KR20070105700A - Catalyst for cathode of fuel cell, and membrane-electrode assembly for fuel cell and fuel cell system comprising same - Google Patents

Abstract

A cathodic catalyst for a fuel cell is provided to be superior in catalytic activity and stability against an oxygen reduction reaction. A cathodic catalyst for a fuel cell includes molybdenum carbide(MoC) added with niobium-tantalum(Nb-Ta) alloy and has an average particle size of 1-3 nm. The catalyst comprises 30-35mol% of Mo, 30-40mol% of C, and 22-32mol% of the Nb-Ta alloy. A membrane-electrode assembly(131) includes: an anode electrode(3) and a cathode electrode(5) opposite to each other; and a polymeric electrolyte membrane(1) interposed between the anode electrode and cathode electrode. The cathode electrode comprises the catalyst.

Description

Cathode catalyst for fuel cell, and membrane-electrode assembly and filter cell system for fuel cell including same TECHNICAL FIELD [0001] CATALYST FOR CATHODE OF FUEL CELL, AND MEMBRANE-ELECTRODE ASSEMBLY FOR FUEL Cell

1 is a view schematically showing the structure of a membrane-electrode assembly according to an embodiment of the present invention.

2 is a view schematically showing the structure of a fuel cell system according to another embodiment of the present invention.

3 is a scanning electron micrograph showing a cathode catalyst prepared according to Example 1 of the present invention.

[Industrial use]

The present invention relates to a cathode catalyst for a fuel cell, and a membrane-electrode assembly and a fuel cell system for a fuel cell including the same, and more particularly, to a cathode catalyst for a fuel cell excellent in catalytic activity and stability against an oxygen reduction reaction, and including the same. Membrane-electrode assembly for fuel cell and fuel cell system.

[Private Technology]

The 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 the advantage of generating a wide range of outputs by stacking unit cells, and having 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.

Representative examples of the fuel cell 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 has the advantages of high energy density and high output, but requires attention to handling hydrogen gas and reforms fuel for reforming methane, methanol, natural gas, etc. to produce hydrogen, which is fuel gas. There is a problem that requires additional equipment such as a device.

On the other hand, the direct oxidation fuel cell has a lower energy density than the polymer electrolyte fuel cell, but it is easy to handle fuel and has a low operating temperature, so that it can be operated at room temperature, in particular, it does not require a fuel reformer.

In such a fuel cell system, the stack that substantially generates electricity is comprised of a number of unit cells consisting of a membrane-electrode assembly (MEA) and a separator (also called a bipolar plate). It has a stacked structure of several tens. The membrane-electrode assembly is called an anode electrode (also called "fuel electrode" or "oxidation electrode") and a cathode electrode (also called "air electrode" or "reduction electrode") with a polymer electrolyte membrane containing a hydrogen ion conductive polymer therebetween. ) Is located.

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, the 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, which is the pole, hydrogen ions pass through the polymer electrolyte membrane and are delivered to the cathode. An oxidant is supplied to the cathode, and the oxidant, hydrogen ions, and electrons react on the catalyst of the cathode to generate electricity while producing water.

It is an object of the present invention to provide a cathode catalyst for a fuel cell which is excellent in catalytic activity and stability against an oxygen reduction reaction.

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

It is another object of the present invention to provide a fuel cell system comprising the membrane-electrode assembly.

In order to achieve the above object, the present invention includes a molybdenum carbide (MoC) to which a niobium-tantalum (Nb-Ta) alloy is added, and provides a cathode catalyst for a fuel cell having an average particle size of nano size.

The present invention also provides an anode electrode and a cathode electrode positioned opposite each other, and a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode, the cathode electrode provides a membrane-electrode assembly for a fuel cell comprising the catalyst. .

The present invention also provides an electricity generator including the membrane electrode assembly of the present invention and separators located on both sides of the membrane electrode assembly, a fuel supply unit supplying fuel to the electricity generator, and an oxidant to the electricity generator. It provides a fuel cell system comprising an oxidant supply.

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

In accordance with the continuing demand for the development of novel non-noble metal catalysts suitable for commercialization and mass production in the field of fuel cells, transition metal carbides with excellent electronic properties and electrical conductivity have been widely studied as non-noble metal catalysts. Among them, tungsten carbide shows high catalytic activity against oxidation of hydrogen or methanol in acid solution, and excellent catalytic activity for oxygen reduction reaction is expected to be applied as anode catalyst and cathode catalyst in fuel cells.

