Catalyst layer production method and method for producing membrane electrode assembly

Abstract

Provided is a catalyst layer production method with which it is possible to produce a catalyst layer applicable to a membrane electrode assembly capable of achieving a fuel cell having excellent power generation durability.　The catalyst layer production method comprises forming a catalyst layer by applying a composition containing a fluorine-containing polymer including a unit having an ion exchange group, a catalyst containing a metal, and a solvent onto a temporary support, wherein the unit having an ion exchange group has two ion exchange groups, the solvent includes an alcohol, the content of propanol in the alcohol is greater than that of alcohols other than the propanol, and the amount of the metal in the catalyst layer is more than 0.2 mg / cm2.

Description

Method for manufacturing a catalyst layer, method for manufacturing a film electrode assembly

[0001] The present invention relates to a method for manufacturing a catalyst layer and a method for manufacturing a film electrode assembly.

[0002] From an environmental perspective, the development of fuel cells that, in principle, do not emit greenhouse gases is progressing. It is known that the membrane electrode assembly of a polymer electrolyte fuel cell has an anode having a catalyst layer, a cathode having a catalyst layer, and a polymer electrolyte membrane disposed between the anode and the cathode. Patent Document 1 discloses a membrane electrode assembly comprising a catalyst layer containing a proton-conducting polymer having a cyclic ether structure and sulfonic acid-type functional groups, and a polymer electrolyte membrane containing a porous material containing a fluorine-containing polymer and a fluorine-containing polymer having sulfonic acid-type functional groups.

[0003] Japanese Patent Publication No. 2024-24047

[0004] Solid polymer fuel cells may be used over long periods of time, and it is required that their power generation performance does not deteriorate when used repeatedly, that is, that they have excellent power generation durability. The present inventors have found that, with respect to the membrane electrode assembly equipped with the components described in Patent Document 1, increasing the amount of catalyst in the catalyst layer may result in insufficient power generation durability, indicating room for improvement.

[0005] The present invention has been made in view of the above problems, and aims to provide a method for manufacturing a catalyst layer that can be applied to a membrane electrode assembly capable of realizing a fuel cell with excellent power generation durability. It also aims to provide a method for manufacturing the above-mentioned membrane electrode assembly.

[0006] The present inventors have diligently studied the above problems and have found that the above problems can be solved by the following configuration: [1] A method for producing a catalyst layer, comprising coating a composition comprising a fluorine-containing polymer containing units having ion exchange groups, a catalyst containing a metal, and a solvent onto a temporary support to form a catalyst layer, wherein the units having ion exchange groups each have two ion exchange groups, the solvent contains an alcohol, the propanol content in the alcohol is greater than that of other alcohols other than propanol, and the amount of the metal in the catalyst layer is 0.2 mg / cm³ ２ A method for producing a catalyst layer, wherein the fluorine-containing polymer contains units having a cyclic ether structure. [2] The method for producing a catalyst layer according to [1], wherein the fluorine-containing polymer contains units having a cyclic ether structure. [3] The method for producing a catalyst layer according to [2], wherein the content of units having a cyclic ether structure is 50 mol% or more relative to the total units of the fluorine-containing polymer. [4] The method for producing a catalyst layer according to any one of [1] to [3], wherein the fluorine-containing polymer contains units derived from tetrafluoroethylene. [5] The method for producing a catalyst layer according to any one of [1] to [4], wherein the ion exchange capacity of the fluorine-containing polymer is less than 1.8 milliequivalents / g dry resin. [6] The method for producing a catalyst layer according to any one of [1] to [5], wherein the ion exchange capacity of the fluorine-containing polymer is less than 1.6 milliequivalents / g dry resin. [7] The method for producing a catalyst layer according to any one of [1] to [6], wherein the ion exchange capacity of the fluorine-containing polymer is less than 1.3 milliequivalents / g dry resin. [8] A method for producing a catalyst layer according to any one of [1] to [7], wherein the metal is platinum. [9] The catalyst comprises a support, and the specific surface area of ​​the support is 700 m². ２A method for producing a catalyst layer according to any one of [1] to [8], wherein the amount of alcohol is 51% by mass or more relative to the total mass of the solvent, according to any one of [1] to [9], according to any one of [1] to

[10] , wherein the catalyst comprises a carrier, and in the composition, the mass ratio of the amount of fluorine-containing polymer to the amount of carrier is 1.3 or less, according to any one of [1] to

[10] , according to any one of [1] to

[11] , according to any one of [1] to

[11] , wherein the solid content concentration of the composition is 10.0% by mass or less, according to any one of [1] to

[11] , according to any one of [1] to

[11] , according to any one of [1] to

[11] , according to any one of [1] to

[12] , according to the method for producing a catalyst layer.

[13] A method for producing a membrane electrode assembly, comprising contacting a catalyst layer obtained by the method for producing a catalyst layer according to any one of [1] to

[12] with a solid polymer electrolyte membrane, and peeling off the temporary support to produce a membrane electrode assembly, according to

[14] A method for producing a membrane electrode assembly according to

[13] , wherein the membrane electrode assembly is used in a solid polymer fuel cell, according to

[13] .

[0007] According to the present invention, a method for manufacturing a catalyst layer is provided that can be applied to a membrane electrode assembly capable of realizing a fuel cell with excellent power generation durability. Furthermore, a method for manufacturing the above-mentioned membrane electrode assembly is also provided.

[0008] This is a cross-sectional view showing an example of a membrane electrode assembly.

[0009] The following definitions of terms apply throughout this specification and the claims unless otherwise specified. “Ion exchange group” means a group capable of exchanging at least some of the ions it contains with other ions, such as the sulfonic acid type functional group and the carboxylic acid type functional group described below. “Sulfonic acid type functional group” refers to an acidic sulfonic acid group (-SO ３ H), and salt-type sulfonic acid groups (-SO ３ M ２ However, M ２ These are alkali metals or quaternary ammonium cations. ) are a general term. "Carboxylic acid type functional group" refers to acid type carboxylic acid groups (-COOH) and salt type carboxylic acid groups (-COOM) １ However, M １) is a general term for alkali metals or quaternary ammonium cations. "Groups that can be converted to ion exchange groups" means groups that can be converted to ion exchange groups by treatments such as hydrolysis and acidification, and are sometimes referred to as "precursor groups". "Groups that can be converted to sulfonic acid type functional groups" means groups that can be converted to sulfonic acid type functional groups by treatments such as hydrolysis and acidification. "Groups that can be converted to carboxylic acid type functional groups" means groups that can be converted to carboxylic acid type functional groups by known treatments such as hydrolysis and acidification.

[0010] In polymers, a "unit" refers to an atomic group derived from a single monomer molecule, formed by the polymerization of monomers. A unit may be an atomic group directly formed by the polymerization reaction, or it may be an atomic group in which a portion of the atomic group is converted to a different structure by processing the polymer obtained by the polymerization reaction. In addition, constituent units derived from individual monomers may be described by adding "unit" to the monomer name. For example, a unit represented by formula (u11) is written as unit (u11). Units represented by other formulas are written similarly.

[0011] In a composition, "solid content" refers to the components that form a film (e.g., a catalyst layer), and does not include the solvent. Furthermore, any component that forms a film is considered solid content, even if its properties are liquid.

[0012] A numerical range represented using "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical ranges described in other step-by-step descriptions. Also, in the numerical ranges described in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples. In this specification, unless otherwise specified, each component may be used alone as one kind of substance corresponding to each component, or two or more kinds may be used in combination. Here, when two or more kinds of substances are used in combination for each component, the content of that component, unless otherwise specified, refers to the total content of the substances used in combination. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment.

