structure with a high aspect ratio is peeled and dispersed in the polymer electrolyte membrane. Compared with conventional reinforced composite membranes using porous supports, they can be applied to direct oxidation fuel cells even in the thin film state because they can increase the diffusion distance of fuel and have excellent barrier properties against hydrocarbon fuels. It becomes possible.

  In addition, the total methanol permeation amount remains the same or less even when the membrane thickness is reduced to about 1/5 compared to the conventional polymer electrolyte membrane for direct oxidation fuel cells of 130 to 180 μm. Therefore, by reducing the thickness of the electrolyte membrane, it is possible to provide a high-power battery that can improve conductivity.

  Further, the durability of the electrode / electrolyte interface is improved by enhancing the dimensional stability.

FIG. 1A is a cross-sectional view of a polymer electrolyte membrane according to the present invention. FIG. 1B shows the structure of the inorganic silicate used in the present invention. FIG. 1C is a cross-sectional view of a membrane-electrode assembly according to the present invention. 1 is a schematic view schematically showing the structure of a direct oxidation fuel cell system of the present invention. 3 is an SEM photograph in which Al mapping is performed on the polymer electrolyte membrane manufactured according to Example 1 of the present invention. 4 is a SEM photograph in which Al mapping is performed on the polymer electrolyte membrane manufactured in Comparative Example 1. FIG. 5 is a graph showing how the volume change rate of the polymer electrolyte membranes manufactured according to Example 1 of the present invention and Comparative Examples 1 and 3 change due to a change in methanol concentration. 1 is a cross-sectional morphology of a polymer electrolyte membrane manufactured according to Example 1 of the present invention. 2 is a cross-sectional morphology of a polymer electrolyte membrane manufactured according to Comparative Example 1. 2 is a graph showing the power density of a fuel cell manufactured according to Example 1 of the present invention. 6 is a graph showing output stability of fuel cells manufactured according to Example 1 and Comparative Example 3 of the present invention. It is a transmission electron micrograph of the polymer electrolyte membrane manufactured by Example 2 of this invention.

  Hereinafter, the present invention will be described in more detail.

  The present invention relates to a polymer electrolyte membrane of a direct oxidation fuel cell. The polymer electrolyte membrane 14 of the present invention is a porous polymer support 10 having a plurality of pores as shown in FIG. And a hydrocarbon fuel diffusion prevention layer 12 formed on the porous polymer support. The hydrocarbon fuel diffusion preventing layer includes a cation exchange resin and an inorganic additive dispersed in the cation exchange resin. The fuel of the present invention means a hydrocarbon fuel in a gas or liquid state, and representative examples thereof include methanol, ethanol, propanol, butanol or natural gas.

  Even if the polymer electrolyte membrane of the present invention having such a structure is formed to a thickness of 5 to 100 μm, more preferably 5 to 50 μm, the support supports against swelling due to moisture and shrinkage during drying. Since the dimensional stability of the polymer electrolyte membrane is improved and the stable electrode / electrolyte interface physical properties are maintained, the life of the battery can be improved.

  Therefore, although there is a problem that the membrane resistance usually increases, the direct oxidation fuel cell can solve the problem of using only a perfluorosulfonic acid membrane having a thickness of about 130 to 180 μm.

  In addition, since the thickness of the polymer electrolyte membrane can be reduced, the membrane resistance can be reduced, the overall size of the fuel cell system can be reduced, and the fuel cell can be reduced in size such as a mobile phone. It can also be applied to electronic equipment.

  Conventional techniques for using inorganic additives in polymer electrolyte membranes are disclosed in Korean Patent Publication Nos. 2004-51287, 2003-45234, and 2004-47240.

  However, these patents are all polymer electrolyte membranes that do not use a porous polymer support, and when a porous polymer support is not used, if a thin film of about 30 μm is used as in the present invention, the mechanical strength However, although hydrogen permeation is improved, there is a problem that excessive crossover of hydrocarbon fuel such as methanol occurs. Therefore, it is very difficult for those who are engaged in the field to predict the effect of the present invention from the patent and to obtain the effect of the present invention.

  Examples of the porous polymer support include polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyimide, and polybenzoxole. It is possible to use homopolymers or copolymers thereof selected among imidazolidines. Since a preferred cation exchange resin is a fluoro resin, a homopolymer of polytetrafluoroethylene or polyvinylidene fluoride is used in order to improve the interfacial bonding force between the polymer support and the cation exchange resin. Or a copolymer is preferred, and a homopolymer of polytetrafluoroethylene is most preferred.

  As the cation exchange resin, all polymer resins having a cation exchange group selected from the group consisting of sulfonic acid group, carboxylic acid group, phosphoric acid group, phosphonic acid group, and derivatives thereof in the side chain are all. Can be used.

  Typical examples of cation exchange resins include fluoropolymers, benzimidazole polymers, polyimide polymers, polyetherimide polymers, polyphenylene sulfide polymers, polysulfone polymers, polyethersulfone polymers. There is at least one hydrogen ion conductive polymer selected from a polymer, a polyether ketone polymer, a polyether-ether ketone polymer, or a polyphenylquinoxaline polymer, a fluoro polymer, A polybenzimidazole polymer or a polysulfone polymer is preferred.

  Examples of fluoropolymers include poly (perfluorosulfonic acid) of the following chemical formula 1 (trade name: Nafion (EI DuPont de Nemours), Aciplex (Asahi Kasei), Flemion (Asahi Glass), and Fumion (Germany). In addition, a fluorocarbon vinyl ether represented by the following chemical formula 2 or a fluorinated vinyl ether represented by the following chemical formula 3 can be used.

Further, U.S. Pat. Nos. 4,330,654, 4,358,545, 4,417,969, 4,610,762, 4,433,082 and 5,094,995. No. 5,596,676 and 4,940,525 can be used.

(In Chemical Formula 1, X is H, Li, Na, K, Cs, tetrabutylammonium or NR ¹ R ² R ³ R ⁴ , and R ¹ , R ² , R ³ and R ⁴ are independently H CH ₃ or C ₂ H ₅ , m is 1 or more, n is 2 or more, x is about 5 to 3.5, and y is 1,000 or more.)

