KR100766977B1 - Cathode catalyst for fuel cell, and membrane-electrode assembly and fuel cell system for fuel cell for fuel cell comprising same - Google Patents

Abstract

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 comprising the same, wherein the cathode catalyst is composed of a compound of AB-Ch (A is Pt, Ru, Rh, and combinations thereof) A metal selected from the group, B is a metal selected from the group consisting of Bi, Pb, Tl, Sb, Sn, In, Ga, Ge, and combinations thereof, Ch is S, Se, Te, and combinations thereof It is an element selected from the group consisting of).

The cathode catalyst for a fuel cell of the present invention has an advantage of improving the performance and selectivity of a fuel cell membrane-electrode assembly and a fuel cell system including the same because of its excellent activity and selectivity for the reduction reaction of the oxidant.

Fuel cell, electrode, catalyst, deactivation

Description

Cathode catalyst for fuel cell, and membrane-electrode assembly and fuel cell system for fuel cell for fuel cell including same TECHNICAL FIELD

1 is a view schematically showing a cross section of a membrane-electrode assembly for a fuel cell according to an embodiment of the present invention.

2 schematically shows the structure of a fuel cell system;

[Industrial use]

The present invention relates to a cathode catalyst for a fuel cell, and a fuel cell membrane-electrode assembly and a fuel cell system including the same, and more particularly, to a fuel cell membrane having excellent activity and selectivity for a reduction reaction of an oxidant. A cathode catalyst capable of improving the performance of an electrode assembly and a fuel cell system, and a membrane-electrode assembly and a fuel cell system for a fuel cell comprising the same.

[Prior art]

A fuel cell is a power generation system that converts chemical reaction energy of hydrogen and oxidant contained in hydrogen or hydrocarbon-based material directly into electrical energy.

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).

Generally, polymer electrolyte fuel cells have the advantages of high energy density and high output, but they require attention to handling hydrogen gas and fuels for reforming methane, methanol, and natural gas to produce hydrogen, which is fuel gas. There is a problem that requires additional equipment such as a reforming device.

On the other hand, the direct oxidation fuel cell has a lower reaction speed than the polymer electrolyte type due to the slow reaction rate, and requires a large amount of electrode catalyst, but it is easy to handle the liquid fuel and the operating temperature is low. In particular, it has the advantage of not requiring a fuel reformer.

In such a fuel cell system, a stack that substantially generates electricity may have several to tens of unit cells consisting of a membrane electrode assembly (MEA) and a separator (or bipolar plate). It has a laminated structure. The membrane-electrode assembly is called an anode electrode (also called "fuel electrode" or "oxide electrode") and a cathode electrode (also called "air electrode" or "reduction electrode") with a polymer electrolyte membrane including a hydrogen ion conductive polymer therebetween. Has a bonded structure.

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, and the fuel is oxidized to generate hydrogen ions and electrons. Reaching the cathode electrode, hydrogen ions pass through the polymer electrolyte membrane and are delivered to the cathode electrode. 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 having excellent activity and selectivity for the reduction reaction of an oxidant.

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

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

In order to achieve the above object, the present invention is a compound of AB-Ch (A is a metal selected from the group consisting of Pt, Ru, Rh, and combinations thereof, B is Bi, Pb, Tl, Sb, Sn, In And Ga, Ge, and a metal selected from the group consisting of a combination thereof, and Ch is an element selected from the group consisting of S, Se, Te, and combinations thereof).

The present invention also provides the addition of an elemental A source and an elemental B source to a solvent to prepare a mixture, drying and vacuuming the mixture to produce a powder comprising the AB containing compound, and mixing the powder with the elemental Ch source. And it provides a method for producing a cathode catalyst for a fuel cell comprising the step of heat treatment after drying and vacuum treatment.

The present invention also includes an anode electrode and a cathode electrode positioned opposite to each other and a polymer electrolyte membrane positioned between the anode and the cathode electrode, wherein the cathode electrode comprises the cathode catalyst of the present invention- Provide an electrode assembly.

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 unit.

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

A fuel cell is a power generation system that obtains electrical energy through oxidation of a fuel and reduction of an oxidant. An oxidation reaction of a fuel occurs at an anode electrode and a reduction reaction of an oxidant occurs at a cathode electrode.

A catalyst capable of promoting the oxidation reaction of the fuel and the reduction reaction of the oxidant is used for the catalyst layers of the anode electrode and the cathode electrode, and platinum-ruthenium is typically used for the catalyst layer of the anode electrode and platinum is used for the catalyst layer of the anode electrode.

