KR20070087790A - Polymer electrolyte for fuel cell, preparing method thereof and membrane-electrode assembly for fuel cell comprising same - Google Patents

Abstract

Provided are a polymer electrolyte membrane for a fuel cell which is excellent in dimension stability and hydrocarbon fuel barrier property, a method for preparing the polymer electrolyte membrane, and a membrane electrode assembly for a fuel cell using the polymer electrolyte membrane. A polymer electrolyte membrane comprises a polymer electrolyte membrane base; and a crosslinked polymer layer which is formed on at least one surface of the polymer electrolyte membrane, wherein the crosslinked polymer layer comprises a polymer matrix formed by crosslinking a curing oligomer and an inorganic additive present in the polymer matrix. Preferably the inorganic additive has an average particle size of 2-1,000 nm and the crosslinked polymer layer has a thickness of 1-10 micrometers.

Description

Polymer electrolyte membrane for fuel cell, method for manufacturing same, and membrane-electrode assembly for fuel cell comprising same TECHNICAL FIELD [0001]

1 is a view schematically showing a membrane-electrode assembly for a fuel cell according to an embodiment of the present invention,

2 is a view schematically showing a fuel cell system according to another embodiment of the present invention.

[Industrial use]

The present invention relates to a polymer electrolyte membrane for a fuel cell, a method for manufacturing the same, and a membrane-electrode assembly for a fuel cell including the same. More specifically, the dimensional stability and the hydrocarbon fuel barrier property can be improved to improve the output density of the fuel cell. A polymer electrolyte membrane for a fuel cell, a method of manufacturing the same, and a membrane-electrode assembly for a fuel cell including the same.

[Prior art]

A fuel cell is a power generation system that directly converts the chemical reaction energy of hydrogen and oxygen contained in hydrocarbon-based materials such as methanol, ethanol and natural gas into electrical energy. This fuel cell is a clean energy source that can replace fossil energy, and has the advantage of generating a wide range of outputs by stacking unit cells, and having an energy density of 4-10 times that of a small lithium battery. It is attracting attention as a compact and mobile portable power source.

Representative examples of the fuel cell include a polymer electrolyte fuel cell (PEMFC) and a direct oxidation fuel cell (Direct Oxidation Fuel Cell). When methanol is used as a fuel in the direct oxidation fuel cell, it is called a direct methanol fuel cell (DMFC).

The polymer electrolyte fuel cell has an advantage of having a high energy density and a high output, but requires attention to handling hydrogen gas and reforms fuel for reforming methane, methanol, natural gas, etc. to produce hydrogen as fuel gas. There is a problem that requires additional equipment such as a device.

On the other hand, the direct oxidation fuel cell has a lower energy density than the polymer electrolyte fuel cell, but it is easy to handle fuel and has a low operating temperature, so that it can be operated at room temperature, in particular, it does not require a fuel reformer.

In such fuel cell systems, the stack that substantially generates electricity comprises several unit cells consisting of a membrane-electrode assembly (MEA) and a separator (also called a bipolar plate). It has a structure laminated to several tens. The membrane-electrode assembly is called an anode electrode (also called "fuel electrode" or "oxidation electrode") and a cathode electrode (also called "air electrode" or "reduction electrode") with a polymer electrolyte membrane containing a hydrogen ion conductive polymer therebetween. ) Is located.

The principle of generating electricity in a fuel cell is that fuel is supplied to an anode electrode, which is a fuel electrode, adsorbed to a catalyst of the anode electrode, and the fuel is oxidized to generate hydrogen ions and electrons. Reaching the cathode electrode, hydrogen ions pass through the polymer electrolyte membrane and are delivered to the cathode electrode. An oxidant is supplied to the cathode, and the oxidant, hydrogen ions, and electrons react on the catalyst of the cathode to generate electricity while producing water.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polymer electrolyte membrane for a fuel cell and a method for producing the same, which are excellent in dimensional stability and fuel resistance, and can improve the output density of a fuel cell.

Another object of the present invention is to provide a membrane-electrode assembly including the polymer electrolyte membrane for a fuel cell.

In order to achieve the above object, the present invention comprises a polymer electrolyte membrane substrate, and a crosslinked polymer layer formed on at least one surface of the polymer electrolyte membrane substrate, wherein the crosslinked polymer layer is a polymer matrix formed by crosslinking a curable oligomer And it provides a polymer electrolyte membrane for a fuel cell comprising an inorganic additive present in the polymer matrix.

