Abstract: Provided are a method for producing a liquid composition which is capable of eliminating clouding of a liquid with cerium (IV) hydroxide particles in a relatively short time, and methods for producing a polymer electrolyte membrane, a catalyst layer and a membrane/electrode assembly, each having excellent durability, in a relatively short time. A method for producing a liquid composition containing a fluoropolymer having sulfonic acid groups, trivalent cerium ions and water, which comprises (1) irradiating a solution containing at least one cerium compound selected from the group consisting of cerium carbonate, cerium hydroxide and cerium oxide, the fluoropolymer and the water, with light at least partially in a wavelength region from 300 to 400 nm so that the ultraviolet irradiance on the surface of the solution is at least 0.

Abstract: To provide a membrane/electrode assembly excellent in the power generation characteristics in a wide temperature range and a wide humidity range; an electrolyte material suitable for a catalyst layer of the membrane/electrode assembly; and a liquid composition suitable for forming a catalyst layer of the membrane/electrode assembly. To use an electrolyte material which is formed of a polymer (H) obtained by converting precursor groups in a polymer (F) having structural units (A) based on a perfluoromonomer having a precursor group represented by the formula (g1), structural units (B) represented by the formula (u2), and structural units (C) based on tetrafluoroethylene, wherein the proportion of the structural units (A) is from 8 to 19 mol %, the proportion of the structural units (B) is from 65 to 80 mol %, and the proportion of the structural units (C) is from 1 to 27 mol %, to ion exchange groups.

Abstract: To provide a membrane/electrode assembly excellent in the power generation characteristics even under low or no humidity conditions or under high humidity conditions, and an electrolyte material suitable for a catalyst layer of the 5 membrane/electrode assembly, an electrolyte material is used which comprises a polymer (H) having a unit (A) which has an ion exchange group and in which all hydrogen atoms (excluding H+ of the ion exchange group) bonded to carbon atoms are substituted by fluorine atoms, a unit (B) which has a 5-membered ring and in which all hydrogen atoms bonded to carbon 10 atoms are substituted by fluorine atoms, and a unit (C) which has neither an ion exchange group nor a ring structure, has an ether bond, and has an ether equivalent of at most 350 as established by the following formula (I) and in which all hydrogen atoms bonded to carbon atoms are substituted by fluorine atoms: Ether equivalent=the molecular weight of the monomer forming the unit (C)/the 15 number of ether bonds in the mo

Abstract: To provide: an electrolyte material having high oxygen permeability as compared with conventional ones; a membrane electrode assembly for a polymer electrolyte fuel cell excellent in power generation characteristics as compared with conventional ones; a liquid composition suitable for forming a catalyst layer for the membrane electrode assembly; and a fluorinated branched polymer useful as e.g. a raw material of the electrolyte material. The electrolyte material comprises a fluoropolymer (H)1 having a structural unit (u1) that has an ionic group and a structural unit (u2) that has an alicyclic structure, wherein the fluoropolymer (H)1 is composed of a branched molecular chain, and has a segment (A)3 comprising a molecular chain having the structural unit (u1) and a segment (B)2 composed of a molecular chain having the structural unit (u2), and the ion exchange capacity of the segment (B)2 is smaller than the ion exchange capacity of the segment (A)3.

Abstract: To provide a process for forming a polymer electrolyte membrane having good durability and few wrinkles, a polymer electrolyte membrane capable of forming a catalyst layer, or a catalyst layer; a process for producing a fluorinated ion exchange resin fluid, or a paste for forming a catalyst layer, which can be used for such a forming process; and a process for producing a membrane/electrode assembly for a polymer electrolyte fuel cell having good durability and power generation properties. A fluorinated ion exchange resin fluid obtained by subjecting a powder or pellets of a fluorinated ion exchange resin having cation exchange groups to hydrogen peroxide treatment, followed by mixing with a solvent, is used.

