KR20070041070A - Method of preparing catalyst coated membrane using mask - Google Patents

Abstract

The present invention provides a method comprising the steps of: (a) providing a mask comprising a masking film layer and a pressure-sensitive adhesive layer, having a pattern in which portions to be catalytically coated are removed; (b) attaching the mask such that the pressure-sensitive adhesive layer of the mask is located on one or both surfaces of the electrolyte membrane; (c) coating the catalyst ink on the removed portion of the mask to form a catalyst layer; And (d) relates to a method for producing a catalyst coated membrane (CCM) comprising the step of removing the mask and a fuel cell comprising a catalyst coated membrane produced thereby.

According to the present invention, by attaching to the electrolyte membrane using a mask consisting of a masking film layer and a pressure-sensitive adhesive layer while having a pattern in which the portion to be coated with the catalyst is removed, the catalyst is coated, thereby preventing swelling of the electrolyte membrane that may occur during catalyst coating. In addition, a catalyst coated membrane (CCM) can be easily produced in a desired membrane region without a complicated step, and a fuel cell including the same can be obtained.

Fuel cell, catalyst coated membrane, electrolyte membrane, masking film, adhesive

Description

Method for producing catalyst coated membrane using mask {METHOD OF PREPARING CATALYST COATED MEMBRANE USING MASK}

1 is a three-dimensional view for explaining a process for producing a catalyst coated membrane according to an embodiment of the present invention.

2 is a photograph of a catalyst coated membrane prepared according to Example 1 of the present invention.

3 is a graph showing a potential change of a unit cell according to current density in a PEMFC fuel cell manufactured according to Example 2 of the present invention.

The present invention relates to a method for producing a catalyst coated membrane (CCM) using a mask and a fuel cell comprising the catalyst coated membrane produced thereby.

A fuel cell is a new power generation method that generates electric power by using hydrogen or methanol as fuel and oxygen or air as oxidant and using electrons generated during the redox reaction.

The unit cell structure of such a fuel cell has a structure in which anodes and cathodes are formed on both sides of an electrolyte membrane made of a polymer material, which is called a MEA (Membrane Electrode Assembly). In the anode, hydrogen or methanol, which is a fuel, is supplied and reacts on the electrode catalyst to generate hydrogen ions (H +). In the cathode, hydrogen ions and oxygen that pass through the polymer electrolyte membrane combine to generate pure water.

In the fuel cell, there are two methods for forming an anode and a cathode in a polymer electrolyte membrane.

First, the electrode is formed on the gas diffusion layer by coating the catalyst ink on a gas diffusion layer (GDL), that is, a porous carbon paper or carbon fiber cloth. Thereafter, the electrode-coated gas diffusion layer and the electrolyte membrane are pressurized with heat to prepare a membrane-electrode assembly. In the membrane-electrode-assembly prepared in this manner, the contact between the electrolyte membrane and the catalyst layer may be insufficient, resulting in a problem of increasing interfacial resistance.

Secondly, the electrode is formed on the electrolyte membrane by coating the catalyst ink on the surface of the membrane. Using this method ensures ionic contact between the electrolyte membrane and the catalyst layer as compared to the first method, which can provide more improved performance, but is generally more difficult to manufacture. Various methods have been developed for spraying catalyst ink onto the surface of the membrane, such as spraying, painting, patch coating and screen printing. However, these methods are generally slow and can cause swelling of the membrane by a large amount of solvent in the catalyst ink during manufacture, resulting in a problem of changing the size of the membrane and consequently making a good electrode.

The present invention has a pattern in which the portion to be coated with the catalyst is removed, and is attached to the electrolyte membrane using a mask composed of a masking film layer and an adhesive layer and then coated with the catalyst, thereby preventing swelling of the electrolyte membrane that can occur during catalyst coating. It is an object of the present invention to provide a method for preparing a catalyst coated membrane which can be coated on the membrane area. It is also an object of the present invention to provide a fuel cell comprising a catalyst coated membrane prepared by the above method.

The present invention provides a method comprising the steps of: (a) providing a mask comprising a masking film layer and a pressure-sensitive adhesive layer, having a pattern in which portions to be catalytically coated are removed; (b) attaching the mask such that the pressure-sensitive adhesive layer of the mask is located on one or both surfaces of the electrolyte membrane; (c) coating the catalyst ink on the removed portion of the mask to form a catalyst layer; And (d) provides a fuel cell comprising a method for producing a catalyst coated membrane (CCM) comprising the step of removing the mask and the catalyst coated membrane produced thereby.