[0013] [Method for Producing Catalyst Layer] The method for producing the catalyst layer of the present invention (hereinafter also referred to as "this production method") is a method for producing a catalyst layer in which a composition containing a fluorine-containing polymer containing a unit having an ion-exchange group, a catalyst containing a metal, and a solvent (hereinafter also referred to as "catalyst layer-forming composition S") is applied onto a temporary support to form a catalyst layer, wherein the unit having an ion-exchange group has two ion-exchange groups, the solvent contains alcohol, the content of propanol in the alcohol is greater than that of other alcohols other than propanol, and the amount of metal in the catalyst layer is 0.2 mg / cm ２It is superior. By using a membrane electrode assembly to which the catalyst layer obtained by this manufacturing method (hereinafter also referred to as "this catalyst layer") is applied, a fuel cell with excellent power generation durability can be realized. The details of this reason are unknown, but it is presumed to be as follows. Hereinafter, when the catalyst layer is applied to a membrane electrode assembly, the fact that a fuel cell with excellent characteristic X (e.g., power generation durability) can be realized will also be simply referred to as "the fuel cell has excellent characteristic X". As design concepts for improving the power generation durability of the final fuel cell obtained with respect to the catalyst layer, there are methods using a fluorine-containing polymer having two ion exchange groups, and methods increasing the amount of metal in the catalyst layer. On the other hand, the inventors have found that when forming a catalyst layer by coating a catalyst layer forming composition on a solid polymer electrolyte membrane, increasing the amount of metal in the catalyst layer can cause cracks in the catalyst layer due to a decrease in polymer dispersibility and stress associated with the swelling and shrinkage of the solid polymer electrolyte membrane, resulting in a decrease in power generation durability. In this manufacturing method, the catalyst layer-forming composition S has a higher propanol content in the solvent than other alcohols, resulting in excellent dispersibility of the fluorine-containing polymer having two ion-exchange groups. Furthermore, in this manufacturing method, the catalyst layer is formed by coating the catalyst layer-forming composition S onto a separate temporary support, thus eliminating stress originating from the solid polymer electrolyte membrane. As a result, this manufacturing method can suppress cracking of the catalyst layer while using a fluorine-containing polymer having two ion-exchange groups and maintaining a metal content above a predetermined amount, and consequently, it is believed to provide superior power generation durability for fuel cells.

[0014] <Catalyst layer formation composition S> The catalyst layer formation composition S is a composition for forming the catalyst layer, and comprises a fluorine-containing polymer (hereinafter also referred to as "polymer H") containing units having ion exchange groups, a catalyst containing a metal, and a solvent.

[0015] The solid content concentration of the catalyst layer-forming composition S is preferably 3.0% by mass or more, more preferably 4.0% by mass or more, and even more preferably 5.0% by mass or more, from the viewpoint of storability. From the viewpoint of coating properties, it is preferably 10.0% by mass or less, more preferably 8.0% by mass or less, and even more preferably 7.0% by mass or less. Here, the solid content concentration is calculated by the following method based on the mass of the catalyst layer-forming composition S before and after heating. After heating 1 g of the catalyst layer-forming composition S at 180°C for 180 minutes, the mass of the residue is weighed and the solid content concentration is calculated by the following formula: Solid content concentration (mass%) = 100 × (mass of residue) / (mass of catalyst layer-forming composition S)

[0016] (Polymer H) Polymer H is a fluorine-containing polymer containing units having ion exchange groups (hereinafter also referred to as "unit A"). Unit A contains two ion exchange groups. Unit A may have a cyclic ether structure, but it is preferable that it does not have a cyclic ether structure. Unit A is preferably a perfluoromonomer unit having two ion exchange groups, and more preferably a perfluoromonomer unit having two sulfonic acid-type functional groups.

[0017] As a perfluoromonomer unit having two sulfonic acid-type functional groups, the unit represented by formula (1) is preferred. Formula (1) -[CF ２ -CF(-L-(SO ３ M) ２ ) ] -

[0018] L is a trivalent perfluorohydrocarbon group which may contain an ether-bonded oxygen atom, and M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation. The ether-bonded oxygen atom may be located at the terminal end of the perfluorohydrocarbon group or between carbon atoms. The trivalent perfluorohydrocarbon group preferably has 1 or more carbon atoms, more preferably 2 or more, preferably 20 or less, and more preferably 10 or less.

[0019] The unit represented by formula (1) is preferably unit (A-1), unit (A-2), or unit (A-3), with unit (A-2) being more preferable because it results in better power generation efficiency for the fuel cell.

[0020]

[0021] In formulas (A-1) to (A-3), R Ｆ１ and R Ｆ２ Each of these independently comprises a perfluoroalkylene group having 1 to 3 carbon atoms, or a perfluoroalkylene group with -CF ２ The - is a divalent group substituted with an ether-bonded oxygen atom, and M is a hydrogen atom, an alkali metal, or a quaternary ammonium cation. In the above divalent group, the ether-bonded oxygen atom may be located at the terminal of the perfluoroalkylene group or between carbon atoms. The number of carbon atoms in the above divalent group is preferably 1 to 3, and more preferably 2 or 3. Ｆ１ and R Ｆ２ A specific example is -CF ２ -, -CF ２ CF ２ -, -CF (CF ３ ) -, -CF ２ CF ２ CF ２ -, -CF (CF ２ CF ３ )-,-CF(CF ３ ) CF ２ -, -CF ２ CF (CF ３ )-,-C(CF ３ ) (CF ３ ) -, -CF ２ OCF ２ CF ２ -, -OCF ２ CF ２ - These are some of the reasons why R is inexpensive, easy to manufacture, and allows for a higher ion exchange capacity of polymer H. Ｆ１ and R Ｆ２ Each is independently a perfluoroalkylene group having 1 or 2 carbon atoms, -CF ２ OCF ２ CF ２ - or -OCF ２ CF ２ - is preferred. In the case of a perfluoroalkylene group having 2 carbon atoms, a straight chain is preferred. Specifically, -CF ２ -, -CF ２ CF２ - or - CF (CF ３ ) - Preferably, -CF ２ - or -CF ２ CF ２ - is more preferable, -CF ２ - is even more preferable.

[0022] In formula (A-2), R Ｆ３ This is a perfluoroalkylene group having 1 to 6 carbon atoms. Ｆ３ A specific example is -CF ２ -, -CF ２ CF ２ -, -CF (CF ３ ) -, -CF ２ CF ２ CF ２ -, -CF (CF ２ CF ３ )-,-CF(CF ３ ) CF ２ -, -CF ２ CF (CF ３ )-,-C(CF ３ ) (CF ３ ) -, -CF ２ CF (CF ３ ) OCF ２ CF (CF ３ )-- is one example. R Ｆ３ A perfluoroalkylene group having 1 to 3 carbon atoms is preferred. Specifically, -CF ２ -, -CF ２ CF ２ - or -CF ２ CF (CF ３ ) - Preferably, -CF ２ CF (CF ３ ) - is more preferable. In formula (A-2), m is 0 or 1.

[0023] The content of unit A is preferably 5 to 50 mol%, more preferably 5 to 30 mol% or more, and even more preferably 10 to 20 mol% relative to the total units of polymer H. Polymer H may contain only one type of unit A, or it may contain two or more types. If it contains two or more types, the above content refers to the total amount of these units.

[0024] Polymer H preferably contains a unit having a cyclic ether structure (hereinafter also referred to as "unit B") in that the power generation durability of the fuel cell is more excellent. Unit B is preferably a unit different from the above-described unit A. Unit B is preferably at least one unit selected from the group consisting of unit (u11), unit (u12), unit (u21), unit (u22), and unit (u24) in that a catalyst layer having more excellent oxygen permeability can be obtained.

[0025]

[0026] In formula (u11), R １１ is a divalent perfluoroalkylene group which may have an ether-bonding oxygen atom. When the perfluoroalkylene group has an ether-bonding oxygen atom, the number of oxygen atoms may be one or two or more. Further, the ether-bonding oxygen atom may be located between carbon-carbon bonds of the perfluoroalkylene group or at the terminal of the carbon atom bond. The perfluoroalkylene group may be linear or branched, but is preferably linear. R <00OO083>, R １３ , R １５ and R １６ are each independently a monovalent perfluoroalkyl group which may have an ether-bonding oxygen atom or a fluorine atom. R １５ [[ID=I9]] and R １６ are preferably at least one of them being a fluorine atom and more preferably both being fluorine atoms in that the polymerization reactivity is high. R １４ is a monovalent perfluoroalkyl group which may have an ether-bonding oxygen atom, a fluorine atom or -R １１ (SO ２ ) X (SO ２ R ｆ [[ID=)]] ａ M ＋ ​​It is a group represented by. When the perfluoroalkyl group has an ether-bonding oxygen atom, the number of oxygen atoms may be 1 or 2 or more. Also, the ether-bonding oxygen atom may be located between carbon-carbon bonds of the perfluoroalkyl group or at the terminal of the carbon atom bond. The perfluoroalkyl group may be linear or branched, but is preferably linear. In formula (u11), when two Rs １１ are included, the two Rs １１ may be the same as or different from each other. M ＋ is H ＋ , a monovalent metal cation (for example, potassium ion, sodium ion) or an ammonium ion in which one or more hydrogen atoms may be substituted with a hydrocarbon group (for example, methyl group, ethyl group). From the viewpoint of high conductivity, H ＋ is preferred. R ｆ is a linear or branched perfluoroalkyl group that may have an ether-bonding oxygen atom. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 8, and particularly preferably 1 to 6. When having two or more Rs ｆ , the two or more Rs ｆ may be the same as or different from each other. X is an oxygen atom, a nitrogen atom or a carbon atom. When X is an oxygen atom, a = 0; when X is a nitrogen atom, a = 1; when X is a carbon atom, a = 2. Specific examples of the -(SO ２ X(SO ２ R ｆ )) ａ ) － M ＋ group include a sulfonic acid group (-(SO ３ － M ＋ group), a sulfonimide group (-(SO ２ N(SO ２ R ｆ )) － M ＋ group), or a sulfonide group (((-SO ２ C(SO ２ R ｆ )) ２ )) － M ＋ group).

