KR102189064B1 - Method for manufacturing electrode, electrode manufactured by using the same, membrane-electrode assembly comprising the electrode, and fuel cell comprising the membrane-electrode assembly - Google Patents

Abstract

The present invention relates to a method of manufacturing an electrode, an electrode manufactured thereby, a membrane-electrode assembly including the electrode, and a fuel cell including the membrane-electrode assembly, wherein the method of manufacturing the electrode comprises mixing a catalyst and an ionomer. Preparing a composition for forming an electrode by applying low-frequency acoustic energy to the composition for forming an electrode to perform resonant vibratory mixing to coat the ionomer on the surface of the catalyst, and the electrode It includes the step of preparing an electrode by coating the forming composition.
The method of manufacturing the electrode is to increase the dispersibility of the catalyst by coating the ionomer in a nano-thickness on the surface of the catalyst to facilitate mixing, and to make the ionomer evenly distributed on the surface of the catalyst, thereby increasing the utilization rate of the catalyst and the ionomer. By doing so, various performances can be improved, and durability can be increased by increasing the coupling efficiency between the catalyst and the ionomer.

Description

A method of manufacturing an electrode, an electrode manufactured thereby, a membrane-electrode assembly including the electrode, and a fuel cell including the membrane-electrode assembly TECHNICAL FIELD [METHOD FOR MANUFACTURED BY USING THE SAME, MEMBRANE-ELECTRODE ASSEMBLY COMPRISING THE ELECTRODE, AND FUEL CELL COMPRISING THE MEMBRANE-ELECTRODE ASSEMBLY}

The present invention relates to a method of manufacturing an electrode, an electrode manufactured thereby, a membrane-electrode assembly including the electrode, and a fuel cell including the membrane-electrode assembly, by coating an ionomer with a nano-thickness on the surface of a catalyst. , By increasing the dispersibility of the catalyst, it is easy to mix, and the ionomer is evenly distributed on the surface of the catalyst, thereby increasing the utilization rate of the catalyst and the ionomer to improve various performances, and to increase the coupling efficiency between the catalyst and the ionomer for durability. The present invention relates to a method of manufacturing an electrode capable of increasing the, an electrode manufactured thereby, a membrane-electrode assembly including the electrode, and a fuel cell including the membrane-electrode assembly.

A fuel cell is a battery 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 low pollutant emissions, it is attracting attention as a next-generation clean energy source that can replace fossil energy.

Such a fuel cell has the advantage of being able to output a wide range of outputs by stacking unit cells, and is attracting attention as a compact and mobile portable power source because it exhibits an energy density of 4 to 10 times that of a small lithium battery. have.

The stack that actually generates electricity in a fuel cell is a stack of several to tens of unit cells consisting of a membrane-electrode assembly (MEA) and a separator (also called a bipolar plate). In general, the membrane-electrode assembly has a structure in which an anode (Anode, or anode) and a cathode (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 state and type of electrolyte. Among them, polymer electrolyte fuel cells have a low operating temperature of less than 100 ℃, Due to its advantages such as fast start-up, response characteristics, and excellent durability, it is in the spotlight as a portable, vehicle and home power supply.

Representative examples of polymer electrolyte fuel cells include Proton Exchange Membrane Fuel Cell (PEMFC) that uses hydrogen gas as fuel, and Direct Methanol Fuel Cell (DMFC) that uses liquid methanol as 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. Oxygen is supplied from the reduction electrode, and oxygen is combined with hydrogen ions and electrons to produce water through a reduction reaction of oxygen.

Meanwhile, the electrode of the fuel cell is composed of a catalyst and an ionomer, and the degree of bonding and dispersion therebetween has a great influence on the performance and durability of the fuel cell.

An object of the present invention is to increase the dispersibility of the catalyst, thereby facilitating mixing by coating the ionomer on the surface of the catalyst in nano-thickness, and to make the ionomer evenly distributed on the surface of the catalyst, thereby increasing the utilization rate of the catalyst and the ionomer. It is to provide a method of manufacturing an electrode capable of improving various performances and increasing durability by increasing the coupling efficiency between a catalyst and an ionomer.

Another object of the present invention is to provide an electrode manufactured by the method of manufacturing the electrode.

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

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

According to an embodiment of the present invention, preparing a composition for forming an electrode comprising a catalyst and an ionomer, by applying low-frequency acoustic energy to the composition for forming the electrode to resonant vibratory mixing It provides a method of manufacturing an electrode comprising the step of coating the ionomer on the surface of the catalyst, and preparing an electrode by coating the composition for forming the electrode.

The low-frequency acoustic energy may have a frequency of 10 to 100 Hz.

The resonance mixing may be achieved by applying an acceleration of 10 to 100 G to the electrode-forming composition including the catalyst and the ionomer.

The resonance mixing may be performed for 30 seconds to 30 minutes.

The composition for forming an electrode may further include a solvent.

According to another embodiment of the present invention, there is provided an electrode comprising a catalyst and an ionomer, wherein the ionomer is coated on a surface of the catalyst to a thickness of 5 nm or less.

The ionomer may be coated on the surface of the catalyst by resonant vibratory mixing by applying low-frequency acoustic energy to the catalyst and the electrode-forming composition including the ionomer.