The present invention provides a mask for a catalyst coating composed of a masking film layer and an adhesive layer and attachable to an electrolyte membrane, which prevents swelling of the electrolyte membrane.

In addition, the present invention is a composite consisting of a mask and an electrolyte membrane, the mask is composed of a masking film layer and the pressure-sensitive adhesive layer, having a pattern to remove the portion to be catalyst coated, the pressure-sensitive adhesive of the mask on one side or both sides of the electrolyte membrane Provided is a composite for catalytic coating of an electrolyte membrane, characterized in that the layer is located.

Hereinafter, the present invention will be described in detail.

In general, when the catalyst ink is directly coated on the electrolyte membrane, the electrolyte membrane swells due to the solvent in the catalyst ink, which changes the size of the membrane and the catalyst coating cannot be made well, resulting in difficulty in making a good electrode. Therefore, in order to prevent swelling of the electrolyte membrane during coating, a support of the electrolyte membrane is separately used.

However, the manufacturing method of the present invention is characterized in that the mask is attached to the electrolyte membrane and coated so that swelling of the electrolyte membrane can be prevented without supporting the electrolyte membrane. That is, the mask used when preparing the catalyst coated membrane of the present invention not only serves as a mask but also serves as a support for the electrolyte membrane.

Accordingly, the mask of the present invention is a mask composed of a masking film layer and an adhesive layer, which is attachable to the electrolyte membrane, and is a mask for catalyst coating of the electrolyte membrane to prevent swelling of the electrolyte membrane. The mask is used having a pattern in which the portion to be catalyst coated is removed.

Specifically, the mask of the present invention serves as a mask in the catalyst coating, so that the coating is well made in a certain area. On the other hand, the mask is composed of a masking film layer and a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer to maintain the proper adhesion between the masking film layer and the electrolyte membrane, the masking film layer to prevent the swelling of the membrane form to maintain the shape of the membrane It serves as a support. In particular, when a mask composed of a masking film layer and an adhesive layer is attached to both surfaces of the electrolyte membrane, the supporting force as a support that can prevent swelling of the electrolyte membrane during coating becomes even larger. Therefore, according to the manufacturing method of the present invention, the catalyst coating can be made well by preventing swelling of the electrolyte membrane during catalyst coating, and as a result, it is possible to manufacture the excellent electrode.

1 is a three-dimensional view for explaining a process for producing a catalyst coated membrane according to an embodiment of the present invention.

In order to produce the catalyst coated membrane of the present invention, first, a mask composed of a masking film layer and an adhesive layer is provided, having a pattern in which a portion to be coated with the catalyst is removed.

Removal of the portion to be catalyst coated can be removed by punching (punching) in the mold.

Next, the mask is attached so that the pressure-sensitive adhesive layer of the mask is located on one side or both sides of the electrolyte membrane. Therefore, as a composite composed of a mask and an electrolyte membrane, the mask is composed of a masking film layer and a pressure-sensitive adhesive layer, having a pattern in which the portion to be catalyst coated is removed, and the pressure-sensitive adhesive layer of the mask is located on one side or both sides of the electrolyte membrane. Composites can be prepared for catalytic coating of the characteristic electrolyte membrane. FIG. 1 shows the formation of a composite consisting of a masking film layer-adhesive layer-electrolyte membrane-adhesive layer-masking film layer by attaching a mask to both sides of the electrolyte membrane.

Then, the catalyst layer is introduced by coating the catalyst ink on the removed portion of the mask attached to one side or both sides of the electrolyte membrane, and FIG. 1 shows that the catalyst layer is formed on both sides of the electrolyte membrane.

After forming the catalyst layer, a catalyst coated membrane may be prepared by removing a mask attached to one or both surfaces of the electrolyte membrane. When the mask is removed, the masking film layer and the pressure-sensitive adhesive layer may be removed together to prepare a membrane coated with a catalyst on one or both sides of the electrolyte membrane. According to FIG. 1, a membrane coated with both sides of the electrolyte membrane may be prepared.

Masking film in the present invention may be made of one or more selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyester, polyethylene, polypropylene, polycarbonate, polyamide and polyimide.

