JP2008098070A - Membrane electrode assembly and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane electrode assembly hardly broken at the time of manufacture and operation of the battery compared with a conventional one. <P>SOLUTION: In the membrane electrode assembly having an anode electrode on one side and a cathode electrode jointed on the other side of an electrolyte membrane, at least one of the electrode is formed using a MEMS (Micro Electro Mechanical System) technology, and the electrode membrane is filled with an electrolyte polymer in holes of the porous membrane. It is preferable that the electrode is composed of a semiconductor material or a conductor material, and has a passage layer in which a passage of fuel or oxidizer is formed, and a porous layer which contacts the bottom part of the passage of the passage layer and in which a catalyst is carried in the holes. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a membrane electrode assembly and a fuel cell.

  Conventionally, for example, a polymer electrolyte fuel cell (PEFC) and a direct methanol fuel cell (DMFC) are known as fuel cells that can be used as a power source for automobiles, cogeneration systems, mobile devices, and the like.

  Among these, since DMFC uses methanol as a fuel, a hydrogen tank, a reformer, and the like are unnecessary as compared with PEFC using pure hydrogen or reformed hydrogen as fuel. Therefore, it has an advantage that it can be easily applied to a power source of a mobile device such as a mobile phone that is required to be reduced in size and weight.

  As a structure of the fuel cell, for example, a structure in which a membrane electrode assembly (MEA: Membrane Electrode Assembly) in which an anode electrode is bonded to one surface and a cathode electrode is bonded to the other surface is sandwiched between separators is widely known. It has been. Moreover, as a structure of both electrodes, a two-layer structure in which a diffusion layer and a catalyst layer are laminated is often adopted.

  Usually, the electrolyte material is a perfluorocarbon sulfonic acid polymer such as Nafion (registered trademark, manufactured by DuPont), and the catalyst layer material is a mixture of platinum-supported carbon and a Nafion solution. Carbon is known as a typical material for the carbon paper and the separator material.

  When power generation is performed using this type of conventional fuel cell, it is necessary to tighten the membrane electrode assembly sandwiched between the pair of separators with a strong force. Therefore, the separator is required to have mechanical strength, and the thickness of the entire battery tends to be relatively thick.

  Therefore, there has been a limit to further miniaturization with the conventional structure.

  Incidentally, in recent years, MEMS (Micro Electro Mechanical System) technology has attracted attention. This MEMS technology is a technology that uses a semiconductor manufacturing process and a microfabrication process to manufacture a microstructure having both mechanical and electrical functions, and is suitable for manufacturing extremely small parts. Yes.

  Recently, a fuel cell having a new structure using the MEMS technology has been proposed.

  For example, in Patent Document 1, using the MEMS technology, a groove is formed on one side of a silicon wafer, a porous silicon layer is formed on the other side from the bottom of the groove, and the porous silicon is formed. A micro fuel cell having a membrane electrode assembly in which a catalyst metal is supported on a layer to form an electrode and a solid electrolyte membrane is sandwiched between the electrodes is disclosed.

JP 2005-105409 A

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

  That is, an electrode manufactured by the MEMS technology is basically a very small structure, and is easily broken when an excessive external force is applied.

  In general, when joining an electrode to an electrolyte membrane, it is often performed to apply an electrolyte material dissolved in a solvent such as isopropanol to the surface of the electrolyte membrane and then thermocompression-bond the electrode.

  However, Nafion membranes and equivalent electrolyte membranes have the property that they absorb alcohol and water and swell to increase their surface area. Therefore, when bonding as described above is performed with an electrode manufactured by the MEMS technology, there arises a problem that the electrode is damaged due to a change in the surface area of the electrolyte membrane.

  Even if the bonding is successful, the electrode may be damaged due to the shrinkage of the film accompanying the subsequent volatilization of the solvent. Further, in the fuel cell, power generation and stop are repeatedly performed. Therefore, the electrolyte membrane is repeatedly exposed to a swollen state and a dry state, and the area change occurs each time. Therefore, an electrolyte membrane such as a Nafion membrane still has a problem that the electrode is damaged within a short period of time.

  This invention is made | formed in view of the said situation, The subject which this invention tends to solve is providing the membrane electrode assembly which is hard to be damaged at the time of the manufacture or battery operation compared with the former.

  In order to solve the above problems, a membrane / electrode assembly according to the present invention comprises an electrolyte membrane having an anode electrode joined to one surface and a cathode electrode joined to the other surface, and at least one of the electrodes is a MEMS. The gist of the electrolyte membrane is that the electrolyte polymer is filled in the pores of the porous membrane.

  At this time, at least one of the electrodes is made of a semiconductor material or a conductor material, and is in contact with the flow path layer in which the flow path of the fuel or the oxidant is formed, and the flow path bottom of the flow path layer. And a porous layer on which a catalyst is supported.

  Further, a current collector layer may be further provided on the surface of the flow path layer.

  The semiconductor material is preferably silicon.

  Further, when the electrolyte membrane is immersed in isopropanol having a liquid temperature of 25 ° C. or an aqueous solution thereof for 1 hour, the area change rate before and after the immersion is preferably 20% or less.

  Moreover, when the said electrolyte membrane is immersed in methanol with a liquid temperature of 25 degreeC or its aqueous solution for 1 hour, it is good in the area change rate before and behind immersion being 20% or less.

  On the other hand, the gist of the fuel cell according to the present invention includes the membrane electrode assembly.

  The thickness of the fuel cell is preferably 2 mm or less.

  The membrane electrode assembly according to the present invention uses a combination of an electrode manufactured by MEMS technology and an electrolyte membrane in which an electrolyte polymer is filled in the pores of the porous membrane.

  Due to its structure, this electrolyte membrane is less likely to absorb alcohol and water and less likely to swell compared to fluorine electrolyte membranes such as Nafion membranes. Therefore, there is little change in the surface area of the membrane, and it is possible to suppress the load caused by the swelling / shrinkage of the electrolyte membrane during the production of the membrane electrode assembly and the battery operation.

  Therefore, the membrane electrode assembly according to the present invention is not easily damaged during production or battery operation.

  Here, when the electrode has an electrode structure in which a flow path layer, a diffusion layer (porous layer), and a catalyst layer (catalyst supported in the hole) are integrally formed, separate members are used. Compared to the membrane electrode assembly sandwiched between the separators, the thickness can be extremely reduced. Therefore, it is advantageous for lamination.

  In addition, when a current collector layer is provided on the surface of the flow path layer, by forming a current collector layer whose electric resistance is smaller than that of a semiconductor, compared to when electricity is taken directly from an end of a semiconductor component There are advantages that the resistance is reduced and a fragile material such as a silicon wafer can be reinforced.