(In Formula 2, Rf is fluorine or a C1-C10 perfluoroalkyl group, Y is fluorine or a trifluoromethyl group, n is an integer of 1 to 3, M is fluorine, a hydroxyl group, an amino group, and -OMe (Me is selected from the group consisting of alkali metals or quaternary ammonium groups)

(In Formula 3, k is 0 or 1, and l is an integer of 3 to 5)
Poly (perfluorosulfonic acid) having a structure represented by Chemical Formula 1 (trade name: Nafion) has a micellar structure when a sulfonic acid group at a chain end is hydrated. Providing a passageway for the same solution as a typical aqueous acid. In the present invention, when perfluorosulfonic acid (trade name: Nafion) is used as the cation exchange resin, X is a monovalent group such as hydrogen, sodium, potassium, cesium, etc., with an ion exchange group (—SO ₃ X) at the end of the side chain. It can be substituted with ions or tetrabutylammonium.

  Or benzimidazole polymer, polyimide polymer, polyetherimide polymer, polyphenylene sulfide polymer, polysulfone polymer, polyethersulfone polymer, polyetherketone polymer, polyether-etherketone Specific examples of the polymer or polyphenylquinoxaline polymer include polybenzimidazole, polyimide, polysulfone, polysulfone derivatives, sulfonated poly (ether ether ketone) (sulfonated-poly (ether-etherketone: abbreviation s) -PEEK)), polyphenylene oxide, polyphenylene sulfide, polyphosphazene, and the like.

  Alternatively, an electrolyte membrane in which a polystyrene sulfonic acid polymer is graft-polymerized with polyethylene, polypropylene, fluoroethylene polymer, or ethylene / tetrafluoroethylene polymer can also be used.

  The cation exchange resin can adjust the conductivity of hydrogen ions according to the equivalent weight.

  On the other hand, the “ion exchange ratio of the ion exchange resin” is defined by the number of carbon and cation exchange groups in the polymer main chain. In the present invention, an ion exchange resin having an ion exchange ratio of 3 to 33 is preferred. This corresponds to an equivalent weight (EW) of about 700 to 2,000.

  The equivalent weight value is defined as the weight of the acidic polymer required to neutralize one equivalent of base (NaOH), and if the equivalent weight is excessively large, the resistance increases correspondingly. In the case where it is small, the mechanical properties deteriorate, so it is preferable to adjust within an appropriate range.

The inorganic additive plays a role of increasing mechanical strength and reducing crossover of hydrocarbon fuel such as methanol. As a typical example, silica (especially fumed silica is preferable, and Aerosil is a trade name). , Cab-O-sil, etc.), alumina, mica, zeolite (trade names include SAPO-5, XSM-5, AIPO-5, VPI-5, MCM-41), barium titanate, ceramic, inorganic Silicate, zirconium hydrogen phosphate, α-Zr (O _a1 PCH _a2 OH) _a (O _b1 PC _b2 H _b4 SO _b5 H) _b · nH ₂ O (where a1, a2, a, b1, b2, b4, b5 and b are the same or independently an integer of 0 to 14, and n is an integer of 0 to 50 _{, Ν-Zr (PO a1)} (H a2 PO a3) a (HO b1 PC b2 H b3 SO b4 H) b · nH 2 O ( where, a1, a2, a3, a , b1, b2, b3, b4 And b are the same or independently an integer of 0 to 14, and n is an integer of 0 to 50), Zr (O _a1 PC _a2 H _a3 ) _a Y _b (where a1, a2, a3 , A and b are the same or independently an integer of 0 to 14), Zr (O _a1 PCH _a2 OH) _a Y _b · nH ₂ O (where a1, a2, a and b are the same) Or independently an integer of 0 to 14 and n is an integer of 0 to 50), α-Zr (O _a1 PC _{a2 Ha a3} SO _a4 H) _a · nH ₂ O (where a1, a2 , A3, a4 and a are the same or independently of each other 0 Is an integer of Itaru 14, n is an integer from 0 to _{50), α-Zr (O} a1 POH) · H 2 O ( where, a1 is an integer of 0 to _{14), (P} 2 _{O 5} ) _{a (ZrO 2) b} (where, a and b are the same or mutually integer from 0 to 14) selected from the group consisting of glass and _{P 2 O} 5 -ZrO 2 -SiO 2 glass One or more mixtures are preferred, and it is most preferred to use inorganic silicates.

  The inorganic silicate is clay, that is, generally a layered silicate, and the basic structure is a silica tetrahedron sheet (a thin layer constituting the topic layer) and alumina as shown in FIG. It is composed of a combination of octahedral sheets, and these two sheets form a layered structure through a hydroxyl group condensation reaction.

  Depending on the amount of negative charge in the silicate, pyrophyllite-talc, montmorillonite (MMT), fluorohectorite, kaolinite vermiculite, vermiculite, categorized as illite, mica, or brittle mica, which can be used in the present invention. In the present invention, it is particularly preferable to use montmorillonite.

Montmorillonite, instead of Al ³⁺ ions in the alumina octahedral ^{sheet, Mg 2+, Fe 2+, Fe} 3+ ions, Al ³⁺ ions instead of Si ⁴⁺ ion in the silicate tetrahedral sheet is substituted The structure has a negative charge amount as a whole. In addition, in order to achieve overall charge balance, exchangeable cations and water molecules are contained between the silicate layers.

  In the silicate, the ratio of the minor axis (thickness direction) to the major axis (aspect ratio) is preferably 1/30 to 1/1000, more preferably 1/100 to 1/800, and most preferably 1/500 to 1/800. preferable.

  When the ratio of the short axis to the long axis of the silicate is larger than 1/30, the separated silicate cannot act as a diffusion barrier for gas and liquid, and therefore, the separation ability is lowered, which is not preferable.

  In addition, when the ratio of the short axis to the long axis of the silicate is smaller than 1/1000, the number of atoms in the short axis direction may be 2 or less, and it is difficult to peel off due to penetration of the cation exchange resin chain. It is not preferable because it is difficult to disperse in a cation exchange resin with a polymer electrolyte membrane manufactured in the following manner.

  The major axis length of the silicate is preferably 0.05 to 0.5 μm, more preferably 0.05 to 0.2 μm. When the long axis length of the silicate is smaller than 0.05 μm, the plate-like structure is not formed and the hydrocarbon fuel blocking effect is reduced. When it is larger than 0.5 μm, it is difficult to penetrate into the pores of the support. Therefore, it is not preferable.

  At the same time, when the silicate layer structure is peeled off, the silicate interlayer distance is preferably at least 3 nm. The silicate interlayer distance indicates the distance when the polymer chains are infiltrated into a silicate plate shape and the layers are separated from each other. The minimum distance is 3 nm, and the polymer chains sequentially infiltrate between the layers. If the gap gradually increases and the silicate layer or the like is dispersed in an amorphous form, it is inappropriate to define the distance between the layers, and the distance between them cannot be measured. Therefore, the minimum distance between the layers is 3 nm, and the maximum value is meaningless.