The present invention also provides a crosslinked polymer layer-forming composition comprising a curable oligomer, an inorganic additive, a reaction initiator, and a solvent, applying the crosslinked polymer layer-forming composition to at least one surface of a polymer electrolyte membrane substrate, and applying the composition. It provides a method for producing a polymer electrolyte membrane for a fuel cell comprising the step of forming a cross-linked polymer layer by irradiating ultraviolet light or electron beam to the composition for forming a cross-linked polymer layer.

The present invention also provides an anode electrode and a cathode electrode which face each other, and a membrane-electrode assembly for a fuel cell comprising a polymer electrolyte membrane having the above configuration and positioned between the anode electrode and the cathode electrode.

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

In the fuel cell, the polymer electrolyte membrane serves as an insulator for electrically separating the anode electrode and the cathode electrode, but serves as a medium for transferring hydrogen ions from the anode electrode to the cathode electrode during cell operation, and simultaneously serves to separate fuel and oxidant.

Therefore, the polymer electrolyte membrane should have excellent electrochemical stability, low ohmic loss at high current density, excellent resolution of reactants during cell operation, and a certain level of mechanical properties and dimensional stability for stack construction. Is required.

Perfluorosulfonate resin membranes used as polymer electrolyte membranes in fuel cells typically have a thickness of 50 to 175 μm, and are manufactured in the form of a film by extrusion or casting. At this time, in order to improve the dimensional stability and mechanical properties by increasing the thickness, the conductivity of the polymer electrolyte membrane is reduced, and when the thickness is decreased to decrease the resistance of the membrane, the mechanical properties of the polymer electrolyte membrane are deteriorated. there was. In addition, the perfluorosulfonate resin film has a thickness and volume change of about 15 to 20% due to swelling and shrinkage of hydrophilic clusters separated from hydrophobic regions and microphases according to temperature and degree of hydration. As a result, there was a disadvantage in that the dimensional stability was degraded in the thin film state.

Particularly, in the direct oxidation fuel cell, when the thickness of the polymer electrolyte membrane is too thin, fuel that is not reacted during the operation of the cell passes through the polymer membrane, resulting in fuel loss, and the fuel that passes through the polymer electrolyte membrane is oxidized at the cathode electrode, thereby reducing oxygen. There is a problem of reducing the battery performance by reducing the seat. In addition, dimensional swelling of the polymer electrolyte membrane due to fuel and water, the dimensional stability is lowered, there is a problem that the electrode and the electrolyte interface deteriorates.

On the other hand, in the present invention, by further forming a crosslinked polymer layer on one surface of the polymer electrolyte membrane substrate, the dimensional stability of the polymer electrolyte membrane and the fuel barrier properties are improved without a decrease in the hydrogen ion conductivity, and thus the output density of the fuel cell. Could improve.

In detail, the polymer electrolyte membrane according to an embodiment of the present invention includes a polymer electrolyte membrane substrate and a crosslinked polymer layer formed on at least one surface of the polymer electrolyte membrane substrate.

The crosslinked polymer layer preferably includes a polymer matrix formed by crosslinking a curable oligomer and an inorganic additive present in the polymer matrix.

Specific examples of the curable oligomer include polydimethylsiloxane, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,3-butylene glycol diacrylate, and ethylene glycol diacrylate. , Pentaerythritol tetraacrylate, triethylene glycol diacrylate, ethylene glycol diacrylate, dipentaerythritol diacrylate, sorbitol triacrylate, bisphenol A diacrylate derivative, trimethyl propane triacrylate, ethylene oxide addition type trimethyl propane Triacrylate, dipentaerythritol polyacrylate, 1,4-butanediol dimethacrylate, 1,3-butylene glycol dimethacrylate, ethylene glycol dimethacrylate, pentaerythritol tetramethacrylate, triethylene glycol Dimethacrylate, Ethylene Glycol Dimethacrylate, dipentaerythritol dimethacrylate, sorbitol trimethacrylate, bisphenol A dimethacrylate derivative, trimethylpropanetrimethacrylate, ethylene oxide addition type trimethylpropanetrimethacrylate, dipentaerythritol polymethacrylate Rate) or a mixture thereof.

 The curable oligomer serves to increase dimensional stability by crosslinking by ultraviolet or electron beam irradiation to form a polymer matrix. In this case, it is preferable that the curable oligomer maintain a degree of crosslinking of about 20 to 70%.

Inorganic additives are present in the polymer matrix.