The masking film layer can be used having a thickness of 10 to 150 microns. Preferably it can be used with a thickness of about 40 to 80 microns. If the thickness of the masking film layer is less than 10 microns, the supporting force for preventing swelling of the electrolyte membrane is insignificant and the catalyst coating cannot be performed well. On the other hand, the larger the thickness of the masking film layer, the larger the bearing capacity, but if it exceeds 150 microns, there is a problem that the operation becomes difficult when masking the film.

In the present invention, the pressure-sensitive adhesive may be made of one or more selected from the group consisting of silicone resins, acrylic resins, urethane resins, epoxy resins and rubbers, but is preferably made of silicone resins in terms of heat resistance and chemical stability.

The pressure-sensitive adhesive layer may be used having a thickness of 2 to 50 microns. Preferably it can be used in a thickness of about 10 to 20 microns. If the thickness of the pressure-sensitive adhesive layer is less than 2 microns, there is an advantage in that it is easy to remove the masking film after the coating process, but there is a disadvantage in that the adhesion between the electrolyte membrane and the masking film cannot be maintained during the coating process and thus a clean edge surface cannot be obtained. On the other hand, if the thickness of the pressure-sensitive adhesive layer exceeds 50 microns, the adhesive force is too strong may cause a problem of damaging the electrolyte membrane when removing the mask consisting of the masking film layer and the pressure-sensitive adhesive layer.

The total thickness of the mask can be used to be 30 to 200 microns. The thinner the masking film, the weaker the support to prevent swelling of the electrolyte membrane, and the thickness of the pressure-sensitive adhesive layer should be thicker than a certain amount to compensate for this. To 100 microns is preferred.

In the present invention, the electrolyte membrane may use a polymer electrolyte membrane. Electrolyte membranes include perfluorosulfonic acid polymers, hydrocarbon-based polymers, polyimides, polyvinylidene fluorides, polyethersulfones, polyphenylenesulfides, polyphenylene oxides, polyphosphazines, polyethylene naphthalates, polyesters, doped polybenzimes It may be composed of one or more selected from the group consisting of doazole, polyether ketone, polysulfone, acid or base thereof.

In addition, the catalyst coating in the present invention may be made by coating the catalyst ink directly. At this time, the coating method of the catalyst ink is not particularly limited, but spray coating, tape casting, screen printing, blade coating, die coating or spin coating may be used.

The catalyst ink may consist of a catalyst, a polymer ionomer and a solvent.

Available catalyst materials are platinum black (Pt black), platinum-ruthenium black (Pt-Ru Black), or platinum-supported carbon catalyst (Pt / C), platinum ruthenium-supported carbon catalyst, platinum-molybdenum black (Pt- Mo), platinum-molybdenum (Pt-Mo) supported carbon catalyst, platinum-rhodium (Pt-Rh) black, platinum-rhodium supported carbon catalyst, and other alloy catalysts based on platinum.

It is preferable to use Pt-Ru or Pt-Ru / C as an anode catalyst and Pt or Pt / C as a catalyst for cathodes.

The catalyst particles may be dispersed in carbon particles or composed of platinum or alloy black.

Polymer ionomers provide a pathway for the transport of ions produced by the reaction between fuels such as hydrogen or methanol to the catalyst to the electrolyte membrane, including but not limited to nafion ionomers, sulfonated polytrifluorostyrene Sulfonated polymers such as

The use ratio of the polymer ionomer is preferably 5 to 30 parts by weight based on 100 parts by weight of the catalyst used. When the polymer ionomer is used at less than 5 parts by weight, the ion transport passage in the catalyst layer is not properly formed and the movement of ions formed by the catalytic reaction is not smooth. On the other hand, if the amount exceeds 30 parts by weight, the ionomer covers the catalyst layer, so that the reaction between the catalyst and the fuel is not easy.

Non-limiting examples of solvents that can be used include water, butanol, IPA (iso propanol), methanol, ethanol, n-propanol, n-butyl acetate, ethylene glycol, etc., these solvents alone or in combination of two or more Can be used. It is preferable to use the same solvent for the anode and the solvent for the cathode.