[0027] The unit (u11) is preferably the unit (u11-1).

[0028]

[0029]

[0030] In formula (u12), R ２１ This is a perfluoroalkylene group having 1 to 6 carbon atoms or a perfluoroalkylene group having 2 to 6 carbon atoms with ether-bonded oxygen atoms between carbon-carbon bonds. When the perfluoroalkylene group has ether-bonded oxygen atoms, the number of oxygen atoms may be one or two or more. The perfluoroalkylene group may be linear or branched, but linear is preferred. ２２ This includes a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 2 to 6 carbon atoms with an ether-bonded oxygen atom between carbon-carbon bonds, or -R ２１ (SO ２ X (SO ２ R ｆ ) ａ ) － M ＋ The group is represented by . When the perfluoroalkyl group has ether-bonded oxygen atoms, the number of oxygen atoms may be one or two or more. The perfluoroalkyl group may be linear or branched, but linear is preferred. In formula (u12), two R ２１ If it includes two R ２１ These may be identical or different from one another. ＋ , R ｆ X and a are M in equation (u11), respectively. ＋ , R ｆ This is synonymous with X and a.

[0031] Specific examples of the unit (u12) include the unit (u12-1) and the unit (u12-2). In formulas (u12-1) and (u12-2), M ＋ M in equation (u11) ＋ It is synonymous with [the above].

[0032]

[0033]

[0034] In formula (u21), R ４１ , R ４２ , R ４３ , R ４４ , R ４５ and R ４６ Each of these is independently a monovalent perfluoroalkyl group or a fluorine atom, which may have an ether-bonded oxygen atom. If the perfluoroalkyl group has an ether-bonded oxygen atom, the number of oxygen atoms may be one or two or more. Furthermore, the ether-bonded oxygen atom may be located between carbon-carbon bonds of the perfluoroalkyl group, or at the carbon-carbon bond ends. The perfluoroalkyl group may be linear or branched, but linear is preferred. ４５ and R ４６ From the standpoint of high polymerization reactivity, it is preferable that at least one of the atoms is a fluorine atom, and it is particularly preferable that both atoms are fluorine atoms.

[0035] The unit (u21) is preferably the unit (u21-1).

[0036]

[0037]

[0038] In formula (u22), s is 0 or 1, and 0 is preferred. ５１ and R ５２ Each of these is independently a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a spiro ring formed by linking them together (where s is 0). ５３ and R ５４ Each of these is independently a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms. ５５ R is a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. ５５ Fluorine atoms are preferred due to their high polymerization reactivity. The perfluoroalkyl and perfluoroalkoxy groups may be linear or branched, but linear is preferred.

[0039] The unit (u22) is preferably the unit (u22-1).

[0040]

[0041]

[0042] In formula (u24), R ７１ ~R ７６ Each of these is independently a monovalent perfluoroalkyl group or a fluorine atom, which may have an ether-bonded oxygen atom. If the perfluoroalkyl group has an ether-bonded oxygen atom, the number of oxygen atoms may be one or two or more. Furthermore, the ether-bonded oxygen atom may be inserted between the carbon-carbon bonds of the perfluoroalkyl group, or it may be inserted at the carbon atom bond ends. The perfluoroalkyl group may be linear or branched, but linear is preferred. ７１ ~R ７４ It is preferable that the atom is a fluorine atom due to its high polymerization reactivity.

[0043] Unit B preferably includes at least one unit selected from the group consisting of units (u21), (u22), and (u24), and more preferably is unit (u22), in order to obtain a catalyst layer with superior oxygen permeability.

[0044] The content of unit B is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more, relative to the total units of polymer H, from the viewpoint of achieving better power generation efficiency of the fuel cell. The content of unit B is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less, relative to the total units of polymer H, from the viewpoint of further suppressing cracking of the catalyst layer and achieving better power generation efficiency of the fuel cell. Polymer H may contain only one type of unit B or two or more types. When two or more types are included, the above content refers to the total amount of these units.

[0045] Polymer H preferably contains units derived from tetrafluoroethylene (TFE) (hereinafter also referred to as "unit C") because it provides superior water repellency to the resulting catalyst layer and superior power generation efficiency of the fuel cell. The content of unit C is preferably 0 to 40 mol%, more preferably 10 to 45 mol%, and more preferably 15 to 30 mol% relative to the total units of polymer H.

[0046] Polymer H may contain units other than those described above: units A, B, and C. Other units include monomer-based units such as perfluoro(3-butenyl vinyl ether), perfluoro(allyl vinyl ether), perfluoroα-olefins (such as hexafluoropropylene), and perfluoro(alkyl vinyl ethers).

[0047] The ion exchange capacity of polymer H is preferably less than 1.8 milliequivalents / g dry resin, more preferably less than 1.6 milliequivalents / g dry resin, even more preferably less than 1.5 milliequivalents / g dry resin, particularly preferably less than 1.3 milliequivalents / g dry resin, and most preferably less than 1.2 milliequivalents / g dry resin, from the viewpoint of superior fuel cell power generation efficiency. The ion exchange capacity of polymer H is preferably 0.8 milliequivalents / g dry resin or more, more preferably 1.0 milliequivalents / g dry resin or more, and even more preferably 1.1 milliequivalents / g dry resin or more, from the viewpoint of superior fuel cell power generation durability. The ion exchange capacity of polymer H is determined by the method described in the Examples section below.

[0048] The softening temperature of polymer H is preferably 140°C or higher, more preferably 150°C or higher, and even more preferably 160°C or higher, from the viewpoint of achieving better power generation efficiency of the fuel cell. The softening temperature of polymer H is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower, from the viewpoint of further suppressing cracking of the catalyst layer. The softening temperature of polymer H is determined by the method described in the Examples section below.

[0049] The polymer H content is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, and more preferably 3.0% by mass or less, and more preferably 2.5% by mass or less, based on the total mass of the catalyst layer forming composition S.

[0050] A method for producing polymer H will be explained using the case where an acidic sulfonic acid group is used as an ion exchange group as an example. As an example of the above production method, the acidic sulfonic acid group is used as a precursor group (specifically, -SO ２ The precursor group of the precursor polymer (hereinafter also referred to as "polymer F"), which is a group represented by F, is an acidic sulfonic acid group (-SO ３ － H ＋ One method is to convert it to the precursor group -SO ２ A specific example of a method for converting the group represented by F to an acidic sulfonic acid group is the -SO group of polymer F. ２ One method involves hydrolyzing the group represented by F to obtain a salt-type sulfonic acid group, and then converting the salt-type sulfonic acid group to an acid-type sulfonic acid group.

[0051] The TQ value of polymer F is preferably 320°C or lower, and more preferably 300°C or lower. If the TQ value is below the upper limit, the solubility or dispersibility of polymer H in the liquid medium is improved, making it easier to prepare the composition. The TQ value of polymer F is preferably 100°C or higher, more preferably 130°C or higher, and even more preferably 160°C or higher. If the TQ value is above the lower limit, polymer H with sufficient molecular weight can be obtained, resulting in excellent strength of the resulting catalyst layer. The TQ value is a value related to the molecular weight of the polymer, and the volumetric flow rate is 100 mm. ３ This is expressed in terms of temperature per second. The volumetric flow rate is measured by melting and flowing a polymer through a constant-temperature nozzle (inner diameter: 1 mm, length: 1 mm) under a pressure of 3 MPa, and measuring the amount of polymer flowing out in mm³. ３ This is expressed in units of per second. The TQ value is an indicator of the molecular weight of the polymer; a higher TQ value indicates a higher molecular weight. The TQ value of polymer F is determined by the method described in the Examples section below.

