Catalyst layer, catalyst layer forming liquid, and membrane electrode assembly

Abstract

Provided are a catalyst layer, a catalyst layer-forming liquid, and a membrane electrode assembly capable of forming a fuel cell with excellent power generation efficiency. The catalyst layer of the present invention comprises: a supported catalyst having a support comprising a metal oxide and a catalyst supported on the support; and a polymer having ion exchange groups, wherein the polymer comprises units containing at least one cyclic ether structure selected from the group consisting of units (u11), units (u12), units (u21), and units (u22), and the total content of units containing cyclic ether structures relative to all units contained in the polymer is 30 mol% or more. #imgabs0#

Description

Technical Field

[0001] The present invention relates to a catalyst layer, a liquid for forming a catalyst layer, and a membrane electrode assembly. Background Art

[0002] Conventional fuel cells have a catalyst layer (the catalyst layer of the electrode of the membrane electrode assembly) that includes a supported catalyst and a polymer (ionomer) made by supporting platinum or a platinum alloy on a carbon support. However, the carbon support is susceptible to corrosion. Therefore, the use of metal oxides as supports in place of carbon supports is being studied.

[0003] Patent Document 1 discloses a catalyst layer for a fuel cell comprising: a catalyst complex (supported catalyst) in which platinum or a platinum alloy is supported on the surface of a SnO2 carrier; and a perfluorosulfonic acid polymer (ionomer) containing an acidic functional group and a cyclic group.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 6315018 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] In recent years, there has been a demand for further improvement in the power generation efficiency of fuel cells.

[0009] The present inventors evaluated a catalyst layer comprising a supported catalyst having a metal oxide support and an ionomer (polymer) having a cyclic structure as described in Patent Document 1 and found that the power generation efficiency of the fuel cell may be insufficient depending on the type and content of the cyclic structure.

[0010] In view of the above-mentioned actual situation, an object of the present invention is to provide a catalyst layer, a catalyst layer-forming liquid, and a membrane electrode assembly capable of forming a fuel cell having excellent power generation efficiency.

[0011] Solutions for solving problems

[0012] The present inventors conducted in-depth research on the above-mentioned issues and found that, in a catalyst layer containing a supported catalyst having a carrier containing a metal oxide and a polymer having ion exchange groups, if the polymer has units containing a specific cyclic ether structure and the total content of the units containing the specific cyclic ether structure is greater than a specific amount relative to all units contained in the polymer, a fuel cell with excellent power generation efficiency can be obtained, thereby completing the present invention.

[0013] That is, the present inventors have found that the above-mentioned problems can be solved by the following configuration.

[0014] [1] A catalyst layer, characterized in that it comprises: a supported catalyst having a support comprising a metal oxide, and a catalyst supported on the support; and a polymer having an ion exchange group, wherein the polymer has a unit comprising at least one cyclic ether structure selected from the group consisting of a unit represented by formula (u11) described later, a unit represented by formula (u12) described later, a unit represented by formula (u21) described later, and a unit represented by formula (u22) described later, wherein the total content of the units comprising the cyclic ether structure is 30 mol% or more relative to all the units contained in the polymer.

[0015] In the formula (u11) described below, R 11 is a divalent perfluoroorganic group optionally having an ethereal oxygen atom, R 12 、R 13 、R 15 and R 16 are each independently a monovalent perfluoroorganic group or a fluorine atom which may have an ethereal oxygen atom, R 14 is a monovalent perfluoroorganic group optionally having an ethereal oxygen atom, a fluorine atom or -R 11 (SO2X(SO2R f ) a ) - M + The group shown. + H + , a monovalent metal cation or an ammonium ion in which one or more hydrogen atoms are optionally substituted by a hydrocarbon group, R f It is a linear or branched perfluoroalkyl group which may have an ethereal oxygen atom, X is an oxygen atom, a nitrogen atom or a carbon atom, and when X is an oxygen atom, a=0, when X is a nitrogen atom, a=1, and when X is a carbon atom, a=2.

[0016] In the formula (u12) described below, R 21 is a perfluoroalkylene group having 1 to 6 carbon atoms or a perfluoroalkylene group having 2 to 6 carbon atoms having an ethereal oxygen atom between carbon-carbon bonds, R 22 is a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 2 to 6 carbon atoms having an ethereal oxygen atom between carbon-carbon bonds, or -R 21 (SO2X(SO2R f ) a ) - M + The group shown. + 、R f and X are the same as above.

[0017] In the formula (u21) described below, R 41 、R 42 、R 43 、R44 、R 45 and R 46 Each independently represents a monovalent perfluoroorganic group or a fluorine atom which may have an ethereal oxygen atom.

[0018] In the formula (u22) described below, s is 0 or 1, R 51 and R 52 are independently a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a spiro ring formed by connecting them together (wherein s is 0), R 53 and R 54 are independently a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms, R 55 It is a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms.

[0019] [2] The catalyst layer according to [1], wherein the unit containing a cyclic ether structure contains a unit represented by the formula (u22).

[0020] [3] The catalyst layer according to [2], wherein the unit containing a cyclic ether structure further contains at least one of the unit represented by the above formula (u11) and the unit represented by the above formula (u12).

[0021] [4] The catalyst layer according to any one of [1] to [3], wherein the polymer further comprises a unit based on a perfluoromonomer, and the unit based on the perfluoromonomer is a unit that does not contain a cyclic ether structure and has an ion exchange group.

[0022] [5] The catalyst layer according to any one of [1] to [4], wherein the polymer further includes units based on tetrafluoroethylene.

[0023] [6] A liquid for forming a catalyst layer, characterized in that it comprises: a supported catalyst having a carrier comprising a metal oxide and a catalyst supported on the carrier; a polymer having an ion exchange group, the polymer having a unit comprising at least one cyclic ether structure selected from the group consisting of a unit represented by formula (u11) described later, a unit represented by formula (u12) described later, a unit represented by formula (u21) described later, and a unit represented by formula (u22) described later; and a solvent, wherein the total content of the units comprising the cyclic ether structure is 30 mol% or more relative to all the units contained in the polymer.

[0024] In the formula (u11) described below, R 11 is a divalent perfluoroorganic group optionally having an ethereal oxygen atom, R 12 、R 13 、R 15 and R 16are each independently a monovalent perfluoroorganic group or a fluorine atom which may have an ethereal oxygen atom, R 14 is a monovalent perfluoroorganic group optionally having an ethereal oxygen atom, a fluorine atom or -R 11 (SO2X(SO2R f ) a ) - M + The group shown. + H + , a monovalent metal cation or an ammonium ion in which one or more hydrogen atoms are optionally substituted by a hydrocarbon group, R f It is a linear or branched perfluoroalkyl group which may have an ethereal oxygen atom, X is an oxygen atom, a nitrogen atom or a carbon atom, and when X is an oxygen atom, a=0, when X is a nitrogen atom, a=1, and when X is a carbon atom, a=2.

[0025] In the formula (u12) described below, R 21 is a perfluoroalkylene group having 1 to 6 carbon atoms or a perfluoroalkylene group having 2 to 6 carbon atoms having an ethereal oxygen atom between carbon-carbon bonds, R 22 is a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 2 to 6 carbon atoms having an ethereal oxygen atom between carbon-carbon bonds, or -R 21 (SO2X(SO2R f ) a ) - M + The group shown. + 、R f and X are the same as above.

[0026] In the formula (u21) described below, R 41 、R 42 、R 43 、R 44 、R 45 and R 46 Each independently represents a monovalent perfluoroorganic group or a fluorine atom which may have an ethereal oxygen atom.

[0027] In the formula (u22) described below, s is 0 or 1, R 51 and R 52 are independently a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a spiro ring formed by connecting them together (wherein s is 0), R 53 and R 54 are independently a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms, R 55 It is a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms.

[0028] [7] The catalyst layer-forming liquid according to [6], wherein the unit containing a cyclic ether structure contains a unit represented by the formula (u22).

[0029] [8] The catalyst layer forming liquid according to [7], wherein the unit containing a cyclic ether structure further contains at least one of the unit represented by the above formula (u11) and the unit represented by the above formula (u12).

[0030] [9] The catalyst layer-forming liquid according to any one of [6] to [8], wherein the polymer further comprises a unit based on a perfluoromonomer, and the unit based on the perfluoromonomer is a unit that does not contain a cyclic ether structure and has an ion exchange group.

[0031]

[10] The catalyst layer-forming liquid according to any one of [6] to [9], wherein the polymer further includes units based on tetrafluoroethylene.

