WO2008032597A1

WO2008032597A1 - Membrane electrode assembly and method for producing the same

Info

Publication number: WO2008032597A1
Application number: PCT/JP2007/067130
Authority: WO
Inventors: Keizo Hayashi; Hideki Hiraoka
Original assignee: Toagosei Co., Ltd.
Priority date: 2006-09-13
Filing date: 2007-09-03
Publication date: 2008-03-20
Also published as: JPWO2008032597A1

Abstract

Disclosed is a membrane electrode assembly which enables to exhibit higher battery performance than the conventional ones in a high load region when used in a fuel cell. Also disclosed is a method for producing such a membrane electrode assembly. Specifically disclosed is a membrane electrode assembly (10) comprising an electrode (18) having a diffusion layer (14) and a catalyst layer (16) on both sides of an electrolyte membrane (12). The electrolyte membrane (12) is obtained by filling pores of a porous membrane (28) with an electrolyte (30). At least one catalyst layer (16) is formed by spraying a liquid composition containing a catalyst (20) and an electrolyte (22) for inside the catalyst layer.

Description

Specification

Membrane electrode assembly and manufacturing method thereof

Technical field

TECHNICAL FIELD [0001] The present invention relates to a membrane electrode assembly and a manufacturing method thereof, and more particularly to a membrane electrode assembly suitable for use in a fuel cell and a manufacturing method thereof.

Background art

Conventionally, as a fuel cell, for example, a polymer electrolyte fuel cell and a direct alcohol fuel cell are known.

[0003] Inside these fuel cells, a membrane electrode assembly (MEA: Membrane Electrode) is generally used.

The member that manages the heart of the battery called Assembly) is built in!

[0004] This membrane electrode assembly usually has an electrode (anode, force sword) force in which a diffusion layer and a catalyst layer are laminated on both sides of an electrolyte membrane, and has a structure in which the catalyst layer side is inward. Have

[0005] The diffusion layer is a layer for supplying reactants (oxidant and fuel) to the catalyst layer and transferring electrons, and is porous and electronically conductive, such as carbon paper. Materials are used.

[0006] On the other hand, the catalyst layer is a layer that serves as a reaction field for battery reaction, and a material containing a catalyst and an electrolyte supported on a carrier is often used!

[0007] As this type of membrane electrode assembly, for example, JP-A-2004-146279 discloses a membrane electrode assembly produced as follows.

That is, first, platinum-supported carbon, a polymer electrolyte solution, and polytetrafluoroethylene dispersion are blended, and water is added and stirred to prepare a catalyst layer coating material.

Next, this catalyst layer coating material is printed on carbon paper (diffusion layer) by screen printing and dried to produce an electrode.

[0010] Next, as the electrolyte membrane, a porous membrane made of crosslinked polyethylene filled with a polymer of 2-acrylamido-2-methylpropanesulfonic acid is used, and on the surface of the electrolyte membrane, The electrode layers of the above electrodes are stacked and heated and pressed, etc. Combine.

Disclosure of the invention

Problems to be solved by the invention

However, the conventional membrane / electrode assembly still has room for improvement in the following points.

That is, when a conventional membrane electrode assembly is directly incorporated into a methanol fuel cell to generate electric power, for example, the cell characteristics in a high load region (high current density region) are not so high, and this needs to be improved. was there.

[0013] Firstly, the catalyst layer is formed by applying the coating material for the catalyst layer. Therefore, it is difficult to form pores in the catalyst layer, and the three-dimensional expansion of the pores is also small. This is because it is difficult for oxidants such as air and fuel to penetrate into the catalyst layer.

[0014] Secondly, due to the small number of pores in the catalyst layer, products such as water (power sword side) and carbon dioxide (anode side) generated by the cell reaction are difficult to be discharged. .

[0015] Further, when the catalyst layer coating is applied to the diffusion layer, the catalyst layer coating is easily impregnated in the pores of the diffusion layer. Therefore, it is considered that one of the causes is that the vacancies in the diffusion layer are blocked, which makes it difficult for the oxidant and the fuel to penetrate into the catalyst layer.

[0016] The present invention has been made in view of the above circumstances, and the problem to be solved by the present invention is that, when used in a fuel cell, it is possible to exhibit higher battery performance than before in a high load region. It is in providing a membrane electrode assembly and its manufacturing method.

Means for solving the problem

[0017] In order to solve the above problems, a membrane electrode assembly according to the present invention has electrodes each having a diffusion layer and a catalyst layer on both sides of an electrolyte membrane, and the electrolyte membrane is porous. The gist is that the pores of the membrane are filled with an electrolyte, and at least one of the catalyst layers is formed by spraying a liquid composition containing the catalyst and the electrolyte in the catalyst layer.

[0018] Here, it is preferable that the surface of the porous membrane is exposed in the electrolyte membrane.

[0019] The catalyst layer is preferably fused to the surface of the electrolyte membrane.

[0020] Further, the porous membrane is made of an olefin resin, and the electrolyte filled in the pores is a polyacrylamide having a 2-acrylamide 2-methylpropanesulfonic acid monomer unit. Or a cross-linked product thereof.

[0021] On the other hand, the method for producing a membrane / electrode assembly according to the present invention is a method for producing a membrane / electrode assembly having electrodes each provided with a diffusion layer and a catalyst layer on both sides of an electrolyte membrane, The membrane is obtained by filling the pores of the porous membrane with an electrolyte, and forming at least one of the catalyst layers by spraying a liquid composition containing the catalyst and the electrolyte in the catalyst layer.

[0022] Here, in the above production method, the catalyst layer may be formed by spraying the liquid composition on at least one surface of the electrolyte membrane.

[0023] Alternatively, the catalyst layer is preferably formed through the following steps (1) to (3).

(1) A step of spraying the liquid composition on the surface of a separately prepared film substrate to form a catalyst layer

(2) Step of transferring the catalyst layer formed in (1) to one surface of the diffusion layer to produce an electrode provided with the catalyst layer

(3) A process of bonding the surface of the catalyst layer of the electrode prepared in (2) and the surface of the electrolyte membrane.

[0024] In this case, more preferably, the electrode is provided between the step (1) and the step (2) and / or between the step (2) and the step (3). It has a process to heat the electrolyte and insolubilize the electrolyte in the catalyst layer!

[0025] The sprayed catalyst layer may be further fused to the surface of the electrolyte membrane.

[0026] Further, the electrolyte membrane may have the surface of the porous membrane exposed.

[0027] The liquid composition may be sprayed in a plurality of times.

The invention's effect

[0028] In the membrane / electrode assembly according to the present invention, at least one of the catalyst layers is formed by spraying the liquid composition. Therefore, in the catalyst layer, the sprayed liquid composition is appropriately aggregated and deposited.

[0029] Therefore, the catalyst layer is presumed to have more pores in the layer than the catalyst layer formed by applying the liquid composition. In addition, there are many three-dimensional vacancies in the layer, and it is assumed that oxidants such as air and fuel can easily penetrate into the catalyst layer. It is. Further, it is assumed that products such as water (power sword side) and carbon dioxide (anode side) generated by the cell reaction are easily discharged due to the large number of pores in the catalyst layer.

[0030] Thus, when the membrane electrode assembly according to the present invention is incorporated in a fuel cell, it has a higher electric power than a conventional one in a high load region (high current density region) that requires a large amount of oxidant and fuel. Pond performance can be expressed.

[0031] Here, when an electrolyte membrane having an exposed porous membrane surface is used as the electrolyte membrane, there are the following advantages.

That is, the electrolyte membrane in which the pores of the porous membrane are filled with the electrolyte and the surface of the porous membrane is exposed has good adhesion to the electrode (catalyst layer), The ionic connectivity between the catalyst layer and the electrolyte in the pores tends to be insufficient.

However, when the liquid composition is sprayed on the surface of the electrolyte membrane to form a catalyst layer, the electrolyte in the catalyst layer contained in the composition spreads on the membrane surface, so The ionic connection between the desolation and the electrolyte in the catalyst layer is improved.

[0034] Further, when a step of forming the catalyst layer by spraying the liquid composition on the surface of the film base prepared separately from the electrolyte membrane, the surface of the film base in the formed catalyst layer is performed. Similarly, the electrolyte in the catalyst layer spreads on the contact surface. Next, when the catalyst layer is transferred to one surface of the diffusion layer for the electrode and an electrode with the catalyst layer is produced, the surface in which the electrolyte in the catalyst layer spreads comes into contact with the electrolyte membrane side. . Therefore, also in this case, the effect of improving the ionic connection between the electrolyte in the hole and the electrolyte in the catalyst layer can be obtained.