However, as the hydrogen ions move through the polymer electrolyte membrane during driving of the fuel cell, the cathode catalyst layer forms a strong acid atmosphere. However, such tungsten carbides are susceptible to corrosion in an acidic atmosphere, making them difficult to use as a cathode catalyst for the oxygen reduction of fuel cells.

On the other hand, in the present invention, by adding an Nb-Ta alloy to a carbide catalyst containing molybdenum having a catalytic activity superior to that of conventional tungsten, the stability and catalytic activity of the carbide catalyst could be improved.

That is, the cathode catalyst for a fuel cell according to the first exemplary embodiment of the present invention has a mean particle size of nano size and includes molybdenum carbide (MoC) to which a niobium-tantalum (Nb-Ta) alloy is added.

The molybdenum (Mo) is able to exhibit excellent catalytic activity for the oxygen reduction reaction, tantalum (Ta) serves to improve the life characteristics of the fuel cell by showing excellent corrosion resistance.

The niobium (Nb) forms a cluster bond with Mo. The cluster bond has a short bond length, so that electrons move rapidly between metals, and have a high surface energy. It is possible to further increase the stability of the metal in active and acidic electrolytes. Accordingly, the alloy of Ta-Nb containing Nb also exhibits excellent corrosion resistance even under acidic conditions due to inactivity, thereby increasing the stability of the catalyst during the oxygen reduction reaction.

In addition, the cathode catalyst has an octahedral structure and is stable in terms of structure.

The cathode catalyst comprises 30 to 35 mol% Mo, 30 to 40 mol% C and 22 to 32 mol% alloy of Nb-Ta, even more preferably Mo 31 to 33 mol%, C 33 to 36 mol% And 25 to 30 mole% of an alloy of Nb-Ta. If the content of Mo is less than 30 mol%, the activity is lowered, which is not preferable. If the content of Mo exceeds 35 mol%, the selectivity is lowered, which is not preferable. In addition, if the content of C is less than 30 mol%, there is a possibility that the activity is lowered, and if it exceeds 40 mol%, there is a fear that the particle size may increase, which is not preferable. If the content of the alloy of Nb-Ta is less than 22 mol%, the catalyst stability is reduced, which is not preferable. If it exceeds 32 mol%, the activity is lowered, which is undesirable.

In addition, the alloy of Nb-Ta comprises Nb: Ta in a weight ratio of 20:80 to 80:20, more preferably 40:60 to 60:40. If the content ratio is out of the range, the size of the particles may increase or the catalyst stability may decrease, which is not preferable.

The cathode catalyst having the composition as described above may have an average particle diameter of 1 to 3 nm, more preferably may have an average particle diameter of 1 to 2 nm. As such, since the catalyst has a very small particle size, the active surface area of the catalyst may be increased, thereby indicating excellent catalytic activity. When the particle size of the cathode catalyst is smaller than 1 nm, the fine particles are rapidly agglomerated, and as a result, the catalyst particle size may increase, and when the particle size exceeds 3 nm, the specific surface area may decrease due to the increase in particle size. It is not preferable because the catalytic activity is lowered.

The cathode catalyst may be used as a black type, which is a metal catalyst itself not supported on a carrier.

The catalyst for the cathode of the fuel cell according to the first exemplary embodiment of the present invention may be prepared by high frequency sputtering (Radio-Frequency magnetron sputtering) of the Nb-Ta alloy with MoC.

By such RF sputtering, a catalyst having a fine particle size can be prepared.

It is preferable to perform the said sputtering process in inert gas atmosphere, such as Ar, and also to lower the pressure of 1x10 <^-4> Pa or less.

