JP5669201B2 - Composition for forming catalyst layer and method for producing catalyst layer - Google Patents

Description

  Composition for forming catalyst layer for electrochemical device such as polymer electrolyte fuel cell (PEFC), method for producing catalyst layer, and catalyst layer, electrode with catalyst layer, and membrane obtained thereby -It is related with an electrode assembly and an electrochemical device.

  The basic structure of an electrochemical device such as a polymer electrolyte fuel cell is composed of a negative electrode and a positive electrode as an electrochemical reaction field, and a diaphragm between the negative electrode and the positive electrode.

  Proton (hydrogen cation) conductive exchange membranes are common as polymer electrolyte membranes for diaphragms, but in recent years, anion conductive exchange membranes such as hydroxide ions have been used for the purpose of reducing the amount of platinum catalyst used. Research is also actively conducted.

  Since the fuel cell is a power generation device that directly converts the chemical energy of the fuel into electrical energy, the “negative electrode” and “positive electrode” are different from the electrode plate with a simple structure of a general battery, and the porous carbon sheet of the gas diffusion layer, It is a reaction plate comprising a catalyst layer fixed on its surface.

  In the fuel cell field, the electrode having such a configuration is referred to as an “electrode with a catalyst layer” in order to distinguish it from the electrode of a general cell, and therefore it is the same in this specification.

  If you prepare two "electrodes with catalyst layers" that are reaction plates and heat-press with a polymer electrolyte membrane in between, a basic unit called a membrane-electrode assembly (MEA) can be obtained (for example, , See Patent Document 1).

  A structure in which only a catalyst layer is added to both surfaces of a polymer electrolyte membrane is called a catalyst layered membrane (CCM). The membrane / electrode assembly MEA can be obtained by hot pressing the catalyst layer-attached membrane CCM between two porous carbon sheets. (For example, see Patent Document 2).

  In any case, the configuration of the membrane / electrode assembly MEA is the same. That is, they are bonded in the order of porous carbon sheet / catalyst layer / polymer electrolyte membrane / catalyst layer / porous carbon sheet.

  When the structure of the “catalyst layer” is viewed in detail, it is composed of three components: an ion conductive electrolyte polymer, metal fine particles as a catalyst for electrochemical reaction, and carbon black carrying a catalyst with electronic conductivity. In general, a “catalyst paste” in which carbon black supporting metal fine particles, an electrolyte polymer solution, an alcohol solvent and the like are mixed is applied to a carbon sheet or a polymer film and dried.

  In recent years, various researches have been conducted to reduce the cost and performance of catalyst layers not only in battery manufacturers and material manufacturers.

  In order to improve the performance of the catalyst layer, it is important to form a “three-phase interface” necessary for the electrochemical reaction in the catalyst layer. The “three-phase interface” is a highly reactive site where a liquid phase of an electrolyte and a gas phase of fuel gas can come into contact with a solid phase such as a platinum catalyst.

  For this reason, after adding sodium chloride powder to the catalyst paste and applying and drying to form a catalyst layer, the sodium chloride powder is eluted and removed by washing with water to form pores that tend to become “three-phase interfaces” (for example, , See Patent Document 3).

  In addition, in improving the performance of the catalyst layer, it is important to improve the durability, and after applying the catalyst paste mixed with the electrolyte polymer, prepolymer, crosslinking aid, etc., it is crosslinked and fixed by light irradiation, An improved production method that suppresses the loss (for example, see Patent Document 4), and a method for enhancing conductivity while reinforcing the surface of a fluorine-based polymer substrate by graft polymerization of an ion conductive group-containing monomer (for example, Patent Document) (See 5-8.) And other improved production methods have been studied.

  On the other hand, various attempts have been made to reduce the cost of the catalyst layer while reducing the amount of noble metal particles used while maintaining the catalyst function.

For example, a molded body obtained by applying and molding a paste of an electrolyte polymer and a carbon carrier is immersed in an aqueous solution of a platinum-based compound (platinum ammine complex chloride) and adsorbed, and then reduced in hydrogen gas and applied to the surface of the carrier. For example, the platinum catalyst is distributed intensively. (For example, see Patent Documents 9 to 10.)
The inventors of the present invention have been continuously researching industrial applications of radiation processing technology, and in recent years, various studies have been made on the application of the above-mentioned fuel cell electrodes, and various research results have been obtained. Cite.

  Last year's research result was to establish a technology to generate metal particles (catalyst) "in situ" at the required site by irradiation, and apply it to the formation of the catalyst layer described above.

Specifically, a catalyst layer forming composition comprising a carbon support, an electrolyte polymer, a metal precursor, an alcohol solvent, and water is applied to a carbon electrode substrate, and the carbon electrode substrate is directly irradiated with an electron beam to directly This is a method for producing an electrode with a catalyst layer by a simple process, and a patent application has already been filed. (Japanese Patent Application No. 2010-001574)
However, the composition for forming a catalyst layer had several points to be improved in terms of workability and cost, such as the necessity of an expensive and hardly soluble “perfluorosulfonic acid electrolyte polymer”.

Japanese Examined Patent Publication No. 62-61118 Japanese Examined Patent Publication No. 2-48632 JP-A-6-236762 JP 2009-295442 A JP 2009-104967 A JP 2007-528843 A JP 2010-067368 A JP 2005-108604 A JP 2000-12040 A JP 2009-212008

  An object of the present invention is to solve the conventional problems and to provide a measure for realizing a catalyst layer of an electrode with a catalyst layer for a polymer fuel cell in a simple and low cost manner.

  The present invention is characterized by the following in order to solve the above problems.

  That is, the present invention relates to a catalyst layer forming composition used for forming a catalyst layer of an electrode with a catalyst layer of an electrochemical device, a metal that can introduce ion conductivity, and a metal that is a precursor of metal fine particles. The vinyl monomer is polymerized by irradiation to form an ion conductive polymer, and the metal compound is reduced by irradiation to form metal fine particles. This is a composition for forming a catalyst layer to be formed.

