KR20060066892A - Electrode for fuel cell, method for preparating the same, membrane-electrode assembly comporising the same, and fuel cell system comprising the same - Google Patents

Abstract

The present invention relates to a fuel cell electrode, a method for manufacturing the same, a membrane-electrode assembly including the same, and a fuel cell system including the same, and more particularly, including an electrode substrate and a catalyst layer. The present invention relates to a fuel cell electrode having a porosity, a thickness of 50 nm to 1 μm, and a thickness deviation of ± 5%, a manufacturing method thereof, a membrane-electrode assembly including the same, and a fuel cell system including the same.

The electrode for a fuel cell of the present invention has an advantage of having a high density of the catalyst layer, a thin thickness, and excellent contact with an electrode substrate, and a fuel cell system including the same may exhibit excellent efficiency.

Fuel cell, porosity, density, thickness deviation, electrode, spray, rotation

Description

ELECTRODE FOR FUEL CELL, METHOD FOR PREPARATING THE SAME, MEMBRANE-ELECTRODE ASSEMBLY COMPORISING THE SAME, AND FUEL CELL SYSTEM COMPRISING THE SAME }

1 is a cross-sectional view showing an example of an electrode for a fuel cell of the present invention.

Figure 2 is a perspective view showing an example of a coating apparatus used in the production of the electrode for fuel cells of the present invention.

Figure 3 is a cross-sectional view showing an example of the membrane-electrode assembly of the present invention.

4 is a configuration diagram showing an example of a fuel cell system of the present invention.

[Industrial use]

The present invention relates to a fuel cell electrode, a method for manufacturing the same, a membrane-electrode assembly including the same, and a fuel cell system including the same. More specifically, the thickness of the catalyst layer is thin, and the electrode for the fuel cell and the method for producing the same, Membrane-electrode assembly comprising the same, and a fuel cell system comprising the same.                         

[Private Technology]

A fuel cell is a power generation system that directly converts the chemical reaction energy of hydrogen and oxygen supplied from a hydrocarbon-based material such as methanol, ethanol, and natural gas into electrical energy.

A fuel cell is classified into a phosphoric acid fuel cell, a molten carbonate fuel cell, a solid oxide fuel cell, a polymer electrolyte type or an alkaline fuel cell according to the type of electrolyte used. Each of these fuel cells operates on essentially the same principle, but differs in the type of fuel used, operating temperature, catalyst, and electrolyte.

Among these, the polymer electrolyte fuel cell (PEMFC), which is being developed recently, has superior output characteristics compared to other fuel cells, has a low operating temperature, fast start-up and response characteristics, and a mobile power source such as an automobile. Of course, it has a wide range of applications, such as distributed power supply for homes, public buildings and small power supply for electronic devices.

Such a PEMFC basically includes an electric generator (or stack), a reformer, a fuel tank, a fuel pump, and the like to configure a system. The electric power generation unit forms a main body of the fuel cell, and the fuel pump supplies the fuel in the fuel tank to the reformer. The reformer reforms the fuel to generate hydrogen gas and supplies the hydrogen gas to the electric generator.

Therefore, the PEMFC supplies fuel in the fuel tank to the reformer by operation of the fuel pump, reforming the fuel in the reformer to generate hydrogen gas, and electrochemically reacting the hydrogen gas and oxygen in the electric power generation unit to generate electricity. Generates energy.

On the other hand, the fuel cell may employ a direct methanol fuel cell (DMFC) method that can supply the liquid methanol fuel directly to the electric power generation unit. Such a direct methanol fuel cell fuel cell, unlike the polymer electrolyte fuel cell, the reformer is excluded.

In the fuel cell system as described above, the electric power generation unit that generates electricity substantially is a unit cell composed of a membrane electrode assembly (MEA) and a separator (also called a bipolar plate) alone. It exists, or has a structure stacked in a few to several tens.

The membrane-electrode assembly has a structure in which an anode electrode (also called "fuel electrode" or "oxide electrode") and a cathode electrode (also called "air electrode" or "reduction electrode") are attached with an electrolyte membrane interposed therebetween. . The separator supplies fuel required for the reaction of the fuel cell to the anode electrode and simultaneously serves as a path for supplying oxygen to the cathode electrode and a conductor for connecting the anode electrode and the cathode electrode in series in each membrane-electrode assembly. Perform.

In this process, the electrochemical oxidation of the fuel occurs at the anode electrode, the electrochemical reduction of oxygen occurs at the cathode electrode, and electricity, heat, and water can be obtained together due to the movement of the generated electrons.

