KR20090053096A - Membrane-electrode assembly for fuel cell and method of producing same - Google Patents

Abstract

The present invention relates to a membrane-electrode assembly for a fuel cell and a method for manufacturing the membrane, wherein the membrane-electrode assembly includes: an anode electrode and a cathode electrode positioned to face each other; And a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode, wherein at least one of the anode electrode and the cathode electrode includes pores having an average pore size of 3 to 30 nm, and a specific surface area of 25 to 40 m ² / g, the catalyst layer.

In the membrane-electrode assembly of the present invention, pores having a large average size are uniformly formed, thereby preventing crossover of reactants and improving battery performance.

Electrode, transfer, pore, catalyst utilization

Description

Membrane-electrode assembly for fuel cell and method for manufacturing same {MEMBRANE-ELECTRODE ASSEMBLY FOR FUEL CELL AND METHOD OF PRODUCING SAME}

The present invention relates to a membrane-electrode assembly for a fuel cell and a method of manufacturing the same, and more particularly, to a fuel cell membrane having a pore having a large average size uniformly formed to prevent crossover of reactants and improving battery performance. It relates to an electrode assembly.

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 a 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 of military equipment 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 handle 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 membrane-electrode assembly for a fuel cell that can form pores with a large average particle size in a uniform distribution to prevent crossover of reactants and improve cell performance.

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

Technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the present invention is 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, wherein at least one of the anode electrode and the cathode electrode includes pores having an average pore size of 3 to 30 nm, and a specific surface area of 25 to 40 m ² / It provides a membrane-electrode assembly for a fuel cell comprising a catalyst layer that is g.

The present invention also applies a catalyst layer composition to a kepton release substrate to form a first catalyst layer; Positioning a polymer electrolyte membrane so as to face the first catalyst layer of the release substrate; Rolling the first catalyst layer and the polymer electrolyte membrane and removing a release substrate from the rolled product to form a polymer electrolyte membrane and a second catalyst layer formed on the polymer electrolyte membrane; It provides a method for producing a fuel cell membrane-electrode assembly comprising the step of placing an electrode substrate in the second catalyst layer.

The method of manufacturing the membrane-electrode assembly of the present invention can uniformly form pores to prevent crossover of reactants and improve battery performance.

Hereinafter, the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

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.

One method of manufacturing the membrane-electrode assembly includes coating a catalyst layer composition on a release substrate, placing the release substrate on a polymer electrolyte membrane for transferring the coating layer, and then transferring the coating layer by rolling or the like. .

However, this method is performed by applying a pressure of 100 kgf / cm ² at a temperature of about 130 ° C. for 3 to 5 minutes in the rolling process, and generally by a bar coater process. There has been a problem in that the diffusion of fuel and oxidant has become difficult.

The present invention is to solve the problems caused by the formation of this dense catalyst layer. That is, as the catalyst layer formed by the production method of the present invention has pores and the pores are large in size with a uniform distribution, the reactants of the fuel and the oxidant can be easily diffused to efficiently use the fuel and the oxidant. Can be. In the present invention, by appropriately adjusting the pore size and distribution, the reactant is easily convinced, and the problem of fuel crossover does not occur, thereby improving performance (reducing mixed potential), increasing durability, and increasing fuel economy. In addition, when a mixture of hydrocarbon fuel and water is used as a fuel, water crossover can be prevented and water flooding can be prevented at the cathode electrode. Also, a small amount of water generated at the cathode electrode in the fuel cell system is prevented. Due to the circulation, a smaller volume of capacitors can be used, thereby reducing the overall volume of the fuel cell system.

Hereinafter, the manufacturing method of the membrane-electrode assembly of the present invention will be described in detail.

First, a catalyst composition including a catalyst, a binder, and a solvent is applied to a polyimide release substrate to form a first catalyst layer.

The polyimide release substrate may be one commercially available under the trade name Kapton, but is not limited thereto.

The coating step is preferably performed after placing the release substrate on a heating plate, so that the coating and drying steps can be performed simultaneously. The temperature of the heating plate is preferable because 40 to 50 ° C. rapidly evaporates the solvent and does not deteriorate the physical properties of the catalyst.

