KR20100080103A - Membrane and electrode assembly for fuel cell, manufacturing method, and fuel cell using the same - Google Patents

Abstract

PURPOSE: A membrane and electrode assembly is provided to enhance ion conductance between electrolyte membrane and electrode catalyst layer and to manufacture fuel cell with improved performance. CONSTITUTION: A method for manufacturing membrane and electrode assembly comprises: a step of applying a composition for forming fuel cell, containing electrode cell catalyst, first ion-conductive material, and solvent on a first supply film to form a first transfer film; a step of applying a composition for forming air cell, containing air cell catalyst, second ion conductive material, and solvent to form a second transfer film; a step of transferring the first transfer film; and a step of transferring a second transfer film.

Description

Membrane and electrode assembly for fuel cell, manufacturing method, and fuel cell using the same}

A membrane electrode assembly for a fuel cell, a manufacturing method thereof, and a fuel cell including the membrane electrode assembly are disclosed. More specifically, a membrane electrode assembly for a fuel cell including a fuel electrode and a cathode having different ion conductivity and moisture content, a method of manufacturing the same, and a fuel cell including the membrane electrode assembly are disclosed.

A fuel cell is a power generation system that converts energy contained in fuel into electrical energy by chemical reaction. Polymer electrolyte fuel cells obtain electrical energy through chemical reactions that produce water from hydrogen and oxygen. This energy conversion is made in the membrane electrode assembly described later, the membrane electrode assembly is a key component that determines the performance of the fuel cell.

In a polymer electrolyte fuel cell using hydrogen and air as main fuels, a method of preparing a membrane electrode assembly includes a catalyst coated membrane (CCM) and a catalyst coated gas diffusion layer (CCG).

The catalyst coating membrane method has been reported to be advantageous for the fabrication of membrane electrode assemblies because the interface resistance between the electrolyte membrane and the electrode catalyst layer is lower than that of the catalyst coating gas diffusion layer method and is advantageous for the formation of a thinner electrode catalyst layer (Journal of Power Sources). 170 (2007), 140).

 A method of coating the electrode catalyst layer directly on the electrolyte membrane by the spray coating method using a catalyst coating method, and preparing a transfer (decal) film by using a transfer sheet, and then transferring the transfer film to the electrolyte membrane to obtain a membrane electrode assembly. There are two ways to form. Among these, the spray method has a long manufacturing time in the method of manufacturing the membrane electrode assembly, and the safety of the electrode slurry is a problem. In addition, the transfer method using a decal film has a limitation in reducing the membrane electrode interface resistance since the electrode is first formed on the support and then transferred to the electrolyte membrane secondly.

One aspect of the present invention is to provide a membrane electrode assembly having excellent ion and mass transfer.

Another aspect of the present invention is to provide a method of manufacturing the membrane electrode assembly.

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

According to one aspect of the invention,

A fuel electrode containing a first ion conductive material; An air electrode containing a second ion conductive material; And an electrolyte membrane interposed between the fuel electrode and the air electrode,

A membrane electrode assembly is provided in which the ion conductivity of the anode is higher than the ion conductivity of the cathode, and the moisture content of the cathode is lower than that of the anode.

The first ion conductive material and the second conductive material each independently include a perfluoro-based proton conductive polymer film, a sulfonated polysulfone copolymer, a sulfonated poly (ether-ketone) -based polymer, and a perfluorinated sulfonic acid group. At least one selected from the group consisting of a containing polymer, a sulfonated polyether ether ketone polymer, a polyimide polymer, a polystyrene polymer, a polysulfone polymer, and a clay-sulfonated polysulfone nanocomposite Can be.

The ion conductivity of the first ion conductive material may be 0.09 S / cm or more, and the water content of the second ion conductive material may be 40 wt% or less.

In the membrane electrode assembly, the equivalent EW1 of the first ion conductive material and the equivalent EW2 of the second ion conductive material may satisfy Equations 1 to 3 below:

&Quot; (1) "

800 g / eq ≤ EW1 ≤ 1100 g / eq,

<Equation 2>

900 g / eq ≤ EW2 ≤ 1200 g / eq,

<Equation 3>

EW1 <EW2.

