KR20070000253A - Electrode for fuel cell and fuel cell system comprising same - Google Patents

Abstract

Provided are an electrode for a fuel cell which is high in the oxidation activity of an alcohol-based fuel and is reduced in the poisoning of a catalyst, and a fuel cell system containing the electrode. The electrode comprises an electrode support which is made of a conductive substrate; and a catalyst layer which is formed on the electrode support and comprises Ag or Au catalyst supported on a ZrO2, Fe2O3 or TiO2 support and a conductive material. Preferably the conductive material is an electrically conductive polymer or carbon. Preferably the electrically conductive polymer is selected from the group consisting of polyacetylene, polythiophene, polypyrrole, polyacene and polyaniline.

Description

Electrode for fuel cell and fuel cell system including same TECHNICAL FIELD

[Industrial use]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell electrode and a fuel cell system comprising the same, and more particularly, to a fuel cell electrode exhibiting high catalytic activity and having reduced poisoning of the catalyst and a fuel cell system including the same.

[Prior art]

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

Representative examples of the fuel cell system include a polymer electrolyte fuel cell (PEMFC) and a direct oxidation fuel cell (Direct Oxidation Fuel Cell). When methanol is used as a fuel in the direct oxidation fuel cell, it is called a direct methanol fuel cell (DMFC).

The polymer electrolyte fuel cell is a clean energy source that can replace fossil energy, and has high power density and energy conversion efficiency, can be operated at room temperature, and can be miniaturized and encapsulated. It can be widely used in fields such as portable power supply and military equipment.

In general, a polymer electrolyte fuel cell using hydrogen as a fuel has the advantages of high energy density and high output, but requires careful handling of hydrogen gas and methane, methanol and natural gas to produce hydrogen as fuel gas. There is a problem in that an auxiliary facility such as a fuel reforming device for reforming the back is required.

In contrast, the direct oxidation fuel cell has a slower reaction rate, and thus has a lower energy density, a lower output, and a larger amount of electrode catalyst than the gaseous polymer electrolyte fuel cell. However, fuel handling is easy and the operating temperature is low. In particular, it has the advantage of not requiring a fuel reformer.

An object of the present invention is to provide an electrode for a fuel cell, which exhibits high catalytic activity and reduces poisoning of the catalyst.

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

In order to achieve the above object, the present invention includes an electrode support made of a conductive substrate and a catalyst layer formed on the electrode support. This catalyst layer contains an Ag or Au catalyst and a conductive material supported on a ZrO ₂ , Fe ₂ O ₃ or TiO ₂ carrier.

The present invention also refers to a fuel cell system comprising at least one membrane-electrode assembly comprising the electrode and at least one electricity generator comprising a separator, a fuel supply and an oxidant supply. In the electricity generating unit, the electrodes are anode electrodes and cathode electrodes located opposite to each other, and a polymer electrolyte membrane located between the anode electrode and the cathode electrode is located. At least one of the anode electrode and the cathode electrode is preferably the electrode of the present invention, and most preferably the anode electrode is the electrode of the present invention. The fuel supply unit serves to supply fuel to the electricity generation unit, and the oxidant supply unit serves to supply an oxidant to the electricity generation unit.

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

The present invention relates to an electrode for a fuel cell, which comprises an Ag or Au catalyst and a conductive material supported on a ZrO ₂ , Fe ₂ O _3, or TiO ₂ carrier. In the present invention, the Au catalyst is preferably supported on a ZrO ₂ carrier.

Ag or Au used as a catalyst in the electrode of the present invention has a very high oxidation reaction activity against alcohol fuel, thereby improving battery performance. In addition, the catalysts may increase the life of the battery since the catalyst poisoning by CO generated in the reaction of the fuel cell using alcohol fuel is hardly generated.

The catalysts are supported on a ZrO ₂ , TiO ₂ or Fe ₂ O ₃ carrier, and since the carrier is not carbon, the electrical conductivity may be somewhat lowered, so that an electrically conductive polymer or carbon is used as a conductive material. .

Examples of the electrically conductive polymer include polyacetylene, polythiophene, polypyrrole, polyacene, or polyaniline.

The conductive material is included in the catalyst layer in an amount of 10 to 20% by weight based on the total weight of the catalyst layer.

The electrode for fuel cells of this invention contains a binder. As the binder, any material generally used in an electrode for a fuel cell may be used. Examples thereof include polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, polyvinyl alcohol, cellulose acetate, poly (Perfluorosulfonic acid) and the like can be used.