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 Silver, at least one transition metal selected from the group consisting of Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Mo, W, Rh and Ru) The above catalyst 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 nanotubes, carbon nanofibers, carbon nanowires, carbon nanoballs or activated carbon may be used, or alumina, silica, titania, Inorganic fine particles such as zirconia may also be used, but in general, carbon-based materials are widely 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 and fluorovinyl ether containing sulfonic acid groups, sulfide polyether ketones, aryl ketones, poly (2,2'-m-phenylene) -5,5'-bibenzimidazoles [poly ( 2,2'-m-phenylene) -5,5'-bibenzimidazole] or poly (2,5-benzimidazole) may be used including one or more hydrogen ion conductive polymers.

The hydrogen ion conductive polymer may replace H with Na, K, Li, Cs or tetrabutylammonium in a cation exchanger at the side chain terminal. 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 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 At least one selected from the group consisting of silbenzenesulfonic acid and sorbitol is more preferred.

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.

Next, the polymer electrolyte membrane of the fuel cell is positioned to face the first catalyst layer and then rolled.

The rolling process may be performed at a temperature of 100 to 140 ° C. for 2 to 10 minutes under a pressure condition of 1 to 7 t (metric ton).

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 group, carboxylic acid group, phosphoric acid group, phosphonic acid group and derivatives thereof in the side chain.

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 one or more selected from polymers, polyether-etherketone-based polymers or polyphenylquinoxaline-based polymers, 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)- And at least one selected from 5,5'-bibenzimidazole [poly (2,2'-m-phenylene) -5,5'-bibenzimidazole] or poly (2,5-benzimidazole). .

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 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 release substrate is removed from the obtained rolled product. According to this process, the catalyst layer formed on the release substrate is transferred to the polymer electrolyte membrane, thereby producing a fuel cell membrane-electrode assembly. The usual step of placing the electrode substrate in the catalyst layer may be further performed.

In the present invention, the catalyst layer has pores of 3 to 30nm, preferably 3 to 11nm size. As such, the catalyst layer of the present invention has pores of the same size before and after the rolling process, that is, before and after the transfer process. Therefore, the catalyst layer formed by the conventional transfer method is very dense, even if almost no pores are formed or formed, the size is about 4nm is too small to solve the problem that the diffusion of the reaction is hardly made. That is, the catalyst layer of the present invention has an optimum pore size that can effectively prevent crossovers in which the reactants are excessively moved, while facilitating the diffusion of the reactants.

At this time, the thickness of the formed catalyst layer is preferably 10 to 13㎛. If the thickness of the catalyst layer is out of the above range, the resistance in the electrode is increased and the battery performance is lowered, which is not preferable. In addition, the catalyst layer is formed very uniformly. This is because the conventional method for coating the catalyst composition directly on the electrode substrate (CCS: Catalyst Coated Substrate) can form large pores, but can solve the problem caused by the non-uniformly formed catalyst layer.

The electrode substrate plays a role of supporting the electrode and diffuses the fuel and the oxidant to the catalyst layer, thereby serving to easily access the fuel and the oxidant to the catalyst layer. The electrode substrate is a conductive substrate, and representative examples thereof include carbon paper, carbon cloth, carbon felt, or metal cloth (porous film or polymer fiber composed of metal in a fibrous state). The metal film is formed on the surface of the formed cloth) 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 and the like can be preferably used. As the solvent, alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, and the like, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone and the like can 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 of the present invention manufactured by the above-described process includes an anode electrode and a cathode electrode positioned opposite each other, and includes a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode.

In this case, at least one of the anode electrode and the cathode electrode includes a catalyst layer having pores having an average pore size of 3 to 30 nm and a specific surface area of 25 to 40 m ² / g. More preferred average pore size is 3 to 11 nm and more preferred specific surface area is 25 to 30 m ² / g. The catalyst layer having the average pore and the specific surface area can facilitate the diffusion of the reactant while effectively preventing the crossover of the reactant from moving excessively.

As such, the catalyst layer of the present invention has an average particle size of 3 to 30 nm uniformly, and the average particle size of 10 to 10 is formed by a method of coating a conventional catalyst composition directly on an electrode substrate (CCS: Catalyst Coated Substrate). Since the pore distribution is narrower than that of 50 nm, it is possible to solve the problem that the catalyst layer is formed nonuniformly according to the wide pore distribution.

In addition, a method of forming a catalyst layer on a polymer electrolyte membrane (CCM: Catalyst Coated Membrane), which is generally formed by a transfer method, is formed with only about 4 nm of pores, so that the pore size is so small that the reactants hardly diffuse. This can solve the problem that the battery output is lowered.

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. 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 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.

