KR102141882B1 - The mixed catalysts composition for fuel cell electrode, the electrode of fuel cell and manufacturing method of the electrode - Google Patents

Abstract

The present invention relates to a composition for forming a fuel cell electrode, a fuel cell electrode, and a method for manufacturing the same, wherein the electrode for a fuel cell includes a first catalyst and a first catalyst comprising a first metal particle supported on the first carrier, the second It may be configured to include a second catalyst, an ionomer, and a solvent including a carrier and second metal particles supported on the second carrier.
The present invention can provide a multi-carrier catalyst with improved catalyst utilization compared to a single carrier catalyst, and an electrode capable of obtaining excellent current density and power density with a small amount of catalyst material.

Description

A composition for forming a fuel cell electrode containing a mixed catalyst, an electrode for a fuel cell and a manufacturing method therefor{THE MIXED CATALYSTS COMPOSITION FOR FUEL CELL ELECTRODE, THE ELECTRODE OF FUEL CELL AND MANUFACTURING METHOD OF THE ELECTRODE}

The present invention relates to a composition for forming a fuel cell electrode, a fuel cell electrode, and a method for manufacturing the same, comprising a multi-carrier catalyst with improved catalyst utilization through mixing between single carrier catalysts versus a single carrier catalyst.

A fuel cell is a cell equipped with a power generation system that directly converts chemical reaction energy such as oxidation/reduction reactions of hydrogen and oxygen contained in hydrocarbon-based fuel materials such as methanol, ethanol, and natural gas into electrical energy. Due to its efficiency and eco-friendly features with less pollutant emissions, it is spotlighted as a next-generation clean energy source that can replace fossil energy.

These fuel cells have the advantage of being capable of producing a wide range of outputs in a stacked configuration by stacking unit cells, and are attracting attention as small and portable mobile power sources because they exhibit energy density of 4 to 10 times that of small lithium batteries. have.

In the fuel cell, a stack that substantially generates electricity is composed of several to tens of unit cells composed of a membrane-electrode assembly (MEA) and a separator (also referred to as a bipolar plate). It has a structure, and the membrane-electrode assembly generally has a structure in which an anode (or anode) and a cathode (or cathode) are formed on both sides of an electrolyte membrane.

Fuel cells can be classified into alkaline electrolyte fuel cells and polymer electrolyte fuel cells (PEMFC), depending on the type of electrolyte membrane. Among them, polymer electrolyte fuel cells have a low operating temperature of less than 100°C and quick start. Due to its advantages such as over-response characteristics and excellent durability, it has been spotlighted as a portable, vehicle and home power supply.

A typical example of a polymer electrolyte fuel cell is a hydrogen ion exchange membrane fuel cell (PEMFC) using hydrogen gas as a fuel, and a direct methanol fuel cell (DMFC) using liquid methanol as a fuel. And the like.

To summarize the reactions that occur in a polymer electrolyte fuel cell, first, when a fuel, such as hydrogen gas supplied to the oxidizing electrode, the oxide electrode hydrogen ion (H ⁺⁾ and electrons (e ^-) by the oxidation reaction of hydrogen is generated. The generated hydrogen ions are transferred to the cathode through the polymer electrolyte membrane, and the generated electrons are transferred to the cathode through an external circuit. At the cathode, oxygen is supplied, and oxygen is combined with hydrogen ions and electrons to produce water by a reduction reaction of oxygen.

On the other hand, the electrode of the fuel cell may be prepared through a composition for forming an electrode composed of a catalyst, an ionomer, and a solvent, and the degree of bonding and dispersion between them greatly affects the performance and durability of the battery. In addition, in order to improve the battery performance by increasing the content of the catalyst, the catalyst may be supported on a carrier to be used. In this case, it is difficult to uniformly support the catalyst.

Republic of Korea Registered Patent No. 10-1275155 (Public: 2012.11.21.)

An object of the present invention is to provide a composition for forming a fuel cell electrode, which improves efficiency by mixing and using a catalyst containing two or more heterogeneous carriers.

Another object of the present invention is to provide a fuel cell electrode manufactured using the composition for forming a fuel cell electrode and a method for manufacturing the same.

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

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

According to an embodiment of the present invention, a first catalyst comprising a first carrier and first metal particles supported on the first carrier, a second carrier and a second carrier comprising the second metal particles supported on the second carrier 2 It comprises a catalyst, an ionomer, and a solvent, and the first carrier and the second carrier are to provide a composition for forming a fuel cell electrode that is different from each other.

The first metal particles or the second metal particles are platinum, ruthenium, osmium, and platinum-M alloys (M is Pd, Ir, Os, Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Mo, W, Rh, Ru and any transition metal selected from the group consisting of alloys) and mixtures thereof.

The first carrier or the second carrier is carbon black, hollow carbon capsule (HCC), multimodal porous carbon (MPC), carbon nanotube (CNT), carbon nanofiber ( Carbon nanofiber (CNF), mesoporous carbon (Mesoporous carbon), graphene (Graphene), may be any one selected from the group consisting of high surface area highly conductive carbon black and combinations thereof.