The inorganic additive is a hydrophilic inorganic ion conductor, has no electrical conductivity and is water-insoluble. The inorganic additive is dispersed in the polymer matrix in the form of fine powder, thereby increasing the migration site of the hydrogen ions, thereby preventing the reduction of the hydrogen ion conductivity.

 The inorganic additive preferably has an average particle size of 2 to 1000 nm, preferably an average particle size of 10 to 300 nm. If the average particle size of the inorganic additive is smaller than 2 nm, the inorganic additive does not serve as a hydrogen transfer site and is not preferable. In addition, when it exceeds 1000 nm, since it is difficult to disperse, it is not preferable.

Such inorganic additives include phosphotungstic acid, phosphomolibdic acid, silicon tungstenic acid, zirconium hydrogen phosphate, and α-Zr (O _a1 PCH _a2 OH) _a (O _b1 PC _{b2 H b4 SO b5 H) b} · nH 2 O, γ-Zr (PO a1) (H a2 PO a3) a (HO b1 PC b2 H b3 SO b4 H) b · nH 2 O, Zr (O a1 PC a2 _{H a3) a Y b, Zr} (O a1 PCH a2 OH) a Y b · nH 2 O, α-Zr (O a1 PC a2 H a3 SO a4 H) a · nH 2 O, α-Zr (O a1 POH NH ₂ O, (P ₂ O ₅ ) _a (ZrO ₂ ) _b glass, P ₂ O ₅ -ZrO ₂ -SiO ₂ glass and their cation exchanged hetero polyacids One or more mixtures selected from the group consisting of can be used. Wherein a1, a2, a3, a, b1, b2, b3, b4, b5 and b are the same or independently from each other an integer from 0 to 14 and n is an integer from 0 to 50.

In addition, the inorganic additive may be used in a form supported on the inorganic carrier.

The inorganic additives supported on the inorganic carrier may be dispersed in a predetermined size in the polymer matrix to further improve mechanical properties. Examples of the inorganic carrier include silica (fumed silica, trade name: Aerosil, Cabo-sil, etc.), clay, alumina, mica, or zeolite (trade name: SAPO-5, XSM-5, AIPO-5, VPI-5, and MCM- 41 and the like) can be used. The clay includes pyrophylite-talc, montmorillonitel (MMT), saponite, fluorohectorite, kaolinte, vermiculit, laponite (laponite) laponite, illite, mica, brittle mica, tetrasilicic mica. The inorganic carrier may be used in an amount of 1 to 10 parts by weight, more preferably 1 to 3 parts by weight based on 100 parts by weight of the inorganic additive. If the content of the inorganic carrier is less than 1 part by weight, the properties of the inorganic support do not appear, which is not preferable.

The inorganic additive may be included in an amount of 1 to 15% by weight, and more preferably 2 to 5% by weight, based on the total weight of the crosslinked polymer layer. If the content of the inorganic additive is less than 1% by weight is not preferable because the hydrogen ion transfer force is lowered, if it exceeds 15% by weight it is not preferable because it may lower the dimensional stability through crosslinking.

As described above, the crosslinked polymer layer including the polymer matrix formed by crosslinking the curable oligomer and the inorganic additive present in the polymer matrix preferably has a thickness of 1 to 10 μm, more preferably 2 to 5 μm. It may have a thickness of. If the thickness of the crosslinked polymer layer is less than 1 mu m, it is not preferable because it is difficult to maintain dimensional stability, and if it exceeds 10 mu m, the hydrogen transfer force is lowered, which is not preferable.

The crosslinked polymer layer is located on at least one surface of the polymer electrolyte membrane substrate. More preferably, it may be located on both sides of the polymer electrolyte membrane substrate.

The polymer electrolyte membrane substrate has an ion exchange function for transferring hydrogen ions generated in the catalyst layer of the anode electrode to the catalyst layer of the cathode electrode, and is generally used as a polymer electrolyte membrane in a fuel cell and has a hydrogen ion conductivity. Anything prepared with may be used. Representative examples thereof include a polymer resin having a cation exchange group selected from the group consisting of sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, phosphonic acid groups and derivatives thereof in the side chain.

In addition, the cation exchange resin preferably has an ion exchange ratio of 3 to 33 and an equivalent weight (EW) of 700 to 2,000. The ion exchange ratio of the ion exchange resin is defined by the number of carbon and cation exchange groups in the polymer backbone. Moreover, when ion exchange ratio is 3-33, the equivalent weight corresponds to 700-2,000.