In the membrane electrode assembly, the weight ratio α ₁ of the first ion conductive material to the weight of the anode and the weight ratio content α ₂ of the second ion conductive material to the weight of the cathode may satisfy Equations 4 to 6 below. :

<Equation 4>

25 wt% ≦ α ₁ ≦ 35 wt%.

<Equation 5>

20 wt% ≤ α ₂ ≤ 33 wt%

<Equation 6>

α ₁ ≥ α _2.

According to another aspect of the invention,

Forming a first transfer film by applying a composition for forming an anode including a cathode catalyst, a first ion conductive material, and a solvent on the first support film; Forming a second transfer film by applying a composition for forming an anode, the cathode including a cathode catalyst, a second ion conductive material, and a solvent, on a second support membrane; Transferring the first transfer film to one side of an electrolyte membrane; And transferring the second transfer film to the other side of the electrolyte membrane, wherein the ion conductivity of the anode is higher than the ion conductivity of the cathode, and the moisture content of the cathode is lower than that of the anode. A method for producing a membrane electrode assembly is provided.

The transferring of the first transfer film and the second transfer film may be performed by a thermocompression method or a roll-to-roll method.

The manufacturing method includes removing a first support film from the transferred first transfer film; And removing the second support layer from the transferred second transfer film.

According to another aspect of the invention, there is provided a fuel cell comprising the membrane electrode assembly described above.

According to one embodiment of the present invention, a fuel cell having improved cell voltage may be provided using a membrane electrode assembly having excellent ion and mass transfer.

Hereinafter, a membrane electrode assembly for a fuel cell and a manufacturing method thereof according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, the membrane electrode assembly 10 for a fuel cell according to an embodiment of the present invention includes an electrolyte membrane 11 and electrode catalyst layers 12 and 12 ′.

The electrolyte membrane 11 is a perfluoro type proton conductive polymer membrane represented by Nafion (Dupont), a sulfonated polysulfone copolymer, a hydrocarbon polymer represented by a sulfonated poly (ether-ketone) system, and a perfluorinated sulfonic acid At least one ion conductivity selected from the group consisting of group-containing polymers, sulfonated polyether ether ketones, polyimides, polystyrenes, polysulfones and clay-sulfonated polysulfone nanocomposites It may include a polymer.

The electrode catalyst layers 12 and 12 'may include a metal catalyst such as conventional Pt or Pt alloy (PtRu, etc.) applied to a fuel cell or a supported catalyst carrying such a metal catalyst on a separate carrier. As the carrier, for example, carbon powder, activated carbon powder, graphite powder, or powder which is a carbon molecular sieve may be used. Specific examples of the activated carbon powder include Vulcan XC-72, ketjen black, and the like.

The fuel electrode 12 including the first ion conductive material among the electrode catalyst layers 12 and 12 'is adhered to one side of the electrolyte membrane 11 and has a higher ion conductivity than the air electrode 12'. The cathode 12 ′ including the second ion conductive material in the electrode catalyst layer is adhered to the other side of the electrolyte membrane 11 and has a lower moisture content than the fuel electrode 12.

The principle of generating electricity in a fuel cell is that fuel is supplied to an anode electrode which is a fuel electrode, adsorbed to a catalyst of the anode electrode, and the fuel is oxidized to generate hydrogen ions and electrons as shown in Scheme 1 below.

<Scheme 1>

H ₂ → 2H ^{+ +} 2e ^-

The generated electrons reach the cathode electrode which is the cathode according to an external circuit, and the hydrogen ions pass through the polymer electrolyte membrane and are transferred to the cathode electrode. An oxidant is supplied to the cathode, and the oxidant, hydrogen ions, and electrons generate electricity on a catalyst of the cathode by generating water through a reaction as in Scheme 2 below.

<Scheme 2>

^{2H + + 2e - + 1 /} 2O 2 → H 2 O

The membrane electrode assembly according to an embodiment of the present invention can increase the transfer of fuel, hydrogen ions, etc. between the electrolyte membrane and the anode by maintaining the ion conductivity of the anode higher than the cathode, and the reaction by-products by maintaining the moisture content of the cathode lower than the anode It is possible to prevent the channel of air between the electrolyte membrane and the air electrode from being blocked and to facilitate mass transfer.