  The vinyl monomer capable of introducing ion conductivity is preferably composed of styrene styrene and its derivatives, acrylic acid and its derivatives, vinyl sulfonic acid and its derivatives, perfluorinated vinyl sulfonic acid and its derivatives. One or more vinyl monomers selected from the group of cationic vinyl monomers.

  The vinyl monomer capable of introducing ion conductivity is preferably trimethylammonium methylstyrene chloride, triethylammonium styrene chloride, dimethylvinylbenzylamine, 2- (dimethylamine) ethyl methacrylate, or a styrene derivative having an ammonium group. One or more vinyl monomers selected from the group of anionic vinyl monomers consisting of a styrene derivative having a secondary or tertiary amine group, and an acrylic acid derivative having a secondary or tertiary amine group .

  Furthermore, the present invention is a method for producing a catalyst layer of an electrode with a catalyst layer of an electrochemical device, wherein the above-described catalyst layer forming composition is applied to the surface of a substrate, and then irradiated with radiation, An electrode with an electrode for a catalyst layer of an electrochemical device in which an ion conductive polymer is formed on a surface from a vinyl monomer contained in the composition for forming a catalyst layer, and metal particles are formed from a metal compound to produce a catalyst layer. It is a manufacturing method of a catalyst layer.

Moreover, the above-described base material is preferably a porous carbon sheet or a polymer film.
Further, the present invention is an electrode with a catalyst layer for an electrochemical device, wherein the catalyst layer and the catalyst layer obtained by the production method described above are at least a part of the configuration.

  Further, the present invention is an electrochemical device in which the above-mentioned electrode with a catalyst layer is at least a part of its configuration.

  Furthermore, the present invention is a membrane / electrode assembly obtained by bonding the porous carbon sheet with a catalyst layer obtained by the above-described production method as an electrode to both surfaces of a polymer electrolyte membrane.

  Moreover, this invention is a polymer electrolyte membrane with a catalyst layer which transferred the polymer film with a catalyst layer obtained by the above-mentioned manufacturing method to both surfaces of a polymer electrolyte membrane, and formed the catalyst layer. Further, the present invention is a membrane / electrode assembly obtained by bonding a porous carbon sheet to both surfaces of a polymer electrolyte membrane with a catalyst layer obtained by the production method described above.

  The present invention also relates to a polymer fuel cell including the membrane / electrode assembly described above.

The present invention uses a vinyl monomer having an ion conductive group and a metal compound of a catalyst precursor as raw materials without using expensive and hardly soluble perfluorosulfonic acid electrolyte polymers, catalyst fine metal particles, and the like as main materials. And a vinyl polymer having an ion conductive group “in-situ” after being applied to a substrate and then irradiated with radiation. Since the metal fine particles functioning as a catalyst are formed to form a catalyst layer, the catalyst layer can be obtained by a simple and low-cost means .

  The composition for forming a catalyst layer used for forming a catalyst layer of an electrode with a catalyst layer of an electrochemical device of the present invention includes a vinyl monomer capable of introducing ion conductivity, a metal compound that is a precursor of metal fine particles, and It contains a carbon support.

  The vinyl monomer is polymerized by irradiation to form an ion conductive polymer, and the metal compound is reduced by irradiation to form metal fine particles.

And in the manufacturing method of the catalyst layer of this invention, after applying the composition for catalyst layer formation to a base material, it irradiates with a radiation, and the catalyst of a metal microparticle is simply an ion conductive polymer on a carbon support | carrier. A fixed catalyst layer is used.
<Composition for catalyst layer formation and preparation thereof>
The composition of the composition for forming a catalyst layer essentially includes a vinyl monomer capable of introducing ion conductivity, a metal compound that is a precursor of metal fine particles, and a carbon support.

  Further, the mixing of the dispersion solvent and other additives is appropriately considered. In addition, not only a metal compound but a metal microparticle can also be simultaneously mix | blended with a composition.

  Vinyl monomers become electrolyte polymers by “in situ” polymerization upon irradiation. The electrolyte polymer plays a role of ionic conductivity and binder property of the catalyst layer.

  Metal fine particles generated from the metal compound of the composition serve as a catalyst for the catalyst layer.

The carbon support is used for supporting metal fine particles. Moreover, the carbon support bears the electronic conductivity of the catalyst layer.
(Vinyl monomer capable of introducing ion conductivity)
Vinyl monomers capable of introducing ionic conductivity include styrene sulfonate and derivatives thereof, acrylic acid and derivatives thereof, vinyl sulfonic acid and derivatives thereof, and perfluorovinylsulfone as known vinyl monomers capable of introducing cation conductivity. Examples include acids and their derivatives. Among them, one or more types can be used. Preferred are styrene sulfonate and its derivatives.

  Also, vinyl monomers capable of introducing ion conductivity are known vinyl monomers capable of introducing anion conductivity such as vinyl benzyl trimethyl ammonium chloride, vinyl benzyl triethyl ammonium chloride, trimethyl ammonium methyl styrene chloride, triethyl ammonium styrene chloride. Dimethylvinylbenzylamine, 2- (dimethylamine) ethyl methacrylate, styrene derivatives having an ammonium group, styrene derivatives having a secondary or tertiary amine group, acrylic acid derivatives having a secondary or tertiary amine group, etc. Can be mentioned. Among them, one or more types can be used. Preferred are vinylbenzyltrimethylammonium chloride and its derivatives.

A vinyl monomer having hydrogen ion (H ⁺ ) conductivity or hydroxide ion (OH ⁻ ) conductivity may be converted into a target cation electrolyte polymer or anion electrolyte polymer by a simple processing operation after radiation polymerization. it can. Other vinyl monomers can be used in the catalyst layer composition as long as they are hydrolyzable and ion-exchangeable. After forming the catalyst layer, it can be easily converted to the target electrolyte polymer by known chemical conversion. it can.

