JP2013020753A - Method for correcting catalyst layer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a proper method for correcting a catalyst layer sheet, which produces a catalyst layer sheet that does not contain aggregate or a foreign substance and further prevents production of pinholes, and thereby realizes a membrane electrode assembly that suppresses deterioration in battery characteristics.SOLUTION: The method for correcting a catalyst layer sheet 23 that includes a base film 21 and a catalyst layer 22 provided at one face of the base film 21, and comprises the steps of: removing a part of the catalyst layer 22 by a predetermined amount, which contains aggregate or a foreign substance 24 therein, out of the catalyst layer 22; filling the removed part of the catalyst layer 22 with a correction ink 26; and drying the correction ink 26.

Description

  The present invention relates to a method for correcting a catalyst layer sheet suitable for use in a membrane electrode assembly for a polymer electrolyte fuel cell.

  As a method for producing a membrane electrode assembly for a polymer electrolyte fuel cell, a method in which a catalyst layer sheet provided with a catalyst layer on a base film is thermocompression bonded to a polymer electrolyte membrane is known. The method for producing a catalyst layer sheet is produced by applying a catalyst ink to a base film and drying it.

  In the catalyst layer of the catalyst sheet, catalyst agglomerates and foreign matters generated in the production process may be mixed. When the catalyst layer sheet with aggregates and foreign matters attached is thermocompression bonded to the polymer electrolyte membrane, the polymer electrolyte membrane is made thinner, and further, holes are made in the polymer electrolyte membrane, causing pinholes in the membrane electrode assembly. There is a risk of becoming. Such a pinhole of the membrane electrode assembly causes a decrease in battery performance.

  In addition, when aggregates or foreign matters are peeled off from the catalyst layer sheet before thermocompression bonding, the catalyst layer becomes a pinhole in which a hole is formed in the catalyst layer. A membrane / electrode assembly having a catalyst layer pinhole tends to cause deterioration of the polymer electrolyte membrane in the catalyst layer pinhole portion, which easily causes pinholes in the membrane / electrode assembly.

  FIG. 3 is a cross-sectional view illustrating a catalyst layer sheet in which aggregates or foreign substances are present. A catalyst layer sheet 33 having a catalyst layer 32 formed on one surface of the base film 31 may contain catalyst agglomerates or foreign matter 34 as shown in FIG. Since such agglomerates or foreign matters 34 are mostly embedded in the catalyst layer 32, when the aggregate or foreign matter 34 is peeled off from the catalyst layer sheet 33, as shown in FIG. There is a risk of pinholes 37 being generated. Here, the size of the aggregates or foreign matter 34 is often about several tens of μm to several hundreds of μm, and these aggregates or foreign matter 34 cause the pinhole 37.

  When a membrane electrode assembly is produced by thermocompression bonding a catalyst layer sheet 33 containing aggregates or foreign matter 34 as shown in FIG. 3A to a polymer electrolyte membrane not shown in FIG. If the polymer electrolyte membrane is thinned due to the insertion of 34 into the polymer electrolyte membrane and the foreign matter is larger than the thickness of the polymer electrolyte membrane, pinholes may occur in the polymer electrolyte membrane.

  On the other hand, when the membrane / electrode assembly is produced from the catalyst layer sheet of FIG. 3B from which the aggregates and foreign matter 34 have been peeled off, it is directly applied to the polymer electrolyte membrane as in the example shown in FIG. Although there is no damage, the polymer electrolyte membrane in the portion of the catalyst layer 32 where the pinhole 37 is present is likely to be deteriorated, causing a pinhole in the membrane electrode assembly.

  In order to prevent this, pinhole detection methods and correction methods for membrane electrode assemblies have been studied (for example, Patent Documents 1 and 2).

JP 2004-325346 A JP 2004-214089 A

  However, the methods of Patent Documents 1 and 2 are a method of detecting a pinhole of a membrane electrode assembly after it has occurred, and a method of filling the pinhole portion with a material other than a polymer electrolyte, It was not a method aimed at preventing the occurrence of pinholes.

  Therefore, the present invention provides a catalyst layer sheet that is free from aggregates and foreign matter and that prevents the generation of pinholes, and that can be used to achieve a membrane electrode assembly that prevents deterioration of battery characteristics. The purpose is to provide a simple correction method.

  As means for solving the above problems, the invention described in claim 1 is a method for correcting a catalyst layer sheet comprising a base film and a catalyst layer provided on one surface of the base film, Removing a predetermined amount of the catalyst layer including aggregates or foreign matters, filling the removed portion of the catalyst layer with correction ink, and drying the correction ink. It is a correction method of the catalyst layer sheet | seat characterized by providing.

