JP2008147031A - Manufacturing method of membrane-electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a membrane-electrode assembly capable of providing a high-quality membrane-electrode assembly by preventing a crack and separation of a catalyst layer by obviating the need of a drying process after catalyst slurry application. <P>SOLUTION: This application relates to this manufacturing method of a membrane-electrode assembly formed by stacking a catalyst layer on an electrolyte membrane including: a slurry preparation process of preparing slurry containing a catalyst, an electrolyte and a solvent; a catalyst powder preparation process of preparing catalyst powder by removing the solvent in the slurry; a catalyst layer formation process of forming the catalyst layer by compressively molding the catalyst powder by a die; and a joint process of jointing the catalyst layer or a constituent material of the catalyst layer to the electrolyte membrane. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a membrane electrode assembly which can be suitably used for, for example, a fuel cell.

  In recent years, expectations for fuel cells as a power source for portable electronic devices and the like are increasing. In a fuel cell, electric power is generated by electrochemically oxidizing and reducing fuel at a fuel electrode and air at an air electrode. Conventionally, an indirect coating method, a direct coating method, or the like has been used as a method for producing a membrane electrode assembly that can be used in a polymer electrolyte fuel cell. In any of these methods, a catalyst layer production slurry in which catalyst particles, water, a solvent, an electrolyte solution, and the like are dispersed is used as a catalyst layer constituent material. In general, it is applied to a molecular electrolyte membrane.

  Here, the indirect coating method is to form an electrode by coating the catalyst layer slurry with screen printing or the like on a release sheet having excellent release properties such as a fluororesin, and the electrode is polymerized together with the release sheet. In this method, the electrodes are laminated in close contact with the electrolyte membrane, and then the electrode on the release sheet is transferred to the polymer electrolyte membrane by hot pressing or the like. Further, a method of using a diffusion layer such as carbon paper instead of the release sheet and joining the electrode together with the diffusion layer to the solid polymer electrolyte membrane is also included. On the other hand, the direct coating method is a method in which the slurry for producing the catalyst layer is directly applied to the polymer electrolyte membrane with an air brush, a spray gun or the like.

  In a fuel cell electrode catalyst layer produced by a conventional method for producing a fuel cell electrode catalyst layer, cracks and cracks often occur, and this tendency is observed as the thickness of the fuel cell electrode catalyst layer increases. It becomes more prominent. The cracks and the like are generated when the solvent is dried after the slurry in which the catalyst particles including the catalyst-supporting carbon fine particles are dispersed is applied.

  In Patent Document 1, since the surface tension of water used when dispersing the dried catalyst-carrying carbon fine particles is large, the drying shrinkage force at the time of solvent drying is large, and a commonly used ethanol solvent or 1-propanol solvent and an electrolyte are used. It is found that cracks are generated due to two points that the interaction (ie, intermolecular force) becomes too large, and a tertiary alcohol is used instead of water as a liquid medium for wetting the dried catalyst-carrying carbon fine particles, It has been proposed that the occurrence of cracks and the like can be effectively suppressed by employing an organic solvent having a dielectric constant of 20 or less in place of general alcohol as a liquid solvent for dissolving the solid polymer electrolyte.

However, even in the above technique, the catalyst layer preparation process still includes a process of drying after applying water and an organic solvent contained in the slurry for producing the catalyst layer. Cracks and the like occur in the process. On the other hand, when laminating the slurry in multiple stages in small portions, the electrolyte in the catalyst layer applied and dried in the former stage sucks the solvent in the slurry in the latter stage, so it becomes difficult to dry due to the distance from the outer surface becoming far. Further, there is a problem that peeling occurs due to the weakness of the catalyst layer.
JP 2003-208903 A

  MEANS TO SOLVE THE PROBLEM This invention solves said subject and prevents the crack and peeling of a catalyst layer by making the drying process after catalyst slurry application | coating unnecessary, and the membrane electrode composite which can obtain a high quality membrane electrode composite It aims at providing the manufacturing method of this.

