KR20080041843A - Method of producing membrane-electrode assembly for fuel cell - Google Patents

Abstract

A method for producing a membrane-electrode assembly for a fuel cell is provided to obtain an electrode having excellent catalytic activity through a simple and easy process. A method for producing a membrane-electrode assembly for a fuel cell comprises the steps of: applying a catalyst layer composition onto a donor film including a release substrate(32) formed on a support(30) to form a catalyst layer(34); disposing a polymer electrolyte membrane(36) so that the membrane faces the catalyst layer of the donor film; and irradiating laser beams in the direction from the donor film toward the polymer electrolyte. The laser beam irradiation step is performed under a dose of 5-20W.

Description

Manufacturing method of membrane-electrode assembly for fuel cell {METHOD OF PRODUCING MEMBRANE-ELECTRODE ASSEMBLY FOR FUEL CELL}

1A to 1C illustrate a method of manufacturing a membrane-electrode assembly for a fuel cell of the present invention.

2 schematically illustrates the structure of a fuel cell system;

Figure 3a is a SEM photograph of the catalyst layer formed on the LTHC in the membrane-electrode assembly process of Example 1 of the present invention.

Figure 3a is a SEM photograph of the catalyst layer transferred to the polymer electrolyte membrane in the membrane-electrode assembly process of Example 1 of the present invention.

[Industrial use]

The present invention relates to a method for manufacturing a fuel cell membrane-electrode assembly, and more particularly, to a method for manufacturing a fuel cell membrane-electrode assembly having an electrode having excellent catalytic activity in a simple process.

[Prior art]

The 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.

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 is a clean energy source that can replace fossil energy, and has high power density and energy conversion efficiency, can be operated at room temperature, and can be miniaturized and encapsulated. It can be widely used in fields such as portable power supply and military equipment.

The polymer electrolyte fuel cell has the advantages of high energy density and high output, but requires attention to handling hydrogen gas and reforms fuel for reforming methane, methanol, natural gas, etc. to produce hydrogen, which is 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 absorb the fuel and has a low operating temperature, and thus can be operated at room temperature. It is recognized as a suitable system for small and general purpose mobile power supplies. In addition, the stack configuration by stacking unit cells has the advantage that can produce a wide range of output, it is attracting attention as a new portable power source because it shows an energy density of 4-10 times compared to a small lithium battery.

An object of the present invention is to provide a method for producing a membrane-electrode assembly for a fuel cell which can produce an electrode having excellent catalytic activity in a simple and easy process.

In order to achieve the above object, the present invention is to apply a catalyst layer composition to a donor film having a release substrate formed on a support substrate to form a catalyst layer, to place a polymer electrolyte membrane to face the catalyst layer of the donor film, the polymer electrolyte in the donor film A method of manufacturing a membrane-electrode assembly for a fuel cell, comprising the step of irradiating a laser beam in the membrane direction.

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

The fuel cell stack refers to a structure in which several to tens of unit cells including a membrane-electrode assembly and a separator are stacked. The membrane-electrode assembly includes an anode electrode and a cathode electrode, and a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode. The anode electrode and the cathode electrode include an electrode substrate and a catalyst layer formed on the electrode substrate. In addition, the separator has a flow path, which serves as a passage for supplying fuel and oxidant required for the reaction of the fuel cell.

Therefore, when the fuel and the oxidant are supplied to the stack, the fuel and the oxidant are supplied to the catalyst layers of the anode electrode and the cathode electrode through the flow path of the separator to cause the electrochemical redox reaction of the fuel cell.

Therefore, the actual catalytic reaction of the fuel cell is generated only along the flow path of the separator, whereas the catalyst layer of the conventional fuel cell is formed on the front surface of the electrode substrate, so there is a problem in that the catalyst loss that does not participate in the reaction is large. It was very expensive, so the economic loss was huge. Accordingly, the method of forming the catalyst layer only in the shape of the flow path of the separator has recently been studied.

As a method of forming a catalyst layer in the shape of a flow path, a decal transfer method, an inkjet screen printing method, and the like have been studied. However, the inkjet or screen printing method has a problem in that it is difficult to form the catalyst layer in the same shape as the flow path, particularly in the same shape as the flow path of the multi-channel, because it is difficult to realize precise and fine shapes.

In addition, after coating the target composition for transferring to a release substrate, the release substrate is placed in such a manner that the coating layer is brought into contact with the substrate to which the coating layer is to be transferred, and then attempted to be the most effective method of transferring the coating layer by rolling or the like. However, this method is subjected to a process of applying a pressure of 100kgf / cm ² for 3 to 5 minutes at a temperature of about 130 ℃ in the rolling process, there is a problem that the catalyst layer formed is too dense, the diffusion of fuel and oxidant is difficult.