The proportion of the solvent in the catalyst ink is preferably 100 to 5000 parts by weight based on 100 parts by weight of the catalyst used. If the amount of the solvent used is less than 100 parts by weight, the viscosity of the catalyst ink becomes so high that the dispersibility of the catalyst particles during coating decreases and formation of a uniform catalyst layer is difficult. On the other hand, if the amount exceeds 5000 parts by weight, the viscosity of the catalyst ink is so low that the thickness of the catalyst layer to be coated at one time is too thin, coating must be repeated several times, resulting in poor productivity.

The mixture of a catalyst, a polymer ionomer, a solvent and the like is stirred using a high speed mixer, a mechanical stirrer, an ultrasonic wave or the like to prepare a catalyst slurry in which catalyst particles are uniformly dispersed.

After the catalyst layer is formed, it is preferable to go through a drying process at 20 to 90 ℃, especially 25 ~ 30 ℃.

In the present invention, the thickness of the catalyst layer is preferably 1 to 60 microns after drying. If the thickness is less than 1 micron, a uniform catalyst layer may not be formed, which may result in a decrease in durability due to the lack of a catalytic amount. If the thickness exceeds 60 microns, the catalyst layer becomes so thick that diffusion of the gas supplied to the catalyst layer becomes difficult and the progress of the reaction becomes difficult.

Catalyst coated membranes (CCM) made by the process of the present invention can be used to form membrane-electrode-assemblies (MEAs). That is, the gas diffusion layer (GDL) may be introduced and used in the prepared catalyst coated membrane.

The substrate for the gas diffusion layer may be any conventional one used in a fuel cell, and non-limiting examples include a carbon woven fabric, a nonwoven carbon fiber layer or a carbon fiber paper. The gas diffusion layer can be treated to be hydrophobic and can include additional carbon black micro layers and catalyst layers as needed.

The introduction of the gas diffusion layer into the catalyst coated electrolyte membrane can be carried out by conventional methods known in the art. For example, thermal pressurization can be used.

In addition, the fuel cell of the present invention may comprise a catalyst coated membrane prepared according to the method of the present invention. That is, the fuel cell may be configured to include a membrane-electrode-assembly using a catalyst coated membrane. The fuel cell may be a polymer electrolyte membrane fuel cell (PEMFC) or a direct methanol fuel cell (DMFC).

Hereinafter, preferred examples are provided to help understanding of the present invention. However, the following examples are only to illustrate the present invention more easily, the present invention is not limited by the following examples.

Example 1 Preparation of Catalyst Coated Membrane (CCM )

The masking film layer was made of polyethylene terephthalate having a thickness of 75 microns and the silicone layer having a thickness of 15 microns. The adhesive layer was then punched and removed from the mold by attaching the catalyst coating (25 cm 2) to the catalyst coating. To prepare a mask.

As the electrolyte membrane, a Nafion membrane (Nafion 112) manufactured by DuPont, a perfluorosulfonic acid polymer, was used. The mask was attached to both sides of the electrolyte membrane so that the pressure-sensitive adhesive layer of the mask was positioned to prepare a composite for catalyst coating of the electrolyte membrane.

In order to prepare a catalyst ink, a platinum supported carbon catalyst (Pt / C) was used as an anode and a cathode catalyst. Nafion solution, IPA, water were mixed and mixed with the catalyst to make a catalyst: nafion dry weight: solvent = 1: 0.3: 20, then stirred to disperse well, and then through a high speed mixer (2 hours) The catalyst ink was prepared by mixing uniformly.

By spraying the prepared catalyst ink on the portion removed for the catalyst coating of the mask by using a spray coater, a catalyst layer was formed on each side of the electrolyte membrane (anode and cathode) by 0.4 mg / cm 2, respectively. After that, a solution prepared by mixing Nafion and isopropanol (IPA) in a ratio of 1: 1 on the surface of the catalyst layer was applied. Then, the catalyst coated membrane (CCM) of the present invention shown in FIG. 2 was prepared by removing the masks attached to both sides of the electrolyte membrane.

Unlike the conventional method of fixing with a jig and coating the catalyst ink for a long time to prevent the expansion of the electrolyte membrane, the catalyst coated membrane (CCM) prepared according to Example 1 of the present invention is tacky as shown in FIG. By using this mask, it was possible to cleanly coat the catalyst ink quickly while suppressing swelling of the electrolyte membrane.