[0035] Furthermore, when the transfer method as described above is used, since the material constituting the electrode is a heat-resistant material such as carbon fiber, it can be heated more easily than the electrolyte membrane.

[0036] A perfluorocarbon sulfonic acid polymer such as naphthion (registered trademark) is generally used as the electrolyte in the catalyst layer. Usually dissolved or dispersed in a mixed solvent such as alcohol or water. Has been. For this reason, simply removing the solvent by volatilization will cause power generation performance to deteriorate due to swelling or dissolution in an environment in contact with water or methanol, such as DMFC. In order to prevent this, it is better to insolubilize the electrolyte in the catalyst layer by heating.

[0037] The insolubilization by heating as described above is about tens of minutes to several hours at a temperature of about 140 to 200 ° C. When the catalyst layer is sprayed directly onto the electrolyte membrane, the electrolyte membrane must have a sufficiently high heat resistance, and the usable electrolyte membrane is limited.

[0038] For this reason, in the method of transferring onto the diffusion layer, a heating step can be inserted before the transfer or after the transfer step and before the step of bonding to the electrolyte membrane, and the options for the electrolyte membrane are widened. In particular, an electrolyte membrane that uses an olefin resin as the porous substrate to expose the surface of the porous substrate is softened and fused at the temperature at which the electrodes are bonded together to strengthen the adhesion to the electrodes. Therefore, when combined with such a membrane, an excellent membrane electrode assembly can be obtained.

[0039] As described above, when the ionic connection is improved, the utilization factor of the catalyst existing on the outer surface of the pore portion of the electrolyte membrane is improved, and the low load region (low current density region) where the influence of the catalyst utilization factor is large. However, high battery performance can be achieved. In other words, in this case, there is an advantage that the battery performance can be expressed in both the high load range and the low load range.

Yes

[0040] Further, in the membrane electrode assembly according to the present invention, when the catalyst layer is fused to the electrolyte membrane surface, the adhesiveness between the electrolyte membrane and the catalyst layer is excellent. It becomes difficult to peel off and the durability of the membrane electrode assembly is improved.

[0041] The porous membrane is made of olefin resin, and the electrolyte filled in the pores is a polymer having a 2-acrylamido-2-methylpropanesulfonic acid monomer unit or a crosslinked product thereof. In this case, an electrolyte membrane having high! / Proton conductivity is obtained.

[0042] This is because the monomer has good polymerizability and good water solubility, so that it is easy to increase the filling rate into the pores.

[0043] On the other hand, according to the method for producing a membrane / electrode assembly according to the present invention, as described above, a membrane / electrode assembly capable of exhibiting higher battery performance than before can be obtained in a high load region.

Here, as described above, the liquid composition is sprayed on the surface of the electrolyte membrane to form a catalyst layer, or the liquid composition is applied to the surface of a film base prepared separately from the electrolyte membrane. When the catalyst layer is formed by spraying and transferred to one surface of the electrode diffusion layer to form the catalyst layer, the electrolyte in the catalyst layer contained in the composition spreads on the membrane surface, so The ionic connection between the electrolyte inside the catalyst and the electrolyte inside the catalyst layer is improved. [0045] Therefore, the utilization rate of the catalyst present on the outer surface of the pores of the electrolyte membrane is improved, the influence of the catalyst utilization rate is large, and the battery performance is high even in a low load region (low current density region). A membrane electrode assembly can be obtained. This is particularly effective when using an electrolyte membrane in which a porous membrane having no ion conductivity is exposed on the surface.

[0046] When the spray-formed catalyst layer is further fused to the surface of the electrolyte membrane, the adhesion between the electrolyte membrane and the catalyst layer is improved. Therefore, the catalyst layer is difficult to peel off, and a membrane electrode assembly with excellent durability can be obtained. This is particularly effective when an electrolyte membrane having a porous membrane exposed on the surface is used.

[0047] When the liquid composition is sprayed in a plurality of times, it becomes easier to form more pores in the catalyst layer.

Brief Description of Drawings

FIG. 1 is a cross-sectional view schematically showing an example of the present MEA.

FIG. 2 is a cross-sectional view schematically showing an example of a catalyst layer in this MEA. BEST MODE FOR CARRYING OUT THE INVENTION

[0049] Hereinafter, the membrane electrode assembly according to the present embodiment (hereinafter sometimes referred to as "the present MEA") and the manufacturing method thereof (hereinafter also referred to as "the present manufacturing method") will be described in detail. To do.

[0050] 1. This MEA

FIG. 1 is a cross-sectional view schematically showing an example of this MEA. In this MEA 10, electrodes 18 each having a diffusion layer 14 and a catalyst layer 16 are laminated on both surfaces of an electrolyte membrane 12. The MEA preferably has the catalyst layer 16 bonded to the electrolyte membrane 12, but in the present application, the MEA includes one in which the catalyst layer 16 is not bonded to the electrolyte membrane 12.

[0051] 1.1 Electrolyte membrane

In this MEA, the electrolyte membrane is a membrane in which the pores of the porous membrane are filled with electrolyte.

[0052] (Porous membrane)

The porous membrane mainly forms the skeleton of the electrolyte membrane, and has a large number of through-holes penetrating from one surface to the other surface of the membrane. In addition to the through holes, non-through holes may exist. In this case, for example, the through hole may penetrate substantially perpendicularly to the film surface, or may penetrate through the film surface at an angle of less than 90 °. Moreover, it may penetrate at random, such as meandering or zigzag.

[0054] The cross-sectional shape of the through hole is not particularly limited as long as it can be filled with an electrolyte. Specific examples of the cross-sectional shape of the through hole include a circle, an ellipse, a polygon, a shape in which these are connected, and a combination thereof.

[0055] The upper limit of the porosity of the porous membrane is preferably 95% or less, more preferably 90% or less, more preferably 85% or less, and still more preferably 80% or less. On the other hand, the lower limit of the porosity of the porous membrane is most preferably 5% or more, preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. This is because if the porosity of the porous membrane is within the above range, the balance between the electrolyte group amount per unit area and the membrane strength is good.

[0056] The porosity is obtained by determining the volume from the thickness and area of the porous membrane, measuring the weight, and calculating the proportion of air in the total volume from the specific gravity of the constituent material. The power to seek is S. Specifically, it can be obtained by the following equation.

Porosity% = (Porous membrane thickness X Porous membrane area Porous membrane weight / Constituent material specific gravity) / (Porous membrane thickness X Porous membrane area) X 100

[0057] The upper limit of the pore diameter of the porous membrane is preferably a force S of 50 m or less, more preferably 10 m or less, from the viewpoint of easily holding the electrolyte filled in the pore l ^ Most preferred is m or less. On the other hand, the lower limit of the pore diameter of the porous membrane is preferably 0.001 m or more, force S, and more preferably 0.01 · m or more from the viewpoint of easy filling of the pores.

[0058] If the pore diameter of the porous membrane is within the above range, the pores can be filled with the electrolyte relatively easily, and the filled electrolyte can be retained well, and it is difficult to drop off when the membrane is deformed. Because. In addition, the said hole diameter is a value measured by the mercury intrusion method.

[0059] The material of the porous membrane is not particularly limited as long as the above-described through-holes can be formed. For example, it is possible to exemplify organic materials such as polymers, inorganic materials such as ceramics (alumina, mritite, etc.), metals (including alloys), and composite materials composed of these materials. Of these, the hole is relatively easy to form, lightweight, etc. From this point of view, a polymer can be preferably used.

[0060] Specific examples of the polymer include, for example, ethylene resins (resins mainly composed of an ethylene monomer such as polyethylene), polyolefin resins such as polypropylene and polymethylpentene, and polychlorinated salts. Butyl chloride resin such as bur, polytetrafluoroethylene, polytrifluoroethylene, polychlorotrifluoroethylene, poly (tetrafluoroethylene hexafluoropropylene), poly (tetrafluoroethylene par Fluoroalkyl resins such as fluoroalkyl ester), polyamide resins such as nylon 6 and nylon 66, polyester resins, aromatic polyimide, aramid, polysulfone, polyphenylene oxide, poly ether ether ketone, Polycarbonate, phenol resin, epoxy resin, unsaturated polyester, etc. It can be exemplified. One or more of these may be included. Two or more kinds of polymers may be laminated. The polymer may be cross-linked as necessary.

[0061] Of the above polymers, thermoplastic polymers such as polyolefin resins such as polyethylene, polysulfone, polyphenylene oxide, polyamide resins, polyester resins, and the like can be preferably used. More preferred is an olefin resin such as an ethylene resin.