The cathode catalyst prepared by the above method is a catalyst for a fuel cell according to the first exemplary embodiment of the present invention is a catalyst having a much higher catalytic activity than the WC-Nb catalyst, which has recently been studied as a platinum replacement catalyst. In addition, the cathode catalyst has excellent selectivity and stability with respect to the reduction reaction of the oxidizing agent can be effectively used as a cathode catalyst for fuel cells. Specifically, the cathode catalyst for the fuel cell of the present invention may be used in a polymer electrolyte fuel cell (PEMFC), a direct oxidation fuel cell (PEFCC), or the like. In addition, by using a catalyst that selectively acts only on the oxidation reaction of the fuel in the anode catalyst layer and a catalyst that selectively acts only in the reduction reaction of the oxidant in the cathode catalyst layer, even if a mixture of fuel and oxidant is injected into the anode and the cathode catalyst layer In the above, the fuel cell may be employed without limitation in a mixed reactant fuel cell in which only the oxidation reaction of the fuel and only the reduction reaction of the oxidant occurs in the cathode catalyst layer.

Cathode catalyst of the present invention has excellent selectivity to the oxygen reduction reaction, it can be used more effectively in a direct oxidation fuel cell problem of fuel crossover, and is most suitable for a direct methanol fuel cell (DMFC) Can be used effectively.

The present invention also provides a fuel cell membrane-electrode assembly comprising the cathode catalyst for fuel cell of the present invention.

The membrane-electrode assembly of the present invention includes an anode electrode and a cathode electrode positioned to face each other and a polymer electrolyte membrane positioned between the anode and the cathode electrode, wherein the anode electrode and the cathode electrode are formed of an electrode substrate and a conductive substrate. It includes a catalyst layer formed on the electrode substrate.

1 is a view schematically showing a cross section of the membrane-electrode assembly 131 according to an embodiment of the present invention. Hereinafter, the membrane-electrode assembly 131 of the present invention will be described with reference to the drawings.

The membrane-electrode assembly 131 generates electricity through oxidation of a fuel and reduction of an oxidant, and one or several are stacked and mounted in a stack.

A reduction reaction of the oxidant occurs in the catalyst layer 53 of the cathode electrode, and the catalyst layer includes a cathode catalyst for fuel cells containing Co—Fe—O—N. The cathode catalyst shows excellent activity and selectivity for the reduction reaction of the oxidant, thereby improving the performance of the cathode electrode 5 and the membrane-electrode assembly 131 including the same.

In the catalyst layer 33 of the anode electrode, an oxidation reaction of fuel occurs, and a catalyst capable of accelerating this may be included. A platinum-based catalyst, which is conventionally used, may be used. As the platinum-based catalyst, platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, platinum-M alloy (M is Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Transition metals selected from the group consisting of Cu, Zn, Sn, Mo, W, Rh, and combinations thereof), and combinations thereof. In the direct oxidation fuel cell, a platinum-ruthenium alloy catalyst is more preferable as the anode electrode catalyst in order to prevent the catalyst poisoning caused by CO generated during the anode electrode reaction. Specific examples include Pt, Pt / Ru, Pt / W, Pt / Ni, Pt / Sn, Pt / Mo, Pt / Pd, Pt / Fe, Pt / Cr, Pt / Co, Pt / Ru / W, Pt / Ru One or more selected from the group consisting of / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni, and Pt / Ru / Sn / W can be used.

In addition, such a metal catalyst may be used as the metal catalyst (black) itself, or may be supported on a carrier. As the carrier, carbonaceous materials such as graphite, denka black, ketjen black, acetylene black, carbon nanotubes, carbon nanofibers, carbon nanowires, carbon nanoballs or activated carbon may be used, or alumina, silica, zirconia, Inorganic fine particles such as titania may be used, but carbon-based materials are generally used.

The catalyst layers 33 and 53 of the anode electrode and the cathode electrode may further include a binder resin to improve adhesion of the catalyst layer and transfer of hydrogen ions.

It is preferable to use a polymer resin having hydrogen ion conductivity as the binder resin, more preferably a cation exchange group selected from the group consisting of sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, phosphonic acid groups and derivatives thereof in the side chain. All the polymer resin which has a can be used. Preferably, a fluorine polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer, a polyether ketone polymer, a polyether One or more hydrogen ion conductive polymers selected from ether ketone polymers or polyphenylquinoxaline polymers, more preferably poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), Copolymers of tetrafluoroethylene with fluorovinyl ethers containing sulfonic acid groups, defluorinated sulfided polyether ketones, aryl ketones, poly (2,2'-m-phenylene) -5,5'-bibenzimidazole It includes a hydrogen ion conductive polymer selected from the group consisting of (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole), poly (2,5-benzimidazole) and combinations thereofIt can be used.