The anode electrode and the cathode electrode of the fuel cell include an electrode substrate and a catalyst layer. Conventionally, in order to form a catalyst layer, the slurry coating method was mainly used, but the catalyst layer coated by this method was thick, the porosity was low, and the surface was not uniform, and there was a limit in increasing the efficiency of the fuel cell.

The present invention is to solve the above problems, an object of the present invention is a thin, uniform, excellent adhesion to the electrode substrate electrode for fuel cells and its manufacturing method, a membrane-electrode assembly comprising the same, and the like It is to provide a fuel cell system.

In order to achieve the above object, the present invention includes an electrode substrate and a catalyst layer, wherein the catalyst layer has a porosity of 10 to 80%, a thickness of 50 nm to 1 μm, and a thickness deviation of ± 5%. To provide.

The present invention also comprises the steps of preparing a catalyst coating liquid by mixing a catalyst, a binder and a solvent; Coating the catalyst coating solution while rotating an electrode substrate at 10 to 10000 rpm; And it provides a method for producing an electrode for a fuel cell comprising the step of drying the catalyst coating liquid to form a catalyst layer.

The present invention also provides a fuel cell electrode; And it provides a fuel cell membrane-electrode assembly comprising a polymer electrolyte membrane for a fuel cell.

The present invention also includes an electricity generation unit including the membrane-electrode assembly and the separator located on both sides of the membrane-electrode assembly; A fuel supply unit; And it provides a fuel cell system comprising an oxygen supply.                     

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

1 is a cross-sectional view showing an example of an electrode for a fuel cell of the present invention. As shown in FIG. 1, the fuel cell electrode 10 of the present invention includes an electrode base 1 and a catalyst layer 2. The catalyst layer 2 preferably has a porosity of 10 to 80%, more preferably a porosity of 50 to 80%, and most preferably a porosity of 70 to 80%. When the porosity of the catalyst layer exceeds 80%, the conductivity of electrons generated by the catalyst may be lowered, and when the porosity of the catalyst layer is less than 10%, the fuel or oxygen may not be smoothly supplied, thereby reducing the efficiency of the fuel cell.

In addition, the thickness of the catalyst layer is preferably 50 nm to 1 μm or less, more preferably 50 nm to 0.1 μm. When the thickness of the catalyst layer exceeds 1 μm, the supply and discharge of the reactants and products may be undesired and the efficiency may be reduced.

The catalyst layer preferably has a thickness deviation within ± 5%, more preferably within a thickness deviation within ± 2%. If the thickness deviation of the catalyst layer exceeds ± 5%, the reaction is uneven and the activity efficiency is lowered.

The electrode for a fuel cell of the present invention is a catalyst layer formed by using a support plate equipped with an aspirator, and is manufactured by a method of sucking on an aspirator on another side of the electrode substrate while coating a catalyst coating solution on one surface of the electrode substrate. It is possible to form a catalyst layer having porosity, thickness and thickness deviation.

The catalyst layer included in the electrode for the fuel cell is platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M = Ga, Ti, V, Cr, Mn, Fe, Co) , At least one metal catalyst selected from the group consisting of Ni, Cu, and Zn).

In addition, the catalyst layer is platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M = Ga, Ti, V, Cr, Mn, Fe, Co supported on the carrier) And at least one metal catalyst selected from the group consisting of Ni, Cu and Zn). The carrier may be any material as long as it is conductive, but is preferably a carbon carrier.

The catalyst layer preferably contains 10 to 80% by weight of the metal catalyst, more preferably 20 to 60% by weight of the metal catalyst, based on the weight of the entire catalyst layer. When the content of the metal catalyst is less than 10% by weight, the thickness of the catalyst layer must be thickened, so that the supply and discharge of the reactants and products are undesired. When the content of the metal catalyst exceeds 80% by weight, the particle size of the catalyst is large, and the reaction specific surface area is reduced. The efficiency is lowered, and waste of catalyst can increase, leading to increased manufacturing costs.

The support plate of the coating device is not limited to a particular form, but preferably is a rotatable form. The support plate rotates the electrode substrate at the same time as the coating to enable a uniform coating. The support plate is not necessarily rotated, however, when the support plate is rotated, the rotation speed of the support plate is preferably 10 to 10000 rpm, more preferably 50 to 8000 rpm. If the rotational speed of the support plate is less than 10 rpm, the effect of the rotation is insignificant, and if it exceeds 10000 rpm, the porosity of the catalyst layer may be smaller than necessary.

The electrode substrate included in the fuel cell electrode serves to transfer electrons generated in the catalyst layer together with the diffusion action of fuel or oxygen. Therefore, the electrode base material is preferably made of a carbon material having electronic conductivity.