[0032]

[11] A membrane electrode assembly characterized in that it comprises: an anode having a catalyst layer, a cathode having a catalyst layer, and a solid polymer electrolyte membrane arranged between the anode and the cathode, and at least one of the catalyst layer of the anode and the catalyst layer of the cathode is the catalyst layer described in any one of [1] to [5].

[0033] Effects of the Invention

[0034] According to the present invention, a catalyst layer, a catalyst layer forming liquid, and a membrane electrode assembly capable of forming a fuel cell having excellent power generation efficiency can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic cross-sectional view showing an example of the membrane electrode assembly of the present invention. DETAILED DESCRIPTION

[0036] The meanings of the terms used in the present invention are as follows.

[0037] A "unit" in a polymer refers to an atomic group derived from a single molecule of a monomer, formed by polymerization of the monomer. A unit may be formed directly through a polymerization reaction, or may be formed by treating the polymer obtained by polymerization to convert a portion of the unit into another structure. The content (mol %) of each unit relative to the total units in the polymer can be determined by analyzing the polymer using nuclear magnetic resonance spectroscopy.

[0038] The "precursor group of an ion exchange group" means a group that can be converted into an ion exchange group by a treatment such as hydrolysis treatment, acidification treatment, or salt exchange with other metal cations.

[0039] The "average particle size of the carrier" refers to the arithmetic mean of the particle sizes (diameters) of 100 random carriers observed using a TEM (transmission electron microscope). When the observed particles are non-spherical, they are considered spherical and their diameters are measured. The same applies to the average particle size of the catalyst.

[0040] The "TQ value" of a polymer is the volume flow rate value of the polymer, which is determined using the method described in the Examples. The TQ value is an indicator of molecular weight.

[0041] The unit represented by the formula (u11) is referred to as unit (u11). The units represented by other formulae are described similarly.

[0042] In addition, the monomer represented by formula (m11) is referred to as monomer (m11). The monomers represented by other formulae are described similarly.

[0043] The group represented by formula (g1) is referred to as group (g1). The same applies to groups represented by other formulae.

[0044] A unit containing at least one cyclic ether structure selected from the group consisting of unit (u11), unit (u12), unit (u21), and unit (u22) may be referred to as a "specific cyclic ether structure unit."

[0045] Monomer (m11), monomer (m12), monomer (m21), and monomer (m22) may be collectively referred to as "specific cyclic monomers."

[0046] [Catalyst layer]

[0047] The catalyst layer of the present invention (hereinafter also referred to as "the present catalyst layer") comprises: a supported catalyst having a support containing a metal oxide and a catalyst supported on the support, and a polymer having a specific cyclic ether structural unit and an ion exchange group (hereinafter also referred to as polymer (H)).

[0048] Furthermore, the total content of the specific cyclic ether structural units is 30 mol% or more relative to all units contained in the polymer (H).

[0049] The use of this catalyst layer can provide a fuel cell with excellent power generation efficiency. The details of the reason for this are not clear, but it is presumed to be based on the following reasons.

[0050] It is speculated that the interaction between the ether-bonded oxygen atoms contained in the specific cyclic ether structural unit of polymer (H) and the oxygen atoms of the metal oxide of the support allows polymer (H) to be uniformly attached to the surface of the metal oxide. This is believed to effectively demonstrate the function of the catalyst layer and improve the power generation efficiency of the fuel cell. In particular, the specific cyclic ether structural unit has a three-dimensional structure, resulting in excellent oxygen permeability.

[0051] <Supported Catalyst>

[0052] The present catalyst layer includes a supported catalyst having a support including a metal oxide and a catalyst supported on the support.

[0053] The method for producing the supported catalyst is not particularly limited, and specific examples thereof include a reverse micelle method, a colloid method, and an impregnation method.

[0054] (Carrier)

[0055] Specific examples of metal oxides contained in the carrier include oxides of at least one metal element selected from the group consisting of rare earth elements, alkaline earth metals, transition metals (preferably niobium, zirconium, molybdenum, tantalum, and tungsten), bismuth, tin, antimony, and indium. From the perspective of better power generation efficiency of the fuel cell, oxides containing tin are preferred.

[0056] From the perspective of improving electrical conductivity, the carrier can also be doped with a dopant. As a specific example of the dopant, the metal elements contained in the above-mentioned metal oxide can be cited. For example, when the main element (that is, the metal element with the highest content in the metal oxide) is tin, as the dopant, at least one selected from the group consisting of vanadium, niobium, tantalum, chromium, molybdenum, tungsten, phosphorus, arsenic, antimony, bismuth, fluorine, chlorine, bromine and iodine can be cited. From the perspective of further improving electrical conductivity, at least one metal element selected from the group consisting of antimony, tungsten, niobium and tantalum is preferred, and at least one metal element selected from the group consisting of antimony, tungsten and niobium is particularly preferred.

[0057] The shape of the carrier is not particularly limited. The average particle size of the carrier is also not particularly limited as long as it can support the catalyst. From the perspective of achieving better power generation efficiency, it is preferably 5 to 500 nm, more preferably 5 to 200 nm, further preferably 5 to 100 nm, and particularly preferably 20 to 100 nm.

[0058] In the present catalyst layer, the ratio of the mass of the polymer (H) to the mass of the support (polymer (H) content / support content) is preferably 0.05 to 0.3, particularly preferably 0.05 to 0.1, from the perspective of achieving better power generation efficiency of the fuel cell.

[0059] (catalyst)

[0060] The catalyst is supported on a carrier, preferably on the surface of the carrier.

[0061] Specific examples of the material constituting the catalyst include noble metals, and platinum or a platinum alloy is preferred from the viewpoint of excellent catalytic activity and stability.

[0062] The shape of the catalyst is not particularly limited, but is preferably a pellet shape.

[0063] The average particle size of the catalyst is not particularly limited as long as it can exhibit its performance, but is preferably 1 to 100 nm, particularly preferably 1 to 20 nm.

[0064] From the perspective of achieving better power generation efficiency of the fuel cell and cost, the amount of the supported catalyst is preferably 5 to 50% by mass, particularly preferably 5 to 20% by mass, relative to the total mass of the supported catalyst.

[0065] <Polymer (H)>

[0066] The polymer (H) is a polymer having an ion exchange group and has a specific cyclic ether structural unit, that is, a unit containing at least one cyclic ether structure selected from the group consisting of the following unit (u11), unit (u12), unit (u21) and unit (u22).

[0067]

[0068] R 11 It is a divalent perfluoroorganic group optionally having an ether-bonded oxygen atom. The organic group is a group having one or more carbon atoms. As the divalent perfluoroorganic group, a perfluoroalkylene group is preferred. When the perfluoroalkylene group has an ether-bonded oxygen atom, the number of oxygen atoms may be one or two or more. In addition, the oxygen atom may be located between carbon-carbon bonds of the perfluoroalkylene group or at the end of a carbon atom bond. The perfluoroalkylene group may be linear or branched, preferably linear.

[0069] R 12 、R 13 、R 15 and R 16 Each independently represents a monovalent perfluoro organic group or a fluorine atom optionally having an ethereal oxygen atom. As the monovalent perfluoro organic group, a perfluoroalkyl group is preferred. In terms of high polymerization reactivity, R 15 and R 16 At least one of them is a fluorine atom, and more preferably both of them are fluorine atoms.

[0070] R 14 is a monovalent perfluoroorganic group optionally having an ethereal oxygen atom, a fluorine atom or -R 11 (SO2X(SO2R f )a ) - M + The group shown. As a monovalent perfluoro organic group, a perfluoroalkyl group is preferred. When the perfluoroalkyl group has an ether-bonded oxygen atom, the number of oxygen atoms may be 1 or more. In addition, the oxygen atom may be located between the carbon-carbon bonds of the perfluoroalkyl group or at the end of the carbon atom bond. The perfluoroalkyl group may be linear or branched, preferably linear. In formula (u11), two R 11 When 2 R 11 They are optionally the same as or different from each other.

[0071] M + H + , monovalent metal cations (e.g., potassium ions, sodium ions), or ammonium ions in which one or more hydrogen atoms are optionally substituted with hydrocarbon groups (e.g., methyl groups, ethyl groups). From the viewpoint of high conductivity, H + .

[0072] R f is a linear or branched perfluoroalkyl group optionally having an ethereal oxygen atom. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 8, particularly preferably 1 to 6. In formula (u11), two or more R f When 2 or more R f They are optionally the same as or different from each other.

[0073] 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; and when X is a carbon atom, a=2.