[0062] Since these thermoplastic polymers can be softened or melted by heating, the surface of the porous membrane is softened or melted when the spray-formed catalyst layer is heated and pressurized, and the like. This is because there are advantages such as easy fusion of the catalyst layer. For the thermoplastic polymer, a material having a softening temperature or a melting temperature higher than the operating temperature may be selected in consideration of the operating temperature of the fuel cell to which the MEA is applied.

[0063] As the upper limit of the thickness of the porous membrane, from the viewpoint of the internal resistance of the battery, 200 m or less is preferable, 150 m or less is more preferable, and 100 m or less is most preferable. On the other hand, the lower limit of the thickness of the porous membrane is preferably 1 am or more from the standpoint of maintaining the membrane strength and preventing defects such as tearing during electrode joining and incorporation into fuel cells. More preferably, 5 m or more is more preferable, and 10 m or more is most preferable.

[0064] If the thickness of the porous membrane is within the above range, the balance between membrane strength and membrane resistance is good. Also, when fuel such as methanol is used, permeation is easy to suppress. Because.

[0065] (Electrolyte)

The electrolyte filled in the pores of the porous membrane has a role of imparting ion conductivity to the membrane.

[0066] Specific examples of the electrolyte include an electrolyte polymer, an electrolyte polymer bridge (hereinafter, these may be collectively referred to as "electrolyte polymer"), an acid, a room temperature molten salt, and the like. A polymer containing an electrolyte can be exemplified as a suitable one. These include one or more types! /, May be! /.

[0067] When an electrolyte polymer or the like is used as the electrolyte, the electrolyte polymer or the like filled in the pores may exist as a polymer before being filled in the pores, or an electrolyte polymer or the like is generated. After the possible polymer precursor is filled in the pores, the polymer may be polymerized and bridged to form an electrolyte polymer. A specific method for filling the electrolyte polymer and the like will be described later in “2. Production method”.

[0068] Specific examples of the electrolyte group contained in the electrolyte polymer include, for example, acidic groups such as a sulfonic acid group, a sulfonimide group, a phosphonic acid group, a phosphonous acid group, and a carboxylic acid group. S can. One or more of these may be included. Of these, from the viewpoint of easily obtaining high proton conductivity, it is possible to suitably use a sulfonic acid group.

[0069] Specific examples of the electrolyte polymer include all polymer skeletons such as a perfluorocarbon sulfonic acid polymer such as naphthion, a perfluorocarbon phosphonic acid polymer, and a trifluorostyrene sulfonic acid polymer. Or a partially fluorinated fluoropolymer having an electrolyte group; polymer skeleton such as polysulfonesulfonic acid, polyaryletherketonesulfonic acid, polybenzimidazolealkylsulfonic acid, polybenzimidazolealkylphosphonic acid Does not contain fluorine! /, A hydrocarbon-based polymer having an electrolyte group; a monomer having an electrolyte group, a monomer having a functional group that can be converted to an electrolyte group, and an electrolyte group introduced before and after polymerization Monomers with possible sites, combinations of these An electrolyte monomer and the like Align the like may be exemplified polymers having as monomer units. These are one or more It may be included above.

Specific examples of the monomer having an electrolyte group include 2- (meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acrylamide-2-methylpropanephosphonic acid, and styrenesulfonic acid. , (Meth) aryl sulfonic acid, vinyl sulfonic acid, isoprene sulfonic acid, (meth) acrylic acid, maleic acid, crotonic acid, burphosphonic acid, acidic phosphate group-containing (meth) acrylate, etc. .

“(Meth) acryl” means “acrylic and / or methacrylic”, “(meth) aryl” means “aryl and / or methallyl”, “(meth) arylate” means “attalylate and / or metatalylate” (The same shall apply hereinafter).

[0071] Specific examples of the monomer having a functional group that can be converted into an electrolyte group before and after the polymerization include salts, anhydrides, esters, and the like of the above compounds. When the acid residue of the monomer to be used is a derivative such as a salt, an anhydride, or an ester, proton conductivity can be imparted by making it into a protonic acid type after polymerization.

[0072] Specific examples of the monomer having a site capable of introducing an electrolyte group before and after the polymerization include monomers having a benzene ring such as styrene, α-methylstyrene, chloromethylstyrene, and t-butylstyrene. can do. Specific examples of the method for introducing an electrolyte group into these include a method of sulfonation with a sulfonating agent such as chlorosulfonic acid, concentrated sulfuric acid, sulfur trioxide, and the like.

[0073] As these electrolyte monomers, from the standpoint of excellent proton conductivity, a bulle compound having a sulfonic acid group, a bur compound having a phosphoric acid group, and the like are more preferable, and preferably have a high polymerizability. From the point of view, 2- (meth) acrylamide-2-methylbutanesulfonic acid.

[0074] It is preferable that substantially all of the pores of the porous membrane are filled in the electrolyte from the viewpoint of obtaining high ionic conductivity. However, not all pores in the porous membrane need to be filled with electrolyte, so long as it does not adversely affect ionic conductivity, fuel permeability, etc., the electrolyte is filled. V, nare, les that may have holes partially.

[0075] The electrolyte membrane included in the MEA has been described above. The electrolyte membrane is a porous membrane If the electrolyte is filled in the pores, the electrolyte layer may be covered on the membrane surface (that is, outside the pores), or the porous membrane may be exposed on the membrane surface. The latter is preferred.

[0076] Since the porous membrane forming the skeleton of the electrolyte membrane and the catalyst layer can be directly fused, the interfacial strength is increased, the durability of the MEA can be improved, and a catalyst layer is provided on the membrane surface. The catalyst layer is formed by spraying or forming a catalyst layer on the surface of a film substrate prepared separately from the electrolyte membrane and transferring it to one side of the diffusion layer to form an electrode with the catalyst layer. The electrolyte in the membrane spreads over the membrane surface and can improve the ionic connection between the electrolyte in the pores and the electrolyte in the catalyst layer.

[0077] In this case, the porous film may be almost entirely exposed on the film surface, or the porous film may be partially exposed on the film surface.

[0078] 1. Two electrodes

In this MEA, the electrode includes a diffusion layer and a catalyst layer. The diffusion layer is a layer for supplying reactants (oxidant for a force sword electrode and fuel for an anode electrode) to the catalyst layer and for transferring electrons. On the other hand, the catalyst layer is a layer serving as a reaction field for battery reaction. The catalyst layer is disposed on the membrane surface side of the electrolyte membrane.

[0079] Specifically, as the structure of the electrode, for example, as illustrated in FIG. 1, a structure in which the catalyst layer 16 and the diffusion layer 14 are laminated in this order from the electrolyte membrane 12 side may be exemplified. it can. In addition, for example, an intermediate layer containing conductive powder such as carbon powder and a binder such as thermoplastic polymer is interposed between the catalyst layer and the diffusion layer from the viewpoint of increasing the catalyst utilization rate. You can let it. Note that the intermediate layer may be present on either one of the electrodes, or may be present on both of the electrodes.

[0080] In the above electrode, the diffusion layer and the catalyst layer may be bonded to each other or simply in contact as long as each layer can achieve the above-described purpose. Further, in either one electrode, both layers may be bonded to each other, and in the other electrode, both layers may be in contact with each other. Preferably, the diffusion layer and the catalyst layer are bonded to each other in at least one, more preferably both electrodes. If both layers are integrated, the battery is easy to handle and can be manufactured more efficiently. is there.

[0081] The electrode laminated on one surface of the electrolyte membrane functions as a force sword electrode, and the electrode laminated on the other surface of the electrolyte membrane functions as an anode electrode. Therefore, as long as each electrode functions as an anode and a force sword, the material of each diffusion layer and catalyst layer may be the same or different.

[0082] Specifically, the material of the diffusion layer is, for example, a conductive powder such as carbon paper, carbon cloth, carbon non-woven fabric, carbon black or the like formed into a sheet shape together with a binder such as PTFE. Examples thereof include foam metal, metal mesh, and metal mesh fixed with conductive powder with a binder. These may be used alone or in combination of two or more. From the viewpoints of corrosion resistance, good strength, and easy handling, carbon paper, carbon cloth, etc. can be suitably used.

[0083] Further, the diffusion layer on the force sword side may be subjected to a hydrophobic treatment, for example, by treating carbon paper or the like with a hydrophobic polymer such as fluorine resin. On the other hand, for the diffusion layer on the anode side, for example, carbon paper or the like is heated in air, oxidized with a strong acid, or treated with a hydrophilic polymer such as polybutyl alcohol. Even if it is hydrophilized,

[0084] The thickness of the diffusion layer is not particularly limited, and can be appropriately set in consideration of the size of the electrode, the current range mainly used, the size of the system, and the like.