  The compounding quantity of the vinyl monomer which can introduce | transduce ion conductivity in the composition for catalyst layer formation is 10-60 mass% of the total amount of what becomes a catalyst layer solid content, Preferably it is the range of 25-40 mass%.

If the blending amount is less than 10% by mass, the ion conductivity and binder property of the produced electrolyte polymer are not sufficiently functioned, and a stable catalyst layer is hardly formed. On the other hand, if it exceeds 60% by mass, a large number of fine metal particles and carbon support are coated with the electrolyte polymer, and the catalytic ability becomes difficult to work and the electron conductivity may be lowered.
(Metal compounds that are precursors of fine metal particles)
Known metal compounds that are precursors of fine metal particles include platinum, ruthenium, osmium, palladium, iridium, rhodium, chromium, nickel, manganese, molybdenum, gallium, aluminum, gold, iron, lead, copper, cobalt, nickel, etc. Examples thereof include chlorides, nitrates, complexes and the like.

For example, examples of platinum chloride, nitrate and complex include chloroplatinic acid H ₂ PtC1 ₆ , tetraamineplatinum nitrate Pt (NH ₃ ) ₄ (NO ₃ ) ₂ , potassium hexachloroplatinate K ₂ PtCl ₆ , and the like. Can do. These metal compounds may be used alone or in combination of two or more.

  The blending amount of the metal compound is calculated backward from the amount of metal fine particles to be blended in the catalyst layer. That is, the amount of the metal fine particles to be blended in the catalyst layer forming composition is in the range of 2 to 60% by mass, preferably 10 to 50% by mass, based on the total amount of the catalyst layer solid content. The most preferable range is 20 to 40% by mass. If the blending amount is less than 2% by mass, the catalyst performance may be difficult to work. When it exceeds 60% by mass, the cost tends to be high with respect to the degree of improvement of the catalyst function, and the performance / cost tends to be low.

  If the particle size of the metal fine particles is too large, the catalyst surface area is small, and the catalytic performance per unit mass is reduced. Conversely, when too small, the stability of a catalyst will fall. The particle size is preferably 1.0 to 15 nm, more preferably 1.5 to 5.0 nm.

  Depending on the degree and amount of the precursor metal compound blended and dispersed in the composition for forming the catalyst layer, the type and combination of the solvent system of the composition, the amount of radiation irradiation, etc., the particle size of the metal fine particles to be reduced and precipitated can be controlled.

(Metal fine particles)
In the catalyst layer forming composition, not only the precursor metal compound but also metal fine particles can be blended simultaneously within an allowable range. The blending ratio is in the range of 2 to 60% by weight, preferably 10 to 50% by weight, based on the total amount of the catalyst layer solid content together with the precursor-derived one. The most preferable range is 20 to 40% by mass.

  Examples of the metal fine particles include platinum, ruthenium, osmium, palladium, iridium, rhodium, chromium, nickel, manganese, molybdenum, gallium, aluminum, gold, iron, lead, copper, cobalt, nickel and the like.

In recent years, “a carbon support carrying metal fine particles having catalytic ability” has been put on the market as one of the product forms. It is preferable that these metal fine particle-supported carbon carriers, for example, platinum-supported carbon black (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) can be used as a coating target for the composition for forming a catalyst layer, because a higher-performance catalyst layer can be formed.
(Carbon support)
The carbon carrier can be used without limitation as long as it is a carbon material having a known electronic conductivity. Examples of such a carbon carrier include carbon black, graphite, graphite, activated carbon, carbon nanotube, and carbon nanofiber. Carbon nanowires, carbon nanohorns, vapor grown carbon fibers, and the like can be used. These carbon carriers may be used alone or in combination of two or more. Among these, carbon black is particularly preferable. The blending ratio is 2 to 60% by mass, preferably 10 to 50% by mass, based on the total amount of the catalyst layer solid content. The most preferable range is 20 to 40% by mass. If the blending amount is less than 2% by mass, the catalyst may be insufficiently retained. If it exceeds 60% by mass, the catalyst layer becomes undesirably bulky as compared with the function.

(Dispersion solvent)
Any solvent that can dissolve the vinyl monomer can be used as the solvent used for dispersing the above-mentioned catalyst layer forming composition to prepare a catalyst paste.

  When a metal compound is used as the precursor of the metal fine particles, a mixed solvent system of water and an alcohol solvent is particularly suitable for the reduction of the metal compound and the production of metal fine particles. Also, a mixed solvent system of water and alcohol is preferable because it is easily available, inexpensive, and easy to operate. Examples of the alcohol solvent include methanol, ethanol, 1-propyl alcohol, and 2-propyl alcohol.

(Other additives)
Other components can be added to the composition for forming a catalyst layer of the present invention within a range not impairing the effects of the present invention.

  These include, for example, perfluorovinylsulfonic acid polymers that enhance ionic conductivity (such as “nafion” (registered trademark) manufactured by DuPont), and polytetrafluoroethylene that secures the gas flow path of the catalyst layer. Examples thereof include a porous body, a calcium carbonate inorganic salt that forms a porous structure in the catalyst layer, and a surfactant that stabilizes the composition.

The additive is not particularly limited as long as it does not interfere with the function of the catalyst layer, and can be easily removed by simply immersing it in water or an aqueous acid solution, or can be removed by drying. . Further, it is more preferable that the catalyst layer has functions such as ion conductivity, electron conductivity, gas diffusibility and the like and does not need to be removed.
(Preparation of catalyst layer forming composition)
In order to adjust the composition for forming a catalyst layer used in the present invention, it is necessary to disperse each component sufficiently uniformly. As a dispersion method, methods such as stirring, supersonic field dispersion, hard sphere meal, and mixer dispersion can be used, and the dispersion method is not particularly limited.

The prepared paste of the catalyst layer forming composition only needs to have a viscosity that can be directly applied to the porous carbon sheet or polymer film. The viscosity can be adjusted based on the amount of the dispersion solvent used and the particle size of the blended components.
<Manufacture of catalyst layer>
The prepared composition for forming a catalyst layer is applied to a substrate and then irradiated with radiation. A catalyst layer is produced by this process.

