KR20080044492A - Membrane electrode assembly for fuel cell, preparing method for same, and fuel cell system comprising same - Google Patents

Abstract

A membrane-electrode assembly for a fuel cell is provided to prevent a electrode substrate from being deformed or compressed by a pressurizing process, and to facilitate mass transfer through the pores of the electrode substrate, thereby improving the quality of a fuel cell. A membrane-electrode assembly for a fuel cell comprises: an anode(20') and a cathode(20) facing to each other; and a polymer electrolyte membrane(50) interposed between the anode and the cathode, wherein at least one of the anode and the cathode comprises an electrode substrate(40,40') including pores, and a catalyst layer(30,30') formed in the electrode substrate, wherein the pores in the electrode substrate is filled with a pore-maintaining polymer(42). The pore-maintaining polymer is selected from the group consisting of poly (meth)acrylic acid, polyvinyl alcohol, polyalkylene glycol, aliphatic polyester, and copolymers and blends thereof.

Description

Membrane-electrode assembly for fuel cell, method for manufacturing same, and fuel cell system comprising same {MEMBRANE ELECTRODE ASSEMBLY FOR FUEL CELL, PREPARING METHOD FOR SAME, AND FUEL CELL SYSTEM COMPRISING SAME}

1 is a schematic view showing a structure of a membrane-electrode assembly according to an embodiment of the present invention.

Figure 2 is a schematic diagram showing the structure of a fuel cell system according to another embodiment of the present invention.

[Industrial use]

The present invention relates to a membrane-electrode assembly for a fuel cell, a method for manufacturing the same, and a fuel cell system including the same, and more particularly, there is no fear of deformation and crushing of an electrode substrate according to a pressing process during manufacturing, and thus, an electrode substrate. The present invention relates to a fuel cell membrane-electrode assembly, a method for manufacturing the same, and a fuel cell system including the same, capable of facilitating material movement through pores, thereby improving performance of a fuel cell.

[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). The use of methanol as fuel in the direct oxidation fuel cell 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 a fuel cell system, the stack that substantially generates electricity is comprised of a number of unit cells consisting of a membrane-electrode assembly (MEA) and a separator (also called a bipolar plate). It has a stacked structure of several tens. The membrane-electrode assembly is called an anode electrode (also called "fuel electrode" or "oxide 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 generating water.

An object of the present invention is that there is no fear of deformation and crushing of the electrode substrate according to the pressing process in the manufacture of the membrane-electrode assembly, thereby facilitating material movement through the pores in the electrode substrate to improve the performance of the fuel cell. It is to provide a membrane-electrode assembly for a fuel cell.

Another object of the present invention is to provide a method for manufacturing the fuel cell membrane-electrode assembly.

Still another object of the present invention is to provide a fuel cell system including the fuel cell membrane-electrode assembly.

In order to achieve the above object, the present invention includes an anode electrode and a cathode electrode positioned opposite to each other, a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode. At least one of the anode electrode and the cathode electrode includes an electrode substrate including pores and a catalyst layer formed on the electrode substrate, and the pores in the electrode substrate are filled with a pore holding polymer.

The present invention also prepares an electrode substrate having pores, fills pores contained in the electrode substrate with a pore-maintaining polymer, and forms a catalyst layer on the electrode substrate including pores filled with the pore-maintaining polymer It provides a method of manufacturing a membrane-electrode assembly comprising the step of bonding with the electrode substrate after bonding to the electrolyte membrane, or to form a catalyst layer on the polymer electrolyte membrane.

The present invention also includes the membrane-electrode assembly and the separator, and includes at least one electricity generating unit for generating electricity through an electrochemical reaction between a fuel and an oxidant, a fuel supply unit supplying fuel to the electricity generating unit, and an oxidant. It provides a fuel cell system including an oxidant supply unit for supplying to the electricity generating unit.

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

The operating characteristics of the fuel cell are characterized by the porosity, average pore size, pore size distribution, electrical resistivity and gas permeability of the electrode substrate in the membrane-electrode assembly. Greatly influenced by Therefore, in order to improve the performance of the fuel cell, it is important to minimize the resistance to mass movement by maintaining the pores contained in the electrode substrate in an optimal state.