The ionomer coated with a thickness of 5 nm or less on the surface of the catalyst may be 55% to 95% by weight based on the total weight of the ionomer.

The ionomer aggregated without being coated on the catalyst surface may be 0% to 45% by weight based on the total weight of the ionomer.

The catalyst may include catalyst metal particles alone or catalyst metal particles supported on a carrier.

The weight ratio (I/C ratio) of the ionomer to the carrier represented by Equation 1 below may be 0.75 to 1.6.

[Equation 1]

I/C ratio = W _I / W _C

W _I = total weight of ionomer

W _C = total weight of the carrier

According to another embodiment of the present invention, an anode electrode and a cathode electrode disposed opposite to each other, and an ion exchange membrane disposed between the anode electrode and the cathode electrode, wherein the anode electrode, the cathode electrode, and both Any one selected from the group consisting of is one comprising the electrode-provides an electrode assembly.

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

The present invention provides a nano-thick coating of the ionomer on the surface of the catalyst, thereby facilitating mixing by increasing the dispersibility of the catalyst, and allowing the ionomer to be uniformly distributed on the surface of the catalyst, thereby increasing the utilization rate of the catalyst and the ionomer. It is possible to improve durability and increase the coupling efficiency between the catalyst and the ionomer.

1 is a schematic diagram showing a process of coating an ionomer on a catalyst surface.
2 is a schematic cross-sectional view of a membrane-electrode assembly according to an embodiment of the present invention.
3 is a schematic diagram showing the overall configuration of a fuel cell according to an embodiment of the present invention.
4 and 5 are transmission electron microscopy (TEM) photographs of electrodes prepared in Example 1 and Comparative Example 1 of the present invention, respectively.
6 is a graph showing the performance evaluation results of the membrane-electrode assembly prepared in Example 1 and Comparative Example 1 of the present invention.

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

Unless otherwise specified in the specification, when a part such as a layer, film, region, plate, etc. is said to be'on the' other part, it is not only the case where the other part is'directly above', but also the case where there is another part in the middle. Include.

The method of manufacturing an electrode according to an embodiment of the present invention comprises the steps of preparing a composition for forming an electrode including a catalyst and an ionomer, and applying low-frequency acoustic energy to the composition for forming an electrode to resonant mixing. vibratory mixing) and coating the ionomer on the catalyst surface, and coating the electrode-forming composition to prepare an electrode.

First, a composition for forming an electrode comprising a catalyst and an ionomer is prepared.

Any catalyst that can be used as a catalyst for hydrogen oxidation reaction and oxygen reduction reaction may be used, and a platinum-based metal is preferably used.

The platinum-based metal is platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), platinum-M alloy (M is palladium (Pd), ruthenium (Ru), iridium ( Ir), osmium (Os), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper ( Any one selected from the group consisting of Cu), silver (Ag), gold (Au), zinc (Zn), tin (Sn), molybdenum (Mo), tungsten (W), lanthanum (La) and rhodium (Rh) The above) and combinations thereof may include one selected from the group consisting of, and more preferably, a combination of two or more metals selected from the platinum-based catalyst metal group may be used, but the present invention is not limited thereto. Any platinum-based catalyst metal that can be used in the technical field may be used without limitation.

In addition, as the catalyst, a metal itself (black) may be used, or a catalyst metal may be supported on a carrier.

The carrier may be selected from a carbon-based carrier, a porous inorganic oxide such as zirconia, alumina, titania, silica, ceria, and zeolite. The carbon-based carrier is super P, carbon fiber, carbon sheet, carbon black, Ketjen Black, acetylene black, and carbon nanotubes. (carbon nano tube, CNT), carbon sphere, carbon ribbon, fullerene, activated carbon, and one or more combinations thereof, but is not limited thereto. The carrier that can be used in can be used without limitation.

The catalytic metal particles may be located on the surface of the carrier, or may penetrate into the carrier while filling internal pores of the carrier.

When a noble metal supported on the carrier is used as a catalyst, a commercially available one may be used, or a noble metal supported on the carrier may be prepared and used. Since the process of supporting the noble metal on the carrier is widely known in the art, a detailed description thereof may be omitted in the present specification, and thus it is a content that can be easily understood by those in the field.

The catalytic metal particles may be contained in an amount of 20% to 80% by weight based on the total weight of the catalyst, and if it is contained in less than 20% by weight, there may be a problem of deterioration of activity, and if it exceeds 80% by weight, Aggregation of the catalytic metal particles reduces the active area, and thus the catalytic activity may conversely decrease.

The catalyst may be contained in an amount of 50% to 80% by weight based on the total weight of the electrode, and if it is less than 50% by weight, there may be a problem of deterioration in activity due to lack of catalyst, and if it exceeds 80% by weight The lack of ionomers can be detrimental to ion conduction.

Meanwhile, the ionomer may be a cationic conductor having a cation exchange group such as a proton, or an anion conductor having an anion exchange group such as a hydroxy ion, carbonate, or bicarbonate.

The cation exchange group may be any one selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphoric acid group, an imide group, a sulfonimide group, a sulfonamide group, and a combination thereof, and generally may be a sulfonic acid group or a carboxyl group. have.

