KR20200060851A - Binder for membrane electrode assembly electrode and manufacturing method thereof membrane electrode assembly having the same and polymer electrolyte membrane fuel cell having the same - Google Patents

Abstract

The present invention relates to a binder for a membrane-electrode assembly electrode which is obtained by adding a second solvent, which is one selected from ethylene glycol and diethylene glycol or a mixture thereof, to an ionomer solution containing a first solvent and ionomer so as to substitute a solvent. The present invention also relates to a membrane-electrode assembly and fuel cell including the same. Accordingly, electrochemical properties can be significantly improved.

Description

Membrane-electrode assembly Binder for electrode, manufacturing method thereof and membrane-electrode assembly and polymer electrolyte fuel cell including the same }

The present invention relates to a binder for a membrane-electrode assembly electrode, a method of manufacturing the same, and a membrane-electrode assembly and a fuel cell comprising the same.

Polymer Electrolyte Membrane Fuel Cell (PEMFC) is generally composed of a structure including a fuel electrode, a polymer electrolyte membrane and an air electrode. In the anode, electrochemical oxidation of hydrogen used as fuel occurs to generate electrons, and in the cathode, oxygen, an oxidizing agent, consumes electrons, and electrochemical reduction occurs, thereby generating electrical energy. In addition, when the unit cells are stacked, the voltage can be increased, and if the area of the unit cells is increased, the amount of current generated can be increased, so that the fuel cell system can be configured according to required performance.

In addition, a polymer electrolyte fuel cell including a solid electrolyte includes a polymer electrolyte membrane capable of transferring charge to a solid electrolyte, a fuel electrode generating electrons, and an air electrode consuming electrons, in order to maximize the interface reaction area It is compressed at high temperature and manufactured as a membrane electrode assembly (MEA) to be used as a unit cell.

A catalyst for the redox reaction of the fuel is required at the anode and the cathode of the polymer electrolyte fuel cell, and a Pt-based catalyst is generally used. In addition, an ionomer is included in the electrode of the polymer electrolyte fuel cell as a binder so that hydrogen ions generated at the anode can be delivered to the cathode along with the catalyst for the redox reaction. The ionomer serves as a hydrogen ion conductor, but also serves as a binder that physically bonds Pt-based catalyst particles constituting the electrode. The binder is composed of a solution containing an ionomer and a solvent for dissolving it. Here, the temperature at which the electrode is baked varies depending on the characteristics of the solvent used, and accordingly, the shape of the electrode changes, thereby improving the performance and durability of the fuel cell. Affects.

In the past, the binder used for manufacturing the electrode for the membrane-electrode assembly used in the polymer electrolyte fuel cell was produced by using a solution dispersed in a low-boiling-point solvent or partially adding a high-boiling-point solvent to the low-boiling-point solvent dispersion solution. It is difficult to satisfy all of the durability, and a study on a method capable of supplementing this is necessary.

An object of the present invention to solve the above problems is to provide a binder for a membrane-electrode assembly electrode substituted with a solvent having a low solubility for an ionomer.

In addition, another object of the present invention is to provide a membrane-electrode assembly having a significantly improved durability and performance, including an electrode prepared by mixing with a catalyst, and a polymer electrolyte fuel cell including the same.

As a result of research in order to achieve the above object, the membrane-electrode assembly electrode binder according to the present invention is a first solvent and an ionomer solution comprising an ionomer, which is selected from ethylene glycol and diethylene glycol, or a mixture thereof. After adding 2 solvents, the solvent was replaced by heating.

The ionomer according to an aspect of the present invention may be a perfluorinated ionomer.

The first solvent according to an aspect of the present invention may have a lower boiling point than the second solvent.

The binder according to an aspect of the present invention may contain 0.1 to 50% by weight of the ionomer, based on the total weight of the binder, even after solvent substitution.

Another aspect of the present invention is a) preparing a dispersed ionomer solution containing an ionomer in a first solvent, b) mixing a second solvent in the ionomer solution, and c) heating the mixed solution to heat the first solvent. And removing the solvent to remove the solvent, wherein the boiling point of the first solvent is lower than the boiling point of the second solvent, and the second solvent is a membrane selected from ethylene glycol and diethylene glycol or a mixture thereof. -Electrode assembly It is a method of manufacturing a binder for electrodes.