  The silicate is preferably used after being treated with an organic agent, and when treated with an organic agent, a plate-like silicate layer structure that is difficult to peel and disperse in a polymer resin due to strong van der Waals attraction. A low molecular weight organic agent is inserted between them, which facilitates penetration of the polymer resin, and is easy to peel and disperse.

  As the organic agent, an alkylamine having 1 to 20 carbon atoms, an alkylenediamine having 1 to 20 carbon atoms, a quaternary ammonium salt having 1 to 20 carbon atoms, aminohexane, or a nitrogen-containing heterocyclic compound can be used. .

  Specific examples of the alkylamine include methylamine hydrochloride, propylamine, butylamine, octylamine, decylamine, dodecylamine, hexadecylamine, octadecylamine, N-methyloctadecylamine and the like.

  Examples of alkylene diamines include 1,6-hexamethylene diamine and 1,12-dodecane diamine.

  The quaternary ammonium salts include dimethyl quaternary ammonium, benzyl quaternary ammonium, 2-ethylhexyl quaternary ammonium, bis-2-hydroxyethyl quaternary ammonium, methyl quaternary ammonium, tetramethylammonium chloride, and brominated (brominated) octadecyl. Trimethylammonium, brominated dodecyltrimethylammonium, brominated dioctadecyldimethylammonium, bis (2-hydroxyethyl) methyloctadecylammonium chloride, and the like can be used.

  As aminohexane, 6-aminohexane, 12-aminohexane and the like can be used, and as the nitrogen-containing heterocyclic compound, 1-hexadecylpyridium chloride and the like can be used.

  In addition, inorganic silicates can be used after being treated with an organic agent, but inorganic silicates that have already been organically treated can also be used directly. Examples of inorganic silicates that have been organically treated in this manner include those manufactured by Southern Clay Products, Inc., USA. There are Cloisite 6A, Cloisite 10A, Cloisite 15A, Cloisite 20A, Cloisite 25A, Cloisite 30B and the like, and it is preferable to use Cloisite 10A.

  The cation exchange resin and the inorganic additive can all be present in the pores and surface of the polymer support. Alternatively, the cation exchange resin may be entirely present in the pores and surface of the polymer support, and the inorganic additive may be present only on the surface. Most preferably, they are all present in the pores and the surface.

The polymer support has a porosity of 80% or more, preferably 80 to 90%. When the porosity of the polymer support is less than 80%, the non-conductive polymer weight component is too high, and the conductivity drop of the composite membrane occurs, which is not preferable. Further, it is particularly preferable that the porosity is 80 to 90%, and the mechanical properties of the support can be further improved, which is suitable for a continuous process for film formation.

  The difference in conductivity between one surface of the polymer electrolyte membrane of the present invention and the other surface opposite thereto, that is, the both surfaces on which the catalyst layer is formed is preferably 5% or less, more preferably 3 to 5%. Since the value of the surface with low conductivity in the thickness direction of the polymer electrolyte membrane determines the membrane resistance, it is preferable that the difference between the conductivity is as small as 5% or less because hydrogen ion conduction is likely to occur.

At the same time, the porosity of the polymer electrolyte membrane of the present invention is preferably 1 to 10%, more preferably 1 to 5%.

  In the polymer electrolyte membrane of the present invention, the support preferably has a thickness of 10 to 15 μm, and the hydrocarbon fuel diffusion prevention layer preferably has a thickness of 2 to 10 μm. When the thickness of the hydrocarbon fuel diffusion preventing layer is included in the above range, the electrolyte membrane surface roughness increases and the effective surface area per unit area increases, which is preferable because the contact area of the catalyst / electrolyte membrane increases. .

  When the thickness of the hydrocarbon fuel diffusion prevention layer is greater than 10 μm, the barrier property is improved, but the surface becomes flat, and the effect of increasing the contact area of the catalyst / electrolyte membrane cannot be obtained. Is unfavorable because the contact area increases, but the barrier properties are lowered.

  In such a polymer electrolyte membrane, the layered inorganic additive is peeled off as a nanometer-class thin film by permeation of the cation exchange resin chain, and the liquid phase or gas phase fuel is the polymer electrolyte membrane. When passing through, the transmission path is lengthened, that is, it serves as a fuel cutoff. In addition, the polymer support can improve the dimensional stability and mechanical properties of the polymer electrolyte membrane in a thin state.

  In the polymer electrolyte membrane of the present invention, the cation exchange resin is 50 to 90% by weight, the porous polymer support is 2 to 30% by weight, and the inorganic additive is 0.5 to 20% by weight. , Preferably in an amount of 70 to 80% by weight of cation exchange resin, 2 to 15% by weight of porous polymer support and 0.5 to 10% by weight of inorganic additives.

  When the content of the porous polymer support and the inorganic additive is larger than the above range, since both of the two materials are non-conductive, it is not preferable because the conduction decrease occurs, and the porous polymer support and the inorganic additive are not preferable. If the content of is less than the above range, it is not preferable because desired effects such as mechanical strength, dimensional stability complementation, and hydrocarbon fuel cutoff enhancement cannot be obtained.

  In the present invention, the hydrocarbon fuel diffusion preventing layer may further contain a low molecular weight acrylate polymer. As the acrylate polymer, polyethylene glycol diacrylate or polyethylene glycol dimethacrylate having a molecular weight of 1,000 or less can be used. Such low molecular weight acrylate polymers have a low molecular weight, so if they are additionally used, they can be more easily inserted into the inorganic additive, resulting in more active stripping of the inorganic additive. This is preferable. The content of the acrylate polymer is preferably 5 to 10 parts by weight with respect to 100 parts by weight of the cation exchange resin.

  The method for producing the polymer electrolyte membrane according to the present invention is as follows.

  A mixed solution is produced by mixing a cation exchange resin solution produced by dissolving a cation exchange resin having a cation exchange group in the side chain in a first organic solvent and a solid or liquid inorganic additive. .

  In this mixing step, the cation exchange resin chain penetrates between the layers of the inorganic additive, and the layer of the inorganic additive is peeled into a nano-sized (nanometer class, for example, 0.5 nm to 15 nm) plate shape. Therefore, when an electrolyte membrane is produced with this solution, the plate-like inorganic additive is dispersed in the cation exchange resin in the produced electrolyte membrane, while significantly increasing the mechanical properties of the polymer electrolyte membrane, When liquid or gaseous fuel passes through the polymer electrolyte membrane, the transmission path can be lengthened to significantly reduce fuel permeation.

