KR20070041124A - Membrane electrode assembly for fuel cell, method for preparing the same, and fuel cell system comprising the same - Google Patents

Abstract

The present invention relates to a membrane-electrode assembly for a fuel cell, a method of manufacturing the same, and a fuel cell system including the same, wherein the membrane-electrode assembly for a fuel cell includes an anode electrode and a cathode electrode disposed to face each other, and between the anode electrode and the cathode electrode. It includes a polymer electrolyte membrane located, wherein at least one of the anode electrode and the cathode electrode is located between the electrode substrate, the electrode substrate and the polymer electrolyte membrane, and comprises a catalyst layer formed in a predetermined pattern.

The membrane-electrode assembly for a fuel cell of the present invention can reduce the catalyst loading while maintaining the cell output, and can improve the life characteristics of the cell.

Membrane-electrode assembly, catalyst layer, polymer electrolyte membrane, catalyst loading, thickener.

Description

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

1 is a schematic view showing a structure of a fuel cell system according to the present invention,

2 is a graph showing changes in voltage and output of a fuel cell according to current densities according to Example 1 and Comparative Example 1,

3 is a graph illustrating a voltage change according to a driving time of a fuel cell according to Example 1 and Comparative Example 1. FIG.

[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, can exhibit excellent cell output even with a reduced catalyst loading amount, and can improve battery life characteristics. 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.

[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. 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 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 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 comprising a membrane-electrode assembly (MEA) and a separator (also called a bipolar plate). It has a stacked structure of several tens. In addition, the membrane-electrode assembly includes an anode electrode (also called "fuel electrode" or "oxidation electrode") and a cathode electrode (also called "air electrode" or "reduction electrode") with a polymer electrolyte membrane including 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, the fuel is ionized by an oxidation reaction, and electrons are generated, and the generated electrons are oxidized according to an external circuit. Reaching the cathode, which is the pole, hydrogen ions pass through the polymer electrolyte membrane and are delivered to the cathode. 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.

It is an object of the present invention to provide a membrane-electrode assembly for a fuel cell which can exhibit excellent cell output even with a reduced catalyst loading and can improve cell life characteristics.

Another object of the present invention is to provide a manufacturing 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, according to the first exemplary embodiment of the present invention, an anode electrode and a cathode electrode are disposed to face each other, and a polymer electrolyte membrane is disposed between the anode electrode and the cathode electrode, and among the anode electrode and the cathode electrode. At least one is provided between the electrode substrate and the electrode substrate and the polymer electrolyte membrane, and provides a fuel cell membrane-electrode assembly comprising a catalyst layer formed in a predetermined pattern.

According to a second exemplary embodiment of the present invention, a fuel comprising forming a catalyst layer in a predetermined pattern on a polymer electrolyte membrane using a catalyst layer-forming composition comprising a metal catalyst and a binder resin and then binding the electrode substrate thereon. Provided is a method of manufacturing a membrane-electrode assembly for a battery.

According to a third exemplary embodiment of the present invention, the membrane-electrode assembly and a separator located on both sides of the membrane-electrode assembly include at least one electricity generating electricity through an electrochemical reaction between a fuel and an oxidant. It provides a fuel cell system including a generator, comprising a fuel supply unit for supplying fuel to the electricity generation unit and an oxidant supply unit for supplying an oxidant to the electricity generation unit.

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

The present invention can exhibit excellent battery output with a reduced catalyst loading by forming the catalyst layer in a predetermined pattern, and further includes a thickener in the composition for forming a catalyst layer to reduce the penetration of the solvent into the polymer electrolyte membrane, and As a result, the swelling of the polymer electrolyte membrane was reduced, thereby improving structural stability and battery life characteristics of the fuel cell.

That is, the membrane-electrode assembly for a fuel cell according to the first exemplary embodiment of the present invention,

An anode electrode and a cathode electrode located opposite each other; And

It includes 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, and

Located between the electrode substrate and the polymer electrolyte membrane, and comprises a catalyst layer formed in a predetermined pattern.

