KR20090019175A - Method of manufacturing membrane-electrode assembly for fuel cell, and membrane-electrode assembly for fuel cell manufactured accordingly - Google Patents

Abstract

The present invention relates to a method for manufacturing a membrane-electrode assembly for a fuel cell and a membrane-electrode assembly manufactured according to the above, the method for forming a microporous layer by applying a composition for forming a microporous layer on a transfer substrate. ; Forming a catalyst layer by applying a composition for forming a catalyst layer on the microporous layer; Transferring the microporous layer and the catalyst layer to the polymer electrolyte membrane by placing the polymer electrolyte membrane so that the catalyst layer and the polymer electrolyte membrane face each other with respect to the transfer substrate on which the microporous layer and the catalyst layer are sequentially formed; And bonding the electrode substrate so that the microporous layer and the electrode substrate face each other with respect to the polymer electrolyte membrane to which the microporous layer and the catalyst layer are transferred.

The method of manufacturing a membrane-electrode assembly for a fuel cell according to the present invention can improve the utilization rate of the catalyst because of excellent catalyst transfer rate, and there is no fear of peeling between the catalyst layer and the microporous layer. A fuel cell comprising a shows excellent cell characteristics.

Description

METHOD OF PREPARING MEMBRANE-ELECTRODE ASSEMBLY FOR FUEL CELL, AND MEMBRANE-ELECTRODE ASSEMBLY FOR FUEL CELL PREPARED THEREBY}

The present invention relates to a method of manufacturing a membrane-electrode assembly for a fuel cell and a membrane-electrode assembly for a fuel cell manufactured according to the present invention. More specifically, the utilization rate of the catalyst can be improved, and there is a fear of separation between the catalyst layer and the microporous layer. The present invention relates to a fuel cell membrane-electrode assembly capable of improving battery characteristics and a fuel cell membrane-electrode assembly manufactured accordingly.

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 the 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 a “fuel electrode” or an “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 method for producing a membrane-electrode assembly for a fuel cell, which can improve the utilization of the catalyst and can improve the battery characteristics without fear of peeling between the catalyst layer and the microporous layer.

Still another object of the present invention is to provide a membrane-electrode assembly for a fuel cell manufactured by the above method.

In order to achieve the above object, the present invention is to form a microporous layer by applying a composition for forming a microporous layer on the transfer substrate; Forming a catalyst layer by applying a composition for forming a catalyst layer on the microporous layer; Transferring the microporous layer and the catalyst layer to the polymer electrolyte membrane by placing the polymer electrolyte membrane so that the catalyst layer and the polymer electrolyte membrane face each other with respect to the transfer substrate on which the microporous layer and the catalyst layer are sequentially formed; And positioning the electrode substrate so that the microporous layer and the electrode substrate face each other with respect to the polymer electrolyte membrane to which the microporous layer and the catalyst layer are transferred.

The method of manufacturing a membrane-electrode assembly for a fuel cell according to the present invention can improve the utilization rate of the catalyst because of excellent catalyst transfer rate, and there is no fear of peeling between the catalyst layer and the microporous layer. A fuel cell comprising a shows excellent cell characteristics.

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

In a fuel cell, the membrane-electrode assembly is composed of a polymer electrolyte membrane and anode and cathode electrodes located on both sides of the polymer electrolyte membrane, and the electricity is generated by the oxidation of the fuel and the reduction reaction of the oxidant in the membrane-electrode assembly. do. The reaction occurring in the membrane-electrode assembly may occur well when the interfacial adhesion between the polymer electrolyte membrane and the electrode is excellent, and the contact area with the electrode at the interface should be wide.

Typically, the membrane-electrode assembly is manufactured by forming a catalyst layer on an electrode substrate and then bonding it to the polymer electrolyte membrane, or first forming a catalyst layer on the polymer electrolyte membrane and then joining the electrode substrate. In this case, the catalyst layer is dried by directly applying the composition for forming a catalyst layer to a polymer electrolyte membrane or an electrode substrate, or by applying and drying the composition for forming a catalyst layer on a substrate for transfer to form a catalyst layer on a film and then transferring to a polymer electrolyte membrane. It may be prepared by a decal transfer method.

