JP5958597B2 - Method for producing membrane electrode assembly for polymer electrolyte fuel cell, method for producing polymer electrolyte fuel cell unit cell, and method for producing polymer electrolyte fuel cell stack - Google Patents

Description

  The present invention relates to a membrane electrode assembly for a polymer electrolyte fuel cell, a method for producing the membrane electrode assembly, a solid polymer fuel cell single cell using the membrane electrode assembly, and the polymer electrolyte fuel cell The present invention relates to a polymer electrolyte fuel cell stack using a single cell.

  A fuel cell is a power generation device that generates electricity by converting chemical energy into electric energy by electrochemically reacting a fuel gas such as hydrogen and an oxidant gas such as air, and has high efficiency and low environmental impact. Have advantages such as. Among them, a polymer electrolyte fuel cell using a polymer as an electrolyte is expected to be used as a power source for home use or on-vehicle use because it can operate at a low temperature.

  A polymer electrolyte fuel cell includes a membrane electrode assembly in which electrodes are provided on both sides of a polymer electrolyte membrane. As a method for producing this membrane electrode assembly, a catalyst ink in which catalyst particles, a conductive substance in contact with the catalyst particles, and a polymer electrolyte are dispersed in a solvent is applied onto a transfer sheet used as a substrate, and dried. And forming an electrode catalyst layer and hot pressing the electrode catalyst layer on the transfer sheet to bond the electrode catalyst layers to both surfaces of the polymer electrolyte membrane.

  In addition, using a gas diffusion layer as a base material, applying a catalyst ink on the gas diffusion layer, drying, hot pressing the gas diffusion layer on which the electrode catalyst layer is formed on the polymer electrolyte membrane, A method of bonding the electrode catalyst layer to both surfaces of the polymer electrolyte membrane by directly applying and drying the catalyst ink is also included.

  The produced membrane electrode assembly is incorporated into a single polymer electrolyte fuel cell unit cell. As a structure inside the single fuel cell, there is a gas diffusion layer outside the membrane electrode assembly, and a separator is joined so as to sandwich them.

  The separator has a gas flow path. The fuel electrode (anode) mainly contains hydrogen as a fuel gas, and the air electrode (cathode) mainly contains oxygen and air as an oxidant gas, and the anode and cathode through the flow path. Have a role to supply.

  Further, the separator also has a role as a current collector that collects a current that flows due to an electromotive force generated in the membrane electrode assembly, and therefore needs to be made of a conductive material. When the gas supplied to the anode and the cathode is mixed, the electrochemical reaction at the electrode is inhibited. Therefore, it is necessary to seal the mixture so as not to mix the polymer electrolyte membrane on the outer periphery of the membrane electrode assembly. A gasket is arranged to cover.

  Note that the fuel cell refers to a stack in which a plurality of fuel cell single cells are connected in series in order to secure a large current in a practical machine such as an in-vehicle device or a home device.

  For example, in Patent Document 1, as a method for producing a membrane electrode assembly, a polymer electrolyte membrane is preheated, a transfer sheet used as a substrate is cooled, and heated and pressed to peel off the transfer substrate. Techniques for improving are disclosed.

  In Patent Document 2, the step of stretching the polymer electrolyte membrane while heating it at a temperature (first temperature) that is higher than the glass transition temperature and lower than the melting point and restrains the contraction of the stretched polymer electrolyte membrane. And a technique for suppressing shrinkage of the polymer electrolyte membrane by applying a heat treatment such as transfer of the catalyst layer at a temperature equal to or higher than the first temperature and lower than the melting point.

  In addition, it is known that when the gas diffusion layer is sandwiched outside the membrane electrode assembly, it is known that the membrane electrode assembly is bonded by hot pressing. However, in Patent Document 3, the membrane electrode assembly is heated at a temperature higher than the glass transition temperature of the polymer electrolyte. By heating and maintaining at a temperature below the temperature at which it does not decompose, the degree of crystallization of the electrolyte polymer in the electrode catalyst layer is promoted, and the solubility of the electrolyte polymer in the water generated by the power generation and the humidified water is reduced, and the membrane electrode A technique for suppressing deterioration of a joined body is disclosed.

JP 2001-196070 A JP 2010-257598 A JP 2009-4384 A

  However, in the method for producing an electrode catalyst layer described in Patent Document 1, the polymer electrolyte membrane is preheated. However, since the transfer sheet is cooled, the temperature of the transfer sheet rapidly increases during the heating of the main transfer. Will go up. As a result, the transfer sheet expands according to the linear expansion coefficient of the material, and there is a problem that the positions of the electrode catalyst layers of the anode and the cathode are shifted.

  Further, there is a problem that residual solvent and moisture in the electrode catalyst layer fly by heating to form bubbles, and pressure is applied while the bubbles are sealed, thereby wrinkling the membrane electrode assembly.

  In addition, as described in Patent Documents 2 and 3, when the heating temperature to the polymer electrolyte membrane is equal to or higher than the glass transition temperature of the polymer electrolyte membrane, the polymer electrolyte membrane is likely to be stretched, but dimension stable. There was a problem that the membrane electrode assembly was wrinkled.

