KR20090009643A - An electrode for proton exchange membrane fuel cell comprising double catalyst layer and method for preparation of the same - Google Patents

Abstract

A fuel cell electrode for a proton exchange membrane fuel cell(PEMFC) is provided to improve the utilization efficiency of a catalyst by increasing the probability contacting the reactants generated in each electrode with the catalyst due to double catalyst layers. A fuel cell electrode for a proton exchange membrane fuel cell(PEMFC) includes an electrode equipped at both sides of an electrolyte film and a gas diffusion layer equipped at the side facing the electrolyte film. The electrode comprises a first layer(A) coated with a first catalyst layer and a first ionomer layer successively on the electrolyte film; and a second layer(B) coated with a second catalyst layer(2) and a second ionomer layer successively on the first layer.

Description

Electrode for polymer electrolyte fuel cell comprising a multilayer catalyst layer and a method of manufacturing the same {AN ELECTRODE FOR PROTON EXCHANGE MEMBRANE FUEL CELL COMPRISING DOUBLE CATALYST LAYER AND METHOD FOR PREPARATION OF THE SAME

The present invention relates to an electrode for a polymer electrolyte fuel cell including a multilayer catalyst layer and a method of manufacturing the same.

Recently, as the depletion of existing energy resources such as oil and coal is predicted, interest in energy that can replace them is increasing. As one of the alternative energy sources, the fuel cell is particularly attracting attention due to its advantages such as high efficiency, no pollutants such as NO _x and SO _x , and abundant fuel used.

A fuel cell is a power generation system that converts chemical reaction energy of a fuel and an oxidant into electrical energy. Hydrogen, a hydrocarbon such as methanol, butane, and the like are typically used as an oxidant.

In fuel cells, the most basic unit for generating electricity is a membrane electrode assembly (MEA), which is composed of an electrolyte membrane and anode and cathode electrodes formed on both sides of the electrolyte membrane. Referring to FIG. 1 and Reaction Formula 1 (Reaction formula of a fuel cell when hydrogen is used as a fuel) showing the electricity generation principle of a fuel cell, an oxidation reaction of a fuel occurs at an anode electrode, and hydrogen ions and electrons are generated. The electrolyte moves through the electrolyte membrane to the cathode electrode, where water is generated by reaction between oxygen (oxidant) and hydrogen ions transferred through the electrolyte membrane and electrons. This reaction causes the movement of electrons in the external circuit.

The ^{_{anode: H 2 → 2H + + 2e}} -

^{_{Cathode: 1 / 2O 2 + 2H +}} + 2e - → H 2 O

Total Reaction Formula: H ₂ + 1 / 2O ₂ → H ₂ O

Fuel cells include polymer electrolyte fuel cells (PEMFC), direct methanol fuel cells (DMFC), phosphoric acid fuel cells (PAFC), alkaline fuel cells (AFC), molten carbonate fuel cells (MCFC), and solid oxide fuels. Batteries (SOFC) and the like. Among them, polymer electrolyte fuel cells have been researched most actively because of their high energy density and high output.

3 is a schematic cross-sectional view of an electrode used in a conventional polymer electrolyte fuel cell. Conventional electrodes include a catalyst layer (2) and ionomer layer (3), the amount of catalyst used to form the catalyst layer (2) is about 0.4 mg / ㎠, the thickness of the catalyst layer (2) produced through the use of this catalyst Becomes about 20 micrometers.

However, since the thickness of the catalyst portion actually participating in the electrode reaction is about 10 μm, the remaining catalyst portion not participating in the electrode reaction rather acts as a resistance in mass transfer and proton migration. Therefore, there is a need to increase the efficiency of the battery by participating in the electrode reaction all the catalyst for the fuel cell, which is quite expensive.

The technical problem to be achieved by the present invention is to solve the above-mentioned problems of the prior art, to provide a polymer electrolyte fuel cell electrode and a method for manufacturing the same, which can improve the efficiency of the fuel cell by increasing the use efficiency of the catalyst.

