Electrolyte membrane, electrolyte membrane with catalyst layer, and electrochemical cell

Abstract

The present invention provides an electrolyte membrane and a catalyst-attached electrolyte membrane that exhibit good electrochemical performance and can reduce material costs. [Solution] An electrolyte membrane having a first layer composed of an electrolyte mainly composed of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less, and a second layer composed of a composite electrolyte formed by compounding an aromatic hydrocarbon polymer having a different chemical structure from the first layer and an ion exchange capacity of 2.0 meq / g or more and 5.0 meq / g or less with a porous substrate, wherein the thickness of the first layer is half or less of the thickness of the second layer.

Description

[Technical Field]

[0001] The present invention relates to an electrolyte membrane, an electrolyte membrane with a catalyst layer, and an electrochemical cell. [Background technology]

[0002] In response to the increasingly serious energy problem in recent years, hydrogen is attracting attention as an energy source with a low environmental impact. By using hydrogen as fuel for polymer electrolyte fuel cells, it can be converted into electricity with theoretically higher energy efficiency than power generation using heat engines, and since it does not emit harmful substances such as carbon dioxide, it is a highly efficient clean energy source.

[0003] In hydrogen production, using surplus electricity from renewable energy sources to electrolyze water allows for the conversion of electricity into hydrogen energy while minimizing carbon dioxide emissions. While there are two main methods for hydrogen production through water electrolysis—alkaline water electrolysis and polymer electrolyte membrane-based water electrolysis—polymer electrolyte membrane-based water electrolysis offers the advantage of high current density operation and flexibility in adapting to the large output fluctuations of renewable energy sources.

[0004] In typical polymer electrolyte fuel cells, the fuel gas reacts in the catalyst layer at the anode electrode to produce protons and electrons. The electrons are sent to the external circuit via the electrode, while the protons are conducted to the polymer electrolyte membrane via the electrode electrolyte. Meanwhile, at the cathode electrode, the oxidizing gas, protons conducted from the polymer electrolyte membrane, and electrons conducted from the external circuit react in the catalyst layer to produce water.

[0005] In solid polymer electrolyte water electrolysis, water is supplied to an electrolytic cell, which is generally divided into an anode and a cathode by a polymer electrolyte membrane. Oxygen is produced at the anode and hydrogen at the cathode.

[0006] Fluorine-based polymer electrolytes, such as perfluorocarbon sulfonic acid, are generally known as polymer electrolyte membranes for solid polymer fuel cells and solid polymer water electrolysis. However, fluorine-based polymer electrolytes have drawbacks, such as being expensive and having poor gas barrier properties. Furthermore, fluorine-based polymer electrolytes are a type of PFAS (perfluoroalkyl and polyfluoroalkyl compounds) compound, raising concerns about their environmental impact. On the other hand, various hydrocarbon-based polymer electrolyte membranes have been developed as alternatives to fluorine-based polymer electrolyte membranes (see, for example, Patent Document 1).

[0007] In solid polymer water electrolysis devices, a "crossover" occurs where hydrogen generated at the cathode permeates the electrolyte membrane and reaches the anode, potentially contaminating the oxygen generated at the anode and reducing its purity. Since an explosion risk arises when the hydrogen concentration in oxygen exceeds 4%, reducing the hydrogen concentration in the oxygen gas is required (see, for example, Patent Document 2).

[0008] To improve the performance of electrolyte membranes, multilayer electrolyte membranes, which consist of stacked polymer electrolytes, have been reported. By stacking electrolyte membranes with different chemical structures, the power generation characteristics and durability of polymer electrolyte fuel cells can be improved (see, for example, Patent Documents 3-6). [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2016-216826 [Patent Document 2] Japanese Patent Publication No. 2008-240069 [Patent Document 3] Japanese Patent Publication No. 2004-303541 [Patent Document 4] Japanese Patent Publication No. 2007-87853 [Patent Document 5] International Publication No. 2007 / 086309 [Patent Document 6] Japanese Patent Application Laid-Open No. 2021-51996

Summary of the Invention

Problems to be Solved by the Invention

[0010] For electrolyte membranes used in electrochemical cells such as solid polymer electrolysis and solid polymer fuel cells, various properties are required, such as high proton conductivity, low gas permeability, chemical stability, and mechanical strength. To meet these required properties, hydrocarbon-based polymers used in conventional electrolyte membranes require complex chemical structures, and mainly due to the large number of synthesis steps, the material cost has been high. In addition, the conventionally used fluorine-based polymer electrolytes are also expensive and raise concerns about their impact on the environment.

[0011] In view of the above problems, an object of the present invention is to provide an electrolyte membrane and a catalyst-coated electrolyte membrane having good electrochemical properties and capable of reducing material costs.

Means for Solving the Problems

[0012] In response to the above problems, the inventors considered that by combining a porous substrate and a hydrocarbon-based polymer electrolyte that can be synthesized at a low material cost, an electrolyte membrane having the mechanical strength required for solid polymer fuel cell applications and solid polymer electrolysis applications can be provided at a low material cost. In solid polymer fuel cell applications and solid polymer fuel cell applications, the ion exchange capacity of the polymer electrolyte has a great influence on the ionic conductivity and mechanical strength of the electrolyte membrane. Generally, by increasing the number of ionic groups in the polymer, the ion exchange capacity increases and the ionic conductivity of the electrolyte membrane improves, but the mechanical strength of the electrolyte membrane decreases. Therefore, the polymer electrolyte constituting the electrolyte membrane for solid polymer fuel cell applications and solid polymer electrolysis applications requires an ion exchange capacity that can achieve both good ionic conductivity and mechanical strength.

[0013] As a result of intensive research, the inventors have found that an electrolyte membrane composed of a composite electrolyte in which an aromatic hydrocarbon polymer having an ion exchange capacity of 2.0 meq / g or more and 5.0 meq / g or less is combined with a porous substrate exhibits good ion conductivity and mechanical strength. Further, by disposing a thin film of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less on the main surface side of the composite electrolyte membrane, an electrolyte membrane having excellent characteristics for use in a solid polymer fuel cell and a solid polymer water electrolysis, not containing a fluorine-based polymer, and capable of reducing the material cost was found, and the present invention was completed.

[0014] That is, the present invention provides a practically excellent electrolyte membrane, an electrolyte membrane with a catalyst layer, a membrane electrode assembly, and an electrochemical cell used in a water electrolysis device and a fuel cell device by taking the following configurations. [1] A first layer composed of an electrolyte mainly composed of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less measured by a neutral titration method, and a second layer composed of a composite electrolyte in which an aromatic hydrocarbon polymer having an ion exchange capacity of 2.0 meq / g or more and 5.0 meq / g or less and a porous substrate are combined, and the thickness of the first layer is half or less of the thickness of the second layer. [2] A first layer composed of an electrolyte mainly composed of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less measured by a neutral titration method, a second layer composed of a composite electrolyte in which an aromatic hydrocarbon polymer having an ion exchange capacity of 2.0 meq / g or more and 5.0 meq / g or less and a porous substrate are combined, and a third layer composed of an electrolyte mainly composed of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less in this order, and the thickness of each of the first layer and the third layer is half or less of the thickness of the second layer. [3] The electrolyte membrane according to claim 1, wherein the thickness of the first layer is 1 μm or more and less than 20 μm, and the thickness of the second layer is 40 μm or more and 150 μm or less. [4] The electrolyte membrane according to claim 2, wherein the thickness of the first layer and the third layer is 1 μm or more and less than 20 μm, and the thickness of the second layer is 40 μm or more and 150 μm or less. [5] The electrolyte membrane according to [1], wherein the aromatic hydrocarbon polymer constituting the first layer is a polyether ketone polymer. [6] The electrolyte membrane according to [2], wherein either or both of the aromatic hydrocarbon polymers constituting the first layer and the third layer are polyetherketone polymers. [7] The electrolyte membrane according to [1], wherein the aromatic hydrocarbon polymer constituting the first layer is a block polymer polyetherketone polymer. [8] The electrolyte membrane according to [2], wherein either or both of the aromatic hydrocarbon polymers constituting the first layer and the third layer are block polymer polyetherketone polymers. [9] The electrolyte membrane according to [1], wherein the aromatic hydrocarbon polymer of the second layer is a polysulfone polymer having a polysulfone structure as its main backbone.