  In addition, when an electrolyte membrane having an area change rate of 20% or less before and after immersion in isopropanol or an aqueous solution thereof is used, the membrane electrode assembly is particularly difficult to break during manufacture.

  In addition, when an electrolyte membrane having an area change rate of 20% or less before and after immersion in methanol or an aqueous solution thereof is used, the membrane electrode assembly is particularly difficult to break during battery operation.

  On the other hand, the fuel cell according to the present invention includes the membrane electrode assembly. Therefore, it is excellent in durability, reliability and the like as compared with the conventional case.

  Moreover, if the thickness of the fuel cell is 2 mm or less, a small and thin fuel cell suitable for a mobile device power source or the like can be obtained.

  Hereinafter, the membrane electrode assembly according to the present embodiment (hereinafter sometimes referred to as “the present MEA”), the manufacturing method thereof (hereinafter also referred to as “the present manufacturing method”), and the fuel to which the present MEA is applied. The battery (hereinafter sometimes referred to as “the present fuel cell”) will be described in detail.

1. This MEA
As illustrated in FIG. 1, in the MEA 10, an anode electrode 14 a is bonded to one surface of an electrolyte membrane 12, and a cathode electrode 14 c is bonded to the other surface.

1.1 Electrolyte Membrane In the present MEA, the electrolyte membrane is a membrane in which an electrolyte polymer is filled in the pores of the porous membrane.

(Porous membrane)
The porous membrane mainly forms a skeleton of the electrolyte membrane, and has a large number of through holes penetrating from one surface of the membrane to the other surface. In addition to the through holes, non-through holes may exist.

  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, you may penetrate at random, such as meandering or zigzag.

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

  The upper limit of the porosity of the porous membrane is preferably 95% or less, more preferably 90% or less, still more preferably 85% or less, and most preferably 80% or less. On the other hand, the lower limit of the porosity of the porous film is preferably 5% or more, more preferably 10% or more, still more preferably 15% or more, and most 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.

The porosity can be obtained by determining the volume from the thickness and area of the porous membrane, measuring its weight, and calculating the proportion of air in the total volume from the specific gravity of the constituent material. it can. Specifically, it can be obtained by the following equation.
Porosity% = (thickness of porous membrane × area of porous membrane−weight of porous membrane / of constituent material
Specific gravity) / (Porous membrane thickness × Porous membrane area) × 100

  The upper limit of the pore diameter of the porous membrane is preferably 50 μm or less, more preferably 10 μm or less, and most preferably 1 μm or less from the viewpoint of easily holding the electrolyte polymer filled in the pores. On the other hand, the lower limit of the pore diameter of the porous membrane is preferably 0.001 μm or more, and more preferably 0.01 μm or more from the viewpoint of easy filling of the electrolyte polymer into the pores.

  If the pore diameter of the porous membrane is within the above range, it is relatively easy to fill the electrolyte polymer in the pore, and the retention of the filled electrolyte polymer is good, and it is difficult to drop off when the membrane is deformed. It is. In addition, the said hole diameter is a value measured by the mercury intrusion method.

  The material of the porous film is not particularly limited as long as the through hole as described above can be formed. Examples thereof include organic materials such as polymers, inorganic materials such as ceramics (alumina, mullite, etc.), metals (including alloys), and composite materials obtained by combining these materials. Of these, a polymer can be suitably used from the viewpoints of easily forming the hole portion relatively easily and being lightweight.

  Specific examples of the polymer include, for example, ethylene resins (resins mainly composed of ethylene monomers such as polyethylene), olefin resins such as polypropylene and polymethylpentene, and vinyl chlorides such as polyvinyl chloride. Resin, fluorinated resins such as polytetrafluoroethylene, polytrifluoroethylene, polychlorotrifluoroethylene, poly (tetrafluoroethylene-hexafluoropropylene), poly (tetrafluoroethylene-perfluoroalkyl ether), nylon 6, nylon Examples include polyamide resin such as 66, polyester resin, aromatic polyimide, aramid, polysulfone, polyphenylene oxide, polyether ether ketone, polycarbonate, phenol resin, epoxy resin, unsaturated polyester, etc. It can be. These may be contained alone or in combination of two or more. Two or more kinds of polymers may be laminated. The polymer may be cross-linked as necessary.

  Of the above polymers, thermoplastic polymers such as olefin resins such as polyethylene, polysulfone, polyphenylene oxide, polyamide resins, and polyester resins can be preferably used.

  Since these thermoplastic polymers can be softened or melted by heating, when the electrode is thermocompression bonded, the porous membrane surface softens or melts, making it easier to fuse the electrolyte membrane and the electrode. Because there is. 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 present MEA is applied.

  Of the thermoplastic polymers, an olefin resin such as polyethylene is more preferable from the viewpoint of being less likely to swell with alcohol such as isopropanol or methanol or water.

  The upper limit of the thickness of the porous membrane is preferably 200 μm or less, more preferably 150 μm or less, and most preferably 100 μm or less from the viewpoint of the internal resistance of the battery. On the other hand, the lower limit of the thickness of the porous membrane is preferably 1 μm or more from the viewpoint of maintaining the strength of the membrane and preventing defects such as tearing when joining the electrode or incorporating it into the fuel cell. The above is more preferable, and 10 μm or more is most preferable.

  This is because if the thickness of the porous membrane is within the above range, the balance between membrane strength and membrane resistance is good. Further, when a fuel such as methanol is used, permeation thereof is easily suppressed.

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

  Specific examples of the electrolyte polymer include a polymer having one or more electrolyte groups in the main chain and / or side chain, and a polymer containing an electrolyte such as an acid or a room temperature molten salt. Can be exemplified. One or two or more of these polymers may be contained. Further, these polymers may be cross-linked products cross-linked as necessary.

  The electrolyte polymer may exist as a polymer before being filled in the pores, or after the polymer precursor capable of generating the electrolyte polymer is filled in the pores, polymerization, crosslinking, etc. are performed. The electrolyte polymer may be used. A specific filling method of the electrolyte polymer will be described later in “2. Production method”.

  Specific examples of the electrolyte group contained in the electrolyte polymer include acidic groups such as a sulfonic acid group, a sulfonimide group, a phosphonic acid group, a phosphonous acid group, and a carboxylic acid group. These may be contained alone or in combination of two or more. Among these, a sulfonic acid group can be preferably used from the viewpoint of easily obtaining high proton conductivity.