Specifically, the electrode base material is preferably a gas diffusion layer selected from carbon cloth or carbon paper, and may further include a microporous layer as necessary.

The microporous layer comprises at least one carbon material selected from the group consisting of graphite, carbon nanotubes (CNT), fullerenes (C60), activated carbon, vulcans, ketjen black, carbon black, and carbon nano horns. It is preferable to include, and may further include at least one binder selected from the group consisting of poly (perfluorosulfonic acid), poly (tetrafluoroethylene) and florinated ethylene-propylene.

The fuel cell electrode is prepared by mixing a catalyst, a binder and a solvent to prepare a catalyst coating solution; Coating the catalyst coating solution while rotating an electrode substrate at 10 to 10000 rpm; And drying the catalyst coating solution to form a catalyst layer.

The support plate of the coating device is not limited to a particular form, but preferably is a rotatable form. The support plate rotates the electrode substrate at the same time as the coating to enable a uniform coating. The support plate is not necessarily rotated, but when the support plate is rotated, the rotation speed of the support plate is preferably 10 to 10000 rpm, more preferably 50 to 8000 rpm. If the rotational speed of the support plate is less than 10 rpm, the effect of the rotation is insignificant, and if it exceeds 10000 rpm, the porosity of the catalyst layer may be too small.

Catalysts used in the preparation of the catalyst coating solution are platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M = Ga, Ti, V, Cr, Mn, Fe, Preference is given to using at least one metal catalyst selected from the group consisting of Co, Ni, Cu and Zn).

 In addition, the catalyst is platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M = Ga, Ti, V, Cr, Mn, Fe, One or more metal catalysts selected from the group consisting of Co, Ni, Cu and Zn) may be used. The carrier may be any material as long as it is conductive, but is preferably a carbon carrier.

The binder is preferably at least one selected from the group consisting of poly (perfluorosulfonic acid), poly (tetrafluoroethylene) and florinated ethylene-propylene.

The solvent used in the preparation of the catalyst coating solution may be used a conventional coating solvent, preferably at least one selected from the group consisting of isopropyl alcohol, normal propyl alcohol, ethyl alcohol, methyl alcohol and normal butyl acetate Solvents may be used. However, the solvent used for the catalyst coating liquid of the present invention is not limited to the above examples.

 In the catalyst coating liquid, the content of the binder and the solvent can be appropriately adjusted according to the coating method and other needs, it is not particularly limited in the present invention.

2 is a perspective view showing an example of a coating apparatus used for coating the catalyst coating solution. Referring to FIG. 2, the coating apparatus 500 may coat a support plate 504 and a catalyst coating liquid designed to be rotatable in a glove box 503 in which a gas inlet 501 and a gas outlet 502 are formed. Injector 505, the support plate is connected to the spin controller 506 that can control the rotational speed. The electrode substrate 507 is positioned on the support plate, and the catalyst substrate may be coated on one surface thereof while the electrode substrate 507 is rotated.

As the coating method of the catalyst coating solution, a conventional slurry method, screen printing method, doctor blade method, spray coating method, or the like may be used, and among them, spray coating method is preferable. However, the coating method of the catalyst coating liquid of the present invention is not limited to the above method.

The coating process of the catalyst coating liquid is preferably carried out in a hydrogen atmosphere, a nitrogen atmosphere or an inert atmosphere.

Preferably, the electrode substrate used in the manufacture of an electrode for a fuel cell of the present invention is a gas diffusion layer selected from carbon cloth or carbon paper, and the electrode substrate may further include a microporous layer. have.

The microporous layer comprises at least one carbon material selected from the group consisting of graphite, carbon nanotubes (CNT), fullerenes (C60), activated carbon, vulcans, ketjen black, carbon black, and carbon nano horns. It is preferable to include, and may further include at least one binder selected from the group consisting of poly (perfluorosulfonic acid), poly (tetrafluoroethylene) and florinated ethylene-propylene.

After the coating process is completed, by forming a catalyst layer through a drying process, it is possible to manufacture the electrode for a fuel cell of the present invention. At this time, the drying temperature is not particularly limited because it can be appropriately adjusted according to the production time, the type and amount of the solvent used, but is preferably 60 to 80 ℃.

In the fuel cell electrode manufacturing method, the porosity of the catalyst layer can be freely adjusted by controlling the rotational speed of the electrode substrate, and the catalyst layer has a thinner thickness and excellent surface uniformity than the conventional fuel cell electrode containing the same amount of catalyst metal. It is possible to manufacture an electrode comprising.