Typically, the membrane-electrode assembly is prepared by forming a catalyst layer on an electrode substrate using a suitable technique and then thermocompression bonding with the polymer electrolyte membrane. However, the electrode substrate is made of a flexible material such as carbon paper, and the heat and pressure applied when the membrane-electrode assembly is manufactured will cause the electrode substrate and the pores contained in the electrode substrate to be pressed or deformed. Accordingly, it is difficult to properly exhibit the reactant diffusion ability using the porosity of the electrode substrate. As a result, the resistance to mass transfer in the electrode substrate is increased, resulting in a decrease in the performance of the fuel cell.

 In contrast, in the present invention, a membrane-electrode assembly is prepared using an electrode substrate filled with pores with a water-soluble polymer having excellent adhesion to pores, so that there is no fear of deformation and crushing of the electrode substrate due to the pressing process during manufacturing. Accordingly, material movement through the pores in the electrode substrate may be facilitated, thereby improving performance of the fuel cell.

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

Referring to FIG. 1, 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 50.

The cathode electrode 20 and the anode electrode 20 'include an electrode substrate 40, 40' and a catalyst layer 30, 30 ', respectively.

The electrode substrates 40 and 40 'serve to support the electrode and diffuse fuel and oxidant to the catalyst layers 30 and 30', thereby easily accessing the fuel and oxidant to the catalyst layer.

As the electrode substrates 40 and 40 ', a conductive substrate may be used. Representative examples thereof include carbon paper, carbon cloth, carbon felt, and metal cloth (such as a metallic cloth in a fiber state). The metal film is formed on the surface of the fabric formed of the porous film or the polymer fiber (referred to as metalized polymer fiber) and a combination thereof may be used, but is not limited thereto.

In addition, using the water-repellent treatment with a fluorine-based resin as the electrode substrates 40 and 40 'can prevent the reactant diffusion efficiency from being lowered by the electrochemically generated water in the catalyst layer of the cathode when the fuel cell is driven. It is preferable. As the fluorine-based resin, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated ethylene propylene, polychlorotrifluoroethylene, or fluoroethylene polymer may be used.

In addition, the electrode substrates 40 and 40 ′ may be porous materials having pores for easy movement of the reactants. More preferably, the electrode substrate may have a porosity of 50 to 90% by volume with respect to the total volume of the electrode substrate, and more preferably may have a porosity of 75 to 85% by volume. If the porosity of the electrode substrate is less than 50% by volume, smooth dispersion of fuel and the discharge of by-products are not easy. If the porosity of the electrode substrate exceeds 90% by volume, the mechanical resistance to crushing may be lowered, which is not preferable.

The pores in the electrode substrates 40 and 40 'may also be filled by the pore retention polymer 42.

The pore-maintaining polymer is water-soluble and has excellent adhesion, and specifically, selected from the group consisting of poly (meth) acrylic acid, polyvinyl alcohol, polyalkylene glycol, aliphatic polyester, copolymers thereof, and mixtures thereof. It may be used, wherein the alkylene means alkylene having 1 to 6 carbon atoms. Preferably, polyacrylic acid, polymethacrylic acid, polyvinyl alcohol, polyethylene glycol, polytetramethylene glycol, polypropylene glycol, polyhydroxybutyrate, copolymers thereof, and mixtures thereof may be used. .

In addition, the pore-maintaining polymer may have a number average molecular weight of 1000 to 500000, more preferably may have a number average molecular weight of 20000 to 200000. If the number-average molecular weight of the pore-holding polymer is less than 1000, the pore-coating effect is insignificant in the liquid form, and if it exceeds 500,000, pore penetration is not preferable due to the high viscosity.

The pore holding polymer is preferably filled in 5 to 40% by volume, more preferably 10 to 20% by volume based on the total pore volume of the electrode substrate. If the filling amount of the pore-maintaining polymer is less than 5% by volume, the pore-holding effect is insignificant, and if it exceeds 40% by volume, it is rather undesirable because it serves to block the pores, thereby preventing mass transfer.

