KR20070094128A - Cathode catalyst for fuel cell and membrane-electrode assembly for fuel cell comprising same - Google Patents

Abstract

An anode catalyst for fuel cells is provided to exhibit excellent catalytic activity in an alkaline fuel cell. An anode catalyst for fuel cells comprises a carrier including a Cu-Ni alloy, and an active material including an Fe-Ni alloy supported on the carrier. A content of Cu in the carrier is 25-70wt%. A content of Ni in the active material is 30-70wt%. The membrane-electrode assembly(17) for fuel cells has an anode electrode and a cathode electrode which are opposite to each other, and an electrolyte placed between the anode electrode and cathode electrode, wherein the anode electrode contains the anode catalyst.

Description

Cathode catalyst for fuel cell and membrane-electrode assembly for fuel cell comprising same TECHNICAL FIELD

1 is a schematic diagram of a structure of a fuel cell system including a membrane-electrode assembly of the present invention;

[Industrial use]

The present invention relates to an anode catalyst for a fuel cell and a membrane-electrode assembly for a fuel cell including the same, and more particularly, to an anode catalyst for a fuel cell having excellent catalytic activity in an alkaline fuel cell.

[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. This fuel cell is a clean energy source that can replace fossil energy, and has a merit that can produce a wide range of outputs by stacking unit cells, and has an energy density of 4-10 times that of a small lithium battery. It is attracting attention as a compact and mobile portable power source.

Such fuel cells include phosphoric acid fuel cells, molten carbonate fuel cells, alkali electrolyte fuel cells, and polymer electrolyte fuel cells depending on the type of electrolyte.

The principle of generating electricity in a fuel cell is that fuel is supplied to an anode electrode, which is a fuel electrode, adsorbed to a catalyst of the anode electrode, fuel is ionized by an oxidation reaction, and electrons are generated, and the generated electrons are oxidized according to an external circuit. Reaching the cathode electrode, which is the pole, ionized fuel passes through the polymer electrolyte membrane and is delivered to the cathode electrode. An oxidant is supplied to the cathode electrode, and the oxidant, ionized fuel and electrons react on the catalyst of the cathode electrode to generate electricity while producing water.

An object of the present invention is to provide an anode catalyst for a fuel cell having excellent catalytic activity.

Another object of the present invention is to provide a membrane-electrode assembly for a fuel cell comprising the anode catalyst.

In order to achieve the above object, the present invention provides an anode catalyst for a fuel cell comprising a carrier comprising a Cu-Ni alloy and an active material comprising a Fe-Ni alloy supported on the support.

The invention also provides a membrane-electrode assembly for a fuel cell, which is located opposite each other and comprises an anode and a cathode and an electrolyte located between the anode and the cathode, the anode comprising the anode catalyst. do.

The anode catalyst and the membrane-electrode assembly are preferably used in an alkaline electrolyte fuel cell.

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

The present invention relates to a catalyst used for the anode electrode of a fuel cell. In particular, the present invention relates to a catalyst used for an anode electrode of an alkaline electrolyte fuel cell (AFC) using an alkaline solution as an electrolyte. Such alkali electrolyte fuel cells have high power density, low operating temperature, and rapid driving, and thus, research is being conducted for special purposes such as power supply for spacecraft and submarines. It is a battery that is attracting attention as a power source in extreme regions because it operates at temperature.

In the alkaline electrolyte fuel cell, H ₂ fuel and OH ⁻ present in the electrolyte react to generate water and electrons, and the generated electrons move to the cathode electrode, where oxygen, water, and electrons react to form oxygen and water. It is a battery that generates electricity by forming OH ^- ions.

The anode catalyst of the present invention includes a carrier containing a Cu—Ni alloy and an active material including a Fe—Ni alloy supported on the support.

Conventionally, Pt has been mainly used as an anode catalyst, but poisoning due to fuel has been frequently generated during operation of the cell, particularly in direct oxidizing fuel cells, and recently, alloys of Pt and other metals such as Pt-Ru and Pt-Sn have been used. Catalysts have been proposed. However, these alloy catalysts are somewhat low in catalytic activity, and excellent catalyst activity is required to study a catalyst that can prevent catalyst poisoning.

The Fe-Ni alloy active material used in the present invention is a material having a very high catalytic activity, and is particularly excellent in an alkali electrolyte fuel cell. In addition, among the alkaline electrolyte fuel cells, the activity in the direct oxidation fuel cell using a hydrocarbon fuel is more excellent, and the catalytic activity in the direct ethanol fuel cell using ethanol as the fuel is very excellent. It is most useful in battery.