 Representative examples of the polymer resin include a fluorine polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer and a polyether ketone At least one hydrogen ion conductive polymer selected from a polymer, a polyether-etherketone-based polymer and a polyphenylquinoxaline-based polymer may be used, and more preferably poly (perfluorosulfonic acid), poly (perfluorocarboxyl) Acid), copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, defluorinated sulfide polyether ketones, aryl ketones, poly (2,2'-m-phenylene) -5,5'-bi One or more selected from the group consisting of benzimidazole (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole) and poly (2,5-benzimidazole) can be used.

In the hydrogen ion conductive group of the hydrogen ion conductive polymer, H may be substituted with Na, K, Li, Cs or tetrabutylammonium. In case of replacing H by Na in the ion-exchange group of the side chain terminal, NaOH is substituted in the preparation of the catalyst composition, and tetrabutylammonium hydroxide is used in the case of using tetrabutylammonium, and K, Li or Cs is also substituted with appropriate compounds. It can be substituted using. Since this substitution method is well known in the art, detailed description thereof will be omitted.

The polymer electrolyte membrane substrate preferably has a thickness of 10 to 200㎛. Since the method for producing the polymer electrolyte membrane substrate, the method and the conditions of the hot rolling are well known in the art, detailed description thereof will be omitted.

The polymer electrolyte membrane for a fuel cell having the configuration as described above may be prepared by the following manufacturing method.

Method for producing a polymer electrolyte membrane for a fuel cell according to an embodiment of the present invention to prepare a composition for forming a cross-linked polymer layer comprising a curable oligomer, an inorganic additive, a reaction initiator and a solvent, the composition for forming a cross-linked polymer layer And applying to at least one surface of the polymer electrolyte membrane substrate, and irradiating ultraviolet rays or electron beams to the applied composition for forming a crosslinked polymer layer to form a crosslinked polymer layer.

Specifically, first, a composition for forming a crosslinked polymer layer including a curable oligomer, an inorganic additive, a reaction initiator, and a solvent is prepared.

The crosslinking polymer layer-forming composition preferably contains 65 to 90 wt% of a curable oligomer, 1 to 15 wt% of an inorganic additive, 2 to 10 wt% of a reaction initiator, and a residual solvent, and a curable oligomer based on the total weight of the composition. More preferably, it contains 75 to 85% by weight, 2 to 5% by weight of inorganic additive, 2 to 7% by weight of reaction initiator, and 10 to 25% by weight of solvent. Within the content range, it is preferable to form a crosslinked polymer layer having excellent dimensional stability and excellent fuel barrier property.

The curable oligomer and the inorganic additive are the same as described above.

The reaction initiator plays a role for initiating curing of the oligomer. When the manufacturing process is completed to form a crosslinked polymer layer, the reaction initiator does not remain in the formed crosslinked polymer layer.

The reaction initiator is not particularly limited as long as it is a compound capable of initiating a crosslinking reaction of the oligomer. Typically, benzoin; Benzoin alkyl ethers such as benzoin methyl ether, benzoin ethyl ether and benzoin isopropylethyl; Acetophenones such as acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, and 1,1-dichloroacetophenone; 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropaneone-1,2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 Aminoacetophenones such as these; Anthraquinones such as 2-methylanthraquinone, 2-ethylanthraquinone and 2-t-butylanthraquinone; Thioxanthones, such as 2, 4- dimethyl thioxanthone; Ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; Benzophenones such as benzophenone; Xanthones; Triazines; Imidazoles; (2,6-dimetholoxybenzoyl) -2,4,4-pentylphosphineoxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylforce Phosphine oxides such as pin oxide and ethyl-2,4,6-trimethylbenzoylphenylphosphinate; Or it may be used such as various peroxides acids, preferably α- amino acetophenone: A (α-Amino Acetophenone Irgacure907 ^®, Ciba Specialty Chemicals Corp.).

The reaction initiator is preferably included in a predetermined ratio with respect to the content of the curable oligomer, more preferably may be included in 2 to 10 parts by weight based on 100 parts by weight of the curable oligomer. If the content of the reaction initiator is less than 2 parts by weight, the molecular weight of the oligomer is not preferable, and if it exceeds 10 parts by weight, it is difficult to control the reaction rate is not preferable.

The solvent may be appropriately selected and used according to the solubility and coating property of the composition for forming a crosslinked polymer layer. Specifically, N-methyl-2-pyrrolidinone, dimethylformamide, dimethylacetamide, tetrahydrofuran, Dimethyl sulfoxide, acetone, methyl ethyl ketone, tetramethyl urea, trimethyl phosphate, butyrolactone, isophorone, carbitol acetate, methyl isobutyl ketone, N-butyl acetate, cyclo hexanonone, diisobutyl ketone, ethyl Acetoacetate, glycol ether, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, etc. can be illustrated, These can be used individually or in mixture of 2 or more types.