The pore-maintaining polymer 42 provides strength to the electrode substrates 40 and 40 'by filling the pores, thereby depressing and deforming the electrode substrates 40 and 40' by the pressurization process in the manufacture of the fuel cell. Can be prevented. In addition, the pore-maintaining polymer 42 is dissolved by the fuel supplied when the fuel cell is driven. As a result, when the fuel cell is driven, pores held in the electrode substrates 40 and 40 'can be provided in a circular shape, so that pores in the electrode substrates 40 and 40' can be secured even under a pressurized condition. Material movement through can be made more smooth. When applied to methanol, ethanol fuel cell or hydrogen fuel cell that can generate water, it can have a better effect.

In addition, since the pore-maintaining polymer 42 has an adhesive force, the adhesion between the electrode substrates 40 and 40 'and the catalyst layers 30 and 30' may be improved when the membrane-electrode assembly is manufactured.

Catalyst layers 30 and 30 'are positioned on the electrode substrates 40 and 40'.

The catalyst layers 30 and 30 'catalyze the associated reactions (oxidation of fuel and reduction of oxidant) and include a catalyst.

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. As the platinum-based catalyst, platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, platinum-M alloy (M is Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Transition metal selected from the group consisting of Cu, Zn, Sn, Mo, W, Rh, and combinations thereof), and a catalyst selected from the group consisting of combinations thereof. 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 / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni, Pt / Ru / Sn / W, and mixtures thereof may 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.

The catalyst layers 30 and 30 '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. 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 A hydrogen ion conductive polymer selected from the group consisting of ether ketone polymers, polyphenylquinoxaline polymers, and combinations thereof, and more preferably poly (perfluorosulfonic acid), poly (perfluorocarr) Acids), copolymers of tetrafluoroethylene and fluorovinyl ethers containing sulfonic acid groups, defluorinated sulfided polyether ketones, aryl ketones, poly (2,2'-m-phenylene) -5,5'- Hydrogen ion conductive polymer selected from the group consisting of bibenzimidazole (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole), poly (2,5-benzimidazole), and combinations thereof To Can be used.

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 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 More preferably, they are selected from the group consisting of silbenzenesulfonic acid, sorbitol, copolymers thereof and mixtures thereof.

In addition, the membrane-electrode assembly 151 according to the present invention may further be formed with a microporous layer (not shown) to enhance the diffusion effect of the reactants in the electrode substrate (40, 40 '). 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, and the like.

The microporous layer is prepared by coating a composition comprising a conductive powder, a binder resin and a solvent on 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, dimethyl sulfoxide, N-methylpyrrolidone and the like can be preferably used. The coating process may be a screen printing method, a spray coating method or a coating method using a doctor blade or the like depending on the viscosity of the composition, but is not limited thereto.

The membrane-electrode assembly 151 including the electrodes 20 and 20 'having the above structure includes the polymer electrolyte membrane 50 positioned between the anode and the cathode electrode.

The polymer electrolyte membrane 50 functions to ion exchange the hydrogen ions generated in the catalyst layer 30 'of the anode electrode 20' to the catalyst layer 30 of the cathode electrode 20. Therefore, it is preferable to use a polymer having excellent hydrogen ion conductivity as the polymer electrolyte membrane 50.

Representative examples thereof include 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.

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 Ether ketone-based polymers, polyphenylquinoxaline-based polymers, and those selected from the group consisting of combinations thereof may be used, more preferably poly (perfluorosulfonic acid) (generally marketed as Nafion), 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'-bibenzimidazole (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole), poly (2,5-benzimidazole) and combinations thereof Can use .

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 membrane-electrode assembly having the above structure comprises the steps of preparing an electrode substrate having pores; Filling the pores contained in the electrode substrate with a pore-maintaining polymer; Forming a catalyst layer on the electrode substrate including pores filled with the pore-maintaining polymer and then bonding to the polymer electrolyte membrane or forming a catalyst layer on the polymer electrolyte membrane and then bonding the electrode substrate to the electrode substrate. Can be prepared.

In more detail below, first, an electrode substrate having pores is prepared.

The electrode substrate is the same as described above.

The electrode substrate may also be water-repellent treated with a fluorine-based resin according to a conventional method so as to facilitate the discharge of water, which is a reaction by-product, prior to filling with the pore-maintaining polymer.

Next, the pores included in the electrode substrate are filled with a polymer for retaining pores.