The binder resin may be used in the form of a single substance or a mixture, and may also be optionally used with a nonconductive compound for the purpose of further improving adhesion to the polymer electrolyte membrane. It is preferable to adjust the usage-amount so that it may be suitable for a purpose of use.

Examples of the non-conductive compound include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro alkylvinylether copolymer (PFA), and ethylene / tetrafluoro Copolymers of ethylene / tetrafluoroethylene (ETFE), ethylenechlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), More preferably, it is selected from the group consisting of dodecylbenzenesulfonic acid, sorbitol, and combinations thereof.

The electrode substrates 31 and 51 of the anode electrode and the cathode electrode support the electrode and diffuse the fuel and the oxidant to the catalyst layer, thereby serving to easily access the fuel and the oxidant to the catalyst layer. Conductive substrates are used as the electrode substrates 31 and 51, and representative examples thereof include carbon paper, carbon cloth, carbon felt, or metal cloth (porosity composed of metal cloth in fiber state). The film or the metal film formed on the surface of the cloth formed of polymer fibers (referred to metalized polymer fiber)) may be used, but is not limited thereto.

In addition, it is preferable to use the water repellent treatment of the electrode substrates 31 and 51 with a fluorine-based resin because it prevents the reactant diffusion efficiency from being lowered by water generated when the fuel cell is driven. Examples of the fluorine-based resin include polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, and fluorinated ethylene propylene ( Fluorinated ethylene propylene), polychlorotrifluoroethylene or copolymers thereof can be used.

In addition, a microporous layer (not shown) may be further included to enhance the diffusion effect of the reactants on the electrode substrates 31 and 51. These microporous layers are generally conductive powders having a small particle size, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotubes, carbon nanowires, and carbon nanohorns. -horn or carbon nano ring, and the like.

The microporous layer is prepared by coating a composition comprising a conductive powder, a binder resin and a solvent on the electrode substrate. The binder resin may be polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride, alkoxy vinyl ether, polyvinyl alcohol, cellulose acetate Or copolymers thereof and the like can be preferably used. As the solvent, alcohols such as ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, tetrahydrofuran, etc. 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.

The polymer electrolyte membrane 1 functions as an ion exchange to move hydrogen ions generated in the catalyst layer 33 of the anode electrode to the catalyst layer 53 of the cathode electrode.

Therefore, generally used as the polymer electrolyte membrane (1) in the fuel cell, anything made of a polymer resin having hydrogen ion conductivity can be used. Representative examples thereof include a polymer resin having a cation exchange group selected from the group consisting of sulfonic acid group, carboxylic acid group, phosphoric acid group, phosphonic acid group and derivatives thereof in the side chain.

Representative examples of the polymer resin include a fluorine polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer and a polyether ketone Polymers, polyether-etherketone-based polymers, or polyphenylquinoxaline-based polymers, and the like, and more preferably, tetra (fluoro) containing poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), and sulfonic acid groups. Copolymers of roethylene and fluorovinyl ether, defluorinated sulfide polyether ketones, aryl ketones, poly (2,2'-m-phenylene) -5,5'-bibenzimidazole (poly (2,2 It is preferable to use one selected from the group consisting of '-(m-phenylene) -5,5'-bibenzimidazole), poly (2,5-benzimidazole) and combinations thereof.

In the hydrogen ion conductive group of the hydrogen ion conductive polymer, H may be substituted with Na, K, Li, Cs or tetrabutylammonium. In case of replacing H by Na in the ion-exchange group of the side chain terminal, NaOH is substituted in the preparation of the catalyst composition, and tetrabutylammonium hydroxide is used in the case of using tetrabutylammonium, and K, Li or Cs is also substituted with appropriate compounds. It can be substituted using. Since this substitution method is well known in the art, detailed description thereof will be omitted.

The present invention also provides a fuel cell system comprising the membrane-electrode assembly of the present invention as described above.