However, in the method of directly applying the composition for forming the catalyst layer on the polymer electrolyte membrane, the polymer electrolyte membrane is swelled by the solvent contained in the composition to deform the form, and as a result, the interface adhesion with the catalyst layer There was a problem of deterioration. Particularly, in the case of the cathode electrode, pores must be included for the discharge of water, which is a reaction product generated by the reaction in the cathode electrode. In this case, there is a problem in that the interfacial adhesion with the polymer electrolyte membrane is lowered due to the pores in the cathode catalyst layer.

In addition, in the dry transfer method, a tear occurs between the transfer substrate and the catalyst layer, and thus the catalyst transfer rate is low, and in the case of a hydrocarbon electrolyte membrane having a glass transition temperature of 200 ° C. or more, between the catalyst layer and the electrode substrate, or between the catalyst layer and the microporous layer. There existed a problem that there was a high possibility of peeling in between.

In contrast, in the present invention, the microporous layer and the catalyst layer are sequentially formed on the transfer substrate in the preparation of the membrane-electrode assembly, and then transferred to the polymer electrolyte membrane, thereby improving the catalyst transfer rate and adhering force between the catalyst layer and the microporous layer. Can be increased.

Unless otherwise specified in the present specification, the following terms mean the following.

An "alkyl group" is an alkyl group having 1 to 20 carbon atoms, an "alkoxy group" is an alkoxy group having 1 to 20 carbon atoms, an "alkylene group" is an alkylene group having 2 to 20 carbon atoms, an "arylene group" is an aryl having 6 to 24 carbon atoms It means Rengi.

1 is a process diagram briefly showing a method of manufacturing a membrane-electrode assembly according to an embodiment of the present invention.

Referring to Figure 1, the manufacturing method of the membrane-electrode assembly according to an embodiment of the present invention comprises the steps of applying a composition for forming a microporous layer on the transfer substrate to form a microporous layer (S1); Forming a catalyst layer by applying a composition for forming a catalyst layer on the microporous layer (S2); Transferring the microporous layer and the catalyst layer to the polymer electrolyte membrane by placing the polymer electrolyte membrane so that the catalyst layer and the polymer electrolyte membrane face each other with respect to the transfer substrate on which the microporous layer and the catalyst layer are sequentially formed (S3); And attaching the electrode substrate so that the microporous layer and the electrode substrate face each other with respect to the polymer electrolyte membrane to which the microporous layer and the catalyst layer are transferred (S4).

Hereinafter, the method of manufacturing the membrane-electrode assembly will be described in more detail at each step. First, the microporous layer is formed on the transfer substrate to form a microporous layer (S1).

As the transfer substrate, any substrate can be used as long as the substrate can easily peel off the microporous layer formed normally. Specifically, a glass substrate or a release film can be used, and it is more preferable to use a release film that can be peeled off smoothly without peeling off the catalyst layer.

Examples of the release film include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and ethylene / tetrafluoroethylene (ETFE)), polyvinylidene fluoride, copolymers thereof, and mixtures thereof; Or in the group consisting of polyimide (manufactured by Kapton ^® DuPont), polyethylene, polypropylene, polyethylene terephthalate, polyester (manufactured by Mylar ^® DuPont), copolymers thereof and mixtures thereof The non-fluorine-based high molecular film of choice can be used.

The microporous layer-forming composition may be prepared by dispersing and dissolving a conductive powder and a binder resin in a solvent.

The conductive powder is generally a conductive powder having a small particle size, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotube, carbon nanowire, carbon nano horn (carbon nano) -horn, carbon nano ring, and mixtures thereof may be used.

The binder resin may be polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, polyvinyl alcohol, cellulose acetate And those selected from the group consisting of copolymers and mixtures thereof.

The binder resin is preferably contained in 3 to 30% by weight, more preferably 10 to 15% by weight based on the total weight of the composition for forming the microporous layer. When the content of the binder resin in the composition for forming the microporous layer is less than 3% by weight, peeling with the substrate for transferring in the transfer process is not easy, and the adhesion to the catalyst layer is lowered, which is not preferable. In addition, when the content of the binder resin exceeds 30% by weight, the electrical resistance increases due to the decrease in the relative content of the conductive powder in the microporous layer, which is not preferable.