In the fuel electrode, a first ion conductive material having a higher ion conductivity than a second ion conductive material contained in the air electrode and / or a content of the first ion conductive material in the anode is greater than or equal to the content of the second ion conductive material in the cathode. By doing so, the ion conductivity of the anode can be kept higher than the ion conductivity of the cathode.

In the cathode, a first ion conductive material having a lower moisture content than the second ion conductive material contained in the fuel electrode is used, and / or a content of the second ion conductive material in the cathode is less than or equal to that of the first ion conductive material contained in the anode. By using it, the moisture content of an air electrode can be kept lower than the moisture content of a fuel electrode.

Each of the first ion conductive material and the second ion conductive material, independently, the first ion conductive material and the second conductive material, each independently, a perfluoro-based proton conductive polymer membrane, sulfonated polysulfone air Copolymer, sulfonated poly (ether-ketone) polymer, perfluorinated sulfonic acid group-containing polymer, sulfonated polyether ether ketone polymer, polyimide polymer, polystyrene polymer, polysulfone polymer and clay-sulfonated poly One or more may be selected from the group consisting of clay-sulfonated polysulfone nanocomposite.

Among the compounds, the first ion conductive material may be selected to have an ion conductivity of 0.09 S / cm or more. Within this range, the ion transport characteristics of the anode are further improved. The upper limit of the ion conductivity of the first ion conductive material is not particularly limited, but may be a maximum value of the ion conductivity that the materials may have since the first ion conductive material may be selected from the above-listed materials.

The second ion conductive material in the compound may be selected to have a water content of 40% by weight or less. Within this range, the mass transfer properties of the air electrode become more excellent. In general, as the moisture content increases, the ion conductivity tends to increase. In the air electrode, adjusting the moisture content to a predetermined value or less may be an important factor for maintaining excellent mass transfer characteristics. On the other hand, the lower limit of the ion conductivity of the second ion conductive material is not particularly limited, but may be a minimum value of the moisture content of the materials because the second ion conductive material can be selected from the above-listed materials.

With respect to other properties of the first and second ion conductive materials, the first ion conductive material has 800 to 1100 equivalents (EW, g / eq) and the second ion conductive material has 900 to 1200 equivalents (EW) It may be selected so that the equivalent of the first ion conductive material is less than the equivalent of the second ion conductive material. By selecting the first and second ion conductive materials to have such a range, the membrane electrode junction according to the embodiment of the present invention can be maintained excellent in the ion transport in the anode and the material transport in the cathode. More preferably, in the range where the first ion conductive material has an equivalent weight (EW) of 900 to 1000 and the second ion conductive material has an equivalent weight (EW) of 1000 to 1100, the equivalent weight of the first ion conductive material is equal to the second ion. It may be selected to be less than the equivalent of the conductive material.

The content of the first ion conductive material may be 25 to 35% by weight based on the weight of the anode. In the range of 25% by weight or more, the effect of ion transport of the anode is maintained better, and in the range of 35% by weight or less, such an ion conductive material is prevented from blocking a channel through which fuel, hydrogen ions, or by-products can move. Can be.

The content of the second ion conductive material may be 20 to 33 wt% based on the weight of the cathode. When the content is 25% by weight or more, it is more preferable that a site capable of reacting air can be provided sufficiently. When the content is 33% by weight or less, it is possible not only to prevent the air reactant from clogging the moving channel, but also to maintain a moisture content below a certain level so that fuel can be smoothly moved.

Within the above range, the ion conductivity of the anode may be higher than the ion conductivity of the cathode by using the content of the first ion conductive material above the content of the second ion conductive material.

2 is a view for explaining a method of manufacturing a membrane electrode assembly according to an embodiment of the present invention. Like reference numerals in the drawings shown above indicate the same components or parts of the same components.

Hereinafter, a method of manufacturing the membrane electrode assembly 100 according to a preferred embodiment of the present invention will be described in detail with reference to FIG. 2.

First, the first support film 200 and the composition for forming the anode are prepared. In addition, a second support layer 200 ′ and a composition for forming an air electrode are prepared separately.