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

The electricity generating portion includes a membrane-electrode assembly and a separator (also called bipolar plate). The membrane-electrode assembly includes a polymer electrolyte membrane and cathode and anode electrodes existing on both sides of the polymer electrolyte membrane. The electricity generation unit serves to generate electricity through the oxidation reaction of the fuel and the reduction reaction of the 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 may include hydrogen or hydrocarbon fuel in gas or liquid state. Representative examples of the hydrocarbon fuel include methanol, ethanol, propanol, butanol or natural gas.

The fuel cell system of the present invention can be employed without limitation in Polymer Electrolyte Membrane Fuel Cell (PEMFC), Direct Oxidation Fuel Cell, and Mixed Reactant Fuel Cell. Can be.

A schematic structure of a fuel cell system 100 according to an embodiment of the present invention is shown in FIG. 2, which will be described in more detail with reference to the following. 2 shows a system for supplying fuel and oxidant to the electricity generation unit 130 using pumps 151 and 171, but the membrane-electrode assembly 131 for fuel cells of the present invention is limited to such a structure. Of course, it can be used in a fuel cell system having a diffusion structure without using a pump.

The fuel cell system 100 includes a stack 110 having at least one electricity generator 130 for generating electrical energy through an oxidation reaction of a fuel and a reduction reaction of an oxidant, and a fuel supply unit 150 for supplying the fuel. ) And an oxidant supply unit 170 for supplying an oxidant to the electricity generation unit 130.

The fuel supply unit 150 supplying the fuel includes a fuel tank 153 for storing fuel and a fuel pump 151 connected to the fuel tank 153. The fuel pump 151 serves to discharge the fuel stored in the fuel tank 153 by a predetermined pumping force.

The oxidant supply unit 170 for supplying an oxidant to the electricity generating unit 130 of the stack 110 includes at least one oxidant pump 171 that sucks the oxidant with a predetermined pumping force.

The electricity generating unit 130 is a membrane-electrode assembly 131 for oxidizing and reducing a fuel and an oxidant and a separator (bipolar plate) 133 and 135 for supplying fuel and an oxidant to both sides of the membrane-electrode assembly 131. ), The electricity generating unit 130 is at least one gather to constitute a stack (110).

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)

First, the surface of the glass carbon rod was polished with a mirror finish using a resting film wrapping tape (LT-06000). An Nb-Ta plate (thickness 0.1 mm, area 1 cm ² ) was placed on the sintered MoC target, and the Nb-Ta was added to the MoC catalyst (MoC + NbTa catalyst) to which Nb-Ta was added by high frequency sputtering under Ar atmosphere. Prepared by depositing on lash carbon rod substrate. At this time, the sputtering pressure in the chamber was 1 × 10 ^-4 Pa.

The prepared cathode catalyst included 33 mol% Mo, 35 mol% C and 32 mol% Nb-Ta, and the alloy weight ratio of Nb-Ta was 60:40 with a mixed weight ratio of Nb: Ta.

(Comparative Example 1)

First, the surface of the glass carbon rod was polished with a mirror finish using a resting film wrapping tape (LT-06000). An Nb plate (thickness of 0.1 mm, area 1 cm ² ) was placed on the sintered WC target, and Nb was added to the WC catalyst (WC + Nb catalyst) with Nb by RF sputtering (Radio-Frequency) under Ar atmosphere. Prepared by depositing on lash carbon rod substrate. At this time, the sputtering pressure in the chamber was 1 × 10 ^-4 Pa.

The molar ratio of W: C: Nb in the prepared WC + Nb catalyst was 1: 1.1: 1.4, and the average particle diameter of the catalyst was 8 nm.

(Comparative Example 2)

First, the surface of the glass carbon rod was polished with a mirror finish using a resting film wrapping tape (LT-06000). A Ta plate (0.1 mm thick, 1 cm ² ) was placed on a sintered WC target, and Ta was added to a WC catalyst (WC + Ta catalyst) with Ta added by RF sputtering (Radio-Frequency) under Ar atmosphere with WC. Prepared by depositing on lash carbon rod substrate. At this time, the sputtering pressure in the chamber was 1 × 10 ^-4 Pa.

The molar ratio of W: C: Ta in the prepared WC + Ta catalyst was 1: 0.9: 1.2, and the average particle diameter of the catalyst was 9 nm.

Scanning electron microscope (SEM) images were taken of the cathode catalyst prepared according to Example 1. The results are shown in FIG. In FIG. 3 the scale bar represents 20 nm.