  Specific examples of the electrolyte polymer include all or part of a polymer skeleton such as a perfluorocarbon sulfonic acid polymer such as Nafion (registered trademark), a perfluorocarbon phosphonic acid polymer, and a trifluorostyrene sulfonic acid polymer. Is a fluorinated fluorine-based polymer having an electrolyte group; polysulfone sulfonic acid, polyaryl ether ketone sulfonic acid, polybenzimidazole alkyl sulfonic acid, polybenzimidazole alkyl phosphonic acid, etc. does not contain fluorine Hydrocarbon polymer having an electrolyte group; monomer having an electrolyte group, monomer having a functional group that can be converted to an electrolyte group, and monomer having a site capable of introducing an electrolyte group before and after polymerization An electrolyte monomer and the like Align the like can be exemplified a polymer having as monomer unit. These may be contained alone or in combination of two or more.

Specific examples of the monomer having an electrolyte group include 2- (meth) acrylamide-2-methylpropanesulfonic acid, 2- (meth) acrylamide-2-methylpropanephosphonic acid, styrenesulfonic acid, (meth ) Allyl sulfonic acid, vinyl sulfonic acid, isoprene sulfonic acid, (meth) acrylic acid, maleic acid, crotonic acid, vinyl phosphonic acid, acidic phosphoric acid group-containing (meth) acrylate and the like can be exemplified.
“(Meth) acryl” means “acryl and / or methacryl”, “(meth) allyl” means “allyl and / or methallyl”, and “(meth) acrylate” means “acrylate and / or methacrylate”. (The same shall apply hereinafter).

  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 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.

  Specific examples of the monomer having a site capable of introducing an electrolyte group before and after the polymerization include, for example, 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, and sulfur trioxide.

  As these electrolyte monomers, a vinyl compound having a sulfonic acid group, a vinyl compound having a phosphoric acid group, and the like are preferable from the viewpoint of excellent proton conductivity, and more preferably, from the viewpoint of having high polymerizability. -(Meth) acrylamido-2-methylpropanesulfonic acid and the like.

  It is preferable that substantially all of the pores of the porous membrane are filled in the electrolyte polymer from the viewpoint of obtaining high ion conductivity. Of course, not all pores of the porous membrane need to be filled with electrolyte polymer, but within the range that does not adversely affect ion conductivity, fuel permeability, etc., electrolyte polymer is filled. There may be a portion of the hole that is not present.

  In the above, each structure of the electrolyte membrane which this MEA has was demonstrated. Here, when the membrane in the dry state is immersed in isopropanol having a liquid temperature of 25 ° C. or an aqueous solution thereof for 1 hour, the area change rate before and after immersion is 20% or less in any concentration range. It is preferable that

  If the area change rate is in the range of 20% or less, for example, when an electrolyte material dissolved in a solvent such as isopropanol is applied to the surface of the electrolyte membrane, the membrane is formed by solvent absorption when the electrode is joined to form MEA. This is because it is easy to suppress damage to the electrode caused by surface area change due to swelling of the film and shrinkage of the film due to solvent volatilization.

  The upper limit of the area change rate is preferably 20% or less, more preferably 15% or less, and most preferably 10% or less.

  In addition, when the membrane in a dry state is immersed in methanol or an aqueous solution thereof at a liquid temperature of 25 ° C. for 1 hour, the area change rate before and after the immersion is 20% or less in any concentration range. Preferably there is.

  If the area change rate is in the range of 20% or less, even when the present MEA is used as the MEA of a fuel cell using alcohol such as methanol as a fuel, the membrane swells or This is because it becomes easy to suppress damage to the electrode caused by a change in surface area due to shrinkage of the film due to drying.

  The upper limit of the area change rate is preferably 20% or less, more preferably 15% or less, and most preferably 10% or less.

The above-mentioned area change rate is calculated by the following formula by measuring the surface area S1 of the electrolyte membrane dried for 1 hour at a temperature of 70 ° C. and the surface area S2 after being immersed in the isopropanol or methanol or an aqueous solution thereof. It is the value.
Area change rate = (S2-S1) / S1 × 100

  The electrolyte membrane may be coated with an electrolyte polymer layer on the membrane surface (that is, outside the pores) as long as the electrolyte polymer is filled in the pores of the porous membrane, or the membrane surface may be porous. The film may be exposed. From the standpoint of excellent adhesion between the porous membrane forming the skeleton of the electrolyte membrane and the electrode, the latter is preferred.

1.2 Electrode In this MEA, either one or both of an anode electrode and a cathode electrode (hereinafter sometimes simply referred to as “electrode”) are formed using at least a MEMS technique.

  Here, the MEMS technology refers to a technology for manufacturing a micro structure having both a mechanical function and an electrical function by using a semiconductor manufacturing process or a microfabrication process used in a semiconductor integrated circuit or the like. .

  Until now, the mainstream was an electrode having a two-layer structure in which a catalyst layer and a diffusion layer were laminated. In general, a separator having a flow path for supplying fuel and an oxidant, a current collector for collecting generated electricity, and the like are usually separate members.

  However, by using MEMS technology, it is possible to build an extremely small structure. Therefore, the necessity of preparing each battery member as a separate member, such as conventional electrodes, separators, and current collectors, has been reduced.

  That is, it is possible to produce an electrode as an integral member in a form that incorporates not only a catalyst function and a diffusion function but also a fuel and oxidant supply function (flow path function) and a current collection function.

  In the present invention, “electrode” is used in such a broad sense. Therefore, “forming an electrode using MEMS technology” means at least one or more functions selected from a catalyst function, a diffusion function, a fuel and oxidant supply function (flow path function), and a current collection function This means that a structure capable of exhibiting this is formed using MEMS technology.

  As a specific configuration of this electrode, for example, as illustrated in FIG. 1, a flow path layer 18 in which a flow path 16 of fuel (in the case of the anode electrode 14a) or oxidant (in the case of the cathode electrode 14c) is formed. And an electrode 14a (14c) having a porous layer 20 in contact with the flow path bottom of the flow path layer 18 and having a catalyst supported in the pores, as illustrated in FIG. Further, an electrode having a current collector layer 22 on the surface of 18 can be exemplified.

  In the above configuration, the porous layer corresponds to the diffusion layer, and the catalyst layer supported in the pores of the porous layer corresponds to the catalyst layer. That is, in the above configuration, the diffusion layer / catalyst layer is provided.

  In the above electrode configuration, the channel shape of the channel layer is not particularly limited as long as fuel or an oxidant can be supplied.

  FIG. 1 exemplifies a flow path layer having an uneven cross-section in which concave portions and convex portions 23 to be actual flow paths 16 are alternately arranged in a straight line. A serpentine shape (such as a single serpentine shape such as a single serpentine) or a flow path layer formed in a spiral shape may be used.