[0074] As -(SO2X(SO2R f ) a ) - M + Specific examples of the group include sulfonic acid group (-SO3 - M + sulfonimide (-SO2N(SO2R f ) - M + yl), or sulfonemethide group (-SO2C(SO2R f )2) - M + base).

[0075] The unit (u11) is preferably the following unit (u11-1).

[0076]

[0077] R 21A perfluoroalkylene group having 1 to 6 carbon atoms or a perfluoroalkylene group having 2 to 6 carbon atoms having an ether-bonded oxygen atom between carbon-carbon bonds. When the perfluoroalkylene group has an ether-bonded oxygen atom, the number of oxygen atoms may be 1 or 2 or more. The perfluoroalkylene group may be linear or branched, but is preferably linear.

[0078] R 22 is a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 2 to 6 carbon atoms having an ethereal oxygen atom between carbon-carbon bonds, or -R 21 (SO2X(SO2R f ) a ) - M + When the perfluoroalkyl group has an ether-bonded oxygen atom, the number of oxygen atoms may be 1 or more. The perfluoroalkyl group may be linear or branched, preferably linear. In formula (u12), the group containing 2 R 21 When 2 R 21 They are optionally the same as or different from each other.

[0079] M + 、R f , X and a are respectively the same as M in formula (u11) + 、R f , X and a are synonymous.

[0080] Specific examples of the unit (u12) include the following units (u12-1) and (u12-2).

[0081] Where M + and M in formula (u11) + Synonymous.

[0082]

[0083]

[0084] R 41 、R 42 、R 43 、R 44 、R 45 and R 46 Each independently represents a monovalent perfluoroorganic group or fluorine atom optionally having an ethereal oxygen atom. As the monovalent perfluoroorganic group, a perfluoroalkyl group is preferred. When the perfluoroalkyl group has an ethereal oxygen atom, the number of oxygen atoms may be 1 or 2 or more. In addition, the oxygen atom may be located between carbon-carbon bonds of the perfluoroalkyl group or at the end of a carbon atom bond. The perfluoroalkyl group may be linear or branched, preferably linear.

[0085] From the perspective of high polymerization reactivity, R45 and R 46 It is preferred that at least one of them is a fluorine atom, and it is particularly preferred that both of them are fluorine atoms.

[0086] The unit (u21) is preferably the following unit (u21-1).

[0087]

[0088] s is 0 or 1, preferably 0.

[0089] R 51 and R 52 Each independently represents a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a spiro ring formed by connecting these groups (when s is 0).

[0090] R 53 and R 54 Each independently represents a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms.

[0091] R 55 is a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms. 55 A fluorine atom is preferred.

[0092] The perfluoroalkyl group and the perfluoroalkoxy group may be linear or branched, but are preferably linear.

[0093] The unit (u22) is preferably the following unit (u22-1).

[0094]

[0095] The total content of the specific cyclic ether structural units relative to all units contained in the polymer (H) is 30 mol% or more, preferably 40 mol% or more, more preferably 65 mol% or more, from the perspective of better power generation efficiency of the fuel cell.

[0096] The upper limit of the total content of the specific cyclic ether structural units relative to all units contained in the polymer (H) is preferably 100 mol%, particularly preferably 80 mol%.

[0097] The polymer (H) may contain only one specific cyclic ether structural unit or two or more specific cyclic ether structural units. When only one specific cyclic ether structural unit is contained, the total content mentioned above means the content of only one specific cyclic ether structural unit.

[0098] The polymer (H) may further include units based on perfluoromonomers (hereinafter also referred to as "perfluoromonomer units"). The perfluoromonomer units include units that do not contain a cyclic ether structure and have an ion exchange group.

[0099] Examples of the unit based on a perfluoromonomer include the following unit (u31) and unit (u32). From the viewpoint of more excellent power generation efficiency of the fuel cell, the unit (u32) is preferred.

[0100]

[0101] Z is a fluorine atom or a trifluoromethyl group, m is an integer from 0 to 3, p is 0 or 1, n is 1 to 12, and m+p>0.

[0102] M + With the above formula (u11) M + Synonymous.

[0103]

[0104] Q 1 It is a perfluoroalkylene group which may have an ethereal oxygen atom.

[0105] Q 2 It is a single bond or a perfluoroalkylene group which may have an ethereal oxygen atom.

[0106] Q 1 and Q 2 When the perfluoroalkylene group has an ether-bonded oxygen atom, the number of oxygen atoms may be 1 or 2 or more. In addition, the oxygen atom may be located between carbon-carbon bonds of the perfluoroalkylene group or at the end of a carbon bond.

[0107] The perfluoroalkylene group may be linear or branched, preferably linear. The perfluoroalkylene group preferably has 1 to 6 carbon atoms, particularly preferably 1 to 4. A carbon number of 6 or less lowers the boiling point of the raw fluorinated monomer, making distillation purification easier. Furthermore, a carbon number of 6 or less suppresses the reduction in the ion exchange capacity of the polymer (H), improving proton conductivity.

[0108] Q 2 Preferably, it is a perfluoroalkylene group having 1 to 6 carbon atoms which may have an ethereal oxygen atom. 2 is a perfluoroalkylene group having 1 to 6 carbon atoms which may have an ethereal oxygen atom, and Q 2 Compared with the case of a single bond, the stability of power generation performance is excellent when the fuel cell is operated for a long time.

[0109] Optimum Q 1 and Q 2 At least one of the fluorinated monomers is a C1-6 perfluoroalkylene group having an etheric oxygen atom. The fluorinated monomer containing a C1-6 perfluoroalkylene group having an etheric oxygen atom can be synthesized without a fluorination reaction using fluorine gas, and thus has a good yield and is easy to produce.

[0110] Y is a fluorine atom or a monovalent perfluoro organic group. Y is preferably a fluorine atom or a C1-6 linear perfluoroalkyl group which may have an ethereal oxygen atom.

[0111] q is 0 or 1.

[0112] R f , X and a are respectively the same as R f , X and a are synonymous.

[0113] From the viewpoint of easy production and easy industrial implementation, the unit (u32) is preferably the units (u32-1) to (u32-3), and more preferably the unit (u32-1).

[0114]

[0115] The total content of the perfluoromonomer units is preferably 5 to 40 mol%, more preferably 10 to 35 mol%, particularly preferably 15 to 30 mol%, based on all units contained in the polymer (H).

[0116] The polymer (H) may contain only one type of perfluoromonomer unit or two or more types. When the polymer (H) contains only one type of perfluoromonomer unit, the total content means the content of only one type.

[0117] The polymer (H) may further contain units derived from tetrafluoroethylene (hereinafter also referred to as "tetrafluoroethylene units"). This imparts water repellency, thereby increasing the ability of the catalyst layer to discharge water and improving the power generation efficiency of the fuel cell.

[0118] The content of the tetrafluoroethylene units is preferably 5 to 40 mol %, more preferably 5 to 35 mol %, and particularly preferably 5 to 30 mol %, based on all units contained in the polymer (H).

[0119] The polymer (H) may also contain units other than those mentioned above. Specific examples of units other than those mentioned above include units based on monomers such as perfluoro(3-butenyl vinyl ether), perfluoro(allyl vinyl ether), perfluoroα-olefins (such as hexafluoropropylene), and perfluoro(alkyl vinyl ether).

[0120] The ion exchange group contained in the polymer (H) is preferably the following group (g1).

[0121] -(SO2X(SO2R f ) a ) - M + (g1)

[0122] M + 、R f , X and a are respectively the same as M in the above formula (u11)+ 、R f , X and a are synonymous.

[0123] Specific examples of the group (g1) include sulfonic acid groups (-SO3 - M + sulfonimide (-SO2N(SO2R f ) - M + methyl), or sulfonylmethyl (-SO2C(SO2R f )2) - M + Group), preferably sulfonic acid group (-SO3 - M + base).

[0124] The polymer (H) is a polymer having an ion-exchange group. However, when the specific cyclic ether structural unit in the polymer (H) has an ion-exchange group, it is not necessarily necessary to contain other units having an ion-exchange group. When the specific cyclic ether structural unit in the polymer (H) does not have an ion-exchange group, it is necessary to contain a unit having an ion-exchange group such as a perfluoromonomer unit.

[0125] A preferred embodiment of the polymer (H) is an embodiment in which the unit containing a cyclic ether structure contains the unit (u22) from the viewpoint of further improving the power generation efficiency of the fuel cell.