Another aspect of the present invention is a catalyst slurry comprising a binder and a catalyst for the membrane-electrode assembly electrode described above.

Another aspect of the present invention is a membrane-electrode assembly comprising an electrolyte membrane and electrodes prepared from the catalyst slurry described above on both sides of the electrolyte membrane.

A gas diffusion layer may be further included on the electrode according to an aspect of the present invention.

The membrane-electrode assembly according to an aspect of the present invention may have a current density of 0.3 A/cm 2 or more.

The membrane-electrode assembly according to an aspect of the present invention may have an ohmic loss of 0.8 Pa/cm 2 or less.

Another aspect of the present invention is a polymer electrolyte fuel cell including the above-described membrane-electrode assembly.

The binder for a membrane-electrode assembly electrode according to an aspect of the present invention is substituted with a solvent having low solubility in an ionomer, and despite this, has an advantage that the ionomer can maintain improved dispersibility at a high content.

In addition, the membrane-electrode assembly according to an aspect of the present invention, the membrane-electrode assembly comprising an electrode prepared by including a binder for an electrode has low activation loss and ohmic loss, thereby improving electrochemical properties. It has the advantage that it can be significantly improved.

In addition, the membrane-electrode assembly according to an aspect of the present invention has an advantage that a membrane-electrode assembly including an electrode prepared by including a binder for an electrode may be formed of small and uniform particles to have a more compact structure.

In addition, a polymer electrolyte fuel cell including a membrane-electrode assembly according to an aspect of the present invention has an advantage that a voltage reduction rate is remarkably low when used for a long time in preparation for an initial open circuit voltage.

1 is a graph of IV polarization of a binder for a membrane-electrode assembly electrode according to an embodiment of the present invention and a comparative example.
2 is a cyclic voltammetry curve of a membrane-electrode assembly according to an embodiment and a comparative example of the present invention.
3 is a graph of OCV values according to durability evaluation through an accelerated life test of a membrane-electrode assembly according to an embodiment and a comparative example of the present invention.
FIG. 4 is a photograph of the surface observed by a scanning electron microscope before and after the durability evaluation of the membrane-electrode assembly according to one embodiment and one comparative example of the present invention.

Hereinafter, a binder for a membrane-electrode assembly electrode according to the present invention, a method for manufacturing the membrane-electrode assembly and a polymer electrolyte fuel cell including the same, will be described in more detail through examples. However, the following examples are only a reference for explaining the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used in the description herein are only intended to effectively describe specific embodiments, and are not intended to limit the present invention.

In the present invention, “substituting a solvent” means changing the first solvent in the ionomer solution containing the first solvent and the ionomer so that most of the second solvent is present to prepare a second solvent and an ionomer solution containing the ionomer. do.

The present invention for achieving the above object relates to a binder for a membrane-electrode assembly electrode, a method for manufacturing the membrane-electrode assembly and a polymer electrolyte fuel cell including the same.

When the ionomer is dispersed in a solvent, coated for electrode formation, and then dried to form an electrode, the solid phase characteristic changes depending on the solvent used, and the structure and shape of the electrode vary depending on the characteristic of the solvent, resulting in fuel It is known to affect the performance and durability of the battery.

Accordingly, the present inventors have completed the present invention by discovering that a method for providing a solvent capable of controlling an ionomer structure in a binder for a membrane-electrode assembly electrode can realize significantly improved fuel cell characteristics.

The present invention will be described in detail as follows.

The binder for a membrane-electrode assembly electrode according to the present invention replaces a solvent by introducing a first solvent and a second solvent, which is a mixture of ethylene glycol and diethylene glycol, or a mixture thereof, into an ionomer solution containing an ionomer and heating it. Ordered.

Existing ethylene glycol or diethylene glycol has a low solubility with respect to the ionomer, so it is difficult to dissolve or disperse the ionomer with a high content to provide it as a binder for a membrane-electrode assembly electrode.

Alternatively, the binder for the membrane-electrode assembly electrode according to the present invention is a first solvent having excellent solubility in an ionomer and an ionomer solution containing an ionomer, a second solvent selected from ethylene glycol and diethylene glycol, or a mixture thereof. By replacing the solvent by injecting, the ionomer is contained in a high content, the dispersibility is excellent, and the fuel cell efficiency can be remarkably improved.