The solvent may be included as a remainder in the composition for forming a crosslinked polymer layer to form a crosslinked polymer layer with an appropriate viscosity.

The prepared cross-linked polymer layer-forming composition is applied to a polymer electrolyte membrane substrate.

The coating process is selected from the group consisting of screen printing method, spray coating method, coating method using a doctor blade, gravure coating method, dip coating method, silk screen method, painting method and slot die coating method according to the viscosity of the composition It may be carried out by a method, but is not limited thereto. More preferably, the screen printing method can be used.

The polymer electrolyte membrane substrate may be the same as described above.

Thereafter, the polymer electrolyte membrane may be prepared by irradiating an ultraviolet ray or an electron beam to a polymer electrolyte membrane substrate coated with a composition for forming a crosslinked polymer layer to form a crosslinked polymer layer.

Since the curable oligomer forms a polymer matrix having a network structure by a crosslinking reaction in a uniformly mixed state with an inorganic additive, it is possible to effectively improve the dimensional stability of the polymer electrolyte membrane and also to suppress crossover through the polymer electrolyte membrane of the reactants. have.

The polymer electrolyte membrane prepared as described above has excellent dimensional stability and fuel barrier property, and when the electrolyte membrane is applied to a fuel cell, the output density can be improved.

Such a polymer electrolyte membrane may be positioned between the cathode electrode and the anode electrode to form a membrane-electrode assembly.

That is, the membrane-electrode assembly for a fuel cell according to an embodiment of the present invention includes an anode electrode and a cathode electrode disposed to face each other; And the polymer electrolyte membrane positioned between the anode electrode and the cathode electrode.

1 is a schematic cross-sectional view of a membrane-electrode assembly for a fuel cell of the present invention.

Referring to FIG. 1, the membrane-electrode assembly 10 according to an exemplary embodiment of the present invention may include the polymer electrolyte membrane 50 and the fuel cell electrodes 20 and 20 disposed on both surfaces of the polymer electrolyte membrane 50, respectively. Include '). The electrodes 20 and 20 'include electrode substrates 40 and 40' and catalyst layers 30 and 30 'formed on the surface of the electrode substrate.

In the membrane-electrode assembly 10, the electrode 20 disposed on one surface of the polymer electrolyte membrane 50 is called an anode electrode (or a cathode electrode), and the electrode 20 ′ disposed on the other surface is called a cathode electrode ( Or anode electrode). The anode electrode 20 causes an oxidation reaction to generate hydrogen ions and electrons from the fuel transferred to the catalyst layer 30 through the electrode base 40, and the polymer electrolyte membrane 50 is hydrogen generated from the anode electrode 20. Ions are moved to the cathode electrode 20 ', and the cathode electrode 20' passes through the hydrogen ions supplied through the polymer electrolyte membrane 50 and the electrode base 40 'and is transferred to the catalyst layer 30'. Causes a reduction reaction to produce water.

 The catalyst layer catalyzes the related reaction (oxidation of fuel and reduction of oxidant) and preferably includes a metal catalyst. The metal catalyst may be platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, platinum-M alloy, platinum-ruthenium-M alloy (M = Ga, Ti, V, Sn, W, One or more selected from the group consisting of Rh, Mo, Cr, Mn, Fe, Co, Ni, Cu, and Zn). As described above, the anode electrode and the cathode electrode may use the same material, but in order to prevent the catalyst poisoning caused by CO generated during the anode electrode reaction in the direct oxidation fuel cell, a platinum-ruthenium alloy catalyst is used as the anode. It is more preferable as an electrode catalyst. Representative examples include Pt, Pt / Ru, Pt / W, Pt / Ni, Pt / Sn, Pt / Mo, Pt / Pd, Pt / Fe, Pt / Cr, Pt / Co, Pt / Ru / W, Pt / One or more selected from the group consisting of Ru / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni, and Pt / Ru / Sn / W can be used.

In addition, such a metal catalyst may be used as the metal catalyst (black) itself, or may be supported on a carrier. As the carrier, carbon such as acetylene black, denka black, activated carbon, ketjen black, graphite may be used, or inorganic fine particles such as alumina, silica, titania, zirconia or the like may be used. .