However, the platinum used as the cathode catalyst lacks the selectivity for the reduction reaction of the oxidant, and is depolarized by the fuel that has passed through the electrolyte membrane to the cathode region in a direct oxidation fuel cell. As a result, there is a problem of deactivation, and attention is focused on a catalyst that can replace platinum.

The cathode catalyst of the present invention is a compound of AB-Ch (A is a metal selected from the group consisting of Pt, Ru, Rh, and combinations thereof, B is Bi, Pb, Tl, Sb, Sn, In, Ga, Ge And a metal selected from the group consisting of a combination thereof, and Ch is an element selected from the group consisting of S, Se, Te, and a combination thereof.

In the compound of A-B-Ch, A is a platinum-based element selected from the group consisting of Pt, Ru, Rh, and combinations thereof, and has a high activity for the reduction reaction of the oxidant. However, A is easy to combine with oxygen by absorbing oxygen in the air, and the combined oxygen blocks the active center of A where the reduction reaction of the oxidant occurs, making the reduction reaction of the oxidant difficult and the oxidation reaction of the fuel. Promote

B is a metal selected from the group consisting of Bi, Pb, Tl, Sb, Sn, In, Ga, Ge, and combinations thereof, and exhibits various electronic properties. As one of the electronic characteristics, B forms a cluster bond with A. The cluster bond has a short bond length, which causes rapid electron transfer between the metals, and also has a high surface energy for oxidant reduction of the metals forming the bond. It is possible to further increase the stability of the metal in active and acidic electrolytes.

In addition, Ch is an element selected from the group consisting of S, Se, Te, and combinations thereof, and prevents oxygen in the air from binding to A, thereby promoting a reduction reaction of the oxidant and inhibiting the oxidation reaction of the fuel. Do it.

For this reason, the cathode catalyst of the present invention has a high activity and selectivity for the reduction reaction of the oxidant, and has the advantage that it is not inactivated by the fuel.

In the compound of AB-Ch, A is preferably 15 to 50 atomic%, B is 30 to 40 atomic%, and Ch is preferably contained at 10 to 55 atomic%, more preferably A is 20 to 40 atomic% %, B is 33 to 37 atomic%, and Ch may be included at 23 to 43 atomic%. Within the content range as described above, it may exhibit excellent catalytic activity, but if it is out of the content range, the particle size is increased, so that the catalytic activity for the reduction reaction of the oxidant may be lowered.

If the content of A is less than 15 atomic%, the center of the catalyst is small and there is a possibility that the catalytic activity may be lowered. If the content of A exceeds 50 atomic%, the selectivity may be lowered, which is not preferable. In addition, when the content of B is less than 30 atomic%, the electron donor amount may be small, and the activity may be lowered. When the content of B is higher than 40 atomic%, the stability of the A-B alloy may be reduced, which is not preferable. If the content of Ch is less than 10 atomic%, there is a possibility that the active site may not be protected and the selectivity may be lowered.

The compound of A-B-Ch can be used not only as a catalyst itself but also on a carrier. When supported on a carrier, the electrical conductivity of the catalyst can be improved, and the size of the catalyst particles can be reduced, thereby increasing the surface area per unit mass, that is, the specific surface area. In addition, by increasing the specific surface area, the activity per unit mass of the catalyst can be increased.

As the carrier, carbonaceous materials such as graphite, denka black, ketjen black, acetylene black, carbon nanotube, carbon nanofiber, carbon nanowire, carbon nanoball or activated carbon may be used, and alumina, silica, titania, zirconia Although inorganic fine particles, such as these, can be used, carbon can be used more preferably.

The compound of A-B-Ch may be supported on the carrier at 5 to 75% by weight, more preferably 30 to 60% by weight based on the total weight of the catalyst. If the supported amount is less than 5% by weight, there is a problem that the activity per unit mass of the catalyst is too low. If the amount is more than 75% by weight, it is not preferable because the aggregation of catalyst particles occurs and the activity is lowered.

In the cathode catalyst having the composition as described above, a mixture of A element source and B element source is added to a solvent to prepare a mixture, and the mixture is dried and vacuumed to prepare a powder containing an AB-containing compound, and the powder is It can be prepared by a catalyst preparation method comprising mixing with an elemental source, drying and vacuuming and then heat treatment.