[0085] The upper limit of the thickness of the diffusion layer is preferably 5000 m or less force S, more preferably 1000 m or less, and most preferably 500 m or less. On the other hand, the lower limit of the thickness of the diffusion layer is most preferably 30 m or more, preferably 5 111 or more, more preferably 10 m or more. Note that the thickness of the diffusion layer on the force sword side and the thickness of the diffusion layer on the anode side may be the same or different.

Here, as shown in FIG. 2, the catalyst layer 16 includes a catalyst 20 and an electrolyte 22 in the catalyst layer as essential components. In this case, the catalyst 20 may be contained in the catalyst layer 16 in a state of being supported on a conductive carrier 24. In FIG. 2, 26 is a hole. 28 is a porous membrane. Reference numeral 30 denotes an electrolyte filled in the pores of the porous film 28. Further, in FIG. 2, the electrolyte membrane 12 is exemplified by the case where the surface of the porous membrane 28 is exposed. Yes.

[0087] Examples of the catalyst include noble metal fine particles and noble metal alloy fine particles. Specific examples include platinum, platinum ruthenium alloy, palladium, platinum-cobalt alloy, platinum-iron alloy, and the like. One or more of these may be included.

[0088] More specifically, as the force sword side catalyst, for example, platinum can be suitably used. On the other hand, as the catalyst on the anode side, for example, a platinum ruthenium alloy that can easily reduce the poisoning of the catalyst by carbon monoxide can be suitably used.

[0089] Specific examples of the carrier include carbon black. One or more of these are included! /, May be! /.

[0090] Examples of the electrolyte in the catalyst layer include electrolyte polymers exemplified as the electrolyte filled in the pores. These may be used alone or in combination of two or more. Among these, from the viewpoint of excellent oxidation resistance, ion conductivity, catalyst binding, methanol resistance, and the like, a fluorine-based polymer having an electrolyte group can be preferably used.

[0091] Here, in the present MEA, at least one of the catalyst layers is formed by spraying a liquid composition containing the catalyst and the electrolyte in the catalyst layer. In the present application, “spraying” and “application” are used separately as different terms.

[0092] In the catalyst layer thus formed, the spray-formed liquid composition is appropriately aggregated and accumulated, so that a large number of pores are formed and the pores are three-dimensionally expanded. Become more.

[0093] Preferably, both catalyst layers are formed by spraying the liquid composition from the standpoint of easily improving battery performance in a high load range.

[0094] "Liquid" as used in the above liquid composition means that the composition has fluidity that allows the composition to be sprayed by a spraying device such as a spray. Therefore, the fluidity of the liquid composition is different from that of the composition prepared in a paste form when the catalyst layer is printed by screen printing or the like.

[0095] Specifically, the liquid composition can be obtained by diluting the catalyst and the electrolyte in the catalyst layer to a viscosity suitable for spraying using a diluent such as water or a solvent. Can [0096] Since the above-mentioned liquid composition will be described in detail in "2. Production method", only the above description will be given here.

[0097] The catalyst layer may be formed by spraying the liquid composition once, or may be formed by spraying the liquid composition a plurality of times (split spray)! / Good. In the case where the catalyst layer is dividedly formed, the composition of the liquid composition sprayed in each divided layer may be the same! /, And the layer may be different in each divided layer. ,.

[0098] The catalyst layer is preferably divided and formed! /. This is because vacancies tend to spread three-dimensionally because the sprayed liquid composition is repeatedly condensed and deposited. Another advantage is that it is easy to control the amount of catalyst contained in the catalyst layer during production of this MEA.

[0099] The thickness of the catalyst layer is not particularly limited, and can be set as appropriate in consideration of the amount of catalyst required for battery design, the load during power generation, and the like.

[0100] As the upper limit of the thickness of the catalyst layer, if it is too thick, from the viewpoint of increasing the resistance of the catalyst layer itself, 200 ^ 111 or less force S is preferable, Ο δΟ ^ ιη or less force S is preferable, l OO ^ m or less is most preferable. On the other hand, the lower limit of the thickness of the catalyst layer is preferably 1 m or more, more preferably δ μ ηι or more from the viewpoint of increasing the number of reaction points by increasing the three-phase interface and improving battery performance. 10 m or more is most preferable.

[0101] The thickness of the catalyst layer on the force sword side and the thickness of the catalyst layer on the anode side may be the same or different.

[0102] The catalyst layer may be laminated in contact with the surface of the electrolyte membrane, or may be bonded to the surface of the electrolyte membrane, for example. From the viewpoint of excellent durability when incorporated in a fuel cell, the catalyst layer is preferably bonded to the surface of the electrolyte membrane, and more preferably, the catalyst layer is porous on the surface. It should be fused to the surface of the electrolyte membrane where the membrane is exposed. It should be noted that the catalyst layer and the diffusion layer may be joined together, or may be acceptable, or may be contacted or removed.

[0103] 2. Manufacturing method

This production method is a method capable of producing this MEA. In this manufacturing method, at least one of the two electrodes formed on both surfaces of the electrolyte membrane, preferably both The catalyst layer in the electrode is formed by spraying a liquid composition containing the catalyst and the electrolyte in the catalyst layer.

[0104] (Preparation of electrolyte membrane)

In this manufacturing method, an electrolyte membrane in which an electrolyte is filled in the pores of the porous membrane is used. The detailed configuration of the electrolyte membrane is as described in “1. MEA”.

[0105] Here, the method for obtaining the porous film differs depending on the material, but for example, a method by stretching, a solution of a film material in which a pore former is dispersed or a melt is applied in a film shape, Solvent is removed by volatilization or the film material in the molten state is cooled to form a film, and the pore former is removed to form a hole. Punching and drilling are performed on the film material formed in the film shape. , Laser, chemical / physical etching and other processing methods to form holes, and after pouring a melt of polymer material or other material into a bowl that can transfer holes, peel it off By doing so, a method of transferring the hole to the film surface can be exemplified.

[0106] When the material of the porous membrane is a polymer, the most general method is a method by stretching. That is, in this method, a film material such as a polymer and a liquid or solid pore former are mixed by a method such as melt mixing, and the pore former is once finely dispersed and extruded from a T die or the like. While stretching, the pore former is removed by a method such as washing to form a porous film.

[0107] As stretching methods, there are methods such as uniaxial stretching and biaxial stretching. The force S can be used to determine the shape of the hole, etc., depending on the stretching ratio, the ratio and type of pore former, the blending amount, and the type of membrane material.

[0108] When the porous membrane is formed of a hydrophobic polymer material, at least one of the surfaces of the porous membrane may be subjected to a hydrophilic treatment. When the porous material is impregnated with a highly hydrophilic electrolyte material, if the porous membrane has been hydrophilicized in advance, the impregnation property into the pores can be improved, and the productivity of the membrane electrode assembly can be improved. Because.

Specific examples of the hydrophilic treatment method include surfactant treatment, corona treatment, sulfonation treatment, hydrophilic polymer graft treatment, and the like. One or more of these treatments may be used in combination.

[0110] The method of filling the electrolyte in the pores of the porous membrane is not particularly limited. Specifically, for example, an electrolyte solution or dispersion, or molten electrolysis After impregnating the pores with a solution or dispersion of an electrolyte precursor or a molten electrolyte precursor, the electrolyte is generated from the electrolyte precursor impregnated in the pores. A method etc. can be illustrated.

[0111] As the impregnation method, specifically, for example, a method of immersing the porous membrane in the above solution or the like, various coating methods (die coating method, comma coating) on the porous membrane of the above solution or melt. For example, a coating method, a gravure coating method, a roll coating method, a bar coating method, a reverse coating method, etc.). These may be used alone or in combination of two or more.

[0112] When the electrolyte to be filled is an electrolyte polymer or the like, as a method of filling the electrolyte polymer or the like in the pores of the porous membrane, specifically, for example, a solution or dispersion of the electrolyte polymer or a melt A method of impregnating the electrolyte polymer in the state of the pores, a solution or dispersion of the polymer precursor of the electrolyte polymer or a polymer precursor in the molten state in the pores, and then the polymer precursor impregnated in the pores. Examples thereof include a method for producing an electrolyte polymer by polymerization or by converting a functional group that can be converted to an electrolyte group into an electrolyte group after polymerization.

[0113] At the time of the above impregnation, one kind of a crosslinking agent, a polymerization initiator (such as a photopolymerization initiator, a thermal initiator, a redox-based polymerization initiator), a curing agent, a surfactant, etc. Or two or more may be added.