The cation conductor includes the cation exchange group, and a fluorine-based polymer containing fluorine in a main chain; Benzimidazole, polyamide, polyamideimide, polyimide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, polyetherimide, polyester, polyethersulfone, polyetherimide, poly Hydrocarbon-based polymers such as carbonate, polystyrene, polyphenylene sulfide, polyetheretherketone, polyetherketone, polyarylethersulfone, polyphosphazene or polyphenylquinoxaline; Partially fluorinated polymers such as polystyrene-graft-ethylenetetrafluoroethylene copolymer or polystyrene-graft-polytetrafluoroethylene copolymer; And sulfone imide.

More specifically, when the cationic conductor is a hydrogen ion cationic conductor, the polymers may include a cation exchange group selected from the group consisting of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group and a derivative thereof in the side chain, and the Specific examples include poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, defluorinated sulfurized polyether ketone, or a mixture thereof. Fluorine-based polymer containing; Sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (SPEEK), sulfonated polybenzimi Dazole (sulfonated polybenzimidazole (SPBI)), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated poly Quinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, sulfonated polyether sulfone, sulfonated polyether ketone polyether ketone), sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenyl Sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene ether nitrile ( sulfonated polyarylene ether ether nitrile), polyarylene ether sulfone ketone, And hydrocarbon-based polymers including mixtures thereof, but are not limited thereto.

In addition, the cationic conductor may replace H with Na, K, Li, Cs, or tetrabutylammonium in the cation exchange group at the end of the side chain. When H is substituted with Na in the cation exchange group at the side chain terminal, NaOH is substituted with tetrabutylammonium when preparing the catalyst composition, and tetrabutylammonium hydroxide is used, and K, Li or Cs are also appropriate. It can be substituted using a compound. Since the substitution method is widely known in the art, a detailed description thereof will be omitted herein.

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

Examples of the non-conductive compound include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene/tetrafluoro Ethylene/tetrafluoroethylene (ETFE), ethylene chlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), Dode At least one selected from the group consisting of silbenzenesulfonic acid and sorbitol may be used.

The anion conductor is a polymer capable of transporting anions such as hydroxy ions, carbonates or bicarbonates, and the anion conductors are commercially available in the form of hydroxide or halide (generally chloride), and the anion conductors are industrial water purification (water purification), metal separation, or catalytic processes.

As the anionic conductor, a polymer doped with a metal hydroxide may be generally used, and specifically, poly(ethersulfone), polystyrene, a vinyl polymer, poly(vinyl chloride), poly(vinylidene fluoride) doped with a metal hydroxide , Poly(tetrafluoroethylene), poly(benzimidazole), poly(ethylene glycol), or the like can be used.

Commercially commercialized examples of the ionomer include Nafion and Aquibion.

The ionomer may be included in an amount of 20% to 50% by weight based on the total weight of the electrode. When the content of the ionomer is less than 20% by weight, the generated ions may not be transferred well, and when it exceeds 50% by weight, the supply of hydrogen or oxygen (air) is difficult due to insufficient pores, and the active area that can react This can be reduced.

The electrode-forming composition may be specifically prepared by adding the catalyst to the ionomer or adding the ionomer to the catalyst, and it is not necessary to mix the prepared electrode-forming composition after the addition, but the resonance mixing It is also possible to mix by the usual method prior to. At this time, the general mixing method may use any one or more dispersion methods selected from ultrasonic dispersion, stirring, 3-roll mill, ball mill, planetary stirring, high pressure dispersion, and mixing methods thereof.

The electrode-forming composition may further include a solvent together with the catalyst and the ionomer. In this case, the electrode-forming composition is prepared by adding the catalyst to the solvent to prepare a catalyst solution, and then adding the ionomer to the catalyst solution. It may be prepared by adding, and after preparing an ionomer solution by adding the ionomer to the solvent, it may be prepared by adding the catalyst to the ionomer solution, or may be prepared by mixing the catalyst solution and the ionomer solution.

The solvent may be a solvent selected from the group consisting of water, a hydrophilic solvent, an organic solvent, and one or more mixtures thereof.

The hydrophilic solvent is one selected from the group consisting of alcohols, ketones, aldehydes, carbonates, carboxylates, carboxylic acids, ethers, and amides containing a linear, branched saturated or unsaturated hydrocarbon having 1 to 12 carbon atoms as a main chain. It may have the above functional groups, and these may include an alicyclic or aromatic cyclo compound as at least a part of the main chain. Specific examples of alcohols include methanol, ethanol, isopropyl alcohol, ethoxy ethanol, n-propyl alcohol, butyl alcohol, 1,2-propanediol, 1-pentanol, 1.5-pentanediol, 1.9-nonandiol, and the like; Heptanone, Octanone, etc. as a ketone; Examples of aldehydes include benzaldehyde and tolualdehyde; Examples of esters include methylpentanoate, ethyl-2-hydroxypropanoate, and the like; Examples of the carboxylic acid include pentanoic acid and heptanoic acid; Examples of ethers include methoxybenzene and dimethoxypropane; Examples of amides include propanamide, butylamide, dimethylacetamide, and the like.

The organic solvent may be selected from N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, and mixtures thereof.