The electrode substrate plays a role of supporting the electrode and diffuses the fuel and the oxidant to the catalyst layer, thereby serving to easily access the fuel and the oxidant to the catalyst layer. A conductive substrate is used as the electrode substrate, and representative examples thereof include carbon paper, carbon cloth, carbon felt, or metal cloth (porous film or polymer composed of metal cloth in a fibrous state). The metal film formed on the surface of the fabric formed of fibers (referred to as metalized polymer fiber) may be used, but is not limited thereto.

In addition, it is preferable to use a water-repellent treatment with a fluorine-based resin as the electrode base material because it can prevent the reactant diffusion efficiency from being lowered by water generated when the fuel cell is driven. As the fluorine-based resin, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated ethylene propylene, polychlorotrifluoroethylene, fluoroethylene polymer, or the like may be used.

In addition, a microporous layer may be further included on the electrode substrate to enhance the diffusion effect of the reactants on the electrode substrate. These microporous layers are generally conductive powders having a small particle diameter, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotubes, carbon nanowires, and carbon nanohorns. -horn or carbon nano ring. The microporous layer is prepared by applying a composition containing a conductive powder, a binder resin and a solvent to the electrode substrate. As the binder resin, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, cellulose acetate, and the like may be preferably used. The solvent may be ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, or the like. Alcohol, water, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone and the like can be preferably used. The coating process may be screen printing, spray coating, or a coating method using a doctor blade according to the viscosity of the composition, but is not limited thereto.

The polymer electrolyte membrane is the same as described above.

The membrane-electrode assembly having such a structure can be employed in both phosphoric acid type, polymer electrolyte type and direct oxidation type fuel cell systems.

The present invention also provides a fuel cell system comprising the membrane-electrode assembly.

The fuel cell system of the present invention includes at least one electricity generating portion, a fuel supply portion and an oxidant supply portion.

The electricity generating portion includes a membrane-electrode assembly and a separator (also called bipolar plate). The membrane-electrode assembly includes a polymer electrolyte membrane and cathode and anode electrodes existing on both sides of the polymer electrolyte membrane. The electricity generation unit serves to generate electricity through the oxidation reaction of the fuel and the reduction reaction of the oxidant.

The fuel supply unit serves to supply fuel to the electricity generation unit, and the oxidant supply unit serves to supply an oxidant such as oxygen or air to the electricity generation unit.

In the present invention, the fuel may include hydrogen or hydrocarbon fuel in gas or liquid state. Representative examples of the hydrocarbon fuel include methanol, ethanol, propanol, butanol or natural gas.

A schematic structure of the fuel cell system of the present invention is shown in FIG. 2, which will be described in more detail with reference to the following. Although the structure shown in FIG. 2 shows a system for supplying fuel and oxidant to an electric generator using a pump, the fuel cell system of the present invention is not limited to such a structure, and a fuel cell using a diffusion method without using a pump is shown. Of course, it can also be used for system architecture.

The fuel cell system 1 of the present invention includes at least one electricity generation unit 3 for generating electrical energy through an oxidation reaction of a fuel and a reduction reaction of an oxidant, a fuel supply unit 5 for supplying the fuel, And an oxidant supply unit 7 for supplying an oxidant to the electricity generation unit 3.

In addition, the fuel supply unit 5 for supplying the fuel may include a fuel tank 9 storing fuel and a fuel pump 11 connected to the fuel tank 9. The fuel pump 11 serves to discharge the fuel stored in the fuel tank 9 by a predetermined pumping force.

The oxidant supply unit 7 for supplying the oxidant to the electricity generating unit 3 includes at least one oxidant pump 13 for sucking the oxidant with a predetermined pumping force.

The electricity generator 3 is composed of a membrane-electrode assembly 17 for oxidizing and reducing a fuel and an oxidant, and a separator 19 and 19 'for supplying fuel and an oxidant to both sides of the membrane-electrode assembly. At least one of these electricity generating units 3 constitutes a stack 15.

 Hereinafter, examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

(Example 1)

After dissolving 80% by weight of polyethylene glycol diacrylate (Aldrich, MW = 742) curable oligomer and 5% by weight of an inorganic additive of phosphotungstic acid supported by montmorillonite in 10% by weight of dimethylformamide, mechanical Stirred. Then 5 wt% of chlorobenzophenone was further added and stirred for 5 minutes to prepare a composition for forming a crosslinked polymer layer.