[0114] When the polymer precursor is used, the polymer precursor contains at least one or more of the above-described electrolyte monomers. Furthermore, a cross-linking agent may be included as necessary.

[0115] In this case, since a crosslinking point can be formed at the time of production of the electrolyte polymer, it becomes easy to form a crosslinked body of the electrolyte polymer. Therefore, the insolubility and infusibility of the electrolyte polymer filled in the pores of the electrolyte membrane are improved, and it is difficult for the electrolyte polymer to fall off the pores.

[0116] Specific examples of the crosslinking agent include, for example, a compound having two or more polymerizable functional groups in one molecule, and a polymerizable double bond and other crosslinking reactions in one molecule. Examples thereof include compounds having both functional groups. One or more of these may be included. [0117] Specific examples of the former cross-linking agent include, for example, N, N'-methylenebis (meth) acrylylamide, N, N, -butylenebis (meth) acrylamide, polyethylene glycol di (meth) acrylate, polypropylene glycol Di (meth) atarylate, trimethylolpropane diolenoreatenore, pentaerythritoretriolinoreatenore, divinino benzene, bisphenol di (meth) acrylate, isocyanuric acid di (meth) acrylate, tetraaryl Examples thereof include crosslinkable monomers such as oxetane, triallylamine, and diallyloxyacetate.

[0118] Specific examples of the latter cross-linking agent include cross-linking monomers such as N-methylol acrylamide, N-methoxymethyl acrylamide, and N-butoxymethyl acrylamide. These can be heated after radical polymerization of a polymerizable double bond to cause a condensation reaction or the like to crosslink, and can be heated simultaneously with radical polymerization to cause a similar crosslinking reaction.

[0119] The cross-linking agent is not limited to a compound having a carbon-carbon double bond, and a compound having a bifunctional or higher functional epoxy compound, a phenyl group having a hydroxymethyl group, etc., although the polymerization reaction rate is slightly low. Can also be used. When the epoxy compound is used, a bridge point is formed by reacting with an acid such as a carboxyl group contained in the polymer.

[0120] The polymer precursor may further contain a monomer copolymerizable with the electrolyte monomer and / or the crosslinking agent, if necessary. Specific examples of this type of monomer include (meth) acrylic acid esters, (meth) acrylamides, maleimides, styrenes, organic acid butyls, aryl compounds, and methallyl compounds. Ability to do S. One or more of these are included! /, May be! /.

[0121] The method for polymerizing the electrolyte monomer contained in the polymer precursor is not particularly limited, and any generally known method can be used. Specifically, for example, thermal initiators such as peroxides and azo compounds, thermal polymerization using redox polymerization initiators, and photopolymerization initiators that generate radicals upon irradiation with light such as ultraviolet rays are used. Examples include photopolymerization, polymerization by electron beam, radiation, etc. The These may be used alone or in combination of two or more.

[0122] When the electrolyte membrane is produced, the electrolyte polymer and polymer precursor itself can be impregnated into the pores of the porous membrane as they are when they themselves are liquid and have a low viscosity. In this case, the preferred viscosity is 1 to 25 ° C., about lOOOOmPa ′s.

[0123] On the other hand, it is difficult to impregnate the pores of the porous membrane as it is! / In some cases, a solution in which the electrolyte polymer and / or polymer precursor is dissolved in an appropriate solvent, or an appropriate A dispersion liquid dispersed in a suitable dispersion medium is preferable. In this case, the preferred viscosity is 1 to 25 ° C, about lOOOOmPa's. The viscosity is a value measured with a B-type viscometer.

[0124] Specific examples of the solvent and the dispersion medium include, for example, aromatic organic solvents such as toluene, xylene, and benzene, aliphatic organic solvents such as hexane and heptane, black mouth honolem, and dichloroethane. Chlorinated solvents such as ethers, ethers such as jetyl ether, ketones such as methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, cyclic ethers such as 1,4 dioxane and tetrahydrofuran, dimethylformamide, Examples include amide solvents such as dimethylacetamide and N-methyl 2-pyrrolidone, water, and alcohols. One or more of these may be included. Of these, water is preferably mainly contained. This is because it is excellent in handling and economy.

[0125] As the lower limit of the concentration of the solution or dispersion, it is necessary to repeat the impregnation step if the concentration is too low. From the viewpoint of productivity, 5% by mass or more is preferable, and 10% by mass or more is more preferable. Most preferred is 20% by mass or more.

[0126] When an electrolyte polymer layer is formed on the surface of the porous membrane when the electrolyte membrane is manufactured, as a method for removing it, specifically, for example, a brush made of resin fiber or the like, a brush or the like Examples of the method include rubbing with a scraper and scraping with a scraper. At this time, the above method may be carried out after moistening with water or the like or while washing. These methods may be used alone or in combination of two or more.

[0127] (Preparation of liquid composition) As described above, the liquid composition contains at least a catalyst and an electrolyte in the catalyst layer. In addition, it is preferable to include a suitable diluent capable of volatilization. When the above-mentioned diluent is included, the diluent is volatilized and deposited from the liquid composition when the catalyst layer is formed by spraying the liquid composition, or the sprayed object is heated. This is because the diluent can be volatilized instantaneously, which makes it easier to make a porous body.

In this case, specific examples of the diluent include aromatic organic solvents such as toluene, xylene and benzene, aliphatic organic solvents such as hexane and heptane, chloroform and dichloroethane. Chlorine solvents, ethers such as jetyl ether, ketones such as methylolethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, cyclic ethers such as 1,4 dioxane and tetrahydrofuran, dimethylforma Examples include amide solvents such as amide, dimethylacetamide, N-methyl-2-pyrrolidone, water, alcohols, and the like. These may be included alone or in combination of two or more. From the viewpoints of economy, handleability, safety, etc., water, alcohols and the like can be preferably used. Moreover, you may add a dispersing agent etc. suitably.

[0129] The upper limit of the catalyst concentration (in terms of solid content) in the liquid composition is preferably 90% by mass or less, more preferably 80% by mass or less, and most preferably 70% by mass or less. The lower limit of the catalyst concentration in the liquid composition is preferably 20% by mass or more, preferably 10% by mass or more, and most preferably 30% by mass or more.

[0130] The upper limit of the concentration of the electrolyte in the catalyst layer in the liquid composition (in terms of solid content) is from the viewpoint of easily maintaining the dispersed state of the catalyst and preventing clogging of the spray nozzle and the like. 50 mass% or less is preferred 40 mass% or less is more preferred 30 mass% or less is most preferred. On the other hand, the lower limit of the concentration of electrolyte in the catalyst layer in the liquid composition (in terms of solid content) is preferably 1% by mass or more from the viewpoint of efficiently forming the catalyst layer without repeating it many times. 5% by mass or more is more preferable. 10% by mass or more is most preferable.

[0131] The upper limit of the viscosity (25 ° C) of the liquid composition is preferably lOOOOmPa's or less, more preferably 5000 mPa's or less, force S, and most preferably 2000 mPa's or less. On the other hand, the lower limit of the viscosity (25 ° C) of the above liquid composition is preferably 100 mPa-s, preferably lOmPa's or more. More preferable is 500 mPa's or more.

[0132] (Formation of electrodes)

In this production method, the liquid composition is sprayed to form the catalyst layer in at least one, preferably both electrodes. Spraying of the liquid composition may be performed on the surface of the diffusion layer, or may be performed on the surface of the electrolyte membrane. Alternatively, it may be sprayed once on the surface of a film substrate different from the electrolyte membrane and transferred to a diffusion layer constituting the electrode. Further, these may be combined.

Therefore, as a method of forming the electrode on the surface of the electrolyte membrane, specifically, for example, after a catalyst layer is spray-formed on the surface of the diffusion layer, the catalyst layer side is used as the surface of the electrolyte membrane. After the catalyst layer is spray-formed on the surface of the electrolyte membrane, a diffusion layer is laminated on the outer surface of the catalyst layer, and once sprayed on a film substrate different from the electrolyte membrane, the electrode is attached. Examples thereof include a method for transferring to the surface of the diffusion layer to be formed. These methods may be used alone or in combination of two or more.

[0134] The liquid composition is preferably sprayed on the surface of the electrolyte membrane. Also preferred is a method in which the liquid composition is once sprayed on a film substrate different from the electrolyte membrane to form a catalyst layer, which is then transferred to the diffusion layer. In the catalyst layer contained in the composition, the electrolyte spreads directly on the membrane surface, the catalyst layer once spread in the surface direction of the film substrate, and the electrolyte directly contacts the electrolyte membrane surface. When an exposed electrolyte membrane is used, the electrolyte in the catalyst layer also adheres to the exposed porous membrane surface, making it easier to improve the ionic connection between the electrolyte in the pores and the electrolyte in the catalyst layer. Power.

