KR20060102849A - Electrode for fuel cell and fuel cell comprising same - Google Patents

Abstract

The present invention relates to a fuel cell electrode and a fuel cell including the same, wherein the fuel cell electrode includes a gas diffusion layer including a conductive powder, a fluorine resin and a conductive substrate, and a catalyst layer deposited on the gas diffusion layer.

In the present invention, since the conductive material is mixed and formed together during the water repellent treatment of the gas diffusion layer, the same effect as that of the conventional microporous layer may be obtained by a simple process, and the catalyst layer may be formed by a deposition process to form a uniform thin film. Can be. In addition, since the catalyst can be present on the surface of the electrode close to the polymer electrolyte membrane, the catalyst efficiency can be improved.

Fuel cell, electrode, deposition, catalyst efficiency

Description

Electrode for fuel cell and fuel cell including same TECHNICAL FIELD

1 is a view showing a gas diffusion layer of the present invention.

2 schematically illustrates an operating state of a fuel cell comprising an electrode of the invention.

[Industrial use]

The present invention relates to a fuel cell electrode and a fuel cell including the same, and more particularly, to a fuel cell electrode and a fuel cell including the same, which can be manufactured by a simple process and excellent efficiency.

[Prior art]

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 is 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.

It is an object of the present invention to provide a fuel cell electrode which can be manufactured by a simple process and has improved catalytic efficiency.

Another object of the present invention is to provide a fuel cell including the fuel cell electrode.

In order to achieve the above object, the present invention is a gas diffusion layer comprising a conductive powder, a fluorine-based resin and a conductive substrate; And it provides a fuel cell electrode comprising a catalyst layer deposited on the gas diffusion layer.

The invention also includes at least one membrane / electrode assembly comprising an anode and a cathode electrode positioned opposite each other, and a polymer electrolyte membrane positioned between the anode and the cathode electrode; And a separator in which a flow channel is formed in contact with one of the anode and the cathode of the membrane / electrode assembly to supply gas, and at least one of the anode and the cathode includes a conductive powder, a fluorine resin, and a conductive substrate. A gas diffusion layer; And it provides a fuel cell comprising a catalyst layer deposited on the gas diffusion layer.

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a fuel cell, and in general, an electrode of a fuel cell is generally composed of a gas diffusion layer and a catalyst layer. In addition, since the pore size of the gas diffusion layer is somewhat large, gas diffusion may not occur uniformly, and in order to obtain a more uniform gas diffusion effect, a fine pore layer is formed in the gas diffusion layer with a small pore size. The electrode of the fuel cell having such a configuration is a water repellent treatment of the gas diffusion layer in order to prevent the gas diffusion layer is blocked by the water generated during operation of the fuel cell, and then the microporous layer on the water-repellent gas diffusion layer As to form, there was a complicated problem in the process.

On the other hand, in the present invention, in the process of water repellent treatment of the gas diffusion layer by mixing the carbon powder of the conductive material to perform a water repellent treatment, it was possible to obtain a water repellent treatment effect and a uniform gas diffusion effect according to conventional microporous layer formation at the same time.

An electrode for a fuel cell of the present invention includes a gas diffusion layer containing a conductive powder, a fluorine resin and a conductive substrate, and a catalyst layer deposited on the gas diffusion layer.

The gas diffusion layer is formed by applying a composition containing a conductive powder and a fluorine resin to a conductive substrate, and has a structure as shown in FIG. 1. That is, the electrode of the present invention has a constitution of a gas diffusion layer 1 and a catalyst layer 10 formed on the gas diffusion layer 1, as shown in FIG. 1, wherein the gas diffusion layer 1 constitutes a conductive substrate. Since the conductive powder 7 is present between the framework structure 5 or the pores of carbon paper or carbon cloth, the pore size of the conductive substrate is reduced. Therefore, since the pore size of the conductive substrate is large and the gas is not evenly diffused, an effect obtained by further forming a fine pore layer in the gas diffusion layer can be obtained.

In addition, in order to prevent the gas diffusion efficiency from being lowered by water generated when the fuel cell is driven, conductive powder is added to the composition used in the step of water repellent treatment with a fluorine-based resin to form a gas diffusion layer. There is a simple advantage.

As the conductive material, carbon powder, carbon black, activated carbon, acetylene black or Ketjen black may be used.

As the fluorine resin, polytetrafluoroethylene, polyvinylidene difluoride (PVdF, poly vinylidene difluoride), polyvinylidene difluoride-hexafluoropropane (PVdF-HFP, poly vinylidene difluoride-hexafluoropropane) may be used. have. In addition, the solvent used in the composition may be alcohol, water or a mixed solution of alcohol or water. Isopropyl alcohol may be used as the alcohol representatively, but is not limited thereto.

The catalyst layer is formed by depositing a metal on the gas diffusion layer thus formed. That is, the catalyst layer is formed on the gas diffusion layer by a deposition process such as sputtering or evaporation (thermal or electron beam evaporation). As such, when the catalyst layer is formed by the deposition process, the catalyst layer may be coated with a uniform thin film as compared with the conventional slurry coating process. Therefore, when the catalyst layer is formed in the conventional slurry coating process, the catalyst layer is formed thick, so that the catalyst located at a side far from the polymer electrolyte membrane, i.e., close to the gas diffusion layer, rarely participates in the reaction. It can be solved because it can exist a lot, and thus can improve the catalyst efficiency.