[0126] In addition, as a more preferred embodiment of the polymer (H), from the perspective of particularly excellent power generation efficiency of the fuel cell, the above-mentioned unit containing a cyclic ether structure contains at least one of the unit (u22), the unit (u11) and the unit (u12).

[0127] Another more preferred embodiment of the polymer (H) is an embodiment comprising the unit (u22), a perfluoromonomer unit, and a tetrafluoroethylene unit, from the viewpoint of particularly excellent power generation efficiency of a fuel cell.

[0128] <Physical properties>

[0129] The ion exchange capacity of polymer (H) is preferably 1.1 to 2.8 milliequivalents / g dry resin, more preferably 1.2 to 2.8 milliequivalents / g dry resin, and particularly preferably 1.3 to 2.3 milliequivalents / g dry resin. When the ion exchange capacity is above the lower limit, the conductivity of polymer (H) is enhanced, thereby enabling sufficient battery output when used as a polymer in a fuel cell catalyst layer. When the ion exchange capacity is below the upper limit, polymer synthesis is facilitated.

[0130] From the viewpoint of preventing cracking of the electrode, the TQ value of the polymer (H) is preferably 200°C or higher, more preferably 210°C or higher. From the viewpoint of preventing thermal decomposition of the fluororesin, it is preferably 330°C or lower, more preferably 310°C or lower, and particularly preferably 300°C or lower. Furthermore, when the TQ value is at least the lower limit and at most the upper limit, the polymer (H) also exhibits excellent hot water resistance.

[0131] <Purpose>

[0132] The present catalyst layer can be suitably used as a catalyst layer in a membrane electrode assembly described later.

[0133] <Method for producing polymer (H)>

[0134] The polymer (H) is produced, for example, by polymerizing a specific cyclic monomer with at least one of a perfluoromonomer and tetrafluoroethylene as needed, and converting the precursor groups of the obtained polymer (F) having ion-exchange group precursors into ion-exchange groups.

[0135] Hereinafter, each monomer (monomer (m11), monomer (m12), monomer (m21), and monomer (m22)) that can be used for producing the polymer (H) will be described.

[0136] (Single (m11))

[0137]

[0138] R 11 ~R 16 Respectively with R of formula (u11) 11 ~R 16 Synonymous.

[0139] Specific examples of the monomer (m11) include the following monomers (m11-1) to (m11-4). Monomer (m11-1) is preferred because of its ease of synthesis and high polymerization reactivity.

[0140]

[0141] The monomer (m11) can be synthesized by the methods described in, for example, International Publication No. 2003 / 037885, Japanese Patent Application Laid-Open No. 2005-314388, and Japanese Patent Application Laid-Open No. 2009-040909.

[0142] (Single (m12))

[0143]

[0144] R 21 and R22 Respectively with R of formula (u12) 21 ~R 22 Synonymous.

[0145] Specific examples of the monomer (m12) include the following monomer (m12-1) and monomer (m12-2).

[0146]

[0147] The monomer (m12) can be synthesized by the method described in, for example, JP-A-2006-152249.

[0148] (Single (m21))

[0149]

[0150] R 41 ~R 46 Respectively with R of formula (u21) 41 ~R 46 Synonymous.

[0151] Specific examples of the monomer (m21) include the following monomers (m21-1) and (m21-2). Monomer (m21-1) is particularly preferred in terms of ease of synthesis and high polymerization reactivity.

[0152]

[0153] The monomer (m21) can be synthesized by the method described in, for example, International Publication No. 2000 / 056694, pamphlet; Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1989, vol. 4, pp. 938-42.

[0154] (Single (m22))

[0155]

[0156] R 51 ~R 55 and s are respectively related to R 51 ~R 55 Synonymous with s.

[0157] Specific examples of the monomer (m22) include the following monomers (m22-1) to (m22-11), and the monomer (m22-1) is particularly preferred because it has a high effect of further improving the electrode performance of the polymer (H).

[0158]

[0159] The monomer (m22) can be synthesized by the method described in, for example, Macromolecule, Vol. 26, No. 22, 1993, pp. 5829-5834; Japanese Patent Application Laid-Open No. 6-92957, and the like.

[0160] In the production of the polymer (H), a perfluoromonomer containing no cyclic ether structure and a precursor group of an ion exchange group may be used.

[0161] Examples of the perfluoromonomer include the following monomer (m31) and monomer (m32). Monomer (m32) is preferred because it provides better power generation efficiency of the fuel cell.

[0162] (Single (m31))

[0163] CF2=CF(OCF2CFZ) m O p (CF2) n SO2F(m31)

[0164] Z, m, p and n have the same meanings as Z, m, p and n in formula (u31), respectively.

[0165] The monomer (m31) is preferably monomers (m31-1) to (m31-3).

[0166] CF2=CFO(CF2) n1 SO2F(m31-1)

[0167] CF2=CFOCF2CF(CF3)O(CF2) n2 SO2F(m31-2)

[0168] CF2=CF(OCF2CF(CF3)) m3 O(CF2) n3 SO2F(m31-3)

[0169] Here, n1, n2, and n3 are integers of 1 to 8, and m3 is an integer of 1 to 3.

[0170] The monomer (m31) can be synthesized by the method described in, for example, Prog. Polym. Sci., Vol. 12, 1986, pp. 233-237; U.S. Patent No. 4,330,654, and the like.

[0171] (Single(m32))

[0172]

[0173] Q 1 , Q 2, Y and q are respectively the same as Q in formula (u32) 1 , Q 2 , Y and q are synonymous.

[0174] From the viewpoint of easy production of the polymer (H) and ease of industrial implementation, the monomer (m32) is preferably the following monomers (m32-1) to (m32-3), and the monomer (m32-1) is particularly preferred.

[0175]

[0176] The monomer (m32) can be synthesized by the method described in, for example, International Publication No. 2007 / 013533, Japanese Patent Application Laid-Open No. 2008-202039, and the like.

[0177] Tetrafluoroethylene can also be used in the production of the polymer (H).

[0178] Monomers other than those mentioned above may be used in the production of polymer (H). Specific examples of such monomers include perfluoro(3-butenyl vinyl ether), perfluoro(allyl vinyl ether), perfluoroα-olefins (such as hexafluoropropylene), and perfluoro(alkyl vinyl ethers).

[0179] An example of a method for converting a precursor group (—SO 2 F) of an ion-exchange group into an ion-exchange group is shown below.

[0180] As a method for converting the group represented by -SO2F into a sulfonic acid group (-SO3 - H + ) method, the following method (i) can be cited as a method for converting the group represented by -SO2F into a sulfonimide group (-SO2N(SO2R f ) - H + ) method, the following method (ii) can be mentioned.

[0181] (i) A method in which a group represented by -SO2F is hydrolyzed to form a sulfonate, and the sulfonate is converted into an acid form to a sulfonic acid group.

[0182] (ii) A method in which the group represented by -SO2F is imidized to form a salt-type sulfonyl imide group, and then further acidified to convert it into an acid-type sulfonyl imide group.

[0183] (i) Method:

[0184] Hydrolysis is carried out, for example, by contacting a polymer having a precursor of an ion exchange group with a basic compound in a solvent. Examples of the basic compound include sodium hydroxide and potassium hydroxide. Examples of the solvent include water and a mixed solvent of water and a polar solvent. Examples of the polar solvent include alcohols (methanol, ethanol, etc.) and dimethyl sulfoxide.

[0185] The conversion to an acid form in (i) is carried out, for example, by bringing the polymer having a sulfonate into contact with an aqueous solution of hydrochloric acid, sulfuric acid or the like.

[0186] The hydrolysis and acidification are usually carried out at 0 to 120°C.

[0187] (ii) Method:

[0188] As imidization, the following methods can be mentioned.

[0189] (ii-1) The group represented by -SO2F is combined with R f Method for SO2NHM reaction.

[0190] (ii-2) In the presence of an alkali metal hydroxide, an alkali metal carbonate, MF, ammonia or a primary to tertiary amine, the group represented by -SO2F is reacted with R f Method of SO2NH2 reaction.

[0191] (ii-3) The group represented by -SO2F is combined with R f Method for the reaction of SO2NMSi(CH3)3.

[0192] Wherein, M is an alkali metal or a primary to quaternary ammonium.

[0193] The acidification in (ii) is performed by treating the polymer having a salt-type sulfonimide group with an acid (sulfuric acid, nitric acid, hydrochloric acid, etc.).

[0194] It should be noted that the polymer (H) whose ion exchange group is a sulfonimide group can also be produced by polymerizing a monomer obtained by converting the group represented by -SO2F of monomer (m11), (m12), (m31) or (m32) into a sulfonimide group with monomer (m21) or monomer (m22).

