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 0.1 mW/cm.sup.2 or (2) adding a reducing agent to 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.

To provide a membrane electrode assembly capable of forming a fuel cell excellent in power generation efficiency, and a polymer electrolyte fuel cell. The membrane electrode assembly of the present invention comprises an anode having a catalyst layer containing a proton-conducting polymer and a catalyst, a cathode having a catalyst layer containing a proton-conducting polymer and a catalyst, and a solid polymer electrolyte membrane disposed between the anode and the cathode, wherein the proton-conducting polymer contained in the catalyst layer of at least one of the anode and the cathode, is a polymer (H) having a cyclic ether structural unit and an ion exchange group, and the solid polymer electrolyte membrane contains a fluorinated polymer (S) having an ion exchange group; and the thickness of the solid polymer electrolyte membrane is from 5 to 15 μm, and the ratio of the content M1 [mol %] of the cyclic ether structure unit to the thickness T1 [μm] of the solid polymer electrolyte membrane is 4.5 or more.

To provide a membrane electrode assembly capable of forming a fuel cell excellent in power generation efficiency, and a polymer electrolyte fuel cell. The membrane electrode assembly of the present invention comprises an anode having a catalyst layer containing a proton-conducting polymer and a catalyst, a cathode having a catalyst layer containing a proton-conducting polymer and a catalyst, and a solid polymer electrolyte membrane disposed between the anode and the cathode, wherein the proton-conducting polymer contained in the catalyst layer of at least one of the anode and the cathode, is a polymer (H) having a cyclic ether structural unit and an ion exchange group, and the solid polymer electrolyte membrane contains a fluorinated polymer (S) having an ion exchange group; and the thickness of the solid polymer electrolyte membrane is from 5 to 15 μm, and the ratio of the content M1 [mol %] of the cyclic ether structure unit to the thickness T1 [μm] of the solid polymer electrolyte membrane is 4.5 or more.

The present invention relates to new anion exchange polymers and (blend) membranes made from polymers containing highly fluorinated aromatic groups by means of nucleophilic substitution and processes for their production by means of nucleophilic aromatic substitution and their areas of application in membrane processes, in particular in electrochemical membrane processes such as fuel cells, electrolysis and redox flow batteries.

The present invention relates to new anion exchange polymers and (blend) membranes made from polymers containing highly fluorinated aromatic groups by means of nucleophilic substitution and processes for their production by means of nucleophilic aromatic substitution and their areas of application in membrane processes, in particular in electrochemical membrane processes such as fuel cells, electrolysis and redox flow batteries.

The invention relates to a membrane which contains crosslinked phosphonated pentafluorostyrene. The invention also relates to the use of a membrane or membrane electrodes containing crosslinked phosphonated pentafluorostyrene in an electrochemical cell at a temperature of 0 to 380° C. The invention also describes the use of a membrane or membrane electrodes containing non-crosslinked phosphonated pentafluorostyrene in an electrochemical cell at a temperature of 0 to 380° C. In addition, the invention discloses a nonwoven fabric containing phosphonated polypentafluorostyrene. The invention also relates to the use of the nonwoven fabric in a membrane or in a membrane electrode unit in electrochemical applications at temperatures up to 380° C.

The invention relates to a membrane which contains crosslinked phosphonated pentafluorostyrene. The invention also relates to the use of a membrane or membrane electrodes containing crosslinked phosphonated pentafluorostyrene in an electrochemical cell at a temperature of 0 to 380° C. The invention also describes the use of a membrane or membrane electrodes containing non-crosslinked phosphonated pentafluorostyrene in an electrochemical cell at a temperature of 0 to 380° C. In addition, the invention discloses a nonwoven fabric containing phosphonated polypentafluorostyrene. The invention also relates to the use of the nonwoven fabric in a membrane or in a membrane electrode unit in electrochemical applications at temperatures up to 380° C.

A coated electrode assembly (CEA) comprising: i) a gas diffusion layer (GDE); and ii) a coating. The GDE comprises a gas diffusion layer (GDL) and a catalyst layer. The catalyst layer is disposed between the coating and the GDL. The catalyst layer comprises a hydrophobic polymer and/or an ionomeric polymer and the coating comprises a hydrophobic polymer and/or an ionomeric polymer. A method for making a CEA is provided. The CEA may have improved performance and stability compared to a membrane electrode assembly (MEA).

Disclosed is an antioxidant for a polymer electrolyte membrane of a fuel cell including cerium hydrogen phosphate (CeHPO.sub.4). The presence of cerium hydrogen phosphate in the antioxidant enhances the dissolution stability of cerium and improves the ability to capture water, leading to an increase in proton conductivity. In addition, the cerium hydrogen phosphate has a crystal structure composed of smaller cerium particles. This crystal structure greatly improves the ability of the antioxidant to prevent oxidation of the electrolyte membrane. Also disclosed are an electrolyte membrane including the antioxidant, a fuel cell including the electrolyte membrane, a method for preparing the antioxidant, a method for producing the electrolyte membrane, and a method for fabricating the fuel cell.

Disclosed is an antioxidant for a polymer electrolyte membrane of a fuel cell including cerium hydrogen phosphate (CeHPO.sub.4). The presence of cerium hydrogen phosphate in the antioxidant enhances the dissolution stability of cerium and improves the ability to capture water, leading to an increase in proton conductivity. In addition, the cerium hydrogen phosphate has a crystal structure composed of smaller cerium particles. This crystal structure greatly improves the ability of the antioxidant to prevent oxidation of the electrolyte membrane. Also disclosed are an electrolyte membrane including the antioxidant, a fuel cell including the electrolyte membrane, a method for preparing the antioxidant, a method for producing the electrolyte membrane, and a method for fabricating the fuel cell.