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 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 17 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)

An anode catalyst layer was formed by applying an anode catalyst composition comprising a Pt-Ru catalyst, a perfluorosulfonate (trade name: Nafion) binder, and an isopropyl alcohol solvent, supported on a Cettone release film placed on a 45 ° C. heating plate. . At this time, the mixing ratio of the catalyst and the binder was 93: 7 wt%. The catalyst loading of the anode catalyst layer was 6 mg / cm ² .

A cathode catalyst composition was prepared by mixing a Pt catalyst, a perfluorosulfonate (trade name: Nafion) binder, and an isopropyl alcohol solvent supported on a carbon carrier. At this time, the mixing ratio of the catalyst, the binder and the solvent was 93: 7 wt%. The cathode catalyst composition was applied to a carbon paper electrode substrate (10DA of SGL Corporation) to prepare a cathode.

Subsequently, a commercial Nafion 115 (perfluorosulfonic acid) polymer electrolyte membrane and the release film were positioned to face the anode catalyst layer toward the polymer electrolyte membrane, followed by a pressure of 6.5 tons at a temperature of 135 ° C. After rolling for 10 minutes, the anode catalyst layer was transferred to one surface of the polymer electrolyte membrane. The carbon electrode base (10 GL) was placed on the anode catalyst layer not in contact with the polymer electrolyte membrane, and the cathode was placed on the other side of the polymer electrolyte to which the anode catalyst layer was not transferred. The unit cell, which is a membrane-electrode assembly, was prepared by hot-pressing at a pressure of metric ton for 3 minutes.

(Comparative Example 1)

An anode electrode was prepared by applying a catalyst composition comprising a Pt-Ru catalyst supported on a carbon carrier, a perfluorosulfonate (trade name: Nafion) binder, and an isopropyl alcohol solvent to a carbon paper electrode base (10 GL). A catalyst layer was formed. At this time, the mixing ratio of the catalyst and the binder was 93: 7 wt%.

A cathode electrode was prepared by applying a catalyst composition comprising a Pt catalyst supported on a carbon carrier, a perfluorosulfonate (trade name: Nafion) binder, and an isopropyl alcohol solvent to a carbon paper electrode substrate (10DA of SGL). At this time, the mixing ratio of the catalyst and the binder was 93: 7 wt%.

A unit cell, which is a membrane-electrode assembly, was manufactured using the anode electrode, the cathode electrode, and the polymer electrolyte membrane used in Example 1.

(Comparative Example 2)

An anode catalyst layer was applied to a polytetrafluoroethylene release film by applying an anode catalyst composition comprising a Pt-Ru catalyst supported on a carbon carrier, a perfluorosulfonate (trade name: Nafion) binder, and an isopropyl alcohol solvent. At this time, the mixing ratio of the catalyst, the binder and the solvent was 93: 7 wt%.

To the polytetrafluoroethylene release film was applied a cathode catalyst composition comprising a Pt catalyst, a perfluorosulfonate (trade name: Nafion) binder and an isopropyl alcohol solvent supported on a carbon carrier to form a cathode catalyst layer. At this time, the mixing ratio of the catalyst and the binder was 93: 7 wt%.

Subsequently, the anode catalyst layer and the cathode catalyst layer were placed on both sides of a commercial Nafion 115 (perfluorosulfonic acid) polymer electrolyte membrane, followed by hot-pressing for 3 minutes at a pressure of 2 tons (metric ton) at a temperature of 125 ° C. After the catalyst layer and the cathode catalyst layer were transferred to the polymer electrolyte membrane, an electrode substrate (anode SGL 10AA, cathode SGL 10DA) was placed on both surfaces not in contact with the polymer electrolyte membrane to prepare a unit cell as a membrane-electrode assembly. .

The cell prepared according to Comparative Example 1 was operated at 0.4V at 50 ° C. for 10 days using 1M methanol as fuel, and then the daily output density was measured. The results are shown in FIG. 2. In addition, on day 4, measurements were also performed at 60 ° C. and 70 ° C. (output densities 71 mW / cm ² and 87 mW / cm ² in FIG. 2, respectively). As shown in FIG. 2, it can be seen that the output density after operating for 10 days is reduced by about 9% in the output density obtained after operating for 3 days.

In addition, 10 unit cells prepared according to Example 1 were operated at 0.4V at 50 ° C. for 7 days using 1M methanol fuel, and then the daily output density was measured. The results are shown in FIGS. Respectively. As shown in FIG. 3, the fuel cell of Example 1 exhibits uniform performance even after several experiments, and it can be seen that the battery has excellent reliability.