[0195] The monomer obtained by converting the group represented by -SO2F into a sulfonyl imide group can be produced as follows: chlorine or bromine is added to the carbon-carbon double bond of monomer (m11), (m12), (m31) or (m32), and the group represented by -SO2F is converted into a sulfonyl imide group by method (ii), followed by dechlorination or debromination reaction using metallic zinc.

[0196] [Catalyst layer forming liquid]

[0197] The catalyst layer-forming liquid of the present invention (hereinafter also referred to as "the present catalyst layer-forming liquid") comprises: a supported catalyst having a support containing a metal oxide and a catalyst supported on the support, a polymer having a specific cyclic ether structural unit and an ion exchange group (polymer (H)), and a solvent.

[0198] Furthermore, the content of the cyclic ether structural unit is 30 mol% or more relative to all units contained in the polymer (H).

[0199] The supported catalyst and polymer (H) contained in the present catalyst layer-forming liquid are the same as the supported catalyst and polymer (H) in the present catalyst layer described above, and therefore, their description is omitted.

[0200] The present catalyst layer-forming liquid can be used to form the above-mentioned present catalyst layer.

[0201] Examples of the solvent include water and organic solvents, and a mixed solvent thereof may also be used.

[0202] Specific examples of the organic solvent include methanol, ethanol, 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. These organic solvents may be used alone or in combination of two or more.

[0203] The solid content of the catalyst layer forming liquid is preferably 15 to 45% by mass, more preferably 20 to 35%, and particularly preferably 20 to 30% by mass relative to the total mass of the catalyst layer forming liquid.

[0204] In addition, the solid content mass of the present catalyst layer forming liquid means the mass excluding the solvent from the present catalyst layer forming liquid.

[0205] [Membrane Electrode Assembly]

[0206] The membrane electrode assembly of the present invention comprises: an anode having a catalyst layer, a cathode having a catalyst layer, and a solid polymer electrolyte membrane arranged between the above-mentioned anode and the above-mentioned cathode, and at least one of the above-mentioned catalyst layer of the above-mentioned anode and the above-mentioned catalyst layer of the above-mentioned cathode is the above-mentioned catalyst layer.

[0207] The membrane electrode assembly can be suitably used in a polymer electrolyte fuel cell.

[0208] The membrane electrode assembly of the present invention comprises the above-mentioned catalyst, and thus can form a fuel cell having excellent power generation efficiency.

[0209] Figure 1 This is a schematic cross-sectional view showing an example of a membrane electrode assembly according to the present invention. The membrane electrode assembly 10 includes an anode 13 having a catalyst layer 11 and a gas diffusion layer 12, a cathode 14 having a catalyst layer 11 and a gas diffusion layer 12, and a solid polymer electrolyte membrane 15 disposed between the anode 13 and cathode 14 in contact with the catalyst layer 11.

[0210] At least one of the catalyst layer 11 included in the anode 13 and the catalyst layer 11 included in the cathode 14 may be the above-mentioned catalyst layer, or both may be the above-mentioned catalyst layers. It should be noted that when one catalyst layer 11 is the above-mentioned catalyst layer and the other catalyst layer 11 is a catalyst layer other than the above-mentioned catalyst layer, a known catalyst layer may be used as the catalyst layer other than the present catalyst layer.

[0211] As a method for forming the catalyst layer 11 , the following method can be mentioned.

[0212] (i) A method of applying a catalyst layer forming liquid onto the solid polymer electrolyte membrane 15, the gas diffusion layer 12, or a carbon layer described later and drying the liquid.

[0213] (ii) A method in which a catalyst layer forming liquid is applied onto a substrate film, dried to form the catalyst layer 11 , and the catalyst layer 11 is transferred onto the solid polymer electrolyte membrane 15 .

[0214] The gas diffusion layer 12 has a function of uniformly diffusing gas in the catalyst layer 11 and a function of serving as a current collector.

[0215] Examples of the gas diffusion layer 12 include carbon paper, carbon cloth, and carbon felt. The gas diffusion layer 12 is preferably subjected to a water-repellent treatment using polytetrafluoroethylene or the like.

[0216] It should be noted that Figure 1 The membrane electrode assembly 10 includes a gas diffusion layer 12 , but the gas diffusion layer is an optional component and may not be included in the membrane electrode assembly.

[0217] The solid polymer electrolyte membrane 15 is a membrane containing a polymer having ion exchange groups.

[0218] Examples of polymers having ion exchange groups include the aforementioned polymer (H) and known polymers having ion exchange groups. Specific examples of known polymers include polymers obtained by converting the group represented by -SO2F of a polymer having units based on monomer (m31) and tetrafluoroethylene units into a sulfonic acid group, and polymers obtained by converting the group represented by -SO2F of a polymer having units based on monomer (m32) and tetrafluoroethylene units into a sulfonic acid group.

[0219] The solid polymer electrolyte membrane 15 can be formed by, for example, applying a liquid polymer composition on a substrate film or the catalyst layer 11 and drying it (casting method).

[0220] 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.

[0221] Heat treatment is preferably performed to stabilize the solid polymer electrolyte membrane 15. The heat treatment temperature depends on the type of polymer, but is preferably 130 to 200°C.

[0222] The solid polymer electrolyte membrane 15 may be treated with hydrogen peroxide water as needed.

[0223] The solid polymer electrolyte membrane 15 may be reinforced with a reinforcing material. Examples of the reinforcing material include porous materials, fibers, woven fabrics, and non-woven fabrics. Examples of the reinforcing material include polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymers, tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymers, polyethylene, polypropylene, and polyphenylene sulfide.

[0224] To further improve durability, the solid polymer electrolyte membrane 15 may contain one or more atoms selected from the group consisting of cerium and manganese. Cerium and manganese decompose hydrogen peroxide, which is a causative agent for degradation of the solid polymer electrolyte membrane 15. Cerium and manganese are preferably present in the solid polymer electrolyte membrane 15 in the form of ions, but may be present in any form within the solid polymer electrolyte membrane 15 as long as they are present in the form of ions.

[0225] The solid polymer electrolyte membrane 15 may contain silicon dioxide or a heteropoly acid (such as zirconium phosphate, phosphomolybdic acid, or phosphotungstic acid) as a moisture retaining agent for preventing drying.

[0226] The membrane electrode assembly 10 is produced, for example, by the following method.

[0227] (i) A method in which the catalyst layer 11 is formed on a solid polymer electrolyte membrane 15 to produce a membrane-catalyst layer assembly, and the membrane-catalyst layer assembly is sandwiched between gas diffusion layers 12 .

[0228] (ii) A method in which the catalyst layer 11 is formed on the gas diffusion layer 12 to form electrodes (anode 13 and cathode 14), and the solid polymer electrolyte membrane 15 is sandwiched between the electrodes.

[0229] The membrane electrode assembly 10 may include a carbon layer (not shown) between the catalyst layer 11 and the gas diffusion layer 12. The carbon layer improves gas diffusivity on the surface of the catalyst layer 11, further enhancing the power generation performance of the fuel cell.

[0230] The carbon layer comprises, for example, carbon and a nonionic fluorine-containing polymer. Specific examples of carbon are preferably carbon nanofibers having a fiber diameter of 1 to 1000 nm and a fiber length of 1000 μm or less. Specific examples of the nonionic fluorine-containing polymer include polytetrafluoroethylene.

[0231] Example

[0232] The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these Examples. It should be noted that Examples 1 to 11 are Preparation Examples, Examples 12 to 20 are Examples, and Examples 21 and 22 are Comparative Examples.

[0233] [Ion exchange capacity]

[0234] The ion exchange capacity of the polymer (H) (polymer after hydrolysis treatment) was determined by the following method.

[0235] The polymer (H) was placed in a glove box and allowed to dry for at least 24 hours in an atmosphere of dry nitrogen. The dry mass of the polymer (H) was measured in the glove box.

[0236] The polymer (H) was immersed in a 2 mol / L sodium chloride aqueous solution, left at 60°C for 1 hour, and then cooled to room temperature. The sodium chloride aqueous solution in which the polymer (H) was immersed was titrated with a 0.5 mol / L sodium hydroxide aqueous solution to determine the ion exchange capacity of the polymer (H).