[10] The electrolyte membrane according to [2], wherein the aromatic hydrocarbon polymer of the second layer is a polysulfone polymer having a polysulfone structure as its main backbone.

[11] The electrolyte membrane according to [1], wherein the porous substrate of the second layer is liquid crystal polyester fiber or PPS (polyphenylene sulfide).

[12] The electrolyte membrane according to [2], wherein the porous substrate of the second layer is liquid crystal polyester fiber or PPS (polyphenylene sulfide).

[13] A catalyst-layered electrolyte membrane comprising an electrolyte membrane according to any one of [1], [3], [5], [7], [9], or

[11] , wherein an anode catalyst is arranged on the surface of the first layer and a cathode catalyst is arranged on the surface of the second layer.

[14] An electrolyte membrane with a catalyst layer, comprising an electrolyte membrane according to any one of claims [2], [4], [6], [8],

[10] , or

[12] , wherein an anode catalyst is arranged on the surface of the first layer and a cathode catalyst is arranged on the third surface. A membrane electrode assembly containing the electrolyte membrane described in

[15] [1]~

[12] . An electrochemical cell containing the electrolyte membrane described in

[16] [1]~

[12] . A polymer electrolyte water electrolysis apparatus including the electrochemical cell described in

[17]

[16] . A polymer electrolyte fuel cell including the electrochemical cell described in

[18]

[16] . [Effects of the Invention]

[0015] According to the present invention, it is possible to provide an electrolyte membrane, an electrolyte membrane with a catalyst layer, and an electrochemical cell that have good electrical properties and durability, and that can reduce material costs. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic cross-sectional view of one embodiment of the catalyst-attached electrolyte membrane of the present invention. [Figure 2] This is a schematic cross-sectional view of another embodiment of the catalyst-equipped electrolyte membrane of the present invention. [Modes for carrying out the invention]

[0017] The embodiments of the present invention will be described in detail below, but the present invention is not limited to the embodiments described below and can be modified and implemented according to the purpose and application.

[0018] Figure 1 is a schematic cross-sectional view of a catalyst-equipped electrolyte membrane according to an embodiment of the present invention. The electrolyte membrane 4 has a first layer 1 and a second layer 2. The catalyst-equipped electrolyte membrane 7 has an anode catalyst layer 5 disposed on the surface of the first layer side of the electrolyte membrane 4 and a cathode catalyst layer 6 disposed on the surface of the second layer side.

[0019] Figure 2 is a schematic cross-sectional view of another catalyst-equipped electrolyte membrane according to an embodiment of the present invention. The electrolyte membrane 4 has a first layer 1, a second layer 2, and a third layer 3 in that order. The catalyst-equipped electrolyte membrane 7 has an anode catalyst layer 5 disposed on the surface of the first layer side of the electrolyte membrane 4, and a cathode catalyst layer 6 disposed on the surface of the third layer side.

[0020] [Electrolyte membrane] In one embodiment, the electrolyte membrane of the present invention comprises, in this order, a first layer composed of an electrolyte mainly composed of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less; a second layer composed of a composite electrolyte formed by compounding an aromatic hydrocarbon polymer having a chemical structure different from that of the first layer and having an ion exchange capacity of 2.0 meq / g or more and 5.0 meq / g or less with a porous substrate; and a third layer composed of an electrolyte mainly composed of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less.

[0021] From the viewpoint of reducing material costs, the first and third layers are thinner than the second layer, with the thickness of each layer being less than half the thickness of the second layer. A specific preferred thickness is 20 μm or less, and a particularly preferred thickness is 10 μm or less. On the other hand, in order to ensure sufficient mechanical strength and gas barrier properties, a thickness of 1 μm or more is preferable.

[0022] Another form of the electrolyte membrane in the present invention is a laminated structure comprising a first layer composed of an electrolyte mainly composed of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less, and a second layer composed of a composite electrolyte formed by compounding an aromatic hydrocarbon polymer having an ion exchange capacity of 2.0 meq / g or more and 5.0 meq / g or less with a porous substrate.

[0023] In the present invention, when the electrolytic film is composed of a first layer and a second layer, the thickness of the first layer is less than or equal to half the thickness of the second layer, with a specific preferred thickness of 20 μm or less, and a particularly preferred thickness of 10 μm or less. On the other hand, in order to ensure sufficient mechanical strength and gas barrier properties, a thickness of 1 μm or more is preferable.

[0024] The thickness of the second layer is preferably relatively thick when the electrolyte membrane is used for solid polymer water electrolysis, in order to suppress the occurrence of crossover, where hydrogen generated at the cathode permeates the electrolyte membrane and reaches the anode. Specifically, a thickness of 40 μm or more is preferred, 50 μm or more is more preferred, and 60 μm or more is particularly preferred. On the other hand, in order to ensure good water electrolysis performance, the thickness of the second layer is preferably 150 μm or less, and 120 μm or less is particularly preferred.

[0025] Here, ion exchange capacity (IEC) is the molar amount of ionic groups introduced per unit dry weight of the polymer electrolyte, and a larger value indicates a greater amount of ionic groups introduced. In this invention, IEC is defined as the value obtained by neutralization titration. The calculation of IEC by neutralization titration can be performed using the method described in the examples.

[0026] [Layer 1 and Layer 3] Aromatic hydrocarbon polymers, which are the main components of the hydrocarbon electrolytes constituting the first and third layers, are preferably used because they have high mechanical strength and gas barrier properties. Examples include polysulfone (PSU), polyethersulfone (PES), polyetherethersulfone (PEES), polyphenylene oxide (PPO), polyarylene ether polymers, polyphenylene sulfide (PPS), polyphenylene sulfide sulfone, polyparaphenylene (PPP), polyarylene polymers, polyarylene ketone, polyether ketone (PEK), polyether ketone ketone, polyether ether ketone ketone, and polyether ketone ether ketone ketone.

[0027] In particular, polyetherketone polymers having a repeating etherketone structure are preferred because they possess properties such as high chemical stability, good mechanical strength, and high gas barrier properties.

[0028] The aromatic hydrocarbon polymer, which is the main component of the hydrocarbon electrolyte constituting the first and third layers in the present invention, may have any ionic group having proton exchange ability. Suitable ionic groups include sulfonic acid groups, sulfonimide groups, phosphonic acid groups, phosphoric acid groups, and carboxylic acid groups. Among these, sulfonic acid groups, which have excellent proton exchange ability, are particularly preferred. The polymer may contain two or more types of ionic groups having proton exchange ability. In the present invention, the ion exchange capacity of the aromatic hydrocarbon polymer, which is the main component of the hydrocarbon electrolyte constituting the first and third layers, is preferably 0.5 meq / g or more in order to improve the proton conductivity of the electrolyte membrane, and is particularly preferably 1.0 meq / g or more and 2.5 meq or less in order to achieve both excellent proton conductivity and mechanical strength.