Abstract: To provide a process for forming a polymer electrolyte membrane having good durability and few wrinkles, a polymer electrolyte membrane capable of forming a catalyst layer, or a catalyst layer; a process for producing a fluorinated ion exchange resin fluid, or a paste for forming a catalyst layer, which can be used for such a forming process; and a process for producing a membrane/electrode assembly for a polymer electrolyte fuel cell having good durability and power generation properties. A fluorinated ion exchange resin fluid obtained by subjecting a powder or pellets of a fluorinated ion exchange resin having cation exchange groups to hydrogen peroxide treatment, followed by mixing with a solvent, is used.

Abstract: It is to provide an electrolyte material with which an increase in the water content can be suppressed even when the ion exchange capacity of a polymer having repeating units based on a monomer having a dioxolane ring is high; and a membrane/electrode assembly excellent in the power generation characteristics under low or no humidity conditions and under high humidity conditions. It is to use an electrolyte material, which comprises a polymer (H) having ion exchange groups converted from precursor groups in a polymer (F), and having an ion exchange capacity of at least 1.35 meq/g dry resin, the polymer (F) having repeating units (A) based on a perfluoromonomer having a precursor group of an ion exchange group and a dioxolane ring and repeating units (B) based on a perfluoromonomer having no precursor group and having a dioxolane ring, and having a TQ of at least 200° C.

Abstract: To provide a liquid composition capable of forming a catalyst layer that is excellent in resistance to hydrogen peroxide and peroxide radicals, can further increase the output voltage of a membrane/electrode assembly, and can maintain a high output voltage for a long period of time; a method for its production; and a membrane electrode assembly for a polymer electrolyte fuel cell using said liquid composition. Provided is a liquid composition to be used for forming a catalyst layer constituting an electrode of a membrane electrode assembly for a polymer electrolyte fuel cell, wherein the liquid composition comprises a liquid medium, a fluoropolymer (H) having sulfonic acid groups and ring structures, and trivalent or tetravalent cerium ions, and the content of the trivalent or tetravalent cerium ions is from 1.6 to 23.3 mol % to the sulfonic acid groups (100 mol %).

Abstract: A polymer electrolyte membrane includes: (A) an ion exchange resin comprising cation exchange groups which comprise protons; (B) a cerium ion; and (C) at least one second ion selected from the group consisting of a cesium ion and a rubidium ion. A proportion of the cerium ion to the number of the cation exchange groups (100 mol %) is from 0.7 to 30 mol % such that some of the protons in the cation exchange groups are ion-exchanged by the cerium ion. A proportion of the at least one second ion to the number of the cation exchange groups (100 mol %) is from 0.2 to 15 mol % such that some of the protons in the cation exchange groups are ion-exchanged by the at least one second ion.

Abstract: To provide an electrolyte material with which a membrane/electrode assembly in which flooding in a catalyst layer and breakage of a polymer electrolyte membrane are less likely to occur and which is excellent in the power generation characteristics, can be obtained; and a process for producing an electrolyte material having a low water content even though the material is formed of a polymer having units derived from a perfluoromonomer having a dioxolane ring. An electrolyte membrane which is formed of a polymer (H) obtained by converting —SO2F groups of a polymer (F) having units derived from a perfluoromonomer having a —SO2F group and a dioxolane ring, units derived from a perfluoromonomer having no —SO2F group and having a dioxolane ring, and units derived from tetrafluoroethylene, to ion exchange groups, which has an ion exchange capacity of from 0.9 to 1.3 meq/g dry resin, and which has a water content of from 20 to 100%.

Abstract: To provide a membrane/electrode assembly excellent in the power generation characteristics even under low or no humidity conditions or under high humidity conditions, and an electrolyte material suitable for a catalyst layer of the membrane/electrode assembly.

Abstract: To provide a polymer electrolyte membrane for polymer electrolyte fuel cells having high mechanical strength and excellent dimensional stability when it contains water even when it is made thin and the concentration of ionic groups is increased so as to reduce the electrical resistance, and a membrane/electrode assembly providing high output and having excellent durability.

Abstract: An electrolyte material, which comprises a polymer (H) having ion exchange groups converted from precursor groups in a polymer (F) having repeating units (A) having a precursor group represented by the formula (g1) and repeating units (B) based on a perfluoromonomer having a 5-membered ring, and having a density of at most 2.03 g/cm3, the polymer (H) having an ion exchange capacity of from 1.3 to 2.3 meq/g dry resin: wherein Q1 and Q2 are a perfluoroalkylene group having an etheric oxygen atom, or the like, and Y is F or the like; the electrolyte material being suitable for a catalyst layer of the membrane/electrode assembly; the membrane/electrode assembly being excellent in power generation characteristics under low or no humidity conditions and under high humidity conditions.