At least one of the anode electrode and the cathode electrode includes a catalyst layer and an electrode substrate supporting the same.

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

The catalyst layer supported by the electrode substrate is formed in a predetermined pattern, and the pattern of the catalyst layer preferably corresponds to the shape of the flow path of the separator. In this case, the flow path shape of the separator may have a channel shape or an island shape, and in the case of a channel shape, the separator may have a single or multi-channel shape.

By making the shape of the catalyst layer coincide with the shape of the flow path of the separator as described above, the catalyst loading can be reduced to 30 to 70% while showing the same battery output as compared with the case where the catalyst layer is formed on the entire surface of the polymer electrolyte membrane.

Further, more preferably, in order to prevent the polymer electrolyte membrane from being directly exposed to the fuel, the pattern of the catalyst layer preferably has a channel shape having a width of 1 to 2 mm larger than the width of the flow channel of the separator.

In addition, the catalyst layer includes micropores formed as the additionally included thickener used in the preparation of the catalyst layer is removed during the manufacturing process, thereby reducing the diffusion resistance of the reactants, and reducing water and carbon dioxide (CO ₂ ) and Ejection of the same reaction product is easy. In addition, the catalytic activity may be increased by increasing the reaction surface area of the catalyst layer due to the formation of micropores. More preferably, the catalyst layer has a porosity of 10 to 90% by volume relative to the total volume of the catalyst layer, and more preferably has a porosity of 30 to 70% by volume. If the porosity of the catalyst layer is out of the range, the mechanical strength of the catalyst layer may be lowered, which is not preferable.

In addition, the catalyst layer includes a metal catalyst and a binder resin.

The metal catalyst assists in the relevant reactions in the catalyst layer (oxidation of fuel and reduction of oxygen), typically platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy At least one member selected from the group consisting of (M = Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, W, Mo, Rh, Sn and Zn) And Pt, Pt / Ru, Pt / W, Pt / Ni, Pt / Sn, Pt / Mo, Pt / Pd, Pt / Fe, Pt / Cr, Pt / Co, Pt / Ru One or more selected from the group consisting of / W, Pt / Ru / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni, and Pt / Ru / Sn / W can be used.

In addition, such a metal catalyst may be used as the metal catalyst (black) itself, or may be supported on a carrier. As the carrier, carbon such as acetylene black, denka black, activated carbon, ketjen black, graphite may be used, or inorganic fine particles such as alumina, silica, titania, zirconia may be used, but carbon is generally used. More preferably, a carbon-based platinum or binary alloy catalyst based on carbon may be 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.

The metal catalyst is preferably included in 20 to 95% by weight, more preferably 50 to 95% by weight relative to the total weight of the catalyst layer. If the content is less than 20% by weight, the redox rate of the reactant is not preferable, and if it is more than 95% by weight, the resistance to hydrogen ion conduction in the catalyst layer is high.

The binder resin serves to improve adhesion between the catalyst layer and the polymer electrolyte membrane and to improve hydrogen ion conductivity. Therefore, it is preferable to use a polymer resin having ion conductivity as the binder resin, and more preferably 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. The polymer resin which has is 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 polymers selected from ether ketone polymers and polyphenylquinoxaline polymers can be used. Most preferably poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), copolymers of tetrafluoroethylene and fluorovinylethers containing sulfonic acid groups, defluorinated sulfided polyetherketones, aryl ketones, Poly (2,2'-m-phenylene) -5,5'-bibenzimidazole (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole) and poly (2,5- One or more polymers selected from benzimidazole), more preferably poly (perfluorosulfonic acid).

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.

The non-conductive polymer may be polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro alkyl vinyl ether copolymer (PFA) ethylene / tetrafluoro Copolymers of ethylene (Ethylene / Tetrafluoroethylene (ETFE)), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride, and polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) At least one selected from the group consisting of is preferable.

The binder resin is preferably contained in 3 to 50% by weight, more preferably 5 to 40% by weight based on the total weight of the catalyst layer. If the content is less than 3% by weight, it is not preferable because the resistance to hydrogen ion conduction in the catalyst layer is increased. If the content exceeds 50% by weight, the effective surface area of the catalyst for redox reaction is increased because the electron transfer resistance is increased and the surface of the platinum-based catalyst is blocked. It is lowered and is not preferable.