[0029] In the present invention, the first layer polyetherketone polymer is preferably a block copolymer having one or more segments having ionic groups (ionic segments) and one or more segments not having ionic groups (nonionic segments). Here, a segment refers to a partial structure in a copolymer polymer chain consisting of repeating units exhibiting specific properties, with a molecular weight of 2,000 or more. Block copolymers are preferable to random copolymers in that they readily form channels for proton conduction and exhibit superior proton conductivity, and are therefore preferably used in the first and / or third layers of the present invention. In particular, using a block copolymer in either the first or third layer is preferable because it can achieve high proton conductivity.

[0030] In the present invention, as the aromatic hydrocarbon polymer which is the main component of the hydrocarbon electrolyte constituting the first and third layers, a polyetherketone block copolymer is particularly preferred to be used. This copolymer contains segments that include ionic groups and structural units represented by the following general formula (1), and segments that do not contain ionic groups and include structural units represented by the following general formula (2).

[0031]

Chem.

[0032] In general formula (1), Ar 1 ~Ar 4 has an arbitrary divalent arylene group, and Ar 1 and / or Ar 2 has an ionic group, and Ar 3 and Ar 4 may or may not contain an ionic group. Ar 1 ~Ar 4 may be optionally substituted, and two or more types of arylene groups may be used independently of each other. * indicates the bonding site with general formula (1) or other structural units.

[0033]

Chem.

[0034] In general formula (2), Ar 5 ~Ar 8 represents an arbitrary divalent arylene group, may be optionally substituted, and does not contain an ionic group. Ar 5 ~Ar 8 may be two or more types of arylene groups used independently of each other. * represents the bonding site with general formula (2) or other structural units.

[0035] Here, Ar 1 ~Ar 8Preferred divalent arylene groups include, but are not limited to, hydrocarbon arylene groups such as phenylene groups, naphthylene groups, biphenylene groups, and fluoroorangeyl groups, and heteroarylene groups such as pyridinediyl, quinoxalinediyl, and thiophenediyl. Here, phenylene groups can be of three types depending on the location of the bond site between the benzene ring and other structural units: o-phenylene groups, m-phenylene groups, and p-phenylene groups. In this specification, unless otherwise specified, these will be used as a general term. The same applies to other divalent arylene groups such as naphthylene groups and biphenylene groups. 1 ~Ar 8 Preferably, it is a phenylene group containing a phenylene group and an ionic group, most preferably a p-phenylene group containing a p-phenylene group and an ionic group. Also, Ar 5 ~Ar 8 While the group may be substituted with groups other than ionic groups, an unsubstituted state is more preferable in terms of water electrolysis performance, chemical stability, and physical durability.

[0036] In the present invention, the weight-average molecular weight of the aromatic hydrocarbon polymer, which is the main component of the hydrocarbon electrolyte constituting the first and third layers, is preferably 10,000 or more, more preferably 50,000 or more, and particularly preferably 100,000 or more, in order to improve the mechanical durability of the electrolyte membrane.

[0037] Here, the weight-average molecular weight in this invention is defined as the value on a standard polystyrene basis, measured using gel permeation chromatography (GPC), as described in the examples below.

[0038] The first layer and / or the third layer may contain various additives, such as antioxidants, surfactants, radical scavengers, hydrogen peroxide decomposers, non-electrolyte polymers, elastomers, fillers, etc., to the extent that they do not impair the effects of the present invention. [Second layer] In the present invention, the second layer is composed of a composite electrolyte formed by compounding an aromatic hydrocarbon polymer with a porous substrate. Furthermore, the aromatic hydrocarbon polymer that is the main component of the hydrocarbon electrolyte membrane constituting the second layer has a different chemical structure from the polyetherketone polymer that is the main component of the hydrocarbon electrolyte membrane constituting the first layer. It is preferable that the aromatic hydrocarbon polymer that is the main component of the hydrocarbon electrolyte membrane constituting the second layer has a chemical structure that can be synthesized more easily than the polyetherketone polymer that is the main component of the hydrocarbon electrolyte membrane constituting the first layer, in order to reduce costs.

[0039] Aromatic hydrocarbon polymers such as polysulfone (PSU), polyethersulfone (PES), polyetherethersulfone (PEES), polyphenylene oxide (PPO), polyarylene ether polymers, polyphenylene sulfide (PPS), polyphenylene sulfide sulfone, polyparaphenylene (PPP), polyarylene polymers, polyarylene ketone, polyether ketone (PEK), polyether ketone ketone, polyether ether ketone, polyether ether ketone ketone, and polyether ketone ether ketone ketone are preferred due to their high mechanical strength and gas barrier properties. Among these, polysulfone polymers with repeating sulfone structures are preferred because they have low material costs, high chemical stability, and high gas barrier properties.

[0040] The ionic groups in the aromatic hydrocarbon polymer used in the composite electrolyte constituting the second layer of the present invention can be any ionic groups having proton exchange ability. Preferred ionic groups include sulfonic acid groups, sulfonimide groups, phosphonic acid groups, phosphoric acid groups, and carboxylic acid groups. Among these, sulfonic acid groups, which have excellent proton exchange ability, are particularly preferred. The polymer may contain two or more types of ionic groups having proton exchange ability.

[0041] In the present invention, the ion exchange capacity of the aromatic hydrocarbon polymer used in the composite electrolyte constituting the second layer is preferably 2.0 meq / g or more to improve the proton conductivity of the electrolyte membrane, more preferably 2.0 meq / g to 5.0 meq, and particularly preferably 2.0 meq / g to less than 4.0 meq to achieve both excellent proton conductivity and mechanical strength. In the second layer, the mechanical strength of the second layer can be increased by the porous substrate, so an aromatic hydrocarbon polymer with a high ion exchange capacity can be used.

[0042] The weight-average molecular weight of the aromatic hydrocarbon polymer used in the composite electrolyte constituting the second layer in the present invention is preferably 10,000 or more, more preferably 50,000 or more, and particularly preferably 100,000 or more, in order to improve the mechanical strength of the electrolyte membrane.

[0043] In the present invention, the composite electrolyte constituting the second layer is preferably in which an aromatic hydrocarbon polymer electrolyte is filled (impregnated) into the pores of a porous substrate. Examples of porous substrates include woven fabrics, nonwoven fabrics, porous films, and mesh fabrics. Examples of porous substrates include hydrocarbon porous substrates mainly composed of hydrocarbon polymer compounds.

[0044] Preferred hydrocarbon polymers as porous substrates include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyacrylate, polymethacrylate, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyester, liquid crystal polyester, polycarbonate (PC), polysulfone (PSU), polyethersulfone (PES), polyphenylene oxide (PPO), polyarylene ether polymers, polyphenylene sulfide (PPS), polyphenylene sulfide sulfone, polyparaphenylene (PPP), polyarylene polymers, polyarylene ketone, polyetherketone (PEK), polyarylene phosphine oxide, polyetherphosphine oxide, polybenzoxazole (PBO), polybenzthiazole (PBT), polybenzimidazole (PBI), polyamide (PA), polyimide (PI), polyetherimide (PEI), polyaramid, and polyimide sulfone (PIS).