  The present invention has been made to solve the above problems, and a method of thermally bonding an electrode catalyst layer applied to a substrate to a polymer electrolyte membrane to form an electrode catalyst layer on the polymer electrolyte membrane In this case, it is possible to prevent wrinkles on the membrane electrode assembly and improve the alignment accuracy of the anode and cathode catalyst layers. Moreover, in this specification, although a base material is described as a transfer sheet, the same effect is acquired also about the membrane electrode assembly at the time of using a gas diffusion layer as a base material.

  The present invention employs the following configuration in order to solve the above problems.

  The present invention is a membrane electrode assembly for a polymer electrolyte fuel cell. The membrane electrode assembly for a polymer electrolyte fuel cell includes a polymer electrolyte membrane, a first electrode catalyst layer, and a second electrode catalyst layer. The polymer electrolyte membrane is sandwiched between the first electrode catalyst layer and the second electrode catalyst layer, and the polymer electrolyte membrane is sandwiched between the first electrode catalyst layer and the second electrode catalyst layer. The polymer electrolyte membrane, the first electrode catalyst layer, and the second electrode catalyst layer are heated at a preheating temperature X that satisfies 80 ° C. ≦ X <glass transition temperature (Tg) of the polymer electrolyte membrane. It is characterized by that.

  The polymer electrolyte membrane, the first electrode catalyst layer, and the second electrode catalyst layer preferably contain perfluorosulfonic acid.

  The present invention is a method for producing a membrane electrode assembly for a polymer electrolyte fuel cell. The manufacturing method includes a first electrode catalyst layer and a second electrode in a membrane electrode assembly for a polymer electrolyte fuel cell including a polymer electrolyte membrane, a first electrode catalyst layer, and a second electrode catalyst layer. A first step of forming a catalyst layer on a substrate, a heating step of heating the polymer electrolyte membrane and the substrate at a preheating temperature X and a preheating time Y, and a group on which the first electrode catalyst layer is formed A polymer electrolyte membrane sandwiched between the surface of the material on which the first electrode catalyst layer is formed and the surface of the substrate on which the second electrode catalyst layer is formed on the surface on which the second electrode catalyst layer is formed The process is provided. The preheating temperature X is 80 ° C. ≦ X <glass transition temperature (Tg) of the polymer electrolyte membrane.

  The second step includes an alignment step of performing alignment when the polymer electrolyte membrane is sandwiched between the surface on which the first electrode catalyst layer is formed and the surface on which the second electrode catalyst layer is formed. The alignment step is preferably performed while heating at the preheating temperature X.

  The preheating time Y is preferably 30 seconds or longer.

  In the heating step, it is preferable to heat the polymer electrolyte membrane with at least one surface of the polymer electrolyte membrane exposed.

  The present invention is a polymer electrolyte fuel cell single cell using the membrane electrode assembly for a polymer electrolyte fuel cell described above.

  The present invention also provides a polymer electrolyte fuel cell stack comprising a plurality of the polymer electrolyte fuel cell single cells, wherein the fuel cell single cells are stacked.

  According to the present invention, the polymer electrode membrane and the transfer sheet are preheated, and the alignment is performed in the preheated state, so that the residual solvent and moisture are volatilized, so that there is no wrinkle. Can be produced. In addition, the position of the catalyst layers of the anode and the cathode is reduced by the fact that bubbles are not generated during alignment due to the residual solvent and moisture flying in advance, and the polymer electrolyte membrane and transfer sheet are already heated and stretched. Matching can be performed easily.

  That is, by applying the preheating temperature X to the polymer electrolyte membrane, it is possible to remove residual solvent and moisture contained in the polymer electrolyte membrane. Further, when the temperature of the polymer electrolyte membrane once subjected to the preheating temperature X is lowered from X, moisture in the air is absorbed, but residual solvent is not absorbed. On the other hand, in the polymer electrolyte membrane to which no pre-heat treatment is applied, the residual solvent flies from the polymer electrolyte membrane when the main transfer is heated.

  The residual solvent flew from the polymer electrolyte membrane during the heating of the main transfer is sandwiched between the transfer sheet and the polymer electrolyte membrane to form bubbles, and pressure is applied while the bubbles are sealed. Although it becomes a factor of generation | occurrence | production of a wrinkle of a body, in the manufacturing method of this invention, since there is no residual solvent, it becomes difficult to generate | occur | produce a wrinkle.

  In addition, the first and second electrode catalyst layers on the substrate may also suppress the occurrence of wrinkles in the membrane electrode assembly by applying the preheating temperature X before the second step, so that the residual solvent can fly. it can.

  Further, in the method for producing a membrane electrode assembly of the present invention, in the second step, the alignment of the polymer electrolyte membrane and the first and second electrode catalyst layers on the substrate is performed by the polymer electrolyte membrane and By performing the preheating temperature X on the first and second electrode catalyst layers on the substrate, not only the polymer electrolyte membrane and the residual solvent in the first and second electrode catalyst layers on the substrate, It can be carried out in the absence of moisture. In this state, since the residual solvent and moisture are not sealed with the transfer sheet, the generation of wrinkles in the membrane electrode assembly can be further suppressed.