The solvent may be contained in an amount of 80 to 95% by weight based on the total weight of the electrode forming composition, and if it is less than 80% by weight, the solid content is too high and there may be a problem of dispersion due to cracks and high viscosity during electrode coating, If it exceeds 95% by weight, it may be detrimental to electrode activity.

Next, the electrode-forming composition is resonantly mixed to coat the ionomer on the surface of the catalyst.

The resonance mixing is a mixing process in which mixing resonates, and the resonance of mixing may occur as a result of a combination of vibration and acceleration of the mixed components. When the resonance mixing is performed, a large number of strong mixing regions having a diameter of about 50 μm are generated, thereby eliminating dead-zones, thereby enabling uniform mixing as a whole.

The resonance mixing can minimize contamination because it does not require parts necessary for stirring such as an impeller, can reduce loss, and the range of soluble viscosity is 1 cP to 1 million cP or more, and vacuum or temperature can be adjusted. .

As a commercially available device capable of resonant mixing, a Resodyn ^® Resonant Acoustic Mixer (RAM) or the like may be used.

The inventors of the present invention discovered that the ionomer can be coated with a nano-thickness of 5 nm or less on the surface of the catalyst by using the resonance mixing and completed the present invention.

1 is a schematic diagram showing a process of coating the ionomer on the surface of the catalyst. Referring to FIG. 1, the surface of the catalyst metal particles 2 supported on the carrier 1 by the resonance mixing is coated in a nano-thickness by the ionomer 3. That is, the ionomer 3 in a softer form may be coated on the surface of the catalyst metal particle 2 having a harder structure by using the resonance mixing.

To this end, the resonance mixing may be performed by applying low-frequency acoustic energy. The low-frequency acoustic energy is a linear or spherical energy propagation through a tangible medium within a frequency range of 10 to 20000 Hz, and in the present invention, in order to coat the ionomer on the catalyst surface with a nano-thickness, a frequency of 10 to 100 Hz, specifically As a result, low-frequency acoustic energy having a frequency of 50 to 70 Hz is used.

In addition, the resonance mixing may be achieved by applying an acceleration of 10 to 100 G, specifically 40 to 100 G to the electrode-forming composition containing the catalyst and the ionomer under the frequency (here, G denotes acceleration due to gravity, For example, 10 G means 10 times the acceleration of gravity).

If the acceleration is less than 10 G, an unmixed region may exist, and performance may be degraded because coating is not performed, and if it exceeds 100 G, ionomers agglomerate, phase separation, and change in mixing conditions and performance decrease due to heat generation, There may be problems such as flooding.

The method for applying the low-frequency acoustic energy and the acceleration in the frequency domain to the electrode-forming composition is not particularly limited in the present invention, and any conventionally known method may be used. As an example, in the case of using the Resodyn ^® Resonant Acoustic Mixer, the acoustic energy is supplied by a periodic linear displacement of the container filling the mixture of the catalyst and the ionomer, and for this purpose, a plurality of mechanical or electronic transducer arrangements are used. , More specifically, oscillator drives for transferring vibration and acceleration to the container and a variable elastic member such as a spring are included. For information on the resonance sound mixer, reference may be made to US Patent Registration No. 71 88993 and US Patent Publication No. 2010-0294113.

The resonance mixing may be performed for 30 seconds to 30 minutes, and specifically, may be performed for a short time of 1 minute to 10 minutes. If the time of the resonance mixing is less than 30 seconds, less mixing or coating properties may not be confirmed, and if it exceeds 30 minutes, the sample or composition may be changed.

In addition, since the resonance mixing is possible to mix a wide range of materials such as solid-solid, solid-liquid, liquid-liquid, liquid-gas, etc., when the resonance mixing is used, the electrode-forming composition does not contain a solvent and Solid-solid mixing including only the ionomer is possible, and solid-liquid or liquid-liquid mixing in which the catalyst, the ionomer, and both of them contain a solvent is also possible.

Finally, an electrode is prepared by coating the electrode-forming composition.

The step of preparing the electrode is not particularly limited in the present invention, but as a specific example, it may further include a step of preparing an electrode by coating the composition for forming an electrode on a release film, and transferring the electrode to an ion exchange membrane. .

When coating the electrode-forming composition on the release film, the electrode-forming composition containing the catalyst is continuously or intermittently transferred to a coater and then uniformly applied to the release film in a dry thickness of 10 to 200 µm. It is desirable to do.

More specifically, according to the viscosity of the electrode-forming composition, it is continuously transferred through a pump to a coater such as a die, gravure, bar, comma coater, etc., and then slot die Coating, bar coating, comma coating, screen printing, spray coating, doctor blade coating, brush, etc. are used to uniformly apply the dry thickness of the electrode layer on the decal film to 10 to 200 μm, more preferably 10 to 100 μm. And volatilize the solvent by passing through a drying furnace maintained at a constant temperature.

When the electrode-forming composition is coated with a thickness of less than 1 µm, the catalyst content is small, and the activity may decrease, and when the composition is coated with a thickness exceeding 200 µm, the movement distance of ions and electrons increases, so that resistance may increase. have.

The drying process may be drying at 25° C. to 90° C. for 12 hours or more. If the drying temperature is less than 25 °C and the drying time is less than 12 hours, a problem may occur that a sufficiently dried electrode may not be formed, and when drying at a temperature exceeding 90 °C, cracks of the electrode may occur. .