The binder for the membrane-electrode assembly electrode according to the present invention can be provided by substituting the solvent with the second solvent, thereby affecting the structure and shape of the electrode or catalyst layer of the membrane-electrode assembly electrode, so that the electrode, fuel, and electrolyte are simultaneously It is possible to induce the formation of a three-phase interface, a point of contact.

According to an aspect of the present invention, the first solvent may be a solvent having excellent solubility and dispersibility with respect to the ionomer, and is a different solvent from the second solvent. Preferably, it may be any one or two or more mixed solvents selected from water and alcohol-based solvents. For a specific example, it may be an alcohol-based solvent that is water selected from purified water, distilled water, and the like, or a mixture of any one or two or more selected from methanol, ethanol, n-propanol, isopropanol, and butanol, but is not limited thereto.

The second solvent according to the present invention is any one selected from ethylene glycol and diethylene glycol or mixtures thereof. Other than the solvent selected from propylene glycol and triethylene glycol, it can provide significantly improved electrochemical properties and durability of the fuel cell.

According to an aspect of the present invention, the first solvent may have a lower boiling point than the second solvent. As described above, it is possible to provide a binder for a membrane-electrode assembly electrode in which the first solvent is removed by heating to a low boiling point of the first solvent and replaced with the second solvent.

According to an aspect of the present invention, the heating may be heated to a temperature higher than the boiling point of the first solvent and lower than the boiling point of the second solvent, for example, 100° C. or higher, preferably 100 to 180° C., more Preferably it may be 110 to 170 ℃. By heating to the above-mentioned temperature, only the first solvent can be selectively removed to replace the solvent with the second solvent.

According to an aspect of the present invention, the ionomer may be a perfluorinated ionomer in order to improve the performance and durability of the fuel cell through the solvent substitution method according to the present invention, although not particularly limited, as long as it is an ion conductive polymer. Preferably, the perfluorinated ionomer may include one or more ion conductive functional groups selected from sulfonic acid, carboxylic acid, and salts thereof. For a specific example, the perfluorinated ionomer includes lithium sulfonate salt, sodium sulfonate salt, potassium sulfonate salt, magnesium sulfonate salt, calcium sulfonate salt, ammonium sulfonate salt, alkyl ammonium sulfonate salt, lithium carboxylate salt, sodium carboxylate salt, and carbohydrate It may be to include any one or two or more ion-conducting functional groups selected from potassium carboxylate and alkyl ammonium carboxylate. More preferably, the perfluorinated ionomer may include sulfonate, but is not limited thereto.

According to one aspect of the present invention, the binder may contain 0.1 to 50% by weight of the ionomer, relative to the total weight of the binder, even after solvent replacement. Preferably, the ionomer may contain 5 to 50% by weight based on the total weight of the binder, and more preferably, the ionomer may contain 5 to 30% by weight based on the total weight of the binder. Previously, ethylene glycol or diethylene glycol had difficulty in dispersing or dissolving such high content of ionomer. Alternatively, the binder for the membrane-electrode assembly electrode according to the present invention may contain a high content of ionomer even though it is substituted with a second solvent that is one or a mixture selected from ethylene glycol and diethylene glycol through a method of substituting a solvent. Can be.

The binder for the membrane-electrode assembly electrode according to the present invention has low activation loss and ohmic loss, which can significantly improve durability as well as electrochemical properties.

Another aspect of the present invention is a) preparing a dispersed ionomer solution containing an ionomer in a first solvent, b) mixing a second solvent with the ionomer solution, and c) heating the mixed solution to heat the first solvent. And removing the solvent to remove the solvent, wherein the boiling point of the first solvent is lower than the boiling point of the second solvent, and the second solvent is a membrane selected from ethylene glycol and diethylene glycol or a mixture thereof. -Electrode assembly This is a method of manufacturing a binder for electrodes.

The binder for the membrane-electrode assembly electrode according to the present invention is provided by the above-described manufacturing method, and by preparing the binder by substituting the solvent using two different solvents as described above, significantly improved polymer electrolyte fuel cell performance And durability can be remarkably improved.

Specifically, according to an aspect of the present invention, the membrane-electrode assembly including the electrode prepared by including the binder for the membrane-electrode assembly electrode prepared as described above has low activation loss and ohmic loss. loss) to significantly improve the electrochemical properties.