The catalyst layer includes a so-called metal catalyst that catalyzes the related reaction (oxidation of fuel such as hydrogen and reduction of oxidant such as oxygen, air, etc.), and a platinum group metal of the periodic table of the elements, that is, platinum or ruthenium is preferable. Can be used. Also generally, those supported on a carrier are used. As the carrier, carbon such as acetylene black or graphite 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 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.

In fuel cells, the cathode and anode electrodes are not distinguished by materials, but by their role, and the fuel cell electrodes are distinguished from anodes for fuel oxidation and cathodes for reducing oxidants. Therefore, the fuel cell electrode of this invention can be used for all the electrodes of a cathode and an anode electrode. That is, in a fuel cell, fuel is supplied to the anode and oxidant is supplied to the cathode to generate electricity by an electrochemical reaction between the anode and the cathode. Oxidation of the fuel occurs at the anode and reduction of the oxidant at the cathode results in a voltage difference between the two electrodes.

2 schematically shows an operating state of a fuel cell including a membrane / electrode assembly 20 in which a polymer electrolyte membrane 15 is positioned between a cathode 10a and an anode 10b electrode.

The polymer electrolyte membrane 15 is made of a proton-conducting polymer material, that is, an ionomer, and is generally a tetrafluoroethylene and a fluorovinyl ether copolymer containing a sulfonic acid group, and a defluorinated sulfide polyether ketone. , Aryl ketone or polybenzimidazole and the like can be used, but is not limited thereto. In general, the polymer electrolyte membrane has a thickness of 10 to 200㎛.

The membrane / electrode assembly 20 is inserted between the gas flow channel and the bipolar plate on which the cooling channel is formed to manufacture a unit cell, and the stack is manufactured by stacking the membrane. The fuel cell can be manufactured by insertion. Fuel cells can be readily manufactured by conventional techniques in the art.

Hereinafter, 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)

Carbon powder and polytetrafluoroethylene were mixed in a 40:60 weight ratio in water and an isopropyl alcohol solvent to prepare a conductive water repellent treatment composition. The conductive water repellent treatment composition was coated on a carbon paper conductive substrate to prepare a gas diffusion layer.

Platinum was sputtered on the gas diffusion layer to form a catalyst layer, thereby preparing an electrode for a fuel cell.

(Comparative Example 1)

A gas diffusion layer was prepared by water repelling carbon paper with polytetrafluoroethylene.

Applying a coating composition for forming a fine pore layer formed by mixing carbon powder and polytetrafluoroethylene in water and isopropyl alcohol solvent in a 40:60 weight ratio to the water diffusion treated gas diffusion layer to form a fine pore layer on the gas diffusion layer. Formed.

Subsequently, a catalyst slurry was applied to the microporous layer to form a catalyst layer, thereby preparing an electrode for a fuel cell. The catalyst slurry was prepared by mixing a mixed solvent of water and isopropyl alcohol with platinum-supported carbon powder (Pt / C), a polytetrafluoroethylene polymer, and a solvent.

As described above, the present invention is formed by mixing the conductive material together during the water repellent treatment of the gas diffusion layer, it is possible to obtain the same effect as in the case of forming a conventional fine pore layer by a simple process and by forming the catalyst layer by the deposition process It can be formed into a uniform thin film. In addition, since the catalyst can be present on the side closer to the polymer electrolyte membrane, the catalyst efficiency can be improved.

Claims (8)

A gas diffusion layer comprising a conductive powder, a fluorine resin and a conductive substrate; And Catalyst layer deposited on the gas diffusion layer Electrode for a fuel cell comprising a. The electrode for a fuel cell of claim 1, wherein the conductive powder and the fluorine-based resin are present together in pores between the conductive fibers. The electrode of claim 1, wherein the gas diffusion layer is formed by applying a composition containing a conductive powder and a fluorine resin to a conductive substrate. The electrode of claim 1, wherein the conductive material is selected from the group consisting of carbon powder, carbon black, activated carbon, acetylene black, and ketjen black. The fuel cell electrode of claim 1, wherein the fluorine resin is selected from the group consisting of polytetrafluoroethylene, polyvinylidene difluoride, and polyvinylidene difluoride-hexafluoropropane. At least one membrane / electrode assembly comprising an anode and a cathode electrode positioned opposite each other, and a polymer electrolyte membrane positioned between the anode and the cathode electrode; And a separator in which a flow channel is formed in contact with any one of an anode and a cathode of the membrane / electrode assembly to supply gas. At least one of the anode and the cathode electrode is a gas diffusion layer comprising a conductive powder, a fluorine-based resin and a conductive substrate; And a catalyst layer deposited on the gas diffusion layer. Fuel cell comprising a. The fuel cell of claim 6, wherein the conductive powder and the fluorine-based resin are present together in pores between the conductive fibers. The fuel cell of claim 6, wherein the gas diffusion layer is formed by applying a composition containing a conductive powder and a fluorine resin to a conductive substrate.

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