More specifically, the pores in the electrode substrate are filled with a composition containing a pore-maintaining polymer at a concentration of 20 to 70 wt%, more preferably 30 to 50 wt%. At this time, the composition may be an aqueous solution containing a pore-maintaining polymer, or may be an organic solution.

In addition, when the concentration of the pore-maintaining polymer in the composition is less than 20% by weight, the filling amount of the pore-maintaining polymer in the electrode substrate is small, which may form an empty space. The high viscosity of the polymer solution for oils and fats does not penetrate the pores in the electrode substrate, making it difficult to fill the pores. Pore retention polymer is the same as described above. As the solvent, an organic solvent showing polarity is preferable. Specifically, an alcohol solvent such as methanol, ethanol or isopropyl alcohol, an amide solvent such as dimethylacetamide, a sulfoxide solvent such as dimethyl sulfoxide or N-methyl Polar solvents such as pyrrolidone may be used.

Filling the pore-maintaining polymer is preferably a method selected from the group consisting of dipping method, pressure dipping method, reduced pressure dipping method, spray method, doctor blade method, silk screen method and combinations thereof. More preferably, a vacuum immersion method in which the pores in the electrode substrate are evacuated and then the electrode substrate is precipitated in the polymer solution for pore maintenance may be used, or a pressure immersion method in which the electrode substrate is precipitated in the polymer solution for pore retention and applying a high pressure may be used. have.

Thereafter, a fine pore layer may be formed on the electrode substrate including the pores optionally filled with the pore holding polymer.

The microporous layer may be formed by coating a composition including a conductive powder, a binder resin, and a solvent on the electrode substrate.

Next, a catalyst layer is formed on an electrode substrate including pores filled with the pore holding polymer and then bonded to a polymer electrolyte membrane, or a catalyst layer is formed on a polymer electrolyte membrane and then bonded to the electrode substrate to form a membrane-electrode assembly. Manufacture.

The catalyst layer formation may be performed by direct application or transfer coating.

When the catalyst layer is formed by the direct coating method, the composition for forming the catalyst layer may be directly applied to the electrode substrate or the polymer electrolyte membrane and then dried to form it. At this time, the coating process is made of 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 method according to the viscosity of the composition. It may be carried out by a method selected from the group, but is not limited thereto. More preferably, the screen printing method can be used.

When the catalyst layer is formed by the transfer coating method, the catalyst layer may be formed by applying the catalyst layer-forming composition to a release film and drying to form a catalyst layer and transferring it to an electrode substrate or a polymer electrolyte membrane by hot rolling.

Examples of the release film include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer having a thickness of about 200 μm. Fluorine resin films such as PFA) ethylene / tetrafluoroethylene (ETFE), or non-fluorine polymer films such as polyimide (manufactured by Kapton ^® DuPont) and polyester (manufactured by Mylar ^® DuPont) , The coating step of the composition for forming a catalyst layer on the release film is as described above.

In the transfer process, the catalyst layer formed on the release film is placed on the polymer electrolyte membrane and then hot rolled to transfer it. The temperature at the time of hot rolling is 100-250 degreeC, More preferably, it is 100-200 degreeC. In addition, the pressure during hot rolling is preferably from 300 to 2000 psi, more preferably from 300 to 1500 psi. Within the above temperature and pressure range, the catalyst layer is smoothly transferred, and if it is out of the above range, the catalyst layer is not completely transferred or the catalyst layer has an excessively dense structure.

The polymer electrolyte membrane and the catalyst layer are the same as described above, and the method of binding the electrode substrate to the polymer electrolyte membrane is well known in the art, and thus detailed description thereof will be omitted.

The membrane-electrode assembly manufactured as described above is filled with pores in the electrode substrate with a pore-maintaining polymer, thereby preventing the electrode substrate from being pressed and deformed by pressurization during manufacture, and then pore by fuel when driving the fuel cell. By dissolving the holding polymer, it is possible to provide the original pores of the electrode substrate, thereby facilitating material movement and improving the output characteristics of the fuel cell of the fuel cell.

According to an embodiment of the present invention, there is provided a fuel cell system including the 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. 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 using a diffusion method without using a pump is shown. Of course, it can also be used in the battery system structure.