[0045] Since the porous substrate serves to reinforce the strength of the second layer, a porous substrate with high strength is preferred, and from this viewpoint, mesh fabrics are preferred. Compared to porous substrates that have been commonly used in this field, mesh fabrics have a relatively large fiber diameter and high strength. As for the material of the fibers constituting the mesh fabric, polyester, liquid crystal polyester, polyphenylene sulfide, polyether ketone, polyether ether ketone, and polyether ketone ketone are preferred. Among these, liquid crystal polyester and polyphenylene sulfide are particularly preferred from the viewpoint of strength and chemical stability.

[0046] The second layer in the present invention may contain various additives, such as antioxidants, surfactants, radical scavengers, hydrogen peroxide decomposers, non-electrolyte polymers, elastomers, fillers, etc., as long as they do not impair the effects of the present invention.

[0047] [Film forming method] In the present invention, known methods can be used to form the first, second, and third layers, such as coating a hydrocarbon-based electrolyte solution or dispersion onto a substrate and then drying it, or by melt extrusion molding. Hereinafter, electrolyte solutions or dispersions will be collectively referred to as electrolyte solutions.

[0048] The method for applying the electrolyte solution onto the substrate is not particularly limited, and known coating methods can be used. Examples include dip coating, reverse coating, spray coating, bar coating, knife coating, direct roll coating, Meyer bar coating, gravure coating, rod coating, die coating, spin coating, extrusion coating, and curtain coating. Die coating is particularly preferred as it allows for coating with a uniform thickness and is suitable for mass production.

[0049] Known polymer films can be used as substrates for film formation. Examples of polymer film materials include polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polycarbonate, polyetherimide, polyphenylene sulfide polyimide, polystyrene, polytetrafluoroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, and perfluoroalkoxy fluororesin. Among these, polyester is preferred from the viewpoint of chemical resistance, heat resistance, and cost, and polyethylene terephthalate is particularly preferred.

[0050] The electrolyte membrane in the present invention, composed of a first layer, a second layer, and a third layer, may be laminated by first forming the first layer, then the second layer, followed by the third layer; or by forming the third layer, then the second layer, followed by the first layer; or by forming the second layer, then the first layer, followed by the first layer; or by forming the second layer, then the third layer, followed by the first layer; or by forming the second layer, then the first and third layers, followed by the first layer.

[0051] In the present invention, if the electrolyte membrane is composed of a first layer and a second layer, the second layer may be laminated after the first layer has been formed, or the first layer may be laminated after the second layer has been formed.

[0052] The above coating method involves sequentially applying and drying an electrolyte solution in each layer to create a laminate. The above transfer method involves transferring and laminating a layer formed on a film-forming substrate onto a layer formed on a transfer sheet using a heat press or the like.

[0053] In the formation of electrolyte membranes, hydrocarbon electrolytes can be used in which the ionic groups form salts with alkali metal or alkaline earth metal cations. In this case, it is preferable to perform a step in which the alkali metal or alkaline earth metal cations are exchanged for protons. This step is preferably a step in which the molded electrolyte membrane is brought into contact with an acidic aqueous solution, and more preferably a step in which the molded electrolyte membrane is immersed in an acidic aqueous solution. In this step, the protons in the acidic aqueous solution are replaced with cations that are ionically bonded to the ionic groups, and residual water-soluble impurities, residual monomers, solvents, residual salts, etc., are removed at the same time.

[0054] The acidic aqueous solution is not particularly limited, but it is preferable to use sulfuric acid, hydrochloric acid, nitric acid, acetic acid, trifluoromethanesulfonic acid, methanesulfonic acid, phosphoric acid, citric acid, etc. Sulfuric acid is preferred due to its ease of handling and cost. [Anode catalyst layer] When a catalyst-equipped electrolyte membrane is used for water electrolysis, the anode catalyst layer may consist solely of iridium as the noble metal element, or it may contain iridium and at least one other noble metal element selected from the group consisting of platinum, ruthenium, rhodium, palladium, gold, silver, and osmium. These noble metal elements function as catalysts in the anode catalyst layer. As other noble metals besides iridium used in the anode catalyst layer, platinum or palladium are preferred, with platinum being particularly preferred due to its high catalytic performance.

[0055] The form in which the iridium element and other precious metal elements are incorporated into the anode catalyst layer is not particularly limited, and known forms can be used. For example, (I) a form that incorporates particles containing the iridium element (hereinafter referred to as "iridium-based particles") and particles containing other precious metal elements (hereinafter referred to as "other precious metal-based particles"), (II) a form that uses alloy particles of iridium and other precious metals, and (III) a form in which iridium and other precious metals are layered by sputtering or vapor deposition.

[0056] Iridium-based particles and other precious metal-based particles can be synthesized or manufactured by known methods. Commercially available products can also be used. Examples of commercially available products include, as iridium oxide particles, "IrO2 catalyst Elyst by Umicore" and "iridium oxide powder by Tokuriki Honten"; as platinum black, "HISPEC1000 by Johnson Matthey," "TEC90300 and TEC90400 by Tanaka Kikinzoku Kogyo," "PtBlack by BASF," "Platinum Black by Tokuriki Honten," and "Platinum Black by Ishifuku Kinzoku Kogyo"; and as palladium black, "Palladium Black by Soegawa Rikagaku," "Pd-black by Alfa Aesar," and "Pdblack by Wako Pure Chemical Industries." These particles can also be used after being ground to a desired particle size, for example, around 1 to 100 nm.

[0057] The anode catalyst layer preferably further contains a polymer electrolyte. As the polymer electrolyte, the aforementioned hydrocarbon-based polymer electrolytes or fluorine-based polymer electrolytes can be used. Since the anode is in a high-potential environment in a water electrolysis device, it is preferable to use a fluorine-based polymer electrolyte that has relatively good resistance to electrochemical oxidation.

[0058] In the anode catalyst layer, the mass ratio (C / I) of the catalyst mass (C) to the polymer electrolyte mass (I) is preferably 3.0 or higher, more preferably 4.0 or higher, and particularly preferably 6.0 or higher. Furthermore, the above ratio is preferably 15.0 or lower, more preferably 14.0 or lower, and particularly preferably 13.0 or lower. The catalyst mass (C) above refers to the total mass of the entire catalyst in its additive form. For example, if catalyst-supported particles are used, it is the mass including the support. The catalyst mass (C) in the cathode catalyst layer described later is the same as above.

[0059] The thickness of the anode catalyst layer is preferably 0.5 μm or more, more preferably 1 μm or more, and particularly preferably 3 μm or more, from the viewpoint of gas diffusion and durability. Furthermore, the above thickness is preferably 100 μm or less, more preferably 50 μm or less, and particularly preferably 30 μm or less.

[0060] In polymer electrolyte water electrolysis, degradation of the electrolyte membrane is likely to occur on the anode catalyst layer side where oxygen is generated. Therefore, when the electrolyte membrane in the present invention is composed of a first layer and a second layer, it is preferable to place the anode catalyst layer on the surface of the first layer. On the other hand, in polymer electrolyte fuel cells, degradation of the electrolyte membrane is likely to occur on the cathode catalyst layer side where oxygen is reacted and reduced. Therefore, when the electrolyte membrane in the present invention is composed of a first layer and a second layer, it is preferable to place the cathode catalyst layer on the surface of the first layer. [Cathode catalyst layer] The cathode catalyst layer can be made from metals such as platinum group elements (platinum, ruthenium, rhodium, palladium, osmium, iridium), iron, lead, gold, silver, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum, as well as alloys and oxides of these metals. Among these, platinum is preferred.