  The invention according to claim 2 is characterized in that the correction ink contains a catalyst, a polymer electrolyte, and a solvent, and the solid content of the correction ink is 10% or more and 90% or less of the entire correction ink. The method for correcting a catalyst layer sheet according to claim 1.

  According to a third aspect of the present invention, in the step of filling the removed portion of the catalyst layer with the correction ink, the correction ink is applied to the removed portion of the catalyst layer while heating the catalyst layer sheet in advance. 3. The method for correcting a catalyst layer sheet according to claim 1, wherein the catalyst layer sheet is filled.

  Moreover, invention of Claim 4 is the membrane electrode assembly manufactured using the catalyst layer sheet | seat corrected by the method as described in any one of Claim 1 to 3.

  The invention according to claim 5 is a polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 4.

  According to the method for correcting a catalyst layer sheet of the present invention, it is possible to produce a catalyst layer sheet that is free from agglomerates and foreign matters and prevents the occurrence of pinholes. Holes can be prevented and battery performance degradation can be prevented. Moreover, since it can correct even if an aggregate and a foreign material generate | occur | produce in the manufacturing process of a catalyst layer sheet | seat, the yield of a catalyst layer sheet | seat can be improved. Further, by making the area of the catalyst layer to be removed constant in the step of removing aggregates and foreign matters, the amount of correction ink required in the step of arranging the correction ink can be made constant. It can be corrected accurately.

It is a figure showing the process of the correction method of the catalyst layer sheet which is one Embodiment of this invention. 1 is an exploded perspective view of a polymer electrolyte fuel cell to which an embodiment of the present invention can be applied. It is a figure explaining the catalyst layer sheet | seat with a catalyst aggregate or a foreign material.

  Embodiments of the present invention will be described below.

  First, a polymer electrolyte fuel cell using a membrane electrode assembly to which an embodiment of the present invention can be applied will be described. FIG. 2 is a schematic view showing a polymer electrolyte fuel cell 13 according to an embodiment of the present invention. As shown in FIG. 2, the polymer electrolyte fuel cell 13 according to this embodiment includes a membrane electrode assembly 12 having an electrode catalyst layer 2 and an electrode catalyst layer 3 on both surfaces of a polymer electrolyte membrane 1, and an electrode An air electrode side gas diffusion layer 4 and a fuel electrode side gas diffusion layer 5 are arranged to face the catalyst layer 2 and the electrode catalyst layer 3, and an air electrode 6 and a fuel electrode 7 are formed, respectively. The separator 10 is made of a material that is conductive and impermeable. The separator 10 includes a gas flow path 8 for gas flow and a cooling water flow path 9 for cooling water flow formed on a main surface opposite to the surface on which the gas flow path 8 is formed. As shown in FIG. 2, the separator 10 is disposed so as to sandwich the air electrode side gas diffusion layer 4 and the fuel electrode side gas diffusion layer 5. Fuel gas is supplied from the gas flow path 8 of the separator 10 on the fuel electrode 7 side. An example of the fuel gas is hydrogen gas. An oxidant gas is supplied from the gas flow path 8 of the separator 10 on the air electrode 6 side. As the oxidant gas, for example, a gas containing oxygen such as air is supplied.

  As shown in FIG. 2, the polymer electrolyte fuel cell 13 according to the present embodiment includes a set of separators 10, a polymer electrolyte membrane 1, an electrode catalyst layer 2, an electrode catalyst layer 3, and an air electrode side. This is a so-called single-cell solid polymer fuel cell 13 in which the gas diffusion layer 4 and the fuel electrode side gas diffusion layer 5 are sandwiched. However, in the present embodiment, it is also possible to employ a stacked stack structure in which a plurality of cells are stacked in series via the separator 10.

  FIG. 1 is a diagram for explaining a method for correcting a catalyst layer sheet according to an embodiment of the present invention. In the method for correcting a catalyst layer sheet according to the present embodiment, as shown in FIG. 1A, a catalyst layer sheet formed by forming a catalyst layer 22 on a base film 21 (in FIG. 1, representatively a catalyst layer sheet). 23)), a part of the catalyst layer including the aggregates or the foreign matter 24 is removed by a predetermined amount to obtain the state shown in FIG. By filling 26, the catalyst layer sheet 23 is corrected as shown in FIG.