In order to achieve the above technical problem, in the polymer electrolyte fuel cell comprising an electrode provided on both sides of the electrolyte membrane and a gas diffusion layer provided on the surface facing the electrolyte membrane in the electrode, the polymer electrolyte fuel of the present invention The battery electrode includes a first layer formed by sequentially coating a first catalyst layer and a first ionomer layer on an electrolyte membrane, and a second layer formed by sequentially coating a second catalyst layer and a second ionomer layer on the first layer. Characterized in that. The electrode of the present invention comprises a catalyst layer composed of a plurality of layers to relatively increase the surface area of the catalyst involved in the reaction, thereby increasing the reaction efficiency of the activated hydrogen or oxygen generated from the electrode, thereby providing a fuel cell with high efficiency.

In the electrode of the present invention, the first catalyst layer and the second catalyst layer each have a thickness of 4 to 5 μm, the amount of the catalyst used is 0.1 to 0.2 mg / cm 2, and a platinum black catalyst or platinum as a metal catalyst supported on a carbon-based support. It is preferred to include a / carbon catalyst, the first catalyst layer is preferably a platinum black catalyst.

In addition, in the electrode of the present invention, the first ionomer layer and the second ionomer layer may include Nafion ionomer or sulfonated polytrifluorostyrene which is a polymer ionomer.

Method for producing an electrode for a polymer electrolyte fuel cell according to the present invention,

(A) preparing an ink for forming a catalyst layer;

(B) coating the ink on a predetermined position of the electrolyte membrane by using a coater to form a first catalyst layer;

(C) coating a polymer ionomer on the first catalyst layer to form a first ionomer layer; And

(D) sequentially coating the second catalyst layer and the second ionomer layer on the first ionomer layer in the same manner as in the steps (B) and (C)

It characterized in that it comprises a, after each coating step may be more rough drying step.

In the electrode manufacturing method of the present invention, the catalyst layer forming ink may include a metal catalyst, a polymer ionomer and a solvent supported on a carbon-based support, and the metal catalyst and polymer ionomer immersed on the carbon-based support are as described above. The solvent is preferably a single substance or a mixture of two or more selected from the group consisting of water, butanol, iso propanol, methanol, ethanol, n-propanol, n-butyl acetate and ethylene glycol. This is not restrictive.

The electrode of the present invention described above may be used in a membrane electrode assembly (MEA) for a polymer electrolyte fuel cell in combination with an electrolyte membrane, and the electrolyte membrane according to the present invention may be a perfluorosulfonic acid polymer, a hydrocarbon-based polymer, or a polyimide. , Polyvinylidene fluoride, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyphosphazine, polyethylene naphthalate, polyester, doped polybenzimidazole, polyetherketone, polysulfone, acids thereof and Polymers selected from the group consisting of bases can be preferably used.

In addition, the membrane electrode assembly using the electrode of the present invention can be used in a polymer electrolyte fuel cell.

As described above, in the polymer electrolyte fuel cell electrode of the present invention, since the catalyst layer is composed of a plurality of layers, the probability that the reactants of the reactions generated at each electrode may come into contact with the catalyst may increase the efficiency of using the catalyst. As a result, the use efficiency of the battery can be improved.

Hereinafter, the present invention will be described in detail. The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

A polymer electrolyte fuel cell comprising electrodes provided on both sides of an electrolyte membrane and a gas diffusion layer provided on a surface of the electrode opposite to the electrolyte membrane, wherein the electrode for a polymer electrolyte fuel cell of the present invention is formed on an electrolyte membrane. And a first layer formed by sequentially coating the first catalyst layer and the first ionomer layer, and a second layer formed by sequentially coating the second catalyst layer and the second ionomer layer on the first layer. The electrode of the present invention described above is composed of two layers each of a catalyst layer and an ionomer layer, thereby increasing the surface area where activated oxygen or hydrogen can react, thereby increasing the reaction efficiency of activated hydrogen or oxygen generated from the electrode, Provide a fuel cell with high efficiency.