The first carrier is carbon black, the second carrier is a hollow carbon capsule, multi-pore carbon, carbon nanotubes, carbon nanofibers, mesoporous carbon, graphene, high surface area highly conductive carbon black and combinations thereof It may be any one selected from the group.

The first catalyst may have metal particles supported on a spherical carbon black carrier having a surface area of 200 to 1500 m ² /g and a particle size of 30 to 100 nm.

The first catalyst and the second catalyst may be included in a weight ratio of 95:5 to 80:20.

The ratio of the loading ratio of the first catalyst and the second catalyst calculated by Equation 1 below may be 1:0.2 to 1:0.8.

[Equation 1]

The loading rate of each catalyst = (weight of metal particles / (weight of carrier + weight of metal particles)) X 100

The deviation of the loading rates of the first catalyst and the second catalyst calculated by Equation 3 below may be independently 0 to 10%.

[Equation 3]

Deviation of loading rate of each catalyst = (loading rate of each catalyst / average loading rate of all catalysts) X 100

[Equation 1]

The loading rate of each catalyst = (weight of metal particles / (weight of carrier + weight of metal particles)) X 100

[Equation 2]

Average supported ratio of all catalysts = sum of supported ratios of each catalyst / number of each catalyst

The average size deviation of the first catalyst and the second catalyst calculated by Equation 4 below may be independently 0 to 10%.

[Equation 4]

Deviation of average size of each catalyst = (average size of each catalyst / average size of all catalysts) X 100

[Equation 5]

Average size of all catalysts = Sum of average size of each catalyst / Number of catalysts

The solvent may be any one selected from the group consisting of water, isopropyl alcohol, ethoxy ethanol, N-methylpyrrolidone, ethylene glycol, propylene glycol and mixtures thereof.

The composition for forming a fuel cell electrode may be included in 40 to 70 parts by weight of an ionomer and 1000 to 1400 parts by weight of a solvent with respect to 100 parts by weight of the first catalyst and the second catalyst.

The composition for forming a fuel cell electrode may further include a third catalyst comprising a carrier different from the first catalyst and the second catalyst.

According to another embodiment of the present invention, a first catalyst comprising a first carrier and first metal particles carried on the first carrier, a second carrier and a second metal particle supported on the second carrier A second catalyst, and an ionomer, wherein the first carrier and the second carrier provide an electrode for a fuel cell that is different from each other.

According to another embodiment of the present invention, preparing a first catalyst by supporting the first metal particles on a first carrier, preparing a second catalyst by supporting the second metal particles on a second carrier, the Provided is a method for manufacturing an electrode for a fuel cell, comprising the steps of preparing a composition for forming an electrode by adding a first catalyst, the second catalyst, and an ionomer to a solvent, and preparing an electrode by applying the composition for forming an electrode. .

The first catalyst and the second catalyst may be independently prepared by any one reduction method selected from the group consisting of a polyol reduction method, an electron beam reduction method, a sodium borohydride (NaBH ₄ ) reduction method, and a urea-assisted uniform reduction method.

According to another embodiment of the present invention, there is provided a membrane-electrode assembly including the electrode for the fuel cell.

According to another embodiment of the present invention, there is provided a fuel cell including the electrode for the fuel cell.

The present invention can provide a composition for forming a fuel cell electrode comprising a multi-carrier catalyst with improved catalyst utilization through mixing between single-carrier catalysts and a single carrier catalyst.

The present invention can also provide a fuel cell having excellent current density and power density by using the composition for forming the fuel cell electrode.

1 is a schematic diagram showing a fuel cell electrode in which a heterogeneous catalyst is mixed according to an embodiment of the present invention.
2 is a schematic diagram showing a membrane-electrode assembly for a fuel cell according to another embodiment of the present invention.
3 is a schematic diagram of a fuel cell according to another embodiment of the present invention.
FIG. 4 is a TEM photograph of a heterogeneous catalyst used for mixing in Example 1 of the present invention, and a SEM photograph of the catalyst mixing them.
5 is a TEM photograph of a heterogeneous catalyst used for mixing in Example 2 of the present invention.
6 is a SEM photograph of the catalyst used in Comparative Example 1 of the present invention.
7 is a graph showing the results of evaluating the performance of the membrane-electrode assembly in Experimental Example 1 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of claims to be described later.

Unless otherwise specified in this specification, when a part such as a layer, film, region, plate, etc. is said to be “above” another part, this is not only when the other part is “directly above” but also when there is another part in the middle. Includes.

According to an embodiment of the present invention, a first catalyst comprising a first carrier and first metal particles supported on the first carrier, a second carrier and a second carrier comprising the second metal particles supported on the second carrier 2 It includes a catalyst, an ionomer, and a solvent, and the first carrier and the second carrier provide a composition for forming a fuel cell electrode that is different from each other.