As the first and second supporting films 200 and 200 ', a polyethylene film (PE film), a mylar film, a polyethylene terephthalate (PET) film, a teflon film, a polyimide film, a polytetrafluoroethylene film And the like can be used.

The anode forming composition includes an anode catalyst, a first ion conductive material, and a first solvent. The composition for forming the cathode includes a cathode catalyst, a second ion conductive material, and a second solvent.

As the anode catalyst, a metal catalyst or a metal supported catalyst such as platinum or platinum-ruthenium may be used, and a metal catalyst or a metal supported catalyst such as platinum, platinum-cobalt or platinum-nickel may be used as the cathode catalyst. As a carrier used for the metal supported catalyst, solid particles having micropores that are conductive and can carry catalyst metal particles, such as carbon powder, may be used. Examples of the carbon powder include carbon black, ketjen black, acetylene black, activated carbon powder, carbon nanofiber powder, or a mixture thereof.

The first and second ion conductive materials include those described above, and for example, Nafion and similar polymer materials supplied by DuPont may be used. The first and second ion conductive materials are each dispersed in a first solvent. As the first and second solvents, water, ethylene glycol, isopropyl alcohol, polyalcohol, N-butyl alcohol, N-butyl acetate, or a mixture thereof may be used, respectively. Triton X-100 can be added to facilitate the injection of 2 ion conductive materials. The content of the first and second solvents may be 100 to 1,700 parts by weight based on 100 parts by weight of the catalyst, depending on the specific volume of the catalyst.

Next, the composition for forming the anode 102 is coated and dried on the first support layer 200 to obtain a first transfer film. At this time, the coating method is not particularly limited, and doctor blades, bar coatings, spin coatings, screen printing, and the like may all be used. The drying is carried out at a temperature of 50 to 160 ℃ to control the solvent residual ratio is 30% or less. By controlling the solvent residual ratio as described above, it is possible to prevent the electrode catalyst layer 102 and the electrolyte membrane 101 from being contaminated or weakening of the adhesion force between them.

The protective film (not shown) is covered on the electrode layer of the first transfer film and cut to a desired size, and then the protective film is removed and immediately disposed on one surface of the electrolyte membrane 101 to be bonded. Here, a release polyethylene terephthalate film may be used as the protective film.

Separately, the second transfer film is obtained by coating and drying the composition for forming the electrode catalyst layer 102 'on the second support layer 200'.

Next, the anode 102 of the first transfer film and the cathode 102 ′ of the second transfer film are disposed adjacent to one surface and the other surface of the electrolyte membrane 101, respectively, and the first transfer film and the second The transfer film is transferred onto one surface and the other surface of the electrolyte membrane 101, respectively. Subsequently, the first supporting film 200 and the second supporting film 200 'are peeled off from the resultant. The transfer of the first transfer film and the second transfer film may be performed simultaneously or separately.

The transfer of the first transfer film and the second transfer film may be performed by a thermocompression method or a roll-to-roll method. The thermocompression method is a method in which two or more objects are pressed together under high temperature. When the transfer is performed by such thermocompression method, the transfer conditions include a temperature of 100 to 160 ° C., a pressure of 1 to 300 kgf / cm ² , and 1 to A time period of 20 minutes is preferred. The roll-to-roll method is a method of attaching two or more objects by continuously passing between rollers.

Through the transfer process, a catalyst coating membrane (CCM) having a pair of electrode catalyst layers 102 and 102 ′ formed on one surface and the other surface of the electrolyte membrane 101 may be obtained.

The membrane electrode assembly according to the present invention can manufacture a fuel cell having improved performance such as cell voltage by increasing ion conductivity and reducing material transfer resistance between the electrolyte membrane and the electrode catalyst layer.

Hereinafter, although an Example is given and described this invention, this invention is not limited only to a following example.