  The pitch of the concavo-convex portions, the width of the convex portions, the width of the concave portions, the groove depth of the concave portions, etc. are not particularly limited. Depending on the shape and size of the power generation part and the required battery performance, the amount of generated hydrogen and carbon dioxide emissions changes, which causes clogging of the flow path, and conversely, excessive drainage causes the membrane to dry. The design should be made in consideration of the oxidant such as air, the flow rate of the fuel, the flow velocity, and the like.

  In the above electrode configuration, the channel bottom (bottom surface of the recess) of the channel layer is in contact with the surface of the porous layer. More specifically, a part of the surface of the porous layer laminated adjacent to the channel layer is used as the channel bottom of the channel layer (the surface of the porous layer is at the channel bottom). Exposed).

  Here, the porous layer has a large number of through-holes penetrating from the channel bottom of the channel layer to the surface of the porous layer on the electrolyte membrane side. The porous layer may have non-through holes other than the through holes.

  In this case, for example, the through hole may penetrate substantially perpendicularly to the surface of the porous layer, or may penetrate through the film surface at an angle of less than 90 °. Moreover, you may penetrate at random, such as meandering or zigzag.

  The cross-sectional shape of the through hole is not particularly limited. Specific examples of the cross-sectional shape of the through-hole include, for example, a circle, an ellipse, a polygon, a shape in which these are connected, a combination thereof, and the like.

  The upper limit of the porosity of the porous layer is preferably 90% or less, more preferably 80% or less, and even more preferably 75% or less from the viewpoints of mechanical strength, electric resistance of the catalyst layer, and the like. On the other hand, the lower limit of the porosity of the porous layer is preferably 20% or more, more preferably 30% or more, and even more preferably 50% or more, from the viewpoints of supply of fuel and the like, catalyst layer formation process and the like.

  In the case of porous silicon, the porosity can be obtained from the weight measurement before and after the porous formation by anodic oxidation and the volume measurement of the porous layer by cross-sectional observation.

  The upper limit of the pore diameter of the porous layer is preferably 100 μm or less and more preferably 10 μm or less from the viewpoint of fuel permeability. On the other hand, the lower limit of the pore diameter of the porous layer is preferably 10 nm or more, and more preferably 50 nm or more from the viewpoint of the catalyst layer forming process.

  In addition, the said hole part diameter can be calculated | required by electron microscope observation.

  In the above electrode configuration, the catalyst is supported on the pore surface of the porous layer, or the catalyst metal itself forms the porous layer.

  The method for supporting the catalyst is not particularly limited. For example, a particulate catalyst may be chemically and physically attached to the hole surface, or the catalyst may be plated on the hole surface.

  The catalyst is preferably supported on the surface of the hole by plating from the viewpoint that a relatively inexpensive plating technique can be used and the catalyst is difficult to drop from the hole.

  The catalyst may be distributed over the entire area of the porous layer, or from a surface on the electrolyte membrane side of the porous layer toward the flow path layer side over a distance less than the thickness of the porous layer. May be distributed.

The upper limit of the catalyst content, preferably 10 mg / cm ² or less, 5 mg / cm ² or less being more preferred. If the amount is too large, the particle size of a catalyst such as platinum tends to be large, and the utilization efficiency per catalyst weight tends to decrease, and in order to keep the particle size small, the catalyst layer must be thickened. This is because the catalyst utilization rate in a place far from the electrolyte membrane tends to decrease. On the other hand, the lower limit of the catalyst content, in terms of maintaining performance, preferably 0.01 mg / cm ² or more, 0.1 mg / cm ² is more preferable.

  In the above electrode configuration, the current collector layer is formed on the surface of the convex portion of the flow path layer. The current collector layer may be formed on the entire convex surface of the flow path layer or may be partially formed on the convex surface as long as necessary current collection can be performed.

  Specific examples of the flow path layer material include conductive materials such as titanium, nickel, and alloys thereof, silicon, germanium, selenium doped with ions, GaAs, GaP, InP, CdTe, ZnSe. Semiconductor materials such as those obtained by ion doping a compound semiconductor such as SiC can be preferably used. Preferably, a semiconductor material can be suitably used.

  Of the semiconductor materials, silicon can be used as the most suitable material from the viewpoint that semiconductor processing technology can be applied and processing is easy, and the compound semiconductor is easy to break.

  More specifically, as the silicon, for example, n-type silicon having a relatively high etching rate can be suitably used, and the resistivity is preferably set to be from the viewpoint of reducing the loss of electric energy. Highly doped n-type silicon having a resistance of 01Ω or less, more preferably 0.005Ω or less, can be most suitably used.

  As the porous layer material, specifically, for example, a material obtained by making the flow path layer material porous can be suitably used.

  Specific examples of the catalyst material include noble metals such as platinum, platinum-ruthenium alloy, palladium, platinum-cobalt alloy, and platinum-iron alloy, and noble metal alloys. These may be contained alone or in combination of two or more.

  More specifically, as the catalyst on the cathode electrode side, for example, platinum or the like can be suitably used. On the other hand, as the catalyst on the anode electrode side, for example, a platinum-ruthenium alloy that can easily reduce the poisoning of the catalyst by carbon monoxide can be preferably used.

  Specific examples of the current collector layer material include copper, silver, gold, platinum, palladium, alloys thereof, and stainless steel. These may be contained alone or in combination of two or more.

  The thickness of the electrode is not particularly limited, and can be set as appropriate in consideration of weight reduction and electrical resistance.

  The upper limit of the thickness of the electrode is preferably 1 mm or less from the viewpoint of being advantageous for weight reduction and size reduction. On the other hand, the lower limit of the thickness of the electrode is preferably 0.05 mm or more from the viewpoint that, when the thickness is excessively thin, it becomes difficult to secure a flow path for fuel or the like, and handling during the MEMS process is deteriorated.

  Under the present circumstances, as an upper limit of the thickness of the said flow-path layer, 1 mm or less is preferable and 0.5 mm or less is more preferable. On the other hand, the lower limit of the thickness of the flow path layer is preferably 0.01 mm or more, and more preferably 0.05 mm or more.

  The upper limit of the thickness of the porous layer is preferably 100 μm or less, more preferably 50 μm or less, and most preferably 20 μm or less from the viewpoints that, if the thickness is too large, the resistance is increased and the battery performance is lowered. On the other hand, the lower limit of the thickness of the porous layer is preferably 1 μm or more, more preferably 2 μm or more, and most preferably 5 μm or more from the viewpoint that if the thickness is too thin, the strength cannot be maintained and the material tends to collapse.

  The upper limit of the thickness of the current collector layer is preferably 500 μm or less, and more preferably 100 μm or less from the viewpoint that if it is too thick, the current collector layer is easily damaged by plating stress. On the other hand, the lower limit of the thickness of the current collector layer is preferably 1 μm or more and more preferably 5 μm or more from the viewpoint that resistance is generated when the current collector layer is too thin.