[0135] At this time, the liquid composition may be sprayed at one time, or may be sprayed in a plurality of times (divided). When performing divided spraying, the composition of the liquid composition may be the same for each spray, or the composition may be different. When the liquid composition contains a volatilizable diluent, it is preferable to heat the material to be sprayed. This is because the diluent volatilizes quickly and easily develops three-dimensional vacancies!

[0136] The spraying conditions for the liquid composition are satisfactory if the optimum conditions are selected in consideration of the viscosity and concentration of the liquid composition to be used. [0137] In the above method, the sprayed catalyst layer is preferably heated and pressurized by hot pressing or the like. This is because the catalyst layer formed by spraying is not lifted, the adhesion to the diffusion layer or the electrolyte membrane can be improved, and the catalyst layer is difficult to peel off.

[0138] When the sprayed catalyst layer is fused to the surface of the electrolyte membrane, in particular, the exposed porous membrane, by heating and pressurization, the catalyst layer becomes more difficult to peel off. A membrane electrode assembly having excellent durability can be obtained.

[0139] When the catalyst layer is spray-formed on the surface of the electrolyte membrane, the diffusion layer may be heated and pressurized simultaneously with the catalyst layer by overlaying the diffusion layer on the outer surface of the catalyst layer. In this case, since the diffusion layer can also be integrated, it is possible to obtain a membrane / electrode assembly excellent in handleability when the fuel cell is incorporated.

[0140] The heating temperature and the applied pressure during the heating and pressurization may be appropriately selected in consideration of the material of the porous membrane, the material of the electrolyte in the catalyst layer, and the like.

[0141] In general, when the heating temperature and the applied pressure are excessively high, the porous membrane may be deformed or the pores in the catalyst layer may be reduced. On the other hand, when the heating temperature and pressure are excessively low, the effect tends to decrease. Therefore, it is advisable to pay attention to these when heating and pressurizing the catalyst layer.

[0142] If the electrolyte used for the spray-formed catalyst layer is naphth ion, it is insolubilized by heating, and excessive swelling in water and methanol can be prevented, so the catalyst layer is heated. Is preferred. In that case, use a method of spraying to the diffusion layer, or a method of spraying once on the surface of the film substrate different from the electrolyte membrane or electrode and transferring it to the electrode before forming a membrane electrode assembly. Heating is preferred because the choice of electrolyte membranes that can be used is widened and can be easily combined with an electrolyte membrane that exposes a part of a porous substrate made of polyolefin or the like.

[0143] 3. Use of this MEA

This MEA can be suitably used for polymer electrolyte fuel cells, direct alcohol fuel cells such as direct methanol fuel cells, and the like.

Example

[0144] Hereinafter, the present invention will be described more specifically with reference to Examples. [0145] 1. Preparation of electrolyte membrane

1. 1 Electrolyte membrane (1)

2 Acrylamide-2 Methylpropanesulfonic acid (Toagosei Co., Ltd., “ATBS”) 45 g, N, N, -ethylenebisacrylamide 5 g, nonionic surfactant 0.005 g, UV radical generator 0.005 g, 50 g of water was stirred and mixed until a uniform solution was obtained, thereby preparing a polymer precursor solution of an electrolyte polymer.

[0146] Next, a porous film made of a crosslinked polyethylene (thickness 30 m, porosity 37%, average pore diameter about 0. Ιπι) was immersed in the polymer precursor solution, and the solution was put in the pores. Impregnated

Yes

[0147] Next, after pulling up the porous membrane from the above solution, the porous membrane was sandwiched between PET films (thickness 50 m, manufactured by Toray Industries, Inc., "Lumirror T50") so as to prevent bubbles, and a laminate was obtained. .

[0148] Next, using a high-pressure mercury lamp, both surfaces of the laminate were irradiated with ultraviolet rays of 1000 mj / cm ² to polymerize the polymer precursor in the pores.

[0149] Next, remove the PET film from this laminate, and rub it with a scourer made of a resin fiber nonwoven fabric while wetting the membrane surface with pure water to remove the electrolyte polymer adhering to the membrane surface.

The membrane was allowed to air dry.

[0150] As a result, in the pores of the cross-linked polyethylene porous membrane, as an electrolyte polymer, 2

An electrolyte membrane (1) filled with a cross-linked polymer having an acrylamide-2-methylpropanesulfonic acid monomer unit was obtained.

[0151] When water droplets were dropped on the surface of the electrolyte membrane (1), water was repelled. Therefore, the electrolyte membrane (

It was a component that the porous film made of cross-linked polyethylene was exposed on the surface of 1).

[0152] AC impedance measurement from 100Hz to 40MHz at 25 ° C using a sample sandwiched between two platinum plates immersed in pure water at 25 ° C for 1 hour and swollen. The proton conductivity was measured. As a result, the proton conductivity of the electrolyte membrane (1) was 11.3 S / cm 2.

[0153] The methanol permeability of the electrolyte membrane (1) was confirmed by a penetration experiment at 25 ° C.

[0154] Specifically, the electrolyte membrane (1) was sandwiched between glass cells, 10% by mass aqueous methanol solution was placed in one cell, and pure water was placed in the other cell. And the metaphor that permeates the pure water side The amount of ol was measured over time by gas chromatographic analysis, and the permeation coefficient and permeation flux of methanol were measured.

As a result, the methanol permeation flux (representing the amount of methanol permeating through the electrolyte membrane) of the electrolyte membrane (1) was 0 · 28 kg / (m ² ′ h).

[0156] 1. 2 Electrolyte membrane (2)

In the preparation of the electrolyte membrane (1), after peeling off and removing the PET film from the laminate, the membrane surface was not rubbed and the electrolyte polymer layer adhering to the membrane surface was not removed. (2) was obtained.

[0157] When water droplets were dropped on the surface of the electrolyte membrane (2), water was repelled. Therefore, it was found that the porous membrane made of crosslinked polyethylene was not exposed on the surface of the electrolyte membrane (2).

[0158] The proton conductivity of the electrolyte membrane (1) measured in the same manner as the electrolyte membrane (1) was 11.6 S / cm ² and the methanol permeation flux was 0 · 29 kg / (m ² 'h). It was.

[0159] 2. Preparation of liquid composition used for catalyst layer formation

2. 1 Liquid composition for spray (1)

Solid content of 60 g of a commercially available catalyst with carbon black supported on platinum (Tanaka Kikinzoku Kogyo Co., Ltd., “T EC10E50E”) and 5% by weight fluorine electrolyte polymer solution (manufactured by DuPont, “Nafion”) 20g and 5g of polytetrafluoroethylene dispersion in terms of solid content were mixed and stirred and mixed with a ball mill, then 235g of isopropyl alcohol and 235g of water were added and stirred to form a catalyst layer for a force sword electrode A liquid composition for spraying (1) used in the above was prepared.

[0160] 2.2 Liquid composition for spray (2)

In the preparation of the above liquid composition for spray (1), instead of a commercially available catalyst in which platinum is supported on carbon black, a commercially available catalyst in which platinum and ruthenium are supported on carbon black (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) A liquid composition for spraying (2) used for forming the catalyst layer of the anode electrode was prepared in the same manner except that “TEC61E54”) was used.

[0161] 2.3 Composition for screen printing (1)

In the preparation of the above liquid composition for spray (1), after stirring and mixing with a ball mill, A screen printing composition (1) for use in forming a catalyst layer of a force sword electrode was prepared in the same manner except that the mixture was made into a paste without diluting and stirring with addition of sopropyl alcohol and water.

[0162] 2.4 Composition for screen printing (2)

In the preparation of the above liquid composition for spray (1), instead of a commercially available catalyst in which platinum is supported on carbon black, a commercially available catalyst in which platinum and ruthenium are supported on carbon black (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) The catalyst layer of the anode electrode was formed in the same way except that it was paste-like without using TEC61E54), stirring and mixing with a ball mill, and then diluting with isopropyl alcohol and water. A screen printing composition (2) to be used for was prepared.

[0163] 3. Fabrication of membrane electrode assembly according to Example

[0164] (Example 1)

The electrolyte membrane (1) cut into a 10 cm square was fixed on a stainless steel plate with an adhesive tape, and placed on a hot plate heated to 120 ° C. On this electrolyte membrane (1), a PTFE resin mask that was cut through a 2.23 cm square was placed.