From the parts shown in bold in Figure 3, it can be seen that the size of the catalyst for the cathode of Example 1 is 1 to 2m.

Oxygen gas was bubbling for 2 hours in a sulfuric acid solution of 0.5 M concentration to prepare an oxygen saturated sulfuric acid solution, and the catalyst of Example 1 and the catalyst of Comparative Example 1 were each glassy carbon. 3.78 × 10 ⁻³ mg was loaded onto the working electrode, and a platinum mesh was placed in the sulfuric acid solution as a counter electrode, and the current density was measured while changing the voltage. The results are shown in Table 1 below.

Current density (mA / cm ² , at 0.7V) Example 1 1.27 Comparative Example 1 0.5

As a result of the measurement, the catalyst prepared according to Example 1 showed a higher current density than the catalyst of Comparative Example 1. From this, it was confirmed that the catalyst of Example 1 exhibited excellent catalytic activity compared to the catalyst of Comparative Example 1.

The current density of the catalyst of Comparative Example 2 was measured, and the current density corresponding to that of Comparative Example 1 was shown. From this, it was confirmed that the catalyst of Example 1 exhibited excellent catalytic activity as compared to the catalyst of Comparative Example 2.

The cathode catalyst of the present invention has very good selectivity for catalytic activity and oxygen reduction reaction.

Claims (14)

Molybdenum carbide (MoC) added with niobium-tantalum (Nb-Ta) alloy, Cathode catalyst for fuel cells having an average particle size of nano size. The method of claim 1, The catalyst is a cathode catalyst for a fuel cell comprising 30 to 35 mol% Mo, 30 to 40 mol% C and 22 to 32 mol% alloy of Nb-Ta. The method of claim 1, The alloy of Nb-Ta is a cathode catalyst for a fuel cell comprising Nb: Ta in a weight ratio of 20 to 80:80 to 20. The method of claim 1, The catalyst is a cathode catalyst for a fuel cell having an average particle size of 1 to 3nm. The method of claim 1, The catalyst is a cathode catalyst for a fuel cell that is produced by a process of high-frequency sputtering Nb-Ta alloy with MoC. The method of claim 5, The high frequency sputtering process is a cathode catalyst for a fuel cell that is carried out in an atmosphere of inert gas. The method of claim 1, The catalyst is a cathode catalyst for a fuel cell which is a cathode catalyst that can be applied to a fuel cell selected from the group consisting of a polymer electrolyte fuel cell, a direct oxidation fuel cell and a mixed injection fuel cell. An anode electrode and a cathode electrode positioned opposite each other; And A polymer electrolyte membrane positioned between the anode electrode and the cathode electrode, The cathode comprises a catalyst according to any one of the preceding claims. Membrane-electrode assembly for fuel cell. The method of claim 8, The polymer electrolyte membrane comprises a polymer resin having a cation exchange group selected from the group consisting of sulfonic acid group, carboxylic acid group, phosphoric acid group, phosphonic acid group and derivatives thereof in the side chain. The method of claim 9, The polymer resin may be a fluorine polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer, a polyether ketone polymer, a poly A membrane-electrode assembly for a fuel cell, which is a polymer resin selected from the group consisting of ether-ether ketone polymers, polyphenylquinoxaline polymers, and copolymers thereof. The method of claim 8, The anode electrode is platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, platinum-M alloy (M is Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, A transition metal selected from the group consisting of Zn, Sn, Mo, W, Rh, and combinations thereof), and a catalyst selected from the group consisting of combinations thereof. An electricity generating unit including an anode electrode and a cathode electrode positioned opposite to each other, and a membrane-electrode assembly including a polymer electrolyte membrane positioned between the anode and the cathode and separators disposed on both sides of the membrane-electrode assembly; A fuel supply unit supplying fuel to the electricity generation unit; And An oxidant supply unit for supplying an oxidant to the electricity generating unit, The cathode electrode fuel cell system comprising a cathode catalyst according to any one of claims 1 to 7. The method of claim 12, The fuel cell system is selected from the group consisting of a polymer electrolyte fuel cell, a direct oxidation fuel cell and a mixed injection fuel cell. The method of claim 12, And the fuel cell system is a direct oxidation fuel cell.

Images