  The present invention relates to a method for producing a membrane electrode assembly in which a catalyst layer is laminated on an electrolyte membrane, a slurry preparation step for preparing a slurry containing a catalyst, an electrolyte, and a solvent, and a solvent in the slurry. Catalyst preparation step for removing catalyst to prepare catalyst powder, catalyst powder compression molding with catalyst mold to form catalyst layer, and joining of catalyst layer or constituent material of catalyst layer to electrolyte membrane And a process for producing a membrane electrode assembly.

  In the method for producing a membrane electrode assembly of the present invention, the removal of the solvent in the catalyst powder preparation step is preferably performed while kneading the slurry.

  In the method for producing a membrane electrode assembly of the present invention, the mold is preferably a porous metal. In this case, it is preferable that the constituent material of the catalyst layer bonded to the electrolyte membrane in the bonding step is the porous metal.

  In the method for producing a membrane electrode assembly of the present invention, the slurry preferably further contains conductive fibers.

  In the method for producing a membrane electrode assembly of the present invention, the catalyst layer is preferably a fuel electrode catalyst layer of a fuel cell. In this case, the thickness of the catalyst layer is preferably 50 μm or more.

  In the method for producing a membrane electrode assembly of the present invention, the catalyst layer is formed by compressing the catalyst powder obtained by drying the solvent of the slurry containing the catalyst with a mold, thereby preventing cracking and peeling of the catalyst layer. Thus, it is possible to obtain a high quality membrane electrode composite.

  Further, according to the present invention, a catalyst layer having a large thickness and high quality, which was difficult to produce by the conventional method, can be formed at a low cost by a small number of steps.

  The present invention relates to a method for producing a membrane electrode assembly in which a catalyst layer is laminated on an electrolyte membrane, the production method comprising a slurry preparation step for preparing a slurry containing a catalyst, an electrolyte, and a solvent; A catalyst powder preparation step for preparing a catalyst powder by removing the solvent, a catalyst layer forming step for forming the catalyst layer by compressing the catalyst powder by a mold, and a catalyst layer or a constituent material of the catalyst layer are joined to the electrolyte membrane. Joining process. The membrane electrode assembly produced in the present invention typically has a configuration in which catalyst layers are laminated on both surfaces of an electrolyte membrane.

[Embodiment 1]
Hereinafter, typical embodiments of the present invention will be described with reference to the drawings.

<Slurry preparation process>
In the slurry preparation step, a slurry containing a catalyst, an electrolyte, and a solvent is prepared. The slurry can be prepared, for example, by mixing the catalyst, electrolyte and solvent under stirring. In the present invention, the catalyst may be contained alone in the slurry, but it is preferable to use catalyst fine particles, for example, in a state of being supported on a carrier made of conductive powder.

  As the catalyst, for example, noble metals such as Pt, Ru, Au, Ag, Rh, Pd, Os, Ir, and base metals such as Ni, V, Ti, Co, Mo, Fe, Cu, and Zn can be preferably used. These can be used alone or in combination of two or more.

  Further, as the conductive powder used as a carrier for supporting the catalyst, for example, carbon powder such as acetylene black, ketjen black, furnace black, carbon nanotube, carbon nanohorn, fullerene can be preferably used.

  As the electrolyte, for example, polymer electrolytes such as Nafion (registered trademark) (manufactured by DuPont) and Flemion (registered trademark) (manufactured by Asahi Glass) can be preferably used. In the slurry preparation step, these can be preferably used in the form of a solution, for example. As the solvent, for example, ethylene glycol dimethyl ether, n-butyl acetate, isopropanol and other lower alcohols can be preferably used.

  The slurry may be composed of only a catalyst, an electrolyte, and a solvent, but may contain other components. For example, carbon powder or the like to which PTFE (polytetrafluoroethylene) has been added as a water repellency imparting agent or ethylene glycol or the like as a viscosity modifier may be added to the electrolyte solution. Further, water or the like may be contained in the slurry.