The first metal particles and the second metal particles may participate in the reaction of the fuel cell and can use anything that can be used as a catalyst, and specifically, a platinum-based catalyst.

The platinum-based catalyst includes platinum, ruthenium, osmium, and platinum-M alloy (where M is Pd, Ir, Os, Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Mo, W, Rh, Ru and any one of the metal particles selected from the group consisting of transition metals) and mixtures thereof.

The anode electrode and the cathode electrode of the fuel cell may use the same material, but more specifically, 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 and Pt/Ru/Sn/ Any one selected from the group consisting of W can be used.

In addition, the metal particles may be used as the catalyst itself, or may be used by being supported on a carrier.

As the carrier, carbon-based materials such as graphite, denka black, ketjen black, acetylene black, carbon nanotube, carbon nanofiber, carbon nanowire, carbon nanoball, and activated carbon may be used, or alumina, silica, zirconia, Inorganic fine particles such as titania may be used, but a carbon-based material may be generally used.

More specifically, the carbon-based carrier includes hollow carbon capsules (HCC), multimodal porous carbon (MPC), carbon nanotubes (CNT), and carbon nanofibers; CNF), mesoporous carbon (mesoporous carbon), graphene (graphene), it is most preferably any one selected from the group consisting of high surface area highly conductive carbon black and combinations thereof.

At this time, the metal particles may be located on the surface of the carrier, or may fill the pores of the carrier and penetrate into the carrier.

The first metal particle and the second metal particle may use the same material or different materials. However, in the present invention, the first carrier and the second carrier are characterized by using different carriers.

Specifically, the first carrier is carbon black, the second carrier is a hollow carbon capsule, multi-pore carbon, carbon nanotubes, carbon nanofibers, mesoporous carbon, graphene, high surface area high conductivity carbon black and their It may be any one selected from the group consisting of combinations.

As the first catalyst and the second catalyst include different carriers, their surface area, degree of graphitization, surface characteristics, shape, and size may be different from each other. For example, the first catalyst may be a commercial catalyst in which metal particles are supported on a spherical carbon black carrier having a surface area of 200 to 1500 m ² /g and a particle size of 30 to 100 nm, and the second catalyst may have various surface areas. It may be a catalyst in which metal particles are supported on a nano-structured carbon or high-graphitized carbon and a high surface area carbon black carrier having various nanostructures such as a linear, spherical, and three-dimensional structure.

In the composition for forming a fuel cell electrode, the first catalyst and the second catalyst may be included in a weight ratio of 95:5 to 80:20. When the weight ratio of the second catalyst with respect to the first catalyst exceeds 80:20, that is, when the content of the second catalyst exceeds 80 parts by weight with respect to 80 parts by weight of the first catalyst, solvent, ionomer, additive, etc. It is necessary to change the catalyst due to deterioration in performance because the amount of the product deviates from the existing composition capable of exhibiting optimum activity, there may be problems such as economics, and when the content ratio is less than 95:5, that is, the first catalyst is 95 parts by weight In contrast, when the content of the second catalyst is less than 5 parts by weight, the mixing effect may be insignificant due to a small change in performance.

At this time, it is preferable to select the first carrier, which occupies a larger proportion, at a lower price when compared to the second carrier.

On the other hand, when the composition for forming an electrode for a fuel cell includes carriers different from each other, there is a problem that metal particles are not uniformly supported on each carrier. That is, one carrier carries a large amount of metal particles per unit weight of the carrier, but the other carrier has a problem that less metal particles are supported per unit weight of the carrier.

However, the composition for forming an electrode for a fuel cell of the present invention is characterized in that the ratio of metal particles supported on each carrier is uniform while including heterogeneous catalysts containing different carriers.

Specifically, the loading rate of the first catalyst and the loading rate of each of the second catalyst may be 1:0.2 to 1:0.8, and the deviation of the loading rate of the first catalyst and the second catalyst may be independently 0 to 10%. Can be

The loading rate of each catalyst may be calculated by Equation 1 below.

[Equation 1]

The loading rate of each catalyst = (weight of metal particles / (weight of carrier + weight of metal particles)) X 100

That is, the loading rate of the first catalyst can be calculated as (the weight of the first metal particles / (the weight of the first carrier + the weight of the first metal particles)) X 100, and the loading rate of the second catalyst is (the 2 weight of metal particles / (weight of the second carrier + weight of the second metal particles)) X 100.

When the loading rate of the first catalyst and the loading rate of the second catalyst are each less than 0.2, only the effect of improving the high current performance of the first catalyst may be exhibited, rather than the performance improvement. Can.

The variation in the loading rate of each catalyst may be calculated by Equation 3 below.

[Equation 3]

Deviation of loading rate of each catalyst = (loading rate of each catalyst / average loading rate of all catalysts) X 100

In Equation 3, the loading rate of each catalyst may be calculated by Equation 1, and the average loading rate of the total catalysts may be calculated by Equation 2 below.