[0061] Furthermore, catalysts supported on carbon particles (catalyst metal-supported carbon particles) are also preferably used. The carbon particles are not particularly limited as long as they are fine particles, conductive, and do not corrode or deteriorate upon reaction with the catalyst, but carbon black, graphite, activated carbon, carbon fiber, carbon nanotubes, and fullerene particles can be preferably used. Platinum-supported carbon particles are preferred as the catalyst in the cathode catalyst layer.

[0062] The cathode catalyst layer preferably further contains a polymer electrolyte. As the polymer electrolyte, the aforementioned hydrocarbon-based polymer electrolytes or fluorine-based polymer electrolytes can be used. Among these, fluorine-based polymer electrolytes are preferred.

[0063] In the cathode catalyst layer, the mass ratio (C / I) of the catalyst mass (C) to the polymer electrolyte mass (I) is preferably less than 4.0, more preferably less than 3.5, and particularly preferably less than 3.0. Furthermore, the above ratio is preferably 1.0 or higher, more preferably 1.5 or higher, and particularly preferably 1.7 or higher.

[0064] The thickness of the cathode catalyst layer is preferably 0.5 μm or more, more preferably 1 μm or more, and particularly preferably 3 μm or more, from the viewpoint of gas diffusion and durability. Furthermore, the above thickness is preferably 100 μm or less, more preferably 50 μm or less, and particularly preferably 30 μm or less.

[0065] [Method for fabricating electrolyte membranes with catalyst layers] Methods for laminating a catalyst layer onto an electrolyte membrane include, for example, a coating method, a transfer method, or a combination of a coating method and a transfer method. These methods are not particularly limited, and known methods can be employed.

[0066] The coating method involves applying a coating solution for the catalyst layer onto the electrolyte membrane. Specifically, one method involves applying the coating solution for the anode catalyst layer to the first layer side of the electrolyte membrane, drying it to form the anode catalyst layer, and then applying the coating solution for the cathode catalyst layer to the opposite side of the electrolyte membrane, drying it to form the cathode catalyst layer. The stacking order of the anode catalyst layer and the cathode catalyst layer may be reversed from the above. When employing the coating method, it is preferable to stack a film-forming substrate or a new support substrate on the side of the electrolyte membrane opposite to the side to which the catalyst layer coating solution is applied.

[0067] One transfer method involves preparing an anode catalyst layer transfer sheet, which has an anode catalyst layer laminated on a transfer substrate, and a cathode catalyst layer transfer sheet, which has a cathode catalyst layer laminated on a transfer substrate. The anode catalyst layer transfer sheet is attached to the first solid layer side of the electrolyte membrane, and the cathode catalyst layer transfer sheet is attached to the opposite side of the electrolyte membrane. These sheets are then heated and pressed to transfer the anode catalyst layer and the cathode catalyst layer, respectively.

[0068] [Membrane electrode assembly] The membrane electrode assembly includes the catalyst layer-equipped electrolyte membrane and gas diffusion layers (gas diffusion electrodes) arranged on both sides thereof. Specifically, the cathode gas diffusion electrode is arranged on the cathode catalyst layer side of the catalyst layer-equipped electrolyte membrane, and the anode gas diffusion layer is arranged on the anode catalyst layer side.

[0069] The gas diffusion layer is generally composed of a material that is gas permeable and electrically conductive, such as a porous carbon material or a porous metal material. Examples of porous carbon materials include carbon paper, carbon cloth, carbon mesh, and nonwoven carbon fabric. Examples of porous metal materials include metal mesh, foamed metal, metal fabric, sintered metal body, and nonwoven metal fabric. Examples of metals include titanium, aluminum, copper, nickel, nickel-chromium alloy, copper and its alloys, silver, aluminum alloy, zinc alloy, lead alloy, titanium, niobium, tantalum, iron, stainless steel, gold, and platinum.

[0070] The gas diffusion layer can be treated with water-repellent treatment to prevent a decrease in gas diffusion and permeability due to water retention, partial water-repellent and partial hydrophilic treatments to form water discharge channels, and the addition of carbon powder to reduce resistance. Furthermore, the gas diffusion layer can be provided with a conductive intermediate layer containing at least an inorganic conductive material and a hydrophobic polymer on the electrolyte membrane side of the catalyst layer. In particular, when the gas diffusion layer is composed of carbon fiber fabric or nonwoven fabric with a high porosity, providing a conductive intermediate layer can suppress performance degradation caused by the catalyst solution seeping into the gas diffusion layer.

[0071] The thickness of the gas diffusion layer is preferably 50 μm or more, more preferably 100 μm or more, and particularly preferably 200 μm or more. Furthermore, it is preferably 2,000 μm or less, more preferably 1,500 μm or less, and particularly preferably 1,000 μm or less.

[0072] The cathode gas diffusion layer and the anode gas diffusion layer may be made of the same material or different materials. When the membrane electrode assembly is applied to a water electrolysis apparatus, it is preferable that the cathode gas diffusion layer and the anode gas diffusion layer are made of different materials. For example, it is preferable that the cathode gas diffusion layer is made of a porous carbon material and the anode gas diffusion layer is made of a porous metal material.

[0073] The catalyst-layered electrolyte membrane according to an embodiment of the present invention may be completed during the manufacturing process of the membrane electrode assembly. For example, it may be obtained by joining a catalyst-layered gas diffusion layer, in which a catalyst layer is laminated on a gas diffusion layer, with an electrolyte membrane. Specifically, the catalyst-layered electrolyte membrane can be completed by placing and joining an electrolyte membrane between an anode catalyst-layered gas diffusion layer, in which an anode catalyst layer is laminated on an anode gas diffusion layer, and a cathode catalyst-layered gas diffusion layer, in which a cathode catalyst layer is laminated on a cathode gas diffusion layer.

[0074] The membrane electrode assembly of the present invention may be one in which the electrolyte membrane with a catalyst layer and the gas diffusion layer, or the electrolyte membrane and the gas diffusion layer with a catalyst layer, are bonded in advance, or the electrolyte membrane with a catalyst layer and the gas diffusion layer may be placed in a cell, or the bond may be formed in a tightening process after the electrolyte membrane and the gas diffusion layer with a catalyst layer are placed in a cell.

[0075] [Examples of application] The electrolyte membrane and catalyst-equipped electrolyte membrane of the present invention are applicable to a variety of uses, but are preferably used in electrochemical cells. Examples of electrochemical cells include fuel cells, redox flow batteries, water electrolysis, and hydrogen compression, but water electrolysis devices are preferred, and water electrolysis type water generators are particularly preferred. [Examples]

[0076] The present invention will be described in more detail below based on examples. However, the present invention is not limited to the following examples.

[0077] The evaluation methods for each example and comparative example are described below.

[0078] (1) Molecular weight of polymer The number-average molecular weight and weight-average molecular weight of polymers were measured by GPC. A Tosoh HLC-8022GPC, an integrated UV detector and differential refractometer, was used. Two Tosoh TSKgelSuperHM-H columns (6.0 mm inner diameter, 15 cm length) were used as GPC columns. Measurements were performed using N-methyl-2-pyrrolidone solvent (containing 10 mmol / L lithium bromide) at a flow rate of 0.2 mL / min. The number-average molecular weight and weight-average molecular weight were then determined based on standard polystyrene equivalents.