[0052] (Metal-containing catalysts) In metal-containing catalysts (hereinafter also simply referred to as "catalysts"), the metal is preferably supported on a carrier. That is, the catalyst preferably contains a carrier and a metal supported on the carrier.

[0053] In metal-containing catalysts, the metal is preferably supported on a carrier. The metal preferably contains at least one of platinum and iridium, with platinum being preferred. Examples of platinum-containing metals include platinum and platinum alloys, with platinum being preferred. Examples of platinum alloys include alloys of platinum with at least one metal selected from the group consisting of platinum group metals other than platinum (ruthenium, rhodium, palladium, osmium, iridium), gold, silver, chromium, iron, titanium, manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zinc, and tin, with cobalt and platinum alloys being preferred. Examples of iridium-containing metals include iridium, iridium oxide, composite oxides containing iridium oxide and other metallic elements, and iridium alloys of iridium and other metals. As iridium oxide, iridium oxide having a core-shell structure is preferred. Other metals used in composite oxide catalysts and iridium alloys include, for example, ruthenium, titanium, zirconium, hafnium, niobium, tantalum, molybdenum, tungsten, and gold.

[0054] The shape of the metal is not particularly limited, but particulate is preferred. The average particle size of the metal (number average particle size D50) is not particularly limited as long as the performance can be achieved, but it is preferably 1 nm or more, more preferably 2 nm or more, preferably 10 nm or less, and more preferably 5 nm or less. The average particle size of the metal is measured by TEM (transmission electron microscope) or SAXS (small-angle X-ray scattering).

[0055] The metal content is preferably 20.0% by mass or more, and more preferably 30.0% by mass or more, relative to the total mass of the catalyst, in terms of achieving superior power generation efficiency of the fuel cell. From the viewpoint of power generation efficiency of the fuel cell, the metal content is preferably 70.0% by mass or less, and more preferably 60.0% by mass or less, relative to the total mass of the catalyst.

[0056] Catalysts containing metals preferably contain a support. A porous support is preferred as the support. Specific examples of support include carbon support, mesoporous carbon, Ketjenblack, and acetylene black. Specific examples of carbon support include carbon black powder, graphitized carbon, carbon fiber, and carbon nanotubes.

[0057] The shape of the carrier is not particularly limited, and the average particle diameter of the primary particles of the carrier is also not particularly limited as long as it can support the metal. However, the average particle diameter of the primary particles of the carrier is preferably 30 nm or more, more preferably 50 nm or more, preferably 300 nm or less, and more preferably 200 nm or less. The average particle diameter of the primary particles of the carrier refers to the arithmetic mean of the particle diameters (diameters) of any 100 primary particles of the carrier observed with a TEM (transmission electron microscope). If the observed particle shape is not spherical, it is considered to be spherical and its diameter is measured.

[0058] The specific surface area of ​​the support material is 500 m² per gram of support material, as this can further suppress cracking in the catalyst layer and improve the power generation durability of the fuel cell. ２ Preferably 700m ２ More preferably 750m / g or more, ２ A value of 1 / g or more is even more preferable. The specific surface area of ​​the carrier is 1400 m², which is preferable because it provides better oxidation resistance to the fuel cell. ２ Preferably less than / g, and 1300m ２ More preferably less than / g, and 1200m ２ A value of less than or equal to / g is even more preferable. The specific surface area of ​​the carrier can be calculated from the pore distribution. The pore distribution is obtained by analyzing the sample to be measured using an automated specific surface area / pore distribution analyzer (Shimadzu Corporation, model number: Tristar II 3020, measurement method: constant volume nitrogen adsorption method) by the BJH method.

[0059] If the catalyst contains a support, the support content is preferably 30.0% by mass or more, and more preferably 40.0% by mass or more, relative to the total mass of the catalyst. Furthermore, in terms of achieving better power generation efficiency of the fuel cell, the support content is preferably 80.0% by mass or less, and more preferably 70.0% by mass or less, relative to the total mass of the catalyst.

[0060] When the catalyst contains a support, the ratio of the content (mass) of polymer H to the content (mass) of the support in the catalyst layer forming composition S (mass of polymer H / mass of support, I / C) is preferably 1.4 or less, more preferably 1.3 or less, and even more preferably 1.2 or less, from the viewpoint of improving the efficiency, power output, and durability of the fuel cell. The I / C is preferably 0.3 or more, and more preferably 0.5 or more, from the viewpoint of improving the efficiency, power output, and durability of the fuel cell.

[0061] The catalyst content is preferably 3.0% by mass or more, more preferably 4.0% by mass or more, and more preferably 7.0% by mass or less, and more preferably 6.0% by mass or less, based on the total mass of the catalyst layer forming composition S.

[0062] (Solvent) The solvent includes alcohols. Specific examples of alcohols include methanol, ethanol, propanol (specifically 1-propanol, 2-propanol), 1-butanol, 2-methyl-1-propanol, 2-butanol, 2-methyl-2-propanol, 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoro-1-propanol, 2,2,3,3-tetrafluoro-1-propanol, 4,4,5,5,5-pentafluoro-1-pentanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 3,3,3-trifluoro-1-propanol, 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexanol, and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-octanol.

[0063] The alcohol contains propanol. The alcohol may contain other alcohols besides propanol, but the propanol content in the alcohol is greater than that of the other alcohols. The propanol content in the alcohol is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass, based on the total mass of the alcohol. The content of other alcohols besides propanol in the alcohol is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 1% by mass or less, and most preferably 0% by mass, based on the total mass of the alcohol, from the viewpoint of having better power generation durability of the fuel cell. Note that if the solvent contains 1-propanol and 2-propanol, the propanol content is the sum of these amounts.

[0064] The alcohol content is preferably 15% by mass or more, more preferably 28% by mass or more, even more preferably 51% by mass or more, and particularly preferably 55% by mass or more, relative to the total mass of the solvent, from the viewpoint of superior power generation durability of the fuel cell. The alcohol content is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, relative to the total mass of the solvent, from the viewpoint of superior power generation durability of the fuel cell. The propanol content is preferably 15% by mass or more, more preferably 28% by mass or more, even more preferably 51% by mass or more, and particularly preferably 55% by mass or more, relative to the total mass of the solvent, from the viewpoint of superior power generation durability of the fuel cell. The propanol content is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, relative to the total mass of the solvent, from the viewpoint of superior power generation durability of the fuel cell.

[0065] The solvent may contain other solvents besides alcohol, and it is preferable that it contains water. From the viewpoint of achieving better power generation efficiency of the fuel cell, the water content is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, relative to the total mass of the solvent. From the viewpoint of achieving better power generation efficiency of the fuel cell, the water content is preferably 85% by mass or less, more preferably 72% by mass or less, even more preferably 49% by mass or less, and particularly preferably 45% by mass or less, relative to the total mass of the solvent.

[0066] The catalyst layer forming composition S may contain other components besides those described above.

[0067] <Temporary Support> In this manufacturing method, the temporary support is a member that supports the formed catalyst layer, and it is preferable that it is ultimately removed by peeling. The temporary support preferably has release properties and flexibility.

[0068] The temporary support may be single-layered or multi-layered. Specific examples of materials constituting the temporary support include ETFE (a copolymer of TFE and ethylene), PET (polyethylene terephthalate), and PE (polyethylene). The thickness of the temporary support is preferably 10 to 300 μm.

[0069] <Catalyst Layer> This catalyst layer contains polymer H and a metal-containing catalyst. The content of polymer H is preferably 20 to 50% by mass, and more preferably 25 to 35% by mass, based on the total mass of the catalyst layer. The content of the catalyst is preferably 50 to 80% by mass, and more preferably 65 to 75% by mass, based on the total mass of the catalyst layer.

[0070] In the film electrode assembly described later, this catalyst layer may be either the catalyst layer of the anode layer or the catalyst layer of the cathode layer, but it is preferable that it be the catalyst layer of the cathode layer because it is effective in achieving higher current output.