The fuel cell system 100 of the present invention includes a stack 105 having at least one electricity generator 150 for generating electrical energy through an electrochemical reaction between a fuel and an oxidant, and a fuel supply unit for supplying the fuel. 101 and an oxidant supply unit 103 for supplying an oxidant 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 of the stack 105 may include at least one oxidant pump 130 that sucks the oxidant with a predetermined pumping force.

The electricity generator 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.

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

As an electrode substrate, a carbon paper (manufactured by Toray Corporation) having a thickness of 200 μm and a porosity of 80% by volume, and a pore having an average pore diameter of 1 μm was prepared, and the carbon paper electrode substrate was added to a 40% by weight polyacrylic acid solution. After immersion, it was taken out again and dried to fill a polyacrylic acid having a number average molecular weight 300000 into the pores of the electrode substrate. The process was repeated several times to uniformly fill the pores with polyacrylic acid. At this time, the polyacrylic acid filled in the pores of the electrode base material was 20% by volume relative to the total pore volume of the electrode base material.

Commercial NAFION 115 membranes (molecular weight: 50 ~ 800,000, thickness: 125㎛) were treated with 90% of 3% hydrogen peroxide and 0.5M sulfuric acid aqueous solution for 2 hours, and then washed with deionized water at 100 ° C for 1 hour and H ⁺ Type NAFION 115 membrane was prepared as a polymer electrolyte membrane.

4.5 g of 10 wt% Nafion (NAFION ^® , manufactured by Dupont) aqueous dispersion was added dropwise to 3.0 g of Pt black (Hispec ^® 1000, manufactured by Johnson Matthey) and Pt / Ru black (Hispec ^® 6000, manufactured by Johnson Matthey) mechanically By stirring, a composition for forming a catalyst layer was prepared.

The catalyst layer forming composition was directly coated on one surface of the polymer electrolyte membrane by screen printing. At this time, the catalyst layer forming area is 5 X 5 cm ^{2 And the} catalyst loading amount is 3 mg / cm ² respectively. The same was true for the other side of the polymer electrolyte membrane to form an anode electrode and a cathode electrode catalyst layer on both sides of the polymer electrolyte membrane.

Thereafter, the electrode substrate including the pores filled with the polyacrylic acid is physically bonded to both surfaces of the polymer electrolyte membrane in which the catalyst layer is formed, inserted between two gaskets, and then a gas channel channel and a cooling channel having a predetermined shape are formed. A single cell was prepared by inserting into two separators and pressing between copper end plates.

Example 2

A single cell was prepared in the same manner as in Example 1, except that a carbon cloth having a porosity of 50% by volume was used as an electrode substrate and a polyvinyl alcohol having a number average molecular weight of 1000 was used as a pore-holding polymer. . At this time, the polyvinyl alcohol filled in the pores of the electrode base material was 40% by volume with respect to the total pore volume of the electrode base material.

Example 3

A single cell was prepared in the same manner as in Example 1, except that carbon paper having a porosity of 90% by volume was used as the electrode substrate, and polyethylene glycol having a number average molecular weight of 500000 was used as the pore-holding polymer. . At this time, the polyethylene glycol filled in the pores of the electrode base material was 5% by volume based on the total pore volume of the electrode base material.

Example 4

A single cell was carried out in the same manner as in Example 1 except that a carbon felt having a porosity of 70% by volume was used as an electrode substrate and a polyhydroxybutyrate having a number average molecular weight of 300000 was used as a pore-holding polymer. Prepared. At this time, the polyhydroxybutyrate filled in the pores of the electrode substrate was 25% by volume relative to the total pore volume of the electrode substrate.

Example 5

As an electrode substrate, a carbon paper (manufactured by Toray Corporation) having a thickness of 200 μm and a porosity of 80% by volume, and a pore having an average pore diameter of 1 μm was prepared, and the carbon paper electrode substrate was added to a 40% by weight polyacrylic acid solution. After immersion, it was taken out again and dried to fill a polyacrylic acid having a number average molecular weight 300000 into the pores of the electrode substrate. The process was repeated several times to uniformly fill the pores with polyacrylic acid. The polyacrylic acid filled in the pores of the electrode base material was 30% by volume relative to the total pore volume of the electrode base material.

