KR101125651B1 - A membrane/electrode assembly for fuel cell and a fuel cell comprising the same - Google Patents

Abstract

The present invention relates to a fuel cell polymer membrane / electrode assembly and a fuel cell comprising the same, wherein the polymer membrane / electrode assembly comprises: an anode and a cathode comprising a catalyst layer and an electrode support; And a polymer film positioned between the anode and the cathode electrode, and a chelate functional group capable of collecting metal impurities on the surface of the polymer film is introduced. The polymer membrane may collect metal impurities melted from various members of the fuel cell during operation of the fuel cell to improve the electrochemical reaction efficiency of the fuel cell.

Fuel Cell, Metal Impurities, Polymer Membrane, Chelate Functional Group

Description

Polymer membrane / electrode assembly for fuel cell and fuel cell comprising same {A MEMBRANE / ELECTRODE ASSEMBLY FOR FUEL CELL AND A FUEL CELL COMPRISING THE SAME}

1 is a schematic view showing an operating state of a fuel cell including a polymer membrane.

2 is a cross-sectional view of the membrane-electrode assembly of the present invention.

<Description of the symbols for the main parts of the drawings>

1: fuel cell 3: anode

5: cathode 7: polymer membrane

10: membrane / electrode assembly 100, 100 ': electrode

101, 101 ': electrode support 103,103': catalyst layer

105,105 ': microporous layer

[Industrial use]

The present invention relates to a polymer membrane / electrode assembly for a fuel cell and a fuel cell including the same, and more particularly, to a fuel cell polymer membrane capable of improving an electrochemical reaction efficiency by introducing a chelate functional group capable of collecting metal impurities. It relates to an electrode assembly and a fuel cell comprising the same.

BACKGROUND ART [0002]

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

Fuel cells are classified into phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, polymer electrolyte or alkaline fuel cells, etc., depending on 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, electrolyte, and the like.

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 a stack, a reformer, a fuel tank, a fuel pump, and the like to constitute a system. The stack forms the 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 stack. The PEMFC thus feeds the fuel in the fuel tank to the reformer by operation of a fuel pump, reforming the fuel in the reformer to generate hydrogen gas, and electrochemically reacting the hydrogen gas and oxygen in the stack to produce electrical energy. Generate.

FIG. 1 is a view schematically showing an operating state of a fuel cell 1 including an anode 3, a cathode 5, and a polymer electrolyte membrane 7. Referring to FIG. 1, when hydrogen gas or fuel is supplied to the anode 3, an electrochemical oxidation reaction occurs and is oxidized while being ionized with hydrogen ions H ⁺ and electrons e ⁻ . Ionized hydrogen ions move to the cathode 5 through the polymer electrolyte membrane 7 and electrons move to the cathode 5 through an external circuit. The hydrogen ions transferred to the cathode 5 cause an electrochemical reduction reaction with oxygen supplied to the cathode 5 to generate heat of reaction and water, and electrical energy is generated by the movement of electrons.

In such a fuel cell system, a stack that substantially generates electricity is stacked with several to several tens of unit cells including a membrane electrode assembly (MEA) and a bipolar plate closely attached to both surfaces thereof. Has a structure. The membrane / electrode assembly has a structure in which an anode electrode and a cathode electrode are coupled with an electrolyte membrane interposed therebetween. The bipolar plate separates the respective membrane / electrode assemblies and serves as a passage for supplying hydrogen gas and oxygen required for the reaction of the fuel cell to the anode electrode and the cathode electrode of the membrane / electrode assembly, and for each membrane / electrode assembly. It simultaneously serves as a conductor that connects the anode and cathode electrodes in series. Hydrogen gas is supplied to the anode electrode through the bipolar plate, while oxygen is supplied to the cathode electrode.