IV characteristics and CV characteristics (current density measurement at constant voltage) of the batteries of numbers 1 to 10 shown in FIG. 3 were measured, and the results are shown in FIGS. 4 and 5, respectively. As shown in Figs. 4 and 5, the cell results of Nos. 1 to 10 appeared very similarly, so that the fuel cell of Example 1 can reliably know that a uniform result is obtained.

The cells of Nos. 3, 6, 8, and 10 were operated for 13 days at 0.4V at 50 ° C using 1M methanol fuel, and then the daily power densities were measured and the results are shown in Fig. 6, respectively. From this result, the performance decay rate (PDR) was measured, and the performance deterioration rate during long time use was determined. As shown in Fig. 6, it can be seen that the batteries of Nos. 6, 8, and 10 of Example 1 did not deteriorate, but rather improved (because of the deterioration rate, the value "-" means that the performance rather improved). In addition, the battery of No. 3 had a decrease in performance by about 4.2%, which is very low compared to the reduction of about 9% in the case of the battery of Comparative Example 1 shown in FIG. 2. Therefore, it can be seen that the fuel cell of Example 1 can be used for a long time because its performance does not decrease when used for a long time.

Experiments for observing changes over time at high temperatures were performed on the cells of two batteries (No. 11 and 12) prepared according to Example 1 above. That is, the batteries of Nos. 11 and 12 were measured at 50 ° C. for 3 days, and from Day 4, the experiments were performed to measure the output densities of 50 ° C., 60 ° C., and 70 ° C. for one day, and the results are shown in FIG. 7. Indicated. As shown in Fig. 7, it can be seen that there is almost no decrease in the output density even when operating at high temperature (70 ° C) for 9 days.

On the other hand, the battery of Comparative Example 2 was tested in the same manner as in Example 1 to observe the change over time at high temperature, and is shown in FIG. 8. As shown in FIG. 8, it can be seen that the output density decreases as the operating time passes at a high temperature.

Methanol crossover, water crossover and methanol-electricity conversion of unit cells prepared according to Example 1 and Comparative Examples 1 and 2 were measured, and the results are shown in FIG. 9. The results shown in FIG. 9 show that 10 cells were produced by the method of Example 1, Comparative Examples 1 and 2, respectively, and then the methanol crossover, water crossover, and methanol current conversion experiments were respectively performed on the cells, and the maximum values thereof were obtained. And the minimum value. As shown in FIG. 9, in the unit cell manufactured according to Example 1, the methanol crossover showed the same level as that of Comparative Example 2 in both the maximum value and the minimum value, but was reduced by 20 to 30% compared to that of Comparative Example 1, and the water crossover It can be seen that is significantly reduced compared to Comparative Examples 1 and 2. In addition, the methanol current conversion was improved compared to Comparative Examples 1 and 2, and in particular about 40% compared to Comparative Example 1, it can be seen that a high output can be obtained even using a small amount of fuel.

In addition, a nitrogen adsorption experiment was conducted to determine the surface area of the catalyst layer of the anode electrode of Example 1, and the results are shown in FIG. 10. In addition, nitrogen adsorption experiments were conducted to determine the pore size distribution of the catalyst layers of the anode electrodes of Example 1, Comparative Example 1 and Comparative Example 2, and the results are shown in FIG. 11. Nitrogen adsorption tests were prepared a catalyst layer by applying an anode catalyst composition prepared in Example 1 in 45 ℃ Kapton film, 40cm ² in an amount of 6mg / cm ^2, the hot-after pressing, into a test-tube to measure the nitrogen adsorption After drying at 120 ° C to remove moisture, it was carried out by the ASAP2010 method.

In FIG. 10, CCFL Ads (adsorption) is a measure of adsorption while applying pressure to the catalyst bed, and CCFL Des (desorption) is a measure of adsorption while removing pressure from the catalyst bed. As shown in FIG. 10, it can be seen that the specific surface area is almost 30.97 m ² / g. In addition, as shown in FIG. 11, the pores formed in Example 1 were almost distributed in the range of about 3 to 11 nm, whereas in Comparative Example 1, the pores were distributed in the range of 10 to 50 nm, and in the case of Comparative Example 2 It can be seen that the distribution is almost 4nm.

The specific surface area of Example 1 shown in FIG. 10 and the pore size shown in FIG. 11 are summarized in Table 1 below. Also, Comparative Examples 1 and 2 were subjected to nitrogen adsorption experiments in the same manner as in Example 1, and thus the specific surface area. The results are shown in Table 1 below. In addition, the pore volumes of Example 1, Comparative Examples 1 and 2 are also shown in Table 1 below.