[0079] (2) Ion exchange capacity (IEC) The measurements were performed using the neutralization titration methods shown in A to D below. Three measurements were taken, and the average value was calculated. A. The polymer electrolyte, which had been proton-substituted and thoroughly washed with pure water, was vacuum-dried at 100°C for 12 hours, and its dry weight was determined. B. 50 ml of 5 wt% sodium sulfate aqueous solution was added to the polymer electrolyte and allowed to stand for 12 hours to perform ion exchange. The resulting sulfuric acid was titrated using a 0.01 mol / L sodium hydroxide aqueous solution. A commercially available titration phenolphthalein solution (0.1 w / v%) was added as an indicator, and the endpoint was reached when the solution turned a pale reddish-purple. D.IEC was calculated using the following formula. IEC (meq / g) = [Concentration of sodium hydroxide solution (mmol / ml) × Droplet volume (ml)] / Dry weight of sample (g).

[0080] (3) Measurement of the thickness of the thin film Measurements were taken using a Mitutoyo ID-C112 model granite comparator mounted on a Mitutoyo BSG-20 stand.

[0081] (4) Evaluation of water electrolysis performance To evaluate the water splitting performance of the electrolyte membrane with a catalyst layer, a membrane electrode assembly was fabricated according to the following procedure. [Membrane electrode assembly] A membrane electrode assembly was fabricated by laminating a commercially available gas diffusion electrode 24BCH manufactured by SGL Corporation as a cathode gas diffusion layer on the cathode catalyst layer side of the electrolyte membrane with a catalyst layer prepared in the examples and comparative examples, and a commercially available porous titanium sintered plate as an anode gas diffusion layer on the anode catalyst layer side. [Evaluation of water electrolysis performance] The membrane electrode assembly prepared above is placed in a Fuel Cell Store water electrolysis cell "Electrolyzer Hardware-Square" (electrode area 50 cm²). 2 The cell was set to ) and fastened so that the average CCM pressure was 4 MPa. Deionized water with an electrical conductivity of 1 μS / cm or less was supplied to both the cathode electrode and anode electrode, which were set to a cell temperature of 60°C, at a flow rate of 0.2 L / min at atmospheric pressure, and 2 A / cm² was applied. 2 A constant current was used to perform a water electrolysis reaction, generating hydrogen and oxygen gases. In constant current measurements, lower cell voltages were associated with superior water electrolysis characteristics. (2 A / cm²) 2 In the constant current measurement, the cell voltage after 1 hour (initial cell voltage) and the cell voltage after 24 hours were measured and evaluated. [Polymer synthesis] [Synthesis Example 1] (Synthesis of 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane (K-DHBP), represented by the chemical formula (1-1) below) In a 500 mL flask equipped with a stirrer, thermometer, and distillation tube, 49.5 g of 4,4′-dihydroxybenzophenone, 134 g of ethylene glycol, 96.9 g of trimethyl orthoformate, and 0.50 g of p-toluenesulfonic acid monohydrate were charged and dissolved. The mixture was then kept warm and stirred at 78-82°C for 2 hours. The internal temperature was then gradually increased to 120°C and heated until the distillation of methyl formate, methanol, and trimethyl orthoformate completely stopped. After cooling the reaction mixture to room temperature, it was diluted with ethyl acetate, and the organic layer was washed with 100 mL of 5% potassium carbonate aqueous solution. After liquid-liquid extraction, the solvent was removed by distillation. 80 mL of dichloromethane was added to the residue to precipitate crystals, which were then filtered and dried to obtain 52.0 g of 2,2-bis(4-hydroxyphenyl)-1,3-dioxolane.

[0082] [ka]

[0083] (Synthesis of disodium-3,3'-disulfonate-4,4'-difluorobenzophenone represented by the general formula (1-2) below) 109.1 g of 4,4'-difluorobenzophenone (Aldrich reagent) was reacted in 150 mL of fuming sulfuric acid (50% SO3) (Wako Pure Chemical Industries, Ltd. reagent) at 100°C for 10 hours. Then, the mixture was gradually added to a large volume of water, neutralized with NaOH, and 200 g of sodium chloride (NaCl) was added to precipitate the product. The resulting precipitate was filtered and recrystallized in an aqueous ethanol solution to obtain disodium-3,3'-disulfonate-4,4'-difluorobenzophenone, represented by the following chemical formula (1-2).

[0084] [ka]

[0085] (Synthesis of nonionic oligomer a1 (terminal: hydroxyl group)) In a 2,000 mL SUS polymerization apparatus equipped with a stirrer, nitrogen inlet tube, and Dean-Stark trap, 16.59 g of potassium carbonate (Aldrich reagent, 120 mmol), 25.83 g (100 mmol) of the above-mentioned K-DHBP, and 20.3 g of 4,4'-difluorobenzophenone (Aldrich reagent, 93 mmol) were added. After nitrogen purging, 300 mL of N-methylpyrrolidone (NMP) and 100 mL of toluene were added, and dehydration was carried out at 160°C. After raising the temperature to remove the toluene, polymerization was carried out at 180°C for 1 hour. Reprecipitation and purification with a large amount of methanol were performed to obtain nonionic oligomer a1 (terminated: hydroxyl group). The number-average molecular weight of this nonionic oligomer a1 (terminated: hydroxyl group) was 10,000. (Synthesis of nonionic oligomer a1 (terminal: fluoro group)) In a 500 mL three-necked flask equipped with a stirrer, nitrogen inlet tube, and Dean-Stark trap, 1.1 g of potassium carbonate (Aldrich reagent, 8 mmol) and 20.0 g (2 mmol) of the above nonionic oligomer a1 (terminated by a hydroxyl group) were added. After purging the apparatus with nitrogen, 100 mL of NMP and 30 mL of cyclohexane were added, and the mixture was dehydrated at 100 °C. The temperature was then raised to remove the cyclohexane. Furthermore, 4.0 g of decafluorobiphenyl (Aldrich reagent, 12 mmol) was added, and the reaction was carried out at 105 °C for 1 hour. Reprecipitation and purification with a large amount of isopropyl alcohol were performed to obtain nonionic oligomer a1 (terminated by a fluoro group) represented by the following general formula (1-3). The number-average molecular weight was 11,000.

[0086] [ka]

[0087] (Synthesis of ionic oligomer a2 represented by the following chemical formulas (1-4)) In a 2,000 mL SUS polymerization apparatus equipped with a stirrer, nitrogen inlet tube, and Dean-Stark trap, 27.6 g of potassium carbonate (Aldrich reagent, 200 mmol), 12.9 g (50 mmol) of the above K-DHBP, 9.3 g (50 mmol) of 4,4'-biphenol (Aldrich reagent, 50 mmol), 40.1 g (95 mmol) of the above disodium-3,3'-disulfonate-4,4'-difluorobenzophenone, and 17.9 g (82 mmol) of 18-crown-6 (Wako Pure Chemical Industries, Ltd.) were added. After purging with nitrogen, 300 mL of NMP and 100 mL of toluene were added, dehydration was performed at 150 °C, the temperature was raised to remove the toluene, and polymerization was carried out at 170 °C for 6 hours. Reprecipitation and purification with a large amount of isopropyl alcohol were performed to obtain ionic oligomer a2 (terminus: OM group) represented by the following chemical formula (1-4). The number average molecular weight was 21,000. In equation (1-4), M represents either Na or K.