In the power generation system of a polymer fuel cell, the performance of a polymer membrane / electrode assembly (MEA) has a great influence on the power generation characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel cell polymer membrane / electrode assembly capable of capturing metal impurities melted from various members of a fuel cell during operation of the fuel cell to improve the electrochemical reaction efficiency of the fuel cell, and a fuel cell including the same. It is to.

In order to achieve the above object, the present invention is an anode and cathode electrode consisting of a catalyst layer and an electrode support; And a polymer membrane positioned between the anode and the cathode, and a polymer membrane / electrode assembly for a fuel cell having a chelating functional group capable of collecting metal impurities on the surface of the polymer membrane.

The invention also includes at least one membrane / electrode assembly comprising an anode and a cathode electrode positioned opposite each other, and a polymer membrane positioned between the anode and the cathode electrode; And a bipolar plate having a flow channel for contacting any one of an anode and a cathode of the membrane / electrode assembly and supplying gas, wherein the polymer membrane has a fuel having a chelate functional group introduced therein to collect metal impurities on its surface. Provide a battery.

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

In the fuel cell system, the reformer and bipolar plate are generally made of metal, so that metal impurities may occur while the reaction gas passes through them. If the fuel cell is operated for a long time at high temperature, various metal components used for the electrode catalyst may melt. To form impurities. The polymer membrane of the fuel cell should be impermeable to gases used as fuel in addition to hydrogen ions, and should not allow metal impurities that may melt during prolonged operation of the fuel cell.

In order to solve this problem, the present invention uses a polymer having a chelate functional group introduced therein capable of collecting metal impurities into the polymer membrane. As the polymer, fluorine-based polymers, benzimidazole-based polymers, ketone-based polymers, ester-based polymers, amide-based polymers, imide-based polymers, etc. may be used. Specific examples thereof include poly (perfluorosulfonic acid) and polysulfone. , Poly (perfluorocarboxylic acid), polystyrene, polyphenylene, polyetheretherketone (PEEK), tetrafluoroethylene and fluorovinylether copolymer including sulfonic acid groups, defluorinated sulfided polyetherketone, Aryl ketones, polyimides, or poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole) (polybenzimidazole (PBI)) (poly (2,2'- polybenzimidazole such as (m-phenylene) -5,5'-bibenzimidazole)) and poly (2,5-benzimidazole), and the like, but are not limited thereto.

Ethylene diamine tetraacetic acid (EDTA) of Formula 1, 1,2-cyclohexadiamine tetraacetic acid (CyDTA), nitrilotriacetic acid (NTA) of Formula 2 may be used as the chelate functional group.

[Formula 1]

[Formula 2]

The chelate functional group capable of collecting the metal fraction is preferably introduced at 2 to 10 mol%, more preferably at 5 to 10 mol% with respect to the polymer membrane. When the amount of the chelate functional group is less than 2 mol%, the effect of removing metal impurities is insignificant, and when the amount of the chelate functional group is more than 10 mol%, there is a problem of lowering the hydrogen ion conductivity, which is not preferable. In addition, the chelate functional group is preferably located in the reaction portion which is a portion in contact with the electrode.

The chelating functional group may directly introduce a chelating functional group into the molded polymer membrane or may introduce a chelating functional group into the polymer to form the polymer membrane. The first method may be a method of impregnating a polymer membrane into a composition comprising a chelate functional group-containing compound. The second method may be, for example, a method in which a compound including a chelating functional group is added to a polymer solution and then molded into a polymer membrane.

The polymer membrane is positioned between the cathode and the anode in a fuel cell to form a membrane / electrode assembly. A cross-sectional view of this membrane / electrode assembly is shown in FIG. As shown in FIG. 2, the membrane / electrode assembly includes a polymer electrolyte membrane 110 and an anode electrode 100 and a cathode electrode 100 ′ disposed on both surfaces of the polymer electrolyte membrane 110, respectively. The electrodes include electrode supports 101 and 101 'and catalyst layers 103 and 103', respectively.