  Moreover, in this invention, it is preferable that a slurry further contains a conductive fiber. In this case, the porosity of the catalyst layer can be adjusted within a desired range so that the fuel can be supplied to the catalyst layer and the product discharged from the catalyst layer can be efficiently performed. Examples of the conductive fiber include carbon fiber (for example, VGCF manufactured by Showa Denko), carbon nanotube, and the like.

A more specific composition of the slurry is not particularly limited, but Pt / C is used as a carbon powder supporting a noble metal catalyst, a Nafion (registered trademark) solution is used as a polymer electrolyte solution, and an organic solvent is used as a dilution solvent. When each of the solvents is used, Pt / C is contained within a range of 1 to 30 mg Pt / cm ² with respect to the area of the electrode to be prepared, and Nafion (registered trademark) solution is added at 0.5 to 15 mg / It comprises in the range of cm ^2, the organic solvent, a slurry having a composition containing in the range of 30~900mg / cm ² is preferred.

More typically, a slurry having a composition capable of forming a coating state containing ² mg Pt / cm ^{2 of} Pt / C, 1.0 mg / cm ^{2 of} Nafion (registered trademark) solution, and 60 mg / cm ^{2 of} an organic solvent can be exemplified. . As a method for uniformly mixing and dispersing each substance constituting the slurry, a method using a bead mill or an ultrasonic homogenizer can be preferably employed.

<Catalyst powder forming step>
In the catalyst powder forming step, the solvent in the slurry obtained above is removed to prepare catalyst powder. The solvent can be removed by, for example, drying. The removal of the solvent is preferably performed while the slurry is kneaded. In this case, the external force acts on the slurry to suppress the aggregation of constituent materials in the slurry, so that the volatilization rate of the solvent can be improved, A uniform catalyst powder having a small particle size can be obtained. As a kneading method, for example, a method of grinding with a mortar can be preferably employed.

<Catalyst layer formation process>
In the catalyst layer forming step, the catalyst powder obtained above is compression-molded with a mold to form a catalyst layer. FIG. 1 is a schematic diagram illustrating a preferred embodiment of the method for producing a membrane electrode assembly according to the present invention. In FIG. 1, for the sake of simplicity, a catalyst layer laminated on one surface of the electrolyte membrane is shown as a representative.

  First, a mold 30 in which a catalyst powder filling space 31 is formed is stacked on the substrate 1 (FIG. 1A), and the substrate 1 and the mold 30 are fixed. As the base material 1, for example, a diffusion layer represented by carbon paper, a Teflon (registered trademark) sheet excellent in releasability, a high concentration, excellent in diffusibility of fuel used in fuel cells and products in the fuel cells It is possible to use a permeation control film that controls the amount of fuel supplied. By changing the size of the catalyst powder filling space 31, a desired area of the catalyst layer can be realized. Further, by changing the thickness of the mold 30, a desired catalyst layer thickness can be realized.

  Next, the catalyst powder filling space is filled with the catalyst powder, and preferably compression molding is performed by using a press machine from above and below the laminate of the base material 1 and the mold 30 through the spacer, and the catalyst layer 2 (FIG. 1B). After completion of the compression molding, the mold 30 is removed (FIG. 1C). By compression molding, a more uniform and dense catalyst layer can be produced. Further, when the catalyst is supported on a carrier made of, for example, conductive powder, the contacts between the conductive powders are increased by compression molding, and the ohmic resistance of the catalyst layer can be reduced.

  The mold 30 preferably has a certain degree of rigidity and heat resistance so as not to be greatly deformed when pressed. Examples of preferable materials for the mold 30 include acrylic, PTFE (polytetrafluoroethylene), PEEK (polyether ether ketone), PPS (polyphenylene sulfide), PI (polyimide), and the like.

Moreover, it can prevent that the base material 1 is crushed too much by using a spacer. The thickness of the spacer is preferably thinner than the sum of the thickness of the substrate 1 and the thickness of the mold. In this case, it is possible to produce a uniform and dense catalyst layer by compression molding. Moreover, it does not specifically limit as a press pressure, However, It is preferable that it is 5-20 kgf / cm < ² >.