[Equation 2]

Average supported ratio of all catalysts = sum of supported ratios of each catalyst / number of each catalyst

For example, the average loading rate of the total catalyst can be calculated as (the loading rate of the first catalyst + the loading rate of the second catalyst) / 2. Here, the number of each catalyst is 2 because there are two types of the first catalyst and the second catalyst. Meanwhile, when the composition for forming a fuel cell electrode further includes a third catalyst or the like, the number of each catalyst may be three or more. In addition, the deviation of the loading rate of the first catalyst can be calculated as (the loading rate of the first catalyst / the average loading rate of all catalysts) X 100, and the deviation of the loading rate of the second catalyst (the loading rate of the second catalyst / It can be calculated as the average loading rate of the total catalyst) X 100.

The smaller the variation in the loading ratio of the first catalyst and the second catalyst is, the better the performance improvement effect is, and when it exceeds 10%, the metal particles are mixed in different carriers and mixed with the metal particles and different carriers as in the present invention. There may be a problem that there is no difference from the case of mixing and loading.

In addition, when the composition for forming a fuel cell electrode includes carriers that are different from each other, the size of the catalyst may vary depending on the type of carrier. In this case, there is a problem in that variations are severe depending on a batch of samples. However, in the composition for forming a fuel cell electrode of the present invention, when the metal particles of the same content are supported, the average size deviation of the first catalyst and the second catalyst is each independently 0 to 10%.

The average size deviation of each catalyst can be calculated by Equation 4 below.

[Equation 4]

Deviation of average size of each catalyst = (average size of each catalyst / average size of all catalysts) X 100

In Equation 4, the average size of each catalyst may be calculated by dividing the sum of the total size of the first catalyst particles by the number of total particles of the first catalyst in the case of the first catalyst. It can be calculated by the following equation (5).

[Equation 5]

Average size of all catalysts = Sum of average size of each catalyst / Number of catalysts

For example, the average size of the entire catalyst can be calculated as (average size of the first catalyst + average size of the second catalyst) / 2. Here, the number of each catalyst is 2 because there are two types of the first catalyst and the second catalyst. Meanwhile, when the composition for forming a fuel cell electrode further includes a third catalyst or the like, the number of each catalyst may be three or more. In addition, the average size deviation of the first catalyst can be calculated as (average size of the first catalyst / average size of all catalysts) X 100, and the average size deviation of the second catalyst is (average size of the second catalyst / total size) It can be calculated as the average size of the catalyst) X 100.

The smaller the average size deviation of the first catalyst and the second catalyst is, the better the performance improvement effect is, and when it exceeds 10%, the metal particles are mixed in different carriers and mixed with the metal particles and different carriers as in the present invention. There may be a problem that there is no difference from the case of mixing and loading.

The solvent may be any one selected from the group consisting of water, isopropyl alcohol, ethoxy ethanol, N-methylpyrrolidone, ethylene glycol, propylene glycol and mixtures thereof.

The ionomer may be any polymer resin having 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. More specifically, fluorine polymer, benzimidazole polymer, polyimide polymer, polyetherimide polymer, polyphenylene sulfide polymer, polysulfone polymer, polyether sulfone polymer, polyether ketone polymer, poly It may include one or more hydrogen ion conductive polymers selected from ether-ether ketone-based polymers and polyphenylquinoxaline-based polymers, and more specifically poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid) , Copolymer of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, sulfide polyether ketone, aryl ketone, poly(2,2'-m-phenylene)-5,5'-bibenzimidazole [Poly (2,2'-m-phenylene)-5,5'-bibenzimidazole] and poly(2,5-benzimidazole) may be used.

The polymer resin having hydrogen ion conductivity may substitute H, Na, K, Li, Cs, or tetrabutylammonium in a cation exchange group at the side chain end. In the ion exchanger at the side chain end, when H is replaced with Na, NaOH is used when preparing the catalyst composition, and when substituted with tetrabutylammonium, tetrabutylammonium hydroxide is used, and K, Li or Cs are also suitable compounds. Can be substituted. Since the substitution method is widely known in the art, detailed description thereof will be omitted.

The ionomer may be used in the form of a single substance or a mixture, and may be optionally used together with a non-conductive compound for the purpose of further improving adhesion to the polymer electrolyte membrane. It is preferable to use the amount adjusted to suit the intended use.

The non-conductive compound includes polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro alkylvinyl ether copolymer (PFA), ethylene/tetraflo Ethylene/tetrafluoroethylene (ETFE), ethylene chlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), dode Silbenzenesulphonic acid and one or more selected from the group consisting of sorbitol (Sorbitol) may be used.

The ionomer and the solvent are preferably included in 40 to 70 parts by weight of the ionomer and 1000 to 1400 parts by weight of the solvent relative to 100 parts by weight of the first catalyst and the second catalyst.