(Example 2: Preparation of Electrolyte-electrode Assembly Using Catalyst Coated Membrane and Performance Measurement of Unit Cell )

A gas distribution layer (hydrophobized carbon paper) supplied from SGL was applied to both surfaces of the catalyst coated membrane (CCM) prepared in Example 1 and installed in a PEM single cell. For negative electrode with 300μm gasket for maintaining gas tightness around membrane-electrolyte assembly (MEA), close to polymer electrolyte part except electrode part, flow path for supplying hydrogen and uniform pressure to MEA A unit cell was manufactured by closely contacting a plate with a plate for positive electrode for injecting air and giving uniform pressure to the MEA.

Using the prepared unit cell, the potential change of the unit cell according to the current density was measured, and the result is shown in FIG. It was tested under the influence of hydrogen / air at a cell temperature of 70 ° C. and an operating pressure of 2 bar. The gas stoichiometry was 1.2 (anode gas) and 2.4 (cathode gas).

According to Figure 3, the fuel cell employing a catalyst coated membrane (CCM) prepared according to Example 1 of the present invention showed a high performance of 0.55W / ㎠ or more at 0.6V for a long time.

According to the present invention, by attaching to the electrolyte membrane using a mask consisting of a masking film layer and a pressure-sensitive adhesive layer while having a pattern in which the portion to be coated with the catalyst is removed, the catalyst is coated, thereby preventing swelling of the electrolyte membrane that may occur during catalyst coating. In addition, a catalyst coated membrane (CCM) can be easily produced in a desired membrane region without a complicated step, and a fuel cell including the same can be obtained.

Claims (17)

(a) providing a mask consisting of a masking film layer and an adhesive layer, with a pattern having portions removed from the catalyst coating; (b) attaching the mask such that the pressure-sensitive adhesive layer of the mask is located on one or both surfaces of the electrolyte membrane; (c) coating the catalyst ink on the removed portion of the mask to form a catalyst layer; And (d) removing the mask; The catalyst coating of claim 1, wherein the masking film comprises at least one member selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyester, polyethylene, polypropylene, polycarbonate, polyamide, and polyimide. Method for preparing membranes. The method of claim 1 wherein the masking film layer is 10 to 150 microns thick. The method of claim 1, wherein the pressure-sensitive adhesive is made of a silicone resin. The method of claim 1, wherein the pressure-sensitive adhesive layer is 2 to 50 microns thick. The method of claim 1, wherein the mask has a total thickness of 30 to 200 microns. The method of claim 1, wherein the electrolyte membrane is a perfluorosulfonic acid polymer, a hydrocarbon-based polymer, polyimide, polyvinylidene fluoride, polyethersulfone, polyphenylene sulfide, polyphenylene oxide, polyphosphazine, polyethylene naphthalate, poly A process for preparing a catalyst coated membrane, characterized in that it comprises one or more selected from the group consisting of esters, doped polybenzimidazoles, polyetherketones, polysulfones, acids or bases thereof. A catalyst coated membrane prepared by the method of any one of claims 1 to 7. A fuel cell comprising a catalyst coated membrane prepared by the method of claim 1. 10. The fuel cell of claim 9, wherein the fuel cell is a polymer electrolyte membrane fuel cell (PEMFC) or a direct methanol fuel cell (DMFC). A mask comprising a masking film layer and an adhesive layer and attachable to an electrolyte membrane, wherein the mask for catalyst coating of the electrolyte membrane prevents swelling of the electrolyte membrane. 12. The catalyst coating mask of claim 11, wherein the mask has a pattern in which portions to be catalyst coated are removed. The method of claim 11, wherein the masking film of the electrolyte membrane, characterized in that consisting of at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyester, polyethylene, polypropylene, polycarbonate, polyamide and polyimide. Mask for catalyst coating. 12. The mask of claim 11, wherein the masking film layer has a thickness of 10 to 150 microns. 12. The mask for catalyst coating of an electrolyte membrane according to claim 11, wherein the pressure-sensitive adhesive is made of a silicone resin. 12. The mask of claim 11, wherein the pressure sensitive adhesive layer has a thickness of 2 to 50 microns. A composite comprising a mask and an electrolyte membrane, wherein the mask has a pattern in which portions to be catalyst coated are removed, and is composed of a masking film layer and an adhesive layer, and an adhesive layer of the mask is positioned on one or both surfaces of the electrolyte membrane. Composite for catalyst coating of electrolyte membrane.

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