2. This manufacturing method This manufacturing method is a method which can manufacture this MEA. In this manufacturing method, at least MEMS technology is used for forming the electrode.

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

  Here, the method for obtaining the porous film differs depending on the material, but for example, a stretching method, a solution of a film material in which a pore former is dispersed or a melt is applied in a film shape, and the solvent is volatilized. Removing or cooling the film material in a molten state to form a film and removing the pore former to form holes, punching, drilling, laser, A method of forming a hole using a processing means such as chemical / physical etching, and after pouring a melt of a film material such as a polymer into a mold capable of transferring the hole, the film is peeled off. Examples thereof include a method of transferring a hole to a surface.

  When the material of the porous membrane is a polymer, the most common 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. Stretching and removing the pore former by a method such as washing to form a porous membrane.

  Examples of the stretching method include uniaxial stretching and biaxial stretching. It should be noted that the shape of the hole can be determined by the ratio of stretching, the ratio and type of pore former, the blending amount, the type of membrane material, and the like.

  When the porous membrane is formed of a hydrophobic polymer material, at least one surface of the surface of the porous membrane may be subjected to a hydrophilic treatment. When the porous part is impregnated with a highly hydrophilic electrolyte material, if the porous film is previously hydrophilized, the impregnating ability 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.

  Moreover, the method of filling the electrolyte polymer in the pores of the porous membrane is not particularly limited. Specifically, for example, a method of impregnating a solution or dispersion of an electrolyte polymer or a molten electrolyte polymer in the pores, a solution or dispersion of a polymer precursor of an electrolyte polymer or a polymer precursor in a molten state in the pores After the impregnation, a method of generating an electrolyte polymer by polymerizing a polymer precursor impregnated in the pores, or converting a functional group that can be converted into an electrolyte group after polymerization into an electrolyte group, etc. It can be illustrated.

  Specific examples of the impregnation method include, for example, a method of immersing a porous film in the above solution and the like, and various coating methods (die coating method, comma coating method, gravure coating) on the porous film. Examples thereof include a coating method using a method, a roll coating method, a bar coating method, a reverse coating method and the like. These may be used alone or in combination of two or more.

  In addition, at the time of the impregnation, one or more kinds of a crosslinking agent, a polymerization initiator (such as a photopolymerization initiator, a thermal initiator, and a redox-based initiation polymerization initiator), a curing agent, and a surfactant are used as necessary. It may be added.

  When using the polymer precursor, the polymer precursor contains at least one or more electrolyte monomers described above. Furthermore, you may contain a crosslinking agent as needed.

  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.

  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 functional groups capable of crosslinking reaction in one molecule. Examples of such compounds are as follows. These may be contained alone or in combination of two or more.

  Specifically, as the former crosslinking agent, for example, N, N′-methylenebis (meth) acrylamide, N, N′-ethylenebis (meth) acrylamide, N, N′-propylenebis (meth) acrylamide, N , N'-butylene bis (meth) acrylamide, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylolpropane diallyl ether, pentaerythritol triallyl ether, divinylbenzene, bisphenol di (meth) acrylate, isocyanuric acid Examples thereof include crosslinkable monomers such as di (meth) acrylate, tetraallyloxyethane, triallylamine, and diallyloxyacetate.

  Specific examples of the latter crosslinking agent include crosslinking monomers such as N-methylolacrylamide, N-methoxymethylacrylamide, and N-butoxymethylacrylamide. These can be crosslinked after radical polymerization of a polymerizable double bond and heated to cause a condensation reaction or the like, or can be heated simultaneously with radical polymerization to cause a similar crosslinking reaction.

  In addition, the said crosslinking agent is not restricted to the compound which has a carbon-carbon double bond, Although the polymerization reaction rate is a little small, the compound etc. which have the bifunctional or more epoxy compound, the phenyl group which has a hydroxymethyl group, etc. are used. You can also. When using the said epoxy compound, a crosslinking point is formed by reacting with acids, such as a carboxyl group contained in a polymer.

  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 vinyls, allyl compounds, methallyl compounds, and the like. it can. These may be contained alone or in combination of two or more.

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

  When producing the electrolyte membrane, the electrolyte polymer and polymer precursor can be impregnated into the pores of the porous membrane as they are when the electrolyte polymer and polymer precursor itself are liquid and have low viscosity. In this case, a preferable viscosity is about 1 to 10,000 mPa · s at 25 ° C.

  On the other hand, when it is difficult to impregnate the pores of the porous membrane as it is, the electrolyte polymer and / or polymer precursor is dispersed in a solution dissolved in a suitable solvent or a suitable dispersion medium. A dispersion is preferred. In this case, the preferred viscosity is about 1 to 10000 mPa · s at 25 ° C. The viscosity is a value measured with a B-type viscometer.

  Specific examples of the solvent and dispersion medium include, for example, aromatic organic solvents such as toluene, xylene and benzene, aliphatic organic solvents such as hexane and heptane, chlorine solvents such as chloroform and dichloroethane, diethyl Ethers such as 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, dimethylacetamide, N-methyl-2-pyrrolidone Examples thereof include amide solvents such as water, alcohols, and the like. These may be contained alone or in combination of two or more. Of these, water is preferably mainly contained. It is because it is excellent in handleability and economy.

  The upper limit of the concentration of the solution or dispersion is preferably 100% by mass or less, more preferably 90% by mass or less, and most preferably 80% by mass or less from the viewpoint of higher performance when the concentration is higher. On the other hand, the lower limit of the concentration of the above solution or dispersion is 5 from the viewpoint of insufficient filling when the concentration is too low, or difficulty in filling unless the number of times is repeated, resulting in poor productivity. % By mass or more is preferable, 10% by mass or more is more preferable, and 20% by mass or more is most preferable.

  When an electrolyte polymer layer is formed on the surface of the porous membrane when the electrolyte membrane is produced, as a method of removing the layer, specifically, for example, a method of rubbing with a resin fiber or the like, rubbing with a brush, The method of scraping with a scraper etc. can be illustrated. 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.

2.2 Formation of Electrode In this manufacturing method, MEMS technology is used to form at least one of the electrodes.

  In the case of forming the electrode configuration described above, specifically, for example, a step of forming a flow path layer by etching one surface of a substrate having a certain thickness such as a silicon wafer to a depth that does not penetrate, A method of forming a porous layer by forming a porous layer from the bottom of the flow path to the other surface of the substrate and a method of supporting a catalyst in the pores of the porous layer (hereinafter referred to as “first”). 1 electrode forming method ”)) and the like.