In addition, the electrode of the present invention includes an electrode substrate for supporting the catalyst and the polymer. The electrode substrate serves to easily access the reaction source to the catalyst. A conductive substrate is used as the electrode substrate, and representative examples thereof may include carbon paper, carbon cloth, carbon felt, or metal cloth, but are not limited thereto.

The electrode of the present invention having the above configuration can be used as a cathode electrode and an anode electrode in a fuel cell, it is preferable to be used as an anode electrode.

The process of manufacturing the electrode of the present invention having such a configuration can be carried out by the process of forming a catalyst layer on the electrode support by a conventional method such as spray coating, doctor blade, the catalyst composition comprising a catalyst, a binder and a solvent. Since the electrode manufacturing process is well known in the art, detailed description thereof will be omitted.

In addition, when using the electrode for fuel cells of this invention only as an anode electrode, the platinum-type catalyst cathode electrode conventionally used conventionally can be used as a cathode electrode. The platinum-based catalyst may be platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy or platinum-M alloy (M is Ga, Ti, V, Cr, Mn, Fe, Co, Ni, At least one catalyst selected from the group consisting of Cu and Zn, and at least one transition metal selected from the group consisting of Cu and Zn.

When using a precious metal supported on a ZrO ₂ , Fe ₂ O ₃ or TiO ₂ carrier as a catalyst, a commercially available commercially available one may be used, and also prepared by supporting a precious metal on a ZrO ₂ , Fe ₂ O ₃ or TiO ₂ carrier. Can also be used. Since the process of supporting the noble metal on the ZrO ₂ , Fe ₂ O ₃ or TiO ₂ carrier is well known in the art, the detailed description thereof will be easily understood by those skilled in the art even if the detailed description thereof is omitted.

In addition, the cathode electrode also includes the same electrode substrate as the anode electrode of the present invention.

The fuel cell system of the present invention including the electrode of the present invention includes at least one electricity generator, a fuel supply and an oxidant supply.

The electricity generating unit includes a membrane-electrode assembly including a polymer electrolyte membrane and an electrode of the present invention on both sides of the polymer electrolyte membrane, and includes a separator (bipolar plate) positioned on both sides of the membrane-electrode assembly. The electricity generation unit serves to generate electricity through the oxidation reaction of the fuel and the reduction reaction of the oxidant.

The polymer electrolyte membrane includes a polymer having excellent hydrogen ion conductivity, preferably a fluorine polymer, a polyamide polymer, a polyether polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, At least one hydrogen ion conductive polymer selected from polyphenylene sulfide polymer, polysulfone polymer, polyether sulfone polymer, polyether ketone polymer, polyether ether ketone polymer or polyphenylquinoxaline polymer More preferably, poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), copolymer of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, defluorinated sulfided polyether ketone , Aryl ketone, poly (2,2'-m-phenylene) -5,5'-bibenzimidazole (poly (2,2 '-(m-phenylene) -5,5'-bibenzimid azole) or poly (2,5-benzimidazole) may be used, including one or more hydrogen ion conductive polymers, which generally have a thickness of 10 to 200 mu m.

The fuel supply unit serves to supply fuel to the electricity generation unit, and the oxidant supply unit serves to supply an oxidant to the electricity generation unit. The fuel means hydrogen or hydrocarbon fuel in gas or liquid state, and typical hydrocarbon fuels include methanol, ethanol, propanol, butanol or natural gas. Examples of the oxidant include oxygen or air.

A schematic structure of the fuel cell system of the present invention is shown in FIG. 1, which will be described in more detail with reference to the following. Although the structure shown in FIG. 1 shows a system for supplying fuel and oxidant to an electric generator using a pump, the fuel cell system of the present invention is not limited to such a structure, and a fuel cell using an osmotic method without using a pump is shown. Of course, it can also be used for system architecture.

The fuel cell system 100 of the present invention supplies a stack 7 having at least one electricity generating unit 19 for generating electrical energy through a reaction of fuel oxidation and a reduction of oxidant, and the fuel described above. And an oxidant supply unit 5 for supplying an oxidant to the electricity generating unit 19.

In addition, the fuel supply unit 1 for supplying the fuel includes a fuel tank 9 for storing fuel and a fuel pump 11 connected to the fuel tank 9. The fuel pump 11 serves to discharge the fuel stored in the fuel tank 9 by a predetermined pumping force.