  In addition, it is easy to align the anode and cathode catalyst layers because no bubbles are generated due to residual solvent and moisture flying, and the polymer electrolyte membrane and transfer sheet are already heated and stretched. Can do.

1 is an exploded schematic view of a single polymer electrolyte fuel cell unit cell according to an embodiment of the present invention. The figure which shows the preheating process of the polymer electrolyte membrane and transfer sheet of one Embodiment The figure which shows the alignment process of the polymer electrolyte membrane of one Embodiment, an anode catalyst layer, and a cathode catalyst layer

  Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described below, and modifications such as design changes can be made based on the knowledge of those skilled in the art, and such modifications have been added. Embodiments can also be included in the scope of the present invention.

  In the following description, a membrane electrode assembly for a polymer electrolyte fuel cell is simply referred to as a membrane electrode assembly, and a polymer electrolyte fuel cell single cell is simply referred to as a fuel cell single cell. The molecular fuel cell stack is simply referred to as a fuel cell stack.

<Membrane electrode assembly>
FIG. 1 is an exploded schematic view of a fuel cell single cell 13 including a membrane electrode assembly 12 according to an embodiment of the present invention.

  As shown in FIG. 1, in the membrane electrode assembly 12, the cathode catalyst layer 2 and the anode catalyst layer 3 face each other with the polymer electrolyte membrane 1 interposed therebetween, and the cathode catalyst layer 2 and the anode catalyst layer 3 A membrane electrode assembly 12 is formed with the polymer electrolyte membrane 1. Hereinafter, the membrane electrode assembly 12 will be described in more detail.

  The polymer electrolyte membrane 1 used for the membrane electrode assembly 12 only needs to have proton conductivity, and a fluorine-based polymer electrolyte, a hydrocarbon-based polymer electrolyte, or the like 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., Gore Select (registered trademark) or the like can be used. Moreover, as the hydrocarbon polymer electrolyte membrane, for example, an electrolyte membrane such as sulfonated polyether ketone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, sulfonated polysulfide, and sulfonated polyphenylene can be used. Among these, a material containing perfluorosulfonic acid as the fluorine-based polymer electrolyte can be suitably used as the polymer electrolyte membrane 1.

  The polymer electrolyte contained in the cathode catalyst layer 2 (sometimes referred to as a first electrode catalyst layer) and the anode catalyst layer 3 (sometimes referred to as a second electrode catalyst layer) has proton conductivity. Any material can be used, and the same material as the polymer electrolyte membrane 1 can be used, and a fluorine-based polymer electrolyte, a hydrocarbon-based polymer electrolyte, or the like can be used. In addition, as a fluorine-type polymer electrolyte, the Dufon Nafion (trademark) type material etc. can be used, for example. Further, as the hydrocarbon polymer electrolyte membrane, for example, a polymer electrolyte membrane such as sulfonated polyether ketone, sulfonated polyethersulfone, sulfonated polyetherethersulfone, sulfonated polysulfide, sulfonated polyphenylene or the like is used. it can. Among these, a material containing perfluorosulfonic acid as the fluorine-based polymer electrolyte can be suitably used as the polymer electrolyte.

  In consideration of the adhesion between the electrode catalyst layers and the polymer electrolyte membrane, it is preferable to use the same material as the polymer electrolyte membrane 1 described above. Hereinafter, the cathode catalyst layer 2 and the anode catalyst layer 3 may be simply referred to as an electrode catalyst layer.

  The catalyst particles used in the present embodiment include platinum, palladium, ruthenium, iridium, rhodium, osmium, platinum group elements, iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, and the like. These metals or their alloys can be used. In addition, oxides, double oxides, and the like can be used. Moreover, the particle size of these catalysts is preferably 0.5 nm to 1 μm, more preferably 1 to 5 nm.

  Carbon particles are generally used as the conductive carrier for supporting these catalyst particles. Any kind of carbon particles may be used as long as they are in the form of fine particles, have conductivity and are not affected by the catalyst particles, such as carbon black, graphite, graphite, activated carbon, carbon fiber, carbon nanotube, fullerene, etc. Can be used.

  In addition, if the particle size of the carbon particles is too small, it becomes difficult to form an electron conduction path, and if it is too large, the gas diffusibility of the electrode catalyst layer is reduced, or the utilization rate of the catalyst particles is reduced. About 10-1000 nm is preferable, More preferably, it is 10-100 nm. Furthermore, the catalyst particles may not be supported on the conductive carrier, or may be mixed only.

  The solvent used as a dispersion medium for the catalyst ink can dissolve the polymer electrolyte in a highly fluid state or be dispersed as a fine gel without eroding the conductive carrier carrying the catalyst particles or the polymer electrolyte. There is no particular limitation as long as there is something.

  The solvent preferably includes a volatile organic solvent or water, and the organic solvent is not particularly limited, but methanol, ethanol, 1-propanol, 2-propanol, 1 Alcohols such as butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, pentaanol, acetone, methyl ethyl ketone, pentanone, methyl isobutyl ketone, heptanone, cyclohexanone, methylcyclohexanone, acetonyl acetone, diisobutyl Ketone solvents such as ketones, ether solvents such as tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, dibutyl ether, other dimethylformamide, dimethylacetamide, N-methylpyrrole Emissions, ethylene glycol, diethylene glycol, diacetone alcohol, 1-methoxy-2-propanol polar solvents such as are used. Moreover, what mixed 2 or more types of these solvents and water can also be used. A dispersant may be included.