  In addition to the first method, for example, a step of forming a porous layer by making one surface of a substrate having a certain thickness porous to a depth that does not reach the thickness, and in the pores of the porous layer, And a step of forming a flow path layer by etching the other side of the substrate to a depth reaching the porous layer (hereinafter referred to as “second electrode formation method”). .), Forming a porous layer by making one surface of a substrate having a certain thickness porous to a depth not reaching the thickness, and etching the other surface of the substrate to a depth reaching the porous layer. Examples of the method include at least a step of forming a flow path layer and a step of supporting a catalyst in the pores of the porous layer. Although not efficient in production, an electrode structure can be formed by joining a substrate having a porous layer and a substrate having a flow path layer.

  In the electrode forming method, the etching may be wet etching or dry etching such as plasma etching. The selection can be made in consideration of the electrode material, the flow path shape, and the like.

  Moreover, as a method for making a part of the substrate porous, for example, when the electrode material is silicon, an anodic oxidation method can be exemplified. The pore size, shape, layer thickness, etc. of the silicon porous layer include parameters such as resistivity of the silicon single crystal to be used, current density during anodization, anodizing time, liquid composition of the anodizing solution, concentration, and liquid temperature. It is possible to control by preparing.

The upper limit of the current density during the anodization, and less likely to occur electropolishing, from the viewpoint of easy to promote pore formation, preferably 10000 A / ^{m 2} or less, more preferably 5000A / ^{m 2} or less, 2000A / ^{m 2} The following are most preferred. On the other hand, the lower limit of the current density during the anodization, in view of too porosity decreases, 1A / ^{m 2} or more is preferable, 100A / ^{m 2} or more preferably, 500A / ^{m 2} or more and most preferable.

Examples of the anodic oxidation solution include one or more compounds that can be dissolved in water, alcohol, or the like, such as hydrofluoric acid, sodium fluoride, or ammonium fluoride, to generate fluorine ions, and may be appropriate such as water or alcohol. A liquid dissolved in a solvent can be exemplified. The concentration of fluorine ions in the anodizing liquid, typically ^may be a 0.5mol / dm ³ ~25mol / dm 3 approximately.

  The upper limit of the temperature of the anodic oxidation solution is preferably 25 ° C. or less, more preferably 20 ° C. or less, from the viewpoint of reaction uniformity. On the other hand, the lower limit of the temperature of the anodic oxidation solution is preferably 0 ° C. or higher and more preferably 10 ° C. or higher from the viewpoint of reaction rate.

  Specific examples of the method for supporting the catalyst in the pores of the porous layer include plating methods such as electroless plating and electrolytic plating, sputtering methods, adsorption of metal colloids, and the like. Among these, the plating method is preferable from the viewpoints of easily retaining the catalyst in the hole, being relatively easy to control, and being an inexpensive method, and being established as a catalyst loading method.

  The plating solution used for the plating method can be prepared, for example, by dissolving one or more soluble salts containing a supported catalytic metal as a constituent element in an appropriate solvent such as water. In this case, when the porous layer material is silicon, when performing electroless plating, fluorine ions may be contained in the plating solution using hydrofluoric acid or the like.

  A catalytic metal such as platinum, which has a lower ionization tendency than silicon, receives electrons from silicon, is reduced and spontaneously precipitates, and plating proceeds. However, with the progress of plating, it is conceivable that an insulating film (silicon oxide film) serving as a barrier to the progress of plating is formed on the surface of the hole. For this reason, the formation of this insulating film is suppressed by the presence of fluorine ions, and the plating is facilitated to proceed.

The upper limit of the current density during plating, in view of the metal ions supplied to the internal porous layer is preferably from 100A / m ² or less, 10A / m ² or less is more preferable. On the other hand, the lower limit of the current density during plating, deposition overvoltage, in view of the growth of precipitate nuclei, 0.1 A / ^{m 2} or more is preferable, 1A / ^{m 2} or more is more preferable.

  The upper limit of the temperature of the plating solution is preferably 25 ° C. or less and more preferably 20 ° C. or less from the viewpoint of nucleus growth and the like. On the other hand, the lower limit of the temperature of the plating solution is preferably 0 ° C. or higher, more preferably 5 ° C. or higher, from the viewpoint of reaction rate.

  Hereinafter, the first and second electrode forming methods will be described in more detail with reference to the drawings.

  FIG. 2 is a cross-sectional view schematically showing an example of the first electrode forming method.

  First, the surface of the substrate W such as a silicon wafer having a certain thickness is wet-etched to form the flow path layer 18 made of uneven portions (FIG. 2A).

  Next, in order to ensure electrical conduction, a conductive film 24 such as a copper film is formed by sputtering or the like (FIG. 2B). Next, a protective film 26 such as a resist film is formed on the surface of the conductive film 24 (FIG. 2C). Next, the anodization is performed by bringing the back surface of the substrate W into contact with the anodic oxidation solution, and the porous layer 20 ′ is made porous from the back surface of the substrate W to the flow channel bottom of the flow channel layer 18. Form (FIG. 2D).

  Next, the porous layer 20 ′ is immersed in a plating solution and plated to form the porous layer 20 in which the catalyst is supported in the pores (FIG. 2E). As a result, the porous layer (diffusion layer) and the catalyst layer are formed overlappingly.

  Next, the protective film 26 is removed by dissolving the resist film using a solvent such as acetone (FIG. 2F). Next, the conductive film 24 is removed by dissolving the copper film using ferric chloride or the like (FIG. 2G). As a result, an electrode 14a (14c) having a flow path layer 18 in which the flow path 16 is formed and a porous layer 20 that is in contact with the flow path bottom of the flow path layer 18 and in which the catalyst is supported is obtained. It is done.

  On the other hand, FIG. 3 is a cross-sectional view schematically showing an example of the second electrode forming method.

  First, a conductive film 24 such as a copper film is sputtered to secure electrical continuity on the surface of a substrate W such as a silicon wafer having a certain thickness, or to be used as an etching mask such as plasma etching. (FIG. 3A).

  Next, a photoresist film 26 is formed on the surface of the conductive film 24 for patterning the flow path pattern (FIG. 3B).

  Next, a photomask depicting a flow path pattern is placed on the surface of the resist film 26 and exposed to light. After the flow path pattern is transferred to the resist film 26 and baked, the resist is removed (FIG. 3C). )).

  Next, the exposed conductive film 24 such as a copper film is dissolved using an etchant such as ferric chloride, and the conductive film 24 is removed along the pattern (FIG. 3D).

  Next, the resist film 26 is removed using a solvent such as acetone (FIG. 3E).

  Next, anodization is performed by bringing the back surface of the substrate W into contact with the anodic oxidation solution, and the porous layer 20 ′ is formed by making a certain distance from the back surface of the substrate W less than the thickness of the substrate W. (FIG. 3 (f)).