Between the anode electrode and the cathode electrode there is a polymer electrolyte membrane having an ion exchange function for moving the hydrogen ions generated in the catalyst layer of the anode electrode to the catalyst layer of the cathode electrode.

As such a polymer electrolyte membrane, a polymer having excellent hydrogen ion conductivity can 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. Preferred polymer electrolyte membranes include fluoropolymers, benzimidazole polymers, polyimide polymers, polyetherimide polymers, polyphenylenesulfide polymers, polysulfone polymers, polyethersulfone polymers, and polyether ketone polymers. , A polyether-etherketone-based polymer and a polyphenylquinoxaline-based polymer may include one or more hydrogen ion conductive polymers, and more preferably poly (perfluorosulfonic acid), poly (purple) Fluorocarboxylic acid), copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, defluorinated sulfide polyether ketones, aryl ketones, poly (2,2'-m-phenylene) -5, At least one hydrogen ion selected from the group consisting of 5'-bibenzimidazole (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole) and poly (2,5-benzimidazole) Evangelize The thing containing a polymeric polymer can be used.

In addition, when the perfluorosulfonic acid (trade name: Nafion) is used as the polymer electrolyte membrane, X is a monovalent ion such as sodium, potassium, cesium, etc. in an ion exchange group (-SO ₃ X) at the side chain end; Or it is more preferable to substitute by using tetrabutylammonium ion.

When the ion-exchange group of the side chain end is used as described above, the thermal stability is increased, so that the polymer resin is deteriorated even if the heat treatment is performed at a high temperature of 200 ° C. or higher during the hot rolling process during fabrication of the membrane-electrode assembly. Or there is no fear that the life of the fuel cell is reduced accordingly. In addition, a polymer electrolyte membrane having an ion exchange group substituted with ions such as sodium, potassium, cesium, or tetrabutyl ammonium, for example, when substituted with sodium ions, the sodium-form polymer electrolyte membrane is then subjected to acid treatment for the catalyst layer. Upon resulfonation, it becomes a proton-form polyelectrolyte membrane.

In addition, the membrane-electrode assembly may further include a microporous layer on the electrode substrate to enhance the gas diffusion effect. This microporous layer may generally comprise a conductive powder having a small particle diameter, such as carbon powder, carbon black, acetylene black, ketjen black, activated carbon, carbon fiber, fullerene or carbon nanotubes. 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, a polymer having electrical conductivity may be used. Specifically, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, cellulose acetate, or the like may be preferably used. As the solvent, alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone and the like 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.

The membrane-electrode assembly for a fuel cell having the above structure includes forming a catalyst layer in a predetermined pattern on a polymer electrolyte membrane using a catalyst layer-forming composition including a metal catalyst and a binder resin, and then binding the electrode substrate. It can be produced by the method for producing a membrane-electrode assembly for a fuel cell according to a second exemplary embodiment of the present invention.

More specifically, a method of manufacturing a membrane-electrode assembly for a fuel cell may include preparing a composition for forming a catalyst layer comprising a thickener, a metal catalyst, and a binder resin; Forming a catalyst layer by applying the catalyst layer forming composition to a surface of a release film in a predetermined pattern; Transferring the catalyst layer to a polymer electrolyte membrane; Acid treating the polymer electrolyte membrane to which the catalyst layer is transferred; And binding an electrode substrate to the acid treated catalyst layer-forming polymer electrolyte membrane.

Specifically, first, a metal catalyst and a binder resin are added to a solvent to prepare a composition for forming a catalyst layer. In this case, the composition for forming the catalyst layer may further include a thickener.