  Moreover, the dispersion process at the time of producing catalyst ink can be performed using various apparatuses. For example, as the dispersion treatment, treatment with a ball mill or roll mill, treatment with a shear mill, treatment with a wet mill, ultrasonic dispersion treatment, and the like can be given. Moreover, you may use the homogenizer etc. which stir with centrifugal force.

  Note that if the solid content in the catalyst ink is too high, the viscosity of the catalyst ink increases, so that the surface of the electrode catalyst layer tends to crack. In the range of 0.1 mass% or more and 50 mass% or less. The viscosity of the catalyst ink is preferably in the range of 0.1 cP to 2000 cP, and more preferably in the range of 5 cP to 100 cP.

<Fuel cell single cell>
In the fuel cell single cell 13, first, the cathode gas diffusion layer 4 is disposed on one side of the cathode catalyst layer 2, and the anode gas diffusion layer 5 is disposed on one side of the anode catalyst layer 3. Thus, an air electrode 6 (hereinafter referred to as a cathode 6) and a fuel electrode 7 (hereinafter referred to as an anode 7) are formed. A gas flow path 8 for gas flow is constituted by ribs 11, and a pair of separators 10 made of a conductive and impervious material having cooling water flow paths 9 for cooling water flow are arranged on opposite surfaces. (See FIG. 1).

  For example, a gas containing oxygen is supplied as an oxidant gas from the gas flow path 8 of the separator 10 on the cathode 6 side. On the other hand, for example, hydrogen is supplied as a fuel gas from the gas flow path 8 of the separator 10 on the anode 7 side. An electromotive force can be generated between the anode 6 and the cathode 7 by causing an electrode reaction between the oxidant gas and the fuel gas in the presence of the catalyst.

  Further, the cathode gas diffusion layer 4 and the anode gas diffusion layer 5 in the polymer electrolyte fuel cell single cell 13 according to the present embodiment may be anything as long as they are made of a material having gas diffusibility and conductivity. For example, porous carbon materials such as carbon paper, carbon cloth, and non-woven fabric can be used. Further, a water repellent process may be applied as the gas diffusion layer, or an MPL (microporous layer) may be formed on the gas diffusion layer subjected to the water repellent process. These water-repellent gas diffusion layers and MPL-attached gas diffusion layers may be used for either the cathode 6 or the anode 7.

  Further, the separator 10 in the polymer electrolyte fuel cell unit cell 13 according to the present embodiment may be anything as long as it has a gas flow path 8 for supplying fuel gas and has a role as a current collector. . The base material of the fuel cell separator is classified into a non-metallic system and a metallic system. As the non-metallic separator, for example, a carbon-based material such as dense carbon graphite, or a resin material can be used. As the metal material, for example, stainless steel (SUS), titanium, aluminum, or the like can be used. The gas diffusion layers and the separator 10 may be integrated. In the case of a metal system, a type coated with a conductive resin for preventing rust prevention may be used.

<Fuel cell stack>
The solid polymer fuel cell shown in FIG. 1 is a single cell. However, in the present invention, a stack in which a plurality of cells are stacked via a separator 10 (fuel cell stack) may be used.

  Next, an example of the manufacturing method of a membrane electrode assembly is demonstrated.

  First, the preheating process of the polymer electrolyte membrane 1 and the transfer sheet is shown. FIG. 2 is a diagram showing a preheating process of the polymer electrolyte membrane 1 and the transfer sheet. In the following, heating in the case where the hot plate 14 is used will be described for simplification. However, the heating in the present invention may be performed by heating the entire member, and the heating means is not limited to the hot plate. IR dryers can also be used.

  First, the hot plate 14 is set to the preheating temperature X, and the cathode transfer sheet 15 coated with the polymer electrolyte membrane 1, the cathode catalyst layer 2, and the anode transfer sheet 16 coated with the anode catalyst layer 3 are respectively heated on the hot plate 14. It arrange | positions above and it is set as the preheating time Y, and heats in this period.

  Then, by heating, residual solvent and moisture fly from the polymer electrolyte membrane 1, the cathode catalyst layer 2, and the anode catalyst layer 3. In addition, when the polymer electrolyte membrane 1, the cathode catalyst layer 2, and the anode catalyst layer 3 are removed from the hot plate 14, the water is absorbed, but the residual solvent that has once flew is not absorbed.

  In the case where the preheating step as described above is not included, the residual solvent flew from the polymer electrolyte membrane 1, the cathode catalyst layer 2, and the anode catalyst layer 3 during the heating of the transfer is transferred to the transfer sheets 15 and 16 and the polymer electrolyte. It is sandwiched between the membrane 1 and becomes air bubbles, and pressurizing while the air bubbles are sealed, which causes wrinkling of the membrane electrode assembly 12, but in the manufacturing method of the present embodiment, the residual Since there is no solvent, wrinkles are less likely to occur.