  Here, the aggregate or foreign matter 24 is, for example, a catalyst aggregate contained in the catalyst layer 22, fibers, dust, metal particles, polymer pieces, or a base film mixed in the manufacturing process of the catalyst layer sheet 23. This refers to a minute protruding portion of the catalyst layer 23 that is generated when air bubbles enter between 21 and the catalyst layer 22.

  For removal of the agglomerates or foreign matter 24, if a rod-like instrument 25 having a sticky tip at the contact with the catalyst layer containing the agglomerate or foreign matter 24 to be removed is used, only the part to be removed can be removed. As for the rod-shaped instrument 25, it is desirable that the front-end | tip part is flat. If the tip is flat, the area of the contacting catalyst layer can be made constant by pressing against the catalyst layer. Further, the shape of the contact surface of the tip portion that contacts the catalyst layer containing the aggregate or foreign matter 24 to be removed may be any shape as long as the area of the contacting catalyst layer can be made constant, such as a circle or a rectangle. The tip of the rod-shaped instrument 25 is preferably large enough to remove agglomerates or foreign matters of several tens to several hundreds of μm. Specifically, it is desirable that the diameter or one side of the contact surface with the catalyst layer at the tip is a size of several hundred μm to several mm corresponding to about 10 times the size of the aggregate or foreign matter. However, if the contact area of the tip portion with the catalyst layer can be accurately matched with the area of the catalyst layer containing the aggregate or foreign matter 24 to be removed, the diameter or one side of the contact surface with the catalyst layer of the tip portion is: It may be in the range of about 2 to 10 times the size of the aggregate or foreign matter. If such a device is used to remove the agglomerate or foreign matter 24 and the catalyst layer around it, the agglomerate or foreign matter can be reliably removed. In addition, since a part of the catalyst layer including aggregates or foreign matters can be removed by a predetermined amount, the pinhole 27 portion of the catalyst layer after removing the aggregates or foreign matters 24 has a predetermined volume. be able to.

  The removal of the aggregate or foreign matter 24 is not particularly limited as long as it is a means capable of removing a predetermined amount of the catalyst layer including the aggregate or foreign matter in addition to the rod-shaped instrument 25 described above. Here, the predetermined amount for removing a part of the catalyst layer is determined by the size of aggregates or foreign substances contained in the catalyst layer, and specifically, the contact of the tip of the rod-shaped instrument 25 with the catalyst layer. It is theoretically calculated from the area and the thickness of the catalyst layer.

  The material of the tip of the rod-shaped instrument 25 is not particularly limited as long as it is a material having such a degree of adhesive that it can remove the aggregates or foreign matter 24 and the surrounding catalyst layer, but an adhesive or a tacky rubber is used. Good to do. Specifically, rubber-based, acrylic-based, silicon-based, urethane-based materials, and the like can be given.

  The pinhole 27 portion of the catalyst layer formed after the aggregate or foreign matter 24 and the surrounding catalyst layer are removed by the rod-shaped instrument 25 is filled with the correction ink 26 by a known method such as a microdispenser or a micropipette. . Thereafter, when the filled correction ink 26 is dried, the corrected catalyst layer sheet 23 can be manufactured.

  The amount of the correction ink 26 filled in the pinhole 27 portion of the catalyst layer does not protrude from the catalyst layer 22 when dried, so that the volume of the correction ink 26 is less than the pinhole 27 of the catalyst layer when the correction ink 26 is dried. It needs to be adjusted. If the size of the contact surface of the tip portion in contact with the catalyst layer containing the aggregates or foreign matter 24 to be removed in the rod-shaped instrument 25 is made constant, the area of the contacted catalyst layer becomes constant. The correction ink 26 necessary for filling the 27 portions can always be a constant amount.

  On the other hand, when the correction ink 26 is filled in the pinhole portion of the catalyst layer formed by removing only the aggregates or foreign matters in the catalyst layer and removing the aggregates or foreign matters, the size of each pinhole portion is large. Accordingly, a predetermined amount of the correction ink 26 must be filled. As a result, when the correction ink 26 is less than the predetermined amount, it is not preferable because the pinhole portion of the catalyst layer cannot be covered. Further, when the amount of the correction ink 26 is larger than the predetermined amount, it is not preferable because it protrudes from the catalyst layer surface, and the protruding portion causes the polymer electrolyte membrane to be thinned.