The inventors of the present invention completed the present invention using laser induced thermal imaging (LITI) while working to solve such a problem. Hereinafter, the method for forming the catalyst layer of the present invention will be described in more detail with reference to FIGS. 1A to 1C.

First, as shown in FIG. 1A, a donor film having a release substrate 32 attached to a base film 30 is manufactured. In general, a polyester film may be used as the support substrate 30, and a representative example thereof may be a poly (ethylene) terephthalate or poly (ethylene naphthalate) film.

In addition, as the release substrate 32, a light-to-heat conversion layer (LTHC layer) may be used to transfer light into heat and convert laser energy into heat. The LTHC layer may be made of any material mainly composed of carbon black, and may be commercially available from LTM for the LTHC layer.

Subsequently, as shown in FIG. 1B, a catalyst composition including a catalyst, a binder, and a solvent is applied to the release substrate 32 and dried to form a catalyst layer 34.

The catalyst may be used for both the anode and the cathode of the fuel cell, and representative examples thereof include platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M Is a transition metal selected from the group consisting of Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Mo, W, Rh, Ru, and combinations thereof. A catalyst more than a species is mentioned.

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, carbonaceous materials such as graphite, denka black, ketjen black, acetylene black, carbon nanotube, carbon nanofiber, carbon nanowire, carbon nanoball or activated carbon may be used, or alumina, silica, zirconia Inorganic fine particles such as titania and the like may be used, but carbon-based materials are generally used. In the case of using the noble metal supported on the carrier as a catalyst, a commercially available commercially available product may be used, or the noble metal supported on the carrier may be prepared and used. Since the process of supporting the precious metal on the carrier is well known in the art, detailed descriptions thereof will be readily understood by those skilled in the art even if the detailed description is omitted.

It is preferable to use a polymer resin having hydrogen ion conductivity as the binder, and more preferably have 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 present can be used. Preferably, 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 One or more hydrogen ion conductive polymers selected from ether ketone polymers or polyphenylquinoxaline polymers, more preferably poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), Copolymers of tetrafluoroethylene with fluorovinyl ethers containing sulfonic acid groups, defluorinated sulfided polyether ketones, aryl ketones, poly (2,2'-m-phenylene) -5,5'-bibenzimidazole One containing at least one hydrogen ion conductive polymer selected from (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole) or poly (2,5-benzimidazole) may be used.

The hydrogen ion conductive polymer may replace H with Na, K, Li, Cs or tetrabutylammonium in an ion exchange group at the side chain end. In case of replacing H with Na in the side chain terminal ion exchanger, NaOH is substituted for the preparation of the catalyst composition, and tetrabutylammonium hydroxide is substituted for tetrabutylammonium, and K, Li or Cs may be 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 binder may be used in the form of a single substance or a mixture, and may also be optionally used with a nonconductive polymer 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 nonconductive polymer include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro alkylvinyl ether copolymer (PFA), and ethylene / tetrafluoro Ethylene / tetrafluoroethylene (ETFE), ethylenechlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), dode At least one selected from the group consisting of silbenzenesulfonic acid and sorbitol is more preferred.

Subsequently, as shown in FIG. 1C, the polymer electrolyte membrane 36 of the fuel cell is positioned to face the catalyst layer 34, and then the laser beam is irradiated toward the polymer electrolyte membrane toward the supporting substrate. It is preferable to perform laser beam irradiation under the energy conditions of 5-20W. If the laser beam irradiation is performed at less than 5W, the transfer effect is insignificant and undesirable. If the laser beam irradiation is performed at more than 20W, the polymer is deteriorated, which is not preferable. In addition, the laser beam irradiation is preferably carried out at a sweep rate of 0.1 to 1m / min.

According to the laser beam irradiation, the catalyst layer 34 formed on the release substrate 32 is transferred to one surface of the polymer electrolyte membrane 36 in the direction of the laser beam irradiation.

Further, the laser beam is irradiated to have the same shape as the flow path of the separator, or a mask is used to form a catalyst layer having the same shape as the flow path of the separator in the polymer electrolyte membrane. Therefore, since the catalyst layer can be formed only in the portion corresponding to the flow path through which the fuel and the oxidant are supplied, it is economical because the waste due to the catalyst layer is prevented in the portion not participating in the reaction of the fuel cell.

The polymer electrolyte membrane is generally used as a polymer electrolyte membrane in a fuel cell, and any one made of a polymer resin having hydrogen ion conductivity 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 It may include at least one selected from a polymer, a polyether-etherketone-based polymer or a polyphenylquinoxaline-based polymer, more preferably poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), Copolymers of tetrafluoroethylene with fluorovinyl ethers containing sulfonic acid groups, defluorinated sulfided polyether ketones, aryl ketones, poly (2,2'-m-phenylene) -5,5'-bibenzimidazole or at least one selected from (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole) or poly (2,5-benzimidazole).