When the ionomer is less than 20 parts by weight, a problem may occur in ion transfer, and when it exceeds 70 parts by weight, a problem may occur in mass transfer due to a reduction in pores.

If the solvent is less than 1000 parts by weight, a problem may occur in catalyst wetting or dispersion and coating, and when it exceeds 1400 parts by weight, problems in viscosity control, coating and drying may occur.

The composition for forming a fuel cell electrode may further include a third catalyst including a carrier different from the first catalyst and the second catalyst.

The composition for forming a fuel cell electrode may further include other types of carriers to improve performance and durability. The third catalyst includes a carrier different from the first catalyst and the second catalyst, and is composed of various carriers of a third carrier or more to improve performance and durability. In the case of 3 or more types, the entire catalyst control problem may occur.

The composition for forming a fuel cell electrode according to the present invention leads to uniform mixing of the catalyst-ionomer by mixing heterogeneous or heterogeneous multi-carriers, thereby increasing the utilization rate of the catalyst compared to a single catalyst and improving the performance of the catalyst. That is, since the performance is improved with the same amount of catalyst, excellent current density and power density can be obtained even with a small amount of catalyst.

According to another embodiment of the present invention, there is provided a fuel cell electrode manufactured using the composition for forming a fuel cell electrode.

Accordingly, the electrode for the fuel cell includes a first carrier and a first catalyst including the first metal particles supported on the first carrier, a second carrier and a second including the second metal particles supported on the second carrier. Catalysts, and ionomers.

The electrode for the fuel cell may be represented by a schematic diagram as shown in FIG. 1. 1 is a schematic diagram schematically showing a configuration of an electrode 40 for a fuel cell according to one example of the present invention.

Referring to FIG. 1, the fuel cell electrode 40 is a mixture of the first catalyst 10 and the second catalyst 20, and around the first catalyst 10 and the second catalyst 20. On the ionomer 30 is in a form that is wrapped.

At this time, in the first catalyst 10, the first metal particles 11 are supported on the spherical first carrier 12 such as carbon black, and the second catalyst 20 is the second metal particles (21) is supported on a second carrier 22 having a fiber shape such as carbon nanofibers. Since the fuel cell electrode 40 is manufactured using the composition for forming an electrode according to the present invention, it is understood that the metal particles are uniformly distributed on the first carrier 12 and the second carrier 22. Can be.

In addition, the electrode for the fuel cell may optionally further include an electrode substrate. The electrode base serves to support the electrode, and serves to easily access fuel or oxidant by diffusing fuel and oxidant with the catalyst.

The electrode base material may be carbon paper, carbon cloth, carbon felt, carbon fiber, or a combination thereof, preferably carbon fiber. have.

The electrode substrate may include pores, and the performance of the fuel cell may be improved by controlling the size and porosity of the pores. Specifically, the electrode base material may include a mean pore having a diameter of 20 to 40 μm with a porosity of 30 to 80% by volume relative to the total volume of the electrode base material. Specifically, the average pores having a diameter of 20 to 30 μm may be included in a porosity of 50 to 80% by volume relative to the total volume of the electrode substrate.

In addition, the electrode for the fuel cell may further include a microporous layer (Microporous layer) for selectively enhancing the diffusion effect of the reactants. The microporous layer may have a thickness of 3 to 80 μm, and specifically, may have a thickness of 10 to 70 μm. When the thickness of the microporous layer is within the above range, it is possible to prevent an increase in resistance due to mass transfer limitation caused by water flooding in a humidifying condition of 80% relative humidity, and manufacturing a fuel cell stack It is possible to prevent cracks or detachment caused by pressing by the flow path of the separation plate due to the tightening pressure.

The microporous layer is generally a conductive powder having a small particle size, for example, carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotube, carbon nanowire, carbon nanohorn ), Carbon nano ring or a combination thereof.

The microporous layer may be prepared by coating the electrode substrate with a composition comprising the conductive powder, a binder resin, and a solvent.

Examples of the binder resin include polytetrafluoroethylene, polyvinylidenefluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonylfluoride, alkoxyvinyl ether, polyvinyl alcohol, and cellulose acetate , These copolymers and the like can be used.

According to another embodiment of the present invention, preparing a first catalyst by supporting the first metal particles on a first carrier, preparing a second catalyst by supporting the second metal particles on a second carrier, the Provided is a method for manufacturing an electrode for a fuel cell, comprising the steps of preparing a composition for forming an electrode by adding a first catalyst, the second catalyst, and an ionomer to a solvent, and preparing an electrode by applying the composition for forming an electrode. .

In the preparation steps of the first catalyst and the second catalyst, the first catalyst and the second catalyst are selected from the group consisting of polyol reduction, electron beam reduction, and sodium borohydride (NaBH ₄ ) reduction, and urea-assisted uniform reduction. It can be prepared by one reduction method.

In the step of preparing the composition for forming an electrode, an ionomer is added to a solvent together with the prepared first catalyst and the second catalyst, followed by mixing to prepare the composition for forming an electrode. The first catalyst, the second catalyst, the ionomer and the description of the solvent are as described above.