The binder resin is preferably included 5 to 50 parts by weight, more preferably 7 to 30 parts by weight with respect to 100 parts by weight of the conductive powder. When the content of the binder resin to the conductive powder is less than 5 parts by weight, it is not preferable to form a coating layer due to the decrease in bonding strength, and when it exceeds 50 parts by weight, the electrical resistance increases, which is not preferable.

The solvent may be preferably an alcohol solvent such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, tetrahydrofuran, or the like. .

The microporous layer forming composition is for dispersibility improvement of the conductivity in addition to the above components, a stereo version light Jin, dihydrate castor oil or disabled peobik (disperbyk ^®, byk Co.) further comprise a dispersing agent such as additives, such as It may be.

Thereafter, the prepared microporous layer-forming composition may be mixed more uniformly by mechanical mixing or ultrasonic mixing.

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

The composition for forming the microporous layer coated on the transfer substrate is dried by a conventional method such as natural drying and hot air dryness to form a microporous layer which serves to enhance the diffusion effect of the reactants on the electrode substrate.

A catalyst layer is formed by applying a composition for forming a catalyst layer on the microporous layer (S2).

The composition for forming a catalyst layer may be prepared by dispersing and dissolving a catalyst which catalyzes a reaction (oxidation of fuel and reduction of an oxidant), and optionally a binder resin in a solvent.

As the catalyst, any one that can be used as a catalyst may participate in the reaction of the fuel cell, and as a representative example, a platinum-based catalyst may be used. The platinum-based catalyst is platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, or platinum-M alloy (M is Ga, Ti, V, Cr, Mn, Fe, Co, Ni , At least one catalyst selected from the group consisting of Cu, Zn, Sn, Mo, W, Rh, and Ru). Specific 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 / Ru One or more selected from the group consisting of / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni, and Pt / Ru / Sn / W can be used.

In addition, such a catalyst may be used as the catalyst itself (black), or may be used on a carrier. As the carrier, carbon-based materials such as graphite, denka black, ketjen black, acetylene black, carbon nanotube, carbon nanofiber, carbon nanowire, carbon nanoball, or activated carbon may be used, and alumina, silica, zirconia, Or inorganic fine particles such as titania may be used, but carbon-based materials are generally used.

It is preferable to use the solvent which shows polarity as said solvent. Specifically water; Alcohol solvents such as methanol, ethanol and isopropyl alcohol; Amide solvents such as N, N-dimethylacetamide (DMAC), N-methyl pyrrolidone (NMP) and dimethylformamide (DMF); And sulfoxide solvents such as dimethyl sulfoxide and the like.

The catalyst layer forming composition may further include a binder resin to improve adhesion of the catalyst layer and transfer of hydrogen ions.

It is preferable to use a polymer resin having hydrogen ion conductivity as the binder resin, more preferably 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. Any polymer resin which has can be used. Specifically, a fluorine polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer, a polyether ketone polymer, a polyether Hydrogen-ion conductive polymers selected from the group consisting of ether ketone polymers, polyphenylquinoxaline polymers, and combinations thereof, preferably poly (perfluorosulfonic acid), poly (perfluorocarboxylic 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 Benzimidazole] (poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole]), poly (2,5-benzimidazole), and a hydrogen ion selected from the group consisting of a combination thereof Use conductive polymer can do.

It is also possible to substitute H with Na, K, Li, Cs or tetrabutylammonium in the cation exchanger of such a hydrogen ion conductive polymer. In the cation exchanger of the hydrogen-ion conductive polymer, NaOH is substituted when H is replaced with Na, and tetrabutylammonium hydroxide is substituted when replacing with tetrabutylammonium, and K, Li or Cs may be substituted with an appropriate compound. It can be substituted. Since this substitution method is well known in the art, detailed description thereof will be omitted.

The binder resin may be used in the form of a single substance or a mixture, and may also be optionally used with a nonconductive compound for the purpose of further improving adhesion to the polymer electrolyte membrane. It is preferable to adjust the usage-amount so that it may be suitable for a purpose of use.