The oxidant supply unit 5 for supplying the oxidant to the electricity generating unit 19 of the stack 7 includes at least one air pump 13 which sucks air with a predetermined pumping force.

The electricity generator 19 is a membrane / electrode assembly 21 for oxidizing / reducing a fuel and an oxidant and a separator (bipolar plates) 23 and 25 for supplying fuel and an oxidant to both sides of the membrane / electrode assembly. It consists of.

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 catalyst slurry was prepared by mixing an Ag catalyst, a polyacetylene electrically conductive polymer, a polyperfluorosulfonate binder, and a mixed solvent of isopropyl alcohol and water supported on a ZrO ₂ carrier. This catalyst slurry was applied to a carbon paper electrode support to prepare an anode electrode for a fuel cell.

A cathode catalyst slurry was prepared by mixing 5 wt% Nafion / H ₂ O / 2-propanol solution, dipropylene glycol and deionized water and Pt black (Johnson Matthey, HiSpec 1000) particles, followed by screen printing on a Teflon film and drying To produce a cathode electrode for a fuel cell.

The anode electrode and the cathode electrode for fuel cell were placed on the Nafion (perfluorosulfonic acid) polymer electrolyte membrane, respectively, and then thermally compressed for 3 minutes at 200 kgf / cm 2 at 200 ° C., respectively. Cathode and anode electrodes were formed to have a mg / cm 2 loading.

Subsequently, an ELAT electrode substrate (gas diffusion layer) manufactured by E-Tek was placed on a cathode electrode and an anode electrode in which the polymer electrolyte membrane is located in the center, and the binder was manufactured to prepare a membrane-electrode assembly.

The prepared membrane / electrode assembly was inserted between polytetrafluoroethylene-coated glass fiber gaskets, and then inserted into two bipolar plates in which gas flow channels and cooling channels of a predetermined shape were formed. Subsequently, the unit cell was manufactured by pressing between copper end plates.

(Comparative Example 1)

Anode for a fuel cell prepared by applying a catalyst slurry prepared by mixing a PtRu catalyst (supporting amount: 60 wt%), a polyperfluorosulfonate polymer, and a mixed solvent of isopropyl alcohol and water supported on a carbon paper electrode support A unit cell was manufactured in the same manner as in Example 1, except that the electrode and the cathode electrode were used, respectively.

Since the electrode for a fuel cell of the present invention includes a catalyst having a high oxidation reaction activity of a hydrocarbon fuel and a reduced poisoning phenomenon, it is possible to provide a fuel cell having excellent performance and a long service life.

1 is a schematic view showing a configuration of a fuel cell system of the present invention.

Claims (10)

An electrode support made of a conductive substrate; A catalyst layer formed on the electrode support and including an Ag or Au catalyst and a conductive material supported on a ZrO ₂ , Fe ₂ O ₃ or TiO ₂ carrier. Electrode for a fuel cell comprising a. The method of claim 1, The carrier is a fuel cell electrode ZrO ₂ . The method of claim 1, The conductive material is an electrically conductive polymer or carbon electrode for fuel cells. The method of claim 3, wherein The electrically conductive polymer is a fuel cell electrode selected from the group consisting of polyacetylene, polythiophene, polypyrrole, polyacene, and polyaniline. The method of claim 1, The electrode is a fuel cell electrode is an anode electrode. At least one membrane / electrode assembly comprising an anode electrode and a cathode electrode positioned opposite each other, and a polymer electrolyte membrane positioned between the anode and the cathode electrode; And at least one electricity generating unit including a separator. A fuel supply unit supplying fuel to the electricity generation unit; And Oxidant supply unit for supplying an oxidant to the electricity generating unit Including, At least one of the anode electrode and the cathode electrode An electrode support made of a conductive substrate; It is formed on the electrode support, comprising a catalyst layer comprising an Ag or Au catalyst and a conductive material supported on a ZrO ₂ , Fe ₂ O ₃ or TiO ₂ carrier Fuel cell system. The method of claim 6, The carrier is ZrO ₂ fuel cell system. The method of claim 6, The conductive material is an electrically conductive polymer or carbon fuel cell system. 7. The fuel cell system of claim 6, wherein the electrically conductive polymer is selected from the group consisting of polyacetylene, polythiophene, polypyrrole, polyacene, or polyaniline. The method of claim 6, The anode electrode An electrode support made of a conductive substrate; And a catalyst layer formed on the electrode support and including an Ag or Au catalyst and a conductive material supported on a ZrO ₂ , Fe ₂ O _3, or TiO ₂ carrier.