  In other words, when nano-sized plate-like inorganic additives are peeled and dispersed within the polymer electrolyte membrane, the contact surface area between the organic polymer and the inorganic inorganic additive increases, and the intermolecular attractive force increases. When the mechanical properties increase and are delaminated in this way, it can act as a barrier to fuel permeation and significantly reduce crossover of gas or liquid hydrocarbon fuels.

  The cation exchange resin solution is preferably produced by dissolving 1 to 10 parts by weight of the cation exchange resin with respect to 100 parts by weight of the first organic solvent. When the cation exchange resin is used in an amount of less than 1 part by weight, it is easy to insert the cation exchange resin between the layers of the inorganic additive, but the drying process becomes longer and the viscosity is lowered to reduce the porosity. Coating (spraying, printing, film application, roller coating, brush coating, etc. in a broad sense) such as coating or coating on a polymer support becomes difficult, and if it is used in excess of 10 parts by weight, the process of inserting an inorganic additive between layers becomes long. This is not preferable.

In this step, when a commercially available cation exchange resin dissolved in a solvent is used, for example, the brand name Nafion, which is perfluorosulfonic acid, is a 5 wt% Nafion / H ₂ O / 2-propanol solution. Since it is sold in the form, it is said that it is dried at room temperature to completely remove the H ₂ O / 2-propanol solvent, and then redissolved in an organic solvent.

  The dissolution process is performed by stirring at 90 to 120 ° C. for 6 to 72 hours.

  As the first organic solvent, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMA), tetrahydrofuran (THF), dimethyl, Sulphoxide (dimethylsulfoxide; DMSO), acetone, methylethylketone (MEK), tetramethylurea, trimethylphosphate, butyrolactone, phtholone, isophorone Carbitolate, methylisobutylketone, N-butylacetate, cyclohexanone, diacetone alcohol, diisobutylcetone ether, diisobutylacetone etherate, (Glycolether), propylene carbonate (propylene carbonate), ethylene carbonate (ethylene carbonate), dimethyl carbonate (dimethyl carbonate), diethyl carbonate (diethyl carbonate) te) or it may be a mixture thereof.

  As the inorganic additive, the inorganic additive can be used as it is in a solid form, or it can be used by dispersing in a second organic solvent to produce an inorganic additive liquid. The inorganic additive liquid described in the present specification is not limited to the state as long as the inorganic additive is added to the liquid organic solvent such as a suspended state, a dispersed state or a dissolved state of the inorganic additive and the organic solvent. Means.

  When using an inorganic additive in a liquid state, the inorganic additive is added to the second organic solvent to produce an inorganic additive liquid. At this time, 1-propanol, 2-propanol or a mixture thereof can be used as the second organic solvent.

  The mixing ratio of the cation exchange resin liquid and the inorganic additive is preferably such that the inorganic additive is 0.5 to 10 parts by weight with respect to 100 parts by weight of the cation exchange resin. When the amount of the inorganic additive is less than 0.5 parts by weight, the degree of dispersion is small, which is preferable because the degree of permeation of hydrocarbon fuel increases. When the amount exceeds 10 parts by weight, an excessive amount of inorganic additive is produced. Since the polymer electrolyte membrane is dispersed in the cation exchange resin and the plate-like inorganic additive is not peeled off, there is a problem that the mechanical strength is lowered.

  Further, a low molecular weight acrylate polymer can be further added to the mixed solution. The low molecular weight acrylate polymer is generally used in a liquid state. The addition amount of the acrylate polymer is preferably 5 to 10 parts by weight with respect to 100 parts by weight of the cation exchange resin.

The resulting mixed solution is coated on a polymer support to produce a polymer electrolyte membrane. As a method of the coating process, any general coating process may be used, but the number of times is important for obtaining the effect of the present invention. In other words, it is preferable to carry out the coating step twice or more because the ionic conductivity of the polymer electrolyte membrane can be made uniform, and it is more preferred to carry out the coating step 3 to 5 times. The amount of coating solution used during the coating step, can be adjusted to the film thickness of the polymer support, said polymer support of approximately 50μm thickness with a mixed solution of about 1g body 200 cm ² Can be coated, but a slight overage is generally used.

  When the coating process is performed only once, or when the mixed solution is cast as it is to produce a polymer electrolyte membrane in a film state, the pores of the support are not completely blocked, so that the ionic conductivity becomes non-uniform. It is not preferable.

  In the coating step, it is more effective to coat both surfaces of the polymer support. Further, the thickness of the produced polymer electrolyte membrane is preferably 5 to 100 μm, and in order to obtain a polymer electrolyte membrane having such a thickness, it should be dried at 100 ° C. or higher after the coating step.

  In addition, before the mixed solution is coated on the polymer support, a step of coating only the cation exchange resin solution on the polymer support may be further performed. When this further step is carried out, only the cation exchange resin exists in the inside of the polymer support, that is, the pores, and the pores are completely blocked by the cation exchange resin. A polymer electrolyte membrane having a hydrocarbon fuel diffusion preventing layer in which a cation exchange resin and an inorganic additive are present is produced. In this step, the thickness of the hydrocarbon fuel diffusion preventing layer is preferably 1/3 or more of the thickness of the polymer support.

  In the coating process, after the porous substrate is adhered to both sides of the porous polymer support, the mixed solution is applied onto the carbon paper, and the process of rolling and drying is repeated. When the mixture solution is uniformly penetrated into the fine pores of the support by capillary action and the solvent is dried, the inorganic additive and the cation exchange resin from which the pores of the support are completely separated are removed. It is more preferable because it can be closed.

  In the case of existing polymer electrolyte membranes such as perfluorosulfonic acid, a thickness of 130 to 180 μm is used to suppress hydrocarbon fuel crossover, but the hydrogen ion conductivity decreases as the thickness increases. There is a disadvantage that the cost of the polymer electrolyte membrane increases.

  In contrast, in the case of the polymer electrolyte membrane according to the present invention, the mechanical properties can be improved by the role of the polymer support and the nano-sized plate-like inorganic additive, and the hydrocarbon fuel crossover is remarkably increased. Even if the thickness of the polymer film is reduced to 5 to 100 μm, more preferably 5 to 50 μm, an excellent effect can be obtained.

  In the polymer electrolyte membrane, since the dispersed inorganic additive exists in the resin, the diffusion path of the hydrocarbon fuel becomes long, and the permeability of the hydrocarbon fuel can be reduced.