In the electrode of the present invention, the thickness of each of the above-described first catalyst layer and the second catalyst layer is not particularly limited, but is preferably 4-5 μm, but in order to sufficiently react oxygen or hydrogen, the thickness must be at least 4 μm. If it exceeds 5㎛ not only does not contact with oxygen or hydrogen occurs, but rather acts as a resistance to inhibit the mass transfer and the movement of hydrogen ions (proton), so the efficiency of the reaction does not increase significantly in proportion to the thickness of the catalyst layer In addition, the catalyst layer and the ionomer layer are more effective in suppressing the increase in the overall volume due to the double layer.

In the first layer and the second layer of the electrode of the present invention described above, the amount of catalyst used in each catalyst layer is not particularly limited, but is preferably 0.1 to 0.2 mg / cm 2 in order to form a preferable thickness of the catalyst layer. The amount of the catalyst is less than the amount of the conventional catalyst and is more economically advantageous by reducing the amount of the expensive catalyst.

The catalyst used in each catalyst layer according to the present invention may be used without limitation as long as it is a catalyst used in the art, and preferably, a catalyst body in which a metal catalyst is supported on a carbon-based support. As the carbon-based support according to the present invention, for example, carbon black or carbon powder may be representatively used, and as the metal catalyst, for example, platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, A platinum-palladium alloy or a platinum-transition metal alloy can be used, preferably platinum can be used.

As the metal catalyst supported on the carbon-based support used in the present invention, a platinum black catalyst or a platinum / carbon catalyst is preferable. In addition, the catalyst used for the first catalyst layer and the catalyst used for the second catalyst layer may be the same or different, and in the case where the above-described first layer is applied to the electrolyte membrane, the catalyst used for the first catalyst layer is platinum black. The catalyst is more preferable because it can widen the active area with the electrolyte membrane.

Each ionomer layer according to the present invention may comprise a polymer ionomer, which may comprise a Nafion ionomer or a sulfonated polytrifluorostyrene.

The manufacturing method of the electrode for a polymer electrolyte fuel cell of the present invention,

(A) preparing an ink for forming a catalyst layer;

(B) coating the ink on a predetermined position of the electrolyte membrane by using a coater to form a first catalyst layer;

(C) coating a polymer ionomer on the first catalyst layer to form a first ionomer layer; And

(D) sequentially coating the second catalyst layer and the second ionomer layer on the first ionomer layer in the same manner as in the steps (B) and (C)

Characterized in that it comprises a.

In the manufacturing method of the electrode of the present invention, after each coating step may further comprise a drying step to improve the stability of the coating layer.

3 schematically illustrates a polymer electrolyte fuel cell electrode in which a first layer A and a second layer B are coated on an electrolyte membrane 1 according to one embodiment of the present invention. The manufacturing method of the electrode will be described in detail.

First, a catalyst layer forming ink for applying a catalyst layer to the electrolyte membrane 1 is prepared. The ink for forming a catalyst layer according to the present invention may include a metal catalyst, a polymer ionomer and a solvent supported on a carbon-based support.

The metal catalyst supported on the carbon-based support may be used without limitation as long as it is a catalyst used in the art. As the carbon-based support according to the present invention, for example, carbon black or carbon powder may be representatively used, and as the metal catalyst, for example, platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum Palladium alloy or platinum-transition metal alloy may be used, preferably platinum may be used.

As the metal catalyst supported on the carbon-based support used in the present invention, a platinum black catalyst or a platinum carbon catalyst is preferable. In addition, the catalyst used in the first catalyst layer and the catalyst used in the second catalyst layer may be the same or different, and as the catalyst of the first catalyst layer described above, a platinum black catalyst may increase the active area with the electrolyte membrane. It is more preferable as it can.

The polymer ionomer is preferably a sulfonated polymer such as nafion ionomer or sulfonated polytrifluorostyrene.

As the solvent, one or a mixture of two or more selected from the group consisting of water, butanol, iso propanol, methanol, ethanol, n-propanol, n-butyl acetate and ethylene glycol may be preferably used. .