  Next, as shown in FIG. 3, the temperature of the hot plate 14 is set to the preheating temperature X, and the cathode transfer sheet 15 on which the cathode catalyst layer 2 produced through the process shown in FIG. The polymer electrolyte membrane 1 is sandwiched between the anode transfer sheet 16 coated with the anode catalyst layer 3 manufactured through the steps shown in FIG. 2, and the anode catalyst layer 3 and the cathode catalyst layer 2 are aligned.

  By aligning the anode catalyst layer 3 and the cathode catalyst layer 2 on the hot plate 14, it is possible to keep not only the residual solvent already flying but also moisture.

  Further, by performing alignment on the hot plate 14, residual solvent and moisture are not sealed by the transfer sheets 15 and 16, so that alignment is performed without generating wrinkles in the membrane electrode assembly 12. It can be performed.

  The preheating temperature X is preferably 80 ° C. ≦ X ≦ the glass transition temperature (Tg) of the polymer electrolyte membrane 1. When the preheating temperature X is lower than 80 ° C., the boiling point of the residual solvent is not reached, and the solvent may not fly. On the other hand, when the preheating temperature X exceeds the glass transition temperature (Tg) of the polymer electrolyte membrane 1, the fluidity of the polymer electrolyte membrane 1 increases, and expansion and contraction with respect to external force occurs, so that alignment is easy. In some cases, the polymer electrolyte membrane 1 may become wrinkled or wrinkled.

  In addition, when the heating time at the preheating temperature X is a preheating time Y, the preheating time Y is desirably 30 s (seconds) or more. If the preheating time Y is set to a time shorter than 30 s, the residual solvent and moisture may not sufficiently fly from the polymer electrolyte membrane 1, the cathode catalyst layer 2, and the anode catalyst layer 3. Note that if the preheating temperature X is within the range of 80 ° C. ≦ X ≦ the glass transition temperature (Tg) of the polymer electrolyte membrane 1, there is no problem even if the preheating time Y is long.

  In the step of preheating the polymer electrolyte membrane 1, it is desirable that at least a part of one side of the polymer electrolyte membrane 1 is exposed. The polymer electrolyte membrane 1 may be provided with a protective film on both sides or one side of the membrane, but even if preheated with the protective film on both sides, there is no escape space for the residual solvent and moisture, Residual solvent and moisture are not completely removed, and the above effects are not sufficiently exhibited.

  Further, in the method of manufacturing the membrane electrode assembly 12 according to the present embodiment, the membrane electrode assembly 12 is produced from catalyst particles, a catalyst ink containing a conductive substance and a polymer electrolyte in contact with the catalyst particles. There are many ways to do this.

  For example, as an example of a method for producing the membrane electrode assembly 12, a catalyst ink is applied on a substrate selected from a transfer sheet or a gas diffusion layer, the coating film is dried, and each electrode catalyst layer 2 is formed on the substrate. 3, each electrode catalyst layer 2, 3 on the substrate and the polymer electrolyte membrane 1 are hot-pressed, and when the substrate is a transfer sheet, the sheet is peeled off to form a membrane electrode assembly 12. is there.

  Further, for example, when the membrane electrode assembly 12 is produced using a transfer sheet as a base material, the transfer sheet used as the base material may be a material having good transferability. When a transfer sheet is used as the base material, the electrode catalyst layers 2 and 3 are bonded to the polymer electrolyte membrane 1 and then the transfer sheet is peeled off. The electrode catalyst layers 2 and 3 are attached to both surfaces of the polymer electrolyte membrane 1. It can be set as the membrane electrode assembly 12 provided. The transfer sheet may have a release agent attached thereto.

  In addition, in this embodiment, it can implement also by the method of using a transfer sheet as a base material, and the method of using a gas diffusion layer.

  As a method for applying the catalyst ink, a doctor blade method, a dipping method, a screen printing method, a roll coating method, a spray method, or the like can be used.

  In addition, the temperature of the drying step is not particularly limited, but it is preferably performed at a temperature of the base material or higher and 150 ° C. or lower. If the temperature is higher than this, the occurrence of uneven drying of the electrode catalyst layers 2 and 3 and the influence of the heat treatment on the polymer electrolyte in the electrode catalyst layers 2 and 3 become large, which is not appropriate. When the temperature of the drying step is equal to or higher than the boiling point of the solvent in the catalyst ink, the evaporation rate is remarkably increased. Therefore, the temperature is preferably less than the boiling point of the solvent.

  The pressing pressure applied to the polymer electrolyte membrane 1 and the electrode catalyst layers 2 and 3 in the hot pressing step affects the battery performance of the membrane electrode assembly 12. In order to obtain a membrane electrode assembly 12 with good battery performance, the press pressure applied to the polymer electrolyte membrane 1 and the electrode catalyst layers 2 and 3 is preferably in the range of 0.5 MPa to 20 MPa, and more preferably 1 MPa. It is preferably within the range of 15 MPa or less. When the pressing pressure exceeds the above range, the electrode catalyst layers 2 and 3 are excessively compressed, and the battery performance may be deteriorated. Moreover, when press pressure is less than the said range, the joining property of each electrode catalyst layer 2 and 3 and the polymer electrolyte membrane 1 will fall, and battery performance will fall.