(Base material)
The substrate on which the composition for forming the catalyst layer is to be applied, but as a support for the catalyst layer of the electrochemical device, the reactant is transported to the catalyst layer by interposing between the reactant channel and the catalyst layer. Since a role for transporting electrons to the outside of the catalyst layer is required, a porous body having electron conductivity is suitable, and examples thereof include a porous carbon sheet.

  As specific examples of the porous carbon sheet, carbon paper, carbon cloth, carbon felt and the like can be used as appropriate. Examples of these include carbon paper TGP series manufactured by Toray Industries, Inc., carbon cloth manufactured by E-TEK, and the like.

  Further, the porous carbon sheet described above may have a surface provided with functions such as hydrophobicity and hydrophilicity. Examples of these include carbon paper that has been hydrophobically treated with a fluoropolymer, and carbon paper on which a microporous layer made of a fluoropolymer and carbon particles is deposited.

  A polymer film other than the above-described porous carbon sheet may be used as a “base material” in a broad sense in the process of forming the catalyst layer.

  In that case, the polymer film is not a component of an electrochemical device such as a fuel cell, but is temporarily used as a tool necessary to form a catalyst layer. The catalyst layer is formed on the surface of the polymer film, and then the polymer film is removed by “transfer” to both sides of the polymer electrolyte membrane by hot pressing, and the catalyst layer is firmly fixed on both sides of the polymer electrolyte membrane. Is done. In the fuel cell field, this process is called “transcription”.

Polymer films include polytetrafluoroethylene (PTFE), ethylene / tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), and ethylene / polypropylene copolymer with good releasability and high chemical stability. Fluorine films such as coalescence (FEP), polytetrafluoroethylene / perfluoroalkoxy vinyl ether (PFA), and films such as polyimide, polyester, and polyethylene can be used, and the thickness is preferably about 25 to 250 μm.
(Application)
As a coating method, a coating method can be selected according to the viscosity of the composition for forming a catalyst layer. These coating methods are not particularly limited as long as they can be uniformly applied, for example, spray coating, roll coater, brush coating, brush coating, bar coater coating, knife coater coating, dip coater, spin coater, die coater, General methods such as curtain coater, doctor blade method, screen printing, gravure coater, ink jet method and the like can be mentioned.

The coating thickness of the catalyst layer forming composition is not particularly limited, but is 5 to 150 μm, preferably 15 to 50 μm. If it is less than 5 μm, the amount of the catalyst layer is insufficient, and if it exceeds 150 μm, it is not preferable because a sufficient transport route for the reactant cannot be secured.
(Radiation irradiation)
The radiation irradiation is desirably performed when the composition for forming a catalyst layer is immediately after coating and is wet or undried. In the dry state, the vinyl monomer may volatilize or the auxiliary agent necessary for the reduction reaction of the metal compound may be lost. Moreover, there is a possibility that the catalyst layer cannot be formed into a porous structure where a three-phase interface is easily formed.

  By irradiation, a vinyl monomer capable of introducing ion conductivity can be polymerized “in situ” in the catalyst layer in the paste applied on the porous carbon sheet or polymer film, and the polymerized polymer can be crosslinked.

  In addition, the precursor metal compound is subjected to a reducing action by radiation irradiation to become metal fine particles “in situ” and is supported on the surface of the carbon support.

  Although radiation (irradiation) polymerization is well known conceptually, there are few known points or contrivances of the embodiment, and there are few appropriate known documents. For example, in radiation (irradiation) polymerization, the inventors have found that the ratio of polymerization / crosslinking can be controlled by selecting a solvent system such as an alcohol solvent or an aqueous solvent, and an arbitrary crosslinked polymer can be prepared. There is no description in publicly known literature. This knowledge is effectively utilized in the method for producing a catalyst layer of the present invention.

  The formed crosslinked polymer exhibits ionic conductivity and binder properties required for the catalyst layer as a crosslinked electrolyte polymer by a simple chemical conversion as required.

  Moreover, the water in the catalyst layer forming composition generates hydrated electrons when irradiated with radiation. Furthermore, the alcohol solvent in the composition for forming a catalyst layer has a trapping action for hydrated electrons and has a role of efficiently generating hydrated electrons. Since the produced hydrated electrons have a strong reducing action, the metal compound in the catalyst layer forming composition can be quickly reduced to metal fine particles.

  As the radiation, gamma rays and electron beams are preferable. An electron beam is more preferably irradiated with an electron beam because a dose rate 1000 times or more than that of a gamma ray can be obtained.

  The radiation dose determines the properties of the vinyl monomer and / or metal compound in the composition of the catalyst layer. The dose required for the polymerization of the vinyl monomer and the reduction of the metal compound is usually 1 to 200 kGy. If the irradiation dose is small, polymerization of the vinyl monomer is insufficient, or the metal precursor is not sufficiently reduced, so that some vinyl monomer or metal precursor may be wasted. Further, if the radiation dose is too large, the dose is wasted and the catalyst layer may be damaged.

  As irradiation conditions, it is preferable to carry out in inert gas substitution atmosphere.

There are no particular limitations on the temperature conditions during radiation irradiation. Usually, it is carried out at room temperature (ordinary temperature), but cooling and heating conditions in the range of 0 to 100 ° C. can also be adopted.
(Chemical conversion / drying treatment)
When a hydrogen ion conductive or hydroxide ion conductive vinyl monomer is used as the vinyl monomer in the composition of the catalyst layer, the polymerized electrolyte polymer may not be chemically converted as it is.
On the other hand, when other vinyl monomers are used, it is necessary to convert the polymerized polymer into an electrolyte polymer having a role in the catalyst layer through chemical conversion such as known hydrolysis or ion exchange reaction. . The timing of such chemical conversion treatment is preferably performed after irradiation. Moreover, it can also carry out after a drying process or a membrane-electrode joining process.