However, the method of applying and drying the electrode-forming composition is not limited to the above.

Optionally, after the step of preparing an electrode by drying the electrode-forming composition, it may further include cutting the dried electrode and the release film to a required size and bonding it to the ion exchange membrane.

The ion exchange membrane includes an ion conductor. The ion conductor may be a cationic conductor having a cation exchange group such as a proton, or an anion conductor having an anion exchange group such as a hydroxy ion, carbonate, or bicarbonate.

The cation exchange group may be any one selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphoric acid group, an imide group, a sulfonimide group, a sulfonamide group, and a combination thereof, and generally may be a sulfonic acid group or a carboxyl group. have.

The cation conductor includes the cation exchange group, and a fluorine-based polymer containing fluorine in a main chain; Benzimidazole, polyamide, polyamideimide, polyimide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, polyetherimide, polyester, polyethersulfone, polyetherimide, poly Hydrocarbon-based polymers such as carbonate, polystyrene, polyphenylene sulfide, polyetheretherketone, polyetherketone, polyarylethersulfone, polyphosphazene or polyphenylquinoxaline; Partially fluorinated polymers such as polystyrene-graft-ethylenetetrafluoroethylene copolymer or polystyrene-graft-polytetrafluoroethylene copolymer; And sulfone imide.

More specifically, when the cationic conductor is a hydrogen ion cationic conductor, the polymers may include a cation exchange group selected from the group consisting of a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group and a derivative thereof in the side chain, and the Specific examples include poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, defluorinated sulfurized polyether ketone, or a mixture thereof. Fluorine-based polymer containing; Sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (SPEEK), sulfonated polybenzimi Dazole (sulfonated polybenzimidazole (SPBI)), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, Sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, sulfonated polyether sulfone, sulfonated poly Ether ketone (sulfonated polyether ketone), sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone (sulfonated polyphenylene sulfide sulfone), alcohol Sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene Ether ether nitrile (sulfonated polyarylene ether ether nitrile), polyarylene ether sulfone ketone (sulfonated polyarylene ether sulfone ketone), and hydrocarbon-based polymers including a mixture thereof, but is not limited thereto.

The anion conductor is a polymer capable of transporting anions such as hydroxy ions, carbonates or bicarbonates, and the anion conductors are commercially available in the form of hydroxide or halide (generally chloride), and the anion conductors are industrial water purification (water purification), metal separation, or catalytic processes.

As the anionic conductor, a polymer doped with a metal hydroxide may be generally used, and specifically, poly(ethersulfone), polystyrene, a vinyl polymer, poly(vinyl chloride), poly(vinylidene fluoride) doped with a metal hydroxide , Poly(tetrafluoroethylene), poly(benzimidazole), poly(ethylene glycol), or the like can be used.

Meanwhile, the ion exchange membrane may be in the form of a reinforced membrane in which the ion conductor fills the voids of a fluorine-based porous support such as e-PTFE or a porous nanoweb support manufactured by electrospinning.

A method of bonding the electrode and the ion exchange membrane may use a transfer method, for example, and the transfer method includes hot pressing in which heat and pressure are applied by attaching a metal press alone or a soft plate of rubber material such as a silicone rubber material to the metal press ( hot pressing).

The transfer method may be performed under conditions of 80° C. to 150° C. and 50 kgf/cm ² to 200 kgf/cm ² . When hot pressing under conditions of 80° C. and 50 kgf/cm ² , the transfer of the electrode on the release film may not be performed properly. When it exceeds 150° C., the polymer of the ion exchange membrane burns and the electrode is There is a risk of structural degeneration, and when hot-pressing under conditions exceeding 200 kgf/cm ² , the effect of compressing the electrode is greater than the transfer of the electrode, so that transfer may not be performed properly.

An electrode according to another embodiment of the present invention may be manufactured by the method of manufacturing the electrode described above. Accordingly, the electrode includes a catalyst and an ionomer, and the ionomer is coated on the surface of the catalyst by applying low-frequency acoustic energy to the composition for forming an electrode including the catalyst and the ionomer and mixing it with resonance, wherein the ionomer coating layer is 5 It may have a nano-thickness of less than or equal to nm, specifically, a nano-thickness of 0.5 to 4 nm. When the thickness of the ionomer coating layer is 5 nm or less, it is preferable in terms of improving the performance of the catalyst.

In addition, when the ionomer is coated on the surface of the catalyst using the resonance mixing, ionomer aggregation layers having various thicknesses may be significantly reduced.

When the catalyst and the ionomer are mixed by other conventional methods, ionomer aggregation layers having various thicknesses are formed, but when the ionomer is coated on the catalyst surface by using the resonance mixing, the catalyst has a thickness of 5 nm or less. The ionomer layer coated with may be formed almost uniformly over the entire area of the electrode.

The ionomer coated with a thickness of 5 nm or less on the catalyst surface may be 55 to 95% by weight, and specifically 80 to 90% by weight, based on the total weight of the ionomer. When the ionomer coated with a thickness of 5 nm or less on the surface of the catalyst is less than 55% by weight based on the total weight of the ionomer, problems such as reduction in performance due to the uncoated portion and reduction in stability due to the limitation of connection between catalyst-ionomer conjugates It may be present, and if it exceeds 95% by weight, catalytic activity may be lowered due to aggregation of ionomers.