[0071] The amount of metal in this catalyst layer is 0.2 mg / cm³. ２ It is superior, and in terms of fuel cell power generation efficiency, it is 0.3 mg / cm³. ２ The above is preferred, and 0.4 mg / cm³ ２The above is more preferable. The amount of metal in this catalyst layer is 0.9 mg / cm³, which better suppresses cracking of the catalyst layer and provides superior power generation durability. ２ The following is preferred: 0.8 mg / cm³ ２ The following are more preferable. Examples of methods for adjusting the amount of metal in the catalyst layer include adjusting the thickness of the catalyst layer, adjusting the amount of metal contained in the catalyst, and adjusting the amount of catalyst contained in the catalyst layer forming composition S. The amount of metal in the catalyst layer can be measured by fluorescent X-ray analysis.

[0072] The thickness of the catalyst layer is preferably 2 to 50 μm, and more preferably 5 to 40 μm. The thickness of the catalyst layer can be measured by observing the cross-section of the layer using an optical microscope and a scanning electron microscope (SEM).

[0073] <Procedure> This manufacturing method involves applying the catalyst layer-forming composition S described above onto a temporary support to produce a catalyst layer. This yields a transfer film containing a temporary support and a catalyst layer formed on the temporary support. The catalyst layer obtained by this manufacturing method may also be a catalyst layer obtained by removing the temporary support from the transfer film. Details of the catalyst layer-forming composition S and the temporary support are as described above.

[0074] The amount of catalyst layer-forming composition S applied to the temporary support can be appropriately adjusted so that the amount of metal per unit area of ​​the catalyst layer is the desired amount. The catalyst layer-forming composition S can be applied to the temporary support according to a conventional method. Specific examples of application methods include die coating and spin coating.

[0075] It is preferable to form the catalyst layer by drying the coating film of the catalyst layer-forming composition S to remove the solvent. The drying temperature is preferably 50 to 100°C, and more preferably 60 to 90°C. The drying time is preferably 5 minutes to 2 hours, and more preferably 15 minutes to 1 hour. The film obtained by drying the coating film may be further heat-treated to form the catalyst layer. The heat treatment temperature is preferably 100 to 200°C, and more preferably 130 to 180°C. The heat treatment time is preferably 10 seconds to 1 hour, and more preferably 3 minutes to 30 minutes.

[0076] [Method for Manufacturing a Membrane Electrode Assembly] The method for manufacturing a membrane electrode assembly of the present invention includes the step of bringing the catalyst layer into contact with a solid polymer electrolyte membrane, peeling off the temporary support, and transferring the catalyst layer to the solid polymer electrolyte membrane. More specifically, the method for manufacturing a membrane electrode assembly of the present invention preferably includes a contact step of bringing the catalyst layer of a transfer film having the catalyst layer and temporary support obtained by the present manufacturing method into contact with a solid polymer electrolyte membrane, and a peeling step of peeling off the temporary support from a laminate having the obtained membrane electrode assembly, the catalyst layer, and the temporary support in this order. In the above contact step, it is preferable to bring the solid polymer electrolyte membrane and the catalyst layer into contact and heat-press bond. The pressure during the heat-press bond is preferably 0.5 to 4.5 MPa, and more preferably 1.0 to 3.5 MPa. The temperature during the heat-press bond is preferably 100 to 200°C, and more preferably 130 to 180°C. The bonding time is preferably 10 seconds to 10 minutes, and more preferably 1 minute to 5 minutes. The removal of the temporary support during the peeling process can be carried out according to conventional methods.

[0077] <Solid Polymer Electrolyte Membrane> A solid polymer electrolyte membrane is a membrane containing a polymer having ion exchange groups. Examples of polymers having ion exchange groups include the polymer H mentioned above and known polymers having ion exchange groups. A specific example of a known polymer is the polymer -SO, which has units based on the monomer (m31) and units based on tetrafluoroethylene, as described in International Publication No. 2020 / 145287. ２ Polymers in which the group represented by F is converted to a sulfonic acid group, and polymers having units based on the monomer (m32) described in International Publication No. 2020 / 145287 and units based on tetrafluoroethylene -SO ２ Examples include polymers in which the group represented by F has been converted to a sulfonic acid group.

[0078] Solid polymer electrolyte membranes can be formed, for example, by a method (casting method) in which a liquid polymer composition is applied to a substrate film or catalyst layer and dried. The liquid composition is a dispersion in which a polymer is dispersed in a solvent containing at least one of an organic solvent and water.

[0079] To stabilize the solid polymer electrolyte membrane, heat treatment is preferable. The heat treatment temperature is preferably 130 to 200°C, although this depends on the type of polymer. The solid polymer electrolyte membrane may also be treated with hydrogen peroxide solution if necessary.

[0080] The solid polymer electrolyte membrane may be reinforced with a reinforcing material. Examples of reinforcing materials include porous materials, fibers, woven fabrics, and nonwoven fabrics. Examples of materials for the reinforcing material include polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer, polyethylene, polypropylene, and polyphenylene sulfide.

[0081] The solid polymer electrolyte membrane may contain one or more atoms selected from the group consisting of cerium and manganese to further improve its durability. Cerium and manganese decompose hydrogen peroxide, which is a substance that causes degradation of the solid polymer electrolyte membrane. It is preferable that cerium and manganese exist as ions in the solid polymer electrolyte membrane, and they may exist in any state within the solid polymer electrolyte membrane as long as they exist as ions. The solid polymer electrolyte membrane may also contain silica and heteropoly acids (zirconium phosphate, phosphomolybdic acid, phosphotungstic acid, etc.) as water-retaining agents to prevent drying.

[0082] <Membrane Electrode Assembly> The membrane electrode assembly obtained by the manufacturing method of the membrane electrode assembly of the present invention (hereinafter also simply referred to as "this membrane electrode assembly") comprises a catalyst layer and a solid polymer electrolyte membrane. Preferably, this membrane electrode assembly comprises an anode having a catalyst layer, a cathode having a catalyst layer, and a solid polymer electrolyte membrane disposed between the anode and the cathode. Preferably, at least one of the catalyst layers of the anode and the cathode is this catalyst layer, and at least the catalyst layer of the cathode is this catalyst layer.

[0083] One of the catalyst layers may be a catalyst layer produced by a method other than the present manufacturing method. Other methods include, for example, the following: (i) a method of coating a catalyst layer forming composition onto a solid polymer electrolyte membrane and drying it; (ii) a method of coating a catalyst layer forming composition different from catalyst layer forming composition S onto a temporary support, drying it, and transferring it to a solid polymer electrolyte membrane. The catalyst layer forming composition in method (i) may be the catalyst layer forming composition S described above, or it may be a catalyst layer forming composition different from catalyst layer forming composition S. When using method (ii), the transfer in the present manufacturing method and the transfer in method (ii) may be performed sequentially or simultaneously.

[0084] Figure 1 is a cross-sectional view showing an example of the film electrode assembly. The film electrode assembly 10 includes an anode 13 having a catalyst layer 11A and a gas diffusion layer 12A, a cathode 14 having a catalyst layer 11C and a gas diffusion layer 12C, and a solid polymer electrolyte membrane 15 disposed between the anode 13 and the cathode 14 in contact with the catalyst layers 11A and 11C. At least one of the catalyst layers 11A and 11C is manufactured by the present manufacturing method. One of the catalyst layers 11A and 11C may be manufactured by a method other than the present manufacturing method. The present manufacturing method and other methods are as described above.

[0085] The gas diffusion layer 12C has the function of uniformly diffusing gas into the catalyst layer 11C and also functions as a current collector. Examples of materials for the gas diffusion layer 12C include carbon paper, carbon cloth, and carbon felt. It is preferable that the gas diffusion layer 12C is treated to be water-repellent with polytetrafluoroethylene or the like. Although the film electrode assembly 10 in Figure 1 includes the gas diffusion layer 12C, the gas diffusion layer is an arbitrary component and does not have to be included in this film electrode assembly.

[0086] A specific example of the gas diffusion layer 12A of the anode 13 is the same as the specific example of the gas diffusion layer 12C described above, and the gas diffusion layer 12A is any material, just like the gas diffusion layer 12C.

[0087] The membrane electrode assembly 10 can be manufactured, for example, by transferring catalyst layers 11A and 11C onto a solid polymer electrolyte membrane 15 to form a membrane catalyst layer assembly, and then sandwiching the membrane catalyst layer assembly between gas diffusion layers (gas diffusion layer 12A and gas diffusion layer 12C).