  The correction ink 26 includes at least a catalyst, a polymer electrolyte, and a solvent, and the solid content thereof is preferably 10% or more and 90% or less, and more preferably 20% or more and 70% or less of the entire correction ink. If the solid content is less than 10%, the solvent content is large, and the nearby catalyst layer may be dissolved by the solvent of the correction ink. On the other hand, when the solid content is larger than 90%, the viscosity of the correction ink becomes high and it is difficult to fill a predetermined amount, which is not preferable.

  The correction ink filled in the pinhole 27 portion of the catalyst layer is dried by heating. When the correction ink 26 has a low solid content and a high solvent content, the surrounding catalyst layer may be dissolved and the thickness of the catalyst layer may become non-uniform. Therefore, the correction ink 26 is heated while heating the catalyst layer sheet 23 in advance. It is desirable to remove the solvent immediately after filling. The heating temperature when drying is preferably in the range of 60 ° C to 150 ° C.

  Any heating means may be used as long as the portion filled with the correction ink 26 can be heated. For example, a method of installing a heating device such as a heater on the surface of the base film 21 opposite to the catalyst layer 22 or a method of installing a heater in the space of the catalyst layer 22 opposite to the base film 21 may be used.

  The correction ink 26 is adjusted to have the same composition as the catalyst layer 22 after being dried. The correction ink 26 can be manufactured by mixing a catalyst, a polymer electrolyte, and a solvent and applying a dispersion treatment. Examples of the dispersion method include ball mill, bead mill, roll mill, shear mill, wet mill, ultrasonic dispersion treatment, and homogenizer.

  As the catalyst contained in the catalyst layer 22 and the correction ink 26, a catalyst in which a catalyst substance is supported on carbon can be used. Catalyst materials include platinum, palladium, ruthenium, iridium, rhodium, osmium, platinum group elements, and other metals such as iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum. Alternatively, alloys thereof, oxides, double oxides, or the like can be used. Any carbon particles can be used as long as they are in the form of fine particles, have conductivity and are not affected by the catalyst, but carbon black, graphite, graphite, activated carbon, carbon fiber, carbon nanotube, and fullerene are used. it can.

  The solvent of the correction ink 26 may be any solvent that can dissolve or disperse the polymer electrolyte and the catalyst. Specifically, water, methanol, ethanol, 1-propanol, 2-propanol 1-butanol, isobutyl alcohol, tert-butyl alcohol, pentanol, ethylene glycol, diacetone alcohol, 1-methoxy-2-propanol, etc. Examples include alcohols, acetone, methyl ethyl ketone, pentanone, methyl isobutyl ketone, diisobutyl ketone and other ketones, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and the like. Among these, the solvent of the correction ink 26 is preferably one that can be easily removed by heating, and the boiling point is preferably 150 ° C. or lower.

  The polymer electrolyte contained in the catalyst layer 22 and the catalyst ink 26 may be any polymer electrolyte as long as it has proton conductivity. For example, a fluorine polymer electrolyte or a hydrocarbon polymer electrolyte can be used. As the fluorine-based polymer electrolyte, for example, Nafion (registered trademark) manufactured by DuPont, Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd., Aciplex (registered trademark) manufactured by Asahi Kasei Co., Ltd., or the like can be used. As the hydrocarbon polymer electrolyte, electrolytes such as sulfonated polyetherketone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, sulfonated polysulfide, and sulfonated polyphenylene can be used.

  The polymer electrolyte membrane 1 of the membrane electrode assembly of the present invention can also be used as the polymer electrolyte membrane.

  The base film 21 may be made of a material having good transferability. For example, ethylene tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroperfluoroalkyl vinyl ether copolymer Fluorine resins such as coalescence (PFA) and polytetrafluoroethylene (PTFE) can be used. Polymer films such as polyimide, polyethylene terephthalate, polyamide (nylon), polysulfone, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyetherimide, polyarylate, and polyethylene naphthalate can also be used. You may use what processed the release layer etc. to these base materials.

<Preparation of catalyst layer ink>
A platinum-supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and a 20% by mass polymer electrolyte solution (Nafion: registered trademark, manufactured by Dupont) are mixed with a mixed solvent of water and ethanol. Dispersion treatment was performed to prepare a catalyst ink. The catalyst ink was coated on a PTFE film using an applicator and dried in an oven at 80 ° C. to prepare a catalyst layer sheet. In the application of the catalyst ink, the applicator was adjusted so that the thickness of the dried catalyst layer was 20 μm. It was confirmed that the catalyst layer of the catalyst layer sheet had catalyst aggregates and foreign matters having a size of about 200 μm.