When the thickener is included, the composition for forming the catalyst layer includes 10 to 35 wt% of a thickener, 10 to 35 wt% of a metal catalyst, and 30 to 80 wt% of a binder resin, and more preferably 15 to 15 wt%, based on the total weight of the composition. To 25 weight percent, 15 to 25 weight percent metal catalyst and 35 to 60 weight percent binder resin. Within the above content range, the concentration and viscosity of the composition may be controlled to form a catalyst layer having a uniform thickness by a method such as silk screen printing. Not.

It is preferable that the prepared composition for forming a catalyst layer has a viscosity of 1,000 to 100,000 cps, more preferably 2,000 to 50,000 cps. If the viscosity of the composition for forming the catalyst layer is less than 1,000 cps, the flowability is increased, which is not preferable for forming a catalyst layer having a predetermined thickness, and if it exceeds 100,000 cps, the printability is lowered, which is not preferable.

The metal catalyst and binder resin are the same as described above. The binder resin is preferably used in a solution state, and in one embodiment of the present invention, a binder resin solution is used at a concentration of 5 wt%.

The thickener prevents a solvent contained in the composition for forming a catalyst layer from penetrating into the polymer electrolyte membrane and swelling the polymer electrolyte membrane to reduce structural stability of the membrane-electrode assembly when the catalyst layer is directly formed on the polymer electrolyte membrane. Play a role. However, since the thickener may be decomposed chemically during the redox reaction caused by the fuel cell operation when remaining in the catalyst layer, thereby reducing the ion conductivity or the electronic conductivity of the catalyst layer, the catalyst layer does not remain in the catalyst layer of the finally prepared membrane-electrode assembly. It is preferable to remove by acid treatment after formation.

In addition, the thickener may be removed during the acid treatment to convert the catalyst layer into a microporous structure, thereby providing a passage for smooth inflow of the reactants and rapid removal of the reaction by-products.

The thickener may be glycerin, dipropylene glycol, methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl ethyl cellulose, carboxymethyl cellulose, polyether polymer, chrysotile asbestos (Chrysotile asbestos). ), Polyamide polymer and Carbopol can be used.

The solvent may be an alcohol such as ethanol, isopropyl alcohol, ethyl alcohol, n-propyl alcohol, butyl alcohol, N-methyl-2-pyrrolidinone (NMP), dimethylformamide ( dimethylformamide (DMF), dimethyl acetamide (DMA), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), acetone, methyl ethyl ketone (MEK), tetramethylurea (tetramethylurea), trimethyl phosphate, butyrolactone, isophorone, carbitol acetate, methyl isobutyl ketone, N-butyl acetate acetate, cyclohexanone, diacetone alcohol, diisobutyl ketone, ethyl acetoacetate, glycol ether, propylene carbonate (propylene carbonate), ethylene carbonate (ethylene carbonate), dimethyl carbonate (dimethyl carbonate), diethyl carbonate (diethyl carbonate), deionized water and one or more selected from the group consisting of a mixture thereof may be used, more preferably It is possible to use a mixture of water and 2-propanol.

The solvent may be included in the amount of the balance in the composition for forming the catalyst layer, and preferably may be included in an amount of 20 to 80% by weight based on the total weight of the composition for forming the catalyst layer to form a catalyst layer with an appropriate viscosity. If the content of the solvent is less than 20% by weight, the viscosity is lowered and flowability is increased, and therefore, it is not preferable for coating of a uniform area, and if it is more than 80% by weight, the viscosity is high and the printability is not preferable.

The catalyst layer forming composition further comprises a defoamer; Deflocculants for preventing aggregation, including water-soluble polymers such as polyphosphates, lignosulfonates, quebracho, etc .; It may further include additives such as fixing agents. These, like the thickeners, are all removed during the acid treatment during catalyst layer preparation.

Thereafter, the prepared composition for forming a catalyst layer may be uniformly mixed by mechanical mixing or ultrasonic mixing.

Next, the catalyst layer forming composition is applied to one surface of the release film in a predetermined pattern and dried to form a catalyst layer.

Examples of the release film include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer having a thickness of about 100 mm. PFA) fluorine resin films such as ethylene / tetrafluoroethylene (ETFE); Or polyimide (Kapton ^® , Manufactured by DuPont), Polyester (Mylar ^® , Non-fluorine polymer films, such as those manufactured by DuPont, can be used.