The prepared catalyst layer ink is applied to an electrolyte membrane using a coater commonly used in the art to form a first catalyst layer 2, and to apply a first ionomer layer 3 on the first catalyst layer 1 layer (A) formation).

The ionomer used for the first ionomer layer may use the polymer ionomer described above.

As described above, the second catalyst layer 2 and the second ionomer layer 3 are sequentially coated on the first ionomer layer in the same manner as the method of forming the first layer, thereby applying the second layer B. Form. Here, as described above, the catalyst of the catalyst layer of the first layer and the catalyst of the catalyst layer of the second layer may be different from each other.

Gas diffusion layer may be further formed on the side of the electrode of the present invention prepared as described above. The gas diffusion layer is formed by applying the ink for preparing the gas diffusion layer to a predetermined position and drying it. The ink for preparing the gas diffusion layer may include a carbonaceous material, a fluorine resin, and a solvent.

Examples of the carbon-based material include graphite (graphite), carbon black, acetylene black, denka black, canyon black, activated carbon, mesoporous carbon, carbon nanotubes, carbon nanofibers, carbon nanohorns, carbon nanorings, carbon nanowires, One or a mixture of two or more selected from the group consisting of fullerene (C60) and super P can be preferably used.

The fluororesin may be polytetrafluoroethylene, polyvinylidene fluoride (PVdF), polyvinyl alcohol, cellulose acetate, copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) or styrene-butadiene Rubber (SBR) may be preferably used.

As the solvent, one or a mixture of two or more selected from the group consisting of water, butanol, iso propanol, methanol, ethanol, n-propanol, n-butyl acetate and ethylene glycol may be preferably used.

As described above, the polymer electrolyte fuel cell electrode manufactured according to the present invention may be used in the preparation of a membrane electrode assembly for a polymer electrolyte fuel cell together with an electrolyte membrane through a method commonly practiced in the art.

The electrolyte membrane may be a perfluorosulfonic acid polymer, a hydrocarbon-based polymer, polyimide, polyvinylidene fluoride, polyether sulfone, polyphenylene sulfide, polyphenylene oxide, polyphosphazine, polyethylene naphthalate, polyester, doping Polymers selected from the group consisting of polybenzimidazoles, polyetherketones, polysulfones, acids and bases thereof can be preferably used.

In addition, the electrode of the present invention described above can be used in the production of a polymer electrolyte fuel cell with a separator, a gasket, etc. through a method commonly practiced in the art.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

1 part by weight of platinum black catalyst, 6 parts by weight of Nafion ionomer, 6 parts by weight of water and 6 parts by weight of isopropanol were prepared to prepare an ink for forming a catalyst layer, 1 part by weight of platinum / carbon catalyst and 6 parts by weight of Nafion ionomer. 6 parts by weight of water and 6 parts by weight of isopropanol were mixed to prepare an ink (b) for forming a catalyst layer.

The ink (a) was applied to an electrolyte membrane using a coating machine (PULSE SPRAY COATING SYSTEM, NORDSON Co., Ltd.), and then dried. The amount of catalyst applied to the electrolyte membrane was 0.1 mg / cm 2, and the thickness of the catalyst layer was 5 μm.

Nafion ionomer was applied to the catalyst layer and dried, and then the ink (b) was applied thereon using a coater and then dried. At this time, the applied catalyst amount was 0.1 mg / cm 2, and the thickness of the catalyst layer was 5 μm.

Nafion ionomer was again applied and coated on the catalyst layer to prepare an electrode for a polymer electrolyte fuel cell.

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to.

1 is a schematic view for explaining the principle of electricity generation of the fuel cell.

2 is a cross-sectional view schematically showing a state in which an electrode for a polymer electrolyte fuel cell of the present invention is coated on an electrolyte membrane.

3 is a cross-sectional view schematically showing a state where a conventional polymer electrolyte fuel cell electrode is coated on an electrolyte membrane.