In addition, the ionomer aggregation layer made of an ionomer aggregated without being coated on the catalyst surface may be 0 to 45% by weight, and specifically 10 to 20% by weight, based on the total weight of the ionomer. When the ionomer aggregation layer exceeds 45% by weight based on the total weight of the ionomer, the ionomer aggregation and catalytic activity due to the uncoated catalyst may be reduced.

The ionomer coated with a thickness of 5 nm or less on the catalyst surface means that the thickness is 5 nm or less when the electrode is observed with a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM), and is not coated on the catalyst surface. Aggregated ionomer means that the thickness exceeds 5 nm when the electrode is observed with TEM or STEM, or that the aggregated ionomer is observed with a TEM, STEM or scanning electron microscope (SEM). In addition, the ionomer may include an ionomer coated with a thickness of 5 nm or less on the catalyst surface and an ionomer other than the ionomer aggregated without being coated on the catalyst surface in the remaining content. The content of the ionomer coated with a thickness of 5 nm or less on the catalyst surface or the content of the aggregated ionomer may be a content value measured for the entire electrode, and on a TEM or STEM photograph of at least 5 locations of the electrode The content of the ionomer coated with a thickness of 5 nm or less on the existing catalyst surface or the content of the aggregated ionomer may be measured, and then an average value thereof may be calculated.

In addition, when the ionomer is a fluorine-based ionomer, the ionomer-coated catalyst is analyzed by energy dispersive X-ray spectroscope (EDS) under TEM or SEM analysis conditions. Coated and uncoated areas can be identified by the ionomer distribution.

In addition, when the ionomer contains a sulfonic acid group as an ion exchange group, the ionomer-coated catalyst is sulfur (S) when analyzed by energy dispersive X-ray spectroscope (EDS) under TEM or SEM analysis conditions. ), the ionomer distribution can be confirmed, and the coated and uncoated areas can be identified by the ionomer distribution.

As described above, since the ionomer is uniformly coated on the surface of the catalyst, a higher amount of ionomer is required compared to other conventional methods. Specifically, the weight ratio (I/C ratio) of the ionomer to the carrier of the catalyst represented by Equation 1 below may be 0.75 to 1.6. This may be that the I/C ratio is improved by 0.05 to 0.2 compared to the existing electrode. The existing electrode does not contain an ionomer coating layer of 5 nm or less, and may be manufactured using an existing mixing method such as a ball mill.

[Equation 1]

I/C ratio = W _I / W _C

W _I = total weight of ionomer

W _C = total weight of the carrier

In addition, the electrode may exhibit an electrochemical active surface area (ECSA) of 1 to 30% performance improvement compared to the conventional electrode, and specifically, 5 to 20% performance improvement. The electrochemical effective surface area may be measured by measuring a cyclo-voltammetry using a rotating disk electrode to obtain a hydrogen oxidation reaction area. The conventional electrode does not include an ionomer coating layer of 5 nm or less, and may be manufactured using an existing mixing method such as a ball mill.

A membrane-electrode assembly according to another exemplary embodiment of the present invention includes an anode electrode and a cathode electrode disposed opposite to each other, and the ion exchange membrane disposed between the anode electrode and the cathode electrode. Any one selected from the group consisting of the anode electrode, the cathode electrode, and both may include the electrode according to the embodiment of the present invention. Since the description of the electrode and the method of manufacturing the electrode is the same as described above, a repetitive description will be omitted.

2 is a schematic cross-sectional view of the membrane-electrode assembly. Referring to FIG. 2, the membrane-electrode assembly 100 includes the ion exchange membrane 50 and the electrodes 20 and 20' disposed on both surfaces of the ion exchange membrane 50, respectively. The electrode (20, 20') includes an electrode substrate (40, 40') and a catalyst layer (30, 30') formed on the surface of the electrode substrate (40, 40'), and the electrode substrate (40, 40') A microporous layer (not shown) including conductive fine particles such as carbon powder and carbon black is formed between the catalyst layers 30 and 30 ′ and the electrode substrates 40 and 40 ′ to facilitate the diffusion of substances from the electrode substrates 40 and 40 ′. It may include more.

In the membrane-electrode assembly 100, an oxidation reaction that generates hydrogen ions and electrons from fuel disposed on one surface of the ion exchange membrane 50 and transferred to the catalyst layer 30 through the electrode substrate 40 is performed. The resulting electrode 20 is referred to as an anode electrode, and is disposed on the other side of the ion exchange membrane 50 to pass the hydrogen ions supplied through the ion exchange membrane 50 and the electrode substrate 40' to the catalyst layer 30'. The electrode 20 ′ that causes a reduction reaction that generates water from the oxidizing agent transferred to is referred to as a cathode electrode.

The catalyst layers 30 and 30 ′ of the anode and cathode electrodes 20 and 20 ′ include an electrode according to an embodiment of the present invention including the catalyst, ionomer, and polyacrylic acid.