3 is a cross-sectional view showing an example of the membrane-electrode assembly of the present invention. Referring to FIG. 3, the membrane-electrode assembly 100 of the present invention includes the fuel cell electrodes 10 and 10 ′; And a polymer electrolyte membrane 20 for a fuel cell, and the fuel cell electrodes 10 and 10 'are disposed on both sides of the polymer electrolyte membrane 20.

The fuel cell polymer electrolyte membrane may be a perfluoro polymer having excellent hydrogen ion conductivity, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer , Polyether ketone-based polymer, polyether-etherketone-based polymer, and polyphenylquinoxaline-based polymer, and preferably include at least one hydrogen ion conductive polymer selected from the group consisting of poly (perfluorosulfonic acid), poly ( Perfluorocarboxylic acid), copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, defluorinated sulfide polyether ketones, aryl ketones, poly (2,2 '-(m-phenylene)- 5,5'-bibenzimidazole) (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole)) and poly (2,5-benzimidazole) More preferably comprises at least one hydrogen ion conductive polymer.

The electrode disposed on one surface of the polymer electrolyte membrane for fuel cells serves as an anode to generate electrons and hydrogen ions, and the electrode disposed on the other surface of the polymer electrolyte membrane serves as a cathode and the hydrogen ions transferred through the polymer electrolyte membrane. Water is produced from oxygen supplied from the outside.

4 is a configuration diagram showing an example of a fuel cell system of the present invention. Referring to FIG. 4, the fuel cell system of the present invention includes an electric generator 110 including the membrane electrode assembly 100 and separators 101 disposed on both sides of the membrane electrode assembly; A fuel supply unit 120; And an oxygen supply unit 130.

The fuel cell system includes both a polymer electrolyte fuel cell (PEMFC) and a direct methanol fuel cell (DMFC), and in the case of a polymer electrolyte fuel cell, the fuel cell system further includes a reformer for generating hydrogen gas from a fuel containing hydrogen. can do.                     

Hereinafter, preferred embodiments 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

Example 1

A catalyst coating solution was prepared by mixing 2 g of a platinum catalyst (platinum content 20 wt%) supported on carbon with 4.8 g of a poly (perfluorosulfonic acid) solution (Nafion ^™ solution manufactured by DuPont).

A carbon paper having a thickness of 200 μm was placed on a rotatable support plate, under a hydrogen atmosphere, the support plate was rotated at 1000 rpm, and coated by spray spraying the catalyst coating solution on the carbon paper. After the coating process was dried at a temperature of 60 ℃ to prepare an electrode for a fuel cell.

Example 2

A fuel cell electrode was manufactured in the same manner as in Example 1, except that the support plate was rotated at 500 rpm.

Comparative Example 1

A catalyst slurry was prepared by mixing 2 g of a platinum catalyst (platinum content 20 wt%) supported on carbon with 4.8 g of a poly (perfluorosulfonic acid) solution (Nafion ^™ solution manufactured by DuPont).

The catalyst slurry was slurry coated to a thickness of 50 μm on carbon paper having a thickness of 200 μm, and dried at 60 ° C. to prepare an electrode for a fuel cell.                     

The porosity, thickness, and thickness variation of the catalyst layers of the fuel cell electrodes prepared according to Examples 1 to 2 and Comparative Example 1 were measured, and the results are summarized in Table 1 below.

The porosity was measured by the porosimeter method, the thickness was measured by the thinkness profiler method, the thickness deviation was calculated as the ratio of the highest and lowest values to the average of the thickness.

TABLE 1

Porosity (%) Thickness (nm) Thickness deviation (%) Example 1 60 50 ± 5 Example 2 70 60 ± 2 Comparative Example 1 20 100 ± 15

As shown in Table 1, it can be seen that the fuel cell electrode manufactured according to Examples 1 to 2 of the present invention has a large porosity, a thin thickness, and a small thickness variation of the catalyst layer.

Examples 3 to 4 and Comparative Example 2

Membrane-electrode assemblies were prepared by bonding the fuel cell electrodes prepared according to Examples 1 and 2 and Comparative Example 1 to both sides of poly (perfluorosulfonic acid) having a thickness of 120 μm, respectively. The separator was disposed in the fuel cell, and the fuel supply unit and the oxygen supply unit were installed in the configuration as shown in FIG. 4 to manufacture the fuel cell systems according to Examples 3, 4, and Comparative Example 2.

The voltage characteristics at 0.6 V of the fuel cell systems prepared according to Examples 3 to 4 and Comparative Example 2 were measured, and the results are shown in Table 2 as a relative value with respect to the current of the fuel cell system of Comparative Example 2. Indicated.