Specifically, a mixture of A element and B element is added to the solvent to prepare a mixture.

As the element A source, a water-soluble compound or salt containing an element selected from the group consisting of elements A, that is, Pt, Ru, Rh, and combinations thereof may be used. Specifically, ruthenium chloride, ruthenium It is preferably selected from the group consisting of acetylacetonate, ruthenium nitrozylnitrate, H ₂ RhCl ₄ , H ₂ PtCl ₆ , Pt (CH ₃ COCHCOCH ₃ ) ₂ , and combinations thereof. Can be used.

As the B element source, a water-soluble compound or salt containing an element selected from the group consisting of Bi, Pb, Tl, Sb, Sn, In, Ga, Ge, and combinations thereof may be used. rate _{(bismuth nitrate), BiCl 3,} Pb (NO 3) 3, InCl 3, GeCl 4, Sb (NO 3) 2, Sn (NO 3) 2, Tl 2 (SO) the group consisting of _4, and combinations thereof What is selected from may be preferably used.

As the solvent, organic solvents such as toluene, acetone, methanol and tetrahydrofuran may be preferably used.

The mixing ratio of the elemental A source and the elemental B source may be appropriately adjusted in consideration of the content ratio of each component in the final catalyst.

In addition, when preparing a catalyst supported on the carrier, it is preferable to add the carrier together when mixing the element A source and the element B source.

The carrier may be the same as described above, and the addition amount of the carrier is also preferably adjusted in consideration of the carrier content in the final catalyst.

The resulting mixture is then dried and vacuumed to produce a powder comprising the A-B containing compound.

The drying process is preferably carried out at a temperature of 70 to 100 ℃, more preferably may be carried out at 80 to 90 ℃. If the temperature is less than 70 ℃ during drying there is a risk that the drying may not be sufficient, and if it exceeds 100 ℃ there is a possibility that the catalyst particles are agglomerated to increase the size of the catalyst particles is not preferable.

In addition, the vacuum treatment is preferably carried out at a temperature range of 150 to 300 ℃, more preferably at 200 to 250 ℃. If the temperature during the vacuum treatment is less than 150 ° C., there is a concern that the reaction between the element A source and the element B source may not be sufficiently performed. If the temperature is higher than 300 ° C., the catalyst particles may aggregate to increase the size of the catalyst particles. It is not desirable.

By such a vacuum treatment, a powder containing the A-B-containing compound or the A-B-containing compound supported on the carrier can be produced.

The powder can then be mixed with a Ch element source in a solvent, dried and vacuumed and then heat treated to produce the cathode catalyst according to the invention.

The Ch element source may be a powder of an element selected from the group consisting of S, Se, Te, and combinations thereof, or an oxide including the same. Specifically, one selected from the group consisting of S powder, Se powder, Te powder, H ₂ SeO ₃ , H ₂ SeO ₃ , H ₂ TeO ₃ , and a combination thereof can be used.

The addition amount of the elemental Ch source is preferably adjusted in consideration of the Ch content in the final catalyst to be added.

The solvent includes water; Alcohols such as methanol and ethanol; Or a mixed solvent thereof.

The drying process and the vacuum treatment process are the same as described above. The drying process is preferably carried out at a temperature of 70 to 100 ℃, more preferably may be carried out at 80 to 90 ℃. If the temperature is less than 70 ℃ during drying there is a risk that the drying may not be sufficient, and if it exceeds 100 ℃ there is a possibility that the catalyst particles are agglomerated to increase the size of the catalyst particles is not preferable.

In addition, the vacuum treatment is preferably carried out at a temperature range of 150 to 300 ℃, more preferably at 200 to 250 ℃. If the temperature during vacuum treatment is less than 150 ° C., precursors such as AB-containing compounds and Ch element sources are not completely decomposed, which is undesirable. If the temperature exceeds 300 ° C., the catalyst particles may aggregate to increase the catalyst particle size. It is not desirable to have.

After the drying and vacuum treatment, heat treatment is performed.

The heat treatment is preferably performed in a reducing atmosphere such as hydrogen (H ₂ ), nitrogen (N ₂ ), or a combination thereof, and more preferably in a hydrogen atmosphere.

In addition, the temperature during the heat treatment is preferably carried out at a temperature of 200 to 500 ℃, more preferably at a temperature of 300 to 350 ℃. If the temperature during the heat treatment is less than 200 ℃ there is a risk that the reaction between the precursors may not be sufficient, and if it exceeds 500 ℃ it is not preferable because the particle size is large due to the aggregation of the catalyst particles.