[0237] [TQ value]

[0238] The polymer (H) was melt-extruded using a flow tester (CFT-500D, manufactured by Shimadzu Corporation) equipped with a nozzle of 1 mm in length and inner diameter of 1 mm at an extrusion pressure of 2.94 MPa (gauge pressure) while changing the temperature. The extrusion amount of the polymer (H) was measured while changing the temperature. The extrusion amount was set to 100 mm. 3 The temperature at which the temperature drops to 0.05°C / s was determined as the TQ value of the polymer (H).

[0239] [Synthesis of Monomer (m11-1)]

[0240] Monomer (m11-1) was synthesized according to the method described in Examples on pages 37-42 of International Publication No. 2003 / 037885.

[0241]

[0242] [Synthesis of Monomer (m12-1)]

[0243] According to the method described in Example 1 of JP-A-2006-152249, a monomer (m12-1) was synthesized.

[0244]

[0245] [Synthesis of Monomer (m31-4)]

[0246] The monomer (m31-4) was synthesized by a known method.

[0247]

[0248] [Synthesis of Monomer (m31-5)]

[0249] The monomer (m31-5) was synthesized by a known method.

[0250] CF2=CFOCF2CF2SO2F(m31-5)

[0251] [Synthesis of Monomer (m32-1)]

[0252] Compound (m32-1) was synthesized according to the method described in Example 1 of JP-A-2008-202039.

[0253]

[0254] [Synthesis of Monomer (m21-1)]

[0255] The monomer (m21-1) was synthesized according to a known method.

[0256]

[0257] [Synthesis of Monomer (m22-1)]

[0258] The monomer (m22-1) was synthesized according to a known method.

[0259]

[0260] [Synthesis of Monomer (m24-1)]

[0261] The monomer (m24-1) was synthesized according to a known method.

[0262]

[0263] [Free radical polymerization initiator]

[0264] As radical polymerization initiators, the following compounds (i-1) to (i-3) were prepared.

[0265] <Compound (i-1)>

[0266]

[0267] <Compound (i-2)>

[0268] ((CH3)2CHOCOO)2(i-2)

[0269] <Compound (i-3)>

[0270] (C3F7COO)2(i-3)

[0271] [Solvent]

[0272] The following compounds (s-1) and (s-2) were prepared as solvents.

[0273] <Compound (s-1)>

[0274] CClF2CF2CHClF(s-1)

[0275] <Compound (s-2)>

[0276] CH3CCl2F(s-2)

[0277] [Manufacturing of supported catalyst]

[0278] 2.7 g of chloroplatinic acid hexahydrate was dissolved in 300 ml of ultrapure water, and 15.3 g of sodium sulfite was added and stirred. The solution was diluted with 1100 ml of water and the pH of the solution was adjusted to 5 using NaOH. Hydrogen peroxide was then added and the pH was readjusted to 5 using NaOH.

[0279] The obtained solution was mixed with 300 mL of ultrapure water in which 4 g of SnO2 powder having an average particle size of 30 nm was dispersed, and stirred at 90° C. for 3 hours. After cooling to room temperature, the mixture was filtered, washed with ultrapure water and alcohol, and dried at 80° C. to obtain a Pt-loaded SnO2 catalyst powder as a supported catalyst. Using high-frequency induction heating emission spectroscopy (ICP), it was confirmed that the Pt loading was 20% by mass.

[0280] [Example 1: Preparation Example]

[0281] Into a 125 mL stainless steel autoclave were placed 9.15 g of compound (m22-1), 45.65 g of compound (m32-1), and 6.4 mg of compound (i-2). The mixture was thoroughly degassed under cooling with liquid nitrogen. The temperature was then raised to 40°C and maintained for 24.5 hours. The autoclave was then cooled to terminate the reaction.

[0282] The product was diluted with compound (s-1), and n-hexane was added to coagulate the polymer, which was then filtered. The polymer was then stirred in compound (s-1), re-coagulated with n-hexane, and dried under reduced pressure at 80°C overnight to obtain polymer (F-1). The yield was 4.5 g. The density of polymer (F-1) was measured. The results are shown in Table 1.

[0283] The polymer (F-1) was immersed in a 50°C aqueous solution containing 20% ​​by mass of methanol and 15% by mass of potassium hydroxide for 40 hours to hydrolyze the -SO2F group in the polymer (F-1) and convert it into a -SO3K group. Then, the polymer was immersed in a 3 mol / L hydrochloric acid aqueous solution for 2 hours at room temperature. The hydrochloric acid aqueous solution was replaced and the same treatment was further performed 4 times to obtain a polymer (H-1) in which the -SO3K group in the polymer was converted into a sulfonic acid group. The polymer (H-1) was thoroughly washed with ultrapure water. The ion exchange capacity of the polymer (H-1) was measured. The results are shown in Table 1.

[0284] A mixed solvent of ethanol and water (ethanol / water = 60 / 40 by mass ratio) was added to the polymer (H-1), and the solid content concentration was adjusted to 15% by mass. The mixture was stirred at 105°C for 8 hours using an autoclave to obtain a liquid composition (D-1) in which the polymer (H-1) was dispersed in the dispersion medium.

[0285] [Example 2: Preparation Example]

[0286] Into a 230 mL stainless steel autoclave, 32.4 g of compound (m22-1), 166.70 g of compound (m32-1), and 101 mg of compound (i-2) were placed and thoroughly degassed under cooling with liquid nitrogen. Subsequently, 3.87 g of tetrafluoroethylene (TFE) was added, the temperature was raised to 24°C, and after stirring for 24 hours, the autoclave was cooled to terminate the reaction.

[0287] The product was diluted with compound (s-1), and n-hexane was added to coagulate the polymer, which was then filtered. The polymer was then stirred in compound (s-1), re-coagulated with n-hexane, and dried under reduced pressure at 80°C overnight to obtain polymer (F-2). The yield was 45.9 g. The density of polymer (F-2) was measured. The results are shown in Table 1.

[0288] Using polymer (F-2), polymer (H-2) was obtained in the same manner as in Example 1. The ion exchange capacity of polymer (H-2) was measured. The results are shown in Table 1.

[0289] Using the polymer (H-2), a liquid composition (D-2) was obtained in the same manner as in Example 1.

[0290] [Example 3: Preparation Example]

[0291] Into a 230 mL stainless steel autoclave were placed 37.45 g of compound (m22-1), 120.20 g of compound (m32-1), and 25.2 mg of compound (i-2). The mixture was thoroughly degassed under cooling with liquid nitrogen. Then, 4.39 g of TFE was added, the temperature was raised to 24°C, and the mixture was stirred for 12 hours and 30 minutes. The autoclave was then cooled to terminate the reaction.

[0292] The product was diluted with compound (s-1), and n-hexane was added to coagulate the polymer, which was then filtered. The polymer was then stirred in compound (s-1), re-coagulated with n-hexane, and dried under reduced pressure at 80°C overnight to obtain polymer (F-3). The yield was 29.6 g.

[0293] Using polymer (F-3), polymer (H-3) was obtained in the same manner as in Example 1. The ion exchange capacity of polymer (H-3) was measured. The results are shown in Table 1.

[0294] Using the polymer (H-3), a liquid composition (D-3) was obtained in the same manner as in Example 1.

[0295] [Example 4: Preparation Example]

[0296] Into a 125 mL stainless steel autoclave, 8.50 g of compound (m22-1), 59.5 g of compound (m31-4), and 20.4 mg of compound (i-2) were placed and thoroughly degassed under cooling with liquid nitrogen. Subsequently, 2.5 g of TFE was added, the temperature was raised to 24°C, and after stirring for 24 hours, the autoclave was cooled to terminate the reaction.

[0297] The product was diluted with compound (s-1), and n-hexane was added to coagulate the polymer, which was then filtered. The polymer was then stirred in compound (s-1), re-coagulated with n-hexane, and dried under reduced pressure at 80°C overnight to obtain polymer (F-4). The yield was 11.1 g.

[0298] Using polymer (F-4), polymer (H-4) was obtained in the same manner as in Example 1. The ion exchange capacity of polymer (H-4) was measured. The results are shown in Table 1.

[0299] Using the polymer (H-4), a liquid composition (D-4) was obtained in the same manner as in Example 1.

[0300] [Example 5: Preparation Example]

[0301] Into a 125 mL stainless steel autoclave, 9.80 g of compound (m22-1), 37.4 g of compound (m31-5), and 14.1 mg of compound (i-2) were placed and thoroughly degassed under cooling with liquid nitrogen. Subsequently, 2.5 g of TFE was added, the temperature was raised to 24°C, and after stirring for 24 hours, the autoclave was cooled to terminate the reaction.