  Therefore, even if it is manufactured to a thin film of about 5 to 100 μm, it can obtain the same or higher hydrocarbon fuel cutoff effect as that of using the existing 180 μm thick polymer electrolyte membrane. Can be provided. In addition, the manufacturing method is simple and mass production becomes possible.

  As shown in FIG. 1C, the polymer electrolyte membrane 14 of the present invention is positioned between the cathode 16 and the anode 18 to form a membrane-electrode assembly.

  The cathode and anode are composed of an electrode substrate and a catalyst layer. The catalyst layer contains a so-called metal catalyst that catalytically assists the related reactions (fuel oxidation and oxidant reduction), platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium. Alloy or platinum-M alloy (M is one or more transition metals selected from the group consisting of Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) One or more catalysts are preferably included, and one or more selected from platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, platinum-cobalt alloy, or platinum-nickel alloy. More preferably, the catalyst is included.

  In general, a metal catalyst supported by a carrier is used. As the carrier, carbon such as acetylene black and graphite can be used, and inorganic fine particles such as alumina, silica, zirconia, and titania can also be used. When a noble metal supported on a carrier is used as a catalyst, a commercially available product that is commercially available can be used, or it can be produced by using a noble metal supported on a carrier. The step of supporting the noble metal on the carrier is a content that is widely known in the field, and therefore can be easily understood by those who are engaged in the field even if a detailed description thereof is omitted.

  Fuel of the fuel cell is supplied to the anode electrode, and an oxidant such as air or oxygen is supplied to the cathode electrode, and electricity is generated by an electrochemical reaction between the anode electrode and the cathode electrode. A fuel oxidation reaction takes place at the anode, and a oxidant reduction reaction takes place at the cathode, generating a potential difference between the two electrodes.

  As the electrode substrate, carbon paper, carbon cloth, carbon felt, or metal cloth can be used, but it is not limited thereto. The electrode base material serves to support the electrode for the fuel cell, and diffuses the reaction gas to the catalyst layer so that the reaction gas can easily approach the catalyst layer.

  In addition, it is preferable to use carbon paper or carbon cloth that has been subjected to water repellency treatment with a fluorine-based resin, because the gas diffusion efficiency can be prevented from being lowered by water generated when the fuel cell is driven. As the fluorine-based resin, polyvinylidene fluoride, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer resin, trifluorochloroethylene resin, fluoroethylene polymer, or the like can be used.

  The electrode may further include a fine pore layer in order to further enhance the gas diffusion effect between the electrode substrate and the catalyst layer.

  The microporous layer is formed by applying a composition containing a conductive powder material, a binder, and optionally an ionomer. Examples of the conductive powder include carbon powder, carbon black, acetylene black, activated carbon, or carbon nanotube, carbon nanofiber, carbon nanowire, carbon nanohorn (nanosize carbon cone tube), or carbon nanoring (nanosize carbocycle). So-called nanocarbon can be used. As the binder, polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), polyvinyl alcohol, cellulose acetate, or the like can be used.

  The fuel cell system of the present invention including the membrane-electrode assembly of the present invention includes at least one electricity generation unit, a fuel supply unit, and an oxidant supply unit.

  The electricity generating unit includes a polymer electrolyte membrane, a membrane-electrode assembly including a cathode and an anode electrode present on both sides of the polymer electrolyte membrane, and a separator present on both sides of the membrane-electrode assembly. The electricity generating unit plays a role of generating electricity through a fuel oxidation reaction and an oxidant reduction reaction.

  The fuel supply unit serves to supply fuel to the electricity generation unit, and the oxidant supply unit serves to supply oxidant to the electricity generation unit.

  The schematic structure of the fuel cell system of the present invention is shown in FIG. 2 and will be described in more detail with reference to FIG.

  The structure shown in FIG. 2 shows a system for supplying the fuel and the oxidant to the electricity generator by the pump. However, the fuel cell system of the present invention is not limited to such a structure, and the pump is used. Of course, it can be used for the structure of a fuel cell system using a diffusion system.

  The fuel cell system 400 of the present invention includes a stack 43 having at least one electricity generation unit 40 that generates electric energy through an electrochemical reaction between a fuel and an oxidant, a fuel supply unit 4 that supplies fuel, an oxidation The oxidant supply unit 5 is configured to supply the agent to the electricity generation unit 40.

  The fuel supply unit 4 that supplies fuel can include a fuel tank 45 that stores fuel and a fuel pump that is connected to the fuel tank 45. The fuel pump functions to discharge the fuel stored in the fuel tank 45 with a predetermined pumping force.

  The oxidant supply unit 5 that supplies an oxidant to the electricity generation unit 40 of the stack 43 includes at least one air pump 13 that sucks air with a predetermined pumping force.

  The electricity generating unit 40 includes a membrane-electrode assembly 51 that oxidizes / reduces a fuel and an oxidant, and a separator (a bipolar plate is used for supplying fuel and oxidant to both sides of the membrane-electrode assembly). (May be) 53, 55.

  Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following embodiment is a preferred embodiment of the present invention, and the present invention is not limited to the following embodiment.

A commercially available 5% by weight Nafion / H ₂ O / 2-propanol (Solution Technology, Inc., equivalent weight EW = 1,100) solution was stirred at room temperature and evaporated under reduced pressure to obtain a solid Nafion resin. Obtained. The obtained solid Nafion resin was added in an amount of 5 parts by weight with respect to 100 parts by weight of dimethylacetamide (Aldrich, DMAC), and mechanically stirred at 100 ° C. for about 24 hours. 5 wt% Nafion / DMAC) was produced.

  Montmorillonite treated with an organic agent in a cation exchange resin solution (Southern Clay Product, trade name: Cloisite 10A), aspect ratio: 1/500 (in the state where the organic agent is completely intercalated, the long axis length : About 0.3 μm) at a ratio of 2 parts by weight with respect to 100 parts by weight of the cation exchange resin, and then mixed with a magnetic stirrer at 100 ° C. for 24 hours, and ultrasonic waves were applied to the interlayer of montmorillonite. A cation exchange resin chain (Nafion / MMT / DMAC) from which the silicate was peeled off was prepared by intercalating the cation exchange resin chain between the two. At this time, the peel distance between the silicate layers was 3 nm or more.