As described above, after preparing the first catalyst in which the first metal particles are supported on the first carrier and the second catalyst in which the second metal particles are supported on the second carrier, they are mixed to form electrodes. Since the composition is prepared, the metal particles can be uniformly distributed on the first carrier and the second carrier.

Finally, the electrode-forming composition is applied to prepare an electrode.

The coating process may be a screen printing method, a spray coating method, a coating method using a doctor blade or the like depending on the viscosity of the composition for forming an electrode, and the present invention is not limited thereto.

In addition, the electrode may be applied to a thickness of 1 to 100 ㎛. When the thickness is less than 1 μm, the reaction area may be small and the activity may be deteriorated. When the thickness is more than 100 μm, resistance may be increased due to an increase in the travel distance of ions and electrons.

Meanwhile, after applying the composition for forming an electrode, the composition for forming an electrode may be selectively dried, and the drying process may be drying at 25 to 90° C. for 12 hours or more. When the drying temperature is less than 25 °C and the drying temperature is less than 12 hours, a problem that a sufficiently dried electrode may not be formed may occur, and drying at a temperature exceeding 90 °C may cause cracking of the electrode. .

According to another embodiment of the present invention, there is provided a membrane electrode assembly for a fuel cell including the electrode 40 for a fuel cell.

2 is a cross-sectional view schematically showing the membrane-electrode assembly. Hereinafter, the membrane-electrode assembly will be described with reference to FIG. 2.

The membrane-electrode assembly 150 includes an anode electrode 110 and a cathode electrode 110 positioned to face each other; And a polymer electrolyte membrane 130 positioned between the anode electrode 110 and the cathode electrode 110.

At least one of the anode electrode 110 and the cathode electrode 110 is used for the fuel cell electrode 40 of the present invention described above.

The polymer electrolyte membrane 130 is a solid polymer electrolyte having a thickness of 10 to 200 μm, and has a function of ion exchange to move hydrogen ions generated from the anode electrode 110 to the cathode electrode 110.

The polymer electrolyte membrane 130 may be a hydrocarbon-based polymer electrolyte membrane, a fluorine-based polymer electrolyte membrane, and one or more mixtures or copolymers thereof.

The hydrocarbon-based polymer electrolyte membrane may include a hydrocarbon-based polymer, and the polymer is a styrene, imide, sulfone, phosphazene, ether ether ketone, ethylene oxide, polyphenylene sulfide or a homopolymer or copolymer of aromatic groups and these. And derivatives thereof, and these polymers may be used alone or in combination. The production of an electrolyte membrane using a hydrocarbon-based polymer is cheaper than the fluorine-based polymer, and is easy to manufacture, and exhibits high ionic conductivity.

The suitable hydrocarbon film is more preferably sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherketone, sulfonated polyether ether ketone. ketone), sulfonated poly aryrene ether sulfone, sulfonated poly aryrene ether sulfone, sulfonated poly aryrene ether benzimidazole ) And one or more selected from the group consisting of an ion-conducting membrane.

The fluorine-based polymer electrolyte membrane may be used without particular limitation as long as it is a material having mechanical strength and high electrochemical stability to form a film with an ion conductive membrane. Specific examples of the fluorine-based polymer electrolyte membrane include perfluorosulfonic acid resins, copolymers of tetrafluoroethylene and fluorovinyl ether, and the like. The fluorovinyl ether moiety has the function of conducting hydrogen ions. The copolymer is commercially available as it is sold under the trade name Nafion by Dupont.

According to another embodiment of the present invention, there is provided a fuel cell including the membrane-electrode assembly. 3 is a schematic diagram showing the overall configuration of the fuel cell.

For reference, the fuel cell may be a variety of electrolyte fuel cells, such as a phosphate electrolyte fuel cell (PAFC), a polymer electrolyte fuel cell, a hydrogen ion exchange membrane fuel cell (PEMFC), a direct methanol fuel cell (DMFC) and a high temperature PEMFC. In the present invention, the type is not limited.

Referring to FIG. 3, the fuel cell 200 includes a fuel supply unit 210 for supplying a mixed fuel mixture of fuel and water, and a reforming unit for reforming the mixed fuel to generate a reformed gas containing hydrogen gas ( 220), a reforming gas containing hydrogen gas supplied from the reforming unit 220 generates an electrochemical reaction with an oxidizing agent to generate electrical energy, and an oxidizing agent to the reforming unit 220 and the stack It includes an oxidizing agent supply unit 240 to supply to (230).

The stack 230 induces oxidation/reduction reactions of a reforming gas containing hydrogen gas supplied from the reforming unit 220 and an oxidizing agent supplied from the oxidizing agent supply unit 240 to generate a plurality of unit cells generating electric energy. To be equipped.