In addition, according to an aspect of the present invention, the membrane-electrode assembly including the electrode prepared by including the binder for the membrane-electrode assembly electrode prepared as described above may be formed of small and uniform particles, thereby having a more compact structure. .

In addition, according to an aspect of the present invention, the polymer electrolyte fuel cell including the membrane-electrode assembly prepared as described above may have a significantly lower voltage reduction rate when used for a long time compared to an initial open circuit voltage.

Another aspect of the present invention is a catalyst slurry comprising a binder and a catalyst for the membrane-electrode assembly electrode described above. The catalyst slurry as described above may be provided as an electrode for a membrane-electrode assembly. By providing the electrode for a membrane-electrode assembly according to an aspect of the present invention, the catalytic reaction activity point is increased to form a more excellent three-phase interface, and the catalyst efficiency can be improved.

Even when the same solvent was used using a high boiling point solvent such as N-methylpyrrolidone, etc., which is not the second solvent according to the present invention, the dispersibility for the catalyst was not good, and thus the performance and durability were not affected.

According to an aspect of the present invention, the catalyst may include a metal catalyst that promotes oxidation of hydrogen and reduction of oxygen. For a specific example, the catalyst may be a platinum-based catalyst, and selected from ruthenium, osmium, palladium, potassium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc alone or in combination with the platinum. It may include a platinum-based alloy or a mixture containing any one or more.

According to one aspect of the present invention, the metal catalyst may be used in a state generally supported by a carrier. The carrier may be a carbon-based material such as acetylene black or graphite; Or inorganic fine particles such as alumina, silica, etc.; may be used, but is not limited thereto.

Another aspect of the present invention is a membrane-electrode assembly comprising an electrolyte membrane and electrodes prepared from the catalyst slurry described above on both sides of the electrolyte membrane.

According to an aspect of the present invention, the electrolyte membrane is a semipermeable membrane called a proton exchange membrane or a polymer electrolyte membrane (PEM). It carries only protons, that is, protons, and is impermeable to gases such as oxygen or hydrogen. Specifically, when used as a membrane-electrode assembly in a fuel cell, the electrolyte membrane is saturated with water and transmits protons, but does not transmit electrons.

For a specific example, the electrolyte membrane may be a commercially available polymer electrolyte membrane, a fluorine-based Nafion, or the like, and may be replaced with an electrolyte membrane used in a similar polymer electrolyte fuel cell field.

According to an aspect of the present invention, the membrane-electrode assembly may include a catalyst layer prepared from the catalyst slurry on both sides of the electrolyte membrane. The catalyst layer as described above is manufactured from the catalyst slurry to have a dense structure, and can minimize contact resistance and material transfer resistance. In addition, excellent bonding with the electrolyte membrane can significantly reduce the interface resistance, thereby ensuring excellent performance.

According to an aspect of the present invention, a gas diffusion layer may be further included on the electrode. Specifically, catalyst layers are formed on both sides of the electrolyte membrane, and a gas diffusion layer may be formed on the catalyst layer.

According to an aspect of the present invention, the gas diffusion layer may include carbon paper or carbon cloth, but is not limited thereto. The gas diffusion layer serves to support the electrode for the membrane-electrode assembly, and may diffuse the reaction gas to the catalyst layer, so that the reactor gas can be easily accessed by the catalyst layer. The gas diffusion layer may be a water-repellent treatment of a carbon paper or a carbon cloth with a fluorine-based resin such as polytetrafluoroethylene. The water-repellent carbon paper or carbon cloth as described above can prevent flooding caused by moisture generated when the fuel cell is driven from being prevented from deteriorating in gas diffusion efficiency.

According to an aspect of the present invention, the catalyst layer may be formed by coating on the electrolyte membrane, or may be formed on a gas diffusion layer to form an electrode, but is not limited thereto. The coating method is not particularly limited, but is selected from a spray coating method, a die coating method, a screen printing method, a tape casting method, a tape casting method, or a brushing method. After coating by the coating method, it may be formed by drying.