  Next, the porous layer 20 ′ is immersed in a plating solution and plated to form the porous layer 20 in which the catalyst is supported in the pores (FIG. 3G). As a result, the porous layer (diffusion layer) and the catalyst layer are formed overlappingly.

  Next, using the copper film 24 as a mask, etching such as plasma etching is performed from the surface side of the substrate W up to the porous layer 20 to form the flow path layer 18 (FIG. 3H). Note that a conductive film such as a copper film on the surface of the flow path layer 18 can be used as the current collector layer 22, but if unnecessary, it may be removed by further etching or the like.

  Thereby, the flow path layer 18 in which the flow path is formed, the porous layer 20 in contact with the flow path bottom of the flow path layer 18 and carrying the catalyst in the hole, and optionally on the surface of the flow path layer 18 An electrode 14a (14c) having a current collector layer 22 is obtained.

2.3 Joining of Electrolyte Membrane and Electrode As a method of joining the electrode to the electrolyte membrane, specifically, for example, an electrolyte material dissolved in a solvent such as isopropanol is used as the surface of the electrolyte membrane and / or the porous layer of the electrode. Examples of the method include a method in which an electrolyte membrane and an electrode are stacked after being applied to the surface of the film and heated and pressed by a hot press or the like.

  Specific examples of the electrolyte material include fluorine electrolyte polymers such as Nafion, ionomers made of hydrocarbon polymers such as polystyrene sulfonic acid, styrene sulfonate ethylene copolymer, and sulfonated polyether sulfone. can do. These may be used alone or in combination of two or more.

  Further, the heating temperature and pressure during the heating and pressurization may be appropriately selected in consideration of the material of the porous film, the type of electrolyte material dissolved in the solvent, and the like.

  In general, when the heating temperature and the applied pressure are excessively high, there is a tendency that the porous membrane is deformed or the electrode is easily damaged. On the other hand, when the heating temperature and the applied pressure are excessively lowered, the adhesiveness tends to be lowered. Therefore, it is preferable to pay attention to these when joining the electrolyte membrane and the electrode.

3. Fuel Cell The fuel cell includes the MEA. In this fuel cell, one or more MEAs may be stacked. As fuel to be supplied to the fuel cell, alcohol such as methanol, ethanol, propanol and butanol, hydrogen and the like can be used. Preferably, it is methanol. On the other hand, oxygen, air, or the like can be used as the oxidant supplied to the fuel cell.

  Hereinafter, the present invention will be described more specifically with reference to examples.

1. Preparation of electrolyte membrane 1.1 Electrolyte membrane (1)
45 g of 2-acrylamido-2-methylpropanesulfonic acid (manufactured by Toagosei Co., Ltd., “ATBS”), 5 g of N, N′-ethylenebisacrylamide, 0.005 g of nonionic surfactant, 0.005 g of ultraviolet radical generator Then, 50 g of water was stirred and mixed until a uniform solution was obtained to prepare a polymer precursor solution of an electrolyte polymer.

  Next, a porous film made of crosslinked polyethylene (thickness: 16 μm, porosity: 37%, average pore diameter: about 0.1 μm) was immersed in the polymer precursor solution, and the pores were impregnated with the solution.

  Next, after the porous membrane was pulled up from the solution, it was sandwiched between PET films (thickness 50 μm, manufactured by Toray Industries, Inc., “Lumirror T50”) so as to prevent bubbles, thereby obtaining a laminate.

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.

  Next, the PET film was peeled and removed from the laminate, and further rubbed with a scrubbing made of a resin fiber nonwoven fabric while the membrane surface was wetted with pure water to remove the electrolyte polymer adhering to the membrane surface, and the membrane was naturally dried.

  As a result, an electrolyte membrane (1) is obtained in which a crosslinked body of a polymer having a 2-acrylamido-2-methylpropanesulfonic acid monomer unit is filled as an electrolyte polymer in the pores of the porous membrane made of crosslinked polyethylene. It was.

  In addition, when a water droplet was dripped on the surface of the obtained electrolyte membrane (1), water was repelled. Therefore, it was confirmed that a porous film made of crosslinked polyethylene was exposed on the surface of the electrolyte membrane (1).

1.2 Electrolyte membrane (2)
As a comparative electrolyte membrane, a commercially available fluorine-based electrolyte membrane (manufactured by DuPont, “Nafion 112”) was used as an electrolyte membrane (2).

2. Production of Electrode A highly doped n-type silicon wafer having a thickness of 110 μm was cut into a 15 mm square, and a copper thin film (having a thickness of about 100 nm) was formed on one surface thereof by sputtering.
The silicon wafer has a (100) surface polished on both sides. Moreover, the resistivity was 0.001-0.003 ohm-cm.

  Next, a photoresist (manufactured by Tokyo Ohka Kogyo Co., Ltd., “OFPR-800”) was applied to the surface of the copper thin film to form a resist film (thickness 50 μm).

  Next, a photomask in which a linear flow path pattern having a mask width and an opening width of 100 μm and a pitch of 200 μm, respectively (with a flow path interval of 100 μm for each of the convex portion and the concave portion) is formed in a 5 mm square region on one side of the wafer center The resist pattern was formed by developing after exposing the flow path pattern by irradiating with ultraviolet rays.

  Next, after removing copper along the resist pattern using a 42 degree Baume (about 48 wt%) ferric chloride solution, the resist pattern was removed using acetone. Furthermore, this was annealed at 400 ° C. for 15 minutes. As a result, a copper mask pattern was formed on the surface of the silicon wafer.

Next, the back side of the silicon wafer having a copper mask pattern formed on the surface was brought into contact with a mixed solution in which hydrofluoric acid (purity 46 mass%) and ethanol were mixed at a volume ratio of 1: 1. Then, using a silicon wafer as an anode, anodic oxidation was performed by applying a current for 390 seconds at a liquid temperature of 10 ° C. and a current density of 70 mA / m ² . As a result, a porous layer was formed in a depth range of about 10 μm from the back surface of the silicon wafer.

Next, the porous layer is immersed in a plating solution (1.0 MH ₂ SO ₄ +20 mM H ₂ PtCl ₄ +300 mM HF) having a liquid temperature of 20 ° C., the plating solution is slowly stirred, and electroless plating is performed for 15 minutes. went. As a result, the platinum catalyst was supported in the pores of the porous layer. In addition, when the cross section of the silicon wafer after platinum catalyst formation was observed by SEM, the platinum catalyst was deposited in layer form over the whole porous layer. Further, the platinum catalyst was mainly deposited in a range of about 7 μm in depth from the back surface of the silicon wafer.