  At the stage of the bath treatment such as hydrolysis, the excess metal compound which remains the precursor of the metal fine particles is also removed, so that the noble metal compound such as platinum can be recovered and reused. This manufacturing method has advantages.

Then, in order to remove the dispersion solvent etc. in the formed catalyst layer, well-known drying is performed. By drying, the catalyst layer is firmly fixed to the porous carbon sheet or polymer film.
(Heat press)
When a porous carbon sheet with a catalyst layer is used, prepare two sheets as electrodes, sandwich one polymer electrolyte membrane prepared in advance, and form a membrane-electrode assembly by a known hot press method. To manufacture.

  When a polymer film with a catalyst layer is used, hot pressing is carried out by sandwiching one separately prepared polymer electrolyte membrane between two polymer films with a catalyst layer by a known transfer method. Thus, after the catalyst layers are attached to both surfaces of the polymer electrolyte membrane, the polymer film is peeled off. Next, the obtained polymer electrolyte membrane with a catalyst layer is sandwiched between two porous carbon sheets prepared in advance, and a membrane / electrode assembly is produced by a known hot press method.

(Polymer electrolyte membrane)
As the polymer electrolyte membrane prepared in advance, a known cation exchange membrane or anion exchange membrane can be used. Cation exchange membranes include perfluorinated polymer electrolyte membranes such as Nafion “Nafion” (registered trademark) manufactured by DuPont and “Gore-Select” (registered trademark) manufactured by Gore, and sulfonated aromatic hydrocarbons. Examples thereof include a polymer electrolyte membrane and a polymer electrolyte membrane in which a sulfonic acid group is introduced into a fluorine-based film by graft polymerization and / or chemical conversion reaction. As the anion exchange membrane, a strongly basic anion exchange membrane having a tertiary or quaternary amine group is preferable.

  When an electrolyte polymer having cation conductivity is formed on the catalyst layer, the polymer electrolyte membrane used for the membrane / electrode assembly is preferably a cation exchange membrane.

  When an electrolyte polymer having anion conductivity is formed on the catalyst layer, the polymer electrolyte membrane used for the membrane / electrode assembly is preferably an anion exchange membrane.

  If the polymer electrolyte membrane has the same polymer structure as that of the electrolyte polymer in the catalyst layer, it can be expected that the bonding property is improved, and thus the polymer electrolyte membrane is more preferable.

The thickness of the polymer electrolyte membrane is usually about 10 to 250 μm, preferably about 20 to 150 μm.
(Features of the catalyst layer forming composition of the present invention)
a) An expensive perfluorosulfonic acid electrolyte polymer is not used.
b) No complicated and expensive solvent system of perfluorosulfonic acid based electrolyte polymer is required.
c) Any solvent that can dissolve the vinyl monomer can be used without limitation, and can be a readily available solvent solvent system such as a mixed solvent system of water and an alcohol solvent.

When a metal compound is used as the precursor of the metal fine particles, a mixed solvent system of and an alcohol solvent is particularly effective as the solvent.
d) Since the metal fine particles functioning as a catalyst are not directly blended and used, the precursor metal compound is blended and reduced to metal fine particles by irradiation on the spot in the catalyst layer formation to form a catalyst. The excess metal compound can be recovered, and the amount used can be saved greatly. The solvent system used in the composition for forming a catalyst layer is also easy to obtain, such as the above-described mixed solvent system of water and alcohol solvent, is inexpensive and easy to operate, and there is no problem.

Monomer is polymerized by irradiation to become an electrolyte polymer, and at the same time, cross-linking also progresses, and while the electrolyte polymer is fixed on the catalyst layer, the cross-linked electrolyte polymer fixes other catalyst layer components in place, so it is highly active A long-life catalyst layer can be obtained.
f) Since both the formation of the electrolyte polymer by polymerization of the vinyl monomer and the reduction of the metal compound and the formation of the catalyst can occur simultaneously by irradiation, the catalyst layer formation process is completed in a single step, and the production effort is reduced. Cost can be greatly reduced.
g) When water and alcohol are blended in the composition for forming a catalyst layer, hydrated electrons generated by the cooperative action of both components triggered by radiation irradiation are responsible for reduction of the metal compound and formation of the catalyst. The catalyst of metal fine particles can be generated very efficiently, and there is no secondary trouble.
h) The catalyst layer itself is low-cost, highly active, and has a long life.
<Electrochemical devices such as fuel cells>
According to the present invention, an electric device such as a polymer fuel cell, a redox battery, and a gas sensor, a water electrolysis system, a hydrohalic acid electrolysis system, a salt electrolysis system, and the like can be configured.

  The polymer electrolyte fuel cell of the present invention includes a membrane-electrode assembly produced by the production method of the present invention.

  In the polymer electrolyte fuel cell, fuel such as hydrogen gas or methanol solution is supplied to the negative electrode, and oxygen or air is supplied to the positive electrode. An electrochemical reaction occurs at each electrode, and power can be generated.

  A fuel cell having cation conductivity in the electrolyte polymer and polymer electrolyte membrane of the catalyst layer is called a proton exchange membrane fuel cell (PEMFC). The electrochemical reaction using hydrogen as fuel is shown as follows.

^{_{Anode: 2H 2 → 4H + + 4e}} -
^{_{Cathode: O 2 + 4H + + 4e}} - → 2H 2 O
Total reaction: 2H ₂ + O ₂ → 2H ₂ O
A fuel cell having anion conductivity in the electrolyte polymer and polymer electrolyte membrane of the catalyst layer is an alkaline fuel cell and is also called an anion exchange membrane fuel cell (AEMFC). The electrochemical reaction using hydrogen as fuel is shown as follows.

^{_{Anode: 2H 2 + 4OH - → 4H}} 2 O + 4e -
The positive _{electrode: O 2 + 2H 2 O +} 4e - → 4OH -
Total reaction: 2H ₂ + O ₂ → 2H ₂ O
The performance of the battery is evaluated by a known method. For example, if the current density is the same, the higher voltage is evaluated as higher performance. In general, the higher the voltage at the same current density, the higher the battery performance. Also, the efficiency of the fuel cell depends on the voltage. The higher the voltage, the higher the fuel cell efficiency.