The physical properties of the active material depend on the type of carrier, and the Cu-Ni alloy carrier used in the present invention is a carrier capable of further improving the activity of the catalyst supported on the carrier. Therefore, the active material containing the Cu-Ni alloy support of the present invention and the Fe-Ni alloy supported on the support is a catalyst having excellent catalytic activity.

In the Cu-Ni alloy which is a carrier of the anode catalyst of the present invention, the Cu content is preferably 25 to 70 wt%, and the Ni content is 30 to 70 wt% in the Fe-Ni alloy, which is the active material having the catalytically active site. desirable. If the content of Cu exceeds 70% by weight, the selectivity is lowered, and if the content of Cu is less than 30% by weight, the activity is lowered, which is undesirable, and if the content of Ni exceeds 70% by weight, the particle size is increased, which is undesirable. If it is less than 30% by weight, the activity is low, which is not preferable.

In the anode catalyst of the present invention, the weight ratio of the carrier to the active substance is preferably 1: 1 to 2.3 weight ratio. If the amount of the carrier used is higher than the above range, the amount of the catalyst is reduced to decrease the activity, and if the amount of the carrier is used, the catalyst particles are agglomerated with each other and the catalyst particle size is increased, which is very undesirable because the activity is very low.

The anode catalyst of the fuel cell of the present invention can be prepared by the following method. The Fe-Ni alloy is supported on the Cu-Ni alloy.

The nickel containing compound, the iron containing compound and the CuNi carrier are stirred in a solvent at a temperature of 50 to 100 ° C. for 1 to 24 hours. In this process, the solvent is almost volatilized to produce a catalyst. As for the mixing ratio of the said nickel containing compound and iron containing compound, 0.1-10 weight ratio is preferable. At this time, there is a problem that the catalyst performance is reduced when out of the weight ratio.

As the nickel-containing compound, at least one kind of nickel carbonyl, nickel chloride, or nickel nitrate may be used, and as the iron-containing compound, at least one kind of iron carbonyl, iron chloride, or iron nitrate may be used. In addition, benzene, water or ethanol may be used as the solvent.

If the stirring temperature is less than 50 ℃ there is a problem that the reaction does not occur, if it exceeds 100 ℃ there is a problem that the solvent is rapidly evaporated and stirring is not possible, if the stirring time is less than 1 hour the problem that the reaction does not occur sufficiently If it exceeds 24 hours, there exists a problem that catalyst drying progresses too much.

The catalyst of the present invention is used for the anode electrode and the catalyst of the cathode electrode may be used Au-Ag alloy, PdP, AuP or MnO _2-x (where x is 0.1 to 0.5) and the like, in addition to the alkali electrolyte fuel Anything used as a cathode catalyst in the cell can be used. In addition, the catalyst may be used in a black type or a form supported on a carrier which is not supported on a carrier, and a carrier such as activated carbon, denka black, ketjen black, acetylene black, or graphite may be used. Alternatively, inorganic fine particles such as alumina, silica, zirconia, titania, and the like may be used, but carbon is generally used.

In addition, the catalysts of the cathode electrode and the anode electrode are both formed on the electrode substrate. The electrode substrate plays a role of supporting the electrode and diffuses the fuel and the oxidant to the catalyst layer, thereby serving to easily access the fuel and the oxidant to the catalyst layer. The electrode substrate is a conductive substrate, and representative examples thereof include carbon paper, carbon cloth, carbon felt, or metal cloth (porous film or polymer fiber composed of metal cloth in a fibrous state). The metal film is formed on the surface of the cloth formed of (referred to as a metalized polymer fiber) may be used, but is not limited thereto.

In addition, in order to enhance the gas diffusion effect, a microporous layer may be further included on the electrode substrate. This microporous layer may generally comprise a conductive powder having a small particle size, such as carbon powder, carbon black, acetylene black, ketjen black, activated carbon, carbon fiber, fullerene or carbon nanotubes.

The microporous layer is prepared by coating a composition comprising a conductive powder, a binder resin and a solvent on the electrode substrate. As the binder resin, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, cellulose acetate, or the like may be preferably used. As the solvent, alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone and the like may 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.

In addition, the membrane-electrode assembly for a fuel cell including the cathode electrode including the catalyst for cathode of the present invention, and having an anode electrode having the above configuration includes an electrolyte.

An electrolyte of the alkaline fuel cell is OH ^- ions as a material which serves to selectively transmit, gatah an alkali aqueous solution or -OH, OH ^- is also possible to use a solid electrolyte film having the ability to pass the ions. As the aqueous alkali solution, one kind or a mixture of one or more kinds of KOH, NaOH, or LiOH is typically used. A commercially available Tokuyama series electrolyte membrane may be used as the solid electrolyte membrane having the OH- ions.