Examples of the non-conductive compound include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro alkylvinylether copolymer (PFA), and ethylene / tetrafluoro Ethylene / tetrafluoroethylene (ETFE), ethylenechlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), dode More preferably, they are selected from the group consisting of silbenzenesulfonic acid, sorbitol, copolymers thereof and mixtures thereof.

Thereafter, the prepared composition for forming a catalyst layer may be subjected to additional mechanical mixing or ultrasonic mixing in the same manner as described above to mix each component in the composition more uniformly.

The coating process of the composition for forming a catalyst layer may be performed by a coating method suitable for viscosity of the composition, in the same manner as the method for applying the composition for forming a microporous layer, but is not limited thereto. More preferably, a coating method using a doctor blade capable of forming screen printing or a catalyst layer with a uniform thickness may be used.

The catalyst layer-forming composition coated on the microporous layer is dried by conventional methods such as natural drying and hot air dryness to form a catalyst layer.

The polymer electrolyte membrane is positioned so that the catalyst layer and the polymer electrolyte membrane face each other with respect to the transfer substrate on which the microporous layer and the catalyst layer are sequentially formed, followed by hot rolling to transfer the microporous layer and the catalyst layer to the polymer electrolyte membrane (S3).

The polymer electrolyte membrane functions as an ion exchange to transfer 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 is made of a polymer resin having hydrogen ion conductivity. Anything can be used.

It is preferable to use a polymer having excellent hydrogen ion conductivity as the polymer electrolyte membrane. Representative examples thereof include a polymer resin having a cation exchange group selected from a 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, that is, a hydrogen ion conductive group.

Specifically, hydrocarbon polymer, fluorine polymer, benzimidazole polymer, polyimide polymer, polyetherimide polymer, polyphenylene sulfide polymer, polysulfone polymer, polyether sulfone polymer, polyether ketone It can be used selected from the group consisting of a polymer, a polyphenylquinoxaline-based polymer, copolymers thereof and mixtures thereof.

Examples of the hydrocarbon-based polymer include a hydrogen ion conductive group, and a material selected from the group consisting of polyether ether ketone, polyalkylene oxide, polyacrylic acid-based ionomer, polyarylene ether, and combinations thereof. Preferably it is selected from the group consisting of sulfonated polyether ether ketone, sulfonated polypropylene oxide, sulfonated polyacrylic acid series ionomer, sulfonated polyarylene ether, and combinations thereof.

Such hydrocarbon-based polymers form small sized ion clusters in contact with an aqueous alcohol solution, thereby facilitating the reception of high molecular hydrogen ions.

Further, a hydrogen ion conductive polymer other than the hydrocarbon-based polymer is preferably tetrafluoro containing poly (perfluorosulfonic acid) (generally sold as Nafion), poly (perfluorocarboxylic acid), sulfonic acid group. Copolymers of ethylene and fluorovinyl ether, defluorinated sulfide polyether ketones, aryl ketones, poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole [(poly [2, 2 '-(m-phenylene) -5,5'-bibenzimidazole]), poly (2,5-benzimidazole), and combinations thereof.

It is also possible to substitute H with Na, K, Li, Cs or tetrabutylammonium in the cation exchanger of such a hydrogen ion conductive polymer. In the cation exchanger at the side chain terminal, Na is used for replacing H with Na, and tetrabutylammonium hydroxide is used for tetrabutylammonium, and K, Li or Cs may be substituted with an appropriate compound. It can be substituted. Since this substitution method is well known in the art, detailed description thereof will be omitted.

The transfer process may be performed by hot rolling the microporous layer and the catalyst layer formed on the transfer substrate to face the polymer electrolyte membrane.

The temperature at the time of hot rolling is preferably 130 to 200 ° C, more preferably 135 to 150 ° C. In addition, the pressure during hot rolling is preferably 40 to 200 kgf / cm ² , more preferably 50 to 150 kgf / cm ² . Within the temperature and pressure range, the batch transfer of the microporous layer and the catalyst layer is smooth, and preferably, the batch transfer of the microporous layer and the catalyst layer is not complete or the microporous layer or the catalyst layer has an excessively dense structure. It is undesirable for the ingress and removal of reactants.