The pattern of the catalyst layer is as described above.

The coating process is a group consisting 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 the method selected from, but is not limited thereto. More preferably, the screen printing method using the mask (mesh # 100-300) of the same shape as the flow path of a separator can be applied.

Thereafter, the catalyst layer formed on the release film is placed on the polymer electrolyte membrane, and then hot rolled under the conditions of 100 to 250 ° C. and 300 to 2000 psi to transfer to the polymer electrolyte membrane. More preferably, it can be transferred by hot rolling under the conditions of 130 to 200 ° C and 500 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 is the same as described above, and preferably has a thickness of 10 to 200㎛. Since the method for preparing the polymer electrolyte membrane is well known in the art, a detailed description thereof will be omitted.

Thereafter, the catalyst layer transferred to the polymer electrolyte membrane (catalyst coated membrane) is subjected to an acid treatment for about 1 hour at 80 to 100 ℃, 1 M aqueous solution conditions, and washed with 100 ℃ deionized water for 1 hour. In this case, sulfuric acid may be used as the acid. If the above condition is exceeded, the thickener component in the catalyst layer may not be completely removed, and there is a risk of chemical decomposition in the strong redox atmosphere of the fuel cell when it remains.

After the acid treatment all organic components, including thickeners, are removed, so that only the metal catalyst and binder resin are present in the catalyst layer. Since the thickener is non-conductive, electrical resistance after acid treatment is further reduced, and micropores are formed in the catalyst layer as the thickener is removed, thereby increasing the roughness and porosity of the catalyst layer.

Thereafter, an electrode substrate is bonded to both surfaces of the acid-treated catalyst-forming polymer electrolyte membrane to prepare a 5-layer membrane-electrode assembly.

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

The membrane-electrode assembly for a fuel cell prepared as described above exhibits excellent cell output even with a reduced catalyst loading by including a catalyst layer formed in a predetermined pattern. In addition, the thickener used in the formation of the catalyst layer prevents the swelling of the polymer electrolyte membrane due to solvent penetration into the polymer electrolyte membrane, thereby improving the life characteristics of the battery. In addition, since the micropores in the catalyst layer are formed, it is possible to increase the flow speed (flow speed) of the reactants, it is easy to discharge the reaction product, such as CO ₂ . In addition, the catalytic activity may be increased by increasing the reaction surface area of the catalyst layer due to the formation of the micropores.

According to a third exemplary embodiment of the present invention, there is provided a fuel cell system including the membrane-electrode assembly having the above configuration.

The fuel cell system includes at least one electricity generating unit including separators on both sides of the membrane-electrode assembly and the membrane-electrode assembly, and generates a fuel supply unit and an oxidant to supply fuel to the electricity generating unit. And an oxidant supply unit for supplying to the 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. 1, which will be described in more detail with reference to the following. Although the structure shown in FIG. 1 shows a system for supplying fuel and oxidant to an electric generator by 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 a stack 7 having at least one electricity generator 19 for generating electrical energy through an electrochemical reaction between a fuel and an oxidant, and a fuel supply unit for supplying the fuel. (1) and the oxidant supply part 5 which supplies an oxidant to the said electricity generating part 19 is comprised.

In addition, the fuel supply unit 1 for supplying the fuel has a fuel tank 9 for storing fuel.

The oxidant supply unit 5 for supplying the oxidant to the electricity generating unit 19 of the stack 7 may include at least one oxidant pump 13 for sucking the oxidant with a predetermined pumping force.

The electricity generating unit 19 is a membrane-electrode assembly 21 for oxidizing and reducing a fuel and an oxidant and a separator (bipolar plates) 23 and 25 for supplying fuel and an oxidant to both sides of the membrane-electrode assembly. It consists of.