[0302] The product was diluted with compound (s-1), and n-hexane was added to coagulate the polymer, which was then filtered. The polymer was then stirred in compound (s-1), re-coagulated with n-hexane, and dried under reduced pressure at 80°C overnight to obtain polymer (F-5). The yield was 10.5 g.

[0303] Using polymer (F-5), polymer (H-5) was obtained in the same manner as in Example 1. The ion exchange capacity of polymer (H-5) was measured. The results are shown in Table 1.

[0304] Using the polymer (H-5), a liquid composition (D-5) was obtained in the same manner as in Example 1.

[0305] [Example 6: Preparation Example]

[0306] In a 125 mL stainless steel autoclave, 3.5 g of compound (m21-1), 76.33 g of compound (m32-1), and 8.5 mg of compound (i-2) were placed and thoroughly degassed under cooling with liquid nitrogen. The mixture was then heated to 40°C and stirred for 24 hours before cooling the autoclave to terminate the reaction.

[0307] The product was diluted with compound (s-1), and n-hexane was added to coagulate the polymer, which was then filtered. The polymer was then stirred in compound (s-1), re-coagulated with n-hexane, and dried under reduced pressure at 80°C overnight to obtain polymer (F-6). The yield was 6.4 g. The density of polymer (F-6) was measured. The results are shown in Table 1.

[0308] Using polymer (F-6), polymer (H-6) and liquid composition (D-6) were obtained in the same manner as in Example 1. The ion exchange capacity of polymer (H-6) was measured. The results are shown in Table 1.

[0309] [Example 7: Preparation Example]

[0310] Into a 125 mL stainless steel autoclave were placed 5.97 g of compound (m11-1), 13.70 g of compound (m22-1), 13.75 g of compound (s-1), and 17.1 mg of compound (i-1). The mixture was thoroughly degassed under cooling with liquid nitrogen. The temperature was then raised to 65°C and maintained for 6 hours. The autoclave was then cooled to terminate the reaction.

[0311] The product was diluted with compound (s-1), and n-hexane was added to coagulate the polymer, which was then filtered. The polymer was then stirred in compound (s-1), re-coagulated with n-hexane, and dried under reduced pressure at 80°C overnight to obtain polymer (F-7). The yield was 3.7 g.

[0312] Using polymer (F-7), polymer (H-7) was obtained in the same manner as in Example 1. The ion exchange capacity of polymer (H-7) was measured. The results are shown in Table 1.

[0313] A mixed solvent of ethanol and water (ethanol / water = 60 / 40 by mass) was added to the polymer (H-7), and the solid content concentration was adjusted to 15% by mass. The mixture was stirred at 105°C for 8 hours using an autoclave to obtain a liquid composition (D-7) in which the polymer (H-7) was dispersed in the dispersion medium.

[0314] [Example 8: Preparation Example]

[0315] Into a 125 mL stainless steel autoclave were placed 15.0 g of compound (m22-1), 15.29 g of compound (m12-1), 10.0 g of compound (s-1), and 23 mg of compound (i-1). The mixture was thoroughly degassed under cooling with liquid nitrogen. The temperature was then raised to 65°C, stirred for 18 hours, and the autoclave was cooled to terminate the reaction.

[0316] The product was diluted with compound (s-1), and n-hexane was added to coagulate the polymer, which was then filtered. The polymer was then stirred in compound (s-1), re-coagulated with n-hexane, and dried under reduced pressure at 80°C overnight to obtain polymer (F-8). The yield was 12.0 g.

[0317] Polymer (F-8) was used in the same manner as in Example 1 to obtain polymer (H-8). The ion exchange capacity of polymer (H-8) was measured. The results are shown in Table 1.

[0318] Using the polymer (H-8), a liquid composition (D-8) was obtained in the same manner as in Example 1.

[0319] [Example 9: Preparation Example]

[0320] Into a 230 mL stainless steel autoclave, 21.2 g of compound (m11-1), 170 g of compound (s-1), and 9.5 mg of compound (i-2) were placed and thoroughly degassed under cooling with liquid nitrogen. Subsequently, 20 g of TFE was added, the temperature was raised to 40°C, and after stirring for 7 hours, the autoclave was cooled to terminate the reaction.

[0321] The product was diluted with compound (s-1), and n-hexane was added to coagulate the polymer, which was then filtered. The polymer was then stirred in compound (s-1), re-coagulated with n-hexane, and dried under reduced pressure at 80°C overnight to obtain polymer (F-9). The yield was 11.5 g.

[0322] Using polymer (F-9), polymer (H-9) and liquid composition (D-9) were obtained in the same manner as in Example 1. Furthermore, the ion exchange capacity of polymer (H-9) was measured. The results are shown in Table 1.

[0323] [Example 10: Preparation Example]

[0324] Into a 125 mL stainless steel autoclave were placed 49.64 g of compound (m31-4), 28.22 g of compound (s-1), and 38.9 mg of compound (i-3) dissolved in compound (s-1) at a concentration of 3.2% by mass. The mixture was thoroughly degassed under cooling with liquid nitrogen. The temperature was then raised to 30°C, and TFE was introduced into the system, maintaining the pressure at 0.37 MPaG. After stirring for 4.8 hours, the autoclave was cooled to terminate the reaction.

[0325] After diluting the product with compound (s-1), compound (s-2) was added, the polymer was coagulated, and filtered. The polymer was then stirred in compound (s-1), re-coagulated with compound (s-2), and dried under reduced pressure at 80°C overnight to obtain polymer (F-10). The yield was 15.0 g.

[0326] Using polymer (F-10), polymer (H-10) and liquid composition (D-10) were obtained in the same manner as in Example 1. Furthermore, the ion exchange capacity of polymer (H-10) was measured. The results are shown in Table 1.

[0327] [Example 11: Preparation Example]

[0328] In a 125 mL stainless steel autoclave, 41.7 g of compound (m24-1), 31.3 g of (m32-1), and 25.0 mg of compound (i-3) dissolved in compound (s-1) at a concentration of 3.2% by mass were placed. The mixture was thoroughly degassed under cooling with liquid nitrogen. The temperature was then raised to 20°C, stirred for 20 hours, and the autoclave was cooled to terminate the reaction.

[0329] The product was diluted with compound (s-1), then n-hexane was added to coagulate the polymer, which was then filtered. The polymer was then stirred in compound (s-1), re-coagulated with n-hexane, and dried under reduced pressure at 80°C overnight to obtain polymer (F-11). The yield was 5.9 g. The density of polymer (F-11) was measured. The results are shown in Table 1.

[0330] Using polymer (F-11), polymer (H-11) and liquid composition (D-11) were obtained in the same manner as in Example 1. The ion exchange capacity of polymer (H-11) was measured. The results are shown in Table 1.

[0331] In Table 1, "the total content of the specific cyclic ether structural unit" means the total content (mol %) of the above-mentioned unit (u11), unit (u12), unit (u21) and unit (u22) relative to all units contained in the polymer after hydrolysis treatment.

[0332] [Table 1]

[0333]

[0334] [Example 12]

[0335] 25 g of water was added to 10 g of the above-mentioned supported catalyst, and ultrasonic waves were irradiated for 10 minutes to obtain a dispersion of the catalyst. 1.6 g of the liquid composition (D-1) was added to the dispersion of the catalyst, and 28 g of ethanol was added to adjust the solid content concentration to 22% by mass to obtain a liquid for forming a catalyst layer. The liquid was applied to a sheet (trade name: AFLEX 100N, manufactured by AGC Co., Ltd., with a thickness of 100 μm) (hereinafter referred to as an ETFE sheet) prepared separately and dried at 80°C for 30 minutes. The sheet was then heat-treated at 160°C for 30 minutes to form a catalyst layer with a platinum content of 0.2 mg / cm 2 catalyst layer.

[0336] The liquid composition (D-1) was applied to an ETFE sheet using a die coater, dried at 80°C for 30 minutes, and further heat-treated at 190°C for 30 minutes to form a 17 μm thick solid polymer electrolyte membrane.

[0337] After peeling the ETFE sheet from the solid polymer electrolyte membrane, the solid polymer electrolyte membrane was sandwiched between two catalyst layers with ETFE sheets and heated and pressed at a pressing temperature of 160°C, a pressing time of 5 minutes, and a pressure of 3 MPa. The catalyst layers were bonded to both sides of the solid polymer electrolyte membrane and the ETFE sheet was peeled from the catalyst layer to obtain an electrode with an area of ​​25 cm 2 membrane catalyst layer assembly.

[0338] On the gas diffusion layer formed of carbon paper, a carbon layer formed of carbon and polytetrafluoroethylene is formed.