The heat treatment is preferably carried out for 2 to 6 hours. If the heat treatment time is less than 2 hours, there is a possibility that the reaction may be incomplete, and if it exceeds 6 hours, the particle size becomes large due to aggregation of the catalyst particles, which is not preferable.

A-B-Ch catalyst prepared by the above production method has excellent activity and selectivity for 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.

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 the cathode catalyst for fuel cell of the present invention. 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 the fuel occurs, and a catalyst capable of promoting this is included. A representative example thereof may be a platinum-based catalyst. 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, A transition metal selected from the group consisting of Cu, Zn, Sn, Mo, W, Rh, and combinations thereof) and a catalyst selected from the group consisting of combinations thereof. 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 / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni, Pt / Ru / Sn / W, and combinations thereof may 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 nanotube, carbon nanofiber, carbon nanowire, carbon nanoball or activated carbon may be used, or alumina, silica, titania, Although inorganic fine particles, such as zirconia, can also be used, carbon is generally used widely.

The catalyst layer may further include a binder resin for improving the adhesion of the catalyst layer and the 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 group, carboxylic acid group, phosphoric acid group, phosphonic acid group and derivatives thereof in the side chain. Any polymer resin which has 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 and fluorovinyl ethers containing sulfonic acid groups, defluorinated sulfided polyether ketones, aryl ketones, poly [2,2 '-(m-phenylene) -5,5'-bibenziimi Dazole] (poly [2,2 '-(m-phenylene) -5,5'-bibenzimidazole]), poly (2,5-benzimidazole) and combinations thereof To include 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 polymer 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 nonconductive polymer include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro alkylvinyl ether copolymer (PFA), and ethylene / tetrafluoro Copolymer 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 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 in a fibrous state). The metal film is formed on the surface of the formed cloth) may be used, but is not limited thereto.

In addition, it is preferable to use a water-repellent treatment with a fluorine-based resin as the electrode base material because it can prevent the reactant diffusion efficiency from being lowered by water generated when the fuel cell is driven. As the fluorine-based resin, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated ethylene propylene, polychlorotrifluoroethylene, or fluoroethylene polymer may be used.

In addition, a microporous layer may be further included to enhance the reactant diffusion effect in the electrode substrate. These microporous layers are generally conductive powders having a small particle diameter, 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. 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. Alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone and the like can be preferably used. The coating process may be a screen printing method, a spray coating method or a coating method using a doctor blade or the like depending on 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 a polymer electrolyte membrane in a 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 tetrafluoro-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 '-(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 generating portion, a fuel supply portion and an oxidant supply portion.

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.

 The mixed-injection fuel cell uses an anode and a cathode in which a mixture of fuel and oxidant is mixed 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 when injected into the catalyst layer, only the oxidation reaction of the fuel occurs in the anode catalyst layer and only the reduction reaction of the oxidant occurs in the cathode catalyst layer. The mixed-injection fuel cell eliminates the need for a separator, which is required for a conventional fuel cell, thereby greatly reducing the manufacturing cost of the fuel cell and contributing to miniaturization of the fuel cell.

 The cathode catalyst of the present invention is excellent in selectivity for the oxygen reduction reaction, it can be used more effectively in the direct oxidation fuel cell problem of fuel crossover, and in the direct methanol fuel cell (DMFC) It can be used most effectively.

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 fuel cell membrane-electrode assembly 131 of the present invention is limited to such a structure. Of course, it can be used in a fuel cell system having a structure using a diffusion method 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 one preferred embodiment of the present invention and the present invention is not limited to the following examples.

Example  One.

To 5 ml of anhydrous tetrahydrofuran, 2.5 g of ruthenium chloride, 1.7 g of bismuth nitrate, and 1 g of ketjen black were added and mixed for 2 hours to prepare a mixture. The mixture was dried at 80 ° C. and vacuumed at 200 ° C. for 24 hours to obtain a powder. 1 g of the powder and 0.21 g of H ₂ SeO ₃ were added to 5 ml of water, mixed, dried at 80 ° C., and vacuumed at 200 ° C. for 24 hours. Subsequently, heat treatment was performed at 250 ° C. for 3 hours in a hydrogen atmosphere to prepare a cathode catalyst of Ru-Bi-Se supported on Ketjenblack.