[0088] [ka]

[0089] (Synthesis of polyetherketone block polymer (PEK-1)) In a 2,000 mL stainless steel polymerization apparatus equipped with a stirrer, nitrogen inlet tube, and Dean-Stark trap, 0.56 g of potassium carbonate (Aldrich reagent, 4 mmol) and 21 g (1 mmol) of oligomer a2 (terminus: OM group) containing ionic groups were added, and the apparatus was purged with nitrogen. Subsequently, 100 mL of NMP and 30 mL of cyclohexane were added, and the mixture was dehydrated at 100°C. After raising the temperature to remove the cyclohexane, 11 g (1 mmol) of oligomer a1 (terminus: fluoro group) that does not contain ionic groups was added, and the reaction was carried out at 105°C for 24 hours. By reprecipitation and purification with a large amount of isopropyl alcohol, polyether ketone block polymer (PEK-1) was obtained. The weight-average molecular weight of PEK-1 was 320,000, and the ion exchange capacity was 2.1 meq / g. [Synthesis Example 2] (Synthesis of polyether ethersulfone polymer (PEES-1a)) A polyether ether sulfone polymer represented by the structural formula of PEES-1 shown below was synthesized. PEES-1a was synthesized using the method described in Japanese Patent Publication No. 2008-117750.

[0090] [ka]

[0091] In a flask equipped with a stirrer, thermometer, and distillation tube, 12.77 g, 26.0 mmol, Tokyo Chemical Industries, Ltd. reagent, 4,4'-dichlorodiphenylsulfone-3,3'-disulfonic acid disodium salt, 4,4'-dichlorodiphenylsulfone (4.10 g, 14.3 mmol, Tokyo Chemical Industries, Ltd.), 4,4'-dihydroxydiphenyl ether (8.09 g, 40.0 mmol, Wako Pure Chemical Industries, Ltd. reagent), potassium carbonate (6.6 g, 47.8 mmol, Wako Pure Chemical Industries, Ltd. reagent), 50 ml of NMP, and 14 ml of toluene were added. The mixture was stirred at 160°C for 4 hours, and then stirred at 200°C for 16 hours. After the reaction mixture cooled to room temperature, it was poured into 1 L of water to precipitate the polymer. The precipitated polymer was washed with pure water and then dried under reduced pressure at 80°C for 12 hours to obtain PEES-1a (with a charging ratio of 4,4'-dichlorodiphenylsulfone-3,3'-disulfonic acid disodium salt to 4,4'-dichlorodiphenylsulfone of 65:35). The weight-average molecular weight of PEES-1a was 150,000, and the ion exchange capacity was 2.4 meq / g. [Synthesis Example 3] (Synthesis of polyether ether sulfone polymer (PEES-1b)) In a flask equipped with a stirrer, thermometer, and distillation tube, 8.84 g, 18.0 mmol, 4,4'-dichlorodiphenylsulfone-3,3'-disulfonic acid disodium salt (Tokyo Chemical Industries, Ltd. reagent), 6.44 g, 22.4 mmol, manufactured by Tokyo Chemical Industries, Ltd., 8.09 g, 40.0 mmol, 4,4'-dihydroxydiphenyl ether (Wako Pure Chemical Industries, Ltd. reagent), 6.6 g, 47.8 mmol, 4,4'-potassium carbonate (Wako Pure Chemical Industries, Ltd. reagent), 50 ml of NMP, and 14 ml of toluene were added. The mixture was stirred at 160°C for 4 hours, and then stirred at 200°C for 16 hours. After the reaction mixture cooled to room temperature, it was poured into 1 L of water to precipitate the polymer. The precipitated polymer was washed with pure water and then dried under reduced pressure at 80°C for 12 hours to obtain PEES-1b (with a charging ratio of 4,4'-dichlorodiphenylsulfone-3,3'-disulfonic acid disodium salt to 4,4'-dichlorodiphenylsulfone of 45:55). The weight-average molecular weight of PEES-1b was 160,000, and the ion exchange capacity was 1.8 meq / g. [Preparation of coating solution] By adding 40g of NMP to 10g of the above polymer electrolyte (PEK-1) and stirring at room temperature for 24 hours, a 20% by weight NMP solution of PEK-1 (EK-1) was obtained. Similarly, by adding 40g of NMP to 10g of the above polymer electrolyte (PEES-1a) and stirring at room temperature for 24 hours, a 20% by weight NMP solution of PEES-1 (ES-1a) was obtained. Similarly, by adding 40g of NMP to 10g of the above polymer electrolyte (PEES-1b) and stirring at room temperature for 24 hours, a 20% by weight NMP solution of PEES-1b (ES-1b) was obtained.

[0092] [Example 1] (Fabrication of electrolyte membrane (A-1)) A PET film "Lumirror" (registered trademark) 125T60 manufactured by Toray Industries, Inc. was bonded and fixed to a SUS plate using "Kapton" (registered trademark) tape. A coating liquid (EK-1) was then applied to this PET film by casting with an applicator, and dried at 100°C for 4 hours to obtain a first layer (film thickness 10 μm). Subsequently, a coating liquid (ES-1a) was applied to the first layer by casting with an applicator. A mesh fabric made of liquid crystal polyester fibers (fiber diameter 25 μm, mesh thickness 35 μm, opening 52 μm, opening area 45%) manufactured in Manufacturing Example 1 of International Publication No. 2019 / 188960 was brought into contact with the coating film obtained by casting and impregnated into the coating film. After drying the obtained impregnated film at 100°C for 4 hours, the coating solution (ES-1a) was further applied by casting with an applicator and dried at 100°C for 4 hours to form a second layer (film thickness 80 μm) reinforced with a porous substrate. Subsequently, the coating solution (EK-1) was applied by casting onto the second layer using an applicator and dried at 100°C for 4 hours to obtain a third layer (film thickness 10 μm). The laminated film including the third layer was immersed in a 10% sulfuric acid aqueous solution at 80°C for 12 hours to undergo proton substitution and deprotection reactions, and then thoroughly washed by immersion in pure water to obtain an electrolyte membrane (A-1) composed of a first layer (electrolyte: PEK-1), a second layer (electrolyte: PEES-1a, reinforced with a porous substrate), and a third layer (electrolyte: PEK-1).