[0088] The membrane electrode assembly 10 may have a carbon layer (not shown) between the catalyst layer and the gas diffusion layer. By arranging the carbon layer, the gas diffusivity of the surface of the catalyst layer 11 is improved, further enhancing the power generation efficiency of the fuel cell. The carbon layer may, for example, contain carbon and a nonionic fluorine-containing polymer. A specific example of the carbon is carbon nanofiber with a fiber diameter of 1 to 1000 nm and a fiber length of 1000 μm or less. A specific example of the nonionic fluorine-containing polymer is polytetrafluoroethylene.

[0089] This membrane electrode assembly is suitably used in polymer electrolyte fuel cells. This membrane electrode assembly may also be used in polymer electrolyte water electrolysis devices (PEM water electrolysis devices).

[0090] A polymer electrolyte fuel cell containing this membrane electrode assembly exhibits excellent power generation durability due to the inclusion of this catalyst layer. A polymer electrolyte fuel cell containing this membrane electrode assembly may also have separators on both sides of the membrane electrode assembly, each having grooves that serve as gas flow channels. Specific examples of separators include metal separators, carbon separators, separators made of a mixture of graphite and resin, and separators made of various conductive materials. In polymer electrolyte fuel cells, power generation is achieved by supplying an oxygen-containing gas to the cathode and a hydrogen-containing gas to the anode. This membrane electrode assembly can also be applied to methanol fuel cells, which generate power by supplying methanol to the anode.

[0091] An example of a PEM water electrolysis apparatus having the film electrode assembly is a PEM water electrolysis apparatus having the film electrode assembly, a water supply unit that supplies water to the anode catalyst layer, and a power supply unit that is electrically connected to the anode catalyst layer and the cathode catalyst layer. The PEM water electrolysis apparatus having the film electrode assembly may have the same configuration as a known water electrolysis apparatus (for example, an oxygen recovery member for recovering generated oxygen, a hydrogen recovery member for recovering generated hydrogen).

[0092] The present invention will be described in detail below with reference to examples. Example 1 is an example, and Examples 2 and 3 are comparative examples. However, the present invention is not limited to these examples.

[0093] [Measurement Method] <Ion Exchange Capacity> The ion exchange capacity of each fluorine-containing polymer was determined by the following procedure. Polymer F-1 was press-molded at 210°C and polymer F-2 at 10°C higher than the TQ value at 4 MPa (gauge pressure) to obtain films (thickness 100-250 μm) of polymers F-1 to F-3. The films of each polymer F were immersed in the alkaline aqueous solution shown in Table 1 at 80°C for 16 hours, and the -SO4 of each polymer F was determined. ２ Hydrolyze F to obtain -SO ３ The polymer film was converted to K. Furthermore, each polymer film was immersed in a 3 mol / L hydrochloric acid aqueous solution at 50°C for 30 minutes, followed by immersion in ultrapure water at 80°C for 30 minutes. The cycle of immersion in hydrochloric acid aqueous solution and ultrapure water was repeated a total of five times, and the -SO of each polymer was converted. ３ K to -SO ３ The polymers were converted to H. Each polymer film was repeatedly washed with ultrapure water until the pH of the water in which it was immersed reached 7. Each polymer film was air-dried between filter paper to obtain polymer H-1 to polymer H-3 films. The obtained polymer H films were dried in a glove box with nitrogen flow until their mass no longer changed, and their mass was determined. Then, each polymer H film was immersed in a 0.85 mol / g sodium hydroxide solution (solvent: water / methanol = 10 / 90 (mass ratio)) at 60°C for 72 hours or more to convert the acid-type sulfonic acid groups to sodium salt-type sulfonic acid groups. The ion exchange capacity of polymer H was determined by back titration of the remaining sodium hydroxide with 0.1 mol / L hydrochloric acid.

[0094] <Proportion of each unit> Analysis of the proportion of each unit in the polymer derived from monomer units: １９ The values ​​were calculated from F-NMR measurements. Note that the content of each unit in polymer H is approximately equivalent to the content of each unit in polymer F.

[0095] ＜１９ F-NMR> １９ F-NMR uses a frequency of 282.7 MHz and a chemical shift reference of CFCl. ３ The measurements were taken under the specified conditions. The compositional analysis of polymer F was performed by adjusting the solution concentration to 10% by mass using hexafluorobenzene as the dissolving solvent.

[0096] <TQ Value> A flow tester (Shimadzu Corporation, CFT-500A) equipped with a nozzle 1 mm in length and 1 mm in inner diameter was used to melt-extrude polymer F at an extrusion pressure of 2.94 MPa (gauge pressure) while varying the temperature. The extrusion volume of polymer F was 100 mm. ３ The temperature at which the extrusion rate per second (TQ value) is obtained was determined. If the TQ value exceeds 300°C, the extrusion rate at four points below 300°C was measured, and the TQ value was calculated by extrapolating from these four measurements. Extrapolation was performed using an approximation formula that logarithmically approximates the correlation between the extrusion rate and the reciprocal of the absolute temperature. For polymers with the same composition, a higher TQ value indicates a larger polymer molecular weight.

[0097] <Softening Temperature> Liquid compositions S (liquid compositions S-1 to S-2 described later), in which polymer H is dispersed in a mixed solvent, were cast into a petri dish and then annealed to prepare a polymer H film. Dynamic viscoelasticity measurements were performed on this polymer H film using a dynamic viscoelasticity measuring device (IT Measurement Control Co., Ltd., DVA-225) under the following conditions: sample width: 5.0 mm, gripping distance: 15 mm, measurement frequency: 1 Hz, heating rate: 2 °C / min, and tensile mode. The tanδ (loss tangent) was calculated from the ratio of the loss modulus E'' to the storage modulus E' (E'' / E'), and a tanδ-temperature curve was created. The value obtained by reading the peak temperature between -100 and 200 °C from the tanδ-temperature curve was defined as the softening temperature of polymer H. The softening temperature corresponds to the temperature at which the material transitions from a glassy state to a rubbery state. The reference dimensions and film thickness of the film used in the calculation were measured under the conditions of temperature: 23 °C and relative humidity: 50% RH.

[0098] <Abbreviations> The abbreviations used in the examples below are as follows: ・TFE: Tetrafluoroethylene ・PFB: CF ３ CF ２ CF ２ C(O)OOC(O)CF ２ CF ２ CF ３ ・HFC-52-13p:CF ３ (CF ２ ) ５ H ・HCFC-225cb: CClF ２ CF ２ CHClF ・HCFC-141b:CH ３ CCl ２ F・V-601: The following compound

[0099]

[0100] ・Compound 1

[0101]

[0102] ・Compound 2

[0103]

[0104] ・Compound 3

[0105]

[0106] [Synthesis of Polymer F] <Polymer F-1> A stainless steel autoclave with an internal volume of 2575 mL was reduced in pressure under an ice bath, and 1116.02 g of compound 1, 340.92 g of compound 2, 407.78 mg of PFB dissolved in HFC-52-13p at a concentration of 3.2 mass%, and 172.0 g of HFC-52-13p were aspirated and charged into the autoclave, and the pressure was reduced again. Then, 56.90 g of TFE was charged, and the temperature was raised to 24°C to start the reaction. Stirring during the reaction was carried out with a double helical ribbon impeller, and the stirring speed was set to 60 rpm until 2.5 hours after the start of the reaction, 30 rpm from 2.5 hours to 3.5 hours, and 10 rpm from 3.5 hours to 10 hours. After stirring for 10 hours, the autoclave was reduced in pressure and unreacted compound 2 and TFE were removed by distillation. The product was then diluted with HFC-52-13p, and this was mixed with a mixture of HFC-52-13p:methanol = 8:2 (mass ratio) to agglomerate the polymer, which was then filtered off. The polymer was washed in a mixture of HFC-52-13p:methanol = 7:3 (mass ratio), separated by filtration, and the solids were dried at 80°C and then vacuum-dried at 210°C to obtain polymer F-1.

[0107] <Polymer F-2> 170 g of compound 3 was placed in a 230 mL stainless steel autoclave and frozen and degassed using liquid nitrogen. After raising the temperature to 65°C, nitrogen was introduced at 0.212 MPa. After confirming that the pressure did not change, TFE was introduced to bring the total pressure to 1.312 MPaG. 2.65 g of a 1.0 mass% solution of V-601 dissolved in HFC-52-13p was added under pressure with nitrogen, and then the addition line was washed with 2.35 g of HFC-52-13p. TFE was continuously supplied while maintaining a constant temperature and pressure. Seven hours after the start of polymerization, the autoclave was cooled to stop the polymerization reaction. The product removed from the autoclave was diluted with HFC-52-13p and added to HCFC-141b, and after the polymer was aggregated, it was filtered. The polymer was washed by repeatedly stirring and filtering it in HCFC-141b, and then dried under reduced pressure at 80°C overnight to obtain polymer F-2.