On the one side of the polymer electrolyte membrane substrate prepared by treating a commercial Nafion 115 membrane (125 μm) with 100% of 3% hydrogen peroxide and 0.5 M sulfuric acid solution for 1 hour and then washing with 100 ° C. deionized water for 1 hour. The cross-linked polymer layer-forming composition was coated and irradiated with 1 kV of ultraviolet rays to form a cross-linked polymer layer having a thickness of 5 μm to prepare a polymer electrolyte membrane.

5 wt% Nafion / H ₂ O / 2-propanol solution, dipropylene glycol and deionized water were added to Pt-Ru black (black, referring to unsupported catalyst, Johnson Matthey, HiSpec 6000) and Pt black (Johnson Matthey , HiSpec 1000) particles were mixed with each other to prepare a catalyst slurry, followed by screen printing on a Teflon film and drying to form a catalyst layer. The catalyst layer was positioned on the previously prepared polymer electrolyte membrane, and then thermally compressed at 135 ° C. at a pressure of 50 kgf / cm 2 for 3 minutes to form a cathode catalyst layer on the polymer electrolyte membrane. An anode catalyst layer was formed on the other side of the polymer electrolyte membrane in the same manner as above. In this case, the catalyst loadings in the cathode catalyst layer and the anode catalyst layer were 4 mg / cm 2, respectively. Subsequently, an ELAT electrode layer (Diffusion Layer) of E-Tek was placed on the cathode and anode catalyst layers to prepare a three-layer membrane-electrode assembly.

The prepared membrane / electrode assembly was inserted between polytetrafluoroethylene-coated glass fiber gaskets, and then inserted into two bipolar plates in which gas flow channels and cooling channels of a predetermined shape were formed. Thereafter, a single cell was manufactured by pressing between copper end plates.

(Comparative Example 1)

Except for using a polymer electrolyte membrane prepared by treating a commercial Nafion 115 membrane (125 μm) with 100% of 3% hydrogen peroxide and 0.5M aqueous sulfuric acid solution for 1 hour and then washing with 100 ° C deionized water for 1 hour. A single cell was prepared in the same manner as in Example 1.

Ion conductivity, dimensional stability, and methanol permeability were measured for the polymer electrolyte membranes of Example 1 and Comparative Example 1.

The ionic conductivity was measured using BekkTech's conductivity measuring cell at an impedance of 60 ° C and a relative humidity of RH 100%, and the dimensional stability of the electrolyte membrane at the center of the polymer electrolyte-compartment diffusion cell at 60 ° C. When the sample was placed and circulated with 15% by weight methanol / deionized water mixed liquid and deionized water at both ends, the concentration of methanol that passed through the electrolyte membrane was measured as a change in refractive index.

In addition, for the unit cells according to Example 1 and Comparative Example 1, the output change of the unit cell according to the battery temperature and the methanol concentration was measured in the state in which methanol and air (ambient air) were introduced. The results are shown in Table 1 below.

Thickness of Polymer Electrolyte Membrane (㎛) Conductivity (S / cm) Area change rate (%) Methanol Permeability (cm ² / sec) Power density at 60 ℃ (0.4V, mV / cm ² ) Example 1 130 0.1 10 5.0X10 ⁷ 120 Comparative Example 1 125 0.1 30 2.0X10 ⁶ 100

As shown in Table 1 above, when compared with the polymer electrolyte membrane of Example 1 and the pure Nafion membrane of Comparative Example 1, the polymer electrolyte membrane of Example 1 had a hydrogen ion conductivity equivalent to that of the pure Nafion membrane of Comparative Example 1 Although shown, it was confirmed that the superior in terms of the dimensional stability and the barrier to methanol.

In addition, as a result of measuring the output density of the unit cells of Example 1 and Comparative Example 1 including the polymer electrolyte membrane, the unit cell of Example 1 including the polymer electrolyte membrane of the present invention shows excellent output density under the same conditions at 60 ℃ operation Could confirm.

The polymer electrolyte membrane according to the present invention is excellent in dimensional stability and fuel barrier property, and can improve the power density of the fuel cell.