  In compression molding, it is preferable that the filling rate of the solid content of the catalyst powder filled in the mold 30 (hereinafter also simply referred to as filling rate) is, for example, 20% or more. As the packing ratio increases, the catalyst surface area per unit volume of the catalyst layer increases and the number of reaction sites increases, so that the characteristics of the membrane electrode assembly and the stability of the characteristics are improved. When the filling rate is 20% or more, the effect of improving the characteristics of the membrane electrode assembly and the stability of the characteristics is particularly good. The filling rate of the catalyst layer is preferably 80% or less. The smaller the filling rate, the more, for example, a passage for discharging by-products in the fuel cell can be secured, so that the stability of the characteristics of the membrane electrode assembly is improved and the liquid leakage caused by the increased pressure in the catalyst layer Further, it is possible to prevent peeling between members. When the filling rate is 80% or less, the effect of improving the stability of characteristics in the membrane electrode assembly and the effect of preventing liquid leakage and peeling are particularly good. The filling rate of the catalyst layer is more preferably in the range of 25 to 70%, and still more preferably in the range of 30 to 60%.

Here, the filling rate of the catalyst layer is
Filling rate = (volume of solid content of catalyst powder to be filled) / (volume of catalyst powder filling space of mold) × 100
It can be calculated by the formula. The volume of the solid content of the catalyst powder to be filled can be determined from the mass of the catalyst powder filled in the mold, the charged mass of each solid content into the catalyst powder, and the density of each solid content.

<Joint process>
In the joining step, the catalyst layer obtained above or the constituent material of the catalyst layer is joined to the electrolyte membrane. In the present invention, since the solvent is removed before forming the catalyst layer, it is possible to prevent cracking or peeling that occurs when the solvent is dried after the catalyst layer is formed. In FIG. 1, the case where the catalyst layer 2 is formed using the mold 30 and then the catalyst layer 2 is joined to the electrolyte membrane will be described. In the present invention, for example, a porous metal as described later is used as the catalyst. The constituent material of the catalyst layer may be joined to the electrolyte membrane in the joining step, as in the method of joining only the porous metal to the electrolyte membrane in advance as a constituent material of the layer. In this case, the joining step is performed before the catalyst layer forming step.

In the joining step, for example, as shown in FIG. 1, an electrolyte membrane 3 is superimposed on a catalyst layer 2 formed on a substrate 1 (FIG. 1D), and the catalyst layer 2 and the electrolyte membrane 3 are pressed. It can be carried out by bonding by means such as (FIG. 1E). In the present invention, a hot press method or the like can be exemplified as a method for joining the catalyst layer or the constituent material of the catalyst layer to the electrolyte membrane. The conditions during hot pressing are selected according to the materials of the catalyst layer and the electrolyte membrane, and it is preferable that the temperature be higher than the softening temperature or glass transition temperature of the polymer electrolyte contained in the electrolyte membrane or catalyst layer, for example. Specifically, for example, when Nafion (registered trademark) is used as the polymer electrolyte, the hot press conditions are, for example, a temperature of 135 ° C., 10 kgf / cm ² , a time of 5 minutes (preheating 2 minutes, press 3 minutes). Can be adopted. By hot pressing, the interface between the electrolyte membrane and the catalyst layer is fused by the electrolyte, and the interface between the electrolytes in the catalyst layer is also fused, so that the proton conduction resistance of the membrane electrode assembly is reduced, and the electrolyte membrane and the catalyst layer It becomes possible to improve the adhesive strength.

  When the membrane electrode assembly of the present invention is used in a fuel cell, the electrolyte membrane 3 has a function of transmitting protons from the fuel electrode catalyst layer to the air electrode catalyst layer, and an electrical connection between the fuel electrode catalyst layer and the air electrode catalyst layer. It has a function of maintaining insulation and preventing a short circuit. The material of the electrolyte membrane is not particularly limited as long as it has proton conductivity and electrical insulation, and a polymer membrane, an inorganic membrane, or a composite membrane can be used.