By the transfer process, the microporous layer and the catalyst layer formed on the transfer substrate are transferred to the polymer electrolyte membrane at once.

The electrode substrate is positioned so that the microporous layer and the electrode substrate face each other with respect to the polymer electrolyte membrane to which the microporous layer and the catalyst layer are transferred (S4).

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. The electrode substrate is a conductive substrate, and representative examples thereof include carbon paper, carbon cloth, carbon felt, or metal cloth (porous film or polymer fiber composed of metal cloth in a fibrous state). The metal film is formed on the surface of the cloth formed with)) 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. Examples of the fluorine-based resin include polytetrafluoroethylene, polyvinylidene fluoride, polypolyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, and fluorinated ethylene propylene ( Fluorinated ethylene propylene), polychlorotrifluoroethylene or copolymers thereof can be used.

The bonding process of the said electrode base material can be performed in accordance with a conventional method. Preferably, the electrode substrate may be subjected to hot rolling after facing the microporous layer transferred to the polymer electrolyte membrane.

The conditions during the hot rolling are the same as in the transfer process of the microporous layer and the catalyst layer to the polymer electrolyte membrane.

The membrane-electrode assembly may be manufactured by the above manufacturing process.

The membrane-electrode assembly manufactured by the above-described manufacturing method has a high catalyst utilization rate, excellent interfacial adhesion between the catalyst layer and the microporous layer, and minimizes deformation of the polymer electrolyte membrane during the manufacturing process, thereby further improving the battery characteristics of the fuel cell. Can be.

The present invention also provides a membrane-electrode assembly manufactured by the above manufacturing method.

2 is a schematic cross-sectional view of a membrane-electrode assembly for a fuel cell of the present invention. Referring to FIG. 2, the membrane-electrode assembly 151 of the present invention includes a cathode electrode 20 and an anode electrode 20 ′ facing each other, and the cathode electrode 20 and the anode electrode ( 20 ') between the polymer electrolyte membrane 10. At least one of the cathode electrode 20 and the anode electrode 20 'includes an electrode substrate 40, 40'; A microporous layer (50, 50 ') formed on the electrode substrate; And catalyst layers 30 and 30 'formed on the microporous layer.

The components of the membrane-electrode assembly are the same as described above.

In general, the catalyst transfer rate can be calculated by the following Equation 1.

Catalyst Transfer Rate (%) = (Transfer Amount / Coating Amount) × 100

The membrane-electrode assembly according to the present invention prepared according to the above production method exhibits a catalyst transfer rate of 95% or more, more preferably 98 to 99.5%. This is a remarkably high level compared with the conventional dry transfer method of forming the catalyst layer on the substrate for transfer to directly transfer the catalyst layer to the polymer electrolyte membrane.

In addition, the microporous layer exhibits a peel strength of 5 to 100 gf / in, more preferably 10 to 50 gf / in of the catalyst layer. While the peel strength is excellent in the adhesion of the microporous layer to the catalyst layer within the above range, the mass transfer resistance is low, but if it is out of the above range, the transfer rate is lowered or excessive pressure is required. Accordingly, the manufacturing method according to the present invention may exhibit excellent effects when applied to the case of preparing a membrane-electrode assembly using a hydrocarbon-based electrolyte membrane having a glass transition temperature of 200 ° C. or more due to excellent adhesion between the microporous layer and the catalyst layer. .

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

The fuel cell system includes at least one electricity generating unit including the membrane-electrode assembly and the separator, and includes a fuel supply unit supplying fuel to the electricity generating unit and an oxidant supply unit supplying an oxidant to the electricity generating unit.

The electricity generating unit includes a membrane-electrode assembly, a separator (also called a bipolar plate), and serves to generate electricity through an oxidation reaction of a fuel and a reduction reaction of an 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. Fuels in the present invention include hydrogen or hydrocarbon fuels 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. 3, which will be described in more detail with reference to the following. Although the structure shown in FIG. 3 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 does not use a pump, but uses a fuel diffusion method. Of course, it can also be used in the battery system structure.