As the electrode substrates 40 and 40', a porous conductive substrate may be used so that hydrogen or oxygen can be supplied smoothly. Typical examples are carbon paper, carbon cloth, carbon felt, or metal cloth (a porous film composed of a fibrous metal cloth or a metal film formed on the surface of a cloth made of polymer fibers. That means) can be used, but is not limited thereto. In addition, it is preferable to use a water-repellent treatment of the electrode substrates 40 and 40' with a fluorine-based resin because it can prevent the reaction product 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, polyperfluorosulfonylfluoride alkoxyvinyl ether, fluorinated ethylene propylene ( Fluorinated ethylene propylene), polychlorotrifluoroethylene, or a copolymer thereof may be used.

The membrane-electrode assembly 100 may be manufactured according to a conventional method of manufacturing a membrane-electrode assembly, except that the electrode according to the present invention is used as the anode or cathode electrodes 20 and 20'.

A fuel cell according to another embodiment of the present invention includes the membrane-electrode assembly.

3 is a schematic diagram showing the overall configuration of the fuel cell.

3, the fuel cell 200 includes a fuel supply unit 210 for supplying a mixed fuel in which fuel and water are mixed, and a reforming unit for generating a reformed gas including hydrogen gas by reforming the mixed fuel ( 220), a reformed gas including hydrogen gas supplied from the reforming unit 220 causes an electrochemical reaction with an oxidizing agent to generate electrical energy, and an oxidizing agent in the reforming unit 220 and the stack It includes an oxidizing agent supply unit 240 for supplying to 230.

The stack 230 includes a plurality of unit cells for generating electric energy by inducing an oxidation/reduction reaction of a reforming gas including hydrogen gas supplied from the reforming unit 220 and an oxidizing agent supplied from the oxidizing agent supply unit 240. Equipped.

Each unit cell refers to a unit cell that generates electricity, and includes the membrane-electrode assembly for oxidizing/reducing oxygen in a reforming gas including hydrogen gas and an oxidizing agent, and a reforming gas and oxidizing agent including hydrogen gas. It includes a separation plate (also referred to as a bipolar plate, hereinafter referred to as a'separator plate') for supplying the membrane-electrode assembly. The separator plate is disposed on both sides of the membrane-electrode assembly. In this case, the separating plates respectively located on the outermost side of the stack may be specifically referred to as an end plate.

A first supply pipe 231 having a pipe shape for injecting a reforming gas including hydrogen gas supplied from the reforming unit 220 into the end plate of the separation plate, and a second pipe shape for injecting oxygen gas. The supply pipe 232 is provided, and the other end plate has a first discharge pipe 233 for discharging the reformed gas including hydrogen gas remaining after being finally unreacted in the plurality of unit cells to the outside, and the unit cell A second discharge pipe 234 for discharging the unreacted and remaining oxidizing agent to the outside is provided.

In addition to the membrane-electrode assembly for a fuel cell, the electrode can be applied to various fields such as a secondary battery or a capacitor.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only intended to specifically illustrate or describe the present invention, and the present invention is not limited thereto. In addition, information not described herein can be sufficiently technically inferred by those skilled in the art, and the description thereof will be omitted.

[Production Example: Preparation of electrode]

(Example 1)

1.0 g of Pt/C (manufactured by Tanaka Corporation) was improved to the container, and 1.0 g of ionomer powder (manufactured by Nafion, DuPont Corporation) was improved and placed in the same container.

The container containing the mixture was mounted on a Resodyn ^® Resonant Acoustic Mixer (RAM). A composition for forming an electrode was prepared by applying low-frequency acoustic energy having a frequency of 60 Hz to the resonance acoustic mixer and mixing for 5 minutes at an acceleration of 70 G.

The electrode-forming composition was bar-coated on a polyimide release film at a coating speed of 10 mm/s and a coating thickness of 100 μm, and then dried at 30° C. for 6 hours to prepare an electrode.

The dried electrode was cut to the required size, and the electrode and the ion exchange membrane were aligned on both sides of the ion exchange membrane (made by DuPont; Nafion 212 Membrane) in contact with each other, followed by heat and pressure conditions of 100° C. and 100 kgf/cm ² for 5 minutes. After compression bonding, transfer was performed by hot pressing in a method of maintaining at room temperature for 1 minute, and the release film was peeled to prepare a membrane-electrode assembly.

(Example 2)

In Example 1, a membrane-electrode assembly was prepared in the same manner as in Example 1, except that low-frequency acoustic energy having a frequency of 60 Hz was applied to the resonance sound mixer and mixed for 10 minutes at an acceleration of 70 G. Was prepared.

(Example 3)

In Example 1, a membrane-electrode assembly was prepared in the same manner as in Example 1, except that low-frequency acoustic energy having a frequency of 60 Hz was applied to the resonance sound mixer and mixed at an acceleration of 80 G for 5 minutes. Was prepared.

(Example 4)

1.0 g of Pt/C (manufactured by Tanaka Corporation) was improved in the container, and 5.0 g of the ionomer solution (Nafion 20% solution, manufactured by DuPont Corporation) was improved and placed in the same container.

The container containing the mixture was mounted on a Resodyn ^® Resonant Acoustic Mixer (RAM). A composition for forming an electrode was prepared by applying low-frequency acoustic energy having a frequency of 60 Hz to the resonance acoustic mixer and mixing for 5 minutes at an acceleration of 70 G.