A 30 cm ² porous polytetrafluoroethylene polymer support (WL Gore, 17 mm Gore-Tex, porosity: 80%) was fixed, and carbon paper (Toray, trade name: TGPH-090) was applied, and 15 g of a Nafion / MMT / DMAC mixed solution was poured and repeatedly coated using a roller, followed by drying at 100 ° C. five times to obtain a total thickness of 25 μm. Thus, a polymer electrolyte membrane for a direct oxidation fuel cell having a porous polymer support and a hydrocarbon fuel diffusion preventing layer was produced. At this time, the polymer support was pulled in the horizontal direction during the coating process, the thickness was reduced to 15 μm, and the hydrocarbon fuel diffusion preventing layer was 10 μm.

  In the produced polymer electrolyte membrane, the weight ratio of the cation exchange resin, the polymer support and montmorillonite was 100: 13.6: 2.

5% by weight Nafion / H ₂ O / 2-propanol solution, dipropylene glycol and deionized water were added to Pt-Ru black (representing a fine particle catalyst not supported on a support, Johnson Matthey, HiSpec 6000) and Pt black (Johnson Matthey) , HiSpec 1000) particles are mixed with each other to produce a catalyst slurry, and then screen printed on a Teflon (registered trademark) film and dried, and the resulting catalyst layer is placed on a separately produced polymer electrolyte membrane. After the placement, thermocompression bonding was performed at 200 ° C. under a pressure of 2000 N / cm ² for 3 minutes to form cathode and anode electrocatalyst layers on the polymer electrolyte membrane so as to have a loading amount of 4 mg / cm ² respectively.

  Subsequently, a polymer electrolyte membrane is placed in the middle, and an ELAT electrode base material / gas diffusion layer of E-Tek Co. is placed on the cathode electrode catalyst layer and the anode electrode catalyst layer and bonded together to form a membrane-electrode junction. The body was manufactured.

  After the produced membrane-electrode assembly is inserted between glass fiber gaskets coated with polytetrafluoroethylene, it is sandwiched between two separators each having a predetermined shape of a gas flow channel and a cooling channel, and then made of copper. A unit cell was manufactured by pressurizing and assembling between the end plates, and the change in the output of the unit cell due to the operating temperature was measured with 1M methanol and dry air flowing in.

  It implemented like Example 1 except having used 10 weight part of montmorillonite with respect to 100 weight part of cation exchange resins. The weight ratio of the cation exchange resin, the polymer support and montmorillonite in the produced polymer electrolyte membrane was about 100: 13.6: 2, which was the same as in Example 1.

  The same procedure as in Example 1 was performed, except that kaolinite was mixed with the cation exchange resin solution obtained in Example 1 to produce a cation exchange resin mixture. In the manufactured polymer electrolyte membrane, the weight ratio of the cation exchange resin, the polymer support, and kaolinite was about 100: 13.6: 2.

  The same procedure as in Example 1 was carried out except that the cation exchange resin solution obtained in Example 1 was mixed with fluorohectorite to produce a cation exchange resin mixture. In the produced polymer electrolyte membrane, the weight ratio of the cation exchange resin, the polymer support and the fluorohectorite was about 100: 13.6: 2.

  Except that a polymer electrolyte membrane was prepared by repeatedly coating 130 g of the Nafion / MMT / DMAC cation exchange resin mixture obtained in Example 1 on a 30 μm porous polytetrafluoroethylene support. It carried out similarly. In the produced polymer electrolyte membrane, the weight ratio of the cation exchange resin, the polymer support and montmorillonite was about 100: 13.6: 2.

  45 μg of Nafion / DMAC solution prepared by dissolving the solid Nafion resin obtained in Example 1 in dimethylacetamide was repeatedly coated on a 15 μm porous polytetrafluoroethylene support and dried to be 15 μm free of inorganic additives. After producing the Nafion / polytetrafluoroethylene membrane, 20 g of the Nafion / MMT / DMAC cation exchange resin mixture obtained in Example 1 was additionally coated on both sides of the Nafion / polytetrafluoroethylene membrane. The same operation as in Example 1 was conducted except that a polymer electrolyte membrane having no silicate in the layer was produced. In the manufactured polymer electrolyte membrane, the weight ratio of the cation exchange resin, the polymer support, and montmorillonite was about 100: 13.6: 2.

  Montmorillonite was added in an amount of 4 parts by weight and 2 parts by weight, respectively, with respect to 100 parts by weight of the cation exchange resin produced in Example 1 to produce first and second cation exchange resin mixtures, respectively. The same procedure as in Example 1 was performed, except that the first and second cation exchange resin mixed liquids were coated on both surfaces of the porous polytetrafluoroethylene polymer support. A unit cell was manufactured in the same manner as in Example 1 so that the surface coated with the first cation exchange resin mixture was positioned on the anode electrode side. In the produced polymer electrolyte membrane, the weight ratio of the cation exchange resin, the polymer support and montmorillonite was about 100: 13.6: 2.

  The same procedure as in Example 1 was performed except that the Nafion / MMT / DMAC cation exchange resin mixture was directly coated without using carbon paper. In the produced polymer electrolyte membrane, the weight ratio of the cation exchange resin, the polymer support and montmorillonite was about 100: 13.6: 2.

Comparative Example 1
In the same manner as in Example 1, a mixed solution (Nafion / MMT / DMAC) in which cation exchange resin chains were permeated between montmorillonite layers and silicate was peeled off was produced.

  The mixed solution was applied onto a horizontal glass substrate and dried at 110 ° C. for 12 hours or more to evaporate the solvent, thereby producing a 30 μm thick Nafion / MMT polymer electrolyte membrane. In order to uniformly adjust the surface state of the produced polymer electrolyte membrane, a pressure of 100 ° C., 2 hours, and 275 kPa was applied between 50 μm thick DuPont Kapton membranes.

Comparative Example 2
Commercial 17 wt% Nafion / H ₂ O / 2-propanol (Solution Technology Inc., equivalent weight EW = 1,100) solution was repeated on the 17 μm thick porous polytetrafluoroethylene support used in Example 1. Coating was performed to produce a polymer electrolyte membrane with a total thickness of 25 μm and no inorganic additives present.

Comparative Example 3
E. commercially available. I. A Dupont Nafion 115 (thickness 125 μm) membrane was treated with 3% hydrogen peroxide and 0.5 M sulfuric acid aqueous solution at 100 ° C. for 1 hour, respectively, and then washed with deionized water at 100 ° C. for 1 hour to obtain a polymer electrolyte membrane. Manufactured.