  Examples of the polymer membrane include Nafion (registered trademark) (manufactured by DuPont), Dow membrane (Dow Chemical Company), Aciplex (manufactured by Asahi Kasei), and Flemion (registered trademark), which are perfluorosulfonic acid electrolyte membranes. (Manufactured by Asahi Glass Co., Ltd.), and hydrocarbon electrolyte membranes such as polystyrene sulfonic acid and sulfonated polyether ether ketone.

  Examples of the inorganic film include phosphate glass, cesium hydrogen sulfate, polytungstophosphoric acid, and ammonium polyphosphate.

  Examples of composite membranes include sulfonated polyimide polymers, composites of inorganic materials such as tungstic acid and organic materials such as polyimide, and specific examples include Gore Select membranes (manufactured by Gore) and pore filling electrolyte membranes. It is done.

  The membrane electrode composite obtained by the production method of the present invention is preferably a membrane electrode composite used for a fuel cell. In this case, the catalyst layer formed by the production method of the present invention may be at least one of a fuel electrode catalyst layer and an air electrode catalyst layer, but is more preferably a fuel electrode catalyst layer. In a direct methanol fuel cell (hereinafter also referred to as “DMFC”) that generates electricity by directly extracting protons from methanol, the activation overvoltage when oxidizing methanol supplied to the fuel electrode is low. The problem is that the methanol crossover is large and the methanol fuel introduced into the fuel electrode permeates the air electrode through the electrolyte membrane and burns without contributing to power generation.

  When the production method of the present invention is used, it is possible to produce a fuel electrode catalyst layer having a large thickness, which cannot be produced by the conventional method, in a relatively short time. Therefore, by increasing the amount of catalyst per unit area of the catalyst layer, the catalyst surface area in the catalyst layer can be increased, and methanol oxidation can be performed more efficiently. In addition, by increasing the thickness of the catalyst layer, it is possible to increase the travel distance until the injected fuel reaches the electrolyte membrane, and the frequency with which the fuel is used in the reaction is improved. It becomes possible to reduce the decrease in fuel efficiency.

  The thickness of the fuel electrode catalyst layer is preferably 50 μm or more, and more preferably 200 μm or more. In this case, the oxidation efficiency of methanol and the effect of reducing the decrease in fuel efficiency caused by crossover are particularly good. The thickness of the fuel electrode catalyst layer is preferably 1000 μm or less, for example, in terms of manufacturing cost.

[Embodiment 2]
FIG. 2 is a schematic diagram for explaining another preferred embodiment of the method for producing a membrane electrode assembly according to the present invention. Also in FIG. 2, for the sake of simplification, the catalyst layer laminated on one surface of the electrolyte membrane is shown as a representative. For operations not specifically described below, the same operations as in the first embodiment can be preferably employed. Elements having the same functions as those in FIG. 1 are denoted by the same reference numerals.

  In the present embodiment, in the catalyst layer forming step, the base material 1 is overlapped with the porous metal 4 (FIG. 2A), and the base material 1 and the porous metal 4 are fixed in advance. In the portion where the metal 4 is laminated, the catalyst powder 2 is filled with the catalyst powder from the surface opposite to the laminated surface of the base material 1 into the void of the porous metal 4, and the catalyst layer 2 composed of the catalyst powder and the porous metal is formed. It forms (FIG. 2 (B)).

  In the present embodiment, in the catalyst layer forming step, the porous metal 4 that is also a constituent material of the catalyst layer is used as a mold, and the catalyst powder and the porous metal are filled by filling the voids of the porous metal 4 with the catalyst powder. The catalyst layer 2 comprised by these is formed. As shown in FIG. 2B, when a portion not filled with the catalyst powder is provided in a part of the porous metal 4, a fuel cell take-out electrode 5 made of the porous metal 4 can be formed.