TABLE 2

Current characteristic (relative value) Voltage (V) Example 3 167 0.6 Example 4 200 0.6 Comparative Example 2 100 0.6

As shown in Table 2, it can be seen that the fuel cell system manufactured according to Examples 3 to 4 of the present invention has excellent current characteristics.

  The electrode for a fuel cell of the present invention has a thin thickness of the catalyst layer, and has an advantage of excellent contact with an electrode substrate, and a fuel cell system including the same may exhibit excellent efficiency.

Claims (19)

An electrode substrate and a catalyst layer, wherein the catalyst layer has a porosity of 10 to 80%, a thickness of 50 nm to 1 ㎛, a thickness deviation of ± 5%. According to claim 1, wherein the catalyst layer is a fuel cell electrode having a porosity of 50 to 80%. The method of claim 1, wherein the catalyst layer is platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M = Ga, Ti, V, Cr, Mn, Fe, Co) And at least one metal catalyst selected from the group consisting of at least one transition metal selected from the group consisting of Ni, Cu, and Zn. The method of claim 1, wherein the catalyst layer is platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M = Ga, Ti, V, Cr, And at least one metal catalyst selected from the group consisting of Mn, Fe, Co, Ni, Cu, and Zn). The electrode of claim 1, wherein the catalyst layer comprises 10 to 80 wt% of a metal catalyst based on the weight of the entire catalyst layer. The fuel cell electrode of claim 1, wherein the catalyst layer is formed by rotating and coating an electrode substrate. The fuel cell electrode of claim 1, wherein the electrode base material is a gas diffusion layer selected from carbon cloth or carbon paper. The fuel cell electrode of claim 1, wherein the electrode substrate comprises a microporous layer. The method of claim 8, wherein the microporous layer is selected from the group consisting of graphite, carbon nanotubes (CNT), fullerenes (C60), activated carbon, vulcans, ketjen black, carbon black and carbon nano horn. An electrode for a fuel cell comprising at least one carbon material. The fuel cell of claim 8, wherein the microporous layer comprises at least one binder selected from the group consisting of poly (perfluorosulfonic acid), poly (tetrafluoroethylene), and florinated ethylene-propylene. electrode. Preparing a catalyst coating solution by mixing a catalyst, a binder, and a solvent; Coating the catalyst coating solution while rotating an electrode substrate at 10 to 100000 rpm; And Drying the catalyst coating solution to form a catalyst layer Method for producing an electrode for a fuel cell comprising a. The method of claim 11, wherein the catalyst is platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M = Ga, Ti, V, Cr, Mn, Fe, Co) And at least one transition metal selected from the group consisting of Ni, Cu, and Zn). The method of claim 11, wherein the catalyst is platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy and platinum-M alloy (M = Ga, Ti, V, Cr, Method for producing an electrode for a fuel cell comprising at least one metal catalyst selected from the group consisting of one or more transition metals selected from the group consisting of Mn, Fe, Co, Ni, Cu and Zn. The method of claim 11, wherein the electrode base material rotates at 10 to 10000 rpm. The method of claim 11, wherein the catalyst coating liquid is coated by a spray injection method. An electrode for a fuel cell according to any one of claims 1 to 10; And Polymer electrolyte membrane for fuel cell Membrane-electrode assembly for fuel cell comprising a. The method of claim 16, wherein the polymer electrolyte membrane for fuel cells is perfluoro-based polymer, benzimidazole-based polymer, polyimide-based polymer, polyetherimide-based polymer, polyphenylene sulfide-based polymer polysulfone-based polymer, polyether sulfone-based polymer And a polyether ketone-based polymer polyether-etherketone-based polymer and a polyphenylquinoxaline-based polymer comprising at least one hydrogen ion conductive polymer selected from the group consisting of fuel cell membrane-electrode assembly. 18. The polymer electrolyte membrane of claim 17, wherein the polymer electrolyte membrane for fuel cells is a copolymer of tetrafluoroethylene and fluorovinyl ether containing poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), and sulfonic acid groups, and defluorinated. Sulfide polyether ketones, aryl ketones, poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole) (poly (2,2'-(m-phenylene) -5,5 ' -bibenzimidazole)) and poly (2,5-benzimidazole) and at least one hydrogen ion conductive polymer selected from the group consisting of. a) a fuel cell membrane-electrode assembly comprising i) a fuel cell electrode according to any one of claims 1 to 10, and a polymer electrolyte membrane for a fuel cell, and ii) located on both sides of the membrane-electrode assembly. An electricity generating unit including a separator; b) a fuel supply unit; And c) oxygen supply Fuel cell system comprising a.

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