* SEM / EDS Measurement Among the silicate elements by SEM / EDS of the polymer electrolyte membranes produced in Example 1 and Comparative Example 1, the results of Al mapping analysis are shown in FIGS. 3 and 4, respectively. As shown in FIG. 4, the Nafion / MMT polymer electrolyte membrane manufactured by the normal simple solvent evaporation (that is, the casting process) of Comparative Example 1 has the inorganic silicate evaporated due to the difference in density between the two materials. Since sedimentation occurs, it can be confirmed that the dispersion of the inorganic particles is not uniform within the electrolyte membrane and concentrates on the bottom surface. In addition, when a multilayer structure is formed to prevent this, a resistance component may increase between layers of the electrolyte membrane, which is not preferable.

  On the other hand, when manufactured by performing the coating process five times as in Example 1 shown in FIG. 3, it is possible to confirm that the distribution of the inorganic additive is constant over the entire cross section of the electrolyte membrane. it can.

* Ionic conductivity measurement The ionic conductivity of the electrolyte membranes produced according to Example 1 and Comparative Example 1 was measured by using a conductivity measuring cell of BekkTech to inject humidified hydrogen into the electrolyte membrane. With the humidity adjusted, the frequency was measured from 100 Hz to 1 MHz and the perturbation (small signal superposition) voltage of 10 mV was measured by the AC impedance method. The measurement results are shown in Table 1 below.

  As shown in Table 1, when the ionic conductivity of the electrolyte membrane manufactured according to Example 1 and Comparative Example 1 was measured on both sides, it was found that deviation in conductivity between both ends occurred in Comparative Example 1, In the case of 1, it can be seen that the conductivity on both sides of the electrolyte membrane is comparable. Such a result is considered that Example 1 is mainly distributed on one side while Comparative Example 1 is mainly distributed while the inorganic additive is uniformly dispersed throughout the polymer electrolyte membrane.

* Dimensional stability Changes in dimensional stability of the polymer electrolyte membranes of Example 1 and Comparative Examples 1 and 3 due to deionized water and methanol / deionized water mixed solvent were measured by ASTM-D570, and depended on the methanol concentration of the electrolyte membrane. The results of measuring the volume change rate are shown in FIG. As shown in FIG. 5, in the case of Example 1 in which the electrolyte membrane was reinforced by the polymer support and the inorganic additive was dispersed as a nanometer-class thin film, the best dimensional stability was exhibited, It was confirmed that excessive stress transmission to the gas diffusion layer due to swelling of the electrolyte membrane during actual driving of the battery can be prevented.

* Occlusive property of polymer support SEM photographs showing the states of the polymer supports of Example 1 and Comparative Example 2 are shown in FIGS. 6 and 7, respectively. As can be seen from FIGS. 6 and 7, in the polymer electrolyte membrane of Example 1, the pores on the polymer support are effectively blocked by the cation exchange resin and silicate as compared with Comparative Example 2.

* BET Porosity In order to know the binding property between the cation exchange resin and the polymer support, the BET porosity of Example 1 and Comparative Examples 1 to 3 was measured, and the results are shown in Table 2 below. According to Table 2, the cation exchange resin mixture of Example 1 dissolved in an organic solvent having a high dielectric constant is coated on a polymer support using an alcohol solvent as in Comparative Example 2. Further, it was confirmed that the porosity of the cation exchange resin and the inorganic additive in the polymer support having high hydrophobicity was improved and the porosity was decreased. In addition, the polymer electrolyte membrane of Example 1 obtains a lower porosity than the commercial electrolyte membrane of Comparative Example 3 due to the strong mutual bond between the cation exchange resin and the inorganic additive, and has a methanol fuel permeation blocking property. It can be seen that it can be obtained.

* Methanol permeability The methanol permeability of the electrolyte membrane is determined by placing the electrolyte membrane sample in a 2-compartment discharge cell and circulating a 15 wt% methanol / deionized water mixture and deionized water in both compartments. The concentration of methanol that permeated the membrane was measured by refractive index change. Mechanical properties were measured by ASTM-D882.

  As shown in Table 3, it can be seen that the methanol permeability of Examples 1 and 2 is significantly lower than those of Comparative Examples 2 to 3. In particular, it can be seen that the methanol permeability is lower than that of a conventionally used polymer electrolyte membrane having a thickness of 130 μm. This is considered to be because the pores on the polymer support were more effectively blocked in the polymer electrolyte membrane of Example 1 than in Comparative Examples 2 and 3, as shown in FIGS. It is done.

  Further, as shown in FIG. 8, the methanol permeability of Example 1 is similar to that of Comparative Example 1 shown in Table 3, but the conductivity at both ends of the electrolyte membrane of Example 1 is about the same. It can be seen that the battery output density was further superior to that of Comparative Example 1.

  FIG. 9 shows a case where 1M methanol is injected as a fuel into a fuel cell manufactured using the polymer electrolyte membranes of Example 1 and Comparative Example 3, and the moisture state and flow rate of air are adjusted as an oxidant. Inject and operate the battery once a day at 60 ° C. and again shut-down (shown as On / Off counts in FIG. 9) while driving the unit cell to As a result of measuring the change in inclination, Example 1 which was superior in membrane resistance (thickness / conductivity), fuel cutoff, dimensional stability, etc. of the electrolyte membrane compared to Comparative Example 3 using a commercial Nafion 115 membrane. Excellent output stability was demonstrated.

  FIG. 10 is a transmission electron micrograph of the electrolyte membrane produced according to Example 2, in which the cation exchange resin chain penetrates into the inorganic silicate plate having a layered structure, and the distance between the silicate additive plate and the plate. Is expanded to have an interlayer distance of about 3 nm, and in order for the silicate to exfoliate in the cation exchange resin to obtain a methanol barrier property, does the silicate collapse the plate-like structure having a certain interlayer distance? It was confirmed that the distance between the silicate layers should be maintained at 3 nm or more. However, when a small number of silicate particles are added in an excessive amount in the cation exchange resin, hydration of the cation exchange resin is hindered, resulting in a decrease in conductivity.