  Moreover, it is preferable to set the temperature of the heat press in the vicinity of the glass transition point (Tg) of the polymer electrolyte of the polymer electrolyte membrane 1 and the electrode catalyst layers 2 and 3. Specifically, the temperature of the hot press is in the range of not less than the glass transition point of the polymer electrolyte membrane −40 ° C. (Tg−40 ° C.) and not more than the glass transition point of the polymer electrolyte membrane + 60 ° C. (Tg + 60 ° C.). Is preferred. When the temperature of hot pressing is lower than the glass transition point of the polymer electrolyte membrane −40 ° C. (Tg−40 ° C.), sufficient interfacial adhesion is obtained between the electrode catalyst layers 2 and 3 and the polymer electrolyte membrane 1. Battery performance is degraded. On the other hand, when the temperature of the hot press exceeds the glass transition point of the polymer electrolyte membrane + 60 ° C. (Tg + 60 ° C.), the polymer electrolyte is softened and the pores of the electrode catalyst layers 2 and 3 are crushed, resulting in gas and generated water. The diffusibility of the battery is lowered, and the battery performance is lowered.

  The electrode catalyst layers 2 and 3 and the polymer electrolyte membrane 1 may be bonded together as long as pressure and heat are applied. In addition to hot pressing, methods such as thermal lamination can also be used.

Hereinafter, although this invention is further demonstrated based on Example 1, a reference example , and Comparative Examples 1-5, this invention is not restrict | limited by the following example.

Example 1
The manufacturing method of the membrane electrode assembly 12 according to the first embodiment includes a “first step” and a “second step” described below.

"First step"
The first step is a step of forming an electrode catalyst layer on the substrate. Specifically, it is as follows.

  First, water and 1-propanol were mixed at a weight ratio of 1: 2 with a platinum-supported carbon catalyst having a platinum-supported amount of 60% by weight, and dispersed with a planetary ball mill to obtain a catalyst ink.

  Thereafter, the substrate was fixed on the plate, and the catalyst ink was applied onto the substrate with a doctor blade. Then, the substrate on which the coating film made of the catalyst ink is formed is placed in an oven (hot air circulating constant temperature dryer 41-S5H / Satake Chemical Machinery Co., Ltd.), and the oven temperature is set to 50 ° C. and dried for 5 minutes. Then, an electrode catalyst layer was produced on the transfer sheet as a substrate.

Next, two transfer sheets on which the electrode catalyst layer is formed are cut out at 150 cm ² for the cathode catalyst layer 2 and the anode catalyst layer 3, and the amount of platinum supported is about 0.3 mg / cm ² for the cathode catalyst layer 2. The catalyst layer 3 was adjusted to about 0.5 mg / cm ² .

  Next, the “second step” will be described. In Example 1, a step of applying preheating between the “first step” described above and the “second step” described later (“preheating step”). ")including. Hereinafter, the “preheating step” will be described.

"Preheating process"
The hot plate 14 was heated, and the transfer sheets of the cathode catalyst layer 2 and the anode catalyst layer 3 prepared in the first step were disposed with the base material side as the hot plate 14 side. Moreover, the protective film of the membrane electrode assembly 12 was peeled on one side, and the remaining protective film was placed on the hot plate 14 side.

The temperature of the hot plate 14, that is, the preheating temperature X and the preheating time Y are as follows.
Hot plate temperature (preheating temperature X): 100 ° C
(Confirmed that each material surface temperature is 100 ° C with a contact thermometer)
Preheating time Y: 300s

"Second step"
The second step is a step of manufacturing the membrane electrode assembly 12. Specifically, it is as follows.

  First, on the hot plate 14, the base material was arranged so that the cathode catalyst layer 2 and the anode catalyst layer 3 face each other on both surfaces of the polymer electrolyte membrane 1 that had undergone the preheating step, and alignment was performed. The temperature of the hot plate 14 at the time of alignment was set to 100 ° C.

  Thereafter, the transfer sheet on which the electrode catalyst layers 2 and 3 were formed and the polymer electrolyte membrane 1 were sandwiched from both sides on the hot plate 14 with a protective film used during hot pressing. Further, a press member was sandwiched between the two sides, placed on a hot press machine, and hot pressed under the conditions of a press temperature of 130 ° C., a press time of 10 minutes, and a press pressure of 7.8 MPa. After the hot pressing, the transfer sheet was peeled off to obtain a membrane electrode assembly 12.

( Reference example )
The manufacturing method of the membrane electrode assembly 12 according to this reference example is different from the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above only in the following points. That is, in the second embodiment of the method for manufacturing the membrane electrode assembly 12 according to the first embodiment described above, the temperature of the hot plate 14 at the time of alignment is set to RT (Room Temperature: room temperature). 1 is the same as the production method of engaging Ru membrane electrode assembly 12.

(Comparative Example 1)
The manufacturing method of the membrane electrode assembly 12 according to Comparative Example 1 is different from the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above only in the following points. That is, in the manufacturing method of the membrane electrode assembly 12 according to the above-described Example 1, the “preheating step” is performed between the “first step” and the “second step”. In the method for manufacturing the membrane electrode assembly 12, the “preheating step” is not performed.