According to an aspect of the present invention, the membrane-electrode assembly may have a current density of 0.3 A/cm 2 or more. Preferably, the current density may be 0.35 A/cm 2 or more, more preferably 0.4 A/cm 2 or more. Specifically, the current density may be 0.3 to 0.7 A/cm 2, preferably the current density may be 0.35 to 0.7 A/cm 2, and more preferably, the current density may be 0.4 to 0.7 A/cm 2. By providing the excellent current density as described above, it is possible to realize significantly improved fuel cell performance.

The membrane-electrode assembly according to an aspect of the present invention may have an ohmic loss of 0.8 Pa/cm 2 or less. Preferably, the ohmic loss is 0.7 Ω/cm 2 or less, and more preferably, the ohmic loss is 0.6 Ω/cm 2 or less. Specifically, the ohmic loss may be 0.01 to 0.8 Pa/cm 2, preferably 0.1 to 0.7 Pa/cm 2, more preferably 0.1 to 0.6 Pa/cm 2. By having a significantly low ohmic loss value as described above, a voltage drop of the fuel cell can be prevented, and significantly improved fuel cell performance and durability can be realized.

Another aspect of the present invention is a polymer electrolyte fuel cell including the above-described membrane-electrode assembly.

The polymer electrolyte fuel cell has a low activation loss and an ohmic loss, thereby significantly improving electrochemical properties.

The polymer electrolyte fuel cell may have a significantly lower voltage reduction rate when used for a long time compared to the initial open circuit voltage.

Such an effect can be realized by being manufactured by including a binder for a membrane-electrode assembly electrode prepared by the solvent substitution method according to the present invention.

Hereinafter, the present invention will be described in detail with reference to Examples. However, these are for explaining the present invention in more detail, and the scope of the present invention is not limited by the following examples.

In addition, the unit of the additive not specifically described in the specification may be weight%.

[Method of measuring properties]

1. Dynamic light scattering (DLS)

Dynamic light scattering is a non-invasive technique that measures the size of nanoparticles in a dispersion, and measures the intensity of scattered light over time in a particle suspension using Brownian motion. By analyzing the intensity fluctuations of the scattered light, it is possible to determine the diffusion coefficient for knowing the average diameter of the particles, and it is possible to know the average diameter of the particles from the above coefficients through the Stoke-Einstein equation.

A zetasizer from Malvern was used to measure the average diameter of colloidal particles by utilizing the dynamic light scattering method.

[Example 1]

1) Preparation of a binder for a membrane-electrode assembly electrode.

After adding 100 parts by weight of an ionomer binder (Solvey, Aquivion D72-BS, weight average molecular weight 720 g/mol) in which Aquibion is dispersed in water (Diwater, DW) by 25% by weight, ethylene glycol is added to the ionomer binder ( Ethylene glycol, EG) 225 parts by weight was added. The evaporation flask was coupled to a RE100-Pro LCD Digital Rotary evaporator manufactured by Dragon Lab to evaporate water at 100 rpm and 120°C. At this time, when the evaporated binder solution reached a target weight of 10% by weight of solid content, the evaporation flask was separated from the evaporator to prepare a binder for membrane-electrode assembly electrodes (Aquivion D72 dispersion in EG).

2) Preparation of catalyst slurry.

The platinum-based catalyst (Tanaka Kikinzoku Kogyo KK, TEC10F50E, platinum carrying amount 46.5 wt% Pt/C) and the binder for the membrane-electrode assembly electrode prepared as described above were stirred in a vial bottle of a nitrogen atmosphere with a magnetic stirrer for 10 min, followed by ultrasonic washing. After stirring for 5 cycles at 30 min intervals, the mixture was further stirred overnight with a magnetic stirrer.

3) Preparation of membrane-electrode assembly.

In the CCM (Catalyst-coated membrane) method, a membrane-electrode assembly (MEA) was prepared by coating an electrode on a polymer electrolyte membrane.

The catalyst slurry prepared as described above was coated on a decal transfer paper to a thickness including 0.4 mg/cm 2 catalyst amount. The coated catalyst slurry was dried in a vacuum oven at 120° C. for 1 hour to prepare an electrode.

The electrode was cut to a size of 4 cm x 4 cm to fit the size of the cell applied to the fuel cell station, and then placed on both sides of the polymer electrolyte membrane (Nafion 212). Thereafter, a membrane-electrode assembly was prepared by bonding the electrode to the polymer electrolyte membrane for 3 minutes at 135°C and 30 MPa using a hot pressing machine.