Comparative Example 1 Comparative Example 2 Example 1 Specific surface area (m ² / g) 3.42 19.21 30.97 Pore Volume (cm ³ / g) 0.0128 0.0208 0.0454 Pore size (nm) 10-50 4 3-11

As shown in Table 1, the anode catalyst layer of Example 1 has a large specific surface area, and in particular, the specific surface area is very large as compared with Comparative Example 1, so that the reaction area is large, so that the performance of the fuel cell can be improved. Can be predicted. In addition, since the pores of 3 to 11nm are distributed, the anode catalyst layer prepared according to Example 1 has a pore size of 3 to 11nm, and the pore size is larger than that of Comparative Example 2, so that it is easy to predict the diffusion of reactants.

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

1 schematically illustrates the structure of a fuel cell system;

FIG. 2 is a graph showing the output density after measuring a cell prepared according to Comparative Example 1 using 0.4 M fuel at 10 ° C. for 10 days using 1 M methanol as fuel.

Figure 3 is a graph showing the unit cell prepared according to Example 1 of the present invention after operating the 0.4V at 50 ℃ using 1M methanol fuel, measuring the output density.

Figure 4 is a graph showing the measurement of IV specific for the unit cell prepared according to Example 1 of the present invention.

Figure 5 is a graph showing the measured CV characteristics for the unit cell prepared according to Example 1 of the present invention.

Figure 6 is a graph showing the performance degradation rate of the battery prepared according to Example 1 of the present invention.

7 is a graph for checking the change over time of the high temperature of the battery prepared according to Example 1 of the present invention.

8 is a graph for determining the change over time of the high temperature of the battery prepared according to Comparative Example 2.

FIG. 9 is a graph showing methanol crossover, water crossover, and methanol-electricity conversion of unit cells prepared according to Example 1 and Comparative Examples 1 to 2 of the present invention.

10 is a graph showing the measurement of the surface area of the catalyst layer of the anode electrode of Example 1 of the present invention.

11 is a graph showing the pore size distribution of the catalyst layers of the anode electrodes of Example 1, Comparative Examples 1 and 2 of the present invention.

Claims (10)

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 It includes pores having an average pore size of 3 to 30nm, comprising a catalyst layer having a specific surface area of 25 to 40m ² / g Membrane-electrode assembly for fuel cell. The method of claim 1, The catalyst layer comprises a pore having an average pore size of 3 to 11nm, the specific surface area of the membrane-electrode assembly for a fuel cell is 25 to 35m ² / g. Applying a catalyst layer composition to a polyimide release substrate to form a catalyst layer; Positioning the polymer electrolyte membrane so as to face the catalyst layer of the release substrate; Rolling the catalyst layer and the polymer electrolyte membrane; Removing the release substrate from the rolled product to transfer the catalyst layer to the polymer electrolyte membrane A method of manufacturing a membrane-electrode assembly for a fuel cell comprising a step. The method of claim 3, The catalyst layer has a pore having an average pore size of 3 to 30nm is formed, the specific surface area of 25 to 40m ² / g manufacturing method of a fuel cell membrane electrode assembly. The method of claim 3, And the first catalyst layer forming step is performed after the release substrate is placed on a heating plate. The method of claim 5, The temperature of the heating plate is a method of manufacturing a membrane-electrode assembly for a fuel cell. The method of claim 3, The rolling process is a method for producing a fuel cell membrane-electrode assembly for 2 to 10 minutes at a temperature of 100 to 140 ℃ under a pressure condition of 1 to 7 t (metric ton). The method of claim 3, The catalyst layer is a method of producing a membrane-electrode assembly for a fuel cell having a thickness of 10 to 13㎛. An electricity generator including a membrane-electrode assembly; A fuel supply unit supplying fuel to the electricity generation unit; And Oxidant supply unit for supplying an oxidant to the electricity generating unit A fuel cell system comprising: The membrane-electrode assembly includes 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, At least one of the anode electrode and the cathode electrode A fuel cell system comprising pores having an average pore size of 3 to 30 nm and comprising a catalyst layer having a specific surface area of 25 to 40 m ² / g. The method of claim 9, Wherein the catalyst layer comprises pores having an average pore size of 3 to 11 nm and has a specific surface area of 25 to 35 m ² / g.

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