Each unit cell refers to a cell of a unit that generates electricity. The membrane-electrode assembly for oxidizing/reducing oxygen in a reforming gas containing hydrogen gas and oxidizing agent, and a reforming gas and oxidizing agent containing hydrogen gas And a separator for supplying the membrane-electrode assembly (also referred to as a bipolar plate, hereinafter referred to as a'separator'). The separator is centered on the membrane-electrode assembly and is disposed on both sides. At this time, the separation plates located on the outermost sides of the stack are also referred to as end plates.

The end plate of the separation plate has a pipe-shaped first supply pipe 231 for injecting a reforming gas containing hydrogen gas supplied from the reforming unit 220, and a pipe-shaped second for injecting oxygen gas. A supply pipe 232 is provided, and the other end plate includes a first discharge pipe 233 for discharging the reformed gas including hydrogen gas remaining unreacted and remaining in a plurality of unit cells to the outside, and the above-described unit cell Finally, a second discharge pipe 234 for discharging the unreacted and remaining oxidant to the outside is provided.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only for specifically illustrating or describing the present invention, and the present invention is not limited thereto. In addition, the contents not described herein will be sufficiently technically inferred by those skilled in the art, and the description thereof will be omitted.

[ Manufacturing example 1: Preparation of a composition for forming a fuel cell electrode]

< Example 1>

2.79 g of Pt/CB (Tanaka, TEC10E50E) as the first catalyst, and 0.31 g of Pt/CNF (Vinatech, VFC-HE60) as the second catalyst were mixed (see FIG. 4). The mixed catalyst was immersed in 22 g of a soaking solution. To the immersed mixed catalyst, 6.5 g of a 20% ionomer solution and 9 g of additional solvent were added.

< Example 2>

The first catalyst was Pt/CB (Tanaka, TEC10E50E) 2.79 g, and the second catalyst was Pt/MPC 0.31 g (self-made) (see FIG. 5). The mixed catalyst was immersed in 22 g of a soaking solution. To the immersed mixed catalyst, 6.5 g of a 20% ionomer solution and 9 g of additional solvent were added.

< Example 3>

2.79 g of Pt/CB (Tanaka, TEC10E50E) was used as the first catalyst, and 0.31 g of Pt/HCC (self-made) was mixed as the second catalyst. The mixed catalyst was immersed in 22 g of a soaking solution. To the immersed mixed catalyst, 6.5 g of a 20% ionomer solution and 9 g of additional solvent were added.

< Comparative example 1>

As the first catalyst, 3.1 g of Pt/CB (Tanaka, TEC10E50E) was immersed in 22 g of a soaking solution (see FIG. 6). To the immersed mixed catalyst, 6.5 g of a 20% ionomer solution and 9 g of additional solvent were added.

[ Manufacturing example 2: Preparation of membrane-electrode assembly]

The composition for forming a fuel cell electrode prepared in the above production example was bar coated on a polyimide release film under conditions of a coating speed of 10 mm/s and a coating thickness of 100 μm, and then dried for 30 hours at 6° C. to prepare an electrode.

Cut the dried electrode to the required size, align the electrode surface and the electrolyte membrane on both sides of the polymer electrolyte membrane (manufactured by DuPont; Nafion 212 Membrane), and then press them for 5 minutes under heat and pressure conditions of 100°C and 10 MPa. Thereafter, the film was hot-pressed and transferred by a method maintained at room temperature for 1 minute, and the release film was peeled to prepare a membrane-electrode assembly.

[ Experimental Example 1: Performance evaluation of membrane-electrode assembly]

The output characteristics of the voltage and current density of the electrode were evaluated for the membrane-electrode assembly prepared using the composition for forming the fuel cell electrodes of Example 1 and Comparative Example 1 in Preparation Example 2, and the results are shown in FIG. 7. Did.

Referring to FIG. 7, it was confirmed that the voltage current density of Example 1 consisting of a multi-carrier catalyst and an ionomer was better than that of Comparative Example 1 consisting of a single carrier catalyst and an ionomer only.

10: first catalyst
11: 1st metal particle 12: 1st carrier
20: second catalyst
21: second metal particles 22: second carrier
30: ionomer
40: electrode
110: anode electrode and cathode electrode
130: polymer electrolyte membrane
150: membrane-electrode assembly
200: fuel cell
210: fuel supply unit 220: reforming unit
230: stack 231: first supply pipe
232: second supply pipe 233: first discharge pipe
234: second discharge pipe 240: oxidizing agent supply unit

Claims (17)