  Since the porous metal 4 used as a mold plays the role of the core of the catalyst layer 2, according to the present embodiment, the strength of the catalyst layer can be further improved. Further, the porous metal 4 can be used as a take-out electrode of the fuel cell. In this case, the electrons generated or supplied in the catalyst layer 2 pass through a portion of the porous metal having a lower resistance than the portion derived from the catalyst powder, whereby the ohmic loss can be further reduced. In the conventional manufacturing method, when the solvent is volatilized after the catalyst slurry is filled in the porous metal, the portion derived from the catalyst slurry contracts and the proton conduction path is disrupted. Since the catalyst is filled in the state coated with the electrolyte, a catalyst layer having a proton conduction path can be produced.

  In the present invention, it is preferable to fill the catalyst powder after fixing the porous metal 4 to the substrate 1 using the substrate 1, but the catalyst powder is applied to the porous metal 4 without using the substrate 1. You may fill.

  The material of the porous metal 4 is preferably a metal because it has a small specific resistance and suppresses a decrease in voltage even when a current is taken in the layer thickness direction in a fuel cell, has an electron conductivity, and is in an acidic atmosphere. A metal having corrosion resistance is more preferable. Specifically, it can be exemplified by noble metals such as Au, Pt, Pd, metals such as Ti, Ta, W, Nb, Ni, Al, Cr, Ag, Cu, Zn, Su, C, Si, etc., stainless steel An alloy such as Ti—Pt is also preferable. These nitrides and carbides can also be used. Among these, it is more preferable that at least one element selected from the group consisting of Ti, Au, Cu, Ni, and W is included.

  In addition, when using a metal having poor corrosion resistance in an acidic atmosphere such as Cu, Ag, Zn, etc., a material having corrosion resistance such as Au, Ag, Pt, a conductive polymer, a conductive oxide Etc. can be used as a surface coating. In this case, the lifetime of the membrane electrode assembly can be further extended.

  The shape of the porous metal 4 is, for example, that it can supply fuel and air in the application of a fuel cell and has good discharge efficiency of exhaust gas generated at the fuel electrode and water generated at the air electrode. It is preferable that the porous layer has a plurality of holes. Furthermore, in order to promote the discharge of the exhaust gas generated at the fuel electrode, for example, a porous layer such as a foam, a nonwoven fabric, or a mesh knitted with a wire is more preferable.

  In the joining step, the electrolyte membrane 3, the catalyst layer 2, and the base material 1 are stacked in this order, and joined by the same method as in the first embodiment (FIG. 2C). A membrane electrode assembly can be formed by the above method.

[Embodiment 3]
In the present embodiment, an embodiment will be described in which the catalyst layer is formed by joining the constituent material of the catalyst layer and the electrolyte membrane and then filling the porous metal with the catalyst powder.

  FIG. 3 is a schematic diagram for explaining another preferred embodiment of the method for producing a membrane electrode assembly according to the present invention. Also in FIG. 3, for the sake of simplicity, the catalyst layer laminated on one surface of the electrolyte membrane is shown as a representative. For operations not specifically described below, operations similar to those in the first or second embodiment can be preferably employed. Elements having the same functions as those in FIGS. 1 and 2 are denoted by the same reference numerals.

  In the method shown in FIG. 3, a porous metal 4 similar to that described in Embodiment 2 is used as a mold (FIG. 3A). The porous metal 4 is joined to the electrolyte membrane 3 (joining step) (FIG. 3B), and then the porous metal 4 is bonded to the electrolyte membrane 3 in the same manner as described in the second embodiment. The catalyst powder 2 is filled into the porous metal 4 from the surface opposite to the joint surface to form the catalyst layer 2 (FIG. 3C) (catalyst layer forming step). At this time, since neither electrons nor protons are exchanged at the interface between the electrolyte membrane 3 and the porous metal 4, the electrolyte membrane 3 and the porous metal 4 are bonded using an adhesive having no electron conductivity and proton conductivity. It is also possible to join. In this case, it is possible to use a cheaper adhesive, and it is possible to provide a more stable membrane electrode assembly by improving the bonding force between the members.