The fuel cell system 100 of the present invention includes at least one electricity generation unit 150 for generating electrical energy through an electrochemical reaction between a fuel and an oxidant, a fuel supply unit 101 for supplying the fuel, and an oxidant. It is configured to include an oxidant supply unit 103 for supplying to the electricity generating unit 150.

In addition, the fuel supply unit 101 for supplying fuel includes a fuel tank 110 for storing fuel, and optionally, may further include a fuel pump 120 connected to the fuel tank 110. The fuel pump 120 serves to discharge fuel stored in the fuel tank 110 by a predetermined pumping force.

The oxidant supply unit 103 supplying the oxidant to the electricity generating unit 150 may include at least one oxidant pump 130 that sucks the oxidant with a predetermined pumping force.

The electricity generation unit 150 includes a membrane electrode assembly 151 for oxidizing and reducing a fuel and an oxidant, and separators 152 and 153 for supplying fuel and an oxidant to both sides of the membrane electrode assembly. At least one generation unit 150 may form a stack.

Hereinafter, preferred 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  One

10ml de-ionized water while Vulcan XC 72R carbon black, 0.7g, and 60% polytetrafluoroethylene by stirring at 250rpm for 1 hour, then a solution by the addition of 0.98g of ethylene emulsion and discharge peobik of 20 ml (disperbyk ^®, byk Co.) wetting and dispersing And a dispersion prepared by further mixing 2.7 g of carbon black was mechanically stirred to prepare a composition for forming a microporous layer.

The composition for forming the microporous layer was directly applied to a release film of polytetrafluoroethylene (PTFE) by screen printing and dried to form a microporous layer.

10 g of 10 wt% Nafion (manufactured by Nafion ^® Dupont) aqueous dispersion was added to 3.0 g of Pt / C (20 wt%, manufactured by E-tek) in 30 ml of isopropyl alcohol, and then formed by mechanical stirring to form a cathode catalyst layer. The composition was directly applied onto the microporous layer by screen printing and then dried to prepare a cathode catalyst layer. At this time, the cathode catalyst layer forming area was 5 X 5 cm ² and the catalyst loading was 3 mg / cm ² respectively.

Except for using a PtRu black catalyst was carried out in the same manner as above to form a microporous layer and an anode catalyst layer on a release film. At this time, the anode catalyst layer formation area was 5 X 5 cm ² and the catalyst loading was 3 mg / cm ² respectively.

Between the prepared cathode electrode and the anode electrode, a commercial Nafion 115 membrane (thickness: 125 μm) was treated for 2 hours in 90% 3% hydrogen peroxide, 0.5M sulfuric acid aqueous solution, respectively, and then deionized water at 100 ° C. for 1 hour. Place the H ⁺ Nafion 115 membrane prepared by washing and then pressurized for 100 minutes at 135 ° C by 100kgf / cm ² using a compression molder to simultaneously form the microporous layer and the catalyst layer at each electrode with a polymer electrolyte membrane. Killed.

It was prepared an electrode assembly - the microporous layer and the catalyst layer is transferred with the polymer electrolyte membrane to Place the water-repelling-treated tansoji electrode substrate with Teflon on both sides using a compression molder pressure during 135 ℃ 100kgf / cm ^2, 3 bun film .

The prepared membrane-electrode assembly was inserted between two gaskets, and then inserted into two separators having a predetermined gas flow channel and a cooling channel, and pressed between copper end plates to prepare a unit cell.

Comparative example  One

10 g of 10 wt% Nafion (manufactured by Nafion ^® Dupont) aqueous dispersion was added to 3.0 g of Pt / C (20 wt%, manufactured by E-tek) in 30 ml of isopropyl alcohol, and then formed by mechanical stirring to form a cathode catalyst layer. The composition was directly applied to a release film of polytetrafluoroethylene (PTFE) by screen printing by screen printing and then dried to prepare a cathode catalyst layer. At this time, the cathode catalyst layer forming area was 5 X 5 cm ² and the catalyst loading was 3 mg / cm ² respectively.

Except for using the PtRu black catalyst was carried out in the same manner as above to form an anode catalyst layer on a release film. At this time, the anode catalyst layer formation area was 5 X 5 cm ² and the catalyst loading was 3 mg / cm ² respectively.