<Production of correction ink>
A platinum-supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) and a 20% by mass polymer electrolyte solution (Nafion: registered trademark, manufactured by Dupont) are mixed with a mixed solvent of water and ethanol. Dispersion treatment was performed to prepare a correction ink. The weight ratio of platinum-supporting carbon and polymer electrolyte was the same as that of the catalyst layer ink. The weight ratio of the solid content of the correction ink was 20%.

<Example>
<Modification of catalyst layer sheet>
Using a pen with a circular adhesive with an area of 1 square mm at the tip, aggregates and foreign matters on the catalyst layer and the surrounding catalyst layer were transferred to the pen adhesive and removed from the catalyst layer. The volume removed at this time was 0.02 cubic mm. Place the catalyst layer sheet in the oven with the surface of the base film in contact, and heat at 80 ° C., remove the foreign matter and remove the catalyst layer, and use the micro dispenser to remove the catalyst layer. A fixed amount of correction ink was introduced so as to coincide with the above, and the solvent was dried to correct the portion where there were aggregates and foreign matters.

<Comparative example>
<Modification of catalyst layer sheet>
Using a pen with a spherical adhesive at the tip (the tip area during crimping is approximately 0.1 to 0.5 square mm), the agglomerates and foreign matter on the catalyst layer and the surrounding catalyst layer are adhered to the pen. It moved to the material and removed from the catalyst layer. Place the catalyst layer sheet in the oven in contact with the surface of the base film and heat it at 80 ° C, remove the foreign matter, remove the catalyst layer, and use a micro dispenser to correct the fixed amount Ink was introduced and the solvent was dried to correct the areas where there were aggregates and foreign matter.

<Preparation of membrane electrode assembly>
Membrane electrode assemblies were prepared from the catalyst layer sheets of the examples and comparative examples. Nafion 211 (registered trademark, manufactured by Dupont) was used as the polymer electrolyte membrane. A catalyst layer sheet was placed on both sides of the polymer electrolyte membrane, and the substrate film was peeled off by pressurizing at 150 ° C. for 5 minutes with a hydraulic hot press to prepare a membrane electrode assembly.

  The cross section of the part where the aggregates and foreign matter were present in the membrane electrode assembly produced from the catalyst layer sheet of the example and the membrane electrode assembly produced from the catalyst layer sheet of the comparative example was observed by SEM. In the cross section of the membrane electrode assembly produced from the catalyst layer sheet of Comparative Example 1, it was confirmed that the polymer electrolyte membrane was crushed and made thinner than the other portions because the corrected ink had a portion protruding from the catalyst layer surface. did. In the membrane / electrode assembly produced from the catalyst layer sheet of Example 1, it was confirmed that the correction ink did not protrude from the catalyst layer surface and the polymer electrolyte membrane was not thinned.

  When the membrane / electrode assembly produced from the catalyst layer sheet of the present invention is used in a polymer electrolyte fuel cell, pinholes are less likely to occur and problems in long-term durability are less likely to occur. Therefore, the present invention can be suitably used for a fuel cell using a polymer electrolyte membrane, particularly a stationary cogeneration system and a fuel cell vehicle.

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte membrane 2, 3 Electrode catalyst layer 4 Air electrode side gas diffusion layer 5 Fuel electrode side gas diffusion layer 6 Air electrode 7 Fuel electrode 8 Gas flow path 9 Cooling water flow path 10 Separator 12 Membrane electrode assembly 13 Solid polymer Fuel cell 21, 31 Base film 22, 32 Catalyst layer 23, 33 Catalyst layer sheet 24, 34 Aggregate or foreign matter 25 Bar-shaped device 26 Correction ink 27, 37 Pinhole of catalyst layer

Claims (5)

A method for correcting a catalyst layer sheet comprising a base film and a catalyst layer provided on one surface of the base film,
Removing a part of the catalyst layer containing aggregates or foreign matters by a predetermined amount;
Filling the removed portion of the catalyst layer with a correction ink;
A method of correcting the catalyst layer sheet, comprising the step of drying the correction ink.   The catalyst layer sheet according to claim 1, wherein the correction ink includes a catalyst, a polymer electrolyte, and a solvent, and the solid content of the correction ink is 10% or more and 90% or less of the entire correction ink. How to fix.   2. The step of filling the removed portion of the catalyst layer with the correction ink includes filling the removed portion of the catalyst layer with the correction ink while heating the catalyst layer sheet in advance. 3. A method for correcting a catalyst layer sheet according to 2.   The membrane electrode assembly manufactured using the catalyst layer sheet | seat corrected by the method as described in any one of Claim 1 to 3.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 4.

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