[0165] Next, the liquid composition for spraying (1) was sprayed for 3 seconds at an ejection pressure of 1.4 MPa from a cone type nozzle having a tip fixed 20 cm above the surface of the electrolyte membrane (1), and left for 15 seconds. This was defined as one cycle, and this cycle was repeated until the platinum power contained in the spray-formed catalyst layer was mg / cm ² .

[0166] Next, the electrolyte membrane (1) is turned over, the spray liquid composition (1) is switched to the spray liquid composition (2), and platinum contained in the spray-formed catalyst layer in the same manner as described above. The above cycle was repeated until the total amount of ruthenium was 3 mg / cm ² .

[0167] Next, both sides of the membrane on which the catalyst layer is formed are sandwiched between two 0.1 mm thick PTFE films, and further, both sides of the stainless steel plate are 10 cm on a side and 3 mm in thickness. Clamped with 2 sheets.

[0168] Next, this laminate was hot-pressed using a hydraulic hot press machine with a hot plate heated to 120 ° C and a cylinder cross-sectional area of 50 cm ² at a gauge pressure IMPa of the hot press machine for 5 minutes. And an electrolyte membrane with a catalyst layer was produced. [0169] Next, a 0.2 mm thick carbon paper treated with PTFE for water repellent treatment on the force sword side of the electrolyte membrane with a catalyst layer, and a thickness of 0. A 2 mm carbon paper was contacted.

[0170] Thus, a membrane electrode assembly according to Example 1 was obtained.

[0171] The membrane-electrode assembly was immersed in a beaker containing 25 ° C water for 24 hours, and the electrode adhesion in water was confirmed. As a result, the electrode showed extremely good electrode adhesion without peeling off.

[Example 2]

In the production of the membrane / electrode assembly according to Example 1, in the hot pressing step, each carbon paper was further arranged in accordance with each catalyst layer, and each catalyst layer and each carbon paper were hot pressed at the same time. Thus, a membrane / electrode assembly according to Example 2 in which each carbon paper was adhered to each catalyst layer was obtained.

[0173] As in Example 1, as a result of confirming the electrode adhesion in water of the membrane electrode assembly, the electrode showed extremely good electrode adhesion with no peeling.

[0174] (Example 3)

A liquid composition for spraying (1) is sprayed onto carbon paper having a thickness of 0.2 mm that has been subjected to water repellent treatment with PTFE in the same manner as in Example 1, and the platinum weight contained in the sprayed catalyst layer Was lmg / cm.

[0175] Next, the sprayed liquid composition (2) is sprayed in the same manner onto a carbon paper having a thickness of 0.2 mm that has not been subjected to water repellent treatment, and the platinum layer contained in the spray-formed catalyst layer. The total amount of ruthenium was 3 mg / cm ² .

[0176] Next, each carbon paper on which the catalyst layer was formed was cut into squares each having a side of 2.23 cm.

[0177] Next, both sides of each cut-out carbon paper were sandwiched between two 0.1 mm thick PTFE films, and further, both sides were stained with a stainless steel plate with a side force of Ocm and a thickness of 3 mm. Clamped with 2 sheets.

[0178] Next, each of these laminates was hot-pushed for 5 minutes at a gauge pressure IMPa of the hot-press machine using a hydraulic hot-press machine with a cylinder cross-sectional area of 50 cm ² heated to 120 ° C. A pair of carbon paper with a catalyst layer (forced sword electrode, anode electrode) was prepared.

[0179] Next, both surfaces of the electrolyte membrane (1) were sandwiched between the pair of carbon papers with a catalyst layer (the catalyst layer surface was the membrane surface side), and the both surfaces were 10cm thick on one side. Was sandwiched between two 3 mm stainless plates.

[0180] Next, this was hot-pressed (heated and pressurized) under the same conditions using the hot press machine.

[0181] Thus, a membrane electrode assembly according to Example 3 was obtained.

[0182] As in Example 1, the electrode adhesion in water of the membrane electrode assembly was confirmed. As a result, the electrode showed extremely good electrode adhesion without peeling off.

[0183] (Example 4)

In the production of the membrane / electrode assembly according to Example 1, the membrane / electrode assembly according to Example 4 was obtained in the same manner except that the catalyst layer was sprayed and then hot pressing was not performed.

[0184] As in Example 1, as a result of confirming the electrode adhesion in water of the membrane electrode assembly, a part of the catalyst layer was observed to drop, but the electrode adhesion within an allowable range was observed. Indicated.

[Example 5]

In the production of the membrane electrode assembly according to Example 1, the electrolyte membrane (2) was used instead of the electrolyte membrane (1), and each carbon paper was further added to each catalyst layer in the hot press process. A membrane electrode assembly according to Example 5 was obtained in the same manner except that the catalyst layers and the carbon papers were simultaneously hot pressed.

[0186] As in Example 1, as a result of confirming the electrode adhesiveness of the membrane electrode assembly in water, partial peeling of the catalyst layer was observed.

[0187] (Example 6)

The PTFE film was fixed to a stainless steel plate and placed on a hot plate heated to 120 ° C. Next, a force sword side catalyst layer was formed on the PTFE film under the conditions described in Example 1. At that time, spraying was carried out until the amount of platinum contained in the sprayed catalyst layer was lmg / cm ² . Similarly, an anode side catalyst layer was formed as described in Example 1. At that time, the total amount of platinum and ruthenium contained in the spray-formed catalyst layer Was sprayed to 3 mg / cm ² .

[0188] Next, the force sword and anode PTFE films on which the catalyst layer was formed were cut into squares each having a side of 2.23 cm.

[0189] Next, the catalyst layer of the cut out film was turned to the carbon paper side, and the thickness was set to 0.

2mm of carbon paper (force cathode side having been subjected to the water repellent treatment with PTFE, the anode side that performs no water-repellent treatment) superimposed respectively, is 50 cm ² cylinder Ichidan area heated to 0.99 ° C Using a hydraulic hot press machine, hot pressing was performed at a gauge pressure of IMPa for 10 minutes, and the PTFE film was carefully peeled off to obtain a pair of carbon paper with a catalyst layer (a cathode electrode and an anode electrode).

[0190] Next, these electrodes were placed in an oven heated to 150 ° C and in a nitrogen atmosphere, and heat-treated for 1 hour.

[0191] Next, the catalyst layer surface of these pair of electrodes was placed on the membrane side, and the electrolyte membrane was sandwiched between them.

Hot pressing was performed under the same conditions as in 1 to obtain a membrane electrode assembly. As a result of confirming the electrode adhesion in water as in Example 1, the electrode did not peel off and showed good adhesion.

[0192] (Comparative Example 1)

1 side 2. Using a screen plate having a square 23 cm printed shape, screen-print the paste-like composition for screen printing (1) on one side of the electrolyte membrane (1), Dried for 5 minutes. This was defined as one cycle, and this cycle was repeated until the amount of white metal contained in the printed catalyst layer reached 1 mg / cm ² .

[0193] Next, the electrolyte membrane (1) is turned over, and a paste-like composition for screen printing (2) is prepared in the same manner as described above, so that the total amount of platinum and ruthenium contained in the printed catalyst layer is 3 mg. It was repeated the cycle until the / cm ^2.

[0194] Next, after screen printing, the four sides of the film were fixed with heat-resistant tape so that the film would not curl, and dried in an oven at 120 ° C for 1 hour.

[0195] Next, both sides of the membrane on which the catalyst layer was formed were sandwiched by two PTFE films having a thickness of 0.1 mm, and further, both sides of the stainless steel plate having a side of 10 cm and a thickness of 3 mm. Clamped with 2 sheets.

[0196] Next, the laminate was heated in an oil plate having a cylinder cross-sectional area of 50 cm ² heated to 120 ° C. Using a pressure hot press machine, hot press for 5 minutes with the gauge pressure IMPa of the hot press machine

(Heating and pressing) to prepare an electrolyte membrane with a catalyst layer.

[0197] Next, a 0.2 mm thick carbon paper treated with PTFE for water repellent treatment on the force sword side of the electrolyte membrane with the catalyst layer, and a thickness of 0.

A 2 mm carbon paper was contacted.

[0198] Thus, a membrane electrode assembly according to Comparative Example 1 was obtained.

[0199] As in Example 1, as a result of confirming the electrode adhesion in water of the membrane electrode assembly, the electrode showed extremely good electrode adhesion that did not peel off.

[0200] (Comparative Example 2)

Platinum contained in the catalyst layer formed by printing the screen printing composition (1) on carbon paper with a thickness of 0.2 mm treated with PTFE in the same manner as in Comparative Example 1. The amount was lmg cm '.