The active material of Ru-Bi-Se contained 47 atomic% Ru, 33 atomic% Bi and 20 atomic% Se, and the supporting amount of the active material of Ru-Bi-Se was 55% by weight.

Example  2.

To 5 ml of water, 2.5 g of ruthenium chloride, 1.7 g of indium chloride and 1 g of ketjen black were added and mixed for 2 hours to prepare a mixture. The mixture was dried at 80 ° C. and vacuumed at 200 ° C. for 24 hours to obtain a powder. 1 g of the powder and 0.21 g of H ₂ SeO ₃ were added to 5 ml of water, mixed, dried at 80 ° C., and vacuumed at 200 ° C. for 24 hours. Subsequently, heat treatment was performed at 250 ° C. for 3 hours in a hydrogen atmosphere to prepare a cathode catalyst of Ru-In-Se supported on Ketjenblack.

The compound of Ru-In-Se contained 50 atomic% Ru, 40 atomic% In and 10 atomic% Se, and the supporting amount of the active material of Ru-Bi-Se was 59% by weight.

Example  3.

To 5 ml of water, 2.7 g of ruthenium chloride, 1.2 g of Sb (NO ₃ ) ₂ and 1 g of ketjen black were added and mixed for 2 hours to prepare a mixture. The mixture was dried at 80 ° C. and vacuumed at 200 ° C. for 24 hours to obtain a powder. 1 g of the powder and 0.21 g of H ₂ SeO ₃ were added to 5 ml of water, mixed, dried at 80 ° C., and vacuumed at 200 ° C. for 24 hours. Subsequently, heat treatment was performed at 250 ° C. for 3 hours under a hydrogen atmosphere to prepare a cathode catalyst of Ru—Sn-Se supported on Ketjenblack.

The compound of Ru-Sn-Se included 50 atomic% Ru, 40 atomic% Bi and 10 atomic% Se, and the supported amount of the Ru-Sn-Se compound was 60% by weight.

Example  4.

To 5 ml of water, 1.75 g of ruthenium chloride and 0.7 g of bismuth nitrate were added and mixed for 2 hours to prepare a mixture. The mixture was dried at 80 ° C. and vacuumed at 200 ° C. for 24 hours to obtain a powder. 1 g of the powder and 0.21 g of H ₂ SeO ₃ were added to 5 ml of water, mixed, dried at 80 ° C., and vacuumed at 200 ° C. for 24 hours. Then, a cathode catalyst of Ru-Bi-Se was prepared by heat treatment at 250 ° C. for 3 hours under a hydrogen atmosphere.

The compound of Ru-Bi-Se included 41 atomic% Ru, 40 atomic% Bi and 19 atomic% Se.

Comparative example  One.

0.6 g of ruthenium carbonyl, 0.03 g of Se powder and 1 g of ketjen black were added to 150 ml toluene, followed by mixing at 140 ° C. for 24 hours to prepare a mixture. The filtrate obtained by filtration of the mixture was dried at 80 ° C., and then filtrated at 250 ° C. for 3 hours under a hydrogen atmosphere to prepare a cathode catalyst of Ru-Se supported on Ketjenblack.

The active material of Ru-Se contained 75 atomic% of Ru, and 25 atomic% of Se, and the supporting amount of the active material was 47 weight%.

Oxygen gas was bubbled in a 0.5 M sulfuric acid solution for 2 hours to prepare an oxygen saturated sulfuric acid solution. 3.78 × 10 ⁻³ mg of carbon was loaded onto the working electrode, and the platinum density 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 0.7 V) Example 1 1.60 Comparative Example 1 0.50

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 catalysts of Examples 2 to 4 were also subjected to the same method as described above to measure the current density.

As a result, it was confirmed that the catalysts of Examples 2 to 4 also exhibited excellent catalytic activity by exhibiting the same current density as those of the catalyst of Example 1.

The cathode catalyst for a fuel cell of the present invention is excellent in activity and selectivity for a reduction reaction of an oxidant, and has an advantage of improving performance of a fuel cell membrane-electrode assembly and a fuel cell system including the same.