[Example]
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
(Slurry preparation process)
A catalyst-supported carbon particle (TEC66E50, manufactured by Tanaka Kikinzoku Co., Ltd.) having a Pt loading amount of 32.5 wt% and a Ru loading amount of 16.9 wt%, and 20 wt% Nafion (registered), comprising Pt particles, Ru particles, and carbon particles. (Trademark) alcohol solution (manufactured by Aldrich), isopropanol, and zirconia beads at a predetermined ratio in a container made of PTFE (polytetrafluoroethylene) and mixed for 50 minutes at 500 rpm using a stirrer. A catalyst slurry was prepared. In addition, using catalyst-supported carbon particles (TEC10E50E, manufactured by Tanaka Kikinzoku Co., Ltd.) having a Pt support amount of 46.8 wt% made of Pt particles and carbon particles, under the same production conditions as the catalyst slurry for the fuel electrode, A catalyst slurry was prepared.

(Catalyst powder preparation process)
The produced catalyst slurry for the fuel electrode was put in a mortar, and the solvent was dried while kneading with a pestle in an atmosphere of 25 ° C. to produce a catalyst powder. The catalyst powder preparation step took 3 hours.

(Catalyst layer formation process)
Next, the catalyst layer of the fuel electrode was formed by the method shown in FIG. A carbon paper (GDL35BC, manufactured by SGL Carbon Co.) having a thickness of 0.32 mm is used as the base material 1 for the fuel electrode, and a 0.6 mm thick acrylic mask provided with a catalyst powder filling space 31 of 23 × 23 mm is used as a mold 30. After filling the catalyst powder, a step of applying a spacer in the thickness direction so that the base material 1 is not crushed and repeating the pressure in the thickness direction is repeated three times, and finally the mold 30 is removed, whereby the catalyst layer 2 is formed on the base material 1. A fuel electrode catalyst layer was prepared. As the spacer, a frame-shaped Teflon (registered trademark) sheet having a thickness of 0.8 mm was used. The mold 30 filled with the catalyst powder is installed in the central opening of the frame-shaped Teflon (registered trademark) sheet, and a PET film having the same outer size as the frame-shaped Teflon (registered trademark) sheet is placed between the substrate 1 and the mold 30. The laminate was placed at the top and bottom of the laminate and pressed at a pressing pressure of 10 kgf / cm ² for 1 minute. The catalyst forming step for forming the fuel electrode catalyst layer took 0.5 hour.

On the other hand, an air electrode catalyst layer was also formed by a method different from the above. As a base material 1 for an air electrode, a carbon paper having a thickness of 0.32 mm (GDL35BC, manufactured by SGL Carbon Co., Ltd.) is used, cut into a size of 23 × 23 mm, and the amount of supported catalyst Pt is 1 mg / cm ² . An air electrode catalyst layer was prepared by applying a catalyst slurry for the air electrode by screen printing.

(Joining process)
The fuel electrode catalyst layer and the air electrode catalyst layer formed above were placed on both sides of a 175 micron thick Nafion (registered trademark) membrane (manufactured by DuPont) for 5 minutes at a temperature of 135 ° C. and a pressure of 10 kgf / cm ² (preheating 2 minutes). , Press 3 minutes) hot pressing.

A membrane electrode assembly was produced by the above method. In the membrane electrode assembly, the thickness of the fuel electrode catalyst layer was 600 μm, and the thickness of the air electrode catalyst layer was 20 μm. The membrane electrode assembly is incorporated in such a manner as to be sandwiched between characterization cells (FC05-01SP-REF, manufactured by Electrochem), and 3M methanol aqueous solution is sent to the anode flow path at a flow rate of 5.0 ml / min, and 200 ml / min. When hydrogen was sent to the cathode channel at a flow rate of 30 and a fuel electrode was generated under a load of 30 mA / cm ² in a measurement environment of 40 ° C., the output voltage was 0.36V.

