KR20060000536A - 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, the fuel cell electrode comprising: a catalyst layer; And an electrode support having a gas diffusion layer and a fine pore layer, and having a pore size of 10 to 30 μm.

Since the electrode for a fuel cell of the present invention includes an electrode support having an optimum pore size and porosity, it is possible to provide a fuel cell that can operate in a non-humidity condition and to form a thin thickness of the electrode support, thereby providing a relatively catalyst layer. Since it can form thickly, the efficiency of a fuel cell can be improved.

Fuel cell, no humidification, rolling, porosity, pore size

Description

Electrode for fuel cell and fuel cell including same TECHNICAL FIELD

1 is a cross-sectional view schematically showing the structure of a membrane / electrode assembly including an electrode of the present 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 use the fuel cell even under unhumidified conditions and can improve battery life characteristics. It is about.

[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 an electrode for a fuel cell which can provide a fuel cell operable under humidification conditions.

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 catalyst layer; And a gas diffusion layer and a fine pore layer, and includes an electrode support having a pore size of 10 to 30 μm.

The present invention also provides a catalyst layer; And a cathode and an anode electrode including a gas diffusion layer and a fine pore layer, the electrode support having a pore size of 10 to 30 μm; At least one membrane electrode assembly comprising a polymer membrane present between the cathode and the anode electrode; And a bipolar plate in contact with both ends of the membrane electrode assembly and having a gas flow channel formed therein.

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 includes a catalyst layer and an electrode support. The electrode support is composed of a gas diffusion layer and a microporous layer for enhancing the gas diffusion effect of the gas diffusion layer.

The gas diffusion layer plays a role of supporting the fuel cell electrode while diffusing the reaction gas into the catalyst layer to easily access the reaction gas to the catalyst layer, and is generally composed of a conductive substrate. As the conductive substrate, carbon paper or carbon cloth is generally used, but is not limited thereto.

In addition, the gas diffusion layer is more preferably used by water repellent treatment with a fluorine-based resin composition in order to prevent the gas diffusion efficiency is lowered by the water generated when the fuel cell is driven. As the fluorine-based resin, polytetrafluoroethylene, polyvinylidene fluoride and FEP (poly-tetrafluoroethylene-co-hexafluoropropylene) may be used. Such fluorine-based resins are generally used in a state of being dispersed in a surfactant such as water. In addition, the solvent used in the composition may be used isopropyl alcohol, mixed solvent of isopropyl alcohol and water or kerosene.

For example, IPA: H2O = 3: 1 solution may be used as a specific example. (Question 1: If there are solvents other than alcohol as a solvent, please inform us and provide specific examples of the solvents).

The microporous layer may include conductive powder having a small particle diameter, for example, carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, or carbon nanotube, in the gas diffusion layer. The microporous layer is prepared by coating a composition including a conductive powder, a binder resin, and a solvent on the gas diffusion layer. As the binder resin, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, cellulose acetate, and the like may be preferably used. The solvent may be ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, or the like. Alcohols, water, dimethylacetamide, dimethylsulfoxide, 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 electrode support having the above constitution has a structure in which pores are formed as a result. In the present invention, the size and porosity of the pores are adjusted to control operating conditions and physical properties of the fuel cell.

The electrode support of the present invention preferably has a pore size of 10 to 30㎛. The preferred pore size of the electrode support varies depending on the degree of humidification conditions. In the case of no humidification, since the humidification should be performed using water generated in a chemical reaction, the smaller pores of the electrode support contain water well so that the water in the membrane Can be supplied. However, if the pore size is too small (less than 10 μm), the resulting water may not be easily discharged and may overflow. If the pore size is too large (30 μm), the water discharge may be too good to remove water from the electrode support layer. It is difficult to contain, so it is difficult to operate in a non-humidifying type.

In addition, the electrode support of the present invention preferably has a porosity of 60 to 90%. If the porosity is less than 60%, it is easy to contain water, but it is not easy to discharge water, so it is easy to flood, and if the porosity is greater than 90%, the water is discharged well, so that additional humidified fuel or air It is not desirable to use.