[0093] (Fabrication of electrolyte membranes with catalyst layer) The anode catalyst layer transfer sheet 1 shown below was placed on the first layer side of the electrolyte membrane (A-1) obtained above, and the cathode catalyst layer transfer sheet 1 shown below was placed on the third layer side of the electrolyte membrane. The membrane was then heated and pressed at 150°C and 5 MPa for 3 minutes, and after being cooled to below 40°C under pressure, the pressure was released to obtain an electrolyte membrane with a catalyst layer. <Preparation of Anode Catalyst Layer Transfer Sheet 1> A catalyst ink was prepared by mixing an iridium oxide catalyst manufactured by Umicore and DuPont's "Nafion"® at a mass ratio of 67:33. This catalyst ink was then applied to a commercially available "Teflon"® film with an iridium content of 2.5 mg / cm². 2 The material was coated in this manner to create a transfer film of the anode catalyst layer. <Preparation of Cathode Catalyst Layer Transfer Sheet 1> A catalyst ink was prepared by mixing TEC10E50E platinum catalyst manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. with DuPont's "Nafion" (registered trademark) in a mass ratio of 67:33. This catalyst ink was then applied to a commercially available "Teflon" (registered trademark) film with a platinum content of 0.3 mg / cm². 2 The material was coated in this manner to create a transfer film of the cathode catalyst layer. (evaluation) Using the catalyst-equipped electrolyte membrane obtained as described above, a membrane electrode assembly was fabricated and its water electrolysis performance was evaluated at 2 A / cm². 2 In the constant current water electrolysis reaction, the cell voltage after 1 hour was 2.1V, and the cell voltage after 24 hours remained unchanged at 2.1V. [Comparative Example 1] (Fabrication of electrolyte membrane (B-1)) An electrolyte membrane (B-1) was obtained by the same method as described in Example 1, except that ES-1b was used as the coating liquid for the second layer, and the membrane consisted of a first layer (electrolyte: PEK-1), a second layer (electrolyte: PEES-1b, reinforced with a porous substrate), and a third layer (electrolyte: PEK-1). (evaluation) Using electrolyte membrane (B-1), a catalyst-equipped electrolyte membrane and a membrane electrode assembly were fabricated in the same manner as described in Example 1, and the water electrolysis performance was evaluated at 2 A / cm². 2 In the constant current water electrolysis reaction, the cell voltage after 1 hour was 2.3V, and the cell voltage after 24 hours was also 2.3V. [Comparative Example 2] (Fabrication of electrolyte membrane (B-2)) A PET film "Lumirror" (registered trademark) 125T60 manufactured by Toray Industries, Inc. was bonded and fixed to a SUS plate using "Kapton" (registered trademark) tape. A coating solution (ES-1a) was then applied to this PET film by casting using an applicator, and dried at 100°C for 4 hours to obtain a first layer (film thickness 10 μm). Subsequently, a coating solution (EK-1) was applied to the first layer by casting using an applicator. A mesh fabric made of liquid crystal polyester fibers (fiber diameter 25 μm, mesh thickness 35 μm, opening 52 μm, opening area 45%) manufactured in Manufacturing Example 1 of International Publication No. 2019 / 188960 was brought into contact with the coating film obtained by casting and impregnated with the coating solution. The resulting impregnated film was dried at 100°C for 4 hours to obtain a second layer (film thickness 80 μm). Next, the coating solution (ES-1a) was applied by casting using an applicator and dried at 100°C for 4 hours to obtain a third layer (film thickness 10 μm). The laminated film obtained above was immersed in a 10% sulfuric acid aqueous solution for 12 hours to undergo proton substitution and deprotection reactions, and then thoroughly washed by immersion in pure water to obtain an electrolyte membrane (B-2) composed of a first layer (electrolyte: PEES-1a), a second layer (electrolyte: PEK-1), and a third layer (electrolyte: PEES-1a). (evaluation) Using electrolyte membrane (B-2), a catalyst-equipped electrolyte membrane and a membrane electrode assembly were fabricated in the same manner as described in Example 1, and the water electrolysis performance was evaluated at 2 A / cm². 2 In the constant current water electrolysis reaction, the cell voltage after 1 hour was 2.4V, and the cell voltage after 24 hours was 2.6V.

[0094] Table 1 shows the evaluation results of the above examples and comparative examples. It can be seen that the electrolyte membrane provided by the present invention exhibits good water electrolysis characteristics over a long period of time.

[0095] [Table 1] [Explanation of symbols]

[0096] 1. The first layer 2. Second layer 3. The third layer 4 Electrolyte membrane 5. Anode catalyst layer 6. Cathode catalyst layer 7. Catalyst-equipped electrolyte membrane

Claims

1. An electrolyte membrane comprising: a first layer composed of an electrolyte mainly consisting of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less as measured by neutralization titration; and a second layer composed of a composite electrolyte formed by compounding an aromatic hydrocarbon polymer having a different chemical structure from the first layer and an ion exchange capacity of 2.0 meq / g or more and 5.0 meq / g or less with a porous substrate, wherein the thickness of the first layer is half or less of the thickness of the second layer.

2. An electrolyte membrane having, in this order: a first layer composed of an electrolyte mainly composed of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less as measured by neutralization titration; a second layer composed of a composite electrolyte formed by compounding an aromatic hydrocarbon polymer having a different chemical structure from the first layer, an ion exchange capacity of 2.0 meq / g or more and 5.0 meq / g or less, and a porous substrate with an aromatic hydrocarbon polymer having a different chemical structure from the first layer; and a third layer composed of an electrolyte mainly composed of an aromatic hydrocarbon polymer having an ion exchange capacity of 0.5 meq / g or more and 2.5 meq / g or less, wherein the thickness of each of the first and third layers is half or less of the thickness of the second layer.

3. The electrolyte membrane according to claim 1, wherein the thickness of the first layer is 1 μm or more and less than 20 μm, and the thickness of the second layer is 40 μm or more and 150 μm or less.

4. The electrolyte membrane according to claim 2, wherein the thickness of the first layer and the third layer is 1 μm or more and less than 20 μm, and the thickness of the second layer is 40 μm or more and 150 μm or less.

5. The electrolyte membrane according to claim 1, wherein the aromatic hydrocarbon polymer constituting the first layer is a polyetherketone polymer.

6. The electrolyte membrane according to claim 2, wherein either or both of the aromatic hydrocarbon polymers constituting the first layer and the third layer are polyetherketone polymers.

7. The electrolyte membrane according to claim 1, wherein the aromatic hydrocarbon polymer constituting the first layer is a block copolymer polyetherketone polymer.

8. The electrolyte membrane according to claim 2, wherein either or both of the aromatic hydrocarbon polymers constituting the first layer and the third layer are block copolymer polyetherketone polymers.

9. The electrolyte membrane according to claim 1, wherein the aromatic hydrocarbon polymer of the second layer is a polysulfone polymer having a polysulfone structure as its main backbone.

10. The electrolyte membrane according to claim 2, wherein the aromatic hydrocarbon polymer of the second layer is a polysulfone polymer having a polysulfone structure as its main backbone.

11. The electrolyte membrane according to claim 1, wherein the porous substrate of the second layer is liquid crystal polyester fiber or polyphenylene sulfide.

12. The electrolyte membrane according to claim 2, wherein the porous substrate of the second layer is liquid crystal polyester fiber or polyphenylene sulfide.

13. A catalyst-layered electrolyte membrane comprising an electrolyte membrane according to at least one selected from claims 1, 3, 5, 7, 9, and 11, wherein an anode catalyst is arranged on the surface of the first layer and a cathode catalyst is arranged on the surface of the second layer.

14. An electrolyte membrane with a catalyst layer, comprising an electrolyte membrane according to at least one selected from claims 2, 4, 6, 8, 10, and 12, wherein an anode catalyst is arranged on the surface of the first layer and a cathode catalyst is arranged on the third surface.

15. A membrane electrode assembly comprising an electrolyte membrane according to any one of claims 1 to 12.

16. An electrochemical cell comprising an electrolyte membrane according to any one of claims 1 to 12.

17. A polymer electrolyte water electrolysis apparatus comprising the electrochemical cell described in claim 16.

18. A polymer electrolyte fuel cell comprising the electrochemical cell described in claim 16.

Images