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)

3.0 g of deionized water was added dropwise to 3.0 g of a catalyst of Pt black (Hispec ^® 1000, manufactured by Johnson Matthey) and Pt / Ru black (Hispec ^® 6000, manufactured by Johnson Matthey), and the catalyst particles were wetted with water. The catalyst 10wt% Nafion (Nafion ^®, Dupont Co.) aqueous dispersion was added dropwise to 4.5g and stirred mechanically and 1M TBAOH / methanol solution was added to 0.5g and 4.0g of dipropylene glycol mechanical stirring at 30-minute intervals and ultrasound After the stirring was repeated three times, the mixture was further mechanically stirred using a magnetic stirrer for 12 hours to prepare a composition for forming a catalyst layer.

The composition for forming the catalyst layer was coated with a thickness of about 100 mm on a Teflon film having a thickness of 50 mm using a 150 mesh stainless steel mask that matches the flow channel pattern of the separator. In this case, 40% of the non-coated portion of the coating layer does not exist among the total 5 × 5 cm ² . After drying the catalyst layer-coated Teflon film for 6 hours in an 80 ° C. drying furnace in a nitrogen atmosphere, the solvent was evaporated, the catalyst layers were aligned on both sides of the polymer electrolyte membrane of sodium-form Nafion 115, and then 200 ° C. The catalyst layer was transferred to the polymer electrolyte membrane by applying a temperature and a pressure of 500 psi for 3 minutes.

The polymer electrolyte membrane in which the catalyst layer was formed was treated for 1 hour in a 1 M sulfuric acid solution at 100 ° C., and the organic components in the catalyst layer were extracted while converting the Nafion of the catalyst layer and the electrolyte membrane into a proton-form. Finally, the sulfated polymer electrolyte membrane was washed in deionized water at 100 ° C. for 1 hour. The platinum catalyst loading of the anode electrode and the cathode electrode was adjusted to 2 mg / cm ² , respectively.

The membrane-electrode assembly was physically bonded with E-Tek's catalyst layer-free ELAT gas diffusion body having fine pores formed on one surface of TGPH090 carbon paper treated with 10% water repellency as an electrode substrate, and between two gaskets. After the insertion, the separator was inserted into two separators in which a gas channel channel and a cooling channel were formed, and pressed between copper end plates to prepare a 25 cm ² unit cell.

(Comparative Example 1)

A unit cell was prepared in the same manner as in Example 1, except that the composition for forming a catalyst layer was prepared at 5 × 5 cm ² without a solid portion, and the catalyst loading amounts of the anode and the cathode were adjusted to 4 mg / cm ² , respectively. It was.

For the fuel cells prepared according to Example 1 and Comparative Example 1, 1 M methanol and dry air were stoichiometry introduced at a condition of 3.0. Voltage and power density were measured.

In addition, a constant current of 0.2 A / cm ² was applied and the voltage change was observed according to the driving time. The results are shown in FIGS. 2 and 3.

2 is a graph showing the voltage and output change of the fuel cell according to the current density according to Example 1 and Comparative Example 1, wherein ○ and ● are the fuel cell of Comparative Example 1 Results. In addition, Figure 3 is a graph showing the voltage change according to the operating time of the fuel cell according to Example 1 and Comparative Example 1.

As shown in Figure 2, the fuel cell of Example 1 according to the present invention can be confirmed that the voltage and output density is higher than that of Comparative Example 1. The amount of catalyst loading in the fuel cell of Example 1 corresponds to 50% of the amount of catalyst loading in the fuel cell of Comparative Example 1. From this, the fuel cell according to the present invention has excellent power density even with a reduced amount of catalyst loading. It can be seen that.

In addition, as shown in Figure 3, the fuel cell of Example 1 according to the present invention, the initial voltage is slightly lower than the fuel cell of Comparative Example 1, but the change rate of the voltage as the operating time is smaller, the fuel cell of Comparative Example 1 It was found to be more stable and have excellent life characteristics.

The membrane-electrode assembly for a fuel cell of the present invention can exhibit excellent cell output even with a reduced catalyst loading, and can improve the life characteristics of the cell.