[0339] The membrane-catalyst layer assembly was sandwiched between gas diffusion layers so that the carbon layer and the catalyst layer were in contact with each other, thereby obtaining a membrane-electrode assembly.

[0340] [Examples 13~22]

[0341] A membrane electrode assembly was produced in the same manner as in Example 12 except that the liquid composition (D-1) used for forming the catalyst layer was changed to each of the liquid compositions (D-2) to (D-11).

[0342] [Evaluation test]

[0343] <Power Generation Efficiency>

[0344] Each of the obtained membrane electrode assemblies was assembled into a power generation cell, and the following evaluation of power generation efficiency was performed.

[0345] The temperature of the membrane electrode assembly was maintained at 80°C, and hydrogen gas pressurized to 150 kPa (absolute pressure) was supplied to the anode (utilization rate 70%), and air pressurized to 150 kPa (absolute pressure) was supplied to the cathode (utilization rate 50%). Both hydrogen gas and air were humidified to a relative humidity of 30% RH, and the current density was recorded at 0.5 A / cm 2 The battery cell voltage at was evaluated according to the following criteria. The results are shown in Table 2.

[0346] In addition, if the evaluation result is B or higher, it can be said that the power generation efficiency is excellent.

[0347] A: The battery cell voltage is above 0.5V

[0348] B: The battery cell voltage is greater than 0.45V and less than 0.5V

[0349] C: Battery cell voltage is less than 0.45V

[0350] [Table 2]

[0351]

[0352] As shown in Table 2, it can be confirmed that a fuel cell with excellent power generation efficiency can be obtained by using the following catalyst layer, wherein the catalyst layer comprises: a supported catalyst having a carrier comprising a metal oxide and a catalyst supported on the above-mentioned carrier; and a polymer having a specific cyclic ether structural unit and an ion exchange group, wherein the content of the specific cyclic ether structural unit is 30 mol% or more relative to all units contained in the polymer (Examples 12 to 20).

[0353] In contrast, it was confirmed that when a polymer not having a specific cyclic ether structural unit was used, the resulting fuel cell had poor power generation efficiency (Examples 21 and 22).

[0354] Note that the entire contents of Japanese Patent Application No. 2019-001000 filed on January 8, 2019 including the specification, claims, drawings, and abstract are incorporated herein by reference in their entirety and are incorporated as a disclosure of the specification of the present invention.

[0355] Description of Reference Numerals

[0356] 10 Membrane Electrode Assembly

[0357] 11 Catalyst layer

[0358] 12 Gas Diffusion Layer

[0359] 13 Anode

[0360] 14 cathode

[0361] 15. Solid Polymer Electrolyte Membrane

Claims

1. A catalyst layer, characterized in that: Include: A supported catalyst having a support comprising a metal oxide and a catalyst supported on the support; and polymers having ion exchange groups, The polymer only has: units containing a cyclic ether structure, units based on a perfluoromonomer, optionally units based on tetrafluoroethylene, and optionally units based on at least one selected from perfluoro(3-butenyl vinyl ether), perfluoro(allyl vinyl ether), and perfluoroα-olefins, wherein the units containing a cyclic ether structure are at least one selected from the group consisting of units represented by formula (u21) and units represented by formula (u22), or, The polymer only has: a unit containing a cyclic ether structure, an optional unit based on tetrafluoroethylene, and an optional unit based on at least one selected from perfluoro(3-butenyl vinyl ether), perfluoro(allyl vinyl ether), and perfluoroα-olefins, wherein the unit containing a cyclic ether structure is a unit represented by formula (u12), The total content of the units containing the cyclic ether structure is 30 mol% or more relative to all units contained in the polymer, In formula (u12), R 21 is a perfluoroalkylene group having 1 to 6 carbon atoms or a perfluoroalkylene group having 2 to 6 carbon atoms having an ethereal oxygen atom between carbon-carbon bonds, R 22 is a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 2 to 6 carbon atoms having an ethereal oxygen atom between carbon-carbon bonds, or -R 21 (SO2X(SO2R f ) a ) - M + The group shown, M + H + , a monovalent metal cation or an ammonium ion in which one or more hydrogen atoms are optionally substituted by a hydrocarbon group, R f is a linear or branched perfluoroalkyl group optionally having an ethereal oxygen atom, 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, In formula (u21), R 41 、R 42 、R 43 、R 44 、R 45 and R 46 are each independently a monovalent perfluoroorganic group or a fluorine atom which may have an ethereal oxygen atom, In formula (u22), s is 0 or 1, R 51 and R 52 are independently a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a spiro ring formed by connecting them when s is 0, R 53 and R 54 are independently a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms, R 55 is a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms; The perfluoromonomer-based unit is a unit that does not contain a cyclic ether structure and has an ion exchange group, and the ion exchange group is the following group (g1), -(SO2X(SO2R f ) a ) - M + (g1) In formula (g1), M + 、R f , X and a are respectively the same as M in the above formula (u12) + 、R f , X and a are synonymous.

2. The catalyst layer according to claim 1, wherein The unit containing a cyclic ether structure is the unit represented by the formula (u22).

3. The catalyst layer according to claim 1 or 2, wherein The polymer has the perfluoromonomer-based units. The catalyst layer according to claim 1 or 2, wherein The polymer has the tetrafluoroethylene-based units.

5. A liquid for forming a catalyst layer, characterized in that: Include: A supported catalyst comprising a support comprising a metal oxide and a catalyst supported on the support; polymers having ion exchange groups, The polymer comprises only units containing a cyclic ether structure, units based on a perfluoromonomer, optionally units based on tetrafluoroethylene, and optionally units based on at least one selected from perfluoro(3-butenyl vinyl ether), perfluoro(allyl vinyl ether), and perfluoroα-olefins, wherein the units containing a cyclic ether structure are at least one selected from the group consisting of units represented by formula (u21) and units represented by formula (u22), or The polymer only has: a unit containing a cyclic ether structure, an optional unit based on tetrafluoroethylene, and an optional unit based on at least one selected from perfluoro(3-butenyl vinyl ether), perfluoro(allyl vinyl ether), and perfluoroα-olefins, wherein the unit containing a cyclic ether structure is a unit represented by formula (u12); and solvents, The total content of the units containing the cyclic ether structure is 30 mol% or more relative to all units contained in the polymer, In formula (u12), R 21 is a perfluoroalkylene group having 1 to 6 carbon atoms or a perfluoroalkylene group having 2 to 6 carbon atoms having an ethereal oxygen atom between carbon-carbon bonds, R 22 is a fluorine atom, a perfluoroalkyl group having 1 to 6 carbon atoms, a perfluoroalkyl group having 2 to 6 carbon atoms having an ethereal oxygen atom between carbon-carbon bonds, or -R 21 (SO2X(SO2R f ) a ) - M + The group shown, M + H + , a monovalent metal cation or an ammonium ion in which one or more hydrogen atoms are optionally substituted by a hydrocarbon group, R f is a linear or branched perfluoroalkyl group optionally having an ethereal oxygen atom, 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, In formula (u21), R 41 、R 42 、R 43 、R 44 、R 45 and R 46 are each independently a monovalent perfluoroorganic group or a fluorine atom which may have an ethereal oxygen atom, In formula (u22), s is 0 or 1, R 51 and R 52 are independently a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a spiro ring formed by connecting them when s is 0, R 53 and R 54 are independently a fluorine atom or a perfluoroalkyl group having 1 to 5 carbon atoms, R 55 is a fluorine atom, a perfluoroalkyl group having 1 to 5 carbon atoms, or a perfluoroalkoxy group having 1 to 5 carbon atoms; The perfluoromonomer-based unit is a unit that does not contain a cyclic ether structure and has an ion exchange group, and the ion exchange group is the following group (g1), -(SO2X(SO2R f ) a ) - M + (g1) In formula (g1), M + 、R f , X and a are respectively the same as M in the above formula (u12) + 、R f , X and a are synonymous.

6. The catalyst layer forming liquid according to claim 5, wherein The unit containing a cyclic ether structure is the unit represented by the formula (u22).

7. The catalyst layer forming liquid according to claim 5 or 6, wherein The polymer has the perfluoromonomer-based units.

8. The catalyst layer forming liquid according to claim 5 or 6, wherein The polymer has the tetrafluoroethylene-based units.

9. A membrane electrode assembly comprising: 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, At least one of the catalyst layer of the anode and the catalyst layer of the cathode is the catalyst layer according to any one of claims 1 to 4.

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