Abstract: To provide a polymer electrolyte membrane and a membrane/electrode assembly for a polymer electrolyte fuel cell, excellent in the durability to hydrogen peroxide or peroxide radicals. A polymer electrolyte membrane 15 comprising an ion exchange resin having cation exchange groups, which contains cerium element and at least one member selected from cesium element and rubidium element; and a membrane/electrode assembly 10, comprising an anode 13 having a catalyst layer 11 containing a catalyst and an ion exchange resin, a cathode 14 having a catalyst layer 11 containing a catalyst and an ion exchange resin, and a polymer electrolyte membrane 15 disposed between the anode 13 and the cathode 14, wherein the polymer electrolyte membrane 15 contains cerium element and at least one member selected from cesium element and rubidium element.

Abstract: A membrane/electrode assembly for a polymer electrolyte fuel cell, comprising an anode and a cathode each having a catalyst layer containing a proton conductive polymer, and a polymer electrolyte membrane disposed between the anode and the cathode, wherein the proton conductive polymer has an electrical conductivity of at least 0.07 S/cm at a temperature of 80° C. at a relative humidity of 40% and has a water content less than 150 mass %.

Abstract: To provide a fuel cell system provided with a polymer electrolyte fuel cell which is excellent in the power generation characteristics under high temperature and low or no humidity conditions. A fuel cell system 20 comprising a polymer electrolyte fuel cell 22 having a membrane/electrode assembly 10 having a catalyst layer containing a polymer (H) which has repeating units based on a perfluoromonomer having an alicyclic structure and has ion exchange groups, a temperature controlling means for controlling temperature of the polymer electrolyte fuel cell 22, a temperature sensor 38 for detecting temperature of the polymer electrolyte fuel cell 22, and a controlling device 40 for controlling the temperature controlling means based on temperature information from the temperature sensor 38 so that the maximum temperature of the polymer electrolyte fuel cell 22 becomes within the range of from 90 to 140° C.

Abstract: A membrane/electrode assembly for a polymer electrolyte fuel cell capable of exhibiting high power generation performance constantly for a long period of time in a high temperature and low humidity environment, and a polymer electrolyte membrane whereby such a membrane/electrode assembly is obtainable. A polymer electrode membrane 15, comprising a proton conductive polymer which has an electrical conductivity of at least 0.07 S/cm at a temperature of 80° C. at a relative humidity of 40% and which has a water content of less than 15 mass; and a membrane/electrode assembly 10 comprising an anode 13 and a cathode 14 each having a catalyst layer 11, and a polymer electrolyte membrane 15 disposed between the anode 13 and the cathode 14.

Abstract: A polymer electrolyte membrane made of a polymer has a low electrical resistance, high heat resistance and is strong against repeats of swelling and shrinkage. Thus, a membrane/electrode assembly for polymer electrolyte fuel cells having high power generation performance and excellent in durability can be provided. For a polymer electrolyte membrane 15 or for a catalyst layer 11 constituting electrodes 13 and 14, a polymer comprising units (U1) and units (U2) is used: Q1, Q2: a perfluoroalkylene group which may have —O— or the like; Rf1, Rf2: a perfluoroalkyl group which may have —O—; X: an oxygen atom or the like; a: 0 or the like; Y, Z: a fluorine atom, or a monovalent perfluoroorganic group such as —CF3; S: 0 to 1; and t: 0 to 3.

Abstract: To provide a polymer electrolyte material for polymer electrolyte fuel cells, which is an electrolyte material having a high ion exchange capacity and a low resistance, and which has a higher softening temperature than a conventional electrolyte material.

Abstract: A polymer electrolyte membrane made of a polymer having a low electrical resistance, high heat resistance and is strong against repeats of swelling and shrinkage. Thus, a membrane/electrode assembly for polymer electrolyte fuel cells having high power generation performance and excellent in durability can be provided.