[0201] Next, the screen printing composition (2) was sprayed on the carbon paper having a thickness of 0.2 mm that had not been subjected to the water-repellent treatment in the same manner as in Comparative Example 1, and the printed catalyst layer The total amount of platinum and ruthenium contained in was 3 mg / cm ² .

[0202] Next, each carbon paper on which the catalyst layer was formed was cut into squares each having a side of 2.23 cm.

[0203] Next, both sides of each cut out carbon paper were sandwiched between two PTFE films with a thickness of 0.1 mm, and further, both sides were stained with a stainless steel plate with a side force of Ocm and a thickness of 3 mm. Clamped with 2 sheets.

[0204] Each of these laminates was then hot-pressed (heated) for 5 minutes at a gauge pressure IMPa of the hot-press machine using a hydraulic hot-press machine with a cylinder cross-section of 50 cm ² heated to 120 ° C. And a pair of carbon paper with a catalyst layer (forced sword electrode, anode electrode) was produced.

[0205] Next, both surfaces of the electrolyte membrane (1) are sandwiched between the pair of carbon papers with a catalyst layer (the catalyst layer surface is the membrane surface side), and the both surfaces are 10 cm thick on one side. Was sandwiched between two 3 mm stainless plates.

[0206] Next, this was hot-pressed (heated and pressurized) under the same conditions using the hot-press machine. It was.

[0207] Thus, a membrane electrode assembly according to Comparative Example 2 was obtained.

[0208] As in Example 1, the electrode adhesion in water of the membrane electrode assembly was confirmed. As a result, the electrode showed extremely good electrode adhesion that did not peel off.

[0209] 4. Fuel cell evaluation

Evaluation of the membrane electrode assemblies according to Examples and Comparative Examples was performed as follows. In other words, each membrane electrode assembly was directly incorporated into a single methanol fuel cell, and the current-voltage characteristics of the single cell were measured by changing the load with an electronic load.

[0210] Then, for each single cell, the voltage at a high load of a current density of 300 mA / cm ² was relatively compared. In addition, the voltage at low load with a current density of 20 mA / cm ² was also relatively compared.

[0211] The fuel used was a 10 wt% aqueous methanol solution, air was used as the oxidant, and the cell temperature was 50 ° C.

[0212] Table 1 summarizes the details of the fabricated membrane electrode assembly and the battery evaluation results.

[0213] [Table 1]

(* 1) After spray formation of the catalyst layer on the PTFE film, it is transferred to the surface of the diffusion layer

[0214] According to Table 1 above, the following can be understood. That is, in comparison with the membrane electrode assemblies of Comparative Examples 1 and 2 in which the catalyst layer was formed by screen printing, an example in which the catalyst layer was spray formed by spraying; all of the membrane electrode assemblies of! When the voltage in the high load range (high current density range) is high, the force is S component.

[0215] This is because the catalyst layer in the example has a larger number of pores than the catalyst layer in the comparative example, and air or methanol having a large three-dimensional spread of these pores is the catalyst. This is presumably due to the fact that it easily penetrated into the inside of the bed and the discharge of products such as water (power sword side) and carbon dioxide (anode side) generated by the cell reaction was promoted.

[0216] Further, when the examples are compared, the following can be understood.

[0217] First, the membranes of Examples 1 and 2 in which the catalyst layer was spray-formed on the surface of the electrolyte membrane rather than the membrane-electrode assembly of Example 3 in which the catalyst layer was spray-formed on the diffusion layer (in this case, carbon paper) The electrode assembly and the membrane electrode assembly of Example 6 in which a catalyst layer spray-formed on the surface of a separately prepared PET film is transferred to the diffusion layer are superior in voltage characteristics from the high load range to the low load range. It was.

[0218] This is because the liquid composition for spraying is sprayed on the surface of the electrolyte membrane or the liquid composition for spraying is separately sprayed on the surface of the PET film, so that the pores of the diffusion layer are not blocked. It is presumed that the voltage characteristics in the high load region were improved because methanol easily penetrated from the diffusion layer to the catalyst layer.

[0219] It should be noted that the amount of liquid composition sucked into the diffusion layer is much smaller than that in which the catalyst layer is printed on the diffusion layer. This has the advantage of forming a catalyst layer.

[0220] In addition, by spraying the liquid composition for spraying on the surface of the electrolyte membrane, or spraying the liquid composition for spraying on the surface of a separately prepared PET film, the electrolyte polymer contained in the composition becomes the surface of the membrane. It is presumed that the ionic connection with the electrolyte polymer in the pores was improved, so that the catalyst in contact with the exposed porous membrane surface was effectively used and the voltage characteristics in the low load region were improved.

[0221] Next, the membrane electrode assembly of Examples 1, 2, and 6 in which the spray-formed catalyst layer was hot pressed rather than the membrane electrode assembly in Example 4 that was not hot pressed on the surface of the electrolyte membrane. The water The electrode bondability after immersion was excellent and the durability was excellent. This is because the catalyst layer is fused to the surface of the electrolyte membrane, thereby improving the bondability between the two. In addition, the membrane electrode assemblies of Examples 1, 2, and 6 were superior to the membrane electrode assembly of Example 4 in handleability when forming the catalyst layer.

[0222] Next, an electrolyte membrane in which the porous membrane surface was exposed was used rather than the membrane electrode electrolyte membrane of Example 5 using the electrolyte membrane in which the porous membrane surface was covered with the electrolyte polymer in the pores. The membrane electrode assemblies of Examples 1, 2, and 6 were excellent in durability with excellent electrode bondability after immersion in water.

[0223] This is presumably because the electrolyte polymer in the pores adhering to the electrolyte membrane surface absorbed moisture and did not cause a decrease in strength.

[0224] Next, the membrane electrode assemblies of Examples 1, 2, and 6 were all excellent in battery performance with high voltage characteristics in a high load region and a low load region. In particular, since the membrane / electrode assembly of Example 2 was also integrated with the diffusion layer, it was excellent in the alignment and properties when assembled in the battery! /.

[0225] Although the functional film manufacturing method according to the present embodiment and examples has been described above, the present invention can be variously modified without departing from the spirit of the present invention.

Claims

The scope of the claims

[1] A membrane electrode assembly having an electrode having a diffusion layer and a catalyst layer on both surfaces of an electrolyte membrane,

The electrolyte membrane is a porous membrane filled with an electrolyte, and at least one of the catalyst layers is formed by spraying a liquid composition containing a catalyst and an electrolyte in the catalyst layer. There is a membrane electrode assembly characterized in that there is.

[2] The membrane electrode assembly according to [1], wherein a surface of the porous membrane is exposed in the electrolyte membrane.

[3] The membrane / electrode assembly according to [1] or [2], wherein the catalyst layer is fused to the surface of the electrolyte membrane.

[4] The porous film is made of olefin resin,

4. The electrolyte according to claim 1, wherein the electrolyte filled in the pores is a polymer having 2-acrylamido-2-methylpropanesulfonic acid monomer units or a crosslinked product thereof. 2. The membrane electrode assembly according to 1.

[5] A method for producing a membrane / electrode assembly having electrodes each provided with a diffusion layer and a catalyst layer on both sides of an electrolyte membrane,

The electrolyte membrane is a porous membrane filled with an electrolyte, and at least one of the catalyst layers is formed by spraying a liquid composition containing a catalyst and an electrolyte in the catalyst layer. A method for producing a membrane electrode assembly.

6. The method for producing a membrane / electrode assembly according to claim 5, wherein the catalyst layer is formed by spraying the liquid composition on at least one surface of the electrolyte membrane.

[7] The method for producing a membrane / electrode assembly according to [5], wherein the catalyst layer is formed through the following steps (1) to (3).

(1) A step of spraying the liquid composition onto the surface of a separately prepared film base to form a catalyst layer

(3) The surface of the catalyst layer of the electrode prepared in (2) is bonded to the surface of the electrolyte membrane. About

[8] Between the step (1) and the step (2) and / or between the step (2) and the step (3), the electrode is heated to form a catalyst layer. The method for producing a membrane / electrode assembly according to claim 7, further comprising a step of insolubilizing the electrolyte.

[9] The method for producing a membrane / electrode assembly according to any one of [5] to [8], wherein the catalyst layer formed by spraying is further fused to the surface of the electrolyte membrane.

[10] The method for producing a membrane / electrode assembly according to any one of [5] to [9], wherein a surface of the porous membrane is exposed in the electrolyte membrane.

[11] The method for producing a membrane / electrode assembly according to any one of [5] to [10], wherein the liquid composition is sprayed in a plurality of times.