The electrode supports 101 and 101 'may be carbon paper, carbon cloth, carbon felt, or the like, and may be used by water repellent treatment with polytetrafluoroethylene (PTFE) or the like. Can be. The electrode support serves to support the polymer membrane / electrode assembly and also serves as a gas diffusion layer (GDL) for diffusing the reactant into the polymer membrane / electrode assembly.

The catalyst layers 103 and 103 'are formed by depositing a so-called metal catalyst which catalyzes a related reaction (oxidation of hydrogen and reduction of oxygen), and the metal catalyst is platinum, ruthenium, osmium, or platinum-transition. Metal alloys and the like can be preferably used. Examples of the transition metal include ruthenium, osmium, chromium, copper, nickel and the like. These metal catalysts are preferably supported by a carrier and used. As the carrier, carbon such as acetylene black, graphite, or the like may be used, or inorganic fine particles such as alumina or silica may be used. In the case of using the noble metal supported on the carrier as a catalyst, a commercially available one may be used, or a noble metal supported on the carrier may be prepared and used.

The fuel cell membrane / electrode assembly of the present invention includes a microporous layer (105, 105 ') to enhance the gas diffusion effect between the electrode support (101, 101') and the catalyst layer (103, 103 '). It may further include. The microporous layer serves to uniformly supply the reaction gas to the catalyst layer and to transfer electrons formed in the catalyst layer to the electrode support. In general, conductive particles having a small particle size, such as carbon powder, carbon black, acetylene black, activated carbon, fullerene, carbon nanotube, carbon nano horn, carbon nano wire, carbon nano ring And the like.

The fuel cell inserts a membrane / electrode assembly between a gas flow channel and a bipolar plate on which a cooling channel is formed to manufacture a unit cell. It can be prepared by. Fuel cells can be readily manufactured by conventional techniques in the art.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only one preferred embodiment of the present invention and the present invention is not limited to the following examples.

(Example 1)

A Nafion 112 (manufactured DuPont) film was impregnated in 0.5M aqueous solution of ethyldiaminetetraacetic acid disodium salt dihydrate (EDTA) for 24 hours to prepare a polymer membrane into which EDTA functional groups were introduced. The polymer membrane was placed between an anode and a cathode and rolled to prepare a membrane / electrode assembly. The anode and the cathode were prepared by coating carbon paper with a catalyst slurry prepared by mixing isopropyl alcohol with a platinum-supported carbon powder (Pt / C), a polytetrafluoroethylene binder polymer and a solvent.

The prepared membrane / electrode assembly is inserted between two gaskets, and then inserted into two bipolar plates in which a gas channel and a cooling channel of a predetermined shape are formed, and then compressed between copper end plates. The cell was prepared.

(Example 2)

A unit cell was prepared in the same manner as in Example 1, except that a mixed solution was prepared by mixing Nafion 112 (manufactured DuPont) solution and 0.5M EDTA (Ethylenediaminetetraacetic acid disodium salt dihydrate) solution to form a polymer film. It was.

(Comparative Example 1)

A unit cell was manufactured in the same manner as in Example 1, except that a Nafion 112 film was used as the polymer film.

In the cells of Examples 1 and 2, it was confirmed that the reaction efficiency was increased by about 20% compared to Comparative Example 1 by collecting the chelate functional groups introduced into the polymer membrane, which may be generated during operation of the fuel cell.

In the polymer membrane of the present invention, by introducing a functional group capable of trapping metal in the reaction portion of the membrane, metal impurities which may occur during operation of the fuel cell may be removed, thereby maintaining excellent battery efficiency.