The catalyst amount was confirmed through the following equation 1. When the weight after transfer to the polymer electrolyte membrane was subtracted from the total weight of the transfer paper and the electrode when it was first cut to 4 cm×4 cm, it was calculated as X, and the catalyst amount of the electrode was derived using X.

[Equation 1]

[Example 2]

It was carried out in the same manner as in Example 1, except that diethylene glycol (Diethylene glycol, DG) was used instead of ethylene glycol.

[Comparative Example 1]

It was carried out in the same manner as in Example 1, except that propylene glycol (Propylene glycol, PG) was used instead of ethylene glycol.

[Comparative Example 2]

It was carried out in the same manner as in Example 1, except that triethylene glycol (triethylene glycol, TG) was used instead of ethylene glycol.

[Comparative Example 3]

In Example 1, as a binder for the membrane-electrode assembly electrode, 100 parts by weight of an ionomer binder (Solvey, Aquivion D72-BS, weight average molecular weight 720 g/mol) in which Aquibion is dispersed in water (Diwater, DW) by 25% by weight. The same was performed except that 150 parts by weight of water was further mixed and diluted.

[Experimental Example 1]

Particle size analysis

The membrane-electrode assembly binders of Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to dynamic light scattering (DLS) to measure the average particle diameter of particles in the binder. As a result, it was confirmed that Example 1 had an average particle size distribution of 53 nm, Example 2 33 nm, Comparative Example 1 73 nm, Comparative Example 2 31 nm, and Comparative Example 3 2,456 nm. This confirmed that the membrane-electrode assembly binder according to the present invention had a significantly smaller average particle diameter than Comparative Example 1 and Comparative Example 3. Through this, it was found that the dispersibility of the binder is remarkably excellent, and the electrode can form a dense structure.

[Experimental Example 2]

Current-voltage characteristics

The membrane-electrode assembly binders of Examples 1 and 2 and Comparative Examples 1 to 3, through the IV polarization graph as shown in Figure 1, open circuit voltage (OCV, open terminal voltage), maximum power density (Max PD, maximum power) density), the current density at 0.6 V (CD, current density) and ohmic loss are measured and are shown in Table 1 below.

Open circuit voltage
(V) Power density
(W/㎠) Current density
(A/㎠) Ohm loss
(Ω/㎠) Example 1 0.956 0.516 0.722 0.43 Example 2 0.959 0.503 0.721 0.43 Comparative Example 1 0.948 0.278 0.333 0.86 Comparative Example 2 0.933 0.266 0.243 0.95 Comparative Example 3 0.941 0.239 0.278 1.02

As shown in Table 1, the membrane-electrode assembly prepared in Examples 1 and 2 according to the present invention has a maximum power density of at least 1.8 times higher than the comparative example, a current density of at least 2.1 times higher, and a significantly lower minimum of 1 It was confirmed that it had a ohm loss of about /2. That is, it was confirmed that ohm loss, which is one of the causes of the voltage drop of the fuel cell, can be remarkably lowered, and excellent fuel cell performance can be achieved while realizing high power density.

It can be seen that when Examples 1 and 2 were compared with Comparative Example 3, the solvent of the binder for the membrane-electrode assembly electrode according to the present invention was replaced with ethylene glycol or diethylene glycol, thereby having significantly improved performance. . In addition, as compared with Comparative Examples 1 and 2, even the same glycol-based solvent, by using ethylene glycol or diethylene glycol as a solvent for a binder for a membrane-electrode assembly electrode, it can be seen that remarkably improved performance can be realized.

[Experimental Example 3]

Catalytic activity area measurement.

By analyzing the cyclic voltammetry method (CV) graph shown in FIG. 2, an electrochemically-active surface area (ECSA) value was measured. The ECSA value was calculated through Equation 2 below, and the CV graph was analyzed to calculate the current density (q _pt ) of Pt used as a catalyst, Г is the amount of charge required for hydrogen ions in Pt, and L is the catalyst supported by Pt The active area was calculated.