A first catalyst comprising a first carrier and first metal particles supported on the first carrier,
A second catalyst comprising a second carrier and second metal particles supported on the second carrier,
Ionomers, and
Contains a solvent,
The first carrier is a first carbon black,
The second carrier is a hollow carbon capsule (HCC), multimodal porous carbon (MPC), carbon nanotube (CNT), carbon nanofiber (CNF), mesoporous Carbon (Mesoporous carbon), graphene (Graphene), or a second carbon black having a higher surface area and higher conductivity than the first carbon black,
The first catalyst and the second catalyst are included in a weight ratio of 95:5 to 80:20,
The ratio of the loading ratio of the first catalyst and the loading ratio of the second catalyst, which is calculated by Equation 1 below, is 1:0.2 to 1:0.8,
Composition for forming a fuel cell electrode:
[Equation 1]
The loading rate of each catalyst = (weight of metal particles / (weight of carrier + weight of metal particles)) X 100. According to claim 1,
The first metal particles or the second metal particles are platinum, ruthenium, osmium, and platinum-M alloy (where M is Pd, Ir, Os, Ga, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn, Mo, W, Rh, Ru and any one of a transition metal selected from the group consisting of alloys) and mixtures thereof. delete delete According to claim 1,
The first catalyst has a surface area of 200 to 1500 m ² /g, a particle diameter of 30 to 100 nm, a spherical carbon black carrier having metal particles supported on the composition for forming a fuel cell electrode. delete delete According to claim 1,
The composition for forming a fuel cell electrode, in which the deviation of the loading rate of the first catalyst and the deviation of the loading rate of the second catalyst are respectively independently calculated from Equation 3, respectively, from 0 to 10%:
[Equation 3]
Deviation of loading rate of each catalyst = (loading rate of each catalyst / average loading rate of all catalysts) X 100
Here, the average loading rate of the total catalyst is calculated by the following Equation 2:
[Equation 2]
The average loading rate of all catalysts = the sum of the loading rates of each catalyst / the number of each catalyst. According to claim 1,
The composition for forming a fuel cell electrode, wherein the average size deviation of the first catalyst and the average size deviation of the second catalyst, which are respectively calculated by the following Equation 4, are each independently 0 to 10%:
[Equation 4]
Deviation of average size of each catalyst = (average size of each catalyst / average size of all catalysts) X 100
Here, the average size of the total catalyst is calculated by Equation 5 below:
[Equation 5]
Average size of all catalysts = sum of average size of each catalyst / number of catalysts. According to claim 1,
The solvent is any one selected from the group consisting of water, isopropyl alcohol, ethoxy ethanol, N-methylpyrrolidone, ethylene glycol, propylene glycol and mixtures thereof. According to claim 1,
The composition for forming a fuel cell electrode is a composition for forming a fuel cell electrode, which comprises 40 to 70 parts by weight of an ionomer and 1000 to 1400 parts by weight of a solvent with respect to 100 parts by weight of the first catalyst and the second catalyst. According to claim 1,
The composition for forming a fuel cell electrode further comprises a third catalyst comprising a different carrier than the first catalyst and the second catalyst. A first catalyst comprising a first carrier and first metal particles supported on the first carrier,
A second catalyst comprising a second carrier and second metal particles supported on the second carrier, and
Contains ionomers,
The first carrier is a first carbon black,
The second carrier is a hollow carbon capsule (HCC), multi-pore carbon (MPC), carbon nanotube (CNT), carbon nanofiber (CNF), mesoporous carbon, graphene, or higher surface area than the first carbon black And high conductivity second carbon black,
The first catalyst and the second catalyst are included in a weight ratio of 95:5 to 80:20,
The ratio of the loading ratio of the first catalyst and the loading ratio of the second catalyst, which is calculated by Equation 1 below, is 1:0.2 to 1:0.8,
Fuel cell electrodes:
[Equation 1]
The loading rate of each catalyst = (weight of metal particles / (weight of carrier + weight of metal particles)) X 100. Preparing a first catalyst by supporting the first metal particles on a first carrier,
Preparing a second catalyst by supporting the second metal particles on a second carrier,
Preparing the electrode forming composition by adding the first catalyst, the second catalyst, and ionomer to a solvent, and
Preparing an electrode by applying the electrode forming composition
Including,
The first carrier is a first carbon black,
The second carrier is a hollow carbon capsule (HCC), multi-pore carbon (MPC), carbon nanotube (CNT), carbon nanofiber (CNF), mesoporous carbon, graphene, or higher surface area than the first carbon black And high conductivity second carbon black,
The first catalyst and the second catalyst are included in the composition for forming the electrode in a weight ratio of 95:5 to 80:20,
The ratio of the loading ratio of the first catalyst and the loading ratio of the second catalyst, which is calculated by Equation 1 below, is 1:0.2 to 1:0.8,
Method for manufacturing a fuel cell electrode:
[Equation 1]
The loading rate of each catalyst = (weight of metal particles / (weight of carrier + weight of metal particles)) X 100. The method of claim 14,
Each of the first catalyst and the second catalyst is independently produced by a polyol reduction method, an electron beam reduction method, a sodium borohydride (NaBH ₄ ) reduction method, or a urea-assisted uniform reduction method, which is produced by any one reduction method selected for a fuel cell. Method of manufacturing an electrode. A membrane-electrode assembly comprising the electrode for a fuel cell according to claim 13. A fuel cell comprising the electrode for a fuel cell according to claim 13.

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