Next, using the copper mask pattern, silicon was plasma etched along this pattern. The etching conditions were as follows: etching time: about 100 minutes, gas flow rate: SF ₆ 12 sccm, O ₂ 5 sccm, RF output: 50 W, vacuum value: 2.2 to 2.8 Pa. Thereby, a channel layer in which each channel bottom portion was in contact with the porous layer was formed.

  As described above, the flow path layer in which the flow path is formed, the porous layer that is in contact with the flow path bottom (recessed portion) of the flow path layer, and in which the platinum catalyst is supported, and the surface (convex surface) of the flow path layer. A plate-like electrode having a copper layer as a current collector layer was obtained on the part surface.

3. Production of Membrane / Electrode Assembly A membrane / electrode assembly was produced using the produced electrolyte membrane and electrode.

(Membrane electrode assembly according to Example 1)
The prepared electrodes were bonded to both surfaces of the prepared electrolyte membrane (1).

  That is, first, the porous layer surface of the produced electrode was immersed in isopropanol, and then a Nafion solution (5% Nafion solution: isopropanol = 1: 6) was applied to the surface of the porous layer.

  Next, after the produced electrolyte membrane (1) was immersed in the Nafion solution, the electrolyte membrane (1) was sandwiched between two electrodes and hot-pressed at a pressure of 0.24 MPa and 100 ° C. for 30 minutes.

  Thereby, the membrane electrode assembly which concerns on the Example whose thickness is 230 micrometers was produced.

(Membrane electrode assembly according to comparative example)
In the production of the membrane electrode assembly according to the example, the production of the membrane electrode assembly according to the comparative example was tried in the same manner except that the electrolyte membrane (2) was used instead of the electrolyte membrane (1). However, the flow path portion and the porous layer were damaged by the swelling deformation of the Nafion film.

4). Evaluation 4.1 Proton conductivity of electrolyte membrane AC impedance measurement from 100 Hz to 40 MHz at 25 ° C using a sample sandwiched between two platinum plates immersed in pure water at 25 ° C for 1 hour. And proton conductivity was measured.

As a result, the proton conductivity of the electrolyte membrane (1) was 28 S / cm ² . On the other hand, the proton conductivity of the electrolyte membrane (2) was 3.6 S / cm ² .

4.2 Methanol permeability of electrolyte membrane Methanol permeability of the electrolyte membrane was confirmed by an infiltration experiment at 25 ° C.

  That is, the electrolyte membrane 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. Then, the amount of methanol penetrating into the pure water side was measured over time by gas chromatographic analysis, and the methanol permeability coefficient and permeation flux at the steady state 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 0.53 kg / (m ² · h). On the other hand, the methanol permeation flux of the electrolyte membrane (2) was 0.31 kg / (m ² · h).

4.3 Area change due to swelling of electrolyte membrane The electrolyte membrane was dried under reduced pressure at 70 ° C for 5 hours, and the dry area was measured. Next, the electrolyte membrane in a dry state was immersed in an aqueous solution of isopropanol or methanol having a different concentration at 25 ° C. for 1 hour, and the area change rate before and after the immersion was measured.

  FIG. 4 shows the relationship between the isopropanol concentration (% by weight) of the aqueous isopropanol solution and the area change rate (%) of the film. FIG. 5 shows the relationship between the methanol concentration (% by weight) of the aqueous methanol solution and the area change rate (%) of the membrane.

  From these results, when immersed in either an isopropanol aqueous solution or a methanol aqueous solution, the area change rate of the electrolyte membrane (1) was 20% or less in any concentration range. On the other hand, when the electrolyte membrane (2) was immersed in either an isopropanol aqueous solution or a methanol aqueous solution, it was confirmed that the area change rate rapidly increased as the concentration increased.

4.4 Power Generation Test A fuel cell using the membrane electrode assembly according to the example is sandwiched between a pair of clamps and set in a thermostatic chamber, and then air and anode electrodes are flown in the channel layer of the cathode electrode. A power generation test was conducted by flowing hydrogen through the road layer. At this time, the operating conditions of the battery were an air flow rate of 10 sccm / min, a hydrogen flow rate of 10 sccm / min, and the temperature in the thermostatic bath were 303K, 313K, 323K, and 333K.

  FIG. 6 shows current-voltage and current-power characteristics of the fuel cell according to the example. According to FIG. 6, since the fuel cell according to the example uses the membrane electrode assembly according to the present example, it is confirmed that the fuel cell can operate as a battery and is excellent in durability and reliability. did it.

  Although one embodiment and one example of the present invention have been described above, the present invention can be variously modified without departing from the spirit of the present invention.

It is the figure which showed an example of the structure of this MEA typically. It is sectional drawing which showed typically an example of the 1st electrode formation method. It is sectional drawing which showed typically an example of the 2nd electrode formation method. It is the figure which showed the relationship between the isopropanol density | concentration (weight%) of isopropanol aqueous solution, and the area change rate (%) of a film | membrane. It is the figure which showed the relationship between the methanol concentration (weight%) of methanol aqueous solution, and the area change rate (%) of a film | membrane. It is the figure which showed the current-voltage and current-power characteristic of the fuel cell which concerns on an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Membrane electrode assembly 12 Electrolyte membrane 14a Anode electrode 14c Cathode electrode 16 Channel 18 Channel layer 20 Porous layer 22 Current collector layer

Claims (8)

A membrane electrode assembly in which an anode electrode is joined to one surface of an electrolyte membrane and a cathode electrode is joined to the other surface,
At least one of the electrodes is formed using MEMS technology,
The membrane electrode assembly, wherein the electrolyte membrane is a porous membrane filled with an electrolyte polymer. At least one of the electrodes is made of a semiconductor material or a conductor material,
A flow path layer in which fuel or oxidant flow paths are formed;
The membrane electrode assembly according to claim 1, further comprising a porous layer in contact with a flow path bottom of the flow path layer and having a catalyst supported therein.   The membrane electrode assembly according to claim 2, further comprising a current collector layer on a surface of the flow path layer.   The membrane electrode assembly according to any one of claims 1 to 3, wherein the semiconductor material is silicon.   5. The electrolyte membrane according to claim 1, wherein when the electrolyte membrane is immersed in isopropanol having a liquid temperature of 25 ° C. or an aqueous solution thereof for 1 hour, the area change rate before and after immersion is 20% or less. Membrane electrode assembly.   6. The electrolyte membrane according to claim 1, wherein when the electrolyte membrane is immersed in methanol having a liquid temperature of 25 ° C. or an aqueous solution thereof for 1 hour, the area change rate before and after immersion is 20% or less. Membrane electrode assembly.   A fuel cell comprising the membrane electrode assembly according to any one of claims 1 to 6.   The fuel cell according to claim 7, wherein the thickness is 2 mm or less.

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