  According to the composition for forming a catalyst layer of the present invention and the method for producing a catalyst layer using the composition, a functional member for a polymer electrolyte fuel cell can be easily produced as follows.

  When a catalyst layer is formed on a porous carbon sheet, an electrode with a catalyst layer is obtained. Subsequently, a membrane / electrode assembly MEA can be easily obtained by sandwiching a polymer electrolyte membrane between two electrodes with a catalyst layer and performing hot pressing.

  On the other hand, when a catalyst layer is formed on a polymer film, a polymer film with a catalyst layer is obtained. If the polymer film with a catalyst layer is transferred onto both sides of the polymer electrolyte membrane by hot pressing by a transfer method, a polymer electrolyte membrane with a catalyst layer CCM can be easily obtained. Further, when the polymer electrolyte membrane CCM with catalyst layer is sandwiched between two porous carbon sheets and hot-pressed, a membrane / electrode assembly MEA can be obtained.

  The obtained membrane-electrode assembly MEA can be used for electrochemical devices such as solid polymer fuel cells, redox cells, gas sensors, water electrolysis systems, hydrohalic acid electrolysis systems, salt electrolysis systems, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.

In the following examples and comparative examples, those shown below were used.
Cation conductive vinyl monomer: sodium styrenesulfonate, manufactured by Tosoh Organic Chemical Co., Ltd., trade name, NaSS;
Anion conductive vinyl monomer: vinyl benzyl trimethyl ammonium chloride, manufactured by AGC Seimi Chemical Co., Ltd., trade name, QBm;
Platinum-supported carbon black (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E, platinum content 50%);
Carbon support: carbon black (VULCAN (registered trademark) XC-72 manufactured by Cabot Corp.);
Metal compound: Chloroplatinic acid complex (H ₂ PtC 1 ₆ · 6H ₂ 0, molecular weight 517.9, platinum atom content 37.5%, general commercial product);
・ Alcohol solvent: isopropyl alcohol (iPrOH), general commercial product;
-Porous carbon sheet: SGL Carbon Japan, trade name, GDL25BC;
-Polymer film: Polytetrafluoroethylene (PTFE), 50 microcentimeters thick, general commercial product;
Proton exchange type polymer electrolyte membrane: Nafion 212 (registered trademark) (manufactured by DuPont).
Anion exchange type polymer electrolyte membrane: Neocepta AHA (trade name, manufactured by Tokuyama) anion hydrocarbon membrane <Preliminary Experiment Example 1>
As the first preparation step, 0.5 g of sodium styrenesulfonate, 1.0 g of platinum-supported carbon black, 10.0 g of isopropyl alcohol, and 10.0 g of water are put in a glass bottle, and a rotational speed of 500 rpm is used with a magnetic stirrer. The mixture was stirred for 1 hour, and further dispersed with ultrasonic waves for 30 minutes.
In the second application step, the obtained paste was uniformly applied to the surface of the porous carbon sheet with a brush. The porous carbon sheet had a length of 100 cm, a width of 10 cm, and an area of 1000 cm ² .

  In the third irradiation step, the coated porous carbon sheet is sealed in a vinyl bag, placed on a conveyor of an electron beam irradiation apparatus (manufactured by Nissin Electric Co., Ltd.), and conveyed at a speed of 2 m / min. Irradiated with rays. The electron beam irradiation was performed under the conditions of an acceleration voltage of 1 MV and an acceleration current of 6 mA, and the irradiation dose was 30 kGy. At this time, sodium styrene sulfonate polymerized by irradiation to become sodium polystyrene sulfonate (Poly (NaSS)).

As the fourth chemical conversion / drying process step, the sodium polystyrene sulfonate (Poly (NaSS)) produced by ion exchange with 1M HCl solution at room temperature for 24 hours is converted to polystyrene sulfonic acid (Poly (SS)). Converted to. Then, it dried at 40 degreeC for 24 hours, and obtained the porous carbon sheet with a catalyst layer, ie, an electrode.
In the fifth hot pressing step, the manufactured electrode was cut into a size of 5 cm × 5 cm, attached to both sides of a proton ion exchange polymer electrolyte membrane having a size of 10 cm × 10 cm, and heated at 140 ° C. at 0 ° C. with a hot press device. After holding at 5 MPa for 1 minute, thermocompression bonding was carried out at the same temperature for 5 MPa for 1 minute to obtain a membrane / electrode assembly.

The membrane / electrode assembly was incorporated into a fuel cell (Toyo, 25 cm ² ), and the fuel cell was evaluated by supplying hydrogen to the negative electrode and oxygen to the positive electrode. The battery voltage is shown in Table 1.
<Example 1>
In the first preparation step of Preliminary Experimental Example 1, a catalyst paste was prepared using 0.5 g of carbon black and 1.3 g of chloroplatinic acid complex instead of 1.0 g of platinum-supported carbon black.

A membrane / electrode assembly was obtained through the second coating step, the third irradiation step, the fourth chemical conversion / drying step, and the fifth hot press step under the same conditions as in Preliminary Experimental Example 1.
In the irradiation step, sodium polystyrene sulfonate (Poly (NaSS)) was converted to polystyrene sulfonic acid (Poly (SS)). The chloroplatinic acid complex was reduced to platinum fine particles by irradiation and supported on carbon black.
The fuel cell was evaluated under the same conditions as in Preliminary Experimental Example 1. The battery voltage is shown in Table 1.
<Preliminary Experiment Example 2>
The catalyst layer paste obtained in the first preparation step of Preliminary Experimental Example 1 was uniformly applied to the PTFE film surface as a second application step. The PTFE film had a length of 100 cm, a width of 10 cm, and an area of 1000 cm ² .