Claims (14)

An anode and a cathode comprising a catalyst layer and an electrode support; And It includes a polymer film located between the anode and the cathode, The chelate functional group which can collect a metal impurity is introduce | transduced into the surface of the said polymer film, Wherein the chelate functional group is a polymer membrane / electrode assembly for a fuel cell is present in 2 to 10 mol% based on the polymer membrane. The polymer membrane / electrode assembly of claim 1, wherein the polymer is at least one selected from the group consisting of a fluorine polymer, a benzimidazole polymer, a ketone polymer, an ester polymer, an amide polymer, and an imide polymer. . The method of claim 1, wherein the polymer comprises poly (perfluorosulfonic acid), polysulfone, poly (perfluorocarboxylic acid), polystyrene, polyphenylene, polyetheretherketone (PEEK), sulfonic acid group Tetrafluoroethylene and fluorovinylether copolymers, defluorinated sulfided polyetherketones, aryl ketones, polyimides, poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazoles) (Polybenzimidazoles (PBI)) (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole)), poly (2,5-benzimidazole) perfluorosulfonate, Polyimide, polysulfone, polystyrene, polyphenylene, polyetheretherketone (PEEK), arylketone, poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole] (polybenz Polymer membrane / electrode assembly for fuel cells, which is at least one selected from the group consisting of imidazole (polybenzimidazole, PBI)), and poly (2,5-benzimidazole). The method of claim 1, wherein the chelate functional group is ethylene diamine tetraacetic acid (EDTA) of formula 1, 1,2-cyclohexadiamine tetraacetic acid (CyDTA) of formula (2), and nitrilotriacetic acid (NTA) Polymer membrane / electrode assembly for at least one fuel cell selected from the group consisting of: [Formula 1]

[Formula 2]

delete The polymer membrane / electrode assembly of claim 1, further comprising a fine pore layer between the catalyst layer and the electrode support. The method of claim 6, wherein the microporous layer is carbon powder, carbon black, acetylene black, activated carbon, fullerene, carbon nanotube, carbon nano horn (carbon nano horn), carbon nano wire, carbon nano ring (carbon nano ring) And a conductive powder selected from the group consisting of a mixture thereof. At least one membrane / electrode assembly comprising an anode and a cathode electrode positioned opposite each other and composed of a catalyst layer and an electrode support, and a polymer membrane positioned between the anode and the cathode electrode; And a bipolar plate having a flow channel for supplying a gas in contact with one of an anode and a cathode of the membrane / electrode assembly. The polymer membrane has a chelate functional group capable of collecting metal impurities on the surface thereof, The chelate functional group is present in the fuel cell is 2 to 10 mol% based on the polymer membrane. The fuel cell of claim 8, wherein the polymer is at least one selected from the group consisting of a fluorine polymer, a benzimidazole polymer, a ketone polymer, an ester polymer, an amide polymer, and an imide polymer. The method of claim 8, wherein the polymer comprises poly (perfluorosulfonic acid), polysulfone, poly (perfluorocarboxylic acid), polystyrene, polyphenylene, polyetheretherketone (PEEK), sulfonic acid group Tetrafluoroethylene and fluorovinylether copolymers, defluorinated sulfided polyetherketones, aryl ketones, polyimides, poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazoles) (Polybenzimidazole (PBI)) (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole)), poly (2,5-benzimidazole) perfluorosulfonate, Polyimide, polysulfone, polystyrene, polyphenylene, polyetheretherketone (PEEK), arylketone, poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole] (polybenz Imidazole (polybenzimidazole, PBI)), and poly (2,5-benzimidazole) is at least one selected from the group consisting of fuel cells. The method according to claim 8, wherein the chelate functional group is composed of ethylene diamine tetraacetic acid (EDTA) of Formula 1, 1,2-cyclohexadiamine tetraacetic acid (CyDTA) of formula (II) and nitrilotriacetic acid (NTA). At least one fuel cell selected from the group: [Formula 1]

[Formula 2]

delete The fuel cell of claim 8, further comprising a fine pore layer between the catalyst layer and the electrode support. The method of claim 13, wherein the fine pore layer is carbon powder, carbon black, acetylene black, activated carbon, fullerene, carbon nanotube, carbon nano horn (carbon nano horn), carbon nano wire, carbon nano ring (carbon nano ring) And a conductive powder selected from the group consisting of a mixture thereof.

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