In the present invention, the pore size and porosity of the electrode support was adjusted by rolling the electrode support, rolling conditions are preferably carried out by applying a pressure of 1 to 50Mpa in consideration of humidification conditions and operating temperature, 10 to 30 Mpa It is more preferable to carry out by applying pressure. The rolling step can be carried out by a rolling method such as hot rolling or hot pressing.

As the electrode support of the present invention has the pore size and porosity, the gas diffusion effect can be increased to form a thinner electrode support, and thus a catalyst layer can be formed relatively thick, thereby increasing the catalytic activity. have.

In addition, the electrode support enables the development of a non-humidifying fuel cell that does not require a separate humidifier. In general, fuel cells operate at a constant level of humidity, so it is necessary to maintain humidity at an appropriate level. However, in this case, since a separate humidification device is required, the fuel cell system is enlarged and the cost is increased. Recently, research on a non-humidified fuel cell has been conducted, and the electrode support of the present invention has such a non-humidified fuel. Development as a battery can be enabled.

In the fuel cell electrode of the present invention, the catalyst layer includes a so-called metal catalyst which catalyzes the related reaction (oxidation of hydrogen and reduction of oxygen), and preferably a two- or four-membered alloy of platinum or platinum and transition metal. Can be used. Ruthenium, copper, nickel or iron can be used as this transition metal. 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 the fuel cell, the cathode and the anode electrode are not distinguished by materials but in their role, and the fuel cell electrode is divided into an anode for hydrogen oxidation and a cathode for reducing oxygen. 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, hydrogen or fuel is supplied to the anode and oxygen is supplied to the cathode to generate electricity by an electrochemical reaction between the anode and the cathode. An oxidation reaction of the organic fuel occurs at the anode and a reduction reaction of oxygen occurs at the cathode, thereby generating 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 and then between the two end plates. 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 one preferred embodiment of the present invention and the present invention is not limited to the following examples.

(Example 1)

The carbon paper was water repelled with a fluorine resin composition composed of a mixed solvent (3: 1 volume ratio) of polytetrafluoroethylene, isopropyl alcohol, and water dispersed in water. Carbon powder was coated on the water-repellent carbon paper to form a fine pore layer, and then rolled at a pressure of 10 Mpa to prepare an electrode support. Platinum was sputtered on the electrode support to form a catalyst layer to prepare an electrode for a fuel cell.

(Comparative Example 1)

It carried out similarly to Example 1 except not having performed a rolling process.

Since the electrode for a fuel cell of the present invention includes an electrode support having an optimum pore size and porosity, it is possible to provide a fuel cell that can operate in a non-humidity condition and to form a thin thickness of the electrode support, thereby providing a relatively catalyst layer. Since it can form thickly, the efficiency of a fuel cell can be improved.

Claims (10)

Catalyst layer; And An electrode support comprising a gas diffusion layer and a fine pore layer, the pore size of 10 to 30㎛ Electrode for a fuel cell comprising a. The electrode of claim 1, wherein the electrode support has a porosity of 60 to 90%. The method of claim 1, wherein the electrode support is Forming a fine pore layer in the gas diffusion layer; An electrode for a fuel cell, wherein the obtained product is produced by applying a pressure of 1 to 50 MPa. The fuel cell electrode as claimed in claim 1, wherein the catalyst is platinum or a two- to four-membered alloy of platinum and a transition metal. The electrode of claim 4, wherein the transition metal is selected from the group consisting of ruthenium, chromium, copper, and nickel. Catalyst layer; And a cathode and an anode electrode including a gas diffusion layer and a fine pore layer, the electrode support having a pore size of 10 to 30 μm; And at least one membrane electrode assembly comprising a polymer membrane present between the cathode and anode electrode; And A bipolar plate in contact with both ends of the membrane electrode assembly and having a gas flow channel formed therein; Fuel cell comprising a. The fuel cell of claim 6, wherein the electrode support has a porosity of 60 to 90%. The method of claim 6, wherein the electrode support Forming a fine pore layer in the gas diffusion layer; A fuel cell which is produced by applying a pressure of 1 to 50 Mpa. The fuel cell of claim 6, wherein the catalyst is platinum or a two- to four-membered alloy of platinum and a transition metal. 10. The fuel cell of claim 9, wherein the transition metal is selected from the group consisting of ruthenium, chromium, copper and nickel.