Claims (13)

Polymer electrolyte membrane substrates; And It includes a cross-linked polymer layer formed on at least one surface of the polymer electrolyte membrane substrate, The crosslinked polymer layer is A polymer matrix formed by crosslinking of a curable oligomer; And Including an inorganic additive present in the polymer matrix Polymer electrolyte membrane for fuel cell. The method of claim 1, The curable oligomer is polydimethylsiloxane, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,3-butylene glycol diacrylate, ethylene glycol diacrylate, pentaerythritol tetra Acrylate, triethylene glycol diacrylate, ethylene glycol diacrylate, dipentaerythritol diacrylate, sorbitol triacrylate, bisphenol A diacrylate derivative, trimethyl propane triacrylate, ethylene oxide addition type trimethyl propane triacrylate, Dipentaerythritol polyacrylate, 1,4-butanediol dimethacrylate, 1,3-butylene glycol dimethacrylate, ethylene glycol dimethacrylate, pentaerythritol tetramethacrylate, triethylene glycol dimethacrylate Ethylene Glycol Dimethacrylate , Dipentaerythritol dimethacrylate, sorbitol trimethacrylate, bisphenol A dimethacrylate derivative, trimethylpropanetrimethacrylate, ethylene oxide addition type trimethylpropanetrimethacrylate, dipentaerythritol polymethacrylate, etc.) And a polymer electrolyte membrane for a fuel cell that is selected from the group consisting of these. The method of claim 1, The inorganic additive is a polymer electrolyte membrane for a fuel cell having an average particle size of 2 to 1000nm. The method of claim 1, The inorganic additive is phosphotungstic acid (phosphotungstic acid), phosphorus molybdate (phosphomolibdic acid), silicon tungstenic acid (silicotungstic acid), zirconium hydrogen phosphate, α-Zr (O _a1 PCH _a2 OH) _a (O _b1 PC _b2 H _b4 SO _b5 H) _b · nH ₂ O (a here, a1, a2, a, b1 , b2, b4, b5 and b are the same or independently represent an integer of 0 to 14 to each other, 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 is the same or independently of each other is an integer from 0 to 14, n is an integer from 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 of each other an integer from 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 from each other an integer from 0 to 14 , n is an integer of 0 to 50), α-Zr (O a1 PC a2 H a3 SO a4 H) a · nH 2 O ( where, a1, a2, a3, a4 and a The same or independently represent an integer of 0 to 14 to each other, n is an integer of 0 to 50), (in which α-Zr (O _a1 POH) · nH ₂ O, a1 is an integer of 0-14), (P ₂ O ₅ ) _a (ZrO ₂ ) _b (where a and b are the same or independently of each other an integer from 0 to 14) glass, P ₂ O ₅ -ZrO ₂ -SiO ₂ glass and their cation exchanged hetero At least one polymer electrolyte membrane for fuel cells selected from the group consisting of polyacids. The method of claim 1, The inorganic additive is a polymer electrolyte membrane for a fuel cell, the inorganic additive is supported on an inorganic carrier. The method of claim 1, The inorganic carrier is at least one polymer electrolyte membrane for a fuel cell selected from the group consisting of silica, clay, alumina, mica and zeolite. The method of claim 1, The inorganic additive is a polymer electrolyte membrane for a fuel cell that is contained in 1 to 15% by weight based on the total weight of the crosslinked polymer layer. The method of claim 1, The crosslinked polymer layer is a polymer electrolyte membrane for a fuel cell having a thickness of 1 to 10㎛. The method of claim 1, The polymer electrolyte membrane substrate is a fuel cell polymer electrolyte membrane comprising a polymer resin 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. Preparing a composition for forming a crosslinked polymer layer comprising a curable oligomer, an inorganic additive, a reaction initiator, and a solvent, Applying the composition for forming a crosslinked polymer layer to at least one surface of a polymer electrolyte membrane substrate, Method for producing a polymer electrolyte membrane for a fuel cell comprising the step of forming a cross-linked polymer layer by irradiating the applied composition for forming a cross-linked polymer layer with ultraviolet light or electron beam. The method of claim 10, The crosslinked polymer layer-forming composition includes a fuel cell polymer electrolyte comprising 65 to 90 wt% of a curable oligomer, 1 to 15 wt% of an inorganic additive, 2 to 10 wt% of a reaction initiator, and the remainder of the solvent based on the total weight of the composition. Method of preparing the membrane. The method of claim 10, The reaction initiators are benzoin, benzoin alkyl ethers, acetophenones, aminoacetophenones, anthraquinones, thioxanthones, ketals, benzophenones, xanthones, triazines, imidazoles, phosphines Method for producing a polymer electrolyte membrane for a fuel cell which is at least one selected from the group consisting of oxides and peroxides. An anode electrode and a cathode electrode located opposite each other; And The polymer electrolyte membrane according to any one of claims 1 to 9, which is located between the anode electrode and the cathode electrode. Membrane-electrode assembly for fuel cell comprising a.

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