  Furthermore, in the second step of the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above, the temperature of the hot plate 14 at the time of alignment is changed to RT, and the membrane electrode junction according to Example 1 described above is used. This is the same as the manufacturing method of the body 12.

(Comparative Example 2)
The manufacturing method of the membrane electrode assembly 12 according to Comparative Example 2 is different from the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above only in the following points. That is, in the method of manufacturing the membrane electrode assembly 12 according to Example 1 described above, the “preheating step” was performed between the “first step” and the “second step”. The manufacturing method of the membrane electrode assembly 12 is the same as the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above, except that the “preheating step” is not performed.

(Comparative Example 3)
The manufacturing method of the membrane electrode assembly 12 according to Comparative Example 3 is different from the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above only in the following points. That is, the temperature of the hot plate 14 in the “preheating step”, that is, the preheating temperature X was set as follows.
Hot plate temperature (preheating temperature X): 60 ° C
(Confirmed that each material surface temperature is 60 ° C with a contact-type thermometer)

  Furthermore, the membrane electrode according to Example 1 described above except that the temperature of the hot plate 14 at the time of alignment in the second step of the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above is 60 ° C. This is the same as the manufacturing method of the joined body 12.

(Comparative Example 4)
The manufacturing method of the membrane electrode assembly 12 according to Comparative Example 4 is different from the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above only in the following points. That is, the temperature of the hot plate 14 in the “preheating step”, that is, the preheating temperature X was set as follows.
Hot plate temperature (preheating temperature X): 160 ° C
(Confirmed that the surface temperature of each material is 160 ° C with a contact thermometer.

  Furthermore, the membrane electrode according to Example 1 described above except that the temperature of the hot plate 14 at the time of alignment in the second step of the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above is 160 ° C. This is the same as the manufacturing method of the joined body 12.

(Comparative Example 5)
The manufacturing method of the membrane electrode assembly 12 according to Comparative Example 5 is different from the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above only in the following points. That is, it is the same as the manufacturing method of the membrane electrode assembly 12 according to Example 1 described above except that the preheating time Y in the “preheating step” is as follows.
Preheating time Y: 10 s

In each of the above Examples , Reference Examples and Comparative Examples, the polymer electrolyte membrane is a Nafion 211 membrane (registered trademark / manufactured by DuPont), the platinum-supporting carbon catalyst is TEC10E60TPM (Tanaka Kikinzoku Co., Ltd.), and the transfer sheet is a PTFE sheet. used. As a result of thermal analysis, it is known that the Tg of the Nafion 211 film is around 120 ° C.

<result>
About membrane electrode assembly 12 produced through the steps of Example 1, Reference Example , and Comparative Examples 1 to 5, the preheating conditions, the temperature at the time of alignment, the wrinkles at the time of alignment, and the state of wrinkles after bonding It described in Table 1.

In Table 1, the state of wrinkles is shown by the following three.
○: No wrinkles △: Some wrinkles ×: Many wrinkles do not form a membrane electrode assembly

From Table 1, Example 1 and the reference example are the appearance at the time of alignment, and are better than Comparative Example 2, Comparative Example 4, and Comparative Example 5. This is because the residual solvent and moisture contained in the polymer electrolyte membrane 1, the anode catalyst layer 3, and the cathode catalyst layer 2 in Example 1 due to preheating, and the residual solvent in the reference example was volatilized at the time of alignment. It is thought that wrinkles were less difficult during alignment.

  Since Comparative Example 2 was not preheated and Comparative Example 5 was short in preheating time, the position of the polymer electrolyte membrane 1, the anode catalyst layer 3, and the cathode catalyst layer 2 with the residual solvent and moisture remained was changed. Since it was heated at the time of combining, the residual solvent and moisture were volatilized, and it was sandwiched between the transfer sheet and the polymer electrolyte membrane 1 to form bubbles and wrinkles.

  Further, in Comparative Example 4, since the preheating temperature is higher than the glass transition temperature (Tg) of the polymer electrolyte membrane 1, the fluidity of the polymer electrolyte membrane 1 is increased, and expansion and contraction with respect to external force occurs, so that the polymer electrolyte It seems that the film 1 has been wrinkled.

  On the other hand, Comparative Example 1 and Comparative Example 3 have good wrinkles at the time of alignment, but these are residual solvents contained in the polymer electrolyte membrane 1, the anode catalyst layer 3, and the cathode catalyst layer 2 at the temperature at the time of alignment. This is probably because the solvent has not volatilized.

Next, about the external appearance after bonding, Example 1 and a reference example are wrinkles-free compared with Comparative Examples 1-5, and have become favorable.

In the first embodiment described above, the residual solvent and moisture contained in the polymer electrolyte membrane 1, the anode catalyst layer 3, and the cathode catalyst layer 2 are obtained by the preheating step and the alignment step. In the reference example , the residual solvent is obtained by the preheating step. Since it has already volatilized and the residual solvent did not volatilize due to the temperature at the time of this pasting (hot pressing), the appearance seems to have improved.

Note that the appearance shape of Example 1 is better than that of the reference example because both the residual solvent and moisture in Example 1 and only the residual solvent is volatilized in the reference example . In the reference example, it is considered that the membrane electrode assembly 12 was wrinkled by the amount of moisture removed.