The electrode-forming composition was bar-coated on a polyimide release film at a coating speed of 10 mm/s and a coating thickness of 100 μm, and then dried at 30° C. for 6 hours to prepare an electrode.

The dried electrode was cut to the required size, and the electrode and the ion exchange membrane were aligned on both sides of the ion exchange membrane (made by DuPont; Nafion 212 Membrane) in contact with each other, followed by heat and pressure conditions of 100° C. and 100 kgf/cm ² for 5 minutes. After compression bonding, transfer was performed by hot pressing in a method of maintaining at room temperature for 1 minute, and the release film was peeled to prepare a membrane-electrode assembly.

(Comparative Example 1)

1.0 g of Pt/C (manufactured by Tanaka Corporation) was improved in the container, and 5.0 g of the ionomer solution (Nafion 20% solution, manufactured by DuPont Corporation) was improved and placed in the same container.

The mixture was dispersed and stirred using a ball mill to prepare a composition for forming an electrode.

Thereafter, the step of preparing a membrane-electrode assembly by coating and drying the electrode-forming composition on a decal film was carried out in the same manner as described in the above example to prepare a membrane-electrode assembly.

[Experimental Example 1]

(Experimental Example 1: TEM photograph observation)

Transmission Electron Microscope (TEM) photographs of the electrodes prepared in Example 1 and Comparative Example 1 are shown in FIGS. 4 and 5, respectively.

Referring to FIGS. 4 and 5, as in Example 1, in the electrode manufactured by resonance mixing, the ionomer coating phenomenon was clearly observed on the surface of the catalyst, and the coating thickness was 5 nm or less. Specifically, the wave pattern of the arrow portion in FIG. 4 indicates that the ionomer is coated with 5 nm or less, and it can be seen that the coating portion is spread throughout. In addition, it can be seen that the agglomeration phenomenon in which the ionomers of Comparative Example 1 made of a ball mill are piled up was not observed.

(Experimental Example 2: CV analysis)

For the membrane-electrode assemblies prepared in Example 1 and Comparative Example 1, the voltage and current output from the electrode were measured, and the output characteristics (discharge performance) of the voltage-current density were compared and evaluated, and the results are shown in FIG. Done.

Referring to FIG. 6, it can be seen that the membrane-electrode assembly manufactured in the above example has superior voltage performance according to the current density compared to the membrane-electrode assembly manufactured in the comparative example. It can be seen that the electrode exhibits a larger electrochemical effective surface area than the electrode prepared in the comparative example, that is, the activity of the catalyst is increased.

Although the preferred embodiments of the present invention have been described in detail above, the above-described embodiments are presented as a specific example of the present invention, and the present invention is not limited thereto, and the scope of the present invention will be described later. Various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in are also within the scope of the present invention.

1: carrier
2: catalyst metal particles
3: ionomer
20, 20': electrode
30, 30': catalyst layer
40, 40': electrode substrate
50: ion exchange membrane
100: 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: oxidizer supply unit

Claims (13)

Preparing a composition for forming an electrode comprising a catalyst and an ionomer,
Coating the ionomer on the surface of the catalyst by applying low-frequency acoustic energy having a frequency of 10 to 100 Hz to the electrode-forming composition to perform resonant vibratory mixing, and
Coating the composition for forming an electrode to prepare an electrode
Method of manufacturing an electrode comprising a. The method of claim 1,
The electrode-forming composition is a solid-solid mixture containing only the catalyst and the ionomer, a method for producing an electrode. The method of claim 1,
The resonance mixing is a method of manufacturing an electrode which is formed by applying an acceleration of 10 to 100 G to the electrode-forming composition containing the catalyst and the ionomer. The method of claim 1,
The method of manufacturing an electrode wherein the resonance mixing is performed for 30 seconds to 30 minutes. The method of claim 1,
The electrode-forming composition further comprises a solvent. It includes a catalyst and an ionomer,
The ionomer is coated with a thickness of 5 nm or less on the surface of the catalyst by performing resonance mixing by applying low-frequency acoustic energy having a frequency of 10 to 100 Hz to the electrode-forming composition including the catalyst and the ionomer. electrode. delete The method of claim 6,
The ionomer coated with a thickness of 5 nm or less on the surface of the catalyst is 55% to 95% by weight based on the total weight of the ionomer. The method of claim 6,
The electrode that is not coated on the catalyst surface and aggregated ionomer is 0% to 45% by weight based on the total weight of the ionomer. The method of claim 6,
The catalyst is an electrode comprising a catalyst metal particle alone or a catalyst metal particle supported on a carrier. The method of claim 10,
The electrode having a weight ratio (I/C ratio) of the ionomer to the carrier represented by Equation 1 is 0.75 to 1.6.
[Equation 1]
I/C ratio = W _I / W _C
W _I = total weight of ionomer
W _C = total weight of the carrier An anode electrode and a cathode electrode positioned opposite each other, and
And an ion exchange membrane positioned between the anode electrode and the cathode electrode,
Any one selected from the group consisting of the anode electrode, the cathode electrode, and both includes the electrode according to claim 6. A fuel cell comprising the membrane-electrode assembly according to claim 12.

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