Example 1

To prepare a composition for forming the cathode, a 10 wt% solution of Nafion having a equivalent weight (g / eq) of 1100, an ionic conductivity of 0.09 S / cm, and a water content of 25 wt% in a mixed solvent of 37 g of water and 19 g of 1-propanol. (Dupont, Nafion Dispersion, DE 1021) 19 g, 5 g of catalyst (45 wt% Pt / Ketjen black) and 4 g of Triton X-100 (20 wt%, solvent: deionized water) were added, and an ultrasonicator (Bransonic, Branson 8510) and Disperse homogeneously using a mill (Daihan Scienticfic. WiseMix ^™ ). Meanwhile, in order to prepare a composition for forming an anode, a 10 wt% Nafion solution having an equivalent weight (g / eq) of 1000, an ionic conductivity of 0.12 S / cm, and a water content of 27 wt% in a mixed solvent of 37 g of water and 19 g of 1-propanol. (Dupont, Nafion Dispersion, DE 1020) 19 g, 5 g of catalyst (45 wt% Pt / Ketjen Black) and 4 g of Triton X-100 (20 wt%, solvent: deionized water) were added, and an ultrasonicator (Bransonic, Branson 8510) and Disperse homogeneously using a mill (Daihan Scienticfic. WiseMix ^™ ).

Using the slit die coater (slit die coater) was applied to the transfer paper (SCK, SKC Skyrol ^® M30) on the transfer paper (SCK, SKC Skyrol ^® M30) at 0.25 mgPt / ㎠ based on the platinum catalyst to obtain a first transfer film. Thereafter, a composition for forming an cathode on the transfer paper was applied to the transfer sheet in the same manner as the first transfer film to prepare a second transfer film.

Subsequently, the first and second transfer films prepared above were simultaneously disposed adjacent to each other on one surface and the other surface of the NRE211 (Dupont, 25 μm thick) membrane, which is a polymer electrolyte membrane, and transferred under high temperature and high pressure to prepare a membrane electrode assembly. . Transfer conditions were 130 ℃, 120kgf / ㎠, 2 minutes 30 seconds.

In the membrane electrode assembly, the first transfer electrode is referred to as a fuel electrode, and the second transfer electrode is referred to as an air electrode.

Comparative Example 1

The membrane electrode assembly was manufactured in the same manner as in Example 1, except that the first and second ion conductive materials used in the anode and cathode formation compositions were all Nafion having an equivalent weight of 1100 g / eq.

Comparative Example 2

A membrane electrode assembly was manufactured in the same manner as in Example 1, except that both the first and second ion conductive materials used in the anode and cathode formation compositions were Nafion having an equivalent weight of 1000 g / eq.

Evaluation example

In order to test the unit cell performance of the membrane electrode assembly prepared in Example 1 and Comparative Examples 1 and 2, a gas diffusion layer (SGL 10BC, commercially available GDL, SGL Carbon Group) was adjacent to each of both surfaces of the prepared membrane electrode assembly. And assembled to unit cells. Maintain the temperature of the anode inlet / cell / electrode inlet at 65/65/65 ℃ and the pressure at atmospheric pressure and pressure difference (0 psig), respectively. Drive.

The unit cells according to Example 1 and Comparative Examples 1 and 2 were operated to investigate cell voltages according to current densities, and the results are shown in FIG. 3.

Referring to FIG. 3, it can be seen that the cell voltage characteristics of the unit cell of Example 1 are improved compared to those of Comparative Examples 1 and 2.

Although the preferred embodiments according to the present invention have been described above with reference to the drawings and the embodiments, these are merely exemplary, and various modifications and equivalent other embodiments are possible to those skilled in the art. You will understand. Therefore, the protection scope of the present invention should be defined by the appended claims.

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

2 is a view for explaining a method of manufacturing a membrane electrode assembly according to an embodiment of the present invention.

3 is a graph showing changes in cell voltage according to current density in fuel cells manufactured according to Example 1 and Comparative Examples 1 and 2 of the present invention.