  A polymer film with a catalyst layer was obtained through the third irradiation step and the fourth chemical conversion / drying treatment step under the same conditions as in Preliminary Experimental Example 1.

  In the fifth hot pressing step, the produced polymer film with a catalyst layer is cut into a size of 5 cm × 5 cm, attached to both sides of a proton ion exchange type polymer electrolyte membrane having a size of 10 cm × 10 cm, and a hot press apparatus. After holding at 140 ° C. and 0.5 MPa for 1 minute, and thermocompression bonding at 5 MPa for 1 minute at the same temperature, the PTFE film was removed, and the catalyst layer was transferred to both surfaces of the polymer electrolyte membrane. Next, a porous carbon sheet (5 cm × 5 cm) is sandwiched between both surfaces of the polymer electrolyte membrane with a catalyst layer and held at 140 ° C. and 0.5 MPa for 1 minute by a hot press apparatus, and then at the same temperature, 5 MPa, A membrane-electrode assembly was obtained by thermocompression bonding for 1 minute.

The fuel cell was evaluated under the same conditions as in Preliminary Experimental Example 1. The battery voltage is shown in Table 1.
<Example 2>
The catalyst layer paste obtained in the first preparation process of Example 1 is subjected to the second coating process, the third irradiation process, the fourth chemical conversion / drying process process, and the fifth process under the same conditions as in Preliminary Experimental Example 2. Through the hot pressing step, a membrane / electrode assembly was obtained.
The fuel cell was evaluated under the same conditions as in Preliminary Experimental Example 1. The battery voltage is shown in Table 1.
<Comparative Example 1>
Polystyrene sulfonic acid 0.5 g, platinum-supported carbon black 1.0 g, isopropyl alcohol 10.0 g, and water 10.0 g were mixed in a glass bottle, and stirred using a magnetic stirrer at 500 rpm for 1 hour. Dispersed with ultrasound for 30 minutes. The obtained catalyst paste was uniformly applied to the surface of the porous carbon sheet under the same conditions as in the second application step of Preliminary Experimental Example 1. The applied porous carbon sheet was dried at 40 ° C. for 24 hours to obtain a porous carbon sheet with a catalyst layer, that is, an electrode.

  The manufactured electrode was subjected to the fifth hot pressing process of Preliminary Experimental Example 1 to obtain a membrane / electrode assembly.

The fuel cell was evaluated under the same conditions as in Preliminary Experimental Example 1. The battery voltage is shown in Table 1.
<Preliminary Experiment Example 3>
In the first preparation step of Preliminary Experimental Example 1, a catalyst layer paste was prepared using 0.7 g of vinylbenzyltrimethylammonium chloride (QBm) instead of 0.5 g of sodium styrenesulfonate (SSNa).

  The second coating step and the third irradiation step were performed under the same conditions as in Preliminary Experimental Example 1. In the irradiation process, the irradiation dose was set to 10 kGy. At this time, vinylbenzyltrimethylammonium chloride (QBm) was polymerized by irradiation to form polyvinylbenzyltrimethylammonium chloride (Poly (QBm)).

In the fourth chemical conversion / drying treatment step, the porous layer carbon sheet obtained in the third irradiation step was ion-exchanged with a 1M KOH solution by a room temperature treatment for 24 hours to produce polyvinylbenzyltrimethylammonium chloride ( Poly (QBm)) was converted to poly (vinylbenzyltrimethylammonium hydroxide) (Poly (QBOH)). Then, it dried at 40 degreeC for 24 hours, and obtained the porous carbon sheet with a catalyst layer, ie, an electrode.
As a fifth hot pressing step, the manufactured electrode was cut into a size of 5 cm × 5 cm, attached to both surfaces of an anion exchange type polymer electrolyte membrane having a size of 10 cm × 10 cm, and a hot press apparatus at 140 ° C. After holding at 5 MPa for 1 minute, thermocompression bonding was performed at the same temperature for 5 MPa for 1 minute to obtain a membrane / electrode assembly.

The fuel cell was evaluated under the same conditions as in Preliminary Experimental Example 1. The battery voltage is shown in Table 2.
<Example 3>
In the first preparation step of Preliminary Experimental Example 3, 0.7 g of vinylbenzyltrimethylammonium chloride (QBm), 1.3 g of chloroplatinic acid complex, 10.0 g of isopropyl alcohol, and 10.0 g of water are placed in a glass bottle to form a catalyst layer. A composition is prepared.

A membrane / electrode assembly was obtained through the second coating step, the third radiation irradiation step, the fourth chemical conversion / drying treatment step, and the fifth hot pressing step under the same conditions as in Preliminary Experimental Example 3.
In the irradiation process, the irradiation dose was set to 30 kGy. At this time, polyvinylbenzyltrimethylammonium chloride (Poly (QBm)) was produced, and the chloroplatinic acid complex was reduced to platinum fine particles by irradiation and supported on carbon black.
The fuel cell was evaluated under the same conditions as in Preliminary Experimental Example 1. The battery voltage is shown in Table 2.
<Preliminary Experiment Example 4>
A catalyst layer paste was prepared under the same conditions as in the first preparation step of Preliminary Experimental Example 3.

The polymer film with a catalyst layer was obtained through the 2nd application | coating process of the preliminary experiment example 2, the 3rd irradiation process of the preliminary experiment example 3, and the 4th chemical conversion and drying process process.
As the fifth heat press fixation, the produced polymer film with a catalyst layer was cut into a size of 5 cm × 5 cm, attached to both sides of an anion exchange type polymer electrolyte membrane having a size of 10 cm × 10 cm, and a hot press apparatus. After holding at 140 ° C. and 0.5 MPa for 1 minute, and thermocompression bonding at 5 MPa for 1 minute at the same temperature, the PTFE film was removed, and the catalyst layer was transferred to both surfaces of the polymer electrolyte membrane. Next, a porous carbon sheet (5 cm × 5 cm) is sandwiched between both surfaces of the polymer electrolyte membrane with a catalyst layer, and held at 140 ° C. and 0.5 MPa for 1 minute by a hot press apparatus, and then 5 MPa at the same temperature. A membrane-electrode assembly was obtained by thermocompression bonding for 1 minute.