The fuel cell system of the present invention including the membrane-electrode assembly having the above configuration includes at least one electricity generating portion, a fuel supply portion and an oxidant supply portion.

The electricity generating unit includes a membrane-electrode assembly, a separator (also called a bipolar plate), and serves to generate electricity through an oxidation reaction of a fuel and a reduction reaction of an oxidant.

The fuel supply unit serves to supply fuel to the electricity generation unit, and the oxidant supply unit serves to supply an oxidant such as oxygen or air to the electricity generation unit. In the present invention, the fuel includes hydrocarbon-based fuel or hydrogen in gas or liquid state. Methanol or ethanol may be used as the hydrocarbon-based fuel.

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 an 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 system using a diffusion method without using a pump is shown. Of course, it can also be used for construction.

The fuel cell system 1 of the present invention includes at least one electricity generation unit 3 for generating electrical energy through an oxidation reaction of a fuel and a reduction reaction of an oxidant, a fuel supply unit 5 for supplying the fuel, And an oxidant supply unit 7 for supplying an oxidant to the electricity generation unit 3.

In addition, the fuel supply unit 5 for supplying the fuel may include a fuel tank 9 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 7 for supplying the oxidant to the electricity generating unit 3 includes at least one oxidant pump 13 for sucking the oxidant with a predetermined pumping force.

The electricity generator 3 is composed of a membrane-electrode assembly 17 for oxidizing and reducing a fuel and an oxidant, and a separator 19 and 19 'for supplying fuel and an oxidant to both sides of the membrane-electrode assembly. At least one of these electricity generating units 17 constitutes a stack 15.

Hereinafter, preferred 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)

0.97 g of nickel carbonyl, 3 ml of iron carbonyl and 1 g of CuNi carrier were stirred for 24 hours at 100 ° C. in 100 ml benzene. At this time, benzene was almost volatilized to prepare a catalyst including a carrier containing a Cu—Ni alloy and an active material including a Fe—Ni alloy supported on the support. In the prepared catalyst, the content of Cu was 25% by weight, the content of Ni in the active material was 50% by weight, and the weight ratio of the support to the active material was 1: 1.

(Comparative Example 1)

A commercially available 5 wt% supported Pt / C catalyst was used.

As a result of measuring the catalytic activity of the anode catalyst prepared according to Example 1 and Comparative Example 1, the catalytic activity of Example 1 was found to be very excellent compared to Comparative Example 1.

The anode catalyst of the present invention has very good catalytic activity.

Claims (12)

A carrier comprising a Cu—Ni alloy; And Active material containing Fe-Ni alloy supported on the carrier An anode catalyst for a fuel cell comprising a. The method of claim 1, The content of Cu in the carrier is 25 to 70% by weight anode catalyst for fuel cells. The method of claim 1, The content of Ni in the active material is 30 to 70% by weight anode catalyst for fuel cells. The method of claim 1, In the anode catalyst, the weight ratio of the carrier to the active material is a cathode catalyst for a fuel cell is 1: 1 to 2.3. The method of claim 1, The fuel cell cathode catalyst is a cathode catalyst for fuel cell, which is an alkali electrolyte type cathode catalyst. The method of claim 1, The anode catalyst for fuel cell is an anode catalyst for fuel cell which is a cathode catalyst for alkaline electrolyte type direct oxidation fuel cell. The method of claim 1, The anode catalyst for fuel cell is an anode catalyst for fuel cell which is an alkaline electrolyte type direct ethanol type fuel cell cathode catalyst. An anode electrode and a cathode electrode positioned opposite each other; And An electrolyte located between the anode electrode and the cathode electrode Including, The anode electrode comprises the anode catalyst of any one of claims 1 to 7. Membrane-electrode assembly for fuel cell. The method of claim 8, The fuel cell membrane electrode assembly is a fuel cell membrane electrode assembly for an alkaline electrolyte fuel cell. The method of claim 8, The fuel cell anode catalyst is a fuel cell membrane-electrode assembly for an alkaline electrolyte type direct oxidation fuel cell cathode catalyst. The method of claim 8, The fuel cell anode catalyst is a fuel cell membrane-electrode assembly for an alkaline electrolyte type direct ethanol fuel cell cathode catalyst. The method of claim 8, The electrolyte is a membrane-electrode assembly for a fuel cell which is a solid electrolyte membrane having an aqueous alkali solution or -OH group.

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