A microporous layer-forming composition prepared by mixing 5 g of carbon black and 2 g of polytetrafluoroethylene in 100 ml of isopropyl alcohol was screen printed on the pore-filled electrode substrate, and then sintered at 350 ° C. for 30 minutes to form a microporous layer. Formed.

Commercial NAFION 115 membranes (molecular weight: 50 ~ 800,000, thickness: 125㎛) were treated with 90% of 3% hydrogen peroxide and 0.5M sulfuric acid aqueous solution for 2 hours, and then washed with deionized water at 100 ° C for 1 hour and H ⁺ Type NAFION 115 membrane was prepared as a polymer electrolyte membrane.

4.5 g of 10 wt% Nafion (NAFION ^® , manufactured by Dupont) aqueous dispersion was added dropwise to 3.0 g of Pt black (Hispec ^® 1000, manufactured by Johnson Matthey) and Pt / Ru black (Hispec ^® 6000, manufactured by Johnson Matthey) mechanically By stirring, a composition for forming a catalyst layer was prepared.

The catalyst layer forming composition was directly coated on one surface of the polymer electrolyte membrane by screen printing. At this time, the catalyst layer forming area is 5 X 5 cm ^{2 And the} catalyst loading amount is 3 mg / cm ² respectively. The same was true for the other side of the polymer electrolyte membrane to form an anode electrode and a cathode electrode catalyst layer on both sides of the polymer electrolyte membrane.

Thereafter, the electrode substrate including the pores filled with the polyacrylic acid is physically bonded to both surfaces of the polymer electrolyte membrane in which the catalyst layer is formed, inserted between two gaskets, and then a gas channel channel and a cooling channel having a predetermined shape are formed. A single cell was prepared by inserting into two separators and pressing between copper end plates.

Comparative Example 1

A single cell was prepared in the same manner as in Example 1, except that the electrode substrate of Example 1 was used without filling of polyacrylic acid.

For the cells prepared in Example 1 and Comparative Example 1, the battery performance was measured under hydrogen / air and 1M methanol / air, and the performance of the electrode substrate was evaluated. The results are shown in Table 1 below.

Evaluation item Example 1 Comparative Example 1 Operating voltage at 60 ℃, 200mA / cm ² (V) 0.46 0.41

As shown in Table 1, the unit cell of Example 1 including the electrode substrate according to the present invention of Comparative Example 1 under the same operating conditions (1M methanol / air (5ccpm / 50ccpm), 200mA / cm ² at 60 ℃) Compared with a single cell, it showed a high drive voltage and showed the outstanding output density.

In addition, the gas permeability of the cells of Example 1 and Comparative Example 1 was measured at 80 ° C. under hydrogen / air (relative humidity 100/75%).

Evaluation item Example 1 Comparative Example 1 Gas permeability (cm ³ / cm ² sec) 0.46 0.41

As a result of the measurement, the electrode substrate in Example 1 showed a higher gas permeability than the electrode substrate of Comparative Example 1. As a result, the electrode substrate of Example 1 has a lower diffusion resistance of the gaseous reactants than the electrode substrate of Comparative Example 1, thus exhibiting a high Gurley Number and at the mass transport during fuel cell operation. It can be expected that the high limit current generated by the battery will exhibit excellent battery characteristics.

Gas permeability was measured also by the same method as the above about the unit cells of the said Examples 2-5.

As a result, the gas permeability was the same level as in Example 1.

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.

The membrane-electrode assembly for a fuel cell according to the present invention has no fear of deformation and crushing of the electrode substrate due to the pressurization process during manufacture, thereby facilitating material movement through pores in the electrode substrate, thereby improving the performance of the fuel cell. Can be improved.