Claims (21)

An anode electrode and a cathode electrode located opposite each other; And It includes 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, and Located between the electrode substrate and the polymer electrolyte membrane, the catalyst layer formed in a predetermined pattern Membrane electrode assembly for a fuel cell comprising a. The method of claim 1, The pattern of the catalyst layer corresponds to the shape of the flow path of the separator membrane-electrode assembly for a fuel cell. The method of claim 2, The flow path of the separator is a channel-shaped or island-shaped membrane-electrode assembly for a fuel cell. The method of claim 1, The pattern of the catalyst layer is a fuel cell membrane-electrode assembly having a single channel shape. The method of claim 1, The pattern of the catalyst layer is a fuel cell membrane-electrode assembly having a channel shape having a width of 1 to 2mm wider than the channel width of the separator.  The method of claim 1,  The catalyst layer is a fuel cell membrane-electrode assembly having a porosity of 10 to 90% by volume relative to the total volume of the catalyst layer. The method of claim 1, The catalyst layer is a fuel cell membrane-electrode assembly comprising a metal catalyst and a binder resin. The method of claim 1, The metal catalyst may be platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy or platinum-M alloy (M = Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, At least one metal selected from the group consisting of W, Mo, Rh, Sn, and Zn). The method of claim 1, Wherein the metal catalyst is a fuel cell membrane-electrode assembly that is contained in 20 to 95% by weight based on the total weight of the catalyst layer. The method of claim 1, The binder resin is a fuel cell membrane-electrode assembly 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. The method of claim 1, The binder resin is a fuel cell membrane-electrode assembly that is contained in 3 to 50% by weight based on the total weight of the catalyst layer. The method of claim 1, Wherein 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 may include a monovalent ion selected from the group consisting of sodium, potassium and cesium in an ion exchange group -SO ₃ X at the side chain terminal; Or perfluoro sulfonic acid substituted with tetrabutylammonium ions. A method of manufacturing a membrane-electrode assembly for a fuel cell, comprising: forming a catalyst layer on a polymer electrolyte membrane in a predetermined pattern by using a composition for forming a catalyst layer including a metal catalyst and a binder resin and then binding the electrode substrate. The method of claim 14, The manufacturing method Preparing a composition for forming a catalyst layer comprising a thickener, a metal catalyst and a binder resin; Forming a catalyst layer by applying the catalyst layer forming composition to a surface of a release film in a predetermined pattern; Transferring the catalyst layer to a polymer electrolyte membrane; Acid treating the polymer electrolyte membrane to which the catalyst layer is transferred; And Binding an electrode substrate to the acid-treated polymer electrolyte membrane Method for producing a membrane-electrode assembly for a fuel cell comprising a. The method of claim 15, The composition for forming a catalyst layer is a fuel cell membrane-electrode assembly manufacturing method comprising a thickener 10 to 35% by weight, a metal catalyst 10 to 35% by weight and a binder resin 30 to 80% by weight based on the total weight of the composition. The method of claim 15, The catalyst layer forming composition is a method of manufacturing a membrane-electrode assembly for a fuel cell having a viscosity of 1000 to 100,000cps. The method of claim 15, The thickener is glycerol, glycerin, dipropylene glycol, methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl ethyl cellulose, carboxymethyl cellulose, polyether polymer, chrysotile asbestos, poly A method of producing a membrane-electrode assembly for a fuel cell comprising at least one selected from the group consisting of amide polymers and carbopol. The method of claim 15, The release film is composed of polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkylvinylether copolymer, ethylene / tetrafluoroethylene, polyimide and polyester Method for producing a membrane-electrode assembly for a fuel cell that is a polymer film selected from the group. The method of claim 15, The transfer process is a method of manufacturing a membrane-electrode assembly for a fuel cell that is carried out by hot rolling at 100 to 250 ℃ and 300 to 2000 psi. 14. A membrane-electrode assembly according to any one of claims 1 to 13 and separators located on both sides of the membrane-electrode assembly, wherein at least one electricity generation generates electricity through an electrochemical reaction of fuel and oxidant. part; A fuel supply unit supplying fuel to the electricity generation unit; And Oxidant supply unit for supplying an oxidant to the electricity generating unit Fuel cell system comprising a.

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