[Equation 2]

ECSA(㎡ _pt /g _pt ) = q _pt / (Г× L)

The catalytically active area measured in this way was 36.7 m 2 _pt /g _{pt in} Example 1, Example 2 is 31.0㎡ _pt /g _pt , It was confirmed that Comparative Example 1 had 25.1 m 2 _pt /g _pt and Comparative Example 2 had 18.0 m 2 _pt /g _pt . Through this, even if the same glycol-based solvent, ethylene glycol or diethylene glycol is used as a solvent for a binder for a membrane-electrode assembly electrode, it can be seen that an excellent catalytically active area can be realized.

[Experimental Example 4]

Durability check.

Durability was confirmed through accelerated life test based on the experimental protocol (MEA Chemical Stability and Metrics) of the US DOE. As shown in Table 2 and FIG. 3, when the value of 20% decrease based on the initial OCV value was measured, it can be confirmed that the initial OCV value in the comparative example is significantly lower or is reduced by a steep slope. Through this, it can be seen that the membrane-electrode assembly according to the present invention is excellent in durability as well as in excellent performance and can be used in the long term.

Estimated life time(hr) @ 20% OCV loss Early OCV
(V) Slope
(×10 ⁴ , V/hr) Example 1 410 0.956 2.31 Example 2 270 0.974 2.96 Comparative Example 1 240 0.970 2.72 Comparative Example 2 205 0.947 4.05 Comparative Example 3 190 0.961 7.77

In addition, as shown in Figure 4, when the surface of the membrane-electrode assembly prepared in Examples 1 and 2 of the present invention compared to Comparative Example 3 was observed with a scanning electron microscope (Ultra plus, Zeiss), a compact structure without cracks was obtained. It was confirmed that it had. After performing the accelerated life test for 100 hours as described above, when the surface was observed with a scanning electron microscope, it was confirmed that cracks hardly occur even in comparison with Comparative Examples 1 and 2. Moreover, in Comparative Examples 1 to 3, when the inside of the crack generated on the electrode surface reacted, it was physically accumulated, and thus, a smooth discharge source of water interfered with resistance, resulting in a decrease in electrochemical properties.

Membrane-electrode assembly according to the present invention It was confirmed that the membrane-electrode assembly prepared by including the binder for the electrode has remarkably excellent durability.

The present invention described above is only exemplary, and those skilled in the art to which the present invention pertains will appreciate that various modifications and other equivalent embodiments are possible. Therefore, it will be understood that the present invention is not limited to the forms mentioned in the above detailed description. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

Accordingly, the spirit of the present invention should not be limited to the described embodiments, and should not be determined, and all claims that are equivalent or equivalent to the scope of the claims as well as the claims described below belong to the scope of the spirit of the invention. .

Claims (11)

A binder for a membrane-electrode assembly electrode, in which a solvent is substituted by heating after introducing a second solvent, which is one or a mixture selected from ethylene glycol and diethylene glycol, to an ionomer solution containing a first solvent and an ionomer. According to claim 1,
The ionomer is a perfluorinated ionomer and a binder for a membrane-electrode assembly electrode. According to claim 1,
The first solvent is a binder for a membrane-electrode assembly electrode having a lower boiling point than the second solvent. According to claim 1,
The binder is a binder for a membrane-electrode assembly electrode containing 0.1 to 50% by weight of the ionomer with respect to the total weight of the binder even after solvent replacement. a) preparing an ionomer solution containing an ionomer dispersed in a first solvent,
b) mixing a second solvent in the ionomer solution, and
c) removing the first solvent by heating the mixed solution to replace the solvent,
The boiling point of the first solvent is lower than the boiling point of the second solvent,
The second solvent is a method for producing a binder for a membrane-electrode assembly electrode, which is one or a mixture selected from ethylene glycol and diethylene glycol. A catalyst slurry comprising a binder and a catalyst for the membrane-electrode assembly electrode of any one of claims 1 to 4. Electrolyte membrane and
A membrane-electrode assembly comprising electrodes prepared from the catalyst slurry of claim 6 on both sides of the electrolyte membrane. The method of claim 7,
A membrane-electrode assembly further comprising a gas diffusion layer on the electrode. The method of claim 7,
The membrane-electrode assembly is a membrane-electrode assembly having a current density of 0.3 A/cm 2 or more. The method of claim 7,
The membrane-electrode assembly is a membrane-electrode assembly having an ohmic loss of 0.8 Pa/cm 2 or less. A polymer electrolyte fuel cell comprising the membrane-electrode assembly of claim 7.

Images