The fuel cell was evaluated under the same conditions as in Preliminary Experimental Example 1. The battery voltage is shown in Table 2.
<Example 4>
In the first preparation step of Example 3, a composition for forming a catalyst layer was prepared.
Through the same coating process, irradiation process, chemical conversion / treatment process, and hot press process as in Preliminary Experimental Example 4, a membrane / electrode assembly was obtained.
In the irradiation process, the irradiation dose was 30 kGy. At this time, polyvinylbenzyltrimethylammonium chloride (Poly (QBm)) was produced, and the chloroplatinic acid complex was reduced to platinum fine particles by irradiation and supported on carbon black.
The fuel cell was evaluated under the same conditions as in Preliminary Experimental Example 1. The battery voltage is shown in Table 2.
<Comparative example 2>
0.7 g of poly (vinylbenzyltrimethylammonium hydroxide), 1.0 g of platinum-supported carbon black, 10.0 g of isopropyl alcohol, and 10.0 g of water are placed in a glass bottle and are rotated at 500 rpm using a magnetic stirrer. The mixture was stirred for 1 hour and further dispersed with ultrasonic waves for 30 minutes. The obtained catalyst paste was uniformly coated on the surface of the porous carbon sheet under the same conditions as in the second coating step of Preliminary Experimental Example 3. The applied porous carbon sheet was dried at 40 ° C. for 24 hours to obtain a porous carbon sheet with a catalyst layer, that is, an electrode.

The manufactured electrode was subjected to the same hot pressing process as in Preliminary Experimental Example 3 to obtain a membrane / electrode assembly.
The fuel cell was evaluated under the same conditions as in Preliminary Experimental Example 1. The battery voltage is shown in Table 2.

  As apparent from the cell voltage of the proton exchange membrane fuel cell in Table 1, it was found that the cell voltage of the example was much higher than the cell voltage of the comparative example. This is because a large three-phase interface required for the electrochemical reaction can be secured by generating the electrolyte polymer “in situ”. Moreover, there is a possibility that the production cost of the catalyst layer can be greatly reduced by generating “in-situ” the metal fine particles that are the electrolyte polymer or the catalyst. From Table 2, the significance of the present invention is apparent also in the anion exchange membrane fuel cell.

  As a future study subject, regarding the anion exchange membrane fuel cell, it is to improve various performances by examining various process conditions and compositions in the same manner as the proton exchange membrane fuel cell. In any case, it is clear that the catalyst layer forming composition and the catalyst layer manufacturing method of the present invention can achieve both cost reduction and high performance of the catalyst layer.

Claims (13)

Used for forming a catalyst layer of an electrode with a catalyst layer for an electrochemical device, and after being applied to a substrate, irradiated with radiation, "in situ", an ion conductive polymer that is a vinyl polymer having an ion conductive group, and , by forming a fine metal particles functioning as a catalyst a composition for forming a catalyst layer for a catalyst layer, a vinyl monomer capable of introducing the ion-conductive metal compound which is a precursor of the metal fine particles, carbon Including a carrier and a dispersion solvent ,
The vinyl monomer is polymerized by the irradiation, it is intended to form the ion-conducting polymer,
The metal compound may be reduced by the irradiation, which forms the metal fine particles,
The catalyst layer forming composition , wherein the dispersion solvent is a mixed solvent of water and alcohol .   The vinyl monomer capable of introducing ion conductivity is a cationic vinyl monomer group consisting of styrene sulfonate and its derivatives, acrylic acid and its derivatives, vinyl sulfonic acid and its derivatives, perfluorinated vinyl sulfonic acid and its derivatives. The composition for forming a catalyst layer according to claim 1, wherein the composition is one or two or more types of vinyl monomers selected from among the above.   The vinyl monomer capable of introducing ion conductivity is trimethylammonium methylstyrene chloride, triethylammonium styrene chloride, dimethylvinylbenzylamine, 2- (dimethylamine) ethyl methacrylate, a styrene derivative having an ammonium group, secondary or 3 One or more vinyl monomers selected from the group of anionic vinyl monomers consisting of a styrene derivative having a secondary amine group, an acrylic acid derivative having a secondary or tertiary amine group, The composition for forming a catalyst layer according to claim 1.   It is a manufacturing method of the catalyst layer of the electrode with a catalyst layer for electrochemical devices, Comprising: After apply | coating the composition for catalyst layer formation as described in any one of Claim 1 to 3 to the base-material surface Irradiating with radiation to form an ion conductive polymer from the vinyl monomer contained in the catalyst layer forming composition on the substrate surface, and forming metal fine particles from the metal compound to produce a catalyst layer; A method for producing a catalyst layer.   The method for producing a catalyst layer according to claim 4, wherein the substrate is a porous carbon sheet.   The method for producing a catalyst layer according to claim 4, wherein the substrate is a polymer film.   A catalyst layer obtained by the production method according to any one of claims 4 to 6.   An electrode with a catalyst layer for an electrochemical device, wherein the catalyst layer according to claim 7 is at least a part of the structure.   9. An electrochemical device, wherein the electrode with a catalyst layer according to claim 8 is at least a part of its configuration.   6. A membrane / electrode assembly comprising a porous carbon sheet with a catalyst layer obtained by the production method of claim 5 as an electrode and bonded to both surfaces of a polymer electrolyte membrane.   A polymer electrolyte membrane with a catalyst layer, which is formed by transferring the catalyst layer-attached polymer film obtained by the production method of claim 6 onto both sides of the polymer electrolyte membrane and transferring the catalyst layer.   A membrane / electrode assembly comprising a porous carbon sheet bonded to both surfaces of the polymer electrolyte membrane with a catalyst layer according to claim 11.   A polymer fuel cell comprising the membrane-electrode assembly according to claim 10 or 12.