[0108] <Polymer F-3> 123.8 g of compound 3, 35.2 g of HCFC-225cb, and 63.62 mg of 2,2'-azobis(isobutyronitrile) as a polymerization initiator were charged into an autoclave (230 mL internal volume, Hastelloy), and the mixture was cooled with liquid nitrogen to degass it. The temperature was then raised to 70°C, and TFE was introduced into the system, maintaining a pressure of 1.14 MPaG. Polymerization was carried out by continuously adding TFE to maintain a constant pressure of 1.14 MPaG. After 7.9 hours, when the amount of TFE added reached 12.4 g, the autoclave was cooled, and the gas in the system was purged to stop the polymerization. The resulting polymer solution was diluted with HCFC-225cb, and then HCFC-141b was added to induce aggregation. After washing with HCFC-225cb and HCFC-141b, the mixture was dried to obtain 25.1 g of polymer F-3, which is a copolymer of TFE and compound 3.

[0109] [Synthesis of Polymer H] Using each polymer F, powders of polymers H-1 to H-3 were obtained by the following method. Each polymer F was cooled with dry ice and then pulverized. Each polymer F, pulverized at 80°C, was immersed in the alkaline aqueous solution shown in Table 1 for 40 hours, and the -SO of each polymer F was obtained. ２ Hydrolyze F to obtain -SO ３ The polymers were converted to K. Furthermore, each obtained polymer was immersed in a 3 mol / L hydrochloric acid aqueous solution at 80°C for 30 minutes, followed by immersion in ultrapure water at 80°C for 30 minutes. The cycle of immersion in hydrochloric acid aqueous solution and ultrapure water was repeated a total of 10 times, and the -SO of each polymer was converted. ３ K to -SO ３ The polymers were converted to H. Each polymer was repeatedly washed with ultrapure water until the pH of the water in which it was immersed reached 7. The polymers were dried using a nitrogen flow to obtain powders of each polymer H.

[0110] [Preparation of Liquid Composition S] <Liquid Composition S-1> 18.70 g of polymer H-1 powder (18.22 g of polymer H-1, 0.48 g of water, solid content concentration 97.4% by mass), 22.81 g of ultrapure water, and 54.36 g of 1-propanol were added to a glass autoclave with an internal volume of 0.2 L. The mixture was stirred at 300 rpm at 115°C for 13 hours, and then diluted with 31.0 g of ultrapure water. After stirring at 110°C for 1 hour, the solution was allowed to cool and removed from the autoclave. To this solution, 13.8 g of ultrapure water and 12.5 g of 1-propanol were added to dilute it, and after stirring at 110°C for 1 hour, it was allowed to cool. The solution was then filtered using a pressure filter (filter paper: Advantec Toyo Co., Ltd., PF040) to obtain a liquid composition S-1 in which polymer H-1 was dispersed in the mixed solvent at a concentration of 11.9% by mass.

[0111] <Liquid Composition S-2> A liquid composition S-2 in which polymer H-2 is dispersed was obtained using polymer F-2 as a raw material and the method described in Production Example 4 of Japanese Patent Application Publication No. 2018-55877.

[0112] <Liquid Composition S-3> A liquid composition S-3 (solid content concentration 26.0% by mass, ethanol / water = 60 / 40 (mass ratio)) in which polymer H-3 is dispersed was obtained using polymer F-3 as a raw material and the method described in Production Example 4 of Japanese Patent Application Publication No. 2018-55877.

[0113] [Preparation of Cathode Catalyst Layer Formation Composition CI] <Metal-containing catalyst> The following catalyst 1 was prepared as a metal-containing catalyst.

[0114] (Catalyst 1) Metal type: Platinum particles Number of platinum particles Average particle size: 2.4 nm Platinum particle content relative to total catalyst mass: 46.9% by mass Carbon support content relative to total catalyst mass: 53.1% by mass Type of porous support: Carbon support (carbon black powder) Specific surface area of ​​carbon support (per 1g of carbon support): 800 m² ２ / g

[0115] <Composition CI-1-1 for Catalyst Layer Formation> 3.0 g of catalyst 1 was mixed with 14.87 g of water and 24.78 g of 1-propanol. 10.71 g of liquid composition S-1 was added to this mixture so that the I / C (mass ratio of polymer H content to carbon support content) was 0.8 and the solid content concentration was 8.0% by mass. Dispersion was performed using a planetary ball mill (Ito Seisakusho, model: LP-4) with 5 mm zirconia beads at a rotation speed of 300 rpm for 180 minutes, and then filtered using a SUS316 mesh with a mesh diameter of 53 μm. 40.80 g of the recovered filtrate was diluted by adding 5.44 g of water and 8.16 g of 1-propanol to obtain composition CI-1-1 for cathode catalyst layer formation.

[0116] <Composition CI-1-2 for Catalyst Layer Formation> 3.0 g of catalyst 1 was mixed with 24.69 g of water and 14.96 g of 1-propanol. 10.71 g of liquid composition S-1 was added to this mixture so that the I / C ratio was 0.8 and the solid content concentration was 8.0% by mass. Dispersion was performed using a planetary ball mill (Ito Seisakusho, model: LP-4) with 5 mm zirconia beads at a rotation speed of 300 rpm for 180 minutes, and then filtered using a SUS316 mesh with a mesh diameter of 53 μm. 40.80 g of the recovered filtrate was diluted by adding 8.16 g of water and 5.44 g of 1-propanol to obtain composition CI-1-2 for cathode catalyst layer formation.

[0117] <Composition CI-2 for Catalyst Layer Formation> 3.0 g of catalyst 1 was mixed with 21.68 g of water and 13.31 g of ethanol. 4.71 g of liquid composition S-2 was added to this mixture so that the I / C ratio was 0.8 and the solid content concentration was 10.0% by mass. The mixture was dispersed using a planetary ball mill (Ito Seisakusho, model: LP-4) with 5 mm zirconia beads at a rotation speed of 300 rpm for 180 minutes, and then filtered using a SUS316 mesh with a mesh diameter of 53 μm. The filtrate yielded composition CI-2 for cathode catalyst layer formation.

[0118] [Preparation of Composition AI-1 for Anode Catalyst Layer Formation] Using liquid composition S-3, 3.0 g of catalyst 1 was mixed with 21.6 g of water and 13.2 g of ethanol. 4.9 g of liquid composition S-3 was added to this mixture so that the I / C ratio was 0.8. The mixture was dispersed using a planetary ball mill (Ito Seisakusho, model: LP-4) with 5 mm zirconia beads at a rotation speed of 300 rpm for 180 minutes, and then filtered using a SUS316 mesh with a mesh diameter of 53 μm. Composition AI-1 for anode catalyst layer formation was obtained as the filtrate.

[0119] [Fabrication of catalyst layer and membrane electrode assembly] <Example 1> On an ETFE (tetrafluoroethylene copolymer) sheet, 0.5 mg / cm of the catalyst layer forming composition CI-1-1 with platinum ２ The material was applied with an applicator, dried at 80°C for 10 minutes, and then heat-treated at 150°C for 15 minutes to obtain the cathode catalyst layer CC-1-1. On an ETFE (tetrafluoroethylene-ethylene copolymer) sheet, the anode catalyst layer formation composition AI-1 was added at a platinum content of 0.4 mg / cm². ２ The material was coated using a die coater, dried at 80°C for 10 minutes, and then heat-treated at 150°C for 15 minutes to obtain the anode catalyst layer AC-1. As the solid polymer electrolyte membrane, SO4 was used, which is a copolymer of TFE and compound 3. ２ F group SO ３ A 25 μm thick ion exchange membrane (ion exchange capacity: 1.25 mm equivalent / g dry resin) was prepared from a polymer having acid-type sulfonic acid groups converted to H groups. A cathode catalyst layer CC-1-1 was placed on one side of the solid polymer electrolyte membrane, and an anode catalyst layer AC-1 was placed on the other side. The cathode catalyst layer CC-1-1 and anode catalyst layer AC-1 were pressed onto the solid polymer electrolyte membrane at 160°C and 3.0 MPa (absolute pressure) for 2 minutes. The ETFE sheet, which was a temporary support for the cathode catalyst layer CC-1-1 and anode catalyst layer AC-1, was then peeled off to form a membrane electrode assembly (electrode area: 25 cm²). ２ ) ME-1 was obtained.