<Explanation of symbols for the main parts of the drawings>

10, 100: membrane electrode assembly 11, 101: polymer electrolyte membrane

12, 12 ', 102, 102': electrode catalyst layer

Claims (13)

A fuel electrode containing a first ion conductive material; An air electrode containing a second ion conductive material; And an electrolyte membrane interposed between the fuel electrode and the air electrode, wherein the membrane electrode assembly for a fuel cell includes: And the ion conductivity of the anode is higher than that of the cathode, and the moisture content of the cathode is lower than that of the anode. The method of claim 1, The first ion conductive material and the second conductive material each independently include a perfluoro-based proton conductive polymer film, a sulfonated polysulfone copolymer, a sulfonated poly (ether-ketone) -based polymer, and a perfluorinated sulfonic acid group. At least one selected from the group consisting of a containing polymer, a sulfonated polyether ether ketone polymer, a polyimide polymer, a polystyrene polymer, a polysulfone polymer and a clay-sulfonated polysulfone nanocomposite Membrane electrode assembly, characterized in that. The method of claim 1, The ion conductivity of the first ion conductive material is 0.09 S / cm or more, the moisture content of the second ion conductive material is 40% by weight or less, characterized in that the membrane electrode assembly. The method of claim 1, An equivalent weight EW1 of the first ion conductive material and an equivalent weight EW2 of the second ion conductive material satisfy the following Equations 1 to 3: &Quot; (1) &quot; 800 g / eq ≤ EW1 ≤ 1100 g / eq, <Equation 2> 900 g / eq ≤ EW2 ≤ 1200 g / eq, <Equation 3> EW1 <EW2. The method of claim 1, Membrane electrode for fuel cell, characterized in that the weight ratio α ₁ of the first ion conductive material to the weight of the anode and the weight ratio content α ₂ of the second ion conductive material to the weight of the cathode satisfy the following Equations 4 to 6. Conjugate: <Equation 4> 25 wt% ≦ α ₁ ≦ 35 wt%. <Equation 5> 20 wt% ≤ α ₂ ≤ 33 wt% <Equation 6> α ₁ ≥ α _2. Forming a first transfer film by applying a composition for forming an anode including a cathode catalyst, a first ion conductive material, and a solvent on the first support film; Forming a second transfer film by applying a composition for forming an anode, the cathode including a cathode catalyst, a second ion conductive material, and a solvent, on a second support membrane; Transferring the first transfer film to one side of an electrolyte membrane; And Transferring the second transfer film to another side of the electrolyte membrane, The ion conductivity of the anode is higher than the ion conductivity of the cathode, the method of manufacturing the membrane electrode assembly is lower than the moisture content of the cathode. The method of claim 6, The first ion conductive material and the second ionic material each independently contain a perfluoro-based proton conductive polymer film, a sulfonated polysulfone copolymer, a sulfonated poly (ether-ketone) system, and a perfluorinated sulfonic acid group. Membrane characterized in that at least one selected from the group consisting of polymers, sulfonated polyether ether ketones, polyimides, polystyrenes, polysulfones and clay-sulfonated polysulfone nanocomposites Method for producing an electrode assembly. The method of claim 1, The ion conductivity of the first ion conductive material is 0.09 S / cm or more, the water content of the second ion conductive material is 40% or less method for producing a membrane electrode assembly. The method of claim 6, A method of manufacturing a membrane electrode assembly for a fuel cell, wherein the equivalent EW1 of the first ion conductive material and the equivalent EW2 of the second ion conductive material satisfy the following Equations 1 to 3. &Quot; (1) &quot; 800 g / eq ≤ EW1 ≤ 1100 g / eq, <Equation 2> 900 g / eq ≤ EW2 ≤ 1200 g / eq, <Equation 3> EW1 <EW2. The method of claim 6, Membrane electrode for fuel cell, characterized in that the weight ratio α ₁ of the first ion conductive material to the weight of the anode and the weight ratio content α ₂ of the second ion conductive material to the weight of the cathode satisfy the following Equations 4 to 6. Method of preparation of the conjugate: <Equation 4> 25 wt% ≦ α ₁ ≦ 35 wt%. <Equation 5> 20 wt% ≤ α ₂ ≤ 33 wt% <Equation 6> α ₁ ≥ α _2. The method of claim 6, The transferring of the first transfer film and the second transfer film is a method of manufacturing a membrane electrode assembly for a fuel cell, characterized in that made by a thermocompression method or a roll-to-roll method. The method of claim 6, Removing the first support film from the transferred first transfer film; And A method of manufacturing a membrane electrode assembly for a fuel cell, further comprising the step of removing the second support film from the transferred second transfer film. A fuel cell comprising the membrane electrode assembly according to any one of claims 1 to 5.

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