Between the prepared cathode electrode and the anode electrode, a commercial Nafion 115 membrane (thickness: 125 μm) was treated for 2 hours in 90% 3% hydrogen peroxide, 0.5M sulfuric acid aqueous solution, respectively, and then deionized water at 100 ° C. for 1 hour. After washing and preparing the H ⁺ type Nafion 115 membrane, pressurization was carried out at a pressure of 100 kgf / cm ² for 3 minutes at 135 ° C. using a compression molder to transfer the catalyst layer at each electrode to the polymer electrolyte membrane.

The same composition for forming a microporous layer as in Example 1 was applied directly to one surface of a carbon paper electrode substrate water-repellent treated with Teflon by screen printing, followed by drying to form a microporous layer.

The carbon-electrode substrate on which the microporous layer was formed was placed on both surfaces of the polymer electrolyte membrane to which the catalyst layer was transferred, and then pressurized at 135 ° C. for 100 kgf / cm ² for 3 minutes using a compression molder to prepare a membrane-electrode assembly.

The prepared membrane-electrode assembly was inserted between two gaskets, and then inserted into two separators having a predetermined gas flow channel and a cooling channel, and pressed between copper end plates to prepare a unit cell.

In the electrodes of the unit cells prepared in Example 1 and Comparative Example 1, the catalyst transfer rate and the peel strength between the catalyst layer and the microporous layer were measured. The results are shown in Table 1 below.

At this time, the catalyst transfer rate was measured by comparing the amount of catalyst coating used in the production of a single cell, and the amount of catalyst remaining in the catalyst layer after preparation, respectively, to calculate the catalyst transfer rate from the catalyst transfer rate.

Peel strength between the catalyst layer and the microporous layer was measured using ASTM D 3330M.

In addition, the current density of the unit cells prepared in Example 1 and Comparative Example 1 was measured under the driving conditions (hydrogen / air and 3M methanol / air) of the direct oxidation fuel cell. The results are shown in Table 1 below.

Evaluation item Example 1 Comparative Example 1 Catalyst Transfer Rate at Anode Electrode (%) 98 91 Catalyst Transfer Rate at Cathode Electrode (%) 99 92 Peel strength between microporous layer and catalyst layer (gf / in) 12 7 Current density at 50 ° C, 0.4V (mA / cm ² ) 400 350

As shown in Table 1, the unit cell of Example 1 including the membrane-electrode assembly manufactured by the manufacturing method of the present invention had a catalyst transfer rate of 98% or more at both the cathode electrode and the anode electrode, In the case of a single cell, the catalyst transfer rate was as low as 92%. This is because in the unit cell of Comparative Example 1, the catalyst layer was not peeled smoothly due to tearing during transfer of the catalyst layer formed directly on the release film to the polymer electrolyte membrane.

In addition, in terms of the peel strength between the microporous layer and the catalyst layer, the unit cell of Example 1 showed a significantly better value than the unit cell of Comparative Example 1. From this, it can be seen that in the fuel cell manufactured by the manufacturing method of the present invention, the adhesion between the microporous layer and the catalyst layer is excellent.

As can be expected from the above results, it was confirmed that the unit cell of Example 1 exhibited a higher current density than the unit cell of Comparative Example 1 under the same operating conditions (3M methanol / air at 50 ° C.), thereby having excellent output characteristics.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

1 is a process diagram schematically showing a method of manufacturing a membrane-electrode assembly for a fuel cell according to an embodiment of the present invention.

2 schematically illustrates a membrane-electrode assembly for a fuel cell according to another embodiment of the present invention.