Claims (22)

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 An electrode substrate including pores; And It includes a catalyst layer formed on the electrode substrate, The pores in the electrode substrate is filled with a pore holding polymer Membrane-electrode assembly for fuel cell. The method of claim 1, The pore-maintaining polymer is selected from the group consisting of poly (meth) acrylic acid, polyvinyl alcohol, polyalkylene glycol, aliphatic polyester, copolymers thereof, and mixtures thereof. The method of claim 1, The pore-maintaining polymer is a fuel cell membrane-electrode assembly having a number average molecular weight of 1000 to 500000. The method of claim 1, The pore-maintaining polymer is a fuel cell membrane-electrode assembly that is contained in 5 to 40% by volume based on the total pore volume of the electrode substrate. The method of claim 1, The electrode substrate is a fuel cell membrane-electrode assembly selected from the group consisting of carbon paper, carbon cloth, carbon felt, metal cloth and combinations thereof. The method of claim 1, The electrode substrate is a fuel cell membrane-electrode assembly having a porosity of 50 to 90% by volume relative to the total volume of the electrode substrate. The method of claim 1, The membrane-electrode assembly further comprises a microporous layer between the electrode substrate and the catalyst layer. The method of claim 1, The microporous layer includes carbon powder, carbon black, acetylene black, ketjen black, activated carbon, carbon nanotube, carbon nanofiber, carbon nanowire, carbon nanohorn, carbon nano ring, carbon aerogel, carbon cregel, fullerene and Membrane electrode assembly for a fuel cell comprising a conductive powder selected from the group consisting of a mixture thereof. Preparing an electrode substrate having pores; Filling the pores contained in the electrode substrate with a pore-maintaining polymer; Forming a catalyst layer on the electrode substrate including pores filled with the pore-maintaining polymer and then bonding it to the polymer electrolyte membrane, or forming a catalyst layer on the polymer electrolyte membrane and then bonding it to the electrode substrate Method of manufacturing a membrane-electrode assembly comprising a. The method of claim 9, Wherein the electrode substrate has a porosity of 50 to 90% by volume with respect to the total volume of the electrode substrate. The method of claim 9, The method for producing a membrane-electrode assembly for a fuel cell, wherein the pore-maintaining polymer is selected from the group consisting of poly (meth) acrylic acid, polyvinyl alcohol, polyalkylene glycol, aliphatic polyester, copolymers thereof, and mixtures thereof. . The method of claim 9, The method for manufacturing a membrane-electrode assembly for a fuel cell that the pore-maintaining polymer has a number average molecular weight of 1000 to 500000. The method of claim 9, The filling step is performed by a method selected from the group consisting of dipping method, pressure dipping method, reduced pressure dipping method, spray method, doctor blade method, silk screen method and a combination thereof to manufacture a membrane-electrode assembly for a fuel cell Way. A membrane-electrode assembly comprising an anode electrode and a cathode electrode positioned opposite to each other, and a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode, and a separator, and generating electricity through an electrochemical reaction between a fuel and an oxidant At least one electricity generating unit; A fuel supply unit supplying fuel to the electricity generation unit; And An oxidant supply unit for supplying an oxidant to the electricity generating unit, At least one of the anode electrode and the cathode electrode includes an electrode substrate including pores; And a catalyst layer formed on the electrode substrate, The pores in the electrode substrate is filled with a pore holding polymer. The method of claim 14, The pore-maintenance polymer is selected from the group consisting of poly (meth) acrylic acid, polyvinyl alcohol, polyalkylene glycol, aliphatic polyester, copolymers thereof, and mixtures thereof. The method of claim 14, The pore-maintaining polymer is a fuel cell system having a number average molecular weight of 1000 to 500000. The method of claim 14, The pore holding polymer is 5 to 40% by volume based on the total pore volume of the electrode substrate. The method of claim 14, The pore-maintaining polymer is dissolved in and removed from the fuel supplied during operation of the fuel cell. The method of claim 14, Wherein said electrode substrate is selected from the group consisting of carbon paper, carbon cloth, carbon felt, metal cloth, and combinations thereof. The method of claim 14, The electrode substrate is a fuel cell system having a porosity of 50 to 90% by volume relative to the total volume of the electrode substrate. The method of claim 14, The membrane-electrode assembly further comprises a microporous layer between the electrode substrate and the catalyst layer. The method of claim 14, The microporous layer includes carbon powder, carbon black, acetylene black, ketjen black, activated carbon, carbon nanotube, carbon nanofiber, carbon nanowire, carbon nanohorn, carbon nano ring, carbon aerogel, carbon cregel, fullerene and A fuel cell system comprising a conductive powder selected from the group consisting of a mixture thereof.

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