<Comparative Example 1>
Use carbon paper (GDL35BC, manufactured by SGL Carbon Co., Ltd.) with a thickness of 0.32 mm as the base material for the fuel electrode, cut into a size of 23 × 23 mm, and for the fuel electrode so that the supported amount of catalyst PtRu is 3 mg / cm ² A membrane electrode assembly was produced in the same manner as in Example 1 except that the fuel electrode catalyst layer was produced by applying the catalyst slurry by screen printing. In the obtained membrane electrode assembly, the thickness of the fuel electrode catalyst layer was 42 μm, and the thickness of the air electrode catalyst layer was 20 μm as in Example 1. When the characteristics of the obtained membrane electrode assembly were evaluated in the same manner as in Example 1, the output voltage was 0.37V.

  From the above results, it can be seen that according to the production method of the present invention, a catalyst layer capable of reducing overvoltage can be formed.

<Comparative example 2>
A membrane electrode assembly was produced in the same manner as in Comparative Example 1 except that the amount of PtRu supported on the fuel electrode was 30 mg / cm ^{2. In} order to form a fuel electrode catalyst layer having a thickness of 600 μm, the fuel electrode was formed by screen printing. It was necessary to repeat the process of applying and drying the catalyst slurry for 150 times, and the process for forming the fuel electrode catalyst layer took 25 hours.

  From the above results, it can be seen that the time for forming the catalyst layer can be greatly shortened in the production method of the present invention.

<Example 2>
A membrane electrode assembly produced in the same manner as in Example 1 except that VGCF (manufactured by Showa Denko) was further contained in the catalyst slurry for the fuel electrode so as to be 10% by mass with respect to the catalyst-supported carbon, When evaluated by the same method as in Example 1, the output voltage was 0.35V.

  From the above results, it is confirmed that when the conductive fiber is contained in the slurry in the production method of the present invention and the membrane electrode assembly is produced using the slurry, the fuel cell characteristics can be further improved. It was done.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The membrane electrode assembly produced by the production method of the present invention can be suitably applied to, for example, a fuel cell.

It is a schematic diagram explaining the preferable one aspect | mode of the manufacturing method of the membrane electrode assembly which concerns on this invention. It is a schematic diagram explaining another preferable aspect of the manufacturing method of the membrane electrode assembly which concerns on this invention. It is a schematic diagram explaining another preferable aspect of the manufacturing method of the membrane electrode assembly which concerns on this invention.

Explanation of symbols

  1 base material, 2 catalyst layer, 3 electrolyte membrane, 4 porous metal, 5 extraction electrode, 30 type, 31 catalyst powder filling space.

Claims (7)

A method for producing a membrane electrode assembly comprising a catalyst layer laminated on an electrolyte membrane,
A slurry preparation step of preparing a slurry containing a catalyst, an electrolyte, and a solvent;
A catalyst powder preparation step of preparing a catalyst powder by removing the solvent in the slurry;
A catalyst layer forming step of compressing the catalyst powder with a mold to form a catalyst layer;
A bonding step of bonding the catalyst layer or the constituent material of the catalyst layer to an electrolyte membrane;
A process for producing a membrane electrode assembly.   The method for producing a membrane electrode assembly according to claim 1, wherein the removal of the solvent in the catalyst powder preparation step is performed while the slurry is kneaded.   The method for producing a membrane electrode assembly according to claim 1 or 2, wherein the mold is a porous metal.   The manufacturing method of the membrane electrode assembly according to claim 3, wherein the constituent material to be joined to the electrolyte membrane in the joining step is the porous metal.   The manufacturing method of the membrane electrode assembly according to any one of claims 1 to 4, wherein the slurry further contains conductive fibers.   The method for producing a membrane electrode assembly according to any one of claims 1 to 5, wherein the catalyst layer is a fuel electrode catalyst layer of a fuel cell.   The method for producing a membrane electrode assembly according to claim 6, wherein the catalyst layer has a thickness of 50 μm or more.

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