4 Fuel Supply Unit 5 Oxidant Supply Unit 14 Polymer Electrolyte Membrane 40 Electricity Generating Unit 43 Stack 45 Fuel Tank 51 Membrane-Electrode Assembly 53, 55 Separator (may be a bipolar plate)
400 Fuel cell system

Claims (22)

2 to 30% by weight of a porous polymer support having a porosity of 80 to 90%; and 50 to 90% by weight of cation exchange provided on and in the polymer support A resin and a fuel diffusion preventing layer containing 0.5 to 20% by weight of a plate-like or thin-film inorganic additive dispersed in the cation exchange resin;
A polymer electrolyte membrane for a direct fuel cell comprising:
The inorganic additive is selected from the group consisting of silica, alumina, mica, zeolite, barium titanate, inorganic silicate, and zirconium hydrogen phosphate;
The difference in conductivity of the other side of the ions one surface facing thereto of the polymer electrolyte membrane state, and are less than 5%,
The polymer electrolyte membrane has a thickness of 5 to 100 μm;
Polymer electrolyte membrane for direct methanol oxidation fuel cell.   The porous polymer support is selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyimide, polybenzoxazole, polybenzimidazole, and copolymers thereof. The polymer electrolyte membrane for a direct methanol oxidation fuel cell according to claim 1.   3. The direct methanol oxidation fuel cell according to claim 2, wherein the porous polymer support is selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, and copolymers thereof. Polymer electrolyte membrane.   The polymer electrolyte membrane for a direct methanol oxidation fuel cell according to claim 3, wherein the porous polymer support is a polytetrafluoroethylene homopolymer.   The cation exchange resin is a polymer resin having 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. The polymer electrolyte membrane for a direct methanol oxidation fuel cell according to any one of claims 1 to 4, wherein the polymer electrolyte membrane is a direct methanol oxidation fuel cell.   The cation exchange resin may be a fluoro polymer, polybenzimidazole polymer, polyimide polymer, polyetherimide polymer, polyphenylene sulfide polymer, polysulfone polymer, polyethersulfone polymer, poly The one or more hydrogen ion conductive polymers selected from the group consisting of an ether ketone polymer, a polyether-ether ketone polymer, and a polyphenylquinoxaline polymer. The polymer electrolyte membrane for a direct methanol oxidation fuel cell according to any one of 1 to 5.   The direct methanol oxidation fuel cell according to claim 6, wherein the cation exchange resin is selected from the group consisting of a fluoropolymer, a polybenzimidazole polymer, and a polysulfone polymer. Polymer electrolyte membrane.   The polymer electrolyte membrane for a direct methanol oxidation fuel cell according to any one of claims 1 to 7, wherein the inorganic additive is an inorganic silicate.   The inorganic silicate may be pyrophyllite-talc, montmorillonite (MMT), fluorohectorite, kaolinite, vermiculite, illite (illite). And a polymer electrolyte membrane for direct methanol oxidation fuel cells according to claim 8, wherein the polymer electrolyte membrane is selected from the group consisting of brittle mica.   The polymer electrolyte membrane for a direct methanol oxidation fuel cell according to claim 8 or 9, wherein the distance between the layers of the plate-like or thin-film inorganic silicate is 3 nm or more.   The polymer electrolyte membrane includes 70 to 80% by weight of the cation exchange resin, 2 to 15% by weight of the polymer support, and 0.5 to 10% by weight of the inorganic additive. The polymer electrolyte membrane for a direct methanol oxidation fuel cell according to any one of claims 1 to 10.   The polymer electrolyte membrane for a direct methanol oxidation fuel cell according to any one of claims 1 to 11, wherein the fuel diffusion preventing layer further includes an acrylate polymer.   The polymer electrolyte membrane for a direct methanol oxidation fuel cell according to any one of claims 1 to 12, wherein the porous polymer support has a thickness of 10 to 15 µm. Cation exchange resins having a cation exchange group in the side chain are N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMA), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), acetone. , Methyl ethyl ketone (MEK), tetramethyl urea, trimethyl phosphate, butyrolactone, isophorone, carbitol acetate, methyl isobutyl ketone, N-butyl acetate, cyclohexanone, diacetone alcohol, diisobutyl ketone, ethyl acetoacetate, glycol ether, propylene carbonate, ethylene A positive electrode produced by dissolving in a first organic solvent selected from the group consisting of carbonate, dimethyl carbonate, diethyl carbonate and mixtures thereof. And-exchange resin solution, silica, alumina, zeolite, barium titanate, no opportunity silicate, and a mixture of inorganic layered additive selected from the group consisting of zirconium hydrogen phosphate, the inorganic layered additive plate-like or film-like A step of obtaining a mixed solution existing in a state of being peeled; and a distribution of the inorganic layered additive on the porous polymer support having a porosity of 80 to 90%, and the electrolyte layer as a whole. The fuel diffusion prevention layer provided on the polymer support and in the polymer support is formed by coating twice or more so as to be constant over the cross section and then drying twice or more at 100 ° C. or more. Stage;
A method for producing a polymer electrolyte membrane for a direct methanol oxidation fuel cell, comprising: The method for producing a polymer electrolyte membrane for a direct methanol oxidation fuel cell according to claim 14 , wherein the inorganic layered additive is an inorganic silicate. The method for producing a polymer electrolyte membrane for a direct methanol oxidation fuel cell according to claim 14 or 15 , further comprising a step of treating the inorganic silicate with an organic agent before the step of obtaining the mixed solution. Method. The organic agent includes an alkylamine having 1 to 20 carbon atoms, an alkylenediamine having 1 to 20 carbon atoms, a quaternary ammonium having 1 to 20 carbon atoms, an alkyl ammonium salt having 1 to 20 carbon atoms, and a nitrogen-containing heterocyclic compound. The method for producing a polymer electrolyte membrane for a direct methanol oxidation fuel cell according to claim 16 , wherein the polymer electrolyte membrane is selected from the group consisting of: Claims wherein the inorganic layered additive 1-propanol, and 2-propanol and characterized in that it is mixed with the cation exchange resin in a state of being added to a second organic solvent selected from the group consisting of a mixture thereof Item 18. A method for producing a polymer electrolyte membrane for a direct methanol oxidation fuel cell according to any one of Items 14 to 17 . The mixing ratio of the cation exchange resin liquid and the inorganic layered additive claims wherein the inorganic additive to the cation exchange resin liquid 100 parts by weight, characterized in that 0.5 to 10 parts by weight The manufacturing method of the polymer electrolyte for direct methanol oxidation fuel cells of any one of 14-18 . Claims prior to the step of the coating, to the mixed solution, a step of adding an acrylate polymer in an amount of 5 to 10 parts by weight based on the cation exchange resin 100 parts by weight, characterized in that it further comprises Item 20. The method for producing a polymer electrolyte membrane for a direct methanol oxidation fuel cell according to any one of Items 14 to 19 . The method for producing a polymer electrolyte membrane for a direct methanol oxidation fuel cell according to any one of claims 14 to 20 , wherein the step of obtaining the mixed solution is performed by applying ultrasonic waves to the mixed solution. A direct methanol oxidation type comprising: an anode electrode and a cathode electrode arranged opposite to each other; and the polymer electrolyte membrane according to any one of claims 1 to 13 arranged between the anode electrode and the cathode electrode. Fuel cell system.