<Explanation of symbols described in the drawings>

1: electrolyte membrane

2: catalyst layer

3: ionomer layer

Claims (16)

In the polymer electrolyte fuel cell comprising an electrode provided on both sides of the electrolyte membrane and a gas diffusion layer provided on the surface facing the electrolyte membrane in the electrode, the electrode A first layer formed by sequentially coating the first catalyst layer and the first ionomer layer on the electrolyte membrane; And A second layer formed by sequentially coating a second catalyst layer and a second ionomer layer on the first layer; Electrode for a polymer electrolyte fuel cell comprising a. The method of claim 1, The polymer electrolyte fuel cell electrode, wherein the first catalyst layer and the second catalyst layer each have a thickness of 4 to 5 μm. The method of claim 1, The amount of catalyst used in the first catalyst layer and the second catalyst layer is a polymer electrolyte fuel cell electrode, characterized in that 0.1 to 0.2mg / ㎠. The method of claim 1, The first catalyst layer and the second catalyst layer are each a polymer electrolyte fuel cell electrode, characterized in that it comprises a catalyst selected from the group consisting of platinum black catalyst and platinum / carbon catalyst. The method of claim 1, The first catalyst layer is a polymer electrolyte fuel cell electrode, characterized in that it comprises a platinum black catalyst. The method of claim 1, The first ionomer layer and the second ionomer layer, respectively, the polymer electrolyte fuel cell electrode, characterized in that it comprises a Nafion ionomer or sulfonated polytrifluorostyrene. (A) preparing an ink for forming a catalyst layer; (B) coating the ink on a predetermined position of the electrolyte membrane by using a coater to form a first catalyst layer; (C) coating a polymer ionomer on the first catalyst layer to form a first ionomer layer; And (D) sequentially coating the second catalyst layer and the second ionomer layer on the first ionomer layer in the same manner as in the steps (B) and (C) Method for producing an electrode for a polymer electrolyte fuel cell comprising a. The method of claim 7, wherein Method for producing a polymer electrolyte fuel cell electrode characterized in that it further comprises a drying step after each coating step. The method of claim 7, wherein The catalyst layer forming ink includes a metal catalyst, a polymer ionomer, and a solvent supported on a carbon-based support. The method of claim 9, The metal catalyst supported on the carbon-based support is a method for producing an electrode for a polymer electrolyte fuel cell, characterized in that the platinum black catalyst or platinum / carbon catalyst. The method of claim 9, The polymer ionomer is a method for producing a polymer electrolyte fuel cell electrode, characterized in that it comprises Nafion ionomer or sulfonated polytrifluorostyrene. The method of claim 9, The solvent is a polymer electrolyte, characterized in that one or a mixture of two or more selected from the group consisting of water, butanol, iso propanol, methanol, ethanol, n-propanol, n-butyl acetate and ethylene glycol Method for manufacturing an electrode for fuel cell type. The method of claim 7, wherein The first catalyst layer is a method for producing a polymer electrolyte fuel cell electrode, characterized in that it comprises a platinum black catalyst. In the membrane electrode assembly comprising an electrolyte membrane and electrodes provided on both sides of the electrolyte membrane, Membrane electrode assembly for a polymer electrolyte fuel cell, characterized in that the electrode is the electrode of any one of claims 1 to 6. The method of claim 14, The electrolyte membrane is a perfluorosulfonic acid polymer, a hydrocarbon-based polymer, polyimide, polyvinylidene fluoride, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyphosphazine, polyethylene naphthalate, polyester, doped poly Membrane electrode assembly for a polymer electrolyte fuel cell, characterized in that the polymer selected from the group consisting of benzimidazole, polyether ketone, polysulfone, acid and base thereof. In the polymer electrolyte fuel cell comprising an electrode provided on both sides of the electrolyte membrane and a gas diffusion layer provided on the surface of the electrode facing the electrolyte membrane, A polymer electrolyte fuel cell, wherein the electrode is an electrode according to any one of claims 1 to 6.

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