Since the laser transfer method can form a desired shape very finely and precisely, unlike the conventional inkjet process, a catalyst layer having the same shape as that of a complicated channel such as a multi-channel cannot be easily formed. Can be. In addition, unlike the decal transfer method, the catalyst layer can be prevented from being formed too densely.

The catalyst layer forming method of the present invention can be applied to both the anode and the cathode catalyst layers. That is, after the catalyst layer is formed on one surface of the polymer electrolyte membrane and the same laser transfer process is formed on the other surface of the polymer electrolyte membrane in which the catalyst layer is not formed, a catalyst layer serving as an anode electrode and a cathode electrode can be formed on both surfaces of the polymer electrolyte membrane. .

The electrode base material is placed on the outer surface of the polymer electrolyte membrane prepared by the above-described process, and the anode catalyst layer and the cathode catalyst layer formed on both surfaces, thereby constructing the membrane-electrode assembly of the present invention.

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). It means that the metal film is formed on the surface of the cloth formed of fibers) 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, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, and fluorinated ethylene propylene ( Fluorinated ethylene propylene), polychlorotrifluoroethylene or copolymers thereof can be used.

In addition, a microporous layer may be further included to enhance the reactant diffusion effect in 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 coating a composition comprising a conductive powder, a binder resin and a solvent on the electrode substrate. The binder resin may be polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, polyvinyl alcohol, cellulose acetate Or copolymers thereof and the like can be preferably used. As the solvent, alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, tetrahydrofuran, etc. may be preferably used. The coating process may be screen printing, spray coating, or coating using a doctor blade according to the viscosity of the composition, but is not limited thereto.

In addition, 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, 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 1)

A Pt catalyst, a perfluorosulfonate (trade name: Nafion) binder, and a mixture of distilled water and isopropyl alcohol supported on a carbon carrier in a donor film having an LTHC layer composed mainly of carbon black commercially available from 3M on a polyethylene terephthalate support substrate. The catalyst composition containing the solvent (1: 1 volume ratio) was apply | coated and dried, and the catalyst layer was formed. In this case, the mixing ratio of the catalyst, the binder and the solvent was 1 g of the catalyst, 0.1 g of the binder and 3 g of the solvent.

Next, a commercial Nafion 115 (perfluorosulfonic acid) polymer electrolyte membrane and the donor film were positioned facing the catalyst layer toward the polymer electrolyte membrane. Subsequently, a laser beam was irradiated from the supporting substrate of the donor film toward the polymer electrolyte membrane to transfer the catalyst layer to one surface of the polymer electrolyte membrane. The laser beam irradiation step was performed under conditions of 0.5 m / min with an energy of 10 W.

The SEM photograph of the catalyst layer formed on the LTHC layer is illustrated in FIG. 3A, and the SEM photograph of the catalyst layer transferred to the polymer electrolyte membrane is illustrated in FIG. 3B.

The laser transfer process was similarly performed on the other surface of the polymer electrolyte in which the catalyst layer was not transferred, thereby forming catalyst layers on both sides of the polymer electrolyte, and then placing a carbon paper electrode substrate on the catalyst layer to prepare a membrane-electrode assembly.

The method of the above embodiment can produce the electrode simpler and easier than the conventional, it is economical and can exhibit excellent catalytic activity.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

The electrode manufacturing method of the present invention can produce the fuel cell electrode with excellent catalytic activity economically and easily.

Claims (7)

Applying a catalyst layer composition to a donor film having a release substrate formed on a support substrate to form a catalyst layer; Positioning the polymer electrolyte membrane to face the catalyst layer of the donor film; Irradiating a laser beam toward the polymer electrolyte from the donor film A method of manufacturing a membrane-electrode assembly for a fuel cell comprising a step. The method of claim 1, Wherein the laser beam irradiation step is performed under an energy condition of 5 to 20 W. The method of claim 1, The support substrate is a method for producing a membrane-electrode assembly for a fuel cell. The method of claim 3, The supporting substrate is a (ethylene) terephthalate or poly (ethylene naphthalate) film manufacturing method for a fuel cell membrane-electrode assembly. The method of claim 1, The release substrate is a light-to-heat conversion layer (LTHC layer) is a layer capable of transferring light to heat and converting laser energy into heat. The method of claim 1, Wherein the laser beam is irradiated to have the same shape as a flow path of a separator positioned on both sides of the membrane-electrode assembly. The method of claim 1, And the laser beam is irradiated to have the same shape as a flow path of a separator positioned on both sides of the membrane-electrode assembly using a mask.

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