  On the other hand, in Comparative Examples 1, 3, and 5, the residual solvent and moisture contained in the polymer electrolyte membrane 1, the anode catalyst layer 3, and the cathode catalyst layer 2 remain without being volatilized in the preheating step and the alignment step. The residual solvent volatilizes depending on the temperature at the time of this bonding (hot pressing), and is sandwiched between the transfer sheet and the polymer electrolyte membrane 1 to form bubbles and wrinkles.

  Moreover, in Comparative Examples 2 and 4, it is considered that the wrinkles were emphasized during the hot press because the wrinkles were caused during the alignment for the above reasons.

  Moreover, in the polymer electrolyte membrane 1 before pasting through the preheating step of Example 1 and the polymer electrolyte membrane 1 before pasting in Comparative Example 1, the residual solvent of Example 1 was measured by gas chromatography. It was confirmed that the amount was less than that of Comparative Example 1.

  Furthermore, even if the inventor sniffs the odor of each polymer electrolyte membrane 1, it was confirmed that the odor of the polymer electrolyte membrane 1 of Comparative Example 1 was stronger than that of Example 1.

From the above results, the membrane / electrode assembly 12 produced by the production method of Example 1 and the reference example has less wrinkles and the appearance shape than the membrane / electrode assembly 12 produced by the production methods of Comparative Examples 1 to 5. Was good.

  In addition, bubbles do not occur due to residual solvent and moisture flying, and the polymer electrolyte membrane and transfer sheet are already heated and stretched, making it easy to align the anode and cathode catalyst layers. I was able to.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used for a polymer electrolyte fuel cell, in particular, a polymer electrolyte fuel cell single cell or stack in a fuel cell system for home use, a fuel cell vehicle and the like.

DESCRIPTION OF SYMBOLS 1 .... Polymer electrolyte membrane 2 .... Cathode catalyst layer 3 .... Anode catalyst layer 4 .... Cathode gas diffusion layer 5 .... Anode gas diffusion layer 6 .... Air electrode (Cathode)
7 ... Fuel electrode (anode)
DESCRIPTION OF SYMBOLS 8 .... Gas flow path 9 ... Cooling water flow path 10 ... Separator 11 ... Rib 12 ... Membrane electrode assembly 13 ... Solid polymer fuel cell single cell 14 ... Hot plate 15 ... Cathode transfer sheet 16 ... Anode transfer sheet

Claims (5)

A method for producing a membrane electrode assembly for a polymer electrolyte fuel cell comprising a polymer electrolyte membrane, a first electrode catalyst layer, and a second electrode catalyst layer,
Forming a first electrode catalyst layer on a first substrate which is a transfer sheet, and forming a second electrode catalyst layer on a second substrate which is a transfer sheet ;
Using a hot plate, a preheating step of preheating the polymer electrolyte membrane, the first base material and the second base material for 30 seconds or more at a preheating temperature X;
On the hot plate maintained at the preheating temperature X , the first electrode catalyst layer is formed in a state where the first electrode catalyst layer and the second electrode catalyst layer are heated and moisture absorption is suppressed. is the second electrode catalyst layer in said second substrate, wherein the said first surface electrode catalyst layer is formed a second electrode catalyst layer is formed in the first base material which is the form And the second step of sandwiching the polymer electrolyte membrane, and aligning the surface so that the first electrode catalyst layer and the second electrode catalyst layer face each other ,
A hot pressing step of hot pressing the polymer electrolyte membrane, the first electrode catalyst layer, and the second electrode catalyst layer,
The preheating temperature X is 80 ° C. ≦ X <the glass transition temperature (Tg) of the polymer electrolyte membrane,
The temperature of the hot pressing step is not less than the glass transition temperature of the polymer electrolyte membrane −40 ° C. (Tg−40 ° C.) and not more than the glass transition temperature of the polymer electrolyte membrane + 60 ° C. (Tg + 60 ° C.). A method for producing a membrane electrode assembly for a polymer electrolyte fuel cell.   2. The membrane electrode assembly for a polymer electrolyte fuel cell according to claim 1, wherein in the preheating step, the polymer electrolyte membrane is heated in a state where at least one surface of the polymer electrolyte membrane is exposed. 3. Production method.   3. The polymer electrolyte fuel cell according to claim 1, wherein the polymer electrolyte membrane, the first electrode catalyst layer, and the second electrode catalyst layer contain perfluorosulfonic acid. 4. Of manufacturing membrane electrode assembly for use. A step of producing a membrane electrode assembly for a polymer electrolyte fuel cell by the method for producing a membrane electrode assembly for a polymer electrolyte fuel cell according to any one of claims 1 to 3,
A method for producing a single polymer electrolyte fuel cell unit cell, comprising a step of sandwiching a membrane electrode assembly for a polymer electrolyte fuel cell with a gas diffusion layer and a separator. A step of producing a plurality of polymer electrolyte fuel cell single cells by the method for producing a polymer electrolyte fuel cell single cell according to claim 4;
A process for producing a polymer electrolyte fuel cell stack, comprising the step of laminating the polymer electrolyte fuel cell single cells.

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