[0120] <Example 2> As a solid polymer electrolyte membrane, a copolymer of TFE and compound 3 is used. ２ F group SO ３A 25 μm thick ion exchange membrane (ion exchange capacity: 1.25 mm equivalent / g dry resin) was prepared from a polymer having acid-type sulfonic acid groups converted to H groups. On the above solid polymer electrolyte membrane, a cathode catalyst layer formation composition CI-1-2 was added with a platinum content of 0.5 mg / cm³. ２ The mixture was applied with an applicator, dried at 80°C for 10 minutes, and then heat-treated at 150°C for 15 minutes to obtain a solid polymer electrolyte membrane with a cathode catalyst layer CC-1-2 formed on one side. Next, the anode catalyst layer formation composition AI-1 was applied to an ETFE (tetrafluoroethylene-ethylene copolymer) sheet at a platinum content of 0.4 mg / cm². ２ The material was coated using a die coater, dried at 80°C for 10 minutes, and then heat-treated at 150°C for 15 minutes to obtain the anode catalyst layer AC-1. The solid polymer electrolyte membrane surface on which the cathode catalyst layer CC-1-2 was formed was placed over the anode catalyst layer AC-1, and the anode catalyst layer AC-1 was pressed against the solid polymer electrolyte membrane at 160°C and 3.0 MPa (absolute pressure) for 2 minutes. The ETFE sheet of the anode catalyst layer AC-1 was then peeled off to form a membrane electrode assembly (electrode area: 25 cm²). ２ ) ME-2 was obtained.

[0121] <Example 3> Except that composition CI-2 for forming the cathode catalyst layer was used instead of composition CI-1-2 for forming the cathode catalyst layer, a membrane electrode assembly ME-3 was obtained in the same manner as in Example 2, with the anode catalyst layer AC-1, solid polymer electrolyte membrane, and cathode catalyst layer CC-2 arranged in this order.

[0122] [Evaluation] <Power generation durability> Membrane electrode assemblies ME-1 to ME-3 were each incorporated into a power generation cell along with a gas diffusion layer with a microporous layer, and the output was 0.7 A / cm². ２After conditioning for 14 hours with a constant current, the cell temperature was set to 80°C and atmospheric pressure, and hydrogen (0.05 L / min) / nitrogen (0.2 L / min) was supplied. The dew point on the anode side was 80°C, the dew point on the cathode side was 80°C (relative humidity inside the cell: 100% RH), the voltage width was 0.6-1.0 V, the voltage waveform was triangular wave, the scanning speed was 50 mV / sec, and the time required per cycle was 16 sec. 10,000 cycles were performed. Initially, power generation performance evaluations (interim diagnoses) were performed at 100 cycles and 500 cycles, and thereafter every 1,000 cycles. The power generation performance evaluation (interim diagnosis) was conducted with a cell temperature of 80°C and a back pressure of 50 kPaG, supplying hydrogen (70% utilization rate) and air (50% utilization rate), with a dew point at 80°C on both the anode and cathode sides (relative humidity inside the cell: 100% RH), and a current density of 1.4 A / cm². ２ The cell voltage (V) was measured. The voltage value at 10,000 cycles (voltage value after the durability test) was determined and judged according to the following evaluation criteria: "A": Voltage value at 10,000 cycles is 0.665V or higher "B": Voltage value at 10,000 cycles is 0.660V or higher and less than 0.665V "C": Voltage value at 10,000 cycles is 0.650V or higher and less than 0.660V "D": Voltage value at 10,000 cycles is less than 0.650V

[0123] Table 1 below shows the materials and composition used in each catalyst layer forming composition, the composition and properties of polymer F, the manufacturing method and properties of polymer H, and the composition of liquid composition S. Table 2 below shows the composition and evaluation of each membrane electrode assembly ME. The measurement methods for various physical properties are as described above. In Table 1, aqueous solution A is potassium hydroxide / dimethyl sulfoxide / water = 15 / 30 / 55 (mass ratio), and aqueous solution B is potassium hydroxide / methanol / water = 15 / 20 / 65 (mass ratio). In Table 1, "Propanol content in alcohol" indicates the alcohol content (unit: wt%) relative to the total mass of alcohol contained in each catalyst layer forming composition. In Table 1, "I / C" indicates the mass ratio of polymer H content / carbon support content in the cathode catalyst layer forming composition. In Table 2, "Platinum content of cathode catalyst layer [mg / cm²]" ２]" refers to the amount of platinum in each cathode catalyst layer (unit: mg / cm³). ２ Table 2 shows the following. In Table 2, "Cathode Catalyst Layer Manufacturing Method" indicates a method for manufacturing the cathode catalyst layer, "Temporary Support Coating" indicates that the catalyst layer was manufactured by coating the cathode catalyst layer forming composition onto a temporary support (ETFE), and "Film Coating" indicates that the catalyst layer was manufactured by coating the cathode catalyst layer forming composition onto a solid polymer electrolyte film.

[0124]

[0125]

[0126] From the evaluation results of Examples 1 to 3, it was confirmed that this manufacturing method can form a catalyst layer applicable to a membrane electrode assembly that can realize a fuel cell with excellent power generation durability. The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2025-011559, filed on January 27, 2025, are incorporated herein by reference as disclosure of the present invention.

[0127] 10 Membrane electrode assembly 11A, 11C Catalyst layer 12A, 12C Gas diffusion layer 13 Anode 14 Cathode 15 Solid polymer electrolyte membrane

Claims

1. A method for producing a catalyst layer, comprising coating a composition comprising a fluorine-containing polymer containing units having ion-exchange groups, a catalyst containing a metal, and a solvent onto a temporary support to form a catalyst layer, wherein the units having ion-exchange groups each contain two ion-exchange groups, the solvent contains an alcohol, the propanol content in the alcohol is greater than that of other alcohols, and the amount of the metal in the catalyst layer is 0.2 mg / cm³. ２ A method for manufacturing a catalyst layer.

2. The method for producing a catalyst layer according to claim 1, wherein the fluorine-containing polymer includes units having a cyclic ether structure.

3. The method for producing a catalyst layer according to claim 2, wherein the content of units containing the cyclic ether structure is 50 mol% or more relative to the total units of the fluorine-containing polymer.

4. The method for producing a catalyst layer according to claim 1 or 2, wherein the fluorine-containing polymer includes units derived from tetrafluoroethylene.

5. The method for producing a catalyst layer according to claim 1 or 2, wherein the ion exchange capacity of the fluorine-containing polymer is less than 1.8 milliequivalents / g of dry resin.

6. The method for producing a catalyst layer according to claim 1 or 2, wherein the ion exchange capacity of the fluorine-containing polymer is less than 1.6 milliequivalents / g of dry resin.

7. The method for producing a catalyst layer according to claim 1 or 2, wherein the ion exchange capacity of the fluorine-containing polymer is less than 1.3 milliequivalents / g of dry resin.

8. The method for manufacturing a catalyst layer according to claim 1 or 2, wherein the metal is platinum.

9. The catalyst includes a carrier, and the specific surface area of ​​the carrier is 700 m². ２ A method for producing a catalyst layer according to claim 1 or 2, wherein the amount is 1 / g or more.

10. The method for producing a catalyst layer according to claim 1 or 2, wherein the alcohol content is 51% by mass or more relative to the total mass of the solvent.

11. The method for producing a catalyst layer according to claim 1 or 2, wherein the catalyst comprises a carrier, and in the composition, the mass ratio of the content of the fluorine-containing polymer to the content of the carrier is 1.3 or less.

12. The method for producing a catalyst layer according to claim 1 or 2, wherein the solid content concentration of the composition is 10.0% by mass or less.

13. A method for manufacturing a membrane electrode assembly, comprising contacting a catalyst layer obtained by the method for manufacturing a catalyst layer according to claim 1 or 2 with a solid polymer electrolyte membrane, and then peeling off the temporary support to manufacture a membrane electrode assembly.

14. The method for manufacturing a membrane electrode assembly according to claim 13, wherein the membrane electrode assembly is used in a polymer electrolyte fuel cell.

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