Claims (25)

Compound of AB-Ch (A is a metal selected from the group consisting of Pt, Ru, Rh, and combinations thereof, B is Bi, Pb, Tl, Sb, Sn, In, Ga, Ge, and combinations thereof A metal selected from the group consisting of, Ch is an element selected from the group consisting of S, Se, Te, and combinations thereof). The method of claim 1, The compound of A-B-Ch is a cathode catalyst for a fuel cell comprising A 15 to 50 atomic%, B 30 to 40 atomic%, and Ch 10 to 45 atomic%. The method of claim 2, The A-B-Ch compound is a cathode catalyst for a fuel cell that A comprises 20 to 40 atomic%, B is 33 to 37 atomic%, and Ch is 23 to 43 atomic%. The method of claim 1, The A-B-Ch compound is a cathode catalyst for a fuel cell that is supported on a carrier. The method of claim 1, The A-B-Ch compound is a cathode catalyst for a fuel cell is supported on 5 to 75% by weight relative to the total weight of the catalyst. The method of claim 4, wherein And the carrier is selected from the group consisting of carbonaceous materials, inorganic fine particles, and combinations thereof. The method of claim 1, The cathode catalyst for a fuel cell is a cathode catalyst for a fuel cell which is a cathode catalyst for a polymer electrolyte fuel cell. The method of claim 1, The cathode catalyst for fuel cell is a cathode catalyst for fuel cell which is a cathode catalyst for direct oxidation type fuel cell. The method of claim 1, The fuel cell cathode catalyst is a fuel cell cathode catalyst is a mixed-injection fuel cell cathode catalyst. A mixture is prepared by mixing an element A source and an element B source, Drying and vacuuming the mixture to prepare a powder comprising the A-B containing compound, Mixing the powder comprising the A-B containing compound with a Ch element source and then drying, vacuuming and heat treating, A is selected from the group consisting of Pt, Ru, Rh, and combinations thereof, B is selected from the group consisting of Bi, Pb, Tl, Sb, Sn, In, Ga, Ge, and combinations thereof, Ch Is S, Se, Te, and a method for producing a cathode catalyst for a fuel cell that is selected from the group consisting of a combination thereof. The method of claim 10, The A element source is a method for producing a cathode catalyst for a fuel cell is a water-soluble compound or salt containing an element selected from the group consisting of Pt, Ru, Rh and combinations thereof. The method of claim 10, The B element source is a method for producing a cathode catalyst for a fuel cell is a water-soluble compound or salt containing an element selected from the group consisting of Bi, Pb, Tl, Sb, Sn, In, Ga, Ge, and combinations thereof. The method of claim 10, The drying process is a method of producing a cathode catalyst for a fuel cell that is carried out at a temperature of 70 to 100 ℃. The method of claim 10, The vacuum treatment process is a method of producing a cathode catalyst for a fuel cell that is carried out at a temperature of 150 to 300 ℃. The method of claim 10, The Ch element source is S, Se, Te, and a method for producing a cathode catalyst for a fuel cell is a powder or oxide of the element selected from the group consisting of a combination thereof. The method of claim 10, The heat treatment step is a method of producing a cathode catalyst for a fuel cell that is carried out under a reducing atmosphere. The method of claim 10, The heat treatment step is a method of producing a cathode catalyst for a fuel cell that is carried out at 200 to 500 ℃. An anode electrode and a cathode electrode located opposite each other; And A polymer electrolyte membrane positioned between the anode and the cathode electrode, 10. The membrane-electrode assembly of a fuel cell, wherein the cathode comprises the cathode catalyst according to any one of claims 1-9. The method of claim 18, 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 19, 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 Membrane-electrode assembly for fuel cell, which is at least one polymer resin selected from the group consisting of ether-etherketone-based polymers and polyphenylquinoxaline-based polymers. The method of claim 19, 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, Zn, Sn, Mo, W, Rh, and a transition metal selected from the group consisting of a combination thereof). A membrane-electrode assembly for a fuel cell comprising a catalyst selected from the group consisting of. At least one electricity generating unit including an anode electrode and a cathode electrode positioned opposite to each other, and at least one membrane-electrode assembly including a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode, and a separator; A fuel supply unit supplying fuel to the electricity generation unit; And An oxidant supply unit for supplying an oxidant to the electricity generation unit, The cathode electrode system of claim 1, wherein the cathode electrode comprises the cathode catalyst of claim 1.  The method of claim 22, The fuel cell system is selected from the group consisting of a polymer electrolyte fuel cell system, a direct oxidation fuel cell system and a mixed injection fuel cell system. The method of claim 22, The fuel cell system is a direct oxidation fuel cell system. The method of claim 1, The A-B-Ch compound is a cathode catalyst for a fuel cell that is supported on the carrier at 55 to 75% by weight relative to the total weight of the catalyst.

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