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

[Description of main part of drawing]

10 polyelectrolyte membrane

20 cathode electrodes

20 'anode electrode

30, 30 'catalyst bed

40, 40 'electrode substrate

50, 50 'microporous layer

100 fuel cell system

101 fuel supply

103 Oxidizer Supply

150 electricity generator

151 Membrane-electrode assembly

152, 153 separator

Claims (18)

Forming a microporous layer by applying a composition for forming a microporous layer on a transfer substrate; Forming a catalyst layer by applying a composition for forming a catalyst layer on the microporous layer; Transferring the microporous layer and the catalyst layer to the polymer electrolyte membrane by placing the polymer electrolyte membrane so that the catalyst layer and the polymer electrolyte membrane face each other with respect to the transfer substrate on which the microporous layer and the catalyst layer are sequentially formed; And Positioning the electrode substrate so that the microporous layer and the electrode substrate face each other with respect to the polymer electrolyte membrane to which the microporous layer and the catalyst layer are transferred; Method of manufacturing a membrane-electrode assembly for a fuel cell comprising a. The method of claim 1, The transfer substrate is a method of manufacturing a membrane-electrode assembly for a fuel cell that is glass or a release film. The method of claim 2, The release film is polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkylvinylether copolymer, ethylene / tetrafluoroethylene (Ethylene / Tetrafluoroethylene ( ETFE)), polyvinylidene fluoride, copolymers thereof, and mixtures thereof; Or a non-fluorine-based polymer film selected from the group consisting of polyimide, polyethylene, polypropylene, polyethylene terephthalate, polyester, copolymers thereof, and mixtures thereof. A method of manufacturing an electrode assembly. The method of claim 1, The microporous layer forming composition comprises a conductive powder, a binder resin and a solvent manufacturing method for a fuel cell membrane electrode assembly. The method of claim 4, wherein The conductive powder is selected from the group consisting of carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotubes, carbon nanowires, carbon nano horns, carbon nano rings, and mixtures thereof. Method for producing a membrane-electrode assembly for a fuel cell. The method of claim 4, wherein The binder resin may be polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, polyvinyl alcohol, cellulose acetate, Method of producing a membrane-electrode assembly for a fuel cell is selected from the group consisting of copolymers and mixtures thereof. The method of claim 4, wherein The binder resin is a method for producing a fuel cell membrane-electrode assembly comprising 3 to 30% by weight based on the total weight of the composition for forming the microporous layer. The method of claim 1, The coating process of the composition for forming the microporous layer is screen printing method, spray coating method, coating method using a doctor blade, gravure coating method, dip coating method, silk screen method, painting method, coating using a slot die (slot die) A method for producing a membrane-electrode assembly for a fuel cell, which is carried out by a method selected from the group consisting of a method, and a combination thereof. The method of claim 1, The catalyst layer forming composition is a method for producing a fuel cell membrane-electrode assembly comprising a platinum-based catalyst. The method of claim 9, The catalyst layer forming composition further comprises a binder resin 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 in the side chain. Method of manufacturing membrane-electrode assembly. The method of claim 1, The polymer electrolyte membrane comprises 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 in the side chain. The method of claim 1, The polymer electrolyte membrane has a hydrocarbon-based polymer, a fluorine-based polymer, a benzimidazole-based polymer, a polyimide-based polymer 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 thereof. A group consisting of a polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer, a polyether ketone polymer, a polyphenylquinoxaline polymer, a copolymer thereof and a mixture thereof The method of manufacturing a membrane-electrode assembly for a fuel cell. The method of claim 12, Wherein the polymer electrolyte membrane is a hydrocarbon-based polymer 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 a side chain thereof. The method of claim 1, The hot rolling process is a method of manufacturing a membrane-electrode assembly for a fuel cell that is carried out at a temperature range of 130 to 200 ℃. The method of claim 1, The hot rolling process is a method of manufacturing a membrane-electrode assembly for a fuel cell that is carried out by applying a pressure of 40 to 200kgf / cm ² . It is prepared by the manufacturing method according to any one of claims 1 to 15, An anode electrode and a cathode electrode located opposite each other; And a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode, At least one of the anode electrode and the cathode electrode, a fuel cell membrane-electrode assembly comprising an electrode substrate, a microporous layer formed on the electrode substrate, and a catalyst layer formed on the microporous layer. The method of claim 16, The catalyst layer is a fuel cell membrane-electrode assembly having a catalyst transfer rate of at least 95% obtained by the following equation (1). [Equation 1] Catalyst Transfer Rate (%) = (Transfer Amount / Coating Amount) × 100 The method of claim 16, The microporous layer is a fuel cell membrane-electrode assembly having a peel strength of 5 to 100 gf / in with respect to the catalyst layer.

Images